The microstructure and ductility of directionally solidified Ni50Al20Fe30 were studied. Calculation and experiment show that the elastic modulus of the sample with completely eutectic lamellar structure is higher than that of the sample with dendritic structure. During deformation, in the samples with dendritic structure, some load is transferred from the proeutectic area to the γ-rich eutectic area and enhances the ductility of the sample.The existence of thick interdendritic γ phase and thick lamellar γ phase in the eutectic area of the dendritic sample is very effective in suppressing the microcrack propagation and also contributes to the ductility enhancement.

Powders with a nanostructured mixture of pure Al and Pb phase were produced by mechanical milling of elemental blends of Al and Pb with a composition of Al90Pb10 (wt. %). Under a pressure of 1.5 GPa at 280 °C, the as-milled powders were successfully consolidated into bulk, full-density samples (>99.5% theoretical density) while the average grain sizes of Al and Pb in the compacted samples remain unchanged with respect to those in the as-milled powders. The achievement of the full density without grain coarsening in the consolidation process could be reasonably attributed to melting of the nanometer-sized Pb particles of which the melting point is considerably depressed.

A new X7R type dielectric ceramics for the PMN-BT-PT system with a high dielectric constant (4832) and a low firing temperature (1100–1130 °C) was prepared by the mixed-sintering method. The results of XRD, SEM, EDAX, and dielectric measurements showed that the dielectric ceramics is a two-phase composite with the high dielectric constant originating from the ferroelectric relaxor, and the temperature stability of the dielectric properties from two-phase coexistence.

This communication describes a new method for producing stable, high concentrations of Sc2+ in optically clear CaF2 crystals. We have achieved Sc2+ concentrations as high as 3 × 1018 cm−3 without degradation of optical quality. We have converted as much as 5% of the scandium dopant to the divalent state. The concentration of divalent scandium is stable during room temperature storage for periods of at least one year.

Silver-sheathed Bi–Pb–Sr–Ca–Cu–O (2223) superconducting tapes (with a starting composition of Bi1.8Pb0.4Sr2Ca1Cu2O8, calcium cuprate, and CuO) were fabricated by the powder-in-tube technique. The tapes were sintered at various temperatures to optimize the formation of Bi1.8Pb0.4Sr2Ca2Cu3O10 phase within the tape. The results show that sintering within the temperature range of 815–825 °C can produce tapes with high critical current density (Jc). The Jc of samples sintered at the higher temperature of 825 °C, where more liquid is present, depended markedly on the rate at which tapes were cooled from the sintering temperature; samples sintered at lower temperatures did not exhibit such a cooling-rate effect. The optimum combination of phase purity and microstructure that yielded an average transport Jc of ≥ 2.5 × 104 A/cm2 was obtained when the tapes were sintered at 825 °C for 150 h and cooled at a rate of 25 °C/h from the sintering temperature. Quenching studies indicate that the Bi-2223 phase becomes unstable below 700 °C during slow cooling. This result may have important implications for processing Bi–Sr–Ca–Cu–O tapes with high Jc. Addition of 15 vol.% Ag flakes to the monolithic core exerted no significant effect on Jc.

The particle segregation mode of two different inclusion phases of Y2BaCuO5 (Y211: a dissolving phase in a Ba–Cu–O liquid phase) and BaCeO3 (a nondissolving phase) was investigated in the melt-textured YBa2Cu3O7−y (Y123) with BaCeO3 addition (0–20 wt. %), and with 30 wt.% Y211 plus BaCeO3 (0–20 wt. %). The segregation mode of the inclusion phases is dependent not only on the type of the inclusion phases but also their amounts. When the trapped amount of the Y211 is small, they make an X-like pattern on the diagonal planes of the Y123 crystal. When the amount of the Y211 is large, meanwhile, the Y211 particles are trapped within four tetrahedral spaces (normal to the c-axis) bounded by the diagonal planes of the Y123 crystal, with no Y211 trapping within two tetrahedral spaces parallel. On the other hand, the nondissolving BaCeO3 particles make linear tracks normal to the {100} growth fronts of the Y123 crystal.

Microstructures of 27-filament (Bi, Pb)2Sr2Ca2Cu3O10+x (BPSCCO 2223) tape at various stages of repetitive rolling and sintering have been investigated using TEM and SEM. It was found that the dislocation density increases with increasing sintering time with the maximum dislocation density of 1012/cm2 achieved for tapes sintered for 220 h. The interface between Ag-sheath and oxide core was observed to be wavelike. Small irregular 2223 colonies and cracks in the oxide cores were often observed near the Ag-sheath/oxide core interface. Repetitively rolled and sintered specimen with a total sintering time of 220 h was observed to have optimum phase purity of 2223 phase. Prolonged sintering results in recrystallization of the 2223 grains, degrading the texture of the oxide core.

The solvent, supercritical antisolvent technique (SAS) has been used to produce submicronic particles of yttrium acetate for the synthesis of YBCO superconductors. For this purpose, in a continuous SAS apparatus dimethylsulfoxide (DMSO) as yttrium acetate solvent and supercritical carbon dioxide as antisolvent have been adopted. Experiments have been performed in the pressure range between 70 and 160 bar and for temperatures between 40 and 70 °C. Different concentrations of yttrium acetate in DMSO have also been tested. Various morphologies of yttrium acetate particles have been obtained, having mean particle diameters from 0.1 to 7 μm. At 40 °C and pressures larger than 120 bar, submicronic spherical particles of yttrium acetate of about 0.1 μm diameter and with a narrow particle size distribution have been achieved.

To investigate the hydrogen embrittlement and Mn ductilization effects in TiAl, the electronic structures of pure, H-doped, Mn-doped, and Mn, H-codoped TiAl have been studied by the first-principles discrete variational Xa calculations. Local environmental total bond order (LTBO), which is developed for the description of the cohesive properties in a local atom environment involving impurities, should be regarded as a new microscopic criterion for embrittlement. The larger LTBO presents the stronger cohesion and the better ductility of the system. Our results show that H obviously decreases LTBO while Mn increases it, which suggests H as an embrittler while Mn as a ductilizer. It is of key importance to understand hydrogen embrittlement in which hydrogen causes the weakening of its surrounding metal-metal bonds.

Matrix microstructure of a pitch-based carbon-carbon composite was controlled by an iodine treatment. Coal-tar pitch having the softening point of 101 °C was used as a matrix precursor. The iodine treatment was carried out on a pitch-impregnated specimen at 90 °C for 3–20 h. The specimen was carbonized at 800 °C and graphitized at 2000–3000 °C. The carbon yield increased from 73% to 93% by the iodine treatment. Microstructures of carbonized specimens changed from a flow type texture to a mosaic type one by the iodine treatment. The microstructural development to graphitic structure was suppressed by the iodine treatment.

Two nonequilibrium processes (melt-spinning and ball-milling) were successfully employed to synthesize Al1−xPbx (x = 5, 10, 20, 30 wt. %) nanocomposites with distinct microstructures. In the melt-spun (MS) Al–Pb alloys, the nanometer-sized Pb particles are uniformly distributed in the micrometer-grained Al matrix and have an orientational relationship with the matrix, while in the ball-milled (BM) samples, both Pb and Al components are refined with prolonged milling time, forming nanocomposites with Pb particles homogeneously dispersed into the Al matrix. The minimum particle size of Pb in the milled samples linearly increases with the Pb content. The microhardness of the BM Al–Pb samples is much larger than that of the MS samples, which mainly results from strengthening effects of the nanometer scale Al grains following the Hall–Petch relationship. The microhardness for both BM and MS Al–Pb samples varies with the Pb content, and maximum hardness for both samples exists when Pb content is about 5 wt. %, indicating that small amounts of Pb, in the form of nanoparticles, may strengthen the Al matrix.

It was found in a previous work that the Al–Si alloy could spontaneously infiltrate into carbon preforms in air. In this study, the initiation stage of the infiltration process was investigated in detail through two different infiltration experiments. In one experiment, carbon preforms were fully dipped into an alloy bath that was exposed to air, and in the other experiment a carbon preform was only partially dipped into an alloy bath that was protected with a flowing Ar or N2 gas. Experimental results have suggested that the initiation of infiltration is controlled by the pressure of oxidizing gases such as O2 or CO at the infiltration front and is not affected by the presence or absence of N2 gas. The critical pressure of oxidizing gases is estimated to be on the order of 10−4 atm for systems investigated in our experiments. An effective way to reduce the O2 or CO pressure is to flush a preform with nonoxidizing gases during or before infiltration, or to use an active metal to reduce the O2 pressure and thus the corresponding CO pressure.

Mixed crystalline titanium (IV) phosphate-phenylphosphonates were synthesized under hydrothermal conditions using tetramethylammonium hydroxide as a templating reagent. It was found that at a relatively low molar ratio H3PO4 : PhPO3H2 in the reaction mixture (<1) only a pure α-titanium phenylphosphonate is formed. At the molar ratio H3PO4 : PhPO3H2 = (3–5): 1 the formation of a novel mixed compound titanium (IV) dihydrogenphosphate-hydrogenphosphate-phenylphosphonate takes place. Further increase of the ratio H3PO4 : PhPO3H2 gives mechanical mixtures of different phases. Preliminary results on the characterization of the novel compound of formula Ti(H2PO4)1.25(HPO4)0.12(C6H5PO3)1.25 · 0.3H2O are presented.

The addition of B4C powder retarded the nitridation of the silicon powder green body by the formation of a borosilicate layer in interfaces between Si grains. The viscous layers hindered the SiO formation and the Si and N diffusion. Despite the presence of borosilicate layers, the Fe impurity in the green body still promoted the Si nitridation process by the formation of fluid iron silicide and the promotion of the B4C conversion to BN in gaps or holes in the viscous borosilicate layers. The addition of 5% H2 in the N2 atmosphere accelerated the Si + B4C nitridation, where the hydrogen acted as an oxygen getter, thus reducing the amount of glassy borosilicate in the interface.

Metallurgical reactions controlling the Ti activation in brazing of Al2O3 have been studied by means of microstructural and thermodynamic analysis. The reactions of titanium with oxygen and copper are shown to be decisive in active brazing. Themiscibility gap in the Ag–Cu–Ti system divides the liquid braze into Ag-rich (L1) and TiCu-rich (L2) liquids. The liquid L2 reacts with alumina forming the mixed oxide (Ti, Al)4Cu2O. Besides with alumina, Ti reacts with oxygen that the filler alloys usually contain and forms a brittle ribbon composed of TixO and Ti–Cu–O phases in the braze. The formation of Ti oxides next to the alumina is possible only in the filler alloys of highest Ag content.

[Si–Y–O–C–N] amorphous powders were synthesized by the pyrolysis at 1000 °C in N2 of chemically modified perhydropolysilazane using n-decyl alcohol and yttrium tri-methoxide. [Si–Y–O–C–N] amorphous powders yielded a unique fibrous microstructure by heat treatment in N2 at 1800 °C. The fibrous microstructure was composed of β–Si3N4 whiskers of submicron in diameter and more than 10 μm in length. Fully dense Si3N4 –SiC–Y2O3 ceramics were also fabricated by heat treatment at 1800 °C followed by powder-vehicle hot pressing at 1700 °C. After these two-step processings, [Si–Y–O–C–N] amorphous powders yielded a unique fine-grained microstructure composed of submicron grains with high aspect ratio.

Reactive ion etching damage to Pt/Pb(Zr, Ti)O3/Pt ferroelectric capacitors was evaluated under Ar bombardment and CHClFCF3 etch plasmas. The hysteresis and degradation properties, including fatigue and leakage current, were examined systematically to study the mechanism of damage. The damage was measured quantitatively by comparing the relative voltage shift with respect to the initial hysteresis loops. The damage effects were found to be dependent on etching time and mainly due to the physical effect of ion bombardment. The electrical properties of the etched Pt/Pb(Zr, Ti)O3/Pt capacitors were substantially recovered by annealing at 400 °C for 30 min.

Pt-coated silicon substrates with strong (111) Pt texture were annealed in an oxidizing atmosphere at temperatures from 500 °C to 750 °C. BaTiO3 thin films were deposited by pulsed laser ablation on the substrates. Observation by transmission electron microscopy showed that the substrate anneal caused the formation of TiO2 in the Pt layer, accompanied by the formation of a high density of faceted protrusions on the Pt surface, particularly at the higher anneal temperatures. The Pt protrusions had (111) facets, parallel to the substrate surface, on which (100)-oriented BaTiO3 grains were observed. BaTiO3 grains with an epitaxial relationship to the Pt lattice were observed on inclined facets of the Pt protrusions [which were not (111) planes], and also on the nonplanar regions of the Pt surface. These epitaxial BaTiO3 grains had (111) preferred orientation relative to the substrate surface. Thus, the BaTiO3 films displayed bimodal growth behavior, with both (100) texture and (111) epitaxy. We propose a model for this behavior based on surface energy considerations.

Two different electron energy loss spectroscopy (EELS) quantitative analytical methods for obtaining complete compositions from interface regions are applied to ultrathin oxide-based amorphous grain boundary (GB) films of ∼ 1 nm thickness in high-purity HIPed Si3N4 ceramics. The first method, 1, is a quantification of the segregation excess at interfaces for all the elements, including the bulk constituents such as silicon and nitrogen; this yields a GB film composition of SiN0.49±1.4O1.02±0.42 when combined with the average film thickness from high resolution electron microscopy (HREM). The second method, II, is based on an EELS near-edge structure (ELNES) analysis of the Si–L2,3 edge of thin GB films which permits a subtraction procedure that yields a completeEELS spectrum, e.g., that also includes the O–K and N–K edges, explicitly for the GB film. From analysis of these spectra, the film composition is directly obtained as SiN0.63±0.19O1.44±0.33, close to the one obtained by the first method but with much better statistical quality. The improved quality results from the fewer assumptions made in method II; while in method I uniform thickness and illumination condition have to beassumed, and correction of such effects yields an extra systematic error. Method II is convenient as it does not depend on the film thickness detected by HREM, nor suffer from material lost by preferential thinning at the GB. In addition, a chemical width for these films can be deduced as 1.33 ± 0.25 nm, that depends on an estimation of film density based on its composition. Such a chemical width is in good agreement with the structural thickness determined by HREM, with a small difference that is probably due to the different way in which these techniques probe the GB film. The GB film compositions are both nonstoichiometric, but in an opposite sense, this discrepancy is probably due to different ways of treating the surface oxidation layers in both methods.

The structure, morphology, and mechanical properties of sol-gel zirconia films have been examined using XRD, AES depth profiling, AFM, and ultramicro indentation. There is a systematic variation in the structure and morphology of the zirconia films with increasing thickness. These changes include increases in the amount of monoclinic phase, substrate oxides, and a decrease in grain size. Ultramicro indentation measurements indicate measured hardness increases with film thickness. The highest hardness value was 6.12 GPa for a 900 nm thick film. However, these values may be influenced by the substrate oxide layer at the film/substrate interface which increases with film thickness. The modulus of the films appears to be thickness independent. As the films are made up of a number of separately fired layers, it appears that the property changes observed are also related to the number of thermal cycles experienced by the sample.