Indium Tin Oxide (ITO) Coatings Fabricated Using Mixed ITO Sols

Cheong, Deock-Soo,Yun, Dong-Hun,Park, Sang-Hwan,Kim, Chang-Sam The Korean Ceramic Society 2009 한국세라믹학회지 Vol.46 No.6

ITO films were achieved by sintering at $500{\sim}550{^{\circ}C}$. This was possible by inducing a seeding effect on an ITO sol by producing crystalline ITO nanoparticles in situ during heat treatment. Two kinds of ITO sols (named ITO-A and ITO-B) were prepared at 2.0 wt% from indium acetate and tin(IV) chloride in different mixed solvents. The ITO-A sol showed a high degree of crystallinity of ITO without any detectable Sn$O_2$ on XRD at $350{^{\circ}C}$/1 h, but the ITO-B sol showed a small amount of Sn$O_2$ even after annealing at $600{^{\circ}C}$/1 h. The 10 wt% ITO-A//ITO-B showed the sheet resistance of 3600$\Omega$/□, while the ITO-B sol alone showed 5200 $\Omega$/□ by sintering at $550{^{\circ}C}$ for 30 min. Processing parameters were studied by TG/DSC, XRD, SEM, sheet resistance, and visible transmittance.

Synthesis of a Cr2AlC-Ti2AlC ternary carbide

Deock-Soo Cheong,김창삼,Sung Ik Hwang,하정수,강승민 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.1

The Cr2AlC ternary carbide is excellent in chemical and oxidation resistances as well as mechanical properties at high temperatures. Therefore it satisfies most requirements for as an interconnector material in solid oxide fuel cells (SOFCs). However, its thermal expansion coefficient is higher than those of the anode and cathode so that a high thermal stress is generated unavoidably between them during heating and cooling SOFCs. Thus we attempted to reduce the thermal expansion coefficient through a solid solution with Ti2AlC which has a lower thermal expansion coefficient. Dense and single phase (Cr1-xTix)2AlC solid solutions with a relative density of 99.5% or more were synthesized by hot pressing a mixture of CrCx,Ti2C, Al powders at 1250 oC for 4 h. The limitation of Ti substitution was found to be less than 20 mol%. When Ti substitution exceeded this limit, unreacted Ti2C, Cr7C3, and Cr3C2 remained as second phases. The grain size decreased with Ti substitution. With 5 mol% Ti substitution, the thermal expansion coefficient could be lowered by 5% compared with the case without substitution in the temperature range of 700-800 oC.

Effect of Strain Rate on Plastic Deformation Behavior of Y-CSZ Single Crystal

Cheong, Deock-Soo,Kim, Chang-Sam Materials Research Society of Korea 2010 한국재료학회지 Vol.20 No.1

Yttria stabilized zirconia (Y-CSZ) single crystals show plastic deformation at high temperatures by activating dislocations. The effect of strain rate on the plastic behavior of this crystal was studied. As increasing strain rate from $\varepsilon=1.04\times10^{-5} sec^{-1}$ to $2.08\times10^{-5} sec^{-1}$ the yield drop was suppressed and resulted in higher Young's modulus and yield stress. Dislocation structures of the strained crystals were analyzed using a transmission electron microscope to elucidate the plastic behavior of these crystals. In the early stage of plastic deformation, dislocation dipoles and prismatic dislocation loops were formed in both samples. However, dislocation density was increased by increasing strain rate. Strong sessile dislocations were observed in the sample with higher strain rate, which may cause the higher work hardening.

Effect of Orientation on Plastic Deformation Behavior of Yttria Stabilized Zirconia Single Crystal

Cheong, Deock-Soo,Lee, Jeon-Kook Materials Research Society of Korea 2009 한국재료학회지 Vol.19 No.12

Yttria stabilized zirconia single crystals show plastic deformation at high temperatures by activating dislocations. The plastic deformation is highly dependent on crystallographic orientation. When the samples were deformed at different orientations, stress-strain curves changed by operating different slip systems. The strength of samples was also highly dependent on crystallographic orientation, i.e., samples without yield drop showed higher strength than that of samples exhibiting yield drop. The slip systems in the sample deformed along <112>, <111> and <001> agreed with the theoretical values of the plastic deformation, following Schmid's Law. Dislocations play a major role in the plastic deformation of this crystal. At the early stages of plastic deformation, all samples exhibited dislocation dipoles and, in the later stages, dislocation interactions occurred by forming nodes, tangles and networks. In this study, three different orientations, [11-2], [111] and [001] were employed to explain the plastic deformation behavior. A microstructural analysis was performed to elucidate the mechanism of the plastic behavior of this crystal.

Indium Tin Oxide (ITO) Coatings Fabricated using Nanoparticle Slurry and Sol

Cheong, Deock-Soo,Yun, Dong-Hun,Kim, Dong-Hwan,Han, Kyoung-R. The Korean Ceramic Society 2011 한국세라믹학회지 Vol.48 No.6

Indium tin oxide (ITO) coatings were made using an ITO slurry and an ITO sol. This was achieved by dispersing nanosized ITO powder in a mixed solvent without any dispersant and developing an adhesive ITO sol from indium acetate and tin tetrachloride in a mixture of DMF and n-butanol. Coating was carried out in one step by spin coating an ITO slurry, which was then followed by an ITO sol over it. Here, the sol penetrates into the nano ITO particle layers to make them adhere to each other as well as to a glass substrate. This is then followed by sintering at 500$^{\circ}C$ for 1 h to produce a uniform film consisting of ITO particles of about 50 nm and 10 nm. ITO films were obtained with sheet resistances from 450 to 1500 ohm/${\Box}$ by varying spin speed and concentration. Transmittance is higher than 90% at 550 nm.

Self diffusion of cation in yttria stabilized zirconia single crystal

Cheong, Deock-Soo The Korea Association of Crystal Growth 2009 韓國結晶成長學會誌 Vol.19 No.5

Dislocation dipoles were formed in the early stage of deformation of Y-CSZ single crystal at high temperatures. And the dipoles were pinched off to break into dipoles loops by dislocation climb. Dislocation loop annealing was peformed in Y-CSZ single crystal to evaluate the diffusivity of cation which was the rate-controlling ion.

A Simple Way to Prepare Nanosize NiO Powder by Mixing Acidic Ni Compound with Basic Ni Compound

Cheong, Deock-Soo,Yun, Dong-Hun,Park, Sang-Hwan,Kim, Chang-Sam The Korean Ceramic Society 2009 한국세라믹학회지 Vol.46 No.6

Nanosize NiO powder was prepared by mixing acidic nickel nitrate with basic nickel carbonate. The particle size and morphology of NiO were mainly governed by the mole ratio of the nitrate to the carbonate. The effects were studied by DSC, XRD, FTIR, and SEM. Heat treatment conditions influence the particle size distribution of produced NiO powder extensively for the case of 3N7C (3 moles of the nitrate and 7 moles of the carbonate) and 4N6C, but only slightly for 1N9C and 2N8C. Uniform pseudospherical NiO particles were obtained in $50{\sim}70$ nm for 1N9C and $30{\sim}60$ nm for 2N8C by calcination at $750{^{\circ}C}$ for 2 h.

Change of Phase Transformation Temperature at Fabricated Membrane using Sol-gel Method

Cheong, Hun,Choi, Duck-Kyun,Cheong, Deock-Soo The Korean Ceramic Society 2001 한국세라믹학회지 Vol.38 No.10

The supported and unsupported boehmite ($\gamma$-AlOOH) membranes were prepared using a boehmite sol. The supported membrane was consisted of a porcelain support, two intermediate $\alpha-{Al_2}{O_3}$ layers, and a top boehmite membrane. XRD patterns showed that the supported top membrane had a higher $\theta-$ to $\alpha-{Al_2}{O_3}$ transformation temperature compared to the unsupported membrane. This result was also confirmed from microstructural study of the membrane. The shift in the phase transformation temperature should be explained by difference of a stress generated in the supported top membrane due to interaction between the support layers and the top membrane.

First reports of a distinctive theropod track assemblage from the Jinju Formation (Lower Cretaceous) of Korea provides strong correlations with China

Kim, Kyung Soo,Lim, Jong Deock,Lockley, Martin G.,Xing, Lida,Ha, Su Jin,Kim, Cheong Bin,Paik, In Sung,Ahn, Jae Hong,Mun, Seok Chan Elsevier 2018 Cretaceous research Vol.81 No.-

<P><B>Abstract</B></P> <P>Despite the extreme, well-documented abundance of tracks of herbivorous dinosaurs (ornithopods and sauropods), avian theropods and pterosaurs, from the Cretaceous of Korea the footprints of non-avian theropods have previously been reported only sporadically from the Cretaceous Gyeongsang Supergroup of Korea, without clear attribution to any ichnogenus. Here we report an assemblage of well-preserved theropod tracks from the Lower Cretaceous (?Aptian) Jinju Formation of the Jinju City area that contains distinctive ichnogenera including <I>Grallator sensu lato</I>, <I>Corpulentapus</I> and <I>Asianopodus</I>. These ichnotaxa were previously only known to co-occur in the Lower Cretaceous of China. In combination with other track evidence from the Lower Cretaceous of both China and Korea, this assemblage strengthens previous interpretations of the distinctive, apparently endemic nature of many East Asian dinosaurian ichnotaxa. The assemblage also helps refine debate over the age of track assemblages in the Lower Cretaceous of East Asia, and differences between assemblages from the lower and upper stages of the Lower Cretaceous.</P> <P><B>Highlights</B></P> <P> <UL> <LI> First report of three diagnostic theropod tracks from Jinju Formation Korea. </LI> <LI> First report theropod tracks from Korea with reliable ichnotaxonomy. </LI> <LI> Theropod tracks allow strong regional correlation with Aptian tracks from China. </LI> <LI> Track assemblage obtained as part of major government regulated development. </LI> <LI> First report in English showing scale of excavation and extent of material obtained. </LI> </UL> </P>

알루미나 여과막의 상전이와 미세구조 변화: I. 지지체의 기공율에 의한 영향

정훈,황광택,최덕균,정덕수,Cheong, Hun,Hwang, Kwang-Taek,Choi, Duck-Kyun,Cheong, Deock-Soo 한국재료학회 2002 한국재료학회지 Vol.12 No.3

The HPS(High Porosity Support, 39.3%) and the LPS( Low Porosity Support, 18.7%) were fabricated to investigate the phase transformation and the chance of microstructure with porosity of alumina support. Alumina sol was made using aluminum tri-sec $butoxide(ATSB,\; Al(O-Bu)_3)$, the membrane on porous support with different porosity and the membrane without support were fabricated. The $\theta$-to ${\alpha}-A1_2O_3$ phase transformation in the membranes was investigated using thin film X-ray diffraction (XRD), and the change of microstructure was observed using scanning electron microscopy(SEM). XRD patterns showed that the membrane on LPS and HPS had 10$0^{\circ}C$, 5$0^{\circ}C$ higher $\theta$-to ${\alpha}-A1_2O_3$ transformation temperature compared to the unsupported membrane. A similar effect was also observed in microstructure of the membranes, theoritical temperature difference were 97$^{\circ}C$ and 44$^{\circ}C$ by Crapeyron equation.