The carbides and nitrides of transition metals known as “MXenes” refer to a fast-growing family of two-dimensional materials discovered in 2011. Thanks to their unique nanolayer structure, superior electrical, mechanical, and thermal properties, MXenes have shown great potential in addressing the critical overheating issues that jeopardize the performance, stability, and lifetime of high-energy-density components in modern devices such as microprocessors, integrated circuits, and capacitors, etc. The outstanding intrinsic thermal conductivity of MXenes has been proved by experimental and theoretical research. Numerous MXenes-enabled high thermal conductivity composites incorporated with polymer matrix have also been reported and widely used as thermal management materials. Considering the booming heat dissipation demands, MXenes-enabled thermal management material is an extremely valuable and scalable option for modern electronics industries. However, the fundamental thermal transport mechanisms behind the MXenes family remain unclear. The MXene thermal conductivity disparities between the theoretical prediction and experimental results are still significant. To better understand the thermal conduction in MXenes and provide more insights for engineering high-performance MXene thermal management materials, in this article, we summarize recent progress on thermal conductive MXenes. The essential factors that affect MXenes intrinsic thermal conductivities are tackled, selected MXenes-polymer composites are highlighted, and prospects and challenges are also discussed.

Raman spectroscopy-based temperature sensing usually tracks the change of Raman wavenumber, linewidth and intensity, and has found very broad applications in characterizing the energy and charge transport in nanomaterials over the last decade. The temperature coefficients of these Raman properties are highly material-dependent, and are subjected to local optical scattering influence. As a result, Raman-based temperature sensing usually suffers quite large uncertainties and has low sensitivity. Here, a novel method based on dual resonance Raman phenomenon is developed to precisely measure the absolute temperature rise of nanomaterial (nm WS₂ film in this work) from 170 to 470 K. A 532 nm laser (2.33 eV photon energy) is used to conduct the Raman experiment. Its photon energy is very close to the excitonic transition energy of WS₂ at temperatures close to room temperature. A parameter, termed resonance Raman ratio (R3) is introduced to combine the temperature effects on resonance Raman scattering for the A_1g and E_2g modes. Ω has a change of more than two orders of magnitude from 177 to 477 K, and such change is independent of film thickness and local optical scattering. It is shown that when Ω is varied by 1%, the temperature probing sensitivity is 0.42 K and 1.16 K at low and high temperatures, respectively. Based on Ω, the in-plane thermal conductivity (k) of a ~25 nm-thick suspended WS₂ film is measured using our energy transport state-resolved Raman (ET-Raman). k is found decreasing from 50.0 to 20.0 Wm⁻¹ K⁻¹ when temperature increases from 170 to 470 K. This agrees with previous experimental and theoretical results and the measurement data using our FET-Raman. The R3 technique provides a very robust and high-sensitivity method for temperature probing of nanomaterials and will have broad applications in nanoscale thermal transport characterization, non-destructive evaluation, and manufacturing monitoring.

Laser-assisted manufacturing (LAM) is a technique that performs machining of materials using a laser heating process. During the process, temperatures can rise above over 2000 ℃. As a result, it is crucial to explore the thermal behavior of materials under such high temperatures to understand the physics behind LAM and provide feedback for manufacturing optimization. Raman spectroscopy, which is widely used for structure characterization, can provide a novel way to measure temperature during LAM. In this review, we discuss the mechanism of Raman-based temperature probing, its calibration, and sources of uncertainty/error, and how to control them. We critically review the Raman-based temperature measurement considering the spatial resolution under near-field optical heating and surface structure-induced asymmetries. As another critical aspect of Raman-based temperature measurement, temporal resolution is also reviewed to cover various ways of realizing ultrafast thermal probing. We conclude with a detailed outlook on Raman-based temperature probing in LAM and issues that need special attention.