Responsive, biocompatible substrates are of interest for directing the maturation and function of cells in vitro during cell culture. This can potentially provide cells and tissues with desirable properties for regenerative therapies. Here, we demonstrate a straightforward and scalable approach to attach, align, and dynamically load cardiomyocytes on responsive liquid crystal elastomer (LCE) substrates. Monodomain LCEs exhibit reversible shape changes in response to cyclic heating, and when immersed in an aqueous medium on top of resistive heaters, shape changes are fast, reversible, and produce minimal temperature changes in the surroundings. We systematically characterized the strain response of LCEs in water and demonstrated the attachment and alignment of neonatal rat ventricular myocytes on LCE substrates. Cardiomyocytes attached to both static and stimulated LCE substrates, and under cyclic stimulation, cardiomyocytes aligned along the primary direction of strain. This work demonstrates the potential of LCEs as stimuli-responsive substrates for dynamic cell culture.

Atomic engineering of complex oxide thin films is now reaching a new paradigm: the possibility to control the cation coordination by oxygen anions. Here, we show two examples of stabilization of novel structural phases by manipulating the oxygen sublattices in complex Cu-based oxide thin films grown on SrTiO3: (i) epitaxial strain stabilization of a near cubic form of CuO and (ii) thickness-dependent structural transformation from bulk planar (polar) to chain-type (nonpolar) in SrCuO2 thin films that relieves the electrostatic instability. Experimental investigation on ultrathin CuO layer identifies the existence of an elongated (c/a ∼ 1.34) rocksalt-type CuO phase, pointing to metastable 6-fold coordinated Cu with the hole occupied in the 3dx2−y2 orbital. For ultrathin SrCuO2 layers, we demonstrate the possibility of moving oxygen ion from CuO2-plane to Sr-plane forming chain-type structure. X-ray absorption spectroscopy reveals preferential hole-occupation at the Cu-3d3z2−r2 orbital for chain-type structure unlike to the planar case. Our findings testify unique stabilization processes through atomic rearrangement and provide new insight into the experimental realization of novel cuprate-hybrids to look for exciting electronic properties.

InGaN/GaN green light-emitting diodes (LEDs) have been prepared by metal-organic chemical vapor deposition with various growth temperatures for p-GaN layer. The structural and optoelectronic properties of as-grown multiple quantum wells (MQWs) and LEDs are studied in detail. It reveals that with the growth of p-GaN layer, the crystalline qualities of the as-grown n-GaN layer are improved significantly, while the optoelectronic properties of MQWs are decreased dramatically. Furthermore, the mechanisms for the effect of p-GaN growth temperature on the properties of InGaN/GaN green LEDs are proposed. It is demonstrated that the p-GaN layer grown at a suitable temperature of 950 °C shows the highest optoelectronic properties due to the fact that this suitable temperature for p-layer growth is good for the Mg doping and would not cause the fluctuation of indium in the MQWs, and eventually benefits to the effective recombination of carriers. This work provides an optimized p-GaN layer growth temperature for realizing highly efficient InGaN/GaN green LED devices.

A three-dimensional nanostructured graphene oxide–Mn3O4 hybrid was synthesized by a coprecipitation method and used as an anode material of lithium ion batteries, which reached an initial specific capacity of 1400 mA h/g. This method was developed to simplify the process of fabricating uniform composite nanomaterials for abundant applications. In this work, Mn3O4 particles were coordinately distributed on the surface of reduced graphene oxide nanosheets to avoid detrimental stacking of graphene layers by forming 3D nanostructures, as characterized by a scanning electron microscope. As demonstrated by the in situ observation of a scanning probe microscope, severe pulverization of Mn3O4 particles during charge/discharge processing was significantly abstained when graphene layers constrained swelling and shrinkage. The as-prepared graphene–Mn3O4 nanomaterials exhibited a large specific capacity of 949 mA h/g, high-rechargeable efficiency of ∼98%, and exceptional cyclic stability. After 100 constant-current charging/discharging cycles at 100 mA/g, the specific capacity remained at 792 mA h/g with a coulombic efficiency of 98.1%. Furthermore, the coprecipitation method proposed in this work provides a strategy to fabricate other nanostructured composites for different kinds of applications.

Yttrium disilicates (Y2Si2O7), well known for its complex polymorphism, are promising candidates for high-temperature structural materials and environmental barrier coatings due to their good properties in harsh environments. In this study, the crystal structure, elastic stiffness, and temperature dependence of the lattice thermal conductivity of β-, γ-, and δ-Y2Si2O7 are studied using first-principles calculations. Divergences of elastic stiffness are attributed to the different crystal structures and bonding strength of the polymorphs. Specially, the Si–O–Si bridge of δ phase bends with an angle of 158.1°, and this configuration enhances the bonding heterogeneity but weakens the bonding strength and stability. According to the prediction of lattice thermal conductivity using the Debye–Slack model, β-, γ-, and δ-Y2Si2O7 are characterized with very low thermal conductivity. In addition, the deviation of lattice thermal conductivities of Y2Si2O7 polymorphs is dominated by two vital factors, anharmonicity of phonon scattering and complexity of crystal structure. The present method could be used to investigate the specific factors dominating lattice thermal conductivity and may promisingly be generalized to search novel candidates with extremely low lattice thermal conductivity.

An AlTiCrN coating was prepared on a YT14 cutting tool, whose friction and wear behaviors were investigated with a wear test at 900 and 1000 °C, respectively. The results show that the phases of the AlTiCrN coating mainly are composed of AlN, CrN, and TiN. The elements of Al, Ti, Cr, and N in the coating show gradient and transition distributions at the bonding interface; the C atoms of the substrate have diffused into the lattices of TiN, AlN, and CrN to form the obvious interdiffusion layer; and the interface bonding strength is 57.65 N. The coating is composed of different metal oxides and compound oxides at 900 and 1000 °C. The worn surface is relatively smooth at 900 °C, whose average coefficient of friction (COF) is 0.42, while the worn surface produces severe plastic deformation at 1000 °C, whose average COF is 0.45. There are enriched and depleted stripes with uniformly distributed chemical elements on the worn scar, which is expressed with uniform wear at the high temperatures.

In this work, the effects of different preparation methods on the microstructures and properties of the Ti45.7Zr33Ni3Cu5.8Be12.5 alloy were systematically studied by both experimental and numerical ways. It is found that the heating methods and the cooling rate during the process of preparation have great influences not only on the morphology and crystalline structure of the solid solutions but also on the thermal stability of the amorphous phase. Furthermore, the different crystalline structures and micromorphologies of the ductile phase will also influence the mechanical properties. And the uniaxial compression tests at room temperature verify that the Ti45.7Zr33Ni3Cu5.8Be12.5 samples obtained by different preparation methods possess different degrees of plasticity. The better comprehensive properties were found for samples with a larger size under the copper mold cooling conditions. The variation of the morphology of the solid solution phase under different preparation conditions is believed to be the vital factor that leads to the diversity in properties.

A method based on the electroforming technique has been proposed for the fabrication of nanoparticle-reinforced copper-matrix composites using an electrolyte of copper sulfate–sulfuric acid solution containing 1 cm3/L of the nanoparticles without surfactants. Of the tested nanoparticles such as Al2O3, SiO2, TiO2, ZrO2, and CeO2, whose sizes ranged from 10 to 30 nm, only TiO2 nanoparticles were successfully embedded in the copper matrix during electroforming, owing to their positive charge in the electrolyte solution. It should be noted that there was very little contamination in the copper matrix, because surfactants were absent during electroforming. Therefore, the electrical conductivity of the specimen that was electroformed in the electrolytes with TiO2 nanoparticles was not significantly different from that of pure copper. Nevertheless, the hardness, yield, and ultimate tensile strength were significantly improved by a small amount (0.3 mass%) of TiO2 nanoparticles primarily because of strengthening by Orowan mechanics. The electroforming process is thus a promising means to prepare copper-matrix composites with an excellent balance of electrical conductivity and mechanical strengths.

Transmission electron microscopy (TEM) based orientation mapping has been used to measure the length fraction of coherent and incoherent Σ3 grain boundaries in a series of six nanocrystalline Cu thin films with thicknesses in the range of 26–111 nm and grain sizes from 51 to 315 nm. The films were annealed at the same temperature (600 °C) for the same length of time (30 min), have random texture, and vary only in grain size and film thickness. A strong grain size dependence of Σ3 (coherent and incoherent) and coherent Σ3 boundary fraction was observed. The experimental results are quantitatively compared with three physical models for the formation of annealing twins developed for microscale materials. The experimental results for the nanoscale Cu films are found to be in good agreement with the two microscale models that explain twin formation as a growth accident process.

The metadynamic recrystallization (MDRX) behaviors in deformed Nimonic 80A superalloy were investigated by isothermal interrupted hot compression tests on a Gleeble-1500 thermo-mechanical simulator. Compression tests were performed using double hit schedules in the deformation temperature range of 1050–1150 °C, the interpass time range of 0.5–10 s, the strain rate range of 0.01–4 s−1, and the prestrain range of 0.30–0.50. To characterize the MDRX behaviors of the alloy, the effects of deformation temperature, strain rate, and prestrain on the metadynamic softening and recrystallized grain size were analyzed. The results reveal that the effects of deformation temperature and strain rate on the metadynamic softening fraction and recrystallized grain size are significant. However, the effects of prestrain on the metadynamic softening fraction and recrystallized grain size are not very marked and can be neglected. Then, by regression analysis of the experimental data, the MDRX kinetic model and recrystallized grain size model were proposed. The predicted results show good agreement with the experimental ones, which indicates that the proposed models can give an accurate prediction of the softening behaviors and microstructural evolution for Nimonic 80A.

Some Fe-rich amorphous alloys of Fe–B–P–Si and Fe–B–P–Si–C systems were found to exhibit simultaneously good soft magnetic properties with high-saturation magnetization values near 1.7 T, which are higher than those for previously reported Fe-based amorphous and glassy alloys, in addition to rather good amorphous ribbon formability, good bending ductility, and rather high corrosion resistance. The corrosion resistance increased with increasing P content, accompanying by the increase in thermal stability of the amorphous phase. The decrease in the outer surface velocity of the wheel, which results in the increase of ribbon thickness, also causes an improvement of surface smoothness of the melt-spun amorphous alloy ribbons. The syntheses of new high-saturation Fe-based soft magnetic amorphous alloys without any other transition metals hold promise for future extension of Fe-based soft magnetic amorphous materials.

The mechanical behavior of a Zircaloy-4 sheet as induced by a pulsed laser was studied with an accurately developed computational process that was validated with experiments. A modified Gaussian model of the heat source and the use of experimentally obtained thermal and mechanical properties of Zircaloy-4 in the computational process provided reliable simulation results of the phase transition and mechanical deformation of Zircaloy-4. A parametric study of the pulsed laser welding conditions of Zircaloy-4 was undertaken using the developed computational process. The analyzed parameters were the laser power, pulse duration, and pulse frequency. The simulation results revealed that the deformation was significantly dependent on the geometry of the molten zone and the heat-affected zone, which can be designed by the analyzed laser parameters.

Microstructure modification and room temperature tensile properties of Ti–6Al–4V plates fabricated by electron-beam melting (EBM) were investigated. Firstly, Ti–6Al–4V slabs were direct rolled at various preheat temperatures below β transus with various reductions, then the deformed samples were annealed at 800 °C for various soaking times. After rolling, the microstructure modification consists of elongation, bending, kinking, and rotation of α lamellae. Specimens rolled below 900 °C exhibited flow instability (local deformation bands). The mean aspect ratio of α lamellae was further decreased following annealing, and the fraction of α particles showed a relatively strong dependence on preceding rolling reduction. The variations of mean aspect ratio and spheroidization fraction with annealing time were rationalized on the basis of various processes during spheroidization. The mechanical properties of Ti–6Al–4V plates fabricated by EBM were significantly improved after rolling compared with as-cast Ti–6Al–4V plates. The following annealing of 1 h resulted in significant improvements on elongation without obvious loss of ultimate tensile strength (UTS).

Material property measurements at the micro-/nanoscale are required for within many materials systems, such as thin-films, coatings, nanostructured materials, and interface/interphase. An innovative approach through micro-/nano-indentation testing with a cylindrical flat-tip indenter and coupled with computer modeling was proposed to characterize the material's elastic–plastic properties. A mechanical model proposed for directly extracting the yield strength of the tested materials, based on the hemi-spherical stress–strain distribution assumption, was analytically derived and numerically validated. Specimens being tested are aluminum alloy, low carbon steel, and alloy steel. A micro-/nano-indentation solid model was constructed and computer modeling was conducted. The load point in the indentation load–depth curve and the modifier for extracting the yield strength were identified through computer modeling and validated by indentation tests. The material properties measured by indentation were compared with tensile tests. The indentation testing errors induced by residual stresses in specimens were investigated by a residual stress measurement system.

The effect of gamma radiation in vacuum on the isothermal crystallization kinetics of syndiotactic polystyrene (sPS) was investigated via differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), and x-ray diffraction (XRD). Amorphous sPS samples were irradiated in vacuum, heated to 310 °C, cooled down to crystallization temperatures (Tcs) from 220 to 260 °C, and annealed for different times. Upon reheating, overlapping endothermic melting peaks depicted the various crystallization forms, α, β, and β′. The endotherms were resolved using Gaussian functions relating enthalpy changes to the endothermic envelope. Isothermal crystallization kinetic data were analyzed using Avrami's model with Gaussian functions. The extent of crystallization of β and β′ forms increased with increasing crystallization time and temperature, while that of α form decreased. Crystallization half-time followed a modified Arrhenius equation. Crystallization activation energies for the β and β′ forms of sPS increased with increasing radiation doses. The results are compared to those of air irradiated sPS reported in the literature.