Semnan University Press Progress in Physics of Applied Materials 2783-4794 6 4 2026 12 01 Carbon Ash: From Waste Material to Flexible Paper-Based Pressure Sensor 331 341 10661 10.22075/ppam.2026.40653.1209 EN Dania Dhafer Hameed College of Science, Al-Karkh University for Science, Baghdad, Iraq Ghaiath A Fadhil College of Engineering, Al-Karkh University for Science, Baghdad, Iraq Burak Yahya Kadem College of Science, Al-Karkh University for Science, Baghdad, Iraq Journal Article 2026 02 20 Carbon ash waste obtained from an Iraqi factory was converted into poly (vinyl alcohol) (PVA)-based composite materials intended for sensor applications. The carbon ash was ground, sieved through a 0.045 mm mesh, suspended in distilled water, and subsequently sonicated for 3 hours. The material was then dried at 100 °C for 15 min. Surface modification was carried out using acetic acid (S1), hydrochloric acid (S2), and sulfuric acid (S3) prior to embedding the modified carbon ash into the PVA matrix to form polymer composites. FTIR spectra showed absorption bands attributed to oxygen‑containing functional groups, which improved the interaction between the polymer and carbon ash, particularly in the S3 sample. Electrical conductivity increased to 15.1 S·cm⁻¹ for S3. Hall effect results indicated an increase in both carrier mobility and carrier concentration in the acid‑treated composites. Cyclic voltammetry showed that the S3 sample had the most pronounced electrochemical response, consistent with its enhanced chemical and electrical properties. Morphological analysis indicated improved filler dispersion in the acid‑treated composites, which exhibited a more uniform microstructure, particularly for S3. The pressure sensors fabricated from these materials demonstrated enhanced electromechanical performance, with S3 achieving the highest sensitivity and good structural stability. https://ppam.semnan.ac.ir/article_10661_8afdc3631535a83a98542c75469d87a9.pdf