Film density

The film density is chosen to be D-D = 2.0 as the values for Oj, G and G/Oj, in EN 584-1 refer to this density. For the value of the gradient G the condition given by the value G/op of the standard has to be considered, that means the value of the gradient has mostly to be greater than the minimum gradient of the film system class. 

Modem NDT film systems (with Pb screens) are very linear X-ray detectors. This is shown in fig.l for different NDT film systems and a X-ray tube at 160 kV. Note that for histoncal reasons the film response curve is often plotted as film density versus log (radiation dose), which hides this linear relationship. The film density is the difference between the measured optical film density and the fog density Db of the film base. 

The resulting relationship for the film density depending on the wall thickness changeAw is as following ... 

Dnom - film density at wall thickness Wnom Dtro - film density at wall thickness Wnom + w)... 

After this calibration step (the effective absorption coefficient is determined from a known wall thickness change and the corresponding variation of the optical film density) the evaluation of local wall thickness changes Aw (corresponding to De,o) from the nominal wall thickness w o , (corresponding to Dnom) can be done according to ... 

It has been found that the contrast in film density caused by very small local variations in mass density of the concrete is considerable, e g. S D = 0.12 for a 6 mm diameter hole in a 250 mm thick concrete beam. The image quality provided by fine-grained films (Agfa Gaevert D7) was sufficient to distinguish the thin walls of a pre-stressing duct in a 750 mm thick concrete bridge slab. 

The temperature of the anodizing solution also has an effect on the anodic film stmcture. Thus chillers are used to maintain a consistent temperature in the bath while the part is being anodized, and air agitation is continuously appHed to ensure a uniform temperature. The result is a consistent anodic film density of uniform pore size. 

Optical Properties. The index of refraction of a deposited material is sensitive to the film density. A lower index of refraction is found at less than bulk densities. The reflectance of a metallic surface is affected by the growth morphology of the film. 

Mechanical Properties. The mechanical properties of thin films is affected by the film density and composition. In many appHcations, the properties of the substrate material is important to the functionaHty of the thin film in mechanical appHcations. 

Numerical solution of Eq. (51) was carried out for a nonlocal effective Hamiltonian as well as for the approximated local Hamiltonian obtained by applying a gradient expansion. It was demonstrated that the nonlocal effective Hamiltonian represents quite well the lateral variation of the film density distribution. The results obtained showed also that the film behavior on the inhomogeneous substrate depends crucially on the temperature regime. Note that the film exhibits different wetting temperatures on both parts of the surface. For chemical potential below the bulk coexistence value the film thickness on both parts of the surface tends to appropriate assymptotic values at x cx) and obeys the power law x. Such a behavior of the film thickness is a consequence of van der Waals tails. The above result is valid when both parts of the surface exhibit either continuous (critical) or first-order wetting. 

The outstanding resistance to corrosion exhibited by the high-silicon alloys is believed to be due to the development of a corrosion-resistant film containing a large proportion of silica. The full protective value of the film does not develop for most applications until at least 14-25% silicon is present in the alloy (Fig. 3.61). Increase in the content of silicon above 14-5% does not have a dramatic effect upon the corrosion resistance of the alloy (Fig. 3.61), although the further increase in film density is of service if the casting is to be exposed to solutions containing halide ions, especially hydrochloric acid. 

Since the nuclear and electronic scattering cross sections for alpha particles are well known, the relative concentrations of the elements and their depth profiles can be easily obtained. The relative element concentrations are determined by the relative scattering intensities. The depth profile is obtained from the energy spread of the scattered particles, which lose energy before and after the nuclear collision, by inelastic scattering with electrons. The knowledge of the elements areal density and of the film thickness allows the determination of film density. 

Figure 19. Film density as a function of hydrogen gas concentration in the (EU+Ar) beam during ion beam sputter deposition.

Precursor Structure Effects. The precursor structure can impact a broad range of properties, including crystallization temperature, the formation of intermediate phases during thermal treatment and film density, among other properties. Table 2.4 reports some of the key precursor properties that may affect densification and crystallization behavior, as well as the final film microstructure. 

The first term represents the temperature dependence of the film density, being directly related to the thermal expansion coefficient of the film, and also indirectly related to that of the substrate. Generally, the thermal expansion coefficient of the organic substance is much larger than that of the inorganic substance like glass. In the case of the alternate LB film of fatty acid/alkylamine or fatty acid/alkylaniline, the pyroelectric coefficient p decreased as the thermal coefficient of the substrate increased [18]. 

Image Quality. Resolution of screens were measured at 50 KV peak x-ray exposures at film densities of 1.0 using standard lead resolution grids with sets of etched lines about I line pair per mm up to 15 line pairs per mm. The results are reported as the maximum set of line pairs resolved per mm. 

Mass of film = (volume of film)(density of film)... 

It may still be desirable to have a moderately high wafer temperature for other reasons. For example, at very low temperatures, film density may be low, or temperature may play an important role in determining film structure. Nonetheless, it is possible to operate at lower wafer temperatures than would be allowed by a strictly thermal process. 

We observe that as the partial pressure of NH3 is increased, the amount of hydrogen incorporated into the film rises from 14 to 26 atomic %. The film density is a maximum where the Si/N ratio is 0.75. 

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