Slip deformation of crystalline mercury between 77°K and 234°K.

Various orientations of single crystals of mercury, grown by a modified Bridgman technique from triply-distilled mercury containing direction operates very readily at about 200°K in crystals for which the associated Schmid factor is sufficiently large. In this case slip can occur on any plane containing this direction, and the macroscopic slip plane tends to lie near the maximum resolved shear stress plane. The results of the bend-tests indicated that slip asymmetry can be pronounced for slip in the direction. Whether this effect is due to structural asymmetry influencing the cores of the dislocations involved in the slip processes, or whether it is due to opposite normal stresses across the slip planes is however difficult and perhaps impossible to ascertain. Wear the melting point temperature it was shown that non-crystallographic slip in the direction can also operate particularly for the bend-tests in which the choice of the bend-axis influences the slip systems and the macroscopic slip plane. This unexpected behaviour appears to arise because of the constraints imposed by the bending mode of deformation. In the case of wavy slip the macroscopic slip plane tends to be nearer the crystallo-graphic {111} slip plane than the m.r.s.s.p. At lower temperatures slip in irrational directions has been observed in several crystals, and the operative slip plane was determined as crystallographic {111}. The orientation dependence of this slip mode is interpreted using Schmid-factors for the most highly stressed variants of the maximum resolved shear stress direction, {111} slip system and the , m.r.s.s.p. slip system. Tensile tests at about 200°K gave critical resolved shear stresses of 0.08 +/- 0.02 Nn[-2] and 0.06 +/- 0.02 Nm[-2] for {111} and {111} slip respectively. The ratio of these values is consistent with the ratio of at least 1.9 deduced from Schmid factors, although in the bend-tests a ratio of 1.3 was obtained. The resolved shear stress for slip at yield is both temperature and orientation dependent for temperatures below about 150°K, and below 84°K a critical value for the r.s.s.s. in , and irrational directions cannot be deduced. At 77° K, the slip systems '{ }' and {111} '' are approximately four times larger than those for the system {111} . The orientation dependence of the r.s.s.s. at yield cannot be attributed either to the normal stresses across the slip planes' or to slip in more than one system. A critical resolved shear strain criterion is also considered but unfortunately cannot be fully investigated until accurately determined values of the six elastic constants for all test temperatures become available. It is concluded that the controlling factor for the thermal component of the r.s.s.s. at yield is probably some average between a c.r.s. stress and a c.r.s. strain criterion

Slip deformation of crystalline mercury between 77°K and 234°K.

Various orientations of single crystals of mercury, grown by a modified Bridgman technique from triply-distilled mercury containing direction operates very readily at about 200°K in crystals for which the associated Schmid factor is sufficiently large. In this case slip can occur on any plane containing this direction, and the macroscopic slip plane tends to lie near the maximum resolved shear stress plane. The results of the bend-tests indicated that slip asymmetry can be pronounced for slip in the direction. Whether this effect is due to structural asymmetry influencing the cores of the dislocations involved in the slip processes, or whether it is due to opposite normal stresses across the slip planes is however difficult and perhaps impossible to ascertain. Wear the melting point temperature it was shown that non-crystallographic slip in the direction can also operate particularly for the bend-tests in which the choice of the bend-axis influences the slip systems and the macroscopic slip plane. This unexpected behaviour appears to arise because of the constraints imposed by the bending mode of deformation. In the case of wavy slip the macroscopic slip plane tends to be nearer the crystallo-graphic {111} slip plane than the m.r.s.s.p. At lower temperatures slip in irrational directions has been observed in several crystals, and the operative slip plane was determined as crystallographic {111}. The orientation dependence of this slip mode is interpreted using Schmid-factors for the most highly stressed variants of the maximum resolved shear stress direction, {111} slip system and the , m.r.s.s.p. slip system. Tensile tests at about 200°K gave critical resolved shear stresses of 0.08 +/- 0.02 Nn[-2] and 0.06 +/- 0.02 Nm[-2] for {111} and {111} slip respectively. The ratio of these values is consistent with the ratio of at least 1.9 deduced from Schmid factors, although in the bend-tests a ratio of 1.3 was obtained. The resolved shear stress for slip at yield is both temperature and orientation dependent for temperatures below about 150°K, and below 84°K a critical value for the r.s.s.s. in , and irrational directions cannot be deduced. At 77° K, the slip systems '{ }' and {111} '' are approximately four times larger than those for the system {111} . The orientation dependence of the r.s.s.s. at yield cannot be attributed either to the normal stresses across the slip planes' or to slip in more than one system. A critical resolved shear strain criterion is also considered but unfortunately cannot be fully investigated until accurately determined values of the six elastic constants for all test temperatures become available. It is concluded that the controlling factor for the thermal component of the r.s.s.s. at yield is probably some average between a c.r.s. stress and a c.r.s. strain criterion

Recovery of Thorium by High-Capacity Biopolymeric Sorbent

The potential of prepared alginate biopolymers as a natural, economic, effective, non-toxic biosorbent was investigated for the recovery of thorium ions in this study. The experiments were carried out to study the effects of various physico-chemical parameters on biosorption and desorption of thorium. The biosorption process was examined by various isotherm models and equilibrium data were successfully described by a Langmuir model very well. The monolayer biosorption capacity was found as 169.50 mg/g. The thermodynamic parameters such as variations of enthalpy, entropy, and Gibbs free energy for thorium biosorption were also defined and the results suggest that endothermic nature of the process. The prepared alginate biopolymers exhibit high uptake capacity and regeneration potential for biosorption of thorium. © 2013 Copyright Taylor and Francis Group, LLC

bentonite composite adsorbent

The algae-clay composite adsorbent was tested for its ability to recover U(VI) from diluted aqueous solutions. Macro marine algae (Ulva sp.) and clay (Na bentonite) were used to prepare composite adsorbent. The ability of the composite adsorbent to adsorp uranium(VI) from aqueous solution has been studied at different optimized conditions of pH, concentration of U(VI), temperature, contact time. Parameters of desorption were also investigated to recover the adsorbed uranium. The adsorption patterns of uranium on the composite adsorbent followed the Freundlich and Dubinin-Radushkevich isotherms. The thermodynamic parameters such as the enthalpy Delta H, entropy Delta S and Gibbs free energy Delta G were calculated from the slope and intercept of lnK(d) vs. 1/T plots. The results suggested that the Ulva sp.-Na bentonite composite adsorbent is suitable as sorbent material for recovery and biosorption/adsorption of uranium ions from aqueous solutions.C1 Pamukkale Univ, Fac Arts & Sci, Dept Chem, Denizli, Turkey.Ege Univ, Inst Nucl Sci, TR-35100 Bornova, Turkey

Recovery of Thorium by High-Capacity Biopolymeric Sorbent

The potential of prepared alginate biopolymers as a natural, economic, effective, non-toxic biosorbent was investigated for the recovery of thorium ions in this study. The experiments were carried out to study the effects of various physico-chemical parameters on biosorption and desorption of thorium. The biosorption process was examined by various isotherm models and equilibrium data were successfully described by a Langmuir model very well. The monolayer biosorption capacity was found as 169.50mg/g. The thermodynamic parameters such as variations of enthalpy, entropy, and Gibbs free energy for thorium biosorption were also defined and the results suggest that endothermic nature of the process. The prepared alginate biopolymers exhibit high uptake capacity and regeneration potential for biosorption of thorium

Chapter 16 - Biosorption of Uranium and Thorium by Biopolymers

Biosorption can be defined as the removal of substances, such as metal or metalloid species, compounds, and particulates from solution by biological material or their products, especially bacteria, algae, yeast, and fungi by physicochemical binding. Among these biosorbents, biopolymers have been preferred over other materials because of their advantages, including biodegradability, hydrophilicity, and presence of carboxylic groups. The increase in the nuclear industry and other anthropogenic activities has intensified environmental pollution, with the accumulation of radioactive elements as uranium and thorium. Therefore, it is very important to identify potential effective and environmentally safe adsorbents for the removal and recovery of uranium and thorium. This chapter reviews the state of art of biosorption of uranium and thorium by biopolymers and compares the results found in the literature and the biosorption results on uranium and thorium by Ca-alginate biopolymer beads. © 2014 Elsevier B.V. All rights reserved

Distribution of uranium on zeolite X and investigation of thermodynamic parameters for this system

Actinides-97 Conference -- SEP 21-26, 1997 -- BADEN BADEN, GERMANYWOS: 000074686200166The sorption of U(VI) from aqueous solutions on zeolite X has been studied by a batch technique. Distribution coefficients (K-d) were determined for sorption systems as a function of sorbate concentration, pH, contact time and temperature. The sorption isotherm was formed according to the Langmuir isotherm. Thermodynamic parameters have been determined at different temperatures. The Delta H degrees values for U(VI) on zeolite X were -29.5147 kT mol(-1) at 313 K at pH 3 and -19.8705 kJ mol(-1) at 303 K at pH 9. The sorption of U(VI) on zeolite X is an exothermic in nature. Negative values of Delta G degrees show the spontaneous values for U(VI) that become less negative at higher temperatures, which shows that sorption is less favoured at higher temperatures. (C) 1998 Elsevier Science S.A