pattern with a hyperfine field of 25.04 T. A similar study reports on the Co/Ni
synthesis, characterization and properties [38].
M50 steel powder has been obtained by sonochemical decomposition of organometallic precursors, namely Fe(CO) 5 , (Et x C 6 H 6Àx ) 2 Cr, (Et x C 6 H 6Àx ) 2 Mo, and
V(CO) 6 in decalin [39]. The morphology of the amorphous (as evidenced by X-ray
patterns) M50 powder was shown to be a porous coral-like microstructure. The
consolidated iron pellet (the consolidation was carried out by vacuum hot press,
conditions: 275 MPa, at 700
C for 1 h) had a density of 100%. The iron sample
had a high Rockwell C (RC) hardness of 37 as compared to 4–5 RC for conventional iron. The hardness of the M50 steel sample was 66.3 RC compared with
58–62 for conventional M50 steel after tempering. The authors attribute the extremely high hardness of the consolidated iron to the nanometer size particles, as
well as to the low carbon and oxygen contamination.
In a different study [40], argon-saturated aqueous solutions of NaAuCl 4 and
PdCl 2 or K 2 PtCl 4 were reduced simultaneously by ultrasound irradiation to prepare noble metal alloy nanoparticles. The AuaPd nanoparticles exhibited monodispersive distribution (8 nm), and consisted of a gold core and a palladium shell.
AuaPt alloy nanoparticles could not be produced from NaAuCl 4 and K 2 PtCl 4
aqueous solutions by either simultaneous or successive reduction.
An aqueous solution of AgNO 3 in the presence of ammonia and Fe(CO) 5 was
sonicated [41] under a H 2 /Ar mixture, yielding a nanostructured homogeneous
phase of Ag/Fe 2 O 3 . This composite material was further reduced at 300
C under
hydrogen to produce the nanophased Fe/Ag solid mixture. Finally, a ternary nanosized amorphous alloy, Fe/Ni/Co, was prepared by sonochemical decomposition of
solutions of volatile organic precursors, Fe(CO) 5 , Ni(CO) 4 , and Co(NO)(CO) 3 in
decalin, under an argon pressure of 100 to 150 kPa at 273 K [42]. Magnetic measurements indicated that the as-prepared amorphous FeaNiaCo alloy particles
were super-paramagnetic. The observed magnetization measured up to a field of
1.5 kG of the annealed FeaNiaCo samples (75–87 emu g
À1 ) was significantly lower
than that for the reported multidomain bulk particles (175 emu g
À1 ), reflecting the
ultrafine nature of our sample.
6.1.1.4 Sonochemical Deposition of Nanoparticles on Spherical and Flat Surfaces
Metallic nanoparticles were deposited on ceramic and polymeric particles using
ultrasound radiation. A few papers report also on the deposition of nanomaterials
produced sonochemically on flat surfaces. Our attention will be devoted to spheres.
In a typical reaction, commercially available spheres of ceramic materials or polymers were introduced into a sonication bath and sonicated with the precursor of
the metallic nanoparticles. In the first report Ramesh et al. [43] employed the Stober method [44] for the preparation of 250 nm silica spheres. These spheres were
introduced into a sonication bath containing a decalin solution of Ni(CO) 4 . The asdeposited amorphous clusters transform to polycrystalline, nanophasic, fcc nickel
on heating in an inert atmosphere of argon at a temperature of 400
C. Nitrogen
adsorption measurements showed that the amorphous nickel with a high surface
area undergoes a loss in surface area on crystallization.
6.1 Sonochemistry 121
synthesis, characterization and properties [38].
M50 steel powder has been obtained by sonochemical decomposition of organometallic precursors, namely Fe(CO) 5 , (Et x C 6 H 6Àx ) 2 Cr, (Et x C 6 H 6Àx ) 2 Mo, and
V(CO) 6 in decalin [39]. The morphology of the amorphous (as evidenced by X-ray
patterns) M50 powder was shown to be a porous coral-like microstructure. The
consolidated iron pellet (the consolidation was carried out by vacuum hot press,
conditions: 275 MPa, at 700
C for 1 h) had a density of 100%. The iron sample
had a high Rockwell C (RC) hardness of 37 as compared to 4–5 RC for conventional iron. The hardness of the M50 steel sample was 66.3 RC compared with
58–62 for conventional M50 steel after tempering. The authors attribute the extremely high hardness of the consolidated iron to the nanometer size particles, as
well as to the low carbon and oxygen contamination.
In a different study [40], argon-saturated aqueous solutions of NaAuCl 4 and
PdCl 2 or K 2 PtCl 4 were reduced simultaneously by ultrasound irradiation to prepare noble metal alloy nanoparticles. The AuaPd nanoparticles exhibited monodispersive distribution (8 nm), and consisted of a gold core and a palladium shell.
AuaPt alloy nanoparticles could not be produced from NaAuCl 4 and K 2 PtCl 4
aqueous solutions by either simultaneous or successive reduction.
An aqueous solution of AgNO 3 in the presence of ammonia and Fe(CO) 5 was
sonicated [41] under a H 2 /Ar mixture, yielding a nanostructured homogeneous
phase of Ag/Fe 2 O 3 . This composite material was further reduced at 300
C under
hydrogen to produce the nanophased Fe/Ag solid mixture. Finally, a ternary nanosized amorphous alloy, Fe/Ni/Co, was prepared by sonochemical decomposition of
solutions of volatile organic precursors, Fe(CO) 5 , Ni(CO) 4 , and Co(NO)(CO) 3 in
decalin, under an argon pressure of 100 to 150 kPa at 273 K [42]. Magnetic measurements indicated that the as-prepared amorphous FeaNiaCo alloy particles
were super-paramagnetic. The observed magnetization measured up to a field of
1.5 kG of the annealed FeaNiaCo samples (75–87 emu g
À1 ) was significantly lower
than that for the reported multidomain bulk particles (175 emu g
À1 ), reflecting the
ultrafine nature of our sample.
6.1.1.4 Sonochemical Deposition of Nanoparticles on Spherical and Flat Surfaces
Metallic nanoparticles were deposited on ceramic and polymeric particles using
ultrasound radiation. A few papers report also on the deposition of nanomaterials
produced sonochemically on flat surfaces. Our attention will be devoted to spheres.
In a typical reaction, commercially available spheres of ceramic materials or polymers were introduced into a sonication bath and sonicated with the precursor of
the metallic nanoparticles. In the first report Ramesh et al. [43] employed the Stober method [44] for the preparation of 250 nm silica spheres. These spheres were
introduced into a sonication bath containing a decalin solution of Ni(CO) 4 . The asdeposited amorphous clusters transform to polycrystalline, nanophasic, fcc nickel
on heating in an inert atmosphere of argon at a temperature of 400
C. Nitrogen
adsorption measurements showed that the amorphous nickel with a high surface
area undergoes a loss in surface area on crystallization.
6.1 Sonochemistry 121