Effect Of Boron Doping Research Articles

Effect of surface modification on optical and electronic properties of graphene quantum dots

Optical and electronic properties of graphene quantum dots (GQDs) could be modified either by introducing heteroatoms on their surface or by covalently linking these with certain groups. In this work, time-dependent density functional theory (TD-DFT) with functional B3LYP/6-31G* has been used to study the effects of boron doping and surface-modified configurations of GQDs on the HOMO-LUMO gap and absorption spectra. The photoluminescence properties and quantum yield of GQDs have also been explored. Doping as well as a surface modification with boron configurations resulted in a decrease in the band gap and a red shift in absorption and photoluminescence/fluorescence spectra. As compared to surface modified GQDs, the presence of B atom in the edge modified GQDs has a pronounced effect on the tuning of the energy bandgap. Also, BCO2 is found to affect the electrical structures of GQDs more significantly as compared to BC2O. The fluorescence of surface-modified GQD is found fall in the near-infrared region with a quantum yield of 29 % rendering them suitable for bio-imaging applications. The results thus obtained are in good consonance with those reported in the literature.

Magnetostructural phase transitions and magnetocaloric effect in Mn-Fe-Ni-Ge-B alloys

The search for room-temperature high-performance magnetocaloric materials is highly stimulated towards magnetic refrigeration techniques. Here we report the boron doping effect on the magnetostructural transition and magnetocaloric effect of the Mn 0.89 Fe 0.11 NiGe alloy. Our studies reveal that the addition of only 0.2 at% boron induces a large magnetic entropy change (∆ S m ) of − 69.4 J kg −1 K −1 at 298.5 K under μ 0 H up to 7 T, which is ~ 34.0% higher than that of − 51.8 J kg −1 K −1 in the host alloy Mn 0.89 Fe 0.11 NiGe obtained at a much lower temperature of 267.5 K. With the increase of boron content, the phase transition temperature M s showed a nonlinear change that first increased and then decreased. The investigation of the microstructure by transmission electron microscopy suggests that the minor B atoms will get into the interstitial site of Mn 0.89 Fe 0.11 NiGe alloy, increase the cell volume, and stabilize the orthorhombic structure of the alloy. This could be the main reason for the increase in magneto-structural transition temperatures. Otherwise, the excessive B atoms will introduce precipitates, and cause the reduction of the magnetostructural transition temperature. It suggests that proper doping point defects are effective to tailor magneto-structural transition toward achieving the magnetocaloric effect. • B causes a nonlinear change of the magneto-structural transition temperature of Mn 0.89 Fe 0.11 NiGe. • Adding 0.2 at% B enhances magnetic entropy change by~ 34.0%. • The minor boron atoms will increase the cell volume and stabilize the martensitic phase. • Nano-precipitates at high B contents hinder the phase transition and decrease the transition temperature.

Effects of Boron Doping on the Bulk and Surface Acoustic Phonons in Single-Crystal Diamond.

We report the results of the investigation of bulk and surface acoustic phonons in the undoped and boron-doped single-crystal diamond films using the Brillouin-Mandelstam light scattering spectroscopy. The evolution of the optical phonons in the same set of samples was monitored with Raman spectroscopy. It was found that the frequency and the group velocity of acoustic phonons decrease nonmonotonically with the increasing boron doping concentration, revealing pronounced phonon softening. The change in the velocity of the shear-horizontal and the high-frequency pseudo-longitudinal acoustic phonons in the degenerately doped diamond, as compared to that in the undoped diamond, was as large as ∼15% and ∼12%, respectively. As a result of boron doping, the velocity of the bulk longitudinal and transverse acoustic phonons decreased correspondingly. The frequency of the optical phonons was unaffected at low boron concentration but experienced a strong decrease at the high doping level. The density-functional-theory calculations of the phonon band structure for the pristine and highly doped samples confirm the phonon softening as a result of boron doping in diamond. The obtained results have important implications for thermal transport in heavily doped diamond, which is a promising material for ultra-wide-band-gap electronics.

The effect of boron concentration on the electrical, morphological and optical properties of boron-doped nanocrystalline diamond sheets: Tuning the diamond-on-graphene vertical junction

In this paper, the effect of boron doping on the electrical, morphological and structural properties of free-standing nanocrystalline diamond sheets (thickness ~ 1 μm) was investigated. For this purpose, we used diamond films delaminated from a mirror-polished tantalum substrate following a microwave plasma-assisted chemical vapor deposition process, each grown with a different [B]/[C] ratio (up to 20,000 ppm) in the gas phase. The developed boron-doped diamond (BDD) films are a promising semiconducting material for sensing and high-power electronic devices due to band gap engineering and thermal management feasibility. The increased boron concentration in the gas phase induces a decrease in the average grain size, consequently resulting in lower surface roughness. The BDD sheets grown with [B]/[C] of 20,000 ppm reveal the metallic conductivity while the lower doped samples show p-type semiconductor character. The charge transport at room temperature is dominated by the thermally activated nearest-neighbor hopping between boron acceptors through impurity band conduction. At low temperatures (<300 K), the Arrhenius plot shows a non-linear temperature dependence of the logarithmic conductance pointing towards a crossover towards variable range hopping. The activation energy at high temperatures obtained for lowly-doped sheets is smaller than for nanocrystalline diamond bonded to silicon, while for highly-doped material it is similar. Developed sheets were utilized to fabricate two types of diamond-on-graphene heterojunctions, where boron doping is the key factor for tuning the shape of the current-voltage characteristics. The graphene heterojunction with the low boron concentration diamond sheet resembles a Schottky junction behavior, while an almost Ohmic contact response is recorded with the highly doped BDD sheet of metallic conductivity. The free-standing diamond sheets allow for integration with temperature-sensitive interfaces (i.e. 2D materials or polymers) and pave the way towards flexible electronics devices.

Effect of Boron Doping on the Interlayer Spacing of Graphite.

Boron-doped graphite was prepared by the heat treatment of coke using B4C powder as a graphitization catalyst to investigate the effects of the substitutional boron atoms on the interlayer spacing of graphite. Boron atoms can be successfully incorporated into the lattice of graphite by heat treatment, resulting in a reduction in the interlayer spacing of graphite to a value close to that of ideal graphite (0.3354 nm). With an increase in the catalyst mass ratio, the content of substituted boron in the samples increased significantly, causing a decrease in the interlayer spacing of the boron-doped graphite. Density functional theory calculations suggested that the effects of the substitutional boron atoms on the interlayer spacing of the graphite may be attributed to the transfer of Π electrons between layers, the increase in the electrostatic surface potential of the carbon layer due to the electron-deficient nature of boron atoms, and Poisson contraction along the c-axis.

Effect of boron doping on energy storage performance of PLZST ceramics

In this paper, thick film antiferroelectric ceramics (1-x)(Pb0.97La0.02)(Zr0.46Sn0.48Ti0.06)O3-xH3BO3 ((1-x)PLZST-xH3BO3, x = 0–0.025) were prepared by solid state sintering and tape-casting method. The effects of boron-doping on the microstructure, dielectric properties and energy storage properties of (1-x)PLZST-xH3BO3 ceramics were investigated. Appropriate boron-doping can improve the stability of antiferroelectric phase, delay phase transition and increase saturation polarization strength. Compared with the undoped PLZST thick films, the maximum polarization intensity increased by 1.9 times and the residual polarization decreased by 37%. When x = 0.020, the maximum recoverable energy storage density is 2.74 J/cm3, and the energy storage efficiency is 88.12%.

Effect of boron doping on luminescent properties of silicon--vacancy and germanium--vacancy color centers in diamond particles obtained by chemical vapor deposition

The effect of doping with boron on the luminescent properties of diamond particles synthesized by Hot Filament Chemical Vapor Deposition technique with color centers embedded during the growth process has been studied. It is shown that at low boron doping level, the photoluminescence intensity of a narrow zero-phonon line of the silicon-vacancy color center (738.2 nm) demonstrates a strong dependence on the concentration of boron atoms at the sites of the diamond lattice. The dependence of the intensity of a broad photoluminescence band in the wavelength range 520-800 nm on the concentration of boron atoms in the gas mixture in the range from 14 to 64000 ppm has been analyzed. The Raman scattering spectra of the obtained particles have been studied. At the concentration of boron atoms in the gas mixture up to 1540 ppm, the Raman scattering spectra of diamond particles practically do not change when the boron concentration is varied. At high boron doping level, the diamond band in the Raman spectra exhibit a spectral response typical of the Fano resonance. Keywords: diamond particles, color centers, boron doping, photoluminescence, chemical vapor deposition.

Effect of boron doping on structural, optical, and electrical properties of hydrogenated nanocrystalline silicon thin films grown by Cat-CVD method

Effect of boron doping on structural, optical, and electrical properties of hydrogenated nanocrystalline silicon thin films grown by Cat-CVD method

Investigation on thermal conductivity of graphene/Si heterostructure based on molecular dynamics simulation

The effect of doping and defects on thermal conductivity of Graphene/Si interface structure based on molecular dynamics simulation is investigated. With the nitrogen and boron doping defect ration increasing, the thermal conductivity of heterostructure shows decline trend. But the boron doping effect to thermal conductivity of heterostructure is higher than that of nitrogen doping. It is analyzed that due to the mass of nitrogen and boron is different, the harmonic effect of lattice vibration happens to some extent. The interfacial thermal conductivity decreases monotonously with hydrogenation rate. Hydrogenated graphene has a greater influence on the thermal conductivity in Zigzag direction. When the hydrogenation rate reaches 5%, the thermal conductivity decreases to 77.8 W/mK. Intrinsic defects of graphene will greatly reduce the thermal conductivity of single-layer graphene/Si interface, and single vacancy defects have the greatest influence on thermal conductivity. It builds a basis for future work on progress investigation of thermal property of graphene film heterostructure.

Enhancing mechanical properties of the boron doped Al0.2Co1.5CrFeNi1.5Ti0.5 high entropy alloy via tuning composition and microstructure

High entropy alloys (HEAs) have attracted considerable attention due to their excellent mechanical properties, which provides new insights for designing next generation structural materials. A series of Al0.2Co1.5CrFeNi1.5Ti0.5Bx (x = 0, 0.15, 0.3, 0.45, 0.6, 0.75 and 0.9, in molar ratio) HEAs was prepared by vacuum arc melting to investigate the effect of boron doping on the phase evolution, microstructure transformation and mechanical properties. The results indicated that the HEAs with trace boron doping (x = 0.15) maintained single FCC phase, while it evolved to FCC phase, in-situ borides (TiB2 and Cr2B) and Laves phase when the boron molar ratio higher than 0.3. With the boron molar content increased from 0 to 0.9, the microstructures of the HEAs transformed from complete dendrite to dendrites, irregularly shaped TiB2, needle-shaped Cr2B and lamellar eutectic structure which composed by alternate layers of FCC phase and Laves phase. B doping improved the strength and hardness of the HEAs. The enhanced mechanical properties of the boron doped HEAs was attributed to the synergistic strengthening effect among interstitial solid solution strengthening, second phase strengthening, dislocation strengthening, fine grain strengthening and heterostructure strengthening.

Investigation of doped carbon nanotubes on desalination process using molecular dynamics simulations

Carbon nanotubes (CNTs) with their natural nanoscale pores are excellent candidates for the reverse osmosis and ion-selection processes. Previous works also showed that the doping of CNTs is an important way to improve the different properties of the carbon materials. In this research, we have investigated the effects of silver (Ag), silicone (Si), nitrogen (N), and boron (B) doping in (10,10) CNT on desalination process using molecular dynamics (MD) simulation. The results have been also compared with the silicon carbide (SiC), and boron nitride (BN) nanotubes. We have also examined the possible use of heterojunction nanotubes (HNTs) including doped, SiC, and BN nanotubes as new membranes in the desalination process. The different properties including water and ion flux, radial distribution function, potential of mean force, and the water-nanotube interaction energy have been investigated. Our results indicated that the BN and SiC nanotubes have the most water flux and ion rejection, respectively. Also, positioning of Ag-doped CNT and SiC tube at the first part of a hetero-junction system decreases the water and ion fluxes whereas positioning of BN at the last part increases the ion flux.

Boron-Doped Edges as Active Sites for Water Adsorption in Activated Carbons.

Investigating the surface properties of heteroatom-doped carbon materials is essential because these versatile materials have found use in a variety of energy and environmental applications; an understanding of these properties would also lead to an improved appreciation of the direct interaction between the reactant and the functionalized surface. Herein, we explore the effect of boron (B) doping on the surface properties of activated carbon (AC) materials based on their water adsorption behavior and oxygen reduction reaction. In the high-temperature B doping process, B-doped AC materials at 1400 °C exhibit an open pore structure with B-O bonds, whereas at a temperature of 1600 °C, a nonporous structure containing a large amount of B-C bonds prevails. The B-O species act as active sites for water adsorption on the carbon surface. On the basis of the isothermal adsorption heat, we suggest that B atoms are present at the pore openings and on the surfaces. The B-O moieties at the open edges improve the electrocatalytic activity, whereas the B-C bonds at the closed edges decrease the electrocatalytic activity because of the stable structure of these bonds. Our findings provide new evidence for the electrocatalytic properties associated with the structure of B-doped edges.

Boron doped cryptomelane as a highly efficient electrocatalyst for the oxygen evolution reaction

In this study, cryptomelane-type (1D) MnO2 was doped with boron powder by ball-milling in an inert organic solvent under various experimental conditions. The structural, thermal, morphological, and surface features of samples prepared by the ball-milling method were characterized by powder X-ray diffraction, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy, scanning and transmission electron microscopy, and surface measurements. The electrocatalytic oxygen evolution reaction (OER) performances of the samples were tested and compared with the bare cryptomelane to reveal the effect of boron doping into manganese oxide. It was found that boron particles transformed to trigonal BO3 units in the cryptomelane structure via mechanical activation, and accordingly, the oxidation state of manganese in this structure relatively changed. The 0.25% B-doped cryptomelane sample prepared at 12 h grinding time exhibited the overpotential of 425 mV at a current density of 1 mAcm−2 with a Tafel slope of ∼95 mV dec−1. It showed a remarkable catalytic performance among the other electrocatalysts under neutral pH compared to bare cryptomelane. When the elemental boron doping exceeded 1%, the electrochemical performance dramatically decreased depending on the blocking of the Mn3+ active sites.

Operando XRD study on the Effect of Boron Doping on the Failure Mechanisms of Na-, Ni- and Mn-based Positive Electrodes in Sodium-Ion Batteries

Layered oxides have emerged as one of the most promising candidates for high capacity positive electrode materials in sodium-ion batteries (SIB). It has been demonstrated that Na, Ni and Mn-based layered oxide materials are relatively sustainable in terms of their composition, and high capacities have been achieved. However, it has been noted that at higher voltages, the crystal structure of these materials tends to degrade during cycling1,2. Doping the electrode with different transition metals such as Fe, Mg, Ti etc., has been an immensely popular strategy to avoid this degradation3–5. However, there has been little attention on doping with lighter electrochemically inactive elements such as boron that do not lower the materials' theoretical capacity.In this study, layered oxide cathode materials with varying Na, Ni and Mn contents were synthesised. Electrodes were made from synthesised materials (using 80% active material, 10% conductive additive and 10% binder) and measured in sodium-ion battery half-cells using the galvanostatic charge-discharge method (GCD). The best performing material was doped with 10% boron to investigate its influence on the materials' capacity during galvanostatic cycling (Figure 1a). Operando XRD was used to evaluate the changes in the crystal structure of synthesised layer oxides during galvanostatic cycling (Figure 1b). XRD diffractograms were measured on different cell potentials, which corresponded to voltage plateaus from previous galvanostatic charge-discharge measurements. Crystallite size, lattice parameters, and atom occupancies were calculated from measured diffractograms to evaluate changes in crystal structure during cycling. Operando XRD measurements were coupled with electrochemical impedance spectroscopy to tie structural degradation with contact impedance. Figure 1

Effects of boron doping on the fabrication of dense 6H-SiC ceramics by high-temperature physical vapor transport

In this paper, boron-doped dense 6H-SiC ceramics was fabricated by the high-temperature physical vapor transport (HTPVT) method. The effect of B doping on the crystal structure stability of 6H-SiC was investigated based on density functional theory (DFT). The results show that B doping can be realized even under thermodynamical equilibrium conditions. Nevertheless, it is found that the B doping effects on the (0001) of Si-plane and (000-1) of C-plane are significantly different. The doping experiments demonstrated that B can observably change the crystal growth morphology, leading to the formation of elongated 6H-SiC crystals.

Operando XRD study on the Effect of Boron Doping on the Failure Mechanisms of Na-, Ni- and Mn-based Positive Electrodes in Sodium-Ion Batteries

In this work, Na0.64Ni0.31Mn0.68O2 was synthesized via the glycine-nitrate combustion synthesis method and investigated as positive electrode material in sodium-ion batteries. Na-, Ni- and Mn-based layered oxide positive electrode materials are prone to capacity fade. In this study, boron was investigated as an additive to increase capacity retention. The physical properties of obtained positive electrode materials were characterized using XRD and XRF. The materials were electrochemically characterized using the galvanostatic charge-discharge method. In addition, the material with the highest initial capacity was further examined using the operando XRD method to characterize the changes in the material's crystal lattice in real-time during galvanostatic cycling.

Boron- and nitrogen-doped graphene quantum dots with enhanced supercapacitance

Graphene quantum dots (GQDs) with their very large specific surface area and numerous edges can offer promising novel features as metal-free and inexpensive electrodes of supercapacitors. Here, we investigated the effect of boron and nitrogen doping in GQDs on their electrochemical energy storage properties. The GQDs as well as B-GQDs and N-GQDs were synthesized by a facile hydrothermal method and characterized by X-ray diffractometry, UV-Vis absorption spectrophotometry, transmission electron microscopy, and energy-dispersive X-ray mapping techniques. Electrochemical properties of the nanoparticles were investigated in a three-electrode setup using cyclic voltammetry and galvanostatic charge/discharge techniques in KOH electrolyte. The N-GQDs electrode showed the highest specific capacitance of 283 F/g at 1 A/g as compared to the GQDs and B-GQDs electrodes. The N-GQDs electrode exhibited the specific energy and specific power of 6.2 Wh/Kg and 108 W/Kg, respectively. The N-GQDs electrode showed also better cycling stability (80% capacity retention) than the GQDs and B-GQDs electrodes.

Understanding the enhancement effect of boron doping on the electrochemical performance of single-crystalline Ni-rich cathode materials

Ni-rich layered oxides are considered as promising cathode materials for Li-ion batteries (LIBs) due to their satisfying theoretical specific capacity and reasonable cost. However, poor cycling stability caused by structural collapse and interfacial instability of the Ni-rich cathode material limits the further applications of commercialization. Herein, a series of B-doped single-crystal LiNi0.83Co0.05Mn0.12O2 (NCM) are designed and fabricated, aiming to improve the structural stability and enlarge the Li+-ions diffusion paths simultaneously. It reveals that B-doping at TM layers will facilitate the formation of stronger B-O covalent bonds and expand the layered distance, significantly enhancing the thermodynamics and kinetic of NCM electrode. With the synergistic effect of single-crystalline architecture and appropriate B-doping, it can effectively alleviate the occurrence of internal strain with structural degradation and boost the intrinsic rate capability synchronously. As anticipated, the 0.6 mol % B-doped NCM electrode exhibits enhanced rate property and superior cycle stability, even at the harsh condition of high-temperature and elevated cut-off voltage. Remarkably, when tested in pouch-type full-cell, it maintains high reversible capacity with superior capacity retention of 91.35% over 500 cycles with only 0.0173% decay per cycle. This research illustrates the feasibility of B-doping and single-crystalline architecture to improve the electrochemical performance, which is beneficial to understand the enhancement effect and provides the design strategy for the commercialization progress of Ni-rich cathode materials.

Effect of boron and nitrogen doping on mechanical and electronic properties of graphane under uni-axial strain conditions: A DFT study

Graphane has grabbed the attention of scientific community for its remarkable properties. Present study reveals the effect of boron and nitrogen doping on electronic and mechanical properties of graphane through density functional calculations. Doping concentration has been varied from 2 to 8 percent, strain is applied along the Zig-zag direction and is within the elastic limit of sheet. Band and strength of graphane are reduced to a greater extent with the introduction of B dopants in comparison to N dopants.

Study of Tribological Properties of Textured Boron-Doped Diamond Film under Water Lubrication

To explore the effects of different surface textures and boron doping on the surface friction properties of diamond film, cemented carbide tools were provided with elliptical and groove textures using laser technology. Undoped diamond (UDD), boron-doped un-textured diamond (BDUTD), boron-doped elliptical textured diamond (BDETD), and boron-doped grooved textured diamond (BDGTD) films were prepared by bias-enhanced hot filament chemical vapor deposition (BEHFCVD). The effects of different surface texture and lubrication conditions on the tribological properties of diamond coated tools were studied by TBT-M5000 ball-on-disk friction tester. The surface morphology, film quality, adhesion strength and residual material composition of diamond films were characterized by SEM, Raman, Rockwell hardness tester and EDS, respectively. The results show that boron-doped can effectively improve the film quality and the existence of texture further improves the adhesion strength of diamond film. Under water lubricated condition, the average friction coefficients of UDD and BDGTD film are 0.1426 and 0.123, respectively. The wear rate of the steel ball corresponding to BDGTD film shows excellent anti-friction performance, which is 1.37 × 10−8 mm3 / Nm. From the wear morphology, the UDD film pair has the largest wear diameter, which is 1.536 mm. The steel ball corresponding to BDGTD film has the smallest wear diameter, which is 1.258 mm. Compared with the other three films, the wear of UDD film is the most serious and BDGTD film shows the best wear morphology, this is due to the fact that texture can promote the lubricant to enter the friction contact surface, make the contact surface fully lubricated and can collect wear debris.