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Unlocking High-Temperature Nanofluid Research with In Situ DLS
In critical industries like renewable energy and advanced materials, performance under extreme conditions is everything. For developers of next-generation materials like molten salt nanofluids, understanding how nanoparticles behave at temperatures exceeding 300 °C is not just an academic curiosity; it’s essential for creating more efficient and reliable energy systems.
However, most labs are limited by their characterization tools. Standard analytical instruments are designed for ambient or slightly elevated temperatures, providing data that is a poor substitute for real-world performance. This forces researchers to rely on indirect methods or assumptions, leading to slow development cycles and materials that fail to meet their potential.
To truly engineer materials for high-temperature applications, scientists need a direct, real-time window into nanoparticle behavior at operating temperatures. As pioneering research demonstrates, this is now possible by adapting a powerful analytical technique—Dynamic Light Scattering (DLS)—for extreme environments.
A Technique Redefined for Extreme Conditions
Understanding the limits of the standard approach reveals why a new method was necessary.
Dynamic Light Scattering (DLS) is the gold standard for measuring the hydrodynamic size of particles in a suspension. By analyzing the random Brownian motion of particles, it determines their effective size in a liquid. It is the definitive tool for assessing colloidal stability—whether particles remain dispersed or clump together.
However, conventional DLS systems operate within a closed, temperature-controlled chamber that typically maxes out below 100 °C. This is perfectly adequate for aqueous solutions but completely unusable for materials like molten salts, which don’t even become liquid until well over 200 °C. The technique was right, but the hardware was a roadblock.
Real-Time Monitoring in Practice
A 2019 study in Powder Technology demonstrated how to overcome this barrier. Researchers at the Universitat Jaume I set out to perform the first-ever DLS measurements of nanoparticles directly within molten solar salt.
By pairing a custom-designed high-temperature cuvette with the VASCO KIN™️ particle size analyzer, they created a setup capable of monitoring nanoparticle stability at temperatures up to 300 °C. The key was integrating the VASCO KIN’s remote DLS optical head, allowing it to take measurements through the quartz windows of the heated steel cell without any physical contact.
The results were groundbreaking. The DLS data revealed that in the high-ionic environment of molten salt, silica nanoparticles rapidly formed large, micron-sized agglomerates that settled out of the suspension. More importantly, when comparing silica to Al/Cu nanoparticles, the team made a critical discovery:
After 4 hours at 300 °C, the settled silica agglomerates were irreversible.
In contrast, the Al/Cu agglomerates could be completely broken up and returned to their initial particle size distribution with simple mechanical stirring.
This real-time data provided an unprecedented insight: for these systems, redispersibility is a more critical parameter than initial stability. This is a game-changing piece of information for designing functional high-temperature nanofluids.
The Challenge of High-Temperature In Situ Measurement
This type of analysis requires specialized instrumentation. Attempting to characterize a high-temperature sample by cooling it down and moving it to a separate analyzer is not a viable option. The sample’s properties, especially its aggregation state, will change dramatically during the process, rendering the data meaningless.
The only way to get accurate data is to bring the measurement directly to the sample. An in situ DLS system with a remote, contactless probe head allows for measurement within the harsh environment itself—be it a high-temperature reactor or a custom-built cell—without disturbing the system.
About the VASCO KIN™️ Particle Size Analyzer
The VASCO KIN™️ is engineered for exactly these types of demanding, real-time applications. It is the ideal time-resolved DLS instrument for performing kinetic analyses in materials science and nanotechnology.
The key is its in situ and contactless remote optical head, which allows you to measure your nanoparticles right where the action is happening. This eliminates the need to extract or disturb the sample, ensuring the data you collect is a true reflection of its behavior under operational conditions. As demonstrated by the researchers, by decoupling the optics from the sample environment, the VASCO KIN™️ provides the critical stability data needed for a complete characterization in previously inaccessible conditions.
For scientists and engineers looking to move beyond assumptions and toward true process understanding at high temperatures, direct measurement is the future. By enabling reliable in situ DLS analysis, the VASCO KIN™️ is an essential tool for unlocking the full story of your advanced materials.
Source:
Navarrete, N., Gimeno-Furió, A., Forner-Escrig, J., Juliá, J. E., & Mondragón, R. (2019). Colloidal stability of molten salt–based nanofluids: Dynamic Light Scattering tests at high temperature conditions. Powder Technology, 352, 1–10.
