The strength degradation test of returnable glass bottles was carried out over ten years with emphasis on the bursting strength, thermal shock resistance, internal pressure-thermal shock strength and so forth. The results obtained are summarized as follows:
1) The strength of bottles decreased rapidly during the first three or four years and level off.
2) In bursting strength test, the fracture origin was dependent significantly on the degree of ellipticity of the side wall, and the relationship between the internal hydraulic pressure P(kg·cm^-2) and the length of crack developed to the branch point L(cm) was given by the following equation, P⋅L^0.48≅81
3) When the internal pressure and thermal shock were applied simultaneously to the bottles, a linear relationship was obtained between the internal pressure and the thermal shock (temperature difference) at the bottle breakage.
Furthermore, pattern of fracture, situation of fracture origin, distribution of tensile strain have been investigated. Based on the experimental results elasto-mechanical analysis has been developed.

View full abstract

Solid state reactions between sintered Nb₂O₅ and five kinds of Al₂O₃-CaO compounds (3CaO⋅Al₂O₃, 12CaO⋅7Al₂O₃, CaO⋅Al₂O₃, CaO⋅2Al₂O₃, CaO⋅6Al₂O₃) have been studied at the temperature range from 1225°C; to 1300°C; in air. The reaction products formed at the interface of each reaction were examined by using EPMA and X-ray diffraction. In the cases of the reactions between Nb₂O₅ and three compounds, namely, 3CaO⋅Al₂O₃, 12CaO⋅7Al₂O₃ and CaO⋅Al₂O₃, three kinds of Nb₂O₅-CaO compounds (CaO⋅Nb₂O₅, 2CaO⋅Nb₂O₅, 3CaO⋅Nb₂O₅) were formed by the one-way diffusion of CaO into the Nb₂O₅. While, the reactions between Nb₂O₅ and the other compounds, CaO⋅2Al₂O₃ or CaO⋅6Al₂O₃, yielded CaO⋅Nb₂O₅, 2CaO⋅Nb₂O₅ and Al₂O₃⋅Nb₂O₅ by the one-way diffusion of Nb₂O₅ into the Al₂O₃-CaO system. The prismoidal and tabular CaO⋅Nb₂O₅, the tabular 2CaO⋅Nb₂O₅ and the spherical Al₂O₃⋅Nb₂O₅ having the particle size of 2-3μm, were distributed in the reaction layers. The reaction rate “x” followed the parabolic law “x²=2Dt”. The rate of the reactions of the former compounds (3CaO⋅Al₂O₃, 12CaO⋅7Al₂O₃ and CaO⋅Al₂O₃) were smaller than those of the latter compounds (CaO⋅2Al₂O₃ and CaO⋅6Al₂O₃).

View full abstract

Mixtures of natural kaolinite and carbon black were heated between 1350°C; and 1500°C; for 0 to 4h in flowing nitrogen to obtain sialon powders. The carbon contents in the mixtures were 18.87 and 20.37wt%. With increasing heating time the residual carbon content in sialon powder decreased and the nitrogen content increased. The reduction and nitridation of kaolinite took place simultaneously during heating. The evaporation of SiO was observed during heating. The ratios of silicon to aluminum contents in sialon powders, obtained under various conditions, were around that of β-sialon with z=3.2. On the other hand, the ratios of nitrogen to oxygen contents depended largely on the reaction conditions. It was possible to obtain powders which were mostly composed of β-sialon.

View full abstract

The thermal conductivity (λ_F) of alumina and zirconia fibrous insulators with various bulk densities was measured by the hot wire method between room temperature and 1400°C in air. The thermal conductivity of as-received alumina fiber which consisted of δ-Al₂O₃ phase increased with increasing temperature. The temperature dependence of thermal conductivity of alumina fibers heated at temperatures above 1250°C having densities larger than 0.2g/cm³, showed parabolic curves with a minima between 300°C and 500°C. It was found that the difference in temperature dependence of thermal conductivities was caused by the transformation of δ-Al₂O₃ into α-Al₂O₃ which has a high thermal conductivity in the low temperature region. The thermal conductivity of zirconia fiber increased with increasing temperature as in the case of δ-Al₂O₃ fiber. The low bulk density ceramic fibers showed high λ_F-values at high temperatures due to the contribution of thermal radiation, while at low temperatures λ_F-values were small. The polycrystalline fibrous insulators such as alumina and zirconia fibers showed λ_F-values lower than those of glassy one such as kaolin wool in the high temperature region because of the reflection of radiation at the fiber surfaces. The following experimental relation between λ_F (thermal conductivity) and θ (temperature) was obtained for fibrous insulators:
λ_F=a⋅exp(bθ).
It was found that a certain relationship exists between the constants a and b and the volume fraction of fiber. The λ_F-value and its temperature dependence of δ-Al₂O₃ ceramics were estimated on the basis of the relation.

View full abstract

Two kinds of phenol resins (resol- and novolac-type) and the fractionated pitches (benzene-soluble, benzene-insoluble/pyridine-soluble and pyridine-insoluble pitches) were mixed in an equal weight ratio by two different methods, mechanical-mixing and solvent-mixing. An agate mortar was used in the former, while pyridine was employed as a solvent in the latter. The mixtures were carbonized up to 600°C after curing at 120°C and post-curing at 200°C. The microtexture of these carbonized samples were examined under a polarized light microscope. The carbonized samples prepared by the mechanical mixing showed a heterogeneous texture, consisting of anisotropic regions of the pitch and isotropic enclaves of the resin, which suggests the independent carbonization of pitch and resin. On the other hand, the solvent-mixing technique was found to be necessary for obtaining a homogeneous texture of pitch-phenol resin carbons. The carbon with a fine mosaic texture was obtained from the mixture of benzene-soluble pitch and resol-type resin, although the carbonization of the pitch or resin itself gave a coarse mosaic or isotropic texture, respectively. It was observed that the carbonized mixture of benzene-soluble pitch and novolac-type, and of bezene-insoluble/pyridine-soluble pitch and resol-type resin had an isotropic texture. The present results suggest the possibility for controlling the microtexture and also the size of domains of fine mosaic texture of carbons, if the solventmixing method is applied to the pitch-resin systems.

View full abstract

The conductivity-temperature characteristics of anatase was found to have hystereses, and these behaviours were explained by the two kinds of chemisorbed oxygen ions, one of them predominates at the temperature below 300°C and the other is present at 700°C. The conductivity-oxygen partial pressure characteristics of anatase was also measured, and the results showed two kinds of dependence of σ on P_O2 i.e. in the range of P_O2 above 0.3Pa, σ increased with decreasing P_O2, and below 0.3Pa, σ was independent of the decrease in P_O2. The above dependence in high P_O2 region was affected by the microstructure. The results of isotopic exchange showed two kinds of oxygen releases. These results were able to be explained by the presence of the chemisorbed oxygen.

View full abstract

Float glasses and non-float glasses were examined for their residual surface stresses by both Sénarmont biascope and cross section photoelasticity techniques. Most surfaces gave compression stresses. However, biascope gave far higher stress values than cross section photoelasticity. This suggested the existence of very thin low-expansivity layers on the surfaces. The layers seemed to originate from Na⁺ or Na₂O out-diffusion or evaporation during manufacturing processes.

View full abstract