The purpose of series of studies is to know what is the mechanism of surface crystallization of borosilicate glasses. 70SiO₂⋅15B₂O₃⋅15Na₂O glass samples were kept at various temperatures in a muffle furnace.
Dendritic crystals grown on the surface were characterized.
The results were as follows.
(1) Platelet hillocks with a crater on the middle top were grown in the temperature range between 670°C and 750°C under atmospheric condition. The slope of the hillock was about 4 degrees.
(2) The composition of crystalline colonies was rich in silica and poor in sodium. The crystalline colonies were dendritic and were identified to be orientated cristobalite by X-ray diffraction analysis of surface crystalline layer hundreds micron thick.
The chemical composition of this surface layer was almost the same as that of the mother glass.
(3) A fairly linear relationship was found between the growth of the dendritic disk and the time duration of the heat-treatment. The growth rate could be obtained from the slope of the straight line and the activation energy from the Arrhenius plot was about 75kcal/mol up to 850°C.
(4) The growth could be accelerated by addition of water vapor into the furnace chamber.
There results indicate that the surface crystallization is initiated by evaporation of sodium borate component from the liquid layer appeared on the mother glass surface.

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Problems in slip casting of barium titanate are discussed and analyzed. The most important factors to control the casting slips are the particle size, particle-size distribution, and the calcination temperature of the mixture of BaCO₃ and TiO_O. The rheological properties of slips are discussed also.

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Oxidizing reaction of Ni_0.7Fe_2.3O₄ ferrite in a gaseous flow was studied by measuring cation valence, saturation magnetizaton and crystal lattice constant of the samples heattreated at various temperatures between 530° and 1250°C in air, in pure nitrogen, and in nitrogen containing 5 or 0.5vol% oxygen. It was found that oxidation makes the amount of Fe²⁺, saturation magnetization and crystal lattice constant decrease, and that there are two kinds of reactions for oxidation of the ferrite. One of them is an oxidation in which α-Fe₂O₃ is separated as the second phase by the amount nearly corresponding to the excess oxygen given at the heat-treatment of the sample. The other is an oxidation in which the second phase is unseparated. By the latter oxidizing reaction the spinel structure of the ferrite becomes to contain cation vacancies on its B-sites (octahedral sites). To calculate the crystal lattice constant of the spinel containing cation vacancies, application of “the mean size of cation vacancies” was suggested.
The two reactions proceed as follows:
Ni_0.7²⁺Fe_0.3²⁺Fe₂³⁺O₄+δ/2O₂
→3δFe₂O₃+1/aNi_0.7a²⁺Fe_(0.3-2δ)a²⁺Fe_(2-4δ)a³⁺O₄
(Oxidation in which the second phase is separated)
→1/bNi_0.7b²⁺Fe_(0.3-2δ)b²⁺Fe_(2+2δ)b³⁺CV_(3/4)δbO₄
(Oxidation in which the second phase is unseparated)
where, a=1/(1-2δ), b=4/(4+δ), and CV is the cation vacancy.

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The temperature dependency of the total emission intensity and the decay time constant of the ⁵D₀ level after the CTB excitation was investigated in various glasses containing Eu³⁺, and nonradiative process of Eu³⁺ center was discussed in connection with the effect of host composition.
The broad UV excitation band induced by Eu³⁺ was considered to be ascribed to the charge transfer states of Eu³⁺-anion complex. This band was found to displace toward higher energy in the the series silicate->germanate->borate-glass and, comparing the effect of alkali ions, K⁺>Na⁺>Li⁺ respectively. In a series of borate glasses, the minimum in the change of the ν_max appeared at around 85mol% B₂O₃.
On the basis of correlation of the Q_T with the ν_max, it may be noted that the temperature dependency of the emission characteristics increases as the interaction of the environment with Eu³⁺ increases. Borate glasses, however, showed much greater temperature dependency than germanate glass in spite of a little difference on the ν_max. This may be attributed to larger phonon energy in borate glasses.
It was found that the decrease of the emission intensity began at lower temperature than the decrease of the decay time constant. This result indicates that the nonradiative transitions occur at the transition process from the CTB directly excited, through which the excitation of the emitting ⁵D₀ level is achieved.
The activation energy for the thermal quenching was in the range of 1400-1700cm^-1. Comparing these values and the ν_max with the results on LaAlO₃ the model which excited ions are coupled with the ground states via the CTB may be reasonably received as the mechanism on the nonradiative process of Eu₃₊ in glasses.

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Dynamic viscoelasticity of glasses in the systems As-S and As-Se was measured by a method of forced torsional vibration with dynamic modulus approximately from 10¹⁰ to 10⁸ dyne/cm². The dispersions of dynamic elasticity (G′) and dynamic loss (G″) with temperature (ω=0.26rad/sec) for the glasses with As content at 40 atomic per cent in the both systems As-S and As-Se appeared at the highest temperature in the same system. However, the viscoelastic behavior which is represented by the change of G′ and G″ appeared even near the fixed temperature T_f, which is the temperature of isoviscosity η=2×10¹³ poise, when S or Se content became above 80 atomic per cent.
Frequency-temperature superposition of each run for all samples was successful in this range. And so, at T_f of each sample we could draw master curves as shown in Fig. 6 and 7. As to the shift factor, a_T, log a_T vs. 1/T plots give essentially a straight line for each sample as shown in Fig. 8. Therefore, for the dynamic viscoelastic relaxation of glass, the apparent activation energy can be calculated by the following equation, ΔH=Rd (log where R is the gas constant. The results are shown in Fig. 9. a_T)/d(1/T), In the As-S system, the activation energy is about 70kcal/mole at As₂S₃ (As 40atom%) and it decreases gradually with increasing S contents. But it shows an unusual maximum around As₂S₈ (S 80atom%). On the other hand, in the As-Se system, the activation energy is about 65kcal/mole at As₂Se₃ (As 40atom%) and decreases with increasing Se content. However, it increases again with Se content above 80 atomic per cent.
The distribution of relaxation time can be expressed approximately by the following formula, dG′(ω)/dlogω=ψ_L(log τ). The results are shown in Fig. 10. The distribution curves for all the samples go through the maximum. The peak appears at the longest period at As₂S₃ and As₂Se₃ (As 40atom%) in As-S and As-Se systems, respectively, and shifts to shorter period with increasing S and Se contents.

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The penetration method is most favorable for the measurement of non-oxide glass viscosity from 10⁷ to 10¹³ poise. The principle of this method consists of measurement of the rate of penetration of a cylindrical indenter rod under a known load into the glass specimen maintained at a constant temperature. The indenter rods used were nickel cylinders of 0.5, 1.0 and 2.0mm in diameter. Cylindrical specimens (NBS 710 glass) were 4.0, 5.0 and 6.0mm in diameter and were 6.0mm thick. To obtain absolute viscosity values, the apparatus constant must be experimentally determined, for the rate of penetration is not directly related to that of shear. The author proposes, however, that the apparatus constant is equal to 2/3πγ, where γ is the radius of the cylindrical rod. Consequently the viscosity of glass, η, can be calculated by the following equation, η=2P/3πγV₀, where P is the applied load and V₀ the penetration rate. This penetration rate depended on the rod diameter irrespective of sample diameter, and if the sample thickness was not extremely thin, that rate was constant irrespective of thickness.

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The mixture of silica powder and milk of lime was stirred in an autoclave and treated hydrothermally under the following conditions; molar ratio of CaO/SiO₂ 0.80, weight ratio of water/total-solid 12, pressure 8kg/cm², temperature 175°C, for 4-8hrs. Thus milky slurry consisting of tobermorite was prepared.
The slurry contains 8% of total solid matter and its viscosity is 1.5-2.0 poise. Crystals are tobermorite whose (002) spacings are 11.2-11.3Å. Grains are spherical aggregates with 5-70μm diameter having inter-twining structures of plate-like tobermorite crystals as shown in Fig. 5, 6 and Fig. 8.
The slurry is easily dehydrated and shaped in a mold under pressure and the molded material can be hardened only by drying. The properties of thus obtained light molded material are following as shown in Table 1; density 0.2, bending strength 3-4kg/cm², thermal durability 900°C, shrinkage at 1000°C 2-3%.

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Glass-forming region in the system As-S-Tl has been re-examined because the procedure of Flaschen et al. is doubtful on the point of homogeneous melting free from oxygen contamination. The As-S-Tl glass-forming system was found to be substantially comparable with the As-S-Ag glass-forming system reported already (Fig. 1).
Such properties as density, thermal expansion and infrared absorption have been measured on As₂S₃-Tl₂S and As₂S₃-Ag₂S glasses (Figs. 2 to 6). Both glasses exhibited some new absorption peaks in their infrared spectra in addition to the peak at 698cm^-1 observed for As₂S₃ glass and these peaks were most distinct at the composition TlAsS₂ or AgAsS₂. On the basis of the crystal structure of As₂S₃ (orpiment), TlAsS₂ (rolandite), AgAsS₂ (trechmannite or smithite) and Ag₃AsS₃ (xanthoconite or proustite), the assignment of the peaks observed for As₂S₃, TlAsS₂ and AgAsS₂ glasses was made using the equation v=A(r-B)^-3/2, where v, r, A and B are wave number, bond length and constants, respectively (Fig. 7). All the peaks observed may be assigned to the vibration of As-S bond with different bond length and, on the other hand, the absorption peaks calculated for the compounds As₂S₃, TlAsS₂ and AgAsS₂ agreed very closely with those observed experimentally for the corresponding glasses (Fig. 8). Consequently the above each glass may be considered to have the structure similar to that of the corresponding compound. Furthermore, it may be assumed that the absorption peak would be observed nearly at 696cm^-1 if a glass could be obtained at the Ag₃AsS₃ composition (Table 1).
In view of the above facts the most reasonable conclusions to be drawn from the infrared absorption and density data are the followings: The structure of skeleton composed of As and S changes successively as Tl₂S or Ag₂S is added to the As₂S₃ glass. In the case of the As₂S₃-Tl₂S glasses orpiment-like (AsS_3/2)_n sheet structure transforms to (AsS₂)_n chain structure found in rolandite and then to short chain structure. On the other hand, in the case of the As₂S₃-Ag₂S glasses (AsS_3/2)_n sheet structure transforms to discrete As₃S₆ group structure found in smithite or trechmannite and then to isolated AsS₃ pyramid structure found in xanthoconite or proustite.

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The time and temperature dependences of the absorption current in an electronic-conducting glass (5Fe₂O₃⋅35BaO⋅60SiO₂) and a plate glass were investigated using vacuum evaporated Au electrodes.
The curves in log (absorption current) vs. log (time) diagrams for both glasses seemed to be the sum of two kinds of decreasing current. Part A was observed at the initial stage and decreased rapidly. On the other hand, Part B decreased slowly. Part A was masked by Part B at high temperature. The absorption current designated as Part A was converted to ε′ by Hamon's approximation formula. The value of experimental activation evergy and the lack of voltage dependence suggested that Part A was caused by dielectric absorption in bulk glass.
Part B vanished when the electronic-conducting glass was heated at 350°C for 4 hours in vacuum before the deposition of Al-Au electrodes. This suggested that Part B of this glass was caused by space charge polarization at electrode-glass interface and that adsorbed or absorbed water on glass surfaces was responsible for the polarization.
For the case of plate glass, Part B could not be removed by prior heat-treatment at high temperature in vacuum. Part B of the plate glass seemed to be the result of space charge polarization caused by the displacement of alkali-ions.

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