Highly anisotropic Si3N4 ceramics were successfully fabricated by tape-casting of raw α–Si3N4 powders with β–Si3N4 single-crystal particles as seed particles and Y2O3 as an effective sintering aid, followed by hot isostatic pressing at a temperature of 2773 K for 2 h under a nitrogen gas pressure of 200 MPa. The microstructure consists of very large elongated grains (diameter ~10 μm; length of ~200 μm), highly oriented in the tape-casting direction. The thermal conductivity along this direction reaches 155 W m-1K-1 at room temperature, but varies significantly between room temperature and 1273 K. This thermal conductivity is closely related to (1) formation of extremely large elongated β–Si3N4 grains with a reduced amount of crystal defects due to the high-temperature firing and to (2) orientation of β–Si3N4 grains due to addition of seed particles and to tape-casting.

γ–Fe2O3 spherical particles with diameters between 5 and 3.5 nm—very uniform in size—have been prepared by laser pyrolysis of iron pentacarbonyl. The infrared spectra of the samples showed features that indicated different degrees of crystallinity according to the preparation conditions. Low saturation magnetization values (≈10 emu/g) and very high coercivities at low temperature (3000 Oe) have been found for the γ–Fe2O3 nanoparticles with the smaller particle size and the highest structural disorder. To explain the magnetic properties, it was necessary to consider additional anisotropies caused by the increase in surface and structural disorder as the particle size decreased.

Both epitaxial and crystallographically fiber-textured ZnO films can exhibit a surface texturing (“cratered”) morphology when grown by pulsed laser deposition at temperatures in the range of 350–750 °C in a background pressure of oxygen. The surface texturing is a consequence of the nucleation of oriented c axis grains that grow geometrically and impinge laterally. It is concluded that the surface texturing is due to nonequilibrium growth, being the result of a competition between the arriving flux, diffusive flux along the surface, and, possibly, concurrent ion etching from the laser-ablated plasma plume. At higher temperatures, no surface texturing occurs, presumably because of concurrent grain growth and more rapid surface smoothing by diffusion.

Ink-jet printing is an important image transfer technology. In this technology, the electronic capabilities are often constrained by shortcomings of materials functions. One of the constraints for fast reproduction of high-resolution photographic quality color images is the print dry time. This presents a challenge in the film technology where large quantities of solvent must be rapidly removed without transporting colorants outside the targeted areas. In this work, this is achieved by chemical immobilization of water by organic polymers incorporated into the film matrix. In this dense film, immobilization of large volumes of water becomes possible by a transient local swelling of the matrix—as much as 600–700%. This mechanism of water immobilization not only creates a virtually dry state instantaneously, but also leads to a tighter containment of colorants within the targeted areas, resulting in a significant improvement in edge acuity and image resolution. In addition, the film is printer and ink nonspecific and produces a high gloss on photographic paper.

Control of Co particle size was archived by a germ-growth method during inverse micelle synthesis. Magnetic coercivity and blocking were both a function of the particle size, which ranged from 38 to 88 Å. Interparticle dipolar interaction was proven to be important in order to interpret the magnetic properties for large-size particles.

Formation of TiSi2 in titanium on nitrogen-implanted (001)Si with a thin interposing Mo layer has been investigated. The presence of a Mo thin interposing layer was found to decrease the formation temperature of C54–TiSi2 by about 100 °C. A ternary (Ti, Mo)Si2 phase was found to distribute in the silicide layer. The ternary compound is conjectured to provide more heterogeneous nucleation sites to enhance the formation of C54–TiSi2. On the other hand, the effect of grain boundary for decreasing transformation temperature was found to be less crucial. For Ti/Mo bilayer on 30 keV BF2+ or As+ + 20 keV, 1 × 1015/cm2 N2+ implanted samples, a continuous C54–TiSi2 layer was found to form in all samples annealed at 650–950 °C. The presence of nitrogen atoms in TiSi2 is thought to lower the silicide/silicon interface energy and/or the silicide surface energy to maintain the integrity of the C54–TiSi2 layer at high temperatures.

Two kinds of aqueous precursor solutions are used to synthesize Mn–Zn ferrite powders: (i) nitrate (NO) precursor—derived from solutions of Mn(NO3)2, Zn(NO3)2, and Fe(NO3)3; and (ii) acetate (AC) precursor—derived from solutions of Mn(CH3COO)2, Zn(CH3COO)2, and Fe(NO3)3. The composition of the powders synthesized from the precursor AC is very uniform, whereas powders derived from the precursor NO have Mn and Zn segregated on the particle surfaces. In addition, the powders synthesized from precursor AC are solid spherical particles with fine porosity, whereas many hollow and fragmented particles are observed in the powder derived from precursor NO. Overall, the properties of Mn–Zn ferrite cores prepared from the precursor AC are superior to those prepared from the precursor NO. The reasons for the differences are explained and described in detail. The AC precursor powders synthesized by spray pyrolysis produced Mn–Zn ferrite cores with good magnetic properties.

An indirect observation of 90° domain reversal under the influence of a poling field process was undertaken by an x-ray diffraction study in the Pb0.88Eu0.08Ti1™y MnyO3 (y = 0, 0.01, 0.02, and 0.03) piezoelectric anisotropic system. The optimum condition kp → 0 was achieved for y = 0.02 composition. A large percentage of 90° domain rotation was necessary, but not a sufficient condition for the ultrahigh electromechanical anisotropy manifestation. A large microstrain originated by structural defects in unpoled samples seemed to play a crucial role in the attainment of this piezoelectric anisotropy. A breaking in the translational periodicity due to induced vacancy in Pb and O sites by Eu3+ and Mn2+ substitutions was manifested in the nonuniform variance of the tetragonality (c/a), the large microstrain, and the detriment of crystallinity observed.

A versatile procedure of sputter deposition, well-adapted for getting a large range of Te/M ratios (with M = Zr or Nb), has led to the synthesis of several highly anisotropic zirconium and niobium polytellurides in thin film form. Upon tuning the two key parameters of the process, i.e., the Te percentage in the target and the substrate temperature during the deposition, preparation of systems ranging from ZrTe0.72 to ZrTe6.7, on the one hand, and from NbTe1.28 to NbTe7.84, on the other, has been achieved. Besides their amorphous or crystalline (with or without preferential orientations) behavior and their relationship to known structural types, the most striking feature of these films is their large departure from the stoichiometry of the bulk MTex reference compounds. This peculiarity, together with the possible changes of composition under annealing, are described and interpreted in terms of variable amounts of Te and M atoms trapped or intercalated within the parent structures.

Intrinsic stresses which arise during the chemical vapor deposition (CVD) of diamond were controlled by multistep processing. Film stresses (thermal and intrinsic) were measured with the bending plate method. The thermal stresses are compressive and arise due to the mismatch in thermal expansion coefficient between the film and substrate. The dominant intrinsic stresses are tensile and evolve during the deposition process. These stresses increase with deposition time. An intermediate step consisting of annealing the film when the diamond crystallites are only partially coalesced reduces the intrinsic stress by more than 50%. Annealing at longer growth times (i.e., after complete coalescence) does not produce large reductions in intrinsic stress. Our results are consistent with stress generation due to the formation of nonequilibrium grain boundary structures. The intermediate annealing step does not produce a large, direct stress reduction; instead, it alters the film microstructure in some subtle way which reduces stress generation during subsequent growth.

Crystallographically coherent precipitates of vanadium dioxide (VO2) have been formed in the near-surface region of single crystals of sapphire (Al2O3) using a combination of ion implantation and thermal treatments. As in the case of either bulk VO2 single crystals or thin films of VO2, the thermally induced semiconductor-to-metal phase transition of the embedded VO2 precipitates is accompanied by a large hysteretic change in the infrared optical transmission. The VO2 precipitate transition temperature (Tc = 72 to 85 °C) is higher than that of bulk VO2 (Tc = 68 °C) and is sensitive to the implantation conditions. The present results show that the damage resulting from the coimplantation of vanadium and oxygen into an Al2O3 host lattice dictates the final microstructure of the VO2 precipitates and, consequently, affects the transition temperature, as well as the optical quality of the VO2/Al2O3 surface-nanocomposite precipitate system.

Protective residual stresses may be developed in the near surface layers of tribological contacts which enable loads sufficiently large to cause initial plastic deformation to be accommodated purely elastically in the longer term. This is the process of shakedown and, although the underlying principles can be demonstrated by reference to relatively simple stress systems, the situation is complex under a moving Hertzian pressure distribution. Bounding theorems can be used to generate appropriate load or shakedown limits not only for uniform half-spaces but also those with plastic and/or elastic properties which vary with depth. In this way, shakedown maps, which delineate the boundaries between potentially safe and unsafe operating conditions, can be generated for both hardened and coated surfaces.

Diamondlike carbon (DLC) films have been prepared on radio-frequency (rf) biased substrates maintained at low temperature using electron cyclotron resonance CH4–Ar plasma. The effects of negative rf bias and reactant gas composition on the bonding structure, hardness, and resistivity of the films were systematically investigated. DLC films deposited on PMMA (polymethyl methacrylate) were examined by optical methods to determine the absorption coefficients and the optical band gap. It was found that DLC films synthesized at bias voltage of 2(80–100) V and FCH4/FAr of 0.075–0.086 exhibit extreme hardness of more than 3000 kgf mm−2, high electrical resistivity up to 1014 Ω cm, band gap larger than 2.5 eV, and excellent optical transparency. The results indicate that ECR CH4–Ar plasma with low negative rf bias and suitable CH4/Ar gas ratio can process optically transparent and hard protective DLC films on PMMA plastics.

Epitaxial and polycrystalline thin films of bismuth layer-structured ferroelectrics, SrBi2Nb2O9 (SBN) and SrBi2Ta2O9 (SBT), were prepared on single-crystal SrTiO3(001) and polycrystalline yttria-stabilized zirconia substrates, respectively, by the coating-pyrolysis process. The epitaxial relationship of the films and substrates was SBN, SBT (001)//SrTiO3(001) and SBN, SBT [100]//SrTiO3[100],[010], where pseudotetragonal indices were adopted for SBN and SBT. The lattices of the epitaxial films were found to be slightly strained owing to stress from the substrate. Atomic force microscopy observations showed that the epitaxial films as well as polycrystalline films consisted of round-shaped, islandlike grains of submicrometer size.

Y2O3 : Eu phosphor particles were directly prepared by a spray pyrolysis method. Photoluminescence, morphology, and crystallinity of the as-prepared particles were investigated. The as-prepared particles above 600 °C had good crystallinity, and the crystallinity increased with increasing reactor temperatures. The particles had spherical morphology and were nonaggregated. The mean size of the particles increased from 0.34 to 1.2 µm when the solution concentration was increased from 0.03 to 1 M. The as-prepared particles had good red emission without annealing at high temperatures when excited with uv light. The main emission peak was 612 nm. The brightness of the as-prepared particles increased with increasing temperatures because of good activation and crystallization at high temperatures.

We have sputter deposited NiMnSb/PtMnSb Heusler alloy superlattices with bilayer periods from 9–160 Å. X-ray diffraction and cross-sectional transmission electron microscopy (TEM) measurements indicate that even for short bilayer periods, the superlattices are compositionally modulated, epitaxial, and maintain the Heusler alloy C1b structure. Low- and high-angle diffraction profiles are in agreement with simulations of the superlattice peaks. TEM images reveal defects, including stacking faults, which help relieve lattice mismatch strain. Energy minimization calculations of the stacking fault density are within a factor of 3 of the density observed by TEM. The saturation magnetization of the superlattices is close to bulk PtMnSb and NiMnSb, with a tendency for perpendicular magnetization at short bilayer periods.

Hard and transparent diamondlike carbon (DLC) films have been prepared on room-temperature substrates by using a C2H2–Ar plasma immersion ion processing (PIIP) method. The optical properties of the DLC films with different thicknesses deposited on PMMA (polymethyl methacrylate), silicon wafers, and glass plates were systematically examined. It was found that careful control of substrate bias voltage was needed for favorable growth of DLC films with low atomic hydrogen content, high hardness and wear resistance, and excellent optical properties. The resultant DLC films exhibited a low friction coefficient, high optical gap energy, and very high optical transmittance both in infrared and visible light ranges. The study confirmed that C2H2–Ar PIIP with low negative bias voltages and suitable C2H2/Ar gas ratios can produce optically transparent and hard DLC films on optical materials.

Electric domains in single-crystal and polycrystalline barium titanate (BaTiO3) have been observed by use of scanning electron acoustic microscopy (SEAM). A model is presented of the SEAM signal generation, spatial resolution, and contrast mechanism associated with the imaging of electric domains in ferroelectric materials. The SEAM signal is found to depend directly on the sum of the piezoelectric coupling coefficient and spontaneous polarization of the domain, on the charge density of the electron beam interaction volume, and inversely on both the permittivity and the elastic constants of the material. Application of the model to BaTiO3 yields a contrast of roughly 3.5% from 90° domain structures and 6.8% from 180° domain structures.

Crystal defects in mordenite materials were observed and characterized by high-resolution electron microscopy (HREM). These defects are identified as line, planar, and 3D defects, which may result in pore blockage of the mordenite channel structure and be detrimental to their chemical properties for catalytic applications. The planar defects are the most severe ones affecting the structural properties of mordenite because of their density and scale. The main emphasis of this investigation is focused on the crystallographic aspects of these defects.

Homogeneous maghemite (γ–Fe2O3) nanoparticles with an average crystal size around 5 nm were synthesized by successive hydrolysis, oxidation, and dehydration of tetrapyridino-ferrous chloride. Morphological, thermal, and structural properties were investigated by transmission electron microscopy (TEM), differential scanning calorimetry (DSC), and x-ray diffraction (XRD) techniques. Rietveld refinement indicated a cubic cell. The superstructure reflections, related to the ordering of cation lattice vacancies, were not detected in the diffraction pattern. Kinetics of the solid-state phase transition of nanocrystalline maghemite to hematite (α–Fe2O3), investigated by energy dispersive x-ray diffraction (EDXRD), indicates that direct transformation from nanocrystalline maghemite to microcrystalline hematite takes place during isothermal treatment at 385 °C. This temperature is lower than that observed both for microcrystalline maghemite and for nanocrystalline maghemite supported on silica.