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261.
262.
ABSTRACT The traditional importance of hard chromium electroplating in surface engineering is recognised and the key features of this well-established technology are summarised. Despite the high hardness, corrosion protection and wear resistance of chromium electrodeposits, a number of alternative coating compositions and application techniques have been developed for specific applications in tribology. Environmental challenges associated with hard chromium electroplating are highlighted and the need to develop and evaluate alternative coatings is stressed. Key examples of the alternative coatings are described, including their method of application, microstructure and tribological performance in controlled service environments. Research needs requiring rapid development are highlighted. A summary is given of the most competitive coatings and those having the potential to match the performance of hard chromium in selected applications are identified. 相似文献
263.
Surface morphology and photoluminescence properties of ZnO thin films obtained by PLD 总被引:2,自引:1,他引:2
ZnO thin films on Si(111) substrate were deposited by laser ablation of Zn target in oxygen reactive atmosphere, Nd-YAG laser with wavelength of 1 064 nm was used as laser source. XRD and FESEM microscopy were applied to characterize the structure and surface morphology of the deposited ZnO films. The optical properties of the ZnO thin films were characterized by photoluminescence. The UV and deep level (yellow-green) light were observed from the films. The UV light is the intrinsic property and deep level light is attributed to the existence of antisite defects (Ozn). The intensity of UV and deep level light depends strongly on the surface morphology and is explained by the surface roughness of ZnO film. A strongly UV emission can be obtained from ZnO film with surface roughness in nanometer range. 相似文献
264.
S. Tsipas 《Surface & coatings technology》2007,201(8):4489-4495
Ferritic steels are usually used in boiler or supercritical steam turbines which operate at temperatures between 600 and 650 °C under pressure. Protective coatings are often applied in order to increase their oxidation resistance and protect them against degradation. In this study, new Al-Mn protective coatings were deposited by CVD-FBR on two ferritic steels (P-92 and HCM12). The initial process parameters were optimized by thermodynamic calculations using Thermo-Calc software. Then, those parameters were used in the experimental procedure to obtain Al-Mn coatings at low temperature and atmospheric pressure. Co-deposition was achieved at moderate temperatures in order to maintain the substrates' mechanical properties. The coatings' microstructure and phase constitution was characterized. Fe-Al intermetallic coatings containing Cr and Mn were obtained. The phase constitution is discussed with reference to the Fe-Al-Mn ternary phase diagram. The effect of diffusion heat treatment on the phase transformations was investigated. 相似文献
265.
ZHANG Yujuan YAN Pengxun WU Zhiguo ZHANG Pingyu 《稀有金属(英文版)》2005,24(4):370-375
Titanium nitride (TIN) films with nanostructure were prepared at ambient temperature on a (111) silicon substrate by the filtered cathodic arc plasma (FCAP) technology with an in-plane "S" filter. The effects of deposition parameters on the grain size, texture and nano-hardness of the films were systematically investigated. The grain size was obtained through calculation using the Scherrer formula and observed by TEM. The results of X-ray diffraction and electron diffraction indicated that increasing either negative substrate bias or argon flow promoted the formation of (111) preferred orientation. High argon flow leads to biaxial texture. The micro-hardness of the TIN films as a function of grain size showed a behavior according to the Hall-Petch relation under high argon flow. 相似文献
266.
267.
The experimental researches on the chemical deposition of Ni-Mo-P amorphous alloys were carried out by adding Na2 MoO4 into acidic solutions. The optimum technology conditions were obtained by orthogonal design experiments. The structures and the relationship between compositions and their thermal stability were studied by energy spectrum (EC), scanning electron micrograph and X-ray diffraction spectrum. Compared with Ni-P amorphous alloys, the Ni-Mo-P amorphous alloys have high crystallization temperature and thermal stability, and the hardness reaches its peak when the annealing temperature is 500 ℃. With the increase of the heat treatment temperature, the surface morphology of the alloys changes. 相似文献
268.
Halloysite template, a ceramic substrate, is of a hollow cylindric structure, on which the fine Pd nanoparticles are uniformly formed by the reduction of palldate chloride to initiate electroless deposition. The electroless deposition of Ni is catalyzed by the Pd particles, which results in a uniform layer of Ni-P alloy on halloysite. The alloy is of a nanocrystalline structure, of which the average diameter is about 6 nm. After being heat-treated at 400 ℃, it contains both Ni and Ni12P5 crystal, meanwhile, the Ni crystal gets larger with an average size of 51.9 nm.The content of phosphorous in the Ni layer has a great influence on crystal structure. The metallized halloysite has a higher inherent coercive force, and a much lower saturation magnetization in its as-plated state, while after heattreatment, the inherent coercive force decreases drastically. These magnetic properties have great relationship with the superparamagnetism of Ni nanocrystalline and the stress anisotropy in Ni layer. 相似文献
269.
NaCl在A3钢大气腐蚀中的作用 总被引:2,自引:0,他引:2
研究了温度为25℃、相对湿度为80%时NaCl对A3钢大气腐蚀的影响.结果表明,A3钢腐蚀失重随NaCl沉积量的增加而增加,同时随暴露时间的延长也呈增加趋势;但暴露一定时间后,腐蚀失重增加趋缓.采用扫描电镜(SEM/EDAX)及光电子能谱(XPS)对腐蚀形貌及产物成分进行了分析,腐蚀表面呈现不均匀的凹凸形貌,腐蚀产物上有细微裂缝.探讨了该条件下A3钢的大气腐蚀过程. 相似文献
270.
反应溅射制备AlN薄膜中沉积速率的研究 总被引:14,自引:2,他引:14
通过对浅射过程中辉光放电现象及薄膜沉积速率的研究,发现随着氮浓度的增大,靶面上形成一层不稳定的AlN层,由于AlN的溅射速率远小于Al,从而使薄膜的沉积速率显著下降。同时还研究了其它溅射参数对薄膜沉积速率的影响。结果表明:随靶基距的增大靶功率的减小,不同程度引起沉积速率的下降;随着溅射气压的增大,最初沉积速率不断增大,当溅射气压增大到一定程度时,沉积速率达到最大值,之后随溅射气 压的增大,又不断减小。 相似文献