A novel binary gaining–sharing knowledge-based optimization algorithm for feature selection

Neural Computing and Applications - To obtain the optimal set of features in feature selection problems is the most challenging and prominent problem in machine learning. Very few human-related...     

Microwave-assisted preparation of mesoporous-activated carbon from coconut (Cocos nucifera) leaf by H3PO4 activation for methylene blue adsorption

Mesoporous-activated carbon was prepared from fallen coconut (Cocos nucifera) leaf, an agricultural waste through a microwave-induced H₃PO₄ activation process. The characterization of the coconut leaf–activated carbon (CAC) was evaluated through the iodine number, ash content, bulk density, and moisture content. Fourier transform infrared spectroscopy, scanning electron microscope, Brunauer–Emmett–Teller (BET) surface area, X-ray diffraction, and pH_PZC. CAC has a mesopore content of 84% with an average pore size of 36.5?Å and a large BET surface area of 632?m²/g. The uptake properties of the CAC with methylene blue was evaluated at different CAC dosage levels (0.2–10?g/L), initial pH (3–10), methylene blue concentration (50–350?mg/L), and time (0–360?min) using batch mode operation. The kinetic profiles were described by the pseudo-second-order kinetics. The equilibrium data were well fitted to the Langmuir model with a maximum monolayer adsorption capacity of 250?mg/g at 30°C. Thermodynamic functions indicate a spontaneous and exothermic nature of the adsorption process. This study indicates that coconut leaves are a promising renewable precursor that can be utilized to develop an efficient mesoporous-activated carbon.     

Microstructure and High Temperature Impression Creep Properties of Mg–3Ca–xZr (x = 0.3, 0.6, 0.9 wt%) Alloys

The current study has investigated the influence of zirconium (Zr) addition to Mg–3Ca–xZr (x = 0.3, 0.6, 0.9 wt%) alloys prepared using argon arc melting on the microstructure and impression properties at 448–498 K under constant stress of 380 MPa. Microstructural analysis of as-cast Mg–3Ca–xZr alloys showed grain refinement with Zr addition. The observed grain refinement was attributed to the growth restriction effect of Zr in hypoperitectic Mg–3Ca–0.3 wt% Zr alloys. Heterogeneous nucleation of α-Mg in properitectic Zr during solidification resulted in grain refinement of hyperperitectic Mg–3Ca–0.6 wt% Zr and Mg–3Ca–0.9 wt% Zr alloys. The hardness of Mg–3Ca–xZr alloys increased as the amount of Zr increased due to grain refinement and solid solution strengthening of α-Mg by Zr. Creep resistance of Mg–3Ca–xZr alloys increased with the addition of Zr due to solid solution strengthening of α-Mg by Zr. The calculated activation energy (Q_a) for Mg–3Ca samples (131.49 kJ/mol) was the highest among all alloy compositions. The Q_a values for 0.3, 0.6 and 0.9 wt% Zr containing Mg–3Ca alloys were 107.22, 118.18 and 115.24 kJ/mol, respectively.     

Effect of V2O5–TeO2 Glass Addition on Dielectric Properties of CaCu3Ti4O12 Ceramics Prepared by Solid State Method

CaCu₃Ti₄O₁₂ (CCTO) is well known to have colossal dielectric constant in the range of 10⁵. However, CCTO has considerably high dielectric loss values (tanδ > 0.1) at room temperature and 1 kHz. In this work, addition of glass to CCTO was suggested in order to improve its dielectric properties. The effect of V₂O₅–TeO₂ (VT) glass addition on microstructure and dielectric properties of CCTO ceramics were investigated. Dielectric measurements were carried out for (1 ? x) CCTO-(x) V₂O₅–TeO₂ (x = 0, 0.03, 0.05, 0.10) samples in the frequency range of 10²–10⁶ Hz using impedance spectrometer. Electron micrographs showed that low melting VT glass addition facilitated the grain growth of CCTO. As VT glass amount increased, dielectric constant decreased. The drop, though within reasonable values (~10⁵), may related to the presence of grain boundary glassy phase which itself has low dielectric constant. However, the dielectric loss of the composite has decreased after VT glass addition. The low melting V₂O₅–TeO₂ glass aided in liquid phase sintering and improved the grain boundary resistance which resulted in decreased leakage currents.     

Microstructure and Hardness Properties Investigation of Ti and Nb Added FeNiAlCuCrTi x Nb y High Entropy Alloys

Properties of pure metals can be enhanced by alloying with other metallic or non-metallic elements according to the need. However, as multiple alloying elements in an alloy may lead to the formation of many intermetallic compounds with complex microstructures and poor mechanical properties, new types of metallic alloys called high entropy alloys with at least five elements with equimolar ratios were developed. In this study, FeNiAlCuCrTi _x Nb _y (x, y = 0, 0.5, 1.0, 1.5) alloys have been prepared using Ar arc melting technique. Microstructural studies using scanning electron microscope and XRD showed that Ti addition promoted secondary BCC₂ phase whereas, Nb acted as FCC stabilizer. Samples with combined Nb and Ti addition showed FCC₁ and FCC₂ structure with Nb-rich FCC₂ dendritic phase as dominant phase. Though, individual Nb and Ti additions have resulted in increased hardness, combined additions have resulted in highest hardness of 797 HV under 1 kg load.     

Anomalous Optical Properties of xSrO–10PbO–(90 − x)B<Subscript>2</Subscript>O<Subscript>3</Subscript> Glass System

Raman and UV–Vis spectral analysis of xSrO–10PbO–(90 ? x)B₂O₃ glasses were carried out to elucidate the structural and optical behaviour due to borate anomaly. Raman analysis revealed that the glasses consisted of mainly trigonal groups (metaborate) and tetrahedral groups (ditri/dipentaborate and diborate) at lower SrO content. Concentration of diborate groups reached a maximum value at x = 30 mol% and were replaced by pyroborate, metaborate and orthoborate groups as SrO content in the glass increased. Maximum value of optical band gap (E _opt ) and minimum values of electronic polarizability (α_O2?), optical basicity (Λ) and refractive index (n) were obtained when x = 25 mol%, which was lower compared to maximum of diborate group (x = 30 mol%) as observed from Raman spectroscopic analysis. Observed mismatch in diborate groups and E _opt maxima was attributed to the formation of weak coordinated covalent bonds during structural transformation and addition of cation with high polarizability to the xSrO–10PbO–(90 ? x)B₂O₃ glass.     

Effect of Mo on the High-Temperature Creep Resistance and Machinability of a Recycled Al-Alloy with High Iron Impurity

Journal of Materials Engineering and Performance - Reported work focuses on the effect of morphology of the Fe-rich intermetallic phases on the machinability of Al-alloy containing &gt;2wt.%...     

Microstructural and Mechanical Properties Investigation of TiC Reinforced Hardface Alloy Deposited on Mild Steel Substrate

Wear is one of the major problems faced in industry that reduces the life of industrial components and increases the operating costs. Therefore, hardfacing is widely employed by engineers to minimize components’ wear, in which single or multiple layers of hard material that mainly consists of carbides deposited on the base metal. However, these carbide-based materials suffer from solidification cracking due to lack of ductility. In this study, titanium carbide (TiC) reinforced alloy steel deposited using self-shielded flux cored arc welding technique. The microstructure and phase analysis in the hardfaced deposit by scanning electron microscope, energy dispersive x-ray and X-ray diffractometer revealed that the microstructure consists of finely distributed TiC within matrix of martensite and some retained austenite. Microhardness test and pin-on-disk wear test had shown that the clad deposit posses better hardness and wear resistance. Retained austenite formation and TiC precipitation were discussed in detail and correlated with the mechanical properties.     

Effect of Zr Addition on Microstructure and Properties of FeCrNiMnCoZr x and Al0.5FeCrNiMnCoZr x High Entropy Alloys

In this study, the effect of Zr addition on phase formation, microstructure, and hardness of FeCrNiMnCoZr _x and Al_0.5FeCrNiMnCoZr _x were investigated. High entropy alloys (HEA) were synthesized using arc melting technique in argon (Ar) atmosphere (x = 0, 0.1, 0.2, 0.3). Ingots were homogenized for 24 h at 900 °C in Ar atmosphere. Phase formation, microstructure and hardness of HEAs were investigated using field emission scanning electron microscope, X-ray diffraction and Vickers microhardness tester. Electron micrographs of HEAs showed majorly dendritic(DR) and interdendritic(ID) phases. For both FeCrNiMnCoZr _x and Al_0.5FeCrNiMnCoZr _x alloys, amount of ID phases is seen to increase with increased Zr content. Aluminium containing HEAs showed fine needle-shaped precipitates dispersed throughout the matrix phase. XRD results confirmed the presence of mixed FCC/BCC phases in FeCrNiMnCoZr _x alloys and BCC as majority phase in Al_0.5FeCrNiMnCoZr _x alloys. As the Zr content increased, hardness of HEA increased.