Browsing by Author "Jones, Paul M."
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Item Open Access Extending the functionality and efficiency of energy storage tanks in solar power plants(2011-09-23T00:00:00Z) Sansom, Christopher L.; Dorey, Robert A.; Jones, Paul M.; Peterson, J.; Jakubczyk, EwaImprovements to the efficiency of Solar Power Plants are a key objective as the technology matures. Oneopportunity yet to be explored involves energy harvesting from hot components located within the powerplant, utilizing waste heat. We describe two approaches to energy harvesting in this context. These are basedfirstly on TEC device technology, where we describe the use of both commercially available components andour work to develop more efficient TEC devices based on nanostructured oxides. Secondly, we describe analternative thermomagnetic approach based on nanoparticle ferrofluids for thermal scavenging and theconversion of heat to usable electrical energy. For both approaches we present concept designs for theharvesting of waste heat from thermal energy storage (TES) tanks, in order to demonstrate the potential of thetechnology.Item Open Access Innovative method to produce large-area freestanding functional ceramic foils(Elsevier, 2018-03-31) Leighton, Glenn J. T.; Jones, Paul M.; Lonne, Quentin; Dorey, Robert A.; Giuliano, FabienUsing thick and thin films instead of bulk functional materials presents tremendous advantages in the field of flexible electronics and component miniaturization. Here, a low-cost method to grow and release large-area, microscale thickness, freestanding, functional, ceramic foils is reported. It uses evaporation of sodium chloride to silicon wafer substrates as sacrificial layers, upon which functional lead titanate zirconate ceramic films are grown at 710 °C maximum temperature to validate the method. The freestanding, functional foils are then released by dissolution of the sacrificial sodium chloride in water and have the potential to be integrated into low-thermal stability printed circuits and flexible substrates. The optimization of the sodium chloride layer surface quality and bonding strength with the underlying wafer is achieved thanks to pre-annealing treatment.Item Open Access Insights into the relationship between inherent materials properties of PZT and photochemistry for the development of nanostructured silver.(Royal Society of Chemistry, 2007-09-25) Dunn, Steve; Tiwari, Divya; Jones, Paul M.; Gallardo, Diego E.Recently there has been great interest in using patterned ferroelectric materials for the photochemical growth of metal nanostructures. Variations in surface and sub-surface structure influence the photochemical processes. Here we show that crystallography, and hence remnant polarization, of the ferroelectric affects photo-deposition. The ratio of metal growth on c– and c+ domains varies from 1 : 2 for [100] to 1 : 100 for [111]. This is shown to be dependent on the variations in the band structurItem Open Access Interaction of Stern layer and domain structure on photochemistry of lead-zirconate-titanate.(Institute of Physics, 2009-03) Jones, Paul M.; Dunn, StevePerovskite ferroelectric materials such as PZT have long been known to have wideband semiconducting properties. It has also been found that they have interesting spatially controllable surface photochemical effects that are not seen in 'normal' semiconductors. This has led to their being studied as possible tools in areas such as metal salt reduction and oxidation for nanoparticle growth. This paper discusses the effects of incident photon energy on the reduction of Ag0 onto PZT(30/70) surfaces with particular emphasis on the part played by energy band bending and the Stern layer. It was found that for increasing photon energy between 4.4 and 5.0 eV both the [1 1 1] and the [1 0 0] orientations of PZT followed a similar trend in that the average Ag0 cluster cross-sectional area increased by a ratio of ca 1.6 to 1. This increase was put down to the higher energy photons exciting more electrons from deeper in the density of states for the material allowing a greater reduction rate of Ag+ at the surface.Item Open Access Nanoparticle Synthesis via Thin Film Ferroelectric Templates:Surface interactions and effects(Cranfield University, 2008) Jones, Paul M.; Dunn, S. C.An investigation into the processes taking place at the surface interface of ferroelectric Pb(Zr1-x,Tix)O3 immersed in metal salt solution under ultraviolet illumination is presented. The semiconducting and switchable dipolar nature of this material allows the spatial separation and control of photo-induced reduction and oxidation across its surface interface. These properties can be of application in novel techniques such as the controlled growth of metallic nanoparticles across specific polar domains. 70nm thick Pb(Zr0.3,Ti0.7)O3 samples, PZT(30/70), are manufactured using the sol gel methodology, two crystallographic orientations being produced. The orientation being controlled by the substrate used; Si was used for [111] orientation and MgO for [100]. The initial work with wideband ultraviolet light shows that the reduction and growth of silver on the PZT surface is greatly influenced by the structure of the film. The crystallographic orientation of the film affects metal deposition such that on [111] films the metal deposits only on positive domains, where as the [100] films experience deposition on both positive and negative domains. This is shown to be due to the difference in width of the space charge region, Δw = 4.4nm, between the [111] and [100] samples so that the negative domain on [100] samples have 10 19 times higher chance of electron tunnelling compared to the [111]. It is also shown that grain boundaries have the greatest effect on the growth of metal, with a metal cluster growth rate 51 times faster than elsewhere on the surface. This increased rate of growth is due to the effect a grain boundary has on the surrounding area, the energy band bending at the boundary attracting charge carriers from the grains around it. The interface types ranked from greatest to lowest influence are grain boundaries, positive domains, domain boundaries and finally interphase boundaries.ii It is shown that the stern layer, strongly adsorbed charged ions of opposite sign to the surface charge, at the PZT/solution interface act as an insulating layer to metal reduction. The accumulation of photoexcited charge carriers at points along grain boundaries causes the surface potential gradient to alter and allows metal reduction and thus clusters to nucleate. The energy required to cause this variation is investigated by use of narrow band, 5nm bandwidth, ultraviolet. For energy from 4.4eV to 5 eV, it is found there is an increase in the average silver cluster cross sectional area by a ratio of ca 1.6 to 1 for both the [111] and [100] orientations of PZT. Finally it is shown that the type of metal salt used in the photochemical process affects the type of reaction that takes place at the sample surface. For a cation to reduce on positive domains its reduction potential needs to be below the bottom edge of the conduction band of PZT. Chloride salts, that sit above the conduction band, cause decomposition of the negative domains. Use is made of these effects to find the position of the bottom of the conduction band for PZT. It is found that across similar [111] PZT samples FeCl2 can both reduce on positive domains and decompose negative domains, this puts the bottom of the conduction band for PZT(30/70) between 4.06 and 4.36 eV from vacuum. It is also discovered that the type of anion affects the decomposition of the negative domains. Nitrate salts with cations above the conduction band cause no decomposition whereas chlorides do. The decomposition is shown to be the loss of Pb from the negative surface.Item Open Access Photo-reduction of silver salts on highly heterogeneous lead zirconate titanate(Institute of Physics, 2007) Jones, Paul M.; Dunn, SteveThis paper presents the work undertaken to determine the influences on the photo-induced growth of silver nanoclusters on the surfaces of lead zirconate titanate thin films. The lead zirconate titanate films were grown on indium tin oxide coated glass. They exhibited a highly textured surface and can be treated as wide bandgap semiconductors that exhibit ferroelectric behaviour. We show that there is a preferential deposition of silver metal on the ferroelectric films that is related not only to the polarization state of the ferroelectric domains but also to the surface defects such as grain boundaries and defects within the film. The greatest deposition rates are found to occur at grain boundaries where there is an approximately 40:1 ratio of silver clusters when compared to the native positive domains exhibited by the lead zirconate titanate. We propose that the mechanism for cluster growth depends on the availability, and diffusion rate, of electrons into the growing cluster and that the clusters grow from a discrete nucleation point. We also show that the growth of a monolayer of silver is sufficient to prevent the formation of electron–hole pairs by blocking the UV irradiation and that the silver nanoparticles are readily removed from the surface using an ultrasonic bath leading to a possible new method of manufacturing metal nanoparticles.Item Open Access A straightforward route to sensor selection for IoT systems(Taylor and Francis, 2018-09-12) Jones, Paul M.; Lonne, Quentin; Talaia, Pedro; Leighton, Glenn J. T.; Botte, Gerardine G.; Mutnuri, Srikanth; Williams, LeonThe Internet of Things (IoT) allows for remote management and monitoring of many aspects of everyday life at the individual and industrial levels. However, designing these systems within constraints of cost and operational context can be a real challenge. The sensor network must be strategically designed, which means selecting the most appropriate sensors to collect a specific measurement in a specific environment and then optimizing their deployment and utilization. To facilitate sensor selection, we propose a straightforward, color-coded, three-sieve selection tool and demonstrate the efficacy of this method through real-life exemplars. The selection tool could be applied to other kinds of technologies as well.Item Open Access Synthesis and characterization of Mn0.5Zn0.5Fe2O4 and Fe3O4 nanoparticle ferrofluids for thermo-electric conversion(Elsevier Science B.V., Amsterdam., 2013-06-30T00:00:00Z) Sansom, Christopher L.; Jones, Paul M.; Dorey, Robert A.; Beck, C.; Stanhope-Bosumpim, A.; Peterson, J.Ferrofluids containing nanoparticles of Mn0.5Zn0.5Fe2O4 (MZ5) and Fe3O4 (magnetite) have been examined as potential thermal transport media and energy harvesting materials. The ferrofluids were synthesized by chemical co-precipitation and characterized by EDX to determine composition and by TEM to determine particle size and agglomeration. A range of particle coatings and carrier fluids were used to complete the fluid preparation. Commercially available ferrofluids were tested in custom built rigs to demonstrate both thermal pumping (for waste heat removal applications) and power induction (for power conversion and energy harvesting applications). The results indicate that simple ferrofluids possess the necessary properties to remove waste heat, either into thermal storage or for conversion to electrical power.