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The utilization of high‐sulfur coal, especially high‐organic coal, has always been a difficult hot spot in the energy field. To study the influence of sulfur in coal on coal‐based graphite products, a series of coal samples with different sulfur content and different degrees of coalification were collected for proximate analysis, ultimate analysis, and sulfur species analysis. The structural characteristics of coal‐based graphite products were analyzed by X‐ray diffraction (XRD). The relationships between the sulfur in coal and the yield (Y), graphitization degree (G), cell diameter (La), and stacking height (Lc) of coal‐based graphite products were explored. The yield of coal‐based graphite ranges from 8.92 % to 64.45 %, and it was found that the yield of coal‐based graphite is not only affected by the degree of coalification, fixed carbon content, and volatile matter content of coal but also significantly inhibited by organic sulfur in coal when the reflectance is less than 2.00 %. The graphitization degree (G) of coal‐based graphite is distributed between 76.02 % and 91.02 %, and positively related to the degree of coalification, and negatively related to the content of volatile matter. Organic sulfur in coal is an unfavorable factor for the graphitization degree (G) of coal‐based graphite. Both the cell diameter (La) and stacking height (Lc) of coal‐based graphite are positively correlated with the degree of coalification and negatively correlated with the volatile matter content in coal. Organic sulfur in coal plays an important inhibitory role on the cell diameter (La) of coal‐based graphite. Still, it has almost no effect on the stacking height (Lc) of coal‐based graphite, resulting in a low ratio of horizontal‐to‐vertical (La/Lc), which is not conducive to the horizontal development of coal‐based graphite cells. [ABSTRACT FROM AUTHOR]

Two X-ray diffraction methods were chosen to determine the degree of structural order (degree of graphitization) of natural carbonaceous matter. Factors influencing the graphitization processes during the progressive and regressive stages of metamorphism are examined. The correlation of the degrees of structural order of the carbonaceous material with the sequence of mineral growth allows the metamorphic history of the graphite-bearing rocks to be traced. The obtained data can be used for the evaluation of graphite as a raw material. [ABSTRACT FROM AUTHOR]

Summary: In this paper, polyacrylonitrile‐based graphite felt (GF), carbon felt (CF) and the effect of thermal activation on them with or without the catalyst (BiCl3) are comprehensively investigated for iron‐chromium redox flow battery (ICRFB) application. The physical‐chemical parameters of GF and CF after the thermal activation is affected significantly by their graphitization degree, oxygen functional groups, and surface area. Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) results manifest that GF and CF before and after the thermal activation have different electrocatalytic activities owing to oxygen functional groups number increase and the graphitization degree decrease. In terms of the capacity decay rate, as oxygen functional groups provide shorter electrocatalytic pathways than bismuth ions, the performance of GF and CF after the thermal activation is more ideal. As a result, GF before and after the thermal activation exhibits higher efficiency (EE: 86%) and better stability at a charge‐discharge current density of 60 mA·cm−2 than those of CF during charge‐discharge cycling, as the dominant limitation in an ICRFB is ohmic and activation polarization. Therefore, GF after thermal activation together with the addition of BiCl3 in the electrolyte is a more promising electrode material for ICRFBs application than CF. [ABSTRACT FROM AUTHOR]

Abstract Carbon/carbon-boron nitride (C/C-BN) composites were manufactured by adding hexagonal boron nitride (h-BN) powders into carbon fiber preform and a subsequent chemical vapor infiltration (CVI) process for deposition of pyrolytic carbon (PyC). Microstructure and oxidation behavior of carbon/carbon composites with 9 vol% h-BN (C/C-BN9) were studied in comparison to carbon/carbon (C/C) composites. Results showed that with the addition of h-BN powders, a regenerative laminar (ReL) PyC with higher texture was achieved. Note that the introduction of h-BN powder make great contributes to graphitization degree of PyC, leading to larger oxidation activation energy. Moreover, under an air atmosphere, h-BN started to oxidize above 800 °C, and generated molten boron oxide (B 2 O 3) which prohibited oxygen diffusion by filling in pores, cracks and other defects. As these reasons mentioned above, after oxidation tests under an air atmosphere, mass losses of C/C-BN9 composites were lower than that of C/C composites at all test temperatures (600–900 °C), indicating that the oxidation resistance of C/C-BN9 composites is better than that of C/C composites. [ABSTRACT FROM AUTHOR]

In this study, comparative experiments were conducted on the adsorption of cationic blue onto graphene oxides (GOs) synthesized by graphites with various graphitization degrees. XRD, XPS, FT-IR, Raman, AFM and BET were used to characterize the prepared GOs. The results demonstrated that graphites with lower graphitization degrees were more easily oxidized, and GOs prepared from those graphites had more oxygen-containing groups, higher degrees of defects, thinner layers and higher specific surface areas. The equilibrium data was in better agreement with the Langmuir model than both the Freundlich model and the Temkin model. In addition, the adsorption of cationic blue on the GOs was well-described by the pseudo-second order kinetics model according to the kinetic experiments. Moreover, the thermodynamic parameters demonstrated that the adsorption was both an endothermic and spontaneous process. [ABSTRACT FROM AUTHOR]

High density graphite is widely used in friction and sealing area. The pore structure inside, which were mainly affected by molding method, has a great effect on its thermophysical properties and friction performance. Herein, isostatic pressing, compression molding and hot molding method were utilized in our work to prepare high density graphite with different pore structure in order to study the relationship between pore structure and the comprehensive property. The results showed that the properties of graphite vary significantly in different directions, which was mainly affected by porosity, pore size distribution, the specific surface area, pore shape and fractal dimension. The influence mechanism of three graphite materials with different pore structures on thermophysical properties was delved, and the correlation between the comprehensive properties of graphite materials and their pore structures was verified. The in-plane comprehensive properties of hot molding graphite were the best, the graphitization degree was the highest (75.4%) and the total porosity was the lowest (15.08%). Especially, according to the pore structure analysis of the graphite, we found a positive correlation between the fractal dimension and the friction and wear properties of the graphite materials. Furthermore, research of pore structure explained the properties of graphite materials and proved the potential application of graphite in friction and sealing fields. [Display omitted] • Graphite with different pore structures were prepared by different forming process. • The evolution of pore structure was deduced during the preparation of graphite products. • Pore structure characteristic parameters effect the comprehensive property of graphite. • Hot Molding can improve the orientation and degree of graphitization of the graphite. • Fractal dimension was positively correlated with the friction and wear properties. [ABSTRACT FROM AUTHOR]

• The influence of graphitization degree on HTGR reactor physics calculation is studied. • The k eff can be underestimated if graphitization degree is not taken into account. • The result is of significance for graphite reactors. Nuclear graphite is widely used in traditional and advanced nuclear reactors. Especially in High Temperature Gas-cooled Reactors (HTGRs), nuclear graphite is the main composition of fuel element and reflector. The graphite cross section data libraries used in practical reactor physics calculations are generally evaluated from ideal single crystal graphite material. However, the actual nuclear graphite is not ideal but contains a certain proportion of amorphous carbon, which is measured as graphitization degree. By this short paper, it is shown that the graphitization degree of nuclear graphite has a considerable influence on HTGR reactor physics calculation. The observation would be important for the engineering design of various types of graphite reactors. [ABSTRACT FROM AUTHOR]

An experimental study was performed by employing a seal pair of phenolic resin impregnated graphite and high chromium martensitic stainless steel 9Cr18. A purpose-built test rig was designed and fabricated to study the effect of face temperature on the surface morphology of a seal ring made of phenolic resin impregnated graphite with different graphitization degrees for varying PV values (pressure × velocity). As revealed by the results, the effect of rotational speed on heat generation between the two mating surfaces was more significant than that of fluid pressure. The effects of surface frictional temperature between the two faces were found different when the phenolic resin impregnated graphite ring with different graphitization degrees. The worn surfaces of the phenolic resin impregnated graphite rings were examined with the assistance of scanning electron microscopy and 3D measuring laser microscopy to investigate the wear mechanism for these different mating rings. Both adhesive and abrasive wear mechanisms were discovered under the working conditions. It was found out that the phenolic resin impregnated graphite ring with a high degree of graphitization was worn more severely at high PV values. Under the conditions of high speeds or high PV values, the phenolic resin impregnated graphite with fine and compact graphite matrix particles, medium degree of graphitization, high thermal conductivity and hardness is the top choice. ∙ This paper studies the effect of face temperature under different PV values on frictional characteristics of impregnated phenolic resin graphite rings with different graphitization degrees. ∙The influence mechanism of PV values on face temperature of mechanical seal is revealed. And the effects of face temperature on phenolic resin graphite stationary rings with different graphitization degrees are studied. ∙This paper provides some important conclusions for choosing the proper phenolic resin impregnated graphite stationary ring under the conditions of high speeds or high PV values. [ABSTRACT FROM AUTHOR]