High vacuum technique

Surface defects (Section VII-4C) are also influenced by the history of the sample. Such imperfections may to some extent be reversibly affected by processes such as adsorption so that it is not safe to regard even a refractory solid as having fixed surface actions. Finally, solid surfaces are very easily contaminated detection of contamination is aided by ultra-high-vacuum techniques and associated cleaning protocols [24]. 

Soriaga M P 1992 Ultra-high vacuum techniques in the study of single-crystal electrode surfaces Prog. Surf. Sc/. 39 325... 

For continuing polymerization to occur, the ion pair must display reasonable stabiUty. Strongly nucleophilic anions, such as C/ , are not suitable, because the ion pair is unstable with respect to THE and the alkyl haUde. A counterion of relatively low nucleophilicity is required to achieve a controlled and continuing polymerization. Examples of anions of suitably low nucleophilicity are complex ions such as SbE , AsF , PF , SbCf, BE 4, or other anions that can reversibly coUapse to a covalent ester species CF SO, FSO, and CIO . In order to achieve reproducible and predictable results in the cationic polymerization of THE, it is necessary to use pure, dry reagents and dry conditions. High vacuum techniques are required for theoretical studies. Careful work in an inert atmosphere, such as dry nitrogen, is satisfactory for many purposes, including commercial synthesis. 

Some elements, such as the rare eartlrs and the refractory metals, have a high afflnity for oxygen, so vaporization of tlrese elements in a irormaT vacuum of about 10 " Pa, would lead to the formation of at least a surface layer of oxide on a deposited flhrr. The evaporation of these elements therefore requires the use of ultra-high vacuum techniques, which can produce a pressure of 10 Pa. 

Roberts, M.W. (1960, August) High-vacuum techniques, J. Roy. Inst. Chem. 275. 

On his return to Princeton after the war, Hugh Taylor organized catalytic research at the Frick Chemical Laboratory. He applied high vacuum technique, liquid air cryoscopy to the study of adsorptive characteristics of catalysts, correlating rates of catalytic reactions and rates of adsorption. He introduced the concept of activated adsorption and defended it against all comers. ... 

Yarwood, j., 1955, High Vacuum Technique-, London, Chapman Hall. 

P. H. Plesch, High Vacuum Techniques for Chemical Syntheses and Measurement, Cambridge University Press, Cambridge (1989). 

It does seem curious that no p+ between the extremes of ca. 104 and 108 1 mol"1 s 1 have been reported for chemically initiated polymerisations. The most likely reason is the sheer technical difficulty of measuring polymerisation rates for such systems with [M] in the range of 4-8 mol/1 and of determining reliably the nature and the concentration of the propagating species and the ratio of unpaired to paired ions. This the more so, since nothing less than the high-vacuum techniques used by Sigwalt, Pepper, Plesch, et al. [4] which have fallen into disuse would be required for such an enterprise. 

The first holder of the BIP studentship was Peter H. Westermann. He thoroughly enjoyed starting up a new project, and very soon he had produced his own mystery He had found no difficulty in manipulating anhydrous perchloric acid as initiator and in making the polymers by the high vacuum techniques which had become the speciality of the... 

In organic chemistry this is called a retro-pericyclic reaction and it should indeed have a low barrier of activation. Under the high vacuum techniques applied, on clean surfaces, the reaction proceeds already below 140 K (the temperature at which desorption of the weakly co-ordinated butadiene is observed). 

Moreover, despite the many advances in electrochemical measurement and modeling, our understanding of SOFC cathode mechanisms remains largely circumstantial today. Our understanding often relies on having limited explanations for an observed phenomenon (e.g., chemical capacitance as evidence for bulk transport) rather than direct independent measures of the mechanism (e.g., spectroscopic evidence of oxidation/reduction of the electrode material). At various points in this review we saw that high-vacuum techniques commonly employed in electrocatalysis can be used in some limited cases for SOFC materials and conditions (PEEM, for example). New in-situ analytical techniques are needed, particularly which can be applied at ambient pressures, that can probe what is happening in an electrode as a function of temperature, P02, polarization, local position, and time. 

Hadjichiistidis N, latrou H, Pispas S et al. (2000) Anionic polymerization high vacuum techniques. J Polym Sci Part A Polym Chem 38 3211-3234... 

J. Yarwood, High Vacuum Technique, Science Paperbacks and Chapman and Hall, London, 1975. 

High vacuum technique (h.v.t.) is one of several types of experimental technique which can be employed to obtain a controlled experimental environment. The most usual reason for wanting this is the necessity to exclude oxygen and/or water and, less commonly, carbon dioxide from the reaction being studied. Perhaps the most primitive example of creating a controlled environment is the use of a soda-lime tube to protect a store of sodium hydroxide from the ingress of carbon dioxide. 

High vacuum techniques for chemical syntheses and measurements... 

Polymerizations were carried out at 30°C in all glass, sealed reactors using breakseals and standard high vacuum techniques (3). For the calorimetric measurements, a 1 liter sample of a 0.03M solution of each polymeric lithium compound with M of ca. 4,000 was prepared in benzene solution using sec-butyl-lithium as initiator and transferred to the glove box. 

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