贫铀表面钛镀层的抗腐蚀性能研究

利用电化学测试技术、扫描电镜(SEM)及X射线能谱(EDS)对贫铀表面钛镀层的抗腐蚀性能进行了研究。结果表明:在50μg/gCl-的KCl溶液中,钛镀层的腐蚀电位远高于贫铀的腐蚀电位,钛镀层对贫铀是阴极性镀层,对贫铀的保护是基于其对腐蚀介质的物理屏障作用;贫铀表面完整钛镀层的极化电阻和电化学阻抗幅值远大于贫铀,腐蚀电流远小于贫铀,完整钛镀层对贫铀具有良好的抗腐蚀保护作用;贫铀表面钛镀层的腐蚀特征为局部腐蚀,由孔蚀向电偶腐蚀转变;破坏的钛镀层将加速铀基体的腐蚀。     

电流特性和纳米颗粒对电刷镀复合镀层耐腐蚀性能的影响

为获得性能优良的镀层,利用不同的电沉积方法(直流、脉冲电流及脉冲换向电流)制得了Ni、Ni/n-SiO2和Ni/n-Al2O3复合镀层,分别对其表面形貌(SEM)进行了观测和分析,测试了镀层的孔隙率,并通过海水浸泡方法检测其耐腐蚀性能.比较测试结果后发现:电流特性和纳米颗粒对电刷镀复合镀层的耐腐蚀性能均有影响,采用脉冲换向电流沉积得到的Ni/n-SiO2复合镀层具有致密精细的表面形貌、较小的孔隙率和较好的耐腐蚀性能.     

柠檬酸铵浓度对脉冲电镀Ni-Cr-Mo合金镀层的影响

目的揭示柠檬酸铵浓度对脉冲电镀Ni-Cr-Mo合金镀层元素含量、沉积速率、表面形貌和耐蚀性的影响规律。方法采用脉冲电镀法在Q235钢表面制备Ni-Cr-Mo合金镀层,利用辉光放电光谱仪、扫描电镜、Tafel曲线和电化学阻抗谱考察柠檬酸铵浓度对镀层元素含量、沉积速率、表面形貌和耐蚀性的影响。结果随柠檬酸铵浓度的增大,镀层镍含量减小,铬、钼含量增大,镀层沉积速率减小,镀层表面颗粒的尺寸减小,镀层在3.5%Na Cl溶液中的耐蚀性先增强后减弱。结论柠檬酸铵质量浓度为196 g/L时,镀层具有最大的自腐蚀电位(-0.537 V)、最小的腐蚀电流密度(0.313μA/cm~2)和最大的电荷转移电阻(2075?·cm~2),耐蚀性最好。     

脉冲参数对镍镀层在H2SO4溶液中腐蚀性的影响

采用正交试验法,研究了脉冲电镀参数对镍镀层在硫酸溶液中的耐腐蚀性能的影响;采用扫描电镜(SEM)观察镀层腐蚀前后的表面形貌;利用浸泡腐蚀试验,及阳极极化曲线测试检测镀层的耐腐蚀能力。利用阳极极化曲线测试结果作为正交试验指标,分析了脉冲参数及pH值对镀层耐腐蚀性能的影响,表明脉冲频率越大,占空比越小,脉冲平均电流密度在3.5 A/cm2左右,pH值为3.3时,镀层耐腐蚀性能达到最好。     

稀土-Ni-W-P-SiC脉冲复合镀层的耐蚀性研究

采用腐蚀溶液浸泡、绘制阳极极化曲线和中性盐雾试验三种方法研究了稀土(RE)-Ni-W-P-SiC脉冲复合镀层的耐蚀性.结果表明:无论是在镀态条件下还是在400℃热处理条件下,脉冲RE-Ni-W-P-SiC镀层在各腐蚀溶液中的耐蚀性均优于相应的直流镀层,更优于不锈钢(1Cr18Ni9Ti);镀层在HCl、H2SO4、H3PO4溶液中的腐蚀速率都比较低,而镀层在FeCl3溶液中的腐蚀速率远大于前三者;脉冲频率f=33Hz,占空比r=0.6时获得的镀层具有较好的耐腐蚀性.表面形貌分析表明稀土-Ni-W-P-SiC脉冲镀层比其直流镀层平整细腻;相结构分析表明脉冲镀层经400℃热处理后非晶态减少并产生Ni3P新相.     

高频脉冲电沉积镍钻合金镀层的硬度研究

在硫酸盐电解液中,采用脉冲电源电沉积了镍钻合金.研究了电解液中COS04的浓度及脉冲参数对镀层中Co含量和镀层显微硬度的影响.采用SEM和XRD研究了镀层的表面形貌和微观结构.结果表明,镀层中的Co含量对镀层硬度有显著影响,当CO含量小于55 mass%时,镀层的硬度随着Co含量的增加递增.Co含量较低时,合金由面心立方结构(fcc)的固溶体组成.     

尿素含量对脉冲电镀Ni-Cr-Mo合金镀层的影响

采用脉冲电镀法在Q235钢表面制备了Ni-Cr-Mo合金镀层。利用辉光放电光谱仪、扫描电镜、Tafel曲线和电化学阻抗谱考察了尿素含量对镀层元素含量、沉积速率、表面形貌和耐蚀性的影响。结果表明,随尿素含量的增大,镀层镍含量先增大后缓慢减小,铬含量先增大后减小、钼含量先减小后增大;镀层沉积速率先增大后减小;镀层表面颗粒尺寸减小;镀层在3.5%NaCl溶液中耐蚀性先增强后减弱。尿素含量为60 g·L~(-1)时制备的镀层具有最大的自腐蚀电位(-0.535 V)、最小的腐蚀电流密度(0.123μA·cm~(-2))和最大的电荷转移电阻(2 550Ω·cm~2),耐蚀性最好。     

脉冲换向电刷镀Ni/n-Al2O3复合镀层的耐腐蚀性能研究

利用脉冲换向电刷镀方法制得了Ni/n-Al2O3复合镀层,对其表面形貌(SEM)进行了观测和分析,测试了镀层的孔隙率,并通过海水浸泡法检测其耐腐蚀性能,并与其他工艺条件下的电刷镀镀层进行比较,结果发现,采用脉冲换向电刷镀工艺得到的Ni/n-Al2O3复合镀层具有致密精细的表面形貌、较小的孔隙率和较好的耐腐蚀性能。     

电沉积方式对Ni-Cr-Mn合金镀层耐蚀性的影响

采用直流、单脉冲和换向脉冲三种不同电沉积方式在Q235钢表面电镀制备Ni-Cr-Mn合金镀层。利用辉光放电光谱仪、形状测量激光显微系统、Tafel曲线和电化学阻抗谱,研究了电沉积方式对镀层元素含量、沉积速率、3D形貌和耐蚀性的影响。结果表明:按照直流、单脉冲和换向脉冲的顺序,镀层中镍含量减小,铬、锰含量增大,沉积速率先增大后减小,表面粗糙度降低,耐蚀性增强。直流方式制备的镀层表面存在个别较大的颗粒,单脉冲方式制备的镀层表面颗粒大小较为均匀,但仍存在个别较大颗粒,换向脉冲方式制备的镀层总体均匀致密。换向脉冲方式制备的镀层表面粗糙度最低,在3.5%NaCl溶液中,该镀层具有最大的腐蚀电位(-0.305 V)、最小的腐蚀电流密度(7.467×10~(-8)A·cm~(-2))和最大的电荷转移电阻(5972Ω·cm~2),耐蚀性最佳。     

热等静压处理对铀表面铝镀层耐腐蚀性能的影响

采用热等静压(HIP)技术对铀表面铝镀层进行处理,利用电化学测试技术、扫描电镜(SEM)及X射线能谱(EDS)对样品在50 μL/L Cl-的KCl水溶液中的电化学腐蚀行为进行研究。结果表明：200 ℃, 0.5 h, 60 MPa HIP处理的铝镀层耐腐蚀性能优于未处理镀层;480 ℃, 1.0 h, 60 MPa HIP处理镀层的耐腐蚀性能下降较为明显;HIP处理后样品的腐蚀特征为典型的局部腐蚀,在腐蚀过程中会出现镀层的破裂、剥落     

The influence of crystallographic orientation distribution on 316LVM stainless steel pitting behavior

In this research, the influence of crystallographic orientation on pitting corrosion susceptibility of 316LVM stainless steel surface has been investigated using orientation imaging microscopy (OIM) technique. It has been shown that the susceptibility of the surface to pitting corrosion depends strongly on the crystallographic orientation of the planes parallel to the surface. This has revealed an anisotropic nature of pitting initiation on the surface, suggesting that controlling the texture of the material can be considered as a means of ameliorating the material’s pitting resistance. The generalized spherical harmonic functions have been used to express the pitting susceptibility of various crystallographic planes. Using the proposed formula and the texture inverse pole figure of the investigated material (obtained from orientation distribution function, ODF), the pitting susceptibility index (PSI) of the surface is predicted based on texture measurements. The results obtained thus demonstrate a novel method of improving pitting resistance of SS316LVM by designing the desired texture.     

电沉积超薄金刚石切割刀片背面结瘤缺陷的形成机理

用扫描电子显微镜(SEM)、原子力显微镜(AFM)和能谱仪(EDS)对切割刀片背面结瘤的形貌、电沉积前铝合金基体处理过程中的表面形貌及成分演变等进行观察和分析,得出刀片背面结瘤缺陷的形成机理。结果表明:铝合金基体前处理过程中,其表面析出物周围的铝合金逐渐溶解,析出物脱落,2次浸锌后的铝基体表面留下0～6 μm的孔洞;镍-金刚石复合电沉积过程中的镍在孔洞处沉积,去除部分铝合金基体后,在刀片背面形成0～6 μm的凸起,即镍瘤。      

表面镀镍层对904L在氢氟酸溶液中耐蚀性的影响

采用电化学测试、质量损失分析等方法研究了化学镀镍处理对904L奥氏体不锈钢在氢氟酸中腐蚀行为的影响,并利用光学显微镜(OM)、扫描电镜(SEM)对904L不锈钢表面腐蚀形貌进行分析。结果表明:酸性化学镀镍使904L奥氏体不锈钢表面获得了一层分布不均的珊瑚状镀镍层,与原始904L奥氏体不锈钢相比,含镀镍层904L奥氏体不锈钢耐蚀性得到了提高。低浓度的氢氟酸溶液中,镀镍层904L表面可以迅速产生致密的氟化镍沉积层,避免904L表面贫铬区遭受晶间腐蚀。     

Electrodeposition and characterization of Ni-TiB2 composite coatings

Nickel-titanium diboride (Ni-TiB₂) composite coatings were successfully fabricated by pulse electrodeposition techniques from nickel sulfamate bath containing dispersed submicron TiB₂ particles. The effect of TiB₂ codeposition on the morphological, microstructural, microhardness and anti-corrosive properties of the composite coatings have been investigated by using scanning electron microscopy coupled with energy dispersive spectroscopy system, X-ray diffraction (XRD), vickers microhardness, and electrochemical impedance spectroscopy (EIS) techniques. Incorporation of TiB₂ particles into the nickel matrix has modified the regular crystal growth of nickel. The XRD patterns revealed that the preferred (100) crystallite orientation of pure nickel has been modified into mixed orientations by the enhancement of (111) and attenuation of (200) diffraction intensities by the incorporation of TiB₂ particles into the nickel matrix. Vickers microhardness of the Ni-TiB₂ composite coating is found to be increased which is nearly 3 times higher than pure nickel coating. The results obtained by polarization curves and EIS analysis in 3.5 wt% NaCl solution have shown the improved corrosion resistance properties of Ni-TiB₂ composite coating over pure nickel electrodeposit.     

钛合金TC4表面纳米化及其热稳定性

利用超音速微粒轰击技术(supersonic fine particles bombarding,SFPB)对钛合金TC4进行了表面纳米化处理,并对SFPB处理后的试样进行不同温度2 h退火处理。借助X射线衍射、显微硬度计、透射电子显微镜和差热分析对纳米化及热处理后的试样进行了组织和性能表征,研究钛合金表面纳米化机理及其热稳定性。结果表明:经过SFPB处理后的试样在表层形成了纳米结构层,随着处理时间的延长,变形层厚度不断增加,晶粒尺寸逐步细化,当SFPB处理30 min后晶粒尺寸趋于稳定,在表层形成了晶粒尺寸约为15 nm具有随机取向的纳米等轴晶。纳米化后的试样在750℃退火时,纳米晶未发生明显粗化,因而具有很好的热稳定性。     

Electroless deposition of copper from methane sulphonate complexed bath

Abstract

Electroless copper deposition is widely used for printed circuit applications. A new bath based on copper methane sulphonate replacing copper sulphate, EDTA and paraformaldehyde has been developed, which is very useful for plating on non-conductors and through hole plating in printed circuit manufacturing processes. The new bath has a higher rate of deposition of 3·3 μm h^?1 than the conventional sulphate bath (with a rate of 1·5 μm h^?1) and the bath stability and the quality of the deposits are very good. Scanning electron microscopy, X-ray diffraction and atomic force microscopy studies have been carried out and the crystallite size of the copper is measured to be 134 nm with a preferred orientation of 200 planes. The deposit obtained is pure copper and the surface roughness is of the order of 10 nm.     

The use of EELFS spectroscopy for an analysis of the local atomic structure of thin surface layers of 3d-metal-oxygen systems

Simple formulas for describing the extended fine structures of spectra of electron energy losses (EELFS) with allowance for the multipolarity of the process of excitation of the inner level of atoms by electron impacts have been derived. The experimental M _2,3 EELFS spectra of nickel and K EELFS spectra of oxygen were obtained from pure samples of nickel and stoichiometric oxide film on the surface of nickel. Good agreement has been obtained between the experimental and calculated results, as well as between the parameters of a local atomic structure obtained from the experimental EELFS spectra and available crystallographic data.     

Effects of ultrasonic dispersion on structure of electrodeposited Ni coating on AZ91D magnesium alloy

To obtain the refined electrodeposited nickel layer on AZ91D magnesium alloy, ultrasonic technology was applied in the processes of pre-treatment and electrodeposition. The phases of pre-treatment layer and the nickel coating were analyzed by X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS), and the microstructure was observed by scanning electron microscopy (SEM). Then, the effects of ultrasonic dispersion on the microstructure of pre-treatment layer and the grain refinement of electrodeposited nickel layer were discussed. The results showed that the pre-treatment electrodeposited Cu-Sn layer with compact microstructure could be synthesized in alkaline copper-tin liquid with ultrasonic agitation, as a result, smooth and refined nickel coating formed on AZ91D magnesium alloy. On the other hand, preferred orientation in the coating decreased because of the refined grains.     

The Structure and Protective Properties of Zinc and Nickel Alternate Electrodeposits

A NEW TYPE of coatings consisting of a large numberof laminar deposits has been the keen subject of muchresearch,because these layered-structure coatingspossess improved properties or novel phenomenon suchas increased mechanical strength,micro-hardness,giantmagnetoresistance and corrosion resistance[1"6'.Thesecoating systems with individual layers making upoverall structure are also called compositionallymodulated multilayer(CMM)coatings'3"5'.In view ofthe plating historical use of surface…