جستجوی مقالات مرتبط با کلیدواژه « nanoparticles » در نشریات گروه « فنی و مهندسی »

In this paper an optical tweezer with the ability to manipulate and sense nanoparticles using the coupling of surface plasmons of two gold strips and its nano-focusing is proposed. To investigate the performance of the proposed structure, at first the plasmonic modes have been calculated by the finite difference Eigen-mode method and then using the finite-difference time-domain method and calculating Maxwell stress tensor the optical forces have been obtained. The simulation results show that the proposed structure has the ability to trap and manipulate nanoparticles. Due to the dependency of the trapping sites on the incident light frequency, the proposed structure, in addition to the ability to move nanoparticles by mechanical movement of the optical tweezer, can also move nanoparticles by tuning the frequency. Also, the simulation results show that due to the dependency of the reflected power on the refractive index of the trapped nanoparticle, the trapped nanoparticle can be sensed by analysing the reflected power. We believe this structure can be used in various fields, especially in biological sciences, to study and move nanoparticles.

In this study, the performance of biochar and titanium dioxide nanoparticles in combination with epoxidized soybean oil as a biolubricant is investigated. biochar nanoparticles were produced from sugarcane bagasse coal using the ball mill. Then, after the production of biochar nanoparticles, in order to check their quality and size, samples are photographed using a scanning electron microscope. Titanium dioxide nanoparticles were also prepared commercially. In the next step, nanoparticles with weight percentages of 0.1, 0.2, and 0.5 were combined with biological fluid, after ensuring the stability of the nanofluid, the prepared samples were tested to determine the wear and friction properties. The results show the friction coefficient changes for nano titanium dioxide fluids are better than nano biochar lubricants. At the concentration of 0.1, the average friction coefficient of titanium dioxide nanoparticles was recorded as 0.092 and nano biochar as 0.115. For titanium dioxide and nano-biochar with a concentration of 0.2, it is 0.067 and 0.143, respectively, and for a concentration of 0.5, it is 0.064 and 0.111, respectively. The results of the wear test also show the wear rate of nano-lubricant discs with concentrations of 0.1, 0.2, and 0.5 containing titanium dioxide compared to nanobiochar 24.65, 35.43, and 85.48% is decreased respectively.

Iron oxide nanoparticles have been gaining much attention lately due to their magnetic properties and biocompatibility. This research focused on investigating the properties and synthesis of iron oxide nanoparticles that have been substituted with zinc ZnxFe3-xO4 (x= 0.0, 0.2, 0.4, 0.6)  using the hydrothermal method. The synthesized samples were analyzed using X-ray diffraction and found that they have a space group of fd3m. The crystal size of the samples was found to be smaller than 20 nm. Vibrating sample magnetic analysis (VSM) was used to determine the magnetic behavior of the nanoparticles. The analysis showed that the nanoparticles exhibited superparamagnetism. In addition, the saturation magnetization values of the nanoparticles for samples with x = 0, 0.2, 0.4, and 0.6 were 44.10, 49.09, 43.51, and 48.07 emu/g, respectively. The microstructure and grain size of magnetic nanoparticles were analyzed using a field emission electron microscope (FESEM). The FESEM images revealed that the majority of the grains are spherical and have uniform distribution. The average grain size for the sample ranges between 10 and 30 nm. Based on these results, it can be concluded that these particles are suitable for use in medical and catalytic applications.

Copper oxide is obtained by various methods, including electrolysis, recovery of copper salts or copper oxide, thermal oxidation and hydrothermal treatment. Electrochemical method is very interesting due to its low cost, low temperature, ease of operation, high purity and compatibility with the environment. In this research, the effects of NaCl, Na2SO4 and CTAB (cetyltrimethylammonium bromide, C19H42BrN) electrolytes on the synthesis of Cu2O nanoparticles by electrochemical method were investigated. Changes of NaCl in three values of 58.5, 117 and 175.5 (g/lit); changes of Na2SO4 in concentrations of 24, 32 and 48 (g/lit) and changes of CTAB in the range of 2, 4, 6 and 15 (g/lit) were selected. The current density and temperature were fixed and equal to 0.4 (amps/cm2) and 70°C, respectively, and the fixed distance between the cathode and the anode was considered to be 2.5 cm. FESEM and XRD were used to observe the morphology of the samples and identify the composition and determine the particle size. The results showed that by increasing the concentration of NaCl and Na2SO4 electrolyte, the purity of Cu2O increased. The size of Cu2O crystals was below 100 nm and the formation of Cu2O was polycrystalline. Also, high concentration of NaCl gave better results compared to Na2SO4. CTAB effectively prevents the growth of Cu2O nanoparticles and the particle size was inversely related to the increase of CTAB. The best result was obtained in the sample with 4 (g/lit) CTAB and 175(g/lit)NaCl. Cu2O nanoparticles with high purity and crystal size of 27.87 nm were produced.

In recent years, there has been a significant interest in lanthanum-based perovskites due . Lanthanum strontium manganite (LSMO) is one of the most well-known materials. In this research, the synthesis and investigation of the effect of oleic acid on the structural and magnetic properties of La0.7Sr0.3MnO3 nanoparticles by the combustion sol-gel method is discussed. The structural and magnetic properties of the prepared samples were investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), magnetic properties analysis (VSM), and field emission electron microscopy (FESEM). In the XRD study, it was found that the crystal structure of the samples is hexagonal. Also, the average crystal size in the samples increased from 18 nm to about 33 nm as a result of adding oleic acid. The images obtained from FESEM show that the presence of oleic acid in the synthesis of nanoparticles caused it to affect the shape of the particles as a surface layer. Synthesized nanoparticles have a particle size between 20-100 nm, and with the increase of oleic acid, the particle size becomes more than 100 nm. FTIR spectroscopy revealed the effective bonding between LSMO nanoparticles and oleic acid, based on these results, it clearly shows the presence of oleic acid molecules on the surface of magnetic particles. In the investigation of magnetic properties, it was found that the presence of non-magnetic sodium oleate surface layer, which due to the addition of oleic acid on nanoparticles, the saturation magnetization value decreased from 38.55 emu/g to 28.46 emu/g.

Nanoparticles have brought significant advantages in a wide range of fields due to their unique size-dependent physical and chemical properties. In this research, the combustion solution method is used to make La0.7Sr0.3MnO3 (LSMO) nanoparticles. Then the nanoparticles are covered with polyethylene glycol polymer. Due to the presence of hydrophilic molecular chains and high flexibility, polyethylene glycol is one of the most ideal coating agents to increase the colloidal stability and biocompatibility of LSMO nanoparticles. Using X-ray diffraction (XRD), the crystal structure, nanoparticle size and nanoparticle composition of LSMO were investigated, and a hexagonal structure with a crystal size of 18.4 nm was observed. Field emission electron microscopy (FESEM) was used to investigate the shape and size distribution of nanoparticles. The images showed that most of the grains are spherical with uniform distribution and the grain size in the processed sample is between 20 and 60 nm. The behavior of nanoparticles was estimated as ferromagnetic using Vibrating Sample Magnetic Analysis (VSM) and the saturation magnetization value before and after nanoparticle coating is 24.8 (emu/g) and 23.6 (emu/g), respectively. FTIR spectroscopy showed effective bonding between LSMO nanoparticles before and after treatment with polyethylene glycol.

In this study, we employed the active TIG method with ultrasonic vibration (UV) for welding 316L steel. Throughout the active tungsten inert gas (A-TIG) welding process, a high-frequency ultrasonic generator produced high-intensity acoustic waves at an optimal frequency of 20.3 kHz and a vibration amplitude of 8 micrometers. These waves were directed into the molten weld pool, covered by SiO2 nanoparticles serving as an activating flux. The effect of UV and nanoparticles on weld geometry and weld microstructure was analyzed and compared with conventional TIG welding proces. The results indicated that the use of nanopowder not only increased weld penetration by approximately 17.5% but also reduced the Weld Bead Width (WBW) by 28% compared to Conventional TIG. These values increased by 25% and decreased by 35%, respectively, in the presence of ultrasonic waves. Additionally, the introduction of nanomaterials into the molten pool led to finer grains. The ultrasonic waves played a crucial role in ensuring the uniform distribution of these nanomaterials in the melt, ultimately resulting in an enhanced microstructure of the weld.

Preparing composites before welding and using nanocomposites is one of the new methods of joining. In this research, the mechanical strength of thermosetting composites surface prepared by chemical etching using polyvinyl chloride (PVC) polymer in the presence of aluminum oxide nanoparticles has been investigated. Thermal analysis of PVC containing different weight percentages of aluminum oxide nanoparticles shows a 45% increase in thermal conductivity. A regression model based on the response surface methodology using the effective parameters of welding time, weight percentage of nanoparticles and thermal conductivity obtained from variance analysis was developed to predict the maximum force and displacement of joint failure. The results show the maximum breaking strength and strain of 59 MPa and 0.04 of the welded sample, respectively, in the presence of 1% by weight of aluminum oxide nanoparticles. The increase of 1.3 and 1.2 times of the maximum tensile strength and breaking strain of the joint, respectively, in comparison with pure PVC samples, indicates the improvement of mechanical properties. Examining the microstructure with SEM shows that a uniform connection has been established along the weld line.