Platy α-SiC crystals, 2-3mm in diameter were obtained by the method. Growth experiments were performed using purified dense graphite crucible (bulk density>1.80) and high pure silicon as a solvent at 2200°C for 5 hours or less.
These crystals were consisted of mainly 6 H type. The probability to form wurtzite type twinning, the angle between basal plane being ca. 70°30′ in these crystals is less than that in these obtained by sublimation method.
Though some of the crystals include very thin silicon layer, generally these inclusions show a tendency to localize in a part of a crystal. Fine and dispersed inclusion such as carbon particle in the crystals by sublimation method is not observed in these crystals. The relation between the polality of the basal surfaces and their growth rate is studied by chemical etching, and it is suggested that there is reverse relation between crystals grown from silicon solution and sublimation.

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The authors have previously reported a structural studies of the glasses in the system As₂S₃-Sb₂S₃ and the analogous studies of the glasses in the pseudo-ternary system As₂S₃-Sb₂S₃-S are described in this paper.
Such properties as density, thermal expansion, infra-red absorption, vickers hardness, and extraction of ring type sulfur (S₈) with CS₂, have been measured for the As₂S₃-Sb₂S₃-S glasses and, in addition, X-ray diffraction studies of aAs₂S₅⋅bSb₂S₃ glasses (b/a=0/8, 1/7, 2/6, 3/5, 4/4, and 5/3) have been performed.
The radial distribution curve of the As₂S₅ glass was subtracted from the distribution curve obtained for each glass, taking into account the molecular content of As₂S₅. The first peak in the resultant curve is found to correspond in area to the sum of the peaks due to the Sb-S pair (2.54A) and the S-S pair (2.04A). It implies that the series of the As₂S₅-Sb₂S₃ glasses have the microheterogeneous structure composed of As₂S₅ and Sb₂S₃ regions that are joined together by the As-S-S-Sb linkages.
In addition to X-ray diffraction study, the results obtained from the study of other properties permit the following conclusion. When sulfur is added to the As₂S₃-Sb₂S₃ glasses (the microheterogeneous structure consisting of both As₂S₃ and Sb₂S₃ regions) it enters only into the As₂S₃ region. Subsequently the As₂S₃region alters to the As₂S_x(x>3) region whose structure is similar to that of the As-S glasses. Sulfur taken part in the As₂S_x(x>3) region exists only as the chain type sulfur in the composition range of small sulfur content but, at higher sulfur content, not only the chain type sulfur but also the ring type sulfur exists in the glass structure.
Consequently, in the system As₂S₃-Sb₂S₃-S, the glasses have the microheterogeneous structure composed of the As₂S_x(x>3) and Sb₂S₃ regions that joined together by the As-S-S-Sb linkages.

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V₂O₅燐酸ナトリウム系試料におけるV (IV) のESRスペクトルを測定し, バナジウムの溶存状態について検討した. その結果を総括すると次のようになる.
(1) V₂O₅を80mol%以上含むV₂O₅-NaPO₃系試料では, V (IV) はV-O-Vの網目構造中にあるものと, monomericでmodifierとして挙動するものがある. そして, このV-O-V網目構造中のV (IV) の電子は非局在化するが, monomericなV (IV) では電子は局在化しており, 他のV (V)の核スピンとの相互作用は小さい.
(2) 組成が塩基性になると, V (IV) はV-O-Vの網目構造中にあるよりもmonomericな状態の方が酸化反応に対して安定である.
(3) NaPO₃含有量の大きい組成では, V (IV) は前報の結果と一致して, monomericであり, その構造はバナジル錯体と同様にVO²⁺構造をとっている. このV (IV) の構造は組成あるいは塩基性の変化によってはほとんど変化しない.

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Crystallization of a glass having the composition SiO₂ 63.2, Al₂O₃ 20.1, MgO 2.6, MgF₂ 8.2, Li₂O 5.9% in weigt and some properties of the crystallized glass were investigated.
The results are summarized as follows;
1) Small unknown crystals of about 80 Å in size were already found in the original glass, which might have precipitated during cooling of the melt. Heat treatment of the glass caused first the precipitation of another kind of unknown crystal and subsequently the precipitation of the main crystal, that is, β-quartz solid solution. It was conjectured that the presence of the former crystals might have facilitated the crystallization of the latter crystal in the bulk of the glass.
2) Crystallization of β-quartz solid solution at 680°C and 700°C was easier at the surface than in the interior of the samples. At 740°C, however, little difference was observed in the amount of the precipitated β-quartz solid solution between the surface and the interior supposedly because of a rapid in increase of the amount of the crystal throughout the sample. β-quartz solid solution precipitated at 700°C transformed into β-spodumene solid solution at higher temperatures than 950°C.
3) The bending strength of the crystallized glass increased somewhat with time of heat-treatment at 680°C and 700°C, while no increase was observed at 840°C. The bending strength of the glass heated at 700°C for 5hours and then further heat-treated at 800°C, 900°C, 950°C or 1000°C for 3 to 8 hours was slightly smaller than that of the glass subjected to the only heat-treatment at 700°C. The bending strength decreased markedly upon heating up to 1050°C.
4) The thermal expansion coefficient of the crystallized glass was relatively low (3-7×10^-7/°C) when the glass was heat-treated at 800°C or 900°C after the heat treatment at 700°C for 5 hours and relatively high (23×10^-7/°C) when heat treated at 950°C. The thermal expansion coefficient decreased again slightly (18×10^-7/°C) when the glass was heat-treated at 1000°C and decreased markedly (0×10^-7/°C) when heat-treated at 1050°C.

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Structural changes in zirconia, induced with explosive shock treatment and mechanical grinding, were studied by powder X-ray diffractometry. As a result of these treatments, extensive broadening of diffraction lines and decrease of the intensity were observed. Considerable difference on the process of recovery in a series of successive annealings was found between specimens treated by both methods, respectively.
Transformation temperatures on monoclinic-tetragonal inversion in ZrO₂ were directly measured by high temperature X-ray technique. Lowering of the transformation temperature on heating was found on the zirconia mechanically ground for long period. While, on the explosively shocked zirconia, the transformation temperature shifted toward higher one on heating.
Distinct change of the temperature on cooling was not found on the both type of the specimens.

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The strength changes due to the “conversion” in alumina cement mortar have been investigated under various conditions, mainly on the stand point of the mineralogical changes.
The characteristics of the strength change have been found in the hardened alumina cement (Fig. 6.). The strength of alumina cement mortar or concrete decreased with the proceeding of the conversion reaction from CAH₁₀ to C₃AH₆. The strength reached the minimum value (point A in Fig. 6.), when the reaction had been completed, C₃AH₆ and AH₃ being the only observed hydrates. Thereafter, the strength increased again with aging time up to the maximum value, point B. Through the stage from A to B the species of hydrates did not change, but the crystals of hydrates grew up and formed a tight structure, resulting the increase in the strength above mentioned. During the further aging the strength diminished again gradually and reached a constant value, the hydrates changing into an unhydrated compound, C₁₂A₇.
These characteristic points, A, B and C, were plotted as functions of the temperature and the aging time in Fig. 7. From the Figure the following experimental equations were derived for each point,
A log t=10^1.87×T^-0.758 (1)
B log t=10^2.25×T^-0.806 (2)
C log t=10^2.51×T^-0.833 (3)
where, t=aging time (minute), T=temperature (°C).
From the equation (1) the term of strength-fall at 20°C is calculated to be about 76 years. Therefore, if the concrete made with alumina cement is kept at low temperatures, it is considerd that the decrease in long-term strength is very little at the practical point of view.
On the basis of these results, the test method for predicting the long-term strength was discussed.

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An orthorhombic aluminate named “granular phase” from its morphology has been found in the crystallization product of the melt with the composition approximate to the interstitial material of Portland cement clinker. The chemical composition of this phase is very similar to that of the prismaticphase, yet the granular phase can be readily distinguished from the prismatic phase under the microscope by its form, birefringence and the mode of twinning.
Both granular and prismatic phases are pseudo-cubic. The granular phase has an orthorhombic unit cell with the dimensions of 15.36×15.40×15.17ų, and the space group is Pbam or Pba2. The axes, a and b, of the granular phase lie diagonally to those of the prismatic phase when both structures are in corresponding orientation.
The prismatic and granular phases have been shown to be isomorphous with the lowand high-Na₂O forms of the orthorhombic C₃A in the C₃A-Na₂O system respectively. These isomorphous relations indicate that the existence of Na₂O is of primary importance to the stabilization of the anisotropic dark interstitial material in cement clinker, and that the granular phase contains more Na₂O than the prismatic phase. NC₈A₃, which may contain a small amount of SiO₂ as an indispensable constituent, is structurally referable to the granular phase or to the high-Na₂O form of orthorhombic C₃A.
In the granular phase as well as the prismatic phase, a topotaxial transformation into cubic C₃A caused by the vaporization of Na₂O at high temperatures was observed. A compositional transformation between the high- and low-Na₂O forms of orthorhombic C₃A also was suggested.

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