Sharif Digital Repository

Electrical behavior of hybrid conductive composites made of phenolic resin, graphite woven, glass woven and graphite nano powder has been studied for the first time in the present research to apply as collecting plates in electro static precipitators. To this purpose, two types of four-layer composites smeared with phenolic resin by different amounts of graphite nano powder then produced at 120°C and 200 bars with proper curing cycle. Finally, electrical resistivity of all the plates undergoing impact loading after different rapping cycles was measured by means of a repetitive rapping tester system particularly manufactured for this task. This study performs changes in mechanical behavior of... 

Pervious concrete (PC) has been detecting application in pavement and concrete structures such as dams, small retaining walls, and etc during the past decades. Also, in recent years, the types of resins have been introduced to apply in concrete owing to the enhancing in mechanical and durability characteristics. However, few studies have investigated the mechanical behavior of high performance pervious concrete (HPPC) incorporated by polyester and epoxy resins as polymeric composites, where ordinary cement material has been completely deleted. The purpose of this investigation is to compare the mechanical properties, permeability, and durability of HPPCs made by polymeric composites (i.e.... 

The synthesis and swelling behavior of a new superabsorbent hydrogel based on natural salep grafted with polyacrylamide is described. The new biopolymer was synthesized via simultaneous crosslinking and graft copolymerization of acrylamide monomer onto a salep backbone using radiochemical methods. Various parameters such as relative contents of salep and acrylamide, as well as total dose of γ-rays were examined. The best synthesis condition is reported and a mechanism for superabsorbent hydrogel formation suggested. Factors affecting the swelling behavior of hydrogel were also studied. © 2008 Elsevier B.V. All rights reserved  

Polymer-layered silicate nanocomposites have been noticed recently due to their outstanding properties. The mechanical properties and deformation mechanism of epoxy/montmorillonite nanocomposites under compressive and flexural loadings were investigated. A reduction in compressive and flexural yield stress and also glass transition temperature with increasing the amount of organoclay was observed. This change in mechanical behavior of epoxy can be explained with observation of plastic deformation mechanism. The study of deformation mechanism revealed that presence of organoclay accelerates shear yielding in epoxy. Microscopic evaluation illustrated that nanoparticles in this system act as... 

The application of agricultural fibers for making particleboards has been studied in two types of composites: (i) type I particleboards were composites of wheat straw and rice husk fibers with polymeric methylene di-phenyl diisocyanate resin (pMDI) as a binder made by compression moulding; (ii) type II particleboards were composites of rice husk and polypropylene made by extrusion and injection moulding. In type I particleboards, the effects of varying the resin content and various combinations of wheat straw/rice husk fibers were investigated and characterised in terms of physical and mechanical properties of particle boards such as modulus of rupture, modulus of elasticity, compression... 

The reaction kinetics and chemical equilibrium of the reversible catalytic hydrolysis reaction of a methyl acetate to acetic acid and methanol using a strongly acidic ion exchange resin catalyst named Amberlyst 15 were studied. To investigate the different behavior of Amberlyst 15 in the adsorption of reactants and product species, the equilibrium behavior of binary non-reactive liquid mixtures, consisting of one reactant and one product were studied experimentally. The Langmuir model was used to describe the equilibrium condition, quantitatively. Then the employed model was compared with the more complicated thermodynamic models to describe the equilibrium between the catalytic polymer... 

In the present work, Tetrahydrofuran was produced from 1,4-butanediol by catalytically dehydration of 1,4-butanediol in contact with a catalyst. Material used as catalyst were Synthesized and natural zeolites as well as alumina and silica. Synthesized zeolites were investigated in different aspect such as pore size, cation and Si/Al ratio. Results indicated that with increasing the Si/Al ratio, the activity of the zeolite used for 1, 4-butanediol dehydration step was reduced. Furthermore, it was observed that, upon the replacement of sodium with hydrogen and ammonium cations, the conversion of the 1, 4-butanediol into tetrahydrofuran was increased. It was shown zeolites possessing smaller... 

Kinetics of oxidation of MgO-C refractory bricks containing 14.3% graphite, 80.9% magnesia, and 4.8% phenolic resin is investigated comprehensively. Effect of temperature and grain size distribution on the rate of oxidation of graphite is evaluated by application of a mathematical model developed on the basis of shrinking core/progressive conversion regime to the gas-solid processes involved. Incorporation of the experimental data into the mathematical model indicates that a mixed controlling mechanism governs the oxidation rate. Three activation energies were recognized: (a) 68 kJ/mol for chemical adsorption of gas on the surface of the graphite flakes, (b) 22 kJ/mol for pore diffusion of... 

In this research, the properties of Dolomite Graphite refractories with different additives were evaluated. The samples were prepared with various amounts of Graphite and resin content. After preparation of the samples, the physical, mechanical properties, slag corrosion and thermal shock resistance were evaluated. The properties of the samples were evaluated up to 11% total Carbon (10% Graphite and 1% residual Carbon from resin) in the system. The reduction in MOR of the specimens, before and after heat treatment was measured, as a measure for the thermal shock resistance evaluation. The slag corrosion test was conducted based on the crucible test, at 1600°C for 5 hr. Then, the depth of... 

Continuous fixed-bed column studies were carried out by using Amberlite CG-400 anion exchange resin for the recovery of uranium from aqueous solutions (synthetic solutions and uranium conversion facility (UCF) liquid waste). Effects of operating parameters such as flow rate and bed height were studied. The breakthrough capacity decreases with increasing flow rate, but this dependence was not significant with a long column. The maximum breakthrough capacity of uranium ions were achieved by CG-400 resin at a flow rate of 0.2 mL min-1 and bed height 9.1 cm (4 g resin). The elution behavior of uranium from CG-400 resin by various eluents have been investigated and the results show that 0.5 mol... 

A numerical analysis for determination of the stagnant and dispersion thermal conductivities in the Resin Transfer Molding (RTM) process is presented. A solution was obtained for the momentum and energy equations, which are used in this study and which represent the Brinkman- Forchheimer-extended Darcy model, and one-temperature energy equation. Subject to the appropriate boundary conditions, the governing equations are solved by the finite volume method on a collocated grid. In order to satisfy the pressure-velocity coupling in the solution, the SIMPLE algorithm was used and for determining the mass flux flowing past the cell faces, the Rhie-Chow interpolation was applied. Both constant and... 

In this paper, uranium sorption onto amberlite CG-400 anion exchange resin in the presence of phosphate anions was studied. The effect of contact time between the sorbent and aqueous solution, pH, initial concentration of uranium and temperature were also investigated. Kinetic studies show that uranium sorption onto amberlite CG-400 resin in the presence of phosphate is a fast process and follows pesudo-second-order kinetics. It was also found that the pH value and the presence of phosphate play very important roles in the uranium sorption onto CG-400 resin. Optimum pH for uranium sorption in the presence of phosphate anions was about 3.5. The experimental sorption isotherm is successfully... 

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 and 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... 

Polystyrene resin was functionalized by diethanolamine for the efficient removal of p-toluenesulfonic acid (p-TSA) from aqueous solution. Functionalized adsorbent (DEA-PS) was characterized by elemental analysis, Fourier transform infrared spectroscopy, point of zero charge measurement and field-emission scanning electron microscopy. According to the results, maximum removal of p-TSA was observed at the pH range of 2.5-5. The adsorption kinetics of p-TSA onto DEA-PS was represented by pseudo-first-order model and the equilibrium data followed Langmuir model well. The adsorption process was endothermic and spontaneous, along with the positive change of entropy. The regeneration of DEA-PS was... 

Uranium (VI) sorption using an anionic exchanger resin, namely Amberlite IRA910, in the presence of sulfate anions was the subject of current study. Batch sorption experiments were carried out to evaluate the influence of operational parameters such as pH, contact time, initial concentration and existence of various anions (including phosphate, sulfate, chloride, fluoride, and nitrate) in the solution on Amberlite IRA910 sorption behavior. Experiments revealed that uranium adsorption was fulfiled at pH>3 and 50 min to amount of 80%. Kinetics study revealed that the pseudo-second-order model showed better curve-fitting regression of the experimental data than the pseudo-first-order one.... 

In this article, a continuum-based constitutive model is developed to predict the mechanical behavior of 5052 resin epoxy reinforced by multiwalled carbon nanotubes (MWCNTs) based on experimentally generated data. For this purpose, MWCNTs/epoxy specimens with various percentages of functionalized and nonfunctionalized MWCNTs are prepared. The SEM graphs indicate that functionalization leads to a better bound between epoxy and MWCNTs and a higher level of dispersion. The specimens are then tested under standard ASTM D638-02 a procedure and their true plastic stress–strain curves are extracted. Investigations on experimentally generated data reveal that a wt% dependent equation which is... 

In the present paper, phase and microstructural characterization of low carbon MgO-C refractories with addition of Fe-catalyzed phenolic resins as binder were investigated. Initially, phenolic resin was modified using various amounts of Fe particles as catalyst originated from iron nitrate ([Fe(NO3)3·9H2O]). The MgO-C matrix compositions were prepared by using 7% of modified phenolic resin, shaped and cured at 200 °C for 24 h. The cured samples were coked in the temperature range from 800 to 1400 °C and then characterized by XRD and FE-SEM techniques. Based on attained results, in-situ graphitic carbons, particularly in carbon nanotubes (CNTs) network were gradually formed from Fe-catalyzed...