Traditional manufacturing methods restrict the expansion of thermoelectric technology. Here, we demonstrate a new manufacturing approach for thermoelectric materials. Selective laser melting, an additive manufacturing technique, is performed on loose thermoelectric powders for the first time. Layer-by-layer construction is realized with bismuth telluride, Bi2Te3, and an 88% relative density was achieved. Scanning electron microscopy results suggest good fusion between each layer although multiple pores exist within the melted region. X-ray diffraction results confirm that the Bi2Te3 crystal structure is preserved after laser melting. Temperature-dependent absolute Seebeck coefficient, electrical conductivity, specific heat, thermal diffusivity, thermal conductivity, and dimensionless thermoelectric figure of merit ZT are characterized up to 500 °C, and the bulk thermoelectric material produced by this technique has comparable thermoelectric and electrical properties to those fabricated from traditional methods. The method shown here may be applicable to other thermoelectric materials and offers a novel manufacturing approach for thermoelectric devices.

Three photosensitizers containing zinc(II) porphyrin, ruthenium(II) dipyridine, and their combined porphyrin–polypyridyl metal complexes were used to modify TiO2 nanotubes that were obtained through the hydrothermal method to get inorganic–organic nanocomposite photocatalysts. The photosensitizer with distinctive structure can expand the photoresponse range of TiO2 toward the range of visible light, and the complexes with large conjugated π-electron systems are beneficial for improving the separation of photoelectrons from vacancies, effectively extending the life of excited electrons and thus enhancing the photocatalytic efficiency, thus establishing a favorable foundation for an efficient photocatalysis reaction. The photocatalytic reduction of CO2 aqueous solution into methanol was used to evaluate the photocatalytic effect of sensitized samples. All the photosensitized catalysts exhibited superior selectivity in liquid products during this process and methanol was the only liquid product in the system. The ZnPyP–RuBiPy sensitized TiO2 nanotubes showed the best photocatalytic effect. A possible mechanism for the photoreduction was also proposed in this paper.

The wetting of Cu–19Ni–5Al alloy on Ni-coated WC–8Co substrates with different coating thicknesses was investigated, and the brazing of Ni-coated WC–8Co to SAE1045 steel was performed by using the Cu–19Ni–5Al alloy as the filler metal. All the Cu–19Ni–5Al/Ni-coated WC–8Co systems present excellent wettability with a final contact angle of ∼10°. The thicknesses of the β + γ phase enriched with Co, Ni, and Al at the two joint interfaces increase and decrease with the Ni coating thickness, brazing temperature, and holding time increasing, respectively. The joint shear strength increases first and then decreases with the increase of Ni coating thickness, brazing temperature, or holding time. The maximum joint shear strength of ∼328 MPa is obtained while Ni plating for 90 min and brazing at 1210 °C × 5 min.

In the present study, gradient microstructure and texture development in wedge-based severe plastic burnishing of oxygen-free high conductivity copper was investigated. Microstructural response and evolution of crystallographic texture in severe surface plastic deformation was shown to be controllable in terms of both magnitude and gradient through control of the incident wedge angle and burnishing parameters. Equiaxed ultra-fined grains and micro/nanoscale elongated grains were produced in the subsurface region, which is indicative of dynamic recrystallization at large strains in the subsurface. Subsurface regions exhibited a significant fraction of shear texture components along the 〈110〉 partial fibers. Texture evolution simulated using the visco-plastic self-consistent framework revealed variations in strain level controlling different mechanisms for rotation of these partial fibers from their ideal orientation. Controllability of subsurface properties and microstructure for such materials is briefly discussed. These results allude to fundamental limits in material processing by severe shear using scalable deformation configurations.

In this work, three Mg–Zn–Y–Ca alloys reinforced by icosahedral quasicrystal phase through trace Y addition were extruded at a low temperature of 503 K. With increasing the contents of Zn and Y, the grain size of the as-extruded alloy was significantly reduced while both the size and volume fraction of nanosized precipitates were increased. The grain refinement in the Mg–Zn–Y–Ca alloy was related to dynamical recrystallization during extrusion and the pinning effect of nanosized precipitates on the grain boundaries. After extrusion, the yield strength (YS) and ultimate tensile strength (UTS) of the three alloys were significantly increased. The YS of 294.0 MPa, UTS of 337.5 MPa, and elongation of 10.6% were obtained in the case of Mg–2.09Zn–0.26Y–0.12Ca (at.%) alloys. The improvement in the mechanical properties could mainly be due to the grain boundary strengthening and Orowan strengthening. The as-cast alloy exhibited a typical cleavage fracture while the as-extruded alloy possessed a mixture fracture of dimple fracture and cracking along the twinning.

The immobilization of cytochrome c (cyt c) on tea polyphenol functionalized and reduced graphene oxide (TPG) was carried out by a simple adsorption process. Intriguingly, TPG with large surface area exhibited excellent adsorption behaviors and good biocompatibility. The adsorbed materials were characterized by various methods including scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and Fourier transform infrared spectroscopy (FTIR). And the effects of adsorption behavior of cyt c were discussed in detail. The results showed the adsorption behavior was dependent on the pH value and showed a high adsorption capacity as high as 1.414 × 104 mg/g and was friendly to normal cells (mouse fibroblast cell line, L929). In conclusion, we proposed the introduction of TPG as novel material and used the adsorption method to immobilize cyt c, which would provide a novel material and simple method for the enrichment of protein.

Open literature publications, in the period from 2010 to the end of January 2018, on refractory high entropy alloys (RHEAs) and refractory complex concentrated alloys (RCCAs) are reviewed. While RHEAs, by original definition, are alloys consisting of five or more principal elements with the concentration of each of these elements between 5 and 35 at.%, RCCAs can contain three or more principal elements and the element concentration can be greater than 35%. The 151 reported RHEAs/RCCAs are analyzed based on their composition, processing methods, microstructures, and phases. Mechanical properties, strengthening and deformation mechanisms, oxidation, and corrosion behavior, as well as tribology, of RHEA/RCCAs are summarized. Unique properties of some of these alloys make them promising candidates for high temperature applications beyond Ni-based superalloys and/or conventional refractory alloys. Methods of development and exploration, future directions of research and development, and potential applications of RHEAs are discussed.

A facile synthesis procedure of nitrogen-self-doped porous carbon (NPC) derived from abundant natural biological materials has been presented. The pyrolysis temperature and the weight ratio of Co3O4 to carbon play a key role in determining microscopic structure and electrochemical performances of the final materials. The ordered mesostructures with nanopores in the channel walls provided support for immobilization of well-dispersed Co3O4 nanoparticles. They also served as a highly conductive substrate for effectively alleviating severe particle aggregation during the charge/discharge processes, which prevented capacity fading from deteriorated electric contact between the components. Taking advantage of the interconnected porous structures and high specific surface area (1799 m2/g) of carbon substrate, the Co3O4/NPC composite as anode in lithium-ion battery delivers a stable reversible capacity of 903 mA h/g after 400 cycles. It is expected that by loading other electrode active materials on such carbon material, the manufacture of the promising anode materials with excellent cycle stability is highly possible.

We present a fast method to prepare hybrid materials of polyaniline (PAni) with carbon nanotubes (CNTs, both undoped and nitrogen-doped) by ball milling without solvents or strong oxidants. PAni forms nanoparticles, attached to CNTs in a nanocomposite structure, with the nanotubes well dispersed among the polymer. This is achieved with only a few minutes of ball milling. Raman spectroscopy confirms that PAni was synthesized in its conductive state and suggests a good CNT–PAni interaction, particularly with nitrogen-doped CNTs. We found that water increased polymer yield, which we optimized, together with the nanocomposite conductivity, as function of amount of water and of oxidant (FeCl3). The nanocomposite conductivity is four orders of magnitude higher than that of PAni, for both types of nanotubes. Scanning electron microscopy and X-ray diffraction both show negligible damage to the CNT during this mechanosynthesis procedure, while dry milling and milling CNT in water without aniline does damage nanotubes, indicating that the reaction absorbs most of the mechanical energy.

In this investigation, an electron beam melting-processed γ-TiAl alloy (Ti–48Al–2Cr–2Nb, at.%) was oxidized in air to improve its in vitro tribological, electrochemical, and biocompatibility properties. The γ-TiAl alloy samples were oxidized at 400, 600, and 800 °C for 1 and 4 h. The oxidized layer thickness, composition, and surface morphology found to change with oxidation temperature. The oxidation thickness varied between 1.29 ± 0.2 and 2.18 ± 0.2 μm. The primary oxides on the surface were Al2O3 and TiO2 with minor concentrations of Cr2O3, Nb2O5, and nitrides of Ti. The surface hardness of the alloy increased by 1.7-fold with increasing temperature from 400 to 800 °C with 1 h soaking, and at 4 h, the maximum hardness was 12.26 GPa. The high hardness of the oxidized γ-TiAl alloy resulted in two orders of magnitude lower wear rate than the bare γ-TiAl alloy. Oxidation at 800 °C for 4 h resulted in significant reduction in corrosion current and no passivity breakdown was observed. In vitro cell culture experiments, using mouse preosteoblast cells, revealed high cell density on the oxidized γ-TiAl alloy, suggesting its enhanced cell proliferation compared to the bare γ-TiAl alloy and CP-Ti.

The evolution of fatigue performance and surface mechanical properties of AISI 304 stainless steel induced by the electropulsing-assisted ultrasonic surface rolling process (EP-USRP) was systematically investigated by integrating instrumented indentation, scanning electron microscopy with electron backscatter diffraction, and transmission electron microscopy. The results indicate that higher hardness, greater strength, finer ultra-refined grains, and higher residual compressive stress are formed within the strengthened layer compared with the original ultrasonic surface rolling process (USRP). EP-USRP with the optimized experimental parameters can produce a higher average rotating bending fatigue strength for AISI 304 stainless steel than USRP. Anomalously and noteworthily, all fatigue specimens treated by EP-USRP showed an incomplete fracture, revealing a higher reservation of safety in practical engineering applications. The further modified structure strengthening and stress strengthening induced by EP-USRP are likely the primary intrinsic reasons for the observed phenomena. Furthermore, the influence mechanism of EP-USRP was discussed scrupulously.

Tensile properties of different directions of X70 pipeline steel plate were tested, and microstructural evolutions of different zones along the transverse direction (TD) were also investigated using electron backscatter diffraction. The highest strength values (yield strength and ultimate strength) appear at TD, and the diagonal direction shows the largest uniform elongation. The elongations of the polygonal ferrite and quasi polygonal ferrite grains increase with the decrease in the distance to the fracture zone. The ratio between high-angle grain boundaries and low-angle grain boundaries in the as-received steel is about 7/3 and starts to decrease from the fillet zone to the fracture zone. The refinement of grains occurs adjacent to the fracture section with the formation of subgrains. With the increase in tensile strain, the intensities of cube and γ-fiber textures increase sharply, and the reinforcement of the (111)$\left[ {\bar{1}\bar{1}2} \right]$ component was obviously larger than the (111)$\left[ {1\bar{2}1} \right]$ component in the γ-fiber texture during tensile deformation.

Although laser solid forming (LSF) has a wide range of applications in material manufacturing, the technique has been severely limited due to the solidification cracks during rapid laser melting/solidification. In this paper, an LSF technology assisted by friction stir processing (FSP) is proposed to eliminate the LSF crack through the FSP thermomechanical coupling effect, with the Ni–16Cr–8Fe alloy as a representative material. By FSP-assisted LSF, the cracks at the top surface of the Ni–16Cr–8Fe alloy layer were eliminated. Meanwhile, the severe plastic deformation layers can be observed and gradient grains with tens of nanometers to tens of micrometers from the top surface to the inner. The LSF-printed dendrite microstructure was transformed into nanocrystals or nanotwins in the deformation zone with twining as the main deformation mechanism. The grain refinement results in the increase of hardness about 30%.

Porous carbon derived from biomass materials with enrich, low cost, clean, and renewable merits, exhibits various physical and chemical properties. So, it is of great significance to rationally utilize biomass materials for producing porous carbon with low cost to reduce overusing fossil fuel and environmental pollution. In this report, porous carbon has been fabricated using fruits shells of the Paulownia tomentosa by a facile method of KOH-activation. The as-obtained porous carbon containing a larger number of micropores and slight mesopores possesses a high specific surface area (1914.4 m2/g) and well hierarchical porosity. As the anode for sodium ion batteries, the porous carbon sample displays superior cycling stability and rate capability, delivering a reversible specific capacity of 179 mA h/g at 50 mA/g after 100 cycles and a discharge specific capacity of 100 mA h/g at 1 A/g.

Efficiency potential of crystalline Si solar cells is analyzed by considering external radiative efficiency (ERE), voltage, and fill factor losses. Crystalline Si solar cells have an efficiency potential of more than 28.5% by realizing ERE of 20% from about 5% and normalized resistance of less than 0.05 from around 0.1. Nonradiative recombination losses in single-crystalline and multicrystalline Si solar cells are also discussed. Especially, nonrecombination and resistance losses in multicrystalline Si solar cells are shown to be higher than those of single-crystalline cells. Importance of further improvement of minority-carrier lifetime in crystalline Si solar cells is suggested for further improvement of crystalline Si solar cells. High efficiency of more than 28.5% will be realized by realizing high minority-carrier lifetime of more than 30 ms. Key issues for those ends are reduction in carbon concentration of less than 1 × 1014 cm−3, oxygen precipitated and dislocations even in single-crystalline Si solar cells, and reduction in dislocation density of less than 3 × 103 cm−2 in multicrystalline Si solar cells.

The aim of this study was to investigate the in vivo degradation mechanism and the mechanical properties of poly(lactide-co-glycolide)/beta-tricalcium phosphate (PLGA/β-TCP) composite anchors. Anchors composed of PLGA and β-TCP were implanted in the dorsal subcutaneous tissue of beagle dogs for 6, 12, 16, and 26 weeks. The degradation of the materials was evaluated by measuring the changes in thermal behavior, crystallinity, and mechanical properties. Scanning electron microscope (SEM) was used to observe the surface and longitudinal section of the material. The evaluation of mechanical strength retention and degradation properties suggest that the addition of β-TCP particles efficiently enhances their mechanical properties and thermal characteristics and delays their degradation rate. By analyzing the results of SEM, X-ray diffraction, and differential scanning calorimetry, we can infer that after 12 weeks, the connection between β-TCP and PLGA becomes less compact, which accelerates the decline of mechanical strength.

The concept of high-entropy alloys has been extended to ceramics, polymers, and composites. “High-entropy materials (HEMs)” are named to cover all these materials. Recently, HEMs has become a new emerging field through the collective efforts of many researchers. Basically, high mixing entropy can enhance the formation of solution-type phases for alloys, ceramics, and composites at high temperatures, and in general leads to simpler microstructure. Large degrees of freedom in composition design as well as process design have been found to provide a wide range of microstructure and properties for applications. There are many opportunities for HEMs to overcome the bottlenecks of conventional materials. In this article, several possible breakthrough applications are pointed out and emphasized for turbine blades, thermal spray bond coatings, high-temperature molds and dies, sintered carbides for cutting tools, hard coatings for cutting tools, hardfacings, and radiation-damage resistant materials. In addition, more possible breakthrough examples are briefly described.