جستجوی مقالات مرتبط با کلیدواژه « Nano » در نشریات گروه « مهندسی شیمی، نفت و پلیمر »

Crystal glazes are used as functional coatings with applications such as decorating ceramic bodies or improving mechanical, opacity and other properties. Depending on the glaze conditions, ceramic body and heat program, various crystals are created in the liquid phase of the glaze that sometimes create or improve the properties and sometimes create special luster and unique effects in the glaze. These glazes can be classified based on size (macro, micro, nano), type of crystal and composition (hematite, anorthite, pyroxin, etc. /zircon, silver, gold, etc.). Silica, fluxes and crystallizers are the main components of the crystalline glaze base composition and the crystalline formation mechanism in the glaze is the same as the nucleation and growth mechanism.Factors affecting the formation and growth of crystals: the composition, thickness, type and amount of nucleates and coloring agents in the glaze, design and duration of heat firing curve (heating and cooling), temperature and time of absorption in the growth process, furnace atmosphere and also the composition and geometric form of the ceramic body. In this study, some of these factors will be briefly explained.

In this work a computational fluid dynamic (CFD) and experimental study of Fischer–Tropsch Synthesis (FTS) process in a fixed-bed reactor is presented. The reactor was a 1.2 cm diameter and 80 cm length steel tube in which ceramic particles were employed to dilute the catalyst bed and thus prevent the emergence of hot spots in it. An axi-symmetric CFD model with an optimized mesh of 22016 square cells was developed to model hydrodynamics, chemical reaction and heat and mass transfer in the reactor. Non-ideal thermodynamic behavior of gas mixture was modeled using Peng-Rabinson equation of state. Kinetic models for FTS and Water–Gas-Shift (WGS) reaction rates based on Langmuir–Hinshelwood type for each of species were employed. Good agreement was achieved between bench experimental data and the model. Because of the high price of reaction experiments and also safety the validated model used as numerical setup and the CFD simulations considered as numerical experiments. A sensitivity analysis was carried out in order to find the effect of temperature, pressure, and GHSV and H2/CO ratio on the reactor performance.

In this research, the adsorption of sulfur compounds from propane and butane streams (real gas from Assaluyeh) using faujasite-type zeolite in constant pressure and temperature was studied. Zeolite NaY was synthesized in order to specify the effect of NaY size on adsorption of sulfur compounds. The synthesized samples were characterized by XRD, FE-SEM and BET analyses then three different sizes of NaY zeolite (60nm, 800nm, 2400nm) were selected to specify the effect of the particle size on the sulfur compound’s removal performance. The outlet gas streams were characterized using a potentiometric method (UOP212). Breakthrough curves were plotted for each stream; moreover, the breakthrough curves were modeled using BDST (bed depth service time) model and Yoon-Nelson model in order to determine the effect of adsorbent’s size, type of inlet gas and the amount of sulfur compounds on the parameters of Yoon-Nelson and BDST models. After making a comparison between the results from breakthrough modeling, it was concluded that for BDST model, decreasing the size of NaY zeolite increased the adsorption capacity index while the proportionally constant model was being decreased; however, in Yoon-Nelson model, decreasing the size of NaY zeolite increased time to %50 of breakthrough curve and decreased the proportionally constant model.

The presence of nanoparticles in the polymer matrix will cause an increase in the mechanical performance of nano-composite. In this research the nature of reinforcing material was investigated by mixing pure polyurethane with two different nanoparticles, silicon carbide or alumina. The composition was selected in three levels; 1, 2.5 and 5 in weight percent. The dispersion and distribution of nanoparticles were examined by scanning electron microscopy (SEM). Adhesion, abrasion and hardness tests were applied to study the physical properties of the coated layers. The results were confirmed that in case of silicon carbide by increasing the amount of additive to 5%, all the adhesion, abrasion and hardness values reduced. While by substituting alumina with silicon carbide this trend has been changed to a positive value. Polyurethane-5% Alumina nanoparticles shows 25% increase in adhesion, 23% increase in abrasion and the hardness increases from 3H to 5H.

Stevia or sweet plant is a native plant in the continent of America. It was studied by a Spanish physician for the first time in 1888. The people of brazil and Paraguay were used it as a sweetener and as a medicine for high blood pressure, gastro burn, uric acid control, and fatness since centuries ago. At present many countries such as Japan have marketed stevia extract as a replacement for unnatural sweeteners such as saccharine, aspartame and cyclamate to avoid their hazardous effects. The sweetening compounds (glycosides) are stevioside, rebaudioside A, etc. in this project different methods of stevia glycoside production were investigated such as solvent and super critical fluid extractions, nano, ultra and membrane filtrations. Finally a suitable schedule was designed to produce stevia sweetener.

Titanium dioxide is used in many different fields, from industry to the area allocated to health and use of this materials to progress. Hence, reviewed synthesis and properties of porous titanium dioxide nanoparticles as a new and growing field is examined. Porous structure of titanium dioxide synthesized different methods for example, sol-gel and precipitation method. Also, The characterization of this type of nano-structures have been investigated.

This study was designed to investigate the effect of nano silica particles on the pressure-sensitive acrylic adhesive bonding on polypropylene film. In this work, the effect of plasma treatment on polypropylene films was examined. Selected variables including plasma treatment time, power and gas type at three levels were considered. Results were analyzed by Taguchi method and optimum condition of high adhesive strength at 7 minutes, power of 100 W and argon gas was obtained. Then varying amounts of silica nanoparticles were added to the acrylic adhesive. Adhesion strength test method was evaluated and the results showed that the strength increases to maximum value at 5.0 weight of nano silica. Functional groups on PP surface following plasma treatment were also detected using ATR- FTIR method; moreover, the etching condition of the surface was examined by both SEM and AFM methods.

Metallic nanoparticles are widely used in high energy materials (explosives, propellants and pyrotechnics). Nanoparticles are used in solid propellants as fuel additives in order to improve the performance. In this paper, the role of nano-aluminum particles on burning behavior of solid composite propellant has been investigated. Nano-aluminum particles are considered as one of the most important energetic components of metallic fuel in the solid composite propellants. Studies showed that the addition of nano-aluminum particles increases the burning rate, reducing the amount of agglomeration, decreasing diameter of burning particles, falling combustion temperature and reducing the amount and size of residual ash. The use of nano-aluminium particles leads to reduction the pressure exponent in the burning rate law. Based on reviews size reduction of
nano-aluminium particles from micron to nano, increases the burning rate of solid composite propellants about 100 percent.

Adhesives are one of materials which mankind have been used from many years ago. Adhesive used in many cases and different situations, one of these uses is joints. Joints play an important role in structural uses, so the adhesive which use in joints, must meet the requirement of a structural adhesive and can be use in different service conditions and environmental situation. These days with changes in industrial needs, appearing new technologies, increased commercial availability and reduce prices, reinforcement of adhesives with nano reinforcements widely researched and reported. Nanoreinforcements due to their high ratio aspect and specific area, can improve polymer properties when add to polymer matrix as a reinforcement. In this paper, adhesive and mechanisms of adhesion explained, nanoreinforcements as an appropriate alternative to other kind of fillers and reinforcements are introduced, also those kind of adhesive properties which addition of nanoreinforcements made changes on them are explained. Nano reinforcements in 3 categories (inorganic, Carbon Nanotube and carbon Nanofiber) are introduced and their effects on adhesive polymer are discussed.

Most studies on antimicrobial properties of nano-TiO2 in deionized water deal with its photocatalytic properties. Few studies have shown that the presence of nano-TiO2 can inhibit the growth of the bacteria and it ultimately kills them in a culture medium in the dark. In this study, the antibacterial effects of suspended in a culture medium and immobilized nano-TiO2 systems in cement bed (0.1-1%) were investigated on Thiobacillus thioparus as a bacterium involved in cement biodegradation. The pH and turbidity tests were carried out in order to monitor the viability of the bacteria in the culture medium. The results showed that T. thioparus did not grow in the presence of cements containing nano-TiO2 and at longer contact time the bacterial death occurred. The optimum concentration of nano-TiO2 has been found to be 1% to maintain antibacterial properties. Thus, with evaluation of the toxicity effects, the cementitious antimicrobial coatings could be produced by immobilized nano-TiO2 for self-protected against biodegradation.

UV-curing coating based on novolac epoxy acrylate resin was synthesized and formation of desired structures was confirmed by appearing of 1722, 810 and 945 cm-1 in the FTIR spectrums. In order to study the effect of presence of inorganic silica on the properties of synthesized resin, an organic/inorganic nano-composite was prepared using the synthesized resin and silica nanoparticles. Scanning electron microscope (SEM) revealed very high agglomeration of nano particles, during this process that was due to the incompatibility of two organic and inorganic phases which could lead to inferior properties of the produced nano composite. In order to overcome this problem, the surface of silica nano-particles was modified by vinyltrimethoxy silane coupling agent using sol-gel method in order to increasing the compatibility of two organic and inorganic phases. Completion of surface modification process was investigated by using of FTIR spectroscopy, scanning electron microscope, thermo-gravimetric analysis and helium pycnometer, confirming the proper reaction of silane coupling agent on surface of silica particles. Characteristics of prepared nano-composite were investigated by dynamic mechanical thermal analysis, hardness, scratch resistance, and abrasion resistance, proving better mechanical properties of nanocomposites over the neat coatings. Measuring the haziness showed very little impact of presence of nano particles on the transparency of coatings that was due to surface modification of coatings which has led to more compatibility of organic and inorganic phases.