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821.
Tian Chunpeng Maleki Akbar Motie Saeid Yavarinasab Adel Afrand Masoud 《Journal of Thermal Analysis and Calorimetry》2020,139(4):2847-2857
Journal of Thermal Analysis and Calorimetry - In the recent past, developments in power systems have led to a huge interest among researchers. Transformation from centralized into decentralized... 相似文献
822.
Polyblend and nanocomposite films of sodium salt of carboxymethylcellulose (Na‐CMC)/polyacrylamide (PAM) and Na‐CMC/PAM modified with carbon nanotubes (CNT) were synthesized by the solution casting technique. The effect of PAM and CNT loading on the structural, optical, and nanoscale free volume properties of Na‐CMC was studied. X‐ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy exhibited the existence of strong interactions between Na‐CMC and PAM and the non‐destructive effect of CNT on Na‐CMC/PAM structure. The HR‐TEM revealed the multi‐walled structure of CNT with a 7.06‐nm wall thickness and a 6.92‐nm wall inner diameter. Positron annihilation lifetime spectroscopy (PALS) was done, in a vacuum and at 30°C to 200°C, to investigate the nanoscale free volume properties by using a conventional fast‐fast coincidence spectrometer. It was found that the o‐Ps lifetime (τ3 ) and free volume (Vh) increase with increasing CNT percentage in the Na‐CMC/PAM blend. The distribution of the o‐Ps lifetime was broadened with increasing CNT ratios. Furthermore, the glass transition temperature (Tg) increases with increasing loads of CNT. For the first time, a correlation was done between Urbach energy (EU) and Vh. Finally, the results were represented and discussed in the frame of free volume properties. Optical measurements showed that the transmittance T% of Na‐CMC/PAM was 91.12% and decreased to 68.42% and 36.45% after loading with 1.0 and 2.0 wt % CNT. In addition, the blend shows higher insulating properties compared with the individual polymers. The CNT incorporation reduces the band gap significantly and increases the EU in the films. 相似文献
823.
New Plastic membrane ion-selective electrode for buspirone hydrochloride based on buspironium tetraphenylborate was prepared. The electrode exhibited mean slope of calibration graph of 58.4 mV per decade of BusCl concentration at 25 degrees C. The electrode can be used within the concentration range 6.3 x 10(-5) - 10(-2) M BusCl at a pH range of 2.5-7.0. The standard electrode potentials were determined at different temperatures and used to calculate the isothermal temperature coefficient of the electrode, amounting to 0.00056 V degrees C(-1). The electrode showed a very good selectivity for BusCl with respect to a number of inorganic cations, sugars and amino acids. The electrode was applied to the potentiometric determination of the buspirone ion and its pharmaceutical preparation under batch and flow injection conditions. Also, buspirone was determined by conductimetric titrations. Graphite rod, copper and silver coated wire electrodes were prepared and characterized as sensors for the drug under investigation. 相似文献
824.
825.
Cerium phosphate nanomaterials with different morphologies and sizes were synthesized via a hydrothermal process at 150 °C using cetyl-trimethyl-ammonium-bromide and ethylene-diamine-tetra acid as surfactants. The obtained samples were characterized by X-ray diffraction and a scanning electron microscope. A possible growth mechanism was proposed to reveal the formation process. The structural properties and the electrical conductivities of CePO4 nanomaterials were studied. The activation energies were obtained from Arrhenius plots where E a?=?1.06 eV. The ac conductivity at different temperatures for CePO4 nanomaterials showed frequency independence in the lower frequency range. The dielectric measurements were carried out as a function of frequency and temperature. Variation of the dielectric properties and the ac conductivity with frequency revealed that the dispersion is due to a Maxwell-Wagner type of interfacial polarization in general. 相似文献
826.
Mariem Chaari Adel Matoussi 《Applied Physics A: Materials Science & Processing》2014,116(3):1149-1160
Undoped zinc oxide has been prepared at various growth temperatures by a conventional sintering process. The crystal structures of the prepared samples were studied by X-ray diffraction. The frequency-dependent dielectric dispersion of all the sintered ZnO ceramics was investigated in the temperature range from ?100 to 30 °C and in the frequency range from 1 Hz to 10 MHz by broadband dielectric spectroscopy. An analysis of the complex permittivity and electric modulus as a function of frequency has been performed assuming a distribution of relaxation times. The pellet sintered at 900 °C showed the lowest value of the dielectric strength. The temperature dependent of the parameter α is discussed. While the charge transport through the grain and grain boundary regions was examined by impedance spectroscopy. Activation energy values extracted from conduction measurements were found to be in the range of 0.09 and 0.3 eV. 相似文献
827.
Zayani Jaafar Othman Adel Matoussi Francesca Rossi Giancarlo Salviati 《Applied Physics A: Materials Science & Processing》2014,117(3):1515-1524
The present work investigates the structural and dielectric properties of Zn1?x Mg x O composites prepared by the standard sintering method at 1200 °C during 24 h and doped with different weight percentages of MgO (x = 0–40 %). For this purpose, the scanning electron microscopy (SEM) was used to study the effect of the magnesium’s proportion on the morphology and crystallinity of the obtained samples. The SEM observations have shown rougher surfaces of the samples covered by grains having prismatic shapes and different sizes. The dielectric properties of the ceramics were investigated by spectroscopic impedance at different temperatures and frequencies, thus showing a frequency-dependent dispersion of the permittivity constants and dielectric losses. From these measurements, the relaxation processes were identified and their activation energies extracted. Dielectric responses were correlated with the microstructure and chemical composition of the ZnMgO composites. The mechanisms of ac conductivity are controlled by the polaron hopping and the electron tunneling models. Concerning the tunneling model, two types corresponding to the overlapping large polaron tunneling model for the composites Zn0.9Mg0.1O and Zn0.8Mg0.2O and the small polaron tunneling model for the composites Zn0.64Mg0.36O (in the frequency range 1.7 × 104 Hz–1 MHz) and Zn0.6Mg0.4O were observed. Besides, one type of hopping model corresponding to the correlated barrier hopping for the composites ZnO and Zn0.64Mg0.36O (in the frequency range 6 × 102–1.7 × 104 Hz) was noted. 相似文献
828.
The optical properties of CdxZn1−xS thin films on glass substrate prepared by spray pyrolysis method
A series of CdxZn1−xS thin films have been deposited on glass substrates using spray pyrolysis technique. The crystallinity and microstructure of CdxZn1−xS thin films have been investigated by X-ray diffraction (XRD). Based on the results of Hall measurements, the films obtained were an n-type semiconductor. The X-ray data analysis of CdxZn1−xS thin films showed that the grain size of the CdxZn1−xS increased with increase in Cd composition. It is observed that the band gap increases as the Cd composition decreases. The results also showed a blue shift of absorption edge of optical transmission spectra is increases as Zn ratio increases. The effects of Cd composition on the structural and optical properties of CdxZn1−xS thin films were related to their grain size, stress and carrier concentration. 相似文献
829.
830.
We consider the task of design optimization where the constraint is a state equation that can only be solved by a typically rather slowly converging fixed point solver. This process can be augmented by a corresponding adjoint solver and based on the resulting approximate reduced derivatives also an optimization iteration which actually changes the design. To coordinate the three iterative processes, we use an exact penalty function of doubly augmented Lagrangian type. The main issue here is how to derive a design space preconditioner for the approximated reduced gradient which ensures a consistent reduction of the employed penalty function as well as significant design corrections. Some numerical experiments for an alternating approach where any combination and sequencing of steps are used to improve feasibility and optimality done on a variant of the Bratu problem are presented. 相似文献