Sharif Digital Repository

In this study, ethanol gas sensing of PVP fiber membranes based on Quartz Crystal Microbalance (QCM) was investigated. The fibers were deposited on the QCM's electrodes by electrospinning the viscous blend solutions of PVP. The effects of PVP concentration on morphology of the fibers and their permeability when exposed to ethanol were investigated. Membranes which were prepared using low concentration solutions, contained beads and high packing fibers and showed low permeability. Increase of the PVP concentration to 12 wt% resulted in continuous fine fibers with good permeability. Furthermore, higher PVP concentrations were found to decrease ethanol permeability due to larger fiber radius... 

A two stage chemical deposition (TSCD) technique is used to produce ZnO films on quartz glass (QG), soda lime glass (SLG) and high purity alumina (HPA) from an aqueous solution of zinc complex. The effects of the substrate material on the chemical composition and morphology of the deposited layer are investigated. The effects of different annealing temperatures (180, 300, 500 and 800°C) on the morphology and orientation of the ZnO crystallites are also determined. X-ray diffraction diffractograms show that above 300°C, the intensity of (002) peak considerably decreases with increasing temperature. Results indicate that changing the substrate from QG to SLG does not significantly influence... 

Investigation of radiation heat transfer In vortex engine is an important and new phenomenon in combustion for scientists and combustion researchers. In this research some parts of the combustion chamber wall are insulated using Blanket as a high insulating material. The rate of radiative heat transfer to the chamber wall is calculated using temperature difference between inner and outer surface of chamber. In the experiments this parts are protected from direct contact with hot combustion media using quartz window. The luminous radiative transfer per volume of chamber and also volume of flame in a vortex engine are compared with that in a similar axial flow type engine. A detector sensitive... 

In the last decade, there has been a swift development in several scientific research works in which the quartz crystal microbalance (QCM) technique has played a critical role in unravelling different aspects of energy and environmental materials and biological substances as well as all corresponding molecular interactions within those media. We comprehensively review the numerous types of surface chemistries, including but not limited to hydrogen bonding, hydrophobic and electrostatic interactions, self-assembled monolayers and ionic bonding, that are monitored using QCMs in a variety of fields such as energy and chemical industries in addition to the biology, medicine and nanotechnology... 

An effective and self-organized differentiation of human neural stem cells (hNSCs) into neurons was developed by the pulsed laser stimulation of the cells on graphene films (prepared by drop-casting a GO suspension onto quartz substrates). The effects of graphene oxide (GO) and hydrazine-reduced graphene oxide (rGO) sheets on the proliferation of hNSCs were examined. The higher proliferation of the cells on the GO was assigned to its better hydrophilicity. On the other hand, the rGO sheets, which have significantly better electrical conductivity than GO, exhibited more differentiation of the cells into neurons. The pulsed laser stimulation not only resulted in an accelerated differentiation... 

Graphene nanogrids (crossed graphene nanoribbons synthesized by the oxidative unzipping of multi-walled carbon nanotubes) on a SiO2 matrix containing TiO2 nanoparticles (NPs) were applied as a photocatalytic stimulator in the accelerated differentiation of human neural stem cells (hNSCs) into two-dimensional neural networks. The hydrophilic graphene nanogrids exhibited patterned proliferations of hNSCs (consistent with patterns of the nanogrids), in contrast with the usual random growths occurring on quartz substrates. The number of cell nuclei differentiated on reduced graphene oxide nanoribbon (rGONR) grid/TiO2 NPs/SiO2 increased ∼5.9 and 26.8 fold compared to the number of cells on quartz... 

This paper is a continuation of our previous paper (part 1; 10.1021/ef401857t), which discussed the roles of different phenomena effecting the deposition of asphaltene from model oil systems and before the onset of asphaltene precipitation. The study in this paper is to understand the depositional tendency of asphaltene using a quartz crystal microbalance with dissipation (QCM-D) measurements and their corresponding modeling for real crude oil systems with emphasis after the onset of asphaltene precipitation  

Inorganic scale deposition has been found to affect many industrial processes, including water injection into the oil reservoirs. The incompatibility of high sulfate ion content of seawater with formation water containing calcium ions results in formation damage and production decline. In this study, several simultaneous techniques are utilized for qualitative and quantitative analyses of calcium sulfate scale to get more insight into the formation damage during smart water flooding at micro and nanoscales. In the experimental section, calcium sulfate deposition due to the mixing of the formation water and seawater samples was investigated using the dynamic quartz crystal microbalance... 

The performance of a quartz crystal microbalance (QCM) used as a sensor/detector relies on the performance and quality of the film coated onto the quartz crystal sensor. This study focuses on the sensor coating preparation for the detection of glycine. Cellulose nanofibrils (CNFs), natural polymers, were coated on a quartz crystal (QC) surface by a spin-coating method. The prepared CNF-coated QC was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), cyclic voltammetry (CV), Fourier transform infrared spectrophotometry-attenuated total reflectance (FTIR-ATR), Raman spectroscopy, and water contact angle (WCA). The stable and fully covered QCs without further... 

Among the asphaltene flow assurance issues, the most major concern because of asphaltene is its potential to deposit in reservoir, well tubing, flow lines, separators, and other systems along production lines causing significant production losses. Hence, the focus of this study is to understand the depositional tendency of asphaltene using quartz crystal microbalance with dissipation (QCM-D) measurements. The results are presented in two consecutive papers, with this paper (part 1) dealing with model oil systems. The depositing environment is varied by changing the system temperature, asphaltene polydispersity, solvent (asphaltene stability), depositing surface, and flow rate. This paper... 

Uniform layers of ZnO nanostructures were formed on quartz and alumina substrates through a simple vapor phase transport (VPT) method without any catalyst or buffer layer by making proper growth conditions. The effect of substrate on morphology, crystalline structure and photoluminescence spectra has been investigated. Scanning electron microscopy images revealed that morphlogical grwoth depends on used substrate, aligned rods with flower-like bundels and entangled rods are vertically aligned rods on the quartz and alumina substrates, respectively. X-ray diffraction studies showed that grown films on the quartz substrates possess stronger c-axis orientation compared to those on the alumina... 

Constant volume transparent test combustion chambers are extensively used for investigating injection and fuel burning properties of various combustion engines. Their configuration depends on the engine type and the research purpose. Material of components, shape and dimensions of the chamber and its parts, ease of use, accessibility, sealing and safety of the assembly are the parameters needed to be considered in designing the test cell. This paper explains, structural design of a test combustion chamber and its optical windows using finite element analysis of ANSYS 12.0 software for bearing high pressure variations and thermal shocks of combustion. It was designed for conducting CNG direct... 

The effect of oxygenate modifiers on the performance of PtSnγAl 2O3 catalyst in dehydrogenation of propane was studied. Dehydrogenation reaction was carried out in a fixed-bed quartz reactor in the temperature range of 575620 °C. Two types of oxygenate modifiers, namely water and methanol, were added to the feed. The optimum amounts of water for reaction temperatures of 575, 600 and 620 °C were 84, 120 and 140 ppm, respectively. The optimum amounts of methanol for the same reaction temperatures were 9.9, 25 and 50 ppm, respectively. Any further addition of water or methanol beyond these optimum levels resulted in a loss in activity. The addition of water or methanol led to the formation of... 

Quartz is usually detected as an impurity of kaolinite clays. The present work attempts to evaluate the role and behaviour of quartz particles in geopolymerisation and its probable effects on mechanical behaviour of geopolymeric products. Two kaolinite clays with different free quartz contents were used as raw materials to produce geopolymers. Results showed that using high content quartz kaolin causes higher compressive strength. Scanning electron microscopy studies confirmed that quartz does not participate in geopolymerisation and completely remains in the structure as fine particles. High hardness quartz particles by retarding crack growth in the geopolymer matrix enhance mechanical... 

Amorphous aluminum indium nitride (AlxIn1- xN) thin films were deposited on quartz substrates by plasma-assisted dual source reactive evaporation system. In-rich (x = 0.10 and 0.18) and Al-rich (x = 0.60 and 0.64) films were prepared by simply varying an AC voltage applied to indium wire. The X-ray-diffraction patterns revealed a small broad peak assigned to Al0.10In0.90N (0 0 2) plane, but no perceivable peaks assigned to crystalline AlxIn1- xN were observed for the films with x = 0.18, 0.60 and 0.64. The morphology of the film was changed from clusters of small grains to uniformly shaped particles with decrease of x. The band gap energy of the films increased from 1.08 eV to 2.50 eV as the... 

Local photodegradation of graphene oxide sheets at the tip of ZnO nanorods was used to achieve semiconducting graphene nanomeshes. The chemically exfoliated graphene oxide sheets, with a thickness of ∼0.9 nm, were deposited on quartz substrates. Vertically aligned ZnO nanorod arrays with diameters of 140 nm and lengths of <1 μm were grown on a glass substrate by using a hydrothermal method. The graphene oxide sheets were physically attached to the tip of the ZnO nanorods by assembling the sheets on the nanorods. UV-assisted photodegradation of the graphene oxide sheets (with dimension of ∼5 × 5 μm) at a contact place with the ZnO nanorods resulted in graphene nanomeshes with a pore size of...