共查询到19条相似文献,搜索用时 171 毫秒
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调制式差示扫描量热法在高分子研究中的应用 总被引:3,自引:0,他引:3
介绍了调制式差示扫描量热法(MDSC)的工作原理及其作为一种新的热分析手段的优点。并通过一些实例介绍了MDSC法在高分子研究中的应用。 相似文献
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采用调制差示扫描量热法(MDSC)研究了聚乳酸(PLA)与聚乙二醇单甲醚(MPEG)共混体系的热性能。研究结果表明,MDSC可有效分辨PLA重结晶和熔融的重叠效应,在测试条件下,PLA的α’-α晶型转变与α晶体的熔融几乎同时进行。随着升温速率的加快和调制周期的延长,当增塑剂的质量分数为15%时,PLA-MPEG共混物分割在不可逆曲线的重结晶焓逐渐升高(最高约28J/g),熔融焓逐渐降低(最低约为3.3J/g);分割在可逆曲线的熔融峰逐渐由多重峰变为单峰,且焓变值逐渐升高(最高约66.1J/g),相应的可逆曲线熔融分割比例达到了95.2%。通过提高升温速率和延长调制周期,可使大部分熔融分割在可逆曲线上,但过快的升温速率和过长的调制周期会导致PLA相转变时的周期数过少,DSC调制功能的分辨率下降,设置测试条件时需综合考虑。 相似文献
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用红外光谱、核磁共振和示差扫描量热分析等手段对聚酰胺-46进行了基本表征,并用广角X射线衍射和扫描隧道电子显微镜技术对其聚集态结构进行了分析. 相似文献
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鲱精DNA纤维的差示扫描量热(DSC)谱中,除存在一个高温区的变性峰以外,还有3个低温区的吸热峰,类似于蛋白质DSC分析中出现的“变性前峰”。经过25315K(-20℃)冻结处理的DNA纤维,空间结构稳定性提高,变性前峰峰温增加4~8K。冻结与非冻结两类样品中,变性前峰的焓值分别为-10253和-7765kJ·mol-1。作者探讨了DNA变性前峰的成因,并认为DNA变性过程中的多元性可能与碱基序列特异性有关。 相似文献
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差示扫描量热法(DSC)结果表明,烷基胺氢卤酸盐化合物的相变温度与化合物烷基链链长之间存在明显的规律性,固-固结构相变的主相变峰温随烷基链链长的递增而升高,其逆相变过程表现出明显的热滞后现象;而熔融相变温度则随烷基链链长的递增而降低;实验结果还表明,试样的陈化放置过程以及结晶过程中所用的溶剂对化合物的热致相变历程都有明显的影响。 相似文献
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模拟热谱曲线法(Ⅲ)——可逆反应 总被引:2,自引:2,他引:2
可逆反应是一类重要的复合反应,建立其相应的热动力学研究法有重要意义.刘劲松等[1]建立了可逆反应热动力学的对比进度研究法,曾宪诚等[2]建立了二种可逆反应热动力学无量纲参数研究法.本文根据热动力学理论和文献[3]的基本原理,建立了热导式量热体系的几类(2-2型、2-1型、1-2型)可逆反应通用的模拟热谱曲线研究法.该法无需标定热动力学体系的冷却常数,直接从一张热谱图上同时解析出可逆反应的kf、kb、K,方法更为简便,实用性强,在化学、生化反应的热动力学研究中具有广泛的应用前景.应用该法在15℃、25℃下研究了硝基乙烷… 相似文献
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Temperature Modulated DSC for the Investigation of Polymer Materials: A brief account of recent studies 总被引:1,自引:0,他引:1
Temperature modulated differential scanning calorimetry (TMDSC), the most recent development that adds periodic modulation to the conventional DSC, has recently seen a fast growth due to availability of commercial instrumentation. The use of the technique necessitates a total control of all of the experimental parameters. The paper focuses on recent applications to investigate polymers [1].This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
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The majority of previous studies of the hydration of cements using heat flow calorimetry have been carried out isothermally. However, with oilwell cements the slurry is mixed on the surface at ambient temperature and then gradually increases in temperature as it is pumped down the well. A Setaram C-80 calorimeter has been used to simulate the temperature ramp in API oilwell cement test schedules. This approach has enabled cementing reactions to be studied for the first time under conditions approaching those encountered in the field, and has shown that the results obtained from isothermal experiments may be misleading.The permission of the British Petroleum Company PLC to publish this paper is gratefully acknowledged. 相似文献
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Thermal phenomena at the hydration of calcium sulphate hemihydrate (CaSO4·0.5H2O) are investigated in the paper. Time development of hydration heat of β-calcium sulphate hemihydrate prepared from flue
gas desulphurization (FGD) gypsum is determined using two different types of calorimeter, namely the differential calorimeter
DIK 04 and the isothermal heat flow calorimeter KC 01, and the differences in measured data analyzed. Then, the effects of
plasticizers and hydrophobizers on the hydration process of analyzed gypsum mixtures are studied. 相似文献
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Thermoanalytical instruments are extensively used in R&D as well as in industrial quality control. A quantitative analysis
of the data of a thermoanalytical measurement requires a careful calibration of the instrument. In differential scanning calorimetry
(DSC) the quantities that have to be calibrated are the temperature and the heat flow. These two quantities are usually calibrated
by evaluating melting or solid-solid transitions of some reference materials with well known transition enthalpies and temperatures.
In this contribution we investigate temperature and heat flow calibration in the temperature range between −100 and 160°C.
We included 9 different samples for the analysis and established some general rules for the calibration process. As a result
we found that with a well calibrated instrument the heat flow can be measured with 90% confidence to about ± 3% accuracy in
this temperature range. With respect to temperature calibration we find that accuracies of ±0.8°C (90% confidence) may be
expected. These values represent general accuracy limitations of DSC’s due to varying heat transfer conditions within the
samples.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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M. J. Izard S. Ablett P. J. Lillford V. L. Hill I. E. Groves 《Journal of Thermal Analysis and Calorimetry》1996,47(5):1407-1418
Modulated Differential Scanning Calorimetry? has been applied to frozen sucrose solutions in the concentration range 10–80% w/w. The results from this study present, for the first time, information on the reversing and non-reversing nature of events that occur in these solutions. The study demonstrates the potential benefits of this new technique to help separate complex transitions that can occur in the total heat-flow curves obtained using traditional differential scanning calorimetry. The results illustrate how this new technique can separate the different enthalpic events, which relate to the glass transition and the onset of ice dissolution that occurs during the heating of these frozen systems, by nature of their “reversing” and “non-reversing” contributions to the total heat flow. 相似文献
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This study is to investigate the magnetohydrodynamic (MHD) stagnation point flow and heat transfer characteristic nanofluid of carbon nanotube (CNTs) over the shrinking surface with heat sink effects. Similarity equations deduced from momentum and energy equation of partial differential equations are solved numerically. This study looks at the different parameters of the flow and heat transfer using first phase model which is Tiwari-Das. The parameter discussed were volume fraction nanoparticle, magnetic parameter, heat sink/source parameters, and a different type of nanofluid and based fluids. Present results revealed that the rate of nanofluid (SWCNT/kerosene) in terms of flow and heat transfer is better than (MWCNT/kerosene) and (CNT/water) and regular fluid (water). Graphically, the variation results of dual solution exist for shrinking parameter in range for different values of volume fraction nanoparticle, magnetic, heat sink parameters, and a different type of nanofluid. However, a unique solution exists at , and no solutions exist at which is a critical value. In addition, the local Nusselt number decreases with increasing volume fraction nanoparticle when there exists a heat sink effect. The values of the skin friction coefficient and local Nusselt number increase for both solutions with the increase in magnetic parameter. In this study, the investigation on the flow and heat transfer of MHD stagnation point nanofluid through a shrinking surface with heat sink effect shows how important the application to industrial applications. 相似文献
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In order to measure heats of mixing or heats of dilution for many solutions by a continuous process accurately, a twin conduction type flow microcalorimeter has been constructed, improving the design of the same type of calorimeter reported previously. The thermal stability of the heat sink was enhanced by enlarged contact area of the main heat sink block with a thermostated water bath. Mixing efficiency of the mixing cell and the stability of the base line were improved by the use of a new mixing cell having a long mixing zone and symmetrically arranged sample and reference cells. Waiting time for establishment of thermal steady state was also reduced by sandwiching each of the cell by a pair of wide thermopiles plates and a pair of sub-blocks. Heats of dilution of aqueous urea solutions were measured by a continuous process, and results obtained well agreed with accepted values by Guckeret al. The accuracy and thermal resolution in this calorimeter were estimated to be less than 0.05% and 3 J·s–1.The authors are grateful to Professor S. Murakami of Osaka City University for helpful discussion. 相似文献
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Thirteen observed heat flow values in combination with relevant geological and geophysical information are employed in the current paper to conduct a model study by means of direct inversion. The modeling demonstrates the tectono-thermal evolution of the Tibetan Plateau during the last 40 Ma since the continent-continent collision. The authors stress the fact that the tectonic deformations of terranes are usually the inducing factors for the deep-seated thermal activities in the crust and upper mantle. On this basis a series of kinematic equations of 3-D deformations of terranes in forms of shortening-thickening-uplifting-erosion-mass sliding were deduced using the principle of plate kinematics. These equations are further used as systematically defined initial and boundary conditions for simulating the integrated processes of tectono-thermal evolution, The results of the model study suggest that there exist sharp differences in the tectono-thermal evolution between the old northern terranes and the new 相似文献
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Xiao Lei ZHOU Yong YANG Bao Huai WANG Zhi Fen LI Ai Xiao LIU Lung Fei YEN 《中国化学快报》2000,11(3):243-246
Microtubules, a class of cytoskeletal elements, appear to be present in all eukaryoticcells. The temporal and spatial control of assembly and disassembly of microtubulesis believed to be a key factor in cellular function. Microtubules and their subunits(Q-0 tubulin heterodimers, MW 1 10,000) maintain a dynamic equilibrium in the cellcytoplasm. In addition, it is postulated that the lability of cytoplasmic microtubulescaused by drug is related to their equilibrium. Calorimetry method has been… 相似文献