A photochromic glass containing silver chloride has been investigated. The composition of the glass is SiO₂59.0, B₂O₃20.0, Al₂O₃8.0, Na₂O 13.0% and CuO is added as a sensitizer. The results are as follows:
1) Chlorine is, when added 1%, lost more than 1/2 by batch reaction. Chlorine has the tendency to accompany with silver when it evaporates.
2) Not only crystal of silver chloride, but also crystal of sodium chloride is found in the glass. Concentration of silver chloride crystal increases with the duration of heat treatment and is nearly saturated after 5hr at 600°C. The darkening intensity shows similar tendency. When treated for a long time, the transmission of glass and the darkening intensity decrease.
3) A broad optical absorption band covering from ultra violet (uv) to visible range is formed by uv-irradiation. This band shows different characteristics at about λ=400mμ and at the region of λ>450mμ.
4) About 1/2 of added copper is reduced to Cu⁺ during melting which sensitizes darkening. The darkening intensity normalized with Cu⁺ concentration is linearly related with the product of concentration of silver and chlorine. The darkening intensity D is expressed as D=const. {[Ag][Cl]-0.063}[Cu⁺]^x. [Ag][Cl]=0.063 is considered to correspond to the solubility product of silver chloride in this glass at 600°C.

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The authors have discussed on the properties of effective crystal field around Eu³⁺ by chiefly studying the compositional and temperature dependency of emission spectra of Eu³⁺ in glasses.
Changing the type of network forming ion, it was found that, in the series phosphate-, silicate-, germanate-, borosilicate- and borate-glass, splitting of emission line for the ⁵D₀-⁷F₁ transition due to crystal field increased, emission line for the ⁵D₀-⁷F₀ transition displaced toward higher energy, and the symmetry and uniformity of crystral field around the Eu³⁺ -sites decreased. These results may be explained in connection with strength of interaction of Eu³⁺ with the surrounding oxygen ion, which is depend on bonding strength between the network forming ion and the oxygen ion.
It was recognized about the effect of network modifying ion that the uniformity of crystal field around the Eu³⁺ -sites decreased as the charge of ion increased and the ionic radius decreased.
Half-width of the emission line for the the ⁵D₀-⁷F₀ transition showed less temperature dependency in the range from RT to LNT in glasses in contrast with the case of crystal host. This fact indicates that broadening of the emission line in glass is chiefly due to the nonuiformity of crystal field arizing from the lack of long range order in glass structure.

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Dry-and wet-strength of cast bodies have been expressed as functions of the parameters of solid fraction (F₃), specific surface area (S_a) and degree of hydration (d_s). The reliability of the equations were examined by comparing with the experimentally obtained values. The results were summarized as follows.
1) The dry modulus of rupture (st₀) could practically be given by the equation st₀=B₀(AF₃^2/3)S_a, where A and B₀ denoted the number of contact points on a particle and the binding force of a contact point, respectively. The values of B₀ were experimentally found to be a constant within the range of strength variation on a specific slip.
2) The equation st=Bf(d/ds)(AF₃^2/3) S_a, showing the wet modulus of rupture (st), gave agreeable values with the experimentally observed ones, where d was the thickness of water film on the particles and B was a constant for a slip obtainable from the experimental (st) values at various moisture contents.

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アルミナのホットプレスにおける初期段階でおこる支配的な緻密化機構として塑性変形を考えた. 変形モデルを考えて実効応力と変形速度の関係を調べた.
ホットプレスの初期段階ではアルミナ粒子間の接触面にかかる圧縮応力はたとえ低温でも充分大きく, アルミナの降伏応力よりも大きいと考えられる. 接触面にかかる実効応力を求めるために, いろいろな充填状態について変形の度合と気孔率の関係を計算した. この計算のための仮定はつぎの通りである.
(1) アルミナ粒子は球形である.
(2) ホットプレス中に充填状態は変らない.
(3) 実効応力と外圧の比は1粒子の全表面積と接触面積の比に等しい.
たとえば配位数6の単純立方充填をとれば, 実効応力係数 (F), 1粒子の体積 (V_s) と気孔率 (p) の関係はつぎのようになる.
F=σ_e/σ_a=[4πR²-12πR(R-x)+6πa²]/6πa²
V_s=(4/3)πR³=(4/3)πR₀³-6π∫_x^Ra²dx
p=[(2x)³-V_s]/(2x)³
ここでxは半径Rの粒子の中心から半径aをもった接触面の中央までの距離である. いろいろな充填状態についてpとFの間の関係が計算できる.
リンデ社の1.0Cアルミナについて200kg/cm²の圧力の下で黒鉛型中で1300°-1600℃の温度範囲でホットプレスした. ホットプレス中の試料の収縮を連続的に測定することで相対密度の変化を求めた.
一定温度における緻密化速度と気孔率の関係から, 単純立方充填に対するp-F関係を適用してある変形速度の時の各温度における実効応力を求めた. これらの値はサファイア棒の引っ張り変形からKronbergの求めたlower yield stressの値とよく一致した. 接触面における塑性変形がアルミナのホットプレスの初期段階の緻密化を支配するものと結論した.

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To design the tempering apparatus of glasses, it is important to assess the cooling condition of the given glass. As many authors indicated, residual stresses of the tempered glasses are conducted to the physical properties and behaviors of glasses at high temperatures, its preheating temperatures and its cooling conditions.
In this paper, visco-elastic behaviors of glasses at high temperatures were approximated by Maxwell model, and the analytical solutions of the residual stresses in glasses having various simple shapes were given. The results computed were expressed some simple equations and some figures.
Deformation of glass is easily occurred at high temperature, thence maximum preheating temperature is determined experimentally. Using these results, the cooling condition-that is to assess Biot's number-can be easily decided.

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Critical cooling rates (Q) for vitrifaction of condensed sodium phosphte melts were determined experimentally. The values of Q for the melts with the compositions of 1.00, 1.02, 1.04, 1.20, 1.40, 1.50 and 1.67 in mole ratio Na₂O/P₂O₅ were observed to be 3, 2, 20, 20-30, 30, 50 and above 500°C/sec, respectively. Generally Q decreased with an increase of the mean chain length of the phosphate ion. Structural chemical meaning of Q could be clarified in terms of crystal growth rate (u) involving induction time (τ).
The thickness (D) of the crystallized layer formed at the surface by cooling the melt was represented as a temperature integral of the isothermal crystal growth rate at the surface layer of the glass with the same composition as the melt. That is,
D=∫_Tg^T_m∫₀^t_iu_s{1-exp(-t/τ)}dt⋅dT
where T_m, T_g, t_i and u_s are melting temperature, glass transition point, duration at temperature T_i and growth rate of the layer in a steady state, respectively. It is concluded that Q is the cooling rate above which no crystallization from the surface of the melt can occur, in other words, D is zero.
The crystallization phenomena at the surface of the melts and of the glasses belong to a particular case in a viewpoint of crystal morphology. In the above case, in place of spherulite growth an assembly of small crystals with orientation in a same direction formed, and the crystal growth was restricted to one direction vertical to the surface owing to simultaneous formation of a great number of nuclei at the surface.
The growth rate of the layer is considered to be controlled by a second order nucleation rate at the front of growth and can be expressed by the formula:
u=u_s{1-exp(-t/τ)}
Therefore the vitrifaction of the phosphate melts depends conspicuously on two heterogeneous nucleation processes, namely, those at the surface of the melt and at the front of growth.
The occurrence of bond-exchange reactions among the phosphate anions at temperatures above 600°C was confirmed by the fact that the viscosity of the melts was independent of their mole composition in the concerned temperature range.

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