High-Temperature Technique

Salts of hexafluorovanadate can be obtained by high temperature techniques or from solutions containing hydrofluoric acid. For instance, X-ray patterns and DTA were used for the characterization of 17 double fluorides obtained by solid state reactions in the systems VF3 + MF (M = Li, Na, K, Rb, Cs, Tl) and seven double fluorides in the systems VF3 + MF2 (M = Ca, Sr, Ba, Pb),296 and the lattice constants297,29s and magnetic properties298 of A2B[VF6] (A, B = Cs, Rb, Tl, K, Na, Li) were also reported. The structure of the high temperature j0 phase of Li3VF6 has been determined and compared with the cryolite-type stable a form. The vanadium atoms have an octahedral coordination.299... 

The wealth of information that has accumulated regarding the UPS of the main group halides is not considered here, since it falls outside the purview of this Chapter. Of the transition metal halides the largest amount of work has been done with the halides of the Group 2B metals and their monomethyl derivatives (28, 33, 63, 108, 112, 129, 233). In these studies it was found that the zinc and cadmium dihalides require significantly higher vaporization temperatures than the mercury compounds hence specialized high-temperature techniques were necessary. A summary of these and related methods may be found in a recent review article by Schweitzer (255). 

In addition to silicon and metals, a third important element being deposited as thin films is diamond (Celii and Butler, 1991 May, 2000). For many years, diamonds were synthesized by a high pressure/high temperature technique that produced bulk diamonds. More recently, the interest in diamonds has expanded to thin films. Diamond has a slew of properties that make it a desired material in thin-film form hardness, thermal conductivity, optical transparency, chemical resistance, electrical insulation, and susceptibility to doping. Thin film diamond is prepared using chemical vapor deposition, and we examine the process in some detail as a prototypical chemical vapor example. Despite its importance and the intensity of research focused on diamond chemical vapor deposition, there remains uncertainty about the exact mechanism. 

Low- and high-temperature techniques, spectrometric determination of sample temperature ... 

Investigation of chemical reactions in thermal plasma devices operating at atmospheric pressure involves the use of the plasma as an energy source for the activation of endothermic reactions, which can also be carried out by more conventional high-temperature techniques. It is hoped that the use of plasma will result in the formation of either a cheaper product than the conventional route, or one with superior physical or chemical properties. 

Section 1.2 of this Chapter reviews the crystallization of diamond and cubic boron nitride using high pressure, high temperature techniques. Chapter 4 of Part II deals with the subject of chemical vapor deposition of diamond at low pressure. 

Experimental results were largely independent of the reaction medium [33] and gas-phase calculations are, therefore, sufficient. The thermal decomposition of PPE and several PPE derivatives has been investigated under a range of pyrolysis conditions [33-35]. Fast, high-temperature techniques highlight unimolecular transformations, such as bond scission and intramolecular rearrangements, while slow pyrolysis in the liquid phase allows additional bimolecular and radical chain processes to occur. Under both pyrolysis conditions, the pyrolysis rate and product distribution were found to be substantially influenced by naturally occurring substituents, such as hydroxy and methoxy substituents. 

All the Group 2 and 12 metals form halides of composition MF2, MCI2, MBt2 and MI2. At room temperature all these compounds are solids, but the gaseous molecules can be studied by high temperature techniques. As expected the atoms are joined in the sequence XMX, and the two M-X bond distances are assumed and found to be equal. But are the molecules linear or angular (bent) ... 

See also-. Extraction Solvent Extraction Principles. Gas Chromatography Mass Spectrometry High-Temperature Techniques. Liquid Chromatography Normal Phase Reversed Phase Liquid Chromatography-Mass Spectrometry. Nuclear Magnetic Resonance Spectroscopy - Applicable Elements Nitrogen-15. 

See alsa Carbohydrates Starch. Derivatization of Analytes. Extraction Solvent Extraction Principles. Fluorescence Food Applications. Gas Chromatography High-Temperature Techniques. Lipids Fatty Acids Polar Lipids. Liquid Chromatography Food Applications. Mass Spectrometry Food Applications. Quality Assurance Quality Control Internal Standards. Sample Handling Comminution of Samples. Sampling Theory. 

See also Gas Chromatography Overview Gas-Solid Chromatography High-Temperature Techniques Chiral Separations. 

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