**1. Introduction**

Raman scattering technology is able to reveal phonon/lattice vibrational mechanisms inside materials [1, 2]. By combining this technique with different optical systems, it is feasible for Raman spectroscopy to characterize the physical and chemical changes of materials, including crystal structure deformation and crystal component change [3, 4]. Attributed to its high sensitivity and noncontact detection, the sensing and monitoring applications of the Raman scattering technique for different materials have attracted great interest in both science and engineering fields.

© 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2017 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Graphene is a two‐dimensional (2D) material consisting of a flat monolayer or several layers of carbon atoms arranged in a honeycomb lattice structure [5, 6]. Because of its special Dirac cone structure which satisfies a linear dispersion relation, graphene has excellent electrical properties, and the charge carriers of graphene can transport as massless Dirac fermions with a mobility up to ~200,000 cm2 V−1 s−1 [7–10]. Combined with good mechanical strength [11], outstanding thermal conductivity [12], and excellent optical transparency [13], graphene consequently acts as an attractive candidate for future electronics and photonics applications [14–16]. Previous studies have found that the electrical and thermal characteristics of graphene including electrical resistivity [17], carrier mobility [18], band gap [19], and thermal conduc‐ tivity [20] are sensitive to mechanical deformation as it alters the structure of the graphene band by confining or collimating the electrons and phonon vibration [19–23]. Therefore, the ability to engineer strain and monitor the mechanical strain condition on graphene is critical in order to fully utilize the electrical properties of graphene.

Through investigating phonon vibrations, Raman spectroscopy has been proven as an important, nondestructive tool to discover the properties of graphene [24, 25]. The mechanical strain can effectively change crystal phonon vibration based on the anharmonicity of the interatomic potentials of the atoms. In other words, the impact of strain on phonon vibration of graphene can be correlated with a change in the Raman characteristic peaks. Several studies using Raman spectroscopy to characterize the phonon vibration of graphene have been carried out with different strains induced by engineering methods [23, 26–29]. The strain on graphene can be clearly reflected in the shift of Raman characteristic peak shifts, and the shift rate is found proportional to the Grüneisen parameter [27, 28].

The management of spent nuclear fuel and other high‐level nuclear wastes has drawn great attention from many fields [30]. The growth of an oxide corrosion layer on the cladding, such as zirconium alloy (Zircaloy), is a threat to the nuclear fuel cask storage system, where it may take years for the cladding to cool down due to the slow dissipation of the decay heat [31]. This oxidation process and its product oxide layer are detrimental to the Zircaloy cladding and may play a role in low‐temperature creep and delayed hydride cracking [32].

Monitoring of nuclear fuel cladding in dry cask storage can assist with assurance of the integrity of the fuel within the storage canister and is a necessary path to estimate the health of the cladding. Several studies have been performed to understand the oxidation process of Zircaloy [33–36]. More importantly, many detection methods of oxide corrosion have been developed, including environmental monitoring [37], ultrasonic [38], ion beam radiation [39, 40], and optical spectrum methods [41–43]. Compared to other methods, the use of optical spectrum for observation and detection of the oxidation promises to be more flexible, eco‐ nomical, effective, and practical.

As one advanced optical method, Raman scattering technology has been employed to study the properties of zirconium oxide [44–47]. Based on the lattice mechanism, the Raman spectra can be used to identify zirconium oxide from other oxide materials [48] and provide detail of the formation of a textured oxide layer on the Zircaloy cladding [49]. The phonon vibration status of the crystal structure/phase of zirconium oxide (amorphous, tetragonal, and mono‐ clinic polymorphs) can be finely revealed by the Raman characteristic peaks. These previous studies have resulted in the foundation for further Raman scattering investigation on Zr‐4 cladding health conditions and characteristics.

Graphene is a two‐dimensional (2D) material consisting of a flat monolayer or several layers of carbon atoms arranged in a honeycomb lattice structure [5, 6]. Because of its special Dirac cone structure which satisfies a linear dispersion relation, graphene has excellent electrical properties, and the charge carriers of graphene can transport as massless Dirac fermions with

outstanding thermal conductivity [12], and excellent optical transparency [13], graphene consequently acts as an attractive candidate for future electronics and photonics applications [14–16]. Previous studies have found that the electrical and thermal characteristics of graphene including electrical resistivity [17], carrier mobility [18], band gap [19], and thermal conduc‐ tivity [20] are sensitive to mechanical deformation as it alters the structure of the graphene band by confining or collimating the electrons and phonon vibration [19–23]. Therefore, the ability to engineer strain and monitor the mechanical strain condition on graphene is critical

Through investigating phonon vibrations, Raman spectroscopy has been proven as an important, nondestructive tool to discover the properties of graphene [24, 25]. The mechanical strain can effectively change crystal phonon vibration based on the anharmonicity of the interatomic potentials of the atoms. In other words, the impact of strain on phonon vibration of graphene can be correlated with a change in the Raman characteristic peaks. Several studies using Raman spectroscopy to characterize the phonon vibration of graphene have been carried out with different strains induced by engineering methods [23, 26–29]. The strain on graphene can be clearly reflected in the shift of Raman characteristic peak shifts, and the shift rate is

The management of spent nuclear fuel and other high‐level nuclear wastes has drawn great attention from many fields [30]. The growth of an oxide corrosion layer on the cladding, such as zirconium alloy (Zircaloy), is a threat to the nuclear fuel cask storage system, where it may take years for the cladding to cool down due to the slow dissipation of the decay heat [31]. This oxidation process and its product oxide layer are detrimental to the Zircaloy cladding

Monitoring of nuclear fuel cladding in dry cask storage can assist with assurance of the integrity of the fuel within the storage canister and is a necessary path to estimate the health of the cladding. Several studies have been performed to understand the oxidation process of Zircaloy [33–36]. More importantly, many detection methods of oxide corrosion have been developed, including environmental monitoring [37], ultrasonic [38], ion beam radiation [39, 40], and optical spectrum methods [41–43]. Compared to other methods, the use of optical spectrum for observation and detection of the oxidation promises to be more flexible, eco‐

As one advanced optical method, Raman scattering technology has been employed to study the properties of zirconium oxide [44–47]. Based on the lattice mechanism, the Raman spectra can be used to identify zirconium oxide from other oxide materials [48] and provide detail of the formation of a textured oxide layer on the Zircaloy cladding [49]. The phonon vibration status of the crystal structure/phase of zirconium oxide (amorphous, tetragonal, and mono‐ clinic polymorphs) can be finely revealed by the Raman characteristic peaks. These previous

and may play a role in low‐temperature creep and delayed hydride cracking [32].

V−1 s−1 [7–10]. Combined with good mechanical strength [11],

a mobility up to ~200,000 cm2

124 Raman Spectroscopy and Applications

in order to fully utilize the electrical properties of graphene.

found proportional to the Grüneisen parameter [27, 28].

nomical, effective, and practical.

In this chapter, we demonstrated the employment of the Raman scattering technology to monitor the mechanical property changes of graphene and chemical corrosion in zirconium alloy nuclear fuel claddings. The positions, intensities, and profiles of the Raman characteristic peaks precisely and directly probe the physical and chemical changes within these materials. Therefore, Raman spectroscopy is proven to be a nondestructive tool for monitoring material conditions with high sensitivity and high resolution.
