Water vapor induced self-assembly of islands/honeycomb structure by secondary phase separation in polystyrene solution with bimodal molecular weight distribution

The formation of complex structures in thin films is of interest in many fields. Segregation of polymer chains of different molecular weights is a well-known process. However, here, polystyrene with bimodal molecular weight distribution, but no additional chemical modification was used. It was proven that at certain conditions, the phase separation occurred between two fractions of bimodal polystyrene/methyl ethyl ketone solution. The films were prepared by spin-coating, and the segregation between polystyrene phases was investigated by force spectroscopy. Next, water vapour induced secondary phase separation was investigated. The introduction of moist airflow induced the self-assembly of the lower molecular weight into islands and the heavier fraction into a honeycomb. As a result, an easy, fast, and effective method of obtaining island/honeycomb morphologies was demonstrated. The possible mechanisms of the formation of such structures were discussed.

Water vapor induced self-assembly of islands/honeycomb structure by secondary phase separation in polystyrene solution with bimodal molecular weight distribution

<p>The formation of complex structures in thin films is of interest in many fields. Segregation of polymer chains of different molecular weights is a well-known process. However, here, polystyrene with bimodal molecular weight distribution, but no additional chemical modification was used. It was proven that at certain conditions, the phase separation occurred between two fractions of bimodal polystyrene/methyl ethyl ketone solution. The films were prepared by spin-coating, and the segregation between polystyrene phases was investigated by force spectroscopy. Next, water vapour induced secondary phase separation was investigated. The introduction of moist airflow induced the self-assembly of the lower molecular weight into islands and the heavier fraction into a honeycomb. As a result, an easy, fast, and effective method of obtaining island/honeycomb morphologies was demonstrated. The possible mechanisms of the formation of such structures were discussed.</p>

The Influence of Long-term Ageing on the Microstructure of Sanicro 25 Steel

Sanicro 25 (22Cr25NiWCoCu) is a newly developed austenitic stainless steel used in the boiler pressure superheaters and reheaters with ultra-supercritical high-efficient parameters. The paper presents the results of microstructure testing and secondary phase separation processes after 20,000 h ageing at 700 and 750 °C. In the initial stage of ageing, the precipitation of numerous very small M23C6 chromium carbides and Laves phase were observed. The long-term ageing related to temperature revealed the existence of secondary phases: M23C6, MX, NbCrN, Laves phase and σ phase. The test results presented in the paper are part of the developed material characteristics to be used for predicting the service life of the material of components operated under creep conditions.