Material characteristic properties Frequency limits

Instruments for determination of dynamic-mechanical properties are available from several manufacturers. For the reasons discussed earlier (see Section 16.1.7) measurements are most often made over a limited range of frequencies and a wide range of temperature the technique is then called dynamic-mechanical thermal analysis (DMTA). The great majority of exploratory and product-control measurements are made on highly automated DMTA instruments, which give a rapid broad summary of material characteristics of a sample. 

For different modes and purposes, there are special AFM probes (cantilevers and tips). These differ in terms of their geometry, dimensions, force constants, resonance frequencies, tip position, shape and radius, material, etc. There are numerous commercial sources and we refer to these for finding the appropriate probes for the given experiment and sample. It is also clear based on the rudimentary treatment of tip sample interactions (Chap. 1) and the basic AFM features that the attainable information and resolution are in many cases dictated by the properties and characteristics of the probe tip. The tip physically interacts with the surface and its sharpness and aspect ratio, for instance, determine the degree of convolution in imaging small features or the limited success in the visualization of small pores (Fig. 2.23). 

Two of the Gd isotopes, namely, d and Gd, have excellent neutron-capture characteristics but are present in nature in only low concentrations. As a result, Gd has a very fast burnout rate and has limited use as nuclear control rod material in reactors and power plants [2]. Compounds of gadolinium are used in making phosphors for color TV tubes. The metal has superconductive properties. As little as 1% of the element has been found to improve the workability and resistance of iron, chromium, and related alloys to high temperatures and oxidation. The ethyl sulfate compound has extremely low noise characteristics. Hence, it may find use in multiplying the performance of high-frequency amplifiers. 

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