以多羧酸为桥的锌配合物的合成和热分解动力学研究

在水-甲醇体系中,Zn(C2H3O2)2.2H2O与吡唑、邻苯二甲酸氢钾水热反应,形成以邻苯二甲酸根桥联的在xy平面一维无限的锯齿形链状锌的配位聚合物[Zn(μ2-C6H4(COO)2)(pz)2],用元素分析,红外光谱等进行了表征,并用X-ray测定了配合物的晶体结构.此外,还对配合物进行了非等温热分解动力学研究.研究表明:此配合物的热分解反应是分两步进行的.通过计算,该配合物热分解的第一步反应的可能机理为化学反应,第二步反应的可能机理为成核与生长,n=1/4,其动力学方程分别为:dα/dT=A/βe-E/RT(1-α)2和dα/dT=A/βe-E/RT1/4(1-α)[-Ln(1-α)]-3.热分解反应的表观活化能分别是177.95和303.8 kJ/mol;指前因子InA分别是41.87和53.74 s-1.     

Preparation of basic magnesium carbonate and its thermal decomposition kinetics in air

The thermal decomposition process of basic magnesium carbonate was investigated. Firstly, Basic magnesium carbonate was prepared from magnesite, and the characteristics of the product were detected by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Subsequently, the thermal decomposition process of basic magnesium carbonate in air was studied by thermogravimetry-differential thermogravimetry (TG-DTG). The results of XRD confirm that the chemical composition of basic magnesium carbonate is 4MgCO₃·Mg(OH)₂·4H₂O. And the SEM images show that the sample is in sheet structure, with a diameter of 0.1–1 μm. The TG-DTG results demonstrate that there are two steps in the thermal decomposition process of basic magnesium carbonate. The apparent activation energies (E) were calculated by Flynn-Wall-Ozawa method. It is obtained from Coats-Redfern’s equation and Malek method that the mechanism functions of the two decomposition stages are D3 and A1.5, respectively. And then, the kinetic equations of the two steps were deduced as well.     

聚氧丙烯醚的非等温热分解动力学及寿命

利用热重(TG)分析技术对聚氧丙烯醚的热失重行为进行了研究.采用非等温TG-DTG技术，在5.0、10.0、15.0和20.0 K/min线性升温速率和空气气氛条件下，考察了聚氧丙烯醚的非等温热分解机理及反应动力学.运用Freeman-Carroll、Kissinger、Ozawa、Coats-Redfern和Achar等方法对非等温动力学数据进行分析，确定了聚氧丙烯醚热分解反应的机理函数为Mampel Power法则(m=1)，对应机理为幂函数法则，其表观活化能为62.5 kJ/mol，指前因子为106.17 s-1.同时采用等温TG技术得到失重10%和15%为寿终指标的寿命方程.     

Kinetics of the thermal decomposition of Wangjiatan siderite

The thermal decomposition processes of Wangjiatan siderite samples were studied in nitrogen by thermogravimetric(TG)analysis.The mechanism of thermal decomposition of the siderite obeyed an F n kinetic law and the n-order was between 1.16 and 1.29.The results from non-isothermal experiments show that the size of particles has an obvious effect on the logarithm of pre-exponential factor in kinetics parameter of the thermal decomposition of Wangjiatan siderite.A linear relationship is shown between the size of particles and the logarithm of pre-exponential factor.An F 1 kinetic model containing size factor describes the thermal decomposition of Wangjiatan siderite well.     

(CeO2,MgO)掺杂ZrO2溶胶热分解动力学

利用德国耐驰STA449C型热分析仪结合Kissinger法求解了Zr(OH)4·x(Ce(OH)4)·y(Mg(OH)2)体系的热分解动力学参数.结果显示,Zr(OH)4·x(Ce(OH)4)·y(Mg(OH)2)体系的热分解活化能为60.9 kJ/mol,反应级数2.28;晶态转变活化能为297.6 kJ/mol,相变指数1.6.     

菱铁矿热分解动力学研究

菱铁矿具有热分解特性,在一定温度与气氛条件下,经焙烧后放出CO2气体,并生成强磁性的磁铁矿,利于弱磁选富集.用TG和DTG(热重法和微商热重法)研究了大西沟菱铁矿的热分解过程,判定了发生热分解反应的温度范围,分析了热分解反应的动力学行为,采用微分法计算了大西沟菱铁矿的热分解动力学参数,并判定热分解过程所符合的动力学模型,用多种积分方法和非等温线性拟合法对计算结果进行了验证.结果表明:大西沟菱铁矿的热分解反应温度较低,在400-600℃之间.热分解过程符合F1模型.     

Investigation of the Thermal Decomposition Properties of Polyoxymethylene

By testing the melt index （MI）, tensile strength and breaking extension ratio, the thermal ageing rate of polyoxymethylene （POM） was analyzed and compared. The surface morphology and type of function group of POM surface were observed and analyzed by SEM and XPS. The results show that the MI value increases gradually with the ageing time at 120℃, indicating that the thermal oxidation decomposition occurrs slowly. The effect of 20-day thermal ageing on the tensile strength and breaking extension ratio of POM is not obvious, showing that the ageing of POM is quite a long process. After 105-day, thermal ageing cracking and powdering occurr on the POM surface. XPS determination shows the Cls spectra of samples before and after ageing include two peaks of C-C and C-O, while after ageing the content of C-C decreases and the content of C-O increases, indicating that the thermal ageing of POM is mainly the breaking and decomposing of C-C bond. The Ols/Cls ratio of original samples is 56.98% and after 105-day thermal ageing the ratio is 72.92%.     

Synthesis of zinc oxide nanocrystals by thermal decomposition of Zn-oleate in organic medium

We report the synthesis of uniform-sized hexagonal ZnO nanocrystals by the thermolysis of Zn-oleate complex, which was prepared from the reaction of inexpensive and environmentally friendly reagents such as zinc nitrate and sodium oleate. Two organic compounds with different boiling points, octadecene and octylether, were selected as the medium for thermolysis of Zn-oleate complex. Under optimized reaction conditions, we were able to synthesize ZnO nanoparticles with the size being about 10 nm. X-ray diffraction and transmission electron micrograph (TEM) images confirmed the high crystallinity of the nanocrystals.     

Thermodynamics and kinetics of calcium sulphoaluminate

The formation process of calcium suphoaluminate(C4A3S) was investigated by the X-ray diffraction technique and then the thermodynamics was analyzed, finally the kinetics of which was studied by SC-132. XRD results show that the formation of C4A3S is accomplished in three different kinds of ways: one is by solid reaction of Ca (OH)2/ CaO, Al2O3 and CaSO4, other two ways are through such interstitial products as CaO·Al2O3 and CaO·2Al2O3. The formation thermodynamics shows that C4A3S begins to form at 900 ℃-1 000 ℃ and increases as temperature rising; the quantity of reaches the highest at 1 300 ℃-1 350 ℃ and then falls at >1350℃. Kinetics study shows that the formation rate of C4A3S can be described as first-order kinetics at high temperature, and it belongs to the random nucleation growth mechanism. The apparent activation energy is 456.37 kJ·mol-1 and pre-exponential factor is 1.545×1012.     

The Thermal Decomposition Kinetics of Polysiloxane/Polymethylacrylate IPNs Materials

1Introduction Recently,anincreasingattentionhasbeenpaidtopolysiloxanebecausepolysiloxaneisthermallyresistantpolymerinhightemperaturewiththermalenduranceinoxidativeatmosphereupto300℃andmoreininertat mosphere.Thermoanalyticaltechniques,suchasthermo gravimetric(TG),differentialthermolgravimetric(DTG),anddifferentialscanningcalorimetry(DSC)havewidelybeenusedtocharacterizepolymericmaterials.Qingzeng Zhu[1]investigatedthethermaldecompositionofsilazanepolymerswiththermogravimetrymethodandindicat…     

The Influence of Grain Size on Decomposition Reaction of Limestone in Dispersing State

The thermal behavior and kinetic parameters of decomposition reaction of limestone in a temperature-programmde mode were investigated by means of TG,The experumental results shour that the kinetic model functions in different forms for the theermal decomposition rdactions of different limestone grain sizes in dispersing state under the almosphere of static air are 4(1-a)^3/4 for small size limestone and (1-a) for large size limestone.Information was obtained on the relationship among the decomposition temperature.decomposition time.decomposition fraction.decomposition reaction rate constant and grain grain size of limestone.     

MnO2热分解制备Mn3O4的动力学研究

为了得到MnO2热分解制备Mn3O4的动力学方程,用TG/DTA和XRD研究MnO2的热分解过程。研究表明MnO2的分解是分步进行的,4MnO2=2Mn2O3 O2↑的动力学方程为G(α)=[-ln(1-α)]12(T<625℃)和G(α)=[-ln(1-α)]13(T≥625℃),表观活化能为90.239 kJ/mol;6Mn2O3=4Mn3O4 O2↑的动力学方程为G(α)=[-ln(1-α)]13,表观活化能为204.67 kJ/mol;两个过程属于晶核形成与增长控制过程。     

Non-isothermal curing kinetics and thermal properties of benzoxazine-phenolic copolymers

Using novolac phenolic resin, aniline and formaldehyde as raw materials, benzoxazine-phenolic copolymers with different percentages of benzoxazine rings were prepared. FT-IR was adopted to characterize the molecular structure of the novolac-type phenolic resin and the benzoxazine-phenolic copolymer BP31. In order to understand the curing process of the copolymers, the curing behavior and curing kinetic characteristics were studied by differential scanning calorimetry (DSC), and the catalytical effect of phenolic hydroxyl on the curing behavior of copolymers was investigated. To investigate the thermal properties of this resin, the thermal degradation behaviors of the cured samples were studied by thermal gravimetric (TG) method, and glass-transition temperatures (T _g) of the cured copolymers were also evaluated by DSC. The dynamic Ozawa method was adopted to determine the kinetic parameters of the curing process as well. The activation energy is 78.8 kJ/mol and the reaction rate constant is in the range from 40.0 to 5.2 (K/min) ⁿ according to reaction temperatures. The Ozawa exponent decreases from 2.4 to 0.7 with the increase of reaction temperature, and curing mechanism is expounded briefly according to the results. TG result shows that the highest char yield of copolymers is 50.3%. The highest T _g of copolymers is 489 K, which is much higher than that of pure benzoxazine resin. Foundation item: Project (20050106) supported by the Key Science and Technology Item of Guangdong Province, China     

奇异值分解识别精密机械热动态特性参数的研究

在精密机械热动态过程的离散化模型基础上,提出一种识别精密机械热动态特性参数的新方法--奇异值分解算法.在分析精密机械零部件的非定常导热问题时,由有限元法获得热动态过程空间离散化模型.采用热模态分析方法实现离散化模型解耦变换,模态坐标下的特性参数为热特征值(广义时间常数的倒数).辨识热动态特性参数的方法是通过构造热脉冲响应矩阵,采用矩阵奇异值分解的方法,以最少的参数和最小的阶次来描述精密机械热动态过程,进而求得热特征值.实测数据表明,该方法能有效地识别热特征值和快速估算出热平衡时间.     

Investigation on the thermal decomposition of aged La2O3

The thermal decomposition process of air-aged La203 in argon atmosphere was studied using nonisothermal TG-DSC. X-ray diffraction and TG-DSC analysis showed that the aged powder was composed of La（OH）3 with small amounts of oxycarbonate. The decomposition process of air-aged La2O3 involves the two-step decomposition of La（OH）3 and the decomposition of oxycarbonate. The kinetic analysis of the two-step decomposition of La（OH）3 was carried out using Coats-Redfern and isoconversion （Ozawa） methods. The kinetics of the two-step decomposition can be described in terms of the nucleation and growth model A （m=1.5, m is the model parameter） and A （m=2.5）, respectively. The apparent activation energy for the first step is 136-144 （Coats-Redfern） and 137-164 kJ/mol （isoconversion）. The apparent activation energy for the second step is 191-194 （Coats-Redfern） and 186-213 kJ/mol （isoconversion）.     

二氧化锡微球的制备、表征及其性能研究

介绍了以二水氯化亚锡(SnCl2·2H2O)作为主要原料,无水乙醇和N-N二甲基甲酰胺作为复合溶剂,采用溶剂热法在140℃反应24h成功地制备了二氧化锡微球.通过X射线粉末衍射(XRD)和扫描电子显微镜(SEM)对所制备样品的物相、结构和形貌进行了表征.结果表明:所制备的SnO2具有纯的四方相结构,形状球体,直径约为3μm,且反应温度、反应时间及复合溶剂配比等对样品尺寸、形貌及微球形成过程等均有一定的影响.最后通过紫外可见分光光度计对其光学性能进行了研究.     

火电厂燃料配给模型及其分解方法

从分析火电厂燃料管理的整个过程入手,论述了火电厂燃料配给模型的建立和改进过程。建立了燃料配给模型,并根据实际情况推导出了分解方法,给出了原问题的主导问题的概念及一般形式。最后给出了一个燃料配给应用实例,验证了该模型的实效性,同时分析了该模型的应用前景。     

Ni2P微球的合成、表征及其电化学性能

通过简单溶剂热,以乙二醇(EG)和苯(Benzene)为溶剂,在不添加任何表面活性剂的条件下,成功制备出了Ni2P微球.结果表明,产物为纯的六方相Ni2P,形貌为由大量20nm的粒子组成的球形,微球直径介于1~3μm.通过考察反应温度、溶剂体积比及反应时间等对产物的影响,得到Ni2P微球的最佳制备条件为:反应温度160℃,溶剂比例V(EG)∶V(Benzene)=1∶1,反应时间12h.并以所制备Ni2P微球作为锂电池负极材料,研究了其电化学性能,结果表明样品的初始放电容量达1 915mAh/g.     

Mg/Zn/Al类水滑石的热性质和水化性能研究

采用共沉淀法制备了Mg2Al1，Zn2Al1和Mg1Zn1Al1类水滑石（LDHs），利用XRD，FT-IR和TG／DTA等表征手段，对三种LDHs的热分解性质及焙烧物在Na2CO3水溶液中水化恢复层状结构的能力进行对比研究．结果表明：在400～700℃温度范围内，Zn2Al1 LDH和Mg2Al1 LDH的焙烧物中均出现氧化物相（ZnO和MgO）和尖晶石相（ZnAl2O4和MgAl2P4相），而Mg1Zn1Al1 LDH的焙烧物中始终以ZnO相为主，仅在700℃时出现微弱的MgAl2O4相．三种LDHs的焙烧物经Na2CO3溶液处理后恢复层状结构的能力大小为：Mg1Zn1Al1 LDH〉Mg2Al1 LDH〉Zn2Al1 LDH，其与焙烧物的组成有关．原始LDHs的层间含CO3^2-和NO3^-，而恢复后的LDHs层间仅含CO3^2-．随LDHs中Mg含量增加，热失重温度向高温区移动．     

丙三醇钛直接热分解制备纳米二氧化钛

针对以易水解的一元醇钛盐为前驱物,采用溶胶-凝胶水解法制备纳米二氧化钛时浪费大量溶剂、抑制剂和造成环境污染的问题,制备出一种新型的丙三醇钛盐,并通过直接焙烧丙三醇钛的方法制备了纳米级二氧化钛粉体.运用IR、XRD、DSC、SEM和TEM等手段对制得的丙三醇钛和纳米二氧化钛粉体进行了表征.结果表明,由丙三醇钛直接热分解可制备出具有完整、呈片状结构晶形的纳米二氧化钛,该方法简单可行,污染小、成本低,制得的粉体粒径主要分布在15~50nm范围内.