Surface pretreatment prior

T. Van Schaftinghen, C. Deslouis, A. Hubin, and H. Terryn, Influence of the surface pretreatment prior to the film synthesis on the corrosion protection of iron with pol3fpyrrole films, Electrochim. Acta, 51, 1695-1703 (2006). 

An atmospheric pressure plasma ion bombardment treater together with an atmospheric CO2 composite snow spray cleaning module (see Figure 7.9) was positioned above an un-treated low density polyethylene (LDPE) material used in microelectronic devices (for use within military and aerospace electronic systems) for surface pretreatment prior to application of a Loctite 401 cyanoacrylate adhesive, and separately a Loctite 3553 light-cure acrylic adhesive. 

Substrate Properties. It is clear from equation 5 that higher hardness of the substrate lowers friction. Wear rate of the film also is generally lower. Phosphate undercoats on steel considerably improve wear life of bonded coatings by providing a porous surface which holds reserve lubricant. The same is tme for surfaces that are vapor- or sandblasted prior to appHcation of the soHd-film lubricant. A number of typical surface pretreatments are given in Table 13 to prepare a surface for solid-film bonding (61). 

Condensation Equipment There are two basic types of condensers used for control contact and surface. In contact condensers, the gaseous stream is brought into direct contact with a cooling medium so that the vapors condense and mix with the coolant (see Fig. 25-15). The more widely used system, however, is the surface condenser (or heat exchanger), in which the vapor and the cooling medium are separated by a wall (see Fig. 25-16). Since high removal efficiencies cannot be obtained with low-condensable vapor concentrations, condensers are typically used for pretreatment prior to some other more efficient control device such as an incinerator, absorber, or adsorber. 

The current transients observed upon immersion of n-type Si electrodes in HF of low concentration (2%) depend on the sample pretreatments. Immersion in 50% HF prior to anodization, for example, leads to current densities of up to 30 pA cm-2, which decreases within 1 s to the steady-state dark current value, producing a charge density of 24 pC cnrf 2. This effect has been ascribed to the density of Si-F bonds present on the electrode surface electrode prior to anodization [Be22],... 

The results for Run 19 (Vycor glass reactor), Run 21 (alonized Incoloy 800 reactor), and Run 14 (coke-covered Incoloy 800 reactor) were similar to both the kinetics and type of products obtained. Although neither oxygen or hydrogen pretreatments were tried in Vycor glass or alonized Incoloy 800 reactors prior to acetylene pyrolyses, it is thought that such pretreatments would have little or no effect on acetylene reactions. This conclusion is based on such pretreatments prior to pyrolysis with other hydrocarbons in these two reactors. It has been concluded that all increases in acetylene conversions above those of Runs 14, 19, and 21 were in some way caused by surface reactions. Based on this assumption, surface reactions were of major importance in Runs 15, 18, and 23. 

Surface water can also be processed to become drinking water but it requires some pretreatment prior to the microfiltration step. A filtrate flux of 1,000-1,500 L/hr-m can be realized [Guibaud, 1989]. 

Following the surface preparation, it is the task of surface pretreatment to generate the adhesive forces on the adherend surfaces required for the development of a strong bonded joint. Since almost all materials interesting for bonding have the property to cover the surfaces with impurity layers (oxides, rust, dust, greases), those layers have to be completely removed prior to adhesive application, since otherwise failures in the development of the adhesive forces will occur (Figure 7.5). 

HDPE is approximately a threefold better moisture barrier than LDPE of equivalent thickness. Polythene surfaces need pretreatment prior to printing or adhesive lamination. 

Certain surfaces require some form of pretreatment prior to printing. Foil usually requires primer wash, and polyethylenes and polypropylenes need to have the surface oxidised. The corona process is almost invariably used for films and flame treatment for bottles. Whether a surface has received treatment or not can be detected by immersing it in water and observing whether or not the water runs off. An oxidised surface has a lower wetting angle. If the surface is not printed soon after treatment another treatment may be necessary. Inks will not key onto non-oxidised PE and PP and will be removed when a self-adhesive tape test is employed. 

The nested packed reactor (Fig. 5A0d) allows sample pretreatment prior to injection by means of solid oxidants, reductants, ion exchangers, immobilized enzymes, or suitable surface-active sorbents. The potential of this approach is largely unexploited, since so far such sample pretreatment has been used only to remove unwanted matrix, which is not retained on the column, for sample preconcentration, and for analyte conversion in connection with AAS and ICP (cf. Chapter 4.7). 

AlfOy/Fe surfaces pretreated with water vapor prior to ammonia synthesis is shown in Figure 7.17. The initially inactive A1 0y/Fe(l 10) surface restructures and becomes as active as the Fe(lOO) surface after a 0.05-torr water vapor treatment and as active as the Fe(lll) surface after a 20-torr water-vapor pretreatment. This is about a 400-fold increase in the rate of ammonia synthesis compared with clean Fe(llO) [37]. The activity of the AljOv/Fe(100) surface can also be enhanced to that of the highly active Fe(l 11) surface by utilizing a 20-torr water-vapor pretreatment, and this high activity is maintained indefinitely as in the case for the restructured A1 0y/Fe(l 10). Little change in the activity of the Fe(lll) surface is seen experimentally when it is treated in water vapor in the presence of Al O,. 

Particle size effects. So far, we have shown the effect of the precursor used and the pretreatment (oxidation vs. reduction) in determining the resulting activity. Another important variable, controlled by the preparation and pretreatment, is the crystallite size. Changing the crystallite size was done by selection of the precursor and the pretreatment during its decomposition, as shown for the samples listed in Table 17.3. The activity of the reduced catalysts, with dispersions ranging from 0.29 to 0.76 (samples 6-9), was measured in the 10-port reactor. The catalysts were pretreated prior to reaction in two ways (a) oxidized at 200°C in air for 3 h, or (b) reduced in a 50% Hj-He mixture for 3 h at 200°C. After pretreatment, the CO conversion was determined from ambient to 200°C using a slow linear ramp of 0.5°C/min. Table 17.3 shows the rate per unit mass of catalysts at 100 and 130°C. Figure 17.11 (A-B) shows the TOE, or rate per surface Pt atom, at each temperature. 

Table 4.4.8. Surface Pretreatment Procedures Used by Mansfeld et al. [1982] Prior to Applying Polybutadiene Coatings to 1010 Carbon Steel...

The surface activation pretreatments prior to electroconductive surface modification are similar for polysaccharides and protein. In order to initiate the reaction with monomers, the molecules should be pretreated with alkaline, creating highly polar alkoxide segments. Some highly polar ECMs are however able to break the intermo-lecular bonds of biopolymers at neutral or mild acidic pH [17,19]. Another strategy of pretreatment is preoxidation of biopolymers, creating radicals. The lifetime of the radicals is directly related to environmental physical parameters, such as pH, polarity of solvents, and temperature. 

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