Tungsten Oxide Ceramics SEM Image

In the figure, SEM images of tungsten oxide ceramics prepared by five different sintering processes are shown. As can be seen from the figure, nitrogen has a great influence on the topography of tungsten oxide ceramics.

There are many voids in sample 1, which occupy a relatively large volume, the grain shape is lamellar, and grain boundaries are not easily discernible. Sample 2 has few voids and uniform grain size distribution. Both the sample 3 and the sample 4 have long rod shapes, and the sample 3 has a significantly larger crystallite size than the sample 4. The grain shape and size of Sample 5 are like those of the air-sintered sample, but the voids are more.

Since the crystal grain shape of the tungsten oxide ceramic varies greatly, only the diameter shrinkage of the sample 2 is positive. The other samples have negative diameter shrinkage. The relative density of sample 2 is also greatest, which is greater than the relative density of samples sintered directly in oxygen. This shows that the mass transfer path of Sample 2 in the sintering process is dominated by the mass transfer mechanism from the grain boundary through the lattice diffusion to the neck. The main mass transfer path of other samples in the sintering process is evaporation condensation.

Sample 2 Compared to Sample 3, the same sintering process was conducted with oxygen at the end of the 1100°C incubation period. The difference is that in the cooling phase of Sample 2, there is a period of more cooling rate control and insulation. Results The relative density of sample 2 was much larger than that of the sample, and the distribution of the grain size was also much better than that of sample 3.

In the cooling phase, no cooling rate was set in the sintering process of Sample 3 and Sample 4. Their diameter shrinkage and relative density are basically the same, which shows that the cooling rate has a great influence on the morphology structure of tungsten oxide ceramics.

• < Prev
• Next >