Addition Of B4C Research Articles

The effects of B4C addition on the microstructure and mechanical properties of SiC prepared using powders recovered from kerf loss sludge

Abstract In this study, high purity SiC powders (~ 99.3%), which were recycled from the kerf loss sludge using hydro-cyclone, classifier and direct carbonization and which have purity similar to the commercial SiC powders used to fabricate structural components, were used to investigate the effect of B4C addition on the microstructure and mechanical properties of the sintered SiC. B4C phase and graphite were observed on the grain boundaries between SiC grains, and the amount of B4C phase at the grain boundaries was increased with increasing B4C contents. Both the phases on the grain boundaries impeded the growth of SiC grains and led to the high porosity, which resulted in the decrease in density and hardness. The addition of B4C was found to have negative effect on the density and hardness of SiC. The fracture toughness, however, was enhanced with the increase in the B4C content. The impediment of crack propagation by the B4C phase was found to be related to the improvement of fracture toughness as the amount of B4C content was increased

Effects of B4C Addition on the Microstructure and Magnetic Properties of FePt-C Granular Thin Films for Perpendicular Magnetic Recording

Effects of B4C addition on the microstructure and magnetic properties of FePt and FePt-C thin films have been studied. A high coercivity of 2.11 T with good squareness is achieved by B4C addition. By analyzing the mechanism and different isolation effects of B4C and C as segregants, a double-layer approach has been developed and a coercivity of 1.96 T is achieved with column-like FePt grains. The grain size and the size distribution are not deteriorated substantially compared with the single-layer case. These results indicate that addition of B4C as segregant is beneficial for the modification of microstructure and magnetic properties.

Effect of nano-sized B4C addition on the mechanical properties of ZA27 composites

In order to understand the influence of nano-sized B4C additive on ZA27 alloy, mechanical and physical properties of ZA27-B4C nanocomposites were investigated in terms of B4C content. While physical properties were determined in terms of microstructural studies, density and porosity tests, mechanical properties were determined in terms of ultimate tensile strength (UTS) and hardness experiments. Morphological and microstructural studies were carried out with scanning electron microscopy (SEM). The experimental results indicate that nano-sized B4C can be used to enhance the mechanical properties of ZA27 alloy effectively. The highest mechanical performance can be obtained at ZA27-0.5% B4C (in weight) nanocomposite with values of tensile strength (247 MPa) and hardness (141,18 BH) and low partial porosity (0.5%). After a pick point, increasing B4C ratio may cause the formation of agglomeration in grain boundaries, that’s why density, tensile strength, and hardness values are declined.

Synthesis of TiB2 from a carbon‐coated precursors method

AbstractThis article deals with the synthesis of TiB2 from carbon‐coated TiO2 precursors with the addition of B4C. The carbon‐coated precursors method alters the reaction process, compared with the conventional mixing of reactants, to produce high‐quality TiB2 powders. The produced powders have a single phase, a submicron particle size (~0.3 to 0.8 μm), regular shape, loose agglomeration, and low level of contaminations (less than 0.5 wt% carbon and 0.6 wt% oxygen). The formation mechanism proposed is based on experimental results and thermodynamic evaluations. For comparison, the powders obtained from the mixture of reactants show higher agglomeration, a large particle size (>1 μm), high level of contaminations (0.7 wt% carbon and 1.1 wt% oxygen), and difficulty to control the reaction process (formation of TiBO3 and Ti2O3 as the intermediate phases). The synthesized powders from the precursors method can be hot pressed to a relative density of ~94.5% with the formation of platelike grains at 1800°C under a pressure of 35 MPa without additives.

A high strength alumina-silicon carbide-boron carbide triplex ceramic

A ceramic particulate composite composed of oxide, and carbide ceramics was found to have high strength, hardness, and fracture toughness values. A composition consisting of Al2O3 with 15vol% SiC and 15vol% B4C additions was produced by hot-pressing at 1650°C for 30min, with full density reached after ~5min at temperature. Both WB and WB2 were observed, with the W source presumably an impurity from WC milling media, and Al18B4O33 was also detected following densification. Strength was ~880MPa, which is greater than values reported for comparable composites of Al2O3 containing 30vol% SiC or B4C. Vickers hardness was ~21GPa, and fracture toughness was ~4.5MPam½, comparable to values reported for the binary mixtures. The calculated critical flaw size of the material was similar to the size of the SiC/B4C clusters and microcracking at grain boundaries. The latter resulting from thermal expansion mismatch between the Al2O3 matrix and SiC/B4C reinforcing phases.

Effects of B4C and BN additions on formation of NbB2–Al2O3 composites from reduction-based combustion synthesis

Formation of NbB2–Al2O3 composites was investigated by reduction-based combustion synthesis in the SHS mode. Amorphous boron, B4C, and BN were adopted as the source of boron in three reaction systems composed of Nb2O5–Al–B, Nb2O5–Al–B–B4C and Nb2O5–Al–B–BN. In addition, the effect of excess boron up to 30 at% was examined. For the B- and B/BN-based reaction schemes, the synthesis process involved not only aluminothermal but borothermal reduction of Nb2O5. The latter caused a significant loss of boron in the form of gaseous oxides, and therefore, their resulting products contained NbB, Nb3B4, and NbB2 even if the samples were formulated with boron of 30 atom.% in excess. Besides acting as a boron precursor, B4C was showed to effectively suppress the borothermal reaction for the B/B4C-adopted sample. Consequently, a small amount of excess boron of 10 atom.% was sufficient for the B/B4C-adopted sample to produce the NbB2–Al2O3 composite with trivial minor phases.

Processing, microstructure, and mechanical properties of zirconium diboride-boron carbide ceramics

The processing, microstructure, and mechanical properties of zirconium diboride-boron carbide (ZrB2-B4C) ceramics were characterized. Ceramics containing nominally 5, 10, 20, 30, and 40vol% B4C were hot-pressed to full density at 1900°C. The ZrB2 grain size decreased from 4 to 2µm and B4C inclusion size increased from 3 to 5µm for B4C additions of 5 and 40vol% B4C, respectively. Elastic modulus decreased from 525 to 515GPa and Vickers hardness increased from 15 to 21GPa as the B4C content increased from 5 to 40vol%, respectively, following trends predicted using linear rules of mixtures. Flexure strength and fracture toughness both increased with increasing B4C content. Fracture toughness increased from 4.1MPam½ at 5vol% B4C to 5.3MPam½ at 40vol% B4C additions. Flexure strength was 450MPa with a 5vol% B4C addition, increasing to 590MPa for a 40vol% addition. The critical flaw size was calculated to be ~30µm for all compositions, and analysis of the fracture surfaces indicated that strength was controlled by edge flaws generated by machining induced sub-surface damage. Increasing amounts of B4C added to ZrB2 led to increasing hardness due to the higher hardness of B4C compared to ZrB2 and increased crack deflection. Additions of B4C also lead to increases in fracture toughness due to increased crack deflection and intergranular fracture.

A heat-resistant organic adhesive for joining Al2O3 ceramics in air and argon atmospheres

An organic adhesive for joining Al2O3 ceramics was prepared by using a precursor as a matrix, with B4C and SiO2 additives. The resulting adhesive was characterised by a shear strength test, thermogravimetry-differential scanning calorimetry (TG-DSC), Fourier transform-infrared (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses. The bonded Al2O3 joints were found to exhibit high shear strengths (over 10MPa) after heat treatment at a temperature of 200°C to 1200°C in either an air or Ar atmosphere. In an argon atmosphere, the B4C and SiO2 act as inert fillers. The satisfactory bonding strengths of the Al2O3 joints mainly result from the outstanding adhesive properties of the precursor matrix. In air, the B4C is converted to B2O3 above 500°C and reacts with SiO2 to form a borosilicate phase. The formation of B2O3 and borosilicate glass reduces the volume shrinkage of the adhesive, improves the densification of the bonding layer and enhances the interface joining force, which we believe are responsible for the high shear strengths of the Al2O3 joints (over 40MPa). The high strength and high-temperature resistance enable the application of the adhesive to the joining of ceramic materials for practical applications.

Synthesis of sub-micro sized high purity zirconium diboride powder through carbothermal and borothermal reduction method

Sub-micro sized zirconium diboride (ZrB2) powders were successfully prepared via the boro/carbothermal reduction method using zirconium oxide and boron carbide as the primary raw materials. The prepared mixtures were thermally reacted at 1250°C for 1h. The optimized composition range containing the lowest oxide and carbide impurity, which was 0.14% of oxygen and 0.3% of carbon contents, was determined using crystallographic and elemental analysis. The particle size was reduced from 5µm to 245nm by the addition of B4C as a reductant within a composition range that maintained the highest purity. The morphology changed from faceted to angular hexagonal bar-like with a simultaneous growth in particle size. Changes in the particle structure were a result of the existing liquid B2O3 phase during the reaction. The 245-nm particles contained 12.1% oxygen content and 16.2% oxygen content for the 5-μm particle in the circumstance in which limited oxides could be produced.

Microstructure and Mechanical Behavior of B4C Particulates Reinforced ZA27 Alloy Composites

In comparison to unreinforced alloy, ZA27 reinforced with hard ceramic particles possesses higher strength and hardness. They can be used for automotive parts, machine tools, strength plants, Heavy engineering industries. The aim of the present work is to investigate the effects of adding micro size-B4C particles to ZA27 alloy on the mechanical properties of the composites.The ZA27 alloy reinforced with 3wt. %, 6 wt. %, and 9wt. % of B4C particulate composites were fabricated by stir casting method.Microstructure and mechanical properties such as hardness, ultimate tensile strength and yield strength and percentage elongation of the composites were examined. Microstructure of the samples has been investigated by using optical microscopy and Scanning Electron Microscope to know the micro level uniform distribution of reinforcement particulates in the matrix. It was observed that the hardness, ultimate tensile strength and yield strength of alloy increased as the level addition of B4C particulates increased by 3wt. %, 6wt. % and 9wt. %.From the study, it was revealed that the percentage of elongation decreased as the addition of B4C increased with 3wt. %, 6wt. % and 9wt. %

Effect of Artificial Ageing on Wear Behaviour of Al7010/B4C Composite

In the present work, the study is done about composite material constituting of B4C particulate reinforced into Al7010 matrix with different weight fractions of 3wt%, 6wt%, 9wt% which is fabricated using conventional melt stirring (stir casting) method. Characterization of the prepared composites is studied in detail using Optical Microscope and Scanning Electron Microscope. The uniform distribution of B4C particulates in matrix was clearly evident from microstructure studies. The specimens were T6 heat treated for aging period of 5hour. The wear test is conducted for both non-heat treated and heat treated specimens using pin-on-disc method by considering parameters like load, speed and weight percentage of B4C. The wear results showed that addition of B4C increased the wear resistance and it is found maximum for 9% addition of B4C.

Effect of B4C particle reinforcement on the various properties of aluminium matrix composites: a survey paper

Metal matrix composites (MMCs) possess significantly improved properties including high specific strength, damping capacity, specific modulus and good wear resistance compared to unreinforced alloys. There has been an increasing interest in composites containing low density and cost reinforcements also their ability to be produced by conventional methods adds to the advantage. Aluminium matrix can be strengthened by reinforcing it with hard ceramic particles like SiC, Al2O3 and B4C, etc. This paper presents an overview of the effect of on B4C addition as reinforcement in aluminium alloy highlighting their merits and demerits. Major issues like, fiber-matrix bonding, agglomerating phenomenon and the problems related to distribution of particles is discussed in this paper. Effect of B4C reinforcement on AMCs mechanical properties like tensile strength, strain, hardness, wear and fatigue is also discussed in detail.

Effect of Additives and Carbon Resources on Thermal Shock Resistance of Spinel-C Material

Spinel-C material is important for monolithic stopper and submerged nozzle, which usually determine the application effects. Spinel-C specimens with 8% flake graphite is characterized by good corrosion resistance but poor thermal shock resistance. The effects of additives (Al-Si alloy, silicon powder, B4C and SiC), flake graphite (+199/-199), ultrafine flake graphite, expanded graphite and nickel nitrate + pitch powder on thermal shock resistance of spinel-C material were investigated by using water-quenching method. The results show that: (1) The addition of Al-Si alloy and B4C can significantly decrease the residual strength ratios (RSR) of the specimens. The addition of SiC and silicon powder can improve the RSR obviously. (2) The flake graphite of different particle sizes has little effect on the RSR of the specimens. With the increasing of the expanded graphite content, the RSR of the specimens increases. (3) The addition of mesophase pitch and Carboresâ P can receive the RSR rise of 74% and 59% respectively.

Synthesis & Characterization of Al-Ti-Cr MMC as friction material for disc brakes application

A stir die casting coupled with chill casting technique was used to prepare the Al-Ti-Cr composite with variable percentage of SiC and B4C particles. The electrolytic grade of 300 mesh powder was added in the molten of commercially master alloy of Al-Ti-Cr by the simultaneously addition of SiC and B4C. The SiC and B4C in the composite are varied from 0 to 10wt%.The developed composite were characterized using a Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). F.T.I.R. in corroboration with X.R.D,which confirms the crystallization of corundum (α-Al2O3) as one of the alumina phases.The presence of hard phase in the composite not only improved the ultimate tensile strength, 0.2% proof stress and the hardness of AMC composite. The ductility showed the adverse effect with increase of the SiC and B4Cin the matrix. The results from microstructure confirms the presence of second phase particles at the grain boundaries of aluminium-rich phase as well as within the grain itself which was confirmed by EDAX as well as XRD analysis. These composite have also been subjected to wear and frictiontesting at different operating parameters. Result shows that with increase in wt% of SiC and B4C from 2-10%, the ultimate strength and elongation percent of the Al-Ti-Cr alloy are still higher than that of monolithic alloys. Micro-structural characterization by using SEM depicted that the particles tend to be more agglomerated along with Al2O3 content, confirmed with FTIR analysis. The AFM results revealed that the surface roughness value of the composite is reduced by a factor of ∼3 μm. The results from microstructure showed the presence of second phase particles at the grain boundaries of aluminium-rich phase as well as within the grain itself which was confirmed by FTIR, XRD, AFM and EDAX.

Mechanical, corrosion and wear characteristics of powder metallurgy processed Ti-6Al-4V/B4C metal matrix composites

Titanium alloys are used in aerospace and automotive applications because of its high specific strength, stiffness and good machinability but its wear resistance is inadequate. To eliminate this property lag Boron Carbide (B4C) ceramic particles are reinforced with Ti-6Al-4V through powder metallurgy route (PM). Reinforcement particles are mixed with base alloy for the weight percentage of 0, 5 and 10 so as to analyse the effect of reinforcements on mechanical, corrosion and wear properties. This research outcome corresponds to decreased density, increased hardness and corrosion resistance capability for significant increase in B4C content of the newer composite developed and tested. Applied load signify higher effect on wear performance of the composite specimens followed by B4C addition percentage. Scanning Electron Microscope results reveal that B4C reinforced Ti-6Al-4V composite comprise for higher wear resistance and illustrate mild worn surface when compared to that of unreinforced Ti alloy.

Effect of B4C on the properties and microstructure of Al2O3 -SiC-C based trough castable refractories

The effect of B4C addition (0.5wt%, 1wt%, 1.5wt%, 2wt%) on properties and microstructure of Al2O3-SiC-C (ASC) based trough castables was studied in this paper. The results showed that the bulk density of samples after firing at 1450°C decreased when the addition of B4C was over 1wt%. The cold modulus of rupture of samples improved significantly with the addition of B4C when the treating temperature was over 1100°C. Among them, sample with 1.5wt% of B4C had the best anti-slag performance and thermal shock resistance. The SiC fibers were formed in the non-oxidized zone of ASC castables with addition of B4C after firing at 1450°C in air condition. The obtained fibers rooted in the walls of inner micropores of samples with the diameter of 50–200nm, and the lengths of 10–50µm. The experiment revealed the nucleation of SiC started at about 1000°C, and then the growth of SiC fibers happened at higher temperature in a favorable condition. A stepped twin structure perpendicular to the growth direction of fibers could be observed. Finally, the growth mechanism was interpreted by thermodynamic calculations.

Preparation of ZrB2 and ZrB2-SiC powders in a single step reduction of zircon (ZrSiO4) with B4C

The reduction of zircon (ZrSiO4) with C and B4C results in the formation of impurity phases like ZrO2, ZrC, ZrSi, SiO2, SiC and borosilicate. Synthesis of pure ZrB2 by eliminating SiO2 in ZrSiO4 in a single step reduction with B4C has been studied. Without adding free carbon, zircon was reduced with B4C in different weight ratios (ZrSiO4/B4C=1.6/2.5/3.3) at different temperatures between 1300°C and 1600°C in argon. The ratio of ZrSiO4/B4C and reaction temperature were optimized to produce a single phase ZrB2 free from impurity phases. Addition of carbon or B4C to an optimized mixture of (ZrSiO4/B4C=3.3) has resulted in the formation of (ZrB2-SiC) composite powder. Composite powders of (ZrB2-SiC) and (ZrB2-SiC-B4C) were formed by increasing the B4C content to ZrSiO4/B4C=2.5 and 1.6 respectively.

Investigations on Properties of Al-B<sub>4</sub>C Composites Synthesized through Powder Metallurgy Route

Powder metallurgy is a popular technique to synthesize metal matrix composites with uniform distribution of the reinforcements. The present work aims to synthesize Al-B4C composites through powder metallurgy route and study their properties. The compositions of the composites are Al-5%B4C, Al-10%B4C & Al-15%B4C. Blending of powders, compaction and sintering process were carried out as per standard powder metallurgy procedure. The distributions of the reinforcements were analyzed for the sintered specimens by the help of scanning electron microscope. The effect addition of B4C in the Aluminium matrix on the properties such as density, porosity, hardness and compressive strength were discussed. Results show that addition of B4C improves the properties of Al-B4C composites.

Pressureless Sintering of ZrB2Prepared by Colloidal Processing: Particle Packing, Sintering Conditions, and Additives

Nonaqueous colloidal processing in cyclohexane and slip casting allowed the preparation of green ZrB2compacts with 67.3%TD(theoretical density), which upon pressureless sintering at 2100°C densified to a final density of 92.4%TD. The effect of controllable sintering parameters (temperature, time, and heating rate) on the sintered properties of ZrB2compacts prepared using the nonaqueous colloidal processing method was also studied, to maximize the sintered density and tailor the desired microstructure (i.e., dense final object with small grain size). The competition between pore elimination and grain growth mainly controls the final density achievable. ZrB2compacts with maximum sintered densities of 93%TDcould be achieved by controlling the sintering conditions. Finally, the use of carbon and B4C additives to improve the sintered density and microstructure of ZrB2compacts was also investigated. The additives, compatible with colloidal processing, allowed compacts with greater sintered densities (96–98%TD) and finer grain sizes to be achieved by pressureless sintering, even at a lower temperature of 1900°C.

Investigation the effect of B4C addition on properties of TZM alloy prepared by spark plasma sintering

TZM alloy is one of the most important molybdenum (Mo) based alloy which has a nominal composition containing 0.5–0.8wt.% titanium (Ti), 0.08–0.1wt.% zirconium (Zr) and 0.016–0.02wt.% carbon (C). It is a possible candidate for high temperature applications in a variety of industries. However, the rapid oxidation of TZM alloys at high temperature in air is considered to be one of the drawback. In this study, TZM alloys with additions of 0–5wt.% B4C were prepared by spark plasma sintering (SPS) at 1420°C utilizing 40MPa pressure for 5min under vacuum. The effects of B4C addition on oxidation, densification behavior, microstructure, and mechanical properties were investigated. The TZM alloy with 5wt.% B4C have exhibited an approximately 66% reduction in mass loss under normal atmospheric conditions in oxidation tests made at 1000°C for 60min. And an increase from 1.9GPa to 7.8GPa has been determined in hardness of the alloy.