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正热分析动力学与热动力学是用热分析和量热技术研究某些物理变化或化学反应动力学的分支学科,是目前热化学最活跃的研究领域之一。热分析动力学主要研究反应过程的活化能和机理函数,热动力学则是在量热学、化学热力学和化学动力学的基础上,通过高精度、自动化和连续式的微 相似文献
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热塑弹性体热寿命和热降解动力学 总被引:1,自引:0,他引:1
利用热重法研究了聚苯乙烯/聚二烯烃/聚苯乙烯三嵌段共聚物(SIS,SBS,SI/BS)在氮气气氛条件下以不同升温速率β时热降解动力学及其热寿命。确定了热降解温度与升温速率的关系,求得了热降解过程的表观活化能和热降解速率常数,得到了不同失重率时的热寿命方程,计算出三种化合物在不同温度下的寿命。 相似文献
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用差示扫描量热计,在不同pH值的各种缓冲溶液内、在不同浓度的两种中性盐溶液内,研究了牛红细胞超氧化物歧化酶(SOD)的热变性过程.实验表明PIPES是一个不与SOD结合的缓冲剂;阴离子的结合或多或少地影响热变性过程,且对该酶的氧化形式的影响更显著。实验发现在不同的缓冲溶液内,在高于等电点的合适的pH值处,或者在浓度较高的中性盐溶液内,SOD能形成一种热稳定性较低的新构象。它受热后不可逆地转变成常见的高热稳定性的构象。依据无盐蒸馏水中得到的热力学参数,运用Ooi模型和热力学分析揭示出高值的纯构象变性焓△H_d~c是SOD高热稳定性的热力学原因。 相似文献
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动力锂离子电池(LIB)的安全问题,尤其是热失控这一频发的安全事件严重影响乘车人员的安全以及新能源汽车的推广.本工作使用C80微量量热仪准确测量了商用锂离子电池的内在产热,通过研究分析不同质量比例的负极-电解液产热及不同质量比例的正极-负极产热,明确了LIB在热失控阶段的主要反应分为负极与电解液反应放热(130~200℃),三元镍钴锰酸锂(NCM)正极释氧与负极反应放热(200~240℃)和磷酸铁锂(LFP)正极释氧与负极反应放热(240~300℃)等.通过使用去卷积数学方法对不同质量比例的负极-电解液及不同质量比例的正极-负极产热分析研究表明,在商用锂电池注液系数条件下,电解液会优先与负极反应且被全部消耗,剩余嵌锂负极会进一步与正极反应放热,且反应热与正极材料特性密切相关.残余正极物质虽然结构坍塌仍会释氧,但由于缺少与之反应的负极或电解液,热量不会再明显增加.通过对不同荷电状态(SOC)及不同类型的锂电池主材进行产热测试,能更好地指导电极材料的改性和电池组装的开发设计,从而提高LIB整体热稳定性和安全性,最终获得整包和新能源车的安全提高. 相似文献
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本文建立了一种只需要精选一级反应热谱曲线上2个任意时刻的峰高,而不需要任何其它数据即可算得其反应速度常数的新算法.研究了三乙胺和碘乙烷在二甲亚砜中的季铵化反应,其速度常数的计算值和文献值吻合很好,证明了本法的正确性. 相似文献
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A method for the prediction of the retention time and the resolution of chromatographic peaks in different experimental conditions by starting from few experimental data measured in isothermal and isobaric analyses was published previously. In this paper, the same mathematical model was implemented for calculating the retention times and the column efficiency in programmed pressure runs. Some models originated from the Golay equation and reported in the literature are compared, and a new modified equation for the calculation of the peak width at half height is proposed. The procedure for the prediction of the retention time and the peak width at half height at programmed pressure of the carrier gas and different column temperature and linear gradient by using retention data of different compounds obtained in few isobaric runs is described. The prediction of the retention time and the separation efficiency of compounds with different polarity gave good results for the programmed pressure runs with linear gradient. The effect of the variation of the initial parameters of the experimental analyses and of the mathematical model on the accuracy of the prediction has been evaluated. 相似文献
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Hiroshi Tanaka Nobuyuki Takagi Saburo Okajima 《Journal of polymer science. Part A, Polymer chemistry》1974,12(12):2721-2728
Isotactic polypropylene film was stretched in poly(ethylene glycol) at 140°C and its melting behavior was investigated by using a differential scanning calorimeter (DSC-1B). The shape of the melting curve depends largely on the stretching ratio, v. A sample stretched to moderate extension (1 < v < 3.5–4) has only a single melting peak (163°C) in the thermogram. When the sample is stretched beyond v = 3.5–4, the thermogram becomes more and more complex with increase of v, and some peaks appear when stretched to 10 < v < 13. The lowest peak which is considered to be the melting peak of the intermolecular crystals produced by the unfolding of chain molecules in the lamellae develops gradually with increase of v. In the thermogram for v = 18 the lowest temperature peak is most pronounced, in contrast to the highest temperature peak which decreases markedly in intensity. The phenomenon shows that large amounts of lamellar crystals are converted to intermolecular crystals in this region. On further stretching (v > 20) a very sharp high temperature peak appears, whose half-width is about 1°C. Qualitatively similar results were obtained for the samples stretched in poly(ethylene glycol) at 150°C and in air at 140 and 150°C. 相似文献
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Chi-lai Chen De-yi Kong Xiao-hua Wang Huan-qin Wang Feng Shuang Tao Mei 《化学物理学报(中文版)》2011,24(3):325-329
High field asymmetric wave ion mobility spectrometry (FAIMS) is a powerful tool to detect and characterize gas-phase ions, while the unsolvable partial differential equation of ions moving in ion drift tube poses a big challenge to FAIMS spectral peak analysis. In this work, a universal and effective model of FAIMS spectral peak profile has been proposed by introducing ion trajectory and loss height. With this model, the influence of the structure of ion drift tube, dispersion voltages, compensation voltages, and carrier gas flow rate on the FAIMS spectral peak characteristics like peak shape, full width at half maximum and peak height is analyzed and discussed. The results show that the influence of different factors on the FAIMS spectral peak profile can be qualitatively described by the model which agrees with the experimental data. 相似文献
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Cheng S.-Q. Huang Z. Meng X.-G. Zeng X.-C. 《Journal of Thermal Analysis and Calorimetry》2000,63(2):415-421
This paper presents a novel data processing method for thermokinetics of faster first-order reaction on the basis of the double-parameter
theoretical model of a conduction calorimeter, in which the rate constant of a first-order reaction can be calculated from
only four peak height data from the same thermoanalytical curve without using any peak-area. The saponifications of ethyl
acetate and methyl acetate in aqueous solution and ethyl benzoate in aqueous alcohol have been studied to test the validity
of this method. The rate constants calculated with this method are in fair agreement with those in literature; hence the validity
of this method is demonstrated.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Some problems of quantitative differential thermal analysis have been studied by means of a Du Pont 900 DTA instrument. Applying the equation of heat transfer the features of a thermogram (base line and peak surface) may be interpreted in terms of heat of transition, specific heat and thermal conductivity. Satisfactory results are obtained for substances with thermal conductivities lower than 10-3 cal/sec deg. 相似文献
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Akiyoshi Kawaguchi Shozo Murakami Kanji Kajiwara Ken-ichi Katayama Dittmar Nerger 《Journal of Polymer Science.Polymer Physics》1989,27(7):1463-1476
Wide-angle and small-angle X-ray diffraction patterns of polypivalolactone single crystals were recorded as a function of temperature while heating at a constant rate. Long periods were found to increase abruptly at a certain temperature, while the degree of crystallinity decreased up to that temperature and then recovered on further heating, to an extent depending on the rate of heating. Multiple endotherms were observed in DSC measurements. The temperature at which the first endotherm peak was observed corresponded exactly to the temperature of the long period jump mentioned above. From these data, it is concluded that the original lamellar crystals melt at each peak temperature in the DSC thermogram and new lamellae are produced by subsequent crystallization. Multiple endotherms in the DSC thermogram are thus considered to represent repeated melt-recrystallization processes. 相似文献
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Differential scanning calorimetry (DSC) is used to investigate the thermal phase transitions of a range of N-isopropylacrylamide (NIPAM)-based, carboxylic acid-functionalized microgels with well-defined radial and chain functional group distributions. The transition enthalpies of protonated microgels can be correlated with the hydrophobicity of the functional comonomer, while the transition enthalpies for ionized microgels can be correlated with the degree of microgel deswelling achieved across the thermal phase transition. The peak widths at half-height vary inversely with the average length of NIPAM blocks in each of the microgels, as calculated using a kinetic copolymerization model. Deconvolution of the asymmetric DSC thermograms is accomplished using a two-transition model, thought to relate to core-shell-type transitions induced by the significant local heterogeneities within the functionalized microgels. The ratio between the two transition temperatures of these deconvoluted peaks is a useful quantitative probe of the radial functional group distribution. An additional, low-temperature transition is also observed in the thermogram of the vinylacetic acid-functionalized microgel, indicative of the occurrence of local chain rearrangements prior to the macroscopic phase transition in this microgel. Complementary light scattering analysis suggests that microphase separation may account for this additional transition peak. 相似文献