• Bulletin of the Korean Chemical Society
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• v.9 no.4
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• pp.262-264
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• 1988

• Journal of the Korean Ceramic Society
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• v.35 no.3
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• pp.303-309
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• 1998

The fabrication of Al2O3/Al composite by pressureless infiltration was investigated by the change of Mg and Si content in Al alloy infiltration process and infiltration atmosphere. The effect of alloying elements infiltration atmosphere and interfacial reactants between Al alloy matrix and Al2O3 particles were in-vestigated in terms of bendingstrength and harness test,. The fabrication of Al2O3/Al composite by the vestigated in terms of bending strength and hardness test. The fabrication of Al2O3/Al composite by the pressureless infiltration was done in nitrogen atmosphere with Mg in Al alloy. It was successfully fabricated at $700^{\circ}C$ according to Mg contents in Al alloy and infiltration condition. Because Mg in the Al alloy and ni-trogen atmosphere of infiltratio condition produced Mg-N compound(Mg3N2) it decreased the wetting an-gle between molten Al alloy and Al2O3 particles by coating on surface of Al2O3 particles. The fracture strength of Al2O3/Al-Mg composite was 800MPa and Al2O3/Al-Si-Mg composite was 400MPa. Si in Al alloy decreased the interfacial strength between Al alloy matrix and Al2O3 particles.

• Journal of Electrochemical Science and Technology
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• v.12 no.2
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• pp.272-278
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• 2021

In this study, high nickel layered LiNi_0.8Co_0.1Mn_0.1O₂ cathode materials for lithium-ion batteries were modified by yttrium doping and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) coating. The effects of yttrium doping and PEDOT:PSS coating on the structural and electrochemical properties of the LiNi_0.8Co_0.1Mn_0.1O₂ cathode material were investigated and compared. The substitution of nickel with an electrochemically inert yttrium was confirmed to be successful in stabilizing the layered structure framework. Moreover, coating the surfaces of the LiNi_0.8Co_0.1Mn_0.1O₂ particles with a conductive polymer, PEDOT:PSS, improved the capacity retention, thermal stability, and impedance of the cathode material by increasing its ionic and electric conductivities.

• Current Photovoltaic Research
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• v.3 no.1
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• pp.32-38
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• 2015

CIGS solar cell consisted of various films. In this research, we investigated electrode materials in $Cu(In,Ga)Se_2$ (CIGS) cells, including Al-doped ZnO (ZnO:Al), intrinsic ZnO (i-ZnO), and Al films. The sputtered ZnO:Al film with a sputtering power at 200W showed the lowest series resistance and highest cell efficiency. The electrical resistivity of the 200-W sputtered ZnO:Al film was $5.2{\times}10^{-4}{\Omega}{\cdot}cm$ by the rapid thermal annealing at $200^{\circ}C$ for 1 min. The electrical resistivity of i-ZnO was not measurable due to its high resistance. But the optical transmittance was highest with less oxygen supply and high efficiency cell was achieved with $O_2/(Ar+O_2)$ ratio was 1% due to the increase of short-circuit current. No significant change in the cell performance by inserting a Ni layer between Al and ZnO:Al films was observed.

• Journal of Surface Science and Engineering
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• v.31 no.2
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• pp.91-100
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• 1998

NiCrAlY/YSZ(8wt%$Y_2O_3-ZrO_2$) functionally graded thermal barrier coating (FGC) layers on a Co-base superalloy (HAYNESS 188) substrate were fabstrate were fabicated using Ar shielded single torch air plasma spraying method. Functional grading with the stepwise compositional change throughout layer thickness. Microstructural observation trvealed a successful fabrication of NiCrAlY/YSZ FGC. From the results of the curvature measurement, adhesive strength measurement and thermal shock test for the FGC, it was concluded that the optimum conditions of functionally graded coating layer thinkness and compositional pattern exit to enhance the properties of FGC, which is closely related to the internal residual stess distribution witin it.

• Applied Chemistry for Engineering
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• v.21 no.1
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• pp.63-70
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• 2010

Transition metal based spent catalysts (Ni-Mo and Co-Mo), which were scrapped from the petrochemical industry, were reused for the removal processes of volatile organic compounds (VOCs). Especially the optimum regeneration procedures were determined using the removal efficiency of VOCs. In this work, the spent Ni-Mo and spent Co-Mo catalysts were pretreated with different physic-chemical treatment procedure: 1) acid aqueous solution, 2) alkali solution, 3) chemical agent and 4) steam. The various characterization methods of spent and its regenerated catalysts were performed using nitrogen adsorption, X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with an energy dispersive spectrometry (EDS). It was found that all spent catalysts were found to be potentially applicable catalysts for catalytic oxidation of benzene. The experimental results also indicated that among the employed physico-chemical pretreatment methods, the oxalic acid aqueous (0.1 N, $C_2H_2O_4$) pretreatment appeared to be the most efficient in increasing the catalytic activity, although the catalytic activity of spent Ni-Mo and spent Co-Mo catalysts in the oxidation of benzene were greatly dependent on the pretreatment conditions. The pretreated spent catalysts at optimum condition could be also applied for removing other aromatic compounds (Toluene/Xylene).

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.216-216
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• 2003

현재 상용화되어 있는 리튬 이차전지용 양극재료로는 비교적 작동전압이 높은 층상 암염구조(LiCoO$_2$, LiNiO$_2$) 및 Spinet계(LiMn$_2$O$_4$) 전이금속 산화물이 대부분 이용되고 있다 하지만 LiCoO$_2$나 LiNiO$_2$ 같은 상용화 물질은 비교적 높은 비용과, 강한 독성 때문에 많은 문제점을 가지고 있다. 또 Spinel(LiMn$_2$O$_4$)는 낮은 비용과 환경친화적인 장점에도 불구하고 Jahn-Teller 변형과 관련된 구조적 변형이 심각하기 때문에 사이클시 비가역적인 용량의 감소가 심각하다. 이러한 관점에서 전이금속보다 그 양이 풍부하고 저렴할 뿐만 아니라 독성이 없는 Olivine 구조 (LiFePO$_4$)를 갖는 phosphate계 화합물에 관심을 가지게 되었다. LiFePO$_4$는 리튬 음극과 3.4V의 방전전압을 나타내며, 170mAh/g의 이론용량을 가지고 있어, Fe-base의 장점은 물론 안정적인 결정구조 및 현재 상용화된 재료들과 비슷한 에너지 밀도를 가진다. 따라서 본 연구에서는 양극물질의 기존 두 제조법인 고상반응법과 sol-gel법으로 대표되는 제조법의 단점을 상호 보완될 수 있다고 판단되는 기계적 합금화법(Mechanical Alloying, MA)공정을 도입하여 초미세립 분말 제조에 초점을 맞추어 Olivine phosphate계 양극물질의 제조 및 전기화학적 특성을 연구하였다.

• Progress in Superconductivity
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• v.9 no.1
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• pp.85-90
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• 2007

Lanthanum aluminate($LaAlO_3$) film has been prepared on single crystal and metal substrates by dip coating method. Lanthanum acetate and aluminum were prepared via ligand exchange starting from lanthanum nitrate hexahydrate and aluminum nitrate hexahydrate in acetate glacial acetic acid solution after being refluxed. Coating solution was obtained by diluting the gel with methanol and 2-methoxyethanol to adjust the total cation concentration to 0.67 M. Precursor coated film was prepared by dip-coating with a speed of 25 mm/min on various substrates such as $LaAlO_3$ (001), MgO(001), $SrTiO_3$(001) single crystal, LMO/MgO/Ni-alloy. Thin films have been obtained by heat treating the precursor film at various temperatures from $600^{\circ}C{\sim}900^{\circ}C$ and various heating rate from $0.83^{\circ}C/min{\sim}1.25^{\circ}C/min$ under $Ar/O_2$ mixture containing 1000ppm oxygen. The films have been characterized by scanning electronic microscopy (SEM) and X-ray diffraction (XRD). XRD analysis for the prepared film showed that $LaAlO_3$ thin films with a preferred orientation of (100) plane parallel to substrate surface were obtained at $800^{\circ}C(1.11\;^{\circ}C/min)$ on LMO/MgO/Ni-alloy substrate, but the intensity decreased with the increase of heat treatment temperature.

• Journal of the Korean Ceramic Society
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• v.45 no.4
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• pp.214-219
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• 2008

The zirconia ceramics are widely used because of their excellent mechanical properties. Recently, many researches to make a colored zirconia was achieved to satisfy the individual aesthetic requirements. In this study, the synthesis of black-color spinel-based inorganic pigments which are stable above $1400^{\circ}C$ and the fabrication of black-colored zirconia using the synthesized pigments are investigated. Inorganic pigments which have spinel structure and near black color were synthesized by a solid state reaction method using a $Fe_2O_3,\;Cr_2O_3$, CoO and NiO powder as a starting materials at $1600^{\circ}C$. Most of synthesized pigments were black colored spinel phases and single spinel phase was successfully synthesized at the composition range of $Cr_2O_3:25{\sim}35%,\;Fe_2O_3:45{\sim}55%$, CoO:20% and NiO:$6{\sim}10%$. The black-colored zirconia was fabricated at $1410^{\circ}C$ with the 5 wt% synthesized pigments and their properties were evaluated. The results showed that the strength value was more than 848 MPa, absorption rate was 0.1%, the brightness of color was $L^*:40{\sim}42$, the tone of color is $a^*:0.2{\sim}0.8$ and $b^*:-1.1{\sim}2.4$. As a result, the black-colored zirconia was suitable for a artificial jewelry or decoration zirconia goods.

• Journal of Sensor Science and Technology
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• v.4 no.4
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• pp.75-80
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• 1995

In order to fabricate the piezoelectric thin film of the PZT-PNN ternary compound, the metal alkoxides were used as starting materials. The electrical and crystalline properties of the thin film were evaluated. The X- RD study shows that the crystallization of the film is optimized at $550^{\circ}C$ of sintering temperature. According to the D-E hysterisis curve, the coercive field is 28.8 kV /cm, and the remanent polariztion is $18.3\;{\mu}C/cm^{2}$. The break down voltages of the thin films are $76.0\;{\sim}\;27.0\;MV/m$. When the sintering temperature is raised, the break down voltage is lowered. As a result of measuring the C-V characteristic curve of the ternary compound piezoelectric thin film, the relative dielectric constants are 406 for the composition (50:40:10), 1084 for the composition (50:30:20), 723 for the composition (45:35:20) and 316 for the composition (40:40:20).