尿嘧啶和5-溴尿嘧啶的低温热容

采用综合物性测量系统(PPMS)的热容测量模块在1.9-300 K温度区间内对两种药物中间体(尿嘧啶和5-溴尿嘧啶)的低温热容进行了测量与研究. 结果表明, 在测量温区内两种化合物的低温热容随温度的上升而逐步增加, 无任何热异常现象产生; 在相同温度下, 5-溴尿嘧啶的热容数值始终高于尿嘧啶. 利用低温热容理论模型对热容数据进行了拟合, 并计算得到了0-300 K温区的摩尔熵变、焓变等热力学函数. 此外, 通过热容拟合数据计算得到的尿嘧啶和5-溴尿嘧啶在298.15 K的标准摩尔规定熵分别为(132.48±1.32)和(165.39±1.65) J·K^-1·mol^-1.     

Sm（Val）C13·6H20低温热容及热化学性质

采用精密绝热量热计测定了稀土氨基酸配合物[Sm（Val）C13·6H2O]在80-376K温区的热容,从实验热容值计算出了热力学函数（HT-H298.15和ST-S298.15）。在308K附近,配合物的热容出现一个大的跳跃,可能是其玻璃化转变所致。对该配合物进行热重测试,得到了其可能的分解机理。     

Low-temperature heat capacities and standard molar enthalpy of formation of N-methylnorephedrine C11H17NO（s）

This paper reports that low-temperature heat capacities of N-methylnorephedrine C11H17NO（s） have been measured by a precision automated adiabatic calorimeter over the temperature range from T=78K to T=400K. A solid to liquid phase transition of the compound was found in the heat capacity curve in the temperature range of T=342-364 K. The peak temperature, molar enthalpy and entropy of fusion of the substance were determined. The experimental values of the molar heat capacities in the temperature regions of T=78-342 K and T=364-400 K were fitted to two poly- nomial equations of heat capacities with the reduced temperatures by least squares method. The smoothed molar heat capacities and thermodynamic functions of N-methylnorephedrine C11H17NO（s） relative to the standard refer- ence temperature 298.15 K were calculated based on the fitted polynomials and tabulated with an interval of 5 K. The constant-volume energy of combustion of the compound at T=298.15 K was measured by means of an isoperibol precision oxygen-bomb combustion calorimeter. The standard molar enthalpy of combustion of the sample was calculated. The standard molar enthalpy of formation of the compound was determined from the combustion enthalpy and other auxiliary thermodynamic data through a Hess thermochemical cycle.     

[Gd2(Gly)6(H2O)4](ClO4)6(H2O)5的合成、晶体结构与热化学研究

利用微波技术合成了配合物[Gd₂(Gly)₆(H₂O)₄](ClO₄)₆(H₂O)₅, 进行了化学成分分析、红外表征和热重分析. 应用X衍射仪测定其晶体结构, 该晶体为一维链结构, 属三斜晶系, P 空间群, 晶胞参数: a＝1.1569(17) nm, b＝1.4138(2) nm, c＝1.5642(2) nm, α＝96.910(2)°, β＝102.735(2)°, γ＝105.512(2)°, V＝2.3606(6) nm³, Z＝2, D_c＝2.144 g•cm^－3. 采用精密溶解-反应量热计, 通过设计热化学循环, 计算出了该配合物的标准摩尔生成焓为 －(7960.73±3.23) kJ•mol^－1.     

对氨基苯甲酸热力学性质的量热和热分析研究

在80～400 K温区,用高精度全自动绝热量热仪测定了对氨基苯甲酸摩尔热容,得到摩尔热容随温度的变化的关系式为：     

石墨烯基纤维储能器件的研究进展与展望

随着小型化、可穿戴等特征的智能电子以及物联网传感设备的发展,新型纤维状柔性化、小型化电化学储能器件已成为重要的研究方向。同时,对纤维材料和柔性储能器件的性能提出了更高的要求,如可任意弯折、可拉伸、可折叠、高储能密度等。石墨烯纤维具有独特的结构、优异的导电性、良好机械性能和电化学性质,已证明了是一种极具前景、高性能的新型纤维状柔性储能材料。目前,研究者已开发了多种石墨烯基纤维微观结构的调控策略来进一步改进其性能。本文首先系统总结了石墨烯基纤维的制备方法和其性能提升的策略,然后详细讨论其在柔性化纤维状超级电容器、金属离子电池、热电发电机、太阳能电池和相变材料等储能领域中的最新应用进展。最后,对石墨烯基纤维在能源存储和转换领域中存在的挑战和机会进行了展望。     

Sm(Val)Cl3·6H2O低温热容及热化学性质

采用精密绝热量热计测定了稀土氨基酸配合物[Sm(Val)Cl3·6H2O]在80-376 K温区的热容, 从实验热容值计算出了热力学函数(HT-H298.15和ST-S298.15). 在308 K附近, 配合物的热容出现一个大的跳跃, 可能是其玻璃化转变所致. 对该配合物进行热重测试, 得到了其可能的分解机理.     

水合烟酸钡的合成、结构表征和热化学性质

选择烟酸和氢氧化钡作为反应物,利用室温固相合成方法,借助于球磨技术,合成了一种新的化合物-水合烟酸钡.利用化学分析、元素分析、FTIR和X射线粉末衍射等方法确定了它的组成和结构为Ba(Nic)2·3H2O(s).利用精密自动绝热热量计直接测定了此化合物在78-400 K温区的摩尔热容.在热容曲线上出现了一个明显的吸热峰,通过对热容曲线的解析,得到了相变过程的峰温、相变焓和相变熵分别为(327.097±1.082)K、(16.793±0.084)kJ·mol-1和(51.340±0.164)J·K-1·mol-1将该温区的摩尔热容实验值用最小二乘法拟合得到摩尔热容(Cp,m)对温度(T)的多项式方程,并且在此基础上计算出了它的舒平热容值和各种热力学函数值.另外,依据Hess定律,通过设计合理的热化学循环,选择体积为100mL、浓度为0.5mol·L-1的盐酸作为量热溶剂,利用等温环境溶解-反应热量计分别测量固相反应的反应物和产物在所选溶剂中的溶解焓,利用溶解焓确定固相反应的反应焓为△rH0m=-(84.12±0.38)kJ·mol-1.最后,利用固相反应的反应焓和其它反应物和产物已知的热力学数据计算出水合烟酸钡的标准摩尔生成焓为△rH0m[Ba(Nic)2·3H2O(s)]=-(2115.13±1.90)kJ·mol-1.     

Heat Storage Performance of Disodium Hydrogen Phosphate Dodecahydrate： Prevention of Phase Separation by Thickening and Gelling Methods

Disodium hydrogen phosphate dodecahydrate （Na2HPO4·12H2O） is an attractive candidate for phase change materials. The main problem for its practical use comes from incongruent melting character during thermal cycling. Experimentally, heat of fusion of the pure salt decreased from 200 to 25 jog 1 in a four-run freeze-thaw cycling. Additives such as thickening agent or in-situ synthesized polyacrylate sodium in the molten salt can prevent its phase separation to some extent. In the test, sodium alginate 3.0%-5.0% （w/w） thickened mixture containing Na2HPOn·12H2O and some water showed constant heat storage capacities. Polyacrylate sodium gelled salt was synthesized through polymerizing sodium acrylate in the melt of Na2HPOn·12H2O and some extra water at 50 ℃. Optimum conditions composed of sodium acrylate 3.0%-5.0% （w/w）, cross-linking agent N,N-methylenebis-acrylamide 0.10%-0.20% （w/w）, K2S208 and Na2SO3 （mass ratio 1 ; 1） 0.06%-0.12% （w/w）. As opposed to normal large crystals of pure Na2HPOn·12H2O in solid state, the gelled salt existed in a large number of tiny particles dispersed in the gel network at room temperature, commonly less than 2 mm. But only those sample particles with sizes less than 0.2 mm may have relatively stable thermal storage property. A problem encountered was the poor reproducibility of the synthesis method： heat storage capacity of the product was often very different even though the synthesis was carried out in the same conditions. An alternative gelling method by sodium alginate grafted sodium acrylate was tried and it showed a fairly good effect. Heat capacities and heat of fusion of Na2HPO4·12H2O were measured by an adiabatic calorimeter.     

弛豫量热技术研究固体材料低温比热性质

比热是物质最基础的热力学性质,通过测量并研究物质低温比热不仅可以计算得到熵、焓、吉布斯自由能等热力学函数,还可以获得有关物质物理性质、能量、结构及相变的信息,为相关热力学问题的探索与研究提供重要依据.低温比热测量一般有绝热量热、交流量热和弛豫量热三种技术;其中弛豫量热因测试样品用量少、测量温区低、测量准确度高、操作方便、有商品化仪器可得等优点,已成为近些年来发展最快、应用最广泛的低温比热测量技术.为了使研究者们更全面地了解这种量热技术,本文详细介绍了弛豫量热技术的测量原理、发展历程以及测量技术的研究进展,并结合当前热门研究领域,简要概述了国内外学者利用弛豫量热技术测量材料低温比热并研究相关热力学性质的最新工作进展.