Phase dependent growth of superficial nanowalls-like structure on TiO2 thin films in molecular hydrogen (H2) annealing environment

We report the surface modification and growth of nanostructures on the surface of titanium oxide thin films during post deposition annealing in molecular hydrogen ambient. Titanium oxide thin films of a thickness of 200 nm were deposited by electron-beam evaporation at a substrate temperature of 300 °C. Films were annealed in 50 and 100 sccm flow rates of hydrogen in the temperature range of 200 °C–600 °C for 4 h. X-ray diffraction analysis showed a polycrystalline structure of the films. Anatase-to-rutile phase transformation took place, and was influenced by the hydrogen flow rate. Atomic force microscopy indicated the growth of 4–6 μm domains enclosed by nanowalls-like boundaries on the surface when the rutile phase was formed. Spectrophotometer measurements indicated that the films were transparent and a red shift in absorption edge was observed due to annealing. The direct band gaps of anatase and rutile were found to be 3.5 eV and 3.2 eV, respectively.     

Investigation of biphasic calcium phosphate/gelatin nanocomposite scaffolds as a bone tissue engineering

The porous scaffold of nanobiphasic calcium phosphate (n-BCP) and gelatin from bovine skin type B was prepared by freeze-drying method. The porogen which used was Naphthalene. EDC (N-(3-dimethyl aminopropyl)-N′-ethyl carbodiimide hydrochloride) for stabilization of gelatin by cross-linking method was used. The scaffold was characterized by SEM, XRD and FTIR. As a result, a biocompatible scaffold with good cell attachment, facility in formation in desired shapes and simplicity in production were prepared for bone tissue engineering.     

Process design for gas condensate desulfurization and synthesis of nano-13X zeolite adsorbent: equilibrium and dynamic studies

This paper summarizes the results of a study of adsorption of sulfur compounds from a high-sulfur feed on improved spherical-shaped nano-AgX zeolite. For this purpose, the nano-AgX zeolite was initially synthesized and improved with silver compounds such as silver nitrate, and then it was utilized in the adsorption process. In order to investigate the equilibrium and dynamics of the adsorption process, adsorptive desulfurization of real feed(i.e., sour gas condensate from the South Pars gas field) was carried out in batch and continuous processes under several operating conditions; a temperature-dependent Langmuir isotherm model was used to fit the equilibrium data. The value of monolayer adsorption capacity(q_m) and adsorption enthalpy(ΔH) were calculated to be 1.044 mmol/g and 16.8 kJ/mol, respectively. Furthermore, a detailed theoretical model was employed in order to model the breakthrough experiments. The results revealed that an increase in the feed flow rate and 1/T values will cause linear and exponential increase in the total mass transfer coefficient(ks). Isotherm and dynamic breakthrough models were found to be in agreement with the experimental data.     

A general formulation for admittance of an open-ended rectangular waveguide radiating into stratified dielectrics

A general approach is presented for calculating the aperture admittance of a rectangular waveguide radiating into layered dielectric media. The two specific geometries of stratified, lossy dielectric media that are addressed terminate into either an infinite half-space or a perfectly conducting surface. The geometries describe two prevalent categories of layered dielectric composites and coatings that often are encountered in practical microwave nondestructive evaluation applications. Solutions are found initially by constructing a complete set of field components and subsequently enforcing the continuity of power flow across the aperture interface of the waveguide. Final results are presented as a superposition of transverse electric and magnetic components of the aperture admittance. The solutions presented allow the systematic calculation of admittance in the presence of arbitrary multilayer media, which in turn may be related to experimentaly measurable quantities of interest. With the practical assumption of dominant mode incidence on the aperture, the final expressions may be implemented without intense computational power, which often is desirable in practice where inaccuracies due to random errors and instrumentation sensitivity render incorporation of more rigorous solutions inefficient. Numerically simulated data also are presented to verify and interpret the results.     

Estimation of Formation Enthalpies of Organic Pollutants from a New Structural Group Contribution Method

Chemical stability and reactivity of organic pollutants is dependent to their formation enthalpies. The main objective of this study is to provide simple straightforward strategy for prediction of the formation enthalpies of wide range organic pollutants only from their structural functional groups. Using such an extended dataset comprising 1694 organic chemicals from 77 diverse material classes benefits the generalizability and reliability of the study. The new suggested collection of 12 functional groups and a simple linear regression lead to promising statistics of R²=0.958, Q_Loo²=0.956, and δ_AEE=57 kJ·mol^-1 for the whole dataset. Moreover, unknown experimental formation enthalpies for 27 organic pollutants are estimated by the presented approach. The resultant model needs no technical software/calculations, and thus can be easily applied by a non-specialist user.     

Nonlinear supersonic flutter of truncated conical shells

A numerical model was developed to investigate the flutter instability of truncated conical shells subjected to supersonic flows. The exact solution of Sanders’ best firstorder approximation was used to develop the finite elements model of the shell. Nonlinear kinematics of Donnell’s, Sanders’ and Nemeth’s theories, in conjunction with the generalized coordinates method, were used to formulate the nonlinear strain energy of the shell. A pressure field was formulated using the piston theory with the correction term for the curvature. Lagrangian equations of motion based on Hamilton’s principle were obtained. A variation of the harmonic balance method was used for developing the amplitude equations of the shell, and a numerical method was used for solving these equations. Results of linear and nonlinear flutter of truncated conical shells were validated against the existing data in the literature. It was observed that geometrical nonlinearities have a softening effect on the stability of the shell in supersonic flows.     

Transparent heat mirrors based on tungsten oxide-silver multilayer structures

Transparent heat mirrors based on tungsten oxide/silver three-layer structures were fabricated using thermal evaporation. The optical and morphological properties of the single layers were first investigated to serve as a basis for the fabrication of the heat mirrors. Only silver films with a thickness higher than 18 nm were found to be continuous. Subsequently, WO₃/Ag/WO₃ multilayers were deposited, where the WO₃ layers thickness was fixed at 35 nm, and the thickness of the silver layer was varied from 18 to 39 nm. The optical properties of the multilayers were measured over the visible and near infrared ranges. These multilayers exhibited the desired heat mirror behavior, namely the transmittance was largely confined to the visible range and the reflectance was diminished in that range. The maximum visible transmittance was 88.3% at 554 nm. Increasing the thickness of the silver films resulted in a decrease of the visible transmittance, with a corresponding increase in the infrared reflectance. Optimization of these two opposing trends was evaluated using a figure of merit, from which the best performance was obtained for multilayers with a silver layer of thickness of 24 nm.     

Preparation of ZIF-8—Pebax 1657 nanocomposite membranes for n-hexane/nitrogen separation as a representative of gasoline vapour recovery

Gasoline vapour emission is hazardous to both human health and the ecosystem and also results in capital loss, altogether revealing the necessity of its recovery. Some ZIF-8–Pebax flat nanocomposite membranes were fabricated by the method of solution casting and used for gasoline vapour recovery as represented by n-hexane vapour/nitrogen separation. Microporous ZIF-8 nanoparticles were synthesized and characterized by Fourier transform infrared (FTIR) and Brunauer–Emmett–Teller (BET) analysis. BET results revealed specific surface area, total volume, and average pore diameter of 940.8 m² · g⁻¹, 0.36 cm³ · g⁻¹, and 1.54 nm, respectively. Pure nitrogen and n-hexane vapour/nitrogen gas mixture permeabilities were measured through the membranes. There was a decline in both permeation rate and selectivity up to 5.0 wt.% of ZIF-8 loading and the next increment at their higher loadings to considerably more values that the pristine membrane. The maximum n-hexane vapour permeability and selectivity at 10.0 wt.% loading of ZIF-8 nanoparticles, the feed flow rate of 173 mL · min⁻¹, and permeate side pressure of −200 mbar were observed as 280.1 Barrer and 106.7, respectively, revealing 60.0% and 36.9% improvements compared with those of the pristine Pebax membrane. Observed 86%–92% n-hexane vapour recovery approves the successful application of the ZIF-8–Pebax nanocomposite membranes for n-hexane/nitrogen separation. The long-term separation performance of 5.0 wt.% ZIF-8 loaded nanocomposite membrane was improved by 76.5% compared with that of the pristine Pebax membrane.     

Chitosan/ZIF‐8 Mixed‐Matrix Membranes for Pervaporation Dehydration of Isopropanol

Zeolitic imidazolate frameworks (ZIF‐8) nanoparticles were successfully synthesized and embedded into a chitosan (CS) polymeric matrix to prepare CS/ZIF‐8 mixed‐matrix membranes (MMMs) in order to investigate the effect of ZIF‐8 addition as novel filler on the dehydration performance of the CS polymeric membrane. MMMs were evaluated using pervaporation (PV) dehydration of isopropanol (IPA). The synthesized ZIF‐8 nanoparticles and MMMs were characterized by X‐ray diffraction, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, Fourier transform infrared spectroscopy, and a swelling study. The PV performance of the prepared MMMs with different ZIF‐8 loadings for IPA dehydration was investigated. For the ZIF‐8/CS MMMs, at the optimum loading the total flux increases significantly with low separation factor reduction. The good PV performance of the ZIF‐8‐incorporated CS membranes for dehydration of IPA is demonstrated.     

Characterization of zinc sulfide (ZnS) nanoparticles Biosynthesized by Fusarium oxysporum

A variety of chemical and physical procedures could be used for the synthesis of metal sulfide nanoparticles. However, these methods suffer from some disadvantages including the use of toxic solvents, generation of hazardous by-products, and high energy consumption. In this work, zinc sulfide (ZnS) nanoparticles were synthesized through an environmentally and economically friendly method using the fungus Fusarium oxysporum. The ZnS nanoparticles were characterized using UV–visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Fluorescence spectroscopy. The obtained results demonstrated the presence of ZnS nanoparticles. Transmission electron microscopy (TEM), also determined their morphology as spherical, and their average size to be about 42 nm.