• 한국세라믹학회지
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• 제31권1호
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• pp.74-78
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• 1994

Degradation of thin oxide by doped poly-Si and its improvement were studied. The gate oxide can be degraded by phosphorous in poly-Si doped POCl3. The degradation is increased with the decrement of sheet resistance and poly-Si thickness. Oxide failures of amorphous-Si are higher than those of poly-Si. In-situ double deposition of amorphous-Si, 54$0^{\circ}C$/30 nm, and poly-Si, 6$25^{\circ}C$/220 nm, forms the mismatch structure of grain boundary between amorphous-Si and poly-Si, and suppresses the excess phosphorous on oxide surface by the mismatch structure. The control of phosphorous through grain boundary improves the oxide reliability.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.735-738
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• 2003

Downsizing electronics requires precision position control with an accuracy of sub-micron order, which demands development of ultra-fine displacive devices. Piezoelectric transducer is one of devices transferring electric field energy into mechanical energy and being capable for fine displacement control. The transducer has been widely used as fine Position control device Multilayer piezoelectric actuator, one of typical piezo-transducer, is fabricated by stacking alternatively ceramic and electrode layers several hundred times followed by cofiring process. Electrode material should be tolerable in the firing process maintaining at ceramic-sintering temperatures up to $1100{\sim}1300^{\circ}C$. Ag-Pd can be used as stable electrode material in heat treatment above $960^{\circ}C$. Besides, adding small quantity ceramic powder allow the actuator to be fabricated in a good shape by diminishing shrinkage difference between ceramic and electrode layers, resulting in avoidance of crack and delamination at and/or nearby interface between ceramic an electrode layers. This study presents synthesis of nano-oxide-added Ag/Pd powders and its feasibility to candidate material tolerable at high temperature. The powders were formed in a co-precipitation process of Ag and Pd in nano-oxide-dispersed solution where Ag and Pd precursors are melted in $HNO_3$ acid.

• 한국세라믹학회지
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• 제14권3호
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• pp.163-168
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• 1977

As a wet chemical drying process "hot petroleum drying method" was applied and developed for preparing uniformly fine oxide powder with high purity and sinterreactivity. Using this method solution of sulfates was dried in hot petroleum bath (~17$0^{\circ}C$) to sulfate powder from which corresponding mullite doped by Fe3+ ion was formed. Particle size, shape, decomposition by heat, and phase identification of sulfate andoxide powders determined by DTA, TGA, X-ray diffraction, analysis and electron microscopy: sulfate powder prepared by this drying method is an intimate mixture of the amorphous form of uniformly and finely distributed spherical particles (0.05-0.1$\mu$). Mullitization with the sulfate powder occurs at 110$0^{\circ}C$ in air. The morphology of mullite particle made by firing the sulfate powder at 135$0^{\circ}C$ in oxygen atmosphere is granular of 0.1-0.3$\mu$ in size. This drying process proved to be a very effective method for preparing fine, homogeneous, and highly sinterreactive multicomponent oxide powder without conventional ceramic process of mixing, milling, and granulating. This process can be also applied for preparing electronic ceramic materials which are requisite for high purity and homogeneity.mogeneity.

• 한국재료학회지
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• 제23권10호
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• pp.592-598
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• 2013

Graphene oxide powders prepared by two different drying processes, freeze drying and spray drying, were studied to compare the effect of the drying method on the physical properties of graphene oxide powder. The graphene oxide dispersion was prepared from graphite by chemical delamination with the aid of sulfuric acid and permanganic acid, and the dispersion was further washed and re-dispersed in a mixed solvent of water and isopropyl alcohol. A freeze drying method can feasibly minimize damage to the sample, but it requires a long process time. In contrast, spray drying is able to remove a solvent in a relatively short time, though this process requires exposure to a high temperature for a rapid evaporation of the solvent. The powders prepared by freeze drying and spray drying were characterized and compared by Raman spectroscopy, X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy, and by an elemental analysis. The graphene oxide powders showed similar chemical compositions; however, the morphologies of the powders differed in that the graphene oxide prepared by spray drying had a winkled morphology and a higher apparent density compared to the powder prepared by freeze drying. The graphene oxide powders were reduced at $900^{\circ}C$ in an atmosphere of $N_2$. The effect of the drying process on the properties of the reduced graphene oxide was examined by SEM, TEM and Raman spectroscopy.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2008년도 제34회 동계학술대회 초록집
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• pp.275-275
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• 2008

• 한국분말재료학회지
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• 제8권3호
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• pp.186-191
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• 2001

Several fabrication processes, corresponding nanostructural features and multifunctionality as well has been investigated for oxide ceramic based nanocomposites with metal nanodispersion (i.e., ceramic/metal nanocomposites). Transition metal (Ni, Co, etc) dispersed alumina and zirconia based nanocomposites have been synthesized by reducing and hot-press sintering of ceramic and metal oxide mixtures prepared by several method. Improved fracture strength (1.1 and 1.9 GPa for $Al_2O_3/Ni$ and $ZrO_2/Ni$ nanocomposites, respectively) of these composites have been achieved according to their nanostructures. In addition, ferromagnetic characteristic has been kept. The variation of magnetization with an applied stress has found to be more sensitive as smaller as the magnetic metal dispersion is. This result thus suggests the possibility of fracture and/or stress sensing of the composites by simple magnetic measurement.

• 한국재료학회지
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• 제15권12호
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• pp.818-823
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• 2005

Sub-micron colloidal silica particles coated with nano-sized ceria were prepared by mixing of its silica and cerium salts hydrolysis, and modified by hydrothermal reaction. By using the slurries with and without hydrothermal modification containing above particles, oxide film coated on silicon wafer was polished. The modified slurries had higher polish rate due to increase of ceria fraction to silica through hydrothermal reaction. They revealed higher stability in wide range of pH $2\~10$ than ceria coated silica slurries without its modification.

• 세라미스트
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• 제21권4호
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• pp.366-377
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• 2018

Solid oxide fuel cells (SOFCs) are promising eco-friendly energy conversion system due to their high efficiency, low pollutant emission and fuel flexibility. High operating temperatures, however, leads to the crucial drawbacks such as incompatibility between the components and high thermal stress. Proton-conducting ceramic fuel cells (PCFCs) with proton-conducting oxide (PCO) materials are new types of fuel cells that can solve the problems of conventional SOFCs. Many studies have been proceeded to improve the performance of electrolytes and electrodes, and triple conductive oxides (TCOs) have attracted significant attention as high performance PCFC electrodes.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.53-58
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• 2002

Electrical insulation and mechanical properties of the plasma sprayed oxide ceramic coatings were studied before and after the sealing treatment of the ceramic coatings. Plasma sprayed A1$_2$O$_3$-TiO$_2$ coating as the reference coating was sealed using three commercial sealants based on polymer. Penetration depth of the sealants to the ceramic coating was evaluated directly from the optical microscope using a fluorescent dye. It is estimated that the penetration depth of the sealants to the ceramic coating is from 0.2 to 0.5 mm depending on the sealants used. The preliminary test results with a DC puncture tester imply that the dielectric breakdown voltage mechanism of plasma sprayed ceramic coatings has been determined to be a corona mechanism. Dielectric breakdown voltage of the as-sprayed and as-ground samples have shown a linear trend with regard to the thickness showing an average dielectric strength of 20 kV/mm for the thickness scale studied. It is also shown that grinding the coating before sealing and adding fluorescent dye do not agent the penetration depth of sealants. All of the microhardness, two-body abrasive wear resistance, bond strength, and surface roughness of the ceramic coating after the sealing treatment are improved. The extent of improvement is different from the sealants used. However, three-point bending stress of the ceramic coating after the sealing treatment is decreased. This is attributed to the reduced micro-crack toughening effect since the cracks propagate easily through the lamellar of the coating without crack deflection and/or branching after the sealing treatment.

• 대한기계학회논문집
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• 제19권4호
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• pp.1033-1040
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• 1995

To simulate strength reliability and durability of ceramic parts under gas turbine application environments, particle impact damage behaviors in silicon carbide oxidized at 1673 K and 1523 K for 200 hours in atmosphere were investigated. The long-term oxidation produced a slight increase in the static fracture strength. Particle impact caused a spalling of oxide layer. The patterns of spalling and damage induced were dependent upon the property and impact velocity of the particle. Especially, the difference in spalling behaviors induced could be explained by introducing the formation mechanism of lateral crack and elastic-plastic deformation behavior at impact sit. At the low impact velocity regions, the oxidized SiC showed a little increase in the residual strength due to the cushion effect of oxide layer, as compared with the as-received SiC without oxide layer.