• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.2
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• pp.116-121
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• 2019

Hexagonal boron nitride particles (s-hBN) modified with 3-aminopropyl triethoxysilane (APTES) were used for the preparation of silicone composite materials. The microstructure of the composite materials was observed, and the thermal conduction and mechanical characteristics of the composite sheets were studied based on the compositions and microstructures. When a small amount of s-hBN particles was used, the thermal conductivity of the composite improved as a whole, and the tensile strength of the sheet also increased. The thermal conductivity and tensile strength of the composite in which a small amount of carbon fiber was added along with s-hBN were further improved. However, the use of carbon nanotubes with structural characteristics similar to those of carbon fiber resulted in lower thermal conductivity and tensile strength. Elastic silicone composites exhibiting 2.5 W/mK of thermal conductivity and a low hardness are expected to be used as thermally conductive interfacial sheet materials.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.391-392
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• 2012

Graphene is a perfectly two-dimensional (2D) atomic crystal which consists of sp2 bonded carbon atoms like a honeycomb lattice. With its unique structure, graphene provides outstanding electrical, mechanical, and optical properties, thus enabling wide variety of applications including a strong potential to extend the technology beyond the conventional Si based electronic materials. Currently, the widespread application for electrostatically switchable devices is limited by its characteristic of zero-energy gap and complex process in its synthesis. Several groups have investigated nanoribbon, strained, or nanomeshed graphenes to induce a band gap. Among various techniques to synthesize graphene, chemical vapor deposition (CVD) is suited to make relatively large scale growth of graphene layers. Direct growth of graphene on hexagonal boron nitride (h-BN) using CVD has gained much attention as the atomically smooth surface, relatively small lattice mismatch (~1.7％) of h-BN provides good quality graphene with high mobility. In addition, induced band gap of graphene on h-BN has been demonstrated to a meaningful value about ~0.5 eV.[1] In this paper, we report the synthesis of grpahene / h-BN bilayer in a chemical vapor deposition (CVD) process by controlling the gas flux ratio and deposition rate with temperature. The h-BN (99.99％) substrate, pure Ar as carrier gas, and $CH_4$ are used to grow graphene. The number of graphene layer grown on the h-BN tends to be proportional to growth time and $CH_4$ gas flow rate. Epitaxially grown graphene on h-BN are characterized by scanning electron microscopy, atomic force microscopy, and Raman spectroscopy.

• Composites Research
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• v.32 no.6
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• pp.319-326
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• 2019

To address tremendous needs for developing efficiently heat dissipating material with lightweights, a new class of polymer possessing recyclable and malleable characteristics was synthesized for incorporating model functional hexagonal boron nitride (h-BN) filler. A good interfacial affinity between the polymer matrix and the filler along with shear force generated upon manufacturing the composite yielded the final product bearing highly aligned filler via simple hot pressing method. For this reason, the composite exhibited a high thermal conductivity of 13.8 W/mK. Moreover, it was possible to recover the h-BN from the composite without physical/chemical denaturation of the filler by chemically depolymerizing the matrix, thus the recovered filler can be re-used in the future. We believe this polymer could be beneficial as matrix for incorporating many other functional fillers, thus they may find applications in various polymeric composite related fields.

• Journal of the Korean institute of surface engineering
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• v.40 no.2
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• pp.91-97
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• 2007

In this study we investigated the oxygen effect on the nucleation and its residual stress during unbalanced magnetron sputtering. Up to 0.5% in oxygen flow rate, cubic phase (c-BN) was dominated with extremely small fraction of Hexagonal phase (h-BN) of increasing trend with oxygen concentration, whereas hexagonal phase is dominated beyond 0.75% flow rate. Interestingly, the residual stress in cubic-phase-dominated films was substantially reduced with small amount of oxygen (${\sim}0.5%$) down to a low value comparable to the h-BN case. This may be because oxygen atoms break B-N $sp^3$ bonds and make B-O bonds more favorably, increasing $sp^2$ bonds preference, as revealed by FTIR and NEXAFS. It was confirmed by experimental facts that the threshold bias voltage for nucleation and growth of cubic phase were increased from -55 V to -70 V and from -50 V to -60 V respectively. The reduction of residual stress in O-added c-BN films is seemingly resulting from the microstructure of the films. The oxygen tends to increase slightly the amount of h-BN phase in the grain boundary of c-BN and the soft h-BN phase of 3D network including surrounding nano grains of cubic phase may relax the residual stress of cubic phase.

• Tribology and Lubricants
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• v.37 no.4
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• pp.125-128
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• 2021

A means of enhancing the performance of triboelectric nanogenerators (TENGs) is increasing the differences in work functions between contacting materials. Hexagonal boron nitride (h-BN) exhibits excellent mechanical properties and high chemical stability as well as a high work function. As a result, engineers in the field of energy harvesting have envisioned using h-BN in the electrification layer in TENGs. For the industrial application of h-BN in TENGs, large-scale production is necessary, and h-BN is generally exfoliated and dispersed in various solvents. In this study, we evaluate the performance of a TENG with h-BN nanoflakes in the polyimide (PI) layer. To synthesize a PI composite containing h-BN nanoflakes, h-BN powders are exfoliated and dispersed in poly(amic acid) (PAA), which is the precursor of PI. Then, h-BN dispersion is spin-coated onto the PI film and cured for 2 h under 300℃. This composite material can then be used for the electrification layer in TENGs. Below the electrification layer, an aluminum foil is placed and used as an electrode. When the contact and separation processes with polyethylene terephthalate are repeated, the fabricated TENG shows a maximum power density of 190.8 W/m². This study shows that h-BN is a promising material for enhancing the performance of the electrification layer in TENGs.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.16 no.1
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• pp.36-41
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• 2017

In this paper, $Si_3N_4/hBN$ ceramics with various hexagonal boron nitride (hBN) contents (0, 10, 20, or 30 wt%) were fabricated via spark plasma sintering (SPS) at $1500^{\circ}C$, 50MPa, and 10m holding time. The material properties such as the relative density, hardness, and fracture toughness were systematically evaluated according to the hBN content in the $Si_3N_4/hBN$ ceramics. The results show that relative density, hardness, and fracture toughness continuously decreased as the hBN content increased. In addition, peak-step drilling (with tool diameter $500{\mu}m$) was performed to observe the effects of hBN content in micro-hole shape and cutting force. A machined hole diameter of $510{\mu}m$ (entrance) and stable cutting force were obtained at 30 wt% hBN content. Consequently, $Si_3N_4/30wt%$ hBN ceramic is a feasible material upon which to apply semi-conductor components, and this study is very meaningful for determining correlations between material properties and machining performance.

• Journal of the Microelectronics and Packaging Society
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• v.25 no.4
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• pp.95-99
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• 2018

High thermal conductivity films with electrically insulating properties have a great potential for the effective heat transfer as substrate and thermal interface materials in high density and high power electronic packages. There have been lots of studies to achieve high thermal conductivity composites using high thermal conductivity fillers such alumina, aluminum nitride, boron nitride, CNT and graphene, recently. Among them, hexagonal-boron nitride (h-BN) nano-sheet is a promising candidate for high thermal conductivity with electrically insulating filler material. This work presents an enhanced heat transfer properties of ceramic/polymer composite films using h-BN nano-sheets and PVA polymer resins. The h-BN nano-sheets were prepared by a mechanical exfoliation of h-BN flakes using organic media and subsequent ultrasonic treatment. High thermal conductivities over $2.8W/m{\cdot}K$ for transverse and $10W/m{\cdot}K$ for in-plane direction of the cast films were achieved for casted h-BN/PVA composite films. Further improvement of thermal conductivity up to $13.5W/m{\cdot}K$ at in-plane mode was achieved by applying uniaxial compression at the temperature above glass transition of PVA to enhance the alignment of the h-BN nano-sheets.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.399-399
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• 2012

최근 그래핀 연구와 더불어 2차원 구조의 나노소재에 대한 관심이 급증하면서 육각형의 질화붕소(hexagonal boron nitride; h-BN) 나노시트(nanosheet)[1]나 붕소 탄화질화물(boron caronitride;BCN) 나노시트[2, 3]와 같은 2차원 구조체에 대한 연구가 활발히 진행되고 있다. 그 중 BCN은 반금속(semimetal)인 흑연(graphite)과 절연체인 h-BN이 결합된 나노시트로 원소의 구성 비율에 따라 전기적 특성을 제어할 수 있다는 장점이 있다. 따라서 다양한 나노소자로의 응용을 위한 연구가 활발히 진행되고 있다. 본 연구에서는 열 화학기상증착법(thermal chemical vapor deposition)을 이용하여 폴리스틸렌(polystyrene)과 보레인 암모니아(borane ammonia)를 사용하여 BCN 나노시트를 합성하였다. 합성된 BCN 나노시트의 구조적 특징과 화학적 조성 및 결합 상태를 주사전자현미경(scanning electron microscopy), 투과전자현미경(transmission electron microscopy), X-선 광전자 분광법(X-ray photoelectron spectroscopy), 라만 분광법(Raman spectroscopy)을 통해 조사하였고, 이온성 용액법 (ionic liquid)[4]을 이용하여 전계효과 특성을 측정하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.617-617
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• 2013

최근 그래핀 연구와 더불어 2차원 구조의 나노소재에 대한 관심이 급증하면서 육각형의 질화붕소(hexagonal boron nitride; h-BN) 박막(nanosheet) [1]이나 붕소 탄화질화물(boron caronitride; BCN) 박막 [2,3]과 같은 2차원 구조체에 대한 연구가 활발히 진행되고 있다. 그 중 BCN은 반금속(semimetal)인 흑연(graphite)과 절연체인 h-BN이 결합된 박막으로 원소의 구성 비율에 따라 전기적 특성을 제어할 수 있다는 장점이 있다. 따라서 다양한 나노소자로의 응용을 위한 연구가 활발히 진행되고 있다. 본 연구에서는 폴리스틸렌(polystyrene, PS)과 보레인 암모니아(borane ammonia)를 고체 소스로 이용하여 열화학기상증착법으로 BCN 박막을 SiO2 기판 위에 직접 합성하였다. SEM과 AFM 관측을 통해 합성된 BCN 박막의 두께가 약 10 nm이며, RMS roughness가 0.5~2.6 nm로 매우 낮은 것을 확인하였다. 합성과정에서 PS의 양을 조절하여 BCN 박막의 탄소의 밀도를 성공적으로 제어하였으며, 이에 따라 전기적인 특성이 제어되는 양상을 확인하였다. 또한 합성온도 변화에 따른 BCN 박막의 전기적인 특성이 제어되는 양상을 확인하였다. 추가적으로 같은 방법을 이용하여 BCN 박막을 Cu 위에서 합성하여 SiO2 기판위에 전사하였다. 합성된 BCN 박막의 구조적 특징과 화학적 조성 및 결합 상태를 투과전자현미경(transmission electron microscopy), X-선 광전자 분광법(X-ray photoelectron spectroscopy), 라만 분광법(Raman spectroscopy)을 통해 조사하였고, 이온성 용액법(ionic liquid) [4]을 이용하여 전계효과 특성을 측정하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.08a
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• pp.255-255
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• 2013

최근 그래핀 연구와 더불어 2차원 구조의 나노소재에 대한 관심이 급증하면서 육각형의 질화붕소(hexagonal boron nitride; h-BN) 박막(nanosheet)이나 붕소 탄화질화물(boron caronitride; BCN) 박막과 같은 2차원 구조체에 대한 연구가 활발히 진행되고 있다. 그 중 BCN은 반금속(semimetal)인 흑연(graphite)과 절연체인 h-BN이 결합된 박막으로 원소의 구성 비율에 따라 전기적 특성을 제어할 수 있다는 장점이 있다. 따라서 다양한 나노소자로의 응용을 위한 연구가 활발히 진행되고 있다. 본 연구에서는 폴리스틸렌(polystyrene, PS)과 보레인 암모니아(borane ammonia)를 고체 소스로 이용하여 열화학 기상증착법을 이용하여 BCN 박막를 SiO2 기판 위에 직접 합성하였다. SEM과 AFM 관측을 통해 합성된 BCN 박막을 확인하였으며, RMS roughness가 0.5~2.6 nm로 매우 낮은 것을 확인하였다. 합성과정에서 PS의 양을 조절하여 BCN 박막의 탄소의 밀도를 성공적으로 제어하였으며, 이에 따라 전기적인 특성이 제어되는 양상을 확인하였다. 또한 합성온도 변화에 따른 BCN 박막의 전기적인 특성이 제어되는 양상을 확인하였다. 추가적으로 같은 방법을 이용하여 BCN 박막을 Ni 위에서 합성하여 SiO2 기판위에 전사 하였다. 합성된 BCN 박막의 구조적 특징과 화학적 조성 및 결합 상태를 투과전자현미경(transmission electron microscopy), X-선 광전자 분광법(X-ray photoelectron spectroscopy)을 통해 조사하였다.