Papers by Keyword: Iron Oxide

Abstract: Bad breath is mainly caused by malodorous materials, volatile sulfur compounds (VSC), hydrogen sulfide (H₂S). Pharmaceutical drugs should be effective but limited, because bacteria at deep periodontal pocket may be sterilized but cannot be washed out and the malodorous compounds remain. The absorbents for the malodorous compounds are expected to prevent the teeth from decaying and peiodontics disease. The layered double hydroxides, of which composition is A_1-xB_x(OH)₂C_x/n·mH₂O, where A and B are zinc and Fe ions are effective as the absorbents for VSC. The VSC adsorption capabilities of zinc or iron oxide in comparison with that of layered double hydroxides containing zinc or iron ion. The high capacity of sulfide adsorption of layered double hydroxide may be due to the large number of adsorption sites of layered double hydroxide materials. The layered double hydroxides (LDH) have a structure favorable for ion or free molecules exchange, and high affinity with sulfide may be involved in iron or zinc containing LDH materials.

Abstract: In present study, possibility of developing a new magnetic aluminum-based composite material by using principles of friction stir forming (FSF) is studied. Friction stir forming is a new materials forming technique which uses frictional heat to plasticize and plastically deform the alloy. Local magnetizing and local hardening of A6061 aluminum alloy is discussed by attempts of embedding and dispersing iron oxide powder and steel balls into A6061 aluminum alloy through spotted friction stir forming. Experiments revealed that FSF can be used to mechanically interlock steel balls and iron oxide with aluminum alloy and develop an aluminum metal matrix composite with improved magnetic properties. Results are discussed in terms of microstructural observation, hardness and magnetic properties.

Abstract: Iron oxide nanowires were synthesized on stainless steel mesh substrate using the thermal oxidation process at the varying temperature of 750°C for 60 min. The samples were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The XRD pattern showed that the iron oxide nanowires exhibited the structure of alpha-Fe₂O₃ (hematite). SEM images indicated that the diameter and the length of the nanowires were 80 to 285 nm and more than 5 μm, respectively. The dye-sensitized solar cell (DSC) properties based on the nanowires substrate was also studied. It was found that the power conversion efficiency (η) of the device was 0.11%.

Abstract: In spite of being known for centuries, iron oxides are still important. Such modifications as magnetite Fe₃O₄ and epsilon phase ε-Fe₂O₃ are of great scientific and practical interest due to their promising electromagnetic properties. Nonetheless, only few methods allow synthesizing both of these phases, but they have some well-known disadvantages, which limit the possibility of using them widely. This work shows a unique method of synthesizing these materials in one short-duration plasma dynamic process using a coaxial magnetoplasma accelerator with iron electrode system. The plasma chemical reaction occurs between the iron-containing plasma and gaseous precursor (oxygen). The influence of oxygen pressure on the products of plasma dynamic synthesis was also studied in the framework of this investigation. It was found that the higher oxygen concentration leads to the formation of product with predominant content of epsilon iron oxide ε-Fe₂O₃, as well as lower oxygen concentration results in obtaining the product with the dominance of magnetite phase.

Abstract: The paper affirms that, despite the number of works in the sludge neutralization of waste water containing heavy metal compounds, the proportion of their use remains marginal. Therefore, one of the important directions of nature protection activities and the natural resources rational use is developing a technology for processing these wastes and their involvement in the production of useful products. The research of chemical, mineralogical and granulometric composition of wastewater slurry waste neutralization in production of vanadium pentoxide and ferrovanadium alloys by OJSC "EVRAZ Vanadium Tula" has been carried out. It is proposed to use a slurry waste in the claydite gravel production technology. The introduction of 1% sludge makes it is possible to obtain the following characteristics of claydite gravel: strength brand P 25, a packed density mark - 250. The 3% increase of the sludge provides a claydite gravel with the strength brand P 15 with the packed density of 250 kg/m³.

Abstract: Biogas derived from anaerobic digestion of biological wastes has been extensively used for heating purposes and/or electricity generation. Presence of hydrogen sulfide (H₂S) in biogas affects engine performance adversely, thus reducing H₂S content is a valuable part in practical application before utilizing biogas. Adsorptive separation is very appealing due to being an economical and effective method including the use of iron oxide based adsorbents. Pelletization of iron oxide adsorbents has never been reported among the adsorbents described to date. Therefore, H₂S capture in two iron oxides (ferric oxide (Fe₂O₃) and magnetite (Fe₃O₄)) was experimentally investigated to determine technical feasibility of shaping pellets based on active iron oxide sorbent in removing H₂S from a simulated gas stream (0.35 vol.% H₂S balanced in N₂). Many factors affecting the behavior of gas adsorption such as gas in-flow rate, adsorption temperature, binder loadings and textural characteristics were considered. The pellet strengths were also undertaken using a bulk crushing strength analyzer. The results indicated that higher temperature favors the diffusion of H₂S molecules from the surface into the bulk of iron oxides. The H₂S-sorption capacity of Fe₃O₄ sorbent was higher than that of Fe₂O₃ sorbent corresponding with the different pore volume and surface area in each adsorbent. With the same active Fe₃O₄, the extruded pellet produced with starch binder showed the excellent H₂S uptake and crushing resistance. The higher gas in-flow rate had positive impact to contacting efficiency and mass transfer of solid and gas phase. The adsorbed H₂S gas can be readily desorbed from the pellets with the desorption temperature below 60°C and the H₂S-sorption capacity was consistent over repeated cycles. The pellets can be reused several times for consecutive adsorption/desorption cycles, without loss of performance in a large-scale reactor and therefore represent serious candidates for use in commercial absorbers.

Abstract: Bimetal adsorbent system of calcium oxide impregnated on iron (III) oxide were evaluated as a potential source of basic sites for CO₂ capture. The adsorbents were prepared by impregnation method were calcined at 200 until 600 °C. Several characterizations were carried out using XRD, BET and CO₂-TPD analysis. The CaO loading increased the basicity of the adsorbent significantly enhance the CO₂ chemisorption. Furthermore, it drastically reduced the desorption temperature to 310-490 °C, which is important in chemisorption aspect. The CaO/Fe₂O₃200 which calcined at 200 °C was found to be most efficient. The CO₂ chemisorption (81.29 mg CO₂/g adsorbent) was contributed most compared to physisorption (4.64 mg CO₂/g adsorbent).

Abstract: In this paper the systematized literature data about the PbO-Fe₂O₃ system and new experimental results are presented. Based on the analysis of EDX, DTA and PXRD data on a series of compositions from 5 to 85 mol % PbO, the phase diagram of the PbO-Fe₂O₃ system was updated. Using the obtained data and the data of other authors thermodynamic functions were optimized and the thermodynamic modeling of the phase equilibria in the system was performed, results of which are presented in the form of the PbO-Fe₂O₃ phase diagram.

Abstract: The tableware soda-lime silicate glasses, contained with 0.06 wt% of iron oxide, which were annealed at different times and temperatures, were investigated by UV-Vis spectroscopy. The glasses were produced from high iron sand. The iron content was twice as high in the glasses as it is in normal tableware glasses. The redox reaction of iron around glass transition temperature, Fe²⁺(green) ↔ Fe³⁺(yellow), was found in the annealing process, according to the redox reaction of iron with polyvalent ions in the glass, nFe³⁺ + M^a+ ↔ nFe²⁺ + M^(a+-n) where M is the polyvalent ion in glass. In this study, the glasses were prepared by melting in a platinum crucible. After casting, they were annealed with variable times and temperatures. The results of color in CIE L*a*b* system and Fe²⁺/Fe³⁺ ratio of glasses showed the effect of the annealing process on the redox reaction of iron. The decolorizing was found during the annealing process. The results of this work led to the method for controlling the effect of iron oxide in the glass and the possibility to use high iron sand to produce tableware glasses.Tableware glass, Iron oxide, Redox reaction, Decolorizing

Abstract: A small amount of iron oxide (Fe₂O₃) was added to the commercially available 3 mol% Y-TZP as a sintering aid over a temperature range of 1250°C to 1500°C. Sintered samples were then evaluated to determine the bulk density, Vickers hardness, and fracture toughness. In addition, hydrothermal ageing experiments to determine the tetragonal phase stability were performed on selected sintered samples in superheated steam at 180°C / 10 bar for up to 24 hours. Based on the work carried out, it was revealed that additions of Fe₂O₃ particularly 0.3 wt% was indeed beneficial in aiding densification, improving the matrix stiffness and hardness when compared to undoped Y-TZP sintered at temperatures below 1350°C. Addition of Fe₂O₃ was found to have negligible effects on the fracture toughness of all samples with the exception of the 0.5 and 1 wt% doped Y-YZP sintered above 1400°C. Hydrothermal ageing resistance of Y-TZP was found to be enhanced with the addition of Fe₂O₃ in the Y-TZP matrix.