Argon film

Ebner, C. Saam, W. F., New phase-transition phenomena in thin argon films, Phys. Rev. Lett 1977, 38, 1486-1489... 

J. M. Phillips and T. R. Story, Commensurability Transitions in Multilayers A Response to Substrate-Induced Elastic Stress, Phys. Rev. B 42 (1990) 6944-6953 C. D. Hruska and J. Phillips, Observed Microscopic Structure in the Simulation of Multilayers, Phys. Rev. B 37 (1988) 3801-3804 J. M. Phillips and C. D. I oiska, Methane Adsorbed on Graphite. IV. Multilayer Growth at Low Temperatures, Phys. Rev. B 39 (1989) 5425-5435 J. M. Phillips, Layer by Layer Melting of Argon Films on Graphite A Computer Simulation Study, Phys. Lett. A 147 (1990) 54-58 J. M. Phillips, The Structure near Transitions in Thin Films, Langmuir 5 (1989) 571-575. 

Argon films have been investigated with adsorption isotherms [45—47], and elastic neutron scattering measurements [48]. 

The nature of melting for argon films has also been studied and discussed. Evidence for continuous melting has been obtained from neutron diffraction studies [120-121], from heat capacity measurements [117], and from x-ray diffraction techniques [64,97]. Adsorption isotherms data [62] and LEED results [125,126] indicate a rather sharp transition. Some computer simulations have been interpreted in terms of continuous melting [131], whereas others [132,133] have found a first-order behavior (discontinuous melting). Finally, heat capacity measurement indicates that the melting transition is weakly first order, occurring at a triple line temperature [63]. 

In a concentric-tube nebulizer, the sample solution is drawn through the inner capillary by the vacuum created when the argon gas stream flows over the end (nozzle) at high linear velocity. As the solution is drawn out, the edges of the liquid forming a film over the end of the inner capillary are blown away as a spray of droplets and solvent vapor. This aerosol may pass through spray and desolvation chambers before reaching the plasma flame. 

In this cross-flow arrangement, a thin film of sample solution is obtained as it flows around the edge of a small opening, through which there is a fast linear flow of argon. The liquid film is rapidly nebulized along the rim of the orifice. 

Another variant (the cone spray) allows the sample solution to flow down the sides of an inverted cone and through a hole at the bottom of which flows a fast stream of argon gas. As the liquid film meets the gas, it is ripped apart into a finely dispersed aerosol (Figure 19.15). 

The aim of breaking up a thin film of liquid into an aerosol by a cross flow of gas has been developed with frits, which are essentially a means of supporting a film of liquid on a porous surface. As the liquid flows onto one surface of the frit (frequently made from glass), argon gas is forced through from the undersurface (Figure 19.16). Where the gas meets the liquid film, the latter is dispersed into an aerosol and is carried as usual toward the plasma flame. There have been several designs of frit nebulizers, but all work in a similar fashion. Mean droplet diameters are approximately 100 nm, and over 90% of the liquid sample can be transported to the flame. 

This arrangement provides a thin film of liquid sample solution flowing down to a narrow orifice (0.007-cm diameter) through which argon flows at high linear velocity (volume flow is about 0.5-1 1/min). A fine aerosol is produced. This particular nebulizer is efficient for solutions having a high concentration of analyte constituents. 

The sample solution flows onto a piece of fritted glass through which argon gas flows. The flow of argon is broken down into narrow parallel streams of high linear velocity, which meet the thin film of liquid percolating into the pores of the frit. At the interfaces, an aerosol is formed and is blown from the top of the frit. 

Low pressure argon is the usual medium for industrial sputtering of metals and other soHd films (100) (see Thin films, film formation techniques). 

There are two types of deposited films known as siUcon nitride. One is deposited via plasma-enhanced CVD at temperatures <350° C (18). In this process silane and ammonia react in an argon plasma to form siUcon imide [14515-04-9] SiNH. 

Fig. 1. The effect of (------) coercive force, ( ) lesistivity, and ([[aitl]]) magnetoiesistance coefficient foi Permalloy films (a) at a constant argon...

In a vacuum, uncoated molybdenum metal has an unlimited life at high temperatures. This is also tme under the vacuum-like conditions of outer space. Pure hydrogen, argon, and hehum atmospheres are completely inert to molybdenum at all temperatures, whereas water vapor, sulfur dioxide, and nitrous and nitric oxides have an oxidizing action at elevated temperatures. Molybdenum is relatively inert to carbon dioxide, ammonia, and nitrogen atmospheres up to about 1100°C a superficial nitride film may be formed at higher temperatures in the latter two gases. Hydrocarbons and carbon monoxide may carburize molybdenum at temperatures above 1100°C. 

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