共查询到20条相似文献,搜索用时 531 毫秒
1.
L. Yu. Novoselova E. E. Sirotkina 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2009,83(12):2127-2132
Sorbent samples based on the thermally activated precipitate formed in iron removal from under-ground water (water conditioning
wastes) were studied by low-temperature nitrogen adsorption and thermal and X-ray analysis. The precipitate was found to be
a material with a developed porous structure (the specific surface area of the initial sample was 229.9 m2/g). Calcining at 300°C decreased the specific surface area of the samples by 1.6–1.7 times and increased the volume of sorbing
pores by 1.6 times. The precipitate material largely contained iron phases. An increase in the temperature of calcining contributed
to deeper crystallization of the main phase, α-Fe2O3. 相似文献
2.
Studies were undertaken of phase transitions of iron oxide obtained from iron oxide-hydroxides of type α-, β-, γ- and δ-FeOOH,
and used as a support of ruthenium catalysts Ru/Fe2O3, employed in the water-gas shift reaction. In asprepared pure supports and ruthenium catalysts the main phase was α-Fe2O3. After use in the water-gas shift reaction, the support showed the presence of different phases of iron oxide. The most active
Ru/Fe2O3 catalysts prepared on the basis of α- and δ-FeOOH, after use in the water-gas shift reaction, revealed the presence of Fe3O4 or a mixture of phases Fe3O4 and γ-Fe2O3. The least active catalysts, prepared on the basis of β- and γ-FeOOH, contained a solid solution of Fe3O4-γ-Fe2O3 with traces of α-Fe2O3. 相似文献
3.
S. M. Eyubova V. D. Yagodovskii 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2008,82(13):2362-2366
The oxidation of CO on α-Fe2O3 was studied in a flow reactor. The conversion was complete at 650–660 K. The catalytic activity of iron oxide was higher
than that of the ferrite-containing xMgOyFe2O3 catalyst. The adsorption of CO on iron oxide and the kinetics of interaction of carbon monoxide with oxygen atomically adsorbed
on the surface of α-Fe2O3 were studied. The kinetic parameters of the oxidation of CO are evidence of the participation of adsorbed oxygen atoms, whose
binding energy on the surface of α-Fe2O3 is lower than that on the surface of the magnesium ferrite-containing catalyst. 相似文献
4.
M. Ştefănescu O. Ştefănescu M. Stoia C. Lazau 《Journal of Thermal Analysis and Calorimetry》2007,88(1):27-32
In this
paper we present a study on the synthesis of Fe(III) oxide, by thermal decomposition
of some complex combinations of Fe(III) with carboxylate type ligands, obtained
in the redox reaction between some polyols (ethylene glycol (EG), 1,2-propane
diol (1,2PG), 1,3-propane diol (1,3PG) and glycerol (GL)) and NO3
–
ions (from ferric nitrate). Fe2O3
was obtained by thermal decomposition of the synthesized metal-organic precursors
at low temperatures. γ-Fe2O3
was obtained as nanoparticles at 300°C, while at higher temperatures α-Fe2O3
starts to crystallize and becomes single phase at ~500°C.
The
formation of the metal-organic precursors and their thermal decomposition
were studied by thermal analysis and FTIR spectroscopy. 相似文献
5.
Klára Melánová Ludvík Beneš Vítězslav Zima Jan Svoboda Miroslava Trchová Jiří Dybal 《Journal of inclusion phenomena and macrocyclic chemistry》2007,58(1-2):95-101
Intercalation compounds of α-Zr(HPO4)2 · H2O with 1,2-alkanediols (from C3 to C16) have been prepared by replacing 1-propanol in α-Zr(HPO4)2 · 2C3H7OH with the desired 1,2-alkanediols by a treatment in a microwave field. It was found that the intercalates contain 1.5 molecules
of diol per formula unit. The diol molecules are placed between the host layers in a bimolecular way with their aliphatic
chains tilted at an angle of 51°. The diol molecules are anchored in the interlayer space by H-bonds. A mixed intercalate,
containing 1,2-butanediol and 1,2-decanediol in a roughly equimolar ratio, is formed when the α-Zr(HPO4)2 · 2C3H7OH intercalate, suspended in a mixture of 1,2-butanediol and 1,2-decanediol, is exposed to microwave radiation. No new phase
containing both types of the guest molecules was observed when the 1-propanol intercalate, suspended in a mixture of 1-propanol
and 1,2-octanediol, is exposed to microwave radiation. 相似文献
6.
Ling Hu Aurelien Percheron Denis Chaumont Claire-Helene Brachais 《Journal of Sol-Gel Science and Technology》2011,60(2):198-205
A simple, rapid, one-step synthesis way of pure iron oxide nanoparticles: magnetite (Fe3O4), maghemite (γ-Fe2O3) and hematite (α-Fe2O3) was investigated. Nanoparticles were prepared by microwave synthesis, from ethanol/water solutions of chloride salts of
iron (FeCl2 and FeCl3) in the presence of sodium hydroxide NaOH. X-ray powder diffraction (XRD), Transmission Electron Microscopy (TEM), Fourier
transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to characterize these nanoparticles. 相似文献
7.
C. Sikalidis T. Zorba K. Chrissafis K.M. Paraskevopoulos 《Journal of Thermal Analysis and Calorimetry》2006,86(2):411-415
Phase changes of iron containing solid wastes from steel mill pickling
lines after thermal treatments were investigated aiming the determination
of the appropriate conditions for its transformation to be useful for industrial
raw materials. Above 275°C, the thermally treated wastes contain a mixture
of α-Fe2O3 (hematite)
and γ-Fe2O3 (maghemite)
in different proportions, depending on the maximum heating temperature of
the thermal treatment. Increasing the maximum temperature the maghemite participation
is decreased through its transformation to hematite. Above 850°C hematite
is the main constituent, suggesting that thermal treatment of the wastes in
this temperature will give a product that could be used as red iron pigment. 相似文献
8.
I. P. Suzdalev Yu. V. Maksimov V. K. Imshennik S. V. Novichikhin V. V. Matveev Yu. D. Tret’yakov A. V. Lukashin A. A. Eliseev N. V. Avramenko A. A. Malygin E. A. Sosnov 《Russian Chemical Bulletin》2006,55(10):1755-1767
Nanostructures based on iron oxide clusters 1–300 nm in size were synthesized and studied. Thermodynamic models of nanocluster
nucleation resulting in the formation of both primary nanoclusters and nanocluster aggregates with the sizes up to 70–80 nm
were considered. Models of heat capacity of the nanoclusters were examined, and the twofold increase in the heat capacity
of the iron oxide clusters 2–3 nm in size compared to that of the bulk iron oxide samples was found. The size of the primary
nanoclusters and the intercluster interaction make it possible to vary the magnetic properties of the nanostructures in a
wide range from paramagnetic to magnetically ordered α-Fe2O3-γ-Fe2O3 nanostructures with the first-order magnetic phase transitions, magnetic twinning, and a strong magnetic field (10 Oe) effect
on the magnetization increase at low temperatures.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1693–1704, October, 2006. 相似文献
9.
Xiaoqi Fu Shuang Wang Qian Zhao Tingshun Jiang Hengbo Yin 《Frontiers of Chemistry in China》2011,6(3):206-212
A new kind of nonmetallic nanosensors based on surface-enhanced Raman spectroscopy (SERS) have been successfully prepared
by the assembly of α-Fe2O3 nanoparticles (NPs) onto clean quartz surface via the cross-linker of hexamethylene diisocyanate (HDI). The resultant substrates
have been characterized by electron micrographs, which show that the α-Fe2O3 NPs distribute on the modified surface uniformly with a monolayer or sub-monolayer structure. 4-mercaptopyridine (4-Mpy)
and 2-mercaptobenzothiazole (2-MBT) molecules have been used as SERS probes to estimate the detection efficiency of the α-Fe2O3 thin films. The SERS experiments show that it is possible to record high quality SERS spectra from probe molecules on the
α-Fe2O3 thin films at sub-micromolar ( < 10−6 mol/L) concentration. These results indicate that the highly ordered, uniformly roughed, highly sensitive and low-cost α-Fe2O3 thin films are excellent candidates for nonmetallic SERS-active nanosensors. 相似文献
10.
Xiaojie Zhang Wanzhong Ren Hongtao Cui 《Journal of Sol-Gel Science and Technology》2011,58(1):232-237
A general sol–gel strategy was established for the synthesis of metal ions doped γ-Fe2O3 nanoparticles with narrow particle size distribution. The unique chemistry of the route guarantees the simple preparation
procedure for the preparation of doped γ-Fe2O3 nanoparticles, which includes the boiling of the ethanolic solution of precursor salts after the addition of gelation agent,
and the following drying of the obtained sol solution. On the other hand, it guarantees the production of the nanoparticles
with nearly monodispersed state and median size of about 5 nm on an ultra large scale of about 60 g in a single reaction.
The doping of metal ions in γ-Fe2O3 allows the great promotion of phase transformation temperature from γ-Fe2O3 to α-Fe2O3. Due to the advantages of this strategy over other routes, it is very promising to be applied in the industrial production
of undoped and doped γ-Fe2O3 nanoparticles as a general route. 相似文献
11.
Diol capped γ-Fe2O3 nanoparticles are prepared from ferric nitrate by refluxing in 1,4-butanediol (9.5 nm) and 1,5-pentanediol (15 nm) and uncapped particles are prepared by refluxing in 1,2-propanediol followed by sintering the alkoxide formed. X-ray diffraction (XRD) shows that all the samples have the spinel phase. Raman spectroscopy shows that the samples prepared in 1,4-butanediol and 1,5-pentanediol and 1,2-propanediol (sintered at 573 and 673 K) are γ-Fe2O3 and the 773 K-sintered sample is Fe3O4. Raman laser studies carried out at various laser powers show that all the samples undergo laser-induced degradation to α-Fe2O3 at higher laser power. The capped samples are however, found more stable to degradation than the uncapped samples. The stability of γ-Fe2O3 sample with large particle size (15.4 nm) is more than the sample with small particle size (10.2 nm). Fe3O4 having a particle size of 48 nm is however less stable than the smaller γ-Fe2O3 nanoparticles. 相似文献
12.
采用共沉淀法,在不同煅烧温度下制备一系列Mn改性γ-Fe2O3催化剂(Fe0.7Mn0.3Oz),研究了煅烧温度对Fe0.7Mn0.3Oz催化剂低温SCR脱硝活性的影响,并借助XRD、N2吸附-脱附、EDS及SEM等手段对催化剂进行表征。结果表明,350 ℃煅烧所得Fe0.7Mn0.3Oz催化剂的低温SCR活性最佳,在70 ℃时取得92%的NOx转化率,100~200 ℃可维持100%的NOx转化率,而450 ℃煅烧所得催化剂的低温SCR活性最低;煅烧温度为350 ℃时,催化剂具有最大的比表面积和比孔容、发达的孔隙结构及适当结晶度的γ-Fe2O3,而煅烧温度为400或450 ℃时,催化剂发生烧结且有α-Fe2O3生成,不利于低温SCR反应的进行,因此,Fe0.7Mn0.3Oz催化剂的最佳煅烧温度为350 ℃。 相似文献
13.
V. V. Korolev I. M. Arefyev A. G. Ramazanova 《Journal of Thermal Analysis and Calorimetry》2008,92(3):691-695
The magnetocaloric effect (MCE) of aqua suspensions based on superfine magnetite (Fe3O4), hematite (α-Fe2O3), maghemite (γ-Fe2O3), samarium ferrite (SmFe2O4) and gadolinium ferrite (GdFe2O4) as well as of magnetite-based ferrofluids was calorimetrically determined in the range of the temperatures from 283 to 253
K. MCE has a positive magnitude for all investigated systems except a hematite-based system. For the suspensions on the basis
of MCE temperature dependence it was determined that superfine magnetite transformed into α-Fe2O3 at the temperature above 328 K in contrast to monocrystal magnetite. For aqua suspensions of samarium ferrite and gadolinium
ferrite and magnetite-based ferrofluids MCE temperature dependence has an extreme behavior which is connected with a second-order
phase transition. For the first time it is established that the magnetocaloric effect (MCE) is greatly increased when the
magnet is a nanosized material. 相似文献
14.
α-Fe2O3 films as inorganic red color filter were synthesized through a simple procedure, epoxide assisted sol–gel route. The sol
was prepared through reaction of FeCl2 in boiling ethanol solution with propylene oxide. The films were formed by the dip-coating of sol on substrate, drying and
the following annealing steps. The obtained α-Fe2O3 films were composed of homogeneous distributed α-Fe2O3 nanoparticles with size of 30–50 nm. The film shows strong absorption to the light below 600 nm and high transparency to
the red light (87% at 630 nm). As inorganic red color filter, the optic behavior of this film is nearly as same as the organic
color filter made of dye. 相似文献
15.
The reduction of α-Fe2O3 and Li0.5Fe2.5O4 by hydrogen has been studied to characterise the stages of reduction. The course of reduction as followed by TGA and M?ssbauer
spectroscopy indicates that (i) in the case of α-Fe2O3, the reduction to metallic iron goes through the intermediate formation of Fe3O4, and (ii) in the case of Li0.5Fe2.5O4 the reduction proceeds in a single step to give a mixture of LiFeO2 and Fe. 相似文献
16.
CoO-MoO3/γ-Al2O3 and NiO-MoO3/γ-Al2O3 catalysts were prepared by the reaction of α-boehmite (α-AlOOH) with MoO3 in an aqueous paste, followed by the reaction of the MoO3/α-AlOOH catalyst with Co(OH)2·CoCO3 or 2NiCO3·3Ni(OH)2·4H2O in an aqueous paste, and by subsequent drying and/or calcination. The deposited MoO3 functioned as a thermal stabilizer inhibiting the sintering of the Al2O3 phase during calcination. The deposited Co and Ni were efficient activity promoters in benzothiophene hydrodesulfurization. 相似文献
17.
Wolfgang H. Binder Harald C. Weinstabl 《Monatshefte für Chemie / Chemical Monthly》2007,36(1):315-320
The generation of superparamagnetic iron-oxide nanoparticles bearing fluorescent ligands is described. γ-Fe2O3 nanoparticles (radius ∼4 and 8 nm) bearing octylamine or oleic acid as ligands were prepared by hydrothermal synthesis starting
from Fe-cupferron and iron pentacarbonyl, respectively. Ligand exchange proceeds with 1,2-diols bearing ω-azido or ω-bromo
ligands at elevated temperatures. Subsequent nucleophilic substitution reaction, followed by 1,3-dipolar cycloaddition reactions
with 2,4,6-trinitro-1-O-propargyl-benzene yields superparamagnetic iron-oxide nanoparticles with a fluoresecent ligand on their surface. 相似文献
18.
A. R. Dinesen C. T. Pedersen C. Bender Koch 《Journal of Thermal Analysis and Calorimetry》2001,64(3):1303-1310
The thermal conversion of lepidocrocite (γ-FeOOH) into maghemite (γ-Fe2O3)and hematite (α-Fe2O3) has been studied by dynamic (DSC) and static heating experiments. Dynamic heating defines two main regions: conversion of
lepidocrocite to maghemite (endothermal signal peaking at 255°C) and conversion of maghemite to hematite (exothermal signal
peaking at 450°C). In addition, an exotherm following the lepidocrocite to maghemite endotherm is observed. The maghemite
phase appears as porous aggregates of nanocrystals characterized by an extensive spin-canting. We suggest that the additional
exotherm is associated with structural changes and a decreasing extent of spin-canting in the maghemite phase.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
19.
Ferrous gluconate dihydrate (FeC12H22O14⋅2H2O), was prepared and its thermal decomposition was studied by means of simultaneous thermal analysis, supplemented with a
two probe d.c. electrical conductivity measurements under the atmospheres of static air, dynamic air and dynamic nitrogen.
Under all the atmospheres final product was found to be α-Fe2O3 with FeO, γ-Fe2O3, Fe3O4 etc. as probable intermediates. γ-Fe2O3 was formed under the atmosphere of dynamic air containing water vapour. γ-Fe2O3 thus synthesised was characterised for its structure, morphology, thermal and magnetic behaviour.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
20.
Wolfgang H. Binder Harald C. Weinstabl 《Monatshefte für Chemie / Chemical Monthly》2007,138(4):315-320
Summary. The generation of superparamagnetic iron-oxide nanoparticles bearing fluorescent ligands is described. γ-Fe2O3 nanoparticles (radius ∼4 and 8 nm) bearing octylamine or oleic acid as ligands were prepared by hydrothermal synthesis starting
from Fe-cupferron and iron pentacarbonyl, respectively. Ligand exchange proceeds with 1,2-diols bearing ω-azido or ω-bromo
ligands at elevated temperatures. Subsequent nucleophilic substitution reaction, followed by 1,3-dipolar cycloaddition reactions
with 2,4,6-trinitro-1-O-propargyl-benzene yields superparamagnetic iron-oxide nanoparticles with a fluoresecent ligand on their surface. 相似文献