Vapor-solid method

There are methods for vaporizing solids of low volatility by placing them on a thin wire, which is then raised to a high temperature within a fraction of a second (direct chemical ionization, DCI). This rapid heating allows some vaporization without decomposition, but with the development of later ionization methods, it is now rarely used. 

Sullivan, L. A., and Bin Han., Vapor Delivery Methods for CVD, An Equipment Selection GmdQ, Solid State Technology, pp. 91-101 (May 1996)... 

The most important nanomaterial synthesis methods include nanolithography techniques, template-directed syntheses, vapor-phase methods, vapor-liquid-solid (VLS) methods, solution-liquid-solid (SLS) approaches, sol-gel processes, micelle, vapor deposition, solvothermal methods, and pyrolysis methods [1, 2]. For many of these procedures, the control of size and shape, the flexibility in the materials that can be synthesized, and the potential for scaling up, are the main limitations. In general, the understanding of the growth mechanism of any as-... 

Guerin S, Hayden BE. 2006. Physical vapor deposition method for the high-throughput synthesis of solid-state material libraries. J Comb Chem 8 66-73. 

Akiyoshi, M., Deguchi, T., Sanemasa, I. (1987) The vapor saturation method for preparing aqueous solutions of solid aromatic hydrocarbons. Bull. Chem. Soc. Jpn. 60, 3935-3939. 

Shibata, T. Muranushi, Y. Miura, T. Kishi, T. 1991. Electrical characterization of 2H-SnS2 single crystals synthesized by the low temperature chemical vapor transport method. J. Phys. Chem. Solids 52 551-553. 

Low cost is one of the main advantages of the vapor pressure methods, as compared with calorimetric techniques. An apparatus to measure the vapor pressures of low boiling temperature liquids can be built easily in an undergraduate chemistry laboratory. However, the same is not quite true if we want to measure the vapor pressures of low-volatility substances, such as most solids. In these cases, Knudsen cells are usually the method of choice, but they require more expensive high-vacuum equipment [36]. 

Most of the aforementioned methods use gas-phase feedstock, including CVD via the VLS mechanism in the presence of metal catalysts, evaporation at high temperatures without the use of metal catalysts, or laser vaporization in the presence of metal catalysts. Solution-liquid-solid methods have been explored in the presence of metal catalysts and under supercritical conditions. These two mechanisms can result in either tip or root growth, meaning that the catalysts can be either suspended in space at the tips of the growing nanowires, or anchored at the surface of the substrate, depending on the strength of interactions between the nanoparticles and the substrate. 

M. K. Sunkara, S. Sharma, R. Miranda, G. Lian, and E. C. Dickey, Bulk synthesis of silicon nanowires using a low-temperature vapor-liquid-solid method, Appl. Phys. Lett. 19, 1546-1548... 

Metallization layers are generally deposited either by CVD or by physical vapor deposition methods such as evaporation (qv) or sputtering. In recent years sputter deposition has become the predominant technique for aluminum metallization. Energetic ions are used to bombard a target such as solid aluminum to release atoms that subsequendy condense on the desired substrate surface. The quality of the deposited layers depends on the cleanliness and efficiency of the vacuum systems used in the process. The mass deposited per unit area can be calculated using the cosine law of deposition ... 

Air sampling for occupational exposure to pesticides normally consists of measurement of pesticide concentrations in the worker s breathing zone, with a portable air-sampling pump and a sampling train which includes some type of collection device. The latter device, or sampling media, selected are based on the physical and chemical properties of the compound to be measured. Field workers may be exposed to chemical vapors, solid particulates or water-based aerosols. Examples of sampling media include membrane filters, sorbent tubes, polyurethane foam and charcoal. A discussion of pesticide exposure provides a useful review of methods for respiratory exposure measurement (Nigg etal, 1990). 

The pore size distribution or its mean value of a porous inorganic membrane can be assessed by a number of physical methods. These include microscopic techniques, bubble pressure and gas transport methods, mercury porosimetry, liquid-vapor equilibrium methods (such as nitrogen adsorption/desorption), gas-liquid equilibrium methods (such as permporometry), liquid-solid equilibrium methods (thcrmoporometry) and molecular probe methods. These methods will be briefly surveyed as follows. 

In the case of adsorption of a vapor by a porous material, a three phase system in terms of SAS is produced pore/adsorbed film or capillary condensed vapor/solid. Since the s.l.d. of H2O and D2O are known while the pore space s.l.d. equals to zero, contrast matching conditions are achieved if an appropriate mixture of H2O/D2O that has the same s.l.d. as the solid is used as the adsorbate. In this case the adsorbed film as well as the condensed cluster of pores will cease to act as scatterers, and only the remaining empty pores will produce measurable scattering. In terms of SANS, contrast matching reduces the solid/film/pore system to a binary one [1]. By determining a number of scattering curves corresponding to the same sample equilibrated at various relative pressures, for both the adsorption and desorption branches of the adsorption isotherm, a correlation of the two methods could be possible. If the predictions of the Kelvin equation are in accordance with the SAS analysis, a reconstruction of the adsorption isotherm can be obtained from the SAS data [2]. 

Another vapor phase method involves reacting a solid particulate phase with a gas to form particles. One method is the self-propogating high temperature synthesis (SHS) method. Also used for making sintered bodies, SHS can be used in reacting particles with the gas phase. An example of combustion synthesis involves forming ceramic carbide powders. ... 

The formation of silicon carbide whiskers can occur through one of three general methods vapor-solid (VS), chemical vapor deposition (CVD), vapor-liquid-solid (VLS). The processes vary widely in the raw... 

In the preformulation study, the comprehension of physicochemical properties regarding water-solid surface interaction is beneficial to the handling, formulation, and manufacture of the finished products. Data on sorption/de-sorption isotherm, hydration of salts of drug product, water sorption of pharmaceutical excipients, and kinetics of water adsorption or desorption of a substance can be obtained effectively by the dynamic vapor sorption method. The knowledge may be utilized for dosage form design and supports the understanding of the mechanism of action. 

The range of processing techniques that can be employed to produce FGMs is also broad [1]. Vapor-phase methods e.g., CVD, CVI, and PVD methods), liquid-phase methods e.g., electrodeposition, sol-gel, plasma spraying and molten metal infiltration methods), and a variety of solid-phase methods based on powder metallurgy are available. The solid-state methods include powder stacking techniques, powder infiltration techniques, slurry techniques e.g., sedimentation... 

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