In order to evaluate the spontaneous combustion hazard of sulfide concentrates in storage, three different kinds of sulfide concentrates （sulfur-rich sulfide concentrate, iron sulfide concentrate and copper sulfide c...In order to evaluate the spontaneous combustion hazard of sulfide concentrates in storage, three different kinds of sulfide concentrates （sulfur-rich sulfide concentrate, iron sulfide concentrate and copper sulfide concentrate） were obtained from a storage yard in Dongguashan Copper Mine, China. The reaction processes at different heating rates of 5, 10, 15, 20, and 25 ℃/min in air flow from ambient temperature to 1 000 ℃ were studied by TG-DTG-DSC analysis. By the peak temperatures of DTG curves, the whole reaction process for each sample was divided into different stages, and the corresponding apparent activation energies were calculated by the Ozawa-Flynn-Wall method. It is found that the reaction process of each sample is considerably complex; the apparent activation energy values change from 36 to 160 kJ/mol in different temperature ranges; sulfur-rich sulfide and iron sulfide concentrates have lower apparent activation energy than copper sulfide concentrate below 150 ℃; so they are more inclined to cause spontaneous combustion at ambient temperature.展开更多
This paper reports the effect of sol size on nanofiltration performances of sol–gel derived microporous zirconia membranes. Microstructure, pure water flux, molecular weight cut-off(MWCO) and salt retention of zircon...This paper reports the effect of sol size on nanofiltration performances of sol–gel derived microporous zirconia membranes. Microstructure, pure water flux, molecular weight cut-off(MWCO) and salt retention of zirconia membranes derived from zirconia sols with different sizes were characterized. Thermal evolution, phase composition, microstructure and chemical stability of unsupported zirconia membranes(powder) were determined by thermogravimetric and differential thermal analysis, X-ray diffraction, nitrogen adsorption–desorption and static solubility measurements. Results show that nanofiltration performance of zirconia membranes is highly dependent on sol size. The sol with an average size of 3.8 nm, which is smaller than the pore size of the γ-Al2O3support(pore size: 5–6 nm), forms a discontinuous zirconia separation layer because of excessive penetration of sol into the support. This zirconia membrane displays a MWCO value towards polyethylene glycol higher than 4000 Da. A smooth and defect-free zirconia membrane with a MWCO value of 1195 Da(pore size: 1.75 nm) and relative high retention rates towards Mg Cl2(76%) and Ca Cl2(64%) was successfully fabricated by dip-coating the sol with an appropriate size of 8.6 nm. Zirconia sol with an average size of 12 nm exhibits colloidal nature and forms a zirconia membrane with a MWCO value of 2332 Da(pore size: 2.47 nm). This promising microporous zirconia membrane presents sufficiently high chemical stability in a wide p H range of 1–12.展开更多
A promising preparation method for lithium hexafluorophosphate(LiPF6)was introduced.Phosphorus pentafluoride(PF5) was first prepared using CaF2 and P2O5 at 280℃for 3 h.LiPF6 was synthesized in acetonitrile solvent by...A promising preparation method for lithium hexafluorophosphate(LiPF6)was introduced.Phosphorus pentafluoride(PF5) was first prepared using CaF2 and P2O5 at 280℃for 3 h.LiPF6 was synthesized in acetonitrile solvent by LiF and PF5 at room temperature(20-30℃)for 4 h.The synthesized LiPF6 was characterized by infrared spectrometry and X-ray diffraction(XRD). Atomic absorption and ion chromatography results show that the purity of synthesized LiPF6 reaches 99.98%.Thermal stability of self-synthesized LiPF6 was analyzed by differential thermal analysis and thermogravimetry.The results indicate that the self-synthesized LiPF6 has higher purity,lower impurity contents and better thermal stability than the commercial LiPF6.展开更多
The heated process of raw materials for electron trapping materials (ETM) is investigated by thermo-analysis method. The temperature ranges of raw materials experienced some physical and chemical change processes, suc...The heated process of raw materials for electron trapping materials (ETM) is investigated by thermo-analysis method. The temperature ranges of raw materials experienced some physical and chemical change processes, such as dehydration, organic solvent removal, crystal sulphur burning, oxidation of alkaline earth sulfides and solid phase reaction (rare earth doped) and so on, are obtained. The experimental results also show that the presence of trace oxygen in shielded gas is very harmful to prepare the ETM.The raw material thermo-analysis results provide very important experimental reference for optimizing the ETM preparation techniques.展开更多
目的:探究中国药典和世界卫生组织双氰胺熔点对照品熔点差异的原因。方法:采用差示扫描量热分析(DSC)和热重/差热同步分析(TGA/SDTA)研究双氰胺熔点对照品的熔融过程,DSC升温速率10℃·min-1,干燥气N2流速50 m L·min-1,TGA/SDT...目的:探究中国药典和世界卫生组织双氰胺熔点对照品熔点差异的原因。方法:采用差示扫描量热分析(DSC)和热重/差热同步分析(TGA/SDTA)研究双氰胺熔点对照品的熔融过程,DSC升温速率10℃·min-1,干燥气N2流速50 m L·min-1,TGA/SDTA升温速率20℃·min-1,干燥气N2流速25 m L·min-1;并进一步通过HPLC法分析熔融前、中、后的样品。结果:差示扫描量热分析和热重/差热同步分析发现3个对照品的热力学行为基本一致,提示熔融后期可能已经热降解;HPLC法进一步证实双氰胺的熔融过程伴有部分降解。结论:热稳定性可能是造成中国药典和世界卫生组织双氰胺熔点对照品熔点差异的原因,双氰胺继续作为熔点对照品值得商榷。展开更多
基金Project (2006BAK04B03) supported by the National Science and Technology Pillar Program during the 11th Five-Year Plan Period of ChinaProject (kjdb200902-7) supported by Doctoral Candidate Innovation Research Support Program of Science & Technology Review, China+1 种基金Project (1960-71131100023) supported by Postgraduate Dissertation Innovation Foundation of Central South University, ChinaProject (ZKJ2009008) supported by Precious Apparatus Opening Center Foundation of Central South University, China
文摘In order to evaluate the spontaneous combustion hazard of sulfide concentrates in storage, three different kinds of sulfide concentrates （sulfur-rich sulfide concentrate, iron sulfide concentrate and copper sulfide concentrate） were obtained from a storage yard in Dongguashan Copper Mine, China. The reaction processes at different heating rates of 5, 10, 15, 20, and 25 ℃/min in air flow from ambient temperature to 1 000 ℃ were studied by TG-DTG-DSC analysis. By the peak temperatures of DTG curves, the whole reaction process for each sample was divided into different stages, and the corresponding apparent activation energies were calculated by the Ozawa-Flynn-Wall method. It is found that the reaction process of each sample is considerably complex; the apparent activation energy values change from 36 to 160 kJ/mol in different temperature ranges; sulfur-rich sulfide and iron sulfide concentrates have lower apparent activation energy than copper sulfide concentrate below 150 ℃; so they are more inclined to cause spontaneous combustion at ambient temperature.
基金Supported by the National Natural Science Foundation of China(20906047,21276123)the National High Technology Research and Development Program of China(2012AA03A606)+3 种基金State Key Laboratory of Materials-Oriented Chemical Engineering(ZK201002)the Natural Science Research Plan of Jiangsu Universities(11KJB530006)the"Summit of the Six Top Talents"Program of Jiangsu Provincea Project Funded by the Priority Academic Program development of Jiangsu Higher Education Institutions(PAPD)
文摘This paper reports the effect of sol size on nanofiltration performances of sol–gel derived microporous zirconia membranes. Microstructure, pure water flux, molecular weight cut-off(MWCO) and salt retention of zirconia membranes derived from zirconia sols with different sizes were characterized. Thermal evolution, phase composition, microstructure and chemical stability of unsupported zirconia membranes(powder) were determined by thermogravimetric and differential thermal analysis, X-ray diffraction, nitrogen adsorption–desorption and static solubility measurements. Results show that nanofiltration performance of zirconia membranes is highly dependent on sol size. The sol with an average size of 3.8 nm, which is smaller than the pore size of the γ-Al2O3support(pore size: 5–6 nm), forms a discontinuous zirconia separation layer because of excessive penetration of sol into the support. This zirconia membrane displays a MWCO value towards polyethylene glycol higher than 4000 Da. A smooth and defect-free zirconia membrane with a MWCO value of 1195 Da(pore size: 1.75 nm) and relative high retention rates towards Mg Cl2(76%) and Ca Cl2(64%) was successfully fabricated by dip-coating the sol with an appropriate size of 8.6 nm. Zirconia sol with an average size of 12 nm exhibits colloidal nature and forms a zirconia membrane with a MWCO value of 2332 Da(pore size: 2.47 nm). This promising microporous zirconia membrane presents sufficiently high chemical stability in a wide p H range of 1–12.
基金Project(2007CB613607)supported by the National Basic Research Program of China
文摘A promising preparation method for lithium hexafluorophosphate(LiPF6)was introduced.Phosphorus pentafluoride(PF5) was first prepared using CaF2 and P2O5 at 280℃for 3 h.LiPF6 was synthesized in acetonitrile solvent by LiF and PF5 at room temperature(20-30℃)for 4 h.The synthesized LiPF6 was characterized by infrared spectrometry and X-ray diffraction(XRD). Atomic absorption and ion chromatography results show that the purity of synthesized LiPF6 reaches 99.98%.Thermal stability of self-synthesized LiPF6 was analyzed by differential thermal analysis and thermogravimetry.The results indicate that the self-synthesized LiPF6 has higher purity,lower impurity contents and better thermal stability than the commercial LiPF6.
文摘The heated process of raw materials for electron trapping materials (ETM) is investigated by thermo-analysis method. The temperature ranges of raw materials experienced some physical and chemical change processes, such as dehydration, organic solvent removal, crystal sulphur burning, oxidation of alkaline earth sulfides and solid phase reaction (rare earth doped) and so on, are obtained. The experimental results also show that the presence of trace oxygen in shielded gas is very harmful to prepare the ETM.The raw material thermo-analysis results provide very important experimental reference for optimizing the ETM preparation techniques.
文摘目的:探究中国药典和世界卫生组织双氰胺熔点对照品熔点差异的原因。方法:采用差示扫描量热分析(DSC)和热重/差热同步分析(TGA/SDTA)研究双氰胺熔点对照品的熔融过程,DSC升温速率10℃·min-1,干燥气N2流速50 m L·min-1,TGA/SDTA升温速率20℃·min-1,干燥气N2流速25 m L·min-1;并进一步通过HPLC法分析熔融前、中、后的样品。结果:差示扫描量热分析和热重/差热同步分析发现3个对照品的热力学行为基本一致,提示熔融后期可能已经热降解;HPLC法进一步证实双氰胺的熔融过程伴有部分降解。结论:热稳定性可能是造成中国药典和世界卫生组织双氰胺熔点对照品熔点差异的原因,双氰胺继续作为熔点对照品值得商榷。
