Wettability of metals

Wettability of Metals after a 2 -Hour Equilibration at 0,6% RH (All data obtained at 20°C in nitrogen)... 

Table 1. Wettability of metals, alloys, and glasses on carbides...

Cleanness of the base, i.e. freedom from grease, which improves the wettability of the metal surface, and the removal of oxides, dust or loose paint, etc. already described. The closer the surfaces of paint film and metal, the more secondary valencies originating in the polar constituents of the medium are brought into play. 

The LLNA is the preferred method when compared to the GPMT because (a) it can equivalently predict human contact dermatitis, (b) a dose-response can be obtained, and (c) it is in line with current animal welfare efforts. Nevertheless, several situations exist where the GPMT is advantageous, depending predominantly on the choice of test substances. The LLNA is known for less powerful detection of the sensitization potential of metallic compounds, high molecular weight proteins, strong irritants, and for substances with low adhesion to the skin surface (skin wettability is a prerequisite for the successful application of LLNA) [136-140],... 

This last compound also prevent the penetration of metal salts in the depth of the polymer. Otherwise, other authors such as Janssen et al. [153, 154] investigated the chemical modification of polydimethylsiloxane to prepare materials used in the medical field. Hence, they modified the wettability of PDMS by a treatment of surfaces with ozone followed by UV decomposi-... 

Table IV. Effect of Metal Adherend on Wettability of oj- (/F-Chlorophenyl) dodecylglutaric Acid Films from the Melt°...

The wettability of diamond with Ni-Mn alloys having Ga, Ge, Sn, Mg, A1 and Si additives was determined by means of the sessile drop method at high pressure (5.5 GPa) and temperature (1400° C) following a special procedure [3,4]. The metal pellet melted and attained its equilibrium form owing to surface forces on the diamond plane surrounded by molten NaCl that gives a quasi-hydrostatic enviroment and suppress oxidation of the metal. 

Workers concerned with liquid/solid systems with exceptionally good wettability, such as some braze/metal workpiece systems, find that the drops do not preserve a perfectly circular area of contact because of the sensitivity of the liquid to changes in capillary attraction caused by minor variations in the surface texture of the workpiece. Because of such irregularity, some workers have used the contact area of a small volume of braze as a measure of wettability. Thus Feduska used area measurements to differentiate between the wetting of different stainless steels by a wide range of metals and alloys (Feduska 1959). 

The above distinction between non-reactive and reactive systems does not take into account the possible effect on reactivity and wettability of the furnace atmosphere. The concentration of dissolved oxygen in the liquid close to the S/L/V triple line will lie between two limits. The first of these is that for congruent dissolution of the oxide. This can be calculated using equations (6.8) by assuming that local equilibrium is established between the liquid metal and the oxide at the interface. This limit will be identified as Xq where the superscript I denotes its relevance to the interface. The second limit, Xq(Po2) at the liquid surface, is determined by equilibration with the furnace atmosphere in which the oxygen partial pressure is Pq2 (see Figure 6.3). Note that even if Xq and Xq can be calculated, it is impossible in practice to calculate the actual value of XQ at the... 

Table 7.3. Wettability of SiC by different liquid metals M with a negligible or weak reactivity with SiC.

Figure 7.12. Surface chemistry of SiC in high vacuum as a function of temperature. Wettability of SiC by non-reactive metals is mainly dictated by the oxidation layer on SiC at T T and by the graphite-rich layer formed by Si evaporation at T T. ...

This analysis of the literature on the Al/AIN system reveals the complexity of the surface chemistry of AIN that is influenced strongly, and probably dominated, by oxygen even though the results do not exclude possible effect of other impurities, for instance carbon. A detailed study by spectroscopic techniques, for instance XPS, of the surface chemistry of AIN after heat treatment at different temperatures is needed to clarify the wettability of this ceramic by liquid metals. 

Ti additions to Cu and also to Sn, Ag (Naidich and Kolesnichenko 1968), Ga (Naidich and Chuvashov 1983) or Ni-Pd (Kritsalis et al. 1991) also produce a nonwetting/wetting transition due to the formation of a wettable reaction product (TiC). Note that although there is some uncertainty about the wettability of TiC by pure non-reactive metals, it is clearly established that TiC is wetted by these metals when they contain even low concentrations of Ti leading to the formation of hypostoichiometric TiC at the interface (see Section 7.2, Figure 7.32). An example... 

The wettability of sites where presumably antibody had been deposited on an antigenic film allowed rapid identification on proteins adsorbed on surfaces such as unoxidized metal or on others that were unfit for interference color or Coomassie Blue observation. Since all data confirmed those obtained by other means they will not be listed. Some details are of interest. Wherever water drops condensed and were allowed to evaporate, a dot of matter presumably transported by the moving air/water boundary was deposited in the center of each drop during evaporation. With reexposure to air saturated with water, condensation would start on each dot and result in a pattern identical to the first one. Coomassie Blue staining, or exposure to metal oxide suspensions 110), would show a reticulum of protein concentrated between the water drop sites. 

By comparison with the metal carbides, the industrial demand for the nitrides is very small. This is in part due to the poor wettability of the nitrides by ferrous metals, which makes the manufacture of hard metal alloys more difficult. 

The scope of the present paper is to emphasize that the interactions between support, metal and atmosphere are responsible for both the physical (size distribution, shape of the crystallites, wettability of the substrate by the crystallites and vice versa), the chemical and the catalytic (suppression of chemisorption, increased activity for methanation, etc.) manifestations of the supported metal catalysts. In the next section of the paper, a few experimental results concerning the behaviour of iron crystallites on alumina are presented to illustrate the role of the strong chemical interactions between the substrate and the compounds of the metal formed in the chemical atmosphere. Surface energetic considerations, similar to those already employed by the author (7,8), are then used to explain some of the observed phenomena. Subsequently, the Tauster effect is explained as a result of the migration, driven by strong interactions,... 

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