15081
Step - by - step combustion of carbon from outside the composite powder particles forms the double - shelled SnO2 yolk - shell - structured powder particles .
 Chemical: carbon; Chemical: SnO2
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: carbon; Chemical: SnO2