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1.
Nanoparticles of the spinel ferrite, Co 0.6Ni 0.4Fe 2O 4 have been synthesized by the precursor combustion technique. This synthetic route makes use of a novel precursor viz. metal fumarato hydrazinate which decomposes autocatalytically after ignition to yield nanosized spinel ferrite. The X-ray powder diffraction of the ??as prepared?? oxide confirms the formation of monophasic nanocrystalline cobalt nickel ferrite. The thermal decomposition of the precursor has been studied by isothermal, thermogravimetric and differential thermal analysis. The precursor has also been characterized by FTIR, and chemical analysis and its chemical composition has been fixed as Co 0.6Ni 0.4Fe 2(C 4H 2O 4) 3·6N 2H 4. The Curie temperature of the ??as prepared?? oxide was determined by ac susceptibility measurements. 相似文献
2.
Cobalt zinc ferrite, Co 0.8Zn 0.2Fe 2O 4, nanoparticles have been synthesized via autocatalytic decomposition of the precursor, cobalt zinc ferrous fumarato hydrazinate.
The X-ray powder diffraction of the ‘as prepared’ oxide confirms the formation of single phase nanocrystalline cobalt zinc
ferrite nanoparticles. The thermal decomposition of the precursor has been studied by isothermal, thermogravimetric and differential
thermal analysis. The precursor has also been characterized by FTIR, and chemical analysis and its chemical composition has
been determined as Co 0.8Zn 0.2Fe 2(C 4H 2O 4) 3·6N 2H 4. The Curie temperature of the ‘as-prepared oxide’ was determined by AC susceptibility measurements. 相似文献
3.
CeO 2 was synthesized by calcining Ce 2(C 2O 4) 3·8H 2O above 673 K in air. The precursor and its calcined products were characterized using thermogravimetry and differential scanning calorimetry, Fourier transform infrared spectra, X-ray powder diffraction, scanning electron microscopy, and UV–Vis absorption spectroscopy. The result showed that cubic CeO 2 was obtained when the precursor was calcined above 673 K in air for 2 h. The UV–Vis absorption spectroscopy studies showed that superfine CeO 2 behaved as an excellent UV-shielding material. The thermal decomposition of the precursor in air experienced two steps, which are: first, the dehydration of eight crystal water molecules, then the decomposition of Ce 2(C 2O 4) 3 into cubic CeO 2. The values of the activation energies associated with the thermal decomposition of Ce 2(C 2O 4) 3·8H 2O were determined based on the Starink equation. 相似文献
4.
To improve the performances of p-Dye Sensitized Solar Cell (p-DSSC) for the future, the synthesis of modified p-type nickel oxide semiconductor, commonly used as photocathode in such devices, was initiated with Ni 3O 2(OH) 4 as precursor. This specific nickel oxyhydroxide was first characterized by X-ray photo-electron spectroscopy and magnetic susceptibility measurements. Then its thermal decomposition was thoroughly studied in order to control the particles size of the as-prepared NiO nanopowders. Low temperature decomposition in air of this precursor allows the formation of Ni 1−xO nanoparticles with a large amount of Ni vacancies and specific surface areas up to 250 m 2 g −1. Its ammonolysis at 250 °C leads to nanostructured N-doped NiO (NiO:N) materials. 相似文献
5.
A good precursor is foremost in the preparation of nanosized metal or mixed metal oxides. In the present study a novel precursor,
cobalt zinc fumarato-hydrazinate Co 0.5Zn 0.5Fe 2(C 4H 2O 4) 3·6N 2H 4 has been prepared which decompose at a much lower temperature to give nanosized mixed-metal oxides. X-ray investigations,
confirms the formation of single spinel phase. The FTIR spectra show N-N stretching vibration at 965 cm −1 which confirms the bidentate bridging hydrazine. The thermal decomposition of the precursor has been studied by isothermal,
thermogravimetric and differential scanning calorimetric analysis. The precursor shows two-step dehydrazination followed by
decarboxylation to form Co 0.5Zn 0.5Fe 2O 4, the chemical analysis of the sample is corroborative of this. 相似文献
6.
The Ni-Al layered double hydroxides (LDHs) with Ni/Al molar ratio of 2, 3, and 4 were prepared by coprecipitation and treated under hydrothermal conditions at 180 °C for times up to 20 h. Thermal decomposition of the prepared samples was studied using thermal analysis and high-temperature X-ray diffraction. Hydrothermal treatment increased significantly the crystallite size of coprecipitated samples. The characteristic LDH diffraction lines disappeared completely at ca. 350 °C and a gradual crystallization of NiO-like mixed oxide was observed at higher temperatures. Hydrothermal treatment improved thermal stability of the Ni2Al and Ni3Al LDHs but only a slight effect of hydrothermal treatment was observed with the Ni4Al sample. The Rietveld refinement of powder XRD patterns of calcination products obtained at 450 °C showed a formation of Al-containing NiO-like oxide and a presence of a considerable amount of Al-rich amorphous component. Hydrothermal aging of the LDHs resulted in decreasing content of the amorphous component and enhanced substitution of Al cations into NiO-like structure. The hydrothermally treated samples also exhibited a worse reducibility of Ni 2+ components. The NiAl 2O 4 spinel and NiO still containing a marked part of Al in the cationic sublattice were detected in the samples calcined at 900 °C. The Ni2Al LDHs hydrothermally treated for various times and related mixed oxides obtained at 450 °C showed an increase in pore size with increasing time of hydrothermal aging. The hydrothermal treatment of LDH precursor considerably improved the catalytic activity of Ni2Al mixed oxides in N 2O decomposition, which can be explained by suppressing internal diffusion effect in catalysts grains. 相似文献
7.
The thermal evolution process of RuO 2–IrO 2–SnO 2
mixed oxide thin films of varying noble metal contents has been investigated
under in situ conditions by thermogravimetry-mass spectrometry (TG-MS), infrared
emission spectroscopy (IR) and cyclic voltammetry (CV). The gel-like films
prepared from aqueous solutions of the precursor compounds RuOHCl 3,
H 2IrCl 6 and Sn(OH) 2(CH 3COO) 2–xCl x on titanium metal support were heated in an atmosphere
containing 20% O 2 and 80% Ar up to 600°C. Chlorine
evolution takes place in a single step between 320 and 500°C accompanied
with the decomposition of the acetate ligand. The decomposition of surface
species formed like carbonyls, carboxylates and carbonates occurs in two stages
between 200 and 500°C. The temperature of chlorine evolution and that
of the final film formation increases with the increase of the iridium content
in the films. The anodic peak charge shows a maximum value at 18% iridium
content. 相似文献
8.
The influence of lithium oxide-doping on the thermal stability of Co 3O 4 was studied using DTA, TG, DTG and X-ray diffraction techniques. Pure and doped cobaltic oxide specimens were prepared by thermal decomposition of pure basic cobalt carbonate and the basic carbonate mixed with different proportions of LiOH, in air, at different temperatures between 500 and 1100°C.Pure Co 3O 4 was found to start partial decomposition when heated in air at 830°C yielding the CoO phase. The complete decomposition was effected by heating at 1000°C.Doping of Co 3O 4 with different proportions of Li 2O was found to much increase its thermal stability. The temperatures at which the doped oxide samples started to undergo decomposition were increased to 865, 910 and 1050°C for 0.375, 0.75 and 3% Li 2O-doped solids, respectively. The DTA revealed that the 1.5% Li 2O-doped cobaltic oxide did not undergo any thermal decomposition till 1080°C. The X-ray investigation showed that the prolonged heating of 1.5 and 3% Li 2O-doped solids at 1100°C for 36 h effected only a partial decomposition of Co 3O 4 into CoO. Heating of these solids at temperatures varying between 900 and 1100°C led also to the formation of a new lithium oxide cobaltic oxide phase, the composition of which has not yet been identified.The role of Li 2O in increasing the thermal stability of Co 3O 4 was attributed to the substitution of some of its cobalt ions by Li + ions, according to Verwey and De Boer's mechanism, leading to the transformation of some of the Co 2+ into Co 3+ ions thus increasing the oxidation state of the cobaltic oxide lattice. 相似文献
9.
The paper presents a new, non-traditional method for the synthesis of barium metaniobate, BaNb 2O 6, and of a mixed barium-strontium metaniobate, Ba 0.29Sr 0.71Nb 2O 6, through the thermal decomposition of coprecipitation products. The conditions of quantitative precipitation of the metals as niobic acid and barium or barium-strontium oxalate were established. The mechanism of thermal decomposition of the coprecipitate was deduced from differential thermal analysis and X-ray diffraction date. Barium metaniobate forms at 470°C, below the temperature required in the synthesis based upon the solid-state reaction between Nb 2O 5 and BaCO 3 (1100°C). The mixed barium-strontium compound is formed at 700°C, below the 1100°C used in the reaction between Nb 2O 5, BaCO 3 and SrCO 3. 相似文献
10.
Co 3O 4 nanorods were successfully synthesized from a single precursor via a thermal decomposition and oxidization route. The precursor used was Co(CO 3) 0.35Cl 0.20(OH) 1.10, which was prepared by a hydrothermal reaction using CoCl 2⋅6H 2O with CO(NH 2) 2 at 95–120 °C. Both the precursor and the as-prepared Co 3O 4 were characterized with XRD, TEM, SEM, TGA and XPS. The precursor, as well as Co 3O 4, was found to be composed of nanorods that were radially bunched. The Co 3O 4 nanorods obtained through a thermal treatment at 300 °C for 5 h were found to have a porous structure. 相似文献
11.
The interaction of hydrated uranium(VI) oxide UO3·2.25H2O (schoepite) with an aqueous solution of rubidium hydroxide in an autoclave at 100°C has yielded rubidium uranate Rb2(UO2)6O3(OH)8·6H2O. Composition and structure of the obtained compound have been determined by chemical analysis, IR spectroscopy, X-ray diffraction, and differential thermal analysis. The processes of its dehydration and thermal decomposition have been studied. 相似文献
12.
The mixed oxide LaNiO3 with perovskite structure was prepared by two relatively new and unconventional methods including preparation and thermal decomposition of mixed metal oxalate or carbonate precursors. The intermediates were prepared by reaction in a highly concentrated suspension (paste). The thermal decomposition conditions of these intermediates were described, and the final calcination temperatures were determined, which were done using thermal analysis methods and X-ray diffraction. During the decomposition of mixed carbonates, one-phase LaNiO3 is produced directly, and in case of decomposition of oxalates, a mixture of LaNiO3 and La2O3 is produced due to the formation of La2O2CO3 during the heating. Catalytic decomposition of nitrous oxide at high temperature (650–930 °C) and high loading (GHSV?=?350,000 h?1) has shown high LaNiO3 activity, even at lower temperatures. The results were compared with the same compound obtained by co-precipitation and by solid-state reaction. Methods of preparation based on decomposition of oxalate and carbonate intermediates lead to the preparation of materials with appropriate composition, morphology, specific surface and high catalytic activity. 相似文献
13.
The oxo-diperoxo-molibdenum(VI)-potassium oxalate, K 2[MoO(O 2) 2(C 2O 4)] was synthesized using an adapted version of the method suggested by Dengel. The thermal behavior of the synthesized complex was investigated by simultaneous thermal analysis TG/DTG/DTA, in air or nitrogen atmosphere, to identify and characterize the mass-loss decomposition processes. In addition, for the characterization of the observed decomposition steps, the FT-IR spectra for the initial complex, evolved gaseous compounds and isolated complex at 230 and 430/383 °C in air/nitrogen atmosphere, were recorded. On the 35–500 °C temperature range, the K 2[MoO(O 2) 2(C 2O 4)] complex presented three main decomposition steps, accompanied by mass-loss. The first degradation step is due to the elimination of one oxygen molecule, by the breaking of the peroxo groups, with the formation of an intermediary, like [MoO 3L]. The other two degradation steps can be attributed to the decomposition of the organic ligand, with the final formation of a stable metallic oxide. 相似文献
14.
Bi-peroxotitanate
was synthesized by a peroxo method and after thermal decomposition Bi 2Ti 2O 7
was obtained. DTA, TG and DSC curves of Bi 2[Ti 2(O 2) 4(OH) 6]5H 2O were recorded and used to determine
isothermal conditions suitable for obtaining the intermediate samples corresponding
to the phases observed during the thermal decomposition. The samples were
identified by quantitative analysis, IR spectroscopy and X-ray analysis. The
experimental results were used to propose a mechanism of thermal decomposition
of the investigated compound to a nanosized Bi 2Ti 2O 7.
The optimum conditions were also determined for obtaining Bi 2Ti 2O 7,
which is applicable for piezosensors. 相似文献
15.
A series of Fe 2- xCr xO 3( x = 0, 0.4, 0.8, 1.2, 1.6, 2.0) mixed oxides have been prepared with the chemical coprecipitation method and characterized by specific surface area, transmission electron microscopy (TEM), powder X-ray diffraction (XRD), IR and Mössbauer spectroscopy. Single-phase Fe-Cr mixed oxide nano-crystalline powders with corundum structure are obtained, and the results of the five characterization methods are well accordant with each other. Furthermore, gas-sensitive properties of the sensors made of the oxide powders have been studied. 相似文献
16.
The present study reports on a novel barium acetato-propionate complex, obtained by the reaction of barium acetate with propionic acid, used as an oxide precursor with applications in superconducting thin films deposition. The molecular structure has been determined by X-ray diffraction on single crystals and demonstrated to be [Ba 7(CH 3CH 2COO) 10(CH 3COO) 4·5H 2O]. The barium acetato-propionate is a three-dimensional channel-type polymer. The thermal decomposition of the barium precursor has been studied by simultaneous differential thermal analysis-thermogravimetry-mass spectrometry (DTA-TG-MS) in air at a heating rate of 10 °C/min. Based on these analyses, infrared spectroscopy was further used to characterize the precursor solution by the step-wise addition of the reagents. The X-ray diffraction on the precursor powder at different temperatures was performed. 相似文献
17.
Thermal decomposition of aluminum nitrate hydrate was studied by thermogravimetry, differential scanning calorimetry, and infrared spectroscopy, so that all mass losses were related to the exactly coincident endothermic effects and vibrational energy levels of the evolved gases. The process starts with the simultaneous condensation of two moles of the initial monomer Al(NO 3) 3·8H 2O. Soon after that, the resulting product Al 2(NO 3) 6·13H 2O gradually loses azeotrope HNO 3 + H 2O, then N 2O 3 and O 2 and, through the formation of Al 2O 2(NO 3) 2, is transformed into aluminum oxide. The molecular mechanics method used for comparison of the potential energies of consecutive products of thermal decomposition permits an evaluation of their structural arrangement. On the basis of the results obtained, a probable mechanism for the overall decomposition of Al(NO 3) 3·8H 2O has been proposed. 相似文献
18.
Summary This paper reports the investigation of the thermal stability of three new complexes of Cr(III) with acrylate anion, [Cr 2(C 3H 3O 2) 4(OH) 2(H 2O) 4], [Cr 3O(C 3H 3O 2) 6(C 3H 4O 2) 3](C 3H 3O 2)×5H 2O and [Cr 2(C 3H 3O 2) 5(OH)] ×2H 2O, respectively. This type of complexes is important in proper carbohydrate and lipid metabolism of mammals. The thermal decomposition steps were evidenced. The thermal transformations are complex processes according to TG and DTG curves including dehydration and oxidative degradation of acrylate ion processes. The final product of decomposition is the chromium(III) oxide. 相似文献
19.
Magnesium citrate, obtained by dissolving magnesium oxide in an aqueous solution of citric acid, turned out to be a decahydrate of the composition Mg 3(C 6H 5O 7) 2·10H 2O, which was established by the results of synchronous thermal analysis, X-ray diffraction and IR spectroscopy. It is shown that the thermal decomposition of this salt proceeds in three stages in the temperature ranges of 120–250, 250–370 and 370–550 °C to form nanocrystalline magnesium oxide with grain sizes from 7 to 23 nm. 相似文献
20.
The processes of a ultrafine Ag/ZnO mixture produced by coprecipitation from salt solutions were investigated. The coprecipitation in AgNO 3-ZnNO 3-Na 2CO 3 system was analyzed in the presence of surfactants, considering the pH value and a solution composition contribution. The optimal coprecipitation conditions were Na 2CO 3 precipitating agent excess of ~20%, providing a pH value of ~10, with subsequent thermal decomposition of the mixture at about 700 K. A thermal analysis of the precursor mixtures were carried out. The phase composition, dispersity and morphology of the precipitates were determined before and after a thermal treatment. The size decrease of the precipitated particles, as well as dispersity and distribution uniformity increase of the oxide inclusions in the target composite matrix is due to the presence of surfactants in solutions. 相似文献
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