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Abstract  

A Tian-Calvet heat flux calorimeter has been modified for use with high pressures in measurements of thermal hazards of materials. The system comprising a specially designed high pressure vessel and an associated manifold is described. With this system, comparative measurements using both standard and high pressure vessels can be made, different materials and/or liners can be used for the high pressure vessel and an assessment of the influence of the gaseous environment on thermal behaviour can be made. Calibration was carried out in the range 25 to 300C at different pressures and heating rates, using sapphire and the calibration results were verified with benzoic acid, both reference grade materials. With the new vessel, pressures up to about 70 MPa can be used or recorded during the thermal decomposition of energetic materials. The reproducibility of the baseline, as illustrated by standard error results, was about 0.02% compared with 0.13% for the standard vessel, over the entire temperature range. The corresponding results for the baseline of the pressure vessel at 5.5 MPa (in air and Ar) and in a calibration experiment with sapphire were 0.08%. Experimental data obtained for ammonium nitrate and 2,3-dimethyl-2,3-dinitrobutane in the standard and pressure vessels are compared and discussed. The effect of pressure and the nature of the gaseous environment (inert or oxidizing) on the results for these two materials will be described.

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Abstract  

The quality of measurement of heat capacity by differential scanning calorimetry (DSC) is based on the symmetry of the twin calorimeters. This symmetry is of particular importance for the temperature-modulated DSC (TMDSC) since positive and negative deviations from symmetry cannot be distinguished in the most popular analysis methods. Three different DSC instruments capable of modulation have been calibrated for asymmetry using standard non-modulated measurements and a simple method is described that avoids potentially large errors when using the reversing heat capacity as the measured quantity. It consists of overcompensating the temperature-dependent asymmetry by increasing the mass of the sample pan.

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Abstract  

The quality of measurement of heat capacity by differential scanning calorimetry (DSC) is based on strict symmetry of the twin calorimeter. This symmetry is of particular importance for temperature-modulated DSC (TMDSC) since positive and negative deviations from symmetry cannot be distinguished in the most popular analysis methods. The heat capacities for sapphire-filled and empty aluminum calorimeters (pans) under designed cell imbalance caused by different pan-masses were measured. In addition, the positive and negative signs of asymmetry have been explored by analyzing the phase-shift between temperature and heat flow for sapphire and empty runs. The phase shifts change by more than 180° depending on the sign of the asymmetry. Once the sign of asymmetry is determined, the asymmetry correction for temperature-modulated DSC can be made.

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Abstract  

To understand better the thermal decomposition characteristics of organic peroxides, a C80 heat flux calorimeter was used and the decomposition pattern of cumene hydroperoxide and di-tert-butylperoxide were classified as auto-catalytic and nth order reaction, respectively. Based on the scanning results with the C80 at several differing rates of heating, the thermal decomposition behavior of organic peroxides under isothermal storage at lower temperature was simulated with a model-free simulation. Simulated results showed that the calculated conversion of cumene hydroperoxide as a function of time was in good agreement with experimental data obtained with the TAM-III high sensitivity thermal activity monitor.

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Automated system for kinetic research in thermal analysis

II. Organization of kinetic experiments in ASKR

Journal of Thermal Analysis and Calorimetry
Authors: A. I. Benin, A. A. Kossoy, and F. Yu. Sharikov

The correctness of a kinetic experiment is an essential condition for obtaining reliable results in kinetic investigations. Methods for provision and testing of thermo-physical and concentration correctness are discussed in the present article. Problems connected with the non-isothermal mode of an actual thermoanalytical experiment caused both by programming and by heat release in the sample are considered. Application analysis of the combined partial-linear heating laws in kinetic investigations is given in relation to the heat flux calorimeters ‘SETARAM’.

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Abstract  

Indium was analyzed with both, standard differential scanning calorimetry (DSC) and temperature-modulated DSC (TMDSC) using sinusoidal and saw-tooth modulation. Instrument and sample effects were separated during nucleated, reversible melting and crystallization transitions, and irreversible crystallization with supercooling. The changes in heat flow, time, and sample and reference temperatures were correlated as functions of heating rate, mass, and modulation parameters. The transitions involve three regions of steady state (an initial and a final region before and after melting/crystallization, a region while melting/crystallization is in progress) and one region of approach to steady state (melting peak to final steady state region). Analyses in the time domain show promise when instrument lags, known from DSC, are used for correction of TMDSC. A new method of integral analysis is introduced for quantitative analysis even when irreversible processes occur in addition to reversible transitions. The information was derived from heat-flux calorimeters with control at the heater block or at the reference temperature sensor.

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Journal of Thermal Analysis and Calorimetry
Authors: Katsumi Katoh, Shunsuke Ito, Yuji Ogata, Jun-ichi Kasamatsu, Hiroshi Miya, Masaaki Yamamoto, and Yuji Wada

Abstract  

In order to prevent the spontaneous ignition of nitrocellulose (NC), NC is stabilized by washing with industrial water in its synthesis process. However, there is a possibility that the components in industrial water contribute to the thermal stability of NC. In this way, the purpose of this study is to clarify the effect of industrial water components on the thermal stability of NC. In experiments, a heat flux calorimeter was used to observe the thermal behavior of NC with the residue of vaporized industrial water. The induction period of heat release of NC with 2-mass% residues was approximately 2–5 h shorter than that of NC alone whose induction period was observed at 7 h. Those results indicate that the residue destabilized NC. On the other hand, when the additive amount of the residue was increased, the induction period gradually increased as well. Based upon these results, we assume that inorganic salts contributing to stabilization and destabilization competitively coexist in the industrial water components. The same thermal analysis was performed on NC with CaCO3, CaSO4, CaCl, ZnSO4, NaCl, and CuCl. Those salts are predicted to exist in the industrial water. In the results, the induction period of NC with 2-mass% CaCO3 was approximately 15-h longer than that of NC alone, while the induction period with the inorganic salts CaSO4, CaCl, ZnSO4, NaCl, and CuCl was 4–5-h shorter. Therefore, when the industrial water components accumulate in NC, the destabilization by inorganic salts such as CaSO4, CaCl, ZnSO4, NaCl, and CuCl and the stabilization by compounds such as CaCO3 are thought to countervail against each other.

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Journal of Thermal Analysis and Calorimetry
Authors: Katsumi Katoh, Shunsuke Ito, Shuhei Kawaguchi, Eiko Higashi, Katsuyuki Nakano, Yuji Ogata, and Yuji Wada

Abstract  

In the previous study, it was observed that the stability of nitrocellulose (NC) cannot be determined by thermal analyses such as differential scanning calorimetry (DSC) at heating rates of 1–10 K/min. This was because the thermal curves of NC samples with different stabilities could not be distinguished from one another. In this study, we explain why such thermal analyses cannot be used to evaluate the thermal stability of NC and identify the conditions under which thermal analyses can be used for this purpose. We investigated the effect of heating rate on the thermal behavior of pure NC and NC stabilized with diphenylamine (DPA) or akarditeII (AKII), which is a conventional stabilizer, by using the heat flux calorimeter (C80). At high heating rates (0.2–0.3 K/min), only single exothermic peak was observed in the thermal curves of both pure NC and NC/DPA and the thermal curve of pure NC was practically similar to that of NC/DPA. At low heating rate (0.02 K/min), two exothermic peaks were observed for both pure NC and NC/DPA. The heat amount of the first peak depended on the partial pressure of O2 in the atmosphere. The first peak in the thermal curve of NC/DPA was slightly suppressed as compared to that of pure NC. These results indicate that the stability of NC probably depends on the first exothermic peak that represents oxidation of NC by atmospheric O2. From this, on the thermal analyses at high heating rates, thermal curves of pure NC and NC/DPA could not be distinguished from one another. This is because the decomposition of NC itself occurs in the second exothermic peak before the oxidation of NC by atmospheric O2 in the first peak, which is attributed to the stability of NC. The results of the thermal analyses under isothermal conditions at 393 K in an O2 atmosphere revealed that the induction period of NC/DPA and NC/AKII was longer than that of pure NC. From these results, it is speculated that the stability of NC can be evaluated by thermal analyses carried out under O2-rich conditions at low heating rates.

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≤ 90° and refining data by Rietveld method using the DBWS-9807 program. Samples found in an equilibrium state, after synthesis and thermal treatments, were subjected to differential scanning calorimeter (DCS) analysis. A heat-flux calorimeter

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-2241(02)00066-0 . 9. Isalgue , A , Ortin , J , Torra , V , Viñals , J . 1980 . Heat flux calorimeters: dynamical model by localized time constants . An. Fis . 76 : 192 – 196 . 10

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