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1.
相变储热系统(LTES)可用于太阳能利用、建筑物调温、余热回收及电能错峰调节。本文将正三十烷(C_(30))吸附到有纳米孔的多孔材料(可控孔径玻璃CPGs、硅胶SGs)中,制成定型纳米相变储热材料(nano-PCMs,C_(30)/CPG,C_(30)/SG)。用差示扫描量热法(DSC)测量其相变温度(储热温度)及储热密度,显示两者均与孔径成反比关系。通过调节多孔材料的孔径,C_(30)/CPG复合材料的储热温度最大可在6℃范围内调节,C_(30)/SG材料最大在近9℃范围内调节。该类材料过冷度与纯C_(30)比没有明显增加,熔化过程储热密度没有明显降低,使用过程形状固定、不会出现泄漏。实验结果,为石蜡类可调温度纳米储热材料的使用,提供理论依据。 相似文献
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正十二烷醇与环氧乙烷的加成反应动力学研究──最佳反应时间的确定张仁权,张维冰,李葵英,王万兴(齐齐哈尔轻工学院化工系,齐齐哈尔,161006)关键词正十二烷醇聚氧乙烯醚,碱催化,聚合度在工业生产中脂肪醇与环氧乙烷的加成反应多采用KOH和NaOH等强碱... 相似文献
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用精密自动绝热量热计测定了4-羟甲基吡啶在79~380 K温区的摩尔热容. 实验结果表明, 该化合物在79~301 K温区无相变和热异常现象发生, 在301~331 K, 发生固-液相变, 其熔化温度、摩尔熔化焓及摩尔熔化熵分别确定为:325.12 K, 11.78 kJ•mol-1 和36.23 J•K-1•mol-1. 根据热力学函数关系式, 从热容值计算了4-羟甲基吡啶在80~380 K温区以标准状态(298.15 K)为基准的热力学函数值. 用热重法(TG)对该化合物的热稳定性作进一步考察, 从TG曲线上观察到该化合物在490 K有最大的蒸发失重速率. 相似文献
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纳米氧化锌的低温热容和热力学性质 总被引:1,自引:0,他引:1
用扫描电子显微镜(SEM)测定了纳米氧化锌试样的粒径, SEM结果表明ZnO试样平均粒径为30 nm. 在83~350 K温区, 用精密低温绝热量热计测定了ZnO的等压摩尔热容, 拟合出其等压摩尔热容与热力学温度的函数关系式:
Cp=-3.249+0.2400T-3.413×10-4T 2+4.485×10-7T 3.
根据热容与热力学函数关系, 计算了以298.15 K为基准的纳米ZnO的热力学函数, 并与粗晶ZnO和18 nm ZnO热容文献报导值进行了比较, 从能量角度分析了不同粒径ZnO热容曲线差别产生的原因. 相似文献
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在288.15~318.15K范围内,用等压法测定了四苯硼钠在不同浓度水溶液中的平均活度系数和渗透系数,计算了不同浓度时的超额自由能、相对偏摩尔焓、偏摩尔热容。经计算机曲线拟合给出热力学性质的经验计算公式。 相似文献
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高效液相色谱法测定非洲刺李提取物中阿魏酸二十二烷酯 总被引:2,自引:0,他引:2
建立了非洲刺李提取物中阿魏酸二十二烷酯含量测定方法。采用SpherisorbC18柱,以甲醇为流动相,检测波长326nm,柱温40℃,线性范围10~100mg/L(r=0.9995)。平均回收率98.4%,RSD为1.98%。方法准确可靠,重现性好。 相似文献
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本文用精密自动绝热量热仪测定了2-甲基-2-丁醇在80~305 K温区的热容,从热容曲线(Cp-T) 发现三个固-固相变和一个固-液相变, 其相变温度分别为T = 146.355, 149.929, 214.395, 262.706 K。从实验热容数据用最小二乘法得到以下四个温区的热容拟合方程。在80~140K温区, Cp,m = 39.208 + 8.0724X - 1.9583X2 + 10.06X3 + 1.799X4 - 7.2778X5 + 1.4919X6, 折合温度X = (T –110) / 30; 在 155 ~ 210 K温区, Cp,m = 70.701 + 10.631X + 12.767X2 + 0.3583X3 - 22.272X4 - 0.417X5 + 12.055X6, X = (T –182.5) /27.5; 在220 ~ 250 K温区, Cp,m = 99.176 + 7.7199X - 26.138X2 + 28.949X3 + 0.7599X4 - 25.823X5 + 21.131X6, X = (T – 235)/15; 在 270~305 K温区, Cp,m =121.73 + 16.53 X- 1.0732X2 - 34.937X3 - 19.865X4 + 24.324X5 + 18.544X6, X = (T –287.5)/17.5。从实验热容计算出相变焓分别为0.9392, 1.541, 0.6646, 2.239 kJ×mol-1; 相变熵分别为6.417, 10.28, 3.100, 8.527 J×K-1×mol-1。根据热力学函数关系式计算出80~305 K温区每隔5 K的热力学函数值 [HT –H298.15]和 [ST –S298.15]。 相似文献
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J. Zhang Y. Y. Liu J. L. Zeng F. Xu L. X. Sun W. S. You Y. Sawada 《Journal of Thermal Analysis and Calorimetry》2008,91(3):861-866
Zinc formate dihydrate has been synthesized and characterized by powder X-ray diffraction, elemental analysis, FTIR spectra
and thermal analysis. The molar heat capacity of the coordination compound was measured by a temperature modulated differential
scanning calorimetry (TMDSC) over the temperature range from 200 to 330 K for the first time. The thermodynamic parameters
such as entropy and enthalpy vs. 298.15 K based on the above molar heat capacity were calculated. The thermal decomposition characteristics of this compound
were investigated by thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). TG curve showed that the
thermal decomposition occurred in two stages. The first step was the dehydration process of the coordination compound, and
the second step corresponded to the decomposition of the anhydrous zinc formate. The apparent activation energy of the dehydration
step of the compound was calculated by the Kissinger method using experimental data of TG analysis. There are three sharply
endothermic peaks in the temperature range from 300 to 650 K in DSC curve. 相似文献
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通过小样品精密自动绝热热量计测定了自己合成并提纯的腈菌唑 (C15H17ClN4)
在78 ~ 368K温区的低温摩尔热容。量热实验发现, 该化合物在363 ~ 372 K温区, 有一固-液熔化相变过程, 其熔化温度为 (348.800±0.06)K, 摩尔熔化焓、摩尔熔化熵及化合物的纯度分别为:(30931±11) J•mol-1、(88.47±0.02) J•mol-1•K-1和0.9941(摩尔分数)。用差示扫描量热(DSC) 技术对该物质的固-液熔化过程作了进一步研究,结果与绝热量热法一致。 相似文献
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B. Tong Z. C. Tan J. N. Zhang S. X. Wang 《Journal of Thermal Analysis and Calorimetry》2009,95(2):469-475
The low-temperature heat capacity C
p,m of erythritol (C4H10O4, CAS 149-32-6) was precisely measured in the temperature range from 80 to 410 K by means of a small sample automated adiabatic
calorimeter. A solid-liquid phase transition was found at T=390.254 K from the experimental C
p-T curve. The molar enthalpy and entropy of this transition were determined to be 37.92±0.19 kJ mol−1 and 97.17±0.49 J K−1 mol−1, respectively. The thermodynamic functions [H
T-H
298.15] and [S
T-S
298.15], were derived from the heat capacity data in the temperature range of 80 to 410 K with an interval of 5 K. The standard
molar enthalpy of combustion and the standard molar enthalpy of formation of the compound have been determined: Δc
H
m0(C4H10O4, cr)= −2102.90±1.56 kJ mol−1 and Δf
H
m0(C4H10O4, cr)= − 900.29±0.84 kJ mol−1, by means of a precision oxygen-bomb combustion calorimeter at T=298.15 K. DSC and TG measurements were performed to study the thermostability of the compound. The results were in agreement
with those obtained from heat capacity measurements. 相似文献
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Thermal analysis of the rice and by-products 总被引:2,自引:0,他引:2
J. A. Amorim S. A. Eliziário D. S. Gouveia A. S. M. Simőes J. C. O. Santos M. M. Conceiçăo A. G. Souza M. F. S. Trindade 《Journal of Thermal Analysis and Calorimetry》2004,75(2):393-399
The thermogravimetry (TG) is a technique used in the quality control of foods. In this work the moisture and ash contents
in the rice and by-products (bran and husk), the thermal stability and the gelatinization process by conventional, thermogravimetric
and calorimetric methods were studied. The moisture and ash contents obtained by TG and conventional methods did not present
significant differences. The rice presented higher starch content, while the bran presented higher protein content. The thermogravimetric
data presented the following thermal stability order: rice>bran>husk. The calorimetric curves indicated the gelatinization
of the starch. The kinetic parameters were compatible.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
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Due to their special polar structure, amphiphilic molecules are simple to process, low in cost and excellent in material properties. Thus, they can be widely applied in the preparation of functional film materials and bionics related to cell membranes. Therefore, amphiphilic organic semiconductor materials are receiving increasing attention in research and industrial fields. The structure of organic amphiphilic semiconductor molecules usually consists of three functional parts: a hydrophilic group, a hydrophobic group, and a linking group between them. The adjustment of their correlation to achieve the target performance is particularly important and needs experimental discussion regarding synthetic methodologies. In this work, we focused on the engineering of a substituent alkyl-chain, and an amphiphilic functional molecule (benzo[b]benzo[4, 5] thieno[2, 3-d]thiophene, named CnPA-BTBT, n = 3–11) was proposed and synthesized. This molecule links the hydrophobic semiconductor backbone and hydrophilic polar group through alkyl chains of different lengths. Fundamental properties were investigated by nuclear magnetic resonance (NMR) and ultraviolet-visible spectroscopy (UV-Vis) to conform the structure and the band gap properties of the designed organic semiconductor. Thermodynamic features were investigated by thermogravimetric analysis (TGA) and corresponding differential thermal gravity (DTG), which indicate that the functional molecule CnPA-BTBT (n = 3–11) has a great stability in ambient conditions. Moreover, the results show that the binding ability of the amphiphilic molecule to water molecules was regulated by the odd-even alternating effect of the alkyl chain and the intramolecular coupling with BTBT. Furthermore, differential scanning calorimetry (DSC) and polarized optical microscopy (POM) were used to study the material properties in detail. As the length of the alkyl chain increased, the functional molecule CnPA-BTBT (n = 3–11) gradually changed from "hard" species with no thermodynamic changes to a transition one with a pair of thermodynamic peaks, and eventually to a "soft" one as a typical liquid crystal with clear observation of Maltese-cross spherulites. The cooling and freezing points were further studied, and the values and trends of their enthalpy and corresponding temperature fluctuated and alternated due to the volume effect, odd-even alternating effect, flexibility, and other functions of the alkyl chain. Three molecular models were proposed according to the thermodynamic study results, namely the brick-like model, transition model, and liquid crystal model. This work presents in-depth discussion on material structure and corresponding thermodynamic properties, and it is an experimental basis for the design, synthesis, optimization, and screening of target performance materials. 相似文献
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本文报道用α-萘胺和琥珀酸酐合成1-萘基-琥珀酰亚胺(NPr),并用FT-IR、DSC、X-射线衍射和荧光等方法研究了该化合物的结构与性能.DSC和X-射线衍射结果表明,纯净NPr的熔点与John L. Hubbard报道结果(147~149℃)不同,应为(158.3±0.2℃);熔融淬火样品仍存在部分结晶,并且在一定温度下发生冷结晶;FT-IR结果表明羰基伸缩振动产生反对称振动(1705 cm-1)和对称振动(1779 cm-1)的能级分裂;荧光光谱结果则进-步表明该化合物的电子云排布结构与单体萘环相似, 其原因可归于羰基的诱导效应和共轭效应对氮原子的影响. 相似文献
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Aragão C. F. S. Filho J. M. B. Macêdo R. O. 《Journal of Thermal Analysis and Calorimetry》2001,64(1):185-191
This work proposes thermal characterization as analytical methodology for the identification and purity assay of warifteine,
an alkaloid in Cissampelos sympodialis Eichl. Thermal and kinetic parameters were determined by means of TG and DSC photovisual studies. The TG results showed that
the decomposition of warifteine in air and nitrogen atmospheres proceeds in three and four steps, respectively. The TG data
allowed calculation of the kinetic parameters of warifteine. The activation energy values obtained by different methods displayed
a good correlation. With the DSC photovisual system applied it is possible to detect the impurity level in warifteine after
its purification.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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通过小样品精密自动绝热量热计测定了合成并提纯的 4,6 二甲基 N 苯基 2 嘧啶胺 (嘧霉胺 )在 78~ 3 91K温区的摩尔热容 .量热实验发现 ,该化合物在 3 63~ 3 72K温区 ,有一固 -液熔化相变过程 ,经三次重复测量 ,得其熔化温度、摩尔熔化焓及摩尔熔化熵分别为 :( 3 70 78± 0 0 8)K ,( 2 1 2 3 3± 0 0 13 )kJ·mol-1 和 ( 5 7 2 7± 0 15 )J·mol-1 ·K-1 .通过分步熔化法得到该物质绝对纯样品的熔点为 3 71 0 3 1K .用差示扫描量热 (DSC)技术对该物质的固 -液熔化过程作了进一步研究 ,结果与绝热量热法一致 相似文献