Chemical vapor synthesis

Similar to chemical vapor deposition, reactants or precursors for chemical vapor synthesis are volatile metal-organics, carbonyls, hydrides, chlorides, etc. delivered to the hot-wall reactor as a vapor. A typical laboratory reactor consists of a precursor delivery system, a reaction zone, a particle collector, and a pumping system. Modification of the precursor delivery system and the reaction zone allows synthesis of pure oxide, doped oxide, or multi-component nanoparticles. For example, copper nanoparticles can be prepared from copper acetylacetone complexes [70], while europium doped yttiria can be obtained from their organometallic precursors [71]. 

Veith, M., Mathur, S., Shen, H., Lecerf, N., Huefner, S., and Jilavi, M.H. (2001) Single-step preparation of oxide-oxide nanocomposites chemical vapor synthesis of LnAlOs/ALOs (Ln = Pr Nd) thin films. Chemistry of Materials, 13, 4041-4052. 

In a similar approach, nanocrystalline zinc silicate can be synthesized via chemical-vapor synthesis (CVS) by using the 0-silylated Zn404 cubane [MeZn(OSiMe3)]4. Interestingly, the Zn Si ratio in the latter single precursor... 

Another strategy to synthesize the particle from volatile organometallic precursors is achieved by promoting homogeneous gas-phase nucleation, the so-called chemical vapor synthesis (CVS). " In this case, the precursor is evaporated using a carrier gas and reacted with a co-substrate (e.g., O2) to produce the desired material, which can be collected as powder. The typical experimental setup is assembled according to Figure... 

Figure 16 Experimental setup for chemical-vapor synthesis.Reproduced with permission from Elsevier.

FIGURE 2 Schematic of the different opportunities of Chemical Vapor Synthesis for the preparation of nanocrystalline powders of Zr02 and in the system Zr02/Al203, with different elemental distribution. SOURCE Hahn, private communication. 

Srdic, V., M. Winterer, and H. Hahn. 2000. Sintering behavior of nanocrystalline zirconia doped with alumina prepared by chemical vapor synthesis. Journal of the American Ceramic Society 83(8) 1853-1860. 

Winterer M, Hahn H, Swihart MT. Nanoceramics by chemical vapor synthesis. Z Metallkd 2003 94 1084-90. 

M., Schuhmann, W, and Muhler, M. (2007) Chemical vapor synthesis of secondary carbon nanotubes catalyzed by iron nanoparticles electrodeposited on primary catbon nanotubes. Surf. Coat. Technol, 201, 9232-9237. 

Alyea et al. combined chemical vapor deposition and impregnation in a preparation procedure which they denoted as metal oxide chemical vapor synthesis in order to obtain uniform, well-dispersed supported catalysts [265,266]. In the rotary reaction vessel sketched in Fig. 11, vapors of transition metal oxides... 

Diamonds also occur in meteorites, probably as a result of high pressures produced dynamically by impact (10,11). The shock or explosive mode of synthesis is a viable process for fine diamond powders of both the cubic and hexagonal (lonsdaleite) polymorphs (12) naturally or otherwise. Some diamonds in space appear to have formed by processes more closely related to the low pressure chemical vapor deposition processes described later (see... 

Physics and chemistry researchers approach III—V synthesis and epitaxial growth, ie, growth in perfect registry with the atoms of an underlying crystal, differently. The physics approach, known as molecular beam epitaxy (MBE), is essentially the evaporation (14—16) of the elements, as illustrated in Figure 4. The chemistry approach, organometaUic chemical vapor deposition (OMCVD) (17) is exemplified by the typical chemical reaction ... 

Chemical vapor deposition is a synthesis process in which the chemical constituents react in the vapor phase near or on a heated substrate to form a solid deposit. The CVD technology combines several scientific and engineering disciplines including thermodynamics, plasma physics, kinetics, fluid dynamics, and of course chemistry. In this chapter, the fundamental aspects of these disciplines and their relationship will be examined as they relate to CVD. 

Kurihara, K., Sasaki, K., Kawarada, M., and Koshino, M., High Rate Synthesis of Diamond by DC Plasma Jet Chemical Vapor Deposition, Phys. Lett., 52(6) 437 38 (1988)... 

Up to the present, a number of conventional film preparation methods like PVD, CVD, electro-chemical deposition, etc., have been reported to be used in synthesis of CNx films. Muhl et al. [57] reviewed the works performed worldwide, before the year 1998, on the methods and results of preparing carbon nitride hlms. They divided the preparation techniques into several sections including atmospheric-pressure chemical processes, ion-beam deposition, laser techniques, chemical vapor deposition, and reactive sputtering [57]. The methods used in succeeding research work basically did not... 

The most intensive development of the nanoparticle area concerns the synthesis of metal particles for applications in physics or in micro/nano-electronics generally. Besides the use of physical techniques such as atom evaporation, synthetic techniques based on salt reduction or compound precipitation (oxides, sulfides, selenides, etc.) have been developed, and associated, in general, to a kinetic control of the reaction using high temperatures, slow addition of reactants, or use of micelles as nanoreactors [15-20]. Organometallic compounds have also previously been used as material precursors in high temperature decomposition processes, for example in chemical vapor deposition [21]. Metal carbonyls have been widely used as precursors of metals either in the gas phase (OMCVD for the deposition of films or nanoparticles) or in solution for the synthesis after thermal treatment [22], UV irradiation or sonolysis [23,24] of fine powders or metal nanoparticles. 

The synthesis of MNCGs can be obtained by sol-gel, sputtering, chemical vapor-deposition techniques. Ion implantation of metal or semiconductor ions into glass has been explored since the last decade as a useful technique to produce nanocomposite materials in which nanometer sized metal or semiconductor particles are embedded in dielectric matrices [1,2,4,23-29]. Furthermore, ion implantation has been used as the first step of combined methodologies that involve other treatments such as thermal annealing in controlled atmosphere, laser, or ion irradiation [30-32]. 

According to Ref. [12], template for synthesis of nanomaterials is defined as a central structure within which a network forms in such a way that removal of this template creates a filled cavity with morphological or stereochemical features related to those of the template. The template synthesis was applied for preparation of various nanostructures inside different three-dimensional nanoporous structures. Chemically, these materials are presented by polymers, metals, oxides, carbides and other substances. Synthetic methods include electrochemical deposition, electroless deposition, chemical polymerization, sol-gel deposition and chemical vapor deposition. These works were reviewed in Refs. [12,20]. An essential feature of this... 

In this chapter the potential of nanostructured metal systems in catalysis and the production of fine chemicals has been underlined. The crucial role of particle size in determining the activity and selectivity of the catalytic systems has been pointed out several examples of important reactions have been presented and the reaction conditions also described. Metal Vapor Synthesis has proved to be a powerful tool for the generation of catalytically active microclusters SMA and nanoparticles. SMA are unique homogeneous catalytic precursors and they can be very convenient starting materials for the gentle deposition of catalytically active metal nanoparticles of controlled size. 

---