Titanium and niobium carbides have been synthesized through self-propagating high-temperature reaction by mechanically alloying the elemental powder mixtures. It is found that this reaction is very similar to the conventional self-propagating high-temperature synthesis (SHS) process, but the ignition of the reaction is identified to be the mechanical collisions instead of heating the materials. Analysis of the products reveals that the final products of the Ti-C system are in good agreement with the equilibrium phase diagram, showing less relation with the alloying process. The decrease of the C content shortens the milling time prior to the SHS reaction of TiC by promoting the intimate mixing of the components, but lowers the heat release of the reaction and makes the propagation of the reaction more slowly. The SHS reaction during the mechanical alloying of the Nb-C system shows little difference, but the decrease of the C content can hardly influence the milling time prior to the reaction. By lowering the heat release of the SHS reaction of NbC, it lowers the reaction propagating rate. Mechanical alloying Nb50C50 and Nb55C45 results in the formation of NbC, while mechanical alloying Nb60C40 results in NbC + Nb instead of NbC + Nb2C according to the phase diagram. It was attributed to the fact that the rapid SHS reaction favors the formation of NbC, but hinders the occurrence of Nb2C phase through slow diffusion between NbC and the residual Nb. The measurement of the lattice parameters of TiC and NbC for different composition affirms the observed results. The particle sizes of obtained TiC and NbC are very fine at around or even less than 1 μm.

Sintered AlN ceramics were implanted by 1 × 1017 Ti/cm2 at an energy of 70 keV in order to investigate the role of the chemical properties of the implanted species on the phase formed during the implantation process. The implanted ions were found in a depth profile corresponding to the calculated distribution of the vacancies produced during the implantation process instead of the predicted ion profile. Identification of the local environment of Ti and of the resulting phase led us to conclude that Ti is surrounded by N after the collision cascade and forms TiN after post-implantation annealing. The TiN nucleus if formed by substitution of Al by Ti. Therefore, the heat of formation, which is more negative for TiN than for AlN, is found to be a key parameter to predict the final system.

A phase transformation study was carried out with barium aluminosilicate (BAS) forming powders (BaCO3, Al2O3, and SiO2) in a BAS-Si3N4 system. Powders were heat-treated in air at 1 atm pressure at different temperatures from 600 to 1150 °C at an interval of 50 °C to study the phase transformations during the formation of BAS. The phase transformations of α to β-Si3N4 is studied by heat-treating the powders at 1600 °C for different sintering times in a nitrogen environment at 1 atm pressure. Formation of different phases was identified by using powder x-ray diffraction. Formation of different forms of barium silicates occurs as an intermediate step between 650 and 950 °C and hexagonal BAS forms between 900 and 950 °C. The hexagonal form of BAS always forms first and persists as a metastable phase in the composites with no evidence of the monoclinic phase. An attempt made to fully transform hexagonal BAS to monoclinic BAS by using LiF as a mineralizer proved to be successful. The hexagonal form of BAS forms first when heat-treated at 1000 °C and is fully transformed to monoclinic BAS when heat-treated at 1100 °C.

The crystallization kinetics of the pyrochlore to perovskite phase transformation in lead zirconate titanate (PZT) thin films have been analyzed using rapid thermal processing (RTP). Sol-gel PZT thin films, fabricated on platinum electrodes, were annealed at 550 °C to 650 °C with hold times ranging from 1 s to 5 min. Glancing angle x-ray diffraction (XRD) was used for depth profiling to identify the location of phases in the films. Transmission electron microscopy (TEM) provided information on grain structure, nucleation, and growth. The phase information was correlated to the ferroelectric and dielectric properties. The perovskite phase nucleated in the pyrochlore phase throughout the film thickness, and at 650 °C the transformation was complete in 15 s. Fast growing (100) PZT nucleated at the platinum and consumed a small-grained matrix until a columnar structure was obtained. A ramp rate of 100 °C/s was sufficiently fast to prevent transformation during heating and allowed the direct application of an Avrami model for transformation kinetics. An activation energy of 610 kJ/mol was determined.

A finite-difference model was used to simulate the temperature and composition distributions produced inside a specimen heated with microwave energy during a process involving a change in composition. The dielectric properties of the specimen change with composition, resulting in nonuniform microwave power absorption and steady-state temperature gradients. When the specimen becomes less lossy as it reacts, or if the changes in the microwave heating properties are gradual, the reaction proceeds relatively uniformly and the volumetric microwave heating creates an inside-out reaction profile leading to increased conversions for processes such as reaction bonding and chemical vapor infiltration (CVI). If the specimen becomes more lossy as it reacts, then the reaction proceeds nonuniformly with rapid reaction rates in the hottest parts of the specimen and little or no reaction in the cooler areas. The process may then occur as a reaction front which moves along the specimen, as with combustion synthesis. This type of processing has potential advantages and disadvantages depending on the system.

Combustion synthesis of titanium borides from Ti and B binary powder mixtures having molar ratios B/Ti of 1.9 to 2.4 resulted in the formation of TiB2 as the primary phase and TiB as the secondary phase. The amount of TiB decreased when the particle size of the Ti in the powder mixtures became small and when the B content was increased. The results are discussed in terms of the homogeneity of reactant powder mixtures and the degree of boron saturation of the Ti-B melt. The burning rate increased from 11 to 15 mm/s as the titanium particle size decreased from −100 to −325 mesh with the same boron particle size of –325 mesh.

Effects of thermal annealing on the dielectric/piezoelectric properties of Pb(Zn,Mg)1/3Nb2/3O3-PbTiO3 ceramics (PZMN-PT with Zn/Mg = 6/4) were examined across the rhombohedral/tetragonal morphotropic phase boundary (MPB). Examination of the lattice parameters and the rhombohedral angle indicated that the MPB is in the vicinity of 24 mol% PbTiO3. Both the relative dielectric permittivity (∊r) and the piezoelectric constant (d33)/electromechanical coupling constant (kp) were increased by thermal annealing (800–900 °C) after sintering at 1150 °C for 1 h. The observed improvements in the dielectric and piezoelectric properties were attributed to the elimination of PbO-rich amorphous intergranular layers (about 1 nm thickness) induced by thermal annealing. Both the dielectric analysis using the series mixing model and the microscopic examination by transmission electron microscopy supported this conclusion.

This work presents an analysis on the main microstructural parameters that affect the dielectric and piezoelectric behavior of ceramics of calcium-modified lead titanate with Ca/Pb = 26/74. To this aim, ceramics were prepared under different sintering conditions to get a series of materials with different microstructures. Compositional and microstructural characterization was achieved by x-ray diffraction, energy dispersion spectroscopy, and optical microscopy. Computerized image analysis was carried out on the micrographs to determine grain and pore size distributions. These distributions were thoroughly analyzed using probability plots. Electromechanical coupling factors and piezoelectric coefficients were measured by the resonance method on thickness poled thin disks and rectangular bars. A similar combined effect of the grain size and the percentage of porosity on the inverse of the permittivity, the coupling factors at room temperature, and the temperature behavior of the electromechanical coupling factor k31 is found.

The relationship between grinding forces and the material's resistance to microfracture is investigated in abrasive machining of silicon nitride ceramics. Surface grinding is performed on two forms of silicon nitride with different microstructures, and the grinding forces are measured. In addition, single-point scratching is performed on polished surfaces to amplify the damage associated with the action of an individual abrasive particle in grinding. A thermal wave measurement technique is then used on the cross sections to characterize the density of subsurface microcracks associated with scratching. Compared to a fine-grain silicon nitride, the density of microcracks in a course-grain silicon nitride is significantly larger, while the grinding force is smaller. The smaller grinding force for the coarse-grain silicon nitride is attributed to the ease of local intergranular microfracture and grain dislodgement during grinding.

A modified Pechini process has been successfully developed for preparation of thin films of La1−zSrzCo1−yFeyO3−x (LSCF) on both dense and porous substrates. Results indicatc that the most important processing parameter is the ratio of the polymerization/complexation agent to metal ions. Ceramic films derived from solutions with a relatively low ratio of citric acid to metal ions are usually cracked, while films derived from solutions with a relatively high ratio are crack-free and uniform. The use of ethylenediamine as an additional chelating agent further improves film quality, especially the adhesion and uniformity of the films. A single coating of solution typically yields a ceramic film of thickness about 0.4 μm, and thicker films can be prepared by application of successive coatings. For deposition of thin-film membranes on a porous substrate, however, it is necessary to modify the surface of the porous substrate in order to prevent solution from infiltrating into the pores due to capillary force, and to prevent oxide films from cracking due to surface roughness. The application of an intermediate polymer film to the surfaces of porous substrates has effectively overcome the problems and has resulted in uniform, nonporous membranes of LSCF on porous substrates. Successful deposition of thin-film ceramic membranes on porous substrates is important to fabrication of various ionic and micro-ionic devices based on ceramic thin films.

Single layer Pb(Zr0.53Ti0.47)O3 films up to 0.7 μm thick have been prepared from air-stable titanium and zirconium precursors using a diol-based sol-gel route. Information on film crystallization, surface microstructure, and electrical properties under different firing temperatures and three different heating rates including rapid thermal annealing are presented. Films exhibited (111) preferred orientation, the extent of which reduced with increasing firing temperature or heating rate. It is possible that a PbPtx interfacial reaction product was formed during the prefiring step at 350 °C and this, together with the influence of the 111 bottom platinum electrode, contributed to (111) orientation in the PZT films. Surface microstructure was also influenced by firing temperature and heating rate as well as by film thickness. The 0.4 μm thick films used for electrical measurement had a grain size of ⋚0.1 μm, whereas 0.7 μm thick films made from concentrated sols exhibited “rosette” microstructures with grain sizes up to 0.5 μm. Among the three firing schedules studied, directly inserting the gel coatings in a furnace preset at 700 °C produced films with the most favorable electrical properties. A 0.4 μm thick film gave rise to a remanent polarization, Pr, of 33 μC cm−2 coercive field, Ec, of 46 kV cm−1; relative permittivity, ∊r, of 1100; and dissipation factor, D, of 0.05. For a 0.7 μm single layer film, the respective values were 21 μC cm−2, 36 kV cm−1, 1300, and 0.05.

The oxidation behavior of reaction-formed silicon carbide (RFSC) ceramics was investigated in the temperature range of 1100 to 1400 °C. The oxidation weight change was recorded by TGA; the oxidized materials were examined by light and electron microscopy, and the oxidation product by x-ray diffraction analysis (XRD). The materials exhibited initial weight loss, followed by passive weight gain (with enhanced parabolic rates, kp), and ending with a negative (logarithmic) deviation from the parabolic law. The weight loss arose from the oxidation of residual carbon, and the enhanced kp values from internal oxidation and the oxidation of residual silicon, while the logarithmic kinetics is thought to have resulted from crystallization of the oxide. The presence of a small amount of MoSi2 in the RFSC material caused a further increase in the oxidation rate. The only solid oxidation product for all temperatures studied was silica.