• 제목/요약/키워드: Ultrafine TiO$_2$ Powder

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Co 질산염과 TiO(OH)2 슬러리를 이용한 초미립 TiC-5%Co 제조 및 WC-Co 분말과의 혼합에 따른 소결체 특성 (Synthesis of Ultrafine TiC-5%Co Powder by Using Co Nitrate and TiO(OH)2 Slurry and Evaluation of Sintered Materials Prepared by Mixing WC-Co)

  • 홍성현;김병기
    • 한국분말재료학회지
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    • 제15권2호
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    • pp.107-113
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    • 2008
  • Ultrafine TiC-5%Co powders were synthesized by spray drying of aqueous solution of TiO$(OH)_2$ slurry and cobalt nitrate, followed by calcination and carbothermal reaction. The oxide powders with carbon powder was reduced and carburized at $900^{\circ}C{\sim}1250^{\circ}C$ under hydrogen atmosphere. During reduction, CO gas was mainly evolved by reducing reaction of oxides. Ultrafine TiC-5%Co powders were easily formed by carbothermal reaction at $1250^{\circ}C$ due to using ultrafine powders as raw materials. The ultrafine WC-TiC-Co alloy prepared by sintering of mixed powder of ultrafine WC-13%Co powder and ultrafine TiC-5%Co powder has higher sintered density and mechanical properties than WC-TiC-Co alloy prepared by commercial WC, TiC and Co powders.

화학 증착법에 의한 $TiO_2$ 초미분의 제조 및 입자 특성에 관한 연구 (Synthesis and Characterization of $TiO_2$ Ultrafine Powder by Chemical Vapor Deposition)

  • 염선민;이성호;김광호
    • 한국세라믹학회지
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    • 제32권1호
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    • pp.37-44
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    • 1995
  • TiO2 fine powders were synthesized using oxygenolysis and hydrolysis reaction of TiCl4 vapor in gas phase. The TiO2 powder synthesized showed morphological differences depending on reaction system as follows: TiCl4-O2 reaction system produced the monosized particles having polyhedral shape with well-defined crystal planes and the particles did not agglomerate into secondary particles. TiCl4-H2O reaction system, whereas, produced the spherical secondary particles which consisted of fine primary particles. Other powder characteristics such as particle size, impurity content and rutile content are also reported in this study.

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Synthesis of the Ultrafine $BaTiO_3$ power by hydrothermal Process

  • Bae, Dong-Sik;Han, Kyong-Sop;Park, Sang-Heul
    • 한국결정성장학회:학술대회논문집
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    • 한국결정성장학회 1997년도 Proceedings of the 13th KACG Technical Meeting `97 Industrial Crystallization Symposium(ICS)-Doosan Resort, Chunchon, October 30-31, 1997
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    • pp.87-89
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    • 1997
  • The BaTiO$_3$ fine powder was prepared by hydrthermal method using titanium tetrahydoxide (Ti(OH)$_4$) and barium dihydroxide (Ba(OH)$_2$.8$H_2O$) as raw materials. The fine powder was obtained at temperatures as low as 160 to 185$^{\circ}C$. The properties of the BaTiO$_3$ powder were studied as a function of various parameters (reaction temperature, reaction time, Ba/Ti=ratio, etc). The average particle size of the BaTiO$_3$ increased with increasing reaction temperature. After hydrothermal treatment at 17$0^{\circ}C$ for 8 h, the average particle size of the BaTiO$_3$ powder was about 30 nm and the particle size distribution was narrow.

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공침법에 의한 Ba2Ti9O20의 합성 (Preparation of Ba2Ti9O20 by Coprecipitation Method)

  • 이경희;이병하;오권오
    • 한국세라믹학회지
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    • 제25권6호
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    • pp.671-676
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    • 1988
  • Preparation of high purity ultrafine Ba2Ti9O20 powder was investigated by coprecipitation method. Formation of Ba2Ti9O20 powder from precipitate of coprecipitation takes place at 120$0^{\circ}C$, which is 20$0^{\circ}C$ lower than that from mechanical mixtures of BaCO3 and TiO2. This is apparently due to the nature of the compounds formed by the reaction of mixtures of aqueous solutions of BaCl2 and TiCl4 with an ammoniacal solution of ammonium carbonate and ammouium hydroxide. In this method, the Ba2Ti9O20 powders show low callcining and sintering temperature and it has good sintering and dielectric constant at room temperature.

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Photo Catalytic Ability of Acicular Shaped TiO$_{2}$ Rutile Powder in Aqueous Metal-EDTA Solutions

  • Kim, Sun-Jae;chang-Joo choi;Park, Soon-Dong;Hwang, Jong-Sun;Han, Byung-Sung
    • Transactions on Electrical and Electronic Materials
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    • 제2권2호
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    • pp.37-41
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    • 2001
  • Photo catalytic characteristics of nano-sized TiO$_2$ powder with rutile phase produced using homogeneous precipitation process at low temperatures (HPPLT) were compared with those of commercial P-25 powder by Degussa Co. The TiO$_2$ powder by HPPLT showed very higher photoactivity in the removal rate, showing lower pH values in the solution, than the P-25 powder when eliminating metal ions such as Pb and Cu from aqueous metal-EDTA solutions. This can be inferred the more rapid photo-oxidation or -reduction of metal ions from the aqueous solution, together with relatively higher efficiencies in the use of electron-hole pair formed on the surface of TiO$_2$ particle, under UV light irradiation. Also, in the view of the TiO$_2$ particle morphology, compared to the well-dispersed spherical P-25 particle, the agglomerated TiO$_2$ particle by HPPL T consists of acicular typed primary particle with the thickness ranged of 3∼7 nm, which would be more effective to the photocatalytic reactions without electron-hole recombination on the surface of the TiO$_2$ particle under the UV light irradiation. It is, therefore, thought that the higher photo activity of the rutile TiO$_2$ powder by HPPLT in the aqueous solutions resulted from having its higher specific surface area as well as acicular shape primary particle with very thin thickness.

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마이크로파를 이용한 초미세 균일 분산 BaTiO$_3$ 분말 제조 (Fabrication of Mono-Dispersed Ultrafine BaTiO$_3$ Powder Using Microwave)

  • 김현상;최광진;이상균;김영대;심상준;우경자;김경림;조영상
    • 한국세라믹학회지
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    • 제36권4호
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    • pp.343-353
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    • 1999
  • 2.45 GHz의 microwave가 수열 합성법으로 제조된 BaTiO3 분말의 특성에 미치는 영향을 조사하였다. 700W 출력으로 반응시켰을 때, microwave-autoclave system에서는 약 5분만에 BaTiO3 결정이 형성되기 시작하여, 10분 이상의 반응에서는 더 이상 결정성 증가는 관찰되지 않았다. Microwave-system의 경우에는 15분만에 결정이 형성되기 시작하여, 1시간정도의 반응으로 충분한 BaTiO3 분말을 얻을 수 있었다. Microwave를 이용한 균일가열의 영향으로 분말들은 균일하게 분산되어 있었고, 기존의 전기적인 가열 방법에서 나타나는 응집 현상이나 grain의 성장 등은 보이지 않았다. 제조된 분말의 크기는 보통 30~60 nm정도였는데, 졸 안의 Ba/Ti의 비가 분말의 크기를 결정하는데 중요한 역할을 하였다. 이는 여분의 바륨이 Ba(OH)2등과 같은 다른 상을 형성하여 BaTiO3 분말의 계면에 얇은 막을 형성하여 분말들의 응집 현상이나 grain의 성장을 억제하는 것으로 추정하였다. M1-crowave-autoclave 에서는 15분 정도의 반응만으로도 미량이지만 tetragonal-BaTiO3를 직접적으로 형성할 수 있었고, microwave-reflux에서는 25$0^{\circ}C$의 건조로써 미량의 tetragonal-BaTiO3를 얻을 수 있었다.

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침상구조의 루틸상 TiO2 초미분체를 이용한 광촉매 반응에 대한 연구 (Study on Photocatalytic Reaction Using Acicular TiO2 Rutile Powder)

  • 황두선;구숙경;김광수;민형섭;이은구;김선재
    • 한국재료학회지
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    • 제12권8호
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    • pp.641-649
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    • 2002
  • The redox properties of a homogeneously-precipitated $TiO_2$ rutile powder with a BET surface area of ~$200 m^2$/g, consisting of an acicular primary particle, were characterized using photocatalytic reaction in aqueous 4-chlorophenol, Cu-EDTA and Pb-EDTA solutions under ultraviolet irradiation, compared to those of commercial P-25 X$200 m_2$ powder with a spherical primary particle as well as home-made anatase $TiO_2$ powder with ~$200 m^2$/g BET surface area. Here, the anatase powder also includes mainly the primary particles very similar to the acicular shapes of the rutile $TiO_2$ powder. The rutile powder showed the fastest decomposition rate and the largest amount in the photoredor, compared with the anatase or P-25 powder, while the anatase powder unexpectedly showed the slowest rate and the smallest amount in the same experiments regardless of almost the same surface area. From results, the excellent photoredox abilities of this rutile powder appears to be due to specific powder preparation method, like a homogeneous precipitation leading to direct crystallization from the solution, regardless of their crystalline structures even when having the similar particle shape and surface area.

마그네슘의 금속염 환원에 의한 초미립 탄화티탄 분말 합성거동 (Synthesis and kinetic of ultrafine titanium carbide particles by Mg-thermal reduction of liquid metal chlorides)

  • 이동원;백진호;김병기
    • 한국분말재료학회지
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    • 제11권4호
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    • pp.322-327
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    • 2004
  • Ultrafine titanium carbide particles were synthesized by the reaction of liquid-magnesium and vaporized TiCl$_{4}$+C$_{x}$Cl$_{4}$(x = 1 and 2) solution. Fine titanium carbide particles with about 50 nm were successfully produced by combining Ti and C atoms released by chloride reduction of magnesium, and vacuum was then used to remove the residual phases of MgCl$_{2}$ and excess Mg. Small amounts of impurities such as O, Fe, Mg and Cl were detected in the product, but such problem can be solved by more precise process control. The lattice parameter of the product was 0.43267 nm, near the standard value. With respect to the reaction kinetics, the activation energy for the reactions of TiCl$_{4}$+C$_{2}$Cl$_{4}$and Mg was found to 69 kJ/mole, which was about half value against the use of TiCl$_{4}$+CCl$_{4}$, and such higher reactivity of the former contributed to increase the stoichiometry until the level of TiC$_{0.96}$ and decrease the free carbon content below 0.3 wt.%.

저온 균일침전법으로 $TiOCl_2$ 수용액에서 얻은 $TiO_2$ 초미분체의 형성기구 (Formation Mechanism of Ultrafine $TiO_2$ Powders from Aqueous $TiOCl_2$ Solution by Homogeneous Precipitation Process at Low Temperature)

  • 김선재;이희균;박순동;전치중;이창규;김흥회;이은구
    • 한국세라믹학회지
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    • 제37권5호
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    • pp.473-478
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    • 2000
  • The TiO2 powder with the values of the large specific surface area more than 150$m^2$/g has been prepared with the homogeneous precipitation process below 5$0^{\circ}C$ and its formation mechanism was investigated using the SEM, TEM and Raman Spectroscopy. With the spontaneous hydrolysis of aqueous TiOCl2 solutions, all the precipitates were fully and homogeneously crystallized with the rutile TiO2 phase simply by heating, which as transformed to the anatase TiO2 phase as increasing the addition of SO42- ions to the aqueous TiOCl2 solution. The precipitates were formed with spherical secondary particles which consisted of acicular, spherical and mixed primary particles corresponding to the rutile, anatase and mixed phases, respectively. It can be thought that the formation and phase determination of crystalline TiO2 powders even at ambient temperature would be related with the existence of the capillary force. This force might be varied depending on the shape change of the primary particles.

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