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
These inclusions occur in the quartz phenocrysts of the topazite porphyry inTaishun County of Zhejiang Province. The rock usually has a typically igneousporphyritic texture. Making up 20% of the whole volum, the pheno...These inclusions occur in the quartz phenocrysts of the topazite porphyry inTaishun County of Zhejiang Province. The rock usually has a typically igneousporphyritic texture. Making up 20% of the whole volum, the phenocrysts are com-posed chiefly of the euhedral quartz 1-2 mm in diameter and occasionally of mica.The groundmass of the rock is fine-grained in texture, consisting essentially ofeuhedral-subhedral prismatic topaz （35%） and anhedral quartz （45%）. Thecomponents of the rock are:SiO<sub>2</sub> 79.89%, Al<sub>2</sub>O<sub>3</sub> 15.19%, Fe<sub>2</sub>O<sub>3</sub>, 0.36%, FeO 0.05%,展开更多
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These inclusions occur in the quartz phenocrysts of the topazite porphyry inTaishun County of Zhejiang Province. The rock usually has a typically igneousporphyritic texture. Making up 20% of the whole volum, the phenocrysts are com-posed chiefly of the euhedral quartz 1-2 mm in diameter and occasionally of mica.The groundmass of the rock is fine-grained in texture, consisting essentially ofeuhedral-subhedral prismatic topaz （35%） and anhedral quartz （45%）. Thecomponents of the rock are:SiO<sub>2</sub> 79.89%, Al<sub>2</sub>O<sub>3</sub> 15.19%, Fe<sub>2</sub>O<sub>3</sub>, 0.36%, FeO 0.05%,
