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.

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.

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.

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.

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.

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.

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.

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.

Using first principle density functional calculations, we study the formation of 2D transition metal dichalcogenides (TMDs) on TiC1−xAx, (A = S, Se, and Te) surfaces. We examine the structural misfits between chalcogen-containing TiC and different TMDs and demonstrate that the conditions for formation of TMDs are fulfilled in TiC1−xAx. We also demonstrate the influence of chalcogens on the cohesive properties and electronic structure of the carbides. We find that they react with W and form W-dichalcogenides. In the experimentally reported Ti–C–S nanocomposite coatings, the carbide grains are embedded in an amorphous carbon matrix. We discuss here the role of this matrix in the reaction. We propose that TiC1−xTex and TiC1−xSex are the favorable sources for dichalcogenide formation and suggest an alternative way to produce 2D materials in general. Furthermore, we argue that using Ti–C–Te or Ti–C–Se in nanocomposite coatings may be more advantageous for tribological applications than that of Ti–C–S.

To clarify the underlying mechanism of formation and growth of aluminum coating, the interface microstructures of as-prepared aluminum coating iron were investigated using various experimental methods. The liquid Al–Si, Al–Ge alloys were chosen as the dipping baths. In both cases, the total thickness of the reaction layer is controlled mainly by the well-known diffusion growth of η-Al5Fe2. The melt environment of the Al bath plays a decisive role in the formation and growth of the diffusion layer. The results show that Ge atoms could also decelerate reaction layer growth like Si atoms, which mainly restrain the diffusion of Al atoms. Meanwhile, Ge element represents an abnormal concentration gradient in the η-Al5Fe2 phase. The diverse growth behavior of the diffusion layer is attributed to the strong controlling role of the alloying element in Al baths based on the atomic diffusion and activity analysis.