Surfaces, ozone treatment

Recently, Genzer and coworkers [85] presented an interesting new approach for the preparation of stable silane-based SAM systems. As a substrate, cross-linked polydimethylsiloxane (PDMS) was oxidized by UV/ozone treatment to yield a thin sihcon dioxide surface. The surface was then treated with fluorinated alkyltrichlo-rosilanes from the gas phase while being mechanically stretched by a certain length Ax. After modification, the elastomer was allowed to relax resulting in a mecdianically assembled monolayer (MAM) at the surface (Fig. 9.8). 

An ozone treatment (10 minutes at room temperature) of the HF-etched SiC surface before the metallization step was introduced as a very convenient processing step to produce Schottky diode gas sensors with an increased stability and reproducibility. The use of spectroscopic ellipsometry analysis and also photoelectron spectroscopy using synchrotron radiation showed that an oxide, 1-nm in thickness, was formed by the ozone exposure [74, 75]. The oxide was also found to be close to stochiometric SiO in composition. This thin oxide increased the stability of the SiC Schottky diodes considerably, without the need for any further interfacial layer such as Ta or TaSi which have been frequently used. Schottky diodes employing a porous Pt gate electrode and the ozone-produced interfacial layer have been successfully operated in both diesel exhausts and flue gases [76, 77]. 

The SiC Schottky diodes and capacitors that have been processed by the authors were processed on either 6H or 4H substrates (n-type, about 1 x 10 cm ) with a 5-10- m n-type epilayer (2-6 x lO cm" ) [123, 124]. A thermal oxide was grown and holes were etched for the metal contacts. In the case of the Schottky sensors, the SiC surface was exposed to ozone for 10 minutes before deposition of the contact metal. This ozone treatment produces a native silicon dioxide of 10 1 A, as measured by ellipsometry [74, 75]. The MISiC-FET sensors (Figure 2.9) were processed on 4H-SiC, as previously described [125]. The catalytic metal contacts consisted of 10-nm TaSiyiOO-nm Pt, porous Pt, or porous Ir deposited by sputtering or by e-gun. 

This study reports two gel permeation techniques used to evaluate water at various stages of (potable water) treatment. The water samples were taken from a surface-water pilot treatment plant that employed several levels of ozone treatment. Selected fractions of the permeate were subsequently analyzed by pyrolysis gas chromatography-mass spectrometry (GC-MS). 

Efimenko K, Wallace WE, Genzer J (2002) Surface modification of Sylgard-184 poly(dimethyl siloxane) networks by ultraviolet and ultraviolct/ozone treatment. J Colloid Interface Sci 254 306-315... 

Croll BT. The installation of GAC and ozone surface water treatment plants in Anglian water, UK. Ozone Sci Eng 1996 18 19-40. 

On the other hand, the progress of wet-processes as preparative techniques of metal oxide films has been remarkable. The so-called soft solution process that provides oxide layers by means of electrochemical oxidation of a metal surface is expanding as a synthetic method of various mixed metal oxides with controlled thickness [2], The two-dimensional (2D) sol-gel process based on the hydrolysis of metal alkoxides at the air/water interface has been reported as a preparative technique of ultrathin oxide films (Fig. 6.1a) [3]. It is also known that LB films of metal complexes of long-chain alkyl carboxylic acid can be converted to metal oxide films after removal of organic component by oxygen plasma [4] and UV-ozone treatments (Fig. 6.1b) [5]. Preparation of metal oxide... 

Several reports on the activation of lignocellulosic surface by corona discharge, microwave plasma, and ozone treatments have been published (120-22). Strong bonds were produced between thermoplastics and wood by corona treatment of wood surfaces and particularly by treatment of polyethylene and polystyrene surfaces. With 5-min treatment wood—polymer—wood bonds of over 569 psi... 

Other primary disinfection technologies—chlorine, chlorine dioxide, ozone, UV radiation, and organic disinfectants—are discussed elsewhere (1-3,17-27) in detail. Because most of the utilities that are affected by the Surface Water Treatment Rules and the Ground-Water Disinfection Treatment Rules serve less than 10,000 persons, this chapter wiU emphasize the applications of chlorination and chloramination processes to both small and large utilities. Table 1 indicates that both chlorination and chloramination are comparatively simpler than ozonation UV processes. 

In order to eliminate oxidized surface compounds generated during ozone treatments, the samples regenerated with ozone were heated at 300°C in flowing hydrogen. Such compounds were reduced as expected, but the TPR diagram recorded after these treatments were different from the previous ones. This behavior could be possibly attributed to the exothermicity of oxidized compounds reduction. 

The effect of the surface treatment for longer UV—ozone treatment times (60 min, water contact angle <30°) in terms of adherence and the laterally inhomogeneous distribution of pull-off forces provide evidence for the successful and complete oxidation of the previously hydrophobic PDMS surfaces. Upon storage in ambient conditions, one can observe that the forces gradually increase in heterogeneity with... 

Ozone is residue-free in water due to its self-decomposition into oxygen. As described above, ozone has been extensively used in water and wastewater treatment since its first full-scale application in drinking water treatment at Oudshoorn, Netherlands, in 1893. To date, ozone has been used full scale for disinfection and purification of ground and surface waters, treatment of municipal and industrial wastewater, and treatment of swimming pool and cooling tower waters.P 4 1 1... 

Surface ozone oxidation is applied in polymers because it has the following advantages it introduces peroxides uniformly on the polymer surfaces it is applicable to complex geometries it can be handled easily and it is relatively economical as compared with other techniques such as corona discharge, plasma treatment, flame treatment, irradiation with gamma rays.I 1... 

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