Reaction Pathways at the Iron–microspherical Silica Interface: Mechanistic Aspects of the Formation of Target Iron Oxide Phases

2000 ◽  
Vol 15 (4) ◽  
pp. 944-950 ◽  
Author(s):  
Sivarajan Ramesh ◽  
Israel Felner ◽  
Yuri Koltypin ◽  
Aharon Gedanken
Keyword(s):  
Iron Oxide ◽  
Iron Nanoparticles ◽  
Silica Surface ◽  
Adsorbed Water ◽  
Reaction Pathways ◽  
X Ray ◽  
Degree Of Hydration ◽  
Oxide Phases ◽  
And Control ◽  
Hydrolysis Of

Oxidative hydrolysis of elemental iron nanoclusters on hydroxylated surfaces such as silica or alumina is known to be influenced by the degree of hydration of the surface. The understanding and control of this process is crucial in the synthesis of iron oxide coated silica microspheres with a desired magnetic property. The hydrolysis of iron nanoparticles followed by heat treatment in the case of a hydrated microspherical silica surface results in the formation of maghemite (γ–Fe2O3), whereas a dehydrated surface yielded hematite (α–Fe2O3) nanoparticles. The influence of adsorbed water on the formation of intermediate iron oxides/oxidehydroxides and the mechanistic aspects of their subsequent thermal dehydration iron oxide phases were investigated by thermogravimetric analysis, Fourier transform infrared, and Mössbauer spectroscopies. The reactions on both the hydrated and the dehydrated surfaces were found to proceed through the formation of an x-ray amorphous lepidocrocite [γ–FeO(OH)] intermediate and its subsequent dehydration to maghemite (γ–Fe2O3). Maghemite to hematite transformation was readily facilitated only on a dry silica surface. The retardation of the lepidocrocite →maghemite →hematite transformation in the case of a hydrated silica surface is suggested to arise from strong hydrogen-bonded interactions between the substrate silica and the adsorbed nanoparticles.

scholarly journals Study of the iron nanoparticles phase transformation during thermal annealing

2017 ◽  
pp. 16-25
Author(s):  
Artem Kozlovskiy ◽  
Jumat Kargin ◽  
Malik Kokarev ◽  
Daut Mukhambetov
Keyword(s):  
Magnetic Field ◽  
Heat Treatment ◽  
Phase Transformation ◽  
Phase Composition ◽  
Iron Oxide ◽  
Magnetic Anisotropy ◽  
Hysteresis Loop ◽  
Iron Nanoparticles ◽  
Oxide Phases ◽  
The Magnetic Field

Change in structural properties and phase composition of nanoparticles based on iron oxide was researched in the paper. As a result of conducted studies it was found that during heat treatment oxide phases of (γ-Fe2O3) and α-Fe2O3 maghemite were formed in oxygen atmosphere. Researches of powder array magnetization were showed that the hysteresis loop movement had the form characteristic for ferromagnetic materials. Additionally, loops obtained at different directions of the magnetic field have different characters, which indicate the magnetic anisotropy presence in the samples.

Selective Depositions of Fe-Containing Oxide Films on Mixed Selfassembled Organic Monolayers using Microcontact Printing

1999 ◽  
Vol 576 ◽  
Author(s):  
Hyunjung Shin ◽  
Hyejin Im ◽  
Seungbum Hong ◽  
Kyongmi Lee ◽  
Geunbae Lim ◽  
...  
Keyword(s):  
Iron Oxide ◽  
Aqueous Solutions ◽  
Microcontact Printing ◽  
Thin Layers ◽  
Organic Monolayers ◽  
Selective Deposition ◽  
X Ray ◽  
Si Substrates ◽  
Relief Structure ◽  
Oxide Phases

ABSTRACTIn situ patterning of crystalline iron oxide thin layers has been achieved via microcontact printing (μCP) and selective deposition. μCP was used to pattern two different surface moieties of selfassembled organic monolayers (SAMs) on Au/Cr/Si substrates. An elastomeric stamp (poly(dimethylsiloxane); PDMS) having a submicron-size patterned relief structure was used to transfer either hexadecanethiol (HDT) SAMs, which are to sustain deposition of iron oxide precipitates, or hydrophilic SAMs (e.g. dithiothreitol (DTT)). Selective deposition is realized through precipitation of iron oxide phases from aqueous solutions at ambient temperature (<100°C). Aqueous solutions of 0.05 M of iron nitrate (Fe(NO3)2•9H20) containing urea under nitric acid (pH < 2) were prepared for selective depositions. X-ray photoelectron spectroscopic (XPS) results showed that iron oxide precipitates were deposited onto hydrophilic SAMs, but not onto HDT surfaces. As-deposited films onto DTT-SAM surfaces at 80°C were crystalline α-Fe2O3 (hematite). Fe3O4 and γ-Fe2O3 films were synthesized via annealing of as-deposited α-Fe2O3. Scanning electron microscopy, x-ray diffractometry, vibrating sample magnetometry, and optical microscopy were used to characterize the films' microstructures and properties.

X-ray spectromicroscopy of nanoparticulate iron oxide phases

2016 ◽  
Vol 11 (4) ◽  
pp. 04B402 ◽  
Author(s):  
Paul M. Dietrich ◽  
Wolfgang E. S. Unger ◽  
Sufal Swaraj
Keyword(s):  
Iron Oxide ◽  
X Ray ◽  
Oxide Phases

Identification of iron oxide phases in thin films grown on Al2O3(0001) by Raman spectroscopy and X-ray diffraction

2010 ◽  
Vol 604 (7-8) ◽  
pp. 679-685 ◽  
Author(s):  
Maike Lübbe ◽  
Alexander M. Gigler ◽  
Robert W. Stark ◽  
Wolfgang Moritz
Keyword(s):  
Thin Films ◽  
Raman Spectroscopy ◽  
Iron Oxide ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxide Phases

Radioisotopic study of 11C-labelling methanol decomposition on iron oxide modified mesoporous MCM-41 silica

2009 ◽  
Vol 87 (3) ◽  
pp. 478-485 ◽  
Author(s):  
Eva Sarkadi-Pribóczki ◽  
Tanya Tsoncheva ◽  
Ljubomira Ivanova
Keyword(s):  
Iron Oxide ◽  
Surface Coverage ◽  
Methanol Conversion ◽  
Methanol Decomposition ◽  
Reaction Pathways ◽  
X Ray Diffraction ◽  
Iron Species ◽  
X Ray ◽  
Temperature Programmed ◽  
Mcm 41

Novel 11C-radiolabelling method was applied for the investigation of methanol conversion on iron oxide modified mesoporous MCM-41. Changes in the selectivity were observed varying the state of the loaded iron species or the degree of the surface coverage with 11C-radiolabelling methanol. Combining the Moessbauer spectroscopy, X-ray diffraction (XRD), N2-physisorption, and temperature-programmed reduction- thermogravimetric (TPR-TG) techniques with the high sensitive 11C-radioisotopic catalytic analysis, the contribution of the different reaction pathways of methanol conversion was discussed.

The thermal disintegration of crocidolite in air and in vacuum

1965 ◽  
Vol 35 (269) ◽  
pp. 31-37 ◽  
Author(s):  
J. H. Patterson
Keyword(s):  
Iron Oxide ◽  
Structural Models ◽  
Fibre Axis ◽  
Orientation Relationships ◽  
Incongruent Melting ◽  
Fibre Bundles ◽  
X Ray ◽  
Oxide Phases ◽  
Original Fibre

SummaryThe thermal disintegration of crocidolite has been investigated with X-ray powder and rotation photographs. Initial disintegration products include monoclinic pyroxene, iron oxide phases, and eristobalite as a pseudomorph of the original fibre bundles but at about 1000° C fusion occurs due to incongruent melting of the pyroxene. The products are strongly oriented along the fibre axis and full orientation relationships have been deduced with the aid of structural models. From these relationships it is suggested that regions of the amphibole structure on (100) are retained in the product phases without change in orientation.

β-Ferric Oxyhydroxide

1960 ◽  
Vol 32 (250) ◽  
pp. 545-557 ◽  
Author(s):  
A. L. Mackay
Keyword(s):  
Iron Oxide ◽  
Electron Diffraction ◽  
Spinel Phase ◽  
Intermediate Stage ◽  
Unit Cell ◽  
X Ray ◽  
Hydrated Iron Oxide ◽  
Tetragonal Unit Cell ◽  
Ferric Oxyhydroxide ◽  
Hydrolysis Of

SummaryThe crystallographic properties of the hydrated iron oxide obtained by the hydrolysis of FeCl3 are described. The characterizing X-ray powder pattern can be indexed on a tetragonal unit cell with a 10·48 and c 3·023 Å. This cell is shown to contain eight formula units of FeOOH but Cl- or other anions are necessary for the crystallization of the material The structure is that of hollandite or α-MnO2. The unit cell has been confirmed by electron diffraction from single crystals having dimensions about 5000 × 500 × 500 Å. and twinning, which produces hexagonal stars, has been studied. On heating, the structure breaks down and recrystallizes as α-Fe2O2, probably with an intermediate stage involving a spinel phase.

X-Ray Replication of Submicrometer Linewidth Patterns

1977 ◽  
Vol 35 ◽  
pp. 136-137
Author(s):  
Henry I. Smith ◽  
D.C. Flanders
Keyword(s):  
Electron Beam Lithography ◽  
Cross Sectional ◽  
X Ray ◽  
Electron Backscattering ◽  
Spatial Frequencies ◽  
Cross Sectional Profile ◽  
Carbon Foils ◽  
Sectional Profile ◽  
And Control ◽  
Soft Radiation

Scanning electron beam lithography has been used for a number of years to write submicrometer linewidth patterns in radiation sensitive films (resist films) on substrates. On semi-infinite substrates, electron backscattering severely limits the exposure latitude and control of cross-sectional profile for patterns having fundamental spatial frequencies below about 4000 Å(l),Recently, STEM'S have been used to write patterns with linewidths below 100 Å. To avoid the detrimental effects of electron backscattering however, the substrates had to be carbon foils about 100 Å thick (2,3). X-ray lithography using the very soft radiation in the range 10 - 50 Å avoids the problem of backscattering and thus permits one to replicate on semi-infinite substrates patterns with linewidths of the order of 1000 Å and less, and in addition provides means for controlling cross-sectional profiles. X-radiation in the range 4-10 Å on the other hand is appropriate for replicating patterns in the linewidth range above about 3000 Å, and thus is most appropriate for microelectronic applications (4 - 6).

Identification of acid-insoluble filter-plugging compounds and optimal acid-washing procedures for tubular backpulse pressure filters

TAPPI Journal ◽  
2011 ◽  
Vol 10 (1) ◽  
pp. 17-23
Author(s):  
KEVIN TAYLOR ◽  
RICH ADDERLY ◽  
GAVIN BAXTER
Keyword(s):  
Calcium Sulfate ◽  
Membrane Filter ◽  
Sulfamic Acid ◽  
Xrd Analysis ◽  
Metal Sulfides ◽  
X Ray Diffraction ◽  
X Ray ◽  
Gypsum Formation ◽  
Acid Washing ◽  
Hydrolysis Of

Over time, performance of tubular backpulse pressure filters in kraft mills deteriorates, even with regular acid washing. Unscheduled filter replacement due to filter plugging results in significant costs and may result in mill downtime. We identified acid-insoluble filter-plugging materials by scanning electron microscope/energy-dispersion X-ray spectroscopy (SEM/EDS) and X-ray diffraction (XRD) analysis in both polypropylene and Gore-Tex™ membrane filter socks. The major filter-plugging components were calcium sulfate (gypsum), calcium phosphate (hydroxylapatite), aluminosilicate clays, metal sulfides, and carbon. We carried out detailed sample analysis of both the standard acid-washing procedure and a modified procedure. Filter plugging by gypsum and metal sulfides appeared to occur because of the acid-washing procedure. Gypsum formation on the filter resulted from significant hydrolysis of sulfamic acid solution at temperatures greater than 130°F. Modification of the acid-washing procedure greatly reduced the amount of gypsum and addition of a surfactant to the acid reduced wash time and mobilized some of the carbon from the filter. With surfactant, acid washing was 95% complete after 40 min.

Investigation of the products of carbothermal reduction of yttrium oxide by the hydrolysis method

1984 ◽  
Vol 49 (4) ◽  
pp. 936-943 ◽  
Author(s):  
Bohumil Hájek ◽  
Pavel Karen ◽  
Vlastimil Brožek
Keyword(s):  
Yttrium Oxide ◽  
Carbothermal Reduction ◽  
Stoichiometric Ratio ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hydrolysis Method ◽  
Sample Decomposition ◽  
Products Of Reaction ◽  
Hydrolysis Of ◽  
Lower Carbon

For the investigation of the products of reaction of yttrium oxide with carbon mixed in various proportions, the chemical and X-ray diffraction methods of analysis were combined with the gas chromatographic analysis of the mixture of hydrocarbons and hydrogen formed on the sample decomposition with water. The carboreduction of Y2O3 was examined at relatively low temperatures, convenient for obtaining the reaction intermediates in higher yields. At 1 600 °C and pressures of 10-3 Pa the reduction of a mixture of Y2O3 with carbon in a stoichiometric ratio of 1 : 7 yields YC2 in equilibrium with 20% of Y2OC phase. At lower carbon contents (down to the Y2O3 : C ratio of 1 : 2) tha fraction of the Y2OC phase increases up to approximately 30%. In addition to Y2O3, the reaction mixture contains also Y2C, Y2OC and a phase giving propyne on hydrolysis. The presence of traces of C3 hydrocarbons and small amounts of methane in the product of hydrolysis of the carbide sample prepared by the carbothermal reduction of the oxide can be explained in terms of the occurrence of the Y15C19 phase, probably substituted in part by oxygen, and of the Y2OC phase. The results are compared with those obtained previously for the Sc2O3 + C system.

Sign in / Sign up

Export Citation Format

Share Document