Analysis Of Absorption Kinetics Research Articles

Moisture Absorption Properties and Kinetic Analysis of Three Different Kinds of Gauze

In this paper, the hygroscopic properties of three different gauze, that is common medical gauze, absorbable carboxymethyl gauze and absorbable oxidized gauze, were compared, and the kinetic analysis were studied. The results showed that, at 298K and RH80%, the moisture absorption rate of the three kinds of gauze follows the order of absorbable carboxymethyl gauze > absorbable oxidized gauze > common medical gauze. The moisture absorption kinetic analysis of the three kinds of gauze indicated that the second-order model proposed fits experimental data well with the correlation coefficient greater than 0.999.

Bulk hydrogen retention in neutron-irradiated graphite at elevated temperatures

Bulk hydrogen retention and the analysis of absorption kinetics have been studied on graphite samples irradiated with neutrons at various fluences. There are two kinds of hydrogen trapping sites: interstitial cluster loop edge sites (trap 1) and carbon dangling bonds at edge surfaces of a crystallite (trap 2). Neutron irradiation preferably creates trap 2 sites at lower fluences and trap 1 sites at higher fluences. The dissociation enthalpy becomes 2–3 times higher for neutron-irradiated samples due to the creation of high energy trapping sites. Absorption kinetics, such as diffusion coefficients and absorption rate constants are strongly affected by neutron irradiation and annealing after irradiation.

Hydrogen trapping in neutron-irradiated graphite

Bulk hydrogen retention and the analysis of absorption kinetics have been studied on three brands of graphite irradiated with neutrons at various fluences. Two kinds of hydrogen trapping sites may exist and be additionally produced during irradiation: interstitial cluster loop edge sites (trap 1) and carbon dangling bonds at edge surfaces of crystallites (trap 2). Neutron irradiation preferably creates trap 2 sites at lower fluences and trap 1 sites at a higher fluence above 0.017 dpa. Trap 2 tends to be annealed out at high temperatures, although trap 1 is hardly decreased even at 1873 K. Diffusion coefficients of hydrogen are reduced for 1–2 orders of magnitude after neutron irradiation at 0.047 dpa, although the activation energy of hydrogen diffusion is kept nearly the same level to unirradiated samples.

Hydrogen absorption into neutron-irradiated graphite and estimation of the trapping effect

Bulk hydrogen retention and the analysis of absorption kinetics have been studied on graphite irradiated with neutrons at various conditions. Two kinds of hydrogen trapping sites may exist and be additionally produced during irradiation: interstitial cluster loop edge sites (trap 1) and carbon dangling bonds at edge surfaces of crystallites (trap 2). Neutron irradiation preferably creates trap 2 sites at lower fluences and trap 1 sites at a higher fluence. Trap 2 tends to be annealed out at high temperatures, although trap 1 is hardly decreased even at 1873 K. The activation energy of hydrogen diffusion is found to be increased from 1.04 to 1.60 eV by neutron irradiation.

Water sorption and diffusion studies in an epoxy resin system

The kinetics of water absorption in epoxide materials was studied by the aid of a diglycidyl ether of bisphenol-A–triethylenetetramine (DGEBA–TETA) epoxy–resin system containing various amounts of the plasticizer THIOCOL (0–40 phr). The presence of plasticizer permits the formation of products with different crosslinking densities and hydrophilic characters. Dynamic water absorption experiments were carried out at 15, 40, and 70°C. For the fitting of the experimental results, a new model was used, based on a model proposed earlier by Jacobs and Jones. This model considers epoxide product as a two-phase system consisting of a master phase (where the major part of the water is absorbed), which is homogeneous and nonpolar (phase 1), and of a second phase with different density and/or hydrophilic character (phase 2). By making the assumption that water diffusion can take place independently in the different phases of the material in accordance with Fick's second law, we can calculate the diffusion coefficient D and the water content at saturation M∞ for each phase separately. Equilibrium water sorption measurements were performed at 40°C, and the data were analyzed and discussed based on the Guggenheim–Anderson–de Boer (GAB) equation, the results being in support of the two-phase model used in the analysis of absorption kinetics. The linear expansion coefficient and the glass transition temperature of the materials, employed in the discussion of the results, were measured by thermomechanical analysis. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1165–1182, 1999

Hydrogen solubility and diffusivity in neutron-irradiated graphite

Hydrogen solubility measurements and the analysis of absorption kinetics have been studied on graphite irradiated with neutrons at various fluences up to 5.4×10 24 n/m 2 . The absorption of hydrogen could be expressed as a diffusion-controlled process. The rate constant of hydrogen absorption was different from that for desorption. This difference may be ascribed to the effects of trapping sites in graphite. After neutron irradiation at 1.9×10 24 n/m 2 (~ 0.2 dpa), the hydrogen solubility was 20–50 times larger than that of unirradiated samples. The increase of hydrogen solubility was saturated above the damage level of ~ 0.3 dpa. The diffusivity of hydrogen was decreased by neutron irradiation up to 1.9×10 24 n/m 2 , and then increased above this fluence. This behavior can be ascribed to the production of the trapping sites for hydrogen, and the elongation of the distance between the basal planes by neutron irradiation.