Relationship between material processing

Materials science can be defined as the study of the relationship between materials processing, their structure, and their properties, and the interplay of these parameters (Fig. 7.1). Materials characterization is a powerful tool for understanding how the different parameters involved in the early stages of design and processing, influence their structure and performance. 

Another parameter of relevance to some device appHcations is the absorption characteristics of the films. Because the k quantum is no longer vaUd for amorphous semiconductors, i -Si H exhibits a direct band gap (- 1.70 eV) in contrast to the indirect band gap nature in crystalline Si. Therefore, i -Si H possesses a high absorption coefficient such that to fully absorb the visible portion of the sun s spectmm only 1 p.m is required in comparison with >100 fim for crystalline Si Further improvements in the material are expected to result from a better understanding of the relationship between the processing conditions and the specific chemical reactions taking place in the plasma and at the surfaces which promote film growth. 

The piopeities of a ceramic material that make it suitable for a given electronic appHcation are intimately related to such physical properties as crystal stmcture, crystallographic defects, grain boundaries, domain stmcture, microstmcture, and macrostmcture. The development of ceramics that possess desirable electronic properties requires an understanding of the relationship between material stmctural characteristics and electronic properties and how processing conditions maybe manipulated to control stmctural features. 

For example, finished-product release specifications such as content uniformity are rarely correlated to clinical evidence rather, they are set according to compendial test standards. Furthermore, the functional relationship between in-process material characteristics and finished-product quality is seldom known at a high level hence, the assigned in-process specifications for some operations may over- or underestimate the true level of process capability. As the level of process understanding in the pharmaceutical industry increases, development of science- and evidence-based in-process and release specifications will improve the reliability of Cpk as a tool for process characterization. 

At this point it should be remarked that multivariate regression with latent variables is a useful tool for describing the relationship between complex processes and/or features in the environment. A specific example is the prediction of the relationship between the hydrocarbon profile in samples of airborne particulate matter and other variables, e.g. extractable organic material, carbon preference index of the n-alkane homologous series, and particularly mutagenicity. The predictive power was between 68% and 81% [ARMANINO et al., 1993]. VONG [1993] describes a similar example in which the method of PLS regression was used to compare rainwater data with different emission source profiles. 

The selection of the independent process parameters (which include the choice of specifications for the raw materials and intermediates) is made during development in an effort to ensure the appropriate response of the dependent parameters. The relationship between the independent and dependent variables need not be linear, and may be inverted. The key is to recognize that the selection of the independent variable influences the dependent variable. While this description is simplistic and ignores the possible influence of other variables, it accurately describes the symbiotic relationship between process and product. Without a process (as defined by the selection of the independent variables), there is no product (with its dependent product attributes). Without a product, there is no reason for the process. The PAR approach describes how one is to develop the relationship between the process and its resultant product. There is no reason to choose one over the other consideration and confirmation of both is necessary to validate a product. 

Techniques for the use of existing information and analyzing new data to identify causal relationships between structure, processing and properties is being developed using tools based on distributed data bases [27] and Bayesian neural networks [28], These advanced mathematical techniques permit more effective searches for critical dependencies than traditional methods. In some cases virtual mathematical experiments can be conducted that vary only a single microstructural variable to determine material responses under conditions that are impossible to duplicate in real experiments [29],... 

The distance between the ramp radii used to assist the material into and out of the loop should be spaced apart twice this radius. It is important that this distance is maintained between the ramps. The ramps radii can be the proper size only to have the loop reintroduce the set. Likewise, it does not help to allow more space than twice the radius between the ramps. See the bend radius chart (Table 2) for the relationship between material thickness, the type of material being processed, and proper ramp radii. 

Successful polymer compounding is an interactive relationship between material properties, processing methods and end product properties. 

Many processes are available for the production of plastic products and the choice depends upon the relationship between material properties, processing method and end-product properties, in addition to the choice of forming method, which all have technical and economic aspects. Three important features of plastic melts during processing are shear viscosity, melt flow index (MFI) and melt elasticity. MFI is the quantity of polymer extruded under specific load and temperature conditions in a given time. The elastic properties of the melt are a major factor in determining the residual strain and moulding defects [8]. 

The studies carried out earlier have shown that polymer film samples strength to a considerable extent is defined by growth parameters of stable crack in local deformation zone (ZD) at a notch tip [1-3], As it has been shown in Refs. [4, 5], the fiactal concept can be used successfully for the similar processes analysis. This concept is used particularly successfully for the relationships between fracture processes on different levels and subjecting fracture material microstructure derivation [5]. This problem is of the interest in one more respect. As it has been shown earlier, both amorphous polymers structure [7] and Griffith crack [4] are fractals. Therefore, the possibility to establish these objects fractal characteristics intercommunication appears. The authors of Refs. [8, 9] consider stable cracks in polyarylatesul-fone (PASF) film samples treatment as fractals and obtain intercommunication of this polymer structure characteristics with samples with sharp notch fracture parameters. 

Any electrode process has several stages and the electrochemical step is just one of them. For a consecutive series of transformations with a slow mass transfer step, the overall rate depends solely on the latter. Therefore, kinetic description of such process is determined by mass transfer of the starting material from bulk solution to the electrode surface and/or departure of the products from the reaction zone. Such processes are investigated by dijfusion kinetics and called dijfusion processes. Diffusion kinetics has three main equations. The first one represents a relationship between the process rate and distribution of the reactant concentration near the... 

However, other features of PCD and PCBN that are not so readily specified are also critical to performance. For example, the identity and concentration of impurities, the size distribution of binder-filled pores, the microstructure of the superabrasiveAVC interface, and stress distributions, particularly near the interface with the tungsten carbide support, are all crucial. As yet there are no industry standard tests that can satisfactorily predict abrasion resistance, surface finish, etc., in specific applications. Each manufacturer is therefore forced to maintain strict quality standards for the manufacturing process and to empirically determine the relationship between manufacturing process, material properties, and performance in various applications. 

In Section 3.1 we define two basic flows used in the characterization of polymeric fluids along with the appropriate material functions. These basic flows are also found in polymer processes. In Section 3.2 several constitutive equations capable of describing the viscoelastic behavior of polymer melts are presented. The emphasis in this section is on manipulating these equations for flows in which the deformation history is known. In this section we have added discussion of fiber suspensions as they are commonly processed to yield materials with increased stiffness and strength. In Section 3.3 an introduction into the methods for measuring rheological properties is presented. In Section 3.4 several useful relationships between material functions are presented. These relationships (or correlations) are important as they allow one to obtain estimates, for example, of steady shear material functions from linear viscoelastic data. Because... 

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