When the ceramic green compacts are heated with electric fields, the specimen electric current increases steeply at a certain critical furnace temperature. This phenomenon is called a flash event, and along with this phenomenon, sintering process complete immediately. Flash sintering is a new sintering method that uses this flash event. Various kinds of researches have been reported since Raj et al. found the flash sintering. In addition, some new phenomena induced by the application of electric fields have been pointed out, for example, the change in the point defect configuration due to electric fields. Recently, photo luminescence emission has been found, which is closely related to point defects generated by electric fields during flash event. In this report, we would like to summarize the outline of flash sintering method and to review our recent researches.

Unidirectional anisotropic pore morphologies could be created by using a gelation of mullite particles dispersed slurry with and without an anti-freezing protein additive, and the freezing process, resulting in micrometer-sized cells with very high porosities of up to 91 vol%. The addition of ice binding proteins effectively inhibited the formation of coarse ice crystals, reduced the resultant cell size and provided uniform size distribution in insulators obtained. The insulators prepared showed the thermal conductivity from 0.23 to 0.38 W/mK and the compressive strength around 1.4–21.7 MPa. These properties could be modulated by varying process parameters of the gelation and freezing with solid loading in the initial slurry, anti-freezing protein, sintering additive. This unique approach can be used to produce insulators with macro-cellular anisotropic morphology and very high porosity, suitable for a variety of industrial applications.

In order to clarify plastic deformation behavior and mechanism of fracture energy absorption of Ti₃SiC₂, Vickers indentation tests were conducted for Ti₃SiC₂ sintered bodies with various textured orientations. Textured Ti₃SiC₂ sintered bodies were fabricated by slip casting in a strong magnetic field and spark plasma sintering (SPS), and their orientation distribution were analyzed by SEM/EBSD. It was found that for the textured Ti₃SiC₂, the plastic deformation behavior around Vickers indents such as an indent shape and a grain pile-up were strongly affected by basal slip and kink deformation. Furthermore, the fracture energy absorption mechanism around the indents also depended on the texture orientations. From our results, it is concluded that the most effective factor for suppressing the crack propagation was the grain pile-up, and the second one was crack deflections.

Uniaxial pressing is a utilized technique to prepare powder compacts in regions of ceramics, metal, drug, and functional food. On the other hand, it is known that the inhomogeneous structures are induced by stress distribution resulting from applying the anisotropic stress field to the powder bed and they become the origin which forms defect degrading the performance of products. However, the generation process of inhomogeneous structures has not been clarified experimentally. Directly understanding the formation mechanism of the internal structure during uniaxial pressing is very important to control the particle-assembled structure in the powder bed and the quality of products. In this work, the change process in void morphology under uniaxial pressing was observed dynamic-two-dimensionally and intermittent-three-dimensionally by the novel observation system composed of swept-source optical coherence tomography (SS-OCT) and material testing machine. Moreover, the detected voids were evaluated quantitively to directly clarify particle-packing behavior on the initial stage of pressing.

C-axis oriented (Sr,Ca)₂NaNb₅O₁₅ (SCNN) piezoelectric bulk ceramics was prepared by repeating photopolymerization reaction in a magnetic field. The spin-coated sheet was held in a magnetic field for 150 seconds and then subjected to a photo-curing reaction to obtain a particle-oriented sheet. By repeating this process, a laminate was obtained. In the early stage of sintering, although the boundaries between the stacks were clearly observed, finally the microstructure became continuous and uniform by densification and grain-growth. The c-axis oriented SCNN ceramics had a piezoelectric constant remarkably higher than that measured from the randomly oriented sample. Therefore, it was clarified that the piezoelectric characteristics were improved even in the crystal-oriented ceramics produced by stereolithography in the magnetic field. These results indicate that stereolithography in the magnetic field is an effective manufacturing technique for producing grain-oriented bulk ceramics.

Evaluation of powder wettability is important to prepare well dispersed slurries. Therefore, in this study, a technique for evaluating powder wettability was developed to analyze the increase in the internal pressure of a closed powder bed due to capillary suction to determine the contact angle of the powder. The effect of the powder-bed-preparation method and powder surface area estimation method on the determined value of the contact angle was discussed. We demonstrated that the improved air permeation test proposed in this research can accurately determine the powder surface area, resulting in a faithful determination of the contact angle of the powder. It was also shown that compression under the shearing method could result in a denser and more homogeneous powder bed when compared to the conventional tapping method, indicating high reproducibility for estimating the contact angle.

In this study, the rapid debinding treatment of cordierite ceramic bodies molded by extrusion process was carried out using superheated steam process. The superheated steam treatment was performed with a temperature increase of 10°C/min to a holding temperature range of 600°C to 800°C. For the cordierite ceramic extrusion molded body, the residual carbon content was decrease in the case of debinding treatment with superheated steam temperature of 700°C to 800°C compared with 600°C of superheated steam. The cordierite ceramic extrusion molded bodies contained a residual carbon content of 1% after treated with superheated steam at 800°C. No cracking occurred in cordierite ceramic molded bodies obtained by debinding in superheated steam, although cracks occurred in bodies treated by conventional debinding process in air or nitrogen under similar temperature conditions. Thus, it was found that the superheated steam treatment is highly effective for rapid debinding of extrusion molded cordierite ceramics bodies.

PECS (Pulsed Electric Current Sintering) can lower the sintering temperature and reduce sintering time. However, its sintering mechanism about temperature distribution in the sample is not known clearly. In this study, we used eutectic material of Al-Cu alloy to get temperature distribution by eutectic micro structure. In result, center part of the sample was heated more than outside. From comparison with various current distribution conditions, well-grown neck in center part became conductive path which many electric currents pass through and its upper and lower graphite punch was heated by high current density. Therefore, we can get uniform temperature distribution if the current flowing into the center of the sample is distributed to outer part.