Takahiro Matsuura

Separation-permeation performance of porous Si3N4 ceramics composed of columnar β-Si3N4 grains as membrane filters for microfiltration

The separation–permeation performance of porous silicon nitride (Si3N4) ceramics (consisting of columnar grains connected at random in three dimensions) as membrane filters was evaluated, and compared with commercial Al2O3 membranes having a three-layer structure. Si3N4 membranes separate particles with diameters much less than their pore diameters. The permeability of Si3N4 membranes with separability values the same as those of the Al2O3 membranes was about 1.3–2.4 times as large as the Al2O3 membranes. Dead-end filtration examination, using Al2O3 particles with a particle size distribution, indicated that the Si3N4 membrane filtration mechanism obeyed the cake filtration mechanism although the particle size was smaller than the pore size of the Si3N4 membranes.

One role of titanium compound particles in aluminium nitride sintered body

Microstructure of titanium compound particle in polycrystalline aluminium nitride (AlN) has been investigated using micro-auger electron spectroscopy (μ-AES). AlN-0.5 wt% TiO2-1.5 wt% Y2O3-0.4 wt% CaO system was sintered at 1850°C in nitrogen atmosphere using a graphite furnace. The AES studies show that the composition of the titanium compound particle is titanium, aluminium, carbon, oxygen, nitrogen and calcium. On the other hand, no calcium is observed by AES in the AlN grains and grain boundary. It is found that one role of the titanium compound particle is to trap calcium included in polycrystalline AlN.

Determination of the range of lattice distortion in AIN sintered body by higher order laue zone pattern

To analyse the magnitude and range of lattice distortion which is responsible for the low thermal conductivity in aluminium nitride (AIN) crystal grains, the higher order laue zone (HOLZ) pattern of transmission electron microscopy was used. The HOLZ patterns obtained from various positions in the AIN crystal grain show that the AIN crystal lattice is distorted in the vicinity of the grain-boundary phase, and the magnitude of lattice distortion becomes large as it approaches the grain-boundary phase. Also, the range of distortion extends to approximately 300 nm from the grain-boundary phase.