Synthesis of long chrysotile fibers was studied under hydrothermal dehydration process with an addition of magnesium iodide which had the same structure as the bromide and was found to be effective in the formation of the fibers.
In this experiment free iodine appeared in the slurry by decomposition of hydrogen iodide formed by hydrolysis of magnesium iodide. When the slurry was subjected to hydrogen pressure at initial stage of the reaction, satisfactory results were obtained. The product was a layer like natural chrysotile ore bundled from fibers of the almost same length. Therefore, it was deduced that iodide contained in the intermediates was easily dissociated and the bundling of fibers was carried out at a smaller degree of disturbance as compared with the bromide.
Crystal growth may be controlled by initial hydrogen pressure and dehydration velocities. The velocities were also controlled by the reactivity of metallic iron added to the outside of the slurry container.

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A glass containing Li₂O, Al₂O₃ and SiO₂ as the principal components and P₂O₂ of about 2 wt% and TiO₂+ZrO₂ of about 4 wt% as the so-called nucleating agents can be converted by suitable heat treatment to a transparent glass ceramic material whose average transmission of 5mm thick plate is 80% or over in visible region. It is the purpose of present paper to examine the structural change of the glass during the heat treatment putting the stress on the nucleation phenomenon.
The study was made by electron microscope observation (mainly direct transmission method), electron and X-ray diffraction methods, differential thermal analysis and measurement of thermal expansion coefficient. The results are summarized as follows:
1) The tendency toward phase separation of glass was increased by the addition of nucleating agents.
2) The crystalline nuclei whose mean diameter was 30-80 Å were confirmed to precipitate before the main crystals-β-Quartz solid solution-crystallize out. The position of diffraction peak due to the nuclei in both electron and X-ray diffraction patterns agreed with that of the strongest one of ZrO₂ (cubic system) or ZrTiO₄.
3) It was found that some incubation period (about 40 min at 750°C) was required for the nuclei to precipitate and thereafter the nuclei tended to grow by the diffusion controlled mechanism and to approach to a certain constant size. The higher the temperature at which the glass was heat treated, the larger was the mean size of nuclei.
4) The approximate number of nuclei per unit volume was of the order of 10¹⁶-10¹⁷ and the volume fraction seemed to be less than 2%.
5) The mean size of main crystals which was estimated from the broadening of X-ray diffraction peak increased with increasing heat treatment temperature and time, depending more strongly upon the temperature.
6) The degree of crystallinity which was calculated using an equation proposed by Ohlberg et al. increased in S-shape with increasing heat treatment temperature and time. This change was similar to that in thermal expansion coefficient.
7) A probable mechanism for formation of main crystal was suggested, that is, the region which is close to main crystal in composition but still remains in amorphous state is formed first around nucleus and then the region transforms rapidly to crystalline state after it grew to fairly large size in comparison with nucleus.
8) It was also elucidated that probably one main crystal was formed from one nucleus by the analysis of the relationship between the number of nuclei per unit volume, the mean size of main crystals and the degree of crystallinity which were determined independently each other. This seems to be supported by the direct observation of thin glass films by electron microscope.

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紫外線透過率がたがいに異なる数種のガラスフィルタを光源との間に入れて, 3種の商用硼珪酸ガラスを紫外線で1,000時間照射した. 照射された面に発生した応力は, 使用したフィルタの220mμにおける透過率とほぼ比例した. それゆえ, 220mμあるいはそれ以下の短波長の光が応力を発生させると考えられる. この波長域の光は, 厚さ0.2mmのガラスでほとんど吸収される. それゆえ, 光子エネルギーを吸収することと, そのエネルギーがあるしきい値を超えるごととが反応開始に必要であるという, 光化学の基本原則はこの場合にも満たされている. また, 220mμは5.7eVの光子エネルギーに相当するので, 上記の実験結果は, 応力発生過程は非架橋酸素イオンの励起 (必要な最低エネルギーは4.5eV) またはイオン化 (必要な最低エネルギーは5.5eV) から始まるという, 著者らの提出した仮説とも適合している.

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アルミニウム, シリコン, チタニウム, ハフニウム, ジルコニウムの窒化物をプラズマトーチを用いて合成した. プラズマトーチは陽極が水冷された銅製の坩堝で, 陰極はタングステン棒である移送型として用いた.
作動ガスである窒素は, また反応物として用いた. 合成は窒素雰囲気中で常圧で行なわれた. 合成したAlN, TiN, ZrN, HfN, Si₃N₄はそれぞれ灰白色, 褐色, 褐色, 黄褐色, 白色を呈した. またX線回折によれば六方晶, 立方晶, 立方晶, 面心立方晶, 六方晶とそれぞれの結晶に同定された. AlNは最も容易に合成されたが, Si₃N₄は困難であった. これら5つの窒化物の合成は, 従来の方法によるものよりもはるかに短時間で行なわれた. すなわちAlNでは4-7分間, 他の4つは20-30分間であった.
TlNの結晶成長は光学顕微鏡によれば, 骸晶から出発して樹枝状結晶へと成長したと思われた.
熱天秤, 高温X線回折によれば, AlNは空気中でAl₂O₃に変化しながら, 700℃から徐々に酸化され, 1000°-1200℃で急激になり, 再び1200°-1350℃で徐々に酸化された.
AlNは他の窒化物より熔融ガラスに濡れにくかった.

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The relationship between the growth temperature and the polytype of SiC crystals has been studied experimentally in the range from 2200°C to 2600°C at the condition of low supersaturation.
The results are summarized as follows;
1) In all region of the present experiments, excluding one example in which 4 H-type was involved, the structure of all crystals consisted of 6H-, 15R- and other long c-period types exceeding 21. Among the elemental structures of SiC, 2H, 3C, 4H, 15R, 6H, and 21 R, only the 6H and 15R were found.
2) From the results stated in 1), it was concluded that in the range of 2200°-2600°C, 6H and 15R have the most thermal stability among the structures considered as elemental. In this conclusion, however, the effect of impurity in the crystal and the shift from the stoichiometry were neglected.
3) The relative amount of 15R increased with decreasing temperature; 6H showed an opposite tendency.

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In the previous paper, the authors confirmed that addition of glass powders rich in BaO and TiO₂ to BaTiO₃ crystal powders was effective to extend the firing range of the pressed mixture and to obtain BaTiO₃ ceramics with dielectric properties little influenced by sintering temperature (J. Ceram. Assoc. Japan 75, 278 (1967)). In the present study, temperature characteristics in dielectric properties were measured at 1 kc/sec (applied voltage, 2V) by means of Bridge method in the cooling process of the specimens from 160°C to -60°C. On the same specimens, observation of microstructure by electron microscope was made in order to investigate structure dependency of the temperature characteristics.
The results obtained are summarized as follows: 1) By addition of glass powders of a BaO-Mg(Ca)O-TiO₂-SiO₂-Al₂O₃ system, the BaTiO₃ ceramics with temperature characteristics of dielectric properties little affected by sintering temperature were able to be prepared. 2) The temperature characteristics in dielectric properties of the BaTiO₃ ceramics thus prepared are much influenced by the composition of the glass powders added. The MgO component is especially effective in decreasing the temperature changes of their dielectric properties. 3) Addition of the MgF₂ crystal powders together with the BaO-TiO₂-SiO₂-Al₂O₃ glass powders (glass 7.5, MgF₂ 2.5 by wt%) to BaTiO₃ powders is effective in decreasing temperature changes of dielectric properties and also in raising dielectric constant near room temperature of the BaTiO₃ ceramics. 4) Effects of addition of the glass powders on temperature characteristics of dielectric properties can be reasonably explained on the basis of the electron microscopic observation of the microstructure of the specimens.

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Zirconium diboride (ZrB₂) was deposited on the heated graphite substrate by the chemical vapor reaction of zirconium tetrachloride, boron trichloride and hydrogen. Under certain condition, the resulting deposit was found to have a high density (higher than 99% of theoretical density), a high purity (total impurity less than 100ppm), a high hardness (H_V=2200±100kg/mm²), and to have a preferred orientation in which the (110) or (100) plane of the ZrB₂ crystalline lied parallel to the surface of the graphite substrate.

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