Novel Ceramic Ultrasonic Horn Ensures Vibration Stability up to 800 °C
Abstract
Ultrasonic horns, serving as the terminal tools for vibration amplification, have been widely used in thermal processes. However, traditional metallic horns suffer from material degradation and thermal deformation at high temperatures, leading to frequency drift and system instability. To address this limitation, this study presented the design of a novel Al2O3 ceramic horn to improve the thermal stability of the ultrasonic system. The Al2O3 horn was designed based on longitudinal wave theory and fabricated by pressure less sintering. Finite element modal analysis indicated that as the terminal temperature increased from 25 °C to 800 °C, the Al2O3 horn’s eigenfrequency decreased by only 238 Hz, far lower than the 982-Hz drop in Ti-6Al-4V horn. Experimental modal analysis further confirmed the overall stability of resonant frequency and amplitude of the Al2O3 horn over 25−800 °C. The practical performance of the Al2O3 horn was evaluated in ultrasonic-assisted micro-embossing of PMMA under 2.45 - GHz microwave heating, where high-aspect-ratio, well-defined micro-protrusions were successfully fabricated. The average PMMA-to-mold filling ratio reached 96.79%, 10.72% higher than that of conventional embossing. With its thermal duration and electrical insulation, the designed ceramic horn will unlock the application of high-power ultrasonic systems in extreme environments, particularly those involving high temperatures or intense-electromagnetic fields.