Increased Graphite Content Research Articles

Synthesis and electrical properties of Reused-Graphite/Polyaniline composites

Polyaniline graphite composites have been synthesized using chemical oxidative polymerization method. The graphite powder has been reused which is obtained by used batteries. XRD patterns of graphite show (002) peak and no impurity peaks. Different wt. % (5, 10, 15, 20) of graphite is used for synthesis of composites and studied their electrical conductivity. XRD patterns of composites show increasing intensity with an increasing graphite content. SEM images show plate-like morphology of graphite whereas granular-morphology for PANI. Composite samples show both plate-like morphology and granular morphology indicating that graphite is embedded in the polymer matrix. Electrical characteristics of composite samples have shown a systematic increase in conductivity with an increase in the graphite concentration. Conductive fillers within the polymer matrix can increase the overall conductivity. Higher filler content provides more conductive pathways for electrons, resulting in enhanced conductivity. The detailed studies of these results are discussed and presented in this paper.

Machinability Study on AA6061/2 SiC / Graphite Hybrid Nanocomposites Fabricated through Ultrasonic Assisted Stir Casting

Aluminium-based hybrid metal matrix nanocomposites (AA-HMNCs) have numerous applications due to their higher strength-to-weight ratio and good mechanical and tribological properties. However, the machinability aspect of these materials must be carefully explored before employing them in various engineering applications. The present study involves the fabrication of AA6061/2 wt.% SiC/x wt.% graphite (x= 1, 2, 3) hybrid nanocomposites and subsequently subjecting them to machinability investigation. All the hybrid nanocomposite samples are fabricated through ultrasonic assisted stir casting technique. The effect of machining parameters and graphite content of the sample on cutting force and surface roughness is discussed based on experimental data. Experiments are performed based on the central composite design of response surface methodology, and the corresponding output responses are recorded. ANOVA analysis revealed that the graphite content has the highest authority over surface roughness and cutting force. High cutting speeds accompanied by low feed and depth of cut have resulted in reduced cutting forces and better surface finish. Chip morphology studies have also subsequently indicated better machinability with increased graphite content.

A solid–solid phase change filler with enhanced thermal properties for cooling asphalt mastic

The goal of this work is to improve the latent heat storage capacity and the thermal response rate of a polyurethane solid–solid phase change material (PUSSPCM) for evaluating its applicability as an alternative filler to cool an asphalt mastic. For this purpose, graphite/PUSSPCM (GPCM) structures with various mesh values and contents of graphite were synthesized. The latent heat was initially increased and then decreased with the increasing graphite content. By selecting the optimum content, a GPCM with a larger mesh can possess a higher latent heat. The existence of a relatively large content and mesh of graphite could lead to a higher thermal conductivity for GPCM. The latent heat storage capacity and the thermal conductivity of the synthesized GPCM-8000–1 were 23.2 % and 254.7 % higher than those of PUSSPCM, respectively. Meanwhile, the GPCM-8000–1 material configuration with excellent thermal stability at 200 °C can withstand the high-temperature construction environment of asphalt pavement without liquid leakage and decomposition. As a result, it is recommended as a solid–solid phase change filler to fabricate phase change asphalt mastics. The extracted outcomes from the rheological test results show that the high-temperature deformation resistance, low-temperature cracking resistance and fatigue resistance of the phase change asphalt mastics are improved in contrast to the traditional asphalt mastic. Finally, the cooling effect of the phase change asphalt mastics was evaluated, with the maximum cooling amplitude reaching the value of 5.6 °C.

The control of shear‐zone development and electric conductivity by graphite in granulite: An example from the Proterozoic Lofoten‐Vesterålen Complex of northern Norway

AbstractGraphite impacts crustal rheology and electric conductivity in the lower crust. In a combined geophysical and geological study from the Proterozoic Lofoten‐Vesterålen Complex, Norway, we show the enrichment of graphite resulted in zones with strong schistosity and a sharp strain gradient towards host massive granulite gneiss. Increased graphite content resulted in high‐conductivity zones with true resistivity values <10 Ωm compared with a resistivity of >3,000 Ωm in the low‐conductive crust. The regionally distributed graphite zones contain up to 39% graphite with variable amounts of quartz, feldspars, biotite and pyroxenes and where graphite is present in stable assemblage to orthopyroxene. High‐ordered graphite and biotite with a strong‐preferred orientation define the well‐developed foliation. Our results demonstrate that graphite accounts for the high electric conductivity of this former Proterozoic lower‐crustal segment. The presence of graphite causes strain localisation in the granulite facies crust, reducing crustal strength and may thereby influence continental architecture and evolution of collision zones.

Effect of graphite (GR) content on electrochemical hydrogen storage performances of nanocrystalline and amorphous La9Ce1Mg80Ni5–Ni–GR composites synthesized by mechanical milling

The Mg–Ni-based alloy La9Ce1Mg80Ni5 was fabricated by a vacuum induction furnace with high purity helium gas. The surface modification of the as-cast alloys was operated by mechanical coating Ni and graphite (GR). The composites La9Ce1Mg80Ni5-200 wt% Ni-x wt.% GR (x = 0–4) with nanocrystalline and amorphous structures were synthesized by mechanical milling. Adding appropriate GR brings on the enhancement of ball-milling efficiency and inhibits the agglomeration of alloy powders. Furthermore, the discharge capacity of the composites obtains the maximal values with an optimized GR percentage. Increasing GR content from 0 to 4, the capacity retention rate at 20th cycle (S20 = C20/Cmax) of the 20 h milled composite improves from 72.2% to 74.3% and that of the 80 h milled specimen changes from 54.4% to 56.9%. Electrochemical tests indicate that with the optimization of GR percentage, the composites can get the best electrochemical kinetic property, such as the highest HRD value, the highest hydrogen diffusion coefficient and the lowest charge transfer resistance.

Effect of Graphite Content on Cu–Ni–Graphite Composite for Use as Switch Slide Baseplate Materials Sliding Against U75V Steel

Abstract The rapid development of high-speed railways necessitates the development of new materials for switch slide baseplates. In this study, a Cu–Ni–graphite composite, containing 1 wt% to 6 wt% graphite and prepared by powder metallurgy, was used as a potential material. Pin-on-disk wear tests were conducted to measure the sliding friction of the Cu–Ni–graphite composite against U75 V steel. The results showed that the friction coefficients gradually decreased when the graphite content in the composite ranged from 1 wt% to 4 wt% in the composite. When the graphite content was 4 wt%, the friction coefficient reached the minimum value (0.153). When the graphite content was low (1 wt% to 4 wt%), the primary wear mechanism was microcutting. An increased graphite content facilitated the generation of lubricating films and decreased the wear damage. As the graphite content increased from 4 wt% to 6 wt%, the friction coefficients also increased. The variation in the wear volume rate had the same tendency as the friction coefficient. When the graphite content exceeded 4 wt%, the primary wear mechanism was delamination and fatigue wear. Due to the tendency to form cracks on the subsurface and the plentiful generation of the spalled pits, the graphite fragments could not completely form lubricating films but separated as wear debris. The lubricating films existing on the U75 V steel were in proportion to the graphite content in the composite. The wear weight loss of the U75 V steel exhibited a reduction with increasing graphite content.

Effect of graphite (GR) content on microstructure and hydrogen storage properties of nanocrystalline Mg24Y3–Ni–GR composites

Ternary Mg24Y3–5 wt.% Ni–x wt.% GR (x = 0–10) composites were prepared by mechanical ball-milling. The phase composition, microstructure and hydrogen storage properties were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Sievert's testing method. Results show that adding an appropriate amount of GR has a beneficial effect on reducing particle size and promoting ball-milling efficiency. Sample with 3 wt.% GR content has a composite structure composed of amorphous and nanocrystalline, as a result, showing an excellent hydrogen absorption kinetics even at 100 °C. Differential scanning calorimetry (DSC) tests were used to evaluate the dehydrogenation performance. The peak temperature was reduced from 325 °C to 295 °C with increasing GR content from 0 to 3 wt.%, which can be attributed to the grain refinement and contact improvement between catalytic Ni and Mg24Y3 alloy particles. However, larger flaky Mg24Y3 alloy particles were observed with a further increase of GR content, which is mainly due to the excessive GR addition reduces ball-milling efficiency. The benefit would be completely lost with the GR adding amount up to 10 wt.%.

The Effect of Graphite Content on the Wear Behavior of Ni/WC/G Composite Coating

The Ni/WC/G composite coating was fabricated through vacuum cladding. The effect of graphite content on the wear behavior was investigated, and the worn surface was observed through scanning electron microscopy (SEM). The friction coefficient decreased with the increasing graphite content until the graphite content was 6%, and then increased when the graphite content was 8%. The wear rate decreased with the increasing graphite content for all graphite content. The wear loss of GCr15plate decreased with the increasing graphite content until the graphite content was 6%, and the wear loss of plate was rising when graphite was 8%. There was a layer composed of wear debris that containing oxides and graphite. The covering area increased with the increasing graphite content, which agreed with the changing trend of friction coefficient and wear rate. The net texture-like structure was formed among the composite coating, which could be the main support for load during wear process. There was little single WC particle protruding for support the wear load. Therefore, the Ni-based substrate was not easily to be worn.

Effect of carbon fillers on electrical and road properties of conductive asphalt materials

The electrical and road properties of asphalt materials were modified using different conductive materials, such as graphite and carbon fiber. The material property changes were studied using DMA (Dynamic Machine Analysis) testing, wheel track rutting testing, Marshall stability testing, splitting testing, and electrical property characterizing testing. The results showed decreases in the storage modulus and the loss modulus of the asphalt binders at low temperature when the graphite content was less than 30%. The modulus reached maximum values when the graphite content equaled 40%. Additional graphite reduced the storage modulus and loss modulus of the asphalt binders. With increased graphite content, the peak phase angle shifted from low to high temperature, which showed an increase in the glass transition temperature. The glass transition temperature can be used in the evaluation of the low temperature properties of the asphalt binder and the asphalt mixture. With the addition of 40% graphite and 0.3% carbon fiber by weight to the asphalt mixture, the resistance of the asphalt mixture decreased from ∞ to 835Ω, the Marshall stability increased by 4%, the split strength increased by 18%, and the dynamic stability increased by 78%. However, excessive carbon fiber or too little carbon fiber did not increase pavement strength. In the indirect tensile testing, the evolution processes of the resistivity of the composites were found to have four periods: a reversible sensing period, a balance period, a steadily increasing period, and a sharply increasing period. The four periods correspond to different interior structures of the material, which show that damage and crack self-monitoring is feasible in conductive asphalt mixture.

Tribological behaviour of powder metallurgy-processed aluminium hybrid composites with the addition of graphite solid lubricant

The tribological behaviour of powder metallurgy-processed Al 2024–5wt% SiC–x wt% graphite (x=0, 5, and 10) hybrid composites was investigated using a pin-on-disc equipment. An orthogonal array, the signal-to-noise ratio and analysis of variance were employed to study the optimal testing parameters using Taguchi design of experiments. The analysis showed that the wear loss increased with increasing sliding distance and load but was reduced with increased graphite content. The coefficient of friction increased with increasing applied load and sliding speed. The composites with 5wt% graphite had the lowest wear loss and coefficients of friction because of the self-lubricating effect of graphite. Conversely, due to the effect of the softness of graphite, there was an increase in wear loss and the coefficient of friction in composites with 10wt% graphite content. The morphology of the worn-out surfaces and wear debris was examined to understand the wear mechanisms. The wear mechanism is dictated by the formation of both a delamination layer and mechanically mixed layer (MML). The overall results indicated that aluminium ceramic composites can be considered as an outstanding material where high strength and wear-resistant components are of major importance, particularly in the aerospace and automotive engineering sectors.

Effect of the Graphite Content on the Tribological Behavior of Al/Gr and Al/30SiC/Gr Composites Processed by In Situ Powder Metallurgy (IPM) Method

The influence of graphite content on the dry sliding wear characteristics of Al6061/Gr composites along with Al6061/30SiC/Gr hybrid composites has been assessed using a pin-on-disc wear test. The composites with different volume fraction of graphite particles up to 13% were processed by in situ powder metallurgy (IPM) technique. The porosity and hardness of the resultant composites were also examined. It was found that an increase in the graphite content reduced the porosity, hardness, and friction coefficient of both types of composites. The hybrid composites were more porous and exhibited higher hardness and lower coefficient of friction at identical graphite contents. The increased graphite content in the range of 0–13 vol.% resulted in increased wear rate of Al/Gr composites. The Al/30SiC composite exhibited a lower wear rate as compared with the base alloy and graphite addition up to 9 vol.% improved the wear resistance of these hybrid composites. However, more graphite particles addition resulted in increased wear rate. SEM micrographs revealed that the wear mechanism was changed from mostly adhesive in the base alloy sample (Al/0Gr) to the prominently abrasive and delamination wear for Al/Gr and Al/SiC/Gr/composites.

Selected electrical and thermal properties of polylactide/graphite composites

The influence of graphite on volume and surface resistivity as well as on some thermal properties of composites containing a polylactide matrix was studied. The graphite content was up to 50 wt. %. It was found that the volume and surface resistivity decreased with the increasing graphite content and the percolation threshold appeared at the level of the filler content of 30—40 wt. %. No essential influence of graphite on phase transition temperatures was observed. However, the phenomenon of cold crystallization appeared. The sample mass loss upon heating started at ca. 270 °C.

The Wear of Particulate Cu-Graphite Composite System

Cu–graphite composites were prepared by HIPing in the range of 0 – 50 vol. % of graphite. The same graphite powder was copper coated and composites with 30 and 50 vol. % of graphite were prepared. With increased graphite content the coefficient of friction and wear rate of composites at first decreased slightly from copper values. When percolation threshold of graphite is exceeded, the friction coefficient starts to decrease significantly. However this decrease stops after a certain critical concentration is reached. Then the friction coefficient becomes almost independent of the composition while the wear rate decreases further. Both percolation thresholds and critical concentration significantly depend on the composite structure, i.e., on the size of used graphite powder. Finally an empirical percolation model was proposed to describe this dependence.

Frication and Wear Properties of Cu-Fe-Al Composite Containing Graphite Prepared by Induction Sintering

Cu-Fe-Al composites containing various amounts of graphite additives are prepared by induction sintering method. The mechanical properties of the composites with 0-8 wt. % graphite are measured using the mechanical tester, while the friction and wear properties are evaluated using MRH-3 friction-wear tester. Material components are found by EDS. The worn surface morphologies of the composites are analyzed by means of scanning electron microscopy (SEM). The experimental results show that the composite containing graphite have porous microstructure. The mechanical and tribological properties of composites are related to the induction frequencies and the contents of the graphite as the solid lubricant. The increased graphite content results in reduced mechanical properties and increased friction and wear properties. The composite with 4 wt. % graphite additives and induction frequencies of 35Hz have the lower the friction coefficients and wear rate. Meanwhile, wear mechanism of materials have been changed from abrasive wear to grain wear due to the glaze layer.

Synthesis of New Cu-based Self-lubricating Composites with Great Mechanical Properties

New copper-based self-lubricating composites consisting of different quantities of graphite are prepared by means of powder metallurgy using a designed atomizing Cu-10Ni-3Sn-3Pb (wt.%) alloy with 0.5 wt.% Y2O3 as the matrix. Microstructures and properties of the composites are studied by scanning electron microscopy, X-ray diffraction, a hardness tester, and a wear tester. The results indicate that the composites sintered at 910°C for 4 h have the best mechanical properties. The composites prepared under such a condition are mainly composed of α-solid solution together with some CuNi 2Sn, Pb, and graphite phases. Here, Ni and Sn play the reinforcing role in the materials by either dissolving into the Cu matrix or forming the second phase with Cu, while Pb and graphite as inclusions act as the lubricating phases. The composites have hardness but deteriorated wear and self-lubricating performance with the increasing graphite content. The composite with 1 wt.% graphite possesses better mechanical and frictional properties, while the composite with 2% graphite possesses better self-lubricating properties. These Cu-based composites with low friction coefficient and enough strength are suitable for the application as surface lubricating film to run under a dry friction condition.

Effects of Conductive Fillers on the Dynamic Response and Fatigue life of Conductive Asphalt Concrete

It is currently interesting to use thermal or electrical conductive asphalt concrete for snow-melting and maintenance of asphalt pavements in winter. The addition of conductive fillers may have negative effects on the mechanical properties of asphalt concrete. The performance of conductive asphalt concrete is greatly affected by the initial crack and its propagation. Laboratory tests for neat and conductive asphalt concrete include Dynamic Modulus Test (DMT) and Indirect Tensile Fatigue Test (ITFT). DMT tests indicates that the value of dynamic modulus of asphalt concrete decreases with the increasing graphite content. It means that the conductive asphalt concrete achieves lower stiffness. It can be concluded from ITFT tests that the fatigue life (load cycle times) of conductive asphalt concrete is more than neat ones when stress level is under 1.0 MPa. Meanwhile higher fatigue resistance of conductive asphalt concrete is observed when carbon fibers (2 weight % of total aggregate) were added together with 22% graphite, especially at low stress levels.

Effect of Graphite on Microstructure and Drying Shrinkage of Clay

Graphite specimens bonded by kaolinite‐illite clay, in which planar orientation of the graphite flakes and clay platelets had been produced by deformation, showed enhanced differential drying shrinkage with increased graphite content. The greater shrinkage was perpendicular to the plane of preferred orientation. Comparable additions of quartz grains to the clay made the drying shrinkage less differential. The volume drying shrinkage was first increased and then decreased by successive additions of graphite. The increase was ascribed to the increasing concentration of water in the clay bond as the clay content diminished. The subsequent decrease appeared because the drying shrinkage of the clay was reduced near the graphite and because the graphite itself did not shrink.