6.1.2.7 The Sonochemical Synthesis of Mixed Oxides
In addition to the above reported synthesis of ferrites our search has revealed
that aluminates [119], nickelates [120], and manganates [121], have also been
prepared by the sonochemical method. Nanosized nickel aluminate spinel particles
have been synthesized [119] with the aid of ultrasound radiation by a precursor
approach. Sonicating an aqueous solution of nickel nitrate, aluminum nitrate,
and urea yields a precursor which, on heating at 950
C for 14 h yields nanosized NiAl 2 O 4 particles with a size of ca. 13 nm and with a surface area of about
108 m
2 g
À1 .
Nanostructured LaNiO 3 was prepared by co-precipitation under ultrasonic radiation [120]. Using various characterization methods and evaluation of catalytic
activity, the effects of ultrasound on the structural properties and catalytic activity
of LaNiO 3 were studied. The TEM showed that the ultrasound could cause a decrease in the particle size. The average particle size of LaNiO 3 prepared by sonochemistry is 20 nm. The specific surface area of LaNiO 3 is 11.27 m
2 g
À1 . Ultrasound could lead to increased surface oxide content and surface crystal oxygen
vacancies. The TPR result showed that the LaNiO 3 prepared by sonochemistry has
a lower reduction temperature and a higher ratio of surface oxygen to crystal oxygen. The evaluation of catalytic activity showed that ultrasound could increase the
catalytic activity of LaNiO 3 for NO decomposition.
Lanthanum strontium manganate, known also as LSM, is known for its magnetoresistance properties, and is also used in solid oxide fuel cells (SOFC). Sonochemistry was used for its preparation [121]. Electron magnetic resonance (EMR)
spectra of nanosized sonochemically sintered powders of La 0:7 Sr 0:3 MnO 3 (annealed, T C ¼ 340 K) were studied.
6.1.2.8 The Sonochemical Synthesis of Nanosized Hydroxides
The synthesis of nanosized a-nickel hydroxide has been reported by two groups
[122, 123]. The first reported reaction prepared nanosized a-nickel hydroxide with
an interlayer spacing of 7.2 A ˚ . The synthesized hydroxide was found to possess
good stability in a KOH medium, and the material might be interesting from the
application point of view in secondary alkaline batteries. The second synthesis
prepared nanocrystalline a-Ni(OH) 2 by an ultrasonic precipitation/stirring method
[123]. Compared with the sample prepared without ultrasonic stirring, the crystal
structure of the a-phase sample has been changed from the b-phase. The crystalline size of the sample is about 20 nm, which is smaller than the sample produced
without ultrasonic stirring (70 nm).
Cobalt hydroxide with an interlayer spacing of 7.53 A ˚ and needle-like morphology has been synthesized with the aid of ultrasound radiation [124]. Characterization methods indicate the formation of a-cobalt hydroxide. Thermal decomposition
of the hydroxide at 300
C under air or argon yields nanometer-sized oxide particles of Co 3 O 4 (ca. 9 nm) and CoO (ca. 6 nm), respectively.
In a different study [125], an a-cobalt hydroxide with an interlayer spacing of
12.65 A ˚ was synthesized in sheet shapes with dimensions of 100–120 nm with the
6.1 Sonochemistry 143
In addition to the above reported synthesis of ferrites our search has revealed
that aluminates [119], nickelates [120], and manganates [121], have also been
prepared by the sonochemical method. Nanosized nickel aluminate spinel particles
have been synthesized [119] with the aid of ultrasound radiation by a precursor
approach. Sonicating an aqueous solution of nickel nitrate, aluminum nitrate,
and urea yields a precursor which, on heating at 950
C for 14 h yields nanosized NiAl 2 O 4 particles with a size of ca. 13 nm and with a surface area of about
108 m
2 g
À1 .
Nanostructured LaNiO 3 was prepared by co-precipitation under ultrasonic radiation [120]. Using various characterization methods and evaluation of catalytic
activity, the effects of ultrasound on the structural properties and catalytic activity
of LaNiO 3 were studied. The TEM showed that the ultrasound could cause a decrease in the particle size. The average particle size of LaNiO 3 prepared by sonochemistry is 20 nm. The specific surface area of LaNiO 3 is 11.27 m
2 g
À1 . Ultrasound could lead to increased surface oxide content and surface crystal oxygen
vacancies. The TPR result showed that the LaNiO 3 prepared by sonochemistry has
a lower reduction temperature and a higher ratio of surface oxygen to crystal oxygen. The evaluation of catalytic activity showed that ultrasound could increase the
catalytic activity of LaNiO 3 for NO decomposition.
Lanthanum strontium manganate, known also as LSM, is known for its magnetoresistance properties, and is also used in solid oxide fuel cells (SOFC). Sonochemistry was used for its preparation [121]. Electron magnetic resonance (EMR)
spectra of nanosized sonochemically sintered powders of La 0:7 Sr 0:3 MnO 3 (annealed, T C ¼ 340 K) were studied.
6.1.2.8 The Sonochemical Synthesis of Nanosized Hydroxides
The synthesis of nanosized a-nickel hydroxide has been reported by two groups
[122, 123]. The first reported reaction prepared nanosized a-nickel hydroxide with
an interlayer spacing of 7.2 A ˚ . The synthesized hydroxide was found to possess
good stability in a KOH medium, and the material might be interesting from the
application point of view in secondary alkaline batteries. The second synthesis
prepared nanocrystalline a-Ni(OH) 2 by an ultrasonic precipitation/stirring method
[123]. Compared with the sample prepared without ultrasonic stirring, the crystal
structure of the a-phase sample has been changed from the b-phase. The crystalline size of the sample is about 20 nm, which is smaller than the sample produced
without ultrasonic stirring (70 nm).
Cobalt hydroxide with an interlayer spacing of 7.53 A ˚ and needle-like morphology has been synthesized with the aid of ultrasound radiation [124]. Characterization methods indicate the formation of a-cobalt hydroxide. Thermal decomposition
of the hydroxide at 300
C under air or argon yields nanometer-sized oxide particles of Co 3 O 4 (ca. 9 nm) and CoO (ca. 6 nm), respectively.
In a different study [125], an a-cobalt hydroxide with an interlayer spacing of
12.65 A ˚ was synthesized in sheet shapes with dimensions of 100–120 nm with the
6.1 Sonochemistry 143