Papers by Keyword: Boron

Abstract: Mechanical behavior and microstructure evolution of the cast Ti-43.2Al-1.9V-1.1Nb-1.0Zr-0.2Gd-0.2B alloy were studied at temperatures from 1100 to 1250°С and strain rates in the range 0.001-1 s^-1. Following phase fields (α₂+γ), (α+γ), (α) and (α+β) during heating of alloy were revealed. Microstructure analysis after deformation and mechanical behavior allowed defining main processes of structure formation. Two temperature-strain rate conditions with pronounced superplastic behaviour were found: the first one corresponded to the (α₂+γ)-phase field (1100°C), where the microstructure had mainly a lamellar morphology, and the second was associated with the (α+β)-phase field (1250°C), in which the α-phase dominated. At T=1100°C and έ=0.05 s^-1 the maximum strain rate sensitivity m was of 0.40. At T=1250°C and έ=0.5 s^-1 the maximum strain rate sensitivity m was of 0.59. In the (α₂+γ)-phase field, superplastic behavior was associated with the transformation of the lamellar structure into globular one. In the (α+β)-phase field, it was due to the formation of a homogeneous refined microstructure during dynamic recrystallization. The relationship between coefficient m value and microstructure formed was discussed.

Abstract: Eeffect of Boron addition on the microstructure and mechanical properties of ductile iron, GJS-500-7 grade was studied. Three cast batches with the Boron content of 10, 49 and 131ppm were cast in a casting geometry containing plates with thicknesses of 7, 15, 30, 50 and 75mm. Microstructure analysis, tensile test, and hardness test were performed on the samples which were machined from the casting plates. Addition of 49 ppm Boron decreased pearlite fraction by an average of 34±6% in all the cast plates. However, minor changes were observed in the pearlite fraction by increasing Boron from 49 to 131 ppm. Variation in the plate thickness did not affect the pearlite fraction. The 0.2% offset yield and ultimate tensile strength was decreased by an average of 11±1% and 18±2%, respectively. Addition of 49 ppm Boron decreased Brinell hardness by 16±1%, while 11±2% reduction was obtained by addition of 131ppm Boron.

Abstract: We propose an empirical model to predict electrical activation ratios of aluminium- and boron-implanted silicon carbide with respect to various annealing temperatures. The obtained parameters and model extensions are implemented into Silvaco’s Victory Process simulator to enable accurate predictions of post-implantation process steps. The thus augmented simulator is used for numerous simulations to evaluate the activation behavior of p-type dopants as well as for the full process simulation of a pn-junction SiC diode to extract the carrier and acceptor depth profiles and compare the results with experimental findings.

Abstract: In the present study, a mixture of powders (87.9 at.% Ni, 12 at.% Al, 0.1 at.% B) was used as the initial material to produce sintered Ni₃Al + B alloy. Spark Plasma Sintering (SPS) method was used to compact the powder. The powder mixtures were previously prepared in two ways: mixing the initial powders in a mortar (М1) and mechanical activation (М2). The microstructure was observed using optical microscope (OM). The addition of small amount of boron to the initial mixture of nickel and aluminum improves the density of the sintered Ni₃Al intermetallic compound (98.8%). The results of density, bending and microhardness tests showed, that the provisional three-minute mechanical activation improves almost all properties of the sintered material. The compact obtained by SPS by M2 contributes to the formation of a homogeneous fine-grained structure of the material. It leads to further increase in flexural bending strength up to 2200 MPa. This value is almost 8 times the strength of the intermetallic Ni₃Al stoichiometric composition obtained by SPS.

Abstract: Liquid Silicon Infiltration (LSI) is a technique to manufacture non-oxide ceramic matrix composites such as C/C-SiC or SiC/SiC. In the beginning of this three-step process, fiber preforms are shaped and impregnated with phenolic resins. After curing, the preforms are pyrolyzed to convert the polymer matrix to a porous carbon matrix. This porosity is then used to infiltrate liquid silicon by capillary forces. Simultaneously, an exothermic reaction of silicon and carbon creates a silicon carbide matrix. Generally the liquid silicon reacts with any carbon and even with SiC present in the form of fibers, fiber coatings or matrix. Therefore, especially the fibers must be protected from Si attack effectively. The morphology of silicon carbide was observed to be heavily driven by Ostwald ripening. This can be suppressed by the addition of boron to the melt. The initially formed SiC crystals in C/C-SiC composites are hereby prevented from grain coarsening, resulting in almost completely preserved C/C blocks. For the manufacture of SiC/SiC composites, the silicon boron alloys allow an effective preservation of the nanocrystalline SiC-fibers. Thus, the use of Si based B containing alloys helps effectively to moderate and control the aggressive reaction during LSI process.

Abstract: In this work, B (boron) was added into Sn-1.0Ag-0.5Cu (SAC105) solder alloy using mechanical alloying method in order to develop a new low-silver lead-free solder, Sn-1.0Ag-0.5Cu-xB, where B ranges from 0wt% to 0.2wt%. The melting characteristics, wettability, mechanical properties of welded joints, and microstructure of this solder were studied. The results showed that with adding B into SAC105 alloy, the melting point and melting range was not obviously changed. Although the wettability decreases with the B content increasing, the solder joints exhibited higher shear strength. As a result, the shear strength was the highest at the B content of 0.2wt%. For example, the shear strength of the Sn-1.0Ag-0.5Cu-0.2B solder was 35.12MPa, while that of the B free SAC105 solder was only 28.94MPa. Furthermore, adding B had a significant effect on grain refinement on the SAC105 solder . Observations on solder matrix and weld joints by SEM showed that the IMC thickness of solder joints with the addition of B was less than the SAC105 lead-free solder. Moreover, with the addition of B, the solder grains were refined obviously which had the effect of refining straitening, and the growing rate of brittle IMC in solder joint could be effectively reduced during soldering and aging process. Thus solder joint performance can be improved significantly.

Abstract: Sublimation-grown 3C-SiC crystals were implanted with B ions at elevated temperature (400 °C) using multiple energies (100 to 575 keV) with a total dose of 1.3×10¹⁷ atoms/cm² in order to form intermediate band (IB) in 3C-SiC. The samples were then annealed at 1400 °C for 60 min. An anomalous area in the center was observed in the PL emission pattern. The SIMS analysis indicated that the B concentration was the same both within and outside the anomalous area. The buried boron box-like concentration profile can reach ~3×10²¹ cm^-3 in the plateau region. In the anomalous area a broad emission band (possible IB) emerges at around ~1.7-1.8 eV, which may be associated with B-precipitates having a sufficiently high density.

Abstract: SiC planar VDMOS of three voltages ratings (1.7kV, 3.3kV and 4.5kV) have been fabricated using a Boron diffusion process into the thermal gate oxide for improving the SiO₂/SiC interface quality. Experimental results show a remarkable increase of the effective channel mobility which increases the device current capability, especially at room temperatures. At high temperatures, the impact of the Boron treatment is lower since the major contribution of the drift layer to the on-resistance. In addition, the intrinsic body diode characteristics approximate to that of an ideal PiN diode, and the blocking capability is not compromised by the use of Boron for the gate oxide formation.

Abstract: The microstructure, toughness, hardness and wear resistance of Fe-B-C cast wear-resistant alloy were studied. The results indicate that, the as-cast Fe-B-C alloy comprises pearlite, ferrite and eutectic phase Fe₂ (B, C), and that, with increasing boron and carbon contents, the boride volume fraction (BVF) and macrohardness increase; furthermore, when boron content increases from about 0.5 wt.% to 2.0 wt.%, the increase trend of the macrohardness will become smaller with increasing the carbon content. The results also indicate that, after heat-treatment, the Fe₂ (B, C) becomes coarser than that as cast condition, and the boron content has less effect on the martensite hardness at the same carbon content; with increasing boron and carbon contents, the hardness of the samples increases and inversely the toughness decreases. At a lower BVF, the matrix plays a dominant role on the impact toughness of Fe-B-C alloy; however, at a higher BVF, the BVF plays a dominant role. The wear test results indicate that, with increasing the boron and carbon contents, the weight loss of the samples decreases, namely, the increase of wear resistance.

Abstract: Phosphates have been receiving important attention in various fields and one of the fundamental sources of nutrients required to be used as source of nutrients for plankton growth. The objective of this study is to determine the effect of boron oxide on phosphate ion released from the system SiO₂-B₂O₃-P₂O₅-Na₂CO₃ glasses. The compositions of this glass system [wt%: (55-x)% SiO₂- (15+x)% B₂O₃- 5% P₂O₅- 25% Na₂CO₃] where 15≤x≤40 % have been prepared with the different amount of B₂O₃ (30-55wt%) and P₂O₅ with Na₂CO₃ were fixed. The glass has been prepared by melting in the alumina crucible within 2 h of soaking time at 1300 °C in the furnace and cooled to room temperature. The obtained glass samples were crushed and sieved at mean size of 2 mm – 4 mm. The dissolution studies were determined through the immersion of the glass samples in 50 mL synthetic seawater for 30 days under static condition. The results were obtained and analyzed using Discrete Auto Analyzer. Fourier Transform Infrared (FTIR) with Attenuated Total Reflectance (ATR) method was used to determine the functional group sample of glasses and the glass phase was characterized by X-Ray diffraction (XRD) techniques. Dissolution studies showed that, the concentration of phosphate ion released decreased with increasing B₂O₃ content whilst, increased with immersion time. The obtained experimental data indicated that, the optimum concentration of phosphate ion (10.27 ppm) was achieved at 35 wt% of B₂O₃ at week three.