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.

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.

In this contribution, the structural, mechanical, and thermal properties of MSiO4 have been investigated theoretically and the anisotropy of elastic properties has been discussed in detail. The heterogeneous bonding nature was revealed from density functional theory computations and chemical bond theory (CBT). The Young's modulus and shear modulus of MSiO4 were anisotropic and the anisotropy on different planes was quite different. The thermal expansion coefficients of MSiO4 estimated from CBT were 5.1 × 10−6 and 4.4 × 10−6 K−1 for ZrSiO4 and HfSiO4, respectively. These results were quite consistent with the experiments. The temperature dependent thermal conductivities of MSiO4 were estimated from Slack's model, the minimum thermal conductivity was predicted to be 1.54 and 1.24 W m−1 K−1 for ZrSiO4 and HfSiO4, respectively. Our theoretical results show that MSiO4 are excellent thermal barrier materials with good tolerance to withstand the mechanical damage.

Fluorine-doped tin oxide (FTO) thin films were deposited by spray pyrolysis in a pulse mode at 450 °C on glass substrates, using an alcoholic solution of SnCl4·5H2O and NH4F with different F/Sn ratios in the precursor solution. The film structure was nanocrystalline for all molar F/Sn ratios in the solution from 0 to 1.0. Postdeposition annealing treatments were not carried out. The films with a F/Sn = 0.35–1.0 ratio present a high grain orientation in the (200) crystallographic plane. A minimum sheet resistance of 4.5 Ω/sq, a resistivity of 2.2 × 10−4 Ω cm, a maximum electron mobility of 21.6 cm2/V s, and a carrier concentration of 1.7 × 1021 cm−3, corresponding to a strong degeneration of the electron gas in the conduction band, as well as a mean value of the transmittance of 0.84 in the visible spectral range, were obtained for the films fabricated with a F/Sn = 0.5 ratio. A high value of the figure of merit was obtained using two methods (38.8 × 10−3 Ω−1 and 5.75 Ω−1), that is, comparable with the highest values reported to date.

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 effects of heat treatment for recovering microstructure of a Ni-based single crystal superalloy with carbon addition have been evaluated. The heat treatment resulted in increased levels of chemical homogeneity. All the samples experienced more γ′ coarsening than as-cast samples. Significant changes to as-cast carbide morphologies were observed. Script-type, MC carbide networks transformed during heat treatment to smaller, spherical Ta-rich MC carbides. Heat treatment caused significant MC carbide decomposition and formation of Cr-rich secondary carbides on or near to decomposed carbides in all modifications. The size of carbides after heat treatment was less than that of cast alloy obviously, and the distribution of carbides became more and more dispersion than in cast alloy.

The Cu–Cr system alloys with different Ti contents were prepared and processed by deformation and heat treatment. The microstructures, mechanical, and electrical properties were investigated under as-cast and aged conditions. The results indicate that the Cr precipitates present a dispersed distribution and exhibit a face-centered cubic (fcc) structure rather than equilibrium body-centered cubic (bcc) structure in the initial stage of aging. A certain amount of Ti atoms dissolves in matrix due to the large solid solubility, while the remaining atoms segregate around the interface of the Cr precipitates to form a sandwich structure. Improvement of mechanical properties is achieved with Ti addition and the increasing rolling reduction, which can be ascribed to multiple mechanisms. In addition, Ti has a negative effect on the electrical conductivity, while deformation has a slight effect on conductivity.

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.

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.

The martensitic transformation of Fe–22 wt% Ni austenite was investigated by high-resolution dilatometry as well as differential thermal analysis. Macroscopically discontinuous formation of lath martensite was observed, manifested in a train of transformation-rate maxima. It is proposed that the modulation of the transformation rate is caused by simultaneous formation of blocks in different martensite packages. The origin of simultaneity is ascribed to the interplay of chemical driving force, developing strain energy, and its relaxation upon sufficiently slow cooling. The transformation-rate maxima become more distinct with decreasing cooling rate (CR), clearly indicating the involvement of a thermally activated process in martensite formation. Quantitative analysis of the microstructure of differently cooled specimens revealed smaller martensite block sizes for higher CRs. All observations are compatible with athermal nucleation and thermally activated growth. (Local) strain relaxation in the austenite was identified as the involved thermally activated mechanism.

NiCrMoV steels used in nuclear rotor with heavy section were successfully fabricated by ultra-narrow gap submerged arc welding method. In this study, the mechanical properties including the tensile and impact toughness of the welded joints (WJs) with a wide temperature range were systematically investigated. Microstructural characterization indicated that the high-temperature tempered martensite and tempered bainite, as the main microstructure in WJ, were responsible for the improved comprehensive mechanical properties of the WJ. Microhardness across the WJ was measured as well, showing that the highest value of hardness occurred at the heat-affected zone which represents the appropriate lowest impact toughness of WJ. However, compared with the base metal, the ultimate tensile strength of the WJ displayed approximately equivalent values, while the yield strength was increased with increasing temperature. All the fracture of the WJ specimens occurred on the weld metal. In addition, the Charpy impact energy of weld metal was obtained at various temperatures, and the transition temperature (Tt) of welded metal was determined as 5 °C, which helps for the application design. The fractography indicated that the ductile fracture modes changed to quasi-cleavage ones gradually with decreasing temperature, and also the dimples became smaller and shallower.

An interesting experimental phenomenon was obtained by Mintz that the hot ductility of an austenitic steel decreases with decreasing strain rate whereas that of a ferritic steel increases. However, the mechanism is still unclear. In this study, the critical time and critical cooling rate of nonequilibrium grain-boundary segregation (NGS) are calculated. It is shown that for Mintz's thermal cycle prior to tensile testing, the effective time of the austenitic steel is shorter than the critical time and that of the ferritic steel is longer than the critical time. When the strain rate decreases, the elastic stress aging time increases. As a result, for the austenitic steel, the grain-boundary segregation of impurity increases, thereby reducing the hot ductility, whereas for the ferritic steel, the segregation of impurity decreases, thereby enhancing the hot ductility. Consequently, the hot ductility loss of both austenitic and ferritic stainless steels is induced by NGS of impurity.

We report the first observation of reversible equilibrium crystalline–metastable crystalline phase transformation in mechanically alloyed Ni–Ge powder mixtures. The formation of the equilibrium NiGe and metastable NiGe2 phases was investigated using x-ray diffraction and scanning electron microscopy methods. It was clearly shown that milling of the blended elemental powders first resulted in the formation of the equilibrium NiGe phase and continued milling led to the formation of the metastable NiGe2 phase. However, on milling for a longer time, the metastable phase transformed back to the equilibrium NiGe phase. The formation mechanisms of the stable and metastable phases and the reversibility of the phase transformations have been explained on the basis of the thermodynamic stability of the different phases and the contribution of defect concentration and surface energy effects to the free energy of the milled powder.