فهرست مطالب layeghi

In this research, firstly polyaniline-zinc oxide (PANI-ZnO) nanocomposite was successfully synthesized by chemical polymerization of aniline in the presence of ZnO nanoparticles and then, 5%, 10% and 15% solutions of PANI–ZnO nanocomposites were mixed with a solution of polystyrene (PS) in tetrahydrofurane (THF) and PANI-PS-ZnO nanocomposites were obtained. The prepared nanocomposites were used as coating on iron coupons by solution casting method and their anti corrosive performance were studied by open circuit potential (OCP) and Tafel techniques in 3.5% NaCl solution as corrosive environment. The obtained results showed that the coating of PS-[PANI-ZnO 10%] nanocomposite had superior corrosion protection effect on iron sample compared to that of pure PANI, PANI–ZnO nanocomposite, PANI-PS composite and two other PANI-PS-ZnO nanocomposite coatings. Cyclic voltammetry (CV) studies showed that the prepared PS-[PANI-ZnO 10%] nanocomposite was electroactive and this property was reversible and stable. Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM) techniques were used to characterize the composition and structure of PS-[PANI-ZnO 10%] nanocomposite. To study thermal stability of PS- [PANI-ZnO 10%] nanocomposite, thermogravimetric analysis (TGA) was used.

One of the important issues in regional and national planning is information about land use, land use based on their capacity and the discovery of land use change procedure. By knowing the land use change procedure it would be possible to manage the ecosystem toward balance. This study is to investigate the changes in land use and land degradation in Garmsar Plain. In this study the images of Landsat satellite in the year 2002 and 2011 were reviewed. For producing the land use map of Garmsar plain NDVI index was used. Then, using different methods of supervised classification the land cover map were prepared based on satellite images. Land use in the region from 2002 to 2011 has changed and agricultural land in the study area decreased by 2.49% due to the possible expansion of residential areas in western and north western parts and degradation of agricultural lands in southern parts of the study site.

The use of agriculture residues as filler in composites is increasing due to their strength, abundance and low cost. Soya stalks show promising renewable natural fiber. In polyethylene composites the physical and mechanical properties (flexural resistance, tensile, impacted absorbed energy, water uptake and thickness swelling) was examined at different composites. The results showed that, the mechanical properties increased with soya stalk content However, the physical properties have tended to decrease.

The bending moment resistance under diagonal tensile load of doweled joint in plywood members was investigated. Joint members were cut from 11-ply hardwood plywood (Beech, Hornbeam and Alder) at the nominal thickness of 19 mm. Dowels were made of Beech and Hornbeam woods. Dowel diameters (6, 8 and 10 mm) and depths of penetration (9, 13 and 17 mm) in the joint members were selected as variables. The effect of dowel variables on the bending moment of the corner joints was evaluated. Results showed that the dowel diameter, penetration depth and species exerted a significant effect on the bending moment resistance under diagonal tensile load. Bending moment resistance under diagonal tensile load was increased as the diameter of the dowel increased from 6 to 8 mm and as the penetration depth of dowel increase from 9 to 13 mm. However, increasing the diameter from 8 to 10 mm or the penetration depth from 13 to 17 mm had no significant effect on bending moment resistance under diagonal tensile load. Results also indicated that bending moment resistance of joints made with beech wood dowels provided higher resistance than hornbeam dowels.

In this paper, effect of Ag nanoparticles different contents on heat transfer during press cycle and physical and mechanical properties of particleboard was investigated. Mechanical strength including Internal Bonding (IB) and Bending Strength and physical properties including Water Absorption (WA) and Thickness Swelling (TS) after 2 and 24 hours soaking was determined. Heart transfer process from hot press plates to core layer of the mat during press time was recorded by thermocouples. Energy Dispersive X-Ray Spectroscopy (EDX) and Scanning Electron Microscopy (SEM) result prove presence and dispersion of nanoparticles in glue line well. Results indicate that Ag nanoparticles increase heat transfer to the core layer and cause IB improvement. But nanoparticles had negative effects on physical properties and increased WA and TS after 24 hour soaking. Heat transfer acceleration during hot press cycle is a way to reduce press time that results in efficiency increase by preserving essential strengths.

The purpose of this study was to compare the performance of cellulosic pad made of kraft hand sheet papers and commercial cellulosic pads (CELdek 50×90 and CELdek 70×90). Hand sheet papers were made by the use of a large hand sheet maker at available at pulp and paper laboratory of Wood and Paper Science and Technology department at the University of Tehran and then corrugated with B flute size in Pars carton factory. After cutting, corrugated papers were cross-laminated by kraft adhesive and with 90 degree flute angle. Then, pads were soaked in NS-88 resin and dried at 35±2 oC. Cooling efficiency and water consumption of experiments were measured as a function of air velocity. Cellulosic pads were tested in a wind tunnel at three different levels of air velocity (1.8, 2.25 and 2.67 ms-1). The results showed that cellulosic pads made of kraft hand sheet papers had the highest efficiency compared to the commercial cellulosic pads (CELdek 50×90 and CELdek 70×90). It has also been found that by increasing the air velocity, the cooling efficiency decreased and water consumption increased.

The goal of this study was to investigate bending moment resistance of L-shaped screwed corner joints constructed of plywood members. The thickness of plywood members was nominal 19 mm that were compared with medium density fiberboard (MDF) and particleboard with 18 mm thicknesses. Effects of thread screws (coarse and fine), screw diameter (3.5, 4 and 5 mm), and penetration depth (9, 15 and 28) on bending moment capacity of joints under diagonal tension were investigated. Test results indicated that a screw corner joint becomes stronger as either screw diameter or screw length is increased. Screw length was found to have a greater effect on moment capacity than the diameter. The highest bending moment resistance was observed for joints made with coarse screw which were 5 mm in diameter and 28 mm depth of penetration. The lowest bending moment resistance was observed in joints having fine screw, with 3.5 mm diameter and 9 mm penetrations. Results also showed that bending moment resistance with coarse thread drywall screws was higher than those of the fine thread drywall screws. Bending moment resistance of joints made of plywood was higher than those of joints made of medium density fiberboard (MDF) and particleboard.

The purpose of this study was to investigate the effect of silver and copper nanoclouids on the thermal conductivity of particleboard. For this purpose, nanoclouids with concentration of 4000 (ppm) in four levels of 0, 5, 10 and 15% were applied to the particleboards with the consumed resin, then thermal conductivity of the boards were measured at four temperature profiles (45, 50, 55 and 60 °C). The results showed that with increasing nanoclouids content, the thermal conductivity increased, and the samples containing silver nanoclouids indicate higher thermal conductivity than the samples containing copper nanoclouids at the same conditions. With increasing temperature, thermal conductivity of the boards increased. The increased of thermal conductivity of compact wooden plates was as a positive factor in production process in terms of cost reducing and increase efficiency of the products.

The purpose of this study was to investigate the effects of the screw diameter and pilot holes diameter as well as end distance, thickness of side and main members and screw type on the lateral load of joints made from various screws on commercial wood-plastic composites. Three types of screws, including sheet metal screws with gauges 8, 10, 14 (4, 5, 6 mm, nominally), wood screws with gauge 8 (4mm, nominally), and drywall screws with gauge 8 (4mm, nominally) were used. The results showed that lateral load of joints do not increase continuously with increase of screws diameter and this must be attributed to decrease of net section of joint members. However, with a given diameter of screw, lateral load of joint increased with the increase of end distance, thickness of joint members. Also, results showed that, with the increase of predrilled holes diameter up to root-diameter of screw, lateral load of joint decreased drastically. Concerning screw type effect, the lateral load of joint made using wood screw was higher than joints made with sheet metal and drywall screws.

Withdrawals resistances of screws driven into commercial wood plastic composite (WPC) panels in both face and edge directions have been measured and the results have been compared with those of conventional medium density fiberboard (MDF) and particleboard. Three types of screws namely; sheet metal screw (gauge # 4، 8، 10، 14)، wood screw (gauge #8) and drywall screw (gauge #8) were used. The results have indicated that withdrawal resistances of screws in WPC panels in both directions increase as screw diameter. Similar increases were observed when pilot holes diameter were increased close to the root diameter of the screws. Beyond this limit، increasing the pilot hole diameter up to the nominal diameter of the screws، significantly reduced withdrawal resistance. No significant differences were observed between different types of screw. Face and edge withdrawal resistances of screws in WPC panels were higher as compared with those of MDF and particleboard panels.

Thermal conductivity (TC) of Populus Alba, Carpinus betulus and Acer laetum woods at various temperatures, has been measured experimentally complying with ASTM C177 standard. Two samples with 20×20 Cm2 areas and 1cm thicknesses which have been obtained from the northern part of Iran were utilized to test their thermal conductivity. The results show that thermal conductivity of Populus Alba, Carpinus betulus, and Acer laetum increases linearly with increasing temperature. Furthermore, a tentative relationship is recommended to predict TC of the species. Finally, thermal conductivity of these three species has been compared and it has been found that Carpinus betulus thermal conductivity is higher than Acer laetum and Populus Alba.

The potential of canola stalks for the absorption of Remazol Black B reactive dye from artificial aqueous solution was studied. The results indicated that the absorption efficiency increased with decreasing pH and temperature. Moreover، absorption capacity increased with increasing dye concentration in solution. Absorption rate of Remazol Black B on the canola stalks was fairly rapid and the equilibrium state was reached within 20 minutes in all experiments. Using various concentrations، absorption isotherm study showed that the Remazol Black B dye absorption is well described by both Langmuir and Freundlich models. Langmuir model (R2>0. 99) was better fitted than Freundlich model (R2>0. 98). The constants of Langmuir and Freundlich models were calculated and the highest adsorption capacity was found to be 32. 8 mg/g which is an acceptable value compared to other studied adsorbents.