Search results for "Surfaces"
showing 10 items of 2837 documents
Reactive sputtering of nanostructured multilayer coatings and their tribological properties
1999
Abstract The present study describes and reports on reactive sputtering of nanostructured multilayer coatings. A 3 μm coating for instance may contain up to a few thousand bilayers of two different film materials, and in order to achieve this, a substrate holder rotates through two different sputtering zones in an Alcatel SC 650 sputtering equipment with metal and carbon cathodes operating concurrently in the so-called side-by-side configuration. In reactive sputtering of nitrides, reactive nitrogen was controlled very accurately in order to establish controllable points on a total sputtering pressure versus nitrogen flow curve. Nanostructured multilayer coatings of the type MeN/C–N were de…
Microstructural corrosion of aluminium alloys: a predictive finite element model based on corrosion-mimicking experiments
2013
The purpose of this study is to implement the basis of a finite element model (FEM) based on the resolution of the Nernst–Planck equation in order to progress in the predictive simulation of microstructural corrosion on aluminium alloys. Certain constituent intermetallic particles at the surface of aluminium alloys are considered as preferential sites for the initiation of structural corrosion resulting in localised trenching around the particles and the surrounding Al matrix. In this work, a modified scanning electrochemical microscope (SECM) experiment was used to induce such phenomena via a local alkalinization on 200 nm thick aluminium coatings, promoting their local dissolution in an a…
Effect of microstructure and chemical composition on localized corrosion resistance of a AISI 304L stainless steel after nanopulsed-laser surface mel…
2015
Abstract Changes induced in the surface properties of AISI 304L stainless steel when it is treated with a nanopulsed ytterbium-doped fiber laser were investigated to determine the microscale distribution of its physico-chemical properties. A Gaussian energy distribution was created with a radius of 71 μm (1/e2) at the focal point. Local investigations were carried out using transmission electron microscopy to consider the effect of overlapping individual laser impacts. The results obtained reveal that laser surface melting leads to changes in the crystallographic structure of the steel through the formation of a δ-ferritic phase. It also results in the creation of an oxide layer that increa…
Numerical support for laser welding of zinc-coated sheets process development
2002
Abstract A lap welding process for zinc-coated sheets has been developed with the help of numerical simulations. This process has been improved and is now compatible with industrial requirements. The zinc boiling point (1180 K) is lower than the steel melting point (1800 K). Consequently, a violent boiling of zinc in melted steel produces serious defects in the seam. To get round this difficulty, we choose to consider a two-spots process: the first spot vaporizes the zinc coating at the interface; the second one welds the sheets. Previously, we develop a numerical model that permits a process parameters choice and limits the plan of experimentations. The zinc ablation spotlight shape is cho…
WEAR MECHANISM OF CERAMIC TOOLS
1993
Abstract Cutting tests were performed using ceramic cutting tools under continuous cutting conditions. The tests were carried out on AISI 1040 steel, with cutting speeds ranging from 5 to 11 m s −1 . The wear mechanism was investigated for both crater and flank. Alumina-toughened zirconia of submicron grain size showed the best wear resistance. Alumina with TiC, TiN and ZrO 2 inclusions exhibited a wear resistance a little lower than the above-mentioned materials. Low chemical stability seems to be the reason for the poor performances of the silicon carbide whiskers-reinforced alumina, silicon nitride and the tungsten carbide inserts.
Corrosion resistance of the vacuum arc deposited Ti, TiN and TiO2 coatings on large area glass substrates
2000
An industrial installation for vacuum arc deposition is presented. Its potential in the field of decorative coatings for large area glass sheets is demonstrated. In particular it is possible to deposit patterned coatings through a polymeric textile mask. The ability to deposit uniform multilayer coatings having interference colours onto large silicate glass sheets is shown. Titanium, titanium nitride and titanium dioxide coatings on silicate glass have been characterized in terms of composition and corrosion resistance. Depth profiling was achieved with the aid of Auger electron spectroscopy. The corrosion resistance of TiN coatings is higher than that of TiO 2 . The corrosion resistance of…
WC-based thin films obtained by reactive radio-frequency magnetron sputtering using W target and methane gas
2015
Abstract Deposition of tungsten carbide (WC) films was investigated by radio-frequency reactive sputtering using a tungsten target and methane gas. The effect of some processing parameters (pressure, power, CH 4 -to-Ar gas flow ratio) upon the chemical and structural properties of the films has been investigated. The evolution of the chemical composition has been analyzed by photoemission, the microstructure has been studied through electron microscopy techniques and the crystallographic structure was investigated by X-ray diffraction as well as Raman spectroscopy. This study demonstrates that the formation of tungsten carbide is highly dependent on the deposition conditions: thin films are…
Two-dimensional self-assembly of disulfide functionalized bis-acylurea: a nanosheet template for gold nanoparticle arrays.
2010
A new functional bis-acylurea molecule allows a two-stage self-organization process. It self-organizes--at first--into 2D nanosheets with disulfide groups at the surface, which act--in the second stage--as a template for gold nanoparticle arrays.
Self-assembly of amphiphilic imidazolium-based hexa-peri-hexabenzo-coronenes into fibreous aggregates
2007
Imidazolium-based amphiphilic hexa-peri-hexabenzocoronenes were synthesized and shown to undergo ordered columnar self-assembly in solid-state as well as in solution to yield defined nanofibers upon solution drop casting onto solid substrate.
Low temperature catalytic combustion of propane over Pt-based catalyst with inverse opal microstructure in microchannel reactor
2007
A novel Pt-based catalyst with highly regular, periodic inverse opal microstructure was fabricated in a microchannel reactor, and catalytic testing revealed excellent conversion and stable activity for propane combustion at low temperatures.