Papers by Keyword: Ultrasonic Agitation

Abstract: Nanofibers have high cell affinity due to their fine structure and surface roughness, and are expected to be used as biomaterials. In particular, magnetic nanofibers containing magnetic particles are expected to be used for magnetically induced drug delivery systems and hyperthermia. However, due to the aggregation of the magnetic particles contained in the nanofibers, there is a problem that the aggregation location becomes a starting point of fracture and causes a decrease in tensile strength. In this study, to improve the dispersibility of magnetic particles in Magnetite/PLA nanofiber nonwoven fabrics for suppressing the decrease in tensile strength, magnetite is subjected to surface treatment with oleic acid or stearic acid and ultrasonic agitation. Magnetite/PLA nanofiber nonwoven fabric was prepared by the electrospinning method, and dispersion of magnetite in PLA nanofiber nonwoven fabric and tensile strength were evaluated. Magnetite dispersion was improved by the surface treatment and increasing the ultrasonic agitation time. In particular, by performing the stearic acid treatment and prolonging the ultrasonic agitation time, the magnetite dispersion tended to be improved. This treated Magnetite/PLA nanofiber nonwoven fabric showed higher tensile strength.

Abstract: The various methods of silicon wet etching techniques, which utilize ultrasonic agitation to reduce pyramidal hillocks in etched patterns, were evaluated in NaOH+IPA solution. The comparison of the etching methods composed of; 1.) no agitation + sample horizontally orientated, 2.) ultrasonic agitation + sample horizontally orientated, 3.) ultrasonic agitation + sample vertically orientated, and 4.) ultrasonic with rotation agitation + sample vertically orientated. It was found that the percentages of the etched patterns presenting hillocks after etching were 100%, 79.77%, 32.67% and 2.62%, respectively. Ultrasonic coupled with rotation agitation along with the sample vertically orientated is the most powerful etching technique, offering a high yield of smooth etched surface. The difference in etch rate between without agitation and applying ultrasonic agitation was not observed in this experiment, as it was operated in a solution temperature 60-65°C and a 275nm/min etch rate was achieved. The theories that relate to each evaluated method are also discussed.

Abstract: High frequency acoustic agitation is known to improve mass transport in conventional electroplating and electroforming. To better understand the effect of ultrasonic agitation on microelectroforms with high height-to-width aspect recessed microstructure features, electroforming of Ni from a nickel sulfamate type electrolyte under the influence of high frequency ultrasound (33KHz) at different level of power intensity from 2W/cm2 to 16W/cm2 was investigated experimentally in this paper, and then optimum operating parameters were determined basing on surface topography. A number of microelectroforming experiments assisted with acoustic agitation were further carried out to demonstrate and revise the optimum process parameters and further some metal microdevices were produced. Experimental results showed that fewer drawbacks in the microelectroforms, such as nubbles, pits, blunt-edges, and collapses were observed in the microcomponents when sonication power 12W/cm2~14W/cm2 was drawn on. Microelectroforming with ultrasonic irradiation at appropriate power intensity was characterized by better surface morphology and better uniform filling behavior.

Abstract: This study concerns the development of Pb free solder plating due to environmental concerns. The composition of the bath was 0.1 mol/dm3 SnY and 0.1 mol/dm3 BiY- in 2 mol/dm3 CH3COOH - 2 mol/dm3 CH3COONa buffer solution (pH 4.0). The bath used 100 cm3 of solution. Plating was carried out at a current density of 50 mA/cm2 using ultrasonic agitation (sonication) at 28 kHz (100 W). Various percentages of a Sn - Bi alloy could be plated. A 41wt.%Sn - 59 wt.%Bi alloy with a melting point of 415 K was obtained from a [BiY-]/[BiY-+SnY] = 0.3 bath. The surface morphologies of the plated films showed a striking difference in accordance with a change of composition.