Carbon nanocage structures with Ge and SiC nanoparticles were synthesized by direct current and radio frequency (dc-rf) hybrid arc discharge of C, Ge, and Si elements. High-resolution images showed the formation of Ge and SiC nanoparticles and nanowires encapsulated in carbon nanocapsules and nanotubes. The growth direction of the Ge nanowires was found to be 〈111〉 of Ge, and a structure model for Ge/C interface was proposed. The present work indicates that the various carbon nanostructures with semiconductor nanoparticles and nanowires can be synthesized by the dc-rf hybrid arc-discharge method.

The sol-gel method was used to prepare nickel oxide–silica and nickel–silica nanocomposite materials and the corresponding silica matrices. Different drying conditions were used to obtain aerogel and xerogel materials. The samples were characterized by thermal analysis, x-ray diffraction, N2–physisorption, transmission electron microscopy techniques, and infrared spectroscopy. Aerogel samples had a much higher surface area than the xerogel samples; moreover, different supercritical drying conditions gave rise to a different porous structure, which influenced the size and distribution of the nanoparticles in the matrix.

The crystallization mode of the Zr–Al–Ni–Cu amorphous alloys changed from a single stage to become two stages by the addition of Ag or Pd, and the first-stage exothermic reaction was found to result from the precipitation of nanoscale icosahedral particles with a size of 20 to 50 nm. The precipitation took place by high nucleation and low growth rates in a polymorphous mode for the Ag-containing alloys, and a diffusioncontrolled mode for the Pd-containing alloys. The nanoscale mixed structure alloys exhibited improved strength and ductility as compared with the corresponding amorphous single-phase alloys. The findings of the dispersion strengthening as well as the dispersion ductilization gave a future opportunity to fabricate a new bulk nonequilibrium phase alloy by use of the new phenomenon.

Pure, Nd doped, and Nd–Cr bidoped yttrium calcium oxyborate Yca4O(BO3)3 (YCOB), NdxY1−xCa4O(BO3)3 (NYCOB) with x = 0.86, and Cr:NdxY1−xCa4O(BO3)3 (Cr:NYCOB) with x = 0.45 and a small amount of Cr3+ ions crystallized with a fluorapatite-type structure in the monoclinic system. The unit cell constants were a = 0.8076(7), b = 1.6020(10), and c = 0.3527(2) nm with the angle β of 101.23° for the NYCOB and z = 2. The measured absorption spectra of NYCOB and Cr:NYCOB were compared to Judd–Ofelt (JO) theory. When applied, the JO theory of parity-forbidden electric-dipole transitions of rare earth ions on noncentrosymmetric sites demonstrates good agreement. The experiments showed that the Cr3+ ions were introduced into the crystalline lattice as a sensitizer to absorb the excitation energy and transfer it to the Nd3+ ions in the lattice structure.

The creep behavior of a cryomilled ultrafine-grained Al–Mg alloy was examined. The grain size ranged from 300 to 400 nm. The stress exponents ranged from 7.2 to 7.4. The apparent activation energy for creep, 83.7 kJ/mol at 27.5 MPa and 77 kJ/mol at 38 MPa, agreed well with the activation energy for grain boundary diffusion in aluminum. Transmission electron microscope analysis following creep at 300 °C to approximately 0.2% strain in 1411 h revealed the grain size was unchanged from its as-extruded size indicating significant thermal stability of this material at relatively high fractions of the melting temperature. The creep resistance of the Al–Mg alloy was rationalized in terms of an attractive interaction between grain boundary dislocations and incoherent particles within the boundary region, which suppressed grain boundary deformation. The grain boundary particles also led to high thermal stability by exerting a Zener pinning force on the grain boundaries, thus inhibiting grain growth at high temperatures.

(Y + Sm)–α-sialon compositions with and without α-sialon seeds were hot-pressed at 1800 °C for 1 h and then heat treated at 1800 °C for 4 h. The effect of α-sialon seeds on the microstructures of (Y + Sm)–α-sialon ceramics was studied by scanning electron microscopy. The results showed that hot-pressed α-sialon ceramics with elongated grains can be fabricated by adding 10 wt% seeds. Through heat treatment, the seed-free composition could also develop into a similar microstructure with big elongated grains dispersed in a fine matrix.

SiC, carbon, and Kevlart® fibers were coated with carboxylate–alumoxane nanoparticles and their calcium-, lanthanum-, and yttrium-doped analogs; firing to 1400 °C formed uniform aluminate coatings. Optimum processing sequences were determined. Both carboxylate–alumoxane- and ceramic-coated fibers were examined by field emission scanning electron microscopy, microprobe analysis, and optical microscopy. Coatings produced were stable to thermal cycling under air at 1400 °C. Fiber-reinforced ceramic matrix composites were prepared and results from 3-point bend tests for carbon/Kevlar®-fabric-reinforced ceramic matrix composites (CMCs) and carbon-fiber-reinforced CMCs were determined. Flexure strength for carbon-fiber- and carbon/Kevlart®-fiber-reinforced alumina CMCs was determined.

Alumina/alumina and alumina/kovar/alumina joints were produced via two joining techniques: (i) a moly-manganese process and (ii) active metal brazing. These joints were heat treated at 400 °C for 100 h to evaluate their fracture strength, fracture behavior, and high-temperature reliability. Depending on the joining methods employed, the optimum microstructure of ceramics for joining is different. It was found in most cases, that the active metal brazing resulted in superior joint strength and reliability over the moly-manganese process. The fracture strength and reliability of alumina/kovar/alumina joints were lower than those of alumina/alumina joints and showed different fracture behaviors. After heat treatment, fracture strength and reliability decreased due to the formation of brittle phases at the joint interface. The fraction of brittle debonding at the interface increased with heat treatment, while that of fracture within the alumina decreased.

Spherical particles of α–Fe2O3 80 to 100 nm in size were prepared with the polyol method. Scanning electron microscopy, x-ray powder diffraction, and measurements of the diffuse reflection were used to characterize the powder material. The characteristic red color of hematite was adjusted after brief heating (250 °C, 15 min) which did not lead to further particle growth. The polyol method turned out to be suited for the preparation of quite concentrated (up to 20 wt%) and very stable suspensions of submicron Fe2O3 particles. Based on such suspensions, the red emitting phosphor Y2O2S:Eu was coated as a model substrate. As a result, very homogeneous coatings of α-Fe2O3 on the phosphor material were realized. Individual iron oxide particles on the phosphor surface confirm the presence of nonagglomerated Fe2O3 particles in the polyol medium.

We have found that by varying only the substrate temperature and oxygen pressure five different crystallographic orientations of V2O5 thin films can be grown, ranging from amorphous to highly textured crystalline. Dense, phase-pure V2O5 thin films were grown on SnO2/glass substrates and amorphous quartz substrates by pulsed laser deposition over a wide range of temperatures and oxygen pressures. The films' microstructure, crystallinity, and texturing were characterized by electron microscopy, x-ray diffraction, and Raman spectroscopy. Temperature and oxygen pressure appeared to play more significant roles in the resulting crystallographic texture than did the choice of substrate. A growth map summarizes the results and delineates the temperature and O2 pressure window for growing dense, uniform, phase-pure V2O5 films.