In this work, we coated molybdenum oxide on submicrospheres of amorphous alumina and crystalline alumina, using a sonochemical method. The sonication products were characterized by transmission electron microscopy, x-ray diffraction, differential scanning calorimetry, thermogravimetric analysis, ultraviolet–visible, Raman, Fourier transform infrared spectroscopy, and surface area (Brunauer–Emmett–Teller) measurements. We found that on crystalline alumina, the blue oxide of molybdenum was formed, while on amorphous alumina, the presence of an isolated tetrahedrally coordinated Mo oxide species was confirmed. It seems that the amount and types of surface hydroxyl groups on the surface of alumina play an important role in both the oxidation of Mo and the relative content of Mo species in the sonication product. The surface area of the alumina-coated Mo oxide is about 11 times larger than that of the bare alumina. An explanation for this change is offered.

Nanocrystalline zirconia sols with a metastable cubic phase were synthesized from diglycol-modified zirconium n-propoxide via a novel method, alcohol thermal synthesis. The chemical bonding of diglycol with zirconium was found to be important in obtaining stable nanocrystalline zirconia sols. Sols produced in this way were translucent with the primary particles of 4-nm crystallites, and the corresponding gel was shown to be mesoporous with a pore size from 2.5 to 3.8 nm and Brunauer—Emmett—Teller surface areas between 130 and 266 m2 g−1. This indicates that alcohol thermal synthesis shares the advantages of both the sol-gel process and hydrothermal synthesis.

An ongoing goal of multilayer capacitor research is to lower the firing temperature of the dielectric. This paper gives a detailed study of sintering BaTiO3 with LiF flux, which lowers the firing temperature through liquid-phase sintering. A detailed set of experiments is discussed concerning microstructural evolution and corresponding dielectric properties under a number of processing variables, including amount of LiF, sintering temperature, and particle size. Different scales of chemical inhomogeneity were observed in this system, which reflect two underlying mechanisms: solution reprecipitation with limited grain growth at low temperatures, which resulted in distinct core–shell structures, and flux volatility, which gave rise to microscopic chemical inhomogeneity at higher sintering temperatures.

Composite ceramics with compositions within the ZnO–NiO–TiO2, ZnO–MgO, and ZnO–Ln2O3 (Ln = Nd, Sm) systems were found to exhibit an anomalous positive temperature coefficient of electrical resistivity (PTCR) effect. The investigations revealed, that in all cases when the PTCR effect was identified, the composite ceramics were found to be composed of phases with different electrical resistivities and linear thermal expansion coefficients. Thermal mismatch between the phases in the composites leads to a disconnection of the grains of the low resistivity constituent phase on account of the high thermal expansion of the other high resistivity constituent phase, resulting in a PTCR effect.

We performed ab initio Hartree–Fock molecular orbital calculations of solute elements in amorphous silicon nitride (Si–N) ceramics. To investigate effects of solute elements, X, such as boron, carbon, aluminum, silicon, and phosphorus, on stabilization of the Si–N network, we used model clusters representing local atomic structures in the Si–N network, and the solute elements were substituted for nitrogen. Bonding characteristics around the solute elements were analyzed, and bond energies of Si–X were also calculated using model clusters. It was found that, among these solute elements in amorphous Si–N, the Si–C bond is able to make the Si–N network more stable due to its high covalency.

The kinetics of phase transformation of nanocrystalline anatase samples was studied using x-ray diffraction at temperatures ranging from 600 to 1150 °C. Kinetic data were analyzed with an interface nucleation model and a newly proposed kinetic model for combined interface and surface nucleation. Results revealed that the activation energy of nucleation is size dependent. In anatase samples with denser particle packing, rutile nucleates primarily at interfaces between contacting anatase particles. In anatase samples with less dense particle packing, rutile nucleates at both interfaces and free surfaces of anatase particles. The predominant nucleation mode may change from interface nucleation at low temperatures to surface nucleation at intermediate temperatures and to bulk nucleation at very high temperatures. Alumina particles dispersed among the anatase particles can effectively reduce the probability of interface nucleation at all temperatures.

A model that finds the maximum permissible heating rate for pyrolysis of ceramic moldings is extended to produce multi-segment temperature–time profiles to minimize the binder removal time. The degradation of the polymer and the diffusion of degradation products in solution to the free surface in a cylinder containing 50 vol% alumina and polyalphamethylstyrene is considered. The theory has previously been validated experimentally for fixed heating rates for cylindrical and flat plate geometries and for overpressure debinding. The extended model, presented here, calculates the vapor pressure of monomer over solution and modifies the heating rate to keep this just below ambient pressure. In this way, the temperature follows the maximum allowable rate at each stage to prevent boiling and hence the incidence of defects.

For both Co and Ni, a series of electrodeposited films of varying thickness (2–10 nm) was grown under otherwise identical conditions using potentiostatic control. The substrates were pieces of Si wafer onto which a Cu basal layer had been thermally evaporated. Contact mode atomic force microscopy was used to measure both the root-mean-square peak height (nm) and the areal peak density (μm−2) of each film. Root-mean-square (rms) peak heights for Co initially increase with film thickness and then plateau at a layer thickness of 3 nm. For Ni, the rms peak heights increase almost linearly for layer thicknesses less than 11 nm, reaching a value of 6 nm. Peak density shows the opposite trend, decreasing with layer thickness before reaching an approximately constant value for both metals at a film thickness of 4 nm. The atomic force microscopy data indicate that Ni and Co have different deposition mechanisms. A Co film initially nucleates rapidly; then the nucleation phase is followed by multinuclear, multilayer growth. Ni deposits also have initial rapid nucleation, but the dominant growth mode is primarily vertical, with increasing peak heights but no change in peak density. Increased peak density is linearly correlated with decreased peak height for the thinnest films in both systems.

The evolution of stress in a Ni–Hf diffusion couple during solid-state amorphization reaction has been monitored by substrate curvature measurements and x-ray diffraction. The latter technique allowed an independent determination of the contribution of changes in stress-free lattice parameter to the stress in the crystalline layers. The results indicate that the amorphous phase forms under a large tensile stress, which relaxes as the reaction progresses. This stress in the amorphous phase is consistent with the volume change associated with the reaction. Stresses in the crystalline, elemental phases are considerably smaller and not affected by the reaction. Low-temperature Ni ion irradiation increases the tensile stress in the diffusion couple. The large observed stress variations are not accompanied by variations in the effective interdiffusion coefficient.

The fabrication process of an Al thin-film optical polarizer on LiNbO3 waveguides after CF4 plasma dry etching of a previously deposited SiO2 buffer layer was investigated. The problem in this process is a precipitation of compounds containing C, O, F, and Li on the etched LiNbO3 surface and a chemical deterioration of the Al caused by a reaction with these precipitates. Most notably, the growth of amorphous phase in addition to the crystalline Al metal grains and a partial oxidization of Al were found at the interface using transmission electron microscopy and x-ray photoelectron spectroscopy.

Micro-Raman spectroscopy was used to study the formation of BaFe12O19 (BaM) powders derived from water-in-oil microemulsion at different calcination temperatures. With increase in the calcination temperature, the Raman spectra of the BaM powders become narrower and stronger without apparent frequency shifts of the Raman bands. The calcination temperature dependence of the Raman spectra and the magnetic properties of the BaM powders result from the crystallization rather than size effect. Our results show that there is a strong correlation between the crystallinity and the magnetic properties, which could be explained in terms of the crystallization effect on the superexchange interaction between ferric ions. The γ–Fe2O3 phase occurred in the BaM precursor and the powder calcined at 500 °C. The α–Fe2O3 phase was developed in the powders calcined at 500, 600, and 700 °C, which was not detected by x-ray diffraction. With increasing calcination temperature, the γ–Fe2O3 phase can either react with oxide containing barium to form the BaM phase or transform to the α–Fe2O3 phase. The amount of α–Fe2O3 decreases due to reaction with BaCO3 to form BaM phase at higher calcination temperature.

The properties of thin Y2O3 films grown using an in situ ultraviolet (UV)-assisted pulsed laser deposition (PLD) technique were studied. With respect to Y2O3 films grown by conventional PLD under similar conditions but without UV illumination, the UVPLD-grown films exhibited better structural and optical properties, especially for lower substrate temperatures, from 340 to 400 °C. These layers were highly crystalline and textured along the (111) direction, and their refractive index values were similar to those of reference Y2O3 layers. They also exhibited a better stoichiometry and contained less physisorbed oxygen than the conventional PLD-grown layers.

In this paper we evaluate the in-depth homogeneity of GaN epilayers and the influence of electric field present in strained GaN/AlGaN heterostructures and quantum wells on the yellow and “edge” emission in GaN and AlGaN. Our depth-profiling cathodoluminescence measurements show an increased accumulation of defects at the interface. Inhomogeneities in the doping level are reflected by the enhancement of the yellow emission in the interface region. The piezoelectric effect is found to strongly reduce the emission from the strained AlGaN quantum-well barriers. We also show that Ga droplets, commonly found on surfaces of samples grown in Ga-rich conditions, screen the internal electric field in a structure and thus result in a local enhancement of the edge emission intensity.

Well-aligned carbon nitride nanotubes were prepared with a porous alumina membrane as a template when using electron cyclotron resonance (ECR) plasma in a mixture of C2H2 and N2 as the precursor with an applied negative bias to the graphite sample holder. The hollow structure and good alignment of the nanotubes were verified by field-emission scanning electron microscopy. Carbon nitride nanotubes were transparent when viewed by transmission electron microscopy, which showed that the nanotubes were hollow with a diameter of about 250 nm and a length of about 50–80 μm. The amorphous nature of the nanotubes was confirmed by the absence of crystalline phases arising from selected-area diffraction patterns. Both Auger electron microscopy and x-ray photoelectron spectroscopy spectra indicated that these nanotubes are composed of nitrogen and carbon. The total N/C ratio is 0.72, which is considerably higher than other forms of carbon nitrides. No free-carbon phase was observed in the amorphous carbon nitride nanotubes. The absorption bands between 1250 and 1750 cm−1 in Fourier transform infrared spectroscopy provided direct evidence for nitrogen atoms, effectively incorporated within the amorphous carbon network. Such growth of well-aligned carbon nitride nanotubes can be controlled by tuning the ECR plasma conditions and the applied negative voltage to the alumina template.

Atomic positional disorder of a single-phase natural carbonate fluorapatite (francolite) is revealed from analysis of the atomic displacement parameters (ADPs) refined from neutron powder diffraction data as a function of temperature and carbonate content. The ADPs of the francolite show a strong disturbance at the P, O3, and F sites. When it is heat treated to partially or completely remove the carbonate, the ADPs as well as the other structural parameters resemble those of a fluorapatite (Harding pegmatite) that was measured under the same conditions. The various structural changes are consistent with a substitution mechanism whereby the planar carbonate group replaces a phosphate group and lies on the mirror plane of the apatite structure.

High-field and high-pressure behavior of microwave-prepared xCuO:(45−x) PbO: 55V2O5 (x = 0 to 20) glasses were investigated for the first time. It was found that the addition of CuO significantly alters the nonlinear I–V characteristics of these glasses; while the glasses with x = 10 exhibit a current-controlled negative resistance behavior associated with a memory type transition, glasses with x = 15 show a threshold-type behavior. Remarkable differences were also noticed in the high-pressure electrical resistivity behavior between the low- and high-CuO-containing glasses. Corroborative thermal, electrical, microscopic, and spectroscopic measurements were carried out to understand the structure–property relations. A structural model was proposed, which is based on the chemical nature of the constituents present in the glasses. The model accounts well for the various observed properties of these glasses.

In this paper we report the fabrication of organic/inorganic film for optical secondharmonic generation by a sol-gel method for the purpose of the improvement of thermal stability and chemical resistance. The film contains the azo dye Disperse Orange 3 protected by poly(vinylpyrrolidone) in a reticulation of silica gel, whose structure was developed by the spinodal decomposition and the gel-forming process as temperature increased. Corona-poling at elevated temperature could successively induce the optical second-harmonic nonlinearities. The dependence of temperature and field strength on the second-harmonic intensity was also investigated.

Thin films of polythiophene, a kind of polyheterocyclic compound with hydrogen function groups, were deposited by KrF excimer laser ablation of a compressed solid target in a vacuum chamber. The laser pulse fluence was approximately selected at 2 J/cm2 with a pulse duration of 25 ns. The structural, topographic, and electronic properties of the deposited thin films were analyzed by atomic force microscope, x-ray diffraction, and Raman and infrared spectroscopy measurements. Deposited thin films were observed to have good crystal properties and to be composed of crystalline cubes with a uniform size of 0.1 μm. The electronic structure of the deposited thin films should be different from the target materials, resulting from the laser irradiation effects. The influence of the deposition temperature on the structural and electronic properties of the deposited thin films was studied.

Ni(OH)2 nanoparticles modified with di-n-hexadecyldithiophosphate (DDP) were prepared by a chemical surface modification method. The structure of the nanocluster was investigated using infrared spectroscopy, x-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy, and 31P nuclear magnetic resonance spectroscopy. The thermal stability of DDP coating on the Ni(OH)2 nanoparticles was compared to that of pyridinium di-n-hexadecyldithiophosphate (PyDDP) using thermogravimetric analysis. It was found that coated Ni(OH)2 nanoparticles had an average diameter of about 5 nm. Surface modification with DDP prevented water adsorption and effectively improved the dispersive capacity and antioxidative stability of Ni(OH)2 nanoparticles. The thermal stability of DDP coatings on the surface of nano-Ni(OH)2 particles was higher than that of PyDDP coatings because of the chemical interaction between PyDDP and Ni(OH)2 during the coating process.

In this article we report the influence of surface oxides and relative humidity on the nanomechanical response of hydrophobic and hydrophilic Si surfaces. Depth-sensing nanoindentation combined with force modulation enabled measurement of surface forces, surface energy, and interaction stiffness prior to contact. Several regimes of contact were investigated: pre-contact, apparent contact, elastic contact, and elasto-plastic contact. Both humidity and surface preparation influenced the surface mechanical properties in the pre- and apparent-contact regimes. Meniscus formation was observed for both hydrophobic and hydrophilic surfaces at high humidity. Influence of humidity was much less pronounced on hydrophobic surfaces and was fully reversible. In the elastic and elasto-plastic regimes, the mechanical response was dependent on oxide layer thickness. Irreversibility at small loads (300 nN) was due to the deformation of the surface oxide. Above 1 μN, the deformation was elastic until the mean contact pressure reached 11 GPa, whereby Si underwent a pressure-induced phase transformation resulting in oxide layer pop-in and breakthrough. The critical load required for pop-in was dependent on oxide thickness and tip radius. For thicker oxide layers, substrate influence was reduced and plastic deformation occurred within the oxide film itself without pop-in. Elastic modulus and hardness of both the oxide layer and Si substrate were measured quantitatively for depths <5 nm.