The atomic structure of shear bands in Pd40Ni40P20 bulk metallic glass has been compared to an undeformed matrix phase using pair distribution functions (PDFs) derived from energy filtered nanobeam electron diffraction. Shear bands do not show any characteristic contrast in transmission electron microscopy (TEM) images when specimens are prepared with uniform thickness. PDFs from a shear band exhibit a slight decrease in the first peak, indicating a slight difference in packing density and short range order compared to the undeformed matrix.

A new melt processing route for the fabrication of large grain Gd-Ba-Cu-O (GdBCO) bulk superconductors has been developed based on the use of novel GdBa4Cu3O8−δ (Gd-143) and GdBa6Cu3O10−δ (Gd-163) precursor compositions. The new processing route enables the fabrication of large single grains from precursor powders that contain high concentrations of Ba. The superconducting properties and microstructures of GdBCO single grains with extra Ba fabricated via this new processing route are reported. Most importantly, the possible formation of a new form of Gd1+xBa2−xCu3O7−δ solid solution (Gd-123ss) with x < 0 in single grains fabricated from the Ba-rich precursor are discussed for the first time based on the superconducting, chemical, and structural properties of the large GdBCO grains.

To determine the optimum baking temperatures for nanopowder introduction, the variation of reflective spectrum of baked zinc oxide powders, which are used as pigments for thermal control coatings of spacecraft, has been investigated over the wavelength range of 0.225–2.5 μm after being baked at temperatures between 400 °C and 850 °C. It has been established that baking temperatures over 750 °C result in a reduction of spectral reflectance in the visible light spectrum region. This is due to the formation of absorption bands of intrinsic point defects and thus increasing the spectral reflectance in the near-infrared region. The optimum temperature is 650 °C at which the bleaching effect was observed long after heat treatment. Moreover, an increase in the reflection coefficient occurs in the regions of 380–450 nm and 1100–2500 nm in this case.

To explore potential applications of nanocomposites for microelectronic packaging, the thermal properties were investigated on newly developed nanocrystalline Al composites reinforced by AlN nanoparticles. It was found that the thermal conductivity (TC) is reduced with increasing AlN volume fraction (Vp), since connectivity of Al matrix is decreased by introduction of the nanoparticles. Although AlN nanoparticles introduce thermal resistance, they still have significant contribution to the TC of the composite as high-TC inclusion. Particularly, a percolation behavior of AlN nanoparticles is thought to occur with the threshold at 23–30%. Measurements at elevated temperatures (∼500 °C) show almost no distinct degradation of TC relative to room temperature. Moreover, the coefficient of thermal expansion (CTE) is remarkably lowered as Vp increases, e.g., from 26 × 10−6 to 13.9 × 10−6 K−1, by raising Vp to 39%. Therefore, the nanocomposites may be applicable as electronic packaging material, due to the combination of acceptable TC and low CTE.

NaGd(MoO4)2:Ln3+ (Ln = Eu, Tb) submicrometer phosphors have been synthesized by a composite method including the solid state reaction process at room temperature and the hydrothermal process. It is revealed that temperature and humidity have an influence on the reaction rate and that higher temperature and humidity can speed up the reaction process. Crystalline water is necessary for the solid phase reaction at room temperature. The x-ray diffraction (XRD) patterns indicate that NaGd(MoO4)2:Ln3+ (Ln = Eu, Tb) submicrometer phosphors crystallize well with the scheelite structure. Both scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images illustrate that the average grain size of NaGd(MoO4)2:Ln3+ is about 225 nm without conglomeration. The luminescent lifetime and quantum efficiency for NaGd(MoO4)2:Eu3+ are determined.

Transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and x-ray diffraction (XRD) investigations were conducted on the hot-pressed Ti2SnC bulk ceramic. Microstructure features of bulk Ti2SnC ceramic were characterized by using TEM, and a needle-shaped β-Sn precipitation was observed inside Ti2SnC grains with the orientation relationship: (0001) Ti2SnC // (200) Sn and Ti2SnC // [001] Sn. With the combination of DSC and XRD analyses, the precipitation of metallic Sn was demonstrated to be a thermal stress-induced process during the cooling procedure. The reheating temperature, even as low as 400 °C, could trigger the precipitation of Sn from Ti2SnC, which indicated the low-temperature instability of Ti2SnC. A substoichiometry Ti2SnxC formed after depletion of Sn from ternary Ti2SnC phase. Under electron beam irradiation, metallic Sn was observed diffusing back into Ti2SnxC. Furthermore, a new Ti7SnC6 phase with the lattice constants of a = 0.32 and c = 4.1 nm was identified and added in the Ti-Sn-C ternary system.

A novel route to organic-inorganic composites was described based on biomineralization of poly(ethylene glycol) (PEG)-based hydrogels. The 3-dimensional hydrogels were synthesized by radical crosslinking polymerization of poly(ethylene glycol fumarate) (PEGF) in the presence of ethylene glycol methacrylate phosphate (EGMP) as an apatite-nuclating monomer, acrylamide (AAm) as a composition-modulating comonomer, and potassium persulfate (PPS) as a radical initiator. We used the urea-mediated solution precipitation technique for biomineralization of hydrogels. The apatite grown on the surface and interior of the hydrogel was similar to biological apatites in the composition and crystalline structure. Powder x-ray diffraction (XRD) showed that the calcium phosphate crystalline platelets on hydrogels are preferentially aligned along the crystallographic c-axis direction. Inductively-coupled plasma mass spectroscopy (ICP-MS) analysis showed that the Ca/P molar ratio of apatites grown on the hydrogel template was found to be 1.60, which is identical to that of natural bones. In vitro cell experiments showed that the cell adhesion/proliferation on the mineralized hydrogel was more pronounced than on the pure polymer hydrogel.

The α-, β-, and δ-MnO2 with various morphologies have been synthesized by a novel redox system of KMnO4 and CuCl with HCl added under a hydrothermal condition. The resultant MnO2 products have been characterized by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Upon control of reaction temperature and duration, it was observed that MnO2 polymorphs of different morphology (e.g., flowery δ-MnO2, β-MnO2 nanowires and octahedrons, α-MnO2 nanowires) can be prepared in an adjustable manner. The phenomenon is mainly attributed to the effect of cuprous ions controllably released from CuCl by the action of HCl at different experimental conditions. The corresponding formation mechanism for the MnO2 crystals will also be proposed and discussed.

The uniaxial and biaxial compressive responses of Zr57Nb5Al10Cu15.4Ni12.6–W composite were investigated over a range of strain rates (∼10−3 to 103 s−1) using an Instron universal testing machine (∼10−3 to 10° s−1), drop-weight tower (∼200 s−1), and split Hopkinson pressure bar (103 s−1). The temperature dependence of the mechanical behavior was investigated at temperatures ranging from room temperature to 600 °C using the instrumented drop-weight testing apparatus, mounted with an inductive heating device. The deformed and fractured specimens were examined using optical and scanning electron microscopy. Stopped experiments were used to investigate deformation and failure mechanisms at specified strain intervals in both the drop weight and split Hopkinson bar tests. These stopped specimens were also subsequently examined using optical and scanning electron microscopy to observe shear band and crack formation and development after increasingly more strain. The overall results showed an increase in yield strength with strain rate and a decrease in failure strength, plasticity, and hardening with strain rate. Comparison of uniaxial and biaxial loading showed strong susceptibility to shear failure since the additional 10% shear stress caused failure at much lower strains in all cases. Results also showed a decrease in flow stress and plasticity with increased temperature. Also notable was the anomalous behavior at 450 °C, which lies between the Tg and Tx and is in a temperature regime where homogeneous flow, as opposed to heterogeneous deformation by shear banding, is the dominant mechanism in the bulk metallic glass.

Transition metal multilayers are prime candidates for high reflectivity soft x-ray multilayer mirrors. In particular, Cr/Sc multilayers in the amorphous state have proven to give the highest reflectivity in the water window. We have investigated the influence of impurities N and O as residual gas elements on the growth, structure, and optical performance of Cr/Sc multilayers deposited in high vacuum conditions by a dual cathode direct current magnetron sputter deposition. Multilayer structures with the modulation periods in the range of 0.9–4.5 nm and Cr layer to bilayer thickness ratios in the range of 0.17–0.83 were deposited with an intentionally raised base pressure (pB), ranging from 2 × 10−7 to 2 × 10−5 Torr. Compositional depth profiles were obtained by elastic recoil detection analysis and Rutherford backscattering spectroscopy, while the structural investigations of the multilayers were carried out using hard x-ray reflectivity and transmission electron microscopy. By investigating stacked multilayers, i.e., several multilayers with different designs of the modulation periods, stacked on top of each other in the samples, we have been able to conclude that both N and O are incorporated preferentially in the interior of the Sc layers. At pB ≤ 2 × 10−6 Torr, typically <3 at.% of N and <1.5 at.% of O was found, which did not influence the amorphous nanostructure of the layers. Multilayers deposited with a high pB ∼2 × 10−5 Torr, a N content as high as ∼37 at.% was measured by elastic recoil detection analysis. These multilayers mainly consist of understoichiometric face-centered cubic CrNx/ScNy nanocrystalline layers, which could be grown as thin at 0.3 nm and is explained by a stabilizing effect on the ScNy layers during growth. It is also shown that by adding a background pressure of as little as 5 × 10−6 Torr of pure N2 the soft x-ray reflectivity (λ = 3.11 nm) can be enhanced by more than 100% by N incorporation into the multilayer structures, whereas pure O2 at the same background pressure had no effect.

Optimized compositions for bulk metallic glass (BMG) formation have been determined for the Cu−Hf binary and Cu−Hf−Al ternary systems. The Cu−Hf−Al BMG-forming composition region is identified to correlate with the (L → Cu10Hf7 + CuHf2 + CuHfAl) eutectic reaction. The eutectic temperature is reduced by nearly 50 K relative to that of the binary eutectic, demonstrating the significant role of the third element Al in stabilizing the liquid. The fragility parameter D* of the Cu55Hf45 binary and Cu49Hf42Al9 ternary supercooled liquid was determined from relaxation time measurements, indicating that Al incorporation also leads to a “stronger” liquid. The combination of these thermodynamic and kinetic effects is responsible for the dramatic enhancement of glass-forming ability from the Cu−Hf binary to the Cu−Hf−Al ternary.

Integrating porous low-permittivity dielectrics into Cu metallization is one of the strategies to reduce power consumption, signal propagation delays, and crosstalk between interconnects for the next generation of integrated circuits. The porosity and pore structure of these low-k dielectric materials, however, also affect other important material properties in addition to the dielectric constant. In this paper, we investigate the impact of porogen loading on the stiffness and cohesive fracture energy of a series of porous organosilicate glass (OSG) thin films using nanoindentation and the double-cantilever beam (DCB) technique. The OSG films were deposited by plasma-enhanced chemical vapor deposition (PECVD) and had a porosity in the range of 7−45%. We show that the degree of porogen loading during the deposition process changes both the network structure and the porosity of the dielectric, and we resolve the contributions of both effects to the stiffness and fracture energy of the films. The experimental results for stiffness are compared with micromechanical models and finite element calculations. It is demonstrated that the stiffness of the OSG films depends sensitively on their porosity and that considerable improvements in stiffness may be obtained through further optimization of the pore microstructure. The cohesive fracture energy of the films decreases linearly with increasing porosity, consistent with a simple planar through-pore fracture mechanism.

Synchrotron x-ray tomography was performed on titanium foams with aligned, elongated pores, initially created by sintering directionally freeze-cast preforms using two different powder sizes. Three-dimensional reconstructions of the pore structures were analyzed morphologically using interface shape and interface normal distributions. A smaller powder size leads to more completely sintered titanium walls separating the dendritic pores, which in turn created a more compact distribution of pore shapes as well as stronger pore directionality parallel to the ice growth direction. The distribution of pore shapes is comparable to trabecular bone reported in the literature, indicating the foam's potential as a bone replacement material.

We examined crystalline-texture evolution during ion-beam-assisted deposition (IBAD) of MgO thin films. We have demonstrated for the first time that in-plane crystalline texturing in IBAD of MgO scales with deposition rate. At high ion currents an in-plane texture full width at half-maximum (FWHM) of 10° can be achieved in less than 1 s, and 6° in 2.2 s. MgO texture further improves with thickness of a homoepitaxial layer deposited on top. We have developed an empirical quantification of the texture evolution in both IBAD and homoepitaxial layers. The best texture attained thus far in the MgO layer on polished Hastelloy tape has an in-plane FWHM of 1.6°. The high deposition rates demonstrated here make high-throughput manufacturing of IBAD textured templates a practical and cost-effective concept.

FINEMET-type (Fe75Si15NbBCu) ribbons were heat treated, and their magnetic properties were analyzed. Permeability, thermal, and mechanical sensitivities were measured by commonly used industrial methods, and these properties were correlated with measured magnetic Barkhausen noise parameters. Distributions of peak area, A, and peak noise energy, E, were evaluated. Distribution functions of noise parameters, P(x), were in good agreement with the theory of self-organized criticality (SOC), satisfying power laws in the form P(x)∼x−α. It is found that the noise did not considerably depend on the temperature sensitivity parameter and on the permeability of ribbons. However, a useful correlation between the noise parameters and mechanical sensitivity has been observed. Minimal noise was detected for samples with negligible mechanical sensitivity in an amorphous-nanocrystalline composite state obtained by a heat treatment at 853 K.

Epitaxial growth of a NiSi2 layer was observed on S+ ion-implanted Si(100) at a low temperature of 550 °C. Depending on the S+ dose and the Ni thickness, we identified different nickel silicide phases. High quality and uniform epitaxial NiSi2 layers formed at temperatures above 700 °C with a 20-nm Ni on high dose S+ implanted Si(100), whereas no epitaxy was observed for a 36-nm Ni layer. We assume that the presence of sulfur at the silicide/Si(100) interface favors the nucleation of the NiSi2 phase. The S atom distributions showed ultrasteep S depth profiles (3 nm/decade) in the silicon, which results from the snow-plow effect during silicidation and the segregation of S to the interface due to the low solubility of S in both Si and the silicide.

The effects of FePO4 nanoscale coating on PtRu thin films were investigated on the block of Ru crossover. Ru dissolution was examined by the accelerated-potential cycles between 0.4 and 1.05 V. The results showed that Ru dissolution from FePO4-coated PtRu surface was inevitable due to the direct contact between the PtRu surface and aqueous electrolyte. However, the FePO4 coating layer on PtRu thin-film electrodes effectively retained the dissolved Ru species, thus preventing the dissolved Ru species from diffusing into the electrolyte. Moreover, the retained Ru species within the FePO4-coating layer were redeposited onto the PtRu surface during the cycling in the fresh electrolyte.

In the present paper, we solidified magnesium-based AZ91D alloys in a superconducting magnetic field when an alternating current flowed through the alloy. As the direction of the magnetic field is perpendicular to that of the alternating current, a periodic electromagnetic force is produced to activate an electromagnetic vibration (EMV) on the alloy during solidification. The microstructure formation and microtexture evolution processed by EMV were examined. A significant difference arises in electrical resistivity between a solid and a liquid in the mushy zone of the alloy, making the solid move faster than the liquid and thus generating uncoupled motion, from which melt flow is initiated. The texture evolution obtained by x-ray diffraction and electron backscatter diffraction (EBSD) mapping reveal a strong dependence of melt flow intensity versus vibration frequency. A further analysis reveals that melt flow is rather weak when the vibration frequency is too low and thus the segmentation of growing crystals cannot be thoroughly completed. At medium vibration frequencies, severe fluid flow occurs, which favors fragmentation and thus results in a refined microstructure and a random microtexture. When the vibration frequency is too high, the relative leading distance covered by the mobile solid is rather short and melt flow once again becomes weak. Meanwhile, the static magnetic field makes the crystals orient to their easy magnetization direction and thus yields highly aligned textures. Experimentally, the present systematic observation indicates that the role of melt flow is of substantial importance in revealing the origin of structure formation when the alloy is solidified at various vibration frequencies.

Sodium cholesteryl carbonate ester (SCC) was synthesized, and its phase behavior was studied. The chemical structure was assessed by solid-state infrared spectroscopy based on vibration analysis. The wave number at 1705 and 1276 cm−1 corresponds to a carbonyl carbonate and O–C–O stretching of SCC, respectively. Molecular structure of SCC was further investigated with 1H and 13C NMR spectroscopy. The chemical shift, for the carbonyl carbonate resonance appeared at 155.5 ppm. A molecular mass of SCC was at m/z of 452. Differential scanning calorimetry (DSC), video-enhanced microscopy (VEM) together with polarized light microscopy, and small-angle x-ray scattering (SAXS) were used to characterize the phase behavior as a function of temperature of SCC. Liquid crystalline phase was formed with SCC. Based on the thermal properties and x-ray diffraction, it appears that SCC forms a structure analogous to the type II monolayer structure observed with cholesterol esters.

Synthesis of Pb(Zr1–xTix)O3 (PZT) on a single substrate using a high-throughput molecular-beam epitaxy technique was demonstrated. In situ synthesis of crystalline PZT at elevated substrate temperatures could not be achieved, as reevaporation of Pb (PbO) occurred and the partial pressure of O2 was insufficient to prevent formation of a PbPtx phase during deposition. Instead, ex situ postdeposition annealing was performed on PZT deposited at room temperature. Dense single phase PZT was prepared with a compositional range of 0.1 > x > 0.9, for film thicknesses up to 800 nm. Transmission electron microscopy revealed the grain size increased from 50 nm to ∼0.5 μm with increasing Zr-concentration and became more columnar. Raman, x-ray diffraction, and scanning electron microscopy/energy dispersive spectroscopy results revealed a morphotropic phase boundary between rhombohedral and tetragonal phases occurred at x ∼0.4 rather than at x = 0.47 in bulk ceramics. This was attributed to clamping arising from mismatch in thermal expansion between the film and substrate.