Absorption-reflection thickness

Polymer to Counterface Bonding. Of extreme interest to the tribolo-gist is the nature and structure of interfacial adhesion of polymers to substrate surfaces because it contributes heavily to the adhesive wear of polymers. A very useful tool for the study of this subject is quantitative absorption - reflection thickness infrared spectroscopy (QUARTIR). This device is uniquely suited for the study of preferential orientation of large molecules at interfaces. Thus, insight into the structural interfacial bonding of molecules can be had, adhesion and accordingly adhesive wear better understood. 

Orientation at the interface between polymers and metals where the polymer transfer to the metal can be determined with quantitative absorption-reflection thickness infrared spectroscopy. With an understanding of polymer interfacial orientation, bonding mechanisms can be identified and accordingly adhesion of polymers to metals better understood. 

Absorption-reflection thickness IR spectroscopy (QUARTIR), quantitative, polymer wear analysis, 297... 

These absorptions may reflect the degree of crosslinking and/or the degree of degradation which is proportional to the amount of residual free radicals. The relative absorptions per thickness at 10.6 pm are plotted against the discharge frequency as shown in Fig. 5. The absorptions near 10 pm of the film formed in region HL... 

As in light absorption one uses the term attenuation for the sum of energy losses due to absorption, reflection and scattering. It is expressed in the same units as absorption, but it is not a material property, as depends, e.g. on the sample thickness. 

Emissivity, absorptivity, reflectivity, and transmissivity are the key radiation properties. The relative magnitudes of a, p, and T depend not only on the material, its thickness, and its surface finish, but also on the wavelength of the radiation (Kreith, 1965). Nevertheless, the emission of electromagnetic waves is a property of the material only. 

The phenomena of absorption, reflection, and transmission may be applied to the passage of light through a transparent solid, as shown in Figure 21.7. For an incident beam of intensity /q that impinges on the front surface of a specimen of thickness I and absorption coefficient /S, the transmitted intensity at the back face is... 

Infrared interrogation of thin film water contains two important levels of information. The first is from the spectroscopic signature that can provide insight into the nature of the hydrogen bonding networks. Second, the extent of the spectroscopic response (absorption, reflection or extinction) yields an estimate of the film thicknesses for construction of isotherms and through them thermodynamic properties. 

The detailed examination of the behavior of light passing through or reflected by an interface can, in principle, allow the determination of the monolayer thickness, its index of refiraction and absorption coefficient as a function of wavelength. The subjects of ellipsometry, spectroscopy, and x-ray reflection deal with this goal we sketch these techniques here. 

For thin-film samples, abrupt changes in refractive indices at interfrees give rise to several complicated multiple reflection effects. Baselines become distorted into complex, sinusoidal, fringing patterns, and the intensities of absorption bands can be distorted by multiple reflections of the probe beam. These artifacts are difficult to model realistically and at present are probably the greatest limiters for quantitative work in thin films. Note, however, that these interferences are functions of the complex refractive index, thickness, and morphology of the layers. Thus, properly analyzed, useful information beyond that of chemical bonding potentially may be extracted from the FTIR speara. 

An additional advantage to neutron reflectivity is that high-vacuum conditions are not required. Thus, while studies on solid films can easily be pursued by several techniques, studies involving solvents or other volatile fluids are amenable only to reflectivity techniques. Neutrons penetrate deeply into a medium without substantial losses due to absorption. For example, a hydrocarbon film with a density of Ig cm havii a thickness of 2 mm attenuates the neutron beam by only 50%. Consequently, films several pm in thickness can be studied by neutron reflecdvity. Thus, one has the ability to probe concentration gradients at interfaces that are buried deep within a specimen while maintaining the high spatial resolution. Materials like quartz, sapphire, or aluminum are transparent to neutrons. Thus, concentration profiles at solid interfaces can be studied with neutrons, which simply is not possible with other techniques. 

Measurements were performed on a potassium nitrite melt (KNO3) at 450°C. Fig. 73, curve 1 presents the spectrum obtained for a melt layer 0.05-0.1 mm thick, which was placed on a reflective surface (polished platinum). Fig. 73, curve 2 presents the inverted spectrum (relative to curve 1) of a relatively thin layer placed on an absorptive bottom surface (carbon-glass). 

Fig. 73. IR emission spectra of KNO3 melt at 450X7. Curve l - Layer thickness - 0.05 mm, reflective surface Curve 2 - Layer thickness - -0.1 mm, absorptive surface Curve 3 - Layer thickness - 0.2 mm, absorptive surface (after Agulyartsky and Sakharov [342]).

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