Papers by Keyword: Graphite Powder

Abstract: Fiber reinforced plastics have been widely used for manufacturing aircrafts and spacecrafts structural parts because of their high mechanical, physical properties. These are used in manufacturing of structural composites, printed circuit boards and in a wide range of special-purpose products which are included in medical field as well. Within reinforcing materials chopped strand mats are the most frequently used in structural constructions because of their properties such as viscoelasticity, strength and high thermal stability. The present work focuses on mechanical and thermal properties of chopped strand mat reinforced with polyester resin and filler as graphite powder (which has high melting point) in different weight fractions. Evaluation of material properties is tested using Thermo-Gravimetric Analysis and Dynamic Mechanical analysis at a standard temperature ranging between 20°C - 460°C and evaluated. The results show that inclusion of graphite powder in chopped strand mat exhibit better enhancement in results when compared.

Abstract: The relevance of this paper is based on the increasingly larger volumes of reconstruction of buildings and structures and also with the opportunity to use polymer-bitumen binder based multifunctional materials for construction and installation purposes during such works as sealing cracks and hollows in structural elements. The paper provides a summary analysis of the current situation with the use of composite materials to increase the load-bearing capacity of certain structural elements. It discusses the methods for achieving multi-functionality of materials with the use of polymer-bitumen binders. It further details the procedure for the experimental studies conducted to test several composite materials introduced in a liquid polymer-bitumen mass and applied onto an adhesive polymer-bitumen tape, including the following components: graphite powder, graphite grease, cement and a mixture of graphite powder and cement. When assessing the adhesion characteristics of the samples tested, it was found that the best performance was demonstrated by the following composite materials: polymer-bitumen tape with graphite powder and a mixture of graphite powder and cement. Their adhesion characteristics were shown to be relatively equivalent by using the following two testing methods: the tear-off method with a three day holding period, and the instant adhesion measuring method. However, composite materials with a liquid polymer-bitumen basis failed to produce the desirable results. The authors are of the view that in this case the given adhesion power parameters can be achieved through changing the structure of the materials.

Abstract: Electrical discharge machining (EDM) is a non-conventional machining technique that is well-known for use in fabricating dies and molds owing to machinability of high hardness materials. Although the electro-thermal mechanism of EDM offers many advantages over other available machining methods, its sluggish nature limits the wide application of such machines for mass production. In this research, adding graphite powder to dielectric is proposed to improve EDM performance factors. Material removal rate (MRR) and average surface roughness (Ra) have been monitored and evaluated after addition of graphite powder to dielectric in electrical discharge milling and sinking. It is found that the presence of powder particles in dielectric fluid enhances the MRR steadily up to ~11 and ~17% for milling and sinking process, respectively. Moreover, the highest enhancement if Ra is ~31% at 1g/l graphite powder concentration for electrical discharge milling and up to ~11% for sinking process. Field emission scanning electron microscopy (FESEM) is used to inspect the machined surfaces. The surfaces machined with graphite powder mixed appear significantly unlike the surfaces machined in pure dielectric. Adding powder to dielectric is found to increase the machined surface hardness by ~26%, from 240 to 302 HV.

Abstract: Graphite powder was used to prevent a molten AZ91D magnesium alloy from oxidation and burning in order to develop a new pollution-free protection method with low cost. The protection method is expected to have good protective effect without decreasing the mechanical properties of the alloy. The protective ability of graphite powder on the alloy was investigated. Experimental results showed that graphite powder could protect AZ91D melt. The protective ability increased with graphite powder amount and decreased with holding time. The microstructure, chemical composition and phase composition of the surface films formed on the molten AZ91D alloy were analyzed using scanning electron microscopy, energy dispersive spectrometer and X-ray diffraction, respectively. The protection mechanism was discussed. The surface films produced by the reactions between graphite powder, AZ91D alloy melt and the ambient atmosphere had two layers. The continuous and compact outer layer, mainly consisting of MgO and C, may be the fundamental reason for the fact that graphite powder could protect AZ91D alloy melt.

Abstract: High quality micro sheet rhombohedral graphite crystals were synthesized by Hummer method using compounds of MWCNT, K₂S₂O₈ and P₂O₅. The growth mechanisms were discussed by finite element simulation. The synthetic sheet rhombohedral graphite crystals showed a higher growth rate in radial direction than that in axial direction. Raman spectrum and Fourier transform infrared spectrum indicated that synthesized sheet rhombohedral Graphite had fewer crystal lattice distortions with no impurities. Finite element simulations indicated that the solvent metal convection field in the radial direction was stronger than that in the axial direction. As prepared graphite powder was annealed at 1350 oC to obtain diamond nanoparticles. The as-prepared products were exposed to formaldehyde gas.

Abstract: This research was to study the influence of a sustained load on the electrical resistivity of a cement-based sensor. The cement-based sensor in this study was made of cement paste having water to cement ratio of 0.4 with the addition of graphite powder at 2% and 4% by weight of cement and carbon fibers at 2% and 4% by volume. The sustained load was applied on the cement-based-sensor using a sustain machine to control a compressive force continually at 30% of its ultimate compressive strength for a period of 30 days. The test results showed that the sustained load induced a creep strain on the cement-based-sensor. The graphite incorporated cement-based sensor showed higher creep strain than the plain cement-based sensor while the carbon fiber cement-based sensor showed lesser. In addition, it was shown that the creep strains affect the electrical resistivity of the cement-based sensors.

Abstract: The aim of this research was to implement cement-based sensors in monitoring the change of strain in concrete structures in particular where a compression applies. The experiment was conducted in a laboratory by embedding a cement-based sensor in a 150x150x150 mm normal strength concrete cube. When the sensor-installed concrete cube was loaded, the relation between the fractional change in resistivity (FCR) and strain of the sensors was evaluated. In this study, all cement-based sensors were made of cement paste containing carbon fiber at 2% by volume fraction. They were then varied with the addition of graphite powder at 4% and silica fume at 15% by weight of cement. Thus, there were total four mix proportions. From the experimental results, all sensors provided a good corelation between the FCR and compressive strain. Among them, the carbon fiber plus graphite powder (no silica fume) cement-based sensor yielded the most excellent piezoresistive response.

Abstract: Microwave absorbing material is currently being more and more widely applied in the world. However, conventional absorbent coating material cannot fulfill the complex current requirements of science and technology to have a wide absorption frequency band, and high absorption. This paper describes composite material plates with a multi-layer absorbing structure designed according to impedance-matching and attenuation principles, producing two- and three-layer absorbing structures. Twelve samples were made, containing graphite powder and manganese dioxide at varying concentrations. The results show that in the frequency range 8-18 GHz, the peak absorption of double-layer samples is -12.3dB, the effective bandwidth (R < -10 dB) is 1.8GHz. The absorption peak of three-layer samples is -18 dB, and the effective bandwidth (R < -10 dB) is 8GHz. The findings of this research are useful in improving the absorption bandwidth of absorbing material.

Abstract: Resistance sintering characteristics of electrolytic and atomized copper powders mixed with graphite powder in steps of 10vol% up to 50vol% were experimentally investigated. In the experiments electrifying voltage and time, and applied pressure were varied. Post-electrification pressurization and insertion of low thermal conductive austenitic stainless steel discs between the sintering powder cake and electrodes were attempted to promote the sintering. The effects of the operational parameters including the two devices on sintering performance are discussed. Sintering strength of the resistance-sintered composites is also discussed.