• 한국세라믹학회지
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• 제36권11호
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• pp.1252-1260
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• 1999

The defect chemistry and electrical characteristics of the grain boundaries of semiconducting SrTiO3 ceramics synthesized with wet-chemically surface-coated powders were investigated. The starting powders were separated into groups of 1-10${\mu}{\textrm}{m}$ 10-20${\mu}{\textrm}{m}$ etc by sedimentation and sieving methods. Na+ ions were absorbed on the powder surfaces by wet chemical-treatment method. The width of the grain boundary ranged up to several nm and the intergranular materials was amorphous. The additives coated on the surface of the powders were observed to be present at the grain boundaries of the ceramics. The diffusion depth of the additives into grains was about 30nm for the SrTiO3 ceramics synthesized with 5w/o coated materials, The threshold voltage grain boundary resistance and boundary potential barrier of the ceramics increased from 0.67V/cm 2.27k$\Omega$ and 0.05eV to 80.9V/cm 13.0k$\Omega$ 1.44eV with increasing the amount of the additives from 0 to 5 w/o respectively .

• 한국입자에어로졸학회지
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• 제10권4호
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• pp.177-182
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• 2014

In this study, nickel-coated aluminum (Ni/Al) powders were synthesized for the utilization of energetic applications. Oxide materials present at the surface of Al powders of $45{\mu}m$ in averaged size were removed by using sodium hydroxide(NaOH) solution which is used for controlling pH. Nickel material is coated into the surface of oxide-removed Al powders by electroless-plating process. The microstructure of fabricated Ni/Al powders shows that nickel layers with a few hundreds nm were very homogeneously formed onto the surface of Al powders. The oxidation behavior of Ni/Al exihibit somewhat faster oxidation rate than that of pure Al with surface oxidation. Also, the higher exothermic reaction was observed from the Ni/Al powders. From the result of this, nickel coating is very promising method to obtain highly reactive and safe Al powders for energetic applications.

• 대한화장품학회지
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• 제40권2호
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• pp.121-131
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• 2014

산화아연은 뛰어난 자외선 산란효과로 인해 자외선 차단 화장품에 널리 이용되고 있다. 최근 화장품용으로 쓰이는 산화아연은 자외선 차단 특성, 사용감, 광촉매 활성 저하, 분산성 및 안정성 등을 보다 우수하게 하기 위해 이산화규소 등의 물질로 표면처리 하는 방법이 시행되어지고 있다. 본 연구에서는 광 노화의 원인인 자외선을 차단하는 이산화규소가 코팅된 산화아연 복합 분체를 개발하였다. 화장품 업계에서 일반적으로 쓰이는 마이크로 크기의 산화아연에 사용감, 자외선 차단 특성을 보다 우수하게 하기 위해 산업적인 용도로 많이 쓰이는 규산나트륨을 사용하여 코팅하였다. 이산화규소를 코팅하기 위해 규산나트륨과 산의 가수분해 반응에 의한 수열합성법을 적용하였다. 제조된 복합 분체의 자외선 차단 효과는 UV-Vis과 in-vitro 측정을 통하여 평가하였다. 또한 화장품에 실제 적용 하였을 때의 실질적인 장점을 확인하기 위해 사용자 관능 평가를 통해 비교분석 하였다.

• 한국재료학회지
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• 제25권5호
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• pp.226-232
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• 2015

본 연구에서는 손상된 알루미늄 금형의 복원을 위해 고온플라즈마 용사법을 이용하여 금형의 표면에 $Al/Al_2O_3$ 혼합분말을 용사한 후 코팅층과 모재의 증착강도에 대한 평가를 수행하였다. 증착강도의 평가는 분사노즐의 이동속도, 순수한 알루미늄 bond coat 층의 유무에 따라 평가되었으며, bond coat 층을 생성시키지 않았을 때, 코팅층의 두께는 열팽창에 의한 잔류인장응력의 감소를 위해 두껍지 않아야 하지만 일정두께 이상이 되어야 최대의 증착강도를 얻을 수 있음이 나타났다. 또한 순수한 알루미늄 bond coat 층은 내부 결함이 없는 응고된 금속이기 때문에 두께에 따른 증착강도의 영향을 그대로 받아 두께가 두꺼울수록 bond coat 층을 생성시키지 않은 시험편보다 증착강도가 매우 낮게 측정되었다. 반면, 가장 얇게 bond coating 된 시험편 Bc3(3회의 bond coating층과 분사건의 이동속도가 20 cm/sec인 시험편) 는 bond coating을 하지 않은 시험편 중 가장 높은 증착강도를 가지는 시험편 Wbc20(bond coating층이 없고 분사건의 이동속도가 20 cm/sec인 시험편)보다 약 2배 이상증착강도가 향상되었다. 따라서 금형의 복원시에 중간층의 형성이 반드시 필요하며, 이는 코팅층의 잔류 인장응력을 보완시키며 고인성의 순수한 알루미늄과 같은 코팅층과 유사한 층을 코팅하는 것이 필요한 것으로 사료된다.

• Bulletin of the Korean Chemical Society
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• 제31권2호
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• pp.355-359
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• 2010

A $Li[Co_{1/3}Ni_{1/3}Mn_{1/3}]O_2$ cathode was modified by applying a $ZrF_x$ coating. The surface-modified cathodes were characterized by XRD, SEM, EDS, TEM techniques. XRD patterns of $ZrF_x$-coated $Li[Co_{1/3}Ni_{1/3}Mn_{1/3}]O_2$ revealed that the coating did not affect the crystal structure of the parent powder. SEM and TEM images showed that $ZrF_x$ nano-particles were formed as a coating layer, and EDS data confirmed that $ZrF_x$ distributed uniformly on the surface the powder. Capacity retention of coated samples at high C rates was superior to that of pristine sample. However, as the coating concentration increases beyond the optimum concentration, the rate capability was deteriorated. Whereas, as the increase of coating concentration to 2.0 wt %, the cyclic performances of the electrodes under the severe conditions (high cut-off voltage, 4.8 V, and high measurement temperature, $55^{\circ}C$) were improved considerably.

• 한국환경보건학회지
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• 제30권5호
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• pp.358-365
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• 2004

The photocatalytic oxidation of Rhodamine B(RhB) was studied using photocatalytic reactor filled with module of quartz tube. Module of quartz tube consisted of small quartz tube (inner diameter, 1.5 mm; outer diameter, 3 mm) bundle coated with powder $TiO_2$ and uncoated large quartz tube (inner diameter, 20 mm; outer diameter, 22 mm). Two 30 W germicidal lamp was used as the light source and the reactor volume was 0.5 l. The effects of parameters such as the coating materials and numbers, initial concentration, $H_{2}O_2$ dose and metal deposition (Ag, Pt and Fe) and simultaneous application of $H_{2}O_2$ and metal deposition. The results showed that the initial reaction constant of quartz module coated with powder $TiO_2$ was higher 1.4 time than that of the $TiO_2$ sol and optimum coating number is twice. In order to increase reaction rate, simultaneous application of photocatalytic and photo-fenton reaction using Fe coating and dose $H_{2}O_2$ dose increased reaction rate largely.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2010년도 춘계학술발표대회 초록집
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• pp.32-38
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• 2010

Hybrid material(ceramic+metal) processes were developed for micro filter using ceramics coating at metal filter surface by thermal spray method, micro hole drilling at ceramic coated filter surface by femtosecond laser, and fiber laser direct welding of ceramic and metal (SUS304, SM45C) by capillary effect. Thermal spray process was used for ceramic powders and metal filters. The used ceramic powders were $Al_2O_3+40TiO_2$(Metco 131VF) powder of maximum particle size $5{\mu}m$ and ${Al_2O_3}99+$(Metco 54NS) power of maximum particle size 45m. Ceramic coated filters using thermal spray method had a great influence on powder material, particle size and coating thickness but had a fine performance as a micro filter. CW fiber laser was used to drill the top ceramic layer and melt the bottom metal layer for joining applications.

• Composites Research
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• 제26권6호
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• pp.373-379
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• 2013

냉매의 비등이나 응축같은 열전달 향상을 위하여 금속 표면위에 탄소나노튜브(CNT)를 코팅하는 것을 연구하였다. 다중벽 탄소나노튜브/구리 복합소재는 어트리션 볼밀에 의해서 제작되었으며, 정전 도장 장치로 복합 분말을 구리 기판위에 코팅한 후 전기로에서 소결하였다. 본 논문에서는 CNT/Cu 코팅 표면의 분석 및 소결전후의 탄소나노튜브의 변화를 파악하기 위하여 샘플들을 주사전자현미경, EDAX, 라만분광법에 의해 분석하였다. 아울러 열전달 촉진은 비등열전달로 확인하였다.

• 한국전기전자재료학회논문지
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• 제19권11호
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• pp.1014-1019
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• 2006

The influence of the number of solution coatings on the densification of the PZT thick films was studied. PZT powder and PZT precursor solution was prepared by a sol-gel method and PZT thick films were fabricated by the screen-printing method on the alumina substrates. The powder and solution of composition were (A) PZT(80/20)/PZT(20/80), (B) PZT(70/30)/PZT(30/70) and (C) PZT(60/40)/PZT(40/60), (D) PZT(52/48)/PT. The coating and drying procedure was repeated 4 times. And then the PZT precursor solution was spin-coated on the PZT thick films. A concentration of a coating solution was 0.5 moth and the number of coating was repeated from 0 to 6. The porosity of the thick films was decreased with increasing the number of coatings and the PZT thick films with 6-times coated showed the dense microstructure and thickness of about $60{\mu}m$. A grain size was increased with increasing the coating number. All PZT thick films showed the typical XRD patterns of a typical perovskite polycrystalline structure. The relative dielectric constant of PZT thick films was improved 30-100% as the number of coatings.

• 대한금속재료학회지
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• 제50권1호
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• pp.28-33
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• 2012

Ball-milled Ni-Al powder compacts have been synthesized by the heat of molten cast iron and have been coated on cast iron. The effects of the ball-milling time on the microstructure of the intermetallic coatings have been investigated. The experimental results showed that the ball-milled Ni-Al powder compacts were completely reacted and were successfully coated on the cast iron without re-melting the substrate. Densification of the coating layers was enhanced by increasing the ball-milling time. This might be attributed to the fact that the heat released during the intermetallic reaction was dispersed over a prolonged reaction time by the ball-milling of the elemental powders.