Microwave plasma method

Titanium nitride UFPs synthesized by a microwave plasma method from titanium tetraisopropoxide and NH, or N2 as reactants showed cubic (TiN) and tetragonal (Ti2N) structures, depending on the operational conditions, particularly on the relative nitrogen gas flow rates (62). 

A large number of CVD diamond deposition technologies have emerged these can be broadly classified as thermal methods (e.g., hot filament methods) and plasma methods (direct current, radio frequency, and microwave) [79]. Film deposition rates range from less than 0.1 pm-h to 1 mm-h depending upon the method used. The following are essential features of all methods. 

The new method produces TiN powders with surface areas exceeding 200 m g that are otherwise only accessible using a forced flow reactor and a microwave plasma activator in which titanium metal is reacted with N2 in the gas phase [14]. TiN powders with considerably lower specific surface area (Sg<60m g ) were also synthesized using the nitridation of 10-15 nm-sized... 

An alternative approach for the preparation of supported metal catalysts is based on the use of a microwave-generated plasma [27]. Several new materials prepared by this method are unlikely to be obtained by other methods. It is accepted that use of a microwave plasma results in a unique mechanism, because of the generation of a nonthermodynamic equilibrium in discharges during catalytic reactions. This can lead to significant changes in the activity and selectivity of the catalyst. 

Nearly every area of measurement science can boast of progress in measuring ever-smaller quantities of chemicals, but several stand out in their stunning trace-analysis capabilities. Trace-metal analysis has come to be dominated by methods that volatilize the sample and then either measure its spectroscopic emission or absorption, or measure the masses of the gaseous metal ions using mass spectrometry. Volatilization is accomplished by various thermal means that include flames, furnaces, and inductively coupled or microwave plasmas. The com-... 

Atsuya and Akatsuka [140] have described a method for determining trace amounts of arsenic. The technique, which uses capacitively coupled microwave plasma with an arsine generation system, has been used to determine arsenic in sewage sludge. 

The pesticide industry generates many concentrated wastes that are considered hazardous wastes. These wastes must be detoxified, pretreated, or disposed of safely in approved facilities. Incineration is a common waste destruction method. Deep well injection is a common disposal method. Other technologies such as wet air oxidation, solvent extraction, molten-salt combustion, and microwave plasma destmction have been investigated for pesticide waste applications. 

In microwave plasma destmction, organic material is channeled through a plasma detector tube where destruction is initiated by microwave radiation-producing electrons. The electrons react with the organic molecules to form free radicals and final simple reaction products such as SO2, CO2, CO, H2O, HPO3, COCI2, and Br2 [60]. In bench-scale tests, the plasma method resulted in extensive detoxification (>99% destmction) for several pesticides, including malathion, phenylmercuric acetate (PMA), and Kepone [55]. 

The specific heat of InN was measured using InN microcrystals obtained by the microwave nitrogen plasma method [20]. The specific heat was obtained using differential scanning calorimeter Setaram DSC 92 with a precision better than 1% for the entire temperature range the results of these measurements are listed in TABLE 3. 

InN single crystals of a size suitable for thermal conductivity measurements have not been obtained. The only measurement of the thermal conductivity has been made using InN ceramics [20], InN microcrystals obtained by microwave plasma were sintered under a pressure of 70 kbar at 700°C. The room temperature thermal conductivity was measured by the laser-flash method giving k = 0.45 W/(cm K) [20], This value is much below the estimate by Slack which gives k = 0.8 W/(cm K). This result indicates that the InN ceramic has a high impurity content and consists of small size grains. 

PACVD method is another typical way of making diamond films. Precursor gas molecules can be decomposed into radicals under the effect of plasma. There are three plasma sources commercially available (Davis 1993). Microwave plasma typically uses excitation frequencies of 2.45 GHz. Radio frequency (RF) plasma excitation typically employs frequencies of 13.56MHz (or less commonly 450kHz). Direct current plasmas can be run at low electric powers, named as cold plasma, or at high electric powers, which create an arc, named as thermal plasma. Microwave PACVD method is the most common one among the three methods. 

The silicon carbide-based ceramic layer is obtained by CVD activated by a microwave plasma (2.45 GHz) on the tantalum previously cleaned by an argon plasma (56 min, 133 Pa, 250 W) at a temperature identical to the deposition temperature (T = 570°C), lower than the substrate annealing temperature. After readjustment of the total pressure and microwave power by introduction of a precursor (TMS) in the argon flow, the SiC coating is produced under selected conditions (66 Pa, TMS/Ar = 0.2/5.5 l.h-, T = 570°C, 350 W) derived from a previous parametric study. Coatings obtained then presented low dry friction coefficients. The mechanical properties, which are essential in order to be able to appreciate the mechanical stability, were acquired by several methods ... 

Bings N. H., Olschewski M. and Broekaert J. A. C. (1997) Two-dimensional spatially resolved excitation and rotational temperatures as well as electron number density measurements in capadtively coupled microwave plasmas using argon, nitrogen and air as working gases by spectroscopic methods, Spectrochim Acta, Part B 52 1965-1981. 

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