Nanocrystalline soft ferromagnetic Ni-Co-P thin film on Al alloy by low temperature electroless deposition

Soft ferromagnetic ternary Ni-Co-P films were deposited onto Al 6061 alloy from low temperature Ni-Co-P electroless plating bath. The effect of deposition parameters, such as time and pH, on the plating rate of the deposit were examined. The results showed that the plating rate is a function of pH bath and the highest coating thickness can be obtained at pH value from 8 to10. The surface morphology, phase structure and the magnetic properties of the prepared films have been investigated using scanning electron microscopy (SEM), X-ray diffraction analysis (XRD) and vibrating magnetometer device (VMD), respectively. The deposit obtained at optimum conditions showed compact and smooth with nodular grains structure and exhibited high magnetic moments and low coercivety. Potentiodynamic polarization corrosion tests were used to study the general corrosion behavior of Al alloys, Ni-P and Ni-Co-P coatings in 3.5% NaCl solution. It was found that Ni-Co-P coated alloy demonstrated higher corrosion resistance than Ni-P coating containing same percent of P due to the Co addition. The Ni-Co-P coating with a combination of high corrosion resistance, high hardness and excellent magnetic properties would be expected to enlarge the applications of the aluminum alloys.     

Crystallization and annealing effects of sputtered tin alloy films on electromagnetic interference shielding

Sn, Al and Cu not only possess electromagnetic interference (EMI) shield efficiency, but also have acceptable costs. In this study, sputtered Sn-Al thin films and Sn-Cu thin films were used to investigate the effect of the crystallization mechanism and film thickness on the electromagnetic interference (EMI) characteristics. The results show that Sn-xAl film increased the electromagnetic interference (EMI) shielding after annealing. For as-sputtered Sn-xCu films with higher Cu atomic concentration, the low frequency EMI shielding could not be improved. After annealing, the Sn-Cu thin film with lower Cu content possessed excellent EMI shielding at lower frequencies, but had an inverse tendency at higher frequencies. For both the Sn-xAl and Sn-xCu thin films after crystallization treatment, the sputtered films had higher electrical conductivity, however the EMI shielding was not enhanced significantly.     

激光打靶同步系统电磁兼容性能研究

用电学理论分析了高速数字同步系统电磁兼容的实施处理方法及晃动补偿法原理.对电场f干扰的屏蔽,采用电导率高的金属Cu或Al材料,其屏蔽反射损耗R理想;对磁场的屏蔽,采用高导磁率的坡莫合金材料,其屏蔽反射损耗R理想;采用EMI滤波器,电容温度系数小、精度高,电感材料呈现的等效电阻R与吸收的干扰频段吻合,达到最大抑制电磁干扰的效率.实验证明这些方法是有效的.     

Growth behavior of electroless Ni-Co-P deposits on Fe

The electroless Ni-Co-P films were deposited on Fe film in plating baths using sodium hypophosphite as reducing agent and nickel and cobalt sulphates as ion source at pH value of 9 and plating temperature from 60 to 85 °C. The effect of the mol ratio of CoSO₄/CoSO₄ + NiSO₄ in plating bath on the growth behavior of electroless Ni-Co-P films was studied. The electroless Ni-Co-P films were characterized by transmission electron microscopy for the microstructure and thickness, and energy dispersive spectrometer for the composition. The results showed that the electroless Ni-Co-P films can be deposited on Fe films without the step of sensitization and activization; the surface of electroless Ni-Co-P film on Fe is quite even; the more the Co²⁺ ion in plating bath, the larger the activation energy and the smaller the plating rate of electroless Ni-Co-P films; and the mol ratio of Co/Co + Ni in film is larger than that in plating bath (with the exception of the film deposited in the bath with 0.9 mol ratio of CoSO₄/CoSO₄ + NiSO₄)     

基于PET基底透明屏蔽膜的制备研究

为满足光学器件透红外屏蔽电磁波的要求,在PET柔性基底上制作了金属网栅透明屏蔽膜.分析网栅参数对其屏蔽效率及透过率的影响,选取结构参数.针对PET基底的柔性特点及其热稳定性,经试验研究优化光刻工艺中的提拉速度、烘烤时间及温度等参数,从而得到高质量的图形结构.采用磁控溅射法制备透明屏蔽膜,通过优化溅射功率、溅射气压等参数使膜/基结合更牢固.最后得到线宽为3μm、周期为250μm的金属网栅透明屏蔽膜.采用分光光度计测得其在300~2 200nm波段的平均透过率为77%;采用屏蔽室法测得其在2~18GHz频段的电磁屏蔽效率为12dB以上.     

Electrodeposition of high corrosion resistance Cu/Ni-P coating on AZ91D magnesium alloy

High corrosion resistance Cu/Ni-P coatings were electrodeposited on AZ91D magnesium alloy via suitable pretreatments, such as one-step acid pickling-activation, once zinc immersion and environment-friendly electroplated copper as the protective under-layer, which made Ni-P deposit on AZ91D Mg alloy in acid plating baths successfully. The pH value and current density for Ni-P electrodeposition were optimized to obtain high corrosion resistance. With increasing the phosphorous content of the Ni-P coatings, the deposits were found to gradually transform to amorphous structure and the corrosion resistance increased synchronously. The anticorrosion ability of AZ91D Mg alloy was greatly improved by the amorphous Ni-P deposits, which was investigated by potentiodynamic polarization curve and electrochemical impedance spectroscopy (EIS). The corrosion current density (I_corr) of the coated Mg alloy substrate is about two orders of magnitude less than that of the uncoated.     

光学窗口电磁屏蔽性能分析与验证

为分析不同基底材料光学窗口电磁屏蔽性能,以Kohin的等效薄膜模型为基础,考虑电磁波在材料2个界面中的多次反射和折射,得到电磁波界面反射系数,利用matlab编写程序计算相同网栅、不同厚度、不同材料的屏蔽效率曲线,分析了厚度和材料对光窗屏蔽效率的影响。为验证仿真数据的准确性,在ZnS基底上制作了周期为500 μm、线宽为15 μm,电阻≤20 Ω的测试样片,测试其在8 GHz～18 GHz频段的电磁屏蔽效能。通过对比可看出:测试与理论计算数据较符合,误差约为2 dB～4 dB,计算数据可以预估光学窗口电磁屏蔽性能,为后续的设计工作提供参考。     

中等导电性材料覆盖的金属腔体的电磁屏蔽效能研究

基于传输线和波导理论, 提出了一种用于计算覆盖中等导电性材料的金属腔体电磁屏蔽效能的解析理论模型, 并通过和全波电磁模拟结果的比较检验了该模型的有效性. 计算分析了屏蔽体屏蔽效能的位置效应和谐振效应. 建议了一种评价导电材料电磁屏蔽效能的方法, 能很好的削弱谐振效应和位置效应的影响, 直接反映出材料本身的电磁屏蔽效能. 关键词： 电磁屏蔽 导电材料 金属腔体 屏蔽效能     

A corrosion resistant cerium oxide based coating on aluminum alloy 2024 prepared by brush plating

Cerium oxide based coatings were prepared on AA2024 Al alloy by brush plating. The characteristic of this technology is that hydrogen peroxide, which usually causes the plating solution to be unstable, is not necessary in the plating electrolyte. The coating showed laminated structures and good adhesive strength with the substrate. X-ray diffraction and X-ray photoelectron spectroscopy analysis showed that the coatings were composed of Ce(III) and Ce(IV) oxides. The brush plated coatings on Al alloys improved corrosion resistance. The influence of plating parameters on structure and corrosion resistance of the cerium oxide based coating was studied.     

Influence of embedded particles on microstructure, corrosion resistance and thermal conductivity of CuO/SiO2 and NiO/SiO2 nanocomposite coatings

Homogeneous CuO/SiO₂ and NiO/SiO₂ nanocomposite coatings containing CuO and NiO nanoparticles in silica matrix were successfully synthesized by sol–gel process on an aluminum alloy substrate, respectively. The evolution of phase and morphology of both nanocomposites was characterized by XRD, SEM, TEM and FTIR. The effect of incorporating various nanoparticles on the corrosion behavior and the thermal conductivity of nanocomposite coatings was investigated by potentiodynamic polarization curve and comparative exponential method. The thermal conductivity as well as the corrosion resistance of nanocomposite coatings was significantly improved by the introduction of metal oxide particles. In comparison with NiO/SiO₂ nanocomposite coatings, CuO/SiO₂ composite coatings displayed lower protective behavior as well as higher thermal conductivity. Experimental results revealed that those improvements can directly be related to the nanocomposite effect and the nature of added nanoparticles.     

脉冲高能量密度等离子体沉积(Ti,Al)N薄膜组织及其性能研究

利用脉冲高能量密度等离子体技术在室温条件下在45＃钢基材表面沉积了高硬度耐腐蚀(Ti, Al)N薄膜. 利用扫描电子显微镜、X射线衍射、X射线光电子能谱、俄歇电子能谱分析了薄膜的显微组织.利用纳米压痕仪测试了薄膜的纳米硬度.测试了薄膜在05mol/L H2SO4水溶液中的耐蚀性. 测试结果表明：薄膜主要组成相为(Ti, Al)N，同时含有少量的AlN,薄膜的纳米硬度高达26 GPa,薄膜具有良好的耐蚀性，与1Cr18Ni9Ti奥氏体不锈钢相比，耐蚀性提高了一个数量级. 关键词： 脉冲高能量密度等离子体 薄膜 纳米硬度 耐蚀性     

Effect of substrates on the properties of p-type ZnO films

Influence of substrates on the properties of p-type ZnO films, which were fabricated by N–Al co-doping technique, was studied. Hall measurement results indicated that ZnO films deposited on common glass substrate were p-type conductivity when Zn:N:Al atomic ratio amounts to 1:3:0.1. However, ZnO films deposited on corning 7059 glass substrate showed n-type conductivity. Secondary ion mass spectroscopy demonstrated that Na content incorporated into ZnO films deposited on common glass substrate was more evident than that of corning 7059 glass. In addition, Hall mobility and conductivity of p-type ZnO thin films deposited on silicon substrate were improved largely.     

Contact improvement of carbon nanotubes via electroless nickel deposition

Individual multi-walled carbon nanotubes (CNTs) were deposited onto microelectrodes and embedded in nickel to achieve low-ohmic contact resistances. Electroless deposition of nickel onto gold/iron, palladium, and cobalt microelectrodes was used to form electrically stable bonds at the interfaces between the electrodes and CNTs. Resistance measurements showed that the contact resistances of the CNTs on gold/iron and palladium were significantly improved by nickel embedding, whereas no further improvement was found for the CNTs on cobalt. Electroless metal deposition is a parallel process providing stable electrical and mechanical contacts between CNTs and metallic microelectrodes. PACS 81.07.De     

颗粒对SiC_w/SiC层状陶瓷电磁屏蔽性能的影响

层状陶瓷材料的电磁屏蔽效能对结构功能一体化层状陶瓷材料的设计具有重要影响。采用流延法与化学气相渗透(chemical vapor infiltration,CVI)工艺相结合制备SiC_w/Si C层状陶瓷,研究碳化硅颗粒(Si C particle,SiCp)、氮化硅颗粒(Si_3N_4particle,Si_3N_4p)对SiC_w/Si C层状陶瓷电磁屏蔽性能的影响。结果表明:SiC_w/Si C层状陶瓷具有较高的电磁屏蔽性能,颗粒的加入有助于提高层状陶瓷的电磁屏蔽性能。颗粒粒径越小,材料的电磁屏蔽性能越好;并且SiCp的电磁屏蔽作用强于Si_3N_4p。     

Nanoporous Al sandwich foils using size effect of Al layer thickness during Cu/Al/Cu laminate rolling

The roll bonding technique is one of the most widely used methods to produce metal laminate sheets. Such sheets offer interesting research opportunities for both scientists and engineers. In this paper, we report on an experimental investigation of the ‘thickness effect’ during laminate rolling for the first time. Using a four-high multifunction rolling mill, Cu/Al/Cu laminate sheets were fabricated with a range of thicknesses (16, 40, 70 and 130 μm) of the Al layer. The thickness of the Cu sheets was a constant 300 μm. After rolling, TEM images show good bonding quality between the Cu and Al layers. However, there are many nanoscale pores in the Al layer. The fraction of nanoscale pores in the Al layer increases with a reduction in the Al layer thickness. The finite element method was used to simulate the Cu/Al/Cu rolling process. The simulation results reveal the effect of the Al layer thickness on the deformation characteristics of the Cu/Al/Cu laminate. Finally, we propose that the size effect of the Al layer thickness during Cu/Al/Cu laminate rolling may offer a method to fabricate ‘nanoporous’ Al sandwich laminate foils. Such foils can be used in electromagnetic shielding of electrical devices and noisy shielding of building.     

环氧树脂基碳纳米复合电磁屏蔽材料研究

基于碳纳米材料有序结构优异的结构与功能特点,研究了其在新型电磁防护材料中的应用,结合环氧树脂与碳纳米有序结构在电磁屏蔽效能和力学性能方面表现出的显著优势,论述了环氧树脂基碳纳米管复合电磁屏蔽材料和碳纳米管有序纳米结构研究,通过电磁仿真优化设计构筑三维导电网络结构,得出8~12 GHz电磁波段屏蔽效能≥82.96 dB的理想结构模型,为环氧树脂基碳纳米复合电磁屏蔽材料研究开发提供了指导,有利于该新型电磁屏蔽材料在国防、国民经济各领域的应用。     

Dielectric properties and EMI shielding efficiency of polyaniline and ethylene 1-octene based semi-conducting composites

The preparation of polyaniline (PAni) was carried out by the oxidative emulsion polymerization of aniline and the semi-conducting composites were prepared by mixing it with a polyolefinic thermoplastic elastomer ethylene 1-octene copolymer (EN). Different electrical properties and electromagnetic interference shielding efficiency (EMI SE) of these composites were measured. The results revealed that the incorporation of PAni in EN increases the conductivity, dielectric constant, dielectric loss and EMI SE. These composites exhibit pressure dependent dielectric properties and may act as pressure sensor. There are increase in AC conductivity and decrease in dielectric constant with the increase in applied pressure on composites. A model correlation between EMI SE and AC conductivity at same frequency for the composites having maximum 40% of PAni was obtained through extrapolation and linear regression analysis, which shows that EMI SE has linear relationship with AC conductivity. Because of their semi-conductive behavior these composites can find application as antistatic materials and electromagnetic interference (EMI) shielding material.     

AlN/Al dual protective coatings on NdFeB by DC magnetron sputtering

AlN/Al dual protective coatings were prepared on NdFeB by DC magnetron sputtering in a home-made industrial apparatus. Comparing with Al coating, AlN/Al coatings have a denser structure of an outmost AlN amorphous layer following an inner Al columnar crystal layer. The coatings and NdFeB substrate combine well, and moreover, there is occurrence of metallurgy bonding in the interface layer. Both Al and AlN/Al coatings have a good protective ability to NdFeB. Especially, the corrosion resistance of AlN/Al coated NdFeB is improved largely. AlN/Al and Al protective coatings not only do not deteriorate the magnetic properties of NdFeB, but contribute to their slight increase.     

Corrosion Evaluation of Very Rapid High-Current Vacuum Arc Coatings

The corrosion resistance of Al alloy, Ni, and stainless steel coatings deposited on 1010 steel sample anodes using pulsed high-current vacuum arcs was investigated as a function of the arc parameters. Coating thicknesses of up to 30 ?m were obtained from a sequence of six 70-ms pulses, indicating effective coating rates of up to 72 ?m/s. The thicker coatings, and the best corrosion protection, were obtained at higher currents (600-900 A) and short gaps (3 mm). The coatings were generally well bonded to the substrate. The composition of the coatings was approximately that of the source electrode. With optimal arc parameters, all three coating materials gave full corrosion protection during a 5-h salt-spray test, and Al and Ni coatings showed no signs of corrosion after a 48-h test.