A continuous nonflux inclusion-removal method, rotating gas bubble stirring, is used to purify Mg–10Gd–3Y–0.5Zr melt. The effects of rotating gas bubble stirring process parameters (Ar flow rate, time, and rotating speed) on purifying effectiveness, mechanical properties, and fracture behavior of sand-cast Mg–10Gd–3Y–0.5Zr alloy are studied. The results show that too high or too low Ar flow rate is unfavorable for inclusion-removal. The results also indicate that the high rotary speed of spraying gas is helpful to improve the inclusion-removal and mechanical properties. But when the melt is subjected to overtime gas bubbling treatment, the mechanical properties became poor again. Nonflux purification does not change the microstructure of Mg–10Gd–3Y–0.5Zr alloy. However, rotating gas bubble stirring has a certain effect on the fracture pattern of the alloy. In addition, the melt purifying mechanism of the gas bubble stirring treatment for the sand-cast alloy was discussed systematically.

Driving the field of micro computed tomography toward more quantitative, rather than qualitative, approaches, we here present a new evaluation method, which uses the unique linear relationship between gray values and x-ray attenuation coefficients, together with the energy-dependence of the latter, to identify (i) the average x-ray energy used in the CT device, (ii) the x-ray attenuation coefficients, and (iii), via the x-ray attenuation average rule, the intravoxel composition, i.e., the microporosity, which, amongst others, governs the voxel-specific mechanical properties, such as stiffness and strength. The method is realized for six 3D tricalcium phosphate scaffolds, seeded with pre-osteoblastic cells and differentiated for 3, 6, and 8 weeks, respectively. The corresponding voxel-specific microporosities turn out to increase during the culturing period (resulting in reduced elastic properties, as determined from micromechanical considerations), while the overall macroporosity remains constant. The new methods are expected to further foster the development of a rationally based and computer-aided design of biomaterials and tissue engineering scaffolds.

The grain size dependence of the radiation response of silicon carbide (SiC) has been studied under 1.0 MeV Kr2+ ion irradiation. It was found that radiation resistance decreased with grain refinement, in contrast to previous studies on the same nanocrystalline (nc) SiC material using Si ion and high voltage electron irradiation. The effect of grain size on radiation response may depend upon the ion species used due to a potential change in amorphization mechanism. It was also determined that temperature had a strong effect on the grain size dependence of the radiation response in SiC due to the activation temperatures of critical recombination and migration reactions. This work explores the possible impacts of irradiation species, temperature, and experimental design on the radiation response of SiC.

Hot-rolled Mg–Zn–Ca alloy, followed by annealing, shows high formability at room temperature because of the reduced intensity of the basal texture. [Y. Chino et al., Mater. Trans. 51, 818 (2010).] In the present work, microstructures of the as-rolled Mg–Zn–Ca alloy were investigated using electron backscattered secondary diffraction and transmission electron microscopy. In addition, first-principles calculations were performed to investigate the twinnability of the Mg–Zn–Ca alloy. The microstructural investigations revealed that fine $\left\{ {10\bar 12} \right\}$ twins and local fine-grained microstructures were formed. It is therefore suggested that the fine twins induce this local fine-grained microstructure, which become the nuclei for recrystallization during annealing. As a result, the intensity of the basal texture is reduced. Calculations revealed that the $\left\{ {10\bar 12} \right\}$ twinnability is enhanced by the addition of Ca because of the increased unstable stacking fault energy (γus) and decreased unstable twin fault energy (γut).

Soft, sensitive, and conformable strain sensors can provide tactile sensation to prosthetic limbs and can be used for epidermal and wearable health monitoring. High strain sensitivity is often achieved by using piezoelectric ceramics, such as lead zirconate titanate (PZT), with known issues for large-area scalability, rigidity, and biocompatibility. Here, we report a nature-inspired, piezoresistive, soft, and benign core–shell nanofibrous sensor that exhibits an unprecedented gauge factor in excess of 60, arising from a reversible disjointing/jointing of a large number of interfiber junctions, consequently changing the current path and resistance in response to both tensile and compressive strains. Nanofiber textile sensor arrays are demonstrated with fast, low-voltage, accurate, and repeatable sensing over 1000 cycles for epidermal monitoring of limb and musculoskeletal movements and radial pulse waveform, for real-time monitoring of simulated intermittent Parkinson's tremors, and for biaxial tactile sensing and localization of point of touch.

The influence of aging treatment on the shape memory effect and corrosion resistance of a newly developed Fe–Mn–Si–Cr–Ni-based alloy containing C, N, and V elements was investigated. Results showed that V(CN) and Cr23C6 particles, precipitated during aging, could improve the shape recovery ratio to 72%, compared with that of 21% for the solution treated sample, when the alloy was aged for 24 h. The corrosion behavior in 0.5 M H2SO4 solution was almost the same for all the samples, barring a slight difference in the passivation range. In addition, the passivation current and critical current required for the onset of passivation of the aged samples were almost triple that of the unaged. In 3.5% NaCl solution the corrosion behavior of all aged samples was that of general dissolution with localized attack (pitting), which can be attributed to the micro-cathodic effect of the V(CN) and Cr23C6 particles precipitated during aging. Although the best corrosion resistance in both H2SO4 and NaCl solutions was shown by the solution treated sample, 24 h-aged sample exhibited an improved corrosion resistance, ascribed to the improved chemical homogeneity of the austenite matrix due to long aging time (24 h).

Using galvanostatic pulse deposition, we studied the factors influencing the quality of electroformed Bi1–x Sbx nanowires with respect to composition, crystallinity, and preferred orientation for high thermoelectric performance. Two nonaqueous baths with different Sb salts were investigated. The Sb salts used played a major role in both crystalline quality and preferred orientations. Nanowire arrays electroformed using an SbI3-based chemistry were polycrystalline with no preferred orientation, whereas arrays electroformed from an SbCl3-based chemistry were strongly crystallographically textured with the desired trigonal orientation for optimal thermoelectric performance. From the SbCl3 bath, the electroformed nanowire arrays were optimized to have nanocompositional uniformity, with a nearly constant composition along the nanowire length. Nanowires harvested from the center of the array had an average composition of Bi0.75Sb0.25. However, the nanowire compositions were slightly enriched in Sb in a small region near the edges of the array, with the composition approaching Bi0.70Sb0.30.

Through implicit solvent coarse-grained molecular dynamics simulations, we investigate the equilibrium morphologies resulting from the self-assembly of building blocks composed of anisotropically functionalized icosahedral viral capsid nanoparticles (NPs). We investigate the self-assembled aggregate morphologies for variations in the functional group chain length and solvent quality. We observe specific building block architectures to favor the formation of n-mers, chain- and network-like structures. Our work is in agreement with the earlier simulation studies on icosahedral gold nanocrystals that generate self-assembled chain-like structures. [G. Bilalbegovic, Comput. Mater. Sci.31, 181 (2004).] In addition, our results agree with those by Finn et al., who have shown small predominantly chain-like aggregates with mannose-decorated cowpea mosaic virus (CPMV) [K.S. Raja, Q. Wang, and M.G. Finn, ChemBioChem4, 1348–1351 (2003)] and small aggregates with oligonucleotide functionalization on the CPMV capsid. [E. Strable, J.E. Johnson, and M.G. Finn, Nano Lett.4, 1385–1389 (2004).] Visual inspection suggests that our results most likely span the low temperature limits explored by Finn et al. and show a good degree of agreement with the experimental results at an annealing temperature of 4 °C. [E. Strable, J.E. Johnson, and M.G. Finn, Nano Lett.4, 1385–1389 (2004).] Our investigations reveal the possibility of novel n-mer type aggregates that could be synthesized using icosahedral NPs with appropriate surface functionalization and solvent conditions.

The rapid sol–gel synthesis of macroscopic quantities of nanodiamond aerogel (NDAG) is reported at standard temperature and pressure using acid-catalyzed covalent crosslinking of air-oxidized detonation nanodiamond (DND) nanocrystals. Acetonitrile acts as a polar, aprotic solvent both to form a colloidal dispersion of DND particles and to conduct acid-catalyzed polycondensation reactions between resorcinol and formaldehyde (RF) small molecule precursors. Several characterization techniques show that nanodiamond grains are connected via covalent bonding with RF molecules to form a porous, three-dimensional network. Solvent exchange into liquid carbon dioxide and subsequent supercritical drying of NDAGs are used to recover low-density (151 mg/cm3), three-dimensional monolithic aerogels that exhibit surface areas in excess of 589 m2/g. The large accessible pore volume from the rapidly synthesized, macroscopic NDAG materials suggests a range of potential applications in catalysis, sensing, energy storage, as well as inert excipients for small-molecule pharmaceuticals.

Electrochemical technologies promise to provide the means for electrical energy storage of electricity generated from wind, solar, or nuclear energies. The challenge is to provide this storage in rechargeable batteries or clean fuels at a cost that is competitive with fossil fuels for replacement: (1) of vehicles powered by the internal combustion engine by electric vehicles and (2) of centralized power plants using intermittent electricity generated by wind and solar energy or constant electricity from a nuclear power plant, all serving a variable demand. This perspective outlines existing and possible lines of materials research for the development of rechargeable batteries or the production of clean fuels within the constraints of electrochemical technology.

Water is, perhaps, the most important material known to humankind—fascinating even in its pure state for the range of anomalous properties it displays. There has been an increasing realization that understanding the behavior of water at interfaces—from those of small solutes to biomolecules and polymers to inorganic materials and metals—holds the key to understanding disparate phenomena, from self-assembly, biofouling, and catalysis to corrosion. In this issue of MRS Bulletin, we highlight recent advances in understanding the molecular behavior of water near a range of interfaces of interest to the broader materials community.