Sharif Digital Repository

This research aims to introduce a nanocatalyst based on open-cell nickel foam (NiFm) with 40 pore per inch(ppi) to save energy during methane steam reforming (MSR), an endothermic reaction, by increasing catalyst thermal properties with improved progressive compression strength. The nanocatalyst is synthesized with a chemical stepwise synthesis approach, thermal-chemical pretreatment, pulsed electrocodeposition of Ni-Al2O3 (γ) nanoparticles, and calcination. Herein, a polyurethane (PU) nonconductive substrate is transformed to nickel foam by using replication sponge method. The purchased PU became conductive by nickel electroless bath using sodium hypophosphite with 5-15 (µm) thickness... 

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... 

Phenolic foam are common among the polymeric foams, they can be prepared from resole resin, it is possible to apply an external thermal reservoir to achieve curing and expansion simultaneously, or use an acid as curing agent, without external heating, and utilize heat of curing reaction for expansion of foaming mixture. Because of economic aspect of view and ease of processing the latter method is preferable. However, the existing problem is that the resole resin must be so active to react with acid curing agent and produce suitable heat. Also,physical properties of resin such as viscosity have a great importance to the efficiency of resin in foam processing.In the present work, resole... 

The aim of the work presented in this thesis is deal with some of the aspects in the FEM analysis of sandwich panels containing holes which comprised with foam core. It is a new topic in this field; so the activities that have been done about this case are poor with respect to its performances in engineering. The main emphasis is placed on the treatment of the foam core since the core often is the weakest part of the sandwich and therefore in many ways governs the capacity and lifetime of the whole sandwich structure. Because of increasing application including construction, aircraft and transportation, marine and etc., different load conditions are considered for the analysis and... 

Real modeling of ceramic foam filters, because of their specific tortuosities is not possible and in case of possibility of real modeling of pores in filters, because of restriction of element’s dimensions, the number of elements increases and model can’t be run in a reasonable time with common computers which are accessible nowadays. The common computer simulation of filters in Computational Fluid Dynamic (CFD) and their effect on fluid flow pattern is done by use of permeability properties of porous media. In this research, ceramic foam filters which are used in casting are simulated by Forchhimer and Darcy models. SUT CAST software is used for simulation, because of its ability for... 

Foam concrete is a new covering layer that can be used for several purposes in civil constructions and because of its unique physical specifications, produces a light concrete in which is isolated against thermal conductivity ,with required strength and favorite quality.This cover is made of cement , sand ,water and foam(chemical substance that produces foam) . The foam is mixed with water in a special machine (mixer) with a high speed centrifugal rotation and produces very small stable bubbles called foam. While cement and sand are mixed in special mixer, makes a fluent concrete that can be used in place, metallic or plastic molds. After dehydration, in accordance with percentage of... 

In this research, aluminum composite foams reinforced with silicon carbides were manufactured using melt direct foaming with gas. The density of produced foams changed from 0.1 to 0.35 g cm-3. At first, simulation of bubble configuration was carried out in order to specify the effective parameters on foaming process. As the result, parameters such as ceramic particle volume percentage and gas type were selected. Results showed that, to process foam with acceptable stability, there was a critical minimum of ceramic particles concentration above which, stability of the foam was enhanced. Gas type was also showed to have a significant effect on foam stability. Argon, carbon dioxide and air were... 

The main purpose of this theses is to synthesize graphene by chemical vapor deposition (CVD) of a hydrocarbon gas such as methane on the nickel foam substrate and then to characterize this kind of graphene. Graphene is a single layer of carbon atoms, discovered in 2004, which has led mankind to new eras in all fields by its extraordinary features such as extra high electron mobility, high thermal conductivity, excellent mechanical strength, optical transparence and extra high specific surface. The advantage of this method compared to other methods is that the graphene generated has a better structural quality. Graphene foam firstly, because of the continuity of the foam structure, has better... 

Metal foams are considered as a group of new materials and are applied widely in various areas due to their particular properties such as low density, high strength-to-weight ratio and appropriate mechanical, thermal, physical, electrical and magnetic properties. The aim of the present study is acquiring the technical knowledge of Zinc foam production by melting route and also optimizing the effective parameters on the foam stability. For this reason, 4 Zinc foams were produced at different times and temperatures. The amount of Calcium as the melt fluidity reducing agent and Titanium hydride and Zinc carbonate as the blowing agent were the same in all the specimens. The effect of heat... 

In this project, melamine formaldehyde was chosen as initial substrate for its high porosity. Then for having superhydrophobic surface, surface functional groups were silanized and deactivated as a result. It was assumed that high porosity of prepared sorbent and its nonpolar nature, can increase extraction efficiency. To study extraction efficiency of the prepared sorbent, it was filled inside a needle and used for needle-trap head-space extraction of BTEX (abbreviation for Benzene, Toluene, Ethylbenzene and Xylenes). Needle packed with sorbent was held on headspace of sample containing BTEX and head- space was pumped with a peristaltic pump. Pumping introduces fresh sample to sorbent... 

In this study closed cell aluminum foam was manufactured through accumulative roll bonding (ARB). In this method, aluminum AA1050 strip was used as the matrix and calcium carbonate was selected as blowing agent powder. The strips were roll-bonded with reduction of 50% during each pass. The produced composite was then subjected to different foaming conditions in order to achieve foams with maximum porosity. Subsequently, influences of content of the blowing agent, time, pressure, number of rolling passes and heating rate on the percentage of porosities were evaluated. In optimum condition quantity of the blowing agent, foaming temperature, holding time and number of ARB passes were equal to 1... 

Due to the wide application of lightweight concretes, there have been a lot of research activities in this field. The objectives of these activities have been mainly to increase the strength and endurance, and to reduce the weight and the cost of production of such concretes.
Lightweight concretes, in general, have the following advantages: relatively high strength to density ratio, high thermal and acoustic insulation, and fire resistance. However, foam concretes, as a particular type of lightweight concretes, compared with other types, has the advantage of ease of production. Therefore, in this work various aspects of foam concretes were studied. In this project, using a particular... 

Due to the underbalanced drilling advantages compared to the overbalanced drilling, this drilling method usage is on rise day to day. In this method, the well pressure has to be lower than formation pressure. To achieve this goal, we have to use light fluids such as air, foam, aerated mud, etc. Because of the compressible nature of these fluids, their hydraulics calculation is more complicated than overbalanced drilling fluids. Due to this complexity, a simulator which can predict and optimize the well conditions is very important in designing drilling schedule. In this thesis, by combination of different rheology and pressure drop equations for the foam, a simulator is developed to model... 

Gas injection as an enhanced oil recovery (EOR) method usually suffers from low recovery efficiency. The low viscosity and density of gas as well as reservoir heterogeneity are the main reasons of early breakthrough and override of gas in oil reservoirs. To mitigate the poor sweep efficiency of gas injection, surfactants can be co-injected or injected in an alternating manner with gas to form foam within the reservoir rock. The foam formation can reduce the mobility of the injection fluids in porous media. A significant challenge of foam injection is the stability of the foam in formations and the foam liquid drainage rate is one of the key factors which characterize or show the efficiency... 

Porous media have many applications including heat exchangers, single-phase flow and multi-phase flow packed beds and reactors with different flow patterns, aquifers, and oil and gas reservoirs. To evaluate the behavior of porous media there is need to understand transport phenomena. In this work, we focused on metal foam porous media as an advanced porous media. The effective thermal conductivity of solid matrix, heat transfer in the presence of fluid flow, and pressure drop were investigated using CFD techniques in micro-scale supposing that the solid foam structure consisted of connected kelvin cells. The comparison of simulation results with experimental data reported in literature shows... 

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... 

Process of casting with evaporative patterns and unbonded sand is a new method that due to different economic, environmental and technological benefits is considered to large and small industrial parts manufacturing in recent years. Different parameters are effective on the surface and metallurgical quality in this process, such as foam density, sand type and size, level and mode of vibration, sand compaction, coating and pouring time and temperature. If coating permeability that is function of type, thickness and concentration of coating is chosen improper, pyrolysis vapor of foam don’t exit completely and in this condition carbon of vapor deposit on the metal surface and produces defect... 

Solid foams are novel materials with outstanding characteristics that have found numerous applications in the construction of light, stiff structures during the past two decades. At the micro-level, solid foams benefit from a cellular structure, which is composed of either closed or open cells. Open-cell foams, which were the concern of this study, are described as a network of inter-connected struts (or ligaments) with beam-like action. The mechanical design of foams requires their mechanical properties to meet certain criteria. These criteria can be satisfied by careful selection of the base material and the microstructural morphology (geometry). However, the selected material has to be... 

Nowadays, tissue engineering and stem cells-based therapies have outlined a promising prospect in neural networks regeneration. But it usually requires biocompatible and conductive scaffolds for culturing neural stem cells and directing their differentiation toward the neurons. Graphene due to its unique physical and chemical properties has attracted much interest in tissue engineering. For this purpose, in this study biocompatible graphene oxide foams have been used for neural stem cell culturing. For the first time, graphene oxide foam were fabricated by precipitation of chemically exfoliated graphene oxide sheets in an aqueous suspension onto the PET substrate at ~80 oC under UV... 

In this study, the influence of multi wall carbon nanotube on the thermal properties and microstructure of open cell flexible polyurethane (PU) foam was investigated. To do this untreated CNT (named here n-CNT) along with three different highly functionalized CNTs having carboxyl, hydroxyl and amide functional groups, abbreviated here by CNT-COOH, CNT-OH and CNT-NH-COR, respectively, were employed. A series of PU foam with and without CNTs (both treated and untreated ones) were prepared by cast molding. Prior molding, the CNTs (0.1 wt% loading) were first dispersed into the polyol (Mw = 3000 g/mol and OH No. 56) and then the mixture was subsequently added to the isocynate (TDI). The SEM...