Search results for "Interfaces"
showing 10 items of 1258 documents
Reconstructed bcc Co films on the surface
2007
Abstract Ultrathin epitaxial Co films on Cr ( 1 1 0 ) are examined by scanning tunneling microscopy and spectroscopy (STM and STS). At room temperature Co grows as pseudomorphic bcc layers for the first two monolayers and forms close-packed Co layers with stacking faults for thicker coverages. A periodic lattice distortion appears in two equivalent (3 × 1) reconstruction domains in combination with a regular lattice of dislocation lines oriented along the in-plane close-packed row directions bcc [ 1 1 ¯ 1 ] and bcc [ 1 ¯ 1 1 ] . The reconstruction and the occurrence of dislocation lines are caused by the epitaxial strain. The local density-of-states function is mapped by scanning tunneling …
Strain effects and phonon-plasmon coupled modes in Si-doped AlN
2009
The E 2h and A 1 (LO) phonon modes of AlN films grown on sapphire are analyzed by Raman scattering as a function of silicon doping for concentrations covering from 5.5 x 10 19 cm ―3 to 5.2 x 10 21 cm ―3 . For high doping levels the appearance of a mode around 520 cm ―1 indicates the precipitation of crystalline silicon in the samples and its inhomogeneous incorporation to the AlN layer. The frequency of this mode shifts to lower energies with doping, indicating that the silicon crystals are embedded in the AlN lattice and under tensile strain. On the other hand, the AlN phonon modes are blue-shifted due to the compressive strain as a result of the silicon incorporation. This strain is parti…
Experimental investigation of the influence of adhesion on the frictional conditions in the cutting process
1999
Abstract This paper presents the results of an experimental study on the influence of adhesion on the tribological characteristics of the tool-chip interface. It was established that under orthogonal cutting conditions both the high interface temperature and severe plastic deformation result in relatively strong adhesion between steel and uncoated carbide. In particular, the molecular–mechanical theory of friction was applied to estimate the shear strength of the local adhesive junction, and to divided the rake face friction into two terms—an adhesion term (the interfacial coefficient of friction) and the deformation term. It should be pointed out that the data obtained provide a new approa…
Study and evaluation of fretting critical slip conditions by applying the design of experiments method
2006
Tribological systems are complex systems that require a multi-disciplinary (mechanical, material, physico-chemical) approach where numerous influence factors can be involved. To characterize a contact couple, the intrinsic parameters of the materials as well as the parameters related to the contact loading and the surrounding environment need to be taken into account. Fretting analysis, by means of running condition-fretting maps (RCFM), allows the behavior of the contact couple to be taken into account and to predict the boundary between partial slip and gross slip conditions. This article presents the study of a steel/polycarbonate couple during fretting tests. The study was carried out b…
The influence of Al doping on the photocatalytic activity of nanostructured ZnO: The role of adsorbed water
2018
Abstract Al doped ZnO nanoparticles (labeled as x% A-ZnO, x = 0.0, 0.5, 1.0, and 1.5) were synthesized by a simple sol-gel method, characterized and tested as photocatalysts for the degradation of a model compound under UV-light irradiation. Diffuse reflectance spectroscopy (DRS) and photoelectrochemical analysis have been performed to evidence their optical and electronic behavior. The structural features of the powders were highlighted by means of specific surface area (SSA) analysis, X-ray diffraction (XRD), Fourier-transform infrared (FTIR) and Raman spectroscopy. Al doping results in enhanced photocatalytic activity of the modified powders with respect to pure ZnO. In particular, the h…
Photocatalytic degradation enhancement in pickering emulsions stabilized by solid particles of bare TiO 2
2019
Pickering emulsions provide a new way to enhance the efficiency of photocatalytic degradation of water-insoluble pollutants. Indeed, the semiconductor solid particles dually act as the photocatalyst and stabilizer of the emulsion droplets whose size dramatically affects the photocatalytic reaction. The present work aims at the validation of this concept by using bare TiO 2 without any surface modification. Nanostructured TiO 2 has been prepared by a simple sol-gel process and characterized by X-ray diffraction, specific surface area analysis, scanning electron microscopy, and diffuse reflectance spectroscopy. The emulsions were prepared by using 1-methylnaphthalene (1-MN) as a model organic…
Comparative study of air and vacuum annealing atmosphere towards Pt/Ti–W/SiO2 stability
2013
Abstract The thermal stability of Pt/Ti–W/SiO2 system was studied after annealing under air or vacuum in the present work. A Ti–W adhesive film (30 at. % Ti) was deposited on a SiO2 substrate followed by a thicker Pt layer. Depositions were performed using DC magnetron sputtering. The whole as-deposited films are metallic with a columnar growth of platinum deposit which totally wets the substrate. Whatever the atmosphere is, annealing at 500 °C for 12 h does not change the platinum state but modifies the morphology of platinum particles, the lateral average size of which increasing from less than 10 nm up to ca. 75 nm. Besides, a noticeable diffusion of metallic tungsten through Pt film is …
Imbibition of Femtoliter-Scale DNA-Rich Aqueous Droplets into Porous Nylon Substrates by Molecular Printing
2019
This work presents the first reported imbibition mechanism of femtoliter (fL)-scale droplets produced by microchannel cantilever spotting (μCS) of DNA molecular inks into porous substrates (hydrophilic nylon). Differently from macroscopic or picoliter droplets, the downscaling to the fL-size leads to an imbibition process controlled by the subtle interplay of evaporation, spreading, viscosity, and capillarity, with gravitational forces being quasi-negligible. In particular, the minimization of droplet evaporation, surface tension, and viscosity allows for a reproducible droplet imbibition process. The dwell time on the nylon surface permits further tuning of the droplet lateral size, in acc…
Growth and characterization of AP-MOCVD iron doped titanium dioxide thin films
1999
Abstract Atmospheric pressure metal organic chemical vapor deposition (AP-MOCVD) was used to prepare iron doped titanium dioxide thin films. Thin films, between 40 and 150 nm thick, were deposited on Si, SiO 2 and Al 2 O 3 substrates using titanium tetra isopropoxide and ferrocene as metal organic precursors. TiO 2 iron doping was achieved in the range of 1–4 at.%. The film morphology and thickness, polycrystalline texture and doping content were studied using respectively scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The influence of growth temperature, deposition time, substrate type and dopant partial pressure were studied. Electr…
Mn2+-induced room-temperature ferromagnetism and spin-glass behavior in hydrothermally grown Mn-doped ZnO nanorods
2014
The magnetic properties of Mn-doped ZnO (ZnO:Mn) nanorods grown by hydrothermal process at a temperature of 200 °C and a growth time of 3 h have been studied. The samples were characterized by using powder X-ray diffraction with Rietveld refinement, scanning electron microscopy, energy-dispersive X-ray analysis and SQUID magnetometry. Mn (3 wt%) and (5 wt%)-doped ZnO samples exhibit paramagnetic and ferromagnetic behavior, respectively, at room temperature. The spin-glass behavior is observed from the samples with respect to the decrease of temperature. At 10 K, both samples exhibit a hysteresis loop with relatively low coercivity. The room-temperature ferromagnetism in 5 wt% Mn-doped ZnO n…