Structural film analysis

Table 1 contains the metal-to-metal engineering property requirements for Boeing Material Specification (BMS) 5-101, a structural film adhesive for metal to metal and honeycomb sandwich use in areas with normal temperature exposure. The requirements are dominated by shear strength tests. Shear strength is the most critical engineering property for structural adhesives, at least for the simplistic joint analysis that is commonly used for metal-to-metal secondary structure on commercial aircraft. Adhesive Joints are purposefully loaded primarily in shear as opposed to tension or peel modes as adhesives are typically stronger in shear than in Mode I (load normal to the plane of the bond) loading. 

The very new techniques of scanning tunnelling microscopy (STM) and atomic force microscopy (AFM) have yet to establish themselves in the field of corrosion science. These techniques are capable of revealing surface structure to atomic resolution, and are totally undamaging to the surface. They can be used in principle in any environment in situ, even under polarization within an electrolyte. Their application to date has been chiefly to clean metal surfaces and surfaces carrying single monolayers of adsorbed material, rendering examination of the adsorption of inhibitors possible. They will indubitably find use in passive film analysis. 

X-ray diffraction techniques are the only way of determining the crystal structure of natural and synthetic polymers, although the x-ray data itself obtained from a crystalline polymeric fiber or film is not sufficient to allow complete refinement of the structure. Conformational analysis and electron diffraction represent complementary methods which will facilitate the determination of the structure. The necessary requirements for the x-ray approach are crystallinity and orientation. X-ray data cannot be Obtained from an amorphous sample which means that a noncrystalline polymeric material must be treated in order to induce or improve crystallinity. Some polymers, such as cellulose andchitin, are crystalline and oriented in the native state.(1 )... 

Laser Raman spectroscopy has been applied to materials characterization studies over the past several years. Annual reviews discuss advances in the field and provide references for a number of specialized areas including thin film analysis (1). The attractive features for using Raman spectroscopy to evaluate thin films include a nondestructive j n situ measurement capability plus the ability to acquire both spatially and time-resolved vibrational data from which structural information can be inferred. 

Auger electron spectroscopy with depth profiling via argon ion etching (position and thickness of near-surface layer), transmission electron microscopy of ultramicrotomed cross-sections (physical internal structure), elemental analysis (extent of metal salt conversion), and surface electrical resistivity versus temperature profiles (continuity of near-surface layer). The data from these techniques were used cooperatively to develop a model for these microcomposite polyimide films. The model represents the sample as three distinct regions. Fig. 1. The bulk of the film contains either converted (e.g. Ag) or nonconverted (e.g. C0CI2) additive in a predominately polyimide environment. An oxide-rich (e.g. 0 ) or metal-rich layer (e.g. Ag, Au) interspersed with polyimide accounts for the second region. 

Spread films of polylauryl methacrylate (polydodecyl methacrylate) are also susceptible to investigation by neutron reflectometry and partial structure factor analysis because the main chain backbone and dodecyl substituent can be separately deuterated (Reynolds et al. 1995). From such analysis the distribution of dodecyl substituents of backbone segments and water molecules shown in figure 8.19 was obtained. A notable feature of these distributions is that the methacrylate backbone is completely immersed in the sub-phase, in contrast to the arrangement of polymethyl methacrylate. Secondly, the hydrocarbon substituent penetrates deeper into the sub-phase than does the immersed backbone. At first glance this seems most imlikely however, all of this behaviour can be attributed to the dodecyl substituent. Its hydrophobic nature forces the backbone into the sub-phase. To relieve short-range steric interactions between substituents, rotations about main chain bonds force the dodecyl units slightly deeper into the sub-phase before sufficient bonds in the substituent can rotate... 

Infrared (IR), near-infrared (NIR), and Raman spectroscopy have been successfully used for quantitative and qualitative analysis of polymer films. These methods leverage the fact that vibrational spectra are very sensitive to polymer structure and the strength of chemical bonds of functional groups. NIR spectroscopy has several practical advantages in polymer film analysis, including nondestructive and... 

The availability of synchrotron radiation sources has stimulated the development of interfacial characterization techniques based on scattmng of x-rays and photoelectrons. For example, near-edge x-ray absorption fine structure (NEXAFS) analysis of surface monolayer films gives information on molecular orientation that is complementary to that usually obtained by vibrational spectroscopy. X-ray diffraction from interfaces, in particular x-ray standing wave techniques, now appear to be very promising as tools for providing vertical profiles of well-ordered surface structures at angstrom resolutions. ... 

Sputtered Neutral Mass Spectrometry (SNMS) is the mass spectrometric analysis of sputtered atoms ejected from a solid surface by energetic ion bombardment. The sputtered atoms are ionized for mass spectrometric analysis by a mechanism separate from the sputtering atomization. As such, SNMS is complementary to Secondary Ion Mass Spectrometry (SIMS), which is the mass spectrometric analysis of sputtered ions, as distinct from sputtered atoms. The forte of SNMS analysis, compared to SIMS, is the accurate measurement of concentration depth profiles through chemically complex thin-film structures, including interfaces, with excellent depth resolution and to trace concentration levels. Genetically both SALI and GDMS are specific examples of SNMS. In this article we concentrate on post ionization only by electron impact. 

Complete elemental analysis of complex thin-film structures to several pm depth, with excellent depth resolution... 

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