Large-eddy-simulation-based multiscale modeling of TiO2 nanoparticle synthesis in a turbulent flame reactor using detailed nucleation chemistry

In this work, we present a multiscale computational model for flame synthesis of TiO₂ nanoparticles in a turbulent flame reactor. The model is based on large-eddy simulation (LES) methodology in conjunction with detailed gas-phase chemical kinetics to accurately model the highly complicated combustion and nucleation processes in a turbulent flame. A flamelet-based model is used to model turbulence–chemistry interactions. In particular, the transformation of TiCl₄ to the solid primary nucleating TiO₂ nanoparticles is represented using an unsteady kinetic model considering 30 species and 69 reactions in order to accurately describe the important event of nanoparticle formation. The evolution of the TiO₂ number density function is tracked using the quadrature method of moments (QMOM). For validation purposes, the detailed computational model is compared against experimental data and reasonable agreement is obtained.     

Spectroscopic and Simulation Analysis of Facile PEDOT:PSS Layer Deposition-Silicon for Perovskite Solar Cell

In this research work, we have characterized and simulated a well-known hole transport material (HTM) for perovskite solar cell (PSC) and conductive polyme     

Structural and thermal characterization of CaO–MgO–SiO2–P2O5–CaF2 glasses

The influence of varying the CaO/MgO ratio on the structure and thermal properties of CaO–MgO–SiO₂–P₂O₅–CaF₂ glasses was studied in a series of eight glass compositions in the glass forming region of diopside (CaMgSi₂O₆)–fluorapatite [Ca₅(PO₄)₃F]–wollastonite (CaSiO₃) ternary system. The melt-quenched glasses were characterized for their structure by infrared spectroscopy (FTIR) and magic angle spinning (MAS)-nuclear magnetic resonance (NMR) spectroscopy. Silicon is predominantly present as Q² (Si) species, while phosphorus tends to coordinate in orthophosphate environment. The sintering and crystallization parameters of the glasses were obtained from differential thermal analysis (DTA) while crystalline phase fractions in the sintered glass–ceramics were analyzed by X-ray diffraction adjoined with Rietveld refinement. Diopside, fluorapatite, wollastonite and pseudowollastonite crystallized as the main crystalline phases in all the glass–ceramics with their content varying with respect to variation in CaO/MgO ratio in glasses. The implications of structure and sintering behaviour of glasses on their bioactivity were discussed.     

Integrated ozone–photo–Fenton process for the removal of pollutant from industrial wastewater

The use of hybrid advanced oxidation processes(AOPs) for the removal of pollutants from industrial effluents has been extensively studied in recent literature. The aim of this study is to compare the performance of the photo,Fenton, photo-Fenton and ozone–photo–Fenton processes in terms of color removal and chemical oxygen demand(COD) removal of distillery industrial effluent together with the associated electrical energy per order. It was observed from the experimental results that the O_3/UV/Fe~(2 +)/H_2O_2 process yielded a 100% color and95.50% COD removals with electrical energy per order of 0.015 k W·h·m~(-3) compared to all other combinations of the AOPs. The effects of various operating parameters such as H_2O_2 and Fe~(2+) concentration, effluent pH, COD concentration and UV power on the removal of color, COD and electrical energy per order for the ozone–photo–Fenton process was critically studied and reported. The color and COD removals were analyzed using a UV/Vis spectrometer and closed reflux method.     

Towards β-phase formation probability in spin coated PVDF thin films

This work aimed towards the study on variations in the percentage of β-phase in Poly vinylidene fluoride (PVDF) thin films deposited by spin coating technique. PVDF is a semi-crystalline polymer which exhibits α, β, γ and δ polymorphs. Among these polymorphs, generally it crystallizes in a non-polar α-phase, which is of little importance as far as its applications are concerned. However, the β-phase, which exhibits spontaneous polarity created tremendous interest and showed a path towards the devices based on its pyro- and piezoelectric properties. Fourier Transform Infrared (FTIR) spectroscopy and XRD techniques were used to study the percentage of formation of β-phase in spin coated PVDF thin films at different processing conditions viz. spin rotation speed (rpm), solution concentration and annealing temperature. We identified the β-phase percentage in PVDF thin films, which are (i) Deposited with different rotation speeds ranging from 1000 to 9000 rpm, (ii) Annealed at different temperatures viz.; room temperature to 100C, and (iii) Deposited at various solution concentrations. It is identified that percentage of formation of β-phase is high in the films deposited with 15(w/v)% solution concentration which is annealed at 100C. The films deposited at higher rpm is showing low enhancement in the β-phase with annealing temperature.     

Synergistic influence of alloy grain size and Si content on the oxidation behavior of 9Cr−1Mo steel

The synergistic influence of prior-austenite grain size and silicon content of 9Cr–1Mo steel on the resistance to scale spallation has been studied in air at 773 K (for 500 hr) and 973 K (12 hr). Two steels, irrespective of their grain size and Si content, did not show spallation during oxidation at 773 K. Spallation occurred at 973 K, and fine-grain steels exhibited less spallation resistance than coarse-grain ones (in low-as well as high-Si steels). Among the four possible combinations of grain size ans Si content, the steel with low Si and fine grains showed least resistance to spallation, while the steel with high Si and coarse grains showed the best resistance. Spallation was found to initiate in the areas adjoining the oxide ridges formed at the alloy grain boundaries. Oxide scales at the ridges and within the grains were analyzed by scanning electron microscopy (SEM/EDX) and secondary-ion mass spectrometry (SIMS). These analyses suggest depletion of silicon from the areas adjoining grain boundaries, resulting in thicker scaling that triggers spallation in such areas. For similar grain-size materials, the necessary thickness for spallation was attained earlier with low-Si steel rather than in high-Si steel.     

Improved device performance based on crosslinking of poly (3-hexylthiophene)

Diode devices (glass/ITO/polymer/Al) have been fabricated using poly (3-hexylthiophene) (P3HT) crosslinked with two different biaryl crosslinkers. Crosslinking was performed by exposing the thin films with different wt% of crosslinker to UV irradiation and progress of crosslinking was monitored by IR spectroscopy. An increase in hole mobility of two orders of magnitude has been observed after crosslinking.     

Nanocrystalline electroless nickel poly-alloy deposition: incorporation of W and Mo

Autocatalytic quaternary Ni–W–Mo–P films were prepared using alkaline citrate based baths and compared with binary Ni–P and ternary Ni–W–P, Ni–Mo–P coatings. Energy dispersive X-ray analysis showed that the binary Ni–P deposit contained 12·2 wt-%P. Codeposition of tungsten in Ni–P matrix resulted in ternary Ni–W–P with 4·1 wt-%P and 5·2 wt-%W. Incorporation of molybdenum led to a ternary Ni–Mo–P deposit containing 4·1 wt-%Mo and 11·2 wt-%P. Presence of both sodium tungstate and sodium molybdate in the basic bath resulted in a quaternary coating with 3·6 wt-%W, 6·7 wt-%Mo and 2·5 wt-%P. X-ray diffraction patterns of all the deposits revealed a single peak for Ni (1 1 1). The quaternary alloy exhibited a sharper peak showing the more crystalline nature of the deposit. Field emission scanning electron microscopy studies of the deposits showed the presence of smooth nodules for ternary deposits, but coarse and well defined nodules for quaternary deposits. Phase transformation behaviour of the ternary Ni–W–P deposit revealed a single exothermic peak at 440°C. However, ternary Ni–Mo–P deposit exhibited a split type high temperature peak at 397 and 461°C and the quaternary Ni–W–Mo–P deposit showed a single high temperature peak at 485°C. Microhardness measurements showed that the quaternary Ni–W–Mo–P deposit exhibited increased hardness of 920 HV(50 gf) when heat treated for 1 h at 400°C.     

Stress Corrosion Cracking Study of Aluminum Alloys Using Electrochemical Noise Analysis

Stress corrosion cracking studies of aluminum alloys AA2219, AA8090, and AA5456 in heat-treated and non heat-treated condition were carried out using electrochemical noise technique with various applied stresses. Electrochemical noise time series data (corrosion potential vs. time) was obtained for the stressed tensile specimens in 3.5% NaCl aqueous solution at room temperature (27 °C). The values of drop in corrosion potential, total corrosion potential, mean corrosion potential, and hydrogen overpotential were evaluated from corrosion potential versus time series data. The electrochemical noise time series data was further analyzed with rescaled range (R/S) analysis proposed by Hurst to obtain the Hurst exponent. According to the results, higher values of the Hurst exponents with increased applied stresses showed more susceptibility to stress corrosion cracking as confirmed in case of alloy AA 2219 and AA8090.     

Tensile strengthening in the nickel-base superalloy IN738LC

The tensile properties of superalloy IN738LC with different precipitate microstructures are evaluated at room temperature, 650 °C, 750 °C, and 85 °C at two different strain rates. The properties can be presented in two groups based on the comparable closeness of the values obtained—those of microstructures C and M, with coarse and medium size precipitates, and those of microstructures F and D, with fine and duplex size (medium + fine) precipitates. Preferred orientations, lattice parameters, and metallography are used to characterize the microstructure and tensile testing to determine the yield strength, tensile strength, and strain hardening coefficients. An anomalous increase in yield strength is observed, which occurs at temperatures about 100 °C higher with higher strain rate than with lower strain rate applied. The experimental results show that the yield strength is influenced by preferred orientations and precipitate size, while the tensile strength is effected by the size and morphology of precipitates.