There are many pores on the surface of some zirconia ceramics, but some of them are very smooth and almost no pores. So what is the reason? In fact, it has a lot to do with the sintering of zirconia ceramics. The following is a detailed analysis of mingjue ceramics factory. I hope you can benefit from it.
Zirconia ceramics can be used not only as functional materials, but also as carriers, additives or active components of industrial catalysts, which play an important role in the synthesis of methanol from CO2 and H2. There are many reports about the influence of pore size distribution on sintering and microstructure development. The change of the pore size distribution of the same powder is often caused by the agglomeration of one particle. The results show that not only the density but also the densification rate are greatly affected by the pore size distribution. It is found that the more air holes in the blank, the lower the sintering density. In extreme cases, when the pore size is bimodal distribution, the large pores or so-called secondary pores between aggregates can hardly be excluded. It is found that although the grain growth is affected by the phase structure, the powder and the properties of the green (green density, pore size distribution) do not affect the grain growth in the green during the heating and holding process.
Although the properties of the green body such as density do not affect the grain growth, but affect the size ratio of pores to particles. The properties of billets do not affect the grain growth, but affect the pore growth, so it also affects the densification behavior. The relationship between the grain size and density in the initial stage of densification is as mentioned above. There is a linear relationship between the grain size and density in the middle stage of sintering. According to the definition of sintering stage, there is only densification but no grain growth in the initial stage of sintering.
This phenomenon may exist in the green compacts with large initial particle size, but for the green compacts composed of ultra-fine powders such as the ultra-fine zirconia used in this study, even in the initial stage of sintering, grain growth and densification almost occur at the same time. This result means that for the solid-phase sintering of ultrafine powder, the initial stage of sintering can be considered as nonexistent or at least negligible.
Therefore, the following conclusions can be drawn:
① The grain growth in the green slab is not affected by the properties of the preform:
② The growth of pores is controlled by grain growth and densification. The former causes the growth of pores and grains at the same time, while the latter causes the shrinkage of pores and the decrease of R value of pores;
③ From the beginning of sintering to the end of the middle stage, the linear relationship between grain size and density can be explained according to the same diffusion and mass transfer mechanism of grain growth and densification, and the dependence of grain growth and density on time-dependent in isothermal process;
④ The linear relationship between grain size and density is affected by the properties of the preform, because grain growth is driven by the chemical potential of grain size difference, while densification is driven by the sintering compressive stress acting on the pores;
⑤ Higher dihedral angle, molding density, narrow particle and pore size distribution are favorable for the grain size density relationship track to move to the direction of high density and small grain size.