Welding was successfully used in the fabrication of low pressure steam turbine rotors for nuclear power plants. In this paper, the local brittle zone of the welded joint in NiCrMoV steel with heavy section was investigated by cross-zone fracture toughness test and the effect of martensite–austenite constituent in the simulated reheated zone of welds with different second peak temperature on toughness was analyzed. The results showed that the crack propagated in unstable manner in the reheated zone of welds where the martensite–austenite constituent promoted the initiation and propagation of the crack. The fine structure of martensite–austenite constituent contained retained austenite, martensite, and martensite–austenite mixture microstructure. The impact toughness deteriorated drastically in the incomplete phase transition zone for the simulated reheated zone of welds related to the formation of mixture microstructure in which large blocky martensite–austenite constituent at prior austenite grain boundaries and inside the grains were distributed in the shape of network.

We report a new pulsed chemical vapor deposition (PCVD) process to deposit nickel (Ni) and nickel carbide (Ni3Cx ) thin films, using bis(1,4-di-tert-butyl-1,3-diazabutadienyl)nickel(II) precursor and either H2 gas or H2 plasma as the coreactant, at a temperature from 140 to 250 °C. All the PCVD films are fairly pure with low levels of N and O impurities. The films deposited with H2 gas at ≤200 °C are faced centered cubic-phase Ni metal films with low C content; but at ≥220 °C, another phase of rhombohedral Ni3C is formed and the C content increases. However, when H2 plasma is used, the films are always in rhombohedral Ni3C phase for the entire temperature range.

We develop an asymmetric aqueous supercapacitor using iron oxide anode and cobalt oxide cathode. The anode was fabricated using electrospinning of carbon precursor/iron oxide precursor blend followed by pyrolysis and in situ electrochemical conversion (to oxide) to form the binder-free and freestanding composite anode which delivered a capacitance of 460 F/g at 1 A/g and retained 82% capacitance after 5000 cycles. The superior performance is attributed to easy electrolyte accessibility as well as the porous fibrous carbon morphology, facilitating volume expansion of iron oxide. The cobalt oxide cathode was prepared using a simple chemical synthesis technique. The electrodes were chosen based on high over potential to water splitting reactions in 6 M KOH electrolyte resulting in a potential window of 1.6 V. The asymmetric device operated in 1.6 V achieved a capacitance of 94.5 F/g at 0.5 A/g while retaining 75% of its capacitance after 12,000 cycles, delivering energy and power densities of 40.53 W h/kg and 2432 W/kg, respectively.

It is of the uttermost interest to understand the mechanical performance and deformation mechanisms contributing to small-scale plasticity of materials in micro/nanoelectromechanical systems at their service temperatures, which are usually above room temperature. In recent years, high-temperature nanoindentation experiments have emerged as a reliable approach to characterize the deformation behavior of materials at the nano and submicron scale. In this review, we highlight the role of the temperature in nanoindentation response of a wide variety of materials, with a particular focus on the thermally-activated deformation mechanisms in crystalline and non-crystalline materials under the indenter, e.g., dislocation processes, shear transformation zone, and phase transformations. A brief survey of the temperature-dependent nanoindentation elastic modulus, hardness, and creep behavior of materials is also provided. We also discuss experimental methods for correctly measuring the mechanical properties of materials at high temperatures.

Using kerf-free wafering technologies material losses in semiconductor manufacturing processes can be reduced drastically. By the use of externally applied stress, crystalline materials can be separated along crystal planes with clearly defined thickness. Nevertheless, during this process striations caused by the crack propagation occur. These crack growth features are river and Wallner lines. In this work, we demonstrate a process for spalling that scales favorably for large-area semiconductor substrates with a diameter up to 300 mm. To get rid of the crack growth features, a laser-conditioning process with a high numerical aperture at photon energies below the material bandgap energy, using multi-photon effects is utilized. The process affords a surface roughness R a after spalling of <1 µm.

Solar steam generation is an efficient and green technology for desalination and drinking water purification, however, impeded by high cost, low efficiency, and complicated process. Black titania is expected to exhibit excellent solar steam performance due to its outstanding light absorption properties, chemical stability, low cost, and innocuity. Herein, we design a high absorbing and efficient solar steam generation system based on a black titania/graphene oxide nanocomposite film affixed to airlaid paper wrapped over the surface of expandable polyethylene foam; the system possesses several important criteria required for the ideal solar steam generator: wide-spectrum absorption, adequate water supply, reduced heat loss for localized water heating, and porous structure for steam flow. Remarkably, we realized a solar thermal conversion efficiency of 69.1% under illumination of 1 kW/m2 without solar concentration, and the device delivered remarkable cycle stability.

Centerline segregation is one of the typical internal defects, which occurs during slab continuous casting (CC). To investigate and predict the centerline segregation encountered in a continuously cast slab, a combined 3-D and 2-D hybrid simulation model for centerline segregation was developed. The average deviation between the calculated and experimented results reaches as low as 0.5%, which demonstrates that the hybrid simulation model has relatively high reliability. The centerline segregation of the slab was predicted accurately. The results show that macrosegregation occurring during the slab CC process has heredity. In the casting direction, the concentration of solutes in the liquid pool increases gradually until the casting has solidified completely. After complete solidification, the solutes’ concentration maintains an almost constant value. On the centerline, the maximum segregation degree occurs at a position roughly 614 mm from the slab center. The maximum centerline segregation degrees of C, Si, Mn, P, and S solutes are 1.163, 1.058, 1.045, 1.111, and 1.165, respectively.

We have performed mechanical finishing operations on Sverker 21 (traditional) and Vanadis 6 (advanced powder) steel surfaces: grinding, turning, and turning followed by slide burnishing. Then each specimen was subjected in turn to focused ion beams of helium or krypton up to fluences of 1015 ions/cm2 and finally to scratch resistance testing. Acoustic signals show that krypton implantation reduces microcracks. Helium ions act even more strongly as homogenizers—almost completely eliminating the imperfections. Optical microscopy during scratch testing shows the force level when debris formation begins. Helium ions fitting between the iron atoms increase the resistance against scratching; larger krypton ions produce the opposite effect.

The microstructure and tensile property of extruded Mg–6Zn–1.5Ca (wt%) alloy were examined by means of electron backscattered diffraction, scanning and transmission electron microscopy. A bimodal microstructure featuring fine dynamically recrystallized (DRXed) grains with weaker texture and coarse-deformed region with strong basal texture and fine precipitates was achieved in the as-extruded Mg–Zn–Ca alloy, which resulted in a yield strength as high as 305 MPa and a moderate elongation to fracture of 8.6%. Dynamic precipitation was detected in the deformed region, which inhibited the dynamic recrystallization process. The texture intensity in the DRXed region was weakened compared with that in the deformed region, which was associated with the preferred nucleation during dynamic recrystallization. Such texture weakening effects gave rise to an obvious ductility improvement for the as-annealed alloy.

Axisymmetric reverse extrusion experiments were conducted on annealed Cu rod specimens to form cup-shaped structures with sidewall thicknesses ranging from ∼400 µm down to ∼25 µm. Changes in Cu grain morphology, size, and texture were examined through scanning electron microscopy and electron backscatter diffraction (EBSD). Pole figure and orientation distribution function analysis of EBSD data showed the same texture components in the present small-scale metal forming experiments as those observed in macroscale sheet metal rolling. The plastic deformation became inhomogeneous as the characteristic dimension for extrusion decreased to ∼25 µm, such that the deformation process involved a small number of Cu grains. Extrusion force–punch displacement curves were measured as a function of extruded cup sidewall thickness and compared to outputs of a continuum plasticity finite element analysis in corresponding geometries. The present work illustrates materials characteristics in small-scale metal forming and suggests directions of future work for bringing improved correspondence between experimentation and modeling.

The influences of pressure and aging treatment on microstructures and mechanical properties of rheo-squeeze casting (RSC) Mg–3Nd–0.2Zn–0.4Zr alloys were studied. It was found that the nucleation rate, solid solubility of Nd and Zn in the α-Mg matrix, and dislocation density were increased with increasing applied pressure. After aging treatment, the amount of the Zn2Zr3 phase was increased with increasing pressure; β″ phase and β′ precipitates were observed in the RSC alloy and finer β′ precipitates formed in the permanent mold casting (PMC) alloy. The mechanical properties of as-cast alloys were initially increased and then decreased with increasing pressure, while the properties of T6-treated alloys were increased continuously. Due to the larger grain boundary strengthening contribution, the T6-treated RSC sample showed higher mechanical properties than the PMC sample, and the yield strength, ultimate tensile strength, and elongation could reach 165 MPa, 309 MPa, and 5.7%, respectively.

A review of the literature offers an explanation for the large anomalous electro-optic (e.o.) effect reported by Fujiwara et al. in 1994. It is based on the large e.o. coefficient of ordered water at an interface measured in recent years >1000 pm/V. More broadly, the concept of water-based photonics, where water could be a new platform material for devices and systems, is introduced, suggesting that liquid states of matter can allow ready shaping and exploitation of many processes in ways not previously considered. This paper is a commentary on the significance of this new understanding and the broader interest of water in photonics, particularly its consideration as a new platform material.

The present article addresses design of stiff, elastically isotropic trusses and their mechanical properties. Isotropic trusses are created by combining two or more elementary cubic trusses in appropriate proportions and with their respective nodes lying on a common space lattice. Two isotropic binary compound trusses and many isotropic ternary trusses are identified, all with Young’s moduli equal to the maximal possible value for isotropic strut-based structures. In finite-sized trusses, strain elevations are obtained in struts near the external free boundaries: a consequence of reduced nodal connectivity and thus reduced constraint on strut deformation and rotation. Although the boundary effects persist over distances of only about two unit cell lengths and have minimal effect on elastic properties, their manifestations in failure are more nuanced, especially when failure occurs by modes other than buckling (yielding or fracture). Exhaustive analyses are performed to glean insights into the mechanics of failure of such trusses.

To investigate the effects of adding Au nanoparticles (AuNPs) to TiO2 films on the crystallization, phase transformation, and photocatalysis, films of both TiO2 and TiO2 embedded with AuNPs (Au–TiO2) with various characteristics were prepared by using the dip-coating method with preheating and post-heating treatments. The AuNPs acted as anatase nucleation agents and crystallized a lot of small anatase crystals with sizes of tens of nanometers, which suppressed the growth of anatase crystals that are large enough for them to transform into rutile crystals, resulting in repression of the transformation from anatase into rutile. The AuNPs affected the progress of the photocatalytic and adsorption reactions, resulting in improved photocatalytic activity. Of all the films we tested, the Au–TiO2 film preheated at 400 °C and post-heated at 400 °C (AT400-400), which consisted of small anatase crystals with high covalent character and high crystallinity, contained dispersed AuNPs with the smallest average crystallite size and showed the highest photocatalytic activity. This high activity resulted from the high reaction rate constants for adsorption and photocatalysis.