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Abstract: In the present study, the adsorption and properties of three popularly studied aromatic amino acids, namely phenylalanine, tyrosine, and tryptophan, on the surface of the single-wall boron nitride nanotubes [...]

Switching of static friction and adhesion of a liquid drop on a corrugated solid boron nitride surface is linked to the intercalation of hydrogen, which changes the electric field of in-plane dipole rings and thus reduces the adsorption energy. Stiction versus adhesion in a single liquid drop Stiction, or static friction, is the force required to persuade an object to start sliding across a surface. It is technologically important in devices with moving parts in contact, but is not well understood. Stijn Mertens et al. describe an inorganic model system for the study of the relationships between surface wetting, stiction, adhesion and lubrication. The system is a hexagonal boron nitride monolayer that can be electrochemically switched by intercalation of hydrogen between a corrugated and a flat morphology. The change in the surface structure of the boron nitride alters the adhesion and its balance with stiction of an aqueous drop sliding across the monolayer. The work of adhesion increases in going from the flat to the corrugated surface, whereas the stiction threshold does not change significantly. Thus the authors make a quantitative connection between the macroscopic properties of stiction and adhesion as a result of structural control at the atomic scale. When a gecko moves on a ceiling it makes use of adhesion and stiction. Stiction--static friction--is experienced on microscopic and macroscopic scales and is related to adhesion and sliding friction.sup.1. Although important for most locomotive processes, the concepts of adhesion, stiction and sliding friction are often only empirically correlated. A more detailed understanding of these concepts will, for example, help to improve the design of increasingly smaller devices such as micro- and nanoelectromechanical switches.sup.2. Here we show how stiction and adhesion are related for a liquid drop on a hexagonal boron nitride monolayer on rhodium.sup.3, by measuring dynamic contact angles in two distinct states of the solid-liquid interface: a corrugated state in the absence of hydrogen intercalation and an intercalation-induced flat state. Stiction and adhesion can be reversibly switched by applying different electrochemical potentials to the sample, causing atomic hydrogen to be intercalated or not. We ascribe the change in adhesion to a change in lateral electric field of in-plane two-nanometre dipole rings.sup.4, because it cannot be explained by the change in surface roughness known from the Wenzel model.sup.5. Although the change in adhesion can be calculated for the system we study.sup.6, it is not yet possible to determine the stiction at such a solid-liquid interface using ab initio methods. The inorganic hybrid of hexagonal boron nitride and rhodium is very stable and represents a new class of switchable surfaces with the potential for application in the study of adhesion, friction and lubrication., Author(s): Stijn F. L. Mertens [sup.1] [sup.2] , Adrian Hemmi [sup.3] , Stefan Muff [sup.3] , Oliver Gröning [sup.4] , Steven De Feyter [sup.1] , Jürg Osterwalder [sup.3] , Thomas [...]

Byline: Alexis K. Ault (1,2), Jane Selverstone (1) Keywords: Alps; Fluid--rock reaction; Graphite; Titanite; Carbonic fluid; Embrittlement Abstract: Schists from two mylonitic localities in the footwall of a low-angle normal fault in the eastern Alps record different degrees of embrittlement during exhumation, depending on the extent to which fluid--rock reactions proceeded. At one site, graphitic schists preserve textural evidence for two metamorphic reactions that modified X.sub. CO.sub.2 and/or fluid volume: (1) reaction between graphite and aqueous fluid that increased X.sub. CO.sub.2 without changing the molar amount of fluid, and (2) replacement of titanite by rutile, calcite, and quartz. The latter reaction involved net consumption of increasingly CO.sub.2-rich fluid. Areas where the first reaction proceeded are associated with abundant Mode I microcracks. Fluid inclusion arrays within the microcracks show that X.sub. CO.sub.2 increased from [proportional to]0.1 to 0.6 during decompression from 4.75 to 2 kbar at a reference temperature of 500degC. Titanite consumption is most pronounced within transgranular Mode I microcracks, but microcracks do not crosscut products of this reaction fluid consumption during reaction was coeval with the end of microcracking, at least on a local scale. At the other site, graphitic schists lack small-scale Mode I cracks as well as evidence for graphite consumption during decompression. SEM imaging shows that graphite is anhedral and pitted at the first site, but occurs in clusters of euhedral grains at the second site. Mass balance calculations demonstrate that rocks with partially consumed graphite were infiltrated by an externally derived, [H.sub.2]O-rich fluid that drove subsequent graphite-fluid reaction. Evidence for similar fluid infiltration is absent at the second site. Variations in the degree of reaction progress indicate that fluid pathways and deformation style were heterogeneous on the scale of millimeters to kilometers during exhumation from mid-crustal depths. Author Affiliation: (1) Department of Earth and Planetary Sciences, University of New Mexico, MSC03 2040, Albuquerque, NM, 87131-0001, Mexico (2) Department of Geological Sciences, University of Colorado at Boulder, 2200 Colorado Ave, Boulder, CO, 80309, USA Article History: Registration Date: 17/03/2008 Received Date: 31/08/2007 Accepted Date: 17/03/2008 Online Date: 29/03/2008 Article note: Communicated by T.L. Grove.

Although water/oil-graphite emulsions are widely used in warm forging processes, they carry environmental concerns. In an attempt to replace graphite-based lubricants in warm forging of aluminum alloys, two variants of boron-nitride-silicone lubricants were formulated. The two variants were made by dispersing boron nitride powder in polydimethyl siloxane oil at concentrations of 1% and 8%. The formulated lubricants were initially tested for their thermal degradation characteristics using a thermogravimetric analyzer and compared to the thermal degradation behavior of graphite and silicone oil lubricants. Ring compression tests were then carried out at 260[degrees]C and 370[degrees]C. Boronnitride-silicone lubricant variants did not show significant difference in performance as die temperature was increased from 260[degrees]C to 370[degrees]C. This is in contrast to graphite, which performed much better at 260[degrees]C than at 370[degrees]C, due to thermal oxidation. On the other hand, silicone oil exhibited the worst performance at 260[degrees]C and the best performance at 370[degrees]C. In both boron nitride lubricant variants, the polydimethyl siloxane facilitated hydrostatic/hydrodynamic lubrication at 260[degrees]C, with boron nitride acting as a barrier film that reduced friction. However, the lubrication mechanisms changed at 370[degrees]C, where the depolymerization of polydimethyl siloxane led to formation of silica due to thermal oxidation. Silica, together with boron nitride, acted as a film barrier with low shear strength. The dual lubrication mechanisms make boron-nitride-silicone lubricants suitable for a wide range of aluminum forging temperatures. Keywords: warm forging, lubricant formulation, graphite lubrication, boron nitride

A study of the adsorption of atomic and molecular hydrogen on carbon-doped boron nitride nanotubes is conducted within the ab initio density functional theory. The binding energy of adsorbed hydrogen on carbon-doped boron nitride nanotube is substantially increased when compared with hydrogen on nondoped nanotube.

X-ray absorption near-edge structure (XANES) was used to study the cubic boron nitride (c-BN) content in the BN films deposited on various substrates by different physical vapor deposition or plasma-enhanced chemical vapor deposition methods. By fitting the XANES curves of thinfilm samples using standard spectra of pure c-BN and [sp.sup.2]-bonded BN in the films with suitable weight factors, the c-BN contents at the film's surface region and across the film's thickness have been determined quantitatively. The results agree well with the previous transmission electron microscopic observations. The method is proved to be independent of the optical properties of thin film and provides a possibility to evaluate the cubic content of BN films accurately.

The physisorption and chemisorption of hydrogen in boron nitride (BN) nanotubes are examined by density functional theory and compared with carbon nanotubes. The results have shown that perfect BN nanotubes are not good candidates for hydrogen storage by either mechanism and hence other strategies should be employed if BN nanotubes are to be employed as hydrogen storage media such as using them as supporting media for hydrogen-absorbing metal nanoclusters.

An effective method to remove obstinate boron nitride phase impurities in boron nitride nanotubes (BNNTs) was proposed. The results revealed that the impurities were effectively removed and the resultant BNNTs possessed perfect crystallization.

Calculations using density functional theory were carried out of a heavy carbene to a single-walled carbon (SWCNT) and boron nitride nanotubes (SWBNNT) in an effort to gain insight into activation energies and reaction enthalpies of chemical functionalization of carbon and boron nitride nanotubes. The theoretical observations indicated that all the SWCNT and SWBNNT cycloadducts favor opened rather than closed three-membered ring structures.

The distinctive features of cubic boron nitride (cBN) films grown on diamond are highlighted in contrast to those characteristics to cBN films prepared on silicon substrates is presented. Plasma enhanced chemical vapor deposition (PE CVD) assisted with fluorine chemistry enables growing cBN directly on diamond using a single presetting the deposition conditions at a bias of -10 V.

Specimen preparation method is developed to avoid the damage induced from ion milling for cross-sectional high-resolution transmission electron microscopy in order to investigate the cubic boron nitride (cBN) nucleation and growth mechanisms. It clearly reveals that cBN is nucleated and grows on the top surface, not in the subsurface of the turbostratic boron nitride layer, during chemical vapor deposition.

Periodic spindle-unit boron nitride (BN) nanotubes are obtained in addition to the regular cylindrical nanotubes. The new BN nanostructure is well characterized by high-resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray spectroscopy (EDX).

The synthesis and structural characterization of a novel graphitic tubular form of graphitic boron nitride (BN) displaying hollow conical-helix geometry is reported. A sole dynamic element, enthalpy or postheating temperature is found to determine the disclination configuration of helical-conical nanotubes (HCNTs).

The structure and stability of the (B12N12)n (n = 1, 2) cages are calculated at the B3LYP level of density functional theory. The most stable B24N24 structure deduced from the two B12N12 (Th) cages is found to have an unexpected tube form.

Boron nitride (BN) nanorings were synthesized using a sulfur vapor assisted solid-state method at 600 degree Celsius. High resolution transmission electron microscopy images proved that the nanorings were formed through the coiling of the (002) planes of hexagonal BN.

The isolation of individual boron nitride nanotubes (BNNTs) in aqueous phases is achieved from raw materials based on the combination of peptide wrapping with a sonication procedure. The modulation of the BNNT band gap with peptide wrapping has potential applications of the peptide/BNNT complexes to various nanotechnologies.

The first-principles computations are employed to study the interesting electronic and magnetic properties of fully and partially hydrogenated boron nitride nanoribbons (BNNRs). The electronic and magnetic properties of zigzag BNNRs accurately modulated by controlling the hydrogenation ratio, provided BN nanomaterials many potential applications in the novel integrated functional nanodevices.

Density functional theory calculations have used the local spin density approximation for characterizing triangle-shapes nanohole, nanodot and lattice antidote structures in hexagonal boron-nitride (h-BN) monolayer sheets. The studies have shown that despite lattice contraction due to the presence of multiple holes, antidote super lattices are predicted to be stable, displaying amplified magnetism as well as enhanced half-metallicity.

The first-principles calculations were performed to mechanism underlying the topologically adsorbed fluorine atoms on boron nitride nanotubes which induce long-ranged ferromagnetic spin ordering along the tube to offer strong spin polarization around the Fermi level. The piezomagnetic function and behavior of F-BNNTs offer a new route to facilitate the design of tunable spin devices.

First-principle calculations are used for predicting a novel, stable O-doped boron nitride nanotube (BNNT) configuration. The studies have provided evidence on the existence of O substitutional impurity-induced radiative transitions in BNNT systems.

A spin-polarized density functional theory is used to explore the adsorption and diffusion of carbon adatoms on boron nitride nanotubes (BNNTs) and BN hexagonal sheets. The effective interaction distance between the C-induced magnetic moments evaluated for the diffusion barrier and the adsorption energy of c adatoms on the BN nanotubes/sheets open route for possible fabrication of BN-C-based functional devices by C adsorption on BN nanostructures.

Boron nitride nanotubes (BNNTs), isosteres of carbon nanotubes (CNTs) with unique physical properties, are shown to be noncytoxic. The BNNTs can deliver DNA oligomers to the interior cells with no toxicity, suggesting that BNNTs are superior to CNTs for use as biological probes and in biomaterials.

The electronic structures and electron emission properties of alkali-doped boron-nitride nanotubes (BNNTs) are examined by using density-functional theory calculations. The studies have shown that the alkali-doped BNNT is an excellent electron emitter in terms of the large emission current as well as its chemical and mechanical stability.

The quantum and molecular dynamics simulations were performed on two finite length (5,5) nondefective and Stone-Wales (SW)-defective boron nitride nanotubes (BNNTs) to evaluate the effect of the SW defect on water behavior inside BNNT. Water in an SW-defective (5,5) BNNT was observed to have fewer translocation events, longer translocation time, and a higher axial diffusion coefficient compared to water in a nondefective (5,5) BNNT.

The equimolar mixture adsorption of [H.sub.2] and [D.sub.2] is simulated in selected single-walled carbon nanotubes (CNs) and boron nitride nanotubes (BNs) by using first-principle path integral grand canonical molecular simulations (PI-GCMC). The simulations have shown that in the interior space of both kinds of nanotubes, hydrogen isotopes have formed solid-like structures at 33 K and 10 Pa with densities above the compressed bulk para-hydrogen.

The electronic transport properties of heavily Si-implanted cubic (c-) BN films heteroepitaxially grown on top of diamond(001) are examined and their structure is controlled by Fourier transformed infrared (FTIR) spectroscopy. Temperature dependent Hall effect measurements have confirmed the n-type conduction for these heavily Si-implanted c-BN films.

The mechanisms involved in the aqueous noncovalent functionalization and controlled near-surface carbon doping of multiwalled boron nitride nanotubes (BNNTs) are studied. The doping of these BNNTs with carbon is shown to highly affect the electronic and mechanical properties of the system.

The computational studies of four reaction pathways from diborane and ammonia to borazine carried out to understand the minimum-energy pathway to borazine and to identify intermediates with sufficient stability to serve as precursors to boron nitride is presented.

Boron and nitrogen K-edge angle-resolved x-ray absorption near-edge structure are used to investigate the cubic boron nitride (c-BN) films synthesized by various energetic species assisted physical vapor deposition and chemical vapor deposition methods on Si and diamond-coated Si substrates. The rougher Si substrate is found to result in the decrease of the volume ratio of c-BN in the film compared with that on a mirror-polished Si substrate.

The gas-phase ion chemistry of B[F.sub.3]/N[H.sub.3] mixtures are examined by the joint application of mass-spectrometric techniques and theoretical methods. The species containing BN moiety might represent new promising projective ions in the boron nitride deposition techniques involving high-energy ion beams.

The geometrical structure, relative stability, and nitrogen chemical shifts of five boron nitride hollow octahedral cages are calculated using density functional theory. Results reveal how three typical ranges for nitrogen chemical shifts corresponding to each of the nonequivalent magnetic sites of the N atoms

Morphology dependence of cathodoluminescence (CL) from cubic boron nitride (cBN) is investigated by studying the Cl from different film positions, especially the surface pits and edge area. Raman measurements reveal that hexagonal boron nitride (hBN) grows in the pits and edge area and the peak position fluctuates between the two peaks depending on the hBN concentration in cBN films.

Boron nitride (BN) nanotubes are synthesized through chemical vapor deposition over a wafer made by a LaNi5/B mixture and nickel powder at 1473 K. Suggestions are given regarding the BN nanotubes where the possible existence of strong chemisorption of hydrogen leads to lower discharge capacity of the BN nanotubes.

Two boron nitride (BN) nanostructures, the bamboo-like nanotubes and nanothorns where the nanosize h-BN layers are randomly stacked looking like thorns were synthesized. The study suggests that the N enrichment would decrease the band gap of nanostructures from that of h-BN microcrystals.

For the purpose of understanding the properties of electronic structures of armchair (3,3) boron nitride BN tube and its possible growth mechanisms starting from B12N12, a possible smallest single-walled BN nanotube with the diameter of 0.4nm is proposed. The calculations show that the armchair (3,3) BN tube has a very close thermodynamic stability to and greater kinetic stability than the known zigzag (6,0) one.

Semiempirical MNDO and density functional theory is used to investigate the atomic arrangements, substitution patterns, and properties of BN doped C60 fullerence. The incoming BN group seeks the most highly charged carbon pairs. Up to twenty carbon pairs of C60 may be replaced by heteroatoms.

The substrate pretreatment conditions required for the deposition of cubic boron nitride films without an interfacial amorphous layer is determined by investigating nanostructures, chemical composition, and bonding states of the amorphous layer. The native oxide layer and the ion bombardment effects are found to be cause for the formation of the amorphous layer.

Nanostructures of the turbo-stratic boron nitride (tBN) transition layer in cubic BN (cBN) thin films deposited on silicon substrates by low pressure inductively coupled plasma enhanced chemical vapor deposition are studied by means of cross sectional high resolution transmission electron microscopy. Rhombohedral and hexagonal configurations of boron nitride, and the transformation between rBN and hBN due to dislocation were observed in the BN transition layer.

Reactivities of hydrogen atom/ions with different carbon and boron nitride (BN) phases are studied by means of frontier orbital theory based on ab initio Hartree-Fock calculations. The results show that there is a significant difference in the reactivity of atomic hydrogen with the sp(super 2) and the sp(super 3) carbon phases such that phase selectivity is facilitated during chemical vapor deposition of diamond.

Molecular dynamics simulations are conducted on a finite length (5,5) BNNT and (5,5) CNT, with a diameter of 6.9 angstrom and length of 14.2 angstrom to study the water permeability of boron nitride nanotubes (BNNTs). Results reveal similar water transport properties in a (5,5) as found in a (6,6) carbon nanotube (CNT).

The effect of immobilization of proteins on boron nitride nanotubes (BNNTs) is studied and the immobilization is thought to be due to carboxylation of BNNT-bound amino groups or prominent tube/protein electrostatic interactions. Noncovalently functionalized BNNTs are used for the most effective immobilization.

Highly pure boron nitride nanotubes (BNNTs) are synthesized at high yield by a carbon-free chemical vapor deposition method and are functionalized by wrapping them with a conjugated polymer, poly[m-phenylenevinylene-co-(2,5-dioctoxy-p-phenylenevinylene)] (PmPV). These polymer-wrapped soluble BNNTs have numerous applications in composites and optical devices due to good dispersion and unique luminescence properties.