of the as-prepared product in Ar at 1000
C leads to the formation of a WO 2 aWO 3
mixture containing nanorods (around 50 nm in diameter) and packs of these
nanorods. Heating the product in air for 3 h leads to triclinic WO 3 crystal formation, with a basic size of 50–70 nm.
Finally, Vijaykumar et al. reported on a general sonochemical reaction in which
metal acetates can be converted to the corresponding metal oxides [138]. The acetates examined in this research were, Zn, Cu, Co, and Fe(II), yielding nanocrystalline CuO, ZnO, Co 3 O 4 , and Fe 3 O 4 . The solvents were water and a 10% water–DMF
mixture. The diameters of the particles were: 20 nm (length (L)) and 2 nm (width
(W)), (6), 340 nm (250), 30 nm (20), and 20 nm (8), respectively, when water
(water–DMF) is used as the solvent. The results of DRS are analyzed in detail, and
the band gap energies for CuO, ZnO, and Co 3 O 4 are seen to be 2.18, 3.35, and 2.26
(3.40) eV, respectively.
6.1.2.11 Sonochemical Synthesis of Other Nanomaterials
Metals, metal oxides, and chalcogenides constitute the main body of the sonochemical research. Only very few other groups of materials have been prepared by
using power ultrasound. There may be two reasons for this: first, the difficulty in
preparing these materials and, secondly, lack of interest. However, we believe that
the first reason can explain why an important material such as GaN, for example,
has not been prepared sonochemically.
In this section we will survey briefly other important groups of materials that
have been reported as prepared using ultrasonic waves. Only one paper was found
describing the preparation of nitrides [139]. This reports on a method for the
preparation of nanoparticles of iron nitride powders. Iron nitride particles have
been synthesized by two methods. In the first, Fe(CO) 5 was sonicated in a decane
solution under a gaseous mixture of NH 3 and H 2 (3.5:1 molar ratio) at ca. 0
C.
The second method was based on nitriding the sonochemically prepared amorphous iron at ca. 400
C for 4 h under a mixed stream of NH 3 and H 2 (3.5:1 molar
ratio). Different products were obtained in the two cases. The product of the sonication of Fe(CO) 5 was amorphous Fe 2À3 N and a small quantity of iron oxide. The
X-ray diffraction patterns in the second case showed Fe 4 N as the main product.
The magnetic properties of both products were measured. The coercive force H c of
the Fe 4 N is 190 Oe, and the saturation magnetization s(s), is 170 emu g
À1 .
More publications were found related to carbides. First, Suslick’s early report
[64] that certain carbonyls sonicated in a decalin solvent under argon. For Fe and
Co, nanostructured metals are formed; for Mo and W, metal carbides (e.g., Mo 2 C)
are produced. Molybdenum carbide was used later as a catalyst. The selectivity and
catalytic activity of the Mo and W carbides was examined in the dehydrogenation of
alkanes [140]. Another carbide that has already been mentioned is that of Pd [65],
which was prepared by Maeda’s group. Iron carbide was a byproduct that served as
protective layer in Nikitenko’s work on air-stable iron nanoparticles [70].
Ultrasonic irradiation (22 kHz, Ar atmosphere) of Th(IV) b-diketonates
Th(HFAA) 4 and Th(DBM) 4 , where HFAA and DBM are hexafluoroacetylacetone
and dibenzoylmethane respectively, causes them to decompose in hexadecane
6.1 Sonochemistry 147
C leads to the formation of a WO 2 aWO 3
mixture containing nanorods (around 50 nm in diameter) and packs of these
nanorods. Heating the product in air for 3 h leads to triclinic WO 3 crystal formation, with a basic size of 50–70 nm.
Finally, Vijaykumar et al. reported on a general sonochemical reaction in which
metal acetates can be converted to the corresponding metal oxides [138]. The acetates examined in this research were, Zn, Cu, Co, and Fe(II), yielding nanocrystalline CuO, ZnO, Co 3 O 4 , and Fe 3 O 4 . The solvents were water and a 10% water–DMF
mixture. The diameters of the particles were: 20 nm (length (L)) and 2 nm (width
(W)), (6), 340 nm (250), 30 nm (20), and 20 nm (8), respectively, when water
(water–DMF) is used as the solvent. The results of DRS are analyzed in detail, and
the band gap energies for CuO, ZnO, and Co 3 O 4 are seen to be 2.18, 3.35, and 2.26
(3.40) eV, respectively.
6.1.2.11 Sonochemical Synthesis of Other Nanomaterials
Metals, metal oxides, and chalcogenides constitute the main body of the sonochemical research. Only very few other groups of materials have been prepared by
using power ultrasound. There may be two reasons for this: first, the difficulty in
preparing these materials and, secondly, lack of interest. However, we believe that
the first reason can explain why an important material such as GaN, for example,
has not been prepared sonochemically.
In this section we will survey briefly other important groups of materials that
have been reported as prepared using ultrasonic waves. Only one paper was found
describing the preparation of nitrides [139]. This reports on a method for the
preparation of nanoparticles of iron nitride powders. Iron nitride particles have
been synthesized by two methods. In the first, Fe(CO) 5 was sonicated in a decane
solution under a gaseous mixture of NH 3 and H 2 (3.5:1 molar ratio) at ca. 0
C.
The second method was based on nitriding the sonochemically prepared amorphous iron at ca. 400
C for 4 h under a mixed stream of NH 3 and H 2 (3.5:1 molar
ratio). Different products were obtained in the two cases. The product of the sonication of Fe(CO) 5 was amorphous Fe 2À3 N and a small quantity of iron oxide. The
X-ray diffraction patterns in the second case showed Fe 4 N as the main product.
The magnetic properties of both products were measured. The coercive force H c of
the Fe 4 N is 190 Oe, and the saturation magnetization s(s), is 170 emu g
À1 .
More publications were found related to carbides. First, Suslick’s early report
[64] that certain carbonyls sonicated in a decalin solvent under argon. For Fe and
Co, nanostructured metals are formed; for Mo and W, metal carbides (e.g., Mo 2 C)
are produced. Molybdenum carbide was used later as a catalyst. The selectivity and
catalytic activity of the Mo and W carbides was examined in the dehydrogenation of
alkanes [140]. Another carbide that has already been mentioned is that of Pd [65],
which was prepared by Maeda’s group. Iron carbide was a byproduct that served as
protective layer in Nikitenko’s work on air-stable iron nanoparticles [70].
Ultrasonic irradiation (22 kHz, Ar atmosphere) of Th(IV) b-diketonates
Th(HFAA) 4 and Th(DBM) 4 , where HFAA and DBM are hexafluoroacetylacetone
and dibenzoylmethane respectively, causes them to decompose in hexadecane
6.1 Sonochemistry 147