电沉积铁镍钨合金性能研究

钨合金沉积机理至今未得到合理的解释.采用循环伏安法研究了柠檬酸铵盐体系中电沉积铁镍钨合金的规律,分析了主盐浓度、pH值、电流密度、温度对铁镍钨合金镀层组分及阴极电流效率的影响.结果表明,在pH值恒定为8的条件下,镀层中钨和铁的含量受各因素影响的趋势是一致的,随溶液中铁盐、钨盐、柠檬酸盐的含量、电流密度及温度的增加而增加;镀层组分受pH值的影响较大,镀层中钨含量值在pH值为6时最大.根据X射线衍射结果可知,铁镍钨镀层随着钨含量的增加,由纳米结构转变为非晶态结构.     

电沉积钨及钨合金涂层的研究进展

金属钨及含钨涂层具有优良的性能,如高熔点、高硬度、良好的化学稳定性和较低的热膨胀系数,在多个领域被广泛应用,金属钨及含钨涂层有很多制备方法,其中电沉积法具有重要的地位。综述了熔盐电沉积钨涂层及溶液电沉积钨合金涂层的研究进展,并展望了熔盐电沉积钨涂层及溶液电沉积钨合金涂层的发展趋势。     

脉冲电沉积Ni-W-P合金工艺的研究

为了研究Ni-W-P合金脉冲电沉积中脉冲参数对镀速和镀层中钨、磷含量的影响以及对镀层耐蚀性和硬度的影响,采用称重法、硫酸浸泡法、日本岛津EPMA-1600型电子探针以及HX-1型显微硬度计对Ni-W-P合金工艺进行了研究.结果表明,镀层的沉积速率、镀层成分及镀层的性能都随脉冲频率和占空比的变化而变化;Ni-W-P镀层的脉冲电沉积速率比直流电沉积大,脉冲镀层的耐蚀性和硬度都优于直流镀层,其耐蚀性还优于1Cr18Ni9Ti不锈钢.本工艺操作方便,镀层性能稳定.     

喷射电沉积多孔镍

采用喷射电沉积方法,分别选择不同的电流密度、喷射流量和两极间距及电沉积时间进行试验,分析了各试验参数变化对多孔镍形貌的影响规律,并用图形处理软件ImageJ对多孔镍的孔隙率和相对密度进行分析,找出了最佳试验参数。结果表明：适当大的电流密度、小的喷射流量、适中的喷射间距更有利于形成性能和形貌良好的多孔镍。     

射频PECVD高速沉积微晶硅薄膜

本文采用射频等离子体增强化学气相沉积(RF-PECVD)技术高速沉积微晶硅薄膜。系统研究了射频功率、气体总流量、沉积气压、硅烷浓度等沉积参数对薄膜沉积速率和晶化率的影响。通过沉积参数的优化,使微晶硅薄膜沉积速率达到了3/s左右。     

半导体CdTe薄膜电化学沉积研究

本文研究半导体ＣｄＴｅ薄膜在ＩＴＯ透明导电玻璃基底上的电化学沉积。分析了电化学沉膜过程以及反应机理，对不同电参数下沉积膜进行了性能表征，研究了温度、沉积电压等参数对膜性能的影响，探讨了制备颗粒细小、均匀性好并具有一定择优取向的ＣｄＴｅ薄膜的方法。     

沉积电压对电泳沉积成膜均匀性的影响

沉积电压是电泳沉积工艺的重要参数之一。为研究其对电泳沉积成膜均匀性的影响,对带电粒子的电泳过程进行理论分析,并结合COMSOL多物理场接口,得出电泳过程的仿真图。结果显示:施加电压增大,流场流速增加,但电极间形成的流场相对均匀,膜层的均匀性也较好。沉积电压不高于100 V时,极间形成的均匀流场并不影响粒子均匀沉积;电压高于100 V时,极间形成的明显不均匀流场会影响粒子的运动与沉积,从而降低了膜层的均匀性。     

喷射沉积过程的理论模型

描述了喷射沉积过程原理以及影响沉积体毛坯形状、组织和性能的关键问题,介绍了喷射沉积过程的理论模型,通过理论模型的描述使我们更加了解喷射沉积过程,以便更好地握各种实验参数,使产品的质量得到更好的提高。     

用化学气相沉积方法在石墨表面沉积钨涂层的研究

研究了在一定温度的石墨基体表面上用化学气相沉积钨涂层的方法.通过调节氢气、氯气的气流量,控制流量比,得到了具有一定厚度、晶粒均匀致密的钨涂层,并对试验中仍需解决的问题做了讨论.     

Fe—10Ni合金沉积条件的研究

研完了从酒石酸盐溶液中沉积Fe-10Ni合金,并且确定了镀层的组成和沉积条件之间的关系。同时发现工艺参数对所研究的铁镍体系的影响作用与低铁高镍体系不尽相同,但沉积机理仍属于异常共沉积。     

Hardfacing by chemical vapor deposition of components used in coal gasification units

The Bureau of Mines, as part of an interagency agreement with the Energy Research and Development Administration, is investigating the feasibility of hardfacing the critical surfaces of valves and similar devices by chemical vapor deposition. The objective is to increase the life of these components in the abrasive and erosive environment existing in coal gasification units. Various chemical vapor deposition materials such as the refractory metals, carbides and nitrides were considered for this application and are undergoing laboratory investigation and evaluation. The first hardfacing material investigated was tungsten because of the Bureau's previous experience with this material in lining rocket nozzles. Laboratory research indicated that adherent tungsten coatings could not be obtained on the stainless and carbon steels used in value construction unless they were first electroplated with a thin layer of nickel. Tungsten was deposited by hydrogen reduction of tungsten hexafluoride at temperatures ranging from 450 °C to 650 °C. A large reaction chamber 20 in (0.51 m) in diameter with a rotating gas-dispersion apparatus was fabricated. The large unit was used to coat carbon steel valve seats of inside diameter 10 in (0.25 m) with tungsten, and heating of the ball valve seats to reaction temperature was done by induction. Successfully coated valve seats are undergoing evaluation in the low Btu coal gasification pilot plant at the Morgantown Energy Research Center, Morgantown, W. Va. Results of completed and ongoing chemical vapor deposition research are presented.     

Terahertz Emission from a Monolayer Tungsten Diselenide Surface

Technical Physics Letters - Parameters of terahertz (THz) emission in two-dimensional (2D) tungsten diselenide (WSe2) film grown by chemical vapor deposition from the gas phase have been studied...     

Monolayer Tungsten Disulfide (WS2) via Chlorine‐Driven Chemical Vapor Transport

Large‐scale production of high‐quality tungsten disulfide (WS₂) monolayers is a prerequisite for potential device applications using this promising transition metal dichalcogenide semiconductor. The most researched technique is chemical vapor deposition, typically involving the reaction of sulfur vapors with tungsten oxide. Other techniques such as physical vapor deposition have been explored with some success, but low vapor pressures make growth difficult. This study demonstrates a growth process that relies on halide‐driven vapor transport commonly utilized in bulk crystal growth. Using a small amount of sodium chloride salt as a source of chlorine, nonvolatile WS₂ can react to form gaseous tungsten chloride and sulfur. With an open tube system, a controlled reaction generates mono and few‐layer WS₂ crystals. Optical and physical characterization of the monolayer material shows good uniformity and triangular domains over 50 µm in length. Photoluminescence transient measurements show similar nonlinear exciton dynamics as exfoliated flakes, attributed to multiparticle physics. Requiring only the powder of the desired crystal and appropriate halide salt as precursors, the technique has the potential to realize other layered materials that are challenging to grow with current processes.     

钨涂层的几种沉积制备技术研究进展

难熔金属钨具有高强度、低蒸汽压、无化学腐蚀性等优点,被选为核聚变堆面向等离子体材料。通过各种工艺手段将钨涂覆在基体材料表面,是制作面向等离子体部件的新技术。综述了国内外几种钨涂层的制备工艺,主要包括:气相沉积法、等离子喷涂法以及熔盐电镀,介绍了其各自的优缺点,指出离子液体电沉积技术在室温下就可以完成金属薄膜的制备,值得进一步探索其工程化应用。     

适用于TERS系统的金修饰钨丝探针制备和研究

提出了一种适用于针尖增强拉曼光谱(TERS)系统的金修饰钨丝探针,研究了其制备方法。有限元仿真设计了针尖的形状为内弧形针尖,并进行二氧化硅粘结层和金颗粒外层双镀膜结构纳米修饰;通过调节实验室自主研制的电化学腐蚀探针装置的溶液浓度、电机位移和浸入深度制备符合形状要求的钨丝针尖;在此基础上,通过电感耦合等离子体化学气相沉积技术(ICP-CVD)进行二氧化硅涂层镀制,电子束加热物理气象沉积技术(EB-PVD)进行金涂层镀制。最终完成该探针制备,双层镀膜后针尖曲率半径达30~80nm,可用于TERS研究。     

Growth of tungsten oxide nanorods with carbon caps

Hybrid nanostructures consisting of tungsten oxide nanorods with mushroom-shaped carbon caps were grown on electrochemically etched tungsten tips by thermal chemical vapor deposition with methane and argon. These nanorods grow along the radial direction and are very straight and smooth. Electron microscopy revealed a dominant diameter and length of approximately 50 nm and approximately 0.6 microm, respectively. High-resolution transmission electron microscopy (HRTEM), and electron energy loss spectroscopy (EELS) revealed the presence of crystalline monoclinic W18O49 in the nanorods, and the cap was entirely amorphous carbon. A plausible growth mechanism involves the reduction of tungsten oxide WO3, present on the tungsten surface, by methane at 900 degrees C.     

Reaction mechanism discrimination using experimental film profiles in features

Film profiles in features on patterned substrates are employed as a tool to test proposed reaction mechanisms for low pressure chemical vapor deposition processes. Simulated film profiles in long trenches generated using EVOLVE, a physically based deposition process simulator, are compared to experimental film profiles to determine whether a particular mechanism or rate form should be rejected. We consider two examples: (1) silicon dioxide deposition from tetraethoxysilane (TEOS), and (2) tungsten deposition from hydrogen reduction of tungsten hexafluoride. Of three proposed mechanisms for the deposition of silicon dioxide from TEOS, we find that the mechanism in which TEOS undergoes heterogeneous decomposition with inhibition by a strongly adsorbing byproduct provides the best fit to the experimental profiles. In the second example, we demonstrate that a mechanism that assumes a single rate limiting step is apparently not valid for tungsten depositions involving features that close. A semi-empirical rate expression is presented which can be used to simulate depositions up to and beyond feature closure.     

化学气相沉积制备纳米结构碳化钨薄膜

采用氟化钨(WF6)和甲烷(CH4)为前驱体,采用等离子体增强化学气相沉积(PECVD)方法制备具有纳米结构的碳化钨薄膜。采用SEM、XRD、EDS等方法表征了碳化钨薄膜的形貌、晶体结构和化学组成。通过表征,表明在前驱体混合气体中的甲烷与氟化钨气体的流量比(碳钨比)为20、基底温度为800℃的条件下得到的碳化钨薄膜是由直径为20～35nm的圆球状纳米晶构成。通过分析影响薄膜的晶体结构、化学组成的因素后,认为要得到具有纳米晶结构的碳化钨薄膜,主要应控制前驱体气体中的碳钨比以及基底温度。     

A hot-wire chemical vapor deposition (HWCVD) method for metal oxide and their alloy nanowire arrays

A concept for synthesizing nanowire arrays of transition metal oxides and their alloys using hot wire chemical vapor deposition (HWCVD) is discussed. Here, unlike conventional HWCVD, the hot filaments act as the source of the metal for the synthesis of one dimensional nanostructures. In the present concept, the chemical vapor transport of metal oxides generated by heating the filaments in low amounts of oxygen, onto substrates maintained at lower temperatures leads to the formation of metal oxide nanowires. Experiments performed using tungsten and molybdenum filaments showed that the nucleation density of the resulting metal oxide nanowires could be varied by varying the substrate temperature. Experiments performed using a magnesium source inside the reactor, in addition to tungsten filaments, resulted in the formation of MgWO₄ nanowires. This clearly indicates the possibility of either doping the metal oxide nanowires or alloying during synthesis.     

Growth characteristics of copper of tungsten grown through cementation,vapor deposition and electroplating

The growth characteristics of thin copper deposits grown through cementation, electrodeposition and vapor deposition were evaluated through imaging the coated samples in the field ion microscope at 78 K utilizing a 90% He-10% Ne gas mixture. Although the thicknesses of overgrowths were found to be varied with the method and time of deposition, copper in thin overgrowths (less than approximately 50 atom layers) was observed to grow epitaxially on the tungsten substrate surface. In thicker layer growths the epitaxial growth was found to change to a misfit zone with excessive defect structures followed by a polycrystalline copper arrangement. A prominent feature of these thick overgrowths was observed to be their instability under field-induced stresses of the field ion microscope imaging, thus rendering a layer-by-layer evaluation through the three-zone arrangement quite difficult.The initial tungsten surface was recovered upon controlled field evaporation only in the vapor deposition experiments while in the electroplating and cementation experiments the tungsten surface recovered was quite different from the original substrate imaged, thus indicating that an initial dissolution followed by deposition of copper had taken place in the electroplating and cementation processes. In spite of this initial surface reaction, the copper overgrowths were found to be deposited epitaxially. The observed epitaxy of the face-centered cubic copper on body-centered cubic tungsten substrate end forms at thin coverages was consistent with earlier studies of vapor deposition utilizing the copper overgrowth- tungsten substrate system.