激光熔敷镍石墨烯立方氮化硼涂层的耐磨性能

在AISI 4140基体上采用预置材料激光熔敷的方法制备了镍石墨烯立方氮化硼(Ni-Graphene-CBN)复合材料涂层。X射线衍射(XRD)和Raman测试证明了石墨烯和CBN存在于所制备的涂层材料中。扫描电镜(SEM)图片给出了所制备的复合材料涂层的表面和断面形貌。进行了复合材料涂层的纳米机械性能和耐磨性的测试。测试结果表明:随着CBN含量的增加,复合涂层的硬度及弹性模量相应提高,分别由4.3 GPa提高到6.2 GPa和101 GPa提高到140 GPa; 同时其耐磨性也有明显改善,6% CBN含量的涂层摩擦系数由基体材料的0.2降低到0.15,最大磨损量降到基体磨损量的一半。     

A simple approach to synthesize nanosized sulfur/graphene oxide materials for high-performance lithium/sulfur batteries

We report on a simple and facile synthesis route for the sulfur/graphene oxide composite via ultrasonic mixing of the nano-sulfur and graphene oxide aqueous suspensions followed by a low-temperature heat treatment. High-resolution transmission and scanning electronic microscopy observations revealed the formation of a highly porous structure consisting of sulfur with uniform graphene oxide coating on its surface. The resulting sulfur/graphene oxide (S/GO) composite exhibited high and stable specific discharge capacities of 591 mAh g^?1 after 100 cycles at 0.1 C and good rate capability. This enhanced electrochemical performance could be attributed to the effective confining the polysulfides dissolution and accommodation of the volume changes during the Li-S electrochemical reaction by the functional groups on the graphene oxide coating layer. Furthermore, the highly developed porous structure of S/GO composite favors the enhanced ion transport and electrolyte diffusion.     

Effect of the dispersibility of ZrO2 nanoparticles in Ni-ZrO2 electroplated nanocomposite coatings on the mechanical properties of nanocomposite coatings

ZrO₂ nanoparticles was uniformly co-deposited into a nickel matrix by electroplating of nickel from a Watts bath containing particles in suspension which were monodispersed with dispersant under DC electrodeposition condition. It was found that morphology, orientation and hardness of the nanocomposite coatings with monodispersed ZrO₂ nanoparticles had lots of difference from the nanocomposite coatings with agglomerated ZrO₂ nanoparticles and pure nickel coatings. Especially, the result of hardness showed that only a very low volume percent (less than 1 wt.%) of monodispered ZrO₂ nanoparticles in Ni-ZrO₂ nanocomposite coatings would result in higher hardness of the coatings. The hardness of Ni-ZrO₂ nanocomposite coatings with monodispersed and agglomerated ZrO₂ nanoparticles were 529 and 393 HV, respectively. The hardness value of the former composite coatings was over 1.3 times higher than that of the later. All these composite coatings were two-three times higher than that of pure nickel plating (207 HV) prepared under the same condition. The strengthening mechanisms of the Ni-ZrO₂ nanocomposite coatings based on a combination of grain refinement strengthening from nickel matrix grain refining and dispersion strengthening from dispersion state of ZrO₂ nanoparticles in the coatings.     

Preparation and characterization of nickel nano-Al2O3 composite coatings by sediment co-deposition

Ni-Al₂O₃ composite coatings were prepared by using sediment co-deposition (SCD) technique and conventional electroplating (CEP) technique from Watt's type electrolyte without any additives. The microstructure, hardness, and wear resistance of resulting composites were investigated. The results show that the incorporation of nano-Al₂O₃ particles changes the surface morphology of nickel matrix. The preferential orientation is modified from (2 0 0) plane to (1 1 1) plane. The microhardness of Ni-Al₂O₃ composite coatings in the SCD technique are higher than that of the CEP technique and pure Ni coating and increase with the increasing of the nano-Al₂O₃ particles concentration in plating solution. The wear rate of the Ni-Al₂O₃ composite coating fabricated via SCD technique with 10 g/l nano-Al₂O₃ particles in plating bath is approximately one order of magnitude lower than that of pure Ni coating. Wear resistance for SCD obtained composite coatings is superior to that obtained by the CEP technique. The wear mechanism of pure Ni and nickel nano-Al₂O₃ composite coatings are adhesive wear and abrasive wear, respectively.     

Physical and electrochemical characterizations of Ni-SiO2 nanocomposite coatings

Advances in materials performance often require the development of composite system. In the present investigation, SiO₂-reinforced nickel composite coatings were deposited on a mild steel substrate using direct current electrodeposition process employing a nickel acetate bath. Surface morphology, composition, microstructure and crystal orientation of the Ni and Ni-SiO₂ nanocomposite coatings were investigated by scanning electron microscope, energy dispersive X-ray spectroscopy and X-ray diffraction analysis, respectively. The effect of incorporation of SiO₂ particles in the Ni nanocomposite coating on the microhardness and corrosion behaviour has been evaluated. Smooth composite deposits containing well-distributed silicon oxide particles were obtained. The preferred growth process of the nickel matrix in crystallographic directions <111>, <200> and <220> is strongly influenced by SiO₂ nanoparticles. The average crystallite size was calculated by using X-ray diffraction analysis and it was ~23 nm for electrodeposited nickel and ~21 nm for Ni-SiO₂ nanocomposite coatings. The crystallite structure was fcc for electrodeposited nickel and Ni-SiO₂ nanocomposite coatings. The incorporation of SiO₂ particles into the Ni matrices was found to improve corrosion resistance of pure Ni coatings. The corrosion potential (E _corr) in the case of Ni-SiO₂ nanocomposite coatings had shown a negative shift, confirming the cathodic protective nature of the coating. The Ni-SiO₂ composite coatings have exhibited significantly improved microhardness (615 HV) compared to pure nickel coatings (265 HV)     

Self-lubricative coating grown by micro-plasma oxidation on aluminum alloys in the solution of aluminate-graphite

Aluminum trioxide ceramic coatings with high hardness were grown on surfaces of 2024 Aluminum alloys by micro-plasma oxidation in an aluminate electrolytic solution, which highly improve wear-resisting properties of 2024 Aluminum alloys. However, ceramic coating surfaces are porous and very coarse, which is disadvantageous to practical applications. In this paper, in order to increase the density of the pores and decrease the friction coefficient of the ceramic coatings, different concentrations (2-8 g/l) of graphite were added into the aluminate electrolytic solution. The thickness and hardness of the produced ceramic coatings were measured by HVS-100 micro-hardness tester and thickness tester. The friction coefficient of the coatings was studied by a frictionometer. The phase composition and surface morphology of the MPO films were evaluated through X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that the thickness of the ceramic coating is about 22 ± 1 μm, surfaces of the ceramic coatings are very uniform and that the coatings consist of mainly aluminum trioxides and a certain amount of graphite, which indicates graphite have entered the ceramic films during the micro-plasma oxidation process. Wear properties results show that the friction coefficient of the ceramic coatings decreased when graphite entered the ceramic films. When the concentration of graphite is 4 g/l, the wear properties of the coatings is the most excellent and the friction coefficient decreases to the lowest, that is 0.09.     

脉冲磁控溅射MoS2-Ti涂层常温及高温真空摩擦磨损性能

利用脉冲磁控溅射法,以铝青铜合金(C63200)和硅片为基底,制作不同Ti含量的MoS₂-Ti复合涂层。通过XRD、SEM、EDS、光学显微镜、多环境摩擦试验机等表征了涂层的结构成分和摩擦性能。结果表明：随Ti含量的增加,涂层致密度提升,S、Mo原子比上升。Ti的掺入使涂层由高度结晶态向非晶态转变。Ti含量增加,涂层摩擦磨损性能先上升再下降,常温真空下含3%Ti的涂层拥有稳定和低至0.015的摩擦系数,23%Ti的涂层失去润滑性。温度升高到400℃,涂层摩擦系数由0.015~0.04上升至0.07~0.1,含13%Ti的涂层高温真空下在800s后润滑失效。磨痕形貌显示,含3%Ti的涂层磨痕最窄,温度升高宽度增加不大,含13%Ti的涂层磨损严重,400℃真空环境下很快磨穿,纯MoS₂和13%Ti涂层摩擦时发现大量磨粒和破碎磨屑。     

Investigation of the microstructure and tribological behavior of cold-sprayed tin-bronze-based composite coatings

In this paper, tin-bronze/TiN and tin-bronze/quasicrystal (AlCuFeB) composite coatings were fabricated by cold spray process. Microstructure and microhardness of the prepared coatings were investigated. Ball-on-disc dry sliding wear tests were conducted in an ambient condition to examine the tribological behavior of the composite coatings. The results show that the microhardness and the density of composite coatings increase significantly compared to the pure tin-bronze coating. The friction coefficient of composite coating decreases when reinforcing particles were introduced. Furthermore, the bronze/quasicrystal composite coating has a lower friction coefficient and wear rate than the bronze/TiN coating. Tribological mechanisms of the composite coatings were discussed.     

Wear Performance and Mechanisms of Polyphenylene Sulfide/Polytetrafluoroethylene Wax Composite Coatings Reinforced by Graphene

Polyphenylene sulfide (PPS) composite coatings reinforced by graphene were prepared through a spraying method. Wear performance of the composite coatings were evaluated using a block-on-ring test rig, and the results showed that the wear life of the composite coatings were over seven times higher than that of a pure PPS coating. Wear mechanisms of PPS composite coatings reinforced by graphene are discussed. It was concluded that adhesive wear was the major wear mechanism of the pure PPS coating but the wear form of the composite coatings was dominated by abrasive wear due to the graphene filler that has high mechanical strength. In addition, fatigue wear appeared for composite coatings with higher content of graphene. The formation of a uniform thin transfer film on the counterpart ring and fine wear debris for the composites coatings during abrasion were consistent with the improvement of wear performance. The 3D morphology of the surface of the counterpart ring was also used to discuss the wear mechanism of PPS composite coatings.     

Nanocomposite Ni–TiN coatings prepared by ultrasonic electrodeposition

Nanocomposite Ni–TiN coatings were prepared by ultrasonic electrodeposition and the effects of ultrasonication on the coatings were studied. X-ray diffraction analysis was utilized to detect the crystalline and amorphous characteristics of the composite coatings. The surface morphology and metallurgical structure were observed by scanning electron microscopy, high-resolution transmission electron microscopy and scanning probe microscopy. The results showed that ultrasonication had great effects on TiN nanoparticles in composite coatings. The moderate ultrasonication conduced to homogeneous dispersion of TiN particles in the coatings. Moreover, the TiN nanoparticles that entered and homogeneously dispersed in the composite coating led to an increase in the number of nuclei for nucleation of nickel grains and inhibition of grain growth. Therefore, the introduction of ultrasonication and TiN nanoparticles resulted in the formation of smaller nickel grains. The average grain diameter of TiN particles was ∼33 nm, while Ni grains measured approximately 53 nm.     

Effect of pulse electrodeposition parameters on the properties of Ni/nano-SiC composites

Pure nickel and nickel matrix composite deposits containing nano-SiC particles were produced under both direct and pulse current conditions from an additive-free nickel Watts’ type bath. It has been proved that composite electrodeposits prepared under pulse plating conditions exhibited higher incorporation percentages than those obtained under direct plating conditions, especially at low duty cycles. The study of the textural perfection of the deposits revealed that the presence of nano-particles led to the worsening of the quality of the observed [1 0 0] preferred orientation. Composites with high concentration of embedded particles exhibited a mixed crystal orientation through [1 0 0] and [2 1 1] axes. The embedding SiC nano-particles in the metallic matrix by an intra-crystalline mechanism resulted in the production of composite deposits with smaller crystallite sizes and more structural defects than those of pure Ni deposits. A dispersion-hardening effect was revealed for composite coatings independently from applied current conditions. Pulse electrodeposition significantly improved the hardness of the Ni/SiC composite deposits, mainly at low duty cycle and frequency of imposed current pulses.     

Mechanical properties of the plasma-enhanced magnetron sputtering Si-C-N coatings

The mechanical properties of plasma-enhanced magnetron sputtering Si-C-N hard coatings with various compositions are characterized. The effect of chemical composition on the microstructure and properties of coating is investigated. The results show that the microstructure and mechanical properties of Si-C-N coatings are very sensitive to chemical composition. The nanocrystalline/amorphous composite structure is beneficial to the coating's mechanical properties. It also reveals that Si-C-N coating with low Si and high C concentrations has the highest hardness (≥40 GPa) and the best wear property with dry friction coefficient about 0.2.     

Study on the laser treatment of electroless Ni-P-SiC composite coatings

Effect of the laser treatment on electroless Ni-P-SiC composite coatings was investigated. The microscopic structure, surface morphology, ingredient, and performance of the Ni-P-SiC composite coatings were synthetically analyzed by the use of X-ray diffraction apparatus, scanning electron microscope, energy distribution spectrometer, micro-hardness tester, wear tester and so on. It was found that the composite coatings did make crystalloblastic transformation after laser heating. Structural analysis confirmed that some new types of phase Ni2Si or Ni3Si compound would emerge in the Ni-P-SiC coatings after laser treatment. The micro-hardness measurement results showed that when the laser power was 450 W with scanning speed of 0.5 m/min, the hardness of the coating was superior to the coating obtained by the conventional furnace heating, and wear resistance of the composite coating after laser treating could also improve.     

Electrodeposited nickel-cobalt composite coating containing MoS2

Ni-Co/MoS₂ composite coatings were prepared by electrodeposition in a Ni-Co plating bath containing nano-sized MoS₂ particles to be co-deposited. The polarization behavior of the composite plating bath was examined on a PAR-273A potentiostat/galvanostat device. The friction and wear behaviors of the Ni-Co/MoS₂ composite coatings were evaluated with UMT-2MT test rig in a ball-on-disk contact mode. The morphologies of the original and worn surfaces of the composite coatings were observed on scanning electron microscope (SEM). It was found that the introduction of MoS₂ nano-particulates in the electrolyte caused the shift towards larger negatives of the reduction potential of the Ni-Co alloy coating, and the co-deposited MoS₂ showed no significant effect on the electrodeposition process of the Ni-Co alloy coating. However, the co-deposited MoS₂ led to changes in the surface morphology and structure of the composite coating as well. Namely, the peak width of the Ni-Co solid solution for the composite coating is broader as compared to that of the Ni-Co alloy coating. The co-deposited MoS₂ particulates were uniformly distributed in the Ni-Co matrix and contributed to increase tribological properties of the Ni-Co alloy coating.     

Electrodeposition and tribological properties of Ni-SrSO4 composite coatings

Ni-SrSO₄ composite coatings were electrodeposited on superalloy Inconel 718 from a Watts electrolyte containing a SrSO₄ suspension. Ni-SrSO₄ coatings were investigated by scanning electron microscope, microhardness tester, and friction and wear tester in sliding against a bearing steel ball under unlubricated condition. The incorporation of SrSO₄ into Ni matrix increases the microhardness of electrodeposited coatings. Ni-SrSO₄ composite coating exhibits a distinctly low friction coefficient and a small wear rate as contrasted with pure Ni coating and the substrate. The effect of SrSO₄ particles on microstructure and tribological properties of Ni-SrSO₄ composite coatings is discussed.     

Facile synthesis and electrochemical properties of a novel Ni-B/TiC composite coating via ultrasonic-assisted electrodeposition

A novel Ni-B/TiC composite coating was synthesized by ultrasonic-assisted direct current electrodeposition. Ultrasonic technology was adopted to prevent the agglomeration of nanoparticle, improve the structure and corrosion resistance, using an ultrasonic bath at frequency 40 KHz and acoustic power 300 W. The influences of current density and deposition time on its structure and electrochemical behaviors were studied. Under ultrasonic dispersion, the composite coatings are smooth, compact with protrusion structure sparsely distributed on it. The average roughness (S_a) was about 13.6–26.1 nm. The crystallite size is 10–21 nm. The preferred orientation is Ni (1 1 1) texture. EIS results indicated that the corrosion resistance was greatly improved by ultrasonic-assisted method. The corrosion mechanism is consistent with one-time constant EEC model of R_s(CPE_dlR_ct). With the increase of immersion time, the R_ct of the composite coating often first increased and then decreased. Under ultrasonic, current density 2 A dm⁻² and deposition time 20 min were the appropriate parameters for the optimal corrosion resistance and excellent long-term electrochemical stability in 3.5 wt% NaCl corrosive solution. This coating shows good application prospect for corrosion protection in aggressive environment.     

(Ti,Al,Si,C)N nanocomposite coatings synthesized by plasma-enhanced magnetron sputtering

Materials’ surface service property could be enhanced by transition metal nitride hard coatings due to their high hardness, wear and high temperature oxidation resistance, but the higher friction coefficient (0.4-0.9) of which aroused terrible abrasion. In this work, quinternary (Ti,Al,Si,C)N hard coating 3-4 μm was synthesized at 300 °C using plasma enhanced magnetron sputtering system. It was found that the coating's columnar crystals structure was restrained obviously with the increase of C content and a non-columnar crystals growth mode was indicated at the C content of 33.5 at.%. Both the XRD and TEM showed that the (Ti,Al,Si,C)N hard coatings had unique nanocomposite structures composed of nanocrystalline and amorphous nc-(Ti,Al)(C,N)/nc-AlN/a-Si₃N₄/a-Si/a-C. However, the coatings were still super hard with the highest hardness of 41 GPa in spite of the carbon incorporation. That a-C could facilitate the graphitization process during the friction process which could improve the coating's tribological performance. Therefore, that nanocomposite (Ti,Al,Si,C)N coatings with higher hardness (>36 GPa) and a lower friction coefficient (<0.2) could be synthesized and enhance the tribological performance and surface properties profoundly.     

Microstructure and properties of Ni-Co/nano-Al2O3 composite coatings by pulse reversal current electrodeposition

Ni-Co/nano-Al₂O₃ (Ni-Co/Al₂O₃) composite coatings were prepared under pulse reversal current (PRC) and direct current (dc) methods respectively. The microstructure of coatings was characterized by means of XRD, SEM and TEM. Both the Ni-Co alloy and composite coatings exhibit single phase of Ni matrix with face-centered cubic (fcc) crystal structure, and the crystal orientation of the Ni-Co/Al₂O₃ composite coating was transformed from crystal face (2 0 0) to (1 1 1) compared with alloy coatings. The hardness, anti-wear property and macro-residual stress were also investigated. The results showed that the microstructure and performance of the coatings were greatly affected by Al₂O₃ content and the electrodeposition methods. With the increasing of Al₂O₃ content, the hardness and wear resistance of the composite coatings enhanced. The PRC composite coatings exhibited compact surface, high hardness, better wear resistance and lower macro-residual stress compared with that of the dc composite coatings.     

Scaling up the fabrication of wafer-scale Ni-MoS2/WS2 nanocomposite moulds using novel intermittent ultrasonic-assisted dual-bath micro-electroforming

In the scale-up fabrication process for electroformed Ni-MoS₂/WS₂ composite moulds, the formulation of nanosheets is critical, since the size, charge, and their distribution can largely affect the hardness, surface morphology and tribological properties of the moulds. Additionally, the long-term dispersion of hydrophobic MoS₂/WS₂ nanosheets in a nickel sulphamate solution is problematic. In this work, we studied the effect of ultrasonic power, processing time, surfactant types and concentrations on the properties of nanosheets to elaborate their dispersion mechanism and control their size and surface charge in divalent nickel electrolyte. The formulation of MoS₂/WS₂ nanosheets was optimized for effective electrodeposition along with nickel ions. A novel strategy of intermittent ultrasonication in the dual bath was proposed to resolve the problem of long-term dispersion, overheating, and deterioration of 2D material deposition under direct ultrasonication. Such strategy was then validated by electroforming 4-inch wafer-scale Ni-MoS₂/WS₂ nanocomposite moulds. The results indicated that the 2D materials were successfully co-deposited into composite moulds without any defects, along with the mould microhardness increasing by ∼2.8 times, the coefficient of friction reducing by two times against polymer materials, and the tool life increasing up to 8 times. This novel strategy will contribute to the industrial manufacturing of 2D material nanocomposites under ultrasonication process.     

Friction and wear properties of the co-deposited Ni-SiC nanocomposite coating

Ni-SiC nanocomposite coatings were produced by electrodeposition from a nickel sulfate bath containing SiC nanoparticles with an average particle size of 30 nm. The characteristics of the coatings were assessed by scanning electron microscopy and microhardness test. The friction and wear performance of Ni-SiC nanocomposite coatings and Ni film were comparatively investigated sliding against Si₃N₄ ceramic balls under non-lubricated conditions. The results indicated that compared to Ni film, Ni-SiC nanocomposite coating exhibited enhanced microhardness and wear resistance. The effect of SiC nanoparticles on the friction and wear resistance is discussed in detail.