An argon ion lasar which emitted 200mW of linearly polarized green beam was applied for scattered light photoelasticity of a tempered glass article. Scattered light from a nonalkali alumino silicate glass was observable by naked eye or by magnifying glass. Qualitative estimations of the depth of compression layer and stress therein seemed possible by changing polarization characteristics of incident light by quartz wedg. Effect of refraction on both incident and scattered light was avoided by applying a tiny roof-shaped glass prism. This enabled the observation and measurement without immering glass articles in refractive index liguids.

View full abstract

The existence of the crystallographic transition in BeO was reported for the first time by Engberg et al. in 1958. After this report many researchers measured its transition temperature independently using different experimental methods. Values reported in the literatures, however, disagree with each other. In this work a DTA apparatus was devised to study the thermal changes up to 2400°C. BeO-transition temperature was measured precisely and enthalpy change of the transition was evaluated from the area of the peak in the DTA curve. The transition temperature was also examined for the BeO containing various oxides to study the effect of additives. Results are as follows;
1) Pure BeO: Measurements were made for the BeO of four grades of purities (99.9, 99.5, 99.2 and 99%). Measured transition temperatures agreed with each other within the experimental errors, and was determined to be 2107±7°C (IPTS 1968). In this measurement the calibrations of the thermocouple (W 3% Re-W 25% Re) were made using the melting points of Al₂O₃ (2053°C, IPTS 1968), Pt and Rh. The experimental precision and accuracy were ±3° and ±7°C, respectively. (Sample weight of 20-40mg, heating or cooling rate of 3°C/min and atmosphere of Ar containing a small amount of H₂). The β→α transition took place in the temperature ranges about 20°C lower than the α→β transition range.
2) Enthalpy measurement: The enthalpy change in BeO transition was calculated to be 56±10cal/g (1.3kcal/mol) with reference to the heat of fusion for Al₂O₃ (260cal/g). This value is in good agreement with the one evaluated using the drop technique by Conway et al.
3) Effect of additives: Oxide additives (CaO, MgO, Al₂O₃ Y₂O₃, B₂O₃, ThO₂, ZrO₂, SiO₂, ZnO, NiO, SrO, BaO) were used in this study. Among them, CaO and MgO contents were 1, 2, 5 and 10mol% and the others were 5mol% (mixing in acetone, pressing at 3t/cm² and calcining for 25hrs at 1350°C). The X-ray patterns showed no solid solubility for all oxides. These transition temperatures were varied within the experimental errors. Only the BeO containing MgO additives showed the decreasing transition temperatures at the rate of about 1°C/mol. From the above results it follows that the BeO-transition temperature will be led to the possibility for the second fixed point of temperature over the Al₂O₃-point.

View full abstract

Based on calculated values in respect of the packed volum of high silica roseki crushing aggregates bodies packed by moulding with stick penetration, it had been assumed that optimum particle-size distribution for the closest packing would be formed in a continuous gap-grading, and the results of packing experiments employing either stick penetration or press moulding and sintering agreed with the assumption.
It was found that the closest packing could be achieved when a certain amount of intermediate fractions was removed from a grading having a q value of approximately 0.5, where q was a coefficient in the Andreasen continuous-grading equation for particles below 4mm. Further, it was found that the effect of moulding pressure on packing properties was very large, but the effect of sintering was reversible.
Also, it was shown that the packed volume of a body packed by stick penetration could be expressed as a function of q, and further, the packed volume of a body packed by press moulding could also be expressed as a funcrion of q when the Kawakita equation on powder compression was taken into consideration. And, it was shown that the packed volume of a fired body could also be expressed as a function of q when the expansion and other firing properties onfiring was taken into consideration.

View full abstract

Vacancy diffusion of poly-kinds particle system with the energy barrier (E_i) and the gradients of particle concentration (c_i), vacancy concentration (pc_o) and enthalpy (h_i) was considered and J_i=-D_i*exp(-E_i/RT){∂c_i/∂x-c_i/p⋅∂p/∂x+c_i/RT⋅∂h_i/∂x}=-D_i{∂c_i/∂x-c_i/p⋅∂p/∂x+c_i/RT⋅∂h_i/∂x} was obtained. Up to the present, μ_i=h_i=RTln(c_i/c_o) and μ_v=RTln(p) have been obtained assuming n_i and n_v are both independent variables. If it is assumed that n_v is dependent on n_i, chemical potential related to vacancies, [μ_i]=h_i+RT{ln(c_i/c_o)-ln(p)}, is obtained and the relation, -D_ic_i/RT⋅∂[μ_i]/∂x=-D_i{c_i/RT⋅∂h_i/∂x+∂c_i/∂x-c_i/p⋅∂p/∂x} is derived. Thus J_i is presented as-D_ic_i/RT⋅∂[μ_i]/∂x, despite unable to be presented as-D_ic_i/RT⋅∂μ_i/∂x.

View full abstract

The strength of the Na⁺→K⁺ ion-exchanged glass by electrolysis was measured by means of a concentrated load at the center of the plate.
The strength of the undamaged glass in which potassium ions were introduced at 380°-460°C lied between 40kg/mm² and 90kg/mm² and increased slightly with a decrease in the electrolyzing temperature.
Surface damage made by the indentation of a Vickers-diamond reduced from about 50kg/mm² to about 30kg/mm² the mean strength of the glass Na⁺→K⁺ ion-exchanged for 40hr at 460°C by means of the ordinary diffusion process, while the strength of the potassium-introduced glass by electrolysis was hardly affected by the surface damage.
The glass redistributed with potassium ions by the second electrolysis showed a large spread of the strength for both undamaged and damaged samples; this seems that the glass includes locally very strong and very weak portions on the surface.
With regard to the fracture behaviour of the potassium-introduced glass by electrolysis, the fragments were considerably small and the edges of the fragments crumbled into blunt grains because of the high tensile stress at the boundary of the layer in the glass.

View full abstract

Translucent aluminum oxide-to-translucent aluminum oxide and translucent aluminum oxide-to-Nb metal seals were formed by solder glass method, and the interfaces between different materials were examined by optical and scanning type electron microscope and by electron probe microanalyzer. The solder glass belonged to the system CaO-Al₂O₃-SiO₂-MgO.
The results were as follows:
(1) Both types of seals were formed in vacuum-tight.
(2) Solder glass changed to crystal-glass composites by sealing operation. Although the crystals in the composites differed in shape to each other depending on the type of seal, they were identical in species. The main species was 2CaO⋅Al₂O₃⋅SiO₂ (gehlenite).
(3) At solder glass-translucent aluminum oxide interface, a transition layer was formed by the diffusion of Al₂O₃ between the solder glass and ceramic.
(4) In solder glass-Nb metal interface, the surface layer of Nb metal was oxidized by oxygen which presumably originate in the atmosphere and in the solder glass. Niobium oxide thus formed diffused in to the solder glass forming a transition layer.
(5) The transition layers at the interfaces were expected to be useful in reducing sealing stress and in improving adhesion.

View full abstract

Following methods are usually adopted for measuring the residual surface compression present on tempered glass, (1) Observation of relative retardation of light passing through the cross-section of the plate parallel to its surface by photoelastic techniques. (2) Calculation of the stress by measuring the resultant curvature of the plane when a certain amount of thickness was etched-off by hydrofluoric acid from one side of the sample.
However, these methods are inadequate for the non-destructive measurement of surface stress on commercial glass plates of large dimensions.
The method described here is pertaing to the surface stress-induced birefringence of glass with the result that the angle of total reflection obtained by contacting an optical prism on the sample surface is different between two polarized components. Namely, the refractive indices of the compressed surface for the ordinary ray polarized in plane perpendicular to the surface is greater than that for the extraordinary ray polarized in plane parallel to the surface, thus the critical angle of total reflection of the ordinary ray is greater than that of the extraordinary ray. Since this difference is directly related to the magnitude of the surface stress and is detected in the field view of telescope as two regions of different brightness separated by a sharp boundary, it is possible to measure the surface stress in a rapid and non-destructive manner by calibrating the scale division of the eyepiece field. Calibration was done by giving a known degree of cancellation to the surface compression with the tension caused by bending the central portion of the sample supported freely at both ends.
The constructed instrument provided very sharp boundary lines in the field of eyepiece and made it possible to determine the surface compressive stress on tempered glass with the accuracy of ±0.6kg/mm².

View full abstract