SEM images of (a) the MWNT forest on the silicon wafer and (b) MWNT sheet.
[(a) and (d)] Optical and corresponding thermal images of [(a)–(c)] two-layer MWNT sheet and [(d)–(f)] F32 forest subjected to [(b) and (e)] ac voltage or [(c) and (f)] laser light modulated at . Thermal images for all samples correspond maximum observed temperature. The lowest and highest temperatures in images are shown in black boxes.
Experimental setup used for TA-PA measurements.
Amplitudes of TA signal for S1, S2, and S10 MWNT sheets measured at and normalized by sample conductance as function of . Open and solid symbols correspond to first , third and second , fourth harmonics, respectively. The solid lines are guides for eyes only.
Amplitudes of TA signal for F32 and F233 MWNT forests measured at and normalized by sample conductance as a function of . Both raw experimental data (, , top row) and refined oscillating contributions (, , bottom row) are shown. The solid lines are the result of fitting the latter with empirical equations.
Sound pressure generated by the MWNT sheets (S1–S10) and MWNT forests (F32–F233) subjected to TA and PA excitations. TA intensities were normalized by the supplied electric power. PA intensities were normalized by the supplied laser power and optical absorption of samples. The data were taken at , for the first harmonic of the acoustic signal.
Frequency dependencies of amplitude (left panel), phase, and calculated time delay (right panel) for the S2 MWNT sheet at TA and PA excitations. The recorded amplitudes were normalized by the signal intensity at , . The solid lines represent fit of the acoustic spectra with power equation .
Acoustic spectra of F32 and F233 MWNT forests at TA (left) and PA (right) excitations. Recorded amplitudes were normalized by the signal intensity at , . The solid lines represent fit of the acoustic spectra with power equation .
Fitting parameters for F32 and F233 forests.
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