Preparation and characterization of superhydrophobic coatings

Hsing-I Hsiang,Ming-Tsai Liang,Yu-Lun Chang,Hung-Chin Huang,Fu-Su Yen 한양대학교 세라믹연구소 2010 Journal of Ceramic Processing Research Vol.11 No.3

To obtain a surface with water-repelling and self-cleaning abilities attracts much interest in the nanotechnology age. In this study, a perfluroalkyl surfactant (perflurodecanoic acid, PFDA) was coated on nano-sized boehmite surfaces to obtain hydrophobic nano-particles via surface modification. Then the hydrophobic boehmite was coated on a transparent plastic film using spin-coating to obtain a hydrophobic film. The effects of various amounts of hydrophobic polymer on the adsorption behavior and contact angle for hydrophobic properties were investigated using FTIR, and a contact-angle meter. The adsorption of PFDA onto the surface of boehmite takes place through ionic bonding. The contact angles of the thin film prepared by spin coating PFDA-modified-boehmite on glass substrates were above 150o as the adsorption of PFDA onto the surface of boehmite reached saturation.

Effects of the addition of minute amounts of alumina on the microstructure and sintering behavior of yttria stabilized tetragonal zirconia polycrystals ceramic via a co-precipitation process

Chih-Cheng Chen,Chang-Min Zhou,Hsing-I Hsiang 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.3

It is feasible to add homogeneously minute amounts (0.25 wt%) of Al₂O₃ into 3 mol% yttria stabilized tetragonal zirconia polycrystals using a co-precipitation procedure to produce precursory gel nano-powders. X-ray diffraction, scanning electron microscopy, high-angle annular dark-field-field emission gun transmission electron microscopy, relative density determination, shrinkage, and resistivity measurements using impedance spectroscopy were combined to elucidate the microstructure and sintering behavior of zirconia ceramics produced using 0.25 wt% added Al₂O₃, possibly the limit of solubility of Al₂O₃ in the ZrO₂ structure. Two modes of sintering behavior may be described as: (I) The total solid solution of Al₂O₃ in the solid solution of ZrO₂ structure via a precursory co-precipitation procedure; calcining at 800 oC and sintering at 1275 oC can be shown to indicate the viable solubility of Al₂O₃ in the ZrO₂ structure, designated as stage I of the thermal treatment; and (II) At the higher sintering temperature, above 1275 oC, the segregation of Al₂O₃ at triple junction occurs. Higher bulk and grain boundary resistivity values are found for the sample sintered at 1275 oC, which probably resulted from the dissolution of Al₂O₃ in the ZrO₂ structure. It is feasible to add homogeneously minute amounts (0.25 wt%) of Al₂O₃ into 3 mol% yttria stabilized tetragonal zirconia polycrystals using a co-precipitation procedure to produce precursory gel nano-powders. X-ray diffraction, scanning electron microscopy, high-angle annular dark-field-field emission gun transmission electron microscopy, relative density determination, shrinkage, and resistivity measurements using impedance spectroscopy were combined to elucidate the microstructure and sintering behavior of zirconia ceramics produced using 0.25 wt% added Al₂O₃, possibly the limit of solubility of Al₂O₃ in the ZrO₂ structure. Two modes of sintering behavior may be described as: (I) The total solid solution of Al₂O₃ in the solid solution of ZrO₂ structure via a precursory co-precipitation procedure; calcining at 800 oC and sintering at 1275 oC can be shown to indicate the viable solubility of Al₂O₃ in the ZrO₂ structure, designated as stage I of the thermal treatment; and (II) At the higher sintering temperature, above 1275 oC, the segregation of Al₂O₃ at triple junction occurs. Higher bulk and grain boundary resistivity values are found for the sample sintered at 1275 oC, which probably resulted from the dissolution of Al₂O₃ in the ZrO₂ structure.

Effects of aging on the phase transformation and sintering properties of coprecipitated Al₂O₃-ZrO₂ powders

Chih-Cheng Chen,Hsing-I Hsiang,Fu-Su Yen 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.1

In this study, the effects of aging on the crystalline phases, crystallite sizes and sintering properties of coprecipitated Al₂O₃- ZrO₂ powders are investigated using thermogravimetry (TG), differential thermal analysis (DTA), X-ray diffractometry (XRD), dilatometry, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Coprecipitated Al₂O₃- ZrO₂ powder aging in the solution promoted the dissolution and reprecipitation process, which resulted in the boehmite structure subsequently transforming into bayerite. The densification and microstructural development of the coprecipitated Al₂O₃-ZrO₂ powders were dependent upon the aging time which shifted the θ→α-Al₂O₃ phase transformation to a higher temperature, lowered the crystallite growth rate, and prevented the occurrence of intragranular ZrO₂ particles during sintering. In this study, the effects of aging on the crystalline phases, crystallite sizes and sintering properties of coprecipitated Al₂O₃- ZrO₂ powders are investigated using thermogravimetry (TG), differential thermal analysis (DTA), X-ray diffractometry (XRD), dilatometry, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Coprecipitated Al₂O₃- ZrO₂ powder aging in the solution promoted the dissolution and reprecipitation process, which resulted in the boehmite structure subsequently transforming into bayerite. The densification and microstructural development of the coprecipitated Al₂O₃-ZrO₂ powders were dependent upon the aging time which shifted the θ→α-Al₂O₃ phase transformation to a higher temperature, lowered the crystallite growth rate, and prevented the occurrence of intragranular ZrO₂ particles during sintering.

Preparation and characterization of Y-TZP powders coated with alumina

Chih-Cheng Chen,Shu-Wei Hsu,Hsing-I Hsiang 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.2

In this study, alumina was coated onto yttria tetragonally stabilized zirconia (Y-TZP)core powder using aluminum nitrate with urea in an aqueous solution. Boehmite coating onto the surface of Y-TZP powders was confirmed using transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy and zeta potential measurements. The sintering behaviors of Y-TZP powders with and without an alumina coating were investigated using a dilatometer and scanning electron microscopy (SEM). Boehmite coating onto the surface of Y-TZP powders significantly improved the densification of the resulting ceramic bodies. The relative density of the Y-TZP with a boehmite coating sintered at 1350oC can reach 97.3%. In this study, alumina was coated onto yttria tetragonally stabilized zirconia (Y-TZP)core powder using aluminum nitrate with urea in an aqueous solution. Boehmite coating onto the surface of Y-TZP powders was confirmed using transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), Fourier transform infrared (FTIR) spectroscopy and zeta potential measurements. The sintering behaviors of Y-TZP powders with and without an alumina coating were investigated using a dilatometer and scanning electron microscopy (SEM). Boehmite coating onto the surface of Y-TZP powders significantly improved the densification of the resulting ceramic bodies. The relative density of the Y-TZP with a boehmite coating sintered at 1350oC can reach 97.3%.

Operating Performance Following Acquisitions: Evidence from Taiwan’s IT Industry

Hsu-Huei Huang,Min-Lee Chan,I-Hsiang Huang,Kuo-Hsing Wu 한국증권학회 2014 Asia-Pacific Journal of Financial Studies Vol.43 No.5

This paper examines the performance of Taiwanese firms following acquisitions and findsthat, when contrasted with the acquisitions that take place in the U.S., Taiwanese acquirersexhibit negative industry-adjusted accounting performance. The negative performance ismostly driven by firms with low growth opportunities, but is mitigated under more concen-trated shareholdings and better board structures. These findings suggest that while weak cor-porate governance at the country-level may adversely affect the overall effectiveness of thetakeover market in Taiwan, there is substantial cross-sectional variation in corporate gover-nance at the firm-level. The evidence also shows that the announcement of an acquisition isaccompanied by a positive announcement effect, and the poor operating performance mightbe related to the decreased assets turnover and sales growth rate.