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Chemical Vapor Infiltration of the Hexagonal Boron Nitride Interphase for SiC Fiber-Reinforced HP-Si<sub>3</sub>N<sub>4</sub> Matrix Composite
摘要： This work describes the processing of SiC fiber-reinforced Si3N4 matrix composites with boron nitride (BN) interphase. The BN interphase was processed by chemical vapor infiltration (CVI) with BF3/NH3 gaseous precursors. The BN interphase modification involved the continuous treatment of Hi-Nicalon SiC fibers. The relations between (i) the processing parameters, (ii) the mechanisms controlling the kinetics of the CVI of the BN, and (iii) the structure of the deposited BN are presented. A single- or multi-layer BN interphase can be produced depending on the CVI conditions imposed on the fibers during the continuous process. A surface reaction mechanism controlling the CVI promotes a smooth, isotropic BN coating. An anisotropic BN coating can be produced when the CVI kinetics are controlled by a mass transport mechanism. With a controlled temperature gradient, the BN interphase is then made by stacking successive isotropic and anisotropic layers.
关键词： SiC fibers (Hi-Nicalon),CVI,boron nitride interphase
更新于2025-09-23 15:22:29
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The effect of boron substitution for aluminium on the microstructure of calcium fluoro-aluminosilicate glasses and glass-ceramics
摘要： Calcium fluoro-aluminosilicate (4.5SiO2-3Al2O3-1.5P2O5-3CaO-2CaF2) glasses have significant applications in the medical and dental fields. However, due to the biological hazard of aluminium in the human body, this study focused on the influence of boron substitution for aluminium on the structure and properties of a series of substituted glasses and their correlated glass-ceramics. The results indicated that by increasing the amount of boron, the density of glasses and their glass-ceramics both decreased, whereas the number of bridging oxygens in the glasses increased. The glass transition temperature and the crystallization temperature remained almost unchanged for the glasses with a boron substitution of less than 25 mol%. Boron formed oxygen bridges in all glasses in the form of BO3 triangles and BO4 tetrahedra. Reducing the Al content in glasses, had an effect on the morphology and orientation of the fluorapatite crystal phase formed.
关键词： Mullite,Fluorapatite,Boron-Substitution,Calcium fluoro-aluminosilicate glasses
更新于2025-09-23 15:21:21
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Convergent and Functional-Group-Tolerant Synthesis of B-Organo BODIPYs
摘要： Boron-dipyrromethenes (BODIPYs) are one of the most important fluorescent materials. Despite their potential unique properties, however, B,B-fluoro-organo BODIPYs (BFR-BODIPYs) possessing an organo group (R) on the boron center have not been studied in detail, due in part to challenges related to their synthesis. In this paper, a convergent synthesis of BFR-BODIPYs operative under mild conditions is reported. Conversions of the thus-synthesized functionalized BFR-BODIPYs by cross-coupling, condensation, and SN2 reactions at the R group are also demonstrated.
关键词： convergent synthesis,Boron-dipyrromethenes,fluorescent materials,BODIPYs,functionalized BFR-BODIPYs
更新于2025-09-23 15:21:21
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AIP Conference Proceedings [Author(s) SolarPACES 2017: International Conference on Concentrating Solar Power and Chemical Energy Systems - Santiago, Chile (26–29 September 2017)] - Use of ilmenite and boron waste as a radiation shielding panel
摘要： Ilmenite is an important and interesting metallic oxide mineral. It is a titanium-iron oxide mineral with formula FeTiO3. It is the primary ore of iron and titanium metal. The largest boron mineral reserves in the world are located in Turkey. Each year 900,000 tons of boron waste results from boron production. Boron waste is caused big environmental problem in Turkey. In this study, evaluation of ilmenite and boron waste was performed to investigate the potential use in shielding materials. In this study, incorporation of ilmenite-boron waste has been investigated for its effect on the physical, morphological, mechanical and shielding properties. Several mixtures were prepared with different proportions of ilmenite and boron waste ranging from 0% to 50%. Then they dried and sintered at 1000, 1050 and 1100 (cid:113)C for 2 hours. Sintered samples were characterized.
关键词： environmental problem,ilmenite,boron waste,sintering,radiation shielding
更新于2025-09-23 15:21:21
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Tracing Boron with Fluorescence and PET Imaging of Boronated Porphyrin Nanocomplex for Imaging Guided Boron Neutron Capture Therapy
摘要： Boron neutron capture therapy (BNCT) induces high-energy radiation within cancer cells while avoiding damage to normal cells that without uptake of BNCT drugs, which is holding great promise to provide excellent control over locally invasive malignant tumors. However, lack of quantitative imaging technique to determine local boron concentration has been a great challenge for nuclear physicians to apply accurate neutron irradiation during the treatment, which is a key factor that has limited BNCT’s application in clinics. To meet this challenge, this study describes coating boronated porphyrins with a biocompatible Poly(lactide–co-glycolide)–monomethoxy-poly(polyethylene-glycol) (PLGA-mPEG) micelle for selective tumor accumulation and reduced toxicity comparing with previously reported boronated porphyrin drugs. Fluorescence imaging and PET imaging were performed, unveiling the potential imaging properties of this boronated porphyrin nanocomplex (BPN) to locate tumor region and to determine tissue-localized boron concentration which facilitates treatment planning. By studying the pharmacokinetics of BPN with Cu-64 PET imaging, the treatment plan was adjusted from single bolus injection to multiple times of injections of smaller doses. As expected, high tumor uptake of boron (125.17±13.54 ppm) was achieved with an extraordinarily high tumor to normal tissue ratio: tumor to liver, muscle, fat and blood were 3.24±0.22, 61.46±20.26, 31.55±10.30 and 33.85±5.73, respectively. At last, neutron irradiation with BPN showed almost complete tumor suppression, demonstrating that BPN holds a great potential for being an efficient boron delivery agent for imaging-guided BNCT.
关键词： copper-64,boron neutron capture therapy,theranostics,positron emission tomography,micelle
更新于2025-09-23 15:21:21
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Electrical and Electromagnetic Interference (EMI) shielding properties of hexagonal boron nitride nanoparticles reinforced polyvinylidene fluoride nanocomposite films
摘要： The hexagonal boron nitride nanoparticles (h-BNNPs) reinforced flexible polyvinylidene fluoride (PVDF) nanocomposite films were prepared via a simple and versatile solution casting method. The morphological, thermal and electrical properties of h-BNNPs/PVDF nanocomposite films were elucidated. The electromagnetic interference (EMI) shielding properties of prepared nanocomposite films were investigated in the X-band frequency regime (8–12 GHz). The EMI shielding effectiveness (SE) was increased from 1 dB for the PVDF film to 11.21 dB for the h-BNNPs/PVDF nanocomposite film containing 25 wt% h-BNNPs loading. The results suggest that h-BNNPs/PVDF nanocomposite films can be used as lightweight and low-cost EMI shielding materials.
关键词： Hexagonal boron nitride,PVDF,SEM,EMI shielding,DSC,electrical properties
更新于2025-09-23 15:21:21
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Electronic structure of graphene nanoribbons on hexagonal boron nitride
摘要： Hexagonal boron nitride is an ideal dielectric to form two-dimensional heterostructures due to the fact that it can be exfoliated to be just a few atoms thick and its very low density of defects. By placing graphene nanoribbons on high quality hexagonal boron nitride it is possible to create ideal quasi-one-dimensional systems with very high mobility. The availability of high quality one-dimensional electronic systems is of great interest also given that when in proximity to a superconductor they can be effectively engineered to realize Majorana bound states. In this work we study how a boron nitride substrate affects the electronic properties of graphene nanoribbons. We consider both armchair and zigzag nanoribbons. Our results show that for some stacking configurations the boron nitride can significantly affect the electronic structure of the ribbons. In particular, for zigzag nanoribbons, due to the lock between spin and sublattice degree of freedom at the edges, the hexagonal boron nitride can induce a very strong spin splitting of the spin-polarized, edge states. We find that such spin splitting can be as high as 40 meV.
关键词： heterostructures,graphene nanoribbons,hexagonal boron nitride,spin splitting,electronic structure
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Work function of polarized boron 2D atomic crystal
摘要： We discuss the method to calculate the work function of polarized materials with first principles calculation. Then we take boron 2D atomic crystal as an example. We found that the Alkali metal adsorbates decrease the work function of the surface with adsorbates, while the work function of the other surface is unaffected, when the alkali metal atoms are absorbed on only one surface of the boron sheet. The reason is attributed to the polarization between the alkali metal atoms and the boron sheet.
关键词： work function,2D atomic crystal,boron
更新于2025-09-23 15:21:21
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Effect of low-energy ion impact on the structure of hexagonal boron nitride films studied in surface-wave plasma
摘要： A high‐density surface‐wave plasma source is used to deposit hexagonal boron nitride (hBN) films in a gas mixture of He, H2, N2, Ar, and BF3 under a high ion flux condition using low‐energy ion irradiation. The ion energy is controlled between around zero and 100 eV by applying a negative or positive bias voltage to a substrate, while the ion flux is increased by locating a substrate upstream in the diffusive plasma. For ion energies above ～37 eV, the structure of the films depends upon ion energy more than substrate temperature, typical of subplantation processes. As a result, the structural order and crystallinity of sp2‐bonded phase in the films characterized by Fourier transform infrared spectroscopy and X‐ray diffraction are increased with decreasing ion energy, while the mass density of the films characterized by X‐ray reflectivity is retained relatively high with a slight dependence upon ion energy.
关键词： surface‐wave plasma,Fourier transform infrared spectroscopy (FTIR),chemical vapor deposition (CVD),hexagonal boron nitride (hBN),X‐ray diffraction (XRD),X‐ray reflectivity (XRR)
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Field Emission Performance of Boron Nitride Nanotube Emitters According to Vacuum Pressure
摘要： Field emission performance of boron nitride nanotube filtration-transfer fabricated by simple method, were evaluated according to vacuum pressure to estimate its potential use for robust electron sources. Even though there is little change in the current density-electric field characteristics, the stability test for a relatively long time shows somewhat large degradation at a vacuum pressure of over 10-6 Torr. To investigate a key factor of the degradation, we changed the vacuum ambient from air to argon. Under argon ambient condition, the current degradation and fluctuation rates were almost the same as those measured under air ambient at a vacuum pressure of 10-5 Torr. Consequently, ion bombardment dominantly induced the current degradation of the BNNT field emitters rather than oxidation effect.
关键词： Boron nitride nanotube,field emitter,film emitter,cold cathode
更新于2025-09-23 15:21:21