Benjamin P. Wilson

The formation and characterisation of ultra-thin films containing Ag nanoparticles

A simple three step method for creating ultra-thin films, which contain Ag nanoparticles, on both glass and stainless steel surfaces, is presented. First, during the immersion into N-(2-aminoethyl)-3-aminopropyl-trimethoxysilane (DIAMO) a monolayer of DIAMO is attached on the sample surface after which immersion in silver nitrate is performed and a complex between the two amino groups of DIAMO and silver ions forms, leading to large clusters on the surface. During the annealing step these silver containing clusters are converted into silver nanoparticles which are homogeneously distributed and bound to the surface. The formation of the film was characterised using UV/Vis, FE-SEM and FE-AES. Additionally, SERS activity of the surface and the effect of the attachment of the nanoparticles on their antibacterial nature were also investigated.

QCM study of the adsorption of polyelectrolyte covered mesoporous TiO2 nanocontainers on SAM modified Au surfaces.

Mesoporous TiO(2) nanocontainers (NCs) covered with polyelectrolyte multilayers were adsorbed on self-assembled monolayer (SAM) modified gold substrates at different values of pH and ionic strength. The adsorption process was followed in situ by means of a quartz crystal microbalance (QCM) and the morphology of the adsorbate was investigated by means of FE-SEM images taken of the substrates after each adsorption process. Deposition could be achieved if either the particles and the surface had opposite charge, or if the salt concentration was sufficiently high, reducing the repulsion between the spheres and the surface. In the latter case the adsorption kinetics could be explained in the context of the DLVO-theory. Using conditions of like charges, one has a means to control the speed of deposition by means of ionic strength. However, interparticle aggregation and cluster deposition on the surface were observed at high ionic strength. Such conditions have to be avoided to obtain a uniform deposition of separated nanocontainers on the surface.

Noncovalent Surface Modification of Cellulose Nanopapers by Adsorption of Polymers from Aprotic Solvents

Basic adsorption of hydrophobic polymers from aprotic solvents was introduced as a platform technology to modify exclusively the surfaces of cellulose nanopapers. Dynamic vapor sorption demonstrated that the water vapor uptake ability of the nanopapers remained unperturbed, despite strong repellency to liquid water caused by the adsorbed hydrophobic polymer on the surface. This was enabled by the fact that the aprotic solvents used for adsorption did not swell the nanopaper unlike water that is generally applied as the adsorption medium in such systems. As case examples, the adsorptions of polystyrene (PS) and poly(trifluoroethylene) (PF3E) were followed by X-ray photoelectron spectroscopy and water contact angle measurements, backed up with morphological analysis by atomic force microscopy. The resulting nanopapers are useful in applications like moisture buffers where repellence to liquid water and ability for moisture sorption are desired qualities.

Dissolution Control of Mg by Cellulose Acetate−Polyelectrolyte Membranes

Cellulose acetate (CA)-based membranes are used for Mg dissolution control: the permeability of the membrane is adjusted by additions of the polyelectrolyte, poly(N,N-dimethylaminoethyl methacrylate) (PDMAEMA). Spin-coated films were characterized with FT-IR, and once exposed to an aqueous solution the film distends and starts acting as a membrane which controls the flow of ions and H2 gas. Electrochemical measurements (linear sweep voltammograms, open-circuit potential, and polarization) show that by altering the CA:PDMAEMA ratio the dissolution rate of Mg can be controlled. Such a control over Mg dissolution is crucial if Mg is to be considered as a viable, temporary biomedical implant material. Furthermore, the accumulation of corrosion products between the membrane and the sample diminishes the undesirable effects of high local pH and H2 formation which takes place during the corrosion process.

Investigating changes in corrosion mechanism induced by laser welding galvanised steel specimens using scanning vibrating electrode technique

Abstract A novel three-dimensional scanning vibrating electrode technique (3D SVET) apparatus is described, which uses a bifunctional probe to record topographical and current density data. This apparatus is used to investigate the localised corrosion occurring on 2 cm2 exposed areas of flat specimens of electroplated zinc and galvannealed (Zn-Fe alloy coated) 1·2 mm sheet steel and specimens of the same substrates laser welded together, freely corroding in near neutral, aerated, aqueous chloride electrolyte. On flat galvannealed (IZ) specimens anodic events are highly localised and occur at random over the exposed specimen surface during a 24 h immersion period. This reflects the progressive dezincification of zinc rich areas of the iron zinc intermetallic coating. By contrast on flat electroplated zinc (EZ) specimens anodic activity is localised but corrosion initiates at a single anodic centre, eventually spreading out to form a scar on the metallic surface. This concentration of anodic activity on the specimen leads to greater dezincification than for the IZ coating. The SVET data was used to provide an estimate of the total zinc loss from the 2 cm2 exposed area on the coupons of 544 μg for EZ and 236 μg for IZ respectively. The close physical proximity of anodic and cathodic events in the latter substrate is believed to lead to greater zinc (hydr) oxide formation and hence lower measured zinc loss. Laser welded specimens were prepared by joining IZ to IZ and IZ to EZ coated 1·2 mm steel panels. A 2 cm2 exposed area was investigated using SVET with ca. 1 cm2 exposed either side of the weld. The joining of IZ specimens together using a laser weld changes the localisation of anodic activity in neutral aerated sodium chloride solution dramatically. In this instance focal anodes initially concentrate next to the weld area in a zone enriched in zinc (and depleted in iron) as a result of the welding process. This localisation of anodic and cathodic activity next to the weld reduces the anodic damage on the IZ remote to the heat affected zone. When specimens of EZ and IZ are laser welded together all anodic activity becomes focussed on the EZ specimens with a total zinc loss over 24 h from the 1 cm2 exposed area measured as 489 μg, very close to that of the zinc loss from the EZ specimen (2 cm2) alone. By contrast there is no measurable zinc loss from the IZ portion specimen under these conditions. The increase in zinc loss per unit area from the EZ reflects the additional cathodic area provided by the connected IZ coupon and bimetallic coupling of the metallic coatings.

Life cycle assessment of sponge nickel produced by gas atomisation for use in industrial hydrogenation catalysis applications

PurposeThis paper presents a cradle-to-grave comparative life cycle assessment (LCA) of new gas atomised (GA) sponge nickel catalysts and evaluates their performance against the current cast and crush standard currently used in the industrial hydrogenation of butyraldehyde to butanol.MethodsA comparative LCA has been made, accounting for the energy used and emissions throughout the entire life cycle of sponge nickel catalysts—ranging from the upstream production of materials (mainly aluminium and nickel), to the manufacturing, to the operation and finally to the recycling and disposal. The LCA was performed following ISO14040 principles where possible, and subsequently implemented in the software package GaBi 4.3. The CML2001 impact assessment methodology was used, with primary focus on comparing catalysts for equivalent greenhouse gasses generated over their lifetime and their relative global warming potential and secondary focus on acidification potential. This is justified as the lifetime is dominated by energy use in the operational phase, and acidification is dominated by the production of nickel for which existing ISO14040 collected data has been used. A sensitivity analysis was used to provide a number of scenarios and overall environmental performances of the various sponge nickels considered when compared to the existing industrial standard.Results and discussionIt was found that the energy and emissions during the operation phase associated with a given catalyst significantly outweigh the primary production, manufacturing and recycling. Primary production of the nickel (and to a lesser extent molybdenum when used as a dopant) also has a significant environmental impact in terms of acidification potential, but this is offset by operational energy savings over the catalysts’ estimated lifetime and end of life recyclability. Finally, the impact of activity improvement and lifetime duration of sponge nickel catalysts was determined as both total life cycle energy for operational use and as a total life cycle global warming potential.ConclusionsFrom this assessment, the newly developed, higher activity spongy nickel catalysts produced by gas atomisation could have a significantly lower environmental impact than the current industry standard cast and crush method. Given the potential environmental benefits of such catalysts, applications in other processes that require a catalyst should also be investigated.

Strongly reduced thermal conductivity in hybrid ZnO/nanocellulose thin films

Abstract Utilizing a combination of atomic layer deposition and dip-coating techniques, we have incorporated natural nanocellulose fibers into an inorganic matrix in order to create a layered hybrid inorganic–organic thin-film structure. Such layer-engineered hybrid materials with an unorthodox combination of components are highly potential candidates for exciting new properties. Here, we show a more than an order of magnitude reduction in the cross-plane thermal conductivity for ZnO thin films achieved with the regular inclusion of the cellulose nanofiber layers. We foresee that a similar approach as presented here for ZnO could also be applied to other inorganic materials based on earth-abundant elements to influence their thermal transport properties.

Effect of Additives on Smut-Layer Formation and Pitting during Aluminum Etching in Hydrochloric Acid

The structure of the smut film and underlying surface morphology of aluminum AA1050 electrograined in hydrochloric acid withadditions of acetic acid, citric acid, or disodium phenyl phosphate dihydrate was studied. In addition, a series of titrationexperiments was undertaken to determine changes to the buffering effect of the electrolyte due to the inclusion of the additives.Characterization of the chemical and structural properties of the etch films was performed by both solid state and solution nuclearmagnetic resonance NMR , while surface morphologies with and without smut film were investigated by scanning electronmicroscopy SEM . Experimental results indicate that modifications to electrolyte composition by different types of additive caninfluence the resulting smut-layer formation. Furthermore, the effect of these changes to the chemical nature and smut morphologyby the inclusion of additives is to alter the final pitted surface structure of the underlying aluminum. These results clearlydemonstrate the importance of smut-film formation on pitting and the combination of NMR and SEM as a useful investigative toolfor these types of processes.© 2007 The Electrochemical Society. DOI: 10.1149/1.2800757 All rights reserved.Manuscript submitted July 9, 2007; revised manuscript received August 21, 2007. Available electronically November 5, 2007.

Selective reductive leaching of cobalt and lithium from industrially crushed waste Li-ion batteries in sulfuric acid system

Recycling of valuable metals from secondary resources such as waste Li-ion batteries (LIBs) has recently attracted significant attention due to the depletion of high-grade natural resources and increasing interest in the circular economy of metals. In this article, the sulfuric acid leaching of industrially produced waste LIBs scraps with 23.6% cobalt (Co), 3.6% lithium (Li) and 6.2% copper (Cu) was investigated. The industrially produced LIBs scraps were shown to provide higher Li and Co leaching extractions compared to dissolution of corresponding amount of pure LiCoO2. In addition, with the addition of ascorbic acid as reducing agent, copper extraction showed decrease, opposite to Co and Li. Based on this, we propose a new method for the selective leaching of battery metals Co and Li from the industrially crushed LIBs waste at high solid/liquid ratio (S/L) that leaves impurities like Cu in the solid residue. Using ascorbic acid (C6H8O6) as reductant, the optimum conditions for LIBs leaching were found to be T = 80 °C, t = 90 min, [H2SO4] = 2 M, [C6H8O6] = 0.11 M and S/L = 200 g/L. This resulted in leaching efficiencies of 95.7% for Li and 93.8% for Co, whereas in contrast, Cu extraction was only 0.7%. Consequently, the proposed leaching method produces a pregnant leach solution (PLS) with high Li (7.0 g/L) and Co (44.4 g/L) concentration as well as a leach residue rich in Cu (up to 12 wt%) that is suitable as a feed fraction for primary or secondary copper production.

Lanthanide-alkali double sulfate precipitation from strong sulfuric acid NiMH battery waste leachate

In NiMH battery leaching, rare earth element (REE) precipitation from sulfate media is often reported as being a result of increasing pH of the pregnant leach solution (PLS). Here we demonstrate that this precipitation is a phenomenon that depends on both Na+ and SO42- concentrations and not solely on pH. A two-stage leaching for industrially crushed NiMH waste is performed: The first stage consists of H2SO4 leaching (2 M H2SO4, L/S = 10.4, V = 104 ml, T = 30 °C) and the second stage of H2O leaching (V = 100 ml, T = 25 °C). Moreover, precipitation experiments are separately performed as a function of added Na2SO4 and H2SO4. During the precipitation, higher than stoichiometric quantities of Na to REE are utilized and this increase in both precipitation reagent concentrations results in an improved double sulfate precipitation efficiency. The best REE precipitation efficiencies (98-99%) - achieved by increasing concentrations of H2SO4 and Na2SO4 by 1.59 M and 0.35 M, respectively - results in a 21.8 times Na (as Na2SO4) and 58.3 times SO4 change in stoichiometric ratio to REE. Results strongly indicate a straightforward approach for REE recovery from NiMH battery waste without the need to increase the pH of PLS.