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1.
The effects of TiOx diffusion barrier layer thickness on the microstructure and pyroelectric characteristics of PZT thick films were studied in this paper. The TiOx layer was prepared by thermal oxidation of Ti thin film in air and the PZT thick films were fabricated by electrophoresis deposition method (EPD). To demonstrate the barrier effect of TiOx layer, the electrode/substrate interface and Si content in PZT thick films were characterized by scanning electron microscope (SEM) and X-ray energy dispersive spectroscopy (EDS), respectively. The TiOx barrier thickness shows significant influence on the bottom electrode and the pyroelectric performance of the PZT thick films. The average pyroelectric coefficient of PZT films deposited on 400 nm TiOx layer was about 8.94 × 10−9 C/(cm2 K), which was improved by 70% than those without diffusion barrier layer. The results showed in this study indicate that TiOx barrier layer has great potential in fabrication of PZT pyroelectric device. 相似文献
2.
A transient photocurrent model is used to explain terahertz emission from gas plasma irradiated by a laser pulse and the second harmonic. By introducing the second harmonic, 400 nm, the corresponding terahertz emission is greatly enhanced. The exact dependence of terahertz emission on the intensity ratio of 400–800 nm is studied for the case with total intensity of 5.00 × 1014 W/cm2. Results show the emission reaches the maximum at about the case for energy distribution of Iω = 4.00 × 1014 W/cm2, I2ω = 1.00 × 1014 W/cm2. 相似文献
3.
With Nd3+ doping and Ca2+, Sr2+ modulating in the sol–gel technique, a series of polycrystalline perovskite samples La0.7?xNdx(Ca,Sr)0.3MnO3 (x = 0, 0.05, 0.1, 0.15, 0.20, 0.25) was prepared, their maximum magnetic entropy changes were tuned to room temperature (ΔSH = ?1.47 J/kg K at 298 k for La0.45Nd0.25(Ca,Sr)0.3MnO3), an enhancement of the maximum magnetic entropy change (ΔSH = ?1.89 J/kg K at 315 k) and its refrigerant capacity (about 45.3 J/kg) had also been obtained under 9 kOe magnetic field variation for La0.55Nd0.15(Ca,Sr)0.3MnO3 contrast to La0.7(Ca,Sr)0.3MnO3. 相似文献
4.
《Journal of Molecular Liquids》2006,123(2-3):68-71
The effect of chlorides of magnesium, calcium, strontium and barium on the temperature of the sound velocity maximum (TSVM) of water, Tw, has been studied by determining the ultrasonic velocity using a single crystal variable path interferometer working at 3 MHz. The accuracy in ultrasonic velocity measurement is ± 0.05 m s− 1. The ultrasonic velocity measurements were carried out at ≃ 2 °C intervals over a range of 5 °C to either side of TSVM of the solutions. The accuracy in fixing TSVM is ± 0.2 °C. The shifts in TSVM of water due to the addition of MgCl2 and CaCl2, (ΔTobs), are found to be positive at low concentrations becoming maxima around the weight fraction w ≃ 2.3 × 10− 2 for MgCl2 and w ≃ 3.8 × 10− 2 for CaCl2 and becoming negative around w ≃ 5.6 × 10− 2 for MgCl2 and w ≃ 3.8 × 10− 2 for CaCl2. (ΔTobs) for MgCl2 > CaCl2 > SrCl2 > BaCl2 indicating that the strength of the structural interactions in modifying the hydrogen-bonded structure of water is in the order Mg2+ > Ca2+ > Sr2+ > Ba2+. The results are explained in the light of the structural properties of the anions and cations in the solutions in modifying the three dimensional hydrogen-bonded structure of water. 相似文献
5.
《Journal of Physics and Chemistry of Solids》2003,64(6):939-946
X-irradiation of single crystals of Tp–GeH3 (Tp: triptycene) led to the trapping of the radical Tp–GeH2. The angular variations of the resulting EPR spectra were recorded at 300 and 77 K. The drastic temperature dependence of the spectra was caused by both a strong anisotropy of the g-tensor and a rotation of the GeH2 moiety around the C–Ge bond. The determination of the EPR tensors as well as the analysis of this motion required to take the presence of disorder in the crystal into account. In accordance with DFT calculations, Tp–GeH2 is shown to be pyramidal and to adopt, in its lowest energy structure, a staggered conformation. Rotation around the C–GeH2 bond is blocked at 90 K and is almost free above 110 K. The experimental barrier, obtained after simulation of the EPR spectra as a function of the rotational correlation time, is equal to 1.3 kcal mol−1, which is slightly inferior to the barrier calculated by DFT (3.6 kcal mol−1). Calculations performed on Tp–CH3, Tp–GeH3 and Tp–GeH2 show that the rotation barrier ΔErot around the C–Ge bond drastically decreases by passing from the germane precursor to the germanyl radical and that ΔErot increases by passing from the germane to its carbon analogous. Structural parameters involved in these barrier differences are examined. 相似文献
6.
Aihong Tong Yueming Zhou Cheng Huang Qing Liao Peixiang Lu 《Optics Communications》2011,284(10-11):2505-2508
Using three-dimensional classical ensembles, we have investigated the enhancement of double ionization of perpendicularly aligned H2 molecules by a 800 nm laser pulse with intensity ranging from 1 × 1014 W/cm2 to 6 × 1014 W/cm2. The simulated results show that double ionization probability of H2 strongly depends on R and reaches a maximum at an intensity independent critical distance RC ≈ 5 a.u. Furthermore, the enhancement of double ionization is more pronounced in the cases of weaker or stronger fields. These results, a well indication of the influence of molecular structures and laser–molecule interactions on double ionization of diatomic molecules, are analyzed in detail and qualitatively explained based on the field-induced barrier suppression model and back analysis. 相似文献
7.
《Current Applied Physics》2007,7(1):18-20
We investigated the influence of insulating barrier thickness and the Ti composition dependence of the band structure of Al-oxide on the resistance and tunneling magnetoresistance (TMR) behavior of the magnetic tunnel junction (MTJ). Low resistance × area (RA) value (1.1 MΩ μm2) was achieved by decreasing the Al-oxide thickness down to 1.0 nm. However, this led to the partial oxidation of the bottom ferromagnetic (FM) electrode of the junction and non-continuous thin barriers by the occurrence of pinholes, with low TMR ratio of 8.3%. For an alternative for low RA value, we developed a new Ti-alloyed Al-oxide (TiAlOx) that had lower band gap than Al-oxide as an insulating barrier of MTJ. As the Ti concentration increased up to 5.33 at.% Ti in Al, the RA value of the MTJs was reduced from 9.5 to 0.69 MΩ μm2, owing to the band-gap reduction of TiAlOx caused by the formation of extra bands, mainly composed of Ti-3d orbitals, within the band gap. It was analyzed that TiAlOx has localized d states in the band gap below the conduction band. In addition, the TMR ratio increased with the Ti concentration and reached a maximum of 49% at 5.33 at.% Ti owing to the microstructural evolution of Ti–Al alloy film in the pre-oxidation state. 相似文献
8.
《Journal of Molecular Liquids》2006,123(2-3):139-145
(p, ρ, T) and (ps, ρs, Ts) properties, and apparent molar volumes Vϕ of LiI (aq) at T = 298.15 to 398.15 K, at pressures up to p = 60 MPa were reported, and apparent molar volumes at infinite dilution Vϕ0 have been evaluated. An empirical correlation for density of lithium iodide (aq) with pressure, temperature and molality was derived. The experiments were carried out at molalities m = 0.11053, 0.32532, 0.70013, 1.40459, 2.95059, and 4.88147 mol kg− 1 of lithium iodide. 相似文献
9.
M.S. Islam D.T. Hanh F.A. Khan M.A. Hakim D.L. Minh N.N. Hoang N.H. Hai N. Chau 《Physica B: Condensed Matter》2009,404(16):2495-2498
Among the perovskite manganites, a series of La1?xCaxMnO3 has the largest magneto-caloric effect (MCE) (|ΔSm|max=3.2–6.7 J/kg K at ΔH=13.5 kOe), but the Curie temperatures, TC, are quite low (165–270 K). The system of LaSrMnO3 has quite high TC but its MCE is not so large. The manganites La0.7(Ca1?xSrx)0.3MnO3 (x=0, 0.05, 0.10, 0.15, 0.20, 0.25) have been prepared by solid state reaction technique with an expectation of large MCE at room temperature region. The samples are of single phase with orthorhombic structure. The lattice parameters as well as the volume of unit cell are continuously increased with the increase of x due to large Sr2+ ions substituted for smaller Ca2+ ions. The field-cooled (FC) and zero-field-cooled (ZFC) thermomagnetic measurements at low field and low temperatures indicate that there is a spin-glass like (or cluster glass) state occurred. The Curie temperature TC increases continuously from 258 K (for x=0) to 293 K (for x=0.25). A large MCE of 5 J/kg K has been observed around 293 K at the magnetic field change ΔH=13.5 kOe for the sample x=0.25. The studied samples can be considered as giant magneto-caloric materials, which is an excellent candidate for magnetic refrigeration at room temperature region. 相似文献
10.
《Applied Surface Science》2005,239(3-4):481-489
The current–voltage (I–V) characteristics of Al/SnO2/p-Si (MIS) Schottky diodes prepared by means of spray deposition method have been measured at 80, 295 and 350 K. In order to interpret the experimentally observed non-ideal Al/SnO2/p-Si Schottky diode parameters such as, the series resistance Rs, barrier height ΦB and ideality factor n, a novel calculation method has been reported by taking into account the applied voltage drop across interfacial oxide layer Vi and ideality factor n in the current transport mechanism. The values obtained for Vi were subtracted from the applied voltage values V and then the values of Rs were recalculated. The parameters obtained by accounting for the voltage drop Vi have been compared with those obtained without considering the above voltage drop. It is shown that the values of Rs estimated from Cheung’s method were strongly temperature-dependent and decreased with increasing temperature. It is shown that the voltage drop across the interfacial layer will increase the ideality factor and the voltage dependence of the I–V characteristics. The interface state density Nss of the diodes has an exponential growth with bias towards the top of the valance band for each temperature; for example, from 2.37 × 1013 eV−1 cm−2 in 0.70−Ev eV to 7.47 × 1013 eV−1 cm−2 in 0.62−Ev eV for 295 K. The mean Nss estimated from the I–V measurements decreased with increasing the temperature from 8.29 × 1013 to 2.20 × 1013 eV−1 cm−2. 相似文献
11.
Zekai Hong King-Yiu Lam Ritobrata Sur Shengkai Wang David F. Davidson Ronald K. Hanson 《Proceedings of the Combustion Institute》2013,34(1):565-571
Hydrogen peroxide (H2O2) and hydroperoxy (HO2) reactions present in the H2O2 thermal decomposition system are important in combustion kinetics. H2O2 thermal decomposition has been studied behind reflected shock waves using H2O and OH diagnostics in previous studies (Hong et al. (2009) [9] and Hong et al. (2010) [6,8]) to determine the rate constants of two major reactions: H2O2 + M → 2OH + M (k1) and OH + H2O2 → H2O + HO2 (k2). With the addition of a third diagnostic for HO2 at 227 nm, the H2O2 thermal decomposition system can be comprehensively characterized for the first time. Specifically, the rate constants of two remaining major reactions in the system, OH + HO2 → H2O + O2 (k3) and HO2 + HO2 → H2O2 + O2 (k4) can be determined with high-fidelity.No strong temperature dependency was found between 1072 and 1283 K for the rate constant of OH + HO2 → H2O + O2, which can be expressed by the combination of two Arrhenius forms: k3 = 7.0 × 1012 exp(550/T) + 4.5 × 1014 exp(?5500/T) [cm3 mol?1 s?1]. The rate constants of reaction HO2 + HO2 → H2O2 + O2 determined agree very well with those reported by Kappel et al. (2002) [5]; the recommendation therefore remains unchanged: k4 = 1.0 × 1014 exp(?5556/T) + 1.9 × 1011+exp(709/T) [cm3 mol?1 s?1]. All the tests were performed near 1.7 atm. 相似文献
12.
K. Nagasao T. Masui S. Tajima 《Physica C: Superconductivity and its Applications》2008,468(15-20):1188-1191
Electronic anisotropy was studied for overdoped (Y, Ca)Ba2Cu3O7−δ with various doping levels (p). It was found that the pseudogap-like behavior in the resistivity disappear when p exceeds 0.17, independent of the oxygen deficiency. The anisotropy ratio γ estimated from upper critical fields showed a rapid decrease at around p = 0.18, approaching γ = 3 for p > 0.20. 相似文献
13.
Single crystals of semiorganic material 3-aminophenol orthophosphoric acid (denoted as 3-amphph) of size 29 × 17 × 4 mm3 have been grown by the slow evaporation of an aqueous solution of deionized water at 50 °C. The crystal belongs to orthorhombic system with the non centrosymmetric space group P212121. The lattice parameter values of 3-amphph crystal are a = 4.481(2) Å, b = 9.782(4) Å and c = 18.326(4) Å. The grown crystals are subjected to single crystal XRD studies to identify its morphology and structure. Optical transmittance and second harmonic generation of the grown crystals have been studied by UV–Vis–NIR spectrum and Kurtz powder technique respectively. The transmittance of 3-amphph crystal has been used to calculate the refractive index n, the extinction coefficient k, reflectance R and both the real (?r) and imaginary (?i) components of the dielectric constant as a function of wavelength. The optical band gap of 3-amphph is 4.05 eV with direct transition. The anisotropic mechanical behavior of 3-amphph has been analyzed using Vickers microhardness test. The mechanism of growth is revealed by carrying out chemical etching using water as etchant. 相似文献
14.
《Current Applied Physics》2010,10(4):975-984
Polycrystalline nickel–zinc–copper ferrites with chemical formula Ni0.6+xZn0.2Cu0.2VxFe2−2xO4,(0.0 ⩽ x ⩽ 0.25) were prepared by the ceramic route. The X-ray diffraction (XRD) analysis of the samples results confirms single-phase spinel structure. Scanning electron microscopy (SEM) of the prepared ferrites reveal that vanadium addition resulted in a rapid grain growth with large pores trapped inside the grains as the vanadium concentration increases. The ac conductivity σac has been studied as a function of frequency and temperature over the temperature range (300–600 K). The results obtained for these materials reveal a semiconductor – to semimetal transition as V5+ content increases. All studies composition exhibit a transition with change in the slope of conductivity. The obtained temperature Tc is found to be decrease with the increasing vanadium content. The hopping of electrons between Fe3+ and Fe2+ as well as the hole hopping between Ni3+ and Ni2+ are found to responsible for the conduction mechanism. The relation of the universal exponent s with temperature gives evidence for the presence of the correlation barrier hopping (CHB) mechanism in these compounds. The impedance technique has been used to study effect of grain and grain boundary on the electrical properties. The analysis data show only one semi-circle for all samples except for sample with x = 0.05. The results suggested that the conduction mechanism takes place predominantly through the grain in the studied samples. 相似文献
15.
Chitosan acetate-ammonium nitrate (NH4NO3) films have been prepared by the solution-cast technique. Fourier transform infrared spectroscopy (FTIR) showed that complexation has occurred. FTIR exhibited shifts in amine and carbonyl bands from 1553 to 1520 cm−1 and 1636 to 1617 cm−1. A new peak was also observed at 1746 cm−1. XRD shows that all complexes are amorphous. The highest conductivity at room temperature is 2.53×10−5 S cm−1 for the film containing 45 wt% NH4NO3. The conductivity of the samples is dependent on the number of mobile ions and mobility. 相似文献
16.
In this work, two different types of Co3O4 nano-crystals were synthesized by (i) conventional direct solid state thermolysis of cobalt terephthalate metal-organic framework (MOF-71) and (ii) new indirect solid state thermolysis of Co(OH)2 derived by alkaline aqueous treatment of MOF-71. The products were then characterized by X-ray diffraction technique (XRD), Fourier transforms infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), Reflection electron energy loss spectroscopy (REELS), Brunauer, Emmett, and Teller (BET), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) techniques. By REELS analysis the energy band gap of MOF-71 was determined to be 3.7 eV. Further, electrochemical performance of each Co3O4 nanostructure was studied by the cyclic voltammetry (CV), galvanostatic charge-discharge (GCD), and electrochemical impedance spectroscopy (EIS) in a three-electrode system in KOH electrolyte. An asymmetric supercapacitor was fabricated using indirect Co3O4 nanoparticles as cathode and electrochemically reduced graphene oxide as anode, and the electrochemical properties were studied and showed a high energy density of 13.51 Wh kg−1 along with a power density of 9775 W kg−1 and good cycling stability with capacitance retention rate of 85% after 2000 cycles. 相似文献
17.
The series of Gd4 ? xMxAl2O9 ? x/2 (M = Ca, Sr) with x = 0, 0.01, 0.05, 0.10 and 0.25 was prepared by the citrate complexation method. Both Gd4 ? xCaxAl2O9 ? x/2 and Gd4 ? xSrxAl2O9 ? x/2 show the monoclinic cuspidine structure with space group of P21/c up to 0.05–0.1 and 0.01–0.05 mol for Ca and Sr, respectively. Beyond the substitution limit of Gd4Al2O9, GdAlO3 and SrGd2Al2O7 appear as additional phases. The highest electrical conductivity obtained at 900 °C yielded σ = 1.49 × 10? 4 S/cm for Gd3.95Ca0.05Al2O8.98. In comparison, the conductivity of pure Gd4Al2O9 was σ = 1.73 × 10? 5 S/cm. The conductivities determined are in a similar range as those of other cuspidine materials investigated previously. The thermal expansion coefficient of Gd4Al2O9 at 1000 °C was 7.4 × 10? 6 K? 1. The phase transition between 1100 and 1200 °C reported earlier changes with increasing substitution of Ca and Sr. 相似文献
18.
《Solid State Ionics》2006,177(19-25):1619-1624
The kinetics of the electrochemical reduction of molecular nitrogen at gold micro electrodes on yttria stabilized zirconia (YSZ) solid oxide electrolyte is studied by steady state polarization measurements. From the η / lg i plot for both cathodic and anodic polarization the apparent transfer coefficients αa and αc are evaluated. The sum of αa + αc exceeds unity and thus a multistep electron transfer process is suggested. The concept of the stoichiometric number is applied to the electrode reaction N2 + 6e− = 2N3− supposing that the overall process involves at least two intermediate species. On the basis of the evaluation of the experimental results the reaction N2− + e− ⇌ N22− is suggested as the rate determining reaction step for the cathodic nitrogen reduction and nitride formation. 相似文献
19.
The purpose of this study is to clarify the degree of impregnation resulting from treatment of internal waterlogged wood samples using MRI. On a 1.5 T MR scanner, T1 and T2 measurements were performed using inversion recovery and spin-echo sequences, respectively. The samples were cut waterlogged pieces of wood treated with various impregnation techniques which were divided into different concentrations of trehalose (C12H22O11) and polyethylene glycol (PEG; HO-(C2H4O)n-H) solutions. Then these samples underwent impregnation treatment every two weeks. From the results, we found that the slope of the T1-concentration curve using linear fitting showed the value of the internal area for PEG to be higher than the external area; internal, − 2.73 ms/wt% (R2 = 0.880); external, − 1.50 ms/wt% (R2 = 0.887). Furthermore, the slope of the T1-concentration curve using linear fitting showed the values for trehalose to have almost no difference when comparing the internal and the external areas; internal, − 2.79 ms/wt% (R2 = 0.759); external, − 3.02 ms/wt% (R2 = 0.795). However, the slope of the T2-concentration curve using linear fitting for PEG showed that there was only a slight change between the internal and the external areas; internal, 0.26 ms/wt% (R2 = 0.642); external, 0.18 ms/wt% (R2 = 0.920). The slope of the T2-concentration curve did not show a change in linear relationship between the internal and the external areas; internal, 0.06 ms/wt% (R2 = 0.175); external, − 0.14 ms/wt% (R2 = 0.043). In conclusion, using visualization of relaxation time T1, it is possible to obtain more detail information noninvasively concerning the state of impregnation treatment of internal waterlogged wood. 相似文献
20.
Tuberculosis is an infectious disease caused by the bacterium M. tuberculosis. The aim of this study was to investigate the bactericidal effect and underlying mechanisms of low-frequency and low-intensity ultrasound combined with levofloxacin treatment against M. smegmatis (a surrogate of M. tuberculosis). As part of this study, M. smegmatis was continuously irradiated with low frequency ultrasound (42 kHz) using several different doses whereby both intensity (0.138, 0.190 and 0.329 W/cm2) and exposure time (5, 15 and 20 min) were varied. Flow cytometric analyses revealed that the permeability of M. smegmatis increased following ultrasound exposure. The survival rate, structure and morphology of bacteria in the lower-dose (ISATA = 0.138 W/cm2 for 5 min) ultrasound group displayed no significant differences upon comparison with the untreated group. However, the survival rate of bacteria was significantly reduced and the bacterial structure was damaged in the higher-dose (ISATA = 0.329 W/cm2 for 20 min) ultrasound group. Ultrasound irradiation (0.138 W/cm2) was subsequently applied to M. smegmatis in combination with levofloxacin treatment for 5 min. The results demonstrated that the bactericidal effect of ultrasonic irradiation combined with levofloxacin is higher compared to ultrasound alone or levofloxacin alone. 相似文献