The non-isothermal kinetics of mechanochemical reduction of Ag2O with graphite was studied by DSC and TGA with a model of fitting Malek approach and a model-free advanced isoconversional method of Vyazovkin. To evalua...The non-isothermal kinetics of mechanochemical reduction of Ag2O with graphite was studied by DSC and TGA with a model of fitting Malek approach and a model-free advanced isoconversional method of Vyazovkin. To evaluate the kinetics parameters, Ag2O–graphite mixture of as-received and milled for 2 and 4 h samples were selected. Based on the results obtained by Vyazovkin method calculation, however, the difference between the maximum and minimum values of activation energy is less than 20%-30%of the average activation energy （（99.38±2.36） kJ/mol） and thermal decomposition of mechanically activated Ag2O for 2 h is a multi-step process. Moreover, the thermal decomposition of mechanically activated Ag2O–graphite powder activated for 4 h is a single-step process （the average activation energy=（93.68±2.26） kJ/mol）. The kinetics modeling shows that the complexity of thermal decomposition of as-received Ag2O–graphite mixture is higher than that of the others. While, the autocatalytic tendency of as-received Ag2O–graphite mixture is lower than that of the others.展开更多
Thermal degradation of vegetable-tanned leather fiber(VLF)was investigated by thermogravimetric analysis aiming to know the exact kinetics and degradation mechanism.The thermogravimetric(TG)and differential thermograv...Thermal degradation of vegetable-tanned leather fiber(VLF)was investigated by thermogravimetric analysis aiming to know the exact kinetics and degradation mechanism.The thermogravimetric(TG)and differential thermogravimetric(DTG)curves showed that decomposition of the VLF occurs mainly in the range of 150-600℃,and the latter exhibits asymmetrical peak with a pronounced shoulder.The decomposition process was first analyzed by deconvolution of the experimental DTG curves,followed by reconstruction of the weight loss profiles of two individual processes.Several common isoconversional approaches were applied to calculate the activation energy over a wide range of conversion for the sample,including modified Kissinger-Akahira-Sunose(MKAS),Friedman,and Flynn-Wall-Ozawa.The average activation energy of vegetable-tanned leather fiber was found to be 241.9 kJ mol^(−1) by MKAS method.The activation energy values obtained for the pseudocomponents representing highly-crosslinked and low-crosslinked collagen in VLF were given as 190.6 and 124.8 kJ mol^(−1),respectively.Generalized master plots results suggested that the reaction mechanism for highly-crosslinked collagen follows the random nucleation and growth process at conversion values lower than 0.5.When the conversion is higher than 0.5,the mechanism tends to random scission model.For low-crosslinked collagen,the degradation is mainly governed by random nucleation and nuclei growth.The gaseous products of VLF thermal degradation were analyzed with an online-coupled TG-Fourier transform infrared spectroscopy system.展开更多
文摘The non-isothermal kinetics of mechanochemical reduction of Ag2O with graphite was studied by DSC and TGA with a model of fitting Malek approach and a model-free advanced isoconversional method of Vyazovkin. To evaluate the kinetics parameters, Ag2O–graphite mixture of as-received and milled for 2 and 4 h samples were selected. Based on the results obtained by Vyazovkin method calculation, however, the difference between the maximum and minimum values of activation energy is less than 20%-30%of the average activation energy （（99.38±2.36） kJ/mol） and thermal decomposition of mechanically activated Ag2O for 2 h is a multi-step process. Moreover, the thermal decomposition of mechanically activated Ag2O–graphite powder activated for 4 h is a single-step process （the average activation energy=（93.68±2.26） kJ/mol）. The kinetics modeling shows that the complexity of thermal decomposition of as-received Ag2O–graphite mixture is higher than that of the others. While, the autocatalytic tendency of as-received Ag2O–graphite mixture is lower than that of the others.
基金National Key Research and Development Program(2017YFB0308500)National Natural Science Foundation Commission of China(51673177,U1204504)Science and Technology Project of Henan Province(172102410022).
文摘Thermal degradation of vegetable-tanned leather fiber(VLF)was investigated by thermogravimetric analysis aiming to know the exact kinetics and degradation mechanism.The thermogravimetric(TG)and differential thermogravimetric(DTG)curves showed that decomposition of the VLF occurs mainly in the range of 150-600℃,and the latter exhibits asymmetrical peak with a pronounced shoulder.The decomposition process was first analyzed by deconvolution of the experimental DTG curves,followed by reconstruction of the weight loss profiles of two individual processes.Several common isoconversional approaches were applied to calculate the activation energy over a wide range of conversion for the sample,including modified Kissinger-Akahira-Sunose(MKAS),Friedman,and Flynn-Wall-Ozawa.The average activation energy of vegetable-tanned leather fiber was found to be 241.9 kJ mol^(−1) by MKAS method.The activation energy values obtained for the pseudocomponents representing highly-crosslinked and low-crosslinked collagen in VLF were given as 190.6 and 124.8 kJ mol^(−1),respectively.Generalized master plots results suggested that the reaction mechanism for highly-crosslinked collagen follows the random nucleation and growth process at conversion values lower than 0.5.When the conversion is higher than 0.5,the mechanism tends to random scission model.For low-crosslinked collagen,the degradation is mainly governed by random nucleation and nuclei growth.The gaseous products of VLF thermal degradation were analyzed with an online-coupled TG-Fourier transform infrared spectroscopy system.
