32 research outputs found
Современные концепции управления высшим учебным заведением
Целью и задачами статьи является исследование современных подходов к управлению вузом, их
критический анализ и возможность оптимизации процессов деятельности вуза
Tungsten Doped TiO2 with Enhanced Photocatalytic and Optoelectrical Properties via Aerosol Assisted Chemical Vapor Deposition
Tungsten doped titanium dioxide films with both transparent conducting oxide (TCO) and photocatalytic properties were produced via aerosol-assisted chemical vapor deposition of titanium ethoxide and dopant concentrations of tungsten ethoxide at 500 °C from a toluene solution. The films were anatase TiO2, with good n-type electrical conductivities as determined via Hall effect measurements. The film doped with 2.25 at.% W showed the lowest resistivity at 0.034 Ω.cm and respectable charge carrier mobility (14.9 cm(3)/V.s) and concentration (×10(19) cm(-3)). XPS indicated the presence of both W(6+) and W(4+) in the TiO2 matrix, with the substitutional doping of W(4+) inducing an expansion of the anatase unit cell as determined by XRD. The films also showed good photocatalytic activity under UV-light illumination, with degradation of resazurin redox dye at a higher rate than with undoped TiO2
Synthesis optimization of carbon-supported ZrO2 nanoparticles from different organometallic precursors
We report here the synthesis of carbon-supported ZrO2 nanoparticles from zirconium oxyphthalocyanine (ZrOPc) and acetylacetonate [Zr(acac)4]. Using thermogravimetric analysis (TGA) coupled with mass spectrometry (MS), we could investigate the thermal decomposition behavior of the chosen precursors. According to those results, we chose the heat treatment temperatures (THT) using partial oxidizing (PO) and reducing (RED) atmosphere. By X-ray diffraction we detected structure and size of the nanoparticles; the size was further confirmed by transmission electron microscopy. ZrO2 formation happens at lower temperature with Zr(acac)4 than with ZrOPc, due to the lower thermal stability and a higher oxygen amount in Zr(acac)4. Using ZrOPc at THT C900 °C, PO conditions facilitate the crystallite growth and formation of distinct tetragonal ZrO2, while with Zr(acac)4 a distinct tetragonal ZrO2 phase is observed already at THT C750 °C in both RED and PO conditions. Tuning of ZrO2 nanocrystallite size from 5 to 9 nm by varying the precursor loading is also demonstrated. The chemical state of zirconium was analyzed by X-ray photoelectron spectroscopy, which confirms ZrO2 formation from different synthesis routes
Influence of the Reaction Temperature on the Nature of the Active and Deactivating Species During Methanol-to-Olefins Conversion over H‑SAPO-34
The selectivity toward lower olefins
during the methanol-to-olefins
conversion over H-SAPO-34 at reaction temperatures between 573 and
773 K has been studied with a combination of operando UV–vis
diffuse reflectance spectroscopy and online gas chromatography. It
was found that the selectivity toward propylene increases in the temperature
range of 573–623 K, while it decreases in the temperature range
of 623–773 K. The high degree of incorporation of olefins,
mainly propylene, into the hydrocarbon pool affects the product selectivity
at lower reaction temperatures. The nature and dynamics of the active
and deactivating hydrocarbon species with increasing reaction temperature
were revealed by a non-negative matrix factorization of the time-resolved
operando UV–vis diffuse reflectance spectra. The active hydrocarbon
pool species consist of mainly highly methylated benzene carbocations
at temperatures between 573 and 598 K, of both highly methylated benzene
carbocations and methylated naphthalene carbocations at 623 K, and
of only methylated naphthalene carbocations at temperatures between
673 and 773 K. The operando spectroscopy results suggest that the
nature of the active species also influences the olefin selectivity.
In fact, monoenylic and highly methylated benzene carbocations are
more selective to the formation of propylene, whereas the formation
of the group of low methylated benzene carbocations and methylated
naphthalene carbocations at higher reaction temperatures (i.e., 673
and 773 K) favors the formation of ethylene. At reaction temperatures
between 573 and 623 K, catalyst deactivation is caused by the gradual
filling of the micropores with methylated naphthalene carbocations,
while between 623 and 773 K the formation of neutral poly aromatics
and phenanthrene/anthracene carbocations are mainly responsible for
catalyst deactivation, their respective contribution increasing with
increasing reaction temperature. Methanol pulse experiments at different
temperatures demonstrate the dynamics between methylated benzene and
methylated naphthalene carbocations. It was found that methylated
naphthalene carbocations species are deactivating and block the micropores
at low reaction temperatures, while acting as the active species at
higher reaction temperatures, although they give rise to the formation
of extended hydrocarbon deposits
The relationship between individual, physical and psychosocial risk factors with musculoskeletal disorders and related disabilities in flight security personnel
Gamma-radiation effects on the reduction of hematite to iron in the graphite-iron(III) oxide system
Graphene Oxide as Support for Layered Double Hydroxides: Enhancing the CO<sub>2</sub> Adsorption Capacity
Layered double hydroxides (LDHs) show great potential
as CO<sub>2</sub> adsorbent materials, but require improvements in
stability
and CO<sub>2</sub> adsorption capacity for commercial applications.
In the current study, graphene oxide provides a light-weight, charge-complementary,
two-dimensional (2D) material that interacts effectively with the
2D LDHs, in turn enhancing the CO<sub>2</sub> uptake capacity and
multicycle stability of the assembly. As a result, the absolute capacity
of the LDH was increased by 62% using only 7 wt % graphene
oxide (GO) as a support. The experimental procedure for the synthesis
of the materials is based on a direct precipitation of the LDH nanoparticles
onto GO followed by a structural and physical characterization by
electron microscopy, X-ray diffraction, thermogravimetric analysis,
and Brunauer–Emmett–Teller (BET) surface area measurements.
Detailed titration confirmed the compatibility of the surface chemistry.
After thermal decomposition, mixed metal oxides (MMOs) are obtained
with the basic sites required for the CO<sub>2</sub> adsorption. A
range of samples with different proportions of GO/MMO were prepared,
fully characterized, and correlated with the CO<sub>2</sub> sorption
capacity, established via TGA
Graphene-oxide-supported CuAl and CoAl layered double hydroxides as enhanced catalysts for carbon-carbon coupling via Ullmann reaction
Two efficient catalyst based on CuAl and CoAl layered double hydroxides (LDHs) supported on graphene oxide (GO) for the carbon-carbon coupling (Classic Ullmann Homocoupling Reaction) are reported. The pure and hybrid materials were synthesised by direct precipitation of the LDH nanoparticles onto GO, followed by a chemical, structural and physical characterisation by electron microscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), surface area measurements and X-ray photoelectron spectroscopy (XPS). The GO-supported and unsupported CuAl-LDH and CoAl-LDH hybrids were tested over the Classic Ullman Homocoupling Reaction of iodobenzene. In the current study CuAl- and CoAl-LDHs have shown excellent yields (91% and 98%, respectively) at very short reaction times (25 min). GO provides a light-weight, charge complementary and two-dimensional material that interacts effectively with the 2D LDHs, in turn enhancing the stability of LDH. After 5 re-use cycles, the catalytic activity of the LDH/GO hybrid is up to 2 times higher than for the unsupported LDH