Raman and Fourier transform infrared (FTIR) spectroscopies have been utilized to measure long-wavelength optical lattice vibrations of high-quality quaternary AlxInyGa1−x−yN thin films at room temperature. The AlxInyGa1−x−yN films were grown on c-plane (0 0 0 1) sapphire substrates with AlN as buffer layers using plasma assisted molecular beam epitaxy (PA-MBE) technique with aluminum (Al) mole fraction x ranging from 0.0 to 0.2 and constant indium (In) mole fraction y=0.1. Pseudo unit cell (PUC) model was applied to investigate the phonons frequency, mode number, static dielectric constant, and high frequency dielectric constant of the AlxInyGa1−x−yN mixed crystals. The theoretical results were compared with the experimental results obtained from the quaternary samples by using Raman and FTIR spectroscopies. The experimental results indicated that the AlxInyGa1−x−yN alloy had two-mode behavior, which includes A1(LO), E1(TO), and E2(H). Thus, these results are in agreement with the theoretical results of PUC model, which also revealed a two-mode behavior for the quaternary nitride. We also obtained new values of E1(TO) and E2(H) for the quaternary nitride samples that have not yet been reported in the literature. 相似文献
Li-ion rechargeable batteries based on polymer electrolytes are of great interest for solid state electrochemical devices
nowadays. Many studies have been carried out to improve the ionic conductivity of polymer electrolytes, which include polymer
blending, incorporating plasticizers and filler additives in the electrolyte systems. This paper describes the effects of
incorporating nano-sized MnO2 filler on the ionic conductivity enhancement of a plasticized polymer blend PMMA–PEO–LiClO4–EC electrolyte system. The maximum conductivity achieved is within the range of 10−3 S cm−1 by optimizing the composition of the polymers, salts, plasticizer, and filler. The temperature dependence of the polymer
conductivity obeys the VTF relationship. DSC and XRD studies are carried out to clarify the complex formation between the
polymers, salts, and plasticizer. 相似文献
This paper presents the decomposition by-products of trifluro-iodo-methane and their relative proportions in the gas phase under the occurrence of partial discharge. The experiment was performed in the presence of water vapor from 250 to 400 ppm under a non-uniform electric field configuration. The experimental results reveal that the by-products of C2F6, C2F4, C2F5I with the amount of 1300, 200, and 55 (CH3I) ppm, respectively, were produced for a cumulative charge of 161 mC. Other by-products, such as C3F8, CHF3, C3F6 CH3I were obtained at less than 30 ppm C2F6 was the dominant gas by-product of trifluro-iodo-methane suffering partial discharge. 相似文献
A metallic nanofluid is a suspension of metallic nanoparticles in a base fluid. Multi-metallic nanoparticles are a combination of two or more types of metallic particles. Such multi-metallic nanoparticles were suspended in water using an ultrasonic vibrator for different total volume fractions and different ratios of metallic/metallic nanoparticles. A transient hot wire setup was built to measure the thermal conductivity of the nanofluid at different temperatures. The experimental results were in good agreement with the results in the literature. Then, the experimental results were used as input data for an adaptive neural fuzzy inference system (ANFIS) to predict the thermal conductivity of the multi-metallic nanofluid. The maximum deviation between the ANFIS results and experimental measurements was 1 %. The predicted results and the experimental data were compared with other models. The ANFIS model was found to have good ability to predict the thermal conductivity of the multi-metallic nanofluid over the range of the experimental results. 相似文献
The electronic structures of carbazole, N-phenylcarbazole (NPC), cyanophenylcarbazole (CPC) and N-ethylcarbazole (NEC) have been calculated using the quantum chemical semi-empirical MINDO/3 method. In this paper, electronic ground states and first singlet excited states of the systems mentioned were investigated. It is observed that the excitation energy of carbazole based on the calculated difference in heats of formation agrees quite well with experimental data obtained from supersonic expansion studies. Calculated energy levels of molecular orbitals and their graphical forms are used qualitatively in elucidating the S0 → S1 excitation electronic origin red shifts observed in carbazole derivatives with respect to the electronic origin of the parent carbazole. It is noted that the red shifts are not just a result of the destabilization of the HOMO of carbazole but are also determined by the nature of the substituting moieties. It is also observed that the LUMO of CPC is not derived from the parent carbazole which partially explains the difference in electronic behaviour as compared with the other derivatives. 相似文献
The sonochemical synthesis of gold nanoparticles (GNPs) with different shapes and size distributions by using high‐intensity focused ultrasound (HIFU) operating at 463 kHz is reported. GNP formation proceeds through the reduction of Au3+ to Au0 by radicals generated by acoustic cavitation. TEM images reveal that GNPs show irregular shapes at 30 W, are primarily icosahedral at 50 W and form a significant amount of nanorods at 70 W. The size of GNPs decreases with increasing acoustic power with a narrower size distribution. Sonochemiluminescence images help in the understanding of the effect of HIFU in controlling the size and shapes of GNPs. The number of radicals that form and the mechanical forces that are generated control the shape and size of the GNPs. UV/Vis spectra and TEM images are used to propose a possible mechanism for the observed effects. The results presented demonstrate, for the first time, that the HIFU system can be used to synthesise size‐ and shape‐controlled metal nanoparticles. 相似文献
Erythrocentaurin is a relatively simple natural product present among the members of Gentianaceae. A preparative method for the isolation of erythrocentaurin from the ethyl acetate fraction of Enicostemma littorale using medium‐pressure liquid chromatography has been reported. The method consisted of a simple step gradient from 10 to 20% ethyl acetate in n‐hexane. Using a 70 × 460 mm Si60 column, this method is capable of processing 20 g of material in <3 h (purity ≈ 97%). The recovery of erythrocentaurin was 87.77%. Estimation of erythrocentaurin in extracts and fractions based on high‐pressure thin‐layer chromatography was carried out on silica gel 60 F254 plates with toluene/ethyl acetate/formic acid (80:18:2 v/v/v) as the mobile phase. The densitometric analysis was performed at 230 nm. A well‐separated compact band of erythrocentaurin appeared at Rf 0.54 ± 0.04. The analytical method showed good linearity in the concentration range of 200–1500 ng/band with a correlation coefficient of 0.99417. The limits of detection and quantification were found to be ≈60 and ≈180 ng/band, respectively. Erythrocentaurin exhibited a concentration‐dependent α‐amylase inhibition (IC50 1.67 ± 0.28 mg/mL). The outcome of the study should be considered for pharmacokinetic and biotransformation studies involving E. littorale. 相似文献
Chiral N‐sulfonyldiamine was successfully anchored on mesoporous MCM‐41 silica. The MCM‐41‐supported chiral N‐sulfonyldiamine was used as an efficient heterogeneous chiral ligand in the asymmetric transfer hydrogenation of ketones. This heterogeneous system offered satisfactory enantioselectivities up to 94 % with excellent conversions. 相似文献
An environmentally benign method of sample preparation based on dispersive liquid–liquid microextraction and solidification of floating organic droplets (DLLME-SFO) coupled with high-performance liquid chromatography with ultraviolet detection has been developed for analysis of non-steroidal anti-inflammatory drugs (NSAIDs) in biological fluids. A low-toxicity solvent was used to replace the chlorinated solvents commonly used in conventional DLLME. Seven
conditions were investigated and optimized: type and volume of extraction solvent and dispersive solvent, extraction time, effect of addition of salt, and sample pH. Under the optimum conditions, good linearity was obtained in the range 0.01–10 µg mL−1, with coefficients of determination (r2) >0.9949. Detection limits were in the range 0.0034–0.0052 µg mL−1 with good reproducibility (RSD) and satisfactory inter-day and intra-day recovery (95.7–115.6 %). The method was successfully used for analysis of diclofenac, mefenamic acid, and ketoprofen in human urine. Analysis of urine samples from a patient 2 and 4 h after administration of diclofenac revealed concentrations of 1.20 and 0.34 µg mL−1, respectively.