Nano Hexagonal Boron Research Articles

Determination of Optimum Annealing Time Durations of Nano Boron Nitride Added MgB2 Superconductors

In the present study, I have investigated the effect of different annealing time durations of 0.5h, 1h, 2h and 4h (annealing temperature at 700oC) on the electrical, micro structural and superconducting properties of the nano hexagonal boron nitride (hBN) added/doping magnesium diboride (MgB2) superconducting samples. The aim of this work, hBN added MgB2 superconducting bulk samples are determined to find out the optimum sintering time, also investigated how BN addition effects the optimum fabrication conditions. These superconducting samples were prepared by the conventional solid-state reaction method. Experimental techniques of X-ray diffraction (XRD) were used for structural and microstructural examinations. Critical transition temperatures, difference between Tc-onset and Tc-offset, a and c lattice parameter, grain size, bulk density, residual resistivity ratios (RR) and cross-sectional area fractions (AF) of the pure and nano-hBN added MgB2 materials are obtained using a cryostat equipped with a superconducting magnet. All the experimental results notice that the characteristic features improve regularly with the increment in sintering time durations.

Synthesis and characterization of nano hexagonal boron nitride powder and evaluating the influence on aluminium alloy matrix

An attempt is made to synthesize the nano h-BN powders by high energy ball milling and also aluminium reinforced h-BN composite by powder processing route. The impact of ball milling time on microstructure and particle size reduction of h-BN powder was investigated by FESEM, FTIR, XRD, UV-vis diffuse reflectance spectroscopy and particle size analyser.It was indicated that high energy ball milling is effective up to 10 hours in reducing the particles size a further increase in time is resulting in agglomeration. Microhardness of the composite increases in proportion to increases in weight percentage of reinforcement, h-BN exhibited a poor sinterability without any accelerating agentand with tin addition up to 0.5% low melting point metal.TGA and DTA study shows that there is reduction in melting point from 641°C to 638 °C with addition of 2% weight fraction of h-BN.Selection and Peer-review under responsibility of [Conference Committee Members of Recent Advances In Nano Science and Technology 2015.].

Study of the boron levels in serum after implantation of different ratios nano-hexagonal boron nitride–hydroxy apatite in rat femurs

Boron and its derivatives are effective in bone recovery and osteointegration. However, increasing the boron levels in body liquids may cause toxicity. The aim of our study is to investigate serum boron levels using ICP-MS after implantation of different ratios of nano-hBN-HA composites in rat femurs. All rats were (n=126) divided into five experimental groups (n=24) and one healthy group (6 rats); healthy (Group1), femoral defect + %100 HA (Group2), femoral defect + %2.5 hBN + %97.5 HA (Group3), femoral defect + %5 hBN + %95 HA (Group4), femoral defect + %10 hBN + %90 HA (Group5), femoral defect + %100 hBN (Group6). The femoral defect was created in the distal femur (3mm drill-bit). Each implant group was divided into four different groups (n=24) also 6 rats sacrificed for each groups in one week intervals during four weeks. In our results; at 1, 2, 3, and 4 weeks after implantation near bone tissue, serum levels of boron were evaluated using ICP-MS. We demonstrated that neither short-term nor long-term implantation of hBN-HA composite resulted in statistically increased serum boron levels in experimental groups compared to healthy group. In conclusion, this study investigated the implant material produced form hBN-HA for the first time. Our data suggest that hBN is a new promising target for biomaterial and implant bioengineers.

Nano hexagonal boron nitride–Nafion composite membranes for proton exchange membrane fuel cells

This study investigates the proton conductivity and characterization of nano hexagonal boron nitride–Nafion composite membranes. Proton conducting composite membranes are prepared by mixing Nafion and nano hexagonal boron nitride (NhBN) particles with 3, 5, 10, and 15% weight ratios. Particle size distribution analysis is made for BN nanoparticles and the homogeneity of the membranes is proved by SEM and AFM. FTIR confirms the interaction between NhBN and Nafion. Methanol permeation and water absorption tests are made and it shows that hydrophobic NhBN particles decrease the swelling property and methanol retention of the membranes. X‐ray investigation of the composites supports semi‐crystalline nature of the composite materials. At dry conditions, the maximum proton conductivity was measured as 0.005 S/cm at 150°C for NafBN10, which is much higher than the pure Nafion. The results confirm that boron nitride nanoparticles have high contribution on the proton transfer, which may be explained with the formation of hydrogen bonds between amine and hydroxyl groups of boron nitride and sulfonic acid groups of Nafion. POLYM. COMPOS., 37:422–428, 2016. © 2014 Society of Plastics Engineers

Using polyurethane, ethylene-vinyl acetate hotmelt, and nano hexagonal boron nitride particles to electrospin high surface adhesion polymer fibers

In this study, we presented the use of polyurethane, ethylene-vinyl acetate hotmelt, and nano hexagonal boron nitride particles to prepare high surface adhesion polymer fibers via an elertrospinning method. The shear strength, dynamic tensile properties, and surface morphology have been investigated. These polymer fibers were found to have high shear strength, high tensile stress, and high tensile strain, which may have a good potential application in the matrix materials for thermal interface materials. Polymer fibers with and without nano hexagonal boron nitride particles showed the shear strength of 6.52 MPa and 5.44 MPa respectively on being heated up at 150°C for 45 min.

Wear Characteristics of Traditional Manganese Phosphate and Composite hBN Coatings

In this study, the tribological properties of traditional manganese phosphate coatings and composite hBN coatings composed of nano-hexagonal boron nitride (hBN) in layered manganese phosphate crystals on AISI 1040 steel were investigated. Wear tests were carried out under controlled temperature and humidity using ball-on-disc tribometers for samples that were either submerged in oil or retaining oil on their surfaces at a sliding speed of 2.5 cm/s with loads of 1, 3, 5, and 10 N and sliding distances of 40, 80, 100, and 120 m. The surface profiles before and after the tests were used to characterize the wear. The surfaces of the coated samples were examined using scanning electron microscopy (SEM). The coefficients of friction and wear rates of the coated samples were also measured. The average wear rates of the composite hBN-coated samples were significantly lower than those of the traditional manganese phosphate–coated samples for each of the loading conditions for the oil submersion and retained oil tests. The coefficient of friction (COF) values for the traditional manganese phosphate–coated samples did not change significantly with increasing load. The COF values for the composite hBN coated–samples decreased with increasing load in the oil submersion test.

Preparation and characterization of thermally conductive thermoplastic polyurethane/h‐BN nanocomposites

Polyurethane nanocomposites are versatile engineering polymers with unique properties. In this study, nano hexagonal boron nitride containing thermoplastic polyurethane elastomers were prepared via melt blending and hot‐pressing techniques. The nanocomposites were characterized using Fourier transform infrared, differential scanning calorimetry, thermal gravimetric analysis, tensile tests, and thermal conductivity measurements. The surface morphology of the TPU/h‐BN composites was characterized by scanning electron microscopy. The optical properties of the composites were determined by UV transmittance measurements and as the amount of h‐BN increased, optical transparencies decreased dramatically. Nanocomposites displayed higher E‐modulus values and lower elongation at break values than the pure TPU elastomer. Char yields of TPUs increased with increasing h‐BN percentage. Moreover, thermal conductivity of the composite materials improved with the incorporation of h‐BN. POLYM. COMPOS., 35:530–538, 2014. © 2013 Society of Plastics Engineers

Effect of Nano Hexagonal Boron Nitride Lubricant Additives on the Friction and Wear Properties of AISI 4140 Steel

The aim of this study was to investigate the effects of nano hexagonal boron nitride(hBN) particles on the friction and wear properties of AISI 4140 steel material when the hBN particles are used as an oil additive. Nano hexagonal boron nitride powders, which were produced using a special process, were dispersed in engine oil (SAE10 W) to enhance lubrication. The amount of nano hexagonal boron nitride in the engine oil was varied from 0 to 10% by volume, and four different lubricant samples were prepared. Wear tests were conducted using ball-on-disc geometry. The worn surfaces of substrates were analyzed using scanning electron microscopy (SEM) and energy-dispersive x-ray spectroscopy (EDS). The experiments showed that the nano hexagonal boron nitride particles that were used as an oil additive affected the friction and wear behavior. A 14.4% improvement in the friction coefficient and a 65% decrease in the wear rate were achieved through the use of the nano hBN as an oil additive.

Electrical and mechanical properties of electrically conductive adhesives from epoxy, micro-silver flakes, and nano-hexagonal boron nitride particles after humid and thermal aging

In this study, we incorporated micro-silver flakes and nano-hexagonal boron nitride (BN) particles into a matrix resin to prepare electrically conductive adhesives (ECAs). The humid and thermal aging results under a constant relative humidity level of 85% at 85°C revealed that the aged ECAs containing 3wt% of nano-hexagonal BN particles had high reliability. The contact resistance was low and the shear strength high. Nano-hexagonal BN particles have a good effect on the reliability of ECAs that can be used to improve the properties of ECAs.

Using nano hexagonal boron nitride particles and nano cubic silicon carbide particles to improve the thermal conductivity of electrically conductive adhesives

To satisfy the high electrical and thermal conductivity required for the continuous development of electronic products, nano hexagonal boron nitride (BN) particles and nano cubic silicon carbide (SiC) particles were added into electrically conductive adhesives (ECAs) to improve the thermal conductivity. BN and SiC had little negative effect on the electrical conductivity, but improved the thermal conductivity significantly. When their content was 1.5 wt. %, the thermal conductivity at 100°C, 150°C and 200°C was increased by 71% (100°C), 78% (150°C) and 70% (200°C), and 114% (100°C), 110% (150°C) and 98% (200°C) respectively for BN and SiC comparing with those of the ECAs with no thermal conductive fillers. This method is simple, easy to do, and can be used practically in electronic packaging.