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A laboratory ultrasound technique has been developed to measure the longitudinal velocity of sound in high purity and density boron carbide and lanthanum hexaboride materials prepared by shock wave compression. Using the measured value of the longitudinal velocity of sound υ_L, we have calculated the Young's modulus E, the Bulk modulus K, the Shear modulus G and the Poisson's ratio ν. X-rays diffraction has also been carried out on these materials.

Using hot explosive compacting technology and consolidating B₄C powders in two stage at high temperatures enabled us to obtain compacts with high value of hardness and near theoretical density. This work contains results of calculations of B₄C stress state under the shock loading that is being distributed evenly at a constant rate through the boundary retaining samples.

The electronic and optical properties of pentagonal B₂C (penta-B₂C) monolayer are investigated by means of the first-principles calculations in the framework of the density functional theory. The cohesive energy consideration confirms the good stability of the B₂C nanostructure in this phase. The electronic band structure reveals that the valence band maximum (VBM) is located at $X$-point of the first Brillouin zone (BZ) whereas the conduction band minimum (CBM) is situated at the center of the BZ, resulting in an indirect energy bandgap of about 1.5 eV. Furthermore, a calculated low absorption and low reflection of the material in low energy ranges denote the transparency of the B₂C monolayer in the investigated range for normal light incidence. The obtained results may find application in fabrication of future opto-electronic devices.

In this paper, high purity boron carbide samples were irradiated by ${}^{60}$Co gamma radioisotope source (0.27 Gy/s dose rate) with 50, 100, 150 and 200 irradiation hours at room-temperature. The unirradiated and irradiated boron carbide samples were heated from 30${}^{\circ }$C to 1000${}^{\circ }$C at a heating rate of 5${}^{\circ }$C/min under the argon gas atmosphere of flow rate 20 ml/min. Thermogravimetric (TG) and Differential Scanning Calorimetry (DSC) were carried out in order to understand the thermodynamic kinetics of boron carbide samples. The weight kinetics, activation energy and specific heat capacity of the unirradiated and irradiated boron carbide samples were examined in two parts, T$\le$ 650${}^{\circ }$C and T$\ge$ 650${}^{\circ }$C, according to the temperature. The dynamic of quantitative changes in both ranges is different depending on the irradiation time. While the phase transition of unirradiated boron carbide samples occurs at 902${}^{\circ }$C, this value shifts upto 940${}^{\circ }$C in irradiated samples depending on the irradiation time. The activation energy of the unirradiated boron carbide samples decreased from 214 to 46 J/mol in the result of 200h gamma irradiation. The reduction of the activation energy after the irradiation compared to the initial state shows that the dielectric properties of the irradiated boron carbide samples have been improved. After the gamma irradiation, two energy barrier states depending on the absorption dose of samples were formed in the irradiated samples. The first and second energy barriers occurred in 0.56–0.80 and 0.23–0.36 eV energy intervals, respectively. The existence of two energy levels in the irradiated boron carbide indicates that the point defects are at deep levels, close to the valence band.

In the presented work, a boron carbide sample with a purity of 99.9%, particle size $1$–$3\mu$m and a density of $1.8\mathrm{\text{g}}/{\mathrm{\text{cm}}}^3$ was used. Boron carbide samples were irradiated with linear electrons in the energy range of 2.5 MeV at the doses of $4.16\times 10^{16}$, $1.20\times 10^{17}$ and $1.03\times 10^{18}{\mathrm{\text{cm}}}^{-2}$ at room temperature. XRD results show that only in the crystal structure of ${\mathrm{\text{B}}}_{13}{\mathrm{\text{C}}}_2$ compound, among boron carbide samples irradiated in the dose rate from $4.16\times 10^{16}{\mathrm{\text{cm}}}^{-2}$ to $1.03\times 10^{18}{\mathrm{\text{cm}}}^{-2}$ phase transition does not occur. The observed decrease in the lattice parameter values was explained as the strengthening of the bonds as a result of the recombination of defects in the crystal by influencing electron fluence. Dynamics of Raman spectra change and analytic analysis of intensive and duplex modes in various electron fluxes in (${\mathrm{\text{B}}}_{12}$) CBC-structure were performed and the occurring disorder in Raman active has been identified.

B₄C and B₆Si samples have been irradiated by using swift heavy ions and high intense electron beam. Ion irradiation of the samples was carried at the different electron fluences $4.16\times 10^{16}$, $1.20\times 10^{17}$ and $1.03\times 10^{18}$ cm${}^{-2}$ ion/cm², and energy of ions flux 167 MeV. Also, the samples were irradiated with high energy electron beams at the linear electronic accelerator at different electron fluencies up to $1.03\times 10^{18}$ cm${}^{-2}$ and energy of electron beams 2.5 MeV and current density of electron beams $0.075\mu \mathrm{\text{A}}/{\mathrm{\text{cm}}}^2\cdot$s. The unirradiation and irradiation of the thermodynamic kinetics of samples at low-temperature change with a differential mechanism. In the DSC curves, at the low temperature for unirradiation and irradiation, boron carbide and boron silicide samples do not undergo phase transition. But at the $100\le T\le 330$ K temperature range, the thermodynamic mechanism of ions and electron beam irradiation are very difficult and measuring the temperature of conductivity, thermal conductivity, calibration factor, specific heat capacity becomes more complicated.

The work functions of (001) and (00-1) surfaces of B₄C are investigated with density functional theory and symmetry slab model. These two surfaces are found to be almost nonpolarized and their work functions are 5.15 eV and 5.46 eV, respectively.

Surface composites are developed on Mg RZ 5 alloy by friction stir processing. During FSP, hard reinforcements are introduced into the matrix of RZ 5 alloy and dispersed uniformly by mechanical stirring action. The reinforcements dispersed were boron carbide, carbon nanotubes (multi-walled) and an 80:20 mixture of zirconia and alumina particles. Dynamic recrystallization and grain boundary pinning action by reinforcement particles resulted in the generation of fine-grained surface composites. Corrosion characteristics of the base material and the surface composites are studied by potentiodynamic polarization technique. The corrosion rates estimated for the surface composites are found to be far lesser than the base material while their polarization resistances were higher than the base material. Among all surface composites, B₄C particle reinforced surface composites exhibited the lowest corrosion rate of $\sim$15 mpy. Reduction in the corrosion rate of the surface composites is influenced by fine-grained microstructure and presence of harder reinforcement particles.

Based on the background of automotive mold surface strengthening, the effects of three different enhancements on the microstructure evolution, micro-hardness and wear resistance of laser cladding cobalt-based coatings were studied. The three reinforcing materials were Co45 alloy powder, Co45/8% B₄C mixed powder and Co45/8% B₄C/5% Cr₃C₂ mixed powder. They were respectively used to conduct laser cladding on the surface of die steel with preset powder method, with laser power of 2000W and scanning speed of 4mm/s. According to the test results, the hardness and wear resistance of the cladding coating were the best when Co45/8% B₄C powder was added. In addition, the study also found that B₄C reacted with Cr₃C₂ during laser cladding to eventually generate Cr₂B. The CrB₂ generated for the first time during the reaction was transformed into the most stable Cr₂B with an orthorhombic Fddd symmetry due to its poor stability. Therefore, the sample with Co45/8% B₄C/5% Cr₃C₂ mixed powder was affected with a slight decrease in microhardness and wear resistance.

Friction stir processing (FSP), which was the advancement in the friction stir welding technique, is thought to be an economic approach to alloying in the solid state that can be used to make composites. In this study, FSP was carried out to produce AA7075 (B₄$\mathrm{\text{C}}+\mathrm{\text{T}}$iN) composite by varying the composition of the reinforcement particles. Microstructural analysis was carried out and the homogenous distribution of the reinforced particles on the surface of AA7075 alloy was ensured. X-ray diffraction studies were carried out to analyze the phases present after fabricating the hybrid surface composites. Microhardness test was performed on the specimens before and after the fabrication process. Grain refinement in the friction stir processed zones was evidently seen in the optical microstructures. The combined effect of the ceramic powders and grain refinement led to increase in the microhardness in the hybrid surface composites compared with the base AA7075 plate. A 33.87% increase in microhardness was observed in the sample AA7075 reinforced with 75% B₄C and 25% TiN. Wear testing was carried out at various loads (5, 10, 15 and 20 N) and at different sliding velocities (300, 350, 400 and 450 rpm) and the track distance was maintained at 1000 m. It was observed that the highest wear rate is $3.2\times 10^{-7}$ cm³/Nm for the base plate AA7075 and the sample AA7075 reinforced with 50% B₄C and 50% TiN shows the lowest wear rate of $0.56\times 10^{-7}$ cm³/Nm. It is observed that the addition of B₄C and TiN has resulted in a significant improvement in the wear resistance of the AA7075 alloy.

The corrosion behavior of 316 stainless steel with 10wt.% B₄C composites has been investigated using electrochemical measurements and electron backscattered diffraction (EBSD) and scanning electron microscopy (SEM) analyzes are performed. Spark plasma sintering (SPS) is used to achieve various heat treatments, which are performed at the temperatures of 800^∘C, 900^∘C, and 1000^∘C. It significantly affects the materials’ ability to resist corrosion. The increase in grain size improves corrosion resistance, except at 900^∘C when recrystallization is imperfect. However, grain homogeneity should be taken into consideration. The corrosion behavior of the composites is assessed using Tafel plots. The corrosion rate of the sample at 900^∘C (0.2945mm/yr) is significantly lower than the rates of the samples at 800^∘C and 1000^∘C, respectively, as per the corrosion process of composites of 3.5wt.% NaCl solution. The B₄C contents have a significant impact on the particle size reduction, low-density average crystallite size, mechanical, hardness, corrosion resistance, and thermal stability of composite powder. It is primarily utilized in nuclear applications as a neutron radiation absorbent. The research has revealed that the sample at 900^∘C has fewer grain boundaries and the finest passivation film quality and superior corrosion resistance are found in intermediate grain size.

The gas phase reaction thermodynamics in the chemical vapor deposition (CVD) process of preparing boron carbides via the precursors of BCl₃–C₃H₆(propene)–H₂ is investigated with a set of 325 gaseous species, in which the data for 135 species are evaluated in this work. The thermochemistry data are calculated with accurate model chemistry at G3(MP2) and G3//B3LYP levels. The concentration distribution of all of the 325 species is obtained with the principle of chemical equilibrium. The thermochemistry data include the heat capacities, entropies, enthalpies of formation, and Gibbs free energies of formation. The heat capacities and entropies at temperatures in 298.15–2000 K are evaluated with the standard statistical thermodynamics. The Gibbs free energies of formation in 298.15–2000 K are calculated with the classical thermodynamics based on the developed heat capacities and entropies. By including the crystal B₄C, C(graphite), and B, the results for an example of the 3:1:2 precursors of BCl₃:C₃H₆:H₂ show that the crystal B₄C can be produced at temperatures higher than 700 K while the graphite has a higher molar value and can be produced at lower temperatures. It is also examined that the production of graphite can be controlled by changing the ratio of the injected reactants or pressure. It is interesting that BHCl₂, BCH₃Cl₂, BH₂Cl, and B₂Cl₄ are found to be the most effective species in the CVD process, which is similar to those in the BCl₃–CH₄–H₂ system. The results predicted in this work are consistent with the experiments.

The effect of radiative impacts on the structure of boron carbide has been studied by both classical and ab initio simulations. As a part of this study, a new forcefield was developed for use in studying boron carbide materials. Impact scenarios in boron carbide were simulated in order to investigate the exceptional resistance of this material, and other icosahedral boron solids, to high-energy impact events. It was observed that interstitial defects created by radiative impacts are likely to be quenched locally, utilizing the high substitutional disorder of chains and cages in the boron carbide structure, rather than via impacted atoms recombining with their vacated lattice site.

Boron carbide is one of the advanced ceramic materials which is used in a wide range of applications. However, this material needs a high sintering temperature (~2200°C). Using nano-size powders for producing ceramic parts results in lowering sintering temperature and also enhances toughness and hardness of the material. One of the methods for producing ceramic nano powders is attrition milling. However, as the milling balls and wall are made of steel, some impurities specially iron will be introduced to the powder during milling. Chemical analysis of the milled powder shows that more than 33wt% of the powder consists of iron. These uncontrolled impurities affect the mechanical and physical properties of sintered ceramic parts that are made of such a powder. Therefore, these impurities must be removed from the powder. Hydro metallurgical beneficiation technique with two different solvents has been used for purification of the powder. The result of chemical analysis after purification showed that the weight percentage of iron in powder dropped to 9% and 0.8% (depending on the solvents). Moreover, the sintering behavior of hot-pressed boron carbide powder with different percentages of iron as sintering aid has been studied. The results showed excellent densification and hardness of the sintered parts.

The hardness, toughness and sum of cracks measurement of fine-grained WC-Co hard metals were studied. Thirty commercial and experimental hard metal grades with different additives such as boron carbide (B₄C), vanadium carbide (VC), chromium carbide (Cr₃C₂) and silicon carbide (SiC) were prepared in a commercial sinter HIP furnace. Physical, mechanical and microstructure properties were investigated to build up a representative hardness/sum of cracks measurement band. This band was then used to estimate the most effective sintering temperature and the amount of each additives. Afterwards, influence of grain growth inhibitors in optimum condition were compared. The results showed that the grades, doped with B₄C and VC as growth inhibitor exhibits more hardness than other comparable doped alloys. However, Cr₃C₂ is favorable in toughness improvement.

Spark plasma sintering (SPS) of pure commercially sub-micron B₄C powder at 1700–1900${}^{\circ }$C for 20min has been conducted and their wear properties have been investigated by reciprocating friction and wear test. It was found that the relative density increased with the increase and the grain size increased a little at 1700–1900${}^{\circ }$C. Wear mechanisms in the temperature range of 1700–1900${}^{\circ }$C have been proposed such that at 1700${}^{\circ }$C the wear mechanism was dominated by plastic deformation and intergranular fracture, while at 1800–1900${}^{\circ }$C there was transition to the surface fracture or grain pull-out. A model for the spherical abrasive wear was proposed to describe the friction and wear of the B₄C ceramics which is well-fitting with the experimental results.

This research paper reports the effect of laser power on the degree of porosity of the deposited tracks and characterized the specific porous structures of the deposits. The samples were characterized through the microstructure and the porosity analysis. The results revealed that as the laser power was increased, the degree of porosity was however reduced. Prior the characterization process, titanium alloy and boron carbide (Ti6Al4V-B₄C) composites powder were deposited on Ti6Al4V substrate using laser metal deposition (LMD) process through the application of Ytterbium fibre laser system. The laser power was varied between 800 W and 2400 W at interval of 200 W while all other process parameters were kept constant. The maximum capacity of this laser system is 3.0 KW which provides beam size of 4 mm for the control characterization of the deposited samples. The porosity behaviour of various samples at different laser power were observed in which the degree of their porosities varies as the laser power increases. At a laser power of 2200 W, there was no porosity observed in the composite which revealed that there were no unmelted powder presented in the melt pool after solidification for this particular sample. Percentage porosity was significantly reduced from 0.45% to 0.03%.