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SM ISO690:2012 LEBEDEV, Egor, BABICH, Alexey, NEMTSEVA, Svetlana, DUBKOV, Sergey, MANIUKIEWICZ, Waldemar, MANIECKI, Tomasz, SHERCHENKOV, Alexey, GROMOV, Dmitry. Investigation of the heat effects for the powder Al-Ni thermite materials. In: Central and Eastern European Conference on Thermal Analysis and Calorimetry, Ed. 4, 28-31 august 2017, Chişinău. Germany: Academica Greifswald, 2017, Editia 4, p. 333. ISBN 978-3-940237-47-7. |
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Central and Eastern European Conference on Thermal Analysis and Calorimetry Editia 4, 2017 |
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Conferința "Central and Eastern European Conference" 4, Chişinău, Moldova, 28-31 august 2017 | ||||||
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Pag. 333-333 | ||||||
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Thermite powder materials that react in a self-propagating manner have been used for over a century for joining applications. Currently, development of the fabrication technologies for nanoscale powders opens new opportunities for the improvement of the thermite materials properties and search of new applications: from effective surface bonding to heat source for thermoelectric batteries. In this work, we investigated the Al-Ni thermite mixtures, prepared using 90 nm Al and 70 nm Ni commercially available powders and solvent-based ultrasonic mixing technique. The influence of different pressing force from 0 to 10000 kg on the combustion process is explored in terms of total heat release and propagation rate of the reaction front using simultaneous DSC and TGA measurements and high-speed video camera. It was found that the maximum thermal effect and the combustion rate correspond to the sample pressed by 1000 kg. To identify the sequence of phase transformations, a series of experiments was carried out where each sample was heated at a constant rate of up to 860°C, and XRD PANalytical X'Pert Pro equipped with an Anton Paar XRK900 reactor chamber. Differential scanning calorimetry (DSC-50, Shimadzu) was used for the investigation of thermal properties and thermally induced transformations in the Al-Ni materials. Measurements were carried out at 4 different heating rates (from 2 to 10°C/min) in a nitrogen flow (20 ml/min). Samples were put into Al2O3 pans, and empty Al2O3 pans were used as references. According to the differential scanning calorimetry heat effects in the temperature range of 520650 °C were observed for all investigated materials. However, details of this heat effect range are dependent on the preparation conditions of the samples. For example, only one exopeak is observed at the beginning of this range for the sample obtained with pressing force of 1 ton. In addition, broad exopeak in the temperature range of 255-450 °C is observed only for this sample. Second measurement of the samples showed only one endopeak in the temperature range of 640-645 °C for all samples, which is due to the melting of the eutectic composition in the Al-Ni system. Developed methodic including joint application of the isoconversional model-free method of Ozawa-FlynnWall (OFW), and Coates-Redfern model-fitting method was used for the estimation of the effective activation energies and pre-exponential factors for exothermic reaction as functions of conversion, and determination of reaction models. It was shown that preparation conditions of the samples influence on the effective activation energies and pre-exponential factors dependencies on the conversion. |
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