2 0 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 are a reliable measurement to determine glass content in HA-glass composites. A linear dependence of refractive index with glass composition in volume % is shown in Fig. 5. In addition, the HA was soaked in simulated body fluid (SBF) with an ionic concentration to the human body fluid for varying durations. THz-TDS was performed on HA soaked in SBF for durations of one and seven days. It was thought that the large mass and low mobility of ions found in HA would result in a reduction in THz refractive index with increasing frequency. However, the opposite trend was observed. The absorption coefficient, refractive index, and dielectric constant all increase with increasing frequency, suggesting the distributed glass phase bonds the HA matrix together. The absorption coefficient, refractive index, and dielectric constant of HA all decrease with increased soaking time in SBF. It is suspected this is due to formation of a hydroxycarbonate apatite (HCA) layer on the surface of HA, which is a Ca-rich amorphous or nanocrystalline calcium phosphate structure. THz-TDS was demonstrated to be an effective nondestructive tool for identification and determination of glass content in HA-glass composites and interactions or durations with SBF[27]. CONCLUSION THz-TDS nondestructive characterization and examination of ceramics, glasses, and composites allows for identification, determination, and differentiation of materials composition, structure, and structural changes through THz refractive index and absorption coefficient spectra. Complementary examination of material structure enables development of the structure-THz property relationship for various families of materials. THz spectral changes can be used to identify material composition as well as crystallographic and microstructural changes. Once such a relationship is established, THz-TDS can become a powerful nondestructive examination tool for evaluation of materials under a wide range of service conditions. ~AM&P For more information: S.K. Sundaram, professor, Inamori School of Engineering, Alfred University, 1 Saxon Dr., Alfred, NY 14802, 607.871.2789, sundaram@alfred.edu. Acknowledgment Nicholas Tostanoski acknowledges teaching assistant support from the Inamori School of Engineering. S.K. Sundaram acknowledges support from Kyocera Corp. in the formof the Inamori Professorship. References 1. S. Sundaram, Terahertz TimeDomain Spectroscopy of Glasses, in Springer Handbook of Glass, J.H.J. David Musgraves, Laurent Calvez, eds., p 909-929, Springer, 2019. 2. J.-L. Coutaz, F. Garet, and V.P. Wallace, Principles of Terahertz TimeDomain Spectroscopy, CRC Press, 2018. 3. T. Elsaesser, K. Reimann, and M. Woerner, Concepts and Applications of Nonlinear Terahertz Spectroscopy, Morgan & Claypool Publishers, 2019. 4. M. van Exter, C. Fattinger, and D. Grischkowsky, Terahertz Time-Domain Spectroscopy of Water Vapor, Opt. Lett., Vol 14, p 1128-1130, 1989. 5. M. Hoffmann, Novel Techniques in THz-Time-Domain-Spectroscopy — A Comprehensive Study of Technical Improvements to THz-TDS, Fakultat fur Mathematik und Physik der AlbertLudwigs-Universitat Freiburg im Breisgau, 2006. 6. J. Neu and C.A. Schmuttenmaer, Tutorial: An Introduction to Terahertz Time Domain Spectroscopy (THz-TDS), J. Appl. Phys., Vol 124, p 1-14, 2018. 7. L. Duvillaret, F. Garet, and J.-L. Coutaz, A Reliable Method for Extraction of Material Parameters in Terahertz Time-Domain Spectroscopy, IEEE J. Sel. Top. Quantum Electron, Vol 2, p 739-746, 1996. 8. X.-C. Zhang and J. Xu, Introduction to THz Wave Photonics, Springer, 2010. 9. M.C. Beard, G.M. Turner, and C.A. Schmuttenmaer, Terahertz Spectroscopy, J. Phys. Chem. B, p 7146-7159, 2002. 10. B.B. Hu and M.C. Nuss, Imaging with Terahertz Waves, Opt. Lett., Vol 20, p 1716-1718, 1995. 11. D.M. Mittleman, R.H. Jacobsen, and M.C. Nuss, T-ray Imaging, IEEE J. Sel. Top. Quantum Electron, Vol 2, p 679-692, 1996. 12. D. Mittleman, et al., Recent Advances in Terahertz Imaging, Appl. Phys. B, Vol 68, p 1085-1094, 1999. Fig. 5 — Concentration dependence of the average measured refractive index for HA and HA-glass composites at: (a) 0.6 THz; (b) 1.0 THz; and (c) 1.4 THz. (a) (b) (c)
RkJQdWJsaXNoZXIy MTYyMzk3NQ==