Material characterization methods characteristics

Modulation Spectroscopy has proven to be an important characterization method for semiconductors and semiconductor microstructures. The rich spectra contain a wealth of information about relevant materials, surfaces and interfrces, as well as device characteristics. In general, the apparatus is relatively simple, compact (except EBER), inexpensive (except EBER), and easy to use. One of the main advantages of Modulation Spectroscopy is its ability to perform relevant measurements at room... 

Polymers are typically complex mixtures in which the composition depends on polymerization kinetics and mechanism and process conditions. To obtain polymeric materials of desired characteristics, polymer processing must be carefully controlled and monitored. Furthermore, one needs to understand the influence of molecular parameters on polymer properties and end-use performance. Molar mass distribution and average chemical composition may no longer provide sufficient information for process and quality control nor define structure-property relationships. Modern characterization methods now require multidimensional analytical approaches rather then average properties of the whole sample [1]. 

Clarifying the structure and functions of protein materials in the solid state provides an index with respect to the design of artificial biomaterials. Solid-state NMR has been used as a powerful means for elucidating structure and dynamics in addition to the X-ray diffraction method [le]. The structure and dynamics of some fibrous proteins, such as wool, silk, collagen, tropomyosin, etc., have been characterized using characteristic solid-state NMR chemical shifts as stated above, and much more new information obtained in addition to the results provided by X-ray diffraction. And the individual advantages of these two methods are complementary with each other. Details of appli-... 

Figure 17.3.2 Detection limits, sampling depth, and spot size for several surface spectroscopic techniques. XRP (x-ray fluorescence) EMP (electron microprobe) EEL (electron energy loss), SAM (scanning Auger microprobe) STEM (scanning transmission electron microscopy). Other abbreviations in Figure 17.3.1. This figure is meant to provide a graphic summary of the relative capabilities of different methods modem instmments have somewhat better quantitative performance characteristics than the 1986 values given here. [From A. J. Bard, Integrated Chemical Systems, Wiley, New York, 1994, pp. 103, with permission adapted from Texas Instmments Materials Characterizations Capabilities, Texas Instmments, Richardson, TX, 1986, with permission.]...

Biomaterials such as natural gums are extracted from living matter. The molecules forming these biomaterials are known to be very complex in nature. Water content in biomaterials is an essential characteristic of them. The water content plays a crucial role in its physical properties like electrical conduction through it. Since these materials are either a covalent or a hydrogen bonded system they cannot be used and tested at temperatures above 120°C. It is apparent, therefore, that not all conventional methods of material characterization can be applied. Thus, as a method of material characterization, some of the conventional methods are used in a restricted way so as to retain the biomaterial characteristics. The characterization method used in the study of natural gum Arabica is summarized in the following sections. 

The determination of the buckling constant h by calibration from mercury intrusion porosimetry, or from nitrogen adsorption-desorption, can lead in some cases to different results. It is likely that, beyond the imprecision due to the method, the differences in pore sizes observed arise from a fundamental difference in the pore size concept. lUPAC proposed to define pore size as the distance between two opposite pore walls (Rouquerol, 1994). In the case of materials from the sol-gel process, this definition is not applicable, because pores are not included between walls, but are only delimited by interconnected filaments. In practice, it is considered that the sizes obtained from analysis methods of the texture of porous materials are characteristic pore sizes. Because the different analysis methods are based on different physical phenomena, it is not astonishing that they lead to slightly different characteristic pore sizes. Discrepancies resulting from using different characterization methods appear in several publications, often when the same material is analyzed by nitrogen adsorption-desorption and mercmy intrusion porosimetry (Smith, 1990, Brown, 1974, Milburn, 1988, Minihan, 1994). Me Enaney et al. noted that the distribution profiles obtained by different characterization techniques are often similar, but that differences, sometimes important, between the absolute values of characteristic pore sizes are almost unavoidable (Me Enaney et al., 1995). 

The measurement technique of texture of porous materials that collapse under isostatic mercury pressure is based on the mechanical behavior of the network of interconnected filaments. This method defines, as characteristic size, the length of the edge ofthe reference cubic pore that has the same resistance toward buckling that the true pore that collapses under mercury pressure. The calibration of this technique by other characterization methods is necessary, but results can differ depending on whether the adjustment has been made from nitrogen adsorption-desorption isotherms, or from mercury intrusion porosimelry. In the case of discrepancy, preference is given to this last adjustment method. 

Recently an improvement of the microscopic method for evaluating the swelling characteristics of tablet disintegrants has been proposed authors also considered the changes in particle shape that may take place upon swelling.All the microscopic methods, however, present some limitations in their applicability to routine swelling measurements, especially when irregularly shaped materials or materials characterized by small variations of the particle linear dimensions are considered. 

A study of the hydration of cement and cement compounds in the presence of superplasticizers is useful for theoretical and practical considerations. Many t5 es of thermal techniques including DTA, DSC, TG, DTG, Conduction Calorimetry, and EGA have been used for such studies. They have yielded important results that could be correlated with physical and mechanical characteristics of cement systems. Investigations have included the measurementofheat of hydration, the mechanism of reactions, strength development, microstmcture, permeability, durability aspects, compatibility problems between cement and superplasticizers, the prediction of some properties, material characterization and selection, mathematical modeling of hydration, development of test methods, and cement-superplasticizer interactions. 

Monchalin J-P (1993) Progress towards the application of laser ultrasonics in industry. In Thompson DO, Chimenti DE (eds) Review of progress in QNDE 12. Plenum Press, New York, pp 495-506 Monchalin J-P (2007) Laser-ultrasonics principles and industrial applications. Chap 4. In Chen CH (ed) Ultrasonic and advanced methods for nondestructive testing and material characterization. World Scientific, Singapore, pp 79-115 Pilarski A, Rose JL, Balasubramian K (1990) The angular and frequency characteristics of reflectivity from a solid layer embedded between two solids with imperfect boundary conditions. J Acoust Soc Am 87 532-542... 

---