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The third-order nonlinear optical (NLO) response of colloidal “quantum-dot” cadmium sulfide (CdS) nanocrystals has been measured both in solution and in Langmuir−Blodgett (L−B) multilayers of a polydiacetylene (PDA) “alloy” NLO polymer. The PDA “alloy” was composed of a tailored mixture of diacetylene monomers having carboxylic acid “head” groups and benzamide “head” groups, in each case separated from the diacetylene moiety by an eight-carbon spacer group, so as to disrupt the strong aggregation, leading to excessive light scattering, that normally occurs with L−B films of carboxyl-terminated PDAs. It is shown that at 530 nm the nonlinear refractive index (n 2) of a nanocomposite PDA film containing thiophenol-capped CdS nanocrystals, as measured by both Z-scan and degenerate four-wave mixing (DFWM) techniques, is 11 × 10-8 cm2/MW, while that of an undoped PDA film is only 3 × 10-8 cm2/MW. This demonstrates the concept of a “nonlinear−nonlinear” optical material, in which the NLO response of an embedded quantum-dot semiconductor can add constructively to that of a NLO polymer having complementary wavelength characteristics.

Experimental and analytical techniques have been developed for the determination of the interface heat transfer coefficient for nonisothermal bulk-forming processes. A fixture consisting of two flat IN-100 alloy dies was instrumented with high-response thermocouples. With this tooling, heat-transfer experiments were conducted in which (1) the two dies were heated to different temperatures and brought together under varying pressure levels and (2) the two dies were heated to the same temperature and were used to upset an aluminum alloy 2024-0 ring specimen heated to a higher temperature. Data from both sets of tests were analyzed to determine heat-transfer coefficients by using calibration curves derived from analytical and finite-difference method solutions. By this means, the effects of interface pressure, deformation, and deformation rate on the heat-transfer coefficient were established.

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