Surface crystallization of borosilicate glasses with the composition, xNa₂O⋅(30-x)B₂O₃⋅70SiO₂, zSiO₂⋅(100-z)/2(Na₂O⋅B₂O₃) and 70SiO₂⋅15B₂O₃⋅15Na₂O⋅y(Al₂O₃ or Fe₂O₃), was studied. The results were as follows:
(1) The rate of crystal growth seemed to be controlled by the volatillization of Na₂O and B₂O₃ components.
(2) Phase separation of the glasses increased the growth rate.
(3) Al₂O₃ addition decreased the growth rate, whereas Fe₂O₃ addition affected the crystalline habit.
(4) In the system xNa₂O⋅(30-x)B₂O₃⋅70SiO₂ the parameter x affected both the growth rate and liquidus temperature in a similar way.
(5) The crystals were in most cases cristobalite except in the cases of x≥27.5, in which β-Na₂Si₂O₅ was the primary and α-Na₂Si₂O₅ the secondary stable phase.

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The structure of the magnesium hydroxide layer which was produced by the vaporphase hydration on the {100} surface of magnesia single crystal was studied by using an SEM and X-ray diffractometers.
The orderly accumulation of small laminas of magnesium hydroxide with a considerable amount of cavities was observed in the layer.
The {100} planes of the original magnesia surface preferably formed the array which was parallel with the {101} planes of the resulting magnesium hydroxide layer and the {111} formed that with the (001).
On the basis of the assumption that the hydration preferably proceed on {111} magnesia crystal surface with the transformation of {111} planes of magnesia to (001) planes of magnesium hydroxide, a hydration model is proposed in order to explain the formation of the small laminas of the magnesium hydroxide, the growth of the magnesium hydroxide layer, and the parallel array of the planes.

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As₂O₃ glass was prepared by heating As₂O₃ in the evacuated, sealed silica-glass tube under the conditions given in Table 1, followed by quenching in water. Binary Na₂O-As₂O₃ glasses containing less than 50mol% Na₂O were prepared by melting the batches composed of As₂O₃ and NaAsO₂ in the evacuated, sealed silica-glass tubes for 15-30min at 700°C with subsequent quenching in water or acetone-dry ice mixture. Density, refractive index, thermal expansion, crystallization behavior and infrared absorption of the glass were measured.
The expansion coefficient of As₂O₃ glass was measured to be 37.3×10^-6/deg, which was much larger than that of B₂O₃ or P₂O₅ glass having a layer structure, and the infrared absorption peaks of As₂O₃ glass in a nujol mull were found at the positions entirely identical with those of arsenolite in a KBr pellet. The absorption peak at 600cm^-1 found for the KBr pellet was probably due to some mechanochemical changes of arsenolite which is considered to take place during pressing for pelletizing KBr. It was, therefore, inferred that As₂O₃ glass comprised a majority of As₄O₆ molecules and a small amount of layer- or chain-like linkage of AsO_3/2 pyramids distributed over at random.
In the composition region of low Na₂O content in the binary glass system, the glass showed rapid decreases in thermal expansion coefficient and molar volume with increase of Na₂O, and in its infrared spectrum a shoulder was found at about 830cm^-1. Moreover, when the glass was heated, the crystal of claudetite II as a metastable phase of the system was separated out of it. These revealed that the glasses changed the structure from that of As₂O₃ glass rich in As₄O₆ molecules into a layer network of AsO_3/2 pyramids with one or two nonbridging oxygens per each pyramid. The break of molar refractivity-composition curve at about 15mol% Na₂O was presumably due to the disappearance of As₄O₆ molecule in the network. The experimental facts that the crystal of NaAsO₂ was separated out of the glasses containing more than 20mol% Na₂O and the infrared spectra of the glasses with 40-50mol% Na₂O were similar to that for crystalline NaAsO₂, revealed the resemblance of the structure of glasses in the region of high alkali content to that of crystalline NaAsO₂.
It was assumed that As³⁺ ion was impossible to have tetrahedral coordination because of electrostatic repulsion between the nonbridging oxygen and the unshared electron pair occupying one of sp³ hybrid orbitals of As. This assumption was supported experimentally by the fact that T_g and M_g of the glasses in the composition region of low alkali content were considerably lower than those of As₂O₃ glass.

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数種類の系統の異なる炭素繊維を重クロム酸カリ/燐酸系酸化剤で酸化した.
反応性は大きな結晶子が密に充填している組織のものは小さく, 逆に小さな結晶子が疎らに充填している組織のものは大きい傾向を示した. 結晶子の大きさと組織の緻密性の他に光学顕微鏡ないし走査型電子顕微鏡で認められる規模の構造も反応性に関係する可能性がある. また不純物も影響しているとも思われる.
酸化によって弾性率は余り影響を受けないが, 強度は相当の低下を見る. しかしその程度は繊維によってまちまちで一様でない. 強度の低下はPAN系高強度繊維が最も小さいが, この系統の繊維は同時に反応性も最も悪い. 表面にピット状の孔ができるのが強度低下の主因と推定される.

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Effects of crystal size, crystal composition and irradiation conditions on the absorption spectra induced by the irradiation with UV rays were examined in the photochromic glasses containing silver halide crystals. The UV-induced absorption spectra were measured at liquid nitrogen temperature.
Three absorption bands were observed in the UV-induced absorption spectra of the specimens irradiated at room temperature. Their peaks were located at around 360nm (band I), around 500nm (band II) and above 650nm (band III). Among three bands, the band I was larger relative to other two bands in the specimens containing crystals of smaller size and its peak tended to shift slightly to shorter wave-length with increasing size of crystals. The band II was more pronounced in the specimens containing crystals of larger size and its peak was observed at longer wave-length in such specimens. The peak of band II shifted to longer wave-length with increasing extent of darkening and increasing proportion of Br/(Cl+Br) in crystal. During thermal fading, the peak of band II shifted to shorter wave-length but that of band I stayed at the same wave-length. The band III behaved generally in the manner similar to that of the band II.
From the comparison of the observed positions of band II with the peak wave-lengths calculated on the basis of Mie's theory, the band II could be attributed to small silver colloidal particles formed in the silver halide crystlas by the irradiation with UV rays.

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Effects of various cation added in the lead oxide-silica-metal oxide system frits on the dissolution of Pb ion by 4% acetic acid were studied. When alkali and alkali-earth (except Be, Mg) ions were added in the glass, the amount of dissolution of Pb ion was larger than that of mother glass. This was caused by weak bonding strength of introduced ions, large ionic radii and formation of interstices in the glass structure.
B and Al ions are considered to occupy the position as NWF in the glass structure. A part of Pb ions may be expelled to exist as NWM. In those cases, the amount of dissolution of Pb ion was larger than that of mother glass.
When Mg and Be ions were added in the glass, the amount of dissolution of Pb ion was smaller than that of mother glass. Those cations are considered to contribute to lead a tight structure of glass by binding to oxygen ions having unsaturated valency.

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A defective spinel, CoO⋅3Al₂O₃, constituting cobalt blue pigment was analyzed by X-ray powder diffraction method. The cation distribution and the atomic parameter of oxygen were determined using a least squares computation program for the powder diffraction method, and it was clarified that almost all cobalt atoms were situtated at the tetrahedral sites while almost all vacancies were at the octahedral sites. The atomic parameter of oxygen was obtained to be 0.3800.

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The liquidus curve in the system Al₂O₃-CeO₂ was determined by the use of a heliostat type solar furnace. The cooling curves of melted specimens were obtained in the black body centrifugal cavity with an optical pyrometer. The quenched specimens were examined by powder X-ray techniques and petrographic microscopy.
Anomalies in the liquidus curve of the system were found in the region between 70.0 and 95.0mol% CeO₂. A composition of 90.0mol% CeO₂ was further examined by the high-temperature powder X-ray diffractometry, and the presence of a new orthorhombic phase was established.
A tentative phase disgram for the Al₂O₃-CeO₂ system at high temperatures is presented.

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The rate of dissolution of polycrystalline alumina in molten iron oxide at 1500°C was studied under conditions of free and forced convection by rotating cylindrical alumina specimens in a stationary crucible containing the melt.
Alumina specimen was about 19.4mm in diameter and 30mm long of about 18 percent apparent porosity.
The specimens were rotated for 1-15min at speeds from 0 to 700rpm in the melt.
Then, the dissolution rates in molten iron oxide from 1400°C to 1600°C were studied at 100rpm.
The dissolution rate was calculated with the change of radius of alumina specimens.
The dissolution rate was proportional to U^0.69, where U is the speed of rotation of specimen, and it was dependent on temperature of the melt.
Activation energy for the dissolution was about 55kcal per mol.
The interdiffusion coefficient was estimated to be about 1.4×10^-5-2.1×10^-5 square cm per sec at 1400-1500°C.
Therefore, we obtained the findings that the process of dissolution of alumina in molten iron oxide within the range of this investigation is controlled by diffusion of aluminium ion in the liquid boundary layer.

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