Floating zone method with optical radiation heating was applied to growing a class of R2PdSi3（R=Pr,Tb and Gd） single crystals due to its containerless melting and high stability of the floating zone.One serious prob...Floating zone method with optical radiation heating was applied to growing a class of R2PdSi3（R=Pr,Tb and Gd） single crystals due to its containerless melting and high stability of the floating zone.One serious problem during the single crystal growth,precipitates of secondary phases,was discussed from the following four parts：precipitates from the raw materials and preparation process,precipitates formed during the growing process,precipitates in the melts and precipitates in the grown crystals.Annealing treatment and composition shift can effectively reduce the precipitates which are not formed during the crystallization but precipitated on post-solidification cooling from the as-grown crystal matrix because of the retrograde solubility of Si.展开更多
Gd2PdSi3 single crystals were grown by a vertical floating zone method with radiation heating at a zone traveling rate of 3 mm/h. The compound exhibited congruent melting behavior at a liquidus temperature of about 17...Gd2PdSi3 single crystals were grown by a vertical floating zone method with radiation heating at a zone traveling rate of 3 mm/h. The compound exhibited congruent melting behavior at a liquidus temperature of about 1700 ＆#176;C. The slightly Pd-depleted composition of the crystal, with respect to the nominal Gd2PdSi3 stoichiometry, led to gradual accumulation of Pd in the traveling zone and to a decreasing operating temperature during the growth process. Thin platelet-like precipitates of a GdSi phase were detected in the stoichiometric feed rod growth crystal matrix which can be reduced by annealing treatment. Feed rod composition shift crystal growth was proved to be a better way of getting high quality of Gd2PdSi3 single crystal.展开更多
Ammonium pollution becomes severe during mining of ionic rare earth-ores in southern China.As one of the main clayminerals in soils of ionic rare earth mines,halloysite plays an important role in ammonium adsorption.I...Ammonium pollution becomes severe during mining of ionic rare earth-ores in southern China.As one of the main clayminerals in soils of ionic rare earth mines,halloysite plays an important role in ammonium adsorption.In this study,the saturatedadsorption capacity,factors affecting adsorption and adsorption kinetics of halloysite for ammonium were investigated.The resultsindicated that the ammonium adsorption of halloysite was saturated with1.66mg/g at303K,pH of5.6and initial ammoniumconcentration of600mg/L(about half of the actual initial in-situ leaching concentration).When the initial concentration of NH4?-N,pH values and temperatures(288K to313K)increased,the ammonium adsorption capacity of halloysite increased.The ammoniumisothermal adsorption of halloysite matched the Langmuir and Freundlich isotherms.The adsorption process of ionic rare earthmining soils for ammonium was favorable.And the adsorption process followed closely the pseudo-second kinetic equation.展开更多
基金Project (2008629045) supported by the China Scholarship Council (Constructing High-Level University Project)
文摘Floating zone method with optical radiation heating was applied to growing a class of R2PdSi3（R=Pr,Tb and Gd） single crystals due to its containerless melting and high stability of the floating zone.One serious problem during the single crystal growth,precipitates of secondary phases,was discussed from the following four parts：precipitates from the raw materials and preparation process,precipitates formed during the growing process,precipitates in the melts and precipitates in the grown crystals.Annealing treatment and composition shift can effectively reduce the precipitates which are not formed during the crystallization but precipitated on post-solidification cooling from the as-grown crystal matrix because of the retrograde solubility of Si.
基金Project(51301021)supported by the National Natural Science Foundation of ChinaProjects(2013G1311051,CHD2011JC139)supported by the Fundamental Research Funds for the Central Universities,ChinaProject(SKLSP201302)supported by the State Key Laboratory of Solidification Processing in NWPU,China
文摘Gd2PdSi3 single crystals were grown by a vertical floating zone method with radiation heating at a zone traveling rate of 3 mm/h. The compound exhibited congruent melting behavior at a liquidus temperature of about 1700 ＆#176;C. The slightly Pd-depleted composition of the crystal, with respect to the nominal Gd2PdSi3 stoichiometry, led to gradual accumulation of Pd in the traveling zone and to a decreasing operating temperature during the growth process. Thin platelet-like precipitates of a GdSi phase were detected in the stoichiometric feed rod growth crystal matrix which can be reduced by annealing treatment. Feed rod composition shift crystal growth was proved to be a better way of getting high quality of Gd2PdSi3 single crystal.
基金Project(51674305)supported by the National Natural Science Foundation of ChinaProject(1602FKDC007)supported by Science and Technology Program of Gansu Province,ChinaProject(NSFJ2015-K06)supported by the Jiangxi University of Science and Technology,China
文摘Ammonium pollution becomes severe during mining of ionic rare earth-ores in southern China.As one of the main clayminerals in soils of ionic rare earth mines,halloysite plays an important role in ammonium adsorption.In this study,the saturatedadsorption capacity,factors affecting adsorption and adsorption kinetics of halloysite for ammonium were investigated.The resultsindicated that the ammonium adsorption of halloysite was saturated with1.66mg/g at303K,pH of5.6and initial ammoniumconcentration of600mg/L(about half of the actual initial in-situ leaching concentration).When the initial concentration of NH4?-N,pH values and temperatures(288K to313K)increased,the ammonium adsorption capacity of halloysite increased.The ammoniumisothermal adsorption of halloysite matched the Langmuir and Freundlich isotherms.The adsorption process of ionic rare earthmining soils for ammonium was favorable.And the adsorption process followed closely the pseudo-second kinetic equation.
