Two-phase Transformation Research Articles

Electrochemical behaviors of hexagonal LiMnBO3 as lithium storage host material for lithium-ion batteries

Abstract Hexagonal LiMnBO 3 samples with particle size bewteen 0.2 and 1.0 μm are prepared by a carbothermal reaction using stoichiometric mixture of LiOH·H 2 O, Mn(CH 3 COO) 2 ·4H 2 O, H 3 BO 3 and carbon black as starting materials. Powder X-ray diffraction and infrared studies of the as-prepared products indicate that hexagonal LiMnBO 3 with space group of P-6 is formed under high temperature calcination at 750 °C. Electrochemical study shows that hexagonal LiMnBO 3 as cathode material for lithium-ion batteries can deliver an initial charge capacity of 148.4 m Ah g −1 (0.668 Li) in the potential range 2.5–4.8 V, corresponding to the delithiation plateau at 4.76 V. Combined with the charge–discharge curves, ex-situ structural investigations show that the delithiation–lithiation mechanism of hexagonal LiMnBO 3 cathode is associated with a two-phase transformation reaction. In contrast, hexagonal LiMnBO 3 as anode material for lithium-ion batteries shows a specific discharge capacity of 678.3 m Ah g −1 and corresponding specific charge capacity of 353.9 m Ah g −1 in the potential range 0.0–3.0 V. After 20 cycles, the reversible charge capacity for hexagonal LiMnBO 3 anode is 286.4 m Ah g −1 with the capacity retention of 80.9%. The excellent cycling performance is attributed to the quasi-reversible structural evolution as confirmed by ex-situ studies.

Structural changes on cycling Li2FeSiO4 polymorphs from DFT calculations

Cation mixing has been demonstrated experimentally in the Li-ion battery cathode material Li2FeSiO4. This feature is investigated here using DFT calculations. It is shown that full reversal of Li/Fe site occupations is energetically favoured on delithiation for all three electrochemically active Li2FeSiO4 polymorphs. The common layered topology in the arrangement of SiO4 and FeO4 tetrahedra in all three polymorphs transforms into a 3D-framwork. Calculations show here that such a change in structure leads to a lowering of electrochemical insertion potential from ~3.1 to ~2.8V, in good agreement with experimental data. Calculations also predict the correct anisotropy in the cell expansion on delithiation on Li/Fe site reversals. Partial mixing of Li and Fe site occupations is energetically less favourable, which supports a two-phase transformation mechanism.

Phase Transformation and Lithiation Effect on Electronic Structure of LixFePO4: An In-Depth Study by Soft X-ray and Simulations

Through soft X-ray absorption spectroscopy, hard X-ray Raman scattering, and theoretical simulations, we provide the most in-depth and systematic study of the phase transformation and (de)lithiation effect on electronic structure in Li(x)FePO(4) nanoparticles and single crystals. Soft X-ray reveals directly the valence states of Fe 3d electrons in the vicinity of Fermi level, which is sensitive to the local lattice distortion, but more importantly offers detailed information on the evolution of electronic states at different electrochemical stages. The soft X-ray spectra of Li(x)FePO(4) nanoparticles evolve vividly with the (de)lithiation level. The spectra fingerprint the (de)lithiation process with rich information on Li distribution, valency, spin states, and crystal field. The high-resolution spectra reveal a subtle but critical deviation from two-phase transformation in our electrochemically prepared samples. In addition, we performed both first-principles calculations and multiplet simulations of the spectra and quantitatively determined the 3d valence states that are completely redistributed through (de)lithiation. This electronic reconfiguration was further verified by the polarization-dependent spectra collected on LiFePO(4) single crystals, especially along the lithium diffusion direction. The evolution of the 3d states is overall consistent with the local lattice distortion and provides a fundamental picture of the (de)lithiation effects on electronic structure in the Li(x)FePO(4) system.

Effect of Ce-doping on the structure and electrochemical performance of lithium trivanadate prepared by a citrate sol–gel method

Ce-doped Li 1+ x Ce y V 3− y O 8 (0 ≤ y ≤ 0.015) cathode materials have been prepared through a citrate sol–gel route followed by heating at 550 °C in air. Demonstrated by XRD and elemental mapping, single-phase and homogeneous Li 1+ x Ce y V 3− y O 8 solid solutions are obtained at y ≤ 0.01, while CeVO 4 impurity presents with increasing of y up to 0.015. The Li 1+ x Ce y V 3− y O 8 at y = 0.01 delivers initial capacity of 262.33 mAh g −1 and capacity retention of 98.9% within the first 50 cycles, much better than the pristine Li 1+ x V 3O 8 cathode (261.86 mAh g −1 and 87.7% accordingly). Electrochemical analyses show that an appropriate dosage of Ce can significantly suppress the capacity fading arose from lithiation phenomena around 2.55 and 2.3 V upon cycling. These interesting phenomena are mainly attributed to the stabilization of the microstructure of the material and the modification of their crystallinity and grain morphology, which lead to suppression of structural damage from the two-phase transformation around 2.55 V upon cycling and the dissolution of active material in the electrolyte on the 2.3 V phenomena.

Kinetics of non-equilibrium lithium incorporation in LiFePO4

Lithium-ion batteries are a key technology for multiple clean energy applications. Their energy and power density is largely determined by the cathode materials, which store Li by incorporation into their crystal structure. Most commercialized cathode materials, such as LiCoO(2) (ref. 1), LiMn(2)O(4) (ref. 2), Li(Ni,Co,Al)O(2) or Li(Ni,Co,Mn)O(2) (ref. 3), form solid solutions over a large concentration range, with occasional weak first-order transitions as a result of ordering of Li or electronic effects. An exception is LiFePO(4), which stores Li through a two-phase transformation between FePO(4) and LiFePO(4) (refs 5-8). Notwithstanding having to overcome extra kinetic barriers, such as nucleation of the second phase and growth through interface motion, the observed rate capability of LiFePO(4) has become remarkably high. In particular, once transport limitations at the electrode level are removed through carbon addition and particle size reduction, the innate rate capability of LiFePO(4) is revealed to be very high. We demonstrate that the reason LiFePO(4) functions as a cathode at reasonable rate is the availability of a single-phase transformation path at very low overpotential, allowing the system to bypass nucleation and growth of a second phase. The Li(x)FePO(4) system is an example where the kinetic transformation path between LiFePO(4) and FePO(4) is fundamentally different from the path deduced from its equilibrium phase diagram.

Electron Microscopy Study of Hypostoichiometric Fe-Pd Nanocomposites Resulting from Combined Reactions Thermomechanical Processing

Hypostoichiometric Fe-Pd binary alloys (35-45 at% Pd) were severely deformed (>90%) and subsequently aged to induce concomitant recrystallization, precipitation, and ordering. This thermomechanical processing strategy was articulated by Hornbogen [1] over thirty years ago. The resulting exchange-coupled ferromagnets contain ferrite precipitates and a complex metastable two-phase lamellar transformation product comprised of ordered L10 and a metastable FCC phase. The later duplex microconstituent is suggested to form in conjunction with a so-called pseudospinodal reaction [2] involving emerging cubic and tetragonal phases, whereby phase separation and ordering result from continuous changes in composition and a reduction in symmetry, cubic to tetragonal. The deformation texture of the parent austenite is substantially retained in the transformation product, resulting in anisotropy of the magnetic properties as determined by magnetometry (VSM). This paper presents electron microscopy results elucidating the crystallography and morphology of the phase mixtures including HREM. Magnetic field annealing is also included as a branch of our thermomechanical processing strategy, and we discuss the influence of the external fields on recrystallization, precipitation, and ordering.

Structural and microstructural changes during anion exchange of CoAl layered double hydroxides: anin situX-ray powder diffraction study

Anion-exchange processes in cobalt–aluminium layered double hydroxides (LDHs) were studied byin situsynchrotron X-ray powder diffraction (XRPD). The processes investigated were CoAl–CO3→ CoAl–Cl → CoAl–CO3, CoAl–Cl → CoAl–NO3and CoAl–CO3→ CoAl–SO4. The XRPD data show that the CoAl–CO3→ CoAl–Cl process is a two-phase transformation, where the amount of the CoAl–CO3phase decreases exponentially while that of the CoAl–Cl phase increases exponentially. Energy-dispersive X-ray spectroscopy (EDXS) studies of a partially chloride-exchanged CoAl–CO3LDH sample along within situXRPD data suggested that the individual particles in the CoAl–CO3sample are generally anion-exchanged with chloride one at a time. In contrast with the CoAl–CO3→ CoAl–Cl transformation, the XRPD data show that the reverse CoAl–Cl → CoAl–CO3process is a one-phase transformation. Rietveld refinements indicate that the occupancy factors of the carbon and oxygen sites of the carbonate group increase, while that of the chloride site decreases. In the CoAl–Cl → CoAl–NO3anion-exchange reaction, the XRPD patterns reveal the existence of two intermediate phases in addition to the initial CoAl–Cl and final CoAl–NO3phases. Thein situdata indicate that one of these intermediates is a mixed nitrate- and chloride-based LDH phase, where the disorder decreases as the nitrate content increases. The XRPD data of the partial CoAl–CO3→ CoAl–SO4anion-exchange reaction show that the process is a two-phase transformation involving a sulfate-containing LDH with a 1H polytype structure.

Phase Diagrams for Systems with Low Free Energy Variation: A Coupled Theory/Experiments Method Applied to Li-Graphite

The paper presents a fast and efficient method to compute phase diagrams using first-principles methods and statistical physics coupled with experimental techniques. The method is applied to lithium intercalated graphite for which evidence of experimental anomalies have recently questioned the currently accepted stage II/stage I two-phase transformation in the 0.5 ≤ x ≤ 1.0 composition range. Our coupled experimental and theoretical analysis has led to a full determination of the LixC6 phase diagram in this range of composition, revealing previously unknown phase transitions and the characterization of at least two new phases.

Hydroxylation of androstenedione by resting Rhodococcus sp. cells in organic media

The use of organic solvent-based media for microbial 9α-hydroxylation of androstenedione (AD) by resting Rhodococcus sp. cells was evaluated. Product yields higher than 90% were observed in a two-phase phthalate-buffer transformation medium (3:1, v/v) containing 1.0 g L −1 AD. The results suggest that in these conditions the reaction of Δ 1-dehydrogenation is considerably inhibited. The successful hydroxylation reaction with a product yield exceeding 60% was found to take place also in a phthalate medium under simultaneous forced aeration and maintenance of a minimum water content of about 3% (v/v).

A New Layered Vanadium Oxide Prepared by Electrochemical Transformation of a Solid Precursor.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A New Layered Vanadium Oxide Prepared by Electrochemical Transformation of a Solid Precursor

The new vanadium oxide, with the composition has been prepared by electrochemical oxidation of the solid precursor in aqueous solution. The reaction mechanism is a two-phase transformation involving simultaneously calcium extraction, oxygen insertion, and ion exchange. This poorly crystallized compound has a layered structure, with interlayer and related to that of xerogels and electrolytic The anhydrous compound reversibly intercalates 2.3 Li per formula unit (210 at a slow rate in the 1.5-4 V range, whereas the precursor does not intercalate any lithium under similar conditions. Preliminary cycling data indicate that the capacity depends on the cycling rate and decreases during cycling. © 2001 The Electrochemical Society. All rights reserved.

In situ investigation of electrochemical lithium intercalation into graphite powder

The reaction kinetics for the electrochemical insertion–extraction of lithium into and out of graphite and the electrode intrinsic resistance have been studied using galvanostatic intermittent titration with applied microcurrent pulses (GIT), electrochemical impedance spectroscopy (EIS) and in situ intrinsic (i.e. physical) resistance measurements. The formation of a so-called solid electrolyte interphase (SEI) or ‘passivation layer’ on the graphite surface at about +0.8 V versus Li + /Li increases the total intrinsic resistance within the electrode on the first cycle. The gradual growth (i.e. change in volume) of the SEI film during repeated lithium insertion–extraction results in a continued increase in intrinsic resistance. The good agreement between EIS and in situ intrinsic resistance measurements indicates that the latter is a simple and powerful method for investigating the change in this parameter for graphite electrodes. GIT showed a gradual increase in kinetic rate in an initial single-phase region, followed by a decrease in a two-phase transformation region, which was in turn followed by an increase in kinetic rate in a second single-phase region. This is explained by a shrinking unreacted core model. The controlling step of lithium insertion–extraction during the two-phase transformation region was investigated by EIS and GIT.

Study on the mechanism of zeolite Y formation in the process of liquor recycling

Abstract Crystallization of zeolite Y formation in the process of mother liquor recycling (MLR) has been studied. The zeolite crystallization mother liquor comprises a little sodium silicate as well as minor zeolite, Upon addition of aluminum sulfate, the silicate existed in the mother liquor reacts to form finely divided silica–alumina hydrogel (MLHG) which can be utilized later in zeolite Y formation. The particle of MLHG is relatively small and Si/Al of the gel's framework is a little great. Since amorphous aluminosilicate gel passes through two stages of gelation, the pseudoequilibrium between solid phase and liquid phase of gel is attained rapidly and the time of zeolite Y formation is much reduced. In addition, experiments have also showed that the quantities and the properties of zeolite Y added affect the process of crystallization heavily. Minor quantities of zeolite in the mother liquor have detrimental effect on the zeolite Y formation. Based on studies of crystallization from recycling mother liquor, a model of two-phase transformation for zeolite Y formation has been proposed.

Crafting Democratic Institutions in Taiwan

Previous articleNext article No AccessCrafting Democratic Institutions in TaiwanHung-mao Tien and Tun-jen ChengHung-mao Tien Search for more articles by this author and Tun-jen Cheng Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The China Journal Volume 37Jan., 1997 Published on behalf of the Australian Centre on China in the World at the Australian National University Article DOIhttps://doi.org/10.2307/2950216 Views: 80Total views on this site Citations: 12Citations are reported from Crossref Copyright The China JournalPDF download Crossref reports the following articles citing this article:Felix Wiebrecht Explaining Activity in Authoritarian Assemblies: Evidence from China, Journal of East Asian Studies 66 (Oct 2022): 1–21.https://doi.org/10.1017/jea.2022.19Tian He The Two-Phase Transformation of the Developmental State in Taiwan, (Nov 2020): 155–206.https://doi.org/10.1007/978-3-030-59357-5_4Tian He Ethnic Identity Politics and the Transformation of the Developmental State: Industrial Structure, Democratic Transition, and Policy Constraints in Taiwan, Asian Politics & Policy 41 (Sep 2020).https://doi.org/10.1111/aspp.12536Tian He Towards a theory of the transformation of the developmental state: political elites, social actors and state policy constraints in South Korea and Taiwan, Japanese Journal of Political Science 21, no.22 (Oct 2019): 47–67.https://doi.org/10.1017/S1468109919000197Tun-jen Cheng, Yung-ming Hsu Long in the Making: Taiwan’s Institutionalized Party System, (Dec 2014): 108–135.https://doi.org/10.1017/CBO9781107300385.005O. Fiona Yap Economic Performance and Moments of Political Transition in East and Southeast Asia, SSRN Electronic Journal (Jan 2011).https://doi.org/10.2139/ssrn.1811267Shih-Ya Kuo, Dennis Longmire, Steven J. Cuvelier, Kuang-Ming Chang Prosecutorial Decision Making in Taiwan: A Partial Test of Black’s Behavior of Law, International Journal of Offender Therapy and Comparative Criminology 54, no.66 (Oct 2009): 1023–1046.https://doi.org/10.1177/0306624X09348929Tun-jen Cheng Strategizing Party Adaptation, Party Politics 12, no.33 (Jun 2016): 367–394.https://doi.org/10.1177/1354068806063086Shu-Hsiang Hsu Democratization and Water Management in Taiwan, Water International 29, no.11 (Mar 2004): 61–69.https://doi.org/10.1080/02508060408691749Ching-Ping Tang, Shui-Yan Tang Taiwan, (Jan 2002): 375–392.https://doi.org/10.1007/978-3-662-04794-1_17Robert D. Strom, Shirley K. Strom, Chih-Mei Wang, Yuh-Ling Shen, Dianne Griswold, Hou-Sheng Chan, Chu-Yin Yang Grandparents in the United States and the Republic of China: A Comparison of Generations and Cultures, The International Journal of Aging and Human Development 49, no.44 (Jul 2016): 279–317.https://doi.org/10.2190/DQFF-LVRU-U6W9-8Q6LShui-Yan Tang, Ching-Ping Tang Democratization and the Environment: Entrepreneurial Politics and Interest Representation in Taiwan, The China Quarterly 158 (Feb 2009): 350–366.https://doi.org/10.1017/S0305741000005804

Instantaneous Reactive Power Compensation Based on Neutral Line Current Separating and Combining Method.

Instantaneous compensation theory of reactive power is conventionally based on coordinate transformation method. That is, three phase voltages and currents on three dimensional coordinate are transformed into αβcoordinate or rotating coordinate quantities. Therefore, it is unavoidable for the control system to be complicated and also it is difficult to understand physical meanings of voltages and currents on the original three dimensional coordinate.The authors have been proposed the instantaneous reactive power compensation theory using a three dimensional cross vector. The proposed theory does not use any coordinate transformations, such as a rotating coordinate transformation or a three-phase to two-phase coordinate transformation. Hence, the instantaneous reactive power compensation system based on the proposed theory is essentially simpler than any conventional reactive power compensation system based on such coordinate transformations.In this paper, we apply the Cross vector theory to three-phase four-wire system. Since there is a neutral line in three-phase four-wire system, simplification of a reactive power compensation system is very difficult. Here, the authors develop a new method, that is, neutral line current separating and combining method. Applying the neutral line current separating and combining method to the Cross vector theory, control system of the instantaneous reactive power compensator for the three-phase four-wire system can be simplified.

Consideration on the numerical coefficient of three-phase to two-phase transformation and the physical meaning of the transformation.

Consideration on the numerical coefficient of three-phase to two-phase transformation and the physical meaning of the transformation.

Analysis of two-phase eutectoid transformation

A theoretical model is formulated to describe solid state eutectoid transformation. Solutions incorporating appropriate boundary conditions are derived from transient and steady states. It is shown that the transient solution describes build-up of the interfacial boundary layer, whereas the steady state solution extends into the phase. The presence of this boundary layer with considerable concentration and temperature gradients suggests a solid state analogue to constitutional super cooling, as in the liquid to solid transformation.

Transient and steady-state operation of induction motors with rotor asymmetries

Steady-state analysis of three-phase induction motors with asymmetrical stator external impedances is presented by the application of the symmetrical components theory. New and general equivalent circuits are derived, and it is shown how they can be extended for constant-speed transients, too. State-variable equations are given for the case of asymmetrical stator voltages and external resistances. — By the application of a new two-phase symmetrical component transformation, steady-state equations of an asymmetrical two-phase machine with nonquadrature windings are set up; a new equivalent circuit is also derived. Transient equations are also given.

On the Phase Mixtures Produced by Annealing of Long Duration in the γ-Phase Fe–Ni Invar Alloys

As well known, the two-phase transformation γ→α+γ is extremely difficult to cccur in the Fe–Ni system, leading to an enormous thermal hysteresis. The nature of this unusual process as well as of the 36%Ni–Fe Invar alloy were studied by annealing the γ-phase Invar alloys in the two-phase region for long duration. A “tail part” in the magnetization(M)-temperature(T) curve was found to grow through three stages; first, a reversible tail becomes large, and then it begins to show a thermal hysteresis, finally it tends to disappear in the third stage. The X-ray spectra suggest that at first an imperfect γ→α lattice transformation occurs locally, and then the diffusion of concentration seems to start, where the distortion of the lattice becomes large due to local transformation. It is likely that the 36%Ni–Fe alloy contains a region corresponding to the tail in the M–T curve.

Polyphase to Two-Axis Transformation for Real Windings

The effects of MMF and permeance harmonics on the N-phase to two-phase slip ring transformation are considered. Considerable simplifications occur if MMFs higher than the Nth can be neglected. Particular attention is given to both three-phase and squirrel-cage windings. Practical factors influencing the α,β,O transformation and the choice of coefficients result from the former and the basis and limitation of the harmonic equivalent circuits of the squirrel cage induction motor result from the latter.