Hexagonal Boron Nitride Sheets Research Articles

Computational study of fluorinated defective h-BN sheet controlling corrosion in the marine environment

Chloride ions are responsible for triggering severe corrosion in the marine environment. Hence, there is a need to deploy corrosion resistant materials such as hexagonal boron nitride (h-BN) sheet to protect mechanical components operating under such harsh conditions. In this work, a first-principles approach was employed to investigate the effect of fluorine modification on the thermodynamic and kinetic behaviors of oxygen on different kinds of vacancy-defective hexagonal boron nitride (h-BN) in a Cl-containing marine environment. Geometrical and electronic structures were systematically analyzed along with adsorption and diffusion behaviors. The existence of a low energy barrier implies that there is a relatively attenuated ability to inhibit O diffusion for double vacancy VBN-h-BN sheet compared to single vacancy VB-h-BN and VN-h-BN sheets. Interestingly, the fluorine functionalization for three defective h-BN sheet is found to cause an increased energy barrier of O diffusion. The F@Cl@VN-h-BN sheet possesses the highest diffusion energy barrier, indicating a superior anti-oxidation property in the marine environment. This study provides some fundamental guidelines for realizing high-performance h-BN sheets for protecting equipment and components used in marine applications.

Ultra-fast switching memristors based on two-dimensional materials

The ability to scale two-dimensional (2D) material thickness down to a single monolayer presents a promising opportunity to realize high-speed energy-efficient memristors. Here, we report an ultra-fast memristor fabricated using atomically thin sheets of 2D hexagonal Boron Nitride, exhibiting the shortest observed switching speed (120 ps) among 2D memristors and low switching energy (2pJ). Furthermore, we study the switching dynamics of these memristors using ultra-short (120ps-3ns) voltage pulses, a frequency range that is highly relevant in the context of modern complementary metal oxide semiconductor (CMOS) circuits. We employ statistical analysis of transient characteristics to gain insights into the memristor switching mechanism. Cycling endurance data confirms the ultra-fast switching capability of these memristors, making them attractive for next generation computing, storage, and Radio-Frequency (RF) circuit applications.

The single metal atom (Ni, Pd, Pt) anchored on defective hexagonal boron nitride for oxidative desulfurization.

Single-atom catalysts (SACs) have attracted great attention for various chemical reactions because of their strong activity, high metal utilization ratio, and low cost. Here, by using the density functional theory (DFT) method, the stability of a single VIII-group metal atom (M = Ni, Pd, Pt) anchored on the defective hexagonal boron nitride (h-BN) sheet and its possible application in oxidative desulfurization (ODS) are investigated. Calculations show that the stability of the single M atom embedded in the h-BN surface with B and N vacancies is strikingly enhanced compared to that on the perfect h-BN surface. The catalytic activities of the defective h-BN-supported single metal atom are further studied by the activation of molecular oxygen and subsequent oxidation of dibenzothiophene (DBT). O2 is activated to the super-oxo state with large interaction energies on three M/VN surfaces. However, among the three M/VB surfaces, only Pt/VB performs efficient activation of O2. The oxidation of DBT proceeds in two steps; the rate-determining step is the initial step, in which activated O2 oxidizes DBT to produce sulfoxide. By comparing the energy barrier in the first reaction step, both Ni/VN and Pt/VB are revealed as promising candidates for the ODS reaction.

Functionalized hexagonal boron nitride sheets and charge triggered interpenetrating polymer network based membranes work in tandem towards water remediation

Charge triggered membranes demonstrate excellent resistance to fouling and high rejection rates towards charged dyes.

Fluorine enables h-BN sheet to resist oxidizing failures in sulfur atmosphere

Corrosion is one of the most common ways in which metal components are damaged, especially under extreme conditions in the presence of sulfide ions. Due to the excellent properties of hexagonal boron nitride (h-BN) sheets, they can provide effective protection for facilities exposed to sulfur-containing atmospheres. In this paper, the thermodynamic and kinetic behavior of oxygen adsorbed on h-BN and defective D-h-BN sheets in a sulfur-containing atmosphere were performed by first-principles calculations. The adsorption energies, densities of state, band structures, differential charge densities and diffusion energy barriers were systematically investigated. The presence of sulfur reduces the diffusion energy barrier of oxygen, which accelerates the oxidative failure of h-BN sheets. Surprisingly, the F-modified h-BN sheet possesses a higher oxygen diffusion energy barrier, which explains its superior oxidation resistance. Therefore, h-BN sheets are a promising candidate as a protective material in sulfur-containing atmospheres.

Large Area Hexagonal Boron Nitride Sheet for 2D Electronic Devices

Large Area Hexagonal Boron Nitride Sheet for 2D Electronic Devices

Water-Induced Bandgap Engineering in Nanoribbons of Hexagonal Boron Nitride.

Different from hexagonal boron nitride (hBN) sheets, the bandgap of hBN nanoribbons (BNNRs) can be changed by spatial/electrostatic confinement. It is predicted that a transverse electric field can narrow the bandgap and even cause an insulator-metal transition in BNNRs. However, experimentally introducing an overhigh electric field across the BNNR remains challenging. Here, it istheoretically and experimentally demonstrated that water adsorption greatly reduces the bandgap of zigzag-oriented BNNRs (zBNNRs). Ab initio calculations show that water molecules can be favorably assembled within the trench between two adjacent BNNRs to form a polar ice layer, which induces a transverse equivalent electric field of over 2Vnm-1 accounting for the bandgap reduction. Field-effect transistors aresuccessfully fabricated from zBNNRs with different widths. The conductance of water-adsorbed zBNNRs canbe tuned over 3 orders in magnitude via modulation of the equivalent electrical field at room temperature. Furthermore, photocurrent response measurements aretaken to determine the optical bandgaps of zBNNRs with water adsorption. The zBNNR with increased width can exhibit a bandgap down to 1.17eV. This study offers fundamental insights into new routes toward realizing electronic/optoelectronic devices and circuits based on hexagonal boron nitride.

Confined water transport and desalination mechanism through lamellar Boron-Nitride Channels: A molecular dynamics simulation study

The lamellar channels created by hexagonal boron nitride sheets (hBNSs) offer great promise as membranes for RO desalination plants. However, boron nitride nanochannels (BNNCs) have not yet been extensively explored for their desalination mechanisms. Therefore, to address this gap of knowledge, in this study, molecular dynamics simulations (MDs) are used to investigate the performance of BNNCs in water desalination applications. For this purpose, the effect of various parameters, including channel height in the range of 6.14 Å to 12.38 Å, applied pressure, ion concentration, and membrane flexibility are evaluated. Results show that for channel height ranging 6.14 Å to 8.77 Å, the rejection percentage of double-charged ions is more than single-charged ions. In contrast, this trend is reversed for larger channel heights. Another important point is that 7.675 Å can be selected as an optimum channel height for a design of BNNC membranes. Moreover, the water permeation and ion rejection of flexible membrane decrease and increase, respectively, compared to the rigid membrane. In addition, the Boron Nitride-Nanoflake nanochannel membranes (BNFNC) are investigated as a realistic model of nanosheet-based membranes. Finally, the results of the present study propose that BNNCs can be an appropriate membrane for RO desalination plants.

A Novel Controlled Fabrication of Hexagonal Boron Nitride Incorporated Composite Granules Using the Electrostatic Integrated Granulation Method

Despite the availability of nano and submicron-sized additive materials, the controlled incorporation and utilization of these additives remain challenging due to their difficult handling ability and agglomeration-prone properties. The formation of composite granules exhibiting unique microstructure with desired additives distribution and good handling ability has been reported using the electrostatic integrated granulation method. This study demonstrates the feasible controlled incorporation of two-dimensional hexagonal boron nitride (hBN) sheets with alumina (Al2O3) particles, forming Al2O3-hBN core-shell composite granules. The sintered artifacts obtained using Al2O3-hBN core-shell composite granules exhibited an approximately 28% higher thermal conductivity than those obtained using homogeneously hBN-incorporated Al2O3 composite granules. The findings from this study would be beneficial for developing microstructurally controlled composite granules with the potential for scalable fabrication via powder-metallurgy inspired methods.

Geometrical and magnetic properties of small titanium and chromium clusters on monolayer hexagonal boron nitride.

Magnetic clusters on an insulating substrate are potential candidates for spin-based quantum devices. Here we investigate the geometric, electronic, and magnetic structures of small Ti and Cr clusters, from dimers to pentamers, adsorbed on a single-layer hexagonal boron nitride (h-BN) sheet within the framework of density functional theory. The stable adsorption configurations of the Ti clusters and Cr clusters composed of the same number of atoms are found to be totally different from each other. The difference in their bonding mechanisms has been revealed by the density of states and the charge density difference of the corresponding adsorption systems. While chemical bonds are formed between the Ti atoms and the supporting sheet, the Cr clusters are found in the physisorption state on the substrate. In addition, it is shown that the h-BN sheet is energetically favorable for building three-dimensional Ti clusters. These findings support the use of h-BN as a suitable decoupling substrate for manipulation of quantum spin states in small transition metal (TM) clusters and fabrication of devices based on them.

Functional hBN decorated Ni(OH)2 nanosheets synthesized for remarkable adsorption performance for the elimination of fluoride ions.

Occurrence of fluoride in groundwater is a serious concern due to its fatal effects. Functionalized hexagonal boron nitride sheets have been combined with nickel hydroxide nanoparticles by a one step process and a hybrid adsorbent Ni(OH)2@hBN has been developed with an exceptionally high fluoride adsorption capacity of 365 mg g-1, higher than those of Ni(OH)2 and hBN. This maximum adsorption capacity is higher than those of most common adsorbents used for defluoridation including activated alumina, reported nickel oxide and carbon-based 2D material-supported alumina adsorbents. The presence of functionalized boron nitride significantly increased the surface area to 680 m2 g-1 with a pore volume of 0.33687 cm3 g-1 and provided rich hydroxyl group-containing surface sites for the removal of fluoride present in contaminated water. In addition, the adsorption of fluoride onto boron nitride-modified nickel hydroxide followed pseudo-second-order kinetics and the equilibrium data fitted well with the Langmuir adsorption isotherm, suggesting a monolayer adsorption mechanism. Furthermore, the material developed is tested with the water sample collected from a real affected area, from the Dhar district of India, and the material showed promising results in terms of fluoride removal efficacy.

Morphology-dependent adsorption energetics of Ru nanoparticles on hcp-boron nitride (001) surface - a first-principles study.

Active B5-sites on Ru catalysts can be exploited for various catalytic applications; in particular, the epitaxial formation of Ru nanoparticles with hexagonal planar morphologies on hexagonal boron nitride sheets increases the number of active B5-sites along the nanoparticle edges. The energetics of adsorption of Ru nanoparticles on hexagonal boron nitride were investigated using density functional theory calculations. Then, to understand the fundamental reason for this morphology control, adsorption studies and charge density analysis were performed on fcc and hcp Ru nanoparticles heteroepitaxially formed on a hexagonal boron nitride support. Among the explored morphologies, hcp Ru(0001) nanoparticles exhibited the highest adsorption strength of -31.656 eV. To verify the hexagonal planar morphologies of the hcp-Ru nanoparticles, three different hcp-Ru(0001) nanoparticles-Ru60, Ru53, and Ru 41-were adsorbed onto the BN substrate. In agreement with the experimental studies, the hcp-Ru60 nanoparticles exhibited the highest adsorption energy owing to their long-range and perfect hexagonal match with the interacting hcp-BN(001) substrate.

Comparative evaluation of osteogenic cell growth on titanium surface and titanium coated with boron nitride surface: An in vitro study.

To promote better biological response and osseointegration continuous research is going on to modify the titanium (Ti) implant surface for successful implant treatment modality. This study aims to evaluate the osteogenic cell growth upon the uncoated Ti discs and boron nitride (BN) coated Ti to assess osseointegration and clinical success of dental implants. This is an descriptive experimental study which includes coating of uncoated titanium alloy suraface with boron nitride in the form of hexagonal boron nitride sheets. Than comparative evaluation of osteogenic cell growth upon both coated and uncoated titanium surfaces was done using specific cell growth determinants. In this descriptive experimental study, both BN-coated and uncoated Ti discs were assessed for osteogenic cell growth using 3-(4, 5-dimethyl thiazolyl-2)-2, 5-diphenyltetrazolium bromide assay, 4',6-diamidino-2-phenylindole, is a fluorescent stain assay, and cell adhesion assay. As this study is a descriptive experimental analysis between two variables only so there is no need of statistical analysis or p-value. Overall good cell adhesion, cell differentiation, and cell proliferation occurred in the BN-coated Ti discs as compared to uncoated Ti discs. To promote osseointegration of dental implants, surface coating with BN proved to be an effective approach toward better osseointegration and long-duration success of dental implants as a single unit or implant-supported prosthesis BN which is a biocompatible graphene material with advantages in chemical and thermal stability. BN promoted better osteogenic cell adhesion, differentiation, and proliferation. Hence, it can be used as a new promising Ti implant surface-coating material.

Synergistic effects of boron nitride sheets and reduced graphene oxide on reinforcing the thermal conduction, SERS performance and thermal property of polyimide composite films

AbstractPolyimide (PI) composite films with hybrid fillers containing hBN (hexagonal boron nitride) sheets and rGO (reduced graphene oxide) were successfully fabricated by in‐situ polymerization. Herein, hBN sheets and rGO were obtained by ball milling and chemical reduction, respectively. In PI composite films, hBN can be tightly attached onto the surface of rGO via π‐π interaction, which can benefit the construction of heat‐conduction pathways and reduce boundary of heat resistance. The results show that the addition of rGO and hBN could enhance the thermal conductivity by synergistic effects. Specially, hBN and rGO are at the weight ratio of 1:1 and at the total loading of 33 wt%, thermal conductivity of PI composites can reach up to 1.19 Wm−1 K−1, which is 5.61 times higher than that of pure PI. Thermal property and dynamic mechanical property of composite films were also investigated. Besides, compared with pure PI, mixed fillers have obvious surface‐enhanced Raman scattering signals, indicating the synergistic effect of the mixed fillers. Overall, this study gives insights into heat dissipative and high sensitivity analysis components which may be used in the field of high‐temperature micro fabrication.

Heteroepitaxial Growth of B5 -Site-Rich Ru Nanoparticles Guided by Hexagonal Boron Nitride for Low-Temperature Ammonia Dehydrogenation.

Ruthenium is one of the most active catalysts for ammonia dehydrogenation and is essential for the use of ammonia as a hydrogen storage material. The B5 -type site on the surface of ruthenium is expected to exhibit the highest catalytic activity for ammonia dehydrogenation, but the number of these sites is typically low. Here, a B5 -site-rich ruthenium catalyst is synthesized by exploiting the crystal symmetry of a hexagonal boron nitride support. In the prepared ruthenium catalyst, ruthenium nanoparticles are formed epitaxially on hexagonal boron nitride sheets with hexagonal planar morphologies, in which the B5 sites predominate along the nanoparticle edges. By activating the catalyst under the reaction condition, the population of B5 sites further increases as the facets of the ruthenium nanoparticles develop. The electron density of the Ru nanoparticles also increases during catalyst activation. The synthesized catalyst shows superior catalytic activity for ammonia dehydrogenation compared to previously reported catalysts. This work demonstrates that morphology control of a catalyst via support-driven heteroepitaxy can be exploited for synthesizing highly active heterogeneous catalysts with tailored atomic structures.

Flexible substrate based on sandwich-structure hydrocarbon resin/aligned boron nitride composites with high thermal conductivity and low dielectric loss

Flexible circuit board materials with low dielectric constant (εr), low dielectric loss (tanδ) and high thermal conductivity (TC) were highly desired for high-frequency and high-speed electronic equipment. Herein, hexagonal boron nitride (h-BN) sheets were filled into highly elastic styrene ethylene butylene styrene (SEBS) matrix and oriented along in-plane direction regularly by hot-pressing method. SEBS/h-BN films exhibited high TC and outstanding flexibility except relatively high tanδ and water absorption. The sandwich structure was designed utilizing pure cyclic olefin copolymer (COC) films as outer surface layers and SEBS/h-BN film as interlayer. The introduction of COC films reduced the tanδ and water absorption of SEBS/h-BN film without reducing original TC obviously. Hybrid SEBS/COC/BN films owning the same components with sandwich-structure films were also fabricated to verify the advantages of designed structure. Sandwich-structure films always kept good flexibility and exhibited low εr (2.7–3.6), low tanδ (<1 × 10−3, 10 GHz), high TC (3.8–17.6 W m−1 K−1) and low water absorption (<0.1%). These films were also fabricated into flexible copper clad laminates and patch antenna operated in sub-6G band. The antenna exhibited a return loss of −32.8 dB and a gain of 7.04 dBi. The flexible substrates show great potential and satisfy large-scale production demand in high TC flexible circuit board materials field.

Interlayer spacing control of boron nitride sheets with hydrated cations

Two-dimensional (2D) materials are widely used in various fields, among which the application prospect in filtering and purifying water resources is broad. An important factor in sieving water molecules and other substances is the interlayer spacing of 2D material membranes. The interlayer spacing of graphene oxide and graphene membranes can be controlled by hydrated cations because of hydrated cation–π interaction. Similarly, our simulations show that hydrated cations can also control the interlayer spacing between hexagonal boron nitride (h-BN) sheets, which are smaller than that of graphene oxide sheets and graphene sheets. The interlayer distances are 8.70, 8.62, 7.68, 8.21, 8.93, 8.11 and 8.18 Å for hydrated Li+, Na+, K+, Mg2+, Ca2+, Cu2+ and Zn2+, respectively. Both hydration energy and the radius of the hydrated cation are deciding factors for monovalent hydrated cations and divalent hydrated cations in affecting the h-BN layer spacing. Further calculations indicate that unlike graphene and graphene oxide dominated by the hydrated cation–π interaction, the interactions between h-BN sheets and hydrate cations are mainly hydrogen bonds. However, there is an obvious hydrated cation–π interaction between hydrated K+ and the h-BN sheets. Our results are helpful for future ion sieving applications using the h-BN membranes.

Chemical-free exfoliation of hexagonal boron nitride via cavitation-bubble plasma in water

Hexagonal boron nitride (h-BN) sheets have numerous applications, but current low-cost, environmentally friendly techniques for h-BN exfoliation yield undesirably small sheet sizes. We have developed a novel chemical-free method to prepare large h-BN nanosheets (BNNSs) by the exfoliation of h-BN using plasma with cavitation bubbles in water, named here as cavitation-bubble plasma. Unlike ordinary liquid exfoliation methods, which reduce the sheet size of BNNSs compared with that of the starting h-BN, the cavitation-bubble plasma process exfoliated h-BN without reducing the sheet size. Furthermore, the plasma dramatically improved the exfoliation yield.

Theoretical study on S/Fe-doped hexagonal boron nitride (h-BN) sheet: Electronic and optical properties

Limited by the wide band gap of h-BN, the application of h-BN in photocatalysis is extremely challenging. In this paper, a strategy of co-doping monolayer h-BN with sulphur and iron was proposed to enhance the stability and catalytic activity of photocatalysts. Firstly, based on density functional theory (DFT), several models of monolayer h-BN nanosheets with iron decoration was created and optimized. Secondly, the structural, electronic, and optical properties were investigated in this paper, and the calculations proves that the introduction of impurity energy levels mainly composed of Fe 3d orbitals is the key to solving the wide bandgap of boron nitride. The HOMO-LUMO analysis shows S atoms participate in the redistribution of electrons, which inhibits the recombination of electron-hole pairs. This work verified the higher photocatalytic ability and wider light absorption range of monolayer h-BN co-doped with sulfur and iron. This paper has pointed a promising path for the modification of h-BN in the direction of photocatalysis.

Synergistic enhancement of thermal conductivity in thermal interface materials by fabricating3D‐BN‐ZnOscaffolds

AbstractThree‐dimensional boron nitride/zinc oxide (3D‐BN‐ZnO) scaffolds were prepared by the ice‐templating method, in which ZnO particles were in situ formed by sintering. Then, polydimethylsiloxane (PDMS)/3D‐BN‐ZnO composites were fabricated via vacuum infiltration of PDMS prepolymer into the scaffolds and curing. Compared with the composite prepared by simple blending, the thermal conductivity of the composite prepared based on the ice‐templating method is much higher due to the excellent orientation of hexagonal boron nitride (hBN) sheets. Based on the same content of hBN sheets, the further introduction of 2.7 wt% ZnO particles formed in situ by sintering could promote the thermal conductivity of the composite to the value of 1.45 W m−1 K−1, which is 70.6% higher than that of the PDMS/3D‐BN composite. In addition, compared with the PDMS/3D‐BN composite containing more hBN sheets, the PDMS/3D‐BN‐ZnO composite with 2.7 wt% ZnO particles possesses fewer fillers but higher thermal conductivity. It suggests that ZnO particles could synergistically improve the thermal conductivity. As revealed from the morphology of the composites, many ZnO particles are located between hBN sheets and thus construct thermally conductive paths. This study provides a new strategy for the design of thermal interface materials with high thermal conductivity.