Improving Densification of Zirconium Tungstate with Nano Tungsten Trioxide and Sintering Aids

摘要

Because of the highly negative thermal expansion coefficient, zirconium tungstate (ZT) offers a unique opportunity in engineering applications. However, processing of ZT has not been fully perfected to yield a near thoeretical density. Thus, ZT has relatively a weak strength, which prevented its unique property to be fully utilized in applications. This study investigates the processing methods to improve the packing and subsequent final densities - thus improving the mechanical strength. These methods include (1) use of a wide variety of powders with different size, (2) use of nano-powders and (3) use of sintering aids. Under the same compaction and sintering condition, a variety of powder mixtures were produced, whose initial packing density and final sintered density were measured and compared in order to determine the optimal combination. The elastic modulus of each sample was also tested. By adding nanopowders, the sintered density of zirconium tungstate can be enhanced by 5%. Furthermore, with the sintering aids, the density can be improved by additional 5%. The optimal amount of nanopowders and sintering aids were determined to improve the final density and strength.