• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2009년도 추계학술대회 논문집
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• pp.403-404
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• 2009

• 한국재료학회지
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• 제21권6호
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• pp.314-319
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• 2011

Melt foaming method is one of cost-effective methods to make metal foam and it has been successfully applied to fabricate Mg foams. In this research, AZ31 Mg alloy ingot was used as a metal matrix, using AlCa granular as thickening agent and $CaCO_3$ powder as foaming agent, AZ31 Mg alloy foams were fabricated by melt-foaming method at different foaming temperatures. The porosity was above 41.2%~73.3%, pore size was between 0.38~1.52 mm, and homogenous pore structures were obtained. Microstructure and mechanical properties of the AZ31 Mg alloy foams were investigated by optical microscopy, SEM and UTM. The results showed that pore structure and pore distribution were much better than those fabricated at lower temperatures. The compression behavior of the AZ31 Mg alloy foam behaved as typical porous materials. As the foaming temperature increased from $660^{\circ}C$ to $750^{\circ}C$, the compressed strength also increased. The AZ31 Mg alloy foam with a foaming temperature of $720^{\circ}C$ had the best energy absorption. The energy absorption value of Mg foam was 15.52 $MJ/m^3$ at a densification strain of 52%. Furthermore, the high energy absorption efficiencies of the AZ31 Mg alloy foam kept at about 0.85 in the plastic plateau region, which indicates that composite foam possess a high energy absorption characteristic, and the Vickers hardness of AZ31 Mg alloy foam decreased as the foaming temperature increased.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2001년도 The 6th International Symposium of East Asian Resources Recycling Technology
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• pp.198-201
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• 2001

Porous structures of aluminum foam have been studied by using return aluminum scrap. The apparent foam shape, foam height, density, pore size and their distributions in various section areas of the experimental samples have been investigated. The sample have been cast into metallic mold, using aluminum foam prepared from a precursor based on pure Al ingot and return aluminum scrap mixed with various amounts of 1-2wt% increasing viscosity and foam agent materials. The process provides for flexibility in design of foam structures via relatively easy control over the amount of hydrogen evolution and the drainage processes which occur during foam formation. This is facilitated by manipulating parameters such as the foaming agent, thermal histories during solidification and mix melt viscosities. A metal for producing the foamed are decomposing a foaming agent in a molten metal such that there is an initial and a subsequent expansion due to foaming agent. It has been found that the Al porous foaming with variation amount of 1∼2wt% foam agent and at 2min holding time, which melting temperature has appeared homogeneous pore size at 650∼700$^{\circ}C$. The compression strength were 10-13 kg/min at 125ppi, and increased by higher pore density. The acoustical performance of the panel made with the foamed aluminum is considerably improved; its absorption coefficient shows NRC 0.6-0.8. It has been found that the Al foam is very preferable for the compactness of the thermal system.

• 한국주조공학회지
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• 제30권6호
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• pp.241-246
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• 2010

The viscosity of foam metal is necessary to get the pores, but it is difficult to manufacture net-shape foam, because the fluidity decreases by increasing viscosity. In this study, the A356 alloy which has good fluidity and less defect was selected and fabricated to foam metal. To understand about effect of thickening agent on foaming and mechanical properties, quantity of thickening agent was changed. The pore size, porosity and distribution of foam metal were measured by i-solution program. And compression test were performed by UTM. In case of 3.0wt% Ca in thickening agent, it is found that most of foam consist of homogeneous shape, and the growth height had the highest value of 204 mm in the all fabricated foams. The porosity was 93% and compressive strength was 3.1 MPa. In the microstructure, the $Al_2Si_2Ca$ intermetallic compound and Ti were observed. The vickers hardness value rose with increasing viscosity value.

• 한국재료학회지
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• 제12권9호
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• pp.729-734
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• 2002

Porous Al metal was produced by batch type casting process. In this foaming process, the viscosity and surface tension of molten Al as two most important factors have been investigated in the temperature range of 680-95$0^{\circ}C$ by the ring method and rotational method respectively. The experimental results showed that both the surface tension and viscosity of the melt decreased linearly with increasing temperature. Addition of Ca decreased surface tension, but increased viscosity significantly.

• 한국주조공학회지
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• 제30권6호
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• pp.217-223
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• 2010

Foamed metal has become an attractive material, which has unique physical, thermal, acoustic, damping and mechanical properties, because large amount of pores are distributed in the metal matrix. Therefore, metal foam can be used for the light weight application in automotive, locomotive, aerospace fields. Aluminum foams have been developed successfully and will be employed in the next generation of energy absorption boxes. Magnesium alloys are most eligible candidate to substitute aluminum alloy, especially for lower density and higher damping properties in wide industrial fields. Magnesium alloy foams are expected to be particularly advantageous due to two thirds the density of aluminum. However, foaming magnesium have been weakness of high activity, difficult processing and very dangerous. In order to upgrade this problem, AM50 magnesium alloy which has better characteristic is safe to use through foaming time and alloying element in this study.

• 한국주조공학회지
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• 제31권3호
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• pp.145-151
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• 2011

Metallic foam has been known as a functional material which can be used for absorption properties of energy and sound. The unique characteristics of Al foam of mechanical, acoustic, thermal properties depend on density, cell size distribution and cell size, and these characteristics expected to apply industry field. Al-Zn-Mg-Cu alloy foams was fabricated by following process; firstly melting the Al alloy, thickening process of addition of Ca granule to increased of viscosity, foaming process of addition of titanium hydride powder to make the pores, holding in the furnace to form of cooling down to the room temperature. Metal foams with various porosity level were manufactured by change the foaming temperature. Compressive strength of the Al alloy foams was 2 times higher at 88% porosity and 1.2 times higher at 92% porosity than pure Al foams. It's sound and vibration absorption coefficient were higher than pure Al foams and with increasing porosity.

• 한국포장학회지
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• 제26권2호
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• pp.77-83
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• 2020

바이오매스가 포함된 발포구조체의 발포온도에 따른 SEM, 밀도, 공극률, 수분투과도 측정을 통해 특성 변화를 분석하였으며, 소비자가 해당 용기를 사용할 때의 열적 안정성을 확인하기 위해 MIL-STD규격에 따라 열충격 처리의 영향을 분석하였다. 측정 결과 발포온도가 증가할수록 대체로 기공의 크기는 증가하고 기공의 수는 감소하여 밀도는 통계적으로 유의한 차이가 없음을 확인하였다. 또한 공극률과 수분투과도 측정결과는 서로 다른 경향성을 보이고 있는데 이는 기공의 크기와 수, 기공 간의 구도가 변화하였기 때문인 것으로 사료되며, 이에 대한 추가적인 연구가 필요하다. 열충격 시험 결과, 열충격 반복횟수를 거듭할수록 기공의 크기가 감소하면서 밀도는 증가하고 공극률과 수분투과도는 감소하는 것을 확인할 수 있었다. 이는 시료에 고온을 가함으로써 시료가 연화되었고, 연화된 상태의 시료에 곧바로 저온을 가하여 시료가 수축되면서 기공의 크기와 구도가 변화하였기 때문인 것으로 판단된다. 하지만 밀도의 경우 통계적으로 유의한 차이가 없었으며 수분투과도의 경우 수치가 감소하는 경향을 확인할 수 있었으므로 해당 발포구조체로 제작된 HMR 용기는 열적 안정성이 있다고 판단할 수 있다.

• 한국결정성장학회지
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• 제29권6호
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• pp.298-307
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• 2019

본 연구에서는 Al₂O₃ 소결체 표면에 두 종류의 CaO-Al₂O₃-SiO₂(CAS) 계 유리 분말을 스프레이 코팅(spray coating) 후 소성 거동에 대하여 연구하였다; (1) Si-rich, SiO₂ 함량이 높은 유리, (2) Ca-rich, CaO 함량이 높은 유리. Ca-rich 유리는 점도가 약 10⁷~10⁹ poise일 때 유리 내부에 잔존하는 기포들의 심한 발포 현상이 일어났고 이에 따라 소결 방해에 따른 수축율이 감소하였으며 조도는 증가하였다. 반면, Si-rich 유리의 경우, 1000℃ 이하에서는 Ca-rich와 같은 심각한 발포현상은 없었으나, 1200℃에서 밀도가 낮은 크리스토발라이트(cristobalite) 결정 발생과 함께 기포의 재발포 현상이 일어나 수축율이 감소하였으며 조도가 증가하는 이상 소성 거동을 보였다. 이는 저밀도 크리스토발라이트 결정 생성으로 인한 유리질의 칼슘 함량 증가에 의한 점도 감소로 생각된다. 따라서 CAS계 유리의 경우 저온 소성에서는 발포 현상에 의한 표면조도 상승과 소결 방해를 고려해야 하며, 특히 SiO₂ 함량이 높을 경우, 고온에서 결정화에 의한 이상 발포 현상도 생각해야 한다.

• Elastomers and Composites
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• 제58권1호
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• pp.32-43
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• 2023

The worldwide use of polyurethane foam products generates large amounts of waste, which in turn has detrimental effects on the surroundings. Hence, finding an economical and environmentally friendly way to dispose of or recycle foam waste is an utmost priority for researchers to overcome this problem. In that sense, the glycolysis of waste flexible polyurethane foam (WFPF) from automotive seat cushions using different industrial-grade glycols and potassium hydroxide as a catalyst to produce recovered polyol was investigated. The effect of different molecular weight polyols, catalyst concentration, and material ratio (PU foam: Glycols) on the reaction conversion and viscosity of the recovered polyols was determined. The obtained recovered polyols are obtained as single or split-phase reaction products. Besides, the foaming characteristics and physical properties such as cell morphology, thermal stability, and compressive stress-strain nature of the regenerated flexible foams based on the recovered polyols were discussed. It was observed that the regenerated flexible foams displayed good seating comfort properties as a function of hardness, sag factor, and hysteresis loss compared to the reference virgin foam. With the growing demand for a sustainable and circular economy, a global valorization of glycolysis products from polyurethane scraps can be realized by transforming them into profitable substances.