Laser cladding a surface treatment process that grants superior characteristics such as toughness, hardness, and corrosion resistance to the surface, and rebuilds cracked molds; as such, it can be a strong tool to prolong service life of mold steel. Furthermore, compared with the other similar coating processes – thermal spray, etc., laser cladding provides superior bonding strength and precision coating on a local area. In this study, surface characteristics are studied after laser cladding of low carbon steel using 18%Cr-2.5%Ni-Fe powder (Rockit404), known for its high hardness and excellent corrosion resistance. A diode laser with wavelength of 900-1070 nm is adopted as laser source under argon atmosphere; electrical power for the laser cladding process is 5, 6, and 10 kW. Fundamental surface characteristics such as crossectional microstructure and hardness profile are observed and measured, and special evaluation, such as a soldering test with molten ALDC12 alloy, is conducted to investigate the corrosion resistance characteristics. As a result of the die-soldering test by immersion of low carbon alloy steel in ALDC12 molten metal, the clad layer's soldering thickness decreases.

In this work, a simple nonenzymatic glucose sensor has been proposed based on coconut shell charcoal (CSC) modified nickel foil as working electrode in a three-electrode electrochemical cell. Charcoal was prepared by the pyrolysis of coconut shells. The most important advantages of coconut shells are cost-effectiveness and their abundance in nature. The morphology and phase of the CSC powder were characterized by scanning electron microscopy and X-ray diffraction. The electrochemical performance of the CSC powder coated Nickel foil electrode was investigated by cyclic voltammetry and chronoamperometry. The sensor shows a higher sensitivity of 2.992 mA cm−2 mM−1 in the linear range of 0.5–5.5 mM and slightly lower sensitivity of 1.1526 mA cm−2 mM−1 in the range of 7–18.5 mM glucose concentration with a detection limit of 0.2 mM. The anti-interference property of CSC powder also was investigated and found that the response of interfering species was less significant compared to glucose response. The proposed sensor offers good sensitivity, wide linear range, and a very low response to interfering biomolecules.

아연(zinc) 분말은 철의 부식을 막아주는 희생양극의 기능으로 자동차, 선박 및 철구조물의 부식을 방지하 는데 널리 사용되고 있다. 그러나 아연 분말은 높은 비중 때문에 수지나 용매 내에서 분산성이 저하되고 빠르게 침전이 일어나는 단점을 가진다. 본 연구에서는 실리카(SiOx)를 미세 아연분말의 표면에 코팅함으로써 아연분말의 물성 및 기능을 개선하고자 하였다. 아연분말의 실리카 표면코팅은 졸-겔법을 사용하였고 SEM/EDS의 표면 및 성분분석과 TEM 단면분석을 통하여 불순물이 잔존하지 않는 실리카 코팅이 성공적으로 형성됨과 그 코팅의 두께를 확인 할 수 있었다. 한편 코팅공정의 반복회수와 평균입도 변화와의 관계를 측정하여 2회까지의 반복코팅이 분산안정성을 유지하는데 효과적임을 확인하였다. 이 밖에 실리카 코팅 아연분말의 진비중(true density) 측정을 통해 코팅 공정에 의해 비중이 20% 이상 감소함을 확인하였고 제타포텐셜 측정으로 실리카 코팅에 의해 아연분말의 분산안정성이 4배까지 증가함을 확인하였다. 마지막으로 질산수용액 담지를 통해 실리카 코팅 아연분말의 내산성 향상 또한 확인하였다. 따라서 본 연구에서 제조된 실리카 코팅 아연분말은 방청 안료의 원료로 적합할 것으로 기대된다.

Cu-30 vol% SiC composites with relatively densified microstructure and a sound interface between the Cu and SiC phases were obtained by pressureless sintering of PCS-coated SiC and Cu powders. The coated SiC powders were prepared by thermal curing and pyrolysis of PCS. Thermal curing at 200 oC was performed to fabricate infusible materials prior to pyrolysis. The cured powders were heated treated up to 1600 oC for the pyrolysis process and for the formation of SiC crystals on the surface of the SiC powders. XRD analysis revealed that the main peaks corresponded to the α-SiC phase; peaks for β-SiC were newly appeared. The formation of β-SiC is explained by the transformation of thermally-cured PCS on the surface of the initial α-SiC powders. Using powder mixtures of coated SiC powder, hydrogen-reduced Cu-nitrate, and elemental Cu powders, Cu-SiC composites were fabricated by pressureless sintering at 1000 oC. Microstructural observation for the sintered composites showed that the powder mixture of PCS-coated SiC and Cu exhibited a relatively dense and homogeneous microstructure. Conversely, large pores and separated interfaces between Cu and SiC were observed in the sintered composite using uncoated SiC powders. These results suggest that Cu-SiC composites with sound microstructure can be prepared using a PCS coated SiC powder mixture.

High temperature plasma coating technology has been applied to recover damaged aluminum dies from wear by spraying pure aluminum and alumina powder. However, the coated mixed powder layer composed of aluminum and alumina often undergoes a detachment from the substrate, making the coated substrate die unable to maintain its expected life span. In this study, in order to increase the bonding strength between the substrate and the coating layer, a pure aluminum layer was applied as an intermediate bond layer. In order to prepare the specimen with variable bond coating conditions, the bond coat layers with a various gun speed from 10 cm/sec to 30 cm/sec were prepared with coating cycle variations ranging from three to nine cycles. The specimen with a bond coat layer coated with a gun speed of 20 cm/sec and three coating cycles exhibited ~13MPa of adhesion strength, while the specimen without a bond coat layer showed ~6 MPa of adhesion strength. The adhesion strength with a variation of bond coat layer thickness is discussed in terms of coating parameters.

High-coercive (Nd,Dy)-Fe-B magnets were fabricated via dysprosium coating on Nd-Fe-B powder. The sputtering coating process of Nd–Fe–B powder yielded samples with densities greater than 98%. (Nd,Dy)2Fe14B phases may have effectively penetrated into the boundaries between neighboring Nd2Fe14B grains during the sputtering coating process, thereby forming a (Nd,Dy)2Fe14B phase at the grain boundary. The maximum thickness of the Dy shell was approximately 70 nm. The maximum coercivity of the Dy sputter coated samples(sintered samples) increased from 1162.42 to 2020.70 kA/m. The microstructures of the (Nd,Dy)2Fe14B phases were effectively controlled, resulting in mproved magnetic properties. The increase in coercivity of the Nd-Fe-B sintered magnet is discussed from a micro- structural point of view.

In this research, the coating behavior of Mg and Fe desulfurization powder fabricated by low energy and conventional planetary mill equipment was investigated as a function of milling time, which produces uniform Fe coated powders due to milling energy. Since high energy ball milling results in breaking the Fe coated Mg powders into coarse particles, low energy ball milling was considered appropriate for this study, and can be implemented in desulfurization industry widely. XRD and FE-SEM analyses were carried out to investigate the microstructure and distribution of the coating material. The thickness of the Fe coating layer reaches a maximum of 14 at 20 milling hours. The BCC structures of Fe particles are deformed due to the slip system of Fe coated Mg particles.

Inkjet printing was successfully done using Cu nano powder ink after these Cu nano powders were dry-coated with 1-octanethiol for oxidation prevention. 1-octanethiol, which is Self-Assembled Multi-layers (SAMs), was coated approximately 10-nm thick on the surface of Cu nano powders. 1-Octanol, which has the same chain length as that for 1-octanethiol, was used as a solvent to make the ink for inkjet printing. As a result, the fabricated ink was dispersed for about 4 weeks, and after printing and heat treatment at for 4 hours, the resistivity for the printed pattern was measured to be .

Cu-coated CaS:Eu2+을 1000℃에서 1500℃까지 소성하여 합성하였으며, 이를 스크린 인쇄 방법(screen printing method)을 이용하여 전면 전극층(ITO PET film), 형광층(Cu-coated CaS:Eu2+), 절연층(BaTiO3), 배면 전극층(silver)순으로 적층하였다. 1000℃에서 1500℃까지 소성 온도가 올라감에 따라서 형광체의 grain 크기가 증가 하는 것을 SEM 사진을 통하여 확인하였다. 또한 광 발광(Photoluminescence) 측정에서는 1000℃에서 가장 밝은 발광을 보였으며, 온도가 증가함에 따라 점진적으로 감소하는 경향성을 보였으나, 전계 발광 (Electroluminescence)의 경우에는 1400℃에서 가장 좋은 발광 상태를 보였다. 광 발광과 전계 발광의 경향성 차이는 전계 발광 소자에서의 grain 크기 효과 때문이다. grain 크기가 작아지면 sheet 저항이 낮아지며, 이에 따라 가속되는 전자의 에너지가 증가하여 발광 효율을 높여준 것으로 판단된다.

우리는 마이카, boron nitride, bismuthoxychloride와 같은 판상 분체에 ZnO 나노입자를 코팅한 고 기능성 무기 분체를 합성하였다. 본 실험에서 우리는 수열침전법을 이용하여 합성 분체를 합성하였다. 출발물질은 ZnCl2를 사용하였고 침전제로는 hexamethylenetetramine(HMT)와 urea를 사용하였다. 본 실험의 반응변수로는 출발물질의 농도, 침전제 및 반응온도를 변화시켜 실험하였다. 합성물의 형태, 결정성 및 UV-차단능은FE-SEM, XRD, FT-IR, TGA-DTA, in vitro SPF 테스트를 활용해 분석하였다. 본 실험의 결과, 나토입자 크기를 갖는 ZnO는 동일한 최적의 합성조건하에서 다양한 판상 분체의 종류에 관계없이 균일하게 코팅되었다.

In this study, the pure iron powder was treated with aqueous phosphoric acid to produce phosphate insulating layer on the surface. After drying the powder, it was compacted in a mold with a diameter of 20mm at 800MPa. The powder compacts were then heat treated at for 1 hour. The results showed that insulated iron powder was obtained with uniform phosphate layer by chemical reaction. With increased amount of phosphate layer, the core loss and density of compacts were decreased. It was also found that the addition of ethyl alcohol during insulating reaction resulted in improved core loss value.

The Powder characteristics and sintering behavior of coated were studied. Silica coated powders were prepared by sol-gel method. The particle size of the powders were nm and the thickness of the coating layer was nm. As the content increased, the layers improved the powder dispersion. The Zeta potential of coated was getting close to that of pure silica with a more negative charge, compared with that of the uncoated . The onset temperature of shrinkage curves shifted to higher temperatures with increasing contents

Conductive pastes consist of conductive fillers( Au, Ag, Ni, Cu etc.), organic binders, solvents and additives. Meanwhile, there are some metal powders such as copper, nickel etc that are used for pastes which have serious surface corrosion problems. This problem leads to change of the color and decrease in conductivity and affect storage stability of conductive pastes. By using silane coupling agent and dispersion agent, we can ensure both the corrosion stability and long term storage stability, and enhance the high performance electrical and mechanical properties of EMI shielding silicone sealant.

The compacts of pure and phosphorus-coated iron powder with 0~0.8%C were sintered at for 40 min. in cracked ammonia gas atmosphere. The tensile and impact strengths were measured and the relationship of the results with carbon content, phosphorus, quenching and tempering was investigated. The results obtained can be summarized as follows : (1) The tensile strength of sintered compacts increased slowly with carbon content. Increase in tensile strength by heat treatment was evident especially in the low carbon specimen. The specimen with phosphorus showed higher strength compared to pure iron compacts value. (2) No inflection point of elasticplastic deformation on stress-strain curve was observed in sintered steel. The elastic modulus of sintered steel had the same tendency as tensile strength. But the elongation showed the opposite tendency. (3) The impact absorption energy of sintered steel without addition of phosphorus decreased successively with carbon content and by quenching and tempering. On the contrary, addition of phosphorus resulted in an increase of the impact absorption energy. Quenching and tempering did not affect the impact energy especially in high carbon content. (4) The main fracture source was pore in specimen and the propagation of crack occured mostly along the grain boundaries. But the intragranular fracture was also observed in high carbon, quenched and tempered specimen, and especially in the specimen with phosphorus.

Commercial pure iron powder and iron powder of coated 0.45% phosphorus were mixed with graphite powder in dry mixer to control carbon content from 0 wt% to 0.8 wt%. Mixed powder was pressed in the mould under the pressure of 510 MPa. Compacts were sintered at 118 for 40 min. in cracked ammonia gaseous atmosphere. Some of these sintered specimens were quenched in oil, and tempered in Ar gas. All of these specimens were investigated for microstructure, density and hardness in relation to coated phosphorus and carbon content. The results obtained were as follows: (1) The microstructure of the sintered speciments revealed that the amount of pearlite was increased with increasing C content but decreased by P-addition. (2) The P-addition affected the microstructure of pores in which the pore shape became round and its mean size was decreased by P-addition. (3) After tempering of sintered specimens the structure of pearlite was changed from fine structure to coarse one in P added specimen. (4) Hardness was higher in P added specimens.

The several functions of manufactured the gypsum incorporating oyster shell powder coated by submicro-silver solutionand carrried out the tests for the adsorption of formaldehyde and antibiotic actions. Several environmentally- friendlyarchitectural materials, clay and flyash were tested for the comparison of the adsorption efficiency. The mortar by solidifiedand dried was exposed in the small chamber for the 180min with 4000µg/m3 of the initial concentration of formaldehydeand observed high removal efficiency which result was not any difference in adsorption performance of other tested materials.The microbial flora analysis of oyster mortar coated by submicro-silver solution and the similarity test were performed andobserved that the densities of Aeromonas sp. Enterococcus sp., and Micrococcus sp. were decreased and the densities ofStaphylococcus sp., Escherichia sp., Bacillus sp., were taphylococcus sp, Escherichia sp., and Bacillus sp. were increased.