The effects of W, Re, Cr, and Mo on microstructural stability, such as the morphology of γ′ phase and the topologically close-packed (TCP) phase precipitation are systematically investigated in eleven kinds of Ni-based single crystal superalloys containing certain amounts of Co, Al, and Ta. After heat treatment, all the designed alloys show different sizes of γ′ phases with typical cuboidal morphology occupying 75% of the total volume. With increasing Re content, the size of γ′ decreases obviously, while the size of γ′ decreases slightly with increasing Cr and Mo contents. Increasing W does not affect the size of γ′. As a result of thermal exposure at 1000 °C for 1000 h, some acicular, rod-like, and blocky TCP phases are precipitated in most alloys. It is noted that Mo and Re can strongly promote the precipitation of TCP phase, but W has no obvious effect on TCP phase precipitation. In addition, transmission electron microscope analysis indicates that these TCP phases are σ phase, μ phase, and R phase.

Magnesium based nanocomposites containing 0.66 vol% of different types of oxide (i.e., Al2O3, Y2O3, and ZrO2) nano particles. The nano oxide particles were dispersed using melt processing. Microstructural characterization reveled that Y2O3 and ZrO2 nano particles were relatively better magnesium matrix grain refiner compared to nano-size Al2O3 particles. Mechanical characterization revealed that the oxides used in this study as reinforcement have strong strengthening effect on the magnesium matrix, where Y2O3 particles were most effective and Al2O3 particles were least effective. Ductility and resistance to fracture of magnesium was significantly improved by Al2O3 nano particles, unaffected by Y2O3 nano particles, and adversely affected by ZrO2 nano particles.

Magnetic Fe3O4–polyhedral oligomeric silsesquioxanes (POSS) particles with Si-OH were prepared by hydrosilylation reaction between the Fe3O4–SiH and POSS with hydroxyl and vinyl groups. The magnetic Fe3O4–POSS particles were characterized by using transmission electron microscopy, scanning electron microscopy, Fourier transform infrared absorption spectroscopy, thermogravimetry, and vibrating sample magnetometry. The magnetic saturation value of Fe3O4–POSS particles was 18.77 emu/g. Polyacrylonitrile (PAN)/Fe3O4–POSS nanofibers mats were subsequently fabricated by electrospinning technique. The electret properties of PAN/Fe3O4–POSS nanofibers mats and their aerosol filtration property as electrets filter media were characterized. The stability of the surface potential was remarkably improved and the surface potential retention reached 50% for PAN/Fe3O4–POSS mats with 1 wt% Fe3O4–POSS. Compared with pure PAN, the charge retention of PAN/Fe3O4–POSS was increased by 21% and reached 52.40%. Moreover, the collection efficiency increased and the filter resistance decreased when the PAN nanofibers with Fe3O4–POSS were used as electrets filter media. Our study provided an effective method to prepare novel filter materials with high efficiency and low resistance.

As-annealed commercial pure titanium (grade 1) was selected as a model material whose crystalline structure was hexagonal close-packed. The evolution of the microstructure and micro-orientation induced by high-speed compression was characterized to elaborate the formation mechanism of the high-speed deformation characteristic microstructure in α-titanium. Twinning played a coordinating role for dislocation slipping that was the main plastic deformation mechanism. The high-speed deformation characteristic microstructure of as-annealed commercial pure titanium was an adiabatic shear band (ASB) with an average width of 50 μm at a strain rate of 5400 s−1, whose initial grains were 0.5–1.0 μm in size. The formation and extension of ASB were attributed to the interaction between the shear stress and the adiabatic temperature rise. A formation model of ASB in α-Ti was proposed in terms of the formation mechanism of the high-speed deformation characteristic microstructure.

In this study, a mesoscale dislocation simulation method was developed to study the orthogonal cutting of titanium alloy. The evolution of surface grain structure and its effects on the surface mechanical properties were studied by using two-dimensional climb assisted dislocation dynamics technology. The motions of edge dislocations such as dislocation nucleation, junction, interaction with obstacles, and grain boundaries, and annihilation were tracked. The results indicated that the machined surface has a microstructure composed of refined grains. The fine-grains bring appreciable scale effect and a mass of dislocations are piled up in the grain boundaries and persistent slip bands. In particular, dislocation climb can induce a perfect softening effect, but this effect is significantly weakened when grain size is less than 1.65 μm. In addition, a Hall–Petch type relation was predicted according to the arrangement of grain, the range of grain sizes and the distribution of dislocations.

The thixoforging technology has been proved as an effective method to fabricate the in situ Mg2Sip/AM60B composite with excellent performances. The effects of reheating temperature on microstructure and tensile properties have been investigated. The results indicate that the liquid amount, the solubility of Al in α-Mg particles, and the coarsening of the α-Mg particles are changed as the reheating temperature changes, and thus the subsequent solidification behavior and plastic deformation are thereby changed. The morphology of the Mg2Si particle also varies as the reheating temperature rises owing to partial remelting operating in the edges and corners of the particles. The best ultimate tensile strength and elongation of 209 MPa and 11.9% of the thixoforged composite, which are 93 and 138% higher than the traditional permanent mold casting respectively, are obtained under the reheating temperature of 600 °C.

An Al–10.83Zn–3.39Mg–1.22Cu–0.16Zr–0.16Sc alloy was produced using the spray deposition technology. The microstructure evolution within temperature ranging between 613 K and 733 K during hot pressing process at different initial strain rate was investigated in a transmission electron microscope (TEM). Partial resolution of the primary precipitates in the deposited microstructure, such as η-MgZn2 and Al3(ScZr), took place. Moreover, new secondary η-MgZn2 and Al3(ScZr) precipitated from the super saturated solid solution and their effects on the recrystallization were also analyzed. The Al3(ScZr) and η-MgZn2 precipitation can act as barriers for the movement of both dislocations and grain boundaries, which are the main factors for hindering the recrystallization. Additionally, the dislocation slide during hot deformation was also investigated in detail. The spray deposition Al–Zn–Mg–Cu alloy own the well deformability, and the typical perfect dislocations can be found in the hot deformation Al–Zn–Mg–Cu alloy.

Transition metal dichalcogenides such as WS2 show exciting promise in electronic and optoelectronic applications. Significant variations in the transport, Raman, and photoluminescence (PL) can be found in the literature, yet it is rarely addressed why this is. In this report, Raman and PL of monolayered WS2 produced via different methods are studied and distinct features that indicate the degree of crystallinity of the material are observed. While the intensity of the LA(M) Raman mode is found to be a useful indicator to assess the crystallinity, PL is drastically more sensitive to the quality of the material than Raman spectroscopy. We also show that even exfoliated crystals, which are usually regarded as the most pristine material, can contain large amounts of defects that would not be apparent without Raman and PL measurements. These findings can be applied to the understanding of other two-dimensional heterostructured systems.

The new processing method of spark plasma sintering (SPS) followed by hot extrusion was developed to produce Mg–1Al–xCNTs composites. Microstructural characterization revealed that the reinforcement particles were distributed uniformly in Mg matrix. The results of mechanical properties indicated a fact that compared with monolithic Mg, all Mg–1Al–xCNTs composites, especially the Mg–1Al–0.15CNTs composite, fabricated by SPS followed by hot extrusion exhibited better tensile and compressive properties. Under tension, Mg–1Al–0.15CNTs composite exhibited higher 0.2% tensile yield strength (TYS) (157 MPa versus 98 MPa, increased by ∼60%) and ultimate tensile strength (271 MPa versus 188 MPa, increased by ∼44%) than monolithic Mg. In compression, Mg–1Al–0.15CNTs composite also obtained a great enhancement in 0.2% compressive yield strength (118 MPa versus 81 MPa, increased by ∼46%) and ultimate compressive strength (321 MPa versus 255 MPa, increased by ∼26%) compared to monolithic Mg. Meanwhile, Mg–1Al–0.15CNTs composite maintained a high tensile failure strain of ∼8.8% and a high compressive failure strain of ∼17.9%.

The effect of magnesium nitrate on the thermo-foaming of powder dispersions in molten sucrose for the preparation of alumina foams has been studied. The magnesium nitrate decreases the melting point of sucrose from 180 to 160 °C and acts as a blowing and setting agent. The foaming time and setting time decreases with an increase in foaming temperature as well as an increase in magnesium nitrate concentration. The rapid foaming followed by foam collapse is observed beyond 140 °C. The accelerated foaming and setting is due to an increase in the rate of –OH condensation because of the catalytic effect of H+ generated by the hydrolysis of magnesium nitrate. The porosity of alumina foam increases while cell size and grain size decrease with an increase in magnesium nitrate concentration. A change in foam structure, from partially interconnected cellular to completely interconnected reticulate-like, occurs when the magnesium nitrate concentration increase from 4 to 8 wt%.

In this study, silver nanowires (Ag NWs) were synthesized in a one-pot method from silver nitrate and poly(vinyl pyrrolidone) (PVP), and reduced by ethylene glycol without the presence of chloride ion. The addition of silver nitrate and PVP was controlled by syringes. The syringe rate, and the concentrations of silver nitrate, and PVP, were manipulated to obtain Ag NWs with different widths and lengths. We have observed the phenomena of coarsening and combination of silver nanorods during the growth of the Ag NWs. With these phenomena, we have developed a growth model of Ag NWs, and successfully synthesized Ag NWs with high aspect ratios via the developed model.

Incineration or disposal of carbon fiber waste from the aircraft industry leads to serious energy consumption and environmental pollution. The use of this waste as reinforcement is a wise approach to appreciate the high performance of the carbon fiber. In this study, the sliding wear and frictional behavior of recycled carbon fiber prepreg (rCFP) reinforced polypropylene (PP) prepared via melt compounding method using an internal mixer were studied. The samples were categorized into PP reinforced by carbon fiber with resin (A) and carbon fiber without resin (B). Pin-on-disc method was utilized to evaluate the effect of rCFP content and physical condition of fibers on tribological performance of the composites. The results were supported by morphological analyses using scanning electron microscopy. It was found that polymer composites B for rCFP without resin exhibited better tribological performance than composites category-A. The addition of rCFP into PP was observed to increase its wear resistance with minimum coefficient of friction achieved at 3 wt% of rCFP content for both polymer composites.

In this study, we report a micropillar stress relaxation technique employing a stable displacement-controlled, in-situ scanning electron microscope indenter, and unusually large micropillars to precisely measure stress relaxation in electroplated nanocrystalline Ni thin films. The observed stress relaxation is significant under constant displacement: even well below the 0.2% offset yield strength, the stresses relax by ∼4% within a minute; in the work hardening regime, stress relaxes by ∼9% in 1 min. A logarithmic fit of the relaxation curves is consistent with an Arrhenius thermal activation of plasticity and suggests an activation volume in the vicinity of ∼10 b3. The apparent and effective activation volumes diverge at lower strains, particularly in the “elastic” regime. These measurements are compared to similar measurements performed on free-standing thin film tensile coupons. Both methods yield similar results, thereby validating the applicability of pillar compression to capture time-dependent plasticity. To our knowledge, these are the first micropillar stress relaxation experiments on metals ever reported.

The effects of pre-treatments on the precipitate microstructures of an Al–Zn–Mg–Cu alloy are investigated. Meanwhile, the creep-rupture behavior of the under-aged and peak-aged alloys are comparatively analyzed. Additionally, the effects of pre-treatment on the fracture mechanisms are discussed. It is found that the precipitate microstructures are sensitive to pre-treatments. The intragranular precipitates of the peak-aged alloy are larger than those of the under-aged. The precipitate free zone of the peak-aged alloy is wider than that of the under-aged. Some large intergranular precipitates appear on the grain boundaries of the under-aged alloy, and induce the nucleation of microvoids. Eventually, the creep fracture of the under-aged alloy is accelerated. Therefore, the differences in microstructures lead to the shorter creep-rupture life of the under-aged alloy, compared to the peak-aged alloy.

Carbon nanotubes (CNTs) reinforced Ti matrix composites with tailored microstructures and properties were fabricated by direct metal laser sintering (DMLS). A relationship of processing conditions, distribution characteristics of CNTs, and properties was established. The appearance of balling phenomenon and micropores at relatively low laser energy input reduced the densification level of DMLS CNTs/Ti composites. As a η of 700 J/m was properly settled, the composite part with a near-full 96.8% density was obtained. On increasing the laser energy input, the distribution states of CNTs in Ti matrix changed markedly from agglomeration to homodisperse. The optimally prepared fully dense CNTs/Ti composite with uniform distribution of CNTs had significantly enhanced H d of 9.4 GPa and E r of 328 GPa, which showed respectively ∼2.5- and ∼3.4-fold increase upon that of unreinforced Ti, and resultant a relatively low friction coefficient of 0.23 and reduced wear rate of 3.8 × 10−5 mm3/(N m).

The effect of strain range on dynamic strain aging (DSA) is discussed based on the low cycle fatigue tests for different strain ranges conducted for 316L stainless steel at strain rate of 1 × 10−3 s−1. The variations of stress drop and hardening ratio are both compared for different strain ranges. The variations of stress drop are attributed to the dependence of vacancy concentration on strain range. The hardening ratio is higher at 600 °C than those at 20 °C and secondary hardening behavior occurs for larger strain range. The dependence of DSA on the number of cycles and the wave type for different stages are analyzed. Obvious DSA is observed in first few cycles, followed by weakening serrated yielding. However, the serrated yielding occurs again before fatigue failure. The difference of serrated yielding can be explained by the types of atom atmospheres at different cycles. A serrated wave is observed for smaller strain ranges, however, A, B, A + B, C, and B + C serrated waves can be found at different cycles for larger strain range. Finally, the crack nucleation and propagation on fracture surfaces are characterized by scanning electron microscope (SEM).

A semitransparent CuO film was applied for photoelectrochemical (PEC) cell to produce the record-high photocurrent (6.4 mA/cm2) for nanocrystalline monoclinic CuO photocathode. Large-scale affordable reactive-sputtering method was effectively formed Cu oxide films and sequential thermal processes efficiently controlled the Cu oxide phases with enhanced optical-transparency of Cu oxide films. Structural, physical, optical, and electrical properties of various Cu oxide films (CuO, Cu4O3, and Cu2O) were systematically investigated according to the sputtering condition and thermal processes. It was found that the energy band gap of CuO can be tuned from 1.7 to 1.9 eV by modulating the oxygen flow for reactive sputtering. Mott–Schottky analyses revealed the flat band potential close to the 0.96 V versus reversible hydrogen electrode and energy band edges of Cu oxide films. This state-of-the-art CuO photocathode would provide a strong potential for wide applications of the transparent PEC system of on-site energy generation.