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941.
HADI M MARWANI AMJAD E ALSAFRANI HAMAD A AL-TURAIF ABDULLAH M ASIRI SHER BAHADAR KHAN 《Bulletin of Materials Science》2016,39(4):1011-1019
In this study, an efficiently employed ionic liquid combined with commercially available silica gel (SG–ClPrNTf2) was developed for selective detection of gold(III) by use of inductively coupled plasma–optical emission spectrometry (ICP-OES). The selectivity of SG–ClPrNTf2 was evaluated towards seven metal ions, including Y(III), Mn(II), Zr(IV), Pb(II), Mg(II), Pd(II) and Au(III). Based on pH study and distribution coefficient values, the SG–ClPrNTf2 phase was found to be the most selective towards Au(III) at pH 2 as compared to other metal ions. The adsorption isotherm of Au(III) on the SG–ClPrNTf2 phase followed the Langmuir model with adsorption capacity of 59.48 mg g?1, which was highly in agreement with experimental data of adsorption isotherm study. The kinetics study indicated that Au(III) adsorption kinetics data were well fit with the pseudo-second-order kinetic model on the basis of correlation coefficient fitting (0.996) and adsorption capacity agreement (62.26 mg g?1). Furthermore, SG–ClPrNTf2 phase was effectively performed for the determination of Au(III) in real water samples with satisfactory results. 相似文献
942.
A ASHERY A H ZAKI M HUSSIEN MOURAD A M AZAB A A M FARAG 《Bulletin of Materials Science》2016,39(4):1057-1063
In this work, heterojunction of InSb/InP was grown by liquid phase epitaxy (LPE). Surface morphology and crystalline structure of the heterojunction were characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The frequency and temperature dependences of a.c. conductivity and dielectric properties of the heterojunctions were investigated in the ranges of 100 kHz–5 MHz and 298–628 K, respectively. The a.c. conductivity and its frequency exponents were interpreted in terms of correlated barrier hopping model (CBH), as the dominant conduction mechanism for charge carrier transport. The calculated activation energy, from the Arrhenius plot, was found to decrease with increasing frequency. Experimental results of both dielectric constant ε 1 and dielectric loss ε 2 showed a remarkable dependence of both frequency and temperature. 相似文献
943.
N KRISHNA JYOTHI K K VENKATARATNAM P NARAYANA MURTY K VIJAYA KUMAR 《Bulletin of Materials Science》2016,39(4):1047-1055
The free standing and dimensionally stable gel polymer electrolyte films of polyacrylonitrile (PAN): potassium iodide (KI) of different compositions, using ethylene carbonate as a plasticizer and dimethyl formamide as solvent, are prepared by adopting ‘solution casting technique’ and these films are examined for their conductivities. The structural, miscibility and the chemical rapport between PAN and KI are investigated using X-ray diffraction, Fourier transform infrared spectroscopy and differential scanning calorimetry methods. The conductivity is enhanced with the increase in KI concentration and temperature. The maximum conductivity at 30°C is found to be 2.089 × 10?5 S cm?1 for PAN:KI (70:30) wt%, which is nine orders greater than that of pure PAN (< 10?14 S cm?1). The conductivity-temperature dependence of these polymer electrolyte films obeys Arrhenius behaviour with activation energy ranging from 0.358 to 0.478 eV. The conducting carriers of charge transport in these polymer electrolyte films are identified by Wagner’s polarization technique and it is found that the charge transport is predominantly due to ions. The better conducting sample is used to fabricate the battery with configuration K/PAN + KI/I2+ C + electrolyte and good discharge characteristics of battery are observed. 相似文献
944.
In this study, pure and NH2-functionalized graphene oxide (GO) nanosheets have been added to the cement mortar with different weight percents (0.05, 0.10, 0.15, 0.20 and 0.25 wt%). In addition, the effects of functionalizing GO on the microstructure and mechanical properties (flexural/compressive strengths) of cement composite have been investigated for the first time. Scanning electron microscopy (SEM) images showed that GO filled the pores and well dispersed in concrete matrix, whereas exceeding GO additive from 0.10 wt% caused the formation of agglomerates and microcracks. In addition, mercury intrusion porosimetry confirmed the significant effects of GO and functionalizing groups on filling the pores. NH2-functionalizing helped to improve the cohesion between GO nanosheets and cement composite. Compressive strengths increased from 39 MPa for the sample without GO to 54.23 MPa for the cement composites containing 0.10 wt% of NH2-functionalized GO. Moreover, the flexural strength increased to 23.4 and 38.4% by compositing the cement paste with 0.10 wt% of pure and NH2-functionalized GO, compared to the sample without GO, respectively. It was shown that functionalizing considerably enhanced the mechanical properties of GO/cement composite due to the interfacial strength between calcium silicate hydrates (C-S-H) gel and functionalized GO nanosheets as observed in SEM images. The morphological results were in good agreement with the trend obtained in mechanical properties of GO/cement composites. 相似文献
945.
J EL GHOUL 《Bulletin of Materials Science》2016,39(1):7-12
The synthesis by the sol–gel method, structural and optical properties of ZnO, Zn0.99Al0.01O (AlZ), Zn0.9V0.1O (VZ) and Zn0.89Al0.01V0.1O (AlVZ) nanoparticles was reported. The approach was slow release of water for hydrolysis by esterification reaction followed by a supercritical drying in ethyl alcohol. After thermal treatment at 500°C in air, the obtained nanopowders were characterized by various techniques such as transmission electron microscopy, X-ray diffraction and photoluminescence (PL) spectroscopy. The structural properties showed that the ZnO nanoparticles with an average particle size of 25 nm exhibit hexagonal wurtzite structure. From the optical studies, it was found that the optical band gap was located between 2.97 and 3.17 eV. The obtained electrical properties showed the potential application of the samples in optoelectronic devices. The powder of AlVZ presented a strong luminescence band in the visible range. The PL band energy position presented a small blue shift with the increase of measurement temperature. Different possible attributions of this emission band will be discussed. 相似文献
946.
The photoelectrocatalytic oxidation behaviour of ethylene glycol (EG) was studied in the present work using the TiO2-modified Ti foil (Ti/TiO2) electrode. The Ti/TiO2 nanotube array (Ti-NTA) electrode was prepared by anodizing of the Ti foil in the HF aqueous solution (0.2% v/v). The anodization was conducted in the constant 30 V for 2 h, and then the as-prepared Ti-NTA electrode was calcinated at 50 ° C for 2 h. The surface morphology of Ti- NTA electrode was studied using scanning electron microscopy images. For EG determination, the photocurrent of EG (EG oxidation current in the UV irradiation) was assessed using the hydrodynamic photoamperometric method in the phosphate buffers. Ultimately, the optimum conditions of EG determination were studied in various pH values and applied bias potentials, and the pH = 3.0 and E= 1.0 V (vs. reference electrode) were determined as the optimum conditions. It was found that the photocurrent of EG was linearly dependent on the concentration of EG in the range of 3.0 × 10 ?5 to 0.88 mol l ?1 , and the detection limit of EG determination was found to be 7.2 × 10?6 mol l?1 (3 σ). 相似文献
947.
Transparent borophosphate glasses doped with CuO were prepared by melt quenching technique. X-ray diffraction (XRD), optical and luminescence properties of sodium–calcium borophosphate glasses doped with CuO have been studied. The XRD results showed the amorphous nature of the sample. The introduction of CuO was favourable for the colour changes from light blue to dark bluish green colour. Direct optical energy bandgaps before and after doping with different percents of copper oxide obtained in the range 4.81–2.99 eV indicated the role of copper in the glassy matrix by ultraviolet (UV) spectra. The glasses have more than 80% transparency for emission wavelength range, and strong absorption bands due to the charge transition of the Cu+ and Cu2+ ions were observed. The emission bands observed in the UV and blue regions are attributed to 3d94s–3d10 triplet transition in Cu+ ion. 相似文献
948.
SIAVASH IMANIAN GHAZANLOU ALI SHOKUHFAR SHIVA NAVAZANI REZVAN YAVARI 《Bulletin of Materials Science》2016,39(5):1185-1195
Ni–Co/SiO 2 nanocomposite coatings and Ni–Co alloy coatings were prepared on steel substrate using direct and pulse electrodeposition methods. X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), X-ray map and energy dispersive X-ray spectroscopy (EDX) were employed to investigate the phase structure, surface morphology, and elemental analysis of coatings, respectively. In high discharge rates, the surface morphology was rough, disordered and gross globular; on the contrary, in the low rates, it was smoother, more ordered and fine globular. Also, effect of electrodeposition parameters such as average current density, pulse frequency and duty cycle on the microhardness and grain size of nanocomposite coatings that produced through the pulse current electrodeposition method have been investigated. By amplifying both duty cycles up to 50% and average current density from 2 to 6 A dm?2, microhardness increased, while the grain size decreased. But when duty cycle mounted on more than 50% and the average current density went up to 8 A dm?2, microhardness lessened, while the grain size rose. The optimum value for pulse frequency was about 25 Hz. Results showed that microhardness of nanocomposite coatings which were produced by pulse current method was higher than that of produced by direct current method. 相似文献
949.
The paper suggests a possible cooperation between stochastic programming and optimal control for the solution of multistage stochastic optimization problems. We propose a decomposition approach for a class of multistage stochastic programming problems in arborescent form (i.e. formulated with implicit non-anticipativity constraints on a scenario tree). The objective function of the problem can be either linear or nonlinear, while we require that the constraints are linear and involve only variables from two adjacent periods (current and lag 1). The approach is built on the following steps. First, reformulate the stochastic programming problem into an optimal control one. Second, apply a discrete version of Pontryagin maximum principle to obtain optimality conditions. Third, discuss and rearrange these conditions to obtain a decomposition that acts both at a time stage level and at a nodal level. To obtain the solution of the original problem we aggregate the solutions of subproblems through an enhanced mean valued fixed point iterative scheme. 相似文献
950.
Given the constantly raising world-wide energy demand and the accompanying increase in greenhouse gas emissions that pushes the progression of climate change, the possibly most important task in future is to find a carbon-low energy supply that finds the right balance between sustainability and energy security. For renewable energy generation, however, especially the second aspect turns out to be difficult as the supply of renewable sources underlies strong volatility. Further on, investment costs for new technologies are so high that competitiveness with conventional energy forms is hard to achieve. To address this issue, we analyze in this paper a non-autonomous optimal control model considering the optimal composition of a portfolio that consists of fossil and renewable energy and which is used to cover the energy demand of a small country. While fossil energy is assumed to be constantly available, the supply of the renewable resource fluctuates seasonally. We further on include learning effects for the renewable energy technology, which will underline the importance of considering the whole life span of such a technology for long-term energy planning decisions. 相似文献