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991.
992.
993.
M.A. Del Nobile G.G. Buonocore E. La Notte L. Nicolais 《Journal of food science》2003,68(6):2017-2021
ABSTRACT: We present a mathematical model to predict the oxygen-permeability coefficient of nylon film as a function of the water activity at the upstream and downstream side of the film. To validate the model, oxygen-permeability tests were conducted at 25 °C. The fitting and predictive ability of the proposed model was successfully tested by fitting and predicting the oxygen-permeability coefficient. The obtained results point out the need for a more accurate analysis of the oxygen and water-transport phenomena in the case of water-sensitive packaging films like nylon. 相似文献
994.
Oxygen has always been considered to be a major contaminant in the organo-metallic vapor phase epitaxy (OMVPE) of Al
x
Ga1−x
As. Oxygen incorporation has been invoked as a contributor to low luminescence efficiency, dopant compensation and degradation
of surface morphology among other deleterious effects. This study presents quantitative measurements of oxygen concentration
in nominally high purity Al
x
Ga1−x
As. The oxygen concentration was measured as a function of alloy composition, growth temperature, andV/III ratio. Quantitative secondary ion mass spectroscopy (SIMS) measurements were used to determine the oxygen content as well
as the carbon concentration in the film. The oxygen concentration increases with decreased growth temperature and V/III ratio
while increasing superlinearly with Al content in the epitaxial layer. 相似文献
995.
XPS Studies on Rare Earth Oxide LSCO/YSZ Electrodes 总被引:6,自引:0,他引:6
The X-ray diffraction spectra and X-my photoelectron spectroscopy were measured for Sr-doped Lal-xSrx CoO3 materials with perovskite structure prepared by the solid-state reaction method. The influence of heat-treatment tempera-ture on the average crystal size of Lal-xSrx CoO3 was studied. The surface chemical states of Lal-xSrxCoO3 cathodes with different Sr-doped content were discussed. The experimental results show that average crystal size of Lal-xSrxCoO3 under the condition of heat-treatment in the range of 900- 1200℃ is larger than that at other temperatures, which is of benefit to forming porous electrodes. When La is replaced by Sr gradually, the oxygen vacancy concentration increases. It is of benefit to enhancing the transport property of oxygen ion. 相似文献
996.
A non-Arrhenius segregation isotherm is derived which includes the change in the heat of segregation with surface coverage due to impurity—impurity interactions. It is shown that a linear dependence of log ( Xs ) on the reciprocal temperature, where Xs is the surface atomic ratio, can derive either from a constant heat of segregation, i.e., Arrhenius behavior, or from a heat of segregation that varies as X−1 s . This isotherm is then used to calculate the equilibrium surface coverages of Ca at the {001} surface of MgO1 Mg at the {0001} surface of α-Al2 O3 , γ at the {1012} and {1120} surfaces of α-Al2 O3 , and Na at the {111} and {110} surfaces of Li2 O from the calculated heats of segregation. Where possible, comparisons are made with experiment. The more useful operational definition of the heat of segregation, namely, that derived from the measured coverage or that defined atomistically and obtained by calculation, is discussed. 相似文献
997.
Storage effect on antioxidant content and capacity of grape seeds under different aw conditions (aw 0.33; 0.53; 0.75/50 days, 25 °C) was examined. Total phenol content (determined by the Folin–Ciocalteu method) decreased during storage though changes were trivial for samples stored at 33% or 53% RH. High level of humidity (75%) accelerated degradation and resulted in a ∼50% reduction of total phenol content. Minor loss of the DPPH radical scavenging activity (%RSA) of the extracts was observed. Catechin and epicatechin content monitored by RP-HPLC was reduced during storage, particularly at 75% RH. Epicatechin content proved to be less sensitive to water activity conditions than catechin content. Results of various in vitro assays (Folin–Ciocalteu, FRAP, DPPH, ABTS, CBA, ORAC and copper induced liposome oxidation) did not support difference in terms of resistance to oxidation. Based on the continuous release of gallic acid, our finding was related to hydrolytic reactions. Control of aw of grape seeds can be of practical importance for the wine industry. 相似文献
998.
D.L. Cocke D.E. Mencer M.A. Hossain R. Schennach M. Kesmez J.R. Parga D.G. Naugle 《Journal of Applied Electrochemistry》2004,34(9):919-927
Interest in copper as a technologically important material needs to be met with greater understanding of the fundamental chemical reactions of copper. In particular, there is still a lack of universal agreement on the oxidation process of bulk copper and thin copper films. In this study, the authors demonstrate the use of linear sweep voltammetry (LSV) to study buried structures in the oxide layers on copper. In particular, LSV can be used to detect reactions at buried interfaces. It is also emphasized that surface scientists should recognize Cu3O2 and the decomposition of copper oxides at the metal–oxide interface in new studies on copper oxidation and in interpreting already existing copper oxidation data. The two key parameters that drive oxide growth and decomposition are demonstrated to be oxygen activity and the free energies of formation of the oxides (per mole of oxide ion). The complex nature of the oxidation of copper, as well as other metals and alloys, can be described qualitatively using the Modified Cabrera–Mott (C–M) Model. Surface studies of oxidation of metals and alloys need to be supported and complemented by other techniques such as chemical or electrochemical methods. 相似文献
999.
The influence of dissolved oxygen on titanium oxide film growth at various sweep rates was explored for both pure titanium and a titanium alloy. The results showed that the dissolved oxygen becomes only significant when the sweep rate is sufficiently low, but which can be neglected in the case of enough high sweep rates. It reasonably assumes that there is no adequate time for oxygen to move to the anodic surface when the sweep rate is sufficiently high so that the role of oxygen becomes insignificant. However, the situation was found to be different when the anodic oxide film was growing at a sufficiently low sweep rate dynamically. This is because the reduction of dissolved oxygen in the solution occurs and produces an additional current, which opposes the oxide growth current produced by adsorption and subsequent charge reaction. 相似文献
1000.
研究了组织形态、主要间隙元素O含量及热处理制度对Ti-2Al-2.5Zr钛合金丝材力学性能的影响规律。结果表明,O是丝材延伸率的主要影响因素,应对O含量做严格控制:均匀细小的等轴组织对丝材延伸率及强度的提高有利;在700℃-850℃进行真空退火,可使丝材具有较好的塑性与强度的匹配。通过以上研究,使丝材延伸率有较大提高,塑性、强度均稳定达到了相关标准要求。 相似文献