Papers by Keyword: Graphite

Abstract: Thermal analysis is worldwide used in foundry for control of structure and properties of cast irons. In this paper is presented the experimental study realized to control the inoculation effect by thermal analysis method of inoculated grey cast irons. For this purpose was conducted an in ladle inoculation process with 0.5wt. % inoculant from LaCaAlFeSi and BaCaAlFeSi alloy systems. The main goals of this experimental research work are: to determine the particular characteristics of the registered cooling curves, to notice the solidification parameters that present sensibility as against inoculant addition in treated cast iron and eventually to improve thermal analysis technique of cast irons.

Abstract: In recent year's aluminium and aluminium alloys are widely used in automotive industries. These are light (density of about 2.7 g/cm³), having good malleability and formability, high corrosion resistance and high electrical and thermal conductivity. Metal matrix composites (MMCs) are being employed in industrial applications since they have high specific strength, stiffness, and good wear properties. Due to their favourable properties, composite materials with reinforcements are used in many industries. With the aim to additionally improve some of their properties, especially their tribological properties, several solid lubricants are used in the process of composite production. This paper gives an overview of investigations and possibilities of solid lubricant particles (such as graphite) applying as complementary material, mainly for aluminium base composites that are nowadays common in use in automotive and aeronautics industry.

Abstract: The conductive thin film was made based on bio-based epoxy and graphite compounded with its cross-linker (Methylene Diphenyl Diisocyanate, MDI) and further blended with disparate percentages of pretreated graphite. The preparation of this solution started by drop casting as thin films, where the thickness of thin film was set approximately ~0.1 mm. Optical microscope, Fourier transform infra-red spectroscopy (FTIR) and Ultraviolet-visible (UV-vis) spectrophotometer has been operated to diagnose Graphite/ biopolymer composites in order to have better and accurate results of this work. The current-voltage (I-V) characteristics of the composite thin film samples were measured at room temperature. This study shows the electrical conductivity was discovered and calculated by achieving conductivity of 10³ S/m as a prove that this thin film has the ability to conduct electricity.

Abstract: Graphite reinforced bio-based epoxy composites with different particulate fractions of graphite were investigated for mechanical properties such as tensile strength, elastic modulus and elongation at break. The graphite content was varied from 5 wt.%, 10 wt.%, 15 wt.%, 20 wt.%, 25 wt.%, 30 wt.% by weight percent in the composites. The results showed that the mechanical properties of the composites mainly depend on dispersion condition of the treated graphite filler, aggregate structure and strong interfacial bonding between treated graphite in the bio-based epoxy matrix. The composites showed improved tensile strength and elastic modulus with increase treated graphite weight loading. This also revealed the composites with increasing filler content was decreasing the elongation at break.

Abstract: Application of microwave absorber (MWA) does affect the yield of microwave pyrolysis process. In this study, activated carbon and graphite have been used as microwave absorbers and the results were then compared with the microwave pyrolysis process without microwave absorber. The yield of solid and liquid increased while the yield of gas decreased with the application of MWA. Chemical functional group inside MWA also affected by the microwave pyrolysis process and energy content of MWA slightly increased from 24.54 MJ/kg to 29.57 MJ/kg and 32.17 MJ/kg to 32.24 MJ/kg for activated carbon and graphite, respectively.

Abstract: The structure, mechanical properties and wear resistance of hypereutectoid steel containing 0.09-8.97 wt. %copper were studied. It is found that an increase in copper increases lamellar pearlite microhardness. Triboengineering testings under conditions of sliding friction show that wear resistance of hypereutectoid steel alloyed with 8.97 wt. % copper is ~3.5 times higher than the wear resistance of bronze and by ~23 % higher than the wear resistance of bearing cast iron. Under conditions of friction on fixed abrasive particles a relative wear resistance of the hypereutectoid steel alloyed with copper is ~3 times higher than a relative wear resistance of bronze.

Abstract: Within the German Collaborative Research Center 39 PT-PIESA the forming of micro cavities into aluminum sheets is one challenging task. During this forming process high forces and stresses occur which lead to a high tool wear. Hence, the actually applied cold forming process should be replaced by a warm forming process. This paper shows the tribological investigations for the warm forming process. Within the experiments the barrel compression test is used to determine the friction conditions by varying the size of the cylindrically shaped samples of AlMg4,5Mn0,7, the forming degree and the lubrication condition (dry, graphite, forming oil). The flat punches were made from hardened steel 1.3343. The friction factor was calculated, and surface roughness was evaluated by 3D-laser microscopy. The experiments show that the friction factor increases, especially at forming degrees below 1 and for small specimen size, compared to cold forming processes. In addition to that, an influence of the lubrication condition onto the surface roughness was observed. For experiments conducted with graphite, the surface roughness is significantly higher than for samples, which were formed dryly or with forming oil.

Abstract: High density graphite disks and aluminum nitride ceramics powders have been utilized to obtain joints by Spark Plasma Sintering technique. The joining was carried out in vacuum, at temperatures of 1700°C, 1800°C and 1900°C, under the pressure of 50 MPa with a constant dwelling time of 5 minutes The AlN ceramics to be joined were also synthesized by ceramic technology standard route by using AlN powders and 2.5 % wt.Y₂O₃ powders as sintering additive, which were added in order to increase densification rate and by thus, thermal conductivity. The joining of AlN/C was performed both without and with the aid of a ceramic powder composite AlN+Y₂O₃+C film, as interlayer. Besides the crystalline phases (AlN and C), the Al₅Y₃O₁₂ compounds with a cubic crystallographic structure were identified by X-ray diffraction. The optical microscopy images revealed that all samples, both without and with film as interlayer, had strong joined areas, without any defects and discontinuities at interfaces. The Vickers microhardness and Young Modulus values measured by nanoindentation have shown that using of the film as intermediary layer was leading to the highest values of mechanical properties (HV = 8 – 23 GPa and E= 227-512 GPa) at the AlN/C joints interfaces.

Abstract: Nowadays, graphene (Gr) is one of the most promising materials in the field of nanoscience and nanotechnology and has attracted extensive attention in variety of applications, such as solar energy, environmental management, sensor, electronic device as well as energy storage and conversion. From a theoretical point of view, Gr provides the ultimate two-dimensional (2D) model of a catalytic support with sp² hybridized carbon atoms. Its unique physical, chemical and mechanical properties are outstanding, and could allow the preparation of this composite material with unprecedented characteristics, such as superior electron mobility, good conductivity, excellent transparent property and high chemical stability. These unique characteristics inherent to well-defined 2D Gr are suitable for facilitating a wide range of transformations and may offer extraordinary potential in the design of novel catalytic systems. Herein, a simple and well-controllable Improved Hummer’s method was presented for the first time by controlling it’s stirring duration for high yield production of GO (62.50%). Based on our preliminary results, it was found that large amount of oxygen functional groups appeared after the conversions of graphite into graphene oxide (GO) by applying the vigorous stirring speed for 72 hours continuously. The main reason mainly attributed to the improvement of the mass transfer rate of oxygen molecules during the oxidation reactions; thus, high yield of GO could be achieved under this experimental condition. In addition, the resultants GO exhibited higher short-circuit currents with 290 μA compare to short circuit of Gr with 70 μA under light simulation condition.

Abstract: In the field of material science and engineering, there is a great impact ever since the invention of composites materials. High strength to weight ratio provides the attractive combination that moves composite materials into new era. The conventional materials like cast iron, steel, and aluminium alloy are replaced by the composite materials due to its superficial properties and could be applied in aerospace and automotive applications. Powder metallurgy fabrication technique is one of the best and attractive methods for producing metal matrix composites because of its better distribution of particles and reliability and cost in manufacturing. In this paper, composites based on aluminium alloy (Al 2024) reinforced with 10% weight fraction of hard ceramics like Aluminium oxide (Al₂O₃) and 10% weight fraction of Aluminium oxide (Al₂O₃) with 5% graphite particles is produced by Powder metallurgy method. Hardness and wear test are conducted for the Al 2024, Al-10%Al₂O_3, and Al-10% Al₂O₃-5% Graphite. In addition the surfaces of the composite are analyzed by SEM to study the wear of the composites.