METHOD OF PREPARING BATCH FOR DIAMOND SYNTHESIS Russian patent published in 1998 - IPC

FIELD: synthetic diamonds. SUBSTANCE: petroleum or coal-tar pitch with softening temperature 423-1270 K is mixed with 2-20 wt % graphite. Mixture is carbonized under action of ultrasound with frequency 15-35 kHz and heating to 733-773 K with rate 1-3 C/min. material is then held for 150-180 min in medium containing (in wt %): acetylene, 16-18; propane, 30; hydrogen, 2-4; and methane, the balance. Temperature is measured over three mutually perpendicular directions and comparison regarding temperature gradient for each temperature range of compositions is performed. Petroleum pitch may be utilized with density 1273 kg/cu.m which contains, wt.-%: asphaltenes, 24; carbenes and carboides, 67.1; chloroform-insoluble matters, about 5.53; and volatiles, about 3.18. Pitch is mixed with sludge containing refractory nickel or titanium- based superdoped superalloys formed in operations involving deep, pendulum multipass, or combination grinding. Yield of diamond is 5.0- 5.94 karat per 1 sintering operation, hardness at least 0.430 kg, abrasive capacity at least 4.71 conditional units. EFFECT: reduced cost due to utilizing low-expensive materials. 2 cl, 6 tbl