Uniform Boron Nitride Research Articles

Uniform Boron Nitride Nanospheres with Reactive Surface Defects for Composite Solid-State Electrolytes

Uniform Boron Nitride Nanospheres with Reactive Surface Defects for Composite Solid-State Electrolytes

The effect of boron nitride interphase on the thermal stability of SiC fibers

The SiC fibers were coated with uniform boron nitride interphase by chemical vapor infiltration (CVI). The as-received and BN-coated fibers were heat-treated in flowing nitrogen for 2 h to investigate the effect of BN interphase on the thermal stability of fibers. Tensile strengths of as-received and BN-coated fibers have been measured at room temperature. The effects of heat-treatment on the tensile strengths of fibers were investigated using Weibull distribution. The results showed the deposited BN interphase has turbostratic structure, with nano crystallites of h-BN randomly orientated. Heat-treatment improved the crystallization degree of BN interphase. The as-received fibers had a tensile strength of 2.56 GPa and a Weibull modulus of 5.39. The BN-coated fibers showed lower tensile strength than the as-received fibers, on account of the increased diameter and soft nature of BN. The average strengths of fibers decreased, and BN-coated fibers showed higher strength retention than as-received fibers at the same heat-treatment temperature due to the protection of BN interphase. The BN interphase acts as a compliant layer, which reduces the thermal damage to SiC fibers during heat-treatment.

Coating with boron nitride on SiC fiber using atomic substitution

To increase the mechanical properties of ceramic matrix composite, it is important that formation of lubricant layer for crack deflection between matrix and fiber. Therefore, we fabricated uniform boron nitride (BN) lubricant layer using atomic substitution method. Silicon carbide (SiC) fiber surface was modified with amine groups using (3-amonipropyl)triethoxysilane to coat SiC fiber with BN as a solid lubricant. Then, surface was coated with graphene oxide (GO). Boric acid powder was supplied to the GO-coated fibers and the samples were heat-treated at 1200–1400 ℃ under N2 and NH3 atmospheres. An uniform BN layer could be coated on SiC fiber with 10 nm-1.11 μm. Crystallinity and thickness of BN layer could be controlled by reaction temperature. It was also confirmed that crystalline BN formed under process conditions of higher than 1400 ℃.

The microstructure and mechanical properties of silicon carbide fibers with boron nitride interphase

The 2nd generation SiC tows is a type of essentially polycrystalline fibers (SiC1.46O0.03). Smooth and uniform boron nitride interphase was deposited on SiC fibers by low pressure chemical vapor infiltration (CVI). The scanning electron microscopy(SEM) was used to characterize the microstructure of the BN interphase and fibers while X-ray diffraction(XRD) and TEM were used to characterize the phase constitute of the fibers. The XRD and TEM results showed that the BN interphase prepared by CVI is turbostratic. The effects of thickness on the mechanical properties of SiC fibers were investigated by using two-parameter Weibull distribution. The fibers with thin BN interphase showed higher strength than the as-received fibers, for healing the surface flaws. However, the soft nature of increasing BN thickness had a more dominant effect and resulted in the decrease of fiber strength.

Synthesis, structure and antioxidant performance of boron nitride (hexagonal) layers coating on carbon nanotubes (multi-walled)

Carbon nanotube/Boron nitride(CNT/BN) nanocomposites were performed by a facile method with boric acid (H3BO3) and melamine (C3H6N6). Uniform boron nitride (BN) precursor deposition films were deposited onto the surface of multiwall carbon nanotubes (MWCNTs),which involves attachment of the precursor and subsequent nitridation in ammonia atmosphere at 1050 °C. The qualitative and quantitative analysis of X-ray diffraction (XRD) on the crystal structure and phase composition. Scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to characterize the material surface morphology and coating structure. Chemical composition analysis of surface and chemical bonds formed by X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared Spectroscopy (FTIR) confirmed as well as the oxidation resistance under high temperature by thermal gravimetric analysis and differential thermal analysis (TG-DTA). The results indicate that the boron nitride coating on carbon nanotubes composite has been synthesized successfully by this method and greatly improves the antioxidant performance of carbon nanotubes compared with the original carbon nanotubes (690 °C, compared to 550 °C of original carbon nanotubes), which provides a potential application at high temperatures for carbon nanotube materials.

Straightforward Deposition of Uniform Boron Nitride Coatings by Chemical Vapor Deposition

ABSTRACTBoron nitride (BN) has a very high thermal conductivity and excellent thermal shock resistance. These properties make BN an important material for industrial applications involving surfaces in contact with molten metals. These applications require straightforward deposition methods that produce uniform BN coatings. Using borazine (B3N3H6) as a precursor, we deposited BN coatings on silicon substrates by cold-wall chemical vapor deposition (CVD). The microstructure, composition, and morphology of the coatings were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and electron energy loss spectroscopy (EELS). These characterizations show that the BN coatings deposited are uniform, predominantly of hexagonal structure, and N-rich.

Coating of titanium implants with boron nitride by RF-magnetron sputtering

Surface modification is necessary for titanium implants since it is unable to induce bone apposition. The beneficial effects of boron on bone formation, composition and physical properties make it suitable as a coating material. In the present study, surface properties of boron nitride (BN) coating on titanium implants were evaluated. Twenty-four implants and 12 abutments were coated with BN by RF-magnetron sputtering system. ATR–FTIR measurements were conducted to assess surface chemistry and morphology of BN-coated implants. Adhesion tests were performed by CSM nanoscratch test device to determine adhesion of BN to titanium surface. Surface profilometry and atomic force microscopy (AFM) was used to evaluate surface roughness. Mean roughness values were calculated. Contact angle measurements were done for evaluation of wettability. Surface characterization of coated implants was repeated after RF power of the system was increased and voltage values were changed to evaluate if these settings have an impact on coating quality. Three different voltage values were used for this purpose. Hexagonal-BN was determined in FTIR spectra. RF-coating technique provided adequate adherence of BN coatings to the titanium surface. A uniform BN coating layer was formed on the titanium implants with no deformation on the titanium surface. Similar roughness values were maintained after BN coating procedure. Before coating, the contact angles of the implants were in between 63∘ and 79∘, whereas BN coated implants’ contact angles ranged between 46∘ and 67∘. BN-coated implant surfaces still have hydrophilic characteristics. The change in voltage values seemed to affect the surface coating characteristics. Especially, the phase of the BN coating was different when different voltages were used. According to our results, BN coating can be sufficiently performed on pretreated implant surfaces and the characteristics of BN coated surfaces can be changed with the change in parameters of RF-magnetron sputtering system.

Direct chemical conversion of graphene to boron- and nitrogen- and carbon-containing atomic layers

Graphene and hexagonal boron nitride are typical conductor and insulator, respectively, while their hybrids hexagonal boron carbonitride are promising as a semiconductor. Here we demonstrate a direct chemical conversion reaction, which systematically converts the hexagonal carbon lattice of graphene to boron nitride, making it possible to produce uniform boron nitride and boron carbonitride structures without disrupting the structural integrity of the original graphene templates. We synthesize high-quality atomic layer films with boron-, nitrogen- and carbon-containing atomic layers with full range of compositions. Using this approach, the electrical resistance, carrier mobilities and bandgaps of these atomic layers can be tuned from conductor to semiconductor to insulator. Combining this technique with lithography, local conversion could be realized at the nanometre scale, enabling the fabrication of in-plane atomic layer structures consisting of graphene, boron nitride and boron carbonitride. This is a step towards scalable synthesis of atomically thin two-dimensional integrated circuits.

Dielectric properties of BN modified carbon fibers by dip-coating

Continuous and uniform boron nitride (BN) coatings were synthesized on carbon fibers by dip-coating and their microstructure, chemical composition and dielectric properties were investigated. Results show that the as-prepared coatings are composed of phase mixture of h-BN and amorphous t-BN. The oxidation property of the BN modified carbon fibers is improved with higher initial and final oxidation temperatures. Both the real (ε′) and imaginary part (ε″) of permittivity of the BN modified carbon fibers decrease significantly compared with the pure carbon fibers. The decrease of ε′ can be mainly attributed to the absence of dielectric relaxation effect, while the decrease of ε″ can be ascribed to the large decrease in electrical conductivity. The decreasing permittivity leads to increase of microwave impedance which is beneficial for electromagnetic matching. With improved impedance match and still relatively high ε″, the BN modified carbon fibers exhibit a promising prospect as microwave absorbing materials.