Influence Of Adding NiO-Al And TiO₂-Al-C On The Properties Of ZrO₂ Ceramic

This thesis paper studied the influence of adding binary particles into ZrO₂ matrix ceramic through thermit reactions of NiO-Al and TiO₂-Al-C. Specifically, the effect of the parameters, like the proportion of raw materials, types of raw materials, sintering temperature etc., on the properties ( phase composition, relative density, flexural strength and fracture toughness ) of ZrO₂ ceramic.The results show that when NiO-Al was added into 3YSZ matrix, three different areas existed in the samples which were sintered in range of 1400℃and 1500℃. These three areas were as follows: area of intense thermit reaction, area of slight thermit reaction and area of none thermit reaction; and the main phases of the sintered samples were t-ZrO₂, m-ZrO₂,α-Al₂O₃ and Ni. Moreover, the data indicates that the relative density, flexural strength, and fracture toughness of the samples decreased according to the increase of the addition of NiO-Al in the matrix; they all reached the peak where the addition content is 6.3 wt%, and the values were 93.1%, 386.2 MPa and 7.61 MPa·m^1/2 repectively.When TiO₂-Al-C and extraα-Al₂O₃ were added into 3YSZ matrix, the atmosphere plays an important role in the sintering of the ceramic. In Ar2 atmosphere, cracks on the surface and black area in the inner part of the sintered samples were observed; and the main phases of the black area were t-ZrO₂, m-ZrO₂,α-Al₂O₃, ZrC and graphite. In opposite, samples sintered in N2 atmosphere were in good condition. In N₂ sintering atmosphere, data shows that the relative density, flexural strength, and fracture toughness of the samples decreased in accord with the increase of the addition TiO₂-Al-C; when the addition content increased to 11.5 wt%, the values reached the submit 81.4%, 175.8 MPa and 2.80 MPa·m^1/2. In addition, the extra addition ofα-Al₂O₃ ( from 3 wt% to 15wt%) had limited effect on the sintered samples' relative density but flexural strength and fracture toughness. The samples' flexural strength and fracture toughness decreased along with the upward of theα-Al₂O₃ content, the maximum values were 209 MPa and 2.58 MPa·m^1/2. When no extraα-Al2O3 was added and N2 was chosen as the sintering atmosphere, the XRD analysis results suggest that TiC generated in the ZrO₂ matrix. Compared with the samples which were prepared with 8YSZ and m-ZrO₂ as raw materials, the sintered sample which was prepared with 3YSZ as raw material was superior in properties of relative density, flexural strength, and fracture toughness. The maximum values were 75.5%,85.2 MPa and 1.6 MPa·m^1/2, respectively.Further research suggestes that there were three fracture modes, intergranular fracture, transgranular fracture and mixed-mode fracture, in the ceramic; and the toughening ways were nano particles toughening and metal particles toughening.