The influence of grain growth on microstructure development is reviewed. Consideration is given to cases where grain growth behavior is controlled by interactions between the grain boundary and a liquid phase, a dissolved solute, as well as pores. Grain growth laws are developed for each case; the conditions which stimulate abnormal grain growth are indicated and related to the characteristics (physical and chemical) of the starting powder.

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The sintering of CVD-alumina powders (I: average particle size 0.03μm, mixture of γ-and δ-phases; II: average particle size 0.16μm, mixture of δ-and ι-phases) was investigated in argon atmosphere at 1100°-1600°C. The sinterability of (I) increased remarkably with the phase transition into α-phase by the calcination at 1300°C, although the particle size increased to 0.14μm. Such an increase in sinterability was attributed to the increase in green density of the powder compact. The relative density of the sintered body obtained was 96% by 1500°C-sintering. On the other hand, the phase transition in powder (II) was slow in 1300°C-calcination and the sinterability was lower than that of powder (I), probably due to the low density of powder compact in addition to the large particle size. A denser powder compact obtained by rubber-pressing gave the denser sintered body, supporting the significant effect of the green density on the densification, The high green density was also effective for the suppression of grain growth, which may be due to the homogenization in particle packing. The heating schedule was also important to obtain a homogeneous microstructure.

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The hydration of 3CaO⋅Al₂O₃ in the presence of CaSO₄⋅2H₂O and Ca(OH)₂ is remarkably retarded. The study aimed to clarify the mechanism of the excessive retardation. When 3CaO⋅Al₂O₃ was dispersed in suspension of CaSO₄⋅2H₂O and Ca(OH)₂, the interaction between solid and liquid phases as a function of hydration time was investigated. The results are summarized as follows:
(1) The concentration of Ca²⁺ and SO₄^2- in liquid phase give usually 1.80g CaO/l, 1.02g SO₃/l, respectively, independent on mixing amounts of CaSO₄⋅2H₂O and Ca(OH)₂. On the other hand, Al(OH)₄^- eluted from 3CaO⋅Al₂O₃ is extremely little.
(2) The retention period at the highest concentration differed depend on mixing amounts of CaSO₄⋅2H₂O and Ca(OH)₂.
(3) After the end of this period, the coprecipitate which suggested solid solution consist of 3CaO⋅Al₂O₃⋅CaSO₄⋅12H₂O-4CaO⋅Al₂O₃⋅xH₂O system as shown 7.6-9.6Å phase was rapidly produced on 3CaO⋅Al₂O₃ surface.
Therefore, the added CaSO₄⋅2H₂O and Ca(OH)₂ describes two roles as follows:
(A) CaSO₄⋅2H₂O and Ca(OH)₂ are required to keep at the highest concentration of Ca²⁺ and SO₄^2- in liquid phase.
(B) The remained CaSO₄⋅2H₂O and Ca(OH)₂ except for above (A) is present.
Since CaSO₄⋅2H₂O and Ca(OH)₂ corresponding to above (B) is reacted with 3CaO⋅Al₂O₃, AFt and AFm phases are immediately formed, the resulting 3CaO⋅Al₂O₃ surface is partly coated by these phases. However, this cause was not essentially on the excessive retardation. Because 3CaO⋅Al₂O₃ is covered by the highest concentration of CaSO₄⋅2H₂O and Ca(OH)₂ corresponding to above (A), consequently, during this period, the elution of Ca²⁺ and Al(OH)₄^- from its surface has not been able to recognize. Therefore, the hydrates is not produced, and the hydration stops apparently.

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Binary glasses BaO(40mol%)-Fe₂O₃ and SrO(40mol%)-Fe₂O₃ have been prepared by the splat-quenching method. The coercive force of these crystallized glasses has been discussed in terms of the precipitated phases and their particle size. In crystallized glasses, the antiferromagnetic compounds BaO⋅Fe₂O₃ and SrO⋅Fe₂O₃ existed as a matrix component, and the ferrimagnetic compounds BaO⋅6Fe₂O₃ and SrO⋅6Fe₂O₃ precipitated. The coercive force of these crystallized glasses was mainly dependent upon the particle size of precipitated BaO⋅6Fe₂O₃ and SrO⋅6Fe₂O₃. The crystallized glasses having the small particles were superparamagnetic. The coercive force increased with increasing particle size up to 800Å in BaO-Fe₂O₃ system and 300Å in SrO-Fe₂O₃ system. The crystallized glasses showed the maximum coercive forces, that is, 5.6 and 5.9kOe for 800Å BaO⋅6Fe₂O₃ and 300Å SrO⋅6Fe₂O₃ particles, respectively. The precipitated particles larger than the above size decreased the coercive force.

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Fracture mechanics of a thermally-shocked glass cylinder which develops a straight-front crack was investigated. First, theoretical analyses of thermal hoop stress were carried out and then on the basis of a linear fracture mechanics the fracture toughness of a cylinder under thermal shock was investigated using Bueckner's solution (weight function). Next, a relationship among sidewall thickness, depth of surface crack and thermal shock (temperature difference) was comprehended, using a value of critical surface energy γ_c, obtained by Mecholsky. Further, the theoretical calculations on the glass cylinder was applied to glass bottle with semi-elliptical cracks. The experimental results on the glass bottle agreed well with that of the theoretical prediction.

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The thermally stimulated exoelectron emission and thermo luminescence of Cu⁺ implanted Li₂B₄O₇ glass ceramics and Ag⁺ implanted LiF single crystal were investigated for the purpose of their application to dosimeters. It is found that the thermally stimulated exoelectron emission (TSEE), thermo stimulated luminescence (TL) glow curves and TL spectra of ion implanted Li₂B₄O₇ glass ceramics and LiF single crystal depended on the kind of radiation. Therefore, from the informations on the TSEE and TL of Cu⁺ and Ag⁺ implanted sample it may be possible to measure the dose of each kind of radiation separately in a mixed radiation field.

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Chemical reactions occurring in the conversion of blue ultramarine into reddish one were studied mainly by ESR and electronic spectroscopy. Chemical and ESR spectral analyses showed that S₃^- in contact with H⁺ ion, which is the blue chromophor held in the ultramarine lattice, was decomposed to SH and elemental sulfur and that the resulting SH reacted with oxides of sulfur to form elemental sulfur. S₄, which is the red chromophor in reddish ultramarine, was assumed to have resulted from the elemental sulfur thus formed. When ultramarine blue, previously acidified by heating with NH₄Cl, was oxidized by NO₂, a decrease in S₃^- and an increase in S₃ concentration were observed by electronic spectroscopy. On the contrary, the decrease in S₃ and S₄ and the increase in S₃^- were observed when reddish ultramarine was heated in a basic solution at about 100°C. Heating reddish ultramarine in vacuo above 400°C caused the fading of its color. These facts show that S₄ is unstable at high temperatures as well as under the alkaline condition. Finally, the processes of producing reddish ultramarine were interpreted on the basis of above findings.

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The aggregation of andalusite and sericite crystals is found in the pyrophyllitic deposits and occurs as the massive or veinlets forms. The aggregation consists mainly of andalusite crystals and is used as a fine raw material for refractory bricks. The high temperature reaction between the minerals is studied on sandwiched samples of oriented crystals of andalusite and fine crystal aggregation of sericite. The petrographic and EPMA analytical methods were used to determine the reaction area and identification of minerals. The thermal decomposition of andalusite is affected by the direction Of crystallographic axes. The diffusion of K ions which is introduced by the decomposition of sericite follows the same direction as the decomposition of andalusite. The slow progress of decomposition was observed along the directions of a- and b-axes. In the direction of c-axis, the strong decomposition of the crystal and quick diffusion of K ions are observed and the crystal changes to the glass and fine fibrous crystal aggregation of mullite. The area formed by mullite crystals is equal to the diffussion area of K ions. The glass, produced by the decomposition of andalusite, receives strong reaction of K ions and has a chemical composition similar to the glass produced by the decomposition of sericite. The fibrous and needle crystals of mullite, produced by the decomposition of both minerals, are strongly bonded by the glasses. The apparent activation energy based on the velocity of Potassium diffusion is calculated to be 191kcal/mol in which the decompesition energy of andalusite to mullite is included.

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Haüyne-belite cements have been burnt from the raw mix of fly ash, gypsum and Ca-carbonate in order to make effective use of fly ash. Since the early stage strength depends on the content of alumina in this new type of cement, fly ash containing more alumina is desirable. In this work, 21.40 percent. Forming 20mmφ pellets, clinkers were burnt at 1250°C, 1300°C and 1350°C and pulverized to the fineness around 3000cm²/g, Blaine. Burning was repeated until almost all raw materials converted to desired clinker minerals, haüyne and belite (β and/or α′). Burnability was not so good except 1350°C clinker due to spherical shape of the fly ash. It took 3h and 2h to 1250°C and 1300°C clinkers, respectively, for the completion of burning, where-as 30 min burning was sufficient to 1350°C clinker. Metastable formation of gehlenite was noticed in 1250°C and 1300°C clinkers and this mineral changes into haüyne and belite during the repetition of burning, reacting with anhydrite remaining. Under the microscope belite grains are relatively large, showing rather lower refractive indices than those of β-belite stabilized with minor boron. haüyne grains are generally minute, showing somewhat higher refractive indices than those of pure haüyne. Both belite and haüyne are colourless and transparent. Presence of brownmillerite was encountered in very small amount. The 1300°C and 1350°C clinkers comprise glasses. Continuously, forming 15mmφ pellets, clinkers were burnt at 1250°C, 1300°C and 1350°C for 1h in order to examine the burnability and the effect of secondary addition of gypsum to the cements. In this case burnability was considerably improved except 1250°C clinker in which large amount of gehlenite was still observed. The 1350°C cement showed poor hydration strength probably caused by the enclosure of glass present on minute grains of haüyne. This poor hydration can be improved greatly by 5 percent secondary addition of gypsum to the cement. As a consequence, fly ash can be utilized to haüyne-belite cements, when burnt at 1300°-1350°C without addition of any flux agent. However, the elimination of residual free carbon, unburnt fine grained coal, mechanically mixed in fly ash is indispensable, since much gypsum is consumed due to the action of reduction of the carbon included.

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Amorphous, α-, and β-₃N₄ powders were activated by the vibration ball-mill in purified methanol, and the surface activity of ground powders has been determined by Temperature-Programmed Desorption method (TPD) using ammonia gas. The concentration of active site with a potential energy equivalent to peak temperature (T_p) in spectrum increased remarkably by the ball-milling treatment of amorphous-Si₃N₄. α- and β-Si₃N₄ also had the active sites produced by the ball-milling treatment. The concentration of active site increased with increasing of ball-milling time. A method for measuring surface activity of ceramic raw materials by Temperature-Programmed Desorption has been proposed.

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