Recent Advances in Interface Modification of Cu/graphite Composites and Layered Ternary Carbides of Modified Layer Candidate

We review the fundamental properties and significant issues related to Cu/graphite composites.In particular,recent research on the interfacial modification of Cu/graphite composites is addressed,including the metal-modified layer,carbide-modified layer,and combined modified layer.Additionally,we propose the use of ternary layered carbide as an interface modification layer for Cu/graphite composites.

Protective Graphite Coating for Two-Dimensional Carbon/Carbon Composites

Two-dimensional carbon/carbon(2D C/C)composites are a special class of carbon/carbon composites,generally obtained by combining resin-impregnated carbon fiber clothes,which are then cured and carbonized.This study deals with the preparation of a protective coating for these materials.This coating,based on graphite,was prepared by the slurry method.The effect of graphite and phenolic resin powders with different weight ratios was examined.The results have shown that the coating slurry can fill the pores and cracks of the composite surface,thereby densifying the surface layer of the material.With the increase of the graphite powder/phenolic resin weight ratio,the coating density is enhanced while the coating surface flatness decreases;moreover,the protective ability of coating against erosion first increases(from 1:3 to 2:2)and then decreases(from 2:2 to 3:1).When the weight ratio is about 1:1,the coating for 2D C/C composites exhibits the best erosion resistance,which greatly aids these materials during gas quenching.In this case,the erosion rate is decreased by approximately 41.5%at the impact angle of 30°and 52.3%at normal impact,respectively.This can be attributed to the ability of the coating slurry to infiltrate into the substrate,thereby bonding the fibers together and increasing the compactness of the 2D C/C composites.

ZnO-Embedded Expanded Graphite Composite Anodes with Controlled Charge Storage Mechanism Enabling Operation of Lithium-Ion Batteries at Ultra-Low Temperatures

As lithium(Li)-ion batteries expand their applications,operating over a wide temperature range becomes increasingly important.However,the lowtemperature performance of conventional graphite anodes is severely hampered by the poor diffusion kinetics of Li ions(Li^(+)).Here,zinc oxide(ZnO) nanoparticles are incorporated into the expanded graphite to improve Li^(+)diffusion kinetics,resulting in a significant improvement in lowtemperature performance.The ZnO-embedded expanded graphite anodes are investigated with different amounts of ZnO to establish the structurecharge storage mechanism-performance relationship with a focus on lowtemperature applications.Electrochemical analysis reveals that the ZnOembedded expanded graphite anode with nano-sized ZnO maintains a large portion of the diffusion-controlled charge storage mechanism at an ultra-low temperature of-50℃ Due to this significantly enhanced Li^(+)diffusion rate,a full cell with the ZnO-embedded expanded graphite anode and a LiNi_(0.88)Co_(0.09)Al_(0.03)O_(2)cathode delivers high capacities of 176 mAh g^(-1)at20℃ and 86 mAh g^(-1)at-50℃ at a high rate of 1 C.The outstanding low-temperature performance of the composite anode by improving the Li^(+)diffusion kinetics provides important scientific insights into the fundamental design principles of anodes for low-temperature Li-ion battery operation.

Tribological properties of Ni-base alloy composite coating modified by both graphite and TiC particles

In order to reduce the friction coefficient of Ni-base alloy coating and further improve its wear resistance,Ni-base alloy composite coatings modified by both graphite and TiC particles were prepared by plasma spray technology on the surface of 45 carbon steel.The results show that friction coefficient of the composite coating is 47.45% lower than that of the Ni-base alloy coating,and the wear mass loss is reduced by 59.1%.Slip lines and severe adhesive plastic deformation are observed on the worn surface of the Ni-base alloy coating,indicating that the wear mechanisms of the Ni-base alloy coating are multi-plastic deformation wear and adhesive wear.A soft transferred layer abundant in graphite and ferric oxide is developed on the worn surface of the composite coating,which reduces the friction coefficient and wear loss in a great deal.The main wear mechanism of the composite coating is fatigue delamination of the transferred layer.

Electrochemical Degradation of Indigocarmine Dye at Ni/Graphite Modified Electrode in Aqueous Solution

Nickel Graphite modified electrode (Ni/GME) was prepared by electrochemical method and degradation of Indigocarmine (IC) dye was carried out. An investigation between the efficiency of degradation by graphite electrode and the Ni/graphite modified electrode has been carried out. The different effects of concentration, current density and temperature on the rate of degradation were studied. This study shows that the rate of the degradation is more for Ni doped modified graphite electrode. UV-Visible spectra before and after degradation of the dye solution were observed. The thin film formation of Ni or encapsulated in graphite rod is observed by scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM & EDAX). The instantaneous current effectiveness values of different experimental conditions are evaluated. The anodic oxidation by Ni/ graphite modified electrode showed the complete degradation of aqueous solution indigocarmine, which is confirmed by UV-Visible and chemical oxygen demand (COD) measurements. The dye is converted into CO2, H2O and simpler inorganic salts. The results observed for reuse of modified electrodes indicate that the Ni/graphite modified electrode would be a promising anode for electrochemical degradation of indigocarmine. This method can be applied for the remediation of waste water containing organics, cost-effective and simple.

Tribological behavior and mechanisms of graphite/CaF_2/TiC/Ni-base alloy composite coatings

In order to reduce the friction coefficients and improve the wear resistance of mechanical parts, which work in the severe friction and wear conditions at heavy loads, the graphite/CaFg/TiC/Ni-base alloy composite coatings were prepared by plasma spray and their tribological behavior and mechanisms were investigated. The results show that the friction coefficients of the composite coatings are in the range of 0.22-0.288, which are reduced by 25.9% to 53% compared with those of the pure Ni-base alloy coatings, and the wear rates of the former are 18.6%-70.1% less than those of the latter. When wear against GCr15 steel balls, a transferred layer mainly composed of ferric oxides, graphite and CaF2 may gradually develop on the worn surface of the composite coatings, which made the friction and wear between GCr15 steel ball and the composite coatings change into that between the former and the transferred layer. So the friction coefficients and the wear lubrication effect of the transferred layer. The main wear layer in friction process. rates of the composite coatings are greatly reduced because of the solid mechanism of the composite coatings is delamination of the transferred

Effects of graphite content on microstructure and tribological properties of graphite/TiC/Ni-base alloy composite coatings

In order to reduce the friction coefficients and further improve the anti-wear properties of Ni-base alloy coatings reinforced by TiC particles,graphite/TiC/Ni-base alloy（GTN） coatings were prepared on the surface of 45 carbon steel.The effects of graphite content on the microstructure and tribological properties of the GTN coatings were investigated.The results show that the addition of graphite to the GTN coatings may greatly reduce the friction coefficients and improve their wear resistance.The 6.56GTN and 12.71GTN coatings exhibit excellent integrated properties of anti-friction and wear resistance under low and high loads,respectively.Under a low load,the wear mechanisms of the GTN coatings are mainly multi-plastic deformation with slight abrasive wear and gradually change into mixture of multi-plastic deformation,delamination and micro-cutting wear with the increase of graphite fraction.As the load increases,the main wear mechanisms gradually change from micro-cracks,micro-cutting and adhesive wear to micro-cutting and micro-fracture with the increase of graphite fraction.

Composite polymer electrolyte reinforced by graphitic carbon nitride nanosheets for room-temperature all-solid-state lithium batteries

By virtue of the flexibility and safety, polyethylene oxide(PEO) based electrolytes are regarded as an appealing candidate for all-solid-state lithium batteries. However, their application is limited by the poor ionic conductivity at room temperature, narrow electrochemical stability window and uncontrolled growth of lithium dendrite. To alleviate these problems, we introduce the ultrathin graphitic carbon nitride nanosheets(GCN) as advanced nanofillers into PEO based electrolytes(GCN-CPE). Benefiting from the high surface area and abundant surface N-active sites of GCN, the GCN-CPE displays decreased crystallinity and enhanced ionic conductivity. Meanwhile, Fourier transform infrared and chronoamperometry studies indicate that GCN can facilitate Li+migration in the composite electrolyte. Additionally, the GCN-CPE displays an extended electrochemical window compared with PEO based electrolytes. As a result, Li symmetric battery assembled with GCN-CPE shows a stable Li plating/stripping cycling performance, and the all-solid-state Li/LiNi_(0.6)Co_(0.2)Mn_(0.2)O_(2)(NCM622) batteries using GCN-CPE exhibit satisfactory cyclability and rate capability in a voltage range of 3-4.2 V at 30 ℃.

Effect of graphite powder as a forming filler on the mechanical properties of SiCp/Al composites by pressure infiltration

（38vo1% SiCp ＋ 2vo1% A1203f）/2024 A1 composites were fabricated by pressure infiltration. Graphite powder was introduced as a forming filler in preform preparation, and the effects of the powder size on the microstructures and mechanical properties of the final com- posites were investigated. The results showed that the composite with 15 μm graphite powder as a forming filler had the maximum tensile strength of 506 MPa, maximum yield strength of 489 MPa, and maximum elongation of 1.2%, which decreased to 490 MPa, 430 MPa, and 0.4%, respectively, on increasing the graphite powder size from 15 to 60 μm. The composite with 60 μm graphite powder showed the highest elastic modulus, and the value decreased from 129 to 113 GPa on decreasing the graphite powder size from 60 to 15 μm. The differences between these properties are related to the different microstructures of the corresponding composites, which determine their failure modes.

GALVANIC CORROSION BETWEEN GRAPHITE EPOXY COMPOSITE MATERIALS AND LY12CZ ALUMINUM ALLOY

The electrochemical approach was used to show the nature of the galvanic corrosion when graphite epoxy composite materials(GECM)were coupled to LY12CZ aluminum alloy. An open circuit potential difference of one volt was obtained in 3.5% NaCl solution between GECM and LY12CZ. Corrosion current data (zero impedance technique) indicated that there was serious corrosion at GECM/LY12CZ couple.When GECM/LY12CZ couples were exposed to ASTM salt spray and alternate immersion condition, fiber glass cloth and H06-2 epoxy primer paint were effective methods for preventing galvanic corrosion.The slow strain rate test (SSRT) showed that GECM increased the LY12CZ stress corrosion crack growth rate.

Sintering behavior and thermal conductivity of nickel-coated graphite flake/copper composites fabricated by spark plasma sintering

Nickel-coated graphite flakes/copper（GN/Cu） composites were fabricated by spark plasma sintering with the surface of graphite flakes（GFs） being modified by Ni–P electroless plating. The effects of the phase transition of the amorphous Ni–P plating and of Ni diffusion into the Cu matrix on the densification behavior, interfacial microstructure, and thermal conductivity（TC） of the GN/Cu composites were systematically investigated. The introduction of Ni–P electroless plating efficiently reduced the densification temperature of uncoated GF/Cu composites from 850 to 650℃ and slightly increased the TC of the X–Y basal plane of the GF/Cu composites with 20 vol%–30 vol% graphite flakes. However, when the graphite flake content was greater than 30 vol%, the TC of the GF/Cu composites decreased with the introduction of Ni–P plating as a result of the combined effect of the improved heat-transfer interface with the transition layer, P generated at the interface, and the diffusion of Ni into the matrix. Given the effect of the Ni content on the TC of the Cu matrix and on the interface thermal resistance, a modified effective medium approximation model was used to predict the TC of the prepared GF/Cu composites.

Evaluation of sliding wear behavior of graphite particle-containing magnesium alloy composites

The influence of graphite particle content on the friction and wear characteristics of AZ91 magnesium alloy matrix composite was studied. The results show that the wear resistances of graphite-containing composite are much better than those of the matrix under the test conditions. The anti-wear ability of magnesium alloy composite is improved substantially with the increase of the graphite content from 5% to 20%, and both wear mass loss and coefficient of friction are decreased to low level. Different wear mechanisms operate at different sliding stages. A continuous black lubricating film forms progressively on the worn surface along sliding, which effectively limits the direct interaction between the composite tribosurface and the counterpart, and also remarkably delays the transition from mild wear to severe wear for magnesium alloy composite.

Polyaniline-graphite composite film glucose oxidase electrode

A novel polyaniline-graphite composite film glucose oxidase （PGCF GOD） electrode was developed. The PGCF was synthesized by cyclic voitammetry method in 0.5 mol/L H2SO4 solution containing 1 g/L graphite powder and 0.2 mol/L aniline. The PGCF GOD electrode was prepared by doping GOD into the composite film. The morphology of the PGCF and the response property of the PGCF GOD electrode were investigated by scanning electron microscopy and electrochemical measurement, respectively. The results show that the PGCF has a porous and netty structure and the PGCF GOD electrode has excellent response property such as high sensitivity and short response time. Influences of pH value, temperature, glucose concentration and potential on the response current of the electrode were also discussed. The sensor has a maximum steady-state current density of 357.17μA/cm2 and an apparent Michaelis-Menten constant of 16.57 mmol/L. The maximum current response of the enzyme electrode occurs under the condition ofpH 5.5, 0.8 V and 65℃.

Tribological properties of nickel-graphite composite against different counterfaces at elevated temperatures

Nickel-based graphite-containing composites were prepared by powder metallurgy method. The effect of graphite addition on mechanical properties of nickel-based alloy was investigated and the tribological properties from room temperature to 600 ℃ were tested by a pin-on-disk tribometer with alumina,silicon nitride and nickel-based alloy as counterfaces. The microstructure was analyzed by X-ray diffraction(XRD) and scanning electron microscope(SEM) attached with energy dispersive spectroscopy(EDS). The worn surfaces at high temperature were observed by optical microscope and SEM. The results show that the tensile strength and hardness of composites decrease after adding graphite,while the friction and wear properties are all improved by adding 12%(mass fraction) graphite. Compared with the counterface of alumina and silicon nitride,the friction coefficients and wear rates are lower when the composite rubs against nickel-based alloy containing molybdenum disulfide.

Effect of graphite contents on friction and wear properties of Ni-Cr-W composites

Ni-based alloy/W/graphite self-lubricating composites with different graphite addition amounts were prepared using PM （powder metallurgy） method. It is found that the addtion of graphite can increase the tensile strength and hardness, while the bending strength decreases. The tribological properties of the composites when rubbing with Al2O3 ceramic disc were investigated in the temperature range of 20600℃. The results show that the tribological properties of the alloy are improved by adding graphite. When the graphite content is up to 9%, the friction coefficient at 600℃ is about 0.2, which is one third of that with no graphite. At elevated temperature, the friction coefficients change a little with velocity and load. At room temperature, graphite extruded from the composite plays the the role of lubrication. The synergistic effect of oxide films and graphite are responsible for the reduction of friction coefficient at high temperature.

Effect of WS_2 addition on electrical sliding wear behaviors of Cu-graphite-WS_2 composites

Four kinds of Cu-based composites with different mass ratios of graphite and WS2 as lubricants were fabricated by hot-pressing method. Electrical sliding wear behaviors of the composites were investigated using a block-on-ring tribometer rubbing against Cu-5%Ag alloy ring. The results demonstrated that 800 ~C was the optimum sintering temperature for Cu-graphite-WS2 dual-lubricant composites to obtain the best comprehensive properties of mechanical strength and lubrication performance. Contact voltage drops of the Cu-based composites increased with increasing the mass ratio of WS2 to graphite. The Cu-based composite with 20% graphite and 10% WS2 showed the best wear resistance due to the excellent synergetic lubricating effect of graphite and WS2. The reasonable addition of WS2 into the Cu-graphite composite can remarkably improve the wear resistance without much rise of electrical energy loss which provides a novel principle of designing suitable sliding electrical contact materials for industrial applications.

Fabrication of micro-flow channels on graphite composite bipolar plates using microplaning

A new method of manufacturing micro-flow channels on graphite composite bipolar plate(GCBPP) microplaning using specially designed multi-tooth tool is proposed. In this method, several or even dozens of parallel micro-flow channels ranging from 100 μm to 500 μm in width can be produced simultaneously. But, edge chippings easily occur on the rib surface of GCBPP during microplaning due to brittleness of graphite composites. Experimental results show that edge chippings result in the increase of contact resistance between bipolar plate and carbon paper at low compaction force. While the edge chippings scarcely exert influence on the contact resistance at high compaction force. Contrary to conventional view, the edge chippings can significantly improve performance of microfuel cell and big edge chippings outperform small edge chippings. In addition, the influence of technical parameters on edge chippings was investigated in order to obtain big, but not oversized edge chippings.

The Impact of Filler Content on Mechanical and Micro-Structural Characterization of Graphite-Epoxy Composites

In this study, the characteristics of Graphite/Epoxy Composites (GECs) are evaluated from mechanical perspectives. Different weight percentages of graphite were used (0 - 7 wt%) for tensile and hardness experiments. Then the findings were discussed to ascertain the optimum mixing ratio of the graphite with the epoxy. The primary finding of this study is that the graphite weight fraction has a substantial impact on the composites’ mechanical performance. At a low percentage (1 wt%), the graphite has little influence on the tensile behaviour. An intermediate weight percentage of the graphite is considered optimum for mechanical performance in the epoxy composites as it slightly reduces the tensile properties and significantly improves the hardness. Micrographs of the fractured surface of specimens showed many signs that clearly explained why fractures had occurred. For instance, when graphite/epoxy composite contained a low proportion of graphite, the cleavage failure was very easy to observe because there was no sign of aggregation or the detachment of fillers.

Electroless nickel plated graphite fibers and surface behavior in G_(r(Ni))/6061Al composite

The electroless nickel plated graphite fibers reinforced aluminum matrix composites (Gr(Ni))/Al) were produced by squeeze casting, and the microstructure of Gr(Ni)/Al composite and surface behavior of Ni-P coating were studied. The optimum process of electroless Ni-P plating included: burning to get rid of glue→degreasing→neutralization→acidulating→sensitizing→activation→electroless plating. The surface analysis results show that the electroless nickel plating can diffuse into the graphite fiber surface during the squeeze casting, and the Ni-P coating and aluminum alloys can produce brittle phase NiAl3 or NiAl. The X-ray diffraction(XRD) results indicate that Al4C3 is so little that no Al4C3 peaks are found, and the harmful Al4C3 can be decreased by the electroless plating Ni-P coating. The coating improves the interfacial bonding of continuous graphite fibers reinforced aluminum matrix composites.