Boron Carbide Content Research Articles

Properties of boron carbide ceramics made by various methods for use in ITER

The results of a study of the chemical composition, vacuum and thermal properties of boron carbide ceramics, which is planned to be used in ITER diagnostic ports, are presented. The measured boron carbide content in sintered and hot pressed ceramics is 99,0÷99,7%, they do not contain unauthorized impurities, which in accordance to ITER requirements. The outgassing rate of sintered and hot pressed boron carbide produced by Virial Ltd meets the requirements of the ITER Vacuum Handbook. Sintered ceramic is cheaper than hot pressed, and it is produced in large volumes, which it would be preferable for use in ITER ports, but with its massive use may create a significant gas load on the vacuum system that requires accurate analysis and outgassing tests on all candidated ceramics.

Tailoring the mechanical and tribological properties of B4C/a-C coatings by controlling the boron carbide content

Boron carbide doped DLC coating can combine the property superiority of these two materials to create high-performance carbon-based coating, while the final property of the composite coating is strongly dependent on the proportion of coating components. The aim of this study was to investigate the effect of boron carbide content on the mechanical and tribological properties of the magnetron sputtered B4C/a-C coatings, as well as the relevant low friction mechanism. It was found that both the carbon matrix and introduced boron carbide were amorphous and the composite coating exhibited typical columnar structure. Appropriate doping of boron carbide significantly enhanced coating hardness, toughness as well as the adhesion strength and carrying ability, and all of them reached the optimal value when the B concentration was 2.92at.%. It was also found that the B4C/a-C coating with B 2.92at.% exhibited the lowest steady friction coefficient about 0.05 and highest wear resistance at 20% RH. None of boric acid was formed on the sliding interface under the tested humidity range. Thus, the improved tribological properties were mainly attributed to the enhanced mechanical properties and friction-induced formation of an intact graphitized carbon transfer layer on the counterpart under specific humidity condition.

Influence of the powder mixture composition on the deposition coefficient and the properties of NI+B4C CGDS coatings

The cold gas dynamic spray (CGDS) method used to form composite Ni+B4C coatings from mechanical powder mixture with various content of abrasive components is investigated, and the surface and microstructure of these coatings are considered. An experimental dependence of the deposition coefficient on the abrasive content in the mechanical powder mixture is obtained. The coatings are studied by interference profilometry, optical microscopy, and microindentation methods. The dependence of the bulk and mass B4C content in the sprayed material on the abrasive content in the sprayed powder mixture is obtained. The bulk B4C content in the coating c V ≈ 0.27 is attained. The dependence of the microhardness of composite CGDS coatings on the boron carbide content in them is investigated. The results of this paper demonstrate that the powder mixture composition significantly affects the CGDS coating growth and the properties of these coatings and can be used to control the properties of the CGDS cermet materials.

Effect of gas generator pressure on the physicochemical, oxidation and combustion characteristics of boron-based propellant primary combustion products

To clarify the effect of gas generator pressure on the physicochemical, oxidation and combustion characteristics of the condensed primary combustion products of boron-based propellants, the elemental, composition and morphology of the primary combustion products collected under chamber pressure of 0.2–8 MPa were investigated by energy-dispersive (EDS), X-ray photoelectron spectroscopy and scanning electron microscopy with energy-dispersive (SEM–EDS) individually. The oxidation, ignition and combustion behaviors of these products were further studied by laser ignition system and thermogravimetry–differential scanning calorimetry. We found out that high-pressure condition lowered the content of elementary boron and elementary carbon while raised the content of boron carbide. Numerous spherical carbon particles with a diameter around 100 nm were observed in the products. Boron lumps were partially or almost fully covered with carbon particles on the surface. The reaction mechanisms of thermal oxidation of primary combustion products were given. The onset temperature of boron in the products kept at 500 °C when pressure ranged from 3 to 8 MPa but increased to 583 °C at 0.2 MPa. As the pressure increased from 0.2 to 8 MPa, the emission spectrum intensity of both boron and carbon got enhanced by ~25%, and the ignition delay of boron was significantly shortened by 515 ms. In conclusion, high gas generator pressure is favorable to the secondary ignition and combustion of primary combustion products.

Effect of Boron Carbide Content on Properties of Thermoplastic Natural Rubber Composite as Thermal Neutron Shielding

In this work, thermoplastic natural rubber (TPNR) composites were produced through melt blending method. Boron carbide (B4C) as filler was added into the polymer blend (TPNR) with different weight percent from 0% to 30% and the effect of different B4C contents on mechanical and thermal neutron attenuation properties of TPNR composites has been studied. The phase formation in composites was analyzed using XRD technique. From the results, it showed that the incorporation of B4C fillers into TPNR matrix has enhanced the macroscopic cross section of the composites, however it lessens the tensile strength. Macroscopic cross section of the composites were increased from 3.34 cm-1 to 14.8 cm-1, while the tensile strength of the composites decreased from 3.79 MPa to 1.06 MPa with increasing B4C from 0 wt% to 30 wt%. B4C diffraction peaks were also increased in intensity with increasing B4C content.

Enhancement of oxidation resistance via a self-healing boron carbide coating on diamond particles.

A boron carbide coating was applied to diamond particles by heating the particles in a powder mixture consisting of H3BO3, B and Mg. The composition, bond state and coverage fraction of the boron carbide coating on the diamond particles were investigated. The boron carbide coating prefers to grow on the diamond (100) surface than on the diamond (111) surface. A stoichiometric B4C coating completely covered the diamond particle after maintaining the raw mixture at 1200 °C for 2 h. The contribution of the boron carbide coating to the oxidation resistance enhancement of the diamond particles was investigated. During annealing of the coated diamond in air, the priory formed B2O3, which exhibits a self-healing property, as an oxygen barrier layer, which protected the diamond from oxidation. The formation temperature of B2O3 is dependent on the amorphous boron carbide content. The coating on the diamond provided effective protection of the diamond against oxidation by heating in air at 1000 °C for 1 h. Furthermore, the presence of the boron carbide coating also contributed to the maintenance of the static compressive strength during the annealing of diamond in air.

Preparation of multi-phase composite of tungsten carbide, tungsten boride and carbon by arc plasma melting: characterization of melt-cast product

Arc plasma melting of WC+B4C followed by an in situ furnace cooling produced a multi-phase composite consisting of tungsten carbide, tungsten boride and carbon. The melt-cast product was prepared in six different compositions by varying the boron carbide content (within 1–15wt%) at the charge stage. XRD, SAED and XPS characterizations of the product showed the major phases to constitute of W2B, WB, W2B5 (WB2), WC, W2C and C. Carbon was found to exist in three different forms, such as graphite, diamond / DLC and nanocrystalline diamond (C–C sp3 coordination). FESEM, TEM and BET studies revealed the surface morphology, microstructure and non-porous nature of the composites respectively. From micro Raman spectra it was evident that W2C and all tungsten boride phases were non-Raman active with 514nm radiation (Ar+ laser). Preliminary mechanical characterization of the polished composite samples (in solid forms) showed the hardness to increase with increase in B4C content (range: 1–10wt%). An extraordinary hardness of 3835±80 VHN with corresponding Young’s modulus of 695±33GPa was observed for the typical composition of WC+10wt% B4C. However, the hardness showed decreased value for 15wt% B4C added sample.

Effect of sintering temperature and boron carbide content on the wear behavior of hot pressed diamond cutting segments

The aim of this study was to investigate the effect of sintering temperature and boron carbide content on wear behavior of diamond cutting segments. For this purpose, the segments contained 2, 5 and 10 wt.% B4C were prepared by hot pressing process carried out under a pressure of 35 MPa, at 600, 650 and 700 ?C for 3 minutes. The transverse rupture strength (TRS) of the segments was assessed using a three-point bending test. Ankara andesite stone was cut to examine the wear behavior of segments with boron carbide. Microstructure, surfaces of wear and fracture of segments were determined by scanning electron microscopy (SEM-EDS), and X-ray diffraction (XRD) analysis. As a result, the wear rate decreased significantly in the 0-5 wt.% B4C contents, while it increased in the 5-10 wt.% B4C contents. With increase in sintering temperature, the wear rate decreased due to the hard matrix.

Fe–B–C composites produced using spark plasma sintering

Fe–B–C composites were produced using iron and boron carbide powders. The powders were mixed to produce various compositions, ranging from 1vol.% Fe to 80.1vol.% Fe. Spark plasma sintering (SPS) was used to densify the composite powder green compacts. The sintering temperatures used ranged from 900°C for the composites with a high iron content to 2000°C for those with a high boron carbide content. It was evident that during the sintering process the iron reacted with the boron carbide. XRD analysis showed the presence of FeB, Fe2B, Fe3C, Fe3(B0.6C0.4), Fe23(B,C)6 and residual carbon as reaction products. The composites were found to have hardness values between 9.8 and 33.1GPa with the higher hardness being associated with the higher boron carbide contents. The fracture toughness values determined were in the range of 2.8–5.3MPam0.5. With increasing iron content from 1 to 5vol.%, it is evident that the FeB formed begins to embrittle the material rather than increase the fracture toughness as a result of the high residual stresses between the B4C and FeB phases.

Electric heating property from butyl rubber-loaded boron carbide composites

We researched the electric heating property from butyl rubber-loaded boron carbide composite. The effects of boron carbide content on bulk resistivity, voltage-current characteristic, thermal conductivity and thermal stability of boron carbide / butyl rubber (IIR) polymer composite were introduced. The analysis results indicated that the bulk resistivity decreased greatly with increasing boron carbide content, and when boron carbide content reached to 60%, the bulk resistivity achieved the minimum. Accordingly, electric heating behavior of the composite is strongly dependent on boron carbide content as well as applied voltage. The content of boron carbide was found to be effective in achieving high thermal conductivity in composite systems. The thermal conductivity of the composite material with added boron carbide was improved nearly 20 times than that of the pure IIR. The thermal stability test showed that, compared with pure IIR, the thermal stable time of composites was markedly extended, which indicated that the boron carbide can significantly improve the thermal stability of boron carbide / IIR composite.

Effects of Boron Carbide Content on the Microstructure and Properties of Atmospheric Plasma-Sprayed NiCoCrAlY/Al2O3-B4C Composite Coatings

NiCoCrAlY/Al2O3 and NiCoCrAlY/B4C composite powders were prepared with hydrogen reduction and solid state alloying process. NiCoCrAlY/Al2O3-B4C composite coatings with different contents of B4C were prepared by atmospheric plasma spray technology. The microstructures, mechanical properties, and tribological properties of the composite coatings with different B4C contents were systematically investigated. The results show that the microhardness of the composite coatings increases, while the tensile strength of the composite coatings decreases, with the increase of B4C contents. The wear volume of the composite coatings decreases from room temperature to 800 °C with the increase of B4C contents. Abrasion wear is the main wear mechanism of the NiCoCrAlY/Al2O3-B4C composite coating from room temperature to 800 °C.

Effect of Oxidizer on the Combustion Performance of Boron-Based Fuel-Rich Propellant

Different boron-based fuel-rich propellants were prepared by replacing part of ammonium perchlorate with different content of cyclotrimethylenetrinitramine, cyclotetramethylenetetranitramine, potassium nitrate, and potassium perchlorate. The burning rate of the propellants under different pressures was measured in the strand burner, the combustion temperature of the propellants under 1 MPa was measured by microthermocouple, and differential scanning calorimetry/thermogravimetric analysis experiments of the propellants in argon atmosphere were carried out. The experimental results show that the effect of each oxidizer on the burning rate of the propellant is different; cyclotetramethylenetetranitramine and cyclotrimethylenetrinitramine could increase the combustion temperature and the gaseous products, whereas potassium nitrate, and potassium perchlorate have the opposite effect. The composition of the combustion products under different pressures was calculated based on the minimization of Gibbs free-energy principle, and the results indicate that, although cyclotetramethylenetetranitramine and cyclotrimethylenetrinitramine could decrease the content of boron carbide in the combustion products, cyclotetramethylenetetranitramine and cyclotrimethylenetrinitramine have a lower effect on the heat release of boron because more boron nitride is produced during the combustion process; potassium perchlorate could decrease the content of boron nitride in the combustion products, obviously.

Physical and mechanical properties of stir-casting processed AA2024/B4Cp composites

Abstract In this study, metal matrix composites of an aluminum alloy (AA2024) and B4C particles with volume fractions 3, 5, 7, and 10 vol% and with sizes 29 and 71 μm were produced using stir-casting technique. The effects of B4C particle content and size of boron carbide on the mechanical properties of the composites such as hardness, 0.2% yield strength, tensile strength, and fracture were investigated. Furthermore, the relation between particle content, microstructure, and particle distribution has been investigated. The hardness of the composites increased with increasing particle volume fraction and with decreasing particle size, although the tensile strength of the composites decreased with increasing particle volume fraction and with decreasing particle size. Scanning electron microscopic observations of the microstructures revealed that dispersion of the coarser sizes of B4C particles was more uniform while the finer particles led to agglomeration of the particles and porosity.

Optimization of the composition, structure, and properties of electrode materials and electrospark coatings for strengthening and reconditioningof metal surfaces

The structure and phase composition of Ni-Cr-Al alloys doped with Si, Ti, Mn, and Co have been studied. An eutectic three-phase structure was found to be in the doped alloys. Doping with Si and Ti increases the microhardness and wear resistance of the alloys. The highest coefficient of the mass transfer (0.75) during the electrospark alloying is observed for Co-containig alloys. The coatings with the doped alloys have a higher wear resistance than those with the Ni-Cr-Al basic alloy. Steel 45’s heat resistance is increased after the electrospark doping with Si-, Ti-, Mn-, and Co-containing alloys by 4, 4.3, 5.1, and 4.6 times, respectively. The electrode materials have been developed for the electrospark reconditioning of workpieces based on PE8418 (Ni-Ni3B-Cu-Si) with the additions of titanium carbide, chromium carbide, and tungsten carbide, which make it possible to manufacture coatings up to 5-mm thick. The results of the investigation of the erosion properties of B4C-TiB2 alloys manufactured using the method of reactive sintering under hot pressing of B4C-TiO2 powder blends that were used as the electrode materials for the electrospark hardening of titanium surfaces are presented. The tests show that, in the surface layers of the electrode materials, under the impact of the electric discharge, the boron carbide content substantially decreased, while the quantity of titanium borides increased and new phases of TiCxNy, TiO2, and Ti appeared. Only these components are transferred onto the surface of the titanium alloy and form there a protective coating up to 100 μm thick with high hardness (32–43 GPa) and wear resistance. The materials developed are promising for their application as the electrodes in the electrospark alloying of construction steels and titanium alloys.

A “Sandwich” type of neutron shielding composite filled with boron carbide reinforced by carbon fiber

A “Sandwich” type of neutron shielding composite reinforced by carbon fiber was currently studied in view of the rapidly growing need of nuclear protective materials. Comparison to Scanning Electron Microscopy (SEM) analysis of a variety of carbon fiber surface treatment, a new technology, named acetone–resin ultrasonic pretreatment was better to ensure that the carbon fiber and the resin glue were solidified effectively by diffusion as a whole, and also worked out the traditional problem about full impregnation of carbon fiber. Meanwhile, differential scanning calorimetry (DSC) and thermogravimetic analysis (TGA) of the composite filled with boron carbide were observed. The conclusion was that the effect of the acid anhydride type curing agent (B-570) was better than the polyamide type (TY-203) in the field of heat resistance, and the carbon fiber was helpful to improve the thermal stability of the composite when the adding content was 28.2%. In addition, the “Sandwich” type of neutron shielding composite was prepared for the tensile performance test. Compared to the boron carbide particles added directly into the composite, it has a huge performance improvement in the mechanical properties when the content of boron carbide filled with 20%, meanwhile it significantly upgrade the neutron shielding performance with spraying with 0.4mm.

Ascending Order of Enhancement in Sliding Wear Behavior and Tensile Strength of the Compocast Aluminum Matrix Composites

The emerging demand of light weight alloys and composites for the engineering and structural applications leads to explore the possibility to develop new techniques to achieve materials of high performance. In the present study, Al–B4C reinforced composite has been developed via semi solid technique. The influence of Boron carbide (B4C) content on the dry sliding wear characteristics of Al6061 matrix composites has been assessed using a pin-on-disc wear test. Wear rate was found to increase in ascending order with B4C particles content. On comparing the wear rate, it has been found that the wear resistance offered by coated B4C reinforced Al 6061 alloy matrix composites is higher than both base Al alloy and uncoated composites with incorporation of harder phase. This shows the good interfacial bonding of coated B4C and Al6061 alloy matrix phase.

Tribological Behaviour of Mechanically Synthesized Titanium-Boron Carbide Nanostructured Coating

In this paper, titanium-boron carbide (Ti/B4C) nanocomposite coatings with different B4C nanoparticles contents were fabricated by surface mechanical attrition treatment (SMAT) method by using B4C nanoparticles with average nanoparticle size of 40 nm. The characteristics of the nanopowder and coatings were evaluated by microhardness test, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Friction and wear performances of nanocomposite coatings and pure titanium substrate were comparatively investigated, with the effect of the boron carbide content on the friction and wear behaviours to be emphasized. The results show the microhardness, friction and wear behaviours of nanocomposite coatings are closely related with boron carbide nanoparticle content. Nanocomposite coating with low B4C content shows somewhat (slight) increased microhardness and wear resistance than pure titanium substrate, while nanocomposite coating with high B4C content has much better (sharp increase) wear resistance than pure titanium substrate. The effect of B4C nanoparticles on microhardness and wear resistance was discussed.

Study of the Effect of Boron Carbide Content in Concrete as Radiation Shielding Application

Keywords: Boron carbide, concrete, shielding, neutron, attenuation. Abstract. Boron carbide (B4C) is a ceramic material which is effectively absorb thermal neutron due to wide neutron absorption cross section. In this work, B4C is added into concrete as fine aggregates to test the attenuation properties by getting the attenuation coefficient of the concrete/ B4C. The samples of concrete/ B4C were exposing to the thermal neutron radiation source (241-Americium-Berylium) at the dose rate of 29.08 mR/h. The result show that the attenuation coefficient of the sample with 20wt% B4C is 0.299 cm-1 and the sample without B4C is 0.238 cm-1 and hence, concrete/ B4C is suitable as a shielded for thermal neutron radiation.

Thermal synthesis of Fe–B4C powder master alloys

The paper examines the thermal synthesis of master alloys from a mixture of iron and boron carbide powders. It is shown that the content of boron decreases as compared with the starting mixture and the boron/carbon ratio in the master alloy powder changes with increasing synthesis temperature. Thus the initial content of boron carbide in the mixture insignificantly influences the boron/carbon ratio after sintering. At the same time, the content of boron carbide in the mixture and synthesis temperature essentially influence the structure and phase composition of the master alloy obtained.

Some Crystallographic Features of the Boron-Doped Diamond Single Crystals Synthesized by Fe-Ni-C-B System under HTHP

Boron-doped diamond single crystals were synthesized with Fe-Ni-C-B System catalysts which content of boron carbide (B4C) were different, and their crystallographic features were tested with electron probe microanalysis (EPMA), X-rays diffraction (XRD), Raman spectrum and field emission scanning electron microscopy (FESEM). The experimental results showed that doped boron in the diamond could result in the changes of its crystallographic features. There were different X-ray peak intensities in the different boron-doped diamond crystals, and the intensities were changed with the content of B4C in the catalysts. With the increase of boron content in the diamond, the boron atoms resulted in the change of growing rate in different crystalline face of the diamond. The quality of diamond synthesized with catalyst which contained 0.2 w.t.% boron carbide was worse than others.