High Density Of Fused Silica Ceramics

The fused quartz ceramics refer to the products which use the quartz glass or the fused quartz as raw materials, by a series of ceramic shaping technology, such as brokenness, shaping, sintering. Since the fused quartz ceramics have a series of fine performances, such as excellent shock resistance, low thermal conductivity and low hot expansion coefficient, etc., get more and more extensive application into many fields, such as metallurgy, glass, chemical industry, spaceflight, etc.Gelcasting is a new ceramic shaping technology, which is a ideal combination of the traditional colloidal shaping with the organic chemistry theory, depends on the interparticle forces between the particles and the nature change of the some carriers within the suspension, makes the suspension change from the liquid state into the solid state. While the suspension changes from the liquid state into the solid state, the volume has not shrinkage. Gelcasting utilizes the organic matter of lower content to polymerize in situ the ceramic paricles, improves greatly the homogeneity of the ceramic bodies, increases the reliability of the ceramic materials. We can realize the quartz ceramics production of high strength, high homogeneity and near net-size green body, can also develop greatly the density and reliability of the products.This paper investigated systematically the factors influencing the slurries preparation of fused quartz ceramics, gelcasting parameters as well as drying and sintering of the formed bodies. We prepared successfully the fused quartz ceramics with high strength and high reliability, and have analyzed the crystalline phases and microstructure of the fused quartz ceramics by XRD and SEM. The products were examined by NDT.It was shown that volume content, particle size distribution and the pH value are major factors influencing the properties of the slurries. Components of the starting materials, amount of sintering additives, volume content of the solid particles and the sintering profiles are major factors influencing the properties of the products. The fused quartz ceramic products with high strength high reliability were prepared by dynamic gelcasting.The fused quartz ceramic products possess high strength, excellent homogeneity and high reliability according to the tests. The density is 1.96g/cm3, the bending strength is 65.2MPa, the dielectric constant is 3.18, tg 6 is 5.3 x 10~4 with a difference of less than 0.03 and scattering of 0.7%;the difference of the density through out the whole sample( 330 X 750mm ) is less than 0.04g/cm3 with a scattering of 6.1%, the thermal shock resistance of the materials is 1100 'C . Theproducts possess homogeneous microstructure and high reliability according to industrial CT scanning.