The microstructure of a microwave-densified silicon nitride based ceramic has been assessed in the as-sintered, post-sinter hot-isostatically pressed (HIPed) and annealed conditions. The grain size of the as-sintered material, which is a low substitution β′-Sialon, was significantly finer than observed in conventionally processed materials of similar composition. The as-sintered ceramic exhibits a reverse porosity gradient (with the highest porosity level at the surface) due to heat dissipation to the cooler surroundings during microwave processing. This also results in a higher β′ aspect ratio close to the surface arising from an increased glass viscosity (due to heat loss) and compositional change in this region during sintering. HIPing results in removal of all porosity from the sample core; however, a reduced porosity surface layer is retained. Significant β′-Sialon grain growth is also apparent after HIPing. A fine β′ grain structure was retained after annealing, with partial devitrification of the glassy grain boundary phase to β-Y2Si2O7.

The microstructural changes induced by pulsed laser irradiation in the surface layer of AlN and the initial stage of electroless copper deposition in laser processe specimens have been investigated using transmission electron microscopy (TEM). It was found that a dislocation microstructure is generated by laser processing at laser energy densities of 1.5 J/cm2 or higher. A very sharp change in the dislocation microstructure was seen at a depth of 0.2 to 0.3 μm from the free surface. The dislocation Burgers vector is 〈100〉 and the slip plane is {001}, in agreement with previous reports. AlN was melted and resolidified homo-epitactically from the solid substrate forming a mosaic microstructure with very fine cells having a misorientation of up to 15°. Patches of metallic aluminum were found at the surface of all the specimens irradiated at a laser energy density of 1.5 J/cm2 or higher. Very fine particles of AlN, 20 to 50 nm in diameter, were randomly distributed inside the patches. Immersion of these specimens in an electroless copper bath showed that the electroless solution preferentially etched away aluminum at the Al-AlN interface. At the same time copper islands were deposited in cavities left by AlN particles as well as at the interface with the underlying substrate. These regions are the seeds for further electroless deposition. The TEM observations of laser-induced microstructural changes reported in this paper help to unravel further the mechanisms of adhesion enhancement and surface activation by pulsed laser irradiation.

The gas-condensation technique is used to produce the nanocrystalline (NC) WO3−x, Pt/WO3−x, and Pd/WO3−x powders under different atmosphere and pressure. HRTEM images show that a coherently bonded interface exists between Pt or Pd and WO3−x. The nanocrystal WO3−x, Pt/WO3−x, and Pd/WO3−x grow into a needle shape with a plate inside when these as-evaporated powders are compacted and sintered at 900 °C for 2 h. The plate grows preferentially in {220} plane along the 〈0011〉 direction. However, the mean particle size of nanophase Pt and Pd increases only from <10 nm to 30 nm and 50 nm, respectively. The results of CO oxidation show that nanophase Pt/WO3−x powders have better catalytic effects on converting CO to CO2 than nanophase WO3−x and Pd/WO3−x powders.

High textured (Bi,Pb)2Sr2Ca2Cu3Ox ceramics have been fabricated by aligning deflocculated flakes of (Bi,Pb)2Sr2Ca2Cu3Ox suspended in an organic medium by means of a high de magnetic field (6 T) at room temperature followed by cold isostatic pressing. The proportion of the (Bi,Pb)2Sr2Ca2Cu3Ox phase in the precursor powder was carefully controlled, and the characteristics of the powder, such as size distribution and morphology, were determined. A high degree of grain alignment was found in the specimens after the magnetic alignment, although the bulk density of the materials was low. Cold isostatic pressing substantially increased the density of the magnetically prealigned specimens which also resulted in a slight decrease in the degree of grain alignment. This minor realignment was found to be due to the various kinds of processing defects that appeared in the specimens during compaction due to the grinding and cracking of the grains and their interlocking. The microstructural and superconducting properties of the sintered ceramic have been studied using texture goniometry, high resolution scanning electron microscopy, transmission electron microscopy, ac magnetic susceptometry, and critical current measurements.

Two kinds of methods such as spontaneous nucleation from flux-free stoichiometric melt and CuO flux method have been used for the growth of Pb0.5Sr2.5Y1−xCaxCu2Oy single crystals. The morphologies, phases, and compositions occurring in the crystals grown from the two kinds of methods were compared systematically. Optimum conditions for the growth of larger 1212 phase single crystals are x =0.15, 0.25, and 0.35. The lattice parameters of the crystals with the 1212 phase were found to be increasing upon Ca doping. The resistivity behavior of the PbSrYCaCuO single crystals with the 1212 phase both in the state of as-grown and after extended annealings under various oxygen partial pressure was also discussed briefly.

We have studied the relative diffusion rates of oxygen through dielectric/buffer layers used in high critical temperature superconducting multilayer structures. Epitaxial bilayer films of dielectric (CeO2, LaGaO3, NdGaO3, LaAlO3, MgO, SrTiO3, LaLiTi2O6, or LaNaTi2O6) on YBa2Cu3O7−δ (YBCO) have been deposited onto (001) oriented single-crystal MgO substrates using pulsed laser deposition. These bilayers have been investigated for oxygen diffusion over the temperature range 350 to 650 °C by postdeposition annealing the films for 20 min in 0.5 atm of 18O enriched molecular oxygen gas. Secondary ion mass spectroscopy was used to depth profile the relative concentration of 18O to 16O in each bilayer. Compared to YBCO, the dielectrics MgO, SrTiO3, LaLiTi2O6, and LaNaTi2O6 are relatively slow diffusers, while CeO2, LaGaO3, NdGaO3, and LaAlO3 are relatively fast diffusers.

Changes in particle size, surface properties, and composition brought about by planetary grinding of silicon in air and various permittivity liquids were investigated. Using a variety of spectroscopic techniques (ESR, IRS, and XPS), a mechanically induced surface oxidation was proved. While at grinding in air and organic liquids a part of the centers originating from dangling orbitals on SiIII are preserved, the properties of water-ground silicon are fully governed by the oxide surface shell. The most effective particle size reduction and surface protection can be reached by grinding in nonpolar liquids.

The hardness of thick, high-purity, epitaxially grown silver on sodium chloride is found to be dependent on the size of the indentation for sizes below ≃10 μm. The measurement of the size effect has been made in two ways. In one, the hardness has been calculated from the load-displacement curve obtained from an instrumented microhardness testing machine and assuming a geometric self-similarity in the indenter shape. In the other measurement, the hardness was obtained from the load exerted by the microhardness tester divided by the indentation impression area as measured by atomic force microscopy. The observed variation in microhardness with indentation size is consistent with a simplified strain gradient plasticity model in which the densities of the geometrically necessary and statistically stored dislocations are fitting parameters. An equally good fit can also be made with a simple geometric scaling relationship. Transmission electron microscopy observations of a thin (≃50 nm) epitaxial gold film embedded in the silver layers revealed that the deformation was primarily restricted to the sharp edges of the indentation. In addition, deformation twinning within the indentation impression was observed on the {1H} planes.

Morphology of twinned diamond particles grown by chemical vapor deposition was characterized by atomic force microscopy in both contact and tapping modes. Quantitative angle measurements using a surface normal algorithm were performed on untwinned crystals, penetration twins, re-entrant corners, and fivefold dimples. Tip-sample interaction is discussed. The morphology of the penetration twins and some of the re-entrant corners can be explained by low order Σ3 twins and flat crystallographic surfaces. Abnormally shallow re-entrants with large vicinal faces are attributed to rapid nucleation of new layers at a point along the re-entrant intersection.

The progress of high temperature deformation in samples of two commercial titanium alloys with superplastic (SP) structure, non-SP structure, and with an SP layer sandwiched between the non-SP regions has been studied on the scale of the entire deformed volume and on the scale of grain groups. The results of mechanical behavior showed that samples with SP layer exhibit higher stress level than those with completely SP structure and higher strain rate sensitivity than those with completely non-SP structure. Samples with SP layer demonstrate a more pronounced deccrease in strain rate sensitivity with the increase of strain than samples with completely SP structure. Deformation in the SP layer proceeds as grain shear in a layer-by-layer manner. The deformation of SP layer through the operation of cooperative grain boundary sliding, i.e., sliding of grain groups as an entity along certain grain boundary surfaces, provides the main contribution to the total strain.

The dc-95 MHz hybrid plasma magnetron sputtering has been newly developed for obtaining a-axis oriented YBa2Cu3Ox (YBCO) films with an excellent crystallinity. The crystallinity was found to be the best among the films reported so far: the full width at half maximum value of 0.027°in the rocking curve measurement through the film (200) diffraction peak and Xmin of 2% estimated from the barium signal behind the surface peak in Rutherford backscattering (RBS) measurement using a 1 MeV He+ ion. The success in the excellent crystallinity was explained from the ion acceleration model at the ion sheath formed near the substrate surface considering the high ion density, which was revealed to be a characteristic of hybrid plasma. Almost perfect epitaxial growth was also confirmed by transmission electron microscopy. A characteristic grain boundary structure depending on the substrate was observed for the films on NdGaO3 and SrTiO3 substrates. Twist boundary is dominant for the film on NdGaO3, while symmetrical tilt boundary and basal-plane-faced tilt boundary exclusively exist for the film on SrTiO3. The microstructure of the film on SrTiO3 is very resistive against film relaxation. Strain relief was observed by RBS channeling spectra for the relatively high superconducting films. The results of Raman spectroscopy and RBS oxygen resonant measurements indicated that the oxygen content is not a critical parameter for determining the superconductivity of the a-axis oriented YBCO films, but oxygen ordering in the plane of the Cu-O chain and relief of the film strain are important for the improvement of Tc.

We present optical observations of magnetically melt-textured DyBa2Cu3O7−x with and without 20 wt. % excess of Dy2BaCuO5. From these observations, we propose some kinetic mechanism of the growth of 123 compounds. Kinetic processes can be simulated on computers. Two (very) simple models derived from the well-known Eden model are presented. They simulate the growth of the grain front. The simulated patterns agree with the observations. The microstructure of such materials cannot be explained by thermodynamic and chemical considerations alone, but explanations must include the kinetics of the growth front as well. From our observations, we conclude that the growth probability ratios g110/g100 and g100/g001 are of the order of 10 and 50, respectively.

Structure factors of μ-TiAl equiaxed grain in TiAl duplex intermetallic compound before and after V-alloying were measured by the quantitative electron crystallography method. Then the structure factors were transferred into charge-density distributions of real space. Comparing the charge-density distributions in γ-TiAl with those in V-alloyed γ-TiAl, it was found that V-alloying with the optimum amount decreases the electronic charge density in the Ti-Ti interatomic bond, and increases the electronic charge density in the Al-Al interatomic bond and Ti-Al interatomic bond. Thus, the anisotropy of charge-density distribution in γ-TiAl equiaxed grain is reduced.

Zirconium oxide dispersed in silica was synthesized by the cogelation of tetraethoxysilane and zirconium acetate. For the gelation, acid and basic media were used. The final zirconia concentration was around 6.7 wt. %. Differential thermal analysis, thermogravimetric analysis, as well as electron microscope techniques were used for the characterization of the samples. It was found that the stabilization of the crystalline phases depends on the preparation conditions and thermal treatments. Tetragonal and monoclinic ZrO2 phases were identified in basic preparations. However, in acidic samples only low-temperature tetragonal phase was identified.

Monoclinic ZrO2 and its supported materials Co/Ni/ZrO2 (Co:Ni = 1:1) for catalytic decomposition of N2O have been studied with GC, FTIR, EDAX, XPS, and the evaluation of catalytic activity of the materials. It is found that monoclinic ZrO2 alone has the catalytic effect for N2O decomposition, although higher activities are found for Co/Ni/ZrO2 systems. XPS study shows that only Co exists in the surface region of ZrO2, which is attributed to the formation of NiO–ZrO2 solid solution resulting from an interdiffusion between Ni2+ and ZrO2 matrix. The gas decomposition on Co/Ni/ZrO2 can be described as first order with respect to partial pressure of N2O. Surface reactions on ZrO2 and Co/Ni/ZrO2 will also be addressed.

A new carbon crystal named carbolite has been synthesized by quenching high temperature carbon gas on a room temperature substrate. The crystal has a density as small as 1.46 g/cm3 and is transparent for visible light. The crystal structure is hexagonal, and the dimensions of the unit cell are 1.193 nm in the α-direction and 1.062 nm in the c-direction. Along the c-axis, a parallel array of carbon chains is proposed. The array is made up of a triangular lattice in which the interchain distance is 0.344 nm and the mean interatomic distance within a carbon chain is 0.133 nm. The former value is close to the van der Waals distance between the honeycomb planes of graphite, and the latter value is close to the C-C bond length in the honeycomb plane. Intercalations of potassium, sodium, and iodine atoms are performed.

The relation between stresses of sputtered a-Si: H films and the film deposition conditions are investigated. The film stresses change from a large compressive stress of 1000 MPa to an almost stress-free one. They arise from distortions of the Si network via the following two mechanisms. The first results from the inclusion of the Ar-sputtering gas into the films, which provides volume expansion of the film network. The other is due to structural disorders, such as a deviation of the Si bond angle which is generated during the deposition processes. Moreover, it is found that Si–H terminations in the films contribute to reducing the film stresses because the Si–H termination breaks and relaxes the Si network. These effects can be realized as long as the Si–H terminations are homogeneously distributed in the films.

The effects of annealing temperature and oxygen partial pressure [p(O2)] were investigated on the crystallization and orientation of YBa2Cu3O7−y (YBCO) films on MgO(001) prepared by the dipping-pyrolysis process. The c-axis oriented films without in-plane alignment were prepared by annealing in the YBCO-unstable region, i.e., at low initial p(O2) of 10−4−10−3 atm and 950 °C followed by O2 treatment, through intermediate Y2BaCuO5 and liquid phase. In-plane aligned c- or c/a-axis films were prepared by similar heat treatment with an initial p(02) of 10−4 atm and 900–925 °C through a mixture of BaCu2O2 and YBa3Cu2O6+x. In contrast, nonoriented YBCO films were obtained by annealing at higher initial p(O2)'s and lower temperatures, i.e., by direct reaction among Y2O3, BaCO3, and CuO.

The magnetic torque of oriented bulk specimen of Bi2Sr2CaCu2O8+δ by the shock-loading method was measured under magnetic fields up to 8 kOe in the temperature range from 4.2 to 100 K. The torque amplitude of the shocked specimen was much larger than that of the as-grown bulk specimen measured as a reference. The angular dependence of the torque was reproduced by assuming the Gauss-type distribution for the crystalline orientation. It became clear that the magnetic torque of the shocked specimen showed the high degree of crystalline orientation in which the c-axis is perpendicular to the pellet disk plane and that the flux pinning perpendicular to the pellet disk plane was enhanced by shock-loading.

Mullite-based ceramics added with 0–20 vol % stabilized zirconia have been prepared by alumina/zirconia particles coated with an amorphous silica layer. All samples can be densified through the viscous flow of the amorphous silica layer in the typical temperature range of 1100–1310 °C. For the ZrO2-free mullite ceramics, the viscous densification kinetics is inhibited by increasing the content of the alumina inclusion particles and by crystallization of the amorphous silica layer. However, for the zirconia-mullite ceramics, the addition of the zirconia inclusion particles accelerates the viscous densifcation kinetics. Mullitization kinetics is also enhanced by the addition of zirconia. As the sintering temeperature is high, a porous, duplex microstructure is observed in samples with or without zirconia. Zirconia addition enhances the development of this microstructure. As the sintering temperature and/or zirconia content is increased, ZrO2 particles tend to coarsen, resulting in a decreased tetragonal to monoclinic ratio. Fracture toughness KlC increases with the zirconia content. Mullite-20 vol % ZrO2 composite sintered at 1600 °C has a KlC of 3.8 MPa · m1/2.