Vacuum depositions of Au on highly oriented pyrolytic graphite (HOPG) and SiO2 substrates in iodine vapor of 1 × 10–4 Torr give rise to formation of dispersed nanoscale Au particles at room temperature. The iodine is physisorbed on the Au surface and prevents the Au particles from coalescing. The mean diameter of Au particles on highly oriented pyrolytic graphite (HOPG) is about 40 nm, which is larger than that on SiO2 The particles on HOPG have a narrower and more uniform size distribution than those on SiO2. Radial distribution function of the particles on HOPG showed many well-defined peaks, whereas that on SiO2 had only one peak, indicating highly structured deposition on HOPG by iodine adsorption.

Negative ion states for Li atoms are found in graphite nanoclusters heavily doped with lithium using a semiempirical calculational method. These calculations identify a quasi-stable site for a negative Li ion near the terminated hydrogen atoms, and this site becomes very stable in the presence of the Coulomb interaction between Li ions. The total charge transfer from Li ions to the graphite clusters does not depend on the number of Li atoms per cluster but rather on the relative geometries of the Li atoms on the cluster. The relationship of these findings to the findings in the 7Li nuclear magnetic resonance experiments and to the performance of Li secondary batteries is discussed.

In the present paper, the process of phase separation in calcium aluminosilicate glasses (CAS glasses) containing TiO2 as a nucleating agent is studied. A static electric field promotes the process of phase separation even when the time of heat treatment is short. The effect of electric field on phase separation acts through the higher polarizability of Ti ions. Alkali ions, when present, will diffuse toward the cathode, which may generate different micromorphology at the parts of samples near the cathode and the anode. X-ray photoelectron spectroscopy and Raman spectra analysis confirm the conclusion that the electric field has promoted phase separation in CAS glasses.

CuCl2 and FeCl3 graphite intercalation compounds were prepared by a gas phase reaction method using different carbon host materials. The effect of the microstructure of carbon host materials on the amount of intercalation and the distribution of intercalant was investigated using x-ray diffraction and electron microprobe analysis. For a fiber sample with a core region of onion skin structure in the cross section, a lower concentration of intercalant was measured in the core region. For fiber samples with an oriented-core transverse microtexture, different intercalant distributions along the long axis (oriented-core direction) and the short axis of the elliptical cross section were found.

A lithium reduction technique to condition spent fuel for disposal has been developed at the Argonne National Laboratory. There is a need to ensure adequate vessel longevity through corrosion testing and, if necessary, materials development. Several ferrous alloys and tantalum specimens were submitted to a corrosion test at 725 °C for thirty days in an argon atmosphere, using a lithium-chloride salt saturated with lithium metal and containing small amounts of lithium oxide and lithium nitride. The samples did not show dimensional or weight change, nor could corrosion attack be detected metallographically. The lithium-saturated salt system did not show any behavior similar to that of liquid lithium corrosion. From testing in other gas compositions, it appears that the presence of oxygen in the system is necessary to produce severe corrosion.

A series of rare-earth-(RE-)doped α-sialons (RExSi12–4.5xAl4.5xO1.5xN16–1.5x, with x = 0.40 for RE = Nd, Sm, Yb, and x = 0.48 for RE = Y) were prepared and heat-treated in air at 1350 °C for 66–727 h (3–30 days), and the variations in composition and structure with time of the formed oxide scales and matrix materials were investigated. In the oxide scales of the Nd-, Sm-, and Y-containing samples a liquid was formed, apparently in (quasi-)equilibrium with the crystalline phases cristobalite and mullite, while only crystalline Yb2Si2O7, cristobalite, and mullite were observed in the Yb sample. Apparently, the liquid plays an important role in the oxidation process. In the depleted zone, located between the scale and the matrix, the liquid attacks the matrix phases, and a process takes place in which the originally formed phases dissolve and reprecipitate as more oxygen-rich phases. In the Nd- and Sm-doped systems, where the α-sialon phase is inherently metastable at 1350 °C, an extensive α → β-sialon transformation takes place, creating still more liquid. As a consequence, the oxidation resistance of α-sialons containing Nd and Sm is much lower than those containing Y and, in particular, Yb.

We examined the stress associated with crystallite coalescence during the initial stages of growth in thin polycrystalline films with island growth morphology. As growing crystallites contacted each other at their bases, the side-walls zipped together until a balance was reached between the energy associated with eliminating surface area, creating a grain boundary and straining the film. Our estimate for the resulting strain depends only on interfacial free energies, elastic properties, and grain size and predicts large tensile stresses in agreement with experimental results. We also discuss possible stress relaxation mechanisms that can occur during film growth subsequent to the coalescence event.

The analysis of thermostimulated currents by the fractional polarization procedure is used to understand percolative behaviors in conductor-insulator-like oil-resin mixtures. On the fundamental side oil-poor systems are particularly attractive. They offer for the first time the opportunity to apply a pure Debye-like dielectric treatment of the quasi-elastic dipolar relaxation since the involved dipoles are independent, associated with spatially separated bounded clusters. An unusual compensation phenomenon is observed in the sense that first it does not describe hierarchically correlated motions and secondly it is related to the conducting phase but exhibits characteristics of the insulating phase. This compensation phenomenon is interpreted within the framework of Fröhlich's approach of relaxation processes in biological materials, as significative of a coherent vibration resulting from Böse condensation effects. On the practical side, the surveillance of this compensation phenomenon appears to be a new way to follow the coalescence of conducting bounded clusters with aging.

A process has been invented for growing alumina (Al2O3) whiskers in the matrix of the aluminum-based metal matrix composite by the internal oxidation reaction between aluminum (Al) and molybdenum oxide (MoO3) at 850 °C. The whiskers were formed during the firing stage and distributed uniformly throughout the metal matrix. The fractional volume of the whiskers was about 30%, and their average size was 1 μm in diameter and 10 μm in length. The growth mechanism of the Al2O3 whiskers was studied. It was found that the nutrient for the growth of the whiskers was supplied from the molten Al at the base of the whiskers where they reacted with MoO3 forming the Al2O3 whiskers and the Al–Mo intermetallic phases.

The objective of this work was to determine the mechanism of in-plane texture development in films made by ion-beam-assisted deposition (IBAD). Both in-plane texture and surface roughness were studied as functions of film thickness. A phenomenological growth model based on the preferential growth of aligned grains due to channeling was proposed, linking the surface roughness evolution and texture development. Good correlation was found between the measured roughness and the model prediction, as well as between the roughness evolution and the in-plane texture development. A critical thickness was introduced at which in-plane texture is completed. Both surface roughness and texture results gave a critical film thickness of 114–250 nm for an ion energy of 1000 eV and an R ratio of 0.4. This range of critical film thickness was far beyond the nucleation stage, providing evidence that the development of in-plane texture in IBAD Nb films was growth-controlled.

Films of nanophase diamond are deposited in vacuum onto almost any substrate by condensing multiply charged carbon ions carrying keV energies. These ions are obtained from the laser ablation of graphite at intensities in excess of 1011 W cm−2. The high energies of condensation produce interfacial layers between the film and substrate materials, resulting in levels of adhesion that can support the protection of substrates subjected to harsh environmental conditions. In this article, we give details of the scratch adhesion testing performed on steel and carbide substrates coated with nanophase diamond. A commercially available scratch tester was used and a data analysis was presented to quantitatively assess and measure the adhesion of films on these important substrates. The characterization studies in this work demonstrated nanophase diamond as a highly adherent coating suitable for industrial applications.

The pyramidal indentation-induced surface deformation of brittle ceramics is examined on the basis of extensive test results for indentation load (P)-depth (h) curves during loading/unloading cycle. A mechanically stiff test system is essential for obtaining P-h curves acceptable and reliable for subsequent analyses. Both the loading and unloading P-h curves are expressed by quadratic functions within experimental variations for all the indenters used (Vickers, Berkovich, and Knoop). The loading curve is then related to the Meyer hardness and the unloading curve to Young's modulus by the use of semiempirical equations which enable one to estimate these moduli from the observed loading/unloading parameters. An elastoplastic constitutive equation for indentation surface deformation is theoretically derived. This equation not only predicts well the experimental observations but also gains an important physical insight into the Meyer hardness. The Meyer hardness of brittle materials is not a measure for plasticity, but an elastic/plastic parameter which significantly depends on the geometry of indenter. The concept and experimental determination of “true” hardness as a characteristic material measure for plasticity are proposed.

Fracture modes in a model glass–polymer coating–substrate system indented with hard spheres are investigated. The large modulus mismatch between the glass and polymer results in distinctive transverse fracture modes within the brittle coating: exaggerated circumferential (C) ring cracks that initiate at the upper coating surface well outside the contact (as opposed to the near-contact Hertzian cone fractures observed in monolithic brittle materials); median–radial (M) cracks that initiate at the lower surface (i.e., at the substrate interface) on median planes containing the contact axis. Bonding between the coating and substrate is sufficiently strong as to preclude delamination in our system. The transparency of the constituent materials usefully enables in situ identification and quantification of the two transverse fracture modes during contact. The morphologies of the cracks and the corresponding critical indentation loads for initiation are measured over a broad range of coating thicknesses (20 mm to 5.6 mm), on coatings with like surface flaw states, here ensured by a prebonding abrasion treatment. There is a well-defined, broad intermediate range where the indented coating responds more like a flexing plate than a Hertzian contact, and where the M and C cracks initiate in close correspondence with a simple critical stress criterion, i.e., when the maximum tensile stresses exceed the bulk strength of the (abraded) glass. In this intermediate range the M cracks generally form first—only when the flaws on the lower surface are removed (by etching) do the C cracks form first. Finite element modeling is used to evaluate the critical stresses at crack initiation and the surface locations of the crack origins. Departures from the critical stress condition occur at the extremes of very thick coatings (monolith limit) and very thin coatings (thin-film limit), where stress gradients over the flaw dimension are large. Implications of the results concerning practical coating systems are considered.

Crystallization of the Ti45Ni20Cu25Sn5Zr5 alloy has been studied by means of scanning differential calorimetry, x-ray diffraction, and conventional and high-resolution transmission electron microscopy. The first stage at about 750–800 K is related to the primary crystallization of the Ti8Ni3Cu3SnZr metastable phase having Im3m body-centered-cubic structure with a lattice parameter of a = 0.3069 nm followed by precipitation of the secondary dotlike phase precipitates on its boundaries. The activation energy for the first exothermic reaction determined by Kissinger analysis was found to be 310 kJ/mol. CuTi, Ni2TiZr, and an unknown phase are formed during long-term annealing at high (more than 850 K) temperature.

ZrC films with high hardness were deposited on A3 steel by ion-beam-assisted deposition and had a corrosion rate more than two orders less and a corrosion potential 0.19 V greater than those of the bare A3 steel. The corrosion current of ZrC films was 10 times less and the polarization resistance at least 7.82 times higher than those of both Teflon and ZrN films, respectively. The experimental results confirmed that ZrC films notably enhanced the corrosion resistance of steels.

For the metalorganic chemical vapor deposition (MOCVD) of copper, (hfac)Cu(VTMS) (hfac = hexafluoroacetylacetonate, VTMS = vinyltrimethylsilane) and (hfac)Cu(ATMS) (ATMS = allyltrimethylsilane) were compared, and the effect of L ligand in (hfac)Cu–L was examined. It was found by 1H-NMR (nuclear magnetic resonance) that the thermal stability of (hfac)Cu(VTMS) was better than that of (hfac)Cu(ATMS) due to the relatively weak Cu–ATMS bond. From in situ Fourier transform infrared spectroscopy (FTIR) experiments, the formation of Cu(hfac)2, the product of disproportion reaction of Cu(hfac), was observed in the gas phase and (hfac)Cu(ATMS) was found to be more reactive to form Cu(hfac)2. The minimum temperature for the deposition of copper films from (hfac)Cu(ATMS) was as low as 60 °C, which was about 70 °C lower than from (hfac)Cu(VTMS). The grain size of the film deposited with (hfac)Cu(ATMS) was substantially larger than that with (hfac)Cu(VTMS), which showed that the chemical reactivity of the precursor had an influence on the microstructure along with the deposition temperature.

Two- and three-layer composite models were developed using a beam vibration theory, and the models were applied for measuring Young's moduli of thin metallic films. The Cr, Ni, and Co-coated Si wafer composites (two-layer composite) and (Cr/Ti/Si) composites (three-layer composite) were produced by radio-frequency (rf) magnetron sputtering and used to test the developed models. Young's moduli of (Cr) films obtained by the three-layer composite model agree well with those of (Cr) films obtained by the two-layer composite model, considering (Ti/Si) as the one layer and (Cr) as the other layer. This suggests that moduli of multilayer films may be obtained by using a two-layer composite model repeatedly.

Pure and reactive barium titanate (BaTiO3) and barium orthotitanate (Ba2TiO4) powders have been synthesized by an ethylene glycol (EG), polymerizationcomplexation route. The EG content affected the crystallization behavior and powder morphology. The BaTiO3powder, which had a particle size of approximately 100 nm, crystallized from amorphous to tetragonal phase on calcining at 700 °C for 1 h. Ball-milled BaTiO3 powder sintered to 97% relative density at 1200 °C after 2 h, with a grain size of approximately 200 nm. Ba2TiO4 powder required longer holding times or higher temperatures to be crystallized from the amorphous phase than did BaTiO3. In Ba2TiO4, the phase transformation between low-temperature monoclinic symmetry to high-temperature orthorhombic symmetry was observed by dilatometry and differential scanning calorimetry. A volume decrease of ∼0.5% accompanied the monoclinic-to-orthorhombic transformation on heating. The high-temperature orthorhombic phase could be retained down to room temperature y the addition of at least 6 wt% magnesia (MgO) stabilizer.

In order to investigate the absolute value for the total and exchange-correlation energies of small transition metal clusters, an all-electron mixed-basis approach with the generalized gradient approximation (Perdew–Wang's GGA-1) is applied for the first time to small Cu clusters. We find that the GGA significantly deepens (2.57–2.59 a.u. per atom) both the total and exchange-correlation energies obtained with the local density approximation. A better agreement is obtained with experiments for the binding energy of Cu2 when the spin-dependent calculation is used for an isolated Cu atom.

A mixture of scheelite and magnesium has been mechanically milled together for 100 h, either with graphite or in a nitrogen atmosphere, with the intention of forming tungsten carbide or nitride. The resultant powders were examined by thermal analysis, isothermal annealing, and x-ray diffraction to determine the effect of milling on the reduction of scheelite. With graphite, nanocrystallite W2C was the exclusive tungsten product; WC was not detected even after annealing at 1000 °C. No nitride formed in the system milled with nitrogen; however, 10 nm crystallites of elemental tungsten were formed. The unwanted phases, MgO and CaO, were readily removed by leaching in acid, leaving a fine powder composed of impact welded aggregates of either carbide or 99% pure tungsten metal.