Plasma activation

In most cases, CVD reactions are activated thermally, but in some cases, notably in exothermic chemical transport reactions, the substrate temperature is held below that of the feed material to obtain deposition. Other means of activation are available (7), eg, deposition at lower substrate temperatures is obtained by electric-discharge plasma activation. In some cases, unique materials are produced by plasma-assisted CVD (PACVD), such as amorphous siHcon from silane where 10—35 mol % hydrogen remains bonded in the soHd deposit. Except for the problem of large amounts of energy consumption in its formation, this material is of interest for thin-film solar cells. Passivating films of Si02 or Si02 Si N deposited by PACVD are of interest in the semiconductor industry (see Semiconductors). 

Glaze coatings (58) are appHed to dry or bisque-fired clay ceramics to form a strong, impermeable surface that is aesthetically pleasing. Protective ceramic coatings can also be deposited by CVD (68,90). Plasma activated CVD has been used extensively to produce diamond and diamondlike films. Diamond films can also be used to make optical coatings with a tailored refractive index. 

Plasma activation which typically takes place at much lower temperatures, i.e., 300-500°C. 

Gartner, G., Jamiel, P., and Lydtin, H., Plasma-Activated Metalorganic CVD of Illb Oxides/Tungsten Layer Structures, Proc. of 11th Int. Conf on CVD, (K. Spear and G. Cullen, eds.), pp. 589-595, Electrochem. Soc., Pennington, NJ 08534 (1990)... 

In a plasma-activated reaction, the substrate temperature can be considerably lower than in thermal CVD (see Ch. 5, Sec. 9). This allows the coating of thermally sensitive materials. The... 

However, the nitrogen molecule has afar greater bonding energy than ammonia and is more difficult to dissociate into free atomic nitrogen active species. Consequently, the deposition rate is extremely slow. This can be offset by plasma activation with high frequency (13.56 MHz) or electron cyclotron resonance (ECR) plasmasP Ef l and with micro-wave activation. 

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... 

In order to relate material properties with plasma properties, several plasma diagnostic techniques are used. The main techniques for the characterization of silane-hydrogen deposition plasmas are optical spectroscopy, electrostatic probes, mass spectrometry, and ellipsometry [117, 286]. Optical emission spectroscopy (OES) is a noninvasive technique and has been developed for identification of Si, SiH, Si+, and species in the plasma. Active spectroscopy, such as laser induced fluorescence (LIF), also allows for the detection of radicals in the plasma. Mass spectrometry enables the study of ion and radical chemistry in the discharge, either ex situ or in situ. The Langmuir probe technique is simple and very suitable for measuring plasma characteristics in nonreactive plasmas. In case of silane plasma it can be used, but it is difficult. Ellipsometry is used to follow the deposition process in situ. 

Hammer, Th., Kappes, Th. and Baldauf, M. (2004) Plasma catalytic hybrid processes gas discharge initiation and plasma activation of catalytic processes, Catal. Today 89, 5-14. 

Kuppers, D., and Lydtin, H. Preparation of Optical Waveguides with the Aid of Plasma-Activated Chemical Vapour Deposition at Low Pressures. 89, 107-131 (1980). 

Mihailovic, D., Saponjic, Z., Molina, R., Puac, N., Jovancic, P., Nedeljkovic, J. and Radetic, M. (2010) Improved properties of oxygen and argon RF plasma-activated polyester fabrics loaded with Ti02 nanoparticles. ACS Applied Materials ej Interfaces, 2, 1700-1706. 

Chronic copper poisoning in domestic sheep is first characterized by a period of passive accumulation of copper in the tissues. This period varies from a few weeks to more than a year. During this time the animal appears outwardly normal although the liver may contain more than 1000 mg Cu/kg DW and plasma activities of aspartate transaminase, sorbitol dehydrogenase, lactic... 

At 0.3 mg/kg BW, 1 nestling died after the second dose (age 6 days) and another after the fifth dose vs. no deaths in controls at day 19, brain cholinesterase activity was depressed 51% and plasma activity 49%. At 1.0 mg/kg BW, 1 died after the third dose at day 19, brain cholinesterase activity level was depressed 75% and plasma cholinesterase 25%. At 3.0 mg/kg BW, 9 of 11 tested nestlings died within 8 h of the first dose, another within 8 h of the second dose, and the last was killed by a predator after the second dose. The 2 nestlings that survived a single dose were moribund and their brain cholinesterase activity was depressed 85%... 

Yet another approach is to influence the combustion process itself by ionization, pulsed electromagnetic fields, glow discharge etc. The Institute of Energy at Dnepropetrovsk State University developed a plasma-activated sparking plug, currently in preparation for a full-scale production. 

Alcohol consumption is very difficult to assess. There is widespread belief that individuals underreport their intake and there are no reliable laboratory tests available for definitive diagnosis of alcohol abuse. A combination of abnormalities in the plasma activity of gamma-glutamyl transferase (GGT or yGT), AST and reduction in erythrocyte mean cell volume (MCV) maybe useful and all are routine lab. tests. A potential marker of interest is carbohydrate-deficient transferrin (CDT) which is an abnormal isoform of serum transferrin arising due to defects in the attachment of carbohydrate chains to the protein core. Unfortunately, CDT is a somewhat specialized test, not performed by most laboratories. Other markers which have attracted some research interest are ethyl sulphate and ethyl glucuronide. Excretion in the urine of these metabolites occurs for up to 50 hours after binge drinking so they offer a useful index of recent heavy alcohol intake. 

Recently we have evaluated several exogenous and endogenous tests of liver function in rainbow trout following intoxication by the model hepatotoxicant CCl. The results of these studies indicate that elevated plasma activity of the enzyme glutamate-pyruvate transaminase (GPT) is the most sensitive endogenous index of... 

Effect of Intoxication by MCB or CCI4 on Plasma Clearance of BSP and Plasma Activity of GPT. Twenty four,... 

Azizi, M., Guyene, T. T., ChateUier, G., Wargon, M., and Menard, J. (1997) Additive effects of losartan and enalapril on blood pressure and plasma active renin. Hypertension. 29, 634-640. 

The newer antihistaminics agents e.g. Azelastme inhibits histamine release and also inflammatory reactions evoked by leukotrienes and plasma activating factor (PAF). It is used for seasonal and perennial allergic rhinitis in the form of nasal spray. Mizolastine, a non-sedating antihistaminic is used in allergic rhinitis and urticaria. Ebastine, another non-sedating antihistaminic is used in nasal and skin allergies. 

Inhibition of XO by uric acid apparently occurs under in vivo conditions. Thus, it has been shown [16] that physiological levels of uric acid inhibited XO activity in human plasma. Activity and superoxide production by XO are also inhibited by many metal ions such as Ag+, Hg2+, Zn2+,Cu2+, Cr6+, etc. [17] or hyperoxia and active oxygen species [18]. 

Analysis of dopamine-jS-hydroxylase activity in plasma can not be used to make a definitive diagnosis, as approximately 4% of the population have very low plasma activities. Support for such a diagnosis can come from examining the noradrenaline dopamine ratio in plasma. This is markedly reduced in this condition. Deficiencies of the MAO isoforms have been confirmed from enzymatic analysis of fibroblasts (MAO-A) or platelets (MAO-B). 

Dayal et al. (1989) treated BALB/c mice intraperitoneally with a single dose of 9 mmol/kg bw 2-nitropropane. In male mice, plasma activities of the hepatic enzymes sorbitol dehydrogenase, alanine aminotransferase and aspartate aminotransferase were significantly elevated, while doses of 6.7 mmol/kg bw were ineffective. In female mice, a dose of 6.7 mmol/kg bw was sufficient to cause hepatotoxicity. Histopathological evaluation revealed hepatic damage, particularly in the periportal region. 

The reactions of elemental fluorine with inorganic compounds are exothermic and often have little or no reaction associated activation energies. Most often the major synthetic problem is kinetic and thermodynamic control of these vigorous reactions. It is therefore a very unusual synthetic situation when reactions must be activated by methods such as high temperatures, plasmas, or photochemical means. Examples of such cases are the synthesis of NO+BF4 by the photochemically activated reaction of fluorine and oxygen with boronnitride (52) and the plasma-activated synthesis of (CF112)n from graphite (53). 

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