Microtubes of ZnO have been produced using sputter coating and a fugitive phase technique. ZnO was sputtered onto polyester fibers by dc magnetron sputtering, and the polyester fiber fugitive phase was subsequently burned out by annealing in air or oxygen. Tubes with an inside diameter of 23 μm and a length of 3 cm were obtained. The 3 to 6 μm thick walls of the tubes exhibited a [002] radial texture.

The quantity and character of intergranular phases in mixed α′/β′ sialon ceramics were examined by low-temperature specific heat and internal friction measurements. Present results of specific heat suggest the existence of a small amount of intergranular glassy phase in mixed α′/β′ sialon ceramics. Furthermore, it can be predicted that the material possesses excellent high strength at elevated temperatures, because the temperature dependence of the internal friction in the tested material is similar to that in the annealed Si3N4 ceramics with oxide addition and Si3N4 ceramics without sintering aid.

A new potassium phosphatoantimonate with a composition of 4K2O · 4Sb2O5 · P2O5 · 8H2O, which crystallizes in a monoclinic system with a = 23.952 Å, b = 9.515 Å, c = 8.193 Å, and β = 124.77, was hydrothermally synthesized and characterized by powder x-ray diffraction, chemical composition analysis, x-ray photoelectron spectroscopy, and 31P MAS-NMR techniques. The potassium ion can be exchanged by other monovalent ions.

Ion-beam sputter deposition (IBS) has been developed to a fully oxygen-compatible technology for growth of complex oxides, such as Y1Ba2Cu3O7−δ (YBCO) thin films. The IBS system consists of an rf-plasma ion source with molybdenum grids for sputtering, a dc-plasma electron source for space charge compensation, stoichiometric YBCO and NGO targets, a beam chopper with BaO2, Cu, and Nd blades for stoichiometry control, and an ECR-oxygen-plasma source for in situ film oxidation and photoresist removal. Due to its complexity the IBS process is fully computer-controlled. A salient feature of IBS is the excellent crystallographic and morphological properties of thin (100)/(010)- and (103)-oriented YBCO films on SrTiO3 (STO) and NdGaO3 (NGO) substrates. Sharp interfaces and good superconducting properties render this technology feasible for the fabrication of SIS-ramp-junction SQUID's.

We discuss our results on the growth of YBCO thin films on ultrathin (1-10 nm) Ag underlayers. Substrates were LaAlO3. YBCO was sputter deposited and Ag thermally evaporated. It was observed that Tc remained relatively unaffected by the Ag underlayers, ranging from 86-88 K. Critical currents were found to be consistent with YBCO grown on bulk Ag when the Ag underlayer film reached complete coverage (∼9 nm). Films grown on Ag showed a marked tendency for microcrystalline growth on the basis of atomic-force microscopy (AFM) results.

Epitaxial films of semiconducting iron disilicide (β-FeSi2) have been grown by pulsed laser deposition. We find that pulsed laser deposition creates conditions favorable to the formation of films with the smallest geometric misfit possessed by this material system. In situ reflection high energy electron diffraction results indicate a layer by layer growth of the silicide. Analysis of transmission electron diffraction data has determined that the films are single phase and that this growth method reproduces the epitaxial relationship: β-FeSi2 (001) ‖ Si(111).

Bulk nearly single phase Bi-2223 materials doped with Pb and Sb were prepared using the metallurgical route. Li-doped samples were also synthesized, but Li leads to the 2212 phase and prevents the formation of the 2223 phase. The dependence of the sintering conditions on the phases obtained was studied and the influence of different factors on the melting temperature and the temperature required for the formation of the 2223 phase is discussed. For the materials with nominal composition Bi1.5Pb0.3Sb0.1Sr2Ca2Cu3Sy, Tc(zero) = 111 K was achieved. It was found that the Sb-rich phase segregates on the surface of the superconducting grains.

Small additions of MnO2 up to 15 at. % in YBa2Cu3O7−δ in place of Cu have been carried out to study their influence on the superconducting properties. It has been found that transition temperature and microstructure of Mn-doped samples are highly sensitive to the sintering temperature and Mn content. The normal state resistance increases with Mn content. Microstructure shows plate-like grain growth for low Mn contents (up to x = 0.05) at higher sintering temperature. XRD and microstructure reveals the presence of additional Y2BaCuO5 and Ba3Mn2O8 phases with an increase in Mn content. Also, reduction in the diamagnetic signal and broadening of transition is observed beyond certain Mn content. A detailed discussion of microstructure, XRD, normalized resistance, and magnetic properties has been carried out in correlation with sintering temperature and Mn content.

A gradient in the density of polytypoidal stacking faults was observed through the thickness of chemically derived epitaxial Ba2YCu3O7−x (BYC) films on (001) LaAlO3. Cross-sectional TEM studies indicated that films of less than 100 nm thickness were faulted, with a high density of polytypoidal stacking faults. A decrease in stacking fault density in thicker films (300-500 nm thick) was found with increasing distance from the most defective layer near the film/substrate interface. An abrupt transition from highly faulted material near the substrate to essentially stacking fault-free BYC in the upper part of the films was observed in several cases. The present observations are compared with the previously reported1 decrease in critical current density with increasing thickness of these films. Possible implications for flux pinning in BYC thin films are discussed.

This paper reports a study of the microstructural changes that occur when BSCCO powder is processed by the powder-in-tube method. In this study the initial powder consisted of the 2212 phase plus second phases containing Ca, Cu, Sr, and Pb. When the material was drawn, there was no alignment of the 2212 phase and the second phase particles remained large and blocky. Rolling induced a small amount of alignment into the 2212 phase so that its c-axis was perpendicular to the rolling direction. Rolling also caused the second phase particles to become flatter. When these rolled samples were annealed at 828 °C, the core sintered into a platelet structure, and there was an increase in the amount of aligned material, particularly after annealing treatments of 16 and 32 h. After 8 h at 828 °C, the 2212 variant of the superconducting phase began to transform to the 2223 variant. Pressing this structure improved the alignment, and annealing after pressing allowed further conversion of the 2212 phase to the 2223 phase and apparently removed the strains produced by the pressing. Repeated pressing improved the alignment and repeated annealing allowed more conversion of 2212 to 2223. Both the improved alignment, produced by pressing, and the transformation of 2212 to 2223, produced by the anneals, caused the superconducting properties of the material to improve.

Several substitutions have been attempted in the Hg layer of the Hg 1212 and 1223 cuprate superconductors. A new series of (Hg,Bi)1212 superconducting compounds has been synthesized. The highest Tc of the series (92 K) is found for the composition (Hg0.67Bi0.33)Sr2(Y0.5Ca0.5)Cu2O7−δ, with lattice constants a = 3.811 Å and c = 12.002 Å. X-ray diffraction and SEM with EDX analysis confirm that Hg is indeed incorporated in the structure. High-pressure oxygenation at 250 bar and 400 °C changes the magnetization curve, adding a second transition at ∼42 K; the 92 K transition remains unchanged. High-pressure oxygenation of Pb-substituted composition of the 1223 system, (Hg0.67Pb0.33)Ba2Ca2Cu3O8 also leads to the formation of low temperature phase with Tc = 67 K. The low Tc phase is associated with the incorporation of extra oxygen, possibly in the Hg layer.

Using conventional and high resolution TEM, we have studied the microstructure of C70 polycrystalline films, prepared by sublimation of C70 powder onto glass, carbon holey film, and sapphire substrates held at 200 °C. An fcc structure with lattice parameter 1.50 nm is observed for the films on glass and amorphous carbon. A different structure and stronger adherence to the substrate was observed for the thin film grown on sapphire, suggesting a stronger molecule-substrate interaction in this case. Thicker films on sapphire, however, did have fcc structure. In all cases, the film grows in large grains about 100 nm in size, indicating high effective surface mobility of the C70 molecules. Further analysis of the films on carbon holey substrates indicates a preferred [011] film growth orientation, the existence of twins, and a high density of stacking faults. Extended exposure of the films to oxygen did not result in visible structural changes, but strong illumination for several hours in atmosphere led to partial annealing of planar defects and higher sensitivity to the electron beam, with film amorphization taking place at much shorter times under the electron beam.

In previous studies, sublimed C60-rich fullerene films on silicon, when slid against a 52100 steel ball under dry conditions, have exhibited low coefficient of friction (∼0.12). Films with different purities can be produced by sublimation at different substrate temperatures. In this paper, effects of purity of fullerene films and ion implantation of the films with Ar ions on the friction and wear properties of sublimed fullerene films are reported. C60-rich films (called here films with high purity) exhibit low macroscale friction. An increased amount of C70 and impurities in the fullerene film determined using Raman and Fourier transform infrared (FTIR), increases its coefficient of friction. Microscale friction measurements using friction force microscopy also exhibited similar trends. Low coefficient of friction of sublimed C60-rich films on silicon is probably due to the formation of a tenacious transfer film of C60 molecules on the mating 52100 steel ball surface. Based on scanning tunneling microscopy (STM), transmission electron microscopy (TEM), and high resolution TEM (HRTEM), we found that fullerene films primarily consisted of C60 molecules in a fcc lattice structure. Nanoindenter was used to measure hardness and elastic modulus of the as-deposited films. Ion-implantation with 1 × 1016 Ar+ cm−2 reduced macroscale friction down to about 0.10 from 0.12 with an increase in wear life by a factor of 4; however, doses of 5 × 1016 ions cm−2 gave three times higher friction and poorer wear life; higher doses disintegrated the C60 molecules. Based on STM, TEM, Raman, FTIR, and laser desorption Fourier-transform ion cyclotron resonance mass spectrometer (LD/FT/ICR) studies, we found that the ion implantation with a dose of 1 × 1016 Ar+ cm−2 resulted in smoothening of the fullerene film surface probably by compacting clusters, but without disintegrating the C60 molecules. However, a high dose of 5 × 1016 Ar+ cm−2 damaged the C60 molecules, converting it to an amorphous carbon. Nanoindentation studies show that ion implantation with a dose of 1 × 1016 Ar+ cm−2 resulted in an increase in the hardness from about 1.2 to 4.0 GPa and in elastic modulus from about 70 to 75 GPa and modified the elastic-plastic deformation behavior.

The crystalline quality of a diamond film with two different preferential orientations (100) and (111), obtained in the same run by hot filament chemical deposition, has been studied. The quality of the film determined by Raman spectroscopy measurements was found to be nearly the same for both orientations. The second order Raman spectrum for diamond film was observed by using an infrared excitation.

An attempt to unify the growth mechanisms and conditions for diamond formation is developed via the growth probability calculated by a barrier model between the two phases. From the distribution law of the equal growth probability lines plotted in a pressure-temperature (P-T) diagram, five regions of different growth methods and mechanisms were reasonably delineated. Many experimental results can be generalized and explained by our theory, and the unity of diamond growth mechanism was discussed over the wide region of the P-T condition.

We have developed multilayer composite diamond coatings with improved adhesion and wear resistance on WC(Co) tool substrates. The coatings consist of a first layer of discontinuous diamond crystallites that are anchored to the WC(Co) substrate by an interposing layer of ceramic films. These films consist of TiC, TiN, SiC, Si3N4 or WC deposited to provide a conformal coverage on the first layer of diamond. A second or final layer of continuous diamond film is deposited to provide the cutting edge of the tool. The diamond film in the composite layers is deposited by hot filament chemical vapor deposition (HFCVD) and the interposing layer is deposited by laser physical vapor deposition (LPVD). The different parameters associated with the deposition of diamond and interposing layers are optimized to improve the adhesion and wear resistance. We have studied the adhesion characteristics by indentation tests in which the critical load for peeling of the diamond films is determined. Adhesion and wear resistance of the films are also tested using an overlap polishing on diamond paste with 5–6 μm particle size. The diamond and interposing layers in the composite are characterized by scanning electron microscopy and Raman spectroscopy. Results of improvement in adhesion and wear resistance are correlated with the quality of the diamond film and the interposing layer. Better accommodation of thermal stresses and strains in the composite layers has been shown to be responsible for improvement in the adhesion and wear resistance of the composite diamond films.

The size distributions of aerosol particles generated in N2 and O2 at ambient atmospheric pressure by repetitive excimer laser ablation of solids have been measured in quasi-steady-state from 10 nm to 1 μm diameter with a differential mobility analyzer (DMA). A light scattering technique extended the range of measurable sizes up to 20 μm, beyond the upper limit of sizes observed in the aerosol. Irradiation near focus was required to observe metal particles above 0.1 μm diameter. YBCO ceramic (YBa2Cu3O7) produced copious smaller particles with mild focusing. For an ablated polymer, PMMA, particulate production increased and the size distribution altered shape with continued energy deposition.

CdS-silica xerogel composites were prepared from tetramethoxysilane, acidic water, and formamide mixtures homogenized by high power ultrasounds. Different concentrations of Cd(NO3)2 were added. CdS semiconductor nanoparticles were precipitated by H2S gas diffusion through the sonogel porous structure. Composite mechanical properties were enhanced by an impregnation process by the gel soaking in the same sol as-prepared. Textural parameters evolution is compared to the salt content in order to find the best performance to CdS nanocrystal growth. The impregnation process allows a better composite protection.

Porous copper was produced by electrolytic dealloying of a Cu-Mn alloy (Incramute: Cu, 40-48 wt. % Mn, 1.4-2.3 wt. % Al) conducted in a 0.3 N-NaCl solution at a potential of −0.2 V (SCE). The dealloying time needed for the as-received cold-rolled specimen (50 h) is shorter than that of the annealed specimen (850 °C for 2 h). The pore size, about 1 μm, of the dealloyed cold-rolled specimen is bigger than that, about 0.1 μm, of the dealloyed specimen after annealing. This is probably because annealing reduced the phase inhomogeneity and removed the rolling effects.

Incramute Cu-Mn alloys were dealloyed to remove Mn by selective electrolytic separation. The porous dealloyed specimens were compressed at 0.17-14 GPa, resulting in densities of 55-88% of the density of pure copper. Some porous copper specimens before compression were soaked in a mixture of monomer (MMA) and the initiator (AIBN), compressed, and then polymerized by heating. Young's moduli of both the dealloyed porous copper and its PMMA composite were found to decrease exponentially with porosity and volume fraction of PMMA, respectively. The apparent activation energy for damping of Cu-PMMA composite near the glass transition temperature of PMMA was found to increase with decreasing volume fraction of PMMA.