An Effective Strategy for Template-Free Electrodeposition of Aluminum Nanowires with Highly Controllable Irregular Morphologies.

Aluminum nanowires with irregular morphologies were prepared by template-free electrodeposition from a room-temperature chloroaluminate ionic liquid. The effects of the diffusion condition and deposition potential on the morphologies of Al nanowires were investigated. The decrease of diffusion flux leads to the formation of particular segmented morphologies of Al nanowires. A dynamic equilibrium between the electrochemical reaction and the diffusion of Al2Cl7- results in the current fluctuation and the periodical variation of diameters in the Al nanowires growth period. Al nanowires with several kinds of morphologies can be controllably electrodeposited under a restricted diffusion condition, without using a template. Increasing the overpotential shows the similar influence on the morphology of Al nanowires as the decrease in diffusion flux under the restricted diffusion condition. Most of the segmented Al nanowires have a single crystalline structure and grow in the [100] orientation. This work also provides a new strategy for the fabrication of nanowires with highly controllable irregular morphologies.

[Study on microstructure of jadeite melt and its glass].

Comprehensive experimental as well as theoretical methods were applied to investigate the structure evolution of jadeite in the hot-melt process, especially on the variation of aluminium coordination number. In-situ high temperature Raman spectroscopic technique was used to record the characteristic Raman spectra of jadeite and its melt with the increasing temperature, consequently, density function theory and ab initio calculation methods were applied to analyze the related micro-structures and aluminium coordination number and simulate the Raman spectra. Results showed that aluminum in jadeite crystal is all six-fold and would transform into four-fold coordination at 1 293K while jadeite being melting. Aluminum is prominently in four-fold coordination in the melt, in which TO4 (T = Si, Al) connects to each other as the network of multiple rings. Five-fold coordinated aluminum emerges and it appears the trend of phase separation while the melt transformed into glass by the processing of fast cooling.

[Microstructure study on bismuth triborate crystal and its melt at high temperature by Raman spectroscopy].

Temperature dependent Raman spectra of BiB3 O6 crystal and its melt were recorded and the microstructure of BiB3 O6 melt was predicted. Multiple theoretical methods including quantum chemistry ab initio calculation and DFT (Density Function Theory) methods were applied to simulate the BiB3 O6 crystal and melt structure and Raman spectra. It was demonstrated that B-O triangles and Bi lattice in the crystal reveal little affected in structure while B-O tetrahedra shows severe distortion with increasing temperature, especially B-O tetrahedra disappears after being completely melt. The microstructure of BiB3 O6 melt consists of six-member ring, [B6 O12](6-), which varies in bond lengths and angles individually. Cation Bi behaves to balance the charge of anion cluster, and the oxygen coordination number of cation Bi is 3, different from the crystal situation in which cation Bi is coordinated with 6 oxygens.

[Raman spectroscopic quantitative analysis of cluster structure of binary alkali silicate glasses].

A calibration method for Raman spectroscopic quantitative analysis of binary alkaline silicate glasses is proposed. By applying ab initio quantum chemistry simulation, Raman optical activities (ROA) of various cluster units consisting of silicon-oxygen tetrahedra (SiOT) with different number of non-bridging oxygen (NBO) can be obtained. Thus, experimental results could be calibrated in order to reflect and represent directly the true relative density of various silicon-oxygen tetrahedra existing inside the silicate glasses. Cation effect on the intensity of Raman bands was also observed and discussed.

[A study of phonon vibration like modes for aggregation structure in silicate melts by high temperature Raman spectrum].

Silicate melts are special fractal dimension system that is metastable state of near-way order and far-way disorder. In this paper, the size of nanometer aggregation structure and the frequences of phonon vibration like mode in the low dimension silicate series (CaO-Al2O3-SiO2 and Na2-Al2O3-SiO2 series) synthesized via high temperature melting and sol gel methods were measured by means of small-angle X-ray scattering (SAXS), low wavenumber Raman spectrum (LWRS) and high temperature Raman spectrum (HTRS in situ measuring). The nanometer self-similarity aggregation structure(it's size is about a few nm to a few tens nm) and phonic phonon vibration like modes of low temperature silicate gel, high temperature silicate melts and it's quenching glasses phases were obtained. So a quantitative method by HTRS for measuring the aggregation size in the high temperature melts was established. The results showed that the aggregation size of the silicate melts is smaller at high temperature than at room temperature and the number of bridge oxygen in one Si-O tetrahedron in network structure units is decreasing at high temperature. This study work provides important theory and information for deliberating geochemistry characteristic, crystallization & evolution of natural magma and enhancing performance of low dimension silicate matelials.

[High temperature Raman spectra and structure study of stolzite-structured PbWO4 crystals and its melt].

Raman spectra of stolzite-structured PbWO4 crystal were recorded from 298 to 1 473 K. All the appearing vibrational modes were interpreted and assigned. The most intense mode at 902.7 cm(-1), which is identified as the internal mode upsilon1(Ag) of symmetrical stretching attributed to the vibration of [WO4]2- tetrahedron. Temperature dependent characteristics of the Raman spectra of the crystal were investigated. Band half-widths widened accompanied by the relative intensity decreased, and the lattice became more disorder with the increase in temperature. As being heated up to 1 398 K, PbWO4 crystals began to be melting and have completely transformed to liquid state at 1 473 K, while the internal vibrational modes of isolated [WO4]2- tetrahedron have appeared and the symmetry of vibrational modes transformed from S4 in crystal into Td of [WO4]2- in melt. It suggested that the isolated [WO4]2- structure unit exists in the melt.

[Quantum chemistry ab initio calculation study on microstructure and raman spectra of phosphosilicates].

Quantum chemistry ab initio calculation was applied to study the hyperfine structure of ternary alkali phosphosilicates. Restricted Hartree-Fock method (RHF) with the basis sets of 6-31G(d) was employed to optimize geometric structure and calculate Raman spectra of a series of phosphosilicates model cluster structural units. Stress index of tetrahedron (SIT) was introduced to describe and classify the microstructure of ternary alkali phosphosilicates in order to investigate the effect of phosphorus-oxygen tetrahedron on the micro-environment of silicon-oxygen tetrahedron. It was suggested that the calculated vibrational wavenumbers of symmetric stretching vibration of non-bridging oxygen (NBO) depend not only on the species of the silicon-oxygen tetrahedron, which was called primary structure units, but also on the linkage of the neighboring tetrahedron and ring types. The phosphorus-oxygen tetrahedron exhibits regulative ability of bond angle and conductive ability of stress, so that the vibrational wavenumbers of silicon-oxygen tetrahedron are insensitive to the bond angle. It demonstrated that vibrational wavenumbers of NBO stretching vibration in the high frequency range show linear relationship with the value of SIT.

[Temperature dependent Raman spectra and micro-structure study of cuspidine in solid and liquid phases].

Cuspidine plays an important role in conventional metallurgical continuous casting mould flux. An UV laser source was used to record its ambient and high temperature Raman spectra (temperature range: 298-1 723 K) combined with a charge coupled device (CCD) detector. Both increasing and decreasing processes as well as characteristic spectra and shifts in wavenumber were observed. Micro-structure of cuspidine in liquid state is not unitary and different from that in solid state, suggesting multi clusters coexisting. Density functional theory (DFT) simulation method was applied to calculate its wavenumbers of Raman active vibrations by introducing the crystal spatial configuration model of cuspidine. Thus the experimental vibrational wavenumbers of the characteristic peaks could be assigned. This will help study physical and chemical behavior of cuspidine in continuous casting mould flux and provide an unique in-situ method under varying temperature with Raman spectroscopic technique.

[Hyperfine structure study of binary sodium phosphates by Raman spectroscopy].

Quantum chemistry ab initio calculation was applied to study the hyperfine structure of binary sodium phosphates. A series of phosphate model clusters were designed to simulate the microstructure of phosphates with different components. Closed-shell Hatree-Fock method (RHF) and the basis sets of 6-31G (d, p) were employed to optimize structures and calculate Raman frequencies of these phosphate model clusters. SIT (stress index of tetrahedron), which was well used in the study of silicate microstructures, had been adjusted before it was introduced to describe the microstructure of binary sodium phosphates. It was suggested that SIT of phosphates has good relationship with the Raman shift of the corresponding structures, which means SIT could also be used to study the hyperfine structure of binary sodium phosphates. Raman spectra of both solid and molten Na5P3O10 were determined in the range of room temperature to 1 473 K. A phase transition between 873 and 1 073 K was observed, and the main peaks of Na5P3O10 shifted to a lower frequency with increasing temperature. The microstructure units of Na5P3O10 crystal are the types of Q1(2) and Q2(11) with a ratio of 2 : 1. With the increase in the temperature, various new microstructure units including Q0 , Q1(1), Q1(2), Q2(11), Q2(12) and Q2(22) appeared while Na5 P3 O10 was heated above the melting point, which led to the broadening and asymmetry of Raman spectra of molten Na5P3O10. It came to an understanding that the microstructure units of phosphates may change at different temperature, especially above the melting points. The introduction of SIT and hyperfine structure could help analyze the Raman spectra of phosphates both qualitatively and quantitatively.

[Raman spectroscopic study of binary PbO-TeO2 glasses].

Raman spectra of lead tellurite glasses and their melts were measured. Results show that four coordinate tellurite units convert into three coordinate units with increasing the concentration of PbO, and the number of non-bridging oxygen bonds (NBO) increases accordingly in this system. Three spectral peaks in the high frequency range were assigned to stretching vibration of bridging oxygen in four coordinate tellurite units (Q(b)), stretching vibration of non-bridging oxygen in four coordinate tellurite units (Q(nb)) and in three coordinate tellurite units (T(nb)). The relative density of four coordinate structure units decreases and the three coordinate tellurite units considerably exist in tellurite glasses when the concentration of PbO > 50%. Besides, the Raman frequencies of the three species' peaks become blue-shifted because of the temperature induced crystallization at high temperature, and the peak intensities increase and the peaks sharpen. The peaks merge together and become much broader while the glass is heated above the melting point because of multiple microstructure units coexisting.

[Effect of fluorine in mould fluxes on microstructural units of silicates slag].

In the continuous casting of steel, mold fluxes play an important role in improving surface quality of casting strands and maintaining the continuous casting process. The physiochemical property of mold fluxes is definitely correlated with the microstructure. Fluorides play an important role in modifying the high temperature properties of mold fluxes. So, studying the effect of fluoride on multicomponent silicate structure is helpful to understanding the performance of fluoride in mould fluxes. In the present paper, effects of fluorine on melt, glass and crystal structure of silicate were studied by using Raman spectroscopy and in situ high temperature technique. The results were as follows: While the content of CaF2 increased, the varieties and relative quantities of microstructural units of silicates changed, the polymerization of the silicate network decreased, and the viscosity of the melt decreased; comparing non-fluoride with high-fluorine mold fluxes, the main kind of microstructure of silicates in mold fluxes with high fluorine was mostly monomer, while in fluorine free mold fluxes it was mainly chain of microstructure. It would help to develop fluorine free mold fluxes.

[Ab initio calculation of hyperfine structure and Raman spectra of binary alkali metal silicates].

Ab initio calculation method of quantum chemistry was used to optimize several typical binary alkali metals silicates model clusters under restricted Hartree-Fock method with 6-31G(d) basis sets. The symmetric stretching vibrational frequency of non-bridging oxygen in the high frequency range, its Raman optical activity (ROA) and the influence of different cations of those model clusters were also calculated and evaluated with the concept of hyperfine micro-structure. It was shown that the symmetric stretching vibrational frequency of non-bridging oxygen in the high frequency range is related closely to the environmental hyperfine micro-structure, and ROA enhancement of Q3 species occurs as Q4 species is its nearest neighbor. It can be inferred that the Raman scattering properties of silicates might be predominantly determined by hyperfine micro-structure instead of crude SiO4 tetrahedron as primary micro-structure. It was found that large cation can enhance ROA of the symmetric stretching vibration of non-bridging oxygen by charge transfer mechanism, while ROA weakening effect can be expected on small model clusters due to the excessive charge transfer.

[Analysis of different methods for denoising of high temperature Raman spectra].

Combined with time accumulated resolution and space resolution the SU-HTRS(T/S) set has been realized at Shanghai University. It is impossible to avoid noise at high temperature, so different mathematic methods, such as Savitzky-Golay method, FFT and wavelet methods have been adopted for denoising. For various noise levels, the effects of three methods on the peak location, intensity and covering area as well as the smoothing degree of the reduced spectra were analyzed. It can be concluded that Savitzky-Golay method is simple and quick, while wavelet method offers the best results in denoising process.

[Structure and Raman spectra of titanium oxides].

Under the first-principle density functional theory, structures of several titanium oxides (TiO, Ti2O3, Ti3O5, anatase and rutile) were optimized, and the obtained the structure parameter that coincides with the X-ray crystal diffraction result. The optimized structure parameters coincide well with those obtained by X-ray diffraction method. Molecular vibrational modes were also studied and assigned. Double Numeric including D-polarization function basis set was used with local density approximation, and the local exchange-correlation energy was described with Vosko-Wilk-Nusair and spin non-restricted function. The calculated vibrational wavenumbers were used to interpret observed experimental Raman spectra of those titanium oxides. By comparing the Raman spectra of those titanium oxides with the calculated results, the characteristic peaks of various titanium oxides could be assigned. So the types of titanium oxides could be diagnosed and recognized. This will help to investigate the correlation between the structure and property of materials.

[High temperature Raman spectroscopy techniques and its applications].

Based on the frequency and time domain characters of heat radiation, high temperature Raman spectroscopy techniques were aralyzed and summarized. Thereby, two high temperature Raman systems were set up. One is an accumulated time-resolved macro-Raman spectroscopy system, and the other is an accumulated time-resolved and confocal coupled micro-Raman spectroscopy system. Finally, their applications in the study of high temperature processes such as melt structure and phase transformation, crystallization as well as samples with high fluorescence were intrtoduced.

[Raman active vibrations of aluminosilicates].

Raman spectra of aluminosilicate minerals, namely kyanite, andalusite, and sillimanite and K2O-Al2O3-SiO2 glasses were recorded. Four alumino-silicon tetrahedral model clusters were calculated by self-consistent (SCF) molecular orbital ab-ini-tio calculation of the quantum chem (QC) method. The result shows a decrease tendency in Raman frequencies in the 800-1200 cm(-1) frequency region with increase in four-coordinated Al content, which is assigned to the Si--Onb symmetry stretching vibrations. The Raman spectra in the 700-800 cm(-1) frequency region is attributed to Al-Onb symmetry stretching vibrations.

[Structure analysis on growth solid-liquid boundary layer of BSO crystal at real time].

The micro Raman spectra of solid-liquid boundary layer, the melts and crystal side, were measured at real time, concerning BSO crystal grown with zone-melting method. The structure characters in boundary layer, melts and crystal were analyzed. The process, of which the growth unit structure changed while they transited from melts through boundary layer to crystal lattice, was analyzed. The results show that, there exists Bi3O4 and [SiO4] bonding structure in the melts of BSO crystal. While in the solid-liquid boundary layer, the Bi3O4 molecular units converge into [BiO7] octahedron monomer of polymer in form, the monomer or the polymer converge with the [SiO4] structure units, then all these converged structure enter into crystal lattice sites.

[Raman spectroscopy studies on the aqueous solutions of sodium formate and lithium formate].

The structures of the aqueous solutions of sodium formate and lithium formate are studied according to the growth conditions of the crystals under different supersaturations and temperatures by Raman spectroscopy. The effects of temperature, concentration, supersaturation and cation on the structures of solutions and the structure difference between lithium formate solution and lithium formate monohydrate crystal are analyzed. The result shows that the concentration, temperature and supersaturation effect the structures of the solutions slightly and the cation effects the frequency of the bands greatly.

[High temperature Raman spectra and structure character study of BSO crystal].

The structure character of BSO crystal at room temperature was generalized. The main Raman shifts of lattice vibration at room temperature were interpreted. The Raman spectra of BSO crystal were measured in a temperature range from 293 K to 1123 K with high temperature Raman spectroscopy and time-resolved detection techniques. Temperature-dependence character of the Raman spectra of the crystal was investigated. The vibration mode of the longest bond Bi-O(1) in crystal shifts from 542 cm(-1) to 512 cm(-1) with the temperature increasing from room temperature to 1123 K. It can be attributed to the fact that oxygen atoms are electrostatic bond to Bi atoms. The intensity of 88 cm(-1) modes, which belongs to combination mode of bending and stretching in Bi3O4 unit, changes not so noticeably as other modes, and even the 58 cm(-1) mode of Bi atoms motions in crystal lattice decreases rapidly when the temperature is higher than 873 K, which indicates that the framework structure of the crystal is broken down at high temperature, while the Bi3O4 unit still exists.

[Raman spectra study of thermal transformation of nephrite cat's eye from Sichuan province].

Raman spectrum and X-ray powder diffraction (XRD) were used to study the process andproduct of thermal transformation of nephrite cat's eye from Sichuan province. The results indicate that upon being heated till 900 degrees C, tremolite in the nephrite cat's eye is dehydrated completely and the appearance of a new characteristic band near 671 cm(-1) indicates the form of a new product. At 1 000 degrees C, the intensity of band near 1014 cm(-1) rises obviously, and the weak bands near 573 cm(-1) and 934 cm(-1) present. Up to 1100 degrees C, the band near 1033 cm(-1) appears. All these evidences show that the final thermal transformation product is identified as Ca-Mg pyroxene which is similar to diopside both in structure and in composition. This conclusion is confirmed by XRD.