Boron Precursor Research Articles

An MgB$_2$ Superconducting Shield Prototype for the Future Circular Collider Septum Magnet

A passive superconducting shield was previously proposed to realize a high-field (above 3 T) septum magnet for the Future Circular Collider proton–proton ring (FCC-hh). This paper presents the experimental results of a potential shield material, MgB $_2$ , at a temperature of 4.2 K. A cylindrical shield with a wall thickness of 8.3 mm was manufactured by the reactive liquid magnesium infiltration technique using extra large grain ( $\sim$ 160 $\mu$ m) boron precursor, and tested in a transverse magnetic field. The shield was stable against flux jumps on the virgin curve, but suffered from flux jumps at low-field levels after high-field exposure. The tube could shield a magnetic field of 2.75 T on its surface before field penetration to its interior. Parameters of the critical current density of the material could be estimated from simulations, which indicate a steeper $J_c(B)$ curve than observed previously for large grain ( $\sim$ 100 $\mu$ m) MgB $_2$ , and predict a slightly better shielding performance (3 T) with an ideal geometry. Relaxation of the shielding currents is at an acceptable level. We estimate that a self-supporting shield of a wall thickness of 14 mm could be adequate for the construction of a 3-T septum magnet, if the flux jump problem can be solved. This thickness would correspond to a total septum thickness (including beam pipes, etc.) of around 22 mm, which is an acceptable figure for the FCC-hh.

Effect of Ni doping on microstructure and superconductivity of MgB2 prepared by C - coated B powder

The MgB2 bulk doped with Ni nanoparticles with a composition of (Mg1.05B2)Nix (x = 0, 0.04, and 0.06) has been prepared by an in-situ method using the carbon-coated amorphous boron powder as precursor. The combination influence of Ni and carbon doping on the microstructure and superconductivity of MgB2 sample has been clarified according to the XRD, DSC, SEM and PPMS measurements. It is found that the carbon-coated boron in the present work has benefited to the uniformly refined MgB2 grains, as well as a high level of homogeneous carbon doping in the MgB2 samples. The increased grain boundaries and efficient carbon institution of B has significantly enhanced the Jc (High magnetic field) in the MgB2 bulks due to the more pinning centers compared to the normal amorphous boron precursor. Moreover, it has found that the irreversibility field (Hirr) of MgB2 is greatly improved. However, the positive effect of carbon coated boron has been weakened by Ni doping at low magnetic field. Meanwhile, the formed eutectic liquid by Ni and Mg at 506℃has promoted activity of the C replacement of the B site in MgB2, which distorted the MgB2 grains and worsened the intergranular connectivity.

Synthesis and characterization of Ag2O/B2O3/TiO2 ternary nanocomposites for photocatalytic mineralization of local dyeing wastewater under artificial and natural sunlight irradiation.

In this work, Ag2O/B2O3/TiO2 ternary nanocomposite was synthesized by a combination of green and precipitation method involving mixing of different concentrations of silver nitrate, boric acid, and titanium (IV) isopropoxide precursor with Plumeria acuminate leaf extract. The extract was obtained by boiling the mixture of distilled water and the powdered leaves in a beaker for few minutes followed by filtration. The microstructure, morphology, chemical composition, surface area, phase structure, and optical properties of the various prepared nanomaterials were determined by HRTEM, HRSEM, UV-Vis/DRS, BET, XRD, and XPS. The photocatalytic potential of TiO2 nanoparticles and Ag2O/B2O3/TiO2 nanocomposites to degrade local dyeing wastewater under artificial and natural sunlight irradiation was investigated. The extent of degradation of the organic pollutants was measured using chemical oxygen demand (COD) and total organic carbon (TOC) as indicator parameters. The XRD pattern of Ag2O/B2O3/TiO2 nanocomposites revealed that the formation of pure anatase TiO2 phase and the addition of both silver and boron precursors did not influenced the phase structure of the nanocomposites. The oxidation states of +1 and +3 for both Ag and B on the surface of Ag2O/B2O3/TiO2 nanocomposites were confirmed by XPS. Optical characterization of the sample revealed reduction of band gap energy from 2.6 to 2.0eV for TiO2 and Ag2O/B2O3/TiO2, respectively. The Ag2O/B2O3/TiO2 nanocomposites demonstrated excellent photocatalytic activity under natural sunlight and artificial light than mono and binary oxide systems with TOC and COD degradation efficiencies of 86.11% and 75.69%, respectively. The kinetics of degradation of organic dyes in the wastewater followed the order of Langmuir-Hinshelwood pseudo-first-order > Freundlich > Zero > Parabolic diffusion model. The coupling effect of Ag2O and B2O3 onto TiO2 framework was responsible for the enhanced photochemical stability of the nanocomposites even after five repeated cycles.

Co3O4-nanoparticle-entrapped nitrogen and boron codoped mesoporous carbon as an efficient electrocatalyst for hydrogen evolution.

Co3O4-nanoparticle-entrapped nitrogen and boron codoped mesoporous carbon was synthesized via the molten salt method. Melamine formaldehyde resin (MF resin) was used as the nitrogen and carbon precursor, and boric acid was utilized as the boron precursor. Furthermore, cobalt chloride was used as the cobalt precursor and the template for the formation of mesopores, which could also be removed and partly recovered by acid washing. The characterization results revealed that the as-obtained samples possessed mesoporous structures, with high cobalt, boron, and nitrogen content values. For the sample of Co0.65B0.3NC800, the atomic content values of Co, N, and B are 2.3%, 8.87%, and 8.67%, respectively. Moreover, the carbonation temperature and the amount of salt template could both affect the mesoporous structures of the final samples and then affect the electrocatalytic activities for the hydrogen evolution reaction (HER). When the carbonation temperature was 800 °C, the sample of Co0.65B0.3NC800 showed superior performance for the HER under basic conditions, with high current density, low overpotential, and good stability.

Structural characterization of boron-containing glassy and semi-crystalline Biosilicate® by multinuclear NMR

In vitro, in vivo, and clinical studies - including histopathological, cytotoxicity, and genotoxicity analyses - over the past 25 years have proven the tremendous potential of Biosilicate® in appliance as osteoinductive powders, scaffolds and even monolithic pieces. Within continuing efforts to improve the properties of this bioactive material, in this article we explore the structural consequences of incorporating boron in small amounts and its effects on selected properties, as it is known to influence vital processes such as embryogenesis, bone growth, and psychomotor skills, among others. Solid state 11B MAS NMR studies indicate that in the glassy precursor boron is likely present in the form of three-coordinate pyroborate units, with only minor fractions of four-coordinate species present. In contrast, 31P MAS-NMR spectra reveal that phosphorus is almost exclusively present in the form of orthophosphate. The demand of the anionic borate network former for cationic charge compensation leads to an increase in average connectivity of the silicate network, as evident from 29Si MAS NMR. 31P/11B dipolar recoupling experiments indicate negligible amounts of borate–phosphate linkages in these glasses, presumably because of the low concentrations of each element. Crystallization of the glassy Biosilicate® precursor produces crystalline NaCaPO4 and Na2CaSi2O6 as well as a residual amorphous material for which the fraction of four-coordinate boron is significantly increased and no B-O-P linkages can be detected. Surprisingly, we find that in this particular glass boron reduces the glass stability against crystallization and has only a weak influence upon the TRIS-buffer solution dissolution kinetics.

A novel spark plasma sintering route to process high-strength Ti–4Al–2Fe/TiB nano-composite

ABSTRACTTi–4Al–2Fe alloy and Ti–4Al–2Fe/TiB nano-composite were processed by a novel spark plasma sintering route. KBF4 was used as an alternative and inexpensive boron precursor to form TiB reinforcement in situ during sintering. Fe was used as an alternative to vanadium to make the (α + β) Ti matrix. The processed Ti–4Al–2Fe alloy exhibited excellent mechanical properties (CS = 1798 MPa). The TiB whiskers were distributed homogeneously and were fine (widths 130 nm and lengths from 100 nm to 3 µm). No residual TiB2 was found in the composite, in contrast with other methods. The TiB homogenised and refined the microstructure, while the hardness (710 HV), compressive strength (2414 MPa) and elastic modulus (140 GPa) all increased significantly when compared to the unreinforced alloy.

Potasyum Klorür Kullanılarak Sentezlenen Potasyum Borat Mineralinin Sentez ve Karakterizasyonuna Tepkime Koşullarının Etkisi

In this study, the synthesis and characterization of potassium borate were studied using KCl, NaOH and H 3 BO 3 as the starting materials. The effects of the boron precursor, reaction temperature and time on the structure of the synthesized potassium borate were investigated. X-ray diffraction (XRD) showed the synthesized sample was santite, which has the chemical formula KB 5 O 8 4H 2 O (Powder diffraction file number: 01-1072-1688). The XRD scores increased upon decreasing the reaction temperature and time. The characteristic band values observed for boron and oxygen were investigated using Fourier transform infrared (FT-IR) and Raman spectroscopy. The morphology of the synthesized samples was characterized using scanning electron microscopy (SEM). The samples were found to be on the micro-scale with particle sizes <2.54 µm. The reaction yields were in the range of 75.01–95.03% for Set-1 and 72.04–92.22% for Set-2.

The optimization of the doping level of boron, silicon and nitrogen doped diamond film on Co-cemented tungsten carbide inserts

Boron doped, silicon doped and nitrogen doped diamond films with different doping level in gas phase are deposited on Co-cemented tungsten carbide (WC-Co) inserts using hot filament chemical vapor deposition (HFCVD) method. Trimethyl borate ((CH3O)3B), tetraethoxysilane (Si(OC2H5)4) and urea (CO(NH2)2) are dissolved in acetone to serve as boron, silicon and nitrogen precursors, respectively. The as-deposited diamond films are characterized by field emission scanning electron microscope (FESEM), Raman spectroscopy and indentation tests. The results suggested that doping source and doping level will affect the surface morphology, growth rate, quality and adhesion of diamond film. The optimized doping level to obtain diamond films deposited on WC-Co substrate for mechanical applications with well faceted crystal, low defect, low cluster structure and high adhesive strength is 5000 ppm, 10000 ppm and 10000 ppm for boron, silicon and nitrogen doping, respectively.

Boron Doping and Defect Engineering of Graphene Aerogels for Ultrasensitive NO2 Detection

Boron-doped and defect-engineered graphene aerogels are prepared using triphenyl boron as a boron precursor and subsequent heat treatments. The boron chemistry and concentration in the graphene lat...

One-Step Synthesis of Hexagonal Boron Nitrides, Their Crystallinity and Biodegradation.

Hexagonal boron nitrides (hBNs) have recently been investigated for several novel applications due to their unique properties such as biocompatibility, superhydrophobicity, electrical insulation, and thermal and chemical stability. In addition, their biodegradation products have recently reported to have therapeutic effect on certain cancer types. hBNs are easily synthesized from boron and nitrogen precursors at moderately low temperatures. However, crystallinity and yield vary depending on the type of precursor, reaction temperature, and duration. In this study, a simple one-step hBNs synthesis method is reported without a catalyst, which might be an undesired contaminant for biomedical applications. The influence of boron precursors (boric acid, colemanite, or boron trioxide) on hBNs crystallinity, stability, and biodegradation in suspensions containing oxidative and hydrolytic degradation agents is investigated with the aim of their possible application in biomedicine. We found that the choice of boron precursor is a critically important parameter controlling the hBNs crystallinity and dependently influencing the biodegradation rate.

Copper-mediated nucleophilic radiobromination of aryl boron precursors: Convenient preparation of a radiobrominated PARP-1 inhibitor

The copper-mediated nucleophilic radiobromination of aryl boron precursors with a radiobromide ion is a novel radiolabeling method that is efficient and robust. High radiochemical conversion (RCC) was observed using a variety of solvents, temperatures and catalysts. The reaction is also clean and is feasible for purification to obtain high chemical and radiochemical purity. This method provides a very useful route for the preparation of radiobrominated pharmaceuticals, including a radiobromine labeled PARP-1 inhibitor, and it is a valuable addition to the family of copper-mediated radiolabeling processes.

A novel functionally gradient Ti/TiB/TiC hybrid composite with wear resistant surface layer

Ti/TiB/TiC hybrid composite was processed by a novel one-step in-situ process using spark plasma sintering (SPS). KBF4, which was used as a boron precursor for the first time, reacted with Ti to form the TiB reinforcement insitu. Graphite foils were used on either side of the compact as a carbon source to produce TiC during sintering. Ti reacted with carbon and formed TiC on both the surfaces of the composite. The thickness of the TiC layer was found to be ∼50 μm. The microstructure of the composite was graded with ultrafine TiC on top, fine needles of TiB near the surface and coarser TiB whisker reinforced Ti (Ti-4Al-2Fe/TiBw) in the bulk. The grain size of Ti also varied from 1 μm near the surface to 12 μm in the bulk. The surface layer exhibited very high hardness to the tune of 20 GPa compared to 7 GPa of the bulk Ti-4Al-2Fe/TiB composite. The functionally gradient composite exhibited only mild wear with wear rate that was almost one order of magnitude lower than that of the bulk Ti-4Al-2Fe/TiBw composite. While there were abrasive grooves formed on the Ti-4Al-2Fe/TiB bulk composite, the hybrid composite showed almost nil wear damage under the same test conditions. The surface TiC layer thus acted as an effective protection against wear and tear.

Synthesis and characterization of Ni-B/Al2O3 nanocomposite coating by electrodeposition using trimethylamine borane as boron precursor

A novel Ni-B/Al2O3 nanocomposite coating was synthesized through electrodeposition by reinforcing Ni-B matrix with Al2O3 nanoparticles using trimethylamine borane as boron precursor. The effects of trimethylamine borane, Al2O3 nanoparticle, current density, thermal treatment on the properties of the electrodeposited coatings were examined. The morphology, microstructure, corrosion behavior and wear resistance of the Ni-B/Al2O3 coating in their as-deposited states were investigated by SEM, EDX, XRD and electrochemical techniques. It demonstrates that boron content has a beneficial effect on grain refinement and facilitates the formation of the amorphous phase. The hardness and wear resistance of Ni-B coating can be improved by the addition of Al2O3 particles due to the dispersion hardening of the hard Al2O3 particles. Both the boron and Al2O3 nanoparticle content in the deposited Ni-B/Al2O3 coating decreases as the current density increased from 1 to 7 A dm−2. The incorporation of Al2O3 nanoparticles alters the chemical composition, enhances the microhardness, improves the crystallinity of the Ni-B matrix. Owing to the grain refinement of Ni-B matrix, dispersion hardening of the added nanoparticles, as well as the reduction in the active surface area of Ni-B matrix by the presence of inert particles, Ni-B/Al2O3 nanocomposite coating with dense structure shows superior anti-corrosion and wear resistance than Ni/Al2O3 or Ni-B coating.

“Metal-free” electrocatalysis: Quaternary-doped graphene and the alkaline oxygen reduction reaction

We report the first investigation into a quaternary-doped graphene catalyst material for the oxygen reduction reaction (ORR) under alkaline conditions. The material was synthesized via direct pyrolysis of graphene oxide (GO) with boron, nitrogen, phosphorus and sulfur precursors. The resulting BNPS-Gr catalyst was thoroughly characterized and its composition found via XPS to be 6.4% (B), 6.1% (N), 2.6% (P) and 0.5% (S), while HR-TEM imaging shows a few-layered graphene structure. Electrochemical investigations into the catalytic activity towards the ORR show improved performance of the quaternary-doped graphene with the effective number of electrons transferred being ca. 3.7, compared to single-doped graphenes (2.9–3.2) and significantly lower peroxide production. This demonstrates BNPS-Gr to be a promising alternative to current Pt-group catalysts for the ORR, especially in methanol-fuelled fuel cells, where the presence of methanol in the cathode side from the fuel crossover is shown not to affect the performance of the quaternary-doped graphene catalyst.

Dual-doped graphene/perovskite bifunctional catalysts and the oxygen reduction reaction

We report the first investigation of dual-doped graphene/perovskite mixtures as catalysts for oxygen reduction. Pairwise combinations of boron, nitrogen, phosphorus and sulfur precursors were co-reduced with graphene oxide and mixed with La0.8Sr0.2MnO3 (LSM) to produce SN-Gr/LSM, PN-Gr/LSM and BN-Gr/LSM catalysts. In addition, the dual-doped graphenes, graphene, LSM, and commercial Pt/C were used as controls. The addition of LSM to the dual-doped graphenes significantly improved their catalytic performance, with optimised composition ratios enabling PN-Gr/LSM to achieve 85% of the current density of commercial Pt/C at −0.6V (vs. Ag/AgCl) at the same loading. The effective number of electrons increased to ca. 3.8, and kinetic analysis confirms the direct 4 electron pathway is favoured over the stepwise (2e+2e) route: the rate of peroxide production was also found to be lowered by the addition of LSM to less than 10%.

Solution-processed nanometers thick amorphous carbon-coated boron as an efficient precursor for high-field performance of MgB2

We report the fabrication of high-performance MgB2 bulk superconductors doped with amorphous carbon (aC), derived from PMMA polymer, a safe and cost effective carbon source as compared to explosive gaseous and expensive C-containing nanoadditives. The commonly used C-containing nanoadditives and boron (B) precursor nanopowders are usually prone to agglomeration in solid state mixing which causes poor reactivity and non-uniform distribution that leads to deterioration of critical current properties of MgB2. We have overcome this problem by achieving uniform 3–4 nm thin coating of aC on B nanopowders by pyrolysis of PMMA through solution process. Compared to undoped MgB2, significantly high current-carrying capability (Jc (5 K, 8 T) ∼3.1 × 104 A/cm2 and Jc (20 K, 6 T) > 103 A/cm2) was obtained for aC-doped MgB2, which is comparable to the record high in-field Jc reported for SiC-doped MgB2 and much better than those reported in literature with other C sources. Furthermore, significant improvement in Hirr and Hc2 were also observed for aC-doped MgB2. The improved high-field properties in PMMA-derived aC-doped MgB2 bulk suggest that the solution process could be a powerful technique to obtain uniform mixture of C-coated B to develop high-performance Mg(B1−xCx)2 wires for practical applications.

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.

Towards nanostructured boron nitride films

Boron nitride film could be developed for unique thermal management needs that require electrical insulation and also for applications that benefit from the other advantageous properties of boron nitride. In this work the two related major issues on the neat boron nitride films were identified, including the quality of the precursor boron nitride nanosheets (BNNs) and the dispersion of the BNNs relevant to the film fabrication. These issues were explored by examining various solvent systems and experimental conditions for the exfoliation of commercially acquired hexagonal boron nitride into BNNs and their ability to form relatively stable dispersions. The more stable dispersions were used for the fabrication of neat films of BNNs, and the results suggested that the films were too brittle to serve the film functions as those performed by their carbon-based counterparts. As an alternative approach, a small amount of graphene oxides (GOs) was used as binder for BNNs-GOs composite films of significantly improved mechanical characteristics. Thermal and electrical conductivities in these films were evaluated, so was the tuning of the conductivity ratios via thermal annealing of the as-fabricated films. The challenges and opportunities with the development of BNNs-derived neat boron nitride films are discussed, and their potential technological applications are highlighted.

Magnetic properties of hard magnetic nanoparticles of Nd2Fe14B synthesized using self-assembled block copolymers

Nd2Fe14B nanoparticles are widely used in bonded magnets for actuators in many types of electric equipment, motors in mobile phones and hard disk drives. Magnetic nanoparticles are also used in magnetic storage devices, drug delivery systems, and ferrofluids. Improvement of the magnetic properties of Nd2Fe14B rare-earth magnets would allow for production of small, lightweight, high-torque motors for use in energy-saving household appliances. However, because of the chemical instability of Nd2Fe14B nanoparticles, it is challenging to synthesize them with high purity by chemical synthesis or by conventional metallurgy methods using Nd2Fe14B alloys. In addition, the high reduction potential of Nd3+ makes reduction difficult. In this study, block copolymers were used as templates for chemical synthesis of Nd2Fe14B nanoparticles. In the synthesis, tris(acetylacetonato) iron(III) as an iron precursor, neodymium tris(acetylacetonate) hydrate as a neodymium precursor, and 1,1-bis(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)ferrocene as a boron precursor were introduced into a polystyrene-b-poly(2-vinylpyridine) block copolymer template. Then, the block copolymer was removed by oxidation. After reduction with CaH2 and washing with water to remove residual Ca species, highly pure Nd2Fe14B nanoparticles were obtained. Under the optimized experimental conditions, nanoparticles with a coercivity of 3.5 kOe and a saturation magnetization of 158 emu/g were obtained. The saturation magnetization was 93.5% of the theoretical value of Nd2Fe14B (169 emu/g).

C and O doped BN nanoflake and nanowire hybrid structures for tuneable photoluminescence

Abstract C and O doped BN nanoflakes and hybrid nanoflake-nanowire structures were synthesized in N2+H2 environment using plasma-enhanced hot filament chemical vapour deposition with solid B4C as boron and carbon precursor. Structure and chemical composition of the C and O doped BN nanoflakes and hybrid nanoflake-nanowire hybrid structures were systemically studied using advanced characterization instruments including high resolution transmission electron microscope, micro-Raman spectroscope, Fourier transform infrared spectroscope, X-ray diffractometer, field emission scanning electron microscope, and X-ray photoelectron spectroscope. The obtained results evidence that the C and O doped BN nanowires nucleate and grow directly on the tops of C and O doped BN nanoflakes due to the presence of dangling bonds on the surfaces of tips of C and O doped BN nanoflakes, which were formed by the ion bombardment in plasma. The photoluminescence (PL) properties of C and O doped BN nanoflakes and C and O doped BN nanoflake-nanowire hybrid structures were studied at room temperature using a micro-Raman system with the 325 nm line of He-Cd laser as the excitation source. The results of PL measurements indicate that the PL properties of C and O doped BN nanoflake-nanowire hybrid structures significantly change with the length of C and O doped BN nanostructures due to the interface zones caused by the nanowire length. Thus, the PL properties can be efficiently tuned by the length of nanowires. These achievements can contribute to the synthesis of novel BN-based hybrid nanostructures and the development of the next generation BN-based optoelectronic nanodevices.