Sharif Digital Repository

ZnO/CuO nanofibers, with different CuO concentrations, were fabricated by one-step electrospinning of the polymer precursor and annealing in air. Scanning electron microscopy (SEM) showed smooth and beadless morphology for the synthesized nanofibers, while X-ray diffraction (XRD) analysis revealed formation of hexagonal and monoclinic crystalline structure phases for ZnO and CuO nanofibers, respectively. X-ray photoelectron spectroscopy (XPS) analysis confirmed the presence of CuO on the surface of ZnO nanofibers. For further confirming the formation of chemical bonds, Fourier transform infrared (FT-IR) spectroscopy was employed. The effect of Cu contents in the overall electronic band... 

Bromophenols are known as antioxidant radical scavengers for some biomolecules such as those in marine red alga. Full understanding of the role played by bromophenols requires detailed knowledge of the radical scavenging activities in probable pathways, a focus of ongoing research. To gain detailed insight into two suggested pathways, H-atom transfer and electron transfer, theoretical studies employing first principle quantum mechanical calculations have been carried out on selected bromophenols. Detailed investigation of the aforementioned routes revealed that upon H-atom abstraction or the electron transfer process, bromophenols cause an increase in radical species in which the unpaired... 

This research investigated the long-term environmental effects on bond strength at the interface between fiber- reinforced polymers (FRPs) and timber. A total of 581 timber specimens were bonded with seven types of FRP sheets (unidirectional and bidirectional glass, carbon, aramid, and hybrids) using a wet lay-up technique. The specimens were exposed to acidic, alkaline, fresh water, and sea water solutions with pH of 2.5, 7, 7.25, 10, and 12.5 for 1, 3, 6, 9, and 12 months. A chamber was also used to simulate ultraviolet radiation after 6 months. A series of single-lap shear tests were then conducted to determine the interfacial bond strength reduction. The results showed that bidirectional... 

Al-3003/Zn bi-layer soldering sheets were produced using roll bonding process at different reductions in both cold and hot conditions. The bond strengths of the bi-layer sheets were measured by peel test before and after supplemental annealing treatment. The peeled surfaces were examined using optical and scanning electron microscopy. The results indicate that by increasing the reduction in thickness during rolling and/or the annealing treatment the bond strength improves. Additionally, the decrease of initial sheet thickness and increase of rolling temperature can effectively improve the bond strength. Microscopic examinations show that the fracture type of Al-3003/Zn sheets is... 

Solar energy exists extensively in all parts of the world. However the intermittency of solar energy presents critical challenges to PV system. The intermittency can be covered by storing solar energy in chemical bonds such as hydrogen. This process can be performed by photovoltaic powered electrolysis of water. The energy transfer efficiency between PV and electrolyzer is subject to the distance between maximum power points (MPP) of PV module and operating points. The operating points can be adjusted by optimizing the design parameters of the electrolyzer but the maximum power points are function of PV module characteristics, solar radiation and ambient temperature. Therefore the weather... 

Usage of concrete-filled pultruded glass fiber-reinforced polymer (GFRP) tubes (CFPGT) as columns can increase the service life of structures. However, marine structures such as oil platforms are always prone to fire because of the low resistance to the elevated temperatures. The purpose of this investigation is to evaluate the effects of concrete core strength (30 and 60 MPa), and exposure temperature (25, 100, 200, 300, and 400 °C) and time (60 and 120 min) on the compressive and bond behavior of CFPGTs. The properties of unexposed and exposed concrete core, pultruded GFRP hollow tubes, and CFPGTs were determined via compressive and disk-split tests. Also, the push-out test was used to... 

The purpose of this paper is to investigate the effects of annealing phenomena on the energy absorption of Al-steel bilayer sheets, bonded by cold rolling, through wedge tearing. Tearing by wedge is a dissipating energy system that includes three components: cutting, friction and plastic deformation due to bending. In order to find the bonding and annealing effects on energy absorption, the non-bonded bilayer sheets are prepared in the same condition of bonded ones. The results show that energy absorption of bonded sheets is larger than that of non-bonded ones. This is due to different plastic bending moment of bonded and non-bonded bilayer sheets. Whenever the bond is improved by heat... 

Composite coatings of Hydroxyapatite (HA) with ceramics, polymers and metals are used to modify the surface structure of implants. In this research, HA/TiO2 composite coating was fabricated by electrophoretic deposition (EPD) on 316 stainless steel substrate. HA/TiO2 composite coatings with 5, 10 and 20 wt.% of TiO2, deposited at 40 V and 90 s as an optimum condition. The samples coated at this condition led to an adherent, continuous and crack-free coating. The influence of TiO2 content was studied by performing different characterization methods such as scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), corrosion resistance in simulated body fluid (SBF),... 

This research reports the preparation and examination of Cadmium Telluride (CdTe) Quantum Dots and doping CdTe QDs with Europium (Eu), Gadolinium (Gd), and Manganese (Mn) prepared in aqueous solution using TGA as a capping agent. Magnetic QDs (MQDs) are important agents for fluorescence (FL) /magnetic resonance (MR) dual-modal imaging due to their excellent optical and magnetic properties. Herein, the chemical bonds, structural, fluorescence, and magnetized properties of CdTe QDs and effect of Mn, Eu, and Gd ions doping on their properties were examined by X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTM), Energy-dispersive X-ray spectroscopy (EDX),... 

In this study, tensile strength of gypsum-based composite with aluminum fibers up to 15 vol.% was studied. To increase the interfacial bond strength between fibers and matrix, aluminum fibers were anodized under different conditions. Single fiber pull-out tests were carried out to investigate the bond strength. The interface was examined by scanning electron microscope. The ability of the composites to withstand longitudinal tensile load was also studied by tensile tests of dog bone-shaped, randomly oriented fiber-reinforced gypsum. By the introduction of aluminum fibers in gypsum as a randomly oriented composite, considerable increment in the strength is achieved and the toughness of the... 

Redistribution of alloying elements in the transient liquid phase (TLP) bonding zone of IN738LC/ BNi-3/IN738LC was studied to investigate microstructural evolution in this area. Wavelength dispersive spectrometry and electron probe microanalysis revealed that, during non-isothermal solidification in the TLP bonding zone, enrichment of residual liquid phase with the positive segregating elements caused formation of intermetallic in the bonding zone. Scanning electron microscopy observation Indicated that the redistribution of alloying elements, between TLP bonding zone and base alloy, resulted In formation of a γ′ boundary layer, containing high density of fine γ′, around the bonding zone.... 

Mechanical properties of nano-composites produced by shock wave sintering of aluminum and silicon carbide nano-powders are investigated using Molecular Dynamics (MD) simulations. In this regard, the shock wave response of aluminum and silicon carbide nano-particles, arranged in a BCC super-lattice, is studied via the NPHug Hugoniostat method. Moreover, the effect of the initial hydrostatic compaction of powders as well as the cooling rate of the shocked material on the mechanical properties of the shock-sintered nano-composites is investigated. Employing the Hugoniot curves corresponding to the powders, it is concluded that an initial hydrostatic pressure, leads to a less temperature rise...