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Phonon Confinement Effect in TiO₂ Nanoparticles as Thermosensor Materials

Thermal sensors have the unique ability to forensically retain the complete thermal history (spatial and temporal variation) of an event under extreme conditions.

TiO2 or ZnO nanoparticles (NPs) have a very strong finite-size dependency in their Raman spectra or photoluminescence (PL) spectra due to the phonon confinement effect or the quantum confinement effect. Together with a fast grain growth kinetics and a high stability under high temperature and pressure, they can forensically retain the complete thermal history of an event. By spatially distributing these NPs during thermal events such as blasts or weapon tests, a spatially and temporally non-uniform thermal environment can be determined by a direct read off their Raman or PL spectra at various locations.

Ribbon pyroprobe microheater from CDS Analytical, Inc., which can be heated from room temperature to 1400°C with heating rates from 0.01.°C/min to 20,000°C/s.

These thermosensors can also be used in non-defense applications such as for detecting the transient heating in electronics and measuring the rapid energy release during catastrophic fractures. The protocols developed in this research can be easily extended to the design of other thermosensors where a grain growth or phase transition at lower temperatures is needed to characterize the thermal environment on the biological or cellular level.

Therefore, the objective of this research was to utilize the phonon/quantum confinement effect in Raman/PL spectra and grain growth kinetics in NPs to create thermosensor materials with the ability to forensically retain the complete thermal history (spatial and temporal variation) of a thermal event under extreme conditions.

NPs and substrates chosen for use as thermosensor materials had to meet the following requirements:

NPs:

  1. Strong phonon/quantum confinement effect;

  2. Fast growth kinetics;

  3. Easy synthesis to get spherical NPs;

  4. High thermal and mechanical stability.

Substrates as NPs’ carrier and protector:

  1. High thermal and mechanical stability;

  2. High thermal conductivity.

Small and monodisperse TiO2 and ZnO NPs of 5-6 nm in size were synthesized and loaded onto SBA-15 or graphite nanoplatelets (GNPs) substrates. Raman and PL spectrometers were used to establish the particle size versus the Raman/PL peak position master curves. Systematic isothermal and temperature-dependent heat treatments of NPs using a ribbon pyroprobe microheater (see figures) were carried out to study their grain growth kinetics.

This work was done by Liping Huang, Rensselaer Polytechnic Institute, for the Defense Threat Reduction Agency. DTRA-0008

Topics:
Data management Defense Emissions Exhaust emissions Force Sensors and Resistors Materials Nanomaterials Nanotechnology Nanotechnology Particulate matter (PM) Photonics Pressure Research and development Sensors Smart materials Technical review Test & Measurement Thermal Management Thermal testing
This Brief includes a Technical Support Package (TSP).
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Phonon Confinement Effect in TiO2 Nanoparticles as Thermosensor Materials

(reference DTRA-0008) is currently available for download from the TSP library.

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    Aerospace & Defense Technology Magazine

    This article first appeared in the April, 2018 issue of Aerospace & Defense Technology Magazine (Vol. 3 No. 2).

    Read more articles from this issue here.

    Read more articles from the archives here.

    Overview

    The document titled "Phonon Confinement Effect in TiO2 Nanoparticles as Thermosensor Materials" is a technical report prepared by Liping Huang from Rensselaer Polytechnic Institute, published in January 2018 under the Defense Threat Reduction Agency (DTRA). The report investigates the unique properties of titanium dioxide (TiO2) and zinc oxide (ZnO) nanoparticles, particularly focusing on their phonon confinement and quantum confinement effects, which significantly influence their Raman and photoluminescence (PL) spectra.

    The abstract highlights that TiO2 and ZnO nanoparticles exhibit strong finite-size dependencies in their spectral characteristics due to these confinement effects. This phenomenon is crucial for understanding how the size of nanoparticles affects their thermal sensing capabilities. The report emphasizes the potential of these nanoparticles as effective thermosensor materials, which can be synthesized into spherical forms, making them suitable for various applications.

    The document includes experimental work that explores the thermal sensing properties of bare TiO2 and ZnO nanoparticles. It describes the synthesis process and the characterization of these nanoparticles, showcasing their strong phonon confinement in Raman spectra and quantum confinement in PL spectra. The report also features figures, including images of the nanoparticles obtained through scanning electron microscopy (SEM) and transmission electron microscopy (TEM), illustrating their morphology and size.

    Additionally, the report discusses the use of a ribbon pyroprobe microheater capable of heating from room temperature to 1400°C, with rapid heating rates, which is essential for testing the thermal response of the nanoparticles. The findings suggest that the unique properties of TiO2 and ZnO nanoparticles make them promising candidates for advanced thermosensor applications, potentially enhancing the sensitivity and accuracy of temperature measurements in various fields.

    Overall, the report provides valuable insights into the phonon and quantum confinement effects in TiO2 and ZnO nanoparticles, laying the groundwork for future research and development in thermosensing technologies. The distribution of the report is approved for public release, ensuring that the findings can contribute to broader scientific and technological advancements.

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