Robin J. Francis

An Apparatus for the study of the kinetics and mechanism of hydrothermal reactions by in situ energy dispersive x-ray diffraction

The design and implementation of a pressure cell for the study of hydrothermal reactions by in situ energy dispersive x‐ray diffraction is described. The cell permits the study of both the kinetics and mechanism of formation of a wide range of important solid‐state compounds such as zeolites and other microporous solids. Reactions can be studied over a wide range of temperature (5–230 °C) and autogenous pressure [0–400 psi (gauge)] conditions. The use of this apparatus is illustrated by a study on the synthesis of a microporous tin chalcogenide phase performed on Station 9.7 of the UK Synchrotron Radiation Source.

The First Organically Templated Layered Uranium(IV) Fluorides: (H3N(CH2)3NH3)U2F10⋅2 H2O, (H3N(CH2)4NH3)U2F10⋅3 H2O, and (H3N(CH2)6NH3)U2F10⋅2 H2O

A new series of layered organically templated uranium(IV) fluorides has been exclusively synthesized under hydrothermal conditions. The unprecedented materials contain [U2 F10 ]2- anionic layers that are separated by charge balancing cationic templates and occluded water molecules (see structure depicted). The templates can be fully ion-exchanged for a variety of metals (Na+ , K+ , and Co2+ ) at room temperature.

Novel apparatus for the in situ study of hydrothermal crystallizations using time-resolved neutron diffraction

The design and use of a pressure cell for the in situ study of hydrothermal crystallizations using time-resolved neutron diffraction are described. This novel apparatus allows the kinetics and mechanism of the crystallization of complex inorganic solids, such as zeolites and other microporous materials, to be investigated under laboratory conditions. Reactions can be studied over a wide range of temperatures (25–250 °C) under conditions of autogenous pressure (1–22 bar). The use of the cell is demonstrated by a study of the hydrothermal crystallization of the zeolite sodium hydroxosodalite with time-of-flight neutron diffraction data collected using the Polaris diffractometer of the United Kingdom’s pulsed spallation neutron source, ISIS.

Determination of the kinetics of crystallisation of gibbsite using time resolved in situ energy dispersive powder X-ray diffraction

Time resolved in situ powder X-ray diffraction has been used to study the kinetics of crystallisation of gibbsite from supersaturated synthetic Bayer liquors as a function of temperature and hydroxide ion concentration. It was found that the crystallisation data was best described in terms of the Avrami–Erofe’ev kinetic model. This analysis indicated a two-dimensional growth mechanism with a deceleratory nucleation rate.

Time-resolved, in situ X-ray diffraction studies of the hydrothermal syntheses of microporous materials

Abstract In this paper we describe the use of energy dispersive diffraction using ‘white’ synchrotron radiation and angular dispersive X-ray diffraction with a moving image plate detector to record time-resolved in situ diffraction data on a number of hydrothermal syntheses. We have studied the synthesis of an aluminophosphate, the open framework sulfide TMA-SnS-1, and the gallium fluorophosphate ULM-5, under hydrothermal conditions. The effect of varying the temperature of reaction, reactant source and pH of solution on the syntheses has been investigated. Evidence has been obtained that in cases where crystalline TMA-SnS-1 is formed, the reaction proceeds via an intermediate disordered lamellar phase, before reacting further to form the final product. In the synthesis of ULM-5 at least two intermediates have been observed.

Development of large volume reaction cells for kinetic studies using energy-dispersive powder diffraction

Abstract Two novel sample chambers for the energy-dispersive powder diffraction study of chemical reactions are presented. One for air sensitive samples and the other for hydrothermal synthesis. The use of these vessels is illustrated with data collected during a study of the intercalation of cobaltocene into SnS2.

The kinetics and mechanisms of the crystallisation of microporous materials

The synthesis of microporous materials is one of the major activities in contemporary solid state chemistry. This perspective brings together the current thinking regarding the synthesis and growth mechanisms of these technologically important materials. Also reviewed are the latest experiments being utilised to probe the complex chemistry which occurs during the synthesis of these materials.

Formation of silica–surfactant mesophases studied by real-time in situ X-ray powder diffraction

Real-time in situ energy dispersive synchrotron X-ray powder diffraction data provides evidence for the formation of an intermediate lamellar silica–surfactant intercalate during the synthesis of the hexagonal mesophase derived from the layered polysilicate kanemite, whereas no intermediate phases are observed during the formation of the silica–surfactant mesophase that leads to the mesoporous material MCM-41.

Die ersten Schicht-Uran(IV)-Fluoride mit organischen Templaten: (H3N(CH2)3NH3)U2F10⋅2 H2O, (H3N(CH2)4NH3)U2F10⋅3 H2O und (H3N(CH2)6NH3)U2F10⋅2 H2O

Unter Hydrothermalbedingungen wurde eine neue Serie von Schicht-Uran(IV)-fluoriden mit organischen Templaten synthetisiert. Diese Materialien enthalten anionische Schichten, die aus [U2F10]2−-Einheiten aufgebaut sind und durch kationische Template und eingeschlossene Wassermolekule getrennt werden (siehe abgebildete Struktur). Die Kationen konnen bei Raumtemperatur leicht gegen andere Kationen (Na+, K+, Co2+) ausgetauscht werden.

Organically templated layered uranium(VI) phosphates: hydrothermal syntheses and structures of [NHEt3][(UO2)2(PO4)(HPO4)] and [NPr4][(UO2)3(PO4)(HPO4)2]

Two organically templated layered uranium( VI) phosphates have been prepared under hydrothermal conditions from U 3O 8 and H 3PO 4 using either NPr 4 + or NHEt 3 + ions as structure directing agents; both compounds have layered structures which contain infinite chains of edge-sharing [UO 7] pentagonal bipyramids cross linked by bridging [PO 4] tetrahedra to form two dimensional sheets of [(UO 2) n - (HPO 4) n–1 (PO 4)] m m– anions.