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Structures and electrochemical properties of TiMn2-5x(V4Fe)x(x=0.30,0.35) alloys were investigated. The results of XRD analysis show that the alloys are mainly composed of body centered cubic (bcc) phase, whose lattice parameters are enhanced with the increase of V and Fe content. The SEM images of the alloys show that there are some colonies in the matrix phase. The proportion of colony to the matrix decreases with increasing of V and Fe content. The electrochemical measurements show that TiMn0.25(V4Fe)0.35 alloy has unfavorable activation performance until temperature reaches 327 K, while TiMn0.50(V4Fe)0.30 alloy shows better activation performance, but passivation phenomenon was found in the process of charging at low temperature, which can be eliminated by heating to high temperature. The PCT curves of alloys show that the TiMn0.50(V4Fe)0..30 alloy has a good comprehensive performance, with a favorable plateau pressure at room temperature and wide plateau. The enthalpy and entropy in hydrogen desorption of TiMn0.50(V4Fe)0..30 alloy were also calculated and they are −36.1 kJ/mol, −126.9 J/(mol·K), respectively.

This paper uses finite element method to obtain the three-dimensional temperature field of laser-induced transient thermal grating (TTG) for two-layered structure of diamond film on ZnSe substrate. The numerical results indicate that unique two-times heating process is gradually experienced in the area between two adjacent grating stripes. However, there is a little change for the temperature field along the depth direction for the diamond film due to its great thermal conductivity. It further finds that the thickness of the diamond film has a significant influence on the temperature field in diamond/ZnSe system. The results are useful for the application of laser-induced TTG technique in film/substrate system.

We investigate the photoinduced effects on the spin state for half-metallic ferromagnet CrO2 (TC~390 K), in which the conducting electrons are totally polarized, by means of the time-resolved pump–probe method at the temperature range from 300 K to 470 K. A significant negative change ΔT/T for the transmittance spectrum at 1.55 eV under photo-excitation is found. The ΔT/T value monotonically decreases on approaching to TC from the low temperature side, suggesting a photoinduced spin disorder state. Furthermore, we calculate the saturation magnetization MS of CrO2 in both the ground and photo-excited states by using the local-spin-density approximation plus U (LSDA+U) method, and find a decrease of the MS-value in the photo-excited state. The suppressed MS-value in the photo-excited state is consistent with the experimental data.

Photoinduced effects on the transmission and resistivity in wide-bandwidth manganite La0.7Sr0.3MnO3 films (TC = 350 K) have been investigated at various temperatures in the range of 5–470 K by means of the time-resolved pump–probe method. Below TC, we have observed a negative transmission change ΔTM/TM at 2.54 eV and a positive resistivity change ΔR/R under photo-irradiation at excited energy Eexc = 3.20 eV. With temperature approaching to TC, the values of ΔTM/TM and ΔR/R show a significant reduction. We have ascribed the photoinduced changes on the transmission and resistivity of the La0.7Sr0.3MnO3 film to the charge-ordering fluctuation in the ferromagnetic phase, which is similar to that observed in the narrow-bandwidth La0.7Ca0.3MnO3 films.

Thermal diffusivity has been investigated in a manganite thin film La0.6Sr0.4MnO3 by means of transient grating (TG) technique at room temperature. A new method, which is generalized to two-layered samples of the thin film deposited on a semi-infinite substrate, is established to fit the TG signals. The thermal diffusivity of the La0.6Sr0.4MnO3 thin film with a thickness of 200 nm on an MgO (100) substrate is determined to be 0.92 mm2/s, which is slightly smaller than that of the single crystal sample (1 mm2/s).

We investigate the photoinduced resistance change (ΔR/R) in a La0.6Sr0.4MnO3 film (Tc~325 K) at different applied dc currents I (0.1–2.0 mA) at 295 K. At I = 0.1 mA, we have found a significant photoinduced ΔR/R~17% under photo-irradiation at excitation energy Eexc = 3.05 eV and pump power Ppump = 2.5 mJ/cm2, which has been ascribed to the photo-excited down-spin eg carriers and hence the spin-disorder in the ferromagnetic metallic state. With increasing applied electric current to 2.0 mA, the magnitude of the photoinduced ΔR/R is reduced to 3%, which may be attributed to current-induced ordering of the localized spins.

Thermal diffusivity has been investigated in ordered double perovskite Sr2FeMoO6 by means of transient surface grating technique in the temperature range of 300–450 K. The thermal diffusivity shows an appreciable decrease from 39 mm2/s at 300 K to 37 mm2/s at 360 K in the ferromagnetic phase, and then steeply drops to 10 mm2/s with further increasing temperature above the critical temperature Tc~380 K. Such an abrupt decrease of the thermal diffusivity has been ascribed to the structural phase transition at Tc. We further investigate the lattice effect on the thermal diffusivity in A2FeMoO6 (A = Ca, Sr and Ba) by substitution of Ca2+ or Ba2+ ions for Sr2+ ions at 300 K. We find that the thermal diffusivity increases from 35 mm2/s for A = Ca to 41 mm2/s for A = Ba. Considering the change of the Fe–O–Mo bond angle from 152.4 degrees for A = Ca to 180 degrees for A = Ba, the increased thermal diffusivity for Ba compound has been ascribed to the enhanced hybridization between transition-metal d and oxygen p states due to the larger Fe–O–Mo bond angle and hence the wider one-electron bandwidth W.

Resistivity, thermal diffusivity, lattice and magnetic properties of double perovskite Sr2−xLaxMnMoO6 are investigated with systematic change of La doping concentration x from 0.0 to 0.4. The insulator to metal phase transition is observed with increasing x above 0.3, suggesting that the extra electrons via substitution of La3+ for Sr2+ ions occupy mainly the conduction Mo-4d band. According to the insulator to metal phase transition, the thermal diffusivity of Sr2−xLaxMnMoO6 enhances from 0.33 cm2/s at x = 0.0 to 0.49 cm2/s at x = 0.4. We further investigate the La doping effects on the lattice and magnetic properties.

Droplet spreading behavior on a substrate is closely bound up with the wettability of the substrate, and plays a critical role in many industrial applications, such as lubrication, painting, coating, and mineral flotation. In this paper, a dynamical model of droplet spreading on a smooth substrate is established through a mechanical analysis. According to the lubrication approximation theory and Navier-Stokes equation, a general nonlinear evolution equation or equations are derived, including the momentum equation, the continuity equation, and the evolution equation of film thickness. We adopt numerical methods to solve these equations, and also quantitatively analyze the relation among film thickness, spreading radius, speed of wetting contact line and time in detail. The results show that the droplet spreading process is mainly divided into two phases, namely expansion phase and contraction phase. Moreover, the spreading process is along with mutual transformation among surface energy, kinetic energy, and different kinds of potential energies. In addition, the final spreading radius Rf of droplet is determined by the inherent wettability of solid surface, and the collapse effect, which emerges at t=0.006 s in the spreading process, is related to Laplace pressure difference of curved liquid surface. Finally, by controlling the droplet size, we obtain the scaling law of droplet spreading radius with time, which approximately meets R ～ t1/7. The scaling law is validated both experimentally and numerically. The results of this study are expected to enhance our knowledge of the movement of wetting contact line and also provide some guidance for the wetting theory.

Effects of hydrostatic pressure on the mixed-valence (MV) bismuth complex BaBiO3 have been investigated up to ~9 GPa by means of high-pressure Raman scattering and absorption spectra at 300 K. The pressure-induced hardening behaviour of the Bi-O stretching mode suggests that the predicted pressure-induced MV to the single-valence (SV) phase change cannot occur. Investigation of absorption spectra with pressure shows the enhanced optical gap Egap, which further indicates the remained MV state of Bi ions.

In order to study the effects of working conditions and solid surface topography on the wettability of material, a series of No. 45 steel specimens with the same surface arithmetic average height Sa and different surface microstructures is designed and manufactured by laser surface texturing. All the surfaces are measured by a non-contact three-dimensional (3D) optical profiler Talysulf CCI Lite and characterized by the ISO25178. A series of wetting experiments is carried out with the No. 32 turbine oil on an optical contact angle and surface tension meter SL200 KS. The effects of temperature, droplet volume and surface structure on the wettability are analyzed. Meanwhile, quantitative research of the relationship between the random characteristics of topography and wettability of the solid surface is conducted with parameters obtained from the ISO25178. Based on the fact that the contact angle is an acute angle, the results show that the contact angle of the droplet on the solid surface decreases rapidly to a stable value in the wetting process. The stable value decreases with the increase of the temperature, while it first increases and then decreases with the increase of the droplet volume. The surface wettability can be affected by the laser micro-texturing. Surfaces with similar values of Sa show different wettabilities for different micro-textures with different shapes and directions. Textured surfaces with grooves along the spreading direction of the droplet perform the best wettability in our research. Results also predicate that the wettability of surface is greatly influenced by the amplitude parameters (Sku, Ssk), spatial parameters (Str, Sal), hybrid parameters (Sdq, Sdr), and feature parameters (Sda, Sdv), which are all obtained from the ISO25178. The wettability of hydrophilic surface becomes better with increasing Sku, Sal, and Sdr and reducing Ssk, Str, and Sdq.

Photoacoustic imaging is a hybrid imaging technique based on the photoacoustic effect. As a non-invasive and non-ionizing modality, photoacoustic imaging takes the both merits of the conventional acoustic imaging and optical imaging. Firstly, the contrast of photoacoustic imaging primarily depends on the optical absorption. The unique optical spectra of atoms and molecules makes optical methods to be a widely used modality to probe the molecular and chemical information of biological tissue. Therefore, photoacoustic imaging has its inherent advantage in high-contrast functional and physiological imaging of biological tissue, as well as the optical imaging method. Secondly, photoacoustic imaging has the high spatial resolution in deep tissue in comparison with the pure optical imaging method. Since the strongly optical scattering in biological tissue, pure optical imaging method is difficult to obtain the high-resolution image in the tissue deeper than ～1 mm. Whereas, acoustic wave suffers much less from scattering than optical wave, the acoustic scattering coefficient is about 2-3 orders of magnitude less than the optical scattering coefficient. Photoacoustic imaging can achieve a fine resolution in deep tissue, which equivalent to 1/200 of the imaging depth. Thirdly, non-ionizing radiation used for photoacoustic imaging is much safer than X-ray. Moreover, the low-temperature rises make photoacoustic imaging be safely used in live tissue. A laser-induced temperature rise of 1 mK yields an initial pressure of ～800 Pa in soft tissue. Such a sound pressure level has reached the sensitivities of typical ultrasonic transducers. Fourthly, photoacoustic imaging has the ability of extracting multiple contrasts, including biochemical parameter, biomechanical parameter, blood velocity distribution, tissue temperature, and microstructure information. Photoacoustic imaging can capture more specific and reliable information about the tissue structure, function, metabolism, molecule, and gene. As a result, photoacoustic imaging has become one of the fastest growing biomedical imaging techniques in the past decade.#br#In this review, we will explain photoacoustic effect and the principle of photoacoustic imaging. Then, we introduce the two classical photoacoustic imaging schemes, including photoacoustic tomography and photoacoustic microscopy. Their main specifications, such as resolution, are also preflents. We review the ability of photoacoustic imaging in extracting multiple contrasts and discuss their biomedicine applications. In addition, we also introduce the remarkable breakthroughs in super-resolution photoacoustic imaging. Finally, we look the further development and the limitations of photoacoustic imaging.

The electric field enhancement properties of an active gold nanoshell with gain material inside have been investigated by using Mie theory. As the gain coefficient of the inner core increases to a critical value, a super-resonance appears in the active gold nanoshell, and enormous enhancements of the electric fields can be found near the surface of the particle. With increasing shell thickness, the critical value of the gain coefficient for the super-resonance of the active gold nanoshell first decreases and then increases, and the corresponding surface enhanced Raman scattering (SERS) enhancement factor (G factor) also first increases and then decreases. The optimized active gold nanoshell can be obtained with an extremely high SERS G factor of the order of 1019–1020. Such an optimized active gold nanoshell possesses a high-efficiency SERS effect and may be useful for single-molecule detection.

In this paper, we investigate the effects of the relative size and arrangement of a virtual transducer on the image quality in limited-view photoacoustic tomography. A virtual transducer refers to the acoustic scatterers used to reflect photoacoustic waves and improve the images reconstructed from incomplete PA signal. Size and spatial arrangement determine the performance of the virtual transducer. In this study, the scatterers utilized as virtual transducers are arranged in different manners, such as on a straight line or on an arc line. We find that virtual transducers with a big distributing angle can provide more significant image improvement than with a small distributing angle, which is similar to the true transducers. We also change the size of virtual transducer and study its influence on image quality. It is found that the bigger scatterers provide better images than the smaller ones. Especially, when the size of scatterers is reduced to the wavelength of photoacoustic wave, the image quality observably decreases, owing to the strong diffraction effect. Thus, it is suggested that the size of the acoustical scatterers should be much larger than the photoacoustic wavelength. The simulations are conducted, and the results could be helpful for the application and further study of virtual transducer theory in limited-view photoacoustic tomography.

We investigate the effect of a metallic electrode on the ability for poly[2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylene vinylene] (MEH-PPV) film to undergo amplified spontaneous emission (ASE). The threshold of the device with Ag cladding is about 10 times greater than that of a metal-free device, but metal such as Al completely shuts off ASE. The ASE recurs when a thin spacer layer, such as a few nanometers of SiO2, is introduced between the MEH-PPV film and the Al cladding. Compared with the Cu or Al electrode, the Ag cladding is most suited to serve as an electrode with its low optical loss due to its high work-function and reflectivity.

The local electric field components of the elliptical gold nanotube are calculated based on the finite difference time domain (FDTD) method. It is find that when the wavelength of the incident light is just at a resonant wavelength, the local field enhancement of the gold nanotube reaches a maximum. The increase of the semiminor axis of the ellipse makes the distribution of the local field change from a distribution that is high in both sides and low in the middle part of the nanotube into a distribution that is uniform around the tube. With the increase of the angle between the incident polarization and the semimajor axis, the local electric field components increase rapidly. The increases of the dielectric constants for both the core and the embedding medium cause the local field around the nanotube to decrease.

The optical properties and electronic structure of marokite-type CaMn2O4 are investigated by using UV-vis spectroscopy and the local-spin-density approximation plus the Hubbard-U (LSDA+U) method. Four absorption bands are observed at 638 nm (1.94 eV), 512 nm (2.42 eV), 377 nm (3.29 eV) and 248nm (5.00eV), which are ascribed to the charge transfer transitions O2p↑→Mn3d eg↑, O2p↓→Mn3d eg↑, Mn3d eg↑→Mn3d t2g↓ and O2p↑→Mn3d t2g↓, respectively. We further use CaMn2O4 as a photocatalyst to decompose an azo-dye acid orange 7 (AO7) under irradiation of visible light and find that the decomposition ratio of AO7 reaches 15.9% under the irradiation of visible light for two hours.

In this work, performance enhancements of amplified spontaneous emission (ASE) from poly[2-methoxy-5-(2'-ethyl-hexyloxy)-1, 4-phenylene vinylene] (MEH-PPV) have been achieved via solvent vapour treatment. Correlations between the morphology of the film and the optical performance of polymer-based ASE are investigated. The active layers are characterised by atomic force microscopy and optical absorption. The results show that the solvent-vapour treatment can induce the MEH-PPV self-organisation into an ordered structure with a smooth surface, leading to enhanced optical gain. Thus the solvent-vapour treatment is a good method for improving the optical properties of the MEH-PPV.

The Ag-doping effects on TiO2 nanoparticles are investigated by means of x-ray diffraction (XRD) and Raman scattering spectroscopy. XRD and Raman results indicate that Ag-doping stabilizes the rutile phase in TiO2. We find an Ag-doping induced lattice expansion in both anatase and rutile phases. The Ag-doping has different influences on the lattice distortion for anatase and rutile phases, that is, the c/a-value for the anatase phase decreases with 0.5% Ag-doping and then increases with 1% Ag-doping while that for the rutile phase shows a gradual increase with increasing Ag-doping. We have ascribed the different variations of lattice distortion due to Ag-doping to the change of interfacial interaction between the anatase and rutile phases induced by different Ag con centrations.

Based on a theoretical model for spatial diffusion reflection with two-point-source δ- P 1 approximation to the radiative transport equation for a semi-infinite homogeneous turbid medium, the optical absorption coefficient μ a , reduced scattering coefficient μ ' s , and the second-order parameter γ of the medium are recovered from the measurement data of the reflectance by the nonlinear least squares method. The results show that the two-point-source δ- P 1 approximation can give more satisfactory results for describing irradiance distribution close to source when the source-detector separation is larger than one transport mean free path. We can also obtain the anisotropy factor g according to the relationship between γ and μ ' s . This study is of great significance for the measurement of the optical properties of biological tissues and the application of diffuse reflectance spectroscopy technology.

A novel composite waveguide is proposed to improve the directional emission of phononic crystal waveguide by introducing a point defect array. The finite element simulations indicate that the point defects attached to the output surface of phononic crystal waveguide produce resonant modes, which act as secondary radiation sources. The interferences of sound wave radiated from these radiation sources and waveguide can enhance the normal radiation intensity by 161.21% and reduce the half-power angular width by 85.35%. In addition, when the number of the point defects is large enough, the directivity approaches a steady value. The investigation provides a new method to improve the directional emission of phononic crystal waveguide.

In this work, enhanced poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) bulkheterojunction photovoltaic devices are achieved via slow-solvent-vapour treatment. The correlations between the morphology of the active layer and the photovoltaic performance of polymer-based solar cell are investigated. The active layers are characterized by atomic force microscopy and optical absorption. The results show that slow-solvent-vapour treatment can induce P3HT self-organization into an ordered structure, leading to the enhanced absorption and efficient charge transport.

We investigate multiphoton ionization (MPI) of N2 exposed to femtosecond laser fields at 400 nm and 800 nm experimentally. Photoelectron energy spectra are measured with a high resolution photoelectron spectrometer at laser intensities up to 1014 W/cm2. Prominent resonant peaks observed at 400 nm can be attributed to the resonance with molecular Rydberg states corresponding to different molecular orbitals, revealing the importance of the multiple orbitals contribution in strong field molecular dynamics.

In the process of fabrication of polymer photovoltaic (PV) devices, poly (3, 4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) thin film, acting as an anode buffer layer, is spin-coated under the action of an electric field. The PV devices with a PEDOT:PSS layer spin-coated under the action of a static electric field exhibit improved short-circuit current density (Jsc) and power conversion efficiency (PCE). The investigation of morphology shows that the appropriate intensity of the electric field can increase the roughness of the surface of the PEDOT:PSS layer, which results in improved contact between the anode and hole transport layer and thus enhances the Jsc of the devices. Chemical analysis is also provided by x-ray photoelectron spectroscopy (XPS) spectra.

In this study, numerical experiments are carried out to quantitatively investigate the effects of limited-view scanning on the resolution of photoacoustic tomography. An empirical formula is provided to approach our numerical results.The results of the study are helpful for the design of scanning trajectory and the evaluation of reconstruction.

Since welded seams of pressure vessels are generally rather narrow, for the longitudinal weld the general formulas based on the technique of stereoscopic radiography can be directiy applied for determining the location of the point defect. But for circular weld, owing to that films during photo-taking are curved ones whereas they are to be made flate during observation and measurement on a 3–dimensional detector, so some further equations must be established to satisfy the relations between the stereographic curevd films and the assumed flate films and thereby to determine the spatial point location for the defects in pressure vessels. With these epuations and by surveying of the point image of defects, coordinates ZA, XA and YA can be determined and hence the real position of defects in vessels. Ascertainment of point location of defects is the background for the dimensional location and quantitative analysis of defects. Once ascertained, such geometric parameters as depth of defects, height of defects themselves, their orientation, size and spacing can all be determined consequently.

The performance of TiO2 nanotubes in bulk heterojunction of poly (2-methoxy-5-(2'-ethylhexyloxy)-1, 4-phenylenevinylene) (MEH-PPV)/TiO2 nanotubes is investigated. The transport properties are studied by using the time-of-fight technique (TOF). The carrier mobilities of both holes and electrons are not improved for the MEH-PPV:TiO2 composites compared with the pristine MEH-PPV. However, photoluminescence under the influence of the electric field indicates that the dissociation of excitons in the MEH-PPV:TiO2 composites, which is facilitated by photoinduced charge transfer, only requires a smaller electric field.

The variations of optical absorption of gold nanoshells with the shell thickness, size of the core, and core dielectric constant have been investigated by means of Mie theory. It was found that with the increase in the thickness of the shell, the strength of absorption peak increases first and then decreases. We also observed that with increasing core size the maximum optical absorption of the particles decreases. Furthermore, the increase of the core dielectric constant reduces the strength of absorption peak and the hollow gold nanoshells have the maximum optical absorption. We ascribe the change of the absorption peaks to the plasmon hybridization and the competition between the variations of conduction and oscillation electrons.

The size effects of SrTiO3 nanoparticles are investigated by Raman spectroscopy and UV-Visible absorption spectra with changing grain size in the range of 10—80 nm. It is found that the intensity for the first-order TO2 mode increases significantly as the grain size decreases from 80 to 10 nm. Such behavior suggests the presence of the micropolar regions on the grain boundary induced by the enhanced surface-defect dipoles. Moreover, the first-order TO2 and TO3 modes show red-shifts, indicating the increase of the Ti—O bond-length with decreasing grain size of SrTiO3 nanoparticles. The softening of the Raman mode is consistent with the lattice expansion investigated by XRD. In addition, the UV-Visible absorption spectra indicates the enhancement of absorption due to surface distortion states and hence the lattice expansion, which results in the increase of Eg-value.

The travelling properties of laser-generated surface acoustic wave with broad bandwidth, which propagated on a sample with surface defects, have been investigated in theory. The numerical results of theoretical models with different defects indicate that the surface defects worked as low-pass filter for the travelling surface acoustic waves. The cut-off frequency of low-pass filter is linearly related to the depth of the defect, and decreased against the increasing depth of the defect. The amplitude of the travelling surface acoustic wave is seriously attenuated with increasing width of surface defect. The numerical results provide a theoretical basis for quantitative detection of the surface defects.

We report a set-up for cavity ringdown absorption spectroscopy, and we have measured the line profile of the resonance 6s6p1P1←6s6s1S0 of barium atoms using cavity ringdown spectroscopy method. The absorption spectroscopy line profile of Ba at different temperatures near 553.548nm is gained. The experimental results indicate that the precision for the absorption measurement has reached up to 6×10-7.

Dynamic viscoelasticity of electrorheological fluids based on microcrystalline c ellulose/castor oil suspensions was experimentally investigated in squeeze flow. The dependence of storage modulus G′and loss modulus G″parallel to external e lectric field on electric fields and strain amplitudes is presented. The experim ents show that, when external electric field is higher than the critical field, the viscoelasticity of the ER fluids converts from linear to nonlinear, and the ER fluids transfer from solid-like state to fluid state with the growth of strai n amplitude. The influences of strain amplitude and oscillatory frequency on the nonlinearity of viscoelasticity were also studied.