In this work, the solid solution series directionally solidified eutectic, Co1−xNixO/ZrO2(CaO), 0 ≤ x ≤ 1, was examined as a possible model system for interfacial fracture studies. These materials were grown by the optical floating zone method in an image furnace under controlled atmospheres to prevent the formation of Co3O4. For all compositions, lamellar microstructures were produced. The interface plane orientation relationship {111} Co1−xNixO║{100} ZrO2(CaO) was maintained throughout the solid solution series. The phase compositions were close to nominal values with some solubility of CoO in ZrO2(CaO). Preliminary indentation measurements demonstrate the onset of interfacial delamination for compositions of x <0.2.

The growth and structure of the Co1−xNixO series of single crystals with 0 ≤ x ≤ 1 were investigated with the goal of achieving a single-phase crystal over several centimeters of bulk growth. The single crystals were grown via the floating zone method controlling the partial pressure of oxygen to prevent secondary phase precipitation. The resulting crystals were single phase for all compositions. CoO was a single-domain crystal but contained microvoids. The lattice parameters followed a rule-of-mixtures trend, but the coefficient of thermal expansion exhibited a maximum in the middle of the solid solution, which was attributed to enhanced vacancy formation.

The bonding structure and binding character for the initial stage of thin-film growth of Ni on a rutile (110) surface were studied using first-principles density functional theory. Our results show that, in the first monolayer, Ni atoms are preferentially adsorbed on top of bridging oxygen atoms and upon secondary surface oxygen. The bond strength between Ni adatom and substrate is much stronger than that between Ni adatoms. About 0.3 electrons are transferred from Ni atoms to substrate in low coverage; the adsorption of additional Ni atoms on neighboring sites decreases this transfer. In addition to the ionic bonding component, some covalent character is found in the Ni adatom–substrate bond.

New and modified mechanisms are proposed to account for detailed observations of carbon encapsulation of Fe, Ni, and Co nanocrystals. The mechanisms are based on aerosol and gas phase chemistry and on the catalytic effects of transition metals. Two parameters are found to qualitatively dominate production: the local-path carbon-to-metal ratio (LCM) and the global carbon-to-metal ratio (GCM). LCM's select which mechanisms are active along each pathway within the reactor. The GCM places bounds upon and determines the weighting between different LCM's and thus determines the distribution of different nanoscale products within the collected, macroscopic product. A two part processing parameter → mechanism → product map links the components. The generality of the model is discussed throughout with reference to related processes and the encapsulation of other materials.

Graphitically encapsulated ferromagnetic Ni nanocrystals have been synthesized via a modified tungsten arc-discharge method. By virtue of the protective graphitic coating, these nanocrystals are stable against environmental degradation, including extended exposure to strong acids. The magnetic properties of the encapsulated particles are characterized with regard to the nanoscale nature of the particles and the influence of the graphitic coating which is believed to be benign insofar as the intrinsic magnetic properties of the encapsulated nanocrystals are concerned. The Curie temperature of graphitically encapsulated Ni nanocrystals is the same as that of microcrystalline Ni. However, saturation magnetization, remanent magnetization, and coercivity of these particles are reduced, for a range of temperatures. The unique features are compared with those of unencapsulated nanocrystalline and coarse microcrystalline nickel particles.

Small particles are of interest for magnetic study due to their range of magnetic properties with particle size and unusual magnetic properties. In this study we produced graphite encapsulated magnetic cobalt particles and measured their structural and magnetic properties both before and after annealing at 550° C for 6 hours. No large change in the structural properties (particle size, shape, and lattice parameter) was observed as a result of the annealing. There were, however, significant changes in the magnetic properties. The coercivity was found to decrease at all temperatures, especially at temperatures below 100° K. The possible reasons for this reduction in coercivity are examined, with the change in the shape of the particles appearing most likely.

The macroscopic properties of many materials are controlled by the structure and chemistry at grain boundaries. A basic understanding of the structure-property relationship requires a technique which probes both composition and chemical bonding on an atomic scale. High-resolution Z-contrast imaging in the scanning transmission electron microscope (STEM) forms an incoherent image in which changes in atomic structure and composition across an interface can be interpreted directly without the need for preconceived atomic structure models (1). Since the Z-contrast image is formed by electrons scattered through high angles, parallel detection electron energy loss spectroscopy (PEELS) can be used simultaneously to provide complementary chemical information on an atomic scale (2). The fine structure in the PEEL spectra can be used to investigate the local electronic structure and the nature of the bonding across the interface (3). In this paper we use the complimentary techniques of high resolution Zcontrast imaging and PEELS to investigate the atomic structure and chemistry of a 25° symmetric tilt boundary in a bicrystal of the electroceramic SrTiO3.

We report on high quality Ba1−xKxBiO3 (BKBO) thin films grown by pulsed laser deposition. The best films exhibit resistive and magnetic transition temperatures of 28 K, with a transition width of 0.4 K and critical current densities above 106 A/cm2 measured at 5 K. Surface impedance is measured to be 1 mΩ. Films are single phase and highly oriented in the (100) direction and electron diffraction shows no other phases. Analysis using Moire' fringes shows films to consist of 100 nm size dislocation-free regions which show a high degree of in-plane epitaxy.

The atomic structure of a pristine (undoped) boundary in strontium titanate has been investigated using transmission electron microscopy techniques. Results of electron diffraction studies indicate a pure tilt boundary with a common \001] tilt axis, and a tilt angle of 36.8°, which corresponds to a Σ-= 5 grain boundary in the Coincidence Site Lattice (CSL) notation. High Resolution Transmission Electron Microscopy (HRTEM) indicates a symmetric tilt grain boundary with a (130) type grain boundary plane. No cation non-stoichiometry or impurity segregants could be detected at the interface, within the limits of the Energy Dispersive X-ray microanalysis technique used. The grain boundary has a compact core, with negligible planenormal rigid body translation (RBT). An in-plane RBT of (1/2)d130 (˜ 0.62 A°) was identified from the high resolution electron micrographs. An empirical model of the relaxed atomic structure of the grain boundary is proposed.

Interphase interfaces in the directionally solidified eutectics.(DSEs) of NiO-ZrO2(CaO), NiO-Y2O3 and MnO-ZrO2 have been investigated using a variety of TEM techniques. The unique lamellar morphology of the DSEs allows characterization of interfaces and identification of relaxations along multiple directions, aiding visualization of interface structure in three dimensions. Possible low energy interface orientations were identified through examination of facets. The low energy interface planes almost invariably correspond to polar surfaces of adjacent crystals. An attempt has been made to experimentally identify the variety of interfacial relaxation mechanisms using a variety of analytical TEM techniques and only HRTEM results are summarized in this paper. It was found that most of the DSE systems exhibit very little relaxation and possess tight interface cores.