• 제목/요약/키워드: Silica powder

검색결과 376건 처리시간 0.025초

Powder blasting을 이용한 Fused silica glass의 마이크로 채널 가공 및 특성 평가에 관한 연구 (Evaluation of micro-channel characteristics of fused silica glass using powder blasting)

  • 이정원;김태민;신봉철
    • Design & Manufacturing
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    • 제14권1호
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    • pp.36-41
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    • 2020
  • Recently, due to the development of MEMS technology, researches for the production of effective micro structures and shapes have been actively conducted. However, the process technology based on chemical etching has a number of problems such as environmental pollution and time problems due to multi-process. Various processes to cope with this process are being studied, and one of the mechanical etching processes is the powder blasting process. This process is a method of spraying fine particles, which has the advantage of being an effective process in manufacturing hard brittle materials. However, it is also a process that adversely affects the material surface roughness and material properties due to the impact of the injection of fine particles. In this study, after fabricating micro-channels in fused silica glass with excellent optical properties among the hard brittle materials, we used the nano indentation system to analyze the micro parts using nano-particles as well as machinability and surface roughness analysis of the processed surface. The analysis was performed for the effective processing of powder blasting.

실리카 코어 금 위성입자의 합성 및 표면 증강 라만 산란을 기반으로 한 센서로의 응용 (Synthesis of Silica-Core Gold-Satellite Nanoparticles and Their Surface-enhanced Raman Scattering Based Sensing Application)

  • 최현지;김영국;윤석영;백연경
    • 한국분말재료학회지
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    • 제21권6호
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    • pp.441-446
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    • 2014
  • In this study, we synthesize silica-core gold-satellite nanoparticles (SGNPs) for the surface-enhanced Raman scattering (SERS) based sensing applications. They consist of gold satellite nanoparticles (AuNPs) fixed on the silica core nanoparticles, which sizes of AuNPs can be tunned by varying the amount of reactants (growth solution and reducing agent). Their surface plasmon resonance (SPR) properties were characterized by using UV-vis spectroscopy, showing that the growth of AuNPs on silica cores leads to the light absorption in the longer wavelength region. Furthermore, the size increase of AuNPs exhibited the dramatic change in SERS activity due to the formation of hot spots. The optimized SGNPs showing enhancement factor ${\sim}3.8{\times}10^6$ exhibited a detection limit of rhodamine 6G (R6G) as low as $10^{-8}M$. These findings suggest the importance of size control of SGNPs and their SPR properties to develop highly efficient SERS sensors.

Synthesis and Characterization of Zinc Phosphate Cement Powder and Cement-forming Liquid

  • Park, Choon-Keun
    • The Korean Journal of Ceramics
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    • 제3권4호
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    • pp.269-273
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    • 1997
  • Chemical composition of cement powder influences the setting time and early compressive strength development. The setting time increases as the amounts of zinc oxide and magnesium oxide are increased. For one day compressive strength development, a cement powder with a composition 90% ZnO, 8% MgO and 2% silica resulted in the highest strength (greater than 1, 090 kg/$\textrm{cm}^2$). Cement-forming liquids also need to be buffered, with both aluminum and zinc ions, for a good consistency and a higher strength of the zinc phosphate cement. These liquids control the setting reactions.

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Effect of Reaction Condition and Solvent on The Size and Morphology of Silica Powder Prepared by An Emulsion Technique

  • Park, Won-Kyu;Kim, Dae-Yong
    • The Korean Journal of Ceramics
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    • 제6권3호
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    • pp.229-235
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    • 2000
  • The spherical silica powder was synthesized by varying the kinds of solvent and mixing energy in emulsion method. The stirring speed varied from 500 to 1000 r.p.m. at 5$0^{\circ}C$ for 2h. Toluene in benzyl groups and a series of alkanes were used as dispersant. The average size of spherical silica particles decreased with increasing the stirring speed and the chain length o solvents used in this work. The average size was controlled in the range of 134~28$\mu\textrm{m}$ by selecting a proper solvent and stirring speed. The optimum processing parameters were described in details.

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Emulsion법에 의한 실리카 분말의 합성에서 반응조건이 입자의 형성에 미치는 영향 (The Effect of Reaction Condition on Particle Formation in the Synthesis of Silica Powder Using Emulsion)

  • 이상근;장윤식;문병영;강범수;박희찬
    • 한국재료학회지
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    • 제15권11호
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    • pp.717-721
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    • 2005
  • Silica powders were synthesized using emulsion solution containing water, nonionic surfactant of Triton N-57, and cyclohexane. Silica powders were prepared at low cost using inexpensive starting material of sodium silicate and ammonium sulfate. Morphology, size and size distribution were observed and determined using SEM. The powder was identified as silica by FT-IR and XRD analysis. Particle size and size distributions were affected by concentration of reactants, reaction time, and concentration of surfactant. Particle size were increased with increasing concentration of reactants and particles became dense with increasing reaction time. As R value increased, tile particle size was increased, reached a certain value and then decreased again. The silica powders synthesized under optimum condition were spherical in shape, $0.8{\mu}m$ in average particle size, narrow in particles size distribution, and well dispersed.

페인트 제조 작업자의 6가 크롬 및 실리카 노출평가와 호흡보호구 밀착도 검사 사례 (Case study of Hexavalent Chromium and Silica Exposure Assessment and Respiratory Fit-test for Paint Manufacturing Worker)

  • 이현석;김부욱
    • 한국산업보건학회지
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    • 제31권4호
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    • pp.295-303
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    • 2021
  • Objective: Paint manufacturing industry workers are exposed to various lung cancer carcinogenic substances including hexavalent chromium and crystalline silica. Studies have been conducted on lung cancer in Paint manufacturing industry workers and the concentration of hexavalent chromium in paint industry; however, the concentration of crystalline silica and hexavalent chromium and cases of lung cancer in a single Paint factory has never been reported in Korea. Methods: To determine whether the cancer was related to his work environment, we assessed the level of exposure to carcinogens during pouring and mixing talc and pigment. In addition, a mask fit test was performed for the worker. Results: Analysis of talc and silica bulk powder materials showed that crystalline silica (quartz) was 5% in talc and 100% in silica. The green and yellow pigments contained 87% and 92% of lead chromate, respectively. Our quantitative analysis of pigment powder samples showed that the hexavalent chromium contents quantified in the green and yellow pigment samples were 87% and 92%, respectively. In order to estimate his exposure level of hexavalent chromium, we measured a personal exposure level of hexavalent chromium for a worker in accordance with the National Institute for Occupational Safety and Health #7605 method. The results showed that the worker was exposed to the high level of hexavalent chromium (0.033 mg m-3). In addition, the talc powder also contained 5% quartz, and the worker's exposure level to respirable quartz exceeded OEL. As a result of the respiratory protection fit test for workers, the overall Fit Factor was '15' when wearing a second-grade mask and '25' when wearing a first-grade mask, significantly lower than the US Occupational Safety and Health Agency (OSHA) pass value of "100". Conclusion: Workers who pouring and mixing powder materials such as talc or colored pigments in paint manufacturing company may be exposed to high concentrations of carcinogenic substances. These findings indicate that it is necessary to local ventilation system inspection, safety and health education for employers and workers, and periodically monitoring and manage the working environment.

고성능 콘크리트의 자기 및 건조수축에 미치는 혼화재의 영향 (Influence on the Autogenous and Drying Shrinkage of High Performance Concrete by Mineral Admixture)

  • 배정렬;홍상희;고경택;김성욱;한천구
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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    • pp.415-420
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    • 2002
  • This study is intended to investigate the influence of mineral admixtures on the autogenous and drying shrinkage of high performance concrete. According to results, drying shrinkage increases with increase of fly ash content, and it does not show difference with replacement of blast furnace slag powder. It increases when incorporating silica fume or fly ash and silica fume together. The autogenous shrinkage shows increasing tendency with increase of silica fume and blast furnace slag powder content, and incorporating of silica fume or fly ash and silica fume together has effects on reducing autogenous shrinkage. Therefore, it is considered that application of both silica fume and fly ash can reduce the cracks caused by autogenous shrinkage, including enhancement in strength and placeability of high performance concrete.

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실리카흄을 혼입한 강섬유보강 콘크리트의 내구성에 관한 실험적연구 (An Experimental Studyon the Durability of Steel Field Reinforced Concrete Using Silica Fume)

  • 박승범;홍석주;조청휘;김부일
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 1998년도 봄 학술발표회 논문집(I)
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    • pp.285-291
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    • 1998
  • During recent years, the durability of concrete structures has been considered in concret practice and material research. To preserve the brittleness of concrete as well as energy absorption and impact resistance, amount of fiber usage has greatly increased in the field of public works. Ultra fine powder, silica fume, mixed into concrete, it reduce void of concrete structure. Especially, there's a great effect for strength improvement of concrete by initial pozzolanic reactions. For these reasons, if silica fume mixed into concrete, it decrease the total void by microfilter effect . Pozzolan reaction, between cement particle and silica powder, can elaborate the micro structure of matrix. And so, in this paper, we deal SFRC for the purpose of efficiently using of industrial by-products(silica fume). Also we performed the test for durability such as freeze-thaw resistance and accelerated carbonation of SFRC using silica fume.

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Processing of Silica-Bonded Silicon Carbide Ceramics

  • Chun, Yong-Seong;Kim, Young-Wook
    • 한국세라믹학회지
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    • 제43권6호
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    • pp.327-332
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    • 2006
  • The effect of the processing parameters on the sintered density and strength of silica-bonded SiC (SBSC) ceramics was investigated for three types of batches with different particle sizes. The SBSC ceramics were fabricated by an oxidation-bonding process. The process involves the sintering of powder compacts in air so that the SiC particles bond to each other by oxidation-derived $SiO_2$ glass or cristobalite. A finding of this study was that a higher flexural strength was obtained when the starting powder was smaller. When a ${\sim}0.3_{-{\mu}m}$ SiC powder was used as a starting powder, a high strength of $257{\pm}42\;MPa$ was achieved at a relative density of ${\sim}80%$.

Mineralogical Analysis and Mechano-Chemical Purification of Natural Silica Ore for High Purity Silica Powder

  • Park, Jesik;Lee, Churl Kyoung;Lee, Hyun-Kwon
    • 한국재료학회지
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    • 제26권6호
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    • pp.306-310
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    • 2016
  • To produce 4N grade high-purity silica powder from natural ore, the mineralogical characteristics of natural silica ore were investigated and their effects on the purification process were revealed. The Chinese silica mineral ore used was composed of iron and aluminum as main impurities and calcium, magnesium, potassium, sodium, and titanium as trace impurities; these trace impurities generally exist as either single oxides or complex oxides. It was confirmed that liberation and acidic washing of the impurities were highly dependent on the particle size of the ground silica ore and on its mineralogical characteristics such as the distribution and phases of existing impurities. It is suggested that appropriate size reduction of silica ore should be realized for optimized purification according to the origin of the natural silica ore. A single step purification process, the mechano-chemical washing (MCW) process, was proposed and verified in comparison with the conventional multi step washing process.