Microstructure of materials

We will give here a short overview of the most common XRPD techniques used to study the microstructure of materials, starting from the most used and simple Scherrer method to the quite complex Warren-Averbach method, which is able to extract all the information available on sample microstructure and defects. 

To achieve the goal of required performance, durability, and cost of plate materials, one approach is improvement of the control of the composition and microstructure of materials, particularly the composite, in the material designing and manufacturing process. For example, in the direction of development of thermoplastics-based composite plate, CEA (Le Ripault Center) and Atofina (Total Group) have jointly worked on an irmovative "microcomposite" material [33]. The small powders of the graphite platelet filler and the PVDF matrix were mixed homogeneously by the dispersion method. The filler and matrix had a certain ratio at the microlevel in the powder according to the optimized properties requirements. The microcomposite powders were thermocompressed into the composite plate. 

The authors wish to express appreciation to Mr. Howard Novak and McDonnell-Douglas Astronautics Company, Titusville, FL 32780, and the Microstructure of Materials Center of Excellence (CLO) for partial support of this research. The authors would also like to acknowledge the use of the Polymer Products and Services, Inc. dynamic mechanical instrument in this work. 

The mass diffusive flux m, of Equation (3.2) generally depends on the operating conditions, such as reactant concentration, temperature and pressure and on the microstructure of material (porosity, tortuosity and pore size). Well established ways of describing the diffusion phenomenon in the SOFC electrodes are through either Fick s first law [21, 34. 48, 50, 51], or the Maxwell-Stefan equation [52-55], Some authors use more complex models, like for example the dusty-gas model [56] or other models derived from this [57, 58], A comparison between the three approaches is reported by Suwanwarangkul et al. [59], who concluded that the choice of the most appropriate model is very case-sensitive, and should be selected, according to the specific case under study. 

Although SPP coupling is known to dq>end on the dielectric constants of semiconductor and metal and the surface corrugation [19], its dependence on the microstructure of materials is rarely known. Chen et al have studied the effects of Ag microstructure on the emission enhancement of Ag / InGaN quantum well and find Ag nanocrystals substantially decrease the radiative decay rate of SPP leading to weak SPP mediated emission [24]. 

Figure 10. Flowchart depicts the steps involved in obtaining and evaluating the microstructure of materials from digitally acquired images.

The EDS type of X-ray spectrometer is commonly included as a part of SEMs and TEMs. The reason for using EDS rather than WDS is simply its compactness. With EDS in an electron microscope, we can obtain elemental analysis while examining the microstructure of materials. The main difference between EDS in an electron microscope and in a stand-alone XRF is the source to excite characteristic X-rays from a specimen. Instead of using the primary X-ray beam, a high energy electron beam (the same beam for image formation) is used by the X-ray spectrometer in the microscopes. EDS in an electron microscope is suitable for analyzing the chemical elements in microscopic volume in the specimen because the electron probe can be focused on a very small area. Thus, the technique is often referred to as microanalysis. 

Diffraction Analysis of the Microstructure of Materials, ed. E. J. Mittemeijer and P. Scardi, Springer Series in Materials Science, vol. 68, Springer-Verlag, Berlin, 2004. 

The authors wish to thank the Microstructure of Materials Center of Excellence, College of Engineering, University of Florida for financial support of this research. 

ARM 04] ARMSTRONG N., KALCEFF W., CLINE J.P., BONEVICH I, A Bayesian/maximum entropy method for the certification of a nanocrystallite size NIST standard reference material , in MITTEMEIIER E.J., SCARDl P. (eds.). Diffraction analysis of the microstructure of materials. Springer Series in Materials Science, vol. 68, p 187-227,2004. 

As a result of the undersaturation, the critical crystallite size becomes infinitely large and only the largest nuclei survive because they require more time to dissolve than smaller nuclei. The resulting microstructure of materials heated at high heating rates in the temperature range of 1200-1600°C is coarser than for materials heated at low heating rates [20,29,39]. 

Although, to date, interface anisotropy has received less consideration in the study of microstructure evolution, it is dear that it plays a critical role in determining the final microstructure of materials. It can be said that a desirable microstructure could only be obtained by a dear understanding of interface anisotropy, and making proper use of it. Today, most theoretical developments relating to interface anisotropy and microstructure evolution remain qualitative in nature, due mainly to the lack of a database on the interface anisotropy of the materials in use. Hence, an extensive accumulation of these data, and a better refinement of theory, should further enhance the present understanding of the microstructure evolution of materials. 

Grain shape accommodation is clearly observed in the micrographs of Fig. 10.28 for the W(Ni) system containing 4 wt% Ni. However, many microstructures of materials produced by liquid-phase sintering also show rounded (spheroidal) grains. As an example. Fig. 10.29 shows the microstructure for the same W(Ni) system described in Fig. 10.28 but with a higher amount of liquid (14 wt% Ni). 

The Transmission Electron Microscope (TEM) is a powerful instrument that is used to determine the microstructure of materials at very high resolution (5-lOnm). 

THE OUTLINE OF APPLICATIONS OF THE SOL-GEL METHOD TABLE 1 -2. TYPES OF MICROSTRUCTURES OF MATERIALS PRODUCED BY SOL-GEL METHOD... 

The effect of materials chemistry and microstructure of materials in SCC and the interrelationship between the two is highly complex. The composition of the alloy has a significant bearing on the properties of the passive films and phase distribution. For example, a high amount of carbon in steels tends to form chromium carbide which causes sensitization of steel and leads to intergranular corrosion. Similarly, impinity elements in steels segregates and affects the corrosion dissolution process. 

Microscopy techniques are used for the development of predictive structure-property-process models to develop marketable technologies, such as for TLCPs [613]. Models are used to fully describe the macro and microstructure of materials such as fibers, moldings, and extrudates. As with most polymers, process history and temperature affect these structures and the resulting properties. The discussion that follows includes examples of the types of microscopy techniques that can be helpful for... 

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