Papers by Keyword: Graphitization

Abstract: The conversion of biomass to graphite requires a catalyst to promote the graphitization process. Effective pre-treatment and activation of the carbon precursor are crucial for improving the efficiency and success of biomass graphitization using metal catalysts. In this work, we investigate the combined effects of HCl pre-treatment and single-step impregnation carbon with K₂FeO₄, along with KOH activation, on the graphitization process of Empty Palm Oil Fruit Bunches (EPOFB). X-ray fluorescence (XRF) data reveal that HCl pre-treatment effectively eliminates significant impurities, such as alkali metals, alkaline earth metals, and transition metals, which can hinder the graphitization process. XRD and Raman spectroscopy results indicate that the combination of HCl pre-treatment and single-step impregnation carbon with K₂FeO₄, along with KOH activation significantly improves the graphitic quality of the carbon. High-quality graphitic carbon with an IG/ID ratio of 12.35 for the sample CpreHCl_K₂FeO₄(0.07)_KOH_1200 (EPOFB carbon pre-treated with HCl, followed by impregnation with K₂FeO₄ and activation with KOH, and then pyrolyzed at 1200°C). This particular sample displays a porous surface morphology and has a surface area of 876.407 m²/g. This study underscores the importance of acid pre-treatment and chemical activation in optimizing the preparation of high-quality graphitic carbon from biomass.

Abstract: The quality of the carbon material for application of electrodes in the battery is indicated by its ability to intercalate ions, atoms or molecules. Graphite is a carbon material with good intercalation capability. In this research, a carbon material in the form of activated charcoal produced from biomass of water hyacinth has been prepared, which is carbonized at various temperatures of 400, 500, and 600 °C with three different activators of ZnCl₂, KOH and H₃PO₄. The activated charcoal will be used as a cathode composite in lithium sulfur batteries. To determine the quality of the activated charcoal, the structure properties of activated charcoal were characterized using X-ray diffraction (XRD). Several parameters that are determined from XRD data included the degree of crystallinity, and the degree of graphitization (Y). The degree of crystallinity was found in the ranges between 5.56 and 12.6%, where activated charcoal was dominated by amorphous structures. The value of the degree of graphitization was about 36%.

Abstract: Structural-phase state of the diamond-metallized coating interphase boundary after thermal diffusion metallization of diamond grains by transition metals Fe, Ni and Co were studied. Metallization were conducted under temperature-time mode corresponding to the sintering of cemented carbide matrices with Cu impregnation. The structural-phase state of the metallized coating and diamond-coating interphase boundary was studied by scanning electron microscopy, X-ray phase analysis and Raman spectroscopy. A metallized coating strongly adhered to the diamond forms during thermal diffusion metallization of diamond by iron. The metallized coating has a complex structural phase composition of iron, a solid solution of carbon in iron and graphite phases. Nickel and cobalt cause intense catalytic graphitization of diamond with the formation of numerous traces of erosion on its surface under the heating conditions specified in the experiment. The observed weak adhesive interaction of these metals with diamond is probably due to the high melting temperatures of the Ni-C and Co-C eutectics, which does not allow the metals to react with diamond under given experimental conditions.

Abstract: Structural-phase state of the diamond-metallized coating interphase boundary after thermal diffusion metallization of diamond grains by transition metals Cr, Ti were studied. Metallization were conducted under temperature-time mode corresponding to the sintering of cemented carbide matrices with Cu impregnation. The structural-phase state of the metallized coating and diamond-coating interphase boundary was studied by scanning electron microscopy, X-ray phase analysis and Raman spectroscopy. It was found that a thin continuous metal carbide coating chemically bonded to the diamond and consisting of the corresponding metal, their carbides and small amount of graphite phases is formed during thermal diffusion metallization of diamond by Cr and Ti under the conditions specified in the experiment. It was shown that graphite is formed not by a continuous layer, but in the form of local inclusions. This ensures a strong adhesion of the metallized coating to the diamond through the carbides of the corresponding metals. The results can be useful in the development of compositions and technological methods that provide an increased level of diamond retention in the matrices of tools based on cemented carbide powder mixtures.

Abstract: The effects of temperature and graphite-like structure additive on the graphitization process of amorphous carbon were investigated through molecular dynamics simulation. The molecular models of amorphous carbon and graphite-like structure-amorphous carbon were constructed with the initial density of 1.62 g/cm³ and carbon atoms number of 4096 by rapid quenching method. After annealing treatment at 3200 K, 3600 K and 4000 K respectively, the evolution rules of sp² C atoms and the instantaneous conformations of the graphite-like structure-amorphous carbon system were analyzed to investigate the effects of temperature and graphite-like structure on the graphitization process. It could be found that increasing graphitization temperature properly could improve graphitization degree of amorphous carbon. Addition of graphite-like structure could promote recrystallization of the irregular carbon atoms in amorphous carbon materials, thus accelerating graphitization process and promoting graphitization of the system.

Abstract: The use of fullerene black (FB) as effective modifying additive to cast iron is substantiated by its high potential. Research of nanoadditives to modifier has shown an increase in graphitization degree and the forming of favorable morphology of globular graphite. The results of microstructural analysis and tribological trials have confirmed an improvement of ductile cast iron’s structure and properties when treated with FB-additive.

Abstract: In this paper, nanocrystalline diamond with the average grain size of 50nm was prepared under different sintering pressure, temperature and sintering time. The microstructure of the sample was analyzed by SEM, EDS and XRD, and the mechanical properties tested by micro-hardness tester and wear ratio instrument. The results show that the sample sintered under the optimum conditions of oil pressure 87MPa, heating power 4000W and sintering time 120s possessed hardness of 706.41HV and wear ratio of 3280. It indicated that high performance n-PCD sintered from nanodiamond and silicon system can be formed hardly with diamond to diamond bonding but can be formed with diamond to silicon carbide bonding. The poor mechanical properties of the samples were due to the surface adsorption groups and surface graphitization of nanodiamond during high pressure sintering.

Abstract: 4H-SiC p⁺nn⁺ structures fabricated by implantation of Al into a commercial n-type 4H-SiC epitaxial layer doped to (3-5)Ÿ10¹⁵cm^-3 have been studied. Structures with unstable excess forward current were characterized by electron beam induced current (EBIC) and secondary electron (SE) methods and by Auger-electron spectroscopy (AES). Numerous defects were found with a depth which exceed the thickness of the p⁺-layer. Also, it was demonstrated that the concentration of carbon on the SiC surface always exceeds that of silicon, which may be the reason for the initially unstable conductivity via the defects.

Abstract: Currently diamond like carbon (DLC) coatings application for automotive components is becoming a favorable strategy to cope with new challenges faced by automotive industries. DLC coating is very effective to lower the coefficient of friction and wear rate, which in turn could improve fuel efficiency and durability of the engine components. Commercially available fully formulated lubricating oils are specially produced to enhance the lubrication of ferrous materials. Therefore, nonferrous coating (DLC) interaction with commercial lubricating oil needs to be investigated. In this current investigation, coefficient of friction and wear rate were investigated by ball on plate tribo testing machine at different temperatures in the presence of SAE 40 lubricating oil. At high test temperature coefficient of friction decreases, however wear rate increases for the a-C:H coated plate, however, steel/steel contact shows opposite trend of coefficient of friction and wear rate change.

Abstract: Nowadays environmental awareness issue draws the attention of the scientists; lubricant industry also focuses on environment friendly lubricating oils. Therefore, vegetable oils draw the attention of scientists because of environmental friendly as well as good lubricating characteristics. However, good lubricating vegetable oils often shows inferior property because of low thermal stability, hence, to enhance the performance of vegetable oils self-lubricating diamond like carbon coating is considered, which helps in lowering the friction force which in turn lower friction induced heating, as a result stability of vegetable oils increases. In this current research, three vegetable based oils (sunflower, palm, coconut) are considered as lubricating oil. Tribological tests are conducted by ball on plate tribo-testing machine, tetrahedral type diamond like carbon coated plates and uncoated balls are used in the tribo-pair. Among the testing conditions sunflower oil shows good friction and wear characteristics and coconut oil shows inferior friction and wear characteristics.