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The abnormal lattice expansion of commercial polypropylene (PP)/polyethylene (PE)/polypropylene (PP) separator in lithium-ion battery under different charging current densities was observed by in-situ X-ray diffraction. Significant lattice changes of both PP and PE were found during the low current density charging. The capacity fading and the resistance value of the cell measured at 0.025 C (5th retention, 92%) is unexpectedly larger than that at 1.0 C (5th retention, 97.3%) from the electrochemical impedance spectroscopic data. High-resolution scanning electron microscopy is employed to witness the pore changes of the trilayered membrane. Density functional theory calculations were used to investigate the mechanism responsible for the irregular results. The calculations revealed that the insertion of Li-ion and EC molecule into PP or PE are thermodynamically favourable process which might explain the anomalous significant lattice expansion during the low current density charging. Therefore, designing a new separator material with a more compact crystalline structure or surface modification to reduce the Li insertion during the battery operation is desirable.

Density functional theory is applied to investigate the reductive reactions of reductive-type additive, 1,3-propane sultone (PS), on the formation of solid electrolyte interphase (SEI) near the lithium-ion battery anode surface. Different from the studies that mostly focus on the reduction dissociation of a specific molecule, we adopt an iterative method that systematically considered most possible reactants from the environment in every round of the reaction. The thermodynamically favorable reaction in each round was chosen. Its products then proceed to the following step. At least four iterations of reactions were calculated. The favorable products in each round were then analyzed to understand the trend of the series reactions. With the iterative method, the compounds in every reaction round can be inspected in detail. The method not only predicted the compounds that are consistent with those observed in the experiments but also provide insights into how PS forms an effective SEI. In the solvent state, the most stable reduction states of PS and electrolyte ethylene carbonate (EC) are confirmed as the initial reactants further interact with the environment supplies. First, with the addition of PS, the reduction of PS is prior to EC, which would suppress the reduction of EC and decrease the generation of ethene gas. Second, the compounds from the initial reaction round of PS are lithiated ones and show higher reduction ability than that of EC, while the latter show lower reduction ability than that of the EC, which terminated the reactions. This would be the critical properties for reductive-type additive to form an effective SEI film.

The Li4Ti5O12 (LTO) defect spinel is known for its excellent durability of “10,000” cycle counts and high level of safety as an anode material in lithium-ion batteries, but it shows an intrinsic insulating property and poor electrochemical kinetics. Doping is a direct approach to manipulate the electronic conductivity of LTO. However, doping may induce multiple effects influencing the overall electrochemical kinetics, e.g., changing the size of particles and the ionic and electronic conductivities. Here we systematically investigated the phase stability, electronic conductivity, and electrochemical kinetics of M-doped LTO (M = Na, K, Mg, Ca, Sr, Al, and Ga). With both ab initio calculations and experiments, the mechanism of electron transport within LTO is elucidated, the desired type of dopants for improving electronic conductivity of LTO is clarified, and the role of electronic conductivity in the electrochemical kinetics of LTO is revealed. These results provide an in-depth understanding of metal-doped LTO and would help the development of a variety of electrode materials.

Zeolites are aluminosilicate minerals with multiple channels and cages. They are widely used in industry; further, owing to its increasing demand, the hydrothermal synthesis of zeolites from natural minerals/rocks has attracted great attention. This study aims to discuss the crystal growth mechanisms of zeolites from pumice. Pumice is a widely available porous volcanic glass (mainly consisting of 65–75% SiO2 and 9–20% Al2O3) that can be used in the fabrication of zeolites. In this study, zeolite was formed from pumice via a hydrothermal method with varying alkaline concentrations, reaction times and temperatures, and addition of NaCl. Zeolite Na-P1 was synthesized under conditions of 0.1 or 0.5 M at 150 °C. The feldspar phase (albite) initially occurred, followed by the zeolite phase (zeolite Na-P1). Phillipsite was an unstable intermediate product during this synthesis process. Based on these results, we suggest that the phase transformation sequence follows the order of albite, phillipsite, and zeolite Na-P1. Moreover, it can be speculated that an increase in cation concentration can induce a rapid occurrence of the zeolite phase (zeolite Na-P1). Raman spectrometry analyses provided insights into the formation mechanism of zeolite structures, indicating differences related to the number of sodium ions. Both zeolite Na-P1 and phillipsite are composed of four- and eight-membered rings, and the former is mainly grown with four-membered rings as the main structure. This study provides a low-cost and simple synthetic method for producing zeolite Na-P1 and phillipsite, which can be used as indicator minerals for marine/lake facies and in environmental treatment.

Biodiesel produced from waste cooking oils (WCOs) mixed with methanol was efficiently transesterified using a continuous-fluid-flow system with a focused microwave heating device. Strontium oxide (SrO) was added as the catalyst. The factors that most affect the biodiesel conversion rate were first estimated by considering the effects of the oil:methanol ratio (1:6), added quantity of SrO (3 wt%), and microwave heating power (500 W) on reaction time in a built-in batch unit. The optimal parameter values were then applied to a continuous-fluid-flow system, which simulates the conversion of a scaled-up quantity of WCOs into biodiesel. Under a fluid flow velocity of 160 mL/min and an appropriate output temperature, a biodiesel conversion rate of ca. 93% was reached. The conversion of WCOs into biodiesel and the reaction rate are based on the transesterification reaction, which is associated with the decomposition of ester bonds and the formation of a tetrahedral intermediate substance.

Zinc oxide (ZnO) nanorod based gas sensor was successfully fabricated with interdigital electrode on silicon substrate. The highest sensitivity value is 5.24 at 600 ppm CO2 gas ambient. The influence of growth temperature of ZnO ranging from 90 to 190 °C by the high temperature hydrothermal method was investigated. The ZnO nanorod array were characterized by using field emission scanning electron microscopy (FE-SEM), photoluminescence spectroscopy, X-ray diffraction pattern. From FE-SEM results, the morphology of ZnO nanorods changes from hexagonal structure to sponge-like shape as the growth temperature increases. When the growth temperature is below 150 °C, hexagonal nanorod growth is observed. On the other hand, when the growth temperature is above 170 °C sheet growth is found. In the gas sensor measurements, it is found that ZnO nanorod grown at 150 °C has the best gas sensing performance due to its least intrinsic defects in this study.

The essential properties of graphite-based 3D systems are thoroughly investigated by the first-principles method. Such materials cover a simple hexagonal graphite, a Bernal graphite, and the stage-1 to stage-4 Li/Li$^+$ graphite intercalation compounds. The delicate calculations and the detailed analyses are done for their optimal stacking configurations, bong lengths, interlayer distances, free electron $\&$ hole densities, Fermi levels, transferred charges in chemical bondings, atom- or ion-dominated energy bands, spatial charge distributions and the significant variations after intercalation, Li-/Li$^+$- $\&$ C-orbital-decomposed DOSs. The above-mentioned physical quantities are sufficient in determining the critical orbital hybridizations responsible for the unusual fundamental properties. How to dramatically alter the low-lying electronic structures by modulating the quest-atom/quest-ion concentration is one of focuses, e.g., the drastic changes on the Fermi level, band widths, and number of energy bands. The theoretical predictions on the stage-n-dependent band structures could be examined by the high-resolution angle-resolved photoemission spectroscopy (ARPES). Most important, the low-energy DOSs near the Fermi might provide the reliable data for estimating the free carrier density due to the interlayer atomic interactions or the quest-atom/quest-ion intercalation. The van Hove singularities, which mainly arise from the critical points in energy-wave-vector space, could be directly examined by the experimental measurements of scanning tunneling spectroscopy (STS). Their features should be very useful in distinguishing the important differences among the stage-$n$ graphite intercalation compounds, and the distinct effects due to the atom or ion decoration.

The transformation of pyrite into pyrrhotite above 500 °C was observed in the Chelungpu fault zone, which formed as a result of the 1999 Chi-Chi earthquake in Taiwan. Similarly, pyrite transformation to pyrrhotite at approximately 640 °C was observed during the Tohoku earthquake in Japan. In this study, we investigated the high-temperature phase-transition of iron sulfide minerals (greigite) under anaerobic conditions. We simulated mineral phase transformations during fault movement with the aim of determining the temperature of fault slip. The techniques used in this study included thermogravimetry and differential thermal analysis (TG/DTA) and in situ X-ray diffraction (XRD). We found diversification between 520 °C and 630 °C in the TG/DTA curves that signifies the transformation of pyrite into pyrrhotite. Furthermore, the in situ XRD results confirmed the sequence in which greigite underwent phase transitions to gradually transform into pyrite and pyrrhotite at approximately 320 °C. Greigite completely changed into pyrite and pyrrhotite at 450 °C. Finally, pyrite was completely transformed into pyrrhotite at 580 °C. Our results reveal the temperature and sequence in which the phase transitions of greigite occur, and indicate that this may be used to constrain the temperature of fault-slip. This conclusion is supported by field observations made following the Tohoku and Chi-Chi earthquakes.

An electrolyte additive with boron-nitrogen-oxygen groups for high voltage (5 V) LiNi0.5Mn1.5O4 (LNMO) electrode is investigated by electrochemical performance, material analysis and density function theory first principles calculation (DFT). The 1 wt% Methylboronic acid MIDA ester (ADM) additive in ethylene carbonate and dimethyl carbonate (EC/DMC) electrolyte for LNMO cathode shows a paramount discharge capacity retention of 96% (15% in without additive) after 25 cycles at 75 mA g−1 and 40 °C, also inhibits the impedance growth during cycling. By increasing the charge/discharge current density from 15 mA g−1 to 450 mA g−1, the rate capability of LNMO cell with ADM additive is ca. 40%, while the counterpart is only 1.5%. By characterizations, the results interpret that the ADM additive decomposes and participates in the reaction pathway of cathode electrolyte interface (CEI) formation, which are more protective and resistant to electrolyte oxidative decompositions, and more potent in maintaining the structural integrity of nickel (Ni), manganese (Mn), and PF6−.

Manipulation or detection of domain patterns in ferroelectrics is of great interest due to wide applications for such materials. Among all the simulation methods, q-state Potts model is a common method used to simulate the domain pattern of ferroelectrics. The method, however, expresses the effect of temperature and coupling energy between interacting cells in an implicit way. In this study, we developed a new scheme that can explicitly study the temperature and coupling energy effect on the domain pattern of ferroelectrics. The method combined molecular dynamics (MD) simulations with a modified q-state Potts model. In the traditional q-state Potts model, each state is represented by a constant. Here we propose that the states are a function of temperature. We tested our method with a standard J p in various temperatures. The results are consistent with those by phase-field method. The effect of J p was also studied. By adjusting the J p , effect of external stress/strain or the buffer layer on the domain pattern of PbTiO 3 may be simulated. The correlation between the hysteresis loop and changing of domain pattern was also investigated. This new method provides insights in evolution of domain patterns in terms of temperature, the coupling energy and external electric voltage.

LiNi1/3Co1/3Mn1/3O2 (NCM) is a promising cathode material in Lithium-ion batteries with large capacity and high voltage. However, the capacity fading mechanism and long-term cycling behavior remain a significant problem. It has been reported that these problems are related to kinds of irreversible reactions on the electrode/electrolyte interface, such as decomposition of electrolyte and the dissolution of transition metal ions. Unlike anode materials, the interface between cathode and electrolyte is still lack of information. In this work, ab initio calculations based on density functional theory were performed to examine the initial reactions at NCM/electrolyte interface. The atomistic model of NCM and the slab models of different facets were built. Moreover, various Li-concentrations of slabs are taken into account with different type of adsorptions. With these proposed models, the surface energies of each facet were calculated. Then the simulated morphology of NCM which is also called Wulff shape was successfully constructed. Based on the exposed planes on the Wulff shape, the adsorption models of ethylene carbonate (EC) and propane sultone (PS) were established. The adsorption process was investigated according to adsorption energy, charge density difference and density of states. The result gives the insight to comprehend the initial reaction at the NCM/electrolyte interface.

In this study we have used atomistic simulations to investigate the role of surface on the size-dependent mechanical properties of nano-wires. In particular, we have performed computational investigation on single crystal face-centered cubic copper nano-wires with diameters ranging from 2 to 20 nm. The wire axis for all the nano-wires are considered along the [0 0 1] direction. Characterization of the initial optimized structures revealed clear differences in interatomic spacing, stress, and potential energy in all the nano-wires. The mechanical properties with respect to wire diameter are evaluated by applying tension along the [0 0 1] direction until yielding. We have discussed the stress–strain relationships, Young's modulus, and the variation in potential energy from surface to the center of the wire for all the cases. Our results indicate that the mechanical response (including yield strain, Young's modulus, and resilience) is directly related to the proportion of surface to bulk type atoms present in each nano-wire. Thus the size-dependent mechanical properties of single crystal copper nano-wire within elastic region are attributed to the surface to volume ratio (surface effect). Using the calculated response, we have formulated a mathematical relationship, which predicts the nonlinear correlation between the mechanical properties and the diameter of the wire.

Sintering is an important step in densification of materials. Surfaces play a critical role in sintering, which are magnified for nano-systems (nanowire or nanoparticle). This work focuses on the investigation of the initial stages of nanoparticle sintering by atomistic simulation methods. We have characterized two different distinct systems, Argon clusters and mixed oxide systems, for analysis. Due to better particulate mixing, a combination of nanowire and nanoparticle was easier to sinter than a combination of nanoparticle and nanoparticle for Argon clusters. For a mixed oxide system (rutile-TiO 2 and MgO), our results indicate that size, dimensions and structural stability of oxide nano-structures play an important role during sintering. For TiO 2 nanowire and MgO nanoparticle system, Ti atoms diffuse faster than Mg atoms, while for TiO 2 nanosphere and MgO nanoparticle combination, Mg atoms diffuse faster than Ti atoms during sintering. This diffusion is guided by the relative size and cohesive energies of the nano-systems.

Magnesium oxide (MgO) nanospheres with a high specific surface area were synthesized by the polyol method. The BET specific surface area of the nanopowders was ∼90 m 2 /g by adjusting the molar ratio of the precursor, the reaction time, and the washing solution. It was increased to 102 m 2 /g by calcining at ∼250 °C. Scanning electron microscopic and transmission electron microscopic observations showed that the MgO nanospheres composed of highly folded flakes, which were responsible for the observed high surface area. The high BET characteristic of the MgO nanospheres can be applied to sintering of microwave ceramics at a reducing sintering temperature, uniformed grain size distribution, and high bulk density. Finally, their capacity to remove hexavalent chromium was presented.

Classical molecular dynamics (MD) simulations are used to examine the deposition of polyatomic fluorocarbon (FC) beams on polypropylene (PP) and polystyrene (PS) surfaces. The goal is to investigat...

Polythiophene is a conductive polymer that has attracted much interest in recent years because its propertiesare desirable for applications that include light-emitting diodes, field-effect transistors, and photovoltaics.Optimization of the performance of polythiophene in these devices requires the development of processingmethods that can simultaneously control its chemistry and morphology on the nanometer scale. One suchmethod is surface polymerization by ion-assisted deposition (SPIAD) in which conducting polymer thin filmsare grown on substrates by the simultaneous deposition of hyperthermal polyatomic ions and thermal neutralsin vacuum. Here, mass-selected beams of thiophene ions are deposited on R-terthiophene oligomers inexperiments, and density functional theory-molecular dynamics (DFT-MD) simulations are carried out todetermine the dominant mechanisms responsible for the SPIAD process. Both neutral and positively chargedsystems are considered in the simulations in order to assess the effect of charge on the results. The experimentalresults show that polymerization occurs preferentially under a narrow set of ion energy and ion/neutral ratioconditions. The DFT-MD simulations illustrate the manner in which ion energies affect polymerization andreveal how secondary chemical reactions can substantially modify both the thin film and the substrate.

In this research, the zinc oxide (ZnO) microrods were grown by hydrothermal method on fluorine-doped tin oxide (FTO) glass functionalized by self-assembled monolayer of octadecyltrimethoxysilane (ODS; CH3(CH2)17Si(OCH3)3). The sharp-tip or polygonal shape with specific facets at the top end of ZnO microrods can be obtained by post retention at low temperature. The morphologies were characterized by the field-emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM). The results confirm that the morphology change at the top end is due to self-etching. The mechanism responsible for the formation of various top-end morphologies was proposed. The specific facets that left after 6-h retention were identified. The room-temperature micro-photoluminescence spectra showed a strong ultraviolet emission at 387 nm, and a broad emission at a range of from 500 to 700 nm. The morphology change also influences the photoluminescence (PL) spectra. A satellite peak in the UV emission spectra was observed. The peak may be attributed to the morphology effect of the microrods.

Classical molecular dynamics (MD) simulations are used to study the effect of continuous hydrocarbon (HC) and fluorocarbon (FC) ion beam deposition on a polystyrene (PS) surface. Plasma processing ...