Three natural type IIa diamond crystals were used for forced diffusion of boron. The diffusion was performed under bias otherwise with the same conditions. The boron diffusion coefficient in diamond was found to be 8.4 × 10−15 and 4 × 10−14 cm2/s at 1000 °C, depending on the direction of the electric field. The drift velocity of boron in diamond under 850 V at 1000 °C was found to be about 1.2 × 10−8 cm/s.

The stoichiometric intermetallic compound NbSi2 has been synthesized by mechanical alloying (MA) elemental Nb and Si powders. The alloying process has been investigated by means of x-ray diffraction (XRD) and differential scanning calorimetry (DSC). It was found that the formation of the Nb2Si intermetallic compound occurs abruptly after 65 min of milling without any interruptions during the alloying process. However, short interruptions at a 5 min interval during ball milling result in a gradual reaction for the formation of the NbSi2 compound as well as a new metastable bcc structured solid solution. We conclude that the temperature rise during mechanical alloying plays an important role in initiating the abrupt reaction after an incubation milling time.

Pb(ZrxTi1−x)O3 and PbZrO3 heteroepitaxial thin films were produced in an aqueous solution (10 M KOH) at ambient pressure and low temperatures (90–150 °C) on (001) SrTiO3 and LaAlO3 single crystal substrates. Growth of the Pb(ZrxTi1−x)O3 and PbZrO3 thin films initiates by the formation of {100} faceted islands. Energy dispersive spectroscopy (EDS) analysis of the Pb(ZrxTi1−x)O3 thin film shows that the Zr: Ti ratio is 45: 56, nearly identical to the molar ratio of the precursors. This route might provide a viable low temperature alternative for the formation of high dielectric constant thin films for applications such as dynamic random access memory (DRAM).

Ferroelectric thin films of Pb(Zr, Ti)O3 (PZT) were fabricated on platinum-coated silicon using the process of direct-current glow discharge assisted laser deposition, where the substrate was electrically grounded. The films deposited at 730 °C with +800 V discharge voltage are oriented mostly with the c-axis perpendicular to the substrate surface, and exhibit good ferroelectric hysteresis loops. A possible mechanism for the improvement of the deposition process has been proposed.

The direct current (dc) electrical conductivity of the conducting polymer Versicon™ blended in poly(vinyl chloride) (PVC) was measured from 25 K to 310 K. The data were fitted to various electrical transport models, and the best fit was found with the fluctuation-induced tunneling model, suggesting that tunneling dominates in the mode of electron transport at low temperatures. The parameters, T1 and T0 from the fluctuation-induced tunneling model, were found to be 625 K and 129 K, respectively. The interparticle distance was estimated to be about 13 Å. At higher temperatures, the plot of the log of resistivity versus the reciprocal of the temperature was linear, indicating that thermally activated hopping dominated the mode of electrical transport at these temperatures. The results support earlier findings that VersiconTM forms continuous aggregates in blends. The results also support growing evidence in the literature that these types of aggregate formation tend to strongly influence the mode of electrical transport in composites.

The SiCp/Al nanocomposites were synthesized under high pressure. The reaction behavior between SiC particles and Al matrix within 2–6 GPa pressure range was determined. The high resolution electron microscopy (HREM) observation and the Vickers microhardness measurement show that the reaction is slight and that the adhesion of SiC particles to the Al matrix is good whether the reaction between them occurred or not. This offers an opportunity to tailor the nanocomposite mechanical properties by adjusting the synthesis temperature, pressure, and volume fraction of SiC particles.

The origin of a previously reported anomalous low 2θ x-ray diffraction peak from MoS2 thin films grown by ion beam assisted deposition was investigated. The anomalous peak, observed in a film grown on Si(100), was removed by ion irradiating the film with 180 keV Ar++ ions to a dose of 1 × 1015 ions/cm2. Microstructures of the two films were investigated using x-ray diffraction and cross-section transmission electron microscopy. Diffraction data and bright-field images indicated that the low 2θ peak was due to a local interplanar expansion of the crystal structure normal to MoS2 basal planes. This expansion was attributed to molecular defects.

Raman microspectroscopy (RMS) and imaging Raman microscopy (IRM) were used to probe the composition and spatial distribution of chemical phases in Bi(Pb)–Sr–Ca–Cu–O (BSCCO) ceramic superconductor powders and silver-BSCCO composites. The Raman techniques were used to identify various phases, including alkaline earth cuprates, CuO, Bi-2212, Bi-2223, and Pb-containing phases. Changes in the Ca/Sr ratios in (Ca, Sr)2CuO3 phases were distinguished by differences in orientation with respect to polarization of the exciting radiation. Variations were observed in the content and distribution of lead in various phases formed during intermediate stages of the thermal processing of composite conductors. The spatial distribution of the various phases detected in powder and composite conductors was established to a resolution of a few microns by collecting images of the Raman scattering at wavelengths corresponding to the signature peaks of the observed phases. Reference Raman spectra of the major phases observed in the BSCCO system are also reported. The Raman techniques, when combined with complementary techniques, such as x-ray diffraction and electron microscopy, can provide valuable information about the reaction paths and mechanisms of the high temperature BSCCO superconducting ceramics.

Dense YBa2Cu4O8 (124) ceramics were prepared by the following two-stage sintering: compressed 124 powders were heated to 1203 K for decomposition to YBa2Cu3O7−x (123) and CuO, and then cooled down to 1073 K and annealed for the re-formation of 124 single phase. The relative densities thus obtained were 93–95%, as high as those prepared under high oxygen pressure. The densification was considered to take place due to the liquid phase. In the sintered 124, the island-like fine grains of CuO were observed within the 123 matrix. As a result, it was considered that the re-formation of 124 proceeded in each grain. The geometrical phase distribution in the grains is discussed on the basis of superconducting properties from resistivity measurements.

Barium and potassium hydroxide have been investigated as fluxes for the growth of cuprate single crystals. The relatively high solubility of transition metals and lanthanoids in these salt fluxes at moderate temperatures allows significant lowering of the growth temperatures required for many phases. Also, phases not stable at high temperatures become accessible. Two new cuprates have been prepared in the Ba–Ca–Cu–O and Ba–Y–Cu–O systems from a Ba(OH)2 · H2O flux. The compounds Ba3(Y0.23Cu0.77)2O5.78 and Ba3(Ca0.24Cu0.76)2O4.43 crystallize in a tetragonal (space group I4/mmm) oxygen deficient Sr3Ti2O7-type structure with lattice parameters a = 4.069(2) Å, 4.022(1) Å and c = 21.61(2) Å, 21.63(2) Å, respectively. The compound (Ba0.92Sr0.08) (Ca0.38Cu0.62)O2.1 crystallizes with a doubled perovskite unit cell along all three axes, a = 8.116(4) Å. In addition, single crystals of Ba2Ycu3O7–δ have been prepared from a KOH flux at 750 °C.

Epitaxial Tl2Ba2CaCu2O8 thin films with excellent electrical transport characteristics are grown in a two-step process involving metal-organic chemical vapor deposition (MOCVD) of a BaCaCuO(F) thin film followed by a postanneal in the presence of Tl2O vapor. Vapor pressure characteristics of the recently developed liquid metal-organic precursors Ba(hfa)2 • mep (hfa = hexafluoroacetylacetonate, mep = methylethylpentaglyme), Ca(hfa)2 • tet (tet = tetraglyme), and the solid precursor Cu(dpm)2 (dpm = dipivaloylmethanate) are characterized by low pressure thermogravimetric analysis. Under typical film growth conditions, transport is shown to be diffusion limited. The transport rate of Ba(hfa)2 • mep is demonstrated to be stable for over 85 h at typical MOCVD temperatures (120 °C). In contrast, the vapor pressure stability of the commonly used Ba precursor, Ba(dpm)2, deteriorates rapidly at typical growth temperatures, and the decrease in vapor pressure is approximately exponential with a half-life of ∼9.4 h. These precursors are employed in a low pressure (5 Torr) horizontal, hot-wall, film growth reactor for growth of BaCaCuO(F) thin films on (110) LaAlO3 substrates. From the dependence of film deposition rate on substrate temperature and precursor partial pressure, the kinetics of deposition are shown to be mass-transport limited over the temperature range 350–650 °C at a 20 nm/min deposition rate. A ligand exchange process which yields volatile Cu(hfa)2 and Cu(hfa) (dpm) is also observed under film growth conditions. The MOCVD-derived BaCaCuO(F) films are postannealed in the presence of bulk Tl2Ba2CaCu2O8 at temperatures of 720–890 °C in flowing atmospheres ranging from 0–100% O2. The resulting Tl2Ba2CaCu2O8 films are shown to be epitaxial by x-ray diffraction and transmission electron microscopic (TEM) analysis with the c-axis normal to the substrate surface, with in-plane alignment, and with abrupt film-substrate interfaces. The best films exhibit a Tc = 105 K, transport-measured Jc= 1.2 × 105 A/cm2 at 77 K, and surface resistances as low as 0.4 mΩ (40 K, 10 GHz).

Diamond growth conditions for an atmospheric combustion flame have been optimized using statistical experimental design. Films are grown on a molybdenum bolt for 40 min at a distance of 1 mm from the flame cone. The diamond films have been characterized using Raman spectroscopy, x-ray diffraction, and scanning electron microscope. The input process variables are varied over a range of conditions: total gas flow rate Q = 2–4 standard liter/min, substrate surface temperature Ts = 800–1000 °C, and flow ratio of O2/C2H2 = R = 0.93–0.99. The experimental response outputs are growth rate, full width half maximum (FWHM) of the diamond Raman peak, Raman diamond fraction (β) in the film, ratio of luminescence to diamond peak height (LR), and the relative intensity of the {220}, {311}, {400}, and {331} orientations. The film quality indices FWHM, β, and LR improve by increasing the gas ratio (R), by increasing substrate surface temperature (Ts), and lowering the growth rate by decreasing total gas flow rate. Diamond film shows a small amount texturing in {220} and {400} orientation at low R and Ts. At high R and low Ts crystals are oriented with the {111} direction normal to the substrate surface. Jet and boundary layer theory have been applied to understand the growth rate, the thickness profile, and the morphological instability of the diamond films. Surface Damkühler calculation shows that the deposition process is marginally controlled by mass transfer. Growth rate of an open flame is higher than for an enclosed flame, while the Raman quality measurements of the enclosed flame are more uniform than open flame over the range of the comparison.

Submicrometer-grained (SMG) microstructures are produced in an Al–Mg–Si alloy (6061) by subjecting peak-aged and overaged billets of the alloy to intense plastic strain by a process known as equal channel angular extrusion. Two types of refined structure are distinguished by optical and transmission electron microscopy. One structure is created through intense deformation (four extrusion passes through a 90° die, ε = 4.62) by dynamic rotational recrystallization and is a well-formed grain (fragmented) structure with a mean fragment or grain size of 0.2–0.4 μm. The other structure is produced by post-extrusion annealing through static migration recrystallization, resulting in a grain size of 5–15 μm. Intense deformation of peak-aged material to a true strain ε of 4.62 (four passes) produces a strong, ductile, uniform, fine, and high angle grain boundary microstructure with increased stability against static recrystallization as compared to the overaged material.

Potassium acid phthalate (KAP) crystals are promising as substrates for the growth of highly oriented films of conjugated polymers with exceedingly high and fast nonlinear optical response. We report the KAP optical properties (real and imaginary parts of the refractive index ñ = n + ik) in the near infrared and visible range deduced by ellipsometric measurements and direct inversion of transmittance and near-normal incidence absolute reflectance measurements. In the infrared region n was also deduced by the interference fringes.

Graphite encapsulated nanocrystals produced by a low carbon tungsten arc were analyzed to determine their chemistry, crystallography, and nanostructural morphology. Metallic nanocrystals of Fe, Co, and Ni are in the face-centered cubic (fcc) phase, and no trace of the bulk equilibrium phases of body-centered cubic (Fe) and hexagonal close-packed (Co) were found. Various analytical techniques have revealed that the encased nanocrystals are pure metal (some carbide was found in the case of Fe), ferromagnetic, and generally spherical. The nanocrystals are protected by turbostratic graphite, regardless of the size of the nanocrystals. The turbostratic graphite coating is usually made up of between 2 and 10 layers. No trace of any unwanted elements (e.g., oxygen) was found. The low carbon: metal ratio arc technique is a relatively clean process for the production of graphite encapsulated nanocrystals.

A nanocomposite of a chemically synthesized nanostructured aluminum nitride (AlN) and a polyimide has been studied. Using a nonaqueous polar solvent, N-methylpyrrolidinone (NMP), as the suspension media, the degree of particle agglomeration of AlN was reduced dramatically from micron to nanoscale size. Upon the addition of poly(amic acid) to the AlN/NMP suspension, a further deagglomeration of the particles was observed. The surface physicochemical interactions have been investigated by characteristic model reactions using FTIR spectroscopy. A mechanistic interpretation for the deagglomeration and stabilization behavior is discussed. The formation of the AlN/PI nanocomposite was achieved by the rapid solidification of the precursor suspension followed by compression molding. Such an approach for nanocomposites exhibits better homogeneity with ultrafine fillers and allows a tailorable composition and property at the nanoscale level. Finally, AlN/PI nanocomposites with an increased ceramic loading, up to 65% by volume, were attained and their thermal and mechanical properties, along with the compositional effects, have been investigated.

A porous and discontinuous Si3N4-based fiber coating was evaluated in SiC/Si3N4 minicomposites by fiber push-out and fractography for debond capabilities following high temperature exposures. The exposures consisted of 500 h annealing at 1350 °C, and 25–100 h oxidation in wafer form at 1200–1400 °C. In spite of considerable microstructural coarsening and/or oxidation of the coating, fiber debond and sliding were achieved in all cases, and at stress levels comparable to those reported for tough, as-fabricated SiC/Si3N4 composites with a carbon or boron nitride interphase. Therefore, the porous coating is expected to perform better than C or BN in applications where oxidation is inevitable. The role of porosity in accommodating and mitigating the effects of oxidation is thought to be important.

Epitaxial PbTiO3 films have been grown on vicinal (001) SrTiO3 substrates by pulsed laser deposition. Vicinal SrTiO3 substrates with misorientations up to 9° from (001) were used, and the influence of the direction of misorientation on the resulting domain structure was studied. 4-circle x-ray diffraction analysis indicates that thin (40 nm) PbTiO3 films are completely c-axis oriented [rocking curve full-width-at-half-maximum (FWHM) of 0.25° for the 002 reflection] and that thicker films (∼ 200 nm) contain mixed a-axis and c-axis PbTiO3 domains due to twinning along {011} planes. The [100] axis of the a-axis domains is misoriented by 2.1° to 3.3° toward 〈100〉 substrate directions with respect to the substrate normal. In contrast to growth on well-oriented (001) SrTiO3 surfaces where the four equivalent tilts of the [100] axis of the a-axis domains are equally likely, on vicinal SrTiO3 the a-axis domains are preferentially oriented in an uphill direction with respect to the crystallographic miscut.

Epitaxial lanthanum aluminate (LaAlO3) thin films were deposited on single-crystal substrates by pyrolysis of spin-on mixed nitrate precursors. The films are epitaxial without any second phase. TEM micrographs show that all of these films have pores with sizes ranging from 5 to 30 nm. Grain boundaries are not observed. Selected area diffraction shows that the films are single-crystal-like, despite the porosity. All the films are smooth and crack-free. The precursors first decompose into an amorphous mixture. Heterogeneous nucleation occurs on the lattice-matched, single-crystal substrate surface. The epitaxial films grow upward and consume the amorphous regions. The crystallization temperature of LaAlO3 is lower for thin films than for bulk samples due to nucleation on the substrate. The crystallization of LaAlO3 does not exhibit linear growth kinetics. The Johnson–Mehl–Avrami exponent of growth is between 1.4 and 1.5. This deviation from the linear growth model (n = 1) can be attributed to continuous nucleation on the substrate/film interface.

In-flight modification of MoSi2 powders has been carried out by using an Ar–H2 induction plasma. Reactor pressure, powder feed rate, and plate power level were taken as the experimental parameters to alter the thermal history of the injected powder particles. Metastable hexagonal structure of β–MoSi2 is the major phase observed in the Ar–H2 induction plasma-treated molybdenum disilicide powders, while the stable phase of tetragonal structure of α–MoSi2 usually retains no less than 30 wt. %. Depending on the experimental condition and the deviation from stoichiometry in raw materials, low silicides, Mo5Si3 and Mo3Si, and free Si were observed,