The isothermal oxidation behavior of bulk Ti3SiC2 at intermediate temperatures from 500 to 900 °C in flowing dry air was investigated. An anomalous oxidation with higher kinetics at lower temperatures was observed. This phenomenon resulted from the formation of microcracks in the oxide scales at low temperatures. The generation of these microcracks was caused by a phase change in the oxide products, i.e., the transformation of anatase TiO2 to rutile TiO2. This phase transformation resulted in tensile stress, which provided the driving force for the formation of the microcracks during oxidation. Despite the existence of microcracks, the intermediate-temperature oxidation of Ti3SiC2 generally obeyed the parabolic rate law and did not exhibit catastrophic destruction due to the fact that cracks occurring in the oxide layers were partially filled with amorphous SiO2. Therefore, further high oxidation kinetics was prevented.

The viscoelastic behavior of a soda-lime silica glass (a standard window glass) was investigated by means of Vickers indentation from room temperature to 833 K. Hardness values decrease gradually from 293 to 673 K and drop rapidly above 673 K. The flow kinetics of the glass at high temperature was analyzed in the light of atomic force microscopy observations. It was observed that densification significantly contributes to the permanent deformation at low temperatures, whereas volume conservative flow played a more and more important role as temperature was increased. Master curves of the relaxation modulus and the creep compliance were obtained from constant-rate and constant-load indentation experiments, respectively. A major finding was that the viscous flow process is nonlinear, with a sharp decrease of the apparent viscosity as the mean contact pressure increases.

Titanium foams were produced by the expansion of pressurized argon pores trapped within a preform during a previous powder-consolidation step. Compared with creep expansion at 903 °C, superplastic expansion (induced by a 830–980 °C cycling around the allotropic temperature of titanium) increases foaming rate and final porosity. The pore size and fraction in the preforms were varied by using a range of initial titanium powder sizes and argon pressures. As initial preform porosity increases from 0.06 to 2.7%, foaming rate increases in the early stages of creep and superplastic foaming. However, at a later stage, foaming ceases prematurely for preforms with high initial porosity, as pores connect to the surface, allowing the escape of the pressurized argon. Preforms with 0.40% initial porosity result in foams with an optimal combination of high foaming rate, high final porosity (up to 47%), tailorable open or closed porosity, and Young's modulus as low as 23 GPa.

Quasi-elastic neutron spectroscopy was used to study the changes in the water content of hydrated tricalcium silicate cement paste with decreasing relative humidity (RH). The structurally bound water was divided into water bound in Ca(OH)2 and in calcium-silicate hydrate, or C–S–H-gel, utilizing the inelastic vibrational modes of Ca(OH)2. The quasi-elastic line was analyzed in terms of free and constrained water, and both were observed to decrease as the pores empty of pore-water with drying. An inelastic line related to translational vibrations of immobile water molecules was also extracted from the spectra, and its intensity was found to decrease with lower RH.

Nanoparticles of iron carbides (Fe3C and χ-Fe2.5C) wrapped in multilayered graphitic sheets were synthesized by a developed method in which an electric plasma was generated in an ultrasonic cavitation field containing thousands of tiny activated bubbles in liquid ethanol. Annealing changed the phase composition, structure, and size of the carbon nanocapsules as most of the iron carbides decomposed into the α-Fe phase and graphite. Powder samples annealed at 873 and 973 K have maximal saturation magnetization values equal to 80.6 and 83.4 A m2/kg, respectively, which is approximately 40% of the value of bulk iron. Using this method, it will be possible to synthesize nanoparticles of a metal of choice encapsulated by graphite shells by selecting appropriate materials for the ultrasonic tip and electrodes.

We have studied structure and electrical properties of Si1−YGeY:H films deposited by low-frequency plasma-enhanced chemical vapor deposition over the entire composition range from Y = 0 to Y = 1. The deposition rate of the films and their structural and electrical properties were measured for various ratios of the germane/silane feed gases and with and without dilution by Ar and by H2. Structure and composition was studied by Auger electron spectroscopy (AES), secondary ion mass spectroscopy (SIMS), and Fourier transform infrared (FTIR) spectroscopy. Surface morphology was characterized by atomic force microscopy (AFM). We found that the deposition rate increased with Y, maximizing at Y = 1 without dilution. The relative rate of Ge and Si incorporation is affected by dilution. Hydrogen preferentially bonds to silicon. Hydrogen content decreases for increasing Y. In addition, optical measurements showed that as Y goes for 0 to 1, the Fermi level moves from mid gap to the conduction band edge; i.e., the films become more n-type. No correlation was found between the pre-exponential and the activation energy of conductivity. The behavior of the conductivity γ-factor suggests a local minimum in the density of states at E ≈ 0.33 eV for the films grown with or without H-dilution and E ≈ 0.25 eV for the films with Ar dilution.

The mechanical properties of lead zirconate titanate (PZT) multilayer systems are needed to model and design micro-electromechanical systems (MEMS) devices. Nanoindentation is a promising tool for obtaining the elastic properties of thin films. However, no means exist to obtain the elastic modulus of the lead zirconate titanate (PZT) in the multilayer system. The indentation modulus versus a/t behavior of the multilayered PZT/Pt/SiO2 film system on a silicon substrate was investigated and compared with finite element models and a new analytical solution. Six different PZT film thicknesses were indented (100, 140, 400, 700, 1500, and 2000 nm), using 5-, 10-, and 20-μm radius indenters. Good agreement was shown between the finite element analysis (FEA) and analytical solutions, and the experimental data. However the behavior of multilayer systems is complex, making deconvolution of properties difficult for films of less than a micron thick.

The oxidation behavior of melt-spun Zr75Pd25 and Zr80Pt20 alloys with nanoquasicrystalline phase embedded in amorphous matrix has been studied isothermally as well as nonisothermally in static air. The nature of oxides formed during oxidation has been studied by x-ray diffraction and scanning electron microscopy, and a transition in the structure of the oxides has been shown as one of the primary reasons for the difference in the oxidation behavior of the alloys.

The mechanical properties of nacre constituents from red abalone were investigated. Electron microscopy studies revealed that the tablets are composed of single-crystal aragonite with nanograin inclusions. Both nanoasperities and aragonite bridges are present within the interfaces between the tablets. By means of nanoindentation and axial compression tests, we identified single tablet elastic and inelastic properties. The elastic properties are very similar to those of single-crystal aragonite. However, their strength is higher than previously reported values for aragonite. A finite element model of the interface accounting for nanoasperities and the identified properties revealed that the nanoasperities are strong enough to withstand climbing and resist tablet sliding, at least over the initial stages of deformation. Furthermore, it was observed that the model over-predicts strength and under-predicts ductility. Therefore, we conclude that other interface features must be responsible for the enhanced performance of nacre over its constituents.

Electromigration (EM) in copper dual-damascene interconnects with extensions(also described as overhang regions or reservoirs) in the upper metal (M2) were investigated. It was found that as the extension length increases from 0 to 60 nm, the median-time-to-failure increased from 50 to 140 h, representing a ∼200% improvement in lifetimes. However, further increment of the extension length from 60 to 120 nm did not result in any significant improvement in EM lifetimes. Based on calculations of current densities in the reservoir regions and recently reported nucleation, void movement, and agglomeration-based EM phenomena, it is proposed that there is a critical extension length beyond which increasing extension lengths will not lead to longer EM lifetimes.

The U–6 wt% Nb (U6Nb) alloy in the water-quenched (WQ) state has been in service for a number of years. Its long-term reliability is affected by the changes of the alloy microstructure and mechanical properties during service. In this paper, the water quenched U–6 wt% Nb (WQ-U6Nb) alloy in service for 15 years at ambient temperatures was studied using an analytical transmission electron microscopy (TEM) analysis. We found that the long-term natural aging resulted in a disorder–order phase transformation, leading to the formation of anti-phase boundaries (APBs). The newly found ordered phase was then identified by proposing two phase transform schemes, which were also discussed with regards to the potential subsequence of the microstructural evolution for the alloy in further service. The initial study also provides convincing evidence for the disorder–order transformation, which has been predicted by numerous studies to be a transient thermodynamic event before spinodal decomposition. This suggests that the long-term naturally aged WQ–U6Nb is a good model alloy to study thermodynamic and kinetic phenomena requiring chronic processes.

Systems with typical dimensions in the range of 1–100 nm are in an intermediate state between solid and molecular. Such systems are characterized by the fact that the ratio of the number of surface to volume atoms is not small. This is known to lead to size and shape effects on their cohesive properties. In this work, the phase diagram of nanowires was studied in the framework of classical thermodynamics. The roles of the size, shape, and surface tensions were emphasized. The melting temperatures of nanowires of 21 elements were evaluated theoretically. In the case of binary systems, it was shown that the experimental or theoretical knowledge of the size-dependent phase diagrams of a given binary system allows the evaluation of the one of nanowires. The procedure is described in this paper.

The modified arc-discharge technique was used for the growth of boron-doped multiwalled carbon nanotubes. A variety of weight percentages of boron and sulfur were mixed (0.5–15 wt%) with graphite powder and packed in the consumable anode. Transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis (TGA), and electron energy loss spectroscopy (EELS) were used to characterize the samples. EELS indicated a small percentage of boron present (<1 at.%) in the nanotubes. Sulfur was used primarily to enhance boron incorporation; however, Raman and TGA measurements indicated fewer defects and/or amorphous material present when sulfur was added.

In this article, a novel pressureless solid-liquid reaction method is presented for preparation of yttrium disilicate (γ-Y2Si2O7). Single-phase γ-Y2Si2O7 powder was synthesized by calcination of SiO2 and Y2O3 powders with the addition of LiYO2 at 1400 °C for 4 h. The addition of LiYO2 significantly decreased the synthesis temperature, shortened the calcination time, and enhanced the stability of γ-Y2Si2O7. The sintering of these powders in air and O2 was studied by means of thermal mechanical analyzer. It is shown that the γ-Y2Si2O7 sintered in oxygen had a faster densification rate and a higher density than that sintered in air. Furthermore, single-phase γ-Y2Si2O7 with a density of 4.0 g/cm3 (99% of the theoretical density) was obtained by pressureless sintering at 1400 °C for 2 h in oxygen. Microstructures of the sintered samples are studied by scanning electron microscope.

The alternating current electrical conductivity of a gel-derived glass of composition 55Fe2O3⋅45SiO2 (mol%) was measured over a frequency range of 100 Hz to 6 MHz. The gel was subjected to a reduction treatment at 923 K for ½ h and subsequently heated in ordinary atmosphere at a temperature 773 K for ½ h to grow a Fe-core Fe3O4 shell nanostructure with a median diameter of 6.2 nm. This formed a percolative network within the silica gel. Mossbauer spectra confirmed the presence of Fe3O4 in the nanoshell. Electrical measurements were also carried out on these nanocomposites at different frequencies and temperatures. Isothermal electrical modulus data for both reference and treated glass systems were analyzed using both the CK0 and CK1 Kohlrausch-related frequency response models. Reference-glass shape parameter values, estimated by fitting the experimental data to the K0 model at several temperatures, were found to be ∼0.32. Here, the K0 model led to much better fits than the K1 did. However, for the treated core–shell-structured nanocomposite material, both models yielded good fits with consistent but different shape parameter estimates: very close to ½ for the K0 model and ⅓ for the K1 model. In accordance with the structural measurements and with axiomatic topological considerations that predict a shape-parameter value of ⅓ for one-dimensional motion and ½ for two-dimensional motion, it appears that the ∼0.32 value is consistent with one-dimensional motion of charge carriers along the narrow channels of the interconnected iron-rich three-dimensional phase of the reference glass. Further, although the K1-model ⅓ estimates for the treated material also indicate the presence of one-dimensional charge motion at the two-dimensional interface between the two interconnected phases of the reference glass, the ½ K0 estimates for the same material suggest an effective charge-motion dimension of 2. Importantly, comparison of the high-frequency dielectric constant estimates for the K0 reference glass and the K1 treated one clearly leads to the new but physically plausible conclusion that the bulk frequency-independent dielectric constant of about 30 is independent of the treatment.

Nanoparticles and nanocrystalline particles of pure anatase titania (TiO2) were synthesized by solvothermal processing of TiCl4 ethanol and isopropanol solutions at 120 to 200 °C. This one-step and nonsurfactant approach is versatile and the morphology tuning can be achieved by manipulating the growth kinetics. Dispersed nanocrystals of spherical, cubic, and acicular shapes and hollow spherical and core-shell structured micrometer-sized particles were obtained under different experimental conditions. The obtained hollow spherical- and core-shell–structured particles have an average diameter of 700 nm to 1.0 μm, with an average crystallite size of 5 to 16 nm. The dependence of nucleation/crystal growth and morphology development on solvothermal medium, reaction temperature, and reactant concentration was investigated. The reaction mechanism was then suggested and tentatively discussed from coordination and solution chemistry.

A new configuration of a superdislocation in the γ′ phase of a fourth-generation single-crystal TMS-138 superalloy was found after creep rupture in a [001] tensile test at 1150 °C and 137 MPa. The segments of the superdislocation lie in four directions, i.e., [110], [110], [100], and [010], strictly on a (001) plane with a Burgers vector b = [001]. This superdislocation is pure edge in character and does not dissociate into superpartials. Microstructural evidence shows that this kind of superdislocation is formed by combination of two interfacial dislocations with different Burgers vectors, i.e., 1/2[011] + 1/2[011] → [001].

Thermal stability studies of Co-substituted barium hexaferrites with the U-type structure are reported. Samples were prepared using solid-state reaction and high-energy milling at 1300 and 1250 °C, respectively. The influence of different annealing conditions on their compositions and magnetic properties was studied. Thermal instability of the studied compounds was observed at as low as 600 °C. Through x-ray powder diffraction, chemical analysis, and thermomagnetic measurements it was confirmed that a degradation of the U-hexaferrites occurred during the annealing at 600–800 °C. The observed changes in the samples’ phase compositions and structures did not have a significant influence on their magnetization and microwave properties.

All-polymer multilayer hollow core photonic fiber preforms were fabricated using consecutive deposition from a solvent phase of two polymers with high and low refractive indices (RI). Processing techniques for two polymer pairs—polystyrene (PS)/poly(methyl methylacrylate) (PMMA) and polycarbonate (PC)/poly(vinylene difloride) (PVDF)—were established. The fabrication process involved consecutive film deposition by solvent evaporation of polymer solutions on the inside of a rotating PMMA or PC tube, used as a cladding material. By injecting right volumes of the polymer solutions into a spinning tube the thickness of each layer could be reliably controlled from 20 to 100 μm. Proper selection of solvents and processing conditions was crucial for ensuring high optical and mechanical quality of a resultant preform, as well as compatibility of different polymer films during co-deposition. Preforms of 10 layers for PMMA/PS material combination and 15 layers for PVDF/PC were demonstrated. Fabrication of preforms with higher number of layers is readily possible and is only a question of preform fabrication time. An alternative method of preform fabrication by co-rolling of polymer bilayers is also presented in this paper, drawing of PMMA/PS, PVDF/PC fibers with up to 32 layers is demonstrated.

The electromigration effect upon the γ-InSn4/Cu interfacial reactions have been studied by examining the γ-InSn4/Cu/γ-InSn4 couples annealed at 160 °C with and without current stressing. Scallop-type η-Cu6(Sn,In)5 phase layers are formed in the couples without current stressing and at the γ-InSn4/Cu interface where electrons are flowing from the γ-InSn4 to the Cu. The reaction path is Cu/η-Cu6(Sn,In)5/γ-InSn4. However, very large η-Cu6(Sn,In)5 compounds are found at the Cu/γ-InSn4 interface where electrons are from Cu to the γ-InSn4. Although the melting points of both γ-InSn4 and Cu are higher than 160 °C, the liquid phase is formed at 160 °C in the electrified couple at the downstream γ-InSn4 phase near the Cu/γ-InSn4 interface. The reaction path is Cu/η-Cu6(Sn,In)5/liquid/γ-InSn4. The liquid phase propagates along the grain boundaries of the γ-InSn4 matrix. The very large η-Cu6(Sn,In)5 compounds are the coupling results of the liquid phase penetration and the Cu transport enhancement due to electromigration.