Doping composites

Fibers spun by this method may be isotropic or asymmetric, with dense or porous walls, depending on the dope composition. An isotropic porous membrane results from spinning solutions at the point of incipient gelation. The dope mixture comprises a polymer, a solvent, and a nonsolvent, which are spun into an evaporative column. Because of the rapid evaporation of the solvent component, the spinning dope solidifies almost immediately upon emergence from the spinneret in contact with the gas phase. The amount of time between the solution s exit from the spinneret and its entrance into the coagulation bath has been found to be a critical variable. Asymmetric fibers result from an inherently more compatible solvent/nonsolvent composition, ie, a composition containing lower nonsolvent concentrations. The nature of the exterior skin (dense or porous) of the fiber is also controlled by the dope composition. 

In the past several years noble metal loading, ion doping, composite metal-oxide semiconductors, and multi-component semiconductors have been meticulously designed, fabricated, and then investigated... 

The electron-doped regime (x > 0.5) of the rare earth manganates of the general formula Lni- Ca Mn03 is dominated by charge-ordering effects. While the effects of cation size and size disorder on the charge-ordered states of the hole- and electron-doped compositions are similar, their properties vary markedly as revealed by the comparison of the properties of the hole-doped... 

In the present case we report ESCA examinations of composite systems realized when varying amounts of platinum metals (i.e., Pt or Pd) and other species are doped by some conventional means onto a standard y-alumina support in a manner designed to simulate systems often employed in Pt metals catalysis (1.2). A unique feature of the present study is that the doping compositions are typical of those of real catalysts, e.g., 0.2 < Pt wt% < 0.75. Generally the Pt metals can be assumed to be the principal active metal species added, although the function of that dopent has been suspected to depend significantly on the other species present (3). 

In order to obtain in a very short time an optimum casting dope composition which produces a membrane of required performance, a guide line listed in Table II was established, based on our previous experience of membrane research. Mixtures of high and low boiling, water mlssible solvents for cellulose acetate were employed as solvents for dope. As for additives to the dope... 

Table II GUIDELINE TO AN OPTIMOM CASTING DOPE COMPOSITION...

Recent advances in composite manufacturing techniques permit the fabrication of large optical elements. In Fig. 14, a wide range of organic dye-doped composites are presented. The largest of these measures 30 cm in diameter by 3.5 cm in thickness. Organic dyes represented include coumarin-314T, fluorescein, rhodamine 6G, rhodamine B, and poly(p-phenylene vinylene). 

Laser facet power = /[laser chip slope, epitaxial grating, metal doping composition. .. Laser placement = /[laser chip size, bond temperature, piece part quality. .. ... 

---