The effect of laser surface treatment of Al-Si alloy on the surface hardness and structure

In this paper, some samples of Al-Si alloy with various silicon content were treated by laser beam. The effects on structure, hardness and substructure of samples were investigated. The experimental results show that the primary crystal Al and eutectic silicon in the laser treated samples is got thinning obviously, the mosaic dimension is decreased and the dislocation density is increased.     

Closely packed dense frequency selective surface

In order to realize wideband filtering properties of frequency selective surface(FSS),FSS of closely packed elements is presented.The Y loop elements are chosen as the graphics elements.Based on the spectral domain method,the frequency response is analyzed for different incident angles and polarizations.The result of the numerical analysis shows that the dense FSS has wide passband with better independence of angle and polarization.     

How old is surface science?

Philosophical and literary testimonies from the Classical World (5th century b.c. to 3rd century a.d.) involving solid surfaces are reviewed. Plato thought the surface to be a real entity, whereas Aristotle considered it to possess an unqualified existence, i.e. not to be a substance, but just an accidental entity. The Old Stoics asserted that surfaces do not possess any physical existence, although the Stoic philosopher Posidonius—apparently the only exception in his school—held them to exist both in thought and reality. While both the Atomists and the Epicureans were very little interested in them, the Sceptic philosopher Sextus Empiricus considered surfaces to be the limits of a body, although he maintained that both the view that they are corporeal or the view that they are incorporeal present unsurmountable difficulties.Among Roman authors, the testimony from Pliny the Elder is mostly concerned with metallic surfaces, chemical change occurring there, and surface treatments used in antiquity.Besides the philosophical motivations, the implications of the testimonies are discussed in the light of surface science. The purely geometrical surface of Plato is found to compare favorably to single-crystal surface, Posidonius’ “corporeal” surface is best likened to an air-oxidized, or otherwise ambient-modified surface, and ancient accounts on mixture are compared to XPS results obtained in adhesion studies of enameled steels. I argue that the long-standing dominance of Aristotle’s view from antiquity onwards may have had a part in delaying theoretical speculation into solid surfaces.     

Study on surface acoustic wave rotary motors

On the surface of 128° yx-LiNbO3 substrate, two pairs of Inter-Digital Transducers (IDTs) are parallelly arranged in the propagation direction, which is a stator of surface acoustic wave (SAW) rotary motors. A plastic disk with small balls distributed around the circumference is a rotor. When a high frequency voltage is inputted to two IDTs, two Rayleigh wave beams are generated and are propagating on the substrate in opposite directions with each other. The resulting local relative motion between the particles of the stator and the balls produces two inverse frictional forces to form a moment to drive the rotor. The experimental results and theoretical analysis and calculation for two operating frequencies are accomplished and discussed.     

Temperature dependence in atom–surface scattering

It is shown that a straightforward measure of the temperature dependence of energy resolved atom–surface scattering spectra measured under classical conditions can be related to the strength of the surface corrugation. Using classical perturbation theory combined with a Langevin bath formalism for describing energy transfer, explicit expressions for the scattering probabilities are obtained for both two-dimensional, in-plane scattering and full three-dimensional scattering. For strong surface corrugations results expressed as analytic closed-form equations for the scattering probability are derived which demonstrate that the temperature dependence of the scattering probability weakens with increasing corrugation strength. The relationship to the inelastic rainbow is briefly discussed.     

New “surface” criterion of melting

From the assumption that the pressure exerted on the nanocrystal surface under melting passes into the Laplace surface pressure, an expression for a relative volume within which the solid phase of the nanosystem remains stable at different pressures is derived. It is shown that such a “surface” criterion of melting slightly depends on the crystal size and external pressure and is determined solely by the interatomic potential parameters. Calculations for macrocrystals with van der Waals bonding demonstrate good agreement with experimental data for the relative crystal volume at the melting point.     

Distributed optical fiber surface plasmon resonance sensors

The relationships of the resonant wavelength of optical fiber surface plasmon resonance (SPR) sensors to the modulation layer refractive index, thickness and the refractive index of the bulk medium are obtained by using theoretical calculation model of optical fiber SPR sensors under certain conditions, which indicates that resonant wavelength of the sensors is approximately linear with modulation layer thickness. Based on the linear relationship, multiple SPR sensors with different resonant wavelengths can be fabricated in a single optical fiber named as distributed optical fiber surface plasmon resonance sensors (DOFSPRSs). Experimental results are presented, showing that it is practical to fabricate more than one SPR sensors in a single optical fiber.     

Numerical investigation of the enhanced unidirectional surface plasmon polaritons generator~Numerical investigation of the enhanced unidirectional surface plasmon polaritons generator~Numerical investigation of the enhanced unidirectional surface plasmon polaritons generator

A unidirectional surface plasmon polaritons （SPPs） generator with greatly enhanced generation efficiency is proposed. The SPPs generator consists of an asymmetric single nanoslit coated with a polyviny alcohol （PVA） film and a silver rectangle block. The generation efficiency of this SPPs generator is investigated using the finite difference time domain method. Due to the presence of the silver rectangle block, the SPPs generation efficiency of the asymmetric single nanoslit with PVA film can be greatly enhanced and the corresponding wavelength with the maximum enhancement factor can be tuned flexibly. The influence of the structural parameters on the generation efficiency is also investigated for the enhanced unidirectional SPPs generator.     

Scattering of O? from a graphite surface

Recently an extensive series of measurements has been presented for the angular distributions of oxygen molecules scattered from a graphite surface. Incident translational energies ranged from 291 to 614 meV with surface temperatures from 150 to 500 K. The measurements were taken with a fixed angle of 90° between the source beam and the detector and the angular distributions consisted of a single broad peak with the most probable intensity located at an angle slightly larger than the 45° specular position. Analysis with the hard cubes model for atom-surface scattering indicated that the scattering is primarily a single collision event with a surface having a collective effective mass much larger than a single carbon atom. Limited analysis with a classical diatomic molecular scattering theory was also presented. In this paper a more complete analysis using the classical diatomic molecular scattering theory is presented. The energy and temperature dependence of the observed angular distributions are well described as single collision events with a surface having an effective mass of 1.8 carbon graphite rings. In agreement with the earlier analysis and with other experiments, this suggests a large cooperative response of the carbon atoms in the outermost graphene layer.     

Dynamical van der Waals atom–surface interaction

We obtained new nonrelativistic expression for the dynamical van der Waals atom–surface interaction energy of a very convenient form for different applications. It is shown that classical result (Ferrell and Ritchie, 1980) holds only for a very slowly moving atom. In general case, the van der Waals atom–surface interaction energy manifests strong nonlinear dependence on the velocity and distance. In close vicinity of metal and dielectric surfaces and velocities ranging from 1 to 10 bohr units the dynamical van der Waals potential proves to be several times lower than in the static case and goes to the static values with increasing the distance and (or) decreasing the velocity.     

Frequency selective surface with a flat topped passband

Two frequency selective surface (FSS) configurations with flat topped passband are presented in this paper. One configuration is single layer FSS with,λ/4 thickness dielectric loaded on both sides,and the other is double layers FSS.Based on the modal matching method,the frequency response properties including angle effect and polarization effect of both FSS configurations are analyzed,and the plots of the frequency versus transmission coefficient are obtained for different incident angles and polarizations.It is shown that the structure with the single layer FSS embedded centrally in the ,k/2 thickness dielectric has a wider flat top bandwidth of 6.8 GHz than that of the double layers FSS of 3 GHz.In addition,the fabrication of single layer is relatively easier than the double layers FSS.     

A coordinate–spectral method for rough surface scattering

Abstract

In this paper, we deal with the time-harmonic scattering by one-dimensional rough surfaces separating two homogeneous and isotropic media. The method is based on a rigorous integral formalism. The unknown of the integral equation is projected onto a Fourier basis while the equation itself is sampled as in a classical method of moments. The accuracy is tested against both other methods and experimental results. One of the main interests in choosing a Fourier basis lies in the ability to solve rigorously the scattering of a p polarized incident beam by a shallow metallic rough surface. The role of the surface waves is accurately taken into account and phenomena such as enhanced backscattering are well described. With this method, one can consider that the gap between the domain of validity of perturbation theories and the domain of practical use of rigorous methods is filled.     

The interaction between multiple bubbles and the free surface

The flow is assumed to be potential, and a boundary integral method is used to solve the Laplace equation for the velocity potential to investigate the shape and the position of the bubble. A 3D code to study the bubble dynamics is developed, and the calculation results agree well with the experimental data. Numerical analyses are carried out for the interaction between multiple bubbles near the free surface including in-phase and out-of-phase bubbles. The calculation result shows that the bubble period increases with the decrease of the distance between bubble centres because of the depression effect between multiple bubbles. The depression has no relationship with the free surface and it is more apparent for out-of-phase bubbles. There are great differences in dynamic behaviour between the in-phase bubbles and the out-of-phase bubbles due to the depression effect. Furthermore, the interaction among eight bubbles is simulated with a three-dlmensional model, and the evolving process and the relevant physical phenomena are presented. These phenomena can give a reference to the future work on the power of bubbles induced by multiple charges exploding simultaneously or continuously.     

A “hydrodynamic” theory of surface reaction rates

The Brownian motion of adsorbed particles is described in terms of the first four velocity moments of the distribution function (number density, momentum density, energy density and energy current density). The resulting hydrodynamic equations turn out to be sufficient for a simple derivation and extension of Kramers' results for chemical reaction rates in terms of the friction constant of an underlying Fokker-Planck equation. An interpolation formula is obtained for() containing Kramers' results for small and large as limiting cases. For temperaturesT small compared to the well depthV ₀ one finds a large regionT/V ₀/v ₀V ₀/T in which Eyring's absolute rate theory is approximately valid.On leave of absence from Physikdepartment der TUM, München-Garching     

Formation of graphene on Ru（0001） surface

We report on the formation of a graphene monolayer on a Ru(0001) surface by annealing the Ru(0001) crystal. The samples are characterized by scanning tunnelling microscopy (STM) and Auger electron spectroscopy (AES). STM images show that the Moir\'{e} pattern is caused by the graphene layer mismatched with the underlying Ru(0001) surface and has an $N\times N$ superlattice. It is further found that the graphene monolayer on a Ru(0001) surface is very stable at high temperatures. Our results provide a simple and convenient method to produce a graphene monolayer on the Ru(0001) surface, which is used as a template for fabricating functional nanostructures needed in future nano devices and catalysis.     

The specific acoustic impedance of aperture on cylindrical surface

The acoustic impedance caused by sound radiation at the terminals ofthe aperturc on cylindrical surface is analyzed based upon rigorous soundtheory.In low frequency range,the approximate solution of the specific acousticresistance is derived.Special treatments are introduced in order to simplify the so-lution of the specific acoustic reactance.It is verified that the specific acousticreactancc of such an aperture is equal to that of a similar aperture on the infinitelylarge plane when the small quantities of high order are neglected.     

Phenolic polymer–surface interactions from ab initio computations

Test calculations show that the diamond surface binding energy of C₁₃H₁₁O₂, the simplest model for phenolic, is virtually the same as that of C₆H₅. Using the C₆H₅ model, we compare the binding to a diamond surface, a graphene sheet, a (10, 0) nanotube, and a silica surface. The binding energy is more than 5?eV for the silica and 2.85?eV for the diamond surface. As expected, the binding energy of a second molecule at a site adjacent to the first molecule is larger than the first binding energy for the graphene sheet and the carbon nanotube, since the first C₆H₅ bond breaks a π bond and the second molecule bonds to the unpaired π electron created by adding the first molecule. For all of the systems, adding a C₂ unit between the surface and the C₆H₅ group increases the binding by at least 0.51?eV and up to 2.3?eV. Part of this increase is due to the intrinsically stronger bonding for the sp hybridization and part due to a decrease in the surface–C₆H₅ repulsion.     

Chemisorption of Au on Si（001） surface

The chemisorption of one monolayer of Au atoms on an ideal Si(001) surface is studied by using the self-consistent tight binding linear muffin-tin orbital method. Energies of the adsorption system of a Au atom on different sites are calculated. It is found that the most stable position is A site (top site) for the adsorbed Au atoms above the Si(001) surface. It is possible for the adsorbed Au atoms to sit below the Si(001) surface at the B_1 site(bridge site), resulting in a Au－Si mixed layer. This is in agreement with the experiment results. The layer projected density of states is calculated and compared with that of the clean surface. The charge transfer is also investigated.     

Magnetically tunable Airy-like beam of magnetostatic surface spin waves

In this Letter,we report an Airy-like beam of magnetostatic surface spin wave(Ai BMSSW)supported on the ferromagnetic film,which is transferred from the optical field.The propagation properties of Ai BMSSW were verified with micromagnetic simulation.From simulation results,the typical parabolic trajectory of the Airy-type beam was observed with an exciting source encoding 3/2 phase pattern.The simulation results coincide well with design parameters.Furthermore,simulated results showed that the trajectories of the Ai BMSSW could be tuned readily with varied external magnetic fields.This work can extend the application scenario of spin waves.     

Fabrication of superhydrophobic nanostructured surface on aluminum alloy

A superhydrophobic surface was prepared by consecutive immersion in boiling water and sputtering of polytetrafluoroethylene (PTFE or Teflon®) on the surface of an aluminum alloy substrate. Immersion in boiling water was used to create a micro-nanostructure on the alloy substrate. Then, the rough surface was coated with RF-sputtered Teflon film. The immersion time in boiling water plays an important role in surface morphology and water repellency of the deposited Teflon coating. Scanning electron microscopy images showed a “flower-like” structure in first few minutes of immersion. And as the immersion time lengthened, a “cornflake” structure appeared. FTIR analyses of Teflon-like coating deposited on water treated aluminum alloy surfaces showed fluorinated groups, which effectively reduce surface energy. The Teflon-like coating deposited on a rough surface achieved with five-minute immersion in boiling water provided a high static contact angle (～164°) and low contact angle hysteresis (～4°).