Large-area single-crystalline vanadium dioxide nanoflakes were first fabricated via a thermal reduction method in a tube furnace. The sample was characterized by x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The results show that VO2 nanoflakes are single-crystalline with a monoclinic structure. The VO2 nanoflakes have a width of 200–300 nm, a thickness of 50–100 nm, and a length up to 1–2 μm. It is found that single-crystalline VO2 nanoflakes show a novel and complicated 5–7-step Li-storage behavior for an insertion amount of <0.6 mol lithium per mol of VO2.

For a number of polymers with a variety of chemical structures and different properties, we have performed scratch-resistance tests and investigated the profiles of the grooves formed using a profilometer. Three main kinds of material response are seen: plowing; cutting; and densification. The cross-sectional areas of the grooves include the groove and side top-ridge areas. The latter are smaller than the former, an indication of densification at the bottom and the sides of the groove; the effect can be connected to molecular dynamics simulations of scratch testing. The sum of the groove and top-ridge areas is the highest for Teflon, thus providing another measure of its poor scratch resistance. The Vickers hardness of the polymers was also determined. An approximate relationship exists between the hardness and the groove area. An unequivocal relationship between the hardness and the total cross-sectional area of the material displaced by the indenter is found. The resulting curve can be represented by an exponential decay function.

The electrochemical stability of LiCoO2 thin films was improved by cerium-phosphate coating deposited at room temperature. The cerium-phosphate coating layer also effectively suppressed the increase of charge-transfer resistance during cycling. However, the cycling stability and the initial capacity of the coated LiCoO2 thin films deteriorated as the annealing temperature increased, different from other metal-phosphate coating. These phenomena were attributed to the interdiffusion between the cerium-phosphate coating layer and LiCoO2 thin film, instead of the nanocrystal formation in the amorphous coating layer.

Sm-Fe-N powders were successfully consolidated at 873 K and below by the spark plasma sintering (SPS) method. Although the decomposition temperature of the hard magnetic Sm2Fe17N3 phase has been reported to be 873 K, partial decomposition of the Sm2Fe17N3 phase was noted in the bulk materials obtained by sintering at below that temperature. The resultant bulk materials showed a coercivity of around 0.24 MAm−1, significantly lower than that of the original Sm-Fe-N powder. It was found that decomposition of the Sm2Fe17N3 phase in the SPS method was significantly lowered by the addition of a small amount of Zn powder to the Sm-Fe-N powder. The bulk material obtained by sintering a mixture of Sm-Fe-N and Zn powder (10%Zn) at 723 K exhibited high coercivity, comparable with that of the original Sm-Fe-N powder.

Novel magnetic cobalt ferrite nanostructures with curved surfaces (i.e., nanobowls and hollow nanospheres) in a periodic array have been fabricated by in situ reduction of a cobalt and iron salt solution mixture in the interstitial spaces of three-dimensional, close-packed, polystyrene sphere templates. The effect of the shape created by this nanostructure and magnetocrystalline anisotropy introduced by suitable annealing were used to tailor the coercivity to values relevant to high-density data-storage applications.

The microstructure, hardness, elastic modulus, and indentation creep of Ag/Cu multilayers prepared by magnetron sputtering were investigated by x-ray diffraction, transmission electron microscopy, and nanoindentation. The hardness values obey the Hall–Petch relationship as the periodicity decreases to 20 nm. For multilayers with periodicity smaller than 20 nm, the Hall–Petch relationship breaks down and the hardness values saturate at about 4.6 GPa; moreover, there are shear bands formed around their indents and strain bursts occurring during the load-holding process of indentation creep. These results imply that there is a transition of the deformation mechanism in the region where the periodicity is equal to 20 nm. This transition of the deformation mechanism can be ascribed to grain-size-dependent competition between the dislocations-mediated plasticity and grain-boundary sliding-mediated plasticity.

Biomimetic coating of titanium and related alloys with carbonated apatitic calcium phosphate is an important area of research in implantology. While this paper specifically refers to coating Ti6Al4V, the results are valid with other related alloys as well. One step in the protocol involves an intermediate alkali treatment of Ti6Al4V to form a sodium titanate layer on the alloy surface. This pretreatment enhances the formation of the coating from simulated body fluid (SBF) solutions. Many papers in the biomimetic coating literature demonstrate the presence of cracks in coatings, irrespective of the SBF compositions and placement of the substrates. The presence of cracks may result in degradation and delamination of coatings. To the best of our knowledge, this issue remains unresolved. Therefore, the aim of this study was: (i) to examine and understand the reasons for cracking and (ii) based on the results, to develop a protocol for producing crack-free apatitic calcium phosphate coatings on Ti6Al4V substrates. In this study, the authors focused their attention on the alkali treatment procedure and the final drying step. It is hypothesized that these two steps of the process affect the crack formation the most. In the first case, the surfaces of alkali-treated substrates were examined with/without water-soaking treatment before immersing in SBF. This water treatment modifies the sodium titanate surface layer. In the second case, two different drying techniques (after soaking in SBF) were used. In one procedure, the coated substrates were dried rapidly, and in the other they were dried slowly. It was observed that the water treatment, irrespective of the drying method, provides a surface, which on subsequent soaking in SBF forms a crack-free apatitic calcium phosphate coating. Based on these results, the authors suggest a protocol incorporating a water-soaking treatment after the alkali treatment and prior to the SBF soaking treatment to obtain crack-free coatings.

Varying amounts of Zn (1, 3, 7 wt%) were added to Sn–3.5Ag solder on the electroless Ni(P)/immersion Au metallization, and solder joint microstructures after reflow and isothermal aging (500 h at 150 °C) were investigated using scanning electron microscopy, energy dispersive x-ray spectroscopy, transmission electron microscopy, and x-ray diffraction, which were subsequently correlated to the microhardness and drop test results. Zinc in the solder affected the solder joint intermetallic compounds profoundly, which improved the drop reliability significantly. The effect of Zn was to nucleate Ni5Zn21 and to suppress the formation of Ni3P, Ni3SnP, and Ni3Sn4, which were known to increase the propensity for brittle cracking. Drop test results showed an inverse correlation between the number of drops-to-failure (Nf) and the thickness of Ni3P layer. As the growth of the Ni3P layer was suppressed by Zn, drop reliability increased substantially.

Amorphization of metallic titanium by ball milling was presented. With the introduction of continuous pickup of impurities, hexagonally close-packed (hcp) titanium transformed gradually into an amorphous phase without experiencing any intermediate stage of forming a detectable metastable compound phase. The crystallization temperature of the obtained Ti metal glassy phase is about 640 K. The total concentration of the impurities (oxygen, nitrogen, iron, etc.) in the final product of the milled powders that was obtained after 60 h of milling was 10.85 at.%. The amorphization of metallic titanium may account for the combined effects of the pickup oxygen impurity in small amount and the Gibbs–Thompson effect.

The ability to create small-scale material patterns using lithography has been limited by the feature sizes and assembly of the master stamping system. Developing a simple and robust robotically automated patterning technique for both organic and inorganic materials, which is able to be actively controlled down to scales smaller than the operating features, would enable new capabilities and directions in research. Here, a novel method is presented to form patterns of defined shape and distribution via automated assembly along with force-controlled microstamping. Robotic assembly based particle templates and pyramid structures were used to create controlled distributions of materials. Systems including quantum dots and biomolecules were patterned, demonstrating our ability to create repeatable geometries with size scales smaller than the master stamping system. These patterns were also utilized for constraining cell adhesion and spreading. This work has potential applications in diverse areas from building molecular circuits to probing biological pattern formation.

Photocatalytic titanium dioxide coatings prepared via various processes have been developed for antimicrobial purposes. Among them is arc ion plating, which may provide more advantages than other processes such as high growth rate, strong film adhesion, as well as the ability to obtain anatase phase at a low deposition temperature. This research involves an arc ion plating method to produce TiO2 film on stainless steel. Antimicrobial efficacy is examined as a function of coating parameters. The experimental results show that the deposited film mainly consists of a rutile phase at an initial growth stage, followed by the growth of an anatase phase at a later stage. By increasing oxygen partial pressure, an increased volume of anatase phase is obtained. The volume of anatase phase is found to strongly and positively affect antimicrobial efficiency. Such an arc ion plated TiO2 coating can be potentially served for antimicrobial treatment of medical equipment.

Highly dispersed uniform silver nanoparticles were prepared by reducing silver diamine ions [Ag(NH3)2]+ with D-glucose in the presence of a stabilizing agent. Along with the nature of the dispersing agent, the pH and the temperature of the reaction had the most pronounced effect on the reduction rate, the nucleation of the metallic phase, and ultimately the size and dispersion of the resulting particles. Through suitable manipulations of these parameters, it was possible to prepare uniform Ag nanoparticles ranging in size from 30 to 120 nm. A rapid and complete reduction of the silver species was possible only at elevated pH and temperatures above 50 °C. The reduction of silver diamine ions in these conditions caused the complete cleavage of the C–C bond, resulting in the release of 12 electrons per molecule of D-glucose. It was also found that the addition of ammonia to an already acidified silver nitrate solution leads to the formation of a much more stable and safe-to-handle diamine complex.

The accurate description of the indentation load–displacement relationship of an elastic sharp indenter indenting into an elastic half-space is critical for analyzing the nanoindentation data of superhard materials using the procedure proposed by Oliver and Pharr [J. Mater. Res.7, 1564 (1992)]. A further discussion on this issue is made in the present work to reconcile the apparent inconsistencies that have appeared between the experimental results reported by Lim and Chaudhri [Philos. Mag.83, 3427 (2003)] and the analysis performed by Fischer-Cripps [J. Mater. Res.18, 1043 (2003)]. It is found that the indenter size effect is responsible for this large discrepancy. Moreover, according to our analysis, we found that when the deformation of the indenter is significant, besides the errors caused by the Sneddon’s boundary condition as addressed by Hay et al. [J. Mater. Res.14, 2296 (1999)], the errors induced by the application of reduced modulus should be considered at the same time in correcting the modified Sneddon’s solution. In the present work, for the diamond indenter of 70.3° indenting into an elastic half-space with its Poisson’s ratio varying from 0.0 to 0.5 and the ratio of the Young’s modulus of the indented material to that of the diamond indenter, Ematerial/Eindenter, varying from 0 to 1, a set of new correction factors are proposed based on finite element analysis. The results reported here should provide insights into the analysis of the nanoindentation load–displacement data when using a diamond indenter to determine the hardness and Young’s modulus of superhard materials.

A commercial Mg–6 wt% Zn–0.5 wt% Zr (ZK60) alloy was used to investigate the effect of precipitate shapes on fracture toughness. The ZK60 alloy was extruded at a temperature of 653 K (extruded alloy). The extruded alloy was annealed at 633 K for 86.4 ks (annealed alloy), and then the annealed alloy was aged at 448 K for 100 ks (aged alloy). The average grain size in all the conditions was about the same, 13.5 ± 1.0 μm. The extruded and aged alloys had different shaped precipitates: spherical and rod shaped precipitates, respectively. The plane-strain fracture toughness KIC of the extruded, annealed, and aged alloys were estimated to be 22.4, 20.2, and 21.0 MPam1/2, respectively, by the stretched zone analysis. Transmission electron microscopy (TEM) observations showed that the deformation during the fracture toughness test was dominated by a dislocations on the basal slip planes in all the conditions. Such dislocations are commonly activated in magnesium alloys during the tensile and compression tests. The spherical shaped precipitates were found to be more effective than the rod shaped precipitates for improving the fracture toughness in the magnesium alloy.

For extensive applications of bulk metallic glasses as structural materials, Fe-based bulk metallic glasses Fe73.8−xC7.0Si3.5BxP9.6Cr2.1Mo2.0Al2.0 (at.%, x = 3, 5, 7, 9) have been developed using hot metal, commercial grade pure elements, and industrial ferro-alloys. The alloy Fe68.8C7.0Si3.5B5P9.6Cr2.1Mo2.0Al2.0 can be cast into a fully amorphous rod of 5 mm in diameter through a suction casting method. The glass forming ability of the alloys can be successfully assessed by the difference of Gibbs free energy between liquid and solid phases obtained through thermodynamic calculations.

The Sn/Cu/Sn/Cu/Sn sandwich-type couples prepared by the casting method are used for examining the effects of electromigration on Sn/Cu interfacial reactions. The samples are reacted at 170 and 180 °C for 24–240 h by passing an electric current with a density of 5000 A/cm2. At the interfaces where electrons flow from the Sn side to the Cu side, uniform layers of Cu6Sn5 and Cu3Sn are formed. The results are similar to those without passage of an electric current. The relatively thicker Cu6Sn5 layer is attributed to the extra Cu source from the dissolved Cu during the sample preparation. At the interfaces where electrons flow from the Cu side to the Sn side, large and nonplanar Cu6Sn5 phase regions are formed. Formation of large Cu6Sn5 regions is the result of electromigration-enhanced Cu diffusion through the grain boundaries and surfaces.

Langmuir monolayers floating on supersaturated aqueous subphases can act as templates for the growth of oriented inorganic films—a “bioinspired” nucleation process. We have performed in situ grazing incidence x-ray diffraction studies of the selective nucleation of BaClF and BaF2 under fatty acid monolayers. The arrangement of the fatty acid headgroups, the monolayer charge, and ion-specific effects all play important roles in selecting the inorganic species. When the monolayer is in a neutral state, both BaClF and BaF2 nucleate at the interface and are well aligned, but when the monolayer headgroup is deprotonated, only oriented BaF2 grows at the interface. We also observe an enhanced alignment of BaF2 crystals during growth from highly supersaturated solutions, presumably due to reorganization of preformed crystals at the organic template. These results show that a delicate interplay between multiple factors governs the oriented growth of inorganic films at organic templates.

We have investigated atomic structure of a Fe81B13Si4C2 metallic glass after mechanical creep deformation. We determined the structure function and pair density function resolved for azimuthal angle using x-ray scattering and a two-dimensional detector. The results are analyzed by the spherical harmonics expansion, and are compared to the often-used simple analysis of the anisotropic pair density function determined by measuring the structure function along two directions with respect to the stress. We observed uniaxial structural anisotropy in a sample deformed during creep experiment. The observed macroscopic shear strain is explained in terms of local bond anisotropy induced by deformation at elevated temperature. The bond anisotropy is a “memory” of this deformation after load was removed. We showed that use of sine-Fourier transformation to anisotropic glass results in systematic errors in the atomic pair distribution function.

This study investigated the behavior of Cu-containing intermetallic compounds (IMCs) in liquid Sn–Ag and Sn–Zn solders. Experimental results show that for the intermetallics investigated, Cu–Sn and Cu–Zn compounds, the occurrence of settling was dominated by the crystalline temperature of IMCs, buoyancy due to difference in densities, and dissolution potential for the compounds into the liquid. The complete dissolution of Cu–Zn compounds, which took place in the Sn–Zn solders when the Cu content exceeded a critical value, might be ascribed to the depletion of Zn in the melt.

The photocatalyst BaZn1/3Nb2/3O3 with ABO3 perovskite structure has been synthesized by using a solid-state reaction process. It was characterized by x-ray diffraction and photoluminescence spectroscopy. The luminescence band centers around 285 nm and shows a large Stokes shift compared with the excitation spectrum, indicating a strong electron–phonon interaction in the photocatalyst BaZn1/3Nb2/3O3. The electronic structure of BaZn1/3Nb2/3O3 was calculated by using the pseudopotential method of the density function theory. It shows that the conduction band should be mainly composed of the Nb 4d states, and the valence band should be mainly composed of the O 2p state. The densities of the O 2p states and the Zn 4s states at the bottom of the conduction band are very low. The Zn 4s states show an expanded structure, which was proposed to be helpful for the migration of the photoexcited carriers, thus favoring the photocatalytic activity of BaZn1/3Nb2/3O3.