Plane Of Graphite Research Articles

Gas adsorption analysis for quantifying the edge sites of graphite

The edge plane exposed on the surface of carbon materials is the active site that determines their properties. When graphite is used as the negative electrode in lithium-ion batteries, the edge plane acts as an access point for lithium insertion/desorption. However, because of the low specific surface area and amorphous carbon coating of graphite particles, accurately estimating the number of edge planes is challenging. Therefore, we propose a technique for determining graphite edge planes based on the stepwise adsorption of Kr onto the hexagonal carbon network surface. Graphite particles with highly modified surface structures were prepared by controlling the particle size, heat treatment temperature, and amorphous carbon coating. Electrochemical evaluation revealed significant differences in charge-transfer resistance, an indicator of edge planes. The edge plane determination results obtained using conventional methods such as X-ray diffractometry and Raman spectroscopy did not correlate well with charge-transfer resistance. Meanwhile, Kr adsorption measurements revealed that the stepwise adsorption behavior, because of the interaction of Kr with the energetically homogenous surface, varied significantly depending on the surface properties of graphite particles. The number of edge planes estimated by gas adsorption strongly correlated with charge-transfer resistance. Consequently, we determined that the graphite edge plane tied to the electrochemical index can be derived using gas adsorption analysis. This edge plane determination technique would be applicable not only to graphite but also to highly crystalline carbon materials with an exposed hexagonal carbon network surface.

Adsorption dynamics of gaseous toluene with and without formaldehyde and water vapors on composites of UiO-66-NH2 and microporous carbon

To improve the adsorption capacity/selectivity of activated carbon (AC) against diverse volatile organic compounds (VOCs), a series of AC-based composites have been prepared with UiO-66-NH2 (U6N) and coded as AC-U6Nx (x = 1–20 wt/wt%). The adsorption potential of AC-U6Nx is evaluated against toluene in relation to the effects of composite compositions and the presence of competing feed gases/vapors (e.g., formaldehyde (FA) and water vapor). Although AC-U6N(1%) adsorbs toluene preferentially over FA, the selectivity factor of the former decreases from 6.4 to 2.63 as the x value increases from 1 to 20 wt%. This indicates the crucial role of U6N-NH2 groups in active capturing of FA over toluene through Schiff-base adsorption mechanism. Interestingly, the partition coefficient (PC100%: 0.045 ± 0.004 mol kg−1 Pa−1) of AC-U6N(1%) for 100 ppm FA remains nearly constant across varying toluene levels (1–100 ppm), suggesting the preferential occupation of active sites by FA (pore-filling). The contrasting role of relative humidity (RH) is also evidenced, as AC-U6N(1%), exhibits the highest capacity for toluene and FA under dry (0 % RH) and humid (20 % RH) conditions, respectively. The adsorption behavior of VOC on AC-U6N(1%) surface active sites (e.g., graphitic basal planes, NH2, COO–, and Zr sites) is predictable with a good fit of experimental data to the Freundlich isotherm and pseudo-second-order (PSOM) kinetic models. A density functional theory (DFT) simulation supports the enhancement of toluene adsorption on the interface of AC and U6N-based systems. Overall, this work offers practical guidelines for the construction of advanced functional adsorbents against diverse VOCs under both competitive and non-competitive conditions.

Microfluidic Shape Analysis of Non-spherical Graphite for Li-Ion Batteries via Viscoelastic Particle Focusing.

The size and shape of graphite, which is a popular active anode material for lithium-ion batteries (LIBs), significantly affect the electrochemical performance of LIBs and the rheological properties of the electrode slurries used in battery manufacturing. However, the accurate characterization of its size and shape remains challenging. In this study, the edge plane of graphite in a cross-slot microchannel via viscoelastic particle focusing is characterized. It is reported that the graphite particles are aligned in a direction that shows the edge plane by a planar extensional flow field at the stagnation point of the cross-slot region. Accurate quantification of the edge size and shape for both spheroidized natural and ball-milled graphite is achieved when aligned in this manner. Ball-milled graphite has a smaller circularity and higher aspect ratio than natural graphite, indicating a more plate-like shape. The effects of these differences in graphite shape and size on the rheological properties of the electrode slurry, the structure of the coated electrodes, and electrochemical performance are investigated. This method can contribute to the quality control of graphite for the mass production of LIBs and enhance the electrochemical performance of LIBs.

The Transformation Mechanism of Graphite to Hexagonal Diamond under Shock Conditions.

The formation of a hexagonal diamond represents one of the most intriguing questions in materials science. Under shock conditions, the graphite basal plane tends to slide and pucker to form diamond. However, how the shock strength determines the phase selectivity remains unclear. In this work, using a DFT-trained carbon global neural network model, we studied the shock-induced graphite transition. The poor sliding caused by scarce sliding time under high-strength shock leads to metastable hexagonal diamond with an orientation relationship of (001)G//(100)HD+[010]G//[010]HD, while under low-strength shock due to long sliding distance cubic diamond forms with the orientation (001)G//(111)CD+[100]G//[110]CD, unveiling the strength-dependent graphite transition mechanism. We for the first time provide computational evidence of the strength-dependent graphite transition from first-principles, clarifying the long-term unresolved shock-induced hexagonal diamond formation mechanism and the structural source of the strength-dependent trend, which facilitates the hexagonal diamond synthesis via controlled experiment.

Treatment of Se-Impacted Wastewater Using a Three-Dimensional Packed Bed Electrochemical Reactor

Selenium is an essential element for flora and fauna in trace amounts. It plays a crucial role in bolstering photosynthesis and facilitating thyroid hormone metabolism. However, excessive consumption of selenium can result in health concerns such as reproductive complications and cancer. Selenium usually coexists with minerals such as copper and coal in the natural environment. The associated activities, such as copper mining and coal combustion, have greatly accelerated the mobilization of selenium. The selenium released through coal combustion is mostly captured in the flue gas desulfurization (FGD) wastewater as inorganic selenite and selenate.Our lab previously validated the viability of direct electrochemical reduction (SeDER) to remove dissolved selenite from a simplified FGD water matrix using planar gold and graphite cathodes, where more than 94% of the aqueous selenite can be converted to elemental Se(0) deposited on the cathode surface. Graphite is eventually selected for its low material cost, decent removal performance, and minimum secondary pollution as compared to gold and other non-noble metal cathodes. This direct electrochemical deposition process provides many benefits that existing biological and indirect electrochemical methods lack, such as zero chemical addition and low to zero solid generation. However, this method is only suitable for wastewater with elevated temperatures necessary to generate conductive Se(0) for continuous reduction. The inclusion of a heating process adds complexity to the design, impeding the scalability of the SeDER system. Furthermore, the application of SeDER is constrained to Se-impacted wastewater with an elevated temperature.In this study, we propose a novel reactor design utilizing electrochemical reduction to treat Se-impacted wastewater at ambient temperature. The electrodes we used are made of graphite for the reasoning stated above. The reactor consists of a pair of planar graphite anode and cathode, and the inner chamber is filled with cylindrical graphite particle electrodes (PEs) separated by a nylon spacer to create an anodic chamber and a cathodic chamber. The PEs act as an extension of the planar electrodes, which offers numerous reaction sites and minimizes the travel distance for selenite ions to reach the electrode surface. In our 120-mL batch test with 0.1-mM selenite in 100-mM phosphate buffer, the exact system without filler removed 0% selenite at room temperature, while the filled 3D system removed on average 50% of the selenite in 3 hours. Using the same 3D system, we then investigated performance enhancement with a recirculating operation. The total working volume is fixed at 200 mL, while the flow rate and the applied voltage vary. The flow rate is set at the values with hydraulic retention time (HRT) fixed at 15 min, 30 min, and 60 min. The system-applied voltage is set at -1.9V (just enough for selenite reduction), -2.1V, and -2.3V. We found that the shortest HRT combined with -2.1V system applied voltage yielded the highest selenite removal performance in all tests, with an average of 47% removal in 3 hours. We hypothesized that the shorter HRT provides a faster flow rate that refreshes the PE’s surface from insulative Se(0) deposition, which provides sustainable reaction sites for the incoming selenite. At -2.1V, the potential is negative enough to allow selenite reduction while fewer parasitic reactions (e.g., hydrogen evolution reaction) occur compared to that under -2.3V.With the selected system voltage and flow rate, we eventually explored competing ion behavior and switched from a simplified water matrix to simulated Se-impacted wastewater. We found that of all the commonly found competing ions (i.e., sulfate, nitrate, and chloride), chloride significantly impacts selenite removal, with performance dropping to 10% removal in 3 hours. Nitrate slightly decreased the selenite removal, with an average Se removal performance of 23%. Sulfate, on the other hand, resulted in an increase in selenite removal after addition. We hypothesize that a high sulfate concentration in simulated wastewater could help alleviate the repulsing force from the cathode surface for the selenite ions. The double layer of the PEs could also be compressed by the high ionic strength, which decreases the capacitance and promotes selenite reduction. To confirm this hypothesis, we conducted an electrochemical impedance study to analyze the effect of competing ions on reaction kinetics and capacitance. We also performed surface analysis for the wasted planar electrodes and PEs to investigate the change in morphology and observed possible chemical residue. These characterizations will help us develop a regeneration protocol in long-term operation and help us scale up our prototype to manage actual Se-impacted wastewater.

Controlling Current Distribution in Slurry Electrolytes for Redox Flow Batteries

Slurry electrodes have the potential to decouple the power and storage capacities of hybrid redox flow batteries1 (RFB). In more commonly studied true RFB chemistries, such as all-vanadium, the power and storage capacities can be considered separately2; the power capacity is dependent on the flow cell design while the storage capacity is dependent on the amount of positive and negative electrolyte that can be stored. These decoupled capacities allow true RFB’s to be highly scalable. However, in hybrid RFB chemistries, such as all-iron, solid metal is deposited within the flow cell during charge, limiting the storage capacity of the battery based on the geometry of the flow cell3. This limitation can be addressed by incorporating a slurry electrode in the negative electrolyte. By depositing the reduced metal on this mobile dispersion of electrically conductive carbon particles, hybrid redox RFB’s may achieve high scalability while utilizing less expensive materials, such as iron or zinc1,4. To successfully augment the scalability of hybrid RFB’s, the current distribution of the metal deposition reaction must occur predominantly on the mobile slurry electrode, rather than on the stationary current collector. This current distribution is dependent on numerous factors, including the electrical conductivity of the slurry electrode, the ionic conductivity of the electrolyte, the kinetics of the faradaic reaction, and mass transfer to both the stationary current collector and to the slurry particles. In this work, we explore three approaches to controlling the current distribution in slurry electrodes. In the first approach, we explore the utility of slurry electrodes consisting of multiple types of carbon particles. Our earlier work has shown that slurries of varying carbon type can have significantly different electrochemical performance5. Slurries consisting of carbon black particles with high specific surface area can minimize the kinetic resistance of the faradaic reactions but struggle to distribute current away from the current collector due to their low electrical conductivity. Meanwhile, slurries consisting of more electrically conductive, but lower surface area graphitic particles can facilitate faradaic current away from the current collector but may not minimize kinetic resistance to the same degree. By using a slurry electrode consisting of mostly graphitic particles with a small portion of high surface area carbon black, the faradaic current may be kinetically facile in addition to well distributed through the slurry. In the second approach, we explore options to hinder the ionic conductivity of the electrolyte. The faradaic current distribution through the slurry electrode depends heavily on the competition between the ionically and electronically conductive routes. Typically, the ionic conductivity is heavily favored due to the desire for high per-volume energy density and the low pH required to keep the metallic reactants soluble. By hindering the ionic conductivity of the electrolyte, either by utilizing viscosity increasing additives or by lessening the ionic concentration, the faradaic current may be better spread through the slurry. In the third approach, we explore options for controlling the current distribution via varying reaction kinetics on various electrode surfaces. While considerable work6,7 has been done comparing the reaction kinetics of homogeneous redox reactions on various electrode materials (glassy carbon, basal/edge plane graphite, platinum...) relatively little work has been done regarding metal deposition reactions. By changing the current collector material to one with poor deposition kinetics relative to the slurry electrode material, the current distribution may be enhanced on the slurry.(1) Petek, T. J. Enhancing the Capacity of All-Iron Flow Batteries: Understanding Crossover and Slurry Electrodes. Ph.D. Thesis 2015, No. May.(2) Weber, A. Z.; Mench, M. M.; Meyers, J. P.; Ross, P. N.; Jeffrey, T.; Liu, Q. Redox Flow Batteries, a Review. J. Appl. Electrochem. 2011, 41 (10), 1–72. https://doi.org/https://doi.org/10.1007/s10800-011-0348-2.(3) Dinesh, A.; Olivera, S.; Venkatesh, K.; Santosh, M. S.; Priya, M. G.; Inamuddin; Asiri, A. M.; Muralidhara, H. B. Iron-Based Flow Batteries to Store Renewable Energies. Environ. Chem. Lett. 2018, 16 (3), 683–694. https://doi.org/10.1007/s10311-018-0709-8.(4) Petek, T. J.; Hoyt, N. C.; Savinell, R. F.; Wainright, J. S. Slurry Electrodes for Iron Plating in an All-Iron Flow Battery. J. Power Sources 2015, 294, 620–626. https://doi.org/10.1016/j.jpowsour.2015.06.050.(5) Tam, V.; Wainright, J. Electrochemical Behavior of Low Loading Slurry Electrodes for Redox Flow Batteries. J. Electrochem. Soc. 2023, 170 (1), 010538. https://doi.org/10.1149/1945-7111/acb10a.(6) Mccreery, R. L.; Mcdermott, M. T. Comment on Electrochemical Kinetics at Ordered Graphite Electrodes. Anal. Chem 2012, 84. https://doi.org/10.1021/ac2031578.(7) Chen, P.; McCreery, R. L. Control of Electron Transfer Kinetics at Glassy Carbon Electrodes by Specific Surface Modification. Anal. Chem. 1996, 68 (22), 3958–3965. https://doi.org/10.1021/ac960492r. Figure 1

4D-STEM and Eels Analysis of Complex C-Based Sensor Architectures

Transforming high-carbon precursors into open-porous carbon foams and coatings via thermal processes is gaining attention as a sustainable method for various applications, including catalysis, energy utilization, and sensing [1]. In this research, we adopt a one-step laser patterning approach to selectively pyrolyze doctor-bladed ink coatings on flexible PET substrates, thereby producing highly porous, intricately designed CO2 sensor structures with a thickness of about 50 µm. Our ink formulation includes glucose as a pore-forming agent and adenine as a nitrogen source to enhance sensing capabilities. Laser processing in an oxygen-rich setting results in flexible, highly porous sensor heterostructures characterized by distinct areas enriched with nitrogen and oxygen functionalities. The laser intensity’s attenuation with depth leads to the development of a distinctly porous graphitic surface layer (serving as the electrical transducer layer) and a denser nitrogen-enriched lower sensor layer, linked by a narrow transitional region [2]. To understand the formation and functionality of these sensors, we conducted an in-depth TEM analysis of cross-sections of the complete device, prepared through ultramicrotomy cross-sectioning. STEM-EELS elemental distribution maps distinctly show the chemical composition differences between the upper and lower layers of the sensor. Principal component analysis was utilized to separate the complex sensor structures into their constituent crystalline and amorphous carbon and nitrogen-containing phases. 4D-STEM analysis exposed the arrangement of the crystalline graphitic phase and the orientation of graphite basal planes adjacent to the pores of the open-porous sensor. Analyzing these structural parameters is essential for understanding the electrical performance of the sensor, as depicted in Figure 1 [3]. Figure 1: A (top)) SEM micrograph of sensor embedded in epoxy, (bottom) depth-dependent thermal laser intensity attenuation; B (left)) HA ADF-STEM micrograph showing different sensor layers, (middle) STEM-EELS nitrogen distribution map, (right) PCA bond analysis, C) HRTEM images of sensor from transducer (top) and sensor (bottom) layers with SAED image of respective ROIs (inset); D) 4D-STEM analysis depicting misalignment angle between graphitic carbon basal plane normal relative to the pore surface normalReferences[1] M. Hepp, et al. npj Flexible Electronics 6, 1-9 (2022)[2] H. Wang, et al. Advanced Functional Materials 32, 2207406 (2022)[3] C. Ophus, et al. Microscopy and Microanalysis 28, 390-403 (2022) Acknowledgements: We acknowledge use of the DFG-funded Micro-and Nanoanalytics Facility (MNaF) at the University of Siegen (INST 221/131-1). Figure 1

Semi-quantitative analysis of the structural evolution of mesophase pitch-based carbon foams by Raman and FTIR spectroscopy

Graphitized carbon foams (GFms) were prepared using mesophase pitch (MP) as a raw material by foaming (450 °C), pre-oxidation (320 °C), carbonization (1 000 °C) and graphitization (2 800 °C). The differences in structure and properties of GFms prepared from different MP precursors pretreated by ball milling or liquid phase extraction were investigated and compared, and semi-quantitative calculations were conducted on the Raman and FTIR spectra of samples at each preparation stage. Semi-quantitative spectroscopic analysis provided detailed information on the structure and chemical composition changes of the MP and GFm derived from it. Combined with microscopic observations, the change from precursor to GFm was analyzed. The results showed that ball milling concentrated the distribution of aromatic molecules in the pitch, which contributed to uniform foaming to give a GFm with a uniform pore distribution and good properties. Liquid phase extraction helped remove light components while retaining large aromatics to form graphitic planes with the largest average size during post-treatment to produce a GFm with the highest degree of graphitization and the fewest open pores, giving the best compression resistance (2.47 MPa), the highest thermal conductivity (64.47 W/(m·K)) and the lowest electrical resistance (13.02 μΩ·m). Characterization combining semi-quantitative spectroscopic analysis with microscopic observations allowed us to control the preparation of the MP-derived GFms.

Self-breakdown statistics of a high-pressure spark gap with a microarray graphite cathode.

Comparative measurements with high-pressure spark gaps (gas pressure: 0.2-0.9 MPa nitrogen, gap spacing 5mm) are presented, one with a regular Bruce-profile polished graphite cathode (diameter 25mm, thickness 8mm) and the other with a microarray graphite cathode of equal dimensions. By microstructuring, a V-type graphite microarray is created by purpose-developed laser treatment of a plane graphite electrode. The microarray graphite cathode brings more initial plasma and then produces more initial electrons. It is beneficial for electron emission, which improves the stability of the switch breakdown. The experimental results are achieved at a gas pressure of 0.9 MPa and a 200-kV voltage pulse applied to the switch. With these parameters, the mean breakdown voltage is 91.7kV, the minimum is 91.4kV, and the mean relative standard deviation in breakdown voltage of the first 100 shots is 0.4%. Compared to a plane graphite cathode, the mean breakdown voltage is about 10% lower, and the mean relative standard deviation is reduced by more than 90%. The main result can be stated that microarray graphite cathodes are a suitable choice as electrodes for low-jitter high-pressure spark gaps.

Alkali-fluoride-salt-accelerated oxidation behavior of graphite under air atmosphere

Air ingress accident scenarios may result in the oxidation of graphite matrix materials and cause serious safety problems in molten salt reactor. However, the oxidation behavior of the molten-salt-infiltrated graphite remains elusive. In this study, the effect of alkali fluoride salts (LiF, NaF, KF and ternary salt FLiNaK) on the oxidation behavior of graphite powder under air atmosphere was investigated. Thermogravimetric analysis and oxidation tests manifest that the initial oxidation temperature of the graphite is reduced from 720 °C to 510–610 °C, because of the presence of the alkali fluoride salts. The catalytic oxidation effect follows the order of KF > NaF > LiF. Careful characterizations reveal that the pristine graphite is mainly oxidized at the graphite edges, while salt-infiltrated graphite is mainly damaged at the graphitic basal planes. Density functional theory calculations suggest that the doping of alkali metal atoms does not change the physical adsorption feature of the oxygen molecule on the graphite plane surface, but increases its adsorption energy to facilitate the graphite oxidation reactions.

EVALUATION OF THE GRAPHENE DISPERSIONS FOR KEVLAR FABRICS FUNCTIONALIZATION OBTAINED BY THE LIQUID-EXFOLIATION OF GRAPHITE

The process where pristine graphite is subjected to a solvent treatment seems simple and scalable and has attracted the attention of researchers over many years. However, for successful exfoliation, overcoming the van der Waals attractions between the adjacent layers of graphite is necessary. Over time, several methods have been created to overcome the attraction between layers. Graphene’s liquid phase exfoliation (LPE) occurs due to the strong interactions between the solvent molecules and the basal planes of graphite, overcoming the energetic resistance to exfoliation and subsequent dispersion. Ultra sonication used for exfoliation can produce single or few layered graphene flakes. During sonication the sound waves propagate through liquid medium in alternating high- and low-pressure cycles, strong mechanical and thermal energy released by acoustic cavitation results in splitting up large particles into fine ones and dispersing them. Simultaneous insertion of solvent and/or intercalation molecules in between the graphite layers takes place supporting graphite separation into graphene layers. ; The dispersion capacity of graphene flakes depends on how appropriate the solvent properties are to the corresponding properties of graphene, such as surface tension, Hildebrand, and Hansen solubility parameters. Only certain solvents can disperse graphene well and form a dispersion appropriate for specific future applications. In addition, after exfoliation by ultra sonication graphene flakes aggregation due to the van der Waals attractions must be overcome to prepare in long-term stable dispersions of nanometres-size graphene sheets. ; The research has focused on the preparation of stable dispersion ready for transfer without intermediate processes to the Kevlar fabrics. An experimental comparison of the potentials of the 4 solvents for the application resulted in three corresponding to the intended use, two of them examined in detail, supplementing the composition of the LPE liquid medium with triethanolamine to obtain sufficient performance graphene coverage on Kevlar textile fibres.

Comparing thermoplastic electrode materials: Toward enhanced sensing of O2 and H2O2 in flow devices

AbstractCarbon composite electrodes often suffer from poor electrocatalytic activity and require complex, expensive, or time‐consuming modifications to effectively detect certain analytes such as O2 and H2O2. Thermoplastic electrodes (TPEs) are a new class of composite electrodes, fabricated by mixing commercial graphite with a thermopolymer, that exhibit superior electrochemical properties to typical carbon composite electrodes. This work investigates the properties of TPEs using two thermopolymer binders – polycaprolactone (PCL) and polystyrene (PS) – with sanded and heat‐pressed surface treatments. XPS and SEM analysis suggested that sanded TPEs have a higher density of graphitic edge planes and improved electrochemistry as a result. Electrochemical detection of O2 and H2O2 was demonstrated on sanded PS TPEs. Additionally, this work introduces the first use of a 3D‐printed TPE template as part of a 3D‐printed sensor module that is reversibly sealed with magnets as a proof‐of‐concept flow‐based sensor for detecting H2O2.

Towards realistic structural char models: Generation of stacked graphene-like layers using constrained reactive molecular dynamics simulations

For a molecular understanding of coal combustion, realistic coal and char models are pivotal. We propose a novel top-down method for the construction of char models, consisting of stacked graphene-like layers with defects. We start on the mesoscale with corrugated stacked surfaces as a template. Then the carbon atoms are pre-positioned on these surfaces and surrounded by hydrogen atoms. In a constrained reactive MD simulation the carbon atoms are then rearranged into a chemically reasonable state with dangling bonds saturated by hydrogen atoms. Importantly, the initial shape of the template is maintained to a great extent, leading to a substantial amount of defects in the graphitic planes, especially for high curvatures. In a final step, small molecular fragments and unfavorable arrangements are removed and remaining dangling bonds are saturated with hydrogen atoms. The central advantage over other approaches is the ability to choose the shape and size of the templating planes, with the possibility to use experimental input.The method is validated on single sheets with a protrusion and application examples are shown for stacked graphitic layers with up to 100 Å size and more than 20000 atoms. It represents the first step of a longer term project. In the future, heteroatoms and functional groups will be implemented, and by combining several such stacks, the approach will allow the construction of more realistic char models using the data from HRTEM images as an experimental boundary condition. On this basis important questions like the adsorption and diffusion of volatiles under high temperatures can be studied on a molecular level.

Size-dependent electrochemistry of laser-induced graphene electrodes

Laser-induced graphene (LIG) electrodes have become popular for electrochemical sensor fabrication due to their simplicity for batch production without the use of reagents. The high surface area and favorable electrocatalytic properties also enable the design of small electrochemical devices while retaining the desired electrochemical performance. In this work, we systematically investigated the effect of LIG working electrode size, from 0.8 mm to 4.0 mm diameter, on their electrochemical properties, since it has been widely assumed that the electrochemistry of LIG electrodes is independent of size above the microelectrode size regime. The background and faradaic current from cyclic voltammetry (CV) of an outer-sphere redox probe [Ru(NH3)6]3+ showed that smaller LIG electrodes had a higher electrode roughness factor and electroactive surface ratio than those of the larger electrodes. Moreover, CV of the surface-sensitive redox probes [Fe(CN)6]3– and dopamine revealed that smaller electrodes exhibited better electrocatalytic properties, with enhanced electron transfer kinetics. Scanning electron microscopy, Raman spectroscopy, and X-ray photoelectron spectroscopy showed that the physical and chemical surface structure were different at the electrode center versus the edges, so the electrochemical properties of the smaller electrodes were improved by having rougher surface, more density of the graphitic edge planes, and more oxide-containing groups. The difference could be explained by the different photothermal reaction time from the laser scribing process that causes different stable carbon morphology to form on the polymer surface. Our results give a new insight on relationships between surface structure and electrochemistry of LIG electrodes and are useful for designing miniaturized electrochemical devices.

Facile synthesis of silver nanoparticles loaded spent cathodic Lithium-Ion battery components for enhanced bifunctional photocatalysis: Investigating the influence of magnetic properties

Due to resource depletion and environmental concerns regarding battery disposal, it is becoming more essential to recycle valuable metals from wasted lithium-ion batteries (LIBs). A novel approach is proposed in this study for the efficient bifunctional photocatalysis of LIBs components by integrating AgNPs in an environmentally sustainable manner via a sustainable hydrothermal process. The HRTEM and image mapping reveal a carbon matrix (C/Li3Fe5O8/Ag) with a dispersed arrangement of AgNPs (5–10 wt%). By acting as a reducing agent, graphite plays a crucial role in the transformation of Ag+ ions into AgNPs. The homogenous distribution of Ag NPs observed in the high-resolution TEM images further supports the role of graphite in the modification and decoration of Ag NPs onto the surface of the extracted spent cathode sample. The detection of a spot matching the (200) plane of Ag in the selected area electron diffraction (SAED) measurements confirms the successful formation of AgNPs. Additionally, the presence of a ring corresponding to the (110) plane of graphite in the SAED measurements suggests the coexistence of graphite with AgNPs in the composite heterostructures. The nitrogen adsorption isotherm analysis was conducted to explore the physical properties of the AgNPs@LIBs nanocomposite, providing valuable insights into its pore size distribution and Brunauer–Emmett–Teller (BET) surface area. The nanocomposites exhibited paramagnetic behavior, as revealed by vibrational sample magnetometer (VSM) measurements, with saturation magnetization values ranging from 76.3 × 10−3 to 36.13 × 10−3 emu/g. The study involved the photodegradation of oxytetracycline (OTC), a representative pharmaceutical pollutant, along with an investigation into the potential of Cr(VI) reduction. Under optimal component ratios, a significant improvement in pollutant removal was achieved under UV radiation, reaching up to 75 % for OTC and 80 % for Cr(VI), highlighting the efficiency of the process.

EFFECT OF MAGNESIUM TREATMENT PROCESS ON THE PRODUCING COMPACTED GRAPHITECAST IRON WITH DIFFERENT CASTING THICKNESS

Strength, toughness, machinability and damping capacity are properties of compacted graphite iron that distinguish the properties between flake graphite cast iron and spheroidal cast iron. The formation of compacted graphite can be set to achieve the required specification. The formation of compacted graphite is started from spheroidal to compacted cast iron. The residual magnesium after magnesium treatment and the solidification ratehave a significant role in the formation of compacted graphite. The high content of residual magnesium can obstruct the graphite plane to grow during the transformation from spheroidal to compacted shape. In addition, the cooling rate of the casting can be controlled by varying the casting thickness. The compacted graphite in the cast iron are characterized according to shape, size ai`nd distribution. The optimum compacted graphite in the cast iron that can be produced has 30 mm of casting thickness with 0.017 % of residual magnesium.

Covalently‐Bonded Diaphite Nanoplatelet with Engineered Electronic Properties of Diamond

AbstractDiamond, as a highly promising “extreme” semiconductor material, necessitates electronic property engineering to unleash its full potential in electronic and photonic devices. In this work, the diaphite nanoplatelet, consisting of (11) planes of diamond nanoplatelet covalently bonded with graphite (0001) planes, is facilely synthesized using one‐step microwave plasma enhanced chemical vapor deposition method. The high‐energy plasma created by the pillar plays a crucial role in the formation. Importantly, altered electronic and optical properties are determined in the diaphite nanoplatelet through electron energy loss spectrum, density functional theory calculations, and cathodoluminescence spectroscopy. It is revealed that the strong sp3/sp2‐hybridized interfacial covalent bonding in the diaphite nanoplatelet induces the electron transfer from diamond to graphite. This modulates the electronic structure of the near‐interface layer of diamond and triggers a new local trapping band below the conduction band minimum within the bandgap. Consequently, the covalently‐bonded diaphite exhibits a different optical emission characteristic ranging from 2.5 to 3.64 eV, featuring a significant peak blueshift of 430 meV compared to the H‐terminated diamond. This work demonstrates a novel method to engineer the electronic properties of diamond, opening avenues for functional semiconductor device applications of diamond.

Stiffness and mechanical manipulation of blisters grown on electrochemically intercalated graphite

Electrochemical anion intercalation of highly oriented pyrolytic graphite in mineral acids (such as sulfuric, perchloric, etc.) represents a model system to study (i) the intercalation process of chemical compounds in stratified crystals; (ii) the evolution of gases at the surface and inside the sample and (iii) the evolution of swollen regions of graphite, called blisters. Although the explanation of the blister evolution mechanism can be dated back to the nineties of the last century, many chemical and physical properties have been explored only very recently. In particular, the mechanical properties of blisters on graphite are not widely discussed in the literature. Here, we employ in-situ atomic force microscopy (AFM) to characterize the blister stiffness. The same AFM tip is used to move mechanically the blister on the basal plane or even cut it. As a consequence of this operation, the entrapped gases (namely, CO, CO2 and O2) can deflate and the swollen graphite layers lay down to recompose the graphite basal plane.

The influence of the mass transport regime on laser chemical vapor deposited carbon fibers

Laser Chemical Vapor Deposition (LCVD) is a process through which fibers are additively deposited by the dissociation and deposition of a precursor gas into the solid phase under a translating laser focal point. In the hyperbaric pressure conditions, LCVD has two identified reaction regimes. The first being limited by surface reaction kinetics (SRK) and the second being limited by mass transport (MT). This article examines the effects of mass transport (MT) limitations on carbon fiber growth using either ethane (C2H6) or ethylene (C2H4). Both hydrocarbon precursors reveal a growth rate reduction when transitioning from SRK-to-MT to meet the no-slip condition in fluid dynamics. This transition correlates to a fiber microstructure change from a core shell morphology with a graphitic structure (SRK) to a nodular morphology with an amorphous structure (MT). The fiber fracture stress is generally found to be higher in the MT than SRK regime because of the reduction of easily cleaved graphitic planes in the MT fibers. Collectively, these results demonstrate the importance of the MT limited growth regime and how fiber characteristics can be manipulated when grown in this regime.

Tritium storage and release mechanism in nuclear graphite using first-principles combined thermal desorption theory

Nuclear graphite (NG) is widely applied in nuclear facilities, and its strong interaction with tritium is an essential factor for tritium transport behavior in various reactors and the treatment of radioactive NG waste. Given that NG is a polycrystalline and porous material, interactions between tritium and NG exist in various microstructures, including graphite edges, graphene basal planes, and amorphous structures. In this study, density functional theory which is integrated in Vienna ab initio simulation package (VASP) was combined with thermal desorption theory to elucidate the underlying mechanism of hydrogen isotope storage corresponding to the experimentally observed desorption peaks in NG. The four desorption temperature peaks, ranging from low to high, were mainly attributed to hydrogen isotope desorption from the graphite basal plane surface, amorphous carbon surface, unsaturated armchair and zigzag edges, respectively. The interaction between hydrogen isotopes and carbon nanostructures provides deeper insights into the understanding of tritium enrichment on the NG surface, which is primarily attributed to the adsorption of tritium on graphite basal plane-like surfaces at relatively low temperatures. This study provides a practical method to bridge the gap between the atomic binding structure and desorption temperature peaks from a kinetic perspective, providing insights into temperature-dependent hydrogen desorption in typical carbon structures and deepening our understanding of tritium transport behaviors in advanced nuclear energy systems.