Phase Transformation and Lithiation Effect on Electronic Structure of Li(x)FePO(4): 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 synthesis route on the morphologies of silver nanostructures by galvanic displacement reaction

The present study is concerned with the preparation of Ag nanostructures by reduction of AgNO₃ with zinc foil by galvanic displacement reaction. The results confirm that the synthesis route has a direct influence on the morphologies of Ag nanostructures. In addition, the effect of synthesis conditions, including the concentration of AgNO₃ aqueous solutions and reaction time, are investigated. X-ray diffraction (XRD), filed emission scanning electron microscope (SEM) and UV-vis spectra are used to characterize the obtained products. A reasonable formation process of Ag nanostructures is proposed based on the characterization results.     

A Review of Characteristics of Bio-Oils and Their Utilization as Additives of Asphalts

Transforming waste biomass materials into bio-oils in order to partially substitute petroleum asphalt can reduce environmental pollution and fossil energy consumption and has economic benefits. The characteristics of bio-oils and their utilization as additives of asphalts are the focus of this review. First, physicochemical properties of various bio-oils are characterized. Then, conventional, rheological, and chemical properties of bio-oil modified asphalt binders are synthetically reviewed, as well as road performance of bio-oil modified asphalt mixtures. Finally, performance optimization is discussed for bio-asphalt binders and mixtures. This review indicates that bio-oils are highly complex materials that contain various compounds. Moreover, bio-oils are source-depending materials for which its properties vary with different sources. Most bio-oils have a favorable stimulus upon the low temperature performance of asphalt binders and mixtures but exhibit a negative impact on their high-temperature performance. Moreover, a large amount of oxygen element, oxygen-comprising functional groups, and light components in plant-based bio-oils result in higher sensitivity to ageing of bio-oil modified asphalts. In order to increase the performance of bio-asphalts, most research has been limited to adding additive agents to bio-asphalts; therefore, more reasonable optimization methods need to be proposed. Furthermore, upcoming exploration is also needed to identify reasonable evaluation indicators of bio-oils, modification mechanisms of bio-asphalts, and long-term performance tracking in field applications of bio-asphalts during pavement service life.     

10-Ethyl-acridine-2-sulfonyl Chloride: A New Derivatization Agent for Enhancement of Atmospheric Pressure Chemical Ionization of Estrogens in Urine

The extensive metabolism and treatment of low doses of estrone (E1), estradiol (E2) and estriol (E3) in preclinical animal species necessitates a sensitive analytical method to identify or quantify the estrogens in biological matrixes. In this study, a highly sensitive and specific method based on the derivatization of E1, E2 and E3 with 10-ethyl-acridine-2-sulfonyl chloride (EASC) coupled with liquid chromatography-ion-trap mass spectrometry with APCI-MS (MRM) identification of estrogens has been developed. The EASC derivatization of E1, E2 and E3 introduces an acridine functional group into estrogen molecules. The carbonyl group in EASC core results in the formation of a phenoxide negative ion by the intramolecular keto-enol isomerization that can be accepted a [H]⁺ and readily ionized in commonly used LC mobile phases. Derivatives are sufficiently stable to be efficiently analyzed by LC-APCI-MS and show an intense protonated molecular ion at m/z [M+H]⁺ in positive-ion mode. The collision-induced dissociation of molecular ion forms a distinctive product ion at m/z 222.6, corresponding to the protonated 10-ethyl-acridine moiety. The selected reaction monitoring, based on the m/z [M+H]⁺ → m/z 222.6 transitions, is highly specific for estrogen derivatives. Therefore, the facile EASC derivatization coupling with LC-APCI-MS analysis allows the development of a highly sensitive and specific method for the identification of trace levels of estrogens in urine of root vole (Microtus oeconomus Pallas).     

Stretching and polarizing a dielectric gel immersed in a solvent

This paper studies a gel formed by a network of cross-linked polymers and a species of mobile molecules. The gel is taken to be a dielectric, in which both the polymers and the mobile molecules are non-ionic. We formulate a theory of the gel in contact with a solvent made of the mobile molecules, and subject to electromechanical loads. A free-energy function is constructed for an ideal dielectric gel, including contributions from stretching the network, mixing the polymers and the small molecules, and polarizing the gel. We show that the free-energy function is non-convex, leading to instabilities. We also show that mechanical constraint markedly affects the behavior of the gel.     

Mechanisms of large actuation strain in dielectric elastomers

Subject to a voltage, a dielectric elastomer (DE) deforms. Voltage‐induced strains of above 100% have been observed when DEs are prestretched, and for DEs of certain network structures. Understanding mechanisms of large actuation strains is an active area of research. We propose that the voltage‐stretch response of DEs may be modified by prestretch, or by using polymers with “short” chains. This modification results in suppression or elimination of electromechanical instability, leading to large actuation strains. We propose a method to select and design a DE, such that the actuation strain is maximized. The theoretical predictions agree well with existing experimental data. The theory may contribute to the development of DEs with exceptional performance. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2011     

Analysis of electrostatic discharge suppressors with ultra-low capacitance used for IC protection

The TDMM was successfully used to analyze the capacitance, the electric field, and the ESD current of an ESD suppressor. The obtained capacitance was also validated by measurement data. It is found that the maximum electric fields in the air gap between two discharge electrodes for the air gap width of 5–50 μm are much higher than the threshold electric field for air breakdown. A maximum ESD current of 4.7 mA was obtained during an ESD event, which may be sufficient to cause a malfunction in a high sensitivity integrated circuit.     

The orientation of the self-assembled monolayer stripes on a crystalline substrate

Two-phase monolayers adsorbed on crystalline substrates can form many patterns. After reviewing the experimentally observed patterns on various substrates, we extend a thermodynamic theory to account for the anisotropy in surface stress, substrate stiffness, and phase boundary energy. We solve the elastic field in the anisotropic substrate by using the Stroh formalism. We then focus on the pattern of periodic stripes, and determine the orientation of the stripes that minimizes the free energy. As an example, we examine in detail the (110) surface of a cubic crystal. Depending on the parameters that characterize anisotropy, the stripes can orient along either , or [001], or certain directions off the two crystalline axes. The transition between these orientations can be of either first or second order. The predications point to additional experiments that are needed to further the understanding.     

Plastic ratcheting induced cracks in thin film structures

In the microelectronic and photonic industries, temperature cycling has long been used as a reliability test to qualify integrated materials structures of small feature sizes. The test is time consuming, and is a bottleneck for innovation. Tremendous needs exist to understand various failure modes in the integrated structures caused by cyclic temperatures. This paper presents a systematic study of a failure mechanism recently discovered by the authors. In a thin film structure comprising both ductile and brittle materials, the thermal expansion mismatch can cause the ductile material to plastically yield in every temperature cycle. Under certain circumstances, the plastic deformation ratchets, namely, accumulates in the same direction as the temperature cycles. The ratcheting deformation in the ductile material may build up stress in the brittle materials, leading to cracking. The paper introduces an analogy between ratcheting and viscous flow. An analytical model is developed, which explains the experimental observations, and allows one to design the structure to avert this failure mode. Design rules with increasing levels of sophistication are described. Concepts presented here are generic to related phenomena in thin film structures.     

Global view of microstructural evolution: Energetics,kinetics and dynamical systems

An evolving material structure is in a non-equilibrium state, with free energy expressed by the generalized coordinates. A global approach leads to robust computations for the generalized thermodynamic forces. Those forces drive various kinetic processes, causing dissipation at spots, along curves, surfaces and interfaces, and within volumetric regions. The actual evolution path, and therefore the final equilibrium state, is determined by the energetics and kinetics. A virtual work principle links the free energy landscape and the kinetic processes, and assigns a viscous environment to every point on the landscape. The approach leads to a dynamical system that governs the evolution of generalized coordinates. The microstructural evolution is globally characterized by a basin map in the coordinate space; and by a diversity map and a variety map in the parameter space. The control of basin boundaries raises the issue of energetic and kinetic bifurcations. The variation of basin boundaries under different sets of controlling parameters provides an analytical way to plot the diversity maps of structural evolution. The project supported by the National Science Foundation (USA) through grant MSS-9258115, and by the National Natural Science Foundation of China