Anisotropic thermal conductivity tensor measurements using beam-offset frequency domain thermoreflectance (BO-FDTR) for materials lacking in-plane symmetry

Thermal Energy Transport in Oxide Nuclear Fuel

“…TDTR has been used to study a variety of ion irradiated materials including nuclear fuel [570], nuclear fuel cladding [571], silicon carbide [572] metallic multi-layers [571], silicon [571,573], sapphire [574], and diamond [575] across orders of magnitude in thermal conductivity. MTR, also referred to as spatial domain or beam-offset thermoreflectance [576,577,578,579,580,581], has been used in the majority of studies of ion irradiated actinide oxides and their surrogates. MTR utilizes modulated continuous wave (CW) lasers to inject thermal waves into a sample under investigation.…”

Anisotropic Thermoreflectance Thermometry: A contactless frequency-domain approach to study anisotropic thermal transport

“…The development of novel experimental methodologies to study anisotropic thermal transport has recently become a relevant research objective. A considerable number of experimental techniques and methodologies 9,[14][15][16][17][18][19][20][21][22][23][24][25][26][27] based on variations of the 3-omega method, 28 time-domain thermoreflectance, 29 and frequency-domain thermoreflectance 30 have been developed for this purpose, demonstrating their capability to obtain the components of κ i j . The main differences between these approaches are the dimensionality of the heat source (line or spot), and their contact or contactless fashion (electrical resistor or focused optical spot).…”

“…On the other hand, contactless techniques such as those reported in Refs. [9,[17][18][19][20][21][22][23][24][25][26][27] are based on small Gaussian or ellipse-shaped focused spots, i.e., sensitive to all crystallographic directions simultaneously. Although this is not an intrinsic impediment to obtain κ i j , it substantially complicates the analysis of the measured data with respect to the case of an elongated line-shaped heat source (sensitive to only two cyrstallographic directions simulataneously), as it is evident from Refs.…”

“…Although this is not an intrinsic impediment to obtain κ i j , it substantially complicates the analysis of the measured data with respect to the case of an elongated line-shaped heat source (sensitive to only two cyrstallographic directions simulataneously), as it is evident from Refs. [9,[17][18][19][20][21][22][23][24][25][26][27]. In addition, for Gaussian or ellipse-shaped small focused spots a precise determination of the spatial intensity distribution of the focused laser spot is required, which in some situations can be challenging due to the highly asymmetric shape of the heater spot.…”

“…The main objective of the present work is to provide a new technical approach which combines the key advantages of the experimental methods reported in Refs. [9,[15][16][17][18][19][20][21][22][23][24][25][26][27] but without their drawbacks, i.e., based on a 1-dimensional heat source configuration, which is focused onto the surface of the samples in a contactless fashion.…”