A Novel cathode material based on polyaniline used for lithium/sulfur secondary battery

Polyaniline polysulfide (SPAn) was prepared for high energy secondary lithium batteries as cathode material. Polyaniline was synthesized via a classical chemical oxidation way, and then HCl was used to substitute the H atoms on the 6 member rings, so that polyaniline chloride (CPAn) was gained. The SPAn was prepared by way of substitute the Cl atoms on the aromatic rings of CPAn by S atoms in assistant of Na₂S and element sulfur. Element analysis tests proved that there are more than 7 S atoms on each aniline structural group. FT-IR, Raman and XPS (X-ray photoelectron spectroscopy) analysis were used to confirm the SPAn's configuration. Button type battery was assembled, and charge–discharge test shows an initial discharge capacity of more than 980 mAh g^?1, which is a grafting value.     

X-ray diffraction investigations of well-ordered sexithiophene films deposited on flexible substrates

Through optimizing deposition conditions such as substrate temperature and growth rate, well-ordered sexithiophene films were deposited on flexible substrates of insulating polyvinylpyrrolidone (PVP) and transparent conductive indium tin oxide (ITO). X-ray diffraction investigation showed that well-ordered sexithiophene films were deposited at substrate temperature of 90 °C and growth rate of 10 nm/min on PVP substrate with the main axis of sexithiophene molecules oriented parallel to the PVP surface and the crystallinity was declined with the decrease of substrate temperature. On ITO substrate, substrate temperature notably influenced the sexithiophene molecule orientation. There existed an inclined angle between the main axis of sexithiophene molecules and the ITO surface in the film deposited at room temperature. With the increase of substrate temperature, the main axis tended to parallel to the ITO surface and well-ordered sexithiophene film was deposited at 50 °C and 10 nm/min. Too slow or too rapid growth rate would lead to poor crystallinity of sexithiophene films on both PVP and ITO substrates.     

Effect of interstitial carbon on the mechanical properties of electrodeposited bulk nanocrystalline Ni

Solid solution strengthening by carbon and sulfur in bulk nanocrystalline Ni was studied by electrodeposition and first-principles calculations. Bulk nanocrystalline Ni with a carbon content of 30–1600 ppm and a sulfur content of 140–1200 ppm was prepared using a sulfamate bath with different complexing agents and gloss agents. The hardness values of the bulk nanocrystalline Ni were scattered as the grain size decreased to ～12 nm with increasing carbon and sulfur content. It was found that the scatter could be explained by considering the effect of impurities such as solute atoms on the hardness of electrodeposited Ni, in addition to the Hall–Petch relationship. Thus, to determine the structure of Ni–C and Ni–S solid solutions and estimate the contribution of impurities to hardness, the enthalpy of solution and misfit strain were calculated by first-principles calculations. The results indicate that carbon exists as an interstitial solute atom in the Ni matrix, producing large misfit strains, and sulfur exists as a substitutional solute atom, inducing no significant changes. A model of solid solution strengthening due to interstitial solute atoms was developed by considering the interaction between mobile dislocations and solute atoms. This study has effectively divided the observed solid solution effect from the grain refinement effect in electrodeposited nanocrystalline Ni. The results of this study point to the origin of high-strength electrodeposited bulk nanocrystalline Ni.     

Temperature activated de-trapping processes in vacuum deposited sexithiophene thin films

Photoluminescence (PL) emission spectra of sexithiophene (6T) thin films grown on different substrates by organic molecular beam deposition (OMBD) are studied in the range of temperature from 300 to 7 K. Besides the two vibronic progressions detectable between 300 and 50 K, related to the radiative recombination of the free exciton and to a structural defect state, a new emission is observed at temperatures lower than 40 K, whose origin is discussed in terms of exciton bound to a structural defects.     

Superconductivity in acenes

The vibronic coupling between the lowest unoccupied molecular orbital (LUMO) and molecular vibrations is calculated and analyzed with respect to a series of acenes. The Raman active CC stretching modes of 1400–1600 cm⁻¹ have large coupling constants in small acenes, while both low Raman active modes of 200–300 cm⁻¹ and CC stretching modes of 1400–1600 cm⁻¹ play an important role in the electron–phonon coupling in large acenes. The possible superconducting transition temperatures of the monoanions of benzene (C₆H₆) and acenes are roughly estimated, on the basis of the hypothesis that vibronic interactions between the LUMO and intramolecular vibrations would play an essential role in the occurrence of superconductivity in these molecules.     

High pressure Raman studies on the structural conformation of oligophenyls

The goal of this combined experimental and computational study is to investigate the structural conformation of oligo(para-phenylenes) in the crystalline phase, in particular the planarity of this type of molecules. To this end we have performed Raman experiments on para-terphenyl and para-quaterphenyl in a pressure range from 0 to 70 kbar and at temperatures from 10 to 300 K. The positions and the relative intensities of the C–C interring stretch mode at 1280 cm⁻¹ and the C–H in-plane bend mode at 1220 cm⁻¹ have been tracked. We find that upon increasing temperature at ambient pressure the intensity ratio I₁₂₈₀/I₁₂₂₀ drops rapidly at temperatures that coincide with the crystallographic phase transition for the investigated materials. At ambient temperature also, this intensity ratio drops rapidly upon increasing pressure up to about 15 kbar. In the computational part, the Raman frequencies and activities of isolated 3P and 4P molecules were calculated within restricted Hartree–Fock formalism with the interring tilt angles varying from 0 to 90°. These calculations confirm that the I₁₂₈₀/I₁₂₂₀ intensity ratio can be related to the planarity of the molecules. Three-dimensional bandstructure calculations within density functional theory were applied to determine phonon frequencies and estimate Raman activities for the polymer poly(para-phenylene). These simulations show that the same conclusions hold for crystalline environment.     

Raman study of κ-ET2Cu[N(CN)2]Cl at ambient and ∼300 bars pressures

Anomalies in the temperature dependence of the 246 and 258 cm⁻¹ Raman active phonons below the antiferromagnetic phase transition are reported in κ-ET₂Cu[N(CN)₂]Cl at ambient pressure and are compared to measurements under ∼300 bars that render the compound superconducting. At ambient pressure, due to the Mott-gap opening and/or to the spin–lattice interaction and exchange-phonon modulation, frequency softenings, enhanced intensities and linewidths narrowings of these modes occur at low temperatures.     

Pulsed-laser fabrication of gas-filled hollow Co–Pt nanospheres

We report on nitrogen-filled hollow Co–Pt nanospheres produced via pulsed-laser ablation in ambient nitrogen gas. The resulting nanospheres are characterized by a single-crystalline face-centred cubic Co_55±3Pt_45±3 shell and a void filled with molecular nitrogen, typically occupying the sphere’s central region. The average diameter of the spheres and the voids is 35 ± 8 and 16 ± 2 nm, respectively. The calculated number density of nitrogen atoms, measured within these voids, is 1.58 ± 0.4 nm^?3. The resulting pressure in the voids near ambient temperature (300 K) and at the boiling temperature for the Co–Pt alloy (～3000 K) is estimated to be 1.9 ± 0.3 and 34.3 ± 9 MPa, respectively. The gas-filled Co–Pt hollow spheres are formed in only one step involving two physical processes. First, after each laser pulse, the vaporized, supersaturated Co–Pt ablated species are condensated in the plume under high pressure and temperature, resulting in nitrogen gas trapping. Between two laser pulses, the pressure and temperature in the plume drop rapidly, the nitrogen-rich liquid nanospheres become thermodynamically unstable and the nitrogen gas bubble starts to expand until the solidification of the nanospheres. The fast solidification of the solid shell prevents further outward diffusion of nitrogen and thus an amount of nitrogen gas is preserved in the void. These nanospheres have the potential in biomedical, magnetic and catalytic applications.     

On thermal and vibrational properties of LaGaO3 single crystals

The thermal expansion and vibrational properties of [1 0 0] and [0 0 1] LaGaO₃ single crystals have been studied by thermal mechanical analysis and micro-Raman spectroscopy. A first-order orthorhombic to rhombohedral phase transition has been confirmed by both techniques, as well as by in situ heating using optical microscopy. The appearance of a metastable intermediate phase, tentatively assigned as monoclinic, has been detected both by optical microscopy and Raman spectroscopy upon heating of the [1 0 0] and [0 0 1] LaGaO₃ single crystals. Not only temperature, but the stress-induced orthorhombic to rhombohedral phase transition has also been detected by Raman mapping of the residual impression made by Vickers indentation. The position map of bands belonging to the lower-temperature/pressure orthorhombic and the higher-temperature/pressure rhombohedral phase show that the rhombohedral phase is located inside the impression, where the applied indentation stresses are the highest, whereas no rhombohedral phase is detected outside the impression, where the surface has not been altered by contact stresses.     

Atomic motion during the migration of general [0 0 1] tilt grain boundaries in Ni

We generalize a previous study of the atomic motions governing grain boundary migration to consider arbitrary misorientations of [0 0 1] tilt boundaries. Our examination of the nature of atomic motions employed three statistical measures of atomic motion: the non-Gaussian parameter, the “dynamic entropy” and the van Hove correlation function. These metrics were previously shown to provide a useful characterization of atomic motions both in glass-forming liquids and strained polycrystalline materials. As before, we find highly cooperative, string-like motion of atoms, but the grain boundary migration itself is a longer timescale process in which atoms move across the grain boundary. These observations are consistent with our previous results for Σ5 [0 0 1] tilt boundaries. It is evident from our work that the grain boundary structure and misorientation have a significant influence on the rate of grain boundary migration.     

Thermoelectric properties of Ti1+xS2 prepared by CS2 sulfurization

Titanium disulfide (TiS₂) powder was prepared by sulfurizing TiO₂ powder with CS₂ gas at 1073 K for 4 h. Because CS₂ gas is a powerful sulfurizing agent for TiO₂, CS₂ sulfurization can be performed at a low temperature. The TiS₂ powder thus prepared was first mixed with sulfur powder in a mass ratio of 1:0.04 and pressure sintered at 973 K for 1 h under a uniaxial pressure of 50 MPa in vacuum. The addition of a small amount of sulfur powder to the TiS₂ powder prevents sulfur deficiency in the sintered compact, resulting in the formation of a near-stoichiometric Ti_1.008S₂ composition. X-ray diffraction patterns show that the crystalline ab-axis is preferentially oriented perpendicular to the pressing direction. The Seebeck coefficient, electrical resistivity and thermal conductivity of the oriented TiS₂ sintered compacts with near-stoichiometric and sulfur-poor (titanium-rich) compositions were measured in the temperature range 300–723 K. The thermoelectric figure of merit ZT was enhanced by prevention of sulfur deficiency and formation of the oriented texture. The highest ZT of 0.34 was observed at 663 K in Ti_1.008S₂ for the direction perpendicular to the pressing axis.     

Ex situ XANES,XPS and Raman studies of poly(3,4-ethylenedioxythiophene) modified by iron hexacyanoferrate

X-ray (XPS and XANES) and Raman spectra of poly(3,4-ethylenedioxythiophene) (pEDOT) modified by iron hexacyanoferrate (Fehcf) network are presented. XANES studies allowed to postulate an octahedral surrounding of iron atoms in the material and identified nitrogen and carbon atoms as nearest neighbourhoods. XPS measurements reveal iron–nitrogen and iron–carbon bonds, supporting the XANES results. Chemical interaction between sulphur from pEDOT and iron was also evidenced by XPS. Although both methods give proof of Prussian Blue structure inside the polymer, Raman studies did not show any signal typical for CN at about 2160 cm^?1 (ν). However, the presence of Fehcf was confirmed by the stretching vibrations of Fe–N bond at 146 cm^?1 and Fe–CN vibrations at 270 cm^?1. AFM imaging was performed to illustrate the roughness and morphology of the pEDOT/Fehcf surface.     

Damage-free highly efficient polishing of single-crystal diamond wafer by plasma-assisted polishing

Single-crystal diamond (SCD) is considered to be an ideal material for next-generation power devices. Plasma-assisted polishing (PAP) without using an abrasive was applied to polish SCD fabricated by chemical vapor deposition. Argon-based plasma containing water vapour was used in the PAP to modify the surface of polishing plate and SCD (100), and SCD was polished under a polishing pressure ranging from 10 to 52.6 kPa. Raman spectroscopy measurement showed that there was no residual stress on the polished SCD surface, and a polishing rate of 2.1 μm/h and a surface roughness of 0.13 nm Sq were obtained.     

Effect of alloying elements on the elastic properties of Mg from first-principles calculations

The influence of different alloying elements on the lattice parameters and elastic properties of Mg solid solution has been studied using first-principles calculations within the generalized gradient approximation. The solute atoms employed herein are Al, Ba, Ca, Cu, Ge, K, Li, Ni, Pb, Si, Y and Zn. A supercell consisting of 35 atoms of Mg and one solute atom is used in the current calculations. A good agreement between calculated and available experimental data is obtained. Lattice parameters of Mg–X alloys are found to be dependent on the atomic radii of the solute atoms. A correlation between the bulk modulus of Mg–X alloys and the nearest-neighbor distance between Mg and X is shown. Addition of solute atoms belonging to the s-block and p-block of the periodic table results in a lower bulk moduli than d-block elements. A strong dependence of the elastic modulus of Mg–X alloys on the elastic properties of the solute atoms is also observed. Using the bulk modulus/shear modulus ratio (B/G), the change in the ductility of Mg due to the addition of the solute atom is briefly described. Linear regression coefficients for the elastic constants of each of the alloys are obtained as a tool for predicting the trend in the elastic properties of Mg as a function of concentration of the solute atoms.     

Mechanical behavior of cellular borosilicate glass with pressurized Ar-filled closed pores

High strength borosilicate foams were fabricated by melting glass powder under high-pressure argon gas and subsequent heat treatment of the glass bulk at atmospheric pressure. In the first step, borosilicate glass powder was melted at 1100 °C for 1 h by capsule-free hot isostatic pressing (HIPing) under a high gas pressure of 10–70 MPa. Pressurized Ar-filled spherical pores were introduced into the glass, and argon atoms were dissolved in the glass network structure. The expansion of argon-filled pores and the release of the dissolved Ar gas resulted in the formation of pressurized Ar-filled closed pores by isothermal heat treatment at 800 °C for 10 min. A high porosity of up to 80% with a bimodal distribution of micro-size cells was obtained for the resultant cellular borosilicate glass. By increasing the total gas pressure from 10 to 70 MPa, the compressive strength and the Young’s modulus were increased considerably from 15 to 52 MPa and from 4.1 to 12.6 GPa, respectively, which can be substantially attributed to the high collapse stress from the high enclosed gas pressure. The cellular glass with a high porosity showed a large failure strain under uniaxial compression.     

Influence of the cooling rate on low-temperature Raman and infrared-reflection spectra of partially deuterated κ-(BEDT-TTF)2Cu(N(CN)2)Br

Raman and infrared-reflection spectra of κ-(BEDT-TTF)₂Cu(N(CN)₂)Br and its deuterated and partially deuterated analogues were measured at temperatures between 5 and 300 K and cooling rates from 1 to 20 K/min. It was found that, in partially deuterated samples, the interdimer electron–molecular vibration splitting of ν₃ mode in Raman spectra, and linewidths of some phonon peaks both in Raman and infrared spectra depend on the cooling rate. These observations were explained by disorder-related effects.     

Quantum chemical molecular dynamics study of stress corrosion cracking behavior for fcc Fe and Fe–Cr surfaces

Quantum chemical molecular dynamics simulation was applied to study the oxidation of bare Fe (1 1 1) and Fe–Cr (1 1 1) surfaces with strain in high temperature water. Simulation results implied the surface morphologies differ from Fe to Fe–Cr because of strong bond between oxygen and chromium atoms. Oxygen atoms were trapped around chromium atoms at Fe–Cr surface, whereas oxygen penetrated into the lattice of Fe bare surface. As a result, the oxygen diffusivity into the Fe–Cr crystal surface reduced. It indicated that the preferential oxidation of chromium would take place on Fe–Cr clean surface at the beginning of the oxidation process. Diffusion of hydrogen and oxygen significantly increased when strain applied to the defective surface. Hydrogen atoms being in the lattice of metal possessed the highly negative charge which indicated the surface oxidized by this negative charge H. Negative charged oxygen atoms make bond with the metallic atom which breakage ultimate metal–metal bond. These bond breakages indicated the formation of oxide layer on the surface and play a key role in subsequent localized corrosion nucleation like stress corrosion cracking.     

Effect of boron doped fullerene C60 film coating on the electrochemical characteristics of silicon thin film anodes for lithium secondary batteries

In this work, boron doped fullerene (B:C₆₀) films were prepared by the radio frequency plasma assisted thermal evaporation technique for use as a coating material for the silicon thin film anode in lithium secondary batteries. Raman and XPS analyses revealed that the boron atoms were well inserted into the fullerene film lattices. The effect of the B:C₆₀ film on the electrochemical characteristics of the silicon thin film was studied by charge–discharge tests, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The B:C₆₀ coated silicon film exhibited a high reversible capacity of more than 1200 mAh g^?1 when cycled 50 times between 0 and 2 V at a current density of 1200 μA cm^?2 (1.5 C). The film also showed good rate capacity at different current densities and a more improved coulombic efficiency of 87.7% in the first cycle in comparison with that of the C₆₀ coated film electrode.     

Atomistic simulation of martensitic phase transformation at the crack tip in B2 NiAl

Mechanisms of low-temperature deformation at the crack tip in B2 NiAl are studied by molecular dynamics simulations. The stress-induced martensitic transformation is found to occur at the crack tip when a sufficiently high stress concentration exists. For cracks with 〈1 0 0〉 crack fronts, the layered structures of martensites are formed at the crack tip, which is caused by the atoms’ relative displacement on a basal plane due to the shear stress at the crack tip. The mechanism of the martensitic transformation from the B2 to the L1₀ structures occurs along the Bain path. For cracks with 〈1 1 0〉 crack fronts, the martensitic transformation occurs without any layered structures existing. The phase transformation is caused by the atoms’ relative displacements at different atoms layers in the entire martensite formed region.     

The effect of phosphorus and nitrogen co-doped on the synthesis of diamond at high pressure and high temperature

The synthesis of phosphorus and nitrogen co-doped diamond is investigated in the NiMnCo–C system by adding P₃N₅ or carbonyl iron powders mixed with phosphorus powders under high pressure and high temperature. Experimental results show that the color distribution in diamond crystals with low concentration of P₃N₅ additive is not uniform. The color becomes deep green with the increase of P₃N₅ additive. The optical images and FTIR spectra reveal that the nitrogen atoms are more easily incorporated via {111} than {100} in the same conditions. In addition, the result of FTIR spectra of synthesized diamond indicates that the hydrogen atoms in the form of sp³–CH₂– are more likely to enter the diamond lattice in the P/N co-doped system, compared with the single N-doped system. The absorption peak at 3107 cm^− 1 attributed to vibration of H-related point defects (sp²–CHCH–) is observed in diamonds, which is often found in natural diamonds. The Raman shifting to lower frequency and FWHM value becoming wider are due to the doping of phosphorus atoms.