What are the main components of the pyrophyllite composite block?

　　As a key component in the field of superhard material synthesis, the performance of the pyrophyllite composite block directly depends on its material composition and structural design. The composite block features natural pyrophyllite as its main framework, with a stable structure achieved through precise material ratios and advanced processing techniques.

　　The main material, pyrophyllite, has a chemical composition of Al₂Si₄O₁₀(OH)₂, with a theoretical makeup containing 28.3% alumina, 66.7% silica, and 5% crystalline water. In practical applications, the mineral often contains natural impurities such as quartz and sericite; among these, the quartz content is typically kept between 10% and 15% to strike a balance between mechanical strength and thermal stability. Inside the composite block, conductive steel ring components are usually installed, made from low-carbon steel to ensure stable electrical current conduction.

　　In structural design, the key liner materials commonly used are dolomite (MgCO₃·CaCO₃) or kaolin-based composites. The liner thickness typically accounts for 65%–70% of the total composite block thickness to ensure even stress distribution. Some high-end models incorporate trace amounts of magnesium oxide (MgO) in a ring-shaped component, whose pore design directly influences the uniformity of the temperature field within the synthesis chamber.

　　In diamond synthesis applications, impurity control in composite blocks is particularly critical. The iron oxide (Fe₂O₃) content must be kept below 0.5%, while the total alkali metal oxides (Na₂O + K₂O) should not exceed 1.2%. These parameters directly influence the insulation performance and high-temperature stability of the synthesis chamber. Modern production processes, employing multi-stage magnetic separation and acid leaching treatments, effectively reduce harmful impurities to within industry-standard limits.

　　From a materials science perspective, the ideal mica-based composite block should exhibit three key integrated properties: the mica matrix provides structural support and thermal insulation, the metallic components ensure electrical conductivity, and the ceramic-lined tube facilitates efficient pressure transmission. This unique combination enables the material to maintain its structural integrity even under extreme conditions—specifically, at temperatures as high as 1700°C and pressures up to 5 GPa. Notably, different application scenarios impose varying requirements on the composition ratios; for instance, composite blocks used in fiberglass production demand higher-purity silica, while those intended for refractory materials require an increased proportion of alumina.