We report on mechanisms of highly fluorescent donor− acceptor pair emissions in chalcopyrite AgInS 2 quantum dots (QDs). We observed that photoluminescence quantum yields (PL-QYs) and radiative recombination rates strongly depend on the QD size; smaller QDs exhibit higher PL-QYs and higher radiative recombination rates of up to 60% and 10 6 s −1 , respectively. Such characteristics were examined in terms of concentrations of donors and acceptors estimated from PL decay behaviors analyzed by the theory of Thomas and Hopfield. These analyses revealed that concentrations of donors and acceptors are higher for smaller QDs; this significantly enhances radiative recombination rates and PL-QYs in smaller QDs. In turn, higher concentrations of donors and acceptors in smaller QDs can be attributed to the use of lower synthesis temperatures, which increase the population of donor−acceptor-type lattice defects.
The effect of aluminum acetate coating treatment on the bod strength of the solid-state bonded interface of A6061 aluminum alloy and high-tensile steel plate was investigated by SEM observation of fractured surfaces and interfacial microstructures. The surface of the aluminum alloy was coated by boiling in 5% aqueous solution of NaOH for 20 s and 99.7% acetic acid. Bonding process was performed at bonding temperature of 713-753 K under a load of 20 MPa and bonding time of 900 s. As the result of this study, it was found that the bond strength of the joint increased with the rise in bonding temperature regardless of metal salt coating treatment. Also, it was revealed that with metal salt coating treatment, high tensile strength joint can be obtained lower bonding temperature. From this experimental results, it is inferred that metal salt coating treatment is effective in removing the oxide film and substitution to an aluminum acetate on the aluminum alloy surface.
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