Peter E. Childs

Bio: Peter E. Childs is an academic researcher from University of Leeds. The author has contributed to research in topics: Tetrahydrate & Proton conductor. The author has an hindex of 3, co-authored 4 publications receiving 101 citations.

Fabrication of films of hydrogen uranyl phosphate tetrahydrate and their use as solid electrolytes in electrochromic displays

Abstract: We have found that the high proton conductivity of hydrogen uranyl phosphate tetrahydrate HUO 2 PO 4 ·4H 2 O (HUP) is sufficient to enable an HUP/H x WO 3 electrochromic cell to function as fast as a cell with an acidic solution electrolyte. Switching times down to 0.3 s were found. The fabrication procedure to obtain the stable and uniform films of HUP required has been optimized, and dense sintered films up to 6 cm in diameter have been produced.

Battery and other applications of a new proton conductor: Hydrogen uranyl phosphate tetrahydrate, HUO2PO4.4H2O

Abstract: The recent discovery by Shilton and Howe that hydrogen uranyl phosphate tetrahydrate HUO2PO4.4H2O (HUP) is a rapid proton conductor, with a

Studies of layered uranium (VI) compounds. V. Mechanisms of densification of hydrogen uranyl phosphate tetrahydrate (HUP): Pressure-induced planar glide and solution phase sintering

Abstract: The good proton conductor HUO 2 PO 4 ·4H 2 O (HUP) can be easily fabricated into disks or films suitable for use in electrochromic displays, fuel cells, or batteries. Kinetic studies of the room-temperature densification reveal the presence of two mechanisms. At applied pressures of 20 MN m −2 the observed rapid densification was attributed to the gliding of the structural layers over each other to achieve essentially 100% of the theoretical density. When the powder had been wettened by solution, slow sintering occurred even in the absence of applied pressure, and we attribute this to a solution-phase sintering mechanism. The study is one of the few to be reported on platelet-shaped crystals rather than the usual spherical-shaped particles. This fact, together with the ease of cleavage of the layers, largely accounts for the excellent fabrication properties. The optimum conditions for pressing large clear robust disks are described.

Use of the Proton Conductor Hydrogen Uranyl Phosphate Tetrahydrate as the Solid Electrolyte in Hydride-Air Batteries and Hydrogen-Oxygen Fuel Cells

Abstract: Recent investigations1–9 of the good proton conductor HUO2PO4.4H2O (HUP) have opened up the prospects for its use as a solid electrolyte in a range of electrochemical cells involving transport of H+ ions. Hydrogen concentration cells of the type MHx∣HUP∣M′H2 y and electrochromic cells of the type HxWO3|HUP|HyWO9 3 have been previously described. Perhaps the most unique application of HUP is to hydride-air cells of the type MHx|HUP|O2,H2O, which we describe in this paper, and compare them to the more conventional hydrogen-type fuel cell of the kind H2|HUP|O2.

Electrochromic materials and devices for energy-efficient windows

Abstract: Numerous inorganic and organic electrochromic materials are discussed in the context of developing a film-based optical shutter for a window application. It is possible electronically to alter a window's transmission and reflection properties by use of electrochromic thin films. This allows regulation of conductive and radiative heat transfer rates, with variable optical attenuation. As a result, an aperture can be optically and thermally managed, reducing space heating and cooling loads. The properties of transition metal oxides, such as WO 3 , MoO 3 , Ir 2 O 3 and V 2 O 5 are detailed. Organic systems such as heptyl viologen and polytungsten anion are reviewed. Also, intercalated structures are discussed. Various designs of working devices are outlined with emphasis on solid-state configurations. From this quantification, materials and devices with appropriate deposition techniques for window applications are detailed.

Solid‐state sensors for trace hydrogen gas detection

Abstract: This paper reviews the development, history, theoretical basis, and experimental performance of solid‐state hydrogen detectors under flow‐through conditions available to date such as pyroelectric, piezoelectric, fiber optic, and electrochemical devices. Semiconductor hydrogen detectors will only be reviewed briefly, as excellent reviews on this subject already exist. In view of the fact that almost all the devices that will be discussed later in this paper use Pd as a hydrogen trap, we devote a subsection to examining the role of palladium as a catalyst as well as some of the characteristics of the Pd‐H2 system. Non‐solid‐state hydrogen sensors, such as the flame ionization detector are not the object of this review. A useful feature of this review is a comparison of operating characteristics of each device in a general table in Sec. VII. In that section a general discussion is presented, including a critical comparison of the capabilities and parameters of various solid‐state hydrogen sensors in the form of a table showing data collected from the literature. The Pd‐fiber optic sensor is the most sensitive optical device operating at room temperature. The Pd‐photopyroelectric sensor appears to be most economical and second best in sensitivity at room temperature; it has the best potential for high signal‐to‐noise operation at the widest temperature range, down to cryogenic temperatures. The Pd‐field effect transistor devices exhibit the second highest sensitivity at elevated temperatures.

Transition metal oxide electrochromic materials and displays: a review: Part 1: oxides with cathodic coloration

Abstract: Thin films of a number of transition metal oxides, when employed as electrodes in the appropriate electrochemical cells, exhibit electrochromism by a reversible ion-insertion mechanism. These oxides may be divided into two groups, those which colour cathodically by a reduction process, and those which colour anodically by an oxidation process. At present the former class is known to contain the oxides of W, Mo, V, Nb and Ti, whereas those of Ir, Rh, Ni and Co are contained in the latter class. A two-part in-depth review is given of the electrochromic behaviour of thin films of these oxides. This part of the paper considers cathodically coloured oxides, with anodically coloured oxides the subject of the second part. Special attention is given to tunstic oxides as the most studied example and as a model for the behaviour of other members of its class. Significant advances in the understanding and development of electrochromic displays are highlighted. Fabrication and performance of display electrode and complete display cells based on these materials is described and compared, suggestion put forward regarding the most promising electrochromic material/electrolyte combinations for further study. Emphasis is placed on the method and details of film deposition or growth which determine film stoichiometry (including moisture content) and morphology and in turn strongly influence electrochromic behaviour.

Proton transfer and superionic conductivity in solids and gels

Abstract: Protonic conduction (σ) is a particular case of ionic conduction and can be characterised by the pre-exponential factor (σ0) and activation energy (Ea) in the expression σT = σ0exp - (Ea/kT). A correlation between σ0 and Ea for different types of protonic conductors such as hydrates, anhydrous compounds, ionic and superionic conductors is given, and various materials are classified according to their principal conductivity mechanism. In order to understand these mechanisms, it appears necessary to determine the structure of the rigid framework as well as thet of potentially mobile protonic species and the dynamic and conducting properties of the latter in the very broad frequency range 105–1013 Hz. In the identification of protonic species and in the determination of their configuration, vibrational (optical and neutron) spectroscopy appears particularly efficient; it is also useful in determining the nature and degree of structural disorder. The complex impedance spectroscopic methods, quasi-elastic neutron scattering and proton magnetic resonance, on the other hand, contribute to a better knowledge of proton dynamics. Such structural and dynamic information has been obtained for various materials representing different types of protonic conduction: the ion jumps mechanism in anhydrous and hydrated lattice is illustrated by oxonium (ammonium) β alumina and a low-temperature phase of hydrated uranyl phosphate (HUP), respectively; the quasi-liquid state, in the lattice and on the surface, by the high-temperature phase of HUP, H+(H2O)nβ (β″) alumina and Zr (HPO4)2·nH2O; and the proton transfer assisted by orientational disorder of the rigid framework by H3OClO4 and Cs-HSO4. The influence of the partial water pressure and electrical field on the electrical properties of protonic conductors via proton transfer between mobile species and rigid framework is also discussed.

Electrochromism and smart window design

Abstract: An electrochromic device (ECD) has in its center an electrolyte or ion conductor, which is in contact with films that provide optical modulation, ion storage, and (transparent) electrical conduction. We review designs and properties of ECDs, giving special emphasis to transparent devices, i.e. smart windows. The ECDs are categorized according to the type of electrolyte or ion conductor: liquid, solid inorganic in bulk- or thin-film form, or solid organic (polymer). The electrochromic film is W oxide; this material is used in the majority of all studied ECDs.