Etching, surface treatment

Bonding. Surface treatment, such as chemical etch, corona, or flame treatments, is required for adhesive bonding of Tefzel. Polyester and epoxy compounds are suitable adhesives. 

While polymeric surfaces with relatively high surface energies (e.g. polyimides, ABS, polycarbonate, polyamides) can be adhered to readily without surface treatment, low surface energy polymers such as olefins, silicones, and fluoropolymers require surface treatments to increase the surface energy. Various oxidation techniques (such as flame, corona, plasma treatment, or chromic acid etching) allow strong bonds to be obtained to such polymers. 

Fig. 36. Pari of a Morphology Catalog illustrating the unacceptable morphologies resulting from incorrect surface treatment (a) Turco alkaline clean with no FPL etch, and (b) Amchem deoxidizer with no FPL etch [169. ...

Surface treatment of the composite can have a significant effect on adhesion. Surface treatment enhances one or more of the mechanisms described previously. Wu et al. [15] studied the effects of surface treatment on adhesive bonding for AS-4/APC-2 laminates. They found that the greatest bond strength was achieved from acid etching and plasma etching the composite surface. Table 1 summarizes the various surface treatments that were evaluated. 

Surface preparation of the core foil was originally simple acid etching. As the importance of durable surface treatments became known, a more stable chemical conversion coating with an organic primer-like coating became standard. Still, water ingression into honeycomb structure continued to cause the occasional... 

Figure 14 shows the ATR spectrum of the etched polyethylene surface treated with a chronic acid group [76]. Absorption bands due to surface treatment appear at 3300, 1700, 1260, 1215, and 1050 cm". The band at 3300 cm represents the absorption due to the hydroxyl group and that at 1700 cm " is due to the carbonyl group. The bands at 1260, 1215, and 1050 cm are all due to the alkyl sulfonate group. 

Figure 66D was obtained for the same CdTe(lll) crystal after electrochemical reduction at -2.0 V for 2 minutes. Transitions for both Cd and Te are evident, and the Cd/Te peak height ratio is similar to that observed by other workers for stoichiometric CdTe [393,394]. In addition, well-ordered (1 X 1) LEED patterns (Fig. 67) were observed on both the CdTe(lll)-Cd and CdTe(lll)-Te faces. This is in contrast to CdTe surfaces prepared by ion bombardment, where postbombardment annealing was required to produce a LEED pattern, and the annealing appeared to result in formation of a reconstructed surface. In summary, well-ordered, clean, and unreconstructed CdTe surfaces have been produced using a wet etching/electrochemical treatment. 

Surface treatments of carbon fibers can in general be classified into oxidative and non-oxidative treatments. Oxidative treatments are further divided into dry oxidation in the presence of gases, plasma etching and wet oxidation the last of which is carried out chemically or electrolytically. Deposition of more active forms of carbon, such as the highly effective whiskerization, plasma polymerization and grafting of polymers are among the non-oxidative treatments of carbon fiber surfaces. 

Surface treatments of CD CdSe films deposited from selenosulphate/NTA solutions have a pronounced effect on various optical, electrical, and optoelectronic properties of the films, due to interaction with or modification of such surface states. Mild etching (dilute HCl) of the films reverses the direction of current flow both in CdSe/polysulphide photoelectrochemical cells [108] and in Kelvin probe surface photovoltage (SPV) measurements in air [109], These studies are discussed in more detail in Chapter 9, in Section 9.2 on photoelectrochemical cells. At this point, it is sufficient to state that the effect is believed to be due to preferential trapping of either electrons or holes at surface states that are modified by the etching process. 

Semiconductor electrodes can be used in galvanic cells like metal electrodes and a controlled electrode potential can be applied by means of a potentiostat, if the electrode can be contacted with a suitable metal without formation of a barrier layer (ohmic contact). Suitable techniques for ohmic contacts have been worked out in connection with semiconductor electronics. Surface treatment is important for the properties of semiconductor electrodes in all kind of charge transfer processes and especially in the photoresponse. Mechanical polishing generates a great number of new electronic states underneath the surface 29> which can act as quenchers for excited molecules at the interface. Therefore, sufficient etching is imperative for studying photocurrents caused by excited dyes. 

Phosphoric acid is used as an intermediate in the production of animal feed supplements, water treatment chemicals, metal surface treatments, etching agent, and personal care products such as toothpaste. It is used as a catalyst in the petroleum and polymer industry. Phosphoric acid is used in food as a preservative, an acidulant, and flavor enhancer it acidifies carbonated drinks such as Coca Cola and Pepsi, giving them a tangy flavor. Phosphoric acid is used as a rust remover and metal cleaner. Naval Jelly is approximately 25% phosphoric acid. Other uses for phosphoric acid include opacity control in glass production, textile dyeing, rubber latex coagulation, and dental cements. 

Figure 5. Scanning electron microscope pictures of single-crystal CdSe after sev-eral surface treatments. (0001) face, Cd-side, shown. (1120) and (1010) faces behave similarly. (A) After aqua regia/chromic acid etch (B) after aqua regia etch (C) after aqua regia/photoetch.

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