• 한국주조공학회지
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• 제14권6호
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• pp.530-540
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• 1994

Aluminium-silicon alloy(JIS AC8A) matrix composites reinforced with SiC particles were fabricated by spray-cast forming process, and the microstructure of powders and preforms produced were studied by using an optical and scanning electron microscopy. SiC particles were co-sprayed by mixed phase injection method during the spray casting process. Most of the composite powders formed by this mixed phase injection method exhibit morphology of particle-embedded type, and some exhibits the morphology of particle attached type due to additional attachment of the SiC particles on the surface of the powders in flight. The preforms deposited were resulted in dispersed type microstructure. The pre-solidified droplets and the deposited preform of SiC-reinforced aluminium alloy exhibit finer equiaxed grain size than that of unreinforced aluminium alloy. Eutectic silicons of granular type are crystallized at the corner of the aluminum grains in the preforms deposited, and some SiC particles seem to act as nucleation sites for primary/eutectic silicon during solidification. Such primary/eutectic silicons seem to retard grain growth during the continued spray casting process. It is envisaged from the microstructural observations for the deposited preform that the resultant distribution of SiC injected particles in the Al-Si microsturcture is affected by the amount of liquid phase in the top part of the preform and by the solidification rate of the preform deposited.

• 한국주조공학회지
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• 제13권3호
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• pp.259-267
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• 1993

The effects of casting processes-direct and indirect squeeze casting, permanent mold casting and die casting on the microstructure and mechanical properties were studied for the hypereutectic B390 aluminium alloy. The effects of T5 and T6 heat treatment were also examined. The direct and indirect squeeze casting showed no casting defects such as porosity and shrinkage were observed in permanent mold castings and die castings. The primary silicon phase was refined and homogeneously distributed in the order of indirect squeeze casting, diecasting, direct squeeze casting and permanent mold casting. Depletion of primary silicon phase in die casting surface was disappeared in indirect squeeze casting. Tensile strength of cast and heat treated specimens were increased in the order of direct squeeze casting, permanent mold casting, indirect squeeze casting and die casting. Hardness of indirect squeeze castings was larger than that of other castings. As indirect squeeze casting of B390 aluminium alloy, the time of T6 heat treatment to achieve high strength can be reduced.

• 한국주조공학회지
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• 제26권5호
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• pp.205-210
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• 2006

여러 전자기 재료 프로세싱 연구 중에서 연구 되어지지 않았던 Al-Si 합금의 조직제어를 직류 자기장과 교류 전류장을 사용하여 시도 하였다. 본 연구의 목적은 Al-Si 합금에서의 새로운 거시, 미시 조직제어를 하기 위해 사용된 전자기 진동의 영향을 조사하는 것이다. 전자기 진동이 초정 알루미늄의 형상 변화를 위해 낮은 진동수 (>60Hz)로 주어질 경우, 수지상의 형상이 구상화 형상으로 변해갔다. 전자기 진동이 공정 실리콘 형상 변화를 위해 주어졌을 경우, 높은 진동수 (>500Hz)에서 조대한 판상 조직이던 실리콘이 미세한 섬유상 조직으로 변화하고, 기계적 성질도 우수해졌다.

• 대한금속재료학회지
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• 제50권12호
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• pp.897-905
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• 2012

Directional solidification experiments were carried out in a hypoeutectic Al-11.3Si-3.5Cu system to investigate the microstructural evolution with the solidification rate. At a fixed temperature gradient, a dendritic microstructure was observed at a constant speed of more than $25{\mu}ms^{-1}$, a cellular interface developed at $5{\mu}ms^{-1}$ and the growth rate of $0.5{\mu}ms^{-1}$ led to the stability of the planar interface. The results revealed that primary silicon phases formed among cells, even though the studied Al-Si alloy system formed the composition within a hypoeutectic silicon composition. This suggests that the liquid concentration among cells during solidification reached a higher concentration, i.e., the eutectic concentration. It is, however, interesting that primary silicon phases did not form during a dendritic growth of more than $25{\mu}ms^{-1}$. These experimental observations are explained using the theoretical models on the interface temperatures.

• 대한기계학회논문집B
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• 제40권2호
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• pp.111-117
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• 2016

본 연구의 목적은 실리콘 열전달 조절을 위한 포논의 평균자유행로(Mean free path, MFP) 스펙트럼 열전달 기여도 예측이다. 열전달의 크기 효과는 포논의 MFP 와 재료의 특성길이가 비슷할 때 나타나는데, 나노시스템 응용을 위한 재료의 열전달 증감을 위해 포논 MFP 스펙트럼에 대한 열전달 기여도 예측이 중요하다. 이를 위해 포논의 주파수 의존성이 고려된 볼츠만 수송방정식(Boltzmann transport equation) 근간의 full phonon dispersion 모델을 통해 실리콘 박막(Silicon-on-Insulator) 트랜지스터의 실리콘 박막 두께 변화(41-177 nm)에 따른 포논 MFP 스펙트럼 열전달 특성 및 비등방성을 해석함으로써, 본 연구 결과는 향후 박막 트랜지스터에 대한 고효율 열소산(heat dissipation) 설계전략에 활용될 수 있다.

• Advances in nano research
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• 제12권2호
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• pp.213-221
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• 2022

Silicon carbide (SiC) is a binary carbon-silicon compound. In its two-dimensional form, monolayer SiC is composed of a monolayer carbon and silicon atoms constructed as a honeycomb lattice. SiC has recently been receiving increasing attention from researchers owing to its intriguing electronic properties. In this present work, SiC nanoribbons (SiCNRs) are modelled and simulated to obtain accurate electronic properties, which can further guide fabrication processes, through bandgap engineering. The primary objective of this work is to obtain the electronic properties of monolayer SiCNRs by applying numerical computation methods using nearest-neighbour tight-binding models. Hamiltonian operator discretization and approximation of plane wave are assumed for the models and simulation by applying the basis function. The computed electronic properties include the band structures and density of states of monolayer SiCNRs of varying width. Furthermore, the properties are compared with those of graphene nanoribbons. The bandgap of ASiCNR as a function of width are also benchmarked with published DFT-GW and DFT-GGA data. Our nearest neighbour tight-binding (NNTB) model predicted data closer to the calculations based on the standard DFT-GGA and underestimated the bandgap values projected from DFT-GW, which takes in account the exchange-correlation energy of many-body effects.

• 경영과학
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• 제32권4호
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• pp.19-28
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• 2015

This study presents a mathematical programming model to develop production planning in the manufacturing processes for photovoltaic silicon ingots and wafers. The model is formulated as a linear programming model that maximizes total growth margin, which is composed of production cost, inventory cost, shortage cost, and sales profit while considering the constraints associated with the production environments of photovoltaic materials. In order to demonstrate the utility of the model for production planning, we run operations for a planning horizon of a year for a case study. When the primary results of this mathematical programming are compared with the historical records, the model could have resulted in the considerable increase of the total growth margin by effectively reducing inventory cost if a decision maker had employed the model as a decision support system with perfect information for sales demand.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.917-920
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• 2001

Effects of addition of manganese and final reduction on segregation behavior of sulfur and final mangetic induction during final annealing have been investigated in the 300 ppm sulfur-contained 3% silicon-iron alloy strips with or without manganese. At the same concentration of sulfur, lower final reduction is favorable for final Goss texture. This is because the probability that the initial Goss grains survive under the highly segregated sulfur atmosphere and grow selectively within the segregated sulfur-free time range becomes higher. In the case of 3% silicon-iron with manganese, much lower magnetic induction was obtained, although the weak final reduction of 30% is given to the alloy, comparative to the 40%. This is because MnS particles acted as an reducer in the primary grain size.

• Journal of Welding and Joining
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• 제8권2호
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• pp.27-39
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• 1990

The effect of silicon and manganese, in the ranges of 0.3% to 1.0wt% Si and 0.7 to 2.6wt%Mn, on the microstructure and mechanical properties of flux cored arc welded deposits have been investigated for the purpose of improving mechanical properties. Microstructure of weld metals was mainly influenced by manganese content, and manganese increased the volum fraction of acicular ferrite and refined the microstructure. Also, tensile properties were governed by manganese content, ultimate tensile strength and yield strength were increased by approximately 82MPa and 58MPa per 1% Mn addition to the deposit. Toughness was improved by increasing Mn content and lowering Si content. Optimal impact properties were obtained at above 1.8wt% Mn and below 0.5wt% Si. Acicular ferrite was predominant factor in improving mechanical properties. Formation of acicular ferrite was promoted by manganese and no direct relationship between AF(acicular ferrite) proportion and oxygen in weld metal was found.

• 전기학회논문지
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• 제65권4호
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• pp.561-566
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• 2016

In this paper, effective design method of linear induction motor(LIM) for Maglev is proposed in order to maximize system efficiency of Maglev. For the high system efficiency of Maglev, it is important to minimize weight of traction motor. Light weight design by changing materials of core and winding is conducted without changing volume of LIM. For the silicon steel core of primary part for magnetic flux path, iron-cobalt alloy steel with high magnetic saturation characteristic compared to silicon steel is suggested. Moreover, aluminium winding with light weight instead of copper winding is wounded in the widen slot area due to the high magnetic saturation level. For the verification of performance of proposed model, the characteristics are analyzed by using finite element method(FEM).