Densification processes and microstructural changes of kaolin bodies during firing were examined and their co-relations were discussed.
From the results of the firing shrinkage, bulk density and apparent porosity measurements, following results were obtained. Degree of densification increased with the temperature. The longer the grinding time of the kaolin, the lower the densification of the bodies when fired at 1000°C. However, when fired at temperatures higher than 1100°C, the effect of grinding time on the densification of kaolin resulted inversely.
Shrinkage behaviours were also examined kinematically, and the following results were inferred. The kaolin body shrank at about 500°C, 900°C and 1100°C. Shrinkage occurred at about 900°C might be due to the diffusion sintering process of metakaolin grains. Shrinkage occurred at slightly lower temperatures than 1100°C might be attributed to the viscous flow mechanism and partly diffusion process in the spinel intermediate phase.
Microstructural changes of the fired bodies were also examined by means of X-ray diffraction, polarizing microscope and scanning electron microscope. Further, it was shown that the densification processes and accompanied phenomena of the fired bodies were clearly explained by these microstructural observations.

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The reactivity of phosphoric acid and dihydrogen phosphate additives with expanded vermiculite aggregates and with bond clays at firing temperatures of 800° and 1000°C was investigated from the measurements of X-ray diffraction, water absorption and pH value. The aggregates were prepared by the calcination at 1050°C of the vermiculites from Fukushima Prefecture, Japan and from Palaboroa area, N. E. Transvaal, S. Africa. The bond clays were Mitsuishi-pyrophyllite from Okayama Prefecture and kibushi-clay from Aichi Prefecture. The effect of the additives on the compressive strength of fired insulators of the expanded vermiculite-bond clay system is discussed in connection with the above reactivity investigation. A remarkable increase in strength was observed when magnesium dihydrogen phosphate was added as an additive: The strength was about 22kg/cm² for the test-specimens obtained by the firing at 1000°C of the mixture of 15 expanded vermiculite, 10 kibushiclay and 75 pyrophyllite by wt%, whereas the strength of about 39kg/cm² was achieved when 1.5wt% magnesium dihydrogen phosphate was added into the mixture. This is attributed to the formation of bridge bonds due to both reactions of magnesium dihydrogen phosphate with magnesium oxide component in vermiculites and with aluminum oxide component in bond clays. Little or no change in strength was observed when aluminum dihydrogen phosphate was added. This is connected with the X-ray diffraction evidence that aluminum dihydrogen phosphate does not appreciably react with vermiculites though reacts with bond clays. The thermal conductivity shows a small decrease with increasing the content of additives. This corresponds to the porosity increase due to the dehydration condensation of the additives on firing.

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四塩化珪素とアンモニアとの気相反応による窒化珪素合成反応を, 1050°-1500℃で行ない, 生成物の構造を, X線回折, 赤外吸収スペクトル, 化学分析, 電子顕微鏡により調べ, つぎの結果を得た.
(1) 気相反応の生成物は, Si(NH)₂, Si₃N₄H₃, (SiN)₂-NHのような組成をもち, 過剩のNとHとを含む非晶質物質である. 過剩のNとHの含有量は, 反応温度が高くなると小さくなる.
(2) 生成物は, ほぼ球形で, 粒径が10-100mμの微粒子であった.
(3) 約1400℃での加熱処理により, 生成物はNH₃を放出してα-Si₃N₄へ結晶化する. しかし過剩のNとHの分解は非常に遅く, NH結合は熱的にかなり安定である. これに対して, 低温生成物のSi(NH₂)₄は, 熱処理によって比較的容易に窒化珪素へ変化する. 高温気相反応生成物の窒化珪素への変化が遅いのは, その構造の不規則性に関係していると推定される.
(4) Si(CH₃)₄とアンモニアの反応生成物も, 四塩化珪素の場合と同様に非晶質物質であった. しかし, この場合には加熱処理により, α相に加えてβ相の窒化珪素の生成が認められた.

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The growth rate of silver halide (AgX) liquid particles was measured in the alkali alumino borosilicate glass which could be converted to the photochromic glass with excellent light sensitive properties by appropriate heat treatment.
The size of AgX liquid particles was mainly determined using X-ray line broadening technique assuming the size of liquid particles is equal to that of AgX crystallite found in quenched glass. Three compositions of particles, AgCl, AgCl_xBr_1-x(x-0.79) and AgBr, were selected for measurement. The results were summarized as follows.
(1) The maximum temperature below which the particles could deposit depended upon the composition of liquid. It was approximately 940°C in AgCl, 980°C in AgCl_xBr_1-x(x-0.79) and 1080°C in AgBr, respectively.
(2) Mean diameter of liquid particles of AgCl and AgBr increased in proportion to the cube root of heating time except initial period of time. In consequence the growth was considered to be performed according to the principle that larger particles grew by the dissolution of smaller ones. In case of AgCl_xBr_1-x(x-0.79), the growth rate of liquid particles was smaller at lower temperature and larger at higher temperature than that expected from the cube root relation.
(3) The growth rate for mean volume of liquid particles was approximately expressed by following equation, respectively.
AgCl (510°-600°C)
v/t=4.99×10²exp-92500/RT (cm³⋅sec^-1)
AgCl_xBr_1-x(x-0.79) (530°-700°C)
v/t=1.00×10²exp-96100/RT (cm³⋅sec^-1)
AgBr (585°-705°C)
v/t=1.74×10^-3exp-80000/RT (cm³⋅sec^-1)

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Stress distribution in severely quenched thick plate glasses was examined. Three kinds of glasses (thermal expansion coefficient: 37-94×10^-7/°C) were quenched by air blast from softening ranges of temperature. Photoelastic observations indicated that: 1) Stress distribution in the direction of thickness was not parabolic; stresses and stress gradients were extremely high near the blasted surfaces, 2) Stress distribution was not simple; in some blasting conditions tension at surface layers and saw-teeth-shaped stress distribution were found; 3) The glass with relatively low thermal expantion (60×10^-7/°C) could be stressed as effectively as a soft lead glass; glass transition temperature multiplied by expansion coefficient seemed to be a measure of possible stressing.
Thus we have found non-parabolic stress distribution which had been forecast theoretically but not found experimentally. The results indicate that stress distribution depends on both the degree of air quenching and the deformation of glass plate during blasting.

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ThO₂-YO_1.5系固溶体はイオン正孔複合伝導性を示す. イオン伝導度は酸素欠陥濃度に比例し, 正孔伝導度はPO₂^1/4に比例する. 正孔は,
1/2 O₂(g)+Vo¨=Oo^x+2h^.
で生成するので, 正孔濃度は[Vo¨]^1/2に比例する. イオン伝導度σ_iと正孔伝導度σ_hが等しくなる酸素分圧P₊は, 従来考えられていたモデル-正孔伝導度が正孔濃度に比例する-では
P₊∝[Vo¨]²
となり, 高濃度の酸素イオン欠陥を持つ固溶体での実験値,
P₊∝[Vo¨]^3.3
に合わない.
高濃度の酸素イオン欠陥を持つ物質で, 欠陥が正孔の散乱中心であると考えると, 理論式は
P₊∝[Vo¨]^10/3
となり極めて良い一致を示す. 低濃度の酸素イオン欠陥を持つ固溶体の場合には, 酸素イオン欠陥以外の散乱中心を考える必要がある.

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