Boron Incorporation Research Articles

The B/Ca and Cd/Ca of a subsurface-dwelling foraminifera Pulleniatina obliquiloculata in the tropical Indo-Pacific Ocean: implications for the subsurface carbonate chemistry estimation

Pulleniatina obliquiloculata shells from 16 core-top samples from the tropical Indo-Pacific Oceans are analyzed for the ratios of boron and cadmium to calcium (B/Ca and Cd/Ca). The B/Ca ratios show a very weak positive relationship with [B(OH)4-] and the dissolved carbonate species at the apparent calcification depth of P. obliquiloculata. The boron partition coefficients (KD) between P. obliquiloculata B/Ca and seawater [B(OH)4-]/[HCO3-] distribute around 1.1×10-3–1.3×10-3 with a mean value of (1.19±0.12)×10-3, and are significantly related to the nutrient concentration, especially phosphate. The lack of any clear correlation between the P. obliquiloculata B/Ca and seawater carbonate chemical parameters suggests that the physiochemical controls on boron incorporation are masked by the complexity of natural seawater condition. But the significant dependence of KD on nutrient may likely be explained by a nutrient related growth-rate effect. Cd/Ca of P. obliquiloculata shows significant correlation with seawater phosphate concentration, and its partition coefficients (DCd) are significantly related to temperature. A first-principle methodology of P. obliquiloculata B/Ca is applied, with the aid of Cd/Ca as a phosphate proxy and a constraint on KD, to estimating sea water carbonate chemistry (e.g., pH). The results are fairly promising and allow us to propose the possibility to apply the combination of B/Ca and Cd/Ca proxies (and also Mg/Ca and δ18O for estimating temperature and salinity) for the paleoreconstruction of seawater carbonate chemistry.

Tuning the electronic band alignment properties of TiO2 nanotubes by boron doping

The present study highlights the significant impact of trace level doping of boron in titanium dioxide (TiO2) nanotubes by investigating the structural, optical and electronic properties of samples, TNT and B-TNT. TEM analysis of boron-doped sample confirms the formation of crystalline nanotube structures and the trace level quantification of boron was confirmed by XPS analysis, where B shows feature of Ti–O–B bonding. Raman analysis revealed that the rutile phase becomes prominent after boron doping and Raman bands shift towards higher wavenumber was observed with increase in the tube diameter. The boron incorporation in TiO2 nanotubes reduces the band gaps from 3.3 eV to 3.1 eV and the mid-gap states were created within the band gap of the B-TNT sample. The change in valance band position from 2.5 eV to 2.9 eV after boron doping significantly changed the Fermi level position in TiO2 nanotubes. The work function of pristine and boron doped TiO2 samples are observed as 4.23 eV and 4.27 eV, respectively, as measured by Kelvin probe force microscopy. Here, we have investigated the band alignment of TNT and B-TNT by using state-of-the-art material characterization surface sensitive techniques. It can also be concluded that the electron affinity of the B-TNT sample is enhanced ∼4.07 eV than that of TNT ∼ 3.43 eV. The type –II band alignment is observed to be in between TNT and B-TNT with a valence band offset (VBO) ∼ 0.4 eV and conduction band offset (CBO) ∼ 0.6 eV.

Analyzing Boron in 9-12% Chromium Steels Using Atom Probe Tomography.

Small additions of boron can remarkably improve the long-term creep resistance of 9-12% Cr steels. The improvement has been attributed to boron segregation to grain boundaries during quenching, and subsequent boron incorporation into certain families of precipitates during tempering. However, the detailed mechanisms are not yet fully understood. Atom probe tomography (APT) is an excellent technique for gaining insights into boron distribution, however, in order to acquire accurate analysis of boron in 9-12% Cr steels using APT, there are several key challenges. In order to better understand and address these challenges, we developed a novel method for site-specific APT specimen preparation, which enables convenient preparation of specimens containing specifically selected grain boundaries positioned approximately perpendicular to the axis of the APT tip. Additionally, when analyzing boron at boundaries and in carbides (as diluted solute) and borides, a widening of the profile of boron distribution compared to other elements was repeatedly observed. This phenomenon is particularly analyzed and discussed in light of the evaporation field of different elements. Finally, the possible effects of detector dead-time on quantitative analysis of boron in metal borides are discussed. A simple method using 10B correction was used to obtain good quantification.

Misorientation Angle Dependence of Boron Incorporation Into CVD Diamond Delta Layers

The results of investigations of boron incorporation into the delta layers of diamond, depending on the misorientation angle of the substrate surface relative to the crystallographic plane (001) are presented. Experiments are carried out on specially prepared substrates having several sectors with different miscut angles. The use of such substrates allowed to obtain data on the influence of the miscut angle in single growth process. The influence of the in‐plane orientation of miscut on the boron concentration in the delta layer and on the growth rate is also studied. When studying the incorporation of boron into delta layers, special attention is paid to the investigation of the surface of grown structures. It is found that the use of substrates with small miscut angles leads to formation of pyramidal hillock defects on the surface.

Bioactivity and dissolution behavior of boron-containing bioactive glasses under static and dynamic conditions in different media

Abstract The present study reports the dissolution studies of a family of boron-doped bioactive glasses based on the composition ICIE16. Simulated body fluid (SBF), Tris-buffered solution and lactic acid were used as dissolution media for studies under static and dynamic conditions. The leaching of ions from the glasses under the evaluated conditions and media was compared and the bioactive behaviour of the glasses was evaluated. Influence of the incorporation of boron in the thermal properties of the glass was also analysed. Glasses exhibited faster bioactivity under dynamic dissolution configuration compared to static conditions. Moreover, the glass dissolution rate was faster in acidic conditions than in SBF or Tris solutions. It was found that at increasing boron content the dissolution of the glass is faster.

Thin-felt hollow-B-ZSM-5/SS-fiber catalyst for methanol-to-propylene: Toward remarkable stability improvement from mesoporosity-dependent diffusion enhancement

A hollow-B-ZSM-5/SS-fiber catalyst is developed through alkali leaching of the full-silica core of the silicalite-1@B-ZSM-5 in situ structured onto a thin-felt stainless-steel fiber (20 μm SS-fiber), which is synthesized by a seed-assisted dry-gel vapor-phase transport method. As-obtained catalyst shows marked improvement in the mesoporosity-dependent diffusion (by o-xylene diffusion measurement). Boron incorporation is essential for preventing the framework dealumination during alkali leaching treatment due to the increased framework negative charges. The hollow-B-ZSM-5/SS-fiber catalyst shows remarkable stability improvement in the methanol-to-propylene (MTP) reaction because of the enhanced diffusion of the nano-hollow-structure and the boron-incorporation stabilized framework aluminum. A boron-free hollow-ZSM-5/SS-fiber is also obtainable with the textural properties comparable to the hollow-B-ZSM-5/SS-fiber but shows undesired degeneration of the tetra-coordinated aluminum. The preferential generation of coke in the micropores of the hollow-ZSM-5/SS-fiber causes a rapid deactivation even compared to the parent silicalite-1@ZSM-5/SS-fiber, due to the existence of extra-framework aluminum.

Influence of Boron Antisite Defects on the Electrical Properties of MBE‐Grown GaAs Nanowires

Nanowires provide a platform for the integration of heterogeneous materials in III–V systems grown on Si. BxGa1−xAs is an interesting material for strain applications, which has not yet been studied in nanowire form. The incorporation of boron in GaAs nanowires is investigated via DC‐IV measurements. In transmission electron microscopy analysis a high concentration of boron is found at the nanowire edges, indicating surface segregation during growth. Nanowires grown under boron flux are found to exhibit Ohmic contacts and low contact resistances with p‐type metallizations such as Au/Zn/Au or Cr/Au. Back‐gated measurements confirmed the p‐type behavior of such nanowires, indicating that boron is incorporated on antisite defects where it acts as a doubly‐charged acceptor. This offers a new route for the inclusion of p‐doped layers in GaAs‐based nanowire heterostructures and the subsequent formation of Ohmic contacts.

Suppression of axial growth by boron incorporation in GaAs nanowires grown by self-catalyzed molecular beam epitaxy

The addition of boron to GaAs nanowires grown by self-catalyzed molecular beam epitaxy was found to have a strong effect on the nanowire morphology, with axial growth greatly reduced as the nominal boron concentration was increased. Transmission electron microscopy measurements show that the Ga catalyst droplet was unintentionally consumed during growth. Concurrent radial growth, a rough surface morphology and tapering of nanowires grown under boron flux suggest that this droplet consumption is due to reduced Ga adatom diffusion on the nanowire sidewalls in the presence of boron. Modelling of the nanowire growth puts the diffusion length of Ga adatoms under boron flux at around 700–1000 nm. Analyses of the nanowire surfaces show regions of high boron concentration, indicating the surfactant nature of boron in GaAs.

Cyanide degradation in aqueous solution by heterogeneous photocatalysis using boron-doped zinc oxide

The photocatalytic activity of boron-doped ZnO with varying concentration (1, 1.5 and 2% wt of B) synthesized by sol-gel method was evaluated on cyanide (CN−) degradation in aqueous solution under simulated solar radiation. The obtained catalysts were characterized by XRD, UV–vis/DRS, ICP-OES, FT-IR, and XPS. The photocatalytic experiments were carried out in a quartz batch reactor using 300 mL of cyanide solution adjusted at pH 11, evaluating different parameters such as the amount of B dopant, catalyst loading and initial concentration of cyanide solution. A 23 central composite faced design was used to maximize CN− photocatalytic degradation. The cyanide concentration was measured by ISE potentiometric method and the content of intermediate ions (OCN−, NO3−, and NH4+) was determined by UV–vis spectrophotometry. The boron incorporation into ZnO lattice (ZnO-B) reduced wurtzite crystallite size (25 nm) and narrowed the band gap (3.0 eV) compared to bare ZnO (43 nm and 3.2 eV, respectively). The ZnO-B 1.5 wt% showed better photocatalytic performance by degrading 89% of a 10 mg L-1 CN− solution compared to 75% that was reached by undoped ZnO; using in both cases 1.4 g L-1 of catalyst loading at accumulated energy of 400 kJ m-2.

Microwave-Assisted Hydrothermal Synthesis of CHA Zeolite for Methanol-to-Olefins Reaction

A cost-effective aluminum CHA zeolite was synthesized by seed-assisted hydrothermal synthesis under microwave radiation to shorten the crystallization time to 6 h. The CHA was synthesized under different stirring rates and evaluated in methanol-to-olefins reaction at three different temperatures by using a fixed-bed reactor. Boron was incorporated by in situ synthesis also under microwave radiation. The X-ray diffraction pattern revealed that the synthesized CHA was crystalline and in well agreement with the reference CHA. The reaction evaluation revealed that the reaction temperature affected both the catalyst stability and selectivity to light olefins. At a lower temperature, the synthesized CHA was more stable and less selective to olefins, while at a higher temperature, the catalyst was less stable and more selective to olefins. The incorporation of boron only enhanced the selectivity to ethylene and propylene at the start of the reaction.

Approach for Polishing Diamond Coated Complicated Cutting Tool: Abrasive Flow Machining (AFM)

Lower surface roughness and sharper cutting edge are beneficial for improving the machining quality of the cutting tool, while coatings often deteriorate them. Focusing on the diamond coated WC-Co milling cutter, the abrasive flow machining (AFM) is selected for reducing the surface roughness and sharpening the cutting edge. Comparative cutting tests are conducted on different types of coated cutters before and after AFM, as well as uncoated WC-Co one, demonstrating that the boron-doped microcrystalline and undoped fine-grained composite diamond coated cutter after the AFM (AFM-BDM-UFGCD) is a good choice for the finish milling of the 6063 Al alloy in the present case, because it shows favorable machining quality close to the uncoated one, but much prolonged tool lifetime. Besides, compared with the micro-sized diamond films, it is much more convenient and efficient to finish the BDM-UFGCD coated cutter covered by nano-sized diamond grains, and resharpen its cutting edge by the AFM, owing to the lower initial surface roughness and hardness. Moreover, the boron incorporation and micro-sized grains in the underlying layer can enhance the film-substrate adhesion, avoid the rapid film removal in the machining process, and thus maximize the tool life (1040 m, four times more than the uncoated one). In general, the AFM is firstly proposed and discussed for post-processing the diamond coated complicated cutting tools, which is proved to be feasible for improving the cutting performance

Improved osteogenesis of boron incorporated calcium silicate coatings via immunomodulatory effects.

Osteoimmunology has revealed the importance of a favorable immune response for successful biomaterial-mediated osteogenesis. Boron-incorporated calcium silicate (Ca11 Si4 B2 O22 , B-CS) coating has been reported as a potential candidate for improving osteogenesis in orthopedic applications in vitro. However, relatively little is known about its effects on the immune response and subsequent osteogenesis. In this work, the immunomodulatory properties of the B-CS coating and its specific mechanism of action were explored. We found that the B-CS coating decreased M1 polarization and converted macrophages to the M2 phenotype via restraining the toll-like receptor signaling pathway, thus inducing a significant reduction in pro-inflammatory cytokines and an increase in anti-inflammatory cytokines. Moreover, the B-CS coating inhibited osteoclastogenesis and osteoclastic activities by downregulating osteoclastogenic genes and inhibiting the RANKL/RANK system. BMP2 and VEGF were also significantly upregulated by macrophages and bone mesenchymal stem cells, leading to activation of the BMP2 signaling pathway and subsequent upregulation of osteogenesis-associated genes, finally promoting osteogenic differentiation. These findings show that the B-CS coating could be a promising coating material for hip and knee implants. Furthermore, incorporation of the element boron into bioceramic coatings could be a good strategy in the design of bone biomaterials with beneficial immune responses. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 107A: 12-24, 2019.

Boric acid and borate incorporation in inorganic calcite inferred from B/Ca, boron isotopes and surface kinetic modeling

The boron concentration (B/Ca ratio) and isotopic composition (δ11B) of biogenic calcite are widely applied to reconstruct past changes in seawater carbonate chemistry. Knowledge of B incorporation pathways into calcite is critical for these applications and for improving the theoretical basis of B proxies. While the canonical interpretation of δ11B holds that B in calcite predominantly derives from dissolved borate anion in seawater, recent studies of the B content, coordination, and isotopic composition in calcite suggest more complex B incorporation pathways. To provide new insights into these pathways, here we present δ11B of inorganic calcite precipitated from saline solutions of varying pH, calcium and dissolved inorganic carbon (DIC) concentration for which B/Ca data were previously reported by Uchikawa et al. (2015). Results show that calcite δ11B significantly increases with increasing pH and decreases with increasing [Ca2+] and [DIC]. In combination, these experiments show that the difference in δ11B between solid calcite and aqueous borate linearly decreases with increasing calcite precipitation rate. To interpret these data, we present the first application of surface kinetic modeling (SKM) to boron incorporation. The SKM can simultaneously explain rate-dependent B/Ca and δ11B patterns observed in our and previously published inorganic calcite precipitation experiments when both aqueous borate and boric acid contribute to boron in inorganic calcite. If the B incorporation mechanism shown here for inorganic calcite is applicable to biogenic calcite, precipitation rate variations could modify δ11B patterns by changing the contributions of aqueous boric acid and borate to boron in calcite. However, better knowledge of biogenic calcite precipitation mechanisms and rates is needed to assess the importance of this effect for applications of B proxies in biogenic carbonates.

Ce3+ and Dy3+ doped Ca3(P1-xBxO4)2 phosphors for white light-emitting applications

A series of Ce3+, Dy3+ doped Ca3(P1-xBxO4)2 phosphors were synthesized by a high temperature solid-state reaction method, and their corresponding structure, morphology, and luminescence properties were investigated. It is found that the crystal phase transition from β-Ca3(PO4)2 to Ca5(PO4)3(OH) gradually occurs with increasing the boron content in the phosphors, which can provide various local environments for the doping ions and consequently affect the luminescence properties of the phosphors. A red shift of the emission peak of Ce3+ was revealed upon incorporation of boron into Ce/Dy co-doped phosphors. In addition, the luminescence properties could be well modulated by varying the excitation wavelength. The developed phosphors have great potential as a kind of single component white light-emitting phosphors for white light-emitting diodes.

Irradiation-Induced Modification of the Superconducting Properties of Heavily-Boron-Doped Diamond

Diamond, a wide band-gap semiconductor, can be engineered to exhibit superconductivity when doped heavily with boron. The phenomena has been demonstrated in samples grown by chemical vapor deposition where the boron concentration exceeds the critical concentration for the metal-to-insulator transition of nMIT4×1020/cm3. While the threshold carrier concentration for superconductivity is generally well established in the literature, it is unclear how well correlated higher critical temperatures are with increased boron concentration. Previous studies have generally compared several samples grown under different plasma conditions, or on substrates having different crystallographic orientations, in order to vary the incorporation of boron into the lattice. Here, we present a study of a single sample with unchanging boron concentration, and instead modify the charge-carrier concentration by introducing compensating defects via high-energy ion irradiation. Superconductivity is completely suppressed when the number of defects is sufficient to compensate the hole concentration to below threshold. Furthermore, we show it is possible to recover the superconductivity by annealing the sample in vacuum to remove the compensating defects.

Mechanism of boron incorporation into calcites and associated isotope fractionation in a steady-state carbonate-seawater system

An investigation on the interface reactions and boron isotope fractionation in a steady-state carbonate-seawater system was performed to better understand boron incorporation into CaCO3 in a natural environment. In seawater, inorganic carbonate crystals did not precipitate even when the solution reached saturation and the presence of carbonic anhydrase enzyme promotes the process, indicating the precipitation kinetics of inorganic carbonates from natural seawater is fairly slow. Both theoretical and experimental evidence proved that boron incorporation into calcite might be defined as an adsorption-precipitation process rather than a substitution of CO32− by HBO32− in the crystal lattice, where the charged B(OH)4- ions adsorb preferentially over H3BO3 onto positively charged calcite crystal surfaces and finally co-precipitate into occlusions or inclusions after new layers of calcites formed. The Langmuir isotherm well describes the adsorption process, yielding a maximum adsorption capacity [B]solid-max of 0.33 ± 0.04 mg⋅g−1 and an equilibrium constant K of 0.0053 ± 0.0003. Langmuir kinetics also describes previous studies with [B]solid-max of 71.4–418 μg⋅g−1 for calcite and aragonite, covering the variation of boron contents in a variety of biogenic carbonates. The boron isotope fractionations in ulexite-seawater and calcite-seawater systems are distinct. In the former one the fractionation factor (αulexite-seawater = 0.995 ± 0.001) suggests that both trigonal and tetrahedral species of boron enter into ulexite crystals via rapid precipitation, and in the latter one (α4-3 = 0.9736 ± 0.004) confirms that only the charged B(OH)4- species interacts with the crystal surface in calcite.

Disordering the Atomic Structure of Co(II) Oxide via B-Doping: An Efficient Oxygen Vacancy Introduction Approach for High Oxygen Evolution Reaction Electrocatalysts.

The introduction of oxygen (O) vacancies has been considered to be an important but challenging way to enhance the activity of electrocatalysts for the oxygen evolution reaction (OER). Substitution by heteroatoms with high electron-donating ability may be a feasible strategy for triggering O-vacancies to maintain thermodynamic stability. Herein, density functional theory (DFT) calculations predict that the incorporation of boron (B) is favorable to the generation of O-vacancies in transition metal oxides. Then, CoO nanowires with O-vacancies are prepared via incorporation of B using a facile pyrolysis strategy. As evidenced by the combined results of electron paramagnetic resonance spectroscopy and X-ray absorption near edge structure, O-vacancies in CoO are mainly derived from the disordering of the local structure caused by B doping. DFT calculation results further reveal that the oxidation of *OOH is the rate-limiting step for O-vacancies enriched CoO in the OER and that the presence of O-vacancies can efficiently lower the reaction barrier for breaking CoO bond, contributing to the improvement of OER kinetics. As expected, the O-vacancies enriched CoO exhibits a low overpotential of 280 mV to reach the current density of 10 mA cm-2 under basic conditions.

The Current Status and Perspectives of Delivery Strategy for Boronbased Drugs.

Boron-containing compounds are essential micronutrients for animals and plants despite their low-level natural occurrence. They can strengthen the cell walls of the plants and they play important role in supporting bone health. However, surprisingly, boron-containing compounds are seldom found in pharmaceutical drugs. In fact, there are no inherent disadvantages reported so far in terms of the incorporation of boron into medicines. Indeed, drugs based on boron-containing compounds, such as tavaborole (marked name Kerydin) and bortezomib (trade name Velcade) have been investigated and they are used in clinical treatment. In addition, following the advanced development of boron neutron capture therapy and a new emerging proton boron fusion therapy, more boron-containing medicinals are to be expected. This review discusses the current status and perspectives of delivery strategy for boron-containing drugs.

Bionic boron/silicon‐modified phenolic resin system with multifunctional groups: synthesis, thermal properties and ablation mechanism

A kind of silicon-and-boron-modified phenolic–formaldehyde resin (SBPF) with excellent thermal stability was fabricated via a simple two-step method and used for the matrix of ablation materials. The structure and thermal stability of the modified phenolic–formaldehyde resins (PFs) were characterised. The results showed that boron and silicon elements have been incorporated into SBPF in the form of a chemical bond. Meanwhile, the cured products showed an increase in graphite structure and a decrease in disordered structure due to the incorporation of boron and silicon. Compared with the ordinary phenolic resin, the initial thermal degradation temperature and charring yield at 800°C of SBPF increased by 73°C and 15 wt%, respectively. Further, the modified PFs, nano-Al2O3 powders, glass powders and vitreous silica fibres were used to obtain a novel ceramizable phenolic moulding composite. The morphology, chemical composition and ablative characteristics of the composites were explored. The results showed that a compact and homogeneous SiO2–Al2O3 layer formed on the ablated surface and protected the carbonised matrix and fibres from further oxidation. Compared with the ordinary PF composites, the SBPF composites showed a highly decreased linear/mass ablation rates, indicating the synergistic effect of boron and silicon modification on the enhanced ablation property.

Boron isotopic fractionation during adsorption by calcite – Implication for the seawater pH proxy

Although adsorption at the solid surface is the first step controlling boron incorporation in the crystal lattice during the standard growth mechanism of calcite and aragonite, little is known about the identity, structure and isotopic composition of the boron complexes formed at the CaCO3-solution interface. To generate this important information, we investigated experimentally the boron chemical and isotopic fractionation during adsorption at the calcite-water interface as a function of pH (6.5–11.7) at 4 and 20 °C in 0.01 and 0.1 M NaCl aqueous solutions. The surface complexation modeling of B adsorption and isotopic composition data showed that boron is sorbed at the calcite surface as a tetrahedral complex (>CaB(OH)40) formed by reaction of borate ions with Ca-protonated surface sites (log Kint0 = 1.54 ± 0.37 at 20 °C) and excluded the formation of trigonal B surface complexes (>CaB(OH)3+). The B isotopic composition of >CaB(OH)40 is ∼5‰ and 2‰ heavier than that of aqueous B(OH)4− in 0.01 and 0.1 M NaCl solution, respectively. Consistently, these values suggest that adsorbed borate ions have isotopic compositions intermediate between those of aqueous borate and structural tetrahedral species in calcite, which have been recently predicted to be ∼12‰ heavier than aqueous borate using quantum mechanical calculations (Balan et al., 2018). The good agreement between the isotopic composition of adsorbed boron measured in this study and boron experimentally co-precipitated with calcite in the 8–9 pH range at close to equilibrium conditions (i.e. via ion-by-ion attachment at advancing steps) (Noireaux et al., 2015) indicate that the isotopic composition of structural boron can be inherited from the boron surface complexes formed at the calcite/water interface. The results of this study contradict the assumption of no isotopic fractionation between tetrahedral boron in calcite and the borate ion that sustains the boron paleo-pH proxy, but confirm that trigonal B cannot be directly incorporated in the crystal structure during near equilibrium growth of calcite.