Encapsulated Thermoacoustic Projector Based on Free-Standing Carbon Nanotube Film

 Technical Summary:

There are promising applications for thermophones in high power sonar arrays, flexible loudspeakers, and noise cancellation devices. Transparent CNT sheets have the density of air, the electrical conductivity of metals, and the flexibility to fit to any curved surface. Thermoacoustic (TA) sound generation results from temperature variation in a carbon nanotube (CNT) sheet that is produced by heating the sheet using an applied alternating voltage. A hot CNT sheet heats up surrounding air in the loudspeaker application, thereby inducing volume expansion and subsequent pressure waves. The freestanding aerogel-like CNT sheet as a TA heat source demonstrates, so far, the best performance. The emission spectrum of a liquid-immersed CNT sheet varies smoothly over a wide frequency range of 1-10⁵ Hz. The encapsulated device enhances sound generation efficiency and is usable in harsh environments; working at high pressures and temperatures beyond 2000 K.

Problem:

Most TA devices are open to the air, leading to low applicable temperatures, sensitivity of the heater to the environment, and low sound generation efficiency at low frequencies.

Solution:

To protect the nanoscale aerogel structure of a freestanding carbon nanotube (CNT) sheet heater from harsh environments and to provide optimal thermodynamic conditions, we encapsulated the fragile CNT heater in an inert gas (argon) using rigid vibrating plates or flexible membranes. We have successfully demonstrated several designs of large (6x6”), lightweight (0.3 kg), flat TA projectors with resonance response, high acoustical power (~200 dB), and high energy conversion efficiency in air and water (~10%).

Examples of rigid encapsulated (6x6”) Thermoacoustic Projectors providing 175 dB in air and 200 dB in water. The device is 1 cm thick and weight 300 g.

Applications:

• Flexible, transparent speakers
• Sonar arrays
• Noise cancellation devices

Key Benefits:

• Large size, flexible, light and transparent
• Encapsulated films perform well in air and underwater

Inventors:

Ali Aliev, Ph.D.

Ray Baughman, Ph.D.

Publication:

1. A. E. Aliev, M. D. Lima, S. Fang, R. H. Baughman. “Underwater Sound Generation Using Carbon Nanotube Projectors.” Nano Letters 10.7 (2010): 2374-380.
2. A. E. Aliev, Y. N. Gartstein, R. H. Baughman, Increasing the Efficiency of Thermoacoustic Carbon Nanotube Sound Projectors, Nanotechnology 24 (2013) 235501.
3. A. E. Aliev, N. K. Mayo, R. H. Baughman, D. Avirovik, S. Priya, M. R. Zarnetske, J. B. Blottman, Thermal Management of Thermoacoustic Sound Projectors Using a Free-Standing Carbon Nanotube Aerogel Sheet as Heat Source, Nanotechnology 25 (2014) 405704 11.
4. A. E. Aliev, N. K. Mayo, M. Jung de Andrade, R. O. Robles, S. Fang, R. H. Baughman, M. Zhang, Y. Chen, J. A. Lee, S. J. Kim, Alternative Nanostructures for Thermophones, ACS Nano 9 (2015) 4743–4756.
5. A. E. Aliev, S. Perananthan, J. P. Ferraris, Carbonized Electrospun Nanofiber Sheets for Thermophones, ACS Appl. Mater. Interfaces 8 (2016) 31192–31201.
6. A. E. Aliev, N. K. Mayo, R. H. Baughman, D. Avirovik, S. Priya, M. R. Zarnetske, J. B. Blottman, Thermoacoustic Excitation of Sonar Projector Plates by Free-Standing Carbon Nanotube Sheets, J. Physics D: Appl. Phys. 47 (2014) 355302 9.
7. A. E. Aliev, N. K. Mayo, R. H. Baughman, B. T. Mills and E. Habtour, Subwoofer and nanotube butterfly acoustic flame extinction, Journal of Physics D: Applied Physics, 50, 29 (2017) LT01.
8. A. E Aliev, et al. Thermoacoustic Sound Projector: Exceeding the Fundamental Efficiency of Carbon Nanotubes, Nanotechnology, 29, 32 (2018) 325704.

IP Status: US Patent 9,635,468 issued on April 25, 2017.

Licensing Opportunity: This technology is available for exclusive or non-exclusive licensing.

ID Number: MP-13024

Contact: otc@utdallas.edu