Oxidation in Air at 1400 K and Optical Properties of Inconel 625, FeCrAlloy and Kanthal Super ER

Oxidation of Metals - The materials used for the design of solar receivers are one of the critical parts of the concentrated solar power (CSP) plants. An increase in the working temperature of a...     

Effect of nitrogen addition on optical properties of fluorozirconate glasses

The linear and non-linear optical properties of fluorozirconate glasses with and without nitrogen, namely ZrF₄? BaF₂? LaF₃? AIF₃ and ZrF₄? BaF₂? LaF₃? AIF₃? AIN, have been studied. The glass containing nitrogen exhibits a 5 nm shift of the transmittance edge in the UV region towards longer wavelength, whereas there is no change in the IR transmittance. Measurements show a small increase in the linear index of refraction in the visible region and a small decrease in the non-linear (intensity-dependent) refractive index coefficient n₂. Longitudinal and transverse sound velocities estimated from Brillouin-scattering experiments for both glasses amount to 6311 and 4514 ms^?1, respectively.     

Structure and hardness of titanium surfaces carburized by pulsed laser melting with graphite addition

Titanium foils coated with graphite films 20 μm thick were irradiated by means of a pulsed Nd-YAG in order to harden this metal by surface melting and alloying. The relationships between irradiation parameters, microstructure and hardness of the synthesized composite coatings were determined. Four relevant parameters were defined as governing the irradiation processes. The parametric working field of the laser source was investigated next to its periphery. The influences of the relevant irradiation parameters on the microstructure and hardness of the melted zone were deduced from the metallographic analyses and Vickers micro-indentation tests of the cross sections of this composite zone. Such a zone was constituted always with hard titanium carbide and ductile metallic titanium, some times with the presence of lubricating graphite inclusions. The main advantage of such a surface treatment of titanium is to synthesize, under clearly defined irradiation conditions, a self-lubricating composite coating that resists abrasive or adhesive wear.     

Modulating the Ferromagnet/Molecule Spin Hybridization Using an Artificial Magnetoelectric

Spin‐polarized charge transfer at the interface between a ferromagnetic (FM) metal and a molecule can lead to ferromagnetic coupling and to a high spin polarization at room temperature. The magnetic properties of these interfaces can not only alter those of the ferromagnet but can also stabilize molecular spin chains with interesting opportunities toward quantum computing. With the aim to enhance an organic spintronic device's functionality, external control over this spin polarization may thus be achieved by altering the ferromagnet/molecule interface's magnetic properties. To do so, the magnetoelectric properties of an underlying ferroelectric/ferromagnetic interface are utilized. Switching the ferroelectric polarization state of a PbZr_0.2Ti_0.8O₃ (PZT) bottom layer within a PZT/Co/FePc‐based (Pc ‐ phthalocyanine) device alters the X‐ray magnetic circular dichroism of the Fe site within the phthalocyanine molecular top layer. Thus, how to electrically alter the magnetic properties of an interface with high spin polarization at room temperature is demonstrated. This expands electrical control over spin‐polarized FM/molecule interfaces, which is first demonstrated using ferroelectric molecules, to all molecular classes.     

Use of Hydroxyl Functionalized (Meth)acrylic Cross‐Linked Polymer Microparticles as Chain Transfer Agent in Cationic Photopolymerization of Cycloaliphatic Epoxy Monomer, 2

This study is related to the use of hydroxyl functional acrylic cross‐linked polymer microparticles (CPM, also named microgels) as a chain transfer agent in cationic photopolymerization of cycloaliphatic epoxy monomer. All CPM were based on butyl acrylate and were consequently rubbery at ambient temperature. The effect of the stabilizing acrylate monomer used during the CPM synthesis was evaluated with respect to the viscoelastic properties of the photopolymerized cationic‐type epoxy films. The viscoelastic properties were correlated to the photopolymerized film morphology observed by transmission electron microscopy. Two acrylate monomers used as stabilizing agents during CPM synthesis were compared: cardura acrylate (CA) and lauryl acrylate (LA). CA was a good stabilizer for CPM in epoxy monomer before photocure and the CPM were well dispersed into the network after reaction. In contrast, LA was a poor stabilizer resulting in large CPM aggregation. The blend of these two types of CPM led to intermediate morphology, probably because of the flocculation of the CPM stabilized with LA. Conversely, CPM synthesized with a blend of the two stabilizing acrylate monomers induced in epoxy matrix a specific bi‐continuous morphology and consequently unique viscoelastic properties.

TEM micrographs of a photopolymerized film with 15 wt.‐% CPM(BA + 20%HEA)‐20%CA + 15% CPM(BA + 18%HEA)‐27%LA used as chain transfer agents.     

Use of Functional (Meth)acrylic Cross‐Linked Polymer Microparticles as Toughening Agents for Epoxy/Diamine Thermosets

(Meth)acrylic cross‐linked polymer microparticles (CPM, also named microgels) were used as toughening agent for an epoxy/amine network. CPM were mainly based on butyl acrylate and consequently they were rubbery at ambient temperature. Various types of reactive groups were introduced onto the CPM: epoxy, carboxy (meth)acrylic double bonds, and epoxy + acrylic double bonds, carboxyl + methacrylic double bonds. Non functional microparticles were also used. Before any reaction, most of the CPM were soluble in the thermoset precursors. Nevertheless, the CPM functionality strongly influenced their initial miscibility in the epoxy‐amine monomers and their final dispersion in the cross‐linked matrix, as well as the mechanical properties of the network. Non‐functional CPM did not lead to a high increase of fracture toughness because of the low adhesion between microparticles and epoxy matrix. However, fracture toughness was increased with reactive CPM because of better adhesion between the microparticles and the matrix. The best toughness was obtained with microparticles containing two types of reactive groups, allowing at the same time cross‐linking reactions between CPM and chemical bonding between CPM and the epoxy matrix. In this case, fracture toughness can be greatly improved, up to 3‐times if the chemical composition of the microparticles was wisely chosen, without significantly reducing the thermal properties.

Viscoelastic properties of toughened DGEBA/MCDEA networks.     

Multi-view dense 3D modelling of untextured objects from a moving projector-cameras system

Structured light methods achieve 3D modelling by observing with a camera system, a known pattern projected on the scene. The main drawback of single projection structured light methods is that moving the projector changes significatively the appearance of the scene at every acquisition time. Classical multi-view stereovision approaches based on the appearance matching are then not useable. The presented work is based on a two-cameras and one single slide projector system embedded in a hand-held device for industrial applications (reverse engineering, dimensional control, etc). We propose a method to achieve multi-view modelling for camera pose and surface reconstruction estimation in a joint process. The proposed method is based on the extension of a stereo-correlation criterion. Acquisitions are linked through a generalized expression of local homographies. The constraints brought by this formulation allow an accurate estimation of the modelling parameters for dense reconstruction of the scene and improve the result when dealing with detailed or sharp objects, compared to pairwise stereovision methods.     

Structural, energetic, and dynamical properties of rotaxanes constituted of alpha-cyclodextrins and an azobenzene chain

The [3]rotaxane synthesised as a single isomer constituted of two cyclodextrins (CDs) and an azobenzene chain [M.R. Craig, T.D.W. Claridge, M.G. Hutchings, H.L. Anderson, Synthesis of a cyclodextrin azo dye [3]rotaxane as a single isomer, Chem. Commun. 16 (1999) 1537-1538] has been investigated using molecular mechanics (MM) and dynamics (MD) with the MM3 force field in order to evaluate the stability of various configurations of the complex in the isolated and solvated states. The influence of the blocking groups and the presence of energy barriers along the azo chain were first investigated through the calculation of an energy profile. It revealed that the CD could translate along the chain at room temperature without any decomplexation. Next, MD simulations of three different types of configurations, i.e., head-to-head, head-to-tail, and tail-to-tail, of the [3]rotaxane were carried out. The non-solvated phase simulations showed structures with the CDs close to each other while the solvated ones showed structures with CDs separated by larger distances. This separation occurs due to the solute-solvent interactions. When the systems are in isolated state, the observed structure of the complexes are less stable due to an unfavourable arrangement of the hydroxyls groups of the adjacent CD faces. When considering solvation, energies of the three configurations are roughly identical due to the large distance between the faces of the CDs.