In this work, the mechanism of WC formation during mechanical alloying and subsequent annealing of nickel, aluminum, tungsten, and graphite powder mixtures was investigated. X-ray diffraction was used to evaluate phase changes. Microstructural and morphological evaluations of the powders were examined by FESEM and TEM. The XRD results confirmed that phase changes occurred by increasing milling time. After 10?h of ball milling, NiAl and W2C phases formed and new tungsten carbides were synthesized by increasing of milling time. After 40?h, W was consumed completely and WC, WC1-x, W2C carbides along with NiAl were produced. After heat treatment of 40?h milled powder, W2C and WC1-x phases disappeared and NiAl/WC nanocomposite was formed. The results confirmed that the WC formation was a gradual reaction controlled by atomic diffusion. 相似文献
The pile bearing capacity is considered as the most essential factor in designing deep foundations. Direct determination of this parameter in site is costly and difficult. Hence, this study presents a new technique of intelligence system based on the adaptive neuro-fuzzy inference system (ANFIS)-group method of data handling (GMDH) optimized by the imperialism competitive algorithm (ICA), ANFIS-GMDH-ICA for forecasting pile bearing capacity. In this advanced structure, the ICA role is to optimize the membership functions obtained by ANFIS-GMDH technique for receiving a higher accuracy level and lower error. To develop this model, the results of 257 high strain dynamic load tests (performed by authors) were considered and used in the analysis. For comparison purposes, ANFIS and GMDH models were selected and built for pile bearing capacity estimation. In terms of model accuracy, the obtained results showed that the newly developed model (i.e., ANFIS-GMDH-ICA) receives more accurate predicted values of pile bearing capacity compared to those obtained by ANFIS and GMDH predictive models. The proposed ANFIS-GMDH-ICA can be utilized as an advanced, applicable and powerful technique in issues related to foundation engineering and its design.
Water Resources Management - Long-term sustainability in water supply systems is a major challenge due to water resources depletion, climate change and population growth. This paper presents a... 相似文献
In this paper, a switching scheme is presented to reduce the capacitive digital-to-analog converter (DAC) switching energy, area, and the number of switches in successive approximation register (SAR) analog-to-digital converters (ADCs). In the proposed DAC switching method, after a few most significant bits (MSBs) decision, the sampled differential input signal is shifted into two special regions where the required DAC switching energy and area is less than the other regions. This technique can be utilized in most of the previously reported DAC switching schemes to further reduce the capacitive DAC switching energy and area. The conventional and two recently presented DAC switching techniques are utilized in the proposed SAR ADC to evaluate its usefulness. 相似文献
The electrocatalytic oxidation of ethanol in alkaline medium has been studied using Ag/Pd bimetallic nanoparticles modified carbon ionic liquid electrode (Ag/PdCILE). The electrochemical characterizations were performed using cyclic voltammetry (CV), chronoamperometry and electrochemical impedance spectroscopy (EIS). The results show that the electrode reveals excellent characteristics such as high catalytic activity, stability, tolerance toward poisoning effects (even at very high ethanol concentrations) and capacity for electrooxidation of ethanol in alkaline medium. The results show that this electrode is very attractive for application in direct ethanol fuel cells. 相似文献
Metals and Materials International - In this paper, the mechanical properties and microstructure of Al6061-graphene oxide (GO) nanocomposites material, produced by stir casting and hot rolling... 相似文献
CuO-VO2/TiO2 as a new nanocomposite was synthesized through hydrothermal method and identified by various spectroscopic techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray analysis (EDX), UV–visible, differential reflectance spectroscopy (DRS), and Mott–Schottky. The presence of nanotubes/nanosheets in the synthesized nanocomposite was confirmed by HR-TEM. The anatase and rutile crystalline forms of TiO2 were detected by Raman spectroscopy and X-ray diffraction (XRD). XPS analysis confirmed the presence of CuO and VO2 in the nanocomposite. The surface area and the band-gap energy of the nanocomposite were determined via N2 adsorption–desorption analysis and DRS. The presence of a p–n junction between TiO2 (n-type) and CuO/VO2 (p-type) was confirmed by the Mott–Schottky analysis. The photocatalytic activity of the nanocomposite against methylene blue (MB), methyl orange (MO), and cango red (CR) was studied under visible-light irradiation. The times of degradation for the decomposition of the dyes were 10–25 min. The rate constants of degradation for MB, MO, and CR were calculated as 0.34, 0.090, and 0.155 min?1, respectively. The catalyst was recovered four times. In addition, the mineralization of the dyes was investigated by chemical oxygen demand (COD). The reaction was performed in the presence of different radical scavengers, and the ·OH was found to be the predominantly active species in the photodegradation of the dyes.
An efficient photocathode consisting of reduced graphene oxide/Cu2O/Cu (rGO/Cu2O/Cu) has been successfully prepared in this work via a facile two step method, consisting of chemical oxidation of a copper foil in alkaline solution using (NH4)2S2O8 as the oxidizing agent, dipping the prepared samples in graphene oxide (GO) solution and calcination at vacuum to form a rGO layer onto Cu2O/Cu photocathode, which acts as a protective layer. The products were composed of a thin Cu2O layer topped with a thin rGO film as the protective coating. The chemical composition and rGO amount in the composite materials were easily controlled by changing the immersion time to enhance PEC performance. UV–Vis spectroscopy, Raman spectroscopy, XRD, SEM, TEM and FTIR spectroscopy were used in the optical and morphological characterization of the graphene oxide and prepared photocathodes. Distinct patches of GO film are formed on the Cu(OH)2 nanostructure surface, as shown by SEM results. Linear sweep voltammetry and chronoamperometry analysis have been applied in the photoelectrochemical characterizations in the dark and under illumination conditions. Photocurrent density provided by rGO/Cu2O/Cu photocathode ??2.54 mA cm??2 is three times greater than that of bare Cu2O/Cu photocathode ??0.82 mA cm??2 at 0 V vs. RHE under illumination. Low photostability of 42% is exhibited by bare Cu2O/Cu photocathode after 200 s irradiation whereas rGO/Cu2O/Cu photocathode shows approximately 98% of the initial photocurrent density. Therefore, a strategy has been developed in this work for the synthesis of this new photocathode using Cu2O/Cu as an effective photocathode for photoelectrochemical (PEC) water splitting. 相似文献