Fe-sheathed MgB2 tapes were fabricated using powder chemically treated through an ex situ process employing a powder-in-tube (PIT) technique. The treatment of MgB2 powder in a benzene solution of benzoic acid caused the pulverization and disappearance of large grains. Compared with the pristine powder without treatment, the tape made from this powder showed a fivefold increase in critical current density (Jc) in 10 T. This was due to the pulverization of grains by the chemical treatment and the removal of surface MgO layers from MgB2 grains by dissolution in the acid solution. The removal of MgO layers was effective in promoting substitution of carbon from the solvent for boron.

The nucleation mechanism of deformation-induced martensite was investigated by x-ray diffraction and transmission electron microscope in an ultra-low carbon austenitic stainless steel deformed by equal channel angular pressing at room temperature. It was found that two types of martensite transformation mechanism, stress-assisted and strain-induced, occurred via the sequences of γ (fcc) → ɛ (hcp) → α′ (bcc) and/or γ → α′. In both cases, the crystallographic relationships among γ, ɛ, and α′ followed the Kurdjumov-Sachs orientation relationships: {111}γ //{0001}ɛ //{011}α′ and 〈110〉γ//〈1120〉ɛ//〈111〉α′.

The effect of the substrate surface, structure, and chemistry on the interfacial interaction in Ni(thin film)/SiC was examined, with a focus on the recently discovered formation of a nickel intercalated graphite phase. Very thin Ni films (∼7 nm) were deposited onto heated 6H–SiC(0001) substrates prepared with: (i) an oxide layer, (ii) a surface reconstruction, and (iii) a pristine surface (no oxide and no reconstruction), followed by further annealing. Characterization using x-ray diffraction and atomic force microscopy revealed remarkable differences between the samples in terms of both surface morphology and crystallography. Nickel silicides were present in all samples; however, the phase composition differed depending on sample preparation. Furthermore, the pristine surface was the only one that clearly promoted the growth of the nickel graphite intercalation compound (Ni-GIC).

A longer lifespan is still being sought for biomaterials used for joint repair. We developed a new nanocomposite material of polytrimethylene carbonate (PTMC), hydroxyapatite (HAP), and multiwalled carbon nanotubes (MWNT) to mimic real cartilage. Experimental results were compared with those of natural cartilage and the conventional joint replacement material ultrahigh-molecular-weight polyethylene (UHMWPE). Friction experiments showed that our developed composite material had a coefficient of friction close to that of articular cartilage. Nanoindentation experiments indicated that the surface elastic behavior was similar to that of cartilage. The surface attraction forces on a silicon atomic force microscope tip were much higher for cartilage than those for the other two materials. These results hold promise for this artificial cartilage composite material’s performance in vivo, following further experimental investigations and chemical modifications.

The microstructural evolution and interfacial reactions of fluxless-bonded, Au-20wt%Sn/Cu solder joint were investigated during reflow and aging. After reflowing at 310 °C, only one thick and irregularly shaped ζ(Cu) layer was formed at the interface. After the prolonged reflow reaction, the AuCu layer was formed between the ζ(Cu) layer and the Cu substrate. During reflowing, the Cu substrate reacted primarily with the ζ-phase in the solder matrix. The solid-state interfacial reaction was much faster at 250 °C than at 150 °C. After aging at 250 °C for 100 h, thick ζ(Cu), AuCu and AuCu3 IMC layers were formed at the interface. The formation of the AuCu3 intermetallic compound (IMC) was caused by Cu enrichment at the AuCu/Cu layer interface. After aging for 500 h, cracks were observed inside the interfacial AuCu layer. The study results clearly demonstrate the need for an alternative surface finish on Cu, to ensure the high temperature reliability of the Au-20Sn/Cu solder joint.

Infrared (IR) luminescence covering 1.1 to ∼1.6 μm wavelength region was observed from bismuth-doped barium silicate glasses, excited by a laser diode at 808 nm wavelength region, at room temperature. The peak of the IR luminescence appears at 1325 nm. A full width half-maximum (FWHM) and the lifetime of the fluorescence is more than 200 nm and 400 μs, respectively. The fluorescence intensity increases with Al2O3 content, but decreases with BaO content. We suggest that the IR luminescence should be ascribed to the low valence state of bismuth Bi2+ or Bi+, and Al3+ ions play an indirect dispersing role for the infrared luminescent centers.

Single-crystal rods of Cu–Al–Ni shape-memory alloy fabricated from a molten pool of 82 wt% Cu, 14 wt% Al, and 4 wt% Ni by the Czochralski method were first heated to ∼870 °C and then quenched to obtain austenitic microstructures. Various microanalysis techniques were used to determine the chemical composition, microstructure, and phase-transformation temperatures of the produced alloy. Cyclic tensile tests with in situ temperature control demonstrated the occurrence of pseudoelastic deformation at elevated and close to phase-transformation temperatures and provided insight into the temperature dependence of the phase-transformation stress, damping characteristics, and cyclic straining of single-crystal Cu–Al–Ni alloy. The stress hysteresis observed in the pseudoelastic deformation cycles decreased at elevated temperatures. The stress response at different temperatures is associated with the formation, growth, and coalescence of martensite variants. Stress-induced phase-transformation mechanisms, coalescence of twin variants, and energy dissipation by pseudoelastic deformation are discussed in the context of experimental findings. The results illustrate the potential of single-crystal Cu–Al–Ni as a structural material for dynamic microsystems and temperature sensors.

The mechanical behavior of Zr-Cu-Al bulk metallic glasses (BMGs) and in situ Ta-particle-containing composites (BMGCs) was investigated at 77 K. Their strengths increased significantly whereas the plastic strains remained at comparable levels, when compared to that at 298 K. The interaction between shear bands and particles shows that shear extension in particles has limited penetration, and shear bands build up around particles. Pair distribution functions (PDFs), which carried out at cryogenic and ambient temperatures on the as-cast Zr-Cu-Al bulk metallic glasses, were studied, and simulations with reverse Monte Carlo (RMC) were performed by combining icosahedral and cubic structures as the initial structures. Based on the studies of the pair distribution functions and the Reverse Monte Carlo simulations, the concept of free volume was defined—spaces between clusters with longer bond lengths of atom pairs; the structural model of BMGs was proposed—the strongly bonded clusters correlated with each other and separated by free volume. An attempt has been made to connect the relationship between amorphous structures and their mechanical properties.

In the present paper, Sr4Nd2Ti4Nb6O30 ceramics with filled tungsten bronze structure were prepared, and the dielectric characteristics over a broad temperature range (123 to 623 K) were investigated. Two dielectric abnormities were observed in the entire frequency range (100 Hz to 1 MHz). One is at higher temperature corresponding to a diffuse ferroelectric transition (P4/mbm → P4bm), and the other at lower temperature shows relaxor characteristics in both ϵ′ and tan δ curves. An activation energy and freezing temperature of 0.1659 eV and 148.05 K, respectively, were obtained by analyzing the frequency dependence of the dielectric maximum temperature using the Vogel–Fulcher relationship. The relaxor behavior is attributed to a polar-glassy system with thermally activated polarization fluctuations above the freezing temperature. In addition, the dielectric constant was almost stable with both temperature and frequency in the temperature range of 300 to 430 K (between the two dielectric abnormities).

The importance of the secondary electron emission of the protective layer in the alternating current plasma display panels is widely known. However, the difficulty in measuring the secondary electron emission coefficients (γ) of insulating materials has hampered efforts to obtain accurate estimates of their values. To overcome the difficulty of direct measurement, we devised a calculating γ using the spectra of x-ray photoelectron spectroscopy (XPS) and a well-defined theory. The XPS spectra of the valence and core bands of MgO, Al2O3, and Y2O3 films, which were deposited by e-beam evaporation, were measured. Calculations of the γ values were conducted for the case when gas ions such as He, Ne, Ar, and Xe slowly approach the solid surface.

Near infrared (NIR) absorbing nanoparticles synthesized by the reduction of HAuCl4 with Na2S exhibited absorption bands at ∼530 nm, and in the NIR region of 650–1100 nm. The NIR optical properties were not found to be related to the earlier proposed Au2S–Au core-shell microstructure in previous studies. From a detailed study of the structure and microstructure of as-synthesized particles in this work, S-containing, Au-rich, multiply-twinned nanoparticles were found to exhibit NIR absorption. They consisted of amorphous AuxS (where x = 2), mostly well mixed within crystalline Au, with a small degree of surface segregation of S. Therefore, NIR absorption was likely due to interfacial effects on particle polarization from the introduction of AuxS into Au particles, and not the dielectric confinement of plasmons associated with a core-shell microstructure.

Large strain extrusion machining (LSEM) is presented as a method of severe plastic deformation for the creation of bulk nanostructured materials. This method combines inherent advantages afforded by large strain deformation in chip formation by machining, with simultaneous dimensional control of extrusion in a single step of deformation. Bulk nanostructured materials in the form of foils, plates, and bars of controlled dimensions are shown to result by appropriately controlling the geometric parameters of the deformation in large strain extrusion machining.

A novel method for in situ scanning electron microscope (SEM) micro-compression tests is presented. The direct SEM observation during the instrumented compression testing allows for very efficient positioning and assessment of the failure mechanism. Compression tests on micromachined Si pillars with volumes down to 2 μm3 are performed inside the SEM, and the results demonstrate the potential of the method. In situ observation shows that small diameter pillars tend to buckle while larger ones tend to crack before failure. Compressive strength increases with decreasing pillar diameter and reaches almost 9 GPa for submicrometer diameter pillars. This result is in agreement with earlier bending experiments on Si. Difficulties associated with precise strain measurements are discussed.

We report the direct deposition of epitaxial 215-nm-thick vanadium sesquioxide (V2O3) films on a- and c-plane sapphire substrates from powder-pressed V2O3 targets via pulsed-laser deposition (PLD) in an evacuated deposition chamber devoid of O2. The films were characterized using x-ray diffraction (XRD), x-ray photoemission spectroscopy (XPS), x-ray absorption fine structure (XAFS) spectroscopy, and atomic force microscopy (AFM). XPS measurements confirmed that the stoichiometry of the powder was conserved in the films. XRD patterns together with XAFS measurements proved that V2O3 was epitaxial on the a-sapphire substrate with epitaxial relation (110)film//(110)substrate, and the results are consistent with the epitaxy on the c-plane substrate as well. The room-temperature resistivities of V2O3 films on a- and c-plane substrates were 1.49 × 10−4 and 3.00 × 10−5 Ω m, respectively. The higher resistivities of the films compared to bulk V2O3 might be attributed to thermal stresses resulting from difference in thermal expansion coefficients (TECs) of the films and the substrates.

In this study, bulky titanate nanotubes with dense microstructures were successfully fabricated by a hydrothermal hot-pressing (HHP) technique with water as a reactive solvent. Titanate-based nanotubes of about 10 nm outer diameter and 5 nm inner diameter and a few hundred nanometers in length were synthesized by a hydrothermal treatment of anatase-type TiO2 powder in a 10 M NaOH aqueous solution. From results of N2-adsorption and transmission electron microscopy observation, it was obvious that HHP processed samples were composed of nanotubular structures and that the obtained bulks possessed mesopores and high Brunauer–Emmett–Teller surface area. These results suggested that the obtained bulks possessed functionality as good as that of powders of titanate nanotubes. Thus, the HHP technique may be a useful method for fabricating bulky titanate nanotubes and may be applied in the solidification of the other some nanotubular materials.

Results of the mechanical alloying of binary Mg–Ti and ternary Mg–Ti–Ni mixtures using two different process control agents are reported. Both high- and low-energy milling resulted in the formation of cubic compounds. When all starting reactants had disappeared, a mixture of two face-centered cubic (fcc) phases was formed with lattice constants around 4.40 and 4.25 Å. The electrochemical hydrogen storage capacity, 450 mAh/g for (Mg0.65Ti0.35)0.95Ni0.05, was about one-third that reported for Mg–Ti thin films. This suggested that only one of the two fcc phases was active at ambient conditions. Prolonged mechanical alloying of (Mg0.60Ti0.40)0.95Ni0.05resulted in full conversion of the material into one fcc-phase with a very small crystallite size, an intermediate lattice constant (4.33 Å), and a sharply decreased storage capacity.

The effect of zirconium (Zr) addition on the glass-forming ability (GFA) and mechanical properties of the Ni61.5Nb38.5 alloy has been studied. The addition of Zr improves the GFA. When x = 5 for Ni61.5Nb38.5−xZrx (in at.%) alloys, the alloy exhibits the best GFA and can be cast into 3-mm-diameter amorphous samples by using the copper mold injection-casting method. Differential scanning calorimetry measurements indicated that the thermal parameters, such as Trg and γ, have not a good correlation with the GFA in the Ni–Nb–Zr alloys. Compression tests reveal that the addition of Zr just decreases the fracture strength slightly from 3.4 to 3 GPa and that all of the tested samples exhibit a little compressive plasticity of about 2%. When x = 9, the feature of the fracture surface indicates that the alloy has a tendency for transition from the ductile to the brittle. And delicate “dimple” and microscale vein pattern structures have been observed on it.

Although GaN is one of the important electronic materials of this decade, thermodynamic data for this compound are not known with sufficient reliability. The limited information available is not internally consistent. Measured in this study are high-temperature heat capacities using a differential scanning calorimeter and Gibbs energies of formation employing a solid-state electrochemical technique. The solid-state cell was based on single-crystal CaF2 as the electrolyte and Ca3N2 as the auxiliary electrode to convert the nitrogen chemical potential established by the equilibrium between Ga and GaN into an equivalent fluorine potential. The heat capacity of GaN at ambient pressure can be represented by the equation: CoP / J mol−1 K−1 = 74.424 − 0.00106T + (46720/T2) − (685.9/T0.5), in the temperature range from 350 to 1075 K. The standard Gibbs energy of formation of GaN in the range from 875 to 1125 K can be expressed as: ΔfGo/ J mol−1 (±465) = −128,749 + 115.029 T. This corresponds to a decomposition temperature of 1119 ± 4 K for GaN in pure nitrogen at standard pressure. On the basis of these new measurements and a critical assessment of information that is available in the literature, a refined set of data for GaN in the temperature range from 298.15 to 1400 K is presented.

The effects of ionic doping in Bi0.5Na0.5TiO3 (BNT) ceramics were investigated. Pure and doped BNT samples containing 0 to 16 at.% Ba2+ and 0 to 1.0 at.% Ce4+ were synthesized at 1135 to 1200 °C for 2 h in ambient atmosphere. Temperature dependences of dielectric properties were analyzed. These results suggest that Ba2+ and Ce4+ replace the ions in A and B sites of perovskite structures, and the lattice structure is altered. The component differences of each crystal domain lead to variance of phase transition temperature, which enhances the relaxation character in BNT ceramics, and the dielectric properties were consequently improved.

Polymer-derived ceramics have shown promise as a novel way to process low-dimensional ceramics such as environmental barrier coatings. Composite coatings have been developed as oxidation and carburization barriers on steel using poly(hydridomethylsiloxane) matrix and titanium disilicide as reactive fillers. A systematic study of the phase transformations and microstructural changes in the coatings and their components during pyrolysis in air is presented here. The system evolves from an amorphous polymer filled with a binary metal at room temperature to an inorganic amorphous network of oxidized silicon and titanium at the target temperature of 800 °C. Crystallization of the composite occurs at higher temperatures to reach cristobalite and rutile by 1600 °C. The polymer-to-ceramic conversion occurs between 200 and 600 °C. The oxidation of the expansion agent and the densification of the composite take place between 300 and 800 °C.