Nanocrystalline manganese oxide powders have been prepared at 25 °C by precipitation from Mn(NO3)2 aqueous solution. The presence and addition sequence of H2O2 significantly influence particle characteristics of the resulting manganese oxides, including crystal structure, particle size and morphology, and surface area, depending upon molar ratio of H2O2 with respect to Mn. The precipitation from preoxidized manganese solution by H2O2 results in flakelike-shaped amorphous hydrous manganese oxide (MnO2xH2O). In the absence of H2O2, on the other hand, amorphous Mn(OH)2 is obtained, and a part of Mn(OH)2 subsequently transforms into crystalline Mn3O4 by oxidation in air. Relative population of amorphous Mn(OH)2 decreases by dissolution when post-treated with H2O2. At Mn:H2O2 = 1:4, the well-defined 16-nm-sized nanocrystalline Mn3O4 with homogenous particle morphology is prepared. The treatment with excess H2O2, however, destroys crystalline Mn3O4 and leads to further oxidation of the aqueous manganese species. Under these conditions, a mixture of needlelike Mn2O3 and cubelike Mn3O4, including amorphous MnO2xH2O, is obtained.

The role of 12.4 vol% ZrO2 addition in the microstructure evolution of alumina compacts during the intermediate and final stages of sintering was investigated by means of small-angle neutron scattering measurements and stereological analysis. Both the pore-size evolution results and the grain-growth data indicate a narrowly defined onset density for the transition to the final sintering stage. The presence of ZrO2 as a second phase apparently maintains the stability of the intermediate sintering stage out to significantly higher density than in single-phase alumina and plays an important role in inhibiting grain growth and in preventing pore–grain boundary separation. The influence of the ZrO2 second phase on pore evolution, grain growth, and sinterability of the alumina–zirconia composite is discussed and compared to the behavior of single-phase alumina. The samples were prepared from commercially available powders, with naturally occurring porosity distributions, rather than from artifact(model) pore compacts prepared from nominally pure research-grade materials. The goal was to gain an improved understanding of microstructure development in real materials.

Metalorganic liquid precursors were used to examine the effects of processing atmosphere on texture development in oriented Pb(Zr0.60Ti0.40)O3 thin films. After removal of organic ligands via pyrolysis, the films were heated at 25 °C/min in a 5% H2/Ar atmosphere until a switching temperature, after which the atmosphere was switched to pure oxygen. The films were heated to a maximum temperature of 650 °C with switching temperatures ranging from 450 to 600 °C. The degree of (111) orientation in the lead zirconate titanate (PZT) films increased with increasing switching temperature, resulting in highly textured (111) PZT films. These results suggest that atmosphere control plays a significant role in texture development during rapid thermal processing.

The microstructure of a bearing-grade silicon nitride, prepared by pressureless sintering with Y2O3, AlN, and TiO2 additives and then hot-isostatically pressed, is examined with high-resolution transmission electron microscopy, scanning electron microscopy, and x-ray diffraction. The material consists of large acicular β–Si3N4 grains and small equiaxial α–Si3N4 grains. An amorphous phase containing the sintering aids is observed at the two-grain boundaries and at the grain pockets. No crystalline boundary phase is identified. The α-to-β and β-to-β grain boundaries appear straight and well defined. The dominant crystalline planes observed at the β-grain boundaries are (1010) and (1120). The intergranular spacing of the two-grain boundaries (α-to-β and β-to-β) is 1.0 nm when a high-contrast boundary phase is present, and it is 0.8 nm when a low-contrast boundary phase is present, confirming that the film thickness is strongly dependent on the boundary-phase composition. The α-to-α boundaries are often curved, and the thickness of the amorphous film at these boundaries varies from 0.7 to 1.1 nm. Evidence of near-intimate contact between β-grains is also observed.

Enthalpies of formation were determined for β-sialon phases (Si6–zAlzOzN8–z, z = 0.46 to 3.6) by high-temperature oxidative drop solution calorimetry using an alkali-metal borate (52 wt% LiBo2; 48 wt% NaBO2) solvent. Oxygen gas was bubbled through the melt to accelerate oxidation of the oxynitride samples during dissolution. Sialons near z = 2 appear less stable energetically than ones with higher or lower nitrogen content. A large configurational entropy contribution for sialons with z > 2 may further stabilize these materials. This larger free energy driving form may be the reason for success in pulse-activated processing of these materials. The enthalpies of formation further suggest that a greater driving form for oxynitride formation exists in batch synthesis using SiO2 rather than Al2O3.

Ca4(PO4)2O (TetCP) reacts with an acidic polyelectrolyte in the absence of a solvent to form a composite composed of Ca10(PO4)6(OH)2 (hydroxyapatite, or HAp) and the Ca salt of the polyelectrolyte. Mixtures of an acrylic copolymer and TetCP powders were hot-pressed, and the effects of temperature, pressure, and time on HAp formation were studied. Reaction starts when the copolymer is heated to above Tg. Initial carboxyl site neutralization liberates water, continued TetCP hydrolysis, liberates Ca2+ ions, which react with the copolymer forming its Ca salt. When 90% conversion to HAp was achieved, the composite had an average tensile strength of 51 MPa, a Vickers hardness of 145 kg/mm2 and a Tg ˜50 °C.

Elastic response behavior of four different plasma-sprayed deposits has been investigated using depth-sensing micro-indentation technique. Due to the high degree of porosity and inhomogeneity of the coatings, the characteristic elastic moduli were found to be in the range of 20–75% of that of the dense bulk material (200 GPa). Considering the wide variation of properties, 150 data points were generated with five different indentation loads for each coating, and statistical tools were employed to represent the scatter of the data. The characteristic elastic moduli of all the coatings were observed to be almost doubled when the magnitude of indentation load was reduced from the highest (1000 mN) to the lowest (30 mN). The coatings were subsequently heat treated at 1100 °C, the operational temperature of a gas turbine, for 2, 25, and 100 h, and in all the coating grades the corresponding elastic moduli increased significantly. However, the stiffening effect was not uniform in two grades and was more pronounced for the smaller indentation loads. The increase in elastic modulus is attributed to elimination of fine porosity and sintering neck formation, an assumption also supported by the results of mercury porosimetry.

Nanocrystalline powders of ferroelectric bismuth vanadate, Bi4V2O11 (n-BiV), with crystallite size less than 50 nm, were obtained by mechanical milling of a stoichiometric mixture of bismuth oxide and vanadium pentoxide. The n-BiV powders on sintering yielded high-density, fine-grained ceramics with improved dielectric and polar characteristics. Dielectric studies on samples obtained from milled powders indicated that the ferroelectric-to-paraelectric phase transition temperature is strongly frequency dependent. The Curie–Weiss law is found to be valid only at a temperature away from the transition temperature, confirming the diffused nature of the transition, which is attributed to the presence of compositional inhomogeneity, because of partial reduction of vanadium.

Thin films of composition (Ba,Sr)yTiO2+y with 0.43 ≤ y ≤; 1.64, were deposited by metalorganic chemical vapor deposition on (100) MgO substrates at various growth conditions. X-ray diffraction and transmission electron microscopy studies showed that the films were composed of epitaxial Ba1–xSrxTiO3 (x ≈0.06) grains and an amorphous phase. The orientation of the tetragonal Ba1–xSrxTiO3 grains (pure a axis, pure c axis, or a mix of the two) was found to be strongly dependent upon film composition. This composition dependence is explained for the majority of the Ti-rich films by an analysis of average strains in the two-phase films, assuming a compressive strain of ≈1% in the amorphous phase.

When powder mixtures of {Al2(SO4)3 + Na2SO4}or {γ–Al2O3 [obtained by heating Al2(SO4)3 at 900 °C for 3 h] + Na2SO4} were heated in an alumina crucible at 1100 °C for 1 h, α–Al2O3 platelets were formed. The powder mixture of {Al2(SO4)3 + 2Na2SO4} yielded aggregations of platelets that were less than 5 μm in size. The size of the aggregations increased in proportion to the amount of Na2SO4, and aggregations of 120 μm were obtained using a mixture of {Al2(SO4)3 + 6Na2SO4}. The powder mixture of {γ–Al2O3 + 2Na2SO4 yielded hexagonal platelets having an average diameter of 3.7 μm and an average thickness of 0.3 μm. In addition to aggregation size, the size of the hexagonal platelets also increased in proportion to the amount of Na2SO4, and platelets having an average diameter of 5 μm were obtained using a mixture of {γ–Al2O3 + 6Na2SO4}.

In situ transmission electron microscopy (TEM) was performed to study dislocation motion during temperature cycles in aluminum films passivated with a SiO2 layer. The films were cycled from room temperature to 450 °C. Wedge-haped cross-sectional TEM samples were used to retain the constraint of the Si substrate. Besides interactions between dislocations and interfaces, the movement of threading dislocations within the constrained aluminum film was observed. This observation provides an experimental corroboration of the occurrence of threading dislocation motion, which is the basis for rationalizing the high-ield strength of thin films in available models of thin-film plasticity.

The epitaxial PbTiO3 thin films of different thickness were prepared on MgO(001) substrates by the reactive direct-current magnetron sputtering. The volume fraction of c domains, α, which was measured by x-ray diffractometry, increased rapidly from zero with the film thickness, being saturated at about 90% above 100 nm. The films were annealed in a PbO atmosphere at 700 °C for 8 h, and they were used to study the composition change in the Pb/(Pb + Ti) ratio and the relaxation of the residual intrinsic stress. The relationship between change of α and composition was weak. The stress state was calculated through the finite-element method. As for the small thickness, the tensile epitaxial stress overwhelmed compressive intrinsic and thermal stresses, and the domain structure was a-domain oriented. As for the large thickness, the compressive intrinsic stress together with the thermal stress overcame the tensile epitaxial stress, and the population turned into c domain.

Thin AlN films were grown by molecular beam epitaxy on MgO(001) substrate with a thin TiN buffer layer. The as-prepared AlN/TiN/MgO(001) interfaces have been characterized by cross-sectional high-resolution electron microscopy (HREM). It is found that the thin TiN buffer layer is epitaxially grown on the MgO(001) substrate and hexagonal AlN epitaxially on the as-received TiN(001). Based on the growth orientation relationship and HREM images, atomistic structure models for the AlN/TiN interface are proposed, image simulated, and compared with experimental images.

The mechanisms are studied for enhanced formation of C54–TiSi2 at about 700 °C when rapid thermal annealing at 3 °C/s in N2 is performed on 32-nm-thick codeposited Ti–5.9 at.% Ta on Si(100) single-crystal substrates. The enhancement is related to an increased C54–TiSi2 nucleation rate due to the development of a multilayered microstructure. The multilayer microstructure forms at temperatures below 600 °C with the formation of an amorphous disilicide adjacent to the Si substrate and a M5Si3 (M = Ti, Ta) capping layer. This amorphous disilicide crystallizes at higher temperatures to C49–TiSi2. The multilayer microstructure introduces an additional interface that increases the area available for the heterogeneous nucleation of C54. The capping layer is identified as hexagonal Ti 5Si3 or its isomorphous compound (Ti1–xTax)5Si3. Crystal simulations demonstrate that C54(040) has a lattice mismatch of 6–7% relative to Ti5Si3(300) suggesting that a pseudomorphic epitaxial relationship may lower the interfacial energy between these two phases and reduce the energy barrier for C54 nucleation. A C40 disilicide phase was also observed at temperatures above that required to form C54–TiSi2 suggesting that, in the present experiments, the C40 phase does not play a major role in catalyzing C54 formation.

The paraelectric–ferroelectric structural transition of potassium lithium tantalite niobate has been studied by both Raman scattering and thermal measurements. A condensed soft lattice vibrational mode at the phase transition has been analyzed. It originates from the symmetric O2/O3–Nb/Ta–O3/O2 in-plane bending of the Nb/TaO6 group. The soft optical phonon mode concerns the extraordinary transverse optical phonons propagating along the [1 1 0] direction. The thermal expansion experiments show a displacive phase transition and a big thermal contraction in the c direction of the crystal, with an average linear expansion coefficient αc = −4.52 × 10−5 K−1. The phase transition temperature and enthalpy are 358 K and 0.50 J/g, respectively. Curie temperature measured by four methods is within 353 and 360 K.

A variable-temperature (79, 145, and 293 K) extended x-ray absorption fine structure study, using rare-earth LIII absorption edges, is reported for phosphate glasses doped with rare-earth elements (R, where R = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, and Er) with compositions close to metaphosphate, R(PO3)3. The results yield nearest-neighbor R–O distances that demonstrate the lanthanide contraction in a glassy matrix and an R–O coordination intermediate between 6 and 7 for rare-earth ions with smaller atomic number (Z) and 6 for rare-earth ions with larger Z. Thermal parameters show no significant changes in R–O distances or coordination numbers between 293 and 79 K. There is evidence of an R–P correlation between 3.3 and 3.6 Å and the beginning of a second R–O correlation at approximately 4 Å. No R–R correlations up to a distance of approximately 4 Å were observed.

Calcium phosphate coatings, obtained at different deposition rates by pulsed laser deposition with a Nd:YAG laser beam of 355 nm wavelength, were studied. The deposition rate was changed from 0.043 to 1.16 Å/shot by modification of only the ablated area, maintaining the local fluence constant to perform the ablation process in similar local conditions. Characterization of the coatings was performed by scanning electron microscopy, x-ray diffractometry, and infrared, micro-Raman, and x-ray photoelectron spectroscopy. The coatings showed a compact surface morphology formed by glassy grains with some droplets on them. Only hydroxyapatite (HA) and alpha-tricalcium phosphate (α–TCP) peaks were found in the x-ray diffractograms. The relative content of (α–TCP diminished with decreasing deposition rates, and only HA peaks were found for the lowest rate. The origin of (α–TCP is discussed.

Silicide formation in implanted channels and interfacial reactions of Ni, Co, Ti, and Cu contacts under high current density have been investigated. Silicide lines, forming in the implanted channels, were observed in Ni and Cu/p+–Si samples but not in Ti and Co samples. The silicide line formation is correlated to the high diffusivity of metals in Si. For the Ni/p+–Si sambles, silicode line was found to initiate form the cathode contact. Network structures at the cathode were found in both Co and Ni samples. The depth of silicide formation was found to extend to the junction depth. The relationships between the silicide length and contact size, the applied current, and the method of the applied current are discussed.