Porosity critical factors

Critical factors. In general, porosity is caused by the entrapment of gas during the welding process or during solidification of the weld metal. Surface contamination may provide a gas source during the welding operation. 

This relationship has been displayed in Figure 9.13. For small values of d> and compatible elements are such that /ciRssfclL. This means that , L and compatible elements such as Ni, Cr, or Mg are virtually unaffected by zone-refining. Incompatible elements are such that ktR/ktLat

efficient scavenging by ascending molten zones. Again, residual porosity is a critical factor for incompatible-element distributions. 

The porosity is a critical factor for growth and integration of a tissue into the bioceramic implant. In particular the open porosity, that which is connected to the outside surface, is critical to the integration of tissue into the ceramic especially if the bioceramic is inert. Several methods have been developed to form porous ceramics, two of these are starch consolidation and drip casting. 

We are interested in three quantities (1) the size of the pores, (2) the distribution of the porosity, and (3) the total amount of porosity in the sample. Usually the actual shape of the pores is less important, although there may be situations in which the shape would be a critical factor. We can see pores in transmission electron microscopy (TEM), scanning electron microscopy (SEM), and atomic force microscopy (AEM). If they are large enough, we will also see them in visible light microscopy (VLM). None of these observations will give a statistical measurement of the... 

The morphology, magnitude, and interconnection of the scaffolds porosity are critical factors in assessing their viability as tissue engineering devices. The structure of the scaffolds and their porosity should transmit the cues for... 

Rapid equilibration of solute ions within the ion-exchange material is another critical factor. This is frequently achieved by using resins with accessible exchange sites, often concentrated near the outer surface, and a resin with sufficient porosity-... 

As mentioned at the beginning of this section, the temperature factor absorbs other unaccounted or incorrectly accounted effects. The most critical are absorption, porosity and other instrumental or sample effects (see Chapter 3), which in a systematic way modify the diffracted intensity as a function of the Bragg angle. As a result, the B parameters of all atoms may become negative. If this is the case, then the absorption correction should be re-evaluated and re-refined or the experiment should be repeated to minimize the deleterious instrumental influence on the distribution of intensities of Bragg peaks. 

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