Effect of nano-size nickel particles on wear resistance and high temperature oxidation resistance of ultrafine ceramic coating

In order to improve the wear resistance and high temperature oxidation resistance of titanium and titanium alloy, the high temperature ultra fine ceramic coating containing nano-size nickel particles was prepared by flow coat method on the surface of industrially pure titanium TB1-0. The effects of nano-size nickel particles on the wear resistance and high temperature oxidation resistance of coating substrate system were investigated through oxidation kinetics experiment and wear resistance test. The morphologies of the specimens were examined by means of optical microscopy, scanning electron microscopy and X-ray diffraction. The results show that the high temperature ultra fine ceramic coating has notable protection effect on industrially pure titanium TB1-0 from oxidation. The oxidation and wear resistance properties of the coating can be effectively improved by adding nano-size nickel particles. The oxidative mass gain of the specimen decreases from 11.33 mg·cm-2 to 5.25 mg·cm-2 and the friction coefficient decreases from 1.1 to 0.6 by adding nano-size nickel particles, and the coating containing 10% （mass fraction） nano-size nickel shows the optimum properties.

A Facile Route for Synthesis of LiFePO_4/C Cathode Material with Nano-sized Primary Particles

A facile and practical route was introduced to prepare LiFePO4/C cathode material with nano-sized primary particles and excellent electrochemical performance. LiH2PO4 was synthesized by using H3PO4 and LiOH as raw materials. Then, as-prepared LiH2PO4, reduced iron powder andα-D-glucose were ball-milled, dried and sin-tered to prepare LiFePO4/C. X-ray diffractometry was used to characterize LiH2PO4, ball-milled product and LiFePO4/C. Differential scanning calorimeter-thermo gravimetric analysis was applied to investigate possible reac-tions in sintering and find suitable temperature for LiFePO4 formation. Scanning electron microscopy was em-ployed for the morphology of LiFePO4/C. As-prepared LiH2PO4 is characterized to be in P21cn（33） space group, which reacts with reduced iron powder to form Li3PO4, Fe3（PO4）2 and H2 in ball-milling and sintering. The appro-priate temperature for LiFePO4/C synthesis is 541.3-976.7 ℃. LiFePO4/C prepared at 700 ℃ presents nano-sized primary particles forming aggregates. Charge-discharge examination indicates that as-prepared LiFePO4/C displays appreciable discharge capacities of 145 and 131 mA·h·g^-1 at 0.1 and 1 C respectively and excellent discharge ca-pacity retention.

Deformation behavior of explosive detonation in electroformed nickel liner of shaped charge with nano-sized grains

Nickel liner of shaped charge with nano-sized grains was prepared by electroforming technique and the ultra-highstrain-rate deformation was performed by explosive detonation.The as-electroformed and post-deformed microstructures of electroformed nickel liner of shaped charge were observed by optical metallography(OM),scanning electron microscopy(SEM) and transmission electron microscopy(TEM) and the orientation distribution of the grains was analyzed by electron backscattering pattern(EBSP) technique.Both melting phenomenon in the jet fragment and recovery and recrystallization in the slug after ultra-high-strain-rate deformation were observed.The research evidence shows that dynamic recovery and recrystallization play an important role in ultra-high-strain-rate deformation for electroformed nickel liner of shaped charge with nano-sized grain.

Dispersion of Micro Diamond Particles in Electroless Nickel Solution

The dispersion behavior of micro-diamond particles ranging from 0 to 0.5 micron was compared between in DI water and in electroless nickel solution. The effects of the concentration of electroless solution, temperature, ultrasonic treatment, stirring speed, and baffles on the size distribution of micro diamond particles in electroless nickel solution were studied. Results show that the dispersion of micro diamond particles in DI water is obviously superior to that in electroless nickel solution. Micro diamond particles agglomerate evidently when the concentration of electroless solution Velect：VDI in dispersion media exceeds 5%0. Diamond particles agglomerate more and more seriously with the increase of the ion concentration. Applying ultrasonic, increasing stirring speed and adding baffles are helpful to improving the dispersion of diamond particles in the electroless nickel solution and its uniform distribution in the Ni-P coating.

Evolution of ferronickel particles during the reduction of low-grade saprolitic laterite nickel ore by coal in the temperature range of 900–1250℃with the addition of CaO–CaF_(2)–H_(3)BO_(3)

The method of producing ferronickel at low temperature(1250–1400℃)has been applied since the 1950s at Nippon Yakin Kogyo,Oheyama Works,Japan.Limestone was used as an additive to adjust the slag composition for lowering the slag melting point.The ferronickel product was recovered by means of a magnetic separator from semi-molten slag and metal after water quenching.To increase the efficiency of magnetic separation,a large particle size of ferronickel is desired.Therefore,in this study,the influences of CaO,CaF_(2),and H_(3)BO_(3) additives on the evolution of ferronickel particle at≤1250℃were investigated.The experiments were conducted at 900–1250℃with the addition of CaO,CaF_(2),and H_(3)BO_(3).The reduction processes were carried out in a horizontal tube furnace for 2 h under argon atmosphere.At 1250℃,with the CaO addition of 10 wt%of the ore weight,ferronickel particles with size of 20μm were obtained.The ferronickel particle size increased to 165μm by adding 10 wt%CaO and 10 wt%CaF_(2).The addition of boric acid further increased the ferronickel particle size to 376μm,as shown by the experiments with the addition of 10 wt%CaO,10 wt%CaF_(2),and 10 wt%H_(3)BO_(3).

Effect of initial nickel particle size on stability of nickel catalysts for aqueous phase reforming

The deactivation behavior by crystallite growth of nickel nanoparticles on various supports（carbon nanofibers, zirconia, Si C, α-Al2O3 and γ-Al2O3） was investigated in the aqueous phase reforming of ethylene glycol. Supported Ni catalysts of ~10 wt% were prepared by impregnation of carbon nanofibers（CNF）,Zr O2, SiC, γ-Al2O3 and α-Al2O3. The extent of the Ni nanoparticle growth on various support materials follows the order CNF ~ ZrO2〉 SiC 〉 γ-Al2O3〉〉 α-Al2O3 which sequence, however, was determined by the initial Ni particle size. Based on the observed nickel leaching and the specific growth characteristics; the particle size distribution and the effect of loading on the growth rate, Ostwald ripening is suggested to be the main mechanism contributing to nickel particle growth. Remarkably, initially smaller Ni particles（~12 nm） supported on α-Al2O3 were found to outgrow Ni particles with initially larger size（~20 nm）. It is put forward that the higher susceptibility with respect to oxidation of the smaller Ni nanoparticles and differences in initial particle size distribution are responsible for this behavior.

Coarsening behavior of γ' particles in a nickel-base superalloy

The coarsening behavior of γ particles in a nickel-base superalloy FGH95 was investigated by means of experimental observations and growth kinetics calculations. The results show that when aging at 1000,1080 and 1140°C for different times,the relation of average particle size to time obeys the cube law ( a /2)3= kt,where k is 15.49 × 103,77.5 × 103 and 230.04 × 103 nm3/min,respectively. The particle size distributions are better fit to the LSW theoretical distributions when aging at 1000°C within 1440 min....

Pulse electroforming of nickel under perturbation of hard particles

Nickel deposits were prepared by pulse electroforming, in which an aluminium alloy cylinder mandrel rotated in hard particles filling between the electrodes. The microstructure and properties of the deposits were studied by contrasting with electroforming using direct current. The results show that the surface of the deposits obtained by pulse electroforming displays more obvious abrasion marks and (200) preferred orientation to that electroformed using direct current at the same average current density. Besides, the deposits represent higher microhardness and better high-temperature corrosion resistance. It is also found that the orientation index of plane (200) and microhardness significantly increase with the reduction of duty cycle of pulse current. During pulse electroforming, the longer off-time and higher peak current density are helpful to strengthening the hard particles’ polishing effect on the surface of deposits and perturbing effect on crystal nucleation of atoms.

Effect of particle size on bioleaching of low-grade nickel ore in a column reactor

Biological column leaching of Ni from low-grade Ni ore was studied,and the effects of ore particle size on leaching rate were investigated.The Ni ore with an average Ni content of 0.23%was crushed into four different particle size fractions:>10 mm,5−10 mm,2−5 mm and<2 mm.The main strain components at the genus level were acidithiobacillus(53.11%),leptospirillum(43.52%),and acidiphilium(3.37%).The leaching tests were carried out at pH 2.0 and~23℃.The Ni leaching rates from ores with particle sizes>10 mm(bioleaching),5–10 mm(acid leaching),5–10 mm(bioleaching),and 2–5 mm(bioleaching)were 23.76%,22.15%,32.42%and 54.17%,respectively,after 180 d of bioleaching.The ore particle size changed after leaching,compared with the original ore size,the proportion of the same size of 2−5 mm ore decreased to 44.64%.Ore with particle size of 2–5 mm was most suitable for column bioleaching,and effective Ni extraction was achieved with appropriate control of ore granularity.

The Study of Structural and Magnetic Properties of NiO Nanoparticles

Nickel Oxide (NiO) is an important transition metal oxide with cubic lattice structure. Among the magnetic nanoparticles, fabrication of nickel nanoparticles is often more difficult than that of the other particles. This is because they are easily oxidized. To achieve pure nickel nanocrystals, numerous methods have been conducted in organic environments in order to prevent formation of hydroxide or oxidation. In the present work, we report the synthesis of NiO nanoparticles. Magnetic properties of NiO nanoparticles with different sizes and at different temperatures are compared. The phase structures, particle sizes and magnetic properties of NiO nanoparticles have been characterized by X-ray diffraction, TEM images and Vibrating Sample Magnetometer (VSM). We collected the experimental data reported in the literature, for the same conditions, and after fitting, extrapolating and doing some calculations. The magnetization for smaller nanoparticles is bigger for the samples we consider here. This difference could be explained by the difference of surface volume ratio of nanoparticle which shows the contribution of the paramagnetic surface is more important with respect to the anti-ferromagnetism of the core for smaller particles. Also the nanoparticle at lower temperatures shows bigger magnetization.

Effect of Substitution of Al for Fe on Magnetic Properties and Particle Size of Ni-Co Nanoferrite

Nanocrystalline Al doped nickel-cobalt ferrite [Ni0.6Co0.4Fe2-xAlxO4 (x = 0.0, 0.1, 0.3, 0.5 and 0.7)] powders have been synthesized by sol-gel auto-ignition method and the effect of non-magnetic aluminum content on the nanosize particles and magnetic properties has been studied. The X-ray diffraction (XRD) revealed that the powders obtained are single phase with inverse spinel structure. The calculated grain size from XRD data have been verified using transmission electron microscopy (TEM). TEM photograph shows that the powders consist of nano meter sized grain. The size of nanoparticles decreases as the non magnetic Al content increases. Magnetic hysteresis loops were measured at room temperature with maximum applied magnetic field of 20 KOe. As aluminum content increases, the measured magnetic hysteresis curves became narrow and saturation magnetization (Ms), and coercive force (Hc) decreased. The reduction of magnetization with the increase of aluminum content is caused by non-magnetic Al3+ ions and weakened interaction between sub-lattices.

Electrochemical performance of a nickel-rich LiNi0.6Co0.2Mn0.2O2 cathode material for lithium-ion batteries under different cut-off voltages

A spherical-like Ni0.6Co0.2Mn0.2(OH)2precursor was tuned homogeneously to synthesize LiNi0.6Co0.2Mn0.2O2as a cathode material for lithium-ion batteries. The effects of calcination temperature on the crystal structure, morphology, and the electrochemical performance of the as-prepared LiNi0.6Co0.2Mn0.2O2were investigated in detail. The as-prepared material was characterized by X-ray diffraction, scanning electron microscopy, laser particle size analysis, charge–discharge tests, and cyclic voltammetry measurements. The results show that the spherical-like LiNi0.6Co0.2Mn0.2O2material obtained by calcination at 900°C displayed the most significant layered structure among samples calcined at various temperatures, with a particle size of approximately 10 μm. It delivered an initial discharge capacity of 189.2 mAh•g−1at 0.2C with a capacity retention of 94.0% after 100 cycles between 2.7 and 4.3 V. The as-prepared cathode material also exhibited good rate performance, with a discharge capacity of 119.6 mAh•g−1at 5C. Furthermore, within the cut-off voltage ranges from 2.7 to 4.3, 4.4, and 4.5 V, the initial discharge capacities of the calcined samples were 170.7, 180.9, and 192.8 mAh•g−1, respectively, at a rate of 1C. The corresponding retentions were 86.8%, 80.3%, and 74.4% after 200 cycles, respectively. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

Compression Mechanical Behaviour of 7075 Aluminium Matrix Composite Reinforced with Nano-sized SiC Particles in Semisolid State

The 7075 aluminium matrix composite reinforced with nano-sized Si C particles was fabricated by ultrasonic assisted semisolid stirring method. The compression mechanical behaviour of the fabricated composite in semisolid state was investigated. The results show that the microstructure of the composite before semisolid compression consists of fine and spheroidal solid grains surrounded by liquid phase.Semisolid compression led to a nonuniform plastic deformation of solid grains. A slight plastic deformation occurred in the locations near the free surface due to the dependence of deformation on liquid flow and flow of liquid incorporating solid grains. However, obvious plastic deformation occurred in the central location and location contacting to die due to the contribution of plastic deformation of solid grains.The true stress–strain curve of the sample compressed at 500 °C consists of rapid increase of true stress and steady stage. However, rapid increase of true stress and decrease of true stress and steady stage are involved in the true stress–strain curves of the samples compressed at 550, 560, 570, 580 and 590 °C.The true stress–strain curve at 600 °C is similar to that at 500 °C. Apparent viscosity decreases with an increase of shear rate, indicating a shear thinning occurrence. When soaking time increases from 5 min to 15 min, the peak stress and steady stress decrease significantly. A further increase of the soaking time led to a slight change. Peak stress and steady stress increase with increasing volume fraction of Si C particles. A sudden increase or decrease of compression velocity led to a significant increase or decrease of the steady stress. The destruction of the samples compressed at solid state temperature mainly depends on cracks parallel to compression direction. However, the destruction forms of the samples compressed at semisolid temperatures consist of cracks parallel to compression direction and partial collapse. Increasing soaking time led to an obvious change of the destruction forms. Compression velocity affects slightly the macro appearance of the sample compressed at semisolid temperatures.

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.

Deactivation studies of nano-structured iron catalyst in Fischer-Tropsch synthesis

A nano-structured iron catalyst for syngas conversion to hydrocarbons in Fischer-Tropsch synthesis（FTS） was prepared by micro-emulsion method.Compositions of bulk iron phase and phase transformations of carbonaceous species during catalyst deactivation in FTS reaction were characterized by temperature-programmed surface reaction with hydrogen（TPSR-H 2 ）,and XRD techniques.Many carbonaceous species on surface and bulk of the nano-structured iron catalysts were completely identified by combined TPSR-H 2 and XRD spectra and which were compared with those recorded on conventional co-precipitated iron catalyst.The results reveal that the catalyst deactivation results from the formation of inactive carbide phases and surface carbonaceous species like graphite,and it will be increased when the particle size of iron oxides was reduced in FTS iron catalyst.

Experimental study by online measurement of the precipitation of nickel hydroxide: Effects of operating conditions

The objective of this work is using the online measurement method to study the process of precipitation of nickel hydroxide in a single-feed semi-batch stirred reactor with an internal diameter ofD = 240mm. The effects of impeller speed, impeller type, impeller diameter and feed location on the mean particle size d43 and particle size distribution （PSD） were investigated, d43 and PSD were measured online using a Malvern Insitec Liquid Pro- cess Sizer every 20 s. It was found that d43 varied between 13 kwh and 26 lain under different operating conditions, and it decreased with increasing impeller diameter. When feeding at the off-bottom distance of D/2 under lower impeller speeds, d43 was significantly smaller than that at D/3. PSDs were slightly influenced by operating conditions.

电沉积法制备高纯镍粉

采用电沉积法制备高纯度镍粉,用Zeta电位仪、电感耦合等离子体发射光谱仪、扫描电子显微镜和X射线衍射分析等手段分别表征产物镍粉的粒度、化学成分、微观形貌和微观晶体结构。系统探究了工艺参数电流密度、镍离子质量浓度、电解液pH值、NH_(4)Cl质量浓度、电解温度和取粉时间等因素对电积镍粉粒度、电流效率以及镍粉微观形貌的影响。结果表明,工艺参数电流密度、镍离子质量浓度、电解液pH值、NH_(4)Cl质量浓度、电解温度和取粉时间均对电积镍粉的粒度分布和形貌等有显著影响;电极板间距为30 mm时的最佳工艺参数条件为:电流密度为3000 A/m^(2)、电积液Ni^(2+)质量浓度为5 g/L、pH值为5、温度40℃、添加剂NH_(4)Cl质量浓度为10 g/L、取粉时间间隔为120 s,在此试验条件下所得镍粉粒度分布均匀,颗粒微观形貌为树枝状,镍粉纯度可达到99.87%;模拟工业生产电解液成分人工配制的含杂质离子Fe^(3+)、Cu^(2+)的硫酸镍溶液为电解液进行电积试验,可得到镍粉纯度为99.84%、粒度分布均匀、微观形貌呈树枝状的高纯镍粉。研究结果可为工业电积镍制备高纯镍粉提供参考。

无保护层纳秒脉冲激光强化对DD5单晶合金耐磨性能的影响

目的提高发动机涡轮叶片榫头材料DD5单晶高温合金的高温耐磨性能。方法采用不同能量的无保护层纳秒脉冲激光对DD5单晶合金试样表面进行处理,利用摩擦磨损试验机获得DD5单晶合金在650℃下的摩擦磨损性能参数,并通过显微硬度计、扫描电子显微镜、能谱仪、共聚焦三维表面轮廓仪对磨损前后的DD5单晶试件进行表征分析,揭示纳秒脉冲激光强化技术提高单晶高温合金耐磨性能的机理。结果采用纳秒脉冲激光处理DD5单晶高温合金后,材料表层发生了重熔现象,并在重熔层中生成了弥散分布的铝的氧化物颗粒,其粒径为5~50nm;纳秒脉冲激光处理后产生的弥散分布的氧化铝颗粒为硬质相,它提升了单晶表面的显微硬度;经纳秒脉冲激光处理后,试样的磨损率降低了19.7%~37.6%,单晶合金的磨损机制以磨粒磨损为主。结论经纳秒脉冲激光处理后,单晶表面生成了含有弥散分布的纳米氧化铝颗粒的重熔层,在它与激光诱导的等离子体冲击波产生的硬化层的共同作用下,提升了镍基单晶高温合金在高温下的耐磨性能。

高效三维电极电Fenton降解苯酚实验研究

酚类化合物是一种有毒污染物,难以生物降解。电Fenton技术是去除酚类物质的有效手段之一。通过热溶剂—涂覆—焙烧法制备Fe_(3)O_(4)负载碳纳米管修饰泡沫镍(Fe_(3)O_(4)/CNT/NF)粒子电极,可在电解系统中同时产生H_(2)O_(2)和Fe^(2+)。以Fe_(3)O_(4)/CNT/NF作为粒子电极构建三维电极电Fenton系统对苯酚进行降解,苯酚去除率明显高于基于Fe_(3)O_(4)/NF和NF粒子电极的三维电极及二维电极体系。对反应条件进行优化后,在降解时间60 min、极板间距3.0 cm、Fe_(3)O_(4)/CNT/NF粒子电极投加量8.0 g/L、电流350 mA、电解质浓度100 mmol/L、初始pH为4的条件下,苯酚去除率可达76.23%。猝灭实验结果表明,该体系中羟基自由基(·OH)在降解过程中起主要作用。此外,电极稳定性能优异,6次循环实验后对苯酚的去除率仅降低6.09%。

Ni-Fe/PAC颗粒电极电芬顿降解焦化废水生化尾水的研究

针对焦化废水生化尾水中还存在大量难降解有机物的问题,采用活性炭负载镍铁的颗粒电极Ni-Fe/PAC进行降解处理。SEM、XRD、FTIR和BET表征结果显示,Ni-Fe/PAC负载的金属为镍铁合金,暴露于空气后,表面会形成铁氧化物,经碱液浸渍后的比表面积从717.95 m^(2)/g增加到了835.43 m^(2)/g,孔径主要分布在1~10 nm内。投加0.1 mmol/L的H_(2)O_(2)后,能显著提高·OH产生量和TOC的去除效率,且在0.2 A和水力停留时间60 min下,TOC和COD的去除效率达到64.9%和85%。处理后出水的pH为11.31,线性伏安扫描(LSV)和循环伏安扫描(CV)显示,碱性条件下,Ni-Fe/PAC的电化学活性面积(ECSA)面积达到250.17 cm^(2),析氢和析氧的Tafel斜率分别为148 mV/dec和261 mV/dec。电极使用后,表面形貌、晶体结构和官能团未发生明显改变,催化性能稳定。