Papers by Keyword: Hydrothermal Conditions

Abstract: This paper deals with hydrothermal stability of inorganic aluminosilicate polymers, which were prepared by mixing blast furnace slag, fly ash and cement kiln dust in ratio 4:2:1. Cement kiln dust was used as alkaline activator with 4M sodium hydroxide solution. Samples were cured under hydrothermal conditions up to 170 °C for 24h and changes in mechanical properties, phase composition and porosity were monitored. During the hydrothermal process, the formation of zeolite from cancrinite group was monitored. The effect of the change of composition on the thermal expansion/shrinkage was studied by thermal dilatometry. Autoclaved samples were subjected to significant irreversible shrinkage during heating to 900 °C.

Abstract: 3D-ordered dumbbell-like ZnO microcrystals were prepared under hydrothermal conditions without using any additive, template or surfactant. FE-SEM images show that 3D-ordered dumbbell-like ZnO microcrystals are made of two elements-(Ⅰ) dumbbell-like microrods and (Ⅱ) nanorods that grow on the two ends of microrods. The thermal radiation properties of 3D-ordered dumbbell-like ZnO microcrystals were discussed in detail.

Abstract: (Zr0.8Sn0.2)TiO4 nanopowders for microwave ceramics were prepared by a hydrothermal synthesis route. Effects of hydrothermal conditions on crystal structure, morphology and sintering performance of the powders were characterized by X-ray, SEM and TG-DTA, respectively. The powders with mean size of 80 ~ 200 nm was obtained. Ceramics with 92.3% of theoretical density were fabricated at 1260°C with the powders. Dielectric properties of the samples were measured and it gives a dielectric constant of 35-36 and Q×f value of 4500-10000 GHz.

Abstract: Very fine diamond powder (1-3 ~m) was readily sintered under hydrothermal conditions, with new bond formation occurring between the diamond particles in a l0M-NaOH solution at 573 K maintained at 1 GPa pressure, for 24 hours. This new bonding material can be formed by carbonization, from a chlorinated hydrocarbon such as dichloromethane and 1, 1,1–trichloroethane. The carbonized material forms a new bond between the hydrogenated diamond particles by the release of hydrogen chloride. Using Raman spectroscopy and hydrogenated cubic boron nitride substrates it was indisputably demonstrated that diamond was synthesized under these alkaline hydrothermal conditions. The surface morphology of the hydrothermal product on the cubic boron was similar to the new growth on the diamond substrates.