R2MoO6:Eu3+ (R = Gd, Y, La) phosphors were prepared by the Pechini sol-gel process. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), reflectance spectra, photoluminescence (PL) spectra, and lifetimes were used to characterize the resulting phosphors. The results of XRD indicate that all of the R1.96Eu0.04MoO6 (R = Gd, Y, La) phosphors crystallized completely at 800 °C. Y1.96Eu0.04MoO6 and Gd1.96Eu0.04MoO6 are of isomorphous monoclinic (α) structure, while La1.96Eu0.04MoO6 preferentially adopts the tetragonal (γ) form. FE-SEM study reveals that the samples mainly consist of aggregated particles with an average grain size ranging from 100 to 250 nm. The luminescent properties of R2MoO6:Eu3+ (R = Gd, Y, La) phosphors are largely dependent on their structure, grain size, and powder morphology. The isomorphous Y2MoO6:Eu3+ and Gd2MoO6:Eu3+ phosphors show very similar luminescence properties, which differ greatly from that of the La2MoO6:Eu3+ phosphor.

The thermal stability of amorphous Zr:Al mixed oxide films of different composition, produced on (001) silicon wafers by the atomic layer deposition method is studied by transmission electron microscopy during in situ heating experiments. The temperatures at which phase separation and crystallization occur are composition dependent. The crystallization of thick films (55–70 nm), deposited on HF-treated silicon surfaces covered with a 15 cycles Al2O3 layer, results in the formation of cubic ZrO2 and cubic γ–Al2O3. In very thin films (5 nm), deposited on silicon surfaces covered with a 0.5 nm SiO2 thin film, the formation of tetragonal zirconium disilicide (ZrSi2) is observed in the microscope vacuum, at temperatures above 900 °C. This effect depends on the thickness of the as deposited thin film.

A new type of bioactive materials, hydroxyapatite (HA)/α-wollastonite (α-Wol) composites, were prepared. The sintering behavior, phase evolution, and in vitro bioactivity of hydroxyapatite/α-wollastonite composites were examined. The properties of HA/α-Wol composites were quite different from those of HA ceramics or α-Wol ceramics. HA/α-Wol composites sintered 1300 °C for 2 h exhibited a dense microstructure consisting of grains in the range of 0.3–1.0 μm in diameter. During sintering, a complex phase evolution between HA and α-Wol was observed. At 1300 °C, the formation of the Si substituted HA and the additional α-tricalcium phosphate (TCP) were observed using Fourier transform infrared and x-ray diffraction analysis. Further heat treatment at 1350 °C transformed part of the HA and α-Wol into a new phase with the composition: Ca12P6Si2O31. The in vitro bioactivity of the HA/α-Wol composites with a weight ratio of 25:75 and 50:50 sintered at 1300 °C was better than that of α-Wol monophasic ceramics. This result revealed that the silica of α-Wol and the orthosilicate of Si substituted HA provided nucleation sites for the bonelike apatite layer. The phosphate present in the HA or α-TCP phases promoted the nucleation of a bonelike apatite layer on the surface of the composites. The dissolution rate of α-Wol phase in simulated body fluid was faster than α-TCP or HA phase. Therefore, HA/α-Wol composite is the bone replacement material of controllable bioactivity and degradation rate with relative content between HA and α-Wol phase.

Cone-shaped nanostructures of mixed composition (nanocones) and largely graphitic nanofibers were synthesized on silicon substrates using iron/platinum alloy nanoparticles as the catalyst in a direct-current plasma enhanced chemical vapor deposition reactor. The catalyst nanoparticles were monodisperse in size with an average diameter of 3 (±1) nm. The nanocones were produced on laterally widely dispersed catalyst particles and were oriented perpendicular to the substrate surface with an amorphous internal structure. The nanocones were produced by gas phase mixing and deposition of plasma-sputtered silicon, nitrogen, carbon, and oxygen species on a central backbone nucleated by the Fe–Pt catalyst particle. Field emission measurements showed that a very high turn-on electric field was required for electron emission from the nanocones. In contrast, the graphitic nanofibers that were produced when silicon sputtering and redeposition were minimized had the “stacked-cup” structure, and well-defined voids could be observed within nanofibers nucleated from larger catalyst particles.

Thin film specimens of austenitic 304 stainless steel implanted with 100 keV Xe ions at room temperature were investigated. Microstructural evolution and phase transformation were characterized and analyzed in situ with conventional and high-resolution transmission electron microscopy. The phase transformation in a sequence from austenitic γ face-centered cubic (fcc) to hexagonal close-packed (hcp), and then to a martensitic α body-centered cubic (bcc) structure was observed in the implanted specimens. The fraction of the induced α(bcc) phase increased with increasing Xe ion fluence. Orientation relationships between the induced α(bcc) phase and austenitic γ(fcc) matrix were determined to be (011)α//(111)γ and [111]α//[011]γ. The relationship was independent of the induced process of the martensitic phase transformation for austenitic 304 stainless steel specimen, in agreement with the Kurdjumov–Sachs (K-S) rule. It is suggested that the phase transformation is induced mainly by the formation of the highly pressurized Xe precipitates, which generate a large stress level in stainless steels.

Catalytic synthesis of spindle-type hematite particles was studied for the first time under the conditions of boiling reflux and pH values ranging from 4 to 7, using Fe2(SO4)3 and NaOH as raw material, a trace amount of FeSO4 as the catalyst, and NaH2PO4 as the growth-regulating agent. The final products were characterized by x-ray diffraction, high-resolution electron microscopy, scanning electron microscopy, and Fourier transform infrared techniques. Primarily, the catalytic effect of ferrous ion on the conversion of ferric hydroxide was investigated. It was found that the addition of a trace amount of ferrous ion promoted fast conversion of ferric hydroxide and remarkably accelerated the transformation process to hematite. The reaction conditions affecting the conversion rate and morphologies in the presence of trace amount of ferrous ion were investigated. The final particles prepared had the characteristics of controlled size, a narrow particle size distribution, and good reproducibility.

Nanocrystalline magnetite powders were synthesized by an electrocoagulation technique, in which an electric current was passed across two plate electrodes of carbon steel immersed in NaCl(aq) electrolyte, and the microstructure of the oxide powder was found to evolve in roughly three stages. The first stage involves formation and growth of severely defective colloidal crystallites. This is followed by agglomeration among the oxide crystallites to form mesoporous agglomerates containing predominantly inter-crystallite pores, and the average crystallite size was found to reach a plateau. Finally, coarsening of the crystallites within the agglomerates leads to another rapid increase in crystallite size and reduction in pore opening. The synthesized powders typically showed a saturation magnetization of ∼75 emu/g and a coercivity Hc of ∼118 Oe. A mechanism involving competition between nucleation and growth of free colloids and coarsening of the skeletal framework was proposed to explain the temporary level-off in crystallite size during the synthesis.

A stable mesoporous multilamellar silica vesicle (MSV) was developed with a gallery pore size of about 14.0 nm. A simulative enzyme, hemoglobin (Hb), was immobilized on this newly developed MSV and a conventional mesoporous silica material SBA-15. The structures and the immobilization of Hb on the mesoporous supports were characterized with x-ray diffraction, transmission electron microscopy, N2 adsorption-desorption isotherms, Fourier transform infrared, ultraviolet-visible spectroscopy, and so forth. MSV is a promising support for immobilizing Hb due to its large pore size and high Hb immobilization capacity (up to 522 mg/g) compared to SBA-15 (236 mg/g). Less than 5% Hb was leached from Hb/MSV at pH 6.0. The activity study indicated that the immobilized Hb retained most peroxidase activity compared to free Hb. Thermal stability of the immobilized Hb was improved by the proctetive environment of MSV and SBA-15. Such an Hb-mesoporous support with high Hb immobilization capacity, high activity, and enhanced thermal stability will be attractive for practical applications.

A unique combination of in situ synchrotron x-ray diffraction and in situ micro-Raman spectroscopy was used to study the growth process of YBa2Cu3O6+x films obtained by metal organic decomposition using trifluoroacetate precursor on LaAlO3 substrates. The techniques give complementary information: x-ray diffraction gives insight into the structural growth, whereas micro-Raman spectroscopy gives information of the chemical composition with additional information on the texture. To perform both experiments in situ, a special high-temperature process chamber was designed.

It was found that directional coarsening was induced by phase transformation stress due to non-uniform distribution of μ phase in an experimental nickel-based superalloy. The mechanism based on the existing diffusion and coherency strain energy theory has been discussed. It was concluded that directional coarsening was the course of dissolving of γ′ portion with high free energy, diffusing and growing on the existed γ′ particles along a preferential direction.

Y2O3:Eu nanophosphors were prepared by flame synthesis using ethanol or water as precursor solutions. The effects of precursor solvents and flame temperature on particle size, morphology, and photoluminescence intensity were investigated. The results showed that flame synthesis using ethanol solution could produce nanoparticles with better homogeneity, smoother surface structure, and stronger photoluminescence intensity than using water. It was found that the concentration quenching limit of the as-prepared nanophosphors from both ethanol and water solution was 18 mol% Eu, which is higher than the reported limit at similar particle size. The x-ray diffraction (XRD) spectra showed that the ethanol precursor solvent produced monoclinic phase Y2O3:Eu nanoparticles at a lower flame temperature than previously reported. It was also shown that the particle size could be controlled by varying the precursor concentration and flame temperature.

Researchers have constructed a number of DNA-based nanodevices that undergo stepped configuration changes through the application of single-stranded DNA oligomers. Such devices can be incorporated into gel networks to create new classes of active materials with controllable bulk mechanical properties. This concept was demonstrated in a DNA-crosslinked gel, the stiffness of which was modulated through the application of DNA strands. Each crosslink incorporated a single-stranded region to which a DNA strand with a complementary base sequence (called the fuel strand) bound, thereby changing the nanostructure of the gel network. The gel was restored to its initial stiffness through the application of the complement of the fuel strand, which cleared the fuel strand from the crosslink via competitive binding. Stiffness changes in excess of a factor of three were observed. The ability to switch the mechanical properties of these gels without changing temperature, buffer composition, or other environmental conditions, apart from the application of DNA, makes these materials attractive candidates for biotechnology applications.

We studied the devitrification kinetics for the binary (80GeS2–20Ga2S3, mol%) and ternary (77GeS2–15Ga2S3–6CsI, mol%) glass compositions using the differential thermal analysis (DTA) technique. The overall activation energies for devitrification for these two types of glasses were determined by using the Kissinger method and the Johnson–Mehl–Avrami equation from the DTA data. The t-t-t curves were calculated using the activation energy for devitrification for each composition derived from the DTA experiments. The experimental evidences have shown that the incorporation of SnS2 and Sb2S3 in a ternary-based GeS2 glass slows down the overall devitrification rate significantly, which is confirmed by the reduction in the overall area under the crystallization exotherm.

The crystallization mechanisms for potentially high mobility molybdenum-indium-oxide (IMO) film were studied. The crystalline IMO films were deposited on unheated glass substrates via high-density plasma evaporation, and subsequent vacuum annealing was performed at 150, 200, and 250 °C for 30 min. The results of x-ray diffraction and x-ray photoelectron spectroscopy and electrical properties suggested that the room-temperature crystallization was induced from the highest compressive strain, caused by the charged clusters and oxygen vacancies. The highest mobility of 75.8 cm2/Vs obtained at 250 °C was due to the charged In–Mo+6–O clusters and strain relaxation with (222)/(440) orientation change.

A two-step replication strategy to two-dimensional ordered polymer hollow sphere and convex structure arrays is presented based on polystyrene colloidal monolayer and inverse opal made of FeO(OH). We can control formation of a small hole on top of the hollow spheres by the concentration of polymer precursors, which could be of importance in selective permeability, nutrient and drug deliver, biotechnology, and even study of black-body irradiation in micro or nano space. In addition, the fabrication strategy is suitable for the most soluble polymer materials, which can solidify when they are concentrated.

In this work, we performed infrared reflectivity measurements of RETiTaO6 dielectric ceramics for rare-earth (RE) = Y, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, and Yb. The infrared spectra were analyzed through the four-parameter semi-quantum model based on two orthorhombic (aeschynite and euxenite) structures presented by the ceramics. We discerned the strongest phonon modes that contribute to the intrinsic dielectric behavior of the two families. Then the unloaded quality factors and the dielectric permittivities were estimated at the microwave region. The variations of the intrinsic dielectric response of both systems with RE ion substitution are discussed in terms of changes in their dielectric polarizabilities. It is proposed that the covalency of the RE–O bonds play an important role in the evolution of dielectric permittivity as well as in the sign of the temperature coefficient of the resonant frequency.

A new Mg–Cu–Ni–Ag–Zn–Y–Gd alloy with significantly improved glass forming ability (GFA) was developed in this work. Mg65Cu7.5Ni7.5Ag5Zn5Y5Gd5 bulk metallic glass (BMG) with a diameter of 14 mm was successfully fabricated by conventional copper mold casting method in air atmosphere. The critical cooling rate for glass formation was estimated to be about 20 K/s. When the maximum diameter for glass formation was compared with those previously reported for Mg-based alloys, the Mg65Cu7.5Ni7.5Ag5Zn5Y5Gd5 alloy showed the highest GFA. However, when the GFA was compared with those of Mg-TM-RE alloys (TM: Cu, Ni, Zn, and Ag; RE: Y and Gd), the significant improved GFA of the Mg–Cu–Ni–Zn–Ag–Y–Gd alloy cannot be properly represented by ΔTx, Trg, K, and γ parameters. In contrast to most of the Mg-based BMGs reported so far, the Mg65Cu7.5Ni7.5Ag5Zn5Y5Gd5 BMG exhibits yielding and plastic deformation during compressive loading.

A splat-quenched, thick Al–Si deposit was manufactured by low-pressure plasma spraying (LPPS) and investigated in terms of microstructural inhomogeneity, Si solid solubility in α–Al, formation of metastable phases, and thermal stability. The LPPS Al–Si deposit had an inhomogeneous, layered microstructure consisting of splat-quenched lamellae and the incorporation of unmelted or partially melted particles. The splat-quenched Al–Si lamellae were formed by deposition of a fully liquid droplet and had an almost featureless microstructure at relatively low magnifications. There was a significant reduction in the α–Al lattice parameter in the LPPS Al–Si deposit because of extended Si solubility in the α–Al matrix. Transmission electron microscopy investigations showed that the splat quenching of liquid Al–Si droplet led to (i) columnar grain growth of α–Al(Si), (ii) formation of nano-sized Si precipitates in the Al matrix which was supersaturated with Si; and (iii) formation of amorphous Si phase embedded in the crystalline Al matrix. On reheating, the amorphous Si transformed into fine crystalline Si by interdiffusion of Al and Si atoms. Simultaneously, Si precipitation occurred in the supersaturated α–Al matrix. The overall activation energy for the Si crystallization/precipitation was estimated as ∼81 kJ/mol from a modified Kissinger analysis.

The evolution of nearly dense stoichiometric silicide compacts via powder processing is presented in this paper. For specific single-phase Mo(Si,Al)2 compacts, room-temperature environmental degradation, phenomenologically similar to the pesting behavior of binary MoSi2 was observed. This degradation occurs over a series of a few months and results in grain boundary decohesion, which leads to crumbling of polycrystalline compacts in air at room temperature. Auger electron spectroscopy, transmission electron microscopy, and energy dispersive spectroscopy of the boundaries revealed the presence of an array of lens-shaped particles each comprised of silicon carbide and aluminum. The reaction of these phases with atmospheric species was accelerated by the presence of humidity. The trace presence of carbon was unavoidable due to the use graphite pressing dies. Alloying additions were made to tie up carbon by forming more stable carbides while maintaining the desired matrix phase stoichiometry. The pest phenomenon and alloying remedy were proven applicable to other silicide systems through experimentation and ThermoCalc modeling.

The indentation behavior of cold-rolled AA6061 Al alloy was investigated. Following the approach suggested by Tabor, indentation stress–indentation strain curves were constructed and analyzed. The indentation stress required to create the same indentation strain increases with an increase in the reduction of thickness, suggesting a strong effect of plastic deformation history on the deformation behavior of materials. Through the dislocation dynamics, the evolution of the dislocations underneath the indentation was correlated with the plastic deformation history and the indentation load. The plastic energy dissipated in indentation was then calculated and found to be proportional to the 3/2 power of the indentation load and the 3/4 power of the average dislocation density underneath the indentation. The ratio of the dissipated plastic energy to the total energy in the indentation was demonstrated to be a function of the deformation state in materials, independent of the indentation load.