Surface layers preparation doping

Organic photoreceptors can be prepared in either a flexible web or drum format. Webs are usually prepared on polymer substrates, polyethylene tere-phthalate being the most common. The substrates are between 100 to 200 pm in thickness and coated with a conducting surface layer. The substrates often contain layers on the reverse side for reduced curl, static discharge prevention, and control of frictional characteristics. The web configuration is also widely used for laboratory studies. For drums, the substrate is a metal cylinder, usually Al. Recently, however, drums of a poly(phenylene sulfide) resin doped with conductive C black have been developed (Kawata and Hikima, 1996). Drums are widely used in low- and mid-volume applications. Drums, however, are not well suited for research purposes. Thus, the preparation and characterization of drum photoreceptors is usually related to a specific application. 

For example, continuous multilayered ZSM-5 films were grown on cordierite modules.[59] Similar films were generated on as-prepared and acid-treated honeycomb substrates.[60] The latter treatments led to silica-rich surface layers their composition affected the Si/Al ratios of the zeolites crystallized on the cordierite. Thin, defect-free Mid-type films were also made on porous alpha-alumina and yttria-doped zirconia substrates using tclrapropylammonium hydroxide (TPAOH) as a structure-directing agent.[61]... 

Composites of PANI-NFs, synthesized using a rapid mixing method, with amines have recently been presented as novel materials for phosgene detection [472]. Chemiresistor sensors with nanofibrous PANI films as a sensitive layer, prepared by chemical oxidative polymerization of aniline on Si substrates, which were surface-modified by amino-silane self-assembled monolayers, showed sensitivity to very low concentration (0.5 ppm) of ammonia gas [297]. Ultrafast sensor responses to ammonia gas of the dispersed PANI-CSA nanorods [303] and patterned PANI nanobowl monolayers containing Au nanoparticles [473] have recently been demonstrated. The gas response of the PANI-NTs to a series of chemical vapors such as ammonia, hydrazine, and triethylamine was studied [319,323]. The results indicated that the PANI-NTs show superior performance as chemical sensors. Electrospun isolated PANI-CSA nanofiber sensors of various aliphatic alcohol vapors have been proven to be comparable to or faster than those prepared from PANI-NF mats [474]. An electrochemical method for the detection of ultratrace amount of 2,4,6-trinitrotoluene with synthetic copolypeptide-doped PANI-NFs has recently been reported [475]. PANI-NFs, prepared through the in situ oxidative polymerization method, were used for the detection of aromatic organic compounds [476]. 

The specimen preparation problem for TEM GBs in ceramics must be considered in terms of both their structure and chemistry (even in so-called pure materials). Just as the wetting behavior of a surface may be altered by the doping of the surface layer, so it is important to identify and characterize the segregation of impurities and additives to GBs in these materials. The problem here is 2-fold the features of the GB (its misorientation and plane) must be identified and the distribution of foreign elements must then be accurately measured. The last part of this process is actually even more difficult than you might expect. The added complexity arises from the methods that are, at present, routinely used to prepare samples of ceramic materials for examination in the TEM. 

Asymmetric hollow fiber membranes of polysulfone, polyethersulfone, and polyphenylsulfone can be prepared by phase inversion spinning solvent/nonsolvent dopes, i.e., N-methylpyrrolidone/formamide. These asymmetric hollow fiber membranes possess a microscopically observable skin supported by a porous open cellular network. The walls of the open cells of the matrix are composed of arrays of interconnected spherical micelles. With increasing proximity to the outer surface, the packing density of the spherical micelles increase with a concomitant decline in interstitial porosity. At the outer surface layers, the packing of the micelles becomes... 

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