The surface properties of heavy and colloidal calcium carbonate heat-treated under flowing nitrogen were examined from SEM, XRD, IR, specific surface area measurements and desorbed gas analysis by using modified temperature programmed desorption method. As a result, it was suggested that the structure of heavy calcium carbonate surface was almost as same as bulk. The physisorbed water molecules on the surface were desorbed over the range of room temperature to 200°C. The remarkable surface pyrolysis of calcium carbonate occurred with degassed carbon dioxide at 500°C. On the other hand, the surface component of colloidal calcium carbonate was similar to calcium hydroxide in several surface layers. The physisorption water molecules were desorbed until 250°C. The thermal decomposition of calcium carbonate under the layer of calcium hydroxide was slightly observed at above 500°C. It was concluded that the difference of surface properties between heavy and colloidal calcium carbonate, such as desorption temperature of physisorbed water, and surface thermal decomposition mechanism, was affected by a difference of surface initial condition.

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Layered double hydroxides (LDHs) of M²⁺-Al³⁺-CO₃^2- systems (M²⁺=Mg²⁺, Zn²⁺, Ni²⁺) have been prepared by the coprecipitation method to examine as a precursor of chemical fixation agent of carbonate ion for the recovery of carbon dioxide from flue gases, in which 0.5 mol·dm^-3 mixed solution of MCl₂ and AlCl₃ was added to a Na₂CO₃ solution at pH 10 and 40°C with vigorous agitation. After the calcination of the LDHs at various temperatures, the intercalation behavior of carbonate ion by the resulting oxide solid solution powders has been investigated quantitatively. At the M²⁺/Al³⁺ molar ratio of 1-6, the high crystalline LDH products formed both in the Mg-Al and Zn-Al systems, but the lower crystalline LDH product formed in the Ni-Al system at the Ni²⁺/Al³⁺ molar ratio of 2-6. According to the thermal analysis, the elimination temperature of carbon dioxide from the LDHs was in order; Zn-Al<Ni-Al<Mg-Al systems. As the result of the rehydration reaction of the oxides in 0.05 mol·cm^-3 Na₂CO₃ solution at 25°C, the Mg-Al and Zn-Al oxides calcined at 600°C having the M²⁺/Al³⁺ molar ratio of 2 were found to show the largest intercalation capacity for carbonate ion as 97-124 mg-CO₃^2-/g-oxide with reconstructing the original LDH structure. However, the rehydration reaction did not occur for the Ni-Al oxide. It was concluded from the repeated calcination-rehydration experiments that both of the Mg-Al and Zn-Al oxides can be used as the practical fixation agent of carbonate ion.

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Fire resistant stone (FRS) in Niijima island of Tokyo consists mainly of glassy aluminosilicate. The purpose of this study is to develop a fluorophlogopite mica glass-ceramic from crashed FRS powder. A batch of starting materials was prepared by mixing 100 parts by weight FRS, 15 of magnesium oxide, 15 of potassium carbonate, 15 of magnesium fluoride and 10 sodium borate (anhydrous). The batch was melted at 1450°C for 2 hours and quenched in air. The gray glass obtained was reheated at 1150°C for 6 hours. The resulting light brown fluorophlogopite mica glass-ceramic had the following properties, i.e., thermal expansion coefficient of 100×10^-7/°C, Shore hardness of 85, specific gravity of 2.6 and almost the same machinability as “Macor”.

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Porous SiC ceramics were fabricated by the reaction with mullite. SiC particle of 0.6μm was intimately mixed with 5-20 wt.% mullite with the average grain size of about 1.4μm by ball-milling procedure. The mixed powder was uniaxialy compressed and CIPed. Next, the green compact was sintered at 1970°C for 2 h under vacuum. The products showed the porosity of 40 to 55%, and 2μm of mean pore size. The reaction of gasification was expressed by following the equation.
SiC+2SiO₂→3SiO (g) +CO (g)
The component of alumina in the mullite was effected on the sintering of SiC grain because of the formation of liquid phase. As a results, the strength of the product with 40% porosity was about 80 MPa.

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Set plaster of gypsum, which can withstand higher temperature, is expected for casting mold etc. Two kinds of gypsum with different Na contents derived from sodium citrate which affected for crystal habit during crystal growth were used. As the results, the set plaster of gypsum with low Na content withstoods at higher temperature than that with high Na contents. Moreover, the effects of additives into gypsum with low Na content are investigated. Two kinds of sulfate hydrate (CaSO₄·2H₂O and MgSO₄·7H₂O) and amorphous silica hydrate for additives are effective for prevention of thermal decomposition.

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In this paper, the reinforcement mechanism of plant fiber reinforced gypsum composites has been studied. Results show, using compound excitation agent in composites, the latent hydraulicity of slag could be excited, so that the cementing materials are formed and the internal microstructures of gypsum matrix composites are improved. Moreover, treating the surface of plant fiber with styrene-acrylic acid latex, the interface bonding strength between fiber and gypsum matrix is increased, and the mechanical properties of composites are raised remarkably.

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Ni compound-coated CaCO₃ particles were prepared by heating nickel nitrate solution with the suspensions of CaCO₃ particles. The morphology of coated Ni compound depended on reaction temperatures and nickel nitrate concentration. Most uniform coating was achieved by the reaction at 70°C, under [Ni (NO₃) ₂] = 0.01M, and suspension of calcite = 0.1M for 5 hours

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Porous SiC ceramics were fabricated by the reaction with silicon nitride. SiC powder of 0.6 μm was intinately mixed with 10-30 wt.% silicon nitride by ball-milling. The mixture was formed in the platelet shape and CIPed. The green compact was sintered at 1970°C for 2 h in flowing Ar gas, and then annealed at 1800°C for 2 h inder vacuum. The products had the porosity of 35 to 50%, and 1-2 μm pf mean pore size. The gasification was in duced by the following equation.
Si₃N₄→3Si+N₂↑
The product with 40% porosity showed the bensing strength of about 80 MPa.

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