• Journal of the Korean Ceramic Society
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• v.56 no.4
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• pp.360-364
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• 2019

PZT suspensions for photo-curable 3D printing were fabricated and their characteristics were evaluated. After mixing the PZT, photopolymer, photo-initiator, and dispersant for 10 min by using a high-shear mixer, the viscosity characteristics were investigated based on the powder content. To determine an appropriate dispersant content, the dispersant was mixed at 1, 3, and 5 wt% of the powder and a precipitation test was conducted for two hours. Consequently, it was confirmed that the dispersibility was excellent at 3 wt%. Through thermogravimetric analysis, it was confirmed that weight reduction occurred in the photopolymer between 120? and 500?, thereby providing a debinding heat treatment profile. The fabricated suspensions were cured using UV light, and the polymer was removed through debinding. Subsequently, the density and surface characteristics were analyzed by using the Archimedes method and field-emission scanning electron microscopy. Consequently, compared with the theoretical density, an excellent characteristic of 97% was shown at a powder content of 87 wt%. Through X-ray diffraction analysis, it was confirmed that the crystallizability improved as the solid content increased. At the mixing ratio of 87 wt% powder and 13 wt% photo-curable resin, the viscosity was 3,100 cps, confirming an appropriate viscosity characteristic as a stereolithography suspension for 3D printing.

• Journal of Biosystems Engineering
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• v.28 no.4
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• pp.351-360
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• 2003

This study was carried out to settle the plugging problem which occurs frequently when agricultural wettable powder is used in pest control work using the crushing and the dispersing effects caused by irradiation of ultrasonic wave. Sonication was applied to the wettable powder suspension in a beaker for 30 seconds using a 28 kHz, 200 W PZT BLT, and the image of suspension before and after sonication was observed using a microscope and a SEM. The image of tow commercial wettable powder suspensions in water observed using an optics microscope showed that the agglomerated particles were irregularly distributed over the whole observed region when stirred mechanically, while showing more uniform distribution composed of comparatively single particles in the whole observed region after sonication. Concerning the above, the projected areas of particles in the four suspensions after sonication were decreased distinctively in the observed range of the microscope and the atomization of crystals was much developed. Over the measured range of 5.6∼4,157 ${\mu}$m particle size, the overall projected area of particles was decreased to 58.3∼89.6% on the average after sonication. When the SEM images of sonicated wettable powder suspensions dissolved in water and CH$_3$OH were compared to the suspensions before sonication, such phenomena as the atomization of particles, the expansion of voids between particles, the reduction and the decrease of agglomerated particle groups, and the progress of crack developments on the surface of flake-shaped particles were observed. It seemed possible that the plugging problem that occurs frequently in pest control machine when using wettable powder would be settled by the use of sonication.