Search results for "Exchange"
showing 10 items of 2035 documents
Investigation of the swelling behavior of cationic exchange resins saturated with Na+ ions in a C3S paste
2015
Ion exchange resins (IERs) are widely used by the nuclear industry to decontaminate radioactive effluents. Spent products are usually encapsulated in cementitious materials. However, the solidified waste form can exhibit strong expansion, possibly leading to cracking, if the appropriate binder is not used. In this work, the interactions between cationic resins in the Na+ form and tricalcium silicate are investigated during the early stages of hydration in order to gain a better understanding of the expansion process. It is shown that the IERs exhibit a transient swelling of small magnitude due to the decrease in the osmotic pressure of the external solution. This expansion, which occurs jus…
Facile hydrothermal synthesis of crystalline Ta2O5 nanorods, MTaO3 (M = H, Na, K, Rb) nanoparticles, and their photocatalytic behaviour
2014
Alkali metal tantalates are of interest for applications in photocatalysis as well as in high temperature resistance or capacitor dielectric materials. We have synthesized nanosized Ta2O5 rods and MTaO3 cubes (M = Na, K, Rb) hydrothermally and demonstrate the pH dependence of the synthesis of tantalum oxide and tantalate nanoparticles. The morphologies of the nanoparticles range from particle agglomerates in acidic reaction media over rods at neutral pH to tantalate cubes in basic reaction media. Whereas there is no apparent influence of the base cation on the particle morphology, there is a pronounced effect on the particle composition. At high base concentrations cubic tantalate particles…
Evaluation of Silver Ion Bioavailability from Silver Doped Hydroxyapatite
2014
Thein vitrobehavior of silver doped hydroxyapatite (HAp/Ag) prepared by two wet precipitation routes were studied in water and simulated body fluid (SBF). In order to evaluate the silver ion bioavailability from HAp/Ag, the samples were soaked in SBF or water and kept at 37°C for fixed periods of time up to one year. After fixed periods of time, analyses of SBF and water solutions were performed and silver ion concentration within the solutions determined. According to silver release data from dense and porous HAp/Ag ceramic scaffolds, release rate of silver ions were reduced in water as the ion exchange there was slower compared to SBF solution. X-ray diffraction and scanning electron micr…
Assembly and Speed in Ion-Exchange-Based Modular Phoretic Microswimmers.
2017
We report an experimental study on ion-exchange-based modular microswimmers in low-salt water. Cationic ion-exchange particles and passive cargo particles assemble into self-propelling complexes, showing self-propulsion at speeds of several micrometers per second over extended distances and times. We quantify the assembly and speed of the complexes for different combinations of ion-exchange particles and cargo particles, substrate types, salt types and concentrations, and cell geometries. Irrespective of the experimental boundary conditions, we observe a regular development of the assembly shape with increasing number of cargo. Moreover, the swimming speed increases stepwise upon increasing…
Charged colloidal model systems under confinement in slit geometry: a new setup for optical microscopic studies.
2013
A new experimental setup for optical microscopic studies of charged colloidal model systems under confinement between two flat walls is presented. The measurement cell consists of optically flat quartz substrates attached to piezo actuators. Those facilitate fast and flexible adjustment of the confining geometry. Optionally, the local cell height can be quantitatively controlled by in situ interferometric measurements. Proper choice of materials guarantees sufficient chemical inertia against contamination with salt ions. For efficient preparation of charged colloidal suspensions under strongly deionized conditions, the cell can be connected to a conventional pump circuit including a mixed b…
Crystal growth, structure, magnetic properties and theoretical exchange interaction calculations of Cu2MnBO5
2016
Single crystals of ludwigite Cu2MnBO5 were synthesized by flux growth technique. The detailed structural and magnetic characterizations of the synthesized samples have been carried out. The cations composition of the studied crystal was determined using X-ray diffraction and EXAFS technique, the resulting composition differ from the content of the initial Mn2O3–CuO components of the flux. Magnetic susceptibility measurements and the calculations of the exchange integrals in frameworks of indirect coupling model revealed that monoclinic distortions strongly affect exchange interactions and appearance of magnetic ordering phase at the temperature T=93 K. The hypothesis of the existence of sev…
Smart High-κ Nanodielectrics Using Solid Supported Polyoxometalate-Rich Nanostructures
2011
Utilizing Langmuir-Blodgett deposition and scanning probe microscopy, we have investigated the extent to which cations alter the self-assembly processes of hybrid polyoxometalates (POMs) on surfaces. The well-defined 2D hexagonal nanostructures obtained were extensively characterized and their properties were studied, and this has revealed fascinating dielectric behavior and reversible capacitive properties. The nanostructures are extremely stable under ambient conditions, and yet exhibit fascinating self-patterning upon heating. These findings present POMs as effective smart nanodielectrics and open up a new field for future POM applications. (c) 2011 American Chemical Society.
Centrifugal Water Pump Driven With a DC Motor Powered by an Emulator of MK5-E Proton Exchange Membrane Fuel Cell Stacks
2004
Direct Current (DC) motors can be directly powered by Proton Exchange Membrane Fuel Cell (PEMFC) Stacks, to obtain plants with little maintenance and good reliability. To obtain a suitable efficiency working plant, it’s necessary to correctly match the load in order to operate in proximity to the best power line of the FC stacks generator. Otherwise by a proper field current regulation of a separately excited DC motor directly powered by a FC stacks generator, it is possible to extract from the generator itself the correct power for every temperature level. The present interest for this problem has advised the Authors to perform an experimental investigation, whose results are reported in t…
Temperature measurements along a vertical borehole heat exchanger: A method comparison
2019
Abstract The standard thermal response tests (TRT) provide integral and effective thermal parameters of the ground in the vicinity of borehole heat exchangers (BHE). However, typical ground properties are heterogeneously distributed. As a result, advanced TRT such as distributed and enhanced TRT are growing in popularity as they provide more spatial information of the thermal properties. Thus, the objective of this study is to compare various instruments to measure the depth-dependent temperatures using standard Pt100-sensors, fiber optical thermometers and novel instruments such as Geowire, Geoball and GEOsniff®. The investigations are carried out in a 30 m length test borehole. The result…
Sample building orientation effect on porosity and mechanical properties in Selective Laser Melting of Ti6Al4V titanium alloy
2022
Abstract In recent decades, the focus of research has shifted towards new production technologies with the aim of optimizing production and reducing costs. These innovative technologies include additive manufacturing processes as Selective Laser Melting (SLM). The analysis of the literature on the identification of optimal building orientation to maximize the mechanical properties and minimize porosity of the final products highlights contrasting results, denoting that the thermomechanical complexity of the process, as associated with the variation of the building orientation, has not been fully clarified. A study in which the building orientation effect was evaluated together with the geom…