The stability of BaFe12O19 and BaFe2O4 was studied by the oxygen coulometric titration technique between 700 °C and 1000 °C using a solid-state electrochemical cell. This temperature range is technologically important for the deposition of BaFe2O19 magnetic thin films. The thermodynamic information obtained from the titration measurements was corroborated with structural identification of phases prepared under electrochemically controlled conditions. Accordingly, a section of the Ba–Fe–O ternary phase diagram around the BaFe12O19 composition was constructed in this temperature range. The standard Gibbs free energy change for the decomposition of BaFe12O19 into BaFe2O4, Fe3O4, and O2 is given by the expression ΔG°[J/mol] = 7.23 × 105 −480T. In the oxygen pressure-temperature domain, the thermodynamic stability limits of BaFe12O19 and BaFe2O4 are given by the expressions In[Po2(atm)] = 69.37 −1.04 × 105 T−1 and In[Po2(atm)] = 27.68 −7.12 × 104 T−1, respectively. The stability limits determined here help define the process conditions for the successful synthesis of these phases.

The reaction between the Ba-Cu-O melt (with a Ba to Cu ratio of 3-5 or 3-7) used for crystal pulling of Y-123 and several prospective crucible materials (MgO, Y2O3, Al2O3, and YSZ) has been investigated by dipping these materials into the melt at 985 °C and 1050 °C in air. For comparison, MgO, YSZ, LaAlO3, and SrTiO3 single crystals were also investigated. In the case of MgO single crystals, no wetting or reactive layer has been observed, although with increasing time an increasing amount of MgO has been dissolved into the melt. The contact angle between melt and MgO single crystal can be estimated to be about 40°, assuming a surface tension of 0.3 N/m. For all other materials, increasing time was accompanied by increasing wetting and/or an increasing reaction layer. For MgO polycrystals increased wetting with increasing time has been observed. For example, it takes about 30 min to wet the first 10 mm. The melt completely permeates samples with an apparent density of up to 85%. However, the permeated depth becomes very thin in samples with an apparent 95% density. It was found that Y2O3 is a better barrier to the melt at lower densities because even at 85% density the permeated layer is very thin, but the surface wetting occurs at a slightly faster rate for Y2O3 than for MgO.

The HNaMP2O7 (where M = Co and Ni) new Na+ superionic pyrophosphates were obtained by the hydrothermal method at lower PT conditions (T = 250 °C, P = 100 atm). The solubility, complexation with reference to the solvent-solute interaction, and the growth process have been studied in detail. A new investigation on the crystal structure of these compounds showed that the title compounds do not contain Zr as reported previously. The crystal morphology and properties have also been studied.

The effects of annealing on B2O3-contained ZnO varistors with particular emphasis on the degradation behavior, nonlinear coefficient, trap density, donor density, and Schottky energy barrier were investigated. The thermal stability of ZnO varistors was considerably improved by the thermal annealing process.

The influence of NaCl (3% of Cl−by weight of cement) on the reactivity of High Alumina Cement (HAC) in water has been studied over a period of one month. The changes in microstructure were monitored by x-ray diffraction and scanning electron microscopy. The pore-solution, extracted by the application of high mechanical pressure (500 MPa), was studied for the chemical composition and changes caused by chloride and sodium ions.

Free-standing CVD diamond disk-shaped films of varying thicknesses between ∼40 and 1000 μm were fractured in ball-on-ring flexure using a high-precision hydraulic testing machine. Some of the films were smooth on the side formerly in contact with the substrate and rough (large crystallites) on the reverse side and some of the films were polished. Raman spectroscopic examination showed some of the films to be of high quality and others to be of lower quality (higher levels of non-diamond carbon mixed with diamond phase). All fracture surfaces were examined to identify the origin of failure. Strength varied between 650 and 971 MPa, and the fracture toughness was determined from fracture surface analysis to average 8 ± 1 MPam1/2.

We describe a growth mechanism of CVD diamond films consisting of a series of surface reactions. It is derived from experimental observations of a sequential deposition process in which incident carbon flux and atomic hydrogen flux were independently varied. In this sequential process, film growth rate increased with atomic hydrogen exposure, and a saturation in the utilization of carbon was observed. These features are consistent with a surface growth process consisting of the following steps: (i) the carburization of the diamond surface, (ii) the deposition of highly disordered carbon on top of this surface, (iii) the etching of disordered carbon by atomic hydrogen, (iv) the conversion of the carburized diamond surface to diamond at growth sites by atomic hydrogen, and (v) the carburization of newly grown diamond surface. The nature of the growth sites on the diamond surface has not been determined experimentally, and the existence of the carburized surface layer has not been demonstrated experimentally. The surface growth mechanism is the only one consistent with the growth observed in conventional diamond reactors and the sequential reactor, while precluding the necessity of gas phase precursors.

A thick as-grown diamond film was examined directly by conventional transmission electron microscopy (TEM) without thinning, and the important microstructures near the growth surface were characterized. Specimen preparation for TEM involved simply fracturing the film; some of the diamond grains located on the specimen edge were thin enough to be directly examined by TEM. The 3-D topography of the diamond grains located at the intersection of the growth and the fracture surfaces was obtained using secondary electron images, so that the 2-D projected grain geometry could be derived easily to help interpret the TEM images. A diamond film grown with a 〈001〉 texture and having grains 2–3 μm diameter with {001} facets parallel to the substrate and four inclined {111} facets was examined. Grains with fracture surfaces that intersected the top (001) facet, grains with fractures that intersected only {111} facets, and unfractured grains were studied. It was found that the core volume bounded by the (001) top facet and its projected column defined by orthogonal internal {110} were free from microtwins, but contained a few dislocations. The remaining volume around this core, bounded by {111} facets (or grain boundaries) and the internal {110}, was filled with microtwins. The microtwins were not merely at the {111} surfaces. Our results reveal a growth mechanism in which microtwins are formed as material is added to {111} but not {001}. The formation of microtwins in CVD diamond is thus clearly associated with growth on {111} surface facets.

The interface between diamond and silicon, fabricated by growing diamond films on (001) silicon by microwave plasma assisted chemical vapor deposition (MPACVD), was characterized by high-resolution transmission electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS). Two types of interface morphology were identified. Type A interfaces contain an amorphous transition layer composed of silicon, carbon, and oxygen; the diamond overgrowth on this layer consists of nanocrystalline grains with random orientations. Type B interfaces consist of large diamond grains having special orientations with respect to the silicon substrate, without an obvious presence of a glassy phase and with a much lower oxygen content than type A interfaces.

A novel technique to enhance the nucleation of low-pressure diamond on silicon (100) was discussed in this study. It was found that coating the silicon with ballpoint pen ink can greatly increase the diamond nucleation density when the coating was followed by heat treatment at 100 °C–400 °C. Moreover, the optimum enhancement effect was reached when the ink coating was pre-heat-treated at 300 °C × 30 min. Further SEM observation showed that heat treatment at 200 °C-400 °C produced many tiny carbonaceous particles on ballpoint pen ink-coated silicon. Particularly, the nucleation density of diamond on differently treated silicon, such as ink-coated, diamond paste scratched and polished silicon wafers, was compared using the SEM technique. The diamond structure was also characterized by Raman spectroscopy.

The measured room temperature magnetic susceptibility of a bulk sample of buckytubes (buckybundle) is −10.75 × 10−6 emu/g for the magnetic field parallel to the buckybundle axis, which is approximately 1.1 times the perpendicular value and 30 times larger than that of C60. The experimental results are discussed in terms of a graphite-like electronic structure model.

Three coating techniques (metal-organic chemical vapor deposition, magnetron sputtering, and plasma-enhanced chemical vapor deposition) were employed to deposit different coating materials (alumina, a superalloy, and silicon nitride) on graphite-fiber-reinforced polyimide composites to protect against oxidation at elevated temperatures. Adhesion and integrity of the coatings were evaluated by isothermal aging (371 °C for 500 h) and thermal cycling (25 to 232 °C for 1000 cycles and −18 to 232 °C for 300 cycles). Best results were achieved with a plasma-deposited, amorphous silicon nitride (a-SiN: H) coating, which withstood stresses from 0.18 to −1.6 GPa. The major factors affecting the suitability of a-SiN: H as an oxidation protective coating are the surface finish of the polymer composite and the presence of a sizable hydrogen content in the coating.

Cd-arachidat in the form of Langmuir-Blodgett films and thick photoresist layers of AZ5412H have been exposed to 15N-ion beams. The physico-chemical state of these targets as a function of the 15N fluence has been monitored by the 15N nuclear reaction with the respective H component. In this way, radiolytic changes in H distribution and bonding have been measured. In particular, diffusion and desorption processes have quantitatively been followed up to fluences of about 1 × 1016 N/cm2 at temperatures as low as 40 K. The correlated changes in H bonding, obtained by analyzing the concomitant Doppler widths as a function of the 15N fluence, consist of both decomposition and restoration of C-H and H-H molecular groups.