Abstract: Clay minerals produced in Henan procince, which have good sealing performance and pressure transmitting property, can take place of pyrophyllite in the use of pressure transmitting medium.The new pressure transmitting medium introduced in the paper was made by sealing layer and pressure transmitting layer together.The sealing layer was made by the clay minerals, which were divided into three size range(-1.4 mm+0.5 mm,-0.5 mm+0.25 mm and-0.25 mm) and the weight proportion was 4∶4∶2.whereas the pressure transmitting layer was made by dolomite, which was divided into two size range(-0.18 mm+0.15 mm and-0.15 mm) and the weight proportion was 8∶2.In addition, adding 5; and 8; binder(sodium silicate) to the sealing material and pressure transmitting material respectively.The two kinds of materials were molded by pressure, in which the sealing material was in the outside and pressure transmitting material was in the inside, and roasted at a certion temperature.The external sizes of the new medium were 65 mm×65 mm×32.5 mm, and the size of internal cavity was 38.5 mm.With the pressure transmitting medium, a large number of diamond synthesis tests were conducted.The tests results showed that the per unit yield of diamond was 116.0 ct, the proportion of crystals whose compression strength and grain size were more than 130 N and 40/60 mesh were 28.0; and 77.5; respectively, as well as the cemented carbide anvil consumption was less than 0.28 g per 1 g of the produced diamond.The new medium made by clay minerals has the same effect as that made by pyrophyllite material on diamond synthesis.

Key words: Clay minerals produced in Henan procince, which have good sealing performance and pressure transmitting property, can take place of pyrophyllite in the use of pressure transmitting medium.The new pressure transmitting medium introduced in the paper was made by sealing layer and pressure transmitting layer together.The sealing layer was made by the clay minerals, which were divided into three size range(-1.4 mm+0.5 mm,-0.5 mm+0.25 mm and-0.25 mm) and the weight proportion was 4∶4∶2.whereas the pressure transmitting layer was made by dolomite, which was divided into two size range(-0.18 mm+0.15 mm and-0.15 mm) and the weight proportion was 8∶2.In addition, adding 5; and 8; binder(sodium silicate) to the sealing material and pressure transmitting material respectively.The two kinds of materials were molded by pressure, in which the sealing material was in the outside and pressure transmitting material was in the inside, and roasted at a certion temperature.The external sizes of the new medium were 65 mm×65 mm×32.5 mm, and the size of internal cavity was 38.5 mm.With the pressure transmitting medium, a large number of diamond synthesis tests were conducted.The tests results showed that the per unit yield of diamond was 116.0 ct, the proportion of crystals whose compression strength and grain size were more than 130 N and 40/60 mesh were 28.0; and 77.5; respectively, as well as the cemented carbide anvil consumption was less than 0.28 g per 1 g of the produced diamond.The new medium made by clay minerals has the same effect as that made by pyrophyllite material on diamond synthesis.