氢氧化镍粉末的化学镀Co-Zn合金表面改性研究

采用化学沉积技术对由水溶液络合沉淀法合成的氢氧化镍粉末进行了表面包覆Co—Zn改性处理,利用扫描电子显微镜分析、比表面积测量、X一射线光电子能谱及原子吸收光谱等对处理前后氢氧化镍粉末的表面形貌、微晶结构、比表面积、元素化学态及镀层组成等进行了表征和研究。结果表明,Co—Zn合金镀层可以均匀包覆在氢氧化镍颗粒表面,氢氧化镍经化学镀处理后其表面微观组织形貌发生了明显变化。化学镀表面改性使氢氧化镍粉末的比表面积有所降低,镀层中的Co、Zn元素均以氧化态形式存在。     

Electrochemical preparation and characterization of Ni/SiC compositionally graded multilayered coatings

In our study, Ni/SiC functionally graded coatings have been obtained by electrochemical deposition of silicon carbide microparticles (mean diameter 2 μm) from nickel Watts baths with different concentrations of SiC particles in solution. The SiC particles were characterized by electroacustics technique in order to determine zeta potential and particle size. Moreover, the effect of the concentration of SiC particles in solution on the amount of SiC deposited in the nickel layer was investigated. Further experiments showed that the degree of particle incorporation provoked changes in the texture of the nickel matrix. The characterization of the coatings proved that the Ni/SiC graded composite coatings were bright and compact, presented good adhesion and improved the hardness and wear resistance of pure nickel electrodeposits.     

Soft-template synthesis of ordered mesoporous carbon/nanoparticle nickel composites with a high surface area

Ordered mesoporous carbon/nanoparticle nickel composites have been synthesized via multi-component co-assembly strategy associated with a direct carbonization process from resol, tetraethyl orthosilicate, Ni(NO₃)₂·6H₂O and triblock copolymer F127 and subsequent silicates removal with NaOH solution. The incorporation of rigid silicates in the pore walls can reduce framework shrinkage significantly during the pyrolysis process, creating large mesopores. Moreover, plenty of complementary small pores caused by silica removal are observed in the carbon pore walls, which contribute to the large surface area. The mesoporous carbon/nanoparticle nickel composites with a low Ni content (1.7 wt%) possess ordered two-dimensional hexagonal structure, large mesopores (6.8 nm), high surface area (1580 m² g⁻¹) and large pore volume (1.42 cm³ g⁻¹). Magnetic Ni nanocrystals with particle size of ∼16.0 nm are confined in the matrix of carbon frameworks. With increase of Ni content, the surface area and pore volume of the composites decrease. The particle size of metallic Ni nanocrystals increases up to 20.3 nm, when its content increases to 10 wt%. These carbon/nanoparticle nickel composites with high surface area, large pore size and superparamagnetic property show excellent adsorption properties for bulky dye fuchsin base and an easy separation procedure.     

Fabrication and mechanical properties of metal matrix composite with homogeneously dispersed ceramic particles

Titanium carbide (TiC) particles were coated with nickel (Ni) to increase their compatibility with a metal matrix, leading to an improvement in the dispersibility of TiC particles in the molten matrix. TiC particles were dispersed into a basic aqueous solution of pH 12, and then nickel nitrate (Ni(NO₃)₂), as a Ni precursor, was added to the TiC suspension. The interaction between the TiC particles and the Ni precursor is driven by the attractive force between the Ni cations and the TiC particles with negative charge. An inoculant (ferrosilicon), which has been used in the foundry industry to improve crystal growth of graphite, was used as a core particle. The Ni-treated TiC particles were coated onto the surface of the inoculant using an inorganic binder converted into its glass phase by sol–gel reactions. The reinforcement particles prepared through the dual-coating process were then injected into the molten matrix based on iron at 1500 °C. The crystal phase of the graphite is more finely and shortly grown in the reinforced metal matrix than in that without the reinforcement particles. This means that the reinforcement particles are homogeneously and uniformly dispersed into the matrix without any aggregation of particles, implying that the mechanical properties of the reinforced matrix would be greater than those of a non-reinforced matrix. Consequently, metal matrix composites with reasonable properties can be fabricated successfully using the reinforcement particles prepared by the dual-coating process.     

γ-Al2O3负载铜锌氧化物催化剂的N2O催化分解性能

以γ-Al₂O₃为载体,采用共浸渍法合成了负载量为35%（以CuO与ZnO总质量计）的CuZn金属氧化物催化剂,分别考察了金属助剂（Co、Ni,、Mg、Fe、Mn、Ba和Ce）对催化剂的影响。采用XRD、BET和H₂-TPR等方法对制备的催化剂进行表征,在微反装置上对催化剂的N₂O催化分解活性进行评价。结果表明,合成的CuZn氧化物催化剂均具有CuxZn_1-xAl₂O₄的类Co₃O₄尖晶石结构;加入金属助剂使催化剂的比表面积不同程度得到提高,催化剂的N₂O催化分解反应活性不仅与Cu³⁺还原为Cu²⁺的温度有关,还与晶粒尺度大小和催化剂比表面积等有关;其中,含金属助剂Ni的催化剂具有相对较高的N2O催化分解反应活性,其N₂O完全转化温度为567 ℃。除含金属助剂Ba催化剂以外,加入其他金属助剂有利于N₂O催化分解反应进行。     

Electrochemical behavior of activated-carbon capacitor material loaded with nickel oxide

In order to enhance specific capacitance and energy density of carbon-based supercapacitor, some nanometer-scale amorphous particles of nickel oxide were loaded into activated-carbon by suspending the activated-carbon in a Ni(NO₃)₂ solution followed by neutralization. A hybrid type electrochemical capacitor was made and tested, in which the activated-carbon loaded with nickel oxide was used as cathode material and activated-carbon was used as anode material. Although the BET surface area of the activated-carbon decreased upon nickel oxide loading compared to that of the starting material, its specific capacitance increased 10.84%, from 175.40 to 194.01 F g⁻¹ and the potential of oxygen evolution on the composite material electrode was 0.076 V higher than that of the pure activated-carbon electrode, in the electrolyte of 6 mol/L KOH solution, so the hybrid capacitor had larger energy density. Similar to the pure activated-carbon electrode, no obvious change appears on the specific capacitances of the composite material electrode at various discharge currents and the composite material electrode exhibiting good power characteristics.     

Hardening effect induced by incorporation of SiC particles in nickel electrodeposits

Pure Ni and nickel matrix composite electrocoatings containing micron- and nano-SiC particles (1 μm and 20 nm respectively) were produced under direct and pulse current conditions from an additive-free Watts type bath. The effect of the particle size, codeposition percentage of SiC and type of imposed current on the microhardness as well as on the microstructure of the electrodeposits were investigated. Ni/SiC composite deposits prepared under either direct or pulse current conditions exhibited a considerable strengthening effect with respect to pure Ni coatings. The improved hardness of composite coatings was associated to specific structural modifications of Ni crystallites provoked by the adsorption of H⁺ on the surface of SiC particles, thus leading to a (211) texture mode of Ni crystal growth. Pulse electrodeposition significantly improved the hardness of the Ni/SiC composite coatings, especially at low duty cycles, in which grain refinement and higher SiC incorporation (vol. %) was achieved. The enhanced hardness of Ni/nano-SiC deposits, as compared to Ni/micron-SiC composites, was attributed to the increasing values of the number density of embedded SiC particles in the nickel matrix with decreasing particle size. In addition, the observed hardening effects of the SiC particles might be associated to the different embedding mechanisms of the particles, which could be characterized as inter-crystalline for micron-SiC and partially intra-crystalline for nano-SiC particles.     

Vacuum thermal treated electroless NiP-TiO2 composite coatings

Composite NiP-TiO₂ layers were prepared by simultaneous electroless deposition of Ni-P and TiO₂ on steel substrate, from a solution in which TiO₂ particles were kept in suspension by stirring. Deposits were characterized for its structure, morphology and hardness. It was found that the chemical composition of Ni-P matrix has been influenced by the incorporation of TiO₂ particles. TiO₂ particle incorporation increases with increase in their bath concentrations (0.5-2.0 g/l). An improvement (up to 20%) in microhardness was observed in both as plated and vacuum heat-treated composite coatings compared to Ni-P coatings. Electroless deposited composite coatings exhibit an amorphous structure of the nickel matrix in which crystalline titanium oxide is incorporated. Vacuum heat treatment leads to the formation of a crystalline layer in which the Ni and Ni₃P crystallites appear apart from those of the TiO₂ (anatase). Potentiodynamic polarization measurements made on these deposits in 3.5 wt.% sodium chloride solution showed decrease in the corrosion resistance for the as-plated and heat-treated composite coatings.     

CO3O4/MPS催化氧化NO性能

微乳法制备的介孔二氧化硅（MPS）负载Co3O4构成了Co3O4/MPS催化剂,考察了负载量、焙烧温度等制备条件和反应温度、空速、NO进口浓度、O2体积分数等操作条件对Co3O4/MPS催化氧化NO性能的影响,并对载体及催化剂进行了BET和XRD表征。结果表明：MPS比表面积远大于其它载体,Co3O4呈立方晶型,MPS负载25%的Co3O4在300 ℃下焙烧3 h得到催化剂的晶体颗粒最小,分散性好,具有最佳催化氧化活性和良好的稳定性,在NO进口浓度500 μL/L、O2体积分数10%、空速12 000 h－1的条件下,250 ℃时NO氧化率可达50%～60%（此时可获得最高的NOx吸收效率）,300 ℃氧化率达到80%以上,接近热力学平衡值。     

Preparation of Ni-coated TiC particles using potential hydrogen (pH) for dispersion into a molten metal

Titanium carbide (TiC) particles have been coated with nickel (Ni) particles to increase compatibility between the TiC particles and the metal matrix based on Ni, leading to the improvement in the dispersion of TiC particles into a molten matrix, as functions of the potential hydrogen (pH) of TiC suspension, and the heat-treatment condition. The TiC particles were dispersed into the aqueous solution with various pH values, and then nickel nitrate (Ni(NO₃)₂) as a Ni precursor was added at the TiC suspension. As the pH is increased the content of Ni phase on the surface of TiC particle is increased, due to the increment of attractive force between the TiC particle and the Ni ion by the augmentation of negative value on the surface of TiC particle. The Ni-coated TiC particles heat treated at 500 °C under H₂ atmosphere indicate the TiC and Ni phases only, whereas those heat treated at 1000 °C under Ar atmosphere show a titanium oxide (TiO₂) with the TiC and Ni phases, which is resulted from the oxidation of TiC particle by oxygen contained in Ar gas. The dispersibility of TiC particles into a molten metal would be improved through the coating of Ni particles (or phase), inducing the improvement and reliability of mechanical properties.     

载体氧化铝的粒径对对硝基苯酚加氢催化剂Ni/Al2O3的影响

The catalytic hydrogenation of p-nitrophenol to p-aminophenol was investigated over Ni/Al2O3 catalyst on alumina support with different particle size. It is found that support particle size has significant influences on physiochemical properties and catalytic activity of the resulting Ni/Al2O3 catalyst, but little influence on the selec-tivity. At a comparable amount of Ni loading, the catalytic activity of Ni/Al2O3 prepared with alumina support of smaller particle size is lower. The reduction behavior of the catalyst is a key factor in determining the catalytic activity of Ni/Al2O3 catalyst. The supported nickel catalyst 10.3Ni/Al2O3-3 improves the life span of the membrane by reducing fouling on the membrane surface compared to nano-sized nickel.     

载体氧化铝的粒径对对硝基苯酚加氢催化剂Ni/Al2O3的影响

The catalytic hydrogenation ofp-nitrophenol to p-aminophenol was investigated over Ni/Al2O3 catalyst on alumina support with different particle size. It is found that support particle size has significant influences on physiochemical properties and catalytic activity of the resulting Ni/A12O3 catalyst,but little influence on the selectivity. At a comparable amount of Ni loading,the catalytic activity of Ni/Al2O3 prepared with alumina support of smaller particle size is lower. The reduction behavior of the catalyst is a key factor in determining the catalytic activity of Ni/A12O3 catalyst. The supported nickel catalyst 10.3Ni/Al2O3-3 improves the life span of the membrane by reducing fouling on the membrane surface compared to nano-sized nickel.     

Effect of fluorine on hydrogenation of cyclohexene on sulfided Ni (or Co)Mo/Al2O3 catalysts

The effect of fluorine incorporation on alumina support on the surface structure of unpromoted molybdenum, promoted cobalt—molybdenum and nickel—molybdenum catalysts, and their activity for hydrogenation of cyclohexene has been studied. The incorporation of 0.2 and 0.8 wt.-% fluorine on the alumina was carried out by impregnation with NH₄F solutions. The catalysts in the oxidic state were characterized by X-ray diffraction and ammonia adsorption and in the sulfide state by X-ray photoelectron spectroscopy (XPS) and infra-red spectroscopy (IR) of adsorbed NO. The absence of significant changes in the binding energy values of Mo3d and Ni2p (or Co2p) levels in the XPS spectra of the fluorine-containing catalysts as compared to the fluorine-free counterpart does not support the existence of an electronic effect of fluorine. The quantitative XPS results showed, however, that fluorine clearly increases the dispersion of molybdenum and promoter, this being linearly correlated to surface fluorine content. The IR results of adsorbed NO also indicate that fluorine incorporation leads generally to minor sizes of MoS₂ slabs, and more exposed promoter atoms, except for the cobalt in the CoMo/F(0.2)A catalyst. It is suggested that the increase in the dispersion of the supported active phase is a secondary effect of fluorine incorporation, which may result from the observed textural changes of the alumina and its small partial solubilization provoked by NH₄F solution. It was found that the incorporation of fluorine enhances appreciably, moderately and considerably the hydrogenation activity of molybdenum, cobalt—molybdenum an nickel—molybdenum catalysts, respectively. Such increase in hydrogenation activity is not directly correlated to the exposed atoms probed by NO adsorption, and is only loosely related to molybdenum dispersion for the molybdenum and cobalt—molybdenum catalysts. The lack of similar reliable correlations for the nickel—molybdenum catalysts suggests that other structural parameters such as extent of reduction-sulfidation and certain configurations of molybdenum ions and sulfur vacancies may govern hydrogenation activity.     

One-step synthesis of single-phase (Co,Mg, Ni,Cu, Zn) O High entropy oxide nanoparticles through SCS procedure: Thermodynamics and experimental evaluation

Evaluation of the thermodynamic aspects of the synthesis process offers a better insight through the single-step synthesis of high entropy oxide particles. The thermodynamic calculations were used to specify the required conditions (fuel type and fuel amount) for the synthesis of single-phase (Co, Mg, Ni, Cu, Zn) O particles. Moreover, the impact of the activities coefficients alteration on the formation of (Co, Mg, Ni, Cu, Zn) O single-phase was calculated. Experiments were carried out using glycine, urea, citric acid, and hexamine at various fuel to oxidizer ratios (φ = 1.05, 1, 0.95, and 0.9) to explore the effect of fuel type and φ values on physicochemical properties of final product. Obtained results indicated that single-phase (Co, Mg, Ni, Cu, Zn) O powders were synthesized using glycine at the fuel-lean condition. Prepared powders exhibited promising crystallinity (59%), the thermal stability of 400 °C, 28 nm particle size, high porosity, and 15 m². g^?1 surface area.     

Composite Ni/Al2O3 coatings and their corrosion resistance

Composite coatings Ni/Al₂O₃ were electrochemically deposited from a Watts bath. Al₂O₃ powder with particle diameter below 1 μm was codeposited with the metal. The obtained Ni/Al₂O₃ coatings contained 5-6% by weight of corundum. The structure of the coatings was examined by scanning electron microscopy (SEM). It has been found that the codeposition of Al₂O₃ particles with nickel disturbs the nickel coating's regular surface structure, increasing its microcrystallinity and surface roughness. DC and AC electrochemical tests were carried out on such coatings in a 0.5 M solution of Na₂SO₄ in order to evaluate their corrosion resistance. The potentiodynamic tests showed that the corrosion resistance of composite coating Ni/Al₂O₃ is better than that of the standard nickel coating. After 14 days of exposure the nickel coating corrodes three times faster than the Ni/Al₂O₃ coating. The electrochemical behaviour of the coatings in the corrosive solution was investigated by electrochemical impedance spectroscopy (EIS). An equivalent circuit diagram consisting of two RC electric circuits: one for electrode, nickel corrosion processes and the other for processes causing coating surface blockage, were adopted for the analysis of the impedance spectra. The changes in the charge transfer resistance determined from the impedance measurements are comparable with the changes in corrosion resistance determined from potentiodynamic measurements.     

化学镀Ni-P-Cr2O3和Ni-P-SiO2复合镀层的研究

本文对化学镀镍及化学镀镍磷基质中SiO2与Cr2O3的共沉积进行了研究.微粒在不断生长的膜层中共沉积引起了新的化学复合镀层的出现,这些复合镀层许多都具有优异的耐磨及耐蚀性能.通过选取镀层合金/复合微粒/金属基体的组分可改进镀层,获得所需的性能,以满足特别的需求.在对这些复合镀层的应用需求正在迫近与增长的同时,其市场正在迅速扩张.本文开发出了一种合适的复合化学镀镍液,并通过维氏硬度法对化学复合镀镍层进行了表征.采用动电位极化及交流阻抗法测定了镀层的Taber耐磨性能及耐蚀性能.采用SEM及XRD对复合镀层的表面形貌进行了分析.     

Dry Reforming of Methane with a Ni/Al2O3‐YSZ Catalyst: The Role of the Catalyst Preparation Protocol

Many studies of Ni based ceramic supporting reforming catalysts are found in the literature. A synthesis of the reported results shows that their efficiency and durability are significantly affected by their fabrication protocol. This research has been aimed at evaluating how the conditions of 1) the ceramic support preparation and 2) the Ni deposition, through an impregnation‐drying‐calcination‐reduction protocol, affect the catalytic activity and the catalyst deactivation over time during methane dry reforming. The catalyst support used in this study was obtained by the mixing and pressing of alumina and YSZ (Yttria Stabilized Zirconia) powders, then calcining the mixtures at high temperature to form pellets of limited porosity (specific surface of 1.5‐10 m²/g), without inducing change to the crystalline phases. The results show that the surface density of the nickel particles, the catalyst activity, and its life span are highly dependent upon the catalyst preparation protocol. The initial nitrate solution concentration, the duration of the impregnation and the specific surface of the ceramic support have, all of them, a considerable influence on the size range of the deposited nickel particles. The surface density, the amount and the size of the latter highly affect the catalytic activity. It has been also shown that an increase in the ratio CH₄/CO₂ is detrimental to the catalytic activity of the tested formulations; a small excess of methane is enough to initiate the deactivation process of the catalyst very quickly for all of the composition tested in this study. A phenomenological deactivation kinetics model has been built and optimized. Although there are differences in deactivation rates among the different formulations tested, the model shows that the deactivation rate is highly dependent upon the reaction rate constant and that zero‐ and first‐order kinetics give statistically the same prediction error; the latter is always lower or equal to the experimental error.     

电沉积Ni-S-Co/ZrO_2复合电极及其催化析氢性能

在镀液中悬浮粒径为200～400 nm的ZrO2固体颗粒,以电沉积方法制备了Ni-S-Co/ZrO2复合电极。XRD和SEM测试结果表明,沉积层由非晶态的Ni、Co、S和单斜晶型的ZrO2粒子组成。镀层表面呈团粒状结构,无裂隙,与基体结合牢固。电化学测试结果表明,25℃时,Ni-S-Co/ZrO2复合电极在质量分数28%NaOH水溶液中,在电流密度100 mA/cm2下的超电势为145 mV,与未复合纳米ZrO2粒子的Ni-S-Co电极相比降低了50 mV。表明超细ZrO2的掺入有效提高了电极对析氢反应的催化效果。实验表明,沉积的最佳电流密度为70 mA/cm2,最适宜的ZrO2用量为15 g/L,采用Ni-S-Co作为过渡层可以显著改善复合镀层与基体的结合。     

Cathodic behaviour of RuO2-doped Ni/Co3O4 electrodes in alkaline solutions: hydrogen evolution

RuO2-doped Co3O4 electrodes were prepared by thermal decomposition of the corresponding nitrates using Ni as a support. The RuO2 content was varied between 0 and 20mol%. The kinetics of hydrogen evolution from alkaline solution was studied by recording quasisteady state polarization curves at several NaOH concentrations. A mechanism is proposed on the basis of Tafel slopes and reaction orders. The electrocatalytic activity of the mixed oxides has been found to go through a maximum at intermediate RuO2 contents. Some evidence of instability has emerged.     

电流密度对不锈钢基β-二氧化铅-二氧化钛-四氧化三钴复合镀层性能的影响

研究了电流密度对不锈钢基β-PbO2-TiO2-Co3O4复合镀层的沉积速率、显微硬度、表面形貌、结合力、电催化活性等性能的影响。镀液组成和其他工艺条件为:Pb(NO3)2250g/L,HNO310g/L,NaF0.5g/L,TiO215g/L,Co3O430g/L,温度50℃,pH1～2,沉积时间4h。通过扫描电镜、能谱仪和X射线衍射仪分析了复合镀层的形貌、组成和构相。结果表明,最佳电流密度为4A/dm2。在4A/dm2下,β-PbO2-TiO2-Co3O4复合镀层的沉积速率为15.31g/(h·dm2),显微硬度为653.3HV,表面平整、致密。镀层中Ti、Co的摩尔分数分别为2.22%和4.37%,表明TiO2和Co3O4颗粒与β-PbO2镀层实现了共沉积。