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
The precipitation behaviour during cooling from solution annealing of high alloyed 7049A aluminium alloy was investigated, covering the complete cooling-rate-range of technical interest. This ranges from slow cooling ...The precipitation behaviour during cooling from solution annealing of high alloyed 7049A aluminium alloy was investigated, covering the complete cooling-rate-range of technical interest. This ranges from slow cooling rates close to equilibrium up to rates above complete supersaturation and is covering seven orders of magnitude in cooling rate （0.0005 to 5000 K/s）. The continuous cooling precipitation behaviour of 7049A alloy was recorded by combining different differential scanning calorimetry （DSC） techniques and microstructure analysis by SEM and Vickers hardness testing. The high alloyed, high strength and quench sensitive wrought aluminium alloy 7049A was investigated during quenching from solution annealing by conventional DSC in the cooling rate range of 0.0005 to 4 K/s. In this range at least two exothermal precipitation reactions were observed： a high temperature reaction in a narrow temperature interval of 450-430℃, and a low temperature reaction in a broad temperature interval down to about 200 ℃. Intensities of both reactions decreased with increasing cooling rate. Quenching from solution annealing with rates up to 1000 K/s was investigated by differential fast scanning calorimetry （DFSC） and the differential reheating method （DRM）. A critical quenching rate to suppress all precipitation reactions of 100-300 K/s was been determined.展开更多
The effect of a novel active nucleating agent(TBC8-eb) on the isothermal crystallization of poly(L-lactic acid) (PLLA) was studied by differential scanning calorimetry(DSC) and Fourier transform infrared spectroscopy(...The effect of a novel active nucleating agent(TBC8-eb) on the isothermal crystallization of poly(L-lactic acid) (PLLA) was studied by differential scanning calorimetry(DSC) and Fourier transform infrared spectroscopy(FTIR) . The analysis on kinetics demonstrates that TBC8-eb can not only accelerate the crystallization rate but also transform most of the original spherulite crystals of PLLA into sheaf-like crystals. Furthermore,the free energy of folding(σe) of PLLA and PLLA with TBC8-eb is 0.15 and 0.06 J·m-2,respectively,which suggests that the addition of TBC8-eb favors the regular folding of molecule chains in the crystallization of PLLA,improv-ing its crystallization rate. The FTIR results show that TBC8-eb can accelerate the conformational ordering of PLLA in the isothermal crystallization. The conformational ordering of PLLA nucleated with TBC8-eb begins with the interchain interaction of CH3,and then a short helix emerges where a couple of CH3 groups interact.展开更多
In this work, the group contribution method of Chickos et al. was applied to estimate the fusion enthalpy of isonicotinic acid, and the obtained result(29.2 k J·mol^(-1)) showed a large difference with the value(...In this work, the group contribution method of Chickos et al. was applied to estimate the fusion enthalpy of isonicotinic acid, and the obtained result(29.2 k J·mol^(-1)) showed a large difference with the value(135 k J·mol^(-1)) as reported from literatures and as determined by differential scanning calorimetry(DSC). The results of DSC/TG measurement showed that the phase transition of isonicotinic acid from 187.27 °C to277.47 °C underwent a sublimation process, with a sublimation enthalpy of 128.03 k J·mol^(-1). An efficient analytical technique combining pyrolysis and gas chromatography/mass spectrometry(Py-GC/MS) was used to prove this conclusion.展开更多
Formulation of poorly water-soluble crystalline drugs in their amorphous counterpart is a common approach to enhance their biodisponibility. In this study, the amorphous forms of ketoprofen and flurbiprofen were obtai...Formulation of poorly water-soluble crystalline drugs in their amorphous counterpart is a common approach to enhance their biodisponibility. In this study, the amorphous forms of ketoprofen and flurbiprofen were obtained by supercooling of the melt in a DSC （differential scanning calorimetry） apparatus and then investigated, especially under the stability point of view. The average rate of molecular motions at any given temperature is probably the most important parameter to know for amorphous pharmaceutical materials, and it was used to explain and predict the stability of ketoprofen and flurbiprofen. A quantitative estimate of the product＇s behaviour upon storage is obtained with additional data, such as the heat capacity of crystalline and amorphous samples and the distribution of molecular relaxation times. Amorphous flurbiprofen demonstrated greater physical stability at any aging temperature tested, when compared to ketoprofen and a different dependence from aging temperature. Both amorphous drugs could he classified as ＂fragile＂ ones.展开更多
The drawn copper wires have been analyzed by differential scanning calorimeter(DSC) and a new method, which uses DSC measurements to determine the Johnson-Mehl-Avrami-Kolmogorov(JMAK) exponent via introducing Arrheniu...The drawn copper wires have been analyzed by differential scanning calorimeter(DSC) and a new method, which uses DSC measurements to determine the Johnson-Mehl-Avrami-Kolmogorov(JMAK) exponent via introducing Arrhenius behavior and modifying the baseline of DSC curves, has been proposed. The results show that JMAK exponent and recrystallization activation energy of the drawn copper wires with a strain of 2.77 are about 2.39 and 125 k J/mol, respectively. The line linking the tangency points of DSC curve hypotenuse can be used as the baseline when calculating recrystallization fraction. The JMAK exponent obtained by the DSC method is in a good agreement with that obtained by microhardness measurements. Compared to traditional methods to measure the exponent, the proposed method is faster and less labor intensive.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funding of this work by a scholarship of the German State of Mecklenburg-Vorpommern via University of Rostock,Interdisciplinary Faculty
文摘The precipitation behaviour during cooling from solution annealing of high alloyed 7049A aluminium alloy was investigated, covering the complete cooling-rate-range of technical interest. This ranges from slow cooling rates close to equilibrium up to rates above complete supersaturation and is covering seven orders of magnitude in cooling rate （0.0005 to 5000 K/s）. The continuous cooling precipitation behaviour of 7049A alloy was recorded by combining different differential scanning calorimetry （DSC） techniques and microstructure analysis by SEM and Vickers hardness testing. The high alloyed, high strength and quench sensitive wrought aluminium alloy 7049A was investigated during quenching from solution annealing by conventional DSC in the cooling rate range of 0.0005 to 4 K/s. In this range at least two exothermal precipitation reactions were observed： a high temperature reaction in a narrow temperature interval of 450-430℃, and a low temperature reaction in a broad temperature interval down to about 200 ℃. Intensities of both reactions decreased with increasing cooling rate. Quenching from solution annealing with rates up to 1000 K/s was investigated by differential fast scanning calorimetry （DFSC） and the differential reheating method （DRM）. A critical quenching rate to suppress all precipitation reactions of 100-300 K/s was been determined.
基金Supported by the National Natural Science Foundation of China （20876042） Program of Shanghai Subject Chief Scientist （10XD1401500） Research Fund for the Doctoral Program of Higher Education of China
文摘The effect of a novel active nucleating agent(TBC8-eb) on the isothermal crystallization of poly(L-lactic acid) (PLLA) was studied by differential scanning calorimetry(DSC) and Fourier transform infrared spectroscopy(FTIR) . The analysis on kinetics demonstrates that TBC8-eb can not only accelerate the crystallization rate but also transform most of the original spherulite crystals of PLLA into sheaf-like crystals. Furthermore,the free energy of folding(σe) of PLLA and PLLA with TBC8-eb is 0.15 and 0.06 J·m-2,respectively,which suggests that the addition of TBC8-eb favors the regular folding of molecule chains in the crystallization of PLLA,improv-ing its crystallization rate. The FTIR results show that TBC8-eb can accelerate the conformational ordering of PLLA in the isothermal crystallization. The conformational ordering of PLLA nucleated with TBC8-eb begins with the interchain interaction of CH3,and then a short helix emerges where a couple of CH3 groups interact.
文摘In this work, the group contribution method of Chickos et al. was applied to estimate the fusion enthalpy of isonicotinic acid, and the obtained result(29.2 k J·mol^(-1)) showed a large difference with the value(135 k J·mol^(-1)) as reported from literatures and as determined by differential scanning calorimetry(DSC). The results of DSC/TG measurement showed that the phase transition of isonicotinic acid from 187.27 °C to277.47 °C underwent a sublimation process, with a sublimation enthalpy of 128.03 k J·mol^(-1). An efficient analytical technique combining pyrolysis and gas chromatography/mass spectrometry(Py-GC/MS) was used to prove this conclusion.
文摘Formulation of poorly water-soluble crystalline drugs in their amorphous counterpart is a common approach to enhance their biodisponibility. In this study, the amorphous forms of ketoprofen and flurbiprofen were obtained by supercooling of the melt in a DSC （differential scanning calorimetry） apparatus and then investigated, especially under the stability point of view. The average rate of molecular motions at any given temperature is probably the most important parameter to know for amorphous pharmaceutical materials, and it was used to explain and predict the stability of ketoprofen and flurbiprofen. A quantitative estimate of the product＇s behaviour upon storage is obtained with additional data, such as the heat capacity of crystalline and amorphous samples and the distribution of molecular relaxation times. Amorphous flurbiprofen demonstrated greater physical stability at any aging temperature tested, when compared to ketoprofen and a different dependence from aging temperature. Both amorphous drugs could he classified as ＂fragile＂ ones.
基金Projects(51171135,51371132,51471123) supported by the National Natural Science Foundation of ChinaProjects(2012K07-08,2013KJXX-61) supported by Key Science and Technology Program of Shaanxi Province,ChinaProject(2013JC14) supported by the Education Department Foundation of Shaanxi Province,China
文摘The drawn copper wires have been analyzed by differential scanning calorimeter(DSC) and a new method, which uses DSC measurements to determine the Johnson-Mehl-Avrami-Kolmogorov(JMAK) exponent via introducing Arrhenius behavior and modifying the baseline of DSC curves, has been proposed. The results show that JMAK exponent and recrystallization activation energy of the drawn copper wires with a strain of 2.77 are about 2.39 and 125 k J/mol, respectively. The line linking the tangency points of DSC curve hypotenuse can be used as the baseline when calculating recrystallization fraction. The JMAK exponent obtained by the DSC method is in a good agreement with that obtained by microhardness measurements. Compared to traditional methods to measure the exponent, the proposed method is faster and less labor intensive.
