Thin films aging behavior

Hoffmann, M. Hofer, C. Schneller, T. Bottger, U. Waser, R. 2002. Preparation and aging behavior of chemical-solution-deposited (Pb(Mg1/3Nb2/3)03)i x-(PbTi03)x thin films without seeding layers. J. Am. Ceram. Soc. 85 1867-1869. 

Solid-state NMR spectroscopy was also used to examine the post reaction behavior of pTrMPTrA samples prepared in bulk as thin films, as described in the experimental. All of the spectra in this aging study required a minimum of 720 scans on approximately 50 mg of sample with a 100 s pulse delay to achieve adequate signal/noise. Under these conditions, reliable peak areas could be obtained from the curve fits of the carbonyl region. Figure 3 depicts the evolution of the solid state spectrum of the sample stored under N2 over time and upon heating. The area of the peak at 174 ppm for the carbonyl adjacent to the reacted double bond increases as the peak at 166 ppm for pendant unsaturation decreases. The results of the aging study are given in Table I. 

The scope of the present paper is to emphasize the role of wetting and spreading in the aging by sintering, and in the redispersion of supported metal catalysts. In the next section, some experimental results regarding the behavior of iron supported on alumina are presented to demonstrate that surface phenomena do play a major role. This is followed by stability considerations which are employed to explain the coexistence of multilayer surface films with crystallites in an oxygen atmosphere and the rupture of thin films into crystallites in a hydrogen atmosphere. 

However, direct investigation of the interphase properties inside an adhesive bond is very difficult, for experimental reasons. In contrast, ultra-thin polymer films on metal substrates provide access for a number of analytical techniques. Hence, to some extent, they are suited to monitoring of interphase properties and processes. By varying the film thickness, it is possible to discriminate the influence of the metal substrate on the aging behavior in the interphase. 

This paper reports the study of the aging behavior of ultra-thin epoxy films on PVD layers of Al, Au, and Cu under varying environmental conditions by FTIR external reflection absorption spectroscopy (ERAS), to reveal influences of interphase interactions on crosslinking and on chemical aging processes at moderate temperature. 

Our results show that thin-film samples are suited to monitoring specific substrate influences on the aging behavior in the interphase. Nevertheless, further experiments are needed to correlate the observed evolution of IR bands definitely with chemical reaction mechanisms. 

Depth-Resolved Analysis of the Aging Behavior of Epoxy Thin Films by Positron Spectroscopy... 

The results of the PALS investigations of the aging behavior of thin epoxy films are presented here. The decisive parameters of the PALS analysis for polymers are the formation probability lo.ps of ortho-positronium and its average lifetime To-ps- While lo-Ps predominantly represents the effectivity of the electron acceptor groups in the polymer, Tq.ps is directly correlated with the sizes of the free-volume voids. 

Here, cj q is the tritium concentration at the time of formation. Aging for one year, for example, leads to a conversion of more than 5 /o of the original tritium inventory to He. We shall briefly review now some of the results published in the open literature concerning the aging behavior, He release and micromorphology of aged tritides. Early work on thin tritide films of Er, Ho, Sc, Ti and Y and pressed pellets of yttrium tritide showed a steady expansion of the samples with age and in the case of the thin films even spalling and bubble rupture after a few years. 

Baer and coworkers demonstrated that thin glassy films without free interfaces exhibited bulk physical aging behavior. For instance, PSF, when confined between polyolefin layers, showed no dependence of film thickness on the rate of physical aging. Motivated by these studies, Roth and coworkers devised a set of experiments to directly investigate the influence of an adjacent mbbery layer on Tg and physical aging in thin polymeric films [137]. The sample geometry consisted of a thin PS... 

For better understanding the diverse relaxation behavior of confined polymers, researchers have utilized models or simulation tools to capture the kinetic features of the material at the molecular level, aiming to represent the results observed in experiments. The FVHD model, which has been widely employed in characterizing physical aging in bulk polymers, is reformulated to describe the relaxation behavior of polymers under nanoconfinement. A dual mechanism combines the effect of vacancy diffusion and lattice contraction, and was recently applied with time-dependent internal length scales to characterize the free volume reduction in the aging process [169]. The dual mechanism model (DMM) fits the data of thin film permeability fairly well. The potential predictive capability of the DMM model depends on the accuracy of the relationship between the internal length and time scale on the description of complex material dynamics [161]. 

M. Laugier, Unusual adhesion-aging behavior in ZnS Films, Thin Solid Films 75 (1981) L19. 

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