Direct chemical vapor deposition growth of graphene on Ni particles using solid carbon sources

Graphene has attained a considerable amount of popularity as an attractive ultra-thin reinforcement for nickel(Ni)matrix composites in recent years.However,its excellent reinforcement efficiency is suffered from the agglomeration of graphene nanosheets in manufacturing process and the poor bonding strength of graphene with Ni matrix.To overcome these two problems,one of the efficient strategies is to in-situ grow graphene reinforcements on Ni particles for powder metallurgy.This work aims to synthesize uniform graphene@Ni composite particles by using polymethyl methacrylate(PMMA)as the solid sources for chemical vapor deposition(CVD)process.The results demonstrate that few-layer or multilayer graphene with different morphologies can be grown on the particles by controlling the PMMA content and annealed temperature,respectively.The optimum condition for the formation of high-quality few-layer graphene is 1.0 mg·ml^(-1) PMMA and 900℃.A competition mechanism rises from the growth kinetic,and the spatial confinement effect has led to the formation of graphene with different microstructures and morphologies.

Effect of Ni on Removal of Pentachlorophenol with Fe Nanoparticles

Chlorinated phenols are a kind of environmental priority pollutants that attract much attention. The effect of Ni on the removal of pentachlorophenol （PCP） with Fe nanoparticles was investigated in this study. Fe nanoparticles and Ni submicron particles were synthesized using chemical reduction method and wet chemical techniques, respectively. And the concentrations of PCP and chloride ion in solutions were measured with and without Ni present. The results showed that the dechlorination of PCP was promoted in the presence of Ni particles, and the dechlorination efficiency was reduced along with the increase of Ni size. When the diameter of Ni particle was smaller than 300 nm, the removal efficiency of PCP was obviously increased in the initial 4 h, and then became the similar to that of the system with Fe only. When the diameter of Ni particle was between 400 nm and 1 μm, the removal efficiency of PCP was increased in the initial 1 h. Then the removal of PCP was inhibited, and the inhibition was increased with the increase of Ni size. Later, the removal efficiency was the similar in various systems.

Effect of solidification process parameters on dry sliding wear behavior of AlNiBi alloy

As-cast samples of the Al-3wt.%Ni-lwt.%Bi alloy resulting from the horizontal directional solidification process were subjected to the micro-abrasive wear test.The effects of the solidification thermal and microstructural parameters,such as the growth and cooling rates and the cellular and primary dendritic spacings(VL and TR;λ1 and λc;respectively),were evaluated in the wear resistance of the investigated alloy.The tribological parameters analyzed were the wear volume and rate(Vw and Rw).The solidification experiments and the wear tests were carried out by means of a water-cooled horizontal directional solidification device and a rotary-fixed ball wear machine,respectively.The results show lower Vw and Rw values correspond to finer microstructures and the Vw dependence on λ1 is characterized by an experimental mathematical equation.A better distribution of Bi soft droplets and Al3Ni hard intermetallic particles is observed within the finer interdendritic region and,in consequence,the better wear resistance is achieved in as-cast samples with dendritic morphology rather than cellular morphology.A transition of wear mechanism from adhesive to abrasive is observed.

Effect of the Ni size on CH4/CO2 reforming over Ni/MgO catalyst：A DFT study

Carbon deposition is sensitive to the metal particle sizes of supported Ni catalysts in CH_4/CO_2 reforming.To explore the reason of this phenomenon,Ni4,Ni8,and Ni12 which re flect the different cluster thicknesses supported on the MgO(100) slabs,have been employed to simulate Ni/MgO catalysts,and the reaction pathways of CH_4/CO_2 reforming on Nix/MgO(100) models are investigated by density functional theory.The reforming mechanisms of CH_4/CO_2 on different Nix/MgO(100) indicate the energy barriers of CH_4 dissociated adsorption,CH dissociation,and C oxidation three factors are all declining with the decrease of the Ni cluster sizes.The Hirshfeld charges analyses of three steps as described above show only Ni atoms in bottom two layers can obtain electrons from the MgO supporters,and the main electron transfer occurs between adsorbed species and their directly contacted Ni atoms.Due to more electron-rich Ni atoms in contact with the MgO supporters,the Ni/MgO catalysts with small Ni particles have a strong metal particle size effect and lead to its better catalytic activity.

Pyrochlore La_(2)Zr_(2-x)Ni_(x)O_(7)anodes for direct ammonia solid oxide fuel cells

Developing efficient anode catalysts for direct ammonia solid oxide fuel cells(NH_(3)-SOFCs)under intermediate-temperatures is of great importance,in support of hydrogen economy via ammonia utilization.In the present work,the pyrochlore-type La_(2)Zr_(2-x)Ni_(x)O_(7+δ)(LZN_(x),x=0,0.02,0.05,0.08,0.10)oxides were synthesized as potential anode catalysts of NH_(3)-SOFCs due to the abundant Frankel defect that contributes to the good conductivity and oxygen ion mobility capacity.The effects of different content of Ni^(2+)doping on the crystal structure,surface morphology,thermal matching with YSZ(Yttria-stabilized zirconia),conductivity,and electrochemical performance of pyrochlore oxides were examined using different characterization techniques.The findings indicate that the LZN_(x)oxide behaves as an n-type semiconductor and exhibits an excellent high-temperature chemical compatibility and thermal matching with the YSZ electrolyte.Furthermore,LZN_(0.05)exhibits the smallest conductive band potential and bandgap,making it have a higher power density as anode material for NH_(3)-SOFCs compared to other anodes.As a result,the maximum power density of the LZN_(0.05)-40YSZ composite anode reaches 100.86 mW/cm^(2)at 800℃,which is 1.8 times greater than that of NiO-based NH_(3)-SOFCs(56.75 mW/cm^(2))under identical flow rate and temperature conditions.The extended durability indicates that the NH_(3)-SOFCs utilizing the LZN_(0.05)-40YSZ composite anode exhibits a negligible voltage degradation following uninterrupted operation at 800℃for 100 h.