• 제목/요약/키워드: Hexagonal particle

검색결과 73건 처리시간 0.022초

Influence of Crystal Structure on the Chemical Bonding Nature and Photocatalytic Activity of Hexagonal and Cubic Perovskite Compounds

  • Lee, Sun-Hee;Kim, In-Young;Kim, Tae-Woo;Hwang, Seong-Ju
    • Bulletin of the Korean Chemical Society
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    • 제29권4호
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    • pp.817-821
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    • 2008
  • We have investigated the influence of the crystal structure on the chemical bonding nature and photocatalytic activity of cubic and hexagonal perovskite A[$Cr_{1/2}Ta_{1/2}$]O3 (A = Sr, Ba) compounds. According to neutron diffraction and field emission-scanning electron microscopy, the crystal structure and particle size of these compounds are strongly dependent on the nature of A-site cations. Also, it was found that the face-shared octahedra in the hexagonal phase are exclusively occupied by chromium ions, suggesting the presence of metallic (Cr-Cr) bonds. X-ray absorption and diffuse UV-vis spectroscopic analyses clearly demonstrated that, in comparison with cubic Sr[$Cr_{1/2}Ta_{1/2}$]$O_3$ phase, hexagonal Ba[$Cr_{1/2}Ta_{1/2}$]$O_3$ phase shows a decrease of Cr oxidation state as well as remarkable changes in interband Cr d-d transitions, which can be interpreted as a result of metallic (Cr-Cr) interactions. According to the test of photocatalytic activity, the present semiconducting materials have a distinct activity against the photodegradation of 4-chlorophenol. Also the Srbased compound was found to show a higher photocatalytic activity than the Ba-based one, which is attributable to its smaller particle size and its stronger absorption in visible light region.

미세입자 분사가공 시 분사높이 변화에 따른 육각형 가공형상 특성 (Hexagonal Shape Characteristics according to the Change in Standoff Distance during Fine Particle Blasting)

  • 이형태;이세한;왕덕현
    • 한국기계가공학회지
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    • 제20권9호
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    • pp.76-83
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    • 2021
  • This study examines the characteristics of spraying conditions based on the change in standoff distance during fine particle spraying while measuring the surface roughness, maximum depth, and maximum width of the sprayed surface. The processing shape of the sprayed surface is analyzed to understand the effects of injection pressure, nozzle diameter, standoff distance, processing shape, processing cycle, processing speed, and injection particles, which are the main factors of fine particle injection processing. Based on the derived characteristics, we attempt to determine the interrelationships of these major factors. The standoff distance is set as a variable factor and a spray machining experiment using a hexagonal shape (from among polygons) instead of square and circular shapes is conducted. Results reveal that research on the characteristics of spraying conditions could be expanded based on changes in the shapes of workpieces.

S/Zn의 몰비에 따른 중적외선 투과용 ZnS 세라믹스의 소결과 광학적 특성 (Optical Properties of Mid-infrared Transparent ZnS Ceramics with Different Molar Ratio of S/Zn)

  • 여서영;박범근;김창일;백종후
    • 센서학회지
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    • 제28권4호
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    • pp.256-261
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    • 2019
  • In this study, mid-infrared transparent zinc sulfide (ZnS) ceramics were fabricated through hydrothermal synthesis with different molar ratios of S/Zn (S/Zn = 0.8, 1.0, 1.2, 1.4, and 1.6). The ZnS ceramics were sintered at a relatively low temperature of $850^{\circ}C$ to prevent the occurrence of the hexagonal phase featuring optical anisotropy. The phase composition, microstructure, and optical properties of the ZnS ceramics were subsequently investigated by employing X-ray diffraction, scanning electron microscopy, and Fouriertransform infrared spectroscopy. The results obtained indicate that the ZnS nanoparticles feature the cubic phase, without the hexagonal phase. Moreover, with increasing S, the crystallinity and particle size of the ZnS nanoparticles increased. The crystallinity and density of the ZnS ceramics improved when the molar ratio of S was higher than the molar ratio of Zn, thereby enhancing the transmittance. Furthermore, the ZnS ceramic with an S/Zn value of 1.2 was found to exhibit the highest transmittance of approximately 69% owing to the reduced occurrence of the hexagonal phase and a high density of 99.8%.

규칙입자의 충전 -치밀된 탄화규소 소결체의 제조(제 1 보)- (A Study on Packing of Regular Particles - Preparation of Dense Sintered Silicon Carbide (1) -)

  • 문병훈;남건태;최상욱
    • 한국세라믹학회지
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    • 제31권9호
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    • pp.989-994
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    • 1994
  • This study aims at finding the closest packings of regular shape particles such as sphere, circle rod and hexagonal rod type. As the ratio of particle size to container lowered to less than 1/10, the wall effect decreased gradually. The tap density of spherical particles with almost orthorhombic arrangement was 59.5%, while those of circle rod and hexagonal rod type particles were 63.5% and 63.0% respectively. And it was decreased with increasing the aspect ratio of regular particles. The tap density of binary mixtures was larger than that corresponding to the monosized particles packing by about 15%. The tap density of ternary mixtures was larger than that of corresponding to the packing of binary mixtures by about 9%. This work employed the binary mixture of 60% coarse particles and 40% fine particles with size ratio of 1.0 to 1/10 and the ternary mixture of 60% coarse particles, 20% medium and 20% fine particles with size ratio of 1:1/10:1/400 respectively.

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공침법에 의한 $Ni_2Y$ 자성 분말의 합성 (Synthesis of $Ni_2Y$ magnetic particles by coprecipitation method)

  • 김한근;사공건
    • E2M - 전기 전자와 첨단 소재
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    • 제9권9호
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    • pp.906-910
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    • 1996
  • Ferroxplana N $i_{2}$Y(B $a_{2}$N $i_{2}$F $e_{12}$ $O_{22}$ ) magnetic particles, which is one of the hexagonal ferrite were synthesized by a coprecipitation method. The coprecipitates were prepared by adding aqueous solution of BaC $I_{2}$ - 2 $H_{2}$O, NiC $I_{2}$ - 6 $H_{2}$O and FeC $I_{3}$ - 6 $H_{2}$O(of which the mole ratio is $Ba^{+2}$ : N $i^{+2}$ : F $e^{3+}$= 1 : 1 : 6) to a mixture of NaOH and N $a_{2}$C $O_{3}$. The shape of Ferroxplana N $i_{2}$Y magnetic particles obtained at 1, 100(.deg. C) was hexagonal plate-like, average particle size and aspect ratio were 2(.mu.m) and 7, respectively.y.

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Ferroxplana Y-type($Ni_2Y$) 자성(磁性) 분체의 합성 (Synthsis of Ferroxplana Y-type($Ni_2Y$) Magnetic Particles)

  • 박상하;김한근;사공건
    • 대한전기학회:학술대회논문집
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    • 대한전기학회 1993년도 하계학술대회 논문집 B
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    • pp.1140-1142
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    • 1993
  • It has been prepared by a coprecipitation method for Ferroxplana $Ni_2Y\;(Ba_2Ni_2Fe_{12}O_{22}$ magnetic particles, which is one of the Hexagonal ferrite. The coprecipitates were synthesized by adding aqueous solution of $BaCl_2{\cdot}2H_2O,\;NiCl_2{\cdot}6H_2O\;and\;FeCl_2{\cdot}4H_2O$ (of which the mole ratio is $Ba^{2+}:Ni^{2+}:Fe^{2+}$=1:1:6) to a mixture of NaOH and $Na_2CO_3$ solution. The shape of Ferroxplana $Ni_2Y$ magnetic particles obtained at the calcined temperature 1,100($^{\circ}C$) was hexagonal plate-like, average particle size was 2(${\mu}m$), and aspect ratio was more than 7.

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$Fe_2O_3$몰비 및 B\ulcorner첨가가 Sr-Ferrite 특성에 미치는 영향 (Effect of Molar Ratio of $Fe_2O_3$ and BaO Addition on the Characteristics of Sr-Ferrite)

  • 문기훈;심영재;조성걸
    • 한국세라믹학회지
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    • 제34권5호
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    • pp.453-460
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    • 1997
  • Sr-ferrite having magnetoplumbite structure is similar to Ba-ferrite in magnetic characteristics, but better magnetic characteristics for using motor application. To improve remanence magnetic flux density(Br) and coercive force(iHc), it is necessary that sintered ferrites must have high density and grain size less than 1 $\mu$m. By varying n values in SrO.nFe2O3 basic composition, calcination temperature, and BaO addition, Sr-ferrite powder and sintered specimen was prepared. The n values, calcination temperature, and BaO addition affected secondary phase formation, particle size, and particle shape. BaO addition enhanced Fe2O3 secondary phase and hexagonal shape particle. Fe2O3 phase reduced sintered density which greatly decreased Br.

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PLA법에 의한 Si 미립자 제작 (Fabrication of various Si particle by Pulsed Laser Ablation)

  • 김민성
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2001년도 추계학술대회 논문집 Vol.14 No.1
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    • pp.121-125
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    • 2001
  • We study the feasibility of synthesizing Si particles using PLA method. In the previous studies, it was possible to control the size of Si nanoparticles by the He gas pressure. In this study, we fabricated sub-micron size Si particles with various shapes such as conical, hexagonal, and ring by controlling not only the ambient gas pressure but also the laser energy density. Furthermore, we found that the conical Si particles were uniform-sized and had step shape when observed from FE-SEM and AFM. The conical Si particle has the same crystal structure as the bulk single crystalline Si by the analysis of the Raman scattering. It is shown that the relationship between the laser energy density and the He gas pressure inside the chamber affects the shape of the Si particle.

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PLA법에 의한 Si 미립자 제작 (Fabrication of various Si particle by Pulsed Laser Ablation)

  • 김민성
    • 한국전기전자재료학회:학술대회논문집
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    • 한국전기전자재료학회 2001년도 추계학술대회 논문집
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    • pp.121-125
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    • 2001
  • We study the feasibility of synthesizing Si particles using PLA method. In the previous studies, it was possible to control the size of Si nanoparticles bythe He gas pressure. In this study, we fabricated sub-micron size Si particles with various shapes such as conical, hexagonal, and ring by controlling not only the ambient as pressure but also the laser energy density. Furthermore, we found that the conical Si particles were uniform-sized and had step shape when observed from FE-SEM and AFM. The conical Si particle has the same crystal structure as the bulk single crystalline Si by the analysis of the Raman scattering. It is shown that the relationship between the laser energy density and the He gas pressure inside the chamber affects the shape of the Si particle.

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수열성장법에 의한 코런덤($\alpha$-Al_{2}O_{3}$) 제조 : I. 반응온도와 종자결정의 영향에 관한 연구 (Preparation of corundum ($\alpha$-Al_{2}O_{3}$) by hydrothermal growing process : I. A study on the effects of reaction temperature and seed crystal)

  • 반종성;이기정;서경원;목영일;이철경
    • 한국결정성장학회지
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    • 제6권2호
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    • pp.129-140
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    • 1996
  • 본 연구에서는 수열성장법을 이용해서 알루미늄 수화물로부터 코런덤($\alpha$-Al_{2}O_{3}$) 단결정을 지조하였고, 합성 조건에 관해 조사하였다. 수열 조건에 영향을 미치는 주요인자는 반응온도, 종자결정 및 반응시간이었으며, 특히 종자결정은 코런덤의 입도와 결정형태에 큰 영향을 미쳤다. 영양제로 사용한 일본산 깁사이트에 종자결정을 첨가해서 2시간 동안 수열반응 시킨 결과 $460^{\circ}C$에서 중량평균입경이 $11\;\mu\textrm{m}$인 육방정의 코런덤 결정이 합성되었으며, 또다른 유형의 러시아산 깁사이트로부터는 $420^{\circ}C$에서 중량평균입경이 $6\;\mu\textrm{m}$인 육방정의 코런덤 결정이 합성되었다.

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