Presence Of BN Research Articles

A novel temperature-responsive mixed matrix ultrafiltration membrane based on boron nitride nanomaterial

A novel mixed matrix membrane was prepared by blending polysulfone with two-dimensional boron nitride followed by its hydroxyl functionalization. Prepared nanocomposite membranes were characterized for the surface morphology, surface roughness, zeta potential and hydrophilicity. Uniform dispersion of boron nitride nanoparticles in polysulfone matrix and consequent changes in membrane properties were confirmed by scanning electron microscope images, atomic force microscope images, zeta potential, contact angle analysis, and X-Ray photoelectron spectroscopy. Differential scanning calorimetry (DSC) technique was used to determine the glass transition temperature (Tg) of the modified membrane and the results revealed the presence of BN in the membrane matrix. The highest water flux of 329.52 Liters per sqm per hour (LMH) was obtained in case of PS/BN (1%) as compared to 151.87 LMH of virgin membrane and Albumin rejection also increased by nanocomposites membranes up to certain concentration of Boron nitride. A unique behavior of temperature responsiveness of nanocomposite membrane was observed, where a steep increment in permeate flux by 205% at higher temperature was noted as compared to the virgin Polysulfone membrane where only 103% increase was recorded for the same temperature range. Moreover, the water uptake capacity of nanocomposite membranes were measured to understand the changes with nanomaterial incorporation. The membrane showed a good promise for high-temperature separation applications.

Role of heteroatoms and substituents on the structure, reactivity, aromaticity, and absorption spectra of pyrene: a density functional theory study

Abstract Effect of heteroatoms viz. BN and substituents viz. –Me (methyl), –OH (hydroxyl), –NH2 (amine), –COOH (carboxyl), and –CN (cyano) on the structural parameters, global reactivity, aromaticity, and UV-visible spectra of pyrene are studied with the help of density functional theory (DFT). Global reactivity parameters such as global hardness (η) and electrophilicity (ω) are calculated using density functional reactivity theory (DFRT). Time dependent density functional theory (TD-DFT) is explored for interpreting the UV-visible absorption spectra. Aromaticity of the pyrene rings are predicted from the nucleus independent chemical shift (NICS) values. Presence of BN unit and substituent induces reasonable impact on the studied parameters. The observed absorption spectra lie predominantly within the UV-region (both blue and red shifts are observed in presence of BN and substituent). HOMO energy and absorption spectra are affected nominally in solvent phase.

Corrosion Behavior of SHS-Produced Cu–Ti–B Composites

Metal-matrix Cu–Ti–B nanocomposites were prepared by SHS method and their corrosion behavior was characterized by XRD, atomic force microscopy, polarization testing, and electrochemical impedance spectroscopy. Microhardness of synthesized composites attained a value of up to 544 HV. The presence of BN, Cu3Ti, and TiO phases leads to formation of Cu/BN, Cu/Cu3Ti, and Cu/TiO galvanic pairs which accelerate corrosion.

Synergistic effect of BN and MWCNT hybrid fillers on thermal conductivity and thermal stability of ultra-high-molecular-weight polyethylene composites with a segregated structure

The thermal conductivity of ultra-high-molecular-weight polyethylene (UHMWPE)/boron nitride particle (BNp), UHMWPE/BN sheet (BNs), and UHMWPE/(BN+MWCNT) hybrid filler composites with segregated structures was investigated using a powder mixture and hot-pressing process. The morphology of the fillers and composites was observed by optical microscopy, atomic force microscopy, and scanning electron microscopy, respectively. The results showed that the torispherical BNp filler contained particles of various dimensions, ranging from 200 to 500 nm, while the saucer-shaped BNs filler with irregular prominence on the edge exhibited uniformity of size, with widths of 100–150 nm and height of 3–5 nm. The networks of thermally conductive fillers and the interfacial thermal resistance at the filler boundaries played a major role in the thermal conductivity of the segregated composites, as revealed in an almost linear enhancement of conductivity with increasing filler content. In comparison to the 2D saucer-shaped BNs fillers, the varied size of the 0D BNp was more conducive to the formation of effective filler stacks, as the gaps between larger BNp fillers facilitated access by the smaller BNp fillers. The thermal conductivity of the UHMWPE composite with the addition of 50 wt% BNp increased from 0.4591 to 1.385 W/m·K, approximately 16.2 % higher than that of the UHMWPE/BNs composite (1.192 W/m·K). The synergistic effect of the BN+MWCNT hybrid fillers helped to improve the thermal conductivity of the UHMWPE composites. Compared with the 0D BNp filler, the 2D BNs was more readily entangled with 1D MWCNT and formed compact and overlapping thermally conductive networks. As such, the thermal conductivity of the UHMWPE/(BNs+MWCNT) hybrid filler composite (1.641 W/m·K for 50 wt% filler content) was superior to that of the UHMWPE/(BNp+MWCNT) composite (1.533 W/m·K). Additionally, the crystallization behavior and thermal stability of UHMWPE was almost unchanged in the presence of BN and BN+MWCNT hybrid fillers.

Electronic properties of T graphene-like C–BN sheets: A density functional theory study

We have used density functional theory to study the electronic properties of T graphene-like C, C–BN and BN sheets. The planar T graphene with metallic property has been considered. The results show that the presence of BN has a considerable effect on the electronic properties of T graphene. The T graphene-like C–BN and BN sheets show semiconducting properties. The energy band gap is increased by enhancing the number of BN units. The possibility of opening and controlling band gap opens the door for T graphene in switchable electronic devices.

Three-Dimensional Model for Erosion of a Hall-Effect Thruster Discharge Channel Wall

The erosion of the channel wall in Hall-effect thrusters limits the maximum thruster operating lifetime. Hall-effect thruster channel wall materials are often binary composites of BN and . The heterogeneity of the material drives the development of complex surface features and roughness during the erosion process. A three-dimensional model of the atomic sputtering of a heterogeneous material is developed. The model investigates, through a ray-tracing technique and empirical erosion rate models of each phase, the interaction between the plasma and the material microstructure. Simulated surface profiles are compared with experimental data collected from the eroded channel wall of the U.S. Air Force Research Laboratory/University of Michigan P5 Hall-effect thruster. The channel wall is composed of M26, a composite material. Simulated surface features and roughnesses for an ion incidence angle of 30 deg resemble those observed through scanning electron microscopy and optical profilometry of the P5 channel wall. Predicted root mean square roughnesses, for 30 deg ion incidence, of are within 33% of the root mean square measured experimentally. The composition of the channel wall surface is investigated via x-ray photoelectron spectroscopy and is comparable to prior work, but the reduction in the presence of BN with erosion is not adequately captured by this model.

Fabrication of an ultrasensitive impedimetric buprenorphine hydrochloride biosensor from computational and experimental angles.

For the first time, an ultrasensitive impedimetric buprenorphine hydrochloride (BN) biosensor based on immobilization of bovine serum albumin (BSA) onto multi-walled carbon nanotubes (MWCNTs)/glassy carbon electrode (BSA/MWCNTs/GCE) has been developed using initial characterization by computational methods and complementing them by experimental observations. Computational results showed that the BSA hydrophobically binds to MWCNTs which is energetically favorable and leads to spontaneous formation of the stable BSA/MWCNTs nanobiocomposite (bioconjugate). Computational results also showed that the interaction of BN with BSA is mainly driven by hydrophobic interactions. The interactions of BSA with MWCNTs and BN with BSA were also monitored by fluorescence and UV-vis spectroscopic techniques, and their results were consistent with the computational results. Morphology and electrochemical properties of the fabricated composite electrodes were examined by scanning electron microscopy (SEM), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). Besides complementing the computational studies, experimental results showed that the addition of MWCNTs to the surface of the GCE greatly facilitated the electron transfer reactions, and also showed that the presence of BSA inhibits the interfacial electron transfer in some extent due to the non-conductive properties of BSA. On the other hand, the presence of BN may form an electroactive complex with BSA which accelerates the interfacial electron transfer and leads to obvious Faradaic impedance changes. The Faradaic impedance responses were linearly related to BN concentration between 5.0 nM and 72.0 nM and a limit of detection (LOD, 3S(b)/b) of 1.5 nM was achieved. Finally, the proposed biosensor was successfully applied to determination of BN in urine samples of both healthy and addict volunteers. The results were satisfactory and comparable to those obtained by applying the reference method based on high performance liquid chromatography-ultraviolet detection (HPLC-UV). It is expected that the distinctive features of BSA/MWCNTs nanobiocomposite would make it potentially advantageous for a broad range of biosensing, and clinical applications.

Incorporation of boron and nitrogen in carbon nanomaterials and its influence on their structure and opto-electronical properties

The presence of hexagonal boron nitride in the initial C:BN:Ni:Y 2O 3 mixture in the arc-discharge process leads to the modification of carbon nanostructures and to the creation of B x C y N z entities. BN-incorporation into these carbon nanostructures (single-wall nanotubes and carbon flakes) has been analyzed by high resolution transmission electron microscopy and electron energy loss spectroscopy. The optical absorption spectroscopy measurements have revealed a monotonous increase of the bandgap value of the synthesized nanotubes with the increase of the content of BN phase in the initial mixture of the synthesis compounds. Furthermore, a narrowing of the nanotube diameter distribution in favor of small diameters takes place in the presence of BN during the synthesis process.

Heat treatment of silica-fiber-reinforced BN-Si3N4 matrix composite

A new wave-transparent composite reinforced by silica fibers with a hybrid matrix comprising BN and Si3N4 was prepared by precursor infiltration and pyrolysis, and it was heat-treated at elevated temperatures. The variations of the composite during heat treatments were characterized and investigated by Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The as-received composite exhibits good mechanical properties, and it is almost amorphous. When treated at 1600°C, it turned brittle, and silica fibers in it were fused; the composite showed a good crystalline form. When treated at 2100°C, the composite broke into pieces, and the composition showed only BN. Si3N4 was decomposed, and silica fibers were volatilized. The presence of BN probably affected the phase transitions of silica fibers.

The effect of BN addition on thermal shock behavior of fiber reinforced porous ceramic composite

Fiber reinforced ceramic composite (mullite fiber/α-Al 2O 3 powder) was produced by the organic flocculating method. Air-quenching was employed to determine the drop in bending strength of the composite after thermal shock, and the critical temperature of the composites with different fiber contents. The thermal shock behavior was found to improve significantly by the addition of 3% hexagonal boron nitride (H-BN). The critical temperature reached up to 1000 °C, compared to 500 °C without presence of BN. The mechanism was investigated through a relative experiment and XRD study.

Interaction of ZDDP with Borated Dispersant Using XANES and XPS

The thermochemical reaction and tribochemical reaction of zinc dialkyldithiophosphate (ZDDP), a borated dispersant, and the mixture of ZDDP and borated dispersant on steel surfaces were investigated. Both pin-on-disk and ball-on-disk were used to generate tribofilms. The chemical state of nitrogen, boron, phosphorus, and sulfur in heated oil solutions, thermal films, and tribofilms were analyzed by X-ray absorption near edge structure (XANES) spectroscopy to obtain the chemical nature of species on the surface and in the bulk of the films. High-resolution X-ray photoelectron spectroscopy (XPS) has also been used to analyze boron (B) in tribofilms.The borated dispersant in base oil by itself yields good anti-wear behavior. This can be attributed to the presence of boron in the dispersant. The wear scar widths (WSW) for ZDDP alone, and in combination with the dispersant, yield similar results within the experimental error. It was found that the borated dispersant facilitates the decomposition of ZDDP and the formation of phosphate in tribofilms and thermal films. B K-edge XANES shows that boron has a trigonal coordination in the untreated additive, but the coordination changes partially to a tetrahedral coordination in the tribofilm upon rubbing. No BN was detected in the film analyzed by B K-edge or N K-edge. Boron 1s XPS also did not show the presence of BN in the film.

ESCA characterization of boron and silicon carbide mixed layers deposited on HR and HM carbon fibres by RCVD: properties of the as-coated fibres

Coatings of mixed boron and silicon carbides were produced on the surface of various carbon fibres by a reactive chemical vapour deposition process using a mixture of BCl 3, SiCl 4 and H 2. For application as reinforcing components in advanced composites, the surface of the some coated fibres was characterized by electron spectroscopy for chemical analysis since the properties of a composite material can depend on possible reactions between the two components of the material. Experimental parameters, such as treatment time, temperature and initial composition of the gaseous phase, have been studied in order to fabricate a mixed layer which did not contain boron or silicon elements, boron silicides or oxidized compounds. In addition to SiC and B 4C, the presence of BN was also found in the coating of T300 fibres based on poly(acrylonitrile); this BN formation is explained by a reaction between nitrogen which is an impurity in the raw fibre and the gas input in the reactor. Thermodynamic calculations and experiments confirmed this hypothesis. Analytical investigations were supplemented by strength measurements, which showed that the coating has only a small effect on the tensile strength of the fibres. Scanning electron microscopic examination of a coated fibre/A1 composite (fabricated by a squeeze-casting method) evidenced no trace of reaction between the fibre and matrix.

Chemoselective deprotection of benzyl esters in the presence of benzyl ethers, benzyloxymethyl ethers and n-benzyl groups by catalytic transfer hydrogenation

-COOBn, -PO(OH)OBn, -O-CBz and -N-CBz groups are efficiently and chemoselectively deprotected in the presence of Bn and BOM ethers and N-Bn groups by hydrogenolysis under catalytic transfer hydrogenation using 10 % palladium on carbon as the catalyst and cyclohexadiene as the hydrogen donor.