Nano-boron Carbide Research Articles

TiO2-loaded boron self-doped carbon derived from nano boron carbide as a non-noble metal bifunctional electrocatalyst for oxygen reduction and evolution reactions

TiO2-modified boron self-doped carbon/nano B4C (TiO2/B-C/B4C) was used as a non-noble metal electrocatalyst for the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) in 0.1 M KOH. Titanium oxide-modified boron carbide (TiO2/B4C) was prepared by microwave treatment of the mixture of titanyl sulfate and B4C. TiO2/B-C/B4C was obtained after heating the TiO2/B4C at 700 °C in vacuum for 3 h. The TiO2/B-C/B4C exhibited a good ORR activity with an average electron transfer number of 3.9, which was close to that obtained with 20 wt% Pt electrocatalyst. The resultant TiO2/B-C/B4C electrocatalyst showed satisfying OER performance with an overpotential of 0.31 V at 10 mA cm−2. Thus, the TiO2/B-C/B4C electrocatalyst with good ORR/OER activity can be potentially used for unitized regenerative fuel cells in new generation energy-storage systems.

Tribological Properties of B4C Nano Particulates Reinforced Copper Matrix Nanocomposites

Abstract Pure copper (Cu) matrix composites reinforced with different weight percentages of Nano boroncarbide particles (B4C) were successfully produced through powder metallurgical route. Nano sized B4C particles with 0, 0.5, 1.0 and 1.5 weight % were mechanically mixed with Cu powder of size 125 μm and then compacted at 248 bar pressure. SEM analysis revealed that the B4C nanoparticles were uniformly distributed in Cu matrix. Addition of 1.5 wt.% Nano B4C particles in Cu matrix, increases the Vickers micro hardness from 32 to 93. The wear measurements of pure Cu exhibited high wear loss than the Nano B4C mixed copper matrices. Nano composites reinforced with 1.5 wt.% of Nano B4C showed maximum wear resistance property. In general, increase of normal load and sliding velocity increases the wear rate. The worn surfaces of pure Cu show deep long grooves while Cu-Nano composites show narrow grooves.

Investigations on mechanical behavior of Al7075 - nano B4C composites

The paper is the result of investigations made on microstructure and mechanical behavior of 3 and 6 weight percentage of nano sized B4C particulate reinforced to Al7075 alloy composites. Al7075 matrix composite having nano boron carbide was fabricated by liquid stir casting method. The microstructure of the composites was examined by scanning electron microscopy. Further, mechanical behavior of Al7075 alloy, Al7075-3wt. % B4C and 6 wt. % B4C composites were studied. Tensile properties like hardness, ultimate tensile strength; yield strength, percentage elongation and compression strength were evaluated as per ASTM standards. Micro structural observation revealed uniform distribution of B4C particles in the matrix. The analysis disclosed hardness, ultimate tensile strength, yield strength and compression strength of composites increased due to increase in percentage of nano boron carbide particles and percentage elongation of the composites decreased with increase in B4C particulates in base alloy matrix.

Influence of reaction temperature and time on nanoboron carbide morphology and its thermal stability, optical and electronic properties

Boron carbide powder was prepared via the carbothermic reduction reaction (CRR) using lactose (C12H22O11) and boric acid (H3BO3) as carbon and boron sources. Starting materials were mixed with an excess amount of H3BO3 stoichiometric ratio to reduce the presence of free carbon content in the produced boron carbide samples caused by the great loss of boron during the reaction. The mixed solutions of starting materials were heated in a stainless steel pot at 280 °C for 24 h. The resulted powder was carbothermally reacted under the flowing of an argon gas at different reaction temperatures and times ranging from 1300 to 1500 °C for 3 h and at 1500 °C for 1–3 h, respectively. The synthesized samples at each procedure conditions were characterized using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) techniques. The results showed that the produced samples were in the nanocrystalline scale with no carbon traces. The structural morphology of the synthesized powder studied using scanning electron microscope (SEM) and transmission electron microscope (TEM). The results indicated the possibility of producing B4C with minimal carbon residue via controlling both reaction temperature and time. A significant morphology change of the produced samples was well detected by changing the reaction time. Thermochemical properties of the as-synthesized samples at 1500 °C for 1 and 3 h also studied in order to be exploited in the proper applications. In addition, the optical properties of boron carbide was investigated by UV/visible and photoluminescence measurements along with its electronic properties.

Microstructure Development, Wear Characteristics and Kinetics of Thermal Decomposition of Hybrid Nanocomposites Based on Poly Aryl Ether Ketone, Boron Carbide and Multi Walled Carbon Nanotubes

In the present study a high performance polymer poly aryl ether ketone (PAEK) is reinforced with micro and nano boron carbide (B4C) and functionalized multi walled carbon nanotubes (F-MWCNT) to investigate the individual and hybrid effect of the fillers. Optical microscopy and transmission electron microscopy suggested the dispersion of micro and nano fillers respectively in PAEK matrix. The inclusion of B4C nano fillers increased the hardness of the composites which aided the wear resistance of the composites. The morphological features of the worn surface of the samples are analyzed using scanning electron microscopy. It is found from the izod impact test analysis that the impact strength of the composite enhanced by the F-MWCNT inclusion. The thermal properties of PAEK in the composites are studied using differential scanning calorimetry and it revealed dominant effect of F-MWCNT influencing the thermal transitions than the B4C particles. The kinetics of thermal degradation of various composites is analyzed using Coats–Redfern method. The positive influence of B4C in the matrix indicates that the thermal degradation is delayed due to the higher activation energy it possesses. The overall results shows that the hybrid nanocomposite exhibits better properties compared to individual micro and nano composites.

Nanostructured phenolic matrices: Effect of different nanofillers on the thermal degradation properties and reaction to fire of a resol

SummaryIn this work, the effect of 6 different fillers as a nanomodifier of phenolic matrix was evaluated in thermal stability and reaction to fire. The chosen nanoparticles were montmorillonite, silica, carbon black, and 3 carbides—boron, silicon, and zirconium carbides. The nanofillers were mechanically dispersed in the matrix, and the dispersion and distribution of the nanosized particles in the matrix was evaluated by transmission electron microscopy. The thermal stability of nanocomposites was investigated by thermogravimetric analysis both in nitrogen and in air while the thermal combustion properties were measured using a microscale combustion calorimeter. The experimental data highlighted the remarkable effects of nanoboron carbide on the thermal properties it can confer to the phenolic matrix. Rheological behavior of the blends was also investigated to evaluate the effect of the different fillers on the viscosity of the nanostructured matrices.

Experimental and ANOVA analysis on tribological behavior of Al/B4C micro and nanocomposite

An investigation was undertaken to analyse the effect of addition of micro- and nano-boron carbide particles for the synthesis of Al/B4C nanocomposite (and micro/ nearing nano) using gravitational friction stir processing and to analyse the influence of normal load sliding wear and frictional behaviour of the composite. The normal load was varied from 20 to 40 N and the sliding distance was varied from 1 to 3 km. The sliding wear behaviour was evaluated using a pin-on-disc experimental set-up. Scanning electron microscopy was used to investigate the microstructure of the fabricated Al/B4C nanocomposites. The result showed that Al/B4C nanocomposite exhibited less coefficient of friction and more wear rate when compared to Al/B4C microcomposite. The predominant wear mechanisms observed were abrasive and adhesive during the test.

Tungsten-coated nano-boron carbide as a non-noble metal bifunctional electrocatalyst for oxygen evolution and hydrogen evolution reactions in alkaline media.

Herein, tungsten-coated nano-boron carbide (W-WB4-WCx/B4C) particles were prepared by heating a mixture of B4C and W powder using a spark plasma coating (SPC) method. During the discharge treatment process, metal W in the mixture is activated and reacts with B4C to form WCx, WB4, and graphite nanoribbons. The oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) performance of W-WB4-WCx/B4C is tested in an alkaline solution, and the results show that the W-WB4-WCx/B4C composite electrocatalyst exhibits a low overpotential of 0.36 V at 10 mA cm-2 for the OER, a small overpotential of -0.19 V (j = 10 mA cm-2) for the HER, as well as good stability. The significantly enhanced electrocatalytic performance of the W-WB4-WCx/B4C composites is attributed to their unique structure, in which WCx and WB4 not only improve the catalytic activity for the OER and HER, but also effectively anchor the W coating on the substrate.

Electrical Resistivity, Tribological Behaviour of Multiwalled Carbon Nanotubes and Nanoboron Carbide Particles Reinforced Copper Hybrid Composites for Pantograph Application

This work focuses on the influence and contribution of multiwalled carbon-nanotube (MWCNT)–boron carbide (B4C) to the mechanical and tribological properties of copper matrix composites. Different weight fractions of nano- B4C-containing fixed-weight fractions of MWCNT-reinforced copper composites were prepared using the entrenched cold-press sintering method of powder metallurgy. The wear losses of sintered Cu–MWCNT–B4C composites were investigated by conducting sliding tests in a pin-on-disc apparatus. The addition of reinforcements showed enhancements in the hardness and wear properties of the composites due to the uniform dispersion of the secondary reinforcement in the copper matrix and the self-lubricating effect of the MWCNTs. The effects of the nanoparticle distribution in the matrix, the worn surface morphology, and the elemental composition of the composites were characterized using high-resolution scanning electron microscopy and X-ray diffraction analysis. The electrical resistivity of the fabricated copper hybrid composite preforms was evaluated using a four-point probe tester. Our results highlight the use of experiential reinforcing limits of B4C on the wear and electrical and mechanical behaviour of copper composites.

Effect of nano/micro B4C particles on the mechanical properties of aluminium metal matrix composites fabricated by ultrasonic cavitation-assisted solidification process

Lightweight aluminium metal matrix nanocomposites play a major role in automobile, aerospace and other industries. This work aimed to investigate the effect of the addition of micro- and nano-boron carbide particles to aluminium on the mechanical properties of the composites. The micro- and nanocomposites containing different weight % of B4C particles were fabricated using stir- and ultrasonic cavitation-assisted casting processes. The fabricated micro and nano B4C particle-reinforced composites were characterized using scanning electron microscopy (SEM) and an X-ray diffractometer. Tensile, hardness, impact and wear tests were carried out in order to evaluate the mechanical properties of the micro- and nanocomposites. The tensile test results showed that the properties of the samples containing up to 6% nano B4C-reinforced composites were better than the micro B4C-reinforced composites. The study also indicated that the ductility and impact energy of the nanocomposites were better than the micro B4C particle-reinforced composites. The wear resistance of the nanocomposite significantly increased when the B4C content was increased up to 8% of addition, and this increase was more pronounced than that resulting from micro B4C particle-reinforced composites.

Effect of boron carbide nanoparticles on the thermal stability of carbon/phenolic composites

In this work, the use of nano-boron carbide as a nanomodifier of phenolic matrix was envisioned. Particularly, nano-boron carbide/phenolic-based nanocomposites were produced and investigated. The obtained nanostructured matrices were also used to produce carbon fiber-based bulk molding compounds (BMC). The thermal stability of nanocomposites and BMCs was investigated by thermogravimetric analysis both in nitrogen and in air atmospheres. The good dispersion and distribution of the nanosized particles in the matrix was confirmed by transmission electron microscopy while the post-burning appearance of the BMCs was investigated by visual inspection and scanning electron microscopy. The experimental data highlighted the remarkable effects of nano-boron carbide on the thermal stability and oxidation resistance of the carbon fiber-based BMCs. Moreover, the boron oxide produced by the conversion of boron carbide allowed a substantial improvement of the dimensional stability of the BMC which also exhibited considerable residual structural integrity after burning. POLYM. COMPOS., 2015. © 2015 Society of Plastics Engineers

Optimizing the Dry Sliding Wear Behavior of Copper Hybrid Nano Composites Reinforced with MWCNTs and Nano B4C Using Full Factorial Design

In the present study, full factorial design has been used to optimize the wear test conditions of the copper-multi-walled carbon nanotubes and nano boron carbide reinforced composites prepared through entrenched cold-press sintering method of powder metallurgy. The factors like boron carbide particle, applied load and sliding distance of the wear test have been selected as independent variables. This technique has been designed to achieve momentous effects on two responses, namely specific wear resistance and coefficient of friction and 60 experimental runs have been carried out with one replication. To study the micro structural morphology, particle size, worn surface and wear debris of the prepared copper hybrid nanocomposite, scanning electron microscopy, Atomic force microscopy and X-ray diffraction analysis were used for characterization. The ANOVA results were used to validate the developed design and it shows that the applied load and nano boron carbide addition to the matrix material significantly plays an important role in the wear resistance and coefficient of friction of the hybrid composites respectively. A linear regression equation is developed to relate the responses and the operating factors. The optimal conditions for the wear test were: nano boron carbide particles of 2 wt%, load of 5 N and sliding distance of 500 m for both responses.

Processing and Performance Characteristics of Aluminum-Nano Boron Carbide Metal Matrix Nanocomposites

In this research work, ultrasonic cavitation-assisted casting process was used to fabricate the aluminum alloy-nano boron carbide metal matrix nanocomposites. The optical microscopy results revealed the refined matrix grains in the microstructure of the aluminum alloy-nano boron carbide composites. Boron carbide nanoparticles were uniformly distributed in the aluminum alloy matrix, which can be confirmed by scanning electron microscopic images. The aluminum alloy-nano boron carbide composites show increased dislocation density, compared to the monolithic alloys, which was observed from the transmission electron microscopic images. The addition of nano-boron carbide in aluminum alloy matrix significantly improved its hardness and tensile strength, while the good ductility and impact resistance of the aluminum alloy was almost retained. The results of the dry sliding wear pin-on-disc tests showed improved wear resistance properties of aluminum alloy-nano boron carbide composites compared to the monolithic aluminum alloys.

Transmission Performance of Water-Based Nano Fluid Based on Computational Fluid Dynamics

The nanoboron carbide particle size is 60nm, dispersed in RO reverse osmosis membrane treatment water form water-based nanofluid by adding the dispersant. In experiment, Water-based nanoboron carbide fluid has good resistance sedimentation stability when adding sodium carboxymethyl cellulose as a dispersing agent. Prepared three kinds of water-based nanoboron carbide fluid, the mass fraction of nanoparticles is 0.6%, 0.8%, 1.0%. By establishing a model of U-shaped tube, simulated the water-based nanofluids flow field in U-shaped tube using FLUENT, get velocity flow lines picture and pressure variation graph by CFD post-processing. From simulation results obtained: Water-based nanoboron carbide has good transmission fluid performance when nanoparticles mass fraction of 0.8%.

Nano-boron carbide supported platinum catalysts with much enhanced methanol oxidation activity and CO tolerance

Platinum (Pt) nanoparticles were successfully deposited on the surface of nano-B4C with fragmentary nanostructured carbon thin film through a polyol process in an ethylene glycol solution. The electrochemical surface area of the Pt/B4C was investigated and showed remarkable enhancement compared with conventional Pt/C catalysts, which could be attributed to fast hydroxyl adsorption and high OHad coverage occurring during the hydrogen desorption process. It was also found that the novel Pt/B4C catalysts presented much enhanced methanol oxidation activity and CO tolerance by a negative shift in the onset potential and an increase of the peak current density in comparison to Pt/C catalysts. Meanwhile, the Pt/B4C showed an improved oxygen reduction reaction activity compared to the Pt/C catalyst.

Spark plasma sintered tantalum carbide: Effect of pressure and nano-boron carbide addition on microstructure and mechanical properties

TaC and TaC–1wt.% B4C powders were consolidated using spark plasma sintering (SPS) at 1850°C and varying pressure of 100, 255 and 363MPa. The effect of pressure on the densification and grain size is evaluated. The role of nano-sized B4C as sintering aid and grain growth inhibitor is studied by means of XRD, SEM and high resolution TEM. Fully dense TaC samples were produced at a pressure of 255MPa and higher at 1850°C. The increasing pressure also resulted in an increase in TaC grain size. Addition of B4C leads to an increase in the density of 100MPa sample from 89% to 97%. B4C nano-powder resists grain growth even at high pressure of 363MPa. The formation of TaB2/Carbon at TaC grain boundaries helps in pinning the grain boundary and inhibiting grain growth. The effect of B4C addition on hardness and elastic modulus measured by nanoindentation and the indentation fracture toughness has been studied. Relative fracture toughness increased by up to 93% on B4C addition.

Configurational, electronic entropies and the thermoelectric properties of nanocarbon ensembles

Reaction of disperse ultrananocrystalline diamond (UNCD) and mixtures of UNCD containing 10%–20% nanoboron carbide (B4C) with methane gas at temperatures near 1200K results in mechanically rigid compacts called nanocarbon ensembles (NCE) and boron-doped NCE, respectively. Seebeck coefficient and electrical conductivity results lead to strongly temperature dependent power factors that increase 30–40 fold for boron containing ensembles compared to undoped material. It is likely that boron substitutional doping of nanographite crystallites results in a multiplicity of electronic states within a narrow energy band around the Fermi level leading to an increase in configurational electronic entropy.