Microstructure,Texture, and Mechanical Behavior of As-cast Ni-Fe-W Matrix Alloy

This article describes the tensile properties, flow, and work-hardening behavior of an experimental alloy 53Ni-29Fe-18W in as-cast condition. The microstructure of the alloy 53Ni-29Fe-18W displays single phase (fcc) in as-cast condition along with typical dendritic features. The bulk texture of the as-cast alloy reveals the triclinic sample symmetry and characteristic nature of coarse-grained materials. The alloy exhibits maximum strength (σ_YS and σ_UTS) values along the transverse direction. The elongation values are maximum and minimum along the transverse and longitudinal directions, respectively. Tensile fracture surfaces of both the longitudinal and transverse samples display complete ductile fracture features. Two types of slip lines, namely, planar and intersecting, are observed in deformed specimens and the density of slip lines increases with increasing the amount of deformation. The alloy displays moderate in-plane anisotropy (A_IP) and reasonably low anisotropic index (δ) values, respectively. The instantaneous or work-hardening rate curves portray three typical stages (I through III) along both the longitudinal and transverse directions. The alloy exhibits dislocation-controlled strain hardening during tensile testing, and slip is the predominant deformation mechanism.     

Cobalt(III)-mediated oxidative destruction of phenol using divided electrochemical cell

Mediated electrochemical oxidation is one of the suitable processes for the destruction of hazardous organic compounds and the dissolution of nuclear wastes at ambient temperature and pressure. The electrochemical oxidation of Co(II) was carried out in an undivided and divided electrochemical cell. The formation of Co(III) was studied in an divided electrochemical cell by varying conditions such as temperature and concentration of nitric acid in a batch type electrochemical reactor in recirculation mode. It was found that the formation of Co(III) increased with increasing nitric acid concentration and decreased with increasing temperatures. The produced Co(III) oxidant was then used for the destruction of phenol. It was noted that phenol could be mineralized to CO₂ and water by Co(III) in nitric acid under different nitric acid concentrations and temperatures. The evolved CO₂ was continuously measured and used for the calculation of destruction efficiency. The destruction was increased with increasing nitric acid concentration as well as the temperature. The maximum efficiency was observed to be 78% based on CO₂ evolution for 5,000 ppm phenol solution at 60 °C in a continuous feed mode. The destruction efficiency was increased 28% by addition of silver at 25 °C.     

Carbon nanotubes: are they dispersed or dissolved in liquids?

Carbon nanotubes (CNTs) constitute a novel class of nanomaterials with remarkable applications in diverse domains. However, the main intrincsic problem of CNTs is their insolubility or very poor solubility in most of the common solvents. The basic key question here is: are carbon nanotubes dissolved or dispersed in liquids, specifically in water? When analyzing the scientific research articles published in various leading journals, we found that many researchers confused between "dispersion" and "solubilization" and use the terms interchangeably, particularly when stating the interaction of CNTs with liquids. In this article, we address this fundamental issue to give basic insight specifically to the researchers who are working with CNTs as well asgenerally to scientists who deal with nano-related research domains.Among the various nanomaterials, CNTs gained widespread attention owing to their exceptional properties, good chemical stability, and large surface area [1,2]. CNTs are extremely thin tubes and feature an extremely enviable combination of mechanical, thermal, electrical, and optical properties. Their size, shape, and properties construct them as prime contenders for exploiting the growth of a potentially revolutionary material for diverse applications.Nevertheless, the main intrinsic drawback of CNTs is their insolubility or extremely poor solubility in most of the common solvents due to their hydrophobicity, thus creating it tricky to explore and understand the chemistry of such material at the molecular level and device applications. Though diverse approaches [3] have been introduced to improve the dispersion of CNTs in different solvents including water, challenges still remain in developing simple, green, facile, and effective strategies for a large-scale production of CNT dispersions. To this end, in many studies a wide range of agents have been used. To give a few examples: solvents [4], biopolymers [5], and surfactants [6]. Meanwhile, when analyzing the scientific research articles published in various leading journals, regarding the dispersion of CNTs, it is really puzzling owing to the usage of different terminologies with respect to the dispersion of CNTs. Most of the studies indicated "dispersion"; however, considerable quantities of articles were published with the term "solubilization", which can be evidently seen from the literature analysis [7]. Hence, many researchers confound "dispersion" and "solubilization" and use the terms interchangeably, especially when describing the interaction of CNTs with solvents. Many scientists have mentioned that CNTs can be "solubilized in water or organic solvents" by means of polymers and/or surfactants, which is ambiguous. It is evident that there is, as a result of that, a lot of confusion regarding this fundamental matter. The basic and fundamental key question here is: are CNTs dissolved or dispersed in a liquid?Basically, "dispersion" and "solubilization" are different phenomena. Dispersion and solubilization can be defined as "a system, in which particles of any nature (e.g., solid, liquid, or gas) are dispersed in a continuous phase of a different composition (or state)" [8] and a "process, by which an agent increases the solubility or the rate of dissolution of a solid or liquid solute" [9], respectively. Hence, in general, the dispersion of solute particles in solvents leads to the formation of colloids or suspensions, and solutions may be obtained as a result of solubilization of solute molecules or ions in the specified solvent. Furthermore, dispersion is mostly related to solute particles, whereas solubility or solubilization is generally connected with solute molecules or ions.The main differences between a colloid and a solution are: A solution is homogenous and remains stable and does not separate after standing for any period of time. Further it cannot be separated by standard separation techniques such as filtration or centrifugation. A solution looks transparent and it can transmit the light. Also, solutions contain the solute in a size at the molecular or ionic level, typically less than 1 nm or maximum a few nm in all dimensions. A colloid is a mixture with particles sizes between 1 and 1000 nm in at least one dimension. It is opaque, non-transparent, and the particles are large enough to scatter light. Colloids are not as stable as solutions and the dispersed particles (comparatively larger-sized particles) may be conveniently separated by standard separation techniques such as (ultra)centrifugation or filtration. Frequently, dispersed particles in colloidal systems may slowly agglomerate owing to inter-particle attractions over prolonged periods of time and, as a result, colloidal dispersions may form flocs or flakes.As far as CNTs are concerned, even though the diameter of the tubes is in the nanometer range (approximately between 0.4 and 3 nm for single-walled carbon nanotubes, and 1.4 and 100 nm for multi-walled carbon nanotubes) [10], their length can be up to several micrometers to millimeters. Further, it is a well-known fact that CNTs are not equal in size with respect to both diameter and length. Hence, the result of dispersion techniques mostly used and adopted to produce well-dispersed CNTs in either aqueous and/or organic media are typically dispersions of differently sized tubes. Consequently, based on the definition [6,7] and the abovementioned points, the mixture of CNTs and water or organic solvents, whether in the presence or non-presence of dispersing agents such as surfactants or polymers, is just a colloidal dispersion and not a solution. Figure ​Figure11 shows the schematic illustration for the formation of dispersed CNTs in a liquid with the aid of a dispersing agent. Simultaneously, the dispersion can result in a debundling or individualization of the bundled CNTs.Open in a separate windowFigure 1Schematic showing the transition of the bundled to the individualized, dispersed state of carbon nanotubes in a liquid with the aid of a dispersing agent.Therefore, "solubilization" is a process to achieve a stable solution, whereas "dispersion" is a form of colloidal system. Here we conclude that the mixture obtained by using CNTs and a liquid medium (water or organic solvents) with or without surfactants or polymers is a dispersion of CNTs in the medium, but not a solution. Further, in our opinion, one cannot solubilize CNTs in water or organic solvents. Hence, we recommend to restrict the use of the term "solubilization" or "solution," instead we should use the term "dispersion" or "colloid," when dealing with CNTs. Further, we think that this should be also applicable for nanoparticles of comparable dimensions such as metal and metal oxide nanoparticles, polymer nanoparticles, etc., if the criteria of the definitions given above are fulfilled.In short, the term "dispersion" should exclusively be used as far as CNTs are concerned, and the use of the term "solution" should be avoided or restricted.     

Characterization of MHz pulse repetition rate femtosecond laser-irradiated gold-coated silicon surfaces

In this study, MHz pulse repetition rate femtosecond laser-irradiated gold-coated silicon surfaces under ambient condition were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), and X-ray photoelectron spectroscopy (XPS). The radiation fluence used was 0.5 J/cm² at a pulse repetition rate of 25 MHz with 1 ms interaction time. SEM analysis of the irradiated surfaces showed self-assembled intermingled weblike nanofibrous structure in and around the laser-irradiated spots. Further TEM investigation on this nanostructure revealed that the nanofibrous structure is formed due to aggregation of Au-Si/Si nanoparticles. The XRD peaks at 32.2°, 39.7°, and 62.5° were identified as (200), (211), and (321) reflections, respectively, corresponding to gold silicide. In addition, the observed chemical shift of Au 4f and Si 2p lines in XPS spectrum of the irradiated surface illustrated the presence of gold silicide at the irradiated surface. The generation of Si/Au-Si alloy fibrous nanoparticles aggregate is explained by the nucleation and subsequent condensation of vapor in the plasma plume during irradiation and expulsion of molten material due to high plasma pressure.     

New Insights into the Electrochemical Behavior of Hematite (<Emphasis Type="Italic">α</Emphasis>-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>) Microparticles in Strong Aqueous Basic Electrolyte: Formation of Metallic Iron

A detailed electrochemical study of cubic α-Fe₂O₃ microparticles has been carried out in strong aqueous LiOH electrolyte. The α-Fe₂O₃ was synthesized hydrothermally and investigated in the form of an electrochemical cell using an alkaline solution, ‘α-Fe₂O₃|LiOH (saturated), ZnSO₄ (1 M)|Zn’. In this cell, the α-Fe₂O₃ cathode showed a reversible capacity of ca 220 mAh/g within cut-off voltages of 0 and 1.5 V under the constant current of 0.3 mA. The electrochemical performance was attributed to the reversible formation of both proton and lithium intercalation products (FeOOH and LiFeO₂) detected in the cathode material. Interestingly, at a lower discharge current of 0.1 mA, some of the hematite phase was reduced to metallic iron after yielding 336 mAh/g. The various possible electro-reduction reactions, which have direct electro-hydrometallurgical implications, are analyzed and discussed.     

Raman and infrared study of 100 MeV swift Ag heavy ion irradiation effects in CaSO4·2H2O single crystals

The modifications of calcium sulphate (CaSO₄·2H₂O) single crystals are investigated by means of Raman and Fourier transform infrared spectroscopy (FT-IR) using 100 MeV Ag⁸⁺ ions in the fluence range 1 × 10¹¹ to 5 × 10¹³ ions/cm². It is observed that the intensities of the Raman modes decrease with increase in ion fluence. We determined damage cross-section (σ) for all the Raman active modes and found to be different for different Raman modes. Further, FT-IR studies have been carried out to confirm surface amorphisation for a fluence of 1 × 10¹³ ions/cm². It is observed that the absorption peaks at 1132–1156 cm⁻¹ corresponds to ν₃(SO₄²⁻) mode. The decrease in Raman peaks intensity with ion fluence is attributed to degradation of ν₃(SO₄²⁻) modes present on the surface of the sample.     

Deformation behavior of an ordered B2 phase in Ti–25Al–25Zr alloy

The mechanical behavior of the B2 phase in alloy Ti–25Al–25Zr has been studied under compression. True stress–strain curve exhibits similar behavior to those of typical B2 intermetallics such as NiAl and FeAl. The alloy exhibits highest yield strength in comparison to those reported in other titanium based B2 alloys with around 2% plastic strain. The microstructural characterization of specimen after compression reveals that the B2 phase transforms to an orthorhombic martensitic phase during compression.     

Double Layer Coatings: A New Technique for Maintaining Physico-Chemical Characteristics and Antioxidant Properties of Dragon Fruit During Storage

A double layer coating was evaluated for maintenance of quality of dragon fruit during storage at 10?±?2 °C and 80?±?5 % RH for 28 days. Significant differences (p?<?0.05) were observed between control and the treated fruit. However, a double layer coating with 600 nm droplet size?+?1.0 % conventional chitosan showed promising results in all the tested parameters, while the fruit treated with 1,000 nm droplet size?+?1.0 % conventional chitosan showed some negative effects on fruit surface. Increase in weight loss was 12.0 % in fruit treated with 600 nm droplet size and 1.0 % conventional chitosan as compared to the control. Antioxidants and gaseous analysis also proved the efficacy of double layer coatings with 600 nm droplet size?+?1.0 % conventional chitosan. Thus it can be concluded from the present investigation that double layer coating could be used for maintaining quality in dragon fruit for up to 28 days without any off-flavours.     

Antlion Algorithm Optimized Fuzzy PID Supervised On-line Recurrent Fuzzy Neural Network Based Controller for Brushless DC Motor

In this paper, Antlion algorithm optimized Fuzzy PID supervised on-line Recurrent Fuzzy Neural Network based controller is proposed for the speed control of Brushless DC motor. Learning parameters of the supervised on-line recurrent fuzzy neural network controller, i.e., learning rate (η), dynamic factor (α), and number nodes (N_i) are optimized using Genetic algorithm, Particle Swarm optimization, Ant colony optimization, Bat algorithm, and Antlion algorithm. The proposed controller is tested with different operating conditions of the Brushless DC motor, such as varying load conditions and varying set speed conditions. The time domain specifications such as rise time, overshoot, undershoot, settling time, recovery time, and steady state error and also integral performance indices such as root mean square error, integral of absolute error, integral of squared error, and integral of time multiplied absolute error are measured and compared for above optimized controller. Simulation results show Antlion algorithm optimized Fuzzy PID supervised on-line recurrent fuzzy neural network based controller has proved to be superior than other considered controllers in all aspects. In addition, the experimental verification of proposed control system is presented to test the effectiveness of the proposed controller with different operating conditions of the Brushless DC motor.