Study On The Preparation And Propetries Of Zirconia Ceramics By Spark Plasma Sintering

Based on the shortages of zirconia ceramics prepared by traditionalnon-pressure sintering, such as: small sintering motivation, low density,inhomogeneous microstructure, long production cycle and so on, thecharacterization method of fracture toughness of zirconia ceramics prepared bySPS was researched. The technological parameter of zirconia ceramics by SPSwas optimized by orthogonal test method. The influence of Al2O3content on thestructure and property of zirconia ceramics was studied. The microstructure andproperties of zirconia ceramics by SPS and traditional sintering method, ofAl2O3/ZrO2composite ceramics by SPS, were analysed and compared.Conclusions are showed as follow:1. The indentation crack types are related to the indentation load, the cracktype of ZrO2preparation by SPS is Palmqvist Crack under10kg of indentationload and15s of dwell time. The result of Marshall’s formula is too large, theresults of Niihara’s formula and Shetty’s formula are stable, but they did not considerate the density of zirconia ceramics. In order to accurately reflect theproperty of the materials, In this paper, the Laugier’s equationKIc0.015(d/l)1/2(E/H)2/3(P/c3/2)was selected.2. During the process of preparing zirconia ceramics sintered by SPS, thesintering temperature is the most important factor affecting its properties, thefollowing factor is dwell time. The best process parameters of SPS are1400℃×5min×15MPa. Uniform tetragonal phase morphology are obtainedthrough the best process parameters, and the density, micro hardness, fracturetoughness are96%,1332HV,5.18MPa·m0.5, respectively. The microstructureand properties of zirconia ceramics related to the method of sintering. Thedensity, micro hardness, fracture toughness of zirconia ceramics prepared byconventional sintering are91%,1217HV,7.57MPa· m0.5, respectively.Compared to the samples of SPS, a lot of pores existed in zirconia sintered bytraditional non-pressure sintering, which made its density and micro hardnessless than the SPS samples, however, the fracture toughness higher than thesample by SPS.3. The hardness of Al2O3/ZrO2composite ceramics increased with theincrease of content of Al2O3. The density and fracture toughness increasedbefore the15%content of alumina, and then decreased with the alumina contentincreasing. The grain size of alumina appeared abnormal growth and fracturetoughness decreased rapidly when the alumina content beyond20%. Theα-Al2O3distributes homogeneously in the t phase zirconia substrate, in the15% Al2O3/ZrO2composite ceramics. Its density, micro hardness and fracturetoughness are97.3%,1433HV,4.710MPa·m0.5respectively.4. Under dry friction condition at room temperature, the friction coefficientbetween Si3N4and zirconia ceramics, Al2O3/ZrO2composite ceramics by SPS,and zirconia ceramics by traditional sintering method is0.71,0.65,0.72respectively. The wear mechanisms are both abrasive wear, but the debris of thezirconia ceramics by SPS are large and much, while the debris of Al2O3/ZrO2composite ceramics by SPS are small and less， zirconia ceramics byconventional sintering method is between the two samples. The wear rate ofzirconia, Al2O3/ZrO2composite ceramics by SPS and the zirconia ceramics byconventional sintering method is1.15×10-3mm3/(m·N),4.85×10-5mm3/(m·N),6×10-4mm3/(m·N), respectively.