Papers by Keyword: Boron Carbide

Abstract: In modern engineering low-density composites plays a vital role of which magnesium alloys are very effective due to its high strength with better corrosion resistance and neat cast ability. In this work a micron sized Boron carbide ceramic (B₄C) of about 100 microns is diffused as a reinforcement with AZ91 for preparing a magnesium metal matrix composite (MMMC) through stir casting route. A modified pit furnace setup is used for doing stir casting with varying volume fractions of 0％ and 3% of boron carbide for doing the composites. Furthermore mechanical and metallurgical properties like Tensile test is made through universal testing machine, Micro-hardness through Vickers hardness tester and Micro structure through Optical Microscopy is done for investigation.

Abstract: Aluminium matrix composites (AMCs) have emerged as the substitute for the monolithic (unreinforced) materials over the past few decades. The applications of AMCs are common in automotive, aerospace, defence and biomedical sectors due to its lower weight, high strength, high resistance against corrosion and high thermal and electrical conductivity. In this work, it is aimed fabricate a new class Al 7075 based hybrid composites reinforcing with nanoparticulates suitable for automotive application. Al7075 reinforced with fixed quantity of boron carbide (B₄C) (1.5 wt.%) and varying wt % of flyash (0.5 wt.%, 1.0 wt.%, 1.5 wt.%) is fabricated using ultrasonic-assisted stir casting technique. Physical and mechanical characterization such as density, porosity, micro hardness, tensile strength and impact strength were estimated for three different compositions. The tensile strength and percentage increase in hardness value of the nanocomposite Al7075-B4C (1.5 wt. %)-flyash (0.5 wt. %): HNC3 found maximum as 294 MPa and 32.93%. In comparison with Al7075 alloy the impact strength of HNC3 shows the highest percentage of 9.31% respectively.

Abstract: In the current work Al6061 hybrid composites reinforced with Silicon Carbide (SiC) and Boron Carbide (B₄C) were studied for improvement in hardness and behavior of fracture surface after artificial aging. It was found that after aging at 100 and 200 OC, presence of SiC and B₄C particles in the Hybrid Al6061 Matrix Composites showed substantial improvement in hardness compared to that of the base alloy. Behavior of fracture mechanism after tensile strength have been discussed to conclude the factors which impact the mechanism of crack growth. Presence of SiC and B₄C reinforcement particulates and artificially aged at 100°C for Al6061-SiC+ B₄C hybrid metal matrix composite shows enhancement in hardness by 180% and tensile strength by 80% due to the presence of finer secondary solute rich intermetallic phases of alloying elements. Fractography analysis displays particle interface failure and combination of brittle and ductile mode of failure.

Abstract: Inertial Confinement Fusion (ICF) is an effective way to achieve nuclear fusion. In ICF, boron carbide ceramics are a crucial material to prepare targets due to its high neutron capture section, high hardness, and thermal stability. A common way to prepare boron carbide is the precursor transformation method, which can overcome the difficulty in the shaping of ceramics. Decaborane and olefins are reaction materials to prepare the precursor. However, the mechanism of the reaction is not clear now, and few studies on computational chemistry have been published in this area. In this research, the semi-empirical method of quantum mechanics and Molecular Dynamics in Hyperchem8.0 were used to optimize molecules in geometry. Formation enthalpy, bond energy, bond length and angle were calculated to explain experimental patterns. The optimized data is consistent with some typical phenomena in hydroboration and ring-opening metathesis polymerization. It demonstrates that those computational methods in Hyperchem8.0 can be applied to interpret and predict relevant reactions. In addition, this explanation provides a theoretical foundation for future synthesis on polyborane precursor.

Abstract: Innovative technology of HDTV-borating, that is distinguished by high hardness, strength, wear resistance and corrosion resistance occupies a special place among the hardening processes for steels and construction materials. During the new technology process HDTV-boration of structural steel 65Mn (65Г in Russian) under a mix layer of charge mixture based on fused borate fluxing agent P-0.66, boron carbide and intermetallic compounds Fe_xAl_y, Ni_xAl_y. Using the methods of X-ray phase analysis, spectrography and metallography, the composition and structure of coatings were determined, the microhardness distribution over the coating thickness was studied. In the coatings, new phases of intermetallic compounds, the double superhard boride Fe₂AlB₂, were found; in the coatings, the base iron boride is FeB, what leads to an increase in their hardness and wear resistance. Modification of boride coatings formed by intermetallic compounds with melting temperatures close to the process temperature of HFC surfacing leads to a decrease in the cracks number and the appearance of new consumer qualities of the material.

Abstract: Dense [boron carbide (B₄C)]/[carbon nanomaterials] composites were synthesized and sintered simultaneously using pulsed electric-current pressure sintering (PECPS) at 2173 K for 6.0×10² s (10 min) under 50 MPa in a vacuum. The starting powders were amorphous B and C nanopowders and nanocarbons. The latter were acid-treated carbon nanofiber CNF and carbon nanotube CNT. The sintered composites were evaluated from the viewpoints of mechanical properties at high temperatures up to ~ 2023 K in inert atmosphere. Thus fabricated composites with 10vol%CNF maintained high bending strength σ_b around 750 MPa even at 1973 K; this temperature is 100 K higher than that of conventional B₄C/CNF composites, and furthermore 600 MPa at 2023 K. These high σ_b at elevated temperatures might be explained by both the low content of catalytic Fe particles and the rough surface of CNF after the acid-treatment. On the other hand, B₄C/CNT composites displayed 770 MPa at 1723 K. The stress-strain curves demonstrate that B₄C/CNF composite deformed elastically until 1273 K and plastically up to 1973 K, however, the B₄C/CNT composites displayed elastic deformation up to around 1873 K.

Abstract: In this research work an effort has been made to study the tensile behavior of boron carbide and copper coated short basalt fiber reinforced with Al2014 based hybrid composites are prepared by stir casting technique. To avoid the interfacial reactions between basalt fiber and matrix Al2014 alloy the fibers are coated with copper using copper sulphate solution by electroless deposition method.The coated fiber was observed by scanning electron microscopy (SEM). It has been clearly revealed the uniform deposition of copper on the surface of fiber and tensile behavior of Hybrid composites was increased with increase in the wt% of reinforcements. At 6% boron carbide and 8% copper coated basalt fiber shows maximum tensile property.

Abstract: In the present scenario aluminium is an useful metal due its admirable properties such as light weight, low cost and excellent thermal conductivity.In order to take advantages of these properties aluminium is being used to make the metal matrix composites for tribological application, In this present investigation effort has been made to assess the wear properties of Al–B₄C–Gr metal matrix composite at various temperatures such as 323° K, 373° K and 423° K. Al–B₄C–Gr Hybrid metal matrix composites were fabricated by stir casting technique. The influence of parameters like load, speed, distance and temperature on the wear rate was investigated. A plan of experiments, based on Taguchi model with L27 orthogonal array and analysis of variance was employed to investigate the influence of process parameters on the wear behaviour of these hybrid metal matrix composites. The wear resistance increased with increasing temperature, but wear resistance decreased at higher loads. It was observed that the abrasive wear is dominates while sliding as observed by SEM analysis of worn out specimens.

Abstract: This study explores structure and characteristics of the nickel-chrome steel of the Cr-Ni-Mo-Mn-Si-Ti-Nb-B doping system obtained by surfacing with a flux-cored wire alloyed by boron carbide. It has shown that the deposited metal has a composite structure consisting of a supersaturated with alloyed elements solid solution with an austenite-martensitic matrix and a eutectic component (Mo, Cr, Fe, Nb)₂B in the form of sections along the boundaries of former austenite grains. Because of the significant content of ferrite-forming elements in the process of crystallization, a metastable δ-ferrite is formed in the weld metal in the form of differently oriented interlayers between the martensite rails. As a result of aging of such a deposited metal at 500 °C for 2 hours, the metastable ferrite undergoes decay at the interphase boundaries α/δ with the formation of the σ phase, which represents sharpened plates with the size of 300÷550 nm. Moreover, aging leads to hardening of the matrix by finely dispersed carboboride and intermetallic phases (Cr, Mo, Fe, Nb, Ti)₂₃(С,В)₆, (Fe, Cr, Si)₂(Mo, Ti) и (Ni, Fe)₃Ti, causing high levels of hardness and wear resistance. The usage of this wire as a surfacing material allows to increase significantly the operability and reliability of the stop valve parts, which work on abrasion in contact with corrosive medium.

Abstract: In this study, production and mechanical properties of the hybrid nanocomposite were investigated experimentally and estimated. Hybrid nanocomposites include boron carbide (B₄C) and multi walled carbon nanotube (CNT) in the epoxy resin. B₄C and CNT mixed into the epoxy with different percentages and produced. Tensile strength values of the produced samples was determined and compared. Thermal stability of the samples was analyzed by TGA. Samples are diversified by Taguchi method. The optimum sample was determined by comparison of the experimental and estimated results. Finally, the effects on each of the parameters were determined.