电弧等离子体法在纳米材料制备中的应用

电弧等离子体法可广泛用于多种纳米粉末、纳米管及纳米薄膜的制备。介绍了电弧等离子体法制备纳米材料的基本工作原理及其在制备各种纳米材料的应用，分析了电弧等离子体法的特点与优势，并展望了其发展前景。     

等离子弧焊接铝及其复合材料研究进展

铝合金及铝基复合材料在船舶、汽车、电子电器、航空航天等许多行业中有着广阔的应用前景。而焊接技术是其广泛应用的技术关键。重点介绍了等离子弧焊技术在铝合金及铝基复合材料中的应用现状,综述了等离子弧焊接接头的微观组织性能、铝合金等离子弧焊数值模拟及新型等离子弧焊的应用,并总结了等离子弧焊接铝合金及铝基复合材料目前存在的主要问题,展望了其未来的发展趋势。     

等离子体喷枪中的射流脉动控制

电弧等离子体喷枪中的射流脉动是影响等离子体喷涂质量的一个非常重要的因素,射流脉动很大程度上是由于等离子体喷枪内电弧分流引起的.分析了电弧分流的机理及其对射流脉动的影响.在此基础上,设计了一种直流等离子体喷枪,采用在阳极和阴极中间设置隔离段的方法来限制电弧的大尺度分流.为了研究电弧分流对射流脉动的影响以及检验新喷枪对射流脉动的抑制作用,而建立了专门的试验装置并进行了相关的试验.试验结果表明,电弧分流和射流脉动的频谱特性是一致的,在使用新等离子体喷枪时,电弧分流明显得到了限制.     

焊接电弧光谱信息测控技术及其应用

焊接电孤中含有丰富的光谱信息,利用这些信息对焊接电弧这一复杂的物理现象进行测试（或称诊断）和控制,是提高和发展焊接技术的一种非常有效的方法,具有重要的理论和实际意义。章论述了这方面研究的进展,阐明了电弧光谱信息的测控原理,介绍了电弧光谱信息在电弧诊断,电弧气氛监控,弧焊区成像,特别是近年来在脉冲MIG焊熔滴过渡控制等方面的应用情况。同时,还介绍了这一技术在等离子体现象中的一些重要应用,并总结出几点基本看法,指出了它的发展方向。     

变极性等离子弧焊铝合金厚板工艺研究

变极性等离子弧焊是一种新型焊接方法,由于等离子弧对焊接工艺和规范参数的变化比较敏感,获得良好焊缝接头的合理规范参数范围窄、裕度小.本文通过工艺试验,探讨了变极性等离子弧焊16mm铝合金厚板的技术可行性,论述了其相对于传统弧焊工艺的优点.     

等离子弧焊接熔池和小孔形成过程数值分析

目的 研究等离子弧焊接穿孔过程中熔池内部的金属流动情况和小孔动态变化过程。方法 通过“传热-熔池流动-小孔”之间的相互耦合关系,建立了等离子弧焊接穿孔过程的数值分析模型,通过VOF方法追踪了小孔界面,采用FLOW-3D软件模拟了等离子弧焊接熔池和小孔的形成过程,定量计算了等离子弧焊接温度场、熔池流场及小孔形状;分析了等离子弧焊接熔池和小孔行为;并通过等离子弧焊接实验数据验证了模拟结果。结果 当焊接时间为0~1.0 s时,小孔深度曲线与熔深曲线几乎相同,小孔底部紧贴熔池底部;在2.8 s以后,小孔深度曲线与熔深曲线有一定距离,小孔深度曲线在一定范围内波动,等离子弧焊接电弧挖掘作用到达极限,电弧压力与其他力达到平衡状态。模拟的焊缝熔深为8.04 mm、熔宽为13.20 mm,实验测得的焊缝熔深为8.00 mm、熔宽为13.42 mm。结论 构建的随小孔动态变化的曲面热源模型和电弧压力模型可以描述等离子弧焊接过程中的电弧热-力分布;模拟出了等离子弧焊接熔池和小孔动态演变过程;模拟得到的等离子弧焊接焊缝形貌与实验测得的焊缝形貌基本吻合。     

Numerical and experimental studies on DC plasma spray torch

One of the challenging problems in the plasma spray technique is reproducibility of the coating quality. This problem is mainly associated with arc fluctuations, which affect the plasma jet temperature and velocity, inside the plasma torch. In this study, 3D numerical models are developed to study the arc behavior inside the torch and effect of arc fluctuations on plasma jet temperature and velocity. Plasma arc is simulated for different operating parameters. Different arc sizes are predicted by using thermo-dynamical principle of minimum entropy production for given torch power. The influence of arc current and gas flow rate on the Ar-N₂ plasma arc characteristics, plasma jet and torch efficiency is presented. Predicted torch efficiencies and arc voltages are comparable with measurements. At the nozzle exit, velocity shows stronger three-dimensional effect than temperature. Plasma jets are simulated using different nozzle exit profiles obtained from the plasma arc model and their temperature and velocity distributions are clarified.     

不同介质水蒸气等离子弧焊接7A52铝合金接头组织性能研究

利用水蒸气等离子弧焊切设备,选择水及不同比例丙酮水溶液等作为电弧介质对7A52铝合金进行焊接,对不同介质水蒸气等离子弧的轴向电弧吹力进行测试,对不同介质水蒸气等离子弧焊接7A52铝合金接头的组织和性能进行分析研究。结果表明:丙酮浓度越大,轴向电弧吹力越大,焊缝熔深越深;随着丙酮的添加,电弧的氧化性降低,有利于提高焊接质量,丙酮含量为40%(体积分数)时焊接接头性能最好,焊缝组织比较均匀;接头热影响区存在不同程度的硬化和软化区域,这与轴向电弧吹力大小、电弧热量传导速度、热影响区组织中强化相转化以及时效状态密切相关。     

直流非转移弧等离子喷枪中电弧的工作特性研究

利用计算机数值模拟技术，采用有限容积方法，针对自制的低能耗、高效率内送粉等离子喷涂设备，对喷枪内部电弧长度及其对流体特性的影响进行了分析研究。结果表明，通过增加进气流量和减少电流的大小，均使得等离子电弧长度增加，阳极弧根位置逐渐向下游移动，但是产生这两种现象的机理以及对气流温度和速度的影响是不同的。     

Effect of gas introduction position on substrate etching by means of Ar-dominated graphite-cathodic-arc plasma beam in μT-FAD

Substrate etching by means of Ar-mixed graphite-cathodic-arc plasma beam was investigated in a newly-developed compact-type μT-FAD. The surface level and roughness change were measured as a function of the Ar gas flow rate, when Ar gas was introduced into the arc generation zone and in the vicinity of the substrate. When Ar gas was introduced to the arc generation zone, the etching rate was lower but the surface was relatively not roughened. When Ar gas was introduced in the vicinity of the substrate, the etching rate was higher but the surface was roughened. At the same gas flow rate (and pressure), the substrate was etched more than three times faster when Ar gas was introduced into the arc generation zone than to the vicinity of the substrate. After measuring the discharge and plasma conditions, the results were considered to be caused by the difference in the amount of plasma transported to the substrate.     

Evaluation of coolant power losses in a thermal plasma arc reactor

Coolant power losses, associated with the operation of a research prototype plasma arc reactor, have been studied experimentally and are described herein. These power losses were measured in four separate fluid-cooled plasma arc reactor zones while plasma power input levels were increased from 4.8 to 13.7 k W. During this increase, all other controllable variables, such as plasma gas flow rate and coolant fluid flow rate were held constant. As operating power levels were increased, the coolant power losses in all four fluid-cooled zones of the plasma arc reactor also increased. However, the relative distribution of power losses changed significantly as the plasma power input levels were increased.     

A new type of arc plasma reactor with 12-phase alternating current discharge for synthesis of carbon nanotubes

A new type of arc plasma reactor with 12-phase alternating current (AC) discharge for synthesis of carbon nanotubes (CNTs) is proposed. A couple of six discharge electrodes by which have mutually electrical connection between them to enlarge the high-temperature regions in the reactor are arranged to three-dimensional locations. A new method of CNTs fabrication by this reactor, which accomplishes to enlarge the suitable growth region in high purity and at high yield, was developed.     

高铬铁基药芯焊丝不同堆焊工艺下的显微组织与性能研究

采用高铬铁基耐磨合金细粉做成药芯焊丝,分别用埋弧堆焊和等离子束堆焊方法制备耐磨试样,对试样的显微组织、硬度分布、耐磨性分别进行研究。实验表明：埋弧堆焊和等离子束堆焊组织具有较明显的区别,埋弧堆焊试样结晶定向性更好,晶粒更细化;埋弧堆焊涂层显微硬度平均值为791 HV0.2,等离子束堆焊涂层显微硬度平均值为774HV0.2,埋弧堆焊涂层的显微硬度分布更均匀;耐干砂磨粒磨损性能埋弧堆焊是等离子束堆焊的1.7倍。     

可控硅脉冲等离子弧焊电源的研制

本文介绍了可控硅脉冲等离子弧焊电源的研制成果。在参考国外多种焊机的基础上,设计了比较理想的控制电路。试验结果表明:该电源具有良好的动特性和静特性,能很好地满足脉冲等离子弧焊的要求。     

Numerical simulation of argon twin torch plasma arc for high heating efficiency

Plasma arc heating technology has been applied for volume reduction through melting of bottom and fly ash, and for producing slag. Recently, a twin torch plasma arc, which has two torches at the cathode and anode, has been anticipated for application to disposal of medical waste because it can treat a wide area and can treat non-conductive materials. For this study, a numerical simulation model of a twin torch plasma arc at opposite electrodes was developed to elucidate high-efficiency heating using a twin torch plasma arc. It is defined as Local Thermal Equilibrium (LTE) and calculated in Magneto-Hydro-Dynamic (MHD) equations. Furthermore, the temperature distribution and conditions of high heating efficiency with the radiation loss were addressed and compared to those of a single torch. The heating efficiency decreases with increasing radiation efficiency because of the temperature increment caused by the current and input power. The radiation efficiency of a twin torch is about 5% higher than that of single torch.     

阴极弧等离子体沉积NbN薄膜

利用磁过滤等离子体沉积装置，结合金属等离子体积技术，在Si基底上分别用动态离子束增强沉积和非增强沉积的方法来制备NbN膜，对二者予以比较，并探讨了非增强沉积过程中基底温度对NbN膜层的影响，温度升高使膜层中N的含量先呈上升趋势，随后又稍微降低，温度升高促进晶粒生长，使晶粒尺寸变大，从室温到约300℃的温度下得到的薄膜在（220）峰表现出很强的择优取向，500℃的沉积温度下，（220）峰变的很弱，（200）峰表现出择优取向，500℃时膜层中得到单一的δNbN相；表面形貌方面，温度越低，薄膜越不完整，在500℃左右才能得到光滑完整的NbN膜。与非增强沉积相比，增强沉积不需加热，在温下就能得到光滑致密的NbN膜，膜层中N的含量更高，且没有明显的择优取向。     

Effect of spatial relationship between arc plasma and substrate on the properties of transparent conducting Ga-doped ZnO thin films prepared by vacuum arc plasma evaporation

The effect of the spatial relationship between the arc plasma flow and the substrate surface on the resulting film thickness and electrical properties is investigated in transparent conducting Ga-doped ZnO (GZO) thin films deposited by a vacuum arc plasma evaporation (VAPE) method. It was found that the resulting electrical properties of GZO thin films produced by a VAPE deposition on a fixed substrate were considerably dependent on both the film thickness and the location on the substrate surface, extending from the area nearest the arc plasma source to that at the opposite end of the substrate in a direction parallel to the arc plasma flow; with GZO thin films deposited with various thicknesses in the range from 20 to 200 nm, the films exhibited a thickness dependence of resistivity that was considerably affected by the location on the substrate surface. The variation of resistivity relative to the location on the substrate surface was related to that of carrier concentration, which is mainly attributed to the distribution of the amount of oxygen reaching the substrate surface. In GZO thin films deposited with a thickness of 30-40 nm at a substrate temperature of 250 °C, a resistivity as low as 4 × 10^− 4 Ω cm was obtained in the area of the substrate nearest the arc plasma source.     

阴极真空弧沉积中靶室第二阳极作用对系统性能的影响

介绍了阴极真空弧沉积中 ,弧源在阴极接地和阳极接地两种不同工作状态下的工作特性。发现阳极接地时 ,因沉积靶室入口法兰的第二阳极作用 ,聚焦磁场对弧源放电稳定性的影响不如阴极接地时明显。因此可以加较高的聚焦磁场 ,从而获得流强较高和较稳定的沉积等离子体束     

由二种烟煤制备碳纳米管的探索性研究

以一种中国烟煤和一种新西兰烟煤为原料,采用电孤等离子体法制备碳纳米管。碳纳米管及其副产物富勒烯烟灰的表征采用扫描电镜（SEM）和红外光谱（FT－IR）等技术。结果表明：电弧放电时的缓冲气体压力对碳纳米管的产率影响很大;在一定的缓冲气压下电极间电流和电极间距各存在一最佳值。在He气压力为0.0665MPa、工作电流为40A条件下进行电弧放电,阴极上棒状沉积物的内芯中碳纳米管含量高达75％以上。基于实验结果,讨论了以煤为原料用电弧等离子体法制备碳纳米管过程中的工艺参数对碳纳米管生长的影响。     

Synthesis of graphene flakes using a non-thermal plasma based on magnetically stabilized gliding arc discharge

Abstract

The use of non-thermal plasma at atmospheric pressure has emerged as a technique for the substrate-free, gas-phase synthesis of graphene nanoflakes (GNFs). In this paper, a non-thermal plasma based on magnetically stabilized gliding arc discharge (MSGAD) was employed to prepare GNFs. The effects of the carbon-containing precursor, plasma gas, and arc current on the GNFs synthesis were investigated. The technique produced GNFs with sizes of 50–200?nm and 1–20 layers, spherical carbon nanoparticles with 10–40?nm diameters, and graphitic particles. The results showed that the formation of GNFs depended on the selection of proper process parameters, such as precursors with a high H/C ratio, an Ar-N₂ plasma gas, a low arc current, a low precursor flow rate, and a suitable plasma gas flow rate. Correlations between the process parameters and the product morphology indicated that abundant H atoms and fewer polycyclic aromatic hydrocarbons were favorable for the formation of GNFs.