• Bulletin of the Korean Chemical Society
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• 제31권2호
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• pp.355-359
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• 2010

A $Li[Co_{1/3}Ni_{1/3}Mn_{1/3}]O_2$ cathode was modified by applying a $ZrF_x$ coating. The surface-modified cathodes were characterized by XRD, SEM, EDS, TEM techniques. XRD patterns of $ZrF_x$-coated $Li[Co_{1/3}Ni_{1/3}Mn_{1/3}]O_2$ revealed that the coating did not affect the crystal structure of the parent powder. SEM and TEM images showed that $ZrF_x$ nano-particles were formed as a coating layer, and EDS data confirmed that $ZrF_x$ distributed uniformly on the surface the powder. Capacity retention of coated samples at high C rates was superior to that of pristine sample. However, as the coating concentration increases beyond the optimum concentration, the rate capability was deteriorated. Whereas, as the increase of coating concentration to 2.0 wt %, the cyclic performances of the electrodes under the severe conditions (high cut-off voltage, 4.8 V, and high measurement temperature, $55^{\circ}C$) were improved considerably.

• 한국재료학회지
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• 제26권3호
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• pp.160-165
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• 2016

To increase the capacitance of an Al electrolytic capacitor, the anodic oxide film, $Al_2O_3$, was partly replaced by an $Al_2O_3-ZrO_2$ (Al-Zr) composite film prepared by the vacuum infiltration method and anodization. The microstructure and composition of the prepared samples were investigated by scanning electron microscopy and transmission electron microscopy. The coated and anodized samples showed multi-layer structures, which consisted of an inner Al hydrate layer, a middle Al-Zr composite layer, and an outer $Al_2O_3$ layer. The thickness of the coating layer could go up to 220 nm when the etched Al foil was coated 8 times. The electrical properties of the samples, such as specific capacitance, leakage current, and withstanding voltages, were also characterized after anodization at 100 V and 600 V. The capacitances of samples with $ZrO_2$ coating were 36.3% and 27.5% higher than those of samples without $ZrO_2$ coating when anodized at 100 V and 600 V, respectively.

• 한국세라믹학회지
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• 제41권5호
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• pp.349-352
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• 2004

Organic-inorganic hybrid sol based on ZrO$_2$-SiO$_2$ system was prepared by sol-gel process. Firstly, ZrO$_2$ non-aqueous precursor sol was synthesized and then organosilane compounds which include epoxy silane (GPTS; 3-g1ycidoxypropyl tri-methoxysilane) and acryl silane (ACS; (3-(tri-methoxysilyl)propylmethacrylate)) were added to ZrO$_2$precursor sol for hybridization. Finally, com-mercial silica sol was added to improve the mechanical properties. Synthesized organic-inorganic Zr-hybrid sol was coated on polycarbonate substrate for enhancing it’s mechanical properties, especially hardness. Vicker’s hardness of polycarbonate sub strate was increased from 13.6 to 17.8 MPa and its pencil hardness was increased from 2 to 7 H, respectively, after coating and drying at 10$0^{\circ}C$ for 30 min.

• 한국세라믹학회지
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• 제35권7호
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• pp.653-658
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• 1998

Zirconia coated NiO powders were prepared by the thermal hydrolysis of $Zro(NO_3)_2$.$6H_2O$ in a mixed solvent of alcohol and water. Amorphous zirconium hydroxide was uniformly coated on the surface of NiO powder with the thickness of 20nm. The $ZrO_2$ coating layer was crystallized to tetragonal $ZrO_2$ with the size of 40-60nm at $900^{\circ}C$. The coated NiO powder containing 15 vol% $ZrO_2$ was found to have a similar isoelectric point to that of the $ZrO_2$ The grain growth inhibition effect of the coated powders was superior to the mechanically mixed powders.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 1995년도 특별강연 및 추계학술발표 개요집
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• pp.123-125
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• 1995

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2012년도 추계총회 및 학술대회 논문집
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• pp.170-170
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• 2012

• 항공우주기술
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• 제8권1호
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• pp.138-143
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• 2009

액체로켓엔진 연소기에 적용된 대기 플라즈마 코팅 및 전해/무전해 도금 코팅의 열차폐 효율과 내구성 평가를 수행하였다. 연소시험 결과 대기 플라즈마 방식의 $ZrO_2$, NiCrAlY 코팅은 로켓엔진 연소기의 초음속 유동영역에서 코팅이 표면에서 박리되는 현상이 간헐적으로 발생하였으며 따라서 이러한 문제를 극복할 수 있는 대체 코팅 방식이 요구되었다. 시험 결과 열차폐 효율 및 내구성 관점에서 대기 플라즈마 방식의 $ZrO_2$, NiCrAlY 코팅의 대안으로 무전해/전해 방식을 사용한 니켈-크롬 코팅을 사용할 수 있음을 알 수 있었다.

• Korean Chemical Engineering Research
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• 제46권1호
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• pp.69-75
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• 2008

Mechanochemical process로 제조된 $LiCoO_2$ 전극의 경우에 4.3 V 이상의 전위영역에서 용량감소현상이 두드러지게 나타난 반면에, Zr을 피복한 $LiCoO_2$의 경우에는 4.5 V의 전위에서도 안정성을 유지하였다. 본 연구에서 제작한 Zr이 피복된 $LiCoO_2$ 전극은 3.0~4.5 V 구간에서 197 mAh/g의 용량을 나타내었으며, 50 사이클 후에 96%의 방전용량을 유지하므로 전지의 안정성을 확보하였다.

• Bulletin of the Korean Chemical Society
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• 제28권12호
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• pp.2279-2282
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• 2007

Highly crystalline, uniform Fe nanoparticles were successfully synthesized and encapsulated in zirconia shell using sol-gel process. Two different approaches have been employed for the coating of Fe nanoparticle with zirconia. The thickness of zirconia shell can be readily controlled by altering molar ratio of Fe nanoparticle core to zirconia precursor in the first case where as reaction time was found to be most effective parameter to controlled the shell thickness in the second method. The structure and magnetic properties of the ZrO2-coated Fe nanoparticles were studied. TEM and HRTEM images show a typical core/shell structure in which spherical α-iron crystal sized of ~25 nm is surrounded by amorphous ZrO2 coating layer. TGA study showed an evidence of weight loss of less than 2% over the temperature range of 50-500 °C. The nanoparticles are basically in ferromagnetic state and their magnetic properties depend strongly on annealing temperature. The thermal treatment carried out in as-prepared sample resulted in reduction of coercivity and an increase in saturation magnetization. X-ray diffraction experiments on the samples after annealing at 400-600 °C indicate that the size of the Fe@ZrO2 particles is increased slightly with increasing annealing temperature, indicating the ZrO2 coating layer is effective to interrupt growing of iron particle according to heat treatment.

• 한국세라믹학회지
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• 제37권5호
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• pp.497-504
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• 2000

In this study, mullite-zirconia comosite was fabricated by adding ZrOCl2.8H2O using of boehmite gel coating to Hadong kaolin (pink A grade) in order to enhance strength of the mullite specimens. The influence of ZrOCl2.8H2O content and fireing temperature on the crystall phase, microstructure, bulk density, strength of the specimens was investigated. Mullite-zirconia composite was produced in the process of coating zirconia to mullite powder synthesized thereafter and mixing simultaneously of starting materials with boehmite-zirconia gel. Maximum strength with in this study was 251 sintered at 1$600^{\circ}C$ for 2h. Bulk density and strength of the composite with zirconia coated mullite was higher than simultaneous on mixture of starting materials.