Abstract isopropoxide as a precursor and Al2O3

Abstract

Al2O3-TiO2
composites can be used as thermal-resistant parts, catalysts, wear-resistant
coatings, and lubricative additives, solar cell chemical, marine industries and
humidity sensor. Titania-alumina nanocomposite will be prepared by using
different ratios of  TiO2 and
Al2O3 individually prepared by using sol-gel method. TiO2
Will be prepared by using Titaium tetra isopropoxide as a precursor and
ethanol, water as solvents and HCl.Mixture of  water and HCL will be added drop wise in the
mixture of TTIP and ehtanol. Al2O3 will be prepared by
usimg Aluminium nitrate as the starting material first aluminium nitrate and
water solution is mad and then ethanol will be added dropwise in this solution.
TiO2 Will be prepared by using Titaium tetra isopropoxide as a
precursor and Al2O3 will be prepared by usimg Aluminium
nitrate as the starting material and then TiO2-Al2O3
composite will be prepared by using mechano-chemical method. The role of alumina
content on the structural properties, phase transformation, surface area and
particle size of titania will be investigated. The samples will
be characterized by using X-Ray Diffraction (XRD), Scanning Electron Microscopy
(SEM) and UV-vis spectroscopy.

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Introduction       

Nanoparticles
and nanostructural materials have been considered an attractive family of materials
over the last decades due to their novel properties that are not present in the
bulk. The unique properties of nanomaterials result from the small sizes and
large specific surface areas. The design and fabrication of the nanostructured
materials have received considerable attention due to their interesting
physical and chemical properties, and their potential applications in industry
and technology. Nanocrystalline titanium dioxide has a widespread range of new
applications as important material in photocatalyst, solar cell, chemical, marine
industries and humidity sensor (Ahmed and Abdel-Messih, 2011). Al2O3-TiO2
composites can be used as thermal-resistant parts, catalysts, wear-resistant
coatings, and lubricative additives. However, homogeneous distribution of the
constituents Al2O3 and TiO2 remains a big challenge
to fabricate composites of high performance. There have been immense efforts to
prepare Al2O3/TiO2 mixtures, among which sol-gel
method offers great advantages of low-cost, molecular-scale mixing and
feasibility of composition and structure control (Yang et al.,
2015).

Al2O3-TiO2
nanocomposites prepared by sol-gel method to obtain highly dispersed and small
particle sizes of Al2O3. Highly ordered mesoporous Al2O3-TiO2
was employed for solar cells applications and highly efficient photocatalyst.
Nonmetalic elements and metalic elements such as Ru, Si, and Te were doped TiO2/Al2O3
composite films for environmental applications. 
TiO2-Al2O3 nanocomposites either
membrane or film were employed for photodegradation of different pollutants
such as dyes. All the prepared TiO2-Al2O3
nanocomposites photocatalysts exhibited their the superiority as efficient
photocatalysts more than pure TiO2 (Ismail et al.,
2015). Improving the antimicrobial
activity and radical scavenging ability of a textile-based nanocomposite is the
key issue in developing a good and flexible wound dressing. In this
work,flexible textile attached with Al2O3-TiO2
nanoparticles was prepared by dipping the textile in a suspension containing Al2O3-TiO2
nanoparticles. Increased antimicrobial activity measured by optical density at
600 nm recorded for textile/Al2O3-TiO2 bimetal
oxide nanocomposites showed better interaction between Al2O3
and TiO2 nanoparticles (Parham et al.,
2016).

Aims and objective

In
the present research work, TiO2-Al2O3 composite
will be prepared by using sol-gel technique using different ratios of  TiO2 and Al2O3.
Then these samples will be characterized by using X-Ray Diffraction (XRD), Scanning
Electron Microscoy (SEM) and UV-vis spectroscopy.

Review  of Literature

A
lot of work has been done on composite of TiO2-Al2O3.
Preparation of TiO2-Al2O3 by using different
techniques had been discussed by many researchers. TiO2-Al2O3
structures are used in various applications including catalysis, solar cells,
photocatalytic, and self-cleaning. TiO2-Al2O3
nano-composites can also be used as thermal resistant materials due to their
excellent thermal expansion.

An
unagglomerated, monosized A12O3-TiO2 composite
powder was prepared by the stepwise hydrolysis of titanium alkoxide in an A12O3
dispersion. Particle size was controlled by selecting the particle size of the
starting A12O3 powder TiO2 content was
determined by the amount of alkoxide hydrolyzed. A composite-powder compact
containing 50 mol% TiO2, when fired at 1350°C for 30 min, showed nearly
theoretical density with aluminum titanate phase formation. Al2O3-TiO2composite
powder can be sintered to form either an aluminum titanate or a rutile corundum
composite ceramic by controling the sintering conditions (Okamura et al.,
1986). TiO2 particles heating
such powders in air shows that 
structural behaviour is influenced by the micromorphology of the
composite particle.Transformation temperatures 
of  the  titania 
phases seem to depend upon some size parameter which would represent
their  morphology within  the 
powders. Studies performed on a series of non-equimolar Al2O3-TiO2
composite powders showed that the temperature of ?-Al2O3
formation may be decreased by ~210 °C possibly due to  a seeding effect of rutile. Pseudobrookite Al2TiO5
was never detected at ? 1300 °C in air. Transformations  of 
the  titania  phases 
are  not always  observable 
in  DTA  whereas 
they  are  readily seen 
from  a  posteriori 
recorded  X-ray  diffraction patterns (Brugger et al.,
1986). Catalyst support materials based
upon composite metal oxides often incorporate the beneficial aspects of the
constituents. For the case of TiO2-Al2O3
composites, however, it has proven difficult to retain a high anatase content
and surface area at temperatures of 900 °C and above. This work reports a
sol-gel synthesis method that solves these problems. The action of acetic acid
in the preparation mixture during sol formation and calcination, augmented by
solid solution formation between TiO2 and Al2O3
during calcinations, seems to account for these results (Subramanian et
al., 2006).

In
the present research, self-cleaning Al2O3-TiO2
thin films were successfully prepared on glass substrate using a sol–gel
technique for photocatalytic applications. We investigated the phase structure,
microstructure, adhesion and optical properties of the coatings by using XRD,
SEM, scratch tester and UV/Vis spectrophotometer. Four different solutions were
prepared by changing Al/Ti molar ratios such as 0, 0.07, 0.18 and 0.73. Glass
substrates were coated by solutions of Ti-alkoxide, Al-chloride, glacial acetic
acid and isopropanol. The obtained gel films were dried at 300 °C for 10 min
and subsequently heat-treated at 500 °C for 5min in air. The oxide thin films
were annealed at 600 °C for 60 min in air. TiO2, Ti3O5,
TiO, TiO2, ?-Al2O3 and AlTi phases were
determined in the coatings. The microstructural observations demonstrated that
Al2O3 content improved surface morphology of the films
and the thickness of film and surface defects increased in accordance with
number of dipping. It was found that the critical load values of the films with
0, 0.07, 0.18 and 0.73 Al/Ti molar ratios were found to be 11, 15, 22 and 28
mN, respectively. For the optical property, the absorption band of synthesized
powders shifted from the UV region to the visible region according to the
increase of the amount of Al dopant. The oxide films were found to be active
for photocatalytic decomposition of methylene blue (Celik et al.,
2007). Al2O3-TiO2
nanocrystalline powders were synthesized by sol–gel process. Aluminum
sec-butoxide and titanium isopropoxide chemicals were used as precursors and
ethyl acetoacetate was used as chelating agent. Thermal and crystallization
behaviors of the precursor powders were investigated by thermal
gravimetric-differential thermal analysis, Fourier-transform infrared spectrum
and X-ray diffraction. The average crystalline size of heat treated Al2O3-TiO2
powders at 1100 °C is ~100 nm. Energy dispersive x-ray EDX line scan analysis
indicates that the Al2O3 and TiO2 phases are
homogeneously distributed in the Al2O3-13 wt% TiO2
nanocrystalline powders (Chen and Jordan, 2009).

Nanostructured
Al2O3-TiO2 composite films were prepared on
glass substrates by metalorganic chemical vapor deposition (MOCVD) using
aluminum acetylacetonate and titanium tetraisopropoxide precursors.Oxygen and
argon were used as the reactive and carrier gases, respectively. Deposition
temperature (Tdep) was varied from 723 to 873 K and total pressure was kept
constant at 133–266 Pa. The formation of composite films was achieved by mixing
the precursor vapors, which were obtained by heating the aluminum and titanium
precursors at 403 and 323-353 K, respectively. The films were characterized by
XRD, SEM and TEM. The crystalline structure and the surface morphology of the
nanostructured Al2O3-TiO2 composite films were
strongly dependent on the precursor and deposition temperatures (Pérez et al., 2010). Highly ordered
mesoporous Al2O3/TiO2 was prepared by sol-gel
reaction and evaporation-induced self-assembly (EISA) for use in dye-sensitized
solar cells. The prepared materials had two-dimensional, hexagonal pore
structures with anatase crystalline phases. The average pore size of mesoporous
Al2O3/TiO2 remained uniform and in the range
of 6.33-6.58 nm. The thin Al2O3 layer was located mostly
on the mesopore surface, as confirmed by X-ray photoelectron spectroscopy
(XPS). The Al2O3 coating on the mesoporous TiO2
film contributes to the essential energy barrier which blocks the charge
recombination process in dye-sensitized solar cells.The resultant materials Al2O3/TiO2
with a highly ordered mesoporous structure to DSSC and conformed the thin Al2O3
layer improved both the pore structure and photovoltaic characteristics (Kim et al.,
2010). Composite fibers of TiO2-Al2O3
were prepared by electrospinning a sol–gel and polymer mixture to form
template polymeric fibers followed by calcination. The resulting fibers were
characterized using thermogravimetric analysis (TGA), X-ray diffraction (XRD),
diffuse reflectance ultraviolet–visible (UV-vis) spectroscopy, scanning
electron microscopy (SEM), transmission electron microscopy (TEM), X-ray energy
dispersive spectroscopy (XEDS), and X-ray photoelectron spectroscopy (XPS).
Calcination at 973 K resulted in mixture of anatase (A) titania and gamma (?)
alumina phases. We calculated a band gap energy of 3.3 eV and found the average
diameter of the resulting fibers in the 150-400 nm range. Both XEDS and XPS
reveal that fibers are predominantly made of titania (Lotus et al.,
2010).  

Al2O3-xTiO2
composite coatings were deposited onto mild steel substrates by atmospheric
plasma spraying of mixed micron-sized Al2O3 and
nano-sized TiO2 powders.Phase transformation from mainly stable ?-Al2O3
and anatase-TiO2 in the powders to predominant metastable ?-Al2O3
and rutile-TiO2 in the coatings was observed. Hardness was
found to decrease with increasing TiO2 content while fracture toughness
increased. The average wear rates of composite coatings determined by sliding
wear test were lower than that of monolithic Al2O3 coating
by approximately 40% (Dejang et al.,
2010). Nitrogen doping TiO2
and ?-Al2O3 composite oxide granules (N-TiO2/?-Al2O3)
were prepared by co-precipitation/oil-drop/calcination in gaseous NH3
process using titanium sulphate and aluminum nitrate as raw materials. After
calcination at 550 °C in NH3 atmosphere, the composite granules showed
anatase TiO2 and ?-Al2O3 phases with the
granularity of 0.5-1.0 mm. The anatase crystallite size of composite granules
was range from 3.5?25
nm calculated from XRD result. The product granules could be used as a
photocatalyst in moving bed reactor, and was demonstrated a higher
visible-light photocatalytic activity for 2,4-dichlorophenol degradation
compared with commercial TiO2. The high visible-light photocatalytic
activity might be a synergetic effect of nitrogen doping and the form of binary
metal oxide of TiO2 and ?-Al2O3 (Huang et al.,
2013). The polymer polyvinylidene
fluoride (PVDF) membranes were modified by blending with nanometer particles to
improve its hydrophilic property and anti-fouling performances in the process
of waste water treatment. The organic macromolecule composite ultrafiltration
(UF) membranes modified by the inorganic nanometer TiO2 and Al2O3
were prepared by a phase inversion process. The composite membranes
performances, such as water flux, mechanical strength, water contact angle,
retention rate, pores size and pores size distribution, were compared to those
of organic membranes. The surface and sectional structures of membranes were
observed by scanning electron microscope (Hong et al.,
2013).

In
this work, TiO2-Al2O3 nano-composite films
were deposited on glass substrates by the sol gel method. The structural and
optical properties of TiO2-Al2O3 nanocomposite
films were characterized for different Al2O3:TiO2
volume ratio in TiO2-Al2O3 solution. The
crystal size of TiO2 nanoparticles in TiO2-Al2O3
nanocomposite films was determined for the different Al2O3:TiO2
volume ratios. Band gap energy values of the films were controlled by changing
Al2O3:TiO2 ratios. The properties of TiO2-Al2O3
nano-composite films were characterized by X-ray diffraction (XRD), atomic force
microscopy (AFM), ultraviolet–visible spectroscopy (UV-vis), scanning electron
microscopy (SEM), spectrophotometer (Perkin Elmer), and Fourier transform
infrared spectroscopy (FTIR). SEM results showed flower-like TiO2-Al2O3
nano-composite films (Akkaya Arier and Tepehan, 2014). Titanium
dioxide (TiO2) is usually introduced into dielectric layer of
aluminum electrolytic capacitor to enhance capacitance performance via forming
Al2O3-TiO2composite film. However, there is a
big obstacle caused by high crystallization temperature of TiO2 to
capacitance enhancement. In present work, a facile route was proposed to
synthesize crystalline TiO2 with the size of 3-10 nm at room temperature
using lactic acid (LA) and acetylacetone (Acac) as double chelators. After
being introduced into the surface of etched aluminum foils as dielectric layer,
TiO2 boosted the specific capacitance by about 24% compared to that
without TiO2, and about 11% compared to that with TiO2
using lactic acid as only chelator (Du et al.,
2015).

Equimolar
Al2O3-TiO2 composite powders were  prepared via controlled  hydrolysis 
of organo-metallic precursors,sometimes in the presence of submicrometre
commercial ?-Al2O3 or anatase- The Microstructure and
Morphology of 70% TiO2-30% Al, 70% TiO2-30% Al2O3,
55% TiO2 – 45% Al and 55% TiO2-45% Al2O3
composite powders were prepared by Smart Mini Ball Miller. They are
characterized by XRD, SEM, EDAX, FTIR and TG/DSC. The XRD results showed that
composite powders were mainly in the amorphous anatase phase with high
crystallinity. The SEM study of composite powders reveals the average particle
size is 100±20nm. In FTIR, peaks observed at around 460 cm-1to 560
cm-1. The peaks at Ti-O-Ti bond and TiO2 lattice in FTIR
spectra of TiO2-Al and TiO2-Al2O3 composite
powders confirm the formation of TiO2 based compound in the
composite powders. The TG curve of 55% TiO2-0- -045% Al2O3
showed weight loss where as that of 55% TiO2-45%Al showed weight
gain and DSC curve showed formation and decomposition of composite powders (Mahalingam et
al., 2017). The present investigation reveals
the effect of processing parameters on the properties of  Al2O3-TiO2
nanocomposites.A polymer-assisted co-precipitation route has been employed to
synthesize Al2O3-TiO2 nanoparticles. Thermal
behaviour of the prepared powder samples have been studied using differential
scanning calorimeter/thermal gravimetric analysis and dilatometer. Formation of
aluminium-titanate (Al2TiO5) phase has been confirmed
using X-ray diffraction analysis. Al2O3-TiO2
nanocomposite powder can be sintered at 1650?C with more than 96% of
relative density. Phase analysis of sintered sample shows formation of Al2TiO5
phase (Singh et al.,
2017).

Materials and methods

Al2O3
and TiO2 will be prepared individually by the Sol-gel method
and
then
mixing
the different ratio Of  TiO2 and
Al2O3. Al2O3 nanoparticles will synthesize by
using ethanol solution of aluminum nitrate. At start Al(NO3)3.9H2O
was completely dissolved in pure water of ethanol solution will add drop by
drop to the solution at 800 °C. The white product will evaporated for 3 hours
and cool to room temperature then finally calcined at 500 °C for 5 Hours.
TiO2
will be prepared by employing tetraisopropoxide (TiOCH(CH3)24;
TIP) as a starting precursor. Ethanol and water will be employed as solvents,
and HCl as an acidic catalyst. Using a sol-gel method, TTIP will be  ?rst dissolved in ethanol. The mixture of
distilled water and HCl will  be then
added dropwise under vigorous stirring at room temperature. The mixture will
further stirred for 3h, and the obtained gels will centrifuged, washed to remove
excess reactants and catalyst, and dried at 80°C for 24 h. Following the drying
process in the oven, the samples will becalcined at 500°C for 3 h at a heating
rate of 5°C/min. After preparing both TiO2 and Al2O3
individually prepare Al2O3-TiO2 composite
by using different ratios. Different ratios i.e 30% Al2O3
and 70%  TiO2, 60% Al2O3
and 40% TiO2, 90% Al2O3 and 10% TiO2
 will prepared by mechano chemical
method (Rajender et al., 2016).
The
structural analysis of the samples was conducted by an X-ray Diffraction (XRD) system.
The morphology of the samples was studied by scanning electron microscopy
(SEM).The UV  spectra of the samples were
generated by a UV-Visible double-beam spectrophotometer and  used to calculate  their 
band gap (Alivisatos et al.,
2004).