Composite properties microstructure

The electromagnetic properties of steels depend on their composition, their microstructures and applied stresses. It is therefore natural to try to use magnetic and electrical parameters of steels to evaluate their microstructure. 

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 composite microstructure (and, therefore, its composite properties and polishing performance) is largely determined by the mode of manufacture. A summary of the major process variables associated with pad manufacturing and the anticipated effects on physical properties is given in Table II. 

Just as the electrical properties are clearly related to the phase composition and microstructure of the electrolyte, so are its key mechanical proper-... 

A.H. Deutchman and R.J. Partyka (Beam Alloy Corporation observe, "Characterization and classification of thin diamond films depend both on advanced surface-analysis techniques capable of analyzing elemental composition and microstructure (morphology and crystallinity), and on measurement of macroscopic mechanical, electrical, optical and thermal properties. Because diamond films are very thin (I to 2 micrometers or less) and grain and crystal sizes are very small, scanning electron microscopy... 

Ultrasound is used to obtain information about the properties of a material by measuring the interaction between a high frequency sound wave and the material through which it propagates. This interaction depends on the frequency and nature of the ultrasonic wave, as well as the composition and microstructure of the material. The parameters most commonly measured in an ultrasonic experiment are the velocity at which the wave travels and the extent by which it is attenuated. To understand how these parameters are related to the properties of foods it is useful to consider the propagation of ultrasonic waves in materials in general. 

A ceramic matrix composite or CMC is composed of two or more solids, the matrix of which consists of a ceramic material or carbon. The crystalline, ceramic matrix is moulded and/or densified at a temperature of at least 1000 K. To the matrix one ormore solid inorganic substances are added, e.g. in the form of particles or fibres in order to alter the (thermo) mechanical properties of the pure matrix. In the composite s microstructure these additives can still be distinguished by their chemicalcomposition or geometry even after they have undergone a temperature treatment of at least 1000 K. 

The Nicalon fibre (10-20 pm) available commercially consists of a mixture of P-SiC free carbon and Si02 [28], The properties of Nicalon start to degrade above about 600°C because of the thermodynamic instability of the composition and microstructure. Ceramic-grade Nicalon fibres, designated the NL series, having low oxygen content are also available. 

Pratapa, S., Low, I.M. O Connor, B.H. (1998) Infiltration-processed functionally-graded AT/alumina-zirconia composites I, Microstructure and physical properties. J. Mater. Sci. 33, 3037-3046. 

Alternative processing methods also offer the potential to control the microstructure and final properties of nanocomposites. Both self-propagating high-temperature sintering and spark plasma sintering offer means to obtain metastable yet dense nanocomposites. Subsequent heat treatments can then be used to approach equilibrium microstructures, where the properties will be a function of the heat treatment temperature and time. In this way a variety of microstructures, and thus variations of the composite properties, can become available. 

Ning, J., Zhang, J., Pan, Y. and Guo, J., Fabrication and mechanical properties of Si02 matrix composites reinforced by carbon nanotube , Materials Science and Engineering, A Structural Materials Properties, Microstructure and Processing, 2003, A357, 392-396. 

The substrates carrying the circuits shown in Fig. 4.5 are a 95-96% alumina. This ceramic has been adopted for its combination of physical and chemical characteristics and, importantly, low cost. It offers a combination of mechanical, thermal and electrical properties which meet the in-service requirements, and compositional and microstructural characteristics suited to thick film printing (see Section 4.2.2). Alumina substrates are manufactured on a very large scale making the unit costs a small fraction of the total circuit cost. 

The technical magnetic properties such as Hc and pi are primarily a function of the magnetocrystalline anisotropy constant (K ) of the material. But once the magnetocrystalline anisotropy has been made small, the soft magnetic properties are still limited by magneto-elastic anisotropies due to internal mechanical stress. Hence, materials development has focused on compositions and microstructures where both K and the saturation... 

Processing conditions required to attain desirable composite properties can be defined more easily if the factors controlling composite microstructure are understood. Such factors include type of precursors employed and the composite s processing history. The microstructure of the matrix may contribute to the performance of the fibers and influence the properties of the composite. Reviewed are experiments to determine matrix micro-structural features, how microstructural variations are achieved, and ways in which thermal expansion and fracture behavior relate to microstructure. 

Wilson et al. [25] analyzed various brands of commercial cements and specified their possible composition, properties, and microstructure. Wilson et al. report the most representative and comprehensive data on commercial porcelain dental cements. These cements consist of powdered alumina-lime-silica glass mixed with phosphoric acid that formed a hard and translucent product. The starter glass powder consists of 31.5-41.6 wt% silica, 27.2-29.1 wt% alumina, 7.7-9.0wt% calcium oxide, 7.7-11.2 wt% sodium oxide, 13.3-22 wt% fluorine and small amounts of phosphorous and zinc oxides. Often very small amounts of magnesium and strontium oxides are also present. 

Like the ultrasonic velocity and attenuation coefficient, the acoustic impedance is a fundamental physical characteristic which depends on the composition and microstructure of the material concerned. Measurements of acoustic impedance can therefore be used to obtain valuable information about the properties of materials. 

NMR is not, of course, the only analytical technique used to establish the composition and microstructure of polymeric materials. Others include >66 ultraviolet-visible spectroscopy (UV-Vis), Raman spectroscopy, and infrared (IR) spectroscopy. IR and Raman spectroscopy are particularly useful, when by virtue of cross-linking (see. e.g. Chapter 9), or the presence of rigid aromatic units (see Chapter 4). the material neither melts nor dissolves in any solvent suitable for NMR. The development of microscopy based on these spectroscopic methods now makes such analysis relatively simple (see below). Space precludes a detailed account of these and many other techniques familiar to the organic chemist. Instead we focus for the remainder of the chapter on some of the techniques used to characterize the physical properties of polymeric materials. 

Materials Analysis. The next level of complexity involves the measurement of dielectric properties for the determination of composition and microstructure as well as thicknesses. Thin films are typically microscopically inhomogeneous with substantial fractions of grain boundaries and voids, so their dielectric properties are rarely equal to those of the corresponding materials in bulk form. As an example, the pseudodielactric function <(> film deposited by low pressure... 

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