Boron Precursor Research Articles

Rhombohedral and turbostratic boron nitride: X-ray diffraction and photoluminescence signatures

Boron nitride (BN) layers with sp2 bonding have been grown by metal organic chemical vapor deposition on AlN underlayers, which are deposited on c-plane sapphire substrates. Two different boron precursors were employed—trimethylboron and triethylboron—while ammonia was used as the nitrogen precursor. The BN obtained epitaxial BN films contain ordered rhombohedral (rBN) and partially ordered turbostratic (tBN) stackings as evidenced by x-ray diffraction analysis. We discriminatively identify the PL signatures of the rBN and tBN from those typical of the hexagonal (hBN) and Bernal stackings (bBN). The optical signature of tBN appears at 5.45 eV, and it intercalates between the two recombination bands typical of rBN at 5.35 eV (strong intensity) and 5.55 eV(weaker intensity). The analogs of the high intensity band at 5.35 eV in rBN sit at 5.47 eV for hBN and at 5.54 eV for bBN.

Tailoring a multifunctional, boron and fluoride-enriched solid-electrolyte interphase precursor towards high-rate and stable-cycling silicon anodes

Rational design and construction of stable artificial interface for silicon (Si) anodes exhibits great promise in shielding the Si particles against their intrinsic volumetric changes and minimizing the side reactions, both constituting prerequisites towards the long-term stability of the high-energy density Si-based batteries. Herein, a multifunctional solid-electrolyte interphase (SEI) precursor of 4-trifluoromethylphenylboronic acid (TFPBA) nano-layer is tailored, which readily polymerizes to form 2,4,6-tris-4-(trifluoromethylphenyl)boroxine (TTFPB) on Si surface during high-temperature drying process of the electrodes. After one-electron reduction, the BO bonds in TTFPB molecule break where the radical molecules are thus generated, initiating the spontaneous polymerization to form the poly-4-trifluoromethylphenylboronic acid (PTFPBA) with repeated B–O chains. Such polymerized nano-layer not only manifests a desirable artificial SEI for its high robustness and elasticity in accommodating the volume expansions, but also effectively improves the electrolyte absorption rate of the electrode, providing accelerated kinetics for Li+ transfer. Under the stable framework formed by PTFPBA, preferential adsorption of LiPF6 molecules is enabled with the electron-deficient boron (B) species, further inducing a continuous and dense SEI rich in benzene rings and inorganic substances. As such, the as-obtained Si@TTFPB anode demonstrates significantly enhanced rate capability and long-cycle performance. After 500 cycles at 0.2 C rate, the modified Si electrode still delivers a capacity of 1778.7 mA h g−1, while the reference Si anode has almost no capacity.

Sol-gel synthesis of borate-based 13-93B3 bioactive glass powders for biomedical applications

ABSTRACT In this study, borate-based 13–93B3 bioactive glass powders were synthesised through a sol-gel method using tributyl borate as the boron precursor. Any gel formation was not observed in the glass sol during processing and upon the solvent evaporation, a gel-like layer was obtained. Calcinations were performed between 450 °C and 625 °C in air atmosphere to decompose the nitrates leading to the formation of metal oxides in the glass network. Results showed that use of high calcination temperatures to remove the nitrates from precursor materials caused the formation of partially crystalline structures. In vitro mineralisation experiments revealed that synthesised powders calcined at 550 °C converted to hydroxyapatite phase after immersion in simulated body fluid for 1 day. It was concluded that sol-gel- derived 13–93B3 glass powders have enhanced bioactivity and can be an alternative to conventional melt-derived borate-based bioactive glasses synthesised at much higher temperatures.

Boron-doped carbon nanospheres for efficient and stable electrochemical nitrogen reduction

Electrochemical reduction of dinitrogen (N2) to ammonia (NH3) at the ambient condition is a promising alternative to the traditional Haber-Bosch process due its energy-saving and eco-friendly natures. However, the extremely stable NN triple-bonds in N2 molecules and the competitive hydrogen evolution reaction (HER) have been regarded as the two essential issues in the electrocatalytic nitrogen reduction reaction (eNRR), making the simultaneous achievement of a high NH3 yield rate and a satisfactory Faradaic efficiency (FE) very difficult. To address this issue, we herein report a metal-free electrocatalyst, the boron-doped carbon nanosphere, to effectively activate the NN triple-bonds and suppress the HER during the eNRR process. In this protocol, the B–C configurations can be easily tailored by simply changing the boron precursor amount, and the one that is (i.e., BC3) beneficial to the enhancement of eNRR can achieve the maximum relative content of ∼43% in the optimum sample. Under this boron-doping amount, the material simultaneously delivers a high NH3 yield of 33.8 μg h−1 mg−1cat and a high FE of 39.2% at −0.7 V vs. reversible hydrogen electrode, accompanied with a superior stability for a continuous eNRR. This study thus offers an efficient, stable, and low-cost carbon-based catalyst for eNRR.

Synthesis of Highly Functionalizable Symmetrically and Unsymmetrically Substituted Triarylboranes from Bench-Stable Boron Precursors.

A novel and convenient methodology for the one‐pot synthesis of sterically congested triarylboranes by using bench‐stable aryltrifluoroborates as the boron source is reported. This procedure gives systematic access to symmetrically and unsymmetrically substituted triarylboranes of the types BAr2Ar’ and BArAr'Ar’’, respectively. Three unsymmetrically substituted triarylboranes as well as their iridium‐catalyzed C−H borylation products are reported. These borylated triarylboranes contain one to three positions that can subsequently be orthogonally functionalized in follow‐up reactions, such as Suzuki‐Miyaura cross‐couplings or Sonogashira couplings.

Cerium tetraboride synthesized by a molten salt method and its Congo red adsorption performance

Widely used synthetic dyes are one of the main pollutants that contaminate water environments seriously. From the environmental perspective, efficient adsorption of these wastes such as Congo red (CR) is of great importance, and numbers of adsorbents including inorganic materials have been developed. Herein, a lanthanide tetraboride nanocrystal powder CeB4 with an average particle size of 50 nm synthesized for the first time via inorganic molten salt synthesis route using cerium fluoride (CeF3) and sodium borohydride (NaBH4) as the cerium and boron precursors in argon atmosphere exhibits good performance for the adsorption of CR. Essential effluence factors, such as initial pH value, contacting time, and initial concentration, were experimentally evaluated. The adsorption was pH dependent, and the kinetic data follow the pseudo–second–order kinetic model. It was also found that the equilibrium adsorption data could be represented by Langmuir and Freundlich isotherm models, with a maximum capacity of 491.8 mg/g. On the basis of the adsorption–desorption experiments, CeB4 exhibits good reusability.

A new class of high-entropy M3B4 borides

A new class of high-entropy M3B4 borides of the Ta3B4-prototyped orthorhombic structure has been synthesized in the bulk form for the first time. Specimens with compositions of (V0.2Cr0.2Nb0.2Mo0.2Ta0.2)3B4 and (V0.2Cr0.2Nb0.2Ta0.2W0.2)3B4 were fabricated via reactive spark plasma sintering of high-energy-ball-milled elemental boron and metal precursors. The sintered specimens were ∼98.7% in relative densities with virtually no oxide contamination, albeit the presence of minor (4–5 vol%) secondary high-entropy M5B6 phases. Despite that Mo3B4 or W3B4 are not stable phase, 20% of Mo3B4 and W3B4 can be stabilized into the high-entropy M3B4 borides. Vickers hardness was measured to be 18.6 and 19.8 GPa at a standard load of 9.8 N. This work has further expanded the family of different structures of high-entropy ceramics reported to date.

Boron regulated dual emission in B, N doped graphene quantum dots

Abstract Graphene quantum dots are promising candidates for LED and solar cell studies with their low toxicity, inexpensive production cost and high luminescence capacity. However, controlling optical properties of graphene quantum dots is a challenge, which can be partially done by heteroatom doping. In this study, we synthesized dual emissive boron and nitrogen doped graphene quantum dots through a bottom-up synthesis method. Dual emission properties of boron and nitrogen doped quantum dots appeared in the presence of high amount of boron precursor in synthesis medium. Dual emissive features of quantum dots were controlled via controlling amount of boron content in quantum dot structure. Boron and nitrogen doped graphene quantum dots showed dual emissive properties at different excitation wavelengths, therefore they were suitable for applications concerning white – LED and solar cells. With their low toxicity, low production cost and controllable dual emission properties, dual emissive boron and nitrogen doped graphene quantum dots can be considered as a powerful alternative to cadmium and indium based quantum dots.

Hybrid Physical Chemical Vapour Deposition (HPCVD) of Superconducting MgB2 Thin Films on three Dimensional Copper Substrates

The present work reports the design, development and application of a novel Hybrid Physical Chemical Vapour Deposition (HPCVD) technique for depositing MgB2 thin films, with potential superconductivity, directly on three dimensional (3D) surfaces. A novel solenoid magnetron based set up was used for depositing MgB2 thin films on 3D surfaces of Cu tube. Mg rod was used as the sputter target and source of Mg while high purity BBr3 was used as a novel boron precursor, which was injected into the system using Argon as carrier gas. The plasma mediated decomposition of BBr3 in presence of H2 gas was followed by chemical reaction between Mg and B atoms to deposit MgB2 film on the substrate. Samples were characterized by SEM, EDX, XRD and SQUID techniques. SEM-EDX confirmed deposition of a homogeneous, pore free and dense MgB2 film, while XRD analysis revealed the film to be polycrystalline and multiphasic rather than being purely c-axis oriented. Superconductivity analysis carried out using SQUID measurements indicated a sharp transition with Tc value of 39 K. From the M-H hysteresis loop, the lower critical field Hc1 and critical current density Jc at 4.2 K were calculated to be 700 Oe and 3.5 x 10 7 A/cm 2 , respectively.

Synthesis in Molten Salts and Characterization of Li6B18(Li2O)x Nanoparticles.

Lithium borides have been synthesized exclusively through classical solid-state chemistry processes that lead to bulk materials. Indeed, due to the lack of reactivity of the solid boron precursors usually employed and to the high covalent connectivity in such solids, high temperatures and long reaction times are necessary to obtain lithium borides. These conditions result in extensive crystal growth. Here we present the synthesis of nanoparticles of a lithium boride bearing tunnel-like cavities templated by neutral Li2O species, which have been reported to be labile. To reach this goal, a liquid-phase synthesis in inorganic molten salts has been developed. The Li6B18(Li2O)x nanoparticles have been characterized by scanning and transmission electronic microscopy (SEM and TEM), X-ray diffraction (XRD), and Raman spectroscopy. We provide an in-depth structural characterization by using 1H, 7Li, and 11B solid-state nuclear magnetic resonance (NMR) coupled with DFT modeling to provide the first assignment of 7Li and 11B solid-state NMR signals in lithium borides. We then assess the nanoparticle morphology oriented along the direction of the cavities. This feature shows similarities with structurally related hexagonal tungsten bronzes and could therefore affect the electrochemical and ion exchange properties.

Size reduction of boron particles by high-power ultrasound for optimization of bulk MgB2

Critical current density, J c, in superconductors is strongly connected with size of defects in the material. Frequently, the smaller defects, the higher J c. In this work, we tried to reduce the size of cheap commercial boron precursor powder using high energy ultra-sonication in ethanol media. The resulting powder was then utilized in synthesizing bulk MgB2 via sintering at 775 °C. Effect of boron powder ultra-sonication on superconducting properties of the bulk MgB2 was studied and discussed. SEM of ultra-sonicated boron showed fine particles with sharp edges (high-energy surfaces), irregular shapes and clustering of fine particles occurred for longer ultra-sonication durations. XRD proved a high quality of MgB2 with only small traces of MgO. Around 36% improvement in Jc at 20 K and Tc close to 39 K were observed in MgB2 bulk prepared with boron ultra-sonicated for 15 min. Microstructure studies showed numerous nanometre sized MgB2 grains in the bulk. Other bulks (made of boron ultra-sonicated longer, for 30, 45, and 60 min) have larger grains. It resulted in slightly lower J c, anyway, still by 22% higher than in reference bulk. The present results demonstrate that the high performance bulk MgB2 can be achieved without reduction in T c via employing a cheap boron, reduced in size by high-energy ultra-sonication.

Method for the production of pure and C-doped nanoboron powders tailored for superconductive applications

The present paper describes the improvement of the performances of boron powder obtained applying the freeze-drying process (FDP) for the nanostructuration and doping of B2O3, which is here used as boron precursor. After the nanostructuration process, B2O3 is reduced to elemental nanoboron (nB) through magnesiothermic reaction with Mg. For this work, the usefulness of the process was tested focusing on the carbon-doping (C-doping), using Cblack, inulin and haemoglobin as C sources. The choice of these molecules, their concentration, size and shape, aims at producing improvements in the final compound of boron: in this case the superconductive magnesium diboride, which has been prepared and characterized both as powder and wire. The characteristics of B2O3, B and MgB2 powder, as well as MgB2 wire were tested and compared with that obtained using the best commercial precursors: H. C. Starck micrometric boron and Pavezyum nanometric boron. Both the FDP and the magnesiothermic reaction were carried out with simplicity and a great variety of doping sources, i.e. elements or compounds, which can be organic or inorganic and soluble or insoluble. The FDP allows to produce nB suitable for numerous applications. This process is also very competitive in terms of scalability and production costs if compared to the via gas technique adopted by nanoboron producers currently available on the world market.

Sol‐gel assisted synthesis of TiB2‐B4C composite powder

AbstractComposite powders containing titanium diboride and boron carbide have been prepared by sol‐gel method at 1450°C using titanium isopropoxide (titanium precursor), boric acid (Boron precursor), sucrose (carbon source), and acetic acid (AcOH) as a solvent. The effect of boron source (trimethyl borate and boric acid) and B2O3/TiO2, C/B2O3 mole ratios of starting materials on the final phases has been studied. The progress of reactions was determined using thermal analysis (TGA‐DTA). The resultant powders were characterized by X‐ray diffraction (XRD) analysis and field‐emission scanning electron microscope (FESEM). XRD patterns confirmed the formation of TiB2, B4C, and TiC phases after heat treatment at 1450°C at mole ratio of B2O3/TiO2 = 4.5, C/B2O3 = 2.4. With increasing the content of boron oxide, the unwanted phases such as TiC and C were reduced. TiB2 and B4C composite powders (~5 µm diameter) containing residual carbon (<4 wt%) were synthesized using the mole ratio of B2O3/TiO2 = 10 and C/B2O3 = 1.9 at low temperature of 1450°C.

Synthesis of cobalt boride nanoparticles and h-BN nanocage encapsulation by thermal plasma

Synthesis of cobalt boride nanoparticles and h-BN nanocage encapsulation were conducted using a triple direct current (DC) thermal plasma jet system. Mixed cobalt and boron powder were used as the starting material. The thermal plasma jet was generated using mixed Ar–N2 and Ar–H2 gases. The nanostructure of the synthesized nanoparticles varied according to the gas composition. In the Ar–N2 plasma, the dissociated nitrogen anticipated a chemical reaction with the boron precursor and synthesized h-BN nanocages that encapsulated cobalt boride nanoparticles, additionally, c-BN nanoparticles were synthesized. In the Ar–H2 plasma, only <20 nm spherical cobalt boride nanoparticles were synthesized and their size distribution was controlled by the growth time or quenching rate, which was controlled by changing the flow rate of plasma forming gasses. These synthetic processes were comparatively investigated thermodynamically.

Characterization of Freeze-Dried Boron Nanopowders and Parameter Optimization in Ex Situ MgB2 Wire Production

This article reports a study to identify optimal synthesis parameters for a pure boron precursor prepared following a patented process developed at CNR-SPIN laboratories, performed in the framework of a collaboration between CNR-SPIN and CERN. Boron is a precursor that plays a crucial role in the MgB2 wire manufacturing, as a consequence, the synthesis parameters of the superconducting phase have been investigated. In this article, we report results for MgB2 samples synthesized at 870 °C for 17nbsp;h under Ar/5% H2 flow and 760 °C for 0.2 h. Magnesiothermic amorphous nanoboron (MANB) and commercial boron nanopowders (purchased from Pavezyum) have been compared in terms of morphological features. MgB2 derived from both sources has been characterized and the superconductive properties in the wire form have been compared. Results demonstrate that the MANB performance is comparable with the nanoboron obtained via gas synthesis.

Comparative Study of Boron Precursors for Chemical Vapor‐Phase Deposition‐Grown Hexagonal Boron Nitride Thin Films

Two different boron precursors, diborane (B2H6) and trimethyl boron ((CH3)3B, TMB), are investigated for chemical vapor‐phase deposition (CVD)‐grown hexagonal boron nitride (h‐BN) on α‐Al2O3 (0001) substrates. The BN layer grown using TMB includes a large amount (2 × 1020 cm−3) of carbon atoms, which is 60 times higher than that in the BN layer grown using B2H6. The X‐ray diffraction 2θ/ω scans for BN film grown using B2H6 exhibit the h‐BN (002) peak. The BN film obtained using TMB includes turbostratic BN (t‐BN). The E2g Raman peak frequencies in B2H6 and TMB h‐BN are observed at 1368.8 and 1369.7 cm−1, respectively. The Raman peak shift to a higher frequency indicates that a larger compressive strain is induced using TMB than using B2H6. The full width at half maximum of the B2H6 and TMB Raman peak frequencies is 21.8 and 42.7 cm−1, respectively. The cathodoluminescence spectra of B2H6 h‐BN show the band‐edge emissions at 225 and 232 nm, whereas only a 300 nm broadband is obtained in TMB h‐BN. It is suggested that the carbon atoms in TMB prevent the formation of highly crystalline h‐BN thin films.

Incorporation of Boron in Mesoporous Bioactive Glass Nanoparticles Reduces Inflammatory Response and Delays Osteogenic Differentiation

AbstractMesoporous bioactive glass nanoparticles (MBG) are multifunctional building blocks for tissue regeneration and nanomedicine applications. Incorporation of biologically active ions can endow MBG with additional functionalities toward promoted therapeutic effects. Here, boron is incorporated into MBG by using a sol–gel approach. The concentration of boron incorporated is controllable by tuning the amount of boron precursor. Two types of boron‐doped MBG, namely 10B‐ and 15B‐MBG (5.8 and 6.5 mol% of B2O3, respectively) are synthesized. Boron incorporation does not significantly influence the particle morphology. All synthesized particles exhibit a sphere‐like shape with a size ranging from 100 to 300 nm. 10B‐ and 15B‐MBG show large specific surface area (346 and 320 m² g−1, respectively) and pore volume. Both boron‐doped MBG exhibit remarkable in vitro bioactivity and noncytotoxicity. Boron incorporation is shown to reduce the inflammatory response linked to macrophages as indicated by downregulated expression of pro‐inflammatory genes. However, boron incorporation delays the osteogenic differentiation in osteoblasts as indicated by the downregulated expression of pro‐osteogenic genes. The results demonstrate the promising potential of using boron‐doped MBG to modulate inflammatory response for bone regeneration under inflammatory conditions, as shown in this study for the first time.

Electrodeposited TiB2 Coating on Graphite As Wettable Cathode for Al Production

Greenhouse gas (GHG) emission from the Canadian aluminum industry was about 6 Mt of CO2 eq in 2017, an amount equivalent to the GHG emitted by about 1.3 million cars [1-2]. The use of inert anodes, like Ni-Fe-Cu alloys [3], instead of carbon anodes to produce O2 rather than CO2 during aluminum electrolysis is paramount to curb GHG emissions from that industry. However, to maintain the energy efficiency of the process, the opposite cathode material must be wetted by molten aluminum to decrease the anode-to-cathode distance and thus reduce the overall cell voltage. TiB2 presents a good wettability by molten Al. Also, it has good electrical conductivity and good chemical stability under Al electrolysis. Accordingly, TiB2 is considered as an interesting cathode material to use in conjunction with inert anodes. However, its production as dense bulk cathode is challenging.In this work, the electrodeposition of TiB2 on graphite substrate was performed by periodically interrupted current method in a molten LiF-NaF-KF salt at 600°C containing K2TiF6 and KBF4 as titanium and boron precursors, respectively [4]. The impact of the electrodeposition parameters on the crystalline structure, morphology, adhesion strength, Al wettability and Al penetration resistance of the TiB2 deposits will be presented.[1] 2017 sustainable development report. Aluminium Association of Canada.[2] Greenhouse Gas Emissions from a Typical Passenger Vehicle. United States Environnemental Protection Agency, 2018[3] S. Helle, M. Pedron, B. Assouli, B. Davis, D. Guay, L. Roué, Structure and high-temperature oxidation behaviour of Cu–Ni–Fe alloys prepared by high-energy ball milling for application as inert anodes in aluminium electrolysis. Corros. Sci. 52 (2010) 3348.[4] G. Ett, E.J. Pessine, Electrochim. Acta. 44 (1999) 2859. Figure 1: (A) SEM cross-section image of electrodeposited TiB2 coating on graphite substrate. Optical images of Al droplet at 1000 °C on (B) TiB2-coated and (C) pure graphite substrates.Fig Figure 1

Synthesis of boron and nitrogen co-doped carbon nanotubes and their application in hydrogen storage

Boron and nitrogen codoped carbon nanotubes (B,N-CNTs) were synthesized by floating catalyst chemical vapor deposition (FCCVD) using ethanol, ferrocene, boric acid and imidazole as carbon source, catalyst, boron and nitrogen precursors, respectively. The samples were analyzed using transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis and X-ray photoemission spectroscopy. 1.5 at% B and 1.34 at% N could be doped in the resultant structure, which has higher length (few μm) with higher thermal stability (621 °C). At pressure 16 bar, hydrogen adsorption for B,N-CNTs was found to be 1.96 and 0.35 wt% at 77 K and 303 K, respectively. Hydrogen storage as function of time was also reported for both the cases. The adsorption process follow pseudo second order kinetics. The present study reveals that the codoping of CNTs aid in tuning properties of CNTs for hydrogen storage application.

Microwave assisted synthesis of boron and nitrogen rich graphitic quantum dots to enhance fluorescence of photosynthetic pigments

Energy transfer between quantum dots and biomolecules is of interest due to high absorption capacity and high quantum efficiency of quantum dots. Amongst all types of quantum dots, graphene and graphitic quantum dots have great potential for energy transfer studies due to their high biocompatibility and low toxicity. In this study, a simple route to synthesize boron and nitrogen rich graphitic quantum dots (C-BN) and boron carbon nitride (BCN) quantum dots is demonstrated. Quantum dots were synthesized in a domestic microwave oven. Composition of quantum dots was controlled by tuning initial mole ratio of boron and nitrogen precursors. As molar ratio of boron precursor was increased, formation of C-BN quantum dots was favoured. C-BN quantum dots were mainly composed of boron and nitrogen (with around 10 % carbon) in their main composition, and sized around 2 nm with bright photoluminescence. To the best of our knowledge, this is the first study which proposes a bottom-up synthesis method to synthesize C-BN quantum dots based on domestic microwaves. Also, treating photosynthetic pigments with quantum dots resulted in 20 % enhancement of fluorescence of photosynthetic pigments at 670 nm, which demonstrates that C-BN and BCN quantum dots can be important constituents of artificial antenna systems for photosynthetic organisms.