• Title, Summary, Keyword: Silicon carbide

Search Result 682, Processing Time 0.062 seconds

Exposure Assessment of Airborne Dust in Manufacturing Industries Using Silicon Carbide in Korea (우리나라 실리콘카바이드 취급사업장의 공기 중 분진 노출평가)

  • Lee, Jun Jung;Phee, Young Gyu
    • Journal of Korean Society of Occupational and Environmental Hygiene
    • /
    • v.21 no.3
    • /
    • pp.177-183
    • /
    • 2011
  • Occupational exposure to silicon carbide dust of manufacturing industries has seldom been evaluated in Korea. Accordingly, we evaluated various silicon carbide dust concentrations in the breathing zone of workers between May 2010 and July 2010. To compare silicon carbide dust concentrations, three dust samplers including the Institute of Occupational Medicine (IOM) sampler, 37mm cassette sampler, and Aluminum cyclone sampler were used. A total of 5 manufacturing industries producing abrasive and refractory materials using silicon carbide were investigated. The geometric mean concentrations were 2.04, 0.97, and $0.48mg/m^3$ in inhalable, total and respirable silicon carbide dust, respectively. The geometric mean concentrations of silicon carbide in abrasive material manufacturing industries were slightly higher than that of refractory manufacturing industries, and finishing operations were higher than that of other operations. It was found that the results of exposure assessment in airborne dust at manufacturing industries using silicon carbide in Korea showed exceeding rate to American Conference of Governmental Industrial Hygienists Threshold Limit Value ($3mg/m^3$) was 10% in respirable dust samples. Therefore, with the consideration of the close relationship between smaller dust size and the occurrence of occupational respiratory diseases, it is suggested to promulgate the new occupational exposure limit for respirable silicon carbide dust.

Effects of Interface Boundary Strength on Wear and Wear Transition during Sliding in Silicon Carbide Ceramics (탄화규소계 세라믹스에서 미끄럼시의 마모 및 마모천이에 미치는 계면강도의 영향)

  • Kim, Dong-Jin;Park, Seong-Khil;Ryu, Hyun;Um, Chang-Do;Cho, Seong-Jai;Kim, Seock-Sam
    • Tribology and Lubricants
    • /
    • v.11 no.4
    • /
    • pp.21-27
    • /
    • 1995
  • The effects of interface boundary strength on wear and wear transition during sliding have been investigated in silicon carbide ceramics. Three different microstructures, i.e., solid state sintered silicon carbide, liquid phase sintered silicon carbide and liquid phase sintered silicon carbide composite reinforced with TiB$_{2}$ particulates, were designed by hot pressing. Examinations of crack patterns and fracture modes indicated that interface boundaries were relatively strong between silicon carbide grains in the solid state sintered silicon carbide, intermediate in the liquid phase sintered silicon carbide and weak between silicon carbide grains and TiB$_{2}$ particles in the composite. Wear data and examinations of worn surfaces revealed that the wear behavior of these silicon carbide ceramics could be significantly affected by the interface strength. In the solid state sintered silicon carbide, the wear occurred by a grooving process. In the liquid phase sintered silicon carbide and composite, on the other hand, an abrupt transition in wear mechanism from initial grooving to grain pull-out process occurred during the test. The transition occurred significantly earlier in the composite than in the carbide.

The Effects of Various Anti-Oxidation Additives in Silicon Carbide Refractory Saggars (탄화규소질 내화판에 있어서 내산화 첨가제의 영향)

  • 이준근
    • Journal of the Korean Ceramic Society
    • /
    • v.17 no.3
    • /
    • pp.145-150
    • /
    • 1980
  • This paper deals with the clay-bonded silicon carbide refractory saggars in terms of its oxidation resistance. Oxidation is one of the major causes of failure in silicon carbide refractory saggars during its services. Various anti-oxidation additives are coated on or added into silicon carbide refractories and their effects are studied while other conditions are equal. Several conclusions can be derived for optimum anti-oxidation additive as: 1. The additive should wet each silicon carbide grain completely during its firing. 2. The additive should have high viscosity at temperatures around $1, 350^{\circ}C$ where most silicon carbide refractory saggars are being used. 3. The additive should have ability to absorb or desorb oxygen depending on the local atmosphere inside of saggar during it service. 4. The addition should be kept as minimum as possible to prevent any "sweating" or "bloating" phenomena.ing" phenomena.mena.

  • PDF

Thermodynamic Consideration for SiC synthesis by Using Sludged Silicon Powder (폐슬러지를 이용한 SiC 합성에 관한 열역학적 고찰)

  • 최미령;김영철
    • Journal of the Semiconductor & Display Technology
    • /
    • v.2 no.1
    • /
    • pp.21-24
    • /
    • 2003
  • Sludged silicon powders that are generated during silicon ingot slicing process have potential usage as silicon source in fabricating silicon carbide powders by adding carbon. A thermodynamic calculation is performed to consider a plausible formation condition for the silicon carbide powders. A thin silicon oxide layer around silicon powder is sufficient to supply equilibrium oxygen partial pressure at the formation temperature($1400^{\circ}C$) of the silicon carbide in the Si-C-O ternary system. Formation of silicon carbide by using the sludged silicon powders is more efficient than by using silicon oxide powders.

  • PDF

Mechanical Properties of Chemical-Vapor-Deposited Silicon Carbide using a Nanoindentation Technique

  • Kim, Jong-Ho;Lee, Hyeon-Keun;Park, Ji-Yeon;Kim, Weon-Ju;Kim, Do-Kyung
    • Journal of the Korean Ceramic Society
    • /
    • v.45 no.9
    • /
    • pp.518-523
    • /
    • 2008
  • The mechanical properties of silicon carbide deposited by chemical vapor deposition process onto a graphite substrate are studied using nanoindentation techniques. The silicon carbide coating was fabricated in a chemical vapor deposition process with different microstructures and thicknesses. A nanoindentation technique is preferred because it provides a reliable means to measure the mechanical properties with continuous load-displacement recording. Thus, a detailed nanoindentation study of silicon carbide coatings on graphite structures was conducted using a specialized specimen preparation technique. The mechanical properties of the modulus, hardness and toughness were characterized. Silicon carbide deposited at $1300^{\circ}C$ has the following values: E=316 GPa, H=29 GPa, and $K_c$=9.8 MPa $m^{1/2}$; additionally, silicon carbide deposited at $1350^{\circ}C$ shows E=283 GPa, H=23 GPa, and $K_c$=6.1 MPa $m^{1/2}$. The mechanical properties of two grades of SiC coating with different microstructures and thicknesses are discussed.

Finite element modeling of the vibrational behavior of multi-walled nested silicon-carbide and carbon nanotubes

  • Nikkar, Abed;Rouhi, Saeed;Ansari, Reza
    • Structural Engineering and Mechanics
    • /
    • v.64 no.3
    • /
    • pp.329-337
    • /
    • 2017
  • This study concerns the vibrational behavior of multi-walled nested silicon-carbide and carbon nanotubes using the finite element method. The beam elements are used to model the carbon-carbon and silicon-carbon bonds. Besides, spring elements are employed to simulate the van der Waals interactions between walls. The effects of nanotube arrangement, number of walls, geometrical parameters and boundary conditions on the frequencies of nested silicon-carbide and carbon nanotubes are investigated. It is shown that the double-walled nanotubes have larger frequencies than triple-walled nanotubes. Besides, replacing silicon carbide layers with carbon layers leads to increasing the frequencies of nested silicon-carbide and carbon nanotubes. Comparing the first ten mode shapes of nested nanotubes, it is observed that the mode shapes of armchair and zigzag nanotubes are almost the same.

Effect of Specific Surface Area on the Reaction of Silicon Monoxide with Porous Carbon Fiber Composites

  • Park, Min-Jin;Lee, Jae-Chun
    • The Korean Journal of Ceramics
    • /
    • v.4 no.3
    • /
    • pp.245-248
    • /
    • 1998
  • Porous carbon fiber composites (CFCs) having variable specific surface area ranging 35~1150 $\m^2$/g were reacted to produce silicon carbide fiber composites with SiO vapor generated from a mixture of Si and $SiO_2$ at 1673 K for 2 h under vacuum. Part of SiO vapor generated during conversion process condensed on to the converted fiber surface as amorphous silica. Chemical analysis of the converted CFCs resulting from reaction showed that the products contained 27~90% silicon carbide, 7~18% amorphous silica and 3~63% unreacted carbon, and the composition depended on the specific carbide, 7~18% amorphous silica and 3~63% unreacted carbon, and the composition depended on the specific surface area of CFCs. CFC of higher specific surface area yielded higher degree of conversion of carbon to silicon and conversion products of lower mechanical strength due to occurrence of cracks in the converted caron fiber. As the conversion of carbon to silicon carbide proceeded, pore size of converted CFCs increased as a result of growth of silicon carbide crystallites, which is also linked to the crack formation in the converted fiber.

  • PDF

Preparation and Characterization of Silicon Carbide Nanofiber (탄화규소 나노섬유의 제조 및 물성)

  • 신현익;송현종;김명수;임연수;이재춘
    • Journal of the Korean Ceramic Society
    • /
    • v.37 no.4
    • /
    • pp.376-380
    • /
    • 2000
  • Carbon nanofibers with an average diameter of 100nm were reacted with SiO vapor generated from a mixture of Si and SiO2 to produce silicon carbide nanofibers at temperature ranging 1200∼1500$^{\circ}C$ under vacuum. The nanofiber reacted at 1200$^{\circ}C$ for two hours consisted of silicon carbide with an average crystallite size of 10-20nm, amorphous silica and a significant amount of unreacted carbon. The surface area of silicon carbide nanofiber, obtained after removal of amorphous silica and unreacted carbon from converted carbon nanofibers at 1200$^{\circ}C$, was as high as 150㎡/g. With increasing reaction temperature to 1500$^{\circ}C$, the surface area was decreased to 14㎡/g. Growth of SiC crystallite size with increasing conversion temperature of carbon nanofiber was confirmed from Scherrer formula using the (111) diffraction line and TEM images of converted carbon nanofibers.

  • PDF

Studies on the Oxide Bonded Silicon Carbide Porous Materials (산화물 결합 탄화규소 다공질 소재에 관한 연구)

  • 이재춘;국일현
    • Journal of the Korean Ceramic Society
    • /
    • v.27 no.2
    • /
    • pp.179-186
    • /
    • 1990
  • Silicon carbide porous materials used for hot gas filters were prepared using oxide binder. Chamotte, frit and H3PO4 were starting materials to synthesize the oxide binder for high temperature-use. Room temperature bending strength of the silicon carbide porous body was increased with increasing firing temprature or with the amount of the content of frit in the oxide binder. However, in the oxidebinder fired above132$0^{\circ}C$, cristobalite form of AlPO4 phase which undergoes rapid inversion became more prominent with increasing firing time. the average pore size of the silicon carbide filter materials was found to be about one third of the average grain size of the silicon carbide powder used in this study.

  • PDF

Production of Fe-Si-Cr Ferro Alloy by Using Mixed Silicothermic and Carbothermic Reduction (실리콘 및 탄소 복합 열환원 반응을 이용한 페로실리크롬 합금철의 제조)

  • Kim, Jong Ho;Jung, Eun Jin;Lee, Go-Gi;Jung, Woo-Gwang;Yu, Seon Jun;Chang, Young Chul
    • Korean Journal of Materials Research
    • /
    • v.27 no.5
    • /
    • pp.263-269
    • /
    • 2017
  • Fe-Si-Cr ferroalloy is predominantly produced by carbothermic reduction. In this study, silicothermic and carbothermic mixed reduction of chromite ore to produce Fe-Si-Cr alloy is suggested. As reductants, silicon and silicon carbide are evaluated by thermochemical calculations, which prove that silicon carbide can be applied as a raw material. Considering the critical temperature of the change from the carbide to the metallic form of chromium, thereduction experiments were carried out. In these high temperature reactions, silicon and silicon carbide act as effective reductants to produce Fe-Si-Cr ferroalloy. However, at temperatures lower than the critical temperature, silicon carbide shows a slow reaction rate for reducing chromite ore. For the proper implementation of a commercial process that uses silicon carbide reductants, the operation temperature should be kept above the critical temperature. Using equilibrium calculations for chromite ore reduction with silicon and silicon carbide, the compositions of reacted metal and slag were successfully predicted. Therefore, the mass balance of the silicothermic and carbothermic mixed reduction of chromite ore can be proposed based on the calculations and the experimental results.