Nano-boron Carbide Research Articles

Comparative tribological study of the material intended for a lightweight HAMNC brake rotor sliding against NAO brake pad material

Abstract The present work studies the lightweight Hybrid Aluminium Metal Matrix Nanocomposite (HAMNC) for brake rotor application. The novel HAMNC brake rotor material is fabricated by reinforcing 1 wt. % nano Boron carbide (nB4C) and 0.75 wt.% nano Titanium dioxide (nTiO2) employing ultrasonic-squeeze-assisted stir-casting process. The developed HAMNC and a commercial Gray Cast Iron (GCI) brake rotor material was subjected to density, hardness, thermal, corrosion, and tribological studies. The results indicated that the HAMNC brake rotor material is 60% lighter and extremely corrosive resistant compared with GCI material. Also, the dry sliding wear study done using Non Asbestos Organic (NAO) commercial brake pad as the pin material exhibited that the HAMNC brake rotor material possessed a higher wear-resistant behavior compared to GCI.

Wear behavior and tribo-surface characteristics of nano magnesium composites

A nano magnesium composite was synthesized with the addition of 5.6 wt.% of titanium, 3 wt.% of aluminum and 2.5 wt.% of nano boron carbide particles through the disintegrated metal deposition process. To validate the metallurgical features of the synthesized magnesium composite, the samples were exposed to X-ray diffraction study and scanning electron microscopic analysis with dispersive spectroscopy analysis. Wear behavior of the nano magnesium composite was studied through pin-on-disc dry sliding wear experiments by changing the load and sliding velocity over a sliding distance of 3000 m. Further, wear rate of the produced material was analyzed for varied wear parameters. Wear behavior of the magnesium composite revealed an adverse effect with an increased load and a positive effect with increased sliding velocity. The microscopic analysis of the worn surface and the collected debris revealed the characteristics of the wear surface of the nano magnesium composite. Adhesion, abrasion, delamination, oxidation and thermal softening were the mechanisms observed in the post-failure analysis.

Tribological Behavior on Stir-Casted Metal Matrix Composites of Al8011 and Nano Boron Carbide Particles

The aluminum metal matrix composites were broadly exploited in the applications of automotive, aerospace, and other defense with functionally graded materials-related application. Above applications definitely required excellent mechanical characteristics. Therefore, in this way, the major attempt was made on the nano-based composites with aluminum alloy utilization. In this research, aluminum alloy AA8011 and the ceramic-based reinforcement particles of nano boron carbide (B4C) were selected for producing the metal matrix composites by the liquefying process or stir casting route. The weight percentage of nano boron carbide particles having 15 wt% was subjected to add into the aluminum alloy during the stir casting process. Then, processed nano boron carbide and AA8011 specimens were prepared to conduct tribological behaviors with various processing conditions like sliding velocity, setting wear temperature, and applied load by the tribometer setup. The scanning electron microscope was employed to examine the processed composites samples and worn-out surface samples. Finally, the multiobjective optimization was used to measure the individual performances of the tribological parameters by the gray relational technique.

Investigation of microstructural and mechanical properties of Al alloy 7075-T6/B4C nanocomposite concocted via friction stir process

Magnanimously Aluminium metal matrix composites (MMCs) are acknowledged worldwide for keeping exceptional strength to weight ratio for which these are incorporated extensively in Aerospace and Automobile industries and gained potential limelight. Moreover, the material response outreach potential or the composite functionality potential are exclusively driven by tuning of the reinforcement materials. Herein, Al composites were concocted by introducing micro and nano Boron Carbide (B4C) powder into aluminium alloy AA 7075-T6 material matrix through Friction Stir Processing (FSP) with a motivation to enhance the mechanical and damping properties. Further the influence of physical structure alteration of reinforcement B4C from micro to nano dimension on the composites were validated through various characterizations. The microstructure of the composites was observed with optical microscope and Electron back scattered diffraction (EBSD) methods respectively. A significant grain refinement was observed with nano-reinforced composite by clinching average grain size reduced to 2.9 μm relative to base material grain size of 37 μm. The average hardness of nano-reinforced MMCs was found to be 66% higher than base material recorded a value of 141 HV. Furthermore, the AA7075-T6 composites were studied for their thermal and mechanical cyclic damping performance in the temperature range from ─ 60 to 60 °C and depicted exceptionally good damping property.

Microstructure and elevated temperature tensile behavior of nano boron carbide particles reinforced Al7475 alloy composites

In the this research an attempt has been made to prepare 2 and 4 wt% of nano boron carbide particles reinforced Al7475 alloy composites by stir cast process. The synthesized composites were subjected to microstructural evaluation by SEM, EDS and XRD. Density measurements were carried out on as cast Al7475 alloy and Al7475 alloy with 2 and 4 wt% of nano particles composites to now the suitability of fabrication process. Further, hardness of prepared samples was conducted using Brinell hardness tester. Tensile behavior of as cast Al7475 alloy and Al7475 alloy with 2 and 4 wt% of nano composites were evaluated at room temperature as well 50 and 100 °C elevated temperatures. SEM micrographs showed the distribution of nano sized particles all over the Al7475 alloy matrix. Further, EDS and XRD patterns confirmed the presence of various elements and boron carbide particles in the Al7475-B4C nano composites. The density of Al alloy decreased with the addition of nano particles. Hardness and tensile properties of nano boron carbide particles composites increased as weight % of particles increased with slight reduction in ductility. However, testing temperatures affected the tensile behavior of Al7475 alloy and its composites. At elevated temperatures there was slight decrease in the strength as compared to room temperature.[copyright information to be updated in production process]

Influence of reinforcing particles on microstructure and mechanical properties of friction stir processed aluminium alloy AA7075‐T651

AbstractThis paper emphasis the improvement of mechanical properties of AA7075‐T651 using friction stir processing through localized surface modification by adding nano boron carbide particles. The reinforcement techniques such as the groove and blind hole methods were used by changing reinforcements of nano boron carbide and a matrix of AA7075‐T651 surface composites volume percentages (2 %, 4 %, and 6 %) along with tool rotational speed and processing speeds. Optical microscopy, scanning electron microscope and x‐ray diffraction analysis were used to examine the particle dispersion for the surface composites and to correlate with the enhanced mechanical properties. Results revealed that high input parameters have given grain coarsening and precipitate agglomeration and low input parameters provide poor nugget metal consolidation and no vertical material flow. The L9 orthogonal Array designed and optimized the process parameters for enhancing the surface properties of processed samples. Mechanical properties like ultimate tensile strength, yield strength, hardness, percentage of elongation and impact strength were evaluated for the groove friction stir processing method and blind‐hole friction stir processing methods. From the results, it has been observed that the blind‐hole technique resulted in higher hardness and the homogenous dispersion of nano boron carbide particles in the stir zone than the groove method. Consequently, for blind‐hole friction stir processing, grey relational analysis (GRA) and particle swarm optimization (PSO) approaches were proposed to optimise process parameters. From the compared optimization results between grey relational analysis and particle swarm optimization, particle swarm optimization approach was shown the best optimization results. Successively, the optimum condition in the respective experimentation is accomplished. Based on these observation and results, final validation tests were carried by changing the volume percentages of reinforcement keeping tool rotation speed and tool processing speed as constant. It is apparent that dynamic recrystallization in aluminium alloy at the processed zone due to presence of heterogeneous nucleation sites with nano boron carbide particles.

Influence of Heat Treatment on Stress Intensity Factor of Nano Boron Carbide Hybrid Al2219 Composites with MoS2

The current work emphasizes on study of influence of heat treatment on Stress Intensity factor (KIC) of Al alloy matrix hybrid composites. Hybrid composites with a constant Nano B4C content of 3 weight % and MoS2 of 4 weight % as reinforcements to Al2219 alloy matrix are fabricated by using two step stir casting technique and tested for Stress Intensity factor and fracture toughness as per ASTM standards. One set of composites are subjected to T6 type heat treatment. Compact Tension (CT) Specimen were prepared using wire EDM process and tested in BISS Axial Universal Testing Machine to find Stress Intensity factor (KIC). From this study stability of crack propagation under mode-I failure is analyzed. Results show generous increment in energy required to open the crack and crack propagation is delayed in heat treated composites when compared to non-heat treated composites and furthermore improvement in fracture toughness of the heat treated specimen over non-heat treated specimen.

Comparison of response surface methodology with artificial neural network for prediction of the tensile properties of friction stir-processed surface composites

In the present work, nanoboron carbide is integrated in the aluminum matrix using friction stir processing: by varying process parameters, that is, tool pin profile, tool rotational speed and tool traverse speed, based on Taguchi L16 design of experiment. A self-assembled monolayer is successfully developed on the substrate to homogeneously and uniformly distribute the reinforcement particles. Response surface methodology and artificial neural network models are developed using ultimate tensile strength and total elongation as responses. Percentage absolute error between the experimental and predicted values of ultimate tensile strength and total elongation for the response surface methodology model is 3.537 and 2.865, respectively, and for artificial neural network is 2.788 and 2.578, respectively. For both the developed models experimental and forecasted values are in close approximation. The artificial neural network model showed slightly better predictive capacity compared to the response surface methodology model. From the scanning electron microscopy micrograph, it is evident that throughout the matrix B4C reinforcement particles are well distributed also; with increasing tool rotational speed grain size decreases up to 1200 r/min; on further increasing the tool rotational speed particles starts clustering.

Dry sliding wear behavior of nano boron carbide particulates reinforced Al2214 alloy composites

In the current research wear behaviour of nano B 4 C particles with Al2214 alloy composites were studied. Al2214 alloy with 2 to 6 varying weight percentages of nano B 4 C particles composites were developed using stir cast route. Further, these developed composites were evaluated for the microstructural studies using SEM and EDS. The wear behaviour of Al2214 alloy and Al2214 with 2, 4 and 6 wt% of nano B 4 C composites were analysed using pin-on-disc wear apparatus. The dry wear tests were conducted at various loads and sliding speeds with 2500 m sliding distance as a constant parameter. The microstructural explanations revealed the thorough circulation of nano particles in the Al2214 alloy matrix, further the boron carbide particles were confirmed in the composites in the form of boron and carbon components. The Al2214 alloy with nano B 4 C composites displayed the greater wear resistance properties. The applied load and speed were impacted the wear of as cast alloy and its composites. Various wear mechanisms were identified by using SEM images of wear surfaces.

Preparation of the novel B4C–SiC composite aerogel with high compressive strength and low thermal conductivity

A novel B4C–SiC composite aerogel is synthesized using nano boron carbide suspension, 3-aminopropyltriethoxysilane (APTES), and resorcinol–formaldehyde (RF) as precursors through the sol–gel route and carbothermal reduction process. The effects of different B/Si molar ratios and calcination temperatures on the physical chemistry properties of B4C–SiC composite aerogels are investigated. The addition of the B4C phase is beneficial for improving the comprehensive properties of composite aerogel. The results show that the compressive strength of B4C–SiC composite aerogel is as high as 3.05 MPa. The specific surface area can reach 692.81 m2/g, which ensures that it has a thermal insulation capacity under elevated temperatures. After heat-treated at 1650 °C for 3 h, the thermal conductivity of carbon fiber mat reinforced composite aerogel is 0.058 W/m K (25 °C). This composite aerogel material has great application prospects in the field of high temperature insulation.

B, N Co‐doped Nanocarbon Derived In Situ from Nanoboron Carbide as Electrocatalyst for Oxygen Reduction Reaction

AbstractHeteroatom‐doped metal free carbon materials, especially boron and nitrogen co‐doped carbons have been widely researched as promising oxygen reduction electrocatalysts because of their low cost, high activity and environmental friendliness. However, B, N‐doped carbon electrocatalysts are usually prepared at high temperature and accompanied by the formation of B−N bonds resulting in the inactivation of the active sites. This paper proposed a strategy for synthesizing B and N co‐doped carbons for oxygen reduction reaction in‐situ derived from nano‐boron carbide by one‐step heat treatment at low temperature. This strategy can produce B‐ and N‐doped active sites while avoiding formation of B−N bonds, allowing electrocatalysts to exhibit excellent catalytic activities (Eonset=0.93 V, E1/2=0.79 V) and better stability (current density remained 93.3% after 12,000 s) comparable to commercial Pt/C (20 wt%). New ideas were provided by this work to massively produce the B and N co‐doped carbon electrocatalysts candidates for ORR.

Monitoring the neural network modelling of wear behaviour of Ti-6Al-4 V reinforced with nano B4C particle

The main objective of the study is to fabricate nano boron carbide (B 4 C) reinforced with titanium metal matrix composite (Ti-6Al-4 V) through powder metallurgy route. Composites preforms of Ti-6Al-4 V- (2–10) wt. % of nano boron carbide were fabricated. The characterization of the fabricated samples was preformed through Scanning electron microscope and X-Ray diffraction. Pin-on-disk wear testing machine was used to describe the lubricating wear behavior of the composites by varying loads and sliding distances. The surface morphology of worn out surfaces was also examined. Investigations over basic and functional properties of developed MMC revealed that the addition of nano B 4 C decrease the specific wear rate (SWR) and coefficient of friction (CoF). To predict the tribological properties of titanium matrix composites, Artificial Neural Network (ANN) technique was adopted to arrive at optimal values of the input parameters based on the experimental data. The results illustrated that the mathematical models of tribological properties of Ti-6Al-4 V-B 4 C are reliable with a less error and high level of accuracy.

Synthesis and corrosion behavior of cold sprayed dual nanoparticle reinforced Al coatings

This study investigates the synergistic and individual effects of nano boron carbide (nB4C) and boron nitride nanoplatelets (BNNP) on the corrosion behavior of cold spray aluminum matrix composite (MMC) coatings. Cryomilling and cold spraying were used to synthesize four novel Al MMC coatings with reinforcements consisting of either 2 vol.% nB4C, 2 vol.% BNNP, or dual nanoparticle reinforcement consisting of 1 vol.% nB4C plus 1 vol.% BNNP. Cold sprayed coatings were evaluated using microhardness testing which revealed an 11.7% increase in hardness in the dual nanoparticle reinforced composite coating. Coatings were subjected to 500 h and 2000 h corrosion tests in a salt fog chamber consisting of 3.5% NaCl to simulate an aggressive marine environment. Coatings were evaluated post-salt fog chamber by mass and thickness change measurements, optical microscopy, scanning electron microscopy, and energy dispersive spectroscopy. Following 500 h corrosion testing, each composite coating experienced mild to severe pitting throughout a significant portion of the coating. Following 2000 h exposure, in addition to severe pitting, all coatings experienced galvanic corrosion at the coating/substrate interface.

Dry sliding wear behavior of ultrasonic stir cast boron carbide reinforced aluminium nanocomposites

In the present work ultrasonic stir casting method is used to fabricate aluminium metal matrix nanocomposites reinforced with nano boron carbide (nB4C) particles with varying (0.5, 1, 1.5 and 2) weight percentages. Microhardness and nanoindentaion hardness of the nanocomposite is found to increase with increasing reinforcement content. Pin on disk apparatus is used to study the room temperature dry sliding wear behavior of fabricated composites and base alloy. Nominal contact pressures of 0.354–1.412 MPa and sliding speeds of 0.16–0.66 m s−1 are employed. Each test run is conducted for the fixed contact period of 15 min. Field emission scanning electron microscopy (FESEM) equipped with energy dispersive spectroscopy (EDS) is used to observe worn surface and wear debris to understand the undergoing wear mechanisms. It is observed that base alloy underwent mild to severe plastic deformation led oxidative delamination wear. Nanocomposites are subjected to combination of oxidative, abrasive and mild delamination wear. Nanocomposites display less mass loss and wear rate as compared to base alloy due to the protective tribolayer formed in the contact interface. Part of the mechanically mixed transfer layer is found to adhere firmly to the composite surface under higher load-speed condition. Extremely hard nB4C particle reinforcement is found beneficial for improving the wear resistance of aluminium alloy at varying combinations of load and speed.

Design and fabrication of a Nano-based neutron shield for fast neutrons from medical linear accelerators in radiation therapy

BackgroundPhoto-neutrons are produced at the head of the medical linear accelerators (linac) by the interaction of high-energy photons, and patients receive a whole-body-absorbed dose from these neutrons. The current study aimed to find an efficient shielding material for fast neutrons.MethodsNanoparticles (NPs) of Fe3O4 and B4C were applied in a matrix of silicone resin to design a proper shield against fast neutrons produced by the 18 MeV photon beam of a Varian 2100 C/D linac. Neutron macroscopic cross-sections for three types of samples were calculated by the Monte Carlo (MC) method and experimentally measured for neutrons of an Am-Be source. The designed shields in different concentrations were tested by MCNPX MC code, and the proper concentration was chosen for the experimental test. A shield was designed with two layers, including nano-iron oxide and a layer of nano-boron carbide for eliminating fast neutrons.ResultsMC simulation results with uncertainty less than 1% showed that for discrete energies and 50% nanomaterial concentration, the macroscopic cross-sections for iron oxide and boron carbide at the energy of 1 MeV were 0.36 cm− 1 and 0.32 cm− 1, respectively. For 30% nanomaterial concentration, the calculated macroscopic cross-sections for iron oxide and boron carbide shields for Am-Be spectrum equaled 0.12 cm− 1 and 0.15 cm− 1, respectively, while they are 0.15 cm− 1 and 0.18 cm− 1 for the linac spectrum. In the experiment with the Am-Be spectrum, the macroscopic cross-sections for 30% nanomaterial concentration were 0.17 ± 0.01 cm− 1 for iron oxide and 0.21 ± 0.02 cm− 1 for boron carbide. The measured transmission factors for 30% nanomaterial concentration with the Am-Be spectrum were 0.71 ± 0.01, 0.66 ± 0.02, and 0.62 ± 0.01 for the iron oxide, boron carbide, and double-layer shields, respectively. In addition, these values were 0.74, 0.69, and 0.67, respectively, for MC simulation for the linac spectrum at the same concentration and thickness of 2 cm.ConclusionResults achieved from MC simulation and experimental tests were in a satisfactory agreement. The difference between MC and measurements was in the range of 10%. Our results demonstrated that the designed double-layer shield has a superior macroscopic cross-section compared with two single-layer nanoshields and more efficiently eliminates fast photo-neutrons.

Mechanical Behavior and Fractography of Al2218 Nano B4C Metal Composites

In the present examination, the mechanical properties of Al2218-nano B4C composites displayed. The composites containing 4 to 8 wt. % of nano boron carbide in ventures of 4 wt.% were readied utilizing liquid metallurgy method through stir casting. For every composite, fortification particles were preheated to a temperature of 400˚C and afterward added in ventures of two into the vortex of liquid Al2218 compound to improve the wettability and dispersion. Microstructural examination was carried out by SEM and elemental investigation was finished by EDS. XRD Analysis used to recognize the B4C phases in the Al grid. Density, tensile, compression and hardness tests were done to distinguish various properties of composites. The aftereffects of this investigation uncovered that as the weight % level of nano B4C particles were expanded, there was noteworthy increment in hardness, UTS, yield and compression strength of Al2218 amalgam composites. Further, there was slight drop in the density and malleability of the Al2218 amalgam composites when contrasted with the base. Tensile fractured surfaces analysis was conducted by using SEM.

Silica–Phenolic Nanocomposite Ablatives for Thermal Protection Application

A novel class of ablative materials using phenolic resin, silica fabric, and nano-zirconium dioxide is being developed as a potential alternative for use in high-heat-flux thermal protection applications. Four new silica–phenolic ablatives have been fabricated using tandem nanocomposite formulations. Each of the tandem composites consist of nano-zirconium dioxide with small amounts of one of the following additives: multiwalled carbon nanotubes, nano-graphene platelets, alumina nanofibers, and nano-boron carbide. Materials have been fabricated, characterized, and compared using thermal and microanalysis. Thermogravimetric analysis and microscale combustion calorimetry were used to compare char yield, thermal stability, and flammability properties. Oxy-acetylene test bed aerothermal ablation testing was used to evaluate the composites under a high heat flux of environment. Data analysis on recession rate, mass loss rate, backside heat-soaked temperature, surface temperature, and materials surface behavior were collected and used as a comparison tool to rank ablation performance of candidate materials. After testing of the candidates, it was determined that the nanocomposite containing nano-boron carbide in tandem with nano-zirconium dioxide was the best-performing candidate, demonstrating superior ablation properties, such as mass loss, recession rate, and insulative properties.

Nano-carbides as accelerants for boron oxidation reaction

Nano-materials are potential substitutes for micro-sized solid propellant ingredients for improving energy density and reaction activity. So far, several nano-carbides act as accelerants for boron (B) oxidation reaction but their promotive effects and corresponding action mechanisms have rarely been reported. In this work, four nano-carbides [nano-boron carbide (nB4C), nano-titanium carbide (nTiC), nano-zirconium carbide (nZrC), and nano-silicon carbide (nSiC)] were evaluated by thermogravimetric differential scanning calorimetry-combined thermal analysis system and thermodynamic software FactSage 6.2. Among the four nano-carbides, nTiC ranked as the best accelerant by reducing the initial oxidation temperature of B by 10.7% and increasing heat release by 16.0%. By comparison, nB4C and nZrC were ranked as second and third best accelerants with abilities of decreasing the initial oxidation temperature (by 5.4% and 3.3%, respectively) and raising heat release (both by 6.2%). On the other hand, though nSiC slightly decreases the initial oxidation temperature of B, heat release of B + nSiC was lower than that of original B. The action mechanisms of nano-carbides were found complex, and one nano-carbide can accelerate B oxidation following one or several approaches. First, the nano-carbide can be oxidized before B to offer extra heat and induce the oxidation of B. The produced gaseous oxidation product CO2 by nano-carbide may then help break down the liquid oxide film deposited on B particle surface. Third, the reaction between nano-carbide and B would generate borides, which may diminish accumulated liquid oxide film at low temperatures. Finally, the corresponding oxide will be produced to catalyze the oxidation of B. Overall, these findings look promising for future performance improvement of B-based solid propellants.

Thermal expansion of nano–boron carbide under constant DC electric field: An in situ energy dispersive X-ray diffraction study using a synchrotron probe

Abstract

Effect of nanoboron carbide particles on properties of copper-matrix/graphite composite materials

In this study, a new type of copper (Cu)-matrix self-lubricating composite was successfully prepared, which was based on nanoboron carbide (n-B4C) particles, Cu-coated graphite, and Cu powders, combined by powder metallurgy. These composites contained 2 wt% graphite as the lubricating phase and 0.2, 0.3, 0.5, 0.8, and 1.2 wt% n-B4C as the reinforcing phase. The effects of different amounts of n-B4C particles on composite properties and the composite wear mechanism were examined. All composites were characterized in terms of microstructure, density, porosity, hardness, compressive yield strength, and friction wear. The results showed that, with n-B4C particle addition, the hardness, compressive strength, friction, and wear properties were improved. With >0.2 wt% n-B4C, composite porosity gradually increased, and hardness, compressive strength, and friction and wear properties sharply decreased. With n-B4C addition, the main wear mode of the composites changed from adhesive to abrasive wear, then to adhesion and peeling wear with increased n-B4C particle content.