A Monolithic Integrated CMOS Thermal Vacuum Sensor

The monolithic integrated micro sensor is an important direction in the fields of integrated circuits and micro sensors. In this paper,a monolithic thermal vacuum sensor based on a micro-hotplate （MHP） and operating under constant bias voltage conditions was designed. A new monolithic integrating mode was proposed,in which the dielectric and passiva- tion layers in standard CMOS processes were used as sensor structure layers,gate polysilicon as the sacrificial layer,and the second polysilicon layer as the sensor heating resistor. Then, the fabricating processes were designed and the monolithic thermal vacuum sensor was fabricated with a 0. 6μm mixed signal CMOS process followed by sacrificial layer etching technology. The measurement results show that the fabricated monolithic vacuum sensor can measure the pressure range of 2- 10^5 Pa and the output voltage is adjustable.

Quantum Fluctuation Properties of Polariton System in Thermal Vacuum State Field

Using the theory of thermal field dynamics (TFD), a model polariton system is investigated and the squeezing properties of the polariton system at finite temperature is discussed. It is shown that when the photon field is initially in a thermal vacuum state and the phonon initially in its lowest energy level state (the vacuum state), the phonon, photon and also the polariton system can exhibit nonclassical behaviour.

Thermal vacuum state corresponding to squeezed chaotic light and its application

For the density operator（mixed state） describing squeezed chaotic light（SCL） we search for its thermal vacuum state（a pure state） in the real-fictitious space. Using the method of integration within ordered product（IWOP） of operators we find that it is a kind of one- and two-mode combinatorial squeezed state. Its application in evaluating the quantum fluctuation of photon number reveals： the stronger the squeezing is, the larger a fluctuation appears. The second-order degree of coherence of SCL is also deduced which shows that SCL is classic. The new thermal vacuum state also helps to derive the Wigner function of SCL.

Experimental Investigation of Loop Heat Pipe with Two Evaporators/Two Condensers under Thermal Vacuum Condition

Multiple loop heat pipe is a high-functional thermal transport device. This work was conducted to confirm the working performance of Multiple loop heat pipe under thermal vacuum ambience with the working fluid ammonia. Asmall multiple loop heat pipe with two evaporators and two ra- diators was designed and fabricated. Then thermal vacuum test was conducted. The heaters were fasten on both evaporators, both radiators, both compensation chambers. In the case that both evaporators were heated, the multiple loop heat pipe can transport 120/120 W for 1.5 m, in the case that only one evaporator was heated, evaporator 1 can transport 80 W for 1.5 m, while eva- porator 2 can transport 120 W for 1.5 m. Two flow regulators were installed near the confluence of liquid line to prevent uncondensed vapor penetrating into returning liquid when the tempera- ture difference exists between two radiators. In the case that the heat load at both evaporators were 40/40 W and one radiator was heated, the flow regulator1 can tolerate the 160 W of heat load which was supplied to radiator1 while the flow regulator2 can tolerate the 100 W of heat load which was supplied to radiator2. To demonstrate the multiple loop heat pipe’s startup behavior at lowheat load, each of the compensation chamber was preheated to change the initial distribution of liquid and vapor in the evaporator and compensation chamber, in the result, each evaporator can start up at 5W through preheating.

Process of producing magnesium by thermal vacuum reduction using silicocalcium as reductant

A new process of producing magnesium by thermal vacuum reduction using dolomite and magnesite as materials and silicocalcium as reductant was studied in this study. The reduction process of MgO by silicocalcium was analyzed by phases analysis of reduction slag through X-ray diffraction （XRD） and the factors influencing the reduction ratio of MgO were investigated. The experi- mental results show that when using silicocalcium as reductant, the reduction ratio of MgO can be over 93 %. In the reduction process, calcium in silicocalcium takes part in the reduction reaction of MgO firstly below 1,000 ℃ and it makes CaSi2 decompose. It also releases elemental silicon which has more reactive activity and improves the reduction reaction of MgO. That is the main cause that the reduction ratio of MgO using silicocalcium as reductant is 8 %-10 % higher than that by Pidgeon process using fer- rosilicon as reductant under the same conditions.

System on chip thermal vacuum sensor based on standard CMOS process

An on-chip microelectromechanical system was fabricated in a 0.5μm standard CMOS process for gas pressure detection. The sensor was based on a micro-hotplate （MHP） and had been integrated with a rail to rail operational amplifier and an 8-bit successive approximation register （SAR） A/D converter. A tungsten resistor was manufactured on the MHP as the sensing element, and the sacrificial layer of the sensor was made from polysilicon and etched by surface-micromachining technology. The operational amplifier was configured to make the sensor operate in constant current mode. A digital bit stream was provided as the system output. The measurement results demonstrate that the gas pressure sensitive range of the vacuum sensor extends from 1 to 105 Pa. In the gas pressure range from 1 to 100 Pa, the sensitivity of the sensor is 0.23 mV/Pa, the linearity is 4.95%, and the hysteresis is 8.69%. The operational amplifier can drive 200 Ω resistors distortionlessly, and the SAR A/D converter achieves a resolution of 7.4 bit with 100 kHz sample rate. The performance of the operational amplifier and the SAR A/D converter meets the requirements of the sensor system.

Numerical Simulation of Vacuum Heat Treatment Thermal Hysteresis Time of GH4169 Superalloy Workpiece

A nonlinear finite element model of vacuum heat treatment process was developed. In this model, influence of many factors, such as nonlinear heat radiation, temperature-dependent thermal physical properties of material are considered. The temperature field of GH4169 alloy workpiece during vacuum heat treatment process was calculated using finite element software MSC.Marc, and the thermal hysteresis time of the workpiece was predicted. An experiment of vacuum heat treatment of GH4169 superalloy workpiece was carried out to verify the calculation. The experimental results of temperature profile agree well with the simulated results. This work lays a theoretical foundation for optimizing technical parameter of vacuum heat treatment process.

In-situ growth of a CdS window layer by vacuum thermal evaporation for CIGS thin film solar cell applications

Highly crystalline and transparent CdS films are grown by utilizing the vacuum thermal evaporation （VTE） method. The structural, surface morphological, and optical properties of the films are studied and compared with those prepared by chemical bath deposition （CBD）. It is found that the films deposited at a high substrate temperature （200 ℃） have a preferential orientation along （002） which is consistent with CBD-grown films. Absorption spectra reveal that the films are highly transparent and the optical band gap values are found to be in a range of 2.44 eV-2.56 eV. Culnl_xGaxSe2 （CIGS） solar cells with in-situ VTE-grown CdS films exhibit higher values of Voc together with smaller values of Jsc than those from CBD. Eventually the conversion efficiency and fill factor become slightly better than those from the CBD method. Our work suggests that the in-situ thermal evaporation method can be a competitive alternative to the CBD method, particularly in the physical- and vacuum-based CIGS technology.

Isolated Cobalt Nanoparticles Prepared on HOPG in Ultrahigh Vacuum Using Thermal Annealing

Cobalt nanoparticles on the surface of highly oriented pyrolytic graphite have been studied by atomic force microscopy. Thermal annealing in ultrahigh vacuum was used to change the size of cobalt nanoparticles and their surface distribution. The effect of two key parameters, annealing time and temperature, on the size and the surface distribution of nanoparticles has been studied. The dependence of the particle size on these parameters has been obtained. It has been shown that the main mechanism of the nanoparticle growth is Ostwald ripening.

Initiation of vacuum breakdown and failure mechanism of the carbon nanotube during thermal field emission

The carbon nanotube （CNT）-based materials can be used as vacuum device cathodes. Owing to the excellent field emission properties of CNT, it has great potentials in the applications of an explosive field emission cathode. The falling off of CNT from the substrate, which frequently appears in experiments, restricts its application. In addition, the onset time of vacuum breakdown limits the performance of the high-power explosive-emission-cathode-based diode. In this paper, the characteristics of the CNT, electric field strength, contact resistance and the kind of substrate material are varied to study the parameter effects on the onset time of vacuum breakdown and failure mechanism of the CNT by using the finite element method.

Numerical Analysis of Thermal Distortion and Residual Stresses in H13 Steel Due to Vacuum Gas Quenching

Heat treated steel components often suffer distortion and residual stress effects when cooled to room temperature. A numerical analysis of a vacuum gas quenched die block made of H 13 was carried out utilising a nonlinear thermoelastic-plastic stress model together with the fluid flow and thermal profiles within the furnace. Simulation procedures for stress behaviour of the die were developed for both direct quench and marquench processes. Results of the initial thermal analysis indicated that the temperature difference between the surface and core of the die during direct quenching (gas pressure is 4 bar) was larger than that due to marquenching ( gas pressure is 4 bar at the beginning and 2 bar near isothermal hold). Simulation of the cooling rates at the surface and core of the die during marquenching correlated well with the experimental data. Further stress simulation indicated that the final thermal distortion and residual stresses in the die after direct quenching were larger than those due to marquenching. The findings of the numerical analysis suggested that marquenching is recommended for this die because it could reduce the temperature difference in the die and thus result in less thermal distortion and residual stresses.

Micro thermal shear stress sensor based on vacuum anodic bonding and bulk-micromachining

This paper describes a micro thermal shear stress sensor with a cavity underneath, based on vacuum anodic bonding and bulk micromachined technology. A Ti/Pt alloy strip, 2μm×100μm, is deposited on the top of a thin silicon nitride diaphragm and functioned as the thermal sensor element. By using vacuum anodic bonding and bulk-si anisotropic wet etching process instead of the sacrificial-layer technique, a cavity, functioned as the adiabatic vacuum chamber, 200μm×200μm×400μm, is placed between the silicon nitride diaphragm and glass （Corning 7740）. This method totally avoid adhesion problem which is a major issue of the sacrificial-layer technique.

低表面能氟碳聚合物涂层真空热循环及防爬移特性研究

低表面能氟碳聚合物涂层是一种抑制空间用油脂润滑剂爬移流失的关键材料,该材料的应用可为空间油脂润滑活动机构实现长寿命、高可靠运行提供技术保障。采用水接触角测试仪、X射线荧光能谱仪、光学显微镜等对自研的氟碳聚合物涂层进行了真空热循环前后的接触角、表面能变化以及对多烷基环戊烷(MACs)润滑油防爬移特性的研究。结果表明,9Cr18不锈钢、2A12铝合金和TC4钛合金三种不同金属基体表面涂覆聚合物涂层后的表面能分别为8.797 mN/m、9.083 mN/m和9.203 mN/m;在温度−45~+90℃下,经过30天、60次真空热循环后,涂层的表面能分别为8.915 mN/m、9.209 mN/m和9.266 mN/m,仍然较低。涂层与MACs润滑油之间存在明显界面,涂层上距离润滑油200μm界面处的XPS分析未发现MACs润滑油的特征峰,表明没有润滑油爬移扩散至涂层处,低表面能氟碳聚合物涂层对MACs润滑油能够起到有效的“防爬移”作用。

保温时间对钛合金板翅式换热器真空钎焊过程温度场及残余应力的影响

钛合金板翅式换热器成品率较低、残余应力较大,该文针对钛合金板翅结构真空钎焊过程开展热-固耦合建模与仿真研究,阐述了钎焊过程温度均匀性及残余应力分布特征,探明保温时间对钛合金板翅式换热器真空钎焊过程温度场及残余应力的影响机理.结果表明,板翅结构两侧温度较高,中部温度较低,延长保温时间可有效改善板翅结构的温度均匀性.残余应力均主要集中于翅片上表面与隔板背侧中部,在钎缝及夹持点处存在明显的应力集中现象,保温时间越长翅片钎缝的残余应力越小.模拟得到钛合金板翅式换热器真空钎焊中残余应力与试验结果相吻合,相对误差为5.3%,验证了该模型的准确性.

高真空环境模拟卧式超长综合试验平台

文章设计了一套高真空环境模拟卧式超长综合试验平台,包括真空腔体、抽真空系统、热模拟系统、冷却水循环系统、控制及数据采集系统以及其他辅助保证系统等。该环境模拟系统主要是为全系统模拟真空环境试验提供条件保障,满足试验过程中关键技术指标的验证要求以及关键设备可以在清晰成像距离范围内实现对目标运动轨迹的标定,为后续项目研发和改进提供技术和测试数据支撑。

航天器密封舱水分含量测量与除水工艺方法研究

航天器密封舱在进行真空热试验时处在真空容器内部,常规的水分含量测量和除水方法均无法满足密封舱除水要求。本文针对航天器密封舱在真空热试验时的除水难题,设计了一套适合密封舱内水分含量测量的装置,经过标定确保其满足真空环境下水蒸气含量的测量要求。设计的密封舱除水系统通过双向密封法兰与密封舱连接,可以在真空容器外完成对密封舱的除水。试验验证结果表明,该除水方法能够保证在真空热试验过程中密封舱内气体的露点温度低于0℃。

FOX-7颗粒形貌对其热性能及放气量的影响

为获得FOX-7颗粒形貌对其热性能及放气量的影响规律,首先通过原位拉曼光谱证实了FOX-7的典型相变过程;采用差示扫描量热法(DSC)对比了原料FOX-7、重结晶FOX-7以及碾碎的重结晶FOX-7三种颗粒的转晶及热分解行为,并采用真空安定性测试比较了3种具有典型粒径及形貌差异的FOX-7的放气速率及放气量。结果表明,两种具有更多缺陷的FOX-7颗粒第一步热分解峰温度均低于重结晶样品;当FOX-7粒径较小,会导致其在DSC曲线上β到γ相变吸热峰消失;通过增加单次测试样品量或增加升温速率,增强相变热效应聚集,仍可观察到该相变过程;当加热时间相同,小粒径的FOX-7放气总量大于大粒径的颗粒;当大粒径颗粒表面具有缺陷,其放气量会更快达到最大值;当小粒径颗粒表明无明显缺陷,其加热初期放气量较小,但随着加热时间延长,其总放气量会显著增加并最终超过大粒径颗粒;FOX-7颗粒粒径决定了总放气量,而其颗粒缺陷决定了放气速率;苯胺类安定剂对FOX-7具有较好的放气抑制效果。

Numerical Simulation of the Thermal Conductivity of Thermal Insulation Pipeby Vacuum and High Pr essur e Ar gon Pre- filled

By analyzing the insulation effect of argon-filled tubing and vacuum-insulated tubing before and after hydrogen permeation respectively,a conclusion can be drawn that the insulated tubing filled with high pressure argon is better than the vacuum insulated tubing considering the lifetime and heat insulation effect.

真空蒸馏法从镁渣中回收镁的研究

我国是镁生产大国,近些年每年产生超过450万t镁渣,对镁渣的研究表明,镁渣中可能存在单质状态的镁,对镁渣进行预分离选择镁单质含量高的镁渣,采用真空蒸馏的方式,选择700℃为试验温度、真空度维持在10 Pa以下,并通过合理的试验流程和试验装置,回收了部分单质镁,镁元素的回收率达到了37.35%,回收的镁含镁量99.51%。