Carbon nanocage structures with Ge and SiC nanoparticles were synthesized by direct current and radio frequency (dc-rf) hybrid arc discharge of C, Ge, and Si elements. High-resolution images showed the formation of Ge and SiC nanoparticles and nanowires encapsulated in carbon nanocapsules and nanotubes. The growth direction of the Ge nanowires was found to be 〈111〉 of Ge, and a structure model for Ge/C interface was proposed. The present work indicates that the various carbon nanostructures with semiconductor nanoparticles and nanowires can be synthesized by the dc-rf hybrid arc-discharge method.

The polymerization mechanism of a modified Pechini process was investigated by 87Sr nuclear magnetic resonance spectroscopy for the mixed solution of strontium nitrate, citric acid, and ethylene glycol. The C-ratio (the ratio of citric acid to metal ions in the polymer complex) is suggested to have a strong influence on the quality of the derived film. An analysis of the chemical shift variation, as a function of C-ratio, indicates the presence in the solution of two species: solvated strontium ions and strontium ions bound to the polymer complex, with a stoichiometry of 1:7. A polymeric precursor model based on this stoichiometry is proposed. Through a relaxation rate study of the strontium sites, it was found that the polymerization mechanism is predominantly bimolecular within the concentration region being studied. The equilibrium rate constant for the polymerization was calculated to be 104 s−1. A kinetic study of the fast cation exchange between the two identified strontium sites indicates that the inhomogeneity of the polymeric network leads to film cracking during pyrolysis.

A key difficulty in isothermal, isobaric chemical vapor infiltration is the long processing times that are typically required. With this in mind, it was important to minimize infiltration times. This optimization problem was addressed here, using a relatively simple model for dilute gases. The results provided useful asymptotic expressions for the minimum time and corresponding conditions. These approximations were quantitatively accurate for most cases of interest, where relatively uniform infiltration was required. They also provided useful quantitative insight in cases where less uniformity was required. The effects of homogeneous nucleation were also investigated. This does not effect the governing equations for infiltration of a porous body; however, powder formation can restrict the range of permissible infiltration conditions. This was analyzed for the case of carbon infiltration from methane.

Researchers may use several different instruments to determine chemical and mechanical properties of materials with nanometer-scale vertical, and occasionally, lateral, resolution. Three such instruments are the depth-sensing indenter, the atomic force microscope, and the surface forces apparatus. Until now, these methods were individually modeled, and an analysis of their mechanical response was never done in a general way. In this article, we show that these instruments can be treated as a class—a class that we call mechanical properties nanoprobes (MPNs)—that can be described by a single universal linear model. Using this model, we solved both the quasistatic and dynamic response as a function of excitation frequency and complex compliance using an electrical analog for the mechanical system. Earlier work did not find correct solutions for the amplitude and phase, did not examine the influence of finite stiffness in the head of the MPN, and overlooked the difference between a partial and full derivative and its influence on quasistatically acquired force curves. The equations here will allow scientists to correctly interpret their results concerning elastic and anelastic materials response, especially for low-modulus, high-damping samples such as polymers.

On-line monitoring of the dissolved impurities in molten metals is important for better process control during alloying and metal refining operations. Disposable-type oxygen sensors are commercially available and are used in the iron and steel industry worldwide. However, there is a need for developing low-cost, reliable, long-life oxygen sensors for continuous monitoring of dissolved oxygen in molten metals. In this paper we present the results of the physical and electrical characterization of the solid electrolyte material ZrO2 (8 mol%Y2O3). The experimental results of the application of long-life solid-state electrochemical sensors designed using yttria-stabilized zirconia solid electrolyte for the measurement of oxygen potential in molten tin between 823 to 1273 K and standard Gibbs energy of formation of SnO2 from its elements are also reported.

Fe(III)-doped TiO2 (anatase) was prepared by the oxidation of FexTiS2. Two calcination methods were used to oxidize FexTiS2. In the first, sulfide was calcined in air at a given temperature for 2 h. In the second method, the sulfide was heated in air at a finite heating rate (2.5 K/min) and then held at a constant temperature for 2 h. Fe(III) ions completely dissolved into TiO2 (anatase), forming Fe(III)-doped TiO2 (anatase), in the composition range of 0 ⩽ Fe/Ti ⩽ 0.3 (mole ratio). The properties of the obtained oxide depended on the oxidation method of FexTiS2. The electronic property and the valence stage of the Fe(III)-doped TiO2 (anatase) were examined. The activation energy of electronic conduction decreased with an increase of the doped amount of Fe(III) ions. The x-ray photoelectron spectroscopy result showed that the electron density on the Ti ion in the Fe(III)-doped TiO2 (anatase) was decreased by the Fe(III) doping.

Dielectric ceramics in the BaO–Sm2O3–TiO2–Ta2O5 quaternary system were prepared and characterized for five typical compositions: BaSm5Ti7Ta3O30, Ba2Sm4Ti6Ta4O30, Ba3Sm3Ti5Ta5O30, Ba4Sm2Ti4Ta6O30, and Ba5SmTi3Ta7O30. The latter three compositions tended to form the tungsten–bronze phase, and the ceramics based on these compositions had a high dielectric constant (134–175) and a low dielectric loss (on the order of 10−3) but a larger temperature coefficient of the dielectric constant. Meanwhile, the former two compositions generally had a more complex phase constitution, containing the tungsten–bronze phase combined with some unknown phase, and a relatively small temperature coefficient of the dielectric constant in the temperature range of 20 to 85 °C could be achieved in these two compositions.

Changes in the structure of Ti5Si3 were measured by x-ray and neutron diffraction as carbon, nitrogen, or oxygen atoms were systematically incorporated into the lattice. Additionally, the lattice parameters and variable atomic positions of pure Ti5Si3 were determined to be a = 7.460 Å, c = 5.152 Å, xTi = 0.2509, and xSi = 0.6072. The measured trends in lattice parameters as carbon, nitrogen, or oxygen atoms were added to Ti5Si3 showed that most of the previous studies on supposedly pure Ti5Si3 were actually contaminated by these pervasive light elements. Also, oxygen and carbon additions were shown to strongly draw in the surrounding titanium atoms—evidence for bonding between these atoms. The bonding changes that occurred on addition of carbon, nitrogen, or oxygen acted to decrease the measured anisotropic properties of Ti5Si3, such as thermal expansion.

Measurements of fatigue failure strength of laser-cracked fused silica in air at room temperature for different numbers of laser shots and laser fluences are presented. The failure-strength variability is found to be due mainly to the spectrum of crack depths. Agreement with theory suggests the incorporation of a residual term into the failure–strength equation. Due to its sign, the residual stress is of mouth-opening displacement nature at the crack. Analysis of the residual stress data shows a linear proportionality with crack depth, whereas the failure–strength is inversely proportional to the square root of the crack depth.

The influence of operating parameters on the morphology of particles prepared by spray pyrolysis was investigated using a temperature-graded laminar flow aerosol reactor. Experimentally, zirconia particles were prepared by spray pyrolysis using an aqueous solution of zirconyl hydroxide chloride. Hollow particles were formed if the reactor temperature was high, the temperature gradient was too large, the flow rate of carrier gas was high, and the initial solute concentration was low. A numerical simulation of the pyrolysis process was developed using a combination of two previous models. The simulation results compared well with the experimental results.

The dielectric properties of Mn-doped Pb(Fe2/3W1/3)1−xMnxO3 (x = 0, 0.001, 0.003, and 0.005) in the temperature range 200–600 K were investigated. Two sets of dielectric peaks, located at 200–350 K and 350–600 K, were observed. The intensity of the dielectric permittivity and loss factor peaks for both relaxations decreased with the increase in the Mn content and no peak occurred when x = 0.005. Nonlinear current–voltage (I–V) behavior was observed in the samples containing less than 0.005Mn. The activation energy values for the relaxations at 200–350 K and at 350–600 K were around 0.42 and 0.56 eV, respectively. The direct current conduction activation energies were around 0.41 eV. Nitrogen annealing eliminated the relaxation peaks at 200–350 K while oxygen annealing enhanced them. Both annealings eliminated the dielectric peaks at 350–600 K. The nonlinear I–V characteristic tended to vanish either after the oxygen or the nitrogen annealing treatments. Relaxation mechanisms are proposed and discussed. It is suggested that the relaxation at 200–350 K is related to electron hole while the relaxation at 350–600 K is attributed to microstructure-dependent space-charge polarization.

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.

The sol-gel method was used to prepare nickel oxide–silica and nickel–silica nanocomposite materials and the corresponding silica matrices. Different drying conditions were used to obtain aerogel and xerogel materials. The samples were characterized by thermal analysis, x-ray diffraction, N2–physisorption, transmission electron microscopy techniques, and infrared spectroscopy. Aerogel samples had a much higher surface area than the xerogel samples; moreover, different supercritical drying conditions gave rise to a different porous structure, which influenced the size and distribution of the nanoparticles in the matrix.

The structural surrounding of Zn in inactive nuclear glasses was determined using extended x-ray absorption fine structure spectroscopy. Zn was found in tetrahedralcoordination ([4]Zn) with [4]Zn–O distances of 1.95 Å. ZnO4 tetrahedra shared corners with SiO4 tetrahedra [d(Zn–Si) around 3.20 Å]. The oxygens of the Zn–O–Si bonds were charge compensated by Na+ and, to a minor extent, by Cs+. The influence of [4]Zn on the formation of charge-compensating cations at the expense of network modifiers may explain the stabilizing effect of Zn in these glasses.

The sol-gel technique was applied to the preparation of Eu3+ ion–doped films, which showed persistent spectral hole burning. A gel film of ∼3500-nm thickness was prepared by dip-coating of the solution synthesized from Si(OC2H5)4, CH3Si(OC2H5)3, Eu(NO3)3 · 6H2O, and hydropropyl-cellulose. The spectral hole was burned in the 7F0 → 5D0 transition band of the Eu3+ ions at 7 K, the depth of which was 24% of the total fluorescence intensity and decreased as the heat-treatment temperature of film increased. It was found that the hole was thermally filled and erased above ∼170 K; the temperature at which the hole was erased was lower for the film heated at high temperature.

Thin films of ZrO2 were deposited from aqueous solution on Si(100) substrates precovered by functionalized alkyltrichlorosilane self-assembled monolayers (SAMs). The interface structure, thermal stability, and densification of these films in the temperature range from room temperature to 750 °C in vacuum were measured using in situ x-ray reflectivity. The growth rate is a nonlinear function of time in solution, with a pronounced nonuniformity during the first 30 min. The as-deposited films exhibit about 3-nm roughness and a density below that of bulk ZrO2. Measurements in vacuum reveal decreasing film thickness, increasing film density, and decreasing roughness upon annealing up to 750 °C. The densification saturates at the highest measured temperatures, presumably following evaporation of residual contaminants from the aqueous synthesis procedure. Above 200 °C the SAM/ZrO2 interface began to deteriorate, possibly due to interdiffusion. The ZrO2 film structure obtained at the highest annealing temperatures persisted upon cooling to room temperature, and there was no visible evidence of stress-induced microstructural changes, such as peeling or cracking.

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.

Barium hexaferrite is a well-known ceramic permanent magnet and due to its high coercivity, remanence, and large uniaxial magnetic anisotropy, finds applications that compete with metallic magnets. Even though a number of the high-temperature properties of barium hexaferrite have been studied extensively, its anisotropic thermal expansion has not been reported so far. Dynamic high-temperature x-ray diffraction (HT-XRD) is one powerful method to obtain thermal expansion data for anisotropic polycrystalline materials in a very short period of time. In this paper the anisotropic nature of the thermal expansion coefficient of the barium hexaferrite phase is reported with the use of a dynamic HT-XRD setup. The thermal expansion coefficient (linear fit) was determined to be 8.36 × 10−6 K−1 along the a–b plane to 1.4 × 10−5 K−1 along the c axis between the temperature range of 293 to 1343 K.

The crystallographic thermal expansion coefficients of Ti5Si3 from 20 to 1000 °C as a function of B, C, N, O, or Ge content were measured by high-temperature x-ray diffraction using synchrotron sources at Cornell University (Cornell High Energy Synchrotron Source; CHESS) and Argonne National Laboratory (Advanced Photon Source; APS). Whereas the ratio of the thermal expansion coefficients along the c and a axes was approximately 3 for pure Ti5Si3, this ratio decreased to about 2 when B, C, or N atoms were added. Additions of O and Ge were less efficient at reducing this thermal expansion anisotropy. The extent by which the thermal expansion was changed when B, C, N, or O atoms were added to Ti5Si3 correlated with their expected effect on bonding in Ti5Si3.

The thermal diffusivities (D) of porous α–Al2O3 specimens prepared from nano-size γ–Al2O3 powder and from conventional submicrometer-size alumina powders were measured at room temperature, and the thermal conductivity (κ) was calculated from D. Plots of κ versus the volume fraction of porosity (P) showed that the data from both sets of samples followed similar linear curves. Similarly, data of Vickers hardness versus P obtained from the same specimens also followed a single linear curve. The good correlation of thermal diffusivity with P suggests that grain boundaries have a lesser effect on thermal transport than porosity.