Sharif Digital Repository

Friction stir processing (FSP) is a solid state route with a capacity of preparing fine grained nanocomposites from metal sheets. In this work, we employed this process to finely distribute TiO2 nanoparticles throughout an Al–Mg alloy, aiming to enhance mechanical properties. Titanium dioxide particles (30 nm) were preplaced into grooves machined in the middle of the aluminium alloy sheet and multipass FSP was afforded. This process refined the grain structure of the aluminium alloy, distributed the hard nanoparticles in the matrix and promoted solid state chemical reactions at the interfaces of the metal/ceramic particles. Detailed optical and electron microscopic studies showed that the... 

Reduced graphene oxide (RGO) was used to improve the hydrogen sensing properties of Pd and Pt-decorated TiO2 nanoparticles by facile production routes. The TiO2 nanoparticles were synthesized by sol–gel method and coupled on GO sheets via a photoreduction process. The Pd or Pt nanoparticles were decorated on the TiO2/RGO hybrid structures by chemical reduction. X-ray photoelectron spectroscopy demonstrated that GO reduction is done by the TiO2 nanoparticles and Ti–C bonds are formed between the TiO2 and the RGO sheets as well. Gas sensing was studied with different concentrations of hydrogen ranging from 100 to 10,000 ppm at various temperatures. High sensitivity (92%) and fast response time... 

TiO2 nanoparticles were synthesized by hydrothermal assisted sol-gel technique. The preparation parameters including pH value, the amount of water, titanium tetra isopropoxide content, temperature and time of hydrothermal process were investigated by Taguchi statistical experiments to determine the influence of synthesizing variables on the optimal conditions and to realize the highest degree of crystallinity or smallest crystallite size. X-ray diffraction (XRD) analysis and direct band gap energy (Eg) values, measured via diffuse reflectance spectra (DRS), proved that all the samples consist of anatase as a unique phase. Transmission electron microscopy (TEM) and specific surface area... 

Polysulfone (PSU) and polyethersulfone (PES) porous membranes; and mixed polymer with nanoparticles TiO2, were prepared for air humidification. The mechanical properties and morphology of these membranes were studied by Tensile tester and SEM/EDX. The effects of membrane composition and operating factors on humidifier performance were investigated. The results revealed that the membrane composition and its structure have significant effect on humidification. The porous membranes with finger type cavities had higher humidification performance but lower mechanical properties. Water flux of the membranes was about 0.16-0.2L/hm2 at 25°C. Furthermore, adding 0.1wt% TiO2 nanoparticles to casting... 

We report a simple and inexpensive synthesis route of TiO2 nanoparticles using electrical arc discharge between titanium electrodes in oxygen bubbled deionized (DI) water followed by heat treatment. The resulting nanoparticles were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), dynamic light scattering (DLS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). XRD patterns demonstrate formation of TiO2 phase in oxygen bubbled water after heat treatment and dominance of rutile to anatase phase. The size and morphology of TiO2 nanoparticles were studied using different arc currents as a crucial parameter in properties of final... 

A carbon paste electrode (CPE) chemically modified with TiO2 nanoparticles and quinizarine (QZ) was used as a selective electrochemical sensor for the simultaneous determination of minor amounts of d-penicillamine (D-PA) and tryptophan (Trp). This modified electrode showed very efficient electrocatalytic activity for anodic oxidation of both d-PA and Trp. Substantial decreases of anodic overpotentials for both compounds made this analysis possible. Results of square wave voltammetry (SWV) using this modified electrode showed two well-resolved anodic waves for the oxidation of d-PA and Trp, which makes the simultaneous determination of both compounds possible. The peak potential for the... 

In the present paper, the use of a carbon paste electrode modified by 2,2′-[1,2 buthanediylbis (nitriloethylidyne)]-bis-hydroquinone (BH) and TiO2 nanoparticles prepared by a simple and rapid method was described. The modified electrode showed an excellent character for electrocatalytic oxidization of norepinephrine (NE), acetaminophene (AC) and folic acid (FA). Using differential pulse voltammetry (DPV), a highly selective and simultaneous determination of NE, AC and FA has been explored at the modified electrode. Differential pulse voltammetry (DPV) peak currents of NE, AC and FA increased linearly with their concentration at the ranges of 4.0-1100.0 μM, 12.5-500.0 μM and 200.0-3200.0 μM,... 

A carbon paste electrode (CPE) modified with 2,2′-[1,2 butanediylbis(nitriloethylidyne)]-bis-hydroquinone (BBNBH) and TiO2 nanoparticles was used for the sensitive voltammetric determination of epinephrine (EP). The electrochemical response characteristics of the modified electrode toward EP and acetaminophen (AC) were investigated by cyclic and differential pulse voltammetry (CV and DPV). The results showed an efficient catalytic activity of the electrode for the electrooxidation of EP, which leads to a reduction in its overpotential by more than 270 mV. The effects of pH and potential sweep rate on the mechanism of the electrode process were investigated. The modified electrode exhibits an... 

In the present paper, the use of a novel carbon paste electrode modified by N,N'(2,3-dihydroxybenzylidene)-1,4-phenylenediamine (DHBPD) and TiO2 nanoparticles prepared by a simple and rapid method for the determination of dopamine (DA) was described. In the first part of the work, cyclic voltammetry was used to investigate the redox properties of this modified electrode at various solution pH values and at various scan rates. A linear segment was found with slope value of about 48 mV/pH in the pH range 2.0 -12.0. The apparent charge transfer rate constant (ks) and transfer coefficient (α) for electron transfer between DHBPD and TiO2 nanoparticles-carbon paste electrode were calculated. In... 

Reduced graphene oxide (RGO) was used to improve the hydrogen sensing properties of Pd and Pt-decorated TiO2 nanoparticles by facile production routes. The TiO2 nanoparticles were synthesized by sol-gel method and coupled on GO sheets via a photoreduction process. The Pd or Pt nanoparticles were decorated on the TiO2/RGO hybrid structures by chemical reduction. X-ray photoelectron spectroscopy demonstrated that GO reduction is done by the TiO2 nanoparticles and Ti-C bonds are formed between the TiO2 and the RGO sheets as well. Gas sensing was studied with different concentrations of hydrogen ranging from 100 to 10,000 ppm at various temperatures. High sensitivity (92%) and fast response time... 

Colloidal stability of dextran (Dex) and Dex/poly ethylene glycol (PEG) coated TiO2 nanoparticles (NPs) were investigated. The particles were successfully synthesized by a hydrothermal assisted sol-gel technique. The results of Ultraviolet-visible (UV-vis) spectrophotometry showed that Dex and PEG additions during hydrothermal process (HTP) led to the formation of long-term (more than 60 days) stable colloids, while the addition of dispersants after HTP did not have a significant impact on the colloidal stability of NPs. X-ray diffraction (XRD) and selected area electron diffraction (SAED) analyses proved that PEG and/or Dex coated NPs had less crystallinity than the plain TiO2. Fourier... 

A new facile strategy for fabrication of high surface area electrode in the form of mixtures of coated carbon nanotubes (CNTs) and TiO2 nanoparticles with various weight ratios is reported. The so-called polymeric gel process was used to deposit thick film containing uniform distribution of TiO2 nanoparticles and coated CNTs with high porosity by dip coating for dye-sensitized solar cells (DSSCs) applications. Based on simultaneous differential thermal analysis, the minimum annealing temperature to obtain inorganic- and organic-free films was determined at 500°C. X-ray diffraction analysis revealed that deposited films were composed of primary nanoparticles with crystallite size in the range... 

Hydrolysis of titanium isopropoxide alcoholic solution has been used to prepare the crystallized TiO2 nanoparticles at low temperature. Concentration ratio was used to control the pathway of sol-gel process and change the physical characteristics of TiO2 nanopowders. The crystallinity, morphology and size of aged TiO2 nanopowders were studied by X-ray diffraction and Scanning Electron Microscopy (SEM). FTIR and, Thermo-Gravimetric (TG) analysis were used to identify the functional groups and thermal behavior of prepared samples. Experimental results have shown that high crystalline TiO2 nanomaterial with anatase polymorph can be obtained at room temperature. It has been found that the... 

A modified carbon paste electrode was prepared by incorporating the TiO2 nanoparticles in the carbon paste matrix. The electrochemical behavior of gallic acid (GA) is investigated on the surface of the electrode using cyclic voltammetry and differential pulse voltammetry. The surface morphology of the prepared electrode was characterized using the scanning electron microscopy. The results indicate that the electrochemical response of GA is improved significantly at the modified electrode compared with the unmodified electrode. Furthermore, the capabilities of electron transfer on these two electrodes were also investigated by electrochemical impedance spectroscopy. Under the optimized... 

Friction stir processing (FSP) is a solid state route with a capacity of preparing fine grained nanocomposites from metal sheets. In this work, we employed this process to finely distribute TiO2 nanoparticles throughout an Al-Mg alloy, aiming to enhance mechanical properties. Titanium dioxide particles (30 nm) were preplaced into grooves machined in the middle of the aluminium alloy sheet and multipass FSP was afforded. This process refined the grain structure of the aluminium alloy, distributed the hard nanoparticles in the matrix and promoted solid state chemical reactions at the interfaces of the metal/ceramic particles. Detailed optical and electron microscopic studies showed that the... 

The influence of particle size and surface modification on sonocatalytic activity of TiO2 nanoparticles was investigated by measuring the degradation efficiency of methyl orange (MO) as a model pollutant. Crystalline TiO2 nanoparticles with different particles and aggregate size were prepared through solution-phase method with varying synthesis temperatures. Coating with polyvinyl alcohol was performed to enhance colloidal stability of the particles over a wide range of pH values (1.5–7.5). Characterization was carried out using X-ray diffraction, high-resolution transmission electron microscopy, dynamic light scattering, and Fourier-transformed infrared techniques. It was found that... 

Herein, we report the impact of light scattering mechanism on photovoltaic and photoelectrochemical performance of dye-sensitized solar cell (DSC) devices composed of TiO2 nanoparticles and hollow cubes. DSCs are designed by two different light scattering modes (i.e., mode I in form of single layer electrode containing nanoparticles and hollow cubes and mode II in the form of double layer electrode comprising active and scattering layers made of nanoparticles and mixtures of nanoparticles and hollow cubes, respectively). The synthesized anatase-TiO2 hollow cubes (200–400 nm) and nanoparticles (15–30 nm) are employed to enhance the optical length and light harvesting of photoanodes,... 

Herein, enhancement of dye-sensitized solar cell (DSC) performance is reported by combining the merits of the dye loading of TiO2 nanoparticles and light scattering, straight carrier transport path, and efficient electron collection efficiency of TiO2 cubes. We fabricate DSC devices with various arrangement styles and compositions of the electrodes in the forms of monolayer and double layer films. For this purpose, the solvothermal synthesized TiO2 cubic particles (100-600 nm) are employed as the scattering layer, whereas TiO2 nanoparticles (15-30 nm) synthesized via a combination of solvothermal and sol-gel routes are used as the active layer of devices. We improve the photovoltaic... 

In recent decades, utilizing of water-based muds (WBMs) in drilling oil and gas wells is ever increasing comparing to oil-based muds and synthetic-based muds due to the lower environmental issues. However, the main drawbacks with WBMs are rheological properties inefficiency and shale swelling which have caused attentions turn to improvement of WBMs’ rheological properties. In this study, the effects of various nanoparticles (NPs) namely titanium dioxide (TiO2), silicon dioxide (SiO2), and zinc oxide (ZnO) on improving rheological properties and shale recovery rate of a WBM sample at two temperatures (25 and 50 °C) were investigated. The concentrations of NPs in the base mud were set at 0.01,... 

In this study, apatite formation ability on TiO2 nanotubes (TNTs) synthesized by anodizing process were compared with TNTs decorated by MnO nanoparticles. The MnO nanoparticles used for decoration process were fabricated via thermal decomposition method. At first, it was strived to find the optimal condition of anodizing process and the effect of applied voltages (15 V, 20 V, and 25 V) and process times (15 min, 20 min, and 25 min) on the diameter of the synthesized TNTs was investigated. Results of microscopic characterizations showed that the completely uniform structure of nanotubes with a diameter in the range of about 100–130 nm was achieved after 20 min of anodizing process at an...