Papers by Keyword: Graphite

Abstract: For estimating effectiveness of adding solid fillers for composites with ultra-high molecular weight polyethylene matrix tribotechnical characteristics of UHMWPE mixture with graphite, molybdenum disulfide and polytetrafluoroethylene were investigated under dry friction, boundary lubrication and abrasion. The optimum filler weight fraction was determined in terms of increasing wear resistance. Permolecular structure and surface topography of wear tracks for UHMWPE composites with different weight fraction of the fillers was studied. The mechanisms of wear of polymeric composites “UHMWPE-graphite”, “UHMWPE-PTFE” and “UHMWPE-MoS₂” under dry sliding friction and abrasive wear are discussed.

Abstract: Non-traditional machining process had made possible the machining of hard to cut materials. Among several non-traditional processes electrochemical machining has been given attention since there occurs no burrs or tool wear. Composites with nano reinforcements had outclassed their counterparts in terms of the properties shown by the nano composites. In the present work aluminium matrix has been reinforced with boron carbide and nano graphite which is added as a solid lubricant to improve tribological properties. The composite is subjected to electrochemical machining with a view of optimizing the process parameters. The process involves introducing abrasive particles while machining which aids in machining. Optimization of process parameters was based on the response surface methodology techniques with four independent input parameters such as voltage, current, electrolytic concentration and feed rate and ECM process performance in terms of material removal rate and overcut.

Abstract: The wearing of bush made of brass in various applications is a cause for major concern. This study aims to analysing the various causes, mechanisms, environmental effects that influence the wearing and reduction in efficiency of the brass-steel sliding pair. The anti-friction and anti-wear properties are analysed under various conditions using a multitude of approaches. The particulate size of the dispersed lubricant (graphite and nanographite) and the temperature under which the experiment is being conducted is directly responsible for the sliding and wear properties of the brass specimen. The current studies and observations involved the use of a pin on disc apparatus, where the test specimen as the pin and slid against the steel plate (EN-31) at various speeds, loads, levels of lubrication and temperatures. The depth of wear under the different loading and sliding speeds are determined individually by means of an LVDT measurement.

Abstract: There is a growing demand for polymeric composite materials, mainly, in industrial applications. For instance, bipolar plates for polymer electrolyte fuel cell in automobile applications. This kind of composite can replace with lower cost and greater efficiency metallic components. The basic requirement is that the composite must possess adequate electrical and mechanical properties for the particular application. The goal of the present paper is to analyze the effect of graphite powder and carbon Black weight percentages on the electrical properties of epoxy composite plates. Electrical conductivity tests were performed in different composites. This study shows that is possible to obtain a semiconductor behavior with both epoxy/graphite and epoxy/Carbon Black composites.

Abstract: In this research, the anti-corona lacquer with different SiC content was fabricated. The surface resistivity of the lacquer at different voltage levels was measured, and the effect of the SiC content on electrical properties of SiC anti-corona coating was investigated. The results showed that the initial surface resistivity ρ_s decreased with increasing mass ratio of SiC to resin, while the non-linear coefficient β varied the opposite way. The surface resistivity was improved by adding suitable amount of graphite, which suited the requirements of multiple sections anti-corona structure.

Abstract: The electrochemical processes occurring at the surface of a highly ordered pyrolytic graphite electrode were investigated, to understand the effects of dimethoxyethane as a co-solvent on the formation of a surface film. In-situ electrochemical atomic force microscopy revealed that a thin film of ~5 nm thickness was formed on the graphite surface after the first potential cycling. There was no evidence of co-intercalation of the solvent molecules. The cyclic voltammetry analysis revealed that a irreversible reduction peak closely related to the film formation was present at ~1.7 V vs. Li⁺/Li.

Abstract: Graphite heat conductor technology can effectively overcome the mixed crystal defect caused by geometric factors during the forming process of single crystal component. The simulation results show that, As for the component that uses heat conductor technology, the heat elimination condition in the corner of component is improved significantly. Before the melt body generating the supper-cold region at the platform end, the solidification interface will advance into the platform from the blade body with the relatively faster speed. According to the analysis of macro structure, the component with heat conductor, because of the diminution of supper-cold time and supper-cold region, the trend to generate mixed crystal on the platform reduces obviously, on one side near the wall of insulation heater, there is almost no mixed crystal on the platform.

Abstract: Nuclear energy is one of the most promising energy sources to satisfy energy security, environmental protection, and efficient supply. The High Temperature Gas-cooled Reactor (HTGR) has attractive inherent safety features and it can be used as many kinds of heat applications such as hydrogen production, electricity generation, process heat supply, district heating and desalination. Many countries, especially developing countries, show their interests in HTGR. Graphite materials are used for the core components of the HTGR. IG-110 graphite, fine-grained isotropic graphite, with high strength and high oxidation resistance is used in the High temperature Engineering Test Reactor (HTTR) of Japan Atomic Energy Agency (JAEA) and High Temperature Reactor-Pebble-bed Modules (HTR-PM) in China. IG-110 graphite is a major candidate for the core graphite components of the Very High Temperature Reactor (VHTR) which is one of HTGRs and one of the most promising candidates as the Generation-IV nuclear reactor systems. This paper describes design of core components of HTTR and R&D on nuclear graphite for HTGR. JAEA established the graphite structural design code and inspection standard of graphite to construct the HTTR. JAEA developed an in-service inspection method and a draft graphite structural design code for future HTGR on the basis of the HTTR technologies. Moreover, JAEA are now developing the design data base of IG-110 graphite and IG-430 graphite including irradiation data for HTGR.

Abstract: In this paper, the effect of ratio of silicon dioxide and graphite for the synthesis of silicon carbide nanowhiskers by microwaves heating was reported. The mixtures of SiO₂ and graphite with different ratio were prepared by ultrasonic mixing using ethanol as medium. The mixtures were dried on hotplate and cold pressed by using hydraulic hand press uniaxially into a pellet die. The mixture in the form of pellet were heated up to 1400 °C at heating rate of 20 °C/min and soaked for 30 minutes. Scanning electron microscopy was used to study the morphology of sample of each different ratio of mixture. It was found that almost complete conversion of graphite and silica to silicon carbide nanowhiskers was observed for sample of mixture SiO₂ and graphite in the ratio of 1:3. Result from x-ray diffraction analysis also indicated that single β-SiC phase was present in the diffractogram of silicon carbide nanowhiskers synthesized from mixture SiO₂ and graphite in the ratio of 1:3.

Abstract: In this investigation, micro crystalline diamond (MCD) and nanocrystalline diamond (NCD) films are deposited on cemented carbide (WC-Co) balls by hot filament chemical vapor deposition (HFCVD) technique. After deposition, MCD and NCD films are characterized by field emission scanning electron microscopy (FESEM) and Raman spectroscopy. Then frictional tests are carried out between CVD diamond coated balls and graphite. The results show that the MCD-graphite and NCD-graphite tribo-pairs exhibit comparable frictional coefficients, while the wear rate of graphite in MCD-graphite working pair is much higher than that of graphite in NCD-graphite working pair. Furthermore, the element oxygen is detected in the wear groove of graphite, suggesting the oxycarbide of working materials at the increased temperature due to the heat generated from the mechanical friction.