Nondestructive techniques

Stress-corrosion cracks tend to be fine, tight, and easily overlooked. Various nondestructive techniques are available to aid in the discovery of cracks, such as dye penetrant, and ultrasonic and radiographic techniques. 

Welding stresses are not visually observable. The common nondestructive technique available for determining residual stresses is x-ray diffraction. 

The chemical composition of particulate pollutants is determined in two forms specific elements, or specific compounds or ions. Knowledge of their chemical composition is useful in determining the sources of airborne particles and in understanding the fate of particles in the atmosphere. Elemental analysis yields results in terms of the individual elements present in a sample such as a given quantity of sulfur, S. From elemental analysis techniques we do not obtain direct information about the chemical form of S in a sample such as sulfate (SO/ ) or sulfide. Two nondestructive techniques used for direct elemental analysis of particulate samples are X-ray fluorescence spectroscopy (XRF) and neutron activation analysis (NAA). 

Ellipsometry is a very powerfiil, simple, and totally nondestructive technique for determining optical constants, film thicknesses in multilayered systems, sur ce and... 

As with other diffraction techniques (X-ray and electron), neutron diffraction is a nondestructive technique that can be used to determine the positions of atoms in crystalline materials. Other uses are phase identification and quantitation, residual stress measurements, and average particle-size estimations for crystalline materials. Since neutrons possess a magnetic moment, neutron diffraction is sensitive to the ordering of magnetically active atoms. It differs from many site-specific analyses, such as nuclear magnetic resonance, vibrational, and X-ray absorption spectroscopies, in that neutron diffraction provides detailed structural information averaged over thousands of A. It will be seen that the major differences between neutron diffraction and other diffiaction techniques, namely the extraordinarily... 

Numerous other nondestructive techniques can be used to identify incipient problems in plant equipment or systems. However, these techniques either do not provide a broad enough application or are too expensive to support a predictive maintenance program. Therefore, these techniques... 

The usefulness of this nondestructive technique may go further than pigment characterization, and it is proposed as an additional method for checking the authenticity of ancient archaeological artifacts. 

While most polymer/additive analysis procedures are based on solvent or heat extraction, dissolution/precipita-tion, digestions or nondestructive techniques generally suitable for various additive classes and polymer matrices, a few class-selective procedures have been described which are based on specific chemical reactions. These wet chemical techniques are to be considered as isolated cases with great specificity. 

In many instances when analyzing archaeological objects, removing a sample may be aesthetically deleterious to the object, therefore rendering the removal of samples totally inadequate, or allowing the removal of extremely small samples so as not to affect the appearance of the objects. In such cases it is often necessary to turn to specialized techniques, such as nondestructive techniques, which do not require the removal of samples altogether, or to micro analytical techniques, for which extremely small samples are needed (see Textbox 11). 

The next question to address is to what extent does the study of a (deeply) frozen biological sample provide information that is relevant for an understanding of its functioning in a living cell at whatever the ambient temperature of this cell happens to be First and foremost, let us state the fact of experience that solutions of biomacromolecules such as metalloproteins can be frozen and thawed many times without any detectable deterioration of their biological activity. Combined with the rather low intensity (<0.2 W) of the microwave source of an EPR spectrometer, this leads to the proposition that EPR spectroscopy is a nondestructive technique. 

In the museum context, nondestructive (or quasi-nondestructive) techniques such as X-ray fluorescence (XRF) (Chapter 5) are often preferred for the analysis of inorganic objects, although microanalysis by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) (Chapter 9) is growing in importance, since the ablation craters are virtually invisible to the naked eye. Raman and infrared spectroscopy (Chapter 4) are now being used for structural information and the identification of corrosion products to complement X-ray diffraction (Section 5.4). 

There are cases where application of nondestructive techniques such as cyclic voltammetry is not sufficient to establish the reaction mechanism unambiguously. Analyzing the distribution of products at the preparative-... 

Measurement of radionuclides in marine solids may be accomplished by either destructive or nondestructive techniques. The nondestructive... 

This method is based on the principle of capillary equilibrium, providing a nondestructive technique in which the total porosity and capillary pressure-saturation data are measured [198,199]. The idea is that when two partially saturated porous materials are in contact, the system moves toward an equilibrium state in which the capillary pressure of a liquid in one of fhe samples is the same for fhe ofher material. 

Given that NIRS is a rapid, nondestructive technique and that most pharmaceutical blend constituents absorb in the NIR, it has been applied off-line to assess blend homogeneity. In the mid-1990s scientists at Pfizer utilized on-line NIRS to successfully characterize powder blending. ... 

Carbon - The aerosol collected on the Tissuequartz filters was analyzed for total carbon by the nondestructive technique of proton-induced gamma-ray emissions (17) and graphitic carbon (soot) by calibrated optical reflectance at Washington University, St. Louis, Missouri. The estimated error in measurement of total carbon per filter was 5 yg or 20%, whichever was greater. The estimated error for soot was lyg or 20%, whichever was greater. 

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