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Synthetic graphite of complex fractional composition was mixed with phenolic resin as a binder and pore-forming component. The mixtures were pressed and subsequently heat-treated to obtain porous matrices. The structural transformations of phenolic resin by heating up to 900 °C in oxygen and inert gas media were studied and the patterns of amorphization of fixed carbon formed on the walls of the pore system during carbonization were investigated. We found regularities in the changes in matrix volume density in the function of the open porosity and the average pore diameter. It is shown that, in order to obtain graphitized carbon matrices with a density of 1 g/cm3 and an open porosity of at least 50%, it is necessary to introduce no more than 20% of phenolic resin into the molding powder with an equal content of 60, 100 and 250 μm graphite fractions. This allows for high intensity and completeness of bulk silicon infiltration. [ABSTRACT FROM AUTHOR]

Mechanical qualities play a critical role in increasing the industrial applications of carbon-carbon composite materials as their porosity determines the strength of the material. In this study, carbon blocks with improved packing properties were produced by controlling various particle size distributions of coke particles. Particle-size diversity and geometric packing structure favorably affected the packing properties of the powder. Coke samples with tap densities up to 1.258 g/mL were prepared by controlling the size distribution of the coke particles. The porosity of the carbon block was calculated using three density definitions. The closed pores were reduced by up to 13.68% through the packing density of the particles, and the open pores were controlled by the coke/pitch mixing conditions regardless of the tap density. The carbon block showed a total porosity of 21.61% and a maximum compressive strength of 131 MPa by controlling the tap density of the coke. The proposed technique will be useful in various industries that require appropriate tap density control and will improve the compressive strength of composite materials. [ABSTRACT FROM AUTHOR]

The rheological behavior of anode slurries for lithium-ion batteries, containing both natural and synthetic graphite as active material, was investigated with a focus on the different graphite morphologies. When the solid content is low, slurries containing synthetic graphite with a discotic shape display greater viscoelasticity than slurries containing natural graphite with a relatively more spherical shape. This result is attributed to the anisotropic geometry and interparticle force of the synthetic graphite. When the solid content is high, slurries comprising synthetic graphite exhibit lower viscoelasticity than slurries containing natural graphite. Tap density and sedimentation experiments reveal that, due to discotic shape and surface-to-surface attraction, synthetic graphite aggregates to a more densely packed aggregate than natural graphite. Consequently, in conditions of high solid contents where graphite has a greater chance of formation of densely packed aggregates, it is expected that synthetic graphite will have a more compact aggregate structure and a smaller effective volume. The smaller viscoelasticity of synthetic graphite slurries at more concentrated regions, where the effective volume of clusters plays more important role than in dilute regions, is attributed to the surface-to-surface aggregated structure of the synthetic graphite and the resulting small effective volume. Although the effective volume fraction of the graphite aggregates is reduced, slurries made of synthetic graphite demonstrate significant strain stiffening. Our findings suggest that the strain stiffening observed may originate from the anisotropic morphology, which possesses a significant surface area and is accompanied by jamming and high friction. [ABSTRACT FROM AUTHOR]

Current hydrogen and carbon production technologies emit massive amounts of CO 2 that threaten Earth's climate stability. Here, a new solar-thermal methane pyrolysis process involving flow through a fibrous carbon medium to produce hydrogen gas and high-value graphitic carbon product is presented and experimentally quantified. A 10 kW e solar simulator is used to instigate the methane decomposition reaction with direct irradiation in a custom solar reactor. From localized solar heating of fibrous medium, the process reaches steady-state thermal and chemical operation from room temperature within the first minute of irradiation. Additionally, no measurable carbon deposition occurs outside the fibrous medium, leaving the graphitic product in a form readily extractable from the solar reactor. Parametric variations of methane inlet flow rate (10–2000 sccm), solar power (0.92–2.49 kW) and peak flux (1.3–3.5 MW/m2), operating pressure (1.33–40 kPa), and medium thickness (0.36–9.6 mm) are presented, with methane conversion varying from 22% to 96%. [Display omitted] • New methane pyrolysis process in a fibrous medium directly irradiated by solar power. • Co-production of hydrogen and high-quality graphite with zero CO 2 emissions. • Steady thermochemical conditions from room temperature within first minute. • All theoretical carbon product collected in a readily extractable form. • Parametric effects of flow rate, solar power, pressure, and medium thickness reported. [ABSTRACT FROM AUTHOR]

In this paper, a method for optimizing the mixing ratio of filler coke and binder for high-strength carbon–carbon composites is proposed. Particle size distribution, specific surface area, and true density were analyzed to characterize the filler properties. The optimum binder mixing ratio was experimentally determined based on the filler properties. As the filler particle size was decreased, a higher binder mixing ratio was required to enhance the mechanical strength of the composite. When the d50 particle size of the filler was 62.13 and 27.10 µm, the required binder mixing ratios were 25 and 30 vol.%, respectively. From this result, the interaction index, which quantifies the interaction between the coke and binder during carbonization, was deduced. The interaction index had a higher correlation coefficient with the compressive strength than that of the porosity. Therefore, the interaction index can be used in predicting the mechanical strength of carbon blocks and optimizing their binder mixing ratios. Furthermore, as it is calculated from the carbonization of blocks without additional analysis, the interaction index can be easily used in industrial applications. [ABSTRACT FROM AUTHOR]

Graphene oxide (GO) is of great interest due to its unique structure and properties and potential applications, including water purification. In this work, we report the synthesis of GO samples with different oxidation degree from two different sources of graphite using Hummers method. Natural flake graphite with a high degree of crystallinity, and synthetic fine powder graphite were used. All produced materials were characterized by CHNS analysis, X-Ray Diffractive analysis (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Raman spectroscopy, Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM). It was shown that the oxidation process for natural and synthetic graphite sources proceeds in different ways. The factors, affecting for the structure and properties of GO are the degree of crystallinity and the lateral size of the graphite flakes. The sorption activity of underoxidized, normally oxidized and overoxidized GO was compared toward the methylene blue (MB) dye in aqueous solution. The most efficient sorption was registered for GO produced from synthetic graphite with the use of 2.0 and 4.5 wt. eq. KMnO 4. The sorbents removed 94 % and 100 % of MB from the solution, respectively, in approximately 10 min. Our results reveal that the structure and sorption properties of GO can be tuned by varying the oxidation degree as well as the graphite source, which may open the way to new developments in the GO-based materials applications. [Display omitted] • The oxidation process for natural and synthetic graphite sources proceeds in different ways. • The determining factors are the degree of crystallinity and the lateral size of graphite flakes. • Effect of different degrees of GO oxidation on properties and adsorption activity was studied. • Underoxidized and overoxidized GO samples obtained from synthetic graphite showed an excellent MB removal activity. [ABSTRACT FROM AUTHOR]

Abstract Graphite has been used in a wide range of applications since the discovery due to its great chemical stability, excellent electrical conductivity, availability, and ease of processing. However, the synthesis of graphite materials still remains energy‐intensive as they are usually produced through a high‐temperature treatment (>3000°C). Herein, we introduce a molten salt electrochemical approach utilizing carbon dioxide (CO2) or amorphous carbons as raw precursors for graphite synthesis. With the assistance of molten salts, the processes can be conducted at moderate temperatures (700–850°C). The mechanisms of the electrochemical conversion of CO2 and amorphous carbons into graphitic materials are presented. Furthermore, the factors that affect the graphitization degree of the prepared graphitic products, such as molten salt composition, working temperature, cell voltage, additives, and electrodes, are discussed. The energy storage applications of these graphitic carbons in batteries and supercapacitors are also summarized. Moreover, the energy consumption and cost estimation of the processes are reviewed, which provides perspectives on the large‐scale synthesis of graphitic carbons using this molten salt electrochemical strategy.

Abstract Synthetic graphite is produced by a heat treatment process using a carbon precursor (pitch, coke), but it is difficult to produce synthetic graphite of high quality due to the high-temperature process (minimum 3000 °C). Elements used as additive to lower temperature the graphitic process include boron, phosphorus, and nitrogen. Boron is known as a graphitization additive, because it accelerates the homogeneous continuous graphitization process of the entire carbon without any formation of specific carbon components such as graphite. In this study, various amounts of boron and PFO (pyrolysis fuel oil, carbon precursor) were used in an attempt to reveal the boron additive effect. Pitch was produced using a boric acid and pyrolysis fuel oil (PFO), and high-temperature carbonization was carried out at 2600 °C. As a result, synthetic graphite exhibiting high crystallinity at a relatively low temperature was produced. The electrochemical performance of several boron-doped and non-doped carbon materials with different structures as anodes in lithium-ion batteries was investigated by a structure analysis.

Global electrification of mobility and energy storage is driving an unprecedented demand for lithium‐ion batteries (LIBs) for which graphite is one of the major components. Multiple prior studies have attempted to assess the environmental footprint of LIBs by way of life cycle analysis (LCA), and the poor quality of inventory data on the production of graphite (at various purities) has been highlighted consistently. This work reviews the available inventories used in the assessment of natural and synthetic battery‐grade graphite production, and demonstrates that some upstream, downstream, and peripheral processes—including important processes associated with mining, calcination, and other steps—are often omitted, leading to greatly underestimated impacts. It proposes a new rigid framework for comparing different graphite production routes and a corresponding indicative inventory for synthetic graphite production. This inventory is used to estimate the global warming potential and energy demand of synthetic graphite, yielding results of 13.8 kgCO2‐eq/kg and 45.9 MJ/kg, respectively, suggesting that prior literature may have underestimated these results by a factor of two or more. The work concludes by highlighting the need to evaluate a broader suite of applicable impact categories and to fully account for the full suite of by‐and co‐products in future LCAs. [ABSTRACT FROM AUTHOR]

Polyamide 4.6 has excellent properties, such as high temperature resistance, crystallinity, fatigue resistance, melting temperature, excellent creep resistance, toughness, and good wear properties, but low thermal conductivity values. For this reason, its use in thermal applications has been limited. In this study, its use in thermal applications can be increased by increasing its thermal conductivity with carbon‐based fillers and reinforcements added to the PA46 structure. The aim of this study is to examine the carbon fiber (CF), synthetic graphite (SG) and graphene nanoplatelet (G) loading on the mechanical, thermal, physical, and electrical properties of polyamide 4.6, which are produced using co‐ rotating twin‐screw extrusion. Tensile and flexural strength of polyamide 4.6 increased with the addition of CF at all weight fractions. The highest electrical conductivity value was measured as 4.01 S/cm in PA46‐20CF‐20SG‐3G composite material. The highest in‐plane thermal conductivity achieved in this study at 20 wt% CF, 20 wt% synthetic graphite, and 5 wt% graphene loading was 20.43 W/mK. However, the highest through‐plane thermal conductivity value was obtained to be 4.19 W/mK at 20 wt% CF. Graphene and synthetic graphite are more efficient to increase the in‐plane thermal conductivity, while CF is more efficient to increase the through‐plane thermal conductivity. [ABSTRACT FROM AUTHOR]

The exfoliation process via the modified Hummers' method has been well established as the main method to produce graphene oxide. Previously, however, the process only involved commercial graphite as a precursor material for the production of graphene oxide. In this study, synthetic graphite has been successfully produced using oil palm trunk waste as potential carbon sources. Different values of the heating parameter, i.e, 500, 800, and 1000 °C, have been applied. The heating also varied from 5 to 10°/min and to 20°/min to control the heating condition. After heating treatment, the samples were characterised using X-ray diffraction and analysed by X'Pert HighScore Plus software. The graphite nature of the synthetic graphite produced was additionally supported by Raman analysis. Morphological study was carried out using a scanning electron microscope. Based on the analysis, the optimum processing parameters were found, namely the temperature of 800°C and the heating rate of 20°/min. The as-produced synthetic graphite was then subjected to further exfoliation to form graphene oxide via the modification of Hummers' method. The graphene oxide produced was then characterised to confirm its graphitic nature. [ABSTRACT FROM AUTHOR]

Hard carbon is difficult to prepare as high-crystallinity synthetic graphite even with graphitization (over 2400 °C), so only soft carbon has been used as a raw material for the preparation of synthetic graphite. Therefore, the selection of raw materials for synthetic graphite preparation is limited. In this study, synthetic graphite was prepared from hard carbon-based carbon black (HCCB) to overcome the issue of the limited selection of synthetic graphite raw materials. Synthetic graphite was prepared by a 3-step heat treatment from a mixture of HCCB and Si. SiC was synthesized from HCCB by a first heat treatment, and unreacted HCCB was removed through a second heat treatment. In a third heat treatment, synthetic graphite was prepared by removing Si from SiC. The prepared synthetic graphite had a high-crystallinity and few defects, and the powder electrical conductivity was approximately 22.7 times higher than that of graphitized HCCB. The introduced new method is expected to induce diversification of raw materials for the preparation of synthetic graphite, thereby solving the problems of the traditional preparation method. [ABSTRACT FROM AUTHOR]

Even partial replacement of graphite in the anode of lithium-ion batteries with silicon can significantly increase their specific energy. But the issue is the insufficient life cycle of such batteries due to the accelerated degradation of the liquid organic electrolyte with traditional lithium hexafluorophosphate, especially at elevated temperatures. The subject of discussions and further research are the processes involving a natural oxide layer on the surface of silicon in the manufacture and electrochemical litiation–delitiation of Si-containing electrodes. Among the most promising areas for solving the issues of practical application of silicon are new additives to the electrolyte and polymeric binders for electrode masses. This paper demonstrates the capability of trimethylsilylisocyanate (with aminosilane and isocyanate functional groups) as an additive to a liquid organic electrolyte (LiPF6 / fluoroethylene carbonate + ethyl methyl carbonate + vinylene carbonate + ethylene sulfite) to scavenge the reactive HF and PF5 species that alleviates the thermal decomposition of fluoroethylene carbonate at elevated temperatures. This makes it possible to increase the electrochemical parameters of half-cells with a hybrid graphite–nanosilicon working electrode when using water-based binders – carboxymethylcellulose and styrene-butadiene rubber. The addition of trimethylsilylisocyanate in the electrolyte significantly improves the reversible capacity of hybrid electrodes and reduces the accumulated irreversible capacity during prolonged cycling at normal temperature and after exposure at 50 °C, therefore to be effective for use in high-energy lithium-ion batteries. Even partial replacement of graphite in the anode of lithium-ion batteries with silicon can significantly increase their specific energy. But the issue is the insufficient life cycle of such batteries due to the accelerated degradation of the liquid organic electrolyte with traditional lithium hexafluorophosphate, especially at elevated temperatures. The subject of discussions and further research are the processes involving a natural oxide layer on the surface of silicon in the manufacture and electrochemical litiation–delitiation of Si-containing electrodes. Among the most promising areas for solving the issues of practical application of silicon are new additives to the electrolyte and polymeric binders for electrode masses. This paper demonstrates the capability of trimethylsilylisocyanate (with aminosilane and isocyanate functional groups) as an additive to a liquid organic electrolyte (LiPF6 / fluoroethylene carbonate + ethyl methyl carbonate + vinylene carbonate + ethylene sulfite) to scavenge the reactive HF and PF5 species that alleviates the thermal decomposition of fluoroethylene carbonate at elevated temperatures. This makes it possible to increase the electrochemical parameters of half-cells with a hybrid graphite–nanosilicon working electrode when using water-based binders – carboxymethylcellulose and styrene-butadiene rubber. The addition of trimethylsilylisocyanate in the electrolyte significantly improves the reversible capacity of hybrid electrodes and reduces the accumulated irreversible capacity during prolonged cycling at normal temperature and after exposure at 50 °C, therefore to be effective for use in high-energy lithium-ion batteries. [ABSTRACT FROM AUTHOR]

The crystalline and porous structure of pitch coke, petroleum coke, and shale coke for use as filler in the production of carbon materials is considered. Information is presented regarding the influence of the structure on the properties of the coke and the materials in which it is used as filler. The change in structure and properties of the coke on heat treatment is determined, over a broad temperature range. [ABSTRACT FROM AUTHOR]

A special characteristic of the coal bottom ash is the content of unburned carbon, due to incomplete combustion in the boiler furnace. A special, multi-objective procedure for separation of ash particles containing unburned carbon was developed with the purpose of obtaining synthetic graphite and it was presented in the first part of the paper. In order to achieve full recycling of the ash landfill content, various secondary waste materials resulting from separation and concentration phases of the process flow must be further processed and sorted in order to ensure properties that guarantee recyclability. The process flow presented incorporates the graphitization process flow in such way that all secondary waste fractions can be recycled in various directions. The fix carbon content (FCC) and the mass breakdown weight (MBW) were determined for each separation process in order to choose the optimal process flow. [ABSTRACT FROM AUTHOR]

Ash dump sites -- landfills -- contain an aqueous mixture of bottom (BA) ash and fly ash (FA) accumulated over time in artificial pond-like structures. The content of the ash landfills has complex and non-homogenous properties, which limit drastically the applicability of complete recycling procedures aiming to landfill reclamation. The authors propose a technology to separate various components of the mixture depending on desired recyclability characteristic. A special characteristic of the BA component is the content of unburned carbon, due to incomplete combustion in the boiler furnace. A special, multi-objective procedure for separation of ash particles containing unburned carbon was developed with the purpose of obtaining synthetic graphite. The first part of the paper presents the methodology used to concentrate the unburned carbon, the results being analised in the second part of the paper. [ABSTRACT FROM AUTHOR]

The aim of this work was to search the colloidal systems characterized by maximal effects of water interaction with a solid surface and micro-coagulation, as well development of control methods of thixotropic properties, by addition of solid and liquid hydrophobic compounds into the colloidal systems. Water state and its thermodynamic characteristics, namely the values of free interfacial energy for concentrated colloidal systems based on hydrated blends of hydrophobic compounds (polymethylsiloxane, PMS and methylated nanosilica AM1) and hydrophilic nanosilica A-300, were studied using low-temperature 1H NMR spectroscopy and electron microscopy. It was established that the free interfacial energy of water, determining the thixotropic properties of the concentrated suspensions under condition of great hydration, is firstly affected by the structure of inter-particulate space, especially by the nanocoagulation effects and influence of a surface on the formation of the hydrogen bonds network in the adsorption layer. For the blend with A-300 and AM1 (1:1 w/w), the free surface energy of interaction with water is nearly ten times greater than that for the initial silicas alone. However, the micro-coagulation effects are poorly visible in microscopic images because these oxides are composed of similar nanoparticles. Similar effects of enhancement of the free surface energy are observed for a blend with A-300 and PMS. For this blend, the microcoagulation effect is observed in microscopic images. It is maximal for the blend prepared without strong mechanical loading. PMS has a twice greater surface area than that of A-300. Therefore, water filling voids in PMS aggregates forms clusters of smaller sizes than that bound in A-300. However, hydrophilicity or hydrophobicity is not a predominant factor determining the free surface energy of bound water. If strongly hydrated treated powders of PMS (or AM1) and A-300 are placed into a hydrophobic medium with weakly polar CDCl3 that this solvent could diffuse into hydrophobic component and displace water from narrow interparticle voids toward larger ones. However, this effect is much weaker for a hydrophilic component with A-300. These effects appear in a strong dependence of the γS value on the type of the dispersion medium for PMS and a weak dependence for A-300. The stronger the decreasing effects of a hydrophobic liquid onto the γS value, the stronger is diminution of the thixotropic properties on the composites. The blends of hydrophobic and hydrophilic powders with the bulk density < 0.2 g/cm3 are most perspective thixotropic compositions since they demonstrate the maximal values of γS and a strong microcoagulation effect. [ABSTRACT FROM AUTHOR]

Abstract In this study, the milled carbon fibre (MCF), multi-walled carbon nanotubes (MWCNT), synthetic graphite (SG) and polypropylene (PP) were fabricated using the compression moulding technique to produce a bipolar plate. The electrical conductivity and mechanical properties of the composite materials were also investigated based on different applied compositions. The studies indicated that compositions of 5PP/11MCF/1xGNP/3SG obtained the highest mechanical performance; 30 HD at 1.3 g/cm3 due to the homogenous filler dispersion within the polymer resin. These were attributed to good electrical conductivity (3.32 S/cm) compared to 5PP/13MCF/1xGNP/2SG at 1.3 S/cm. The addition of primary filler (MCF) addition onto the composite mixture was investigated, although the electrical conductivity appeared to deteriorate. The studies also reported that the composite mixture was able to withstand high-temperature application (~ 400 °C). The results obtained from this study revealed that the different filler geometry would results in different material performance. Therefore, it is important to be discussed especially in high-temperature bipolar plate applications. [ABSTRACT FROM AUTHOR]

Abstract In the present research, mechanical properties of silicon carbide sintered with four carbon forms as a sintering aid were examined. As the source of carbon, the following substrates were used: multilayer graphene (MLG), carbon black, highly oriented pyrolytic graphite (HOPG) and synthetic graphite. The sinters were prepared with the use of powder metallurgy technique and consolidated at 1900 °C using the Spark Plasma Sintering (SPS) method. The influence of carbon form on mechanical properties, such as microhardness, hardness, fracture toughness, and elastic properties such as Young's modulus was investigated. Transmission electron microscope (TEM) analysis of the obtained sinters was also performed. Differences between mechanical properties were observed for samples with varied forms of carbon. An analysis of the obtained results shows that the form of carbon can determine the mechanical properties of silicon carbide and generate significant differences in hardness and fracture toughness despite the similarities in the microstructure. [ABSTRACT FROM AUTHOR]

Polypropylene (PP) was filled with synthetic graphite (SG) and graphene nanoplatelets (G) at different weight fractions. Composites were prepared by the melt mixing process by using a co‐rotating twin screw extruder. Mechanical tests were carried out to determine tensile and flexural properties of composites. Dynamic Mechanical Analysis of composites was performed to determine their thermo‐mechanical properties, such as storage modulus and loss modulus. Scanning Electron Microscopy was used to observe the fracture surfaces of the composites after tensile tests. The effect of SG and G on thermal properties such as melting and crystallization temperature, thermal conductivity, thermal stability, and coefficient of thermal expansion of PP was investigated. Tensile strength and flexural strength of PP increased with the addition of 10 wt% SG. The highest thermal conductivity achieved in this study at 50 wt% SG and 3 wt% G loading was 4.6 W/mK. POLYM. COMPOS., 40:277–287, 2019. © 2018 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

Abstract We report the results of a simulation of the laser-induced breakdown spectra of graphite and synthetic shergottite glass in an atmosphere similar to that of Mars using a 1-D, Lagrangian hydrodynamic model, a spherical geometry description of the laser ablation and plume expansion and a local thermodynamic equilibrium (LTE) approach for the emission spectra. We compare the LIBS spectra of two calibration targets on board of the Curiosity rover to the simulated ones calculated under nominally the same conditions as those encountered on Mars. The simulations provide an additional way, to laboratory based comparative studies, to better understand the effects of laser parameters and atmospheric pressures. We report on the effect of laser irradiance and ambient pressure on the electron and ion temperature, electron number density, and fluid velocity parameters characterizing the plasma. Finally, we show the effects of laser irradiance and ambient pressure on the simulated emission spectra of graphite and shergottite and compare them to those acquired by ChemCam. The agreement between the two is good, particularly for the prominent emission lines. Graphical abstract Unlabelled Image Highlights • Simulation of the LIBS spectra of graphite and synthetic shergottite glass under Mars conditions • Comparison of simulated and measured LIBS spectra under Mars ChemCam conditions • Effect of pressure and laser irradiance on LIBS spectra under Mars ChemCam conditions [ABSTRACT FROM AUTHOR]

We have prepared samples of carbon reinforced alumina ceramics with different volume fractions of synthetic graphite (0-20%) and graphene (0-4%) and measured their electrical conductivity. It has been shown that increasing the volume percent of the conductive component increases the electrical conductivity of the samples from 10-8 to 2 × 10-3 S/cm. The results have been analyzed in terms of percolation theory and tunneling conduction theory. The synthetic graphite-based samples show linear current-voltage behavior and their electrical conductivity increases by a factor of 1.4 to 2.8 in the temperature range 300-550 K, with a sharp rise above 550 K. The temperature dependences of their electrical conductivity are analyzed in terms of hopping transport and thermally induced tunneling conduction mechanisms. The conclusion is made that the conduction mechanism in the corundum-carbon ceramics differs significantly from that in polymer composite materials. [ABSTRACT FROM AUTHOR]

An earth-abundant and low cost bituminous coal was used as precursor to prepare synthetic graphite materials through preliminary carbonization coupled with further high temperature graphitization treatment at 2000–2800 °C. The microstructure characteristics of the obtained synthetic graphite materials were characterized by means of X-ray diffraction, scanning electron microscope, transmission electron microscope, Raman spectroscopy and nitrogen adsorption–desorption. The results show that the microstructures of synthetic graphite materials are strongly dependent on the graphitization temperature. The synthetic graphite graphitized at 2800 °C has perfect ordered layered structure with high graphitization degree and relatively large surface area with well-developed mesopores, which offers a favorable pathway for the electrochemical intercalation-deintercalation of lithium ions in carbon matrix. Such synthetic graphite applied as anode materials for lithium-ion batteries presents a maximum reversible capacity of 310.3 mAh·g − 1 at current rate of 0.1C and still remains as high as 143.9 mAh·g − 1 at current rate of 5C. Moreover, the synthetic graphite also exhibits superior rate capability and outstanding cycling performance with over 95.3% initial capacity retention after 100 cycles. This study demonstrates a promising feasibility for large-scale production of synthetic graphite materials from bituminous coal for high performance lithium-ion batteries. [ABSTRACT FROM AUTHOR]

To lower the carbon content but to exhibit a better thermal shock resistance with MgO-C refractories containing 14 wt% flaky graphite, a new approach, based on the addition of artificial graphite, is reported for enhancing the thermal shock resistance of such refractories with 10 wt% graphite in the present work. The addition of artificial graphite (not more than 2 wt%) has a slight influence on the flexural strength of the specimens, but apparently enhances their thermal shock resistance. In particular, the specimen containing 2 wt% artificial graphite has a higher flexural strength after thermal shocks and a relatively closer residual strength ratio as compared to the reference specimen with 14 wt% flaky graphite, as it is related with the formation of more AlN reinforced phases, decreased coefficient of thermal expansion as well as increased work of fracture. [ABSTRACT FROM AUTHOR]

The mesocopic structure features in the coke fillers and binding carbon regions of a synthetic graphite grade have been examined by high resolution transmission electron microscopy (TEM) and Raman spectroscopy. Within the fillers, the three-dimensional structure is composed of crystal laminae with the basal plane dimensions (L a ) of hundreds nanometres, and thicknesses (L c ) of tens of nanometres. These laminae have a nearly perfect graphite structure with almost parallel c-axes, but their a–b planes are orientated randomly to form a “ crazy paving ” structure. A similar structure exists in the binding carbon regions, with a smaller L a . Significantly bent laminae are widely seen in quinoline insoluble inclusions and the graphite regions developed around them. The L a values measured by TEM are consistent with estimates from the intensity ratios of the D to G Raman peak in these regions. Atomistic modelling finds that the lowest energy interfaces in the crazy paving structure comprise 5, 6 and 7 member carbon rings. The bent laminae tend to maintain the 6 member rings, but are strained elastically. We suggest that a 7 member carbon ring leaves a cavity representing an arm-chair graphite edge contributing to the Raman spectra D peak. [ABSTRACT FROM AUTHOR]

Trace amounts of edge sites in natural graphite, synthetic graphite and high-temperature treated coke are quantitatively analyzed from the numbers of hydrogen atoms and oxygen-containing functional groups at carbon edge sites. For the analysis of hydrogen content, a new analytical technique is developed. The oxygen-containing functional groups are analyzed with a highly sensitive temperature-programmed desorption (TPD) technique. These techniques allow us to estimate the trace amounts of edge sites in the range of 1–10 × 10 −4 at.% with extremely high accuracy and reveal that the concentration and the type of edges sites differ depending on the type and the particle size of these graphitized carbons. Moreover, the average sizes of graphene sheets in these carbons are estimated from the total number of edge sites. The graphene sheet size thus obtained is compared with the crystallite sizes, L a , and the average particle size, and such comparison provides deep insight into the understanding of carbon molecular structure in the graphitized carbons. [ABSTRACT FROM AUTHOR]

Single crystal Li[Ni0.5Mn0.3Co0.2]O2 materials in NMC532/artificial graphite cells have excellent long term charge-discharge cycle lifetime which greatly exceeds that of conventional NMC532 materials. There are a few patents from industry regarding the synthesis of single crystal NMC. In addition, there have only been a few reports in the academic literature showing that single crystal NMC with a grain size of ~2-5 µm having good electrochemical performance was successfully synthesized, but these workers used complex approaches. This work systematically studies the steps required to synthesize single crystal NMC materials. The key synthesis steps including the impact of the Li to transition metal ratio, sintering temperature, precursor size and sintering time are discussed. This work provides guidance for the synthesis of single crystal NMC positive electrode materials that may be suitable for lithium-ion cells with high energy density and long lifetime. [ABSTRACT FROM AUTHOR]

Natural graphite (NG) negative electrode materials can perform poorly compared to synthetic, or artificial, graphite (AG) negative electrodes in certain lithium ion cells. LiNi0.5Mn0.3Co0.2O2(NMC532)/(AG or NG) pouch cells were tested with various loadings of an electrolyte additive blend to study the effect of the graphite type as well as the formed solid electrolyte interphase (SEI). Cells underwent testing using ultra-high precision coulometry, isothermal microcalorimetry, in-situ pressure measurements, long term cycling and in-situ gas measurements. In short term experiments NMC532/AG and NMC532/NG cells showed similar coulombic efficiencies, parasitic heat flows, and gas production with large electrolyte additive loadings, but NG cells showed worse capacity retention in long-term tests. With low additive loadings NMC532/NG cells showed lower coulombic efficiency, higher capacity fade, more parasitic heat flow, and more gas production. In-situ cell stack pressure measurements showed that NMC532/NG cells irreversibly expanded during cycling while NMC532/AG cells did not. Although these results lead one to propose a simple model for the poor performance of NMC532/NG cells, NMC622/NG and NMC622/AG cells showed very different behavior in long term tests suggesting that positive/negative interactions play a strong role in governing the behavior of graphites in Li-ion cells. [ABSTRACT FROM AUTHOR]

Carbon has unique and desirable properties for use in applications such as fuel cells and batteries. The properties can vary widely depending on its structure and surface characteristics. Two types of carbon, a synthetic graphite produced from petroleum coke and an extruded graphite rod, were characterized using Raman spectroscopy and X-ray Photoelectron spectroscopy and the features were correlated with electrochemical properties of the material. The graphite rod was found to have a more disordered structure, greater sp³ character, and a greater surface oxygen content as compared to the synthetic graphite from coke. Our results show that the characteristics of electrodeposited platinum and polyaniline depend on the type of substrate; the preferable carbon for producing composite materials for catalyst applications is the graphite from petroleum coke. [ABSTRACT FROM AUTHOR]

A highly crystalline graphite powder was prepared from the low temperature (800-1000 °C) graphitization of renewable hard carbon precursors using a magnesium catalyst. The resulting graphite particles are composed of Voronoi-tessellated regions comprising irregular sheets; each Voronoi-tessellated region having a small 'seed' particle located near their centroid on the surface. This suggests nucleated outward growth of graphitic carbon, which has not been previously observed. Each seed particle consists of a spheroidal graphite shell on the inside of which hexagonal graphite platelets are perpendicularly affixed. This results in a unique high surface area graphite with a high degree of graphitization that is made with renewable feedstocks at temperatures far below that conventionally used for artificial graphites. [ABSTRACT FROM AUTHOR]

A multi-scale approach for fracture simulation, based on the Cellular Automata technique, has been developed and then applied to a nuclear graphite that is used in structural components of the UK Advanced Gas-cooled Reactors (AGR). High resolution X-ray computed tomographs of Gilsocarbon grade graphite, with up to 68% weight loss by radiolytic oxidation, provide quantitative descriptions of the porosity within its constitutive filler particles and their surrounding matrix. The statistical distributions for tensile strength and elastic modulus obtained from small models of the filler and matrix are introduced to a large scale model of the heterogeneous microstructure. These microstructure-derived simulations achieve a good agreement with experimental data. The computationally efficient analysis is then used to investigate the stochastic effects on mechanical properties of possible variations in the microstructure between individual small test specimens. As these may represent material of nominally the same microstructure, there is an apparent increase in the variability of strength and modulus at high weight loss. [ABSTRACT FROM AUTHOR]

This concept paper describes a new electrochemical method for the graphitization of amorphous carbons. The graphitization is achieved by a simple cathodic polarization of the carbons at merely ≈1100 K in molten CaCl2. This electrochemical process is applicable to both graphitizable and non-graphitizable carbons, generating porous graphitic structures of high-crystallinity nanosheets. The transformation of carbon blacks, microspheres, and fibers to porous graphites, hollow graphite spheres, and pipes with porous shells have been demonstrated and the potential graphitization mechanism discussed. [ABSTRACT FROM AUTHOR]

The time-of-flight technique has been used to investigate the stiffness of nuclear graphite with respect to the grade and grain direction. A loading rig was developed to collect time-of-flight measurements during cycled compressive loading up to 80% of the material's compressive strength and subsequent unloading of specimens along the axis of the applied stress. The transmission velocity (related to Young's modulus), decreased with increasing applied stress; and depending on the graphite grade and orientation, the modulus then increased, decreased or remained constant upon unloading. These tests were repeated while observing the microstructure during the load/unload cycles. Initial decreases in transmission velocity with compressive load are attributed to microcrack formation within filler and binder phases. Three distinct types of behaviour occur on unloading, depending on the grade, irradiation, and loading direction. These different behaviours can be explained in terms of the material microstructure observed from the microscopy performed during loading. [ABSTRACT FROM AUTHOR]

To improve the thermal stability of lithium-ion batteries (LIBs) at elevated temperatures, the roles of positive or negative electrode materials in thermal runaway should be clarified. In this paper, we performed accelerating rare calorimetry analyses on two types of LIBs by using an all-inclusive microcell (AIM) method, where the AIM consists of all LIB components. We found that the thermal runaway in LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA)|LiPF 6 dissolved in ethylene carbonate (EC)/diethyl carbonate solution (DEC) (EC/DEC = 1/1 by volume); LiPF 6 (EC/DEC)|artificial graphite (AG) and LiNi 1/3 Co 1/3 Mn 1/3 O 2 (NCM)|LiPF 6 (EC/DEC)|AG cells is brought about by different electrodes, i.e., NCA for the former, and AG for the latter. The above difference is attributed to the different oxidation temperature of the EC/DEC solvents, indicating that we first pay attention which electrodes govern the thermal runaway. Trials for improving the thermal stability of NCA are also reported. [ABSTRACT FROM AUTHOR]

This paper deals with the enhancement of gypsum composites through the synergic work of polypropylene fibers (PPF) and isostatic graphite filler (IGF) additions. IGF is a waste by-product that has shown a good performance in plain gypsum, and in this research it is demonstrated that it can also be revalorized as gypsum matrix activator in reinforced gypsum-based composites. Hence, several series of gypsum composites with a 0–0.6% volume of PPF and with 0–5–10–15–20–25% of graphite addition by weight substitution of gypsum were developed and the mechanical and physical properties tested. The microstructure of the composite and the contact surface with fiber are also analyzed by Scanning Electron Microscopy (SEM). The progressive increase of graphite addition modifies the composite properties, increasing mechanical resistances (compressive strength, flexural strength, Young’s modulus, toughness), density and thermal conductivity and on the other hand, reducing their porosity and their water absorption. The mechanical performance obtained with PPF and IGF is similar to the increase of the fiber length or the volume fraction of the fiber added in gypsum-based composites, which can favor the manufacture of reinforced gypsum composites. This improvement is achieved through the activation of the gypsum matrix, through the nucleation of the hydrated calcium sulfate in contact with IGF, and the increase of fiber/matrix bond when IGF is added. Gypsum composites with IGF and PPF addition can be used in boards and renders in the construction industry, obtaining more durable and sustainable materials. [ABSTRACT FROM AUTHOR]

The electrochemical performance of mechanically spheroidized natural and synthetic graphite particles is significantly influenced by the type of spheroidization process used and the applied conditions. In order to guarantee a consistent and high material quality, spherical graphite particles have to be carefully benchmarked before use. Three spherical natural graphites and three spheroidized synthetic graphites are characterized using several physical analysis methods. A special focus is laid on the internal morphology and texture, which has been studied by scanning electron microscopy (SEM) – focused ion beam (FIB) cross-sections and tomography. For the spheroidized natural graphites under investigation this method indicates a volume of closed pores in the range of 4–5% and of open pores of 0.5% or less of the total particle volume. With increasing energy impact during the spheroidization process the open porosity increases and the closed porosity decreases. [ABSTRACT FROM AUTHOR]

In order to improve the electrochemical performance and decrease the volume changes of artificial graphite, Li 2 SiO 3 and Li 2 CO 3 have been in situ prepared to co-modify the graphite by ball milling and heating the precursors of Li 4 SiO 4 and graphite. The as-obtained graphite-based samples were characterized using various techniques, and the effects of Li 4 SiO 4 content were investigated. The results show that the co-modified graphite with 20 wt.% Li 4 SiO 4 exhibits the highest reversible capacity and the best cycling performance among the graphite-based samples. Compared to the pristine graphite, the initial reversible capacities of the co-modified graphite with 20 wt.% Li 4 SiO 4 respectively increase 10.1%, 16.4%, 28.9%, and 62.4% at the current rates of 0.1, 1.0, 2.0 and 5.0C, while the capacity fade ratios respectively decrease 3.8%, 10.0%, and 23.2% at the current rates of 1.0, 2.0 and 5.0C after 50 cycles. Furthermore, co-modification by Li 2 SiO 3 and Li 2 CO 3 decreases the polarization degree as well as the charge transfer reaction and diffusion resistances of pure graphite. Non-destructive stress-strain tests were adopted to real time monitor the macroscopic stress safety properties of the cells, and the results indicate that the combination of Li 2 SiO 3 and Li 2 CO 3 relieves the swelling of the graphite electrode during cycles, and the stress value of the cell surface decreases 34.4% after 50 cycles at the current rate of 1.0C. The relationship between residue stress and capacity fade along with possible reaction mechanisms is discussed. The good results pave a novel facile way to enhance the performance of current energy materials using combined lithium salts via in situ reaction. [ABSTRACT FROM AUTHOR]

An efficient and economical material has been developed for the removal of arsenic (III) and (V) from contaminated water using commercially available synthetic graphite (SG) flakes. To enhance adsorption capacity of SG, it was treated with 3 - mercaptopropionic acid followed by functionalization with zinc peroxide nanoparticles. Interestingly, the adsorption efficacy of functionalized synthetic graphite (FSG) enhanced several times in comparison to pure SG. The proposed materials efficiently removes arsenic (III) and (V) in the pH range 7.5–8.0 and 3.9–4.5 respectively below detection limits of Atomic Absorption Spectrometer- Hydride Generator. The water purified by FSG can be used for several applications including potability as per described standards of world health organization (WHO) and United State-Environmental Protection Agency (US-EPA). The adsorption data were fitted to kinetics and isotherm models to analyze the adsorption mechanism and it has been found that adsorption data were best fitted with pseudo second order kinetic model and Fruendlich adsorption isotherm, indicating chemisorption and multilayer adsorption on heterogeneous surface respectively. [ABSTRACT FROM AUTHOR]

The main objective of this work was to obtain the damping factor (xi ) as well as the elasticity modulus (E) of two kinds of synthetic graphite (HLM and ATJ), using the modal analysis technique. Prismatic beams of square section (~ 11 x 11 mm) and length over thickness ratio (L/t) of about 22.7 were tested in the free - free boundary condition. The first four modes of vibration were taken into account in the non-destructive evaluation of the materials. In addition, numerical simulations were also carried out in this investigation. The agreement between the theoretical and the experimental results was quite good. The average values of E and xi for the HLM graphite were 20% and 90% higher, respectively, than those presented by the ATJ graphite, indicating that the HLM graphite has, proportionally, more damping mechanisms than the ATJ graphite.