碳纤维表面化学镀钴–镍合金工艺研究

采用以硫酸钴和硫酸镍为主盐,柠檬酸钠为配位剂,次磷酸钠为还原剂的镀液,在碳纤维表面化学镀钴-镍合金,得到碳纤维/钴-镍合金复合粒子。研究了次磷酸钠含量、氨水含量和温度对化学镀所得复合粒子的导电性和微观形貌的影响,获得碳纤维化学镀钴-镍合金镀层的最优配方和工艺为:NiSO_4·6H_2O 15g/L,COSO_4·7H_2O 15 g/L,NaH_2PO_2·H_2O 30 g/L,Na_3C_6H_5O_7 30 g/L,26%(体积分数)NH_3·H_2O 140 mL/L,温度80℃,时间30 min。在最优工艺条件下所得碳纤维/Co-Ni合金复合粒子的体积电阻率为3.27×10^(-2)Ω·cm,比未镀碳纤维低1个数量级。碳纤维表面的合金镀层均匀、致密,主要由面心立方结构的Co-Ni合金构成。

电流密度对喷射电沉积钴–镍合金镀层组织及性能的影响

采用NiSO_4·6H_2O与CoSO_4·7H_2O的质量浓度比不同的镀液在黄铜上喷射电沉积Co–Ni合金,研究了电流密度对Co–Ni合金镀层表面形貌、元素组成、晶体结构、显微硬度和耐磨性的影响。结果表明:随着电流密度的增大,Co–Ni合金镀层的晶粒先细化后粗化,Co含量减小。镀层在Co含量高于85%时基本为密排六方(hcp)相,低于85%时为hcp和面心立方(fcc)两相共存。镀层的晶粒越细,则显微硬度越高,耐磨性越好。在CoSO_4·7H_2O和NiSO_4·7H_2O的质量浓度分别为200 g/L和100 g/L的条件下,镀层受电流密度的影响较小,Co含量稳定在96%左右,表面均匀致密,显微硬度高达425 HV,耐磨性较好。

Thermodynamic analysis on synthesis of fibrous Ni-Co alloys precursor and Ni/Co ratio control

According to the principles of simultaneous equilibrium and mass equilibrium, a series of thermodynamic equilibrium equations in Ni（II）-Co（II）-C2O4^2--NH3-NH4^＋-H2O system at ambient temperature were deduced. The diagrams of logarithm ion concentrations versus pH values at different solution compositions were drawn. The results show that Ni^2＋ and Co^2＋ can completely precipitate at pH less than 5.0 and the predefined Ni/Co ratios can be well kept in the precursor. The precursor morphology is granular aggregation. However, rod aggregation precursor is obtained in the pH range of 5.0-8.0, and fibre-shape precursor is got at pH value higher than 8.0. The Ni/Co ratios in the above two precursors are not reproduced as that in the feed due to the formhtion of multi-coordinated Ni（NH3）n^2＋ and Co（NH3）n^2＋ （n=1-6）. Modification of precipitation medium is favorable for the precursors to keep the predefined Ni/Co ratios of the feed in the pH range of 2.0-8.6. Meanwhile, the precursors with fibrous morphology can be obtained.

Shape-controlled synthesis of novel precursor for fibrous Ni-Co alloy powders

A novel precursor of nickel-cobalt alloy powders with an appropriate Ni to Co molar ratio was prepared under selectively synthetic conditions. The composition and morphology of the precursor were characterized by X-ray diffractometry （XRD）, scanning electron microscopy （SEM）, Fourier transform infrared spectrometry （FT-IR） and energy dispersive spectrometry （EDS）. The effects of pH value, reaction temperature, metal ion concentrations and surfactant on the morphology and the dispersion of precursor were investigated. The results show that the morphology of precursor depends on ammonia content in the precursor. A fibriform precursor is a complicated ammonia-containing nickel-cobalt oxalate. The uniform shape-controlled fibrous precursor is obtained under the following optimum conditions： ammonia as complex agent as well as pH adjustor, oxalate as coprecipitator, 50-65 °C of reaction temperature, 0.5-0.8 mol/L of total concentration of Ni2＋ and Co2＋, PVP as dispersant, and pH 8.0-8.4.

Composition Dependent Magnetic Properties of Ni-Co-P Coated Carbon Nanotubes

Carbon nanotubes were coated with a layer of nickel-cobalt-phosphorus （Ni-Co-P） alloy with different compositions of Ni/Co through electroless plating. The effects of the concentration ratio of Co^2＋ to Ni^2＋, bath temperature, and pH on deposition rate are discussed. The prepared carbon nanotubes covered with Ni-Co-P were characterized and analyzed by fieldemission scanning electron microscopy, transmission electron microscopy, X-ray diffraction, energy dispersive spectroscopy, and a vibrating sample magnetometer. The results show that the deposition rate reached the maximum when the concentration ratio of Co^2＋ to Ni^2＋ is 1 and the pH is 9; the deposition rate increases with the increase of bath temperature. The measurements of the magnetic properties of the obtained carbon nanotubes covered with Ni-Co-P indicate that the magnetic properties greatly depend on the concentration ratio of Co^2＋ to Ni^2＋, and the magnetic saturation reaches the maximum value when the Co^2＋ to Ni^2＋ ratio is 1. In addition, there are two peaks in the coercivity curve at Co^2＋ to Ni^2＋ ratios of 1/2 and 4/1, while the two peaks in the magnetic conductivity curve are located at Co^2＋ to Ni^2＋ ratios of 1/4 and 4/1.

Effect of heat treatment on tensile deformation behavior of Ni-Co film/Fe substrate systems

The effects of heat treatment on microstructure and tension property of Ni-Co film/Fe substrate systems were investigated. The deformation and fracture morphologies of Ni-Co films/Fe substrate systems were studied by in-situ scanning electron microscopy（in-situ SEM）before and after heat treatment.The results show that a Ni-Co/Fe diffusion layer appears between the film and substrate after heat treatment;the elongation of film/substrate system increases with increasing the heat treatment temperature. Both the strength and ductility of the film/substrate system are preferable when heat treatment temperature is 650 o C,meanwhile the maximum elongation is up to 46%.During tensile deformation,the deformation behaviors of Ni-Co film/Fe substrate are quite different before and after heat treatment.The samples after heat treatment went through the progress of holes’emergence,growth and extension,whereas the samples without heat treatment accompanied with no holes,just cracked instead,showing that appropriate heat treatment is helpful to improve the toughness of material,and mechanical properties.

Inconel 617 and Stellite 6 alloys for tooling in thixoforming of steels

Thermal fatigue and high temperature wear are the two principle failure mechanisms for thixoforming dies. Samples of Inconel 617 and Stellite 6 alloys were submitted to thermal cycling under conditions which approximate thixoforming of steels and to sliding wear tests at 750 ℃. The experimental results thus obtained were compared with those of the X32CrMoV33 hot work tool steel. The Inconel 617 and Stellite 6 samples are much more resistant to oxidation and to softening than the hot work tool steel, providing a superior resistance to thermal fatigue cracking. The wear resistance of the Inconel 617 and Stellite 6 alloys at 750 ℃ is also markedly superior. The adhesive oxides growing slowly on Inconel 617 and Stellite 6 alloys sustain the wear action without spalling and are claimed to be responsible for the superior wear resistance of these alloys at 750 ℃.

Electrodeposition of Compositionally Modulated Zinc-cobalt Alloy Multilayer Coatings

The effects of pulse parameters on the cobalt content, surface morphologies and grain size of Zn-Co alloy deposits were studied using a pulse plating technique with a square-wave current containing reverse pulse. Average current density and reverse anodic current density amongst the variables investigated have very strong effects on the cobalt content in the Zn-Co alloy deposits. Grain size, surface appearance and internal stress in the deposit were improved significantly by introducing the reverse current. Varieties of Zn-Co alloy compositionally modulated multilayer (CMM) coatings with large differences in cobalt contents for different sublayers were electrodeposited by designing corresponding waveforms using a computer-aided pulse plater and characterized in terms of surface morphologies. Cross-sectional morphologies of the Zn-Co alloy CMM coatings, examined using field emission gun scanning electron microscopy (FEGSEM), confirmed the layered structure.

Synthesis, Spectral Properties, Antibacterial and Antitumor Activity of Salinomycin Complexes with the Transition Metal Ions Co（ll）, Ni（ll）, Cu（ll） and Zn（ll）

SalNa （sodium salinomycin） reacts with divalent transition metal ions of Co（II）, Ni（II）, Cu（II） and Zn（II） to produce novel compounds characterized by various spectroscopic methods. The interaction of metal （II） ions with SalNa results in the formation of mononuclear complexes of a general composition of [M（Sal）2·（H2O）2] nH2O （n = 0 or 2） where the divalent cations replace Na~ ions from the cavity of initial compound. The new compounds （disalinomycinates） possess an enhanced antibacterial activity against Gram-positive microorganisms as compared to both SalNa and SalH （salinomycinic acid）, respectively. The metal （II） complexes manifest strong concentration dependent cytotoxic effect in experiments using human leukemia cell lines. The complexes of Co0I） and Cu（lI） proved to exert superior activity as compared to the Ni（II） and Zn（II） analogues and are much more cytotoxic than SalNa and SalH. Further studies should be conducted to determine the therapeutic indexes of the new compounds.

Synthesis of silicon-functionalized polyolefins by subsequent cobalt-catalyzed dehydrogenative silylation and nickel-catalyzed copolymerization

Metal catalyzed olefin hydrosilylation and metal mediated olefin polymerization are both of great academic and industrial importance, In this article, these two aspects are combined to prepare silicon- functionalized polyolefin materials, First, pyridine-diimine cobalt-catalyzed dehydrogenative silylations of various terminal olefins with alkylsilanes lead to the formation of a variety of allylsilanes at high yields, Then, the allylsilanes are copolymerized with ethylene using an α-diimine nickel catalyst, leading to the formation of branched polyolefins with high molecular weight and moderate comonomer incorporation. This subsequent catalytic process is an efficient strategy for the synthesis of silicon-functionalized polyolefins using widely available and inexpensive starting materials.

Electrodeposited Ni and Ni-Co alloys using cysteine and conventional ultrasound waves

Ni-Co alloys were electroplated from sulphate electrolyte using addition agents including sodium gluconate, boric acid and eysteine on copper foil by the galvanostatic technique and ultrasound waves. The chemical composition, surface morphologies, crystalline structure and hardness of the Ni-Co alloys were studied using energy dispersive spectroscopy, scanning electron microscope, X-ray diffraction and Vickers testing method, respectively. The effect of current density and addition agents on the microstructure and morphology of Ni-Co alloys were examined. The appropriate concentration of additives and ultrasound waves were found to produce fine and smooth crystals leading to higher hardness of Ni-Co alloys. The microhardness of the Ni-Co alloys was varied between 4860-7530 HV. The surface morphology of coatings was changed from granular to fine due to using of gluconate, boric acid, cysteine and ultrasound waves. The mechanical properties of nanocrystalline Ni-Co alloys showed an increase of the hardness with the growing of Ni content in the alloy. The X-ray diffraction studies indicated that nanocrystalline structure was face-centred cubic for pure Ni and Ni-Co alloys with Co content in the range of 1-75 wt.%. A hexagonal closed-package structure was obtained for pure Co and Ni-Co alloys with the cobalt content with range of 75-99 wt.%.