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The effect of manganese oxide precursors on the characteristics of LiMn2O4 cathode particles
강윤찬,Seo Hee Ju,Hee Chan Jang,Man-Jong Lee 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.2
Manganese oxide particles with nanometre and several micrometre sizes were prepared by spray pyrolysis from aqueous and polymeric spray solutions. The LiMn2O4 particles prepared from Mn2O3 particles obtained from an aqueous solution with a manganese nitrate precursor had micrometre sizes and a spherical shape. On the other hand, the LiMn2O4 particles prepared from nano-sized Mn2O3 particles obtained from polymeric spray solutions had a fine size, a narrow size distribution, and regular morphology irrespective of the type of manganese precursors. The discharge capacities of the LiMn2O4 particles obtained from an aqueous spray solution with a manganese nitrate precursor dropped from 136 to 115 mAh/g by the 25 th cycle at a current density of 0.1 C. On the other hand, the discharge capacities of the LiMn2O4 particles obtained from a polymeric spray solution with a manganese nitrate precursor dropped from 121 to 105 mAh/g.
강윤찬,정윤섭,박승빈 한국화학공학회 2000 Korean Chemical Engineering Research(HWAHAK KONGHA Vol.38 No.1
FEAG process를 사용한 분무열분해법에 의해 전자빔이나 UV에 의해 빨간색을 발생시키는 YAG : Cr 형광체 입자를 제조하고 그 특성들을 조사하였다. 질산염 혼합용액으로부터 분무열분해법에 의해 제조된 입자들은 1,100도의 낮은 열처리 온도에서도 순수한 YAG 결정을 얻을 수 있었다. 제조된 입자들은 밀링과정을 거치지 않고도 구형의 형태를 가졌으며, 서브마이크론 크기의 균일한 크기분포를 나타내었다. 용액의 총 농도가 0.01에서 0.2M까지 변화시켰을 때 CPSA로부터 측정한 입자들의 평균크기는 0.34에서 0.83 ㎛까지 증가했다. 제조한 입자들을 1,200도에서 5시간 열처리했을 때는 원래의 구형의 형태를 유지하고 있으나 1,400도에서는 구형의 형태가 사라지면서 입자들간의 응집현상이 나타나고, 1,500도에서는 입자들간의 응집이 완전히 일어났다. Cr의 도핑농도가 2 at%일 때 가장 좋은 발광특성을 나타냈다. YAG : Cr 입자의 발광특성에 가장 좋은 열처리 온도는 1,400도였다. Chromium-doped Yttrium Aluminum Garnet(YAG) phosphor particles, which generate red light when excited with e-beam or UV, were prepared from mixed nitrate solutions by spray pyrolysis using the FEAG process, and their characteristics were investigated. The prepared particles had an amorphous phase, which turned into phase pure YAG particles after annealing above 1,100℃. The prepared particles had spherical morphology, submicron size, and narrow size distribution without milling process. The mean size of the YAG : Cr particles varied from 0.34 to 0.83 ㎛ when the overall solution concentrations were changed from 0.01 to 0.2 M. The particles calcined below 1,200℃ maintained spherical morphology, but aggregation between particles was occurred after calcination above 1,400℃. The particles calcined at 1,500 ℃ had hard aggregation. The optimum doping concentration of Cr and calcination temperature for the maximum brightness of phosphor particles was 2 at% and 1,400 ℃, respectively.
액적 분급 장치를 적용한 분무열분해 공정으로부터 합성된 실리카 분말의 특성
강윤찬,주서희,구혜영,강희상,박승빈,Kang, Yun-Chan,Ju, Seo-Hee,Koo, Hye-Young,Kang, Hee-Sang,Park, Seung-Bin 한국재료학회 2006 한국재료학회지 Vol.16 No.10
Silica powders with spherical shape and narrow size distribution were prepared by large-scale ultrasonic spray pyrolysis applying the droplet classification apparatus. On the other hand, silica powders prepared by large-scale ultrasonic spray pyrolysis without droplet classification apparatus had broad size distribution. Droplet classification apparatus used in this paper applied the principles of cyclone and dispersion plate with small holes. The droplets formed from the ultrasonic spray generator applying the droplet classification apparatus had narrow size distribution. The droplets with fine and large sizes were eliminated by droplet classification apparatus. The optimum flow rate of the carrier gas and diameter of the hole of the dispersion plate were studied to reduce the size distribution of the silica powders prepared by large-scale ultrasonic spray pyrolysis. The size distribution of the silica powders prepared by large-scale ultrasonic spray pyrolysis at the optimum preparation conditions was 0.76.
화염분무열분해 공정에 의해 합성되어진 Zn<sub>2</sub>SiO<sub>4</sub>:Mn 형광체
강윤찬,손종락,정경열,Kang Y. C.,Sohn J. R.,Jung K. Y. 한국재료학회 2004 한국재료학회지 Vol.14 No.8
$Zn_{2}SiO_{4}:Mn$ phosphor particles were prepared by a flame spray pyrolysis method. It has been generally known that the high-temperature flame enables fast drying and decomposition of droplets. In the present investigation, the morphology and luminescent property of $Zn_{2}SiO_{4}:Mn$ phosphor were controlled in a severe flame preparation condition. The particle formation in the flame spray pyrolysis process was achieved by the droplet-to-particle conversion without any evaporation of precursors, which made it possible to obtain spherical $Zn_{2}SiO_{4}:Mn$ particles of a pure phase from a droplet. Using colloidal solutions wherein dispersed nano-sized silica particles were adopted as a silicon precursor. $Zn_{2}SiO_{4}:Mn$ particles with spherical shape and filled morphology were prepared and the spherical morphology was maintained even after the high-temperature heat treatment, which is necessary to increase the photoluminescence intensity. The $Zn_{2}SiO_{4}:Mn$ particles with spherical shape, which were prepared by the flame spray pyrolysis and posttreated at $1150^{\circ}C$, showed good luminescent characteristics under vacuum ultraviolet (VUV) excitation.
The properties of Li-Ni-Mn-O powders prepared by spray pyrolysis
강윤찬,Eun Byul Jo,주서희,Hee Chan Jang 한양대학교 세라믹연구소 2007 Journal of Ceramic Processing Research Vol.8 No.5
Li-Ni-Mn-O cathode powders with various ratios of nickel and manganese components were prepared by ultrasonic spray pyrolysis from polymeric precursor solutions. The precursor powders obtained from the polymeric precursor solutions containing citric acid and ethylene glycol were several micrometre in size, had a spherical shape and hollow morphology irrespective of the ratios of nickel and manganese components. However, the morphology of the post-treated Li-Ni-Mn-O cathode powders were affected by the ratios of nickel and manganese components. The LiMn1.5Ni0.5O4 and LiNi0.5Mn0.5O2 cathode powders were several micrometre in size, had a hollow and spherical morphology. However, the LiMn2O4 and LiNi0.75Mn0.25O2 cathode powders had a fine size and regular morphology. The mean sizes of the LiMn2O4 and LiNi0.75Mn0.25O2 cathode powders were 1.2 and 0.26 μm, respectively. The initial discharge capacities of the prepared Li-Ni-Mn-O cathode powders were changed from 120 to 206 mAhg−1 according to the ratios of nickel and manganese components. Li-Ni-Mn-O cathode powders with various ratios of nickel and manganese components were prepared by ultrasonic spray pyrolysis from polymeric precursor solutions. The precursor powders obtained from the polymeric precursor solutions containing citric acid and ethylene glycol were several micrometre in size, had a spherical shape and hollow morphology irrespective of the ratios of nickel and manganese components. However, the morphology of the post-treated Li-Ni-Mn-O cathode powders were affected by the ratios of nickel and manganese components. The LiMn1.5Ni0.5O4 and LiNi0.5Mn0.5O2 cathode powders were several micrometre in size, had a hollow and spherical morphology. However, the LiMn2O4 and LiNi0.75Mn0.25O2 cathode powders had a fine size and regular morphology. The mean sizes of the LiMn2O4 and LiNi0.75Mn0.25O2 cathode powders were 1.2 and 0.26 μm, respectively. The initial discharge capacities of the prepared Li-Ni-Mn-O cathode powders were changed from 120 to 206 mAhg−1 according to the ratios of nickel and manganese components.
Preparation of Pb-based glass powders by spray pyrolysis using a filter expansion aerosol generator
강윤찬,Seung Kwon Hong,Hye Young Koo,정대수,Jung Sang Cho 한양대학교 세라믹연구소 2007 Journal of Ceramic Processing Research Vol.8 No.4
PbO-B2O3-SiO2 glass powders were directly prepared by a filter expansion aerosol generator (FEAG) process. Glass powders were formed by melting and cooling processes of the powders inside the hot wall reactor which was maintained at a low pressure. The powders prepared at temperatures below 800oC had a spherical shape and submicrometre size. One glass powder was formed from one droplet at preparation temperatures below 800oC. On the other hand, the powders prepared at a temperature of 900oC had a bimodal size distribution with nanometre and submicrometre size. The mean size of the glass powders prepared by the FEAG process at a temperature of 800oC was 320 nm. In the DSC curve, the glass transition temperature (Tg) of the glass powders was 411.5oC. The transparencies of the dielectric layers formed from the glass powders obtained by the FEAG process were higher than 90% within the visible light range at annealing temperatures above 500oC.
강윤찬,Hye Young Koo,Seung Kwon Hong 한양대학교 세라믹연구소 2007 Journal of Ceramic Processing Research Vol.8 No.4
High brightness Y2O3:Eu phosphor particles with a spherical shape and fine size were prepared by spray pyrolysis from spray solutions with polymeric precursors, a drying control chemical additive and ammonium chloride flux. The phosphor particles prepared from the spray solution with the ammonium chloride flux had a hollow and porous structure after post-treatment. However, the phosphor particles prepared from the spray solution with polymeric precursors, a drying control chemical additive and ammonium chloride flux had a spherical shape and filled inner structure after post-treatment. The optimum content of the NH4Cl flux showing the maximum photoluminescence intensity of the Y2O3:Eu phosphor particles was 6 wt%. The improvement of the photoluminescence intensity of the Y2O3:Eu phosphor particles by additions of ammonium chloride flux, polymeric precursors and a drying control chemical additive into the spray solution was 37%. High brightness Y2O3:Eu phosphor particles with a spherical shape and fine size were prepared by spray pyrolysis from spray solutions with polymeric precursors, a drying control chemical additive and ammonium chloride flux. The phosphor particles prepared from the spray solution with the ammonium chloride flux had a hollow and porous structure after post-treatment. However, the phosphor particles prepared from the spray solution with polymeric precursors, a drying control chemical additive and ammonium chloride flux had a spherical shape and filled inner structure after post-treatment. The optimum content of the NH4Cl flux showing the maximum photoluminescence intensity of the Y2O3:Eu phosphor particles was 6 wt%. The improvement of the photoluminescence intensity of the Y2O3:Eu phosphor particles by additions of ammonium chloride flux, polymeric precursors and a drying control chemical additive into the spray solution was 37%.