Densification volumetric

While the photocurable polymers used for S-FlL avoid the viscosity and thermal concerns associated with the thermoplastics used in NIL, they are not without then-problems. During polymerization, the photocurable polymers undergo a volumetric shrinkage or densification due to chemical bond formation. Consequently, the feature size, shape, and position could be affected. Studies have shown, however, that by controlling the resist composition, the shrinkage is limited to the z-direction, resulting in a reduced aspect ratio [131,137],... 

Hot pressing equations can be derived from the creep equations with certain modifications. In practices, sintering data are usually present as density versus time to obtain densification rate. Because sintering compacts are porous before they are fuUy densified, the creep equations developed for dense solids should be modified to be suitable for hot pressing equations. First, the creep rate that is a linear strain rate should be related to the densification rate which is a volumetric strain rate. Second, the porosity should be compensated. In hot pressing, the mass M of the powder and the cross-sectional area A of the die, are constants, while the density... 

Mix and compact the mixture with the selected aggregate gradation at five different bitumen contents (at the estimated content above, the estimated bitumen content 0.5% and the estimated bitumen content +1.0%). During compaction, keep densification data. Determine compaction and volumetric properties with respect to bitumen content. 

Tree glassy-state drifts in the dense selective membrane s properties resulting from a slow volumetric consolidation or densification of this layer of the membrane. 

Table 1. Comparison of the densification coefficient and volumetric expansion coefficient P, values deduced from TEC data and the stationary limiting current measurements for two AgNO concentration values.

Taking Ip as approximately equal to the grain size G, and writing the densification rate in the form of a volumetric strain rate, Eq. (8.47) becomes... 

In the hot pressing of powders, the data are normally acquired in the form of density versus time from which the densification rate can be determined. Furtha--more, considerable porosity is present over a large part of the process. The modification of the creep equations derived for dense solids therefore attempt to incorporate these two factors (1) relating the creep rate (a linear strain rate) to the densification rate (a volumetric strain rate) and (2) compensating for the presence of porosity. 

The rule of mixtures assumes the densification of the composite to be a weighted average of the independent densification rates of the matrix and of the inclusions that is, it assumes that in the composite, each phase densifies in the same way as it would independently by itself. If, for example, we consider the /mcar densification rate e, defined as one-third the volumetric densification rate (llp)dpldt, then according to the rule of mixtures... 

A representation of constant heating rate data should take into account the simultaneous occurrence of densification and coarsening. As a first approximation, we can modify the theoretical equations for isothermal sintering to account for the effect of changing temperature on the densification and coarsening processes. Following Eq. (8.118), the linear densification rate (equal to one third the volumetric densification rate) can be written... 

Stage III Void formation continues, but bubble collapse dominates and causes the bubbles to contract (inward) and the graphite foam to shrink dimensionally and volumetrically (i.e., densification). 

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