Laser vaporization of metals

A Co/Ni alloy is the next active catalyst among the binary combinations within the iron-group metals in the arc discharge method (51). Laser vaporization of metal/ carbon composite in argon atmosphere at high temperature (1200°C) can also produce SWNTs (41). Guo et al. (41) reported that the Co/Ni alloy was the most effectual, with a yield of 50-90% in the laser ablation method. 

A method which combines laser vaporization of metal targets with controlled condensation in a diffusion cloud chamber is used to synthesize nanoscale metal oxide and metal carbide particles (10-20 nm). The silica nanoparticles aggregate into a novel web-like microstructure. These aggregates are very porous and have a very large surface area (460 m /g). Bright blue photoluminescence from the nanoparticle silica has been observed upon irradiation with UV light. The photoluminescence is... 

C. Polymerization Initiated by Plasma Laser Vaporization of Metals... 

Figure Cl. 1.1. Schematic of a typical laser vaporization supersonic metal cluster source using a pulsed laser and a pulsed helium carrier gas.

Huang and Freiser (132, 133) were able to prepare exohedral metal C60 ions [MC60]+ by direct reaction of the bare metal ions Fe+, Ni+, Co+, Cu+, Rh+, and La+ with Cgo vapor produced from a heated probe. The [MC60]+ ions when subjected to low-energy collision-induced dissociation with argon all produced the Cg0 ion. These results show that the metal ions attach to the outer surface of C60. The exohedral metallofullerene ions differ from the endohedral metallofullerenes produced by laser ablation of metal oxide-graphite mixtures and support the observations of Smalley and co-workers (148) who found that endohedral metallofullerene ions dissociate by loss of C2 units. 

Before that time, experimental evidence for the existence of heterofullerenes was very rare. In 1991 Smalley and co-workers [4,5] reported on the mass spectrometric detection of borafullerenes C5q B (n = 1-6) generated by laser vaporization of graphite-boron nitride composites. Later, in the same year, the preparation of several clusters was reported [6-8]. However, none of these species has been isolated or structurally characterized. In 1994 Clemmer et al. presented evidence for heterofullerenes containing a metal as part of the framework [9]. Muhr etal. reported on the preparation of monoborafullerenes however, presumably due to the instability of these systems, no pure material could be isolated and completely characterized [10]. Real preparative heterofullerene chemistry began in 1995. The... 

That pulsed laser vaporization of rdractory metal substrates can produce metal vapor has long been recognized for example, see J. F. Ready, Effects of High Power Laser Irradiation, Academic, New York, 1971. 

A similar regularity in the mass distribution of the various Zr-substituted met-cars was observed for different Ti/Zr molar ratios and was used as an argument in favor of a pentagonal dodecahedron structure in which all metal sites are equivalent. In subsequent studies, binary metal metallocarbohedrenes of titanium and other metals Ti cM Ci2 (x -I- y = 8) have been obtained either by the standard method using pure metal powders of Ti and M as a target for laser vaporization and a mixture of helium with 10% methane as carrier gas (M = Nb, Ta, Y, Si), or by direct laser vaporization of a mixture of titanium carbide and pure M metal (M = Y, Nb, Mo, Ta, W). ... 

Fig. 4.21 Production of cold metal clusters by laser evaporation of metal vapors...

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