A nanocrystalline magnetic particle/oligomer hybrid was successfully synthesized by polymerization of iron(III) 3-allylacetylacetonate (IAA) followed by in situ hydrolysis. An iron oxide particle/oligomer hybrid was synthesized by hydrolysis of the IAA oligomer under alkaline and reducing conditions by the addition of hydrazine or methylhydrazine. Crystalline particles of approximately 10 nm were found to be dispersed in the oligomeric matrix. The nanocrystalline particles were identified to be iron oxide spinel by x-ray diffraction analysis and electron diffraction. The nanometer-sized ferrimagnetic iron oxide particle/oligomer hybrid showed a typical superparamagnetic behavior.

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.

Boron (B) films and B-rich BNx films with different N contents (4.1–40.3 at.%.) were deposited by dual ion-beam deposition. The films consist of a B-rich phase constructed of icosahedral atomic clusters and a graphitelike boron nitride phase. The films with N content ≤20.3 at.% is dominated by the B-rich phase. Their hardness rises with increasing N content to reach a maximum value of 18.8 GPa. The hardness-to-elastic modulus ratio (H/E) and the critical load of the films also increase, showing stronger wear resistance of the films. These results can be explained if some N–B–N chains are formed at the interstitial sites in the network of the B-rich phase, which cross-link different icosahedral atomic clusters in the B-rich phase and strengthen the rigidity of the structure. For the films with higher N contents, the volume fraction of the graphitelike boron nitride phase becomes higher, and the hardness drops as a consequence. However, the change in the H/E ratio is rather mild. This implies that the wear resistance of the films is not altered and explains why the critical load of the films remains almost unchanged. In addition, the friction coefficient μ of all the films depends on the normal load L in the form of μ = aLy, where a and y are numerical parameters and are insensitive to the change in the N content. Furthermore, compressive stress was found to increase from about 0.12 to 1.7 GPa when the N content increased from 4.1 to 40.3 at.%.

Powder x-ray diffraction data of yttria (Y2O3) were obtained from room temperature to melting point with the thin wire resistance heating technique. A solid-state phase transition was observed at 2512 ± 25 K and melting of the high-uemperature phase at 2705 ± 25 K. Thermal expansion data for α–Y2O3 (C-type) are given for the range 298–2540 K. The unit cell parameter increases nonlinearly, especially just before the solid-state transition. The x-ray diffraction spectrum of the high-temperature phase is consistent with the fluorite-type structure (space group Fm3) with a refined unit cell parameter a = 5.3903(6) Å at 2530 K. The sample recrystallized rapidly above 2540 K, and above 2730 K, all the diffraction lines and spots disappeared from the x-ray diffraction spectrum that suggests complete melting.

The dependences of various nanoindentation parameters, such as depth of penetration d, indentation diameter a, deformation zone radius R, and height h of hills piled up around indents, on applied load were investigated for the initial (unrecovered) stage of indentation of the (100) cleavage faces of MgO crystals by square pyramidal Si tips for loads up to 10 μN using atomic force microscopy. The experimental data are analyzed using theories of elastic and plastic deformation. The results revealed that (i) a, R, and h linearly increase with d; (ii) the development of indentation size and deformation zone and the formation of hills are two different processes; (iii) the load dependence of nanohardness shows the normal indentation size effect (i.e., the hardness increases with a decrease in load); and (iv) there is an absence of plastic deformation involving the formation of slip lines around the indentations. It is found that Johnson's cavity model of elastic–plastic boundary satisfactorily explains the experimental data. The formation of hills around indentations is also consistent with a new model (i.e., indentation crater model) based on the concept of piling up of material of indentation cavity as hills.

A laser sintering/creep technique has been established to determine the creep behavior of thermal barrier coatings under steady-state high heat flux conditions. For a plasma sprayed zirconia–8 wt.% yttria coating, a significant primary creep strain and a low apparent creep activation energy were observed. Possible creep mechanisms involved include stress induced mechanical sliding and temperature and stress enhanced cation diffusion through the splat and grain boundaries. The elastic modulus evolution, stress response, and total accumulated creep strain variation across the ceramic coating are simulated using a finite difference approach. The modeled creep response is consistent with experimental observations.

Carbon nanocapsules with SiC and Au nanoparticles were produced by thermal decomposition of polyvinyl alcohol at about 500 °C in Ar gas atmosphere. The formation mechanism of nanocapsules and a structural model for the nanocapsule/SiC interface were proposed. In addition, carbon clusters were formed at the surface of carbon nanocapsules, and carbon onions were produced by electron irradiation of amorphous carbon produced from polyvinyl alcohol. The present work indicates that the pyrolysis of polymer materials with clusters is a useful fabrication method for the mass production of carbon nanocapsules and onions at low temperatures compared to the ordinary arc discharge method.

This study investigates the effects of sintering atmosphere and temperature on the interfacial properties of Cr3C2/Al2O3 composites. Thermodynamic considerations and calculations with computer-assisted methods for the equilibrium compositions in the Al–O–Cr–C system were used to simulate the interfacial reaction in Cr3C2/Al2O3 composite during sintering. The results were in good agreement with the experimental analysis. Cr3C2 is more stable during sintering in a system with carbon due to the lower equilibrium oxygen partial pressure. Controlling CO and O2 gas concentration, Cr3C2 first oxidized, decarbonized, and then transformed to Cr7C3 before reacting with Al2O3. An interfacial reaction between Cr3C2 and Al2O3 was not observed.

Three different kinds of morphology are found in undercooled Pd80Si20, and they dominate at different undercooling regimens ΔT, defined as ΔT = T1 – Tk, where T1 is the liquidus of Pd80Si20 and Tk is the kinetic crystallization temperature. In the small undercooling regimen, i.e., for ΔT ≤ 190 K, the microstructures are typically dendritic precipitation with a eutecticlike background. In the intermediate undercooling regimen, i.e., for 190 ≤ ΔT ≤ 220 K, spherical morphologies, which arise from nucleation and growth, are identified. In addition, Pd particles are found throughout an entire undercooled specimen. In the large undercooling regimen, i.e., for ΔT ≥ 220 K, a connected structure composed of two subnetworks is found. A sharp decrease in the dimension of the microstructures occurs from the intermediate to the large undercooling regimen. Although the crystalline phases in the intermediate and the large undercooling regimens are the same, the crystal growth rate is too slow to bring about the occurrence of grain refinement. Combining the morphologies observed in the three undercooling regimens and their crystallization behaviors, we conclude that phase separation takes place in undercooled molten Pd80Si20.

The formation of metastable tetragonal zirconia nanophase by thermal treatment of a zirconia gel derived from zirconyl chloride has been studied by high-resolution transmission electron microscopy (HRTEM) and differential scanning calorimetry (DSC). HRTEM observations revealed that a fully crystallized sample consists of nanocrystals, around 13 nm in size. This nanocrystalline t-ZrO2 has practically the same crystal structure as that of the high-temperature tetragonal zirconia phase. The nonisothermal crystallization rate is very fast in as-prepared zirconia gel. DSC data at various heating rates can be described by a two-parameter model which predicts the crystallization kinetics in isothermal conditions very well. The Johnson–Mehl–Avrami (JMA) model can be used, however, in partially crystalline samples (crystallinity >30%) where the rate of crystallization process is considerably slower. The kinetic exponent of the JMA model (m = 1.0 ± 0.1) then corresponds to linear dependence of the crystallization rate as a function of the fraction crystallized.

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.

Crystals of (Ca1.95□0.05) (Si0.9P0.1)O4, where □ denotes a vacancy, composed of both the α′L and β phases, were prepared and examined by the precession method. The β phase was exclusively twinned on (100)β, and the relative volumes of the twin-related variants were almost identical with each other. On the basis of the lattice correspondence between the two phases and their cell parameters, the phenomenological crystallographic theory was applied to determine the habit planes and the shape deformations upon α′L-to-β martensitic transformation. The habit planes, which define the coherent interphase boundaries between α′L and β, were nearly parallel to either (100)α′L or (010)α′L·. The alternate shape deformations that produce the former habit planes resulted in the actual (100) twin structure of the β phase. The total displacement was along [100]α′L with the magnitude of 0.008. Because the transformation involved a very small volumetric shrinkage of 0.6%, the strain accommodation would be almost completed. The coherency at the interface boundaries between the two phases and the effective strain accommodation probably caused the thermoelasticity of the Ca2SiO4 solid solutions.

The magnetic properties of carbon-coated Co and Ni nanoparticles aligned in chains were determined using transmission electron holography. The measurements of the phase change of the electron wave due to the magnetization of the sample were performed. The ratio of remnant magnetization to bulk saturation magnetization Mr/Ms of Co decreased from 53% to 16% and of Ni decreased from 70% to 30% as the particle diameter increased from 25 to 90 nm. It was evident that the inhomogenous magnetic configurations could diminish the stray field of the particles. After being exposed to a 2-Tesla external magnetic field, the Mr/Ms of Co increased by 45% from the original values with the same dependency on the particle size. The Mr/Ms of Ni particles, on the other hand, increased only 10%. The increased magnetization could be attributed to the merging of small domains into larger ones after the exposure to the external magnetic field. The validity of the interpretation of the holograms was established by simulation.

In this paper, a new method to study cyclic plastic deformation in thin metal films is presented. Cu films were deposited onto compliant substrates allowing the film to be subjected to tensile and compressive stresses on loading and unloading of the film/substrate composite. The film stress was measured in situ by x-ray diffraction. First results lend to characteristic stress-strain hysteresis curves, indicative of fatigue processes in small dimensions.

The phase diagram of urea–p-nitrophenol system, in the form of a temperature-composition curve, shows the formation of a 1: 1 molecular complex surrounded by two eutectics containing 0.216 and 0.777 mole fraction of p-nitrophenol. Data on growth velocity (v), obtained by measuring the rate of movement of the interface at different undercoolings (ΔT), suggest that they obey the Hillig–Turnbull equation, i.e., v = u (ΔT)n, where u and n are constants depending on the nature of materials involved. From the heat of fusion values, determined by the differential scanning calorimetry (DSC) method, heat of mixing, entropy of fusion, roughness parameter, interfacial energy, radius of the critical nucleus, and the excess thermodynamic functions were calculated. While the x-ray diffraction data show that the eutectics are not mechanical mixtures of the components under investigation, the microstructural investigations give their characteristic features.

The types and structures of oxide phases produced during the incongruent reduction of sapphire (single-crystal Al2O3) by molten magnesium were examined. Polished faces of sapphire were exposed to molten magnesium at 1000 °C for 100 h. Such exposure resulted in the formation of a continuous, epitaxial layer of spinel (MgAl2O4) on sapphire and a continuous, epitaxial layer of magnesia (MgO) on the spinel. X-ray pole figure analyses indicated that two variants of spinel and magnesia had formed in a manner consistent with the following orientation relationships:

Studies of the structure-property relations of lead zirconate titanate (PZT) modified with lower valent substitutions on the A- and B-sites have been performed as a function of substituent concentration. These investigations have yielded common changes induced by these substitutions on ferroelectric phases. The commonalties are the presence of fine domains and polarization pinning effects. Differences in domain morphologies were observed between the rhombohedral and tetragonal ferroelectric phases. Rhombohedral ferroelectrics were found to exhibit “wavy” domain patterns with increasing dopant concentrations, whereas a lenticular domain shape was preserved as the domain size was decreased for tetragonal ferroelectrics. These differences were explained in terms of different pinning mechanisms based on the differences in local elastic strain accommodations. Investigations of high Zr-content PZT have revealed that the ferroelectric rhombohedral phase becomes stabilized over the antiferroelectric orthorhombic with increasing concentrations of lower valent modifications. This change was explained in terms of the enhanced coupling between oxygen octahedra due to the bonding of oxygen-vacancy dipoles.

Profile evolution simulations during chemical vapor deposition based on a 2D continuum model reveal that the type of surface kinetics plays an important role in determining step coverage of films deposited in high aspect ratio trenches and vias. Linear surface kinetics, resulting from an adsorption rate limited process, is found to cause difficulty in bringing about conformal step coverage in deep narrow trenches without reducing the growth rate considerably. Under such condition, void-free filling cannot be achieved while maintaining a growth rate acceptable to integrated circuit (IC) manufacturing. The numerical study also suggests that the high tendency of the precursor for chemical equilibrium on a surface, resulting in nonlinear kinetics by a surface reaction limited process, is crucial to achieve a uniform step coverage as typically observed in SiO2 deposition from tetraethylorthosilicate (TEOS).

Processes that constrain or promote cavity growth and fast fracture at elevated temperatures are examined. Solutions are given for the stress caused by inhomogeneous deposition of matter in metal-ceramic and alumina grain boundaries and for the tensile stress near the top of a hemispherical pore during pore growth. Velocities of dislocation climb that could promote fast fracture are calculated for elastic stresses acting upon dislocations arising from both a crack tip and interface repulsion. The rates for the atomic diffusive processes and the magnitudes of stresses resulting from them are found to agree well with experimental rate of pore growth, and new data on pore growth and fracture at an aluminum-sapphire interface are presented.

The occurrence of segregation and its influence on microstructural and phase evolution have been studied in MgO–MgAl2O4 powders synthesized by thermal decomposition of aqueous nitrate precursors. When the nitrate solutions of Mg and Al were spray-pyrolyzed on a substrate held at 673 or 573 K, homogeneous mixed oxides were produced. Spraying and drying the nitrate solutions at 473 K resulted in the formation of compositionally inhomogeneous, segregated oxide mixtures. It is suggested that segregation in the dried powders was caused by the difference in solubility of the individual nitrate salts in water which caused Mg-rich and Al-rich salts to precipitate during dehydration of the solutions. The occurrence of segregation in the powders sprayed at 473 K and not 573 or 673 K is ascribed to the sluggish rate at which the early stages of decomposition occurred during which the cations segregated. The phase evolution in segregated and segregation-free MgO–MgAl2O4 powders has been compared. The distinguishing feature of the segregated powders was the appearance of stoichiometric periclase grain dimensions in excess of 0.3 μm at temperatures as low as 973 K. By comparison, the segregation-free powders displayed broad diffraction peaks corresponding to fine-grained and nonstoichiometric periclase. The grain size was in the range 5–30 nm at temperatures up to 1173 K. The key to obtaining fine-grained periclase was the ability to synthesize (Mg Al)O solid solutions with the rock salt structure. In the temperature range 973–1173 K, spinel grain size varied from 5 to 40 nm irrespective of its composition and did not appear to be influenced by segregation.