The non-isothermal heating process of Mg-Sn powder mixture was studied by differential scanning calorimetry(DSC) technique and the synthesis kinetics of Mg2Sn was evaluated by the model-free and model-fitting methods....The non-isothermal heating process of Mg-Sn powder mixture was studied by differential scanning calorimetry(DSC) technique and the synthesis kinetics of Mg2Sn was evaluated by the model-free and model-fitting methods.The activation energy and conversion function of Mg2Sn synthesis reaction are calculated to be 281.7 kJ/mol and g(α)=[-ln(1-α)] 1/4,respectively.The reaction mechanism of 2Mg+Sn→Mg2Sn under non-isothermal condition is regarded as "nucleation and growth" .During the non-isothermal heating process,the phase transformation occurred in the Mg-Sn powder mixture was analyzed by XRD and the microstructure evolution of Mg2Sn was observed by optical microscopy,which is in good agreement with the reaction mechanism of 2Mg+Sn→ Mg2Sn deduced from the kinetic evaluation.展开更多
Experiments on thermal decomposition of nano-sized calcium carbonate were carried out in a thermo-gravimetric analyzer under non-isothermal condition of different heating rates (5 to 20K·min-1). The Coats and Red...Experiments on thermal decomposition of nano-sized calcium carbonate were carried out in a thermo-gravimetric analyzer under non-isothermal condition of different heating rates (5 to 20K·min-1). The Coats and Redfern's equation was used to determine the apparent activation energy and the pre-exponential factors. The mechanism of thermal decomposition was evaluated using the master plots, Coats and Redfern's equation and the kinetic compensation law. It was found that the thermal decomposition property of nano-sized calcium carbonate was different from that of bulk calcite. Nano-sized calcium carbonate began to decompose at 640℃, which was 180℃lower than the reported value for calcite. The experimental results of kinetics were compatible with the mechanism of one-dimensional phase boundary movement. The apparent activation energy of nano-sized calcium carbonate was estimated to be 151kJ·mol-1 while the literature value for normal calcite was approximately 200kJ·mol-1. The order of magnitude of pre-exponential factors was estimated to be 10~9 s-1.展开更多
The thermal decomposition of abietic acid in air was investigated under non-isothermal condition using thermogravimetric analysis-differential thermal analysis （TGA-DTA） technique with heating rates of 5, 10, 15 and...The thermal decomposition of abietic acid in air was investigated under non-isothermal condition using thermogravimetric analysis-differential thermal analysis （TGA-DTA） technique with heating rates of 5, 10, 15 and 25 K.min-~. The non-isothermal kinetic parameters were obtained via the analysis of the thermogravimetric and differential thermogravimetric （TG-DTG） curves by using Flynn-Wall-Ozawa method and Kissinger method. The thermal decomposition mechanism of abietic acid was studied with four integral methods （Satava-Sestak, MacCallum-Tanner, ordinary integral and Agrawal）. The results show that the thermal decomposition mechanism is nu- cleation and growth, and the mechanism function is Avrami-Erofeev equation with n equates 1/2. The activation energy and the pre-exponential factor are 64.04 kJ.mol^-1 and 5.89×10^5 s^-1, respectively.展开更多
基金Project(2007CB613706)supported by the National Basic Research Program of ChinaProject(0330005412901)supported the Key Disciplines Development of Beijing Municipality("Resources,Environment and Recycling Economy"Interdisciplinary),ChinaProject(X0104001200905)supported by the Scientific Research Foundation for the New Doctoral Teachers,Beijing University of Technology,China
文摘The non-isothermal heating process of Mg-Sn powder mixture was studied by differential scanning calorimetry(DSC) technique and the synthesis kinetics of Mg2Sn was evaluated by the model-free and model-fitting methods.The activation energy and conversion function of Mg2Sn synthesis reaction are calculated to be 281.7 kJ/mol and g(α)=[-ln(1-α)] 1/4,respectively.The reaction mechanism of 2Mg+Sn→Mg2Sn under non-isothermal condition is regarded as "nucleation and growth" .During the non-isothermal heating process,the phase transformation occurred in the Mg-Sn powder mixture was analyzed by XRD and the microstructure evolution of Mg2Sn was observed by optical microscopy,which is in good agreement with the reaction mechanism of 2Mg+Sn→ Mg2Sn deduced from the kinetic evaluation.
基金Supported by the Key Research of Science & Technology of Education(No.0202)and the Fundamental Research Plan of HuoYingdong(No.81063).
文摘Experiments on thermal decomposition of nano-sized calcium carbonate were carried out in a thermo-gravimetric analyzer under non-isothermal condition of different heating rates (5 to 20K·min-1). The Coats and Redfern's equation was used to determine the apparent activation energy and the pre-exponential factors. The mechanism of thermal decomposition was evaluated using the master plots, Coats and Redfern's equation and the kinetic compensation law. It was found that the thermal decomposition property of nano-sized calcium carbonate was different from that of bulk calcite. Nano-sized calcium carbonate began to decompose at 640℃, which was 180℃lower than the reported value for calcite. The experimental results of kinetics were compatible with the mechanism of one-dimensional phase boundary movement. The apparent activation energy of nano-sized calcium carbonate was estimated to be 151kJ·mol-1 while the literature value for normal calcite was approximately 200kJ·mol-1. The order of magnitude of pre-exponential factors was estimated to be 10~9 s-1.
基金Supported by the National＇Natural Science Foundation of China （20976031, 31060102）, the Natural Science Foundation of Guangxi Autonomous Region （2011GXNSFD018011,0991030, 2010GXNSFA013042）, the Science and Technology Program Foundation of Wuzhou City （200901011）, the Scientific and Technological Project of Guangxi （1099060-2）, the Scientific Research Innovative Foundation of Doctor Candidate （105930901008）.
文摘The thermal decomposition of abietic acid in air was investigated under non-isothermal condition using thermogravimetric analysis-differential thermal analysis （TGA-DTA） technique with heating rates of 5, 10, 15 and 25 K.min-~. The non-isothermal kinetic parameters were obtained via the analysis of the thermogravimetric and differential thermogravimetric （TG-DTG） curves by using Flynn-Wall-Ozawa method and Kissinger method. The thermal decomposition mechanism of abietic acid was studied with four integral methods （Satava-Sestak, MacCallum-Tanner, ordinary integral and Agrawal）. The results show that the thermal decomposition mechanism is nu- cleation and growth, and the mechanism function is Avrami-Erofeev equation with n equates 1/2. The activation energy and the pre-exponential factor are 64.04 kJ.mol^-1 and 5.89×10^5 s^-1, respectively.
