Papers by Keyword: Thermo-Gravimetry (TG)

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Authors: W. M. Abdel-Wareth, Xu Xu
Abstract: Effects of various grain sizes (10~390 µm) under heating rate of 40 °C/min on ammonium perchlorate (AP) decomposition characteristic parameters, the decomposition thermal behavior and kinetic parameters (activation energy and pre-exponential factor), were investigated by simultaneous DSC/TGA in a dynamic nitrogen atmosphere. In addition, the specific surface areas were measured by the BET-method. Moreover, the kinetic parameters were determined by a simplified approach based on the isoconversional method. The results showed that, the higher the AP particle size the lower the determined decomposition kinetic parameters. In addition, the results were in acceptable agreements with some important literatures. Moreover, it was highly recommended to apply the higher agreeable heating rates for AP samples to determine that parameters more accurately.
Authors: Urszula Narkiewicz, Marcin Podsiadły, Iwona Pełech, Waleran Arabczyk, M.J. Woźniak, Krzysztof Jan Kurzydlowski
Abstract: Nanocrystalline cobalt was carburised with ethylene in the range 340– 500°C to obtain Co(C) nanocapsules. The carbon deposit was reduced by a flow of hydrogen in the range 500– 560°C. The reduction kinetics were studied using thermogravimetry, described by the equation: α = Α[1-exp(-kt)n]. The apparent activation energy of the reduction process of the carbon deposit was determined. After carburisation and reduction the samples were examined by XRD and HRTEM.
Authors: Aurélie Vande Put, Djar Oquab, Daniel Monceau
Abstract: During service, TBC can suffer degradation by CMAS, FOD, erosion or spallation. Whereas the first three are due to foreign particles, the last one is related to thermal cycling. When subjected to high temperature exposures followed by rapid coolings under oxidizing conditions, a TBC system undergoes morphological changes and stress development. This will initiate cracks which propagate and finally lead to failure by spallation. Consequently, the aim of the present study is to understand better the mechanisms responsible for such spallation events. Two kinds of TBC systems with different bond coatings (NiCoCrAlYTa or Pt-modified nickel aluminide bond coatings) are thermally cycled. Subsequently, SEM investigations on TBC systems after spallation concentrate on failure path, defect, morphological and microstructural changes to propose way for improving TBC system lifetime.
Authors: Yu Zhong Li, Xiao Qian Ma, Yu Ting Tang, Zi Lin Cai
Abstract: The combustion of paper mill sludge and bituminous coal in air was analyzed using a thermogravimetric instrument. TG and DTG curves for the blends lies between that of the individual fuels, and the main combustion characteristics of blends depended on individual fuels and followed the weighted average. As the blending ratio of paper mill sludge was increased from 10% to 90%, the ignite temperature (Ti) decreased from 529.6°C. to 275.6°C., and residual weight increased from 19.28% to 47.39%. The TG profiles of sample were almost the same at different heating rates, however there was a big difference between the DTG profiles. The maximum weight loss rate of sample increased obviously with the increment of heating rate. This work contributes to the comprehensive understanding of paper mill sludge and bituminous coal combustion and development of co-combustion technology.
Authors: Xiu Chen, Lei Chen, Yin Nan Yuan, Yong Bin Lai, Xing Qiao, Ling Ling Cai
Abstract: The chemical composition of palm and rapeseed biodiesel (fatty acid methyl ester, FAME) was analyzed by gas chromatography-mass spectrometry. Combustion characteristics of biodiesel were studied by thermogravimetry-differential scanning calorimetry and collision theory. Combustion characteristic index C was put forward for describing biodiesel combustion characteristic. The reactive atom combustion mechanism was put forward. Biodiesel combustion process comprised three steps, viz., volatilizing, dissociating and combining. First, biodiesel volatilizes, viz., FAME (liquid) volatilize and became FAME (gas). Second, FAME, O2 and N2 molecular were dissociated into C*, H*, O* and N* reactive atoms. Third, C*, H* and N* reacted, respectively, with O* to CO2, CO, H2O and NOx, and released energy. The study showed that the biodiesel was mainly composed of FAME: C14:0-C24:0, C16:1-C22:1, C18:2 and C18:3. Biodiesel had a good burnability. Combustion characteristic indexes of palm methyl ester (PME) and rapeseed methyl ester (RME) were 4.97E-05 and 3.65E-05, respectively. The combustion characteristic had relation to chemical composition. The combustion characteristic of biodiesel was better with increasing saturated fatty acid methyl esters and length of carbon-chain, and was poorer with increasing unsaturated fatty acid methyl esters and unsaturated degree. The combustion characteristic of PME was better than that of RME.
Authors: Chuan Cheng Zhang, Hai Jun Lu, Zhan Wen He
Abstract: The combustion characteristics of some biomass samples, such as rice straw and its cellulose, were investigated. Non-isothermal thermogravimetry, where the sample was heated in air and the temperature of which increased at a linear rate of 10°C/min, 20°C/min, 30°C/min, was used to investigate the combustion characteristics of the biomass samples. The differences in the TG-DTG-DSC curves of the samples were determined and discussed in detail. Conventional TG parameters, ignition index of samples were estimated which provided elaborate information on their basic combustion features. Results showed that cellulose with higher combustion characteristics.
Authors: Chuan Cheng Zhang, Hai Jun Lu, Xiang He
Abstract: The combustion characteristics of some biomass samples, such as rice straw and its cellulose, were investigated. Non-isothermal thermogravimetry, where the sample was heated in air and the temperature of which increased at a linear rate of 10°C/min, 20°C/min, 30°C/min, was used to investigate combustion process of the biomass samples. The differences in the TG-DTG-DSC curves of the samples were determined and discussed in detail. Results showed that combustion process can be described in terms of first order reaction.
Authors: Osvaldo A. Lambri, José Ignacio Pérez-Landazábal, Federico G. Bonifacich, Vicente Recarte, Melania L. Lambri, Griselda I. Zelada, Federico Tarditti, Damián Gargicevich
Abstract: The wide damping maximum which is reported to appear in bones, involving both cortical and cancellous parts, between around 280 K and 420 K; has been determined to be a composition of different processes taking place at different temperatures in cancellous and cortical parts. In fact, in the present work the mechanical response of cow ribs bones has been analysed by coupling mechanical spectroscopy, differential scanning calorimetry, thermogravimetry and scanning electron microscopy studies. Cancellous part develops two damping maxima at around 320 K and 350 K. Cortical part exhibits a wide maximum in damping between around 310 K and 410 K and another damping relaxation between 390 K and 410 K. The physical-chemical driving force giving rise to the above relaxation processes are discussed.
Authors: Kornel Csach, Alena Juríková, Jozef Miškuf, Martina Koneracká, Vlasta Závišová, Martina Kubovčíková, Peter Kopčanský
Abstract: Magnetic nanoparticles used in biomedicine have to be biocompatible what can be achieved by the modification of the magnetic particle surface with an appropriate biocompatible substance. In the work protein bovine serum albumin (BSA) was chosen to modify the surface of magnetite nanoparticles. BSA coated magnetite nanoparticles (MFBSA) with different feed weight ratios of BSA to the magnetite Fe3O4 were prepared and thermally characterized using thermogravimetric analysis.
Authors: Zbigniew Jurasz, Krzysztof Adamaszek, Romuald Janik, Zbigniew Grzesik, Stanisław Mrowec
Abstract: Detailed investigations of nonstoichiometry as well as chemical and self-diffusion in nickel oxide have shown that doubly ionised cation vacancies and electron holes are the predominant defects in this material. The present work is an attempt to demonstrate that aliovalent impurities (Cr, Al, Na and Li) may considerably influence the concentration of these defects and, consequently, the oxidation rate of nickel at high temperatures. It has been shown that small amounts of tri-valent impurities (Cr, Al) bring about an increase of the oxidation rate, while mono-valent ones (Li, Na) decrease the rate of oxidation. These phenomena may satisfactorily be explained in terms of a doping effect. All experiments have been carried out as a function of temperature (1373-1673 K) and oxygen pressure (1-105 Pa) and consequently, it was possible to determine the influence of impurities not only on the oxidation rate but also on the activation energy of reaction and its pressure dependence. The results of these investigations could again be elucidated in terms of doping effect.
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