Search results for "SCALE"

Fabrication and characterization of micrometer-scale ZnO memristors

2015

Memristors are an interesting class of resistive random access memory (RRAM) based on the electrical switching of metal oxide film resistivity . They are characterized for exhibiting resistive switching between a high-resistance state (HRS) and a low-resistance state (LRS) and have been recently considered as one of the most promising candidates for next-generation nonvolatile memory devices because of their low power consumption, fast switching operation, nondestructive readout, and remarkable scalability. The device structure is simply an oxide layer sandwiched between two metal electrodes. The switching behaviour is dependent both on the oxide material and the choice of metal electrodes.…

Multiscale Approach in Studying the Influence of Annealing Conditions on Conductivity of TiO2 Nanotubes

2015

Titanium oxide nanotubes (NTs) have attracted much attention during last decade due to their special characteristics such as one-dimensional highly ordered geometry with large surface area and good chemical and optical stability.

Photoelectrochemical evidence of inhomogeneous composition at nm length scale of anodic films on valve metals alloys

2015

Anodic films of different thickness (∼30 nm and 70 nm) were grown by anodizing sputtering-deposited Ta-19at% Al to different formation voltages. N incorporation into the anodic films was inducing by performing the anodizing process in ammonium containing solutions. Layered anodic films were prepared by a double formation procedure with a first anodizing step in ammonium biborate solution and second anodizing step in borate buffer solution, or vice versa. Glow Discharge Optical Emission Spectroscopy was employed to show the distribution of N across the oxide. Photoelectrochemical measurements evidenced a red shift of the light absorption threshold due to N incorporation. A model was proposed…

Hierarchical modelling of electrodialysis desalination process

2017

In recent years, thanks to the development of ion exchange membranes (IEMs) manufacturing industry, Electrodialysis (ED) is spreading as a viable alternative to the more common membrane desalination processes. Therefore, many research efforts have been recently devoted to studying this process both via experimental and modelling activities. In the present work a novel mathematical model for ED was developed using a multi-scale approach. This method allows to build a hierarchical simulation tool that is able to gauge the impact of all the phenomena involved in the process. The lower-hierarchy model describes the behaviour of the elementary unit of an ED stack, namely cell pair. This model is…

Reverse electrodialysis with saline waters and concentrated brines: A laboratory investigation towards technology scale-up

2015

Abstract The use of concentrated brines and brackish water as feed solutions in reverse electrodialysis represents a valuable alternative to the use of river/sea water, allowing the enhancement of power output through the increase of driving force and reduction of internal stack resistance. Apart from a number of theoretical works, very few experimental investigations have been performed so far to explore this possibility. In the present work, two RED units of different size were tested using artificial saline solutions. The effects of feed concentration, temperature and flowrate on process performance parameters were analysed, adopting two different sets of membranes. These experiments all…

Modelling of Electrodialysis units by a multi-scale process simulator

Drinking water production by desalination is an interesting alternative to face water scarcity issues. Electrodialysis (ED) is an electro-membrane process that is actually gaining attention as a competitive alternative for seawater and brackish water desalination due to recent developments in manufacturing of high performance ion exchange membranes (IEMs). In this context, a suitable process simulator can be a very effective tool in order to drive the design of optimized ED systems. In this work a novel mathematical model of ED units was developed by a hierarchical simulation strategy of separation of scales, in order to address the full simulation problem. The model was implemented in PSE …

Feasibility of Producing Electricity, Hydrogen, and Chlorine via Reverse Electrodialysis

2022

Reverse electrodialysis (RED) is a technology to generate electricity from two streams with different salinities. While RED systems have been conventionally used for electricity generation, recent works explored combining RED for production of valuable gases. This work investigates the feasibility of producing hydrogen and chlorine in addition to electricity in an RED stack and identifies potential levers for improvement. A simplified one-dimensional model is adopted to assess the technical and economic feasibility of the process. We notice a strong disparity in typical current densities of RED fed with seawater and river water and that in typical water (or chlor-alkali) electrolysis. This …

Electrodialysis with Bipolar Membranes for the Sustainable Production of Chemicals from Seawater Brines at Pilot Plant Scale

2023

Environmental concerns regarding the disposal of seawater reverse osmosis brines require the development of new valorization strategies. Electrodialysis with bipolar membrane (EDBM) technology enables the production of acid and base from a salty waste stream. In this study, an EDBM pilot plant with a membrane area of 19.2 m2 was tested. This total membrane area results much larger (i.e., more than 16 times larger) than those reported in the literature so far for the production of HCl and NaOH aqueous solutions, starting from NaCl brines. The pilot unit was tested both in continuous and discontinuous operation modes, at different current densities (200-500 A m-2). Particularly, three differe…

Process modelling of a novel acid-base flow battery based on bipolar-membranes

2021

The storage of electrical energy is crucial for a deeper penetration of renewable energies with intermittent nature, e.g. solar and wind energy. The Acid/Base Flow Battery (AB-FB) is a novel, sustainable, environmental-friendly storage technology with high energy density of the electrolyte solutions. The process is based on reversible electrodialytic techniques with bipolar membranes, which convert the electrical energy in the chemical energy associated to pH gradients and vice versa. The charge phase is a bipolar membrane electrodialysis process, while the discharge phase is a bipolar membrane reverse electrodialysis process. The stack consists of several repetitive units, called triplets,…

CFD simulations of early- to fully-turbulent conditions in unbaffled and baffled vessels stirred by a Rushton turbine

2021

Abstract Laboratory scale unbaffled tanks provided with a top cover and a baffled tank both stirred by a Rushton turbine were simulated by carrying out RANS simulations. Three different turbulence models were adopted (k- ω SST, k- e and the SSG Reynolds stress model) to predict the flow field and the relevant performance parameters (power and pumping numbers) of the tank operated from early to fully turbulent conditions. CFD results were compared with literature experimental data and DNS simulation results to validate and properly compare the models. In the range of Reynolds numbers investigated, results showed that, for the unbaffled tank, the SSG model based on Reynolds stresses is a bett…