Nanoembedded aluminum alloys with bimetallic dispersoids of Sn and Pb of compositions Sn82–Pb18, Sn64–Pb36, and Sn54–Pb46 were synthesized by rapid solidification. The two phases, face-centered-cubic Pb and tetragonal Sn solid-solution, coexist in all the particles. The crystallographic relation between the two phases and the matrix depends upon the solidification pathways adopted by the particles. For Al–(Sn82–Pb18), we report a new orientation relation given by [011]Al//[010]Sn and (o11)A1//(101)Sn. Pb exhibits a cube-on-cube orientation with Al in few particles, while in others no orientation relationship could be observed. In contrast, Pb in Sn64–Pb36 and Sn54–Pb46 particles always exhibits cube-on-cube orientation with the matrix. Sn does not show any orientation relationship with Al or Pb in these cases. Differential scanning calorimetry studies revealed melting at eutectic temperature for all compositions, although solidification pathways are different. Attempts were made to correlate these with the melting and heterogeneous nucleation characteristics.

Pb(Mg1/3Ta2/3)O3 (PMT) powders and heteroepitaxial thin films on (001) SrTiO3 (STO) substrates were prepared by the chemical solution deposition method. The phase development in PMT powders and thin films was investigated by x-ray diffraction, and the microstructure of PMT thin films was studied by transmission electron microscopy. Phase transformation from pyrochlore to perovskite in the PMT powder samples occurred in the temperature range of 700–800 °C, and perovskite phase was mainly observed in samples annealed above 800 °C. However, perovskite phase in PMT thin films on STO substrates was formed mainly in samples annealed as low as 750 °C/1 h, and it shows an epitaxial orientation relationship of [100](001)PMT∥[100](001)STO.

The friction and wear performance were correlated with the thermal stability of reactively sputtered Si–aC:H thin films containing various Si and H concentrations. The average steady-state friction coefficients as measured by dry sliding pin-on-disk tests decreased with increasing Si and H content. Furthermore, the films with high Si and H formed thick transfer films as compared to the films with little or no Si and H content. Minimums in average ball abrasion rate and average film wear rate were observed at the Si/C = 0.10 film composition. The most intense and distinct “graphitic” Raman peaks were collected from the Si/C = 0.10 transfer film debris. In addition, the Si/C = 0.10 film also had the most distinguishable graphitic Raman signature after annealing in air at 500 °C compared to the other Si–aC:H films, suggesting a possible relationship between the nature of transfer films resulting from dry sliding in air and the bulk films that were annealed in air.

Precipitation-strengthened tin-based eutectic Sn–3.5 Ag alloy was investigated for its creep behavior at three temperatures ranging from 303 to 393 K, under the tensile stress range of σ/E = 10−4 to 10−3. The steady-state creep rates cover seven orders of magnitude (10−3 to 10−9 s−1). The initial microstructure was found to have Ag3Sn intermetallic compound finely dispersed in the matrix of β–Sn. By incorporation of a threshold stress, σth, into the analysis, the creep data of eutectic Sn–Ag at all temperatures can be fitted by a single straight line with a slope of seven after normalizing the steady-state creep rate and the effective stress, indicating that the creep rates are controlled by the dislocation-pipe diffusion in the Sn matrix. The steady-state creep rate, , can then be expressed as , where QC is the creep activation energy, G is the temperature-dependent shear modulus, b is Burger's vector, R is the universal gas constant, T is the absolute temperature, σ is the applied stress, A is a material-dependent constant, and , in which σOB is the Orowan bowing stress and kR is the relaxation factor.

Recent experimental work by a number of researchers has demonstrated that unusual high porosity thin films may be obtained in physical deposition systems by combining glancing angle deposition with in situ substrate motion control. The microstructure of these films consists of isolated columns engineered into shapes such as helices, posts, or chevrons. Due to the isolated nature of the columns, the films present a unique opportunity to study fundamental thin film growth behavior and, in particular, the influence of the self-shadowing mechanism in three dimensions. Apart from this academic motivation, there is the need to characterize the physical constraints imposed on the engineering of these films. In particular, this study will have implications for the realization of isolated, periodically arranged nanostructures envisioned for certain applications such as photonic band gap crystals. Results from an ongoing study of growth dynamics, morphology, porosity, and scaling behavior, and the dependence of these features on deposition parameters are presented.

Macroscopic residual stresses in Al2O3/Al plates of graded composition were determined experimentally and by the finite element method (FEM). Experimental stress data were determined by sawing a notch in the plates and measuring displacements by Moiré interferometry. Residual stresses were calculated from the displacements using the weight function method. Experimentally determined stresses agreed with FEM data only if measured thermomechanical properties for the different compositions were used for finite element calculations.

In this study, the interactions between transformation toughening and plastic stretching were investigated experimentally. Zirconia and metals, nickel or silver, were incorporated simultaneously into an alumina matrix. The extent of phase transformation of zirconia particles was enhanced due to the coexistence of soft metals. The ductility of nickel was also enhanced in the Al2O3–Ni–ZrO2 composites. However, the presence of zirconia particles at the alumina/silver interface reduced the ability of silver to deform plastically. Due to the interactions, the ratio of composite toughness to matrix toughness for the Al2O3–Ni–ZrO2 composite was higher than the product of the ratio of the composites containing only nickel and only zirconia.

Metal contact of compound semiconductors has been extensively studied using various characterization tools. However, there was little work of scanning transmission electron microscopy (STEM) done previously for the study of the InP contact systems. Using STEM and Auger electron spectroscopy analyses, we correlated the resistance with interfacial reactions in the AuGe/Ni/Au/Cr/Au contacts to n-InP. Detailed nanoscale structural and chemical information was uniquely revealed by the STEM compared to other techniques. For the high-resistance samples, little interfacial reaction between n-InP and Au occurred. For the low-resistance samples, significant out-diffusion of P in the Au and Ni layers occurred, forming Au–P and Ni–P metallic compounds. Accumulation of Ge in the Ni layer was also detected. We suggest that Ni–P may be very critical in obtaining low contact resistance for n-InP.

The effect of pressure on the crystallization behavior of Zr55Al10Ni5Cu30 bulk metallic glass was investigated by differential scanning calorimetry, x-ray diffraction, and transmission electron microscopy. Although the crystallization products under high pressure were about the same as those under ambient pressure, the evident changes in the relative crystallization fraction of each phase were observed. The applied pressure enhanced the crystallization temperature. Pressure annealing of the bulk metallic glass produced a composite with dispersion of very fine nanocrystallites in the amorphous matrix. A full nanocrystallization was obtained for the sample annealed under 5 GPa at 793 K. The mechanism for the pressure-induced nanocrystallization is discussed.

An AlN ceramic fired at 2173 K for 100 h under a reduced N2 atmosphere with carbon possessed a room-temperature conductivity of 272 Wm−1K−1, slightly lower than the value for high-purity, single-crystal AlN. However, the thermal conductivity of the ceramic at temperatures below 100 K was much lower than that of single crystal. This is mainly due to phonon scattering by grain junctions that possess an amorphous film with a thickness of under 1 nm. At 500 to 1000 K, no significant difference in the conductivity was observed between the ceramic and the single crystal.

Transmission electron microscopy (TEM) was used to study microstructures formed in GaN irradiated with 600-keV O+ ions at room temperature. Three types of defect clusters were identified in the irradiated GaN: (i) basal-plane stacking faults with dimensions ranging from 5 to 30 nm, (ii) pyramidal dislocation loops, and (iii) local regions of highly disordered material. High-resolution TEM imaging clearly revealed that one type of the basal-plane stacking faults corresponded to insertion of one extra Ga–N basal plane in the otherwise perfect GaN lattice. The interpretation of these results indicated that interstitials of both Ga and N preferentially condensed on the basal plane to form a new layer of Ga–N under these irradiation conditions. The formation of these extended defects and their interactions with the point defects produced during irradiation contributed to a dramatic increase in the dynamic recovery of point defects in GaN at room temperature.

Single-phase barium-filled skutterudite compounds, BayFexCo4−xSb12 (x = 0 to 3.0, y = 0 to 0.7), were synthesized by a two-step solid-state reaction method. The maximum filling fraction of Ba (ymax) in BayFexCo4–xSb12 increased with increasing Fe content and was found to be rather greater than that of CeyFexCo4–xSb12. The ymax varied from 0.35 to near 1.0 when Fe content changed from 0 to 4.0. BayFexCo4–xSb12 showed p-type conduction at a composition range of x = 0 to 3.0, y = 0 to 0.7. Carrier concentration and electrical conductivity increased with increasing Fe content and decreased with increasing Ba filling fraction. The Seebeck coefficient increased with increasing Ba filling fraction and with decreasing Fe content. Lattice thermal conductivity decreased with increasing Ba filling fraction and reached a minimum at a certain Ba filling fraction (y = 0.3 to 0.4). The greatest ZT value of 0.9 was obtained at 750 K for p-type Ba0.27Fe0.98Co3.02Sb12. It is expected that further investigation on the optimization of filling fraction would result in a higher ZT value at the moderately low Fe content region.

Results of magnetization and magnetic susceptibility measurements on undoped and Co-doped FeSi2.5 single crystals are presented. The temperature dependence of the magnetic susceptibility of the Co-doped sample in the range of 5–300 K can be explained by temperature-dependent contributions due to paramagnetic centers and the carriers excited thermally in the extrinsic conductivity region. The values of the paramagnetic Curie temperature and activation energy of the donor levels were estimated. It is also shown that the magnetic susceptibility of Co-doped samples cooled in zero external field and in a field are different. This resembles the properties of spin-glasses and indicates the presence of coupling between magnetic centers.

The growth of polycrystalline silicon on glass by low-pressure chemical vapor deposition and in situ laser induced recrystallization was investigated with the aim to study the influence of the seed layer and the mechanism of the recrystallization dynamics on the structural and morphological properties of the grown film. A seed layer was used to trigger the solidification process of many additional in situ laser-crystallized overlayers. One-dimensional calculations of the thermal flow produced by laser irradiation were used to clarify the complex interaction between the substrate and the molten silicon surface layer during nucleation and growth. The experiments show the relevant role played by the seed layer and the peculiar shaping of the film surface due to the preferential aggregation of molten silicon. Compact polysilicon films with thicknesses up to 4 μm with almost monocrystalline grains of 1–2-μm size were obtained.

The isothermal oxidation behavior of Ti2AlC at intermediate temperatures of 500, 600, 700, 800, and 900 °C in flowing air was investigated by means of thermogravimetric analysis, x-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM)/energy dispersive spectroscopy. An anomalous oxidation with higher kinetics at lower temperatures of 500 and 600 °C was observed although Ti2AlC exhibited good oxidation resistance at higher temperatures. As revealed by SEM scale morphology observation, oxidation-induced cracks present at temperatures of 500 and 600 °C resulted in poor protectivity of scales and accounted for the anomalous oxidation. The weight gain data for the remaining temperatures were analyzed with an instantaneous parabolic rate constant method by assuming a parabolic rate law. The variations of instantaneous parabolic rate constant with time reflected the complexity of the oxidation behavior of Ti2AlC at intermediate temperatures. These variations were discussed from the viewpoint of phase transformation of oxidation products on the basis of XRD, Raman spectroscopy, and SEM scale morphology observation. As indicated by XRD and Raman spectra, the scale formed on Ti2AlC at higher temperature was stable α–Al2O3 and rutile TiO2, while transition aluminas of γ–Al2O3, δ–Al2O3, θ–Al2O3, and TiO2 (anatase) were detected at lower temperatures. The whisker morphology of θ–Al2O3 at 800 °C and ridged morphology of α–Al2O3 at 800 and 900 °C were confirmed by SEM.