Using an infrared camera, we observed in situ dynamic shear-banding operations during compression of a bulk metallic glass at various strain rates. We demonstrated that the shear-banding events are highly dependent on strain rates, either intermittent at the lower strain rate or successive at the higher strain rate. Serrated plastic-flow behaviors are a result of shear-banding operations. These observations provide a new insight into inhomogeneous deformation of metallic glasses.

Teflon AF/Ag nanocomposites with various metal concentrations were fabricated by an evaporation process. Transmission electron microscopy examination showed that for low metal concentrations, the silver formed isolated individual nanoparticles. At higher metal concentrations, percolating metallic networks within the polymer matrix were formed. Optical absorption measurements showed a transition from individual plasmon absorption peaks for individual Ag nanoparticles to broadband optical absorption for the metallic networks. The absorption profile closely matches the solar radiation spectrum for an intermediate metal concentration of 45%. Thus, these novel polymer-metal nanocomposites have significant potential for photovoltaic applications.

In this work, a consumable anode composed of a solid solution of titanium carbide and titanium monoxide was prepared via carbothermic reduction of TiO2. Upon electrolysis, the anode fed Ti2+ into solution and carbon monoxide was generated; no excess carbon remained to contaminate the melt. On the cathode, high-purity titanium (>99.9%) was produced. Our results suggest anode and cathode current efficiencies of 93.5% and 89% respectively, indicating that the method is viable and extremely cost-effective, potentially dropping the cost of titanium to near that of aluminum.

In this work, we report recent progress in the control of the interface quality between buffer layers and YBa2Cu3O7 (YBCO) thin films grown by the trifluoroacetates route (TFA) and how it influences the critical current Jc of the coated conductors (CCs). We have mainly focused on the two most used cap layers, i.e., CeO2 and SrTiO3. We show that for CeO2 buffer layers, the key for high-quality YBCO epitaxy is to obtain atomically flat (001) terraced CeO2 surfaces. CC YBCOTFA/CeO2sputt/YSZ/CeO2/Ni with Jc (77 K) ∼ 1 MA/cm2 and chemical CC YBCOTFA/CeO2MOD/y-stabilized zirconia and ion beam assisted deposition (YSZIBAD)/stainless steel (SS) with Jc (60 K)=2.3MA/cm2 were obtained. For metalorganic deposited (MOD) SrTiO3 the main issue is to reduce the overall surface roughness that tends to increase film porosity due to an enhanced {100} YBCO nucleation. Improved roughness can be achieved by growing the buffer layers at lower temperatures. An all-chemical CC, YBCOTFA/SrTiO3MOD/BaZrO3MOD/NiO–SOE/Ni, with promising in-plane texture, ΔϕYBCO = 6.6° was grown.

ZnO films are grown by the ultrasonic spray pyrolysis method on ZnO seeding layer deposited on Si (100) by pulsed laser deposition. The resultant film possesses a columnar microstructure perpendicular to the substrate and exhibits smooth, dense, and uniform morphology. The preferred orientation along the c-axis of the film is significantly enhanced compared to that without the seeding layer. ZnO film grown on ZnO-seeded silicon exhibits higher hall mobility, lower resisitivity, and higher photoluminescence intensity.

A series of n-alkyldiamines with the general formula H2N(CH2)nNH2 (n = 2–6) has been intercalated into crystalline lamellar-hydrated barium phenylphosphonate from ethanolic solutions. The amount intercalated was followed batchwise and the variation in interlayer distance (d) for the original host and the respective intercalated compounds was followed by x-ray diffraction patterns. Linear correlation with good fits were obtained for (d) or for the number of moles intercalated (nf) as a function of the number of carbon atoms in the aliphatic chains (nc): d = (1436 ± 65) + (108 ± 14)nc and nf = (2.24 ± 0.15) – (0.31 ± 0.03)nc. The energetic effect caused by amine intercalation was determined through reaction-solution calorimetry at the solid-liquid interface from ethanolic solutions. The resulting exothermic enthalpies for intercalation give rise to a monomolecular layer guest molecule arrangement with a longitudinal axis inclined by 58° to the inorganic sheets. The thermodynamic data showed that the system is favored by exothermic enthalpy, negative Gibbs free energy, and positive entropic values.

This article is a study of monodispersed, submeter-sized solid carbon spheres having smooth surfaces and almost perfectly round shapes. These spheres were synthesized by pyrolysis of tetrahydrofuran in the absence of a catalyst. Microstructures of carbon spheres before and after graphitization were systematically investigated using electron microscopy, thermogravimetric analysis, and x-ray diffraction. The sphere is believed to consist of an underdeveloped spiral-shell core and a surface with discrete fragments of concentrically arranged graphene layers. Under lower temperature heat treatment, the underdeveloped spiral-shell structure changes to a well-developed spiral-shell structure. After graphitization, the spiral-shell core is shown to transform into continuous and closed polyhedral secondary shells, whereas the exterior discrete fragments of graphene sheets transform into discontinuous polyhedral surface shells. The mechanisms of these microstructural changes are discussed.

Based on the best bulk metallic glass (BMG) forming alloy in the Mg−Cu−Y ternary system, we introduced Ag (or Ni) to partially substitute for Cu to improve the glass-forming ability (GFA). The objective of this paper is twofold. First, we illustrate in detail a recently developed search strategy, which was proposed but only briefly outlined in our previous publication [H. Ma, L.L. Shi, J. Xu, Y. Li, and E. Ma: Discovering inch-diameter metallic glasses in three-dimensional composition space. Appl. Phys. Lett. 87, 181915 (2005)]. The protocol to navigate in three-dimensional composition space to land large BMGs is spelled out step-by-step using the pseudo-ternary Mg−(Cu,Ag)−Y as the model system. Second, our ability to locate the best BMG former in the composition tetrahedron allows us to systematically examine, and conclude on, the effects of a given alloying element. The large improvement in glass-forming ability in the Mg−(Cu,Ag)−Y system relative to the based ternary will be contrasted with the reduced glass-forming ability in the Mg−(Cu,Ni)−Y pseudo ternary system. It is demonstrated that the improvement of glass-forming ability requires judicious choice of substitutional alloying elements and concentrations, rather than simple additions of multiple elements assuming the “confusion principle.”

Melt-spun and annealed Al85Ni5Y8Co2 metallic glass, with a large supercooled liquid region, were investigated by means of differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and small-angle x-ray scattering (SAXS). TEM studies revealed that the as-quenched ribbons were fully amorphous. Further, the SAXS measurements showed that no evidence for compositional inhomogeneities associated with amorphous phase separation was found in the as-quenched state and the early stage annealing prior to devitrification. The primary crystallization of this glass was characterized, intriguingly, which appeared to be proceeded with an initial thermal relaxation, then α-Al nanocrystal nucleation with a limited number, finally a high density of nanocrystals nucleation and growth.

Shearing behavior of Sn-37Pb, Sn-3Ag-0.5Cu, and Sn-3Ag-0.5Cu-8 in solder joints on tape ball grid array (TBGA) substrates were investigated with different shearing speeds from 7 μm/s to 700 μm/s and over a wide temperature range from −25 °C to 150 °C. Both shearing speed and testing temperature were found to have strong effects on the shearing strength and fracture mechanisms of the solder joints. At certain temperature, the shearing force increases sharply with the increase of shearing speed due to a small amount of grain boundary deformation and incomplete dislocation movement as well as more work hardening at a high strain rate. With a fixed speed, the shearing force decreases dramatically with the increase of shearing temperature as a result of a small amount of work hardening and more dynamic recovery, as well as a reduction in Young’s modulus at elevated temperatures. Two lead-free solder joints were much stronger than the tin-lead solder joints under any given shearing condition. At a low temperature of −25 °C, the tin-lead solder joints failed with a combination of intermetallic compounds (IMC) fracture and solder/IMC interface detachment, whereas both lead-free solder joints failed by IMC/Ni interfacial separation. From 25 °C to 150 °C, the fracture mode of all solder joints was complete ball cut through the bulk solder with a ductile rupture. The underlying mechanisms for different shearing performance are interpreted in relation to the properties of the interconnecting materials.

A sol-gel technique was used to prepare Gd2Ti2O7:Eu3+-coated submicron silica spheres (SiO2@Gd2Ti2O7:Eu3+). The resulted SiO2@Gd2Ti2O7:Eu3+ core-shell particles were characterized by x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), energy-dispersive x-ray spectra (EDS), transmission electron microscopy (TEM), photoluminescence (PL) spectra, as well as kinetic decays. The XRD results demonstrate that the Gd2Ti2O7:Eu3+ layers begin to crystallize on the SiO2 spheres after annealing at 800 °C and the crystallinity increases with raising the annealing temperature. The obtained core-shell phosphors have perfect spherical shape with narrow size distribution (average size ∼620 nm), non-agglomeration, and smooth surface. The thickness of the Gd2Ti2O7:Eu3+ shells on the SiO2 cores could be easily tailored by varying the number of deposition cycles (60 nm for four deposition cycles). Under the irradiation of 310 nm ultraviolet, the SiO2@Gd2Ti2O7:Eu3+ samples show strong emission of Eu3+. For the samples annealed from 600 to 800 °C, the emission is dominated by 613 nm red emission ascribed to 5D0–7F2 transition of Eu3+, while for those annealed from 900 to 1000 °C, the emission is dominated by 588 nm orange emission due to 5D0–7F1 transition of Eu3+. The PL intensity of Eu3+ increases with increasing the annealing temperature and the number of coating cycles.

Electromigration (EM) in copper dual-damascene interconnects with extensions(also described as overhang regions or reservoirs) in the upper metal (M2) were investigated. It was found that as the extension length increases from 0 to 60 nm, the median-time-to-failure increased from 50 to 140 h, representing a ∼200% improvement in lifetimes. However, further increment of the extension length from 60 to 120 nm did not result in any significant improvement in EM lifetimes. Based on calculations of current densities in the reservoir regions and recently reported nucleation, void movement, and agglomeration-based EM phenomena, it is proposed that there is a critical extension length beyond which increasing extension lengths will not lead to longer EM lifetimes.

All-polymer multilayer hollow core photonic fiber preforms were fabricated using consecutive deposition from a solvent phase of two polymers with high and low refractive indices (RI). Processing techniques for two polymer pairs—polystyrene (PS)/poly(methyl methylacrylate) (PMMA) and polycarbonate (PC)/poly(vinylene difloride) (PVDF)—were established. The fabrication process involved consecutive film deposition by solvent evaporation of polymer solutions on the inside of a rotating PMMA or PC tube, used as a cladding material. By injecting right volumes of the polymer solutions into a spinning tube the thickness of each layer could be reliably controlled from 20 to 100 μm. Proper selection of solvents and processing conditions was crucial for ensuring high optical and mechanical quality of a resultant preform, as well as compatibility of different polymer films during co-deposition. Preforms of 10 layers for PMMA/PS material combination and 15 layers for PVDF/PC were demonstrated. Fabrication of preforms with higher number of layers is readily possible and is only a question of preform fabrication time. An alternative method of preform fabrication by co-rolling of polymer bilayers is also presented in this paper, drawing of PMMA/PS, PVDF/PC fibers with up to 32 layers is demonstrated.

Tantalum zirconium oxynitrides in the Ta–Zr–O–N system of Ta(3−x)Zrx(O/N)6 and Ta(3−x)ZrxN(5−x)Ox (0 ≤ x ≤ 0.6) compositions have been synthesized by the nitridation of the amorphous tantalum zirconium oxides, obtained by sol-gel technique, with flowing ammonia at temperatures in the range 1023–1123 K for several hours. Different coloration has been obtained, going from yellow to red, whose intensity is a function of the nitrogen content in each sample. The structure of these oxynitrides has been refined from powder x-ray diffraction by the Rietveld method. The present study shows that the baddeleyite phase is formed in the preliminary stages of the nitridation and then transformed to the Ta3N5-type phase. Below 1123 K, a baddeleyite-type structure with a monoclinic symmetry, space group P21/c, is observed in these phases. When the nitration temperature increases, a marked increase in the nitrogen content takes place, and these materials adopt the Ta3N5 structure, space group C2/m. Diffuse reflectance spectra and CIE-LAB color coordinates suggest that the solid solutions Ta(3−x)Zrx(O/N)6 and Ta(3−x)ZrxN(5−x)Ox (0 ≤ x ≤ 0.6) are expected to be promising candidates for new ecological pigments.

The film stress evolutions induced by the phase transformation of Sn/Ni(P) films during thermal treatment were investigated using an in situ measurement of wafer curvature by laser scanning. Apparently, tensile stress developed due to the layer-by-layer formation of Ni3Sn4 and Ni3P phases for Sn/Ni(11.7P) films, and a compressive stress evolved for Sn/Ni(3P) films, despite the same phase transformation. The molar volume mismatch and x-ray diffraction analyses before and after the reaction between Sn and Ni(P) films suggested that a compressive stress existed in the Ni3Sn4 layer while the Ni3P layer was under a tensile stress state. The apparent stress states (tensile or compressive) for overall thickness of the films formed by the layer-by-layer transformation in Sn/Ni(P) were determined by the competition between compressive stress related to Ni3Sn4 formation and tensile stress caused by Ni3P formation. The stress states were dependent upon the relative thickness of the product layers with varying P content.

Interfacial reactions of Sn-Cu alloys with Ni substrate at 250 °C have been investigated by varying the Cu contents from 0.3wt%Cu to 3.0wt%Cu. The Cu6Sn5 phase is not found in the Sn-0.3wt%Cu/Ni couple. The interfacial reaction sequence of the Sn-0.6wt%Cu/Ni couple is similar to that of the Sn-0.7wt%Cu/Ni. The reaction follows Cu6Sn5 formation stage, growth stage, detachment stage, Cu6Sn5 layer continuing growth stage, Ni3Sn4 formation stage, Cu6Sn5 phase dissolution stage, Ni3Sn4 detachment stage, and Ni3Sn4 phase dissolution stage. Similar results are found for the couples prepared with higher Cu contents, 0.8wt%Cu, 1.0wt%Cu, 2.0wt%Cu, and 3.0wt%Cu, but the detachment positions are different. For the couples with higher Cu-content, the layer detaches at the Cu6Sn5/Ni interface; however, for the 0.6wt%Cu and 0.7wt%Cu couples, the Cu6Sn5 phase layer fractures and detachment occurs inside the layer. Morphologies of the Cu6Sn5 phase are also found to change with Cu contents: the pyramidal shape in the 0.3wt%Cu couple changes to the rod-shape in the 0.8wt%Cu couple, and becomes a very fine rod shape in the 2.0wt%Cu couple.

The microstructure in a small amount of Al2O3-doped Y2O3-stabilized tetragonal zirconia polycrystal (Y-TZP) sintered at 1100–1650 °C was examined to clarify the effect of Al3+ ions segregated at grain boundaries on cubic-formation and grain-growth processes. The sintering rate in Y-TZP was remarkably enhanced by Al2O3-doping. In addition, at temperatures >1500 °C, grain growth remarkably proceeded, and the fraction of the cubic phase increased in comparison with that of undoped Y-TZP. High-resolution electron microscopy and nanoprobe x-ray energy dispersive spectroscopy measurements revealed that no amorphous layer existed along the grain-boundary faces in Al2O3-doped Y-TZP and that Y3+ and Al3+ ions segregated at grain boundaries over widths of ∼10 and ∼6 nm, respectively. At 1100 °C, Al3+ ions started to segregate at grain boundaries, and the segregation peak of Al3+ ions increased as the sintering temperature increased. Cubic-formation and grain-growth behaviors in Al2O3-doped Y-TZP were reasonably interpreted by taking into account the effect of Al3+ ions segregating along grain boundaries.

Immobilization of titania nanoparticles on submicron-sized silica carrier spheres was achieved, and the relevant photocatalytic efficiency was studied. In contrast to the commonly adopted practice of either free suspending nano-sized catalyst particles or immobilized catalyst particles on large supports for photocatalytic applications, the present approach offers a third option, avoiding the disadvantages of the above-mentioned two practices. In the model system of photo-degradation of methylene blue, the photocatalytic efficiency of the present catalyst form was found comparable to that of free-suspending P25 nanoparticles, a popular commercial titania photocatalyst, of the same total catalyst surface area. The present photocatalytic process was found to be diffusion dominant, and its impressive catalytic performance was attributed to the well-separated, smaller than usual titania particles immobilized on the surfaces of submicron-sized silica spheres.

An instrumented indentation microscope was constructed and applied to the measurements of the Meyer hardness and the elastic modulus of several engineering materials ranging from ductile metals to brittle ceramics. Because of the in situ optical observation and determination of the indentation contact area that is synchronized to the indentation load versus depth relation, the mechanical properties determined on the indentation microscope are precise and reliable without any undesirable approximations and assumptions required for estimating the contact area. It is also demonstrated that the instrumented indentation microscope is capable of determining in a quantitative manner the in situ contact profiles of impression (sinking-in/piling-up profiles). The present work suggests that the instrumented indentation microscope will be a powerful tool in the science and engineering of indentation contact mechanics.