جستجوی مقالات مرتبط با کلیدواژه "ferrofluid" در نشریات گروه "مواد و متالورژی"

In this study, we first synthesized zinc ferrite nanoparticles by using co-precipitation method and adding zinc to iron ferrite in different amounts. Redistribution of Fe and Zn cations in tetrahedral and octahedral locations can significantly alter and increase saturation magnetization. The saturation magnetization of the synthesized ferrite nanoparticles was 57% higher than that of iron ferrite, and the nanoparticles had an average size of 35 nm. The synthesized nanoparticles were then functionalized using oleic acid and polyethylene glycol and three types of stable fluids based on water, engine oil and ethylene glycol were prepared. Optimal Ferro-fluid with the highest stability properties and amount of saturated magnetization was used to investigate the rheological properties. The non-Newtonian behavior of the fluid with different percentages of nanoparticles was investigated and the greatest change in behavior from the Newtonian state was related to the fluid with 15% by volume of nanoparticles.

Electromagnetic energy converters have been used as electrical energy suppliers. The use of solid magnets in these devices, for producing of magnetic induction, has produced difficulties for the design and application of these systems in various forms and frequencies. Magnetic fluids as a substitute for solid magnets have recently been considered for the use of these devices in low frequency ranges and different designs. In this study, a simple vibrational energy converter was designed using magnetite ferrofluid. For this purpose, the nanoparticles of magnetite were synthesized by co-precipitation method and surface modified by oleic acid. The XRD, FTIR, VSM testes and SEM studies were done to investigate properties of the samples. The nano magnetite particles had the average size of 70 nm and the saturation magnetization of 41.63 emu/gr. Three types of fluid including water, kerosene and brake oil were used to make magnetite stable ferrofluid. The most stable ferrofluid was brake oil based ferrofluid. The fabricated energy converter converted mechanical vibrations to induction voltage and voltage increased with frequency of vibration and applied magnetic field.

Preparation of ion stable ferrofluid with water liquid carrier is presented in this paper. Iron oxide nanoparticles and tetramethyl ammonium hydroxide (TMAH) were used as solid phase and stable agent respectively. Magnetic properties of nanoparticles and ferrofluid were investigated by VSM. Particle size was calculated by Sherrer formula and magnetic data and compared with the sizes estimated by TEM micrograph. The size of particles were about 10 nm and their saturation magnetization were between 65.5 and 84 emu/g. Saturation magnetization of ferrofluid, its density and the density of suspended particles were calculated using magnetic data and compared with those calculated by direct measurement and a simple method for estimating magnetization of ferrofluid was proposed. Results showed that the extent of stirring the fluid during preparation affect its quality. Also the content of magnetic phase in the fluid directly affects its saturation magnetization and initial susceptibility.

In this research، magnetite iron oxide nanoparticles were synthesized via coprecipitation method and their colloidal stability was investigated using 3 different comb polymeric surfactants based on polyacrylic acid-co-polyethylene glycol acrylate in water media. The difference of these surfactants is in tree type of polyethylene glycol with molecular weights of 1000، 2000 and 4000 which is connected to hydrophobic acrylate chain. The effects of synthesis temperature and time on particle sizes were studied. The temperature and time range was determined 27-90C and 10-40 min، respectively. To synthesis of magnetite nanoparticles، ferric and ferrous chlorides were precipitated with pH adjustment using ammonia (25 wt %) solution. The size distribution and stability of particles were studied via dynamic light scattering (DLS) and turbidimetry، respectively. The attachment of surfactants on nanoparticles was studied using fourier transform infrared spectroscopy (FTIR). Results showed that the particle sizes are different related to molecular weights of polyethylene glycol in comb polymeric surfactants. The com polymeric surfactant with polyethylene glycol Mw=2000 was lead to lower mean particle size and better stability relative to others. Moreover it was revealed that the best magnitude colloidal stability was with 22 wt % from comb polymeric surfactant having polyethylene glycol Mw=2000 at 70C for 20 min. The hydrodynamic size of particles was 80nm in this condition.