• Title/Summary/Keyword: 기공 밀도

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Modified Gurson Model to Describe Non-linear Compressive Behaviour of Polyurethane Foam with Considering Density Effect (폴리우레탄 폼의 비선형 압축거동을 모사하기 위한 밀도 영향이 고려된 수정 Gurson 모델의 제안)

  • Lee, Jeong-Ho;Park, Seong-Bo;Kim, Seul-Kee;Bang, Chang-Seon;Lee, Jae-Myung
    • Journal of the Computational Structural Engineering Institute of Korea
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    • v.28 no.5
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    • pp.543-551
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    • 2015
  • Polyurethane Foam(PUF), a outstanding thermal insulation material, is used for various structures as being composed with other materials. These days, PUF composed with glass fiber, Reinforced PUF(R-PUF), is used for a insulation system of LNG Carrier and performs function of not only the thermal insulation but also a structural member for compressive loads like a sloshing load. As PUF is a porous material made by mixing and foaming, mechanical properties depend on volume fraction of voids which is a dominant parameter on density. Thus, In this study, density is considered as the effect parameter on mechanical properties of Polyurethane Foam, and mechanical behavior for compression of the material is described by using modified Gurson damage model.

Manganese Doped LiFePO4 as a Cathode for High Energy Density Lithium Batteries (고에너지밀도 리튬전지를 위한 망간이 첨가된 LiFePO4 양극재료)

  • Kim, Dul-Sun;Kim, Jae-Kwang;Ahn, Jou-Hyeon
    • Journal of the Korean Electrochemical Society
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    • v.16 no.3
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    • pp.157-161
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    • 2013
  • Porous $LiMn_{0.6}Fe_{0.4}PO_4$ (LMFP) was synthesized by a sol-gel process. Uniform dispersion of the conductive carbon source throughout LMFP with uniform carbon coating was achieved by heating a stoichiometric mixture of raw materials at $600^{\circ}C$ for 10 h. The crystal structure of LMFP was investigated by Rietveld refinement. The surface structure and pore properties were investigated by SEM, TEM and BET. The LMFP so obtained has a high specific surface area with a uniform, porous, and web-like nano-sized carbon layer at the surface. The initial discharge capacity and energy density were 152 mAh/g and 570 Wh/kg, respectively, at 0.1 C current density, and showed stable cycle performance. The combined effect of high porosity and uniform carbon coating leads to fast lithium ion diffusion and enhanced electrochemical performance.

A Study on the Possibility of Bulk Graphite Manufacturing using Coal Tar as a Binder and an Impregnant (콜타르를 결합재 및 함침재로 이용한 벌크 흑연 제조)

  • Lee, Sang-Min;Lee, Sang-Hye;Kang, Dong-Su;Roh, Jae-Seung
    • Composites Research
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    • v.34 no.1
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    • pp.51-56
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    • 2021
  • This paper studied the possibility of manufacturing bulk graphite using coal tar, a precursor of coal tar pitch, as a binder and impregnant. Carbonization was conducted after mixing and molding with natural graphite as a filler and coal tar as a binder. Impregnation-recarbonization was performed five times after carbonization. Coal tar used as impregnant. Measuring density, porosity, compressive strength, and anisotropy ratio was conducted. The maximum density of bulk graphite specimen was 1.76 g/㎤ and the minimum porosity was 15.6% which could be controlled by process control. The highest compressive strength was 20.3 MPa. Then the maximum anisotropic ratio of bulk was shown 0.34 through XRD analysis. Therefore, it was confirmed that it was possible to manufacture artificial graphite in a bulk form by using coal tar as a binder and an impregnant.

Geographic Variation in Needle Characteristics of Pinus densiflora in Korea (우리나라 자생 소나무의 지역에 따른 침엽특성 변이)

  • Shin, Chang-Ho;Kim, Kyu-Sick;Lee, Cheul-Ho
    • Korean Journal of Plant Resources
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    • v.20 no.4
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    • pp.336-341
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    • 2007
  • This study was carried out to investigate geographic variation in needle characteristics of Pinus densiflora, one of the most economically important tree species in Korea. Needles were collected from 35 natural populations and their morphological and anatomical characteristics were studied. ANOVA showed statistically significant differences among populations as well as among individuals within populations in needle length, needle width, number of stomata row, density of stomata in $0.25mm^{2}$, number of serrations in 0.5mm, and number of resin ducts. In all these traits, variance components among individuals within populations were larger than those among populations. The density of stomata in $0.25mm^{2}$ increased as the latitudes and elevations of the populations increased, while the number of serrations in 0.5mm decreased as the decrease of latitudes and elevations. The number of resin ducts was higher in inland populations than in coastal populations. The resin duct index appeared to be higher in western populations than in eastern populations. Cluster analysis based on morphological characteristics divided populations into three groups. The third group was composed of populations selected from the Taebaek mountains. The number of serrations in 0.5mm of this group was lower than that of other two groups, while the density of stomata in $0.25mm^{2}$ was higher.

Bread-Making Properties of Domestic Wheats Cultivars (국내산 밀의 제빵 적성에 관한 연구)

  • 남재경;한영숙
    • Korean journal of food and cookery science
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    • v.16 no.1
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    • pp.1-8
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    • 2000
  • Six Domestic Wheat Tapdong, Eunpa, Kobun, Olgru, Uri, Kumgang cultivars and one standard wheat Dark Northern Spring (DNS) were milled and determined bread-making properties of dough and bread made the wheats. The ash contents of DNS showed 0.54%, on the other hand, domestic wheat flours showed lower contents than DNS, and Kumgang was the lowest. The Protein contents which suggest the flour gluten content showed 11.68% in DNS cultivars, however 13.85% in Kumgang, 12.35% in Eunpa, 12.32% in Kobun. Valorimeter value in Farinograph data for Kumgang, Kobun, Eunpa cultivars which evaluate the dough formation time and stability showed better result than DNS. Resistance rate in Extensograph for Tapdong and Kobun showed higher rate than DNS. Gelatinization temperature in Amylograph for DNS, Tapdong, Eunpa, Kobun, Kumgang revealed 59$\^{C}$, 59$\^{C}$, 58$\^{C}$, 58$\^{C}$, 59$\^{C}$ respectively, but Uri, Olgru cultivars showed upper temperature which suggest the two cultivars was not suitable for bread making. W(gluten strength) in Alveograph data for DNS showed 297, however, 386 for Tapdong, 327 for Kumgang which indicated that the upper domestic wheat cultivars satisfactory the bread-making properties. In the CO$_2$production of straight bread doughs measured with Meissle fermenter for 5hr, Kumgang cultivar showed the highest CO$_2$ as 333 mg per 30 g of dough. The breads prepared with the above domestic wheat flours showed acceptable quality in sensory test for parameters such as volume, color of crust, symmetry of form, crust, evenness, grain, color, texture, aroma, taste, but the bread made DNS seemed to be superior in organoleptic property to the breads made with domestic wheat flours. The sponge dough bread made with Kumgang cultivars showed the best organoleptic quality among the wheat flours tested. These results indicate that the Kumgang seemed to be practical wheat variety for bread-making.

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Method to control the Sizes of the Nanopatterns Using Block Copolymer (블록 공중합체를 이용한 나노패턴의 크기제어방법)

  • Kang, Gil-Bum;Kim, Seong-Il;Han, Il-Ki
    • Journal of the Korean Vacuum Society
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    • v.16 no.5
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    • pp.366-370
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    • 2007
  • Nano-scopic holes which are distributed densely and uniformly were fabricated on $SiO_2$ surface. Self-assembling resists were used to produce a layer of uniformly distributed parallel poly methyl methacrylate (PMMA) cylinders in a polystyrene (PS) matrix. The PMMA cylinders were degraded and removed by acetic acid rinsing. Subsequently, PS nanotemplates were fabricated. The patterned holes of PS template were approximately $8{\sim}30\;nm$ wide, 40 nm deep, and 60 nm apart. The porous PS template was used as a dry etching mask to transfer the pattern of PS template into the silicon oxide thin film during reactive ion etching (RIE) process. The sizes of the patterned holes on $SiO_2$ layer were $9{\sim}33\;nm$. After pattern transfer by RIE, uniformly distributed holes of which size were in the range of $6{\sim}22\;nm$ were fabricated on Si substrate. Sizes of the patterned holes were controllable by PMMA molecular weight.

Quantification Analysis of Element Surface by Fractal Dimension (프랙탈 차원에 의한 소자 표면의 정량화 분석)

  • Kyung-Jin, Hong
    • The Journal of the Institute of Internet, Broadcasting and Communication
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    • v.23 no.1
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    • pp.145-149
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    • 2023
  • High-resolution images of surfaces provide detailed information on pores or shapes with specific sizes ranging from nano sizes to micrometers. However, it is not yet clear to determine an efficient association for pores or shapes from high-resolution images of surfaces. For the efficient association of pores and shapes, the surface characteristics of the device were considered as fractal dimensions by taking SEM photographs and binarizing the images. The fractal program was directly coded for surface analysis of the device. The device surface characteristics and electrical characteristics are thought to be related to the fractal dimension. The fractal dimension decreased with an increase in internal pores. The density and grain boundary of particles, which are structural characteristics of the device surface, were related to the fractal dimension. The particle size decreased with an increase in the fractal dimension and was uniformly formed. When the particles were uniformly formed, fewer pores were present and the fractal dimension increased.

블록 공중합체 박막을 이용한 금 나노점 및 실리콘 나노점의 형성

  • Gang, Gil-Beom;Lee, Chang-U;Kim, Yong-Tae;Kim, Seong-Il
    • Proceedings of the Korean Society Of Semiconductor Equipment Technology
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    • 2007.06a
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    • pp.90-93
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    • 2007
  • 밀도가 높고 주기적으로 배열된 실리콘 나노점이 실리콘 기판위에 형성 되었다. 실리콘 나노점을 형성하기 위해 사용된 나노패턴의 지름은 20 나노미터(nm)이고 깊이는 40 nm 이었으며 기공과 기공사이의 거리는 50 nm 였다. 나노미터 크기의 패턴을 형성시키기 위해서 자기조립물질을 사용했으며 폴리스티렌(PS) 바탕에 벌집형태로 평행하게 배열된 실린더 모양의 폴리메틸메타아크릴레이트(PMMA)의 구조를 형성하였다 폴리메틸메타아크릴레이트를 아세트산으로 제거하여 폴리스티렌만 남아있는 나노크기의 마스크를 만들었다. 형성된 나노패턴에 전자빔 기상증착장치를 사용하여 금 박막을 $100\;{\AA}$ 증착하고 리프트오프(lift-off) 방식으로 금 나노점을 만들었다. 형성된 금 나노점을 불소기반의 화학반응성 식각법을 이용하여 식각하고 황산으로 제거하였다. 형성된 실리콘 나노점의 지름은 24 nm 였고 높이는 20 nm 였다.

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Silicon Melt Infiltration of Reaction-Bonded Silicon Carbide (반응소결 탄화규소에서 실리콘의 침윤향상)

  • 신현익;김주선;이종호;김긍호;송휴섭;이해원
    • Journal of the Korean Ceramic Society
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    • v.39 no.7
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    • pp.693-698
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    • 2002
  • Reaction-Bonded Silicon Carbide (RBSC) Ceramics were fabricated which satisfies the maximum packing density of silicon carbide skeleton in the green compacts. Such a high packing density induced incomplete infiltration during reaction-sintering; forms linear void around the interface of large alpha silicon carbide powders. During reaction-sintering, the limited extraction and entrapped gas induced by residue oxide was considered to be a reason of linear void formation. In order to improve infiltration behavior in the highly packed preform, the pre-treatment methods for residue oxide removal were proposed.

Effects of Consolidation Methods and Surface Modified Layer on the Packing Structure of Nanometer Scale Alumina Powder (알루미나 나노분말의 충전구조엣 미치는 충전방법 및 표면개질층의 영향)

  • 이해원;전형우;박종구;이종호;송휴섭
    • Journal of the Korean Ceramic Society
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    • v.37 no.11
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    • pp.1078-1083
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    • 2000
  • 정전안정화 및 입체안정화를 동시에 적용한 복합안정화기구에 의하여 25 부피%의 나노 $Al_2$O$_3$슬러리를 제조하고, 이로부터 얻은 주입성형체, 원심성형체, 진공성형체의 기공구조 분석을 통하여 입자충전거동을 살펴보았다. 나노 알루미나 분말의 습식 성형체의 충전구조는 성형방법에 의하여 가해지는 외력의 영향을 크게 받지만, 반발력을 제공하는 표면장벽층의 상호작용에 의해서도 현저한 차이를 보이는 것으로 나타났다. 예비소결실험을 통하여 나노분말에서도 기공크기가 작고, 크기분포가 좁으며, 높은 밀도를 가진 균일성형체의 미세구조가 소결미세구조를 균일하게 하는데 필수적인 조건임을 확인하였다.

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