As a result of examination on the Cr (VI) immobilization behavior of calcium aluminoferrites, the following results were obtained. Each type of calcium aluminoferrites sorbs Cr (VI) in liquid phase according to the hydration. The Cr (VI) decreasing rate of calcium aluminoferrites is larger than that of OPC or BB, and its immobilization capacity is also large. According to estimation of Cr immobilization capacity per gram of various calcium aluminoferrites, the capacities of C6A2F and C4AF are 109 mg·g-1 and 101 mg·-1 respectively. When calcium aluminoferrites sorbed Cr according to the hydration, they took Cr into the hydrated products in the form of Cr (VI) as it was before. Formation of CrO42- type U-phase was confirmed in a case of high Cr concentration. This phenomenon was supposedly caused by the follows : (1) the main component of the Cr standard solution was K2Cr2O7, (2) both concentrations of alkali metal ions (K, Na) and CrO42- were high by the addition of NaOH for adjusting pH to neutral state. Compared with calcium silicate, OPC and BB, calcium aluminoferrites are resistant to the leaching of Cr (VI) that was sorbed by the hydration, which leads to excellent immobilizing ability for Cr (VI).
As a result of examination on the effect of sulfate ions on the hexavalent chromium immobilization behavior of calcium aluminates, the following conclusions were obtained. Even in a system in coexistence with a large amount of sulfate ions, calcium aluminates immobilize hexavalent chromium in a liquid phase following the progress of hydration. However the immobilization rate became slow through the coexistence with sulfate ions. Calcium aluminates immobilized sulfate ions together with hexavalent chromium in the liquid phase at the same time. The main product in the initial stage of hydration was ettringite, and it was replaced with mono-sulfate, which became the main hydration product afterwards. Hexavalent chromium in the liquid phase tended to decrease prominently from the stage when the formation of mono-sulfate was recognized. The reason why the immobilization rate of hexavalent chromium becomes slow in a system in coexistence with sulfate ions is presumably due to that the formation reaction of ettringite, which scarcely immobilize hexavalent chromium, proceeds predominantly in the initial stage of hydration.
The long-term stability and durability of autoclaved cementitious building materials such as wall and roof is required in connection with the quality assurance systems of houses. For that purpose, the reducing water to powder ratio and formation of crystal 1.1 nm tobermorite are necessary by autoclaved curing. This paper describes the effect of the water to powder ratio on reaction ratio of composite materials and CaO/SiO2 ratio and the shape of calcium silicate hydrates in autoclaved Portland Cement (abbreviated as PC) -α-quartz-water systems at 180°C. The tobermorite having a plate type are observed at 0.5 of water to powder ratio. When the water to powder ratio is 0.3, oriented fiber type crystals of tobermorite was formed. But, when the water to powder ratio is 0.2, crystal tobermorite is not observed and the gel of densely C-S-H is produced. This is based on the high CaO/SiO2 molar ratio of hydrated products due to the reduction for reaction of α-quartz covered by densely C-S-H. Therefore, in autoclaved high strength building materials, 0.3 of water to powder ratio is suitable.
The Marangoni convection is supposed to be an important phenomenon that significantly affects the solidification. For understanding the Marangoni convection mechanism, visualizing the convection phenomenon of molten tin with ultrasonic wave has been conducted. This paper reports development of a tracer material that is used in the molten tin for visualizing the convention by ultrasonic wave. In this research, we have chosen vitreous hollow sphere with approximately 1 mm diameter, examined several plating processes, constructed the equipment of the plating process, and succeeded in coating the surface of vitreous hollow sphere with nickel. The particle obtained is a so-called micro metal balloon (MMB) that has spherical hollow structure with metallic luster. The composition of MMB was almost fixed in a weight ratio of Ni : P=84 : 16, the distribution of Ni thickness was sharp, and finally it was confirmed that the MMB was suitable for the tracer material.
The purpose of this paper is to develop high efficient lithium absorbent of manganese dioxide by mechanochemical treatment, using the same ball mill processing as the method applied to magnesium in the previous work. And the following interesting results are obtained. 1) Both the results of specific surface measurement by gas absorption method and the observation by SEM indicate that the size of primary particle of manganese dioxide powder is not changed and kept almost constant within the experimental condition of 0 to 48 hrs by ball mill handling. 2) The optimum ball mill handling time is pointed out to exist at 24 hrs, at which the maximum lithium adsorption of 10.79 mg lithium ion per 1 g of manganese dioxide was observed. 3) The maximum lithium adsorption quantity mentioned above is pointed out to be about 1.8 times of value on sample with 0 hrs handling, and it is more than twice of the case of magnesium oxide in the previous paper. 4) Above results, from 1) to 3), indicate that high efficient lithium adsorbent of manganese dioxide can be prepared by ball mill handling. described in this paper