Nanotextured Spikes of α-Fe2O3/NiFe2O4 Composite for Efficient Photoelectrochemical Oxidation of Water.

Science.gov (United States)

Hussain, Shabeeb; Tavakoli, Mohammad Mahdi; Waleed, Aashir; Virk, Umar Siddique; Yang, Shihe; Waseem, Amir; Fan, Zhiyong; Nadeem, Muhammad Arif

2018-03-27

We demonstrate for the first time the application of p-NiFe 2 O 4 /n-Fe 2 O 3 composite thin films as anode materials for light-assisted electrolysis of water. The p-NiFe 2 O 4 /n-Fe 2 O 3 composite thin films were deposited on planar fluorinated tin oxide (FTO)-coated glass as well as on 3D array of nanospike (NSP) substrates. The effect of substrate (planar FTO and 3D-NSP) and percentage change of each component (i.e., NiFe 2 O 4 and Fe 2 O 3 ) of composite was studied on photoelectrochemical (PEC) water oxidation reaction. This work also includes the performance comparison of p-NiFe 2 O 4 /n-Fe 2 O 3 composite (planar and NSP) devices with pure hematite for PEC water oxidation. Overall, the nanostructured p-NiFe 2 O 4 /n-Fe 2 O 3 device with equal molar 1:1 ratio of NiFe 2 O 4 and Fe 2 O 3 was found to be highly efficient for PEC water oxidation as compared with pure hematite, 1:2 and 1:3 molar ratios of composite. The photocurrent density of 1:1 composite thin film on planar substrate was equal to 1.07 mA/cm 2 at 1.23 V RHE , which was 1.7 times higher current density as compared with pure hematite device (0.63 mA/cm 2 at 1.23 V RHE ). The performance of p-NiFe 2 O 4 /n-Fe 2 O 3 composites in PEC water oxidation was further enhanced by their deposition over 3D-NSP substrate. The highest photocurrent density of 2.1 mA/cm 2 at 1.23 V RHE was obtained for the 1:1 molar ratio p-NiFe 2 O 4 /n-Fe 2 O 3 composite on NSP (NF1-NSP), which was 3.3 times more photocurrent density than pure hematite. The measured applied bias photon-to-current efficiency (ABPE) value of NF1-NSP (0.206%) was found to be 1.87 times higher than that of NF1-P (0.11%) and 4.7 times higher than that of pure hematite deposited on FTO-coated glass (0.044%). The higher PEC water oxidation activity of p-NiFe 2 O 4 /n-Fe 2 O 3 composite thin film as compared with pure hematite is attributed to the Z-path scheme and better separation of electrons and holes. The increased surface area and greater light

Effect of Fe2O3 on the sintering and stabilization of ZrO2-MgO system

International Nuclear Information System (INIS)

Longo, E.; Paskocimas, C.A.; Ambrosecchia, J.R.; Weffort, L.C.; Baldo, J.B.; Leite, L.R.; Varela, J.A.

1990-01-01

Through X-ray diffraction, it was studied the influence of the iron oxide (Fe 2 O 3 ) as a mineralizer in the development of partially stabilized zirconia phases (cubic/tetragonal) within the system ZrO 2 -MgO. In the preparation of the studied compositions it was utilized a Brazilian comercial zirconia powder and different precursors for the MgO and Fe 2 O 3 additives. It was observed that the main effect of iron oxide consisted on the speed up of the solid solution formation process of Mg + 2 in the Zr +4 sub-lattice, as well as being a very effective sintering agent. (author) [pt

Study on electrolytic reduction with controlled oxygen flow for iron from molten oxide slag containing FeO

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Gao Y.M.

2013-01-01

Full Text Available A ZrO2-based solid membrane electrolytic cell with controlled oxygen flow was constructed: graphite rod /[O]Fe+C saturated / ZrO2(MgO/(FeO slag/iron crucible. The feasibility of extraction of iron from molten oxide slag containing FeO at an applied voltage was investigated by means of the electrolytic cell. The effects of some important process factors on the FeO electrolytic reduction with the controlled oxygen flow were discussed. The results show that: solid iron can be extracted from molten oxide slag containing FeO at 1450ºC and an applied potential of 4V. These factors, such as precipitation and growth of solid iron dendrites, change of the cathode active area on the inner wall of the iron crucible and ion diffusion flux in the molten slag may affect the electrochemical reaction rate. The reduction for Fe2+ ions mainly appears on new iron dendrites of the iron crucible cathode, and a very small amount of iron are also formed on the MSZ (2.18% MgO partially stabilized zirconia tube/slag interface due to electronic conductance of MSZ tube. Internal electronic current through MSZ tube may change direction at earlier and later electrolytic reduction stage. It has a role of promoting electrolytic reduction for FeO in the molten slag at the earlier stage, but will lower the current efficiency at the later stage. The final reduction ratio of FeO in the molten slag can achieve 99%. A novel electrolytic method with controlled oxygen flow for iron from the molten oxide slag containing FeO was proposed. The theory of electrolytic reduction with the controlled oxygen flow was developed.

Fe2 PO5 -Encapsulated Reverse Energetic ZnO/Fe2 O3 Heterojunction Nanowire for Enhanced Photoelectrochemical Oxidation of Water.

Science.gov (United States)

Qin, Dong-Dong; He, Cai-Hua; Li, Yang; Trammel, Antonio C; Gu, Jing; Chen, Jing; Yan, Yong; Shan, Duo-Liang; Wang, Qiu-Hong; Quan, Jing-Jing; Tao, Chun-Lan; Lu, Xiao-Quan

2017-07-10

Zinc oxide is regarded as a promising candidate for application in photoelectrochemical water oxidation due to its higher electron mobility. However, its instability under alkaline conditions limits its application in a practical setting. Herein, we demonstrate an easily achieved wet-chemical route to chemically stabilize ZnO nanowires (NWs) by protecting them with a thin layer Fe 2 O 3 shell. This shell, in which the thickness can be tuned by varying reaction times, forms an intact interface with ZnO NWs, thus protecting ZnO from corrosion in a basic solution. The reverse energetic heterojunction nanowires are subsequently activated by introducing an amorphous iron phosphate, which substantially suppressed surface recombination as a passivation layer and improved photoelectrochemical performance as a potential catalyst. Compared with pure ZnO NWs (0.4 mA cm -2 ), a maximal photocurrent of 1.0 mA cm -2 is achieved with ZnO/Fe 2 O 3 core-shell NWs and 2.3 mA cm -2 was achieved for the PH 3 -treated NWs at 1.23 V versus RHE. The PH 3 low-temperature treatment creates a dual function, passivation and catalyst layer (Fe 2 PO 5 ), examined by X-ray photoelectron spectroscopy, TEM, photoelectrochemical characterization, and impedance measurements. Such a nano-composition design offers great promise to improve the overall performance of the photoanode material. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Phase identification and morphology study of hematite (Fe2O3) with sintering time varitions

Science.gov (United States)

Yazirin, Cepi; Puspitasari, Poppy; Sasongko, Muhammad Ilman Nur; Tsamroh, Dewi Izzatus; Risdanareni, Puput

2017-09-01

Iron oxide has been the interest of many studies due to its applications in various scientific and industrial fields including in environment, corrosion, soil science, and exhaust emissions. Iron oxide (Fe2O3) has potential applications in catalytic reactions in electronic devices such as semiconductors, paint formulations, and lithium rechargeable batteries. Fe2O3 can be synthesized through the process of stirring, decomposition of organic iron, sol-gel, combustion, and evaporating solvents. Most of the methods used involve several steps and take a long time. The aim of this research was to investigate the phase and morphology characterization of iron oxide (Fe2O3) powder with solvent ethylene glycol after being sintered for 1 hour, 2 hours and 3 hours. The characterization tools utilized were XRD, SEM-EDX, and FTIR. The results of XRD analysis showed that the Fe2O3 sintered for 1 hour had the smallest crystallite size with a diameter of 21.05 nm. In the XRD test, the beam of X-ray was shot directly at the grain being tested. The results of SEM analysis showed thatthe Fe2O3 sintered for 1 hour produced the best result due to its crystallite size of 12.36 nm and hada shape of homogeneous nanosphere; the duration of sintering indeed had a great influence on the grain size of iron oxide (Fe2O3). In addition, the results of the elemental composition analysis indicate that the longer the sintering process, the higher the concentration of O but the lower the Fe.

Spin Seebeck effect in insulating epitaxial γ−Fe2O3 thin films

Directory of Open Access Journals (Sweden)

P. Jiménez-Cavero

2017-02-01

Full Text Available We report the fabrication of high crystal quality epitaxial thin films of maghemite (γ−Fe2O3, a classic ferrimagnetic insulating iron oxide. Spin Seebeck effect (SSE measurements in γ−Fe2O3/Pt bilayers as a function of sample preparation conditions and temperature yield a SSE coefficient of 0.5(1 μV/K at room temperature. Dependence on temperature allows us to estimate the magnon diffusion length in maghemite to be in the range of tens of nanometers, in good agreement with that of conducting iron oxide magnetite (Fe3O4, establishing the relevance of spin currents of magnonic origin in magnetic iron oxides.

Electrical resistivity surface for FeO-Fe2O3-P2O5 glasses

Science.gov (United States)

Vaughan, J. G.; Kinser, D. L.

1975-01-01

The dc electrical properties and microstructure of x(FeO-Fe2O3)-(100-x)P2O5 glasses were investigated up to a maximum of x = 75 mol %. Results indicate that, in general, the minimum resistivity of the glass does not occur at equal Fe(2+) and Fe(3+) concentrations, although for the special case where x = 55 mol % the minimum does occur at Fe(2+)/Fe total = 0.5, as reported by other investigators. Evidence presented shows that the position of the minimum resistivity is a function of total iron content. The minimum shifts to glasses richer in Fe(2+) at higher total iron concentrations.

Photocatalytic activity of titanium dioxide modified by Fe{sub 2}O{sub 3} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Wodka, Dawid [J. Haber Institute of Catalysis and Surface Chemistry PAS, Niezapominajek 8, 30-239 Krakow (Poland); Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, 1211 Geneva 4 (Switzerland); Socha, Robert P.; Bielańska, Elżbieta [J. Haber Institute of Catalysis and Surface Chemistry PAS, Niezapominajek 8, 30-239 Krakow (Poland); Elżbieciak-Wodka, Magdalena [J. Haber Institute of Catalysis and Surface Chemistry PAS, Niezapominajek 8, 30-239 Krakow (Poland); Department of Analytical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, 1211 Geneva 4 (Switzerland); Nowak, Paweł, E-mail: ncnowak@cyf-kr.edu.pl [J. Haber Institute of Catalysis and Surface Chemistry PAS, Niezapominajek 8, 30-239 Krakow (Poland); Warszyński, Piotr [J. Haber Institute of Catalysis and Surface Chemistry PAS, Niezapominajek 8, 30-239 Krakow (Poland)

2014-11-15

Highlights: • 1% Fe{sub 2}O{sub 3}/TiO{sub 2} composite showing high activity in the photocatalytic oxidation of organics was synthetized. • Electrochemical analysis indicated that surface modification of Degussa P25 by Fe{sub 2}O{sub 3} causes the appearance of surface states in such a material. • The enhanced activity of the prepared composite may be ascribed to the occurrence of the photo-Fenton process. - Abstract: Photocatalytic activity of Fe{sub 2}O{sub 3}/TiO{sub 2} composites obtained by precipitation was investigated. The composite material containing 1.0 wt% of iron(III) oxide nanoparticles was obtained by depositing Fe{sub 2}O{sub 3} on the Evonic-Degussa P25 titania surface. SEM, XPS, DRS, CV and EIS techniques were applied to examine synthetized pale orange photocatalyst. The XPS measurements revealed that iron is present mainly in the +3 oxidation state but iron in the +2 oxidation state can be also detected. Electrochemical analysis indicated that surface modification of Degussa P25 by Fe{sub 2}O{sub 3} causes the appearance of surface states in such a material. Nevertheless, based on the DRS measurement it was shown that iron(III) oxide nanoparticles modified the P25 spectral properties but they did not change the band gap width. The photocatalytic activity of Fe{sub 2}O{sub 3}/TiO{sub 2} composite was compared to photocatalytic activity of pristine P25 in photooxidation reaction of model compounds: oxalic acid (OxA) and formic acid (FA). Photodecomposition reaction was investigated in a batch reactor containing aqueous suspension of a photocatalyst illuminated by either UV or artificial sunlight (halogen lamp). The tests proved that nanoparticles deposited on titania surface triggers the increase in photocatalytic activity, this increase depends however on the decomposed substance.

First-Principles Fe L _2,3 -Edge and O K-Edge XANES and XMCD Spectra for Iron Oxides

Energy Technology Data Exchange (ETDEWEB)

Sassi, Michel [Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Pearce, Carolyn I. [Pacific Northwest National Laboratory, Richland, Washington 99352, United States; Bagus, Paul S. [Department; Arenholz, Elke [Advanced; Rosso, Kevin M. [Pacific Northwest National Laboratory, Richland, Washington 99352, United States

2017-10-02

X-ray absorption near-edge structure (XANES) and X-ray magnetic circular dichroism (XMCD) spectroscopies are tools in widespread use for providing detailed local atomic structure, oxidation state, and magnetic structure information for materials and organometallic complexes. The analysis of these spectra for transition-metal L-edges is routinely performed on the basis of ligand-field multiplet theory because one- and two-particle mean-field ab initio methods typically cannot describe the multiplet structure. Here we show that multireference configuration interaction (MRCI) calculations can satisfactorily reproduce measured XANES spectra for a range of complex iron oxide materials including hematite and magnetite. MRCI Fe L2,3-edge XANES and XMCD spectra of Fe(II)O6, Fe(III)O6, and Fe(III)O4 in magnetite are found to be in very good qualitative agreement with experiment and multiplet calculations. Point-charge embedding and small distortions of the first-shell oxygen ligands have only small effects. Oxygen K-edge XANES/XMCD spectra for magnetite investigated by a real-space Green’s function approach complete the very good qualitative agreement with experiment. Material-specific differences in local coordination and site symmetry are well reproduced, making the approach useful for assigning spectral features to specific oxidation states and coordination environments.

Biomineralization associated with microbial reduction of Fe3+ and oxidation of Fe2+ in solid minerals

Science.gov (United States)

Zhang, G.; Dong, H.; Jiang, H.; Kukkadapu, R.K.; Kim, J.; Eberl, D.; Xu, Z.

2009-01-01

Iron-reducing and oxidizing microorganisms gain energy through reduction or oxidation of iron, and by doing so play an important role in the geochemical cycling of iron. This study was undertaken to investigate mineral transformations associated with microbial reduction of Fe3+ and oxidation of Fe2+ in solid minerals. A fluid sample from the 2450 m depth of the Chinese Continental Scientific Drilling project was collected, and Fe3+-reducing and Fe2+-oxidizing microorganisms were enriched. The enrichment cultures displayed reduction of Fe3+ in nontronite and ferric citrate, and oxidation of Fe2+ in vivianite, siderite, and monosulfide (FeS). Additional experiments verified that the iron reduction and oxidation was biological. Oxidation of FeS resulted in the formation of goethite, lepidocrocite, and ferrihydrite as products. Although our molecular microbiological analyses detected Thermoan-aerobacter ethanolicus as a predominant organism in the enrichment culture, Fe3+ reduction and Fe2+ oxidation may be accomplished by a consortia of organisms. Our results have important environmental and ecological implications for iron redox cycling in solid minerals in natural environments, where iron mineral transformations may be related to the mobility and solubility of inorganic and organic contaminants.

Study on adsorption of 99Tc on Fe, Fe2O3 and Fe3O4

International Nuclear Information System (INIS)

Liu Dejun; Fan Xianhua; Zhang Yingjie; Yao Jun; Zhou Duo; Wang Yong

2004-01-01

The absorption behavior of 99 Tc on Fe, Fe 2 O 3 and Fe 3 O 4 powders from aqueous 99 TcO 4 - solutions is studied by batch method in atmospheric conditions. After the adsorption reaches equilibrium, the valence state of 99 Tc in the aqueous solution is examined by extraction with tetraphenylarsonium chloride. The experimental results show that the adsorption ratio of 99 Tc on iron powders decreases with the increase of pH (in the range of 5-8) and of CO 3 2- concentration (in the range of 1 x 10 -8 -1 x 10 -2 mol/L). In opposite, the two factors have no significant influence on the absorption of 99 Tc on both Fe 2 O 3 and Fe 3 O 4 powders. The adsorption isotherms of 99 TcO 4 - on Fe, Fe 2 O 3 and Fe 3 O 4 powders can be well described by the Freundlich's equation. The major valence state of 99 Tc is deduced to be Tc(IV) when iron powders is used as the absorbent. In the case of Fe 2 O 3 or Fe 3 O 4 as an absorbent, the 99 Tc remains as the TcO 4 - form

Iron oxide surfaces

Science.gov (United States)

Parkinson, Gareth S.

2016-03-01

The current status of knowledge regarding the surfaces of the iron oxides, magnetite (Fe3O4), maghemite (γ-Fe2O3), haematite (α-Fe2O3), and wüstite (Fe1-xO) is reviewed. The paper starts with a summary of applications where iron oxide surfaces play a major role, including corrosion, catalysis, spintronics, magnetic nanoparticles (MNPs), biomedicine, photoelectrochemical water splitting and groundwater remediation. The bulk structure and properties are then briefly presented; each compound is based on a close-packed anion lattice, with a different distribution and oxidation state of the Fe cations in interstitial sites. The bulk defect chemistry is dominated by cation vacancies and interstitials (not oxygen vacancies) and this provides the context to understand iron oxide surfaces, which represent the front line in reduction and oxidation processes. Fe diffuses in and out from the bulk in response to the O2 chemical potential, forming sometimes complex intermediate phases at the surface. For example, α-Fe2O3 adopts Fe3O4-like surfaces in reducing conditions, and Fe3O4 adopts Fe1-xO-like structures in further reducing conditions still. It is argued that known bulk defect structures are an excellent starting point in building models for iron oxide surfaces. The atomic-scale structure of the low-index surfaces of iron oxides is the major focus of this review. Fe3O4 is the most studied iron oxide in surface science, primarily because its stability range corresponds nicely to the ultra-high vacuum environment. It is also an electrical conductor, which makes it straightforward to study with the most commonly used surface science methods such as photoemission spectroscopies (XPS, UPS) and scanning tunneling microscopy (STM). The impact of the surfaces on the measurement of bulk properties such as magnetism, the Verwey transition and the (predicted) half-metallicity is discussed. The best understood iron oxide surface at present is probably Fe3O4(100); the structure is

Single step thermal decomposition approach to prepare supported γ-Fe2O3 nanoparticles

International Nuclear Information System (INIS)

Sharma, Geetu; Jeevanandam, P.

2012-01-01

γ-Fe 2 O 3 nanoparticles supported on MgO (macro-crystalline and nanocrystalline) were prepared by an easy single step thermal decomposition method. Thermal decomposition of iron acetylacetonate in diphenyl ether, in the presence of the supports followed by calcination, leads to iron oxide nanoparticles supported on MgO. The X-ray diffraction results indicate the stability of γ-Fe 2 O 3 phase on MgO (macro-crystalline and nanocrystalline) up to 1150 °C. The scanning electron microscopy images show that the supported iron oxide nanoparticles are agglomerated while the energy dispersive X-ray analysis indicates the presence of iron, magnesium and oxygen in the samples. Transmission electron microscopy images indicate the presence of smaller γ-Fe 2 O 3 nanoparticles on nanocrystalline MgO. The magnetic properties of the supported magnetic nanoparticles at various calcination temperatures (350-1150 °C) were studied using a superconducting quantum interference device which indicates superparamagnetic behavior.

Phase stability of iron germanate, FeGeO3, to 127 GPa

Science.gov (United States)

Dutta, R.; Tracy, S. J.; Stan, C. V.; Prakapenka, V. B.; Cava, R. J.; Duffy, T. S.

2018-04-01

The high-pressure behavior of germanates is of interest as these compounds serve as analogs for silicates of the deep Earth. Current theoretical and experimental studies of iron germanate, FeGeO3, are limited. Here, we have examined the behavior of FeGeO3 to 127 GPa using the laser-heated diamond anvil cell combined with in situ synchrotron X-ray diffraction. Upon compression at room temperature, the ambient-pressure clinopyroxene phase transforms to a disordered triclinic phase [FeGeO3 (II)] at 18 GPa in agreement with earlier studies. An additional phase transition to FeGeO3 (III) occurs above 54 GPa at room temperature. Laser-heating experiments ( 1200-2200 K) were conducted at three pressures (33, 54, and 123 GPa) chosen to cover the stability regions of different GeO2 polymorphs. In all cases, we observe that FeGeO3 dissociates into GeO2 + FeO at high pressure and temperature conditions. Neither the perovskite nor the post-perovskite phase was observed up to 127 GPa at ambient or high temperatures. The results are consistent with the behavior of FeSiO3, which also dissociates into a mixture of the oxides (FeO + SiO2) at least up to 149 GPa.

Ferrous Iron Oxidation under Varying pO2 Levels: The Effect of Fe(III)/Al(III) Oxide Minerals and Organic Matter.

Science.gov (United States)

Chen, Chunmei; Thompson, Aaron

2018-01-16

Abiotic Fe(II) oxidation by O 2 commonly occurs in the presence of mineral sorbents and organic matter (OM) in soils and sediments; however, this tertiary system has rarely been studied. Therefore, we examined the impacts of mineral surfaces (goethite and γ-Al 2 O 3 ) and organic matter [Suwannee River fulvic acid (SRFA)] on Fe(II) oxidation rates and the resulting Fe(III) (oxyhydr)oxides under 21 and 1% pO 2 at pH 6. We tracked Fe dynamics by adding 57 Fe(II) to 56 Fe-labeled goethite and γ-Al 2 O 3 and characterized the resulting solids using 57 Fe Mössbauer spectroscopy. We found Fe(II) oxidation was slower at low pO 2 and resulted in higher-crystallinity Fe(III) phases. Relative to oxidation of Fe(II) (aq) alone, both goethite and γ-Al 2 O 3 surfaces increased Fe(II) oxidation rates regardless of pO 2 levels, with goethite being the stronger catalyst. Goethite surfaces promoted the formation of crystalline goethite, while γ-Al 2 O 3 favored nano/small particle or disordered goethite and some lepidocrocite; oxidation of Fe(II) aq alone favored lepidocrocite. SRFA reduced oxidation rates in all treatments except the mineral-free systems at 21% pO 2 , and SRFA decreased Fe(III) phase crystallinity, facilitating low-crystalline ferrihydrite in the absence of mineral sorbents, low-crystalline lepidocrocite in the presence of γ-Al 2 O 3 , but either crystalline goethite or ferrihydrite when goethite was present. This work highlights that the oxidation rate, the types of mineral surfaces, and OM control Fe(III) precipitate composition.

Inverse CeO2sbnd Fe2O3 catalyst for superior low-temperature CO conversion efficiency

Science.gov (United States)

Luo, Yongming; Chen, Ran; Peng, Wen; Tang, Guangbei; Gao, Xiaoya

2017-09-01

The paper presents a rational design of highly efficient and affordable catalysts for CO oxidation with a low operating temperature. A series of ceria-iron catalysts were inversely built via a co-precipitation method. The catalytic activity of low-temperature CO oxidation was much higher with CeO2-modified Fe2O3 (CeO2sbnd Fe2O3) than with Fe2O3-modified CeO2 (Fe2O3sbnd CeO2). In particular, the 7.5% CeO2sbnd Fe2O3 catalyst had the highest activity, reaching 96.17% CO conversion at just 25 °C. Catalyst characterization was carried out to explore the cause of the significantly different CO conversion efficiencies between the Fe2O3sbnd CeO2 and Fe2O3sbnd CeO2 catalysts. HRTEM showed a significant inhomogeneous phase in 7.5% CeO2sbnd Fe2O3 with small CeO2 nanoparticles highly dispersed on the rod-shaped Fe2O3 surface. Furthermore, the 7.5% CeO2sbnd Fe2O3 composite catalyst exhibited the highest ratios of Fe2+/Fe3+ and Ce3+/Ce4+ as well as the largest pore volume. These properties are believed to benefit the CO conversion in 7.5% CeO2sbnd Fe2O3.

Interactions in γ-Fe2O3 and Fe3O4 nanoparticle systems

International Nuclear Information System (INIS)

Laha, S.S.; Tackett, R.J.; Lawes, G.

2014-01-01

We have investigated interaction effects in two different systems of iron oxide nanoparticles. Samples of γ-Fe 2 O 3 and Fe 3 O 4 nanoparticles were synthesized using a matrix-mediated precipitation reaction and a chemical co-precipitation technique respectively. The structural properties of these nanoparticles were studied using x-ray diffraction and transmission electron microscopy. We also used temperature dependent ac magnetic susceptibility measurements to carefully investigate the interactions among these nanoparticles. Our analysis showed that the characteristic interaction energy does not depend simply on the average spacing between the nanoparticles but is likely to be strongly influenced by the fluctuations in the nanoparticle distribution

CATALYTIC PERFORMANCES OF Fe2O3/TS-1 CATALYST IN PHENOL HYDROXYLATION REACTION

Directory of Open Access Journals (Sweden)

Didik Prasetyoko

2010-07-01

Full Text Available Hydroxylation reaction of phenol into diphenol, such as hydroquinone and catechol, has a great role in many industrial applications. Phenol hydroxylation reaction can be carried out using Titanium Silicalite-1 (TS-1 as catalyst and H2O2 as an oxidant. TS-1 catalyst shows high activity and selectivity for phenol hydroxylation reaction. However, its hydrophobic sites lead to slow H2O2 adsorption toward the active site of TS-1. Consequently, the reaction rate of phenol hydroxylation reaction is tends to be low. Addition of metal oxide Fe2O3 enhanced hydrophilicity of TS-1 catalyst. Liquid phase catalytic phenol hydroxylation using hydrogen peroxide as oxidant was carried out over iron (III oxide-modified TS-1 catalyst (Fe2O3/TS-1, that were prepared by impregnation method using iron (III nitrate as precursor and characterized by X-ray diffraction, infrared spectroscopy, nitrogen adsorption, pyridine adsorption, and hydrophilicity techniques. Catalysts 1Fe2O3/TS-1 showed maximum catalytic activity of hydroquinone product. In this research, the increase of hydroquinone formation rate is due to the higher hydrophilicity of Fe2O3/TS-1 catalysts compare to the parent catalyst, TS-1.   Keywords: Fe2O3/TS-1, hydrophilic site, phenol hydroxylation

Fe2 O3 addition influence on the Sn O2.Co O.Nb2 O5 varistors system

International Nuclear Information System (INIS)

Antunes, A.C.; Antunes, S.R.M.; Castilhos, J.G.R.; Pianaro, S.R.; Zara, J.A.; Longo, E.; Varela, J.A.

1997-01-01

The effect 0.05 to 0.30 mol% Fe 2 0 3 addition on the electrical and microstructural properties of ternary varistor system composed by tin oxide, niobium oxide and cobaltum oxide was studied in this work. The samples were sintered at 1300 deg C for two hours. The characterizations were performed by Vxi measurements, scanning electron microscopy and X - ray diffraction. The Fe 2 O 3 additions up to 0,10% increased the α values breakdown electric fields (E r ) and it was observed that the barrier voltage (v b ) depends on the chemical composition. The second phase had high concentration of iron that precipitated in the grain boundaries and inhibited the grain growth during sintering. Fe 2 O 3 concentrations upper 0,10 mol% were deleterious for electrical properties of the ceramics. (author)

Higher Fe{sup 2+}/total Fe ratio in iron doped phosphate glass melted by microwave heating

Energy Technology Data Exchange (ETDEWEB)

Mandal, Ashis K., E-mail: ashis@cgcri.res.in [CSIR-Central Glass and Ceramic Research Institute, 196 Raja S.C. Mullick Road, Kolkata 700032 (India); Sinha, Prasanta K. [CSIR-Central Glass and Ceramic Research Institute, 196 Raja S.C. Mullick Road, Kolkata 700032 (India); Das, Dipankar [UGC-DAE Consortium for Scientific Research, Kolkata 700098 (India); Guha, Chandan [Department of Chemical Engineering, Jadavpur University, Kolkata 700032 (India); Sen, Ranjan [CSIR-Central Glass and Ceramic Research Institute, 196 Raja S.C. Mullick Road, Kolkata 700032 (India)

2015-03-15

Highlights: • Iron doped phosphate glasses prepared using microwave heating and conventional heating under air and reducing atmosphere. • Presence of iron predominantly in the ferrous oxidation state in all the glasses. • Significant concentrations of iron in the ferrous oxidation state on both octahedral and tetrahedral sites in all the glasses. • Ratio of Fe{sup 2+} with total iron is found higher in microwave prepared glasses in comparison to conventional prepared glasses. - Abstract: Iron doped phosphate glasses containing P{sub 2}O{sub 5}–MgO–ZnO–B{sub 2}O{sub 3}–Al{sub 2}O{sub 3} were melted using conventional resistance heating and microwave heating in air and under reducing atmosphere. All the glasses were characterised by UV–Vis–NIR spectroscopy, Mössbauer spectroscopy, thermogravimetric analysis and wet colorimetry analysis. Mössbauer spectroscopy revealed presence of iron predominantly in the ferrous oxidation state on two different sites in all the glasses. The intensity of the ferrous absorption peaks in UV–Vis–NIR spectrum was found to be more in glasses prepared using microwave radiation compared to the glasses prepared in a resistance heating furnace. Thermogravimetric analysis showed increasing weight gain on heating under oxygen atmosphere for glass corroborating higher ratio of FeO/(FeO + Fe{sub 2}O{sub 3}) in glass melted by direct microwave heating. Wet chemical analysis also substantiated the finding of higher ratio Fe{sup +2}/ΣFe in microwave melted glasses. It was found that iron redox ratio was highest in the glasses prepared in a microwave furnace under reducing atmosphere.

The influence of oxidation process on exchange bias in egg-shaped FeO/Fe{sub 3}O{sub 4} core/shell nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Leszczyński, Błażej, E-mail: b.leszczynski@amu.edu.pl [NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Hadjipanayis, George C.; El-Gendy, Ahmed A. [Department of Physics and Astronomy, University of Delaware, 217 Sharp Lab, Newark, DE 19716 (United States); Załęski, Karol [NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Śniadecki, Zbigniew [Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznań (Poland); Musiał, Andrzej [NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Institute of Molecular Physics, Polish Academy of Sciences, M. Smoluchowskiego 17, 60-179 Poznań (Poland); Jarek, Marcin [NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Jurga, Stefan [NanoBioMedical Centre, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Skumiel, Andrzej [Faculty of Physics, Adam Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland)

2016-10-15

Egg-shaped nanoparticles with a core–shell morphology were synthesized by thermal decomposition of an iron oleate complex. XRD and M(T) magnetic measurements confirmed the presence of FeO (wustite) and Fe{sub 3}O{sub 4} (magnetite) phases in the nanoparticles. Oxidation of FeO to Fe{sub 3}O{sub 4} was found to be the mechanism for the shell formation. As-made nanoparticles exhibited high values of exchange bias at 2 K. Oxidation led to decrease of exchange field from 2880 Oe (in as-made sample) to 330 Oe (in oxidized sample). At temperatures higher than the Néel temperature of FeO (200 K) there was no exchange bias. An interesting observation was made showing the exchange field to be higher than the coercive field at temperatures close to magnetite's Verwey transition. - Highlights: • Synthesis of monodispersed FeO nanoparticles is shown. • As-made FeO nanoparticle is antiferromagnetically ordered, when it is oxidized to Fe{sub 3}O{sub 4}, the FeO core becomes small and disordered. • Exchange bias in well-ordered and disordered core is different.

Effect of surface Fe2O3 clusters on the photocatalytic activity of TiO2 for phenol degradation in water

International Nuclear Information System (INIS)

Sun, Qiong; Leng, Wenhua; Li, Zhen; Xu, Yiming

2012-01-01

Graphical abstract: Surface modified TiO 2 with iron oxide clusters through adsorption and decomposition of a large Fe(III) complex shows an enhanced activity for phenol degradation in water under UV light. But it was only observed with the clusters in a small size and at very low coverage on anatase. Highlights: ► Iron oxide clusters are made by decomposition of a large Fe(III) complex on TiO 2 . ► The modified anatase shows an enhanced activity for phenol photodegradation. ► The composite catalyst is very stable during four repeated experiments. - Abstract: Surface modification of TiO 2 with Fe 2 O 3 clusters was made through chemisorption of ferric phthalocyaninetetracarboxylate onto TiO 2 , followed by sintering in air to remove organic moiety. Solid characterization with electron paramagnetic resonance spectroscopy and other techniques showed that ferric oxides were highly dispersed on TiO 2 as a noncrystallized cluster, while TiO 2 phases remained unchanged. For phenol degradation in aerated aqueous suspension, only the sample containing less than 0.3 at.% Fe was more active than bare TiO 2 under UV light, whereas no activity was found under visible light. As anatase thermally transferred into rutile, the Fe-containing catalyst became less active than bare TiO 2 , mainly ascribed to the increased size of Fe 2 O 3 clusters. In the presence of H 2 O 2 , all Fe-containing catalysts were more active than bare TiO 2 . Moreover, similar trend in activity among different catalysts was also observed with the formation of hydroxyl radicals, and with the generation of photocurrent measured under N 2 with Fe/TiO 2 electrode. Present work clearly shows that only Fe 2 O 3 clusters in a small size and at low coverage on TiO 2 are beneficial to the photocatalytic reaction, while excess iron oxide is detrimental. Possible mechanism is discussed in the text.

Study of the ZrO2-FeO-Fe2O3 system by thermogravimetry in partial pressure of oxygen and temperatures up to 15000C

International Nuclear Information System (INIS)

Goldschmidt, R.H.; Kiminami, A.

1987-01-01

The dissociation of iron oxide in the ZrO 2 -FeO-Fe 2 O 3 system was investigated in function of the temperature and the constant partial pressure of oxygen by thermal gravimetric analysis. The equilibrium diagram was constructed where the equilibrium relation between the solid phase of zirconium oxide, hematite and magnetite in 1437 0 C and PO 2 = 0.21 atm/m, as well as the equilibrium relation between the solid phase of zirconium oxide and hematite in lower temperatures than 1437 0 C were determined [pt

Facile preparation and enhanced microwave absorption properties of flake carbonyl iron/Fe3O4 composite

International Nuclear Information System (INIS)

Min, Dandan; Zhou, Wancheng; Luo, Fa; Zhu, Dongmei

2017-01-01

Highlights: • Flake carbonyl iron/Fe 3 O 4 composites were prepared by surface oxidation technique. • Lower permittivity and modest permeability was obtained by the FCI/Fe 3 O 4 composites. • Enhanced absorption efficiency and broader absorption band were obtained. - Abstract: Flake carbonyl iron/Fe 3 O 4 (FCI/Fe 3 O 4 ) composites with enhanced microwave absorption properties were prepared by a direct and flexible surface oxidation technique. The phase structures, morphology, magnetic properties, frequency-dependent electromagnetic and microwave absorption properties of the composites were investigated. The measurement results showed that lower permittivity as well as modest permeability was obtained by the FCI/Fe 3 O 4 composites. The calculated microwave absorption properties indicated that enhanced absorption efficiency and broader absorption band were obtained by the FCI/Fe 3 O 4 composite comparing with the FCI composite. The absorption frequency range with reflection loss (RL) below −5 dB of FCI/Fe 3 O 4 composites at reaction time of 90 min at thickness of 1.5 mm is 13.3 GHz from 4.7 to 18 GHz, while the bandwidth of the FCI composite is only 5.9 GHz from 2.6 to 8.5 GHz at the same thickness. Thus, such absorbers could act as effective and wide broadband microwave absorbers in the GHz range.

Bismuth iron oxide thin films using atomic layer deposition of alternating bismuth oxide and iron oxide layers

Energy Technology Data Exchange (ETDEWEB)

Puttaswamy, Manjunath; Vehkamäki, Marko [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland); Kukli, Kaupo, E-mail: kaupo.kukli@helsinki.fi [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland); University of Tartu, Institute of Physics, W. Ostwald 1, EE-50411 Tartu (Estonia); Dimri, Mukesh Chandra [National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, EE-12618 Tallinn (Estonia); Kemell, Marianna; Hatanpää, Timo; Heikkilä, Mikko J. [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland); Mizohata, Kenichiro [University of Helsinki, Department of Physics, P.O. Box 64, FI-00014 Helsinki (Finland); Stern, Raivo [National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, EE-12618 Tallinn (Estonia); Ritala, Mikko; Leskelä, Markku [University of Helsinki, Department of Chemistry, P.O. Box 55, FI-00014 Helsinki (Finland)

2016-07-29

Bismuth iron oxide films with varying contributions from Fe{sub 2}O{sub 3} or Bi{sub 2}O{sub 3} were prepared using atomic layer deposition. Bismuth (III) 2,3-dimethyl-2-butoxide, was used as the bismuth source, iron(III) tert-butoxide as the iron source and water vapor as the oxygen source. The films were deposited as stacks of alternate Bi{sub 2}O{sub 3} and Fe{sub 2}O{sub 3} layers. Films grown at 140 °C to the thickness of 200–220 nm were amorphous, but crystallized upon post-deposition annealing at 500 °C in nitrogen. Annealing of films with intermittent bismuth and iron oxide layers grown to different thicknesses influenced their surface morphology, crystal structure, composition, electrical and magnetic properties. Implications of multiferroic performance were recognized in the films with the remanent charge polarization varying from 1 to 5 μC/cm{sup 2} and magnetic coercivity varying from a few up to 8000 A/m. - Highlights: • Bismuth iron oxide thin films were grown by atomic layer deposition at 140 °C. • The major phase formed in the films upon annealing at 500 °C was BiFeO{sub 3}. • BiFeO{sub 3} films and films containing excess Bi favored electrical charge polarization. • Slight excess of iron oxide enhanced saturative magnetization behavior.

Photodegradation of 2-mercaptobenzothiazole in the γ-Fe2O3/oxalate suspension under UVA light irradiation

International Nuclear Information System (INIS)

Wang Xugang; Liu Chengshuai; Li Xiaomin; Li Fangbai; Zhou Shungui

2008-01-01

The aim of this study is to investigate the effect of various factors on the photodegradation of organic pollutants in natural environment with co-existence of iron oxides and oxalic acid. 2-Mercaptobenzothiazole (MBT) was selected as a model pollutant, while γ-Fe 2 O 3 was selected as iron oxide. The crystal structure and morphology of the prepared γ-Fe 2 O 3 was determined by X-ray diffractograms (XRD) and scanning electron microscopy (SEM), respectively. The specific surface area was 14.36 m 2 /g by Brunauer-Emmett-Teller (BET) method. The adsorption behavior of γ-Fe 2 O 3 was evaluated by Langmuir model. The effect of the dosage of iron oxide, initial concentration of oxalic acid (C ox 0 ), initial pH value, the light intensity and additional transition metal cations on MBT photodegradation was investigated in the γ-Fe 2 O 3 /oxalate suspension under UVA light irradiation. The optimal γ-Fe 2 O 3 dosage was 0.4 g/L and the optimal C ox 0 was 0.8 mM with the UVA light intensity of 1800 mW/cm 2 . And the optimal dosage of γ-Fe 2 O 3 and C ox 0 for MBT degradation also depended strongly on the light intensity. The optimal γ-Fe 2 O 3 dosage was 0.1, 0.25 and 0.4 g/L, and the optimal C ox 0 was 1.0, 0.8, and 0.8 mM with the light intensity of 600, 1200 and 1800 mW/cm 2 , respectively. The optimal initial pH value was at 3.0. The additional transition metal cations including Cu 2+ , Ni 2+ or Mn 2+ could significantly accelerate MBT degradation. This investigation will give a new insight to understanding the MBT photodegradation in natural environment

DLVO and XDLVO calculations for bacteriophage MS2 adhesion to iron oxide particles.

Science.gov (United States)

Park, Jeong-Ann; Kim, Song-Bae

2015-10-01

In this study, batch experiments were performed to examine the adhesion of bacteriophage MS2 to three iron oxide particles (IOP1, IOP2 and IOP3) with different particle properties. The characteristics of MS2 and iron oxides were analyzed using various techniques to construct the classical DLVO and XDLVO potential energy profiles between MS2 and iron oxides. X-ray diffractometry peaks indicated that IOP1 was mainly composed of maghemite (γ-Fe2O3), but also contained some goethite (α-FeOOH). IOP2 was composed of hematite (α-Fe2O3) and IOP3 was composed of iron (Fe), magnetite (Fe3O4) and iron oxide (FeO). Transmission electron microscope images showed that the primary particle size of IOP1 (γ-Fe2O3) was 12.3±4.1nm. IOP2 and IOP3 had primary particle sizes of 167±35nm and 484±192nm, respectively. A surface angle analyzer demonstrated that water contact angles of IOP1, IOP2, IOP3 and MS2 were 44.83, 64.00, 34.33 and 33.00°, respectively. A vibrating sample magnetometer showed that the magnetic saturations of IOP1, IOP2 and IOP3 were 176.87, 17.02 and 946.85kA/m, respectively. Surface potentials measured in artificial ground water (AGW; 0.075mM CaCl2, 0.082mM MgCl2, 0.051mM KCl, and 1.5mM NaHCO3; pH7.6) indicated that iron oxides and MS2 were negatively charged in AGW (IOP1=-0.0185V; IOP2=-0.0194V; IOP3=-0.0301V; MS2=-0.0245V). Batch experiments demonstrated that MS2 adhesion to iron oxides was favorable in the order of IOP1>IOP2>IOP3. This tendency was well predicted by the classical DLVO model. In the DLVO calculations, both the sphere-plate and sphere-sphere geometries predicted the same trend of MS2 adhesion to iron oxides. Additionally, noticeable differences were not found between the DLVO and XDLVO interaction energy profiles, indicating that hydrophobic interactions did not play a major role; electrostatic interactions, however, did influence MS2 adhesion to iron oxides. Furthermore, the aggregation of iron oxides was investigated with a modified XDLVO

Using H2O2 as oxidant in leaching of uranium ores. The new research on the reaction of H2O2 with Fe2+

International Nuclear Information System (INIS)

Gao Xizhen

1997-05-01

The new research on the reaction of H 2 O 2 with Fe 2+ has been studied. Through determining the electric potential, pH and O 2 release during the mutual titration between H 2 O 2 solution and FeSO 4 solution, deduced the chemical equations of H 2 O 2 (without free hydroxyl) oxidizing FeSO 4 and Fe 2 (SO 4 ) 3 oxidizing H 2 O 2 . The research results show that acid is a catalytic agent for decomposing H 2 O 2 to be O 2 and H 2 O besides iron ions. The maximum oxidizing potential is up to about 640 mV. While using H 2 O 2 as an oxidant in uranium heap leaching and in-situ leaching, controlling electric potential can be regarded as a method for adjusting the feeding speed of H 2 O 2 to keep the electric potential below 500 mV, thus the H 2 O 2 decomposition can be reduced. (13 refs., 3 tabs., 1 fig.)

Structural features of layered iron pnictide oxides (Fe{sub 2}As{sub 2})(Sr{sub 4}M{sub 2}O{sub 6})

Energy Technology Data Exchange (ETDEWEB)

Ogino, H., E-mail: tuogino@mail.ecc.u-tokyo.ac.j [Department of Applied Chemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); JST-TRIP, Sanban-cho, Chiyoda-ku, Tokyo 102-0075 (Japan); Sato, S.; Matsumura, Y.; Kawaguchi, N.; Ushiyama, K. [Department of Applied Chemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); JST-TRIP, Sanban-cho, Chiyoda-ku, Tokyo 102-0075 (Japan); Katsura, Y. [Magnetic Materials Laboratory, RIKEN, 2-1 Hirosawa, Wako-shi, Saitama 351-0198 (Japan); Horii, S. [JST-TRIP, Sanban-cho, Chiyoda-ku, Tokyo 102-0075 (Japan); Kochi University of Technology, Kami, Kochi 782-8502 (Japan); Kishio, K.; Shimoyama, J. [Department of Applied Chemistry, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 (Japan); JST-TRIP, Sanban-cho, Chiyoda-ku, Tokyo 102-0075 (Japan)

2010-12-15

Structural features of newly found perovskite-based iron pnictide oxide system have been studied. Compared to REFePnO system, perovskite-based system tend to have smaller Pn-Fe-Pn angle and higher pnictogen height owing to low electronegativity of alkaline earth metal and small repulsive force between pnictogen and oxigen atoms. As-Fe-As angles of (Fe{sub 2}As{sub 2})(Sr{sub 4}Cr{sub 2}O{sub 6}), (Fe{sub 2}As{sub 2})(Sr{sub 4}V{sub 2}O{sub 6}) and (Fe{sub 2}Pn{sub 2})(Sr{sub 4}MgTiO{sub 6}) are close to ideal tetrahedron and those pnictogen heights of about 1.40 A are close to NdFeAsO with optimized carrier concentration. These structural features of this system may lead to realization of high-T{sub c} superconductivity in this system.

Exchange-coupled Fe3O4/CoFe2O4 nanoparticles for advanced magnetic hyperthermia

Science.gov (United States)

Glassell, M.; Robles, J.; Das, R.; Phan, M. H.; Srikanth, H.

Iron oxide nanoparticles especially Fe3O4, γ-Fe2O3 have been extensively studied for magnetic hyperthermia because of their tunable magnetic properties and stable suspension in superparamagnetic regime. However, their relatively low heating capacity hindered practical application. Recently, a large improvement in heating efficiency has been reported in exchange-coupled nanoparticles with exchange coupling between soft and hard magnetic phases. Here, we systematically studied the effect of core and shell size on the heating efficiency of the Fe3O4/CoFe2O4 core/shell nanoparticles. The nanoparticles were synthesized using thermal decomposition of organometallic precursors. Transmission electron microscopy (TEM) showed formation of spherical shaped Fe3O4 and Fe3O-/CoFe2O4 nanoparticles. Magnetic measurements showed high magnetization (≅70 emu/g) and superparamagnetic behavior for the nanoparticles at room temperature. Magnetic hyperthermia results showed a large increase in specific absorption rate (SAR) for 8nm Fe3O4/CoFe2O4 compared to Fe3O4 nanoparticles of the same size. The heating efficiency of the Fe3O4/CoFe2O4 with 1 nm CoFe2O4 (shell) increased from 207 to 220 W/g (for 800 Oe) with increase in core size from 6 to 8 nm. The heating efficiency of the Fe3O4/CoFe2O4 with 2 nm CoFe2O4 (shell) and core size of 8 nm increased from 220 to 460 W/g (for 800 Oe). These exchange-coupled Fe3O4/CoFe2O4 core/shell nanoparticles can be a good candidate for advanced hyperthermia application.

Enhanced Cr(VI) removal from groundwater by Fe0-H2O system with bio-amended iron corrosion

DEFF Research Database (Denmark)

Yin, Weizhao; Li, Yongtao; Wu, Jinhua

2017-01-01

Abstract A one-pot bio-iron system was established to investigate synergetic abiotic and biotic effects between iron and microorganisms on Cr(VI) removal. More diverse iron corrosion and reactive solids, such as green rusts, lepidocrocite and magnetite were found in the bio-iron system than...... transfer on the solid phase. The results also showed that the reduction of Cr(VI) by microorganisms was insignificant, indicating the adsorption/co-precipitation of Cr by iron oxides on iron surface was responsible for the overall Cr(VI) removal. Our study demonstrated that the bio-amended iron corrosion...... in the Fe0-H2O system, leading to 4.3 times higher Cr(VI) removal efficiency in the bio-iron system than in the Fe0-H2O system. The cycling experiment also showed that the Cr(VI) removal capacity of Fe0 in the bio-iron system was 12.4 times higher than that in the Fe0-H2O system. A 62 days of life...

Thermally stimulated iron oxide transformations and magnetic behaviour of cerium dioxide/iron oxide reactive sorbents

Energy Technology Data Exchange (ETDEWEB)

Luňáček, J., E-mail: jiri.lunacek@vsb.cz [Department of Physics, VŠB – Technical University of Ostrava, 17, listopadu 15/2172, 708 33 Ostrava-Poruba (Czech Republic); Department 606, VŠB – Technical University of Ostrava, 17, listopadu 15/2172, 708 33 Ostrava-Poruba (Czech Republic); Životský, O. [Department of Physics, VŠB – Technical University of Ostrava, 17, listopadu 15/2172, 708 33 Ostrava-Poruba (Czech Republic); Department 606, VŠB – Technical University of Ostrava, 17, listopadu 15/2172, 708 33 Ostrava-Poruba (Czech Republic); Jirásková, Y. [CEITEC IPM, Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Žižkova 22, 616 62 Brno (Czech Republic); Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Žižkova 22, 616 62 Brno (Czech Republic); Buršík, J. [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Žižkova 22, 616 62 Brno (Czech Republic); Janoš, P. [Faculty of the Environment, University of Jan Evangelista Purkyně, Králova Výšina 7, 400 96 Ústí nad Labem (Czech Republic)

2016-10-15

The present paper is devoted to detailed study of the magnetically separable sorbents based on a cerium dioxide/iron oxide composite annealed at temperatures T{sub a} = 773 K, 873 K, and 973 K. The X-ray diffraction and high resolution transmission electron microscopy are used to determine the phase composition and microstructure morphology. Mössbauer spectroscopy at room (300 K) and low (5 K) temperatures has contributed to more exact identification of iron oxides and their transformations Fe{sub 3}O{sub 4} → γ-Fe{sub 2}O{sub 3} (ε-Fe{sub 2}O{sub 3}) → α-Fe{sub 2}O{sub 3} in dependence on calcination temperature. Different iron oxide phase compositions and grain size distributions influence the magnetic characteristics determined from the room- and low-temperature hysteresis loop measurements. The results are supported by zero-field-cooled and field-cooled magnetization measurements allowing a quantitative estimation of the grain size distribution and its effect on the iron oxide transformations. - Highlights: •Magnetically separable sorbents based on a CeO{sub 2}/Fe{sub 2}O{sub 3} composite were investigated. •Microstructure of sorbents was determined by XRD, TEM and Mössbauer spectroscopy. •Magnetic properties were studied by hysteresis loops at room- and low-temperatures. •Phase transitions of iron oxides with increasing annealing temperature are observed.

CdS Nanoparticle-Modified α-Fe2O3/TiO2 Nanorod Array Photoanode for Efficient Photoelectrochemical Water Oxidation.

Science.gov (United States)

Yin, Ruiyang; Liu, Mingyang; Tang, Rui; Yin, Longwei

2017-09-02

In this work, we demonstrate a facile successive ionic layer adsorption and reaction process accompanied by hydrothermal method to synthesize CdS nanoparticle-modified α-Fe 2 O 3 /TiO 2 nanorod array for efficient photoelectrochemical (PEC) water oxidation. By integrating CdS/α-Fe 2 O 3 /TiO 2 ternary system, light absorption ability of the photoanode can be effectively improved with an obviously broadened optical-response to visible light region, greatly facilitates the separation of photogenerated carriers, giving rise to the enhancement of PEC water oxidation performance. Importantly, for the designed abnormal type-II heterostructure between Fe 2 O 3 /TiO 2 , the conduction band position of Fe 2 O 3 is higher than that of TiO 2 , the photogenerated electrons from Fe 2 O 3 will rapidly recombine with the photogenerated holes from TiO 2 , thus leads to an efficient separation of photogenerated electrons from Fe 2 O 3 /holes from TiO 2 at the Fe 2 O 3 /TiO 2 interface, greatly improving the separation efficiency of photogenerated holes within Fe 2 O 3 and enhances the photogenerated electron injection efficiency in TiO 2 . Working as the photoanodes of PEC water oxidation, CdS/α-Fe 2 O 3 /TiO 2 heterostucture electrode exhibits improved photocurrent density of 0.62 mA cm - 2 at 1.23 V vs. reversible hydrogen electrode (RHE) in alkaline electrolyte, with an obviously negatively shifted onset potential of 80 mV. This work provides promising methods to enhance the PEC water oxidation performance of the TiO 2 -based heterostructure photoanodes.

Synthesis of α-Fe2O3 and Fe-Mn Oxide Foams with Highly Tunable Magnetic Properties by the Replication Method from Polyurethane Templates

Science.gov (United States)

Feng, Yuping; Fornell, Jordina; Zhang, Huiyan; Solsona, Pau; Barό, Maria Dolors; Suriñach, Santiago; Sort, Jordi

2018-01-01

Open cell foams consisting of Fe and Fe-Mn oxides are prepared from metallic Fe and Mn powder precursors by the replication method using porous polyurethane (PU) templates. First, reticulated PU templates are coated by slurry impregnation. The templates are then thermally removed at 260 °C and the debinded powders are sintered at 1000 °C under N2 atmosphere. The morphology, structure, and magnetic properties are studied by scanning electron microscopy, X-ray diffraction and vibrating sample magnetometry, respectively. The obtained Fe and Fe-Mn oxide foams possess both high surface area and homogeneous open-cell structure. Hematite (α-Fe2O3) foams are obtained from the metallic iron slurry independently of the N2 flow. In contrast, the microstructure of the FeMn-based oxide foams can be tailored by adjusting the N2 flow. While the main phases for a N2 flow rate of 180 L/h are α-Fe2O3 and FeMnO3, the predominant phase for high N2 flow rates (e.g., 650 L/h) is Fe2MnO4. Accordingly, a linear magnetization versus field behavior is observed for the hematite foams, while clear hysteresis loops are obtained for the Fe2MnO4 foams. Actually, the saturation magnetization of the foams containing Mn increases from 5 emu/g to 52 emu/g when the N2 flow rate (i.e., the amount of Fe2MnO4) is increased. The obtained foams are appealing for a wide range of applications, such as electromagnetic absorbers, catalysts supports, thermal and acoustic insulation systems or wirelessly magnetically-guided porous objects in fluids. PMID:29439450

Synthesis and photocatalytic application of α-Fe2O3/ZnO fine particles prepared by two-step chemical method

Directory of Open Access Journals (Sweden)

Patij Shah

2013-06-01

Full Text Available Composite iron oxide-Zinc oxide (α-Fe2O3/ZnO was synthesized by two-step method: in the first one step uniform α-Fe2O3 particles were prepared through a hydrolysis process of ferric chloride at 80 °C. In the second step, the ZnO particles were included in the α-Fe2O3 particles by a zinc acetate [Zn(Ac2·2H2O] assisted hydrothermal method at low temperature (90°C±C. The α-Fe2O3 and ZnO phases were identified by XRD, energy dispersive X-ray analysis (EDX. The photoreactivities of α-Fe2O3/ZnO nanoparticles under UV irradiation were quantified by the degradation of formaldehyde.

Fe2O3 hollow sphere nanocomposites for supercapacitor applications

Science.gov (United States)

Zhao, Yu; Wen, Yang; Xu, Bing; Lu, Lu; Ren, Reiming

2018-02-01

Nanomaterials have attracted increasing interest in electrochemical energy storage and conversion. Hollow sphere Fe2O3 nanocomposites were successfully prepared through facile low temperature water-bath method with carbon sphere as hard template. The morphology and microstructure of samples were characterized by X-ray diffraction (XRD) and Scanning electron microscope (SEM), respectively. Through hydrolysis mechanism, using ferric chloride direct hydrolysis, iron hydroxide coated on the surface of carbon sphere, after high temperature calcination can form the hollow spherical iron oxide materials. Electrochemical performances of the hollow sphere Fe2O3 nanocomposites electrodes were investigated by cyclic voltammery (CV) and galvanostatic charge/discharge. The Pure hollow sphere Fe2O3 nanocomposites achieves a specific capacitance of 125 F g-1 at the current density of 85 mA g-1. The results indicate that the uniform dispersion of hollow ball structure can effectively reduce the particle reunion in the process of charging and discharging.

A Mild Catalytic Oxidation System: FePcOTf/H2O2 Applied for Cyclohexene Dihydroxylation

Directory of Open Access Journals (Sweden)

Baocheng Zhou

2015-05-01

Full Text Available Iron (III phthalocyanine complexes were employed for the first time as a mild and efficient Lewis acid catalyst in the selective oxidation of cyclohexene to cyclohexane-1,2-diol. It was found that the catalyst FePcOTf shown excellent conversion and moderate selectivity relative to other iron (III phthalocyanine complexes. The optimum conditions of the oxidation reaction catalyzed by FePcOTf/H2O2 have been researched in this paper. Iron (III phthalocyanine triflate (1 mol % as catalyst, hydrogen peroxide as oxidant, methanol as solvent, and a mole ratio of substrate and oxidant (H2O2 of 1:1 were used for achieving moderate yields of 1,2-diols under reflux conditions after eight hours.

Influence of Fe{sub 3}O{sub 4}/Fe-phthalocyanine decorated graphene oxide on the microwave absorbing performance

Energy Technology Data Exchange (ETDEWEB)

Li, Jingwei; Wei, Junji; Pu, Zejun; Xu, Mingzhen; Jia, Kun, E-mail: jiakun@uestc.edu.cn; Liu, Xiaobo, E-mail: liuxb@uestc.edu.cn

2016-02-01

Novel graphene oxide@Fe{sub 3}O{sub 4}/iron phthalocyanine (GO@Fe{sub 3}O{sub 4}/FePc) hybrid materials were prepared through a facile one-step solvothermal method with graphene oxide (GO) sheets as template in ethylene glycol. The morphology and structure of the hybrid materials were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectrophotometer (FTIR) and X-ray diffraction (XRD), respectively. The results indicated that the monodispersed Fe{sub 3}O{sub 4}/FePc hybrid microspheres were uniformly self-assembled along the surface of GO sheets through electrostatic attraction and the morphology can be tuned by controlling the amount of 4,4′-bis(3,4-dicyanophenoxy)biphenyl (BPH). As the BPH content increases, magnetization measurement of the GO@Fe{sub 3}O{sub 4}/FePc hybrid materials showed that the coercivity increased, while saturation magnetizations decreased. Electromagnetic properties of the hybrid materials were measured in the range of 0.5–18.0 GHz. The microwave absorbing performance enhanced with the increase of BPH content and a maximum reflection loss of −27.92 dB was obtained at 10.8 GHz when the matching thickness was 2.5 mm. Therefore, the novel electromagnetic hybrid materials can be considered as potential materials in the microwave absorbing field. - Highlights: • Graphene oxide was employed to support Fe{sub 3}O{sub 4}/iron phthalocyanine hybrid particles. • The morphology and magnetic properties of obtained particles can be readily tuned. • A maximum microwave reflection loss of −27.92 dB was obtained at 10.8 GHz.

Redox chemistry of a binary transition metal oxide (AB2O4): a study of the Cu(2+)/Cu(0) and Fe(3+)/Fe(0) interconversions observed upon lithiation in a CuFe2O4 battery using X-ray absorption spectroscopy.

Science.gov (United States)

Cama, Christina A; Pelliccione, Christopher J; Brady, Alexander B; Li, Jing; Stach, Eric A; Wang, Jiajun; Wang, Jun; Takeuchi, Esther S; Takeuchi, Kenneth J; Marschilok, Amy C

2016-06-22

Copper ferrite, CuFe2O4, is a promising candidate for application as a high energy electrode material in lithium based batteries. Mechanistic insight on the electrochemical reduction and oxidation processes was gained through the first X-ray absorption spectroscopic study of lithiation and delithiation of CuFe2O4. A phase pure tetragonal CuFe2O4 material was prepared and characterized using laboratory and synchrotron X-ray diffraction, Raman spectroscopy, and transmission electron microscopy. Ex situ X-ray absorption spectroscopy (XAS) measurements were used to study the battery redox processes at the Fe and Cu K-edges, using X-ray absorption near-edge structure (XANES), extended X-ray absorption fine structure (EXAFS), and transmission X-ray microscopy (TXM) spectroscopies. EXAFS analysis showed upon discharge, an initial conversion of 50% of the copper(ii) to copper metal positioned outside of the spinel structure, followed by a migration of tetrahedral iron(iii) cations to octahedral positions previously occupied by copper(ii). Upon charging to 3.5 V, the copper metal remained in the metallic state, while iron metal oxidation to iron(iii) was achieved. The results provide new mechanistic insight regarding the evolution of the local coordination environments at the iron and copper centers upon discharging and charging.

Synthesis of nanostructured mixed oxide CeO2-Mn2O3 and investigation of their sorption ability for arsenic, ammoniac, iron, manganese

International Nuclear Information System (INIS)

Luu Minh Dai; Dao Ngoc Nhiem; Duong Thi Lim

2012-01-01

The nanostrutured mixed oxide CeO 2 -Mn 2 O 3 have been synthesised at low temperature (350 o C) by the combustion of gel prepared from polyvinyl alcohol (PVA), Ce (NO 3 ) 4 and Mn(No 3 ) 3 , CeO 2 -Mn 2 O 3 characterizations were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM) and BET (Brunauce-Emmet-Teller) measurements. The phase of CeO 2 -Mn 2 O 3 , with large specific surface ares 65.3 m 2 /g was obtained at 350 o C for 2 hours. The nanostructured CeO 2 -Mn 2 O 3 has been investigated for removing iron, manganese, arsenic and ammoniac from water. The sorption characteristics of the nanostrutured CeO 2 -Mn 2 O 3 for AS(V), NH4 + , Fe(III), Mn(II) according to the langmuir isotherm. The sorption capacities of nanostrutured CeO 2 -Mn 2 O 3 are 57.10 mg As(V)g; 154.54 mg NH4 + /g; 72.97 mg Fe(III)/g; 60.27 Mn(II) / g. (author)

Advanced oxidation removal of hypophosphite by O3/H2O2 combined with sequential Fe(II) catalytic process.

Science.gov (United States)

Zhao, Zilong; Dong, Wenyi; Wang, Hongjie; Chen, Guanhan; Wang, Wei; Liu, Zekun; Gao, Yaguang; Zhou, Beili

2017-08-01

Elimination of hypophosphite (HP) was studied as an example of nickel plating effluents treatment by O 3 /H 2 O 2 and sequential Fe(II) catalytic oxidation process. Performance assessment performed with artificial HP solution by varying initial pH and employing various oxidation processes clearly showed that the O 3 /H 2 O 2 ─Fe(II) two-step oxidation process possessed the highest removal efficiency when operating under the same conditions. The effects of O 3 dosing, H 2 O 2 concentration, Fe(II) addition and Fe(II) feeding time on the removal efficiency of HP were further evaluated in terms of apparent kinetic rate constant. Under improved conditions (initial HP concentration of 50 mg L -1 , 75 mg L -1 O 3 , 1 mL L -1 H 2 O 2 , 150 mg L -1 Fe(II) and pH 7.0), standard discharge (<0.5 mg L -1 in China) could be achieved, and the Fe(II) feeding time was found to be the limiting factor for the evolution of apparent kinetic rate constant in the second stage. Characterization studies showed that neutralization process after oxidation treatment favored the improvement of phosphorus removal due to the formation of more metal hydroxides. Moreover, as a comparison with lab-scale Fenton approach, the O 3 /H 2 O 2 ─Fe(II) oxidation process had more competitive advantages with respect to applicable pH range, removal efficiency, sludge production as well as economic costs. Copyright © 2017 Elsevier Ltd. All rights reserved.

Synthesis of novel spherical Fe_3O_4@Ni_3S_2 composite as improved anode material for rechargeable nickel-iron batteries

International Nuclear Information System (INIS)

Li, Jing; Guo, Litan; Shangguan, Enbo; Yue, Mingzhu; Xu, Min; Wang, Dong; Chang, Zhaorong; Li, Quanmin

2017-01-01

Highlights: • Fe_3O_4@Ni_3S_2 microspheres are fabricated through a facile method for the first time. • Fe_3O_4@Ni_3S_2 is firstly proposed as alkaline anode materials for Ni/Fe batteries. • Fe_3O_4@Ni_3S_2 shows enhanced high-rate capability and improved cycle stability. • Ni_3S_2 can suppress the passivation and hydrogen evolution behavior of the iron anode. - Abstract: Fe_3O_4@Ni_3S_2 microspheres as a novel alkaline anode material have been successfully fabricated through a four-step process for the first time. In this composite, Ni_3S_2 nanoparticles are coated tightly on the surface of Fe_3O_4 microspheres. Compared with the pure Fe_3O_4 and Fe_3O_4@NiO microspheres, the proposed Fe_3O_4@Ni_3S_2 delivers a significantly improved high-rate performance and enhanced cycling stability. At a high discharge rate of 1200 mA g"−"1, the specific capacity of the Fe_3O_4@Ni_3S_2 is ∼481.2 mAh g"−"1 in comparison with ∼83.7 mAh g"−"1 for the pure Fe_3O_4. After 100 cycles at 120 mA g"−"1, the Fe_3O_4@Ni_3S_2 can achieve a capacity retention of 95.1%, while the value for the pure Fe_3O_4 electrode is only 52.5%. The favorable electrochemical performance of the Fe_3O_4@Ni_3S_2 is mainly attributed to the beneficial impact of Ni_3S_2. The Ni_3S_2 layer as a useful additive is significantly conducive to lessening the formation of Fe(OH)_2 passivation layer, enhancing the electronic conductivity, improving the reaction reversibility and suppressing the hydrogen evolution reaction of the alkaline iron anode. Owing to its outstanding electrochemical properties, we believe that the novel Fe_3O_4@Ni_3S_2 composite is potentially a promising candidate for anode material of alkaline iron-based batteries.

Synthesis of novel magnetic iron metal-silica (Fe-SBA-15) and magnetite-silica (Fe{sub 3}O{sub 4}-SBA-15) nanocomposites with a high iron content using temperature-programed reduction

Energy Technology Data Exchange (ETDEWEB)

Yiu, H H P [Department of Chemistry, University of Liverpool, Liverpool, Merseyside L69 7ZD (United Kingdom); Keane, M A [Chemical Engineering, School of Engineering and Physical Sciences, Heriot-Watt University, Edinburgh EH14 4AS (United Kingdom); Lethbridge, Z A D [Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL (United Kingdom); Lees, M R [Department of Physics, University of Warwick, Gibbet Hill Road, Coventry CV4 7AL (United Kingdom); Haj, A J El; Dobson, J [Institute of Science and Technology in Medicine, Keele University, Thornburrow Drive, Hartshill, Stoke-on-Trent ST4 7QB (United Kingdom)], E-mail: j.p.dobson@keele.ac.uk

2008-06-25

Magnetic iron metal-silica and magnetite-silica nanocomposites have been prepared via temperature-programed reduction (TPR) of an iron oxide-SBA-15 (SBA: Santa Barbara Amorphous) composite. TPR of the starting SBA-15 supported Fe{sub 2}O{sub 3} generated Fe{sub 3}O{sub 4} and FeO as stepwise intermediates in the ultimate formation of Fe-SBA-15. The composite materials have been characterized by means of x-ray diffraction, high resolution transmission electron microscopy and SQUID (superconducting quantum interference device) magnetometry. The Fe oxide and metal components form a core, as nanoscale particles, that is entrapped in the SBA-15 pore network. Fe{sub 3}O{sub 4}-SBA-15 and Fe-SBA-15 exhibited superparamagnetic properties with a total magnetization value of 17 emu g{sup -1}. The magnetite-silica composite (at an Fe{sub 3}O{sub 4} loading of 30% w/w) delivered a magnetization that exceeded values reported in the literature or obtained with commercial samples. Due to the high pore volume of the mesoporous template, the magnetite content can be increased to 83% w/w with a further enhancement of magnetization.

Moessbauer spectroscopy study on the hydrothermal transformation α-FeOOH → α-Fe2O3

International Nuclear Information System (INIS)

Barb, D.; Diamandescu, L.; Mihaila-Tarabsanu, D.; Rusi, A.; Moraria, M.

1990-01-01

The reaction kinetics of the hydrothermal transformation α-FeOOH→α-Fe 2 O 3 was studied by means of Moessbauer spectroscopy. From the reaction isotherms, a monomolecular, first order reaction was found to characterise the hydrothermal transformation of alpha oxihydroxide to the alpha iron oxide. The rate constant as well as the activation energy of this process were determined. No intermediate phases were identified in the hydrothermal samples. The thermodynamic properties of the hydrothermal system α-FeOOH→α-Fe 2 O 3 in correlation with Moessbauer spectroscopy data are discussed. (orig.)

From iron coordination compounds to metal oxide nanoparticles.

Science.gov (United States)

Iacob, Mihail; Racles, Carmen; Tugui, Codrin; Stiubianu, George; Bele, Adrian; Sacarescu, Liviu; Timpu, Daniel; Cazacu, Maria

2016-01-01

Various types, shapes and sizes of iron oxide nanoparticles were obtained depending on the nature of the precursor, preparation method and reaction conditions. The mixed valence trinuclear iron acetate, [Fe 2 III Fe II O(CH 3 COO) 6 (H 2 O) 3 ]·2H 2 O (FeAc1), μ 3 -oxo trinuclear iron(III) acetate, [Fe 3 O(CH 3 COO) 6 (H 2 O) 3 ]NO 3 ∙4H 2 O (FeAc2), iron furoate, [Fe 3 O(C 4 H 3 OCOO) 6 (CH 3 OH) 3 ]NO 3 ∙2CH 3 OH (FeF), iron chromium furoate, FeCr 2 O(C 4 H 3 OCOO) 6 (CH 3 OH) 3 ]NO 3 ∙2CH 3 OH (FeCrF), and an iron complex with an original macromolecular ligand (FePAZ) were used as precursors for the corresponding oxide nanoparticles. Five series of nanoparticle samples were prepared employing either a classical thermal pathway (i.e., thermal decomposition in solution, solvothermal method, dry thermal decomposition/calcination) or using a nonconventional energy source (i.e., microwave or ultrasonic treatment) to convert precursors into iron oxides. The resulting materials were structurally characterized by wide-angle X-ray diffraction and Fourier transform infrared, Raman, energy-dispersive X-ray, and X-ray fluorescence spectroscopies, as well as thermogravimetric analysis. The morphology was characterized by transmission electron microscopy, atomic force microscopy and dynamic light scattering. The parameters were varied within each route to fine tune the size and shape of the formed nanoparticles.

Core-shell iron-iron oxide nanoparticles

DEFF Research Database (Denmark)

Kuhn, Luise Theil; Bojesen, A.; Timmermann, L.

2004-01-01

We present studies of the magnetic properties of core-shell iron-iron oxide nanoparticles. By combining Mossbauer and X-ray absorption spectroscopy we have been able to measure the change from a Fe3O4-like to a gamma-Fe2O3-like composition from the interface to the surface. Furthermore, we have...

Synthesis, structure and properties of layered iron-oxychalcogenides Nd2Fe2Se2−xSxO3

International Nuclear Information System (INIS)

Liu, Y.; Zhang, S.B.; Tan, S.G.; Yuan, B.; Kan, X.C.; Zu, L.; Sun, Y.P.

2015-01-01

A new series of sulfur-substituted iron-oxychalcogenides Nd 2 Fe 2 Se 2−x S x O 3 (0≤x≤0.4) was synthesized by solid state reaction method, and investigated by structure, transport, magnetic and specific heat measurements. The compounds crystallize in the layered tetragonal structure with I4/mmm space group, and show semiconducting behavior. The large discrepancy between the activation energies for conductivity, E ρ (152–202 meV), and thermopower, E S (15.6–39.8 meV), indicates the polaronic transport mechanism of the carrier. The parent compound Nd 2 Fe 2 Se 2 O 3 exhibits a frustrated antiferromagnetic (AFM) ground state, and the S-substitution induces an enhanced ferromagnetic (FM) component and possible increased degree of frustration. - Graphical abstract: The crystal structure of Nd 2 Nd 2 Fe 2 Se 2−x S x O 3 is built up by stacking fluorite-like Nd 2 O 2 layers and anti-CuO 2 -type Fe 2 O(Se/S) 2 layers with Fe 2+ cations coordinated by two in-plane O 2- and four Se 2- above and below the square Fe 2 O plane. - Highlights: • We have synthesized a new series of layered iron-oxychalcogenides Nd 2 Fe 2 Se 2−x S x O 3 . • They crystallize in layered tetragonal structure and show semiconducting behavior. • The transport analysis indicates the polaronic transport mechanism of the carrier. • The parent compound shows a frustrated antiferromagnetic (AFM) ground state. • The S-substitution induces an enhanced ferromagnetic (FM) component

H2S adsorption and decomposition on the gradually reduced α-Fe2O3(001) surface: A DFT study

Science.gov (United States)

Lin, Changfeng; Qin, Wu; Dong, Changqing

2016-11-01

Reduction of iron based desulfurizer occurs during hot gas desulfurization process, which will affect the interaction between H2S and the desulfurizer surface. In this work, a detailed adsorption behavior and dissociation mechanism of H2S on the perfect and reduced α-Fe2O3(001) surfaces, as well as the correlation between the interaction characteristic and reduction degree of iron oxide, have been studied by using periodic density functional theory (DFT) calculations. Results demonstrate that H2S firstly chemisorbs on surface at relatively higher oxidation state (reduction degree χ 33%. Reduction of iron oxide benefits the H2S adsorption. Further, dissociation processes of H2S via molecular and dissociative adsorption were investigated. Results show that after reduction of Fe2O3 into the oxidation state around FeO and Fe, the reduced surface exhibits very strong catalytic capacity for H2S decomposition into S species. Meanwhile, the overall dissociation process on all surfaces is exothermic. These results provide a fundamental understanding of reduction effect of iron oxide on the interaction mechanism between H2S and desulfurizer surface, and indicate that rational control of reduction degree of desulfurizer is essential for optimizing the hot gas desulfurization process.

Synthesis of α-Fe2O3 and Fe-Mn Oxide Foams with Highly Tunable Magnetic Properties by the Replication Method from Polyurethane Templates

Directory of Open Access Journals (Sweden)

Yuping Feng

2018-02-01

Full Text Available Open cell foams consisting of Fe and Fe-Mn oxides are prepared from metallic Fe and Mn powder precursors by the replication method using porous polyurethane (PU templates. First, reticulated PU templates are coated by slurry impregnation. The templates are then thermally removed at 260 °C and the debinded powders are sintered at 1000 °C under N2 atmosphere. The morphology, structure, and magnetic properties are studied by scanning electron microscopy, X-ray diffraction and vibrating sample magnetometry, respectively. The obtained Fe and Fe-Mn oxide foams possess both high surface area and homogeneous open-cell structure. Hematite (α-Fe2O3 foams are obtained from the metallic iron slurry independently of the N2 flow. In contrast, the microstructure of the FeMn-based oxide foams can be tailored by adjusting the N2 flow. While the main phases for a N2 flow rate of 180 L/h are α-Fe2O3 and FeMnO3, the predominant phase for high N2 flow rates (e.g., 650 L/h is Fe2MnO4. Accordingly, a linear magnetization versus field behavior is observed for the hematite foams, while clear hysteresis loops are obtained for the Fe2MnO4 foams. Actually, the saturation magnetization of the foams containing Mn increases from 5 emu/g to 52 emu/g when the N2 flow rate (i.e., the amount of Fe2MnO4 is increased. The obtained foams are appealing for a wide range of applications, such as electromagnetic absorbers, catalysts supports, thermal and acoustic insulation systems or wirelessly magnetically-guided porous objects in fluids.

Oxygen rocking aqueous batteries utilizing reversible topotactic oxygen insertion/extraction in iron-based perovskite oxides Ca(1-x)La(x)FeO(3-δ).

Science.gov (United States)

Hibino, Mitsuhiro; Kimura, Takeshi; Suga, Yosuke; Kudo, Tetsuichi; Mizuno, Noritaka

2012-01-01

Developments of large-scale energy storages with not only low cost and high safety but also abundant metals are significantly demanded. While lithium ion batteries are the most successful method, they cannot satisfy all conditions. Here we show the principle of novel lithium-free secondary oxygen rocking aqueous batteries, in which oxygen shuttles between the cathode and anode composed of iron-based perovskite-related oxides Ca(0.5)La(0.5)FeO(z) (2.5 ≤ z ≤ 2.75 and 2.75 ≤ z ≤ 3.0). Compound Ca(0.5)La(0.5)FeO(z) can undergo two kinds of reduction and reoxidation of Fe(4+)/Fe(3+) and Fe(3+)/Fe(2+), that are accompanied by reversible and repeatable topotactic oxygen extraction and reinsertion during discharge and charge processes.

Fe{sub 2} O{sub 3} addition influence on the Sn O{sub 2}.Co O.Nb{sub 2} O{sub 5} varistors system; Influencia da adicao de Fe{sub 2} O{sub 3} no sistema varistor Sn O{sub 2}.Co O.Nb{sub 2} O{sub 5}

Energy Technology Data Exchange (ETDEWEB)

Antunes, A.C.; Antunes, S.R.M. [Universidade Estadual de Ponta Grossa, PR (Brazil). Dept. de Quimica; Castilhos, J.G.R.; Pianaro, S.R.; Zara, J.A. [Universidade Estadual de Ponta Grossa, PR (Brazil). Dept. de Engenharia dos Materiais; Longo, E. [Sao Carlos Univ., SP (Brazil). Dept. de Quimica; Varela, J.A. [UNESP, Araraquara, SP (Brazil). Inst. de Quimica

1997-12-31

The effect 0.05 to 0.30 mol% Fe{sub 2} 0{sub 3} addition on the electrical and microstructural properties of ternary varistor system composed by tin oxide, niobium oxide and cobaltum oxide was studied in this work. The samples were sintered at 1300 deg C for two hours. The characterizations were performed by Vxi measurements, scanning electron microscopy and X - ray diffraction. The Fe{sub 2} O{sub 3} additions up to 0,10% increased the {alpha} values breakdown electric fields (E{sub r}) and it was observed that the barrier voltage (v{sub b}) depends on the chemical composition. The second phase had high concentration of iron that precipitated in the grain boundaries and inhibited the grain growth during sintering. Fe{sub 2} O{sub 3} concentrations upper 0,10 mol% were deleterious for electrical properties of the ceramics. (author) 7 refs., 3 figs., 4 tabs.

Structural transformations of heat-treated bacterial iron oxide

Energy Technology Data Exchange (ETDEWEB)

Hashimoto, Hideki, E-mail: hideki-h@cc.okayama-u.ac.jp [Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530 (Japan); JST, CREST, Okayama 700-8530 (Japan); Fujii, Tatsuo [Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530 (Japan); Kohara, Shinji [Japan Synchrotron Radiation Research Institute, Sayo, Hyogo 679-5198 (Japan); Nakanishi, Koji [Office of Society-Academia Collaboration for Innovation, Kyoto University, Uji 611-0011 (Japan); Yogi, Chihiro [SR Center, Ritsumeikan University, Kusatsu, Shiga 525-8577 (Japan); Peterlik, Herwig [Faculty of Physics, University of Vienna, A-1090 Vienna (Austria); Nakanishi, Makoto [Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530 (Japan); Takada, Jun [Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530 (Japan); JST, CREST, Okayama 700-8530 (Japan)

2015-04-01

A bacterial siliceous iron oxide microtubule (diameter: ca. 1 μm, 15Fe{sub 2}O{sub 3}·8SiO{sub 2}·P{sub 2}O{sub 5}·30H{sub 2}O) produced by Leptothrix ochracea was heat treated in air and its structural transformation was investigated in detail by microscopy, diffractometry, and spectroscopy. Although the heat-treated bacterial iron oxide retained its original microtubular structure, its nanoscopic, middle-range, and local structures changed drastically. Upon heat treatment, nanosized pores were formed and their size changed depending on temperature. The Fe–O–Si linkages were gradually cleaved with increasing temperature, causing the progressive separation of Fe and Si ions into iron oxide and amorphous silicate phases, respectively. Concomitantly, global connectivity and local structure of FeO{sub 6} octahedra in the iron oxide nanoparticles systematically changed depending on temperature. These comprehensive investigations clearly revealed various structural changes of the bacterial iron oxide which is an important guideline for the future exploration of novel bio-inspired materials. - Highlights: • Structural transformation of a bacterial iron oxide microtubule was investigated. • Si–O–Fe was cleaved with increasing temperature to form α-Fe{sub 2}O{sub 3}/silicate composite. • Crystallization to 2Fh started at 500 °C to give α-Fe{sub 2}O{sub 3} >700 °C. • FeO{sub 6} octahedra were highly distorted <500 °C. • Formation of face-sharing FeO{sub 6} was promoted >500 °C, releasing the local strain of FeO{sub 6}.

Iron 1s X-ray photoemission of Fe2O3

NARCIS (Netherlands)

Miedema, P. S.; Borgatti, F.; Offi, F.; Panaccione, G.; de Groot, F. M. F.

We present the Is X-ray photoemission spectrum of alpha-Fe2O3 in comparison with its 2p photoemission spectrum. We show that in case of transition metal oxides, because the 1s core hole is not affected by core hole spin-orbit coupling and almost not affected by core-valence multiplet effects, the Fe

The topotactic reduction of Sr3Fe2O5Cl2-square planar Fe(II) in an extended oxyhalide.

Science.gov (United States)

Dixon, Edward; Hayward, Michael A

2010-10-18

The topotactic reduction of the oxychloride Sr(3)Fe(2)O(5)Cl(2) with LiH results in the formation of Sr(3)Fe(2)O(4)Cl(2). Neutron powder diffraction data show that Sr(3)Fe(2)O(4)Cl(2) adopts a body-centered tetragonal crystal structure (I4/mmm, a = 4.008(1) Å, c = 22.653(1) Å at 388 K) with anion vacancies located within the SrO layer of the phase. This leads to a structure consisting of infinite sheets of corner-sharing Fe(II)O(4) square planes. Variable-temperature neutron diffraction data show that Sr(3)Fe(2)O(4)Cl(2) adopts G-type antiferromagnetic order below T(N) ∼ 378(10) K with an ordered moment of 2.81(9) μ(B) per iron center at 5 K consistent with the presence of high-spin Fe(II). The observed structural and chemical selectivity of the reduction reaction is discussed. The contrast between the structure of Sr(3)Fe(2)O(4)Cl(2) and the isoelectronic all-oxide analogue (Sr(3)Fe(2)O(5)) suggests that by careful selection of substrate phases, the topotactic reduction of complex transition metal oxychlorides can lead to the preparation of novel anion-deficient phases with unique transition metal-oxygen sublattices which cannot be prepared via the reduction of all-oxide substrates.

From iron coordination compounds to metal oxide nanoparticles

Directory of Open Access Journals (Sweden)

Mihail Iacob

2016-12-01

Full Text Available Various types, shapes and sizes of iron oxide nanoparticles were obtained depending on the nature of the precursor, preparation method and reaction conditions. The mixed valence trinuclear iron acetate, [Fe2IIIFeIIO(CH3COO6(H2O3]·2H2O (FeAc1, μ3-oxo trinuclear iron(III acetate, [Fe3O(CH3COO6(H2O3]NO3∙4H2O (FeAc2, iron furoate, [Fe3O(C4H3OCOO6(CH3OH3]NO3∙2CH3OH (FeF, iron chromium furoate, FeCr2O(C4H3OCOO6(CH3OH3]NO3∙2CH3OH (FeCrF, and an iron complex with an original macromolecular ligand (FePAZ were used as precursors for the corresponding oxide nanoparticles. Five series of nanoparticle samples were prepared employing either a classical thermal pathway (i.e., thermal decomposition in solution, solvothermal method, dry thermal decomposition/calcination or using a nonconventional energy source (i.e., microwave or ultrasonic treatment to convert precursors into iron oxides. The resulting materials were structurally characterized by wide-angle X-ray diffraction and Fourier transform infrared, Raman, energy-dispersive X-ray, and X-ray fluorescence spectroscopies, as well as thermogravimetric analysis. The morphology was characterized by transmission electron microscopy, atomic force microscopy and dynamic light scattering. The parameters were varied within each route to fine tune the size and shape of the formed nanoparticles.

Viscosity of SiO2-"FeO"-Al2O3 System in Equilibrium with Metallic Fe

Science.gov (United States)

Chen, Mao; Raghunath, Sreekanth; Zhao, Baojun

2013-08-01

The present study delivered the measurements of viscosities in SiO2-"FeO"-Al2O3 system in equilibrium with metallic Fe. The rotational spindle technique was used in the measurements at the temperature range of 1473 K to 1773 K (1200 °C to 1500 °C). Molybdenum crucibles and spindles were employed in all measurements. The Fe saturation condition was maintained by an iron plate placed at the bottom of the crucible. The equilibrium compositions of the slags were measured by EPMA after the viscosity measurements. The effect of up to 20 mol. pct Al2O3 on the viscosity of the SiO2-"FeO" slag was investigated. The "charge compensation effect" of the Al2O3 and FeO association has been discussed. The modified quasi-chemical viscosity model has been optimized in the SiO2-"FeO"-Al2O3 system in equilibrium with metallic Fe to describe the viscosity measurements of the present study.

Treatment of landfill leachate biochemical effluent using the nano-Fe3O4/Na2S2O8 system: Oxidation performance, wastewater spectral analysis, and activator characterization.

Science.gov (United States)

Liu, Zhanmeng; Li, Xian; Rao, Zhiwei; Hu, Fengping

2018-02-15

Nano-Fe 3 O 4 was used as heterogeneous catalyst to activate Na 2 S 2 O 8 for the generation of the sulfate radicals (SO 4 - ) to oxidize the residual pollutants in landfill leachate biochemical effluent. The oxidation performance, wastewater spectral analysis and activator characterization were discussed. Oxidation experimental result shows that nano-Fe 3 O 4 has obvious catalytic effect on Na 2 S 2 O 8 and can significantly enhance the oxidation efficiencies of Na 2 S 2 O 8 on landfill leachate biochemical effluent, with COD and color removals above 63% and 95%, respectively. Based on the analyses of three-dimensional excitation emission matrix fluorescence spectrum (3DEEM), ultraviolet-visible spectra (UV-vis), and Fourier Transform infrared spectroscopy (FTIR) of wastewater samples before and after treatment, it can be concluded that the pollution level of dissolved organic matter (DOM) declined and that the humic acid (HA) fractions were efficiently degraded into small molecules of fulvic acid (FA) fractions with less weight and stable structure. Compared to the raw wastewater sample, the aromaticity and substituent groups of the DOM were lessened in the treated wastewater sample. Moreover, the main structure of the organics and functional groups were changed by the Fe 3 O 4 /Na 2 S 2 O 8 system, with substantial decrease of conjugated double bonds. The micro morphology of nano-Fe 3 O 4 was characterized before and after reaction by the methods of scanning electron microscope spectra (SEM), X-ray diffraction pattern (XRD), and X-ray photoelectron spectroscopy (XPS). The XRD pattern analysis showed that nano-Fe 3 O 4 was oxidized into r-Fe 2 O 3 and that the particle size of it also became smaller after reaction. XPS was employed to analyze the content and iron valence on the nano-Fe 3 O 4 surface, and it can be found that the ratio of Fe 3+ /Fe 2+ decreased from 1.8 before reaction to 0.8 after reaction. From the SEM analysis after the treatment, it was

Reduced graphene oxide wrapped Fe3O4-Co3O4 yolk-shell nanostructures for advanced catalytic oxidation based on sulfate radicals

Science.gov (United States)

Zhang, Lishu; Yang, Xijia; Han, Erfen; Zhao, Lijun; Lian, Jianshe

2017-02-01

In this work, we designed and synthesized a high performance catalyst of reduced graphene oxide (RGO) wrapped Fe3O4-Co3O4 (RGO/Fe3O4-Co3O4) yolk-shell nanostructures for advanced catalytic oxidation based on sulfate radicals. The synergistic catalytic action of the RGO/Fe3O4-Co3O4 yolk-shell nanostructures activate the peroxymonosulfate (PMS) to produce sulfate radicals (SO4rad -) for organic dyes degradation, and the Orange II can be almost completely degradated in 5 min. Meanwhile the RGO wrapping prevents the loss of cobalt in the catalytic process, and the RGO/Fe3O4-Co3O4 can be recycled after catalyzed reaction due to the presence of magnetic iron core. What's more, it can maintain almost the same high catalytic activity even after 10 cycles through repeated NaBH4 reduction treatment. Hence, RGO/Fe3O4-Co3O4 yolk-shell nanostructures possess a great opportunity to become a promising candidate for waste water treatment in industry.

Core–shell structure carbon coated ferric oxide (Fe{sub 2}O{sub 3}@C) nanoparticles for supercapacitors with superior electrochemical performance

Energy Technology Data Exchange (ETDEWEB)

Ye, Yipeng [School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006 (China); Zhang, Haiyan [School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006 (China); Guangdong Provincial Key Laboratory of Functional Soft Condensed Matter, Guangzhou 510006 (China); Chen, Yiming, E-mail: chenym@gdut.edu.cn [School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006 (China); Guangdong Provincial Key Laboratory of Functional Soft Condensed Matter, Guangzhou 510006 (China); Deng, Peng; Huang, Zhikun [School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006 (China); Liu, Liying; Qian, Yannan; Li, Yunyong [School of Materials and Energy, Guangdong University of Technology, Guangzhou 510006 (China); Guangdong Provincial Key Laboratory of Functional Soft Condensed Matter, Guangzhou 510006 (China); Li, Qingyu [School of Chemistry and Chemistry Engineering, Guangxi Normal University, Guilin 541004 (China)

2015-08-05

Highlights: • Fe{sub 2}O{sub 3}@C was prepared by using arc discharge method followed by heat treatment. • KOH activation made the core–shell structure Fe{sub 2}O{sub 3}@C porous. • The activated-Fe{sub 2}O{sub 3}@C supercapacitor exhibited superior electrochemical performance. - Abstract: Core–shell structure carbon coated ferric oxide nanoparticles (Fe{sub 2}O{sub 3}@C) were fabricated by the oxidation of carbon coated iron nanoparticles (Fe@C) prepared by a direct current carbon arc discharge method. Porous activated-Fe{sub 2}O{sub 3}@C was prepared by KOH activation of Fe{sub 2}O{sub 3}@C at the temperature of 750 °C. X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were employed to characterize the structure and morphology of the Fe{sub 2}O{sub 3}@C and activated-Fe{sub 2}O{sub 3}@C. The specific surface area and pore size distribution of the samples were also tested. The activated-Fe{sub 2}O{sub 3}@C electrodes exhibited good electrochemical performance with a maximum specific capacitance of 612 F g{sup −1} at the charge/discharge current density of 0.5 A g{sup −1} with 5 M NaOH electrolyte. After 10,000 cycling DC tests at the charge/discharge current density of 4 A g{sup −1}, a high level specific capacitance of 518 F g{sup −1} was obtained (90.6% retention of the initial capacity), suggesting excellent long-term cycling stability.

Highly efficient Cu-decorated iron oxide nanocatalyst for low pressure CO 2 conversion

Energy Technology Data Exchange (ETDEWEB)

Halder, Avik; Kilianová, Martina; Yang, Bing; Tyo, Eric C.; Seifert, Soenke; Prucek, Robert; Panáček, Aleš; Suchomel, Petr; Tomanec, Ondřej; Gosztola, David J.; Milde, David; Wang, Hsien-Hau; Kvítek, Libor; Zbořil, Radek; Vajda, Stefan

2018-06-01

We report a nanoparticulate iron oxide based catalyst for CO2 conversion with high efficiency at low pressures and on the effect of the presence of copper on the catalyst's restructuring and its catalytic performance. In situ X-ray scattering reveals the restructuring of the catalyst at the nanometer scale. In situ X-ray absorption near edge structure (XANES) shows the evolution of the composition and oxidation state of the iron and copper components under reaction conditions along with the promotional effect of copper on the chemical transformation of the iron component. X-ray diffraction (XRD), XANES and Raman spectroscopy proved that the starting nano catalyst is composed of iron oxides differing in chemical nature (alpha-Fe2O3, Fe3O4, FeO(OH)) and dimensionality, while the catalyst after CO2 conversion was identified as a mixture of alpha-Fe, Fe3C, and traces of Fe5C2. The significant increase of the rate CO2 is turned over in the presence of copper nanoparticles indicates that Cu nanoparticles activate hydrogen, which after spilling over to the neighbouring iron sites, facilitate a more efficient conversion of carbon dioxide.

Bacteria-assisted preparation of nano α-Fe2O3 red pigment powders from waste ferrous sulfate

International Nuclear Information System (INIS)

Li, Xiang; Wang, Chuankai; Zeng, Yu; Li, Panyu; Xie, Tonghui; Zhang, Yongkui

2016-01-01

Highlights: • A route to prepare nano α-Fe 2 O 3 red pigment from waste ferrous sulfate is proposed. • Acidithiobacillus ferrooxidans is introduced for accelerating iron oxidation. • The particle size of synthetic α-Fe 2 O 3 is ranged from 22 nm to 86 nm. • The prepared nano α-Fe 2 O 3 red pigment fulfills ISO 1248-2006. - Abstract: Massive ferrous sulfate with excess sulfuric acid is produced in titanium dioxide industry each year, ending up stockpiled or in landfills as solid waste, which is hazardous to environment and in urgent demand to be recycled. In this study, waste ferrous sulfate was used as a second raw material to synthesize nano α-Fe 2 O 3 red pigment powders with a bacteria-assisted oxidation process by Acidithiobacillus ferrooxidans. The synthesis route, mainly consisting of bio-oxidation, precipitation and calcination, was investigated by means of titration, thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray fluorescence (XRF) to obtain optimum conditions. Under the optimum conditions, nano α-Fe 2 O 3 red pigment powders contained 98.24 wt.% of Fe 2 O 3 were successfully prepared, with a morphology of spheroidal and particle size ranged from 22 nm to 86 nm and averaged at 45 nm. Moreover, the resulting product fulfilled ISO 1248-2006, the standards of iron oxide pigments.

Thermodynamic study of sodium-iron oxides. Part 2. Ternary phase diagram of the Na-Fe-O system

International Nuclear Information System (INIS)

Huang, Jintao; Furukawa, Tomohiro; Aoto, Kazumi

2003-01-01

Studies on ternary phase diagrams of the Na-Fe-O system have been carried out from the thermodynamic point of view. Thermodynamic data of main ternary Na-Fe oxides Na 4 FeO 3 (s), Na 3 FeO 3 (s), Na 5 FeO 4 (s) and Na 8 Fe 2 O 7 (s) have been assessed. A user database has been created by reviewing literature data together with recent DSC and vapor pressure measurements by the present authors. New ternary phase diagrams of the Na-Fe-O system have been constructed from room temperature to 1000K. Stable conditions of the ternary oxides at 800K were presented in predominance diagram as functions of oxygen pressure and sodium pressure

Iron oxides characterization by Moessbauer spectroscopy

International Nuclear Information System (INIS)

Basurto Sanchez, R.

1993-01-01

In this work rust development on low carbon wire surface after the conformation process at different temperatures was studied by Moessbauer spectroscopy. The characterization was made by determining the following spectral parameters; 1) Quadrupole splitting, 2) Isomer shift, and 3) Magnetic splitting. The area quantification determined the percentage amount of three different iron oxides. These iron oxides were: a) Wustite (Fe O), b) Hematite (Fe 2 O 3 ), and c) Magnetite (Fe 3 O 4 ) which were present in the rust studied. With the results it was possible to establish the best temperature to favor the development of each of these iron oxides. (Author)

Investigations on FCAM-III (Ca2.38Mg2.09Fe3+10.61Fe2+1.59Al9.33O36): A new homologue of the aenigmatite structure-type in the system CaO-MgO-Fe2O3-Al2O3

Science.gov (United States)

Zöll, Klaus; Kahlenberg, Volker; Krüger, Hannes; Tropper, Peter

2018-02-01

In the course of a systematic study of a part of the quaternary system Fe2O3-CaO-Al2O3-MgO (FCAM) the previously unknown compound Ca2.38Mg2.09Fe3+10.61Fe2+1.59Al9.33O36 (FCAM-III) has been synthesized. By analogy with the so-called SFCA series [1-5], our investigation in the system of FCAM shows the existence of a stoichiometric homologous series M14+6nO20+8n, where M = Fe, Ca, Al, Mg and n = 1 or 2. In air, we can prove the formation of coexisting FCAM-III and FCAM-I solid solutions at 1400 °C. By increasing the temperature up to 1425 °C FCAM-I disappears completely and FCAM-III co-exists with magnesiumferrite and a variety of calcium iron oxides. At 1450 °C FCAM-III breaks down to a mixture of FCAM-I again as well as magnesioferrite and melt. Small single-crystals of FCAM-III up to 35 μm in size could be retrieved from the 1425 °C experiment and were subsequently characterized using electron microprobe analysis and synchroton X-ray single-crystal diffraction. Finally the Fe2+/Fetot ratio was calculated from the total iron content based on the crystal-chemical formula obtained from EMPA measurements and charge balance considerations. FCAM-III or Ca2.38Mg2.09Fe3+10.61Fe2+1.59Al9.33O36 has a triclinic crystal structure (space group P 1 ̅). The basic crystallographic data are: a = 10.223(22) Å, b = 10.316(21) Å, c = 14.203(15) Å, α = 93.473(50)°, β = 107.418(67)°, γ = 109.646(60)°, V = 1323.85(2) ų, Z = 1. Using Schreinemaker's technique to analyze the phase relations in the system Fe2O3-CaO-Al2O3-MgO it was possible to obtain the semi-quantitative stability relations between the participating phases and construct a topologically correct phase sequence as a function of T and fO2. The analysis shows that Ca2Al0.5Fe1.5O5 (C2A0.25F0.75) and CaAl1.5Fe2.5O7 (CA0.75F1.25) with higher calculated Fe2+ contents are preferably formed at lower oxygen fugacity and react to CaAl0.5Fe1.5O4 (CA0.25F0.75) by increasing fO2. Spinel-type magnesium

Investigation on effect of iron and corundum content on corrosion resistance of the NiFe-Al2O3 coatings

International Nuclear Information System (INIS)

Starosta, R.; Zielinski, A.

1999-01-01

The alloy NiFe and composite NiFe-Al 2 O 3 coatings, obtained by electrodeposition on the base of cast iron, were investigated. The iron content in alloy coatings was dependent on iron content in galvanic bath, and was estimated by means of X-ray microanalysis at 18.5 wt. pct. and 41.2 wt. pct. No existence of ordered Ni 3 Fe phase was found by diffraction technique. Both potentiodynamic and impedance measurements disclosed that a presence of Al 2 O 3 or increasing iron content in the layer caused the decrease in corrosion resistance. (author)

Hydrothermal synthesis of Fe_2O_3/polypyrrole/graphene oxide composites as highly efficient electrocatalysts for oxygen reduction reaction in alkaline electrolyte

International Nuclear Information System (INIS)

Ren, Suzhen; Ma, Shaobo; Yang, Ying; Mao, Qing; Hao, Ce

2015-01-01

Graphical abstract: Fe_2O_3/polypyrrole/graphene oxide electrocatalysts for oxygen reduction reaction (ORR) are successfully prepared through one simple polypyrrole-assisted hydrothermal method and possess very high ORR activity and are able to selectively reduce O_2 to water through the four-electron transfer reaction mechanism in alkaline electrolyte. - Abstract: Advantages in low cost, and excellent catalytic activity of Fe-based nanomaterials dispersed on nitrogen-doped graphene supports render them to be good electrocatalysts for the oxygen reduction reaction (ORR) in fuel cells. Here, Fe_2O_3/polypyrrole/graphene oxide (Fe_2O_3/Ppy/GO) composites with the Fe_2O_3 embedded in the Ppy modified GO are synthesized using hydrothermal method. With an optimal iron atom content ratio of 1.6% in graphene oxide and heat treatment at 800 °C, the Fe_2O_3/Ppy/GO exhibited enhanced catalytic performance for ORR with the onset potential of −0.1 V (vs SCE), cathodic potential of −0.24 V (vs SCE), an approximate 4e"− transfer process in O_2-saturated 0.1 M KOH, and superior stability that only reduced 5% catalytic activity after 5000 cycles. The decisive factors in improving the electrocatalytic and durable performance are the intimate and large contact interfaces between nanocrystallines of Fe_2O_3 and Ppy/GO, in addition to the high electron withdrawing/storing ability and the high conductivity of GO doped with nitrogen from Ppy during the hydrothermal reaction. The Fe_2O_3/Ppy/GO showed significantly improved ORR properties and confirmed that Fe-N-C-based electrocatalysts played a key role in fuel cells.

Facile preparation and enhanced microwave absorption properties of flake carbonyl iron/Fe{sub 3}O{sub 4} composite

Energy Technology Data Exchange (ETDEWEB)

Min, Dandan, E-mail: mdd4776@126.com; Zhou, Wancheng; Luo, Fa; Zhu, Dongmei

2017-08-01

Highlights: • Flake carbonyl iron/Fe{sub 3}O{sub 4} composites were prepared by surface oxidation technique. • Lower permittivity and modest permeability was obtained by the FCI/Fe{sub 3}O{sub 4} composites. • Enhanced absorption efficiency and broader absorption band were obtained. - Abstract: Flake carbonyl iron/Fe{sub 3}O{sub 4} (FCI/Fe{sub 3}O{sub 4}) composites with enhanced microwave absorption properties were prepared by a direct and flexible surface oxidation technique. The phase structures, morphology, magnetic properties, frequency-dependent electromagnetic and microwave absorption properties of the composites were investigated. The measurement results showed that lower permittivity as well as modest permeability was obtained by the FCI/Fe{sub 3}O{sub 4} composites. The calculated microwave absorption properties indicated that enhanced absorption efficiency and broader absorption band were obtained by the FCI/Fe{sub 3}O{sub 4} composite comparing with the FCI composite. The absorption frequency range with reflection loss (RL) below −5 dB of FCI/Fe{sub 3}O{sub 4} composites at reaction time of 90 min at thickness of 1.5 mm is 13.3 GHz from 4.7 to 18 GHz, while the bandwidth of the FCI composite is only 5.9 GHz from 2.6 to 8.5 GHz at the same thickness. Thus, such absorbers could act as effective and wide broadband microwave absorbers in the GHz range.

Quasicubic α-Fe{sub 2}O{sub 3} nanoparticles embedded in TiO{sub 2} thin films grown by atomic layer deposition

Energy Technology Data Exchange (ETDEWEB)

Tamm, Aile [Institute of Physics, University of Tartu, W. Ostwaldi 1, 50411 Tartu (Estonia); Seinberg, Liis [National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn (Estonia); Kozlova, Jekaterina [Institute of Physics, University of Tartu, W. Ostwaldi 1, 50411 Tartu (Estonia); Link, Joosep [National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn (Estonia); Pikma, Piret [University of Tartu, Institute of Chemistry, Ravila 14A, 50411 Tartu (Estonia); Stern, Raivo [National Institute of Chemical Physics and Biophysics, Akadeemia tee 23, 12618 Tallinn (Estonia); Kukli, Kaupo [Institute of Physics, University of Tartu, W. Ostwaldi 1, 50411 Tartu (Estonia); Department of Chemistry, University of Helsinki, P.O. Box 55, FI-00014 Helsinki (Finland)

2016-08-01

Monodispersed quasicubic α-Fe{sub 2}O{sub 3} nanoparticles were synthesized from ferric nitrite (Fe(NO{sub 3}){sub 3}), N,N-dimethyl formamide and poly(N-vinyl-2-pyrrolidone). Layers of nanoparticles were attached to HF-etched Si substrates by dip coating and subsequently embedded in thin titanium oxide films grown by atomic layer deposition from TiCl{sub 4} and H{sub 2}O. The deposition of TiO{sub 2} onto Fe{sub 2}O{sub 3} nanoparticles covered the nanoparticles uniformly and anatase phase of TiO{sub 2} was observed in Si/Fe{sub 2}O{sub 3}/TiO{sub 2} nanostructures. In Si/Fe{sub 2}O{sub 3}/TiO{sub 2} nanostructure magnetic domains, observable by magnetic force microscopy, were formed and these nanostructures implied ferromagnetic-like behavior at room temperature with the saturative magnetization and coercivity of 10 kA/m. - Highlights: • Cubic-shaped iron oxide crystallites were supported by thin titanium oxide films. • The process chemistry applied allowed formation of heterogeneous composite. • Atomic layer deposition of titanium oxide on nanocubes was uniform and conformal. • The nanostructures formed can be regarded as magnetically susceptible materials.

Magnetic characteristics of ultrafine Fe particles reduced from uniform iron oxide particles

Science.gov (United States)

Bridger, K.; Watts, J.; Tadros, M.; Xiao, Gang; Liou, S. H.; Chien, C. L.

1987-04-01

Uniform, cubic 0.05-μm iron oxide particles were formed by forced hydrolysis of ferric perchlorate. These particles were reduced to α-Fe by heating in hydrogen at temperatures between 300 and 500 °C. The effect of reduction temperature and various prereduction treatments on the microstructure of the iron particles will be discussed. Complete reduction to α-Fe was established by 57Fe Mössbauer spectroscopy and x-ray diffraction. Magnetic measurements on epoxy and polyurethane films containing these particles with various mass fractions gave coercivities as high as 1000 Oe. The relationship between the magnetic measurements and the microstructure will be discussed. Na2SiO3 is found to be the best coating material for the process of reducing iron oxide particles to iron.

Fe3O4/Reduced Graphene Oxide Nanocomposite: Synthesis and Its Application for Toxic Metal Ion Removal

Directory of Open Access Journals (Sweden)

Nguyen Thi Vuong Hoan

2016-01-01

Full Text Available The synthesis of reduced graphene oxide modified by magnetic iron oxide (Fe3O4/rGO and its application for heavy metals removal were demonstrated. The obtained samples were characterized by X-ray diffraction (XRD, nitrogen adsorption/desorption isotherms, X-ray photoelectron spectroscopy (XPS, Fourier transform infrared spectroscopy (FT-IR, and magnetic measurement. The results showed that the obtained graphene oxide (GO contains a small part of initial graphite as well as reduced oxide graphene. GO exhibits very high surface area in comparison with initial graphite. The morphology of Fe3O4/rGO consists of very fine spherical iron nanooxide particles in nanoscale. The formal kinetics and adsorption isotherms of As(V, Ni(II, and Pb(II over obtained Fe3O4/rGO have been investigated. Fe3O4/rGO exhibits excellent heavy metal ions adsorption indicating that it is a potential adsorbent for water sources contaminated by heavy metals.

Sulfur isotope fractionation during oxidation of sulfur dioxide: gas-phase oxidation by OH radicals and aqueous oxidation by H2O2, O3 and iron catalysis

Directory of Open Access Journals (Sweden)

J. N. Crowley

2012-01-01

Full Text Available The oxidation of SO2 to sulfate is a key reaction in determining the role of sulfate in the environment through its effect on aerosol size distribution and composition. Sulfur isotope analysis has been used to investigate sources and chemical processes of sulfur dioxide and sulfate in the atmosphere, however interpretation of measured sulfur isotope ratios is challenging due to a lack of reliable information on the isotopic fractionation involved in major transformation pathways. This paper presents laboratory measurements of the fractionation factors for the major atmospheric oxidation reactions for SO2: Gas-phase oxidation by OH radicals, and aqueous oxidation by H2O2, O3 and a radical chain reaction initiated by iron. The measured fractionation factor for 34S/32S during the gas-phase reaction is αOH = (1.0089±0.0007−((4±5×10−5 T(°C. The measured fractionation factor for 34S/32S during aqueous oxidation by H2O2 or O3 is αaq = (1.0167±0.0019−((8.7±3.5 ×10−5T(°C. The observed fractionation during oxidation by H2O2 and O3 appeared to be controlled primarily by protonation and acid-base equilibria of S(IV in solution, which is the reason that there is no significant difference between the fractionation produced by the two oxidants within the experimental error. The isotopic fractionation factor from a radical chain reaction in solution catalysed by iron is αFe = (0.9894±0.0043 at 19 °C for 34S/32S. Fractionation was mass-dependent with regards to 33S/32S for all the reactions investigated. The radical chain reaction mechanism was the only measured reaction that had a faster rate for the light isotopes. The results presented in this study will be particularly useful to determine the importance of the transition metal-catalysed oxidation pathway compared to other oxidation pathways, but other main oxidation pathways can not be distinguished based on stable sulfur isotope measurements alone.

Synthesis of 3D hierarchical porous iron oxides for adsorption of Congo red from dye wastewater

International Nuclear Information System (INIS)

Jia, Zhigang; Liu, Jianhong; Wang, Qiuze; Li, Shengbiao; Qi, Qin; Zhu, Rongsun

2015-01-01

Highlights: • Bowknot-like precursor is obtained via poval-mediated precipitation reaction. • The growth mechanism of the hierarchical superstructure has been discussed. • Mesoporous iron oxide superstructures have been successfully synthesized. • The magnetic superstructures can adsorb CR from aqueous solution effectively. • The adsorption kinetics and isotherm processes are discussed. - Abstract: In this study, 3D hierarchical porous iron oxides were prepared by a precursor thermal conversion method and their adsorption properties for Congo red were reported. The products were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), electron microscopy (EM) and nitrogen adsorption-desorption isotherms. Results demonstrated that the 3D magnetic bowknot-like iron oxides were constructed by three-dimensional self-assembly of nanorods with porous nanostructures. The effect of experimental parameters including polymer concentration, reaction temperature, reaction time and heat treatment atmosphere were studied. Bowknot-like α-Fe 2 O 3 , Fe 3 O 4 and γ-Fe 2 O 3 superstructures were obtained by the thermal transformation of the oxalate precursor under the various atmosphere. These porous iron oxide superstructures exhibited ferromagnetic property at room temperature. Adsorption of Congo red (CR) onto the as-prepared samples from aqueous solutions was investigated and discussed. The results indicated that pseudo-second-order kinetic equation model can better describe the adsorption kinetics of CR onto α-Fe 2 O 3 and γ-Fe 2 O 3 , and Lagergren-first-order kinetic model is better fitted for the adsorption of CR onto Fe 3 O 4 . The hierarchically α-Fe 2 O 3 bowknots showed better adsorption ability for CR than Fe 3 O 4 and γ-Fe 2 O 3 superstructure

Synthesis of 3D hierarchical porous iron oxides for adsorption of Congo red from dye wastewater

Energy Technology Data Exchange (ETDEWEB)

Jia, Zhigang, E-mail: zjchemyue@126.com; Liu, Jianhong; Wang, Qiuze; Li, Shengbiao; Qi, Qin; Zhu, Rongsun

2015-02-15

Highlights: • Bowknot-like precursor is obtained via poval-mediated precipitation reaction. • The growth mechanism of the hierarchical superstructure has been discussed. • Mesoporous iron oxide superstructures have been successfully synthesized. • The magnetic superstructures can adsorb CR from aqueous solution effectively. • The adsorption kinetics and isotherm processes are discussed. - Abstract: In this study, 3D hierarchical porous iron oxides were prepared by a precursor thermal conversion method and their adsorption properties for Congo red were reported. The products were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), electron microscopy (EM) and nitrogen adsorption-desorption isotherms. Results demonstrated that the 3D magnetic bowknot-like iron oxides were constructed by three-dimensional self-assembly of nanorods with porous nanostructures. The effect of experimental parameters including polymer concentration, reaction temperature, reaction time and heat treatment atmosphere were studied. Bowknot-like α-Fe{sub 2}O{sub 3}, Fe{sub 3}O{sub 4} and γ-Fe{sub 2}O{sub 3} superstructures were obtained by the thermal transformation of the oxalate precursor under the various atmosphere. These porous iron oxide superstructures exhibited ferromagnetic property at room temperature. Adsorption of Congo red (CR) onto the as-prepared samples from aqueous solutions was investigated and discussed. The results indicated that pseudo-second-order kinetic equation model can better describe the adsorption kinetics of CR onto α-Fe{sub 2}O{sub 3} and γ-Fe{sub 2}O{sub 3}, and Lagergren-first-order kinetic model is better fitted for the adsorption of CR onto Fe{sub 3}O{sub 4}. The hierarchically α-Fe{sub 2}O{sub 3} bowknots showed better adsorption ability for CR than Fe{sub 3}O{sub 4} and γ-Fe{sub 2}O{sub 3} superstructure.

Identification of ε-Fe{sub 2}O{sub 3} nano-phase in borate glasses doped with Fe and Gd

Energy Technology Data Exchange (ETDEWEB)

Ivanova, O.S.; Ivantsov, R.D. [L.V. Kirensky Institute of Physics, Siberian Branch of RAS, 660036 Krasnoyarsk (Russian Federation); Edelman, I.S., E-mail: ise@iph.krasn.ru [L.V. Kirensky Institute of Physics, Siberian Branch of RAS, 660036 Krasnoyarsk (Russian Federation); Petrakovskaja, E.A. [L.V. Kirensky Institute of Physics, Siberian Branch of RAS, 660036 Krasnoyarsk (Russian Federation); Velikanov, D.A. [L.V. Kirensky Institute of Physics, Siberian Branch of RAS, 660036 Krasnoyarsk (Russian Federation); Siberian Federal University, 660036 Krasnoyarsk (Russian Federation); Zubavichus, Y.V. [NRC “Kurchatov Institute”, 123182 Moscow (Russian Federation); Zaikovskii, V.I. [Boreskov Institute of Catalysis, Siberian Branch of RAS, 630090 Novosibirsk (Russian Federation); Novosibirsk State University, 630090 Novosibirsk (Russian Federation); Stepanov, S.A. [Vavilov State Optical Institute, All-Russia Research Center, 192371 Petersburg (Russian Federation)

2016-03-01

A new type of magnetic nanoparticles was revealed in borate glasses co-doped with low contents of iron and gadolinium. Structure and magnetic properties of the particles differ essentially from that of the α-Fe{sub 2}O{sub 3}, γ-Fe{sub 2}O{sub 3}, or Fe{sub 3}O{sub 4} nanoparticles which were detected earlier in similar glass matrices. Transmission electron microscopy including STEM-HAADF and EDX, synchrotron radiation-based XRD, static magnetic measurements, magnetic circular dichroism, and electron magnetic resonance studies allow referring the nanoparticles to the iron oxide phase-ε-Fe{sub 2}O{sub 3}. Analysis of the data set has shown that it is Gd atoms that govern the process of nanoparticles’ nucleation and its incorporation into the particles in different proportions can be used to adjust their magnetic and magneto-optical characteristics. - Highlights: • Alumina-potassium-borate glasses co-doped with Fe and Gd are studied. • Magnetic nanoparticles with structure close to ε-Fe{sub 2}O{sub 3} are shown to arise in glasses • Magnetic hysteresis loops and EMR evidence on the ferromagnetic and paramagnetic nano-phases coexistence. • Magnetic circular dichroism for ε-Fe{sub 2}O{sub 3} is studied for the first time.

Synthesis of highly efficient α-Fe{sub 2}O{sub 3} catalysts for CO oxidation derived from MIL-100(Fe)

Energy Technology Data Exchange (ETDEWEB)

Cui, Lifeng; Zhao, Di; Yang, Yang [Environment and Low-Carbon Research Center, School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093 (China); Wang, Yuxin [Institute of Applied Biotechnology, Taizhou Vocation & Technical College, Taizhou, Zhejiang 318000 (China); Zhang, Xiaodong, E-mail: fatzhxd@126.com [Environment and Low-Carbon Research Center, School of Environment and Architecture, University of Shanghai for Science and Technology, Shanghai 200093 (China)

2017-03-15

Mesoporous hollow α-Fe{sub 2}O{sub 3} bricks were synthesized via a hydrothermal method to create a precursor MIL-100(Fe) and a subsequent calcination process was applied to prepare the Fe{sub 2}O{sub 3} phase. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) results showed the morphology of hollow α-Fe{sub 2}O{sub 3} bricks which inherited from the MIL-100(Fe) template. The catalytic activities of hollow α-Fe{sub 2}O{sub 3} bricks for CO oxidation are studied in this work. Due to better low temperature reduction behavior, mesoporous hollow α-Fe{sub 2}O{sub 3} bricks obtained at calcination temperature of 430 °C displayed high catalytic activity and excellent stability with a complete CO conversion temperature (T{sub 100}) of 255 °C. - Graphical abstract: Synthesis of highly efficient α-Fe{sub 2}O{sub 3} catalysts for CO oxidation derived from MIL-100(Fe). - Highlights: • α-Fe{sub 2}O{sub 3} is prepared by the thermolysis of a MIL-100(Fe) template. • The morphology of hollow α-Fe{sub 2}O{sub 3} bricks is inherited from MIL-100(Fe) template. • α-Fe{sub 2}O{sub 3} obtained at calcined temperature of 430 °C displays high activity • Enhanced activity is attributed to crystal plane and reduction behavior.

Magnetization measurements and XMCD studies on ion irradiated iron oxide and core-shell iron/iron-oxide nanomaterials

Energy Technology Data Exchange (ETDEWEB)

Kaur, Maninder; Qiang, You; Jiang, Weilin; Pearce, Carolyn; McCloy, John S.

2014-12-02

Magnetite (Fe3O4) and core-shell iron/iron-oxide (Fe/Fe3O4) nanomaterials prepared by a cluster deposition system were irradiated with 5.5 MeV Si2+ ions and the structures determined by x-ray diffraction as consisting of 100% magnetite and 36/64 wt% Fe/FeO, respectively. However, x-ray magnetic circular dichroism (XMCD) indicates similar surfaces in the two samples, slightly oxidized and so having more Fe3+ than the expected magnetite structure, with XMCD intensity much lower for the irradiated core-shell samples indicating weaker magnetism. X-ray absorption spectroscopy (XAS) data lack the signature for FeO, but the irradiated core-shell system consists of Fe-cores with ~13 nm of separating oxide crystallite, so it is likely that FeO exists deeper than the probe depth of the XAS (~5 nm). Exchange bias (Hex) for both samples becomes increasingly negative as temperature is lowered, but the irradiated Fe3O4 sample shows greater sensitivity of cooling field on Hex. Loop asymmetries and Hex sensitivities of the irradiated Fe3O4 sample are due to interfaces and interactions between grains which were not present in samples before irradiation as well as surface oxidation. Asymmetries in the hysteresis curves of the irradiated core/shell sample are related to the reversal mechanism of the antiferromagnetic FeO and possibly some near surface oxidation.

Fabrication, characterization, and photocatalytic property of α-Fe2O3/graphene oxide composite

International Nuclear Information System (INIS)

Li Hong; Zhao Qidong; Li Xinyong; Zhu Zhengru; Tade, Moses; Liu Shaomin

2013-01-01

Spindle-shaped microstructure of α-Fe 2 O 3 was successfully synthesized by a simple hydrothermal method. The α-Fe 2 O 3 /graphene oxide (GO) composites was prepared using a modified Hummers’ strategy. The properties of the samples were systematically investigated by X-ray powder diffraction (XRD), UV–Vis diffuse reflectance spectrophotometer, transmission electron microscope, atomic force microscope, X-ray photoelectron spectroscopy, and Raman spectroscopy (Raman) techniques. GO nanosheets act as supporting materials for anchoring the α-Fe 2 O 3 particles. The average crystallite sizes of the α-Fe 2 O 3 and α-Fe 2 O 3 /GO samples are ca. 27 and 24 nm, respectively. The possible growth of α-Fe 2 O 3 onto GO layers led to a higher absorbance capacity for visible light by α-Fe 2 O 3 /GO than α-Fe 2 O 3 composite. The photocatalytic degradation of toluene over the α-Fe 2 O 3 and α-Fe 2 O 3 /GO samples under xenon-lamp irradiation was comparatively studied by in situ FTIR technique. The results indicate that the α-Fe 2 O 3 /GO sample synthesized exhibited a higher capacity for the degradation of toluene. The composite of α-Fe 2 O 3 /GO could be promisingly applied in photo-driven air purification.

Fabrication, characterization, and photocatalytic property of α-Fe2O3/graphene oxide composite

Science.gov (United States)

Li, Hong; Zhao, Qidong; Li, Xinyong; Zhu, Zhengru; Tade, Moses; Liu, Shaomin

2013-06-01

Spindle-shaped microstructure of α-Fe2O3 was successfully synthesized by a simple hydrothermal method. The α-Fe2O3/graphene oxide (GO) composites was prepared using a modified Hummers' strategy. The properties of the samples were systematically investigated by X-ray powder diffraction (XRD), UV-Vis diffuse reflectance spectrophotometer, transmission electron microscope, atomic force microscope, X-ray photoelectron spectroscopy, and Raman spectroscopy (Raman) techniques. GO nanosheets act as supporting materials for anchoring the α-Fe2O3 particles. The average crystallite sizes of the α-Fe2O3 and α-Fe2O3/GO samples are ca. 27 and 24 nm, respectively. The possible growth of α-Fe2O3 onto GO layers led to a higher absorbance capacity for visible light by α-Fe2O3/GO than α-Fe2O3 composite. The photocatalytic degradation of toluene over the α-Fe2O3 and α-Fe2O3/GO samples under xenon-lamp irradiation was comparatively studied by in situ FTIR technique. The results indicate that the α-Fe2O3/GO sample synthesized exhibited a higher capacity for the degradation of toluene. The composite of α-Fe2O3/GO could be promisingly applied in photo-driven air purification.

A novel hydrothermal approach for synthesizing α-Fe2O3, γ-Fe2O3 and Fe3O4 mesoporous magnetic nanoparticles

International Nuclear Information System (INIS)

Jayanthi, S. Amala; Nathan, D. Muthu Gnana Theresa; Jayashainy, J.; Sagayaraj, P.

2015-01-01

A novel method to synthesize the three phases of iron oxide nanoparticles (hematite, maghemite and magnetite) using the same non-toxic inorganic precursors via a water–organic interface under the low temperature hydrothermal conditions is reported. The synthesized particles are characterized by Powder X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM) and Transmission Electron Microscopy (TEM). The Brunauer–Emmett–Teller (BET) results reveal the mesoporous nature of the particles. The magnetic properties of the nanoparticles are studied by Vibrating Sample Magnetometer (VSM) at various low temperatures and also at room temperature. The XRD peaks corresponding to each sample clearly depict the presence of the respective phase of the as-prepared magnetic nanoparticles. The nanoparticles of maghemite and magnetite have saturation magnetization of 58.56 and 40.30 emu/g respectively at room temperature, whereas the particles of hematite possess very low saturation magnetization value of 1.89 emu/g. Further, the magnetization is studied at four different temperatures and the zero field cooled (ZFC) and field cooled (FC) magnetization are reported. - Graphical abstract: Display Omitted - Highlights: • Hematite, maghemite and magnetite are obtained under hydrothermal synthesis. • α-Fe 2 O 3 , γ-Fe 2 O 3 and Fe 3 O 4 prepared are mesoporous and nearly monodisperse. • Near superparamagnetism is observed at room temperature for maghemite and magnetite

High pressure Moessbauer spectroscopy of perovskite iron oxide

International Nuclear Information System (INIS)

Nasu, Saburo; Suenaga, Tomoya; Morimoto, Shotaro; Kawakami, Takateru; Kuzushita, Kaori; Takano, Mikio

2003-01-01

High-pressure 57 Fe Moessbauer spectroscopy using a diamond anvil cell has been performed for perovskite iron oxides SrFeO 3 , CaFeO 3 and La 1/3 Sr 2/3 O 3 . The charge states and the magnetic dependency to pressure were determined. Pressure magnetic phase diagrams of these perovskite iron oxides are determined up to about 70 GPa. To be clear the magnetic ordered state, they are measured up to 7.8 T external magnetic fields at 4.5K. The phase transition of these perovskite oxides to ferromagnetisms with high magnetic ordered temperature is observed. In higher pressure, high spin-low spin transition of oxides besides CaFeO 3 is generated. The feature of Moessbauer spectroscopy, perovskite iron oxide and Moessbauer spectroscopy under high pressure are explained. (S.Y.)

Preparation of three-dimensionally ordered macroporous perovskite-type lanthanum-iron-oxide LaFeO3 with tunable pore diameters: High porosity and photonic property

International Nuclear Information System (INIS)

Sadakane, Masahiro; Horiuchi, Toshitaka; Kato, Nobuyasu; Sasaki, Keisuke; Ueda, Wataru

2010-01-01

Three-dimensionally ordered macroporous (3DOM) lanthanum-iron-oxide (LaFeO 3 ) with different pore diameters was prepared using a colloidal crystal of polymer spheres with different diameters as templates. Ethylene glycol-methanol mixed solution of metal nitrates was infiltrated into the void of the colloidal crystal template of a monodispersed poly(methyl methacrylate) (PMMA) sphere. Heating of this PMMA-metal salt-ethylene glycol composite produced the desired well-ordered 3DOM LaFeO 3 with a high pore fraction, which was confirmed by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), mercury (Hg) porosimetry, and ultraviolet-visible (UV-vis) diffuse reflectance spectra. 3DOM LaFeO 3 with pore diameters of 281 and 321 nm shows opalescent colors because of photonic stop band properties. Catalytic activity of the 3DOM LaFeO 3 for combustion of carbon particles was enhanced by a potassium cation, which was involved from K 2 S 2 O 8 used as a polymerization initiator. - Graphical abstract: Well-ordered three-dimensionally ordered macroporous LaFeO 3 materials with pore sizes ranging from 127 to 321 nm were obtained in a high pore fraction.

2, 3-dimercaptosuccinic acid-modified iron oxide clusters for magnetic resonance imaging.

Science.gov (United States)

Xiong, Fei; Yan, Caiyun; Tian, Jilai; Geng, Kunkun; Zhu, Ziyi; Song, Lina; Zhang, Yu; Mulvale, Matthew; Gu, Ning

2014-12-01

Over the last decade, various magnetic nanomaterials have been developed as magnetic resonance imaging (MRI) contrast agents; the greatest challenges encountered for clinical application have been insufficient stability. In this paper, a lyophilization method for 2, 3-dimercaptosuccinic acid-modified iron oxide (γ-Fe2 O3 @DMSA) nanoparticles was developed to simultaneously overcome two disadvantages; these include insufficient stability and low-magnetic response. After lyophilization, the clusters of γ-Fe2 O3 @DMSA with the size of 156.7 ± 15.3 nm were formed, and the stability of the lyophilized powder (γ-Fe2 O3 @DMSA-LP) increased up to over 3 years. It was also found that rehydrated γ-Fe2 O3 @DMSA-LP could be ingested by RAW264.7 cells in very large quantities. Results of pharmacokinetics and biodistribution studies in vivo indicated that γ-Fe2 O3 @DMSA-LP is a promising liver-targeted material. Furthermore, it also exhibited higher MRI efficiency and longer imaging time in the liver than the well-known product Feridex(®) . Moreover, results of vascular irritation and long-term toxicity experiments demonstrated γ-Fe2 O3 @DMSA-LP could be a nontoxic, biocompatible contrast agent in vivo. Therefore, the proposed γ-Fe2 O3 @DMSA-LP can be used as a potential MRI contrast agent in clinic for hepatic diseases. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

Low levels of iron enhance UV/H2O2 efficiency at neutral pH.

Science.gov (United States)

Ulliman, Sydney L; McKay, Garrett; Rosario-Ortiz, Fernando L; Linden, Karl G

2018-03-01

While the presence of iron is generally not seen as favorable for UV-based treatment systems due to lamp fouling and decreased UV transmittance, we show that low levels of iron can lead to improvements in the abatement of chemicals in the UV-hydrogen peroxide advanced oxidation process. The oxidation potential of an iron-assisted UV/H 2 O 2 (UV 254  + H 2 O 2  + iron) process was evaluated at neutral pH using iron levels below USEPA secondary drinking water standards (UV/H 2 O 2 systems. The effects of iron species (Fe 2+ and Fe 3+ ), iron concentration (0-0.3 mg/L), H 2 O 2 concentration (0-10 mg/L) and background water matrix (low-carbon tap (LCT) and well water) on HO production and compound removal were examined. Iron-assisted UV/H 2 O 2 efficiency was most influenced by the target chemical and the water matrix. Added iron to UV/H 2 O 2 was shown to increase the steady-state HO concentration by approximately 25% in all well water scenarios. While CBZ removal was unchanged by iron addition, 0.3 mg/L iron improved NDMA removal rates in both LCT and well water matrices by 15.1% and 4.6% respectively. Furthermore, the combination of UV/Fe without H 2 O 2 was also shown to enhance NDMA removal when compared to UV photolysis alone indicating the presence of degradation pathways other than HO oxidation. Copyright © 2017 Elsevier Ltd. All rights reserved.

Altering the structure and properties of iron oxide nanoparticles and graphene oxide/iron oxide composites by urea

Energy Technology Data Exchange (ETDEWEB)

Naghdi, Samira [Physics department, Bu-Ali Sina University, 65174 Hamedan (Iran, Islamic Republic of); Department of Mechanical Engineering, College of Engineering, Kyung Hee University, 446-701 Yongin (Korea, Republic of); Rhee, Kyong Yop, E-mail: rheeky@khu.ac.kr [Department of Mechanical Engineering, College of Engineering, Kyung Hee University, 446-701 Yongin (Korea, Republic of); Jaleh, Babak [Physics department, Bu-Ali Sina University, 65174 Hamedan (Iran, Islamic Republic of); Park, Soo Jin [Chemistry, Colloge of Natural Science, Inha University, 402-751 Incheon (Korea, Republic of)

2016-02-28

Graphical abstract: - Highlights: • Iron oxide (Fe{sub 2}O{sub 3}) nanoparticles were directly grown on graphene oxide (GO) using a facile microwave assistant method. • The effect of urea concentration on Fe{sub 2}O{sub 3} nanoparticles and GO/Fe{sub 2}O{sub 3} composite was examined. • Increasing urea concentration altered the morphology and decreased the particle size. • The increased concentration of urea induced a larger surface area with more active sites in the Fe{sub 2}O{sub 3} nanoparticles. • The increase in urea concentration led to decreased thermal stability of the Fe{sub 2}O{sub 3} nanoparticles. - Abstract: Iron oxide (Fe{sub 2}O{sub 3}) nanoparticles were grown on graphene oxide (GO) using a simple microwave-assisted method. The effects of urea concentration on Fe{sub 2}O{sub 3} nanoparticles and GO/Fe{sub 2}O{sub 3} composite were examined. The as-prepared samples were characterized using X-ray powder diffraction, Raman spectroscopy, and transmission electron microscopy. The Fe{sub 2}O{sub 3} nanoparticles were uniformly developed on GO sheets. The results showed that urea affects both Fe{sub 2}O{sub 3} morphology and particle size. In the absence of urea, the Fe{sub 2}O{sub 3} nanostructures exhibited a rod-like morphology. However, increasing urea concentration altered the morphology and decreased the particle size. The Raman results of GO/Fe{sub 2}O{sub 3} showed that the intensity ratio of D band to G band (I{sub D}/I{sub G}) was decreased by addition of urea, indicating that urea can preserve the GO sheets during synthesis of the composite from exposing more defects. The surface area and thermal stability of GO/Fe{sub 2}O{sub 3} and Fe{sub 2}O{sub 3} were compared using the Brunauer–Emmett–Teller method and thermal gravimetric analysis, respectively. The results showed that the increased concentration of urea induced a larger surface area with more active sites in the Fe{sub 2}O{sub 3} nanoparticles. However, the increase in urea

The Partial Molar Volume and Thermal Expansivity of Fe2O3 in Alkali Silicate Liquids: Evidence for the Average Coordination of Fe3+

Science.gov (United States)

Liu, Q.; Lange, R.

2003-12-01

was obtained in a fit to a linear volume equation in which the other oxide components have the following fitted partial molar volumes (cm3/mol) at 1100° C: SiO2 = 26.85+/-0.04, Na2O = 26.57+/-0.07, K2O = 42.34+/-0.10, and FeO = 12.84+/-0.28, and the following fitted fitted partial molar thermal expansivities (10-3 cm3/mol-K): Na2O = 7.73+/-0.12, K2O = 11.99+/-0.24, and FeO = 2.88+/-1.22. For the three sodic liquids not included in this regression, the most iron-rich (18.2 mol% Fe2O3) has a value for VFe2O3 of 44.1 cm3/mole, whereas the most iron-poor (4.4 mol% Fe2O3) has a value for VFe2O3 of 37.0 cm3/mole. This trend may reflect a greater proportion of four-fold ferric iron in iron-rich liquids, which mirrors the trend of increasing ferric-ferrous ratios in sodic liquids as a function of total iron content (Lange and Carmichael, 1989). The most polymerized liquid in our data set was a sodic liquid that has a value for VFe2O3 of 45.0 cm3/mole. It thus appears that most (13 of 16) of our experimental liquids, which span a wide compositional range, lead to a VFe2O3 (41.6 cm3/mol) which is constant with composition and temperature. However, there are three important outliers that may have implications for the appropriate value to apply to magmatic liquids.

When Density Functional Approximations Meet Iron Oxides.

Science.gov (United States)

Meng, Yu; Liu, Xing-Wu; Huo, Chun-Fang; Guo, Wen-Ping; Cao, Dong-Bo; Peng, Qing; Dearden, Albert; Gonze, Xavier; Yang, Yong; Wang, Jianguo; Jiao, Haijun; Li, Yongwang; Wen, Xiao-Dong

2016-10-11

Three density functional approximations (DFAs), PBE, PBE+U, and Heyd-Scuseria-Ernzerhof screened hybrid functional (HSE), were employed to investigate the geometric, electronic, magnetic, and thermodynamic properties of four iron oxides, namely, α-FeOOH, α-Fe 2 O 3 , Fe 3 O 4 , and FeO. Comparing our calculated results with available experimental data, we found that HSE (a = 0.15) (containing 15% "screened" Hartree-Fock exchange) can provide reliable values of lattice constants, Fe magnetic moments, band gaps, and formation energies of all four iron oxides, while standard HSE (a = 0.25) seriously overestimates the band gaps and formation energies. For PBE+U, a suitable U value can give quite good results for the electronic properties of each iron oxide, but it is challenging to accurately get other properties of the four iron oxides using the same U value. Subsequently, we calculated the Gibbs free energies of transformation reactions among iron oxides using the HSE (a = 0.15) functional and plotted the equilibrium phase diagrams of the iron oxide system under various conditions, which provide reliable theoretical insight into the phase transformations of iron oxides.

Density functional study on the heterogeneous oxidation of NO over α-Fe_2O_3 catalyst by H_2O_2: Effect of oxygen vacancy

International Nuclear Information System (INIS)

Song, Zijian; Wang, Ben; Yu, Jie; Ma, Chuan; Zhou, Changsong; Chen, Tao; Yan, Qianqian; Wang, Ke; Sun, Lushi

2017-01-01

Highlights: • NO and H_2O_2 adsorption on perfect and oxygen defect α-Fe_2O_3 (0 0 1) surface were studied by DFT calculations. • H_2O_2 shows high chemical reactivity for its adsorption on oxygen defect α-Fe_2O_3 (0 0 1) surface. • Oxygen vacancy plays an important role of the catalytic oxidation of NO by H_2O_2 over the α-Fe_2O_3 catalyst surfaces. • Mechanism of NO oxidation over α-Fe_2O_3 (0 0 1) surface by H_2O_2 was explained. - Abstract: Catalytic oxidation with H_2O_2 is a promising method for NOx emission control in coal-fired power plants. Hematite-based catalysts are attracting increased attention because of their surface redox reactivity. To elucidate the NO oxidation mechanism on α-Fe_2O_3 surfaces, density functional theory (DFT) calculations were conducted by investigating the adsorption characteristics of nitric oxide (NO) and hydrogen peroxide (H_2O_2) on perfect and oxygen defect α-Fe_2O_3 (0 0 1) surfaces. Results show that NO was molecularly adsorbed on two kinds of surfaces. H_2O_2 adsorption on perfect surface was also in a molecular form; however, H_2O_2 dissociation occurred on oxygen defect α-Fe_2O_3 (0 0 1) surface. The adsorption intensities of the two gas molecules in perfect α-Fe_2O_3 (0 0 1) surface followed the order NO > H_2O_2, and the opposite was true for the oxygen defect α-Fe_2O_3 (0 0 1). Oxygen vacancy remarkably enhanced the adsorption intensities of NO and H_2O_2 and promoted H_2O_2 decomposition on catalyst surface. As an oxidative product of NO, HNO_2 was synthesized when NO and H_2O_2 co-adsorbed on the oxygen defect α-Fe_2O_3 (0 0 1) surface. Analyses of Mulliken population, electron density difference, and partial density of states showed that H_2O_2 decomposition followed the Haber–Weiss mechanism. The trends of equilibrium constants suggested that NO adsorption on α-Fe_2O_3 (0 0 1) surface was more favorable at low than at high temperatures, whereas H_2O_2 adsorption was favorable between 375 and

Catalytic Oxidation of Propene over Pd Catalysts Supported on CeO2, TiO2, Al2O3 and M/Al2O3 Oxides (M = Ce, Ti, Fe, Mn

Directory of Open Access Journals (Sweden)

Sonia Gil

2015-04-01

Full Text Available In the following work, the catalytic behavior of Pd catalysts prepared using different oxides as support (Al2O3, CeO2 and TiO2 in the catalytic combustion of propene, in low concentration in excess of oxygen, to mimic the conditions of catalytic decomposition of a volatile organic compound of hydrocarbon-type is reported. In addition, the influence of different promoters (Ce, Ti, Fe and Mn when added to a Pd/Al2O3 catalyst was analyzed. Catalysts were prepared by the impregnation method and were characterized by ICP-OES, N2 adsorption, temperature-programmed reduction, temperature-programmed oxidation, X-ray diffraction, X-ray photoelectron spectroscopy and transmission electron microscopy. Catalyst prepared using CeO2 as the support was less easily reducible, due to the stabilization effect of CeO2 over the palladium oxides. Small PdO particles and, therefore, high Pd dispersion were observed for all of the catalysts, as confirmed by XRD and TEM. The addition of Ce to the Pd/Al2O3 catalysts increased the metal-support interaction and the formation of highly-dispersed Pd species. The addition of Ce and Fe improved the catalytic behavior of the Pd/Al2O3 catalyst; however, the addition of Mn and Ti decreased the catalytic activity in the propene oxidation. Pd/TiO2 showed the highest catalytic activity, probably due to the high capacity of this catalyst to reoxidize Pd into PdO, as has been found in the temperature-programmed oxidation (TPO experiments.

Redox process catalysed by growing crystal-strengite, FePO4,2H2O, crystallizing from solution with iron(II) and hydroxylamine

Science.gov (United States)

Lundager Madsen, Hans Erik

2014-09-01

In an attempt to grow pure crystals of the iron(II) phosphate vivianite, Fe3(PO4)2,8H2O, from a solution of Mohr's salt, Fe(NH4)2(SO4)2,6H2O, added to a solution of ammonium phosphate, hydroxylammonium chloride, NH3OHCl, was added to the iron(II) stock solution to eliminate oxidation of iron(II) by oxygen from the air. However, the effect turned out to be the opposite of the expected: whereas hydroxylamine reduces iron(III) in bulk solution, it acted as a strong oxidant in the presence of growing iron phosphate crystals, causing the crystallization of the iron(III) phosphate strengite, FePO4,2H2O, as the only solid phase. Evidently the crystal surface catalyses oxidation of iron(II) by hydroxylamine. The usual composite kinetics of spiral growth and surface nucleation was found. The surface-nucleation part yielded edge free energy λ in the range 12-45 pJ/m, virtually independent of temperature and in the range typical for phosphates of divalent metals. The scatter of values for λ presumably arises from contributions from different crystal forms to the overall growth rate. The low mean value points to strong adsorption of iron(II), which is subsequently oxidized at the crystal surface, forming strengite. The state of the system did not tend to thermodynamic equilibrium, but to a metastable state, presumably controlled by the iron(II) rich surface layer of the crystal. In addition to crystal growth, it was possible to measure nucleation kinetics by light scattering (turbidimetry). A point of transition from heterogeneous to homogeneous nucleation was found, and from the results for the homogeneous domain a rather precise value of crystal surface free energy γ=55 mJ/m2 was found. This is a relatively low value as well, indicating that the redox process plays a role already at the nucleation stage.

Preparation, characterization and catalytic behavior of hierachically porous CuO/α-Fe2O3/SiO2 composite material for CO and o-DCB oxidation

Institute of Scientific and Technical Information of China (English)

Xiaodong Ma; Xi Feng; Xuan He; Hongwen Guo; Lu Lü

2011-01-01

Hierachically porous (HP) CuO/α-Fe2O3/SiO2 composite material was fabricated by sol-gel method and multi-hydrothermal processes using HP-SiO2 as support.The resulting material was characterized by N2 adsorption-desorption,X-ray diffraction and scanning electron microscopy.The as-prepared CuO/Fe2O3/HP-SiO2 sample,with α-Fe2O3 and CuO nanocrystals,possessed a co-continuous skeleton,through-macroporous and mesoporous structure.Its catalytic behavior for CO and o-DCB oxidation was investigated.The result showed that CuO/Fe2O3/HP-SiO2 catalyst exhibited high catalytic activity for both CO and o-DCB oxidation,indicating its potential application in combined abatement of CO and chlorinated volatile organic compounds.

The Role of Fe2O3 Species in Depressing the Formation of N2O in the Selective Reduction of NO by NH3 over V2O5/TiO2-Based Catalysts

Directory of Open Access Journals (Sweden)

Moon Hyeon Kim

2018-03-01

Full Text Available Promotion of 2.73% Fe2O3 in an in-house-made V2O5-WO3/TiO2 (VWT and a commercial V2O5-WO3/TiO2 (c-VWT has been investigated as a cost effective approach to the suppression of N2O formation in the selective catalytic reduction of NO by NH3 (NH3-SCR. The promoted VWT and c-VWT catalysts all gave a significantly decreased N2O production at temperatures >400 °C compared to the unpromoted samples. However, such a promotion led to the loss in high temperature NO conversion, mainly due to the oxidation of NH3 to N-containing gases, particularly NO. Characterization of the unpromoted and promoted catalysts using X-ray diffraction (XRD, NH3 adsorption-desorption, and Raman spectroscopy techniques could explain the reason why the promotion showed much lower N2O formation levels at high temperatures. The addition of Fe2O3 to c-VWT resulted in redispersion of the V2O5 species, although this was not visible for 2.73% Fe2O3/VWT. The iron oxides exist as a highly-dispersed noncrystalline α-Fe2O3 in the promoted catalysts. These Raman spectra had a new Raman signal that could be tentatively assigned to Fe2O3-induced tetrahedrally coordinated polymeric vanadates and/or surface V-O-Fe species with significant electronic interactions between the both metal oxides. Calculations of the monolayer coverage of each metal oxide and the surface total coverage are reasonably consistent with Raman measurements. The proposed vanadia-based surface polymeric entities may play a key role for the substantial reduction of N2O formed at high temperatures by NH3 species adsorbed strongly on the promoted catalysts. This reaction is a main pathway to greatly suppress the extent of N2O formation in NH3-SCR reaction over the promoted catalysts.

Enhanced magnetic properties of Fe soft magnetic composites by surface oxidation

Energy Technology Data Exchange (ETDEWEB)

Zhao, Guoliang; Wu, Chen, E-mail: chen_wu@zju.edu.cn; Yan, Mi, E-mail: mse_yanmi@zju.edu.cn

2016-02-01

Fe soft magnetic composites (SMCs) with low core loss were fabricated via surface oxidation of the Fe powders by H{sub 2}O and O{sub 2} at elevated temperatures. Surface oxidation prevents magnetic dilution due to the formation of the ferromagnetic iron oxide coating layer, giving rise to high magnetic flux density and effective permeability of the SMCs compared with those fabricated with traditional phosphate coating. Mechanism of the oxidation process has been investigated where Fe{sub 3}O{sub 4} forms by reactions of Fe with H{sub 2}O and O{sub 2}. The Fe{sub 3}O{sub 4} coating layer tends to convert into γ-Fe{sub 2}O{sub 3} with increased oxidation temperature and time. By controlling composition of the coating layer, low core loss of 688.9 mW/cm{sup 3} (measured at 50 mT and 100 kHz) and higher effective permeability of 88.3 can be achieved for the Fe SMCs. - Highlights: • Surface oxidation as a new method to fabricate Fe Soft magnetic composite (SMCs). • Oxidation mechanism revealed where Fe reacts with H2O and O2 at high temperatures. • Evolution of the iron oxide coating with growth temperature and time investigated. • The iron oxide insulation coating results in improved magnetic performance.

Synthesis, structure and magnetic properties of a new iron phosphonate-oxalate with 3D framework: [Fe(O3PCH3)(C2O4)0.5(H2O)

International Nuclear Information System (INIS)

Zhang Yangyang; Qi Yue; Zhang Ying; Liu Ziyu; Zhao Yinfeng; Liu Zhongmin

2007-01-01

A new iron phosphonate-oxalate [Fe(O 3 PCH 3 )(C 2 O 4 ) 0.5 (H 2 O)] (1), has been synthesized under hydrothermal condition. The single-crystal X-ray diffraction studies reveal that 1 consists of layers of vertex-linked FeO 6 octahedra and O 3 PC tetrahedra, which are further connected by bis-chelate oxalate bridges, giving to a 3D structure with 10-membered channels. Crystal data: monoclinic, P2 1 /n (no. 14), a=4.851(2)A, b=16.803(7)A, c=7.941(4)A, β=107.516(6) o , V=617.2(5)A 3 , Z=4, R 1 =0.0337 and wR 2 =0.0874 for 1251 reflections [I>2σ(I)]. Mossbauer spectroscopy measurement confirms the existence of high-spin Fe(III) in 1. Magnetic studies show that 1 exhibits weak ferromagnetism with T N =30K due to a weak spin canting

Thermal decomposition of barium ferrate(VI): Mechanism and formation of FeIV intermediate and nanocrystalline Fe2O3 and ferrite

International Nuclear Information System (INIS)

Machala, Libor; Sharma, Virender K.; Kuzmann, Ernö; Homonnay, Zoltán; Filip, Jan; Kralchevska, Radina P.

2016-01-01

Simple high-valent iron-oxo species, ferrate(VI) (Fe VI O 4 2− , Fe(VI)) has applications in energy storage, organic synthesis, and water purification. Of the various salts of Fe(VI), barium ferrate(VI) (BaFeO 4 ) has also a great potential as a battery material. This paper presents the thermal decomposition of BaFeO 4 in static air and nitrogen atmosphere, monitored by combination of thermal analysis, Mössbauer spectroscopy, X-ray powder diffraction, and electron-microscopic techniques. The formation of Fe IV species in the form of BaFeO 3 was found to be the primary decomposition product of BaFeO 4 at temperature around 190 °C under both studied atmospheres. BaFeO 3 was unstable in air reacting with CO 2 to form barium carbonate and speromagnetic amorphous iron(III) oxide nanoparticles (<5 nm). Above 600 °C, a solid state reaction between BaCO 3 and Fe 2 O 3 occurred, leading to the formation of barium ferrite nanoparticles, BaFe 2 O 4 (20–100 nm). - Highlights: • We explained the mechanism of thermal decomposition of barium ferrate(VI). • We confirmed the formation of Fe(IV) intermediate phase during the decomposition. • The mechanism of the decomposition is influenced by a presence of carbon dioxide.

Facile synthesis of iron oxides/reduced graphene oxide composites: application for electromagnetic wave absorption at high temperature

OpenAIRE

Lili Zhang; Xinxin Yu; Hongrui Hu; Yang Li; Mingzai Wu; Zhongzhu Wang; Guang Li; Zhaoqi Sun; Changle Chen

2015-01-01

Iron oxides/reduced graphene oxide composites were synthesized by facile thermochemical reactions of graphite oxide and FeSO4?7H2O. By adjusting reaction temperature, ?-Fe2O3/reduced graphene oxide and Fe3O4/reduced graphene oxide composites can be obtained conveniently. Graphene oxide and reduced graphene oxide sheets were demonstrated to regulate the phase transition from ?-Fe2O3 to Fe3O4 via ?-Fe2O3, which was reported for the first time. The hydroxyl groups attached on the graphene oxide ...

Core-Shell Nano structure of a-Fe2O3/Fe3O4: Synthesis and Photo catalysis for Methyl Orange

International Nuclear Information System (INIS)

Tian, Y.; Wu, D.; Yu, B.; Jia, X.; Zhan, S.

2011-01-01

Fe 3 O 4 nanoparticle was synthesized in the solution involving water and ethanol. Then, a-Fe 2 O 3 shell was produced in situ on the surface of the Fe 3 O 4 nanoparticle by surface oxidation in molten salts, forming α-Fe 2 O 3 /Fe 3 O 4 core-shell nano structure. It was showed that the magnetic properties transformed from ferromagnetism to superparamagnetism after the primary Fe 3 O 4 nanoparticles were oxidized. Furthermore, the obtained a-Fe 2 O 3 /Fe 3 O 4 core-shell nanoparticles were used to photo catalyse solution of methyl orange, and the results revealed that a-Fe 2 O 3 /Fe 3 O 4 nanoparticles were more efficient than the self-prepared α-Fe 2 O 3 nanoparticles. At the same time, the photo catalyzer was recyclable by applying an appropriate magnetic field.

Cadmium uptake by and translocation within rice (oryza sativa l.) seedlings as affected by iron plaque and Fe/sub 2/O/sub 3/

International Nuclear Information System (INIS)

Lai, Y.; Xu, B.O.; Mou, S.

2012-01-01

A hydroponics culture experiment was carried out to investigate the effect of iron plaque and/or Fe/sub 2/O/sub 3/ on Cadmium (Cd) uptake by and translocation within rice seedlings. Uniform rice seedlings grown in nutrient solution for two weeks were selected and transferred to nutrient solution containing ferrous iron (Fe/sup 2+/) (30 mg/L) for 24 h to induce the formation of iron plaque on the root surface. Then rice seedlings were exposed to different level of Cd (1.0 mg/L and 0.1 mg/L), and simultaneously Fe/sub 2/O/sub 3/ was added into hydroponic system for three days. At harvest Cd content in dithionite-citrate-bicarbonate (DCB) extracts, roots and shoots were determined. The results of this study showed that iron plaque could sequester more Cd on root surfaces of rice seedlings, however, Fe/sub 2/O/sub 3/ reduced Cd adsorbed on root surfaces. Both of iron plaque and/or Fe/sub 2/O/sub 3/ did not block Cd uptake by and translocation within rice seedlings. Although iron plaque could alleviate Cd toxicity to rice seedlings under low concentration of Cd (0.1 mg/L), the root tissue played more important role in reducing Cd translocation into shoot. And the long period experiment of hydroponic and soil culture was still needed to verify the potential effect of iron plaque and/or Fe/sub 2/O/sub 3/ on alleviating Cd toxicity to rice seedlings. (author)

Bacteria-assisted preparation of nano α-Fe{sub 2}O{sub 3} red pigment powders from waste ferrous sulfate

Energy Technology Data Exchange (ETDEWEB)

Li, Xiang; Wang, Chuankai; Zeng, Yu; Li, Panyu; Xie, Tonghui; Zhang, Yongkui, E-mail: zhangyongkui@scu.edu.cn

2016-11-05

Highlights: • A route to prepare nano α-Fe{sub 2}O{sub 3} red pigment from waste ferrous sulfate is proposed. • Acidithiobacillus ferrooxidans is introduced for accelerating iron oxidation. • The particle size of synthetic α-Fe{sub 2}O{sub 3} is ranged from 22 nm to 86 nm. • The prepared nano α-Fe{sub 2}O{sub 3} red pigment fulfills ISO 1248-2006. - Abstract: Massive ferrous sulfate with excess sulfuric acid is produced in titanium dioxide industry each year, ending up stockpiled or in landfills as solid waste, which is hazardous to environment and in urgent demand to be recycled. In this study, waste ferrous sulfate was used as a second raw material to synthesize nano α-Fe{sub 2}O{sub 3} red pigment powders with a bacteria-assisted oxidation process by Acidithiobacillus ferrooxidans. The synthesis route, mainly consisting of bio-oxidation, precipitation and calcination, was investigated by means of titration, thermogravimetric analysis (TGA), X-ray diffraction (XRD), scanning electron microscope (SEM) and X-ray fluorescence (XRF) to obtain optimum conditions. Under the optimum conditions, nano α-Fe{sub 2}O{sub 3} red pigment powders contained 98.24 wt.% of Fe{sub 2}O{sub 3} were successfully prepared, with a morphology of spheroidal and particle size ranged from 22 nm to 86 nm and averaged at 45 nm. Moreover, the resulting product fulfilled ISO 1248-2006, the standards of iron oxide pigments.

Interaction of γ-Fe2O3 nanoparticles with Citrus maxima leaves and the corresponding physiological effects via foliar application.

Science.gov (United States)

Hu, Jing; Guo, Huiyuan; Li, Junli; Wang, Yunqiang; Xiao, Lian; Xing, Baoshan

2017-07-11

Nutrient-containing nanomaterials have been developed as fertilizers to foster plant growth and agricultural yield through root applications. However, if applied through leaves, how these nanomaterials, e.g. γ-Fe 2 O 3 nanoparticles (NPs), influence the plant growth and health are largely unknown. This study is aimed to assess the effects of foliar-applied γ-Fe 2 O 3 NPs and their ionic counterparts on plant physiology of Citrus maxima and the associated mechanisms. No significant changes of chlorophyll content and root activity were observed upon the exposure of 20-100 mg/L γ-Fe 2 O 3 NPs and Fe 3+ . In C. maxima roots, no oxidative stress occurred under all Fe treatments. In the shoots, 20 and 50 mg/L γ-Fe 2 O 3 NPs did not induce oxidative stress while 100 mg/L γ-Fe 2 O 3 NPs did. Furthermore, there was a positive correlation between the dosages of γ-Fe 2 O 3 NPs and Fe 3+ and iron accumulation in shoots. However, the accumulated iron in shoots was not translocated down to roots. We observed down-regulation of ferric-chelate reductase (FRO2) gene expression exposed to γ-Fe 2 O 3 NPs and Fe 3+ treatments. The gene expression of a Fe 2+ transporter, Nramp3, was down regulated as well under γ-Fe 2 O 3 NPs exposure. Although 100 mg/L γ-Fe 2 O 3 NPs and 20-100 mg/L Fe 3+ led to higher wax content, genes associated with wax formation (WIN1) and transport (ABCG12) were downregulated or unchanged compared to the control. Our results showed that both γ-Fe 2 O 3 NPs and Fe 3+ exposure via foliar spray had an inconsequential effect on plant growth, but γ-Fe 2 O 3 NPs can reduce nutrient loss due to their the strong adsorption ability. C. maxima plants exposed to γ-Fe 2 O 3 NPs and Fe 3+ were in iron-replete status. Moreover, the biosynthesis and transport of wax is a collaborative and multigene controlled process. This study compared the various effects of γ-Fe 2 O 3 NPs, Fe 3+ and Fe chelate and exhibited the advantages of NPs as a foliar fertilizer

Structural and magnetic properties of core-shell iron-iron oxide nanoparticles

DEFF Research Database (Denmark)

Kuhn, Luise Theil; Bojesen, A.; Timmermann, L.

2002-01-01

We present studies of the structural and magnetic properties of core-shell iron-iron oxide nanoparticles. alpha-Fe nanoparticles were fabricated by sputtering and subsequently covered with a protective nanocrystalline oxide shell consisting of either maghaemite (gamma-Fe2O3) or partially oxidized...... magnetite (Fe3O4). We observed that the nanoparticles were stable against further oxidation, and Mossbauer spectroscopy at high applied magnetic fields and low temperatures revealed a stable form of partly oxidized magnetite. The nanocrystalline structure of the oxide shell results in strong canting...... of the spin structure in the oxide shell, which thereby modifies the magnetic properties of the core-shell nanoparticles....

Optical and structural properties of FeSe2 thin films obtained by selenization of sprayed amorphous iron oxide films

International Nuclear Information System (INIS)

Ouertani, B.; Ouerfelli, J.; Saadoun, M.; Zribi, M.; Rabha, M.Ben; Bessais, B.; Ezzaouia, H.

2006-01-01

We report in this work the optical and structural properties of iron diselenide films (FeSe 2 ) obtained by selenization under vacuum of amorphous iron oxide films predeposited by spray pyrolysis. The structure of the FeSe 2 films was investigated by scanning electron microscopy (SEM), microprobe analyses, atomic force microscopy (AFM) and X-ray diffraction (XRD). XRD and micro-probe analyses showed that FeSe 2 as well as FeSe 2-x phases begin to appear at a selenization temperature of 500 deg. C. As the selenization temperature rises, the iron diselenide films become more stoichiometric with a dominance of the FeSe 2 phase. At 550 deg. C, a single FeSe 2 phase having good crystallinity was obtained. At 600 deg. C, two phases were detected: the major one corresponds to Fe 3 O 4 , and the minor one to FeSe 2 . SEM surface views show that FeSe 2 films have granular structure with small spherical crystallites. However, layered and clustered FeSe 2 films were found, respectively, at 550 deg. C and 600 deg. C. Absorption measurements show that iron diselenide films have a direct and an indirect gaps of about 1.03 eV and 0.3 eV, which were suggested to be due to the stoichiometric FeSe 2 phase and to a Fe-rich non-stoichiometric phase, respectively

Chemical synthesis of Fe{sub 2}O{sub 3} thin films for supercapacitor application

Energy Technology Data Exchange (ETDEWEB)

Kulal, P.M.; Dubal, D.P.; Lokhande, C.D. [Holography and Material Research Laboratory, Department of Physics, Shivaji University, Kolhapur 416004, M.S. (India); Fulari, V.J., E-mail: vijayfulari@gmail.com [Holography and Material Research Laboratory, Department of Physics, Shivaji University, Kolhapur 416004, M.S. (India)

2011-02-03

Research highlights: > Simple chemical synthesis of Fe{sub 2}O{sub 3}. > Formation of amorphous and hydrous Fe{sub 2}O{sub 3}. > Potential candidate for supercapacitors. - Abstract: Fe{sub 2}O{sub 3} thin films have been prepared by novel chemical successive ionic layer adsorption and reaction (SILAR) method. Further these films were characterized for their structural, morphological and optical properties by means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectrum, scanning electron microscopy (SEM), wettability test and optical absorption studies. The XRD pattern showed that the Fe{sub 2}O{sub 3} films exhibit amorphous in nature. Formation of iron oxide compound was confirmed from FTIR studies. The optical absorption showed existence of direct optical band gap of energy 2.2 eV. Fe{sub 2}O{sub 3} film surface showed superhydrophilic nature with water contact angle less than 10{sup o}. The supercapacitive properties of Fe{sub 2}O{sub 3} thin film investigated in 1 M NaOH electrolyte showed supercapacitance of 178 F g{sup -1} at scan rate 5 mV/s.

High pressure Moessbauer spectroscopy of perovskite iron oxide

CERN Document Server

Nasu, S; Morimoto, S; Kawakami, T; Kuzushita, K; Takano, M

2003-01-01

High-pressure sup 5 sup 7 Fe Moessbauer spectroscopy using a diamond anvil cell has been performed for perovskite iron oxides SrFeO sub 3 , CaFeO sub 3 and La sub 1 sub / sub 3 Sr sub 2 sub / sub 3 O sub 3. The charge states and the magnetic dependency to pressure were determined. Pressure magnetic phase diagrams of these perovskite iron oxides are determined up to about 70 GPa. To be clear the magnetic ordered state, they are measured up to 7.8 T external magnetic fields at 4.5K. The phase transition of these perovskite oxides to ferromagnetisms with high magnetic ordered temperature is observed. In higher pressure, high spin-low spin transition of oxides besides CaFeO sub 3 is generated. The feature of Moessbauer spectroscopy, perovskite iron oxide and Moessbauer spectroscopy under high pressure are explained. (S.Y.)

{Fe6O2}-Based Assembly of a Tetradecanuclear Iron Nanocluster

Directory of Open Access Journals (Sweden)

Svetlana G. Baca

2011-01-01

Full Text Available The tetradecanuclear FeIII pivalate nanocluster [Fe14O10(OH4(Piv18], comprising a new type of metal oxide framework, has been solvothermally synthesized from a hexanuclear iron pivalate precursor in dichlormethane/acetonitrile solution. Magnetic measurements indicate the presence of very strong antiferromagnetic interactions in the cluster core.

Effect of Sulfur on Liquidus Temperatures in the ZnO-"FeO"-Al2O3-CaO-SiO2-S System in Equilibrium with Metallic Iron

Science.gov (United States)

Zhao, Baojun; Hayes, Peter C.; Jak, Evgueni

2011-10-01

The phase equilibria in the ZnO-"FeO"-Al2O3-CaO-SiO2-S system have been determined experimentally in equilibrium with metallic iron. A pseudoternary section of the form ZnO-"FeO"-(Al2O3+CaO+SiO2) for CaO/SiO2 = 0.71 (weight), (CaO+SiO2)/Al2O3 = 5.0 (weight), and fixed 2.0 wt pct S concentration has been constructed. It was found that the addition of 2.0 wt pct S to the liquid extends the spinel primary phase field significantly and decreases the size of the wustite primary phase field. The liquidus temperature in the wustite primary phase field is decreased by approximately 80 K and the liquidus temperature in the spinel primary phase field is decreased by approximately 10 K with addition of 2.0 wt pct S in the composition range investigated. It was also found that iron-zinc sulfides are present in some samples in the spinel primary phase field, which are matte appearing at low zinc concentrations and sphalerite (Zn,Fe)S at higher zinc concentrations. The presence of sulfur in the slag has a minor effect on the partitioning of ZnO between the wustite and liquid phases but no effect on the partitioning of ZnO between the spinel and liquid phases.

A comparative study of radiation damage in Al2O3, FeTiO3, and MgTiO3

International Nuclear Information System (INIS)

Mitchell, J.N.; Yu, Ning; Sickafus, K.E.; Nastasi, M.; Taylor, T.N.; McClellan, K.J.; Nord, G.L. Jr.

1995-01-01

Oriented single crystals of synthetic alpha-alumina (α-Al 2 O 3 ), geikielite (MgTiO 3 ) natural ilmenite (FeTiO 3 ) were irradiated with 200 keV argon ions under cryogenic conditions (100 K) to assess their damage response. Using Rutherford backscattering spectrometry combined with ion channeling techniques, it was found that ilmenite amorphized readily at doses below 5x10 14 , alumina amorphized at a dose of 1-2x 15 , and geikielite was amorphized at ∼2x10 15 Ar cm -2 . The radiation damage response of the ilmenite crystal may be complicated by the presence of hematite exsolution lamellae and the experimentally induced oxidation of iron. The relative radiation-resistance of geikielite holds promise for similar behavior in other Mg-Ti oxides

Influence of Fe{sub 3}O{sub 4} nanoparticles on pseudocapacitive behavior of the charge storage process

Energy Technology Data Exchange (ETDEWEB)

Chen, Chien-Chon [Department of Energy Engineering, National United University, Miaoli 36003, Taiwan (China); Research Center for Biomedical Devices and Prototyping Production, Taipei Medical University, Taipei 11031, Taiwan (China); Chen, Chin-Yi; Tsay, Chien-Yie; Wang, Sih-Ying [Department of Materials Science and Engineering, Feng Chia University, Taichung 40724, Taiwan (China); Lin, Chung-Kwei, E-mail: chungkwei@tmu.edu.tw [Research Center for Biomedical Devices and Prototyping Production, Taipei Medical University, Taipei 11031, Taiwan (China); School of Dental Technology, College of Oral Medicine, Taipei Medical University, Taipei 11031, Taiwan (China)

2015-10-05

Highlights: • A simple and inexpensive process formed pseudocapacitive manganese oxide electrode. • Mn(OH){sub x} decomposed into Mn{sub 3}O{sub 4} and Mn{sub 2}O{sub 3} phases and formed many small pores on the film. • The composite film with Fe{sub 3}O{sub 4} added presents small holes and large active surface. • The specific capacitance value can be enhanced by adding iron oxide. • The manganese oxide film has a specific capacitance of 209.9 F/g at 300 °C annealing. - Abstract: Nano-crystalline Fe{sub 3}O{sub 4} powders were added to form manganese oxide/iron oxide composite film electrode in order to combine the excellent capacitance characteristics of manganese oxide and iron oxide. Due to the addition of Fe{sub 3}O{sub 4}, the crack film formation increases the contact area of electrolyte and electrode and the surface and electronic conductivity of pseudo-capacitors increased. The specific capacitance value can be enhanced by adding iron oxide. The surface of the composite film with Fe{sub 3}O{sub 4} added had small holes due to the burnout of organics, and the network of nano-powders formed uniform and fine pores at 300 °C annealing. The EXAFS results to the XRD results, the peaks shift due to the formation of Mn{sub 3}O{sub 4} and Mn{sub 2}O{sub 3} between 250 and 350 °C. The best results in this study were 316.1 F/g obtained at 1 at.% of manganese oxide/iron oxide composite film electrode after 300 °C annealing. The 1 at.% manganese oxide/iron oxide composite film electrode after 1000 cycles, the highest specific capacitance value was 85.8%. The results showed that manganese oxide/iron oxide composite film electrode have good cycle stability of capacitance.

Characterisation of a tertiary mixture of {alpha}-Fe{sub 2}O{sub 3}, {gamma}-Fe{sub 2}O{sub 3} and Fe{sub 3}O{sub 4}

Energy Technology Data Exchange (ETDEWEB)

Srinivasan, M.P.; Narasimhan, S.V. [Water and Steam Chemistry Laboratory (Chemistry Group, BARC) BARC Facilities, Kalpakkam, Tamil Nadu 603 102. (India)

1998-12-31

A method has been developed to quantify the individual components of a ternary mixture containing {alpha}-Fe{sub 2}O{sub 3}, {gamma}- Fe{sub 2}O{sub 3} and Fe{sub 3}O{sub 4} based on the preferential dissolution of the components at a fixed time (fixed time - depending on the strength of the chelating agent) in a dilute chemical formulation (containing a chelant and an organic acid) both in presence and absence of reductant. A ternary component diagram was constructed based on the percentage dissolution of the individual components in 2,6-Pyridine dicarboxylic acid (PDCA), Nitrilo triacetic acid (NTA) and EDTA based formulation at 60degC both in presence and absence of reductant. In these formulations, the observed behaviour that the {alpha}-Fe{sub 2}O{sub 3} dissolved very little both in presence and absence of reductant and {gamma}-Fe{sub 2}O{sub 3} dissolved very little in absence of reductant were used for resolving the ternary physical mixture composition. Physical mixtures of Fe{sub 3}O{sub 4}, {alpha}-Fe{sub 2}O{sub 3} and {gamma}-Fe{sub 2}O{sub 3} based on mole ratio were taken such that the total quantity of Fe present would be 1.37 mM for complete dissolution. In presence and absence of reductant, dissolution percentage of Fe observed at fixed time in these formulations, when fit into the already constructed three component phase diagram for each formulation at the same fixed duration, the experimentally resolved composition showed good agreement with that based on individual components. This method is useful to resolve different polymorphs of metal oxides having the metal ions in single and/or multiple oxidation states. (author)

Hierarchical FeTiO3-TiO2 hollow spheres for efficient simulated sunlight-driven water oxidation.

Science.gov (United States)

Han, Taoran; Chen, Yajie; Tian, Guohui; Wang, Jian-Qiang; Ren, Zhiyu; Zhou, Wei; Fu, Honggang

2015-10-14

Oxygen generation is the key step for the photocatalytic overall water splitting and considered to be kinetically more challenging than hydrogen generation. Here, an effective water oxidation catalyst of hierarchical FeTiO3-TiO2 hollow spheres are prepared via a two-step sequential solvothermal processes and followed by thermal treatment. The existence of an effective heterointerface and built-in electric field in the surface space charge region in FeTiO3-TiO2 hollow spheres plays a positive role in promoting the separation of photoinduced electron-hole pairs. Surface photovoltage, transient-state photovoltage, fluorescence and electrochemical characterization are used to investigate the transfer process of photoinduced charge carriers. The photogenerated charge carriers in the hierarchical FeTiO3-TiO2 hollow spheres with a proper molar ratio display much higher separation efficiency and longer lifetime than those in the FeTiO3 alone. Moreover, it is suggested that the hierarchical porous hollow structure can contribute to the enhancement of light utilization, surface active sites and material transportation through the framework walls. This specific synergy significantly contributes to the remarkable improvement of the photocatalytic water oxidation activity of the hierarchical FeTiO3-TiO2 hollow spheres under simulated sunlight (AM1.5).

Synthesis of TiO2 nanoparticles containing Fe, Si, and V using multiple diffusion flames and catalytic oxidation capability of carbon-coated nanoparticles

KAUST Repository

Ismail, Mohamed; Memon, Nasir K.; Hedhili, Mohamed N.; Anjum, Dalaver H.; Chung, Suk-Ho

2016-01-01

Titanium dioxide (TiO2) nanoparticles containing iron, silicon, and vanadium are synthesized using multiple diffusion flames. The growth of carbon-coated (C–TiO2), carbon-coated with iron oxide (Fe/C–TiO2), silica-coated (Si–TiO2), and vanadium-doped (V–TiO2) TiO2 nanoparticles is demonstrated using a single-step process. Hydrogen, oxygen, and argon are utilized to establish the flame, with titanium tetraisopropoxide (TTIP) as the precursor for TiO2. For the growth of Fe/C–TiO2 nanoparticles, TTIP is mixed with xylene and ferrocene. While for the growth of Si–TiO2 and V–TiO2, TTIP is mixed with hexamethyldisiloxane (HMDSO) and vanadium (V) oxytriisopropoxide, respectively. The synthesized nanoparticles are characterized using high-resolution transmission electron microscopy (HRTEM) with energy-filtered TEM for elemental mapping (of Si, C, O, and Ti), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), nitrogen adsorption BET surface area analysis, and thermogravimetric analysis. Anatase is the dominant phase for the C–TiO2, Fe/C–TiO2, and Si–TiO2 nanoparticles, whereas rutile is the dominant phase for the V–TiO2 nanoparticles. For C–TiO2 and Fe/C–TiO2, the nanoparticles are coated with about 3-5-nm thickness of carbon. The iron-based TiO2 nanoparticles significantly improve the catalytic oxidation of carbon, where complete oxidation of carbon occurs at a temperature of 470 °C (with iron) compared to 610 °C (without iron). Enhanced catalytic oxidation properties are also observed for model soot particles, Printex-U, when mixed with Fe/C-TiO2. With regards to Si–TiO2 nanoparticles, a uniform coating of 3 to 8 nm of silicon dioxide is observed around the TiO2 particles. This coating mainly occurs due to variance in the chemical reaction rates of the precursors. Finally, with regards to V–TiO2, vanadium is doped within the TiO2 nanoparticles as visualized by HRTEM and XPS further confirms the formation of

Synthesis of TiO2 nanoparticles containing Fe, Si, and V using multiple diffusion flames and catalytic oxidation capability of carbon-coated nanoparticles

KAUST Repository

Ismail, Mohamed

2016-01-19

Titanium dioxide (TiO2) nanoparticles containing iron, silicon, and vanadium are synthesized using multiple diffusion flames. The growth of carbon-coated (C–TiO2), carbon-coated with iron oxide (Fe/C–TiO2), silica-coated (Si–TiO2), and vanadium-doped (V–TiO2) TiO2 nanoparticles is demonstrated using a single-step process. Hydrogen, oxygen, and argon are utilized to establish the flame, with titanium tetraisopropoxide (TTIP) as the precursor for TiO2. For the growth of Fe/C–TiO2 nanoparticles, TTIP is mixed with xylene and ferrocene. While for the growth of Si–TiO2 and V–TiO2, TTIP is mixed with hexamethyldisiloxane (HMDSO) and vanadium (V) oxytriisopropoxide, respectively. The synthesized nanoparticles are characterized using high-resolution transmission electron microscopy (HRTEM) with energy-filtered TEM for elemental mapping (of Si, C, O, and Ti), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), nitrogen adsorption BET surface area analysis, and thermogravimetric analysis. Anatase is the dominant phase for the C–TiO2, Fe/C–TiO2, and Si–TiO2 nanoparticles, whereas rutile is the dominant phase for the V–TiO2 nanoparticles. For C–TiO2 and Fe/C–TiO2, the nanoparticles are coated with about 3-5-nm thickness of carbon. The iron-based TiO2 nanoparticles significantly improve the catalytic oxidation of carbon, where complete oxidation of carbon occurs at a temperature of 470 °C (with iron) compared to 610 °C (without iron). Enhanced catalytic oxidation properties are also observed for model soot particles, Printex-U, when mixed with Fe/C-TiO2. With regards to Si–TiO2 nanoparticles, a uniform coating of 3 to 8 nm of silicon dioxide is observed around the TiO2 particles. This coating mainly occurs due to variance in the chemical reaction rates of the precursors. Finally, with regards to V–TiO2, vanadium is doped within the TiO2 nanoparticles as visualized by HRTEM and XPS further confirms the formation of

One step aqueous solution preparation of nanosize iron-doped tin oxide from SnO{sub 2}.xH{sub 2}O gel

Energy Technology Data Exchange (ETDEWEB)

Melghit, Khaled [Chemistry Department, College of Science, P.O. Box 36, Al-Khodh 123, Sultan Qaboos University (Oman)]. E-mail: melghit@squ.edu.om; Bouziane, Khalid [Physics Department, College of Science, P.O. Box 36, Al-Khodh 123, Sultan Qaboos University (Oman)

2006-03-15

Nanosized iron-doped tin oxide solid solution was prepared by mixing tin oxide gel SnO{sub 2}.xH{sub 2}O with a boiling solution of iron nitrate. The XRD data of the as-prepared and annealed sample at 773 K show that the patterns are indexed to the rutile phase without any trace of an extra phase. SEM and TEM results performed on different selected area of the samples reveal a homogeneous composition of 8 at.% of Fe content and a size of about 2 nm of the particles. The particles size was found to increase slightly with temperature; about 7 nm after 24 h at 773 K. Structural and magnetic results seem to indicate that Fe{sup 3+} substitute for Sn{sup 4+} on the as-prepared sample. The system presents some weak ferromagnetic character at room temperature.

Effect of Fe{sub 2}O{sub 3} addition in Yttria-stabilized zirconia properties; Efeito da adicao de Fe{sub 2}O{sub 3} nas propriedades da zirconia estabilizada com itria

Energy Technology Data Exchange (ETDEWEB)

Mendes, Pedro de Freitas Castro; Elias, Carlos Nelson; Santos, Heraldo Elias Salomao dos, E-mail: elias@ime.eb.br [Instituto Militar de Engenharia (IME), Rio de Janeiro, RJ (Brazil). Secao de Engenharia Mecanica e de Materiais. Laboratorio de Biomateriais

2017-04-15

The zirconium oxide (ZrO{sub 2}) polycrystalline partially stabilized by yttrium oxide (Y{sub 2}O{sub 3}) at 3mol%, 3Y-TZP, has its use been increased as a biomaterial. However, as dental prosthetics, its indication is still limited because of its white color and high opacity. Seeking improvements regarding aesthetics without compromising its functional performance, oxides such as iron oxide (Fe{sub 2}O{sub 3}) has been added to the microstructure of zirconia in order to provide a yellow-brownish color similar to natural teeth. This study evaluated the effect of adding Fe{sub 2}O{sub 3} on the microstructure and mechanical and optical properties of 3Y-TZP. Five groups were investigated containing different concentrations of Fe{sub 2}O{sub 3}. Firstly, a chemical characterization of each group was carried out through X-ray fluorescence test (XRF). Microstructural characterization was performed by density and average grain size measurements. Mechanical properties were evaluated by performing hardness and four points flexural strength tests. Quantitative analysis of phase transformation was done using the Rietveld method, for each group submitted to the test of X-ray diffraction (XRD). Fractography by SEM analysis were also made on the fracture surface of the samples from tensile test. The results showed that the Fe{sub 2}O{sub 3} addition influenced the phase transformation process, and proportionally increased the samples hardness and flexural strength when their concentrations varied from 0.02% to 0.17% of the total weight. Above this range, the samples showed losses in their mechanical performance. The Fe{sub 2}O{sub 3} additions showed no significant changes in the density and average grain size of 3Y-TZP. (author)

Persulfate activation by iron oxide-immobilized MnO2 composite: identification of iron oxide and the optimum pH for degradations.

Science.gov (United States)

Jo, Young-Hoon; Do, Si-Hyun; Kong, Sung-Ho

2014-01-01

Iron oxide-immobilized manganese oxide (MnO2) composite was prepared and the reactivity of persulfate (PS) with the composite as activator was investigated for degradation of carbon tetrachloride and benzene at various pH levels. Brunauer-Emmett-Teller (BET) surface area of the composite was similar to that of pure MnO2 while the pore volume and diameter of composite was larger than those of MnO2. Scanning electron microscopy couples with energy dispersive spectroscopy (SEM-EDS) showed that Fe and Mn were detected on the surface of the composite, and X-ray diffraction (XRD) analysis indicated the possibilities of the existence of various iron oxides on the composite surface. Furthermore, the analyses of X-ray photoelectron (XPS) spectra revealed that the oxidation state of iron was identified as 1.74. In PS/composite system, the same pH for the highest degradation rates of both carbon tetrachloride and benzene were observed and the value of pH was 9. Scavenger test was suggested that both oxidants (i.e. hydroxyl radical, sulfate radical) and reductant (i.e. superoxide anion) were effectively produced when PS was activated with the iron-immobilized MnO2. Copyright © 2013 Elsevier Ltd. All rights reserved.

Studies of the rare earth-iron interactions in the orthoferrites GdFeO3 and HoFeO3

International Nuclear Information System (INIS)

Sakata, T.; Enomura, A.

1979-01-01

The magnetic behaviour of GdFeO 3 and HoFeO 3 is investigated by means of a Faraday type magnetic balance in a temperature range where rare earth ions are in the paramagnetic state. The results are analyzed in terms of an effective field at a rare earth ion site. Thereby the isotropic exchange field as well as the magnetic dipole field are taken into account. By this means the exchange integral, J/k(K), between an iron ion and a rare earth ion may be estimated to be 0.23 for GdFeO 3 and 0.25 for HoFeO 3 , respectively. (author)

DFT studies of elemental mercury oxidation mechanism by gaseous advanced oxidation method: Co-interaction with H2O2 on Fe3O4 (111) surface

Science.gov (United States)

Zhou, Changsong; Song, Zijian; Zhang, Zhiyue; Yang, Hongmin; Wang, Ben; Yu, Jie; Sun, Lushi

2017-12-01

Density functional theory calculations have been carried out for H2O2 and Hg0 co-interaction on Fe3O4 (111) surface. On the Fetet1-terminated Fe3O4 (111) surface, the most favored configurations are H2O2 decomposition and produce two OH groups, which have strong interaction with Hg atom to form an OHsbnd Hgsbnd OH intermediate. The adsorbed OHsbnd Hgsbnd OH is stable and hardly detaches from the catalyst surface due to the highly endothermic process. A large amount of electron transfer has been found from Hg to the produced OH groups and has little irreversible effect on the Fe3O4 (111) surface. On the Feoct2-terminated Fe3O4 (111) surface, the Feoct2 site is more active than Fetet1 site. H2O2 decomposition and Hg0 oxidation processes are more likely to occur due to that the Feoct2 site both contains Fe2+ and Fe3+ cations. The calculations reveal that Hg0 oxidation by the OH radical produced from H2O2 is energetically favored. Additionally, Hg0 and H2O2 co-interaction mechanism on the Fe3O4 (111) interface has been investigated on the basis of partial local density of state calculation.

Mn/TiO2 and Mn–Fe/TiO2 catalysts synthesized by deposition precipitation—promising for selective catalytic reduction of NO with NH3 at low temperatures

DEFF Research Database (Denmark)

Putluru, Siva Sankar Reddy; Schill, Leonhard; Jensen, Anker Degn

2015-01-01

Mn/TiO2and Mn–Fe/TiO2catalysts have been prepared by impregnation (IMP) and deposition-precipitation (DP) techniques and characterized by N2 physisorption, XRPD, NH3-TPD, H2-TPR, XPS and TGA. 25 wt% Mn0.75Fe0.25Ti-DP catalyst, prepared by deposition precipitation with ammonium carbamate (AC......) as a precipitating agent, showed superior low-temperature SCR (selective catalytic reduction) of NO with NH3. The superior catalytic activity of the 25 wt% Mn0.75Fe0.25Ti-DP catalyst is probably due to the presence of amorphous phases of manganese oxide, iron oxide, high surface area, high total acidity......, acidstrength and ease of reduction of manganese oxide and iron oxide on TiO2in addition to formation of an SCR active MnOx phase with high content of chemisorbed oxygen (Oα). The optimum catalyst might beused as tail-end SCR catalysts in, e.g., biomass-fired power plants and waste incineration plants....

Synergistic operation of photocatalytic degradation and Fenton process by magnetic Fe3O4 loaded TiO2

Science.gov (United States)

Sun, Qiong; Hong, Yong; Liu, Qiuhong; Dong, Lifeng

2018-02-01

The magnetic Fe3O4 loaded anatase TiO2 photocatalysts with different mass ratios were successfully synthesized by a one-step convenient calcining method. The morphology and structure analysis revealed that Fe3O4 was formed in TiO2 with very fine-grained particles. After a small amount of Fe3O4 loaded onto TiO2, the photocatalytic property enhanced obviously for the degradation of organic dye. Furthermore, the photo-Fenton-like catalysis of the iron-containing samples could also be induced after the addition of hydrogen peroxide. The apparent kinetic constant of the reaction that catalyzed by Fe-TiO2 was about 5.3 and 8.3 times of that catalyzed by TiO2 or Fe3O4 only, respectively, proving an effective synergistic contribution of the photocatalysis and Fenton reaction in the composite. Compared with Fe3O4 or free Fe3+ ions, only 13% of iron in TiO2 dissolved into acidic solution (25% for Fe3O4 and 100% for Fe3+) after the reaction, which confirmed the iron had been well immobilized onto TiO2. In addition, the extremely stable photocatalytic activity in cycling experiments proved the immobilized iron had been tightly attached onto TiO2, indicating the great potential of the catalyst for practical applications.

Fluxing template-assisted synthesis of sponge-like Fe2O3 microspheres toward efficient catalysis for CO oxidation

Science.gov (United States)

Li, Wenge; Hu, Yanjie; Jiang, Hao; Jiang, Yi; Wang, Yang; Huang, Su; Biswas, Pratim; Li, Chunzhong

2018-06-01

Constructing a porous architecture is a considerable strategy to enhance the catalytic activity of metal oxides catalysts for CO oxidation. In this work, we have developed porous sponge-like Fe2O3 microspheres by employing a facile aerosol spray pyrolysis. The NaNO3 salt in the spray solution plays a crucial role as a fluxing sacrifice template in the formation of the sponge-like structure, in which a high surface area of 216.2 m2 g-1 and an average pore size of 4 nm are obtained. This novel Fe2O3 catalyst exhibits an improved catalytic activity compared to usual iron oxides catalysts. Nearly 50% CO conversion at a relatively low temperature of 200 °C and 100% CO conversion at 300 °C at a space velocity of 60 000 ml h-1 g-1 are achieved. Furthermore, it displays an outstanding catalytic stability without distinct decay for 1000 min in a continuous stream at 300 °C. In addition to the effect of plentiful adsorption sites for the gas reactant, the promoted catalytic performance is also attributed to the function of abundant OH groups rooted in the large surface of the sponge-like structure, which induces faster reaction rate of CO oxidation via a bicarbonate route.

Containerless solidification of BiFeO3 oxide under microgravity

Science.gov (United States)

Yu, Jianding; Arai, Yasutomo; Koshikawa, Naokiyo; Ishikawa, Takehito; Yoda, Shinichi

1999-07-01

Containerless solidification of BiFeO3 oxide has been carried out under microgravity with Electrostatic Levitation Furnace (ELF) aboard on the sounding rocket (TR-IA). It is a first containerless experiment using ELF under microgravity for studying the solidification of oxide insulator material. Spherical BiFeO3 sample with diameter of 5mm was heated by two lasers in oxygen and nitrogen mixing atmosphere, and the sample position by electrostatic force under pinpoint model and free drift model. In order to compare the solidification behavior in microgravity with on ground, solidification experiments of BiFeO3 in crucible and drop tube were carried out. In crucible experiment, it was very difficult to get single BiFeO3 phase, because segregation of Fe2O3 occured very fast and easily. In drop tube experiment, fine homogeneous BiFeO3 microstructure was obtained in a droplet about 300 μm. It implies that containerless processing can promote the phase selection in solidification. In microgravity experiment, because the heating temperature was lower than that of estimated, the sample was heated into Fe2O3+liquid phase region. Fe2O3 single crystal grew on the surface of the spherical sample, whose sample was clearly different from that observed in ground experiments.

EPR spectroscopic investigations in 15BaO-25Li2O-(60-x) B2O3-xFe2O3 glass system

Science.gov (United States)

Bhogi, Ashok; Kumar, R. Vijaya; Kistaiah, P.

2018-05-01

Glasses with composition 15BaO-25Li2O-(60-x) B2O3 -xFe2O3 (x = 0, 0.2, 0.4, 0.6, 0.8 and 1 mol %) were prepared by the conventional melt quenching technique. These glasses were characterized using X-ray diffraction (XRD). Electron paramagnetic resonance (EPR) investigations have been carried out as a function of iron ion concentration. The observed EPR spectra of Fe3+ ion exhibits resonance signals at g= 2.0, 4.3 and 8.0. The resonance signal at g= 4.3 is due to isolated Fe3+ ions in site with rhombic symmetry where as the g= 2.0 resonance signal is attributed to the Fe3+ ions coupled by exchange interaction in a distorted octahedral environment and the signal at g= 8.0 arises from axially distorted sites. The number of spins participating in resonance (N) and its paramagnetic susceptibilities (χ) have also been evaluated. The peak-to-peak line width ΔB for the resonance lines at g ≈ 4.3 and at g ≈ 2.0 is increasing as function of the iron ion content. The line intensity of the resonance centered at g ≈ 4.3 and at g ≈ 2.0 increases up to 0.8 mol% of Fe2O3 and for 1 mol% of Fe2O3 its value is found to decrease. The analysis of these results indicated that the conversion some of Fe3+ cations to Fe2+ ions beyond 0.8 mol%.

Rate law of Fe(II) oxidation under low O2 conditions

Science.gov (United States)

Kanzaki, Yoshiki; Murakami, Takashi

2013-12-01

Despite intensive studies on Fe(II) oxidation kinetics, the oxidation rate law has not been established under low O2 conditions. The importance of Fe(II) oxidation under low O2 conditions has been recently recognized; for instance, the Fe(II)/Fe(III) compositions of paleosols, ancient soils formed by weathering, can produce a quantitative pattern of the atmospheric oxygen increase during the Paleoproterozoic. The effects of partial pressure of atmospheric oxygen (PO2) on the Fe(II) oxidation rate were investigated to establish the Fe(II) oxidation rate - PO2 relationships under low O2 conditions. All oxidation experiments were carried out in a glove box by introducing Ar gas at ∼10-5-∼10-4 atm of PO2, pH 7.57-8.09 and 22 °C. Luminol chemiluminescence was adopted to measure low Fe(II) concentrations (down to ∼2 nM). Combining previous data under higher PO2 conditions (10-3-0.2 atm) with the present data, the rate law for Fe(II) oxidation over a wide range of PO2 (10-5-0.2 atm) was found to be written as: d[Fe(II)]/dt=-k[Fe(II)][[]2 where the exponent of [O2], x, and the rate constant, k, change from x = 0.98 (±0.04) and log k = 15.46 (±0.06) at ∼6 × 10-3-0.2 atm of PO2 to x = 0.58 (±0.02) and log k = 13.41 (±0.03) at 10-5-∼6 × 10-3 atm of PO2. The most plausible mechanism that explains the change in x under low O2 conditions is that, instead of O2, oxygen-derived oxidants, H2O2 and to some extent, O2rad -, dominate the oxidation reactions at PO2. The rate law found in the present study requires us to reconsider distributions of Fe redox species at low PO2 in natural environments, especially in paleoweathering profiles, and may provide a deeper understanding of the evolution of atmospheric oxygen in the Precambrian.

A Highly Selective Room Temperature NH3 Gas Sensor based on Nanocrystalline a-Fe2O3

Directory of Open Access Journals (Sweden)

Priyanka A. PATIL

2017-05-01

Full Text Available Nanocrystalline a-Fe2O3 powder was synthesized by simple, inexpensive sol-gel method. The obtained powder was calcined at 700 0C in air atmosphere for 2 hours. The structural and morphological properties of calcined powder were studied by X-ray diffraction (XRD and Field Emission Scanning Electron Microscopy (FESEM respectively. Thermal properties of dried gel were studied by Thermogravimetric Analysis/Differential Scanning Calorimetry (TGA/DSC. The XRD pattern of the powder confirmed the a-Fe2O3 (hematite phase of iron oxide with average crystalline size of 30.87 nm calculated from Scherrer equation. The FESEM images showed uniform wormlike morphology of a-Fe2O3 powder. TGA result indicated that a-Fe2O3 is thermodynamically stable. Room temperature NH3 sensing characteristics of a-Fe2O3 were studied for various concentration levels (250-2500 ppm of NH3 at various humid conditions. The sensor based on a-Fe2O3 exhibited good selectivity and excellent sensitivity (S=92 towards 1000 ppm of NH3 with quick response of 4 sec and fast recovery of 9 sec. Room temperature sensing mechanism is also discussed.

Roentgenoelectronic investigation into oxidation of iron-chromium and iron-chromium-nickel alloys

International Nuclear Information System (INIS)

Akimov, A.G.; Rozenfel'd, I.L.; Kazanskij, L.P.; Machavariani, G.V.

1978-01-01

Kinetics of iron-chromium and iron-chromium-nickel alloy oxidation (of the Kh13 and Kh18N10T steels) in oxygen was investigated using X-ray electron spectroscopy. It was found that according to X-ray electron spectra chromium oxidation kinetics in the iron-chromium alloy differs significantly from oxidation kinetics of chromium pattern. Layer by layer X-ray electron analysis showed that chromium is subjected to a deeper oxidation as compared to iron, and accordingly, Cr 2 O 3 layer with pure iron impregnations is placed between the layer of mixed oxide (Fe 3 O 4 +Cr 2 O 3 ) and metal. A model of the iron-chromium alloy surface is suggested. The mixed oxide composition on the steel surface is presented as spinel Fesub(2+x)Crsub(1-x)Osub(y)

Toxicity effects of Fe2O3, TiO2, ZnO, and Ag engineered nanomaterials (ENMs) on the macrophyte Spirodela species

CSIR Research Space (South Africa)

Thwala, Melusi

2010-09-01

Full Text Available and also waste disposal where they will pose some level of risk. Four of these highly-used enms are selected for the current study. Fe2O3 (iron oxide) nanoscale iron is extensively used in bioremediation (Zhang 2003) and its use in environmental clean...-up operations is increasing. therefore a significant portion of nanoscale iron entering the environment will be introduced intentionally during environmental bioremediation. considering the potential benefits and increasing usage of nanoscale iron and also...

Composition of MBE-grown iron oxide films

NARCIS (Netherlands)

Voogt, F.C; Hibma, T; Smulders, P.J M; Niesen, L

A wide range of iron oxides have been grown epitaxially on MgO(100) substrates using a dual beam technique in which the deposited iron is oxidised by a beam of NO2 particles. At high fluxes magnetite (Fe3-deltaO4) phases with compositions between near-stoichiometric magnetite (Fe3O4, delta = 0) and

Battery Relevant Electrochemistry of Ag7Fe3(P2O7)4 : Contrasting Contributions from the Redox Chemistries of Ag+ and Fe3+

International Nuclear Information System (INIS)

Zhang, Yiman; Marschilok, Amy C.; Stony Brook University, NY; Takeuchi, Esther S.

2016-01-01

Ag 7 Fe 3 (P 2 O 7 ) 4 is an example of an electrochemical displacement material which contains two different electrochemically active metal cations, where one cation (Ag + ) forms metallic silver nanoparticles external to the crystals of Ag 7 Fe 3 (P 2 O 7 ) 4 via an electrochemical reduction displacement reaction, while the other cation (Fe +3 ) is electrochemically reduced with the retention of iron cations within the anion structural framework concomitant with lithium insertion. These contrasting redox chemistries within one pure cathode material enable high rate capability and reversibility when Ag 7 Fe 3 (P 2 O 7 ) 4 is employed as cathode material in a lithium ion battery (LIB). Further, pyrophosphate materials are thermally and electrically stable, desirable attributes for cathode materials in LIBs. In this article, a bimetallic pyrophosphate material Ag 7 Fe 3 (P 2 O 7 ) 4 is synthesized and confirmed to be a single phase by Rietveld refinement. Electrochemistry of Ag 7 Fe 3 (P 2 O 7 ) 4 is reported for the first time in the context of lithium based batteries using cyclic voltammetry and galvanostatic discharge–charge cycling. The reduction displacement reaction and the lithium (de)insertion processes are investigated using ex situ X-ray absorption spectroscopy and X-ray diffraction of electrochemically reduced and oxidized Ag 7 Fe 3 (P 2 O 7 ) 4 . Ag 7 Fe 3 (P 2 O 7 ) 4 exhibits good reversibility at the iron centers indicated by ~80% capacity retention over 100 cycles following the initial formation cycle and excellent rate capability exhibited by ~70% capacity retention upon a 4-fold increase in current.

2:1 Charge disproportionation in perovskite-structure oxide La{sub 1/3}Ca{sub 2/3}FeO{sub 3} with unusually-high-valence Fe{sup 3.67+}

Energy Technology Data Exchange (ETDEWEB)

Guo, Haichuan; Hosaka, Yoshiteru; Seki, Hayato; Saito, Takashi; Ichikawa, Noriya [Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Shimakawa, Yuichi, E-mail: shimak@scl.kyoto-u.ac.jp [Institute for Chemical Research, Kyoto University, Uji, Kyoto 611-0011 (Japan); Integrated Research Consortium on Chemical Sciences, Uji, Kyoto 611-0011 (Japan)

2017-02-15

La{sub 1/3}Ca{sub 2/3}FeO{sub 3} with unusually-high-valence Fe{sup 3.67+} was synthesized at a high pressure and high temperature. The compound crystallizes in a √2a×2a×√2a perovskite cell in which the La and Ca ions at the A site are disordered. At 217 K the Fe{sup 3.67+} shows charge disproportionation to Fe{sup 3+} and Fe{sup 5+} in a ratio of 2:1, and this disproportionation is accompanied by transitions in magnetic and transport properties. The charge-disproportionated Fe{sup 3+} and Fe{sup 5+} are arranged along the <111> direction of the cubic perovskite cell. The local electronic and magnetic environments of Fe in La{sub 1/3}Ca{sub 2/3}FeO{sub 3} are quite similar to those of Fe in La{sub 1/3}Sr{sub 2/3}FeO{sub 3}, and the 2:1 charge disproportionation pattern of Fe{sup 3+} and Fe{sup 5+} in La{sub 1/3}Ca{sub 2/3}FeO{sub 3} is also the same as that in La{sub 1/3}Sr{sub 2/3}FeO{sub 3}. - Graphical abstract: The perovskite-structure oxide La{sub 1/3}Ca{sub 2/3}FeO{sub 3} with unusually-high-valence Fe{sup 3.67+} shows charge disproportionation to Fe{sup 3+} and Fe{sup 5+} in a ratio of 2:1, and the charge-disproportionated Fe{sup 3+} and Fe{sup 5+} are arranged along the <111> direction of the cubic perovskite cell. - Highlights: • La{sub 1/3}Ca{sub 2/3}FeO{sub 3} with unusually-high-valence Fe{sup 3.67+} was synthesized at a high pressure and high temperature. • At 217 K the Fe{sup 3.67+} shows charge disproportionation (CD) to Fe{sup 3+} and Fe{sup 5+} in a ratio of 2:1. • The charge-disproportionated Fe{sup 3+} and Fe{sup 5+} are arranged along the <111> direction of the cubic perovskite cell. • The disproportionation is accompanied by transitions in magnetic and transport properties.

Hydrogen production by ethanol partial oxidation over nano-iron oxide catalysts produced by chemical vapour synthesis

Energy Technology Data Exchange (ETDEWEB)

Ahmed, Wael Ahmed Abou Taleb Sayed

2011-01-13

This work presents the experimental results of the synthesis of unsupported and supported SiC iron oxide nanoparticles and their catalytic activity towards ethanol partial oxidation. For comparison, further unsupported iron oxide phases were investigated towards the ethanol partial oxidation. These {gamma}-Fe{sub 2}O{sub 3} and {alpha}/{gamma}-Fe{sub 2}O{sub 3} phase catalysts were prepared by the CVS method using Fe(CO){sub 5} as precursor, supplied by another author. The {alpha}-Fe{sub 2}O{sub 3} and SiC nanoparticles were prepared by the CVS method using a home made hot wall reactor technique at atmospheric pressure. Ferrocene and tetramethylsilane were used as precursor for the production process. Process parameters of precursor evaporation temperature, precursor concentration, gas mixture velocity and gas mixture dilution were investigated and optimised to produce particle sizes in a range of 10 nm. For Fe{sub 2}O{sub 3}/SiC catalyst series production, a new hot wall reactor setup was used. The particles were produced by simultaneous thermal decomposition of ferrocene and tetramethylsilane in one reactor from both sides. The production parameters of inlet tube distance inside the reactor, precursor evaporation temperature and carrier gas flow were investigated to produce a series of samples with different iron oxide content. The prepared catalysts composition, physical and chemical properties were characterized by XRD, EDX, SEM, BET surface area, FTIR, XPS and dynamic light scattering (DLS) techniques. The catalytic activity for the ethanol gas-phase oxidation was investigated in a temperature range from 260 C to 290 C. The product distributions obtained over all catalysts were analysed with mass spectrometry analysis tool. The activity of bulk Fe{sub 2}O{sub 3} and SiC nanoparticles was compared with prepared nano-iron oxide phase catalysts. The reaction parameters, such as reaction temperature and O{sub 2}/ethanol ratio were investigated. The catalysts

X-Ray Photoelectron Spectroscopic Characterization of Iron Oxide Nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Radu, T., E-mail: Teodora.Radu@itim-cj.ro [National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat Street, 400293, Cluj Napoca (Romania); Iacovita, C. [Department of Pharmaceutical Physics-Biophysics, Faculty of Pharmacy, “Iuliu Hatieganu” University of Medicine and Pharmacy, 400349, Cluj-Napoca (Romania); Benea, D. [Faculty of Physics, Babes Bolyai University, 400271, Cluj-Napoca (Romania); Turcu, R. [National Institute for Research and Development of Isotopic and Molecular Technologies, 67-103 Donat Street, 400293, Cluj Napoca (Romania)

2017-05-31

Highlights: • Characterization of three types of iron oxides magnetic nanoparticles. • A correlation between valence band XPS and the degree of iron oxidation is proposed. • Theoretical contributions of Fe in tetragonal and octahedral environment are shown. - Abstract: We report X-ray photoelectron spectroscopy (XPS) results on iron oxide magnetic nanoparticle (Fe{sub 3}O{sub 4}) synthesized using solvothermal reduction in the presence of polyethylene glycol. The magnetite obtained was employed as precursor for the synthesis of γ-Fe{sub 2}O{sub 3} (by oxygen dissociation) which in turn was transformed into α-Fe{sub 2}O{sub 3}. We confirmed the magnetite, maghemite and hematite structure by Fourier Transformed Spectroscopy (FTIR) and X-ray diffraction (XRD). The analysis of the XPS core level and valence band (VB) photoemission spectra for all investigated samples is discussed in terms of the degree of iron oxidation. This is of fundamental importance to better understand the electronic structure of the obtained iron oxide nanoparticles in order to control and improve their quality for specific biomedical applications. Moreover, theoretical band structure calculations are performed for magnetite and the separate contributions of Fe in tetragonal and octahedral environment are shown.

Coprecipitation synthesis of zinc ferrit (FE 2 O 3 /ZNO) nanoparticles ...

African Journals Online (AJOL)

Zinc ferrite (Fe2O3/ZnO) nanocomposites were successfully synthesized by simple co-precipitation method via iron (III) nitrate 9-hydrate (Fe(NO3)3.9H2O) and zinc nitrate hexahydrate (Zn(NO3)2.6H2O) as precursor in the presence of cetyltrimethylammonium bromide (CTAB) surfactant. The samples were characterized by ...

Fabrication of graphene oxide decorated with Fe3O4@SiO2 for immobilization of cellulase

Science.gov (United States)

Li, Yue; Wang, Xiang-Yu; Jiang, Xiao-Ping; Ye, Jing-Jing; Zhang, Ye-Wang; Zhang, Xiao-Yun

2015-01-01

Fe3O4@SiO2-graphene oxide (GO) composites were successfully fabricated by chemical binding of functional Fe3O4@SiO2 and GO and applied to immobilization of cellulase via covalent attachment. The prepared composites were further characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. Fe3O4 nanoparticles (NPs) were monodisperse spheres with a mean diameter of 17 ± 0.2 nm. The thickness of SiO2 layer was calculated as being 6.5 ± 0.2 nm. The size of Fe3O4@SiO2 NPs was 24 ± 0.3 nm, similar to that of Fe3O4@SiO2-NH2. Fe3O4@SiO2-GO composites were synthesized by linking of Fe3O4@SiO2-NH2 NPs to GO with the catalysis of EDC and NHS. The prepared composites were used for immobilization of cellulase. A high immobilization yield and efficiency of above 90 % were obtained after the optimization. The half-life of immobilized cellulase (722 min) was 3.34-fold higher than that of free enzyme (216 min) at 50 °C. Compared with the free cellulase, the optimal temperature of the immobilized enzyme was not changed; but the optimal pH was shifted from 5.0 to 4.0, and the thermal stability was enhanced. The immobilized cellulase could be easily separated and reused under magnetic field. These results strongly indicate that the cellulase immobilized onto the Fe3O4@SiO2-GO composite has potential applications in the production of bioethanol.

Electrochemical Determination of Paracetamol Using Fe3O4/Reduced Graphene-Oxide-Based Electrode

Directory of Open Access Journals (Sweden)

Nguyen Thi Anh Thu

2018-01-01

Full Text Available The synthesis of magnetic iron oxide/reduced graphene oxide (Fe3O4/rGO and its application to the electrochemical determination of paracetamol using Fe3O4/rGO modified electrode were demonstrated. The obtained materials were characterized by means of X-ray diffraction (XRD, nitrogen adsorption/desorption isotherms, X-ray photoelectron spectroscopy (XPS, transmission electron microscope (TEM, Fourier transform infrared spectroscopy (FTIR, and magnetic measurement. The results showed that Fe3O4/rGO composite exhibited high specific surface area, and its morphology consists of very fine spherical particles of Fe3O4 in nanoscales. Fe3O4/rGO was used as an electrode modifier for the determination of paracetamol by differential pulse-anodic stripping voltammetry (DP-ASV. The preparation of Fe3O4/rGO-based electrode and some factors affecting voltammetric responses were investigated. The results showed that Fe3O4/rGO is a potential electrode modifier for paracetamol detection by DP-ASV with a low limit of detection. The interfering effect of uric acid, ascorbic acid, and dopamine on the current response of paracetamol has been reported. The repeatability, reproducibility, linear range, and limit of detection were also addressed. The proposed method could be applied to the real samples with satisfactory results.

Evolution of the mössbauer spectra of ludwigite Co3 - x Fe x O2BO3 with substitution of iron for cobalt

Science.gov (United States)

Knyazev, Yu. V.; Ivanova, N. B.; Bayukov, O. A.; Kazak, N. V.; Bezmaternykh, L. N.; Vasiliev, A. D.

2013-06-01

A concentration series of single crystals of iron-cobalt ludwigites Co3 - x Fe x O2BO3 ( x = 0.0125, 0.025, 0.050, 0.10, 1.0) has been synthesized. The structure has been studied using X-ray diffraction and Mössbauer effect. A preferred occupation of nonequivalent crystallographic positions by iron in the ludwigite structure has been revealed. It has been found that the valence of substituting iron ions is three. It has been revealed that the structure of the γ-resonance spectrum of Co2FeO2BO3 is complicated due to a composition disorder in the system.

Nanoscale TiO2 and Fe2O3 Architectures for Solar Energy Conversion Schemes

Science.gov (United States)

Sedach, Pavel Anatolyvich

The direct conversion of sunlight into more useable forms of energy has the potential of alleviating the environmental and social problems associated with a dependence on fossil fuels. If solar energy is to be utilized en-masse, however, it must be inexpensive and widely available. In this vein, the focus of this thesis is on nanostructured materials relevant to solar energy conversion and storage. Specifically, this thesis describes the ambient sol-gel synthesis of titanium dioxide (Ti02) nanowires designed for enhanced charge-transfer in solar collection devices, and the synthesis of novel disordered metal-oxide (MOx) catalysts for water oxidation. The introductory chapter of this thesis gives an overview of the various approaches to solar energy conversion. Sol---gel reaction conditions that enable the growth of one-dimensional (1-D) anatase TiO2 nanostructures from fluorine-doped tin oxide (FTO) for photovoltaics (PVs) are described in the second chapter. The generation of these linear nanostructures in the absence of an external bias or template is achieved by using facile experimental conditions (e.g., acetic acid (HOAc) and titanium isopropoxide (Ti(OiPr)4) in anhydrous heptane). The procedure was developed by functionalizing base-treated substrates with Ti-oxide nucleation sites that serve as a foundation for the growth of linear Ti-oxide macromolecules, which upon calcination, render uniform films of randomly oriented anatase TiO2 nanowires. A systematic evaluation of how reaction conditions (e.g., solvent volume, stoichiometry of reagents, substrate base treatment) affect the generation of these TiO 2 films is presented. A photo-organic MO. deposition route (i.e., photochemical metal-organic deposition (PMOD)) used to deposit thin-films of amorphous iron oxide (a-Fe2O3) for water oxidation catalysis is detailed in third chapter. It is shown that the irradiation of a spin-coated metal-organic film produces a film of non-crystalline a-Fe203. It is shown

Ferrite grade iron oxides from ore rejects

Indian Academy of Sciences (India)

Iron oxyhydroxides and hydroxides were synthesized from chemically beneficiated high SiO2/Al2O3 low-grade iron ore (57.49% Fe2O3) rejects and heated to get iron oxides of 96–99.73% purity. The infrared band positions, isothermal weight loss and thermogravimetric and chemical analysis established the chemical ...

Fe2+ oxidation rate drastically affect the formation and phase of secondary iron hydroxysulfate mineral occurred in acid mine drainage

International Nuclear Information System (INIS)

Huang Shan; Zhou Lixiang

2012-01-01

During the processes of secondary iron hydroxysulfate mineral formation, Fe 2+ ion was oxidized by the following three methods: (1) biooxidation treatment by Acidithiobacillus ferrooxidans (A. ferrooxidans); (2) rapid abiotic oxidation of Fe 2+ with H 2 O 2 (rapid oxidation treatment); (3) slow abiotic oxidation of Fe 2+ with H 2 O 2 (slow oxidation treatment). X-ray diffraction (XRD) patterns, element composition, precipitate weight and total Fe removal efficiency were analyzed. The XRD patterns and element composition of precipitates synthesized through the biooxidation and the slow oxidation treatments well coincide with those of potassium jarosite, while precipitates formed at the initial stage of incubation in the rapid oxidation treatment showed a similar XRD pattern to schwertmannite. With the ongoing incubation, XRD patterns and element composition of the precipitates that occurred in the rapid oxidation treatment were gradually close to those in the biooxidation and the slow oxidation treatments. Due to the inhibition of A. ferrooxidans itself and its extracellular polymeric substances (EPS) in aggregation of precipitates, the amount of precipitates and soluble Fe removal efficiency were lower in the biooxidation treatment than in the slow oxidation treatment. Therefore, it is concluded that Fe 2+ oxidation rate can greatly affect the mineral phase of precipitates, and slow oxidation of Fe 2+ is helpful in improving jarosite formation. - Highlights: ► Slow oxidation of Fe 2+ is helpful in jarosite formation. ► The already-formed schwertmannite can be gradually transformed to jarosite. ► Precipitates formation can be inhibited probably by EPS from A. ferrooxidans.

New transition metal oxide fluorides with ReO{sub 3}-type structure

Energy Technology Data Exchange (ETDEWEB)

Nakhal, Suliman; Lerch, Martin [Technische Universitaet Berlin (Germany). Inst. fuer Chemie

2016-08-01

The new niobium oxide fluorides MNbO{sub 2}F{sub 4} [M = (Cr, Fe)], CrNb{sub 2}O{sub 4}F{sub 5}, and Fe{sub 2}Nb{sub 3}O{sub 6}F{sub 9} were prepared by treatment of chromium or iron nitrate with Nb-containing hydrofluoric acid solutions. Crystal structures were investigated by means of X-ray powder diffraction. All new compounds can be structurally refined in the cubic ReO{sub 3}-type. The iron niobium oxide fluorides are reddish orange, and chromium containing phases exhibit a light green color. The niobium atoms are in the highest formal oxidation state.

Fabrication, characterization, and photocatalytic property of {alpha}-Fe{sub 2}O{sub 3}/graphene oxide composite

Energy Technology Data Exchange (ETDEWEB)

Li Hong; Zhao Qidong; Li Xinyong, E-mail: xinyongli@hotmail.com [School of Environmental Science and Technology, Dalian University of Technology, State Key Laboratory of Fine Chemical, Key Laboratory of Industrial Ecology and Environmental Engineering (MOE) (China); Zhu Zhengru [Research Center of Hydrology and Engineering, Academy of City and Environment, Liaoning Normal University (China); Tade, Moses; Liu Shaomin, E-mail: shaomin.liu@curtin.edu.au [Curtin University, Department of Chemical Engineering (Australia)

2013-06-15

Spindle-shaped microstructure of {alpha}-Fe{sub 2}O{sub 3} was successfully synthesized by a simple hydrothermal method. The {alpha}-Fe{sub 2}O{sub 3}/graphene oxide (GO) composites was prepared using a modified Hummers' strategy. The properties of the samples were systematically investigated by X-ray powder diffraction (XRD), UV-Vis diffuse reflectance spectrophotometer, transmission electron microscope, atomic force microscope, X-ray photoelectron spectroscopy, and Raman spectroscopy (Raman) techniques. GO nanosheets act as supporting materials for anchoring the {alpha}-Fe{sub 2}O{sub 3} particles. The average crystallite sizes of the {alpha}-Fe{sub 2}O{sub 3} and {alpha}-Fe{sub 2}O{sub 3}/GO samples are ca. 27 and 24 nm, respectively. The possible growth of {alpha}-Fe{sub 2}O{sub 3} onto GO layers led to a higher absorbance capacity for visible light by {alpha}-Fe{sub 2}O{sub 3}/GO than {alpha}-Fe{sub 2}O{sub 3} composite. The photocatalytic degradation of toluene over the {alpha}-Fe{sub 2}O{sub 3} and {alpha}-Fe{sub 2}O{sub 3}/GO samples under xenon-lamp irradiation was comparatively studied by in situ FTIR technique. The results indicate that the {alpha}-Fe{sub 2}O{sub 3}/GO sample synthesized exhibited a higher capacity for the degradation of toluene. The composite of {alpha}-Fe{sub 2}O{sub 3}/GO could be promisingly applied in photo-driven air purification.

Enhanced Water Oxidation Photoactivity of Nano-Architectured α-Fe2O3-WO3 Composite Synthesized by Single-Step Hydrothermal Method

Science.gov (United States)

Rahman, Gul; Joo, Oh-Shim; Chae, Sang Youn; Shah, Anwar-ul-Haq Ali; Mian, Shabeer Ahmad

2018-04-01

This study reports the one-step in situ synthesis of a hematite-tungsten oxide (α-Fe2O3-WO3) composite on fluorine-doped tin oxide substrate via a simple hydrothermal method. Scanning electron microscopy images indicated that the addition of tungsten (W) precursor into the reaction mixture altered the surface morphology from nanorods to nanospindles. Energy-dispersive x-ray spectroscopy analysis confirmed the presence of W content in the composite. From the ultraviolet-visible spectrum of α-Fe2O3-WO3, it was observed that absorption began at ˜ 600 nm which corresponded to the bandgap energy of ˜ 2.01 eV. The α-Fe2O3-WO3 electrode demonstrated superior performance, with water oxidation photocurrent density of 0.80 mA/cm2 (at 1.6 V vs. reversible hydrogen electrode under standard illumination conditions; AM 1.5G, 100 mW/cm2) which is 2.4 times higher than α-Fe2O3 (0.34 mA/cm2). This enhanced water oxidation performance can be attributed to the better charge separation properties in addition to the large interfacial area of small-sized particles present in the α-Fe2O3-WO3 nanocomposite film.

Synthesis of Mesoporous α-Fe2O3 Nanoparticles by Non-ionic Soft Template and Their Applications to Heavy Oil Upgrading

Science.gov (United States)

Park, Chulwoo; Jung, Jinhwan; Lee, Chul Wee; Cho, Joungmo

2016-12-01

This paper reports the synthetic route of 3-D network shape α-Fe2O3 from aqueous solutions of iron precursor using a non-ionic polymeric soft-template, Pluronic P123. During the synthesis of α-Fe2O3, particle sizes, crystal phases and morphologies were significantly influenced by pH, concentrations of precursor and template. The unique shape of worm-like hematite was obtained only when a starting solution was prepared by a weakly basic pH condition and a very specific composition of constituents. The synthesized nanocrystal at this condition had a narrow pore size distribution and high surface area compared to the bulk α-Fe2O3 or the one synthesized from lower pH conditions. The hydrocracking performance was tested over the synthesized iron oxide catalysts with different morphologies. The worm-like shape of iron oxide showed a superior performance, including overall yield of liquid fuel product and coke formation, over the hydrocracking of heavy petroleum oil.

Fabrication of graphene oxide decorated with Fe3O4@SiO2 for immobilization of cellulase

International Nuclear Information System (INIS)

Li, Yue; Wang, Xiang-Yu; Jiang, Xiao-Ping; Ye, Jing-Jing; Zhang, Ye-Wang; Zhang, Xiao-Yun

2015-01-01

Fe 3 O 4 @SiO 2 –graphene oxide (GO) composites were successfully fabricated by chemical binding of functional Fe 3 O 4 @SiO 2 and GO and applied to immobilization of cellulase via covalent attachment. The prepared composites were further characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. Fe 3 O 4 nanoparticles (NPs) were monodisperse spheres with a mean diameter of 17 ± 0.2 nm. The thickness of SiO 2 layer was calculated as being 6.5 ± 0.2 nm. The size of Fe 3 O 4 @SiO 2 NPs was 24 ± 0.3 nm, similar to that of Fe 3 O 4 @SiO 2 –NH 2 . Fe 3 O 4 @SiO 2 –GO composites were synthesized by linking of Fe 3 O 4 @SiO 2 –NH 2 NPs to GO with the catalysis of EDC and NHS. The prepared composites were used for immobilization of cellulase. A high immobilization yield and efficiency of above 90 % were obtained after the optimization. The half-life of immobilized cellulase (722 min) was 3.34-fold higher than that of free enzyme (216 min) at 50 °C. Compared with the free cellulase, the optimal temperature of the immobilized enzyme was not changed; but the optimal pH was shifted from 5.0 to 4.0, and the thermal stability was enhanced. The immobilized cellulase could be easily separated and reused under magnetic field. These results strongly indicate that the cellulase immobilized onto the Fe 3 O 4 @SiO 2 –GO composite has potential applications in the production of bioethanol

Effectiveness of Iron Ethylenediamine-N,N'-bis(hydroxyphenylacetic) Acid (o,o-EDDHA/Fe3+) Formulations with Different Ratios of Meso and d,l-Racemic Isomers as Iron Fertilizers.

Science.gov (United States)

Alcañiz, Sara; Jordá, Juana D; Cerdán, Mar

2017-01-18

Two o,o-EDDHA/Fe 3+ formulations (meso, 93.5% w/w of meso isomer; and d,l-racemic, 91.3% w/w of d,l-racemic mixture) were prepared, and their efficacy to avoid or to relieve iron deficiency in Fe-sufficient and Fe-deficient tomato plants grown on hydroponic solution was compared with that of the current o,o-EDDHA/Fe 3+ formulations (50% of meso and d,l-racemic isomers). The effectiveness of the three o,o-EDDHA/Fe 3+ formulations was different depending on the iron nutritional status of plants. The three o,o-EDDHA/Fe 3+ formulations tested were effective in preventing iron chlorosis in healthy plants. However, the higher the meso concentration in the formulations, the higher the effectiveness in the recovery of iron chlorotic plants from iron deficiency. Accordingly, o,o-EDDHA/Fe 3+ formulations rich in meso isomer are recommended in hydroponic systems.

Fe3O4 thin films sputter deposited from iron oxide targets

International Nuclear Information System (INIS)

Peng, Yingguo; Park, Chandro; Laughlin, David E.

2003-01-01

Fe 3 O 4 thin films have been directly sputter deposited from a target consisting of a mixture of Fe 3 O 4 and Fe 2 O 3 onto Si and glass substrates. The magnetic properties and microstructures of the films have been characterized and correlated. The columnar growth of the Fe 3 O 4 grains was found to be initialized from the substrate surface without any critical thickness. Substrate bias was found to be a very effective means of improving the crystal quality and magnetic properties of the thin films. The crystallographic defects revealed by high resolution transmission electron microscopy seem to be a characteristic of the films prepared by this method

Behaviour of Fe4O5-Mg2Fe2O5 solid solutions and their relation to coexisting Mg-Fe silicates and oxide phases

Science.gov (United States)

Uenver-Thiele, Laura; Woodland, Alan B.; Miyajima, Nobuyoshi; Ballaran, Tiziana Boffa; Frost, Daniel J.

2018-03-01

Experiments at high pressures and temperatures were carried out (1) to investigate the crystal-chemical behaviour of Fe4O5-Mg2Fe2O5 solid solutions and (2) to explore the phase relations involving (Mg,Fe)2Fe2O5 (denoted as O5-phase) and Mg-Fe silicates. Multi-anvil experiments were performed at 11-20 GPa and 1100-1600 °C using different starting compositions including two that were Si-bearing. In Si-free experiments the O5-phase coexists with Fe2O3, hp-(Mg,Fe)Fe2O4, (Mg,Fe)3Fe4O9 or an unquenchable phase of different stoichiometry. Si-bearing experiments yielded phase assemblages consisting of the O5-phase together with olivine, wadsleyite or ringwoodite, majoritic garnet or Fe3+-bearing phase B. However, (Mg,Fe)2Fe2O5 does not incorporate Si. Electron microprobe analyses revealed that phase B incorporates significant amounts of Fe2+ and Fe3+ (at least 1.0 cations Fe per formula unit). Fe-L2,3-edge energy-loss near-edge structure spectra confirm the presence of ferric iron [Fe3+/Fetot = 0.41(4)] and indicate substitution according to the following charge-balanced exchange: [4]Si4+ + [6]Mg2+ = 2Fe3+. The ability to accommodate Fe2+ and Fe3+ makes this potential "water-storing" mineral interesting since such substitutions should enlarge its stability field. The thermodynamic properties of Mg2Fe2O5 have been refined, yielding H°1bar,298 = - 1981.5 kJ mol- 1. Solid solution is complete across the Fe4O5-Mg2Fe2O5 binary. Molar volume decreases essentially linearly with increasing Mg content, consistent with ideal mixing behaviour. The partitioning of Mg and Fe2+ with silicates indicates that (Mg,Fe)2Fe2O5 has a strong preference for Fe2+. Modelling of partitioning with olivine is consistent with the O5-phase exhibiting ideal mixing behaviour. Mg-Fe2+ partitioning between (Mg,Fe)2Fe2O5 and ringwoodite or wadsleyite is influenced by the presence of Fe3+ and OH incorporation in the silicate phases.

Thermodynamic properties of compounds of Na2O with the oxides of chromium, nickel, and iron

International Nuclear Information System (INIS)

Shaiu, B.J.

1976-10-01

Results of emf measurements on Na 2 O solid electrolytes in binary compounds with Cr 2 O 3 , FeO, and NiO are presented along with thermodynamic properties of these compounds. It was found that reliable thermodynamic data for compounds of NaCrO 2 , Na 2 FeO 2 , NaFeO 2 , Na 2 NiO 2 , and NaNiO 2 at 500 to 800 0 can be obtained by using emf measurements with solid electrolyte cells. The pretreatment of heating the cells in a vacuum of 10 -2 torr at 500 0 C or above for about 12 hours causes the emf dependence on temperature to be very small. The measurements were carried out over the temperature range in which no phase transformations occurred, the ΔC/sub p/ for the compounds involved was reasonably considered as approximately zero. Linear emf-temperature plots were therefore expected for these cells and the equation of ΔG 0 /sub f/ was indeed valid for constant values of ΔH 0 /sub f/ and ΔS 0 /sub f/. The formation of compound NaCrO 2 is thermodynamically favorable in a sodium loop made of austenic stainless steels. The critical oxygen concentration for the formation of NaCrO 2 shows that it is stable in liquid sodium in temperature range from 400 to 1100 0 C and Cr 2 O 3 does not exist with the double oxide in liquid sodium. The existence temperature for (Na 2 O) 2 .FeO in equilibrium with oxygen saturated liquid sodium is 693 0 K or above, for Na 2 FeO 2 it is 1141 0 K or above and for NaFeO 2 it is greater than or equal to 1173 0 K. The double oxides of nickel with sodium oxide are much less stable than the iron double oxides and do therefore not exist in liquid sodium. The nickel in austenitic stainless steel shows the least attack by oxygen saturated liquid sodium