Papers by Keyword: Carbon

Abstract: Carburized-quenched steel has a hard layer on the surface and a soft layer in the core. Internal fatigue cracks are observed around the boundary between these two layers under cyclic stress. In this research, we investigated the microstructures (carbon content, prior austenite grains and retained austenite) in the carburized-quenched chromium molybdenum steel bar (JIS-SCM415, diameter = 10 mm) failed by rotating bending test (RBT) at nominal stress amplitude of 716 MPa. After the investigations, we obtained three conclusions: the carbon content in the area from the surface to 0.1 mm depth was higher than other area; the prior austenite grain (PAG) sizes at 0.1 mm depth from the surface was almost the same as that of 0.6 mm depth; and the retained austenite which was indicated from the ratio of γ to α in the cross section ranging from the surface to 0.1 mm depth was decreased by rotating bending fatigue.

Abstract: Application of energy storage systems such as supercapacitors can not be separated from the magnetic fields effect. In the last decade, it’s rare to find research reports about various low magnetic field effects on supercapacitor performance. Asymmetric supercapacitors based on MnO₂-Carbon were made to analyze its electrochemical performance changes by magnetic field in 0-50 mT. Magnetic field was applied in flow direction from cathode (MnO₂-C) to anode (C) during electrochemical performance test using Galvanostatic Charge-Discharge (C-D) instrument. The electrochemical performance was increasing in charging (91%) and discharging (22%) time of asymmetric supercapacitors. Impressively, the 50 mT magnetic field showed a high specific capacitance of 61.9 F/g at 0.1 A/g. The supercapacitor system delivers specific energy (17.8 Wh/kg), specific power density (329.72 W/kg), and outstanding stability (79% in 50 cycles). The electrochemical improvement by magnetic field indicates a highly promising application of this method in future supercapacitor devices.

Abstract: Iron is a major impurity in many water resources and leads to contamination in drinking water. One technology that can be used to reduce the iron content is adsorption using activated carbon. Activated carbon can be derived from biomass including forestry and agricultural waste. To produce an economic adsorbent, the researcher used bengkirai wood sawdust waste which contains 52.9% cellulose and 24% lignin. This material is treated by physical and chemical activation to produce activated carbon. However, there is no information on the effect of the type and concentration of activator on the performance of bengkirai wood activated carbon in reducing iron content. Thus, the purpose of this research is to understand the effect of activator type and concentration on the performance of activated carbon from bengkirai wood to adsorb iron content. There are five steps in this research which are preparation, carbonization, chemical activation, characterization and performance test. The raw material is prepared by screening to get an uniform size of bengkirai wood sawdust. Then, the uniformed bengkirai sawdust is physically activated in the carbonization step by heating it in the furnace at 600°C for 2 hours. After that, the carbon is activated using acid which are HCl, HNO₃, and H₂SO₄ with concentrations of 0.1 M, 0.3 M and 0.5 M. The characterization done in this study are iodine number test and functional group test using Fourier Transform Infrared Spectroscopy (FTIR). The final step is performance test of activated carbon to adsorb iron in the water by contacting the activated carbon into water containing iron for 1 hour. The concentration of iron in the water is measured using Uv vis spectofometry. The result shows that the carbon activation with H₂SO₄ 0.1 M produce activated carbon with the highest iodine number compared to the other type of activator and concentration. The iodine number for this activated carbon is 839.76 mg/g. However, the activated carbon treated using HNO₃ shows the best performance to adsorb iron in water.

Abstract: The effect of carbon-containing additives on the physical, mechanical and electrical properties of the fluoroanhydrite composition used for self-leveling floors has been investigated. Copper/carbon nanocomposite, crushed technogenic graphite and thermally expanded graphite were used as modifying additives in this research. A method for obtaining thermally expanded graphite was described; the efficiency of its introduction into the plasticized fluoroanhydrite composition was proven: the electrical resistance of the material decreased by 11 times with an insignificant drop in strength on the 7th day from 34.9 to 29.8 MPa (15%). Modification of the composition with copper/carbon nanocomposite did not prove to be effective, leading to a 3-fold decrease in the electrical resistance of the material accompanied by a 4-fold decrease in the compressive strength of the samples. Modification of the composition with micro-sized particles of technogenic graphite lead to a decrease in the strength of the material by 28% without affecting its electrically conductive properties.

Abstract: Carbon nanomaterials have piqued the interest of researchers over the last two decades due to their proven wear and friction properties, in addition to tribological application. This review provides a detailed analysis of the latest discoveries in tribology of four common carbon nanoparticles are carbon nanotubes (CNTs), graphene, nanodiamonds and fullerene. First, the four forms of carbon nanomaterials are described in terms of their applicability in coating for friction and anti-wears. Second, the use of graphene and CNTs as additions to improve tribological behaviours in bulk materials is discussed. Finally, the mechanisms of CNTs, fullerene, fullerene, nanodiamond and graphene, working as additive to lubricate to reduce wear and friction are discussed. Fourth, the advancements in super-lubricity employing carbon nanotubes and graphene are emphasised. Finally, this study finishes with a look ahead at future research on carbon nanoparticles in tribology, their major barriers for practical use, and prospective remedies.

Abstract: The results of thermodynamic simulation of the manganese recovery in the CaO-SiO₂-MgO-Al₂O₃-MnO-Fe₂O₃ system by carbon are presented. Parameters of the initial system are temperature range 1400-at a step of , a total pressure of 0.1 MPa, and N₂. The composition of the oxide system is corresponded by the manganese ore (wt %) 1.1 MnO₂, 44.3 MnO, 28.4 CaO, 9.3 SiO₂, 5.4 MgO, 0.3 Al₂O₃, 11.2 Fe₂O₃ and silicomanganese slag. It contains (wt %) 16.3 MnO, 18.4 CaO, 52 SiO₂, 7.8 MgO, 5.26 Al₂O₃, and 0.24 FeO. The amount of silicomanganese slag in the system was 0, 5, 12, and 25%. Carbon is used as a reducing agent. Its consumption is increased by 5% from the stoichiometry for the recovery of Fe and Mn and by 8% of the metal mass for the formation of iron, manganese, and silicon carbides. The simulation is carried out using HSC Chemistry 6.12 () software package. The thermodynamic characteristics of the Fe₃C, Fe₂O₃, FeO, MnO₂, Mn, Mn₃C, Mn₅C₂, Mn₇C₃, Mn₂₃C₆, and SiC compounds existing in the database are refined. It was determined that an increase in the melt temperature from 1400 to increases the degree of manganese recovery (η_Mn) for all compositions of the systems. An increase of the silicomanganese slag content in the mixture from 0 to 25% decreases η_Mn from 89.3 to 85% at and from 95.8 to 91.5% at . The chemical composition of the high-carbon ferromanganese alloy is (wt %): 71.9-72.8 Mn, 16.6-17.9 Fe, 0.015-1.64 Si, and 9-. The simulation results can be used to develop a technology for producing a high-carbon ferromanganese when silicomanganese slag is involved in metallurgical processing.

Abstract: Analysis of literature sources, as well as practical data indicate that the existing scientific, technical and technological developments to ensure reliable corrosion-mechanical resistance and durability of oil and gas pipelines and other shell metal structures of critical use and subordinate to the State Service for Mining Supervision and Industrial Safety of Ukraine largely find contradictions and uncertainty; there are no quantitatively substantiated recommendations for practical application in order to ensure corrosion and mechanical resistance of pipelines operating in technologically aggressive environments under alternating temperature and barometric conditions and loads; there is a need for a systematic study of the causes, conditions and mechanisms of corrosion and mechanical damage of long-term equipment, which will significantly increase the operational reliability of industrial equipment. Experimental studies have established the causes and substantiated the mechanisms of metal softening with increasing service life (from 0 to 25 years) that leads to its degradation, especially during long-term operation in corrosive environments. A method for forecasting the residual working (accident-free) life of pipeline metal structures has been developed, which makes it possible to purposefully regulate their operational condition. This allows the timely use of technical, design and technological measures to improve the performance of such structures. Numerous and diverse results of experimental tests of metal samples for various purposes have been obtained, which provide an opportunity to create a base for comparative analysis of steels in many parameters of crack resistance, which will become a reliable basis for scientific and practical substantiation of the equivalent replacement of some steel grades with other grades, taking into account technological loads, corrosive environments and others.

Abstract: The paper represents the studies of the process of carbonaceous raw material gasification. The initial material is represented by bituminous coal of grade H with the carbon (C) content of 79.2-85.3 %. Experimental studies have been used to substantiate the parameters of combustible generator gases (СО, Н₂, СН₄) output depending on the temperature of a reduction zone of the reaction channel and gas flow velocity along its length. It has been identified that the volume of the raw material input to be used for gasification process changes in direct proportion depending on the amount of burnt-out carbon and blow velocity. The gasification is intensified in terms of equal concentration of oxygen and carbon in the reaction channel of an underground gas generator. The gasification rate is stipulated by the intensity of chemical reactions, which depend immediately on the modes of blow mixture supply. Moreover, they depend directly on the intensity of oxygen supply to the coal mass and removal of the gasification products.

Abstract: Candlenut Shells is one of the many commodities growing in Indonesia and experiencing rapid progress production development. The shell of candlenut has good characteristic that allow it to be used as carbon. activated carbon is one of material that can be applied for various application. In this paper, we reported the synthesis of activated carbon from candlenut shell in order to get high quality of carbon by controlling the heating temperature in synthesis. Variation of heating temperature in to produce carbon were 300, 400, 500, 600 and 700 °C . FTIR Spectroscopy was carried out to determine the functional groups on the carbon from candlenut shells. FTIR analysis during the carbonization process was indicated the change in functional group of chemical structure from the candlenut shell, which is shown by decreasing the absorption spectrum of some functional groups of the candlenut shell after the carbonization process. The carbonization process has formed aromatic C = C and reduction functional group OH (aromatic compounds), C-H (aromatic ring), C-O (vibration ether structure) dan C=O (Ester compounds). And results of carbonization of candlenut shells at various temperatures have an electrical conductivity value that increases with increasing carbonization temperature. The carbonization temperature that is raised to 700 °C causes carbon to be more conductive with an increased electrical conductivity value. XRF characterization results also showed that in addition to carbon elements in the cundlenut shells, other elements were also found such as calcium, magnesium, aluminum, potassium, strontium, manganese, iron and zinc. Ca and Mg are the largest content besides carbon.

Abstract: Carburizing is a heat treatment process, which used widely for surface hardening. In this process, the parts are placed in a concentrated atmosphere of Carbon atoms. The carbon atoms diffuse in the samples from the surface. In the present article, the effects of carburizing temperature on fatigue life will be studied. The St37 steel material is selected for study due to its wide range of usage in industry and little attention on the carburizing of this material. The samples are prepared by implementing the carburizing process at different temperatures (300, 400, 500, and 600 °C). The holding time is 1 hour for all samples. The two-point bending fatigue tests had been carried out on constant loading stresses. The results of the fatigue life test show that the fatigue life enhances the carburizing process. The fatigue life improved from about 45000 cycles to about 65000 cycles (about 44% increase) by increasing the temperature from 300°C to 600°C. Holding at higher temperatures leads to an increase in fatigue life smoothly due to the increase in the diffusivity coefficient. Also, the fracture surface demonstrates that the crack initiation starts from outer surfaces very slowly and failure happens as a brittle fracture in the samples.