Solution based synthesis of mixed-phase materials in the Li2TiO3–Li4SiO4 system

Abstract

Abstract:As candidate tritium breeder materials for use in the ITER helium cooled pebble bed, ceramic multiphasic compounds lying in the region of the quasi-binary lithium metatitanate-lithium orthosilicate system may exhibit mechanical and physical advantages relative to single phase materials. Here we present an organometallic solution-based synthesis procedure for the low-temperature fabrication of compounds in the Li 2 TiO 3 -Li 4 SiO 4 region and investigate phase stability and transformations through temperature varied X-ray diffraction and scanning calorimetry. Results demonstrate that the metatitanate and metasilicate phases Li 2 TiO 3 and Li 2 SiO 3 readily crystallise in nanocrystalline form at temperatures below 180°C. Lithium deficiency in the region of 5% results from Li sublimation from Li 4 SiO 4 and/or from excess Li incorporation in the metatitanate phase and brings about a stoichiometry shift and product compounds with mixed lithium orthosilicate/ metasilicate content towards the Si rich region and predominantly Li 2 TiO 3 content towards the Ti rich region. Above 1150°C the transformation of monoclinic to cubic γ-Li 2 TiO 3 disordered solid-solution occurs while the melting of silicate phases indicates a likely monotectic type system with a solidus line in the region 1050°-1100°C. Synthesis procedures involving a lithium chloride precursor are not likely to be a viable option for breeder pebble synthesis as this route was found to yield materials with a more significant Li-deficiency exhibiting the crystallisation of the Li 2 TiSiO 5 phase at intermediate compositions.

Behaviour of advanced tritium breeder pebbles under simultaneous action of accelerated electrons and high temperature

“…TiSiO5 [17], or chemisorption products, such as, lithium hydroxide (LiOH) or carbonate (Li2 CO3 ), were detected. After ther-mal pre-treatment, the diffraction peaks of Li4 SiO4 and Li2 TiO3 becomes higher and narrower, due to the increase in crystallinity.…”

Applications of Radiolabelled Curcumin and Its Derivatives in Medicinal Chemistry

“…Tritium is a radioactive nuclide with a 12.3 year half-life that decays to helium-3 emitting β − -particles with an average energy of 5.7 keV. It can be produced in nuclear reactors by the neutron irradiation of lithium-6 or boron-10 [ 78 , 79 ]. From a chemical point of view, bonds involving deuterium and tritium are, to some extent, stronger than the corresponding ones involving hydrogen.…”

A comparison of syntheses approaches towards functional polycrystalline silicate ceramics

“…Silicate ceramics are of emerging relevance as functional materials in a broad range of applications. Numerous crystalline silicate phases of neso-, soro-, ino-, cyclo-and tectosilicates, differentiated by linking of SiO 4 tetrahedra, have been found in recent years to exhibit promising characteristics towards applications as high-frequency dielectrics [1], bioactive ceramics [2,3], battery electrodes [4] and tritium breeders [5][6][7][8]. Silicates are promising multifunctional materials, whose utilisation hinges on our ability to fabricate such materials in controllable and appropriate forms and stoichiometries.…”