Nylon Based Nanocomposites: Influence of Calcium Carbonate Nanoparticles on the Thermal Stability

In this paper thermal and thermo-oxidative stability of nylon 6 based nanocomposites containing up to 5% by weight of fatty acid coated calcium carbonate (CaCO₃) nanoparticles is studied. Thermal stability of compression-moulded samples was evaluated by thermogravimetric analysis (TG) under air and nitrogen atmosphere. Kinetic analysis of TG data was performed by using the Flynn-Wall-Ozawa method. Results show that the presence of coated nanoparticles adversely affects the thermal and thermo-oxidative stability of nylon 6. Kinetic analysis shows that a complex, multi-step decomposition process occurs. Moreover, the presence of nanoparticles do not affect the rate limiting step of nylon 6 decomposition in air, while under nitrogen atmosphere the decomposition process occurs through a diffusion-driven regime in presence of high amounts of CaCO₃.     

甲磺酸帕珠沙星的热分解机理及动力学

采用热重(TG)和差示扫描量热(DSC)法测定了甲磺酸帕珠沙星(PZFX)在氮气氛和空气氛中的热分解过程,测定了PZFX及其在热分解过程中不同阶段残余物的红外光谱,运用量子化学GAMESS软件计算了PZFX分子的键级,推断了PZFX的热分解机理.结果表明PZFX的热分解过程的起始步骤是甲磺酸的分解.采用Ozawa方法计...     

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.     

稀土氨基酸配合物RE(Val)Cl3•6H2O(RE = Nd，Sm)的热分解动力学

合成了稀土氨基酸配合物晶体——三氯化缬氨酸六水合钕、钐，对合成样品进行了EDTA滴定、元素分析、红外光谱分析、热重、差热分析以及熔点测定，推测了配合物的热分解机理，采用Achar法和Coats-Redfern法研究了配合物热分解的非等温动力学过程，给出了各配合物样品失水阶段第一步反应和氨基酸骨架断裂阶段第一步反应的活化能（E）、指前因子的对数值（ln(A)）及热分解反应动力学方程式.     

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.     

Effect of catocene on the thermal decomposition of ammonium perchlorate and octogen

Simultaneous TG/DSC-FT-IR was employed to study the effect of catocene with a high concentration (5, 15, and 25 %) on the thermal decomposition of ammonium perchlorate (AP) and octogen (HMX) with different particle sizes. The experimental results show that catocene has effect on the thermal decomposition of AP and HMX, but the role that catocene playing changes with the concentration of catocene and the particle size of AP and HMX. High concentration of catocene (more than 15 %) benefits the decomposition of fine AP and HMX at low temperature, but has little effect on the decomposition of median and coarse AP. The thermal decomposition of HMX is affected by catocene mainly through increasing the heat release of the first decomposition step, while through both increasing the heat release and decreasing the decomposition temperature of the first decomposition step for the thermal decomposition of AP.     

Thermal decomposition of magnesium peroxoborate

The thermal decomposition of magnesium peroxoborate was studied by means of a derivatograph. It was found that the decomposition involves a sequence of reactions: dehydration and O₂ evolution. The kinetic parameters were obtained in each step of the reaction. The thermal stabilities of three kinds of metal peroxoborates are discussed.     

基于差示扫描量热技术的生物质热解两步连续反应模型研究

采用差示扫描量热分析仪对我国的一种生物质试样在空气气氛中进行了实验, 发现试样从常温到923 K高温的低速升温过程中, 经历了两步明显的放热过程. 对放热机理的分析表明, 第一步主要是由半纤维素和纤维素的有氧热解过程控制, 第二步放热过程则受木质素热解和炭的氧化反应的共同作用. 采用等转化率方法和优化计算方法, 对热解过程的动力学模型进行了研究, 结果表明, 两步连续反应机理可用于描述生物质在空气气氛中热解的放热动力学.     

Thermal decomposition mechanism of tenofovir disoproxil fumarate

Tenofovir disoproxil fumarate (TDF) is an antiretroviral medication widely used to prevent and treat HIV/AIDS and to treat chronic hepatitis B. In this paper, thermal decomposition processes of TDF were measured with thermogravimetry, differential scanning calorimetry and thermogravimetric analysis coupled with Fourier transform infrared spectroscopy. The IR spectra, high-performance liquid chromatography and liquid chromatography mass spectrometry of TDF and the residues of its thermal decomposition at various temperatures were determined. The molecular bond orders were calculated using an ab initio method from the GAMESS program of quantum chemistry. The mechanism of thermal decomposition was discussed. The results indicated that the thermal decomposition of TDF is a three-step process, the initial step of thermal decomposition of TDF is the decomposition of carboxylic ester, the first stage mainly is the decomposition of the phosphoric disoproxil section, and the second stage mainly is the decomposition of the tenofovir section and partially goes through adenine stage. The initial decomposition temperature in either nitrogen or air is 138 °C, and the thermal stability of TDF is not very good under routine temperature.

     

Kinetics of the non-isothermal decomposition of Cu-and Co-itaconato complexes

The kinetics of the thermal decomposition of Cu- and Co-itaconato complexes were studied using dynamic thermogravimetric techniques. The dehydration process was found to proceed in a one-stage reaction, while the thermal decomposition of the anhydrous salts was followed a two-stage reaction. The first stage is the decomposition of the complex to metal carbonate, whereas the second stage is the decomposition of the formed carbonate to the oxide. Kinetic analysis of the dynamic TG curves were discussed with reference to a composite integral method on comparison with the integral methods of Coats and Redfern and Ozawa. The activation parameters were calculated and discussed for each decomposition step.     

The two steps thermal decomposition of titanium hydride and two steps foaming of Al alloy

1 Introduction Al alloy foam with closed pores prepared by melt foaming, realizing the lightness, high specific strength and multifunction of structure material, is becoming one of the hotspots[1―11]. In order to meet the demand of high-tech, preparing s…     

对氯苯甲酸铕与邻菲咯啉络合物热分解动力学参数及寿命的测定

用TG-DTG技术研究了对氯苯甲酸铕与邻菲咯啉络合物在静态空气中的热分解,用Coats-Redfern(CR)法、Horowitz-Metzger(HM)法、Madhusudanan-Krishnan-NInan(MKN)法、Ozawa法和Kissinger法计算了对氯苯甲酸铕与邻菲咯啉络合物第一步热分解反应的动力学参数活化能（E）、指前因子（A）、反应级数（n)等。用等温TG法得到失重10%的E、A值和寿命方程：lnτ=-23.0189 17974.1/T。     

Keggin结构杂多酸热性质研究

本文利用DSC, TG-DTA, X射线衍射, 变温红外光谱和溶解性试验方法, 系统地研究了Keggin结构杂多酸HnXM12O40(X=Si, P, Ge; M=Mo, W)的热稳定性, 提出杂多化合物热分解的新判据, 给出了Keggin结构杂多酸的热分解过程, 推导出预测热分解温度的半经验公式。     

Thermodynamic properties and thermal stability of the synthetic zinc formate dihydrate

Zinc formate dihydrate has been synthesized and characterized by powder X-ray diffraction, elemental analysis, FTIR spectra and thermal analysis. The molar heat capacity of the coordination compound was measured by a temperature modulated differential scanning calorimetry (TMDSC) over the temperature range from 200 to 330 K for the first time. The thermodynamic parameters such as entropy and enthalpy vs. 298.15 K based on the above molar heat capacity were calculated. The thermal decomposition characteristics of this compound were investigated by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). TG curve showed that the thermal decomposition occurred in two stages. The first step was the dehydration process of the coordination compound, and the second step corresponded to the decomposition of the anhydrous zinc formate. The apparent activation energy of the dehydration step of the compound was calculated by the Kissinger method using experimental data of TG analysis. There are three sharply endothermic peaks in the temperature range from 300 to 650 K in DSC curve.     

Application of factor analysis for resolving thermogravimetric-mass spectrometric analysis spectra

Factor Analysis was used for extracting information out of the mixture mass spectra recorded in a thermogravimetric-mass spectrometric analysis. Principal component analysis (PCA) and a special diagram, the contour variance diagram (ContVarDia), were used for performing the factor analysis. The method was applied for studying the thermal decomposition of Kraton 1107 copolymer. Pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) was used for identification of the pyrolysis products of Kraton 1107. The application of factor analysis resulted in the determination of the main thermal decomposition steps and the prediction of the mass spectrum corresponding to each step. Those mass spectra were either pure spectra corresponding to main evolved gases or average spectra corresponding to multiple gases evolved in one decomposition step. The advantages and the limitations of the chemometric approach were discussed.     

Eu2(p-ClC6H4COO)6(C12H8N2)2配合物热分解机理及非等温动力学

The thermal decomposition behaviour of europium p-chlorobenzoate complex with 1, 10-phenanthroline and its kinetics were studied in nitrogen by non-isothermal thermogravimetry.Its thermal decomposition occurs mainly in three steps..The intermediate and residue for each step of decomposition were identified from TGcurve.The kinetic parameters were obtained from analysis of the TG-DTG curves by the Achar method.the Madhusudanan- Krishnan-Niman (MKN) method and Ozawa method respectively.The most probable mechanisms function for the first and second stage were suggested by comparing the kinetic parameters.     

硝酸舍他康唑的热分解机理及动力学

采用热重法(TG)、差示扫描量热法(DSC)测定了硝酸舍他康唑(STCZ)在氮气氛和空气氛中的热分解过程,结果表明STCZ的热分解过程是一个三阶段过程。运用量子化学GAMESS软件计算了STCZ分子的键级,测定了STCZ及其在热分解过程中不同阶段残留物的红外光谱,推断了STCZ的热分解机理,起始步骤是硝酸的分解。根据不同升温速率下的热重曲线计算得到STCZ第一阶段热分解反应的动力学参数,在氮气中,表观活化能Ea=222.2 kJ.mol-1,指前因子A=4.467×1024min-1,在空气中,表观活化能Ea=177.2 kJ.mol-1,指前因子A=1.738×1019min-1。推算了不同使用温度下STCZ的预期寿命。     

Impact of α-C<Subscript>2</Subscript>SH calcination temperature on the mineral composition and heat flow of the products

Nitrate ester plasticized polyether (NEPE) propellant has attracted considerable attention as a kind of high-energy propellant. To investigate the evolution of thermal properties of NEPE propellant during storage life, TG-DSC-MS-FTIR was used to determine the thermal behaviors of the propellant samples before and after 5-year natural storage. It was found out that both samples experience five reaction steps and they are attributed by the evaporation and O–NO₂ bond breaking of nitrate, crystal transition of HMX and thermal decomposition of plasticizer, HMX and ammonium perchlorate. Decomposition process and temperature ranges of each step maintain consistency, but nitrate ester tends to decompose more than evaporate after storage. In the meantime, the area of DSC peak formed in the third step noticeably increased, which accounts for the lower thermal explosion temperature. To further study the decomposition of plasticizer and HMX, their kinetic triplets were solved. It was found out that the activation energy increases significantly on plasticizer decomposition step because of the enlargement of the nitrate’s particle size. Therefore, it can be drawn that the decline of NEPE propellant’s safety property after storage was contributed by the decomposition step of nitrate ester plasticizer.     

Spectral studies of complexes of nickel(II) with tetradentate schiff bases having N2O2 donor groups

Complexes of nickel(II) of N,N'-disalicylidene-1,2-phenylenediamine (H2dsp), N,N'-disalicylidene-3,4-diaminotoluene (H2dst), 4-nitro-N,N'-disalicylidene-1,2-phenylenediamine (H2ndsp) and N,N'-disalicylidene ethylenediamine (H2salen) have been prepared and characterised by elemental analysis, electronic, IR, magnetic susceptibility measurement, 1H NMR and thermal studies. TG studies show that the Ni(dsp) and Ni(salen) complex decomposed in one step and Ni(dst) and Ni(ndsp) complex in two steps. Kinetic and thermodynamic parameters were computed from the thermal decomposition data. The activation energy of either one step decomposition or two step decomposition of complexes lies 72-95 kJ mol(-1) range.     

Nickel peroxide: A more probable intermediate in the Ni(II)‐catalyzed decomposition of peroxomonosulfate

The Ni(II) ion catalyzed thermal decomposition of peroxomonosulfate (PMS) was studied in the pH range 3.42–5.89. The rate is first order in [PMS] and Ni(II) ion concentrations. At pH greater than or equal to 5.23, the reaction becomes zero order in [PMS] and this changeover in the order of the reaction occurs at a higher concentration of nickel ions. The first‐order kinetics in PMS can be explained as a rate‐limiting step and is the transformation of nickel peroxomonosulfate into nickel peroxide. This peroxide intermediate reacts rapidly with another PMS to give oxygen and Ni(II). The formation of nickel peroxide is associated with a small negative or nearly zero entropy of activation. The zero‐order kinetics in [PMS] can be explained by the fact that the hydrolysis of aquated nickel(II) ions into hydroxocompounds is the rate‐limiting step. The turnover number is 2 at pH 3.42 and increases with pH. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 320–237, 2007