The room temperature stabled monoclinic KNbO3 nanowires were found to act as photocatalyst for photocatalytic methane production and dye degradation in this work. Higher activities have been observed for monoclinic ph...The room temperature stabled monoclinic KNbO3 nanowires were found to act as photocatalyst for photocatalytic methane production and dye degradation in this work. Higher activities have been observed for monoclinic phase compared to the reference（orthorhombic phase）. In the photoreduction of CO2 reaction, the monoclinic KNbO3 nanowires exhibited a CH4 evolution rate of 0.025 μmol·g-1·h-1, which was higher than 0.021 μmol·g-1·h-1 of orthorhombic KNbO3 nanowires. In the photodegradation of rhodamine B（Rh B）, almost all the Rh B were degraded after 90 min light illumination for monoclinic KNbO3 nanowires. But for orthorhombic KNbO3 nanowires, the concentration of Rh B only decreased to 62% of the initial value.展开更多
Skeletal form of KNbO3 crystals growing in Li2B4O7 solvent was in-situ observed at 900℃ and it was found that shallow depression started to develop on the surface of KNbO3 crystals when the crystal size exceeded seve...Skeletal form of KNbO3 crystals growing in Li2B4O7 solvent was in-situ observed at 900℃ and it was found that shallow depression started to develop on the surface of KNbO3 crystals when the crystal size exceeded several micron, typically 7 micron. Based on the quantitative criterion derived by Chernov, the estimated critical size of KNbO3 crystals was 1 micron, which was consistent with the experimental measurement. The kinetic coefficients, kcorner and kcr, in the criterion were experimentally obtained in the diffusive-convective and diffusive-advective flow states respectively.展开更多
This paper reports that the rapid solidification of mixed Li2B4O7 and KNbO3 melted in a Pt loop heater has been performed experimentally by the method of quenching, and various morphologies of KNbO3 crystals have been...This paper reports that the rapid solidification of mixed Li2B4O7 and KNbO3 melted in a Pt loop heater has been performed experimentally by the method of quenching, and various morphologies of KNbO3 crystals have been observed in different regions of the quenched melt-solution. Dendrites were formed in the central region where mass transfer is performed by diffusion, whereas polygonal crystals with smooth surface grew in the marginal region where convection dominates mass transport. Based on measurement of KNbO3 concentration along crystal interface by electronic probe analysis, it finds the variety of crystal morphologies, which is the result of different solute distributions： in the central region the inhomogeneity of solute concentration is much sharper and morphological instability is easier to take place; nevertheless in the marginal region the concentration homogeneity has been greatly enhanced by convection which prevents the occurrence of morphological instability. Additional solute distribution in the melt along the primary dendrite trunk axis as well as that in mushy zones has also been determined. Results show that the solute concentration in the liquid increases linearly with distance from the trunk tip and more solutes were found to be concentrated in mushy zones. The closer the mushy zone is to trunk tip, the lower the solute concentration will be there.展开更多
The geometrical structure optimization,band structure,density of states,and charge density contour of potassium niobate(KNbO_(3))in the bulk[100]direction and(100)surface are calculated and analyzed using density func...The geometrical structure optimization,band structure,density of states,and charge density contour of potassium niobate(KNbO_(3))in the bulk[100]direction and(100)surface are calculated and analyzed using density functional theory.The elastic constants,which can describe the bonding characteristics and structural stability,are also computed,and the dielectric function,which can be used to calculate all the other optical properties of the material,is evaluated.Local density approximation functional analysis using CASTEP software is also employed.Several similarities and differences are observed in the properties of the KNbO_(3) bulk and surface.Almost all of the calculated results for the bulk sample are twice those of the surface sample.The results are consistent with the experiment.展开更多
基金supported by the National Basic Research Program of China(973 Program,2013CB632400)the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe National Natural Science Foundation of China(Nos.51272102 and 21103070)
文摘The room temperature stabled monoclinic KNbO3 nanowires were found to act as photocatalyst for photocatalytic methane production and dye degradation in this work. Higher activities have been observed for monoclinic phase compared to the reference（orthorhombic phase）. In the photoreduction of CO2 reaction, the monoclinic KNbO3 nanowires exhibited a CH4 evolution rate of 0.025 μmol·g-1·h-1, which was higher than 0.021 μmol·g-1·h-1 of orthorhombic KNbO3 nanowires. In the photodegradation of rhodamine B（Rh B）, almost all the Rh B were degraded after 90 min light illumination for monoclinic KNbO3 nanowires. But for orthorhombic KNbO3 nanowires, the concentration of Rh B only decreased to 62% of the initial value.
基金The present work was supported by the foundation for key research project of microgravity science from the State Science andTechnology Commission of China(95-Yu-34)the National Natural Science Foundation of China under grant No.59832080.
文摘Skeletal form of KNbO3 crystals growing in Li2B4O7 solvent was in-situ observed at 900℃ and it was found that shallow depression started to develop on the surface of KNbO3 crystals when the crystal size exceeded several micron, typically 7 micron. Based on the quantitative criterion derived by Chernov, the estimated critical size of KNbO3 crystals was 1 micron, which was consistent with the experimental measurement. The kinetic coefficients, kcorner and kcr, in the criterion were experimentally obtained in the diffusive-convective and diffusive-advective flow states respectively.
基金supported by the National Natural Science Foundation of China (Grant Nos 50331040 and 50802105)the Innovation Funds from Shanghai Institute of Ceramics, Chinese Academy of Sciences (Grant No SCX0623)
文摘This paper reports that the rapid solidification of mixed Li2B4O7 and KNbO3 melted in a Pt loop heater has been performed experimentally by the method of quenching, and various morphologies of KNbO3 crystals have been observed in different regions of the quenched melt-solution. Dendrites were formed in the central region where mass transfer is performed by diffusion, whereas polygonal crystals with smooth surface grew in the marginal region where convection dominates mass transport. Based on measurement of KNbO3 concentration along crystal interface by electronic probe analysis, it finds the variety of crystal morphologies, which is the result of different solute distributions： in the central region the inhomogeneity of solute concentration is much sharper and morphological instability is easier to take place; nevertheless in the marginal region the concentration homogeneity has been greatly enhanced by convection which prevents the occurrence of morphological instability. Additional solute distribution in the melt along the primary dendrite trunk axis as well as that in mushy zones has also been determined. Results show that the solute concentration in the liquid increases linearly with distance from the trunk tip and more solutes were found to be concentrated in mushy zones. The closer the mushy zone is to trunk tip, the lower the solute concentration will be there.
文摘The geometrical structure optimization,band structure,density of states,and charge density contour of potassium niobate(KNbO_(3))in the bulk[100]direction and(100)surface are calculated and analyzed using density functional theory.The elastic constants,which can describe the bonding characteristics and structural stability,are also computed,and the dielectric function,which can be used to calculate all the other optical properties of the material,is evaluated.Local density approximation functional analysis using CASTEP software is also employed.Several similarities and differences are observed in the properties of the KNbO_(3) bulk and surface.Almost all of the calculated results for the bulk sample are twice those of the surface sample.The results are consistent with the experiment.
