Browsing by Author "Sheu, Hwo-Shuenn"

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{110}-exposed rutile titanium dioxide nanorods in photocatalytic performance
(2009)
Ke, Tsung-Ying
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Peng, Chih-Wei
;
Lee, Chi-Young
;
Chiu, Hsin-Tien
;
Sheu, Hwo-Shuenn
Single crystalline rutile TiO(2) nanorods were prepared by reacting sodium titanate with hydrochloric acid. The proposed formation mechanism involves a growth pathway. The growth proceeds along [001], and the circumferential faces are {110}, which are identified as the photoactive faces of rutile titanium dioxide. Both the heterogeneous ( photocatalyst only) and the combined heterogeneous/homogeneous (photocatalyst and H(2)O(2)) photocatalytic performances support its activity. The mechanism of formation and photocatalytic property are extensively studied.
Artificial Synthesis of Platelet-Like Kassite and Its Transformation to CaTiO(3)
(2010-03-01)
Huang, Yi-Jen
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Tsai, Min-Chiao
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Chiu, Hsin-Tien
;
Sheu, Hwo-Shuenn
;
Lee, Chi-Young
Platelet-like kassite, a rare mineral CaTi(2)O(4)(OH)(2), wits synthesized by a wet chemical route using Ca(OH)(2) and TiO(2) as reagents in base Solution. The microstructure of the obtained kassite examined by synchrotron radiation and Rietveld refinement are hexagonal (P312) with a = b = 0.52451(2) and c = 0.47844(3) nm. This cell is slightly different from JCPDS No. 88-1722. At heating above 500 degrees C, the layered crystalline kassite rearranges to form disk-like CaTiO(3) and amorphous TiO(2) by removing H(2)O completely. Furthermore, transmission electron microscopy analysis reveals that the vertical axis of disk-like CaTiO(3) along the [0 (2) over bar1] direction converts from that of [001] orkassite.
Artificial Synthesis of Platelet-Like Kassite and Its Transformation to CaTiO3
(2010-03-01)
Huang, Yi-Jen
;
Tsai, Min-Chiao
;
Chiu, Hsin-Tien
;
Sheu, Hwo-Shuenn
;
Lee, Chi-Young
Platelet-like kassite, a rare mineral CaTi2O4(OH)(2), wits synthesized by a wet chemical route using Ca(OH)(2) and TiO2 as reagents in base Solution. The microstructure of the obtained kassite examined by synchrotron radiation and Rietveld refinement are hexagonal (P312) with a = b = 0.52451(2) and c = 0.47844(3) nm. This cell is slightly different from JCPDS No. 88-1722. At heating above 500 degrees C, the layered crystalline kassite rearranges to form disk-like CaTiO3 and amorphous TiO2 by removing H2O completely. Furthermore, transmission electron microscopy analysis reveals that the vertical axis of disk-like CaTiO3 along the [0 (2) over bar1] direction converts from that of [001] orkassite.
Effect of LiClO4 on the thermal and morphological properties of organic/inorganic polymer hybrids
(2008-08-11)
Yen, Ying-Chieh
;
Ye, Yun-Sheng
;
Cheng, Chih-Chia
;
Chen, Hsiu-Mei
;
Sheu, Hwo-Shuenn
This paper describes the thermal properties, morphologies, and interactions within the binary and ternary blends of poly(methyl methacrylate) (PMMA), octa(phenol)octasilsesquioxane (OP-POSS), and LiClO4. In the binary PMMA/OP-POSS blends, the OP-POSS molecules tend to aggregate and result in a decrease (19 degrees C) in the glass transition temperature. In the ternary PMMA/LiClO4/OP-POSS blends, however, the OP-POSS molecules form small sphere-like domains (20 nm) leading to the composite's glass transition temperature increasing by up to 30 degrees C. Based on these FF-IR spectra, the addition of LiClO4 influenced the probability of hydrogen bonds formed between PMMA and OP-POSS and these SEM micrographs, DSC, and XRD data indicated that the addition of LiClO4 is a convenient and simple approach toward dispersing the OP-POSS nanoparticles within PMMA, where the presence of LiClO4 changes the physical effect of OP-POSS from that of a diluent role to a cross-linker role. (c) 2008 Elsevier Ltd. All rights reserved.
Interconversion of rutile TiO2 and layered ramsdellite-like titanates: New route to elongated mesoporous rutile nanoplates
(2008-10-01)
Peng, Chih-Wei
;
Richard-Plouet, Mireille
;
Tsai, Min-Chiao
;
Lee, Chi-Young
;
Chiu, Hsin-Tien
We report the first soft chemistry synthesis of a new "layered ramsdellite-like" titanate structure, NaTi2O4(OH) (lattice parameters: primitive monoclinic system, a = 4.09 nm, b = 0.29 nm, c = 0.94 nm, and beta = 80 degrees), with high-aspect-ratio, platelike morphology (diameter. 20-200 nm; thickness. 10-40 nm; length. 0.05-5 mu m) from TiO2 rutile. The newly prepared titanate can be transformed back to TiO2 rutile with uniquely shaped mesoporous elongated nanoplate morphology. The reaction proceeds via the disintegration of rutile in NaOH(aq) into NaTi2O4(OH). Ion exchange of Na+ in NaTi2O4(OH) into H+ forms another new layered ramsdellite-like titanate, HTi2O4(OH). A final topotatic condensation of the titanate layers in HTi2O4(OH) by heat treatment at relatively low 673 K produces the mesoporous TiO2 rutile product with highly exposed (110) surfaces.
Lithium Ion Intercalation Performance of Porous Laminal Titanium Dioxides Synthesized by Sol-Gel Process
(2009-02-10)
Tsai, Min-Chiao
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Chang, Jian-Chia
;
Sheu, Hwo-Shuenn
;
Chiu, Hsin-Tien
;
Lee, Chi-Young
We have synthesized novel mesoporous titanate nanosheets by reacting titanium isopropoxide (TTIP) with formic acid. The porous nanosheets were characterized as a new titanate structure with intercalation of formate groups and protons, in the form of HCOOH-intercalated titanate. Most interestingly, TiO(2)-B, a well-known but unusual titanium dioxide phase with great potential in applications in Li-ion batteries, was obtained after the nanosheets were heated above 250 degrees C. Mesoporous nanosheets of HCOOH-intercalated titanate, titanium dioxide with mostly TiO(2)-B and titanium dioxide with traces of TiO(2)-B were obtained by heating the as prepared mesoporous titanate nanosheets at 200, 300, and 550 degrees C, respectively. The method reported here is the first to utilize the sol-gel process to synthesize TiO(2)-B. In addition, different anodes were made from HCOOH-intercalated titanate and titanium dioxide with different ratios of TiO2-B to examine the performance of the charging/discharging capacity in Li ion intercalation. The discharging capacity of titanium dioxide with major TiO2-B can reach 357 mA h/g at the first charging cycle and is highest among TiO(2)-B reports so far.
Metal substituted pyrochlore phase LixLa2-xCe1.8Ru0.2O7- (x=0.0-0.6) as an effective catalyst for oxidative and auto-thermal steam reforming of ethanol
(2019-03-21)
Hsieh, Ho-Chen
;
Chang, Yuan-Chia
;
Tsai, Ping-Wen
;
Lin, Yen-Yu
;
Chuang, Yu-Chun
Pyrochlore phase LixLa2-xCe1.8Ru0.2O7- (x = 0.0-0.6) [LLCRO] substituted by Li and Ru in A and B sites was synthesized and studied for performance in oxidative steam and auto-thermal reforming of ethanol (OSRE, ATR). The samples were characterized by powder X-ray diffraction (PXRD), X-ray absorption spectroscopy (XAS), and X-ray photoelectron spectroscopy (XPS) to examine the effect of substituted Li+ and Run+ on OSRE performance. The results indicated that the substituted Li ions modified the oxidation states of Ru and Ce in LLCRO, which led to oxygen vacancies/mobility and played an important role in the catalytic performance of OSRE. Using LLCRO as the catalyst and supported by Al2O3, La2Zr2O7 (LZO) was investigated for its hydrogen production performance. The catalytic stability of the LLCRO (x = 0.6)/LZO catalysts was tested at 350 degrees C under oxidative steam conditions (OSRE) and showed a stable ethanol conversion and hydrogen production (X-EtOH = 98(3)%; S-H2 = 95(3)%). Under autothermal conditions (ATR), the LLCRO (x = 0.6) catalyst supported by LZO exhibited a stable catalytic performance with an average ethanol conversion and hydrogen selectivity of 90(3)% and 71(4)%, respectively. Carbon deposition was significantly suppressed during the OSRE and ATR processes on LLCRO (x = 0.6) catalysts supported by LZO, whereas, a significant carbon deposition was observed for LLCRO (x = 0.6)/Al2O3 as the catalyst. These results indicate that LLCRO (x = 0.6) supported by LZO is an effective catalyst for hydrogen production. The enhanced activity was attributed to the effectively suppressed carbon deposition and the sintering of highly dispersed Ru ions in the LLCRO catalyst, which may be due to the strong binding between the catalyst and LZO.
Near UV-pumped yellow-emitting Sr(8)MgSc(PO(4))(7):Eu(2+) phosphor for white-light LEDs with excellent color rendering index
(2011-01-01)
Huang, Chien-Hao
;
Chen, Yen-Chi
;
Chen, Teng-Ming
;
Chan, Ting-Shan
;
Sheu, Hwo-Shuenn
An Eu(2+)-activated Sr(8)MgSc(PO(4))(7):Eu(2+) yellow-emitting phosphor with strong luminescence was synthesized and its crystal structure has been refined and determined from the XRD profiles using synchrotron light source by Rietveld refinement method. Non-radiative transitions between Eu(2+) ions in the Sr(8)MgSc(PO(4))(7) host have also been demonstrated to be attributable to dipole-dipole interactions, and the critical distance was estimated to be 24.83 angstrom by using spectral overlap methods. In addition, white-light near-UV LEDs were fabricated by using a phosphor blend of composition-optimized yellow-emitting Sr(8)MgSc(PO(4))(7):0.01Eu(2+) and blue-emitting BaMgAl(10)O(17):Eu(2+) commodity pumped with a 400 nm near-UV chip and the Ra value and reduced color temperature of were found to be 96.7 and 5,614 K, respectively. These results indicate that yellow-emitting Sr(8)MgSc(PO(4))(7):xEu(2+) can serve as a promising candidate for application in white-light LEDs.
Near UV-pumped yellow-emitting Sr8MgSc(PO4)(7):Eu2+ phosphor for white-light LEDs with excellent color rendering index
(2011-01-01)
Huang, Chien-Hao
;
Chen, Yen-Chi
;
Chen, Teng-Ming
;
Chan, Ting-Shan
;
Sheu, Hwo-Shuenn
An Eu2+-activated Sr8MgSc(PO4)(7):Eu2+ yellow-emitting phosphor with strong luminescence was synthesized and its crystal structure has been refined and determined from the XRD profiles using synchrotron light source by Rietveld refinement method. Non-radiative transitions between Eu2+ ions in the Sr8MgSc(PO4)(7) host have also been demonstrated to be attributable to dipole-dipole interactions, and the critical distance was estimated to be 24.83 angstrom by using spectral overlap methods. In addition, white-light near-UV LEDs were fabricated by using a phosphor blend of composition-optimized yellow-emitting Sr8MgSc(PO4)(7):0.01Eu(2+) and blue-emitting BaMgAl10O17:Eu2+ commodity pumped with a 400 nm near-UV chip and the Ra value and reduced color temperature of were found to be 96.7 and 5,614 K, respectively. These results indicate that yellow-emitting Sr8MgSc(PO4)(7):xEu(2+) can serve as a promising candidate for application in white-light LEDs.
New SmCG Phases in a Hydrogen-Bonded Bent-Core Liquid Crystal Featuring a Branched Siloxane Terminal Group
(2011-10-05)
Chen, Wei-Hong
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Chuang, Wei-Tsung
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Jeng, U-Ser
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Sheu, Hwo-Shuenn
;
Lin, Hong-Cheu
In this study, we synthesized three analogous bentcore molecules, a hydrogen-bonded complex and a covalent-bonded compound with branched siloxane units (H-SiO and C-SiO, respectively) and a hydrogen-bonded complex with an alkyl unit (H-Alk), and investigated the effects of the hydrogen bonding and branched siloxane terminal units on their mesomorphic properties. The covalent-bonded compound C-SiO and the hydrogen-bonded complex H-Alk exhibited typical SmCP phases; in contrast, the hydrogen-bonded complex H-SiO exhibited a series of general tilt smectic (SmCG) phases with highly ordered layer structures (i.e., SmCG(2)P(F)-USmCG(2)P(A)-SmCG(2)P(F)-SmCGP(F) upon cooling). During the SmCG-type phase transition process, a 2D-modulated ribbon structure transferred into highly ordered layers via undulated layers, as the hydrogen-bonding strength increased with reduced temperatures. As the SmCG domains were aligned under dc electric fields, a gradual decrease in the leaning angle from ca. 60 degrees to 50 degrees (while the tilt angle kept at ca. 31 degrees) could be determined by in situ wide-angle X-ray scattering (WAXS). Combined with Fourier transform infrared and Raman spectroscopic data, our results suggest that the change in the leaning angle was governed by the competition of the hydrogen bonds and microsegregation of siloxane units within the bilayer structure of the hydrogen-bonded complex H-SiO. In addition, the ferroelectric-(antiferroelectric)-ferroelectric transitions proven by the switching current responses in the SmCG-type phases of H-SiO reveal that the polar switching occurred through collective rotations around the long axis of H-SiO. Therefore, novel SmCG phases with a series of highly ordered 2D-structures were induced by the effects of the hydrogen bonding and branched terminal siloxane unit in the bent-core hydrogen-bonded LC complex H-SiO.
One-Step Ge/Si Epitaxial Growth
(2011-07-01)
Wu, Hung-Chi
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Lin, Bi-Hsuan
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Chen, Huang-Chin
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Chen, Po-Chin
;
Sheu, Hwo-Shuenn
Fabricating a low-cost virtual germanium (Ge) template by epitaxial growth of Ge films on silicon wafer with a Ge(x)Si(1-x) (0 < x < 1) graded buffer layer was demonstrated through a facile chemical vapor deposition method in one step by decomposing a hazardousless GeO(2) powder under hydrogen atmosphere without ultra-high vacuum condition and then depositing in a low-temperature region. X-ray diffraction analysis shows that the Ge film with an epitaxial relationship is along the in-plane direction of Si. The successful growth of epitaxial Ge films on Si substrate demonstrates the feasibility of integrating various functional devices on the Ge/Si substrates.
Oxidative steam reforming of ethanol over MxLa2-xCe1.8Ru0.2O7-delta (M = Mg, Ca) catalysts: effect of alkaline earth metal substitution and support on stability and activity
(2019-12-02)
Hsieh, Ho-Chen
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Tsai, Ping-Wen
;
Chang, Yuan-Chia
;
Weng, Sheng-Feng
;
Sheu, Hwo-Shuenn
Alkaline earth metal substitutions on the A-site of pyrochlore oxide MxLa2-xCe1.8Ru0.2O7-delta (M = Mg, Ca) were studied as catalyst materials for oxidative/autothermal steam reforming of ethanol (OSRE/ATR). The as-prepared oxides were synthesized by a combustion method and characterized using powder X-ray diffraction (PXRD), and X-ray photoelectron and absorption spectroscopy (XPS and XAS). PXRD Rietveld analysis and elemental analysis (ICP-AES) support the formation of a pyrochlore-type structure (space group Fd3m) with a distorted coordination environment. The substitution of Mg²⁺ and Ca²⁺ ions affects the oxidation states of Ce^4+/3+ and Ruⁿ⁺ ions and creates oxygen vacancies, which leads to enhanced catalytic activity and reduced ethylene selectivity. A long-term stability test showed optimized catalysts Mg0.3La1.7Ce1.8Ru0.2O7-delta and Ca0.2La1.8Ce1.8Ru0.2O7-delta with SH2 = 101(1)% and SH2 = 91(2)% under OSRE conditions. The initial operation temperatures were lower than that of the unsubstituted catalyst La2Ce1.8Ru0.2O7-delta. Catalysts supported on La2Zr2O7 showed stable OSRE/ATR performance and low carbon deposition compared to catalysts supported on Al2O3. We ascribe the enhanced activity to well-dispersed alkaline earth metal and Ru ions in a solid solution structure, synergistic effects of (Mg, Ca)²⁺/Ce^3+/4+/Ruⁿ⁺ ions, and a strong catalyst-support interaction that optimized the ethanol conversion and hydrogen production.
Pressure-induced structural phase transition in bulk Zn0.98Mn0.02O by angular dispersive X-ray diffraction
(2014-08-15)
Lin, Chih-Ming
;
Lin, Kung-Liang
;
Chern, Yu-Ker
;
Hsu, Chia-Hung
;
Sheu, Hwo-Shuenn
The high pressure induced phase transition in bulk Zn0.98Mn0.02O at ambient temperature have been investigated using angular-dispersive X-ray diffraction (ADXRD) under high pressure up to around 13.80 GPa. For loading run, in situ ADXRD measurements found that a wurtzite-to-rocksalt structural phase transition pressure of bulk Zn0.98Mn0.02O began at 7.35 GPa. The fitting of volume compression data to the third-order Birch-Murnaghan equation of state yielded that the zero-pressure isothermal bulk moduli and the first-pressure derivatives were 157(8) GPa and 8(3) for the B4 phase, respectively. When decompress bulk Zn0.98Mn0.02O to ambient pressure a large part of the bulk Zn0.98Mn0.02O reverted to the B4 phase and only a small amount of the metastable B1 phase remained. We have exhibits the pressure dependence of lattice constant a and c axis, and the normalized ratio c/a of the bulk Zn0.98Mn0.02O. Possible pressure-induced phase transition mechanisms were explored by examining the cell parameters and the internal structural parameter (u) with pressures. The effect of the 3d electrons of manganese to increase the nearest-neighbor distance of O to Zn (Mn) parallel to the c axis may be the main reason for the phase transition of bulk Zn0.98Mn0.02O. An increase in the u value with pressure indicates that the B4-to-B1 phase transformation in bulk Zn0.98Mn0.02O is likely via the hexagonal path. (C) 2014 Elsevier B.V. All rights reserved.
Reversible adapting layer produces robust single-crystal electrocatalyst for oxygen evolution
(2015-08-01)
Tung, Ching-Wei
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Hsu, Ying-Ya
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Shen, Yen-Ping
;
Zheng, Yixin
;
Chan, Ting-Shan
Electrochemically converting water into oxygen/hydrogen gas is ideal for high-density renewable energy storage in which robust electrocatalysts for efficient oxygen evolution play crucial roles. To date, however, electrocatalysts with long-term stability have remained elusive. Here we report that single-crystal Co3O4 nanocube underlay with a thin CoO layer results in a high-performance and high-stability electrocatalyst in oxygen evolution reaction. An in situ X-ray diffraction method is developed to observe a strong correlation between the initialization of the oxygen evolution and the formation of active metal oxyhydroxide phase. The lattice of skin layer adapts to the structure of the active phase, which enables a reversible facile structural change that facilitates the chemical reactions without breaking the scaffold of the electrocatalysts. The single-crystal nanocube electrode exhibits stable, continuous oxygen evolution for 41,000 h. This robust stability is attributed to the complementary nature of defect-free single-crystal electrocatalyst and the reversible adapting layer.
Self-carbonized lamellar nano/micro hierarchical structure C/TiO2 and its Li-ion intercalation performance
(2012)
Chen, Po-Chin
;
Tsai, Min-Chiao
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Chen, Huang-Chin
;
Lin, I-Nan
;
Sheu, Hwo-Shuenn
In this study, two new layered titanates, fibrillar TiO2 center dot(CH3COOH)(1.4) and chrysanthemum-like TiO2 center dot(CH3COOH)(0.9) (named as FT and CT) with acetic acid and acetate intercalation have been synthesized by reacting titanium isopropoxide (TTIP) with acetic acid at different temperatures. Furthermore, nano/micro hierarchical structure TiO2 with high TiO2-B/anatse ratio was obtained by annealing the titanate (CT). For use as an anode for lithium ion batteries, uniform carbon coated titanium dioxide with high TiO2-B content was obtained by "self-carbonizing'' CT under argon atmosphere at 350 degrees C, and the compound was named SC-CT350. The capacity of the anode made from SC-CT350 can reach 144 mA h g(-1) under a high charging/discharging rate (10 C) and showed excellent retention ability.
Size-dependent lattice dynamics of barium titanate nanoparticles
(2007-11-28)
Huang, Tung-Ching
;
Wang, Mei-Tan
;
Sheu, Hwo-Shuenn
;
Hsieh, Wen-Feng
;
光電工程學系
By applying a single-tetragonal-phase model to refine the crystal structure and the coupled-phonon model to analyze transverse optical ( TO) modes of BaTiO3 nanocrystals, we found, upon decreasing the particle size from 140 to 30 nm, that the tetragonality of BaTiO3 nanocrystallites is reduced accompanied by expanding unit-cell volume, which is the dominant mechanism for reducing giant LO-TO splitting in the BaTiO3 system. The weakening coupling of two low-frequency modes among three A(1) ( TO) phonons leads to changing the lowest one from a spectral dip to a peak, whereas the increasing coupling strength between two high-frequency modes repels them farther so that there is less reduction in spectral separation.
Sodium niobate nanowire and its piezoelectricity
(2008-06-19)
Ke, Tsung-Ying
;
Chen, Hsiang-An
;
Sheu, Hwo-Shuenn
;
Yeh, Jien-Wei
;
Lin, Heh-Nan
Nanowires of crystalline orthorhombic sodium niobate (NaNbO3) with diameters of approximately 100 nm and lengths of several to hundreds of microns, as well as cubes with edges of lengths of hundreds of nanometers were obtained by reacting niobium oxide (Nb2O5) with 10 and 12.5 M NaOH solutions, respectively. The microstructures of the synthesized wiry and cubic piezoelectric materials were investigated, and the details of the reactions were elucidated as well. The piezoelectricity of individual NaNbO3 (Pbma) nanowires was confirmed by piezoresponse force microscopy, and an effective piezoelectric coefficient along the vertical direction of around a few pm/V was obtained. To our knowledge, the present work is the first report of the preparation of NaNbO3 nanowires as well as the determination of piezoelectricity.
The synergistic effect of a well-defined Au@Pt core-shell nanostructure toward photocatalytic hydrogen generation: interface engineering to improve the Schottky barrier and hydrogen-evolved kinetics
(2016)
Hung, Sung-Fu
;
Yu, Ya-Chu
;
Suen, Nian-Tzu
;
Tzeng, Guan-Quan
;
Tung, Ching-Wei
A well-defined co-catalyst system TiO2 nanotube-Au (core)-Pt (shell) was demonstrated to be the combination of the localized surface plasmon effect of gold and excellent proton reduction nature of platinum. Furthermore, surface engineering by the descending Fermi energies of gold and platinum was beneficial to electron transfer.
Valence- and element-dependent water oxidation behaviors: in situ X-ray diffraction, absorption and electrochemical impedance spectroscopies
(2017-04-07)
Hsu, Chia-Shuo
;
Suen, Nian-Tzu
;
Hsu, Ying-Ya
;
Lin, Hsuan-Yu
;
Tung, Ching-Wei
Metal oxides of the spinel family have shown great potential towards the oxygen evolution reaction (OER), but the fundamental OER mechanism of spinel oxides is still far from being completely understood, especially for the role of the metal ions. Owing to various coordinated sites of divalent/trivalent metals ions and surface conditions (morphology and defects), it is a great challenge to have a fair assessment of the electrocatalytic performance of spinel systems. Herein, we demonstrated a series of MFe2O4 (M = Fe, Co, Ni, Zn) with a well-controlled morphology to achieve a comprehensive study of electrocatalytic activity toward OER. By utilizing several in situ analyses, we could conclude a universal rule that the activities for OER in the metal oxide systems were determined by the occurrence of a phase transformation, and this structural transformation could work well in both crystallographic sites (Td and Oh sites). Additionally, the divalent metal ion significantly dominated the formation of oxyhydroxide through an epitaxial relationship, which depended on the atomic arrangement at the interface of spinel and metal oxyhydroxide, while trivalent metal ions remained unchanged as a host lattice. The metal oxyhydroxide was formed during a redox reaction rather than being formed during OER. The occurrence of the redox reaction seems to accompany a remarkable increase in resistance and capacitance might result from the structural transformation from spinel to metal oxyhydroxide. We believe that the approaching strategies and information obtained in the present study can offer a guide to designing a promising electrocatalytic system towards the oxygen evolution reaction and other fields.