• Title/Summary/Keyword: silicon carbide powder

Search Result 106, Processing Time 0.028 seconds

Nano-scale Precision Polishing Characteristics using a Micro Quill and Magnetic Chain Structure (미세공구와 자기체인구조를 이용한 초정밀 폴리싱 특성)

  • 박성준;안병운;이상조
    • Journal of the Korean Society for Precision Engineering
    • /
    • v.21 no.8
    • /
    • pp.34-42
    • /
    • 2004
  • A new polishing technique for three dimensional micro/meso-scale parts is suggested using a micro quill and a magnetic chain structure. The principle of this method is to polish the target surface with the collected magnetic brushes at a micro tool by the non-uniform magnetic field generated around the tool. In a typical magnetic abrasive finishing process magnetic particles and abrasive particles are unbonded each other. But, to finish the three dimensional small parts bonded magnetic abrasive have to be used. Bonded magnetic abrasives are made from direct bonding, and their polishing characteristics are also examined. Alumina, silicon carbide and diamond micro powders are used as abrasives. Base metal matrix is carbonyl iron powder. It is found that bonded magnetic abrasives are superior to unbonded one by experiment. finally, the polished surface roughness is evaluated by atomic force microscope.

Synthesis of poly(dialkyl or monoalkyl)silanes as silicon carbide precursors for ceramic matrix composites (탄화규소 선구물질로서의 폴리(디알킬 또는 모노알킬)실란들의 합성과 세라믹 복합체 응용)

  • Lee, Gyu-Hwan
    • Analytical Science and Technology
    • /
    • v.26 no.1
    • /
    • pp.27-33
    • /
    • 2013
  • Polyalkylsilanes such as poly(dialkyl)silanes and poly(monoalkyl)silanes were synthesized by sonochemical dechlorination-condensation method from (dialkyl or monoalkyl)chlorosilanes with sodium metal. Those polyalkylsilanes were analyzed for the properties such as thermal behaviors from TGA analysis and obtained ceramic yields of 10-20% for poly(dialkyl)silanes and 40-60% for poly(monoalkyl)silanes. Ceramic composite discs were prepared by the combined mixture of polyalkylsilanes and SiC powder and were tested by TGA and analyzed by SEM and XRD for the application as binder for ceramic composite precursors.

Ultra Precision Polishing of Micro Die and Mold Parts using Magnetic-assisted Machining (자기연마법을 응용한 미세금형부품의 초정밀 연마)

  • 안병운;김욱배;박성준;이상조
    • Proceedings of the Korean Society of Precision Engineering Conference
    • /
    • 2003.06a
    • /
    • pp.1832-1835
    • /
    • 2003
  • This paper suggests the selective ultra precision polishing techniques for micro die and mold parts using magnetic-assisted machining. Fabrication of magnetic abrasive particle and their polishing performance are key technology at ultra precision polishing process of micro parts. Conventional magnetic abrasives have disadvantages. which are missing of abrasive particle and inequality between magnetic particle and abrasive particle. So, bonded magnetic abrasive particles are fabricated by several method. For example, plasma melting and direct bonding. Ferrite and carbonyl iron powder are used as magnetic particle where silicon carbide and Al$_2$O$_3$ are abrasive particle. Developed particles are analyzed using measurement device such as SEM. Possibility of magnetic abrasive and polishing performance of this magnetic abrasive particles also have been investigated. After polishing, surface roughness of workpiece is reduced from 2.927 $\mu\textrm{m}$ Rmax to 0.453 $\mu\textrm{m}$ Rmax.

  • PDF

Quantification Method of Macro Stickies for Recycled Pulps (재생펄프의 점착성 이물질 정량 분석 방법)

  • 윤병태;오세균
    • Journal of Korea Technical Association of The Pulp and Paper Industry
    • /
    • v.31 no.2
    • /
    • pp.86-91
    • /
    • 1999
  • A new test method has been developed for a quantitative evaluation of macro-stickies in recycled pulps. The method uses a fine slot screen to separate a sticky particles form fiber in the pulp samples. The obtained sticky particles were spread on filter paper and covered with silicon carbide powder in order to make the stickies area with sufficient contrast between stickies and background. The stickies are then counted by a scanner-based image analysis system. The validity of this evaluation method of stickies of KOCC, ONP and white ledger wastepaper recycling plants respectively. It is shown that this method can be applied for a quantitative determination of stickies content in various recycled pulp samples. With this testing method, reproducible and reliable data were obtained for the actual mill pulp samples.

  • PDF

Development of Ultraprecision Finishing Technique using Bonded Magnetic Abrasives (결합된 자성연마입자를 이용한 초정밀 피니싱 기술 개발)

  • 윤종학;박성준;안병운
    • Transactions of the Korean Society of Machine Tool Engineers
    • /
    • v.12 no.5
    • /
    • pp.59-66
    • /
    • 2003
  • This study suggests the new ultraprecision finishing techniques for micro die and mold parts using magnetic field-assisted polishing. Conventional magnetic abrasives have several disadvantages, which are missing of abrasive particle and inequal mixture between magnetic particle and abrasive particle. Therefore, bonded magnetic abrasive particles are fabricated by several method. For example, plasma melting and direct bonding. Carbonyl iron powder is used as magnetic particle there silicon carbide and alumina are abrasive particles. Developed magnetic abrasives are analyzed using SEM. Feasibility of magnetic abrasive and polishing performance of this magnetic abrasive particles also have been investigated. After polishing, surface roughness of workpiece is reduced from 85.4 ㎚ Ra to 9 ㎚ RA.

Effect of the C/Si Molar Ratio on the Characteristics of β-SiC Powders Synthesized from TEOS and Phenol Resin (C/Si 몰 비가 TEOS와 페놀수지를 출발원료 사용하여 합성된 β-SiC 분말의 특성에 미치는 영향)

  • Youm, Mi-Rae;Park, Sang-Whan;Kim, Young-Wook
    • Journal of the Korean Ceramic Society
    • /
    • v.50 no.1
    • /
    • pp.31-36
    • /
    • 2013
  • ${\beta}$-SiC powders were synthesized by a carbothermal reduction process using $SiO_2$-C precursors fabricated by a sol-gel process using phenol resin and TEOS as starting materials for carbon and Si sources, respectively. The C/Si molar ratio was selected as an important parameter for synthesizing SiC powders using a sol-gel process, and the effects of the C/Si molar ratio (1.4-3.0) on the particle size, particle size distribution, and yield of the synthesized ${\beta}$-SiC powders were investigated. It was found that (1) the particle size of the synthesized ${\beta}$-SiC powders decreased with an increase in the C/Si molar ratio in the $SiO_2$-C hybrid precursors, (2) the particle size distribution widened with an increase in the C/Si molar ratio, and (3) the yield of the ${\beta}$-SiC powder production increased with an increase in the C/Si molar ratio.

The Mechanical and Tribological Properties of Silicon Carbide Bodies (탄화규소 소결체의 기계적 특성 및 마찰마모)

  • 이승훈;김홍기;김영호;이경희
    • Journal of the Korean Ceramic Society
    • /
    • v.31 no.11
    • /
    • pp.1307-1314
    • /
    • 1994
  • The aim of this work is to show the way of manufacturing the SiC mechanical seal at the low temperature of 130$0^{\circ}C$ using clay and frit as source of secondary phase. $\alpha$-SiC and $\beta$-SiC powder which showed different distribution of particle were used as starting materials, i.e. average particle size of $\alpha$-SiC was larger than that of $\beta$-SiC. The mechanical and tribological properties of two groups of specimen, i.e. one contained mainly larger $\alpha$-SiC powder and the other mainly fine particle $\beta$-SiC, were measured. The specimen consisted of larger $\alpha$-SiC exhibited lower density flexural strength and wear resistance is comparison with these of sample containning mainly $\beta$-SiC . This difference could be originated from the dependence of capillary force on the particle size. For the larger SiC particle, the liquid phase may not fill the whole pores during sintering, due to low capillary force, whereas the liquid phase can infiltrate into the small ores surrounded small $\beta$-SiC particle. Thus, the course of high flexural strength and high wear resistance of specimen prepared using small particles can be explaced from the easy infiltration of liquid phase.

  • PDF

Microwave Absorbance of Polymer Composites Containing SiC Fibers Coated with Ni-Fe Thin Films

  • Liu, Tian;Kim, Sung-Soo;Choi, Woo-cheal;Yoon, Byungil
    • Journal of Powder Materials
    • /
    • v.25 no.5
    • /
    • pp.375-378
    • /
    • 2018
  • Conductive and dielectric SiC are fabricated using electroless plating of Ni-Fe films on SiC chopped fibers to obtain lightweight and high-strength microwave absorbers. The electroless plating of Ni-Fe films is achieved using a two-step process of surface sensitizing and metal plating. The complex permeability and permittivity are measured for the composite specimens with the metalized SiC chopped fibers dispersed in a silicone rubber matrix. The original non-coated SiC fibers exhibit considerable dielectric losses. The complex permeability spectrum does not change significantly with the Ni-Fe coating. Moreover, dielectric constant is sensitively increased with Ni-Fe coating, owing to the increase of the space charge polarization. The improvements in absorption capability (lower reflection loss and small matching thickness) are evident with Ni-Fe coating on SiC fibers. For the composite SiC fibers coated with Ni-Fe thin films, a -35 dB reflection loss is predicted at 7.6 GHz with a matching thickness of 4 mm.

Synthesis of SiC Nanoparticles by a Sol-Gel Process (나노 실리카와 카본블랙이용 탄화열 반응으로 나노 SiC 합성 및 특성)

  • Jeong, Kwang-Jin;Bae, Dong-Sik
    • Korean Journal of Materials Research
    • /
    • v.23 no.4
    • /
    • pp.246-249
    • /
    • 2013
  • Nano-sized ${\beta}$-SiC nanoparticles were synthesized combined with a sol-gel process and a carbothermal process. TEOS and carbon black were used as starting materials for the silicon source and carbon source, respectively. $SiO_2$ nanoparticles were synthesized using a sol-gel technique (Stober process) combined with hydrolysis and condensation. The size of the particles could be controlled by manipulating the relative rates of the hydrolysis and condensation reactions of tetraethyl orthosilicate (TEOS) within the micro-emulsion. The average particle size and morphology of synthesized silicon dioxide was about 100nm and spherical, respectively. The average particles size and morphology of the used carbon black powders was about 20nm and spherical, respectively. The molar ratio of silicon dioxide and carbon black was fixed to 1:3 in the preparation of each combination. $SiO_2$ and carbon black powders were mixed in ethanol and ball-milled for 12 h. After mixing, the slurries were dried at $80^{\circ}C$ in an oven. The dried powder mixtures were placed in alumina crucibles and synthesized in a tube furnace at $1400{\sim}1500^{\circ}C$ for 4 h with a heating rate of $10^{\circ}C$/min under flowing Ar gas (160 cc/min) and furnace cooling down to room temperature. SiC nanoparticles were characterized by XRD, TEM, and SAED. The XRD results showed that high purity beta silicon carbide with excellent crystallinity was synthesized. TEM revealed that the powders are spherical shape nanoparticles with diameters ranging from 15 to 30 nm with a narrow distribution.

4H-SiC bulk single crystal growth using recycled powder (재생 분말을 활용한 4H-SiC 벌크 단결정 성장)

  • Yeo, Im Gyu;Lee, Jae Yoon;Chun, Myong Chuel
    • Journal of the Korean Crystal Growth and Crystal Technology
    • /
    • v.32 no.5
    • /
    • pp.169-174
    • /
    • 2022
  • This study is to verify the feasibility of SiC single crystal growth using recycled SiC powder. The fundamental physical properties such as particle size, shape, composition and impurities of the recycled powder were analyzed, and the sublimation behavior occurring inside the reactor were predicted using the basic data. As a result of comprehensive judgment, the physical properties of the recycled powder were suitable for single crystal growth, and single crystal growth experiments were conducted using this. 100 mm 4H-SiC single crystal ingot with a height of 25 mm was grown without polytype inclusion. In the case of micro-pipe density was 0.02 ea/cm2 and resistivity characteristics was 0.015~0.020 ohm·cm2, commercial level quality was obtained, but additional analysis related to dislocation density and stacking faults is required for device application.