• Journal of Electrochemical Science and Technology
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• 제13권3호
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• pp.390-397
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• 2022

The use of microwaves as the energy source for synthesis and sintering of ceramics offers substantial advantages compared to conventional gas-fired and electric resistance furnaces. Benefits include much shorter processing times and reaching the sintering temperature more quickly, resulting in superior final product quality. Most oxide ceramics poorly interact with microwave irradiation at low temperatures; thus, a more complex setup including a susceptor is needed, which makes the whole process very complicated. This investigation pursued a new approach, which enabled us to use microwave irradiation directly in poorly coupled oxides. In many solid-state electrochemical devices, the support is either metal or can be reduced to metal. Metal powders in the support can act as an internal susceptor and heat the entire cell. Then sufficient interaction of microwave irradiation and ceramic material can occur as the sample temperature increases. This microwave heating and exothermic reaction of oxidation of the support can sinter the ceramic very efficiently without any external susceptor. In this study, yttria stabilized zirconia (YSZ) and a Ni-YSZ cermet support were used as an example. The cermet was used as the support, and a YSZ electrolyte was coated and sintered directly using microwave irradiation without the use of any susceptor. The results were compared to a similar cell prepared using a conventional electric furnace. The leakage test and full cell power measurement results revealed a fully leak-free electrolyte. Scanning electron microscopy and density measurements show that microwave sintered samples have lower open porosity in the electrode support than conventional heat treatment. This technique offers an efficient way to directly use microwave irradiation to sinter thin film ceramics without a susceptor.

• 소성∙가공
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• 제18권3호
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• pp.262-267
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• 2009

Selective laser sintering is a kind of rapid prototyping process whereby a three-dimensional part is built layer wise by laser scanning the powder. This process is highly influenced by powder and laser parameters such as laser power, scan rate, fill spacing and layer thickness. Therefore a study on fabricating Fe-Ni-Cr powder by selective laser sintering has been performed. In this study, fabrication was performed by experimental facilities consisting of a 200W fiber laser which can be focused to 0.08mm and atmospheric chamber which can control atmospheric pressure with argon. With power increase or energy density decrease, line width was decreased and line surface quality was improved with energy density increase. Surface quality of quadrangle structure was improved with fill spacing optimization.

• 대한전기학회논문지
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• 제36권1호
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• pp.43-51
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• 1987

In this paper, a state-space model of the burnthrough point control system of an industrial sintering process is derived. The model is then used in designing a self-tuning controller which consists of the receding horizon control law and a least-squares prediction algorithm with covariance resetting. By applying this controller to POSCO IV sintering process, satisfactory experimental results have been obtained. This paper presents some of these real-time experimental results and analyzes the control performance through productivity, operation indices, quality, sintered material composition, etc. From these experimental results and simulation results, the validity of the model can be observed. Moreover, the properties of the controller, e.g. stability, steady-state error, are shown based on the model.

• 한국분무공학회지
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• 제17권1호
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• pp.20-26
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• 2012

Inkjet printing is one of the direct writing technologies and is able to form a pattern onto substrate by dispensing droplets in desired position. Also, by inkjet technology manufacturing time and production costs can be reduced, and procedures can be more efficient. To form a metal pattern, it must be harmonized with conductive nano ink, printing process, sintering, and surface treatment. In this study, micro patterning of conductive line has been investigated using the piezoelectric printhead driven by a bipolar voltage signal is used to dispense $20-40{\mu}m$ diameter droplets and silver nano ink which consists of 50 nm silver particles. In addition, hydrophobic treatment of surface, overlap printing techniques, and sintering conditions with changing temperature and times to achieve higher conductivity.

• 한국세라믹학회지
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• 제53권5호
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• pp.506-510
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• 2016

The eutectic melt of BaO-CuO flux is known to be a potential sintering aid for $Ba(Zr,Y)O_3$ (BZY) electrolyte for proton-conducting ceramic fuel cells (PCFCs). A density of BZY higher than 97% of theoretical density can be achieved via sintering at $1300^{\circ}C$ for 2 h using a flux composed of 28 mol% BaO and 72 mol% CuO. In the present study, chemical and structural evolution of BaO-CuO flux throughout the sintering process was investigated. An intermediate holding step at $1100^{\circ}C$ leads to formation of various impurity compounds such as $BaCuO_{1.977}$, $Ba_{0.92}Cu_{1.06}O_{2.28}$ and $Cu_{16}O_{14.15}$, which exhibit significantly larger unit cell volumes than the matrix. The presence of such secondary compounds with large lattice mismatch can potentially lead to mechanical failure. On the other hand, direct heating to the final sintering temperature produced CuO and $Cu_2O$ as secondary phases, whose unit cell volumes are close to that of the matrix. Therefore, the final composition of the flux is strongly affected by the thermal history, and a proper sintering schedule should be used to obtain the desired properties of the final product.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.372-373
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• 2006

Modern business trends call for miniaturization of electronic systems. One of the major impedances in this miniaturization is the conductive and inductive components in chips and circuit boards. Direct Write Technology can write these soft magnetic materials, thus allowing for further miniaturization of inductor devices. Another obstacle in electronics fabrication is the size limitations of thick screen-printing and the material limitations in ink jet printing. Direct Write Technologies address both of these limitations by providing feature sizes less than 20 microns with a wide range of materials possibilities. A discussion of the application of these nano-particulate materials by Direct Write Technologies will be presented.

• 한국분말재료학회지
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• 제28권3호
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• pp.221-226
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• 2021

We fabricate the non-equiatomic high-entropy alloy (NE-HEA) Fe_49.5Mn₃₀Co₁₀Cr₁₀C_0.5 (at.%) using spark plasma sintering under various sintering conditions. Each elemental pure powder is milled by high-energy ball milling to prepare NE-HEA powder. The microstructure and mechanical properties of the sintered samples are investigated using various methods. We use the X-ray diffraction (XRD) method to investigate the microstructural characteristics. Quantitative phase analysis is performed by direct comparison of the XRD results. A tensile test is used to compare the mechanical properties of small samples. Next, electron backscatter diffraction analysis is performed to analyze the phase fraction, and the results are compared to those of XRD analysis. By combining different sintering durations and temperature conditions, we attempt to identify suitable spark plasma sintering conditions that yield mechanical properties comparable with previously reported values. The samples sintered at 900 and 1000℃ with no holding time have a tensile strength of over 1000 MPa.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 춘계학술대회 논문집
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• pp.721-722
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• 2007

• 한국세라믹학회지
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• 제39권3호
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• pp.299-307
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• 2002

본 연구에서는 복잡 형상의 세라믹체를 효율적으로 성형할 수 있어 새로운 성형기법으로 부각되고 있는 직응집성형(Direct Coagulation Casing, DCC)공정기술에 관하여 콜로이드 계면화학을 이용하여 연구하였다. 높은 고형분량을 가지는 안정된 질화규소 슬립을 제조하기 위하여 분산제, 소결조제 그리고 응집제 각각이 다양한 공정변수에 미치는 영향에 대하여 평가하였다. 1.0 wt% Tetraethylammonium Hydroxide(TEAH)를 첨가하여 염기영역에서 소결조제를 포함한 안정된 51vol%의 질화규소 슬립을 제조할 수 있었다. 질화규소 슬립은 첨가된 $Al(CH_3COO)_2OH$의 온도증가에 따른 열분해를 이용하여 직응집성 유도하였다. 염기영역에서 $Al^{3+}$ 이온들이 aluminum hydroxide$(Al(OH)_3)$ 석출되면서 슬립내 $OH^-$ 농도를 감소시켜 질화규소 슬립을 직응집시켰다.

• 한국건축시공학회지
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• 제14권3호
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• pp.230-236
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• 2014

본 연구는 최근 제주도 지역내 현무암 가공과정에서 발생되는 폐기물인 석분슬러지를 재활용하기 위한 방안으로서, 인공경량골재의 제조가능성에 대해 실험하였다. 또한, 현무암 석분 슬러지로 제조된 인공경량골재의 물성을 개선하기 위해 폐유리분말과 탄산칼슘이 사용되었다. 현무암 석분 슬러지와 폐유리분말 그리고 소성방법의 복합적인 요인을 고려할 때 경량골재 내부의 발포성 향상을 위해서 탄산칼슘의 양은 9 wt.%가 적당하였다. 또한, 제조된 인공경량골재의 흡수율을 저하시키기 위해서는 폐유리 분말은 50 wt.%이내로 사용함과 동시에 직화소성의 방법을 적용하는 것이 더 효과적이다. 좀 더 낮은 비중과 흡수율을 가진 고품질의 인공경량골재를 성형하기 위해서는 성형된 경량골재의 표면에 폐유리분말을 도포한 후 그 시료를 직화소성법으로 소성하는 것이 더 효과적일 것으로 판단된다.