Gypsum & Lime
Online ISSN : 2185-4351
ISSN-L : 0559-331X
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Volume 1980, Issue 168
Displaying 1-5 of 5 articles from this issue
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  • Effect of Outgassing Temperature on Surface Properties of Calcium Carbonate
    Masatoshi CHIKAZAWA, Takafumi KANAZAWA
    1980 Volume 1980 Issue 168 Pages 244-249
    Published: September 01, 1980
    Released on J-STAGE: March 07, 2011
    DOIhttps://doi.org/10.11451/mukimate1953.1980.244
    JOURNAL FREE ACCESS
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    CaCO3 prepared by grinding limestone was outgassed at various temperatures under a reduced pressure (10-5 mmHg) for 6-15 hours. The surface area of CaCO3 and adsorbed amount of water vapor on it at 15°C were measured.
    From the V-t plots of nitrogen adsorption on CaCO3 heat-treated, it was found that CaCO3 particles have micropores on their surfaces and their radii were 6Å in size. The water molecules caught strongly inside of these micropores got off entirely at about 180°C and the surface area of CaCO3 increased with increasing the amount of the outgassed water molecules. However, the micropores disappeared gradually by sintering in microscale at above 180°C, then the value of the surface area decreased reversely with temperature rise. The water vapor affinity of CaCO3 outgassed at 330°C was found to be considerably small. In this case, the regularity of ionic configuration on the surface will be enhanced by the sinter-ing. Therefore, it is considered that the water molecules are adsorbed with a regularly oriented structure on the sites, being distributed fixedly on the surface of CaCO3 particle.
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  • Synthesis of Foshagite and Production of Molded Products
    Kazuhiko KUBO, Kazuo SHIBAHARA
    1980 Volume 1980 Issue 168 Pages 249-254
    Published: September 01, 1980
    Released on J-STAGE: March 07, 2011
    DOIhttps://doi.org/10.11451/mukimate1953.1980.249
    JOURNAL FREE ACCESS
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    An aqueous slurry containing foshagite [Ca4Si3O9 (OH) 2] was hydrothermally prepared by stirring a mixture of amorphous silica and milk of lime in an autoclave at a vapor pressure of 15 kg/cm2 and a temperature of 200°C for 10-30 hrs. In the starting mixture the molar ratio of CaO to SiO2 and weight ratio of water to total solid were 1 : 1. 15-1. 35, and 1 : 12, respectively. The properties of the synthesized products were studied through X-ray diffraction analysis and electron microscopic observation.
    Foshagite could be synthesized at 200°C for 10 hrs, which may be practicable conditions in industrial production. Electron microscopic observation showed that the slurry consisted of spherical secondary particles with 10-40 μm in diameter and the structure of the secondary particles were similar to that of the secondary particles of xonotlite obtained under the similar synthetic conditions. It was confirmed that light molded products of high mechanical strength were obtained by adding reinforcing fibers to the foshagite slurry.
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  • Chemical Analytical Method of Calcium Sulfite Hemihydrate
    Tamotsu YASUE, Kazunao FUKUDA, Yasuo ARAI
    1980 Volume 1980 Issue 168 Pages 255-261
    Published: September 01, 1980
    Released on J-STAGE: March 07, 2011
    DOIhttps://doi.org/10.11451/mukimate1953.1980.255
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  • Microstructure of Coral Skeleton
    Hiromutsu WAKANO, Minoru SERIZAWA, Takako TAKAHASHI
    1980 Volume 1980 Issue 168 Pages 261-267
    Published: September 01, 1980
    Released on J-STAGE: March 07, 2011
    DOIhttps://doi.org/10.11451/mukimate1953.1980.261
    JOURNAL FREE ACCESS
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    Some mechanical properties and microstructure of coral skeleton were investigated in a series of studies on natural hard tissues as inorganic and organic composite materials. The coral skeletons used here were Corallium konojoj and Corallium japonicum.
    Their mechanical properties of them were as follows; bending strength : 5-10 kg/mm2, modulus of elasticity : 5.3-6.6 × 103 kg/mm2, compressive strength : 20-30 kg/mm2, and vickers hardness : 230-300. The range of specific gravity was 2.68-2.70. It could be seen by thermal analysis and X-ray diffraction that the most part (more than 96 wt%) of coral skeleton was occupied by carbonate and that the crystal form of the carbonate was calcite.
    In the microstructures of the coral skeletons, micro crystals of various sizes (more than 1μm) and shapes, their dense agglomerations, and vacant holes or voids of various sizes were found by SEM observation. The holes or voids existed irregularly. It was thought that such irregular faults resulted in more variational and lower bending strengths of coral skeletons than those of seashells.
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  • Coal Desulfurization
    Tohru KAWAHARA, Kunio YOSHIDA
    1980 Volume 1980 Issue 168 Pages 269-276
    Published: September 01, 1980
    Released on J-STAGE: March 07, 2011
    DOIhttps://doi.org/10.11451/mukimate1953.1980.269
    JOURNAL FREE ACCESS
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