糖精钠对直流电沉积纳米镍层性能及组织的影响

为了弄清糖精钠对纳米镍镀层结构及性能的影响,采用直流电沉积技术制备了纳米镍层。研究了糖精钠的浓度对镀层光亮性、硬度、柔韧性以及孔隙率的影响,并采用XRD和电化学测量法对镀层进行了表征和分析。结果表明:糖精钠通过吸附在镍晶粒的(200)晶面,抑制其晶面的生长,从而细化了晶粒。

铜/镍纳米多层膜脉冲电沉积法制备及沉积机理初探

利用脉冲电沉积法成功制备出了层状结构清晰的Cu/Ni纳米多层膜。采用线性扫描伏安法、循环伏安法以及铜镍沉积过程中的电压-电流曲线等方法,研究了在硼酸系溶液中铜/镍纳米多层膜的沉积机理,使用扫描电子显微技术观察了多层膜的微观结构。结果表明:铜的沉积为扩散控制步骤,镍的沉积分为2步进行,即中间经历Ni(OH)+的过渡状态;铜、镍的沉积电位分别为-0.5V和-1.1V。经计算和测量对比,本脉冲法制备的多层膜符合基础电沉积原理。

α-Al_2O_3纳米镀镍层中纳米粉含量测定方法的研究

Al2O3经高温1200℃转化为α-Al2O3,其粒径在1～100nm的α-Al2O3在金属镀层显示良好的抗蚀性和耐磨性,比常规镀层各方面性能均有大幅改善,因而测定镀层中的纳米材料多少是十分重要。本法对镀层通过物理方法剥离,用1+1盐酸溶解基体Fe及表层Cr,110℃烘干称重,硝酸溶样,用容量法测定镀层中Ni、Co,其差值为纳米α-Al2O3的含量。

Microstructure and properties of nanocrystalline nickel coatings prepared by pulse jet electrodeposition

The fabrication of nanocrystalline nickel coatings was conducted by pulse jet electrodeposition on the substrate of 45# carbon steel.The effects of average current density on the surface morphology,microstructure,average grain size and microhardness of nickel coatings were investigated by scanning electron microscopy(SEM),X-ray diffractometry(XRD)and microhardness measurement.In addition,the corrosion resistances of coating and substrate were compared.It is revealed that the nickel coatings prepared by pulse jet electrodeposition exhibit a fine-grained structure with a smooth surface and a high density,although some pores and defects are still present in coatings.With the increase of average current density,the average grain size of nickel coatings is reduced at first and then increased.The coating with the optimum compactness,the smallest average grain size(13.7 nm)and the highest microhardness are obtained at current density of 39.8 A/dm2.The corrosion resistance is obviously increased for the coatings prepared by pulse jet electrodeposition;however,the corrosion rate is increased after a certain period due to the penetration of the corrosive media.

Electrodeposition of Ni-Co-Fe_2O_3 composite coatings

Ni-Co-Fe2O3 composite coatings were electrodeposited using cetyltrimethylammonium bromide(CTAB)-modified Watt's nickel bath with Fe2O3 particles dispersed in it.The effects of the plating parameters on the chemical composition,structural and morphological characteristics of the electrodeposited Ni-Co-Fe2O3 composite coatings were investigated by energy dispersive X-ray(EDS) spectroscopy,X-ray diffractometry(XRD) and scanning electron microscopy(SEM).The results reveal that Fe2O3 particles can be codeposited in the Ni-Co matrix.The codeposition of Fe2O3 particles with Ni-Co is favoured at high Fe2O3 particle concentration and medium stirring,and the deposition of Co is favoured at high concentration of CTAB.Moreover,the study of the textural perfection of the deposits reveals that the presence of particles leads to the worsening of the quality of the observed <220> preferred orientation.Composites with high concentration of embedded particles exhibit a preferred crystal orientation of <111>.The more the embedded Fe2O3 particles in the metallic matrix,the smaller the sizes of the crystallite for the composite deposits.

Electrodeposition behavior and characteristics of Ni-carbon nanotube composite coatings

Ni-CNT (carbon nanotube) composite coatings were processed by electrodeposition and their hardness and corrosion characteristics were investigated with variations of CNT concentration in an electrolyte solution and electrodeposition current density. With increasing the CNT concentration in the electrodeposition bath and the current density, more CNTs are incorporated into Ni matrix. Hardness values of the Ni-CNT coatings are irrelevant to the CNT concentration in the solution, the current density, and current mode, implying poor adhesion of CNTs to Ni matrix. With increasing the CNT content in the coating, the corrosion resistance of the Ni-CNT composite coating becomes inferior due to the porous microstructure.

In-situ characterization of metal nanoparticles and their organic coatings using laser-vaporization aerosol mass spectrometry

The development of methods to produce nanoparticles with unique properties via the aerosol route is progressing rapidly. Typical characterization techniques extract particles from the synthesis process for subsequent offiine analysis, which may alter the particle characteristics. In this work, we use laser-vaporization aerosol mass spectrometry （LV-AMS） with 70-eV electron ionization for real-time, in-situ nanoparticle characterization. The particle characteristics are examined for various aerosol synthesis methods, degrees of sintering, and for controlled condensation of organic material to simulate surface coating/functionalization. The LV-AMS is used to characterize several types of metal nanoparticles （Ag, Au, Pd, PdAg, Fe, Ni, and Cu）. The degree of oxidation of the Fe and Ni nanoparticles is found to increase with increased sintering temperature, while the surface organic-impurity content of the metal particles decreases with increased sintering temperature. For aggregate metal particles, the organic-impurity content is found to be similar to that of a monolayer. By comparing different equivalent-diameter measurements, we demonstrate that the LV-AMS can be used in tandem with a differential mobility analyzer to determine the compactness of synthesized metal particles, both during sintering and during material addition for surface functionalization. Further, materials supplied to the particle production line downstream of the particle generators are found to reach the generators as contaminants. The capacity for such in-situ observations is important, as it facilitates rapid response to undesired behavior within the particle production process. This study demonstrates the utility of real-time, in-situ aerosol mass spectrometric measurements to characterize metal nanoparticles obtained directly from the synthesis process line, including their chemical composition, shape, and contamination, providing the potential for effective optimization of process operating parameters.

Molecular dynamics simulation of single crystal Nickel nanometric machining

Molecular dynamics simulation is carried out to study the nanometric machining of single crystal Nickel(Ni). Through an investigation of atomic displacement and the variation of cutting force, it is found that the latter is in accordance with the number variation of elastic displaced atoms in the workpiece. It is further found that the generation of complex stacking faults is the predominant cause of cutting force fluctuation, and the stacking faults with complex structures lead to work-hardening. The temperature of the cutting tool and workpiece is studied during the machining process. It is concluded that the selection of averaging steps has a significant influence on the system temperature distribution. Thus, the time-spatial averaging method, which has a high accuracy and consistency in temperature distribution, is proposed.