GaN grown on sapphire (α–Al2O3) was characterized by laser-induced molecular beam epitaxy. Threading dislocations with Burgers vectors of 1/3〈1120〉, 1/3〈1123〉 and [0001] were observed with a predominance of the first type. Additionally, inversion domains with Ga-polarity existed with respect to the adjacent matrix, which was of N-polarity. The dislocation densities and coherence lengths were deduced from x-ray diffraction and found to be in accordance with those measured by transmission electron microscopy. Both displacement fringe contrast analysis and high-resolution transmission electron microscopy results indicated that the inversion domain boundaries had Ga–N bonds between domains and the adjacent matrix.

We investigated mechanical properties of TiN as a function of microstructure varying from nanocrystalline to single crystal TiN films deposited on (100) silicon substrates. By varying the substrate temperature from 25 to 700 °C during pulsed laser deposition, the microstructure of TiN films changed from nanocrystalline (having a uniform grain size of 8 nm) to a single crystal epitaxial film on the silicon (100) substrate. The microstructure and epitaxial nature of these films were investigated using x-ray diffraction and high-resolution transmission electron microscopy. Hardness measurements were made using nanoindentation techniques. The nanocrystalline TiN contained numerous triple junctions without any presence of amorphous regions. The width of the grain boundary remained constant at less than 1 nm as a function of boundary angle. Similarly the grain boundary structure did not change with grain size. The hardness of TiN films decreased with decreasing grain size. This behavior was modeled recently involving grain boundary sliding, which is particularly relevant in the case of hard materials such as TiN.

Strontium barium niobate (SBN) thin films were crystallized by conventional electric furnace annealing and by rapid-thermal annealing (RTA) at different temperatures. The average grain size of films was 70 nm and thickness around 500 nm. Using x-ray diffraction, we identified the presence of polycrystalline SBN phase for films annealed from 500 to 700 °C in both cases. Phases such as SrNb2O6 and BaNb2O6 were predominantly crystallized in films annealed at 500 °C, disappearing at higher temperatures. Dielectric and ferroelectric parameters obtained from films crystallized by conventional furnace and RTA presented essentially the same values.

Microstructures of potassium hexatitanate (K2Ti6O13) whiskers prepared by calcination of KF and TiO2 mixture were studied through high-resolution electron microscopy. The rod axis of a K2Ti6O13 whisker is along the [010] direction. These whiskers normally have a lamellar structure in their longitudinal direction, and adjacent lamellae usually have the same crystallographic orientation. Each lamella might be further divided into several fine layers with a width on the nanometer scale in the same crystallographic orientation. The whisker can be split in the longitudinal direction along either the boundary between two lamellae or the weak binding crystal plane, such as (100) and (201) planes. The mechanisms for the formation of lamella and layer structures and for the splitting of whiskers are discussed.

We present an x-ray scattering study on the evolution of the growth mode, the surface morphology, and the lattice strain of AlN/sapphire(0001) films during sputter growth. Aligned epitaxial planar layers with strain relaxed to about 2% are nucleated during initial stage growth. As the film thickness increases to an effective “critical” thickness of approximately 250 Å, the growth gradually crosses over to the less aligned island growth. As the growth crossover occurs, the growth front becomes substantially rougher and the residual strain begins to relax. The cogrowth of the planar layer and the islands results in a nonuniform strain distribution.

The diffusion characteristics of Mg–rare-earth diffusion couples were studied. Cylinders of pure Mg and rare earth (Dy, Nd, and Pr) were abutted and annealed at 500 °C for 100 h or 300 h. Point-by-point composition profiles were collected starting in pure Mg, across the diffusion zone, and ending in the pure rare earth, using energy dispersive x-ray spectroscopy with a scanning electron microscope. The intermetallic phases that resulted due to diffusion were identified and compared to existing phase diagrams, for which the data is limited. For each diffusion couple, a plot of concentration versus distance perpendicular to the original plane of contact was obtained and analyzed using the Boltzman–Matano method. The interdiffusion coefficients for each set of phases were then calculated. The results show that diffusion through the intermetallic phases is much slower than is expected in a solid solution.

The life of TiN-coated tools can be improved by a post-coating ion implantation treatment, but the mechanism by which this occurs is still not clear. Nitrogen implantation of both physical-vapor-deposited TiN and CVD TiN leads to surface softening as the dose increases, which has been attributed to amorphization. In this study a combination of transmission electron microscopy and atomic force microscopy was used to characterize the microstructure of implanted TiN coatings on cemented carbide for comparison with mechanical property measurements (nanoindentation, residual stress, etc.), made on the same samples. Ion implantation leads to a slight reduction in the grain size of the TiN in the implanted zone, but there is no evidence for amorphization. Surface softening is observed for physical-vapor-deposited TiN, but this is probably due to a combination of changes in surface composition and the presence of a layer of bubbles generated by the very high implantation doses used.

The objective of the present article is to study the influence of TiB2 addition on the transformation behavior of yttria stabilized tetragonal zirconia polycrystals (Y-TZP). A range of TZP(Y)–TiB2 composites with different zirconia starting powder grades and TiB2 phase contents (up to 50 vol%) were processed by the hot-pressing route. Thermal expansion data, as obtained by thermo-mechanical analysis were used to assess the ZrO2 phase transformation in the composites. The thermal expansion hysteresis of the transformable ceramics provides information concerning the transformation behavior in the temperature range of the martensitic transformation and the low-temperature degradation. Furthermore, the transformation behavior and susceptibility to low-temperature degradation during thermal cycling were characterized in terms of the overall amount and distribution of the yttria stabilizer, zirconia grain size, possible dissolution of TiB2 phase, and the amount of residual stress generated in the Y-TZP matrix due to the addition of titanium diboride particles. For the first time, it is demonstrated in the present work that the thermally induced phase transformation of tetragonal zirconia in the Y-TZP composites can be controlled by the intentional addition of the monoclinic zirconia particles into the 3Y-TZP matrix.

The elastic properties of cubic samples of compressed expanded graphite determined by means of ultrasonic velocity measurements are presented. These materials are highly porous and exhibit porosity-dependent anisotropic moduli. The results are analyzed according to two approaches. The first involves semi-empirical equations fitted to the experimental data, resulting in information about the shape and the connectivity of pores. It is found that pores are oblate ellipsoids, connected parallel to their direction of flatness. The second approach is based on application of the percolation theory near the rigidity threshold. The value of the critical exponent indicates that compressed expanded graphites behave like elastic networks in which central forces are predominant. Results of this study give evidence that ultrasound is a convenient and accurate method for investigation of the critical behavior of the elastic properties in highly tenuous structures.

Two-dimensional simulation of thermal debinding in powder injection molding based on mass and heat transfer in deformable porous media is proposed. The primary mechanisms of mass transport, i.e., liquid flow, gas flow, vapor diffusion, and convection, as well as the pyrolysis of polymers, and their interactions, are included in the model. The simulated results revealed that polymer removal process is primarily affected by liquid flow, which is mainly dominated by pressure-forced flow rather than capillary-driven flow. A significant phenomenon, enrichment with liquid polymer in the outer surface regions of the compact, is explained.

A detailed impedance analysis using the brick-layer model is performed on a high-purity yttria-stabilized tetragonal zirconia polycrystal (Y-TZP). Space-charge impedance is generally formulated and expressions for the respective space-charge models are therefrom derived depending on whether dopant ions are mobile or immobile. Pronounced yttrium segregation in Y-TZP is also considered in the analysis in that the dopant profile is assumed to be frozen from a high-temperature equilibrium distribution. Comparison with experimental observations shows that the electrically measured grain-boundary thickness corresponds to the Schottky-barrier width, slightly modified by the dopant segregation. The grain-boundary resistance is not consistent with any space-charge models and the strong defect interaction due to the yttrium enrichment is suggested to be mainly responsible.

Nanocrystalline nickel oxide–yttrium-stabilized zirconia (NiO/YSZ) composite powder for the solid oxide fuel cells was prepared by solution combustion through control of pH values and contents of glycine fuel in precursor solution. A strongly acidic precursor solution with appropriate amounts of glycine fuel added increased the specific surface area of the synthesized composite powders. This results from the increased binding of metal ions and glycine under strongly acidic solution (pH = 0.5) conditions. After sintering and reducing treatment of nanocrystalline NiO/YSZ composite, the Ni/YSZ pellet showed an ideal microstructure: fine Ni particles of 3 to 5 μm were distributed uniformly, and fine micropores around Ni metal particles were formed, thus leading to an increase in the triple phase boundary area among gas, Ni and YSZ.

Fiber textured {100}-oriented lead magnesium niobate–lead titanate (PMN–PT) (70/30) films with thicknesses between 0.35 and 2.1 mm were prepared using chemical solution processing. The degree of preferred orientation changed little with increasing thickness. However, the measured dielectric constant, remanent polarization, and piezoelectric coefficients (d31) increased with increasing film thickness. The effective d31 coefficients of highly {100}-oriented PMN–PT films on Pt-coated Si substrates were found to range from −16 to −96 pC/N. Ultraviolet illumination during poling resulted in abnormal aging behaviors and lower overall aging rates for the films. The initial nonlinear aging behavior was attributed to the presence of an internal space-charge field that developed from photoinduced charge carriers. As the space-charge field decays over time, the magnitude of d31 increased until 450–500 min after poling, at which time d31 remained either constant or declined slightly. Thus, the changes in d31 were limited to 1–2%/decade 500–600 min after poling.

Polycrystalline BaxSr(1−x)TiO3 (BST) thin films were processed on Pt-coated glass substrates at temperatures below 100 °C by reacting TiO2 films in alkaline solutions containing Ba2+ and/or Sr2+. The TiO2 was deposited by spin-casting a titanium metalorganic precursor onto Pt-coated glass substrates, followed by pyrolysis in air at 400 °C. Film stoichiometry deviated from the initial solution composition, with a preferred incorporation of Sr2+ into the perovskite lattice. The BST thin films had dielectric constants ranging from 100 to 185 and dielectric loss values below 0.25. Capacitance–voltage and current–voltage relationships were examined to determine the effect of phase stoichiometry and processing route on dielectric properties.

Superplastic behavior of heavily drawn Cu–at.% Ag filamentary microcomposite wires was investigated. The filamentary microstructure tended to break up at high temperatures by spheroidization, grooving, and/or recrystallization because of its high interface energy and high cold-work energy. Above 400 °C, extensive recrystallization occurred and the grains 300–500 nm in size were observed in the Cu matrix. As the deformation proceeded, the elongated silver lamellae and/or the region with numerous filaments broke up and rearranged into chevron patterns, which mostly lay perpendicular to the loading axis. The elongation up to 1000% was obtained at 500 °C at the strain rates of 7 × 10−4/s and −3 × 10−3/s, and the elongation up to 600% was obtained at 400 °C at the strain rate of 1 × 10−4/s. Arrays of dislocations in the matrix and near grain and phase boundaries were observed after superplastic deformation, supporting the slip-accommodated grain and/or phase boundary sliding.

Nanometer-scale plowing friction and wear of a polycarbonate thin film were directly measured using an atomic force microscope (AFM) with nanoscratching capabilities. During the nanoscratch tests, lateral forces caused discrepancies between the maximum forces for the initial loading prior to the scratch and the unloading after the scratch. In the case of a nanoscratch test performed parallel to the cantilever probe axis, the plowing friction added another component to the moment acting at the cantilevered end compared to the case of nanoindentation, resulting in an increased deflection of the cantilever. Using free-body diagrams for the cases of nanoindentation and nanoscratch testing, the AFM force curves were analyzed to determine the plowing friction during nanoscratch testing. From the results of this analysis, the plowing friction was found to be proportional to the applied contact force, and the coefficient of plowing friction was measured to be 0.56 ± 0.02. Also, by the combination of nanoscratch and nanoindentation testing, the energetic wear rate of the polycarbonate thin film was measured to be 0.94 ± 0.05 mm3/(N m).

Titania and copper-loaded titania were synthesized by an improved sol-gel method using a homogeneous hydrolysis technique. Unlike the conventional sol-gel procedure that added water directly, the esterification of anhydrous butanol and glacial acetic acid provided the hydrolyzing water. In addition, acetic acid also served as a chelating ligand to stabilize the hydrolysis-condensation process and minimize the agglomeration of titania. Fourier transform infrared spectra confirmed the presence of bidental ligand. The sol was dried, then calcined at 500°C to remove organics and transformed to anatase titania. Transmission electron microscopy revealed that the titania particles were uniform, and the particle size ranged from 10 to 25 nm. The band gaps of TiO2 and Cu/TiO2 ranged from 3.01 to 3.17 eV based on the diffusive reflective ultraviolet-visible spectrometry. X-ray photoelectron spectroscopy analysis showed a positive shift of binding energy of Ti2p3/2 and a negative shift of Cu 2p3/2 in Cu/TiO2. The redistribution of electric charge is due to the Schottky barrier of Cu and TiO2.

An optically polished x-cut KTiOPO4 crystal of size 22×6×1.5mm3 was implanted with 2.8-MeV He ions to a dose of 1.5 × 1016 ions/cm2 at room temperature to form a waveguide. The prism coupling method was used to measure the modes and the fiber probe technique was used to measure the attenuation in the KTiOPO4 waveguide. The refractive index profile, nz, in the KTiOPO4 waveguide was given based on the procedure by Chandler and Lama [P.J. Chandler and F.L. Lama, Optica Acta 33, 123 (1986)]. The waveguide attenuation measured was 2.57 dB/cm for m = 1 mode. After annealing at 260 °C for 30 min, there was no obvious change in the KTiOPO4 waveguide attenuation.

Spontaneous polarization reversal and domain structures of flux-grown ferroelectric KTiOPO4 and isomorphic crystals were studied. Two temperature regions with dominant either ionic or electronic conductivity were found. It was shown that in the high-temperature region mobile cations contributed sufficiently to internal screening process. The ionic leakage current was suppressed at a specific temperature point for each studied crystal. High crystallographic asymmetry of domain wall velocity was observed. This shows that the electrode pattern should be properly oriented relative to the crystal axes of KTiOPO4 and its isomorphs for fabrication of periodically poled domain configurations used in nonlinear optical conversions.

Our phenomenological model without adjustable parameters for the size dependence and dimension dependence of melting point depression and enhancement of nanocrystals is introduced. The predictions of our models are consistent with both of experimental results and other thermodynamic models for metallic nanocrystals while the difference between our model and other theoretical considerations in mesoscopic size range is discussed.