Tuning the peak position of subwavelength silica nanosphere broadband antireflection coatings

Subwavelength nanostructures are considered as promising building blocks for antireflection and light trapping applications. In this study, we demonstrate excellent broadband antireflection effect from thin films of monolayer silica nanospheres with a diameter of 100 nm prepared by Langmuir-Blodgett method on glass substrates. With a single layer of compact silica nanosphere thin film coated on both sides of a glass, we achieved maximum transmittance of 99% at 560 nm. Furthermore, the optical transmission peak of the nanosphere thin films can be tuned over the UV-visible range by changing processing parameters during Langmuir-Blodgett deposition. The tunable optical transmission peaks of the Langmuir-Blodgett films were correlated with deposition parameters such as surface pressure, surfactant concentration, ageing of suspensions and annealing effect. Such peak-tunable broadband antireflection coating has wide applications in diversified industries such as solar cells, windows, displays and lenses.     

On processing of Ni-WC based functionally graded composite clads through microwave heating

Present study focuses on the development of four layered functionally graded clads (FGC) of Ni-WC based composite material on AISI 304 substrate through microwave heating route. Experimental trials were conducted inside a microwave applicator of domestic type at frequency range of 2.45?GHz. The optimal exposure time of 900?W microwave power was varied with compositional gradient and it was from 300 to 360?s. The mechanism of FGC formation through microwave heating was explained and developed FGC was subjected to mechanical and microstructure characterizations. The results of micro-structural analysis revealed that the FGC of ～1.8?mm thickness was produced and was free from any type of interfacial cracks and visible porosity. It was observed that WC particles were randomly dispersed in the nickel matrix. XRD study revealed the formation of inter-metallics, such as NiW₄, NiSi, and Cr₂₃C₆. Maximum value of microhardness was observed in the top FGC layer and was 880?±?30?HV.     

An outlook on comparison of hybrid welds of different root pass and filler pass of FCAW and GMAW with classical welds of similar root pass and filler pass

In the present study, gas metal arc welding and flux cored arc welding were applied on SA516 Gr70 carbon steel material. Two different hybrid passes were applied, wherein flux cored wire and solid wire were applied to root pass and filler pass one by one and vice versa. Besides, two more welds of similar electrode root pass and filler pass of flux cored arc welding and gas metal arc welding were acquired. The comparative analysis was carried out in terms of macrostructure and microstructure examination, tensile testing, hardness variations, and impact testing for these classical welds and hybrid welds. The results reveal that, hybrid welds lead to better impact properties relative to classical welds. Maximum angular distortion of 2.66° was reported with classical weld of gas metal arc welding with solid wire root pass and same filler pass. The maximum impact toughness of 49 J/m³ was reported for flux cored root pass and solid wire filler pass at the weld zone. Maximum tensile strength of 596 MPa was reported for hybrid weld of solid root pass and flux cored filler pass. Microstructures are reported with the presence of different acicular ferrite and grain boundary ferrite. Maximum acicular ferrite of 61% was reported with classical weld of flux cored arc welding.     

Investigation on various welding consumables on properties of carbon steel material in gas metal arc welding under constant voltage mode

In this present work, the influence of different consumables on weld properties of carbon steel plate was studied by automatic gas metal arc welding under constant voltage mode. For all experiments, the process parameters such as welding current of 200 A, voltage of 28 V and welding speed of 200 mm/min were kept constant. The results indicate that the angular distortion remained higher for solid wire, whereas it was minimum for flux-cored wire and the lowest in metal-cored wire. Mechanical properties such as yield strength, tensile strength, elongation and joint efficiency remained high for solid wire relative to cored wire. Excellent impact toughness of the weld metal and heat-affected zone was reported for the flux-cored welds compared with solid wire and metal-cored welds.     

Effect of operating parameters on permeate flux decline caused by cake formation — a model study

A phenomenological model employing cake formation theory has been developed for describing permeate fluxdecline in cross-flow membrane filtration. In the model the physicochemical parameters, which are often difficult to estimate, were excluded. Instead, the flux decline due to cake formation caused by inorganic scaling/precipitation was related to the operating parameters for fouling prediction. The processes of solute deposition on membrane surface and its re-dissolution back to the bulk phase were modeled to estimate dynamic cake formation and permeate flux profiles. The modeled results show that the permeate flux declined rapidly at the early stage of cake formation, then gradually leveled off as time progressed, and eventually reached a steady-state “ultimate” flux when the rate of solid deposition was balanced by back dissolution. Sensitivity analyses show that an increase of cross-flow velocity from 0.06 to 0.14 m/s increased the ultimate flux from 0.016 m/h to 0.035 m/h. Membrane permeability and transmembrane pressure (400-750 kPa) affected the initial flux but not the ultimate flux. The flux decline pattern strongly depended on the specific cake resistance, which affects the time to reach steady state but not the ultimate flux. Verification of the model with data in the literature showed excellent agreement.     

Rapid synthesis of polymer-silica hybrid nanofibers by biomimetic mineralization

Biomimetic formation of silica from polyamines such as poly(ethylene imine) (PEI), inspired by the proteins found in diatoms and sponges, has been actively investigated recently as a potential route to silica formation compared to the conventional sol-gel process. We report silica formation onto nanofibers of PEI blended with poly(vinyl pyrrolidone) (PVP) obtained via electrospinning of their 50:50(w/w) blend. The active component, PEI, catalyzes rapid silica formation, within minutes, upon immersion of the PEI/PVP nanofibers in silica precursor tetramethylorthosilicate (TMOS). The silica formation in nanofibers was then investigated by scanning electron microscopy (SEM), Energy Dispersive X-ray analysis (EDX), differential scanning calorimetry (DSC), thermo-gravimetric analysis (TGA) and Fourier-transform infra-red (FTIR) spectroscopy. The silica content in the PEI/PVP nanofibers could be controlled by pre-treatment of the fibers at different conditions of relative humidity prior to the silicification. Fibers exposed at higher (80%) relative humidity led to higher inorganic (silica) content compared to those exposed to relative dry conditions (<20% relative humidity). Calcination of the fibers indicated that silicification proceeded across the whole fiber cross-section that consisted of nano-structured silica. Such a simple route to rapid formation of organic-inorganic hybrid nanofibers could have applications ranging from catalysis to tissue engineering, and nanocomposites in general.     

Hybridization of filler wire in multi-pass gas metal arc welding of SA516 Gr70 carbon steel

In the present investigation, multi-pass gas metal arc welding (GMAW) of SA516 Gr70 carbon steel was carried out by different filler wires such as solid, metal cored and flux cored, wherein, other process parameters were kept constant. The hybrid approach of multi-pass filler wires was applied to obtain three different welds. The root pass was filled by a solid wire for all three cases while the subsequent filler pass was applied through solid, flux-cored and metal cored filler wires, respectively. Metallographic, mechanical and metallurgical analyses such as macrograph study, optical microscopy, tensile testing and hardness variations were performed to address the quality of weld. The results revealed that defect-free sound welds were produced by the hybrid approach of different filler wires in multi-pass GMAW. Overall cost and time reduction can be achieved through hybrid filler welds, without affecting their mechanical strength. Angular distortion was reported minimum at hybrid weld of solid and metal cored filler wire. Maximum reinforcement with higher penetration was observed at weld of solid and metal cored filler wire. Impact toughness was reported higher in case of hybrid weld of solid and flux cored filler wire. Higher macro hardness was reported at weld of solid and flux cored filler wire.     

Adaptive Neural Fuzzy Inference System for the Detection of Inter-Turn Insulation and Bearing Wear Faults in Induction Motor

The positive features of neural networks and fuzzy logic are combined together for the detection of stator inter-turn insulation and bearing wear faults in single-phase induction motor. The adaptive neural fuzzy inference systems (ANFISs) are developed for the detection of these two faults. These faults are created experimentally on a single-phase induction motor in the laboratory. The experimental data is generated for the five measurable parameters, viz, motor intakes current, speed, winding temperature, bearing temperature, and the noise of the machine. Earlier, the ANFIS fault detectors are trained for the two input parameters, i.e., speed and current, and the performance is tested. Later, the three remaining parameters are added and the five input ANFIS fault detector is trained and tested. It observed from the simulation results that the five input parameter system predicts more accurate results     

Evaluating the use of tricationic reagents for the detection of doubly charged anions in the positive mode by ESI-MS

The analysis of anions remains an important task for many areas of science, and new sensitive analytical methods continue to be of great interest. In this study, we present the use of 17 tricationic reagents for use as gas-phase ion pairing agents for divalent anions. When the anion pairs with the tricationic reagent, an overall positive charge is retained and enables detection by ESI-MS in the positive mode. The 17 tricationic reagents were made from 1 of 4 core structures and 7 terminal charged groups. The effect of these structural elements on the detection sensitivity of the complex is examined empirically. A comparison of signal-to-noise ratios achieved in positive and negative modes also is presented.     

Nanostructured hematite photoelectrochemical electrodes prepared by the low temperature thermal oxidation of iron

We report on a facile low temperature method for the preparation of high surface area, nanostructured α-Fe₂O₃ (hematite) thin films and their application as photoelectrochemical (PEC) water splitting electrodes. The hematite films are fabricated by thermal oxidation in air of DC sputter deposited iron films at temperatures as low as 255 °C. This method results in films with a higher surface area than typically obtained by directly sputtering α-Fe₂O₃. It is shown that beyond a minimum iron thickness, α-Fe₂O₃ nanowires result upon thermal treatment in atmospheric conditions. Structural and optical characteristics of the resulting films are analyzed. The oxidation process is studied in detail and correlated to the photoelectrical properties. The Fe films oxidize in stages via Fe-oxide layers of increasing oxidation states. Resulting photoelectrochemical performance of fully oxidized films is a balance between optical absorption and charge collection, which varies with film thickness. The optimum film achieved a net photocurrent density of 0.18 mA/cm² in 1 M NaOH at 1.23 V vs. RHE under simulated AM1.5 sunlight, amongst the highest values reported for undoped hematite films produced at low temperature.