Bainite transformation in steels is influenced by various factors. In the present work, bainite transformation in medium carbon high alloyed steel was investigated focusing on the influence of preexisting VC carbides on the morphology and transformation kinetics of the subsequently formed bainite. Hot-work die steels were held at 950 °C for various times to precipitate VC carbides, then rapidly cooled from 950 to 350 °C and held at this temperature for the bainite transformation. It is found that the bainite transformation was obviously accelerated by the preexisting VC carbides precipitated at the austenite region. The precipitation of carbides leads to a decrease in carbon concentration in the matrix, which decreases the effective activation energy and increases the highest temperature for the nucleation of bainite. Besides, bainite was observed to grow beside the VC carbides. It suggests that the VC carbides in the matrix act as nucleation sites for the bainite transformation. In the specimens, the bainite transformation is accelerated, and a higher fraction of bainite is formed when there are carbides in the matrix.

Process parameters (laser power and scanning speed) for H13 steel specimens produced by selective laser melting (SLM) are optimized, and microstructural characteristics and mechanical properties are investigated. The optimum process parameters are a laser power of 170 W and a scanning speed of 400 mm/s according to the maximum relative density of 99.2%. The microstructure consists of cellular grains and columnar crystal, which are composed of lath martensite and retained austenite, and there are no carbides or other second-phase particles present. The size of cellular grains is 1 μm. Compared with the common processed (forged and heat-treated) H13, SLM H13 has similar microhardness (561 HV) and tensile strength (1909 MPa) values. However, the elongation (12.4%) is a factor of ∼3 times higher and the impact energy (14.4 J) of the SLM specimen is somewhat lower. The relationship between the microstructure and mechanical properties is discussed. Fine grains and no second-phase precipitation determine the strength and plasticity of SLM samples.

Oligodepsipeptides (ODPs) with alternating amide and ester bonds prepared by ring-opening polymerization of morpholine-2,5-dione derivatives are promising matrices for drug delivery systems and building blocks for multifunctional biomaterials. Here, we elucidate the behavior of three telechelic ODPs and one multiblock copolymer containing ODP blocks at the air–water interface. Surprisingly, whereas the oligomers and multiblock copolymers crystallize in bulk, no crystallization is observed at the air–water interface. Furthermore, polarization modulation infrared reflection absorption spectroscopy is used to elucidate hydrogen bonding and secondary structures in ODP monolayers. The results will direct the development of the next ODP-based biomaterial generation with tailored properties for highly sophisticated applications.

Direct determination of barrier height (ΦBH) value between Ir and single crystal (001) hydrogen-terminated diamond with lightly boron doped has been performed using x-ray photoelectron spectroscopy technique. 70 nm Ir islands were formed on hydrogen-terminated diamond surface using anodic aluminum oxide. The ΦBH value for Ir/hydrogen-terminated diamond was −0.43 ± 0.14 eV, indicating that Ir was a suitable metal for ohmic contact with hydrogen-terminated diamond. The band diagram of Ir/hydrogen-terminated diamond was obtained. The experimental ΦBH was compared with the theoretical ΦBH in this work.

Ternary Al–15 wt% Cu–7 wt% Si and Al–22 wt% Cu–7 wt% Si alloy specimens were generated by transient directional solidification (DS) and rapid solidification (RS) techniques. The microstructures are constituted by an α-Al dendritic matrix surrounded by two eutectic, that is, a binary eutectic (Si + α-Al) and a bimodal eutectic, consisting of cellular-type binary eutectic colonies (α-Al + Al2Cu) in a ternary eutectic matrix consisting of α-Al + Al2Cu + Si. The bimodal eutectic exists at cooling rates from 0.5 to 250 K/s. The secondary dendritic spacing, λ2, of the DS samples varied from 5 to 20 μm and from 10 to 18 μm for both examined alloys. The λ2 from 2.7 to 4.0 μm characterized the RS samples. Mechanical properties have been determined for various samples related to different dendritic spacing values. Based on the evaluation of the rapidly solidified microstructures, it was possible to assess the cooling rates.

Recent molecular dynamics simulations revealed that 〈c + a〉 dislocations in Mg were prone to dissociation on the basal plane, thus becoming sessile. Basal dissociation of 〈c + a〉 dislocations is significant because it is a major factor in the limited ductility and high work-hardening in Mg. We report an in situ transmission electron microscopy study of the deformation process using an H-bar-shaped thin foil of Mg single crystal designed to facilitate 〈c + a〉 slip, observe 〈c + a〉 dislocation activity, and establish the validity of the largely immobile 〈c + a〉 dislocations caused by the predicted basal dissociation. In addition, through detailed observations on the fine movement of some 〈c + a〉 dislocations, it was revealed that limited bowing out movement for some non-basal portions of 〈c + a〉 dislocations was possible; under certain circumstances, i.e., through attraction and reaction between two 〈c + a〉 dislocations on the same pyramidal plane, at least portions of the sessile configuration were observed to be reversed into a glissile one.

With rapid growth of human population and decreasing labefaction of our environment, the usable fresh water is facing severe pollution and global shortage. Bio-inspired engineering and biotemplate-directed engineering thus offer great promise in clean water generation, including desalination, decontamination, and disinfection. This perspective begins with an introduction of solar energy-based interfacial evaporation system inspired by the natural systems of organisms, and then provides a review of the development and recent progress of the interfacial evaporation system for clean water generation. The long-term outlook in this field of clean water generation using bio-inspired interfacial systems is also discussed.

Deformation twinning has been frequently observed in body-centered cubic (BCC) high entropy alloys (HEAs), however, the underlying mechanism remains elusive. We perform molecular dynamics simulations on a representative BCC HEA nanopillar under high-symmetry compression, describe atomic details of deformation twinning, and propose a mechanism of twin nucleation from the surface. We find that twinned regions are formed by partial dislocations and that chemical heterogeneity can reduce local fault energy and promote stacking faults and twins. These results help to understand the propensity for stacking fault formation and twinning in HEAs and may guide the design of novel HEAs through control of active twinning mechanisms.

To understand the effect of pH value on the corrosion and corrosion fatigue behavior of AM60 magnesium alloy, electrochemical tests, viz., electrochemical impedance spectroscopy (EIS) and fatigue tests, were carried out in PBS (phosphate buffered saline) solutions of pH 5.2, 7.4, and 9.0. The microstructure was investigated by scanning electron microscopy (SEM). Results are as follows: (i) the corrosion mechanism of AM60 under different pH values was different according to EIS; (ii) the corrosion resistance and corrosion fatigue life reduced in the following order: pH 9.0 > pH 7.4 > pH 5.2; (iii) the crack initiation was associated with hydrogen embrittlement of AM60 on the basis of fractographic analysis.

Ambient water condenses readily on metal oxides, which can lead to water film formation and water-mediated reactions at the oxide surface. Similar to bulk water, thin water films with thicknesses below 10 molecular layers can modify the oxide surface chemical reactivity and stability. However, due to the confinement of mass transport at the oxide surface, these processes do not proceed exactly as they do in bulk liquid water. In this review article, we will present selected examples from our group and others’ that illustrate the rich interaction of MgO and TiO2 nanostructures with thin water films. We will show that these condensed water films can induce significant chemical, structural, and microstructural transformations of metal oxide nanostructures such as dissolution/precipitation, morphological changes, crystallization, and self-assembly in the solid state.

This article reports on the growth kinetics of cerium oxide (CeO2) nanoparticles prepared via a sintering method. By varying the sintering temperatures and periods of time, particle size of CeO2 nanoparticles was tuned from 11 to 100 nm. Ostwald ripening mechanism prevails in the growth process, and the growth kinetics is determined to follow an equation, D5 = 16.25 + 3.6 × 1020 exp(−344.20/RT) in the temperature range of 700 to 1000°C. After dispersing Pt on CeO2 nanoparticles, the size effect for the catalytic performance of the CO oxidation reaction was researched. When temperature and period of time are set at 700 °C and 2 h, respectively, dispersion of Pt onto CeO2 nanoparticles led to the largest quantity of chemisorbed oxygen species on the surface and the best catalytic performance. The findings reported here would provide a feasible path for the preparation of advanced catalysts in the future and moreover to discover novel size-dependent supports for many catalytic applications.

In this study, for the first time, chemically modified carbon nanotubes (CNTs) were used as a conductive additive in the cathode composite for lithium–sulfur batteries. Oxidation of pure CNTs has been carried out using modified Hummers’ method, and to partially remove oxygen groups from the CNT surface and increase their electronic conductivity, oxidized CNTs have been hydrothermally treated. The cathode slurry was mixed in water with a water-soluble LA133 binder. Despite the decrease in electronic conductivity of CNTs after chemical treatment, the presence of structural defects and oxygen groups provides uniform distribution of modified CNTs in the sulfur-based composite, which results in more than twice higher electrode specific capacity compared with the electrodes comprising pure CNTs. Using chemically modified CNTs as a conductive additive is proposed as an effective way for the preparation of nontoxic and cost-effective water-based cathode slurries in lithium–sulfur batteries.

Cerium oxide nanoparticles (CNPs) are of significant interest to the scientific community due to their widespread applications in a variety of fields. It is proposed that size-dependent variations in the extent of Ce3+ and Ce4+ oxidation states of cerium in CNPs determine the performance of CNPs in application environments. To obtain greater molecular and structural understanding of chemical state transformations previously reported for ceria of ≈3 nm nanoparticles (CNPs) in response to changing ambient conditions, micro-XRD and Raman measurements were carried out for various solution conditions. The particles were observed to undergo a reversible transformation from a defective ceria structure to a non-ceria amorphous oxyhydroxide/peroxide phase in response to the addition of 30% hydrogen peroxide. For CNPs made up of ∼8 nm crystallites, a partial transformation was observed, and no transformation was observed for CNPs made up of ∼40 nm crystallites. This observation of differences in size-dependent transition behavior may help explain the benefits of using smaller CNPs in applications requiring regenerative property.

GH3536 alloy is one of the high-temperature nickel-based alloys and widely applied in aviation and aerospace industries. In this study, a combination of experiment and simulation is proposed to study the effect of processing parameters on the selective laser melting (SLM) of GH3536 powder. It is concluded that the relationship between density and laser input energy during SLM complies with a quadratic function and presents an inverted U-shaped distribution. By fitting density and input power to a quadratic polynomial, the optimal laser input energy during SLM of GH3536 alloy can be obtained. The result shows that using 275 W laser power and 960 mm/s scanning speed, the SLM GH3536 specimens can reach the maximum density. This experimental result is consistent with the simulation result obtained by analyzing molten pool dimension. Furthermore, a full process energy prediction diagram for SLM GH3536 alloy based on the simulated molten pool depth and width is proposed. The result shows that it provides an innovative and efficient method for the selection of processing parameters during SLM of GH3536 powder.

Thermal cycling of planar solid oxide cell (SOC) stacks can lead to failure due to thermal stresses arising from differences in thermal expansion of the stack’s materials. The interfaces between the cell, interconnect, and sealing are particularly critical. Hence, understanding possible failure mechanisms at the interfaces and developing robust sealing concepts are important for stack reliability. In this work, the mechanical performance of interfaces in the sealing region of SOC stacks is studied. Joints comprising Crofer22APU (preoxidized or coated with MnCo2O4 or Al2O3) are sealed using V11 glass. The fracture energy of the joints is measured, and the fractured interfaces are analyzed using microscopy. The results show that choosing the right coating solution would increase the fracture energy of the sealing area by more than 70%. We demonstrate that the test methodology could also be used to test the adhesion of thin coatings on metallic substrates.

A facile one-pot and environmentally friendly method was developed to synthesize multi-branched flowerlike gold (Au) nanostructures by reducing chlorate gold (HAuCl4) with hydrogen peroxide (H2O2) in the presence of sodium citrate. The multibranched Au nanostructures were characterized by transmission electron microscopy and Ultraviolet-visible (UV-vis) absorption spectroscopy. The molar ratio of sodium citrate to HAuCl4 and the concentrations of the reacted reagents play important roles in the formation of multibranched Au nanostructures. The multibranched Au nanostructures with sharp tips exhibit excellent surface-enhanced Raman scattering (SERS) ability of 4-aminothiophenol (PATP). The experimental and simulated results both confirm that the photoinduced catalytic coupling reaction of PATP transformation to 4,4′-dimercaptoazobenzene occurs on the surface of multibranched Au nanostructures at a high power during the SERS measurement. It is believed that these multibranched Au nanostructures may find potential applications in SERS, biosensors, and the photoinduced surface catalytic application fields.

Flexible piezoelectric generators (PEGs) present a unique opportunity for renewable and sustainable energy harvesting. Here, we present a low-temperature and low-energy deposition method using solvent evaporation-assisted three-dimensional printing to deposit electroactive poly(vinylidene fluoride) (PVDF)-trifluoroethylene (TrFE) up to 19 structured layers. Visible-wavelength transmittance was above 92%, while ATR-FTIR spectroscopy showed little change in the electroactive phase fraction between layer depositions. Electroactivity from the fabricated PVDF-TrFE PEGs showed that a single structured layer gave the greatest output at 289.3 mV peak-to-peak voltage. This was proposed to be due to shear-induced polarization affording the alignment of the fluoropolymer dipoles without an electric field or high temperature.