共查询到20条相似文献,搜索用时 31 毫秒
1.
I. A. Zvereva A. M. Sankovich A. B. Missyul’ V. L. Ugolkov 《Glass Physics and Chemistry》2010,36(2):209-216
The processes of phase formation in the Nd2O3-TiO2-Na2CO3 system have been investigated in the temperature range 500–1100°C. The mechanism of the high-temperature solid-phase reaction
of formation of the complex oxide Na2Nd2Ti3O10 has been studied. It has been established that the Na2Nd2Ti3O10 compound is formed from the intermediate product Na0.5Nd0.5TiO3 with a perovskite structure in the temperature range 830–890°C and from the NaNdTiO4 oxide with a perovskite-like layered structure in the temperature range 960–1100°C. 相似文献
2.
The hydrogel of the mixed oxide Al2O3-30% Y0.1Zr0.9O2 was prepared by precipitation of ammonia from a water-alcohol mixture (1 : 5). The Al2O3-30% Y0.1Zr0.9O2 compound thus synthesized was characterized using differential scanning calorimetry, transmission electron microscopy, and
the BET adsorption method. The obtained sample consisted of spherical particles with an average size of 16–20 nm and a specific
surface area of 167 m2/g. The Al2O3-30% Y0.1Zr0.9O2 powder was pressed at 300 MPa and then calcinated at 1600°C for 2 h in air. The topographic and structural features of the
prepared ceramics were determined using atomic force microscopy and X-ray electron probe microanalysis. The porosity, the
Vickers microhardness, and the tensile strength were determined by mercury porometry. 相似文献
3.
In this paper, solvothermal synthesis of submicron nanocrystalline Y2O3: Eu particles with and without surface modifier (β-alanine and Tween-80) is investigated. X-ray diffraction ananlysis confirms
the one-step formation of Y2(OH)5NO3H2O phase during solvothermal process and its conversion to Y2O3: Eu after heat treatment at 600 °C. Fourier transformation infrared spectroscopy showed that C=C, C–C and C–H peaks are corresponded
to the surface modifiers i.e. tween-80 and β-alanine. Scanning electron microscopy and transmission electron microscopy images
also showed that the modifier results in the particle morphology improvement from sheet-like to submicron spherical particles.
Photoluminescence experiments indicated that the emission intensity increases due to the morphology modification. 相似文献
4.
Co3O4 nanorods have been successfully synthesized by thermal decomposition of the precursor prepared via a facile and efficient
microwave-assisted hydrothermal method, using cetyltrimethylammonium bromide (CTAB) with ordered chain structures as soft
template for the first time. The obtained Co3O4 was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM),
and electrochemical measurements. The results demonstrate that the as-synthesized nanorods are single crystalline with an
average diameter of about 20 to 50 nm and length up to several micrometers. Preliminary electrochemical studies, including
cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) measurements, are
carried out in 6 M KOH electrolyte. Specific capacitance of 456 F g−1 for a single electrode could be achieved even after 500 cycles, suggesting its potential application in electrochemical capacitors.
This promising method could provide a universal green chemistry approach to synthesize other low-cost and environmentally
friendly transition metal hydroxide or oxide. 相似文献
5.
The Sb2O3 doping lead-free glass in Bi2O3-B2O3-BaO ternary system were prepared in the composition of several different subsystem, and the glass powder was produced through
the process of water quenching. Glass transition temperatures (T
g
), glass soften temperatures(T
s
), the volume resistivity (ρ) in the temperature range of 80–200°C, and linear thermal coefficients of expansion in the temperatures
range of 25–300°C (α25–300) were measured for subsystems along with the different ratio of Bi2O3, B2O3 and BaO. For these subsystems, T
g
ranged from 458 to 481°C, and T
s
ranged from 490 to 512°C, both decreasing with the increasing of Bi2O3/B2O3 ratio, and increasing with the increasing of BaO/B2O3 ratio. The measured α25–300 ranged from 65.3 to 76.3 × 10−7 K−1, with values increasing with increasing Bi2O3/B2O3 and BaO/B2O3 ratio. The volume resistivity remains at a high standards, which may caused by it’s non-alkali composition, and it fluctuated
from 1013 to 1011 Ω cm with the temperature varied from 80–200°C. The structure of Bi2O3-B2O3-BaO ternary leadfree glass system was mearsured by FT-IR. The IR studies indicate that these glasses are made up of [BiO6], [BO3], and [BO4] basic structural units, and it appears that Ba2+ acts as a glass-modifier in this ternary system, but the Bi3+ has entered the glass network when it is in relative high content so as to change the α25–300, T
s
and T
g
. 相似文献
6.
Mohammad Sadegh Yazdan Parast Ali Morsali 《Journal of Inorganic and Organometallic Polymers and Materials》2011,21(2):365-368
An indium(III) three-dimensional coordination framework, [In2(OH)3(O4C8H4)1.5]
n
(1), was synthesized by hydrothermal method and characterized by elemental analyses, X-ray powder diffraction (XRD) and IR spectroscopy.
Indium(III) oxide nanoparticles was prepared by direct thermal decomposition of 1 at 450 °C in air. The indium(III) oxide nanoparticles were characterized by scanning electron microscopy, X-ray powder diffraction
(XRD) and energy-dispersive X-ray analysis (EDAX). This study demonstrates the coordination polymer frameworks may be suitable
precursors for a simple one-pot preparation of nanoscale metal oxide materials with different and interesting morphologies. 相似文献
7.
V. A. Sokolov T. Ya. Malysheva M. D. Gasparyan 《Refractories and Industrial Ceramics》2008,49(2):146-148
Details are given of the synthesis and testing of flux-cast refractory materials in the alumina-rich region of the Al2O3-MgO-B2O3 system; XRD and petrography indicate that the main structure-forming phases are corundum and magnesian spinel. In subordinate
amounts there are the boroaluminate 9Al2O3·2B2O3 and the previously unknown compound 4Al2O3·MgO·2B2O3, whose composition has been established by microprobe analysis. Corrosion tests showed that three-component systems containing
magnesium and boron oxides at levels of 5–10% do not increase the corrosion resistance of refractories in molten sodium-calcium-silicate
glass and electrovacuum borosilicate glass.
__________
Translated from Novye Ogneupory, No. 3, pp. 161–163, March, 2008. 相似文献
8.
Poly(acrylic acid-co-styrene)/Fe3O4 nanocomposites were prepared using poly(acrylic acid-co-styrene) (P(AA-co-St)) and nano-Fe3O4 particles. The resultant materials were characterized by transmission electron microscope (TEM), Fourier transform infrared
(FTIR), thermogravimetric analysis (TGA), advanced rheology expand system and superconducting quantum interference device
(SQUID) magnetometer. The diameter of the magnetic particles was around 3–14 nm. The experimental results reveal that the
acrylic acid segment of P(AA-co-St) can react with nano-Fe3O4. With increasing reaction time the storage modulus, loss modulus, complex viscosity and shear stress of the P(AA-co-St)/Fe3O4 ethanol suspension were increased, and the suspension changed from liquid-like behavior to gel-like behavior for the reaction
between P(AA-co-St) and Fe3O4, as found during the rheology measurements. The thermal stability of P(AA-co-St) decreased with the addition of nano-Fe3O4, and the nanocomposites exhibited superparamagnetic properties above the blocking temperature. 相似文献
9.
A. Katsaounis 《Journal of Applied Electrochemistry》2008,38(8):1097-1110
The origin of the effect of non-faradaic electrochemical modification of catalytic activity (NEMCA) or Electrochemical Promotion
was investigated via temperature-programmed-desorption (TPD) of oxygen, from polycrystalline Pd films deposited on 8 mol%Y2O3–stabilized–ZrO2 (YSZ), an O2− conductor, under high-vacuum conditions and temperatures between 50 and 250 °C. Oxygen was adsorbed both via the gas phase
and electrochemically, as O2−, via electrical current application between the Pd catalyst film and a Au counter electrode. Gaseous oxygen adsorption gives
two adsorbed atomic oxygen species desorbing at about 300 °C (state β1) and 340–500 °C (state β2). The creation of the low temperature peak is favored at high exposure times (exposure >1 kL) and low adsorption temperatures
(Tads < 200 °C). The decrease of the open circuit potential (or catalyst work function) during the adsorption at high exposure times,
indicates the formation of subsurface oxygen species which desorbs at higher temperatures (above 450 °C). The desorption peak
of this subsurface oxygen is not clear due to the wide peaks of the TPD spectra. The TPD spectra after electrochemical O2− pumping to the Pd catalyst film show two peaks (at 350 and 430 °C) corresponding to spillover Oads and
according to the reaction:
The formation of the spillover oxygen species is an intermediate stage before the formation of the atomic adsorbed oxygen, Oads. Mixed gaseous and electrochemical adsorption was carried out in order to simulate the Electrochemical Promotion conditions.
The initial surface coverage with oxygen from the gas phase plays a very important role on the high or low effect of polarization.
In general mixed adsorption leads to much higher oxygen coverages compare with that observed either under gaseous or electrochemical
adsorption. The binding strength of the atomic adsorbed oxygen (state β2) was investigated as a function of applied potential. It was found that the binding energy decreases linearly with increasing
catalyst potential and work function. Similar behavior has been observed for oxygen adsorption on Pt, Ag and Au deposited
on YSZ in previous studies. 相似文献
10.
V. I. Strakhov I. V. Ivanova A. I. Arsirii K. Velkova V. P. Migal' S. I. Gershkovich 《Refractories and Industrial Ceramics》2005,46(5):322-324
Data on interactions in the ZrO2 - Fe2O3 system stabilized by oxides in a high-temperature form at 1750°C are obtained. Of all zirconia-based compositions, only magnesium-zirconium
cubic solid solution enters into an active reaction with Fe2O3 to yield MgFe2O4. The solid solutions formed by ZrO2 with oxides of yttrium, neodymium, and calcium resist degradation by attack from Fe2O3; part of iron oxide undergoes dissolution in cubic ZrO2.
__________
Translated from Novye Ogneupory, No. 9, pp. 40 – 43, September, 2005. 相似文献
11.
Synthetic spinels of the system MgO-Cr2O3-Al2O3-Fe2O3 are considered and the desirability of organizing their production for the refractory industry is demonstrated.
Translated from Novye Ogneupory, No. 6, pp. 32–35, June 2008. 相似文献
12.
I. Ya. Mittova E. V. Tomina A. A. Lapenko B. V. Sladkopevtsev 《Glass Physics and Chemistry》2011,37(2):230-234
The specific features of the interaction of vanadium(V) oxide nanofilms with the surface of gallium arsenide and indium phosphide
semiconductors under thermal oxidation conditions have been considered. The kinetics and mechanism of thermal oxidation of
GaAs and InP with deposited V2O5 layers 15 and 25 nm in thickness have been studied. It has been revealed that vanadium(V) oxide exerts a specific effect
on the oxidation of gallium arsenide and indium phosphide as compared to other d-metal oxides. It has been established that the oxidation occurs with the formation of a phase predominantly consisting of
indium phosphates or gallium arsenates and intermediate products based on vanadium compounds in different oxidation states.
Schemes have been proposed for the development of the oxidation processes with due regard for the chemical nature of vanadium(V)
oxide. 相似文献
13.
The nanosized Mn3O4 particles were prepared by microwave-assisted reflux synthesis method. The prepared sample was characterized using various techniques such as X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), Raman analysis, and transmission electron microscopy (TEM). Electrochemical properties of Mn3O4 nanoparticles were investigated using cyclic voltammogram (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge analysis in different electrolytes such as 1 M KCl, 1 M Na2SO4, 1 M NaNO3, and 6 M KOH electrolytes. XRD pattern reveals the formation of single-phase Mn3O4 nanoparticles. The FT-IR and Raman analysis also assert the formation of Mn3O4 nanoparticles. The TEM image shows the spherical shape particles with less than 50 nm sizes. Among all the electrolytes, the Mn3O4 nanoparticles possess maximum specific capacitance of 94 F g−1 in 6 M KOH electrolyte calculated from CV. The order of capacitance obtained by various electrolytes is 6 M KOH > 1 M KCl > 1 M NaNO3 > 1 M Na2SO4. The EIS and galvanostatic charge–discharge results further substantiate with the CV results. The cycling stability of Mn3O4 electrode reveals that the prepared Mn3O4 nanoparticles are a suitable electrode material for supercapacitor application. 相似文献
14.
Jae Hyun Koh Ara Cho Sang-il Lee Sang Heup Moon 《Korean Journal of Chemical Engineering》2009,26(4):999-1003
Unsupported MoS2 particles, which were produced in the preparation of MoS2/Al2O3 using a sonochemical method, were successfully separated from the prepared sample catalyst by adding oleylamine as an agent
for dispersing the unsupported particles. The fraction of the unsupported MoS2, which was estimated based on Mo balance, varied between 0.03 and 0.4, independent of the Mo loading levels investigated
(6–54 wt% of Mo). The activity of the unsupported MoS2 for the hydrodesulfurization of dibenzothiophene was nearly the same as that of the Al2O3-supported MoS2, indicating that the activity of the prepared catalyst was not affected by the presence of the unsupported MoS2 particles. 相似文献
15.
S. O. Soloviev 《Catalysis in Industry》2012,4(1):1-10
The catalytic properties of Ni/Al2O3 composites supported on ceramic cordierite honeycomb monoliths in oxidative methane reforming are reported. The prereduced
catalyst has been tested in a flow reactor using reaction mixtures of the following compositions: in methane oxidation, 2–6%
CH4, 2–9% O2, Ar; in carbon dioxide and oxidative carbon dioxide reforming of methane, 2–6% CH4, 6–12% CO2, and 0–4% O2, and Ar. Physicochemical studies include the monitoring of the formation and oxidation of carbon, the strength of the Ni-O
bond, and the phase composition of the catalyst. The structured Ni-Al2O3 catalysts are much more productive in the carbon dioxide reforming of methane than conventional granular catalysts. The catalysts
performance is made more stable by regulating the acid-base properties of their surface via the introduction of alkali metal
(Na, K) oxides to retard the coking of the surface. Rare-earth metal oxides with a low redox potential (La2O3, CeO2) enhance the activity and stability of Ni-Al2O3/cordierite catalysts in the deep and partial oxidation and carbon dioxide reforming of methane. The carbon dioxide reforming
of methane on the (NiO + La2O3 + Al2O3)/cordierite catalyst can be intensified by adding oxygen to the gas feed. This reduces the temperature necessary to reach
a high methane conversion and does not exert any significant effect on the selectivity with respect to H2. 相似文献
16.
N. G. Tyurnina O. L. Belousova A. I. Domanskii L. A. Doronina V. L. Ugolkov 《Glass Physics and Chemistry》2010,36(3):294-303
The glass formation region in the SrO-B2O3-SiO2 system has been refined. The order of formation of crystalline phases in the system has been investigated at SrO contents
of 50–75 mol %. It has been demonstrated that, at low temperatures, the 2SrO · SiO2 and 3SrO · B2O3 phases crystallize first irrespective of the composition. The congruent melting temperature of the 3SrO · B2O3 · SiO2 compound is determined to be 1180 ± 10°C. The triangulation previously performed for the SrO-B2O3-SiO2 system in the concentration range 50–75 mol % SrO has been confirmed. 相似文献
17.
In this study, 10B2O3/polyimide (PI) hybrid materials were synthesized with the aim to improve their thermal stability and neutron shielding properties.
3,3′-Diaminodiphenyl sulfone (DADPS) reacted with 3,3′,4,4′-benzophenonetetracarboxylic dianhydride (BTDA) in N-methyl-2-pyrrolidone (NMP) and mixed with amine functionalized 10B2O3 to prepare a series of poly (amic acid), meanwhile, corresponding PIs were obtained via the thermal imidization procedures.
The morphologies and structures of the prepared hybrid materials were characterized by scanning electron microscopy (SEM)
and Fourier transform infrared spectroscopy (FT-IR). The thermooxidative and flame retardancy properties of the PI films were
examined by thermogravimetric analysis (TGA) and limiting oxygen ındex (LOI). The experimental results showed that as the
amount of functionalized 10B2O3 was increased, flame retardant properties of the hybrid films were increased. Hybrid materials were also irradiated with
thermal neutrons. The neutron shielding properties increasing depends on the amount and the distribution of the 10B isotope. 相似文献
18.
Abstract
Nanosized CexM1−xO2−δ (M = Zr, Hf, Tb and Pr) solid solutions were prepared by a modified coprecipitation method and thermally treated at different temperatures from 773 to 1073 K in order to ascertain the thermal behavior. The structural and textural properties of the synthesized samples were investigated by means of X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), BET surface area, X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy (RS) techniques. The catalytic efficiency has been performed towards oxygen storage/release capacity (OSC) and CO oxidation activity. The characterization results indicated that the obtained solid solutions exhibit defective cubic fluorite structure. The solid solutions of ceria–hafnia, ceria–terbia and ceria–praseodymium exhibited good thermal stability up to 1073 K. A new Ce0.6Zr0.4O2 phase along with Ce0.75Zr0.25O2 was observed in the case of ceria–zirconia solid solution due to more Zr4+ incorporation in the ceria lattice at higher calcination temperatures. The reducibility of ceria has been increased upon doping with Zr4+, Hf4+, Tb3+/4+ and Pr3+/4+ cations. This enhancement is more in case of Hf4+ doped ceria. Among various solid solutions investigated, the ceria–hafnia combination exhibited better OSC and CO oxidation activity. The high efficiency of Ce–Hf solid solution was correlated with its superior bulk oxygen mobility and other physicochemical characteristics. 相似文献19.
L. A. Angolenko G. D. Semchenko E. E. Starolat S. A. Savina S. V. Tishchenko V. V. Povshuk 《Refractories and Industrial Ceramics》2010,51(4):274-278
Comparative characteristics are presented for the physicomechanical properties and oxidation resistance of refractory materials
of Al2O3–Si3N4–C composition based on an ACPB for the original materials (fired at 1400°C) and after impregnation with a sol-gel composition
and heat treatment at 800°C. Areduction in material porosity, increase in strength and reduction in carbon burn-off are due
to development of a glassy phase in the pore space and on graphite flakes due to SiO2formation with thermal destruction of the organosilicon substance. 相似文献
20.
Seung-Chan Baek Jong-Wook Bae Joo Yeong Cheon Ki-Won Jun Kwan-Young Lee 《Catalysis Letters》2011,141(2):224-234