Introduction Of Graphite Research Articles

Graphite Nanosheets as a Platform for the Nanosize GeSe2 Anode with Improved Electrode Performance

GeSe2 anode materials possess energy densities higher than those of the commercial graphite anode for lithium-ion batteries (LIBs). However, the limited cycling life and poor inherent conductivity present significant difficulties for their use in various fields. LIBs’ lifetime and capacity density depend on their electrode materials, where structural stability and a slow diffusion control mechanism are crucial factors. In this study, amorphous nanosize GeSe2 uniformly anchored on graphite sheets (GeSe2/G) was prepared using ball milling. For comparison, the cycle performances of pure GeSe2 and GeSe2 with the same ball milling conditions (M-GeSe2) were tested. The results showed that ball milling enabled uniform anchoring of GeSe2 nanoparticles of ∼200 nm on graphite nanosheets without aggregation, where the introduction of graphite not only served as electron transfer layers to effectively improve the electrical conductivity but also assisted in reducing the volume growth and comminution of GeSe2 during Li+ insertion/extraction procedures. When served as anode materials for LIBs, the GeSe2/G nanocomposites showed high Li+ storage properties, i.e., a high reversible capacity of 812.8 mAh g–1 at 0.1 A g–1. After 50 cycles, GeSe2/G still reached 650 mAh g–1, which was much higher than M-GeSe2 (392.3mAh g–1) and GeSe2 (183 mAh g–1). Even at 1 A g–1, the GeSe2/G anode exhibited a high reversible capacity of 409.6 mAh g–1 and remarkable cycling stability, with a high capacity retention of 63% after 300 cycles.

Вплив графіту на фізико-механічні характеристики та трибологічні властивості вторинного поліетилену

The purpose of the work is to study the influence of graphite on the physical and mechanical characteristics and tribological properties of secondary polyethylene. For this, a study of the physical and mechanical characteristics and tribological properties of the original secondary polyethylene on PCM based on it was carried out. The influence of the concentration of graphite in secondary polyethylene on the value of strength stress and relative elongation under tension at the maximum load and destruction of the samples was determined. It was established that the optimal concentration of graphite should not exceed 2 wt. %. An increase in the volume of the filler in the matrix leads to a significant decrease in the physical and mechanical characteristics of the obtained materials. It was established that the introduction of graphite into the structure of secondary polyethylene, regardless of its volume, leads to an increase in the microhardness of the obtained PCM. It was found that the temperature in the vicinity of friction, under the condition of friction without lubrication on steel 45 and the selected modes, did not exceed 69 ºС. An increase in linear speed above 0.5 m/s or pressure above 1 MPa leads to an increase in the temperature in the friction zone to 72...73 ºС, which is critical for polyethylene and leads to catastrophic wear of the samples. It was established that under the selected modes of friction, linear speed of sliding and pressure do not have a significant effect on the amount of wear and tear. The resulting polymer composite provides performance under the condition that the pressure does not exceed 1 MPa, and the linear speed is up to 0.5 m/s. For use in mechanisms and machines that work in friction conditions according to the criterion PV ≤ 0.5 MPa • m/s, it is possible to recommend the introduction of 2% by mass. graphite into the structure of secondary polyethylene. The introduction of graphite in the amount of up to 2% by mass. will allow to stabilize and moderately increase the strength characteristics of the obtained material, in comparison with unfilled polyethylene.

Improving formability of copper by addition of graphite

Our Project aims to demonstrate the softening process of annealing of copper in an appropriate furnace at an optimum temperature. Copper is soft at its initial state and needs to be bended for various applications and used to the desired shape. Upon bending, Copper tends to have voids development that results in crack formation and make the sheets unusable. Annealing is therefore performed at a temperature high enough usually at 400 DC that causes a new, strain-free material to form and Copper to return to its original soft condition and make the voids in the most compact state. Further on the introduction of graphite would fill up these voids and improve the formability of copper and overall machinability of copper that could be visibly seen by smaller chip formation which machines the surface. Graphite being a conductor itself will not reduce the C of Copper to a large extent so the composite mode can be used as a conductor in place of pure copper. This will also improve the usage of copper in various industrial searches where bending has to be performed without compromising on the crack formation and improve formability. This composite would also be able to handle high temperature working conditions better than pure copper as graphite tends to have a high MP that would also require high Pr.

Enhanced tribological properties of PEEK‐based composite coatings reinforced by PTFE and graphite

AbstractThe lubricating failure problems caused by friction and wear severely inhibit the regular operation and lifetime of artificial implanted joints. In order to improve their wear resistance effectively, the functional nano/micro‐composite coatings consisted of poly(ether‐ether‐ketone) (PEEK)/graphite/polytetrafluoroethylene (PTFE) were successfully prepared through electrophoretic deposition and heat treatment. Additionally, the friction and wear behaviors under different loads and lubricating mediums of the composite coatings were investigated systematically. The results show that the composite coating significantly increased the microhardness and wear resistance of PEEK coating. The introduction of graphite and PTFE fillers reduces the wear rates and coefficient of friction (COF) of the composite coating significantly. Especially under 10 N load conditions, the friction and wear tests show that the composite coatings drop by 80% of friction coefficient and an order of magnitude in wear rates compared to that of PEEK coating. The improved wear resistance can be attributed to the synergistic effect of PTFE and graphite fillers. As a result, the graphite provides good load‐bearing capacity and the PTFE lubricant endow a low friction coefficient for the composite coatings. Thus, this study provides a better approach to improve the wear resistance of PEEK‐based coatings.

Rheological Performance of Magnetorheological Grease with Embedded Graphite Additives.

The use of highly viscous grease as a medium in magnetorheological grease (MRG) provides the benefit of avoiding sedimentation from occurring. However, it limits the expansion of yield stress in the on-state condition, thus reducing the application performance during operation. Therefore, in this study, the improvement in the rheological properties of MRG was investigated through the introduction of graphite as an additive. MRG with 10 wt % graphite (GMRG) was fabricated, and its properties were compared to a reference MRG sample. The microstructure of GMRG was characterized using an environmental scanning electron microscope (ESEM). The rheological properties of both samples, including apparent viscosity, yield stress, and viscoelasticity, were examined using a shear rheometer in rotational and oscillatory modes. The results demonstrated a slight increase in the apparent viscosity in GMRG and a significant improvement in yield stress by 38.8% at 3 A with growth about 32.7% higher compared to MRG from 0 to 3 A. An expansion of the linear viscoelastic region (LVE) from 0.01% to 0.1% was observed for the GMRG, credited to the domination of the elastic properties on the sample. These obtained results were confirmed based on ESEM, which described the contribution of graphite to constructing a more stable chain structure in the GMRG. In conclusion, the findings highlight the influence of the addition of graphite on improving the rheological properties of MRG. Hence, the addition of graphite in MRG shows the potential to be applied in many applications in the near future.

PHYSICAL-MECHANICAL PROPERTIES OF NANOCOMPOSITES BASED ON GRAPHITE AND MODIFIED POLYOLEFINS

The influence of the graphite concentration on the main physical-mechanical properties of nanocomposites based on such polyolefin as high density polyethylene, low density polyethylene and polypropylene is considered. Properties such as tensile yield stress, ultimate tensile stress, and ultimate bending strength, elongation at break, heat resistance, flexural strength, MFI, and melting points are analysed. To improve the compatibility of the mixed components of the mixture, we used an Exxelor PO1040 compatibilizer for all grades of polyethylene and Exxelor PO1020 for polypropylene. Graphite was introduced into the composition of polyolefin at the following concentrations: 1.0, 3.0, 5.0, 10, 15, 20, and 30 wt%. As a result of the research, it was found that the introduction of graphite into the composition of polyolefin was accompanied by an improvement in strength characteristics with maximum at various concentrations. For high density polyethylene, the maximum values of strength characteristics are observed at 3.0 wt%, for low density polyethylene at 10 wt%, and for polypropylene at 5.0 wt% content of graphite. It revealed that such a difference in the value of the threshold concentration of graphite which provides the maximum value of strength indicators,was directly related to the degree of crystallinity of the polymer matrix.

Experimental analysis of hybrid metal matrix composite reinforced with Al2O3 and graphite

Recently the development and use of metal matrix composites. instead of conventional metals, has led to manufacturing cost optimisation to meet various light weight to strength. The MMC has several applications in the field of automotive and aerospace sectors. The paper presents the results of tribological research on Al–Si, Al2O3 and graphite-aluminium metal matrix composite material. It analyses the mechanical properties and compares among themselves with different weight fraction samples. This composite is used as high-tech construction material in many applications, particularly for power to weight applications like pistons, cylinder liners, and bearings. The tribological properties of these materials can be significantly changed by the introduction of graphite, silicon carbide particles. The wear tests were carried out using the pin-on-disc tribometer and analysed by Ducom software. The sliding and wear resistance of the matrix and composite alloy specimens have been subjected to comparative analysis. It was demonstrated that the composite reinforced with graphite is characterised by a lower friction coefficient and lower wear rate was achieved by adding silicon carbide to the matrix composite.

Conventional synthesis of V2O5/graphite composites with enhanced lithium ion storage

For the sake of seeking appropriate electrodes for Lithium ion battery which can be further extended for mass production. In this research, ball milling procedure has been utilized to synthesize V2O5/graphite electrode. The ratio of each phase in the composite can be easily manipulated. Meanwhile, SEM images demonstrated that homogeneous microstructure has been achieved with these different compositions. Specifically speaking, an optimal performance utilized as cathode material for lithium ion battery had been realized with 7.5V2O5/graphite, which maintains a specific capacity of 136 mAh g−1 after 150 cycles under the current density of 50 mAh g−1. Moreover, a relative high specific capacity of 113.3 mAh g−1 (at the current density of 1A g−1) can be retained after 300 cycles. In addition to enhanced cycling stability, the improved rate capability had also been achieved in this composition. Further investigation of CV results revealed that a capacitive behavior contributed by the introduction of graphite was responsible for this enhancement. Here designated composite exhibits great potential in electrochemical field.

Enhanced electrochemical kinetics of magnesium-based hydrogen storage alloy by mechanical milling with graphite

Magnesium nickel alloy (Mg2Ni) which used as the negative electrode material in the nickel-metal hydride (Ni/MH) secondary battery is modified by graphite via mechanical milling. The effects of graphite on the Mg2Ni are systematically investigated by X-ray diffraction (XRD), scanning electron microscope (SEM) and a series of electrochemical tests. The results show that the cycle stability of the Mg2Ni alloy is improved with the addition of 10 wt.% graphite and the discharge capacity at the 20th cycle increase from 116.9 mA g−1 to 178.5 mA g−1. The Tafel polarization test indicates better corrosion resistance of the Mg2Ni/graphite composite. Meanwhile, the results of electrochemical tests indicate that both the charge-transfer reaction rate on the surface of the alloy and the hydrogen diffusion rate inside the bulk of alloy are boosted with the introduction of graphite.

Potentiostatic Co-deposition of Nickel and Graphite Using a Composite Counter Electrode

Nickel and graphite was potentiostatically co-deposited using a composite nickel-graphite composite counter electrode (CCE) with tunable-friability. This was done to achieve steady introduction of graphite into the electrolyte without intermittent mechanical infusion and stirring, thus facilitating a potentiostatic deposition route and promoting homogeneity of deposition. Graphite electrodes were produced at densities of 0.920, 1.026 and 1.188 g/cm3 and their suitability for constitution in a HCE assessed. The surface area of the nickel component of the HCE was varied from 100% to about 60 and 30% surface area and combined with the graphite electrode to form HCE constitutions designated as triplet, doublet and singlet respectively. Deposition was done for about 8 hours in 1 M NiSO4 using the different HCE constitutions, an Ag/AgCl reference electrode and a custom deposition head which served as the working electrode. The mechanism of graphite electrode unraveling was observed to be the formation of oxygen and CO2 due to oxidation reactions at the HCE. Graphite electrode of density 0.920 g/cm3 was selected for the HCE due to its extensive surface porosity, a characteristic determined as favourable to the mechanism of electrode unraveling. Co-deposition of graphite with nickel was observed to increase as nickel surface area was reduced from the triplet to singlet. SEM micrographs show partially and fully embedded graphite particles in the nickel matrix while the presence of nickel and graphite was affirmed.

Fast Prepared Ni-Al2O3 Nanocomposite Through Solution Combustion Synthesis

Solution combustion synthesis (SCS) is a well-known method for fabrication of different materials such as oxides and composite materials in an extensive range. In this investigation, solution combustion synthesis is used for fabrication of Ni-10 wt% Al2O3 nanocomposite. Nickel and aluminum nitrates, urea, and distilled water are used as oxidizer, fuel, and solvent, respectively. The results show that if the fuel to oxidizer ratio exceeds the stoichiometric ratio, the combustion temperature increases. However, introduction of graphite to the solution could conduce to the reduction of the combustion temperature. With the addition of an auxiliary material, graphite, so a nickel oxidation is postponed, Ni-Al2O3 nanocomposite is produced only in one step.

Corrosion Behavior of VN20 Alloy Doped with Graphite or Chromium and Vanadium Carbides

We study the corrosion properties of a composite material based on tungsten carbide on a nickel binder and doped with graphite or chromium and vanadium carbides. It is shown that the introduction of graphite in the VN20 composite decreases its corrosion resistance in a 3-% NaCl solution. The addition of 2 and 4% graphite makes the corrosion current densities 2 and 2.5 times higher, respectively. Doping of the composite with vanadium carbide in amounts of 0.15 and 1% increases the corrosion currents, whereas the introduction of 1% of chromium carbide weakens these currents by about an order of magnitude.

Synthesis of Low-Density Heat-Resisting Polystyrene/Graphite Composite Microspheres Used as Water Carrying Fracturing Proppants

Low-density heat resistamt, low-cost polystyrene (PS)/graphite microspheres were successfully synthesized via in situ suspension polymerization. Scanning electron microscopy (SEM) indicated that PS/graphite composite microspheres had good sphericity, and graphite particles were evenly dispersed in microspheres. Furthermore, density analysis illustrated that the density of composites was about 1.025–1.185 g/cm3 with good suitability for carrying water. Thermodynamic testing revealed that the thermostability of the composite was dramatically improved by the introduction of graphite, which is used deep underground. In addition, the percentage of damage decreased to 1.3% with graphite ratio of 2.5% at 68 MPa. Therefore, PS/Graphite composite microspheres possess entirely feasible applications in oil exploitation as pure water carrying petroleum proppants.

Influence of Sintering Temperature and Atmosphere on Phase Makeup of SiAlON-Graphite Composites

Based on aluminum powder, Silicon powder, activated alumina and flake graphite as the main starting materials, SiAlON-Graphite composites were produced in N2 atmosphere. The influence of firing temperature and atmosphere on Si-Al-O-C-N system was investigated. It is proposed that the introduction of graphite produces a certain CO partial pressure and affects the nitridation of metal silicon, therefore reducing the mass change. In addition, large amount of 15R are formed through carbothermic reduction. CO hinders the growth of β-SiAlON. Z value of β-SiAlON in sample C with graphite is less than sample S without graphite.

Pressureless sintering of ZrC-based ceramics by enhancing powder sinterability

The sinterability of ZrC was enhanced by high-energy ball milling as well as introduction of graphite and SiC as sintering additives. Densification process and microstructure development were investigated for ZrC-based ceramics densified by pressureless sintering. As-received ZrC powder showed poor sinterability. After high-energy ball milling, ZrC powder can be sintered to 98.4% theoretical density at 2100 °C. The obtained ceramic had fine microstructure and fewer entrapped pores. Introduction of 2 wt.% graphite combined with high-energy ball milling lowered the densification temperature of ZrC. The relative density of obtained ceramic reached up to 95% at 1900 °C. Introduced SiC inhibited ZrC grain growth during sintering and consequently avoided the entrapped pores within the grains. The relative density of ZrC–SiC reached up to 96.7% at 2100 °C. ZrC–SiC composite formed an interesting intragranular structure and had high fracture strength at room temperature.

High-Performance Silicon/Carbon/Graphite Composites as Anode Materials for Lithium Ion Batteries

Silicon/carbon and silicon/carbon/graphite composites have been synthesized at room temperature using concentrated as a dehydration agent. As a ductile matrix, the novel amorphous carbon obtained from the dehydration process could effectively buffer the volume change of silicon particles during discharge–charge cycling. The introduction of graphite in the silicon/carbon composite further improved the cycling performance. The composite with of amorphous carbon replaced by graphite demonstrated a stable capacity of and a high capacity retention ratio of 84.1% at over , suggesting it is a favorable candidate as anode material for lithium-ion batteries.

Activation characteristics of graphite modified hydrogen absorbing materials

The activation characteristics for hydrogen absorption of pure Mg, Mg 2Ni, Ti, V and FeTi is compared with that of the materials obtained by adding 10 wt.% of graphite and milling the mixture during 30 min. In all cases, there is a dramatic improvement of the activation characteristics of the material containing graphite. For example, with Mg/G (at 300°C and 10 bar of H 2), the hydrogen contents [H]=4, 5 and 6 wt.% are reached after 0.73, 1.97 and 10.5 h after the first initial exposure to hydrogen, respectively. About 92% of the maximum hydrogen capacity of the material is reached after 20 h. In the same conditions, pure Mg does not absorb. A similar behavior is also observed in the case of Ti, V, Mg 2Ni and FeTi. As far as we can tell from the analysis of the X-ray diffraction pattern, the introduction of graphite does not lead to the formation of any new phase, although milling with graphite is responsible for a sizeable reduction of the crystallite size, even if the milling operation is performed for only 30 min. This reduction of the crystallite size is not responsible for the improved activation characteristics, as materials with similar crystallite size prepared without graphite do not show the same behavior. Instead, it is proposed that graphite inhibits the formation of a new oxide layer of the surface of the materials once the native oxide layer is broken during the milling process.

Effect of a filler on the kinetics of acceptor-catalytic polyesterification, structure and properties of polymers and their composites

The effect of an antifraction filler on the kinetics of acceptor-catalytic polyesterification and the structure and properties of polyesters and filled polymeric systems based on them has been investigated. The filler was found to have a different influence on the activity of the aromatic and aliphatic hydroxyl-containing compounds reflected in the microstructure of the copolyesters. It was established that the introduction of a filler increases the molecular-viscous characteristics of dichlordiane polyterephthalate. The antifrictional properties of filled polymeric systems as a function of the way of introducing the filler have been studied. It is shown that the introduction of graphite at the stage of synthesis of the polymer, rather than in the case of mechanical mixing, leads to a lower and more stable friction coefficient of filled systems.

I. On platinized graphite batteries

In a short note communicated to the Royal Society on March 9th, 1857, and which was read on March 19th, reference was made to the voltaic combination that I had adopted for certain telegraphic purposes; namely, zinc-graphite. Graphite in its crude state had for some years been of great service to me, especially for batteries whose resting time is great in proportion to their working time. Since the date of that notice, I have considerably increased the value of graphite for electrical purposes by platinizing it according to the process first described by Mr. Smee, whose platinized silver battery has been long known and much used. The material to which I refer by the term “Graphite,” is the crust or corrosion that is collected from the interior of iron gas retorts that have been long in use. My first crude graphite battery of twelve pairs of plates was set up on April 5th, 1849, for working the telegraph from my residence at Tonbridge to the Telegraph Office about a mile distant. It was charged with sand saturated with diluted acid; and had not been dismounted in March 1851, when I changed my abode. During the interval, the sand was from time to time moistened with acid water or water only. The plates in this case had been roughly chipped out and rubbed on stone into something like shape. In the mean time I had some sets of plates cut at the Locomotive Works, Ashford, and was thus enabled to obtain further results. I forwarded a graphite battery to the Great Exhibition in 1851, for which a prize medal was awarded. The introduction of graphite into anything like general use was for a long period no easy matter, on account of the difficulty of finding any one who would undertake to cut it into plates, its hardness destroying the tools; and the then limited demand did not encourage any one to construct special machinery for the purpose. My wants at length reached the ear of Mr. J. Robinson of Everton, Liverpool, who took the matter thoroughly in hand, and has succeeded perfectly in cutting plates into any form and to comparatively any size, at a very moderate cost, for which I am much indebted to him. I have before me plates 12 inches x 10 inches, of smooth texture and uniform thickness, and have seen some of double that size.