In this work, Ti pellets were selected as a model system to investigate the influences of oxygen impurity in nitrogen gas on the reaction of a metal with the nitrogen. Analyzing changes in the in situ oxygen partial pressures when titanium specimens were annealed in the oxygen-containing nitrogen shows that the dissolution of oxygen in Ti and TiNx is exothermic, and the solubility decreases as the temperature increases. X-ray diffraction results show that nitridation of Ti occurred before oxidation, even in an oxygen-containing nitrogen atmosphere. Kinetics apparently predominates over thermodynamics at low temperatures in such a system.

Gold-coated polystyrene (PS) beads were fabricated by an in situ metallization route involving a cationic-gold complex with a controlled amount of sulfonic acid groups formed on the PS bead surface. The interaction ratio of SO3− to [Au(phen)Cl2]+ may be estimated to be 2.4, which means that 2.4 sulfonated groups will interact with one gold cationic ligand based on geometric considerations. A modeling methodology was developed to predict the mechanical deformation, conductivity, and contact surface area of a spherical bead under compression.

We investigated the epitaxial growth of CoSi2 (100) on an Si (100) substrate using a modified oxide mediated epitaxy (OME) method to overcome the disadvantages of the OME method. These disadvantages are sensitivity of Co films to contamination by oxygen and the need for reiterating the film growth process to obtain thicker films. To solve these problems, nitrogen atoms were incorporated into chemically grown oxide (SiOx) by NH3 plasma treatment prior to the deposition of a Co film on the oxynitride buffer layer using the metal organic chemical vapor deposition (MOCVD) method. Subsequently, ex situ rapid thermal annealing was performed to grow Co-silicide at a temperature between 400 °C and 700 °C for 1 min. The results show that the diffusion of Co was effectively controlled by the oxynitride buffer layer without the formation of additional SiOx in between Co and Si. Our findings indicate that by using an oxynitride buffer layer, CoSi2 films can be grown epitaxially despite the fact that the initial Co film was exposed to oxygen.

Low solubility dopant-host systems are well suited to study secondary phase segregation-microstructure dependence. We discuss the effect of microstructure on secondary phase segregation in epitaxial/oriented ZnO thin films with Cr as an unfavorable dopant (Cr:ZnO). Since differences in thin film microstructure are a function of the substrate and its orientation, simultaneous chemical vapor depositions were carried out on single crystals of Si (100), c-axis oriented Al2O3 (c-ALO), and r-axis oriented Al2O3 (r-ALO) resulting in epitaxial film growth on r-ALO and c-axis oriented film growth on Si and c-ALO, with a difference in vertical grain boundary density. To enhance the analysis sensitivity to the microstructure difference, the thickness of Cr:ZnO films was maintained at ∼50 nm. High-resolution transmission electron microscopy (HRTEM) analysis indicates uniform stress distribution in Cr:ZnO grown on r-ALO. Surface sensitive x-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (TOF-SIMS) techniques were utilized for analysis of the data. We observe that a higher grain boundary density and the presence of an amorphous layer at the interface for films grown on Si(100) single crystal led to interfacial Cr-based secondary phase segregation as opposed to lower grain boundary density and epitaxial films grown on c-ALO and r-ALO single crystals, respectively. We also discuss the effects of trace carbon solubility on the film microstructure/secondary phase segregation relationship.

The effect of electropulsing treatment (EPT) on the microstructure and mechanical properties of aged Mg-9Al-1Zn alloy strip was studied. EPT was found to accelerate tremendously the β phase spheroidization in the aged Mg-9Al-1Zn alloy. This improved microstructure exhibits excellent mechanical properties, that is, increasing elongation to failure significantly without loss of tensile strength. The spheroidization of the β phase during EPT was attributed to the reduction of the nucleation thermodynamic barrier and enhancement of atomic diffusion.

A modified heat treatment process designated quenching–partitioning–tempering (Q–P–T) process is developed based on the quenching and partitioning process proposed by J.G. Speer et al. [Acta Mater.51, 2611 (2003)] and D.K. Matlock et al. [Mater. Sci. Forum426–432, 1089 (2003)]. A Fe–0.485C–1.195Mn–1.185Si–0.98Ni–0.21Nb steel after Q–P–T process satisfies the designed requirement of tensile strength over 2000 MPa and elongation over 10%. The microstructure characterization indicates that this ultrahigh-strength steel consists of nanomicrostructures including lath martensite, filmlike retained austenite, and dispersive Nb-containing carbides. The effect of tempering time on the mechanical properties is analyzed based on microstructures.

The constraint factor, C (given by the hardness-yield strength ratio H/Y in the fully plastic regime of indentation), in metallic glasses, is greater than three, a reflection of the sensitivity of their plastic flow to pressure. Furthermore, C increases with increasing temperature. In this work, we examine if this is true in amorphous polymers as well, through experiments on amorphous poly(methyl methacrylate) (PMMA). Uniaxial compression as well as spherical indentation tests were conducted in the 248–348 K range to construct H/Y versus indentation strain plots at each temperature and obtain the C-values. Results show that C increases with temperature in PMMA as well. Good correlation between the loss factors, measured using a dynamic mechanical analyzer, and C, suggest that the enhanced sensitivity to pressure is possibly due to β-relaxation. We offer possible mechanistic reasons for the observed trends in amorphous materials in terms of relaxation processes.

In this article, we report on enhanced broadband near-infrared emission in Yb–Bi codoped phosphate glasses. The emission intensity of Yb–Bi codoped glass was ˜32 times larger than that of Bi-doped glass when excited with 980-nm laser diode. The highest 1/e fluorescent lifetime of Yb–Bi codoped glass reached 1650 μs. The dependence of emission intensity and fluorescent lifetime on Yb2O3 concentration was investigated. The enhancement of the near-infrared emission is due to energy transfer from Yb3+ (2F5/2–2F7/2) transition to Bi ions, and the highest energy transfer efficiency reached 50%. Yb–Bi codoped phosphate glass should be a promising candidate for broadband optical amplification.

A simple approach, order–disorder transition (ODT), has been developed to synthesize a novel glass using ZSM-5 as starting materials. In this process, the ZSM-5 powders were pressed uniaxially in a graphite die and rapidly sintered using spark plasma sintering (SPS). High-resolution transmission electron microscopic images revealed that a few crystalline zeolite fragments were still preserved locally inside the SPS consolidated sample. Vickers microhardness and fracture toughness of this as-prepared transparent glass sample at room temperature reaches 7.3 ± 0.2 GPa and 2.0 ± 0.3MPa·m1/2, respectively. It is very interesting that these novel bulk transparent glasses exhibit ultraviolet photoluminescence (PL) properties at about ∼360 nm.

An n-body Ni–Nb–Ta potential is constructed to conduct molecular dynamics simulations using 129 solid solution models with various compositions. Comparing the relative stability of solid solutions versus their disordered counterparts, simulations determine two critical solid-solubility lines, which define a region in the composition triangle. If an alloy is located inside the defined region, a disordered state is energetically favored; if it is located outside, a crystalline solid solution is preserved. The region is therefore named as the metallic glass-forming region.

Tarnishing film was developed on the brass surface in Mattsson's solution at room temperature. The filmed brass was removed from the solution, dried, and subjected to a slow strain rate (loading speed = 0.5 mm/min) in air for studying the effect of the film on crack propagation in the brass substrate. It was observed that initial cracks started to emerge in the film and then propagated to the brass matrix in a brittle intergranular manner. However, it changed into a ductile mode after removing the deposited film. The galvanic current between platinum wire and filmed brass sample in Mattson's solution was investigated. The results showed that periodic current fluctuations were observed when the sample was under a constant applied load. These observations showed that the film rupture-formation occurred at cracks under the stress-corrosion cracking condition.

Commercial-grade dense Ti-6Al-4V alloy substrate was mechanically roughened, cleaned, and treated with a globular protein [bovine serum albumin (BSA)] for 4 h. Biomimetic calcium phosphate (Ca-P) coating was applied onto the above-treated substrate by immersion into simulated body fluid (SBF) at 25 °C for a period of 4 days, with periodic replacement by freshly prepared SBF at 48-h intervals. After 4 days, branched micron-sized fibers of hydroxyapatite (HAp), resembling the structure of bone, were obtained, connecting the clusters of HAp crystal plates in the coating (thickness ∼200 μm) on the substrate surface. Structural and compositional characterization of the coating was carried out using field emission scanning electron microscopy (FE-SEM) with energy-dispersive x-ray analysis unit (EDX) facility, x-ray diffraction (XRD), and Fourier transform infrared (FTIR) data. In vitro cytotoxicity (ISO 10993-5, 1999), cell adhesion assays, and phase contrast microscopy were performed using NIH 3T3 fibroblast cell lines to ascertain the bioactivity of the coated substrates, with and without protein treatment. Based on our study, we propose a correlation between a specific physical structure of the HAp coating and its biological properties.

Antiferroelectric (AFE) Pb0.92La0.08Zr0.95Ti0.05O3 (PLZT) films were grown on nickel foils with lanthanum nickel oxide buffer by chemical solution deposition. We observed field-induced AFE-to-ferroelectric (FE) phase transition. The electric field for the AFE-to-FE phase transition (EAF ≈ 270 kV/cm) and that for the reverse phase transition (EFA ≈ 230 kV/cm) were measured at room temperature on samples with PLZT films of ≈1-µm thickness. Relative permittivity of ≈560 and dielectric loss of <0.05 were measured near zero DC bias field. Hysteresis loop analysis showed that energy densities of ≈53 and 37 J/cm3 can be stored and recovered from the film-on-foil capacitors at 25 and 150 °C, respectively. Highly accelerated life tests were conducted. The projected mean time to failure is >5000 h when the capacitors are operated at room temperature with an applied field of ≈300 kV/cm.

Pb(Mg1/3,Nb2/3)O3-PbTiO3 (PMN-PT, 43% PT) thin films have been developed by modified sol-gel processing with polyvinylpyrrolidone (PVP) as a modifier and lead nitrate as a lead source. With PVP modification, perovskite phase was directly crystallized from amorphous film matrix at a temperature as low as 430 °C, and the crystallinity was significantly enhanced. Kinetics studies show that the crystallization process is controlled by heat transfer phenomena at the annealing temperatures ≤460 °C. At higher annealing temperatures (550–700 °C), it is a diffusion-controlled reaction with an activation energy of 167.7 kJ/mol, almost two times lower than that for the films without PVP modification. The promotion mechanism of perovskite crystallization by PVP addition has been discussed accordingly. The resultant films consisted of nanocrystallines and exhibited relaxor-like dielectric behavior, although the composition of the films located in normal ferroelectrics.

Magnesium alloys are potential materials in biodegradable hard tissue implants. Their degradation products in the physiological environment not only affect the degradation process but also influence the biological response of bone tissues. In the work reported here, the composition and structure of the corrosion product layer on AZ91 magnesium alloy soaked in a simulated physiological environment, namely simulated body fluids (SBFs), are systematically investigated using secondary electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD), and in situ monitoring of the corrosion morphology. Our results show that the corrosion product layer comprises mainly amorphous magnesium (calcium) phosphates, magnesium (calcium) carbonates, magnesium oxide/hydroxide, and aluminum oxide/hydroxide. The magnesium phosphates preferentially precipitate at obvious corrosion sites and are present uniformly in the corrosion product layer, whereas calcium phosphates nucleate at passive sites first and tend to accumulate at isolated and localized sites. According to the cross sectional views, the corrosion product layer possesses a uniform structure with thick regions several tens of micrometers as well as thin areas of several micrometers in some areas. Localized corrosion is the main reason for the nonuniform structure as indicated by the pan and cross-sectional views. The results provide valuable information on the cytotoxicity of magnesium alloys and a better understanding on the degradation mechanism of magnesium alloys in a physiological environment.

Under ambient pressure, an aqueous solution may not enter the nanopores of a hydrophobic ZSM-5 zeolite, which imposes difficulties to cation-exchange treatment. In the current study, a high-pressure cation-exchange technique is developed. With a relatively short treatment time, the degree of hydrophobicity is significantly increased.

Carbon nanofibers (CNFs) with different microstructures were synthesized by thermal chemical vapor deposition using different growth temperatures and methane/nitrogen gas mixtures. High-resolution transmission electron microscopy images revealed that bamboolike structure could be formed both by increasing the growth temperature and by increasing the nitrogen content in the reaction atmosphere at a lower growth temperature. Elemental analysis results indicated that no significant change in the nitrogen concentration was found regardless of the increase of nitrogen flow in the feed gas. The formation of bamboolike structure of CNFs and the effect of nitrogen gas on the microstructure change of CNFs were discussed.

Decreasing scales effectively increase nearly all important mechanical properties of at least some “brittle” materials below 100 nm. With an emphasis on silicon nanopillars, nanowires, and nanospheres, it is shown that strength, ductility, and toughness all increase roughly with the inverse radius of the appropriate dimension. This is shown experimentally as well as on a mechanistic basis using a proposed dislocation shielding model. Theoretically, this collects a reasonable array of semiconductors and ceramics onto the same field using fundamental physical parameters. This gives proportionality between fracture toughness and the other mechanical properties. Additionally, this leads to a fundamental concept of work per unit fracture area, which predicts the critical event for brittle fracture. In semibrittle materials such as silicon, this can occur at room temperature when the scale is sufficiently small. When the local stress associated with dislocation nucleation increases to that sufficient to break bonds, an instability occurs resulting in fracture.

LiBH4/Al mixtures with various mol ratios were prepared by ball milling. The hydrogen storage properties of the mixtures were evaluated by differential scanning calorimetry/thermogravimetry analyses coupled with mass spectrometry measurements. The phase compositions and chemical state of elements for the LiBH4/Al mixtures before and after hydrogen desorption and absorption reactions were assessed via powder x-ray diffraction, infrared spectroscopy, and x-ray photoelectron spectroscopy. Dehydrogenation results revealed that LiBH4 could react with Al to form AlB2 and AlLi compounds with a two-step decomposition, resulting in improved dehydrogenation. The rehydrogenation experiments were investigated at 600 °C with various H2 pressure. It was found that intermediate hydride was formed firstly at a low H2 pressure of 30 atm, while LiBH4 could be reformed completely after increasing the pressure to 100 atm. Absorption/desorption cycle results showed that the dehydrogenation temperature increased and the hydrogen capacity degraded with the increase of cycle numbers.

Polycrystalline manganites within the compositional variation La0.72(Ca1−xSrx)0.28MnO3 (x = 0, 0.25, 0.50, 0.75, 1.0) were synthesized by solid-state reaction method. An initial orthorhombic structure was observed at x = 0, with a subsequent change to rhombohedral structure for x ≥ 0.25. The Curie temperature of the compounds exhibited a marked dependence with the Sr content, with general variations between 190 K (x = 0) and 364 K (x = 1.0), while the saturation magnetization at room temperature showed a small variation between the range 0.30 and 0.38 T. The magnetocaloric effect, measured through heat capacity experiments, showed a maximum entropy variation of −2.56 J/kg · K at x = 0.25, besides a maximum adiabatic temperature variation of 1.13 K. Results are interpreted in terms of the structural transition observed and its effect on the radius of the A-site of the perovskite structure.