• 한국입자에어로졸학회지
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• 제7권3호
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• pp.79-85
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• 2011

Porous $TiO_2-SiO_2$ particles were synthesized by co-assembly of nanoparticles of $TiO_2$ and $SiO_2$ in evaporating aerosol droplets. Poly styrene latex (PSL) particles were employed as a template of porous particles. Flowrate of dispersion gas, weight ratio of $TiO_2/SiO_2$ and $SiO_2$ concentration in the precursor, and PSL size were chosen as process variables. The morphology, crystal structure, chemical bonding, and pore size distribution were analyzed by FE-SEM, XRD, FT-IR, BET. The morphology of porous $TiO_2-SiO_2$ particles was spherical and the average particle size range were from 1 to $10{\mu}m$. The particles were composed of meso and macro pores. The average particle diameter and pore volume of the as prepared particles were dependant on process variables. It was found that UV-Vis absorption of the porous particles was comparable with pure $TiO_2$ nanoparticles even though $TiO_2/SiO_2$ ratio is low in the porous particles.

• 한국세라믹학회지
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• 제32권11호
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• pp.1246-1254
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• 1995

A numerical model for fabrication and deposition of ultrafine SiO2 particles were proposed in the simplified horizontal MCVD apparatus using tube furnace reactor. The model equations such as energy and mass balance equations and the 0th, 1st and 2nd moment balance equations of aerosols were considered in the reactor. The phenomena of SiCl4 chemical reaction, SiO2 particle formation and coagulation, diffusion and thermophoresis of SiO2 particles were included in the aerosol dynamic equation. The profiles of gas temperature, SiCl4 concentration and SiO2 particle volume were calculated for standard conditions. The concentrations, sizes and deposition efficiencies of SiO2 particles were calculated, changing the process conditions such as tube furnace setting temperature, total gas flow rate and inlet SiCl4 concentration.

• 대한화장품학회지
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• 제25권4호
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• pp.43-50
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• 1999

The planarized $SiO_2$ particles were prepared by two-step reduction method of making much smaller particles, micron-sized ones, to improve spreadability, adherence, and smoothness. Various pigments known as flaky extender usually have terrace layers on their surfaces, but $SiO_2$ particles in this study exhibit a smooth surface structure. These single $SiO_2$ particles were used as core particles to prepare the composite particles coated with ultra fine $TiO_2$ particles by a homogeneous precipitation method. The thickness and the morphology of the deposited $TiO_2$ layers could be modified by adjusting the reactant concentrations, the reaction time and the temperature. The characteristics of $SiO_2/TiO_2$ composite in the field of color cosmetics are to give an UV-cut effect and to enhance the chroma of human skin color, one of optical properties.

• 대한화장품학회:학술대회논문집
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• 대한화장품학회 1999년도 IFSCC . ASCS 학술대회 발표 논문
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• pp.43-50
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• 1999

The planarized SiO$_2$ particles were prepared by two-step reduction method of making much smaller particles, micron-sized ones, to improve spreadability, adherence, and smoothness. Various pigments known as flaky extender usually have terrace layers on their surfaces, but SiO$_2$ particles in this study exhibit a smooth surface structure. These single SiO$_2$ particles were used as core particles to prepare the composite particles coated with ultra fine TiO$_2$ particles by a homogeneous precipitation method. The thickness and the morphology of the deposited TiO$_2$ layers could be modified by adjusting the reactant concentrations, the reaction time and the temperature. The characteristics of SiO$_2$/TiO$_2$ composite in the field of color cosmetics are to give an UV-cut effect and to enhance the chroma of human skin color, one of optical properties.

• 대한화장품학회지
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• 제25권1호
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• pp.37-54
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• 1999

분체 특성으로 매끄러운 사용감과 피부 부착력이 우수하며 판상의 체질안료보다 유동성이 큰 실리카 미립자를 제조하기 위해 실리카 조대입자의 제조와 이의 다단계 분쇄 공정을 이용하여 여러 층의 terrace를 가지고 있는 판상 체질안료의 표면과 다른 평골한 표면 상태의 평탄면을 가지는 실리카 미립자를 제조하였다 여기에서 제조된 실리카 단일 입자를 모입자로 사용함으로써 이산화티탄의 균일침전반응법에 의해 제조된 복합입자는 평탄면을 가지게 되어 유동성의 조절과 부착력의 조절에 의해 도포 층이 균일하게 형성되는 분체 특성을 가지고 있다 본 실험에서 가장 적합한 침전 반응의 조건은 요소농도가 0.2~0.3mol/$\ell$이고 황산농도가 0.3~O.4mol/$\ell$이고 황산티타닐의 농도가 0.007~0.015mol/$\ell$며, 반응온도는 60~8$0^{\circ}C$였다 이와 같은 균일 침전 반응의 조건에 따라 초미립자상 이산화티탄의 피복량과 피복된 초미립자의 입경을 제어함으로써 분체의 광학적 특성을 조절하였고, 그 결과 피부 도포 시 피부색에서 600nm이상의 장파장 영역에서 반사율을 증가시켜 강한 피부색 tone을 표현할 수 있도록 하였다.

• Tribology and Lubricants
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• 제39권2호
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• pp.72-75
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• 2023

Silicon carbide (SiC) is used as a substrate material for power semiconductors; however, SiC chemical mechanical polishing (CMP) requires considerable time owing to its chemical stability and high hardness. Therefore, researchers are attempting to increase the material removal rate (MRR) of SiC CMP using various methods. Mixed-abrasive CMP (MAS CMP) is one method of increasing the material removal efficiency of CMP by mixing two or more particles. The aim of this research is to study the mathematical modeling of the MRR of MAS CMP of SiC with SiO₂ and TiO₂ particles. With a total particle concentration of 32 wt, using 80-nm SiO₂ particles and 25-nm TiO₂ particles maximizes the MRR at 8 wt of the TiO₂ particle concentration. In the case of 5 nm TiO₂ particles, the MRR tends to increase with an increase in TiO₂ concentration. In the case of particle size 10-25 nm TiO₂, as the particle concentration increases, the MRR increases to a certain level and then decreases again. TiO₂ particles of 25 nm or more continuously decreased MRR as the particle concentration increased. In the model proposed in this study, the MRR of MAS CMP of SiC increases linearly with changes in pressure and relative speed, which shows the same result as the Preston's equation. These results can contribute to the future design of MAS; however, the model needs to be verified and improved in future experiments.

• Korean Chemical Engineering Research
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• 제44권6호
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• pp.609-613
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• 2006

분무열분해법에 의해 장파장 UV 여기원 하에서 높은 발광세기를 가지는 $Ba_{2-x.}Sr_{x.}SiO_4:Eu^{2+}$ 형광체를 제조하였다. 분무열분해공정 의해 제조된 $Ba_{2-x.}Sr_{x.}SiO_4:Eu^{2+}$ 형광체의 발광특성, 분말 형태 및 결정성에 대해 조사하였다. 분무열분해 공정에 의해 제조된 $Ba_{2-x.}Sr_{x.}SiO_4:Eu^{2+}$ 형광체는 모체를 구성하는 바륨과 스트론튬의 비에 따라 청녹색에서 황색에 이르기까지 다양한 파장대의 색을 구현할 수 있었다. x = 0인 $Ba_2SiO_4:Eu^{2+}$ 형광체의 경우 발광 중심파장이 500 nm였으며, x = 2인 $Sr_2SiO_4:Eu^{2+}$ 형광체의 경우 발광중심 파장이 554 nm였다. 분무열분해 공정에 의해 제조된 $Ba_{2-x.}Sr_{x.}SiO_4:Eu^{2+}$ 형광체는 구형의 형상을 띄지만 중공성의 입자 특성을 가졌다. 반면에 후열처리 과정을 거친 $Ba_{2-x.}Sr_{x.}SiO_4:Eu^{2+}$ 형광체는 큰 입자 크기와 불규칙한 형태를 가졌다. $Ba_{1.488}Sr_{0.5}SiO_4:Eu_{0.012}{^{2+}}$ 형광체가 환원분위기 하에서 후열처리 온도 $1,200^{\circ}C$에서 3시간 동안 후열처리 과정을 거쳤을 때 최적의 발광 세기를 가졌다.

• 한국재료학회지
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• 제14권8호
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• pp.600-606
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• 2004

$Zn_{2}SiO_{4}:Mn$ 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.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집D
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• pp.91-96
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• 2001

Ultrafine particles have been widely used in many high technology industrial areas. The spherical nonagglomerated and uniform nanometer-size $SiO_{2}$ particles are synthesized by the injection of TEOS vapor, ions and reaction gas in furnace. Ions were generated by Corona discharge electrode and these ions charge $SiO_{2}$ particles. As a result, spherical, nonagglomerated and ultrafine particles are generated in various conditions, it's morphology, charging portion and size distribution are examined by using TEM, ESP and SMPS. As the applied voltage of electrode changes from 0 kV to 5.0 kV, it is observed that the mean diameter of $SiO_{2}$ particle decreases from 94 nm to 42 nm.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2002년도 International Meeting on Information Display
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• pp.811-814
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• 2002

$(Ba,Sr)_2SiO_4:Eu^{2+}$ phosphor particles with high brightness were prepared by spray pyrolysis. The changes in the photoluminescence intensity and morphology of $(Ba,Sr)_2SiO_4:Eu^{2+}$ were investigated by changing the posttreatment temperature and the concentration of dopant. The prepared $(Ba,Sr)_2SiO_4:Eu^{2+}$ particles has a dense structure, but irregular shape after the posttreatment. When they were excited by the ultraviolet light of 410 nm, a broad emission band with a peak at 508 nm was observed. The photoluminescence intensity of the prepared $(Ba,Sr)_2SiO_4:Eu^{2+}$ particles was enhanced by increasing the posttreatment temperature up to 1300 $^{\circ}C$ and further improved by adding several rear-earth codopants. The $(Ba,Sr)_2SiO_4:Eu^{2+}$ particles prepared by spray pyrolysis had a good excitation spectrum in the wavelength longer than 350 nm. Therefore, it was concluded that the $(Ba,Sr)_2SiO_4:Eu^{2+}$ prepared by spray pyrolysis is a good green-emitting phosphor for LED application.