Different Atmospheres (different + atmosphere)

Distribution by Scientific Domains


Selected Abstracts


The effect of overload on the fatigue crack growth behaviour of 304 stainless steel in hydrogen

FATIGUE & FRACTURE OF ENGINEERING MATERIALS AND STRUCTURES, Issue 1 2001
M. H. Kelestemur
Fatigue crack growth (FCG) behaviour and its characteristics following tensile overloads were investigated for AISI 304 stainless steel in three different atmospheres; namely dry argon, moist air and hydrogen. The FCG tests were performed by MTS 810 servohydraulic machine. CT specimens were used for the tests and crack closure measurements were made using an extensometer. FCG rates of 304 stainless steel at both dry argon and moist air atmospheres have shown almost the same behaviour. In other words, the effect of moisture on FCG of this material is very small. However, in a hydrogen atmosphere, the material showed considerably higher crack growth rate in all regimes. In general, for all environments, the initial effect of overloads was to accelerate the FCG rate for a short distance (less than a mm) after which retardation occurred for a considerable amount of time. The main causes for retardation were found as crack blunting and a long reinitiation period for the fatigue crack. Regarding the environmental effect, the overload retardation was lowest in a hydrogen atmosphere. This low degree of retardation was explained by a hydrogen embrittlement mechanism. In a general sense, hydrogen may cause a different crack closure mechanism and hydrogen induced crack closure has come in to the picture. Scanning electron microscope and light microscope examinations agreed well with the above results. [source]


Flame retardant properties of EVA-nanocomposites and improvements by combination of nanofillers with aluminium trihydrate

FIRE AND MATERIALS, Issue 5 2001
Günter Beyer
Flame retardant nanocomposites are synthesized by melt-blending ethylene,vinyl acetate copolymers (EVA) with modified layered silicates (montmorillonites). Thermogravimetric analysis performed under different atmospheres (nitrogen and air) demonstrated a clear increase in the thermal stability of the layered silicate-based nanocomposites. The use of the cone calorimeter to investigate the fire properties of the materials indicated that the nanocomposites caused a large decrease in heat release. The char-formation is the main factor important for improvement and its function is outlined. Further improvements of the flame retardancy by combinations of nanofillers and traditional FR-additives on the basis of metal hydroxides were also studied. Copyright © 2002 John Wiley & Sons, Ltd. [source]


High-Temperature Contact Formation on n-Type Silicon: Basic Reactions and Contact Model for Seed-Layer Contacts

ADVANCED FUNCTIONAL MATERIALS, Issue 3 2010
Matthias Hörteis
Abstract Contact formation on n-type silicon, especially using a high-temperature process, has been the subject of research for more than 40 years. After its application in microelectronics, n-type silicon is widely used in silicon solar cells as the emitter layer. The formation of a low ohmic contact grid using an industrially feasible process step is one of the key features required to improve the solar-cell efficiency. The contact materials, typically deposited in a printing step, have to fulfil several functions: opening the dielectric antireflection layer and forming an intimate metal-semiconductor contact with good mechanical adhesion and low specific contact resistance. As the used contact inks typically contain several functional materials, such as silver and a glass frit, the detailed contact formation is still not entirely understood. Therefore, the chemical reactions during the contact firing process have been studied in detail by thermogravimetric differential thermal analysis in combination with mass spectroscopy. Based on these studies, a contact ink has been developed, optimized and tested on silicon solar cells. In this paper, the mechanism of the etching process, the opening of a dielectric layer, the influence of different atmospheres and the impact of the glass-frit content are investigated. The observed microscopic contact structure, the resulting electrical solar-cell parameters and the studied reactions are combined to clarify the physics behind the high-temperature contact formation. [source]


Structural Evidence for Zn Intersititials in Ferromagnetic Zn1,xCoxO Films,

ADVANCED MATERIALS, Issue 19 2007
L. MacManus-Driscoll
Post-annealing studies in different atmospheres combined with high resolution x-ray studies on epitaxial ZnO and Zn1,xCoxO films revealed that the c -axis lattice parameter decreases when interstitial zinc is removed from ZnO. The ,c' parameter change reverses sign when samples are re-annealed in a Zn-rich atmosphere. Stronger ferromagnetism occurs in Zn1,xCoxO film for higher ,c' parameters and hence higher Zn interstitial concentrations. [source]


Shelf life of Turkish whey cheese (Lor) under modified atmosphere packaging

INTERNATIONAL JOURNAL OF DAIRY TECHNOLOGY, Issue 3 2009
HASAN TEM
In this study, the shelf life of Lor cheese stored under different atmosphere compositions was assessed and compared. Lor cheeses were held in four different atmospheres containing: vacuum packaging (VP), 40% CO2/60% N2, 60% CO2/40% N2 and 70% CO2/30% N2 (modified atmosphere packaging). Control cheeses were stored in air. All cheese samples were kept in the refrigerator at 4°C for 45 days and investigated for physicochemical, microbiological and sensory properties. The acidity index value was significantly higher (,P < 0.05) in the control and vacuum packaged samples than in those stored for the same period under CO2. Microbiological results showed that modified atmosphere packaging delayed microbial growth compared with air and VP samples. Of the three modified atmospheres, gas mixtures 60% and 70% CO2 were the most effective for inhibition of growth of micro-organisms. Sensory evaluation (odour and taste) results showed that Lor cheese packaged under modified atmosphere packaging (60% CO2/40% N2 and 70% CO2/30% N2,) retained good characteristics for 45 days of storage, while vacuum and control samples were sensorily unacceptable after 10 days of storage. [source]


Quality of grated carrot (var. Nantes) packed under vacuum

JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 3 2007
Ada MCN Rocha
Abstract The quality of grated carrot (variety Nantes) was evaluated throughout 10 days of storage in two different atmospheres: air and vacuum at 2 °C. The parameters of quality were microbiological and physico-chemical. Sensory evaluation of vacuum-packed grated carrots was performed after the microbiology study. The objective was to study the use of a vacuum for preservation of this type of product. The use of a vacuum was sufficiently promising with respect to the capacity to extend the shelf life of grated carrot by reducing microbial load and by minimising physico-chemical changes. The shelf life of grated carrot under vacuum was extended to 8 days at 2 °C. Copyright © 2006 Society of Chemical Industry [source]


Modified atmosphere packaging affects lipid oxidation, myofibrillar fragmentation index and eating quality of beef

PACKAGING TECHNOLOGY AND SCIENCE, Issue 2 2009
Ina Clausen
Abstract The objective of this study was to evaluate the effects of different modified atmosphere packaging (MAP) systems applied during ageing and retail display on the quality of beef longissimus dorsi. The quality of the steaks was measured by sensory analysis, thiobarbituric acid-reactive substances (TBARS), myofibrillar fragmentation index (MFI), protein oxidation, weight loss, cooking loss and vitamin E content. The study included 11 different packaging systems investigated in two separate trials, using O2, CO2, N2 gas and vacuum in combination or alone during ageing and retail display. In some systems, loins were sliced into steaks before packaging, and in other systems, loins were vacuum packed and aged for 14,18 days, and thereafter were sliced and repacked in different atmospheres. Systems including high O2 MAP resulted in a large increase in warmed-over flavour and in TBARS as well as a decrease in juiciness, tenderness and vitamin E content, compared to anaerobic systems. Also, MFI was lower in high O2 MAP steaks, and an increase in protein oxidation was seen, suggesting that the decrease in meat tenderness was due to reduced proteolysis and/or protein oxidation. In addition, the cooked steaks of high O2 MAP looked well done, although the internal temperature was only 62°C, indicating premature browning. Ageing of steaks in N2 did not affect any measured parameter compared to vacuum thermoforming packed muscle. Steaks stored in vacuum skin pack for 20 days were less tender than steaks stored in 100% N2 for 18 days followed by 2 days in atmospheric air. In conclusion, packaging in high O2 concentrations compromises several aspects of meat quality. Copyright © 2008 John Wiley & Sons, Ltd. [source]