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With increasing nitrogen content of the powder , the porosity within the L-PBF built specimens increased .
 material: nitrogen; material: powder; machanical property: porosity; manufacturing process: L-PBF
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
 Entities: nitrogen, powder, porosity, L-PBF 
Answer:
 material: nitrogen; material: powder; machanical property: porosity; manufacturing process: L-PBF