Graphite Platelets Research Articles

Static and impact performance of engineered cementitious composites with hybrid graphite nano platelets modified PVA and shape memory alloy fibres

Polyvinyl alcohol (PVA) fibre has been widely adopted to produce engineered cementitious composites (ECC), the overall performance of which is highly dependent on the fibre surface characteristics. The traditional approach to improve PVA fibre bridging ability is to tailor the surrounding matrix properties. However, this common practice need to do a lot of laborious experimental works, and thus it has limited efficiency and practicality. Therefore, special surface treatments on PVA fibres are required to create synergistic interactions between fibre and surrounding matrix to retain excellent tensile ductility and better mechanical performance. This paper proposes a novel treatment method for PVA fibres using nano graphite platelets to modify the PVA fibre surface and improve the mechanical properties of PVA fibre reinforced ECC. To evaluate the effectiveness of such treatment, a systematic experimental study was performed. Firstly, static contact angle measurements, scanning electron microscopy and atomic force microscopy were employed to monitor the wettability and physical changes on the fibre surface. Then, the static and dynamic mechanical properties as well as microstructural characteristics of ECC with hybrid modified PVA fibres (2 vol%) and shape memory alloy (SMA) fibres (0.25 vol%, 0.50 vol% and 1 vol%) were examined. The results indicate that the graphite nanoplatelets treated PVA fibres (GPVA) exhibit high hydrophobicity and surface roughness providing steady-state crack propagation, which is a necessary condition to ensure multiple cracking and improving the higher fibre bridging complementary energy. This is evidenced by significantly densified the transition zone between the graphite treated PVA fibres and the matrix, and improved the flexural tensile strength and the toughness. The calculated surface roughness of 28.86 μm and lots of peaks and valleys on the 3D topographical micrographs of the cracking faces confirmed that 1 SMA-2 GPVA specimen efficiently participated in transferring stress through the composite, leading to a greater vertical impact reaction force. Finally, the structure-property relation for flexural versus fracture behaviour and the effectiveness of SMA fibres on the crack-healing feature of the composites were studied by using digitized fractal analysis and through the heat treatment. The disseminated fracture energy (Ws/Gf) value reached 130 and the crack sizes the crack size decreased by 34 %, which were much better than that of the reference composites. The nano treatment of PVA fibres in ECC provides an innovative and sustainable solution for engineering structures with requirement of high tensile ductility and high impact resistance, e.g., military infrastructure and industrial floors.

Carbons‐to‐SiOx Contact Ratio for Faster Graphite/SiOx Electrode Formulation Optimization

AbstractThe optimization of composite electrodes based on a silicon/graphite mixture is essential for battery performance, but is complex due to the multiplicity of parameters that come into play. In this direction, we propose to adjust the amount of surface area developed by all the graphitic carbons, including the conductive additive to that of the silicon phase. This concept, introduced here as graphite and carbon‐to‐silicon contact ratio, is based on the importance of contacts on the mechanical, electrical and electrochemical properties of composite electrodes. The validity of this new formulation parameter is studied here for SiOx/Graphite composite electrodes, which differ in the proportions of two types of graphite (spherical or platelet form) and for different types of conductive additives (carbon black and carbon nanotubes). An optimal contact ratio is determined, allowing at the same time the best gravimetric and volumetric capacities, the best cyclability, and the best power performance.

Electrically Conductive Natural Rubber Composite Films Reinforced with Graphite Platelets.

Green natural rubber (NR) composites reinforced with synthetic graphite platelets, using alginate as a thickening and dispersing agent, were successfully developed to improve mechanical properties, chemical resistance, and electrical conductivity. The fabrication was performed using a latex aqueous microdispersion process. The research demonstrated the effective incorporation of graphite platelets into the NR matrix up to 60 parts per hundred rubbers (phr) without causing agglomeration or phase separation. Graphite incorporation significantly improved the mechanical strength of the composite films. NR with 60 phr of graphite exhibited the highest Young's modulus of 12.3 MPa, roughly 100 times that of the neat NR film. The reinforcement also strongly improved the hydrophilicity of the composite films, resulting in a higher initial water absorption rate compared to the neat NR film. Moreover, the incorporation of graphite significantly improved the chemical resistance of the composite films against nonpolar solvents, such as toluene. The composite films exhibited biodegradability at about 21% to 30% after 90 days in soil. The electrical conductivity of the composite films was considerably enhanced up to 2.18 × 10-4 S/cm at a graphite loading of 60 phr. According to the improved properties, the developed composites have potential applications in electronic substrates.

Enhancing interfacial adhesion and electrical conductivity of steel/polymer composites via molecular adhesion for sustainable structural materials

Steel/Polymer Composites (SPCs) represent a promising class of materials that combine the strengths of steel and polymers, making them ideal candidates for various structural applications. Notably, they offer heat shielding properties, energy absorption, reduced noise, vibration, and harshness, high rigidity, as well as weight reduction benefits. Achieving robust interfacial adhesion between steel and polymer, while maintaining electrical conductivity for welding, presents a significant challenge in SPC development. Conventional SPCs relying on physical adhesion through polymer coating are susceptible to environmental factors, compromising durability. To address this, novel adhesion concepts are explored, leveraging molecular-level interactions. In this study, we investigate the adhesion between electro-galvanized iron steel treated with a phosphate conversion coating and four polymers: polyethylene (PE), acrylonitrile-butadiene-styrene (ABS), Nylon 6, and Polyketone. The primary amines are anchored on the steel surface using 3-aminopropyltriethoxysilane (APTES), while maleic anhydride (MA) is introduced onto the polymer chains. The adhesion strength of the SPCs dramatically increased from 0 to 11.5 MPa for PE, from 1.5 to 11.1 MPa for ABS, from 12.7 to 14.1 MPa for Nylon 6 and from 7.1 to 14.2 for Polyketone. In particular, the adhesion strength of Nylon 6 was maintained at 89.0% for 7 d aging despite moisture absorption being fatal to interfacial adhesion. The findings suggest two presumable interactions at the steel/polymer interface, including molecular adhesion. In order to enable spot welding of these SPCs, mechano-chemistry was employed to embed carbon-based graphitic materials within the plastic matrix, enhancing electrical conductivity. The selection of Polyketone as a core material facilitates the adsorption of conductive fillers, such as Carbon Nanotubes (CNT) and Graphite Platelets (GPs). Graphite Nanoplatelets-Polyketone, with smaller lateral dimensions (50 ∼ 100 nm), exhibits the highest electrical conductivity of 207.5 S/cm. Scanning Electron Microscopy (SEM) confirms effective filler adsorption without pre-treatment. This comprehensive study enhances our understanding of SPC development, shedding light on innovative approaches to achieve robust adhesion, electrical conductivity, and suitability for spot welding applications.

Breaking graphite through a ball-milling process: the thermal conductivity and mechanical properties of polyethylene composites.

Exfoliated graphite platelets (EGPs) have attracted extensive attention owing to their exceptional combinations of thermal conductivity and mechanical properties. Mechanical exfoliation is a facile and high-throughput approach to produce single-layer or few-layer graphite platelets. Herein, octadecylamine (ODA)-grafted EGP (ODA@EGP) and subsequent polyethylene/ODA@EGP (PE/ODA@EGP) composites with different contents of ODA@EGPs were successfully prepared via ball-milling and melt-mixing methods, respectively. The thermal conductivity, crystallinity, and mechanical properties of the composites were investigated using tensile tests, the hot-wire method, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis, and thermogravimetric analysis (TGA). The results demonstrated that the thermal conductivity, mechanical properties, and thermal stability of the composites can be improved by regulating the additive contents of ODA@EGPs. When the content of ODA@EGPs was 10 wt%, the thermal conductivity of the composite reached up to 1.276 W (m-1 K-1), which is 216% higher than that of bare PE, while the tensile strength of the composite was 38.4% higher than that of PE. Additionally, thermal decomposition temperature increased by 16.2 °C. Therefore, the PE/ODA@EGP nanocomposites have great application potential in thermal management.

Upcycling end-of-life bricks in high-performance one-part alkali-activated materials

One-part alkali-activated materials (AAMs) can preserve natural resources and lower embodied carbon of the built environment by accommodating various wastes, industrial by-products, and end-of-life materials in their composition. This study investigates the feasibility of using end-of-life bricks in two physical states, powder and aggregate, to partially replace fly ash precursor and natural aggregate in AAMs, respectively. The mechanical characteristics, microstructure, water absorption, freeze-thaw and fire resistance of the modified AAMs were evaluated. The effect of adding different ratios of nano graphite platelets was also investigated. Results showed that brick-based one-part AAMs can achieve mechanical properties, pore structure, water absorption and freeze-thaw resistance comparable to fly ash-based AAM while having 65% better fire resistivity. Incorporating bricks as aggregate resulted in a maximum improvement of 17% and 27% in the AAMs' compressive and flexural strength levels, respectively, and a general enhancement in the freeze-thaw resistance with showing no reduction in compressive strength after exposure to elevated temperature. Incorporating 0.1 wt% nano-graphite further enhanced flexural strength by 30%, decreased water absorption by 18% and improved freeze-thaw resistance compared to the mix without nano-graphite. Moreover, adding up to 0.5% nano-graphite enhanced the fire resistivity of the composite, allowing it to exhibit 19% better strength performance than before exposure.

Nano graphite platelets/Cu (BDC) MOF coating on polyurethane sponge: A superhydrophobic self-extinguishing adsorbent for static and continuous oil/water separation

The discharge of toxic organic solvents and industrial oil into water is one of the major problems that threaten marine ecology and human health. In this work, a flexible superhydrophobic/superoleophilic polyurethane (PU) sponge was modified by decorating Cu-benzene dicarboxylic acid metal-organic framework (Cu (BDC) MOF) as a flame retardant and nano graphite platelets (NGPs) as a superhydrophobic agent. These materials were attached to the sponge skeleton by poly (styrene-co-butyl acrylate). The PU-Cu (BDC)-NGPs sponge showed high thermal, mechanical, and chemical stability. Moreover, this composite possessed excellent oil/water separation efficiency. The prepared composite showed excellent superhydrophobicity with a water contact angle of 154° and possessed self-extinguishing properties with a limiting oxygen index (LOI) of 24.46%. The oil adsorption capacity at a static state and oil separation efficiency at a continuous oil/water separation process for PU-Cu (BDC)-NGPs sponge were 43.5–132 g/g and 96%, respectively. Moreover, PU-Cu (BDC)-NGPs sponge had excellent stability in harsh conditions and exhibited good compressibility and reusability. Overall, the Cu (BDC) MOF-NGPs coated PU sponge can be a highly efficient sorbent with durability and flame retardancy.

Fabrication and Characterization of ZrB2 Ceramic in Presence of Graphite Platelet and SiC

Fabrication and Characterization of ZrB2 Ceramic in Presence of Graphite Platelet and SiC

Defining graphenic crystallites in disordered carbon: Moving beyond the platelet model

We develop a picture of graphenic crystallites within disordered carbons that goes beyond the traditional model of graphitic platelets at random orientations. Using large atomistic structures containing one million atoms, we redefine the meaning of the quantity La extracted from X-ray diffraction (XRD) patterns. Two complimentary approaches are used to measure the size of graphenic crystallites, which are defined as regions of regularly arranged hexagons. Firstly, we calculate the X-ray diffraction pattern directly from the atomistic coordinates of the structures and analyse them following a typical experimental process. Second, the graphenic crystallites are identified from a direct geometrical approach. By mapping the structure directly, we replace the idealised picture of the crystallite with a more realistic representation of the material and provide a well-defined interpretation for La measurements of disordered carbon. A key insight is that the size distribution is skewed heavily towards small fragments, with more than 75% of crystallites smaller than half of La.

Competitive Formation Zones in Carbon Nanotube Float-Catalysis Synthesis: Growth in Length vs. Growth Suppression.

Catalytic synthesis of carbon nanotubes (CNT) produces numerous various byproducts such as soot, graphite platelets, catalyst nanoparticles, etc. Identification of the byproduct formation mechanisms would help develop routes to more selective synthesis of better carbon-based materials. This work reports on the identification of the formation zone and conditions for rather unusual closed multishell carbon nanocapsules in a reactor for float-catalysis synthesis of longer CNT. Structural investigation of the formed nanocapsule material along with computational fluid dynamics (CFD) simulations of the reactor suggested a nanocapsule formation mechanism, in which CNT embryos are suppressed in growth by the in-reactor turbulence. By means of TEM and FFT investigation, it is found that differently oriented single crystals of γ–Fe2O3, which do not have clear connections with each other, determine a spherical surface. The carbon atoms that seep through these joints do not form crystalline graphite layers. The resulting additional product in the form of graphene-coated (γ–Fe/Fe3C)/γ–Fe2O3 nanoparticles can be a lightweight and effective microwave absorber.

Temperature Dependence of Electrical Resistance in Graphite Films Deposited on Glass and Low-Density Polyethylene by Spray Technology

Graphite lacquer was simply sprayed on glass and low-density polyethylene (LDPE) substrates to obtain large area films. Scanning Electron Microscopy (SEM) images, Raman spectra, X Ray Diffraction (XRD) spectra and current-voltage characteristics show that at room temperature, the as-deposited films on different substrates have similar morphological, structural and electrical properties. The morphological characterization reveals that the films are made of overlapped graphite platelets (GP), each composed of nanoplatelets with average sizes of a few tens of nanometers and about forty graphene layers. The thermoresistive properties of the GP films deposited on the different substrates and investigated in the temperature range from 20 to 120 °C show very different behaviors. For glass substrate, the resistance of the film decreases monotonically as a function of temperature by 7%; for LDPE substrate, the film resistance firstly increases more than one order of magnitude in the 20–100 °C range, then suddenly decreases to a temperature between 105 and 115 °C. These trends are related to the thermal expansion properties of the substrates and, for LDPE, also to the phase transitions occurring in the investigated temperature range, as evidenced by differential scanning calorimetry measurements.

Influence of graphite platelets with and without SiC on the densification and fracture toughness of ZrB2 ceramic sintered by SPS

Influence of graphite platelets with and without SiC on the densification and fracture toughness of ZrB2 ceramic sintered by SPS

Simultaneous fluorination and purification of natural block coaly graphite into fluorinated graphene with tunable fluorination degree

Fluorinated graphene (FG) holds great promise for various applications, but the cost-effective production of FG is still challenging because of the high cost of the starting material such as fluorinated graphite, graphene and graphene oxide. Herein, a novel approach to prepare FG through electrochemical exfoliation of the starting natural block coaly graphite (NBCG) mineral, followed by a hydrothermal reaction is reported. This method uses NH4F solution in the whole process as fluorinating agent to provide fluoride source and purification agent to remove impurity minerals in natural graphite. The morphology, chemical composition and microstructure of the starting NBCG, a series of fluorinated graphene oxide (FGO) samples after electrochemical exfoliation and FG samples after hydrothermal process were characterized in detail by a number of analytical techniques such as TEM, SEM, XPS, TGA, XRD and Raman. The thick and compact graphitic platelets of NBCG have a considerable decrease in the thickness and lateral size during the process, and the prepared FG consists of thin separated nanosheet with a low ash content. Moreover, this method is effective in tuning the fluorination degree of FG with tunable electrical conductivity through the control of the electrolyte concentration in the first step of electrochemical exfoliation. The formation mechanism of FG from NBCG is proposed. It reveals that the electrochemical process results in the oxidation of NBCG and the adsorption of fluorine ions, and those oxygen-containing groups are essential for the further fluorination in subsequent hydrothermal process. Overall, this method paves a way to prepare FG with a low cost due to the avoid of prerequisite of crushing, grinding and purifying procedures for NBCG.

Performance Evaluation of Cementitious Composites Incorporating Nano Graphite Platelets as Additive Carbon Material.

Nano graphite platelets (NGPs) belong to the carbon family and have a huge impact on the construction industry. NGPs are used as multi-functional fillers and have the potential to develop reinforcing within cementitious composites. In this paper, NGPs were incorporated in cementitious composites to investigate the effects of NGPs on the fresh, mechanical, durability, and microstructural properties of concrete. Five mixes were prepared with intrusion of NGPs (0%, 0.5%, 1.5%, 3%, and 5% by weight of cement). The properties studied involved workability, air content, hardened density, compressive strength, tensile strength, flexural strength, sorptivity, ultrasonic pulse velocity (UPV), water absorption, and external sulfate attack. The workability and percent air content decrease by 22.5% and 33.8%, respectively, for concrete with 5% NGPs compared to the control mix. The specimens containing 5% of NGPs revealed the hardened density, compressive, tensile, and flexural strength to increase by 11.4%, 38.5%, 31.6%, and 44.34%, respectively, compared to the control mix. The results revealed that the incorporation of 5%NGPs in cementitious composites reduces the sorptivity and water absorption by 32.2% and 73.9%, respectively, whereas, it increases the UPV value by 7.5% compared to the control mix. Furthermore, the incorporation of NGPs provided better resistance against external sulfate attacks. SEM–EDX spectroscopy was carried out to investigate its microstructural analysis.

Application of graphite platelets for heat transfer enhancement of cementitious composites containing microencapsulated phase change materials

The incorporation of microencapsulated phase change materials (MPCMs) is an effective method to increase the thermal energy storage (TES) capacity of cementitious composites. However, the thermal conductivity of cementitious composites will be reduced upon incorporation of MPCMs, which may reduce the latent heat activation of MPCMs. This study evaluated the effect of adding graphite platelets (GP) on the heat transfer performance of cement paste incorporating polystyrene/n-eicosane MPCM (CP-MPCM). The main purpose is to enhance the thermal conductivity of CP-MPCM, thus achieving faster heat storage and release rates. The cement samples containing different proportions of MPCM and GP were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), thermal conductivity measurement, and thermal cycling test. In the thermal cycling test, the samples were heated and cooled in the same temperature range (13–60 °C) to compare their average heating and cooling durations. The results showed that the addition of 5 wt% GP enhanced the thermal conductivity of CP-MPCM by 44.5–50.1%. The heat storage and release rates of CP-MPCM were improved by up to 25.3% and 23.8%, respectively. By adding 15 wt% MPCM and 5 wt% GP, the heat storage coefficient of pure CP was increased by 55.8%. Hence, the addition of GP can improve the utilization of the latent heat capacity of MPCMs in cementitious composites.

Bio-inspired self-healing and self-sensing cementitious mortar using Bacillus subtilis immobilized on graphitic platelets

This study focuses on exploring the feasibility of immobilizing Bacillus subtilis with inert conductive Graphite nano/micro platelets (GNMPs) as the healing and sensing component of a smart mortar, respectively. The specimens are casted using variable content of GNMPs. The healing potential of smart mortar is accessed via visual inspections and mechanical recovery. Whereas, piezoresistivity of specimens incorporated with a range of GNMPs concentrations derived from theoretical percolation is analyzed under ultimate and cyclic loading to establish a correlation between strain and load with resistivity. Maximum average crack-width healing of 1.30 mm is recorded corresponding to specimens incorporated with 1.4% replacement of GNMPs. 1.5% replacement of GNMPs shows an 80.5% recovery of the compressive strength after healing. The self-sensing capacity of the composite mortar increases with increasing GNMP concentration up to 1.5%, with 1.2% replacement by GNMPs giving the highest gauge factor, making it the most strain-sensitive concentration.

Influence of nano graphite platelets on the behavior of concrete with E-waste plastic coarse aggregates

Past works have used electronic waste (E-waste) plastic as a raw material for the production of plastic aggregate to be used as a substitute for natural aggregates. However, the results have shown that the plastic aggregate reduces the strength properties of resulting concrete limiting its application to non-structural components. Nano graphite platelets (NGPs) are nanofillers that significantly improve the density and hardness of the cementitious composite due to reduction in porosity and reinforcement in microstructure. In the current study, NGPs have been utilized to increase the strength of plastic concrete. The natural coarse aggregates are partially substituted by 25% of E-waste plastic coarse aggregate. Locally available NGPs are utilized, and their structural characteristics were assessed by scanning electron microscopy (SEM), X-ray fluorescence spectroscopy (XRF), X-ray diffraction (XRD), and energy dispersive X-ray (EDX) spectroscopy. A dispersion test is carried out and a ratio of 0.6:1 (surfactant:NGPs) is found to yield maximum dispersion. Different dosages of NGPs (1%, 3%, and 5%) have been introduced into plastic concrete. This research work aims to explore the fresh, mechanical, durability, and microstructure characteristics. The mechanical properties of the cementitious composites declined with the incorporation of E-waste plastic aggregates which were significantly enhanced by incorporating NGPs. The specimens containing 25% of plastic aggregate and 5% of NGPs showed the hardened density, compressive strength, tensile strength, and flexural strength to increase by 2.16%, 13.56%, 15.53%, and 31.42%, respectively compared to the samples without NGPs. Sorptivity and ultrasonic pulse velocity values are found to decrease by 56.5% and increase by 2.53%, respectively for plastic concrete with 5% NGPs compared to the control mix. SEM-EDX spectroscopy was carried out to examine microstructure investigation and it was found that by the inclusion of NGPs in the concrete composites, the hydrated crystals stacked one over the other and became massive and thicker implying that the addition of NGPs is a promising reinforcing agent in plastic concrete.

Magnetic alignment of graphite platelets in polyimide matrix toward a flexible electronic substrate with enhanced thermal conductivity

A soft and stable substrate is an essential component for realizing flexible electronics and displays. We fabricated flexible substrate films by compositing iron oxide nanoparticle-conjugated graphite platelets (mGPs) with polyimide (PI). We controlled the microstructure of the composite film by aligning the mGPs with a low magnetic field in the vertical direction during the PI curing process. After magnetic alignment, the through-plane thermal conductivity of the mGP-PI composite film was enhanced by a maximum of 132% with 20 wt% mGP content compared to that without magnetic alignment. The thermal conductivity of the composite film was constant up to 300 °C and increased with the filler content, reaching 11.3 W/mK with 60 wt% mGP content. In addition, the coefficient of thermal expansion (CTE) of the composite film along the in-plane direction decreased with increasing filler content, reaching approximately 9 ppm/K with 40 wt% mGP content. This work demonstrates a pathway toward a flexible electronics substrate with high thermal conductivity, high thermal stability, and low CTE.

Review of Self-sensing Capability of Ultra-high Performance Concrete

Ultra-high performance concrete (UHPC) has the inherent potential to self-sensing capability due to its inclusion of steel fibers or other electrically conductive materials. Many studies have investigated the electrical and piezoresistive properties of UHPC. With the incorporation of micro steel fibers, carbon nanotubes, carbon nanofibrils, or nano graphite platelets, it opens up great potential to allow UHPC to effectively sense stress, strain, and crack damage. Therefore, the UHPC-based structures can achieve the functionality of structure health monitoring (SHM). This article reviews the recent advances in self-sensing capability of various UHPC-based materials with the focus on sensing capability and mechanisms. Future applications and challenges are also discussed.

Intercalation of barium into graphite by molten salts method: Synthesis of massive samples for crystal structure determination of BaC6

A solid-liquid method is used to synthesize the first stage bulk BaC6 graphite intercalation compound (GIC). This way of synthesis allows the preparation of bulk and massive samples useful for crystal structure determination. Through a eutectic medium LiCl–KCl, and by submerging a graphite platelet in barium-molten solution at 450 °C for several days, the bulk BaC6 compound is obtained and X-ray diffraction investigations allowed a complete structural study. The collected data certify that BaC6 crystallizes in the hexagonal P63/mmc space group with the following parameters a = b = 430.6 pm and c = 1058.2 pm.