In this study we undertookto examine the possibilities of obtaining magnetic crystalline materials by the crystallization of the Na₂O-Fe₂O₃-NiO-B₂O₃-P₂O₅ glass or glass-ceramics and of forming the melts into desired shapes by the ordinary glass-forming technique. The composition of the melts studied were: 10-20mol% Na₂O, 25-35mol% Fe₂O₃, 10-20mol% NiO, 10-40mol% B₂O₃ and 10-45mol% P₂O₅. The magnetic properties, electrical conductivity and dielectric relaxation were measured in the quenched and crystallized specimens of Na₂O-Fe₂O₃-NiO-B₂O₃-P₂O₅ series. The results obtaind are as follows:
1) The melts of the compositions: 10-20mol% Na₂O, 25-30mol% Fe₂O₃ 10-20mol% NiO, 10-40mol% B₂O₃ and 10-45mol% P₂O₅ could be formed into desired shapes during cooling, and some quenched specimen showed magnetization.
2) Magnetization of glass-ceramics increased with the content of Fe₂O₃; the maximum was found at the composition ratio B₂O₃/B₂O₃+P₂O₅≅0.56-0.85. The intensity of magnetization of No. 7 (quenched specimen) reached 25emu/g at the field of 6500 Oe.
3) The existence of crystallites of spinel-type ferrites such as γ-Fe₂O₃ and NiFe₂O₄ was confirmed by chemical analysis, Curie point, X-ray analysis and IR spectra in some quenched specimens containing a high amount of Fe₂O₃ and a relative high amount of NiO.
4) The type of precipitated crystal in No. 14 specimen changed from γ-Fe₂O₃ to α-Fe₂O₃ and then to NiFe₂O₄ as the heat treatment temperature increased.
5) In the d.c. conductivity of the quenched specimens, very high conductivity was observed at the composition containing the γ-Fe₂O₃. An anomalously large dielectric relaxation spectrum was observed in the 20Na₂O⋅25Fe₂O₃⋅10NiO⋅25B₂O₃⋅20P₂O₅ glass-ceramics.
The origin of magnetic properties was related to the formation of a microstructure such as γ-Fe₂O₃, α-Fe₂O₃ and NiFe₂O₄ in the glassy matrix. The formation of a microstructure like this was considered to cause the anomalous behavior of the electrical properties.

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Ferroelectric layer-structure Bi compounds given by a general formula (Bi₂O₂)²⁺(Me_m-1R_mO_3m+1)^2- are useful for piezoelectric and pyroelectric materials. This study was undertaken to investigate the fundamental conditions for obtaining ceramics of these compounds with their polar axes oriented in parallel by unidirectional solidification of their melts. Each of the batch mixtures of seven Bi compounds given in Table 1 was sintered at 1050°C in a Pt crucible, and then melted except the lowest part 2-3mm thick in a temperature gradient furnace shown in Fig. 1. The temperature at the top of the crucible was maintained higher by 170°C and that at the bottom lower by 70°C than the liquidus temperature of the respective composition for 2h. Then both the temperatures were lowered at the same rate of 5°C/h to solidify the melt upwards at a rate of 0.7mm/h. The thermal gradient in the melt was kept at 70°C/cm during the solidification. The lowest part of the sintered batches left unmolten acted as seed crystals. All the ingots were composed of many columnar crystals (Fig. 2) of the layer-structure Bi compounds with their a- or b-axis, polar axes, oriented along the solidification direction (Fig. 3 and Table 3). The ingots of the compositions with high m values had a considerable amount of cavities (Fig. 4 and Table 3). These cavities were identified as shrinkage pores caused by cellular growth of the constituent crystals (Fig. 8). These could not be completely eliminated by the increase in the thermal gradient from 70° to 140°C/cm (Fig. 5 and Table 4). The ingots of the compositions with low m values were almost free from such cavities, but had an appreciable amount of microcracks (Fig. 4 and Table 3). The cause of these microcracks was attributed to thermal stresses due to anisotropic thermal shrinkage of the constituent crystals during their cooling from the solidification temperature (Table 7). Formation of the microcracks could be suppressed effectively by the addition of 0.12PbO, 0.10Bi₂O₃ and 0.18B₂O₃ to the (Bi₂O₂) (PbNb₂O₇) in molar ratio and by the increase in the solidification rate from 0.7 to 1.4mm/h (Figs. 6 and 7, Tables 5 and 6). In these cases, a thin glassy film formed at the grain boundaries of the columnar crystals relieved the thermal stresses by its viscous flow (Fig. 9).

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Mixtures of agglomerated fine alumina and granulated zinc oxide were heated at temperature between 800°C and 1200°C for various hours. The fraction of the ZnAl₂O₄ formation reaction was determined and also the microstructures were examined. Zinc aluminate was formed in the agglomerated alumina around the granulated zinc oxide and the product layers were grown according to the diffusion law. Diffusion constants were calculated from the thickness of the product layers. Activation energy of the diffusion varies from 23.2kcal/mol at temperature between 800°C and 900°C to 42.6kcal/mol at temperature between 1000°C and 1200°C. Jander plot gave convex curve with decreasing slope with time because of the decrease of the contact area, the consumption of the one of the reactants for the inhomogenity of the mixture and the particle size distribution of the reactants. The rate constants determined from the initial slope of the Jander's plot gave the activation energies of 20.0kcal/mol at temperature between 800°C and 900°C and 40.0kcal/mol at temperature between 1000°C and 1200°C which agreed well with the activation energies of the diffusion determined from the thickness of the product layer in the alumina agglomerates. The activation energies of Jander's rate constant for the system with agglomerated alumina was classified into the group of low values of the activation energies reported on the zinc aluminate formation. Discussions were extended to the cause of the lowering of the activation energies of the Jander's rate constant in the system of incomplete mixing which consists of alumina agglomerates and granulated zinc oxide. It was estimated that the increase in the contribution of the surface diffusion process and grain boundary diffusion process in combined diffusion process was a cause of the lowering.

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Hot grinding is applied in the steel snagging operation for energy saving. High hot-strength is required for the grinding wheel to secure safety. Practically, the 25% and 40% zirconia-alumina wheel types and the sintered high impurity alumina wheel are widely used. However, only little is published on their high temperature properties. The bending creep is studied for various resinoid wheel sticks at the temperatures up to 300°C using the 5mm-thickness and 100mm-length test specimen. The static bending test was also made for the same wheel types as a reference. The following results were obtained. The creep rate is generally low at the temperatures below about 200°C, but increased sharply at higher temperatures. The zirconia-alumina wheel types, NZ or AZ 77, show much higher creep resistance than the alumina wheel types, A or WA. The SR-alumina wheel is found to have the same level of creep resistance with the zirconia-alumina wheels. The creep characteristic was correlated well with that of static creep resistance, but the grain size has no significant effect on the creep resistance. Vitrified wheel does not show creep even at 300°C.

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Solid state reactions between sintered Nb₂O₅ and three kinds of Al₂O₃-Y₂O₃ compounds (5Al₂O₃⋅3Y₂O₃, Al₂O₃⋅Y₂O₃, Al₂O₃⋅2Y₂O₃) have been studied at the temperature range from 1250°C to 1325°C in air. The reaction product formed at the interface were examined by using EPMA and X-ray diffraction. The following results were obtained:
Al₂O₃⋅Nb₂O₅ and Y₂O₃⋅Nb₂O₅ were formed by the one-way diffusion of Nb₂O₅ into the compounds in the system Al₂O₃-Y₂O₃. The ellipsoidal particles of Al₂O₃⋅Nb₂O₅ and the spherical particles of Y₂O₃⋅Nb₂O₅ were unevenly distributed with the aggregation state in the reaction layers. The observed separation of reaction couples was probably due to the difference of thermal expansion coefficients between the reaction products and Nb₂O₅. The reaction rate “x” followed the parabolic law “x²=2D_Nbt”, and the apparent activation energy was 90-95kcal/mol.

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This paper discusses an MHD generation channel wall that is made of refractory ceramics. Authors have invented a channel wall that has buffer layers between wall elements and holders. This buffer layer has an important role for avoiding fracture of the element by thermal stress which occurs from restriction of thermal deformation of the element. A wall model is composed for obtaining the thermal resistance of the buffer layer. A buffer layer of the model is consisted to an adhesive layer and a buffer body. The adhesive layer is made of a copper plate, which is 0.3mm thick, and adhered to the element by Refractory Method. The adhesive layer is consisted to three layers, i.e., Cu, Cu₂O and CuO. These three layers seems to give rise to the thermal resistance. The buffer body is made of nickel wires of which radious is 0.4mm and purity is 99.7%. All of the nickel wires are assembled in one direction which is parallel to a center line of the element, and bundled all together. Occupation ratio of nickel is about 78% in a sectional area of the buffer body. One end of the buffer body is soldered to adhesive layer by silver solder and opposite end is soldered to holder by lead solder. An element of the model is made of magnesia ceramics of which purity is about 99.9% and porosity is about 3%. A holder of the model is made of copper block. Results are as follows:
(1) Thermal resistance of the buffer layer is from 1.9 to 2.5K/(W/cm²).
(2) Thermal resistance of the adhesive layer is from 0.43 to 0.87K/(W/cm²).
(3) Thermal resistance of the buffer body is calculated to about 0.7K/(W/cm²) under the estimation at which the heat flows in the nickel wires only.
(4) From above results, thermal resistance of silver soldering layer seems to be same as that of the adhesive layers.
The buffer layer needs more value of the thermal resistance in order to apply to the MHD generation channel. Value of the thermal resistance is easily satisfied by changing of material of the buffer body, increase of thickness of the buffer layer and etc. Then this wall appears to be useful to an MHD generation channel wall.

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Surface optical waveguide effect of a glass ware, if any, enables non-destructive photoelastic surface stress measurement by refractometry or by biascope technique. Glass bottle, cup, tube, bulb and pressed ware were examined by laser beam injection and they all gave surface optical waveguide effects. The effects were attributed to striation layers near the surfaces. Some of refractometer patterns and biascope patterns were presented.

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