The kinetics of thermal decomposition of bismuth oxohydroxolaurate

The bismuth salt of lauric (dodecanic) acidBi₆O₄(OH)₄(C₁₁H₂₃COO)₆ was studied earlier. This salt has layer structure (the interlaminardistance=37.50 Å), under heating this liquid-crystalline state has themesomorphic transformation, turns to the amorphous state, decomposes stepwisewith the formation of well-ordered layers of bismuth nanoparticles. DSC-curveswere used for the study of the decomposition kinetics in the area of decompositionwith small mass loss and exothermic effect (423–483 K).     

An investigation of the thermal decomposition of gold acetate

The thermal decomposition characteristics of gold acetate to produce gold nanoparticles were investigated. A rapid and violent fragmentation of the gold acetate particles was observed at approximately 103±20°C when a rapid heating rate of 25°C min⁻¹ was used, leading to formation of nanosized spherical and partially coalesced gold particles. Particle size analysis was used to investigate possible relationships between the gold acetate crystallite size and the gold nanoparticles produced by thermal decomposition. The results indicate rapid (<0.14 ms) coalescence of the gold particles occurs for fragments in close proximity.     

Thermodynamic and kinetic stability of inclusion compounds under heating

Thermodynamic and kinetic stability of inclusion compounds (so called supermolecular compounds) is discussed. Compounds under study and discussion are clathrates (with coordination compounds matrices) and intercalates (with fluorinated graphite matrices).     

Thermoanalytical study of fluoxetine hydrochloride

The thermal decomposition of two inclusion compounds Mn(HCOO)₂·1/3C₄H₈O₂ and Mn(HCOO)₂·1/3C₄H₈O was studied in the inert atmosphere. The process of both dioxane, and tetrahydrofurane removal has two steps; the intermediate phase is unstable and kinetically hindered. Manganese formate is stable up to 330°C. Thermogravimetric data (obtained at different rates of linear heating) were processed with computer program (with ‘Model free’ approach). Kinetic parameters were calculated for the first decomposition step, and the process is described by equation of n-order reaction with autocatalysis.     

In situ thermo-TOF-SIMS study of thermal decomposition of zinc acetate dihydrate

Time-of-flight secondary ion mass spectrometry (TOF-SIMS) was used for an in situ thermal decomposition study of Zn(CH₃COO)₂·2H₂O forming ZnO nanoparticles. TOF-SIMS spectra were recorded at regular temperature intervals of 25 °C in positive and negative detection modes in a dynamic thermal process. Controlled heating (5 °C min⁻¹) of Zn(CH₃COO)₂·2H₂O was also carried out using thermogravimetric analysis (TGA) in an oxygen atmosphere (20 ml min⁻¹). Nearly spherical ZnO nanoparticles with no agglomeration and a narrow size distribution (diameter ∼50 nm) were observed, which were characterized using scanning electron microscopy, transmission electron microscopy and x-ray diffraction. In situ thermo-TOF-SIMS was used to monitor the ⁶⁴Zn⁺ and ⁶⁶Zn⁺ ion abundances as a function of temperature, which showed a similar profile to that observed for weight loss in TGA during decomposition. Based on the experimental results, a possible decomposition mechanism for the formation of ZnO is proposed. Copyright © 2004 John Wiley & Sons, Ltd.     

Kinetics of thermal decomposition of nickel sulfate hexahydrate

The paper describes the kinetics of all the recorded steps of thermal decomposition of nickel sulfate hexahydrate in air. The thermal decomposition of the salt in air led to NiO at about 1060 K. The kinetic parameters, the activation energyE and the preexponential factorA, and the thermodynamic parameters, the entropy, enthalpy and free energy of activation were evaluated for the dehydration and decomposition reactions. Tentative reaction mechanisms are suggested for each step of the thermal decomposition.     

Kinetics of thermal decomposition of dinitramide

Kinetic regularities of thermal decomposition of dinitramide in aqueous and sulfuric acid solutions were studied in a wide temperature range. The rate of the thermal decomposition of dinitramide was established to be determined by the rates of decomposition of different forms of dinitramide as the acidity of the medium increases: first, N(NO₂)⁻ anions, then HN(NO₂)₂ molecules, and finally, protonated H₂N(NO₂)₂ ⁺ cations. The temperature dependences of the rate constants of the decomposition of N(NO₂)⁻ (k _an) and HN(NO₂)₂ (k′_ac) and the equilibrium constant of dissociation of HN(NO₂)₂ (K _a) were determined:k _an=1.7·10¹⁷ exp(−20.5·10³/T), s⁻¹,k′_ac=7.9·10¹⁶ exp(−16.1·10³/T), s⁻¹, andK _a=1.4·10 exp(−2.6·10³/T). The temperature dependences of the decomposition rate constant of H₂N(NO₂)₂ ⁺ (k _d) and the equilibrium constant of the dissociation of H₂N(NO₂)₂ ⁺ (K _d) were estimated:k _d=10¹² exp(−7.9·10³/T), s⁻¹ andK _d=1.1 exp(6.4·10³/T). The kinetic and thermodynamic constants obtained make it possible to calculate the decomposition rate of dinitramide solutions in a wide range of temperatures and acidities of the medium. In this series of articles, we report the results of studies of the thermal decomposition of dinitramide performed in 1974–1978 and not published previously. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2129–2133, December, 1997.     

On the thermal stability and thermal decomposition kinetics of some mono- and disubstituted furan-2,3-dions

The thermal behaviour of some compounds derived from 5-phenylfuran-2,3-dione was studied. The thermoanalytical data relating to the decomposition steps and intermediates were completed with mass spectrometric analysis and infrared spectroscopy results. For some of the investigated reactions, the kinetic and structural data correlated satisfactorily.     

氢氧化镁分解动力学的研究

以硼泥为原料与硫酸反应制备出七水硫酸镁,以氢氧化钠为沉淀剂制备出符合标准HG/T 3607-2000的氢氧化镁.利用XRD,SEM和TEM对氢氧化镁进行了表征,DTA-TG对氢氧化镁的热分解动力学进行了研究.XRD结果表明:制备粉体为单一Mg(OH)2.SEM和TEM结果表明:样品为片状或针状纤维,片直径大小不一,在20～50 nm之间,针状纤维形状不规则,大小不一致,长度在20～100 nm之间.利用Kissinger法和Ozawa法计算出的氢氧化镁热分解反应活化能分别为135.14和141.61 kJ·mol-1.利用Coats-Redfern法和Dolye法判断氢氧化镁热分解反应机理函数为A1.5.     

三角形纳米银颗粒的制备及其热稳定性的研究

具有独特的光学和化学性质的纳米三角形银纳米颗粒在光电、催化和生物传感器等领域中有广泛的应用.提供一种简单的方法制备三角银纳米颗粒,对其进行表征研究,且详细讨论了其热力学稳定性.     

Paramagnetic behaviour of silver nanoparticles generated by decomposition of silver oxalate

Silver oxalate Ag₂C₂O₄, was already proposed for soldering applications, due to the formation when it is decomposed by a heat treatment, of highly sinterable silver nanoparticles. When slowly decomposed at low temperature (125 °C), the oxalate leads however to silver nanoparticles isolated from each other. As soon as these nanoparticles are formed, the magnetic susceptibility at room temperature increases from −3.14 10⁻⁷ emu.Oe⁻¹.g⁻¹ (silver oxalate) up to −1.92 10⁻⁷ emu.Oe⁻¹.g⁻¹ (metallic silver). At the end of the oxalate decomposition, the conventional diamagnetic behaviour of bulk silver, is observed from room temperature to 80 K. A diamagnetic-paramagnetic transition is however revealed below 80 K leading at 2 K, to silver nanoparticles with a positive magnetic susceptibility. This original behaviour, compared to the one of bulk silver, can be ascribed to the nanometric size of the metallic particles.     

General remarks on the thermal decomposition of some drugs

The thermal decomposition of antituberculous, local anaesthetic and calcium salts of organic acids used as the drugs has been studied by differential thermal and thermogravimetric techniques. General characteristics of their thermal decomposition has been made. The effect of sample size over the range 20–200 mg and heating rate over the range 3–15 deg·min^?1 on the thermal degradation has been investigated. The values of the kinetic parameters has been also determined.     

Mechanism of thermal decomposition of cobalt acetate tetrahydrate

The thermal decomposition of cobalt acetate tetrahydrate (Co(CH₃COO)₂ · 4H₂O) has been studied via thermogravimetric (TG) analysis, in situ X-ray powder diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). The results of TG and XRD showed that the parent salt melted and then the dissolved crystalline water was vaporized in two steps. The dehydration process was followed by a major step concerning the decomposition of the acetate group, leading to basic acetate as an intermediate, which then produced CoO and Co in N₂ and H₂ atmosphere, respectively. Three decomposition intermediates Co(CH₃COO)₂ · 0.5H₂O, Co(CH₃COO)₂, and Co(OH)(CH₃COO) were presumed. In situ XRD experiments revealed that the intermediate basic acetate was poorly crystallized or even amorphous. Evolved gases analysis indicated that the volatile products of acetate decomposition were water vapor, acetic acid, ethylenone, acetone, and CO₂. A detailed thermal decomposition mechanism of Co(CH₃COO)₂ · 4H₂O was discussed.     

Kinetics of thermal decomposition of hexanitrohexaazaisowurtzitane

Thermal decomposition of hexanitrohexaazaisowurtzitane (HNIW) in the solid state and in solution was studied by thermogravimetry, manometry, optical microscopy, and IR spectroscopy. The kinetics of the reaction in the solid state is described by the first-order equation of autocatalysis. The rate constants and activation parameters of HNIW thermal decomposition in the solid state and solution were determined. The content of N₂ amounts to approximately half of the gaseous products of HNIW thermolysis. The thermolysis of HNIW and its burning are accompanied by the formation of a condensed residue. During these processes, five of six nitro groups of the HNIW molecule are removed, and one NO₂ group remains in the residue, which contains amino groups and no C−H bonds. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya, No. 5, pp. 815–821, May, 2000.     

Stages of thermal decomposition of sodium oxo-salts of sulphur

Thermal behaviour of sodium oxo-salts of sulphur: Na₂SO₄, Na₂S₂O₇, Na₂S₂O₆, Na₂SO₃, Na₂S₂O₅, Na₂S₂O₄, Na₂S₂O₃, Na₂S₃O₆ and of sulphides Na₂S and Na₂S₂ was studied on heating up to 1000°C. The experiments were performed with anhydrous compounds obtained from commercial products by recrystallisation and dehydration. The stage mechanisms of decomposition of anionic sub-lattices of the salts have been proposed basing on the Górski’s morphological classification of simple species. The thermal stability and the stage decomposition mechanisms were correlated with the structure and the potential chemical properties of the salt anions. The thermal decomposition processes were studied by means of thermal analysis, and the decomposition products were identified by means of X-ray phase analysis.     

硫化氢热分解制氢过程的化学动力学研究

采用化学热平衡分析方法研究了硫化氢热分解制氢过程,研究了硫化氢在不同温度和体积分数下的分解过程,并与试验数据进行了比较。结果表明,基元反应机理能较好地模拟硫化氢热分解制氢过程。硫化氢的热分解率依赖于反应温度,高温下能获得较好的分解制氢效果;温度较低时,时间是硫化氢趋于平衡的主要影响因素,随着温度的提高,温度成为影响硫化氢趋于平衡的主要影响因素。硫化氢初始体积分数对热分解制氢反应具有较大的影响,采用较低体积分数的硫化氢混合气有利于获得高的硫化氢热分解制氢率。     

Kinetics of thermal decomposition of manganese(ii) oxalate

The kinetics of manganese(II) oxalate thermal decomposition in the helium atmosphere was studied on the basis of isothermal measurements in the temperature range from 608 to 623 K. Manganese(II) oxide, MnO, was found to be the final product of reaction. The Avrami-Erofeev kinetic equation was used to describe all the experimental data in the range of decomposition degrees from 0.1 to 0.9. The determined activation energy equals 184.7 kJ mol^-1 with standard deviation ±5.2 kJ mol^-1. The estimated value of parameter n is 1.9 with standard deviation ±0.01 what suggests that the rate limiting step of MnC₂O₄ decomposition is the nucleation of new MnO phase and that the rate of nuclei growth is rising during decomposition. This revised version was published online in July 2006 with corrections to the Cover Date.     

过氧化苯甲酸叔丁酯的热分解动力学研究及SADT推算

研究了过氧化苯甲酸叔丁酯的热分解动力学及不同包装规格下的自加速分解温度(SADT),利用C600微量热仪测试了过氧化苯甲酸叔丁酯的热分解特征,得到升温速率分别为0.1 K/min、0.2 K/min、0.5 K/min、1 K/min下热流随时间的变化曲线,并使用Friedman等转化率法对所得的实验数据进行分析处理,得到了过氧化苯甲酸叔丁酯的分解反应活化能、指前因子等热动力学参数,推算了不同包装规格的过氧化苯甲酸叔丁酯的SADT。结果表明TBPB分解活化能及指前因子随转化率变化而变化,活化能范围为42-135.5 kJ/mol,指前因子范围为0.25-33.5,在25L聚乙烯桶包装下的SADT为59℃,50L下为52℃,200L下为46℃。     

MgAl-水滑石热分解过程动力学研究

类水滑石化合物Hydrotalcite-like Compounds(简称HTLcs)又称阴离子粘土,是由带正电荷的氢氧化物层和层间阴离子构成[1]。由于在类水滑石结构中含有大量的结构羟基和层间可分解的阴离子,所以其热稳定性较差,易于分解形成具有一定酸碱性及大比表面的复合氧化物,该复合氧化物由于具有晶粒小、活性元素分布均匀、比表面积大等特点,表现出了优异的催化性能[2~5]。近年来,以HTLcs为前体经高温焙烧制备双金属复合氧化物备受关注[6]。揭示类水滑石热解机理、选择焙烧条件是催化剂制备的关键所在。本文利用TG-DTA技术详细研究了不同镁铝比HTL…     

The non-isothermal decomposition of cobalt acetate tetrahydrate

The non-isothermal decomposition of cobalt acetate tetrahydrate was studied up to 500°C by means of TG, DTG, DTA and DSC techniques in different atmospheres of N₂, H₂ and in air. The complete course of the decomposition is described on the basis of six thermal events. Two intermediate compounds (i.e. acetyl cobalt acetate and cobalt acetate hydroxide) were found to participate in the decomposition reaction. IR spectroscopy, mass spectrometry and X-ray diffraction analysis were used to identify the solid products of calcination at different temperatures and in different atmospheres. CoO was identified as the final solid product in N₂, and Co₃O₄ was produced in air. A hydrogen atmosphere, on the other hand, produces cobalt metal. Scanning electron microscopy was used to investigate the solid decomposition products at different stages of the reaction. Identification of the volatile gaseous products (in nitrogen and in oxygen) was performed using gas chromatography. The main products were: acetone, acetic acid, CO₂ and acetaldehyde. The proportions of these products varied with the decomposition temperature and the prevailing atmosphere. Kinetic parameters (e.g.E and lnA) together with thermodynamic functions (e.g. °H, C _p and °S) were calculated for the different decomposition steps. In celebration of the 60^th birthday of Dr. Andrew K. Galwey