Tracer-sectioning technique

The tracer-sectioning technique was employed for the diffusion measurement. The distribution of specific activity C of a radioactive tracer at fixed temperature and oxygen partial pressure is expressed as... 

Sharma and Laskar [129] measured the self-diffusion of potassium in melt-grown potassium azide using a radioactive tracer sectioning technique. The diffusion coefficient in the range 85-254°C was found to be (0.19 0.03) exp [(- 0.80 0.06) eV/kT] cm sec. They concluded that the cation is the predominantly mobile species, with diffusion occurring by a vacancy mechanism. The value of 0.80 0.06 eV (77 kJ/mole) for the enthalpy of migration agrees well with the results of Maycock and Pai Verneker [127]. 

The diffusion of Rb was studied at 184 to 448C by using a tracer-sectioning technique. It was found that the migration of Rb" " occurred via a vacancy mechanism. The temperature dependence of the diffusivity obeyed ... 

Thin-layer deposition and tracer sectioning techniques were used to study the selfdiffusion of The data for temperatures ranging from 404 to 603C could be... 

The tracer sectioning technique was used to study the diffusion of K ions in melt-grown single crystals of potassium azide. The temperature dependence of the diffusion coefficients at 85 to 254C could be represented by ... 

The impurity diffusion of Fe in CoO was measured in air by using the tracer-sectioning technique. The results, at 1001 to 1600C, could be described by ... 

Doney S. C., Jenkins W. J., and Bullister J. L. (1997) A comparison of ocean tracer dating techniques on a meridional section in the eastern North Atlantic. Deep-Sea Res. 44(4), 603-626. 

Figure 5. Tracer diffusion in cobaltous oxide as a function of oxygen pressure [and hence Co/0 ratio given by Equations 9 and 13]. The symbols (X) denote data obtained by a sectioning technique while (0) denote data by the surface decrease method. The slopes of the lines are approximately one-fourth, indicating the existence of singly ionized cation vacancies (6).

By using the serial sectioning technique, the tracer diffusion of l Au into single crystals was studied. Some effect of the dislocation density was detected. This was explained in terms of a model in which vacancy generation occurred at climbing grown-in dislocations. The values of the 2 effective diffusion coefficients for the dissociative mechanism were determined from the present, and literature, results. One coefficient took a value of about 3 x lO cm /s at 900 to llOOC, while the other could be described by ... 

An investigation was made of diffusion into intrinsic n-type crystals which were doped with P to 5 x lO /cm, and into B pre-diffused extrinsic p-type crystals, by using a closed-tube diffusion technique. Profiles were determined by means of neutron activation and Ga radioactive tracer and sectioning techniques. The overall results for 900 to 1050C could be described by ... 

The serial sectioning technique was used to study tracer diffusivity in samples having dislocation densities of between 10 and lO /cm. The results indicated that the pipe diffusivity could be described by ... 

The diffusion of Cs" tracers was measured, at 327 to 447C, by using standard serial sectioning techniques. It was found that the data could be described by ... 

Serial sectioning techniques were used to obtain Zn tracer diffusion data for high-purity single crystals. It was shown that the diffusion of Zn + tracer proceeded substitutionally at 209 to 441C. For 209 to 350C, it was shown that ... 

The self-diffusion of C in hyperstoichiometric UC was measured in the single-phase region, using a radioactive tracer and sectioning technique. The diffusion equations were ... 

The diffusion of uranium was measured using radioactive tracers and sectioning techniques. The diffusion in stoichiometric material as a function of temperature was described by ... 

The tracer diffusion of Ag in dense polycrystalline specimens was investigated. The concentration profiles were measured by using radiotracer plus serial-sectioning techniques. The bulk diffusivity of H Ag in Cu3(Bi,Pb)2Ca2Sr20x could be described by ... 

The diffusion of Fe was measured parallel to the c-axis of single crystals at 708 to 1303C, at an O activity of unity. The tracer penetration profiles were determined by using sectioning techniques. At above 900C, the tracer diffusion could be described by ... 

In this section, we have seen that tracer response techniques can be a very powerful diagnostic tool that can help to uncover the reason(s) for unanticipated reactor... 

NRA is an effective technique for measuring depth profiles of light elements in solids. Its sensitivity and isotope-selective character make it ideal for isotopic tracer experiments. NRA is also capable of profiling hydrogen, which can be characterized by only a few other analytical techniques. Future prospects include further application of the technique in a wider range of fields, three-dimensional mapping with microbeams, and development of an easily accessible and comprehensive compilation of reaction cross sections. 

The neutron activation technique mentioned in the preceding paragraph is only one of a range of nuclear methods used in the study of solids - methods which depend on the response of atomic nuclei to radiation or to the emission of radiation by the nuclei. Radioactive isotopes ( tracers ) of course have been used in research ever since von Hevesy s pioneering measurements of diffusion (Section 4.2.2). These techniques have become a field of study in their own right and a number of physics laboratories, as for instance the Second Physical Institute at the University of Gottingen, focus on the development of such techniques. This family of techniques, as applied to the study of condensed matter, is well surveyed in a specialised text... 

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