Preparation of Pulse Electrodeposited Ni-B Coating with RSM Software and Evaluation of Its Microhardness and Electrochemical Behavior

Metallurgical and Materials Transactions A - In this study, the electrodeposition parameters were optimized to attain Ni-B alloy coatings with high hardness and corrosion resistance. The optimum...     

Secondary Silicon Carbide Formed in the Interaction of Nanosized Silicon Carbide with Iron Oxide

The characteristics of superfine powder composites formed in the interaction of nanosized silicon carbide with iron oxide in vacuum and argon at 1200 and 1400°C, respectively, are analyzed. Silicon carbide (β-SiC), iron silicide and carbide, silicon oxide, and silicon oxynitride are main components of the powder composites. The lattice parameter of SiC in the powder composites synthesized in the SiC–Fe2O3 system is determined. In the interaction in the SiC–Fe2O3 powder mixture in vacuum, secondary SiC is synthesized with a lattice parameter that corresponds to the standard parameter for cubic β-SiC. The interaction in an argon atmosphere is accompanied by the synthesis of secondary SiC with a decreased lattice parameter. The minimum lattice parameter (0.4336 nm) is 0.6% smaller than the standard parameter for cubic β-SiC. The morphology of the powder composite synthesized in the SiC–Fe2O3 system is studied. The average particle size of the powder composite decreases with increasing weight content of secondary SiC.     

碳化硅复合镍磷合金涂层的组织结构、显微硬度及腐蚀性能研究

镍基复合涂层是一项有望替代电镀铬涂层的先进绿色环保表面处理技术。 本文在铝合金表面制备了纯 Ni、 NiP及其与SiC复合涂层, 利用SEM、 EDS和XRD研究了Ni、 NiP及其复合涂层的微观形貌、 成分与组织结构, 利用显微硬度计与电化学工作站研究了其硬度与耐腐蚀性能。 研究结果表明： SiC 复合电镀纯镍涂层的表面较为 粗糙, SiC 复合电镀镍磷合金涂层中晶粒轮廓明显; 电沉积镍磷合金涂层的相结构包括晶体 Ni2P、 Ni12P5 和非晶 NiP。 铝合金基体表面 Ni-P 合金涂层的显微硬度显著高于纯 Ni 涂层, 引入 SiC 纳米颗粒形成复合涂层可提高其 显微硬度; SiC 颗粒有助于提高复合涂层在氯化钠溶液中的腐蚀电位, 降低腐蚀电流密度, 提高其耐蚀性能。     

Structurization of Reaction-Sintered Silicon Carbide Modified by Chromium Carbide

Powder Metallurgy and Metal Ceramics - The structurization and phase composition of reaction-sintered silicon carbide (RSSC) modified by chromium carbide are examined. When hexagonal silicon...     

Synthesis and Properties of Pulse Electrodeposited Ni-CeO2 Nanocomposite

Ni-CeO₂ nanocomposite coatings were pulse electrodeposited from the Watt??s electrolyte containing different concentrations of nanosized CeO₂ particles (10, 20, 30, 40, and 50?g/L). The microhardness, thermal stability, and corrosion resistance of these coatings were evaluated and compared with those of pure nanocrystalline Ni deposited under the same conditions. The results show that the Ni-CeO₂ nanocomposite coating, synthesized from the electrolyte containing 30?g/L CeO₂, has significantly higher hardness, thermal stability, and corrosion resistance than those of the pure nanocrystalline Ni and other Ni-CeO₂ nanocomposite coatings.     

Filamentary and Tubular Silicon Carbide Nanocrystals

Filamentary crystals and nanotubes of 3C-SiC containing -SiC are prepared. The nanostructures of SiC are synthesized from a mixture of hydrocarbons, chlorosilane and hydrogen in the presence of iron (Fe(CO)₅) at 1250° C. The average nanofilament diameter is 30 nm. The nanotube diameter ranges from 10 to 200 nm.__________Translated from Poroshkovaya Metallurgiya, Nos. 1–2(441), pp. 3–7, January–February, 2005.     

熔盐电沉积硅的基础研究

在FLINAK-Na2SiF6熔盐体系中,以Pt为参比电极、硅钢片为工作电极、石墨为辅助电极,在750℃下,用循环伏安法和计时电位法对Si4+的电化学反应机理和扩散系数进行了研究。结果表明:该熔盐体系进行电沉积硅是可行的,该体系中硅离子的还原为扩散控制的可逆电极过程,且产物不可溶;整个还原过程为Si4++4e→Si0;该熔盐体系中阴极电位不应负于-2V,否则会有Na沉积出来,从而影响沉积层质量;Si4+的扩散系数为:D=5 42×10-11m2/s(C=2 58×103mol/m3)。     

Al-Ti合金电镀镀层的耐蚀性

研究了不同含钛量的Al Ti合金电镀镀层在 0 5mol/LH2 SO4、0 1 %NaCl、3 5%NaCl水溶液中的耐蚀性能 ,80 0℃抗高温氧化性能以及 30 0℃、5%SO2 气氛下的抗硫化性能 ,并测定了镀层的硬度。Al Ti合金镀层在稀H2 SO4及含Cl- 的溶液中具有优良的耐蚀性能以及具有良好的抗高温氧化性能及耐硫化性能。增加镀层中的含钛量 ,则可进一步提高Al Ti合金镀层的耐蚀性。     

碳化硅及其在工业炉行业的应用

本文着重介绍了碳化硅制品的基本技术特性及其在工业炉行业的应用     

Molten Salt Corrosion Resistance of Yttria Stabilized Zirconia Coating with Silicon Carbide Interlayer on High Density Graphite

The high temperature corrosion behaviour of yttria stabilized zirconia (YSZ) coated high density graphite (HDG) with and without SiC interlayer was evaluated in LiCl–KCl molten salt at 600 °C. The YSZ coated HDG samples without interlayer were tested for 50, 250, 1000 and 2000 h and the YSZ coated HDG samples with SiC interlayer were studied for 50, 500, 2000 and 3500 h durations. Characterisation of the corrosion tested samples revealed no delamination or failure of the YSZ coating in both the cases, and insignificant weight gain was observed in all the tested samples in the molten salt. The lamellar morphology of the plasma spray coating was intact even after exposure to molten salt for long duration, implying no corrosion attack of the coating and HDG in the molten salt. SEM cross-section examination confirmed neither coating degradation, nor penetration of molten salt into the HDG substrate. X-ray diffraction and Laser Raman spectroscopic analyses ascertained that no phase change occurred in YSZ after the long exposure in molten salt. Present study confirmed the phase stability and durability of YSZ coating in providing corrosion resistance and protection to HDG for high-temperature molten salt applications.     

低温电沉积硅工艺研究进展

半导体硅的传统制备工艺主要有直拉法、区熔法及气相沉积法等,这些制备工艺都需要在高温下进行,且涉及到大型设备,制备成本较高,操作较为复杂。采用低温电沉积法制备硅具有简单可控、低成本的特点,因而受到了研究者青睐。主要从电极、溶剂的选取及电沉积方法等方面阐述了低温电沉积硅工艺研究现状,同时对低温电沉积硅存在的问题和发展趋势进行了讨论。     

Use of Silicon Carbide Materials in Reduction Smelting of Metallic Silicon and Siliceous Ferroalloys

Metallurgist - Industrial implementation of the method of smelting industrial silicon with some fraction of the reducing agent replaced with silicon carbide is exemplified. The prospects for using...     

硬质合金涂层工艺的研究进展

综述了目前硬质合金制造中化学气相沉积、物理气相沉积和复合涂层3种工艺的研究现状,同时提出了今后的发展方向。     

Formation of Silicon Carbide from Rice Hulls

Abstract

SiC whiskers and particles have been produced from rice hulls. The process involves three major steps: coking in free air, reaction at high temperature in a reducing atmosphere of hydrogen gas, and separation of formed SiC from excess carbon by wet methods. The processing steps are reviewed and the chemistry of the process is discussed. The produced SiC was added to a molten Zn–5%Al alloy to check its potency as a reinforcing material. © 1998 Published on behalf of Canadian Institute of Mining and Metallurgy by Elsevier Science Ltd. All rights reserved.

Resume

Des barbes et des particules de SiC ont été produites à partir d'enveloppes de riz. Le processus implique trois é tapes majeures: cokefaction a l'air libre, réaction à haute température dans une atmosph è re reductrice de gaz hydrogene et separation du SiC forme de l'exces de carbone par des methodès humldes. On revoie les etapes de traitement et on discute de la chimie du processus. On a ajoute le SiC ainsi produit à un alliage fondu de Zn–5%Al afin de verifier son potentiel comme matériau de reforcement. © 1998 Published on behalf of Canadian Institute of Mining and Metallurgy by Elsevier ScienceLtd. All nghts reserved.     

单晶高温合金 NiCoCrAlYTa 涂层高温氧化行为研究

飞机发动机及燃气轮机的发展要求更高的燃气进口温度,从而获得更高的推重比或功率输出,抗氧化MCrAlY涂层在其中发挥至关重要的作用。本文采用含有Ta元素的Amdry997粉末进行超音速火焰喷涂,研究涂层的高温氧化行为,并重点关注Al和Ta元素在涂层内不同相中的分布,及其对涂层与基体元素互扩散行为的影响。研究表明,Ta元素对提高γ'-Ni_3(Al,Ta)相稳定性起到重要作用。     

Self-Propagating High-Temperature Synthesis of Silicon Carbide Nanofibers

Russian Journal of Non-Ferrous Metals - The results of investigations into the organization of the synthesis of silicon carbide fibers in the gas phase using silicon powder, an energy additive of...     

碳化硅制品生产工艺技术改造

针对碳化硅制品生产过程中存在的制约因素,客观分析经济性、实用性,保障生产、节能降耗等各方面的情况,通过创新型的技术改造,碳化硅制品各项经济技术指标显著提高,取得了比较好的经济效益和社会效益。     

Structural Changes during Milling of Silicon Carbide

The kinetics of milling and structural changes during milling of commercial silicon carbide powder in a ball mill lined with hard alloy are studied. Data are provided for the specific surface, x-ray patterns, and infrared spectra. It is shown that milling kinetics are described best of all by an exponential relationship and that milling of silicon carbide powder is accompanied by changes in polytype composition. The x-ray patterns and infrared spectra obtained make it possible to assume that during milling the 15R polytype content in the powder composition decreases while the content of structures with less layering (the 4H polytype and -SiC) increases; in this case the number of absorption bands in the infrared spectra decreases.     

SiC复相陶瓷的强化增韧趋势

SiC陶瓷因其具有优良的性能而广泛应用于军事和民用领域.但陶瓷固有的脆性严重影响了其作为结构材料的应用潜力,因此sic陶瓷的强化增韧成为了近年来研究的热点.综述了siC基复相陶瓷的几种主要强化增韧方式,讨论了其强化增韧机制.采用纳米颗粒、晶须协同强化增韧和特殊技术制备纳米复相陶瓷将是提高SiC基陶瓷性能的有效途径.     

Study of the Corrosion Behavior of Nanocrystalline Ni-P Electrodeposited Coating

The corrosion behavior of electrodeposited Ni-P coating in 5 pct (in weight) NaCl solution has been studied. The microstructure of the Ni-P electrodeposit displayed a layered structure composed of nanocrystalline grains revealed by transmission electron microscopy (TEM). With the increase in polarization potential and bath temperature, the corrosion rate as well as the weight loss was significantly increased. Under observation by a field-emission scanning electron microscope (FESEM), the pitting evolved into larger sizes with a diameter of approximately 30 μm as the temperature and potential were increased to 50 °C and 600 mV_SCE, respectively. Cracks and delamination among the layered structure were found inside the deepened corrosion pit. The increase in surface P content and the trace of the formation of phosphate were also observed by using X-ray photoelectron spectroscopy (XPS) analysis.