Browsing by Author "Chiang, Ching-Yu"

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Depth-Profiling Electronic and Structural Properties of Cu(In,Ga)(S,Se)(2) Thin-Film Solar Cell
(2016-09-14)
Chiang, Ching-Yu
;
Hsiao, Sheng-Wei
;
Wu, Pin-Jiun
;
Yang, Chu-Shou
;
Chen, Chia-Hao
Utilizing a scanning photoelectron microscope (SPEM) and grazing-incidence X-ray powder diffraction (GIXRD), we studied the electronic band structure and the crystalline properties of the pentanary Cu(In,Ga)(S,Se)(2) (CIGSSe) thin-film solar cell as a function of sample depth on measuring the thickness-gradient sample. A novel approach is proposed for studying the depth-dependent information on thin films, which can provide a gradient thickness and a wide cross-section of the sample by polishing process. The results exhibit that the CIGSSe absorber layer possesses four distinct stoichiometries. The growth mechanism of this distinctive compositional: distribution formed by a two stage process is described according to the thermodynamic reaction and the manufacturing, process. On the basis of the depth-profiling results, the gradient profiles of the conduction and valence bands were constructed to elucidate the performance of the electrical properties (in this case, V-oc = 620 mV, J(sc) = 34.6 mA/cm(2), and eta = 14.04%); the valence-band maxima (VBM) measured with a SPEM in the spectroscopic mode coincide with this band-structure model, except for a lowering of the VBM observed in the surface region of the absorber layer due to the ordered defect compound (ODC). In addition, the depth-dependent texturing X-ray diffraction pattern presents the crystalline quality and the residual stress for each depth of a thin-film device. We find that the randomly oriented grains in the bottom region of the absorber layer and the different residual stress between the underlying Mo and the absorber interface, which can deteriorate the electrical performance due to peeling-off effect. An anion interstitial defect can be observed on comparing the anion concentration, of the elemental distribution with crystalline composition; a few excess sulfur atoms insert in interstitial sites at the front side of the absorber layer, whereas the interstitial selenium atoms insert at the back side.
Element Effects on High-Entropy Alloy Vacancy and Heterogeneous Lattice Distortion Subjected to Quasi-equilibrium Heating
(2019-10-15)
Huang, E-Wen
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Chou, Hung-Sheng
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Tu, K. N.
;
Hung, Wei-Song
;
Tu-Ngoc Lam
We applied Simmons-Balluffi methods, positron measurements, and neutron diffraction to estimate the vacancy of CoCrFeNi and CoCrFeMnNi high-entropy alloys (HEAs) using Cu as a benchmark. The corresponding formation enthalpies and associated entropies of the HEAs and Cu were calculated. The vacancy-dependent effective free volumes in both CoCrFeNi and CoCrFeMnNi alloys are greater than those in Cu, implying the easier formation of vacancies by lattice structure relaxation of HEAs at elevated temperatures. Spatially resolved synchrotron X-ray measurements revealed different characteristics of CoCrFeNi and CoCrFeMnNi HEAs subjected to quasi-equilibrium conditions at high temperatures. Element-dependent behavior revealed by X-ray fluorescence (XRF) mapping indicates the effect of Mn on the Cantor Alloy.
Multi-scale mapping for collagen-regulated mineralization in bone remodeling of additive manufacturing porous implants
(2019-05-15)
Tsai, Pei-I.
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Lam, Tu-Ngoc
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Wu, Meng-Huang
;
Tseng, Kuan-Ying
;
Chang, Yuan-Wei
Long term success of metallic fusion cages depends on mechanobiological processes through the bone incorporation and rich osseointegration. An optimal configuration of porous titanium-aluminum-vanadium (Ti-6Al-4V) implant fabricated via the additive manufacturing was evaluated in complimentary structure examinations to investigate the growth of autologous osseous at multi-length scales. X-ray microcomputed tomography (micro-CT) and transmission X-ray microscopy (TXM) using newly-built analysis method indicate the porous Ti-6Al-4V is much better for bone ingrowth compared to commercially non-porous titanium (Ti) and porous tantalum (Ta) implants at the ultramicrostructural level. The evolution of bone formation and remodeling acquired by nano X-ray Laue diffraction mapping exhibits the isotropic orientation and low crystallinity of all newly formed bone whereas mature bone in Ti-6Al-4V discloses the preferential alignment and higher crystallinity volumes of constituent hydroxyapatite (HA) crystallites. The high degree in mineral crystallinity of the fully mature bone suggests additive manufactured Ti-6Al-4V pores enhance the collagen-regulated mineralization.
Real-time investigation of the structural evolution of electrodes in a commercial lithium-ion battery containing a V-added LiFePO4 cathode using in-situ neutron powder diffraction
(2013-12-15)
Hu, Chih-Wei
;
Sharma, Neeraj
;
Chiang, Ching-Yu
;
Su, Hui-Chia
;
Peterson, Vanessa K.
In-situ neutron powder diffraction was employed to investigate the structural evolution of the electrode materials in a commercial lithium-ion battery used for electric buses in Taiwan. The battery, containing a vanadium-added LiFePO4 cathode, does not exhibit a delayed phase transition between LiFePO4 (triphylite) and FePO4 (heterosite) suggesting that the delayed phase transition can be suppressed through the use of vanadium-added LiFePO4 cathodes, which also enhances the capacity and prolongs the cycle life of these batteries. Furthermore, we characterize the readily reversible structural change of the anode (LixC6 where 0 < x <= 1) and correlate this to battery voltage. (C) 2013 Elsevier B.V. All rights reserved.
Vanadium Substitution of LiFePO4 Cathode Materials To Enhance the Capacity of LiFePO4-Based Lithium-Ion Batteries
(2012-11-22)
Chiang, Ching-Yu
;
Su, Hui-Chia
;
Wu, Pin-Jiun
;
Liu, Heng-Jui
;
Hu, Chih-Wei
The mechanism of enhancing the capacity of the LiFePO4 cathodes in lithium ion batteries by the addition of a small amount of vanadium, which locate on the lithium site and induce lithium vacancies in the crystal structure, is reported in this article. As a result, the capacity increases from 138 mAh/g found for pristine LiFePO4 to 155 mAh/g for the V-added compound, and the conductivity increases from 4.75 x 10(-4) S/cm for the LiFePO4 without V addition to 1.9 x 10(-2) S/cm for the V-added compound. A possible model to facilitate the enhancement of conductivity and capacity is described with evidence supported by X-ray powder diffraction, X-ray absorption spectroscopy, and neutron powder diffraction data.