Ultrasonic-assisted System Research Articles

Removal of bisphenol A and methylene blue through persulfate activation by calcinated α-MnO2 nanorods: effect of ultrasonic assistance and toxicity assessment.

This work investigates the efficacy of α-MnO2 nanorods for persulfate-mediated degradation of bisphenol A (BPA) and methylene blue (MB), in silent and ultrasonic-assisted systems. The conversion of α-MnO2 nanoparticle flakes to nanorods occurs upon calcination at a temperature of 400°C for 3h under the ramping conditions. The comparative characterization of nanomaterials pre- and post-calcination reveals better physical, chemical, and thermal properties of α-MnO2 nanorods. The impact of various operational parameters such as pH, dosage of nanorods, persulfate dose, selected contaminant concentration, ultrasound frequency and power, scavengers, and landfill leachate medium on the degradation of pollutants is also assessed. The ultrasonic assistance yields higher removal for both BPA and MB than the silent system. This may be attributed to the generation of more radicals as ultrasound activates persulfate. This can be due to acoustic cavitation, which leads to better solute dissociation and excited state. The results obtained through scavenger tests reveal that both OH• and SO4•- can contribute to degradation, but the role of SO4•- is found dominant. Significant removal of BPA and MB ((BPA)silent, 87.12%; (MB)silent, 96.54%; (BPA)ultrasonic, 88.75%; (MB)ultrasonic, 93.86%)) is observed in landfill leachate medium. The degradation pathway for pollutants is also proposed. The toxicity of pollutants and their degradation intermediates are evaluated using Ecological Structure Activity Relationships (ECOSAR) program. The results indicate reduced toxicity of BPA intermediates, while most MB degradation intermediates show higher toxicity. Therefore, it can be affirmed that removing pollutants does not ensure a completely non-toxic process. However, the study proposes a comprehensive toxicity evaluation and eliminating toxic intermediates for completely harmless wastewater treatment.

Using piezoelectric sensor and actuator for ultrasonic assisted system

ABSTRACTAn ultrasonic assisted system mainly consists of the transducer and the match-fitting cutter is designed to provide miniature vibration amplitude. In the transducer, a set of piezoelectric ceramics is used as actuator in charge of generating large enough vibration amplitude, which will be immediately measured by the neighboring sensor also made by piezoelectric ceramics. Since the driving frequency is easily affected by the changing working environment, variation of the vibration output is detected in time by the PZT sensor to support the feedback autoresonance control purpose. However, measurement on the transducer is not equivalent to that on the cutter. Further investigation on the measured output of the cutter in comparison with that of the transducer is carried out. It is found that there exists a reasonable and predictable relation between them. ANSYS is used for modal and harmonic analysis. The estimated resonance frequency and vibration amplitude are approximate to the experimental results, which verifies the accuracy of the proposed measurement method.

Investigating the Effect of Ultrasonic Vibration on Hole Accuracy in Drilling of Metal Matrix Composites

Generally in the drilling of new engineering materials such as metal matrix composites, problems frequently occur in terms of poor finished surface, tool stress, tool wear, high drilling forces as well as low process reliability. A useful and promising method to overcome these problems is the use of ultrasonic vibration as an assistance, where high-frequency and low amplitude vibration are added to the conventional movement of cutting tools or workpieces. This research presents the new design of an ultrasonic assisted system and the experimental investigation of ultrasonically assisted drilling of Al/SiC metal matrix composites under different cutting conditions. The effect of cutting conditions and ultrasonic amplitude on the circularity, cylindericity, and hole oversize of the ultrasonically and conventionally drilled workpieces were investigated. The obtained results show that the ultrasonic vibration can improve the hole quality.

Hybrid cutting of granite by use of ultrasonic assistance

Hybrid technologies offer an important approach to enhance existing limits of conventional cutting manufacturing processes. Superposition of the infeed with adapted ultrasonic vibrations enables reductions of machining forces. This results in diminished tool wear and longer tool life. Furthermore, an increase of removal rates can be achieved. Successful machining of recalcitrant metal-based materials by ultrasonic assisted systems creates a high potential to gain similar effects in machining of mineral-based materials. This will be studied in this article. The state of the art for the machining of stone uses geometrically undefined cutting edges. This paper focuses on the geometrically defined cutting of granite with additional ultrasonic assistance. Cutting tests at a test station with linear cutting motion are being performed. The ultrasonic frequency is maintained at 20 kHz. Different oscillation amplitudes are applied to influence process forces and the wear of the used carbide metal and polycrystalline diamond cutting segments (PCD). A method to observe the wear is developed by use of a stereomicroscope and a 3D measurement system. This will enable conclusions about the applicability of the geometry of the cutting segments and the process parameters. Due to the significant different wear rates of both cutting materials, the cutting force progression by using PCD tools shows completely different characteristics compared to the machining with carbide metal tools.