Search results for "Metallurgy"

INTERACTION BETWEEN MECHANICAL STRESSES AND OXIDATION OF THE NIOBIUM

1998

Reduction of temperature coefficients in multicrystalline silicon solar cells after light-induced degradation

2015

This study focuses on the variations of the temperature coefficients after light-induced degradation (LID) of compensated multicrystalline silicon solar cells from three different ingots. The ingots have been chosen to see the effect of the compensation level, the resistivity and the impact of adding gallium to keep the resistivity as constant as possible along the ingot. The temperature coefficients of the efficiency experience a major decrease after LID on all ingots. We found that this decrease varies along the ingot height and does not correspond to the VOC drop. Moreover, no direct correlation with the interstitial oxygen concentration profiles could be seen.

Fe-N/C catalysts for oxygen reduction based on silicon carbide derived carbon

2017

This work was supported by the projects TK141 “Advanced materials and high-technology devices for energy recuperation systems” (2014-2020.4.01.15-0011), NAMUR “Nanomaterials - research and applications” (3.2.0304.12-0397) and by the Estonian Institutional Research Grant No. IUT20-13.

Parametric study of laser welding of copper to austenitic stainless steel

2018

Abstract Welding of copper to stainless steel is challenging because of sharp difference in thermophysical properties of materials and the presence of miscibility gap in Fe-Cu system. The parametric study of continuous Yb:YAG laser welding between copper and austenitic stainless steel 316L has been performed. The influence of laser power, welding speed and beam offset from joint line on weld composition, microstructure and tensile properties was studied. The corrosion behaviour of the welds was evaluated in 0.1M NaCl with the potentiostatic pulse testing method, salt fog and immersion tests. In function of copper dilution in the melted zone, different types of microstructure were observed: …

Influence of the composition of titanium oxynitride layers on the fretting behavior of functionalized titanium substrates: PVD films versus surface l…

2014

International audience; Abstract In this work we compared the fretting behavior of pure titanium plates functionalized with titanium oxynitride surface layers, obtained by two methods: a Physical Vapor Deposition (PVD) method, reactive magnetron sputtering, and Surface Laser Treatments (SLT), under different mixtures of oxygen and nitrogen. The composition of the layers was determined by nuclear reaction analysis (NRA) and their structure was analyzed by Raman spectroscopy. PVD layers were TiN-like fcc layers, with an oxygen concentration going from 36 to 50 at.%. Three SLT layers were studied. The first one was a TiN-like layer containing ~28 at.% of oxygen. The second one was formed of di…

Influence of Post-machining Thermal Treatment on the Corrosion Behaviour of Copper

2014

Abstract In this paper, the influence of a post-machining thermal treatment (PMTT) on the corrosion behaviour of copper was investigated in a salt fog atmosphere. The corrosion behaviour was affected by the presence of a high density of grain boundaries generated during machining or dislocations formed during PMTT under certain conditions. The obtained results showed that it is possible to find PMTT conditions to cancel changes induced by machining and that the critical factor leading to a sharp increase of the percentage of oxidized surface seems to be the density of dislocations near the machined surface.

A plasticity model for predicting the rheological behavior of paperboard

2017

The sorption of water into the paperboard exposes a container to reversible and irreversible deformations under relative humidity variations. In this study, an elasto-plastic material model is used to demonstrate how through-thickness dry solids content gradients can generate permanent in-plane strains in paperboard. The measurements presented in this paper indicate that in consecutive loading-unloading cycles, the yield stress either remains roughly constant or decreases, and an additional permanent set of strain is obtained even when the maximum tension of repetitions stays constant. Two modified approaches concerning elasto-plastic hardening behavior based on the measurements of this wor…

Highly Stable Thin Films Based on Novel Hybrid 1D (PRSH)PbX3 Pseudo-Perovskites

2021

In this study, the structure and morphology, as well as time, ultraviolet radiation, and humidity stability of thin films based on newly developed 1D (PRSH)PbX3 (X = Br, I) pseudo-perovskite materials, containing 1D chains of face-sharing haloplumbate octahedra, are investigated. All films are strongly crystalline already at room temperature, and annealing does not promote further crystallization or film reorganization. The film microstructure is found to be strongly influenced by the anion type and, to a lesser extent, by the DMF/DMSO solvent volume ratio used during film deposition by spin-coating. Comparison of specular X-ray diffraction and complementary grazing incidence X-ray diffract…

Electrochemical Behaviour and Galvanic Effects of Titanium Implants Coupled to Metallic Suprastructures in Artificial Saliva

2018

The aim of the present study is to analyze the electrochemical behavior of five different dental alloys: two cobalt-chromium alloys (CoCr and CoCr-c), one nickel-chromium-titanium alloy (NiCrTi), one gold-palladium alloy (Au), and one titanium alloy (Ti6Al4V), and the galvanic effect when they are coupled to titanium implants (TiG2). It was carried out by electrochemical techniques (open circuit measurements, potentiodynamic curves and Zero-Resistance Ammetry) in artificial saliva (AS), with and without fluorides in different acidic conditions. The studied alloys are spontaneously passivated, but NiCrTi alloy has a very narrow passive domain and losses its passivity in presence of fluorides…

Impurity analyses of silicon wafers from different manufacturing routes and their impact on LID of finished solar cells

2013

Summarizes the measurements of impurity concentrations in directionally solidified silicon ingots from different feedstocks. The substitutional Carbon and interstitial Oxygen are measured on as-sawn wafers using FTIR. Active iron concentration is mapped on a-Si:H passivated wafers. It is observed that these impurities present in Elkem Solar Grade Silicon (ESS™) concentrations are comparable to the standard polysilicon which are in the acceptable ranges for silicon for solar industry. The measured LID of the finished solar cells is also comparable.