Hydration was studied for highly pure magnesia clinkers and also for electrically fused magnesia grains with an aid of autoclave.
This autoclave was specially designed to prevent the samples from immediate contact with liquidus water.
Uniform magnesia hydroxide layer was clearly observed on the surface of both clinkers and grains.
The hydration process of these grains was considered essentially to be consisted of the hydration itself and the followed disintegration. The hydrated samples were sieved into four fractions for the analysis of the hydration rate of these grains in order to eliminate the influence of the disintegration. The weight gain of each fraction by the hydration was calculated on the basis of the value of the ignition loss.
The weight gain was almost rationalized by a linear function of the reciprocals of the grain diameter. The initial rate of the layer growth of the magnesium hydroxide showed a proportional relation to the hydration time. Under a special hydration condition contacting the samples with liquidus water, the disintegration was promoted for the highly pure clinkers, and depressed for the electrically fused grains. The CaO/SiO₂ ratio contained in the clinkers affected remarkably the hydration.

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Internal friction of polycrystalline Ni-Zn ferrite and Mn-Zn ferrite were measured. Raw materials of industrial grade and specially-prepared grade (with very high purity) were used for the preparation of these ferrite. Internal friction value of grain boundary in Ni-Zn ferrite did not change with the purity of raw material. Mn-Zn ferrite with high purity showed smaller internal friction than the ferrite from industrial grade raw material. When these ferrite were used as head core of video tape recorder, the ferrite which had smaller grain boundary internal friction showed smaller wear. It seems to be that the ferrite which has smaller internal friction of grain boundary has better resistance to wear, and then the ferrite which has high purity has better resistance to wear, especially in Mn-Zn ferrite.

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To elucidate redox equilibria of chromium ions in glass melts of the system Cr₂O₃-RP₂O₆(R; Mg, Ca, Ba, Ca_0.5K), effects of oxygen partial pressure, basicity of melts, and total chromium concentration on the equilibria were studied at 1200°C and 1300°C. Absorption spectra of Cr²⁺ and Cr³⁺ in glasses of these systems were measured, and the results were analyzed in terms of ligand field theory. Oxygen coordination of chromium ions and the nature of Cr-O bond in glass and melts were discussed.
The results are the followings:
(1) Both Cr²⁺ and Cr³⁺ in glass are in octahedral symmetry and the average coordination number is six, as the hydrated complex ions in aqueous solutions. Partial covalent nature is found in Cr³⁺-O bond in glass: Racah's parameter of inter electronic repulsion B of Cr³⁺ in glass is 750cm^-1 and is rather small in comparison with B of free Cr³⁺, 918cm^-1.
(2) Equilibrium concentration ratios of Cr²⁺/Cr³⁺ and Cr³⁺/Cr⁶⁺ in the melts decrease with increasing oxygen partial pressure and basicity of the melts. From these results, redox reactions of chromium ions were described by the following equations:
CrO_l^(2-2l)++1/4O₂+(h-l-1/2)O^2-=CrO_h^(3-2h)+………………………………………(1)
CrO_h^(3-2h)++3/4O₂+(5/2-h)O^2-=CrO₄^2-…………………………………………………(2)
where h and l are the parameters related to the partial covalent nature of chromium-oxygen bonds, not the coordination numbers of chromium oxi-acid complex ions.
(3) The Cr²⁺/Cr³⁺ ratio varies with increasing total chromium concentration through a minimum value, and it is considered that the values of h and l vary with total chromium concentration. In glasses, however, peak positions of Cr³⁺ absorption spectra and B parameter which shows the nature of Cr³⁺-O bond, did not change with Cr³⁺ concentration. The behaviours of chromium ions in melts were discussed in comparison with glasses.

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For determining thermal conductivity of granular materials, the equations for the thermal conductivity of two-phase media were examined by the measurement on the specimens composed of glass particles and silicon rubber.
The results are summarized as follows:
(1) In two-phase mixture where spherical or irregular glass particles were dispersed into silicon rubber, thermal conductivity agreed well with Maxwell-Eucken's relation when volume fraction of particles was low.
(2) Maxwell-Eucken's formula was not affected by the size and shape of the dispersed particles.
(3) On the basis of Maxwell-Eucken's formura, two equations for determination of thermal conductivity when volume fraction was high and the granule was closely packed were derived.
Through these equations, determination of thermal conductivity of the granular part is possible within an error of ±5-±8%.

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An investigation into slip casting of synthetic β-spodumene has been made because casting is the only practicable method of producing special shapes which cannot be pressed.
Investigation showed a direct relation between particle size distribution, ease of fabrication, and the properties of the finished specimens. It further appears that the optimum particle size distribution for slip casting cannot be obtained from usual ball-milling or vibration-milling. For slip casting of complicated, large, thin plates, it is better to add a small amount of plastic clay and pyrophyllite.

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As a measure of supersaturation with respect to Ca(OH)₂ in the solution of portland cement paste, W/C=0.6, a saturation ratio was used, which was defined by the ratio of actually determined product m′_Ca²⁺⋅m′²_OH- to the solubility product, both in molalities, at the same ionic strength. For three of five cements examined, there was seen the time correspondance between the occurrence of maximum saturation ratio of about 3 and the beginning of intensive rise of heat liberation rate. This was ture for the cement paste with or without addition of soluble salt after pre-leaching treatment of cement with a large amount of water. For the other two cements, the maximum saturation ratio was established in an hour, while the rise of heat liberation rate was two to three hours late.

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The packing properties and strength of a body by press moulding and its firedbody were studied of sillimanite refractory batch made by gap-grading. The results obtained were as follow:
a) The spring back phenomenon in press moulding of a grading abound in finer component and a grading having extensive gap, were larger than another grading were.
b) The reduction of volume in press moulding of a grading abound with coarser component was large as like as a grading abound with finer component. It might be considered that the behavior of former was due to the crushing or defacement of grains.
c) The closer packing of fired body could be achieved when a grading having extensive gap (-a grading having the fine component sized finer), and when q of particlesize distribution of pressed body, fell between 0.35 and 0.4 for particles below 3mm, where q was a coefficient in the Andreasen continuous grading. With increasing content of finer component the cold crushing strength also increased.
Another experiment of press moulding and firing experiment of mixes corresponding to the Andreasen continuous grading and the grading having removal tendency of intermediate component of sillimanite, kyanite and synthetic mullite proved that as follow:
d) The closer packing of fired body could be achieved by a continuous grading having removal tendency of intermediate component from a grading having q value of approximately 0.2-0.4 for particles below 4mm. And the content of finer component dependence was observed for permeability.
e) With increasing content of finer component the strength also increased. However, the grading dependence of coarser part was observed especially in cold/hot modulus of rupture.
f) The content of coarser component dependence of thermal spalling resistance was confirmed, and higher resistance could be achieved where the value of q fell between 0.3 and 0.5. Brittle index showed that the grading having removal tendency from Andreasen grading was not so good.
g) The results suggested that sillimanite was a corrosion resistant and thermal spalling refractory due to low porosity, low permeability and high thermal spalling resistance, whereas synthetic mullite was a loadbearing refractory due to high strength, low creep ratio under moderate temperature, high refractoriness under load and low brittle index, however, synthetic mullite was capable of improving by grading for packing properties and thermal spalling resistance.

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The effect of oxygen pressure (4×10^-6 to 140 torr) on initial sintering of nickel oxide has been investigated by measuring the isothermal shrinkage and the electical conductivity of compacts at 850°C. The data were analyzed by using the kinetic equation of initial combined sintering for volume and surface diffusion. The shrinkage data indicated that the term of volume diffusion increased as po₂^1/4.8 in oxygen atmosphere (po₂>4×10^-3 torr) and that of surface diffusion was proportional to po₂^1/4.1 (in the pressure range of O₂ from 4×10^-6 to 140 torr). From the pressure dependence of sinterability and conductivity, it was presumed that the sintering of nickel oxide was controlled by the diffusional transfer of trivalent nickel ions (Ni³⁺) partially associated with cation vacancies.

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