添加剂对喷射电沉积纳米晶镍的影响

纳米晶体材料已成为国际前沿性研究热点,由于电沉积法在制备该材料方面具有独特优势,已引起了广泛关注,作者用XRD和TEM等方法对比研究了邻磺酰苯酰亚胺(糖精)添加剂对电解液喷射电沉积纳米晶镍沉积层微观结构和硬度的影响。结果表明,加入2．5g／L添加剂可使Ni沉积层晶粒尺寸由30nm减小至10nm左右,沉积层织构由原来的(220)织构转变为(111)(200)双织构,其显微硬度亦由HV371升至HV602。     

脉冲摩擦喷射电沉积制备纳米晶镍沉积层

采用脉冲摩擦喷射电沉积和直流喷射电沉积分别在石墨基底上制备了纳米晶镍镀层,利用扫描电镜和X射线衍射分析了脉冲占空比和脉冲频率对镍镀层的表面形貌、晶粒的择优取向及平均晶粒尺寸的影响。结果表明脉冲摩擦喷射电沉积较直流喷射电沉积的沉积效果有较大提高,在喷嘴流量为200L/h,平均电流密度为80A/dm2,阴极转速为6r/min的条件下,脉冲占空比为50%,脉冲频率为2000Hz时可以获得表面较为平整光亮、组织致密的Ni沉积层。     

脉冲电沉积纳米晶镍沉积层的力学性能研究

为了提高镍沉积层的显微硬度和抗拉强度,采用传统的Watt镀液通过脉冲电沉积制得纳米镍沉积层.通过扫描电镜(SEM)、X射线衍射(XRD)方法分析了沉积层的表面形貌、织构和晶粒大小与脉冲参数的关系.分析表明,微观形貌为胞状结构,平均晶粒尺寸为10.3 nm;随着占空比减小,晶粒得以细化.研究了脉冲参数对纳米镍镀层显微硬度、抗拉强度的影响,最大显微硬度达到591 HV,最大拉伸强度达900MPa,分别为直流镍镀层的4.0和1.4倍;热处理试验表明,200℃热处理有利于提高镍镀层的显微硬度.     

电沉积铁镀层沉积织构的研究

主要了在不同的电镀工艺条件下,电沉积层的微观组织特点及织构演化规律。对镀层中的应力状进行了分析,将应力对织构形成的影响因素加以充分考虑,并在此基础上当地了纯铁镀层中的丝织构的形成机理。同时研究了表面能对沉积织构的影响。     

镍基高温合金初始织构对电辅助拉伸宏微观行为的影响

目的研究织构对镍基高温合金电辅助成形的影响规律。方法通过准静态拉伸与电辅助拉伸对比实验,研究了不同初始织构对镍基高温合金电辅助成形宏观力学行为以及微观组织演化的影响规律。结果当初始织构为易变形织构时,拉伸后的纤维织构峰值较低,而电辅助拉伸过程中焦耳热使得试样温度升高,变形抗力得到下降,在一定程度上增大了纤维织构的强度。当初始织构为难变形织构时,材料变形抗力大,拉伸后纤维织构峰值较高,但材料变形过程晶粒细化程度高,缺陷的增多导致电辅助成形过程中焦耳热更为明显,焦耳热导致的高温使得难变形晶粒变形更为协调,最终的纤维织构强度有所下降。结论不同的初始织构对电辅助成形宏微观行为有较大的影响,因此合理利用织构在电辅助成形过程中的影响以完善电辅助成形工艺十分重要。     

喷射电沉积多孔镍

采用喷射电沉积方法,分别选择不同的电流密度、喷射流量和两极间距及电沉积时间进行试验,分析了各试验参数变化对多孔镍形貌的影响规律,并用图形处理软件ImageJ对多孔镍的孔隙率和相对密度进行分析,找出了最佳试验参数。结果表明：适当大的电流密度、小的喷射流量、适中的喷射间距更有利于形成性能和形貌良好的多孔镍。     

电沉积法制备泡沫镍

采用聚胺脂泡沫为基体，经预处理，电镀和烧结还原工艺制备了均匀分布三维网状孔结构的高空隙率泡沫镍，其各项性能均能满足二次电池板料对泡沫镍的要求。     

高脉冲频率对纳米晶镍-铁合金电沉积层性能的影响

为了探讨不同高脉冲频率对Ni-Fe合金镀层性能的影响,在铜锌合金基体上脉冲电沉积了纳米晶Ni-Fe合金层。采用SEM对纳米晶Ni-Fe合金镀层的显微形貌进行了观察,采用XRD对镀层的晶粒尺寸进行了表征,利用2273电化学工作站对其在3.5%NaCl溶液中的动电位极化曲线和交流阻抗谱进行了测试,研究了其耐蚀性能。结果表明:纳米晶Ni-Fe合金镀层致密、均匀;脉冲频率从0.5 kHz逐渐增至3.5 kHz时,镀层中的Fe含量在14.17%～22.77%内呈非线性变化,晶粒尺寸从23 nm逐渐降至15 nm;纳米晶Ni-Fe合金镀层的耐蚀性能呈下凹曲线规律变化,在1.5～2.5 kHz内耐蚀性能较好,1.5 kHz时最佳,自腐蚀电流密度约为0.216μA/cm2,镀层电阻约为1.443×105Ω.cm2。     

Surface texture in electrodeposited films of cuprous oxide

The polycrystalline films of Cu₂O, prepared by electrodeposition, consist of grains with well-defined geometrical shapes. The size and the orientation of grains which define the surface texture can be controlled by controlling the deposition parameters. Grains with a size ranging from a few tenths of a micrometer to about 10m and with a preferential orientation of the (1 0 0) or (1 1 1) planes parallel to substrates can be obtained under certain deposition conditions. The effect of pH, bath temperature and the rate of deposition on the orientation and the size of grains is discussed.     

Preparation and growth mechanism of nickel nanowires under applied magnetic field

Nano-Micro Letters - Nickel nanowires with large aspect ratio of up to 300 have been prepared by a hydrazine hydrate reduction method under applied magnetic field. The diameter of nickel nanowires...     

电流密度对Sm-Fe电沉积膜显微组织及性能的影响

在室温下的水溶液体系中,采用恒流电沉积技术在Cu基体上制备了Sm-Fe合金薄膜。研究了电流密度对沉积膜层的表面形貌、厚度、元素含量以及物相组成的影响,并测试了制备出的Sm-Fe合金膜的磁性能。结果表明,银灰色的沉积膜由金属Sm、Fe及少量的O组成;随着电流密度的增加,膜层中Sm含量呈现先上升后下降的趋势;而Sm含量越多,膜层的表面越平整光亮;沉积膜主要由Sm Fe12、Sm3Fe5O12等化合物组成,电流密度影响了膜层中物相组成的含量,进而影响了膜层的磁性能。     

Surface morphology of epitaxial magnetic tunnel junctions

The surface morphology of epitaxial Fe(001)/MgO(001)/Fe(001) magnetic tunnel junctions, which show the giant tunneling magnetoresistance effect, was investigated by in situ scanning tunneling microscopy. It was observed that an epitaxial MgO barrier layer forms flat surface structures. The surface was flatter with distinct steps and terraces after annealing, which would lead to an increase of the tunneling magnetoresistance ratio. Examination of the local electronic structures of 1.05-nm-thick MgO barrier layers by scanning tunneling spectroscopy revealed no pinholes in the layers, so they would be perfect barriers in magnetic tunnel junctions.     

Template-free synthesis of nickel nanowires by magnetic field

Nickel nanowires were prepared by a template free method combined with chemical reduction and magnetic field. The application of an external magnetic field resulted in the formation of self-aligned metallic nickel nanowires of about 50 nm in diameter. Nickel particles were prepared in the absence of a magnetic field to better illustrate the structure directing role of the magnetic field. Physical properties of the nickel nanochains were examined by scanning electron microscopy (SEM), transmission electron microscope (TEM), X-Ray diffraction (XRD), and thermogravimetric analysis (TGA) methods. This study provides a simple method to prepare Ni nanowires in large scale which broads their practical applications.     

Thermal stability of electrodeposited nanocrystalline nickel and iron–nickel alloys

Abstract

The thermal stability of electrodeposited nanocrystalline nickel and iron–nickel alloys has been studied using TEM, X-ray diffraction, and atom probe analysis. All of the as deposited materials were purely fcc and had grain sizes of 10–20 nm. Heat treatment of nanocrystalline nickel in the range 190–320°C resulted in abnormal grain growth with an activation energy of 122±15 kJ mol^-1. Abnormal grain growth in Fe–50 at.-%Ni was only observed at 400°C but not at 220 or 300°C, where grain growth was very slow. In Fe–33 at.-%Ni, room temperature aging resulted in the formation of large grained areas (～1 µm), some of which transformed to bcc. In heat treated nickel specimens, some evidence of sulphur and carbon enrichment was found at grain boundaries.     

Electrocodeposition of magnetic nickel matrix nanocomposites in a static magnetic field

The effect of an external magnetic field on the electrocodeposition of composites consisting of either Co or magnetite nanoparticles in a Ni matrix has been studied. An alkaline Ni pyrophosphate bath containing citrate was used. The magnetic particles were prepared by thermal decomposition (Co) or chemical precipitation (magnetite) and characterized by transmission electron microscopy, X-ray diffraction, dynamic light scattering, zeta potential and vibrating sample magnetometry measurements. The particle incorporation showed a distinct dependency on the orientation of an externally applied magnetic field. While the particle incorporation increased in a perpendicular field (perpendicular with regard to the electrode surface), it decreased in a parallel orientation. This result is explained with the dominating action of the magnetophoretic force. The structure and the properties of the Ni layers were significantly affected by the particle codeposition. A refinement of the Ni grains was found with increasing plating current density and as a result of the nanoparticle incorporation. The magnetic hardness and the Vickers microhardness of the films increased significantly due to the incorporation of the nanoparticles.     

Microstructure and growth of electrodeposited nanocrystalline nickel foils

In the present work, the structure of electrodeposited pure Ni foils has been investigated by X-ray diffractometry, transmission electron microscopy and by measuring their electrical transport properties. It was found that the as-deposited Ni foils have a nanocrystalline structure covered by a thin amorphous Ni layer on the substrate side: the growth of the electrodeposited foils starts in amorphous form followed by nanocrystalline layers. To explain the formation of the amorphous Ni layer, it is supposed that foreign atoms are incorporated into the nucleating Ni films.