گرافیت

This study was conducted to evaluate the adhesion strength and oxidation behavior of SiC/Mo-Si-B coating applied on graphite substrates. For this purpose, SiC coating was created on graphite substrate using pack cementation method with NH4Cl activator. The secondary layer Mo-Si-B coating was created using atmospheric plasma spraying (APS) with argon protective shower on the samples. Surface morphology and chemical composition of the SiC and Mo-Si-B coatings were inve stigated by Scanning Electron Microscopy (SEM) equipped with an Energy Dispersive Spectroscopy (EDS) system. Surface analysis by X-ray diffraction (XRD) revealed that the structure of SiC was mainly composed of SiC phase. In the case of Mo-Si-B, different phases of Mo and Si, Mo and B, and pure Mo were identified. The adhesion of the multi-layer coating was evaluated by tensile test which indicated a sufficient adhesion and cohesion of the coating. The oxidation test was carried out in the air at 1273 K and the time and weight changes were recorded simultaneously. The results showed that the applied coating significantly improves oxidation resistance of graphite with SiO2 and B2O3 glass layers. 

In this study, the effects of high-energy hydrogen ion irradiation, generated by the MTPF-2 type modern plasma focus device, on the surface and structural properties of graphite were investigated. High-energy protons produced by the plasma focus device were used to irradiate graphite samples in various shots. The radiation-induced changes on the graphite surface were examined using optical microscope and scanning electron microscopy. The modifications on the irradiated samples' surface were clearly observed in the scanning electron microscopyand optical microscope images. The microscopic images of the irradiated samples revealed point sputtering as well as pores on the sample surface, along with point melting, which are dependent on the ion fluence (number of shots). X-ray diffraction analysis was employed to study the structural changes in the graphite caused by the high-energy proton irradiation. The X-ray diffraction spectra of the irradiated samples showed shifts in the peak positions, changes in the peak intensities, and an increase in the crystallite size compared to the X-ray diffractionspectra of the reference sample. Additionally, a Faraday cup detector was used to characterize the hydrogen ion spectrum produced in the plasma focus device. The results indicated that the average energy of the generated ions was ~ 46 keV.

The aim of this study is to develop a novel nickel-boron-graphite (Ni-B-Gr) composite coating via electroless plating, endowed with self-lubricating properties, and to analyze its wear characteristics. Electroless deposition of Ni-B-Gr coatings was achieved on AISI 4140 steel utilizing a sodium borohydride-based electroless nickel bath. The resulting composite features a nickel-boron matrix, characterized by a skewness index of -0.12, offering both hardness and fluid-retaining capabilities, augmented by graphite flakes (< 20 μm) at a concentration of 0.275 g/L, serving as a solid lubricant component. Plasma nitriding treatments were conducted at 400°C for varying durations (30, 60, 120, 180, and 240 minutes) in a gas mixture of 25% nitrogen and 75% hydrogen. Comprehensive characterization of the Ni-B-Gr composite coatings encompassed microstructural analysis via X-ray diffraction (XRD), morphology examination using field emission scanning electron microscopy (FE-SEM), microhardness testing, roughness measurements, and wear assessment through pin-on-disk tests. Notably, the plasma nitrided Ni-B-Gr composite coatings for 60 minutes exhibited a significant enhancement in hardness, with a hardness of 1060 HV0.1. Moreover, compared to as-plated Ni-B-Gr coatings, the 60 minutes plasmanitrided composites demonstrated a remarkable 75% reduction in specific wear rate and a 31% decrease in friction coefficient. The incorporation of graphite as a self-lubricating agent effectively mitigated adhesive wear and oxidation by reducing the contact surface between the steel pin and the coating, thereby enhancing the wear resistance of the composite.

This study aims to compare the effect of graphite content (0–5 wt.%) on the mechanical and ‎tribological properties of aluminum matrix nanocomposites. The bulk samples were prepared ‎by the mechanical milling/hot pressing (temperature 420 °C/ pressure 400 MPa/ time 1h) ‎process. According to the obtained results in this work, the addition of graphite to an ‎aluminum matrix significantly improves the wear properties of aluminum (wear rate and ‎coefficient of friction). The best wear performance was obtained with the sample containing ‎‎5wt.% graphite, which showed a 62% reduction in the wear rate and a 2.5-fold reduction in ‎coefficient of friction compared to the unreinforced aluminum sample. Although increasing ‎the amount of graphite in the range of 0-5 wt.% leads to a continuous improvement in the ‎wear behavior of the composite material, it results in a simultaneous deterioration of the ‎mechanical properties (hardness and compressive strength) and the density of the Aluminum- ‎Graphite composites.‎

One of the most widely used methods to Improving the surface resistance of industrial parts is applying composite coatings such as WC-10Co-4Cr. But this coating, despite its excellent corrosion resistance, does not have a good tribological behavior compared to other tungsten carbide base coatings. For this purpose, in this research, by adding graphite in two amounts of 7% and 14% by weight to WC-10C-4Cr powder and applying coatings by thermal spraying on the steel substrate, their tribological behavior was compared. Investigations were carried out with the help of SEM images, XRD test, roughness measurement and hardness measurement. Pin-on-disk test was also used to evaluate the wear resistance behavior of coatings and substrate. The results showed that despite the relative decrease in hardness and increase in the roughness of the tungsten carbide base coating, graphite leads to a significant improvement in the tribological behavior of the substrate and the tungsten carbide coating. Among the coatings, coating with 7% graphite It had the best wear resistance due to the combination of suitable hardness, low porosity and low friction coefficient. The wear mechanism of the coatings was also investigated with the help of SEM images and EDS analysis. It was found that the dominant mechanism of coatings containing graphite, dellamination and WC-10Co-4Cr coating was adhesive. The most important reason for increasing the tribological properties of coatings in the presence of graphite was the formation of a protective layer of these reinforcing particles in the wear path and around the pin.

In this paper ZrC coating was prepared on SiC coated graphite as a substrate by atmospheric plasma spray (APS) and solid shielding/ shrouded plasma spray (SSPS) methods. Microstructure observation and phase identification of the coatings were performed by scanning electron microscopy and X-ray diffraction. The ablation behavior of the coating was evaluated under supersonic flame for 60s. The results showed that the ZrC coating enhance the ablation resistance of SiC coated graphite remarkably. The results of ablation test revealed that the linear and mass ablation rates of the ZrC coating applied by APS method were 3.7×10-3 mm.s-1 and 22×10-3 g.s-1, while those for SSPS coating were 2.2×10-3 mm.s-1 and 14×10-3 g.s-1, respectively. The excellent ablation resistance is attributed to the formation of continuous zirconia (ZrO2) layer on the surface during the oxidation of the ZrC coating. Moreover, the SPS-ZrC coated sample with lowest pores and cracks have better ablation resistance during the ablation test and can protected the graphite substrate against ablation sufficiently.

Magnesium hybrid surface composites are widely used in automotive and aerospace industries because they have low weight, high specific strength, and suitable wear properties. In this research, a mixture of silica and graphite nanoparticles was used to produce hybrid surface composites on AZ31B magnesium alloy by the use of friction stir processing (FSP). The effect of FSP passes on microstructure, microhardness, and wear resistance of composites was investigated. According to microstructural investigations, after 4 passes, the particles dispersed well and properly prevented grain growth so that the mean grain size of AZ31B–SiO2–graphite composite decreased about 80% compared with as-received AZ31B and above 50% compared with FSPed as-received AZ31B. Furthermore, in comparison with as-received AZ31B, microhardness of the composite increased more than 17% and its wear resistance increased more than 33% after 4 passes. The results indicated that grain size decrease plays a more significant role in composite hardness than dispersion hardening and other strengthening mechanisms. Furthermore, by increasing FSP passes, grain size variance and hardness variance decreased in the stir zone, which indicates that particles are dispersed and the microstructure becomes homogenized.

In this research, a lithium ion conducting lithium aluminum germanium phosphate (LAGP) glass-ceramic with a formula of Li1.5Al0.5Ge1.5(PO4)3 was synthesized by melt-quenching method and subsequent crystallization at 850 °C for 8 h. The prepared glass-ceramic was characterized using X-ray diffraction analysis (XRD) and field emission scanning electron microscopy (FESEM). The XRD patterns exhibited the existence of LiGe2(PO4)3 as the dominant phase with a little impurity phase of GeO2. SEM images revealed the presence of large cubic LAGP grains. Also, the prepared glass-ceramic was used as protective membrane in aqueous lithium ion batteries for their voltage increase. The prepared batteries with graphite as anode, LiMn2O4 as cathode and saturated aqueous solution of lithium nitrate as the electrolyte with assistance of protective membrane exhibited discharge voltage of 3.64 V and discharge capacity of 117 mAh g-1, which are comparable with those in organic-based lithium ion batteries.

The solid electrolyte interphase (SEI) is a passivating film that is formed on the anode surface by electrolyte decomposition in a lithium ion battery. The proper understanding of the SEI formation process on the graphite anodes can create a wider view to overcome the challenges associated with these anodes, which lead to better cyclic performance. In this research, cyclic voltammetry, electrochemical impedance spectroscopy and cyclic charge/ discharge tests were used for graphite anode coin cell to obtain a perfect understanding of SEI formation process on the surface of graphite anode. The results of cyclic voltammetry test indicate that the large part of SEI layer is formed in the first cycle and the SEI will be stable by continued voltammetric cycles. The electrochemical impedance studies show that the charge transfer resistance (Rct) of graphite anode decreases from 122 Ω to 62.5 Ω after electrochemical cycles, which indicates the facility of the charge transfer process after the formation of the SEI layer. The results of cyclic charge/ discharge test also represent that the irreversible capacity of first cycle is consumed to form the SEI, and the reversibility has been sustained after the subsequent charge / discharge cycles.

In this research, the effect of various amounts of aluminum on morphology of graphite in ductile cast irons produced by in-mold casting process is investigated. For this purpose, spherical graphite cast iron containing 0, 3.7, 5.5, 6.4 and 7.5 wt. % aluminum, respectively, were prepared in Y-block form via in-mold process. After casting, samples were prepared for microstructural studies, using conventional methods, followed by optical microscopy (OM) examination. Chemical composition of samples were determined using quantometer, x-ray fluorescence spectroscopy (XRF) and carbon/ sulfur determination method. Increasing the number of spheres from 168 to 668 per square millimeter, reducing the grain size from 21.4 to 8.8 micrometers, and changing the percentage of spherical graphite from 65 to 48 percent was observed.Hardness of samples show increase from 284 to 482 Vickers by increasing aluminum content from 0 to 7.5 weight percent.

structural materials. On the other hand, graphite can easily react with oxygen even at temperatures as low as 400 °C. The graded silicon carbide (SiC) characterized by compositional gradation over microsopic distances, is considered to be the most promising coating material. In this paper, the pack cementation technique was used to make a graded SiC coating on graphite at 1600°C. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis display that the coating obtained by the pack cementation is a dense structure consisting α-SiC and β-SiC with functionally graded structure. the mechanism of formation of SiC coating on graphite is explained by thermodynamics analysis and chemical equilibrium calculations using HSC Chemistry software 6.0.The reaction-path mechanism indicates in the early stages of the process, SiO and CO gas species can be formed during Al2O3 reaction with Si and C and at two reaction Si=SiC and SiO(g)=SiC(g) can be considered as main reactions for SiC coating formation. It was found that the composition of raw materials has not marked effect on the microstructure and property of SiC coating. In fact, this paper proposes a method for the analysis and simulation of pack cementation reactions using HSC Chemistry software package. The results of the simulation are verified by experimental results.

In this study, a brass alloy-based (Cu-30%Zn) composite was fabricated by Graphite particles with initial size of 7µm reinforcement via friction stir processing. Groove with the Width and depth of 0.3mm & 2.5 mm were made on the surface of a brass specimen, respectively and filled by Graphite powder. Friction stir processing was carried out with transverse and rotational speeds of 100mm/min and 800rpm, respectively and the tilt angle of 1°. Single pass and three-pass FSP were conducted on the samples. The microstructure and mechanical properties before and after FSP were investigated. Optical and scanning electron microscope observations revealed that increasing the number of passes exhibits homogeneous distribution of Graphite particles. The wear behavior was examined without lubricant and at room temperature using a pin-on-disc device. The results showed that the wear resistance of composite layers containing MoS2 particles has increased to about 1.5 times the substrate. Maximum hardness in the stir zone was 141 Vickers, while the hardness of base metal was 84 Vickers. TOEFL test results also showed that the corrosion potential layer composite with graphite particles near to the values of the base metal had no significant change. While the corrosion potential in the processed layer without reinforcing particles of the base metal is approximately 48 Mv.

In this article, interface characteristics of aluminum and cast iron bimetal has been investigated. To reach an acceptable composite products, from two materials, interface characteristics needs to be investigated. Aluminum melt was poured, at 700 and 750 ̊C, around cylindrical cast iron bars having melt/solid volume ratios of 3, 5 and 8, respectively. Optical and SEM microscopic observations showed that a reaction layer may form at the interface. This layer is composed of Fe2Al5 intermetallic which forms initially at the rough surface of the insert after making contact with molten metal. Microstructural analysis showed the increasing of temperature and the Vm/Vs ratio leads to formation of a thicker and more uniform intermetallic layer. Microhardness of the Fe2Al5 was 824 HV and the thickness of interaction layer varied from 5μm, for the sample produced at 700 ̊C and 3 Vm/Vs, up to 20μm for the sample poured at 750 ̊C and 8 Vm/Vs. A mechanism is suggested for nucleation and growth of this intermetallic layer and also graphite engulfment of gray cast iron, by aluminum melt, at the interface of two metals.

In this paper, nanotechnology advantages are used to improve oxidation resistance of graphite. The elementary SiC coating has been developed on graphite substrate using a pack cementation method and the secondary coating has been produced using a slurry painting method at 1600 °C during 2 hours. The oxidation resistance of coating have been tested has been performance at 1500 °C. The phase composition and surface microstructures of the coating were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The variations of Gibbs free energy of reactions were calculated using by HSC Chemistry software. The results showed that the coating obtained by the pack cementation is a dense graded structure consisting β-SiC. There were lots of SiC nanofibers on the secondary coating with 50-70 nm diameters. The SiC nanofibers coated samples exhibit good oxidation resistance at high temperature. The graphite was fully destroyed during 1 hour however the mass loss of the SiC nanofibers coated samples after 10 h of oxidation at 1500 °C was 6%.

Graphite powders were used in this project and pellets were made under the pressure of 10 bar. Sodium hydro carbonate was used to dope with graphite. Sodium salt powder were poured inside the pellets and heat treated for 5 hours in vacuum at 800̊ C. XRD analysis showed a shift of characteristic peak of graphite. After that, in order to storehydrogen in the pellets, hydrogen was generated and purged to the pellets in the sealed chamber. The chamber was cooled to 80̊ k to make hydrogen adsorption possible. The pellets were exposed to hydrogen for different times and the hydrogen pressure was 1 MP. DSC analysis in argon atmosphere was carried out to assess hydrogen storage. The results showed that after 20 minutes the pellets doped with sodium could adsorb hydrogen which is good for hydrogen storage.

High refractoriness, chemical resistance to slag, production possibility of clean steel, environmental compatibility and low cost are some of the advantages of Dolomite refractories in steel industry. Because of availability of dolomite in Iran, production ofthese refractories is profitable. One kind of the Dolomite refractories is Doloma Graphite refractories that because of good resistance to corrosion and thermal shock have wide usage in cement and steel industries. In this research, the properties of Dolomite-Graphite refractories with different additives and tempering condition were evaluated. The samples were manufactured with different grain size distribution of Dolomite and various amounts of Graphite and resin. The raw materials and their thermalbehaviors were studied by XRF, XRD and STA. After preparing the samples, the physical and mechanical properties, slag corrosion and thermal shock resistances were evaluated. The properties of the samples were evaluated up to 11% total Carbon in thesystem. The reduction in MOR of the specimens, before and after heat treatment was determined as a measurement of thermal shock resistance. The slag corrosion test was conducted based on the crucible test, at 1600°C for 5 hrs. Then, the depth ofpenetration was measured. The obtained results showed that due to the gradual changes in thermal behavior of resin and its weight reduction, the low temperature properties of the system were affected. The results showed that CCS of the samples was increased at the beginning and then decreased, when Graphite was added to the system. The thermal shock and slag corrosion resistance were also improved by adding graphite to the system

This paper discusses the role of fillers including solid lubricants (graphite and molybdenum disulfide), polytetraflouroethylene and silicon carbide on the tribological behavior of a specific polymer, Phenolic Resin. Polymeric composite material samples are manufactured by compression molding and are evaluated for their friction and wear properties. Using a pin-on-disc apparatus, dry sliding wear behavior under ambient conditions was studied which measured friction coefficient of samples. The counterface was made from hardened steel, AISI 52100. A number of experiments were performed using different filler types and weight percents including: graphite and molybdenum disulfide (10, 15 and 20%), polytetraflouroethylene (5, 10, 15 and 20%) and Silicon Carbide (5 and 10%). In silicon carbide case, two different particle sizes (5, 38) were tested as well. Results showed that addition of fillers with layer structure (graphite and MoS2) decrease the friction coefficient and wear resistance but PTFE powder improves both tribological behaviors. Ceramic filler of SiC exhibited different effect. In this case particle size affects the wear property. Large particles (of about 38) found to protect the polymer matrix better than small particles (of about 5), which partially increase the wear rate.