Dip-coated La2Ti2O7 as a buffer layer for growth of Bi3.25La0.75Ti3O12 films with enhanced (0 1 1) orientation

Thin-films of La2Ti2O7 were obtained by dip-coating process using a precursor salt in nitric acid solution. The effects of solution concentration, withdrawal speed, post-annealing duration and temperature were investigated both on grain size and orientation of the La2Ti2O7 thin layers. In addition, a target with the required stoichiometry for PVD deposition of La-substituted Bi4Ti3O12 (BLT) was successfully sintered by spark plasma sintering (SPS) at 750 ◦C. Finally (0 1 1)-oriented BLT ferroelectric films have been grown by RF sputtering on (1 1 0)-oriented La2Ti2O7 polycrystalline thin-film. A preferential orientation of BLT thin films has been obtained after annealing at a temperature lower than 650 ◦C

Crystallographic origin of cycle decay of the high-voltage LiNi\u3csub\u3e0.5\u3c/sub\u3eMn\u3csub\u3e1.5\u3c/sub\u3eO\u3csub\u3e4\u3c/sub\u3e spinel lithium-ion battery electrode

High-voltage spinel LiNi0.5Mn1.5O4 (LNMO) is considered a potential high-power-density positive electrode for lithium-ion batteries, however, it suffers from capacity decay after extended charge-discharge cycling, severely hindering commercial application. Capacity fade is thought to occur through the significant volume change of the LNMO electrode occurring on cycling, and in this work we use operando neutron powder diffraction to compare the structural evolution of the LNMO electrode in an as-assembled 18650-type battery containing a Li4Ti5O12 negative electrode with that in an identical battery following 1000 cycles at high-current. We reveal that the capacity reduction in the battery post cycling is directly proportional to the reduction in the maximum change of the LNMO lattice parameter during its evolution. This is correlated to a corresponding reduction in the MnO6 octahedral distortion in the spinel structure in the cycled battery. Further, we find that the rate of lattice evolution, which reflects the rate of lithium insertion and removal, is ∼9 and ∼10% slower in the cycled than in the as-assembled battery during the Ni2+/Ni3+ and Ni3+/Ni4+ transitions, respectively

Synthèse et caractérisation de nano-cristallites de TiO à basse température (stabilisation de solutions colloïdales et dépôts par voie chimique)

Parmi les propriétés physico-chimiques des oxydes de titane, la photoactivité est sans doute la plus attractive en raison de ses nombreuses applications dans le domaine de la protection de l environnement: purification de l air et décontamination de l eau, photo-électrolyse de l eau, photo-superhydrophilicité et production d énergie avec le photovoltaïque. La mise en œuvre de ce matériau dans les cellules photovolta ques de IIIème génération nécessite la réalisation d un film mince et dense de TiO2 permettant d éviter les court-circuits, surmonté d un dépôt nanostructuré et poreux afin d optimiser la collecte des porteurs de charge photogénérés, dans un gel photosensible à base d oxyde de titane. Afin d obtenir ces deux dépôts qui possèdent les caractéristiques souhaitées, il importe de mieux comprendre les mécanismes de la polycondensation des oxydes de titane à l échelle atomiqueet de caractériser leurs propriétés; ensuite, il faut préparer des suspensions stables pour réaliser les dépôts par voie humide. Les études précédemment menées au sein de l Institut des Matériaux Jean Rouxel, ont permis de synthétiser différentes variétés d oxyde de titane par l hydrolyse du précurseur [Ti8O12(H2O)24]Cl8.HCl.7H2O en présence de l hydroxyde de tétraméthylammonium (TMAOH) en milieu aqueux, dans des conditions thermiques douces(<=120C) en ajustant le rapport de Ti/TMAOH donc le pH. Pour un rapport R = Ti/OH = 0.47, la structure lamellaire (TMA)2Ti2O4(OH)2 obtenue est caractérisée principalement par diffraction des rayons X et MET. Si la détermination de la structure n a pas pu être complètement résolue, la modélisation par DFT a permis de confirmer un jeu de paramètres de maille dont la validité a été, par la suite, confirmée par affinement du diagramme de diffraction des rayons X. Par ailleurs, les distances interfeuillets ont été modulées par ajout de surfactants qui peuvent être photo-dégradés sous irradiation UV et conduire à des dépôts de TiO2 présentant une morphologie poreuse. Les rapports R = 0.6 et R = 0.8 permettent sélectivement de synthétiser à T<100C, des nanocristallites d oxydes de titane de structure brookite et anatase, respectivement. Leurs formules sont TiO1.89(CO3)0.05(OH)0.13(H2O)0.02 pour R = 0.6 et TiO1.88(CO3)0.03(OH)0.18(H2O)0.09 pour R = 0.8. Les carbonates adsorbés peuvent être liés au cation métallique sous deux formes: bidentate et monodentate La présence de ces groupements carbonates serait responsable des déformations du réseau observées par microscopie électronique sur les formes basse température de TiO2. Afin de vérifier l influence des carboxylates, l ajout d acide malonique a été effectué dans ce système pour R = Ti/OH = 0.4 et pH 8~9. Les particules d anatase croissent préférentiellement selon [101] sous forme de bâtonnets. Les poudres avec R = 0.8 et R = 0.4 contenant l acide malonique s auto-arrangent en plaquettes denses et plates, de dimensions micrométriques. Les conditions de préparations de dépôts ont été étudiées: la stabilité des suspensions, les paramètres de trempage-retrait et tournette, le traitement de substrat SnO2/F. Un dépôt dense d anatase avec une épaisseur de 50/80 nm et un dépôt poreux non cristallisé ont été obtenus. Les recherches visant à améliorer l épaisseur des dépôts et la cristallinité sont en cours pour le développement de cellules photovoltaïques de IIIème générationNANTES-BU Sciences (441092104) / SudocSudocFranceF

Enhanced rate-capability and cycling-stability of 5 V SiO2- and polyimide-coated cation ordered LiNi0.5Mn1.5O4 lithium-ion battery positive electrodes

The ordered LiNi0.5Mn1.5O4 spinel exhibits great promise as a potential high-energy positive electrode for lithium-ion batteries due to its exceptionally high working potential of 4.7 V (vs. Li) and energy density of 640 Wh kg-1. The commercial application of this material at such voltages is unfortunately prevented by reaction phenomena including hydrofluoric acid attack and manganese dissolution, as well as the two-phase mechanism of Li insertion and extraction, with these limiting Li diffusivity and cycling stability. In this work, we demonstrate the improved performance of LiNi0.5Mn1.5O4 achieved by encapsulating the material in a thin layer of silica (SiO2) or polyimide using a simple wet-chemical method and organic solvents. The pristine and coated ordered LiNi0.5Mn1.5O4 spinel are both confirmed to have P4332 symmetry, with only a minor difference in their lattice parameter. The SiO2 coating is found to reduce capacity fade of ordered LiNi0.5Mn1.5O4 by 45 and 65% at 25 and 55 °C, respectively, with the improvement attributed to enhanced Li diffusivity alongside the suppression of the hydrofluoric acid attack. The polyimide coating is found to have a marginally negative effect on both capacity and rate performance of ordered LiNi0.5Mn1.5O4, with this being greatly offset by excellent thermal stability leading to high-temperature protection, with the material having the low capacity fade of 0.0585 mAh g-1 cycle-1 at 55 °C, which is comparable to that at 25 °C. While similar effects of these coatings are found for disordered LiNi0.5Mn1.5O4, the magnitude of enhancement to properties offered by these coatings is significantly lesser than those found here for the ordered LiNi0.5Mn1.5O4. A stabilizing effect of the coatings that mitigates against phase segregation occurring during the additional two-phase reaction in the ordered but not the disordered phase of the material may explain the greater benefit of the coatings to the ordered phase

Mother–infant interaction quality and sense of parenting competence at six months postpartum for first-time mothers in Taiwan: a multiple time series design

Abstract Background For first-time mothers, not knowing how to interact with newborn infants increases anxiety and decreases the quality of the parent–infant interactions. A substantial lack of interactional knowledge can ultimately limit the adjustments necessary for a stable transition into motherhood. This study investigated how postpartum parenting education influenced first-time mothers’ mother–infant interaction quality and parenting sense of competence. Methods Eighty-one healthy first-time-mother and infant dyads were recruited. The control group (n = 40) received postpartum care based on the medical and cultural norms practiced in Taiwan, while the experimental group (n = 41) received, on top of typical care, education by way of a 40-min videotape on infant states, behaviors, and communication cues, as well as a handout on play practices. Data were collected at five points: within the first week, and during follow-ups in the first, second, third, and sixth months after birth. We administered the Chinese versions of the Parenting Sense of Competence Scale and Edinburgh Perinatal Depression Scale, and used the Nursing Child Assessment Teaching Scale to score videotaped mother–infant interactions. Results We observed an increase in the quality of mother–infant interaction within the experimental group only. Furthermore, at the five assessment points, we observed no significant changes in perceived parenting competence. Among all subjects, there were correlations between postpartum depression scores, parenting competency, and quality of mother–infant interaction. Conclusions Our results indicate that first-time mothers in Taiwan who are provided with extra education on infants’ abilities and how to effectively play with infants are likely to exhibit improvements in quality of interaction

Effect of AlF3-Coated Li4Ti5O12 on the Performance and Function of the LiNi0.5Mn1.5O4||Li4Ti5O12 Full Battery-An in-operando Neutron Powder Diffraction Study

The LiNi0.5Mn1.5O4||Li4Ti5O12(LMNO||LTO) battery possesses a relatively-high energy density and cycle performance, with further enhancement possible by application of an AlF3coating on the LTO electrode particles. We measure the performance enhancement to the LMNO||LTO battery achieved by a AlF3coating on the LTO particles through electrochemical testing and use in-operando neutron powder diffraction to study the changes to the evolution of the bulk crystal structure during battery cycling. We find that the AlF3coating along with parasitic Al doping slightly increases capacity and greatly increases rate capability of the LTO electrode, as well as significantly reducing capacity loss on cycling, facilitating a gradual increase in capacity during the first 50 cycles. Neutron powder diffraction reveals a structural response of the LTO and LNMO electrodes consistent with a greater availability of lithium in the battery containing AlF3-coated LTO. Further, the coating increases the rate of structural response of the LNMO electrode during charge, suggesting faster delithiation, and enhanced Li diffusion. This work demonstrates the importance of studying such battery performance effects within full configuration batteries

An efficient multi-doping strategy to enhance Li-ion conductivity in the garnet-type solid electrolyte Li7La3Zr2O12

Lithium-ion (Li + ) batteries suffer from problems caused by the chemical instability of their organic electrolytes. Solid-state electrolytes that exhibit high ionic conductivities and are stable to lithium metal are potential replacements for flammable organic electrolytes. Garnet-type Li 7 La 3 Zr 2 O 12 is a promising solid-state electrolyte for next-generation solid-state Li batteries. In this study, we prepared mono-, dual-, and ternary-doped lithium (Li) garnets by doping tantalum (Ta), tantalum-barium (Ta-Ba), and tantalum-barium-gallium (Ta-Ba-Ga) ions, along with an undoped Li 7 La 3 Zr 2 O 12 (LLZO) cubic garnet electrolyte, using a conventional solid-state reaction method. The effect of multi-ion doping on the Li + dynamics in the garnet-type LLZO was studied by combining joint Rietveld refinement against X-ray diffraction and high-resolution neutron powder diffraction analyses with the results of Raman spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and multinuclear magic angle spinning nuclear magnetic resonance. Our results revealed that Li + occupancy in the tetrahedrally coordinated site (24d) increased with increased multi-ion doping in LLZO, whereas Li + occupancy in the octahedrally coordinated site (96h) remained constant. Among the investigated compounds, the ternary-doped garnet structure Li 6.65 Ga 0.05 La 2.95 Ba 0.05 Zr 1.75 Ta 0.25 O 12 (LGLBZTO) exhibited the highest total ionic conductivity of 0.72 and 1.24 mS cm -1 at room temperature and 60 °C, respectively. Overall, our findings revealed that the dense microstructure and increased Li + occupancy in the tetrahedral-24d Li1 site played a key role in achieving the maximum room-temperature Li-ion conductivity in the ternary-doped LGLBZTO garnet, and that the prepared ternary-doped LGLBZTO was a potential solid electrolyte for Li-ion batteries without polymer adhesion

Improvements and Applications of AMS Radiocarbon Measurement at Peking University

AMS radiocarbon measurements were started at Peking University in 1992 with a modified HICONEX 834 ion source. Some archaeological samples were measured at a sensitivity of 10^-14 with ca. 1.7% precision for modern samples. We have made many improvements in our first two years of operation: a high-intensity Cs sputtering ion source was installed; the graphite sample preparation technique was investigated; and the system stability has been improved. The blank sample background is currently ca. 0.006 MC and a precision within 1% can be reached for modern samples. Geological, archaeological, environmental and biomedical samples can be measured routinely. We present some typical applications.This material was digitized as part of a cooperative project between Radiocarbon and the University of Arizona Libraries.The Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact [email protected] for further information.Migrated from OJS platform February 202

Effect of AlF(3)-coated Li(4)Ti(5)O(12) on the performance and function of the LiNi(0.5)Mn(1.5)O(4)||Li(4)Ti(5)O(12) full battery—an in-operando neutron powder diffraction study

The LiNi₀.₅Mn₁.₅O₄ ||Li₄Ti₅O₁₂ (LMNO||LTO) battery possesses a relatively-high energy density and cycle performance, with further enhancement possible by application of an AlF3 coating on the LTO electrode particles. We measure the performance enhancement to the LMNO||LTO battery achieved by a AlF₃ coating on the LTO particles through electrochemical testing and use in-operando neutron powder diffraction to study the changes to the evolution of the bulk crystal structure during battery cycling. We find that the AlF₃ coating along with parasitic Al doping slightly increases capacity and greatly increases rate capability of the LTO electrode, as well as significantly reducing capacity loss on cycling, facilitating a gradual increase in capacity during the first 50 cycles. Neutron powder diffraction reveals a structural response of the LTO and LNMO electrodes consistent with a greater availability of lithium in the battery containing AlF₃-coated LTO. Further, the coating increases the rate of structural response of the LNMO electrode during charge, suggesting faster delithiation, and enhanced Li diffusion. This work demonstrates the importance of studying such battery performance effects within full configuration batteries.Gemeng Liang, Anoop Somanathan Pillai, Vanessa K. Peterson, Kuan-Yu Ko, Chia-Ming Chang, Cheng-Zhang Lu, Chia-Erh Liu, Shih-Chieh Liao, Jin-Ming Chen, Zaiping Guo, and Wei Kong Pan