Read More
Date: 15-10-2018
907
Date: 25-11-2018
1048
Date: 9-1-2018
993
|
Extraction and manufacture of the group 14elements
Sources of natural graphite are supplemented by manufactured material formed by heating powdered coke (hightemperature carbonized coal) with silica at ≈ 2800 K. Approximately 30% of diamonds for industrial use in the US are synthetic. Diamond films may be grown using a chemical vapour deposition method and hydrothermal processes are currently being investigated. The manufacture of amorphous carbon (carbon black, used in synthetic rubbers) involves burning oil in a limited supply of air. Silicon (not of high purity) is extracted from silica, SiO2,
by heating with C or CaC2 in an electric furnace. Impure Ge can be obtained from flue dusts collected during the extraction of zinc from its ores, or by reducing GeO2 with H2 or C. For use in the electronic and semiconductor industries, ultrapure Si and Ge are required, and both can be obtained by zone-melting techniques . Tin is obtained from cassiterite (SnO2 ) by reduction with C in a furnace but a similar process cannot be applied to extract Pb from its sulfide ore since ΔfGo (CS2,g) is 67 kJ mol-1; thermodynamically viable processes involve the below reactions at high temperatures. Both Sn and Pb are refined electrolytically.
|
|
تفوقت في الاختبار على الجميع.. فاكهة "خارقة" في عالم التغذية
|
|
|
|
|
أمين عام أوبك: النفط الخام والغاز الطبيعي "هبة من الله"
|
|
|
|
|
قسم شؤون المعارف ينظم دورة عن آليات عمل الفهارس الفنية للموسوعات والكتب لملاكاته
|
|
|