B4C Composites Research Articles

Development of New Lead-Free Composite Materials as Potential Radiation Shields.

Utilizing a polymer-based radiation shield offers lightweight, low cost, non-toxic compared to lead and solution for eliminating generated secondary neutrons. Incorporating silicon (i.e., one of the most abundant elements) in new applications, such as shielding, would have an impact on the economy and industry. In this study, seven potential shielding materials, composed of silicon, silicon carbide, and boron carbide embedded ethylene vinyl acetate (EVA) copolymers, are proposed. The shielding performance of these composite materials, including the attenuation coefficients (µ), the mass attenuation coefficients (µm), the half value layer (HVL), the mean free path (MFP), and the radiation protection efficiency (RPE) were examined using photon beams. Measured µm were verified against the calculated values. The averaged agreement was within ±7.4% between the experimental measurements and the theoretical calculation results. The HVL and MFP measured values for the polymer composites were lower than that for the pure EVA polymer, indicating the fillers in the polymers enhanced the shielding performance. The EVA + SiC (30%) and EVA + Si (15%) + B4C (15%) composites required the lowest thickness to stop 50% of the incident photons. The evaluation of experimental results of the RPE revealed that the polymer composites containing SiC (30%), Si (15%) + B4C (15%), or SiC (15%) + B4C (15%) succeeded in blocking 90–91% of X-rays at nearly 80 keV. However, a thicker shield of the proposed composite materials or combined layers with other high-Z materials could be used for higher energies.

Effect on Microstructure and Performance of B4C Content in B4C/Cu Composite

In this paper, boron carbide (B4C) ceramics were added to a copper (Cu) base, to improve the mechanical properties and wear resistance of pure copper. The B4C/Cu composites with different B4C contents, were obtained by mechanical mixing and discharge plasma sintering methods. Scanning electron microscopy (SEM), energy spectrum analysis (EDS), and electron probe microanalysis (EPMA) were used, to observe and analyze the microstructures of the B4C/Cu composites. The influences of the B4C content on the hardness, density, conductivity, and wear resistance were also studied. The experimental results show that B4C has an important effect on Cu. With increasing B4C content, both the density and conductivity of the B4C/Cu composites gradually decrease. The hardness of the Cu-15 wt.% B4C composite has the highest value, 86 HBW (Brinell hardness tungsten carbide ball indenter), which is 79.2% higher than that of pure copper. However, when the B4C amount increases to 20 wt.%, the hardness decreases due to the metallic connection being weakened in the material. The Cu-15 wt.% B4C composite has the lowest volume loss, indicating that it has the best wear resistance. Analyses of worn B4C/Cu composite surfaces suggest that deep and narrow grooves, as well as sharp ridges, appear on the worn pure Cu surface, but on the worn Cu-15 wt.% B4C composite surface, the furrows become shallow and few. In particular, ridge formation cannot be found on the worn Cu-15 wt.% B4C composite surface, which represents the enhancement in wear resistance.

Microstructure, Tensile and Flexural Strength of Boron Carbide Particles Reinforced Al2030 Alloy Composites

Objective: To synthesize and assess the mechanical behaviour of 12 wt. % of 80 to 90 micron sized B4C reinforced Al2030 alloy metal composites. Method: Al2030 alloy with 12 wt. % of B4C reinforced composites were developed by liquid melt stir cast method. These prepared composites were subjected to microstructural characterization by SEM, EDS and XRD. Mechanical properties like hardness, tensile and flexural strength were evaluated according to ASTM standards. Findings: Scanning electron micrograph of Al2030 alloy with 12 wt. % of B4C composites revealed the thorough distribution of boron carbide particles in the Al2030 matrix. EDS and X-ray diffractometer patterns confirmed the presence of boron carbide particles in the Al2030 alloy matrix. The addition of 12 wt. % of B4C particles enhanced the hardness by 74.8%, ultimate strength by 59.2%, yield strength by 64.8% and flexural strength by 44.2% with slight decrease in ductility. Novelty: Al2030 alloy is an aerospace grade aluminium alloy widely used for industrial applications. Advanced metal composites developed with the incorporation of 80 to 90 micron sized B4C particles in Al2030 alloy helps in weight reduction of aerospace components. Keywords: Al2030 Alloy; B 4 C Particles; Microstructure; Tensile Strength; Flexural Strength; Fractography

On the effect of compaction velocity, size, and content of reinforcing particles on corrosion resistance of Mg–B4C composites

In this study, the effect of the compaction velocity as well as the size and volume fraction of the reinforcing particles on the corrosion properties of Mg–B4C composites were investigated. Micron/nano particles of boron carbide at different volume fractions (0, 5, and 10%) were added to the matrix (magnesium powder). Powder mixtures were milled in a planetary ball mill and compacted at 450 °C and different strain rates, using Split-Hopkinson bar (SHB), drop hammer, and Instron devices. Microstructural analysis and corrosion tests were carried out on the produced samples. The results indicated that the samples produced at higher compaction velocities had the lower corrosion rate mainly due to the lower porosity and higher relative density of the samples. For example, the measured corrosion rates for the magnesium samples reinforced with 5 vol% of micron B4C particles and compacted by the SHB method were 54 and 76% lower than the similar samples produced by the drop hammer and Instron device, respectively. It was also shown that decreasing the size and content of the reinforcing particles resulted in a reduction in the corrosion rate values. The recorded corrosion rate values for the samples reinforced with 5 and 10 vol% of B4C nanoparticles and compacted by the drop hammer device were 18.3 and 29.18 mm/year, respectively. These valuses were approximately 16 and 13% lower compared to the similar composites reinforced with micron-sized particles. The lowest corrosion rate (1.84 mm/year) was observed in the pure magnesium sample compacted by the SHB which was 29.42% lower than that of the magnesium sample reinforced with 10 vol% of micron-sized B4C.

Influences of B4C content and particle size on the mechanical properties of hot pressed TiB2–B4C composites

ABSTRACT TiB2 ceramic has attracted many attentions due to its excellent performances both on mechanical and functional properties. However, it is still very difficult to obtain TiB2 bulks with full densification. Herein, TiB2–B4C composites were prepared via hot pressing at 1900°C under the pressure of 35 MPa with TiB2 and B4C as the raw materials. The influences of B4C content (0, 10 vol%, 20 vol% and 30 vol%) and particle size (0.50 µm, 3.12 µm and 7.09 µm) on the phase composition, relative density, microstructure and mechanical properties of TiB2–B4C composites were investigated. The using of 0.50 µm B4C brought more B2O3 which induced oriented growth of TiB2 grains and coarsened the obtained composites. When the raw B4C powders were 3.12 µm and 7.09 µm, the obtained composites with 20–30 vol% B4C could be fully densified. TiB2–30 vol% B4C composite prepared from 3.12 µm B4C powder resulted in the optimal mechanical properties. The bending strength, Vickers hardness, fracture toughness were 671 MPa, 27.93 GPa, and 3.91 MPa·m1/2, respectively. The excellent performance was attributed to its fine and homogenous microstructure.

Characterization and optimization of influence of MoS2 hybridization on tribological behaviours of Mg–B4C composites

Characterization and optimization of influence of MoS2 hybridization on tribological behaviours of Mg–B4C composites

Tribolayer Behaviour and Wear of Artificially Aged Al6061 Hybrid Composites

The current work focuses on enhancing wear resistance due to the presence of reinforcements and the effect of ageing treatment on hybrid composites of Al6061-SiC+B4C. By varying weight percentage, two kinds of reinforcements, viz. silicon carbide and boron carbide, were prepared for hybrid composites by the liquid state process known as the method of stir casting. The solutionising temperature of 550 °C for 2 hours and ageing temperature of 100-200°C at different time intervals were used for both Al6061 alloy and its composites during heat treatment. Microstructural and mechanical characterisation were carried out using a standard testing procedure. Compared to Al6061 matrix alloy, artificially peak aged composites show 100-140% improvement in hardness due to harder reinforcements and precipitation of solute rich secondary phases during ageing treatment. Overall, an 80-100% increase in wear resistance observed during peak ageing of hybrid composites. Analysis of Al6061 matrix alloy wear out surface shows extensive grooving and ploughing of the surface with the matrix material smear at many spots. The presence of tribolayer in Al6061-SiC+B4C composites shows a smoother surface than the Al6061 matrix alloy, which results in an excellent lubrication effect during an improvement in wear resistance. The wear surface of base aluminium alloy doesn’t show the existence of iron in the tribolayer. The research work is significant in forming a thermally activated wear-resistant metallic tribolayer with good tribological properties.

Investigations on Mechanical Behaviour of Micro B4C Particles Reinforced Al6061 Alloy Metal Composites

Objective: To develop and evaluate the mechanical behavior of 3, 6, 9 and 12 wt. % of B4C reinforced Al6061 alloy composites. Method: These composites were produced by utilizing stir cast process. The prepared metal composites were characterized by SEM, EDS and XRD analysis to know the distribution of particles as well as presence of particles in the Al6061 alloy. Various mechanical properties were evaluated as per ASTM standards to know the impact of boron carbide particles on the properties of metal composites. Findings: By adding B4C particles the hardness, ultimate tensile, yield strength and compression strength of the Al6061 alloy matrix was enhanced 23.9%, 15.4 14.9% and 34.7% respectively. Further, there was slight decrease in the percentage elongation of B4C reinforced composites. Novelty: In the present research Al6061 alloy with 3 to 12 wt. % of B4C composites were synthesized by novel stir casting method called as two stage reinforcement addition process. In this process 80 micron sized boron carbide particles added in two stages into the molten Al6061 alloy to improve the wettability between the matrix and reinforcement particles. Keywords Al6061 Alloy, B 4 C Particles, Hardness, Tensile Strength, Microstructure

Microstructure and mechanical properties of TiB2–B4C ceramics fabricated by hot-pressing

In this study, TiB2–B4C composite ceramics were prepared using Y2O3 and Al2O3 as the sintering aids. Different contents of B4C were added to seek promoted comprehensive mechanical properties of the composites. The mixed powders were sintered at 1850 °C under a uniaxial loading of 30 MPa for 2 h via hot-pressing. Through the measurement of XRD, SEM and related mechanical properties, the influence of B4C content on the microstructure and mechanical properties of TiB2–B4C composites ceramics was discussed. The experimental results show that TiB2–B4C composite ceramics exhibit excellent mechanical properties, which can be attributed to the dense microstructure and fine grain size. In addition, TiB2–B4C composite ceramic shows a relatively high comprehensive properties when the addition amount of B4C is 20 wt%. The relative density, Vickers hardness, fracture toughness and flexural strength are measured to be 99.61%, 27.63 ± 1.73 GPa, 4.77 ± 0.06 MPa m1/2, 612.5 ± 28.78 MPa, respectively.

Study On Effect of Boron Carbide, Aluminium Oxide and Graphite On Dry Sliding Wear Behaviour of Aluminium Based Metal Matrix Composite at Different Temperature

The present research has been conducted to study the impact of boron carbide (B4C), aluminium oxide(Al2O3) and graphite on Aluminium 2219 (Al2219). According to current research, B4C and graphite material be a good substitute for Al2219.Reinforced composites and unreinforced Al2219 prepared by a stir casting process. A scanning electron microscope was used to analyze the reinforcement and distribution in the matrix and worn surface of the specimen. Exceptional wear resistance (30%) exhibited by B4C and graphite-reinforced hybrid composite at 150 ºC in contrast with the unreinforced Al2219. The B4C and Gr reinforcement particulate existence improves the strengthening kinetics in the matrix phase at 150 °C. The artificial neural network used to get the test significance, normalized factor importance and absolute relative error of less than 1%.

First-principles investigation of mechanical, electronic, dynamical, and thermodynamic properties of Al3BC

In this paper, Al-12 wt%B4C composites without and with 3 wt%Ti were fabricated via the stir-casting process, the results show that Al3BC was the main component of the reactant at the interface of B4C–Al composites. The first-principles was utilized to conduct an in-depth study of the mechanical, electronic, and thermodynamic properties, and the lattice dynamics of Al3BC. The optimized lattice parameters were agreed well with the experimental values. Al3BC had good thermal stability, but the dynamic stability was poor. The bulk modulus, shear modulus, Young's modulus, Poisson's ratio, B/G, and hardness of Al3BC are 153 GPa, 137 GPa, 317 GPa, 0.16, 1.17, and 26.43 GPa, respectively, these values indicate that Al3BC is a brittle material with high hardness and that brittle failure is the main failure form. Al3BC had a slight elastic anisotropy. It also had semiconductor properties, and its chemical bonding was covalent, metallic, and ionic.

The tensile damage behavior of SiCf/SiC–B4C after oxidation in wet atmosphere based on acoustic emission pattern recognition

AbstractIn this research, SiCf/SiC–B4C composites were prepared through slurry impregnation and reaction melting infiltration (RMI). To explore the damage evolution of this composites after oxidation in wet atmosphere, the changes of damage behavior of composites before and after oxidation were studied using acoustic emission (AE) pattern recognition (PR) technology. Results show that since the damage behavior of the composites changes after oxidation, the optimal number of clusters transforms from 3 to 5. In addition, as the oxidation time increases, the area of concentration of damage events is gradually broadened towards lower stress direction due to the decrease of damage threshold of composites. Meanwhile, because the BN interface is gradually oxidized, the density of C3‐cracks (axial yarns cracks) near the fracture and the proportion of Cluster‐4 (the signals of transverse yarns cracks) will increase, for which the rising of interfacial shear stress should be responsible. Through this research, not only can the damage evolution of SiCf/SiC–B4C composites after oxidation be understood, but also the method employed in this research can be as guide for studying other similar materials.

Chemical Modification of B4C Films and B4C/Pd Layers Stored in Different Environments.

B4C/Pd multilayers with small d-spacing can easily degrade in the air, and the exact degradation process is not clear. In this work, we studied the chemical modification of B4C films and B4C/Pd double layers stored in four different environments: a dry nitrogen environment, the atmosphere, a dry oxygen-rich environment, and a wet nitrogen environment. The XANES spectra of the B4C/Pd layers placed in a dry oxygen-rich environment showed the most significant decrease in the σ* states of the B–C bonds and an increase in the π* states of the B–O bonds compared with the other samples. X-ray photoelectron spectroscopy (XPS) measurements of the samples placed in a dry oxygen-rich environment showed more intensive B-O binding signals in the B4C/Pd layers than in the single B4C film. The results of the Fourier-transform infrared spectroscopy (FTIR) showed a similar decrease in the B–C bonds and an increase in the B–O bonds in the B4C/Pd layers in contrast to the single B4C film placed in a dry oxygen-rich environment. We concluded that the combination of palladium catalysis and the high content of oxygen in the environment promoted the oxidization of boron, deteriorated the B4C composition.

Effects of processing on mechanical properties of B4C-graphene composites fabricated by hot pressing

Abstract Boron carbide (B4C) composites with 4 wt% graphene were fabricated by hot pressing (HP) using two different graphene sources, graphene nanoplatelets (GNPs) and graphene oxide (GO), and two different homogenization methods. B4C–GNPs/GO powder mixtures were homogenized by planetary ball milling and a heterogeneous co-precipitation method using cetyltrimethyl ammonium bromide (CTAB) as the cationic surfactant. The influences of homogenization methods and types of graphene source on the microstructure and mechanical properties of B4C composites were investigated. A maximum flexural strength of 476 MPa was achieved for B4C–GNPs composites homogenized using planetary ball milling with previous ultra-sonication of GNPs in ethanol. Additionally, the fracture toughness of B4C composites was in the range 3.85–5.51 MPa m1/2, which was significantly higher than that of monolithic B4C. Fractography was also performed to evaluate the individual homogenization method. Based on the different processing techniques, the critical flaw sizes of the B4C composites varied from 45 μm to 112 μm. The results reveal that the main fracture origins are processing flaws in the form of structural heterogeneities, graphene agglomerations, and interfacial porosity.

Spark plasma sintering of B4C and B4C-TiB2 composites: Deformation and failure mechanisms under quasistatic and dynamic loading

Spark plasma sintering (SPS) was employed to consolidate powder specimens consisting of B4C and various B4C-TiB2 compositions. SPS allowed for consolidation of pure B4C, B4C-13 vol.%TiB2, and B4C-23 vol.%TiB2 composites achieving ≥99 % theoretical density without sintering additives, residual phases (e.g., graphite), and excessive grain growth due to long sintering times. Electron and x-ray microscopies determined homogeneous microstructures along with excellent distribution of TiB2 phase in both small and larger-scaled composites. An optimized B4C-23 vol.%TiB2 composite with a targeted low density of ∼3.0 g/cm3 exhibited 30–35 % increased hardness, fracture toughness, and flexural bend strength compared to several commercial armor-grade ceramics, with the flexural strength being strain rate insensitive under quasistatic and dynamic loading. Mechanistic studies determined that the improvements are a result of a) no residual graphitic carbon in the composites, b) interfacial microcrack toughening due to thermal expansion coefficient differences placing the B4C matrix in compression and TiB2 phase in tension, and c) TiB2 phase aids in crack deflection thereby increasing the amount of intergranular fracture. Collectively, the addition of TiB2 serves as a toughening and strengthening phase, and scaling of SPS samples show promise for the manufacture of ceramic composites for body armor.

Wear behavior and dry sliding tribological properties of ultra-fine grained Al5083 alloy and boron carbide-reinforced Al5083-based composite at room and elevated temperatures

Tribological behavior and wear mechanisms of mechanically milled Al5083 alloy and Al5083−5wt.%B4C composite at room temperature and 200 °C were discussed. Results revealed that due to the oxidative wear at room temperature, a mechanically mixed layer (MML) was formed to protect the surface of the samples. Under 80 N of load at room temperature, the milled Al5083 and the Al5083−5wt.%B4C samples showed evidence of abrasion with limited volume loss. In this case, the wear rates were 5.8×10−7 and 4.4×10−7 mm3/(m·N), respectively. At 200 °C and under 80 N of applied load, severe wear occurred in the milled Al5083 sample, and wear rate reached 10.8×10−7 mm3/(m·N) while the Al5083−5wt.%B4C sample showed mild wear with local 3-body abrasion and the wear rate reached 5.3×10−7 mm3/(m·N). Strengthening mechanisms such as dislocation pinning and the Hall−Petch theory, high hardness and the load transfer effect were crucial in determining the wear behavior of the Al5083−5wt.%B4C composite. On the other hand, the milled Al5083 sample represented a relatively high wear rate at 200 °C, which seemed to be related to the local grain growth and a drop in its hardness.

Concentrated solar power used in preparation of Ti – B4C composites

Concentrated solar power was employed to sinter compacts of Ti + 15 vol% B4C powder mixture. The sintering experiments were performed under protective argon atmosphere at different temperatures and sintering time without external pressure. The sintering experiments were done in 40 kW horizontal solar furnace (SF40) at Plataforma Solar de Almeria (PSA), Spain.The in situ sintering behavior of the Ti – B4C mixture is significantly affected by exothermic reaction of titanium with B4C. In the solar furnace the ignition temperature of this reaction was found to be around 1380 °C. Therefore, the exothermic reaction of Ti + B4C makes the controlling of the solar sintering of these composites very difficult.The optimal temperature of solar sintering was found slightly below 1340 °C for 30 min. No significant reduction of porosity was observed: All samples have more or less the same final porosity value as green compacts prior sintering. The prepared composite samples are brittle. Decomposition of boron carbide led to the creation of TiB2, TiC and complex TiBxC1-x phases which were confirmed by microstructural investigations.

Microstructural evolution and mechanical behavior of 90 micron sized B4C particulates reinforced Al2219 alloy composites

The microstructure and mechanical behavior of Al2219 metal alloy with 2, 4, 6, 8 and 10 wt% of B4C composites were studied. The composites comprising 2 to 10 wt% of B4C in Al2219 alloy were amalgamated by liquid metallurgy process. The prepared composites were subjected to the microstructural studies using SEM. Further, the mechanical behavior of Al2219 with B4C composites were tested as per ASTM methods. The SEM characterization identified thorough dispersal of particles in the base alloy. Further, mechanical behavior of Al2219 alloy has been improved with the addition of B4C particles. The enhanced hardness and tensile strengths were obtained in the composites. The ductility and density of the Al2219 alloy was reduced after the inclusion of boron carbide particles.

Machinability studies on boron carbide and graphite reinforced aluminium hybrid composites

The effect of machining parameters on the thrust force, torque and burr height while drilling Al 2618, Al2618 with 10% boron carbide (B4C) and Al2618 with 10%B4C and 5% graphite (Gr) hybrid composites are addressed. The composites are produced using a process of liquid metallurgy. The findings indicate that, feed rate had a significant impact on thrust force and the height of the exit burr. The Al2618 + 10% B4C-5%Gr reinforced hybrid composites exhibit smaller thrust force and burr height in contrast to the Al2618 + 10% B4C composite. The reduced thrust force, torque and burr height was due to the strong graphite surface lubrication properties. The chips produced while machining graphitic composites are discontinuous, and hence beneficial.

Wear analysis of Al7075 alloyed with nano B4C: A taguchi approach

The paper discusses about a novel combination of Aluminium 7075 reinforced with Boron Carbide (B4C) in nano form in terms of wear behavior. This type of composites are popular now a day's addressing various needs of industry especially where the weight, mechanical and wear properties of the alloy have a significant effect on end application. The present investigational work involves base metal Aluminium 7075 reinforced with B4C in nano form in various percentages by weight (3 to 12%). The specimens were prepared by stir casting process as per ASTM standards and were tested for their behavioral aspects towards wear using pin on disc. The taguchi approach was applied to optimize the process parameters for the case. The process has four factors, four levels considering, composition of nano B4C as 3%,6%, 9% and 12%, load variations in steps are 10, 20, 30 and 40 N, speeds selected are 100, 200, 300, and 400 rpm respectively and sliding distances preferred are 500,1000,1500 and 2000 m to study the effects on wear. Post experimentation analysis established that the presence of nano B4C particles has shown considerable reduction in wear with the samples.