The thickness dependence of the electrical stability under monotonic and cyclic tensile loading is investigated for Cu films on polymer substrates. As for monotonic tensile deformation, thicker films show better stability than thinner films due to their higher ductility and the larger capability of strain accommodation. For the fatigue resistance, however, a more complex behavior was observed depending on the amount of the applied strain. For low strain amplitude in the high cycle fatigue (HCF) regime, thinner films exhibit longer fatigue life because the larger strength of thinner films suppresses dislocation movement and damage nucleation. However, for high strain amplitudes in the low cycle fatigue (LCF) regime, the fatigue life for thinner films is drastically reduced compared to thicker films. It is shown that fatigue coefficients in the LCF regime can be obtained when applying the Coffin–Manson relationship.

Our research aims at exploring a new oxygen reduction reaction (ORR) catalyst with effective catalytic capability, which can be used in the metal-air batteries. ORR electrocatalysts of carbon black and carbon aerogel supported Pt-based nanoparticles were synthesized by a chemical impregnation reduction method. The electrochemical measurement consisted of cyclic voltammetry (CV) and line scan of scanning electrochemical microscopy (SECM) conducted in alkaline medium as well as the single-cell tests. All the tests indicate that the Pt–Zn/carbon aerogel (Pt–Zn/CA) catalyst, with the specific discharge capacity reaching 1349.5 mA h g−1, exhibits the best catalytic performance among all the tested catalysts. The doping of Zn forms Pt-rich surface, creates more d-band vacancies, and reduces the leaching problem; the use of carbon aerogels brings larger specific surface area. These aspects have all improved the catalytic activity per unit mass.

By combining two types of ligands, phenylpyridine and quinoline, a new type of organometallic IrQ(ppy)2 compound has been synthesized, which exhibits two phosphorescences: green and red. Using an appropriate catalyst, the final IrQ(ppy)2 compound has a good chemical yield up to 60% and becomes a stable dual emitter at room temperature. This compound is important because it exhibits stable red emission which is limited by the quantum yield due to the low energy band gap. As a result, an overlap between the ground state and the excited state occurs due to the vibrations that increase the nonradiative transitions, destroying the red emissions. Structural characteristics of the IrQ(ppy)2 powder reveal a triclinic structure confirmed by x-ray diffraction and scanning electron microscopy images. Thermal analysis of the final compound confirms a good stability against decomposition and structural changes up to 350 °C. X-ray photoelectron spectroscopy reveals Ir–O chemical bonds and several differences between the intermediate and final compounds, such as Ir–Cl bonds. Cathodoluminescence patterns show a phosphorescent triclinic structure with a higher efficiency for the red color. Backscattering electron images prove that there is a uniform distribution of iridium ions in the IrQ(ppy)2 nanocrystals.

We use transmission electron microscopy (TEM) for in situ studies of electron-beam-induced crystallization behavior in thin films of amorphous transition metal silicon carbides based on Zr (group 4 element) and Nb (group 5). Higher silicon content stabilized the amorphous structure while no effects of carbon were detected. Films with Nb start to crystallize at lower electron doses than the Zr-containing ones. During the crystallization, equiaxed MeC grains are formed in all samples with larger grains for ZrC (∼5 nm) compared to NbC (∼2 nm). The phenomenon of self-terminating crystallization at a dimension of 2–5 nm is explained by segregation of Si that is expelled from growing metal carbide grains into the surrounding amorphous phase matrix, which limits diffusion of the metal and carbon.

Fibrous polyethylene terephthalate (PET) was modified by organometallic vapor exposure to form hybrid materials with unique photoluminescent characteristics. Using a sequential vapor infiltration (SVI) process, the elongated exposures of trimethylaluminum (TMA) to PET were examined. As the infiltration temperature increased, the evidence of changes in the reaction between the organometallic vapor and the polymer was observed as well as significant changes in the infiltration depth into the polymer fiber, owing to the variation in the reaction mechanisms of the hybrid material formation. At TMA exposures of 60 °C, the mass of the polymer fiber increased by ∼55 wt%, whereas exposures at 150 °C were limited to ∼25 wt% infiltration. Photoluminescence analysis of PET after TMA infiltration shows an intensity increase of up to ∼13x and an increase in red shift with increasing infiltration temperature, attributed to the variations in the reaction mechanism to form the hybrid modification observed through the spectroscopy analysis.

Stretchable transparent conductors are required for flexible and wearable electronics. This study demonstrates biaxially stretchable transparent conductors that use silver nanowire networks. The use of buckled nanowire networks has previously been reported to lend stretchability to the transparent conductor in a single axis. However, a nanowire network that is prestrained and then buckled out-of-plane biaxially shows a deterioration of the electrical conductivity after a single cycle of stretching and releasing the strain uniaxially. This has been attributed to the loss of good electrical contact between the nanowires. By hot pressing the out-of-plane buckled nanowires to obtain an in-plane wavy nanowire network with good wire-to-wire junctions, a biaxially stretchable transparent conductor that maintains good electrical conductivity with stretching up to 10% is demonstrated. The methods of prestraining the nanowire network to achieve out-of-plane buckled nanowires and hot pressing the out-of-plane buckled nanowires to obtain an in-plane wavy nanowire network with fused junctions are expected to be practical for other classes of percolative networks based on one-dimensional (1D) materials used in flexible and stretchable applications.

Piezoelectricity and magnetoelectricity are contradictory properties with a rather limited set of natural (often hard) materials that exhibit both. Composite materials – almost always restricted to hard ones – provide a limited recourse with the attendant limitations of small strains, fabrication challenges among others. In this article, using the concept of electrets, we propose a simple scheme to design soft, highly deformable materials that simultaneously exhibit piezoelectricity and magnetoelectricity. We demonstrate that merely by embedding charges and ensuring elastic heterogeneity, the geometrically nonlinear behavior of soft materials leads to an emergent piezoelectric and magnetoelectric behavior. We find that an electret configuration made of sufficiently soft (nonpiezoelectric and nonmagnetic) polymer foams can exhibit simultaneous magnetoelectricity and piezoelectricity with large coupling constants that exceed the best-known ceramic composites. Moreover, we show that these properties can be tuned with the action of an external field.

Zn3(VO4)2 nanorods with visible light-driven photocatalytic activity were prepared by hydrothermal reaction and characterized by x-ray diffraction, Fourier transform infrared, scanning electron microscopy, x-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectra, and Brunauer–Emmett–Teller surface area and pore size analyzer. The Zn3(VO4)2 nanorods consisted of rods with a thickness of approximately 30 nm, length in the range 400–600 nm, and width in the range 150–250 nm. The photocatalytic degradation activities for methylene blue (MB) and 4-nitrophenol (4-NP) over the Zn3(VO4)2 nanorods were studied in detail. The photocatalytic activity of the as-prepared photocatalyst for MB and 4-NP in visible light under the same conditions was about 3.5 times and 2.5 times higher than that of N–TiO2, respectively. The main active species in the photodegradation come from •OH, and the photogenerated electrons also partly involved in the photocatalytic degradation process, in which the •OH radicals formed were in proportional to the light illumination time obeying zero-order reaction rate kinetics.

The influence of aging treatment on shape memory effect (SME) and wear resistance of Fe–20Mn–5Si–10Cr–5Ni–0.7V–0.2N (mass%) alloy was investigated. Results showed that vanadium nitride (VN) particles precipitated during aging treatment, and the amount and size of the particles increased with increasing aging time. The sample aged for 8 h exhibited the maximal shape recovery ratio of 74% (compared with that of 16% for unaged) and favorable wear resistance in both dry wear and oil-lubricant wear conditions. The fine VN particles are the key factor to improve the SME by strengthening the alloy and acting as preferential nucleation sites for martensite. However, more and larger particles due to further aging treatment appeared to have negative effects on the SME and wear resistance. After oil-lubricant friction, there existed large amounts of friction-stress-induced ε martensite in the worn surface of the sample. As a result, the wear resistance of samples in oil-lubricant wear condition was remarkably higher than that in dry wear condition.

Thin film silicon tandem junction solar cells based on amorphous silicon (a-Si:H) and microcrystalline silicon (µc-Si:H) were developed with focus on high open-circuit voltages for the application as photocathodes in integrated photoelectrochemical cells for water electrolysis. By adjusting various parameters in the plasma enhanced chemical vapor deposition process of the individual µc-Si:H single junction solar cells, we showed that a-Si:H/µc-Si:H tandem junction solar cells exhibit open-circuit voltage over 1.5 V with solar energy conversion efficiency of 11% at a total silicon layer thickness below 1 µm. Our approach included thickness reduction, controlled SiH4 profiling, and incorporation of intrinsic interface buffer layers. The applicability of the tandem devices as photocathodes was evaluated in a photoelectrochemical cell. The a-Si:H/µc-Si:H based photocathodes exhibit a photocurrent onset potential of 1.3 V versus RHE and a short-circuit photocurrent of 10.0 mA/cm2. The presented approach may provide an efficient and low-cost pathway to solar hydrogen production.

Here we report a general method for the synthesis of layered inorganic nanocrystalline materials using graphene oxide (GO) film as the template. Free-standing three-dimensional (3D) lamellar ZnO, α-Fe2O3, and reduced GO/ZnO hybrid structures were synthesized as examples. Such layered structures could also be exfoliated to obtain 2D assembled nanocrystal microsheets. The abundant nucleation sites on the GO surface and the compact stacking of GO platelets made it possible to tightly control metal oxide crystal size (~15 nm), alter preferential crystal growth direction, and assemble the nanocrystals into sheets, as confirmed by multiple characterization techniques.

The yield behavior of solid polymers may be influenced by the hydrostatic pressure, strain rate, and temperature. In the present work, we focus on evaluating the effect of hydrostatic pressure on the yield strength by instrumented indentation. Using dimensional analysis and finite element analysis, two analytical expressions were derived to relate the indentation data to the plastic properties, and a method for extracting the coefficient of internal friction which reflects the effect of hydrostatic pressure on the yield strength was established. Applications were illustrated on polypropylene (PP), polycarbonate (PC), and unplasticized polyvinyl chloride (UPVC). The coefficient of internal friction determined by this indentation method is 0.20 ± 0.02 for PP, 0.07 ± 0.01 for PC, and 0.10 ± 0.01 for UPVC, which are in good agreement with the values reported in the literature. This demonstrates the proposed indentation method which is useful to evaluate the effect of hydrostatic pressure on the yield strength of solid polymers.