Hot-pressing experiments were carried out with magnesia in graphite dies at the temperatures ranging from 1200° to 1600°C for 30 minutes under the pressure of 200kg/cm². Densification characters were measured by a dilatometric method.
Rapid densification was observed at the early stage of hot-pressing. The densification behavior in this stage was analyzed with a plastic deformation model, in which plastic deformation taking place at the contact areas between the particles was thought to be the major cause of the densification because of the concentrated stress. The effective stress values at the contact areas obtained from this analysis seemed to be reasonable when they were compared with the yield stress values of single crystal and polycrystalline magnesia.
The densification behavior in the later stage was analyzed with several rate equations. The activation energies were estimated according to the equations: 34kcal/mol after Murray's, 56kcal/mol after Rossi's rate equation, and 60kcal/mol for plastic flow and 73kcal/mol for diffusion mechanism after our rate equation. These activation energies were compared with those from diffusion, grain growth and creep experiments on magnesia. Predominant densification mechanism in the later stage was thought to be diffusional.

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This study was conducted to research the formation, color development and application for colored glazes of the spinel solid solutions with the composition of (Co, Zn)O(Al, Cr, Fe)₂O₃.
On specimens prepared by calcing the oxide and hydroxide mixture at 1400°C for 1 hour, the X-ray analysis, measurement of reflectance and the tests of their stability as a glaze stain were carried out. The results were summarized as follows.
1) Formation of continuous solid solution and except a few instances, obedience to Vegard's law were confirmed by means of the X-ray analysis.
2) Colors obtained in ZnO(Al, Cr)₂O₃, as the amount of Cr³⁺ increased, ranged from white, through pink and grayish red to beige, and absorption of Cr³⁺ shifted towards red region.
3) An increase in Fe³⁺ in ZnO(Al, Fe)₂O₃, yielded the colors ranging from white through orange yellow to reddish brown, and the shift of absorption of Fe³⁺ towards red region.
4) Colors developed in ZnO(Cr, Fe)₂O₃, as the amount of Fe³⁺ increased, ranged from beige to reddish brown, and specific absorption resulted from the coexistence of Cr³⁺ and Fe³⁺ was observed within a range of 600-700mμ.
5) Colors obtained in ZnO(Al, Cr, Fe)₂O₃, (inside of the triangular coordinates) ranged from reddish orange, through light brown to reddish brown.
6) Brilliant hue, so-called cobalt-blue, developed in (Co, Zn)OAl₂O₃, and in (Co, Zn)O(Al, Cr)₂O₃, an increase in Cr³⁺ yielded greenish blue and blue green, so-called peacock.
7) Colors developed in (Co, Zn)O(Al, Fe)₂O₃, as the amounts of Fe³⁺ increased, ranged from greenish to dark gray.
8) An increase of Fe³⁺, yielded the colors ranging from blue green to dark gray in (Co, Zn)O(Cr, Fe)₂O₃.
9) Colors obtained in (Co, Zn)O(Al, Cr, Fe)₂O₃, (inside of the triangular coordinates) ranged from grayish olive to dark gray.
10) According to the results of the colored glaze tests, except ZnO(Al, Fe)₂O₃ and (Co, Zn)O(Al, Fe)₂O₃ systems, the spinels, especially with the composition in Cr³⁺ rich region, were appreciated to be stable as a glaze stain.

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Densification process of the triaxial porcelain bodies consisting of 40-55% kaolin, 15-30% quartz and 20-35% feldspar was investigated kinematically by means of isothermal shrinkage measurement, and microstructurally by X-ray diffraction method and observation with polarization and scanning electron microscopes.
From the results of linear thermal expansion and shrinkage measurements of the specimens, it was found that the bodies showed distinct shrinkage of three stages occurred at about 500°, 900° and 1100°C or higher temperatures. It was inferred that the shrinkage occurred at about 500°C was caused by the decomposition of kaolin minerals. The bodies showed complicated expansion and shrinkage processes between 500° and 950°C, but these behaviours could be explained clearly with expansion and shrinkage characters of individual raw material and their content in the bodies. The shrinkage occurred at about 900°C seemed to accompany with diffusion sintering process at metakaolin grain boundary.
The shrinkage observed at about 1100°C might be associated with the densification process occurred by viscous flow of spinel type intermediate phase grains with a small amount of melt formed from a little impurities contained in the kaolin and feldspar fine particles. In the range used in this investigation, regular relations between the apparent activation energy for the shrinkage process and compositions of the bodies could not be found. Further, the change of the firing atmosphere from oxidizing to reducing did not affect the shrinkage process and its kinetics.
It was inferred that the shrinkage occurred at a higher temperature than 1100°C was also caused by viscous flow mechanism. The shrinkage diminished when almost all pores in the body were closed in the glassy matrix. Further, feldspathic melt spreaded through matrix phase, and its viscosity decreased with rising temperature, then coalescence and expansion of the pores were promoted, when the bodies were fired at 1500°C, all bodies showed bloating. Further, changes of the constituent minerals and microstructure of the bodies with the densification process were described.
In general, the vitrification behaviour and microstructure of the triaxial porcelain bodies used in this investigation were not so markedly changed with variation of their compositions. From these results obtained, it was also confirmed that the composition range used was appropriate for the industrial usage.

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Longitudinal wave velocity was measured and related to the physical properties of hardened cement paste. Longitudinal wave, generated by pulse oscillator were propagated to the sample under compressed state from 0 to 15 kb at from room temperature to about 230°C.
The samples of cement paste, composed by normal portland cement and fine quartz sand, were hydrated and cured, in water or, autoclaved by different steam pressures.
The major factors, effecting the longitudinal wave velocity, are thought to be caused by the crystal structure of hydrated products, pore size distribution, and grain contacts.
The results of graphic from represents that the compressional longitudinal wave velocity appears to increase linearly with decrease in porosity and seems to approach to the original value of the calcium silicate hydrates.

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