4785
Reduction in the silicon impurity content in the AA7075 powder gives a chance to reduce susceptibility to cracking with no change of the alloy specification .
 concept or principle: Reduction; material: silicon; machanical property: impurity; material: powder; machanical property: susceptibility; concept or principle: cracking; material: alloy
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: Reduction, silicon, impurity, powder, susceptibility, cracking, alloy 
Answer:
 concept or principle: Reduction; material: silicon; machanical property: impurity; material: powder; machanical property: susceptibility; concept or principle: cracking; material: alloy