High Temperature Superconductor THz Thermal Sensors and Coolers

High temperature Superconductors (HTSCs) are a good candidate for developing THz radiation sensors. They are easy to manufacture and operate in the convenient temperature range of 80–140 K. The speed of operation of a THz sensor need to be controlled by a fast dissipation of heat, by the electrons which act as the sensing element. There is recently a surge in the development of fast and efficient low dimensional thermoelectric, temperature control devices. They would be ideal for cooling of the sensor, over the temperature interval of operation of the HTSCs. Status of these cooling devices towards achieving low temperature self cooling is discussed in the paper. Some results of the modeling study, carried out by the author, in an HTSC hot electron thermal sensor (HETS) are presented.     

Simulated Operational Characteristics of a High-Tc Terahertz (THz) Thermal Sensor

A solution of the time-dependent heat transfer differential equations for the two-temperature (electron and phonon) model for the sensor-lattice and the lattice-substrate interface system is used for a computational analysis of the operational characteristics, for a high-T _c heterodyne thermal sensor. Responsivity and conversion gain of the sensor are analyzed in particular reference to external control parameters, e.g. the bias currents and voltages. Some operational characteristics in the form of three-dimensional graphics of the sensor are presented.     

热作模具钢DM的高温稳定性和热疲劳性能

研究了热作模具钢DM的高温稳定性和热疲劳性能。结果表明,DM钢在620℃热稳保温过程中马氏体板条内的薄片状M₃C型碳化物逐渐向条块状M₇C₃型碳化物转变,在板条的边界生成M₇C₃、M₂₃C₆型碳化物。DM钢的短循环周次热疲劳性能受控于位错重排和湮灭,长循环周次热疲劳性能受控于碳化物的粗化程度。DM钢中M₃C、M₇C₃、M₆C型碳化物的生成自由能分别为27765.5 J/mol、3841.5 J/mol、-7138.1 J/mol,表明在热稳保温与热疲劳试验过程中碳化物的演变机理一致,发生了M3C→M7C3→M6C类型演变。     

Power Handling of High Temperature Superconductors Measured in an HTS/Sapphire Resonator: A Power Reference Film

The power handling of HTS thin films was accurately characterized in an 8.15 GHz HTS/Sapphire resonator as a function of temperature. The surface resistance of a superconductor depends upon the level of the surface magnetic field especially if the value exceeds the lower critical magnetic field. A four-film power round robin was performed, which allowed for both the power handling of each of the HTS films and the statistics about the measurement repeatability to be calculated. A highly nonlinear empirically derived formula was identified and used to interpolate the measurement data. These four HTS films can now be used as power-qualified reference films for future HTS/Sapphire resonator measurements.     

高温热解析在多环芳烃污染土修复中的应用

多环芳烃(PAHs)是一类重毒污染物,其污染土壤对人类的健康造成了严重危害,所以对污染土壤进行修复势在必行。首先讨论了处理多环芳烃(PAHs)污染土壤的多种可行技术;然后详细介绍了回转窑高温热解析在北京某焦化厂多环芳烃污染土壤修复中的应用及效果,研究发现回转窑高温热解析技术不仅能有效去除污染土中的有机污染物,而且还能抑制二噁英等剧毒物的产生。     

某飞机GH1140排气导管裂纹分析

某飞机在进行检查时发现,其起动机GH1140高温合金排气导管内层加强筋处有一条裂纹,采用化学成分分析、金相检验、断口分析等方法对裂纹产生的原因进行了分析。结果表明:由于高温气体的冲刷作用使排气导管内表层晶界出现了贫铬,降低了合金的强度、持久性能和疲劳性能;排气导管开裂主要是由于其内表面曾被打磨,打磨处形成应力集中萌生裂纹源,在起动机内部反复热应力和机械振动等作用下,以及表面氧化物的进一步促进作用下发生的热疲劳开裂。     

某热电厂高温过热器蛇形管开裂原因分析

某热电厂60%的高温过热器蛇形管在安装运行10 h后就发生了开裂失效。采用磁粉探伤检验、化学成分分析、硬度测试、金相检验、拉伸试验等多种手段分析了导致蛇形管早期开裂的原因。结果表明:开裂高温过热器蛇形管原材料由于合金元素钼分布不均匀而存在组织偏析,导致局部区域材料的塑性性能和抗腐蚀性能下降;在高温高压水蒸气和钢管自身强残余应力作用下,最终造成蛇形管由内壁向外壁发生了应力腐蚀开裂。     

Measurements of the Thermal Conductivity of HFC-32 (Difluoromethane) in the Temperature Range from 300 to 465 K at Pressures up to 50 MPa

New measurements of the thermal conductivity of HFC-32, made in a coaxial cylinder cell operating in steady state, are reported. The measurements were performed along several quasi-isotherms between 300 and 465 K in both the liquid and the vapor phases. The pressure ranged from 0.1 to 50 MPa. Based on the experimental data, a background equation is provided to calculate the thermal conductivity outside the critical region as a function of temperature and density. A careful analysis of the various sources of experimental errors leads to an estimated uncertainty of ±1.5%. Comparisons between calculated and experimental values from the literature are presented.     

Ca-(Na,Ce)-Bi-Ti系列高温压电陶瓷材料及其压电性能的研究

本文开展了对ＣａＢｉ４Ｏ１５基料的置换和掺杂的研究，获得一个较好Ｃａ－（Ｎａ，Ｃｅ）－Ｂｉ－Ｔｉ材料系列，并在该材料系列的基础上再进行一元和多元掺杂，使它的ｄ３３值较ＣａＢｉ４Ｔｉ４Ｏ１５有较大程度的改善，其电阻率、电容和损耗的温度系数也均优于ＣａＢｉ４Ｏ１５，是一种较有开发潜力的高温压电陶瓷材料。     

Ca-(Na,Ce)-Bi-Ti系列高温压电陶瓷材料及其压电性能的研究

本文开展了对CaBi4Ti4O15基料的置换和掺杂的研究，获得一个较好的Ca-（Na,Ce）-Bi-Ti材料系列，并在该材料系列的基础上再进行一元和多元掺杂，使它的d33值较CaBi4Ti4O15有较大程度的改善，其电阻率、电容和损耗的温度系数也均优于CaBi4Ti4O15，是一种较有开发潜力的高温压电陶瓷材料．     

The Itinerant 2D Electron Gas of the Indium Oxide (111) Surface: Implications for Carbon‐ and Energy‐Conversion Applications

Transparent conducting oxides (TCO) have integral and emerging roles in photovoltaic, thermoelectric energy conversion, and more recently, photocatalytic systems. The functional properties of TCOs, and thus their role in these applications, are often mediated by the bulk electronic band structure but are also strongly influenced by the electronic structure of the native surface 2D electron gas (2DEG), particularly under operating conditions. This study investigates the 2DEG, and its response to changes in chemistry, at the (111) surface of the model TCO In₂O₃, through angle resolved and core level X‐ray photoemission spectroscopy. It is found that the itinerant charge carriers of the 2DEG reside in two quantum well subbands penetrating up to 65 Å below the surface. The charge carrier concentration of this 2DEG, and thus the high surface n‐type conductivity, emerges from donor‐type oxygen vacancies of surface character and proves to be remarkably robust against surface absorbents and contamination. The optical transparency, however, may rely on the presence of ubiquitous surface adsorbed oxygen groups and hydrogen defect states that passivate localized oxygen vacancy states in the bandgap of In₂O₃.     

铁电性、高温超导电性和庞磁电阻(CMR)效应的共性特征探讨

从结构和相变两个方面探讨了铁电性，高温超导电性和庞磁电阻（CMR）效应的共性，指出这类性质是集体电子行为，是由各种结构层次（晶体结构，电子结构及自旋结构）相互作用，相互耦合共同引起的。     

Thermal Diffusivity of the Aluminum Alloy Al–17Si–4Cu (A390) in the Solid and Liquid States

The thermal diffusivity of the aluminum alloy Al–17Si–4Cu (A390) was measured in the temperature range from room temperature to 730°C using the laser-flash technique. A commercial laser-flash system (Netzsch LFA 427) was used for the measurements. A short laser pulse of 300μs was applied to heat the bottom surface of a disk-shaped specimen, resulting in a time-dependent temperature increase at the top surface. A correction for the laser pulse length as well as the surface radiation and convection was applied in order to evaluate the half time value of the temperature increase. The thermal diffusivity was calculated from the specimen thickness and the half time value. A sapphire crucible was used to contain the specimen in the mushy region and in the liquid state. As the laser is fired from below at the bottom surface of the specimen, the thickness of the melt has to be small to avoid significant buoyancy. The thermal diffusivity of the alloy above the eutectic temperature and in the liquid is drastically lower than in the solid state of the alloy.     

Thermal Conductivity Measurements of Aqueous SrCl2 and Sr(NO3)2 Solutions in the Temperature Range Between 293 and 473 K at Pressures up to 100 MPa

Accurate high-pressure thermal conductivity measurements have been performed on H₂O+SrCl₂ and H₂O+Sr(NO₃)₂ mixtures at pressures up to 100 MPa over a temperature range between 293 and 473 K using a parallel-plate apparatus. The concentrations studied were 0.025, 0.05, 0.10, 0.15, and 0.20 mass fraction of the salts. The estimated accuracy of the method is about ±1.6%. The pressure, temperature, and concentration dependences of the thermal conductivity have been studied. Measurements were made on six isobars, namely, 0.1, 20, 40, 60, 80, and 100 MPa. The thermal conductivity shows a linear dependence on pressure and concentration for all isotherms. Along each isobar, a given concentration shows the thermal-conductivity maximum at a temperature of about 413 K. The measured values of thermal conductivity at atmospheric pressure are compared with the results of other investigators. Literature data at atmospheric pressure reported by Ridel and by Zaitzev and Aseev agree with our thermal conductivity values within the estimated uncertainty.