Sharif Digital Repository

Today, the use of carbon nanostructures hybridized with noble metals has attracted considerable attention for the fabrication of bio-electrochemical sensors. Since the specific surface area has an immense effect on the sensing response, three-dimensional structures of graphene have a great capability to utilize in these sensors. In this research, three-dimensional graphene was provided on the porous nickel foam by chemical vapor deposition technique. By evaluation of raman spectroscopy, the time period of 20 minutes for solving of the carbon atoms into the nickel foam was selected as the main parameter of optimized conditions for the synthesis of graphene. Afterward, production of few-layer... 

The unique characteristics of solid foams make them ideal for both natural and man-made structures. The cellular structure of these materials allows for the construction of natural structures such as bone and wood that have high strength and use minimal primary materials. Their unique structure has inspired studies in the automotive and aerospace industries, leading to a new generation of lightweight materials. The focus of this study was the effects of the microstructure of foams on the macro mechanical response of specific structures. Homogenization methods are well suited for the study of these effects due to the random nature of the microstructures. One major problem in using numerical... 

NiTi Memory alloys have a great range of applications. Porous metallic biomaterials (e.g., stainless steel, chromium- cobalt, titanium and nickel–titanium (NiTi)) represent superior alternatives to traditional non-porous metallic implants for two main reasons. First, open porosity can enhance bone ingrowth and thus improve fixation at the interface between bone and implant. Second, porosity decreases the mismatch in stiffness between bone and implant, thus reducing stress-shielding effects which shorten the lifetime of the implant through bone resorption and loosening. NiTi foams may thus find multi-functional applications such as bone implants, impedance-matching connectors between... 

One of the most common methods for enhancing oil recovery is gas injection. Because of greenhouse effect and environmental problems, carbon dioxide can be used as injected gas. Low viscosity and high relative permeability of gas make the gas injection as an ineffective EOR method. Foam injection is a good replacement because its mobility is much higher than gas. Usually surfactants are used as foam generator agent but the generated foam is not so stable. Using nanoparticles can improve foam stability for a longer time. In this research study fly ash particles is used as a new stabilizer agent to improve carbon dioxide foam stability. This particles are made of silica, aluminum, iron …... 

In this research, aluminium sandwich structure was manufactured by accumulative roll bonding (ARB). In this method, aluminum AA5083 strip was used as the matrix and titanium hydride was selected as the foaming agent powder. Due to the use of particle foaming agent in the first pass, reduction, preheat temperature, rolling speed and the percentage of powder particles parameters were examined. Finally, the 66% reduction, 400 °C preheat temperature and 25 rpm rolling speed, were considered as the optimal values. At the next stage of this process 50% reduction was applied at each pass and this process was repeated up to five passes. After ward, in order to create a sandwich structure, aluminum... 

Purpose of these investigations is modeling and prediction of foam graphene like linear elastic modules and density of that material. In this modeling with two numerical method molecular dynamics and finite element method is used in that with multiscale method various numerical method match together. At the beginning of the modeling various image of foam graphene in Nano abd meso scale in the case of size and scale survaied till with this checking, scale of the work and varios of modeling was created and with this modeling linear elastic modules and density were estimation  

Poly (lactate-co-glycolate) is a typical biocompatible and biodegradable synthetic polymer. Addition of TiO2 nanoparticles improved compressive modulus of PLGA scaffolds and reduced fast degradation. Porous 3D scaffolds, which are synthesized using biocompatible and biodegradable materials, could provide suitable microenvironment and mechanical support for optimal cell growth and function. A novel method has been applied to fabricate PLGA/TiO2 scaffolds without using any organic solvent or porogen for nucleation compared to former ways, with aim of improving the biocompatibility, macroscale morphology and well inter-connected pores efficacy: Air-Liquid Foaming. Adjustment of the foaming... 

Underbalanced drilling is a type of drilling operation in which the pressure of the drilling fluid is less than the pressure of the formation. This pressure difference has created advantages for this method. Less formation damage, reduction of pipe stuck, increasing rate of penetration and production during drilling are the advantages of this method compared to traditional methods. To reduce the pressure of the drilling fluid, very low density fluids should be used. One way to reduce density is to mix a compressible fluid such as gas into water. Due to the difference in density and surface tensile strength of water and gas, these two phases do not combine, so a stable combination of these... 

Auxetic materials have a negative Poisson ratio (NPR), which is their most distinguishable characteristic as compared to regular materials. Test specimens were made of conventional polyurethane (PU) foams according to ASTM ; then, with a thermo-mechanical process, the foam was converted to auxetic PU foam. The reproducibility of specimens' fabrication was checked with CoV= for the final foam thickness. With regard to the fact that changing loading conditions can vary Poisson's ratio, in this study, the variations occurred in Poisson's ratio due to changing loading conditions are investigated. The applied strain and strain rate were altered in experiments and statistical analysis was... 

Due to imminent shortage of fossil fuels, environmental issues that occur from their intensive use, population growth and industrialization of societies moving towards renewable energy sources is inevitable. Sun is the most clean and abundant source of energy but it is needed to be accompanied with an energy storage system as it is intermittent and cannot supply our required energies on demand. Water splitting electrochemical cells are promising solutions to cope with this problem by producing hydrogen as a clean fuel. The overpotential imposed by anode is the bottleneck of the water splitting reaction. The anodes with sufficient efficiency that are used today are made from precious and... 

Metal matrix composites (MMC) and metal foams (MF) have been the topic of numerous researches during the last decades. The appropriate mechanical and physical properties of these materials make them useful in various industries. In this research, a unique approach is introduced for producing MMCs and MFs in which accumulative roll bonding (ARB) is employed in order to achieve a homogeneous distribution of ceramic particles in the metal matrix. Also, foamed structures can be made by subjecting Al/TiH2 composite to an appropriate annealing heat treatment where TiH2 particles decompose to hydrogen and titanium. In this work, the effect of number of ARB cycles on the size and distribution of...