From a viewpoint of the treatment of high level radioactive liquid waste, the immobilization of barium ion from an aqueous solution was studied by using two kinds of crystalline hydrated titania fibers, H₂Ti₄O₉⋅nH₂O and H₂Ti₂O₅⋅nH₂O, as the cation adsorbent. The saturated uptake of barium ions from barium hydroxide solutions gave 4.88meq/g on the H₂Ti₂O₅⋅nH₂O adsorbent and 2.66meq/g on the H₂Ti₄O₉⋅nH₂O adsorbent. The barium ions adsorbed on the former adsorbent were immobilized into a mineral assemblage consisting of BaTi₄O₉ and rutile, and those on the latter one were immobilized into a mineral assemblage of BaTi₅O₁₁, BaTi₄O₉ and rutile at calcination temperatures up to 1100°C. However, the BaTi₅O₁₁ phase was thermally decomposed into BaTi₄O₉ and rutile by calcining at 1200°C. The leachabilities of barium ions in these immobilizers were measured at 25°C under normal atmospheric conditions using distilled water. The results indicated that the Ba-immobilizers are very stable with high leach resistance of maximal 2.7×10^-9g/cm²·d

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A nano second pulse radiolysis was applied to K₂O⋅2B₂O₃ and Na₂O⋅2B₂O₃ glasses. In both glasses the induced absorption intensities were lowered and the decay was accelerated with increasing temperature. At 400°C the intensity of the absorption of the former glass was largely lowered in 1.5μs after irradiation. The decay process was described by a diffusion limited recombination of the short lived component around 1.6eV with the non-bridging oxygen hole center produced on irradiation at the same time. The activation energy of the rate process showed a break around 300°C (lower limit of the glass transition).

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The sintering mechanism of the compacts formed by tapecasting a plate-like Bi₄Ti₃O₁₂ powder was studied by densification measurement and microstructure observation. The sintering behavior is characterized as follows: the dominant mechanism responsible for densification is particle rearrangement, which leads to well-oriented regions of grains and flat and elongated pores, whose long axes are parallel to the sheet plane. The increases in the size of the well-oriented regions and in the contact area between them break up pore connection, resulting in the formation of closed pores at a low density. Grain growth occurs above 1050°C and broadens the grain size distribution.

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The thermal shock resistance of ZrO₂ stabilized by oxides of rare earth element (La, Nd, Ce, Sm, Gd, Dy, Er, and Yb) has been investigated by subjecting disk-shaped specimens to a heat cycle of 1100°C/room temperature at a maximum cooling rate of about 500°C/min. Among these ZrO₂ ceramics, only ZrO₂-Yb₂O₃ system shows improved thermal shock resistance. Especially ZrO₂-8wt% Yb₂O₃ consisting of monoclinic and cubic phases exhibits thermal shock resistance superior to that of ZrO₂-7wt% Y₂O₃ commonly used in the thermal barrier coating for jet engine components. An increase in thermal shock resistance of ZrO₂-8wt% Yb₂O₃ is considered to have resulted from their smaller cubic phases compared with those of ZrO₂-7wt% Y₂O₃. Furthermore, the addition of 2wt% Al₂O₃ to the ZrO₂-8wt% Yb₂O₃ leads to a remarkable thermal shock resistance enhancement. The thermal shock resistance of ZrO₂ ceramics is associated with the volume change during the martensitic transformation of monoclinic→←tetragonal phase. The improved thermal shock resistance of ZrO₂-8wt% Yb₂O₃-2 wt% Al₂O₃ seems to be attributable to its morphology of small and isolated monoclinic grains in the matrix. On the other hand, ZrO₂-8wt% Yb₂O₃ with large agglomerated monoclinic grains is assumed to accelerate the initiation and propagation of cracks in the monoclinic grains during the martensitic transformation and consequently results in poor thermal shock resistance.

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Friction and wear properties of ceramics were measured by a pin-on-disk tester. Four of the most promising fine-ceramics, SiC, Si₃N₄, Al₂O₃ and PSZ were selected, and several samples of each with different raw powders, additives or sintering processes were used in this experiment. The coefficient of friction and specific wear rate were correlated negatively with Vickers hardness, and positively with fracture toughness of pin samples for sliding on each disk material. Positive correlation was also observed between coefficient of friction and specific wear rate. SiC pins showed the lowest coefficient of friction and specific wear rate, followed by Al₂O₃ pins. As Si₃N₄ pins showed a relatively higher coefficient of friction and specific wear rate, some improvement must be made for practical sliding part applications of Si₃N₄ ceramics. The coefficient of friction and specific wear rate of PSZ pins changed drastically according to disk materials, perhaps as an effect of their thermal conductivity. Wear of any ceramic pins except Al₂O₃ pins was lowest for sliding on SiC disk, followed by Si₃N₄, Al₂O₃ and then PSZ disk.

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High cordierite (Mg₂Al₄Si₅O₁₈) and its solid solutions containing Fe, Mn, Ga or Ge were synthesized, and axial thermal expansions of those crystals were measured by means of high temperature X-ray powder diffraction. Each isomorphous substitution caused characteristic modification of axial thermal expansions, and it was revealed that the expansion anisotropy and/or expansion coefficient of high cordierite were diminished by appropriate chemical modifications. The a-parameter increased while the c-parameter decreased with increasing substitution of Fe or Mn for Mg. The thermal expansion along the a-axis decreased, whereas the negative expansion along the c-axis increased to positive side with increasing substitution. The a- and c-parameters increased on the whole with increasing substitution of Ga for Al. However, the reproducibility in the lattice parameters of these syntheses was exceptionally poor. The axial thermal expansion behaviour of Ga-bearing crystals with increasing amount of substitution was almost identical to those of Fe and Mn-bearing crystals. The a- and c-parameters increased linearly with increasing substitution of Ge for Si. The negative thermal expansion along the c-axis further decreased with increasing substitution, however, the expansion along the a-axis varied in a complex manner depending on the amount of substitution.

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The thickness accuracy of the alumina ceramic green tape made by the doctor-blade method has been improved. Caluculated simulation was also undertaken to correlate with the experimental results, and a minimized thickness dispersion of the green tape was achieved by the following recommendations;
(1) low head of a slurry reservoir,
(2) relatively high slurry viscosity,
(3) thick doctor-blade,
(4) high carrier tape transfering speed,
(5) narrow clearance of blade.
These were equivalent to keep the viscous flow part small and to keep the drift flow part large. The experimental results corresponded to the simulation except the condition of 0.5cm doctor-blade thickness, because the edge effect of the blade-transitional flow flux into the slit of the 0.5cm thickness doctor-blade-is not negligible. The thickness dispersion of 6.2% was derived by substituting the fluctuation values of the actual machine and environmental conditions for the simulation formula. Smaller thickness dispersion (3%) in actual production was observed, probably because of the low probability of the combination of the maximum fluctuation values. The above recommendations give rise the following drawbacks which have to be overcome for more thickness accuracy.
(1) Low head brings upon the increasing ratio of head tolerance.
(2) High viscosity results in large viscosity dispersion due to the non-Newtonian slurry characteristics.
(3) Increase of carrier transfer speed leads to over-capacity of dry oven.
(4) Increase of blade thickness seems to lead to an improvement of the accuracy. However there might be a trade-off with the recomendation (1).
(5) Blade clearance should be reserved as an adjustment of the tape thickness.

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Particle induced X-ray emission (PIXE) analysis has been widely used in recent years. A major advantage of PIXE method is its ability to analyze many elements non-destructively at one measurement with high sensitivity. On the one hand, it is very important to develop the method of analysis of fine ceramic raw materials with high sensitivity since the species and the contents of trace elements in raw materials influence the quality of sintered products strongly. So, we tried to analyze trace elements in raw materials by PIXE method using 1-2MeV proton or helium ion beam from the Van de Graaff ion accelerator at GIRIN. In connection with the sample preparation, depth dependences of the proton energy and of the transmitted K X-ray yields of Ca, Fe and Zn were calculated for 2MeV proton bombardment on a MgO target. As a result, it was found that the specimen of 1μm thick was not thin enough for PIXE analysis of materials with an average atomic number of -10 such as MgO, SiC, Si₃N₄, Al₂O₃, etc. Since the average grain size of ceramic raw powders is about 0.1-1μm, it is difficult to prepare specimens thinner than 1μm without chemical treatment. In contrast, it is easy to prepare specimens thicker than 10.33mg/cm², the mean projected range of 2MeV proton in those compounds. Using thick samples, the differences of sensitivities between 2MeV proton and 2MeV helium ion induced X-ray spectroscopy and the effects of X-ray absorber on the sensitivities were investigated.

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Photochromism and photoconduction were investigated on the system CdO-B₂O₃-SiO₂. The optimum photoresponse was determined for various systematic substitutions. By irradiation of the darkening light having a wavelength near the absorption edge, an additional absorption was induced over almost the whole visible region. The photoinduced absorption lasted for a long time and its half fading time was 17h at room temperature in the dark. The optimum composition for photochromism was near the composition, 58CdO⋅25B₂O₃⋅17SiO₂ (mol%). Appreciable photocurrents were also observed as reported by Cáslavská et al., showed the best photoconductioe property. The electric conduction of these glasses was found to be electronic by thermoelectric power measurement, and the activation energy for electric conduction was around 1.8eV which was almost equal to half the optical gap. The compositional changes of photoconduction showed the opposite tendency to those of photochromism. In other words, the glasses exhibiting remarkable photoconduction had a weak photochromic property and vice versa. ESR measurements before and after exposure to UV light indicated that Cd⁺ ions (g=1.998) were responsible for the photochromic behavior. The ESR signal of Cd⁺ ions became larger with increasing photochromic property. On exposing to UV nonbridging oxygens bonding to a Cd²⁺ ion acted as electron donors and an activated electron was trapped by the Cd²⁺ ion. In the glass systems where R_1/2²⁺-OSiO₃ and R_1/2²⁺BO₄ tetrahedron and R_1/2²⁺-OBO₂ triangle coexisted, photochromic property became larger because electrons of oxygens localized due to steric hindrance, therefore, nonbridging oxygens donated an electron readily to Cd²⁺ ion. On the other hand, in the glass systems where many R_1/2²⁺-OBO₂ units and few R_1/2²⁺-OSiO₃ units coexisted, photochromic property became weaker because electrons of oxygens delocalized due to the B-O π bondines.

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Properties and sintering behaviour of twelve high purity (>99.8-99.99%) and fine (0.1-0.5μm) alumina powders were compared experimentally. Some powders contained small amounts of θ-Al₂O₃. In spite of the nominally “same high purity, fine powder”, apparent crystallite size of the α-Al₂O₃, specific surface area, distribution of particle size, and especially shape and appearance of particles of the samples differed considerably with samples. Green density of compacts and sintering behaviour of the samples also differed markedly with samples, and the difference might be explained by their shape and appearance of their particles. From the results obtained, the followings could be concluded. In order to produce dense high purity alumina ceramics, selection of its raw materials is effective means. Good sinterable high purity alumina powder might have following properties: It does not contain any relics of its precursor nor aggregations, and consists of separately isolated, massive, fine α-Al₂O₃ particles of 0.1-0.5μm. Their apparent crystallite size should be 1000Å or larger, and specific surface area of the powder should be 7-10m²/g. But when grain size of the particles is excessively uniform, the powder occasionally shows some tendency of excessive grain growth. The grain growth might be suppressed by addition of small amounts of MgO, i.e., 0.05wt%.

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