B2 Sample Research Articles

High entropy (HfTiZrVNb)B2 ceramic particulate reinforced Al matrix composites: Synthesis, mechanical, microstructural and thermal characterization

This study aims to introduce a novel type of particulate reinforced Al matrix composite. High entropy (HfTiZrVNb)B2 ceramic particulate reinforced Al matrix composites were produced via a combined process of different powder metallurgy methods. Firstly, boride compounds (HfB2, TiB2, ZrB2, VB2, NbB2) were synthesized in the laboratory scale using the related metal oxide, boron oxide, and magnesium by mechanochemical synthesis (MCS) and leaching processes under optimum conditions. Secondly, the synthesized and purified boride powders were mixed in equimolar ratios using a planetary ball mill for 72 h, and they were sintered at 2000 °C under 30 MPa via spark plasma sintering (SPS). Thirdly, equimolar high entropy (HfTiZrVNb)B2 bulks were crushed, converted into powder forms, and added into Al powders at different amounts as 1, 2, 5, 10, and 15 wt %. Lastly, these powder blends were mechanically alloyed in a vibratory ball mill for 6 h, cold pressed and pressureless sintered at 630 °C for 2 h. For characterization techniques, X-ray diffractometry (XRD), thermal analysis, scanning electron microscopy/energy dispersive spectrometry (SEM/EDS), density measurements using pycnometer and Archimedes' methods, microhardness and dry sliding wear tests were conducted on the sintered composites. The highest hardness (∼1.5 GPa) and the lowest wear rate (∼0.0012 mm3/Nm) were obtained in the Al-15 wt % (HfTiZrVNb)B2 sample.

(HfTiZrMnCr)B2 high entropy diboride ceramics: Synthesis mechanism, microstructural, mechanical and thermal characterization

This study explains the synthesis mechanism of (HfTiZrMnCr)B2 high entropy diboride ceramics prepared via a combined route consisting of ball milling and spark plasma sintering. Firstly, metal borides were in-house synthesized using mechanochemical synthesis and leaching processes under optimum conditions from metal oxides, B2O3 and Mg precursors. The (HfTiZr)B2 composition, chosen as the main composition, was hybridized with two different methods: planetary and vibratory ball milling. As a result of milling experiments, 6 h vibratory milling was determined as the optimum duration, and all compositions were produced by spark plasma sintering method (2000 °C, 30 MPa) following this optimum condition. Different compositions were used to see which one of the HfB2, TiB2, ZrB2 compounds acted as a host material. Based on the phase analyses, single-phase HEB structures, Ti-rich phases and Hf, Ti, Zr-oxides were observed in the microstructure. Detailed physical, microstructural, mechanical and termal characterizations were performed: the highest hardness values were observed in the (HfTiMnCr)B2 and (HfTiZrMnCr)B2 samples as ∼ 27 GPa, the lowest wear rate was recorded for the (HfTiZrMnCr)B2 sample as ∼2 × 10−6 Nm/mm3, and the highest oxidation resistance was achieved at the (HfZrMnCr)B2 and (HfTiMnCr)B2 samples as weight gains ∼ 1.90%.

Investigation of the O phase in the Ti–22Al–25Nb alloy during deformation at elevated temperatures: Plastic deformation mechanism and effect on B2 grain boundary embrittlement

The Ti–22Al–25Nb alloy, which possesses a complex microstructure, is a new type of lightweight high-temperature structural material. Revealing the effects of microstructure and temperature on the mechanical properties of this alloy is crucial for applications in the aerospace industry. In this study, we designed three types of microstructures of the Ti–22Al–25Nb alloy, namely, single-phase B2, dual-phase α2 + B2, and triple-phase O + α2 + B2, and investigated their deformation and fracture behavior with increasing temperature (25,750,and 930 °C). The O + α2 + B2 sample possessed the best comprehensive mechanical properties, and the softening of the O phase at elevated temperatures was mainly due to massive {001}<110>O basal slip and twinning. The evolution of O phase twins with increasing temperature can be described as follows: (021) → (021) + (110) → (110). At 750 °C, (021) twins formed in the strip-shaped O phase in B2 grains, while (110) twins formed in the spheroidized O phase at B2 grain boundaries. In addition, B2 grain boundary embrittlement was observed at elevated temperatures, and its mechanism can be summarized as follows. Elevated temperatures induced element segregation at the grain boundaries between hypersaturated-state B2 grains, enriching Ti and Al and diffusing Nb into the B2 grains on the nanometer scale, leading to a thin-shell O phase with a thickness of tens of nanometers precipitating at the B2 grain boundaries. During elevated-temperature fracturing, cracks propagated quickly along the interface between the thin-shell O phase and B2 phase, leading to embrittlement of the B2 grain boundary. The precipitation of many fine granular O or α2 phases at the B2 grain boundaries can inhibit the precipitation of the thin-shell O phase and hinder the propagation of cracks along the grain boundaries. Therefore, the microstructure of this alloy should be controlled to precipitate many fine granular O or α2 phases to occupy the B2 grain boundaries and inhibit its elevated-temperature embrittlement.

Metal-substituted zirconium diboride (Zr1-xTMxB2; TM = Ni, Co, and Fe) as low-cost and high-performance bifunctional electrocatalyst for water splitting

Recent years have witnessed an unprecedented surge in research on earth-abundant and efficient electrocatalysts for the water splitting process. Among those, the development of boron-based advanced catalysts is subject to designing the active and durable compounds, working as bifunctional materials under alkaline medium. In this study, a series of ZrB2-based catalysts with a general formula of Zr(1-x)TMxB2 (x = 0.05, 0.1, and 0.2) (TM = Fe, Co, and Ni) were prepared through a straightforward route and employed as bifunctional electrocatalysts in hydrogen and oxygen evolution reactions (HER and OER). The electrochemical measurements confirmed that the incorporation of Ni into the crystal structure of ZrB2 in the Zr0.8Ni0.2B2 sample led to an onset potential of 1.58 V in OER at a current density of 10 mA cm–2, indicating a remarkable performance with a very low overpotential of 350 mV. Besides, Zr0.8Ni0.2B2 displayed an infinitesimal value of 56.6 mV dec–1 regarding the Tafel slope, which was lesser as compared to the commercial RuO2 (66.2 mV dec–1). For the case of HER, Zr0.8Co0.2B2 showed the best performance compared to other samples with an overpotential of 420 mV and a Tafel slope of 101.6 mV dec–1, following the Volmer mechanism. Both catalysts were examined for their long-term stability, manifesting excellent catalytic durability even after 12 h. Surprisingly, Zr0.8Co0.2B2 exhibited a drop from 420 to 380 mV in the overpotential value after 1000 CV sweeps, providing a promising performance in terms of HER. As-prepared metal-substituted ZrB2 electrocatalysts have great potential to be implemented in various green energy system applications.

High-pressure high-temperature synthesis and thermal equation of state of high-entropy transition metal boride

A high-entropy transition metal boride (Hf0.2 Ti0.2 Zr0.2 Ta0.2 Mo0.2)B2 sample was synthesized under high-pressure and high-temperature starting from ball-milled oxide precursors (HfO2, TiO2, ZrO2, Ta2O5, and MoO3) mixed with graphite and boron-carbide. Experiments were conducted in a large-volume Paris–Edinburgh press combined with in situ energy dispersive x-ray diffraction. The hexagonal AlB2 phase with an ambient pressure volume V0 = 27.93 ± 0.03 Å3 was synthesized at a pressure of 0.9 GPa and temperatures above 1373 K. High-pressure high-temperature studies on the synthesized high-entropy transition metal boride sample were performed up to 7.6 GPa and 1873 K. The thermal equation of state fitted to the experimental data resulted in an ambient pressure bulk-modulus K0 = 344 ± 39 GPa, dK/dT = −0.108 ± 0.027 GPa/K, and a temperature dependent volumetric thermal expansion coefficient α = α0 + α1T + α2 T−2. The thermal stability combined with a high bulk-modulus establishes this high-entropy transition metal boride as an ultrahard high-temperature ceramic material.

The influence of pretreatment step on hollow braided PET fabric as a potential membrane substrate

Self-supporting polymeric hollow fiber membranes prepared using non-solvent induced phase separation (NIPS) often suffer deterioration in mechanical properties due to asymmetric fingerlike and spongelike morphology giving a porous and fragile structure. Hollow braided fibers of Polyethylene terephthalate (PET) have been used as substrate to increase the strength of hollow fiber membranes. However, problems arise from poor interfacial bonding between the braid and coating polymer resulting in peeling off or delamination at the interface. In this work, we report a method of braid treatment and selection with two alkali treatment steps (NaOH and KOH) to study their effect on pure water flux, water contact angle, tensile strength as well as braid morphology of three different braid samples (B1, B2 and B3). B2 sample treated in KOH demonstrated the highest water flux of 1388 L/m2h. Examination of surface morphology of the braids revealed a washing effect and enlargement of braid interspaces making them more porous and hence increased permeability, with a contact angle of 0° with water. The sample also exhibited zero weight loss as well as a remarkable tolerance for high temperature with negligible reduction in tensile strength of only about 0.9%. Membrane fabricated with B2-K was demonstrated to have better adhesion between polymer-braid interface in comparison to the control. The pre-treatment step provides a good braid selection basis for onward membrane development with KOH showing the most favorable outcome without losing braid quality.

Optimization of Ni-B coating bath and effect of DMAB concentration on hardness and wear

In this study, reducing agent amount, stabilizer amount, coating bath temperature and stirring speed parameters were examined for optimization of electroless Ni-B coatings, and the effect of reducing agent amount on hardness and wear of the coating was investigated. The pH of the electroless Ni-B coatings made for 1 h was set to 6, nickel chloride (NiCl2.6H2O) as the nickel source, sodium acetate (C2H3NaO2) as the complexing agent, thiourea as the stabilizer (CH4N2S) and DMAB ((CH3)2NBH2) as the reducing agent was used in the coatings. The bath parameters were varied as; the amount of reducing agent (2 g/L, 3 g/L and 4 g/L), coating bath temperature (65°C, 70°C and 75°C), stabilizer amount (0.5 mg/L, 1 mg/L, and 2 mg/L) and stirring speed (250, 300 and 350 rpm). After determining the optimum conditions, the effects of the amount of reducing agent on the coating were examined. Scanning Electron Microscopy (SEM), X-ray diffractometer (XRD), Vickers nano-hardness test and tribometer were used for characterization of coatings. In the optimization studies, it was observed that the coating morphology was in the form of cauliflower and columnar structures were formed in the cross-section images. According to optimization results on the morphologies, the samples which compact and free-crack have been investigated phase structure, hardness and tribology properties. In XRD analysis, coatings produced with different amounts of reducing (DMAB) are amorphous as-deposited, after annealed at 400°C for 2 h, nickel borides (Ni2B and Ni3B) phases are formed and increased the preferential orientation (111) of the nickel crystal plane. The effect of DMAB concentration on coating was examined in as-deposited condition and post annealing. The formation of nickel borides after annealing increases the hardness. The effect of DMAB concentration on the coating after annealed was examined and it was observed that the wear resistance of the dense and homogeneously dispersed sample in the coating matrix was more perfect than other samples. Consequently, hardness (850 HV), coefficient of friction (0.37) and wear rate (2.92 × 10−7 mm3/Nm) of B2 sample which free-crack and compact was obtained. These results indicate a high strengthen B2 sample produced with 3 g/L DMAB concentration and 70°C bath temperature could utilize in a harsh medium.

Ceramic and Glass Fibre Reinforced Flexible Composites for Particulate Filter Walls – A Novel Approach

Flexible composites from high performance fibres were developed and targeted to replace the wall of existing rigid ceramic Particulate Filters. The composites are made from E Glass fibre webs of different density in the middle, with standard SiC Ceramic fibres webs in in the outer layers, forming a sandwich structure. Different needling densities were applied to form nonwoven composites, and they were stitched diagonally on the surface at specified intervals with continuous glass fibre filament yarn. In total, nine novel flexible composites were developed and evaluated for their structural, surface, mechanical and thermal properties. Based on the results and statistical analysis, the B2 sample is considered to be taken for further research to develop Particulate Matter (PM) filters.

Comparative studies on the performance and emissions of a direct injection diesel engine fueled with neem oil and pumpkin seed oil biodiesel with and without fuel preheater.

In the present experimental analysis, two non-edible oils namely neem oil and pumpkin seed oil were considered. They are converted into respective biodiesels namely neem oil methyl ester (B1) and pumpkin seed oil methyl ester (B2) through transesterification process and their physical and chemical properties were examined using ASTM standards. Diesel was used as a baseline fuel in Kirloskar TV1 model direct injection four stroke diesel engine. A fuel preheater was designed and fabricated to operate at various temperatures (60, 70, and 80°C). Diesel showed higher brake thermal efficiency (BTE) than biodiesel samples. Lower brake specific fuel consumption (BSFC) was obtained with diesel than B1 sample. B1 exhibited lower BSFC than B2 sample without preheating process. High preheating temperature (80°C) results in lower fuel consumption for B1 sample. The engine emission characteristics like carbon monoxide (CO), hydrocarbon (HC), and smoke were found lower with B1 sample than diesel and B2 except oxides of nitrogen (NOx) emission. In preheating of fuel, B1 sample with high preheating temperature showed lower CO, HC, and smoke emission (except NOx) than B2 sample.

The investigation on the regional nanoparticle Ag doping into MgTi0.06B2 bulk for improvement the magnetic levitation force and the bulk critical current

Fabrication methods are important way to improve structural and superconducting properties of MgB2 such as critical current, magnetic levitation force (MLF) and magnetic field trapping capability. Although the graded fabrication technique has been used for single-grain bulk YBCO superconductor to improve critical current and bulk superconducting properties, similar technique as regional doping has not been used for bulk MgB2, until now. In this study, nanoparticle silver doping was carried out in to the bulk MgTi0.06B2 superconductor by using in-situ solid state reaction and partial graded (regional) doping method together, to improve the radius independent uniform bulk current density and the magnetic levitation force as well as the structural properties of the MgB2 bulk superconductors. Both the Jc(0) self-field critical current and Fp (μ0H) pinning force density values enhanced in comparison with the inner region values, when the nanoparticle Ag doping is carried out in to the outer section of the sample. Addition to the enhancement of the structural and the micro electromagnetic properties as Jc(0) and Fp (μ0H), our study also focused on the improved of the bulk Jc and the radius of shielding current loop r, to improve bulk electromagnetic properties as the levitation force. It is seen that the structural properties enhanced and both the vertical levitation force and the lateral guidance force value increased with Ag doping to the outer section of MgTi0.06B2 sample. On the other hand, the increasing ratio of the lateral guidance force of 19.7% and the vertical levitation force of 10.8% of the sample with 3 wt% Ag-doped than the undoped one points out that the regional doping method to the outer section is very suitable for guidance force applications, which is important in the magnetic bearing application such as Maglev and magnetic energy storage systems.

Multiphase ISM in low luminosity radio galaxies: A case study of NGC 708

AbstractWe present a multi-wavelength study of a nearby radio loud elliptical galaxy NGC 708, selected from the Bologna B2 sample of radio galaxies. We obtained optical broad band and narrow images from IGO 2m telescope (Pune, India). We supplement the multi-wavelength coverage of the observation by using X-ray data from Chandra, infrared data from 2MASS, Spitzer and WISE and optical image from DSS and HST. In order to investigate properties of interstellar medium, we have generated unsharp-masked, color, residual, quotient, dust extinction, Hα emission maps. From the derived maps it is evident that cool gas, dust, warm ionized Hα and hot X-ray gas are spatially associated with each other. We investigate the inner and outer photometric and kinematic properties of the galaxy using surface brightness profiles. From X-ray 2d beta model, unsharp masking, surface brightness profiles techniques, it is evident that pair of X-ray cavities are present in this system and which are ~5.6 Kpc away from the central X-ray source.

Study of Bacterial Samples Using Laser Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) technique has been applied to investigate two different types of bacteria, Escherichia coli (B1) and Micrococcus luteus (B2) deposited on glass slides using Spectrolaser 7000. LIBS spectra were analyzed using spectrolaser software. LIBS spectrum of glass substrate was compared with bacteria spectra. Ca, Mg, Na, K, P, S, Cl, Fe, Al, Mn, Cu, C, H and CN-band appeared in bacterial samples in air. Two carbon lines at 193.02 nm, 247.88 nm and one hydrogen line at 656.28 nm with intensity ratios of 1.9, 1.83 and 1.53 appeared in bacterial samples B1 and B2 respectively. Carbon and hydrogen are the important components of the bio-samples like bacteria and other cancer cells. Investigation on LIBS spectra of the samples in He and Ar atmospheres is also presented. Ni lines appeared only in B2 sample in Ar atmosphere. From the present experimental results we are able to show that LIBS technique has a potential in the identification and discrimination of different types of bacteria.

Microstructure and Thermal Shock Behaviour of Alumina Composite Ceramic for Heat Transmission Pipeline

Al2O3 composite ceramics materials used for heat transmission pipeline were prepared by pressureless sintering in air. Calcined bauxite, talc and commercial alumina powder were used as the main raw materials, partially stabilized zirconia was also added to improve the thermal shock resistance of the samples. The effects of composition and sintering temperature on density, phase composition, microstructure and thermal shock behavior of samples were evaluated. It shows that the B2 sample which was sintered at 1400 °C for 2 h has optimal properties with porosity 0.4%, bulk density 3.2 g•cm-3.The bending strength increases 19.46 MPa after 30 times thermal shock cycles from 1100 °C to room temperature. The main phases of B2 are corundum and spinel, meanwhile, a small amount of monoclinic zirconia and α-quartz are also detected according to XRD pattern. Microstructure analysis reveals that spinel crystals are interlocked by prismatic corundum crystals, bright white beaded monoclinic zirconia particles are distributed uniformly, and it is beneficial to improve the thermal shock resistance of sample.

Concept and properties of an infrared hybrid single-beam spectrum and its application to eliminate solvent bands and other background interferences

For infrared (IR) spectral measurements, if a quality single-beam background spectrum with desired intensity could be obtained, the contributions from solvent and other background components could be completely suppressed and their bands would not appear in a final transmittance/absorbance spectrum. In order to achieve this ideal but difficult goal, the concept of hybrid single-beam spectrum is introduced in this paper. The hybrid single-beam spectrum (φ h) is defined as a mixture of two single-beam spectra (φ b1 and φ b2) of the same sample but with different pathlengths (b1 and b2), namely, φ h = αφ b1+(1-α)φ b2, where α (0 ≤ α ≤ 1) is the component factor. The properties of the hybrid spectrum have been investigated. Under conditions of b2 > b1 ≥ 0.7 b2 and A max ≤ 0.60 (Amax is the maximum absorbance of b2 sample in the spectral range of interest), all the synthesized hybrid spectra are free from significant distortion regardless of the component factor. Therefore, the hybrid single-beam spectrum with desired intensity can be easily obtained simply by choosing an appropriate component factor. The proposed methodology has been demonstrated experimentally by the complete removal of the interference from the atmospheric water vapor and solvent.

Multiwavelength Study of Radio Loud Early-Type Galaxies from the B2 Sample

AbstractWe present multiwavelength study of a sample of radio loud early-type galaxies chosen from the B2 sample. We performed surface photometry in BVR broad band filters and Hα narrow band filter on CCD images of sample galaxies using IGO 2m telescope, Pune (INDIA), to get radial profiles of various photometric and geometrical parameters that describe elliptical isophotes fitted to the 2D light distribution of the galaxies. The analysis of radial profiles of quantities such as the (local) surface brightness, the ellipticity, and the deviations from elliptical isophotes parametrized by the Fourier coefficients are main focus of our study. We generated color maps, residual maps, and dust extinction maps, Hα emission maps of the galaxies to study the morphology of the dust and ionized gas content present in the galaxies. We carried out detailed analysis of the properties of the dust present in our sample galaxies. Additionaly, we investigated properties of the dust in the central ~10 arcsec region of our sample galaxies using optical images available from the HST (WFPC2) data archive. We estimated mass and temperature of the dust, molecular gas mass, in the sample galaxies using FIR fluxes of the galaxies obtained from IRAS.We used spectroscopic data available from the SDSS (DR7) to get an estimate of the mass of the central super massive black-hole for B2 1257+28 (NGC 4874). We plotted rotation curve for coma cluster (Abell 1656), which indicates the presence of dark matter halo around the galaxy B2 1257+28.

P01-30 - Folate deficiency in outpatients with a diagnosis of unipolar depression in mental health center

Folate deficiency have been linked to depression, anxiety, persistent depressive symptoms, and poor antidepressant response.ObjectivesDetermine levels of folic acid and vitamin B12 in a sample of depressed patients in the first visit to mental health center.AimsDemonstrate a high prevalence of folate and vitamin B12 deficiency in this group of patients and the relation with the depression and treatment resistant.MethodThe sample was all the patients with a diagnosis of unipolar depression, who were derivated by general practitioner (GP) between January and June 2009 to Vallecas Villa Mental Health Center in Madrid. The sample was 82 patients, they were between 20 and 86 years old. In 62 cases the GP derivated the patients because resistant to treatment, and in 20 cases were naive-treatment. In the first visit folate serum and vitamin B12 were measured.Results69 patients present low levels of folate (84,14%), and 4 low levels of vitamin B12 (4,87%). The mean of folate was 2,2 ng/ml in low-serum folate sample and the mean of vitamin B12 was 93 pg/ml in low vitamin B2 sample. 90,80% (56) of the resistant-treatment group presents low folate serum, in the naive sample was 65% (13).ConclusionsIn our sample depression is associated to a very high prevalence of folate deficiency. The highest prevalence appeared in the resistant-treatment group, so it could be a factor that influence in the persistent depressive symptoms, and poor antidepressant response.

Superconductivity of Nb1−x Mg x B2: Impact of Stretched c-Parameter

We have performed a systematic study on the occurrence of superconductivity in Nb1−x Mg x B2 (0.0≤x≤0.40). X-ray diffraction and magnetization measurements are carried out to determine the changes in lattice parameters, superconducting transition temperature (T c ) and critical field (H c1). The substitution of Mg at Nb site results in considerable stretching of c-parameter with only a slight change in a parameter. Rietveld analysis on X-ray diffraction patterns gives a=3.11 A and c=3.26 A for pure NbB2 while a=3.10 A and c=3.32 A for Nb0.60Mg0.40B2. This increased c-parameter introduces superconductivity in niobium diboride. Magnetization measurements though indicate the absence of superconductivity in NbB2, the same shows a clear diamagnetic signal at about 10 K for Nb0.60Mg0.40B2 sample. The magnetization M(H) plots exhibit weak superconductivity like hysteresis loops. The stretching of c-parameter from around 3.26 to 3.32 i.e. by 0.06 cannot be explained solely by substitution of Nb by Mg in the lattice. It seems that some Nb deficiencies are introduced in the Nb1−x Mg x B2 as Mg is not substituted completely at the vacant Nb sites. This could be seen from XRD results, where one can clearly notice the presence of small amount of MgO in Nb1−x Mg x B2 samples.

Order–disorder transition of vortex matter in Mg0.95B2

Third-harmonic susceptibility has been employed to probe the order–disorder transition of vortex matter of a good-quality sample of MgB2 with random disorder. In the major part of the temperature interval, the measured boundary line can be adjusted by a power-law function, in accordance with theoretical models for the melting of the ordered phase of a 3D vortex-glass. For larger temperatures, however, thermally-induced depinning anticipates disorder, which is also predictable for the vortex matter behavior of a clean system with small amounts of randomly distributed disorder, as is the case of the Mg0.95B2 sample studied here.

Superconductivity in Mg-Doped Layered Intermetallic Compound NbB2

We have performed low temperature resistivity ρ(T) and specific heat C(T) measurements on a superconducting polycrystalline Nb0.75Mg0.25B2 sample. The results indicate that the superconducting transition temperature is ∼ 4.6 K. The zero temperature upper critical field determined from the resistivity and specific heat is 3123 Oe. The electronic coefficient of specific heat γn = 4.51 mJmol−1K2 and the Debye temperature ΘD = 419K are obtained by fitting the zero-field specific heat data in the normal state. At low temperatures, the electronic specific heat in the superconducting state follows Ces/γnTc = 2.84exp(-1.21Tc/T). This indicates that the superconducting pairing in Nb0.75Mg0.25B2 has s-wave symmetry.

Fabrication of the 19-filament Fe/Cu clad MgB2 wire via in situ powder-in-tube method

Using commercial amorphous B powder (92% in purity) and Mg powder (99% in purity) as starting materials, 19-filament Fe/Cu clad MgB2 wires were fabricated by an in situ powder-in-tube method. Heat treatment was performed at 700°C for 1 h under an argon gas atmosphere. The influence of Mg/B ratio on the microstructure and superconducting properties of the wires was investigated. It was found that the major phases of MgB2 wires were MgB2 accompanied with relatively small amounts of MgO and Fe2B impurities. With 5% excess Mg addition, the onset T C slightly decreased. However, the transport J C at 4.2 K and 4 T reached 1.07×104 A·cm−2, increasing by a factor of 1.4 compared to the stoichiometric sample. Moreover, the Mg1.05B2 sample showed an improved field dependence of J C, suggesting that less voids and smaller grain size of the Mg1.05B2 core lead to better grain connectivity and stronger flux pinning.