• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 추계학술대회 논문집
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• pp.217-220
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• 2009

This paper presents fabrication method of nano-structured PMMA substrates as well as evaluations of their optical transmittance. For anti-reflective surface, surface coating method had been conventionally used. However, it requires high cost, complicated process and post-processing times. In this study, we suggested the fabrication method of anti-reflective surface by the hot embossing process. Using the nano patterned master fabricated by anodic aluminum oxidation process. Anodic aluminum oxide(AAO) is widely used as templates or a molds for various applications such as carbon nano tube (CNT), nano rod and nano dots. Anodic aluminum oxidation process provides highly ordered regular nano-structures on the large area, while conventional pattering methods such as E-beam and FIB can fabricate arbitrary nano-structures on small area. We fabricated a porous alumina hole array with various inter-pore distance and pore diameter. In order to replicate nano-structures using alumina nano hole array patterns, we have carried out hot-embossing process with PMMA substrates. Finally the nano-structured PMMA substrates were fabricated and their optical transmittances were measured in order to evaluate the charateristivs of anti-reflection. Anti-reflective structure can be applied to various displays and automobile components.

• 대한치과보철학회지
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• 제45권2호
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• pp.159-168
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• 2007

Statement of problem: Literature showed different results on the durability of bonded ceramic restoration. Purpose: The purpose of this article is to review the effect of surface treatment of ceramics in resin-ceramic bond to get predictable results. Material and method: PubMed data base was utilized to search the articles which were written in English and published in 1986 and 2006. Some electronic published articles which are forthcoming to publish in paper were also included for this review. This review article focused on the effect of acid etching and silane application on the silica based ceramics. The durability of resin-ceramic bonding, the methodology for bond strength test and resin bonding to alumina or zirconia based ceramics were compared in brief at the end of the review. Results and Conclusion: the effect of silane application can be influenced by the contaminations of saliva or solutions. Micromechanical retention by acid etching as well as silane application plays an important role in initial and durable bond strength between resin and ceramic. The use of phosphate modified resin cement following tribochemical silica coating and silane application produced best bond strength for alumina or zirconia based ceramics.

• 한국세라믹학회지
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• 제47권4호
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• pp.283-289
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• 2010

Physical properties of Plasma electrolytic oxidized 8 different kinds of Al alloys, A-1100, A-2024, A-5052, A-6061, A-6063, A-7075, ACD-7B and ACD-12 were investigated. The electrolyte for PEO was $Na_2SiO_3$ and NaOH and some alkali earthen metal salts system solution. $\eta$-alumina, as well as $\gamma$-alumina, was main crystal phase, which were ever reported. Also, $Al_{4.95}Si_{1.05}O_{9.52}$ was found only in this research. So we can conclude that the process conditions of PEO apparatus and composition and concentration of its electrolyte affects crystal structure and physical properties of PEO layers much more than the compositions of Al alloy.

• 한국세라믹학회지
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• 제43권9호
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• pp.564-568
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• 2006

AlO(OH) nano gel is used in precursor of ceramic material, coating material and catalyst. For use of these, not only physiochemical control for particle morphology, pore characteristic and peptization but also studies of synthetic method for preparation of advanced application products were required. In this study, AlO(OH) nano gel was prepared through the aging and drying process of aluminum hydroxides gel precipitated by the hydrolysis reaction of dilute NaOH solution and aluminum sulfate solution. In this process, optimum synthetic condition of AlO(OH) nano gel having excellent pore volume as studying the effect of water and aluminum sulfate mole ratio on gel precipitates has been studied. Water and aluminum sulfate mole ratio brought about numerous changes on crystal morphology, surface area, pore volume and pore size. Physiochemical properties were investigated as using XRD, TEM, TG/DTA, FT-IR, and $N_2$ BET method.

• 한국산업융합학회 논문집
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• 제25권6_2호
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• pp.1037-1045
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• 2022

In this study, nanoscale Al₂O3 ceramic particles were used due its exceptionally high hardness characteristics, chemical stability, and wear resistance properties. These nanoparticles will be used to investigate the optimal process conditions for the electro co-deposition of the Ni-Al₂O₃ composite coatings. A Watts bath electrolytic solution of a controlled composition along with a fixed agitation speed was used for this study. Whereas the current density, the pH value, temperature and concentration of the nano Al₂O₃ particles of the electrolyte were designated as the manipulative variables. The experimental design method was based on the orthogonal array to find the optimum processing parameters for the electro co-deposition of Ni-Al₂O₃ composite coatings. The result of confirmation experimental based on the optimal processing condition through the analysis of variance ; EDX analysis found that the ratio of alumina increased to 8.65 wt.% and subsequently the overall hardness increased to 983 Hv. Specially, alumina were evenly distributed on Nickel matrix and particles were embedded more firmly and finely in Nickel matrix.

• 한국재료학회지
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• 제10권9호
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• pp.619-623
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• 2000

알루미나 여과막은 boehmite 분말 (${\Upsilon}-AlOOH$)을 이용하여 졸-겔법으로 준비되어졌다. 제조된 여과막은 상전이 온도와 미세구조 변화를 관찰하기 위해 지지체 없이 형성된 여과막을 제조하였다. 여과 공정의 응용에서 균일한 기공크기와 분포를 제어하는 것이 중용하다. 다공성 담체 위에 형성된 여과막과 다공성 담체 없이 형성된 여과막의 ${\theta}-to\;{\alpha}-AL_2O_3$로의 상전이는 박막 XRD를 이용하여 분석하였고, 미세구조의 변화의 관찰은 주사전자현미경(SEM)을 사용하여 관찰하였다. XRD에서 분석된 결과는 다공성 담체 위에 형성된 여과막이 다공성 담체 없이 형성된 여과막과 비교하여 $100^{\circ}C$ 더 높은 상전이 온도를 가지는 것을 보여주었다. 이런 유사한 효과는 여과막의 미세구조 변화에서도 관찰되었다.

• 폴리머
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• 제36권3호
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• pp.268-274
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• 2012

실란 커플링제를 사용하여 알루미나 나노 입자의 표면을 처리하였다. 표면을 개질한 나노 입자를 in-mold decoration(IMD) 포일의 경질 코팅 층에 도입하여 표면 경도 및 내마모성을 중심으로 도막의 물성 변화를 평가하였다. 전자빔(electron beam, EB) 조사가 IMD 포일을 구성하는 color layer 및 anchor layer에 미치는 영향을 색도변화와 cross-cut tape 시험을 통하여 평가하였다. 또한 EB 조사 온도에 따른 경화 거동을 표면 물성 변화 평가 및 Fourier transform infrared(FTIR) spectroscopy 관찰을 통해 정량적으로 분석함으로써 EB 경화 공정의 실용화에 필요한 데이터베이스를 구축하였다.

• 한국세라믹학회지
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• 제42권8호
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• pp.554-560
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• 2005

The engineering ceramic needs the properties of high strength, hardness, corrosion-resistance and heat-resistance in order to withstand thermal shock or applied nonuniform stresses without failure. The densely coated porous ceramics can be used for machine component, electromagnetic component, bio-system component and energy-system component by their high-performances from superior coating properties and light-weight characteristics due to the structure including pore by itself. In this study we controlled the porosity of silica and alumina, $8.2\~25.4\%$ and $23.4\~36.0\%$, respectively, by the control of sintering temperature and starting powder size. We made bilayer structures, consisting of a transparent glass coating layer bonded to a thick substrate of different porous ceramics by a thin layer of epoxy adhesive, facilitated observations of crack initiation and propagation. The elastic modulus mismatch could be controlled using different porous ceramics as the substrate layer. Then we applied 150 N force using WC sphere with a radius of 3.18 mm by Hertzian indentation. As a result, the crack initiation in the coating layer was delayed at lower porosity in the substrate layer, and the damage in the coating layer was relatively smaller at the bilayer structure coated on higher elastic substrate.

• 한국전기전자재료학회논문지
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• 제19권7호
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• pp.667-672
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• 2006

Ferroelectric $Pb(Zr_{0.52}Ti_{0.48})O_3$ (PZT(52/48)) thick films were fabricated by the screen-Printing method on the alumina substrates, and $PbTiO_3$ (PT) Precursor solution, which prepared by sol-gel method, was spin-coated on the PZT(52/48) thick films to obtain a densification. Its structural and electrical properties of the PZT(52/48) thick films with the treatment of PT precursor solution coating were investigated. The particle size of the thick films was increased with increasing the number of coatings and the thickness of the PZT-6 (6: number of coatings) films was about $60{\mu}m$. The relative dielectric constant increased and the dielectric loss decreased with increasing the number of PT sol coatings. The relative dielectric constant and dielectric loss of the PZT-6 thick film were 475 and 2 %, respectively. The remanent polarization, coercive field and breakdown strength of the PZT-6 film were $32.6{\mu}C/cm^2$, 15 kV/cm and 60 kV/cm, respectively.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 Techno-Fair 및 합동춘계학술대회 논문집 전기물성,응용부문
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• pp.169-170
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• 2008

The heterolayered PZT/PT thick films were fabricated by two different methods - thick films of the PZT by screen printing method on alumina substrates electrodes with Pt, thin films of $PbTiO_3$ by the spin coating method on the PZT thick films and once more thick films of the PZT by the screen printing method on the $BaTiO_3$ layer The structural and the dielectric properties were investigated for effect of various stacking sequence of sol-gel prepared $PbTiO_3$ coating solution at interface of the PZT thick films. The insertion of $PbTiO_3$ interlayer yielded the PZT thick films with homogeneous and dense grain structure with the number of $PbTiO_3$ layers. The leakage current density of the PZT/$PbTiO_3-1$ film is less that $4.41{\times}10^{-9}\;A/cm^2$ at 5 V.