Addition Of Graphite Research Articles

The Effect of Expanded and Natural Flake Graphite Additives on Positive Active Mass Utilization of the Lead-Acid Battery

The effects of expanded and not expanded (natural flake) graphite additives were evaluated on the discharge utilization of the positive active material (PAM) in the lead-acid battery. Graphite powders were added to the paste at 2.20 vol. % and tested in model 2V battery cells under a wide range of discharge currents from 8C to C/20. The effects of graphite on the PAM pore volume and pore size distribution were measured with mercury porosimetry, and a good correlation was found between the pore volume of the PAM and utilization performance of the cells. It was shown that the powder characteristics of graphite can affect the PAM pore volume. A correlation was found between the graphite additives’ structural order and PAM utilization.

ASSESSMENT OF ABRASIVE WEAR RATE FOR PTFE-BASED COMPOSITES IN COMBINATION WITH STEEL

This paper presents a study of the tribological wear rate for PTFE-based composites in combination with C45 steel. PTFE composites with the addition of glass fibre, bronze, carbon fibre, and graphite were selected for the study. Tribological tests were conducted in a roller-block combination over an expanded contact area with no lubrication, using an SMC-2 machine. The study assessed the mass and volumetric wear for the test materials and the wear rate index. The highest wear values were noted for the PTFE composite with the addition of bronze, while the lowest was for the PTFE composite with the addition of glass fibre. For all the test materials, the formation of a polymer film on the steel counter specimen was noted.

Microwave-assisted co-pyrolysis of chlorella vulgaris and polypropylene: Characteristic and product distribution analyses

The co-pyrolysis characteristics and product yield of Chlorella vulgaris (CV) and polypropylene (PP) under different mixing ratios (10:0, 8:2, 6:4, 5:5, 4:6, 2:8 and 0:10) were studied by microwave oven. Then the effects of different graphite (GP) additions (10%, 20%, 30% and 40%) on the optimum mixing ratio of CV and PP were investigated. The composition of bio-oil was analyzed by GC–MS. The results indicated that the C8P2 (CV/PP = 8:2) group had the best pyrolysis characteristics. The maximum weight loss rate (Rm) and average weight loss rate (Rv) of the C8P2 with 30% GP addition achieved the peak value. In the absence of GP, compared with C10P0 group, the contents of nitrogen compounds in bio-oil of the C8P2 group decreased by 21.58%. After adding GP to the C8P2 group, the nitrogen compounds in bio-oil of 30% GP group was 1.93% lower than that in 0% GP group.

Influence of synthesis approach on the electrochemical properties of (Li3V2(PO4)3-LiVOPO4)/graphite composite material for Li-ion batteries

In this work, a dual-phase Li3V2(PO4)3-LiVOPO4 cathode material was synthesized using a novel vanadium-excess sol-gel process, followed by the addition of graphite by compositing in-situ or ball milling mixing. The different graphite addition approaches did not affect the ratio of the two phases in the composite but significantly influenced its electrochemical performance. The Li3V2(PO4)3-LiVOPO4/G sample prepared by in-situ compositing showed a special flake-like morphology with a uniform distribution of graphite and the cathode material showed significantly superior electrochemical performance in a wide voltage window of 1.5–4.5 V with discharge capacities of 281, 250, and 211 mAh g−1 at a discharge rate of 0.2 C, 1 C, and 10 C, respectively, as well as higher capacity retention of 88% and 67% after 100 and 650 cycles at high discharge rates of 1 C and 10 C, compared to its ball milling mixed counterpart. The excellent electrochemical performance can be ascribed to the mutual modifications induced by in-situ graphite addition and their synergistic effects.

Effect of addition of flyash and graphite on the mechanical properties of A6061-T6

Composites are one of the most successful materials in the recent manufacturing industry. Mostly in recent works it has been found that flyash is inexpensive and a low-density reinforcement. This is available in abundance due to the waste produced from burning of wat in thermal plants and waste from rice mill. So, in the present study the effect of graphite and fly ash on the mechanical properties of Al6061-T6 has been tested. It was found that Al- 6%graphite-30%Fly ash is the preferred composition. Optical microscopy was carried out to reveal uniform dispersion of the reinforcements and no porosity was observed.

Copper Cathode Contamination by Nickel in Copper Electrorefining

Nickel behavior has a significant role in the electrorefining of copper, and although it has been extensively studied from the anode and electrolyte point of view over the past decades, studies on nickel contamination at the cathode are limited. In the current paper, three possible contamination mechanisms—particle entrapment, electrolyte inclusions and co-electrodeposition—were investigated. Copper electrorefining (Cu-ER) was conducted at the laboratory scale, and the cathodes were analyzed by scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDS) and flame atomic absorption spectroscopy (AAS). Particle entrapment was studied by adding NiO and Fe2O3 to the system to simulate nickel anode slime, and the experiments were replicated with industrial anode slime material. The possibility of electrolyte entrapment due to nodulation was explored through the addition of graphite to produce nodules on the cathode. Co-electrodeposition was analyzed by experiments that utilized a Hull cell. The results indicate that particle entrapment can occur at the cathode and is a major source of the nickel contamination in Cu-ER, whereas nickel compounds were not shown to promote nodulation. Inclusions of bulk electrolytes within the surface matrix were observed, proving that electrolyte entrapment is possible. As co-electrodeposition of Ni in Cu-ER is thermodynamically unlikely, these experimental results also verify that it does not occur to any significant extent.

Influence of Electrochemically Exfoliated Graphite Addition on the Dielectric Properties of Epoxy/Montmorillonite Nanocomposites

The influence of hydrophilic electrochemically exfoliated graphite (EEG) and hydrophobic reduced EEG (rEEG) on the electrical conductivity, dielectric properties, and high-frequency dielectric losses of epoxy-based composites with montmorillonite was described. It was confirmed, that the addition of EEG changes the low-temperature conduction mechanism. The electrical conductivity in composite with EEG and montmorillonite was described by correlated barrier hopping model, whereas for composites with montmorillonite and rEEG two models were used: non-overlapping small polaron tunneling and correlated barrier hopping. The addition of EEG drastically changes the activation energy of charge carriers motions from 2.68 to 0.83 eV, whereas the addition of rEEG only to 2.43 eV. Also composite with EEG was characterized by highest high-frequency dielectric losses.

Influence of the parameters of the extrusion process on the properties of PLA composites with the addition of graphite

The main purpose of the work is to determine the influence of the screw diameter on the parameters of the single screw extrusion process, such as power consumption, torque, throughput, the actual temperature of the melt on the extruder die, as well as phase s with the use of a laboratory single-screw extruder.. The research was carried out with the use of various plasticizing systems. Two types of graphite: pre-expanded and normal grade with different grain sizes were used in the research. Flammability tests of the obtained composites were carried out using cone calorimeter.

New insights on lithium storage in silicon oxycarbide/carbon composites: Impact of microstructure on electrochemical properties

In this work, we study the impact of the preceramic precursor vinyltriethoxysilane (VTES) on the electrochemical performance of silicon oxycarbide (SiOC) glass/graphite composites. We apply an innovative approach based on high-power ultrasounds in order to obtain highly homogenous composites with a uniform distribution of small graphitic flakes. This procedure enhances gelation and drying of VTES-based preceramic polymer/graphite blends. The SiOC/graphite composites reveal stable capacities (up to 520 mAh g −1 after 270 cycles), which are much higher than the sum derived from the ratio of the components. Additionally, the first cycle Coulombic efficiencies obtained for the composites are 15% higher than that of the pristine VTES-based SiOC ceramic. These properties are identified as the synergistic effect, originated from the addition of graphite to VTES-based SiOCs. Interestingly, such improvement in electrochemical performance is not noticed in the case of analogous SiOC/graphite composites based on phenyltriethoxysilane (PhTES) precursor. The microstructural investigation of the composites based on two different preceramic precursors using solid-state 29 Si NMR and Raman Spectroscopy unveils the reason for such discrepancy in their electrochemical behaviour. • SiOC/C composites are prepared by a novel high-power ultrasounds-assisted synthesis • Graphitic flakes are uniformly distributed and partially exfoliated within the ceramic • Microstructural dissimilarities of SiOC/C based on various precursors are discussed • Synergistic effect on electrochemical properties of SiOC/C depends on microstructure • SiOC/C electrodes exhibit improved first cycle Coulombic efficiency and high capacity

Effect of carbon on the performance of red mud-molten salt composites for thermal management and waste heat recovery applications

• A novel composite material consisting of red mud, carbon and molten salt is investigated. • Carbon addition enhances the thermal conductivity by up to 13.45% (5 wt.%). • Energy density is only slightly reduced in a temperature range of 25-500 ℃. • However, the elastic modulus and coefficient of thermal expansion are affected. • These properties coupled with thermal cycling lead to progressive porosity increase. Red mud (RM) is a major waste of the aluminium industry with a present amount exceeding 4 billion tones, typically compacted in dams or dykes (stockpiles). This practice is highly problematic due to its high alkalinity and traces of heavy metals. Despite of many efforts, its present global utilization rate is only ∼15%. In this work, we attempt to enhance the thermal properties of previously reported novel composite phase change materials (CPCMs) based on RM, by adding graphite. The fabricated, carbon-containing, CPCMs demonstrate an overall good performance over the temperature range of 25 to 500 ℃. The latent heat ranges from 47.3 to 65.5 J/g, depending on salt and graphite contents. An optimal thermal conductivity is found to be up to 0.79 W/mK (25-500℃) on average. The specific heat capacity is on an average up to 1.23 J/(g ℃) when the PCM is in the solid phase (25-220 ℃) and 1.25 J/(g℃) when the PCM is in the liquid phase (220-500 ℃). No variations in the melting point or latent heat are observed after 96 cycles. Optimal energy storage density is calculated to be 1100 MJ/m 3 . Addition of graphite leads to a reduction in the coefficient of thermal expansion and the elastic modulus of the CPCM resulting in an increase in its porosity and thus a reduction in energy storage density. The working temperature of this novel CPCM makes it a cost-effective and compact solution for high-temperature heat storage/heat recovery applications.

In-Situ Atomic Force Microscopy Observations of the Effect of Addition of Graphite and Titanium Dioxide on Performance of the Negative Active Mass of a Lead-Acid Battery

Atomic force microscopy of lead metal surface under layer of sulfuric acid, while polarized, is used to mimic in-situ visualization of charging/discharging a lead-acid battery. The motivation is to understand the microscopic phenomena influencing longevity of lead-acid batteries operated in partial state of charge. In addition to investigating a pure metal lead surface, two surface modifications were studied; a surface modified with glass fibers and TiO2 powder and a surface modified with glass fibers and graphite powder. The electrochemically active material is stabilized on the studied surface by both the carbon and TiO2 additives. Carbon renders better stability and efficiency in charging and discharging. However, both additives provide better efficiency than a surface without the additives.

Influence of the growth conditions on the formation of macro-steps on the growth interface of SiC-Crystals

Several SiC crystals were grown in the same temperature field with a variation of the gas phase and the resulting step morphologies on the surface are analyzed using Laser Scanning Microscopy (LSM). It is shown that the step morphology changes due to doping, but also due to different C/Si ratios in the gas phase. By the addition of graphite into the source powder a reduction of Si-excess was achieved and an ordered step structure with an average height of 0.014 µm and width of 5.0 µm was formed. In the n-type doped case (n = 5.9∙1018 cm−3) the morphology on the facet differs strongly. Bunched steps with heights of 0.17 µm and widths of 152 µm are found. Between the diverse large macro-steps, a very ordered structure of unit cell height steps with a step spacing of 13.3 µm is found by Field Emission Scanning Electron Microscopy (FESEM) and Atomic Force Microscopy (AFM). A different change in the step morphology occurs over the whole crystal surface when elemental silicon is added into the source material. In contrast to the doping induced case, the bunched steps are more closely spaced and exhibit average heights of 0.20 µm and widths of 22 µm. The steps are noticeably retained at defects like micropipes or threading dislocations. The N2 induced step bunching is related to step kinetics on the main facet but the formation of macro-steps in the Si-rich case is assigned to the formation of stable surface steps. The variation of the inert gas pressure in the growth cell also changes the C/Si ratio in the gas phase as the diffusion from source to seed of the reactive gas species is affected differently. With a low inert gas pressure of 0.2 mbar a larger C/Si ratio in the gas phase is formed leading to steps with heights too small for analysis in the LSM, while the growth in 40 mbar promotes a smaller C/Si ratio leading to the formation of bunched steps with heights of 0.10–0.20 µm and with an average distance of 4.3 µm between them. The crystals grown in a gas phase comprising a large C/Si ratio show a better polytype stability than the crystals grown in Si-rich conditions. The instabilities can partly be attributed to the pile up of the macro-steps at defects exposing large 0001¯ terraces, where 2D-nucleation of foreign polytypes can occur.

Increased dielectric performance of PVDF-based composites by electrochemical exfoliated graphite additives

Adding conductive graphene into polyvinyliden1 fluoride (PVDF) is an effective method to improve the dielectric properties. However, the high conductivity and uniform distribution of graphene in PVDF matrix still meet challenges. In this work, electrochemical exfoliated graphite (EEG) with good conductivity and solution dispersion is used to prepare PVDF/EEG films. By this method no specific conditions are needed such as reduction or hot press. The dielectric properties and flexibility of PVDF/EEG films of different concentrations of EEG are investigated. Especially, when EEG content is 2.6 wt%, composite film has a high dielectric constant of 86 and a low dielectric loss of 0.9 (100 Hz). Simultaneously, the tensile strength of the film was up to 55.1 MPa. The preparation method is simple and convenient, and the obtained material has high dielectric constant and tensile strength. This method paves the way for the application of flexible electronic sensing equipment.

Microstructure, resistivity, and shear strength of electrically conductive adhesives made of silver-coated copper powder

Electrically conductive adhesives were made using silver-coated copper powders (filler) and epoxy. Resistivity, microstructure and shear strength of prepared adhesives were studied using two-point resistance measurements, Scanning Electron Microscope (SEM) and universal tensile tests, respectively. Effect of filler concentration (70–85 wt%), silver concentration (10–50 wt%), particles morphology (flake or spherical) and addition of graphite (2–15 wt%) were investigated on prepared adhesives properties. Results showed that by increasing the filler percentage from 70 to 85 wt%, the electrical resistivity decreases from 6.2 × 10−3 to 3 × 10−3 Ω·cm. Furthermore, the electrical resistivity of adhesives is proportional to the silver content of the filler particles. Regarding the morphological effect of filler particles, it was found that by replacing 40 wt% of the flake with spherical particles in the adhesive with a filler content of 75 wt%, the electrical resistivity of the adhesive reduces from 5.6 × 10−3 to 4.5 × 10−3 Ω·cm, while the electrical resistivity of the adhesive containing 50 wt% of the spherical particles reached to 1.1 × 10−2 Ω·cm. Graphite addition to adhesive formula in concentrations less than 6 wt%, slightly lowered the resistivity of the adhesives. Increasing the graphite addition from 6 to 15 wt% enhanced the electrical resistivity from 2.8 × 10−3 to 1.7 × 10−2 Ω·cm. The shear strength of the adhesives is inversely proportional to the filler percentage in the adhesives.

Effect of graphite addition on dry sliding wear behavior of Self-lubricating Al-SiC-Gr hybrid composites by PM process

The effect of graphite content and material connected parameter on the wear behavior of Al hybrid composite was studied using factorial design. Wear tests were conducted by variable Gr content (5 and 10 wt%) at totally different sliding speeds (1.5 and 3 m/s) and sliding distances (1500 and 3000 m). statistical modeling was used to develop a mathematical relationship on wear below varying conditions of sliding speed, applied load, and sliding distance. The created numerical model showed that high Gr content composite was subject to a low wear loss compared to that of low Gr composite. Increase of speed decreases the damage and increase either load or sliding distance or each will increase the wear loss. The simplest wear resistance is achieved within the hybrid composite containing 10 wt. %Gr particles.

Effect of Ti and C alloyants on the microstructure of laser cladded cobalt-chromium coatings

The article presents the results of Ti and C additives on the microstructure of the Metcoclad 6 coating. Effect of chemical composition with optimal laser cladding parameters has been studied in the terms of modification of the carbide morphology. The experiments were carried out on TruDisk 3302 Yb:YAG disk, equipped with a disc powder feeder. As a deposited material Metcoclad 6 powder produced in inert gas-atomization process was used. To assess the impact of alloying elements on microstructure, SEM observations and EDS analysis were carried out. Vickers microhardness tests were provided on the cross-section of coatings on Wilson Wolpert 401 MVD device. It has been stated that addition of titanium changes the morphology of carbides from lamellar eutectic carbides to isolated primary TiC while addition of Ti and graphite allowed to maintain the structure typical for pure Stellite 6 alloy, but additional formation of primary carbides were observed.

Effects of solid lubricants on the tribological behavior of steel‐backed UHMWPE fabric composites

AbstractAboard ship, the use of lubricating oil in mechanical equipment is sometimes difficult to achieve and applied oil can easily leak. The use of self‐lubricating materials can largely solve this problem. In this study, three kinds of solid lubricant‐enhanced 304 stainless steel‐backed ultrahigh molecular weight polyethylene (UHMWPE) fabric composites were fabricated with the addition of graphite, molybdenum (IV) disulfide, or polytetrafluoroethylene (PTFE). They were tested under various rotating speeds and compared with pure steel‐backed UHMWPE fabric composites. The tribological performance of these composites was evaluated by analysis of friction coefficient, wear rate, and worn face morphology. The results showed that PTFE‐enhanced composites exhibited the best friction reduction performance under all test conditions, better antiwear ability at rotating speeds under 200 rpm, and optimized wear surface morphology, thus indicating better synergy between PTFE and UHMWPE fabric.

Grease-lubricated tribological contacts – Influence of graphite, graphene oxide and reduced graphene oxide as lubricating additives in lithium complex (LiX)- and polypropylene (PP)-thickened greases

Two types of thickener systems, lithium complex (LiX) and polypropylene (PP), were chosen to evaluate graphite, graphene oxide (GO) and reduced graphene oxide (rGO) as grease additives at a concentration of 0.1 wt%. To enhance the additive dispersibility, a mixture of polyalphaolefin oil (PAO) and oil soluble synthetic polyalkylene glycol (OSP-68) was used as base oil. The greases were evaluated in i) silver-coated copper contacts simulating high-load electrical contact applications subjected to fretting and ii) a steel/steel 4-ball wear test equipment. The additives showed no positive effect on friction and wear, neither in fretting nor in 4-ball tests. However, there is a statistically significant difference in wear scar diameter on the 4-ball steel contacts between the two thickener types, LiX and PP. Thus, the PP-grease lubricated steel contacts showed more wear and more tribofilms of iron oxide and grease constituents, indicating more metal-to-metal contact. Hence, the thickener type has a larger impact on the lubricating performance of the grease than do the graphite, GO and rGO additions. The results demonstrate that the addition of graphene-based materials to improve greases is not straightforward. Rather, the grease/graphene-based additive system is complex and many parameters influence the friction and wear results. Hence, more work is needed to obtain a better understanding and possibly better lubricating effects from the graphene-based additives.

Investigation of a Relative Weight Ratio of Graphite/Zinc Matrix Composite with a High-Resistance to Corrosion

There has been a significant increase in the use of composite materials to reinforce metallic structures. Such an increase has been especially noted in marine and underground applications, where there is a higher corrosion impact. Whilst there have been several attempts to investigate the mechanical properties of several synthesized composite materials, few of these have analyzed the corrosion of such composite materials at different weight ratios. The aim of this paper is to explore the best weight ratios of a graphite/Zinc composite matrix that would yield the lowest corrosion rate for a variety of applications. The research is validated using experimentation based on six additives of graphite (1wt%, 2.5wt%, 4wt%, 6wt%, 8wt%, and 10wt%), which are used as reinforcements for a range of weight ratios. The additives were prepared using the powder metallurgy method. The corrosion rate for all specimens used was carried out at the room temperature of 27 °C. Analysis results showed that 1wt% of graphite additive has the highest corrosion resistance compared to other weight ratios tested. This has been verified by examining the microstructure of the composite using an optical microscope for 12h, 24h, and 48h of immersion time in a 1M HCl acid solution.

Microstructure and mechanical testing of Al/graphite/Fly-ash metal matrix composite material

PurposeThis study aims to attempt to make an aluminum-based composite using reinforcement such as graphite and fly ash. Pollution is an enhanced serious issue of concern for global. Industries play a major role in disturbing the balance of the environment system. Composite is made by using the stir casting technique. The waste that is generated by the industries if left untreated or left to be rotten at some place may prove fatal to invite various types of diseases. Proper treatment of these wastes is the need of the hour, the best way to get rid of such kinds of hazardous wastes is to use them by recycling.Design/methodology/approachStir casting technique was used to make a composite. Graphite and fly ash were mixed with equal amounts of 2.5% to 15% in aluminum. The microstructure of composite formed after composite was noticed. After seeing the microstructure it was understood that reinforcement particles are very well-mixed in aluminum.FindingsWhen graphite was mixed with 3.75% and 3.75% fly ash in aluminum, the strength of the composite came to about 171.12 MPa. As a result, the strength of the composite increased by about 16.10% with respect to the base material. In the same way, when 3.75% graphite and 3.75% fly ash were added to aluminum, the hardness of the composite increased by about 26.60%.Originality/valueIn this work, graphite and fly ash have been used to develop green metal matrix composite to support the green revolution as promoted/suggested by United Nations, thus reducing the environmental pollution. The addition of graphite and fly ash to aluminum reduced toughness. The thermal expansion of the composite has also been observed to know whether the composite made is worth using in higher temperatures.