Graphitization Degree Of Carbon Research Articles

Revealing the atomic-scale configuration modulation effect of boron dopant on carbon layers for H2O2 production.

This work reports an atomic-scale carbon layer configuration tuning strategy induced by a boron dopant. Through regulating the doping level of boron, it was found that the boron dopant not only favors carbon layer growth by strengthening the metallic state of the Ni core, but also enhances the abundance of pyrrolic N species and graphitization degree of carbon by tailoring the carbon/nitrogen atom configuration, thereby contributing to more active pyrrolic N/carbon sites and accelerated interface reaction dynamics. Consequently, the developed Ni@B,N-C catalyst achieves remarkable electrochemical H2O2 production performances with a high selectivity of 95.5% and a yield of 795 mmol g-1 h-1. In comparison with previous reports in which the boron dopant mainly acts as an electronic structure regulator, this study reveals the tuning effect of boron dopants on the atomic-scale carbon layer configuration, opening up a new avenue for the development of advanced catalysts.

Wetting behavior and mechanism between hot metal and carbon brick

Wetting behavior between hot metal and carbon brick is the first step to explore the erosion of carbon brick. In order to investigate the wetting behavior, wetting experiments between hot metal (with carbon content 2.87, 3.47, 4.12, 4.51, and 4.96 mass%) and carbon brick were carried out. The wetting angle under different conditions was measured, the reaction interface morphology and carbon structure were analyzed, the mechanism of hot metal wetting carbon brick was clarified based on interfacial energy and scaling law. The results show that: The wetting angle decreased gradually with the increase of wetting time for all initial carbon content experiments, the wetting angle increased with the increase of initial carbon content in hot metal. The dissolution of carbon occurred during the wetting process, which left a concave on carbon brick. The graphitization degree of carbon in carbon brick increased after the wetting behavior. In the initial stage of the wetting reaction, the change of interfacial energy caused by carbon dissolution reaction was the essential reason for the change of wetting angle. In the final stage of the wetting reaction, the wetting angle mainly depended on the concave shape after the concave was formed. The wetting model was established to explore the wetting behavior with dissolution reaction, the scaling relationship between the spreading radius of iron drop and time was obtained, which was convenient to evaluate the wetting behavior between hot metal and carbon brick.

Prussian blue analogue derived carbon-based composites toward lightweight microwave absorption

Carbon-based composites derived from metal organic frameworks (MOFs) have attracted much interest for microwave absorption. However, most studies only focus on the influence of heating temperature rather than the composition of derivatives on microwave absorption ability. In this work, four kinds of derivatives are obtained from Prussian blue analogue (PBA) after heating treatment. It is found that the annealing atmosphere has a significant influence on material compositions, thus the electromagnetic (EM) parameters and carbon graphitization degree are tuned. As a result, the CoFe/Carbon (CoFe/C) composite was derived from CoFe-PBA precursor with Ar atmosphere, which reached minimum reflection loss (RLmin) value of −44.6 dB and effective absorption bandwidth (fe, the RL value less than −10 dB) of 5.5 GHz at 2.15 mm. For the NiFe/Carbon (NiFe/C) composite, the RLmin of −41 dB and fe of 4.8 GHz can be obtained at the thickness of 1.65 mm. The optimal fe of 6.0 GHz is obtained when the matching thickness was 2.0 mm. Given the lightweight, ultrathin, strong microwave attenuation capability, as well as broad effective absorption bandwidth, these carbon-based composites derived from PBA precursors are promising for practical applications.

High-performance Ti0.95Co0.05N@NC–based ORR catalysts: organic-nitrogen nitrogenize and their application in rechargeable Zn-air batteries

The exploration of cheap, stable, and highly efficient non-precious metal catalyst is conducive to extending the practical applications of zinc-air batteries (ZABs). Herein, a simple, environmental friendly and low-cost method was proposed to fabricate nitrogen-doped carbon–coated TiN nanoparticle composites (TiN@NC). Dicyandiamide was applied as the nitrogen source instead of ammonia reduction, based on which Ti0.95Co0.05N@NC was synthesized. Oxygen reduction reaction (ORR) measurement shows that the onset potential of Ti0.95Co0.05N@NC was 30 mV higher compared to TiN@NC, which is attributed: (i) Cobalt was doped into TiN lattice. (ii) After cobalt doping, the graphitization degree of carbon was increased to facilitate electron transport. (iii) Controlling the reservation of nitrogen to form more N-C active sites in Ti0.95Co0.05N@NC may further promote the performance of ORR. The performance of the ZABs was effectively improved after cobalt doping. It is believed to make it more convenient to prepare binary transition metal nitride nanostructures.

Metal-organic framework-derived metal-free highly graphitized nitrogen-doped porous carbon with a hierarchical porous structure as an efficient and stable electrocatalyst for oxygen reduction reaction

Nitrogen-doped carbon materials are promising oxygen reduction reaction (ORR) electrocatalysts owing to high performance and stability. Herein, a three-dimensional porous bio-MOF-1, Zn8(Ad)4(Bpdc)6O·2Me2NH2 (Ad = adeninate; Bpdc = biphenyldicarboxylate), was used as precursor to fabricate N-doped porous carbon materials (NPC-1000-ts, where 1000 stands for the carbonization temperature and t represents the carbonization time, t = 2, 3 and 4 h) by simple carbonization under Ar atmosphere. The porous carbon materials had different contents of graphitic N and graphitization degrees of carbon. The catalytic activities of NPCs as metal-free ORR electrocatalysts were studied. The obtained NPC-1000-4 (pyrolysis under 1000 °C for 4 h) displayed outstanding ORR performance, with a positive onset potential (−0.012 V), a higher half-wave potential (E1/2) (−0.13 V) and a larger limiting current density (−5.76 mA/cm2) at −0.8 V (vs. Ag/AgCl) in KOH solution (0.1 M) than those of commercial Pt/C (20 wt%) catalyst (Eonset = −0.014 V, E1/2 = −0.14 V and −5.08 mA/cm2 at −0.8 V vs. Ag/AgCl). Obviously, the onset potential of NPC-1000-4 surpassed that of Pt/C, which was rare among currently available studies on metal-free nitrogen-doped porous carbon materials. Graphitic N significantly affected ORR catalytic performance besides graphitization degree of carbon. Meanwhile, NPC-1000-4 allowed an effective 4e−-dominant ORR process, and most importantly, coupled with much higher long-term stability (89.5%) than that of commercial Pt/C (20 wt%, 65.8%) catalyst and higher resistance to methanol poisoning. The remarkable ORR activity of NPC-1000-4 can be ascribed to large surface area, considerable hierarchical porosity, high graphitization degree and synergism between enriched active sites and high portion of graphitic N. Overall, the findings guide the development of MOF-derived metal-free N-doped carbon materials as high-activity non-precious electrocatalysts for ORR.

Bilayer N-doped carbon derived from furfuryl alcohol-wrapped melamine sponge as high-performance supercapacitor

Bilayer carbon is synthesized via carbonization of furfural alcohol-wrapped melamine sponge. Such materials combine the merits of carbonized furfuryl alcohol and melamine sponge: melamine sponge-derived three dimensional N-doped carbon serves as skeleton and support to avoid the agglomeration of furfuryl alcohol; while the furfuryl alcohol coating enhances the carbon yield, avoids the nitrogen loss of melamine sponge and introduces the second carbon layer. Carbonized furfuryl alcohol-wrapped melamine sponge shows the highest specific capacitance of 184 F g−1 at the scan rate of 5 mV s−1, which is almost four times that of carbonized melamine sponge without furfuryl alcohol coating (47.3 F g−1 at 5 mV s−1). Based on the electrochemical measurements, it suggests that the nitrogen content, especially the quaternary nitrogen content and the graphitization degree of carbon are two key dominant factors in enhancing the capacitive performance after furfuryl alcohol coating.

Microstructures, dielectric response and microwave absorption properties of polycarbosilane derived SiC powders

Carbon-rich SiC powders with high dielectric loss were prepared via pyrolysis of polycarbosilane (PCS). The effects of pyrolysis temperature on microstructures, dielectric response and microwave absorption properties in X-band (8.2–12.4GHz) of PCS-derived SiC powders were investigated. The PCS-derived SiC powders are mainly composed of SiC nanocrystal, turbostratic carbon and amorphous phase (SiC and/or C). The size of SiC nanocrystals and the graphitization degree of carbon both increase with the elevation of pyrolysis temperature. Furthermore, the residual carbon is transformed from amorphous into turbostratic structure with a phenomenon of regional enrichment. Moreover, the relative complex permittivity increases notably with the higher pyrolysis temperature. Meanwhile, the dielectric loss tangent increases from 0.19 to 0.57, while the microwave impedance decreases from 73.20 to 53.58. The optimal reflection loss of −35dB for PCS-derived SiC powders is obtained when the pyrolysis temperature is 1500°C, which exhibits a great application prospect in microwave absorbing materials.

Sulfur-Doped Carbon with Enlarged Interlayer Distance as a High-Performance Anode Material for Sodium-Ion Batteries.

S-doped carbon is investigated as a high-performance anode material for sodium-ion batteries. Due to the introduction of a high-content of S atoms, the as-obtained S-doped carbon shows an enlarged interlayer distance. As an anode, a high specific capacity of up to 303 mAh g-1 is achieved, even after 700 cycles at 0.5 A g-1.

Effects of cobalt precursor on pyrolyzed carbon-supported cobalt-polypyrrole as electrocatalyst toward oxygen reduction reaction.

A series of non-precious metal electrocatalysts, namely pyrolyzed carbon-supported cobalt-polypyrrole, Co-PPy-TsOH/C, are synthesized with various cobalt precursors, including cobalt acetate, cobalt nitrate, cobalt oxalate, and cobalt chloride. The catalytic performance towards oxygen reduction reaction (ORR) is comparatively investigated with electrochemical techniques of cyclic voltammogram, rotating disk electrode and rotating ring-disk electrode. The results are analyzed and discussed employing physiochemical techniques of X-ray diffraction, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, inductively coupled plasma, elemental analysis, and extended X-ray absorption fine structure. It shows that the cobalt precursor plays an essential role on the synthesis process as well as microstructure and performance of the Co-PPy-TsOH/C catalysts towards ORR. Among the studied Co-PPy-TsOH/C catalysts, that prepared with cobalt acetate exhibits the best ORR performance. The crystallite/particle size of cobalt and its distribution as well as the graphitization degree of carbon in the catalyst greatly affects the catalytic performance of Co-PPy-TsOH/C towards ORR. Metallic cobalt is the main component in the active site in Co-PPy-TsOH/C for catalyzing ORR, but some other elements such as nitrogen are probably involved, too.

Low temperature one-step synthesis of cobalt nanowires encapsulated in carbon

The one-step method of carbon nanotubes filled with continuous cobalt nanowires (CoF-CNT) synthesis is presented. Co/ZSM-5 (8 wt% Co) was used as catalyst for CoF-CNT production by methane decomposition at the temperature of 400 °C and 800 °C at atmospheric pressure in a conventional gas-flow system. The average diameter of the CoF-CNT is about 25 and 40 nm for products obtained at 400 °C and at 800 °C, respectively. The average size of coherently scattering domains along the normal to graphite layers L c , the interlayer spacing d 002, the graphitization degree of carbon, and the relative intensities of the G and D bands in Raman spectroscopy were determined to characterize the quality of carbon. It was proved that cobalt-filled carbon nanotubes can be produced by a simple method. The results of XRD, FE-SEM, and TEM show that CoF-CNT can be obtained even at 400 °C by catalytic decomposition of methane. On the basis of XRD, TEM, Raman spectroscopy was found that at a temperature of 800 °C, a better quality of carbon was produced.

Further performance enhancement of a DME-fueled solid oxide fuel cell by applying anode functional catalyst

In order to increase the coking resistance of SOFCs operating on DME fuel, a Pt/Al2O3–Ni/MgO mixture catalyst was investigated for internal partial oxidation of DME. Catalytic test demonstrated the mixture catalyst has higher activity for DME partial oxidation and lower CH4 selectivity than the individual Pt/Al2O3 and Ni/MgO catalysts. O2-TPO analysis demonstrated that the mixture catalyst also had much higher coke resistance than sintered Ni-YSZ anode, especially at high O2 to DME ratio. Raman spectroscopy of the carbon-deposited catalysts demonstrates that the graphitization degree of carbon is reduced with introducing O2 into DME, and the carbon deposited on the mixture catalyst is almost in amorphous structure. Two operation modes of the mixture catalyst for indirect internal partial oxidation of DME, i.e, directly depositing on the anode surface and locating in the anode chamber were tried. The performance of the cells operating on DME fuel through both operation modes was studied by I–V polarization test and EIS characterization. The cells delivered attractive peak power density of around 750 mW cm−2 by operating on DME-O2 mixture gas, modestly lower than 1012–1065 mW cm−2 operating on pure hydrogen fuel at 700 °C. The direct deposition of Pt/Al2O3–Ni/MgO onto anode surface to perform as a functional layer and a DME to O2 ratio of 2:1 in the mixture gas is preferred to minimize coke formation and maximize power output for the cell to operate on DME fuel.

Effect of Graphitization Degree on Machinability of Carbon

The purpose of the present study is to establish the standards for carbon products.This paper reports the effect of the graphitizing degree on the machinability of carbons.The test was carried out by machining eight grade of carbons of different graphitizing degree with milling machine.The Results show that there exists a remarkable correlation between the machinability and the graphitization degree of carbon.

ウラン炭化物製造に関する研究

(1) Single phase uranium monocarbide was prepared by the solid-solid reaction uranium hydride and carbon above 900°C. At 1, 100°C the reaction completes in 2 hr. The sample form and the graphitization degree of carbon have little effects on the reaction rate. The activation energy of the reaction is estimated to be in the range of 2545 kcal/mol. The rate of the reaction is supposed to depend upon the diffusion of carbon rather than that of uranium.(2) Uranium sesquicarbide can be prepared by the solid-solid reaction between uranium monocarbide and carbon at 1, 500°1, 700°C. No stress is necessary for its formation. In the preparation of uranium dicarbide, it was found that the temperature highar than 1, 800°C was necessary to prepare it in a pure single phase.The authors wish to thank Messrs. Toshio Uchijima, Kazuya Takano, Yukio Kawarazaki, Kinji Ouchi and Kunihiro Goto for their assistance in the experiment.They are grateful to Dr. Masayuki Kawasaki for providing uranium metal, to Tokai Electrode Mfg. Co. for providing carbon sample and to Nippon Electrode Co. for graphitization service. They are also indebted to Drs. Keichi Oshima, Toshio Nakai and Kenjiro Kimura for their continuous encouragement.

(89)カルシウム・カーバイドに関する研究(第5報)炭素材の黒鉛化度とその石灰との反応性について

(89)カルシウム・カーバイドに関する研究(第5報)炭素材の黒鉛化度とその石灰との反応性について