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为了改善纳米复合镀层的物理、力学性能,以电泳-电沉积工艺制备了具有较高纳米Al2O3含量的Ni-Al2O3纳米复合镀层.用SEM、TEM、显微硬度计等对复合镀层的表面微观形貌、显微硬度以及耐磨性能进行了分析;探讨了电泳液中α-Al2O3微粒浓度、电沉积电流密度对复合镀层表面微观形貌、显微硬度及其与基体的结合力的影响.结果表明:α-Al2O3纳米粒子弥散分布于镀层之中,并对基质金属晶粒产生细化作用;电泳液中α-Al2O3微粒浓度对复合镀层表面微观形貌影响较大,电沉积电流密度对微观形貌无明显影响;随着电泳液微粒浓度和电沉积电流密度的增大,复合镀层显微硬度均呈下降趋势,在电泳液微粒浓度8 g/L,电沉积电流密度0.5A/dm2时,复合镀层具有最大显微硬度442 HV,较纯镍镀层有明显提高.镀层中微粒体积分数约为30%时,镀层的耐磨性能及与基体的结合性能最为优异. 相似文献
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α-Al2O3含量对Ni-P复合化学镀层结构及性能的影响 总被引:1,自引:0,他引:1
为改善镍磷复合化学镀层的性能,利用X射线荧光光谱、X射线衍射等分析方法研究了α-Al2O3在镀层中的含量对镀层硬度、耐磨性、孔隙率及镀层结构的影响.结果表明:镀液中α-Al2O3加入量小于1 g/L时,随镀液中α-Al2O3浓度的增大,镀层中α-Al2O3的含量提高,镀层硬度与耐磨性增大,孔隙率略有增加;当镀液中α-Al2O3含量为1 g/L时,镀层中α-Al2O3的含量达到最大值4.8%,镀态硬度达到750 HV,约为Ni-P镀层的1.5倍,耐磨性约是Ni-P镀层的5.0倍;镀态镀层为Ni-P非晶与α-Al2O3晶体组成的复合镀层,经400℃热处理1 h后,镀层晶化为Ni3P晶体、Ni基固溶体,表面生成NiO晶体,镀层中α-Al2O3的结构不变. 相似文献
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Ni-P/纳米Al2O3复合镀层具有良好的耐磨、耐腐蚀性能,但有关脉冲电沉积Ni-P/纳米Al2O3复合镀层的报道较少.采用脉冲电沉积方法制备了Ni-P/纳米Al2O3复合镀层,研究了复合镀层的表面形貌、结构及其在5%NaCl溶液中的耐腐蚀性能,并对300,400,500℃热处理后的复合镀层的显微硬度进行了测试.结果表明:Ni-P/纳米Al2O3复合镀层的耐蚀性优于1Cr18Ni9Ti不锈钢,但比Ni-P合金镀层差;随镀液中纳米Al2O3浓度增大,复合镀层的显微硬度提高,镀液中纳米Al2O3浓度为25.0 g/L时制得的复合镀层的硬度为685.5 HV;Ni-P/纳米Al2O3复合镀层经400℃热处理后硬度最高. 相似文献
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在镀液中添加铁氧体粒子制备Ni-Fe基磁性复合镀层是电沉积技术一个新的发展方向,目前相关研究不多。采用电沉积法在铜片上制备了Ni-Fe-NiFe2O4复合镀层,用电化学方法、金相显微镜及能谱仪研究了镀液中NiFe2O4含量、电流密度、表面活性剂十六烷基三甲基溴化铵(CTAB)等对复合镀层性能的影响。结果表明:复合镀层硬度随镀液中NiFe2O4含量的增加先增大后减小,含量为15 g/L时镀层硬度达370 HV,耐蚀性最好;随电流密度增大,沉积速率加快,镀层显微硬度增加,耐蚀性略有提高;加入CTAB能提高镀层中微粒的复合量,可在较低的电流密度下获得孔隙小、致密度高的镀层,显微硬度也有所提高,但耐蚀性略有下降;在温度为60℃,镀液中NiFe2O4含量为15 g/L,电流密度为5 A/dm2,CTAB含量为0.1%(质量分数)时,可获得性能较好的复合镀层,镀层中NiFe2O4含量较高,均匀致密,微观表面粗糙,无裂纹,与基体结合良好。 相似文献
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镍-磷-氧化铝复合化学镀层的耐磨性研究 总被引:7,自引:2,他引:7
将微粒三氧化二铝与镍-磷化学镀液复合,使三氧化二铝微粒均匀地弥散分布于镍-磷基体中,以提高镀层的耐磨性.着重研究了复合化学镀工艺条件和镀后热处理温度对Ni-P-Al2O3复合镀层耐磨性的影响.试验结果表明:施镀工艺对镀速、三氧化二铝在镀层中的分布有影响,镀后热处理可提高镀层硬度.在pH=5.4、施镀温度为90±2℃、α-Al2O3微粒加入量为5g/L、搅拌速度为400r/min的条件下所得复合镀层加热到400℃、保温1 h后,镀层耐磨性最佳.在相同的磨损条件下,复合镀层的耐磨性比Ni-P镀层提高6~7倍,比45钢淬火态提高30多倍. 相似文献
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添加纳米颗粒的复合镀层较常规单相镀层具有更优异的性能。采用电刷镀技术在2Cr13不锈钢表面制备了Ni/纳米Y2O3复合镀层,研究了纳米Y2O3含量对复合镀层的形貌、成分、硬度和摩擦磨损性能的影响。结果表明:与纯镍镀层相比,复合镀层表面更为平整致密;随着镀液中纳米Y2O3含量的提高,复合镀层的硬度呈现先升高后降低的趋势;当纳米Y2O3颗粒含量为15 g/L时,复合镀层的晶粒最为细小,硬度达到极大值,摩擦系数(0.20)明显低于快速镍镀层(0.38),磨损面的黏着和撕裂现象大大减轻,表现出良好的摩擦磨损性能。 相似文献
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为了提高非晶镀层的硬度,在Ni-P镀液中加入高硬度、高耐磨性的纳米微粒SiC,采用电沉积方法制备了Ni-P非晶纳米SiC复合镀层.研究了工艺温度、电流密度和镀液中SiC浓度对非晶纳米复合镀层中P含量和SiC纳米颗粒分布的影响,并用扫描电镜对镀层表面进行了观察,通过纳米显微力学探针测量了镀层硬度.结果表明:随电流密度增大和镀液中SiC含量的增加,镀层中纳米SiC的复合量增加;镀液温度在60℃时,镀层中SiC含量最大,复合镀层的硬度显著提高,可达到7.4 GPa,比普通的Ni-P非晶镀层大为提高. 相似文献
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介绍了一种新型的凝胶成型法来制备多孔羟基磷灰石支架材料.利用体视显微镜等对制备的多孔羟基磷灰石孔洞结构进行观察.结果表明这种方法可以很好地控制多孔支架材料的孔洞结构与大小.孔分布均匀且内部连通,孔径在300μm~500μm之间.体外模拟试验表明羟基磷灰石具有良好的生物相容性,这种孔洞结构的特点更有利于骨细胞的生长.对压缩性能和孔隙率的测定结果表明,压缩强度和孔隙率随不同工艺参数的变化而变化. 相似文献
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《工程(英文)》2020,6(7):778-788
A new era of electricity is dawning that combines the decarbonization of the grid with the extensive electrification of all sectors of society. A grid as smart as the internet is needed to harness the full potential of renewables, accommodate technology disruptions, embrace the rise of prosumers, and seamlessly integrate nano-, mini-, and micro-grids. The internet is built upon a layered architecture that facilitates technology innovations, and its intelligence is distributed throughout a hierarchy of networks. Fundamental differences between data flows and power flows are examined. The current operating paradigm of the grid is based on the conviction that a centralized grid operator is necessary to maintain instantaneous power balance on the grid. A new distributed paradigm can be realized by distributing this responsibility to sub-grids and requiring each sub-grid to maintain its net power balance. A grid as smart as the internet based on this new paradigm, as well as a hierarchical network structure and a layered architecture of operating principles, is presented. 相似文献
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A 'green' chitosan-silver nanoparticle composite as a heterogeneous as well as micro-heterogeneous catalyst 总被引:1,自引:0,他引:1
In this paper, we report on the catalytic activity of a new metal nanoparticle-polymer composite consisting of Ag nanoparticles (NPs) and environmentally friendly ('green') chitosan. The polymer (chitosan) not only acted as the reducing agent for the metal ions, but also stabilized the product NPs by anchoring them. The majority of the particles produced in this way had sizes less than 5?nm. The catalytic activity of the composite was investigated photometrically by monitoring the reduction of 4-nitrophenol (4NP) in the presence of excess NaBH(4) in water, under both heterogeneous and micro-heterogeneous conditions. The reaction was first order with respect to the concentration of 4NP. We also observed that the apparent rate constant, k(app), for the reaction was linearly dependent on the amount of Ag NPs present in the composite. Moreover, the turn-over frequency (TOF) of the catalyst was found to be (1.5 ± 0.3) × 10(-3)?s(-1), when the reaction was carried out under heterogeneous conditions. The Ag NPs in the composite retained their catalytic activities even after using them for ten cycles. Our observations also suggest that the catalytic efficiency under micro-heterogeneous conditions is much higher than under heterogeneous conditions. Thus the composite we have represents an ideal case of an environmentally friendly and stable catalyst, which works under heterogeneous as well as micro-heterogeneous conditions with the advantage of nanoscopic particles as the catalyst. 相似文献
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Sofian M. Kanan Marsha C. Kanan Howard H. Patterson 《Current Opinion in Solid State & Materials Science》2003,7(6):443-449
Nanoclusters of silver ions, dicyanoaurate ions, and dicyanoargentate ions doped in zeolite hosts have been prepared. Luminescence, Raman, and FT-EXAFS spectroscopies along with extended Hückel calculations indicate the formation of silver and [M(CN)2−]m (M=Au and Ag) oligomers in the zeolite host. The silver and gold nanoclusters in zeolites enhance the photodecomposition rates of NOx, malathion, and carbaryl when compared to the pollutant's behavior in the absence of silver doped zeolites with the observed rate increase attributed to excimer and exciplex formation. 相似文献
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文章论述企业要摆脱困境,在竞争中立于不败之地,必须不断推出新产品,满足消费者日益发展的需要。新产品的来源,一是靠自己开发,二是靠外部引进,三是引用科研部门的研究成果,将其转化为产品。研究成果的转化,如何更好地体现工效?作者建议强化科研与生产融合、开展成果与产品的工效学评价,使科研、生产、商业流通形成一体化,实现良性循环 相似文献
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Mission success with components not as good as new 总被引:1,自引:0,他引:1
Winfrid G. Schneeweiss 《Reliability Engineering & System Safety》1996,52(1):45-53
It is shown how the probability of mission success can be determined for cases of components which are not as good as new at the beginning of a mission and are not repaired during the mission. After a short definition of the appropriate conditional distribution functions of components lives, a few typical examples of plausible missions for redundant systems are discussed. Among these are such that are time-critical or—concerning flights—space-critical. Since only (advanced) probabilistic reasoning is used, there are no limitations as to the types of life distributions. 相似文献
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分析了我国加入WTO后包装业发展所面临的机遇和挑战,指出了包装业应从转变观念、把企业生产经营的立足点转向国际国内两个市场,抓紧创新改革,实现技术升级,努力增加出口等方面迎接挑战。 相似文献