Papers by Keyword: Graphite

Abstract: Asphalt concrete is an insulating material. Conductive materials are added to asphalt concrete in order that improving the conductivity. Conductive asphalt concrete (CAC) has become a promising method to snow melting and self-monitoring. In this study, the piezoresistance of CAC which can be improved the conductivity through graphite are analyzed. Based on the interparticle separation and bitumen film-thickness of graphite particle, a model has been developed to predict the piezoresistance under the applied stress. The influences of applied stress, graphite diameter, graphite volume fraction, compressive modulus on the piezoresistance are interpreted through laboratory experiments. Both the numerical and experimental results show that the theoretical data obtained from the model are found to agree with the experimental ones fairly well. In addition, it was found that all these parameters influence the piezoresistance by altering the change process of interparticle separation of graphite.

Abstract: It has long been recognized that a need for practical methods for maintaining optimum cesium pressure within a thermionic energy converter has been pursued for space applications. An attractive solution to the problem is the use of a sorption type reservoir where cesium absorbed into a lattice. Four graphite materials were initially investigated for the potential usage as cesium storage media. Primary research focusing on the characteristics of loading ability, structural integrity, and dimensional change of these materials was performed by synthesizing proper cesium-graphite lamellar compounds with a two zone vapor transport method. Graphite foams show promising prospect for thermionic application as integral cesium reservoir material.

Abstract: Schemes of structural classification of carbon materials which are based on the types of chemical bonds formed in materials and the number of nearest neighbors with which each atom forms covalent bonds have been proposed. The classification schemes cannot only describe the known phases, but also are the methodological basis for the prediction of new phases and nanostructures. New phases can be obtained by linking, superpositioning or cutting of precursor structures.

Abstract: Synthetic quartz glass is an excellent transmittance material in ultraviolet (UV), visible and near-infrared bands. Homogenization process to synthetic quartz glass optical elements is done in order to make the composition and structure more uniform. The homogenization temperature is above 1800°C. After high-temperature homogenization, the UV transmittance of quartz glass appears a certain extent of decline in the edge partition., After high temperature homogenization process, it is found that the closer the layer to the graphite vessel, the stronger influence on UV transmittance will be. This conclusion is made by comparing the UV transmission of the quartz glass in different layers. Furthermore, the factors affecting the UV transmittance is also analyzed in this article.

Abstract: In recent decades, Electrical Resistance Tomography (ERT) has become a research focus. The application of ERT in practical engineering is still in the research stage, due to the resistivity is very high and not steady, limiting its development. The influencing factors of Graphite Electrically Conductive Concrete (GECC), such as the dosage of graphite, curing age, moisture content and so on, have been analyzed. A set of ERT system of GECC has been proposed and designed based on PXI platform. This paper mainly shows experiments on ERT of GECC structure. The targets given with defects have been used for imaging. By examining, the law of the GECC imaging in different conductivity matrix has been got. Meanwhile, this paper determines the resistivity threshold in the ERT system, and validates the detection accuracy of the model with defects.

Abstract: The steel fiber/graphite conductive concrete is applied in power system grounding. In high soil resistivity regions, the common methods for reducing the grounding resistance are not practical. It is difficult for grounding resistance of substations to meet the requirements of working earthing and safety earthing. In order to solve this problem, a steel fiber/graphite conductive concrete is developed in this paper. Steel fiber and graphite are added as conductive fillers. The long-term stability of the steel fiber/graphite conductive concrete is studied. The experiment results show that steel fiber/graphite conductive concrete not only maintains excellent conductivity, but also has good mechanical strength and corrosion resistance in 300 days.

Abstract: Two-dimensional films of graphene oxide (GO) have been synthesized using various oxidation methods such as the conventional or modified Hummers method. The redox method for graphite has shown promise at producing GO films on a large scale. However, this method is a very exothermic process that liberates gases that are harmful to the environment and humans. This article addresses the characterization of graphene oxide from alternative sources of carbon and using the dry method. Comparative studies performed using Raman spectroscopy suggest that this method is both promising and more environmentally friendly.

Abstract: Abstract. In this study, the effect of Phanerochaete chrysosporium on graphite was investigated, and graphite was used as a substitute of elemental carbon in carbonaceous gold ores. Under the condition of optimum process, the fungal degradation rate of graphite reached to 13.49%, and the carbon content of graphite was decreased by 5.13%. XRD analysis indicated that Phanerochaete chrysosporium could destroy the crystal structure of graphite. FTIR analysis indicated that Phanerochaete chrysosporium could increase the number of aliphatic structures and oxygen-containing groups. The cyanide leaching gold tests showed that Phanerochaete chrysosporium can decrease the preg-robbing capacity of graphite, about 9.52%. It indicated that Phanerochaete chrysosporium is an available microorganism, which was employed to pre-treat carbonaceous matter in carbonaceous gold ores to reduce the interference of gold cyanidation leaching.

Abstract: Abstract. In recent years, Aluminium alloy based metal matrix composites (MMC) are gaining wide spread acceptance in several aerospace and automobile applications. These composites possess excellent wear resistance in addition to other superior mechanical properties such as strength, modulus and hardness when compared with conventional alloys. The hybrid composites are new generation of composites containing more than one type, shape or sizes of reinforcements giving superior combined properties of reinforcements and the matrix. In the present work, Al6061 has been used as matrix material and the reinforcing materials selected were SiC and Graphite particulates of 10 to 30µm size. Composites Al6061-Gr (2- 8 wt. %), Al6061-SiC (2 -10wt. %) and Hybrid composites with Al6061 matrix alloy containing 3wt% graphite and varying composition of 2-10wt% SiCp were prepared by stir casting technique. The cast matrix alloy and its composites have been subjected to solutionizing treatment at a temperature of 530 ± 20C for 6 hours, followed by ageing at a temperature of 175 ± 20C for 6 hours. The mechanical properties of as cast and T6 heat treated composites have been evaluated as per ASTM standards and compared. Addition of Graphite particulates into the Al6061 matrix improved the strength and ductility of the composites. Significant improvement in tensile strength and hardness was noticed as the wt. % of SiCp increases in Al6061-SiC composites. Addition of Graphite into Al6061-SiC further improved the strength and ductility of hybrid composites. The heat treatment process had the profound effect in improving the mechanical properties of the studied composites. The microstructural studies revealed the uniform distribution of SiC and Gr particles in the matrix system.

Abstract: In the present study, the corrosion behaviour of the Al2219, Boron carbide and Graphite has been investigated. The Aluminium Metal Matrix Hybrid Composites were fabricated by two step stir casting technique. Corrosion tests were carried out with the natural sea water (3.5 wt % NaCl) according to standard procedure. The tests were conducted at room temperature by cyclic polarization technique for a definite time interval. After the test, material loss was calculated by weight loss method. The surface morphology of the specimen before and after corrosion was studied using the optical microscope images. The test result reviles that, the corrosion rate of the composite was greater than the base alloy, but the corrosion of the hybrid composite is the most compared to the alloy and monolithic composite.