In this paper we report a novel process for the production of ultralight cellular ceramics. The foams are generated by the heat treatment of crystals of the aluminum chloride isopropyl ether complex [AlCl3(Pri2O)]. The crystals, which are the only foam precursor, are obtained from concentrated solutions of AlCl3, Pri2O, and CH2Cl2. The foams consist of an arrangement of closed cells, 50–300 μm in diameter, having cell walls approximately 1–2 μm thick. An exceptionally high porosity is obtained ranging from 94 to 99%, and the cellular structure is retained during heating at 1500 °C. The foaming mechanism involves two consecutive nonhydrolytic sol-gel chemical reactions and physical processes including crystal dissociation, solvation, phase separation, and foaming. While other foaming mechanisms cited in the literature utilize one or more of the processes above, no analog mechanism exists in the organic, ceramic, or metal foam production processes. The effectiveness of the process originates from an initial precursor which contains all the necessary foaming components in such a way that the application of mild heating accelerates its transformation to a solid, dry, ultralight foamed material.

We report here a study on the electrical and magnetic properties of La1−xBaxCoO3 in the re-entrant semiconducting region (x = 0.20). We find that in this material: (i) the insulator-metal-insulator sequence is unstable and evolves toward a purely semiconducting behavior; the initial r versus T curve can be reinstated upon appropriate annealing treatments; (ii) there are relaxation effects that can be seen by changing the polarity of the electrodes; (iii) there is a negative magnetoresistance Δρ/ρ ∼ 2–3%, for a field as low as 9 kOe, especially at the metal-insulating transition temperatures; and (iv) there are important fluctuations in the electrical resistivity. Taking into account these experimental observations, we can interpret this material as an inhomogeneous system where two thermodynamic phases, one semiconducting and the other metallic and ferromagnetic, coexist, although they are crystallographically indistinguishable.

Nanocrystalline powders of various compositions in the Al2O3–MgO binary system were synthesized using a novel “auto ignition” process. The respective nitrates were used as starting materials and urea as fuel. Thermodynamic calculations of the adiabatic temperatures were performed for various compositions from Al2O3-rich to the MgO-rich side of the phase diagram. The combustion temperatures of the different compositions were also determined experimentally. The as-synthesized powders were characterized by x-ray diffraction (XRD) and transmission electron microscopy (TEM). As a result of processing, spinel, alumina, magnesia, and solid solutions/ nanocomposites thereof formed. Grain sizes and the lattice parameter were calculated based on XRD results. Where appropriate, the lattice parameter versus the composition of these solid solutions satisfied Vegard's law. Spinel grains were in the 13–20 nm range, alumina grains were 30–40 nm, and MgO grains were 2–28 nm. The grain sizes calculated from XRD results were in good agreement with the TEM results.

Ultrahigh molecular weight polyethylene, an important biomaterial for orthopedic implants, was irradiated with 2.6- and 3-MeV H+ ions at low doses from 5.7 × 1011 to 2.3 × 1014 ions/cm2. Fourier transform infrared spectroscopy showed that irradiation resulted in increased free radicals, carbon double bonds, and increased methyl and vinyl end groups. The free radicals resulted in poor polymer oxidative stability, as measured by increased carbonyl concentration. Hydrogen annealing after ion irradiation reacted with the free radicals generated during proton irradiation resulted in a 40–50% decrease in infrared absorption associated with carbonyl and prevented further oxidation.

The mechanics for calculating the quantitative driving force of indentation-induced delamination of thin-film multilayers is presented. The solution is based on the mechanics developed by Marshall and Evans [D.B. Marshall and A.G. Evans, J. Appl. Phys. 56, 2632 (1984).] and extended to the general case of a multilayer by use of standard bending and thin-plate analyses. Presented and discussed are the specific solutions for the bilayer case that show that in the limit of zero thickness of either layer, the solution converges to the single-layer case. In the range of finite thickness, the presence of the superlayer increases the driving force relative to that possible for the original film alone and can be optimized to the experimental situation by proper choice of thickness, elastic constants, and residual stress. The companion paper “Quantitative adhesion measures of multilayer films: Part II. Indentation of W/Cu, W/W, Cr/W” discusses experimental results with copper, tungsten, and chromium thin films.

Iron oxide films were prepared by the polymer precursor method with alkaline metal (Li, Na, and K) ion doping. Alkaline metal ions were used to regulate the thermal decomposition process of the cation-citrate complex, that is, the precursor of the film. The spinel iron oxide films were obtained by firing the precursor with the alkaline ion doping [Na/Fe (atomic ratio) ≧ 0.2 and K/Fe (atomic ratio) ≧ 0.2] at 773 K for 5 min in air. The formation mechanism of the spinel iron oxide films was investigated by differential thermal analysis (DTA) and x-ray photoelectron spectroscopy (XPS) measurements. Formation of the carbon-iron oxide complex was observed, and this reduction atmosphere induced the formation of the spinel iron oxide films. This method gave the spinel iron oxide films of which nanostructures are controlled.

Tobermorite was synthesized successfully from waste incineration fly ash by hydrothermal treatment in the presence of sodium hydroxide solution. The tobermorite synthesis was examined as a function of reaction temperature, time, and NaOH concentration. The formation of tobermorite was identified in all of the fly ash treated with NaOH at 180 °C, followed by the minor generations of sodalite and cancrinite phases with increasing NaOH concentration and extending reaction time. The NaOH-treated fly ash revealed the uptake behaviors for Cs+ and NH4+, whereas the fly ash untreated with NaOH solution did not show that. The uptake amounts of resulting products were also determined: 0.40 mmol/g for Cs+ and 0.35 mmol/g for NH4+ in the fly ash treated with 2.0 M NaOH at 180 °C for 20 h.

The interdiffusion in Ni80Fe20/Mo magnetic multilayers with a repeat length of 3.4 nm has been investigated using x-ray diffraction (XRD) technology. The multilayers have been fabricated by using a magnetron sputtering system. The decay with annealing time in the intensity of the first-order x-ray satellite peak arising from the composition modulation was used to determine the effective interdiffusion coefficient Dλ. As the annealing temperature is below 483 K, the interdiffusion is found to be relatively slow (Dλ < 8.88 × 10−25 m2/s). This result suggests that the Ni80Fe20/Mo multilayers have a strong resistance to the atomic interdiffusion between sublayers. The diffusivities over the temperature range 343–683 K have an Arrhenius-type temperature dependence with a pre-exponential factor D0 = (4.02 ± 1.21) × 10−22 m2/s and an activation enthalpy of about 0.26 ± 0.08 eV. The much lower activation enthalpy is attributed to the coherence strains existing in the multilayers.

Thin films of La0.6Ca0.4MnO3 (LCMO) have been produced on (001) oriented LaAlO3 (LAO) and yttrium-stabilized zirconia (YSZ) substrates by liquid-delivery metalorganic chemical vapor deposition (LD-MOCVD). X-ray diffraction (XRD) analyses showed that the films were epitaxially grown on LAO substrates and were monocrystalline at a thickness of less than 500 Å. At a thickness of greater than 500 Å, the films became polycrystalline but maintained their high texture (preferred crystalline orientation). Films grown on YSZ were always polycrystalline but were also highly oriented. Regardless of the substrate, the 1500 Å thick polycrystalline films exhibited substantially significant magnetoresistance ratios even above room temperature.

Sputtered copper and tungsten thin films both with and without tungsten and chromium superlayers were tested by using nanoindentation probing to initiate and drive delamination. The adhesion energies of the films were calculated from the induced delaminations using the analysis presented in “Quantitative adhesion measures of multilayer films: Part I. Indentation mechanics.” Copper films ranging in thickness from 150 to 1500 nm in the as-sputtered condition had measured adhesion energies ranging from 0.2 to 2 J/m2, commensurate with the thermodynamic work of adhesion. Tungsten films ranging in thickness from 500 to 1000 nm in the as-sputtered condition had measured adhesion energies ranging from 5 to 15 J/m2. The superlayer was shown to induce radial cracking when under residual tension, resulting in underestimation of the adhesion energy when the film was well adhered. Under conditions of weak adherence or residual compression, the superlayer provided an excellent means to induce a delamination and allowed an accurate and reasonably precise quantitative measure of thin film adhesion.

Spark plasma sintering was used to consolidate the crystallized Nd–Fe–B alloy powders. It was found that a higher sintering temperature can improve the consolidation significantly, whereas it deteriorates the magnetic properties drastically due to the appearance of a large amount of α–Fe phase and the grain growth. Sintering at lower temperature can preserve the magnetic properties better, while the powders cannot be consolidated into a fully dense compact, even under the higher pressure of 75 MPa. Finer starting powder particles show similar behavior.

Crack-free and transparent Sr2KNb5O15 (SKN) thin films have been synthesized by the chemical solution deposition method. A homogeneous and stable precursor solution was prepared via controlling the reaction of metal alkoxides. SKN precursor was found to be the complex alkoxide between Sr[Nb(OEt)6]2 and KNb(OEt)6 with high structural symmetry. SKN powders and thin films on fused silica substrates directly crystallized to the polycrystalline tetragonal tungsten bronze phase at 600 °C. Highly oriented SKN thin films with the tetragonal tungsten bronze phase were fabricated on MgO(100) and Pt(100)/MgO(100) substrates. Two crystal lattice planes of SKN were intergrown at an orientation of 18.5° on MgO(100). The dielectric constant of SKN thin films on Pt(100)/MgO(100) was about 590 at 20 °C at 1 kHz.

High-purity SrTiO3 bicrystal sample (the angle between two [001] directions is 24°) was used in the present experiment to develop a thermal grain boundary groove along the bicrystal grain boundary at different temperatures (1150–1400 °C) and times (15–6720 min) in air. An atomic force microscope (AFM) was used to observe the surface morphological change in the annealed bicrystal sample in order to measure the width W and depth h of the developed grain boundary groove. It was found that the log W–log t (at 1150–1400 °C) and the log h°log t (at 1400 °C) relationships are approximately linear, having slopes of approximately 1/4. Using Mullins' formulas, the surface diffusion coefficients of SrTiO3 at different temperatures were calculated. Finally, the surface diffusion coefficient determined in the present experiment appears to correspond to the titanium atom, which has the lowest diffusivity in SrTiO3.

Pb1−xCaxTiO3 thin films with x = 0−0.3 for pyroelectric applications were deposited on platinized silicon wafers by chemical solution processing. Ca-substitution for Pb in PbTiO3 results in a reduced c/a ratio of the unit cell, which, in turn, leads to better pyroelectric properties. Control of nucleation and growth during rapid thermal annealing to 650 °C allowed the formation of either highly porous or dense (111) oriented films. The inclusion of pores creates a matrix-void composite with the low permittivity desired for pyroelectric applications, resulting in a high figure of merit. The growth mechanisms for the microstructural evolution of both dense and porous films were analyzed by x-ray diffraction, transmission electron microscopy, scanning electron microscopy, and Rutherford backscattering spectrometry and allowed establishment of microstructure/property relationships.

Formation of silicon oxide thin films from spin-coated β-chloroethyl silsesquioxane (β-cesq) on silicon, NaCl, and quartz was induced by 193 nm laser pulses. The silicon oxide deposition is characterized by ir, uv, ellipsometry, and Rutherford backscattering spectrometry. The silicon oxide films obtained by uv irradiation were found to have much less carbon and chlorine as impurities and have a higher refractive index as compared to those obtained by annealing. The photoinduced oxide films were found to be smooth, without laser-induced microrough or periodic structures.

Solid-state amorphization was achieved in the Ni48Nb52 multilayers upon thermal annealing by gradually raising the temperature from 250 to 400 °C and staying at 400 °C for 2 h. More interestingly, before complete amorphization, a sequential disordering of first Ni and then Nb crystalline lattices was observed for the first time, and it was essentially the physical origin of an asymmetric growth of the amorphous interlayer during solid-state reaction reported previously in some binary metal systems. In another two multilayered samples with overall compositions of Ni64Nb36 and Ni70Nb30, thermal annealing under similar conditions resulted in the formation of two metastable crystalline phases with face-centered-cubic and hexagonal-close-packed structures, respectively, although an amorphous phase also appeared and coexisted with one of the metastable crystalline phases in the intermediate states. In the ion mixing experiment, such sequential disordering, as well as formation of metastable phases, was also observed in the respective Ni–Nb multilayers upon room-temperature 200-keV xenon ion irradiation. Comparatively, however, ion irradiation eventually induced complete amorphization in all the multilayers at the respective doses, indicating that ion-induced disordering frequently predominated in the competition between amorphization and the growth of a metastable crystalline phase. A Gibbs free energy diagram, including the free energy curves of the newly formed metastable crystalline phases, of the Ni–Nb system was calculated based on Miedema's model. The constructed free energy diagram can give reasonable explanations of the sequential disordering and the thermodynamic possibility of the formation of either an amorphous or a metastable crystalline phase, of which the free energy difference was quite small. It follows naturally that the phase selection, namely, which phase was more favored to be formed eventually than its competitors, was influenced or even determined by the kinetics involved in the respective processes.

Lead zirconate titanate (PZT) has been successfully fabricated via a unique one-step sintering processing route, which is simpler than the traditional precursor-calcinationmilling- pelleting-sintering route and is able to deliver an enhanced sintered density at a much reduced sintering temperature. The hydroxide precursor was prepared by coprecipitation from a mixed nitrate solution containing Pb2+, Zr4+, and Ti4+ ions, and it was then compacted into pellets without being calcined at a low temperature. The precursor pellets were dehydrated at 400, 500, and 600 °C for 4 h, respectively, followed by an isostatic pressing at 350 MPa, prior to being sintered at a high temperature. Dehydration temperature has a large impact on the sintering behavior of these hydroxide-derived PZT ceramics. The PZT dehydrated at 400 °C was seriously cracked when sintered at temperatures ranging from 950 to 1150 °C, due to the incomplete dehydration. A sintered density of 99.2% theoretical density was obtained at 1050 °C for 2 h for the powder pellet dehydrated at 500 °C for 4 h. It exhibits a dielectric constant of 1024 and a dielectric loss of 2.1% at a frequency of 1 kHz at room temperature. A calcination at a too-high temperature, e.g., 600 °C, results in a reduction in the sinterability of the precipitate-derived PZT ceramic.

In this paper we present sol-gel synthesis and thermal and structural characterization of some lithium borophosphates. The as-prepared samples are mostly partially crystalline, and densification heat treatments at 500 °C cause samples to crystallize. In the phosphorus-rich part of the composition triangle we have lithium excess with respect to the nominal composition, which is likely due to the low reactivity of the phosphorus precursor. On the boron-rich side, in contrast, lithium losses are found which probably occur during syneresis.

An aluminothermic reaction starting with inexpensive MoO3, SiO2, and Al powders was utilized to prepare molybdenum disilicide (MoSi2) powders by the micropyretic/combustion synthesis process and leaching. The combustion-synthesized product was porous and could readily be crushed into powders. X-ray diffraction (XRD) analysis revealed that the product of such a reaction consisted of α–Al2O3, MoSi2, and a small amount of Mo(Si,Al)2 and Mo5Si3. The reason for the formation of Mo(Si, Al)2 phase is discussed. MoSi2 powders were obtained by leaching out the Al2O3 from the synthesized powder mixtures in boiling phosphoric acid solution. The synthesized MoSi2 powders, including a small amount of Mo(Si, Al)2 and Mo5Si3, were very fine with an average particle size of about 1 μm.

Amorphous fluorinated silicon nitride films have been deposited with the variation of NF3 flow rate using SiH4, N2, Ar, and NF3 gases by inductively coupled plasma enhanced chemical vapor deposition for the first time, and the absolute composition, oxidation mechanism, and optical properties were investigated. The absolute composition including hydrogen was performed by means of elastic recoil detection time of flight. It was found that the oxygen and fluorine contents in the film dramatically increased, but the hydrogen content decreased to below 4 at.% as the NF3 flow rate increased. The oxidation mechanism could be explained in terms of the incorporation of the activated residual oxygen species in the chamber into the film with unstable open structure by the fluorine-added plasma. It was shown that the density and optical properties such as refractive index, absorption coefficient, and optical energy gap depended on the film composition. The variations of the above properties for fluorinated silicon nitride film could be interpreted by the contents of fluorine and oxygen with high electronegativity.