Sharif Digital Repository

The conductive CuCo2O4 spinel coating is applied on the surface of the AISI 430 ferritic stainless steel by the dip-coating sol-gel process and it is evaluated in terms of the microstructure, oxidation resistance and electrical conductivity. The results show that the CuCO2O 4 coating forms a double-layer scale consisting of a Cr, Fe-rich subscale and Cu-Co spinel top layer after 500 h in air at 800 °C. This scale is protective, acts as an effective barrier against Cr migration into the outer oxide layer and alleviates the cathode Cr-poisoning. The oxidation resistance is significantly enhanced by the protective coating with a parabolic rate constant of 5.8 × 10-13 gr2 cm-4 s -1, meanwhile... 

Sol-gel based solid-phase microextraction fibers supported by a stainless steel wire were fabricated and employed for GC-MS determination of oxadiargyl in real samples. The fibers were based on four compounds with different polarity: polar and non-polar (end-capped) poly(dimethylsiloxane) (PDMS), polyethylene glycol (PEG), and poly(ethylene-propyleneglycol)-monobutyl ether (UCON). For this purpose, the surface of the stainless steel was initially modified by (3-mercaptopropyl) trimethoxysilane. The results of the modification procedure were evaluated by cyclic voltammetry and energy dispersive X-ray (EDX) spectroscopy. After the modification, four different sol-gel based SPME fibers with... 

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... 

Carbon nanotubes with unique physical and mechanical properties have shown great potential for biological applications, including tissue engineering and mimicking the structure and properties of human bones. In the present work, sol-gel synthesized nanocomposite powder of multi-wall carbon nanotube/hydroxyapatite characterized using field-emission scanning electron microscopy, transmission electron microscope, X-ray diffraction, Fourier transform infra-red spectroscopy and thermal analyses. The results show homogenous dispersion of nanotube in well-crystallized hydroxyapatite ceramic matrix. Scanning electron microscopy and transmission electron microscope observations show the sodium... 

Titanium anodes coated with noble metal oxides are widely used in chlorate industry. In fact, these anodes are dimensionally stable. In this article, the electrochemical characteristics of the ternary oxide coating created by sol-gel on titanium, which consisted of Ti, Ru and Ir, were investigated in the number of different layers. The electrochemical properties of anodes, morphology of samples, and phase analysis were investigated respectively by cyclic voltammetry and polarization measurements, Field Emission Scanning Electron Microscope (FESEM) and XRD. The result indicated that the application of the more layer number increases the rate of chlorine evolution. Also, The morphology of the... 

Titanium(IV) tetraisopropoxide was employed as a metal oxide sol-gel precursor to prepare ceramic composite nanofibers by the electrospinning system. To facilitate this process and obtain the desired nanofibers with higher aspect ratios and surface area, poly(vinylpyrrolidone) was added to the sol of titania. Four ceramic nanofibers sheets based on titania were prepared while each sheet contained different transition metals such as Fe-Mn, Fe-Ni, Fe-Co, and Fe-Mn-Co-Ni. The scanning electron microscope images showed good homogeneity for all the prepared ceramic composites with a diameter range of 100-250 nm. The sorption efficiency was investigated by a micro-solid-phase extraction setup in... 

CdS/TiO2/graphene (CTG) nanocomposite thin films were synthesized by a facile production route. The TiO2/graphene (TG) nanocomposite was initially fabricated by sol-gel method in such a way that TiO2 nanoparticles loaded on graphene oxide (GO) sheet via photocatalytic process. Then, CdS nanoparticles were deposited on the TG thin film by successive ion layer adsorption and reaction process (SILAR) approach. Based on atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses, the TG thin film possessed a larger surface area as compared with the pure TiO2 thin film due to presence of graphene sheet. UV/visible spectroscopy exhibited... 

Despite brilliant properties of glass ionomer cement (GIC), its weak mechanical property poses an obstacle for its use in medical applications. The present research aims to formulate hydroxyapatite/yttria-stabilized zirconia (HA/YSZ) in the composition of GIC to enhance mechanical properties and to improve fluoride release of GIC. HA/YSZ was synthesized via a sol-gel method and characterized by applying X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photo-emission spectroscopy (XPS) and simultaneous thermal analysis (STA) along with transmission electron microscopy (TEM) methods. The synthesized nanocomposite was mixed with GIC at a fixed composition of 5.... 

In this research, an attempt was made to improve TiO2 photo-catalyst properties, thus pure, N-Ce co-doped TiO2 thin films were prepared on glass-ceramic substrate using a sol-gel dip-coating technique. The samples were calcinated in air at 475 °C, 550°C, and 650°C for 2 h. The result of simultaneous thermal analysis (STA) and X-ray diffraction (XRD) showed that the presence of Ce in TiO2 could inhibit the phase transformation from anatase to rutile and enhance the thermal stability, and anatase was the dominant phase in N-Ce co-doped TiO2 samples. Also based on the results, the doping results in decreasing the size of TiO 2 crystallite. The results of ultra violet-visible light diffuse... 

Ruthenium oxide was coated on multiwalled carbon nanotubes (MWCNTs) to obtain nanocomposite electrode which has a good response to the pH. To synthesize this electrode, gold and cobalt were coated on a stainless steel 304 substrates, respectively, and then, vertically aligned carbon nanotubes were grown on the prepared substrates by chemical vapor deposition. Gold reduced activity of the stainless steel, while cobalt served as a catalyst for growth of the carbon nanotube. Ruthenium oxide was then coated on MWCNTs via sol-gel method. At last, different techniques were used to characterize the properties of synthesized electrode including scanning electron microscopy (SEM), transmission... 

In this report, crack-free nanostructured barium titanate thin films are prepared by a sol-gel processing method. Glacial acetic acid, barium acetate, titanium tetraisopropyl alkoxide, 2-propanol and deionized water are used as precursors for preparing stable precursor solution. Then very thin films (thickness=26 nm) are deposited on fused silica substrates. In order to prepare crack-free thin films of BaTiO3, much attention is given to solvent evaporation process and a controlled pre-drying process is developed. It is found that the control of the process, especially in the initial stage of drying process is crucial and important for preparation of the crack-free ultrathin nanostructured... 

A molecularly imprinted xerogel (MIX) for fentanyl was successfully prepared on the inner surface of a copper tube by sol-gel technology. Primarily, the tube was treated by self-assembly monolayers of 3-(mercaptopropyl) trimethoxysilane and then [3-(2,3-epoxypropoxy)-propyl]-trimethoxysilane was employed as a precursor for imprinting the template molecule in acidic conditions. During the sol-gel process influential parameters including volume and concentration of fentanyl were carefully investigated to obtain the most efficient and appropriate xerogel. In parallel, a non-imprinted xerogel (NIX) was synthesized in the absence of fentanyl. The extraction efficiencies achieved from MIX and NIX,... 

The low temperature perovskite-type calcium titanate (CaTiO3) thin films and powders with nanocrystalline and mesoporous structure were prepared by a straightforward particulate sol-gel route. The prepared sol had a narrow particle size distribution about 17 nm. X-ray diffraction and Fourier transform infrared spectroscopy revealed that, the synthesized powders had highly pure and crystallized CaTiO3 structure with preferable orientation growth along (1 2 1) direction at 400-800 °C. The activation energy of crystal growth was calculated 5.73 kJ/mol. Furthermore, transmission electron microscope images showed that the average crystallite size of the powders annealed at 400 °C was around 3.5... 

In this research, effects of superhydrophobic nano-coating on frictional drag force have been investigated. The result of this study could be considered to be used as a method in applications concerned with fuel consumption reduction, less CO2 emission and environmental problems as well as speed increase; while, its significance can also be of great use in marine applications. A rotating disc apparatus was used as the experimental set-up to compare the frictional drag force on an aluminum disc with TiO2 superhydrophobic nano-coating and a smooth coatless aluminum disc. The superhydrophobic nano-coating was prepared using sol-gel method and was shown to be able to produce a contact angle of... 

The Multi-walled carbon nanotube (MWCNT)/WO3 nanocomposite thin films with different MWCNT's weight percentages were prepared by sol-gel method as visible light induced photoanode in water splitting reaction. Weight percentage of MWCNT in the all nanocomposite thin films was confirmed by TGA/DSC analysis. According to XPS analysis, oxygenated groups at the surface of the MWCNT and stoichiometric formation of WO3 thin films were determined, while the crystalline structure of the nanocomposite samples was studied by XRD indicating (0 0 2) peak of MWCNT in the monoclinic phase of WO3. The influence of different weight percentage (wt%) of MWCNT on WO3 photoactivity showed that the electron... 

In an attempt to reduce the oxidation and Cr evaporation rates, various protective coating layers with a nominal composition of NiCo 2-xFexO4 (x = 0, 0.5, 1) were deposited on the SUS 430 ferritic stainless steel substrate, as interconnect for solid oxide fuel cell application, by sol-gel dip coating method. Then, the coated samples were soaked at 750 C for 2.5 h in N2 and subsequently for 2.5 h in air. Phase composition and microstructure of the coatings were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Moreover, long-term isothermal oxidation experiment and area specific resistance (ASR) measurement were also carried out on the coated samples. Results... 

Dye-sensitized solar cells (DSCCs) in the form of mixed nanostructures containing TiO2 nanoparticles and nanowires with different weight ratios and phase compositions are reported. X-ray diffraction and field emission scanning electron microscopy analyses revealed that the synthesized TiO 2 nanoparticles had average crystallite size in the range 21-39 nm, whereas TiO2 nanowires showed diameter in the range 20-50 nm. The indirect optical band gap energy of TiO2 nanowires, anatase- and rutile-TiO2 nanoparticles was calculated to be 3.35, 3.28 and 3.17 eV, respectively. The power conversion efficiency of the solar cells changed with nanowire to nanoparticle weight ratio, reaching a maximum at a... 

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... 

This investigation focused on a comparison between hydroxyapatite (HA) and carbon-nanotube-reinforced hydroxyapatite composite (CNTs/HA) coatings. The HA and CNTs/HA composite (with 5wt% CNTs) coatings were prepared with the sol-gel method on 316L stainless steel. Phase evaluation by means of XRD and Raman spectroscopy was performed on the HA and CNTs/HA composite coatings. The coatings were immersed in simulated body fluid (SBF) in order to evaluate the biological properties of the coatings. During the first week of immersion, the increase in the amount of Ca2+ precipitation in the SBF when CNTs/HA was used was lower than for the HA coatings. This behavior can be related to the difference... 

Lanthanum chromite coating occupies a noticeable position as a ceramic coating on metallic interconnects in solid oxide fuel cells because of its excellent electrical conductivity, high oxidation resistance and desirable chemical stability in both oxidizing and reducing atmospheres. In the present work, a sol-gel process based on the dip-coating technique was used to prepare dense and uniform coatings on metallic alloy for interconnect application (AISI 430 type). The effect of strontium and calcium doping into lanthanum chromite structure on electrical conductivity and oxidation behavior of the coated sample has been investigated. The oxidation behavior was evaluated by cyclic oxidation...