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Influence of anode temperature on ignition performance of the IRIT4-2D iodine-fueled radio frequency ion thruster

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Plasma Science and Technology 2022年第1期24卷 139-150页

作者：张兴华张振华贾少霞金婷杨景华李龙刘芳芳蔡勇蔡建 Institute of Microelectronics Chinese Academy of SciencesBeijing 100029People's Republic of China Suzhou Nano-Space Dynamics Technology Co.Ltd Suzhou 215000People’s Republic of China

This paper reports the ignition performance of the iodine-fueled radio frequency(RF)ion thruster(IRIT)at different anode temperaturesT_(a0).The experimental results show that the anode temperature plays important role on the ignition process of the IRIT.There were two characteristic temperatures related to the anode:the minimum ignition temperatureT_(i0)and the stable ignition temperatureT_(is),which were much lower than the pipeline temperature and the storage tank temperature.AtT_(a0)sublimation-clearing inside the thruster.The research helps improve the preheating design of the iodine-fueled electric thruster.

关键词： radio frequency ion thruster iodine propellant ignition deposition sublimation clog

In situ observation of sublimation-enhanced magnesium oxidation at elevated temperature

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Nano Research 2016年第9期9卷 2796-2802页

作者： Zijiao Zhang Xiaoqian Fu Minmin Mao Qian Yu Scott X.Mao Jixue Li Ze Zhang Center of Electron Microscopy and State Key Laboratory of Silicon Materials Department of Materials Science & EngineeringZhejiang UniversityHangzhou 310027China Department of Mechanical Engineering & Materials Science University of PittsburghPittsburghPA 15261USA

Oxidation plays a tremendous role in the long-term performance of metals. As an important lightweight metal for industrial applications, magnesium suffers from its high reactivity with oxygen and increased evaporation at high temperatures. To understand the oxidation mechanism of magnesium at elevated temperatures, in situ environmental transmission electron microscopy (E-TEM) was performed on magnesium nanoparticles. At a relatively low temperature, the growth of a MgO lamellae via the outward diffusion of bulk magnesium atoms dominated the oxidation process. In contrast, a sublimation-enhanced oxidation via gas phase reaction occurred at 200 °C, leading to the growth of MgO dendrites over the particle that finally leads to the degradation of the magnesium structure. This study provides a direct observation and model of the oxidation mechanism of a direct gas–gas reaction that improves our understanding of the oxidation mechanism at elevated temperatures.

关键词： oxidation magnesium sublimation nanoparticle

Low-Angle Grain Boundaries in sublimation Grown 6H-SiC Crystals

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Journal of Rare Earths 2006年第Z1期24卷 8-10页

作者： Jiang Shouzhen Li Xianxiang Dong Jie Chen Xiufang Xu Xiangang Hu Xiaobo State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China State Key Laboratory of Crystal Materials Shandong University Jinan 250100 China

High-resolution X-ray diffractometry (HRXRD) was used to assess the quality of 6H-SiC crystals grown by sublimation method. The results show the occurrence of low-angle grain boundaries (LB) is close relative to the inclination of the crystal interface. At the central faceted region with 0° inclination the crystal is of high structural perfection. However, at the region close to the facet with less than 5° inclination LB occurs slightly and at the region close to the peripheral polytype ring with more than 5° inclination LB defect occurs heavily. The density of LB can be drastically reduced by decreasing radial temperature gradient that determines the shape of the crystal growth interface.

关键词： low-angle grain boundaries sublimation 6H-SiC radial temperature gradient

The sensitivity of snowpack sublimation estimates to instrument and measurement uncertainty perturbed in a Monte Carlo framework

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Frontiers of Earth Science 2018年第4期12卷 728-738页

作者： D.M.HULTSTRAND S.R.FASSNACHT EASC-Watershed Science Colorado State UniversityFort CollinsCO 80523-1482USA ESS-Watershed Science Colorado State UniversityFort CollinsCO 80523-1476USA Cooperative Institute for Research in the Atmosphere Fort CollinsCO 80523-1375USA Geographisches Institut Abt.KartographieGIS &FemerkundungGeorg-August-Universitat Gottingen37077GottingenGermany Natural Resources Ecology Laboratory Fort CollinsCO 80523-1499USA

The bulk aerodynamic flux equation is often used to estimate snowpack sublimation since it requires meteorological measurements at only one height above the snow surface. However, to date the uncertainty of these estimates and the individual input variables and input parameters uncertainty have not been quantified. We modeled sublimation for three (average snowpack in 2005, deep snowpack in 2011, and shallow snowpack in 2012) different water years (October 1 to September 30) at West Glacier Lake watershed within the Glacier Lakes Ecosystem Experiments Site in Wyoming.We performed a Monte Carlo analysis to evaluate the sensitivity of modeled sublimation to uncertainties of the input variables and parameters from the bulk aerodynamic flux equation. Input variable time series were uniformly adjusted by a normally distributed random variable with a standard deviation given as follows: 1) the manufacturer’s stated instrument accuracy of 0.3°C for temperature (T), 0.3 m/s for wind speed (Uz), 2% for relative humidity (RH), and 1 mb for pressure (P); 2) 0.0093 m for the aerodynamic roughness length (z0) based on z0 profiles calculations from multiple heights; and 3) 0.08 m for measurement height (z). Often z is held constant; here we used a constant z compared to the ground surface, and subsequently altered z to account for the change in snow depth (ds). The most important source of uncertainty was z0, then RH. Accounting for measurement height as it changed due to snowpack accumulation/ablation was also relevant for deeper snow. Snow surface sublimation uncertainties, from this study, are in the range of 1% to 29% for individual input parameter perturbations. The mean cumulative uncertainty was 41% for the three water years with 55%, 37%, and 32% occurring for the wet, average, and low water years. The top three variables (z varying with ds, z0, and RH) accounted for 74% to 84% of the cumulative sublimation uncertainty.

关键词： snow sublimation uncertainty aerodynamic methods

In Situ Imaging of Layer-by-Layer sublimation of Suspended Graphene

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Nano Research 2010年第1期3卷 43-50页

作者： Jian Yu Huang Liang Qi Ju Li Center for Integrated Nanotechnologies(CINT) Sandia National LaboratoriesAlbuquerqueNew Mexico 87185USA Department of Materials Science and Engineering University of PennsylvaniaPhiladelphiaPennsylvania 19104USA

An individual suspended graphene sheet was connected to a scanning tunneling microscopy probe inside a transmission electron microscope,and Joule heated to high temperatures.At high temperatures and under electron beam irradiation,the few-layer graphene sheets were removed layer-by-layer in the viewing area until a monolayer graphene was formed.The layer-by-layer peeling was initiated at vacancies in individual graphene layers.The vacancies expanded to form nanometer-sized holes,which then grew along the perimeter and propagated to both the top and bottom layers of a bilayer graphene joined by a bilayer edge.The layer-by-layer peeling was induced by atom sublimation caused by Joule heating and facilitated by atom displacement caused by high-energy electron irradiation,and may be harnessed to control the layer thickness of graphene for device applications.

关键词： Graphene sublimation in situ electron microscopy vacancy hole bilayer edge

Deposition and characterization of Pd-Ti thin film by sublimation

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Radiation Detection Technology and Methods 2020年第4期4卷 465-471页

作者： Zhang Zhiwei Yang Yuchen Ma Yongsheng Wang Xujian Liu Baiqi He Ping Institute of High Energy Physics Chinese Academy of SciencesBeijing 100049China University of Chinese Academy of Sciences Beijing 100049China

Introduction Pd/Ti double-layer thin film as non-evaporable getter(NEG)was deposited by sublimation,and its activation temperature was as low as 100℃.The Pd film was deposited in situ after Ti deposition to ensure no oxidization on Ti film.Pumping speed test and characterization method The pumping speed of the coated pipe was measured by a pumping speed test system.The sticking factor was calculated by Molflow.The surface morphology was observed by a scanning electron microscope(SEM).The chemical composition of the film was measured by an energy-dispersive spectrum inbuilt with the SEM.The crystalline structure of the film was measured using grazing incidence X-ray diffraction.Conclusion It was found that the pumping performance of the Pd/Ti film still remained high after 15 times of activation.The maximum pumping speed after heating at 100℃for 24 h was 1.1 L/s cm^(2)and 0.49 L/s cm^(2)for H_(2)and CO,respectively.It can be concluded that the key to reducing the activation temperature of NEG materials is to enhance the oxidation resistance of the surface of NEG.

关键词： Pd/Ti film Low activation temperature sublimation Non-evaporable getter Ultra-high vacuum

In situ synthesis of a porous high-Mn and high-Al steel by a novel two-step pore-forming technique in vacuum sintering

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Journal of Materials Science & Technology 2020年第4期39卷 82-88页

作者： Chuanbing Zhuang Zhigang Xu Shangyu Huang Yu Xia Chuanbin Wang Qiang Shen Hubei Key Laboratory of Advanced Technology for Automotive Components Wuhan University of TechnologyWuhan 430070China Hubei Collaborative Innovation Center for Automotive Components Technology Wuhan University of TechnologyWuhan 430070China School of Materials Science and Engineering Wuhan University of TechnologyWuhan 430070China State Key Lab of Advanced Technology for Materials Synthesis and Processing Wuhan University of TechnologyWuhan 430070China Hubei Engineering Research Center for Green Precision Materials Forming Wuhan University of TechnologyWuhan 430070China

In this work, a novel in-situ two-step pore-forming process in vacuum sintering(ITPVS) technique combining low-temperature processing to produce open pores through the interdiffusion among the intrinsic components in the base steel, and subsequent high-temperature processing to further improve the porosities by the sublimation of Mn via previously formed open pores, was proposed to produce a lab-scale porous Fe Mn Al steel. For the first time, a high-Mn and high-Al steel with open and overall porosities of ~59.6 vol.% and ~63.7 vol.%(percent in volume, vol.%) was synthesized by isothermal holding of the quaternary elemental Fe/Mn/Al/C powder mixture at 640℃ for 1 h and the subsequent sintering at 1200℃ for 1 h. Elemental Al partly incorporated into/reacted with α-Fe and α-Mn after sintering at640℃ for 1 h, leading to the overall and open porosities promoting by ~26.6 vol.% and ~25.6 vol.%. After sintering at 1200℃, Fe Mn Al steel with increased porosities mainly comprising of austenite and α-Fe obtained. The compression strength and corresponding strain of the 1200℃-sintered porous specimen without crack on the surface was ~75 MPa and ~25%. The ITPVS technique takes advantage of using the intrinsic components like Al, Mn and Fe in steels to produce porous structure. This is beneficial to avoiding the contamination of the Fe Mn Al steel matrix caused by the employment of the foreign pore-forming agents.

关键词： Porous metal High manganese steel Two-stage sintering Reaction-diffusion sublimation method

Comparison of Different Crucible Materials for the Growth of AlN Crystals

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Chinese Journal of Structural Chemistry 2007年第10期26卷 1203-1207页

作者：李娟胡小波王英民宁丽娜姜守振陈秀芳徐现刚王继扬蒋民华 State Key Laboratory of Crystal Materials Shandong University

Choice of crucible material is a key issue during the growth of AIN crystal. The stabilities at high temperature and life-spans of boron nitride （BN） crucible, tantalum （Ta） crucible and tungsten （W） crucible were compared. Tantalum crucible behaved worse at high temperature and life-span was shortened as compared with the other two crucible materials. It was very crisp and easy to crack. In contrast, self-seeded AIN crystals with different morphologies could be obtained at different high temperatures using BN crucible. The boron nitride crucible was stable below 2200 ℃, above which it would decompose. Thus it was unsuitable for the bulky AIN crystal growth. Tungsten crucible could endure the temperatures higher than 2200℃. Unfortunately we could only get AIN polycrystallines using tungsten crucible. After 50- 100 hours＇ run, the crucible was destroyed completely due to the multiple deep cracks. XRD results of destroyed tungsten crucible indicated that the main phases are tungsten carbide and tungsten nitride.

关键词： aluminum nitride crucible sublimation

The ligand coordination approach for improving the stability of low-mercury catalyst in the hydrochlorination of acetylene

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Chinese Journal of Chemical Engineering 2017年第9期25卷 1217-1221页

作者： Xiaolong Xu Haihua He Jia Zhao Bailin Wang Shanchuan Gu Xiaonian Li Institute of Industrial Catalysis of Zhejiang University of Technology State Key Laboratory Breeding Base of Green Chemistry Synthesis Technology

Mercuric chloride supported on activated carbon(HgCl_2/AC) is used as an industrial catalyst for the hydrochlorination of acetylene. Loss of HgCl_2 by sublimating from the surface of activated carbon causes the irreversible deactivation of mercury catalyst and environmental pollution. In this work, a ligand coordination approach based on the Principle of Hard and Soft Acids and Bases(HSAB) was employed to design more stable lowmercury catalyst. The low-mercury catalysts(4% HgCl_2 loading) were prepared by using HgCl_2 and potassium halides(KX, X = Cl, I) as precursors. The HgCl_2-4KI/AC catalyst showed best catalytic stability than HgCl_2/AC and HgCl_2-4KCl/AC in the hydrochloriantion of acetylene. HgCl_2 could form more stable complex with KI,K_2HgI_4 as the main active component of the HgCl_2-4KI/AC catalyst. The characterizations of XRD and EDX analysis illustrated that the active component of HgCl_2-4KI/AC was highly dispersed on the surface of activated carbon.The sublimation rates of HgCl_2 from the catalysts verified that the active component with larger stability constant had better thermal stability. Using Hg(Ⅱ) complexes with high stability constant as the active component may be the research direction of developing highly stable low-mercury catalyst for the hydrochlorination of acetylene.

关键词： Low-mercury catalyst sublimation K2HgI4 Ligand coordination Acetylene hydrochlorination