The dynamic recrystallization (DRX) behavior of Ni–18.3Cr–6.4Co–5.9W–4Mo–2.19Al–1.16Ti superalloy was investigated by means of isothermal compression tests in the temperature range of 1010–1160 °C and strain rate range of 0.001–1 s−1. It was found that the nucleation mechanisms of discontinuous DRX and continuous DRX (CDRX) occurred simultaneously during hot deformation, and twinning can play an important role in improving the process of DRX. There are three stages in the process of CDRX, i.e., the accumulation and rearrangement of dislocations, the formation of subgrain boundary, and the conversion to high angle grain boundaries (HAGBs) from subgrain boundary. Moreover, the effect of CDRX grows weaker with increasing deformation temperature and decreasing strain rate. Additionally, both the volume fraction of DRX grains and the DRX grain size were closely related to the deformation temperature and strain rate, and a power exponent relationship between the DRX grain size and Z parameter was obtained. Based on the experimental data, the kinetic equations were also developed to evaluate the volume fraction of DRX grains during hot deformation in the alloy.

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 work hardening behavior of electrodeposited nanocrystalline nickel (29 and 19 nm) was investigated under multiaxial loading and compared with coarse-grained nickel. Plastic strain gradients were introduced into the materials using large Rockwell D hardness indentations, and measured through cross-sectional hardness profiles. The results showed that the coarse-grained material exhibited substantial hardening up to twice the hardness of the deformation-free area due to dislocation mediated deformation, while the nanocrystalline materials displayed small hardness variations along the strain gradient, indicative of considerably reduced dislocation interactions. Moreover, the grain structure analysis (cumulative volume fraction and size distribution) for the nanocrystalline materials suggested the operation of both dislocation mediated and grain boundary controlled deformation mechanisms, the latter becoming more significant with increasing cumulative sample volume of very small grains. The plastic deformation zone sizes under Rockwell indentation of the 29 nm Ni are similar to those conventional materials with reduced strain hardening. Microhardness-indentation size effects were negligible in both the nanocrystalline and coarse-grained materials.

The structural color films with enough brilliant color have attracted a special attention because of the great advantages in some practical application, which has currently become a research hot-spot. But their simple fabrication is still a great challenge. This study presents brilliant polymer opal structural color films (PSCFs) from polystyrene spheres under natural light by using a simple preparation and assembly strategy. In this strategy, the black organic dye water solution was used as the dispersion medium for polystyrene spheres, and then polystyrene spheres were rapidly fabricated to one ordered structures by the thermal assistance self-assembly method, which is cheap and commonly available. Contrast to other many structural color films irradiated by external light source under black background, the PSCFs exhibit brilliant and tunable structural colors under natural light even in a white environment, which is significant for the potential application of PSCFs in paint, photonic paper, external decoration of architectures, display, and bioassay.

Using nanoparticulate TiO2 films, the photocatalytic growth of Ag nanoparticles (NPs) in the AgNO3 aqueous solution has been studied in terms of reduction, nucleation, and coalescence. It was proved that Ag primary particles were formed in a growth time of <1 s after the photocatalysis started. The growth dynamics was found to be critical for isotropic and anisotropic growth of Ag NPs, depending on the AgNO3 concentration and surface properties of TiO2 films. In the AgNO3 solutions of ≤300 mg/L, the isotropic growth dominates the growth dynamic behavior, producing irregularly spherical Ag NPs. In the AgNO3 solutions of ≥400 mg/L, the increased reduction rate promotes the formation of Ag nanoplates in the product. Ostwald ripening and oriented attachment were suggested to be the mechanisms dominating the isotropic and anisotropic growth, respectively. A photocatalytic growth model of Ag NPs was proposed by taking Ag atom and Ag+ ion diffusion into consideration. The plasmonic properties of the Ag–TiO2 films were studied in terms of extinction, surface enhanced Raman scattering, and fluorescence enhancement.

Nanometer-sized fibers are recently getting increased attention in heterogeneous catalysis due to the superior transport properties and effective dispersion they offer. A key challenge in this application is creation of nanofibers with internal open porosity that can provide larger accessible catalytic surface and easier mass transport into the fibers. The synthesis of potassium doped iron/aluminum oxides ceramic nanofibers with mesoporous structure is presented herein. Uniform fiber mats were prepared by electrospinning (ES) using two different precursors: an aqueous solution of metal nitrates and an organic solution of metal acetylacetonates. The organic precursors gave rise to a promising mesoporous structure with fibers diameter mainly in the 300–400 nm range. Precursor viscosity was used as a stability indicator and its influence on the ES process was studied. Collection efficiency of as high as 90% was achieved. The increased understanding in fiber morphological evolution can open new possibilities in heterogeneous catalysis.

Vertically aligned, untangled planarized arrays of multiwall carbon nanotubes (MWNTs) with Ohmic back contacts were grown in nanopore templates on arbitrary substrates. The templates were prepared by sputter depositing Nd-doped Al films onto W-coated substrates, followed by anodization to form an aluminum oxide nanopore array. The W underlayer helps eliminate the aluminum oxide barrier that typically occurs at the nanopore bottoms by instead forming a thin WO3 layer. The WO3 can be selectively etched to enable electrodeposition of Co catalysts with control over the Co site density. This led to control of the site density of MWNTs grown by thermal chemical vapor deposition, with W also serving as a back electrical contact. Ohmic contact to MWNTs was confirmed, even following ultrasonic cutting of the entire array to a uniform height.

Indentation as a means to extract creep properties has the advantage that it can be applied directly to micro/nano-structures. Many studies on indentation creep reported at least partially poor agreement with creep parameters derived from uniaxial test. One important reason for the incompatibility is the neglect of transient creep. Another one is the choice of equivalent stress and strain measures to relate the different material responses. Applying a material model that accounts for transient creep effects we propose an efficient method for deriving creep properties from short-time spherical indentation tests. We first determine a subsurface point where the material response is very close to that observed in uniaxial tests. We then map the load–displacement data to the material response, expressed in terms of two dimensionless variables, at this point. Converting the dimensionless variables data to stress, strain, and strain rate data, we finally determine the material's creep coefficient and exponent.

The influence of Pt layer thickness on the fracture behavior of PtNiAl bond coats was studied in situ using clamped micro-beam bend tests inside a scanning electron microscope (SEM). Clamped beam bending is a fairly well established micro-scale fracture test geometry that has been previously used in determination of fracture toughness of Si and PtNiAl bond coats. The increasing amount of Pt in the bond coat matrix was accompanied by several other microstructural changes such as an increase in the volume fraction of α-Cr precipitate particles in the coating as well as a marginal decrease in the grain size of the matrix. In addition, Pt alters the defect chemistry of the B2-NiAl structure, directly affecting its elastic properties. A strong correlation was found between the fracture toughness and the initial Pt layer thickness associated with the bond coat. As the Pt layer thickness was increased from 0 to 5 µm, resulting in increasing Pt concentration from 0 to 14.2 at.% in the B2-NiAl matrix and changing α-Cr precipitate fraction, the initiation fracture toughness (KIC) was seen to rise from 6.4 to 8.5 MPa·m1/2. R-curve behavior was observed in these coatings, with KIC doubling for a crack propagation length of 2.5 µm. The reasons for the toughening are analyzed to be a combination of material's microstructure (crack kinking and bridging due to the precipitates) as well as size effects, as the crack approaches closer to the free surface in a micro-scale sample.

Synchrotron-based x-ray techniques are used to bring complementary information to local probes such as atom probe tomography and transmission electron microscopy. Two examples of nuclear materials used for the cladding of fuel assembly are given: oxide dispersion strengthened (ODS) alloys and M5™ Zr-based alloys. In both cases, synchrotron radiation analyses bring original results concerning nanosized secondary phases: for M5™, radiation-enhanced precipitation of β-Nb precipitates has been evidence and the crystallographic structure (lattice parameter and Nb content) is reported for the first time and for irradiated ODS, the dissolution of larger oxides is evidenced while a finer distribution of complex Y–Ti–O oxides still acts as obstacles for dislocations.

The mechanical properties and internal friction (damping capacity) of Mg–Zn–Y alloys with a long-period stacking ordered (LPSO) structure at different Y/Zn atomic ratios (2/1, 3/2 or 4/3) in cast and extrusion were investigated. It was found that the as-cast Mg–Zn–Y alloys with different Y/Zn atomic ratios possess a single LPSO phase with the same stable 18R-type structure. Among the three alloys, the alloy with 3/2 atomic ratio yields the highest damping capacity in low- and high-strain amplitude stages. Two damping peaks particularly P1 and P2 are detected in the Mg–Zn–Y alloy with 3/2 atomic ratio at approximately 108 and 220 °C, respectively. These results may be attributed to few solute atoms in Mg matrix and grain boundaries. In addition, the studied alloy with 3/2 atomic ratio exhibits excellent comprehensive properties in as-cast and as-extruded states; this alloy yields an ultimate tensile strength of 346 MPa and maintains a certain damping capacity (Q−1 > 0.01) in extrusion.