• 한국세라믹학회:학술대회논문집
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• 한국세라믹학회 2003년도 춘계총회 및 연구발표회 초록집
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• pp.123.2-123
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• 2003

• 한국환경과학회:학술대회논문집
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• 한국환경과학회 2020년도 정기학술대회 발표논문집
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• pp.226-226
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• 2020

• 한국재료학회지
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• 제8권11호
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• pp.1020-1025
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• 1998

Mn-Mo-Ni 저합금강의 중성자 조사에 따른 기계적(미세경도, 인장, 샤피충격시험) 및 자기적(포화자화, 보자력, 잔류자화, Barkhausen Noise(BN)진폭, BN에너지) 성질 변화를 측정하여 이들의 상관관계를 고찰하였다. 기계적 성질시험 결과, 중성자 조사로 인하여 항복강도, 인장강도, 미세경도 및 천이온도($T_{41J}$)는 증가하였고 최대흡수에너지(USE)는 감소하였으며, 인장 시험의 경우 용접금속에서는 모재와 비교했을 때 큰 변화가 없었다. 자기적 성질을 측정한 결과, 잔류자화, BN진폭, BN에너지는 감소하였고 보자력은 급격히 증가하는 것으로 나타났다. 기계적.자기적 성질변화의 상관관계에서 자기적성질인 보자력 증가에 따라 천이온도, 항복강도, 경도는 증가하고 USE는 감소하였고, BN진폭의 경우는 보자력과 반대의 경향을 보였다. 본 실험에서 중성자조사로 인한 기계적.자기적 성질변화가 일관성 있는 상관관계가 있음을 확인하였고, 이들의 변화를 통해 조사손상을 평가하는 데 이용 가능하다.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2015년도 제49회 하계 정기학술대회 초록집
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• pp.60-60
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• 2015

Nanosheets of graphene and related 2D materials have attracted much attention due to excellent physical, chemical and mechanical properties. Single-layer graphene (SLG) was first synthesized by Blakely et al in 1974 [1]. Following his achievements, we initiated the growth and characterization of graphene and h-BN on metal substrates using surface segregation and precipitation in 1980s [2,3]. There are three important steps for nanosheet growth; surface segregation of dopants, surface reaction for monolayer phase, and subsequent 3-D growth (surface precipitation). Surface phase transition was clearly demonstrated on C-doped Ni(111) by in situ XPS at elevated temperatures [4]. The growth mode was clarified by inelastic background analysis [5]. The surface segregation approach has been applied to C-doped Pt(111) and Pd(111), and controllable growth of SLG has been demonstrated successfully [6]. Recently we proposed a promising method for producing SLG fully covering an entire substrate using Ni films deposited on graphite substrates [7]. A universal method for layer counting has been proposed [8]. In this paper, we will focus on the effect of competitive surface-site occupation between carbon and other surface-active impurities on the graphene growth. It is known that S is a typical impurity of metals and the most surface-active element. The surface sites shall be occupied by S through surface segregation. In the case of Ni(110), it is confirmed by AES and STM that the available surface sites is nearly occupied by S with a centered $2{\times}2$ arrangement. When Ni(110) is doped with C, surface segregation of C may be interfered by surface active elements like S. In this case, nanoscopic characterization has discovered a preferred directional growth of SLG, exhibiting a square-like shape (Fig. 1). Also the detailed characterization methodologies for graphene and h-BN nanosheets, including AFM, STM, KPFM, AES, HIM and XPS shall be discussed.

• Composites Research
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• 제32권6호
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• pp.319-326
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• 2019

본 연구에서는 재활용이 가능하며 열가소성 특성을 지닌 신규 고분자 수지를 개발하고 합성하였다. 이렇게 개발된 수지와 판상형 질화붕소(h-BN) 사이의 계면 친화성이 좋음을 계산과학을 통하여 확인하고 열압기(hot press)를 이용하여 복합소재를 제조하였다. 고분자 수지와 필러 사이의 계면 친화성과 함께 복합소재 제조시 발생되는 전단력(shear force) 만으로도 매우 높은 필러 정렬도를 지닌 복합소재를 제조할 수 있었고, 이러한 이유로 복합소재는 최대 13.8 W/mK의 높은 열전도도를 갖는 것을 확인하였다. 또한, 개발된 수지가 화학적으로 분해 가능한 장점을 이용하여 제조된 복합소재로부터 물리/화학적 변성 없이 필러를 회수할 수 있었고 이렇게 회수된 필러는 향후 다양한 신규 복합소재 제조에 재활용이 가능하다.

• Composites Research
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• 제34권1호
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• pp.63-69
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• 2021

일체형 방열 및 기체 차단 재료 개발을 위하여 신규 고분자를 합성하고 판상형 육방정 질화 붕소(hBN) 필러를 포함하는 복합소재를 제조하였다. 복합소재는 필러의 크기 및 함량에 따라 열전도도 및 산소투과도 조절이 가능하였다. 복합소재는 최대 28.0 W·m-1·K-1의 높은 열전도도를 지녔으며 필러 미포함 샘플 대비 산소투과도는 62% 감소하였다. 열전도도 및 기체투과도 실험 측정값과 모델 예측값 비교를 통해 복합소재 내 필러의 종횡비를 계산하였다. 이러한 결과를 토대로 높은 열전도도 및 낮은 기체투과도는 필러 간 효과적인 네트워크 형성 때문이며 이는 복합소재 제조 시 전단 응력 극대화가 가능한 신규 수지의 특성으로부터 유래된것으로 사료된다. 또한, 열전도도로부터 계산된 필러 종횡비와 산소 투과도로부터 계산된 필러 종횡비 값이 서로 다름을 확인하였고 이에 관련하여 복합소재에서 열 전달 및 기체 투과 메커니즘에 대하여 고찰하였다. 본 연구에서 개발된 높은 열전도도 및 낮은 산소투과도를 갖는 고분자 복합소재는 전자 제품의 일체형 방열 및 산화 방지 재료로 사용 될 수 있다.

• 농업과학연구
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• 제49권4호
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• pp.995-1001
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• 2022

The purpose of this study was to compare the effect of solid-state fermentation on soybean using three microbial strains under four different fermentation times. Soybean was fermented for 12, 24, 36 or 48 hours with highly proteolytic microbes, either Bacillus amyloliquefaciens (BA), B. subtilis (BS), or B. subtilis var. natto (BN), and levels of total protein concentration, protein distribution, and antioxidant activity were analyzed. Total protein was highest in the BS 12 h group (9.21 ㎍·µL^-1) and lowest in BN 48 h (6.80 ㎍·µL^-1), respectively (p < 0.001). Furthermore, three microbes decomposed large molecular weight proteins as well as major allergens of soybean such as β-conglycinin, Gly m Bd 30K, and glycinin. Each treatment group showed the highest degradation rate at 48 h fermentation and among the three microbes, BS showed a relatively higher degradation rate. The radical scavenging ability, known as an indicator of antioxidant activity, showed a significant increase in all treatment groups except BA 24 h. The results from this study suggest that protein concentration, and degradation and antioxidant activity were affected by different types of microbial trains and fermentation period and that B. subtilis fermentation might be the most effective way to increase nutritional and functional properties of soybean.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
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• pp.284-284
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• 2016

Topological insulator (TI) is a bulk-insulating material with topologically protected Dirac surface states in the band gap. In particular, $Bi_2Se_3$ attracted great attention as a model three-dimensional TI due to its simple electronic structure of the surface states in a relatively large band gap (~0.3 eV). However, experimental efforts using $Bi_2Se_3$ have been difficult due to the abundance of structural defects, which frequently results in the bulk conduction being dominant over the surface conduction in transport due to the bulk doping effects of the defect sites. One promising approach in avoiding this problem is to reduce the structural defects by heteroepitaxially grow $Bi_2Se_3$ on a substrate with a compatible lattice structure, while also preventing surface degradation by encapsulating the pristine interface between $Bi_2Se_3$ and the substrate in a clean growth environment. A particularly promising choice of substrate for the heteroepitaxial growth is hexagonal boron nitride (h-BN), which has the same two-dimensional (2D) van der Waals (vdW) layered structure and hexagonal lattice symmetry as $Bi_2Se_3$. Moreover, since h-BN is a dielectric insulator with a large bandgap energy of 5.97 eV and chemically inert surfaces, it is well suited as a substrate for high mobility electronic transport studies of vdW material systems. Here we report the heteroepitaxial growth and characterization of high quality topological insulator $Bi_2Se_3$ thin films prepared on h-BN layers. Especially, we used molecular beam epitaxy to achieve high quality TI thin films with extremely low defect concentrations and an ideal interface between the films and substrates. To optimize the morphology and microstructural quality of the films, a two-step growth was performed on h-BN layers transferred on transmission electron microscopy (TEM) compatible substrates. The resulting $Bi_2Se_3$ thin films were highly crystalline with atomically smooth terraces over a large area, and the $Bi_2Se_3$ and h-BN exhibited a clear heteroepitaxial relationship with an atomically abrupt and clean interface, as examined by high-resolution TEM. Magnetotransport characterizations revealed that this interface supports a high quality topological surface state devoid of bulk contribution, as evidenced by Hall, Shubnikov-de Haas, and weak anti-localization measurements. We believe that the experimental scheme demonstrated in this talk can serve as a promising method for the preparation of high quality TI thin films as well as many other heterostructures based on 2D vdW layered materials.

• E2M - 전기 전자와 첨단 소재
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• 제16권1호
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• pp.60.1-60
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• 2003

• The Korean Journal of Ceramics
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• 제2권4호
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• pp.184-187
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• 1996

Diamod nucleation by mw assisted CVD was examined various conditions namely, (1) diamond nucleation on variour substrate materials, such as Si, cubic BN, pyrolytic BN and AIN, (2) AST(Activated species transport) method which promote nucleation of diamond on single crystal and polycrystalline alumina substrate was developed. (3) Effect of bias enhancement of nucleation on single crystalline Si was examined, and finally (4) DST (Double step treatment) method was developed to enhance diamond nucleation on Ni. In this method, we separated carbon diffusing process into Ni, carbon precipitating process from the inside of Ni and diamond precipitation process.