Addition Of Graphite Research Articles

Tailoring mechanical and tribological properties of oscillatory pressure sintered binderless WC ceramics with expanded graphite addition

The fracture toughness and wear resistance of WC-based ceramics are crucial factors that determine their subsequent applications. In this study, the mechanical and tribological properties of expanded graphite (EG) reinforced WC ceramics consolidated by oscillatory pressure sintering (OPS) were investigated. The results demonstrated that the combination of dynamic pressure and EG had a synergistic effect, resulting in a much higher relative density of 0.2 wt% EG/WC ceramics reaching up to 99.78%. Simultaneously, 0.2 wt% EG/WC ceramics demonstrated a reduced grain size, with fracture toughness, flexural strength and wear rate reaching 7.54 MPa·m1/2, 1262 MPa and 2.16×10-7 mm3·N-1·m-1, respectively. EG was present in the form of graphene nanoplatelets (GNPs) within WC ceramics. The primary toughening mechanisms involved the bridging and pulling out of GNPs, as well as the generation of microcracks induced by GNPs. Additionally, the exceptional thermal conductivity of GNPs can facilitate heat dissipation and reduce thermal damage. The wear resistance of WC-EG ceramics was primarily enhanced through improving overall mechanical properties and decreasing the occurrence of oxidation and adhesive wear.

Effect of Mechanically Exfoliated Graphite Flakes on Morphological, Mechanical, and Thermal Properties of Epoxy

Carbon-reinforced polymer composites form an important category of advanced materials, and there is an increasing demand to enhance their performance using more convenient and scalable processes at low costs. In the present study, graphitic flakes were prepared by the mechanical exfoliation of synthetic graphite electrodes and utilized as an abundant and potentially low-cost filler to fabricate epoxy-based composites with different additive ratios of 1–10 wt.%. The morphological, structural, thermal, and mechanical properties of these composites were investigated. It was found that the thermal conductivity of the composites increases by adding graphite, and this increase mainly depends on the ratio of the graphite additive. The addition of graphite was found to have a diverse effect on the mechanical properties of the composites: the tensile strength of the composites decreases with the addition of graphite, whilst their compressive strength and elastic modulus are enhanced. The results demonstrate that incorporating 5 wt% of commercially available graphite into epoxy not only raises the thermal conductivity of the material from 0.223 to 0.485 W/m·K, but also enhances its compressive strength from 66 MPa to 72 MPa. The diverse influence of graphite provides opportunities to prepare epoxy composites with desirable properties for different applications.

Synthesis and characterization of bacterial cellulose composite with graphite and TiO2-ZnO: structural and functional analysis

This research aims to synthesize and characterize a bacterial cellulose (BC)-based composite with graphite and TiO2-ZnO as reinforcement materials using ex-situ synthesis with CTAB as a surfactant. FTIR and SEM-EDS analysis revealed interactions between the matrix and the reinforcement materials, as well as irregular particle distribution in the BC/G-TiO2-ZnO composite. The addition of graphite to BC significantly increased the conductivity of the composite, while the addition of TiO2-ZnO had the opposite effect. The mechanical properties of the composite exhibited an inverse relationship with the conductivity parameter. Swelling tests indicated that pH and the addition of CTAB influenced the swelling behavior of the BC-based composite. The results of this study provide a strong foundation for the development of potential applications in the fields of electronics and pollutant filtration. The synthesis of this composite aims to harness the unique properties of BC, graphite, and TiO2-ZnO, creating a multifunctional material with potential uses in flexible electronics, sensors, biocompatible conductive materials, and advanced filtration systems.

Assessment of thermal-hydraulic-mechanical-chemical (THMC) performances of Ca-type bentonite-graphite mixtures as buffer materials for a high-level radioactive waste repository

The bentonite buffer material is the most important element of the engineered barrier system (EBS) used to dispose of high-level radioactive waste. Therefore, there are functional criteria or performance targets for the bentonite buffer material to maintain the long-term performance of the EBS for the entire disposal system. Thermal conductivity is a key parameter in the design of an EBS as it has the greatest influence on the buffer temperature. As the peak temperature of the buffer should not exceed the thermal design criterion, it is necessary to increase the thermal conductivity of the bentonite buffer material. Therefore, in this study, a small portion of graphite was added to Ca-type bentonite and thermal, hydraulic, and mechanical properties were measured separately, along with overall THMC (thermal-hydraulic-mechanical-chemical) properties. Additionally, while thermal conductivity was examined for varying graphite contents, other properties such as hydraulic conductivity, swelling pressure, and unconfined compressive strength were tested with a 3 % graphite addition. In particular, the thermal conductivity was measured for 3 % graphite addition to the pure bentonite under the different dry densities and saturation conditions and a regression analysis was performed to predict thermal conductivity based on the dry density and degree of saturation values. Furthermore, the saturated hydraulic conductivity, swelling pressure, unconfined compressive strength, and sorption efficiency of cesium (Cs) ions in bentonite and bentonite-graphite mixtures were measured. Moreover, prototype buffer blocks for bentonite-graphite mixtures were manufactured to evaluate viability of production. The addition of 3 % graphite to pure bentonite satisfied the functional criteria of saturated hydraulic conductivity and swelling pressure when the dry density was 1.63 g/cm3 or higher, and the thermal conductivity of the bentonite-3 % graphite mixtures was 10–30 % higher than that of pure bentonite.

Comparative Corrosion Inhibition Test Study in Phosphate Buffer Saline for 316L Stainless Steel with Electrospun PCL Coating with Different Additives

In this study, ten different contents of PCL-based nanofibers containing ZnO, CuO, NiO, 2F TSC, 4F TSC and graphite additives (PCL+Graphite+CuO+NiO+ZnO, PCL+ZnO+Graphite, PCL+ZnO+NiO+CuO, PCL+ZnO, PCL+Graphite, PCL+ZnO+2F TSC, PCL+ZnO+NiO+CuO+4F TSC, PCL+ZnO+NiO+CuO+2F TSC, bare PCL, PCL+ZnO+4F TSC) 316L stainless steel (SS) surface was coated. After coating with these different types of nanofibers, measurements were taken with electrochemical techniques such as potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) in phosphate buffer solution (PBS) for 1 hour to investigate the corrosion inhibition properties. According to the results, the PCL+Graphite+CuO+NiO+ZnO coating provided the highest corrosion inhibition with a protection efficiency value of 98.83%. The PCL+4F+ZnO coating had the lowest inhibition property with a protection efficiency value of 40.72%. At the end of the tests, Nyquist, Bode, Tafel, OCP diagrams of the coatings were obtained and equivalent circuit models were presented.

A composite anode based on intercalation and conversion mechanism for high-rate lithium-ion batteries

To increase the specific capacity and cycle stability of lithium-ion batteries at high current density, we have investigated the anode materials. Among them, black phosphorus has attracted attention because of its large theoretical specific capacity (2596 mA h/g). However, the moderate conductivity of black phosphorus itself makes it less effective. The addition of graphite to form P-C and P-O-C bonds with black phosphorus enhances the performance of the battery cell. Lithium ions are primarily stored in black phosphorus-graphite layered structural materials via an intercalation mechanism, which improves electrochemical performance at tiny current density but is inadequate for charge/discharge cycling at high current density. In addition, lithium ions also can undergo conversion mechanism with metal oxide materials (e.g. Tungsten trioxide). While this conversion mechanism enables more stable battery cycling at high current density, the specific capacity remains insufficiently high. Higher charge/discharge specific capacity and long cycle stability of lithium-ion batteries at high current density can be realized by the joint action of the two mechanisms. In this work, black phosphorus, graphite, and tungsten trioxide (BP/G/WO3) composites are prepared by ball milling method. A comprehensive series of electrochemical analyses reveals that the BP/G/WO3-532 electrode (BP, graphite, and WO3 mass ratio of 5:3:2) exhibits the most substantial enhancement in the cycling stability of lithium-ion batteries. The anode exhibits a high specific capacity of 1463.1 mA h/g at 6 A/g and presents a retention capacity of 1159.8 mA h/g after 300 charge/discharge cycles, indicating a high cycle stability and fast reaction kinetics. This result is mainly attributed to the joint action of two mechanisms of composites.

Comparing additives effects on bioleaching efficiency of Cd-bearing ZnS concentrate in mesophilic conditioning at high pulp density

The roasting-leaching-electrowinning (RLE) process is the most common method for processing sphalerite concentrate. However, this method has disadvantages that can affect the environment. Bioleaching is an eco-friendly method that can replace this method, but the low kinetics of this method is the main barrier to replacing it. In previous research, various additives have been used to solve this problem, but unfortunately, these additives have usually been investigated in low-density pulp, and very limited research has been conducted on the comparison between additives. In this study, the effect of graphite, silver (Ag+), L-cysteine, pyrite, elemental sulfur, and ferrous sulfate additives on the bioleaching of Cd-bearing sphalerite concentrate at 12 % density pulp has been investigated. The results showed that Ag + ions had a higher dissolution rate than the others, and in the optimal condition (60 mg/l), zinc and cadmium extractions were achieved at 82.6 % and 74.5 %, respectively. The bioleached residues have been investigated by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) analyses, and it was found that Ag+ ions cause the surface to become porous.

Influence of localized thermal effect of microwave heating on the carbothermic reduction process of ZnFe2O4

As an environmentally efficient method, microwave heating has been proposed to recover Zn from electric arc furnace dust (EAFD) recently. During the process, microwave irradiation has been shown to promote the reaction by lowering the reaction temperature and activation energy, in addition to providing efficient heat. However, the mechanism by which microwave heating promotes the zinc removal reaction of EAFD remains unclear. Thus, this study focused on ZnFe2O4, the primary component of EAFD, and developed an electromagnetic-thermal-chemical reaction coupling model to investigate the factors influencing the carbothermic reduction process of ZnFe2O4 and analyze the promoting mechanism of the microwave on the reaction. The main results indicate that the localized thermal effect, determined by the microwave distribution, exacerbates temperature differences and leads to non-uniform reaction behavior inside the sample. Increasing microwave power and graphite addition enhances the localized thermal effect, worsening field uniformity. In the simulation, the localized thermal effect of microwave heating reduced the activation energy of the zinc removal reaction to 252.97 kJ/mol, with an R2 reaction model. The assistance of the non-thermal effect in enhancing ion diffusion leads to a significant decrease in the activation energy observed in the actual microwave heating experiments.

Processing and characterization of Ultra High Temperature High‐Entropy (Ti0.2Zr0.2Hf0.2Mo0.2W0.2)B2-based Ceramics: Effect of W granulometry, graphite, and SiC addition

A highly dense and single phase (Ti0.2Zr0.2Hf0.2Mo0.2W0.2)B2 ceramic product is obtained in this work at 1950°C (20 min, 20 MPa) by Spark Plasma Sintering (SPS) from powders prepared by Self-propagating High-temperature Synthesis (SHS). The formation of the (W,Mo)B2 secondary phase is avoided using fine W precursors and adding 1 wt% graphite to the SHS powders before SPS. Kinetic limitations responsible for hindering the synthesis of the high entropy boride are correspondingly eliminated. The resulting 98.5 % dense sample exhibits a homogeneous microstructure, with Vickers hardness of 26.8 GPa. The introduction of 20 vol% SiC produces an increase of the KIC values from 2.32 to 5.11 MPa m1/2. Very relevant is that the volatilization of Mo- and W-oxides occurring during sample oxidation at high temperature, which leads to its rapid degradation with the formation of a very porous oxide scale, can be strongly inhibited by the silicate phases generated in the composite ceramic.

Change in the Properties of Expanded Polystyrene Exposed to Solar Radiation in Real Aging Conditions

Although polystyrene materials with added graphite are actively used for the thermal insulation of buildings, there are serious problems with the detachment and warping of these materials under the influence of solar radiation. However, no systematic studies have yet been carried out on the aging of polystyrene under exposure to solar radiation. The article presents research aimed at determining changes in the thermal conductivity, compressive stress, tensile strength, and water absorption of expanded polystyrene with the addition of graphite, exposed to direct solar radiation under in situ conditions. For this purpose, expanded polystyrene (EPS) with the addition of graphite (gray EPS) and expanded polystyrene made of composite panels (gray EPS and white EPS) were exposed to direct solar radiation under in situ conditions. A third sample (reference), which was entirely white polystyrene (without the addition of graphite), was included in the tests. The results showed that expanded polystyrene with the addition of graphite degraded under the influence of direct solar radiation but improved its strength properties. Expanded polystyrene made of composite improved its compressive strength properties by nearly 11 kPa (18%), and expanded polystyrene with the addition of graphite improved its compressive strength properties by 0.4 kPa (0.5%). And the tensile strength for composite-made expanded polystyrene increased by 7 kPa (9%), and that for expanded polystyrene with the addition of graphite increased by 26 kPa (37%). At the same time, water absorption for expanded polystyrene made of composite also increased by 0.06 kg/m2 (60%), and that for expanded polystyrene with the addition of graphite increased by 0.04 kg/m2 (44%).

Effect and mechanism of graphite addition on microstructures and hydrogen storage properties of Mg–Y–Zn alloy

In this work, the Mg-9.1Y-1.0Zn alloy are prepared by semi-continuous casting, and then mechanical milled with graphite. The microstructures and hydrogen storage properties of milled composite are systematically studied. The results show that the as-cast Mg-9.1Y-1.0Zn alloy exhibits serious agglomeration after milling. The addition of graphite significantly restrains the agglomeration of alloy and further refines the particles. Compared with as-cast Mg-9.1Y-1.0Zn alloy, the hydrogen storage properties of Mg-9.1Y-1.0Zn alloy milled with graphite is greatly improved. It needs only three times activation to be fully activated and its maximum hydrogen storage capacity is about 6.7 wt%. Besides, its dehydrogenation activation energy is decreased by about 40 kJ mol−1 relative to as-cast Mg-9.1Y-1.0Zn alloy. During hydrogen absorption and desorption, the stable YH2 hydride is generated by the disproportionation decomposition of LPSO phase. The graphite and in-situ formed YH2 present the synergistic confinement and catalysis effects on the milled Mg–Y–Zn alloy particles, which is conductive to the enhancment of hydrogen storage properties.

Influence of Graphite and Zirconia Addition on the Tribological Properties of Plasma-Sprayed Alumina Coatings

Al2O3, Al2O3-graphite and Al2O3-ZrO2 coatings were formed on the C45 steel rolls using atmospheric plasma spraying. The influence of graphite and zirconia addition on the surface morphology, phase composition and tribological properties under dry sliding conditions using 30 N load were analyzed. It was found that the addition of graphite or ZrO2 slightly affected the fraction of the α-Al2O3 and γ-Al2O3 phases in the alumina coatings. The highest mass loss rate (~8.84 × 10−4 g/s) was obtained for the friction pair of C45 steel roll and steel plate. The friction coefficient of the Al2O3-graphite coating was slightly lower (up to 7%) compared to the coating of Al2O3-ZrO2. However, the friction pair of Al2O3-ZrO2 coating and steel plate demonstrated the highest wear resistance under dry sliding conditions. The increase in the wear resistance of the Al2O3-graphite and Al2O3-ZrO2 coatings is due to the formation of tribofilm in the sliding contact zone.

Enhancement of thermoelectric properties in Sr0.6La0.4Nb2O6-δ-based ceramics by addition of graphite

Oxide thermoelectric materials have a wide range of applications due to their excellent stability, low cost, and non-toxic properties. However, their low thermoelectric conversion efficiency limits their practical use. Therefore, improving the performance of oxide thermoelectric materials has become the focus of current research. Interface engineering is an important approach to enhance thermoelectric properties by optimizing electrical transport properties through multiphase composite regulation of phase interface structure. A series of Sr0.6La0.4Nb2O6-δ/x wt% graphite (x = 0, 0.6, 1.0, 1.5, 2.0) composite ceramics thermoelectric materials were prepared, and the mechanism for improving their thermoelectric properties was explored. Graphite serves as an electron momentum amplifier within the Sr0.6Ba0.4Nb2O6-δ matrix, thereby augmenting both conductivity and power factor values significantly. Notably, the incorporation of 1.5 wt% graphite led to a remarkable enhancement in the thermoelectric power factor at 1073 K, reaching an impressive value of 254.84 μW/K2m - representing a notable increase of approximately 51 % compared to the unmodified sample - primarily attributed to the elevated electrical conductivity.

Effects of graphite additives in polycrystalline SnS nanostructures for thermoelectric applications

Effects of graphite additives in polycrystalline SnS nanostructures for thermoelectric applications

Effects of Addition of Graphite on the Tribological Behaviour of Al7075-SiC Hybrid Composites Using Design of Experiments

Effects of Addition of Graphite on the Tribological Behaviour of Al7075-SiC Hybrid Composites Using Design of Experiments

Multi-physical field coupling modeling of microwave heating and reduction behavior of zinc oxide

Microwave heating provides a cleaner pyrometallurgical method for separating zinc from electric arc furnace dust (EAFD, a solid waste generated during steel production with excellent dielectric properties). Despite its undisputed heating efficiency, the impact of microwave heating characteristics on the zinc removal process from EAFD remains unclear. This paper focuses on ZnO, one of the primary components of EAFD, and develops an electromagnetic-thermal-chemical reaction model to analyze the effects of microwave power and graphite addition on heating behavior, reduction reactions, field distributions, and reaction kinetics. The results indicate that the heat generated from the interaction between microwaves and materials exhibits inherent non-uniformity, leading to the localized thermal effect and making the error of general temperature measurement methods. Increasing microwave power and adding graphite enhance heating efficiency and promote the reduction reaction but also result in significant internal-external temperature disparity and worse temperature distribution. At 1000 W, with 1.2 times the stoichiometric amount of graphite addition, the temperature measurement error reaches approximately 200 °C, potentially affecting the kinetic results to a certain degree. The non-isothermal kinetics results from simulations indicate that the localized thermal region exhibits a lower average activation energy of 47.5 kJ/mol compared to experimental results, suggesting that the lower activation energy of the ZnO reduction reaction during microwave heating is primarily caused by the localized thermal effect rather than the non-thermal effect. Additionally, in the energy distribution, the higher proportion of return loss during heating underscores the importance of a well-designed microwave heating system.

Determination of “tribological performance working fields” for pure PEEK and PEEK composites under dry sliding conditions

Poly-ether-ether-ketone (PEEK) and PEEK composites are widely used polymers in many engineering applications where dry sliding is required. In this study, the influence of sliding velocity and applied load values on the friction and wear behavior of pure PEEK, 30 wt% glass fiber reinforced PEEK (PEEK-30GF), 30 wt% carbon fiber reinforced PEEK (PEEK-30CF) and 10 wt% carbon fiber+10 wt%graphite +10 wt%poly-tetra-fluoro-ethylene (PTFE) filled PEEK (ie. High (H) pressure (P) and velocity (V) resistant PEEK (PEEK-HPV)) composites rubbing against AISI 304 stainless steel disc was investigated. The experiments were carried out at room temperature under dry sliding conditions in a pin-on-disc wear rig. The applied loads ranged from 30 to 250 N, while the sliding velocities ranged from 1.0 to 4.0 m/s. At these load and velocity ranges, the friction coefficient-wear rate relationship of pure PEEK and composites was established and evaluated. In addition, the operating load-velocity limits of each material were determined and stated. The lowest coefficient of friction and wear rate were obtained in PEEK-HPV, PEEK-30CF, PEEK-30GF composites and pure PEEK polymer, respectively. In addition, it was observed that the coefficient of friction (CoF) decreased and the specific wear rate (SWR) increased with the increase in sliding velocity and applied load in all PEEK materials. The wear rate values of PEEK-HPV and PEEK-30%CF composites are in the range of 10−7 - 10−6 (mm3/Nm), while the wear rate values of pure PEEK and PEEK-30%GF are in the range of 10−6 - 10−5 (mm3/Nm). It was determined that carbon fiber, graphite and PTFE additives added to PEEK polymer as hybrid were very effective in reducing the wear rate of PEEK composite (PEEK-HPV). An adhesive wear mechanism was observed in PEEK-HPV and PEEK-30CF composites both at low load and velocity values and at high load and velocity values.

Qualitative study of carbides in liquid phase sintered M3:2 high speed steel

The microstructure of liquid phase sintered M3:2 high speed steel and the effect of adding carbon and silicon on the microstructure was characterized by scanning electron microscopy, dispersive spectrometry, and X-ray diffraction. Various types of carbides were formed depending on the added carbon and/or silicon, the sintering atmosphere and the cooling rate. The microstructure of sintered M3:2 high speed steel samples in vacuum conditions without the addition of Si and graphite is composed mainly of MC and M6C carbides inside cells and primarily at cell boundaries. The M2C eutectic carbides in these samples were formed at cell boundaries and their amounts and morphology depends on the cooling rate. Sintered samples in N2 atmosphere with added carbon and silicon, M6C eutectic and M7C3 eutectic carbides were dominantly formed while carbonitrides were formed in smaller amounts.

Ensuring fire safety: compliance tests for the use of polystyrene foam in facades systems

Ensuring fire safety is the most important thing in the construction industry, especially when it comes to facade materials. The inherent flammability of polystyrene foam poses significant safety concerns, especially when integrated into facade systems. Therefore, the main focus is on meeting the strict flammability requirements set for construction products, which are assessed by applying rigorous test procedures. This study focuses on the fire resistance testing of a facade system using EPS 70 with graphite additives. The system has been evaluated according to the strict DIN 4102-20 standards. Tests were conducted under real-world conditions to gain insight into the performance of the EPS 70 in real-world fire scenarios. Temperature measurements were taken at various points in the facade system, including at least 3.5 meters above the combustion chamber. The results showed that the temperature does not exceed 500 °C, so it is possible to quantify the thermal properties of the material and the ability to prevent the vertical spread of fire. After the tests, detailed post-test inspections were carried out to evaluate the internal flame propagation after removing the top layer of plaster. The study confirms that polystyrene foam EPS 70 with graphite additives meets the fire safety requirements of DIN 4102-20, which suggests that it can be used more widely in building facades to improve fire safety in residential and commercial buildings. The study highlights the importance of adhering to installation standards, emphasizing the need for accurate installation practices. It also encourages the development of new composite materials with similar or improved fire safety properties, laying the foundation for further innovations in fire-resistant materials

Size Effect of Graphite Nanosheet-Induced Anti-Corrosion of Hydrophobic Epoxy Coatings

In order to broaden the selectivity of graphite nanosheet additives on epoxy resin-based coatings and verify the size effect, this work aims to dope graphite nanosheets of different sizes into the three-dimensional structure produced by cross-linking and curing epoxy resin and polyamide resin. In addition, a micro-nano level secondary structure and a surface with special roughness are constructed to obtain the composite epoxy hydrophobic coating. The influence of the size effect of graphite nanosheets on the hydrophobic performance and corrosion resistance of the coating is summarized as well. Among them, the optimized doping size (2.2 μm) of graphite nanosheets in the epoxy coating showed the largest impedance arc of 2.58 × 108 Ω cm2, which could form an excellent nano-network covering the micropores to impede the diffusion of corrosive medium. Through simulation calculation analysis, we also found that the edge site of graphene is more effective in capturing H2O and O2; therefore, a smaller size of graphene with a large edge can be more favorable. This work will be used as a reference for the industrial application of graphite anti-corrosive coating.