异金属簇{LnCu3}低温磁制冷性能

基于对已报道Gd-Cu配合物的文献调研,发现一类{LnCu₃}簇合物(Ln=Gd(1),Tb(2),Dy(3)),其Cu^Ⅱ离子被Gd^Ⅲ离子有效分隔且分子内部仅拥有铁磁相互作用,因而对其进行了低温磁制冷性能研究。在已报道实验方法上加以改进,用一锅法制备出一系列异金属{LnCu₃}簇合物(Ln=Gd(1),Tb(2),Dy(3)),并运用元素分析、红外、单晶/粉末X-射线衍射等方法对其进行表征,以证明其同构性及相纯度。低温磁热效应的研究结果表明簇合物1-3在ΔH=0~7T下的最大磁熵变值(-ΔS_m)分别为16.1(2K),6.9(5K)和8.1(5K)J·kg^-1·K^-1。簇合物1与已报道的Gd-Cu簇合物的磁熵变对比再次证明了弱铁磁相互作用在3d-4f分子磁制冷剂设计中起到重要的作用。     

分子基低温磁制冷材料的研究进展

磁制冷技术是以磁性物质为工质,通过等温磁化和绝热去磁达到制冷目的的一种极具开发潜力的高新制冷技术．相比于传统的气体压缩制冷,磁制冷以其高效、节能、环保的特点得到研究者越来越多的青睐．近年来研究发现,与合金、纳米磁制冷材料相比,分子基磁制冷材料在超低温制冷领域表现出较大的优势．本文针对分子基低温磁制冷材料的研究报道及本实验室的相关工作进行总结和讨论,并探究了其发展趋势．     

太阳能与生物质能耦合供能系统的应用研究

介绍了太阳能与生物质能溴化锂吸收式制冷机的工作原理,分析了太阳能集热器及溴化锂制冷机组的热效率,利用生物质汽化炉余热弥补太阳能不稳定的缺陷,证明了利用清洁能源作为溴化锂吸收式中央空调热源问题的可行性。     

多功能热管型二级吸附制冷的循环特性研究

设计了一台以氯化钙/活性炭复合吸附剂和氨作为吸附工质对的多功能热管型吸附制冷机组,采用一种新型的基于二次回热的二级循环方式来降低驱动热源的温度梯度,吸附床的加热解吸、冷却吸附及回热过程均由无外加驱动力的多功能热管工作完成.研究结果表明:当解吸温度为103℃及冷却水温度为30℃时,回热型二级循环相对传统二级循环可显著提高机组的工作性能,制冷系数COP及单位质量吸附剂制冷功率SCP提高幅度均在23%以上;相对单级循环,二级吸附循环的最大优点在于能有效利用更低品位的余热和可再生能源作为驱动热源进行制冷,吸附制冷技术在低温热源场合的应用提供了有效途径.     

Preparation, structural and electrical properties of zinc oxide grown on silicon nanoporous pillar array

Polycrystalline thick film of zinc oxide (ZnO) is grown on a unique silicon substrate with a hierarchical structure, silicon nanoporous pillar array (Si-NPA), by using a vapour phase transport method. It is found that as-grown ZnO film is composed of closely packed ZnO crystallites with an average size of $\sim$10\,\mu$m. The film resistivity of ZnO/Si-NPA is measured to be $\sim$8.9\Omega\cdot$\,cm by the standard four probe method. The lengthwise $I$-$V$ curve of ZnO/Si-NPA heterostructure is measured. Theoretical analysis shows that the carrier transport across ZnO/Si-NPA heterojunction is dominated by two mechanisms, i.e. a thermionic process at high voltages and a quantum tunnelling process at low voltages.     

Einstein制冷循环研究新进展

文中介绍了单压吸收式制冷的主要类型,对两种单压吸收式制冷循环进行了对比阐述。就Einstein制冷循环的研究进展进行了归纳总结,对目前研究Einstein制冷循环所面临的部分问题进行了分析,并对进一步研究提出展望。     

Effects of Metal Work Function and Contact Potential Difference on Electron Thermionic Emission in Contact Electrification

Triboelectric nanogenerator (TENG) is a direct measure of the surface charge density, thus providing a novel and powerful tool to study the essential mechanism of contact electrification (CE). A variety of TENGs including a Pt‐Al₂O₃ TENG, Au‐Al₂O₃ TENG, Ti‐Al₂O₃ TENG, Al‐Al₂O₃ TENG, and SiO₂‐Al₂O₃ TENG are prepared in this study. After introducing initial charges on the Al₂O₃ surface of the TENGs, the long‐term evolution of surface charge quantity is investigated at different temperatures. The results show that charge variation of all the TENGs is analogous to exponential decay and is in accord with the thermionic emission model, verifying the electron transfer dominated mechanism of CE. Additionally, it is explored for the first time that the potential barrier of materials can be regulated by changing the contacting metals or dielectrics. Regulation of the barrier at high temperatures fully excludes the influence of ions from moisture and functional groups, which further indicates the dominant role played by electron transfer in CE. Surface state models for explaining barrier regulation during CE for both metal–dielectric and dielectric–dielectric pairs are proposed. This study provides a new perspective of the exploration of CE, and a novel method for further increasing or rapidly eliminating electrification of charged materials.     

喷射制冷循环及其关键技术

本文首先对喷射制冷及复合喷射制冷技术原理和特点进行简要介绍，在对系统循环的COP值理论分析的基础上，结合实验结果提出其技术关键所在，并在文章的最后指出了所面临的主要问题及今后的研究方向。     

扬声器驱动热声制冷机设计研究

热声制冷机主要由声驱动器、共振管、板叠、高低温端换热器、声容等部件组成。它具有运动部件少、运行可靠、振动小和寿命长等优点 ,在军事、航天、微电子、低温物理等领域有着十分诱人的应用前景。文中运用经典线性热声理论对热声制冷机各个组成部件设计进行了介绍 ,在此基础上设计了一台扬声器驱动热声制冷机 ,并用专业计算软件进行了数值模拟验证 ,为热声制冷机进一步优化与发展提供了一个解决方案。     

Study and modeling of the transport mechanism in a Schottky diode on the basis of a GaAs semiinsulator

The current through a metal-semiconductor junction is mainly due to the majority carriers. Three distinctly different mechanisms exist in a Schottky diode: diffusion of the semiconductor carriers in metal, thermionic emission-diffusion (TED) of carriers through a Schottky gate, and a mechanical quantum that pierces a tunnel through the gate. The system was solved by using a coupled Poisson-Boltzmann algorithm. Schottky BH is defined as the difference in energy between the Fermi level and the metal band carrier majority of the metal-semiconductor junction to the semiconductor contacts. The insulating layer converts the MS device in an MIS device and has a strong influence on its current-voltage (I-V) and the parameters of a Schottky barrier from 3.7 to 15 eV. There are several possible reasons for the error that causes a deviation of the ideal behaviour of Schottky diodes with and without an interfacial insulator layer. These include the particular distribution of interface states, the series resistance, bias voltage and temperature. The GaAs and its large concentration values of trap centers will participate in an increase in the process of thermionic electrons and holes, which will in turn act on the I-V characteristic of the diode, and an overflow maximum value [NT = 3 × 10²⁰] is obtained. The I-V characteristics of Schottky diodes are in the hypothesis of a parabolic summit.