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Summary The disposal of used automotive tires has caused many environmental and economical problems to most countries. We propose the use of rice husk as filler for increasing the value of recycled tire rubber. Thermal degradation of both components and their sintering mixtures is presented in this paper. Thermal decomposition of rice husk occurs in various steps in the temperature range between 150 and 550°C. This complex process is the result of the overlapping of thermal decomposition of the three major constituents common in all lignocellulosic materials, i.e., hemicellulose, lignin and cellulose. Hemicellulose is degraded at temperatures between 150 and 350°C, cellulose from 275 to 380°C and lignin from 250 to 550°C. The degradation process of major constituents of scrap tires or their composites is observed at temperatures between 150 and 550°C. For composites, the addition of rice husk (maximum 25%) produces an increase in the mass loss rate. This effect is higher as the amount of rice husk increases. However, the degradation initial temperature of elastomeric matrix is not affected with addition of rice husk. Apparent kinetic parameters were also studied by the isoconversional Friedman method. We observed that the addition of rice husk produces a decrease in apparent activation energy for low conversions (up to 0.6). For higher conversions this decrease was not so clearly observed.

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Thermogravimetric (TG) analysis was applied to the characterisation of the pozzolanic reaction in mortars containing the supplementary cementitious materials (SCMs) pitchstone fines (PF) and fly ash (FA) as partial replacements for Portland cement (PC). TG analysis was used to determine the proportion of calcium hydroxide (CH) present from the hydration of the PC based on the dehydroxylation of the CH present in the blended PC-SCM mortars. The consumption of CH indicated that both SCMs underwent the pozzolanic reaction and that PF was found to compare favourably in its pozzolanic reactivity of FA, the industry and globally accepted standard artificial pozzolan.

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Thermal degradation behavior using thermogravimetry (TG), chemical composition and crystallinity by X-ray diffraction of white and naturally colored cotton fibers (ruby, beige, brown and green) were studied. Flynn-Wall-Ozawa method was used to investigate the thermal decomposition kinetics of the different fibers. The white cotton fiber has higher thermal stability and higher apparent activation energy (E a) value compared to the colored fibers. There are no significant differences in initial temperature of degradation in air or in nitrogen atmosphere for the same type of fiber. Chemical composition and crystallinity influenced the thermal degradation behavior of the fibers studied.

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Mixtures of CuCl2 and KCl with molar ratios of Cu to K from 0.5 to 1.0 were heated at 393 K and then they absorbed water from the surroundings at room temperature. DTA, TG and DTG curves were analyzed for the mixtures with absorbed water in the temperature range between 293 and 473 K. The mechanism of the phase changes and water release from the mixtures in the temperature range from 293 to 473 K is proposed.

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Journal of Thermal Analysis and Calorimetry
Authors: L. Campanella, E. Cardarelli, R. Curini, G. D'Ascenzo, and M. Tomassetti

TG and DTG curves of human renal calculi of patients living in the nineteenth century in the South of Italy are reported and compared with those of presentday patients. Marked differences in calculi composition are found in the two different historical periods, that are hypothetically discussed in terms of different diets and of alimentary customs of countries of the considered patients.

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The thermochemical decomposition of agricultural by-product corn cob impregnated with ZnCl2, as a precursor material for producing the activated carbons, was investigated by thermogravimetric (TG) analysis at the heating rate of 5 and 10°C min–1 under a controlled atmosphere of nitrogen (60 ml min–1). The appearance of a peak in the differential thermogravimetric plot (DTG) in the temperature range of 400–600°C is significantly related to the extent of impregnation. The DTG curve of the sample impregnated with the optimal impregnation ratio of 175% (i.e., the ratio of ZnCl2 mass of 87.5 g in the 200 cm3 of water to corn cobmass of 50 g), which yields an optimal BET surface area of the activated carbon and displays a DTG peak at about 500°C. This may be partially due to the intense chemical activation and results in the formation of a porous structure in the activated solid residue. This observation is also in close agreement with previous results at optimal pyrolysis temperatures of 500°C and with similar experimental conditions. In order to support the results in the TG-DTG analysis, the development of pore structure of the resulting activated carbons thus obtained by previous studies was also examined and explained using the scanning electron microscopy (SEM).

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