共查询到20条相似文献,搜索用时 31 毫秒
1.
E. N. Korytkova A. S. Brovkin T. P. Maslennikova L. N. Pivovarova I. A. Drozdova 《Glass Physics and Chemistry》2011,37(2):161-171
The growth of nanotubes of the Mg3Si2O5(OH)4 composition with a chrysotile structure has been investigated under hydrothermal conditions. It has been established that
the nanotubes in the axial and radial directions grow through the step mechanism due to the recrystallization and mass transfer
of the components. The introduction of seeds considerably promotes the growth process, especially at the nanotube ends. The
evolution of chrysotile nanotubes with a variation in different physicochemical parameters of synthesis, such as the temperature,
time, NaOH concentration in the reaction medium, and introduction of seeds, has been traced. It has been demonstrated that
the controllable variation in these parameters makes it possible to perform a controlled hydrothermal synthesis of chrysotile
nanotubes with specified lengths and aspect ratios. 相似文献
2.
The filling of nanotubes of the synthetic magnesium hydrosilicate Mg3Si2O5(OH)4 with a chrysotile structure by solutions of sodium hydroxide and sodium chloride has been investigated under different temperature-time
conditions. 相似文献
3.
The influence of the thermal prehistory of precursors on the phase transformations occurring in the MgO-SiO2-H2O(NaOH) system during hydrothermal synthesis of nanotubular magnesium hydrosilicates Mg3Si2O5(OH)4 with a chrysotile structure is investigated by in situ Calvet calorimetry. It is demonstrated that the preliminary dehydration of the initial solid-phase reactants substantially affects the kinetics of their hydration and subsequent formation of nanotubes with a chrysotile structure. 相似文献
4.
T. P. Maslennikova E. N. Korytkova E. N. Gatina L. N. Pivovarova 《Glass Physics and Chemistry》2016,42(6):627-630
Nanoparticles with different morphology have been obtained by hydrothermal method in the system MgO–SiO2–TiO2–H2O. It has been found that in the investigated temperature–time interval the formation of nanotubes of hydrosilicate with the structure of chrysotile with a small amount of impurity phases predominantly takes place. 相似文献
5.
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
6.
V. Yu. Filimonov V. I. Yakovlev M. A. Korchagin M. V. Loginova A. S. Semenchina A. V. Afanas’ev 《Combustion, Explosion, and Shock Waves》2008,44(5):591-596
This paper considers the mechanisms of structure formation during gas detonation spraying of coatings of TiAl3 and Ni3Al intermetallic compounds produced under equilibrium and nonequilibrium synthesis conditions. The coating sprayed from TiAl3 has the same phase composition as the initial powder, regardless of the synthesis conditions. During spraying of Ni3Al, the structure of the coating also does not depend on the synthesis conditions and consists of two phases — Ni3Al and NiAl, with the crystal structure varying along the coating thickness. Comparative impact abrasion tests of the coatings
showed advantages of TiAl3 coatings over coatings based on Ni3Al and titanium diboride.
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Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 5, pp. 106–111, September–October, 2008. 相似文献
7.
T. P. Maslennikova E. N. Korytkova O. M. Kuznetsova L. N. Pivovarova 《Glass Physics and Chemistry》2016,42(3):288-294
The interaction of an aqueous solution of silver nitrate with Mg3Si2O5(OH)4 hydrosilicate nanotubes under atmospheric conditions at 50 and 80°C and under dynamic conditions with subsequent annealing at 300°C has been investigated. The intercalation of AgNO3 solutions into the internal channel and interlayer spaces of the nanotube structure and the crystallization of the silver particles of the spherical shapes on the nanotube surface have been established. 相似文献
8.
Nawel Ould Moussa Shinichiro Mouri Gábor Molnár Koichiro Tanaka José Antonio Real Azzedine Bousseksou 《Journal of Inorganic and Organometallic Polymers and Materials》2008,18(1):195-200
Infrared and visible light irradiation effects on the spin state of iron(II) ions have been investigated in the binuclear
molecules {[Fe(bt)(NCSe)2]2(bpym)} (4) and {[Fe(bpym)(NCSe)2]2(bpym)} (2). For compound 2 we could observe LIESST and partial reverse-LIESST effects under visible and infrared light irradiation, respectively. Compound
4 exhibits a wavelength-selective photoconversion at 10 K from the low spin (LS–LS) ground state of the binuclear molecule
to the metastable high spin (HS–HS) state under visible (785 or 532 nm) light irradiation or to the metastable HS–LS state
under infrared (1,342 nm) light irradiation. In addition we also observed the reverse (HS–HS → HS–LS) and the cascade (LS–LS → HS–LS → HS–HS)
photoconversions as well. These phenomena lead to complex and original photomagnetic behaviour due to the intramolecular magnetic
coupling.
This article is dedicated to Professor Didier Astruc in honor of his scientific achievements, with friendship and sincere
respect. 相似文献
9.
S. S. Ordan’yan D. D. Nesmelov S. V. Vikhman 《Refractories and Industrial Ceramics》2009,50(5):391-393
Experiments and calculations have been applied to the structure of the triple eutectic system SiC–W2B5–LaB6(T
eu = 1900 ± 40°C), composition in mol.%: 10 LaB6, 44 SiC, 46 W2B5, error ±2–3%, which opens up prospects for making ceramic materials for various purposes. 相似文献
10.
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
11.
This paper reports on the results of studies on the filling of nanotubes of the Mg3Si2O5(OH)4 composition with aqueous solutions of hydroxide, chloride, and nitrate of cesium under different temperature-time conditions.
It has been established that the nanotubes differently interact with solutions of different chemical nature. 相似文献
12.
The specific features of the chemical state of gold and indium oxide in Au-In2O3 (0.01–1.0 wt % Au) nanocomposites have been investigated by the methods of X-ray diffraction analysis, electron microscopy,
infrared and optical spectroscopy, electron paramagnetic resonance, and thermal analysis. Xerogels, powders, and films obtained
by the introduction of HAuCl4 into the indium hydroxide sol and thermal treatment at 50–700°C have been studied. The mutual influence of the components
on the size of the Au and In2O3 particles and the state of their surface has been established. It has been shown that the synthesis of Au-In2O3 by the sol-gel method leads to the formation of nanosized indium oxide particles with the high concentration of hydroxyl
groups on surfaces and favors the stabilization of gold in the form of nanoclusters and ion forms. 相似文献
13.
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
14.
A. G. Shmakov V. M. Shvartsberg O. P. Korobeinichev M. W. Beach T. I. Hu T. A. Morgan 《Combustion, Explosion, and Shock Waves》2007,43(5):501-508
The chemical and thermal structure of a Mache-Hebra burner stabilized premixed rich CH4/O2/N2 flame with additives of vapors of triphenylphosphine oxide [(C6H5)3PO], hexabromocyclododecane (C12H18Br6), and ethyl bromide (C2H5Br) was studied experimentally using molecular beam mass spectrometry (MBMS) and a microthermocouple method. The concentration
profiles of stable and active species, including atoms and free radicals, and flame temperature pro.les were determined at
a pressure of 1 atm. A comparison of the experimental and modeling results on the flame structure shows that MBMS is a suitable
method for studying the structure of flames stabilized on a Mache-Hebra burner under near-adiabatic conditions. The relative
flame inhibition effectiveness of the added compounds is estimated from changes in the peak concentrations of H and OH radicals
in the flame and from changes in the flame propagation velocity. The results of the investigation suggest that place of action
of the examined flame retardants is the gas phase.
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Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 5, pp. 12–20, September–October, 2007. 相似文献
15.
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
16.
E. Pousse P. A. Glaude R. Fournet F. Battin-Leclerc 《Combustion, Explosion, and Shock Waves》2010,46(2):132-139
In order to better understand the chemistry involved during the combustion of diesel fuel components, the structure of a laminar
lean premixed methane flame doped with indane has been investigated. This flame contains 7.1% (molar) of methane, 36.8% of
oxygen, and 0.90% of indane, corresponding to an equivalence ratio of 0.74 and a C9H10/CH4 ratio of 12.75%, with argon used as a dilutant. The flame has been stabilized on a burner at a pressure of 6.7 kPa, with
the gas velocity at the burner exit equal to 49.2 cm/sec at 333 K. Quantified species include usual methane combustion products
C0–C2, but also eleven C3–C5 hydrocarbons and three C1–C3 oxygenated compounds, as well as 17 aromatic products, namely benzene, toluene, phenylacetylene, styrene, ethylbenzene, xylenes,
trimethylbenzenes, ethyltoluenes, indene, methylindane, methylindene, naphthalene, phenol, benzaldehyde, and benzofuran. The
temperature has been measured by a PtRh(6%)-PtRh(30%) thermocouple settled inside the enclosure: from 800 K close to the burner
up to 2000 K in the burned gases. 相似文献
17.
The electrochemical promotion of the CO2 hydrogenation reaction on porous Rh catalyst–electrodes deposited on Y2O3-stabilized-ZrO2 (or YSZ), an O2− conductor, was investigated under atmospheric total pressure and at temperatures 346–477 °C, combined with kinetic measurements
in the temperature range 328–391 °C. Under these conditions CO2 was transformed to CH4 and CO. The CH4 formation rate increased by up to 2.7 times with increasing Rh catalyst potential (electrophobic behavior) while the CO formation
rate was increased by up to 1.7 times with decreasing catalyst potential (electrophilic behavior). The observed rate changes
were non-faradaic, exceeding the corresponding pumping rate of oxygen ions by up to approximately 210 and 125 times for the
CH4 and CO formation reactions, respectively. The observed electrochemical promotion behavior is attributed to the induced, with
increasing catalyst potential, preferential formation on the Rh surface of electron donor hydrogenated carbonylic species
leading to formation of CH4 and to the decreasing coverage of more electron acceptor carbonylic species resulting in CO formation. 相似文献
18.
Zeolite Mazzite (MAZ) analogue was synthesized directly using piperazine as a structure directing agent. The reactive gel
composition used was (5.0–7.0) piperazine:(6.0–7.0) Na2O:Al2O3:20.0SiO2:400H2O. Using this composition, the reaction time was shortened greatly to 4 days and the crystallization time was reduced as well.
The DTA data showed that piperazine, in as-synthesized zeolite omega decomposed easily. The decomposition of the piperazine
occurred at 400–480°C. NH3-TPD analysis proved that zeolite H-omega from piperazine had strong surface acidity with ammonia desorption temperature up
to 590°C. 相似文献
19.
Liangyu Gong Xiaohong Liu Linghao Su 《Journal of Inorganic and Organometallic Polymers and Materials》2011,21(4):866-870
Nickel hydroxide nanosheets were successfully synthesized by facile solvothermal method without any template. The structure
and morphology of the as-prepared sample were characterized by X-ray diffraction, Fourier transform infrared spectroscopy
and transmission electron microscopy. The observations revealed the formation of hexagonal phase β-Ni(OH)2 nanosheets with an average diameter of about 100–120 nm. Electrochemical studies were carried out using cyclic voltammetry
and galvanostatic charge–discharge tests, respectively. A maximum specific capacitance of 2,342 F g−1, which is the highest reported for a β-Ni(OH)2 electrode, could be achieved in 6 mol L−1 KOH electrolyte within the potential range of 0–0.50 V (vs. SCE) for the obtained β-Ni(OH)2 electrode at 0.4 A g−1, suggesting its potential application in the electrode material for electrochemical capacitors. 相似文献
20.
The effect of replacing lanthanum with praseodymium on the crystal chemistry parameters of solid solutions of La1 − x
Pr
x
BaCuFeO5 + δ has been investigated using X-ray powder diffraction analysis and IR spectroscopy. The thermal expansion, electroconductivity,
and thermopower of these phases have been studied in air in the temperature range 300–1100 K. The values of linear thermal
expansion coefficients (LTEC) of ceramics in different temperature ranges have been determined, and the values of electric
transfer parameters in the above oxides have been calculated. It has been established that replacing lanthanum with praseodymium
resulted in the compression of the elementary oxide unit La1 − x
Pr
x
BaCuFeO5 + δ, decrease in the content of labile oxygen in them (δ), decrease in nonmonotonic electroconductivity, increase in thermopower,
decrease in LTEC, and difficulties in charge transfer in these phases. 相似文献