Browsing by Author "Chang, Yen-Po"

Now showing 1 - 11 of 11

Bioactive TiO2 ultrathin film with worm-like mesoporosity for controlled drug delivery
(2012-04-01)
Chao, Chih-Shin
;
Liu, Kun-Ho
;
Tung, Wei-Lin
;
Chen, San-Yuan
;
Liu, Dean-Mo
Ultrathin mesoporous TiO2 coatings with a wormhole-like architecture were synthesized using evaporation-induced self-assembly method. The morphological and chemical structures of TiO2 films were characterized using small-angle and large-angle X-ray diffraction, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Fourier transformed infrared spectrometry (FTIR). The films demonstrated a thickness of similar to 120 nm and open-porous nanostructure. By taking advantage of the tortuosity of the worm-like mesoporous architecture associated with the chemistry of the TiO2 film, a sustained drug release using ibuprofen and vancomycin as model molecules from the film was determined. Besides, adhesion behavior of osteoblast cells, together with an in vitro apaptitic formation substantiated the cytocompatibility and bioactivity of the mesoporous TiO2 films. Such combined bioactive and drug-releasing functions of the TiO2 films with worm-like mesoporosity ensure an improved therapeutic performance for potential applications included orthopedics, dentistry, and drug delivery. (C) 2011 Elsevier Inc. All rights reserved.
Ca-Rich Ca-Al-Oxide, High-Temperature-Stable Sorbents Prepared from Hydrotalcite Precursors: Synthesis, Characterization, and CO2 Capture Capacity
(2011)
Chang, Po-Hsueh
;
Chang, Yen-Po
;
Chen, San-Yuan
;
Yu, Ching-Tsung
;
Chyou, Yau-Pin
We present the design and synthesis of Ca-rich Ca-Al-O oxides, with Ca(2+)/Al(3+) ratios of 1:1, 3:1, 5:1, and 7:1, which were prepared by hydrothermal decomposition of coprecipitated hydrotalcite-like Ca-Al-CO(3) precursors, for high-temperature CO(2) adsorption at 500-700 degrees C. In situ X-ray diffraction measurements indicate that the coprecipitated, Ca-rich, hydrotalcite-like powders with Ca(2+)/Al(3+) ratios of 5:1 and 7:1 contained Ca(OH)(2) and layered double hydroxide (LDH) phases. Upon annealing, LDH was first destroyed at approximately 200 degrees C to form an amorphous matrix, and then at 450-550 degrees C, the Ca(OH)(2) phase was converted into a CaO matrix with incorporated Al(3+) to form a homogeneous solid solution without a disrupted lattice structure. CaO nanocrystals were grown by thermal treatment of the weakly crystalline Ca-Al-O oxide matrix. Thermogravimetric analysis indicates that a CO(2) adsorption capacity of approximately 51 wt.% can be obtained from Ca-rich Ca-Al-O oxides prepared by calcination of 7:1 Ca-Al-CO(3) LDH phases at 600-700 degrees C. Furthermore, a relatively high CO(2) capture capability can be achieved, even with gas flows containing very low CO(2) concentrations (CO(2)/N(2)=10%). Approximately 95.6% of the initial CO(2) adsorption capacity of the adsorbent is retained after 30 cycles of carbonationcalcination. TEM analysis indicates that carbonation-promoted CaCO(3) formation in the Ca-Al-O oxide matrix at 600 degrees C, but a subsequent desorption in N(2) at 700 degrees C, caused the formation CaO nanocrystals of approximately 10 nm. The CaO nanocrystals are widely distributed in the weakly crystalline Ca-Al-O oxide matrix and are present during the carbonationcalcination cycles. This demonstrates that Ca-Al-O sorbents that developed through the synthesis and calcination of Ca-rich Ca-Al LDH phases are suitable for long-term cyclic operation in severe temperature environments.
Characterization and Structure Evolution of Ca-Al-CO(3) Hydrotalcite Film for High Temperature CO(2) Adsorption
(2010-07-01)
Wu, Chih-Hsiang
;
Chang, Yen-Po
;
Chen, San-Yuan
;
Liu, Dean-Mo
;
Yu, Ching-Tsung
In this work, monodispersed layered double hydroxide (Ca-Al LDHs) nanoparticles were synthesized by hydrothermal coprecipitation. Uniform thin films of layered double hydroxide on porous anodic aluminum oxide (AAO) substrates were formed by a direct precipitation process in a homogeneous suspension containing monodispersed Ca-Al layered double hydroxide nanoparticles. It was found that the formation of a designed hydrotalcite-like phase is strongly dependent on the [Ca2-]/ [Al(3+)] ratios, and that a minor CaCO(3) phase could possibly form simultaneously, which is attributed to the greater insolubility of CaCO(3) and the incompatibility of the ionic size of Al and Ca. The optimal CO(2) adsorption capacity appears in the layered Ca-OH-Al structure with the composition ratio of 3:1. Furthermore, the CO(2) adsorption mechanism varies with treatment temperature. Below 400 degrees C, the CO(2) adsorption is attributed to the LDH structure with a large surface area and pore volume, but above that the adsorption is due to the formation of CaCO(3) and CaO. The permeation behavior and CO(2) absorption can be explained by a preferable chemical and physical absorption of CO(2) on the layered double hydroxide and porous structure of the membrane.
Characterization and Structure Evolution of Ca-Al-CO3 Hydrotalcite Film for High Temperature CO2 Adsorption
(2010-07-01)
Wu, Chih-Hsiang
;
Chang, Yen-Po
;
Chen, San-Yuan
;
Liu, Dean-Mo
;
Yu, Ching-Tsung
In this work, monodispersed layered double hydroxide (Ca-Al LDHs) nanoparticles were synthesized by hydrothermal coprecipitation. Uniform thin films of layered double hydroxide on porous anodic aluminum oxide (AAO) substrates were formed by a direct precipitation process in a homogeneous suspension containing monodispersed Ca-Al layered double hydroxide nanoparticles. It was found that the formation of a designed hydrotalcite-like phase is strongly dependent on the [Ca2-]/ [Al3+] ratios, and that a minor CaCO3 phase could possibly form simultaneously, which is attributed to the greater insolubility of CaCO3 and the incompatibility of the ionic size of Al and Ca. The optimal CO2 adsorption capacity appears in the layered Ca-OH-Al structure with the composition ratio of 3:1. Furthermore, the CO2 adsorption mechanism varies with treatment temperature. Below 400 degrees C, the CO2 adsorption is attributed to the LDH structure with a large surface area and pore volume, but above that the adsorption is due to the formation of CaCO3 and CaO. The permeation behavior and CO2 absorption can be explained by a preferable chemical and physical absorption of CO2 on the layered double hydroxide and porous structure of the membrane.
CO2 Sorbents with Scaffold-like CaAl Layered Double Hydroxides as Precursors for CO2 Capture at High Temperatures
(2013-06-01)
Chang, Po-Hsueh
;
Lee, Tai-Jung
;
Chang, Yen-Po
;
Chen, San-Yuan
;
材料科學與工程學系
A highly stable high-temperature CO2 sorbent consisting of scaffold-like Ca-rich oxides (CaAlO) with rapid absorption kinetics and a high capacity is described. The Ca-rich oxides were prepared by annealing CaAlNO3 layered double hydroxide (LDH) precursors through a sol-gel process with Al(OiP)3 and Ca(NO3)2 with Ca2+/Al3+ ratios of 1:1, 2:1, 4:1, and 7:1. XRD indicated that only LDH powders were formed for Ca2+/Al3+ ratios of 2:1. However, both LDH and Ca(OH)2 phases were produced at higher ratios. Both TEM and SEM observations indicated that the CaAlNO3 LDHs displayed a scaffold-like porous structure morphology rather than platelet-like particles. Upon annealing at 600 degrees C, a highly stable porous network structure of the CaO-based CaAlO mixed oxide (CAMO), composed of CaO and Ca12Al14O33, was still present. The CAMO exhibited high specific surface areas (up to 191m2g-1) and a pore size distribution of 3-6nm, which allowed rapid diffusion of CO2 into the interior of the material, inducing fast carbonation/calcination and enhancing the sintering-resistant nature over multiple carbonation/calcination cycles for CO2 absorption at 700 degrees C. Thermogravimetric analysis results indicated that a CO2 capture capacity of approximately 49wt% could be obtained with rapid absorption from the porous 7:1 CAMO sorbents by carbonation at 700 degrees C for 5min. Also, 94-98% of the initial CO2 capture capability was retained after 50cycles of multiple carbonation/calcination tests. Therefore, the CAMO framework is a good isolator for preventing the aggregation of CaO particles, and it is suitable for long-term cyclic operation in high-temperature environments.
Morphological and structural evolution of mesoporous calcium aluminate nanocomposites by microwave-assisted synthesis
(2014-01-01)
Chang, Yen-Po
;
Chang, Po-Hsueh
;
Lee, Yuan-Tse
;
Lee, Tai-Jung
;
Lai, Yen-Ho
Novel special dual-structure calcium aluminate nanocomposites consisting of mesoporous Ca-containing Al2O3 nanonetworks with Ca12Al14O33 polycrystalline nanorods have been successfully synthesized using the microwave-hydrothermal (M-H) process in an alcohol solution consisting of calcium nitrate and mesoporous alumina, followed by calcination at a lower temperature (e.g., less than 600 degrees C). The mesoporous Ca-containing aluminate nanocomposites possessed a specific surface area of 51 m(2) g(-1) and a broad pore size distribution of 4-12 nm in diameter, as observed from N-2 adsorption/desorption measurements. The results showed that highly dispersed Ca12Al14O33 nanorods grown on the mesoporous nanostructure were obtained by varying the molar ratio of Ca/Al or by controlling microwave heating time, as characterized by scanning electron microscopy (SEM), transmission electron microscopy/electronic energy loss spectroscopy (TEM/EELS) and powder X-ray diffraction (PXRD). The Ca12Al14O33 nanorods with diameters of 50-100 nm and lengths of 200-400 nm were grown in and on the one-dimensional mesochannels. A formation mechanism of the mesoporous Ca-containing aluminate nanocomposites involving amorphous mesoporous hydrated-Al2O3 was also proposed. (C) 2013 Elsevier Inc. All rights reserved.
Self-Reactivated Mesostructured Ca-Al-O Composite for Enhanced High-Temperature CO2 Capture and Carbonation/Calcination Cycles Performance
(2015-03-25)
Chang, Po-hsueh
;
Huang, Wei-Chen
;
Lee, Tai-Jung
;
Chang, Yen-Po
;
Chen, San-Yuan
In this study, highly efficient high-temperature CO2 sorbents of calcium aluminate (Ca-Al-O) mesostructured composite were synthesized using presynthesized mesoporous alumina (MA) as a porous matrix to react with calcium nitrate through a microwave-assisted process. Upon annealing at 600 degrees C, a highly stable mesoporous structure composed of poorly crystalline Ca(12)A(14)O(33) phase and the CaO matrix was obtained. The Ca-Al-O mesostructured sorbents with a Ca2+/Al3+ ratio of 5:1 exhibit an enhanced increasing CO2 absorption kinetics in the CO2 capture capacity from 37.2 wt % to 48.3 wt % without apparent degradation With increasing carbonation/calcination cycling up to 50 at 700 degrees C due to the strong self-reactivation effect of the mesoporous Ca-Al-O microstructure. Remarkable improvements in the CaO-CaCO3 conversion attained from the mesostructured Ca-Al-O composite can be explained using the concept combined with available mesoporous structure and Ca12Al14O33 phase content. However, a high Ca2+/Al3+ =8:1 Ca-Al-O composite causes degradation because the pores become blocked and partial sintering induces CaO agglomeration.
Synthesis and characterization of mesoporous Gd(2)O(3) nanotube and its use as a drug-carrying vehicle
(2010-09-01)
Chang, Yen-Po
;
Liu, Kun-Ho
;
Chao, Chih-Shin
;
Chen, San-Yuan
;
Liu, Dean-Mo
Gd(2)O(3) nanotubes were constructed for the first time by assembling highly crystalline Gd(2)O(3) nanoparticles through the use of combined soft template and sol-gel methods. Amphiphilic block copolymer was used as structure-directing agent and gadolinium isopropoxide as inorganic precursor in non-aqueous solution. The amphiphilic copolymer molecules are known to undergo self-organization above a critical micelle concentration, forming micellular architecture that further provides a structurally ordered active site for the nucleation and growth of Gd monomers. The resulting self-assembly of the Gd(2)O(3) nanocrystals led to the formation of Gd(2)O(3) tubular nanostructure after pyrolytic removal of the template. Transmission electron microscopy analysis indicated a mesoporous channel array along the [1 1 0] direction of the nanotubes where the wall of nanotube is well organized by the assembly of a highly crystalline framework of Gd(2)O(3) nanocrystals. This Gd(2)O(3) nanotube exhibited weak superparamagnetic property and was found to be able to carry and elute a model molecule, i.e. ibuprofen (IBU), in a controllable manner via an external magnetic field. The mechanism of IBU release from the nanotubes with and without the use of magnetic stimulus was proposed. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Synthesis and characterization of mesoporous Gd2O3 nanotube and its use as a drug-carrying vehicle
(2010-09-01)
Chang, Yen-Po
;
Liu, Kun-Ho
;
Chao, Chih-Shin
;
Chen, San-Yuan
;
Liu, Dean-Mo
Gd2O3 nanotubes were constructed for the first time by assembling highly crystalline Gd2O3 nanoparticles through the use of combined soft template and sol-gel methods. Amphiphilic block copolymer was used as structure-directing agent and gadolinium isopropoxide as inorganic precursor in non-aqueous solution. The amphiphilic copolymer molecules are known to undergo self-organization above a critical micelle concentration, forming micellular architecture that further provides a structurally ordered active site for the nucleation and growth of Gd monomers. The resulting self-assembly of the Gd2O3 nanocrystals led to the formation of Gd2O3 tubular nanostructure after pyrolytic removal of the template. Transmission electron microscopy analysis indicated a mesoporous channel array along the [1 1 0] direction of the nanotubes where the wall of nanotube is well organized by the assembly of a highly crystalline framework of Gd2O3 nanocrystals. This Gd2O3 nanotube exhibited weak superparamagnetic property and was found to be able to carry and elute a model molecule, i.e. ibuprofen (IBU), in a controllable manner via an external magnetic field. The mechanism of IBU release from the nanotubes with and without the use of magnetic stimulus was proposed. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
Synthesis, characterization and high temperature CO2 capture capacity of nanoscale Ca-based layered double hydroxides via reverse microemulsion
(2014-02-15)
Chang, Po-Hsueh
;
Chang, Yen-Po
;
Lai, Yen-Ho
;
Chen, San-Yuan
;
Yu, Ching-Tsung
In this study, we report a reverse microemulsion method to prepare stable homogeneous suspensions containing dispersed Ca-Al layered double hydroxide (LDH) nanoparticles. By changing the concentration, reaction time and temperature, the nano-particles with different structural morphology was developed from amorphous aggregation to platelet, regular hexagon and hydrangea-like hierarchical structure. The crystallization and growth of Ca-Al LDH nanoparticles were involved with a nucleation and growth process under nonaqueous polar solvent/surfactant system. After calcination at 700 degrees C, the calcined nano-sized Cal-Al LDH powders synthesized from the reverse microemulsion display remarkable CO2 capture behavior at 600 degrees C, which is strongly dependent on the reaction conditions (concentration, time and temperature). The calcined powder synthesized at 80 degrees C exhibits a faster rate of CO2 absorption and higher CO2 capture capacity of 44 wt% CO2 without apparent degradation under multiple cycles of carbonation-calcination. (C) 2013 Elsevier B. V. All rights reserved.
Synthesis, Characterization, and CO2 Adsorptive Behavior of Mesoporous AlOOH-Supported Layered Hydroxides
(2012)
Chang, Yen-Po
;
Chen, Yu-Chun
;
Chang, Po-Hsueh
;
Chen, San-Yuan
;
材料科學與工程學系
A novel CO2 solid sorbent was prepared by synthesizing and modifying AlOOH-supported CaAl layered double hydroxides (CaAl LDHs), which were prepared by using mesoporous alumina (?-Al2O3) and calcium chloride (CaCl2) in a hydrothermal urea reaction. The nanostructured CaAl LDHs with nanosized platelets (330 nm) formed and dispersed inside the crystalline framework of mesoporous AlOOH (boehmite). By calcination of AlOOH-supported LDHs at 700 degrees C, the mesoporous CaAl metal oxides exhibited ordered hexagonal mesoporous arrays or uniform nanotubes with a large surface area of 273 m2?g-1, a narrow pore size distribution of 6.2 nm, and highly crystalline frameworks. The crystal structure of the calcined mesoporous CaAl metal oxides was multiphasic, consisting of CaO/Ca(OH)2, Al2O3, and CaAlO mixed oxides. The mesoporous metal oxides were used as a solid sorbent for CO2 adsorption at high temperatures and displayed a maximum CO2 capture capacity (approximate to 45 wt?%) of the sorbent at 650 degrees C. Furthermore, it was demonstrated that the mesoporous CaAl oxides showed a more rapid adsorption rate (for 12 min) and longer cycle life (weight change retention: 80?% for 30 cycles) of the sorbent because of the greater surface area and increased number of activated sites in the mesostructures. A simple model for the formation mechanism of mesoporous metal oxides is tentatively proposed to account for the synergetic effect of CaAl LDHs on the adsorption of CO2 at high temperature.