Coarse crystals of Fe(OH)₂ were prepared by adding iron (II) sulfate solutions to concentrated sodium hydroxide solutions at around 80°C. The Fe(OH)₂ gel was oxidized at 7°C by air bubbling. The oxidation of Fe(OH)₂ proceeded by the zeroorder reaction with its rate independent of the size of hexagonal Fe(OH)₂ crystals which turned into acicular α-FeOOH crystals. The rate-determining step of the oxidation may be the dissolution of oxygen into the solution. In the oxidation process of the coarse Fe(OH)₂ gels, star-shaped aggregates composed of six α-FeOOH crystals were formed Electron-diffraction analysis of the star-shaped aggregates indicated that the six equivalent [100] directions in the hexagonal crystal of Fe(OH)₂ coincide with the [010] direction in each of six crystals of orthorhombic α-FeOOH. The oxygen arrangement on the (100)_hex planes of Fe(OH)₂ is equivalent to that on the (010)_orth planes of α-FeOOH. It is concluded that Fe(OH)₂ crystals in the solution are oxidized selectively on their (100) planes, followed by epitaxial growth of α-FeOOH.

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In multi-component ionic diffusion systems, uphill diffusion is frequently observed. The conditions for the development of uphill diffusion were investigated by computer simulation of ion exchange between a glass containing two cations (A, B) and a molten salt containing the third cation (C). The following conclusions are obtained. (1) The uphill diffusion of B ion is observed when D_A>D_B>D_C or D_A>D_C>D_B, if all diffusion coefficients D's are independent of concentration. (2) This uphill diffusion behavior is affected by the molar ratio of A to B in a mother glass. In the simulated ion exchange systems that were investigated, the uphill diffusion was prominent when the molar fraction of B ion is around 0.25. (3) The concentration dependence of D does influence the distribution of ions, however, the relationship between three diffusion coefficients is more important condition for the development of the uphill diffusion. Ion exchange experiments in (Na, Rb) glass/(K) salt and (Na, K) glass/(Tl) salt systems were carried out to confirm the results of simulation. The uphill diffusion of Rb ion and K ion was observed as predicted by the simulation. The diffusion behavior of ions in glass during the ion exchange process for the fabrication of gradient index lens was also investigated by the computer simulation. The progression of ion concentration profiles during this ion exchange process, especially the development of the uphill diffusion of Tl ion in the initial stage of this process, was well reproduced in this simulation study.

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The transverse rupture strength σ (MPa) of TiB₂-5% TaB₂-1% CoB bodies was expressed by σ=1500d^-0.56, where d (μm) is the average grain size of TiB₂. Hence, the higher transverse rupture strength is expected from the raw materials with smaller particle size of TiB₂. However, fine raw powders did not give a high strength and gave more pores. Examination of compositions and oxygen content suggests that the fine raw powders were more oxidized during mixing.

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Aluminium-doped beta silicon carbide powders were activated mechano-chemically by fine grinding in a vibration ball mill. The resultant powders doped with metallic boron (0.2%) and carbon (2%) was normally sintered under Argon flow, and the effect of mechanochemical activation on the densification of β-SiC was investigated. The results obtained are as follows:
(1) The moldability of the ground powders decreased remarkably. The mechanochemical activation made very little contribution to the densification of β-SiC and accelerated only the surface diffusion at lower temperatures.
(2) Fine powders with the average particle size of 0.29μm and maximum size of ca. 1.0μm is recommended as a starting powder.
(3) The ground powders showed a large weight loss during sintering, and stimulated the growth of plate-like crystals at elevated sintering temperatures. The plate-like crystals tend to retard the extensive consolidification of β-SiC.

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Glass transition temperature (T_g) and Raman spectra were measured in the glass series of yMO_1/2⋅xSnO₂⋅(1-y-x) GeO₂ (M: Li, K). The structural models were proposed based on the composition dependence of these properties on the assumption that the SnO₆ octahedron in these glasses is exclusively connected to six GeO₄ tetrahedra at all vertices (isolated SnO₆).
(1) LiO_1/2-GeO₂ binary glasses contain no Ge₄O₁₆ group. In the glass series with constant LiO_1/2 content, GeO₂ is substituted by SnO₂ according to the reaction of type-I; one isolated GeO₆ is substituted by one isolated SnO₆.
(2) In the glass series containing 20-35 mol% KO_1/2, the substitution of SnO₂ for GeO₂ occur preferentially in order of the type-II, -I and-III; type-II and-III are the substitution of two isolated SnO₆ for one Ge₄O₁₆ group and the formation of isolated SnO₆ accompanied by the disappearance of two non-bridging oxygens, respectively. In the glass series containing 40-50mol% KO_1/2, the substitution reaction type-III occurs in competition with I and II by the addition of small amount of SnO₂ because of high content of non-bridging oxygens.
(3) Based on these results, the amounts of all 6 coordinated Ge atoms and Ge₄O₁₆ group in KO_1/2-GeO₂ glasses were calculated. It was confirmed that fair part of 6 coordinated Ge atoms form Ge₄O₁₆ groups in these binary glasses containing 20-50mol% KO_1/2.

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Silicon nitride ceramics containing more than 10wt% silicon carbide whisker can be machined electro discharge because of the low electrical resistivity of less than 10³Ω·cm. Machining properties of Si₃N₄-SiC whisker composite ceramics by the ram-type electrical discharge machining have been studied. Pure copper is used as a tool electrode. Cutting rate of this composite ceramics increases with an increase in machining current. The cutting rate in reverse polarity machining for positive tool electrode is two or three times larger than that in normal polarity machining. The machined surface in the normal polarity machining is rather smooth, while large craters develop on the surface in the reverse polarity machining. Surface roughness after machining is more than 10μm. The wear rate of the copper tool electrode is less than 10%. Silicon carbide formed probably by the decomposition of the ingredients in this composite ceramics and kerosene used as machining oil adheres to the tool electrode, which improves the wear resistance of the tool electrode.

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Si Kα and Al Kα energies in Na₂O-SiO₂ and Al₂O₃-SiO₂ amorphous powders prepared by hydrolysis of the alkoxides were measured. The energy of Si Kα in the former system coincided with that reported previously. The Al Kα energy increases continuously with an increase in the SiO₂ content in Al₂O₃-SiO₂ system.

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The possibility of surface modification of a hydrophilic hydroxy group on silica surface to a hydrophobic butoxy group was investigated on clay roofing tile specimens, and the enhancement in frost durability was experimentally confirmed. The internal surface modification was undertaken by reflux-boiling of rectangular shaped specimens (2.5cm×2.5cm, 1.8cm in thickness) in pure n-butanol for 24 hours. The formation of butoxy group on the internal surface of clay roofing tiles was experimentally confirmed by comparing IR spectra and water absorption between surface-modified and non-modified specimens of clay roofing tiles. The surface modification enhanced the frost durability of clay roofing tiles.

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Silicic acid was extracted with tetrahydrofuran from an (2, 4-pentanedionato) titanium diisopropoaqueous sodium metasilicate solution neutralized with hydrochloric acid. The reaction of silicic acid with his xide led to polytitanosiloxane polymers with good spinnability and stability against condensations. Precursor fiber was obtained on dry spinning of the polymer. Pyrolysis of the precursor at ca. 1000°C provided with SiO₂-TiO₂ fibers of 9.5-9.6μm in diameter.

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