Eco-friendly synthesis of large band gap ZnO nanoparticles by trisodium citrate: investigation of annealing effect on structural and optical properties

In this study, large band gap zinc oxide nanoparticles (ZnO-NPs) were prepared by a facile, cost-effective, and eco-friendly co-precipitation method in aqueous solutions. Trisodium citrate was employed as a green and bio-safe complexing agent for zinc ions without using ammonia and/or any organic solution. The annealing effect on crystal structure, morphology, particle size, composition, UV absorption, and fluorescence (FL) properties of the synthesized ZnO-NPs was evaluated using various techniques. The UV–Visible absorption spectra of the ZnO-NPs showed a strong absorption peak in the UV-C region with a wide band gap energy of 4.2–4.4 eV. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) images demonstrated fine spherical particles with approximate diameters of 20–50 nm. The average hydrodynamic diameter and zeta potential values of the as-prepared and the annealed ZnO-NPs in deionized water were 28.2 nm, ? 32.4 mV, 38.9 nm, and ? 16.1 mV, respectively. The FL and UV–Visible results illustrated that the annealing could considerably influence the emission and absorption spectra of the samples in the UV region. The FL and EDX results revealed that the annealing affects the composition, defect points, and states population in the crystal structure of the ZnO-NPs. Practical experiments of exposing the samples to UV radiation and the FL measurements indicated that the ZnO-NPs were sensitive to the excitation wavelengths, therefore, they have potential application in fabricating various types of UV sensors and filters (blockers), as well as photocatalytic activities.

     

Microstructure and mechanical properties of dual phase steels,with different martensite morphology,produced during TLP bonding of a low C-Mn steel

In this research, production of ferrite - martensite dual phase Steels with different martensite morphology was considered during transient liquid phase bonding of a low carbon steel. The steel was bonded using an iron base interlayer with melting point of 1443 K and 40 μm thickness. Bonding process carried out at 1473 K, under pressure of 0.5 MPa, at different holding time of 10, 20, 30 and 40 minutes. Microstructural studies of joint region showed that isothermal solidification completed at the bonding time of 40 minutes. Microstructure of joints made at the bonding time of 10, 20, and 30 minutes consists of two distinct region, athermal and isothermal solidified zones. Microstructure of these zones was studied and chemical composition of these zones was determined by EDS. Joints made with bonding time of 40 minutes were homogenized at 1008 K and then cooled into cold water to produce dual phase ferrite and martensite microstructure with different martensite morphology. According to shear test results, it was found that the shear strength of ferrite - fibrous martensite microstructure is greater than those with ferrite - continuous martensite and ferrite - blocky martensite microstructure.     

Interaction of dense nitrogen plasma with SS304 surface using APF plasma focus device

The nitridation of SS304 surfaces is obtained by irradiating nitrogen ions from Amirkabir plasma focus device, which use multiple focus deposition shots at optimum distance 10 cm from the anode. The Vickers Micro-Hardness values are improved more than twice for the nitrided samples comparing to the nonnitrided ones. The X-ray diffraction (XRD) analysis is carried out in order to explore the phase changes in the near surface structure of the metals. The results of Scanning Electron Microscopy (SEM) indicate changes in surface morphology which are the emergence of smooth and uniform film on the surface of the nitrided metals.     

Application of response surface methodology for optimization and determination of palladium by in-tube ultrasonic and air-assisted liquid–liquid microextraction coupled with flame atomic absorption spectrometry

A highly sensitive, simple and rapid in-tube ultrasonic and air-assisted liquid–liquid microextraction (IT-UAA-LLME) coupled with flame atomic absorption spectrometry was developed for preconcentration and determination of palladium (Pd) in soil and water samples. The effective parameters were optimized by the Plackett–Burman (P–B) and Box–Behnken design (BBD) methods. Under the optimum conditions, the calibration graph was linear over the range of 5–800 μgL^?1 (R² = 0.998). Detection limit, relative standard deviation (RSD) and the enrichment factor were 0.94 μgL^?1, 2.64% (n = 7, C = 40 μgL^?1) and 156, respectively. The proposed method was successfully applied for the determination of trace amounts of Pd in the soil and water samples.     

A closed-loop electronics cooling by implementing single phase impinging jet and mini channels heat exchanger

This paper reports our works in the design and testing of a closed-loop electronics cooling system that adopts bi-technologies: single phase impinging jet and mini channels heat exchanger. The system has the cooling capacity of 200 W over a single chip with a hydraulic diameter of 12 mm. The equivalent heat flux is 177 W/cm². The cooling system maintains the chip’s surface temperature below 95 °C maximum when the ambient temperature is 30 °C. De-ionized water is the working fluid of the system. For the impinging jet, two different nozzles are designed and tested. The hydraulic diameters (d_N) are 0.5 mm and 0.8 mm. The corresponding volume flow rates are 280 mL/min and 348 mL/min. Mini channels heat exchanger has 6 (six) copper tubes with the inner diameter of 1.27 mm and the total length of about 1 m. The cooling system has a mini diaphragm pump and a DC electric fan with the maximum power consumptions of 8.4 W and 0.96 W respectively. The coefficient of performance of the system is 21.4.     

In situ incorporation of nickel nanoparticles into the mesopores of MCM-41 by manipulation of solvent-solute interaction and its activity toward adsorptive desulfurization of gas oil

In this contribution, different amounts of nickel were incorporated into the mesopores of MCM-41 via an in situ approach. A hydrophobic nickel precursor was incorporated into the nanochannels of mesoporous silica by manipulation of solvent-solute interaction. The synthesized material was characterized using X-ray diffraction, nitrogen physisorption, temperature programmed reduction, and transmission electron microscopy. The results implicate the formation of MCM-41 with well-ordered hexagonal structure and establish also the presence of nickel nanoparticles inside the nanochannels of mesoporous silica. Adsorptive desulfurization of gas oil was conducted using the nickel-incorporated MCM-41 samples. The effects of nickel concentration, temperature of process and feed flow rate on the desulfurization process were examined. The MCM-41 containing 6 wt.% of nickel had both the highest breakthrough sulfur adsorption capacity and total sulfur adsorption capacity, which were 0.69 and 1.67 mg sulfur/g adsorbent, respectively. The breakthrough sulfur adsorption capacity was almost regained after reductive regeneration of spent adsorbent. The obtained results suggest that the method applied for the synthesis of Niy/MCM resulted in formation of well-dispersed, accessible and small nickel nanoparticles incorporated into the pores of MCM-41 which might be an advantage for adsorption of refractory sulfur compounds from low sulfur gas oil.     

Development of a conductive composite based on polythiophene/Y-zeolite and its response towards sulfide ions

A new potentiometric sensor electrode for sulfide based on conducting polymer films is introduced. A composite of polythiophene (PTP) with Y-zeolite was prepared via chemical oxidative polymerization of thiophene (TP) in presence of a dispersion of Y-zeolite (powder) in CHCl3 solvent using anhydrous FeCl3 oxidant. Formation of polythiophene and its subsequent SEM and TEM analysis revealed formation of composite particles with average diameter in the range of 0.3–0.35 μm. DC conductivity value of the PTP-Y-zeolite composite was in the order of 10? 2 S/cm, which was indeed high compared to that of PTP, produced under identical conditions as above without the presence of Y-zeolite. This composite as active component with graphite powder and binding liquid was mixed and then used for preparation of solid state electrodes. The working temperature range for this electrode is between 20 and 40 °C. The linear dynamic range is 1 × 10? 7 – 1 × 10? 4 M and measures total sulfide concentration over a range of pH from 5 to 9. The composite electrode showed high selectivity for sulfide in the presence of many common interfering anions (? log KS, IO3?Pot = 6.3, ? log KS, BrO3?Pot = 5.5, ? log KS, S2O32 ?Pot = 4.8).     

Experimental and Numerical Investigation of Mixed-Mode Interlaminar Fracture of Carbon-Polyester Laminated Woven Composite by Using Arcan Set-up

Composite materials are widely used in marine, aerospace and automobile industries. These materials are often subjected to defects and damages from both in-service and manufacturing process. Delamination is the most important of these defects. This paper reports investigation of mixed-mode fracture toughness in carbon–polyester composite by using numerical and experimental methods. All tests were performed by Arcan set-up. By changing the loading angle, α, from 0° to 90° at 15° intervals, mode-I, mixed-mode and mode-II fracture data were obtained. Correction factors for various conditions were obtained by using ABAQUS software. Effects of the crack length and the loading angle on fracture were also studied. The interaction j-integral method was used to separate the mixed–mode stress intensity factors at the crack tip under different loading conditions. As the result, it can be seen that the shearing mode interlaminar fracture toughness is larger than the opening mode interlaminar fracture toughness. This means that interlaminar cracked specimen is tougher in shear loading condition and weaker in tensile loading condition.