• 공업화학
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• 제20권6호
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• pp.617-621
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• 2009

Zinc oxide (ZnO)을 금(Au)과 fluorine-doped tin oxide (FTO) 촉매로 산화실리콘($SiO_2$) 기판에 산화아연입자 20 nm, $20{\mu}m$를 각각 사용하여 기체-액체-고체(VLS) 합성법으로 성장시켰다. 나노로드의 표면특성, 화학조성, 그리고 결정특성을 엑스레이회절(X-ray diffraction (XRD)), 에너지 분산형 X선 분광기(Energy-dispersive X-ray spectroscopy (EDX)), 표면 방출주사현미경(Field-emission scanning electron microscope (FE-SEM))으로 분석하였다. ZnO의 입자 크기 뿐만 아니라 결정형태가 성장에 크게 영향을 미쳤다. ZnO의 모든 나노구조가 6방정계(六方晶系), 단일결정구조를 가지고 있었다. 최적온도는 $1030^{\circ}C$, 입자크기는 20 nm이다. 그러므로 Au 대신 플루오린 첨가 도핑으로 전기음성도가 증가된 FTO 증착에 의해서 생성된 나노로드는 경제성 있는 대체물질로서의 가치가 있을 것으로 사료된다.

• Journal of Pharmaceutical Investigation
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• 제37권4호
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• pp.217-222
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• 2007

To develop cleansing tissue composed of silicone multiple emulsions which could easily remove make-up residues and confer skin protecting effect without damaging skin, we formulated various silicone multiple emulsions and evaluated the physicochemical properties including viscosity, cleansing effect, and safety effect. Also, cleansing tissue incorporated with silicone multiple (W/Si/W) emulsion was stored for 6 months, and judged its stability through microscopes under accelerated and long-term condition. Cleansing effect was evaluated by chromameter. Skin hydration effect was determined by corneometer and incorporation effect into non-woven fabric cotton was evaluated by volunteer survey. Low viscosity ranged from 400 centipoise (cP) to 1,000 cP was obtained from a stabilized W/Si/W emulsion containing more than 10% volatile silicone. Mean diameter of fresh W/Si/W emulsion was $20{\mu}m$, but after storage for 3 months at $45^{\circ}C$, the particle size of the W/Si/W emulsion increased up to $50{\mu}m$. Both W/Si/W emulsion-incorporated cleansing tissue and commercial product showed equally good cleansing effect. In addition, skin allergies such as erythema, edema, scaling itching, stinging, burning, tightness and prickling were not observed through macroscopic examination. From the transepidermal water loss results, the cleansing tissue consisting of W/Si/W emulsion showed superior hydration effect to commercial product. In conclusion, this study suggests cleansing tissue using W/Si/W emulsion could be used for an excellent efficacy compared with commercialized cleansing tissue.

• 한국재료학회지
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• 제16권6호
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• pp.355-359
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• 2006

Fine silica powders were synthesized via w/o emulsion method using sodium silicate, ammonium sulfate, Triton N-57, and cyclohexane as silica source, precipitating agent, surfactant, and oil phase, respectively. The powders were prepared under a conventional process and an ultrasonic process using the same reactants at room temperature for 1 hr varying the concentration of $Na_2SiO_3$ solution and the mol ratio of $H_2O$/surfactant, respectively. The particle size of the silica powder was reduced with decreasing the concentration of sodium silicate solution and with increasing the mol ratio of $H_2O$/surfactant under with and without ultrasounds. The size of powder with ultrasounds was smaller than that without ultrasounds, which indicates that the application of ultrasound in the synthesis of silica powder is an efficient way to reduce particle size.

• 한국세라믹학회지
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• 제45권7호
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• pp.401-404
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• 2008

Willemite ($Zn_2SiO_4$) are a wide range of applications such as a phosphor host and an important crystalline phase in glass ceramics, electrical insulators, glazes, and pigments. In this study, Willemite precursors were synthesized with zinc silicate gels from mixture of zinc nitrate solution and various sodium silicate solution by the geopolymer technique. To examine the crystallization behavior, precursors were have been monitored by the XRD. A pure willemite phase was obtained at $900^{\circ}C$. TEM investigations revealed that the sample with 50 nm particle size was obtained via heat-treated at $900^{\circ}C$ for W-3.

• Korean Chemical Engineering Research
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• 제56권6호
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• pp.798-803
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• 2018

Si을 리튬이온전지 음극활물질로 사용하기 위해 입도를 $0.5{\mu}m$ 보다 작은 크기로 제어하였고 표면에 탄소를 약 10 nm 두께로 코팅하였다. 그 위에 탄소섬유를 50~150 wt% 양으로 성장시키고 다시 한 번 탄소코팅을 진행하였다. 이렇게 만들어진 Si 합성물질은 전기전도성을 높이기 위한 공정으로 이종 금속을 혼합하였으며 수명 특성을 개선하기 위해 흑연과 복합화하였다. 실험 변수에 따른 재료들의 물리화학적 특성을 XRD, SEM 및 TEM을 사용하여 측정하였고 코인셀을 제조하여 전기화학적 특성을 평가하였다. Si/PC (Pyrolytic Carbon)/CNF (Carbon Nano Fiber)보다 Si/PC/CNF/PC가 전체적으로 Si 함량이 줄어 방전용량은 상대적으로 낮게 나타났지만 전지평가에서 중요한 수명특성에서는 좋은 결과를 보여주었다. 0.2 C rate에서 $1512mA\;h\;g^{-1}$의 초기 방전 용량과 78%의 초기 효율을 나타내었고 10 싸이클에서 94%의 용량 보존율을 보여주었다.

• Bulletin of the Korean Chemical Society
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• 제21권12호
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• pp.1193-1198
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• 2000

The preparation of nanocrystalline hematite, ${\alpha}-Fe_2O_3$, paricles and their surface coating with silica layers are described. The hematite particles with the size of 30~60 nm are firstly prepared by thermal decomposition of trinuclear acetate-hydroxo iron (III) nitrate complex, $[Fe_3$(OCOCH_3)_7$OH${\cdot}$2H_2O]NO_3$, at $400^{\circ}C$. Subsequently the hematite surfaces are coated with siliva layers by a controlled hydrolysis and condensation reaction of TEOS with varying the TEOS concentration and pH. Monodispersed and spherical $SiO_2-coatedFe_2O_3$ particles with the average particle diameter of ~90 nm and extremely narrow size distribution can be obtained at the pH of 11 and the TEOS concentration of 0.68M, which are found to be the optimum conditions in the present study in achieving the homogeneous deposition of silica layers on hematite surfaces. Diffuse reflectance UV-Vis spectra reveal that the characteristic optical reflectance of ${\alpha}-Fe_2O_3$ particles is preserved almost constant even after coating the surfaces, suggesting that the $SiO_2$ layers can be regarded as protecting layers without degrading the optical properties of hematite particles.

• 한국결정성장학회지
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• 제29권6호
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• pp.239-244
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• 2019

수소 분위기 열처리 및 수소 플라즈마 처리의 두 가지 수소화 표면개질을통해 나노다이아몬드 seed 입자의 분산 향상 및 평탄한 초미세 나노결정질 다이아몬드 박막증착을 위한 핵형성 밀도 향상을 확보하였다. 수소화 처리 이후 나노다이아몬드 입자 표면의 탄소-산소 및 산소-수소 결합기가 탄소-수소 결합기로 전환되는 화학적 표면개질이 진행되었고 Zeta 전위가 증가하였다. 분산도 향상에 따라 나노다이아몬드 응집체 크기가 현저하게 감소하였고 핵형성 밀도는 크게 증가하였다. 600℃, 수소분위기에서 열처리 이후 나노다이아몬드 평균 입자 크기가 3.5 ㎛에서 34.5 nm로 크게 감소하였고, seeding 된 Si 기판 표면에서 ~3.9 × 10¹¹ nuclei/㎠의 매우 높은 핵형성 밀도를 확보하였다.

• 자원리싸이클링
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• 제18권6호
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• pp.38-45
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• 2009

마그네사이트 광석의 염산용해 특성 및 불순물 제거에 대한 연구를 수행하였다. 마그네사이트의 용해율은 용해온도가 증가할수록, 광석 입도가 감소할수록 증가하였다. 최적 용해조건은 용해시간 2시간, 용해온도 $80^{\circ}C$, 광석입도 $100\;{\mu}m$ 였으며, 최적 용해조건에서 98%의 Mg를 용해할 수 있었다. Si, Al 성분들은 대부분 용해잔사에 존재하므로 용해 후 여과를 통하여 상당량 제거가 가능하였으며, 용해된 불순물들은 용액의 pH 조절을 통하여 금속 수산화물로 석출시켰다. 또한 석출된 금속 수산화물을 응집, 침강시키기 위하여 고분자 응집제를 사용하였으며, 최적 응집제 주입 조건은 비이온계 고분자 응집제 1 mg/100 ml이었다.

• 한국세라믹학회지
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• 제43권2호
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• pp.114-120
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• 2006

Nano-size Au particle doped $TiO_2$ films were prepared with $Ti(OC_3H_7^i)_4$, polyvinylpyrrolidone(PVP), $HAuCl_4$ and $C_3H_7OH$ etc. by sol-gel method. $TiO_2$ gel films were obtained by the dip-coating method on the $SiO_2$ glass substrates, and then heat-treated at $700^{\circ}C$ for 10 min. The thickness of $TiO_2$ films were $0.7\~1.8\;{\mu}m$. It was found that the thickness of films prepared from PVP containing solution was about $2\~8$ times higher values than that of thin films without PVP. The size of Au particles doped in the films were about $350\~750\;nm$. Nano-size Au particle dispersed $TiO_2$ films showed high absorption peak at visible region 450nm, which made them good candidates for non-linear optical materials and photo-catalytic materials. The contact angle of $TiO_2$ film for water was $12.5^{\circ}$, and therefore it is clear that $TiO_2$ films have very high hydrophilic properties and the self-cleaning effects.

• 한국세라믹학회지
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• 제45권5호
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• pp.303-308
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• 2008

Mullite precursors were synthesized with aluminosilicate gels from mixture of aluminum nitrate and sodium orthosilicate by the geopolymer technique at ambient temperature. Then, the gel was heat-treated in air up to $1200^{\circ}C$ at intervals of $100^{\circ}C$. Raw and heat-treated gels were characterized by TG-DTA, XRD, FTIR, $^{29}Si$ MAS-NMR, TEM. The result to examine the crystallization of behavior though DTA, the synthesized precursors were crystallized in the temperature range from $950^{\circ}C$ to $1050^{\circ}C$. The XRD results showed that the gel compositions were begun to crystallize at various temperature. Also, it was found that the precursors of M-4 begun to crystallize at about $950^{\circ}C$. The M-4 XRD peaks were characterized better than $M-1{\sim}M-3$ at $1000^{\circ}C$. The formation temperature of mullite in this study is much lower than that of previous sol-gel methods, which crystallized at up of $1200^{\circ}C$. TEM investigations revealed that the sample with 10 nm particle size was obtained via heat-treated at $1000^{\circ}C$ for M-4.