The characteristic inhomogeneous distribution of nonsuperconducting Y2BaCuO5 (211) inclusions in melt-processed YBa2Cu3O7−δ (123) grains has generally been attributed to 211 particle pushing by 123 growth fronts during peritectic solidification on the basis of reduced total surface free energy. Analysis of the morphology of the interfaces at the 211–211–123 and 211–211-liquid triple points in seeded melt-processed samples invalidates this assumption for the pure YBCO system and has implications of the mechanism of 211 particle segregation.

A kind of fullerenes, carbon nanoparticle encapsulating β–SiC grain, was precipitated during cooling Al2O3–Y2O3 –CaO oxide melt containing SiC and C from 2023 K. The SiC grains with a diameter of 5–20 nm were covered with 2–4 graphitic carbon layers with the spacing of 0.34 nm as revealed by high resolution transmission electron microscopy. The result provides a new preparation method of carbon nanoparticles through a ceramic process, which contrasts with previous physical methods applying electric arc discharge or electron irradiation in vacuum.

AlZrN protective film with high transmissivity was deposited onto the organic photoconductor (OPC) surface, and the surface hardness was greatly increased by a factor of 1.5–3. The OPC surface protected by (Al100−xZrx)N (x ≤ 58.5%) film was significantly harder than that protected by AlN film. The electrophotographic properties of the OPC coated with (Al100−xZrx)N (x ≤ 37.7%) film were also better than those without coating or protected with AlN film, thus demonstrating the suitability of AlZrN film as a protective coating for enhancing the operating life of OPC.

A set of equations were derived to estimate systematic errors in experimental determinations of volume fractions transformed by microscopy methods. For reactions that occur by continuous nucleation and growth, the experimental values of volume fractions transformed may be subjected to significant errors when the largest grain size of the distribution is close to the microscope resolution limit. For transformations occurring from a fixed number of nuclei, the systematic errors are smaller than those observed in the continuous nucleation case, but can still be significant when reflection methods are used. Transmission methods lead to smaller errors than reflection techniques.

The growth of large grain YBa2Cu3O7−δ (YBCO) by peritectic solidification in the presence of a (Sm,Y)Ba2Cu3O7−δ seed is characterized by the initial seeding process, development of a facet plane around the seed, and finally by continuous nonlocal growth away from the seed. A detailed investigation of the seeding process using electron microscopy, electron probe microanalysis, and thermal analysis techniques is reported here as the first in a series of studies of these key growth features. Results show that the seed partially melts below its nominal melting temperature due to a distribution of yttrium cations across the seed/YBCO interface. The formation of a Sm/YBa2Cu3O7−δ solid solution, which occurs via a reaction between (Sm,Y)2Ba2CuO5 and liquid state Ba3Cu5O8, has been observed across this interface at temperatures below the peritectic temperature Tp of the seed. The temperature window available for melting the YBCO phase while avoiding full peritectic decomposition of the (Sm,Y)Ba2Cu3O7−δ seed is maximized for seeds of high Sm content and thickness in excess of 0.2 mm. Finally, the dwell time at temperatures above Tp should be as short as possible if the integrity of the seed is to be maintained throughout the YBCO growth process.

We have developed a process for the fabrication of (001) oriented SrTiO3 buffer layers onto (001) MgO substrates by rf magnetron sputtering followed by a post-deposition heat treatment in air. Precursor films with Tl :Ba : Ca : Cu ratio 2 : 2 : 2 : 3 were deposited by dc magnetron sputtering onto both these buffered substrates and directly onto (001) SrTiO3 single-crystal substrates, and thalliated at elevated temperatures. Because of Sr diffusion from the substrate/buffer layer, and its subsequent substitution for Ba in the superconducting film, the single Tl–O layer phase Tl(Ba1−xSrx)2Ca2Cu3Oy was stabilized. Diffusion of Ba and Ca in the opposite direction led to the formation of a Ba–Ca–Ti–O compound at the interface. The Tl(Ba1xSrx)2Ca2Cu3Oy films typically have superconducting transition temperatures (Tc's) > 103 K and critical current densities (Jc's) > 2.9 × 105 A cm−2 at 77 K. Rs values measured on these films and scaled to 10 GHz were 3.0 mΩ at 80 K and <200 µΩ at 50 K for the film grown on SrTiO3 buffered MgO, and 2.0 mΩ and 1.0 mΩ at 50 K for the film grown directly onto the (001) SrTiO3 substrate. Films fabricated on (001) SrTiO3 using an in situ deposition technique with a substrate temperature around 100 °C lower than the ex situ thalliation temperature showed no evidence of an interfacial reaction layer.

Measurements of structural and electrical properties as a function of the molding pressure in Y1Ba2Cu3O7−δ superconductors have been performed to investigate the texturing behavior. The magnitudes of the molding pressure were 0.5 × 103 N/cm2, 1 × 103 N/cm2, 2 × 103 N/cm2, and 4 × 103 N/cm2. As the molding pressure increases, the anisotropy of the crystal structure decreases and the crystal grows preferentially along the c-axis. As the molding pressure increases, since the size of the grain becomes larger due to the decreased porosity, denser textures are formed. This result indicates that the critical current density is improved, resulting in increased thermal stability at higher molding pressure. While the molding pressure does not affect the oxygen mole fraction below 500 °C, increases in the molding pressure have a remarkable effect on the formation of textures and on the onset temperature for the superconducting transition in Y1Ba2Cu3O7−δ. These results indicate that structural and electrical properties in Y1Ba2Cu3O7−δ superconductors are affected by the molding pressure during growth.

Depth-sensing indentation measurements are performed with two different Vickers indenters and one Berkovich indenter. The sample materials were mirror polished Ag, Al, Au, Ni, and Ti samples. From the load-indentation depth data, the conventional hardness plots as well as the first derivative are calculated. The latter procedure yields a specific volume related density of deformation energy in the probed material. That specific energy density is shown to be a constant material parameter for extended indentation depths and for different Vickers indenters. Vickers and Berkovch indenters delivered within the error margin the same results.

The high-temperature equilibrated atomic structures and energies of large-unit-cell grain boundaries (GB's) in diamond and silicon are determined by means of Monte-Carlo simulations using Tersoff's potentials for the two materials. Silicon provides a relatively simple basis for understanding GB structural disorder in a purely sp3 bonded material against which the greater bond stiffness in diamond combined with its ability to change hybridization in a defected environment from sp3 to sp2 can be elucidated. We find that due to the purely sp3-type bonding in Si, even in highly disordered, high-energy GB's at least 80% of the atoms are fourfold coordinated in a rather dense confined amorphous structure. By contrast, in diamond even relatively small bond distortions exact a considerable price in energy that favors a change to sp2-type local bonding; these competing effects translate into considerably more ordered diamond GB's; however, at the price of as many as 80% of the atoms being only threefold coordinated. Structural disorder in the Si GB's is therefore partially replaced by coordination disorder in the diamond GB's. In spite of these large fractions of three-coordinated GB carbon atoms, however, the three-coordinated atoms are rather poorly connected amongst themselves, thus likely preventing any type of graphite-like electrical conduction through the GB's.

Precipitates in GaN epilayers grown on sapphire substrates were investigated by atomic number contrast (ANC), wavelength-dispersive x-ray spectrometry (WDS), energy-dispersive spectrometry (EDS), and cathodoluminescence (CL) techniques. The results showed that the precipitates are mainly composed of gallium and oxygen elements and distribute more sparsely and inhomogeneously in directions in the sample grown on substrate nitridated for a longer period. Yellow luminescence intensity was imaged to be stronger in the precipitates. The results suggest that the precipitates are formed on dislocations and grain boundaries by substituting oxygen onto the nitrogen site, and result in the formations of deep levels nearby.

A technique for microstructural control of excimer laser-annealed silicon thin films on SiO2 substrates has been developed. By using single-crystal photolithographically etched silicon seed wafers in intimate contact with the silicon films, we have shown that it is possible to spatially control nucleation. Transmission electron micrographs show the resultant microstructure to consist of large (∼1 µm) grain structures in the area surrounding the seed contact, with distinct organization not previously observed. A theoretical discussion is presented to explain the observed phenomena. Also, results from a numerical simulation are given which outline the effects of the seed wafer on the resultant microstructure of the laser-annealed film, as compared to nonseeded areas.

ZnO ceramics used as varistors are prepared with cobalt oxide as an essential additive to improve nonohmic properties. Because some of its effects during the liquid-phase sintering remain unexplained, we characterize the liquid-phase formation temperatures and phase reactions in the system ZnO–PrO1.5–CoO. Using differential thermal analysis (DTA) during sintering, we detect new thermal phenomena. An addition of cobalt oxide to ZnO–PrO1.5 mixtures (ZnO–5 mol% PrO1.5–10 mol% CoO) significantly decreases the liquid-phase formation temperature to 1272 ± 5 °C, which is about 110 °C lower compared to those in the ZnO–PrO1.5 system. Characterization of ceramics quenched during sintering allows us to describe an isoplethal section with PrO1.5 contents of 5 mol% and solubility limit of Co in ZnO.

Ti and TiNx (x < 1) thin films have been deposited on high speed steel (HSS) substrates by reactive sputtering and then N+ implanted. The increase of the N/Ti ratio of the films during deposition is related to a decrease in their roughness, and N+ implantation produces another additional slight decrease of the roughness. The hardness of samples increases with the nitrogen content in the as-deposited samples; nevertheless, N+-implanted Ti coatings show lower values of hardness than reactive sputtered TiNx films. α–Ti, ε–Ti2N, and δ–TiN phases were identified by grazing x-ray diffraction.

In an attempt to take advantage of charged particle irradiation for studying the effects of irradiation on the mechanical properties of metals, we developed an experimental procedure based on the combination of transmission electron microscopy (TEM) and submicron indentation of ion-implanted layers. We applied this technique to industrial 316L steel, irradiated with krypton ions up to 10 dpa at 873 K. A domain where the penetration range of the ions and the indentation depth are compatible has been identified. The indentation tests then yielded a good estimate of hardness and bulk modulus, while the TEM observations provide microstructural information in the plastic regime. It is shown that the combination of the two techniques is necessary for rationalizing the observed results.

The local structure and crystallization behavior of Nd15Fe77Bx (x = 2−14) melt-spun alloys were studied by Nd L3 extended x-ray absorption fine structure (EXAFS). The conventional x-ray powder diffractometry studies showed that the Nd–Fe–B melt-spun ribbons had the amorphous structure regardless of the boron content. EXAFS studies of the local structure around the Nd atom confirmed that the Nd–Fe–B melt-spun alloys had the amorphous structure and virtually the same nearest neighbor distance from the Nd atom. The amorphous alloys were heated by a differential scanning calorimetry in order to investigate the variation in the local structure during the crystallization process by EXAFS measurements. Although no appreciable difference was found in the nearest neighbor distance of the Nd atom between the amorphous alloys and the crystallized alloys, the small variation in the nearest neighbor distance during the crystallization process was detected by EXAFS measurements.

Graphite encapsulated nanoparticles have numerous possible applications due to their novel properties and their ability to survive rugged environments. Evaporation of Fe, Ni, or Co with graphite in a hydrogen atmosphere results in graphite encapsulated nanoparticles found on the chamber walls. Similar experiments in helium lead to nanoparticles embedded in an amorphous carbon/fullerene matrix. Comparing the experimental results in helium and hydrogen, we propose a mechanism for the formation of encapsulated nanoparticles. The hydrogen arc produces polycyclic aromatic hydrocarbon (PAH) molecules, which can act as a precursor to the graphitic layers around the nanoparticles. Direct evidence for this mechanism is given by using pyrene (C16H10), a PAH molecule, as the only carbon source to form encapsulated nanoparticles.

Silica glass plates (Corning 7940 excimer grade) were implanted sequentially with N+ at 52 keV to different doses, ranging from 0 to 1.2 × 1017 ions cm−2, and then with Fe+ at 160 keV to 6 × 1016 ions cm−2 at room temperature and 4 µA cm−2. The intensity of ferromagnetic magnetic resonance (FMR) absorption and the magnetization calculated by the angular dependence of the FMR field reach maxima at an N/Fe atomic ratio ∼0.2. Two peaks due to Fe 2p3/2 electron are observed at 707.2 ± 0.2 and 710.9 ± 0.2 eV in the x-ray photoelectron spectra. The intensity of the former relative to the latter decreases with increasing the N dose. The conversion electron Mössbauer spectrum reveals the formation of superparamagnetic iron nitride as well as the existence of Fe2+ and Fe3+ in silica when implanting N+ to 7.5 × 1015 ions cm−2 and then Fe+ to 6 × 1016 ions cm−2 at N/Fe = 0.125. These results suggest that sequential ion-implantation of N+ and Fe+ produces iron nitride in silica glasses.

The durability of a specific backfilling pozzolanic cement mortar, which is employed in Spain, in concrete containers for the storage of low (LLW) and medium level wastes (MLW), has been studied by means of the Köch–Steinegger test at the temperature of 40 °C during a period of 365 days. Mortar samples were immersed in a simulated radioactive liquid waste very rich in sulphate (0.68 M), phosphate (0.89 M), and chloride (0.51 M) ions. The changes of the microstructure were followed by x-ray diffraction (XRD), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM). Pore solution was extracted at different periods in order to see the changes of the chemical composition caused by the diffusion of those ions inside the microstructure.

The structural changes and magnetoresistance (MR) properties of as-grown and post-annealed La0.7Ca0.3MnO3 films were investigated by transmission electron microscopy (TEM) and x-ray diffraction (XRD). The data for the films were compared to that for bulk La0.7Ca0.3MnO3 post-annealed under the same conditions. The main structure of the as-grown films was face-centered pseudo-cubic with a doubled perovskite unit cell, of size ∼2ap × ∼2ap × 2ap, where ap is the single perovskite parameter. The phase showed a cube-on-cube epitaxy with the underlying LaAlO3 substrate. Upon annealing to a saturation point, a minor primitive pseudo-tetragonal structure evolved, of cell parameters . A total of four possible orientations of the two structures was observed by TEM, comprised of one orientation of the ∼ 2ap × ∼ 2ap × ∼ 2ap cell, i.e., the cube-on-cube epitaxy, giving rise to (00l) peaks in x-ray, and three orientations of the cell, giving rise to a single (00l)/(hk0) peak in x-ray. The bulk La0.7Ca0.3MnO3 sample also contains the × structure. The difference between the bulk and the film and the effects of annealing on films can be ascribed to the influence of strain between the film and substate, induced by lattice mismatch.

Lead zirconate titanate (PZT) powder is prepared by the sol-gel method. The formation of pyrochlore and perovskite phases is investigated by high temperature x-ray diffraction (XRD) and thermal analysis techniques. The pyrochlore phase first appears in x-ray amorphous form, and then gets converted to crystalline state on annealing in air. We show that vacuum annealing of the pyrolyzed amorphous PZT gel suppresses the formation of the crystalline pyrochlore phase. This, in turn, enhances the kinetics of conversion of pyrochlore to perovskite, such that a pyrochlore-free perovskite phase can be obtained by annealing at about 500 °C. On the other hand, if annealing is carried out in air, a crystalline pyrochlore phase is formed, which requires annealing temperatures higher than 600 °C for transformation to the perovskite phase. These observations are explained tentatively in terms of the oxygen stoichiometry of the two phases.