Vaporization of high-lead silicate glasses (optical glasses SFS 1, SF 11, SF 5, F 2, etc.) at high temperatures, was investigated by means of thermo-gravimetry, chemical analysis, and X-ray diffraction. These glasses evaporated considerably at high temperatures, as compared with such glasses as alkali-silicate glasses. The major volatile component from the melts was PbO, and under the atmosphere containing more than 0.4% of SO₂, K₂O was also volatile. The rate of vaporization, with a few exceptions, was scarcely affected by the heating atmosphere.
The result of this investigation on the change of volatility with time did not obey the formulae proposed by Preston and Turner, Oldfield and Wright, and Barlow. This is probably attributed to the fact that the rates of vaporization of these glasses were governed not only by diffusion of volatile components within melts, but also by the rate of evaporation at the surface of the melts. Therefore, the solution of the diffusion equation with surface evaporation condition given by Crank, was applied here. It is expressed by the following equations: for semi-infinite media,
M_t=(c₂-c₀/h){e^h2Dterfch√Dt-1+2/√πh√Dt}……………………(1)
for limited plane sheet media,
Q_t/Q_∞=1-_??_{2L²e-βn²Dt/l²/β_n²(β_n²+L²+L)}…………………………………………(2)
In these equations, M_t is the total amount of substance diffusing through the unit area of the surface during time t; h=α/D, where α is a constant (here called an apparent surface evaporation rate constant); D is the diffusion coefficient; c₀ and c₂ are the initial concentrations of the diffusing substance in atmosphere and in media, respectively; β_n are the positive root of the equation, β_n tan β_n=L, where L=lα/D; l is the thickness of plane sheet; and Q_t/Q_∞ is the fraction of evaporation.
Both of the equations were found to be applicable to the vaporization of PbO from the molten glass. In early stages of the vaporization process, D and α obtained by equation (1) showed a good agreement with these obtained by equation (2). Apparent activation energies for diffusion and surface evaporation, were about 40kcal/mole and 60-70kcal/mole, respectively. The physical meaning of the former was not clear, whereas the latter probably corresponded to the heat of evaporation of PbO. Thus, at higher temperatures the diffusion process tended to control the over-all process, whereas at lower temperatures the surface evaporation rate became predominant.
Both of D and α depended on the composition. They became larger exponentially with increasing modifier oxide contents (PbO and K₂O).

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Titanium diboride was hot-pressed at the temperature range from 1700°C to 2000°C in graphite molds with additions of 3 to 10% of binder metals-Cr, Fe, Co, Ni, Si, or Ti. Density and bending strength were measured and micro-structures were observed.
Co or Ni additions were the most effective for the densification of titanium diboride at lower hot-pressing temperatures, and Cr addition was effective at higher temperatures.
Grain growth was strongly accelerated by additions of Co or Ni especially at the surface layer of specimens, but it was hardly observed in the specimen containing Cr.
Bending strength (S) of specimens containing 6 or 10% Cr was dependent on porosity (P). The relationships between them were found to be expressed by the following equations.
S₆=45e^-4.0Pkg/mm² S₁₀=38e^-5.7P
The bending strength was also affected by the rate of loading. It was reduced to half by increasing the crosshead speed of Instron Tensile Tester from 0.05 to 5cm/min.

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