Hydrogen Concentration Evaluation

Based on the Langmuir-Hinshelwood expression derived for a unimolecular reaction system (6) Rate =k Ks (substrate) /[I + Ks (substrate)], Table 3 shows boththe apparent kinetic rate and the substrate concentration were used to fit against the model. Results show that the initial rate is zero-order in substrate and first order in hydrogen concentration. In the case of the Schiff s base hydrogenation, limited aldehyde adsorption on the surface was assumed in this analysis. Table 3 shows a comparison of the adsorption equilibrium and the rate constant used for evaluating the catalytic surface. 

A quite different application of GDMS is the measurement of hydrogen and deuterium concentration, including depth profile analysis, e.g. in a gold electroplated layer on a CuSn substrate as described in reference.116 The relative sensitivity coefficient of hydrogen was evaluated by measurements of titanium standard reference material. 

Although in principal SIMS can detect hydrogen, this evaluation is not very reliable. The evaluation of hydrogen concentrations will be discussed in the last section. Due to the wide variation in sputtering secondary ion yields, detection limits on SIMS can vary from 10-9 to 1CT3 depending on the species being studied. The technique is most sensitive to those elements with low ionization potential (i.e., Na, K, etc.). 

In all of our earlier discussions, we have not found any satisfactory technique available to evaluate hydrogen concentration in a thin film. For plasma-enhanced CVD dielectric films, at least, there can be as much as 25 atomic % hydrogen in the film, and its concentration is definitely of interest. 

In order to provide a more convenient method for the evaluation of hydrogen concentration that could be useful for routine process control, the nuclear reaction procedure has been used to provide a standard for an infrared spectrometric technique.17... 

Another technique which can be used to measure hydrogen concentration uses a 2.5-MeV 4He beam.18 Although this is a more attainable energy range (comparable to accelerators used for RBS) than the nuclear method requires, it is still nowhere near as simple as obtaining an infrared spectra. However, it does offer the capability of depth profiling which the evaluation of infrared spectra does not. 

The dependencies both between the hydrogen concentration and the number of the microcracks emerged, and the values of velocity SAW on depth of the hydrogen penetration into the sample, period of diffusion, etc. are received at that. The limit hydrogen concentration in this material can be evaluated concerning the value of velocity SAW from the received dependence for steel (Fig. 4). 

Non-Destructive Evaluation (NDE) Hydrogen Concentration Measurement (HCM) Equipment (PC-XIV/29, paragraph 9.3) ... 

At PWRs with large containm t vessel, generation of hydrogen during a LOCA has been evaluated through the safety evaluation and confirmed that the hydrogen concentration is sufficiently low even after an accident. 

Table II presents the DOS evaluated at the Fermi energy for fixed hydrogen concentration and a range of y values for each of the palladium-noble metal-hydrogen systems considered. These results have been used[14] to calculate the electron-phonon coupling and provide an explanation of the variation (as a function of y) of the superconducting transition temperature T found in Stritzker s[16] experiments.

We believe that an appropriate approach for devising a technique to determine hydrogen concentration in thin metal films begins with the use of the volumetric technique in order to ef tablish its behavior in a direct way. Such parameters as substrate dependence, deposition conditions, thickness dependence and temperature dependence all need careful determination. With this in hand, an evaluation of the QCM approach becomes possible. 

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