排序方式: 共有37条查询结果,搜索用时 46 毫秒
1.
Strong, surprising, and multifaceted effects of the width of the external surface layer Δ(ξ) and internal stresses on surface-induced pretransformation and phase transformations (PTs) are revealed. Using our further developed phase-field approach, we found that above some critical Δ(ξ)(*), a morphological transition from fully transformed layer to lack of surface pretransformation occurs for any transformation strain ε(t). It corresponds to a sharp transition to the universal (independent of ε(t)), strongly increasing the master relationship of the critical thermodynamic driving force for PT X(c) on Δ(ξ). For large ε(t), with increasing Δ(ξ), X(c) unexpectedly decreases, oscillates, and then becomes independent of ε(t). Oscillations are caused by morphological transitions of fully transformed surface nanostructure. A similar approach can be developed for internal surfaces (grain boundaries) and for various types of PTs and chemical reactions. 相似文献
2.
Farrahi Gholam Hossein Javanbakht Mahdi Jafarzadeh Hossein 《Continuum Mechanics and Thermodynamics》2020,32(3):589-606
Continuum Mechanics and Thermodynamics - A thermodynamically consistent phase field model for crack propagation is analyzed. The thermodynamic driving force for the crack propagation is derived... 相似文献
3.
Javanbakht M Badiei A Ganjali MR Norouzi P Hasheminasab A Abdouss M 《Analytica chimica acta》2007,601(2):172-182
A new functionalized nanoporous silica gel with dipyridyl group (DPNSG) was synthesized. Then, the potentiometric response of the copper(II) ion was investigated at a carbon paste electrode chemically modified with this newly designed functionalized nanoporous silica gel. The electrodes with DPNSG proportions of 15.0% (w/w) demonstrated very stable potentials. Calibration plots with Nernstian slopes for Cu2+ were observed, 28.4 (±1.0) mV decade−1, over a wide linear concentration range (1.0 × 10−7 to 1.0 × 10−2 M). The electrode exhibited a detection limit of 8.0 × 10−8 M. Moreover, the selectivity coefficients measured by the match potential method in acetate buffer, pH 5.5, were investigated. The electrode presented a response time of ∼50 s, high performance, high sensitivity in a wide range of cation activities and good long-term stability (more than 9 months). The method was satisfactory and was used to determine the copper ion concentration in waste waters, contaminated by this metal. 相似文献
4.
Mehran Javanbakht Hamid Khoshsafar Mohammad Reza Ganjali Parviz Norouzi Mehdi Adib 《Electroanalysis》2009,21(14):1605-1610
The aim of this work was to obtain an adsorptive stripping voltammetric method for the Ce(III) determination at a carbon paste electrode, chemically modified with N'‐[(2‐hydroxyphenyl)methylidene]‐2‐furohydrazide (NHMF). The electroanalytical procedure comprised two steps: the Ce(III) chemical accumulation at ?200 mV followed by the electrochemical detection of the Ce(III)/NHMF complex, using anodic stripping voltammetry. The factors, influencing the adsorptive stripping performance, were optimized including the modifier quantity in the paste, the electrolyte concentrations, the solution pH and the accumulation potential or time. The resulting electrode demonstrated a linear response over a wide range of Ce(III) concentration (5.0–90 nmol dm?3). The detection limit was found to be 0.8 nmol dm?3 on the basis of a signal to noise ratio of 3. The precision for six determinations of 10 and 55 nmol dm?3 Ce(III) was 5.6% and 2.1% (relative standard deviation), respectively. Application of the procedure to the determination of cerium in phosphate rock and wastewater samples gave good results. 相似文献
5.
Akbar Shabanikia Mehran Javanbakht Hossein Salar Amoli Khadijeh Hooshyari Morteza Enhessari 《Ionics》2015,21(8):2227-2236
In this work, Fe2TiO5 nanoparticles were used for improving the proton conductivity, and water and acid uptake of polybenzimidazole (PBI)-based proton exchange membranes. The nanocomposite membranes have been prepared using different amounts of Fe2TiO5 nanoparticles and dispersed into a PBI membrane with the solution-casting method. The prepared membranes were then physico-chemically and electrochemically characterized for use as electrolytes in high-temperature PEMFCs. The PBI/Fe2TiO5 membranes (PFT) showed a higher acid uptake and proton conductivity compared with the pure PBI membranes. The highest acid uptake (156 %) and proton conductivity (78 mS/cm at 180 °C) were observed for the PBI nanocomposite membranes containing 4 wt% of Fe2TiO5 nanoparticles (PFT4). The PFT4 composite membrane showed 380 mW/cm2 power density and 760 mA/cm2 current density in 0.5 V at 180 °C at dry condition. The above results indicated that the PFT4 nanocomposite membranes could be utilized as proton exchange membranes for high-temperature fuel cells. 相似文献
6.
Mohammad Reza Ganjali Hamid Khoshsafar Farnoush Faridbod Ali Shirzadmehr Mehran Javanbakht Parviz Norouzi 《Electroanalysis》2009,21(19):2175-2178
Room temperature ionic liquids (RTILs), 1‐n‐butyl‐3‐methylimidazolium tetrafluoroborate, [bmim]BF4, and multiwalled carbon nanotubes (MWCNTs) were used for improvement of a praseodymium carbon paste ion selective sensor response. [bmim]BF4 can be a better binder than mineral oils. MWCNTs have a good conductivity which helps the transduction of the signal in carbon paste electrode. The characteristics of these electrodes as potentiometric sensors were evaluated and compared with PVC membrane sensor. The results indicate that potentiometric sensor constructed with ionic liquid shows an increase in performance in terms of Nernstian slope, selectivity, response time, and response stability compared to Pr(III) PVC membrane sensor. 相似文献
7.
Mohammad Reza Ganjali Mahmood Golmohammadi Mohammad Yousefi Parviz Norouzi Masoud Salavati-Niasari Mehran Javanbakht 《Analytical sciences》2003,19(2):223-227
A copper(II) ion-selective PVC membrane sensor based on 2-(1'-(4'-(1'-hydroxy-2'-naphthyl)methyleneamino)butyl iminomethyl)-1-naphthol (BHNB) as a novel Schiff base containing a sensing material has been successfully developed. The sensor exhibits a good linear response of 29 mV per decade within the concentration range of 10(-1)-10(-6) M of Cu2+. The sensor shows good selectivity for copper(II) ion in comparison with alkali, alkaline earth, transition and heavy metal ions. The BHNB-based sensor is suitable for use with aqueous solutions of pH 3.5-7.0 and displays minimal interference by Sr(II), Cd(II), Hg(II), Zn(II) and Pb(II), which are known to interfere with other previously suggested electrodes. The proposed membrane electrode was used as a sensor for determining the Cu(II) content in black tea samples. It was also applied as an indicator electrode in the potentiometric titration of Cu2+ ions with EDTA. 相似文献
8.
Molecularly imprinted polymer based potentiometric sensor for the determination of hydroxyzine in tablets and biological fluids 总被引:1,自引:0,他引:1
Javanbakht M Fard SE Mohammadi A Abdouss M Ganjali MR Norouzi P Safaraliee L 《Analytica chimica acta》2008,612(1):65-74
Molecular imprinting is a useful technique for the preparation of functional materials with molecular recognition properties. In this work, a biomimetic potentiometric sensor, based on a non-covalent imprinted polymer, was fabricated for the recognition and determination of hydroxyzine in tablets and biological fluids. The molecularly imprinted polymer (MIP) was synthesized by precipitation polymerization, using hydroxyzine dihydrochloride as a template molecule, methacrylic acid (MAA) as a functional monomer and ethylene glycol dimethacrylat (EGDMA) as a cross-linking agent. The sensor showed a high selectivity and a sensitive response to the template in aqueous system. The MIP-modified electrode exhibited a Nernstian response (29.4 ± 1.0 mV decade−1) in a wide concentration range of 1.0 × 10−6 to 1.0 × 10−1 M with a lower detection limit of 7.0 × 10−7 M. The electrode demonstrated a response time of ∼15 s, a high performance and a satisfactory long-term stability (more than 5 months). The method has the requisite accuracy, sensitivity and precision to assay hydroxyzine in tablets and biological fluids. 相似文献
9.
M. Javanbakht M. Shakeri S.N. Sadeghi A.R. Daneshmehr 《European Journal of Mechanics - A/Solids》2011,30(6):983-991
Elasticity solution is presented for finitely long, simply-supported, functionally graded shallow and non-shallow shell panel with two piezoelectric layers under pressure and electrostatic excitation. The functionally graded panel is assumed to be made of many sub panels. Each sub panel is considered as an isotropic layer. Material’s properties in each layer are constant and functionally graded properties are resulted by suitable arrangement of layers in multilayer panel. In each interface between two layers, stress and displacement continuities are satisfied. The highly coupled partial differential equations (p.d.e.) are reduced to ordinary differential equations (o.d.e.) with variable coefficients for non-shallow panel and constant coefficients for shallow shell panel by means of trigonometric function expansion in circumferential and longitudinal directions. The resulting ordinary differential equations are solved by Galerkin finite element method and Newmark method is used to march in time. Numerical examples are presented for functionally graded shell panel with a piezoelectric layer as an actuator in external surface and a piezoelectric layer as a sensor in internal surface and the results of the shallow and non-shallow panels are discussed. 相似文献
10.
The two‐state two‐path model is introduced as a minimized model to describe the quantum dynamics of an electronic wave packet in the vicinity of a conical intersection. It involves two electronic potential energy surfaces each of which hosts a pair of quasi‐classical trajectories over which the wave packet is assumed to be delocalized. When both trajectories evolve dynamically either diabatically or adiabatically, the full wave packet dynamics shows only features of the dynamics around avoided level crossings in the vicinity of the conical intersection. When one trajectory evolves adiabatically whereas the other trajectory follows a diabatic evolution, quantum mechanical interference of the wave packet components on each path generates Stueckelberg oscillations in the transition probability. These are surprisingly robust against a dissipative environment and, thus, should be a marker for conical intersections. 相似文献