Effect of film thickness

It can be concluded from Figs. 9.11-9.13 that the achievable anisotropy is found to be a function of the evaporation rate. Therefore, further study is performed focusing the effect of evaporation rate. 

The initial thickness of most molybdenum disulphide coatings has an important influence on the performance and life of the coating . The special case of sputtered films is considered in Chapter 10, and there is little information about thickness effects for in situ or transfer films. Many workers have investigated the effect of film thickness on bonded films, but, as was pointed out earlier, much of this work appears confusing, and sometimes contradictory, because of failure to understand and analyse the effects of running-in or burnishing on the consolidation and resulting structure of the films. 

It may be useful first to consider the minimum acceptable thickness for a film. Although the thinnest films are inherently unlikely to have long lives, there may well be cases in which other design considerations limit the film thickness which can be accommodated. The minimum desirable thickness will obviously depend on the roughness of the substrate and the counterface. Dayson has shown that very thin films increase in friction as film thickness decreases due to an increasing degree of asperity penetration of the film. 

An optimum surface finish of 0.5 /vm c.I.a. is recommended for the substrate for a bonded film. The optimum roughness for a counterface for forming an effective transfer film has not been as well established, but if a similar surface finish is assumed, then the combined roughness parameter will be 0.7 m c.I.a. Under normal circumstances a typical bonded film will have a thickness of between 5 and 10//m, so initially at least there is no risk of asperity penetration. 

If design considerations require it, a much thinner bonded film could be used, or a soft film could be burnished down to much reduced thickness. Under those circumstances it would be possible to use a smoother substrate, but coating performance deteriorates badly if the surface is too smooth, and a miminum acceptable surface roughness would probably be about 0.2 yt/m c.I.a., giving a combined roughness parameter of about 0.3 fjm. It seems probable that in such a case an initial, or a fully-burnished, coating thickness of 1 to 2/ m would give a useful life before any serious problem of asperity penetration arises. 

Hopkins and Campbell used Dual Rub-Shoe and Falex test machines to study the wear lives of a series of polyimide-bonded molybdenum disulphide coatings, with initial coating thicknesses varying from 2.5 //m to 25 yi/m. Both test machines use line contact, and they calculated the initial contact zone stresses as 276 MPa and 669MPa respectively, reducing to 103 MPa and 171 MPa by the end of testing. They 

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Figure 21 Effect of film thickness on the in vitro release time for pulsatile capsules. (From Ref. 66.)...

Molecular-Scale Tribology of Amorphous Carbon Coatings Effects of Film Thickness, Adhesion, and Long-Range Interactions. 

Figure 2.31 Effect of film thickness on the absorbance response of a PXV/PEDOT PSS films bearing (a) 20 (b) 30 (c) 40 (d) 50 and (e) 60 bilayers. Square-wave potential between 0.5 V and —0.9 V and a period of 20s was employed. Taken from [196].

T. Nguyen and E. Byrd, FTIR-RA spectral characteristics of epoxy coatings on cold-rolled steel effects of film thickness and angle of Incidence, Appl. Spectrosc. submit for publication, 1985. 

H.M. Princen, M.P Aronson, and J.C. Moser Highly Concentrated Emulsions. II Real Systems. The Effect of Film Thickness and Contact Angle on the Volume Fraction in Creamed Emulsions. J. CoUoid Interface Sci. 75, 246 (1980). 

The use of FTIR to study reaction kinetics and chemical equilibria is based on the disappearance of a v(COO—) vibrational mode of the deprotonated fatty acid in concurrence with the appearance of the v(C=0) mode of the protonated FA. This type of data has been used to support reaction times of a few minutes to several hours or even days. Also, the extent of the reaction has been reported to be stoichiometric (22,23,39,43,47,53), based on the complete disappearance of the v(COO—) vibrational mode, whereas other studies indicate less than 100% conversion (Fig. 3.5.8) of the carboxylate to the protonated form (48,61,66,70). The effect of film structure on reaction rate has been discussed (61,66,70) however, discrepancies of the extent of the reaction of M-FA with H2S have not been previously addressed. FTIR spectroscopy has also been used to determine the effect of film thickness on reaction rate. For example, for 11-, 21-, and 31-layer CdSt films deposited at 37.5 mN in-1, reactions with H2S were found to slop at 42, 78, and 140 h, respectively (66). 

The effect of film thickness was very evident for films deposited from baths based on A/,A-dimethylselenourea and complexed with both ammonia and either... 

Matsuda, Y., Itooka, T., and Mitsuhashi, Y. (1980), Photostabihty of indomethacin in model gelatin capsules effects of film thickness and concentration of titanium dioxide on the coloration and photolytic degradation, Chem. Pharm. Bull., 28, 2665-2671. 

In the cases of poly (methyl methacrylate) (PMMA) and poly (vinyl chloride-vinyl acetate) (PVC/PV Ac), these polymers generate much more gas during irradiation than polystyrene. Thus, even if the gases accumulated in microvoids, where their enhancement of creep rate might be lessened, the local gas concentration between the polymer chains should still be much higher than in the case of polystyrene. One would thus expect to see an effect of film thickness on creep rate for these polymers. 

In this paper we report on TOFSIMS and XPS analyses of thick and thin films of SAAPS on zinc in order to demonstrate the effect of film thickness. We also present some TOFSIMS results obtained with films of y-APS on mild steel in which the effects of the cleaning process of the substrate and the pH of the silane solution are demonstrated. 

While effects of film thickness have also been reported [275], metal-support interactions seem to be important in governing the properties of the overlayer. For instance, Ni chemically deposited on MgO has shown in particular higher resistance to oxidation as a consequence of electronic interactions with MgO [276]. 

The excellent stability and reproducibility of these modified poly(aniline) electrodes for NADH oxidation allows detailed kinetic studies of the system to be completed. To determine the mechanism of NADH oxidation the effects of film thickness, electrode potential, rotation rate and NAD concentration have been investigated. 

First, the effect of film thickness on the amperometric response was studied. The effect of film thickness has been assessed for eight different film thicknesses at four different NADH concentrations. For thin films, Fig. 2.18 shows that the response increases with film thickness reaching a... 

Effect of Thickness of Adsorbing Film. Earlier studies of effect of film thickness (3) indicated that the trend between graphite film thickness and amount of benzalkonium adsorbed was small, from about 2 to 4 fig. benzalkonium per cm.2 for variation from 200 to 1000 fig. graphite per cm.2. The analyses by chemical methods for heparin adsorbed were not precise enough to show any trend. Chemical analysis did show that from 1.5 to 7.5 fig. of heparin was absorbed on from 400 to 1000 fig. of PVPyr per cm.2, but the range of heparin was so great at each PVPyr level that no clear trend could be seen. More recent autoradiographic studies with each kind of film indicate that for brief exposures to heparin solution in distilled water there is indeed a trend for more heparin to be adsorbed on thicker films of either kind. 

Jung J, Park H-W et al (2010) Effect of film thickness on the phase behaviors of diblock copolymer thin film. ACS Nano 4 3109-3116... 

The Effect of Film Thickness on Lamellar Growth Rate and Morphology... 

Further work was carried out with 3% - 5% of co-sputtered nickel to evaluate the effects of film thickness and test speed and load. He found that the life of a co-sputtered film increased almost linearly with coating thickness, while that of a conventional film reached a maximum at a thickness of about 4000 nm (40,000A), These are far thicker than coatings described by other authors. A comparison of life... 

Bahun, C.J. and Jones, J.R., Influence of Load, Speed and Coating Thickness on the Wear Life of a Bonded Solid Lubricant, Lubric. Eng., 25, 351, (1969). Hopkins, V., Discussion, p. 6, on Rabinowicz, E., Variation of Friction and Wear of Solid Lubricant Films with Film Thickness, ASLE Trans., 10, 1, (1967). Whitehouse, G.D., Nandan, D. and Whitehurst, C.A., The Effect of Film Thickness on Friction Coefficients for Solid Lubricants CaF2, MoSj and Graphite, ASLE Trans., 13, 159, (1970). 

Figure 33.18 Effect of film thickness on Scanning Kelvin Probe potential.

Figure 14 Effect of film thickness and concentration of oxybenzone on coloration rate of sulfisomidine tablets, (o) Control (one point), ( ) 2%, ( ) 0.5%, (3) 5%, ( ) 1%, ( ) 10%. Source. From Ref. 17.

Rochon, P., Bissonnette, D., Natansohn, A., Xie, S. (1993). Azo polymers for reversible optical storage 3. Effect of film thickness on net phase retardation and writing speed. AppL Opt. 32, 7277-7280. 

Fig. 3. The effect of film thickness on band focusing, 500>Ul headspace injection test mixture, (Table 1) A — with liquid nitrogen B — without liqpid nitrogen...

The nanometer-scale thin film may be regarded as a two-dimensional grown film on the GC substrate, so the thickness of the film is an important parameter characterizing the dimension of the film. The effects of film thickness on the AIREs were investigated quantitatively on nm-Pd/GC electrodes. Figure 9 shows a series of MSFTIR spectra recorded on nm-Pd/GC electrodes of different film thickness [dm) measured by using an STM [38,39]. We can observe that following the increase of <7m the intensity of the CO2 band is increased continuously, while the intensity of the... 

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