A new approach has been developed for nanoscale conductance mapping (NCM) based on multidimensional atomic force microscopy (AFM) to efficiently investigate the nanoscale electronic properties of heterogeneous surfaces. The technique uses a sequence of conductive AFM images, all acquired in a single area but each with incrementally higher applied voltages. This generates a matrix of current versus voltage (I–V) spectra, providing nanoscale maps of conductance and current nonlinearities with negligible spatial drift. For crystalline and amorphous phases of a GeSe chalcogenide phase change film, conductance and characteristic amorphous phase “turn-on” voltages are mapped with results providing traditional point-by-point I–V measurements, but acquired hundreds of times faster. Although similar to current imaging tunneling spectroscopy in a scanning tunneling microscope, the NCM technique does not require conducting specimens. It is therefore a promising approach for efficient, quantitative electronic investigations of heterogeneous materials used in sensors, resistive memories, and photovoltaics.

Ceramic volumetric composites xLa0.7Pb0.3MnO3–(1−x)PbTiO3 (x = 0.18 and 0.85) were prepared. X-ray investigations have shown that rather low sintering temperature (800 °C) has allowed us to avoid the reaction and interdiffusion between two initial phases. Heat capacity, thermal expansion, and intensive magnetocaloric effect were measured in a wide temperature range. The sample composition has a low influence on temperatures of the ferromagnetic and ferroelectric phase transitions in composites. Electro- and barocaloric effects were determined by analysis in the framework of thermodynamic theory, electric equation of state, Maxwell relationships, and entropy–temperature–pressure phase diagram. Multicaloric efficiency of composites is discussed and compared with that of initial La0.7Pb0.3MnO3 and PbTiO3 compounds. Variation of a relationship between components can significantly increase both barocaloric and magnetocaloric efficiency of compositional material due to the mechanical stress appearing between grains of different ferroic phases under magnetic field.

Thermomechanical fatigue (TMF) tests have been carried out in a nickel-based single crystal TMS-82 superalloy, and the dynamic evolutions of dislocations and stacking faults have been studied in detail. It is found that the reversible formation of stacking faults is always associated with the loading orientation. Specifically, stacking faults expand under compression and shrink under tension due to the disappearance and appearance of dislocations during the TMF process. Stacking faults result from shear of γ′ precipitates by 1/3<112> dislocations, which arise from the decomposition of 1/2<110> matrix dislocations. The calculations of critically resolved shear stress to push dislocations that glide in the γ′ particles confirm the expansion of stacking faults under compression. However, under tension, dislocations in γ channel prevent 1/2<110> dislocations to enter γ′ cuboids and consequently, stacking faults shrink. Appearance and disappearance of dislocations during TMF cycling are associated with plastic deformation and annealing process, respectively.

To determine whether plastic-hardening behavior occurs in metal nanowires, an atomistic simulation was performed to investigate the tension process in a bicrystal Cu nanowire. The results indicate that bicrystal Cu nanowires exhibit strain-hardening behavior, unlike their single-crystal counterparts. The strain-hardening behavior is related to the orientation of two crystal grains, and the number of atoms determines whether strain-hardening behavior occurs in the asymmetrically tilted bicrystal Cu nanowires. Strain hardening occurs in almost bicrystal Cu nanowires with different orientation angles. The initial yield stress is determined by the grain whose orientation angle is closer to 45° among the two crystal grains, resulting in a high value of the tilting tendency factor, and thus making it easier to generate slip.

Solidification of undercooled Ni–4.5 wt% B alloy melt was investigated by glass fluxing and cyclic superheating. A maximum melt undercooling up to ΔTp = 283 K has been achieved. If ∆Tp < 175 ± 10 K, the primary solidification is L → Ni3B; the structure consists of Ni3B dendrite + lamellar eutectic; the phase sizes and fractions depend on ∆Tp. If ∆Tp ≥ 175 ± 10 K, the primary solidification is L → Ni/Ni23B6; the structure consists of the dot-phase region + the anomalous eutectic/network boundary; the phase fractions mainly depend on ∆Tr; the dot phases are determined as rod eutectic and dot precipitates, while the network boundary is the divorced eutectic. The solidification pathways show that there is a common critical nucleation temperature, 1227 ± 10 K, for metastable eutectic reaction in hypoeutectic and hypereutectic Ni–Ni3B alloys.

Aluminum alloy castings find extensive applications in automobile and other engineering industries. Production of defect-free castings requires a good understanding of the volume deficit characteristic. The volume deficit of a casting depends on the casting material and casting conditions. Patterson and Engler have classified the volume deficit into four types namely, macrocavities, internal porosity, surface sinking, and volumetric contraction. The influence of process parameters on the characteristics determines the casting quality. The process parameters considered in this study are bottom chill, casting shape, and pouring temperature. Two basic shapes rectangle and cylinder are considered. The volume deficit decreases with an increase in the silicon content. The AA 356.0 alloy shows more amount of volume deficit than AA 413.0 alloy. X-ray computer tomography (XCT) helps to reveal the size, shape, and location of defects in castings. Quantification of internal closed porosity of AA 413.0 casting is done using XCT and successfully validated through destructive testing of castings.

In this paper, we demonstrate a thin film Cu–Ni–Nb alloy deposited directly on silicon, without a designated barrier, showing very high thermal stability at a temperature up to 700 °C for 1 h. Thin [Nb–Ni12]Cux films were sputter deposited and annealed, and their material and electrical properties were studied. The results can be explained by the “cluster-plus-glue atom” model for stable solid solutions, where [Nb–Ni12] cuboctahedral clusters are embedded in a Cu matrix. In this model, the clusters are congruent with the Cu minimizing atomic interactions allowing a good stability. The properties of the films were found to be affected by the Ni/Nb ratios. Especially, the (Nb1.2/13.2Ni12/13.2)0.3Cu99.7 film annealed at 500 °C for 1 h had the lowest electrical resistivity of about 2.7 μΩ cm. And even after 40 h annealing at 500 °C, it maintained a low resistivity of about 2.8 μΩ cm, demonstrating extremely high stabilities against silicide formation.

We have fabricated Ag-decorated ZnO nanoplate arrays by combining water-bath heating toward ZnO hexagonal nanoplate arrays and subsequent decoration of Ag films or nanoparticles on the ZnO surfaces by magnetron sputtering or photoreduction. Experimental surface-enhanced Raman scattering (SERS) results show that Ag-film–ZnO hybrid substrates with different Ag sputtering times exhibit a large difference in enhanced SERS signals for Rhodamine 6G (10−7 M). Atomic force microscope analysis reveals that two kinds of positions create abundant “hot spots” in this SERS substrate: one is located at the gap between adjacent separate Ag-film–ZnO hybrid nanoplates, and the other is located at the V-grooves formed by two adjacent interlaced Ag-film–ZnO hybrid nanoplates. The effects of simultaneous changes in interplate spacing and groove wall angle are considered to be the key factors affecting the SERS of our prepared Ag-film–ZnO hybrid substrates, which have also been evaluated by finite-difference time-domain simulation.

In this paper, we report on the well-aligned zinc oxide (ZnO) nanorods synthesized on Ag buffer layer/glass substrate using a modified hydrothermal method, which adopts the strategy of Ag layer facing down. The effects of position, thickness, and annealing temperature of Ag layer on the shape of ZnO nanocrystals were systematically investigated. It was found that the diameter and length of ZnO nanorods decrease with the Ag layer height up to 12 mm, above which no obvious decrease was observed. Oppositely, the density, diameter, and length of ZnO rods all increase with an increase in the Ag layer thickness, except that the length becomes constant above a critical thickness of 60 nm. In addition, when the Ag layer annealing temperature increases from 300 to 400 °C, the nanorod density decreases, the diameter increases, and the length remains nearly invariable, respectively. Surprisingly, randomly inclined nanorods with two different diameters dispersedly coexist on the Ag layer that was annealed at 500 °C. This work may provide an effective approach for the shape control in ZnO-based applications.

The microstructure and thermoelectric properties of InSb–NiSb composite system are investigated. NiSb, ranging from micro- to nanoscale, is introduced as a nonsoluble second phase in the InSb matrix by using the water quenching method. The morphology of the second phase is adjusted by varying the composition from hypoeutectic to hypereutectic alloys. The eutectic composite with a semiconducting InSb matrix and a metallic NiSb fiber on the order of 100-nm diameter is obtained. Melt spinning (MS) is applied to the eutectic composition to change the NiSb dispersion phase to around 200-nm diameter sphere. Transport properties, including Seebeck coefficient, resistivity, Hall coefficient, and thermal conductivity, are measured from 80 to 630 K. Compared to the water quenched (WQ) eutectic sample, the MS process results in a slight increase in the carrier concentration but a remarkable reduction in the mobility and thermal conductivity. Compared to the InSb matrix, ZT of the samples with the NiSb second phase is lower. For the eutectic samples, ZT is significantly reduced after the MS process because of the loss in mobility. ZT of the WQ InSb matrix is the highest in all the samples, ∼0.5 at 600 K.

This work reports the gold-coated self-organized silicon nanopyramidal array prepared by a wet etching and magnetron sputtering process at room temperature. Scanning electron microscopy was used to detect the morphology of gold films. The surface-enhanced Raman scattering (SERS) spectra of the rhodamine 6G (R6G) molecules adsorbed on a nanoscale gold film were recorded. Experimental results show the relationships between gold film thickness and SERS intensity. A full three-dimensional finite difference time domain calculations were carried out, which compare the experimental results and show agreement with ratios of the SERS enhancement for the different thicknesses of gold films. Furthermore, numerical simulations of the array were conducted for both a real gold metal coating and a perfect electrical conductor to determine whether the SERS enhancement was due to diffraction or plasmonic effects. The sample with the fast fabrication process used in this work could provide a new way to obtain a uniform enhancement and low cost SERS substrate.

Bismuth vanadate (BiVO4) hierarchical spheres were synthesized successfully by a facile hydrothermal approach without any additive by using novel vanadium-based nanosheets as precursors. The results indicated that as-prepared BiVO4 samples have monoclinic structure with high crystallinity. Scanning electron microscopy images show that the spheres were self-assembled by dozens of nanosheets with good dispersibility and uniform particle size. Meanwhile, the photocatalytic activities of the resulting BiVO4 were evaluated by photodegradation of methylene blue (MB) under visible light irradiation and exhibited enhanced catalytic efficiency. The excellent performance can be attributed to the high purity, the huge specific surface area, and the novel hierarchical structure. It was also found that the photodegradation of dye pollution is attributed to the oxidation process of the generated hydroxyl radicals and the action of ${\rm{h}}_{{\rm{vb}}}^{\rm{ + }}$ via direct hole oxidation.