1. Introduction: Importance of Thermal Conductivity in Nanomaterials
Nanomaterials are an integral part of modern key technologies. They are used in areas such as nanoelectronics, battery technology, medical technology and the energy industry. Their extraordinary physical properties enable applications that would not be feasible with conventional materials.
One particularly noteworthy property of nanomaterials is their thermal conductivity , which often behaves differently than in bulk materials due to their reduced spatial dimensions. This opens up new areas of application such as increasing the efficiency of thermal management systems, thermoelectric materials and thermal insulation of high-performance components.
Due to the small sample volumes, the often heterogeneous material structure and the special interface effects, conventional methods for measuring thermal properties are often not always applicable and pose a particular challenge. Constantly new materials therefore require simultaneous progress in measurement techniques in order to obtain reliable, reproducible and application-relevant data.
2. Basics of Measurement Technology for Nanomaterials
2.1 Classical methods and their limitations
In materials science, there are various established methods for measuring thermal diffusivity. The laser flash method (LFA) for example, is widely used and provides fast results. Here, the underside of a sample is heated by a short laser pulse and the resulting temperature distribution on the upper side is recorded over time. This method provides information about the thermal diffusivity.
This method is well suited for compact samples, but reaches its limits with nanostructured materials, as the detection time of the time-delayed temperature rise poses a metrological challenge even with insulating materials due to the small sample thickness.
Another method is the plate device method, which uses a stationary heat source to determine the heat flow within a sample. However, it requires a large sample thickness to exclude interfacial influences. This is also unsuitable for nanomaterials. Equally problematic are the hot wire and hot disk methods, in which a heat source is in direct contact with the sample, which can lead to measurement errors due to contact resistance.
2.2 Challenges in measuring nanomaterials
The characterization of the thermal conductivity of nanomaterials requires methods that can handle extremely small sample quantities. Special challenges are:
- Small sample volumes that require precise and non-destructive measurement methods
- Heterogeneous material structures that can lead to anisotropic heat conduction properties
- Contact resistances that can falsify measured values when sensors are applied directly to the sample
3. Application Areas of Thermal Conductivity Measurement for Nanomaterials
3.1 Microelectronics and high-performance materials
Nanomaterials have revolutionized the electronics industry, especially in the field of microelectronics, which now enables new scaling possibilities and continues to satisfy Moore’s Law. However, the miniaturization of electronic components does not only have advantages as it requires more efficient thermal management solutions, as high power densities often lead to overheating problems.
Carbon nanotubes (CNTs) and graphene nanosheets, which are increasingly being used for thermal management in microprocessors, semiconductor components and thermal interface materials, represent a promising solution.
These materials enable faster heat dissipation and prevent thermal damage to sensitive components. Studies show that the targeted use of nanomaterials can significantly improve the service life and performance of high-performance electronics.
3.2 Thermoelectric materials
Thermoelectric generators (TEG) convert heat directly into electrical energy and are becoming increasingly important, particularly in the utilization of waste heat from industrial processes or in the automotive sector.
Nanostructured materials such as bismuth telluride (Bi₂Te₃) exhibit improved thermoelectric properties, as their nanostructured surface disrupts phonon transport and reduces thermal conductivity while maintaining electrical conductivity. This significantly increases the efficiency of thermoelectric materials, making them more attractive for sustainable energy applications.
3.3 Nanofluids in heat transfer
Nanofluids, i.e. liquids mixed with nanoparticles, are used to improve heat transfer in cooling systems. By increasing the thermal conductivity and thermal capacity of coolants, nanofluids enable more efficient heat dissipation in heat exchangers, solar collectors and engine cooling systems.
Metal oxide nanoparticles such as aluminum oxide (Al₂O₃) or copper oxide (CuO) have proven to be particularly effective, as they can significantly increase the thermal conductivity of conventional coolants.
3.4 Construction and energy efficiency
Nanomaterials also play an important role in the construction industry. They are used to develop energy-efficient building materials that regulate heat transfer and thus help to reduce energy consumption in buildings.
Nanoparticles in insulating materials improve the insulating properties of concrete and glass, while reflective nanocoatings on windows can reduce cooling costs in hot climates.
3.5 Medical applications
In biomedicine, nanomaterials are used for the targeted application of heat, for example in hyperthermia therapy for cancer treatment. Here, magnetic nanoparticles are introduced into tumor tissue and heated by a magnetic field to selectively destroy cancer cells.
Precise measurement of the thermal conductivity of these materials is crucial to ensure that the heat spread is limited to the tumor tissue without damaging surrounding healthy tissue.
4. Case Studies - Practical Examples from the Application
Measurements on carbon nanotubes (CNTs) have shown that their thermal conductivity varies considerably depending on dispersion and particle orientation.
Researchers found that improved particle dispersion can increase thermal conductivity by up to 50 %.
Another example is graphene-based nanocomposites in microelectronics, which have been optimized through precise thermal characterization.
5. Future Prospects - New Developments in Measurement Technology
Future developments will focus on:
- Non-contact measurement methods such as Raman thermometry
- AI-supported analyses to efficiently evaluate large data sets
- Miniaturized sensors that precisely detect thermal properties on a nanoscale
6. Conclusion - The Importance of precise Thermal Conductivity Measurements
Thermal conductivity is a critical factor in materials science. In the future, the combination of AI, contactless sensor technology and high-precision data evaluation will open up new possibilities for the characterization and optimization of nanomaterials.
References
Better thermal conductivity by adjusting the arrangement of atoms | University of Basel Link to article
Thermoelectric materials | Max Planck Institute for Iron Research Link to article
Thermoelectric Materials and Applications: A Review | MDPI Link to article
