Papers by Keyword: Boron Carbide

Abstract: The study presents the mechanical performance, particularly energy absorption ability, under uniaxial quasi-static compression of aluminium foams fabricated by melt processing with CaCO₃ blowing agent and B₄C+TiB₂ powder with content varied from 30 to 70%. High-strength Al6Zn2.3Mg alloy comprising brittle eutectic domains was employed for manufacture of the foam. The optimal amount of B₄C + TiB₂ powder was determined to be 50% at which it results in the highest energy absorption. The key role of identity sizes for B₄C + TiB₂ and CaCO₃ powders for the efficiency of the foaming process with the formation of certain particle configurations in the melt was examined and discussed. The results of the present study could be helpful for selecting the aluminium alloy and additives for the foaming process and providing a certain level of the mechanical properties, particularly, energy absorption ability.

Abstract: This study aims to investigate the wear behavior of AA7075 alloy with the reinforcement of Silicon carbide (SiC) and Boron carbide (B4C) particles. Process parameters are crucial for component quality improvement, particularly in metal matrix composites (MMCs), a unique class of materials used in a variety of technical applications, such as but not limited to automobiles, marine, and aeronautics.These are frequently utilized in challenging applications due to their significantly better strength to weight ratios, stiffness, and then standard materials. However, it has numerous disadvantages, including high weight ratios, high deformation and stresses, poor fatigue life cycle, early wear and friction, and so on. Up till now, numerous reinforcements have been employed to address these crucial problems. Due to its superior properties, aluminum matrix composites (AMCs) have been used in many different applications. This work attempts to examine the wear behavior of AA7075 alloy reinforced with silicon (SiC) and boron (B4C) particles utilizing the stir casting process AA 7075-(SiC)-(B4C) composites were produced by employing AA 7075 as the matrix material with silicon carbide (SiC) and boron carbide (B4C) particles as reinforcement in various percentages of weight (5%, 10%, and 15%). Parameters of the composites, including wear behavior, coefficient of friction, frictional force, and pin temperature were assessed through graphical representation.

Abstract: The chemical vapor deposition (CVD) growth of boron carbide (B_xC) layers on 4H-SiC, 4°off substrates was studied. Depending on the polarity of the substrate, different results were obtained. On Si face, the direct CVD growth at 1600°C under a mixture of BCl₃+C₃H₈ systematically led to polycrystalline B_xC films, whatever the C/B ratio in the gas phase. On the C face, heteroepitaxial growth was obtained for C/B ratios = 12 or higher with a step bunched morphology. If a boridation step (10 min at 1200°C under BCl₃ flow) was used before the CVD growth, then heteroepitaxy was successful on both substrate polarities. To explain these results, a mechanism is proposed which involves the nature of the chemical bonds at the early stage of nucleation. It is suggested that a full B coverage of the SiC surface should favor the nucleation of the B-rich (0001) plane of B_xC, promoting thus the heteroepitaxial growth along this direction.

Abstract: In this work, the successful heteroepitaxial growth of boron carbide (B_xC) on 4HSiC(0001) 4° off substrate using chemical vapor deposition (CVD) is reported. Towards this end, a two-step procedure was developed, involving the 4H-SiC substrate boridation under BCl₃ precursor at 1200°C, followed by conventional CVD under BCl₃ + C₃H₈ at 1600°C. Such a procedure allowed obtaining reproducibly monocrystalline (0001) oriented films of B_xC with a step flow morphology at a growth rate of 1.9 μm/h. Without the boridation step, the layers are systematically polycrystalline. The study of the epitaxial growth mechanism shows that a monocrystalline B_xC layer is formed after boridation but covered with a B-and Si-containing amorphous layer. Upon heating up to 1600°C, under pure H₂ atmosphere, the amorphous layer was converted into epitaxial B_xC and transient surface SiB_x and Si crystallites. These crystallites disappear upon CVD growth.

Abstract: The present research shows the possibility of using an ytterbium nanosecond pulsed fiber laser for wear resistance improvement of carbon and alloy steels. The wear test was performed in accordance with the block-on-ring scheme with dry sliding friction on a friction machine. Surface dispersing/alloying was carried out from a boron carbide paste. This leads to a significant wear resistance improvement of steels. It was revealed that the mass loss during wear test reduced by several times after laser treatment compared to the non-treated samples. The wear mechanism differs depending on the type of steel and largely refers to their microstructure and composition. The tribo-oxide layer forms during the wear test.

Abstract: Tetra-Boron Carbide (B4C) are an excellent material for industrial applications in the nuclear, aerospace, and military. It is an excellent neutron absorber for use as a radiation shield. Using B4C as thermal barrier coating reduces the metal surface temperature, shields the substrate metal alloy from excessive heat, and increases system efficiency. In this degraded has been evaluated using non- destructive techniques that are appropriate for the predicament. To track the thermal barrier coating’s integrity over time, a microwave non-destructive technique was used to predict the porosity of the topcoat. Network analyzer (ENA5701C) in X-band (12–18 GHz) was utilized for this investigation. Detection was based on the changes in the electromagnetic properties, such as permittivity . A set of samples contained varied filler ranging of 5, 10, 15, 20 percent particle reinforcement. Most tested samples shows that porosities have maximum permittivity in the range of 15.4 – 16.7 GHz where some resonance occurred when real primitivity represent the capability of B4C to store and dissipate energy. This study suggesting that the proposed methodology could be a valuable aid technique for evaluating degraded on composite material systems in a non-destructive and accurate manner with complex pore morphology

Abstract: Recently, aluminum alloys are extensively used in automobile and aeronautical industries due to its low density and excellent mechanical properties. The aim of this research work is to focus on develop an aluminum matrix composite reinforced with boron carbide particulates under different weight percentages by squeeze casting route. To obtain better results, it is essential to control the process variables involved in the process. The primary work focused to optimize the process variables involved in the fabrication of the composites using full factorial design. The experiments were carried out with various input parameters like squeeze pressure of 50, 100 and 150Mpa, melting temperature of 700, 750 and 800°C and weight fraction of reinforcement of 6, 8 and 10% using L27 orthogonal array. The significant parameters were identified by analysis of variance table and regression analysis was used to model the mathematical relationship for obtaining better mechanical properties. Final results reveal that, mechanical properties of 218VHN hardness and 412MPa tensile strength had been obtained based on the optimum combination levels. Also AA7075-B₄C composites produced through this route with enhanced properties could be used as an alternative material for high strength structural applications like connecting rod, control arms, steering knuckle and other parts.

Abstract: The ultra-dispersive powders of pre-ceramic precursors for boron carbide based composites were obtained by relatively low-temperature (at 200 – 1000 °C) synthesis from liquid charges containing available compounds such as salts and oxides. Boron carbide matrix ceramics were compacted by their reactive spark plasma sintering (SPS) at 1500 – 1700 °C. It is noted that the X-ray diffraction (XRD) peaks corresponding (m)ZrO₂ and WC phases presented in the synthetic pre-ceramic precursors disappear after the SPS is conducted at 1500 °C. It is established that the addition of tungsten and cobalt compounds promotes both the low-temperature synthesis of ceramic components and sintering processes of their powders. Energy dispersive X-ray (EDX) analysis showed that the ceramics contain a small amount of Co (0.8 – 2 wt.%). The density of samples of cobalt-containing ceramics B₄C–ZrB₂–W₂B₅–Co is higher compared to that of cobalt-free ceramics B₄C–ZrB₂–W₂B₅.

Abstract: In this paper, we present the development of new types of boron carbide-based ceramics. Boron carbide is applied in the electronics and nuclear industries as well as for production of the grinding and abrasive materials, protective plates for body armor. The interaction of boron carbide with chromium nano-oxide additives (1-5 wt.%) during sintering was studied by mass spectrometry. It is shown that the formation of chromium nano-boride takes place at the stages of formation of metallic chromium, the lowest chromium boride and chromium carbide. The maximum solubility of chromium in the boron carbide lattice was found to be 0.5 wt.%. A composite material based on boron carbide, В₄С with CrB₂ nano-inclusions, was prepared. The bending strength and modulus of normal elasticity were equal to 44.6 MPa and 449.5 GPa, respectively. Micro-hardness and residual porosity were determined to be 40 GPa and 5-7 %.

Abstract: The optimal modes (temperature, time, pressure force) of spark plasma sintering (SPS) and hot pressing of boron carbide obtained by various methods are determined. The initial powders were obtained from soot and amorphous boron by the mechanochemical synthesis method, by the high-temperature synthesis (SHS) method and by the carbon reduction method. The structure and the properties of SPS sintered and hot-pressed boron carbide blanks were determined. The highest value of the relative density was achieved during SPS sintering of blanks from B₄C powders obtained by mechanosynthesis and SHS methods. It was found out the optimal conditions for sintering blanks from B₄C powder obtained by mechanosynthesis. The density value reaches 99.0 rel.% at 1500 °C/25 MPa and sintering time of 45 min. For powders obtained by the SHS method, the density of sintered blanks is 98.5 rel.%. at 1800 °C/30 MPa with sintering time of 45 min. The highest value of the relative density was achieved during the hot pressing of blanks from B₄C powders obtained by mechanosynthesis.