Oxidation behavior of amorphous boron carbide–silicon carbide nano-multilayer thin films

Bae, K.-E.,Chae, K.-W.,Park, J.-K.,Lee, W.-S.,Baik, Y.-J. Elsevier 2015 Surface & Coatings Technology Vol.276 No.-

<P><B>Abstract</B></P> <P>This experiment studied the effect of nano-multilayer structures of boron carbide film with silicon carbide (SiC) layers on oxidation behavior and hardness. The multilayer films were deposited at 450°C using an unbalanced dual-gun magnetron sputtering system with stoichiometric B<SUB>4</SUB>C and SiC targets. The period of the multilayer system (the thickness of one pair of boron carbide and SiC layers) with a constant film thickness was varied between 2.3nm and 22.1nm. The structures of these multilayer thin films were amorphous irrespective of the period. A remarkable hardness enhancement, frequently observed in crystalline nano-multilayer thin film systems, did not appear. The maximum hardness of the multilayer thin film was measured to be about 36GPa, similar to that of the monolithic boron carbide film deposited under the same condition. Oxidation was, however, greatly reduced by the insertion of the SiC layers. Oxidation was rarely observed at temperatures up to 1200°C, the maximum experimental temperature, whereas significant oxidation was observed at around 700°C in the case of the boron carbide monolithic film.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Investigation of oxidation behavior of silicon carbide - boron carbide nanomultilayers </LI> <LI> Significant reduction of oxidation of BC films by SiC layer insertion up to 1200°C </LI> <LI> Negligible decrease of the hardness of the film caused by the multilayer formation </LI> <LI> BC/SiC nanomultilayer coating as a candidate for cutting tool application used especially at high temperature </LI> </UL> </P>

Combination of TEM and 3D Atom Probe Study of Microstructure and Alloy Carbide in a Nb-V Micro-Alloyed Steel Tempered at 650℃

Qing-dong Liu,Wen-qing Liu,Shi-jin Zhao 대한금속·재료학회 2013 METALS AND MATERIALS International Vol.19 No.4

3D atom probe (3DAP) combined with TEM is applied to characterize the nanostructure and composition of coarsening carbides that precipitate in a Nb-V micro-alloyed steel tempered at 650 °C for 4 h. The results indicate that high temperature tempering of the as-quenched lath-like martensitic structures leads to the coarsening of alloyed carbide in the recovered ferritic matrix. TEM characterization and EDS analysis show that the alloy carbides are typically spherical or ellipsoidal and are enriched with V, Nb and Mo. Crystallographic lattice overlap and distortion create a distinct optical Moiré pattern at the carbide/matrix boundary, as observed by HRTEM. 3DAP gives the compositional distribution at atomic scale in the coarsening carbide and the surrounding matrix. Non-carbide-forming elements such as Si and Al are depleted in the carbide and are enriched at the carbide/matrix heterophase interface. Carbide-forming elements such as Mn, V, Mo and Nb distribute heterogeneously in the whole carbide, leading to the formation of a Mn-, V- and Mo-enriched core and Mo-enriched external shell.

비구면 Glass렌즈 성형용 Silicon Carbide(SiC) 코어 초정밀가공에 관한 연구

김현욱(Hyun Uk Kim),정상화(Sang Hwa Jeong),차두환(Du Hwan Cha),이동길(Dong Kil Lee),김상석(Sang Suk Kim),김혜정(Hye Jeong Kim),김정호(Jeong Ho Kim) 한국기계가공학회 2008 한국기계가공학회 춘추계학술대회 논문집 Vol.2008 No.-

Recently, aspheric glass lens molding core is fabricated with tungsten carbide(WC). If molding core is fabricated with silicon carbide(SiC), SiC coating process, which must be carried out before the Diamond-Like Carbon(DLC) coating can be eliminated and thus, manufacturing time and cost can be reduced. Diamond Like Carbon(DLC) is being researched in various fields because of its high hardness, high elasticity, high durability, and chemical stability and is used extensively in several industrial fields. Especially, the DLC coating of the molding core surface used in the fabrication of a glass lens is an important technical field, which affects the improvement of the demolding performance between the lens and molding core during the molding process and the molding core lifetime. Because SiC is a material of high hardness and high brittleness, it can crack or chip during grinding. It is, however, widely used in many fields because of its superior mechanical properties. In this paper, the grinding condition for silicon carbide(SiC) was developed under the grinding condition of tungsten carbide. A silicon carbide molding core was fabricated under this grinding condition. The measurement results of the molding core were as follows: PV of 0.259 ㎛(apheric surface) and 0.094 ㎛(plane surface), Ra of 5.3 ㎚(aspheric surface) and 5.5 ㎚(plane surface). The fabricated aspheric glass lens was used 5 mega pixel, 4 optical zoom camera phone module.

초미립 WC-Graphene-Al₂O₃ 복합재료 소결 및 기계적 성질

손인진 ( In-jin Shon ) 한국열처리공학회 2023 熱處理工學會誌 Vol.36 No.4

Tungsten carbide has many industrial applications due to its high electrical and thermal conductivity, high melting temperature, high hardness and good chemical stability. Because tungsten carbide is difficult to sinter, it is sintered with nickel or cobalt as a binder and is currently used in nozzles, cutting tools, and molds. Alumina is reported to be a viable binder for tungsten carbide due to its higher oxidation resistance and lower cost than nickel and cobalt. The ultrafine tungsten carbide-graphene-alumina composites were rapidly sintered in a high frequency induction heating active sintering unit. The microstructure and mechanical properties (fracture toughness and hardness) of the composites were investigated and analyzed by Vickers hardness tester and electron microscope. Since the high-frequency induction heating sintering method enables high-speed sintering, ultrafine composites can be prepared by preventing grain growth. In the tungsten carbide-graphene-alumina composites, the grain size of tungsten carbide increased with the amount of alumina participation. The hardness and fracture toughness of the tungsten carbide-5% graphene- x% alumina (x = 0, 5, 10,15) composites were 5.1, 8.6, 8.6, and 8.4 MPa-m^1/2 and 2384, 2168, 2165, and 2102 kg/mm², respectively. The fracture toughness increased without a significant decrease in hardness. Sinterability was improved by adding alumina to tungsten carbidegraphene. (Received June 9, 2023; Revised June 19, 2023; Accepted July 3, 2023)

Effect of air flow rate on preparation of boron carbide by sol-gel low-temperature pyrolysis system

Chengcheng Tian,Yang Li,Yuanxia Wang,Ying Shi,Li-Zhi Liu 한양대학교 청정에너지연구소 2024 Journal of Ceramic Processing Research Vol.25 No.2

The morphology and particle size of boron carbide in the sol-gel low-temperature pyrolysis system were controlled bychanging the air flow rate during the pyrolysis of boric acid glycerin system. Analyzed the infrared absorption propertiesof condensation products and pyrolysis products, as well as the carbon network structure of pyrolysis products and themicrostructure, phase composition, and particle size of boron carbide powder. The research results indicate that the airflowing in the pyrolysis atmosphere can accelerate the thermal decomposition efficiency of boric acid glycerol condensate andeffectively reduce the pyrolysis temperature. The faster the air flow rate during the pyrolysis process, the denser the carbonnetwork structure, smaller pore size, and more pores in the pyrolysis products, and the better the dispersion of boron oxide. Inthe boric acid glycerol system, with the increase of pyrolysis gas flow rate, the average particle size of boron carbide decreasesfrom 10 μm to about 2 μm. In addition, the morphology of boron carbide changes from a hexagonal diamond to a smoothermorphology. This indicates that by changing the air flow rate during the pyrolysis process, the carbon network structure ofthe pyrolysis products can be improved, thereby controlling the morphology and particle size of boron carbide. This paperprovides a new method for the study of the sol-gel low-temperature pyrolysis method to accurately control the morphology ofboron carbide.

Novel Synthesis of Mesoporous Molybdenum Carbide-Carbon Nanocomposite using Interaction Linker: Highly Efficient Electrocatalysts for Hydrogen Evolution

김성빈,박진규,이진우 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1

Molybdenum carbide is promising electrocatalysts for HER, due to its high activity, stability and low price. To enhance the catalytic properties, nanostructure can be introduced in molybdenum carbide. However, the introduction of nanostructure in molybdenum carbide remains great challenge, due to the high temperature for carburization. In our works, we synthesize the mesoporous molybdenum carbide-carbon nanocomposite (m-MoxC) using interaction linker assisted EISA method. To drawing the Mo precursor in the PEO moieties, N-containing molecules are used. By controlling the amount of N-containing molecules, we can control the porosity of materials and the molybdenum carbide distribution. This materials show high activity for hydrogen evolution reaction.

Co기 초합금 ECY768에서 응고 조직 및 탄화물 형성 거동

이정석,김현철,이재현,서성문,조창용,Lee, J.S.,Kim, H.C.,Lee, J.H.,Seo, S.M.,Jo, C.Y. 한국재료학회 2003 한국재료학회지 Vol.13 No.6

Directional solidification experiments were carried out at 0.5-150 $\mu\textrm{m}$/s in the Co-base superalloy ECY 768. As increasing solidification rate, the dendrite length increased and it reached the maximum at 150 $\mu\textrm{m}$/s, where the tip temperature is close to the liquidus. The liquidus and eutectic temperatures could be estimated by comparing the dendrite lengths and the temperature gradients at the solid/liquid interface and those were estimated as $1424.6^{\circ}C$ and $1343^{\circ}C$ respectively. Between the dendrites just below final freezing temperature, MC carbide and $M_{23}$$C_{6}$ carbide were found. It was confirmed that the script or blocky shape was Ta or W-rich MC carbide, and the lamellar shape was Cr-rich eutectic carbide. The solid/liquid interface morphology clearly showed that the Cr-rich eutectic carbide formed just after the script type MC carbide.

Effect of silicon carbide on carbonization and morphology behavior of coal tar pitch

Wenjuan Zhang,Shihua Song,Xianren Zeng,Genhui Teng,Qi Wang 한양대학교 세라믹연구소 2017 Journal of Ceramic Processing Research Vol.18 No.10

Coal tar pitch (CTP) is a quite promising candidate for the production of carbon materials. However, the application of CTP is restricted by its poor properties at elevated temperature. In this paper, silicon carbide was used to modify CTP and thecarbonization and morphology behavior of CTP and the CTP modified with silicon carbide were studied by thermogravimetry and differential scanning calorimetry (TG-DSC), Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results show silicon carbide and CTP can coalesce well when the ratio of silicon carbide to CTP is 12% and the carbonization yield of CTP at 900 o C increases from 35.86% to 40.56% after the modification of CTP. Further, the addition of silicon carbide to CTP can reduce the temperature at which the reaction of thermal polymerization happen during the carbonization process of CTP and can facilitate the carbonization of CTP. In addition, little pore distributes on the surface of the heat-treatment products after the modification of CTP with silicon carbide.

카바이트 처리에 따른 떫은감 '도근조생'의 과실 연화 및 품질

배강순,김호철,김태춘 원광대학교 2003 論文集 Vol.31 No.-

This study was carried out to investigate the effect of calcium carbide on fruit softening and quality of 'Tonewase' persimmon. The fruit weight was 200±4.4g at optimal maturity, and the soluble solids was 13.6±0.7˚ Bx. The fruit peel chromaticity was L^(*)=65.1, a^(*)=25.2, and b^(*)=63.4, and it showed yellow. The fruit peel chromaticity in ethanol and CO_(2) treatments was not changed. The b^(*) value in calcium carbide treatment was low as 26.8 and the fruit peel chromaticity changed red. Fruit softening in 0.1% and over of calcium carbide treatments was properly progressed. The bitterness following fruit softeness occurred in the fruits treated with 0.2% and over of calcium carbide. But the fruits treated with 0.6% and over of calcium carbide was not suitable to eat because of bitterness. The bitterness of fruits treated with 1.0% calcium carbide was decomposed to eat after 3days storage at room temperature.

Tribology of carbon layers fabricated from SiC exposed to different H2/Cl2 gas mixtures

최현주,Heung-Taek Bae,임대순 한양대학교 세라믹연구소 2009 Journal of Ceramic Processing Research Vol.10 No.3

Silicon carbide-based ceramics are some of the best materials for tribological applications. However, their tribological properties still need to be improved for certain uses under severe conditions. In this study, carbon layers were produced by the exposure of ball and disc type SiCs to various compositions of chlorine-hydrogen gas mixtures at a temperature of 1000℃ for 20 hrs. After the chlorination of the silicon carbide materials, the modified layers were characterized by XRD, Raman, and FE-SEM. The effect of the hydrogen gas content on the carbide-derived carbon (CDC) layers and their resulting tribological properties have been investigated. The tribological behaviors of the CDC layers were studied using a ball-on-disk tribometer. Silicon nitride and chlorinated silicon carbide balls were selected as the counterpart material. The results showed that the wear resistance and frictional coefficients of the surface-modified ball and disk-type SiCs were significantly improved compared to those of untreated silicon carbide specimens. Increasing the hydrogen content of the gas mixture improved the tribological performance of the resulting carbon layers. The use of a higher applied load also improved the tribological performance. The possible mechanisms responsible for the tribological properties of the carbon layers are discussed.