共查询到20条相似文献,搜索用时 15 毫秒
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Qing-yang Liu Yi-ling Bei Gui-bin Qi Yuan-jun Ding 《Korean Journal of Chemical Engineering》2008,25(5):980-981
The thermal decomposition kinetics of 5-fluorouracil was studied by thermogravimetric analysis methodology. The decomposition
activation energy was calculated by using Ozawa method by means of TGA in nitrogen atmosphere. Moreover, the decomposition
mechanism and pre-factor were obtained by Coats-Redfern and Achar methods, respectively. It is found that the decomposition
activation energy of fluorouracil is 105 kJ·mol−1. The decomposition mechanisms obtained by Coats-Redfern and Achar methods are G(α)=[−ln(1−α)]2/3 and f(α)=1.5(1−α)[−ln(1−α)]1/3 respectively, lnA is 21.40 min−1. 相似文献
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CraigM. Tarver TriD. Tran RichardE. Whipple 《Propellants, Explosives, Pyrotechnics》2003,28(4):189-193
A chemical kinetic model for the thermal decomposition of the solid high explosive pentaerythritol tetranitrate (PETN) is developed for prediction of times to thermal explosion using the Chemical TOPAZ heat transfer computer code. The model is based on times to thermal explosion measured in a new One Dimensional Time to Explosion (ODTX) apparatus. ODTX experiments are reported for pure PETN and for Semtex 1A. The pure PETN results are accurately modeled using a four reaction decomposition process in which an autocatalytic process produces intermediate reaction product gases, which subsequently react in a second order gas phase process to produce the final reaction products. Semtex 1A exhibits longer times to explosion than PETN at low temperatures, indicating that its endothermic binder decomposition absorbs heat produced by PETN decomposition. This binder reaction is modeled as a first order endothermic process. Three experiments on 5.08 cm diameter unconfined cylinders of PETN ramp heated to explosion at different rates are reported. The PETN model accurately predicts the thermocouple records and explosion times for these unconfined experiments in which only intermediate gaseous products can form. 相似文献
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BorisN. Kondrikov S.P. Smirnov A.V. Minakin RuthM. Doherty 《Propellants, Explosives, Pyrotechnics》2004,29(1):27-33
The kinetics of thermal decomposition of 3‐nitro‐2,4‐dihydro‐3H‐1,2,4‐triazol‐5‐one (NTO) in the temperature interval from 200 °C to 260 °C was investigated using a glass Bourdon gauge. The overall decomposition reaction includes two distinct stages: the fast first‐order decomposition and the subsequent autocatalytic reaction. The importance of the first stage increases with increasing decomposition temperature and decreasing loading density of the Bourdon gauge (m/V). A period of preliminary heating, at a lower temperature, strongly influences the autocatalytic stage when the decomposition is carried out at a higher temperature. In the temperature domain 200–220 °C, the Arrhenius constants of the decomposition reaction are found to be close to the values usually observed for nitrocompounds: E=173 kJ/mol and log10 k≈12.5 (s−1). It is shown that a simple model of NTO decomposition based on an autocatalytic reaction of the m‐th order can describe the course of the decomposition at high temperature but the m number appears to be excessively high, up to 4. A new model of the decomposition is developed, including an initial monomolecular reaction, decomposition of the crystalline substance, and an autocatalytic reaction of NTO dissolved in liquid decomposition products. This model gives the common order of autocatalysis, m=1. 相似文献
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纳米燃速催化剂对7-氨基-6-硝基-4,5-二氧化呋咱热分解的影响 总被引:2,自引:1,他引:2
用DSC和TG研究了A120a、Fe20a、Ti02、SnOz4种纳米燃速催化剂对7-氨基-6-硝基-4,5-二氧化呋咱(CL-18)热分解特性的影响。结果发现它们均使CL-18的起始反应温度降低、终止反应温度升高;Fe2O3、TiO2、SnO2不仅提高了反应放热量而且使整个反应变得相对平稳,随催化剂含量的增加最大失重速率温度先升高后降低.但CL-18的固态残留物量随催化剂含量的增加却一直减少;SnO2和Al2O3对CL-18的两个活化能影响较大,使CL-18的第一活化能分别降低了13.18kJ/mol和16.25kJ/mol,第二活化能分别降低了40.49kJ/mol和43.96kJ/mol;然而Fe20。仅仅对第二活化能有较大影响,降低了40.41kJ/mol。 相似文献
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Shaozong Wang Tonglai Zhang Li Yang Jianguo Zhang Yuanhua Sun 《Propellants, Explosives, Pyrotechnics》2007,32(1):16-19
CsDNBF (cesium 7-hydroxy-4,6-dinitro-5,7-dihydrobenzofuroxanide) was synthesized from the sodium salt of DNBF and cesium nitrate. The thermal decomposition process has been investigated and the results show that the solid residues at 240 °C are RCOOCs, CsNCO, RNO2 and CsNO3. The sensitivity results demonstrate that CsDNBF has better properties than KDNBF, which has been widely used. 相似文献
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The Arrhenius‐type reaction rate parameters for the initiation reactions governing the thermal decomposition of several energetic ionic liquids (EILs) were determined by numerical techniques. The compounds chosen for this purpose were the energetic 4‐amino‐1,2,4‐triazolium nitrate (4ATN) and 1‐hydroxyethyl‐hydrazinium nitrate (HEHN). The supplementary compounds studied for comparison were 4‐amino‐1,2,4‐triazolium chloride (4ATCl) and ammonium nitrate (AN). The reaction rate parameters were obtained by an evolutionary genetic algorithm (GA) that compared the difference between the experimental and simulated species evolution profiles from the decomposition process. The experimental data were generated by confined rapid thermolysis (CRT). The decomposition process was simulated by applying conservation equations to the condensed and gas phases individually. The optimization module recovered the experimental species profiles with reasonable accuracy for all the compounds studied. The processes governing the decomposition of these energetic compounds were found to be autocatalytic in nature, and the autocatalytic agents were the strong acids generated by the initial decomposition step. The activation energy and pre‐exponential factor for the unimolecular decomposition step for 4ATN, HEHN, and 4ATCl were 167–188 kJ mol−1 and 1016 s−1, respectively, similar to previously determined values for AN. 相似文献
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F. Azimfar I. Kohsari S. M. Pourmortazavi 《Journal of Inorganic and Organometallic Polymers and Materials》2009,19(2):181-186
Data on thermal stability of metallocene catalysts such as bis(n-butyl cyclopentadienyl) zirconium dichloride and bis(t-butyl
cyclopentadienyl) zirconium dichloride is required because of their application in high temperature polymerization process.
In the present study, the thermal stability of the bis(n-butyl cyclopentadienyl) zirconium dichloride and bis(t-butyl cyclopentadienyl)
zirconium dichloride was determined by differential scanning calorimetry (DSC) and simultaneous thermogravimetry-differential
thermal analysis (TG-DTA) techniques. The results of TG analysis revealed that the main thermal degradation for the bis(n-butyl
cyclopentadienyl) zirconium dichloride and bis(t-butyl cyclopentadienyl) zirconium dichloride occurs in the temperature ranges
of 194–360 °C and 195–350 °C, respectively. On the other hand, TG-DTA analysis indicated that bis(n-butyl cyclopentadienyl)
zirconium dichloride melts (about 98.7 °C) before it decomposes. However, the thermal decomposition of the bis(t-butyl cyclopentadienyl)
zirconium dichloride was started simultaneously with its melting. Also, the kinetic parameters such as activation energy and
frequency factor for both compounds were obtained from the DSC data by non-isothermal methods proposed by Kissinger and Ozawa.
Based on the values of activation energy obtained by Kissinger and Ozawa methods, the following order for the thermal stability
was noticed: bis(t-butyl cyclopentadienyl) zirconium dichloride >bis(n-butyl cyclopentadienyl) zirconium dichloride. Finally,
the values of ΔS#, ΔH# and ΔG# of their decomposition reaction were calculated. 相似文献
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将环氧树脂(EP)对不同粒径的碳酸氢钠(SB)进行包覆改性得到改性碳酸氢钠(EP@SB),采用扫描电镜(SEM)、红外(FTIR)、差示扫描量热法(DSC)和热重(TG),探究不同粒径SB下改性碳酸氢钠形貌及热分解性能。结果表明,不同粒径的SB在EP包覆改性后其热分解性能有明显改善,其中200目的SB改性后效果较理想,起始分解温度从120.1℃升高到155.2℃,提高幅度达35.1℃;分解温度区间从58.6℃缩小到了22.6℃。极大扩宽了轻量化制品的应用范围。 相似文献
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Wei Zheng Jiangning Wang Xiaoning Ren Laying Zhang Yanshui Zhou 《Propellants, Explosives, Pyrotechnics》2007,32(6):520-524
The thermal decomposition of DNTF‐CMDB propellants was investigated by pressure differential scanning calorimetry (PDSC) and thermogravimetry (TG). The results show that there is only one decomposition peak on DSC curves, because the decomposition peak of DNTF cannot be separated from that of the NC/NG binder. The decomposition of DNTF can be obviously accelerated by the decomposition products of the NC/NG binder. The kinetic parameters of thermal decompositions for four DNTF‐CMDB propellants at 6 MPa were obtained by the Kissinger method. It is found that the reaction rate decreases with increasing content of DNTF. 相似文献
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In this paper, the catalytic effect of Zn nanopowders on thermal decomposition of ammonium perchlorate (AP) as well as those of Zn micropowders has been investigated using differential thermal analysis (DTA). The results show that both nanometer and micrometer Zn powders show similar excellent catalytic effect on the decomposition of AP, while the total heat releases of AP added by Zn nanopowders are generally higher than those of AP added by Zn micropowders. In addition, an attempt has been made to explain the observed results with the help of theoretical considerations and data generated during this work. 相似文献
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The thermal decomposition of ammonium perchlorate has been extensively studied in the past. Nevertheless, the various results published illustrate, on the one hand, significant differences regarding the influence of different parameters on the decomposition and on the other hand, a lack of useful quantitative laws to predict the thermal behaviour of this crystal under a range of conditions (temperature, duration of exposure, presence of confinement). 相似文献
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InderPalSingh Kapoor Pratibha Srivastava Gurdip Singh 《Propellants, Explosives, Pyrotechnics》2009,34(4):351-356
Nanocrystalline transition metal oxides (NTMOs) have been successfully prepared by three different methods: novel quick precipitation method (Cr2O3 and Fe2O3); surfactant mediated method (CuO), and reduction of metal complexes with hydrazine as reducing agent (Mn2O3). The nano particles have been characterized by X‐ray diffraction (XRD) which shows an average particle diameter of 35–54 nm. Their catalytic activity was measured in the thermal decomposition of ammonium perchlorate (AP). AP decomposition undergoes a two step process where the addition of metal oxide nanocrystals led to a shifting of the high temperature decomposition peak toward lower temperature. The kinetics of the thermal decomposition of AP and catalyzed AP has also been evaluated using model fitting and isoconversional method. 相似文献
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Hae Sang Jun Kyung Nam Kim Kun You Park Seong Ihl Woo 《Korean Journal of Chemical Engineering》1995,12(2):156-161
The thermal degradation of polytetrafluoroethylene in flowing helium atmosphere was studied in the temperature range 510–600C.
The products of thermal degradation were analyzed by an on-line gas chromatography and the rates of degradation were obtained.
At relatively lower temperatures (less than 530°C) the rate curves as a function of time showed two peaks. This phenomenon
was explained in terms of diffusion limitation of the gaseous products. Further research was carried out by scanning electron
microscopy (SEM) in order to observe the diffusion limitation and these facts were confirmed by observing the matrix of partially
degraded polymer. The rate curves which have two peaks indicated that the diffusion limitation was disappeared above ca. 50%
conversion. The activation energy in diffusion limitation free region was 78.1 kcal/mole and it was very similar to the result
obtained by Madorsky (80.5 kcal/mole). The activation energy was also consistent with that obtained by thermogravimetry. 相似文献
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DavidE. Chavez BryceC. Tappan MichaelA. Hiskey SteveF. Son Herbert Harry Dennis Montoya Stephanie Hagelberg 《Propellants, Explosives, Pyrotechnics》2005,30(6):412-417
This paper describes the explosive sensitivity and performance properties of two novel high‐nitrogen materials, 3,6‐bis‐nitroguanyl‐1,2,4,5‐tetrazine ( 1 , (NQ2Tz)) and its corresponding bis‐triaminoguanidinium salt ( 2 , (TAG)2(NQ)2Tz)). These materials exhibit very low pressure dependence in burning rate. Flash pyrolysis/FTIR spectroscopy was performed, and insight into this interesting burning behavior was obtained. Our studies indicate that 1 and 2 exhibit highly promising energetic materials properties. 相似文献
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ValeryP. Sinditskii SergeiP. Smirnov ViacheslavYu. Egorshev 《Propellants, Explosives, Pyrotechnics》2007,32(4):277-287
Burning rate characteristics of the low‐sensitivity explosive 5‐nitro‐1,2,4‐triazol‐3‐one (NTO) have been investigated in the pressure interval of 0.1–40 MPa. The temperature distribution in the combustion wave of NTO has been measured at pressures of 0.4–2.1 MPa. Based on burning rate and thermocouple measurements, rate constants of NTO decomposition in the molten layer at 370–425 °C have been derived from a condensed‐phase combustion model (k=8.08⋅1013⋅exp(−19420/T) s−1. NTO vapor pressure above the liquid (ln P=−9914.4/T+14.82) and solid phases (ln P=−12984.4/T+20.48) has been calculated. Decomposition rates of NTO at low temperatures have been defined more exactly and it has been shown that in the interval of 180–230 °C the decomposition of solid NTO is described by the following expression: k=2.9⋅1012⋅exp(−20680/T). Taking into account the vapor pressure data obtained, the decomposition of NTO in the gas phase at 240–250 °C has been studied. Decomposition rate constants in the gaseous phase have been found to be comparable with rate constants in the solid state. Therefore, a partial decomposition in the gas cannot substantially increase the total rate. High values of the activation energy for solid‐state decomposition of NTO are not likely to be connected with a sub‐melting effect, because decomposition occurs at temperatures well below the melting point. It has been suggested that the abnormally high activation energy in the interval of 230–270 °C is a consequence of peculiarities of the NTO transitional process rather than strong bonds in the molecule. In this area, the NTO molecule undergoes isomerization into the aci‐form, followed by C3‐N2 heterocyclic bond rupture. Both processes depend on temperature, resulting in an abnormally high value of the observed activation energy. 相似文献