Nitride Composites Research Articles

Enhanced Boron Nitride/Polyolefin Blends for High Voltage Applications

The effect of improved exfoliation on the electrical properties of hexagonal boron nitride (h-BN) composites based on polyethylene and polypropylene was studied. Chemical and thermal treatments were used to obtain exfoliated h-BN which was initially added to the host polymer at 2 wt. %. Scanning electron microscopy was used to study the particle dispersion, whilst measurements of AC breakdown strength and electrical conductivity were used to assess dielectric performance. It was found that an acid/hydrogen peroxide method was effective at exfoliating h-BN as evinced by an absence of large micron-scale aggregates in electron micrographs. A 20% increase in AC breakdown strength and a factor of 5 decrease in the electrical conductivity was attained relative to the unfilled host polymer. Composites employing exfoliated h-BN were then compared to analogous systems employing untreated h-BN over a wide compositional range. Whilst there was some advantage in incorporating untreated h-BN over the properties of the unfilled host polymer, the use of treated h-BN allowed maximum AC breakdown strength to be obtained at much lower filler loadings (∼2%) than hitherto reported. This allows a much smaller h-BN loading to be used for enhanced dielectric properties, reducing manufacturing costs. In addition, at high filler loadings, the thermal conductivity could be usefully improved. Such enhanced materials could be deployed in high voltage cables and capacitors.

Artificial light-harvesting 2D photosynthetic systems with iron phthalocyanine/graphitic carbon nitride composites for highly efficient CO2 reduction

Fabricating high-efficient 2D artificial photosynthetic systems for CO2 reduction based on phthalocyanine/graphitic carbon nitride composites.

Novel BN‐epoxy/anhydride composites with enhanced thermal conductivity

A new series of high thermal boron nitride (BN) composites are prepared and characterized by several techniques. They are formed by an epoxy‐anhydride matrix and different BN contents, ranging from 30 to 80 wt%, of 120 μm agglomerates. For high BN ratio (≥60 wt%), epoxy mixtures were compressed (75 MPa) during 1 minute before curing, eliminating voids due to the high increase of viscosity, improving the compactness of the material and enhancing the thermal conductivity (TC). The curing process evolution was studied by calorimetric measurements to see if there was an influence of the filler on the curing rate. Rheological tests were performed to obtain the percolation threshold. It was observed that BN filler did not affect negatively the thermomechanical properties of the materials and allowed to enhance the TC from 0.17 W/m K in the case of the neat epoxy, to 3.06 W/m K when 80 wt% of BN agglomerates were added, which represents an improvement of 1700%.

SYNTHESIS, CHARACTERIZATION AND PHOTOCATALYTIC APPLICATIONS OF S-DOPED GRAPHITIC CARBON NITRIDE NANOCOMPOSITES WITH NICKEL DOPED ZINC OXIDE NANOPARTICLES

Coprecipitation method was adopted for the synthesis of undoped and Ni-doped zinc oxide nanoparticles. The photocatalytic activity of the synthesized particles was examined by degradation of methylene blue under UV bulb. The S-doped graphitic carbon nitride was obtained by calcination of thiourea and composites were formed with S-doped graphitic carbon nitride and nickel doped zinc oxide nanoparticles using liquid exfoliation method. The ethanol and water were used as solvents for the liquid exfoliation. The photocatalytic activity was performed under UV and visible light by using a UV-visible spectrophotometer with different concentrations of composites for the degradation of methylene blue. The doping of nickel on zinc oxide nanoparticles and formation of sulfur doped graphitic carbon nitride composites were confirmed by FTIR and XRD analyses. The FTIR analysis sowed a signal at 838cm-1 due to the presence of Ni-O bond. The peaks at 3649cm-1 and 3735cm-1 confirmed the presence of amide group. The shift in absorption maxima from 364nm to 376nm (red shift) in UV spectrum was a confirmation of increased Ni content. The different concentrations of composites showed great impact on the degradation of methylene blue.

Colorful Silver/Carbon Nitride Composites Obtained by Photoreduction

The Ag+ photoreduction by graphitic carbon nitride(g-CN) materials in a high concentration of Ag+ solution is reported, and a series of colorful Ag/g-CN composites is prepared and characterized. The chromatic change correlates to the carbon nitride materials synthesized at different heating temperatures(CNT, where T means heating temperature), taking advantage of the different photocatalytic activities of different CNT. The mechanism beneath this phenomenon is attributed to two factors: the particle size of Ag NPs and the coordinate effect of Ag NPs on CNT sheets. Interestingly, the multicolors of Ag/g-CN composites display only on the CNT materials synthesized from heating melamine-cyanuric acid precursor, but not on the CNT from heating pure melamine. The color of the as-prepared Ag/g-CN composites can endure the corrosion of HNO3 and ethanol, which shows a good chemical stability and may hint its application as chromophores.

Electrochemiluminescence detection for β-amyloid1-42 oligomers using silver nanoparticle decorated CuS@CoS2 double shelled nanoboxes as dual-quencher

A highly effective dual-quenching electrochemiluminescence (ECL) immunosensor premised on the electrochemiluminescence resonance energy transfer (ECL-RET) was constructed using silver nanoparticle decorated CuS@CoS2 double shelled nanoboxes (CuS@CoS2 DSNBs@Ag NPs) as the ECL acceptor and gold nanoparticles functionalized carbon nitride (Au@C3N4) composites as the ECL donor. Generally, the UV–vis absorption spectra of CuS@CoS2 DSNBs@Ag NPs were found effectively overlapped with the ECL spectra of Au@C3N4 composites to trigger dual-quenching process. The fabricated Au@C3N4 composites were also served as substrate to immobilize primary antibody (Ab1) via Au-N bond besides providing excellent ECL signal sources. Moreover, CuS@CoS2 DSNBs@Ag NPs can capture the secondary antibody (Ab2) via the Ag-N bond to complete the sandwich immune interaction, where the ECL emission of Au@C3N4 composites were flexibly regulated by CuS@CoS2 DSNBs@Ag NPs via dual-quenching to indicate the concentration information of the detected antigens. This established immunosensor represented eminent performance for β-amyloid1−42 oligomers (Aβ) detection in a wider detection range of 0.5 pg/mL-20 ng/mL with a much low detection limit of 0.0038 pg/mL (S/N = 3). With high sensitivity and good specificity features, the expected ECL strategy paved a latest pathway to perceive a persuable sensitive detection of Aβ.

Cobalt molybdate nanorods decorated on boron-doped graphitic carbon nitride sheets for electrochemical sensing of furazolidone.

Ananorod-like structured CoMoO4 embedded on boron doped-graphitic carbon nitride composite (CoMoO4/BCN) has been developedby asimple sonochemical method for electrochemical detection of furazolidone (FUZ). Interestingly, the impedance of CoMoO4/BCN fabricated screen-printed carbon electrode (SPCE) possesses a lower resistance charge transfer (Rct), which favors superior electrochemical detection of FUZ. Such CoMoO4/BCN/SPCE exhibits an ultralow detection limit of 1.6nM with aconcentration range of 0.04-408.9μM, and high sensitivity of11.6μAμM-1cm-2 by DPV method. In addition, biological and water samples were used for demonstration of practical application of CoMoO4/BCN/SPCE towards electrochemical detection of FUZ, and the result exhibits a satisfactory recovery.Graphical abstract.

Application of a calcined animal bone to synthesis of graphitic carbon nitride composite

ABSTRACT Graphitic carbon nitride (g-C3N4) is a polymeric organic semiconductor that has been extensively developed for various applications. In this study, composites of g-C3N4 and calcined animal bone (CAB) were facilely synthesized by calcining a mixture of urea and CAB at different temperatures. The results revealed that the calcination temperature influenced yield, crystallinity, and band gap of g-C3N4. In addition, ultraviolet–visible diffuse reflectance spectroscopy indicated a shift in absorption edge to the high wavelength side in the presence of CAB, implying that CAB promoted thermal condensation of urea. However, thermogravimetric measurements revealed that g-C3N4 yield decreased as the calcination temperature increased in the presence of CAB. This is because the amount of g-C3N4 was scarce when the mixture was calcined at 823 K. Furthermore, the results of differential thermal analysis indicated that g-C3N4 and its intermediates were oxidatively decomposed by CAB at 823 K.

Fast and simple determination of estrogens in milk powders by magnetic solid-phase extraction using carbon nitride composites prior to HPLC.

A graphitic carbon nitride (g-C3N4/Fe3O4)-based magnetic solid-phase extraction (MSPE) approach was established for fast and simple analysis of estrogens in milk powders. The composites were characterized by X-ray diffractometer, scanning electron microscope, and Brunauer-Emmett-Teller surface area and pore size distribution analyzer. Compared with the bulk g-C3N4, g-C3N4/Fe3O4 gave a narrower distribution of mesopores and provided an enhanced surface area from 77.1 to 113.7m2/g. Polar analytes of estrogens were selected as model compounds and the extraction of four estrogens was achieved in n-hexane using 15mg of adsorbent within only 2min. Possible extraction mechanism of g-C3N4/Fe3O4 for these estrogens was explored in terms of the polarity of the analytes and the adsorption performance of the adsorbent. The hydrophobicity and the hydrogen-bond interaction between the estrogens and g-C3N4 were responsible for the efficient adsorption. Combined with HPLC, MSPE with the prepared adsorbent gave the enhancement factors of 20 to 24 and the linear ranges of 2-200μg/kg for 17β-estradiol and 17α-ethinylestradiol, 1.5-150μg/kg for estrone, and 3-300μg/kg for hexestrol. The detection limits and quantification limits for the estrogens in milk powders were 0.5-0.9μg/kg and 1.5-3.0μg/kg, respectively. The recoveries varied from 75.1 to 97.2%, with the intra-day and inter-day precisions ≤ 14.2%. Furthermore, the enrichment of the analytes and the clean-up of fat and protein interferences were achieved simultaneously with one-step g-C3N4-based MSPE. The present method was convenient, fast, and sensitive, and therefore could be successfully applied for the determination of estrogens in milk powders. Graphical abstract.

Fabrication of electrically conductive barium aluminum silicate/silicon nitride composites with enhanced strength and toughness

To acquire Si3N4-based composite with combination of high mechanical properties and excellent electrical conductivity, dense multi-walled carbon nanotubes (MWCNTs)-dispersed Si3N4 ceramics were fabricated, using BaCO3–Al2O3–SiO2 (BAS) as a second phase to improve the density and avoid reaction between MWCNTs and Si3N4. The results revealed that 40 wt% BAS prominently benefited the densification of MWCNTs-dispersed Si3N4 composites and promoted the phase transformation of α-Si3N4 to β-Si3N4, thereby contributing to superior mechanical properties. Additionally, the effects of MWCNTs on the densification, phase transformation, microstructure and properties were investigated. MWCNTs were well dispersed without damage in BAS/Si3N4 composites exhibiting excellent electrical conductivity. Consequently, these composites would be expanded to more applications including electrostatic chargeless bearing and electromagnetic interference shielding as well as high-temperature structural applications with geometrically complex morphologies.

Multilayered ultrahigh molecular weight polyethylene/natural graphite/boron nitride composites with enhanced thermal conductivity and electrical insulation by hot compression

AbstractA scalable strategy to fabricate thermally conductive but electrically insulating polymer composites was urgently required in various applications including heat exchangers and electronic packages. In this work, multilayered ultrahigh molecular weight polyethylene (UHMWPE)/natural graphite (NG)/boron nitride (BN) composites were prepared by hot compressing the UHMWPE/NG layers and UHMWPE/BN layers alternately. Taking advantage of the internal properties of NG and BN fillers, the UHMWPE/NG layers played a decisive role in enhancing thermal conductivity (TC), while the UHMWPE/BN layers effectively blocked the electrically conductive pathways without affecting the thermal conductive pathways. The in‐plane TC, electrical insulation, and heat spreading ability of multilayered UHMWPE/NG/BN composites increased with the increasing layer numbers. At the total fillers loading of 40 wt%, the in‐plane TC of multilayered UHMWPE/NG/BN composites with nine layers was markedly improved to 6.319 Wm−1 K−1, outperforming UHMWPE/BN (4.735 Wm−1 K−1) and pure UHMWPE (0.305 Wm−1 K−1) by 33.45% and 1971.80%, respectively. Meanwhile, the UHMWPE/NG/BN composites still maintained an excellent electrically insulating property (volume resistance~5.40×1014 Ω cm; breakdown voltage~1.52 kV/mm). Moreover, the multilayered UHMWPE/NG/BN composites also exhibited surpassing heat dissipation capability and mechanical properties. Our results provided an effective method to fabricate highly thermal conductive and electrical insulating composites.

Facile One-Step Preparation and Efficient Photocatalytic Hydrogen Production of Composite MoS2/g-C3N4 Sensitized by Erythrosin B

MoS2/g-C3N4 (g-C3N4 [Formula: see text] graphitic carbon nitride) composite is considered as a promising photocatalyst for hydrogen production, while the preparation method still needs to be improved. Herein for the first time, nanosized MoS3 and melamine were used as starting materials and a facile one-pot calcination method was successfully applied for the synthesis of MoS2/g-C3N4. The physical and photophysical properties of the as-prepared MoS2/g-C3N4 were characterized by XRD, IR, SEM, TEM and XPS techniques. Sensitized by Erythrosin B (EB), the photocatalytic hydrogen production performance of MoS2/g-C3N4 was investigated and the amount of MoS2 was optimized. An excellent H2 production activity of 1091.2[Formula: see text][Formula: see text] was achieved for 43% MoS2/g-C3N4, which is about 330 times that of pure g-C3N4 (3.3[Formula: see text][Formula: see text]. In addition, its performance was compared with those of three other MoS2/g-C3N4 samples prepared by conventional methods and a possible mechanism of H2 production was proposed based on the photoluminescence and photoelectrochemical results.

Optimizing and characterization of Aluminium based functionally graded Silicon Nitride composite

In the present study Aluminium alloy (ADC-14) reinforced with the spatial distribution of Silicon Nitride particles are fabricated through centrifugal casting. L4 orthogonal array was used to optimize the rotation speed of the mould for which two levels of 800RPM and 1200RPM was chosen. For the optimized mould speed again L4 orthogonal array was used to optimize the two factors ie. size of reinforcement and the volume fraction of Silicon Nitride. The two levels were 8% and 12% and size of reinforcement of 50microns and 100microns. Optical microscopic images were used to characterize the graded distribution of the fabricated functionally graded metal matrix composites (FGMMCs). The results show that there is an increase in hardness of 19% in the outer zone and 7% in the middle zone when compared with the inner zone ie. core of the casting. Highest hardness was obtained for the 12% reinforcement and 50microns of the reinforcement. The Regression equation and ANOVA analysis were carried out to predict the hardness and the most influencing parameter. SEM and EDS were also used to characterize the Silicon nitride reinforced FGM.

In-situ hard template synthesis of mesoporous carbon/graphite carbon nitride (C/CN-T-x) composites with high photocatalytic activities under visible light irridation

Carbon/graphite carbon nitride (C/CN-T-x) hybrid composites with high photocatalytic activities under visible light irradiation were synthesized by an in-situ hard template method using the partially formaldehyde-modified dicyandiamide (PFMD) and tetraethyl orthosilicate (TEOS) as the precursors and template, respectively. The structures of the as-prepared composites were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), elemental analysis, nitrogen adsorption-desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) spectroscopy, and X-ray photoelectron spectroscopy (XPS). The composite prepared under the optimal conditions exhibits the large surface area of 174 m2･g−1 and high photocatalytic activity for the degradation of methylene blue (MB) under visible light irradiation. The significant improvement in photocatalytic activity of the composite, as compared with the pure graphite carbon nitride (CN), is attributed to the large surface area, strong dye adsorption ability and enhanced separation efficiency of photogenerated electron-hole pairs.

Enhanced Thermal Conductivity of Silicone Composites Filled with Few-Layered Hexagonal Boron Nitride.

In this study, we demonstrate the use of silicone/few-layered hexagonal boron nitride (FL-hBN) composites for heat dissipation applications. FL-hBN is synthesized via a green, facile, low-cost and scalable liquid exfoliation method using a jet cavitation process. The crystal structures, surface morphologies and specific surface areas of pristine h-BN and FL-hBN were characterized by XRD, SEM, TEM and AFM (atomic force microscopy). The results confirmed that FL-hBN with a thickness of ~4 nm was successfully obtained from the exfoliation process. In addition, we introduced both pristine h-BN and FL-hBN into silicone with different ratios to study their thermal properties. The results of the laser flash analysis indicate that the silicon/FL-hBN composite exhibited a higher thermal conductivity than that of the silicone/h-BN composite. With the optimal loading content of 30 wt.% FL-hBN content, the thermal conductivity of the composite could be enhanced to 230%, which is higher than that of silicone/h-BN (189%). These results indicate that jet cavitation is an effective and swift way to obtain few-layered hexagonal boron nitride that could effectively enhance the thermal conductivity of silicone composites.

High catalytic performance of a Pd-loaded TaN-TaC electrocatalyst for ethylene glycol oxidation in an alkaline medium

In this work, tantalum nitride and tantalum carbide (TaN-TaC) composites are prepared using a one-step calcination method. The resulting TaN-TaC composites have excellent conductivity, and therefore, potential applications in the electrode materials of fuel cells. Then, palladium nanoparticles loading on TaN-TaC (Pd/TaN-TaC) electrocatalysts are synthesized using the reflux method. The X-ray photoelectron spectroscopy results imply that the valance states of palladium are of the form Pd0 and Pd2+ on the surface of TaN-TaC composites. The electrocatalytic activity of the Pd/TaN-TaC catalysts is measured in a 0.5 mol L−1 KOH solution and 1 mol L−1 of ethylene glycol. These results imply that the Pd/TaN-TaC electrocatalyst modified glassy carbon electrode has a high catalytic activity for ethylene glycol electrooxidation in an alkaline medium. The dosage of Pd is 7% (mass ratio of Pd and TaN-TaC) and it exhibits the higher electrocatalytic activity, and superior to the commercial Pd/C (10%).

Preparation of thermally conductive polycarbonate/boron nitride composites with balanced mechanical properties

AbstractIn this study, thermally conductive polycarbonate/boron nitride (PC/BN) composites were prepared by masterbatch dilution and direct melt mixing methods, respectively. A comparative study of both microstructure and rheological properties of corresponding composites suggests an improved filler distribution is achieved by masterbatch dilution, which is advantageous to the enhancement of both thermal conductivity and tensile properties at a medium filler loading range. In addition, thermogravimetric analysis indicated that thermal stability of masterbatch diluted PC/BN composites is superior to that of direct melt compounded counterparts. However, the char residue of PC in subsequent composites decreases with increasing filler content, which is believed to be related to the incompatibility between fillers and the matrix, as well as the enhancement of thermal conductivity. This work provides a facile method to prepare thermally conductive composites with balanced mechanical properties.

Mechanical and dielectric properties of functionalized boron nitride nanosheets/silicon nitride composites

Uniformly dispersed boron nitride nanosheets (BNNSs) reinforced silicon nitride (Si3N4) composites were prepared by surface modification assisted flocculation combined with SPS sintering. In order to improve the dispersibility of the BNNSs in the composites, the liquid phase stripped BNNSs are surface functionalized by a two-step covalently modification. The amino-modified BNNSs (NH2-BNNSs) and Si3N4 powders have opposite surface potential, mixed evenly by electrostatic interaction during flocculation. The results showed that mechanical properties of Si3N4 composites were obviously enhanced by adding NH2-BNNSs. The fracture toughness and bending strength of Si3N4 composites added 0.75 wt% NH2-BNNSs were increased by 34% and 28%, respectively, compared with monolithic Si3N4. Toughening mechanisms are synergistic action of the torn, pull-out or bridging of BNNSs and crack deflection mechanisms with microstructural analyzes. The dielectric properties of the Si3N4 ceramics are also improved after the addition of NH2-BNNSs.

Composite Materials in the TiN–Cr3C2–C/Matrix System

The influence of modifying additions on the strength and tribological properties of titanium nitride composites has been examined. The lowest contact angle (25–30°) is shown by the PG12N-01 alloy, containing chromium, boron, silicon, and carbon. Relatively porousless structures can be produced in the TiN–PG12N-01 system when chromium carbide and carbon are introduced into the composite as graphite, contributing to the formation of TiCN to improve wetting and adhesion. Graphite introduced additionally as an impurity remains after sintering as an individual uniformly distributed phase integrated into the overall composite structure. This graphite can successfully act as a dry lubricant, improving the service characteristics. In addition, it activates sintering of the composite allowing it to become almost porousless. The optimum sintering temperature falls in the range 1450–1500°C depending on carbon and metal matrix contents. The resultant composites have 300–500 MPa strength and 16.1 GPa hardness. The highest strength can be reached through an optimum combination of graphite and PG12N-01 matrix. The mechanical characteristics deteriorate when the amount of these components is higher or inadequate. The antifriction characteristics of the materials have been tested by dry end friction (at a speed of 8 m/sec, 50 MPa pressure in the contact area, and 10 km sliding path) against a 65G steel counterface with 60 HRC hardness: friction coefficient has been found to be 0.27–0.3 and wear resistance 0.2 ± 0.02 μm/km. The developed ceramic materials thus have high strength and antifriction characteristics and can be used in dry friction conditions at high speeds and loads.

Formation and Impact of Microcracks in Plasma Erosion of M26 Boron Nitride

This Paper investigates the role of microcracks in Hall thruster wall erosion. The formation and growth of microcracks on the surface of M26 grade boron nitride composite due to repeated thermal shock was quantified, and the subsequent impact of microcracks on plasma erosion was assessed. Thermal shock cycles (20 → 800 → 20°C) were provided by a radiation oven to induce thermal stresses similar to those incurred by a Hall thruster wall. The average ratio of crack area to total area was observed to grow as a power law with subunity exponential from 4–5% before thermal cycling to 15–18% after 20 thermal shock cycles. Cycled and control samples were simultaneously exposed to argon plasma with average ion energy of 130 eV. All samples were observed to preferentially retain boron nitride relative to silica, and microcracks were not observed to significantly impact surface composition or feature development.