Porous TiO2–P2O5 oxide was synthesized by the sol-gel method in the presence of tri-block copolymer (EO)20(PO)70(EO)20 (Pluronic123) in queous solution. The TiO2 nanocrystals with anatase structure precipitated in the as-synthesized TiO2–P2O5 materials at 80°C, considerably lower than that for traditional heat treatment in the solid state, which maintained a stable size of 3.6–4 nm upon calcinations below 500°C. It is believed that P2O5 glass phase prevents the coarsening of TiO2 nanocrystals below 500°C. The mixed oxide exhibited a specific surface area of 170–200 m2/g after calcining in the temperature range of 300–500°C.

Europium-doped organic–inorganic hybrid low-melting phosphite glass was prepared from SnCl2, Me2SiCl2, and H3PO3 (phosphonic acid) through the nonaqueous acid–base reaction process. The europium-doped glass melted at 250 °C showed fluorescence with a broad peak at 373 nm due to the 4f6 5d1 → 4f7 transition of Eu2+ ions, whereas no fluorescence from the Eu3+ ions was observed. Almost all of the Eu3+ ions incorporated into the glasses could be successfully reduced to Eu2+ ions at a temperature as low as 250 °C by the strong reducing power of H3PO3.

A strengthening mechanism arising from the mineral bridges in the organic matrix layers of nacre (mother of pearl) is presented by studying the structural and mechanical properties of the interfaces in nacre. This mechanism not only increases the average fracture strength of the organic matrix interfaces by about five times, but also effectively arrests the cracks in the organic matrix layers and causes the crack deflection in this biomaterial. The present investigation shows that the main mechanism governing the strength of the organic matrix layers of nacre relies on the mineral bridges rather than the organic matrix. This study provides a guide to the interfacial design of synthetic materials.

The hydrogen storage performance of a single body-centered-cubic phase Ti-40V-10Cr-10Mn alloy was investigated. A hydrogen absorption capacity of 4.2 wt.% (H/M = 2.1), which is the highest value at room temperature reported so far, was achieved at 293 K under modest pressure (3 MPa) for this as-cast alloy. The effective hydrogen capacities of this alloy were 2.6, 2.8, and 3.2 wt.%, respectively, at 353, 393, and 523 K, which gave hope of bringing Ti-V-based alloys into the reach of practical application for onboard hydrogen storage systems in fuel cell-powered vehicles.

Chemical vapor deposition (CVD) using gold nanoparticles as the catalyst to grow high-quality single-crystal gallium nitride nanowires was developed. This method enables control over several important aspects of the growth, including control of the nanowire diameter by using monodispersed gold clusters, control of the nanowire location via e-beam patterning of the catalyst sites, and control of the nanowire orientation via epitaxial growth ona-plane sapphire substrates. Our work opens up new ways to use GaN nanowires as nanobuilding blocks.

Macrochannelled tetragonal zirconia polycrystals (TZP) coated with a calcium phosphate layer were fabricated using a coextrusion process to produce strong and bioactive porous bioceramics. The initial feedrod, composed of three materials [TZP (shell), calcium phosphate (intermediate layer), and carbon black (core)], was coextruded through a 750-μm orifice at 120 °C, producing a continuous and flexible filament. Each sheet, which was composed of a unidirectional array of filaments, was stacked and then warm-pressed at 140 °C with 10 MPa. After binder burnout, the green billet was sintered between 1350 and 1600 °C for 1 h in air, leaving uniform macrochannels clad on the inside with bioactive calcium phosphate on a strong TZP body. The compressive strength of the specimen was much higher than that of calcium phosphate with a similar structure.

The frequency response of a 37 MHz bulk LiNbO3 surface acoustic wave (SAW) filter with a 200-nm-thick ZnO overlayer exhibited a downshift in the frequency with ultraviolet (UV) light due to acoustoelectric interactions between the photo-generated carriers in the semiconducting ZnO and the surface acoustic waves. In contrast, a 36 MHz ZnO thin film SAW delay-line with insulating ZnO films exhibited an upshift in the frequency. The response was more pronounced at higher harmonics (130–315 MHz) and was attributed to changes in the elastic/dielectric properties in the upper surface layer of ZnO. A linear change in the frequency with UV intensity shows immense applicability for wireless ultraviolet sensor applications.

Silver metal powders were prepared through reduction of AgNO3 in ethylene glycol using microwave-polyol (M-P) and conventional-polyol (C-P) reactions at 100–200 °C. Powders of Ag were rapidly produced by microwave-assisted reaction at temperatures above 160 °C. The formation yield of Ag powders from AgNO3 reached 97.8% after treatment for 135 min at 140 °C and 98.6% after treatment for 23 min at 160 °C. Compared to the formation of Ag powders using a C-P reaction, a M-P reaction led to increased rate of formation by 6.5 times at 160 °C, 5.2 times at 140 °C, and 3 times at 130 °C. Silver particles of 0.3–2 μm in diameter were produced using M-P and C-P reactions at 100–120 °C. The particle size of Ag powders increased with increasing reaction temperatures and times, and particles strongly aggregated at 160 °C using C-P and M-P reactions.

Wet oxidation in the AlAs layer sandwiched between two GaAs plates was investigated for the temperature range of 400 to 480 °C. The oxidation rate increased with increasing thickness of the AlAs layer. Theoretical analysis based on the boundary layer diffusion was performed to account for the thickness effect. The theory is in excellent agreement with the experimental measurement.

Nanocrystalline tin dioxide (SnO2) thin films were prepared on glass substrate by pulse laser deposition for the first time. The thin films were characterized for their composition, morphology, and crystalline structure by x-ray diffraction, transmission electron microscopy, and high-resolution transmission electron microscopy. It was found that the thin films consisted only of the tetragonal phase SnO2 with no structural change, and they were well crystallized during deposition. In most cases, SnO2 particles were overlapped, predominantly grown on preferred (101) plane, and connected with two or three neighbors through necks. The average grain size of the as-prepared thin films was about 12 nm. These facts are of great importance for sensor characteristics, since smaller grains and preferred orientation properties provide higher gas sensitivity to the whole thin films. Our findings indicate that the n-type wide-band-gas semiconductor nanocrystalline thin films can be manipulated by using pulse laser deposition techniques, offering new opportunities to control material fabrication.

Amorphous alloys were synthesized by interface-assisted ion beam mixing in the W-rich portion of the Ag–W system. These alloys are characterized by the largest positive heat of formation among the transition-metal alloys and were formed through a two-step structural transition in the alternately deposited Ag–W films. First, during alternate deposition of the nano-sized Ag and W layers, the interfacial free energy drove the Ag–W interaction, which resulted in an intermediate body-centered-cubic (bcc) supersaturated solid solution. Second, the bcc solid solution transformed into an amorphous state upon irradiation at room temperature by 200-keV xenon ions. We report the experimental observations of the Ag–W amorphous alloy formation and a brief discussion concerning the effects of the interfacial free energy and ion irradiation dose on the structural transition observed in the Ag–W films.

This study seeks to provide a mechanistic rationale for the substrate confinement effect on the strength and plasticity of thin metal films. Atomistic simulations of tensile loading of the freestanding and substrate-bonded films were carried out. Particular attention was devoted to correlating the overall mechanical response and the defect mechanisms on the atomic scale. The existence of an interface with the underlying substrate was observed to constrain significantly the dislocation motion in the film. The extent of film strengthening due to the substrate was dictated by the capability of atoms to slide along the interface.

Sn/Ni interfacial reactions at 100 °C with and without the passage of electric currents were studied by using the Sn/Ni/Sn sandwich-type reaction couples. The Ni3Sn4 and metastable NiSn3 phases were formed at both the Sn/Ni and Ni/Sn interfaces in the couples reacted at 100 °C without the passing through of electric currents. Metallographical analyses revealed that the metastable NiSn3 phase nucleated and grew at the grain boundary, and the growth rate of the NiSn3 phase was much faster than that of the Ni3Sn4 phase. For the couples with the passage of electric currents of 4 × 103 A/cm2 density, the Ni3Sn4 reaction layers were found at both interfaces as well. However, the NiSn3 phase was found only at the Ni/Sn interface where the directions of electron flow and Ni diffusion were the same, and the NiSn3 phase was not found at the Sn/Ni interface. The NiSn3 phase formed at the Ni/Sn interface was found to nucleate and grow much faster than those without the passage of electric currents. It is likely that the electromigration effect enhances the movement of Ni atoms and accelerates the nucleation and growth of the NiSn3 phase while at the Sn/Ni interface, where the directions of electron flow and Ni diffusion are opposite, electromigration effects retard the movement of Ni atoms and inhibit the nucleation of the NiSn3 phase.

The effect of chemical etching on the surface roughness and fracture strength of Nd:yttrium-aluminum-garnet single crystals was investigated. Etching the laser host material in a 1:1 mixture of concentrated sulfuric and phosphoric acid at elevated temperatures enabled material removal from the surface of laser rods cored from single-crystal boules. The roughness on the rod surface increased from the as-drilled condition after etching, but after 17 μm of material was removed, the roughness remained approximately constant. The modulus of rupture increased from 133-530 MPa when 87 μm of material was removed by the chemical etching procedure.

A Sr0.7Bi2.4Ta2O9 (SBT) seed layer approximately 40 nm thick was formed on Pt/Ti/SiO2/Si substrates, and SBT thin films with the same chemical composition were deposited on the substrates with and without seed layer using sol-gel and spin coating methods. The influence of seed layer on the phase formation characteristics of SBT thin films was investigated using x-ray diffraction and scanning electron microscopy analyses. Formation of pyrochlore as well as Aurivillius phase was observed in both the unseeded and seeded SBT films heated at 740 °C. However, it was revealed that Aurivillius phase formation was enhanced in seeded SBT thin films and pyrochlore phase formation was highly suppressed. In this study, two possible mechanisms for the suppression of pyrochlore phase formation were proposed from the perspectives of activation energy difference between Aurivillius and pyrochlore phase formation, and Bi-ion diffusion to pyrochlore phase.

A new Mg65Cu25Gd10 alloy having significantly improved glass-forming ability (GFA) has been developed. In this article, we show that the ternary Mg65Cu25Gd10 bulk metallic glass with diameter of at least 8 mm can successfully be fabricated by a conventional Cu-mold casting method in air atmosphere. The critical cooling rate for glass formation was estimated on the order of magnitude of approximately 1 K/s. When compared with the GFA of Mg65Cu25Y10 alloy, the significantly improved GFA of Mg65Cu25Gd10 alloy cannot be explained by ΔTx and Trg values.

A two-step heating schedule involving pulse electric current sintering, a kind of pressure-assisted vacuum sintering, and a subsequent postsintering in air was used to fabricate sintered porous alumina compacts. During pressure-assisted vacuum sintering, a dense microstructure of the Al2O3–C system was obtained and in the second stage (i.e., during postsintering in air at different temperatures ranging from 800 to 1300 °C for more than 10 h) carbon particles present in the Al2O3–C system burned out to form a highly porous Al2O3 compact. In this work, the porosity (30%) was successfully controlled and did not change with the postsintering temperature. The intriguing aspect of this study is that porous alumina compacts are fabricated with high strength and remain stable against the postsintering temperature and extended soaking time. This behavior merits the material fabricated here as a potential porous compact, mechanically withstanding for high-temperature applications.

Mechanical alloying using a high-energy ball milling technique was used to fabricate a single glassy phase of Zr70Pd20Ni10 alloy powders after 100 h milling time. Annealing the glassy powders at a temperature just below the crystallization onset temperature led to thermally enhanced devitrification and the formation of a metastable big-cube phase with a lattice constant of 1.2289 nm. The same metastable phase was obtained upon subjecting the end product of the glassy powders to further ball milling time (150 h). This metastable big-cube phase could no longer withstand the shear and impact stresses generated by the milling media and transformed into a new metastable phase of face-centered cubic Zr70Pd20Ni10. The lattice constant of this metastable phase was calculated to be 0.56838 nm. These metastable phases are new and have never been, so far as we know, reported for the ternary Zr–Pd–Ni system or its binary phase relations.

The reaction mechanism between electroless Ni–P and Sn was investigated to understand the effects of Sn on solder reaction-assisted crystallization at low temperatures as well as self-crystallization of Ni–P at high temperatures. Ni3Sn4 starts to form in a solid-state reaction well before Sn melts. Heat of reaction for Ni3Sn4 was measured during the Ni–P and Sn reaction (241.2 J/g). It was found that the solder reaction not only promotes crystallization at low temperatures by forming Ni3P in the P-rich layer but also facilitates self-crystallization of Ni–P by reducing the transformation temperature and heat of crystallization. The presence of Sn reduces the self-crystallization temperature of Ni–P by about 10 °C. The heat of crystallization also decreases with an increased Sn thickness.

The Debye temperature and glass transition temperature of a variety of bulk metallic glasses (BMGs) were determined by acoustic measurement and differential scanning calorimetry, respectively. The relationship between the Debye temperature and glass transition temperature of these BMGs was analyzed, and their observed correlation was interpreted in terms of the characteristics of the glass transition in BMGs.