Graphitic Carbon Microspheres Research Articles

Effects of novel carbon sources additives on the solid-state sintering behavior and properties of SiC ceramics

To enhance the density of SiC and improve the purity of the SiC, carbon is frequently used as a sintering additive. SiC ceramics were prepared in this study by using various carbon sources (graphitic carbon microsphere, carbon black, and flake graphite) combined with B4C through spark plasma sintering (SPS) at temperatures ranging from 1800 °C to 1900 °C. Among the above carbon sources, the graphitic carbon microspheres were created by hydrothermal carbonization combined with catalytic graphitization. The influence of the carbon sources on the phase compositions, microstructure, physical properties, and oxidation resistance of the SiC specimens was investigated. The findings revealed that the SiC specimens prepared with graphitic carbon microsphere had a smaller crystallite size than those prepared with other kinds of carbon. The SiC specimens prepared with graphitic carbon microsphere displayed high relative density, hardness, fracture toughness, and remarkable oxidation resistance. This was attributed to the lower oxygen content, better dispersion, and higher chemical reactivity of graphitic carbon spheres. In terms of the oxidation resistance of SiC specimens, factors such as purity (residual carbon) and porosity were found to have a more significant impact than grain size. In general, the use of carbon sources with high reactivity and good dispersion is an effective method in preparing SiC ceramics.

Exploring the Microstructural Effect of FeCo Alloy on Carbon Microsphere Deposition and Enhanced Electromagnetic Wave Absorption.

The rational design of magnetic carbon composites, encompassing both their composition and microstructure, holds significant potential for achieving exceptional electromagnetic wave-absorbing materials (EAMs). In this study, FeCo@CM composites were efficiently fabricated through an advanced microwave plasma-assisted reduction chemical vapor deposition (MPARCVD) technique, offering high efficiency, low cost, and energy-saving benefits. By depositing graphitized carbon microspheres, the dielectric properties were significantly enhanced, resulting in improved electromagnetic wave absorption performances through optimized impedance matching and a synergistic effect with magnetic loss. A systematic investigation revealed that the laminar-stacked structure of FeCo exhibited superior properties compared to its spherical counterpart, supplying a higher number of exposed edges and enhanced catalytic activity, which facilitated the deposition of uniform and low-defect graphitized carbon microspheres. Consequently, the dielectric loss performance of the FeCo@CM composites was dramatically improved due to increased electrical conductivity and the formation of abundant heterogeneous interfaces. At a 40 wt% filling amount and a frequency of 7.84 GHz, the FeCo@CM composites achieved a minimum reflection loss value of -58.2 dB with an effective absorption bandwidth (fE) of 5.13 GHz. This study presents an effective strategy for developing high-performance EAMs.

Integration of Highly Graphitic Three-Dimensionally Ordered Macroporous Carbon Microspheres with Hollow Metal Oxide Nanospheres for Ultrafast and Durable Lithium-Ion Storage

Achieving excellent electrochemical performance at high charging rate has been a long-cherished dream in the field of lithium-ion batteries (LIBs). As a part of the efforts to meet the goal, an innovative strategy for the synthesis of 3D porous highly graphitic carbon microspheres, to which numerous hollow metal oxide nanospheres are anchored, for use as anode in LIBs is introduced. Hollow carbon nanosphere-aggregated microspheres prepared from the spray drying process are graphitized with the aid of metal catalysts, and subsequent oxidation selectively removed amorphous carbon, leading to the formation of highly conductive graphitic carbon matrix. Numerous hollow metal oxide nanospheres formed simultaneously during the oxidation process via nanoscale Kirkendall diffusion are anchored onto the carbonaceous matrix, effectively reinforcing the structural integrity by alleviating volume changes and reducing lithium-ion diffusion lengths. The synergistic effect of combining hollow metal oxide nanospheres with high theoretical capacity with conductive carbon matrix led to accelerated electrochemical kinetics, resulting in high capacity at high charging rate. In addition, trapping the hollow metal oxide nanospheres inside hollow carbon nanospheres could effectively alleviate the volume changes, which led to high structural stability. When applied as LIB anodes, the microspheres exhibit a capacity of 411 mA h g−1 after 2500 cycles at 10.0 A g−1, with ~80% capacity retention. The anode exhibits a high capacity of 274 mA h g−1 at an extremely high current density of 50.0 A g−1, thus demonstrating the structural merits of the microspheres.

Tunable broadband terahertz absorption and shielding of bioderived graphitic carbon microspheres

The rapid advancement of Terahertz (THz) science and technology has led to a growing interest in electromagnetic interference (EMI) shielding in the THz frequency region. There is an urgent need for broadband and tunable devices capable of absorbing terahertz (THz) waves to effectively eliminate undesired THz interference. In this regard, this work demonstrates the facile synthesis of graphitic carbon microspheres from turpentine oil (a natural carbon source) and its broadband absorption and shielding properties in the THz frequency region from 0.2 THz to 1.6 THz. Advanced characterization techniques like XRD, FESEM, RAMAN, and XPS have been employed to explore the structural, microstructural, and elemental properties of graphitic carbon microspheres (GCMs). Herein, an effort has been made to discuss the underlying mechanism for THz absorption by GCMs. The minimum shielding efficacy reaches −27.5 dB covering the broad frequency region from 0.2 to 1.6 THz with a matching thickness of ∼3.75 μm, signifying that more than 99% of the THz radiations can be shielded. Also, GCMs are exhibiting exceptional terahertz absorption (∼86%) spanning from 0.2 to 1.6 THz for the same sample thickness. Our findings reveal valuable insights into the THz shielding properties of graphitic carbon thin films without any complex element doping or functionalization, shedding light on their suitability for future THz-based devices.

One-step synthesis of cobalt nanosheets depositing with carbon microsphere by microwave plasma assisted reduction chemical vapor deposition technique against electromagnetic pollution

The rational design of magnetic carbon composites in both composition and microstructure has significant potential for acquiring excellent electromagnetic wave absorbing materials (EAMs). In this study, Co@carbon magnetic composites were prepared by employing a novel microwave plasma assisted reduction chemical vapor deposition (MPARCVD) technique, which was highly efficient, low-cost, and energy-saving. The depositing of graphitized carbon microspheres on the surface of Co nanosheets could enrich the available loss mechanisms. Furthermore, the lamelliform morphology with a large aspect ratio of the composites was beneficial to subtly improve the dielectric properties under a low filler content. As a consequence, the minimum RL reached up to −65.7 dB and the radar cross-sectional area reduction attained to 22.3 dBm 2 with only 20 wt% loading content. The MARCVD technology opened a novel strategy and avenue for acquiring magnetic carbon composites as candidates for lightweight and high-performance EAMs.

Towards Highly Efficient Lithium-Ion Batteries: Focusing on Electrolytes

Lithium-ion is various advantages and is required by batteries such as high power, so lithium-ion plays a crucial role in lithium-ion batteries. The electrolyte is one of the core materials of lithium secondary battery and primary battery capacity, improves the mobility between the mobile anode and cathode, and plays the role of medium material. The lithium-ion battery's electrolyte, a crucial component, transports ion conduction current between the positive and negative electrodes. Choosing the right electrolyte is also essential for achieving high energy and power densities, long cycle lives, and good safety performance of the lithium-ion secondary battery. First, understand the lithium-ion battery charge and discharge of the working principle of the chemical equation, and the lithium-ion battery is split into four key components, respectively: positive and negative electrode, diaphragm, and electrolyte, then the electrolyte analysis, the electrolyte is composed of organic solution, conductive salt, and additives. Finally, a new type of sulfate additive, ethyl sulfate, is found and studied at the electrolyte level by literature search. By using the constant current charge-discharge test, cyclic voltammetry, scanning electron microscopy, energy scattering spectroscopy, and electrochemical impedance spectroscopy, researchers are examining the effects of additive ethyl sulfate (DTD) on the performance of lithium-ion batteries and the interfacial performance of graphitized carbon microspheres (MCMB) electrode/electrolyte (EIS).

Highly Graphitized Porous Carbon Microspheres Derived from Copolymer of Glucose and Melamine for Advanced Electrodes

AbstractThe N/O co‐doped hierarchical porous graphitized carbon microspheres (N/O‐PCs) are successfully prepared by condensation polymerization of 5‐hydroxymethylfurfural and melamine, and subsequent KOH activation strategy. The obtained carbon materials have a high specific surface area (1685.58 m2 g–1), rich micro‐ and mesopores, and appropriate pore volume (0.828 cm3 g–1). The degree of graphitization for N/O‐PCs is improved because the ratio of IG and ID increases from 0.88 to 1.03. The layer spacing of the lattice plane (002) for the N/O‐PCs is enlarged, facilitating the transmission of electrolyte ions. The high graphitization degree and enlarged layer spacing bring excellent electrical conductivity and wettability for N/O‐PCs as electrode materials. Besides, owing to the higher N (3.59 at%) and O (12.67 at%) content, the N/O‐PCs show excellent specific capacitances of 412 and 284 F g–1 at the current densities of 1 and 10 A g–1 in 2 m H2SO4 aqueous electrolytes, respectively. Outstanding rate performance (200 F g–1 at 50 A g–1) and ideal cycle stability (>10 000 cycles) are achieved. Moreover, the N/O‐PCs‐based symmetric supercapacitor exhibits an energy density of 9.6 Wh kg–1 at 100.8 W kg–1. Thus, the N/O‐PCs provide the potential for high‐performance supercapacitor electrodes.

Synthesis of g-C3N4/NiO-carbon microsphere composites for Co-reduction of CO2 by photocatalytic hydrogen production from water decomposition

In this paper, a g-C3N4/NiO/corn straw derivative carbon microsphere composite photocatalyst was successfully prepared. Photoelectric studies show that a heterojunction was formed between g-C3N4 and NiO nanosheets, and the graphitized carbon microspheres were successfully modified on g-C3N4 and NiO nanosheets. The heterostructure between g-C3N4 and NiO works synergistically with the conductivity of carbon microsphere, resulting in H2 production and CO2 reduction in photocatalysis. Photocatalytic experiments show that the photocatalytic performance of g-C3N4/NiO/carbon microsphere composite is enhanced, and the highest H2 production rate was 36–58 times higher than that of pure g-C3N4. In the presence of CO2 gas, H2 production and CO2 reduction occur simultaneously. The possible mechanism of H2 production combined with CO2 reduction photocatalysis is analyzed from the perspective of thermodynamics and kinetics. The g-C3N4/NiO/carbon microsphere composite has a stronger H2 evolution performance than CO2 reduction performance. The change in free energy (ΔG) for the conversion of CO* to free CO gas is 0.52 eV, and CO release is the key step affecting the synergistic reduction of CO2 by H2. This study provides new strategies for the synergistic reduction of CO2 by photocatalytic technology for H2 production.

Nickel Acetate-Assisted Graphitization of Porous Activated Carbon at Low Temperature for Supercapacitors With High Performances.

Catalytic graphitization opens a route to prepare graphitic carbon under fairly mild conditions. Biomass has been identified as a potentially attractive precursor for graphitic carbon materials. In this work, corn starch was used as carbon source to prepare hollow graphitic carbon microspheres by pyrolysis after mixing impregnation with nitrate salts, and the surface of these carbon microspheres is covered with controllable pores structure. Under optimal synthesis conditions, the prepared carbon microspheres show a uniform pore size distribution and high degree of graphitization. When tested as electrode materials for supercapacitor with organic electrolyte, the electrode exhibited a superior specific capacitance of 144.8 F g−1 at a current density of 0.1 A g−1, as well as large power density and a capacitance retention rate of 93.5% after 1,000 cycles in galvanostatic charge/discharge test at 1.0 A g−1. The synthesis extends use of the renewable nature resources and sheds light on developing new routes to design graphitic carbon microspheres.

Nitrogen and oxygen co‐doped carbon microspheres with partially graphitic structures: Integrated high volumetric capacitance, mass loadings and rate capability for supercapacitors

AbstractSynthesis of porous carbon electrodes with high volumetric capacitance and excellent rate capability, especially for a higher mass loading of 10 mg cm–2, remains a challenge and is important for wide applications of the new generation supercapacitors. We report unprecedented volumetric capacitance of 942.9 F cm–3 in 2 M H2SO4 for partially graphitized carbon microspheres co‐doped with N and O prepared by simple hydrothermal route followed by direct cobalt catalytic pyrolysis, which is comparable to the expensive metal oxide and MnO2‐based pseudo‐capacitors. The resulted carbon also shows excellent rate capability (65.4% and 52.2% capacitance retention as the current density increases from 1 to 20 A g–1 in 2 M H2SO4 and 6 M KOH, respectively) and cyclic stability with a higher mass loading of 9.84 mg cm–2 in acidic/basic electrolytes. More importantly, the high volumetric energy density (22.39 Wh L–1) of the assembled symmetrical supercapacitors in 6 M KOH makes it possible to compete with even some Ni metal hydride batteries. This work offers a way to develop advanced porous carbon materials with ultrahigh volumetric capacitance/mass loadings and fast charge rates for supercapacitors.

Facile synthesis of NiCo2S4 nanosheets on graphitized carbon microspheres for high-performance asymmetric supercapacitors

In this work, the hybrid structure of NiCo2S4 nanosheets onto graphitized carbon microspheres (GCMS@NiCo2S4) electrode material has been rationally fabricated by using a rapid, facile, and efficient strategy, and the synergistic effect of NiCo2S4 and GCMS on the enhanced supercapacitors performance is explored. The GCMS@NiCo2S4 electrode with capacitive dominated feature exhibited a high specific capacitance (1595.1 F g −1 at 1 A g −1) and as well as excellent cyclic stability (92% retention after 5000 cycles), which were higher than these of the electrode without GCMS (i.e. pure NiCo2S4). Charge storage analysis reveals that the capacitive dominated feature of GCMS@NiCo2S4 electrode is observed. Additionally, the as-synthesized asymmetric supercapacitor by using GCMS@NiCo2S4 electrode displays a maximum specific energy of 50.2 Wh kg−1 at a specific power of 799.9 W kg−1, together with good cyclic life with 91% capacity retention over 10000 cycles at 10 A g−1. These remarkable electrochemical performances demonstrate that GCMS@NiCo2S4 has excellent potential applications in high efficient electrochemical supercapacitor.

Degradation of ofloxacin using peroxymonosulfate activated by nitrogen-rich graphitized carbon microspheres: Structure and performance controllable study

Nitrogen-rich graphitized carbon microspheres (NGCs) with hierarchically porous were constructed by self-assembly. Under different heat treatment conditions, the structure, morphology and properties of NGCs were studied by using multiple characterization techniques. The results showed that the chemical microenvironments (e.g. surface chemistry, degree of graphitization and defective, etc.) and microstructures properties (e.g. morphology, specific surface area, particle size, etc.) could be delicately controlled via thermal carbonization processes. The degradation of ofloxacin (OFLX) by NGCs activated peroxymonosulfate (PMS) was studied systematically. It was found that the synergistic coupling effect between optimum N or O bonding species configuration ratio (graphitic N and C=O) and special microstructure was the main reason for the enhanced catalytic activity of NGC-800 (calcination temperature at 800°C). Electron paramagnetic resonance (EPR) experiments and radical quenching experiments indicated that the hydroxyl (•OH), sulfate (SO4•−) and singlet oxygen (1O2) were contributors in the NGC-800/PMS systems. Further investigation of the durability of chemical structures and surface active sites revealed that undergo N bonding species configuration reconstruction and cannibalistic oxidation during PMS activation reaction. The used NGC-800 physicochemical properties could be recovered by heat treatment to achieve the ideal catalytic performance. The findings proposed a valuable insight for catalytic performance and controllable design of construction.

Carbon microspheres with micro- and mesopores synthesized via spray pyrolysis for high-energy-density, electrical-double-layer capacitors

The graphitic properties, optimized pore structure, and surface chemistry of carbon materials are important factors for developing high-performance supercapacitors. In this study, we synthesized partially graphitic carbon microspheres with large surface area and multimodal pore-size distribution (high amount of micropores and small amount of mesopores) using a facile spray pyrolysis process. Vanadium oxide-carbon microspheres were synthesized via spray pyrolysis at 1000 °C. Subsequently, selective etching of vanadium oxide using NH4OH solution resulted in porous carbon (PC) microspheres with large surface area and multimodal pore structure. The post-treatment process of PC microspheres at 900 °C in Ar atmosphere enabled not only the synthesis of partially graphitic carbon microsphere via graphitization, but also the elimination of organic functional groups at the carbon surface. The supercapacitor fabricated with post-treated PC microspheres (PC-900) with a voltage window of 2.5 V exhibited high specific capacitance (110 F g−1 at 30 A g−1) and excellent rate capability in an organic electrolyte. The PC-900 supercapacitor could also produce high energy density (23 Wh kg−1) even at high power density (42 kW kg−1). In addition, the PC-900 supercapacitor exhibited excellent cyclability with capacitance reduction of approximately 5% after 10,000 cycles.

Defect-enriched, nitrogen-doped graphitic carbon microspheres within 3D interconnected super-macropores as efficient oxygen electrocatalysts for breathing Zn-Air battery

Constructing efficient bifunctional oxygen electrocatalyst which integrates highly efficient active sites with desired structures for rapid mass transport is of great importance for designing rechargeable Zn-air battery with high power density and fast charge and discharge performances. Herein, defect-enriched N-doped graphitic carbon microspheres with fully open and 3D interconnected super-macropores are successfully constructed by an elaborate coating-activation synthesis strategy. The resulted novel structures are featured with abundant defects as active sites and bicontinuous structures, i.e., the continuous carbon skeleton and the interconnected super-macropores for fast electron and mass transport, respectively. Our synthesized defect-enriched N-doped graphitic carbon microsphere bifunctional oxygen electrocatalysts display excellent performance. The rechargeable Zn-air batteries exhibit a long time charging-discharging cycles as long as 800 cycles at even 50 mA cm−2. This study provides an attractive guide to improve the bifunctional oxygen catalytic performances and promote the Zn-air battery applications in both electric vehicles and grid energy storage in the future.

Realizing a highly stable sodium battery with dendrite-free sodium metal composite anodes and O3-type cathodes

Room-temperature Na metal batteries have been regarded as promising candidates for energy storage systems due to their high energy density and the widespread availability of low cost sodium. However, the practical application of metallic sodium anode is impeded by its low stripping/plating efficiency and poor cycling performance due to the poor reversibility of sodium anode caused by the formation of inhomogeneous solid electrolyte interphase, the growth of dendritic sodium, and relatively infinite volume change. Here, Na-C composite anode was fabricated by depositing nanoscale metallic sodium in graphitized carbon microspheres which were assembled from graphitized carbon nanosheets. The carbon microspheres function as a mini-nanoreservoir with high-surface-area, conductivity, and mechanical stability, which lower the local current density, ensure a homogeneous Na nucleation and high electrochemical active of Na, and restrict the volume change. As a result, metallic sodium can be reversibly nondendritic stripped/plated with a high Coulombic efficiency of 99.3% up to 4 mA cm−2 for 4 mA h cm−2. Building upon this dendrite-free anode, we demonstrate a full cell using O3-NaNi0.5Mn0.2Ti0.3O2 cathode to achieve a superior long lifespan of ~100 cycles at high current density of 0.5 C.

Mesoporous graphitic carbon microspheres with a controlled amount of amorphous carbon as an efficient Se host material for Li–Se batteries

Graphitic carbon–TiO microspheres with optimum structures are synthesized as host materials for amorphous elemental Se by the modification of activated carbon microspheres. Graphitic carbon–TiO/Se microspheres exhibit excellent electrochemical properties as a cathode material for Li–Se batteries.

Potassium vapor assisted preparation of highly graphitized hierarchical porous carbon for high rate performance supercapacitors

Ultrahigh graphitized carbon microspheres with rich hierarchical pores (AGHPCM-1) have been successfully synthesized through the one-step activation-carbonization strategy (OACS) with porous sulfonated poly-divinylbenzene as the carbon precursor, iron as the hard template and catalyst, and potassium hydroxide (KOH) as activation agent. Through the XRD, TEM, Raman and BET analysis, AGHPCM-1 shows very high graphitization degree and rich micro-, meso- and macro-pores. More importantly, the mechanism for KOH to improve the graphitization degree of carbon materials in OACS has been illustrated by the thermodynamical theory. The tremendous heat releasing from the reaction between the catalyst precursor of Fe2O3 and potassium vapor plays a key role in the formation of graphitized carbon. It may provide a general direction to prepare highly graphitized porous carbon at a moderate temperature. Integrating the advantages of high graphitization degree and rich hierarchical porous structure, the AGHPCM-1 exhibits an excellent rate performance with a response to up to the high current density of 150 A g−1 and high scan rate of 2000 mV s−1. No obvious capacitance decay can be observed after 10000 charge/discharge cycles even at the high current density of 20 A g−1.

Facile synthesis of nitrogen and sulfur dual-doped graphitized carbon microspheres and their high performance in the oxygen reduction reaction

A facile protocol for producing porous carbon spheres co-doped with nitrogen and sulfur is presented.

Encapsulation of α-Fe2O3 nanoparticles in graphitic carbon microspheres as high-performance anode materials for lithium-ion batteries

A novel "spray drying-carbonization-oxidation" strategy has been developed for the fabrication of α-Fe2O3-graphitic carbon (α-Fe2O3@GC) composite microspheres, in which α-Fe2O3 nanoparticles with sizes of 30-50 nm are well-encapsulated by onion-like graphitic carbon shells with a thickness of 5-10 nm. In the constructed composite, the α-Fe2O3 nanoparticles act as the primary active material, providing a high capacity. Meanwhile, the graphitic carbon shells serve as the secondary active component, structural stabilizer, interfacial stabilizer, and electron-highway. As a result, the synthesized α-Fe2O3@GC nanocomposite exhibits a superior lithium-ion battery performance with a high reversible capacity (898 mA h g(-1) at 400 mA g(-1)), outstanding rate capability, and excellent cycling stability. Our product, in terms of the facile and scalable preparation process and excellent electrochemical performance, demonstrates its great potential as a high-performance anode material for lithium-ion batteries.

A Simple Nanocasting Route for Preparation of Mesoporous Titanium Dioxide/GCM Microsphere

Mesoporous titanium dioxide/graphitic carbon microspheres were synthesized by a simple nanocasting route using monodisperse silicon dioxide microspheres as the template. The characterize and the morphology of the titanium dioxide/graphitic carbon microspheres have been analyzed by means of XRD, N2-sorption, SEM, TEM, TG-DTA and EDAX. Indicated by the experimental results and the theoretical analysis, the anatase titanium dioxide nanoparticles of 8-14 nm in diameter were highly dispersed in the graphitic carbon microspheres. The obtained material can be used as catalyst or battery material. Key words: titanium dioxide/graphitic carbon; Microspheres; Nanocasting route;Mesoporous