Nanoscale hollow spheres of amorphous phosphorus nitride (P3N5) were synthesized by reacting PCl3 with NaN3 at 150–250 °C. Transmission electron microscope images show that the hollow spheres have a diameter of 150–350 nm, and the thickness of the shell is 20 nm. A very small amount of curly films were also found in the sample prepared at 150 °C. The infrared spectrum indicates a high degree of purity. X-ray photoelectron spectroscopy indicates the presence of P and N, with a molar ratio of 1:1.62 for P:N. Ultraviolet-visible absorption spectroscopy shows an absorption band at 265–315 nm. Under photoluminescent excitation at 230 nm, the P3N5 emits ultraviolet light at 305 nm. With a band gap of 4.28 eV, the products may be a wide gap semiconductor. A possible mechanism and the influence of temperature on the formation of the hollow spheres are also discussed.

The microstructures of thick plasma-sprayed yttria-stabilized zirconia (8% mass fraction yttria) deposits were studied in a series of Porod small-angle neutron scattering (SANS) and multiple small-angle neutron scattering (MSANS) experiments. Three main void components were identified in the deposits: intrasplat cracks, interlamellar planar pores, and globular pores. The SANS and MSANS measurements were analyzed using the traditional theory for Porod scattering and a recently developed three-component model for MSANS evaluation. The average size, volume fraction, internal surface area, and orientation distribution for each void component within the deposits were determined. This study focused on gaining a better understanding of the effects of initial feedstock particle size and annealing temperatures on the microstructure of deposits sprayed under equivalent particle-impact conditions. Quantitative results are presented for each of four deposit samples: one prepared using the as-received feedstock particle wide-size distribution and three prepared from feedstock powder of different and relatively narrow particle size ranges with average sizes of 32, 47, and 88 μm. Except for the coarse (88 μm) feedstock powder, only mild monotonic variations were found in the microstructural anisotropies, the porosities (13 ± 1%), and the internal surface areas in the as-sprayed deposits. The internal surface area was independent of the feedstock particle size, even with the coarse feedstock. When the deposits were annealed at high temperatures (1100 and 1400 °C), the microstructures were altered with a reduction of the total internal surface area and a mild coarsening of the voids. These changes in the microstructural evolution were well-captured and described by the three-component model. The results were compared and related with those obtained from scanning electron microscopy images and elastic moduli measurements.

A laser-based technique was used to deposit Fe3O4 on A319Al, producing an Fe3O4/Al reaction composite coating. Scanning Auger microscopy indicated a reaction between oxide particles and aluminum-forming Fe–Al intermetallic compounds, Al2O3, and various intermediate reaction products. Analysis of the coating region, fractured in vacuo, indicated substantial toughness of the material due to extremely refined microstructure with finely distributed oxide and intermetallic particles and strong interfacial bonding between particles and the matrix. Mechanical properties of the coating were evaluated by nanoindentation techniques employing both Berkovich and cube-corner indenters. Hardness and elastic modulus values were found to be uniform at 1.24 and 76 GPa, respectively. No radial cracking was observed for either the Berkovich or cube-corner indenters. These results indicate that the laser-induced rapidly solidified composite material is tough and fracture resistant.

Scandia (Sc2O3) is a ceramic material that shows interesting thermal and optical properties, but is difficult to grow as single crystals. As an alternative, in this work we fabricated polycrystalline Sc2O3 transparent ceramics via vacuum sintering, using powders thermally pyrolyzed at 1200 °C from a scandium sulfate salt, Sc2(SO4)3 · 7.8H2O, that we prepared. Characterization of the powders was achieved by differential thermal analysis/thermogravimetry, x-ray diffractometry, Brunauer–Emmett–Teller analysis, and field-emission scanning electron microscopy. Sintering behaviors of the Sc2O3 powders were studied in air via dilatometry. The sulfate salt transforms to oxide at temperatures ≥1000 °C, and the best pyrolysis temperature for transparent ceramics fabrication is 1200 °C, at which the resultant Sc2O3 powder is good in dispersion, ultrafine in particle size (∼80 nm), and almost free from residual sulfur. Transparent ceramics were fabricated from this powder via vacuum sintering at 1625 °C or above. The ceramics sintered at 1700 °C for 4 h exhibit an in-line transmittance of approximately 56–58% in the visible light region at a sample thickness of 1.0 mm.

A comparison of bending and compressive/tensile loading cases of multilayered composites is given. Bending perpendicular to the layer interfaces is suggested as a sensitive and experimentally convenient method for determining the elastic modulus of compliant isotropic layers within a multilayered composite. Different approaches to analyze the strain and compliance behavior of the composite and individual layers are derived. Ranking of the relevant equations with respect to strain sensitivity is made, which favors the bending test perpendicular to the layer interfaces. The derived relationships permit a prediction of the bending behavior and the flexural rigidity of the composite. Furthermore, the properties of a layer within the structure can be determined. Limitations that exist for the bending perpendicular to the layer interfaces in the case of low stiffness of the layers can be overcome using either a compressive or a tensile loading mode. Application of the formulas to buckling and interfacial delamination is considered. Materials, such as plasma-sprayed thermal barrier coatings, that are supposed to behave elastically different in tension and compression are given special consideration. Although determination of elastic moduli is the main interest, in the case of known elastic moduli, the formulas can be used to determine the thickness of individual layers within a composite structure.

Undoped and nitrogen-doped amorphous diamond were deposited on n-type Si(100) substrate by a cathodic arc process. By varying nitrogen partial pressure of the gas mixture in the range of 0 to 55.6%, up to 23 at.% of nitrogen was incorporated in amorphous diamond. The electron spectroscopy for chemical analysis, Raman, and atomic force microscopy measurements indicated that most nitrogen atoms replaced carbon atoms in the amorphous structure. The electron concentration, mobility, and its resistivity were determined by the measurement of Hall effect. With the increasing of nitrogen content, the resistivity curve is U-shaped with a local minimum. The electron emission current in vacuum was characterized based on the diode design. It was found that the electron emission was highly reproducible. This is in contrast to the high variability observed for carbon nanotubes. The lowest resistivity coating had the lowest “turn-on” electrical field of 0.7 V/μxm at the current density of 10 μA/cm2.

Electrochemical codeposition of diamond particles and refractory metal hydroxide films was conducted by combining electrophoretic deposition and anodic dissolution. Anodic corrosion of metal proceeded under the influence of iodide ions, and then metal ions were released to the solvent. Positively charged diamond particles were suspended in the solvent and electrophoretically deposited on the cathode surface at the same time as electrochemical deposition of the metal ions. As a result, diamond dispersed metal hydroxide film was produced. The diamond content of the film was easily controlled by varying the quantity of suspension in the solvent. This codeposition mechanism is investigated in detail.

The corrosion behavior of the bulk glass-forming Mg65Y10Cu15Ag10 alloy was studied in neutral and weakly acidic media. Potentiodynamic polarization studies in cyclic and linear modes were carried out in electrolytes with a pH = 7, containing different anions. The alloy corroded freely in electrolytes with sulfate and pthalate ions, whereas passivity was observed in the electrolyte with borate ions. Further tests were performed in boric-acid-added borate buffer solution with pH = 7, 6, and 5. From Tafel characteristics, corrosion potentials and corrosion current densities were estimated. The data were compared with those of the ternary Mg65Y10Cu15 metallic glass. Potentiostatic anodic polarization tests were conducted on the Mg65Y10Cu15Ag10 alloy in boric-acid-added borate buffer solution with pH = 7 at two different potentials, 800 and 300 mV, saturated calomel electrode, which revealed different current transient characteristics. Auger electron spectroscopy was employed to characterize the anodically generated passive layers. The depth distributions of the elements as well as their chemical states were detected to be different for layers formed in electrolytes (i) with different pH values (8.4 and 7) of the same anion, (ii) with the same pH value but containing different anions (borate, sulfate, and pthalate), and (iii) with the same pH value and anion (borate) but at two different anodic potentials.

The synthesis of microcrystalline and nanocrystalline carbon thin films using sulfur as an impurity addition to chemical vapor deposition (CVD) was investigated. Sulfur-incorporated microcrystalline diamond (μc-D:S) and nanocrystalline carbon (n-C:S) thin films were deposited on Mo substrates using methane (CH4), hydrogen (H2), and hydrogen sulfide (H2S) gas feedstocks by hot-filament CVD. These films were grown under systematically varied process parameters, while the methane concentration was fixed at 0.3% and 2% for μc-D:S and n-C:S, respectively, to study the corresponding variations of the films’ microstructure. Through these studies we obtained an integral understanding of the materials grown and learned how to control key material properties. The nanocrystalline nature of the material was proposed to be due to the change in the growth mechanisms in the gas phase (continuous secondary nucleation). The growth rate (G) was found to increase with increasing TS and [H2S] in gas phase, thus following the chemisorption model that describes the surface reactions. One of the propositions for the increase was that H2S increases the production rates of methane and consequent methyl radicals without much of its own consumption, which is almost negligible and increases the carbon-containing species. This is analogous to the increase of G with increasing methane concentration, but for the relatively high S/C ratio used here, there is a possibility of its incorporation in the material, however small. This particular conjecture was verified. In this context, the results are discussed in terms of the decomposition of reactant gases (CH4/H2/H2S) that yield ionized species. The inferences drawn are compared to those grown without sulfur to study the influence of sulfur addition to the CVD.

This paper aims to contribute to the understanding of column formation mechanisms in Al2O3–TiC ceramics micromachined using excimer lasers. Chemical and structural characterization of columns grown in Al2O3–TiC composite processed with 200 KrF laser pulses at 10 J/cm2 was carried out by scanning electron microscopy, transmission electron microscopy, x-ray photoelectron spectroscopy, and x-ray diffraction analysis. Fully developed columns consist of a core of unprocessed material surrounded by an outer layer of Al2TiO5, formed in oxidizing conditions, and an inner layer, formed in reducing conditions, composed of TiC and Al3Ti or an AlTi solid solution. Possible mechanisms of column formation are discussed.

A new method for making substrate-independent hardness measurements by nanoindentation techniques that applies to soft metallic films on very hard substrates is presented. The primary issue to be addressed is substrate-induced enhancement of indentation pileup and the ways it influences the indentation contact area. On the basis of experimental observations of soft aluminum films deposited on silicon, glass, and sapphire substrates, an empirical relationship was derived that relates the amount of pileup to the contact depth. From this relationship and the associated experimental observations, a method was developed that allows the intrinsic hardness of the film to be estimated, even when the indenter penetrates through the film into the substrate. The method should prove useful for very thin films (<100 nm) in which it is not possible to make measurements at penetration depths small enough to avoid subtrate effects.

Electrochemical synthesis of hard Fe–15.4 mass% Ni–0.70 mass% C alloy film with a hardness 750 HV was carried out from sulfate-based bath containing a small amount of citric acid and L-ascorbic acid. The nature of the alloy was investigated by different characterization techniques including x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, Mössbauer spectroscopy, differential scanning calorimetry, and magnetic measurements. The decomposition behavior of the alloy was also studied and compared with that of thermally prepared martensite. It was found that the electrochemically deposited Fe–Ni–C alloy exists in a state that is ahead of the freshly quenched state of martensite. It is suggested that the state of the electrochemically deposited Fe–15.4 mass% Ni–0.70 mass% C alloy corresponds to the state of thermal martensite, which had been heated to the preprecipitation stage of tempering.

Nanostructured Cu/304 stainless steel (SS) multilayers were prepared by magnetron sputtering. 304SS has a face-centered-cubic (fcc) structure in bulk. However, in the Cu/304SS multilayers, the 304SS layers exhibit the fcc structure for layer thickness of ≤5 nm in epitaxy with the neighboring fcc Cu. For 304SS layer thickness larger than 5 nm, body-centered-cubic (bcc) 304SS grains grow on top of the initial 5 nm fcc SS with the Kurdjumov-Sachs orientation relationship between bcc and fcc SS grains. The maximum hardness of Cu/304SS multilayers is about 5.5 GPa (factor of two enhancement compared to rule-of-mixtures hardness) at a layer thickness of 5 nm. Below 5 nm, hardness decreases with decreasing layer thickness. The peak hardness of fcc/fcc Cu/304SS multilayer is greater than that of Cu/Ni, even though the lattice-parameter mismatch between Cu and Ni is five times greater than that between Cu and 304SS. This result may primarily be attributed to the higher interface barrier stress for single-dislocation transmission across the {111} twinned interfaces in Cu/304SS as compared to the {100} interfaces in Cu/Ni.

We report on the observation of space-selective precipitation of gold nanoparticles in Au2O-doped silicate glass by a method of irradiation with an 800-nm femtosecond laser and further heat treatment. The irradiated region of the glass first became gray in color after irradiation with the femtosecond laser and then turned red after further heat treatment at around 520 °C, indicating that gold nanoparticles have precipitated in the irradiated region of the glass. A possible mechanism has been suggested that the Au+ ions in the region irradiated are reduced to Au0 atoms by the femtosecond laser, and then the Au0 atoms accumulate to form gold nanoparticles with the glass sample heat treated. The observed phenomenon should have potential applications in the fabrication of ultrafast all-optical switches.

Polystyrene (PS) core–TiO2 shell composite particles and TiO2 hollow spheres were fabricated using the liquid phase deposition (LPD) method. Composite particles were prepared using PS particles as templates. Calcination of the composite particles resulted in TiO2 hollow spheres. Uniform TiO2 hollow spheres were obtained when the reaction time of the LPD process was between 4 and 8 h. Furthermore, we fabricated TiO2 hollow spheres whose inner surfaces were functionalized by Pt particles after platinized PS particles were used as templates. The Pt particles were immobilized on the inner surfaces of the hollow spheres.

A thin film of mixed manganese and vanadium oxides was formed on a platinum electrode by electro-oxidation of Mn2+ precursors in aqueous solution with VO3−. X-ray analysis revealed that the film consists of an amorphous phase including trivalent and tetravalent Mn ions. The infrared spectrum exhibited the bands attributable to V2O5, suggesting that protonation and dehydration of VO3− occur to form the polymeric structure. The mixed oxide film showed no electron spin resonance signal in an as-deposited state. After the film-coated electrode was immersed into water and then dehydrated, however, a characteristic signal (g = 2.022) of Mn2+ in the solid phase appeared, accompanying a decrease in the vanadium content. This suggests that Mn3+ ions not in the oxide network, but pairing with unreacted VO3−, are disproportionated to MnO and MnO2 by the reaction with water, while the VO3− is diffused to keep the charge valance of the film.

A controlled introduction of second-phase Y2BaCuO5 (211) nanoparticles into YBa2Cu3O7−δ (123) thin films was achieved for the first time for the purpose of increasing flux pinning. The island-growth mode of 211 on 123 was utilized to obtain an area particle density >1011 cm-2 of 211 thick-disk-shaped nanoparticles in individual layers. Composite layered structures of (211y nanoparticles/123z)×N were deposited by pulsed laser deposition on LaAlO3 substrates, with N bilayers = 24 to 100, y thickness = 1 to 2 nm, and z thickness = 6 to 15 nm (assuming continuous layer coverage). With 211 addition, the critical current densities at 77 K were higher at magnetic fields as low as 0.1 T and increased as much as approximately 300% at 1.5 T. The superconducting transition temperature was reduced by approximately 2 to 4 K for 211 volume fraction <20%. Reinitiation of 123 growth after every 211 layer resulted in a smooth and flat surface finish on the films and also greatly reduced surface particulate formation especially in thicker films (∼ μm).

In this paper, the improvement of casting properties of the high-strength AlZnMgCu alloys is described. This improvement was achieved by additions of Ni, Mg, and Si, which formed eutectic phases, thus reducing the crystallization interval of the alloy. The comparison of the castability and hot-tearing tendency was made for three alloys: nearly single-phase AlZn6Mg2 alloy, quasi-ternary eutectic AlZn7Mg7Cu1Ni3Si3 alloy, and common casting AlSi10 alloy. It was shown that the castability and hot-tearing tendency of the quasi-ternary eutectic alloy are similar to those of the AlSi alloy.

A closed-form model was proposed to evaluate the elastic properties of nanocrystalline materials as a function of grain size. Grain-boundary sliding, present in nanocrystalline materials even at relatively low temperatures, was included in the formulation. The proposed analytical model agrees reasonably well with the experimental results for nanocrystalline copper and palladium.

The phase stability of epitaxial KTaxNb1−xO3 (0 ≤ x ≤ 1) thin films, with compositions over the entire solid solution range, was investigated. KTaxNb1−xO3 thin films were deposited on (100) MgAl2O4 substrates by metalorganic chemical vapor deposition. Films with compositions x ≤ 0.30 were orthorhombic, as determined by x-ray diffraction. Dielectric measurements at room temperature indicated the presence of morphotropic phase boundaries at x = 0.30 and at x = 0.74. Temperature-dependent measurements of the dielectric constant for KNbO3 from 80 to 800 K indicated three structural phase transitions at 710, 520, and 240 K. For intermediate compositions, a decrease in the Curie and tetragonal–orthorhombic transition temperatures was observed with increasing Ta atomic percent, similar to the bulk phase equilibrium. In contrast to bulk materials, an increase in the orthorhombic–rhombohedral transition temperature with increasing x was observed for the films, resulting in the stabilization of a rhombohedral phase at room temperature for compositions 0.45 ≤ x ≤ 0.73. Differences between the phase stability for the thin films and bulk were attributed to lattice misfit strain.