B4C Particle Size Research Articles

Reaction behaviour, microstructure and mechanical properties of TiC–TiB2/Ni composite fabricated by pressure assisted self-propagating high-temperature synthesis in air and vacuum

The dense TiC–TiB2/Ni composite was successfully fabricated via a simple route where the pressure assisted self-propagating high-temperature synthesis (SHS) was directly ignited at 625°C with the incorporation of air. The ignition temperature in air was much lower than that in vacuum (1040°C). The composites made in air possessed the similar phase constituents and microstructure as well as comparable mechanical properties to those made in vacuum. The ignition temperature both in air and vacuum showed a significant dependence on Ni content and reactant particle size while the reaction products only showed a dependence on Ni content and B4C particle size, irrespective of Ti particle size. The density of the composite made in air and vacuum only depended on Ni content while the mechanical properties of the composites made in air and vacuum both showed a similar dependence on the Ni content and reactant particle size.

Effect of boron carbide particle size and volume fraction of TiB–TiC reinforcement on steady state creep behaviour of PM processed titanium matrix composites

AbstractTiB–TiC reinforced titanium matrix composites (TMCs) were synthesised through pressureless sintering of titanium and boron carbide (B4C) powder compacts. Effect of boron carbide (B4C) particle size and volume fraction of TiB–TiC reinforcement on steady state compression creep behaviour of composites was investigated in the temperature range of 773–873 K. The creep rates of composites are found to be about two orders of magnitude lower than those of unreinforced titanium. The creep rates further lowered with decrease in size of B4C particles (from 16 to 3 μm) used in preparation of composites as well as with increase in volume fraction of the TiB–TiC reinforcement from 10 to 30 vol.%. By using the concept of effective stress as well as incorporation of load transfer and substructural strengthening effect produced by the reinforcement into analysis, the entire creep data of Ti and the composites can be made to merge on to a single line within a scatter band of factor of 2–3 and can be represented by...

Effects of heat-treatment temperature and starting composition on morphology of boron carbide particles synthesized by carbothermal reduction

Carbothermal reduction using B2O3 and carbon black was applied for synthesis of B4C powder and the effects of heat-treatment temperature and starting composition of raw mixture on morphology of B4C particles were investigated. Morphology of B4C particles synthesized at 1450°C was mainly spherical shapes. The B4C powder synthesized at 1550°C was large and changed in morphology from polyhedral to skeletal shape, and particle size of B4C increased with an increase in the amount of B2O3 in the starting mixtures. The B4C powder synthesized beyond 1650°C consisted from dendrite-like particles aggregated by small primary particles. Morphology of the primary B4C particles synthesized at 1750°C changed from polyhedral to rounded shape with increasing the amount of B2O3 in the starting mixtures. It is clarified that heat-treatment temperature and the starting compositions of raw mixtures mainly affected B4C nuclei number along with primary particle size and morphology of primary B4C particles, respectively.

Abrasive wear behaviour of B4C particle reinforced Al2024 MMCs

In this study, the effects of volume fraction and particle size of boron carbide on the abrasive wear properties of B4C particle reinforced aluminium alloy composites have been studied. For this purpose, a block-on-disc abrasion test apparatus was utilized where the samples slid against the abrasive suspension mixture at room conditions. The volume loss, specific wear rate and roughness of the samples have been evaluated. The effects of sliding time, particle content and particle size of B4C particles on the abrasive wear properties of the composites have been investigated. The dominant wear mechanisms were identified using scanning electron microscopy. The results showed that the specific wear rate of composites decreased with increasing particle volume fraction. Furthermore, the specific wear rate decreased with increasing the size of particle for the composites containing the same amount of B4C. Hence, it is deduced that aluminium alloy composites reinforced with larger B4C particles are more effective against the abrasive suspension mixture than those reinforced with smaller B4C particles.

Growth fusion of submicron spherical boron carbide particles by repetitive pulsed laser irradiation in liquid media

We studied the fabrication of B4C submicron particles by laser irradiation of boron nanoparticles dispersed in an organic solvent. The spherical shape of the formed particles suggests that instantaneous melt formation and solidification by quenching are involved in the particle-forming process. B4C particles gradually became larger with irradiation time at relatively low laser fluence (1.5 J cm−2 pulse−1) by repetitive melting and fusion of the particles, and the B4C yield increased with irradiation time to 90% for 600 min of irradiation. At higher laser fluences, the B4C yield decreased due to the explosive ablation of boron or B4C to form H3BO3, and thus only the larger B4C particles were observed. The dielectric constant of the organic solvent also affected the generated B4C particle size, probably due to the degree of particle aggregation. Thus, this technique can provide a new approach for fabricating spherical submicron particles of ceramic materials, such as carbides, with simple and safe processes.

Role of Fe incorporation in the self-propagating high-temperature synthesis reaction in an Al–Ti–B4C system

Effects of Fe incorporation into Al–Ti–B4C reactants on the combustion behaviors, reaction mechanism, synthesized products, and possible natural convection of fluids were investigated. The incorporation of Fe significantly promotes the self-propagating reaction and decreases the reaction dependence on the B4C particle size. The prior reaction of Fe with B4C leads to the decomposition of B4C and formation of Fe2B and free carbon. On the other hand, the reaction of Fe with Ti and Al gives rise to the emergence of Fe–Ti and Fe–Ti–Al eutectic liquids. As a result, the diffusivity and reactivity of the dissociated carbon and boron atoms are greatly facilitated and the reaction is substantially promoted, yielding a desirable product of TiC, TiB2, and FeAl phases. Moreover, the incorporation of Fe may enhance free convection of the molten phase in the reaction zone and thus contribute to the combustion synthesis process.

In Situ TiC/TiB2 Particulate Locally Reinforced Steel Matrix Composites Fabricated Via the SHS Reaction of Ni–Ti–B4C System

The composites synthesized with three kinds of B4C particles mainly consist of TiC, TiB2, and the alloy austenite containing Ni element. Ceramic particulate sizes in the composites synthesized with ∼3.5 and ∼45 μm B4C particles are larger than that synthesized with ∼140 μm B4C particle. No pores are found between the reinforcing region and matrix in the composites synthesized with ∼3.5 and ∼45 μm B4C particles, while some large pores exist in the composites synthesized with ∼140 μm B4C particle. With the decrease of B4C particle size, the pores in the composites become fewer and the hardness and wear resistance of the composites increase.

Effect of Reactant Particle Size on the Self-Propagating High-Temperature Synthesis Reaction Behaviors in the Ni-Ti-B4C System

The effect of the reactant particle size on the self-propagating high-temperature synthesis (SHS) reaction behaviors in the Ni-Ti-B4C system was investigated in the present study. The B4C particle size has a significant effect on the ignition behavior and combustion wave velocity, while Ti and Ni particle sizes have only a limited influence. Increasing the B4C particle size retards the reaction initiation and remarkably lowers the combustion velocity and combustion temperature. The reaction products are mainly dependent on the B4C particle size. Nevertheless, decreasing Ni and Ti particle sizes is in favor of perfect products consisting of only TiC, TiB2, and Ni phases.

Reaction synthesis of TiC–TiB2/Al composites from an Al–Ti–B4C system

The TiC–TiB2/Al composites were fabricated by self-propagating high-temperature synthesis (SHS) from Al–Ti–B4C compacts. The addition of Al to the Ti–B4C reactants facilitates the ignition occurrence, lowers the reaction exothermicity, and modifies the resultant microstructure. The maximum combustion temperature and combustion wave velocity decrease with the increase in the Al amount. The B4C particle size exerts a significant effect on the combustion wave velocity and the extent of the reaction, while that of Ti has only a limited influence. The reaction products are primarily dependent on the B4C particle size and the Al content in the reactants. Desired products consisting of only the TiC, TiB2, and Al phases could be obtained by a cooperative control of the B4C particle size and the Al content.

Characterization of boron carbide nanoparticles prepared by a solid state thermal reaction

The production of boron carbide (B4C) nanoparticles was investigated in a conventional high temperature furnace reactor. The reaction was carried out by heating a mixture of amorphous carbon and amorphous boron at 1550 °C to efficiently obtain a quantity of B4C. Scanning electron microscopy studies showed the average size of B4C particles was 200 nm, ranging from 50 nm to 350 nm. X-ray diffraction transmission electron microscopy and electron diffraction studies indicated that the prepared nanoparticles were crystalline B4C with a high density twin structure. High resolution transmission electron microscopy and selected area diffraction were also used to further characterize the structure of the prepared B4C particles, while energy dispersive spectroscopy and electron energy loss spectroscopy were used to determine the stoichiometry of the product. A solid state diffusion reaction mechanism is proposed.

Effect of B4C particle size on microstructure of in situ titanium matrix composites prepared by reactive processing of Ti–B4C system

TiB clusters have been observed in the composite prepared by reactive processing using B 4 C powders of particle size 3.5 μm but were not found when using finer B 4 C powders. After hot extrusion these clusters were reduced. The size of the B 4 C particles affects the microstructure and the mechanical properties of the composite directly, and the utilization of finer B 4 C powders of a narrow size distribution can produce finer TiB whiskers.