X-ray diffraction analyses of the pure components n-tricosane and n-pentacosane and of their binary mixed samples have enabled us to characterize the crystalline phases observed at “low temperature.” Contrary to what was announced in literature on the structural behavior of mixed samples in odd-odd binary systems with Δn = 2, the three domains are not all orthorhombic. This work has enabled us to show that two of the domains are, in fact, monoclinic (Aa, Z = 4), and the other one is orthorhombic (Pca21, Z = 4). The conclusions drawn in this work can easily be transposed to other binary systems of n-alkanes.

The goal of this work was to address the technological problems associated with waveguide preparation by thermal- and electric-field–assisted K+–Na+ ion exchange in two types of soda-lime glass: common FTD and special pure GIL49. The number of modes, depth, profile, and the change in refractive index were measured for waveguides prepared at temperatures between 250 and 410 °C and electric-field values between 0 and 50 V/mm. Although the influence of some admixture content inside the glass was relatively high, all of these parameters were controlled accurately and repeatedly by the electric field.

The pyrolysis of siloxy-anchored, organic self-assembled monolayers (SAMs) on oxide substrates [titanium dioxide powder; hydrolyzed silicon dioxide on (100) silicon] was studied using x-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and mass spectroscopy (MS). Pyrolysis in air began on heating at 200 °C and was complete by 400 °C for both octadecyltrichlorosilane (OTS) and C16-thioacetate (TA) SAMs, as observed in TGA of SAM-coated TiO2 powders, and in XPS studies of TA-SAM-coated TiO2 powders and Si wafers after various heat treatments. In low-oxygen environments, pyrolysis of SAMs began at higher temperatures: between 250 and 400 °C for heating in ultrahigh vacuum (10−8 Torr) as observed in XPS studies of TA-SAMs on Si, and between 300 and 400 °C in nitrogen, as observed in TEM analysis of sulfonate SAMs under a TiO2 thin film on Si substrates.

The adsorption of N2 molecules inside C24Cs has been studied in detail as a function of temperature and pressure using n-diffraction and nuclear resonance photon scattering (NRPS). Large differences were observed between samples derived from highly oriented pyrolytic graphite and those prepared from graphite powder. The tilt angle of the N2 molecular axis was determined by using NRPS and found to lay nearly parallel to the graphite planes. The amount of adsorbed N2 increased with decreasing temperatures, reaching saturation composition C24Cs(N2)1.5 at approximately 100 K with an initial N2 pressure of 2 bar. At higher pressure, 9 bar, two new phases were formed: a second stage C32Cs(N2)2.1 and a first stage C16Cs(N2)1.8 at T < 170 K and are discussed in detail.

Surface heterogeneity, particularly shape and size of pores on the surface of activated carbon spheres were studied by using scanning tunneling microscopy (STM) and field-emission type scanning electron microscopy (FE-SEM). Spheres were carbonized either in N2 or CO2 atmosphere and oxidized ones were used as samples. A new numerical method based on the determination of contour maps from STM images was proposed in order to determine the size distribution in micropores. These results were discussed with respect to the adsorption of gas and liquid molecules. A good correlation between Brunaner, Emmett, and Teller (BET) surface area determined from adsorption isotherms of N2 at 77 K and the number of pores with the size of 0.5–1.8 nm was observed, indicating that the proposed procedure to analyze the pore size distribution is effective.

Whiskerlike-shaped hydroxyapatite single crystals with the calcium-deficient nature were hydrothermally grown under natural convection by using a temperature-gradient-applied pressure vessel. With this method, crystals grew thinner with a smaller tapering angle than those grown under the nonconvection. Maximum length of the crystals grown under natural convection was 8.3 nm. The grown crystals survived without fracture through at least ten times maximum indentation (25 µm) of the three-point bending tests, showing the maximum bending angle of 62°. Average tensile strength of the crystals was 410.0 MPa.

The AlN/TiN/MgO(001) interfaces, prepared by molecular beam epitaxy, have been characterized by cross-sectional high-resolution electron microscopy (HREM). The thin TiN buffer layer, with the thickness of 40 nm, is epitaxially grown on the MgO(001) substrate. Owing to the same structure-type as well as the small mismatch of their lattice parameters, the growth is governed by the parallel orientation relationship of (001)TiN||(001)MgO, (010)TiN||(010)MgO, and (111)TiN||(111)MgO. Two kinds of processes of the hexagonal AlN epitaxial growth on the as-received TiN(001), differed by the (0001)AlN plane parallel to, and the (1012) plane approximately parallel to the MgO substrate surface, respectively, are identified, and within them, several cases are classified which are based on the consideration of crystallographic symmetry. Theoretical calculations based on the geometrical model that was recently proposed and applied to a number of epitaxial systems have been carried out to rationalize these observations.

Textured c-axis oriented LiNbO3 films have been grown for waveguiding applications on silicon substrates by the solid-source metalorganic chemical vapor deposition (MOCVD) method using tetramethylheptanedionate sources. Thermally grown SiO2 layers were used as cladding layers to provide optical confinement in the LiNbO3 films. The texture direction could be varied from the [006] to the [012] direction by either increasing the growth temperature and/or decreasing the growth rate. Under optimal growth conditions, 100% [006] texturing could be achieved without the aid of an electric field or by using a SiNx buffer layer. The crystallinity and surface rms roughness of c-axis oriented films were found to be strongly dependent on the growth rate. Rocking curve full-width half-maximum (FWHM) values of (006) peaks could be decreased to less than 2° by increasing the growth rate. The surface roughness also decreased with growth rate, and rms values as low as 1.5 nm were achieved. On the other hand, too high a growth rate leads to increased roughness due to gas phase nucleation. The optical losses were closely correlated with surface roughness, and the best films had optical losses near 4.5 dB/cm at a wavelength of 632.8 nm.

The structures of ordered and disordered β-eucryptite have been determined from Rietveld analysis of powder synchrotron x-ray and neutron diffraction data over a temperature range of 20 to 873 K. On heating, both materials show an expansion within the (001) plane and a contraction along the c axis. However, the anisotropic character of the thermal behavior of ordered β-eucryptite is much more pronounced than that of the disordered compound; the linear expansion coefficients of the ordered and disordered phases are αa = 7.26 × 10−6 K−1; αc = −16.35 × 10−6 K−1, and αa = 5.98 × 10−6 K−1; αc = −3.82 × 10−6 K−1, respectively. The thermal behavior of β-eucryptite can be attributed to three interdependent processes that all cause an increase in a but a decrease in c with increasing temperature: (i) Si/Al tetrahedral deformation, (ii) Li positional disordering, and (iii) tetrahedral tilting. Because disordered β-eucryptite does not exhibit tetrahedral tilting, the absolute values of its axial thermal coefficients are smaller than those for the ordered sample. At low temperatures, both ordered and disordered β-eucryptite exhibit a continuous expansion parallel to the c axis with decreasing temperature, whereas a remains approximately unchanged. Our difference Fourier synthesis reveals localization of Li ions below room temperature, and we suggest that repulsion between Li and Al/Si inhibits contraction along the a axes.

The resistance of thin diamondlike carbon (DLC) films to anodic breakdown in aqueous electrolytes was investigated using voltammetry. The films were less than 0.5 μm thick and were deposited on type 301 stainless steel substrates using plasma-assisted chemical vapor deposition (PACVD) from either methane, acetylene, or 1,3-butadiene precursors with argon or hydrogen as diluent. A 10 nm thick polysilicon (PS) film was plasma-deposited prior to DLC film deposition to improve adhesion. The electrolytes used for corrosion testing were mixtures of 0.1 M NaCl and 0.1 M Na2SO4 and 0.1 M HCl and 0.1 M Na2SO4 in de-ionized water. The measured anodic current was lowest for the films deposited from butadiene and highest for those deposited from methane. The anodic current also increased with an increase in the hydrogen content in the feed gas mixture. In addition, the DLC films deposited at higher gas flow rates offered more resistance to anodic dissolution than those deposited at lower gas flow rates. Annealing improved the film performance. There appears to be an optimum DLC film thickness which provides the maximum resistance to anodic dissolution. In the best case, the DLC films reduced the anodic dissolution of bare stainless steel by about 4 orders of magnitude in the passive region. Atomic force microscopy studies of coated and uncoated stainless steel showed that the DLC films conformed to the steel substrate surface and had no effect on surface roughness, while DLC coated silicon substrates showed no evidence of pores.

The effects of solute drag on grain growth kinetics were studied in two-dimensional (2D) computer simulations by using a diffuse-interface field model. It is shown that, in the low velocity/low driving force regime, the velocity of a grain boundary motion departs from a linear relation with driving force (curvature) with solute drag. The nonlinear relation of migration velocity and driving force comes from the dependence of grain boundary energy and width on the curvature. The growth exponent m of power growth law for a polycrystalline system is affected by the segregation of solutes to grain boundaries. With the solute drag, the growth exponent m can take any value between 2 and 3, depending on the ratio of lattice diffusion to grain boundary mobility. The grain size and topological distributions are unaffected by solute drag, which are the same as those in a pure system.

Alkaline earth and rare-earth fluoride thin films were prepared on silica glass substrates by a sol-gel process using trifluoroacetic acid (TFA) as a fluorine source. Homogeneous solutions were obtained by stirring a mixture of alkaline earth or rare-earth metal acetates, TFA and H2O, dissolved in isopropanol. The solutions were spin-coated and heated at 300–800 °C. The fluoride thin films were obtained by heat treatment around 400 °C in air. The crystallization behavior, the surface morphology, and the optical properties of the films depended on the heating temperature as well as the chemical species of the metal ions.

A resonant Raman study of polyparaphenylene (PPP) prepared by the Kovacic and the Yamamoto methods and heat-treated at temperatures THT between 650 and 750°C has been performed using different laser excitation energies Elaser between 1.92 and 3.05 eV. For samples treated at low THT, the Raman spectra change with Elaser, and this behavior is ascribed to the coexistence of two forms of the PPP polymer (benzenoid and quinoid) as well as a disordered carbon material. For higher THT samples, only a dispersion of the position of the Raman band as a function of Elaser is observed, and this is explained as due to the carbonization of the original polymer. The transition temperature between these two regions of resonance behavior is lower for the Yamamoto-PPP samples than for the Kovacic-PPP samples.

We studied the influence of thermal annealing on the surface structure of (100) singlecrystal MgO substrates by atomic force microscopy (AFM). By annealing MgO substrates at various temperatures for 4 h in flowing oxygen, we showed that the surface reconstruction could be explained by considering surface diffusion, surface evaporation, and condensation. At an annealing temperature of 1473 K, a stepped structure was formed with screw dislocations acting as step sources. The influence of humidity on the surface morphology of MgO substrates was also studied by exposing them to a constant humidity of 40 and 80% for different times. After an exposure time of 1.5 h in 80% humidity, the substrate surface was already covered by reaction products. For the 40% humidity, the corresponding time is 10 h. The major reaction product was identified as Mg(OH)2 by x-ray diffraction.

Very thin (<,100 nm) amorphous carbon films were grown on silicon substrates by unfiltered and filtered direct carbon ion beams. In situ surface modification was performed using C- energies in the range of 300–500 eV prior to the growth of the film. By lowering the energy of the C− beam to 150 eV, an amorphous carbon film was continuously grown after the surface modification. High-resolution electron microscopy showed that the film/substrate interface was damaged by 400 and 500 eV C− beams. The carbon composition profile at the interface investigated by electron energy-loss spectroscopy illustrated that the 500 eV C− beam generated a 30 nm thick carbon/silicon mixing layer at the interface. The damage and mixing layers were not observed at 300 eV modification. Wear testing found that strong adhesion occurred in samples modified at 400 and 500 eV. However, at 300 eV, modified samples exhibited delamination failure, which indicated inferior adhesion of the films. Surface roughness evolution of 30, 60, and 90 nm thick films was investigated by atomic force microscopy. The film surface roughness decrease as a function of film thickness was much faster when the films were grown by the filtered C− beam.

The surface of carbon spheres was studied by using field-emission scanning electron microscopy and scanning tunneling microscopy paying particular attention to the effects of atmosphere during carbonization and of subsequent oxidation on shape and size of the entrance of micropores. Commercial spheres of glasslike carbon prepared by carbonization of phenol resin spheres in either N2 or CO2 atmosphere were subjected to the oxidation by immersing into nitric acid and then heating in air at 400 °C. The size distribution of pore entrance at nanoscopic scale was determined from scanning tunneling microscope images. Carbon spheres prepared in CO2 atmosphere had predominantly ultramicropores, but those prepared in N2 had a very low porosity. The behavior during the oxidation process in air was found to be quite different on these two carbon spheres; spheres carbonized in N2 were oxidized heterogeneously, but those in CO2 showed homogeneous oxidation, giving a high density of ultramicropores.

Diamondlike carbon (DLC) films have been prepared on radio-frequency (rf) biased substrates maintained at low temperature (∼60 °C) using electron cyclotron resonance CH4 –Ar plasma. The structures of the resultant films were characterized by Fourier transform infrared (FTIR), Raman, and ultraviolet/visible (UV/VIS) spectrometry. The studies revealed that the deposited structures were DLC films with sp3/sp2 bond hybridization, extremely high hardness (>3000 kgf/mm2), and high electrical resistivity (up to 1014 Ω cm). The DLC films deposited on colorless (transparent) polymer plastics were examined to determine visible light transparencies and optical bandgaps. The results indicate that electron cyclotron resonance (ECR) plasma processing with low negative rf bias, low deposition temperature, and suitable CH4/Ar gas composition can form optically visible light transparent and hard protective DLC films on polymer plastic surfaces.

Iron nitride layers were formed by a novel low-temperature gaseous nitriding process. Nitriding occurs at a temperature of 325 °C through NH3 decomposition at the surface of Ni (25 nm) coated Fe, followed by N transport through the Ni film into the underlying Fe, where nitride precipitation takes place. The role of Ni is to protect Fe from oxidation by gas impurities and to serve as a catalyst for NH3 decomposition. The precipitation behavior and the development of microstructure were studied by means of elastic recoil detection, cross-sectional transmission electron diffraction (XTEM), and positron annihilation (PA). From PA and XTEM no evidence was found for the occurrence of porosity during nitriding (an effect found at higher temperatures due to the decomposition of the nitrides into Fe and N2). XTEM showed that the original columnar α–Fe grains transform into smaller ′–Fe4N grains which subsequently transform into larger ε–Fe3−xN grains. This microstructural evolution of smaller ′ grains forming in the original columnar α–Fe structure occurs in one of two growth modes of the nitride in the Fe layer, i.e., throughout the entire depth range of the Fe layer, or preferentially at the Ni/Fe interface when an iron oxide layer is present at this interface.

The dehydrogenation of C60 · H18.7 was studied using thermogravimetric and powder x-ray diffraction analysis. C60 · H18.7 was found to be stable up to 430 °C in Ar at which point the release of hydrogen initiated the collapse of a fraction of fullerene molecules. X-ray diffraction analysis performed on C60 · H18.7 samples dehydrogenated at 454, 475, and 600 °C displayed an increasing volume fraction of amorphous material. The decomposition product comprises randomly oriented, single-layer graphite sheets. Evolved gas analysis using gas chromatograph (GC) mass spectroscopy confirmed the presence of both H2 and methane upon dehydrogenation. Attempts to improve reversibility or reduce hydrogenation/ dehydrogenation temperatures by addition of Ru and Pt catalysts were unsuccessful.

High-quality epitaxial or highly textured NiO thin films can be grown at temperatures of 400–750°C by low-pressure metalorganic chemical vapor deposition (MOCVD) on MgO, SrTiO3, C-cut sapphire, as well as on single crystal and highly textured Ni (200) metal substrates using Ni(dpm)2 (dpm – dipivaloylmethanate) as the volatile precursor and O2 or H2O as the oxidizer/protonolyzer. X-ray diffraction (XRD), scanning electron microscopy/energy dispersive detection (SEM/EDX), and atomic force microscopy (AFM) confirm that the O2-derived NiO films are smooth and that the quality of the epitaxy can be improved by decreasing the growth temperature and/or the precursor flow rate. However, low growth temperatures (400–500 °C) lead to rougher surfaces and carbon contamination. The H2O-derived NiO films, which can be obtained only at relatively high temperatures (650–750 °C), exhibit slightly broader ω scan full width half-maximum (FWHM) values and rougher surfaces but no carbon contamination. Using H2O as the oxidizer/protonolyzer, smooth and highly textured NiO (111) films can be grown on easily oxidized single crystal and highly textured Ni (200) metal substrates, which is impossible when O2 is the oxidizer. The textural quality of these films depends on both the quality of the metal substrates and the gaseous precursor flow rate.