Search results for "engineering.material"

Au nanowire junction breakup through surface atom diffusion.

2018

Metallic nanowires are known to break into shorter fragments due to the Rayleigh instability mechanism. This process is strongly accelerated at elevated temperatures and can completely hinder the functioning of nanowire-based devices like e.g. transparent conductive and flexible coatings. At the same time, arranged gold nanodots have important applications in electrochemical sensors. In this paper we perform a series of annealing experiments of gold and silver nanowires and nanowire junctions at fixed temperatures 473, 673, 873 and 973 K (200 degrees C, 400 degrees C, 600 degrees C and 700 degrees C) during a time period of 10 min. We show that nanowires are especially prone to fragmentatio…

Structural anisotropy and annealing-induced nanoscale atomic rearrangements in metamict titanite

2012

The structural state of metamict titanite was studied by Raman spectroscopy, complementary high-resolution transmission electron microscopy, and single-crystal X-ray diffraction. The results show that Raman scattering collected from metamict titanite is highly anisotropic, which is typical of single crystals. But surprisingly, the observed Raman-scattering dependence on the sample orientation is much more pronounced for heavily metamict than for weakly metamict titanite samples. These radiation-induced anisotropic effects are related to the specific atomic arrangements in metamict titanite. The Raman spectra collected in backscattering geometry from a plane nearly perpendicular to the chain…

Tuning of the Mg Alloy AZ31 Anodizing Process for Biodegradable Implants

2021

Coatings were grown on the AZ31 Mg alloy by a hard anodizing process in the hot glycerol phosphate-containing electrolyte. Anodizing conditions were optimized, maximizing corrosion resistance estimated by impedance measurements carried out in Hank's solution at 37 °C. A post anodizing annealing treatment (350 °C for 24 h) allowed us to further enhance the corrosion resistance of the coatings mainly containing magnesium phosphate according to energy-dispersive X-ray spectroscopy and Raman analyses. Gravimetric measurements revealed a hydrogen evolution rate within the limits acceptable for application of AZ31 in biomedical devices. In vitro tests demonstrated that the coatings are biocompati…

A diamond (1 0 0) surface with perfect phase purity

2015

Abstract Diamond surfaces with (1 0 0) orientation and perfect phase purity regarding the coexistence of sp3 and sp2 bonding as well as near surface nitrogen implanted layers are repeatedly produced from one sample by a cycle of nitrogen implantation, etching in oxygen and wet chemical etching. Comprehensive surface studies carried out by X-ray photoelectron spectroscopy (XPS) involving a deconvolution of the C 1s peak into contributions of C sp3, C sp2 and C sp3(N) reveal the surface and near-surface phase and stoichiometry. It is demonstrated that efficient etching of nitrogen implanted diamond occurs by high temperature annealing in oxygen and a wet chemical treatment.

Investigation of the Absorption of Annihilation Quanta in Solid and Liquid Ga and BiSn Alloy

2001

Defects in Martensitic Stainless Steel 1.4031 (EN) Exposed to Friction as Seen by Positron Annihilation

2010

We present experimental results of measurements of the Doppler broadening of annihilation line and positron annihilation lifetimes in martensitic stainless steel 1.4031 (EN) samples exposed to the dry sliding under different loads. In particular, we tested the subsurface zone under the worn surfaces. As a main result, we obtained information about the defect profiles in this zone and the total extent of the damage region induced by the dry sliding.

Influence of nanoporous structure on mechanical strength of aluminium and aluminium alloy adhesive structural joints

2006

The influence of surface treatments on the mechanical strength of adhesive joints was investigated. The attention was focused on AA2024 alloy because it is extensively used in both the automotive and aerospace industries. Adhesive joints fabricated with pure aluminium were also investigated in order to evidence possible differences in the surface features after identical treatments. Before joining with a commercial epoxy adhesive, metal substrates were subjected to different kinds of treatment and the surfaces were characterized by SEM analysis. The formation of a microporous surface in the AA2024 alloy, upon etching and anodizing, is discussed on the basis of the role of the intermetallic …

The influence of thickness, interpore distance and compositional structure on the optical properties of self-ordered anodic aluminum oxide films

2016

Highly ordered anodic aluminum oxide (AAO) films were fabricated using a two-step anodization process in oxalic acid, sulfuric acid, or ethylene glycol containing sulfuric acid, which are important in design of nanostructured optical devices. The morphology and UV-Vis reflectance spectroscopy of these films were analyzed. The morphological parameters of the AAO films, such as the thickness, pore diameter, interpore distance, porosity, pore arrangement regularity, and anodization electrolyte, were adjusted in order to study the effect of these parameters on the UV-Vis reflectance properties of these films. Raman spectroscopy measurements were then utilized to better understand the chemical d…

Synthesis, characterization and magnetism of monodispersed water soluble palladium nanoparticles

2008

Water soluble, monodispersed Pd nanoparticles with a narrow particle size distribution have been successfully synthesized by controlled reduction of [PdCl4]2−. The resulting aqueous colloids are stable over extended periods of time and can be prepared at high nanoparticle loading (20 g/L of Pd) with no agglomeration. The size of the nanoparticles can be reduced from the nanometer (ca. 3.5 nm) to the sub-nanometer size range (ca. 0.9 nm). Detailed magnetic characterization indicated that the larger, 3.5 nm nanoparticles show ferromagnetic properties at room temperature, while the sub-nanometric ones lose this magnetic behavior.

Morphology, physical properties, silver release, and antimicrobial capacity of ionic silver-loaded poly(l-lactide) films of interest in food-coating …

2014

In the present study, silver ions were incorporated into a poly-(l-lactide) (PLA) matrix by a solvent casting technique using different solvents and glycerol as plasticizer. The effect of the different formulations on the morphology, thermal, mechanical and color properties were first evaluated. Additionally, a thorough study of the silver ions release to an aqueous environment was also monitored over time by anodic stripping voltammetry and correlated with the antimicrobial performance against S. enterica. The incorporation of silver contents of up to 1 wt % did not affect morphology, thermal or mechanical properties of the films. A sustainable, antibacterial effectiveness was found for th…