Nanophase (n-) ZrO2 was produced in its pure and partially stabilized form by the gas-phase condensation method. The material was examined by x-ray diffraction and Raman scattering to obtain information on the structural evolution of the material during sintering. Two types of Y2O3-doped ZrO2 nanophase material were made: one by co-deposition of n-Y2O3 and n-ZrO2 in a consecutive manner and the second by mechanically mixing n-Y2O3 and n-ZrO2. We have determined that the co-deposition process is the most effective means of doping the n-ZrO2.

Several polymers with high temperature and high performance properties have been modified by ion implantation. Ions of As and Xe with energies of 50 keV and 180 keV have been implanted in the dose range of 1015 to 1017 ions/cm2. Electrical conductivities of these originally insulating polymers have been greatly enhanced after the ion implantation. Structural and compositional changes that accompanied these electrical enhancements were observed using infrared (IR) and Raman spectroscopies, scanning electron microscopy (SEM), Rutherford backscattering spectroscopy (RBS), and elastic recoil detection analysis (ERDA) methods. Our high resolution data reveal a two-component conductivity that depends on both one-dimensional variable range hopping (VRH) and three-dimensional VRH. For lightly damaged samples (e.g., 1015 ions/cm2) the 1-D VRH is dominant while for highly damaged samples (e.g., 1017 ions/cm2) the 3-D VRH dominates.

Monocrystalline AlN(0001) films with few defects were deposited on vicinal α(6H)–SiC(0001) wafers via plasma-assisted, gas-source molecular beam epitaxy within the temperature range of 1050–1200 °C. The Al was thermally evaporated from an effusion cell. An electron cyclotron resonance plasma source was used to produce activated nitrogen species. Growth on vicinal Si(100) at 900–1050 °C resulted in smooth, highly oriented AlN(0001) films.

Undoped CeO2 and Y2O3-doped CeO2 powders, with particle sizes of ≍10–15 nm, were prepared under hydrothermal conditions of 10 MPa at 300 °C for 4 h. The compacted powders were sintered freely in air or in O2 at constant heating rates of 1–10 °C/min up to 1350 °C. The undoped CeO2 started to sinter at ≍800–900 °C and reached a maximum density of 0.95 of the theoretical at 1200 °C, after which the density decreased slightly. Isothermal sintering at 1150 °C produced a sample with a relative density of ≍0.98 and an average grain size of ≍100 nm. The samples sintered above 1200 °C exhibited microcracking. The decrease in density and the microcracking above 1200 °C are attributed to a redox reaction leading to the formation of oxygen vacancies and the evolution of O2 gas. Doping with Y2O3 produced an increase in the temperature at which measurable sintering commenced and an increase in the sintering rate, compared with the undoped CeO2. Sintered samples of the doped CeO2 showed no microcracks. The CeO2 doped with up to 3 mol% Y2O3 was sintered to almost full density and with a grain size of ≍200 nm at 1400 °C.

A well-characterized alumina-polypropylene suspension was injection molded as cylinders of 20 and 40 mm diameter. A finite difference method was used to calculate the temperature distributions in the cylinders and in the sprue during solidification which incorporated the enthalpy of crystallization. The times at which pressure in the cavity began to decay, the calculated sprue solidification time, and the calculated time at which pressure in the center of the cavity reached zero were compared as a function of hold pressure. The resulting solidification-induced defects were revealed by radiography and sectioning and explained in terms of the kinetics of solidification.

Effect of surface structures upon ultrathin film interference fringes generated from extremely thin films or epitaxial layers grown on semiconductor wafers has been studied. Since dark regions of fringes correspond to the places where the thin films are destroyed or absent, the fringes are investigated to detect uneven surfaces with undesired structures. Therefore, surface microstructures can be detected and characterized effectively by the modification of the fringes.

The structural environments of Zr, Th, and U in aperiodic (metamict) (Ca, Th)ZrTi2O7 were examined using Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. Samples are aperiodic due to a radiation-induced transformation caused by alpha-decay event damage. In the aperiodic samples, Zr is mainly 7-coordinated [d(Zr−O) ≍ 2.14–2.17 ≍ 0.02 Å]; whereas, Th is mainly 8-coordinated [d(Th–O) ≍ 2.40−2.41 ≍ 0.03 Å]. Nearly identical bond lengths and coordination numbers for these elements were determined for an annealed, crystalline sample. The radiation-induced transition from the periodic to the aperiodic state is characterized by a significant broadening of the distribution of (Zr, Th)–O distances. In one metamict sample with ≍1.9 wt.% U3O8, U is essentially tetravalent. The absence of higher oxidation states (U6+) is consistent with the lack of evidence for alteration (samples are over 500 million years old). The reduced medium-range order around Zr, Th, and U is related to the increase of alpha-decay event damage and precludes decomposition of zirconolite into simple oxides of Zr, Th, or U. Comparison with other metamict (Zr, Th, U)-bearing phases (e.g., ZrSiO4 and ThSiO4) suggests that Zr4+, Th4+, and U4+ prefer 7-, 8-, and 6-coordinated sites, respectively, in aperiodic phases at ambient temperatures and pressures. Examination of the structure of crystalline (Ca, Th)ZrTi2O7 demonstrates that M–O–M angles (M = Ca, Ti, Zr, and Th) are relatively small (≍100–120° for edge-sharing polyhedra). A limited relaxation of the constraints of periodicity around M cations caused by radiation damage (e.g., tilting of polyhedra) dramatically affects the distribution of these angles. This type of structural relaxation may be the mechanism by which long-range periodicity is lost and medium-range order is reduced with increasing radiation damage, while the major cations retain their nearest-neighbor environments. This relaxation may also help explain the lattice expansion observed in zirkelites when they undergo radiation damage.

The formation of hydroxyapatite by an acid-base reaction between solid calcium phosphates at temperatures from 5 to 60 °C was examined. The basic reactant used is Ca4(PO4)2O, while the acidic reactants include CaHPO4, CaHPO4 · H2O, and Ca(H2PO4)2 · H2O. Rates of heat evolution during reaction were determined by isothermal calorimetry. The variations in the proportions of reactants and hydroxyapatite and the formation of intermediate products were assessed by x-ray diffraction. Development of microstructure was observed. Generally, hydroxyapatite formation occurs by rapid initial reaction followed by a period during which reaction occurs slowly. Apparent activation energies calculated for the reaction when CaHPO4 is the acidic reactant show differing values depending on its surface area. When the acidic reactant is Ca(H2PO4)2 · H2O, intermediate products are formed. At low temperatures the intermediate is CaHPO4 · 2H2O, while at higher temperatures it is CaHPO4. Above 38 °C, the rate during the period of slow reaction decreases with increasing temperature. This appears to be related to the retrograde solubilities of the reactants, CaHPO4 · 2H2O and CaHPO4, and of HAp.

(Ca1−x, Mgx)Zr4(PO4)6 (CMZP) ceramics have been made by sol-gel and solid state reaction methods. Single phase (Ca1−x, Mgx)Zr4(PO4)6 (x = 0.4) has been obtained. The densification of CMZP depends on the powder synthesis method. Near theoretical density can be achieved by cold pressing and sintering with the addition of a sintering aid. Bulk thermal expansion of CMZP is shown to depend on the phase composition, grain size, and presence of microcracks. By choosing different sintering temperatures and times, the thermal expansion of CMZP can be controlled. CMZP (x = 0.4) ceramics exhibit near zero bulk thermal expansion, low thermal expansion anisotropy, low thermal conductivity, and thermal stability up to 1500 °C.

The electrical properties of sol-gel prepared aluminosilicate films were investigated for suitability in electronic applications. The aluminosilicate films exhibited apparent closed porosity and a dielectric constant as low as ≍5 with processing temperatures from 373 K to 873 K. The porosity was inaccessible to nitrogen at 77 K, helium at 293 K, and water vapor at 293 K. Both bulk and thin-film samples were analyzed for hydroxyl and carbon contents to elucidate the relative dependence of the measured electrical properties on processing conditions. Experiments indicate it is possible to vary the porosity in bulk material in ways that should improve electrical properties.

The limits of glass formation of new fluoroindate glass compositions have been determined for the basic systems InF3–BaF2–GdF3−20ZnF2−20SrF2–2XFn where × = Na, La and InF3–BaF2−20ZnF2−20SrF2−2GdF3–XFn, where × = Ca and Y. The incorporation of small amounts of GaF3 and/or GdF3 increases strongly the thermal glass stability. All the fluoroindate compositions studied are highly transparent in the mid-infrared range; their transmission edge is shifted beyond 7 μm and the theoretical attenuation coefficient, extrapolated at the CO laser wavelength emission, is typically α = 100 dB/km. Large bulks and preforms have been prepared allowing the drawing of optical fibers.

During the pyrolysis of cured hydridopolysilazane (HPZ) polymer to form Si–C–N ceramic fibers, large quantities of unpaired electrons are produced. For such materials dynamic nuclear polarization (DNP) provides a means of enhancing the intensity of the NMR signal, and supplies information on the localization or delocalization of unpaired electrons. 29Si, 1H, and 13C DNP gives enhancements of 250 for 13C and at least 800 for 29Si. 13C and 29Si DNP-DPMAS experiments yield the following results: (i) there are at least two distinct types of carbon, sp2 and sp3; (ii) there is a distribution of sp3 silicon environments; (iii) the unpaired electrons behave as fixed paramagnetic centers; and (iv) the unpaired electrons are distributed homogeneously throughout the sample. Proton DNP spectra can be obtained even though hydrogen is only a trace element in the finished ceramic.

The chemical diffusion coefficients of lithium ions in LixWO3 films were investigated as a function of lithium concentration and film porosity. Thin films were deposited with different porosities by thermal evaporation of WO3 powder in various partial water pressures. Our results indicate that diffusion coefficients increase with film porosity and decrease with increasing lithium concentration. Large diffusion coefficients that were found for small lithium concentrations appear to be due to the contribution of protons generated from ion exchange reactions between lithium and water incorporated in the film. Simultaneous electrical and in situ optical measurements were carried out to study the effect of porosity on the electrochromic properties of LixWO3. The coloring efficiency of porous WO3 films increases by approximately 70% when deposited in partial water pressure of 10−4 Torr, but decreases with further increments in water pressure.

Fracture toughness of polymethyl methacrylate (PMMA) was evaluated with indentation cracks. The cracks were developed by indenting in a liquid acetone environment, as suggested by previous researchers. Due to the inconsistency in crack configurations with varying indentation loads and to the negligible residual stress from indentation, the application of the indentation strength method was limited in evaluating fracture toughness of PMMA. The semielliptical crack approximation, however, particularly at a low indentation load of 9.8 N, resulted in reasonable agreement with the value determined by three conventional fracture toughness testings using the compact tension (CT), double cantilever beam (DCB), and single edge notched beam (SENB) specimens. Measurements at other indentation load typically were in poor agreement with conventional methods due to poorly developed crack configurations.

We explain observed Hf-site interchange in LiNbO3 and LiTaO3 at high temperatures using solid-state defect chemistry reactions. The model takes into account fully the effects of nonstoichiometry on the ferroelectric-to-paraelectric phase transition. Specifically, we use this model to interpret the temperature dependence of the Hf-site interchange that we measured using perturbed-angular-correlation (PAC) spectroscopy. In this context, the site interchange is an equilibrium, thermodynamic process that involves the partitioning of Hf ions between Li and group-V (Nb and Ta) sites. The Hf ions replace group-V ions by pushing them from their normal sites to the Li sublattice. Based on the temperature dependence of the site occupancy, this reaction requires approximately 2.2 to 2.3 eV.

Syntheses of ultrafine glass powders in the MgO–Al2O3–SiO2 ternary oxide system were effected by drying and calcining sols derived from acetylacetonate-tetraethoxysilane ethanol solutions. A mixture of magnesium and aluminum acetylacetonates, dissolved with Si(OC2H5)4 in an ethanol solution in a 2:4:5 Mg: Al: Si mole ratio, was hydrolyzed, spray-dried, and calcined to yield a glass powder of 70 Å primary particle size, which sintered to densities ≥ 2.5 g/cm3 and which formed μ-cordierite as the only crystalline phase below 1000 °C. Incorporation of dopant quantities of boron and phosphorus, via their alkyl esters in the hydrolysis reaction with Si(OC2H5)4 and the acetylacetonates, afforded powders which crystallized in the α-phase directly after sintering to density = 2.66 g/cm3.

The addition of CaO to Li2O–Al2O3–SiO2–TiO2 (LAST), forming the Li2O–CaO–Al2O3–SiO2–TiO2 (LCAST) system, is used in the preparation of low themal expansion coefficient glass-ceramics. By a progressive weight percent substitution of CaO for SiO2, at constant ratios of concentration of Li2O, Al2O3, and TiO2, a number of properties of these glasses have been studied. The results indicated that these thermal properties increased progressively with increasing CaO concentration. X-ray diffraction analysis was utilized to identify the crystalline phase in glass-ceramics of the Li2O–CaO–Al2O3–SiO2-TiO2 system. The d-spacings of the major crystallites were precisely measured and fitted with those of β-spodumene. The minor crystalline phase of titanite, CaO · TiO2 · SiO2, was also present. The average thermal expansion coefficients from 25 to 700 °C were 3.50 × 10−6/°C, 3.81 × 10−6/°C, and 3.91 × 10−6/°C for samples A, B, and C, respectively.

PMDA-ODA polyimide thin films can be formed by vapor co-deposition of the precursor molecules PMDA (pyromellitic dianhydride) and ODA (4, 4′-oxydianiline) if the resulting polyamic acid film is heated to a 473 to 573 K cure step. We have used laser Raman spectroscopy to study how dose composition, dose rate, and substrate temperature influence the properties of the resulting polyimide films. We find that only doses with excess PMDA produce high quality films. Doses with 1 : 1 stoichiometry or excess ODA produce thermally unstable films that contain imine bonds; these films decompose below 575 K. Dosing onto substrates below 315 K produces the polyamic acid precursor of polyimide. At higher substrate temperatures, films with high defect densities or decomposed films are produced. The equilibrium vapor pressures of ODA and PMDA are reported.

The effect of steam on the reaction kinetics of both mullite and metastable spinel formation from sol-gel precursors, having an Al/Si atomic ratio of 3/1, was studied using dynamic x-ray diffraction (DXRD) coupled with differential thermal analysis (DTA). Steam was observed to accelerate the nucleation of tetragonal mullite in single phase gels at ~980 °C. When single phase gels are formed with a faster hydrolysis step, the presence of steam also increases the nucleation of metastable spinel at this temperature, possibly due to the in situ formation of boehmite in locally enriched alumina regions at <300 °C. In addition, steam also enhances the decomposition of metastable spinel in single phase gels and transient alumina in the diphasic gel at ~1200 °C, probably as a result of surface interactions of water with spinel or transient alumina grains. There was no observable effect of steam on second stage mullite formation (~1250 °C) in either the single or diphasic gels. This is attributed to the hypothesis that the rate-limiting step at this stage might be the dissolution of alumina into the silica-rich amorphous matrix, a step that is unaffected by the presence of steam.

Various factors affecting the coloring and bleaching processes of LixWO3 films have been studied. The rate of the coloring process is limited by the decreasing electromotive force in the LixWO3 film and by the components of the series circuit resistance, including the electrolyte resistance and the diffusion impedance within the film. The bleaching process in a thick film is limited by either the space charge or by the diffusion impedance, depending on the experimental conditions. A more complete and quantitative model of the coloring/bleaching process has been developed and shows good agreement with experimental results. Our analysis also indicates that the lithium concentration value of x near the LixWO3/electrolyte interface can greatly exceed its reversible limit during the coloring process, even though the average x value within the film remains much lower than the reversible limit. This phenomenon may introduce some irreversible structural changes in the film, which in turn may constitute one of the film's degradation mechanisms.