Papers by Keyword: Graphite

Abstract: This study investigates an enhancement of carbon-based materials, including multi-walled carbon nanotubes (MWCNTs) and graphite, through Ion Assisted Reaction (IAR) and metal nanoparticle deposition using Physical Vapor Deposition. The IAR process employed Ar⁺ ion beams in reactive gas environments, effectively introducing hydrophilic functional groups such as hydroxyl (-OH) and carboxyl (-COOH) on the MWCNT surfaces. This modification significantly improved dispersion behavior of the treated MWCNTs, particularly in non-polar solvents like N-Methyl-2-pyrrolidone (NMP). Results indicated that the treated MWCNTs demonstrated a slower sedimentation rate compared to untreated samples, with enhanced stability over 120 minutes in NMP. Graphite was modified with copper nanoparticles on its surface using magnetron sputtering in PVD system, leading to a uniform distribution of the modified graphite in matrix. SEM analysis revealed that this modification enhanced the surface roughness of the graphite, facilitating stronger interfacial adhesion with polymer epoxy resin. Composites incorporating these nanoparticle-coated graphite fillers (NPP graphite) exhibited superior thermal and mechanical properties. For instance, a 15% increment in thermal conductivity was observed in epoxy resin composites containing NPP graphite compared to those with untreated graphite. This improvement was attributed to the metallic Cu nanoparticles acting as thermal bridges, effectively transferring heat within the composite matrix. Mechanical properties were evaluated by blending modified fillers into polymer matrices, including polyvinyl chloride (PVC) and polyethylene (PE), with filler concentrations varying from 5 vol% to 15 vol%. Tensile testing and SEM analysis of the fractured surfaces indicated that NPP graphite composites achieved uniform dispersion, reduced agglomeration, and improved interfacial bonding. This study demonstrates that physical surface modification techniques such as IAR and PVD effectively overcome limitations associated with conventional chemical methods. This approach not only improves the dispersion and interfacial adhesion of carbon-based fillers but also enhances their thermal and mechanical performance.

Abstract: In polymer studies, biocomposite now draws attention as an exciting material obtained from combining natural fiber and matrix, which is an environmentally friendly material with biodegradable properties. One of the natural fibers often used in polymer filler is banana stem fiber. This study aims to prepare carbon-coated waste-dried banana fiber. The waste of banana stems was used as raw material for preparing cellulose-rich banana stem fiber. The banana fiber was soaked in an alkaline solvent, 1% NaOH, to remove the lignin content. The dried banana fiber was then coated with activated carbon and graphite by immersion in the carbon dispersion in ethanol with PVA glue binder added. Fourier-transform infrared (FTIR) and X-ray diffraction (XRD) spectra show different profiles on raw and carbon-coated banana fibers, indicating successful carbon coating. The burning test and thermal analysis results show that carbon-coated banana fibers have better thermal properties than raw banana fiber. This suggests that carbon covered on the fiber surface could enhance its thermal property due to intramolecular bonds between fibers and carbon particles. Graphite-coated banana fibers have the longest burning time and are concluded to have the best fire-retardant properties among all samples. The findings confirmed the potential use of carbon-coated banana fiber as filler material for reinforcing conventional composites.

Abstract: The solidification mechanism of ductile iron is a bit complex due to the precipitation of graphite and silicon. These elements change the solidification pattern of cast iron. Density of these elements is less than iron leads to occupying more volume consequently increase the overall metal volume. There are two aspects on this increase in metal volume. One is, reducing this volume increase to reduce the creation of porosities at the earlier stage of solidification and second is, using this volume increase to remove porosity at the later stage of solidification. Proper understanding of this graphite expansion in cast iron solidification will bring insights on reducing or removing of the risers. The current study focus on correlating the net contraction and austenitic liquidus point with shrinkage. The average contraction found through this study is 1.36 % which is more than the net expansion of 0.25 % (without riser) reported in literature.

Abstract: One of the most significant environmental challenges nowadays is the rising manufacturing of non-biodegradable polymer wastes like polystyrene. In order purpose of manufacture environmentally friendly polystyrene that easily decomposes, a solvent approach was used to create polystyrene based zinc oxide- graphite composites. The surface morphology and materials contained in the modified polystyrene were evaluated by scanning electron microscopy-energy dispersive X-ray analysis to verify the dispersion and distribution of the nanoparticles by scanning electron microscopy and the material contents by energy dispersive X-ray analysis. While the crystal structure, chemical bonds, and functions were determined by X-ray Diffraction and Fourier transform infrared, no change in the chemical structure occurred in polystyrene. Thermogravimetric analysis was used to assess the thermal decomposition. And its results found that the temperature of the decomposition was 46.78° lower in zinc oxide and graphite-based polystyrene composites than in pure polystyrene. It came to light that the presence of zinc oxide nanoparticles causes phase separation and consequently impacts the thermal behaviour of graphite-based polystyrene composites. The phase separation was demonstrated by the Thermogravimetric curves showing two degrading steps. This satisfies the urgent demand to synthesize polystyrene that is eco-friendly and easy to thermally decomposition, as well as easy to recycle, which benefits both the environment and the commercial side.

Abstract: In the current research, titanium carbide (TiC) is used to reinforce the aluminium alloy (AA 6063) in stir-cast hybrid composites at concentrations of 5, 10, and 15 weight percent together with 3 weight percent of graphite. The application of this developed composite is mainly used for automobile suspension parts. The portrayal of characters was performed, and the mechanical properties of the fabricated samples were investigated. Composites with different TiC weight percentages have their mechanical properties, including hardness, tensile strength, compressive strength, and flexural strength, measured and assessed. The results are shows that AA 6063 alloy with 3 wt. percentage of graphite with an increasing weight percentage of TiC composites are better in the mechanical property. The hardness of the AA 6063 alloy composites is greater than that of the base matrix alloy. The tensile strength of Al 6063 alloy composites has been reported to grow with increasing TiC particle content and to be significantly higher than the strength of the matrix alloy. Also, the SEM microstructure images clearly shows that 15 weight percentage of TiC with 3 weight percentage of Graphite shows the maximum distribution in the matrix.

Abstract: Flexible sensors and actuators have broad applications in the fields of wearable electronics for health, sports, functional textiles, robotics and cobot applications. Graphene-or graphite-based polymer nanocomposites are promising materials for the development of soft sensors and actuators. This study investigates strain sensing properties of silicon rubber with various graphene filler concentrations (8wt%-12wt%). Current-voltage characteristics have been measured under various strains. We obtain that the sensor’s electrical resistance, for a given voltage, can be approximated by a linear fit of the logarithmic resistance as function of the extension ratio of the sensor. The obtained mechanically induced logarithmic resistor behavior of the polymer nanocomposite is highly promising for the development of electronic sensing and control. Furthermore, thin film graphite layers were investigated on highly stretchable silicone membranes.

Abstract: GaN-based nanopillar crystals are directly grown on multicrystalline Si and amorphous-carbon-coated graphite substrates whose surfaces are not mirror-polished. Light-emitting diodes (LEDs) of a double-hetero structure are prepared from the nanopillar crystals, and their optical–emission properties are investigated. Despite the substrate type and surface conditions, moderate light emissions are obtained from nanopillar LEDs though the light emissions are not always homogeneous, especially in the LEDs prepared on the graphite-based substrate. Nevertheless, these results will lead to realizations of novel large-area light-emitting devices.

Abstract: Electromyography (EMG) is a method for measuring muscle biopotential signals for monitoring muscle activity. Electrodes are placed on the skin to capture EMG signals from muscles underneath. The most common electrodes used in clinical EMG measurement are Ag/AgCl electrodes in the form of metal plates coated with electrode gel. Electrode gel enhances the contact between the electrode’s metal plate and the skin since it is essential for a good measurement signal quality. Meanwhile, flexible electrodes are made from flexible conductive materials that can be adjusted to the contour of the skin surface; therefore, they can improve the measured biopotential signal quality. This study developed a carrageenan-based bioplastic with the addition of graphite and silver nanoparticles (AgNP) hybrid as a flexible electrode for EMG signal measurement. Fabrication of graphite and AgNP hybrid starts with the functionalization of the graphite powder in a mixture of HNO₃ and H₂SO₄. Next, AgNPs were added using the electrochemical method by utilizing SnCl2 and functionalized graphite powder to form an Ag-Sn/Graphite (Graphite-AgNPs) hybrid conductive material. In order to incorporate conductive materials into bioplastic, the Graphite-AgNPs hybrid conductive material is then mixed into the carrageenan-based bioplastic mixture. It is found that 25% w/w addition of these conductive materials already gives good electrical conductivity. The best electrical conductivity value was determined by varying several conductive material types and concentrations. Finally, the EMG signal was measured with the bioplastic flexible electrodes, and the performance was compared with the commercial Ag/AgCl electrodes.

Abstract: Electrically conductive composites based on silicates offer new possibilities for the use of composites not only in civil engineering but in the construction industry in general. These materials can be used, for example, for resistive heating of roads and highways, surge protection for buildings, EMI shielding, or smart sensors. This article focuses on cement composites where graphite powders are used as electrically conductive fillers. The research focuses on the behaviour and the change of the electrically conductive properties of these materials under mechanical loading. The changes in the resistivity of the composites when loaded in different directions on the electric current flow was investigated and studied. The specimens were loaded in the direction of electric current and in the direction perpendicular to the electric current.

Abstract: Mixing conducting particles in cement present various applications in electromagnetic shielding and in-situ inspection of structures. In this study, graphite was incorporated in cement paste at varying concentrations which enhanced its EM shielding. The samples were characterized using Terahertz Time-Domain Spectroscopy (THz-TDS) to determine its optical properties and calculate for the conductivity. The Ultraviolet-Visible (UV-Vis) spectroscopy was also used to characterize the sample to confirm the variation of graphite content which showed small peaks at 258 nm caused by the excitation of π electrons in the graphitic structure. The refractive index, absorption coefficient and conductivities were determined from the amplitudes and phase difference obtained in the frequency domain. The spectral cut-off in the THz region decreases with increasing graphite content due to THz absorption of graphite. The THz refractive index appeared to be not frequency-independent while the absorption coefficient showed a power-law behavior. The THz conductivities were calculated and was found to be proportional to the graphite content. This is attributed to an increase in the conducting network of cement paste and increase in the charge carriers in the insulating cement matrix.