Investigation of CeTi₂O₆- and CaZrTi₂O₇-containing glass–ceramic composite materials

Abstract

Glass–ceramic composite materials are being investigated for numerous applications (i.e., textile, energy storage, nuclear waste immobilization applications, etc.) due to the chemical durability and flexibility of these materials. Borosilicate and Fe–Al–borosilicate glass–ceramic composites containing brannerite (CeTi2O6) or zirconolite (CaZrTi2O7) crystallites were synthesized at different annealing temperatures. The objective of this study was to understand the interaction of brannerite or zirconolite-type crystallites within the glass matrix and to investigate how the local structure of these composite materials changed with changing synthesis conditions. Powder X-ray diffraction (XRD) and Backscattered electron (BSE) microprobe images have been used to study how the ceramic crystallites dispersed in the glass matrix. X-ray absorption near edge spectroscopy (XANES) spectra were also collected from all glass–ceramic composite materials. Examination of Ti K-, Ce L3-, Zr K-, Si L2,3-, Fe K-, and Al L2,3-edge XANES spectra from the glass–ceramic composites have shown that the annealing temperature, glass composition, and the loading of the ceramic crystallites in the glass matrix can affect the local environment of the glass–ceramic composite materials. A comparison of the glass–ceramic composites containing brannerite or zirconolite crystallites has shown that similar changes in the long range and local structure of these composite materials occur when the synthesis conditions to form these materials or the composition are changed.

A one-step synthesis of rare-earth phosphate–borosilicate glass composites

“…The mole percentage was as follows: 63.5% SiO 2 (EMD Millipore), 16.9% B 2 O 3 (Alfa Aesar; 99.98%), Scheme 1 General synthesis strategies for making LaPO 4 -BG composites using 1-and 2-step synthesis methods. 16.5% Na 2 O (Alfa Aesar), and 3.1% CaO (Acros Organics; 97+%). The oxide powders were ground and mixed using a mortar and pestle, pressed into a pellet at 6 MPa, and annealed in 5% Au/ 95% Pt crucibles at 1100 C for 1 hour followed by quench cooling in water.…”

“…[12][13][14][15] Glassceramic composites capitalize on the advantages of both the glass and ceramic. 12,16 The ceramic crystallites can incorporate actinides into the crystal structure giving the material a high waste loading potential as well as a high chemical resistance and the glass acts as a secondary barrier for the actinides while also being able to accommodate smaller ssion products. 9,12,16 Glass-ceramic composites containing rare-earth phosphates in a glass matrix have been proposed as a potential waste form to sequester high level nuclear waste.…”

“…12,16 The ceramic crystallites can incorporate actinides into the crystal structure giving the material a high waste loading potential as well as a high chemical resistance and the glass acts as a secondary barrier for the actinides while also being able to accommodate smaller ssion products. 9,12,16 Glass-ceramic composites containing rare-earth phosphates in a glass matrix have been proposed as a potential waste form to sequester high level nuclear waste. 2,17 Borosilicate glass (BG) is one proposed type of glass to be used for this application because of the chemical durability of this material and the prospect of recycling glass from other industries.…”

“…One type of synthesis involves a 2-step method where the ceramic and glass phases are synthesized separately before being mixed and then annealed to form a composite material. 12,16,[25][26][27][28][29] The high level waste stream would be added during the production of the ceramic phase which would ensure all the minor actinides would be partitioned into the ceramic phase. 27 A 1-step method is investigated here where all precursors are mixed together from the beginning followed by annealing.…”

CaZrTi2O7 zirconolite synthesis: From ceramic to glass‐ceramic

“…The zirconolite phase is about 40 wt% if it is fully crystallized in residue glass. Physical mixing of the established ceramic and glass before melting has also been used to study the stability of the ceramic phase, but this noninternal crystallization is not ideal for waste form application thus not the focus of our study.…”