• Applied Chemistry for Engineering
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• v.26 no.4
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• pp.394-399
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• 2015

In this study, the Cu catalyst decorated with activated carbon fibers were prepared for improving $SO_2$ adsorption properties. Flame retardant and heat treatments of Lyocell fibers were carried out to obtain carbon fibers with high yield. The prepared carbon fibers were activated by KOH solution for the high specific surface area and controlled pore size to improve $SO_2$ adsorption properties. Copper nitrate was also used to introduce the Cu catalyst on the activated carbon fibers (ACFs), which can induce various reactions in the process; i) copper nitrate promotes the decomposition reaction of oxygen group on the carbon fiber and ii) oxygen radical is generated by the decomposition of copper oxide and nitrates to promote the activation reaction of carbon fibers. As a result, the micro and meso pores were formed and Cu catalysts evenly distributed on ACFs. By Cu-impregnation process, both the specific surface area and micropore volume of carbon fibers increased over 10% compared to those of ACFs only. Also, this resulted in an increase in $SO_2$ adsorption capacity over 149% than that of using the raw ACF. The improvement in $SO_2$ adsorption properties may be originated from the synergy effect of two properties; (i) the physical adsorption from micro, meso and specific surface area due to the transition metal catalyst effect appeared during Cu-impregnation process and ii) the chemical adsorption of $SO_2$ gas promoted by the Cu catalyst on ACFs.

• Korean Journal of Plant Taxonomy
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• v.44 no.1
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• pp.22-32
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• 2014

The petal and sepal micromorphology of five species of Glechoma (Lamiaceae) was investigated to evaluate their taxonomic significance, and a molecular phylogeny using the sequences of internal transcribed spacers (ITS) regions of nuclear ribosomal DNA was carried out to resolve their phylogenetic relationships. Stomatal complexes were mostly found in the inner and outer part of the sepal from all investigated taxa, and the size length of the guard cell was variable among the taxa. Five types of trichomes (uni-cellular non-glandular trichome, multi-cellular non-glandular trichome, short-stalked capitate glandular trichome, long-stalked capitate glandular trichome, and peltate glandular trichome) were variable among the taxa as well as their distribution and density. In molecular phylogenetic studies, the genus Glechoma was composed of three geographically distinct major monophyletic groups (Europe-U.S.A., China-Korea, Japan). G. longituba in Korea and China formed well-supported monophyletic group. G. hederacea in Europe and U.S.A. formed a monophyletic and well-supported clade with G. sardoa, which are endemic species in Italy, with G. hirsuta falling as a sister to this clade. However, G. grandis did not form any phylogenetic relationships with the remaining taxa. The ITS analyses provided taxonomic boundaries of taxa in Glechoma although the petal and sepal micromorphological characters provided weak evidences of the systematic value. As further studies, incorporating more DNA regions to the matrix including other additional morphological analysis will be significant to provide clearer taxonomic structure in Glechoma.

• Proceedings of the KWS Conference
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• 2009.11a
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• pp.72-72
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• 2009

전자부품의 내부접속 및 파워반도체의 다이본딩과 같은 1차실장에는 고온환경에서의 사용과 2차실장에서의 재용융방지를 위해 높은 액상선온도 및 고상선온도를 필요로 하여, Pb-5wt%Sn, Pb-2.5wt%Ag로 대표되는 납성분 85%이상의 고온솔더가 널리 사용되고 있다. 생태계와 인체에 대한 납의 유해성이 보고된 이래, 무연솔더에 대한 연구가 활발히 진행되어 왔으나, Sn-Ag-Cu계로 대표되는 Sn계 합금으로 대체 중인 중온용 솔더와는 달리, 고온용 솔더에 대해서는 대체합금에 대한 연구가 미흡한 실정이다. 대체재의 부재로 인해 기존의 납을 다량함유한 솔더로 1차실장이 지속됨으로서, 2차실장의 무연화에도 불구하고 전자부품 및 기기의 재활용에 큰 어려움을 겪고 있다. 지금까지 고온용 무연솔더로서는 융점에 근거해 Au-(Sn, Ge, Si)계, Bi-Ag계, Zn-(Al, Sn)계의 극히 제한된 합금계만이 보고되어 왔다. Au계 솔더는 현재 플럭스를 사용하지 않는 광학, 디스플레이 분야 등 고부가가치 공정에 사용되고 있으나, 합금가격이 매우 비싸며 가공성이 나빠 대체재료로서는 적합하지 않다. Bi-Ag계 솔더 또한 취성합금으로 와이어 및 박판으로 가공하는데 어려움이 크며, 솔더로서 중요한 특성중 하나인 전기전도도 및 열전도도가 나쁜 편이다. 이에 비해, Zn계 합금은 비교적 낮은 합금가격, 적절한 가공성과 뛰어난 인장강도, 우수한 전기전도도 및 열전도도를 지녀, 고온용솔더 대체재료의 유력한 후보로 생각된다.이전 연구에서, 필자의 연구그룹은 Zn-Sn계 합금을 고온용 무연솔더로서 제안한 바 있다. Zn-Sn계 합금은 충분히 높은 융점과 함께, 금속간화합물이 없는 미세조직, 우수한 기계적 특성, 높은 전기전도도 및 열전도도 등의 장점을 나타내었다. 본 연구에서는 기초합금특성상 고온솔더로서 다양한 장점을 지닌 Zn-30wt%Sn합금을 고온용 솔더의 대표적인 적용의 하나인 다이본딩에 적용하여, 접합부의 강도 및 미세조직, 열피로 신뢰성에 대해 분석을 함으로서 실제 공정에의 적용가능성에 대해 검토하였다. Zn-30wt%Sn을 이용해 Au/TiN(Titanium nitride) 코팅한 Si다이를 AlN-DBC(aluminum nitride-direct bonded copper)기판에 접합한 결과, 양측에 완전히 젖은 기공이 없는 양호한 다이접합부를 얻었으며, 솔더내부에는 금속간화합물을 형성하지 않았다. Si다이와의 계면에는 TiN만이 존재하였으며, Cu와의 계면에는 Cu로부터 $Cu_5Zn_8,\;CuZn_5$의 반응층을 형성하였다. 온도사이클시험을 통한 열피로특성평가에서, Zn-30wt%Sn를 이용한 다이접합부는 1500사이클 지점에서 Cu와 Cu-Zn금속간화합물의 사이에서 피로균열이 형성되며, 접합강도가 크게 감소하였다. 열피로특성 향상을 위해 Cu표면에 TiN코팅을 하여 Zn-30wt%Sn 솔더로 다이접합한 결과, Si다이와 기판 양측에 TiN만으로 구성된 계면을 형성하였으며, TEM관찰을 통해 Zn-30wt%Sn과 극히 미세한 접합계면이 형성하고 있음을 확인하였다. Zn-wt%30Sn솔더와 TiN층의 병용으로 2000사이클까지 미세조직의 변화 및 강도저하가 없는 극히 안정된 고신뢰성의 다이접합부를 얻을 수가 있었다.

• Journal of the Korean Electrochemical Society
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• v.7 no.2
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• pp.100-107
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• 2004

The nano or micro sized structures of conducting polymer had been prepared by synthesizing the desired polymer within the pores of template of nano or micro porous membrane filter. In this study, we had tried to fabricate conducting polymer microstructures on an electrode by using electrochemical deposition adopting template synthesis. Our attention was focused on two different things, attaching template on the electrode and fabricating microstructures only at limited areas of the electrode. A conducting polymer, PEDiTT (poly 3,4-ethylenedithi-athiophene) solution was blended with PVA(polyvinyl alcohol) solution and used as an conducting adhesive. After attaching template membrane, the electrode were immersed in 0.5M pyrrole in 0.1M KCI solution, and electrochemical polymerization was performed. The growth process of the microstructures studied by SEM. The electrochemical fabrication of conducting polymer was performed by using two-electrode system. A large working electrode and a micro scale disc electrode were used for the confined area synthesis. Polymerization potential was 4V in an electrolytic solution made of KCI in deionized water. The optimum polymerization conditions were, i.e. (4V/100sec) for $250{\mu}m$ electrode and (6V/30 sec) for $10{\mu}m$ electrode.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.6
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• pp.243-249
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• 2018

Ceramic tiles, which were manufactured through high-temperature firing process at over $1000^{\circ}C$, are widely used as interior and exterior materials for building construction due to their excellent durability and aesthetic of surface glaze. In recent years, the introduction of digital ink-jet printing in ceramic tiles for architectural use has been rapidly proceeding, and studies on the materials such as ceramic ink, ceramic pigment, glaze have been actively conducted. In this study, the effect of microstructure change of surface glaze on the printing properties of ceramic inks was investigated by micronization of kaolin, which is the raw material of surface glaze. Black ceramic ink was used for ink-jet printing on the surface glaze of ceramic tile to evaluate the printability by measuring the size and roundness of the printed ink dot. The relationship between microstructure change of surface glaze and printability of ceramic ink was also investigated by analyzing the surface roughness and internal micropore distribution of surface glaze.

• Polymer(Korea)
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• v.36 no.6
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• pp.756-760
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• 2012

In this work, the coal tar pitch-based activated carbons (ACs) were prepared by KOH activation for electrode materials of supercapacitor. The effects of activation temperature on electrochemical performance of the ACs were investigated with cyclic voltammogram (CV) measurement. The textural and morphological properties of the ACs were measured by adsorption isotherms and field emission scanning electron microscope (FE-SEM) analyses, respectively. The experimental results indicated that the specific capacitance of the ACs increased with developing the micropore volume by activation temperature. As a result the specific capacitance of the ACs increased, owing to the development of micro pore volume of the ACs.

• Journal of Korean Society of Environmental Engineers
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• v.30 no.2
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• pp.225-233
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• 2008

Accoring to the worldwide interest to control CO$_2$ which contributes to global warming 50%, new techniques to reduce CO$_2$ are under development. Therefore, this study investigated that CO$_2$ absorption/regeneration of Sodium-based dry sorbent and the effect of SO$_2$ concentration in the fixed bed reactor. The dry sorbents were prepared in the condition of different PVA contents and calcination temperatures. As the results of this study, BET surface area showed 832.79 m$^2$/g and SEM result showed possibility as dry sorbent due to having of much micropore distribution. Also, the fixed bed reactor showed decreased CO$_2$ absorption capacity with SO$_2$ injection, because of the generation of $Na_2SO_3$ and $Na_2SO_4$.

• Journal of the Korean Society for Nondestructive Testing
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• v.21 no.6
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• pp.591-597
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• 2001

Ti alloy is used for essential parts of aircraft for high temperature environment. Although Ti alloy has excellent performance in regard to mechanical properties, it is difficult ot find fatigue cracks by nondestructive ultrasonic inspection due to its two-phase microstructure, which consists of hard alpha and beta phases. Sound energy reflected from microstructural features in the component produces a background inspection noise which is seen even when no defects are present. This noise can inhibit the detection of critical internal defects such as pores cracks or inclusions. To obtain fundamental data on ultrasonic inspection of Ti alloy, ultrasonic testing was performed using a specimen with small drill holes and ultrasonic wave propagation velocites were measured.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.28 no.1
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• pp.14-20
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• 2018

Lead zinc niobate (PZN) added lead zirconate titanate (PZT) thick films with thickness of $5{\sim}10{\mu}m$ were fabricated on silicon and sapphire substrates using aerosol deposition method. The contents of PZN were varied from 0 %, 20 % and 40 %. The initial particles (PZT, 2PZN-8PZT, 4PZN-6PZT) had irregular shape and submicron sizes. The as-deposited film had fairly dense microstructure without any crack, and showed only a perovskite single phase formed with nano-sized grains. The as-deposited films on silicon were annealed at the temperatures of $700^{\circ}C$, and the films deposited on sapphire were annealed at $900^{\circ}C$ in the electrical furnace. The effects of PZN addition on the microstructural evolution were observed using by FE-SEM and HR-TEM.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.12 no.6
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• pp.292-298
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• 2002

Densified cordierite matrixes added alumina platelets were studied as a ceramic substrate material having a low thermal expansion coefficient, low dielectric constant and proper strength. Amorphous-type cordierite powders were filled with four kinds of alumina platelet powders in various compositions. All samples were sintered at $1300^{\circ}C$ for 2 h in an air atmosphere. Improved flexural strength of about 80 MPa, low dielectric constant of 5.0 at 1 MHz and low thermal expansion coefficient of $3.5 \times 10^{-6}/^{\circ}C$ were obtained by the control of the microstructure. Isolated micropores were formed in the matrix and the porosity was dependent on the platelet content and size. In the 10 vol% of alumina platelet content, the isolated micropores were 3~8 $\mu \textrm{m}$ in size, and an increase in dielectric constant by adding alumina platelet filler was inhibited by the micropores.