Sharif Digital Repository

In this study, uranium removal from phosphoric acid with doulite resin was examined. Different uptake properties of the doulite resin were examined using batch, stirred and column methods. Langmuier, freundlich and dubinin equation was fitted the isotherm data and freundlich equation showed the best fitting. Adsorption kinetics was controlled by slow intraparticle diffusion of UO22+ ions in resin, and it obeyed a shrinking core model. Also a pseudo-second order chemical reaction fairly fitted the kinetics data  

In recent years, liquid resin injection processes for aviation applications have been considered an alternative to conventional autoclave-based processes. At present, these processes have challenges that have been denied industry trust due to their inability to be objectively reproducible. In the last decade, some software has been developed to simulate the vacuum injection process, but this software does not have enough capability to predict the injection network, and an operator with sufficient empirical knowledge must use this software. In recent years, researchers have used this softwares to simulate the process, but so far no software has been developed that can offer injection... 

In the first stage of this research, different amounts of glycidoxypropyltrimethoxysilane (GPS) were grafted as a coupling agent on the surface of nanosilica particles (NS). Surface characterization was done by Particle Size Analyzer and Thermal Gravimetric Analyzer (TGA) and that way, samples were distinguished from each other. More comparisons were taken by Scanning Electron Microscopy (SEM) and Fourier Transform Infrared Spectroscopy (FTIR). Then the different amounts of modified NS were added into the matrix of an epoxy resin and the physical and mechanical properties of samples were tested with Abrasion Resistance test, Tensile Strength test, Thermal Mechanical Analysis (TMA),... 

This study investigated the effect of oxidized molybdenum disulfide (MoS2) nanosheets on the anti-corrosion and rheological properties of epoxy resin. Raw MoS2 sheets were obtained as layered nanosheets with a thickness of 50 to 100 nm using acid washing, oxidation, and heat shock methods. The use of nanoparticle characterization tests such as XRD, FT-IR, FE-SEM, EDS, and TGA supports this claim. Then, in the next step, epoxy coatings containing different percentages (0, 0.3, 0.5, 0.8, and 1.5 wt%) of MoS2 nanosheets were prepared with polyamide hardener to investigate the effect of adding nanosheets and the optimal percentage. The best effect on the corrosion properties of the coating in a... 

Nowdays, one of the most important concerns for scientists is increasing CO2 emmisions and global warming. To overcome this problem, a large number of studies have been carried out to improve energy system performance and reducing the overall energy consumption. One solution to this problem is using the superhydrophobic surfaces with contact angle larger than 150°.In this study, we try to reduce the pressure drop through the galvanized pipes. So, by reducing the pressure drop, power required for pumps can be reduced. To this end, two different coatings by silica nano-particles which were modified with first hydrophobic agent are used. In first coating which is named as PS coating, stearic... 

The current study was attributed to uranium uptake by Varion-AP resin from Saghand, Iran Uranium Mine, ore leach liquor. A suitable high-efficiency system was designed for continuous ion exchange at the bench scale and the uranium uptake parameters were optimized. In this system, 1 reactors was used with a volume of 3 liters in stage with the same height difference. A leach liquor containing uranium with a concentration of between 200 and 300 mg/l was flowed from the feed storage by gravity between reactor 1 to 10 at a flow rate of 30 lit/h and Varion-AP resin was transferred in counter-current flow from stage 10 to 1 by a pneumatic pump. The output of each reactor had a screener that... 

Epoxy resins are relatively brittle and have low resistance to crack propagation. It is common to add rubber particles to improve crack resistance in epoxies, although these particles may deteriorate the strength of the matrix. Different nanomaterials are used to overcome the inherent brittleness of epoxies and to keep the mechanical properties. Among them, carbon nanotubes has been attracted many attentions. Fractue behavior and mechanical properties of two kind of novel nanocomposites, i.e, epoxy/carbon nanotube and epoxy/rubber/carbon nanotube are investigated in current study. Electron microscopy investigations were done to assure the CNTs distribution and fracture mechanisms as well.... 

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... 

Resin Transfer Molding (RTM) which is one of the categories of Liquid Composite Molding (LCM) process, is considered as one of the most important process in polymer composite manufacturing. To improve this manufacturing method and reaching higher qualities, numerous modified methods has been developed. One of these modified methods is Vaccum Assisted Resin Trasnfer Molding with Flexible Tooling which is considerably applicable in manufacturing parts with high quality, large and complex geometry. Although, this manufacturing method has variety of advantages, there are some problems such as void formation making production difficult and dependent to experimental trial and error. So numerical... 

To protect mild steel against corrosion, an intelligent self-healing epoxy (EP) coating including carbon nanofiber (CNF) modified with polydopamine (PDA)-La (III) complex was successfully fabricated. The high aspect ratio and unique thermal and electrical characteristics of CNF made it an ideal physical barrier against the penetration of corrosive ions. Due to the poor dispersion of CNF, its surface was modified using PDA. PDA, which contains functional groups such as catechol, amine, and imine, can mitigate corrosion reaction by generating the Fe-Catechol complex and also boost the coating's adherence to the metal surface, in addition to anchoring La3+ inorganic corrosion inhibitor.... 

In this research the effects of addition of clay in phenolic glass fiber reinforced composite has been investigated. Layered clay/phenolic nanocomposite resin systems were first prepared with 0.5, 1.5 and 2.5 wt% of Cloisite Na+ (CN) and Cloisite 30B (CB). After that the suspension was hold in an ultrasonic bath for 30 min in order to enhance nanodispersion of the clay platelet within the resin. The phenolic/clay solution was used to impregnate the glass fabric using the solvent impregnation method. After suspension for 2 days in the room with natural condition, the impregnated fabrics were pre-cured at 135 ˚C in an oven for 3.5 min to obtain B-stage prepregs. Seven layers of prepregs (150... 

Because of increasing usage of modified polymers and consequent necessity for investigation and modeling of mechanical behavior of these materials, it is important to get a yield criterion for these materials. For this purpose the Gurson yield criterion presented for porous metals, was modified with regard to mechanical properties of polymers. Indeed pressure sensitivity of polymers and their large elastic strain during deformation, makes using of Gurson yield criterion problematic for modified polymers.
For modification of Gurson criterion, macroscopic hydrostatic yield stress equation was derived for a thick-walled spherical shell of epoxy and then Gurson criterion was modified with... 

The repair of pipes that deteriorate over time or due to various factors is a critical issue in engineering. Consequently, effective and novel repair methods, especially using FRP (Fiber-Reinforced Polymer) composites, have gained significant importance. In this research, the repair and connection of pipes using FRP are examined. In the pipe repair section, through hydrostatic testing, various factors such as the damaged area, the number of sharp corner points, the width of the sheets, the number of layers, and the pre- stress condition of the FRP are studied for their impact on the pipe's ultimate pressure tolerance. Also, in the pipe connection section, with hydrostatic tests, the ultimate... 

Various composite friction materials containing 40 vol.% organic binder (phenolic resin plus styrene-butadiene-rubber (SBR)) with varying phenolic-resin/SBR ratio were prepared. The content of phenolic resin in each composite was indicated by the resin value (RV) index ranging between 0-100%. The composites with RVs greater than 50% form resin-based friction materials in which the primary binder is the phenolic resin. For RVs less than 50%, the composites become the rubber-based materials where the primary binder is the SBR. The analysis of mechanical properties exhibited that the conformability of the composites increases upon incorporation of SBR. The frictional analysis revealed that type... 

Recently nanodiamond has drawn a vast attention of researchers due to exceptional mechanical properties. However, nanodiamond tendency to aggregation in polymer matrix restricts its reinforcement properties. In this research, novolac phenolic resin nanocomposites reinforced by nanodiamond were prepared by solution blending method and their mechanical properties were investigated. In order to prevent nanodiamond aggregation, ultrasonic treatment was used and nanodiamond surface was modified with acid and amine functional groups. FTIR and TGA were performed in order to investigate nanodiamond surface and confirmation of existence of acid carboxylic and oleylamine (OLA) groups. Produced... 

In this study, pyrolysis features and corresponding kinetic behavior of non-metallic fractions of the paper-laminated phenol resin printed circuit boards (P-PCB) and fiberglass-reinforced epoxy resin printed circuit boards (E-PCB) were investigated by the use of simultaneous thermogravimetric analysis (TGA/DTG). The kinetic parameters of the P-PCB abs E-PCB during pyrolysis process were estimated from the experimental data by means of three iso-conversional kinetic models, including Friedman, Flynn-Wall-Ozawa (FWO), and Kissinger-Akahira-Sunose (KAS) methods. The activation energy range obtained for P-PCB and E-PCB utilizing the Friedman method was within 117–594.1 and 88.42-295.3 kJ.mol-1,... 

Polypropylene (PP) is one of the most widely used commercial plastics in various industrial applications due to its desirable physical and mechanical properties and low cost. Engineering properties of this polymer depend very much on its crystalline structure. It is a common practice in polymer industry to modify crystalline structure by means of nucleating agents. Since nucleating agents are added in a rather low level to polymers, some investigators have tried this task in modifying crystalline structure of polypropylene by incorporating nucleating agent masterbatches. However, none have looked at the possible influence of the carrier resin in such masterbatches on the performance of... 

Polymer composites, due to its exclusive properties, has a special place in industry. Epoxy resin with high adhesion property, low density, thermal stability and high chemical resistance has a special place as matrix in fabrication of high technology hybrid composites. Hybrid composites, due to its high strength and long fatigue life, used to reinforcing building structures and manufacturing fuselage. Layer and reactive structure near the firm core and wear-resistant of NDs, used to improvement of epoxy reisn and hybrid NanoComposite interphase properties. In this study, for improvement of the properties of hybrid NanoComposites, used the NDs in 0.25, 0.5 and 1 %wt with amine and carboxyl... 

Nowadays, composites have wide applications in different industries especially in aerospace industry because of their high strength to weight ratio. Epoxy 5052 for its relatively good mechanical properties and high thermal resistance has vaidly use for manufacturing of large composite components. However; fracture toghness of epoxy resins is not good in comparison to their other exceptional properties. Therefore, researchers have endeavored to improve this characteristic with different approaches. One of these methods is nanotechnology. Since the components in aerospace industry are often under impact loads and impact strength of these materials has been less studied, effect of carbon... 

Here, we have simulated isothermal vacuum assisted resin transfer moulding (VARTM) using a control volume/finite element scheme. Two dimensional and dimensional (shell geometries) spatial discretization is used. Resin motion through fibers is enforced by vacuum negative pressure in downstream. The governing equations are mass conservation and well known Darcy equation. Using an unstructured triangular grid, complex geometries could be modelled. Application of a quasi-steady algorithm results in a system of linear equation for pressure distribution. This system must be solved in each time step. The point successive over-relaxation (PSOR) scheme is used to solve the system of linear...