The simulation for liquid phase sintering has been newly developed by Monte Carlo method. The basic three mechanisms in liquid phase sintering, namely (1) liquid wetting on solid surface, (2) rearrangement of solid particle by capillary force of liquid, (3) growth of solid particles by solution-reprecipitation through liquid phase (Ostwald ripening), have been introduced in the simulation. The liquid wetting on a solid plane or solid particle surface progressed more easily as decreasing the energy between solid and liquid (γ_SL). The introduction of rearrangement into the simulation brought the result that relative density increased with decreasing γ_SL and pores remained. The introduction of Ostwald ripening in addition to liquid wetting and rearrangement produced the result that relative density increased on the whole and the effect of γ_SL became clear. The simulation including Ostwald ripening was able to demonstrate clearly and continuously the influence of γ_SL on growth and contiguity of solid particles.

Molecular dynamics simulations were performed to study six grain boundaries of α-alumina (Al₂O₃) with a glassy phase of anorthite (CaAl₂Si₂O₈) composition. We calculated excess energy, diffusion constant and ratio of excess volume with different thickness of the glassy film. It was found that excess energy for some grain boundaries exhibited a minimum. When the thickness of the glassy film was thick adequately, excess energy corresponded to the energy of alumina-glass interface and they were different for each interface. Diffusion constants depended on the thickness of the glassy film. The diffusion constant of thin film was smaller than that of thick film. Excess volume was the maximum when the thickness of the glassy film was 0.2~0.3 nm. When the atomic arrangement of the crystals didn’t fit each either, the excess volume of the grain boundary with the glassy film was smaller than that of the pure grain boundary. When the glassy film width was nm order, the atomic arrangement of the glassy phase was regular and the atomic diffusion behavior was approached that of a solid (crystalline) phase. We need to consider not only solid-liquid interface but also solid-solid (crystalline) interface for the structure of ceramics made by liquid phase sintering.

In this study, rapid debinding of alumina molded bodies was carried out using superheated steam treatment. The superheated steam treatment was performed with a temperature increase of 10°C/min to a holding temperature range of 500°C to 800°C. The molded body after superheated steam treatment to 800°C resulted in a carbon removal rate of 99.3%. No cracking occurred in sintered bodies obtained by debinding in superheated steam and then firing at 1,600°C in air. However, many large cracks occurred in sintered bodies that had been treated in air under similar temperature conditions. Thus, it was suggested that superheated steam treatment is highly effective for rapid debinding of molded bodies. To understand the debinding behavior under superheated steam, thermal analyses were performed with thermogravimetric and differential scanning calorimetric analysis and gas chromatography in humidified atmospheres. These results suggested that the debinding in superheated steam suppressed thermal runaway and the generation of pyrolysis gas caused by the chain of exothermic reactions derived from the oxidation of the forming aid (binder).

The attempt of fabrication of TiC bulk material from elemental Ti and C powder was studied. The effect of mixing method and consolidation temperature on the densification behavior and microstructural properties of the compact were studied. The elemental Ti and C powder were mixed by two different methods, rotating stainless vessel with shaking motion (we call regular mixing in this paper) and ball milling apparatus (MA). The formation of TiC from regular mixed powder was occurred gradually with increasing temperature below 1373 K. On the other hand, MA powder ball milled for 1800 ks was started to form TiC phase at around 750 K. Therefore, only regular mixed powder is able to deform and sinter below 1373 K by pressure sintering due to the existence of metallic Ti phase. At high temperature of 1773 K, MA powder having fine microstructure achieved higher density than regular mixed powder with coarse microstructure.