弗化カルシウムの焼結機構に関する従来の研究は, 互いに矛盾しているように見えるので, とくに粒径の効果について着目し検討を加えた. 弗化カルシウム粉体充填物の800-1000℃の温度範囲での等温収縮を測定し, 焼結体の走査型電顕による観察をおこなった. 粗粒子 (1-5μ) については体積拡散機構が成立つ. 収縮速度から計算した拡散係数は, 単結晶中でのCa²⁺トレーサーの値とほぼ一致した. 頸部成長と開気孔が顕微鏡写真中に認められた. 微粒子 (0.01-0.05μ) の初期焼結に対しては, 格子転位の再編成による塑性流動機構が成立つ. スリップバンドと閉気孔が認められた. 微粒子表面の吸着水分は, 初期焼結を促進したが, 終期段階で閉気孔の膨脹をひき起した.

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Effects of addition of Li⁺, Mg²⁺, Ni²⁺, Cu²⁺ and Fe³⁺ on the disorder-to-order transition in lithium ferrite have been studied. The transition was surpressed by the addition of Li⁺, Mg²⁺, Ni²⁺ and Cu²⁺. In the case of addition of Fe³⁺, the transition was scarcely affected. It is considered that the effects of cation addition on the transition are explained as due to the change in concentration of cation vacancies in ferrites which is caused by the incorporation of cations in the ferrite lattice.
The order-disorder transition temperature was decreased by the addition of cations, but was increased slightly (-5°C) by addition of Li⁺.

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The redox equilibria of transition metals (V, Fe, Cr, and Ce) in phosphate melts (Li₂O-P₂O₅, Na₂O-P₂O₅, K₂O-P₂O₅, and NaPO₃-Ca(PO₃)₂) were investigated at 900 or 1000°C.
Using the oxygen ion activity obtained by an oxygen electrode method, the dependence of the redox equilibria of transition metals on oxygen ion activity was analysed. The same procedure of analysis was applied to the redox equilibrium in sodium silicate melt.
It was shown that with exception of chromium, the redox reactions are represented by the following:
RO_a^(m+n-2a)+=RO_a-h^(m+2h-2a)++(h-n/2)O^2-+n/4O₂
where R is transition metal, a and (a-h) are the numbers of the oxygen atoms constituting the oxyions of the oxidized and reduced metals, respectively, and (m+n) and m are the valences of the oxidizep and reduced metals, respectively. The (reduced)/(oxidized) ratio decreased with the increase of oxygen ion activity in both melts. The decrease was more rapid in acidic composition than in basic region.
That is, h decreased toward zero as the basicity increased. From the fact that the order of the redox ratio about element was different between phosphates and silicate melts, it was suggested that the coordination of solvent oxyanion also effects on the redox equilibrium of transition metals besides the oxygen ion activity.

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As the first step to clarify the mechanism of the strength development of Jet cement, the composition and the structure of the hardened Jet cement paste were analysed by a method of characterization.
On the basis of the experimental results, calculated intra-crystal bond energy and intercrystal coagulation energy of ettringite and calcium silicate hydrate considering the crystal structure and the state of crystal surface showed almost the same value. On the contrary, these energies of calcium monosulfate hydrate were extremely small. From these results it was concluded that both ettringite and calcium silicate hydrate contribute mainly to a strength development.
Adopting the theory of plastic deformation and brittle deformation referring stress-strain relationship of the hardened paste under a tensile and a compressive load, plasto-elasticity analysis was carried out for the effects of the texture and the pore structure of the hardened paste on the strength by a finite element method.
The strength of the hardened Jet cement paste is strongly influenced by the orientation of ettringite crystal to the stress direction.
The area of plastic region obtained from above-mentioned calculation showed a maxium and a minimum value in the case when the direction of stress is parallel and perpendicular to the elongation axis of ettringite crystal, respectively.
In the calcium silicate hydrate, plastic region appeared around the contact point of calcium silicate hydrate and ettringite crystal which has a situation parallel to the stress direction. From these results, it is considered that the strength of calcium silicate hydrate is influenced by the strength of ettringite.
The pore in the hardened paste plays also important role to the stress distribution. Plastic region appeared around the pore and local tensile stress caused by the compressive loading distributed to the line parallel to the compressive stress direction through pore to pore.
These results of calculation coincide in many case with the crack distribution observed in the scanning electronmicrograph of the fracture surface of the hardened Jet cement paste.

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The finding that the addition of seed crystals promoted the formation of potassium titanate fibers from TiO₂ under hydrothermal conditions. using titanium dioxide, led us to the idea that the rate determining step might be the supply of the polyions with structure related to the fiber crystals.
To supply the poly-ions the present authors used a glass of the system K₂O-TiO₂ as starting material instead of TiO₂. With use of the glass (the composition being around K₃TiO_3.5), the synthesis rate of potassium titanate fibers was increased. The glass was superior to titanium oxide on the following points; 1) homogeneity, 2) larger solubility, 3) including the structure related to the fiber crystals and 4) easiness in choosing grain size and shape.
Non-crystalline fibers were also obtained from the glass under hydrothermal conditions, which was later converted into crystalline fibers by heating at above 950°C.
The addition of seed crystals to the glass further improved the formation rate.

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