• 제목/요약/키워드: BN nanoparticles

검색결과 9건 처리시간 0.027초

Hexagonal Boron Nitride Monolayer Growth without Aminoborane Nanoparticles by Chemical Vapor Deposition

  • Han, Jaehyu;Yeo, Jong-Souk
    • 한국진공학회:학술대회논문집
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    • 한국진공학회 2014년도 제46회 동계 정기학술대회 초록집
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    • pp.409-409
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    • 2014
  • Recently hexagonal boron nitride (h-BN), III-V compound of boron and nitrogen with strong covalent $sp^2$ bond, is a 2 dimensional insulating material with a large direct band gap up to 6 eV. Its outstanding properties such as strong mechanical strength, high thermal conductivity, and chemical stability have been reported to be similar or superior to graphene. Because of these excellent properties, h-BN can potentially be used for variety of applications such as dielectric layer, deep UV optoelectronic device, and protective transparent substrate. Ultra flat and charge impurity-free surface of h-BN is also an ideal substrate to maintain electrical properties of 2 dimensional materials such as graphene. To synthesize a single or a few layered h-BN, chemical vapor deposition method (CVD) has been widely used by using an ammonia borane as a precursor. Ammonia borane decomposes into hydrogen (gas), monomeric aminoborane (solid), and borazine (gas) that is used for growing h-BN layer. However, very active monomeric aminoborane forms polymeric aminoborane nanoparticles that are white non-crystalline BN nanoparticles of 50~100 nm in diameter. The presence of these BN nanoparticles following the synthesis has been hampering the implementation of h-BN to various applications. Therefore, it is quite important to grow a clean and high quality h-BN layer free of BN particles without having to introduce complicated process steps. We have demonstrated a synthesis of a high quality h-BN monolayer free of BN nanoparticles in wafer-scale size of $7{\times}7cm^2$ by using CVD method incorporating a simple filter system. The measured results have shown that the filter can effectively remove BN nanoparticles by restricting them from reaching to Cu substrate. Layer thickness of about 0.48 nm measured by AFM, a Raman shift of $1,371{\sim}1,372cm^{-1}$ measured by micro Raman spectroscopy along with optical band gap of 6.06 eV estimated from UV-Vis Spectrophotometer confirm the formation of monolayer h-BN. Quantitative XPS analysis for the ratio of boron and nitrogen and CS-corrected HRTEM image of atomic resolution hexagonal lattices indicate a high quality stoichiometric h-BN. The method presented here provides a promising technique for the synthesis of high quality monolayer h-BN free of BN nanoparticles.

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Neutron attenuation performance of EPDM rubber with BN Nanoparticles/B2O3 composite and studying physical, thermal and mechanical properties

  • H.M. Eyssa;Nabila A. Maziad;Wagdy Kansouh;Wageeh Ramadan
    • Nuclear Engineering and Technology
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    • 제56권11호
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    • pp.4563-4577
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    • 2024
  • The current study has focused on evolving materials with high attenuation performance and vigorous mechanical properties. Nano hexagonal boron nitride (h-BN) has been synthesized from boric acid and urea and then heated at a low temperature. XRD, SEM, EDX-mapping images, and FTIR investigated the nano h-BN synthesized and boron oxide (B2O3) milled. The new nanocomposites based on ethylene propylene diene rubber (EPDM), different concentrations of h-BN NPs, and B2O3 have been prepared. The physical, mechanical, and thermal properties and neutron attenuation behavior of nanocomposites were characterized. The shielding properties were determined by measuring the fast neutrons and total gamma-ray attenuation coefficients of the 239Pu-α-9Be neutron source. It was seen that adding a coupling agent (maleic anhydride) was appropriate for improving interfacial adhesions between EPDM chains and the nanofiller h-BN and B2O3 compared to EPDM unloaded. From the results, we observe that EPDM loaded with nano h-BN and nano h-BN/B2O3 was noticeably boosted over that of the unloaded EPDM for tensile strength (TS), EPDM/nano h-BN/B2O3 had a high TS at a concentration of 3 % h-BN/10 % B2O3 (42 %) compared with unloaded EPDM. Moreover, EPDM/3 % h-BN and EPDM/3 % h-BN/10 % B2O3 had the highest thermal stability until 490 ℃ compared to unloaded EPDM is stable at 350 ℃. Finally, the maximum macroscopic effective shielding behaviors and removal cross-section are estimated by incorporating h-BN 3 % into EPDM.

전기방사에 의한 질화붕소 나노분말의 함량에 따른 질화붕소 나노섬유 합성 및 특성 평가 (Characterization and Synthesis of BN Fibers According to the Content of BN Nanopowder by Electrospinning Method)

  • 이종혁;전명표;황진아;정영근;주제욱
    • 한국전기전자재료학회논문지
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    • 제31권7호
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    • pp.455-461
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    • 2018
  • Boron nitride (BN) nanofibers were fabricated using BN nanoparticles (70 nm) by electrospinning. Morphologies such as the diameter and density of the BN nanofibers are strongly influenced by the viscosity and dispersion state of the precursor solution. In this study, the precursor solution was prepared by ball milling BN nanoparticles and polyvinylpyrrolidone (PVP, Mw~1,300,000) in ethanol, which was electrospun and then calcined to produce BN fibers. High-quality BN nanofibers were well fabricated at a BN concentration of 15 wt% with their diameters in the range of 500 nm to 800 nm; the viscosity of the precursor solution was $400mPa{\cdot}S$. The calcination of the as-electrospun BN fibers seemed to be completed by holding them at $350^{\circ}C$ for 2 h considering the TGA data. The morphologies and phases of the BN fibers were investigated by scanning electron microscopy (SEM) and X-ray diffractometry (XRD), respectively; Fourier transform infrared (FT-IR) was also used for structure analysis.

육방정 질화붕소 나노입자의 결정성에 미치는 불화칼슘 첨가의 영향 (Effect of CaF2 Addition on the Crystallinity of Hexagonal Boron Nitride Nanoparticles)

  • 정재용;김양도;김영국
    • 대한금속재료학회지
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    • 제56권12호
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    • pp.915-920
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    • 2018
  • With the development of modern microelectronics technologies, the power density of electronic devices is rapidly increasing, due to the miniaturization or integration of device elements which operate at high frequency, high power conditions. Resulting thermal problems are known to cause power leakage, device failure and deteriorated performance. To relieve heat accumulation at the interface between chips and heat sinks, thermal interface materials (TIMs) must provide efficient heat transport in the through-plane direction. We report on the enhanced thermal conduction of $Al_2O_3-based$ polymer composites, fabricated by the surface wetting and texturing of thermally conductive hexagonal boron nitride(h-BN) nanoplatelets with large anisotropy in morphology and physical properties. The thermally conductive polymer composites were prepared with hybrid fillers of $Al_2O_3$ macro beads and surface modified h-BN nanoplatelets. Hexagonal boron nitride (h-BN) has high thermal conductivity and is one of the most suitable materials for thermally conductive polymer composites, which protect electronic devices by efficient heat dissipation. In this study, we synthesized hexagonal boron nitride nanoparticles by the pyrolysis of cost effective precursors, boric acid and melamine. Through pyrolysis at $900^{\circ}C$ and subsequent annealing at $1500^{\circ}C$, hexagonal boron nitride nanoparticles with diameters of ca. 50nm were synthesized. We demonstrate that the addition of a small amount of calcium fluoride ($CaF_2$) during the preparation of the melamine borate adduct significantly enhanced the crystallinity of the h-BN and assisted the growth of nanoplatelets up to 100nm in diameters. The addition of a small amount of h-BN enhanced the thermal conductivity of the $Al_2O_3-based$ polymer composites, from 1.45W/mK to 2.33 W/mK.

육방정 질화붕소 나노입자 합성 및 열전도성 복합체 응용 (Synthesis of Hexagonal Boron Nitride Nanocrystals and Their Application to Thermally Conductive Composites)

  • 정재용;김양도;신평우;김영국
    • 한국분말재료학회지
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    • 제23권6호
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    • pp.414-419
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    • 2016
  • Much attention has been paid to thermally conductive materials for efficient heat dissipation of electronic devices to maintain their functionality and to support lifetime span. Hexagonal boron nitride (h-BN), which has a high thermal conductivity, is one of the most suitable materials for thermally conductive composites. In this study, we synthesize h-BN nanocrystals by pyrolysis of cost-effective precursors, boric acid, and melamine. Through pyrolysis at $900^{\circ}C$ and subsequent annealing at $1500^{\circ}C$, h-BN nanoparticles with diameters of ~80 nm are synthesized. We demonstrate that the addition of small amounts of Eu-containing salts during the preparation of melamine borate precursors significantly enhanced the crystallinity of h-BN. In particular, addition of Eu assists the growth of h-BN nanoplatelets with diameters up to ~200 nm. Polymer composites containing both spherical $Al_2O_3$ (70 vol%) and Eu-doped h-BN nanoparticles (4 vol%) show an enhanced thermal conductivity (${\lambda}{\sim}1.72W/mK$), which is larger than the thermal conductivity of polymer composites containing spherical $Al_2O_3$ (70 vol%) as the sole fillers (${\lambda}{\sim}1.48W/mK$).

Lubricating Effect of Water-soluble Hexagonal Boron Nitride Nanolubricants on AISI 304 Steel Sliding Pair

  • Gowtham Balasubramaniam;Dae-Hyun Cho
    • Tribology and Lubricants
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    • 제39권2호
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    • pp.43-48
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    • 2023
  • In this study, we investigate the tribological behavior of AISI 304 stainless steel pairs under deionized water and hexagonal boron nitride (h-BN) water dispersion lubrication. The specimen friction and wear properties are evaluated using a reciprocating ball-on-flat tribometer. The coefficient of friction remains nearly constant throughout the test under both lubricant conditions. The wear depth of the specimens under h-BN lubrication is smaller than that under deionized water lubrication, indicating the inhibition behavior of h-BN nanolubricants on direct metal-metal contacts. Optical micrographs and stylus profilometer measurements are performed to evaluate the severity of damage caused by the sliding motion and to determine the wear morphology of the specimens, respectively. The results show that h-BN nanolubricants does not have a significant effect on the friction behavior but demonstrates reduced wear owing to their trapping effect between the sliding interfaces. Moreover, scanning electron microscopy and energy-dispersive X-ray spectroscopy images of the specimens were acquired to confirm the trapping effect of h-BN between the sliding interfaces. The results also suggest that the trapped lubricants can distribute the contact pressure, reducing the wear damage caused by the metal-metal contact at the interface. In conclusion, h-BN nanolubricants have potential as an anti-wear additive for lubrication applications. Further investigation is needed to provide direct evidence of the trapping effect of h-BN nanoparticles between the sliding interfaces. These findings could lead to the development of more efficient and effective lubricants for various industrial applications.

열전도도 및 전기전도도가 향상된 에폭시/보론나이트라이드/은나노입자 복합체의 제조 (Improvement of Thermal and Electrical Conductivity of Epoxy/boron Nitride/silver Nanoparticle Composite)

  • 김승용;임순호
    • Korean Chemical Engineering Research
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    • 제55권3호
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    • pp.426-429
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    • 2017
  • 본 연구에서는 은나노입자 및 보론나이트라이드의 혼합이 열전도도 및 전기전도도에 미치는 효과에 대해 고찰하였다. 에폭시/보론나이트라이드 복합체의 경우 열전도도가 보론나이트라이드의 함량에 비례하여 증가하였으며 에폭시/은나노입자의 경우는 열전도도가 크게 변화 없었으며 전기전도도는 20 vol%에서 퍼콜레이션 현상을 보여주었다. 퍼콜레이션 함량 이하에서 은나노입자를 고정시키고 보론나이트라이드를 첨가하여 조사한 결과 전기전도도 및 열전도도가 크게 향상됨을 알 수 있었다.

High-Dispersed V2O5-CuOX Nanoparticles on h-BN in NH3-SCR and NH3-SCO Performance

  • Han-Gyu Im;Myeung-Jin Lee;Woon-Gi Kim;Su-Jin Kim;Bora Jeong;Bora Ye;Heesoo Lee;Hong-Dae Kim
    • Nanomaterials
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    • 제12권14호
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    • pp.2329-2343
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    • 2022
  • Typically, to meet emission regulations, the selective catalytic reduction of NOX with NH3 (NH3-SCR) technology cause NH3 emissions owing to high NH3/NOX ratios to meet emission regulations. In this study, V-Cu/BN-Ti was used to remove residual NOX and NH3. Catalysts were evaluated for selective catalytic oxidation of NH3 (NH3-SCO) in the NH3-SCR reaction at 200-300 ℃. The addition of vanadium and copper increased the number of Brønsted and Lewis acid sites available for the reaction by increasing the ratio of V5+ and forming Cu+ species, respectively. Furthermore, h-BN was dispersed in the catalyst to improve the content of vanadium and copper species on the surface. NH3 and NOX conversion were 98% and 91% at 260 ℃, respectively. Consequently, slipped NH3 (NH3-Slip) emitted only 2% of the injected ammonia. Under SO2 conditions, based on the NH3 oxidation reaction, catalytic deactivation was improved by addition of h-BN. This study suggests that h-BN is a potential catalyst that can help remove residual NOX and meet NH3 emission regulations when placed at the bottom of the SCR catalyst layer in coal-fired power plants.