Shaping Silicon Carbide Powder And Its Extrusion Molding

Currently, domestic high-end series of ceramics about silicon carbide, including reaction-bonded silicon carbide (RBSC), recrystallized silicon carbide (R-SiC) and silicon nitride combined with silicon carbide (Si3N4-SiC), however, the performance such as the temperature of usage, strength and service life performance of which have a certain gap with foreign products. Therefore, improve properties of material and forming process and study the link between its structure and properties is necessary for the development of the silicon carbide. But the impact of the green body is an important part of ceramic production, molding density has an important impact on the sintered density of products. Especially in sintering process of re-crystallization, the silicon carbide liquid phase has or no shrinkage at high temperature, the density of products is determined by the densities of green body, so the key to improve the performance of recrystallized silicon carbide is to increase the density of green body.In this paper, use roller-mill, vibration shaping machine, pot mill, and mixing mill to shape the different particle size of silicon carbide powder, observe the apparent morphology and measure the green body density before and after reshaping the silicon carbide powder, and then determine its final shaping methods and which method is suitable for its size. Establish the relationships beteen thickness of the bread,shaping time,feeding size,speed and the tap tensity and so on,then chose the best shaping process. Contrast the green body density which use the silicon carbide powder before and after shaping in the extrusion molding,and analyse the reasons.The experimental results, the roller-mill is suitable for the size range in 100-1000μm silicon carbide powder to shape, which is of short time and high efficiency; vibration shaping machine mill shape the 140μm silicon carbide powder in obvious effect, which is strict to the shaping time;the pot mill is suitable for the size range in 100～1000μm silicon carbide powder to shape, which spents long time, has low efficiency and is disadvantage to product in industy; the mixing mill is suitable for the size range in not more than 100μm silicon carbide powder to shape, which speed is the main factors and the more fine powder has higher requirements for speed.The results showed that 500μm shaped silicon carbide powder is available by roller-mill,which tap density can be achieved 1.94g/cm3; 100μm shaped silicon carbide powder is available by vibration shaping mill,which tap density can be achieved 1.96g/cm3; 500μm and 700μm shaped silicon carbide powder is available by pot mill,which tap density can be achieved1.95g/cm3 and 1.96g/cm3;100μm,12μm and 1.2μm shaped silicon carbide powder is available by mixing mill,which tap densitys separately were 1.96g/cm3,1.56g/cm3,1.50g/cm3 And in a size distribution(700μm65%,100μm10%,12μm15%,1.2μm10%),When use the raw powder its density get its highest point that is 2.56 g/cm3,When the shaping powders substitude the raw powder, the density get its highest point that is 2.46 g/cm3. descends 4.02%. Experiments show that when spherical powder has the high specific surface area, it is disadvantage to closely stack in the extrusion molding,leading to the drop of the green body density.