Alumina and silica based coatings with catalytical properties

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ALUMINA AND SILICA BASED SOL-GEL COATINGS WITH CATALYTIC
PROPERTIES
Maria Crişan1, Mălina Răileanu1, Silviu Preda1, Maria Zaharescu1,
Ana-Maria Kaszoni Pricop2, Elisabeth-Jeanne Popovici2, Vlastimil Matejec3,
Jan Mrazek3 and Valentin Teodorescu4
Institute of Physical Chemistry "I.G.Murgulescu”, Roumanian Academy, 202 Splaiul
Independenţei 060021, PO-Box 12-194, Bucharest, Roumania, E-mail:
[email protected]
2
“Raluca - Ripan” Institute for Research in Chemistry, 30 Fântânele, 400429 ClujNapoca, Roumania
3
Institute of Radioengineering and Electronics, AS CR Chaberska 57, 182 51, Prague
8, Czech Republic
4
National Institute for Physics of Materials, P.O. Box MG 07, Bucharest, Măgurele,
Roumania
1
The increasing interest toward sol-gel synthesis of the oxide thin films is
explained by the method’s advantages: simple and cheap technological equipment,
low temperature necessary for film consolidation leading to a material with specific
controlled porosity properties. This aspect is important for catalytic applications.
Although there are many literature data concerning the alumina and silica based solgel materials, the Mn - doped coatings with catalytic properties are not mentioned.
Our original studies refer to the synthesis of Mn - doped alumina and silica
based gels and thin films with catalytic application, using the both routes of the solgel method: alkoxide and colloidal one. The films were deposited by dipping method
using silica wafers and refractory alloy as substrates. The characterization of the films
was realized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and
spectroellipsometry (SE). The un-supported gels (obtained by the gelation of the
solutions used for the film deposition) were characterized by thermodifferential and
thermogravimetric analysis (DTA/TG), the infrared spectroscopy (IR), transmission
electron microscopy and electron diffraction (TEM and SEAD) and BET method
(adsorbtion of kripton at temperature of liquid nitrogen) for surface area and pores
volume determination. Alumina based gels have consisted from aggregates of 2-3 μm
formed by nano-particles of lamellar morphology with thickness of about 5 nm and
diameter of about 30 nm. Silica based gels show aggregates of some microns, formed
by particles of about 3-5 nm.
Mn-doped alumina and silica based un-supported gels have been tested from
catalytic properties point of view for the ozone decomposition reaction. Both types of
materials are suitable to be used in this field.
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