Atmospheric pressure chemical vapour

The application of NIR laser diode spectroscopy to the on-line analysis of atmospheric pressure chemical vapour decomposition has been reported. In the process of depositing a thin layer of tin on a glass surface the monitoring of methane in the presence of oxygen, water and dichloromethyl tin dichloride in the reactor is important. Laser diode spectroscopy has been used at high sensitivity (detection limit of 0.01%) and at high frequency (5 Hz) for this purpose [40]. 

Ashraf, S., Blackman, C. S., Naisbitt, S. C. and Parkin, I. P. (2008) The gas-sensing properties ofW03-x thin films deposited via the atmospheric pressure chemical vapour deposition (APCVD) of WC16 with ethanol. Measurement Science and Technology 19,025203. 

Binions, R. (2007) A comparison of the gas sensing prop>erties of solid state metal oxide semiconductor gas sensors produced by atmospheric pressure chemical vapour deposition and screen printing. Measurement Science and Technology 18. 

Shaw, G. A., Parkin, I. P. and WiUiams, D. E. (2003) Atmospheric pressure chemical vapour deposition of Cr2-xTix03 (CTO) thin films on to gas sensing substrates. Journal of Materials Chemistry 13,2957-62. 

Lengtenberg et al. [328] used an atmospheric pressure chemical vapour deposition to deposit boron oxide as an intermediate layer for anodic bonding. 

LC-APCI-MS is a derivative of discharge-assisted thermospray, where the eluent is ionised at atmospheric pressure. In an atmospheric pressure chemical ionisation (APCI) interface, the column effluent is nebulised, e.g. by pneumatic or thermospray nebulisation, into a heated tube, which vaporises nearly all of the solvent. The solvent vapour acts as a reagent gas and enters the APCI source, where ions are generated with the help of electrons from a corona discharge source. The analytes are ionised by common gas-phase ion-molecule reactions, such as proton transfer. This is the second-most common LC-MS interface in use today (despite its recent introduction) and most manufacturers offer a combined ESI/APCI source. LC-APCI-MS interfaces are easy to operate, robust and do not require extensive optimisation of experimental parameters. They can be used with a wide variety of solvent compositions, including pure aqueous solvents, and with liquid flow-rates up to 2mLmin-1. 

Dronen DM, Reineccius GA. 2003. Rapid analysis of volatile release from powders using dynamic vapour sorption atmospheric pressure chemical ionization mass spectrometry. Journal of Food Science 68 2158-2162. 

Probably the most common separation systems used in the laboratory today require the sample to be in solution (e.g. HPLC, CE). The solvent may be aqueous or solvent based. However, onemL of such solution yields far too much vapour (1-2L) to be accommodated by a mass spectrometer s vacuum system. Thus the aim of a sample introduction system for such solutions would require the sample to be ionised and the solvent to be separated from these sanple ions. In addition the interface must maintain the integrity of the chromatography. The chromatographic separation must be maintained as well as allowing sufficient analyte through to generate a mass spectmm. A number of methods have been developed to do this, but the two main techniques used today are electrospray and atmospheric pressure chemical ionisation (APCI for short). These are described below under ionisation techniques. 

Rapid analysis of volatile release from powders using dynamic vapour sorption atmospheric pressure chemical ionization... 

III-V nitride films were grown by the two-flow metalorganic chemical vapour deposition (MOCVD) method, details of which are described elsewhere [1]. The growth was conducted at atmospheric pressure. Sapphire with (0001) orientation (C-face), of two-inch diameter, was used as a substrate. 

In the present study, we investigated a series of systematically modified Y zeolites as catalysts for the vapour-phase nitration of benzene. The activity, selectivity and stability of the samples was measured in a microflow fixed bed integral reactor, at 443 K and atmospheric pressure. The influence of sodium and aluminum content, and of the textural properties on the catalytic performance was investigated. The effect of the different treatments on some physico-chemical properties of the catalysts was investigated by means of standard characterization techniques (SEM, AAS, XRD, low pressure Ar adsorption, 29Si MAS solid state NMR). 

The effect of this factor on the size of particles formed in the process of chemical vapour condensation has been reliably established. For instance, in the decomposition of iron pentacarbonil Fe(CO)s in Ar atmosphere, the average size of the iron particles doubles (from 12 to 25 nm) with increasing decomposition temperature from 400 to 1,100 °C [40]. The saturation pressure... 

Explosive Substance. A solid or liquid substance (or a mixture of substances) which is in itself capable by chemical reaction of producing gas at such a temperature and pressure and at such a speed as to cause damage to the surroundings. Included are pyrotechnic substances even when they do not evolve gases. A substance which is not itself an explosive but which can form an explosive atmosphere of gas, vapour or dust is not included. lATA App. A... 

An important hazard in the process industry is the boiling liquid expanding vapour explosion (BLEVE). This is understood to be the explosively rapid vaporization and corresponding release of energy of a liquid, flammable or otherwise, upon its sudden release from containment under greater-than-atmospheric pressure at a temperature above its atmospheric boiling point [37]. It is a physical explosion which is a consequence of sudden pressure relief. If a flammable material is involved a chemical explosion or a fireball can follow. 

The driving force for the permeation of a certain compound A, is given by the difference of its chemical potential between the upstream and the downstream side of the membrane. This difference can be obtained by keeping the partial pressure of the permeating species A-, (Pi = px y,) in the permeate vapour low. Therefore, it is possible to operate at a low total pressure p (the more common choice) or alternatively to use an inert gas carrier to maintain a small value of the mole fraction y,. It is not common to work at a high feed pressure, since the influence of the feed pressure is usually minor, because the chemical potential of a compound in a liquid solution depends only very slightly on this parameter. In theory, a very high feed pressure is only really required if the permeate partial pressure approaches the saturation value. However, it is usually more economic and practical to keep the permeate pressure low or to increase the operative temperature. For these reasons, it is common practice to operate the feed at atmospheric pressure. 

Evaporation of a relatively-small volume of liquid in an enclosed space can produce a flatmuable or toxic vapour hazard. Leakage, or spillage, of a chemical maintained as a liquid above its atmospheric boiling point by pressure (e.g. liquefied petroleum gases) or as a liquid by refrigeration (e.g. ammonia) can result in a sizeable vapour cloud. 

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