应用热分析技术研究菱镁石矿轻烧过程动力学

以辽宁大石桥晶质菱镁石矿为原料,采用TG、DSC热分析技术研究菱镁石粉末分解动力学.实验研究表明,菱镁石在500～700℃发生分解,失重率为43.13%.由TG曲线得出菱镁石分解反应表现活化能E=172.32kJ/mol,反应级数n=0.78;DSC曲线表明反应活化能E=199.44kJ/mol,反应级数n=0.87.TG、DSC曲线研究结果有较好的一致性,表明热分析技术在菱镁石分解动力学中可以得到良好的应用.     

一种含硫聚合物电解质的合成及性能

针对聚氧化乙烯基固态聚合物电解质存在的问题,分别以PEG400、PEG600合成了相应的1,3-二氯-2-丙醇聚乙二醇醚,并通过在Na2S2溶液中聚合,制备了1,3-二氯-2-丙醇聚乙二醇醚基聚硫化合物{PS(DCP-PEG)}。通过红外光谱(IR)、元素分析、交流阻抗、差示扫描量热(DSC)、热重分析(TG)等测试对该聚合物的结构、热力学以及导电性能进行表征。结果表明,合成的产物结构与设计的结果一致.该含硫聚合物电解质力学性能优良,电极接触好,热分解温度在220℃以上,室温电导率可达10-5S/cm,在锂硫聚合物电池中具有实际应用价值。     

Thermal and optical properties of benzofuran-2-yl 3-phenyl-3-methylcyclobutyl thiosemicarbazone

The thermal degradation of the benzofuran-2-yl 3-phenyl-3-methylcyclobutyl thiosemicarbazone (CBSC) was studied under air atmosphere using DSC and simultaneous TG/DTA at the temperature range 20–500 °C. Thermal melting activation energy which are 308.6 and 307.9 kJ/mol were evaluated using Kissinger method from DSC and DTA curves, respectively. The activation energy of thermal decomposition was calculated using the Ozawa method for two decomposition stages. The experimental results showed that the activation energy of decomposition for non-isothermal behavior are 123.8 and 135.2 kJ/mol for the first (at 5% weight loss) and second (at 20% weight loss) decomposition stages, respectively. By using hot probe method, electrical conduction mechanism of CBSC was found as p-type. The values of thermal activation energy of electrical conduction, E₁ and E₂, as calculated from lnσ=f(1000/T) curves, were found to be 3.90 and 0.36 eV, respectively. Optical absorption studies in the wavelength range 190–900 nm showed that direct optical band gap of the benzofuran-2-yl 3-phenyl-3-methylcyclobutyl thiosemicarbazone is 2.80 eV.     

Synthesis, characterization, high temperature phase transition and electrical properties of solid solution AgScMo2O8

AgScMo₂O₈ was synthesized by wet-chemistry method. The samples were characterized by differential thermal analysis/thermogravimetry, differential scanning calorimetry (DTA/TG, DSC), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The novel structure of the sample is different to the other oxide AgLnMo₂O₈ (Ln = lanthanide). The XRD and DTA/TG, DSC results showed that the formation temperature of AgScMo₂O₈ was found to be as low as 450°C, and AgScMo₂O₈ crystallized in a monoclinic-type structure at room temperature. With increasing of the temperature two phase transition processes (monoclinic to hextetrahedral and tetragonal) appeared. The electrical property of the samples was also investigated by using A.C impedance spectroscopy. It showed that an abrupt increase of electrical conductivity was found around 500°C, which attributes to phase transition. The facts indicted that this kind of material shows a potential application in intermediate-temperature solid oxide fuel cells (SOFCs).     

Synthesis and characterization of nanocrystalline Mg2CoH5 obtained by mechanical alloying

The stoichiometric mixture of 2MgH₂ + Co was ball milled under a hydrogen atmosphere to synthesize nanocrystalline metal hydride Mg₂CoH₅. Upon milling, the mixture was analyzed by X-ray powder diffraction (XRD) and thermal methods employing the techniques of differential scanning calorimetry (DSC), thermogravimetry (TG) and differential thermal analysis (DTA). Hydrogen absorption and desorption measured by pressure-composition-temperature (P-C-T) curves indicated that the capacity loss was small after 20 consecutive cycling tests. The enthalpies associated with hydride formation and decomposition were measured to be –69.5 and –83.2 kJ mol^–1 H₂, respectively. At the temperatures of this study (553 to 653 K), hysteresis decreases with increasing temperature.     

氧化锑/高岭土复合阻燃微粉的湿化学法制备及特性

采用湿化学法制备了氧化锑 /高岭土复合阻燃微粉 ,用热重 (TG)、差示扫描量热法 (DSC)对其阻燃特性进行了分析 ,用SEM分析了粒子形貌 ,激光光散射粒度分布仪分析了粒子的分布情况。热分析结果表明 ,与球磨法相比 ,湿化学法制备的样品的失重量大、失重温度范围广、放热峰范围广 ;化学法制备复合微粉的反应活化能与球磨法相差不大。SEM分析及粒度分析表明 :复合微粉大多处于 0 .2 0 μm以下 ,化学法制备的样品中以锑白粉为主 ,高岭土附在锑白粉表面 ,充分与锑白粉发生物理、化学作用。同时发现 ,样品6 0 0℃热处理 2h后 ,粒子结合更加紧密     

Electrical conductivity of solid di(3,5-lutidinium)tetrachloro-manganate(II)

The electrical and thermic properties of solid di(3,5-lutidinium) tetrachloromanganate (II) have been investigated in the temperature range from room temperature to the decomposition point (145°C). It was found that the relatively good electrical conductivity of the sample at room temperature (˜10⁻² S/m) with the activation energy of 13.4 kJ/mol, increases abruptly at 65°C, indicating its nearly superconducting properties. The temperature dependance of electrical conductivity was correlated with the nature of structural transformations, occurring upon the exposure of the sample to the temperature rise. It was suggested, by comparison of the results obtained by IR spectroscopy with those of the thermal analysis (DSC, TG), that the better electrical conductivity at higher temperatures is the result of the loosening and the partial cleavage of the hydrogen bonds, causing an activation of a larger number of the charge carriers.     

自由基引发活性聚碳硅烷交联及其在制备SiC纤维中的应用

在基于先驱体聚碳硅烷转化制备SiC陶瓷纤维过程中, 交联过程是保持纤维形貌和提高陶瓷产率的必要条件。本研究以含丙烯酸酯基的聚碳硅烷(A-PCS)为原料, 通过引入自由基热引发剂在热解升温过程中实现原料的交联成型。采用红外光谱仪(FT-IR)和差示扫描量热仪(DSC)研究了引发剂含量对A-PCS交联程度、交联速率以及热降解速率的影响规律; 采用热失重(TG)、元素分析仪和X射线衍射仪(XRD)分析了陶瓷产率、陶瓷产物组成以及无定形态随温度的变化。研究结果表明: 加入自由基热引发剂可提高A-PCS中的丙烯酸酯基的交联速率, 减少交联阶段的热失重; 将质量百分比为1%自由基热引发剂的A-PCS以5 ℃/min升至250 ℃时, 丙烯酸酯基反应完全, 1500 ℃的陶瓷产率为69.5%; 通过静电纺丝加工工艺可获得直径介于2~5 μm的A-PCS原丝, 并通过后续升温热解转化为SiC纤维; 所得SiC纤维形貌规整、无熔并现象, 且随着热解温度的升高从无定形态向结晶形态转变。     

Thermal Decomposition Study on CuInSe$$_{}$$ Single Crystals

The thermal analysis of the chemical vapor transport (CVT)-grown \(\hbox {CuInSe}_{2}\) single crystals was carried out by recording the thermogravimetric, differential thermogravimetric and differential thermal analysis curves. All the three thermo-curves were recorded simultaneously by thermal analyzer in the temperature range of ambient to 1080 K in inert nitrogen atmosphere. The thermo-curves were recorded for four heating rates of 5 K \(\cdot \,\hbox {min}^{-1}\), 10 K \(\cdot \,\hbox {min}^{-1}\), 15 K \(\cdot \,\hbox {min}^{-1}\) and 20 K \(\cdot \,\hbox {min}^{-1}\). The TG curve analysis showed negligible mass loss in the temperature range of ambient to 600 K, stating the sample material to be thermally stable in this temperature range. Above 601 K to the temperature of 1080 K, the sample showed continuous mass loss. The DTG curves showed two peaks in the temperature range of 601 K to 1080 K. The corresponding DTA showed initial minor exothermic nature followed by endothermic nature up to nearly 750 K and above it showed exothermic nature. The initial exothermic nature is due to absorbed water converting to water vapor, whereas the endothermic nature states the absorption of heat by the sample up to nearly 950 K. Above nearly 950 K the exothermic nature is due to the decomposition of sample material. The absorption of heat in the endothermic region is substantiated by corresponding weight loss in TG. The thermal kinetic parameters of the CVT-grown \(\hbox {CuInSe}_{2}\) single crystals were determined employing the non-mechanistic Kissinger relation. The determined kinetic parameters support the observations of the thermo-curves.     

ZrO_2－SiO_2复合粉体的制备和表征

本文采用气凝氧化硅和氯氧化钻为原料，以共沉淀法制备了ｘＺｒＯ２（１－ｘ）ＳｉＯ２（ｘ＝１０～４０ｖｏｌ％）系列粉料。ＤＴＡ－ＴＧ结果表明，吸附水的释放和Ｚｒ（ＯＨ）４。凝胶的热分解分别引起失重；在差热曲线上９００℃处的放热峰表明四方氧化锆开始析出，并得到Ｘ射线粉末衍射试验的证实，ＸＲＤ还揭示二氧化硅具有稳定ｔ－ＺｒＯ２的作用．透射电镜（ＴＥＭ）观察发现在受热过程中，氧化锆经历了疏松海绵体→密实海绵体→球形颗粒匀颗粒成长的衍变过程。     

Synthesis and physicochemical properties of cobalt aluminium hydrotalcites

Cobalt aluminium hydrotalcites with different compositions were prepared by a coprecipitation method under low supersaturation conditions. The compounds were characterized by X-ray diffraction (XRD), infrared absorption (IR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and BET surface area measurements. XRD and IR studies revealed that all the compounds are single-phase crystallized under a hydrotalcite-like network. Hydrothermal treatments given to the aged sample increased the crystallinity of the samples. TG studies showed two stages of weight loss, the first due to the removal of interlayer water and the second ascribed to the removal of water molecules from the brucite sheet and CO₂ from the interlayer carbonate anion, whose transition temperature depends on the Co/Al atomic ratio. Thermal calcination of these materials results in the formation of high surface area non-stoichiometric spinel phase whose crystallinity increases with increase in the calcination temperature attributed to the sintering of the particles.     

Spectro-thermal decomposition study of 1,4-dinitroglycoluril (DINGU)

Simultaneous thermal analysis and high temperature FTIR study of 1,4-dinitroglycoluril (DINGU) is reported. TG showed 90% weight loss in the temperature range 225-250 degrees C. Isothermal TG of DINGU showed about 70% weight loss in the temperature range 210-230 degrees C. Kinetic parameters evaluated using a computer program showed that alpha-t data are best described by the Avrami-Erofeev's equation for n=2 with an activation energy of 165 kJ/mol. The kinetics of decomposition of DINGU was followed by studying NH (3388 cm(-1)), CO (1770-1810 cm(-1)) and NO2 symmetric stretching (1565-1570 cm(-1)) IR bands. All three bands showed loss of intensity with temperature and time. alpha-t data of decomposition with respect to NO2 stretching was again best described by the Avrami-Erofeev's equation for n=2. Gaseous decomposition products observed in the IR were N2O, NO2, CO2, HCN and NO. PM3 and Hartree-Fock level calculations on various bond lengths, bond angles and dihedral angles were computed to support the analysis of decomposition study using TG and IR. The data showed that CN and NH bonds are much shorter than the NN bonds, indicative of the weaker NN bond and hence, the possibilities of rupture of the same bond preferentially. This paper also discusses the sensitivity and performance properties of DINGU.     

聚乙二醇改性相变微胶囊-木粉/高密度聚乙烯复合材料的制备与热性能

通过原位聚合法制备了以正十二烷醇(DA)为芯材,密胺树脂(MF)或聚乙二醇改性密胺树脂(PMF)为壁材的相变微胶囊DA@MF和DA@PMF,并将相变微胶囊添加到木粉/高密度聚乙烯复合材料(WF/HDPE)中,制备了具有相变蓄热能力的DA@MF-WF/HDPE和DA@PMF-WF/HDPE复合材料。采用DSC、TG和红外热成像等方法对DA@MF、DA@PMF和相变微胶囊-WF/HDPE的热性能进行了分析与表征。测试结果表明,DA@PMF的结晶和熔融热焓值分别提高了35.0J/g和21.5J/g,快速失重温度提高了19.9℃;蓄热能力测试表明,DA@PMF成功添加至WF/HDPE中,且在制备过程中损失较小;DA@PMF-WF/HDPE的相变温度(27.2、11.3℃)、相变潜热(31.6、20.3J/g)和热稳定性(256.9℃,DA开始失重)等性能表明其具备成为相变蓄热材料的潜力。     

无机盐/陶瓷基复合蓄热材料高温稳定性的研究

通过理论分析和XRD、DSC及传统热分析等实验手段研究了新型无机盐/陶瓷基复合蓄热材料的高温稳定性。结果表明,相变材料Na2SO4在1000℃高温下具有热力学稳定性,适合作为复合材料的相变介质;Na2SO4/SiO2复合蓄热材料具有良好的高温热稳定性,经100次热循环后,其热失重率低于1.26%、潜热值降低约6.19%、相变温度基本保持恒定,且熔化-凝固特性和热震稳定性良好。Na2SO4/SiO2复合材料适合作为工业炉高温蓄热器储能用蓄热材料。     

新型邻苯二甲腈基醚化新酚树脂的制备与性能

以碱为催化剂,通过新酚树脂与4-硝基邻苯二甲腈之间的亲核取代反应,制备了邻苯二甲腈醚化新酚树脂(BPX)。流变性能测试结果表明,BPX树脂在165~285℃间黏度值小于400mPa.s,表明该树脂具有优良的加工性能。DSC测试结果表明,BPX树脂的固化温度范围为320~420℃,固化反应峰值温度为386.24℃,固化放热约为182.26 J/g。该树脂的固化物表现出优良的耐热性,其储能模量起始下降温度高于450℃,5%失重温度(T5d)约为519℃,氮气氛围900℃残碳率约为75%。     

Effect of nitrate content on thermal decomposition of nitrocellulose

Data on the thermal stability of energetic materials such as nitrocellulose was required in order to obtain safety information for handling, storage and use. In the present study, the thermal stability of four nitrocellulose samples containing various amount of nitrate groups was determined by differential scanning calorimetery (DSC) and simultaneous thermogravimetery-differential thermal analysis (TG-DTA) techniques. The results of TG analysis revealed that the main thermal degradation for the nitrocellulose occurs in the temperature ranges of 192-209 degrees C. On the other hand, the TG-DTA analysis of compounds indicates that nitrate content of nitrocellulose could has affect on its thermal stability and its decomposition temperature decrease by increasing its nitrogen percent. The influence of the heating rate (5, 10, 15 and 20 degrees C/min) on the DSC behaviour of the nitrocellulose was verified. The results showed that, as the heating rate was increased, decomposition temperature of the compound was increased. Also, the kinetic parameters such as activation energy and frequency factor for the compound was obtained from the DSC data by non-isothermal methods proposed by ASTM E696 and Ozawa.     

Decomposition analysis of binary polyfunctional urethane monomer mixtures

Thermal decomposition in three binary monomer mixture systems containing an experimentally synthesized monomer (EXP3) and a commercial polyfunctional urethane monomer (U–4TXA) was examined in terms of differential thermal analysis (DTA) and simultaneous thermogravimetry (TG) analysis when a sample was heated to 800°C. The binary EXP3/U–4TXA monomer mixtures were visible light-cured (VLC) resins which included CQ (camphorquinone=0.5 wt%) and DMAEMA (dimethylaminoethyl methacrylate=0.5 wt%) as the photoinitiator. Their DTA curves showed that thermal decomposition initiated at around 300°C and finished at around 500°C. TG curves showed complete weight loss at 800°C during thermally induced decomposition: the decomposition reaction at weight losses of 5 to 50% was calculated from the slope of the (1/T) versus log10(Hr) diagram, because the exothermic decomposition temperature shown on DTA curves increased with increasing heating rate from 2 to 20°C/min. Thermal decomposition analysis showed that a decomposition with weight change had exothermic heats ranging from 0.38 to 1.07 kJ/g for the EXP U1 mixture, 1.06 to 1.76 kJ/g for EXP U2 and 1.74 to 2.02 kJ/g for EXP U3. Activation energy ranged from 1.42 to 1.89 kJ/mol at weight losses of 5 to 50% in the three binary EXP3/U–4TXA monomer mixture systems.     

Thermal analysis studies of poly(etheretherketone)/hydroxyapatite biocomposite mixtures

Biocomposite formulations which have the potential to combine the proven mechanical performance of poly(etheretherketone) (PEEK) with the inherent bioactivity of hydroxyapatite (HA), may have a utility as load-bearing materials in a medical implant context. The effect of thermal processing on the relevant properties of the PEEK and/or HA components in any fabricated composite structure is, however, an important consideration for their effective exploitation. This paper reports the results of a detailed thermal characterization study of a series of PEEK/HA mixtures using thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and modulated differential scanning calorimetry (MDSC). The TGA analyses show minimal weight loss for all of the mixtures and for a pure PEEK sample up to 530 °C. Above this point there is a sharp on-set of decomposition for the PEEK component in each case. The temperature at which this feature occurs varies for each mixture in the approximate range 539–556 °C. This observation is supported by the presence of exotherms in the corresponding DSC scans, in the same temperature region, which are also assigned to PEEK decomposition. The temperature at which the degradation on-set occurs is found to decrease with increasing HA contribution. The use of the modulated DSC technique allows a number of important thermal events, not easily identifiable from the data obtained by the conventional method, to be clearly observed. In particular, the glass transition temperature T_g of the polymer can now be accurately determined. Using these thermal analysis data, calculations of the % crystallinity of PEEK in the mixtures have been made and compared with that of a 100% polymer sample. From these studies it is evident that the presence of HA does not adversely affect the degree of crystallinity of the PEEK component in the mixtures of interest over the thermal range studied.     

层状SiO_2材料对PP性能的影响

采用硬脂酸与正硅酸乙酯制备了新型的层状材料SiY1、SiY2,并用X射线衍射(XRD)、差示扫描量热(DSC)表征了其结构,利用热重分析(TG)考察了其热稳定性。并采用DSC、XRD等测试手段考察了PP/SiY1和PP/SiY2的结晶形态和结晶行为,测定了维卡温度和力学性能。结果表明,SiY1和SiY2两种层状材料均能诱导PP晶型由α晶型向β晶型转变;PP/SiY1、PP/SiY2的冲击强度由纯PP的11.28kJ/m2分别提高到38.33kJ/m2和44.5kJ/m2;而弯曲强度和拉伸强度也没有明显下降;SiY2可使聚丙烯(PP)的结晶度明显提高。     

X-ray and thermochemical studies of phase transitions in crystalline host–guest compounds of 1,1′–binaphthyl–2,2′–dicarboxylic acid with ethanol and acetone

The crystal structures of two 1:2 and 1:1 host–guest compounds between BNDA and acetone have been determined by single crystal X-ray diffraction and are comparatively discussed with reference to recently reported BNDA/ethanol clathrates of different composition. Simultaneous thermogravimetry and differential scanning calorimetry (TG–DSC) in combination with the X-ray powder diffraction (XRD) method reveal that the thermal degradation of the BNDA/ethanol 1:2 α–form clathrate takes place in two steps with the intermediate formation of the 2:1 β–form clathrate. On the other hand, desolvation of the BNDA/acetone 1:2 α–form clathrate gives no indication for the formation of any intermediate phase in the TG–DSC traces unlike the XRD studies showing the existence of the β–form during desolvation. A possible explanation of this latter property is the very similar thermal decomposition temperature of both phases. The TG–DSC results for the isothermal inclusion of vaporous ethanol and acetone indicate that this process takes place in a single step with the formation of the 1:2 BNDA/ethanol and 1:1 BNDA/acetone clathrates, respectively.