Electronic performance in semiconducting polymers has improved dramatically in recent years owing to a host of novel materials and processing techniques. Our understanding of the factors governing charge transport in these materials has also been enhanced through advancements in both experimental and computational techniques, with disorder appearing to play a central role. In this prospective, we propose that disorder is an inextricable aspect of polymer morphology which need not be highly detrimental to charge transport if it is embraced and planned for. We discuss emerging guidelines for the synthesis of polymers which are resilient to disorder and present our vision for how future advances in processing and molecular design will provide a path toward further increases in charge-carrier mobility.

This work focused on ascertaining the effect of pile-up during indentation of thin films on substrates. Conventional understanding has postulated that differences in contact area resulting from pile-up or sink-in significantly alter the extraction of material properties. In this work, the specific case of pile-up with compliant, plastically deforming films on stiff, nonplastically deforming substrates was studied. Several literature methods to assess pile-up were leveraged, and a new technique was developed and validated to quantify projected pile-up. Indentation testing was performed on gold films of multiple thicknesses on several ceramic-based substrates. The results indicated that the degree of pile-up was solely a function of indent depth into the film. Pile-up was not influenced by film thickness or substrate elastic modulus. In other words, the pile-up development was insensitive to the presence of the substrate and how it contributes to the composite's elastic properties. In such case, if the elastic response of the film/substrate composite was independent of the degree of pile-up, then elastic data acquired from unloading did not require a contact area correction. The findings are confirmed using the Zhou–Prorok model for extracting film elastic properties for both gold and platinum films.

A novel method for the analysis of the mechanical properties of thin films is presented and uses a modified Winkler (bed of springs) approach to estimate indentation hardness and reduced modulus using nanoindentation data. This method is especially useful in situations where significant plastic deformation occurs in the thin film resulting in pileup of material and a divergence from accepted tip area calculations. The model has been adapted into a MATLAB® script and its derivation is presented. A proof of concept study was completed using Au thin films over a range of thickness and deposition methods. Results are compared with traditional nanoindentation analysis methods and validated against the Hall–Petch relationship. It can be seen that this modified Winkler approach accurately predicts material pile-up as well as contact area for films up to 500 nm in thickness.

The (1 − x)[0.94(K0.5Na0.5)NbO3–0.06LiNbO3]–x(Bi0.5K0.5)TiO3 (abbreviated as: KNLN6–xBKT, x = 0–0.05) lead-free piezoelectric ceramics were prepared using conventional solid sintering method. The effects of BKT on the phase structure, electrical properties, temperature stability, and fatigue behavior of KNLN6 ceramics were systematically studied. Results show that BKT substitution into KNLN6 induces a phase transition from coexistence of orthorhombic and tetragonal phases to a single tetragonal phase with a normal-relaxor ferroelectric transformation and correspondingly shifts the polymorphic phase transition below room temperature. Accordingly, the temperature stability of the properties is significantly improved, and a flat, temperature stable behavior over the temperature range of 25–150 °C is observed in BKT-modified ceramics. Temperature-dependent structural analysis suggests that the good properties insensitive to temperature of the modified samples can be ascribed to the stable tetragonal phase over a wide temperature range, evident by the almost unchanged tetragonality c/a ratio with temperature. Moreover, the BKT-modified ceramics not only exhibit temperature-independent characteristic but also possess fatigue-free behavior. All the electric parameters, including unipolar/bipolar strain S, remnant polarization Pr, permittivity εr, and large signal d33*, display no degradation up to 105 switching cycles. The exceptionally good fatigue resistance and temperature stable behavior make the modified KNN-based materials excellent candidates for lead-free actuators and transducers.

To study the thermal deformation behavior and microstructural evolution of the type 347H austenitic steel, compression experiments were conducted at the temperatures of 800–1100 °C with strain rates of 0.01–10 s−1. The activation energy and constitutive equation of the type 347H steel during thermal deformation process were determined according to the flow stress curves. Both the hot processing maps and microstructure characteristics under different deformation conditions were investigated. Based on the thermal processing maps, two unstable regions under 800 °C/0.01–10 s−1 and 1100 °C/0.01 s−1 were identified. The processing maps were in favor of optimizing thermal processing parameters and improving thermal processing properties of the type 347H austenitic steel. After thermal deformation, the dislocation in the austenite matrix increases significantly. Besides, in the stable regions, the precipitation of carbides is facilitated by thermal deformation.

Dilatometric studies of C–Mn hypoeutectoid steel with an as-cast structure were carried out to study the effects of the heating or cooling rate, heating and cooling process on phase transformation, and the thermal expansion coefficient. As the heating or cooling rate (Vc) increased, the characteristic temperatures of Ac1, Acp, and Ac3 also rose, while Ar3, Ar1, and Arp fell. In addition, the phase transformation temperature range (Ac3–Ac1) rose, while (Ar3–Arp) fell as the heating or cooling rate increased. At the same time, the maximum thermal expansion coefficients│αT│ between the heating and cooling processes during phase transformation showed significant differences, and the difference (│ΔαT│) in the maximum │αT│ between these processes increased along with the heating or cooling rate, and this is because of the different phase transformation rates, with regard to the change from austenite to ferrite on cooling and ferrite to austenite on heating. During the heating process, the phase transformation rate of ferrite to austenite first decreases and then increases as the temperature rises, and the phase transformation rate of austenite to ferrite first increases and then decreases during the cooling process. The evolution of carbon and substitutional alloying elements (Si and Mn) in austenite during heating and cooling is also analyzed in this work.

Carbon nanotube (CNT)-based transparent conducting films (TCFs) have been prepared by filtration of (i) surfactant-based aqueous dispersions and (ii) organic solutions obtained by reductive dissolution of an alkali metal salt of polyelectrolyte nanotubes. Starting from the same source of nanotubes, it is shown that films obtained by the reductive dissolution route present up to one order of magnitude better conductivity for the same transmittance. Light scattering experiments show that the average CNT length is much larger for the reductive dissolution-based organic solutions than for the sonication aided aqueous dispersions. Values of surface resistivity of 200 ohm per square have been obtained for 80% transmittance. Additionally, it is shown that the CNT-based TCFs are undistinguishable from indium tin oxide (ITO) as electrodes in regular environments, whereas they perform efficiently in acidic environments where ITO fails.

This paper details an investigation into the effect of martensite–austenite (M–A) constituent on impact toughness of intercritical heat-affected zone (IC HAZ) in Q690 steel, a low carbon bainitic steel. Large samples with uniform microstructure similar to that of the actual IC HAZ were achieved through combinations of heat treatments. The samples were heated to temperature between 750 and 830 °C for 30 min and then quenched in water. After these heat treatments, hard martensite islands distribute along the boundaries of soft matrix, and the size of martensite islands increases with heating temperature. The microstructure is quite similar to that of the IC HAZ. Using these large samples, the impact toughness could be measured conveniently. It was found that the embrittlement of the IC HAZ depends on the deformability and size of the M–A constituent. When the size of the M–A constituent whose deformability is low exceeds a critical value (2.0 μm), the embrittlement of the IC HAZ occurs.

Nanoindentation is an effective approach for measuring mechanical properties ofnanoscale films coated on substrates, yet results obtained through the classicOliver–Pharr model require additional consideration due to the existenceof a “substrate effect” when the film is much more compliant thanthe substrate. In this study, different models for removing this substrateeffect are compared, with focus on the Gao model, the Saha–Nix model, andthe Hay model and the use of a direct finite element (FE) approach is discussed.Validity of these models is examined using load–displacement dataobtained from simulated indentation of an elastic–plastic film in FEs. Itis found that the performance of the analytical models varies significantly withdifferent testing parameters, including ratio between film modulus and substratemodulus (Ef/Es),indenting ratio (hmax/film thickness), and yieldstrain. Choices of using a nanoindentation model to process experimental datashould be made according to estimated indentation depth and modulus differencebetween film and substrate. An example of applying substrate removal models toexperimental data is also shown.