Search results for "medium"
showing 10 items of 3746 documents
Characterization and properties of PEO coatings on 7075 Al alloy grown in alkaline silicate electrolyte containing KMnO 4 additive
2017
Abstract Plasma electrolytic oxidation (PEO) was used to modify the surface of 7075 Al alloy by applying a bipolar pulsed-current in a silicate based electrolyte containing 0 to 3 g L− 1 KMnO4. For the coating produced in the base electrolyte, crystalline γ-Al2O3 was the main phase, while the coatings formed at the presence of KMnO4 consisted of α-Mn2O3 containing Si and Al oxides. A pancake structure was observed on surface of the coating produced in the base electrolyte, while a foam feature along with some volcano-like areas was detected on the surface of the coatings produced in the presence of KMnO4. The KMnO4 changed the discharge type leading to diminish the pores at the metal/coatin…
Study of the coordination of ortho-tyrosine and trans-4-hydroxyproline with aluminum(III) and iron(III)
2018
Abstract The coordination of amino acids ortho-tyrosine (o-Tyr, 1) and trans-4-hydroxyproline (HPro, 2) with the biologically important trivalent metal ions Al(III) and Fe(III) in aqueous solution was investigated by 1H and 13C high resolution NMR, Laser Desorption Mass Spectrometry (LD-MS), and MS/MS experiments. Potentiometric measurements were also carried out in 0.16 M NaCl, 37 °C, by varying the pH between 2.0 and 3.5. NMR spectra recorded on aqueous solutions of amino acids 1 or 2 in the presence of the appropriate trivalent metal chloride suggested that binding of Al(III) and Fe(III) involved the COOH and NH2 functional groups of ligands, while their phenolic and alcoholic groups whi…
Influence of post-treatment time of trivalent chromium protection coating on aluminium alloy 2024-T3 on improved corrosion resistance
2019
Abstract Low corrosion protection performances of Trivalent Chromium Process (TCP) coatings with reference to Chromium Conversion Coatings (CCC) deposited on aluminium alloys can be overcome by application of post-treatment processes. This work shows the effect of post-treatment bath (containing hydrogen peroxide and lanthanum salt) on the chemical composition, structure and the corrosion performances of TCP coating deposited on AA 2024-T3 aluminium alloy. Different times of post-treatment bath were applied on the TCP coating and the samples were analyzed by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), X-ray Photoelectron Spectroscopy (XPS) and Glow Discharge-Optical Emission …
Metallic interconnects for SOFC : characterization of their corrosion resistance in hydrogen/water atmosphere and at the operating temperatures of di…
2006
International audience; Chromia forming alloys are one of the best candidates for the interconnecting materials in solid oxide fuels cells (SOFC). Recent research has enabled to decrease the operating temperature of the SOFC from 1000 °C to 800 °C. However, low electronic conductivity and high volatility of the chromia scale need to be solved to improve performance of interconnects. In the field of high temperature oxidation of metals, it is well known that the addition of reactive elements into alloys or in thin film coatings, improve the oxidation resistance of alloys at high temperature. The elements of the beginning of the lanthanide group and yttrium are the most efficient. The goal of…
A step forward in disclosing the secret of stradivari's varnish by NMR spectroscopy
2017
It is commonly thought that the varnishes used by the great violin-maker Antonio Stradivari may have a role in determining not only the esthetical features but also the acoustic properties of his instruments, and the idea of a “lost secret” is still widespread among musicians and violin-makers. Previous scientific researches on varnish samples of Stradivari's instruments revealed that they were generally made by a mix of linseed oil with and colophony or metal rosinates in different ratios ranging between 75/25 (oil/resin) and 60/40 (oil/rosinate). However, it is still not clear whether the mixture composition can be related to any structural and/or functional feature of the resulting varni…
The formation of silica high temperature polymorphs from quartz: Influence of grain size and mineralising agents
2015
Abstract The formation of high-temperature silica polymorphs in presence of Na and K has been studied at various temperatures and soaking times, starting from quartzes of different grain size, ex situ as well as in situ. The results show that cristobalite and tridymite formation is strongly influenced by the nature and the amount of mineraliser added. In particular, K seems to discriminate more between the two structures, as it produces the largest observed amount of cristobalite. The disappearance of quartz can be controlled by the proper combination of mineraliser/temperature/time, which in turn control the amount and the type of polymorph formed, together with the amount of amorphous mat…
Reactive blending of functionalized acrylic rubbers and epoxy resins
2001
A high molecular weight acrylonitrile/butadiene/methacrylic acid (Nipol 1472) rubber is chosen to control processability and mechanical properties of a TGDDM (tetra glycidyl diphenyl methane) based epoxy resin formulation for aerospace composite applications. The physical blend of rubber and epoxy resin, achieved by dissolution of all the components in a common solvent, forms a heterogeneous system after solvent removal and presents coarse phase separation during cure that impairs any practical relevance of this material. A marked improvement of rubber-epoxy miscibility is achieved by reactive blending ('pre-reaction') the epoxy oligomer with the functional groups present in the rubber. The…
Organic-inorganic nanocomposites prepared by reactive suspension method: investigation on filler/matrix interactions and their effect on the nanopart…
2017
Epoxy resin/TiO2 nanocomposites prepared by both reactive suspension method, based on in situ synthesis, and conventional mechanical mixing are analysed by solid-state nuclear magnetic resonance and transmission electron microscopy in order to have a deeper insight into the nature of interactions at the polymer/particle interface and their effect on the nanoparticles dispersion. Specifically, solid-state nuclear magnetic resonance experiments showed that the nanoparticles, synthesized by reactive suspension method, can efficiently link the matrix by hydrogen bonds forming a hybrid organic-inorganic 3D network. Such evidences strongly supports our previously reported theory, in which the nan…
Zn(II) and Ni(II) complexes with poly-histidyl peptides derived from a snake venom
2018
Abstract The snake venoms are complex mixtures containing many bioactive peptides and proteins; some of them are aimed to protect the snake glands, where the venom is stored, until the latter is inoculated in the victim. In the venom of some vipers of the genus Atheris , a set of peptides containing poly-His and poly-Gly segments was recently found. Poly-His peptides are not rare in Nature. Although their exact biological function is most often unknown, one thing is certain: they have good binding properties towards the transition metal ions. As a matter of fact, the imidazole side chain of histidine is one of the groups most frequently involved in metal complexation in the active sites of …
Solution-processed transparent ferroelectric nylon thin films
2019
We have developed a method to solution process strongly hydrogen-bonded odd nylons into ferroelectric thin films.