In spite of being rare, actinide elements provide the building blocks for many fascinating condensed-matter systems, both from an experimental and theoretical perspective. Experimental observations of actinide materials are difficult because of rarity, toxicity, radioactivity, and even safety and security. Theory, on the other hand, has its own challenges. Complex crystal and electronic structures are often encountered in actinide materials, as well as pronounced electron correlation effects. Consequently, theoretical modeling of actinide materials and their 5f electronic states is very difficult. Here, we review recent theoretical efforts to describe and sometimes predict the behavior of actinide materials and complexes, such as phase stability including density functional theory (DFT), DFT in conjunction with an additional Coulomb repulsion U (DFT+U), and DFT in combination with dynamical mean-field theory (DFT+DMFT).

Emission properties of Er3+ in Ga2S3–GeS2–Sb2S3 glasses at the mid-infrared region were investigated from the viewpoint of their dependence on the concentration of the active ion and the glass composition. In the Judd–Ofelt analysis, no variation in omega parameters were observed when GeS2 was replaced by Ga2S3, while Ω2 increased as Sb2S3 was replaced by Ga2S3. This is due to the structural similarity and difference between the glass network units, GaS4 and GeS4 tetrahedra, and SbS3 pyramid. Clear mid-infrared emissions were observed at 2750 and 4300 nm assigned to the 4I11/2 → 4I13/2 and 4I9/2 → 4I11/2 transitions, respectively. The lifetime of the initial level of the 4.3 μm emission, 4I9/2, rapidly decreased with the Er3+ concentration because of the cross relaxation of this level, which can take place even at considerably low Er3+ concentration. The cross-relaxation processes were suppressed by the increase in the content of Ga2S3 because the solubility of Er3+ ions in the glasses increases with the Ga2S3 content.

Actinide solid-state and coordination chemistry has advanced through unexpected results that have further revealed the complex nature of the 5f elements. Nanoscale control of actinide materials is emerging, as shown by the creation of a considerable range of cluster and tubular topologies. Departures from established structural trends for actinyl ions are provided by cation-cation interactions in which an O atom of one actinyl ion is an equatorial ligand of a bipyramid of another actinyl ion. The solid-state structural complexity of actinide materials has been further demonstrated by open framework materials with interesting properties. The U(VI) tetraoxide core has been added to this cation's repertoire of coordination possibilities. The emergence of pentavalent uranium solid-state and coordination chemistry has resulted from the prudent selection of ligands. Finally, analogues of the uranyl ion have challenged our understanding of this normally unreactive functional group.

Microorganisms moderate local chemical conditions and alter forms of metals indirectly or directly to meet their cellular, species, and consortia needs. The diversity of microorganisms and the complexity of biogeochemical systems ensures that bacterially mediated processes yield a wide range of products, which await discovery by material scientists. Few types of materials produced by environmental bacteria have been analyzed by modern chemical and material science methods. Research on actinide biomaterials has focused on the biomineralization of a few chemical forms of uranium, neptunium, and plutonium. The materials produced are molecular complexes, microcrystalline minerals (most commonly oxides and phosphates) within cells and biofilms, and mineral adsorbates. The actinide biomaterials that emerge from this new research area will impact nuclear waste isolation and increase our understanding of environmental and geological metal cycles and may yield new bioremediation methods and industrially useful materials.

Ti/AlTiN/Ti-diamondlike carbon (DLC) composite coatings were deposited by mid-frequency magnetron sputtering and Hall ion source-assisted deposition on high-speed steel W18Cr4V substrates. The coating microstructure and mechanical properties, including hardness, elastic modulus, coefficient of friction, and wear properties were investigated by scanning electron microscopy, Raman spectroscopy, scratch and ball-on-disk friction tests, respectively. Fairly smooth composite coating with strong interfacial adhesion and good mechanical properties was produced. The substrate bias increases sp3 bonds contents in the DLC layer, thus coating hardness increased from 14 to 24 GPa and elastic modulus from 190 to 230 GPa with the increased substrate bias. Adhesion of interfaces between Ti-DLC and AlTiN layer, AlTiN and the steel substrate decreased with the substrate bias. The coefficient of friction is between 0.10 and 0.15, except when the substrate bias is 500 V, it is 0.2. Composite coating wear resistance increased with the substrate bias.

Hardness of glass is known to be related to the resistance to permanent deformation. However, the mechanism of permanent deformation of glass under a sharp diamond indenter is not clear yet. One of the deformation modes of oxide glass at room temperature is permanent densification. In this study, the indentation-induced densification of soda-lime glass under diamond indenters was evaluated from the volume recovery of indentation imprint by thermal annealing. The volume change of the indentation imprint by annealing corresponds to the densified volume under the indenter. Using some kinds of diamond indenters, which have different inclined face angles, the ratios of densified volume to the total “lost” volume under the indenters were determined. With an increase in the inclined face angle, the densification contribution decreased and the shear-flow contribution increased. This indenter-shape dependence of densification in glass is discussed in terms of the stress dependence of the deformation mechanisms in glass.

The method we introduced in 1992 for measuring hardness and elastic modulus by nanoindentation testing has been widely adopted and used in the characterization of mechanical behavior at small scales. Since its original development, the method has undergone numerous refinements and changes brought about by improvements to testing equipment and techniques, as well as advances in our understanding of the mechanics of elastic-plastic contact. In this article, we briefly review the history of the method, comment on its capabilities and limitations, and discuss some of the emerging areas in materials research where it has played, or promises to play, an important role.

Because of the lack of universal contact models for nonlinear strain problems, indentation analysis on rubberlike materials is confined to small deformation in which Hertz's solution is applied. Recognizing that deep indentation may provide more material information, in this paper we propose a nonlinear elastic model for large spherical indentation of rubberlike materials based on the higher-order approximation of spherical function and Sneddon's solution. The effect of limiting network stretch is studied on the initial elastic modulus for lightly cross-linked rubbers. With the comparisons of the finite-element simulation and the experimental result, the proposed model is verified to predict the large indentation of rubberlike materials over the indentation depth of 0.8 times the indenter radius.

The formation of Zn whiskers threatens the reliable operation of electronic equipment with an electrical shorting hazard. As with tin whiskers (much more intensively researched than Zn whiskers), the mechanism of formation is still not clear. This work investigated the Zn whisker growth mechanism for an electroplated Zn coating above a carbon steel substrate from a raised floor tile. Iron–zinc (Fe–Zn) intermetallic and Zn oxides were identified by x-ray diffraction analysis (XRD) and electron probe microanalysis (EPMA). Fe–Zn intermetallic compounds formed on the surface of the Zn layer in addition to the interface between the Zn coating and the steel substrate. Zn oxides formed primarily on the surface of the Zn coating. Fe–Zn intermetallic compounds and Zn oxide formation can be the source of a residual stress that promotes Zn diffusion to the surface of electroplated Zn coating, resulting in the formation of Zn whiskers.

Recent discoveries of novel electronic states, including relatively high-temperature superconductivity, in the actinides point to exciting prospects for future discoveries at the bottom of the periodic table. A key ingredient in all of the successes discussed here is the role of high-quality synthesis in enabling advances. Results on PuCoGa51, NpPd5Al2, and single crystal uranium are discussed.

The influence of high magnetic field on nitriding behavior was investigated in a mixture of NH3 and H2. It was found that high magnetic field could shift the equilibrium of nitriding reaction; this proved that the critical nitrogen potential to form γ′-Fe4N and ε-Fe3N phase was evidently enhanced compared with conventional nitriding. This research provides a new approach for a selective nitriding process.

Resistance degradation of Ca-doped BaTiO3 ceramics was investigated. A series of coarse and fine-grained (Ba1–xCax)TiO3 with only Ba site incorporation ranging x from 0 to 0.1, and Ba(Ti1–yCay)O3 ceramics with only Ti site incorporation ranging y from 0 to 0.015, were prepared with similar grain sizes. The increase of x did not cause any distinct difference in degradation, whereas an increase in y caused a significant resistance degradation in both coarse and fine-grained specimens. The variation of ionic transference number (tion) as evaluated by the Warburg impedance was negligible with increase in x, but significantly increased with the increase in y. These results demonstrate that the decrease of lattice parameters and lattice shrinkage by the Ba site incorporation of Ca has little influence on the resistance degradation, and that the oxygen vacancy concentration generated by the Ti site incorporation of acceptor Ca is a very important factor that governs resistance degradation.

After sputter deposition of Sn (layer thickness of 350 nm) on Cu substrates and during subsequent aging at room temperature, Cu and Sn reacted to form the intermetallic phase Cu6Sn5 in the Sn layer at the Cu/Sn interface, which led within a few hours of aging to the development of a compressive stress parallel to the Cu/Sn interface in the Sn layer. One day after aging at room-temperature whisker formation occurred on the surface of the Sn layer. It was shown that whisker growth is associated with long-range Sn diffusion parallel to the Cu/Sn interface. Sn layers of the same thickness sputter deposited on pure Si substrates exhibited throughout the same aging time at room temperature a tensile stress parallel to the Cu/Sn interface (no intermetallic phase formation took place) and whisker formation did not occur. The interrelationship of intermetallic compound formation, stress development, and whisker growth is discussed.

Near-stoichiometric (NS) (Mg:)Er:LiNbO3 crystals were grown from melts containing 0.0/0.5, 0.5/0.5, and 1.0/0.5 mol%/mol% MgO/Er2O3. Crystal composition and optical properties studies show that the Li2O contents in these crystals increase all by ∼1 mol% relative to the congruent point. The 1.0 mol% MgO-doped NS crystal is just near optical damage threshold and withstands a 488 nm light intensity >0.74 MW/cm2 without optical damage. Unpolarized absorption spectra of these NS crystals were measured, and the Er3+ absorption cross-section spectra were determined. The Er3+ spectroscopic properties were studied by Judd–Ofelt theory. The results show that as the crystal composition approaches the stoichiometry, the Er3+ spectroscopic properties change definitely. The Er3+ ion in the NS crystal has smaller absorption cross section and hence weaker oscillator strength, lower emission rate, and longer radiative lifetime. Nevertheless, the radiative quantum efficiency is retained. In addition, the MgO codoping has less effect on the Er3+ spectroscopic properties.