The hot deformation behavior of X45CrSi93 valve steel was investigated by a series of compression and tensile tests by means of the Gleeble-1500 simulator and microstructural analyses. The experimental results show that the flow stress decreases with the increasing temperature between 850 and 900 °C followed by an abnormal increase with the increasing temperature between 900 and 1000 °C under the compressive conditions. A normal decrease of the flow stress is continued with the increasing temperature above 1000 °C. Meantime, the tensile specimen conducted at 1000 °C shows double necking effect. Further microstructural analyses show that the phase transition from α-ferrite to austenite and the solution strengthening caused by carbide dissolution are the main reasons for abnormal variation of flow stress for X45CrSi93. The negative temperature gradient in the tensile specimen results in the symmetrical microstructure and then the double necking phenomenon.

The solidification of undercooled Ni–3.3 wt% B alloy was studied by high-speed video analysis and microstructural analysis. For moderate initial undercooling (ΔTp = 75 K), the solidification interface for primary phase transformation manifests a shape of a planar dendrite, and possesses an constant growth velocity, for eutectic transformation whereas the interface presents multi-dendrite shape and spasmodic growth, so that a constant velocity cannot describe the interface exactly. These differences suggest that primary phase solidification is controlled by far-distance diffusion while eutectic solidification by short-distance diffusion. For large initial undercooling (ΔTp = 262 K), a kinds of large “white dendrites”, which is in fact composed of multiple phases, were found in the microstructure, from inside to outside of which, the eutectic phase changes from dot phases (anomalous structure) to irregular eutectic and then to regular eutectic, indicating that the center of “white dendrites” may be the nucleation zone of eutectic reaction.

The overarching aim of biomimetic approaches to materials synthesis is to mimic simultaneously the structure and function of a natural material, in such a way that these functional properties can be systematically tailored and optimized. In the case of synthetic spider silk fibers, to date functionalities have largely focused on mechanical properties. A rapidly expanding body of literature documents this work, building on the emerging knowledge of structure–function relationships in native spider silks, and the spinning processes used to create them. Here, we describe some of the benchmark achievements reported until now, with a focus on the last five years. Progress in protein synthesis, notably the expression on full-size spidroins, has driven substantial improvements in synthetic spider silk performance. Spinning technology, however, lags behind and is a major limiting factor in biomimetic production. We also discuss applications for synthetic silk that primarily capitalize on its nonmechanical attributes, and that exploit the remarkable range of structures that can be formed from a synthetic silk feedstock.

In this study, Aluminum-based nanocomposites with hybrid reinforcements were successfully prepared by mechanical alloying, followed by consolidation using selective laser melting (SLM). The evolution of particle morphology and microstructural features of the milled powders at various milling times was studied. The results indicated that the milled powder particles experienced a coarsening stage at the early 5 h milling and followed by a continuous refinement during 5–20 h milling. After 20 h of milling, the original coarse needle-like Al3.21Si0.47 evolved into nanometer/submicrometer-sized spherical Al3.21Si0.47. Meanwhile, both fine Al3.21Si0.47 and ex-situ nanoscale TiN particles distributed uniformly within the Al matrix. By SLM processing of the 20-h powder, a near fully dense part with a uniform microstructure consisting of circularly dispersed and submicrometer-sized reinforcement particles embedded in α-Al matrix was obtained. The Vickers hardness and coefficient of friction of the SLM-processed part reached 178 HV0.1 and 0.38, respectively.

To obtain a floating and magnetically recyclable photocatalyst, nano-scaled Fe3O4 particles are first deposited on the surface of the KH-550 modified cenosphere under a hydrothermal condition. The Fe3O4 coated cenosphere is then loaded with a layer of globular-flower-like SiO2 particles by a precipitation method. The Fe3O4/SiO2 double-layer structured cenosphere is finally immobilized with TiO2 nanoparticles doped with rare earth element Eu3+ to enhance the photoactivity of TiO2 using titanium sulfate, urea, and polyvinylpyrrolidone by a hydrothermal treatment. The as-prepared cenosphere is systematically characterized by various characterization techniques. The properties of photocatalytic degradation of methylene blue dye are also investigated. Results show that after being doped with 0.1% Eu3+ ions in relation to Ti4+ ions, the photocatalytic degradation efficiency for the Fe3O4/SiO2/Eu-doped TiO2 coated cenosphere is significantly improved under both ultraviolet and visible light irradiations. The saturation magnetization of the Fe3O4/SiO2/Eu-doped TiO2 coated cenosphere increases to some degree.

The erosion–corrosion properties and interface microstructure of a Fe–B alloy that contains 3.5 wt% B in flowing liquid zinc have been investigated by electron backscattered diffraction, x-ray diffraction, and scanning electron microscopy to clarify the flowing effect of liquid zinc on erosion performance using a rotating-disk technique. The Fe–B alloy erodes at a low and steady rate in flowing liquid zinc. Flowing liquid zinc can accelerate the iron and zinc mass transfer to form Fe–Zn compounds and promote the removal of loose FeZn13. Much residual corrosion-resistant Fe2B and some erosion products coexist at the erosion interface because of the chemical and micromechanical effects that are created by flowing liquid zinc. The failure of the Fe2B corrosion-resistant skeleton in flowing liquid zinc occurs because of the loss of supporting matrix and also the formation and spread of microcracks during erosion.

We report the first observation of reversible equilibrium crystalline–metastable crystalline phase transformation in mechanically alloyed Ni–Ge powder mixtures. The formation of the equilibrium NiGe and metastable NiGe2 phases was investigated using x-ray diffraction and scanning electron microscopy methods. It was clearly shown that milling of the blended elemental powders first resulted in the formation of the equilibrium NiGe phase and continued milling led to the formation of the metastable NiGe2 phase. However, on milling for a longer time, the metastable phase transformed back to the equilibrium NiGe phase. The formation mechanisms of the stable and metastable phases and the reversibility of the phase transformations have been explained on the basis of the thermodynamic stability of the different phases and the contribution of defect concentration and surface energy effects to the free energy of the milled powder.

A previously synthesized hyperbranched poly(butylene adipate) (HPBA) polymer was compared with a commercial dendritic polyol (HPOH) as a toughening agent for a commercial one-part epoxy resin. Both modifiers were added in weight percentages of 1, 3, 5, and 10%. The modified epoxies were characterized using differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), thermogravimetric analysis (TGA), melt rheological tests, and linear elastic fracture mechanics. Blend morphology and matrix–modifier interactions were evaluated using scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR) analysis, respectively. The toughness-improvement effect was achieved without substantial impairment of thermomechanical properties or degradation of the thermal stability of the epoxy resin. A meaningful decrease in viscosity was achieved with both modifiers, contributing to an easier infusion processability. No evidence of new chemical linking was found although phase separation was observed by SEM, leading to the conclusion that only interfacial linkage occurs between modifiers and epoxy chains. SEM analysis also clearly shows the fracture mode changing from brittle to ductile by addition of modifiers, which was more evident for blends of HPBA.

Material property measurements at the micro-/nanoscale are required for within many materials systems, such as thin-films, coatings, nanostructured materials, and interface/interphase. An innovative approach through micro-/nano-indentation testing with a cylindrical flat-tip indenter and coupled with computer modeling was proposed to characterize the material's elastic–plastic properties. A mechanical model proposed for directly extracting the yield strength of the tested materials, based on the hemi-spherical stress–strain distribution assumption, was analytically derived and numerically validated. Specimens being tested are aluminum alloy, low carbon steel, and alloy steel. A micro-/nano-indentation solid model was constructed and computer modeling was conducted. The load point in the indentation load–depth curve and the modifier for extracting the yield strength were identified through computer modeling and validated by indentation tests. The material properties measured by indentation were compared with tensile tests. The indentation testing errors induced by residual stresses in specimens were investigated by a residual stress measurement system.

The present investigation aims to enhance the mechanical properties and shape memory characteristics of Cu–Ni–Al shape memory alloys (SMAs) by alloying additional elements. These additions were found to control the phase morphology and grain size, along with the formation of different volume fractions, sizes, and distributions of precipitates. The features of the precipitates were mainly dependent on the type of alloying element. It was found that a Co (1.14 wt%) alloy gave the best overall improvement in terms of the transformation temperatures, ductility, and shape memory recovery. These improvements were mainly due to the exceptionally high presence of the γ2 phase in the microstructures of the modified alloy. The results of the current investigation were analyzed and compared to those of previous studies related to Cu–Al–Ni SMAs.

This work studies the nitridation of Ta by laser irradiation by means of x-ray photoelectron spectroscopy. The study has been carried out under “in situ” conditions by controlling the nitrogen partial pressure, the presence of traces of oxygen, and the irradiance of the laser. It is found that a thin layer of Ta2O5 is directly obtained when irradiating in the presence of oxygen, while a Ta3N5 surface compound and some minor contributions of nonstoichiometric phases are formed in the presence of nitrogen. For O2:N2 mixtures at 0.1 Pa, preferential nitride formation occurs up to a ratio of 1:4, while Ta2O5 starts to be predominant for ratios above this value. The air stability of the tantalum nitride layer formed by laser irradiation and the surface topography of the irradiated metal are also studied. The possible factors determining this behavior are discussed.

The present study investigates the joining of 5-mm-thick plates of superaustenitic stainless steel, AISI 904L by continuous current (CC) and pulsed current (PC) gas tungsten arc welding (GTAW) using ER2553 and ERNiCrMo-4 fillers. This research article attempts to provide a detailed structure–property relationship of these weldments. Interface microstructure revealed the absence of deleterious secondary phases at the heat affected zone in all the cases. Skeletal delta ferrite morphology at the cap of ER2553 fusion zone and multidirectional grain growth at the ERNiCrMo-4 fusion zone were observed for both the weldments. The average hardness at the fusion zone was found to be higher for PCGTA weldments using ER2553 due to the higher proportions of ferrite. Tensile studies corroborated that the failure occurred at the parent metal in all the cases. Charpy V-notch studies divulged that the CCGTA and PCGTA weldments utilizing ERNiCrMo-4 filler exhibited the greater impact toughness of 69 J and 75 J, respectively. The bend test results conveyed that both the CCGTA and PCGTA weldments using ERNiCrMo-4 exhibited soundness and ductility.

A possible approach to raise the efficiency of single-junction solar cells is to couple them with thermoelectric generators (TEGs). It was shown that TEG contribution to the output power is basically ruled by the characteristics of the photovoltaic (PV) material. In this study, we present a quantitative model that correlates the efficiency of the hybrid thermoelectric–photovoltaic (HTEPV) device with the energy gap and the working temperature of the solar cell. Two HTEPV structures are discussed, one capable only to recover the heat released by relaxation of hot electron–hole pairs; and a second one also capturing the low–energy part of the solar spectrum. We show that in the second case the increase of the conversion efficiency could justify the effort needed to add a TEG stage to the PV device. HTEPV constructions are also shown to enable the use of wide-gap materials that are not currently considered in PV applications.

The variation of properties and evolution of microstructure of Cu–10Ni–3Al–0.8Si alloy during isothermal and aging treatment was studied. The time–temperature–property curves of the alloy were established. The nose temperature of the alloy was about 662 °C, and the alloy presented high quench sensitivity when quenched in the nose temperature zone. Discontinuous precipitation occurred when Cu–10Ni–3Al–0.8Si alloy was isothermally treated at 550 °C, and the discontinuous precipitates at the grain boundary became coarse when the isothermal temperature increased to 650 °C. Further increasing the isothermal temperature to 750 °C, cellular precipitation occurred in the alloy. Both Ni3Al precipitates with L12 ordered structure and δ-Ni2Si precipitates with DO22 ordered structure precipitated in the isothermally treated Cu–10Ni–3Al–0.8Si alloy. The orientation relationships between the precipitates and matrix were determined as ${[001]_{{\rm{Cu}}}}{\left\| {{{[001]}_{{\rm{N}}{{\rm{i}}_3}{\rm{Al}}}}\left\| {[001]} \right.} \right._\delta }$, ${(110)_{{\rm{Cu}}}}{\left\| {{{(110)}_{{\rm{N}}{{\rm{i}}_3}{\rm{Al}}}}\left\| {(010)} \right.} \right._\delta }$, and ${(1\bar 10)_{{\rm{Cu}}}}\left\| {{{(1\bar 10)}_{{\rm{N}}{{\rm{i}}_3}{\rm{Al}}}}} \right\|{(100)_\delta }$.

The search for alternative earth abundant semiconducting nanocrystals for sustainable energy applications has brought forth the need for nanoscale syntheses beyond bulk synthesis routes. Of particular interest are metal phosphides and derivative I–V–VI chalcogenides including copper phosphide (Cu3P) and copper thiophosphate (Cu3PS4). Herein, we report a one-pot, solution-based synthesis of Cu3P nanocrystals utilizing an in situ phosphorus source: phosphorus pentasulfide (P2S5) in trioctylphosphine. By injecting this phosphorus source into a copper solution in oleylamine, uniform and size controlled Cu3P nanocrystals with a phosphorous-rich surface are synthesized. The subsequent reaction of the Cu3P nanocrystals with decomposing thiourea forms nanoscale Cu3PS4 particles having p-type conductivity and an effective optical band gap of 2.36 eV. The synthesized Cu3PS4 produces a cathodic photocurrent during photoelectrochemical measurements, demonstrating its application as a light-absorbing material. Our process creates opportunities to explore other solution-based metal-phosphorus systems and their subsequent sulfurization for earth abundant, alternative energy materials.