1 7 A D V A N C E D M A T E R I A L S & P R O C E S S E S | S E P T E M B E R 2 0 2 2 and actinides, while fission products, e.g., Cs and Sr, are immobilized in hollandite phases. THz optical and dielectric properties allow for identification and differentiation of all ceramic waste forms due to their unique THz frequency signatures. Figure 2 shows the THz refractive index data for various waste forms. Multiphase waste forms self-heat during storage due to β-decay of fusion products. THz-TDS was performed at a temperature range of 25-200°C. Measured refractive index at 0.5 THz shows an exponential increase with an increase in temperature, allowing for distinction of phases at elevated temperatures during long-term storage (Fig. 3). Fig. 1 — (a) THz-TDS setup at Alfred University’s T-Lab including: (b) transmission configuration sample holder; and (c) TPS Spectra program. allow for THz optical and dielectric properties to be correlated to structural changes. This enables THz-TDS to be used as a critical nondestructive material examination and characterization technique to provide information about the THz refractive index and absorption coefficient and, therefore, material composition and structure. The researchers reported earlier detailed results on THz properties of ceramic waste forms, soda-lime silicate (SLS), Borofloat (BF), alumino-borosilicate (ABS), and calcium aluminosilicate (CAS) glasses, and hydroxyapatite (HA)-calcium zinc silicate glass composites. Currently, the authors are focused on the structure-THz property relationship of borosilicate, tellurite, and chalcogenide glasses and the influence of laser exposure on the glass structure, network, and THz properties. NONCONTACT CERAMICS MONITORING The authors identified THz-TDS as a noncontact method for monitoring multiphase ceramic waste forms for nuclear applications[23]. Single-phase zirconolite (CaZrTi2O7), pyrochlore (Nd2Ti2O7), and hollandite (BaCs0.3Cr2.3- Ti5.7O16 and BaCs0.3CrFAl0.3Ti5.7O16) representative of ceramic waste forms were produced via spark plasma sintering (SPS). Zirconolite and pyrochlore phases immobilize rare earth elements (a) (c) (b)
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