• 콘크리트학회논문집
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• 제13권2호
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• pp.87-92
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• 2001

주물공장에서 발생하는 플라이애쉬는 현재까지 그 전부가 매립에 의존하고 있는 상태로 자원절약 및 산업폐기물의 유효이용이라는 측면에서 국가적인 손실이 아닐 수 없다. 따라서 산업폐기물의 유효이용, 콘크리트 제품 제조시 원가 절감, 콘크리트 제품의 품질개선 및 환경보존의 측면에서 플라이애쉬를 시멘트 대체재료로 사용할 수 있도록 이에 대한 연구가 필요하다. 본 연구에서는 주물공장의 폐기물인 플라이애쉬를 건설산업에 활용하는 방안을 수립하는 데 그 목적이 있다. 이를 위하여 주물공장에서 발생하는 플라이애쉬를 시멘트 대체재로 사용한 속빈 콘크리트 블록 및 콘크리트 벽돌을 제작하여, 한국산업규격에 규정한 요구조건에 대한 실험을 실시하였고 제반 특성을 조사하여 콘크리트 제품에 활용할 수 있는 방안을 제시하였다.

• Corrosion Science and Technology
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• 제20권5호
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• pp.315-323
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• 2021

In this study, we examined corrosion behaviors of two types of Pb alloys for a lead acid battery comparatively. One containing 6.6 wt% Sn, 36 mg/kg Bi, and 612.4 mg/kg Ca was prepared by twin-roll continuous casting. The other containing 5.2 wt% Sn, 30.5 mg/kg Ag, and 557 mg/kg Ca was made by twin-belt continuous casting. Potentiodynamic polarization tests were performed to evaluate corrosion resistance. Cyclic voltammetry was done to examine oxidation and reduction reactions occurring on the surface of each alloy in 4.8 M H₂SO₄ solution. Electrochemical test results implied that the Pb alloy prepared with the twin-belt casting method was less stable than that cast with the twin-roll method. Such results might be due to precipitations formed during the casting process. Rolling did not appear to affect the corrosion behavior of the twin-roll samples with Ag < 10 mg/kg, while it reduced the anodic reaction of Ag on the surface of the twin-belt sample with 30.5 mg/kg Ag.

• Nuclear Engineering and Technology
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• 제56권7호
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• pp.2767-2774
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• 2024

In this study, investment casting shell waste successfully utilized to produce cordierite/mullite/zircon composites. Green pellets, consisting of investment casting shell waste, alumina, and magnesia, were prepared and sintered at temperatures between 1250 and 1350 ℃. The influence of the sintering temperature on the crystalline phase composition, densification behavior, flexural strength, microstructure, and radiation shielding properties of the cordierite/mullite/zircon composites is investigated. Phase analysis showed that characteristic cordierite peaks appear at 1250 ℃, but the complete conversation of silica from investment casting shell waste into cordierite requires a sintering temperature of at least 1300 ℃. Notably, the cordierite/mullite/zircon composite sintered at 1350 ℃ exhibited a sixfold increase in flexural strength compared to the ceramic composite directly fabricated from investment casting shell waste at the same sintering temperature. Furthermore, the effect of Y₂O₃ addition on composites' radiation shielding properties is investigated. The results show that the Y₂O₃ addition improves densification behavior, enhancing the shielding capabilities of the composites against fast neutron and gamma radiation. Our findings suggest that the developed ceramic composites show significant potential for gamma-ray and neutron shielding applications.

• 공업화학
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• 제20권3호
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• pp.317-321
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• 2009

고체 산화물 전해질로 사용되고 있는 초 이온 전도체인 $K^+-{\beta}/{\beta}"-Al_2O_3$의 고온 상관계와 소결성 분석을 위하여 $K_2O-LiO_2-Al_2O_3$ 삼성분계로부터 고상반응을 통하여 순수한 $K^+-{\beta}/{\beta}"-Al_2O_3$ 분말을 합성한 후 slip casting방법과 냉간정수압성형에 의하여 tube와 disk형을 각각 제작하였다. Slip casting은 40 wt%의 고체함량을 가지는 슬러리를 사용해 알루미나 몰드에서 이루어졌고 냉간정수압성형은 20 MPa의 압력하에서 수행되었다. 성형체들은 $1600^{\circ}C$, $1700^{\circ}C$, $1750^{\circ}C$에서 각각 소결하여 성형방법에 따른 상관계와 소결밀도를 조사하였다. 냉간정수압성형에 의한 시편이 $1700^{\circ}C$까지 ${\beta}"-Al_2O_3$의 상분율이 월등히 높은 반면, 소결밀도에 있어서는 slip casting방법의 경우가 다소 높았다. 소결 시 상대밀도는 $1750^{\circ}C$에서 1 h 경과 후, 두 경우 모두 약 83%를 나타내었다. 90 min 이상 소결하였을 때는 입자의 과대성장과 기공으로 인해 오히려 밀도가 낮아졌다.

• 한국결정성장학회지
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• 제27권5호
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• pp.229-234
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• 2017

본 연구에서는 자동차 터보차저(turbo charger)용 터빈휠을 제조하기 위하여 고속원심주조법을 이용하여 TiAl 합금을 주조하였다. 여러 가지 조성의 주형을 사용하여 주조결함이 최소화 되는 최적의 몰드 조건을 찾고자 하였으며, 주조된 TiAl 합금의 결정구조와 미세조직을 고찰하였다. TiAl 샘플의 XRD 분석 결과 ${\gamma}$-TiAl 상과 ${\alpha}_2-Ti_3Al$ 상으로 구성되어 있음을 확인하였으며, 광학현미경과 FE-SEM 분석을 통하여 TiAl 샘플은 6-fold 및 4-fold 대칭성으로 이루어진 두 개의 수지상(dendrite) 형태로 이루어져 있음을 확인할 수 있었다. 또한 샘플의 단면에서 표면과 가까운 지점과 내부에서 측정한 원소함량의 차이를 확인할 수 있었으며, 마이크로비커스 경도계를 이용하여 표면에서 $50{\mu}m$ 미만의 영역에서 경도상승 영역 alpha-case 층이 형성되었음을 확인하였다.

• 마이크로전자및패키징학회지
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• 제24권1호
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• pp.1-8
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• 2017

Fe-9.8Si-6.0Al mother alloy was manufactured using by Fe-3.5Si recycled scrap and Si powder. And then, soft magnetic alloy powder of $D_{50}$ size and sphere type were prepared by gas atomization process. To obtain the soft magnetic powder of a high aspect ratio, in the first, we conducted the ball milling process for 8 hours. And heat treatment was performed under $650^{\circ}C$, 2 hours and $N_2$ atmosphere condition for reducing the residual stress of the powder. Based on these process, we made around $50{\mu}m$ diameter Fe-9.8Si-6.0Al powder, which morphology and shape was a similar to the commercial Fe-Si-Al powder. Finally, the soft magnetic sheets were prepared by tape casting process using by those powders. The permeability of the tape casting sheet was measured, and we confirmed the possibility of reusing to the soft magnetic materials of Fe-Si electric sheet scrap.

• Journal of Electrochemical Science and Technology
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• 제1권1호
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• pp.50-56
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• 2010

$La_{0.6}Sr_{0.4}Co_{0.2}Fe_{0.8}O_{3-\delta}$ (LSCF) powders with different particle sizes, synthesized through a citrate complexation method and a gel-casting technique, are used to fabricate porous LSCF cathodes with graded microstructures via tape casting. To create porous electrodes with desired porosity and pore structures, graphite and starch are used as pore former for different layers of the graded cathode. Examination of the microstructures of the as-prepared LSCF cathode using an SEM revealed that both grain size and porosity changed gradually from the catalytically active layer (near the electrodeelectrolyte interface) to the current collection layer (near the electrode-interconnect interface). Impedance analysis showed that a 3-layer LSCF cathode with graded microstructures exhibited much-improved performance compared to that of a single-layer LSCF cathode, corresponding to interfacial resistance of 0.053, 0.11, and 0.27 $\Omega{\cdot}cm^2$ at 800, 750, and $700^{\circ}C$ respectively.

• 한국주조공학회지
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• 제20권5호
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• pp.330-335
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• 2000

Functional metal prototypes are often required in numerous industrial applications. These components are typically needed in the early stage of a project to determine form, fit and function. Recent R/P(Rapid Prototyping) part are made of soft materials such as plastics, wax, paper, these master models cannot be employed durable test in real harsh working environment. Parts by direct metal rapid tooling method, such as laser sintering, by now are hard to get net shape, pores of the green parts of powder casting method must be infiltrated to get proper strength as tool, and new type of 3D direct tooling system combining fabrication welding arc and cutting process is reported. But a system which can build directly 3D parts of high performance functional material as metal park would get long period of system development, massive investment and other serious obstacles, such as patent. In this paper, through the rapid tooling process as silicon rubber molding using R/P master model, and fabricate wax pattern in that silicon rubber mold using vacuum casting method, then we translated the wax patterns to numerous metal tool prototypes by new investment casting process combined conventional investment casting with rapid prototyping & rapid tooling process. With this wax-injection-mold-free investment casting, we developed new investment casting process of fabricating numerous functional metal prototypes from one master model, combined 3-D CAD, R/P and conventional investment casting and tried to expect net shape measuring total dimension shrinkage from R/P pare to metal part.

• 한국생산제조학회지
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• 제20권5호
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• pp.541-546
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• 2011

This study was numerically investigated on thermal deformation of AC4C and AC7A aluminum alloy casting material for manufacturing the automobile tire mold. The metal casting device was used in order to manufacture the mold product of automobile tire at the actual industrial field. The temperature distribution and the cooling time of these materials were numerically calculated by finite element analysis. Thermal deformation with stress distribution was also calculated form the temperature distribution results. The thermal deformation was closely related to the temperature difference between the surface and inside of the casting. As shown by numerical analysis result, the thermal deformation of AC7A casting material became higher than AC4C casting material. In addition, the results of displacement and stress distributions appeared to be larger at the center parts of casting than on its sides because of the shrinkage caused by the cooling speed difference.

• 한국주조공학회지
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• 제33권5호
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• pp.204-209
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• 2013

The family mold casting have advantages which are able to make products with different shapes and dimensions simultaneously in a single mold. In this study, the design of the 4 cavity rotor family mold was used by "Anycasting" software, the defects occurred during die casting were predicted and suggested the best optimization conditions for sound products. The result of the experiment were that the optimum overflow design was needed for gas emission and control of residual oxides. It was clear that the defects positions formed by diecasting were agreed with nearly them predicted by simulation.