超级铝热剂Al/CuO前驱体的制备、表征、热分解机理及非等温分解反应动力学

以硝酸铜、无水乙醇、1,2-环氧丙烷和纳米铝粉为原料, 在超声振荡条件下, 采用溶胶-凝胶法制备了纳米复合含能材料——超级铝热剂Al/CuO的前驱体. 利用热重-差示扫描量热-傅里叶变换红外-质谱(TG- DSC-FTIR-MS)联用技术, 研究了纳米Al/CuO溶胶-凝胶前驱体的热行为和分解过程及机理. 利用不同升温速率下的TG-DTG分析, 研究了纳米超级铝热剂Al/CuO的溶胶-凝胶前驱体的热分解反应机理, 采用了6种动力学分析方法进行动力学参数计算, 得到前驱体分解反应的表观活化能、反应级数、频率因子等动力学参数, 纳米Al/CuO前驱体分解反应的动力学方程为: dα/dt=10^14.0×4α^3/4exp(-2.0×10⁴/T).     

苯胺溶剂中偶氮二异丁腈热分解特性及动力学

偶氮二异丁腈(AIBN)是一种典型的相变吸热与分解放热重叠的物质, 该重叠现象的存在不利于其动力学规律的研究. 为了正确解析AIBN相变吸热对其分解放热的影响, 并研究AIBN在溶剂中的非等温热行为, 利用差示扫描量热仪(DSC)对苯胺、AIBN及AIBN-苯胺溶液(22.18%(w))进行动态扫描, 得到不同升温速率下AIBN在苯胺溶剂中起始分解温度T_onset的范围为79.90-94.47 ℃, 比放热量较固态AIBN高291 J·g^-1左右, 该数值可以视为其比相变热. 基于Kissinger法计算的AIBN与AIBN-苯胺溶液的活化能E和指前因子A的结果相差不大. 采用Friedman法对AIBN与AIBN-苯胺溶液的热分解过程进行计算, 发现固态AIBN相变吸热对其分解放热的影响主要发生在反应进度α小于0.20的范围内, 当α大于0.20后, 两者活化能E(α)和ln(A(α)·f(α))随α的变化趋势基本一致. 分析认为, 相对于AIBN的分解反应而言, 苯胺可以视为一种惰性溶剂, 即其不会干扰AIBN的分解机理. AIBN在苯胺溶剂中的分解机理可以视为固态AIBN的分解机理. 结合Friedman法的计算结果, 采用一般积分法, 即Coats-Redfern法得到AIBN在苯胺溶剂中分解反应的机理函数为G(α)=α^3/2, 符合Mampel power法则,平均表观活化能为139.93 kJ·mol^-1.     

聚羟基丁酸-戊酸的非等温热分解反应动力学

用非等温TG-DTA技术, 在5.0、10.0、15.0和20.0 K•min^-1线性升温条件下, 研究聚羟基丁酸-戊酸(PHBV)的热分解反应动力学. 结果表明, 分解过程分三个阶段：分解初期、分解中期和分解后期. 分解初期的机理函数为Avrami-Erofeev方程(n=1/2), 对应随机成核和随后生长机理, 表观活化能E_a(β→0)为69.44 kJ•mol^-1, 指前因子A(β→0)为106.27 s^-1；分解中期的机理函数为Avrami-Erofeev方程(n =2/5), 对应随机成核和随后生长机理, 表观活化能Ea(β→0)为117.64 kJ•mol^-1, 指前因子A(β→0)为10^11.48 s^-1；分解后期的机理函数为Mampel Power法则(n=1/3), 对应机理为幂函数法则, 表观活化能Ea(β→0)为116.64 kJ•mol^-1, 指前因子A(β→0)为10^8.68 s^-1.     

3,4-二硝基吡唑热分解及非等温动力学

采用TG-DSC综合热分析的方法,对3,4-二硝基吡唑(DNP)的热分解和非等温动力学进行了研究。结果表明DNP的热分解分两阶段进行,并且在升温速率达到15K/min时才能明显区分。分别采用Archar微分法和Coats-Redfen积分法计算了DNP第一阶段热分解反应动力学参数:Ea=91.6kJ.mol-1,lnA=42.7s-1。最可能的DNP热分解机理为随机成核和随后生长机理,符合动力学机理函数Avrami-Erofeev方程,n=3。     

热分析法与分子模拟技术研究芦丁的热降解机理及其分解动力学

利用热重-微分热重技术测得芦丁在氮气气氛中不同升温速率β下的热分解曲线,使用Achar法、Coats-Redfern法、Kissinger法和Ozawa法4种方法同时进行动力学分析,根据第一步热分解的表观活化能Eα和指前因子A计算推断芦丁在不同温度下的贮存期。研究表明,随着升温速率的提高,芦丁的热分解温度逐渐升高;芦丁三步热分解的机理依次是随机成核与随后生长控制、三维扩散控制、随机成核与随后生长控制,分别对应的函数是Avrami-Erofeev方程、Z.-L.-T.方程和Avrami-Erofeev方程;经Gaussian模拟和热重数据结合分析,芦丁在第一步分解时,失去3个O原子;第二步分解时失去10个O原子;第三步分解时失去烷烃分子链和1个苯环。根据第一步热分解的表观活化能Eα和指前因子A推断,在室温25℃下,芦丁的贮存期为1.5～2年。     

超细AgO粉末:制备及热分解非等温动力学

采用化学沉淀法,以臭氧为氧化剂制备了超细AgO粉末,并用XRD、XPS、SEM和粒度分析仪对制备的粉末进行了表征,借助热重分析法(TG)和线性升温理论对超细AgO粉末的热分解过程和非等温热分解动力学机理进行了研究。结果表明,制备的AgO属于单斜晶系,形貌为片状,其粒径分布在45～551nm之间,大部分在200nm左右;AgO的热分解分两步,158℃开始分解,放出氧气形成Ag2O,413℃进一步分解形成Ag;其热分解反应服从核生成和核成长为控制步骤的A2机理,热分解表观活化能为90.26kJ·mol-1,反应频率因子为1.64×108s-1。     

3-硝基邻苯二甲酸锆的制备﹑热分解机理及非等温反应动力学

用3-硝基邻苯二甲酸、氢氧化钠和硝酸氧锆为原料, 制备了3-硝基邻苯二甲酸锆, 采用元素分析、X射线荧光衍射和FT-IR对其结构进行了表征. 用TG-DTG以及变温固相原位反应池/傅里叶变换红外光谱(RSFT-IR)联用技术研究了3-硝基邻苯二甲酸锆的热分解机理, 对主分解反应的DTG峰进行了数学处理, 计算得到了动力学参数和动力学方程. 结果表明, 3-硝基邻苯二甲酸锆的分解反应总共有4个阶段, 其中主分解反应发生在第2阶段, 主分解反应的表观活化能Ea与指前因子A分别为158.84 kJ·mol-1和10^9.85 s-1, 主分解阶段的反应机理服从一级Mample法则, 主分解反应的动力学方程为dα/dt=10^9.85(1-α)e^-1.91×10⁴/T.     

ZnSn(OH)6的热分解动力学

用TG/DTG联用技术, 在2.5、5.0、10.0、15.0、20.0 K·min-1不同线性升温条件下, 研究了ZnSn(OH)6的热分解过程. 结果表明, 在氮气气氛下, ZnSn(OH)6在298-873 K范围内发生了一步分解. 其失重率与理论计算值相符. 应用非等温多重扫描速率法对热分解过程进行了动力学分析, ZnSn(OH)6在氮气中分解的活化能E=128.77 kJ·mol-1, 指前因子lg(A/s-1)=10.61, 机理函数为Mample单行法则.     

热分析法研究五倍子醛的热稳定性及其分解动力学

采用热重法,以氮气为保护气,分别在5、10、15、20℃/min的升温速率下,测得五倍子醛的热重-微分热重(TG-DTG)曲线,并在10℃/min的升温速率下测得样品的差示扫描量热(DSC)曲线。结合热失重数据和五倍子醛结构对其分解机理进行推断和验证,并运用双外推法对五倍子醛的热解动力学进行分析,求得原始状态和热平衡态下的动力学参数。研究结果表明,五倍子醛晶体在升温过程中先经历了非结合水和结合水的受热挥发阶段,然后在163℃之后发生热分解,分子中醛基断裂失去1分子的CO;随着升温速率的升高,五倍子醛的分解反应向高温区域移动,最大失重速率依次减小;热解活化能Eα为286.21 kJ/mol,指前因子lnA为70.21,热解机理函数g(α)=[-ln(1-α)]2/3,反应级数n=2/3;热解活化能随转化率的增加逐渐减小;经动力学参数推断,在室温(25℃)下,五倍子醛的贮存期为4～5年。     

用协同学方法研究化学反应速率和机理问题

用非平衡统计理论中的协同学方法分析了化学动力学中的反应速率和机理问题．对于任何给定的机理，通过引入一种非奇异变换，将相应的反应速率方程组直接地转换成Ｈａｋｅｎ形式，从而得到反应体系序参量以及其它变量的演化解析表达式．讨论了有机分子热分解的Ｒｉｃｅ－Ｈｅｒｚｆｅｌｄ机理．对醚的热分解链反应得到了一级动力学方程，理论结果与实验结果相符合．利用这种方法能解析地求解复杂反应的反应速率方程组，而不必引用在化学动力学中的“稳态近似”假设     

The fire retardant behaviour of huntite and hydromagnesite - A review

Naturally occurring mixtures of hydromagnesite and huntite have found important industrial use. Their endothermic decomposition over a temperature range similar to that of commonly used polymers and their release of water and carbon dioxide, has led to such mixtures being successfully used as fire retardants. They have replaced aluminium hydroxide and magnesium hydroxide in many applications. The current understanding of the thermal decomposition mechanism of both minerals and their combination in natural mixtures has been reviewed and related to their fire retardant action. Both minerals contribute to the reduction in flammability of polymers although the extent of these interactions has not been fully investigated. However, the fire retardant mechanism of these minerals appears more complicated than either aluminium hydroxide or magnesium hydroxide.     

Etude ATD-ATG du polyethylene ignifuge par l’hydroxyde de magnesium

Fire resistance of polyethylene is realized by magnesium hydroxide which is distinguished from halogenated fire-proofing agents by its lower cost and its non toxicity. Magnesium hydroxide decomposed by an endothermic reaction with liberation of water, contributing to fire proofing. The sample used (Kisuma 5A-N^*) is constituted from a powder (0.6–0.8 micrometre) its surface is treated by plastic material in order to ameliorate its compatibility. We studied the thermal decomposition by DTA and TG, of mixtures constituted by polyethylene and magnesium hydroxide. A sudden decomposition began at 385°C for pure polyethylene and decomposition took place at 429°C for the mixture polyethylene-Kisuma (50–50). Incorporation of magnesium hydroxide in polyethylene increases fire resistance.     

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.     

The Effect of Flower-Like Magnesium Hydroxide Nanostructure on the Thermal Stability of Cellulose Acetate and Acrylonitrile–Butadiene–Styrene

Flower-like magnesium hydroxide (Mg(OH)₂) nanostructures were synthesized via a simple hydrothermal reaction at relatively low temperature. The Mg(OH)₂ nanostructures were then added to acrylonitrile–butadiene–styrene (ABS) and cellulose acetate (CA) polymers. The effect of Mg(OH)₂ nanostructures on the thermal stability of the polymeric matrixes has been investigated. The thermal decomposition of the nanocomposites shifts towards higher temperature in the presence of the Mg(OH)₂. The enhancement of thermal stability of nanocomposites is due to endothermically decomposition of magnesium hydroxide that releases of water and dilutes combustible gases. Nanostructures and nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), Fourier transform infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), differential thermal analysis (DTA), UL-94 test and limiting oxygen index (LOI) analysis.     

Kinetics of fluorine binding from gaseous products of thermal decomposition of M-1 fluorocarbon liquid and a telomeric alcohol by alkaline-earth metal oxides and calcium hydroxide

The reactions of products of thermal decomposition of fluorinated compounds with magnesium and calcium oxides and with calcium hydroxide were studied. The kinetic parameters of the processes were determined. Conditions were found for complete binding of fluorine from M-1 fluorocarbon liquid into environmentally safe products, alkaline-earth metal fluorides.     

碱促进的钴酸镁催化剂上的氧化亚氮分解

The direct decomposition of N2O was investigated over a series of magnesium cobaltite catalysts,MgxCo1-xCo2O4(0.0 ≤ x ≤ 1.0) ,which were prepared by the thermal decomposition of stoichiometric amounts of magnesium hydroxide and cobalt acetate. The thermal genesis of the different catalysts from their precursors was explored using thermogravimetric analysis,differential thermal analysis,and X-ray diffraction. Texture analysis was carried out using N2 adsorption at -196 °C. We found that all the catalysts tha...     

Evaluation of magnesium sulphate attack in mortar-metakaolin system by thermal analysis

This paper reports an experimental study on the magnesium sulphate resistance of mortar specimens incorporating 0, 10 and 20% of metakaolin (MK). The evidence of the attack was evaluated through the content of calcium hydroxide (portlandite) and formation of magnesium hydroxide (brucite) by thermal analysis (thermogravimetric and derivative thermogravimetric analysis). The mechanical degradation of the mortar specimens was evaluated through splitting tensile tests after 200 days of exposition to the magnesium solution. The addition of metakaolin resulted in a reduction in the content of calcium hydroxide and in a smaller formation of brucite in comparison with reference mixture. A tensile strength loss of about 7% was observed for the metakaolin mortars submitted to the magnesium solution attack for 200 days.     

一元氯化镁化合物热分解的热力学研究

本文利用Gaussian 03程序,采用量子化学理论,在RHF/6-31G(d)水平上,对一元氯化镁化合物热分解反应机理进行了研究。在对现有4种水氯镁石脱水技术的反应物和产物几何构型进行能量梯度法全优化的同时,计算了不同温度下4种方法的主副反应路径的标准热力学参数(298.15~1000 K)。热力学计算结果表明:所有反应均为吸热反应,当压力为1.01×105 Pa、温度低于1000 K时,所有反应都不能自发进行;从热力学的角度分析,热分解更有利于以苯胺为助剂的复盐法的发生。     

Role of montmorillonite in flame retardancy of ethylene-vinyl acetate copolymer

The effects of non-treated (MMT), organophilic (OMM), and olefin/silicone polymer intercalated (IMM) montmorillonites on the thermal stability of ethylene-vinyl acetate copolymer (EVA) and on the flammability of magnesium hydroxide filled EVA were studied. The influence of various treatments on the delamination of montmorillonites in EVA was detected by rheological measurements and by Raman microscopy. The latter was a unique method for rapid detection of the dispersion also in highly filled EVA. Enhancement of thermo-oxidative stability of EVA and flame-retarded EVA could be observed by thermal analysis in the presence of variously treated montmorillonites. The flame-retardant efficiency of magnesium hydroxide was improved by simultaneous application of MMT and IMM. The increased performance of magnesium hydroxide was explained by the rheological effect of the IMM, catalytic effect of MMT and chemical interactions of montmorillonites with the metal hydroxide.     

纳米阻燃氢氧化镁/聚氧化乙烯复合聚合物电解质

合成了纳米氢氧化镁作为聚氧化乙烯(PEO)基聚合物电解质的增塑剂和阻燃剂,并对其进行X射线衍射(XRD)、透射电子显微镜(TEM)和热重(TG)分析研究.制得的氢氧化镁为片状六方晶体,尺寸在50-80nm之间,纳米氢氧化镁在340℃时开始热分解.对纳米氢氧化镁/PEO复合聚合物电解质的电化学研究结果显示:纳米氢氧化镁/PEO复合聚合物电解质的离子电导率随着添加纳米氢氧化镁的质量分数的增加先增大后减小,其在5%-10%之间时,复合聚合物电解质的离子电导率达到最大值.纳米氢氧化镁的添加使复合聚合物电解质的阳极氧化电位有一定程度的提高,纳米氢氧化镁具有改善PEO阳极抗氧化能力的作用.