The surface properties of calcium carbonate and silica which were modified with isopropyltriisostearoyltitanate were investigated. Especially, the reaction mechanism of surface modification, and the relationship between the surface structure of the modified samples and hydrophobic property were studied. It was realized that the modification reaction progressed when adsorbed water did not exist, from the examination of the modification reaction under the controlled amount of physisorbed water. Moreover, it was confirmed not to influence the value of the saturated surface density of the modifier by the adsorbed water existence. The saturated surface density of modifier on the silica and calcium carbonate was 0.3 nm-2 and 0.9 nm-2 respectively. This difference was presumed to be because of the steric hindrance of modifiers causing by the difference of site distribution on both samples. In addition, the mechanism of hydrophobic on the modified surface was examined by preferential dispersion test. As a result, both samples became hydrophobic at the same density of the modifier of about 0.2 nm-2, though the distribution of the initial reaction site on the surface of both samples is different. This value is considerably lower than the saturated surface density of modifier. From the above-mentioned, it was considered that hydrophobic property on the surface of the modification sample was influenced by the state of distribution of the modifier. Moreover, it was suggested that hydrophobic property increase by the thickness of modification layer, because the continuous structure of the modifier became close more than this density of the modifier.
Hydration reaction of calciumsulphoaluminate type expansive additive containing excess freelime has been studied. Amounts of hydrates and hydration rates of compounds in expansive additive were examined by XRD quantitative analysis (Internal Standard Method) and TG-DTA. In the early stage of the reaction, the free-lime reacted radically, but hauyne and anhydrite hydrated slowly. The hydration products were calcium hydroxide, ettringite, gypsum and monosulphate. The presence of gel was assumed by a material balance of hydration reaction. In the case of calciumsulphoaluminate type, gel phase was consists of CaO, Al2O3, and SO3. On the other hand, in the case of free-lime type expansive additive, gel phase was consists of CaO, SiO2, and SO3. A formula of hydration reaction was estimated on the basis of the results of quantitative analysis. Formation of ettringite from hauyne was formulated by the reaction formula such as 1 molar hauyne produced about 2 molar ettringite and gel.
This paper reported the recycling of incinerated municipal solid wastes in the form of molten slag obtained by melting ash. We stadied the fundamental characteristics of molten slag and examined the applicability to road construction aggregates. Molten slag contained artificial minerals, mainly anorthite (CaAl2Si2O8) and gehlenite (Ca2Al2SiO7). The results of leaching tests satisfied the requirement stated in the Japanese regulatory leaching test (JLT-13) and assured stability and safety of the molten slag. From the results of CBR test, the modified CBR value of 98% was obtained. We have concluded that it could be possible to utilize the molten slag as road construction material.
Antimicrobial activity of the mixed powders of MgO and ZnO and even the solid solution powders of these ceramics was studied by measuring the change in electrical conductivity with bacterial growth of Staphylococcus aureus (Conductance method). MgO and ZnO powders were heated at 1400°C for 3 h in air and then they were mixed with various mass ratios (MgO/ZnO). After milling the mixed powders by planetary ball mill, the powders with a average particle size of 0.1 μm were used in antimicrobial tests. It was clarified that the antimicrobial activity of the mixed powders in the mass ratio (MgO/ZnO) more than 1 was comparable with that of MgO. In the case of the mixed powders with the ratio less than 1, however, the activity decreased, compared with MgO. MgO-ZnO solid solution powders were synthesized by heating at 1400°C for 3 h in air. A single phase with cubic type structure was obtained in the mass ratio (MgO/ZnO) of 4.0 and 1.5, but the ratio of 0.67 resulted in a ZnO phase in addition to MgO-ZnO solid solution. From the results of antimicrobial tests by using the solid solution powders with a particle size of 0.1 μm, it was found that the antimicrobial activity against Staphylococcus aureus decreased with increasing the dopant amount of ZnO in MgO-ZnO solid solution.
Tl-based superconductors, Tl2Ba2Can-1Cu3O2n+4, were synthesized and the effect of calcium concentration on the superconductor phase formation was studied. The method involved the synthesis of T12Ba2Ca2.5Cu3Oy by sintering in an evacuated quartz tube at 860°C for 12 h. The sintering time was required much less than those of other synthesizing methods of superconductors. The superconductor synthesized by this method was found to have the critical temperatures, Tczero=127 K and Tcmag=130 K. It was also found that the Hg doping into the Tl2Ba2Ca2.5Cu3Oy led to the stabilization of T1-2223 structure, and the phase with the composition of Tl1.8Hg0.2Ba2Ca2.5Cu3Oy, exhibited Tczero=127 K and Tcmag=127 K.