Presently, rotational isomeric state (RIS) theory directly addresses polymer chain conformation as it relates to mechanical response trends. The primary goal of this work is to explore the adaptation of this methodology to the prediction of material stiffness. This multiscale modeling approach relies on ionomer chain conformation and polymer morphology and thus has potential as both a predictive modeling tool and a synthesis guide. The Mark–Curro Monte Carlo methodology is applied to generate a statistically valid number of end-to-end chain lengths via RIS theory for four solvated Nafion® cases. For each case, a probability density function for chain length is estimated using various statistical techniques, including the classically applied cubic spline approach. It is found that the stiffness prediction is sensitive to the fitting strategy. The significance of various fitting strategies, as they relate to the physical structure of the polymer, are explored so that a method suitable for stiffness prediction may be identified.

Numerical analysis is conducted to clarify the formation mechanisms of silicide nanoparticles synthesized in an induction thermal plasma maintained at atmospheric pressure. The induction thermal plasma is analyzed by an electromagnetic fluid dynamics approach, in addition to a multi-component co-condensation model, proposed for the silicide nanoparticle synthesis. In the Cr–Si and Co–Si systems, silicon vapor is consumed by homogeneous nucleation and heterogeneous condensation processes; subsequently, metal vapor condenses heterogeneously onto liquid silicon particles. The Mo–Si system shows the opposite tendency. In the Ti–Si system, vapors of silicon and titanium condense simultaneously on the silicon nuclei. Each system produces nanoparticle diameters of around 10 nm, and the required disilicides, with the stoichiometric composition, are obtained. Only the Ti–Si system has a narrow range of silicon content. The numerical analysis results agree with the experimental findings. Finally, the correlation chart, predicting the saturation vapor pressure ratios and the resulting silicon contents, is presented for estimation of nanoparticle compositions produced in the co-condensation processes.

The resistivities of as-deposited Cu(4.2Ir), Cu(2.0W), and Cu(2.2W) films are 32.2, 25.4, and 28.0 μΩcm, respectively. These resistivities are significantly higher thanthat for pure Cu films. After annealing the Cu(4.2Ir) film at constant heating rate to 800 °C and the two Cu(W) films to 950 °C, the resistivities reduce to 28.4, 4.3, and 5.2 μΩcm, respectively. The smaller reduction in resistivity for Cu(4.2Ir) compared with that for Cu(W) is partly a consequence of solute redissolution following precipitation. The variation of resistivity with temperature for the films and the Cu-rich end of the binary phase diagrams are used to categorize the decomposition behavior of the Cu(Ir) and Cu(W). These categories were defined by K. Barmak et al., J. Appl. Phys.87, 2204 (2000). W is placed in category III along with V, Nb, Ta, Cr, Mo, Re, Ru, Os, B, and C. Ir most suitably belongs to Category II together with Fe and Co.

Using transmission electron microscopy we observe the dissociation of 60° misfit dislocations at the interface of SiGe/Si multilayers, extending into the substrate for distances of 5.0–7.5 nm. Analysis using elasticity theory shows that this dissociationis the equilibrium configuration for individual 60° misfit dislocations, as it is for 60° mixed dislocations in bulk Si, and that the compressively strained multilayer film serves mainly to position the partial dislocations and stacking fault with respect to the free surface. We observe both undissociated 60° and Lomer edge dislocations after annealing, and conclude that these result from dislocation climb in the interface. Since the dislocations move off their slip plane during climb, they cannot remain dissociated. Significant climb and Lomer dislocation formation for these low misfit layers is observed at temperatures above 850 °C and for samples with a high initial dislocation density, such as found in thicker as-grown samples. The dislocation configuration formed during annealing is distinct from that reported to form during growth of higher mismatch films: the Lomer dislocations tend to be segmented, with the segments connected by perfect 60° dislocations.

The thermal degradation behavior of indium tin oxide (ITO) thin films coated on glass substrates using radio frequency (rf) magnetron sputtering was investigated over the temperature range of 100–400 °C in air. The resistivity of ITO films increases abruptly after the thermal degradation temperature of 250 °C is reached, with a slight increase from 200 to 250 °C. The x-ray photoelectron spectrometry intensity ratio of O/(In + Sn) in thermally degraded ITO films is higher than that in normal films. The carrier concentration gradually decreases up to 200 °C, sharply drops between 200 and 250 °C with increasing temperature, and then saturates from 275 °C. The Hall mobility drops suddenly at 275 °C. The diffusion of oxygen into oxygen interstitials and oxygen vacancies and the chemisorption of oxygen into grain boundaries decrease the carrier concentration and the Hall mobility, respectively. The former mainly affects the resistivity of ITO films below 250 °C, and the later above 250 °C.

A study was made of radial crack evolution in curved brittle layers on compliant support substrates. Three-dimensional boundary element analysis was used to compute the stepwise growth of radial cracks that initiate at the bottom surfaces of glass on polymeric support layers, from initiation to final failure. The algorithm calculates reconstituted displacement fields in the near-tip region of the extending cracks, enabling direct evaluation of stress-intensity factors. Available experimental data on the same material systems with prescribed surface curvatures were used to validate the essential features of the predicted crack evolution, particularly the stability conditions prior to ultimate failure. It was shown that the critical loads to failure diminish with increasing surface curvature. Generalization of the ensuing fracture mechanics to include alternative brittle-layer/polymer-substrate systems enabled an explicit expression for the critical load to failure in terms of material properties and layer thicknesses. Implications concerning practical layer systems, particularly dental crowns, are briefly discussed.

Well-aligned Ga2O3 nanowires were formed on the sapphire (0001) substrates at temperatures of 650–450 °C using a single precursor of gallium acetylacetonate via a vapor-liquid-solid (VLS) method. Structural analyses reveal that the well-aligned Ga2O3 nanowires are expitaxially grown on the sapphire (0001) with Ga2O3/ sapphire orientational relationship [201]||[0001] and [211]||[1120]. In addition, formation of the flowerlike Ga2O3 nanorod bundles at a temperature of 750 °C via the vapor-solid (VS) mechanism was also demonstrated. Instead of being catalysts in the VLS method, the Au nanoparticles are proposed to play a role in sinking the Ga vapor for forming the nuclei of Ga2O3 nanorods in the VS method.

Sn–3.5Ag solder bumps were formed on electroless Ni/immersion Au (Ni/Au) and organic solderability preservative (OSP) surface-finished bond pads, respectively. The shear strength of the solder bumps was measured as a function of reflow steps. Fracture surfaces and interfacial microstructures were investigated by scanning electron microscope. The shear strength of Ni/Au samples increased up to the seventh reflow step and subsequently decreased after the tenth reflow step. Spalling of Ni3Sn4 intermetallic compounds (IMCs) and the P-rich Ni layer strengthened and weakened the bond, respectively. For OSP samples, although Cu6Sn5 IMCs grew as the reflow step was repeated, no remarkable change in shear strength was observed. Interfacial fractures of OSP samples occurred at the interface between Cu6Sn5 IMC and Cu3Sn IMC. Fracture surfaces of OSP samples showed concave pits that consisted of a Cu3Sn bottom and an Sn wall. The pits were formed by separation of Cu6Sn5 IMC from Cu3Sn IMC and the molten Sn channel between the Cu6Sn5 IMC grains.

Nanoscaled Cr2O3 powder with an average particle size of 20–40 nm, coated on alumina particles, has been produced by means of chemical vapor deposition (CVD) in a fluidized chamber, using the pyrolysis of Cr(CO)6 precursor. Amorphous and crystalline Cr2O3 particles were obtained when the temperatures of the pyrolysis were 300 and 400 °C, respectively. To prepare nanoscaled Cr3C2 powder from the nanometer-sized Cr2O3, carbonizing behavior of the Cr2O3 particles was investigated. It was found that, when amorphous Cr2O3 powders were carbonized in graphite furnace at 1150 °C for 2 h in vacuum (10−3 Torr), the powder was transformed into Cr3C2, while the crystalline Cr2O3 was transformed into a mixture of Cr7C3 and Cr3C2. The examinations by x-ray diffraction, transmission electron microscopy, and energy dispersive spectroscopy confirmed the transformation of the nano-sized Cr3C2 powders. The results of thermogravimetry and differential thermal analysis indicated that the transformation temperature was ∼1089 °C for amorphous Cr2O3 and ∼1128 °C for crystalline Cr2O3.

Solid solutions of (Mg4−xMnx)Nb2O9 (MMN), which have a corundum-type structure, showed a single phase over the entire composition range, and lattice parameters of MMN linearly increased with increased composition x. From the calculation of cation–oxygen bonds in NbO6 and MO6 (M = Mg and Mn) octahedra, it was found that the covalency of the Nb–O bond was decreased by the Mn substitution for Mg; the molecular orbital calculation in (NbM12O45)−61 cluster models also revealed that the covalency of the Nb–O bond in the (NbMn12O45)−61 cluster model is smaller than that of the Nb–O bond in the (NbMg12O45)−61 cluster model. This result is attributed to the differences in the density of state, which arise from the overlap population of Mg-3d, Mn-3d, Nb-5s, and O-2p orbitals. The dielectric constant and Q⋅f values varied from 11 to 16 and from 210,000 to 50,000 GHz, respectively. Thus, it is considered that these variations in the microwave dielectric properties may be related to the covalency of the cation–oxygen bonds.

Thermodynamic properties of the phases in the MgO–Al2O3–SiO2 system were assessed, resulting in a set of self-consistent thermodynamic data. The two ternary compounds, cordierite and sapphirine, were optimized from subsolidus reactions. The liquid phase was described by the ionic two-sublattice model with a new species AlO2−1, yielding the formula (Al+3,Mg+2)P(AlO2−1,O−2,SiO4−4,SiO20)Q. Projection of the liquidus surface was calculated. Various isothermal and isoplethal sections were compared with the experimental data.

The distribution of Au and NiO in NiO/Au ohmic contact on p-type GaN was investigated in this work. Au (5 nm) films were deposited on p-GaN substrates by magnetron sputtering. Some of the Au films were preheated in N2 ambient to agglomerate into semi-connected structure (abbreviated by agg-Au); others were not preheated and remained the continuous (abbreviated by cont-Au). A NiO film (5 nm) was deposited on both types of samples, and all samples were subsequently annealed in N2 ambient at the temperatures ranging from 100 to 500 °C. The surface morphology, phases, and cross-sectional microstructure were investigated by scanning electron microscopy, glancing incident angle x-ray diffraction, and transmission electron microscopy. I-V measurement on the contacts indicates that only the 400 °C annealed NiO/cont-Au/p-GaN sample exhibits ohmic behavior and its specific contact resistance (ρc) is 8.93 × 10−3 Ω cm2. After annealing, Au and NiO contact to GaN individually in the NiO/agg-Au/p-GaN system while the Au and NiO layers become tangled in the NiO/cont-Au/p-GaN system. As a result, the highly tangled NiO-Au structure shall be the key to achieve the ohmic behavior for NiO/cont-Au/p-GaN system.

The stability of interfaces with germanium, which has recently been discussed as a replacement for silicon in ultra-large-scale integrated circuits (ULSIs), was studied. Interfacial oxygen diffusion from high-permittivity gate dielectrics (ZrO2 and HfO2) into germanium substrates must be suppressed to prevent the formation of interfacial layers between the gate dielectrics and the germanium substrates. Oxygen diffusion was simulated through a molecular-dynamics technique that takes into account many-body interactions and charge transfer between different elements. The simulation results show that the addition of yttrium is effective in suppressing interfacial oxygen diffusion at the ZrO2/germanium interfaces. On the other hand, the addition of yttrium is not effective in suppressing interfacial oxygen diffusion at the HfO2/germanium interfaces. The results also show that the diffusion at the ZrO2/Ge(111) and HfO2/Ge(111) interfaces is much more suppressed than the diffusion at the ZrO2/Ge(001) and HfO2/Ge(001) interfaces.

The crystallization process of yttria-stabilized zirconia (YSZ) gate dielectrics deposited on p-Si (001) and SiOx/p-Si(001) substrates and the growth process of SiOx has been investigated directly using high-temperature in situ cross-sectional view transmission electron microscopy (TEM) method and high-temperature plan-view in-situ TEM method. The YSZ layer is crystallized by the nucleation and growth mechanism at temperatures greater than 573 K. Nucleation originates from the film surface. Nucleation occurs randomly in the YSZ layer. Subsequently, the crystallized YSZ area strains the Si surface. Finally, it grows in the in-plane direction with the strain, whereas, if a SiOx layer of 1.4 nm exists, it absorbs the crystallization strain. Thereby, an ultrathin SiOx layer can relax the strain generated in the Si substrate in thin film crystallization process.

We present an analysis, based upon atomistic simulation data, of the effect of Fe impurities on grain boundary migration in Al. The first step is the development of a new interatomic potential for Fe in Al. This potential provides an accurate description of Al–Fe liquid diffraction data and the bulk diffusivity of Fe in Al. We use this potential to determine the physical parameters in the Cahn–Lücke–Stüwe (CLS) model for the effect of impurities on grain boundary mobility. These include the heat of segregation of Fe to grain boundaries in Al and the diffusivity of Fe in Al. Using the simulation-parameterized CLS model, we predict the grain boundary mobility in Al in the presence of Fe as a function of temperature and Fe concentration. The order of magnitude and the trends in the mobility from the simulations are in agreement with existing experimental results.

C60 nanowhiskers fabricated by liquid–liquid interfacial precipitation method and pristine C60 powder were sintered at 800 °C under 5.5 GPa for 2 h. The specimens showed high micro-Vickers hardness about 1100 kg/mm2 and electrical resistivity as low as several Ωm. Structural characterization by x-ray diffraction, high-resolution transmission electron microscopy, Fourier transform infrared, and Raman spectroscopy revealed that most of C60 molecules were broken to form turbostratic graphite by high-pressure and high-temperature treatment. Comparison with the pristine C60 powder sintered under the same conditions suggests that the structural change depends microscopically on the C60 molecules, but the size and the morphology of the starting material also affect the macroscopic sintering process.

A new type of bearing alloy containing ultrafine sized tin and silicon dispersions in aluminum was designed using laser surface alloying and laser remelting techniques. The microstructures of these non-equilibrium processed alloys were studied in detail using scanning and transmission electron microscopy. The microstructures revealed three distinct morphologies of tin particles namely elongated particles co-existing with silicon, globular particles, and very fine particles. Our detailed analyses using cellular growth theories showed that the formation of these globular tin particles was due to the pinching off of the tin rich liquid in the inter-cellular space by the growth of aluminum secondary dendrite arms. Evidence of fine recrystallized aluminum grains at the top layer due to constrained solidification was shown. Thermal analyses suggested that melting of the spherical shaped tin particles was controlled by the binary aluminum-tin eutectic reaction, whereas non-spherical tin particles melted via the tin-silicon eutectic reaction.

To estimate the ratio of densification to Vickers indentation volume, three-dimensional images of Vickers indentations on several glasses, including silicate glasses and bulk metallic glass (BMG), were obtained before and after annealing using an atomic force microscope. Large volume recovery of Vickers indentation by annealing was observed for all glasses but BMG. Following previous studies, this recovered volume almost corresponded to the densified volume under a Vickers indenter, and the compositional dependence of densification was discussed. The ratios of densification to the total indentation volume for silica and soda-lime glasses were 92% and 61%, respectively. It was concluded that densification was a general property for silicate glasses and that the ratios of densification to the total indentation volume for all the glasses correlated well with Poisson’s ratios of the glasses.

With the potential to map mechanical properties of heterogeneous materials on a micrometer scale, there is growing interest in nanoindentation as a materials characterization technique. However, nanoindentation has been developed primarily for characterization of hard, elasto-plastic materials, and the technique has not been validated for very soft materials with moduli less than 5 MPa. The current study attempted to use nanoindentation to characterize the elastic moduli of soft, elastomeric polydimethylsiloxane (PDMS) samples (with different degrees of crosslinking) and determine the effects of adhesion on these measurements using adhesion contact mechanics models. Results indicate that nanoindentation was able to differentiate between elastic moduli on the order of hundreds of kilo-Pascals. Moreover, calculations using the classical Hertz contact model for dry and aqueous environment gave higher elastic modulus values when compared to those obtained from unconfined compression testing. These data seem to suggest that consideration of the adhesion energy at the tip-sample interface is a significantly important parameter and needs to be taken into account for consistent elastic modulus determination of soft materials by nanoindentation.

To understand the role of boundaries in the deformation behavior of TiAl, in situ straining experiments in transmission electron microscopy have been performed on thin foils of polysynthetically twinned (PST) crystal of Ti–49.3 at.% Al. The deformation behavior of PST TiAl is anisotropic, depending on the angle between the lamellar boundaries and the straining axes. For L-orientation, deformation twins and ordinary dislocations transmit across the true-twin (TT) boundaries but are reflected at the pseudo-twin (PT) and rotational order-fault (RO) boundaries. For transverse (T) orientation, deformation twins are transmitted across all TT, PT, and RO boundaries. For I-orientation, shear deformation occurs parallel to the lamellar boundaries. There is a transmission of deformation across the interphase (IP) boundary in longitudinal orientation, but deformation is blocked and reflected at the IP boundary in T-orientation. The role of the various types of boundaries in localized deformation behavior was evaluated by considering Schmid factors and geometric compatibility factors.