The non-isothermal kinetics of CdO nanoparticles prepared from CdCO3 precursor using thermal decomposition method was investigated. A model-fitting Malek approach and a model-free advanced isoconversional method of Vy...The non-isothermal kinetics of CdO nanoparticles prepared from CdCO3 precursor using thermal decomposition method was investigated. A model-fitting Malek approach and a model-free advanced isoconversional method of Vyazovkin were applied to the analysis of the DSC and TGA data. The results showed that CdO nanoparticles prepared from CdCO3 followed an autocatalytic reaction. Sestak–Berggren model could favorably describe the studied reaction process. Moreover, the apparent activation energy of CdCO3 decomposition was calculated to be (119.19±9.97) kJ/mol and the explicit rate equation form of CdCO3 decomposition was established.展开更多
A new method of the multiple rates isotemperature is proposed to define the most probable mechanismg(α) of thermal anlaysis; the iterative isoconversional procedure has been employed to estimate apparent activation e...A new method of the multiple rates isotemperature is proposed to define the most probable mechanismg(α) of thermal anlaysis; the iterative isoconversional procedure has been employed to estimate apparent activation energyE; the pre-exponential factorA is obtained on the basis ofE andg(α). By this new method, the thermal analysis kinetics triplet of dehydration of cobalt oxalate dihydrate is determined, apparent activation energyE is 99.84 kJ·mol?1; pre-exponential factorA is 3.427×109–3.872×109 s?1 and the most probable mechanism belongs to nucleation and growth,A m model, the range ofm is from 1.50 to 1.70. Key words multiple rates isotemperature method - isoconversional method - cobalt oxalate dihydrate - accomodation function - differential scanning calorimetry (DSC) CLC number O 636.1 Foundation item: Supported by the Key Foundation of the Science and Technology Committee of Hubei Province (2001ABA009)Biography: Li Li-qing (1977-), female, Master candidate, research direction: material synthesize and thermal analysis kinetics.展开更多
The electrical resistivity of NZ30K-Mg alloy was measured at different heating rates during continuous heating to stud the precipitation kinetics.Two kinds of metastable phases,β＂ and β＇,formed during the heating....The electrical resistivity of NZ30K-Mg alloy was measured at different heating rates during continuous heating to stud the precipitation kinetics.Two kinds of metastable phases,β＂ and β＇,formed during the heating.Kissinger method and differentia isoconversional method were employed to assess the precipitation kinetic parameters of NZ30K-Mg alloy,activation energy Eα an pre-exponential factor A＇α.The fraction of transformation（α） and the precipitation sequence in NZ30K-Mg alloy were determinec Continuous heating transformation（CHT） and isothermal heating transformation（IHT） diagrams were further obtained for guidin the aging of NZ30K-Mg alloy.The analysis shows that the precipitation kinetic parameters of NZ30K-Mg alloy can be obtaine accurately using isoconversional method.展开更多
The polymorphic phase transformation of β-glycine to α-glycine was carried out both in the absence and presence of various concentrations of oleic acid used as additive at 25 ℃ in a water/ethanol medium. The effect...The polymorphic phase transformation of β-glycine to α-glycine was carried out both in the absence and presence of various concentrations of oleic acid used as additive at 25 ℃ in a water/ethanol medium. The effects of oleic acid and its concentration on phase transformation time were determined by continuously measuring the ultrasonic velocity. The crystals obtained by the completion of the phase transformation were characterized by XRD, SEM, and TG/DTG. The XRD and SEM results indicated that oleic acid significantly impacted phase transformation time and the morphological characteristics of the crystals. In addition to SEM analysis, detailed crystal shape analysis was performed and the circularity, elongation, and convexity parameters were determined quantitatively. TG/DTG analyses were performed to investigate thermal decomposition behavior and to calculate the activation energies based on different kinetic models such as FWO, KAS, Starink, and Tang kinetic models. With the addition of oleic acid to the medium, the calculated activation energy values increased from 89.63–90.63 to153.8–155.4 kJ·mol^（-1）. The activation energy values showed that oleic acid was adsorbed on the crystal surface;this result was supported by FTIR, elemental, and Kjeldahl analyses.展开更多
The thermal decomposition kinetics of Ag2O-graphite mixture was systematically studied using a differential scanning calorimeter（DSC） in terms of model-fitting Malek approach, integral master plot method and model-f...The thermal decomposition kinetics of Ag2O-graphite mixture was systematically studied using a differential scanning calorimeter（DSC） in terms of model-fitting Malek approach, integral master plot method and model-free advanced isoconversional method of Vyazovkin. The results showed that the thermal decomposition occurred in two stages. The first step was the decomposition process of Ag2 O to form porous silver particles as a complex process with the participation of at least two mechanisms, and the second step corresponded to the structural change from porous particles to silver bulk crystals as a single-step process.展开更多
Olive oil is an important food industry product in Mediterranean countries. Large quantities of OWR （olive waste residue） are generated during a two- or three-phase separation process. This represents a major pollut...Olive oil is an important food industry product in Mediterranean countries. Large quantities of OWR （olive waste residue） are generated during a two- or three-phase separation process. This represents a major pollution problem for the industry and oil farms. The OWR is a source of substances of high value and can be used as a low-cost renewable energy. This work studied the behaviour of OWRs during the thermal decomposition process. The experiments of the slow pyrolysis process of three different waste olive products as olive pomace, olive tree pruning and olive kernels were performed under a nitrogen atmosphere at different heating rates, using a thermogravimetric balance. The samples were heated to a maximum temperature of 1,023 K, with four different heating rates of 2, 5, 10, 15 K/min. A comparison of different isoconversional （Flynn-Wall-Ozawa）, not-isoconversional （Kissinger） model-free and model-fitting （Freeman-Carroll） methods to calculate the activation energy and pre-exponential factor is presented. In the Kissinger method the kinetic parameters were invariant for the whole pyrolysis process. While, in the case of Freeman-Carroll, it differs with change of the heating rate. The Flynn-Wall-Ozawa technique revealed the ＂not one-step＂ mechanism of reaction that occurs during the slow pyrolysis process. The kinetic data obtained in nitrogen atmosphere may provide more useful information for engineers for a better and complete description of the pyrolysis process and can be helpful to predict the kinetic model.展开更多
Isoconversional methods combined with thermogravimetry were applied to investigate the decomposition kinetics of bastnaesite concentrates with different amounts of calcium hydroxide added.The apparent activation energ...Isoconversional methods combined with thermogravimetry were applied to investigate the decomposition kinetics of bastnaesite concentrates with different amounts of calcium hydroxide added.The apparent activation energy was calculated,and the results indicate that the overall reaction involves more than one single step.The reaction with a lower content(<15 wt%)of calcium hydroxide can be divided into two steps,while the reaction with a higher content(>15 wt%)involves another step which denotes the decomposition of newly formed calcium carbonate during roasting.The activation energy increases with increasing amount of calcium hydroxide in the lower range(0-15 wt%).This is due to the resistance of calcium hydroxide to heat and mass transport,However,more calcium can promote the decomposition reaction more effectively and thus reduce the activation energy.Nonlinear fitting was performed by fitting the experimental data to Avrami-Erofeev model to determine the reaction model and pre-exponential factor.The theoretical models were proven to be reliable for kinetic prediction.展开更多
文摘The non-isothermal kinetics of CdO nanoparticles prepared from CdCO3 precursor using thermal decomposition method was investigated. A model-fitting Malek approach and a model-free advanced isoconversional method of Vyazovkin were applied to the analysis of the DSC and TGA data. The results showed that CdO nanoparticles prepared from CdCO3 followed an autocatalytic reaction. Sestak–Berggren model could favorably describe the studied reaction process. Moreover, the apparent activation energy of CdCO3 decomposition was calculated to be (119.19±9.97) kJ/mol and the explicit rate equation form of CdCO3 decomposition was established.
文摘A new method of the multiple rates isotemperature is proposed to define the most probable mechanismg(α) of thermal anlaysis; the iterative isoconversional procedure has been employed to estimate apparent activation energyE; the pre-exponential factorA is obtained on the basis ofE andg(α). By this new method, the thermal analysis kinetics triplet of dehydration of cobalt oxalate dihydrate is determined, apparent activation energyE is 99.84 kJ·mol?1; pre-exponential factorA is 3.427×109–3.872×109 s?1 and the most probable mechanism belongs to nucleation and growth,A m model, the range ofm is from 1.50 to 1.70. Key words multiple rates isotemperature method - isoconversional method - cobalt oxalate dihydrate - accomodation function - differential scanning calorimetry (DSC) CLC number O 636.1 Foundation item: Supported by the Key Foundation of the Science and Technology Committee of Hubei Province (2001ABA009)Biography: Li Li-qing (1977-), female, Master candidate, research direction: material synthesize and thermal analysis kinetics.
基金Project (2011ZX04014-052,2012ZX04012011) supported by CNC Machine Tools and Basic Manufacturing Equipment Technology Comments
文摘The electrical resistivity of NZ30K-Mg alloy was measured at different heating rates during continuous heating to stud the precipitation kinetics.Two kinds of metastable phases,β＂ and β＇,formed during the heating.Kissinger method and differentia isoconversional method were employed to assess the precipitation kinetic parameters of NZ30K-Mg alloy,activation energy Eα an pre-exponential factor A＇α.The fraction of transformation（α） and the precipitation sequence in NZ30K-Mg alloy were determinec Continuous heating transformation（CHT） and isothermal heating transformation（IHT） diagrams were further obtained for guidin the aging of NZ30K-Mg alloy.The analysis shows that the precipitation kinetic parameters of NZ30K-Mg alloy can be obtaine accurately using isoconversional method.
基金Supported by Marmara University Scientific Research Projects Commission under the funding FEN-C-DRP-131216-0547
文摘The polymorphic phase transformation of β-glycine to α-glycine was carried out both in the absence and presence of various concentrations of oleic acid used as additive at 25 ℃ in a water/ethanol medium. The effects of oleic acid and its concentration on phase transformation time were determined by continuously measuring the ultrasonic velocity. The crystals obtained by the completion of the phase transformation were characterized by XRD, SEM, and TG/DTG. The XRD and SEM results indicated that oleic acid significantly impacted phase transformation time and the morphological characteristics of the crystals. In addition to SEM analysis, detailed crystal shape analysis was performed and the circularity, elongation, and convexity parameters were determined quantitatively. TG/DTG analyses were performed to investigate thermal decomposition behavior and to calculate the activation energies based on different kinetic models such as FWO, KAS, Starink, and Tang kinetic models. With the addition of oleic acid to the medium, the calculated activation energy values increased from 89.63–90.63 to153.8–155.4 kJ·mol^（-1）. The activation energy values showed that oleic acid was adsorbed on the crystal surface;this result was supported by FTIR, elemental, and Kjeldahl analyses.
文摘The thermal decomposition kinetics of Ag2O-graphite mixture was systematically studied using a differential scanning calorimeter（DSC） in terms of model-fitting Malek approach, integral master plot method and model-free advanced isoconversional method of Vyazovkin. The results showed that the thermal decomposition occurred in two stages. The first step was the decomposition process of Ag2 O to form porous silver particles as a complex process with the participation of at least two mechanisms, and the second step corresponded to the structural change from porous particles to silver bulk crystals as a single-step process.
文摘Olive oil is an important food industry product in Mediterranean countries. Large quantities of OWR （olive waste residue） are generated during a two- or three-phase separation process. This represents a major pollution problem for the industry and oil farms. The OWR is a source of substances of high value and can be used as a low-cost renewable energy. This work studied the behaviour of OWRs during the thermal decomposition process. The experiments of the slow pyrolysis process of three different waste olive products as olive pomace, olive tree pruning and olive kernels were performed under a nitrogen atmosphere at different heating rates, using a thermogravimetric balance. The samples were heated to a maximum temperature of 1,023 K, with four different heating rates of 2, 5, 10, 15 K/min. A comparison of different isoconversional （Flynn-Wall-Ozawa）, not-isoconversional （Kissinger） model-free and model-fitting （Freeman-Carroll） methods to calculate the activation energy and pre-exponential factor is presented. In the Kissinger method the kinetic parameters were invariant for the whole pyrolysis process. While, in the case of Freeman-Carroll, it differs with change of the heating rate. The Flynn-Wall-Ozawa technique revealed the ＂not one-step＂ mechanism of reaction that occurs during the slow pyrolysis process. The kinetic data obtained in nitrogen atmosphere may provide more useful information for engineers for a better and complete description of the pyrolysis process and can be helpful to predict the kinetic model.
基金Project supported by the National Basic Research Program(973 Program,2012CBA01205)。
文摘Isoconversional methods combined with thermogravimetry were applied to investigate the decomposition kinetics of bastnaesite concentrates with different amounts of calcium hydroxide added.The apparent activation energy was calculated,and the results indicate that the overall reaction involves more than one single step.The reaction with a lower content(<15 wt%)of calcium hydroxide can be divided into two steps,while the reaction with a higher content(>15 wt%)involves another step which denotes the decomposition of newly formed calcium carbonate during roasting.The activation energy increases with increasing amount of calcium hydroxide in the lower range(0-15 wt%).This is due to the resistance of calcium hydroxide to heat and mass transport,However,more calcium can promote the decomposition reaction more effectively and thus reduce the activation energy.Nonlinear fitting was performed by fitting the experimental data to Avrami-Erofeev model to determine the reaction model and pre-exponential factor.The theoretical models were proven to be reliable for kinetic prediction.
