• 한국재료학회지
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• 제14권3호
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• pp.218-223
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• 2004

P-type $\beta$-FeSi$_2$ with a nominal composition of $Fe_{0.92}Mn_{0.08}Si_2$ powders has been produced by mechanical alloying process. As-milled powders were spray dried and consolidated by atmospheric plasma thermal spraying as a rapid sintering process. As-milled powders were of metastable state and fully transformed to $\beta$-$FeSi_2$ phase by subsequent isothermal annealing. However, as-thermal sprayed $Fe_{0.92}Mn_{0.08}Si_2$ consisted of untransformed mixture of $\alpha$-$Fe_2Si_{5}$ and $\varepsilon$-FeSi phases. Isothermal annealing has been carried out to induce transformation to the thermoelectric semiconducting $\beta$-$FeSi_2$ phase. Isothermal annealing at $845^{\circ}C$ in vacuum gradually led to the thermoelectric semiconducting $\beta$-$FeSi_2$ phase transformation, but some residual metallic $\alpha$ and $\varepsilon$ phases were unavoidable even after prolonged annealing. Thermoelectric properties of $\beta$-$FeSi_2$ materials before and after isothermal annealing were evaluated. Seebeck coefficient increased and electric conductivity decreased with increasing annealing time due to the phase transition from metallic phases to semiconducting phases. Thermoelectric properties showed gradual increment, but overall properties appeared to be inferior to those of vacuum hot pressed specimens.

• Journal of Welding and Joining
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• 제27권2호
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• pp.38-43
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• 2009

In this study, we investigated photocatalytic ability of plasma sprayed $TiO_2$ and Ag sputtering $TiO_2$(Ag-$TiO_2$) coatings. A sputtering processes were adopted to coat the surface of $TiO_2$ with Ag(99.99%). Ag was sputtered at 10mA, 450V for $1{\sim}11$ seconds. $TiO_2$ and Ag-$TiO_2$ coatings were heat-treated at 250, 300, 350, $400^{\circ}C$ for $0{\sim}240$seconds. Photoelectrical conductivity was measured by four-point probe, and photodegradation was calculated by UV-V is spectrometer. Microstructure observation of $TiO_2$ and Ag-$TiO_2$ coatings were investigated by SEM. Crystal structure of $TiO_2$ and Ag-$TiO_2$ coatings were investigated by XRD. Qualitative analyses of $TiO_2$ and Ag-$TiO_2$ coatings were conducted by EDX. When $TiO_2$ coatings were heat-treated at $350^{\circ}C$ for 30 sec, photoelectrical conductivity and photodegradation were best. And in XRD analysis result, (101)/(110) relative intensity ratio of $TiO_2$(rutile) was comparably changed with photoelectrical conductivity. When Ag-$TiO_2$ coatings were heat-treated at $350^{\circ}C$ for 30 [sec] after sputtering Ag for 7 sec, Photoelectrical conductivity and photodegradation are best. Surface of coatings in such condition has very small and uniform Ag particles.

• 한국통신학회논문지
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• 제17권6호
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• pp.580-588
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• 1992

비행물체에 대한 레이다의 추적 및 탐색거리를 축소시키는 전자방어책의 일환으로 물리적, 기계적 특성이 우수한 전자파 흡수층을 제작하기 위해서 플라즈마 용사방삭을 이용하였다. 이 코팅층은 종래의 M/W흡수층 제작에 사용하던 도전재료인 탄소대신에 탄화규소를, 자성손실재료로는 Ni-Zn ferrite를, 그리고 보지재를 사용하는 대신에 이들 재료분말을 기계적으로 혼합하여 플라즈마 용사코팅으로 모재 표면에 직접 흡수층이 형성되도록 했다. X-band(8~13 GHz)레이다용 탄화규소-페리이트 전자파 흡수체를 실험적으로 설계하고 시험제작하여 전기적 특성을 평가한 결과, -6dB(M/W 에너지 흡수율 75%)의 반사량을 허용한도로 했을경우 약 7.6~8.4%의 대역폭이 얻어졌으며, 최대 흡수두께가 0.5~0.55mm로 매우 양호한 박층형 전자파 흡수체가 얻어졌다.

• Journal of Preventive Medicine and Public Health
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• 제16권1호
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• pp.51-58
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• 1983

This study was carried out to obtain the basic data for the preverition of chronic poisonig by organic phosphate pesticides. 6 sprayers who participated in the summer pest control programs of Jeonju city were chosen as the subjects in this study. Pesticides which were spread in the period of study are DDVP (1.09%), dursban (1.8%) and dibrom (1.9%). And from May 16, 1983 to Aug. 22, 1983, plasma cholinesterase activity, hematological and biochemical parameters were measured with several physical examinations for each sprayers and controls. Major findings are as following; 1. Before pesticides were sprayed, plasma cholinesterase were $7.32{\pm}1.76{\mu}M/20{\mu}l/hr$. in sprayers and $7.13{\pm}1.39{\mu}M/20{\mu}l/hr$. in the control group (p>0.05). 2. At 60th day of spraying, plasma cholinesterase activity of sprayers was $6.78{\pm}2.01{\mu}M/20{\mu}l/hr$. which is significantly decreased from the pre-exposed value (p<0.01), but plasma cholinesterease activity in the control group was not changed. 3. The specific findings which suggested to organophosphorous poisoning were not found through the period of study. 4. Hematological and bichemical parameters were not sigricantly changed in the both groups.

• 공업화학
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• 제31권6호
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• pp.624-629
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• 2020

대기 플라즈마 용사(APS)법을 이용한 지르코니아 열차폐 코팅의 보다 효과적인 온도 제어를 위해서는 기판 온도에 영향을 미치는 매개 변수에 대한 이해가 필수적이며 실험 데이터를 기반으로 한 더 많은 결과가 필요하다. 본 연구는 APS (atmospheric plasma sprayed) 공정에서 기판 온도 제어에 관한 연구를 목적으로 한다. 특히, APS 기판 코팅과정에서 기판 표면 온도 제어를 위한 공랭 시스템, 플라즈마 가스 흐름, 분말 공급 속도, 로봇 속도 및 기판소재 영향 등을 보고하고 있다. 이러한 체계적인 접근은 APS 방식의 표면 코딩에서 온도를 제어하는데 도움이 되며, 이는 코팅 품질의 향상으로 이어질 것이다.

• 한국세라믹학회지
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• 제50권5호
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• pp.326-332
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• 2013

In this study, we prepared yttria stabilized zirconia granules for thermal barrier coatings using a spray drying process. First, we characterized the properties of granules such as flow rate and packing density for utilizing the air plasma spray process. The flow rate and packing density data showed 0.732 g/sec and 2.14 $g/cm^3$, respectively, when we used larger and denser particles, which are better than hollow granules or smaller spherical granules. Second, we chose larger, spherical granules fabricated in alcohol solvent as starting powders and sprayed it on the bondcoat/nimonic alloy by an atmospheric plasma spray process varying the process parameters, the feeding rate, gun speed and spray distance. Finally, we evaluated representative thermal and mechanical characteristics. The thermal expansion coefficients of the coatings were $11{\sim}12.7{\times}10^{-6}/^{\circ}C$ and the indentation stress measured was 2.5 GPa at 0.15 of indentation strain.

• 한국분말재료학회지
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• 제27권4호
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• pp.333-338
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• 2020

In this study, we fabricate a thin- and dense-BCuP-5 coating layer, one of the switching device multilayers, through a plasma spray process. In addition, the microstructure and macroscopic properties of the coating layer, such as hardness and bond strength, are investigated. Both the initial powder feedstock and plasma-sprayed BCuP-5 coating layer show the main Cu phase, Cu-Ag-Cu₃P ternary phases, and Ag phase. This means that microstructural degradation does not occur during plasma spraying. The Vickers hardness of the coating layer was measured as 117.0 HV, indicating that the fine distribution of the three phases enables the excellent mechanical properties of the plasma-sprayed BCuP-5 coating layer. The pull-off strength of the plasma-sprayed BCuP-5 coating layer is measured as 16.5 kg/㎠. Based on the above findings, the applicability of plasma spray for the fabrication process of low-cost multi-layered electronic contact materials is discussed and suggested.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.233.2-233.2
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• 2006

• 동력기계공학회지
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• 제2권2호
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• pp.35-40
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• 1998

In this study, the author investigated the effects of strengthening treatments on the mechanical properties of plasma sprayed Ni-base self fluxing alloy. Strengthening treatments for sprayed specimens were carried out in 4 different temperature conditions in vacuum furnace. The mechanical properties, such as microhardness, thermal shock resistance and erosion resistance were tested for the sprayed specimens after strengthening treatments. And it was proved that the mechanical properties of coating layer were much improved by strengthening treatments.

• Structural Engineering and Mechanics
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• 제4권6호
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• pp.679-702
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• 1996

The finite element method is employed in conjunction with micromechanical modelling in order to assess the performance of ceramic thermal barrier coatings applied to structural components. The study comprises the conditions of the deposition of the coating by plasma spraying as well as the thermal cycling of the coated component, and it addresses particularly turbine blades. They are exposed to high temperature changes strongly influencing the behaviour of the core material and inducing damage in the ceramic material by intense straining. A concept of failure analysis is discussed starting from distributed microcracking in the ceramic material, progressing to the formation of macroscopic crack patterns and examining their potential for propagation across the coating. The theory is in good agreement with experimental observations, and may therefore be utilized in proposing improvements for a delayed initiation of failure, thus increasing the lifetime of components with ceramic thermal barrier coatings.