Phase transformations in SnAg–Ni80P20 films were studied ex situ in parallel with in situ measurements of the corresponding transformation-induced stresses. Layered formation of Ni3Sn4 and Ni3P phases at an early stage of a reaction between SnAg and Ni80P20 films resulted in a tensile stress similar to the stress evolution in Sn–Ni80P20 films, despite the additional formation of Ag3Sn phase. Ag3Sn phase did not significantly affect the degree of stress evolution because of its islandlike and sporadic formation on the top surface of the Ni3Sn4 layer. Isothermal annealing showed that compressive stress, which was induced by the dominant formation of Ni3Sn4, developed after an initial evolution of tensile stress.

Zr–N films were grown on glass and Si (100) substrate by radio-frequency magnetron sputtering using a mixture of high pure nitrogen and argon as sputtering gases. The structure and properties of Zr–N compounds in the films change with N2/(N2+Ar) flow ratio (RN2). At low RN2, a ZrN alloy with the rocksalt structure (denoted as γ-ZrNx) is formed. The N concentration x and lattice constant increases with increasing RN2, and x reaches 1 when the RN2 goes up to 20%. As the RN2 exceeds 20%, the film is composed of γ-ZrN and Zr3N4 phase with Th3P4 structure (denoted as c-Zr3N4). The relative content decreases for the γ-ZrN but increases for the c-Zr3N4 with increasing RN2, and a single phase of c-Zr3N4 was deposited on glass at RN2 of 100%. The c-Zr3N4 behaves with p-type conductivity with a band gap of 2.8 eV. The lattice constant of the c-Zr3N4 was measured to be ∼0.674 nm. The mechanism of the phase transition from γ-ZrN to c-Zr3N4 with increasing RN2 was suggested.

A method allowing for the stable growth of carbon nanotubes (CNTs) on the surface of a fibrous metal mesh substrate (SUS304) was developed with the assistance of the microwave plasma-enhanced chemical vapor deposition process. The controlled addition of up to ∼13% of O2 to the CH4 plasma reacting gas flow was found to promote the growth of the CNTs by oxidizing the amorphous carbon and removing the active H2 radicals. However, excessive amounts of O2 (i.e., fraction of O2 > ∼13%) and H2 were found to play a negative role in the growth of the CNTs. The control of the density and length of the CNTs was also achieved by varying the H2 plasma reduction time and CH4 plasma reacting time, respectively. Longer H2 reduction pretreatment of the catalytic metal islands resulted in the formation of a less dense CNT forest with craters. When the growth time of the CNTs was increased to ∼20 min, their length was increased to ∼10 μm. However, when the growth time of the CNTs exceeded 20 min, their length was significantly decreased, indicating that the continuous presence of O2 in the CH4 plasma destroys the preformed CNTs due to the oxidation reaction.

We report the realization of the p-type conductivity and the enhancement of the photoluminescence (PL) intensity in undoped ZnO films treated with high-energy (1 MeV) electron-beam irradiation (HEEBI), suggesting that the HEEBI process is compatible with a low-temperature requirement for the fabrication of transparent thin film transistors with good efficiency on a plastic substrate. The p-type conductivity of the films was revealed by the Hall, x-ray photoelectron spectroscopy, and PL measurements after being electron-irradiated in air at room temperature. The major acceptor-like defects were determined to be oxygen interstitial and zinc vacancy. A model was proposed in terms of O as well as Zn diffusion to explain the observed results. It was also observed that HEEBI treatment has little influence on the optical transmittance of ZnO films, whereas HEEBI treatment shifts the optical band gap toward the lower energy region from 3.29 to 3.28 eV.

In this work, the correlation between magnetic-domain structure and microstructure in combined reaction-processed equiatomic L10 FePd has been investigated using magnetic force microscopy. The microstructure consisted of approximately equiaxed grains with an average grain size of ∼1 μm and a grain size distribution ranging from below the theoretical critical domain size (Dcrit∼0.2–0.3 μm) up to approximately 5 μm in diameter. The domain structure was characterized as “mixed” in nature, consisting of smaller single-domain grains, larger multidomain grains, and a larger scale interaction domain structure encompassing many grains. The domain boundaries separating interaction domains tended to lie along grain boundaries, and it is proposed that the observed interaction domains should be considered in descriptions of the magnetization and magnetization reversal behavior of this material. In particular, pinning of interaction domain walls by intragranular features of the microstructure such as grain boundaries and single-domain grains could play a role in the measured coercivities.

Under γ-irradiation, thiacetamide (TAA) releases S2− in acidic solutions (e.g., pH = 3), and the S2− can react with available Cd2+ in soft templates to form CdS nanorods. Single-crystalline CdS nanorods were prepared in this study. The effects of various synthesis parameters on the crystalline type, morphology, average particle size, and photoelectric properties were thoroughly investigated, including the concentrations of reactants, dose of irradiation, and the type and dosage of templates. The structure and selected physical and chemical properties of products were characterized by x-ray diffraction (XRD), Fourier transform infrared (FTIR), ultraviolet-visible (UV-vis), selected area electron diffraction (SAED), transmission electron microscopy (TEM), and photoluminescence (PL) spectrophotometer techniques. Results indicated that the ratio of reactants to templates greatly affected the morphology of CdS nanorods; the types of soft templates also had significant effects on the morphology and crystalline type of the nanorod products.

The effects of melt overheating treatment on solidification of Pb-Bi alloys were studied from the viewpoint of liquid-liquid structure change (LLSC). Anomalous temperature dependence of internal friction, electrical resistivity, and entropy of liquid Pb-Bi alloys suggested that discontinuous LLSC occurred within about 520–740 °C, based on which the solidification experiments were carried out with different states of Pb-Bi melts. The results revealed that the LLSC affected the solidification behavior and microstructures significantly, that is, the enlarged undercooling, increased nucleation rate, and refined and improved morphologies were brought about when solidifying from the melt experienced LLSC. It is assumed that the LLSC changed the energy constitution of the melt system, and further affected the effective partition coefficient, thermodynamics, and kinetics of crystal growth, then finally altered the solidification behavior and solidified microstructures. This work brings a novel insight into the effect of melt overheating treatment on solidification, by which it could be more effective to manipulate melts.

The results of positron lifetime and Doppler broadening spectrum of defects in the hydrogen charged non-heat treatable 5xxx Al alloys are presented in this work. The yield stress of the sample was reduced for about 20 MPa after hydrogen was charged. A similar trend was observed in positron lifetime measurement, as the average lifetime τav descended remarkably to almost the level of Al matrix. The change in coincidence Doppler broadening (CDB) spectroscopy was also significant, exhibited by the characteristic change in CDB radio curves of a sample before and after hydrogen was charged. After hydrogen charging, there is an obvious enhancement in the high momentum region compensating dehancement in the low momentum region. This indicates the existence of hydrogen filling effect. The vacancies around the Mg atoms should be preferential filling sites for hydrogen because Mg has a strong affinity for hydrogen. The formation of an Mg–H bond parallel to a grain boundary is an important factor in weakening the grain boundary cohesion.

Ti3SiC2 powder of about 96 wt% purity was produced using TiCx and Si powders. The synthesis process was characterized by an exothermic reaction at ∼985 °C and low activation energy (∼27 kJ/mol) of conversion. Almost complete conversion to Ti3SiC2 phase was observed during sintering. The onset temperature of sintering was found to be at about 1060 °C using dilatometer. The density of nearly 99% (theoretical) was achieved through the pressureless sintering of Ti3SiC2 powder by 1 and 2 wt% Si powder additions. The sample (without sintering aid) sintered at 1500 °C for 4 h showed uniformly distributed angular grains, whereas the bimodal nature of the microstructure was observed when Si was added as a sintering aid.

Correlated force and contact resonance versus displacement responses have been resolved using load-dependent contact-resonance atomic force microscopy (AFM) to determine the elastic modulus of low-k dielectric thin films. The measurements consisted of recording simultaneously both the deflection and resonance frequency shift of an AFM cantilever probe as the probe was gradually brought in and out of contact. As the applied forces were restricted to the range of adhesive forces, low-k dielectric films of elastic modulus varying from GPa to hundreds of GPa were measurable in this investigation. Over this elastic modulus range, the reliability of load-dependent contact-resonance AFM measurements was confirmed by comparing these results with those from picosecond laser acoustic measurements.

We report on the formation of ultrafine-grained Ti66Nb13Cu8Ni6.8Al6.2 composites with in situ precipitated micrometer-sized β-Ti(Nb) phase by spark plasma sintering with crystallization. Microstructure analysis indicated that all alloys consisted of soft (Cu, Ni)Ti2 regions surrounded by hard β-Ti(Nb) regions but displayed different microstructures. The alloys exhibited high fracture strength of more than 2200 MPa and remarkable plasticity of ∼25%. The results provided a promising method for fabricating large-sized bulk composites with excellent mechanical properties by powder metallurgy.

Nonlinear viscoelastic problems are in general not analytically solvable. However, it is shown here that, for any viscoelastic materials describable by a constitutive law with linear elastic and (in general) nonlinear viscous elements arranged in any network fashion, such as the Maxwell or standard linear solid arrangements, it is always possible to eliminate the viscous terms by replacing the displacement, strain, and stress fields of the problem by the jumps in rates of these fields. After the viscous terms are eliminated, the problem is reduced to a linear elastic problem defined on the same spatial domain and with the same elastic constant as in the original viscoelastic problem. Such a reduced elastic problem is analytically solvable in many practical cases, and the solution yields a relation between jumps in the load rate and the displacement rate, pertinent to the boundary conditions in the original problem. Such a relation can often be used as the basis for an experimental scheme to measure the elastic constants of materials. The material can be time- or strain-dependent, and the value of the elastic constant measured corresponds to the time instant or the strain value when the jump in load or displacement rate is implemented.

The electrospray of a colloidal microemulsion (ME) solution and subsequent on-line annealing were used to produce barium titanate nanoparticles (BTO-NPs). The solvent of the ME solution (cyclohexane) was replaced with a high-conductivity solution (solute: ammonium acetate, solvent: tetrahydrofurfuryl alcohol, conductivity: 3.1 × 10−2 S/m) to generate ultrafine droplets during the electrospraying. Well-dispersed and well-crystallized BTO-NPs with a perovskite structure were successfully fabricated at an annealing temperature of 1173 K. The size distribution of the BTO-NPs was successfully measured by applying a differential mobility analyzer and condensation nucleation counter to nanoparticles in-flight. The average size of the BTO-NPs was controlled within a range of 15 to 25 nm by changing the feeding rate. The electrospray of an ME solution with lower conductivity (solvent: 1-octanol, conductivity: 7.0 × 10−4 S/m) yielded amorphous particles with larger particle sizes. Thus, the electrospray of a high-conductivity solution is required to fabricate well-crystallized and dense BTO-NPs with smaller particle sizes.

The effect of porosity on the kinetics of the austenite to bainite isothermal transformation in powder metallurgy steels was characterized using a high-speed quenching dilatometer. The measurements revealed that the presence of porosity shortens the incubation time as well as the overall isothermal transformation time. An Avrami-type equation was fitted to the measured data, and the effect of porosity on the nucleation rate of bainite was quantified. In addition, the activation energy for diffusion of carbon atoms during nucleation of bainite was calculated and was found to decrease with increasing porosity.

Formation and evolution details of a two-phase coupled microstructure in AISI 304 stainless steel are studied by quenching method during directional solidification. Results show that the coupled growth microstructure, which is composed of thin lath-like ferrite (δ) and austenite (γ), crystallizes first in the form of colony from the melt. As solidification develops, the retained liquid transforms into austenite gradually. On cooling, solid-state transformation from ferrite to austenite results in the disappearance of part thinner ferrites and the final two-phase coupled microstructure is formed after the solid-state transformation. The formation mechanism of the two-phase coupled microstructure is analyzed based on the nucleation and constitutional undercooling criterion (NCU) before steady-state growth of each phase is reached.

A novel dispersant “mono-2-(methacryloyloxy)ethyl succinate” was formulated for dispersing 30-nm SiC nanoparticles in vinyl ester resin. The eight carbon rule was used as the guideline to achieve a particle–particle separation of 20 to 60 nm for colloid stability. Fourier transform infrared spectroscopy was performed to characterize the SiC particle surfaces. Only a negligible amount of oxidized layer was observed; which illustrates that the SiC surface is basic. Thus, the Lewis base-Lewis acid reactions make the functional group –COOH an effective adsorbate to the SiC nanoparticle surface. The organofunctional group “methacrylates,” which exhibits the best wet strength with polyester copolymerizes with styrene monomers in the vinyl ester during cure. Hence, this novel dispersant also acts as an efficient coupling agent that reacts with both SiC and vinyl ester. The monolayer coverage dosage of 62 fractional wt% of the dispersant was used to attain the minimum filled resin viscosity. The multicomponent compositional imaging using atomic force microscopy confirmed the monodisperse SiC nanoparticles in vinyl ester. The 3 vol% SiC reinforced vinyl ester achieved a 75% increase in modulus, 42% increase in strength, and 75% increase in toughness as compared with the neat resin without nanofiller reinforcement.

The storage and loss stiffnesses for the composite response of the sample, indenter, and load frame during dynamic nanoindentation are derived. In the first part of the analysis, no physical model is assigned to the composite system. It is shown that this case is equivalent to the conventional nanoindentation analysis. In the second part of the analysis, the sample is modeled as a standard linear solid in series with the indenter and load frame. The results for the storage and loss stiffnesses as computed by the two methods differ by at most ∼3% for the elastomeric system under consideration. Results for the storage and loss moduli are also similar. The relative merits and weaknesses of each analysis are discussed.

We introduce a novel method to correct for imperfect indenter geometry and frame compliance in instrumented indentation testing with a spherical indenter. Effective radii were measured directly from residual indentation marks at various contact depths (ratio of contact depth to indenter radius between 0.1 and 0.9) and were determined as a function of contact depth. Frame compliance was found to depend on contact depth especially at small indentation depths, which is successfully explained using the concept of an extended frame boundary. Improved representative stress-strain values as well as hardness and elastic modulus were obtained over the entire contact depth.

A constitutive theory for metallic glasses is established that is based mainly on the Drucker-Prager model and a free-volume theory. The primary emphasis of this theory is on volume dilatation and its consequences on mechanical responses in metallic glasses that have been known from studies in both experiments and atomistic simulations. We also implemented the constitutive theory in a finite element modeling scheme and conducted numerical modeling of deformation of a metallic glass under plane-strain tension and compression. In particular, we focused our attention on the deviation of the shear band inclination angle, a commonly observed phenomenon for metallic glasses. We found very good qualitative agreement with available experimental data on shear band inclination angle and stress-strain relation. We also give a detailed discussion on different constitutive models, in particular the Coulomb-Mohr model, in the context of predicting the shear band inclination angle.