NiAl-based nanocomposites were successfully fabricated by mechanical alloying proceeded vacuum-hot-pressing sintering, and the mechanical and tribological properties of the NiA–NbC composite were investigated. The results show that the nanostructured powder particles with the average size around 5 nm were successfully obtained by a high-energy-ball mill. After sintering, the composites were consisted of B2-ordered NiAl and NbC second phase, and the crystalline size of the NiAl phase was about 20 nm. The relative density, hardness, and compressive strength of nanostructured NiAl materials increased with increasing the Nb content, which can be attributed to the second phase hardening effect of in situ formed NbC particulates and fine grain strengthening of nanocrystalline NiAl phase. Thereafter, the friction coefficient of the NiAl–3NbC composite was lowered by the addition of silver and that is significantly lower than the NiAl intermetallic compound and NiAl–3NbC composite at elevated temperatures, which was attributed to the lubricating films formed in sliding process at elevated temperatures. While the wear rates of NiAl–3NbC–10Ag composites are higher than that of the NiAl–3NbC composites at each test temperature, especially at 500 °C and 700 °C, which might be attributed to the phase variations on the worn surfaces of the composites.

SnSb nanoparticles are dispersed in carbon nanofibers by electrospinning technology and different SnSb precursors, including Sn0.92Sb0.08O2.04 nanoparticles, Sn(CH3COO)2/Sb(CH3COO)3, and SnCl4·5H2O/SbCl3, are used to tune the morphology of the resultant SnSb/C nanofibers. Porous SnSb/C nanofibers are formed during carbonization Sn0.92Sb0.08O2.04 nanoparticles and Sn(CH3COO)2/Sb(CH3COO)3 are used as precursors of SnSb, while solid nanofibers are observed with SnCl4·5H2O/SbCl3 as the precursor indicating the formation mechanism is closely related to the properties of SnSb precursors. Excellent cycling preference (99% capacity retention after 200 cycles) and high coulombic efficiency (above 99% after 10 cycles) are obtained for the SnSb/C nanofibers using Sn0.92Sb0.08O2.04 as precursor, due to its high surface area and stable SnSb/C structure. It is demonstrated that the uniquely designed composite nanofiber structure with excellent lithium storage performance can be realized simply by selecting precursors with appropriate dissolution and decomposition properties.

Four 9Cr2WVTa deposited metals with different titanium contents were studied to reveal the role of minor elements titanium, which guide for the design of welding consumables for reduced activation ferritic/martensitic steel and meet for the requirements of accelerator driven systems-lead fusion reactors. The microstructural evolution of 9Cr2WVTa deposited metals was analyzed and discussed. Results show that the surface layer of 9Cr2WVTa deposited metal exhibits the columnar structure and the δ-ferrite is seen as a film distributed along the martensite lath. The microstructures are uniform in the middle of the deposited metal and exhibit the equiaxed structure. The fine stripe δ-ferrite decorates along the prior austenite grain boundaries and therefore, refines the grain size. The primary blocky Ti-enriched particles are the main factor affecting the mechanical properties for the 9Cr2WVTa deposited metal. The 9Cr2WVTa deposited metals obtain good mechanical properties when the titanium content does not exceed 0.08 wt%.

2-(3,4 epoxycyclohexyl)ethyltrimethoxysilane (EETMS)/3-glycidoxypropyltrimethoxysilane (GPTMS) mediated, in situ synthesis of functional palladium (Pd) nanocomposites over the graphene oxide (GO) surface is reported. The prepared nanocomposites viz, Pd/EETMS, Pd/GPTMS, Pd/GO/EETMS, and Pd/GO/GPTMS, are encapsulated into mesoporous (2–10 nm) silica-alginate beads to primarily serve the development of cost-effective catalyst for on-board generation of hydrogen. Major findings involve: (i) the synthesis of porous silica alginate beads, with the controlled pore sizes (2–10 nm) as a function of concentration of alkoxysilanes, (ii) onboard release of hydrogen from the decomposition of hydrazine, which is evaluated as: (1) time-dependent disappearance of the N–N bond stretching band at 1069 cm−1 based on the FTIR spectroscopy, (2) volumetric estimation of the equimolar hydrogen using methylene blue (MB); (3) catalytic reduction of p-nitroaniline (PNA). The decomposition of high concentration of hydrazine is made possible using very low concentration of palladium. On calcination the efficiency of catalysts found to enhance further. The noteworthy finding is probing the hydrogen evolution using FTIR spectroscopy. Hydrogen selectivity of ∼100% is obtained from the most efficient catalyst (Pd/GO/EETMS-623 K).

The present work addresses the competition between dislocation plasticity and stress-induced martensitic transformations in crack affected regions of a pseudoelastic NiTi miniature compact tension specimen. For this purpose X-ray line profile analysis was performed after fracture to identify dislocation densities and remnant martensite volume fractions in regions along the crack path. Special emphasis was placed on characterizing sub fracture surface zones to obtain depth profiles. The stress affected zone in front of the crack-tip is interpreted in terms of a true plastic zone associated with dislocation plasticity and a pseudoelastic zone where stress-induced martensite can form. On unloading, most of the stress-induced martensite transforms back to austenite but a fraction of it is stabilized by dislocations in both, the irreversible martensite and the surrounding austenite phase. The largest volume fraction of the irreversible or remnant martensite along with the highest density of dislocations in this phase was found close to the primary crack-tip. With increasing distance from the primary crack-tip both, the dislocation density and the volume fraction of irreversible martensite decrease to lower values.

Oxygen is known to have a significant impact on the strength of Ti alloys, whereas it can also reduce the ductility substantially. Thus, the usage of oxygen to strengthen Ti is restricted in the industry. In this study, we rekindled the research of oxygen behavior in Ti with the purpose of developing Ti alloys with high strength and suitable ductility by using no expensive and poisonous element. To this end, experiments of producing high performance commercially pure Ti using only oxygen solid solution were carried out. The oxygen element was introduced into the Ti by two different powder metallurgy methods. The microstructural examination and mechanical test were performed for the samples, which indicated a strong hardening effect of oxygen in spite of the processing routes. Most importantly, the results suggested that a high elongation to failure of over 20% can still be obtained in the samples having yield stress over 800 MPa, up to an oxygen content of 0.8 wt%, which is far beyond the previously recognized limit.

{001} facets dominant TiO2 nanosheets have attracted intensive attention in the photocatalytic field, due to their undercoordinated Ti5c centers, higher surface energy, and photocatalytic activity than those of any other low-energy facet. However, a fluorine-rich (001) surface is controversial to the photocatalytic activity of TiO2 nanocrystals. We have removed the surface F atoms bonding with Ti by hydrogenation method successfully, and found that {001} facets dominant TiO2 nanosheets without the terminated F atoms showed dramatic enhancement in the photocatalytic activity. Moreover, the clean (001) surface was more in favor of the deposition of PdO than the fluorine-rich surface, and the amorphous structure from the hydrogenation is beneficial to the reduction of PdCl42− to Pd nanoparticles. The PdO attached on {001} facets and the amorphous structure promoted the separation of charge carriers, and Pd nanoparticles transferred plasmonic-induced electrons to the conduction band of hydrogenated TiO2 under simulated solar irradiation. Thus, a significantly enhanced photocatalytic activity of Pd–H–TiO2 is achieved on degrading organic environmental pollution, due to the synergy of palladium species and hydrogenation on {001} facets exposed TiO2.

The influence of hot rolling on the evolution of the interface microstructure as well as mechanical properties of the Mg/Al explosive welding composite plates was investigated. The hardening phenomenon induced by explosive welding could be eliminated effectively through preheating treatment. An intermetallic compound layer consisting of Al3Mg2 and Mg17Al12 was observed at the Mg/Al interface after annealing at 400 °C. The composite plate then was hot rolled at 400 °C with different reduction ratios. The composite plates presented different degrees of warp and edge cracks with increasing the reduction ratio. At the reduction ratio of 30%, the coordination deformation ability of the constituent Mg and Al alloys is consistent with the composite plate. The results showed that the tensile strength and the elongation of the composite plates increased significantly after hot rolling owing to the dynamic recrystallization and the intermetallic compounds thickness decrease during hot rolling.

This work investigates the relative contributions to strengthening from twinning, solid-solution, precipitation, and irradiation hardening mechanisms in sputtered Cu–W thin films irradiated to different doses. A nanograin solid solution strengthening mechanism with a linear compositional dependence is observed for the as-grown alloys and for the alloy samples irradiated to 0.5 dpa. Solid solution strengthening is the major strengthening mechanism for Cu99.5W0.5 at all irradiation doses. Irradiation induces precipitation in samples with W concentrations greater than or equal to 1% at doses above ≈0.5 dpa. The growth of 1–4 nm precipitates enhances the hardness of these alloys, and the degree of strengthening is determined by the interparticle spacing. While the alloys exhibit steady-state properties after a relatively low dose (≈1 dpa), the different time scales associated with detwinning and damage accumulation in pure Cu lead transients at higher doses (>5 dpa).

In the present study, the effect of heat treatment on microstructure and mechanical properties of gas tungsten arc (GTA) welded 15CDV6 high strength low alloy steel is discussed. Experiments were carried out based on Taguchi L9 orthogonal array to weld 15CDV6 plate of thickness 3.7 mm. The input parameters considered in this work were current, voltage, and welding speed. Tensile strength, microhardness, and impact strength were measured as performance characteristics. Post weld heat treatment was carried out on the weldments to study its effect on the properties of weldments and microstructures were characterized using optical microscope and the X-ray diffraction analysis revealed the presence of MO2C and VC precipitates in the weld. Post weld heat treatment of the GTA welded samples and base metal successfully produced properties required for aerospace applications.

It is desirable to evaluate the ratcheting behavior of biomedical magnesium under cyclic loading with and without precorrosion, due to the promising future in biomedical implant field. This study focuses on the investigation of the uniaxial ratcheting strain evolutions of ZEK100 magnesium alloy sheet under various loading conditions and different corrosion time. To illustrate the ratcheting response in detail, the effects of several factors on the ratcheting strain evolution were discussed, including mean stress, stress amplitude, specimen orientations, loading history, and precorroded duration. A series of asymmetrical multistep stress-controlled ratcheting tests were conducted. The mean stress, stress amplitude, and precorrosion duration have significant influence on the ratcheting response of material. ZEK100 magnesium alloy is sensitive to loading history. ZEK100 magnesium alloy exhibits anisotropic behavior, and it is found that the final ratcheting strain of transverse direction (TD) specimens is always larger than that of rolling direction (RD) specimens. The corrosion behavior of ZEK100 magnesium alloy in phosphate buffered solution (PBS) simulated physiological environment was also studied. The corrosion process is characterized by pitting corrosion, and the corrosion rate of material stabilizes at about 2.4 g/(m2 d) after an exponentially decrease at initial stage.

One conceptually different approach has been developed to synthesize Ti3+ self-doped TiO2−x mesocrystals to narrow the band gap of TiO2. This simple and economical one-pot solvothermal method uses TiCl3 and tetrabutyltitanate (TBT) as a precursor and exhibits practical application. Different morphology including uniform spindle shape, tetragonal bipyramid, and capsule-like mesocrystals can be tailored easily by tuning the precursor ratio of TiCl3 to TBT. We have shown that our band gap engineered TiO2−x exhibits unique mesocrystal phase and owns substantial high visible light driven photocatalytic activities. Electron paramagnetic resonance (EPR) studies of this sample verified the presence of oxygen centered radicals, namely, hydroxyl (·OH) and superoxide radicals (O2 −·/·OOH). The catalysts have been characterized using transmission electron microscope, fluorescence spectra, Raman spectra, EPR, X-ray photoelectron spectroscopy, X-ray diffraction (XRD), Ultraviolet–visible absorption spectra, etc. It shows high catalytic stability. The findings of this work provide new insights for developing morphology tailored for visible light driven devices and other applications via controlled band gap engineering.

Porous silicon nitride ceramics are attracting extensive attention due to its high strength and low dielectric loss. However, further strength enhancement at elevated temperatures is hindered by its intergranular phase, forming from sintering additives. This paper describes the fabrication of porous silicon nitride ceramic materials, by using a replacement method of carbothermal nitridation. The initial samples which were obtained from the sintering of mixed powder consisted of 95 wt% Si3N4 and 5 wt% Y2O3. After the removal of the oxide intergranular phase and the infiltration of mixtures of phenolic resins and silica sols, carbothermal nitridation process was carried out at 1550 °C for 2 h under nitrogen. X-ray diffraction and microstructural analysis revealed a complete replacement of oxide intergranular phases by the newly formed Si3N4 intergranular phase. The unmodified ceramic exhibited lower flexural strength at 1400 °C, which was only 50% of the room-temperature strength. Although the modified ceramic attained a slightly lower flexural strength at room temperature after the replacement of intergranular phase, its strength measured at 1400 °C could attain 90% of room-temperature strength.

We outline the scrutiny of the two probe devices formed by placing the nonclassical fullerene molecules CM (20 ≤ M ≤ 30) within semi-infinite gold electrodes using density functional theory. The electronic structure and molecular orbitals of isolated fullerene molecules are broadened to form junction devices with charge injection at zero as well as variegated bias respectively. The molecular junctions thus formed are contemplated for two important electrical constitutions, current, and conductance. These parameters are then elaborated and contemplated for their electronic parameters namely, the density of states, transmission coefficient, molecular orbitals, molecular projected self-consistent Hamiltonian states, electron density, and Mulliken population. We conclude that C20 and C24 fullerene molecule exhibits extremely metallic behavior while others fail to demonstrate such behavior. The molecular device, thus formed, strongly supports the superconductive behavior of the C24 molecule with an ability to easily adapt by modulating its active molecular orbitals under applied potential.

We develop a phase field model for the simulation of chemical diffusion-limited solidification in complex metallic alloys. The required thermodynamic and kinetic input information is obtained from CALPHAD calculations using the commercial software-package ThermoCalc. Within the case study on the nickel-base superalloy Inconel 718, we perform simulations of solidification with the explicit consideration of 6 different chemical elements. The stationary dendritic tip velocities as functions of the constant undercooling temperature obtained from isothermal solidification are compared with the stationary tip temperatures as functions of the imposed pulling velocity obtained during directional solidification. We obtain a good quantitative agreement between the two different velocity—undercooling functions. This indicates that the model provides a self consistent description of the solidification. Finally, the simulation results are discussed in light of experimental solidification conditions found in single crystalline casting experiments of Inconel 718.

This work presents the effects of sintering temperature and mechanical milling on the weight loss of the powder metallurgical Fe–28Mn–3Si (wt%) alloy. Mechanically milled (MM) and blended elemental (BE) Fe–28Mn–3Si powder mixtures were prepared. Both the MM and BE compacts were sintered in a vacuum furnace for 3 h at various temperatures. It was found that weight loss occurred among all the sintered compacts. The weight loss of the sintered MM compacts was much lower than their BE counterparts sintered at the same temperature. The weight loss of the compacts was mainly caused by the sublimation of Mn in the Mn depletion region. A single α-Fe phase was observed on the surface of all the sintered samples. Predominant γ-austenite and minor ε-martensite were detected in all the sintered compacts at locations beyond the Mn depletion region. Mn3Si phase was found in BE alloys sintered at 1000 °C.

Over the years, the search for high performance thermoelectric materials has been dictated by the “phonon glass and electron crystal (PGEC)” paradigm, which suggests that low band gap semiconductors with high atomic number elements and high carrier mobility are the ideal materials to achieve high thermoelectric figure of merit. Complex oxides provide alternative mechanisms such as large density of states and strong electron correlation for high thermoelectric efficiency, albeit having low carrier mobility. Due to vast structural and chemical flexibility, they provide a fertile playground to design high efficiency thermoelectric materials. Further, developments in oxide thin film growth methods have enabled synthesis of high quality, atomically precise low dimensional structures such as heterostructures and superlattices. These materials and structures act as excellent model systems to explore nanoscale thermal and thermoelectric transport, which will not only expand the frontier of our knowledge, but also continue to enable cutting edge applications.

The metadynamic recrystallization (MDRX) behavior of a Nb–V microalloyed nonquenched and tempered steel was investigated by isothermal hot compression tests on Gleeble-1500 thermal-mechanical simulator. Compression tests were performed using double hit schedules at temperatures of 1273–1423 K, strain rates of 0.01–5 s−1, initial grain sizes of 92–149 μm and an inter-pass time of 0.5–10 s. The experimental results show that MDRX softening fraction increases with the increasing of deformation temperature, strain rate, and inter-pass time, while it decreases with the increasing of initial grain size. Based on the experimental results, the MDRX softening fraction kinetic model and recrystallized grain size model of the tested steel was established. Besides, using the above mathematic models, a finite element model was built to simulate the MDRX process of the tested steel. The simulation results show good agreement with the experimental ones, which indicates that finite element method is an effective approach to analyze the MDRX behavior and the established that mathematic models of the tested steel are reliable and accurate.

A systematic analysis of the correlation between the valence electrons and the transformation temperatures of Ti–Ni-based shape memory alloys has been carried out by Zarinjad and Liu. They have shown that the valence electron theory can be successfully applied to estimate these temperatures, although the mechanisms of the temperature shift during alloying remains not completely understood. Other important shape memory alloy systems with technological importance are the Cu–Al based, which deserve a thorough analysis concerning the composition influence on the transformation temperatures and the valence electron theory. In this paper, the valence electron concentration, valence electron density (VED), enthalpy of reaction, and crystallographic compatibility were analyzed to understand the mechanisms, which control the transformation temperatures of Cu–Al-based alloys. It was observed that the larger the VED, the more energy is used in the transformation. The same tendency is present when the crystallographic compatibility is smaller. These results show that the valence electron theory based on the VED plays an important role in the prediction of the temperature transformation and the energies involved in the reaction.