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Figure 1. Characterization of PAN/Zr(OAc)₄ nanofiber membranes at different heat-treated temperatures. (A) The color transformation of PAN/Zr(OAc)₄ membranes at different heat treatment temperatures; (B) Mechanistic effect of Zr(OAc)₄ incorporation on PAN molecular chains under heat treatment conditions; (C) Comparison of conformability for PAN/Zr(OAc)₄ composite nanofiber flexible sensors with conventional PZT rigid sensors, (i and iii) pasted sensor on flat surface; (ii and iv) pasted sensor on curved surface; (D) SEM images of PAN/Zr(OAc)₄ at different heat treatment temperatures: untreated, 150, 260, 350, 450, 550 °C; and (E) histogram of diameter distribution; XRD patterns of (F) Zr(OAc)₄ particles and (G) PAN/Zr(OAc)₄ membranes at untreated and different heat treatment temperatures; (H) FTIR spectra of PAN/Zr(OAc)₄ membranes at different heat treatment temperatures. PAN: Polyacrylonitrile; Zr(OAc)₄: zirconium acetate; PZT: lead zirconate titanate; SEM: scanning electron microscopy; XRD: X-ray diffraction; FTIR: Fourier transform infrared spectroscopy.