微波消解-微波等离子体矩原子发射光谱法测定乳胶管中的铁、钙、镍、镁、锌

本文研究了用HNO3-H2O2微波消解样品,微波等离子体矩原子发射光谱（MPTAES）测定乳胶管中铁,钙,镍,镁,锌的含量方法.详细考察了测定铁、钙、镍、镁、锌的最佳实验条件,以及介质酸、共存离子的影响.本方法测定铁、镍、镁、钙、锌的检出限分别为77.80、7.55、2.70、275.87、46.23 ng/mL,方法的精密度分别为3.10%、2.19%、2.22%、1.27%、2.90%,线性范围分别为0.08～2 mg/L、0.06～2 mg/L、0.001～3 mg/L、0.005～2 mg/L、0.05～1 mg/L,加标回收率分别在97.7%～107.8%、96.0%～106.7%、98.0%～106.2%、92.3%～108.8%、98.7%～106.8%范围.

ICP-AES法同时测定红土型镍矿中镍、钴、铁、镁研究

通过选择分析谱线、处理样品方法和消除干扰因素等实验,建立ICP-AES法同时测定红土型镍矿中镍、钴、铁、镁4种元素的方法,解决利用常规化学法测定步骤繁琐,分析周期长,工作量大等问题,方法回收率为99.2%-105%,精密度（RSDn=10）为0.42%-3.89%。

含镍蛇纹石的综合利用现状

镍蛇纹石中含有大量的镍、镁、铁等资源,但其中的镍等主要以类质同象的形式赋存,采用常规选矿工艺难以实现其中有用矿物的综合利用。本文针对镍蛇纹石中镍、镁、铁、硅等的综合利用做一个简单地介绍,并根据现有的工艺分析推测出镍蛇纹石研究中具有潜力的一些研究方向。

Vermiform Ni@CNT derived from one-pot calcination of Ni-MOF precursor for improving hydrogen storage of MgH_(2)

The Ni-coated carbon nanotubes(Ni@CNT)composite was synthesized by the facile“filtration+calcination”of Ni-based metal−organic framework(MOF)precursor and the obtained composite was used as a catalyst for MgH_(2).MgH_(2)was mixed evenly with different amounts of Ni@CNT(2.5,5.0 and 7.5,wt.%)through ball milling.The MgH_(2)−5wt.%Ni@CNT can absorb 5.2 wt.%H_(2)at 423 K in 200 s and release about 3.75 wt.%H_(2)at 573 K in 1000 s.And its dehydrogenation and rehydrogenation activation energies are reduced to 87.63 and 45.28 kJ/mol(H_(2)).The in-situ generated Mg_(2)Ni/Mg_(2)NiH4 exhibits a good catalytic effect due to the provided more diffusion channels that can be used as“hydrogen pump”.And the presence of carbon nanotubes improves the properties of MgH_(2)to some extent.

Recovery of cobalt and nickel in the presence of magnesium and calcium from sulfate solutions by Versatic 10 and mixtures of Versatic 10 and Cyanex 301

The extraction and stripping characteristics of Versatic 10 and its mixtures with Cyanex 301 were investigated for the recovery of cobalt and nickel from sulfate solutions containing magnesium and calcium. The optimum extraction factors of Versatic 10 were initial pH of 2.5, O/A ratio of 1/3, and saponification rate of 60%. The loaded Versatic 10 was stripped by using 2 mol/L H2SO4 at O/A ratio of 1/1. The optimum volume ratio of Versatic 10 to Cyanex301 was 7/3 in the mixtures, which could effectively reduce the equilibrium pH to 3.50. And the loaded mixtures were stripped by using 2 mol/L H2SO4at O/A ratio of 1/2. The reaction principle of Versatic10 and metal ions is an ion exchange reaction. However, in the extraction reaction of and metal ions, besides the ion exchange reaction, the strong coordination effect between Cyanex 301 and metal ions also exists, which is much weakened in the extraction reaction of the mixtures and metal ions.

Electrochemical hydriding performance of Mg-TM-Mm (TM=transition metals,Mm=mischmetal) alloys for hydrogen storage

Eighteen as-cast binary Mg-Ni, Mg-Mm and ternary Mg-Ni-Mm and Mg-Ni-TM （TM=transition metals （Cu, Zn, Mn and Co）; Mm = mischmetal containing Ce, La, Nd and Pr） alloys were hydrided by an electrochemical process to determine the alloys with the most potential for electrochemical hydrogen storage. The alloys were hydrided in a 6 mol/L KOH solution at 80 °C for 480 min and at 100 A/m2. To assess the electrochemical hydriding performance of alloys, maximum hydrogen concentrations, hydrogen penetration depths and total mass of absorbed hydrogen in the alloys were measured by glow discharge spectrometry. In addition, the structures and phase compositions of the alloys both before and after hydriding were studied by optical and scanning electron microscopy, energy dispersive spectrometry and X-ray diffraction. It was determined that the highest total amount of hydrogen was absorbed by the Mg-25Ni-12Mm and Mg-26Ni （mass fraction, %） alloys. The maximum hydrogen concentrations in the Mg-25Ni-12Mm and Mg-26Ni alloys were 1.0% and 1.6%, respectively. The main hydriding product was the binary MgH2 hydride, and the ternary Mg2NiH4 hydride was also detected in the Mg-25Ni-12Mm alloy. The electrochemical hydriding parameters achieved are discussed in relation to the structures of alloys, alloying elements and hydriding mechanisms.

Role of milling time and Ni content on dehydrogenation behavior of MgH_2/Ni composite

The effects of ball milling time and Ni content on the dehydrogenation performance of MgH2/Ni composite weresystematically investigated.The structural evolution of ball milled MgH2+x%Ni(x=0,2,4,8,20,30,mass fraction)samples duringmechanical milling process and dehydrogenation properties were investigated by a series of experimental techniques.The resultsshow that the desorption kinetics is independent of particle size,grain size and defects as the temperature is above380oC.Thedesorption kinetics is improved by prolonged milling time due to refined and uniformly distributed Ni.The formation of Mg2Ni afterdehydrogenation is proposed to explain the degradation of hydrogen storage properties of MgH2during de-/hydrogenation cyclingprocess.The desorption activation energy of MgH2decreases with the increase of Ni content due to the catalytic effect of Ni.It isfound Ni favors the nucleation of magnesium phase and accelerates the recombination of hydrogen atoms.

Properties of fluoride film and its effect on electroless nickel deposition on magnesium alloys

The physical characteristics and microstructure of the fluoride film formed during activation were investigated using SEM,XPS and SAM,and its stability in electroless nickel(EN) bath was analyzed.The effects of the fluoride film on EN deposition were studied additionally.The results show that the fluoride film on magnesium alloys is a kind of porous film composed of MgF2 with thickness of 1.6-3.2 μm.The composition of the activation bath and pretreatment of EN processing have influence on the composition of the fluoride film.The fluoride is stable and dissolves little in EN bath;as a result,the fluoride film can protect magnesium substrate from the corrosion of EN bath.The composition of fluoride determines the initial deposition of EN and part of the fluoride film finally exists as inclusion in EN coating.

Microstructure of nickel foam/Mg double interpenetrating composites

The magnesium matrix double interpenetrating composites reinforced by nickel foam were fabricated by pressureless infiltration technology.Then the morphology of the nickel reinforcement and the microstructures of composites were characterized by SEM.The results show that not only is the nickel foam reinforcement reticular in three dimensions,but also the struts of foam keep the network structure,which ensures that the Ni foam/Mg composites are double interpenetrating.The interface bonding of composites between magnesium matrix and nickel foam reinforcement is good,without reaction around the interface,which is the indispensable condition that advanced composites should possess.Magnesium matrix distributes in the windows of nickel foam,the triangle center holes and microhole of nickel struts,and the composites have double interpenetrating structure,which makes the composites have unique properties.

Application of response surface methodology in optimization of bioleaching parameters for high-magnesium nickel sulfide ore

The response surface methodology(RSM)was used to optimize the operating parameters during the bioleaching of Jinchuan high-magnesium nickel sulfide ore.The particle size,acid addition,pulp density and inoculation amount were chosen as the investigated parameters.To maximize the leaching efficiency of nickel,copper,cobalt and minimize the dissolution of magnesium and iron ions,the model suggested a combination of optimal parameters of particles less than 0.074 mm being 72.11%,sulfuric acid addition being 300 kg/t,pulp density being 5%and inoculation amount being 12.88%.Under the conditions,the average results of three parallel experiments were 89.43%of nickel leaching efficiency,36.78%of copper leaching efficiency,84.07%of cobalt leaching efficiency,49.19%of magnesium leaching efficiency and 0.20 g/L of iron concentration.The model indicated that the most significant factor in response of the leaching efficiency of valuable metal is the particle size,and the most significant factor in response to the leaching efficiency of harmful ions(Mg2+)is the amount of sulfuric acid addition.And according to the suggested models,no significance of the interaction effect between particle size and acid addition was shown.Under the optimized parameters suggested by models,the valuable metals could be separated from harmful ions during the bioleaching process.

Hydrogenation properties of mechanically milled Mg_2Ni_(0.8)Cr_(0.2)-CoO/Al_2O_3 composites

Mg2Ni0.8Cr0.2-x wt.% CoO/Al2O3 (x=0.5, 1, 2 and 3) composites were prepared by mechanically milling sintered Mg2Ni0.8Cr0.2 alloy and CoO/Al2O3 compound for 45 h. The addition of CoO/Al2O3 compound resulted in the good kinetics properties of hydriding/dehydriding reaction of the composites. The composite with 1.0 wt.% CoO/Al2O3 catalyst could reach the maximum hydrogen absorption capacity (2.9 wt.%) within 5 min at 393 K under H2 pressure of 4 MPa, and can desorb rapidly at 493 K. The decomposition and synthesis of hydrogen molecule on Mg2Ni0.8Cr0.2 alloy surface was promoted by addition of CoO/Al2O3 catalyst. In addition, the formation of metallic Ni particles, strain and defects during the ball milling process also resulted in the improved hydrogenation performance of Mg2Ni-based alloys.

Effect of initial deposition behavior on properties of electroless Ni-P coating on ZK60 and ME20 magnesium alloys

The composition of magnesium alloys is greatly associated with initial deposition behavior of electroless Ni-P coatings.Thus,the initial deposition behavior of electroless Ni–P coatings on ZK60 and ME20 alloys was investigated.The results indicated that differences in the alloy compositions significantly influenced the initial deposition process and the adhesive strength,corrosion resistance,and crystal structure.The initial deposition of coatings on ZK60 and ME20 alloys preferentially occurred on the precipitates.The precipitates in ZK60 alloy had higher chemical activity after HF activation and controlled the initial deposition rate of the coating.The initial deposition rate of the coating on ME20 alloy mainly depended on the density of the Mg F2 film formed by HF activation rather than on the precipitates.Owing to differences in the initial deposition process,the coating on ZK60 alloy had higher adhesive strength and better corrosion resistance than that on ME20 alloy.The coatings on ZK60 and ME20 alloys mainly had crystalline structures,and the coating on ME20 alloy had also a slight microcrystalline structure.

Electrooxidation of methanol and ethanol on carbon electrodeposited Ni–MgO nanocomposite

Ni–MgO nano‐composites were prepared on carbon anodes by electrodeposition from a nickel Watts bath in the presence of fine MgO reinforcement particles. Their performance as electrocata‐lysts for the oxidation of methanol and ethanol in alkaline medium was investigated and compared with that of carbon coated pure Ni （Ni/C）. The chemical composition, phase structure, and surface morphology of the deposited nano‐composites were studied by energy dispersive X‐ray spectros‐copy, X‐ray diffractometry, and scanning electron microscopy, respectively. Different electrochemi‐cal techniques were used to estimate the catalytic activity of the prepared electrocatalyst anodes, including cyclic voltammetry （CV）, chronoamperometry, and electrochemical impedance spectros‐copy （EIS）. The Ni/C electrocatalyst alone exhibited remarkably low catalytic activity and poor stability toward the electrooxidation process. The inclusion of MgO significantly promoted the cata‐lytic activity of the Ni catalyst for the alcohol electrooxidation and enhanced its poisoning re‐sistance. The EIS results confirmed those of CV and revealed a lower charge transfer resistance and enhanced roughness for the Ni–MgO/C nano‐composite electrodes compared with those of Ni/C.

Microstructures and mechanical properties of Ni-coated SiC particles reinforced AZ61 alloy composites

In order to improve the interface bonding of SiCp/AZ61 composites prepared by powder metallurgy followed by hot extrusion, the electroless plating of Ni-P coating on SiCp was carried out. The influence of Ni coating on microstructure and mechanical properties of the composites was analyzed. The results show that SiC particles distribute more uniformly in the composites after surface Ni plating and there are fewer defects in Ni-coated composite. The Ni coating reacts with the magnesium matrix forming the Mg2Ni interfacial compound layer during the sintering process. The relative density of the composite increases from 97.9% to 98.4% compared with uncoated one and the hardness of the Ni-coated composite increases more rapidly as the volume fraction of SiCp increases. The tensile test results show that the tensile strength increases from 320 to 336 MPa when the volume friction of SiC particle is 9% and the Ni-coated composites have larger elongation, indicating that Ni coating improves the interfacial bonding strength and the performance of the composites. In addition, the fracture properties of SiCp/AZ61 composites were analyzed.

Influence of pH values on electroless Ni-P-SiC plating on AZ91D magnesium alloy

A novel Ni-P-SiC composite coating was prepared by electroless plating in order to improve the corrosion capacity and wear resistance of AZ91D magnesium alloy.The influence of pH values on deposition rates and properties of the coatings was studied.The microstructure and phase structure of the Ni-P-SiC coatings were analyzed by scanning electron microscopy(SEM)and X-ray diffractometry(XRD).The corrosion and wear resistance performances of the coatings were also investigated through electrochemical technique and pin-on-disk tribometer,respectively.The results indicate that the composite coating is composed of Ni, P and SiC.It exhibits an amorphous structure and good adhesion to the substrate.The coatings have higher open circuit potential than that of the substrate.The composite coating obtained at pH value of 5.2 possesses optimal integrated properties,which shows similar corrosion resistance and ascendant wear resistance properties to the substrate.

Formation mechanism of electroless plating nickel-based composite coating on highly active rare earth magnesium alloys and its corrosion resistance and adhesion performance

The process of preparing anodic oxide film containing active sites and electroless nickel plating on highly active rare earth magnesium alloy was developed.The formation mechanism of electroless nickel plating on active anodic oxide film and the structure and properties of the composite coating were studied by several surface and electrochemical techniques.The results showed that Ag nanograins with an average size of 10 nm were embedded into the anodic oxide film with pores of 0.1−2μm.Ag nanoparticles provided a catalytic site for the deposition of Ni-B alloy,and the Ni crystal nucleus was first grown in horizontal mode and then in cylindrical mode.The corrosion potential of the composite coating increased by 1.37 V and the corrosion current reduced two orders of magnitude due to the subsequent deposition of Ni-P alloy.The high corrosion resistance was attributed to the misaligning of these micro defects in the three different layers and the amorphous structure of the Ni-P alloy in the outer layer.These findings provide a new idea for electroless nickel plating on anodic oxide film.