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IRVINGTON, NY--(Marketwire - Feb 8, 2012) - MELA Sciences, Inc. (NASDAQ: MELA) today announced that Joseph V. Gulfo, MD, President and CEO, will be presenting at two upcoming investor conferences.
On Thursday, February 16, 2012, Dr. Gulfo will give a presentation at the Leerink Swann 2012 Global Healthcare Conference. To access a live webcast of this presentation, visit the investor relations section of www.melasciences.com. A replay will be available on the company's website for two weeks following the presentation.
On Wednesday, February 29, 2012, Dr. Gulfo will participate in the Lazard Capital Markets 4th Annual Medical Technology Snowbird event at the Snowbird Ski and Summer Resort in Snowbird, UT.
MELA Sciences is a medical device company focused on the design, development and commercialization of non-invasive tools to provide additional information to dermatologists during melanoma skin examinations. The Company's flagship product, MelaFind®, is intended to be used when a trained dermatologist chooses to obtain additional information to help decide whether to biopsy certain indeterminate pigmented skin lesions. MelaFind has received approval from the U.S. Food and Drug Administration and is approved for use in the U.S. In addition, MelaFind has received the CE Mark and is approved for use in the European Union.
This press release includes "forward-looking statements" within the meaning of the Securities Litigation Reform Act of 1995. These statements include but are not limited to our plans, objectives, expectations and intentions and other statements that contain words such as "expects," "contemplates," "anticipates," "plans," "intends," "believes," "assumes," "predicts" and variations of such words or similar expressions that predict or indicate future events or trends, or that do not relate to historical matters. These statements are based on our current beliefs or expectations and are inherently subject to significant known and unknown uncertainties and changes in circumstances, many of which are beyond our control. There can be no assurance that our beliefs or expectations will be achieved. Actual results may differ materially from our beliefs or expectations due to financial, economic, business, competitive, market, regulatory and political factors or conditions affecting the company and the medical device industry in general, as well as more specific risks and uncertainties facing the company such as those set forth in its reports on Forms 10-Q and 10-K filed with the U.S. Securities and Exchange Commission (the "SEC"). Factors that might cause such a difference include whether Melafind® achieves market acceptance or becomes commercially viable. Given the uncertainties affecting companies in the medical device industry such as the Company, any or all of these forward-looking statements may prove to be incorrect. Therefore, you should not rely on any such factors or forward-looking statements. The Company urges you to carefully review and consider the disclosures found in its filings with the SEC which are available at www.sec.gov and www.melasciences.com.


text:
Q: Problems with Managed Beans I'm using primefaces for my webapp and I'm having some problems with my beans. I have a page with two tables, each table has its own bean with an attribute for the selected option in the table, the thing is that when I select a value from the FIRST table and i try to change it, the server crash and tells me that the selected attribute of the SECOND table is null. I don't know why is using the selected attribute of the second table if I'm selecting a row of the first table.
this is my html page:

<h:head>
    <title> BATCH PARAMETRIZATION</title>

</h:head>
<h:body>

<h:form id="form">

                <f:facet name="header">
                    Parametrizacion
                </f:facet>

                    <h:outputText value="$#{Params.valor}" />

                    <h:outputText value="#{Params.porcentaje*100}%" />

                <f:facet name="footer" >

                </f:facet>

                    <h:outputText value="Id:" />
                    <h:outputText value="#{tableMB.selectedParam.id}" />

                    <h:outputText value="Valor" />

                    <h:outputText value="Porcentaje:" />

                    <h:outputText value="Valor" />

                    <h:outputText value="Porcentaje:" />

                    <h:outputText value="#{Premios.premio}" />

                    <h:outputText value="#{Premios.porcentaje*100}%" />

                <f:facet name="footer" >

                </f:facet>

                    <h:outputText value="Id:" />
                    <h:outputText value="#{tablePremiosMB.selectedPremio.id}" />

                    <h:outputText value="Descripcion" />

                    <h:outputText value="Porcentaje:" />

                    <h:outputText value="Descripcion" />

                    <h:outputText value="Porcentaje:" />

</h:form>

</h:body>

this is the bean for the first table:
package ar.com.nortid.mb;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

import javax.faces.bean.ManagedBean;
import javax.faces.bean.ViewScoped;

@ManagedBean(name="tableMB")
@ViewScoped
public class TableMB implements Serializable {

    /**
     *
     */
    private List<Params> precios = new ArrayList<Params>();
    private Params selectedParam;
    private Params nuevoParam = new Params();
    private String expirationDate;

    public TableMB() {
        precios.add(new Params(new Long(1), 2.0, 0.3));
        precios.add(new Params(new Long(2), 5.0, 0.2));
        precios.add(new Params(new Long(3), 10.0, 0.1));
    }

    public List<Params> getPrecios() {
        return precios;
    }

    public void setPrecios(List<Params> precios) {
        this.precios = precios;
    }

    public Params getSelectedParam() {
        return selectedParam;
    }

    public void setSelectedParam(Params selectedParam) {
        this.selectedParam = selectedParam;
    }

    public Params getNuevoParam() {
        return nuevoParam;
    }

    public void setNuevoParam(Params nuevoParam) {
        this.nuevoParam = nuevoParam;
    }

    public String getExpirationDate() {
        return expirationDate;
    }

    public void setExpirationDate(String expirationDate) {
        this.expirationDate = expirationDate;
    }

    public void modificarParametros(){

        int index = -1;
        for(int i=0; i<precios.size(); i++)
            if(precios.get(i).getId() == selectedParam.getId())
                index = i;

        if(index >= 0){
            precios.remove(index);
            precios.add(selectedParam);
        }
    }

    public void agregarParametros(){

        nuevoParam.setId(new Long(precios.size()));
        precios.add(nuevoParam);
        nuevoParam = null;
        nuevoParam = new Params();
    }
}

package ar.com.nortid.mb;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.List;

import javax.faces.bean.ManagedBean;
import javax.faces.bean.ViewScoped;

@ManagedBean(name="tablePremiosMB")
@ViewScoped
public class TablePremiosMB implements Serializable {

    /**
     *
     */
    private List<Premios> premios = new ArrayList<Premios>();
    private Premios selectedPremio;
    private Premios nuevoPremio = new Premios();

    public TablePremiosMB() {
        premios.add(new Premios(new Long(1), "Departamento", 0.001));
        premios.add(new Premios(new Long(2), "Auto", 0.005));
        premios.add(new Premios(new Long(3), "$10000", 0.01));
        premios.add(new Premios(new Long(4), "$100", 0.2));
    }

    public List<Premios> getPremios() {
        return premios;
    }

    public void setPremios(List<Premios> premios) {
        this.premios = premios;
    }

    public Premios getSelectedPremio() {
        return selectedPremio;
    }

    public void setSelectedPremio(Premios selectedPremio) {
        this.selectedPremio = selectedPremio;
    }

    public Premios getNuevoPremio() {
        return nuevoPremio;
    }

    public void setNuevoPremio(Premios nuevoPremio) {
        this.nuevoPremio = nuevoPremio;
    }

    public void modificarPremio(){

        int index = -1;
        for(int i=0; i<premios.size(); i++)
            if(premios.get(i).getId() == selectedPremio.getId())
                index = i;

        if(index >= 0){
            premios.remove(index);
            premios.add(selectedPremio);
        }
    }

    public void agregarPremio(){

        nuevoPremio.setId(new Long(premios.size()));
        premios.add(nuevoPremio);
        nuevoPremio = null;
        nuevoPremio = new Premios();
    }

}

and this is the error that shows up when i try to change a value of the first table:
ADVERTENCIA: /page/BatchParametrization.xhtml @167,83 value="#{tablePremiosMB.selectedPremio.premio}": Objetivo inalcanzable, 'selectedPremio' devolvió nulo
javax.el.PropertyNotFoundException: /page/BatchParametrization.xhtml @167,83 value="#{tablePremiosMB.selectedPremio.premio}": Objetivo inalcanzable, 'selectedPremio' devolvió nulo
    at com.sun.faces.facelets.el.TagValueExpression.getType(TagValueExpression.java:100)
    at org.primefaces.util.ComponentUtils.getConverter(ComponentUtils.java:132)
    at org.primefaces.renderkit.InputRenderer.getConvertedValue(InputRenderer.java:171)
    at javax.faces.component.UIInput.getConvertedValue(UIInput.java:1030)
    at javax.faces.component.UIInput.validate(UIInput.java:960)
    at javax.faces.component.UIInput.executeValidate(UIInput.java:1233)
    at javax.faces.component.UIInput.processValidators(UIInput.java:698)
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214)
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214)
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214)
    at org.primefaces.component.dialog.Dialog.processValidators(Dialog.java:387)
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214)
    at org.primefaces.component.panel.Panel.processValidators(Panel.java:287)
    at javax.faces.component.UIForm.processValidators(UIForm.java:253)
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214)
    at javax.faces.component.UIComponentBase.processValidators(UIComponentBase.java:1214)
    at javax.faces.component.UIViewRoot.processValidators(UIViewRoot.java:1172)
    at com.sun.faces.lifecycle.ProcessValidationsPhase.execute(ProcessValidationsPhase.java:76)
    at com.sun.faces.lifecycle.Phase.doPhase(Phase.java:101)
    at com.sun.faces.lifecycle.LifecycleImpl.execute(LifecycleImpl.java:118)
    at javax.faces.webapp.FacesServlet.service(FacesServlet.java:593)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:504)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1074)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)

as you can see, selectedPremio is returning null but selectedPremio is an attribute of the second table and im try to change a row of the first table. I dont know what to do. Any help you can give me will be great.

redpajama_set_name: RedPajamaStackExchange


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Watch Anchor Pradeep About Pawan Kalyan and Mahesh Babu | Bithiri Sathi Chit Chat With Pradeep here. This news was telecasted on Sunday 05th of February 2017 12:30:00 PM in V6 News Channel. V6 News Channel headed by Senior Journalist Ravi Ankam Watch Latest Updated telugu News videos, Film News, Shows.


text:
UNHCR Officials Highlight Protection Needs of LGBTI Refugees
In recent weeks, two officials from the U.N. Refugee Agency (UNHCR) have taken steps to address the unique challenges facing LGBTI refugees by raising awareness and advocating for further protection. On October 3, in front of various government representatives at UNHCR's Executive Committee meeting in Geneva, Assistant High Commissioner for Protection, Erika Feller spoke of growing awareness that those fleeing persecution due to their sexual orientation or gender identity should qualify as refugees and encouraged more countries to grant refugee status on this basis. She also noted that the "discrimination [LGBTI refugees] encounter can be virulent, their isolation from family and community profound, and the harm inflicted on them severe." Two weeks prior, the Director of UNHCR's Division of International Protection, Volker Türk, speaking in Geneva at a Hebrew Immigrant Aid Society (HIAS) symposium, recognized the "myriad of threats, risks and vulnerabilities" LGBTI refugees face at all stages of displacement. He stressed that the persecution LGBTI refugees flee from is at times repeated in the country of asylum and within refugee communities, and that this limits their access to community support networks and humanitarian services. To improve protection for LGBTI refugees, he announced that UNHCR is updating its Guidance Note on Refugee Claims Relating to Sexual Orientation and Gender Identity, rolling out training for staff and developing a tool and guidance for resettlement staff. In May of this year, we released our report The Road to Safety that examined the plight of LGBTI refugees in Uganda and Kenya, including threats to their physical safety and difficulties in accessing services from government service providers, the UNHCR and NGOs. These statements represent important recognition by UNHCR headquarters of the challenges that LGBTI refugees face as well as some of the steps needed to improve protection and assistance. They follow other recent steps UNHCR has taken to strengthen protection for LGBTI refugees:
A message sent to all UNHCR staff by High Commissioner António Guterres on IDAHO in May 2012 that noted discrimination, including on the basis of sexual orientation and gender identity, will not be tolerated and encouraging staff to reflect on how UNHCR can contribute to increased protection space for LGBTI persons of concern.
The inclusion of the specific concerns of LGBTI asylum seekers in UNHCR's new Detention Guidelines.
The compilation of Age, Gender and Diversity best practice by the Bureau for the Americas that include a focus on LGBTI refugees. LGBTI refugees are an explicit focus of UNHCR's Age, Gender and Diversity Policy issued in 2011.
These are welcome measures and Human Rights First has outlined further steps that UNHCR, host governments, donors and resettlement countries can take to address the specific protection and assistance challenges that LGBTI refugees face. These include:
Measures to protect LGBTI refugees from bias-motivated violence, including through improving access to justice in the country of asylum, supporting new or increased capacity for safe shelter mechanisms and providing access to expedited resettlement.
Measures to ensure that LGBTI refugees are effectively included in protection and assistance programs through targeted outreach and identification strategies, advocacy to address specific barriers that LGBTI refugees may face in accessing government services, training of UNHCR staff and partners, and strategies to ensure that LGBTI refugees are aware of and can access international protection due to persecution on the basis of sexual orientation or gender identity.
To read Human Rights First's detailed recommendations, please click here.
Systemic Injustice-LGBTQI+
10 Key U.S. Allies with Antigay Laws Even Worse than Russia's
By Sharon Kelly McBride This is a cross-post from The Huffington Post. When President Vladimir Putin signed the anti-gay "propaganda" bill on June 30th, he was…
10 Olympic Flame Sites in Russia That Passed Local Antigay Laws
This is a cross-post from BuzzFeed. Before Putin signed Russia's infamous antigay law, 10 regional governments have passed similar laws starting in 2006. Now, the…
8 American Olympians Who Stood Up against Russia's Antigay Law
Human Rights First's report, Convenient Targets, outlines steps the Obama Administration should take to oppose Russia's antigay law. But some American Olympians, both current and former,…
A Refracted Rainbow: Attacks and Bans on Gay Pride Parades (Updated)
As we enter the "Pride Season," with LGBTI events planned across the globe, we'll update this page with news from gay pride marches threatened by…
A Week of Pride in Jamaica
By Elise Adams Jamaica Pride Week began on Monday with a sports day at the University of the West Indies and has continued with events such…
Administration Urged to Press El Salvador on Protection of Transgender Citizens
Washington, D.C.—Following an alarming string of murders of transgender women in El Salvador, Human Rights First today called on the State Department to urge the Salvadoran government to investigate and combat…
Administration Urged to Protect LGBTI Rights
New York City – Human Rights First today marked International Day Against Homophobia and Transphobia by urging the United States Government to continue strengthening protections…
African Leaders Take Action to Support Equality
Washington, D.C. – Human Rights First today praised the African Commission on Human and Peoples' Rights for issuing a resolution calling for established protections against discrimination…
African Voices for Equality
Human Rights First is concerned about the rising tide of legislation in Africa that criminalizes homosexuality or otherwise infringes on basic human rights but we…
African Voices for Equality: Dr. Willy Mutunga
By Trevor Allen Recently, Africa has become a hotbed for homophobic legislation, putting LGBT people and allies at great risk. But a growing number of…
African Voices for Equality: Reverend Christopher Senyonjo
By Dawes Cooke Recently, Africa has become a hotbed for homophobic legislation, putting LGBT people and allies at great risk. But a growing number of…
Ahead of Equality Festival, U.S. Ambassador to Ukraine Called to Support LGBT Ukrainians
Washington, D.C. – Human Rights First today urged U.S. Ambassador to Ukraine Geoffrey Pyatt to raise concerns with his Ukrainian counterparts over the possible cancellation of…

redpajama_set_name: RedPajamaCommonCrawl


text:
当前期刊: Critical Reviews in Solid State and Materials Sciences Go to current issue 加入关注
Progress in cognition of gas-solid interface reaction for non-oxide ceramics at high temperature
Crit. Rev. Solid State Mater. Sci. (IF 6.455) Pub Date : 2020-01-17
Enhui Wang; Xinmei Hou; Yafeng Chen; Zhi Fang; Junhong Chen; Tongxiang Liang; Kuo-chih Chou; Klaus G. Nickel
With the progress in science and technology, non-oxide ceramics (NOCs) are playing a vital role in various fields at high temperature. However, under harsh service conditions, NOCs tend to be confronted with complicated interface reactions with different media, leading to an acceleration in material failure. Among which, the gas-solid reaction is the most common one accompanied by the highest reaction rate, and the corresponding principles and methods are always applicable to solid-solid and liquid-solid reactions. Therefore, deep understanding of the gas-solid interface reaction behavior is significantly important. Herein, contemporary aspects of gas-solid interface reaction of NOCs are reviewed to show how efficient different approaches are to understand the reaction behavior and mechanism. This review covers theoretical approaches based on kinetic models, experimental approaches using advanced instruments as testing and characterization techniques, and simulative approaches with the help of first-principle calculation and molecular dynamics. Different kinetic models applied to different reaction types are introduced and compared, which have a unique advantage in describing and predicting the gas-solid interface reaction behavior of NOCs. Various techniques are illustrated to show the intuitive observation of changes in microstructure and phase composition at the reaction interface. Based on the above two aspects, the effects of external environment on the gas-solid interface reaction are explained and the significance of interface evolution of NOCs themselves is recognized. To reveal the internal reaction essence, the typical application of recently rising simulative approaches is illustrated to show their potentials in observing the reaction path at the atomic and molecular scale and revealing the reaction mechanism. Finally, some research areas worthy being carried out are pointed out. This review will give a deep understanding of the gas-solid interface reaction and provide scientific designing basis for the performance improvement of NOCs.
Recent progress in bismuth ferrite-based thin films as a promising photovoltaic material
Mohammad Moein Seyfouri; Danyang Wang
Application of ferroelectric oxides in photovoltaic devices has been revived by the emergence of bismuth ferrite thin films, a lead-free perovskite with a narrow bandgap ( ∼2.7 eV) and high remnant polarization (up to 100 µC cm−2). Ferroelectrics are known to exhibit above-bandgap photovoltage and switchable photocurrent. They may also display new functionalities if coupled with ferroic orders. Over the past few years, the research in the field of ferroelectric photovoltaic, mainly BiFeO3, has been thriving toward enhanced photovoltaic performance. The power conversion efficiency of 8.1% has been already achieved and larger values were theoretically predicted. In this context, this article summarizes prominent theories associated with ferroelectric-photovoltaic mechanism and provides the most recent progress in BiFeO3-based thin film devices. Emphasis is placed on design principles toward tailoring the photovoltaic effect via interfacial effect of electrodes and oxygen vacancies, as well as bandgap engineering. Finally, critical survey is accompanied with future perspectives, including integration of BiFeO3-based perovskites to other solar absorbers for highly efficient photovoltaic devices.
A review of the current status of graphitic carbon nitride
Nicholas Rono; Joshua K. Kibet; Bice S. Martincigh; Vincent O. Nyamori
Graphitic carbon nitride (g-C3N4) has become an important material because of its attractive optoelectronic properties. It has been applied in various fields such as photovoltaics, biosensing, and photocatalysis. As an analog of graphene, it has layers which can be transformed into different morphologies including nanosheets, nanotubes, and quantum dots. Pristine g-C3N4 exhibits a low specific surface area and a high rate of recombination of photogenerated charges. Therefore, modification is required in order to improve its properties, for instance, by doping it with other atoms and transforming it into another morphology. In this review, the synthesis, modifications, and applications of g-C3N4 are evaluated. The use of theoretical strategies to understand various properties of g-C3N4 and its composites is highlighted. Moreover, the current status on the application of g-C3N4 is explored. Ultimately, this review will shed more light on the uses and modifications of g-C3N4 for future applications.
A comprehensive assessment of laser welding of biomedical devices and implant materials: recent research, development and applications
M. M. Quazi; M. Ishak; M. A. Fazal; A. Arslan; Saeed Rubaiee; M. H. Aiman; Abdullah Qaban; Farazila Yusof; T. Sultan; M. M. Ali; S. M. Manladan
This review comprehensively covers the research accomplished in the field of laser welding of biomedical devices and implant materials. Laser welding technology in the recent past has been envisaged for numerous biomedical applications encompassing the reconstruction, fabrication, joining and sealing of the implanted biomaterials. It is the most studied and an increasingly applied manufacturing technology that garners the distinct advantages of smaller beam diameters leading to minimal thermal cycles that reduce the size of heat affected zone and instigate microstructural refinement. This paper presents a detailed critical review of similar and dissimilar welding of titanium alloys, cobalt-chromium alloys, steel, bulk metallic glasses and polymer-based biomaterials. Mechanical properties of the welded joints such as fatigue load, tensile and flexural strength, elongation, hardness and modulus of elasticity are discussed. The effect of laser processing parameters on microstructural features and the corresponding metallurgical defects encountered such as cracks, porosities, voids or the loss of alloying elements are reviewed. Furthermore, the corrosion behavior, cytotoxicity and biocompatibility of the welded implants in the simulated mediums are discussed. Furthermore, this article also summarizes the present-day applications associated with implant materials and is aimed at the further involvement of the laser precision technology in producing materials and joints with desired biomechanical characteristics. Lastly, the current research gaps on the role of laser welding of implants and the anticipated emerging fronts are summarized.
Effect of graphene filler structure on electrical, thermal, mechanical, and fire retardant properties of epoxy-graphene nanocomposites - a review
Urszula Szeluga; Sławomira Pusz; Bogumiła Kumanek; Karolina Olszowska; Anastasiia Kobyliukh; Barbara Trzebicka
The use of graphene materials, i.e. graphene oxide, reduced graphene oxide, graphene nanoplatelets and their functionalized forms as fillers of epoxy composites, is reviewed. The purpose of the time- and reagent consuming functionalization methods of graphene materials is justified by the noticeable improvement of dispersity and adhesion of the graphene sheets to the epoxy matrix, which affects the final properties of graphene-epoxy composites. The state-of-the-art of multifunctional graphene-epoxy composites developed over the last years is critically reviewed. The influence of the graphene filler structure and dispersion preparing procedure on the morphology of epoxy-graphene composites and, consequently, their electrical and thermal conductivities, mechanical strength and flame retardant characteristics is considered. An evolution from epoxy-graphite microcomposites to epoxy-graphene nanocomposites is presented, showing the benefits of graphene materials for composites. Some recent works on the epoxy composites reinforced with hybrid graphene fillers and combinations of graphene materials with other fillers are described.
Structural electroactive cermets: dielectric and structural properties of conductive metallic reinforced piezoelectric ceramics
Leandro Bolzoni
More efficient transportation, structural energy storage systems, active sensing, and self-diagnosis are examples where disruptive materials are necessary for driving technological innovation forwards. Unprecedented combinations of properties can be achieved when materials of dissimilar nature and contrasting properties like metals and ceramics are merged. For multimaterial systems, the key challenge is to develop suitable manufacturing processes as to be able to, first, successfully produce the material and, second, to achieve the desired behavior without compromising the integrity of the combined materials. A particular interesting class of material is what are defined in this work as structural electroactive cermets: composite materials constituted by conductive ductile metallic particles dispersed within and used as reinforcement for an insulating dielectric matrix. Specifically, chemically unreactive conductive second-phase reinforcing metallic particles such as Ag or Pt are added to piezoelectric ceramics aiming to enhance their brittle mechanical behavior. As analyzed in the present review, the quest for better mechanical properties results in the enhancement of the dielectric properties in general and of the dielectric constant in particular via the percolation effect for which the percolation theory and other alternative models are discussed. Finally, challenges are identified and potential areas of scientific interest for further developments proposed.
Advances in friction stir spot welding
Zhikang Shen, Yuquan Ding, Adrian P. Gerlich
Friction stir spot welding (FSSW) is a variation of linear Friction Stir Welding (FSW), which was invented to compete with resistance spot welding (RSW) and riveting of lightweight alloys in the automobile, shipbuilding and aerospace industries. Recently, the application of FSSW has rapidly extended to a variety of metals and nonmetals. This article provides a comprehensive review of the recent progress on the process fundamentals, parameters optimization, microstructural evolution and mechanical properties, and relevant simulation and modeling of FSSW. The article also evaluates the energy generation, temperature distribution, plastic flow and joining mechanisms. The optimizations of tool design and welding parameters are obtained through experiments and modeling. Furthermore, a particular emphasis is given to microstructural characterization of the recovery, recrystallization and grain growth, and related annealing phenomena after in the welded alloys. The mechanisms of defect formation and liquidation cracking are discussed in detail. The mechanical properties, including hardness, static strength, fatigue performance and failure mechanisms and the relationship between mechanical properties and microstructures are also addressed along with residual stress and corrosion behavior.
Understanding and Tuning the Electrical Conductivity of Activated Carbon: A State-of-the-Art Review
Adrián Barroso Bogeat
During the last decades, there has been a growing interest and research activity in the use of activated carbon (AC) and related materials as electrodes in electrochemical energy conversion and storage devices, like fuel cells, supercapacitors, and lithium-ion batteries. Among other factors, electrical properties, and especially conductivity, are well-known to play a pivotal role on the performance of ACs in these devices. Furthermore, other novel applications of AC-based materials, such as in electroadsorption, electrocatalysis, sensors and actuators, and so on, also rely heavily on their unique electrical properties. Therefore, the knowledge, understanding, and rationalization of these properties are essential with a view to assessing many of the current and future technological applications of ACs. The present paper critically reviews the available literature, including the latest published reports, on the electrical conductivity of AC. The accurate measurement of this property for ACs is rather difficult and requires the application of low to moderate compression to ensure the electrical contact. Estimated conductivity values are the result of a complex combination between a number of factors, among which the intrinsic conductivity of the single particles, their degree of contact and packing should be highlighted. Intrinsic conductivity is mainly determined by the texture, surface chemistry, and graphitization degree of AC, which strongly depend on the feedstock and the preparation method. Thus, the influence of these factors on the electrical conductivity of the resulting ACs is examined. Moreover, the influence of different adsorbed chemical species, mainly oxygen and water, is also dealt with. On the other hand, special emphasis is paid to the temperature dependence of conductivity, as its analysis is a powerful tool to gain insight into the electronic band structure and electron conduction process in carbon materials. In this regard, the different proposed mechanisms for electrical conduction in AC are exposed and compared.
Rolling Contact Fatigue Behavior of Thermal-Sprayed Coating: A Review
Piao Zhong-Yu, Xu Bin-Shi, Wang Hai-Dou, Yu Xiao-Xiao
Rolling contact fatigue (RCF) of sprayed coating is complicated process relating to materials, structures, loading conditions, etc. Herein, the research works over the past decades in RCF of sprayed coatings are summarized here to provide a guidance to further explore the new research interests. Firstly, comprehensive summaries including the common RCF-resisted coating materials, the regular RCF setups, typical failure modes of sprayed coatings, and statistical characterization methods for RCF lifetime are illustrated. Secondly, the influence of surface integrity on RCF behavior of sprayed coating is discussed. The according mechanisms are also discussed by fracture analysis, numerical calculation, and finite element method (FEM). Thirdly, the influence of working condition on RCF behavior of sprayed coating is discussed. The shear stress is recognized as the major contribution of the RCF fracture, and the sliding during rolling contact will deteriorate the lifetime of sprayed coating. Additionally, some new techniques and methodologies have been reported in the investigations of RCF behaviors of sprayed coatings. Nondestructive testing (NDT) and signal processing methods are critical in the detection of micro-fractures within the sprayed coatings. Finally, we have proposed some suggests in future investigation of RCF of sprayed coating based on the previous research achievements.
An overview on TiFe intermetallic for solid-state hydrogen storage: microstructure, hydrogenation and fabrication processes
G. K. Sujan, Zengxi Pan, Huijun Li, Daniel Liang, Nazmul Alam
Hydrogen has been considered as a potential candidate for the replacement of fossil fuels in future due to its renewability, abundance, ease in production, environmental friendliness and high energy efficiency. In this regard, chemical storage of hydrogen in solid state of metal hydrides is the safest method for stationary and portable applications since these can be functioned at lower pressure and ambient temperature. Among the desirable metal hydrides, the intermetallic compound TiFe of cubic CsCl-type structure is well known for absorbing hydrogen reversibly up to 1.9 wt.% to form β-FeTiH and γ-FeTiH2 phases. In this paper, we have discussed the historic background outlining the recent developments on the microstructural modifications, activation kinetics and processing routes of TiFe intermetallic alloys toward the improvement of hydrogenation properties. An in-depth microstructural analysis of TiFe alloys has been presented in terms of crystallography, hydride phase formation and hydrogenation mechanisms. The rate-controlling steps for the mechanisms of (de)hydrogenation processes of TiFe intermetallics have been explained in details. It was found that the rate-controlling steps of the hydriding reaction were dependent on the fraction of β-hydride phase. Intensive research activities were carried out to improve the first hydrogenation kinetics that can be categorized into two groups: alloying and mechanical activation. The mechanisms for improved hydrogenation kinetics in both cases have been explained. Lastly, various fabrication processes to produce TiFe alloys have been presented and correlated with cost-effectiveness and hydrogen-storage capability. Therefore, the focus of this article is to present the basic knowledge and recent developments on TiFe intermetallic alloys for future hydrogen-storage applications which will be beneficial to researchers and practitioners in the field of interest.
Aluminum Matrix Composites Reinforced with Graphene: A Review on Production, Microstructure, and Properties
Nima Seyed Pourmand, Hamed Asgharzadeh
Graphene, a single-atom-thick sheet of sp2 hybridized carbon atoms densely packed within a hexagonal crystal lattice, owes a significant portion of its rapidly expanding usage in various fields of industry and science to its large surface area, lightweight, unique electronic and thermal properties, and extraordinary mechanical properties that it possesses. Using lightweight and high-strength materials leads to a substantial decrease in fuel consumption as well as an increase in payload. Among the numerous candidates to fulfill the aforementioned requirements, Al alloys and specifically, Al matrix composites (AMCs) reinforced with various graphene particles (nano-sheets, nano-platelets, etc.) stand out owing to their inherent lightweight, high specific strength and modulus, superior ductility and excellent thermal conductivity. In this paper, it has been endeavored to provide a comprehensive overview of the various methods of the synthesis and fabrication of graphene-reinforced AMCs with an overall intention of achieving a homogeneous distribution of graphene within the Al matrix. The emphasis of this review has been largely placed upon the detailed examination of the mechanical properties of these composites described in the recent literature published in this field. The strengthening mechanisms of Al/graphene composites, as well as the parameters affecting the strength and ductility achieved by graphene, such as the agglomeration of graphene within the Al matrix and Al/graphene interfacial reactions, have been elucidated. The role of graphene on the electrical and thermal properties of graphene-reinforced AMCs and the directions for future research are addressed. It should be noted, however, that while a diligent analysis of various works published in the field of Al/graphene composites has been carried out in this review, an exact comparison between the varying stages of each work, or their final properties is impractical, mainly due to the differences in the used initial substances, processing, and analyses.
1,3,5-Triazine-Based Liquid Crystals: An Up-to-Date Appraisal of Their Synthetic Design and Mesogenic Properties
Poornima Bhagavath, Rajatha Shetty, Dhanya Sunil
Nature constructs captivating stable structures and assemblies using the principles of order and flexibility. A lot of literature evidence focuses on the design of mesogenic soft materials with a 1,3,5-triazine core due to its appealing structure and properties. Progress in the field of triazine-based liquid crystal molecules with emphasis on their synthesis and mesomorphic features is presented in this review. The prospects that could orient researchers to stimulate further efforts in this area are also presented.
A Review of the Graphene Synthesis Routes and its Applications in Electrochemical Energy Storage
Elochukwu Stephen Agudosi, Ezzat Chan Abdullah, Arshid Numan, Nabisab Mujawar Mubarak, Mohammad Khalid, Nurizan Omar
Graphene – a carbon nanomaterial has gained huge research interest due to its intriguing and extraordinary properties such as large surface area, excellent electrical conductivity, ultra-thinness, high electron mobility, and superior mechanical strength. The combination of graphene with other inorganic nanoparticles can significantly boost its physiochemical properties and hence, opens up new frontiers of its utilization. Grapheneis significantly exploited for the energy storage systems due to its great potential for electrochemical energy storage . However, the experimental electrochemical performance of graphene is still far away from the theoretical facts. This study critically evaluated the existing synthesis routes for the production of graphene, graphene-based composites and their utilization in the energy storage applications. Furthermore, the techno-economic analysis of the synthesis methods was undertaken to determine the best routes in terms of sustainability for commercial graphene production. Lastly, the fundamental understanding of graphene growth mechanisms and the overall intricacies of the synthesis processes were highlighted and the possible way forward is proposed. Therefore, in the quest for the development of effective alternative yet sustainable energy storage devices; it is hoped that this research will give useful insights to researchers and key players in the electronics industry.
Organic solar cells: Materials and prospects of graphene for active and interfacial layers
Tabitha A. Amollo, Genene T. Mola, Vincent O. Nyamori
Photovoltaics is a portentous alternative to the nonrenewable energy resources. Organic solar cells (OSCs) offer several advantages over inorganic counterparts in terms of low-cost device production, simple solution-based processing, flexibility, light-weight and compatibility with roll-to-roll fabrication. This review comprehensively examines the latest research developments towards high-performance OSCs. Device processing conditions and engineering along with material developments for the active and interfacial layers are examined. Different device structures and their benefits and limitations are highlighted. The interfacial layer materials including the polymers and metal oxides together with their integration and performance in functional OSCs are examined. A salient aspect of this review is the design of donor and acceptor materials to address the optical and electronic properties requirement for optimized device efficacy of OSCs. In this regard, the prospects of tailoring the band gap of donor polymers alongside the adoption of non-fullerene acceptors with complementary optical absorption for improved solar energy harvesting is elucidated. Further, graphene's feasibility as an active or interfacial layer material is reviewed. Hence, this article provides perspectives and strategies on further development of solution-processable donor, acceptor and interfacial materials for high efficiency devices, required in commercialization of OSCs.
Integrated Sensors in Advanced Composites: A Critical Review
Hossein Montazerian, Armin Rashidi, Abbas S. Milani, Mina Hoorfar
Piezoelectric, piezoresistive, and optical fiber sensors have attracted considerable attention in structural health monitoring (SHM) applications for strain/temperature measurements in advanced material structures such as composites. Issues pertaining to the fabrication process and integration of these sensors, however, continue to limit their efficiency in detecting SHM parameters in sensitive applications such as aerospace and medical devices, where accuracy and reliability are prime concerns. This paper provides a critical review of recent developments on sensing materials and their integration methods into composites. For piezoelectric sensors, ferroelectric and piezoelectric characteristics of different material compositions are described and the evolution of ferroelectric properties over a range of temperatures and mechanical loadings is addressed. Fabrication processes and characterization of silicon- and carbon-based piezoresistive materials are presented to assess the electromechanical performance of such sensors. Furthermore, the methods developed for concurrent measurement of strain and temperature using optical fiber sensors are reviewed. The implantation of different sensing mechanisms for detecting physical parameters during and after composite manufacturing processes is described. Since composite delamination due to the embedded sensors is a reoccurring issue, mechanical compatibility of different reported sensors with the base material interface is highlighted. Finally, potential future directions of the reviewed sensing mechanisms are outlined.
A review on thermo-mechanical properties of bi-crystalline and polycrystalline 2D nanomaterials
Bharat Bhushan Sharma, Avinash Parashar
Due to outstanding properties, graphene and h-BN nanosheets are emerging as a potential candidate for wide spectrum of applications in the field of engineering and bio-medical science. Graphene and h-BN nanosheets have comparable mechanical and thermal properties, whereas due to high band gap h-BN (∼5eV) have contrasting electrical conductivities. Large size graphene and h-BN nanosheets are synthesized by chemical vapor deposition technique, which results in polycrystalline atomic structure. These polycrystalline nanosheets are characterized either by experimental means or numerical simulations. Experimental techniques are considered as most accurate and practical, but cost and time involved in these techniques limits it application at the nanoscale level. On the other hand, atomistic modeling techniques are emerging as viable alternatives to the experimentations, and are accurate enough to predict the mechanical properties, fracture toughness, and thermal conductivities of polycrystalline graphene and h-BN nanosheets. This comprehensive review article encompasses different characterizing techniques used by the researchers for polycrystalline nanosheets. This review will help in elaborating the properties of polycrystalline graphene and h-BN, and also establishing a perspective on how the microstructure impacts its large-scale physical properties.
Unveiling Corrosion Behavior of Pipeline Steels in CO2-Containing Oilfield Produced Water: Towards Combating the Corrosion Curse
Peter Adeniyi Alaba, Sunday Adeshina Adedigba, Sunday Felix Olupinla, Oluranti Agboola, Samuel E. Sanni
The presence of carbon dioxide (CO2) in oilfield produced water, which could be natural or intentionally injected component in oil and gas production, is extremely corrosive to pipelines and tubings. Oilfield produced water is mainly brine solution comprising organic acids, purely condensed water as well as aggressive ions like SO42−, Cl− and dissolved acid gases (like CO2). CO2 induced corrosion in this media is more detrimental than corrosion induced by HCl. This study critically unveiled the CO2 corrosion behavior of steel in oilfield produced water. The subjects covered include the chemistry of CO2 in water, supercritical CO2 condition, computational fluid dynamics (CFD) and corrosion control. Corrosion resistant alloy has been proved to exhibit remarkable corrosion resistance due to formation of strong protective film that can prevent localized corrosion. Moreover, the use of viable surface-active compounds, which are constituents of crude oil is a promising strategy for pipeline steel corrosion mitigation.
Electrical properties of liquid-phase sintered silicon carbide ceramics: a review
Young-Wook Kim, Yong-Hyeon Kim, Kwang Joo Kim
Silicon carbide (SiC) is an electrical semiconductor with a wide bandgap. Recently, highly conductive liquid-phase sintered SiC (LPS-SiC) ceramics have been developed by the successful doping of N atoms into a SiC lattice. Fully dense N-doped SiC ceramics with electrical conductivity as high as 300 S·cm−1 at 25 °C have been obtained. These ceramics can be formed into complex shapes by electrical discharge machining. This article reviews the influence of critical factors on the electrical conductivity of LPS-SiC ceramics, including SiC polytype, grain boundary structure, soluble atoms, porosity, second-phase addition (nitride, carbide, boride, graphene), grain size, and neutron irradiation. We also discuss the relationship between the solubility of nitrogen in the liquid phase and the electrical conductivity of the resulting ceramics, along with the mechanism for N doping in the SiC lattice and the possibility of controlling the electrical conductivity of the LPS-SiC ceramics. The N doping method used for LPS-SiC ceramics may also be applied for doping other soluble atoms in liquid-phase sintered ceramics.
A review on high stiffness aluminum-based composites and bimetallics
Sajjad Amirkhanlou, Shouxun Ji
The Young's modulus of aluminum-based materials is one of the most important mechanical properties in controlling structural performance. The improvement of the Young's modulus of castable aluminum-based materials is essential for improving their competiveness in light weighting structural applications. Currently, there are limited options for cast aluminum alloys with outstanding Young's modulus. Also, for further stiffness improvement and thereby weight lightening, in-depth understanding of the relevant mechanisms for modulus improvement in aluminum alloys is necessary. This review focuses on the Young's modulus of cast aluminum-based composites, as well as aluminum alloys reinforced with continuous metallic fibers (bimetallic materials). The effect of different chemical elements in cast alloys, the constituents of in-situ and ex-situ formed aluminum matrix composites, and the wire-enhanced bimetallic materials on the Young's modulus of aluminum-based materials are reviewed. The Young's modulus of cast aluminum alloys can be improved by: (a) introducing high modulus reinforcement phases – such as TiB2, SiC, B4C, and Al2O3 – into aluminum by in-situ reactions or by ex-situ additions; and (b) forming bimetallic materials with metallic wire/bar reinforcement in the aluminum matrix. The performance of a stiff aluminum alloy depends on the volume fraction, size, and distribution of the high modulus phases as well as the interface between reinforcement and Al matrix. One of the major concerns is the reduction of the ductility of castings after adding specific high modulus phases to increase the Young's modulus. Further research into the improvement of Young's modulus and the ductility of aluminum alloys is necessary through proper selection of reinforcement, optimizing interface, and distribution of reinforcement.
Physicomechanical Properties of Porous Materials by Spark Plasma Sintering
Abolfazl Azarniya, Amir Azarniya, Mir Saman Safavi, Mohammad Farshbaf Ahmadipour, Melica Esmaeeli Seraji, Saeed Sovizi, Mahboobe Saqaei, Ridvan Yamanoglu, Mohammad Soltaninejad, Hamid Reza Madaah Hosseini, Seeram Ramakrishna, Akira Kawasaki, Stefan Adams, M. V. Reddy
Metallic or ceramic micro/nanoporous materials have attracted particular attention due to some interesting structural and functional properties. There exist a variety of methods for producing porous materials by which optimized features can be reached. Spark plasma sintering (SPS) is one of these new-emerging approaches. This technique is often combined with conventional technologies and produce a variety of porous structures with tailorable microstructure and physicomechanical properties. This review addresses SPS and obtainable porous materials with nanoscale and microscale microstructural features. The processing methods, microstructural phenomena, and physicomechanical properties of these materials are discussed in some details, along with the likely future directions required for this novel field.
Mixed Halide Perovskite Solar Cells: Progress and Challenges
Mohammed S. G. Hamed, Genene Tessema Mola
Single and mixed-halide perovskite solar cells (PSCs) have attracted a lot of research attention in recent years due to their solution process-ability, lightweight and excellent photoelectric conversion which are the necessary conditions for low-cost thin-film solar cell technology. The power conversion efficiency (PCE) of solid-state PSCs has risen quickly to a certified value as high as 22%. There is still tremendous potential for the realization of highly efficient solution processable perovskite-based solar cell. The perovskite produced by way of mixing halogen elements, such as CH3NH3PbI3–xClx and CH3NH3PbI3–xBrx, offered several benefits such as enhanced device stability, improved carrier transport and reduced carrier recombination. Single crystal perovskite film containing organic and inorganic cation reported to have broad optical absorption which covers significant part of the solar spectrum. It also exhibited good thermal stability compared to single halide such as CH3NH3PbI3. The device configuration of PSCs and the choice of suitable hole/electron transport materials played a significant role in the device performances. This review article reports on the recent advances of solution processed PSC with emphasis on the role played by mixed halide elements on the performance of devices. Abbreviations A-Si Amorphous silicon CdTe Cadmium telluride QDs Quantum dots 3D Three-dimensional 3SSC Three step sequential coating ALD Atomic layer deposition BCP Bathocuproine CB Conduction band CIGS Copper indium gallium selenide Cs+ Cesium DMF N, N-dimethylformamide DMSO Dimethyl sulfoxide DSSCs Dye-sensitized solar cells EQE External quantum efficiency ETLs Electron-transporting layers FA Formamidinium FTO Fluorine doped tin oxide GSC Gas–solid crystallization HOMO Highest occupied molecular orbital HTM Hole-transporting materials IPA Isopropyl alcohol ITO Indium tin oxide LiTFSi lithium bis(trifluoromethanesulfonyl)imide LUMO Lowest unoccupied molecular orbital MA Methylammonium MASP Meniscus-assisted solution printin OLED Organic light-emitting diodes OPVs Organic photovoltaics OSSD One-step sequential deposition Pb Lead PCE Power conversion efficiency PV Photovoltaic Rb+ Rubidium SD Sequential deposition SDP Sequential deposition process SET Solvent engineering technique SSPVD Single source physical vapor deposition SVD Sequential vapor deposition t Tolerance factor TBP tert-butylpyridine TSSD Two-step sequential deposition Voc Open circuit voltage VASP Vapor-assisted solution process VB valence band
Process–Structure–Properties in Polymer Additive Manufacturing via Material Extrusion: A Review
G. D. Goh, Y. L. Yap, H. K. J. Tan, S. L. Sing, G. L. Goh, W. Y. Yeong
This article provides a database of the mechanical properties of additively manufactured polymeric materials fabricated using material extrusion (e.g., fused filament fabrication (FFF)). Mechanical properties available in the literatures are consolidated in table form for different polymeric materials for FFF. Mechanical properties such as tensile, compressive, flexural, interlayer, fatigue, and creep properties are discussed in detail. The effects of printing parameters such as raster angle, infill, and specimen orientation on properties are also provided, together with a discussion of the possible causes (e.g., texture, microstructure changes, and defects) of anisotropy in properties. In addition to that, research gaps are identified which warrant further investigation.
Casting lightweight stiff aluminum alloys: a review
Lightweight casting aluminum structural components, in particular shaped castings, are usually designed on the criteria of either yield strength or stiffness (Young's modulus). Currently, there are limited options for the aluminum alloys with outstanding Young's modulus. Following our review on the stiffness of aluminum-based composites and bimetallics, this review focuses on the effect of different chemical elements on the Young's modulus of cast aluminum alloys and their microstructures. The influence of alloying elements on the Young's modulus depends on the state. If the alloying elements are in a solid solution phase, the magnitude of the Young's modulus is determined by the nature of the atomic interactions. If the alloying elements form second phases, the magnitude of the Young's modulus is determined by the volume fraction and the intrinsic modulus of the second phase. Among the available elements, Be, Li, Si, Mn, and Ni are favorite candidates to enhance the modulus of cast aluminum alloys. The increase of Young's modulus in commercial cast aluminum alloys can be significantly improved through adding appropriate alloying elements. Therefore, further research into the improvement of Young's modulus of aluminum alloys is necessary.
Recent Development in Friction Stir Processing as a Solid-State Grain Refinement Technique: Microstructural Evolution and Property Enhancement
Vivek Patel, Wenya Li, Achilles Vairis, Vishvesh Badheka
Increasing demand of lightweight structures with exceptional properties elicits materials processing and manufacturing technologies to tailor blanks in order to achieve or enhance those prerequisite properties. Friction stir processing (FSP) is a solid-state material processing technique, which was derived from friction stir welding (FSW). Initially, FSP was invented to refine the microstructure in way that superplasticity in a material can be achieved. Afterward, FSP has gained much more attraction as a solid-state grain refinement technique to improve the mechanical, tribological, and corrosion properties in a wide range of low strength non-ferrous and high strength steels. FSP is well capable to produce material with microstructure in range of few micron to nanoscale, depending on the processing conditions. Researchers have investigated FSP at different process parameters such as tool rotation and travel speeds, number of passes, and additional cooling in order to evaluate the impact on the resulting properties for different alloys. Recently, FSP has begun to modify the microstructure and properties in hard alloys and superalloys with some modifications in FSP tooling system. Furthermore, FSP has shown great potential to repair or modify the weld or coating structure by microstructure refinement. Therefore, the present review will discuss the state-of-the-art of FSP under the main categories of microstructure evolution, and effect of process parameters. This review also provides a comprehensive summary of research progress on FSP in different materials i.e. aluminum, magnesium, copper, and steels with the contents much emphasized on the microstructure refinement in terms of average grain size and resulting properties like hardness, tensile, wear, and corrosion. Finally, FSP as a new post-processing approach in weld or coating structure has been discussed.
Effects of Different Mechanical Surface Enhancement Techniques on Surface Integrity and Fatigue Properties of Ti-6Al-4V: A Review
Zi-Meng Wang, Yun-Fei Jia, Xian-Cheng Zhang, Yao Fu, Cheng-Cheng Zhang, Shan-Tung Tu
Titanium and its alloys are widely used in aerospace, biomedicine, chemical industries, and other fields due to the excellent properties as high specific strength, strong corrosion resistance, and superior biocompatibility. With the development of mechanical industry, especially of aerospace, the higher fatigue performance of titanium alloys is demanded. Generally, fatigue cracking originates from the materials surface, so the surface roughness, residual stress, and microstructure in surface layer are believed to be the dominant factors in affecting the fatigue crack initiation and propagation, as well as the fatigue strength. Thus, by means of the mechanical surface enhancement techniques, the achievement of reducing the surface roughness, introducing the residual compressive stress, improving the surface microstructure and increasing the surface hardness could significantly enhance the fatigue strength. The effects of various mechanical surface treatments, such as deep rolling, shot peening, and laser shock peening, on surface integrity and fatigue properties of Ti-6Al-4V were reviewed in this article. By comparing surface roughness, hardness, residual stress, surface grain size, depth of grain refinement layer, fatigue properties at room and high temperatures, and residual stress relaxation during fatigue of different surface-treated Ti-6Al-4V, the advantages and the limitations of these surface treatments were identified and evaluated.
Recent Progress in Lithium Lanthanum Titanate Electrolyte towards All Solid-State Lithium Ion Secondary Battery
Yuandong Sun, Peiyuan Guan, Yunjian Liu, Haolan Xu, Sean Li, Dewei Chu
Lithium lanthanum titanate (LLTO) is one of the most promising solid electrolytes for next generation batteries owing to its high ionic conductivity of ∼1 × 10 − 3 S/cm at room temperature. To comprehensively understand the microstructure and ion diffusion mechanism of LLTO, recent research in diffraction and spectroscopy techniques as well as computational study have been reviewed in this paper. The extremely low ionic conductivity at grain boundary as well as the increased electronic conductivity related to the direct contact with metallic lithium has impeded the practical application of LLTO for the solid-state batteries. Various studies including substitution, the introduction of grain boundary layer modifier, high temperature sintering, and synthesis of amorphous LLTO have been applied to solve these major challenges and their effectiveness are discussed in this review. Moreover, different types of synthesis methodologies of LLTO thin films are reviewed and compared in detail. In the end, the recent reports of solid-state battery system are reviewed and discussed.
Towards Al3+ Mobility in Crystalline Solids: Critical Review and Analysis
Tina Nestler, Stanislav Fedotov, Tilmann Leisegang, Dirk C. Meyer
Finding inorganic materials with significant Al ion mobility could push the development of alternative rechargeable batteries, as they could potentially serve as solid electrolytes or intercalation cathodes. While for single‐ and double‐charged ions numerous solid electrolytes are known, the situation is rather unclear and only sparingly researched for ions with a charge higher than two. To assist in the systematic analysis, compounds described in literature as solid electrolytes or intercalation materials for Al3+, as well as some materials generally known for high mobilities for multivalent ions, are critically reviewed and analyzed by the bond‐valence energy landscape approach. For this purpose a thorough list of investigated cathode materials for rechargeable Al batteries is provided first. While it is demonstrated that solid electrolytes for Al3+ cannot be unequivocally identified in literature yet, the analysis of the intercalation cathodes reveals promising structural motifs for comparatively fast Al diffusion, which can be used for the analysis, comparison and design of new promising materials. Furthermore, chances and limits of the bond‐valence energy analysis for high‐valent battery materials are exemplarily shown. Thus, this work aims at encouraging more theoretical and experimental work on Al battery materials and provides guidelines for doing so.
Continuous Differential Speed Rolling for Grain Refinement of Metals: Processing, Microstructure, and Properties
Kotiba Hamad, Young Gun Ko
In recent years, considerable research has been devoted to the development of ultrafine-grained (UFG) structural metals fabricated by various severe plastic deformation (SPD) techniques. Among these techniques, differential speed rolling (DSR) has been considered as the continuous forming method in which bulk sheet materials pass through two identical rolls with different speeds of the rolls, effectively imposing intense plastic strain based on shear deformation. This review describes the principles of the DSR process, including the strain imposed by DSR, processing routes, and macro-shear characteristics associated with the processing routes; it also outlines the processing factors that affect grain refinement, such as total thickness reduction, thickness reduction per pass, rolling speed, roll speed ratio, number of operations, and rolling temperature. The essential features of the resultant microstructural variables, including the grain size and morphology, grain boundaries, deformation textures, and dislocation density developed in materials with HCP, FCC, and BCC crystals deformed by the DSR process are also summarized. In addition, the structural properties of metals subjected to DSR are reviewed, including strength, hardness, and ductility at room and elevated temperatures.
A Review on Graphene-Based Electrospun Conductive Nanofibers, Supercapacitors, Anodes, and Cathodes for Lithium-Ion Batteries
Kashif Javed, Marco Oolo, Natalja Savest, Andres Krumme
Electrospinning has recognized as the most versatile and adaptable method for the fabrication of nanofibers. Fiber scientists have extensively introduced original solutions for harvesting and storing energy from nanofibers in order to improve storage capacity and environmental impact of electrospun supercapacitors, anodes, and cathodes. Among these efforts, graphene gained significant interests for researchers, a multifaceted molecule possessing many unique and desirable properties such as high strength, flexibility, optical transparency, and conductivity. This makes graphene as superior as to many other nanomaterials like carbon nanotubes (CNTs) and conductive nanometallic particles. The reported properties and applications of this two-dimensional (2D) structure have opened up new opportunities for the lightweight future devices and systems. This review article aims to present an overview of the advancements in graphene-based electrospun conductive nanofibers, supercapacitors, and graphene-based electrospun anodes and cathodes for lithium-ion (Li-ion) batteries. Details of the electrospinning processes, reduction methods, and electrical properties are discussed to yield insights on how significant improvements can be made in future developments.
On the Ultra-Precision Fabrication of Damage-Free Optical KDP Components: Mechanisms and Problems
Ning Hou, Liangchi Zhang, Yong Zhang, Feihu Zhang
Potassium dihydrogen phosphate (KDP) crystals have excellent optical properties such as high nonlinear conversion efficiency, superior photoelectric and piezoelectric properties, transparency in a wide range of optical spectra, and good optical homogeneity. Therefore, KDP crystals have been used in many advanced fields, such as in the laser ignition facilities as large aperture crystals for optical switching and frequency conversion. However, extensive trials in the past decades showed that a KDP crystal is an extremely difficult-to-handle material for its high sensitivity to external stresses and environmental conditions, such as contact stresses, temperature variation and moisture invasion. It is also a soft material yet easy to fracture. A critical challenge is that it is unclear about the underlying physics of the damages which have been frequently observed after the ultra-precision surfacing of an optical KDP lens. As a result, when it is used in a Pockels photoelectric switch in a high-density laser system, for instance, its optical performance (e.g., its laser-induced damage threshold) is unexpectedly low. These have hindered significantly the development of high performance laser systems. This paper aims to provide a comprehensive review on the critical integrity issues of KDP components and their characterization methods, from the points of view of microstructure, micro/nano-mechanics, deformation mechanisms and laser-induced damage associated with the most commonly used surfacing technology––ultra-precision machining.
A Review on Recent Progress in Solid State Friction Based Metal Additive Manufacturing: Friction Stir Additive Techniques
Manu Srivastava, Sandeep Rathee, Sachin Maheshwari, Arshad Noor Siddiquee, T. K. Kundra
Friction stir additive techniques (FSATs) constitute innovative approaches aimed at utilizing layer by layer additive manufacturing (AM) principle with solid state friction stir welding (FSW) technique. These constitute a special class of friction based additive techniques (FATs) and can be easily thought of as major breakthrough of metal additive manufacturing (MAM) domain. Ability of MAM techniques to be used for fabricating intricate parts has led them to be considered as a lucrative option for aviation, automotive, and marine sectors. However, fusion based MAM techniques have manifold limitations mainly owing to solidification related as well as poor shear strength issues. FATs overcome drawbacks of fusion based MAM methods chiefly because of their solid-state nature. FATs fabricate defect free components possessing superior structural and mechanical characteristics. Basic principles of additive manufacturing and FSW necessary for highlighting need and concept of FATs are introduced first. All FATs with their basic principles and specific merits are then presented. Special emphasis is given to two most effective FATs based upon FSW, i.e., FSATs which are friction stir additive manufacturing and additive friction stir (AFS). Aim of this work is to present a critical review of timeline and recent developments in the field of FSATs. In addition, challenges and future trends of these innovative techniques are highlighted followed by detailed discussion.
Review of the wettability of solder with a wetting balance test for recent advanced microelectronic packaging
Do-Hyun Jung, Jae-Pil Jung
This paper reviewed the wetting properties of solder for microelectronic packaging. The recent demand for high-density packaging has highlighted the need for a sophisticated and improved solder for the miniaturization of electronics. The wetting properties of molten solder on a substrate, which provides successful soldering and reliable solder joints, is one of the most critical properties for the reliability of components in electronic devices because poor wetting can degrade the reliability of the solder. Therefore, the solder must have good wettability to achieve better solderability. The most common testing method is the wetting balance test known as a Meniscograph. During a wetting test, the analysis can be conducted by calculating the wetting force between the molten solder and substrate as a function of time. In addition, the surface tension and wetting time, which are known as the zero cross time of each sample, are obtained from the respective wetting curves. This paper discusses the wetting balance test, including its principle, parameters, experimental procedure, and analysis of the result from the wetting curve. In addition, this paper introduces the recent advances in the wetting property of solder, such as a nano-reinforced composite solder through the addition of 0.05% of nano-sized La2O3 to the solder matrix, which has resulting in an improved wetting time.
Photocatalytic Nanoheterostructures and Chemically Bonded Junctions Made by Solution-Based Approaches
Andris Šutka, Martin Järvekülg, Kārlis A. Gross
While single compound semiconductors were initially used for photocatalysis, combining two compounds to form a heterojunction significantly increases the photocatalysis performance. This review will outline how heterojunctions are superior, explain the different heterostructure architectures assembled from nanoparticles, and discuss the importance of achieving a large and quality contact in the junction, the heterojunction. Reference is made to methods for increasing the charge carrier performance and reducing recombination. Solution-based synthesis approaches, have been selected as the preferred route of manufacture, for the low cost scalability, and ability to combine a larger number of compounds. The main objective of this review article is to provide insight to the range of chemical solution-based methods for forming chemically bonded junction in nanoheterostructures for photocatalysis. Methods include chemical precipitation, impregnation, chemical bath deposition, hot injection, solvothermal, photo-deposition, electrochemical deposition, cation exchange and linker assisted assembly. The synthesis of different photocatalysts is addressed for each synthesis method. Solution synthesis is offered for coupling oxide semiconductors (i.e. TiO2, ZnO, WO3, Fe2O3, BiVO4) with other oxides or metal chalcogenide quantum dots or metallic plasmonic nanoparticles.
Development and Application of WC-Based Alloys Bonded with Alternative Binder Phase
Jialin Sun, Jun Zhao, Feng Gong, Xiuying Ni, Zuoli Li
WC–Co alloys have enjoyed great practical significance owing to their excellent properties during the past decades. Despite the advantages, however, recently there have been concerns about the challenges associated with the use of Co, i.e. price instability (the major incentive for alternative binder development), toxicity and properties degeneration. Thus, the current study applies towards summarize the current knowledge of the impacts of different binders partial or total substitution of the traditional cobalt binder highlighting the influences of metal, intermetallic compound, ceramics (metal oxide) binders on the sintering behavior as well as mechanical properties of WC-based alloys, so as to provide reference for those who would like to enhance the performance of cemented carbides with better reliability advancing them to further wide applications and prepare the alloys in a way that is environment friendly, harmless to human health and low in production cost. It is concluded that the alternative for cobalt in tungsten carbide cemented carbide is economically and technically feasible. Strict control of the chemical composition of the binder coupled with taking into careful account the effects of sintering process and subsequent treatments is of great importance to improve the sintering behavior and tailor mechanical properties of tungsten carbide-based hardmetals.
Transfer-Free Graphene Growth on Dielectric Substrates: A Review of the Growth Mechanism
Gurjinder Kaur, K. Kavitha, Indranil Lahiri
Ever since the more-than-decade-old discovery of application of mechanical exfoliation to obtain graphene, this 2-dimensional material was known for its soaring promise in various applications, owing to its excellent properties. Graphene, most popularly grown on metallic substrates by chemical vapour deposition, needs to be transferred onto dielectric substrates for multiple optical and electronic applications. During such complex and expensive transfer steps, defects are introduced into graphene, which deteriorates the quality and thus, properties of graphene. An alternative approach to surmount these problems is the elimination of the transfer process and to directly grow graphene on dielectric substrates, for future electronic and optical applications. This review presents a comprehensive and an up-to-date account of the development of synthesis methods, challenges and future directions for transfer-free graphene growth on dielectric substrates. Special emphasis is given on the fundamentals of growth mechanisms of various transfer-free graphene synthesis processes on dielectric materials.
The metal-insulator transition in disordered solids: How theoretical prejudices influence its characterization A critical review of analyses of experimental data
Arnulf Möbius
In a recent experimental study, Siegrist et al. [Nature Materials 10, 202–208 (2011)] investigated the metal-insulator transition (MIT) induced by annealing in GeSb2Te4. The authors concluded that this phase-change material exhibits a discontinuous MIT with finite minimum metallic conductivity. The striking contrast between their work and reports on many other disordered substances from the last decades motivates the present in-depth study of the influence of the MIT criterion used on the character of the MIT derived.
A Review of Advanced Composite and Nanostructured Coatings by Solid-State Cold Spraying Process
Wenya Li, Hamid Assadi, Frank Gaertner, Shuo Yin
Cold spraying (CS) has been widely explored over the last decade due to its low process temperature and limited thermal effect on spray materials. As a solid-state process, the inherent deficiencies of traditional thermal spraying such as oxidation, decomposition, and grain growth are avoided. This article summarizes the research work on the fabrication of composites and nanostructured coatings by the promising CS process. After a brief introduction to CS and its deposition mechanisms, the preparation methods of spray powders are classified. Different methods are appropriate for particles of various properties, and the tendency is to design composite powders by combined methods in order to create coatings with specified properties. Then, the co-deposition mechanism of composite particles as well as research findings on metal–metal, metal–ceramic, and metal–intermetallic composite coatings are reviewed concerning the deposition characteristics, microstructure and its relation to properties. Moreover, CS has been used to deposit a variety of nanostructured materials, including metals, metal–ceramic composites, and even ceramics, retaining their nanocrystalline nature in the coating without grain growth or phase transformation. Finally, the potential applications of CS and issues to be addressed in coating deposition are discussed.
Density Functional Theory Study of Mn+1AXn Phases: A Review
Yuelei Bai, Narasimalu Srikanth, Chee Kai Chua, Kun Zhou
Mn+1AXn phases (MAX phases for short with M: transition metal, A: A group elements, X: C or N, and n = 1–3) have attracted considerable attention due to the unique combination of the ceramic- and metal-like properties. The density functional theory (DFT) has emerged as a powerful theoretical approach that complements experimental testing and serves as a predictive tool in the identification and characterization of MAX phases. After the beginning with a brief introduction of the MAX phase and DFT, we review the DFT study on this class of materials, including crystal structure, electronic structure, point defects, lattice dynamics, and related properties, phase stability, compressibility, and elastic properties. Comparison between the theoretical values and available experimental ones shows that they are in decent agreement for most part, especially in the lattice constants, elastic properties, and compressibility. This article is concluded with an outlook of future research on DFT study of MAX phases, major challenges to be met and possible solutions in some cases.
Single and mixed-halide perovskite solar cells (PSCs) have attracted a lot of research attention in recent years due to their solution process-ability, lightweight and excellent photoelectric conversion which are the necessary conditions for low-cost thin-film solar cell technology. The power conversion efficiency (PCE) of solid-state PSCs has risen quickly to a certified value as high as 22%. There is still tremendous potential for the realization of highly efficient solution processable perovskite-based solar cell. The perovskite produced by way of mixing halogen elements, such as CH3NH3PbI3–xClx and CH3NH3PbI3–xBrx, offered several benefits such as enhanced device stability, improved carrier transport and reduced carrier recombination. Single crystal perovskite film containing organic and inorganic cation reported to have broad optical absorption which covers significant part of the solar spectrum. It also exhibited good thermal stability compared to single halide such as CH3NH3PbI3. The device configuration of PSCs and the choice of suitable hole/electron transport materials played a significant role in the device performances. This review article reports on the recent advances of solution processed PSC with emphasis on the role played by mixed halide elements on the performance of devices.
Recent Developments of Crystallographic Analysis Methods in the Scanning Electron Microscope for Applications in Metallurgy
Rafael Borrajo-Pelaez, Peter Hedström
The field of metallurgy has greatly benefited from the development of electron microscopy over the last two decades. Scanning electron microscopy (SEM) has become a powerful tool for the investigation of nano- and microstructures. This article reviews the complete set of tools for crystallographic analysis in the SEM, i.e., electron backscatter diffraction (EBSD), transmission Kikuchi diffraction (TKD), and electron channeling contrast imaging (ECCI). We describe recent relevant developments in electron microscopy, and discuss the state-of-the-art of the techniques and their use for analyses in metallurgy. EBSD orientation measurements provide better angular resolution than spot diffraction in TEM but slightly lower than Kikuchi diffraction in TEM, however, its statistical significance is superior to TEM techniques. Although spatial resolution is slightly lower than in TEM/STEM techniques, EBSD is often a preferred tool for quantitative phase characterization in bulk metals. Moreover, EBSD enables the measurement of lattice strain/rotation at the sub-micron scale, and dislocation density. TKD enables the transmitted electron diffraction analysis of thin-foil specimens. The small interaction volume between the sample and the electron beam enhances considerably the spatial resolution as compared to EBSD, allowing the characterization of ultra-fine-grained metals in the SEM. ECCI is a useful technique to image near-surface lattice defects without the necessity to expose two free surfaces as in TEM. Its relevant contributions to metallography include deformation characterization of metals, including defect visualization, and dislocation density measurements. EBSD and ECCI are mature techniques, still undergoing a continuous expansion in research and industry. Upcoming technical developments in electron sources and optics, as well as detector instrumentation and software, will likely push the border of performance in terms of spatial resolution and acquisition speed. The potential of TKD, combined with EDS, to provide crystallographic, chemical, and morphologic characterizations of nano-structured metals will surely be a valuable asset in metallurgy.
Hierarchical and Complex ZnO Nanostructures by Microwave-Assisted Synthesis: Morphologies, Growth Mechanism and Classification
E. Mohammadi, M. Aliofkhazraei, M. Hasanpoor, M. Chipara
Zinc Oxide is an important and multi-purpose material in various industries due to its particular chemical and physical properties. Discovering a cheap, fast, clean, safe, and easy to use method, to synthesize this oxide nanoparticle has attracted a lot of attention in recent applications. The unique properties of the microwave and its special heating capabilities have yielded desirable outcomes by combining different synthesis methods. In the recent years, the vast majority of studies focus on the microwave-assisted synthesis of zinc oxide nanoparticles. This review article attempts to go over the recent advancements on the synthesis of zinc oxide nanoparticles with the aid of microwave, different morphologies and applications obtained by this method. Various microwave-assisted synthesis methods are classified, including the solution-based methods such as hydrothermal, sol-gel, and combustion methods. Morphology of the nanoparticles can affect the properties, and subsequently, applications of these nanoparticles. On the other hand, there is great diversity of morphological and synthesis conditions of zinc oxide nanoparticles. Thus, categorizing the synthesis techniques and providing features of them, facilitates the selection of appropriate method for designing new hierarchical structures with potential properties for future applications. Also it is endeavored to focus on the formation mechanisms of these methods. Finally, the various morphologies obtained under microwave radiation and their formation mechanisms are discussed and the effective factors in the synthesis are analyzed and presented. The potential and suitable fields of development and progress in the future studies are also proposed.
Recent Advances in Friction Stir Welding/Processing of Aluminum Alloys: Microstructural Evolution and Mechanical Properties
Z. Y. Ma, A. H. Feng, D. L. Chen, J. Shen
Friction stir welding (FSW), a highly efficient solid-state joining technique, has been termed as "green" technology due to its energy efficiency and environment friendliness. It is an enabling technology for joining metallic materials, in particular lightweight high-strength aluminum and magnesium alloys which were classified as unweldable by traditional fusion welding. It is thus considered to be the most significant development in the area of material joining over the past two decades. Friction stir processing (FSP) was later developed based on the basic principles of FSW. FSP has been proven to be an effective and versatile metal-working technique for modifying and fabricating metallic materials. FSW/FSP of aluminum alloys has prompted considerable scientific and technological interest since it has a potential for revolutionizing the manufacturing process in the aerospace, defense, marine, automotive, and railway industries. To promote widespread applications of FSW/FSP technology and ensure the structural integrity, safety and durability of the FSW/FSP components, it is essential to optimize the process parameters, and to evaluate thoroughly the microstructural changes and mechanical properties of the welded/processed samples. This review article is thus aimed at summarizing recent advances in the microstructural evolution and mechanical properties of FSW/FSP aluminum alloys. Particular attention is paid to recrystallization mechanism, grain boundary characteristics, phase transformation, texture evolution, characteristic microstructures, and the effect of these factors on the hardness, tensile and fatigue properties as well as superplastic behavior of FSW/FSP aluminum alloys.
A Review of Recent Progress in Solid State Fabrication of Composites and Functionally Graded Systems Via Friction Stir Processing
Sandeep Rathee, Sachin Maheshwari, Arshad Noor Siddiquee, Manu Srivastava
Friction stir processing (FSP) is a rapidly emerging newer solid-state technique for composite fabrication. It involves surface modification which in turn enables successful adaptation of surface properties through plastic deformations in solid state. During initial years of FSP inception, it was primarily employed in development of metal matrix composites of light metal alloys like aluminum. However, recently, it has gained an alluring role in fabrication of composites of various nonferrous and ferrous metal alloys as well as of polymers. In addition to composite fabrication, FSP has evolved as a revolutionary technique in developing functionally graded systems/surfaces (FGS) of metal matrix. This article covers all aspects of FSP in which reinforcement particles are embedded in the base matrix to develop composites and FGS. It presents a critical review on domains of recent developments, effects of different types of reinforcement particles and properties enhancement of composites, and FGS fabrication. In addition to this, various issues, challenges, and future work that demand attention are systematically addressed.
Overview of Hydroxyapatite–Graphene Nanoplatelets Composite as Bone Graft Substitute: Mechanical Behavior and In-vitro Biofunctionality
Wan Jeffrey Basirun, Bahman Nasiri-Tabrizi, Saeid Baradaran
Hydroxyapatite (HA) and related materials have been frequently studied as ceramic-based bone graft materials due to their outstanding biocompatibility and osteoconduction. Since the bones are the load supporting parts of a vertebrate, they must have good fracture toughness (KIC) to avoid fracture at high loading during limb movements. However, the main shortcomings of HA are the poor fracture toughness and brittleness. The mechanical properties of HA need to be improved for orthopedic applications, therefore it is often fabricated with other materials into a composite. This article focuses on the effect of carbon nanostructures (CNSs) especially graphene nanoplatelets (GNPs) on the mechanical, physicochemical properties and in-vitro bio-functional performances of HA. We provide an overview on the preparation and characterization of the HA–GNPs composites. To conclude, the challenges in the fabrication of multi-substituted HA–GNPs composites and future outlooks in the biomedical domain are discussed.
The Role of Intra-Yarn Shear in Integrated Multi-Scale Deformation Analyses of Woven Fabrics: A Critical Review
M. Haghi Kashani, A. Hosseini, F. Sassani, F. K. Ko, A. S. Milani
This article attempts to bring an enhanced insight into the analysis of in-plane shear behavior of woven fabrics. Two common methods have been used to characterize the shear behavior of woven preforms, namely the Bias Extension (BE) and Picture Frame (PF) tests. In spite of the identical macro-scale shear deformation of fabrics in these two characterization procedures, the current study demonstrates that their underlying micro- and meso-scale deformation mechanisms are quite distinct. The trellising mechanism, which is based on the well-known Pin-Joint Theory (PJT), has been regarded for a long time as the sole model to describe the meso-scale deformation of woven fabrics in both the BE and PF tests. Throughout this article, this mechanism is challenged for the PF test by undertaking a multi-scale analysis along with a critical review and integration of the previous experimental, analytical, and numerical studies. Intra-yarn shear, which has not been fully understood yet, is substantiated as a potential meso-level deformation mechanism occurring in the PF test. Accordingly, a new meso-level deformation model is proposed and compared with the trellising shear pattern in the BE setup. Afterward, the comparison is extended from meso-level to macro-level in order to provide more in-depth hypotheses for explaining differences reported in the literature between the shear characteristics of fabrics using BE and PF tests. Finally, some guidelines have been sought to select more reliable characterization method given a forming process.
Recent Advancements in Bulk Metallic Glasses and Their Applications: A Review
Muhammad Mudasser Khan, Ali Nemati, Zia Ur Rahman, Umair Hussain Shah, Hassnain Asgar, Waseem Haider
Bulk metallic glasses (BMGs), that display extraordinary properties of high strength, corrosion resistance, polymer-like formability, and excellent magnetic properties, are emerging as modern quintessential engineering materials. BMGs have garnered significant research enthusiasm owing to their tremendous technological and scientific standing. In this article, the recent advancements in the field of BMGs and their applications are put in a nutshell. Novel state-of-the-art production routes and nano/microimprinting strategies with salient features capable of circumventing the processing related complexities as well as accelerating modern developments, are briefly summarized. Heterogeneous BMG composite systems that lead to incredible combination of otherwise conflicting properties are highlighted. Biocorrosion studies and recent developments in the field of magnetic BMGs are presented owing to their significance for prospective biomedical and magnetic applications, respectively. In the last section, the current status of BMGs applications in the field of catalysis, biomedical materials, structural materials, functional materials, microelectromechanical systems (MEMS), and micro/macro devices are summed up.
In2O3- and SnO2-based Ozone Sensors: Design and Characterization
G. Korotcenkov, V. Brinzari, B. K. Cho
This article describes in detail the SnO2 and In2O3 metal oxides as materials for designing solid state conductometric ozone sensors. The main focus of this article is on the description of the SnO2 and In2O3 films' structural parameters important for gas sensor design and on the establishment of the main regularities of the film parameters influence on the sensor characteristics. Advantages and disadvantages of approaches used for optimization of ozone sensor parameters are also analyzed. In particular, surface modification, bulk doping of SnO2 and In2O3, and the use of 1D structures and hybrid materials are considered. The main factors, controlling parameters of SnO2- and In2O3-based ozone sensors, are determined, and recommendations for the process of the SnO2 and In2O3 films deposition, facilitating the search of the film parameters and the fabrication technologies that optimize the ozone sensor performance, are formulated.
Graphene for Thermoelectric Applications: Prospects and Challenges
Tabitha A. Amollo, Genene T. Mola, M. S. K. Kirui, Vincent O. Nyamori
Thermoelectric power generators require high-efficiency thermoelectric materials to transform waste heat into usable electrical energy. An efficient thermoelectric material should have high Seebeck coefficient and excellent electrical conductivity as well as low thermal conductivity. Graphene, the first truly 2D nanomaterial, exhibits unique properties which suit it for use in thermoelectric power generators, but its application in thermoelectrics is limited by the high thermal conductivity and low Seebeck coefficient resulting from its gapless spectrum. However, with the possibility of modification of graphene's band structure to enhance Seebeck coefficient and the reduction of its thermal conductivity, it is an exciting prospect for application in thermoelectric power generation. This article examines the electronic, optical, thermal, and thermoelectric properties of graphene systems. The factors that contribute to these material properties in graphene systems like charge carriers scattering mechanisms are discussed. A salient aspect of this article is a synergistic perspective on the reduction of thermal conductivity and improvement of Seebeck coefficient of graphene for a higher thermoelectric energy conversion efficiency. In this regard, the effect of graphene nanostructuring and doping, forming of structural defects, as well as graphene integration into a polymer matrix on its thermal conductivity and Seebeck coefficient is elucidated.
A Critical Review on Physical Vapor Deposition Coatings Applied on Different Engine Components
Q. M. Mehran, M. A. Fazal, A. R. Bushroa, Saeed Rubaiee
Friction and wear in different engine components have crucial effects on the engine performance, combustion efficiency, oil consumption and lifetime of the internal combustion (IC) engine. Under certain loads, speeds, and temperatures, the metallic components of the IC engine, especially the piston and valve system suffer from a higher friction. Thin film coating is one of the novel techniques to reduce the frictional forces and improve the mechanical properties of engine components. Due to some versatile tribological properties, increasing attention has been paid to the physical vapor deposition (PVD) technology in the recent decade to deposit thin film coating on engine components. This article presents a comprehensive literature review on thin film coatings for IC engine components deposited by PVD technique. Issues related to tribological properties (wear and coefficient of friction) and mechanical properties (hardness and roughness) are also highlighted. Scientific improvements are presented in the light of literature. It is revealed that PVD coating is significantly effective on wear resistance, scuffling resistance, surface roughness, and friction of the components in IC engine. Laboratory test and data from actual service so far suggest that the plasma-activated electron beam evaporation coating is perhaps one of the best choices for smooth surface finishing with improved mechanical and tribological properties. However, there are still some problems in its practical usage. This compressive review paper presents the major shortcomings of PVD coatings on IC engine components and the possible solutions if any. Finally, a number of issues have been reported which need to be encountered for further studies.
Recent Progress on the Dispersion and the Strengthening Effect of Carbon Nanotubes and Graphene-Reinforced Metal Nanocomposites: A Review
Zeeshan Baig, Othman Mamat, Mazli Mustapha
This article reviews the available literature published to date on the reinforcement of metals with carbon-nanofillers (CNTs and graphene), and also offers a specific focus on issues related to the mechanical and tribological properties of nanocomposites. Carbon-nanofillers (later denoted by C-nanofillers) are known to have extraordinary mechanical properties and multifaceted characteristics and are ideal candidates for the reinforcement of metals for numerous applications. However, their incorporation for practical applications has been challenging researchers for decades. The most important issue is uniform dispersion due to sizeable surface differences between carbon-nanofillers and metals. Other concerns are structural integrity, wetting with metals, and interfacial connections. Nanocomposite applications can only be effective when these challenges are properly addressed and overcome.