Solid-State Vapor Generator

Several vapor generation methods use direct contact of the liquid with a carrier gas stream. These include sparging (the carrier gas bubbles through the liquid) syringe injection of the liquid material directly into a carrier gas-flow stream and head-space vapor saturation. Solid-state vapor generation exploits the use of vapors... 

A number of theories have been put forth to explain the mechanism of polytype formation (30—36), such as the generation of steps by screw dislocations on single-crystal surfaces that could account for the large number of polytypes formed (30,35,36). The growth of crystals via the vapor phase is believed to occur by surface nucleation and ledge movement by face specific reactions (37). The solid-state transformation from one polytype to another is believed to occur by a layer-displacement mechanism (38) caused by nucleation and expansion of stacking faults in close-packed double layers of Si and C. 

Ultrathin Films. The demand for artificial materials or so-called designer solids is increasing. Many applications such as solid state lasers and new generations of transistors require ever finer structuring of materials. It is very common for the properties of devices based on heterostructures to depend on the quality of the interfaces. The structures can be grown by chemical vapor deposition (CVD) or molecular beam epitaxy (MBE). Transmission electron microscopy... 

Chemical vapor infiltration (CVI) is a process whereby reactive chemical species are generated in the vapor phase and allowed to react with a solid substrate thus modifying its chemistry. A successful use of this process requires (1) an absolutely continuous and stoichiometric conversion of the initial to the final chemistry in the solid state, and (2) a continuous and eventually complete conversion of the morphology, density, surface tension, mechanical as well all other properties. Discontinuous or incomplete results cause a steep drop in strength, the premier measure of uniformity. By combining the complexities of chemical vapor deposition (this chapter) with those of fiber formation from a precursor fiber (Chapters 8 to 12), the process is therefore intrinsically more difficult to control than any other. 

Inorganic nanoparticles such as metal/semiconductors (M/SC) immobilized in polymer matrices have attracted considerable interest in recent years due to their distinct individualistic and cooperative properties [84]. Although the control of size and shape of M/SC nanoparticles has been widely investigated, the fundamental mechanism of nanostructural formation and evolution is still poorly understood. A novel cryochemical solid-state synthesis technique has been developed to produce M/SC nanocomposites [85]. This method is based on the low-temperature cocondensation of M/SC and monomer vapors, followed by the low-temperature solid-state polymerization of the cocondensates. As a result of the method of stabilizing the metal particle without requiring any specific coordination bonds between the particle surface and the polymer matrix, generated nanoparticles (Ag-nanocrystal mean size 50 A) were embedded in the polymer matrix with well-controlled shapes and a narrow size distribution [86]. 

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