Search results for "engineering.material"
showing 10 items of 2352 documents
Spectroscopic studies of Cr3+ ions in natural single crystal of magnesium aluminate spinel MgAl2O4
2021
Abstract The natural spinel crystal MgAl2O4 containing the Cr3+ ions was studied experimentally and theoretically in this paper. The absorption and emission spectra at room and low temperatures were recorded. The experimental spectroscopic results were aided with the crystal field calculations, which returned the energy level schemes of the Cr3+ ions at the Al sites with the local D3d symmetry. Effects of the trigonal crystal field were clearly seen in the calculated results, which were compared with the experimental spectra to yield a good agreement between both data sets.
Corrosion Protection of Steel with Oxide Nanolaminates Grown by Atomic Layer Deposition
2011
Atomic layer deposited (ALD) aluminum and tantalum oxide (Al 2 O 3 and Ta 2 O 5 ) and their nanolaminates were applied as corrosion protection coatings on AISI 52100 steel. The aim was to combine the good sealing properties of Al 2 O 3 with the chemical stability of Ta 2 O 5 and to optimize the coating architecture in order to obtain the best possible long-term durability. Coating composition and morphology were studied with time-of-flight elastic recoil detection analysis (ToF-ERDA), time-of-flight secondary ion mass spectrometry (ToF-SIMS) and field emission scanning electron microscopy (FESEM) and energy dispersive x-ray spectrometry (EDS). Electrochemical properties were studied with vo…
Effects of electrolyte doping on electrodeposited nanostructured manganese oxide and chromium oxide
2020
Abstract Electrolyte additions are used to control the functionality of a nanostructured oxide. Dopant ions affect the size and shape of deposit crystallites and modify the host structure. Such ions can be incorporated into the deposit or form a separate oxide phase. The manganese dioxide family of polymorphs with ion-molecular sieve properties represents the additional possibilities of “template” effects of dopant ions on the phase composition, heterovalent substitution in the cationic sublattice, changes in morphology and alteration of nanocrystallite size during electrocrystallisation. The effects of electrolyte doping in electrodeposited, non-stoichiometric manganese dioxide (NH4+, Li+ …
Oxide-based nanomaterials for fuel cell catalysis:the interplay between supported single Pt atoms and particles
2017
The concept of single atom catalysis offers maximum noble metal efficiency for the development of low-cost catalytic materials. Among possible applications are catalytic materials for proton exchange membrane fuel cells. In the present review, recent efforts towards the fabrication of single atom catalysts on nanostructured ceria and their reactivity are discussed in the prospect of their employment as anode catalysts. The remarkable performance and the durability of the ceria-based anode catalysts with ultra-low Pt loading result from the interplay between two states associated with supported atomically dispersed Pt and sub-nanometer Pt particles. The occurrence of these two states is a co…
X-ray micro-tomography based FEM modelling of hygroexpansion in PLA composites reinforced with birch pulp fibres
2017
This article presents a microscale modelling approach coupled with X-ray computed micro-tomography for the evaluation of material properties of polylactic acid (PLA) reinforced by birch pulp fibers under the effect of moisture. The results in terms of elastic moduli and hygroexpansion deformation were found in good agreement with the measurements taken at different levels of water uptake.
Laser densification of organic coating: Effects of laser wavelength, operating parameters and substrate properties
2012
International audience; Mechanical bonding and interface behaviour play a key role for any materials deposited on different substrates. Usually, a post-spray heat treatment is required to improve the coating morphology and to enhance mechanical properties of thermal-sprayed polymeric coating. The effects of YAG, CO2 and diode laser radiations on as-sprayed PEEK coating deposited on stainless steel and aluminum substrates were investigated. The results revealed a good coating densification and interface behavior. A correlation between coating and substrate absorption coefficients, their thermophysical properties and laser operating parameters was shown. Besides, the finite element modeling b…
Photothermal Ablation of Cancer Cells Using Folate-Coated Gold/ Graphene Oxide Composite
2017
Objective: A new tumor targeted polymer-coated gold/graphene hybrid has been developed for achieving simultaneously thermoablation and chemoterapy of folate receptor-positive cancer cells. Methods: The gold/graphene hybrid was prepared by depositing gold nanospheres onto graphene oxide and coating it with an inulin-folate conjugate. Paclitaxel was loaded by sonication. The hybrid was characterized by UV-Vis spectroscopy, DSC analysis and SEM microscopy. The cytotoxicity, thermoablation and anticancer activity were evaluated in vitro on MCF-7 and 16 HBE. Results: In vitro tests showed that the paclitaxel-loaded hybrid improved the effectiveness of the drug especially after photothermal treat…
A methodology for the rapid characterization of Mode II delamination fatigue threshold in FRP composites
2019
Abstract A new methodology to measure the Mode II interlaminar fracture in fatigue for FRP composites is developed. The proposed methodology uses a Modified Transvers Crack Tensile (MTCT) specimen and is able to characterize the near threshold behavior in a robust, easier and significantly faster way than standard procedures. Analytical formulae, able to link the crack growth rate to the load or strain amplitudes, were found and verified, and their importance was explained, in particular, for what concerns the characterisation of the near threshold behavior. Experiments were performed both in load and strain control, while the delamination growth was monitored using different techniques inc…
Macroscopic and local electrochemical studies of austempered ductile iron in perchlorate solutions.
2006
The corrosion behavior of austempered ductile iron (ADI) in alkaline environment has been investigated at the microscale by means of the electrochemical microcell technique, surface analysis methods, and at the macroscale using classical electrochemical techniques. Local electrochemical investigations have revealed that the matrix (ausferrite), far from spheres, undergoes passivation in 1 M NaClO 4 , pH 10 solution within a wide potential range, from the corrosion potential (of about -280 mV/SCE) until 800 mV/SCE. Surface observations combined with local electrochemical analysis have shown that corrosion of ADI first occurs in the close vicinity of some graphite spheres and then around oxid…
Passivation-Induced Physicochemical Alterations of the Native Surface Oxide Film on 316L Austenitic Stainless Steel
2019
Time of Flight Secondary Ion Mass Spectroscopy, X-Ray Photoelectron Spectroscopy, in situ Photo-Current Spectroscopy and electrochemical analysis were combined to characterize the physicochemical alterations induced by electrochemical passivation of the surface oxide film providing corrosion resistance to 316L stainless steel. The as-prepared surface is covered by a ~2 nm thick, mixed (Cr(III)-Fe(III)) and bi-layered hydroxylated oxide. The inner layer is highly enriched in Cr(III) and the outer layer less so. Molybdenum is concentrated, mostly as Mo(VI), in the outer layer. Nickel is only present at trace level. These inner and outer layers have band gap values of 3.0 and 2.6-2.7 eV, respe…