高功率CO2激光焊接等离子体的控制

本文分析了高功率CO2激光焊接等离子体的形成机理,系统地总结了等离子体的控制方法,讨论了辅助气体对等离子体的作用。     

超级微波消解-碰撞池-电感耦合等离子体质谱法测定氮化铝粉中钠钨铁锌钛锰

作为制备氮化铝材料的原料,氮化铝粉体中的杂质金属元素含量会对氮化铝制品的导热和介电性能产生重要影响。实验采用硫磷混酸以超级微波消解法处理样品,解决了氮化铝粉难以溶解完全的问题。选择²³Na、¹⁸²W、⁵⁴Fe、⁶⁶Zn、⁴⁶Ti和⁵⁵Mn为待测同位素,控制氦气流量为1.52 mL/min、以氦气碰撞池模式(CCT mode)消除质谱干扰,用50 μg/L ⁸⁹Y校正²³Na、⁵⁴Fe、⁶⁶Zn、⁴⁶Ti、⁵⁵Mn,用50 μg/L ¹⁸⁵Re校正¹⁸²W,建立了碰撞池-电感耦合等离子体质谱法(ICP-MS)测定钠、钨、铁、锌、钛、锰6种杂质金属元素的方法。在优化的实验条件下,6种元素的检出限为0.03~0.64 mg/kg,定量限为0.10~2.13 mg/kg。采用实验方法对氮化铝粉样品进行测定,6种元素测定结果的相对标准偏差(RSD,n=6)均小于4%,加标回收率为96%~103%。采用电感耦合等离子体原子发射光谱法(ICP-AES)和石墨炉原子吸收光谱法进行方法对照试验,测定结果与实验方法基本一致。     

Absorption of electromagnetic waves by the dust particles in a plasma

Inthispaperwestudytheabsorptionofelectromagneticwavesbythechargeddustgrainsimmersedinambientplasma.Theelectromagneticwavepropagationindustyplasmahasbeenahottopicinrecentyears.Mostpaperspublishedsofarfocusontheincreaseofthewavescatteringinadustyplasma[1—4].InthispapertheenergylossoftheincidentelectromagneticwavecausedbyalongitudinalscatteringfieldoftheDebyescatteringispresented.ThephysicalpictureoftheproblemisachargeddustgrainwhichisassumedtobesphericalofradiusasurroundedbyascreeningDebyesphe…     

Summary of US–Japan Exchange 2004: New Directions and Physics for Compact Toroids

Scientists from research institutions in the United States of America and Japan attended a USA Department of Energy sponsored joint international workshop on the subject of Compact Toroids (CT) in Santa Fe, NM, USA in September 2004. We outline here a summary of the topics that were discussed, some of the implications, and new directions that are likely to follow from this research. Experimental, theoretical and computational results were presented. The experimental devices and concepts, along with the theory and computational models comprise investigations of fundamental plasma physics, fusion science, and approaches to fusion energy that require magnetized plasmas.     

Electron temperature control in low-pressure plasmas using a two-mesh-separation technique

Independent control over the electron temperature and ion bombarding flux has been achieved in weakly ionised discharge through the use of two electrically biased meshes. The meshes divide the discharge into two parts; a main RF plasma and dc processing plasma, the latter is sustained through controlled diffusion of particles from the main plasma. By varying the bias to each of the grids separately, and at typical pressures of 2.6 Pa in the processing chamber, the electron temperatures can be varied in the range 0.2-5.6 eV. To an electrically isolated surface, the ion bombarding fluxes can be controlled between 0.2 and 5.4×10¹⁸ m² s⁻¹. This method of electron temperature control, which gives more flexibility than the single grid separation technique, allows ion energies to be varied from 1 to 27 eV, independently of the ion flux. This is useful, both for the fundamental study of plasma-surface interactions and for developing discharges with controlled parameters to tailor the properties of materials such as polymeric surfaces.     

天然气等离子体法制氢技术

传统的天然气蒸汽转化制氢方法在制取氢气的同时,伴随着大量的"温室气体"二氧化碳排放。本文介绍了等离子体技术及其在裂解天然气制氢气和炭黑方面的应用。由分析可知,高温下天然气裂解为氢气和炭黑是一个在热力学上有利的过程,该工艺减少了二氧化碳排放,减轻了环境污染;在产品成本和能耗方面也有竞争力。     

HT-6M托卡马克杂质输运行为研究

以HT -6M托卡马克在欧姆加热条件下的氧、碳杂质空间分布的实际测量结果及该装置背景等离子体的具体特征为基础 ,建立起杂质输运分析程序 ,并由此展开模拟分析 .结果表明 ,该装置氧、碳杂质的浓度分别为 5 %ne和 3 %ne(ne为电子密度 ) ,杂质输运行为是反常的 ;扩散系数为 2 0m2 ·s- 1,有效电荷数Zeff接近 4     

铈钨坯的空心阴极等离子烧结工艺研究

对空心阴极效应的发热机理及空心阴极等离子烧结铈钨坯工艺进行了初步研究。通过合理地控制电流、电压以及气压等影响因素,获得了持续稳定的空心阴极效应,使其阴极达到2500℃以上的高温。将此高温效应用于烧结高熔点材料——铈钨合金,获得了很好的效果。得到的铈钨烧结坯的密度达到17.8 g/cm3,与垂熔烧结方法获得的密度水平相当。     

Observation of an Enhanced Magnetic Helicity Injection Mode by a Rotating Plasma Annulus

Coaxial plasma guns are commonly used to inject magnetic helicity in innovative confinement concepts (ICC’s) for magnetic fusion. One of the key issues in magnetic helicity injection is to maximize the magnetic helicity injection rate. We have identified experimentally an alternative way to increase the magnetic helicity injection rate through rotating plasmas by extending the length of the inner electrode of a coaxial plasma gun so that an additional E × B region interweaves the standard J//B configuration. In the so-called “enhanced helicity injection” mode, the gun voltage is larger compared with the “normal” mode and decays more slowly. Another signature of the enhanced mode is increased edge magnetic field in conjunction with larger edge rotation. The results indicate that tuning plasma rotation is another way to enhance magnetic helicity injection using coaxial plasma guns. An alternative ICC is proposed based on the experimental observations.     

反应等离子喷涂TiN/Ti3O复相陶瓷涂层

采用等离子反应合成技术,制备出了TiN/Ti3O复相陶瓷涂层,并分析了复相涂层的组织及其性能.研究结果表明:复相涂层主要由TiN相组成,并含有少量的钛的氧化物;复相涂层具有典型的层状组织结构,且层与层之间结合较好;制备的复相涂层的韧性得到明显提高,其韧性优于等离子喷涂Al2O3陶瓷涂层;特别是复相涂层具有优于M2钢的耐磨性.