Search results for "Interfaces"

Effect of antisite defects on the magnetic properties of ZnFe2 O4

2013

Magnetic zinc ferrite (ZnFe2O4) nanopowders were synthesized using the sol–gel autocombustion method. X-ray diffraction (XRD) and scanning electron microscopy (SEM) measurements demonstrated that thermal decomposition of the 1-mm-thick xerogel layers in air formed monophasic spinel ferrite nanopowders with a particle size less than 30 nm. X-ray photoelectron spectroscopy (XPS) showed that the obtained reaction product contained antisite defects, with zinc ions occurring at the octahedral sites of the spinel structure. The concentration of antisite defects or inversion degree decreased when the relatively low annealing temperature was increased from 150 to 500 °C. Overall, the obtained ZnFe2…

Back Cover (Phys. Status Solidi A 12/2009)

2009

White Etching Crack Root Cause Investigations

2014

White etching crack (WEC) failure is distinct to classical fatigue and driven by the composition of lubricants under special loading conditions; for example, slippage and electricity. The white etching area (WEA) within WEC contains carbon supersaturated ferrite (bcc-iron) and carbides, with a size of a few nanometers. This article presents investigations supporting the hypothesis that WEC processes start within a failure-free period by successive accumulation of a structural distortion. This can be measured by acoustic emission. Failure statistics show a steep ascent in the Weibull diagram (s values beyond 1) leading to the assumption that WEC processes start unsuspicious, as one would see…

Frictional behaviour of oxygen diffusion hardened titanium in dry sliding against Co–28Cr–5W–4Fe–3Ni–1Si cobalt alloy

2004

Abstract The results of conformal pin-on-disc tribological tests of a hard layer of the solid solution of oxygen in α-titanium sliding against a Co–28Cr–5W–4Fe–3Ni–1Si cobalt alloy counterspecimen are presented. The α-Ti(O) layer was diffusely produced over 2–8 h of oxidising in the superficial zone of a technical quality titanium specimen. The friction and wear responses of the system were recorded and the wear mechanisms were studied. Investigations of the material structure and chemical constitution in micro-areas of the titanium specimen, cobalt alloy counterspecimen and wear debris formed in dry sliding were performed with a Philips XL20 microscope equipped with an EDAX analyser. Crush…

Microsphere tensiometry to measure advancing and receding contact angles on individual particles

1999

In this paper, a method to measure the advancing and receding contact angles on individual colloidal spheres is described. For this purpose, the microspheres were attached to atomic force microscope cantilevers. Then the distance to which the microsphere jumps into its equilibrium position at the air-liquid interface of a drop or an air bubble was measured. From these distances the contact angles were calculated. To test the method, experiments were done with silanized silica spheres (4.1 μm in diameter). From the experiments with drops, an advancing contact angle of 101 ± 4° was determined. A receding contact angle of 101 ± 2° was calculated from the jump-in distance into a bubble. Both ex…

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.