Papers by Keyword: Magnetite

Abstract: On the basis of the experimental data, a method and mechanism for modifying magnesia binders with iron ore concentrate has been proposed. It consists in form of a material reinforced fine-crystalline structure with elongated magnesium oxychloride crystals, which improves its physical and mechanical characteristics. The components of iron ore concentrate and magnesia binder, having improved sorption properties, significantly accelerates the formation of such a structure.

Abstract: The Nimba Range and its western extension are located in the Nimba region on the borders of the Republic of Guinea, Liberia and Côte d'Ivoire. It is a mountainous region made up of metavolcanic and metasedimentary rocks. Metavolcanic rocks are gneisses, granites, amphibolites and quartzites, which constitute the lower part of Archean age. The upper part consists of Proterozoic rocks of metasedimentary origin. It contains important deposits of itabirites which occupy the top of the mountains and hills of the region. The petrographic study of the banded iron formations reveals the existence of silicate banded iron formations (SIF) and oxidized banded iron formations (OIF). The results of the scanning electron microscope (SEM) and metallogenic analyzes show the presence of iron minerals (magnetites, hematites, pyrites, goethites, martites and siderites). These analyzes also reveal the presence of the metamorphic index minerals associated with the banded iron formations, hence the existence of several types of ferriferous formations (silicate (SIF) and oxidized (OIF) banded iron formations). Overall, there is an increase in the degree of regional metamorphism from east to west of the Nimba region. The geochemical analysis of the banded iron formations reveals that with the exception of Na₂O, all the major elements have a negative linear correlation although dispersed with Fe₂O₃. This correlation is explained by a decrease in quartz, garnet, micas (muscovite and biotite), amphibole, pyroxene, plagioclase, titanium and phosphorus contents. Conversely, there is an increase in iron ore content: magnetites, pyrites, hematites, goethite. But the alkali content remains constant in these banded iron formations. Then, the lower the Fe₂O₃ content, the higher the FeO content, while those of SiO₂ and Al₂O₃ are constant in all of these formations in the Nimba region except in the chlorite banded iron formation where both are anticorelated. Finally, the ratio SiO₂ / Fe₂O₃ vs MgO + CaO + MnO / Fe₂O₃ of the banded iron formations of the Nimba region compared to the same formations of the whole world allows to give them Proterozoic age. Some itabirites have high levels of magnetite, hematite, and goethite (same feature as itabirites of Lac supérieur and Pic de fon) and only chlorite itabirite has a low to medium Mg-Si-BIF content.

Abstract: Analysis on magnetic minerals of iron sand in Sampulungan Beach, Takalar Regency based on magnetic susceptibility value has been conducted. Iron sand was taken on 30 points and extracted using a rod magnet, then measured magnetic susceptibility using Bartington susceptibility meter MS2 with the MS2B sensor. Furthermore, types of magnetic minerals were analyzed based on the value of magnetic susceptibility. The results showed that the percentage of magnetic mineral was higher along the trajectory near residential areas. Magnetic susceptibility values ranged from 33932.62 x 10^-8 m³/kg to 71829.96 x 10^-8 m³/kg. Based on the value of magnetic susceptibility, the dominant type of magnetic mineral in Sampulungan Beach is magnetite (Fe₃O₄) of 76 wt.%. The high magnetite potential in Sampulungan Beach can be further processed to be used in the metal industry.

Abstract: The manufacture of optimized heavyweight concrete takes into consideration the type of aggregates, composition of blended cement, water-to-cement ratio, additives etc. The density of concrete depends mainly on the specific gravity of the used aggregates. Generally, concretes with specific gravities higher that 2600 kg m^-3 are called heavyweight concretes and aggregates with specific gravity higher than 3000 kg m^-3 are considered as heavyweight aggregates according to EN [1,2]. Concrete is a low cost material and easy to produce in varied compositions when compared to other shielding materials based on ceramics [3]. It is composed of a well-proportioned mixture of light and heavy nuclei. It is therefore efficient both in absorbing gamma rays and in slowing down fast neutrons by elastic and inelastic scattering [2]. Light materials, especially hydrogenous materials which contained in the water of hydration of the set cement (concrete) attenuate fast neutrons as a consequence of the high cross-section of hydrogen [4].

Abstract: We have studied the influence of oxidation-reduction reactions on the structure and strength behavior of the Kachkanar fluxed pellets both in their initial condition and during reduction. It has been discovered that at heating rates and temperatures found in industrial units the roasted pellets that are not oxidized to a full extent and are characterized by zonal structure do not meet the requirements imposed for the blast-furnace smelting raw materials. To develop a process that would ensure high metallurgical properties, we have analyzed the hematite dissociation reaction. It was found that the temperature and the content of slag-forming oxides influence this reaction. A sinter pot was used to carry out the research and determine metallurgical properties of partially dissociated pellets. The obtained results helped to develop a process to dissociate hematite at lower temperatures with calcium ferrosilicate melt. Such pellets are reduced at the temperatures of over 700^оС, which prevents their destruction in blast furnaces.

Abstract: We report on the results of the study of the lateral photovoltaic effect in the Fe₃O₄/SiO₂/p-Si structure. It is found that maximum of the lateral photovoltage is localized near the measuring contacts and rapidly attenuates when the light spot moves away from them. Correspondence of the photovoltage sign to the conductivity type of the silicon substrate is achieved only taking into account the interface states at the SiO₂/p-Si interface. The extreme dependence of the lateral photovoltage on the thickness of the Fe₃O₄ film is observed, which is due to the fact that the barrier height is laterally inhomogeneous at small thicknesses of magnetite film, whereas at higher thicknesses of the film the lateral photovoltaic effect is short-circuited by this film.

Abstract: In the present study, Fe₃O₄ nanoparticles type/core layer were synthesized by co-precipitation wet method and coated with a polymer mixture of polyethylene glycol (PEG). It was performed a study about the effect of duration in maceration time on the final size of nanoparticles in in order to get reaching the maximum condition of disintegration of the crystals. The samples were synthesized according to the same procedure and amount of reactants used synthetic sequence for all samples, only varying the time spent by each sample maceration process done after synthesis. The different times for the maceration samples were 3 minutes, 5 minutes, 7 minutes, 10 minutes, 12 minutes, 20 minutes and finally 30 minutes. The nanoparticles were characterized by Nanosight, DR-X, rietvield analysis and hysteresis curves plotter techniques. The results showed that the grain size of the particles stabilizes at maceration times of more than 20 minutes. The samples presented a satisfactory hysteresis curve indicating the presence of superparamagnetic behavior expected in hyperthermia treatment.

Abstract: Magnetic magnetite, Fe₃O₄ nanoparticles produced by Massart’s procedure were used to prepare water based magnetite, Fe₃O₄ ferrofluids without addition of any stabilizing agent or surfactant. The thermal properties and suspension stabilization of the ferrofluids were investigated by varying the magnetite, Fe₃O₄ nanoparticles concentration in the ferrofluids prepared. The thermal conductivity of water based ferrofluids prepared using five different volume fraction of magnetite, Fe₃O₄ suspension (0.1, 0.05, 0.02, 0.01 and 0.005) were measured at five different temperature, 25°C, 30°C, 40°C, 50°C and 60°C in order to evaluate its potential application as heat transfer fluid. The results shows that the thermal conductivity of the ferrofluids are higher than the base fluid, and the thermal conductivity of the ferrofluids increased as the magnetite concentration in the ferrofluids decreased however reached its optimum for ferrofluids prepared using 0.01 volume fraction of magnetite suspension over 0.99 volume fraction of water. Accordingly, the thermal conductivity of the ferrofluids significantly increased as the temperature increased where 49.4% enhancement with respect to water were observed at temperature 60°C.

Abstract: Desalination can be carried out in water to remove any salt. The process takes place after tertiary treatment of municipal and industrial waste water as a final treatment before discharge to the recipient. The desalination of seawater using Reverse Osmosis (R.O.) technique is now a tried and proven technology that can provide high-quality water supply. The resulting from R.O. water is not suitable for drinking. The method proposed in this paper is selected desalination via zeolitic micro-particles. The method exhibits some significant advantages such as the easy recovery and reuse of powders (with negligible losses during the release process of trapped ions in liquid solution), the selective removal of ions and the ability of producing directly potable water without the need for further enrichment.

Abstract: Magnetite’s abilities rely on the quantitative phases present in the sample. Magnetite quality can strongly influence several physical properties, such as magnetism, catalytic performance, and Verwey transition. However, differentiation of magnetite and maghemite through the conventional X-ray diffractogram comparison are not relevant for the intermediate phases. In this study, the deviation from the ideal stoichiometric magnetite and the relative quantification of both phases were mathematically achievable through a new XRD technique. Various synthesis conditions were applied to obtain different crystallite sizes, in the range of 9 to 30 nm. Generally, the stoichiometric deviation and maghemite content would be significantly influenced by the final size, whereas system conditions (temperature of solution, agitation rate, and pH of solution) would only have minor significance. In this study, iron oxide nanoparticles prepared using the co-precipitation method was calculated to contain 100% magnetite for particles of 30.26 nm in size, while 100% maghemite was calculated for particles at 9.64 nm.