Graphite Fraction Research Articles

Optimization of machining process parameters in Al 7175 metal matrix composites using Taguchi method

Aluminum-based metal matrix composites (MMC) have been used in various applications in the aerospace and automotive industries. Accomplishing a uniform circulation of support inside the framework is one such challenge, which influences straightforwardly on the properties and nature of composites. MMC is one of the authentic sources to satisfy the demand for engineering materials such as hardness, toughness, high tensile strength, low density, and good wear resistance. In this research work, Al 7175 metal matrix composites reinforced with 25% weight fraction of Sic and 4% weight fraction of graphite were synthesized through stir casting. Experiments were carried out based on L9 standard orthogonal array design for turning operation on Al 7175 using a tungsten carbide tool with three input process parameters, namely cutting speed, feed and depth of cut. The effect of input parameters on performance characteristics such as the material removal rate (MRR) and surface roughness (Ra) was studied. The signal to noise ratio was used to study the performance characteristics in turning operation. Results revealed that Ra reduced either on increasing spindle speed or by reducing feed, but depth of cut was not influential on Ra. MRR increased with increasing any of the three input parameters.

Experimental Investigation and Evaluation of Properties for Hybrid Metal Matrix Composites Reinforced with Fe2o3 And Graphite Powder

Aluminum metal matrix composites with numerous reinforcements (hybrid MMCs) having enormous potentials of satisfying novel demands of progressive engineering applications due to their enhanced mechanical properties such as Brinell hardness, tensile strength and compressive strength. Bottom down Stir casting method is followed to produce aluminum as base metal and their reinforced with various reinforcement level 2,4and 6 % of Fe2o3 and graphite powder use in same fraction. The microstructure distinctive of composites were observed by focusing of inverted metallurgical microscope. In particular emphasis the results were compared in those three different reinforced fractions. Finally, the comparative observation of their composites and their performance improvement and its mechanical properties such as strength and hardness. It is found that there is a good improvement in ultimate tensile strength, hardness and compressive strength up to reinforcement fraction of Fe2o3 and graphite 4% in an aluminum metal matrix composite.

Effect of Strontium Addition in Graphite Morphology and Nodularization of Hypoeutectic Cast Iron

Nodular graphite cast iron or known as spheroidal graphite cast iron structurally has a spherical graphite morphology with a matrix consisting of a ferrite-pearlite phase. In general, cast iron has a main alloy consisting of carbon and silicon where both elements have an influence on the potential of graphitization and castability. In this work, the influence of strontium (Sr) added to molten cast iron with a composition of 0, 0.04, 0.06 and 0.08 wt% to graphite morphology were studied. The sample obtained will be carried out a characterization process by observing macro and microstructures using optical microscope equipped with image data processing software that displays graphite fraction, size, form and nodularity. Analysis showed that Sr addition increase in nodularization of graphite from 19.6 % to 31.5% at 0.08 wt% Sr addition.

Precipitation and evolution of nodular graphite during solidification process of ductile iron

The quantity and morphology of spheroidal graphite have an important effect on the properties of ductile iron, and the characteristics of spheroidal graphite are determined by the solidification process. The aim of this work is to explore the precipitation and evolution of graphite nodules in hypoeutectic, eutectic, and hypereutectic ductile irons by thermal analysis, liquid quenching and metallographic technique. Results show that hypoeutectic ductile iron has the longest solidification time and the lowest eutectic temperature; eutectic ductile iron has the shortest solidification time; hypereutectic ductile iron has the highest eutectic temperature. After solidification is completed, hypoeutectic ductile iron has the lowest nodule count, nodularity and graphite fraction; eutectic ductile iron has the highest nodule count, nodularity and the smallest nodule diameter; hypereutectic has the highest nodule diameter and graphite fraction. The nucleation and growth of graphite nodules in hypereutectic ductile iron starts before bulk eutectic crystallization stage, however, the precipitation and evolution of graphite nodules of hypoeutectic and eutectic ductile irons mainly occur in the eutectic crystallization stage. The graphite precipitated in eutectic crystallization of hypoeutectic, eutectic, and hypereutectic ductile irons, are 61%, 68% and 43% of total graphite volume fraction, respectively. Simultaneously, there are plenty of austenite dendrites in hypoeutectic and hypereutectic ductile irons, which are prone to shrinkage defects. Therefore, the eutectic ductile iron has the smallest shrinkage tendency.

Microstructural analysis of EN-GJS-450-10 ductile cast iron via vibrational casting

EN-GJS-450-10 ductile cast iron was produced with and without vibration to evaluate microstructural features. To investigate the effect of vibration, a reference, and two different castings having amplitudes of 0.9 mm and 1.8 mm were cast with a fixed vibration frequency of 50 Hz. The nodule count (density), form (type), size distribution, nodularity, and the fraction of graphite, percentages of both ferrite and pearlite phases, length of ferrite shell, and pore, were evaluated via optical microscopy using an image analysis software. It is observed that the microstructure of the cast iron is more uniform by vibrational casting than that by non-vibrational casting. Additionally, mechanical vibration enhances nodule count and nodularity, also, more ferritic matrix could be obtained after the application of vibration. Nodule count and nodularity of vibrational casting with 1.8 mm amplitude increased from 226 nodule per mm2 and 80% to 311 nodule per mm2 and 86.5% of non-vibrational casting. Percentages of ferrite and graphite area dramatically improved from 24% and 16.5% for non-vibrational casting to 57% and 22.3% for vibrational casting with 1.8 mm amplitude, whereas the percentages of pearlite and pores decreased significantly from 56.1% and 5% to 20% and 1%, respectively.

Optimization and Effect of Reinforcements on the Sliding Wear Behavior of Self-Lubricating AZ91D-SiC-Gr Hybrid Composites

This article statistically investigates the effect of various parameters such as material factors: silicon carbide (SiC) fraction, graphite (Gr) fraction and mechanical factors: normal load, sliding distance and speed on the sliding wear rate of self-lubricating AZ91D-SiC-Gr hybrid magnesium composites. The self-lubricating hybrid composites were fabricated using advanced vacuum assisted stir casting process. The sliding wear tests have been performed under dry conditions on pin-on-disc tribometer at 10-50 N loads, 1-3 m/s sliding speed and 1000-2000 m sliding distance. It has been examined that hybrid composites yielded improved wear resistance with reinforcement of SiC and solid lubricant graphite. ANOVA and signal-to-noise ratio investigation indicated that applied load was the most critical factor influencing the wear rate of fabricated hybrid composites followed by sliding distance. Further, the AZ91D/5SiC/5Gr hybrid composite has exhibited the best wear properties. From the SEM and EDS analysis of worn surfaces, delamination was confirmed as the dominant wear mechanism for AZ91D-SiC-Gr hybrid composites.

Calculating the effective thermal conductivity of gray cast iron by using an interconnected graphite model

A new theoretical model of gray cast iron taking into account a locally interconnected structure of flake graphite was designed, and the corresponding effective thermal conductivity was calculated using the thermal resistance network method. The calculated results are obviously higher than that of the effective medium approximation assuming that graphite is distributed in isolation. It is suggested that the interconnected structure significantly enhances the overall thermal conductivity. Moreover, it is shown that high anisotropy of graphite thermal conductivity, high volume fraction of graphite, and small aspect ratio of flake graphite will cause the connectivity effects of graphite to more obviously improve the overall thermal conductivity. Higher graphite volume fraction, lower aspect ratio and higher matrix thermal conductivity are beneficial to obtain a high thermal conductivity gray cast iron. This work can provide guidance and reference for the development of high thermal conductivity gray cast iron and the design of high thermal conductivity composites with similar locally interconnected structures.

Microstructure and damping capacity of AA6061/graphite surface composites produced through friction stir processing

The present study is to improve the damping properties of AA6061-T6 alloy by incorporating graphite (Gr) flakes through friction stir processing (FSP). The amount of graphite varied from 5 to 15 vol%. The distribution of graphite particles and the microstructure refinement were analysed using optical and electron microscopy. The grains were indistinguishable in the stirred zone. The hardness of the surface composites decreased with an increase of graphite fraction. The dynamic mechanical analyzer was used to analyze the damping capacity of specimens extracted from the stir zone. The frequency dependent and temperature dependent damping capacity of FSP-ed AA6061 and the surface composites were observed to be better than the base metal. Significantly, the damping capacity of composite with 15 vol% graphite was 3.5 times of base-metal's damping at 250 °C.

Significant enhancement of thermal conductivity in graphite/polyester composite via interfacial π–π interaction

AbstractInterfacial thermal resistance between matrix and filler is one of the most serious factors hindering heat transfer in composites. Here, a type of liquid crystalline polyester (LCP) containing phenyl pendant groups was intended to blend with pristine graphite by interfacial interaction. The intensity at 26.6° of the wide angle X‐ray diffraction pattern which exceeded that of pristine graphite indicated the existence of a strong interfacial π–π interaction. Both DSC and XRD tests showed that the ordered structure of the LCP matrix is directly affected by the mass fraction of graphite, indicating the interfacial interaction between LCP and graphite. By increasing the content of graphite, the thermal diffusivity showed a sharp increment by 1004%. The maximum thermal conductivity of the composite reached 28.613 W m−1 K−1, which was seven times that of traditional thermoplastic blended with graphite. Compared with the data calculated using effective medium theory, interfacial interaction plays a significant role in enhancing the thermal conductivity of the composites. Furthermore, the maximum tensile strength of this series of composites reached 13.3 MPa and the maximum Young's modulus reached 1067 MPa, exhibiting a potential guideline for further applications in flexible electronics. © 2019 Society of Chemical Industry

Effect of Coconut Shell Ash and Graphite Particles on Microstructure and Mechanical Properties of Recycled Aluminium Composites

The current high demand for aluminium (Al) matrix composites with improved physical and mechanical properties has resulted in growing concern in the production of hybrid composites of aluminium at a lower cost. In the present work, an effort has been made to develop a hybrid aluminium matrix composite from waste aluminium cans, coconut shell ash (150 µm) and graphite (150 µm) particles by stir casting method. Composites were prepared by reinforcing recycled aluminium alloy with a combination of 0,2,4,6,8 % weight (wt.) fraction of coconut shell ash (CSA) and constant 2 % wt. the fraction of graphite. The cast produced were machined in accordance with ASTM standard into an appropriate coupon for microstructural examination, density measurement, tensile, impact and hardness tests. The micrograph showed reasonably uniform distribution of CSA and graphite particles in the matrix of aluminium alloy. Casting defects such as shrinkage did not manifest and porosity are minimal. The results also revealed a reduction in density and impact energy within the range of 2.46-2.23 g/cm3 and 12.92-4.76 J respectively. Hardness and tensile strength increased within the range of 220.9-266.4 HV and 27-57 MPa respectively. The result reveals that, the overall reduction of density and impact strength together with improved hardness and ultimate tensile strength of the composites. The control sample confirmed the retention of the reinforcements in the aluminium matrix. This study has affirmed the suitability of recycled aluminium cans reinforced with graphite and coconut shell ash as a candidate material for the production of the most common automobile part.

Heat treatment and its effect on mechanical and wear properties of Al6061/Gr/TiC hybrid MMCs

The objective of this investigation is to explore the mechanical and wear characteristics of heat-treated hybrid metal matrix composites (MMCs) comprising Al6061, 5 wt.% graphite and different fractions of Titanium Carbide. In this, composites of different configurations were prepared by employing liquid metallurgy technique. The accumulation of graphite was kept constant that is 5 wt.% while TiC was varied from 0% to 8 wt.% in a stage of 2% and are subjected to T6 heat treatment. At first, composites were exposed to solutionising heat treatment at 530°C for 8 h and followed by quenching in ice and water. Artificial ageing of quenched composites was performed for an interval of 4-10 h in a step of 2 h. The role of heat treatment and ageing behaviour of composites on mechanical and wear characteristics were investigated and compared with un-heat treated. The result shows superior hardness and wear properties of MMCs for T6 heat treatment.

High Thermal Conductivity and Anisotropy Values of Aligned Graphite Flakes/Copper Foil Composites.

Much attention has been paid to graphite flakes/copper (GFs/Cu) composites for thermal management due to their remarkable thermal properties. Most studies focus on the interface interaction between GFs and Cu in composites. However, controlling the orientation of GFs still remains a challenge. Herein, we report a reliable method to ensure consistent orientation of GFs in the composites. Firstly, the disorder GFs were well arranged on the surface of copper foil by tape casting process in the casting machine. Then highly aligned GFs/Cu composites were fabricated by hot pressing process in a vacuum hot-pressing furnace, with the volume fraction of graphite from 30% to 70%. The SEM images show that the obtained GFs/Cu composites presented a layer-by-layer structure or network structure with a different content of GFs. The thermal conductivity of GFs/Cu composites exhibited an extreme anisotropy due to the highly aligned GFs. The ultrahigh thermal conductivity of GFs/Cu composites with 70 vol% GFs reached 741 W/(m·K), while through-plane thermal conductivity was just 42 W/(m·K). The alignment of GFs and interfacial thermal resistance were deeply analyzed and a thermal conductivity model for GFs/Cu composites was established. Our work provides a new idea to significantly enhance the thermal transportation performance of GFs/Cu composites by well controlled alignment of GFs in Cu matrix.

Functionalization of graphite via Diels-Alder reaction to fabricate poly (vinyl alcohol) composite with enhanced thermal conductivity

Surface modification of filler is often utilized to effectively reduce interfacial thermal resistance in thermal conductive materials. In this work, pristine graphite was modified via Diels-Alder reaction with acrylic acid to improve the inertness of graphite (AA@G). FT-IR, Raman and XPS confirmed the reaction onto the surface of graphite. A series of poly (vinyl alcohol) composite loaded with AA@G and graphite was fabricated to investigate the interfacial interaction between matrix and filler. Both XRD and DSC showed that introducing of AA@G would decrease crystallinity of PVA matrix in composite, providing convincing evidence of strong interfacial interaction. Owing to the excellent interfacial interaction, the maximum TC of composite loaded with 30 wt% AA@G reached to 21.3Wm−1K−1, which was 44% higher that of composite loaded with the same mass fraction of graphite (14.1Wm−1K−1). With the synergistic increment in thermal conductive performance, AA@G exhibited extremely high enhanced efficiency of 358% compared with other literature. Also, good thermal stability makes AA@G potential in thermal management system and flexible electronics.

Effect of graphene, SiC and graphite addition on hardness, microstructure and electrical conductivity of microwave sintered copper MMCs fabricated by powder metallurgy route

Copper MMCs reinforced with graphene, SiC and graphite flakes with varying mass fractions of 2.5, 5, and 7.5 wt% SiC, 2.5, 5, 7.5, and 10 wt% graphite and 0.2, 0.4, 0.6 and 0.8wt% graphene particles were fabricated through powder metallurgy route. The powder mixtures were blended and then compacted under a uniaxial pressure of 400MPa for both Cu-SiC and Cu-Gr composites and 600Mpa for Cu-Gn composites. Green compacts were sintered by microwave (MW) sintering process. MW sintering was performed at 950°C in open atmosphere with a heating rate of 25°C/min for all composites. Densification parameter (DP) was determined for all MMCs and a reduction in DP values were observed with an increase in weight percentage of reinforcement particles as a result of increase in porosity. Higher mass fractions of reinforcement particles in the Cu matrix tend to offer a diffusion barrier to copper atoms. Micro-structural analysis was performed using Optical and scanning electron microscope which revealed a homogeneous microstructure of all composites at low mass fractions of Sic, graphite and graphene. In order to detect the presence of any oxides of Cu and other elements, EDS analysis was carried out. Hardness data showed an increasing trend for Cu-SiC and Cu-Gn composites and a declining trend for Cu-Gr composites. Porosity has a significant effect on the electrical conductivity values of the composites.

Thermoelectric Properties of Sb2Te3-Based Nanocomposites with Graphite

Antimony-telluride-based nanocomposite samples containing different weight fractions of graphite (Sb2Te3 + x% graphite, where x = 0.0, 0.5, 1.0, and 2.5%) are synthesized and studied. The samples are produced by a solid-state reaction with the use of a ball mill. X-ray diffraction measurements show that the Sb2Te3 phase is present in the nanocomposites. All of the diffraction peaks are identified as corresponding to the rhombohedral structure of symmetry $$R\bar {3}m$$ . No additional peaks related to graphite are observed because of its low content. Moreover, the X-ray data show the insolubility of graphite in Sb2Te3: the peaks related to Sb2Te3 remain unchanged upon the addition of graphite. The thermal conductivity, thermoelectric power, and resistivity of the samples are studied in the temperature range 80 K ≤ T ≤ 320 K. The thermal conductivity k of the nanocomposite decreases several times compared to the thermal conductivity of single-crystal Sb2Te3 and reaches k ≈ 0.95 W m–1 K–1 at x = 0.5%. The parameter k unsteadily depends on the content of graphite. The thermoelectric power of the nanocomposites with graphite at x = 1.0% is higher compared to that of nanostructured Sb2Te3.

In-situ synthesis of ZrC in Cu melts using the graphite as the source of C

In this work, ZrC particles have been successfully synthesized in the Cu melts using graphite as the source of C. It is considered that the instantaneous reaction between Zr and C which can realize the reactive wetting of Cu and graphite is attributed to the effective introduction of graphite into the melts. However, because it is impossible that all the graphite can contact with Zr in the mixture by the present method, only a fraction of graphite can be reactive wetted and the others will be burned out. As a result, when the Zr/C atomic ratio is 1:1 in the raw Zr-G mixture, Zr will ultimately be excessive for the formation of ZrC. Increasing the Zr/C ratio in the mixture is one of the effective methods to introducing more graphite into the melts. It is found that, besides the synthesis of more ZrC particles, the morphology, size and distribution of ZrC can also be remarkably improved with the Zr/C ratio increasing.

Evaluation of tribological performance of carbon fibre reinforced epoxy composites loaded with graphite platelets under reciprocating linear motion

The objective of this work was to evaluate the effect of graphite platelets used as matrix epoxy polymer reinforcement in the sliding reciprocating wear performance of carbon fibre composites. First, epoxy reinforced composites with different amounts of graphite in weight were produced (0, 7.5, 11.5 and 30 wt %) to ascertain the optimal composition regarding wear resistance. Additionally, carbon fibre reinforced polymer composites were produced, with and without the addition of 7.5 wt% graphite platelets to the polymer matrix, and its wear resistance was also evaluated. The laminated carbon fibre reinforced polymer composites were produced through vacuum assisted hand lay-up method. Reciprocating sphere-on-plate wear tests, using Ø 6 mm spheres of AISI52100 steel as counter-body, were performed during 6 h at room temperature. The tests were carried out using an applied normal load of 4 N, 2 Hz of frequency and 8 mm stroke per cycle. At the end of the tests, the wear losses were estimated through integration of cross-section wear track profiles and the worn surfaces were examined by scanning electron microscopy. The coefficient of friction was accessed during testing. The results showed that the lowest specific wear rate of the polymer composites without carbon fibre was obtained with the insertion of 7.5 wt% of graphite platelets (9.7 × 10−8 mm3/N m) and that increase in the graphite fraction leads to higher material loss as a result of increased fatigue surface. Furthermore, the addition of 7.5 wt% graphite platelets to the epoxy matrix of carbon fibre reinforced polymer composites leads to enhance its wear resistance. The reinforced matrix supports and protects the fibres reducing fibre failure and, consequently, wear.

Low-temperature activation of carbon black by selective photocatalytic oxidation.

Carbon black is chemically modified by selective photocatalytic oxidation, removing amorphous carbon and functionalizing the graphitic fraction to produce porous, graphitized carbon black, commonly used as an adsorbent in chromatography. In contrast to pyrolytic treatments, this photocatalytic modification proceeds under mild reaction conditions using oxygen, nitric oxide, water vapor and a titanium dioxide photocatalyst at 150 °C. The photo-oxidation can be performed both with the photocatalyst in close proximity (contact mode) or physically separated from the carbon. Structural analysis of remotely photo-oxidized carbon black reveals increased hydrophilic properties as compared to pyrolysis at 700 °C in a N2 atmosphere. Carbon black photo-oxidation selectively mineralizes sp3-hybridized carbon, leading to enhanced graphitization. This results in an overall improved structural ordering by enriching carbon black with sp2-hybridized graphitic carbon showing decreased interplanar distance, accompanied by a twofold increase in the specific surface area. In addition, the photo-oxidized material is activated by the presence of oxygen functionalities on the graphitic carbon fraction, further enhancing the adsorptive properties.

Preparation and Characterization of ZA27-Alumina-Graphite Reinforced Hybrid Composites

Abstract In the present study zinc aluminium based alumina andgraphite particulates MMCs have prepared by using stir castingtechniqueand property analysis has been made. Zinc aluminium and alumina,graphite have been taken as matrix and reinforcement materials respectively. Experiments have been conducted by keeping weight fraction of alumina at 3% and varying weight fraction of graphite (0%, 1%, 3 %,) .And after that by keeping weight fraction of graphite 3% and varying weight fraction of alumina (0%,1%, 3%).Tensile strength and impact strength have been increased. However hardness decreased with dispersion of graphite.

Термоэлектрические свойства нанокомпозитов Sb-=SUB=-2-=/SUB=-Te-=SUB=-3-=/SUB=- c графитом

AbstractAntimony-telluride-based nanocomposite samples containing different weight fractions of graphite (Sb_2Te_3 + x % graphite, where x = 0.0, 0.5, 1.0, and 2.5%) are synthesized and studied. The samples are produced by a solid-state reaction with the use of a ball mill. X-ray diffraction measurements show that the Sb_2Te_3 phase is present in the nanocomposites. All of the diffraction peaks are identified as corresponding to the rhombohedral structure of symmetry $$R\bar {3}m$$ . No additional peaks related to graphite are observed because of its low content. Moreover, the X-ray data show the insolubility of graphite in Sb_2Te_3: the peaks related to Sb_2Te_3 remain unchanged upon the addition of graphite. The thermal conductivity, thermoelectric power, and resistivity of the samples are studied in the temperature range 80 K ≤ T ≤ 320 K. The thermal conductivity k of the nanocomposite decreases several times compared to the thermal conductivity of single-crystal Sb_2Te_3 and reaches k ≈ 0.95 W m^–1 K^–1 at x = 0.5%. The parameter k unsteadily depends on the content of graphite. The thermoelectric power of the nanocomposites with graphite at x = 1.0% is higher compared to that of nanostructured Sb_2Te_3.