Search results for "DEGRADATION"
showing 10 items of 1208 documents
Influence of oxidation level of graphene oxide on the mechanical performance and photo-oxidation resistance of a polyamide 6
2019
The aim of this work is to study the relationship between the chemical-physical properties of graphene oxide (GO) and the performance of a polyamide 6 (PA6) in terms of mechanical reinforcement and resistance to UV-exposure. For this purpose, two samples of GO possessing different oxidation degrees were added (0.75 wt.%) to PA6 by way of a two-step technique and the materials achieved were carefully analysed from a morphological, chemical-physical, mechanical point of view. Photo-oxidation tests were carried out to assess the performance of this class of nanohybrids after 240 h of UV-exposure. The results reveal that both nanocomposites exhibit enhanced mechanical performance and durability…
Kinetic Parameters for Thermal Degradation of Green Asparagus Texture by Unsteady-state Method
1998
An unsteady-state method was developed for estimating texture degradation during heating-cooling of green asparagus spears. The method used a mathematical model of heat transmission for time-temperature history estimation, and a nonlinear regression of texture measurements of asparagus spears to estimate kinetic parameters. The specific heat, conductivity and convective coefficient of green asparagus were determined experimentally and used In the mathematical model for temperature estimation. Values obtained were Ea = 76.19±0.13 kJ/mol and k 1158°C = 0.00528±0.00005 s -1 . Good agreement was found between predicted and observed texture values. The method was compared with the classical stea…
A Multiscale Approach to Polycrystalline Materials Damage and Failure
2014
A two-scale three-dimensional approach for degradation and failure in polycrystalline materials is presented. The method involves the component level and the grain scale. The damage-induced softening at the macroscale is modelled employing an initial stress boundary element approach. The microscopic degradation is explicitly modelled associating Representative Volume Elements (RVEs) to relevant points of the macro continuum and employing a cohesive-frictional 3D grain-boundary formulation to simulate intergranular degradation and failure in the Voronoi morphology. Macro-strains are downscaled as RVEs' periodic boundary conditions, while overall macro-stresses are obtained upscaling the micr…
Optical and photonic material hardness for energetic environments
2009
We studied the effects of dielectric change in the chemical composition and in the realization procedures under radiation exposure. We have compared the radiation effects on Ge-doped and F-doped fibers and preforms: the first play a crucial role in the photosensitivity property, the second improves the dielectric radiation hardness even at low concentrations. The use of different spectroscopic techniques (RIA, OA, EPR) allow the identification of the point defect formation mechanisms at the origin of the optical degradation properties.
Hot carrier effects in n-MOSFETs with SiO2/HfO2/HfSiO gate stack and TaN metal gate
2009
Charge trapping and trap generation in field-effect transistors with SiO2/HfO2/HfSiO gate stack and TaN metal gate electrode are investigated under uniform and non-uniform charge injection along the channel. Compared to constant voltage stress (CVS), hot carrier stress (HCS) exhibits more severe degradation in transconductance and subthreshold swing. By applying a detrapping bias, it is demonstrated that charge trapping induced degradation is reversible during CVS, while the damage is permanent for hot carrier injection case. © 2008 Elsevier B.V. All rights reserved.
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.
Photo-oxidative degradation of poly(ethylene-co-vinyl acetate)/nisin antimicrobial films
2012
The photo-oxidative behaviour of different antimicrobial blown films based on poly (ethylene-co-vinyl acetate) (EVA) was studied. In particular, two samples of EVA containing different level of vinyl acetate comonomer (namely 14% and 28%) were used as matrices while nisin at different concentrations was used as antimicrobial agent. The degradation was followed by analyzing the changes in the spectroscopic behaviour and of the elongation at break measured in tensile tests. Moreover, changes in the antimicrobial activity of the films were followed by measuring the inhibition halo in agar diffusion tests. The results indicate that nisin acts as an excellent UV stabilizer for both samples of EV…
UV-induced Degradation Study of Multicrystalline Silicon Solar Cells Made from Different Silicon Materials
2013
Abstract The effect of ultraviolet-induced degradation (UV-ID) on solar cells made from two different solar grade materials has been compared. By using identical wafer and cell production units, effects originating in the two materials; solar grade produced by the Elkem Solar method (ESS™) was compared to standard polysilicon solar cells. Silicon wafers were selected precisely from similar positions from respective silicon bricks to process identical standard solar cells. The quantum efficiency maps at particular laser wavelengths and IV parameters of all solar cells were measured before and after UV-ID to visualize defects sites in the solar cells and to observe the extent of degradation. …
Effects of weathering on the performance of self-cleaning photocatalytic paints
2019
Abstract The use of photocatalytic products for the surface coating of buildings is spreading more and more, because of the reduction of atmospheric pollutants and the colour maintenance of the paints over time with reduction of the maintenance costs and the improvement of the aesthetic appearance. The study reports the evaluation of the effects of the atmospheric conditions on three commercial photocatalytic paints containing TiO2. In particular tests were carried out by using samples subjected to accelerated aging inside a climate chamber and naturally aged by exposure for two years to the external environment of the city of Palermo (representative of a coastal environment of the Mediterr…
Incorporation of an antibiotic in poly(lactic acid) and polypropylene by melt processing
2016
Purpose In this work an antibiotic, ciprofloxacin (CFX), was incorporated into 2 different polymeric matrices, poly(lactic acid) (PLA) and polypropylene (PP), to provide them with antimicrobial properties. The influence of CFX content on release kinetics and on antimicrobial and mechanical properties was evaluated. Methods CFX was incorporated into both the polymers by melt mixing. Results The effect of CFX incorporation was found to strongly depend on which polymer matrix was used. In particular, the antimicrobial tests revealed that PLA samples containing CFX produced no inhibition zone and only a slight antibacterial activity was observed when the highest concentration of CFX was added t…