Using a prehydrolysis technique, transparent gels with very high aluminum content can be achieved with the use of isopropanol. Here 13C, 27Al, 29Si and 17O NMR at various stages of preparation show that when the aluminum added exceeds the number that silanols can fully protect, the excess aluminum alkoxide groups readily undergo transesterification with isopropanol. The aluminum isopropoxide (Al–OPri) groups thus formed are shown to be sufficiently stable that attack by water is impeded, thus allowing the remaining silicon alkoxide groups to hydrolyze and condense to form a homogeneous gel.

Small additions of Bi2O3 or bismuth titanate improve the dielectric properties of Ba4.5Nd9Ti18O54 at microwave frequencies. It was found that Bi3+ can replace Nd3+ up to 15 mol%, the limiting composition of solid solution being Ba4.5(Nd0.85Bi0.15)9Ti18O54. At the solid solution limit the temperature coefficient of resonant frequency attains its minimum value. The modified ceramic is distinguished by high permittivity of 99 and a Q-value of 5500. The temperature coefficient of resonant frequency is low, 15 ppm/K. After exceeding the solid solubility limit, additional Bi2O3 concentrates as a Bi-rich phase at the grain boundaries, causing considerable reduction of the Q-value and an increase of τf.

A fast-firing technique for the sintering of lead magnesium niobate relaxor ceramics at relatively low temperature has been described. In this process, the samples containing excess PbO (up to 5 wt. %) are directly introduced into a furnace maintained at a temperature of 950 °C and kept there for 15–80 min, followed by a postsintering annealing treatment at 800 °C for 10 h. The importance of fast heating as well as annealing treatment has been justified. The sintered samples are near-phase-pure perovskite materials showing high bulk densities (>94%), uniform and dense microstructure, and satisfactory dielectric properties (Kmax > 13,000). The technique is simple and economic, does not require any controlled atmosphere, and minimizes hazards from lead volatilization.

Thermal waves are used to image damage accumulation digitally beneath Hertzian contacts in ceramics. Alumina ceramics over a range of grain size 3–48 μm are used in a case study. The nature of the images changes with increasing alumina grain size, reflecting a transition in damage mode from well-defined cone fracture in the finer-grain materials to distributed subsurface microfracture in the coarser-grain materials. Quantitative determinations of microcrack densities are evaluated in the latter case by deconvoluting thermal diffusivities from the image data. These determinations confirm the grain-size dependence of degree of damage predicted by fracture mechanics models. Potential advantages and disadvantages of thermal waves as a route to damage characterization in ceramic systems are discussed.

Two techniques are described for synthesizing nanometer-sized TiB2 particles by gas-phase combustion reactions of sodium vapor with TiCl4 and BCl3: a low-pressure, low-temperature burner and a high-temperature flow reactor. Both methods produce TiB2 particles that are less than 15 nm in diameter. The combustion by-product, NaCl, is efficiently removed from the TiB2 by water washing or vacuum sublimation. Material collected from the low-temperature burner and annealed at 1000 °C consists of loosely agglomerated particles 20 to 100 nm in size. Washed material from the high-temperature flow reactor consists of necked agglomerates of 3 to 15 nm particles. A thermodynamic analysis of the Ti/B/Cl/Na system indicates that near 100% yields of TiB2 are possible with appropriate reactant concentrations, pressures, and temperatures.

TiB2 and TiB2/FeB composites have been formed at temperatures below 1000 °C, directly from ilmenite sand by reaction with amorphous boron. The structural transformations occurring during high-energy mechanical milling pretreatment and subsequent annealing of different mixtures of the constituents have been studied. On heating at temperature below 800 °C, complete borothermic reduction of the ilmenite structure is accomplished. The mixture so obtained with an ilmenite-boron ratio equal to 1/6 undergoes a sequence of reactions on further heating to form TiB2, FeB, and the amorphous phase B2O2.

Porous resorbable Ca–P–O glassceramic tooth roots based on calcium biphosphate were prepared by loose-powder-sintering then crystallization-annealing. The glass composition is, by weight, CaO/(CaO + P2O5) = 0.33. The sintering behavior of the glass can be described by a conventional viscous flow model. The resultant glassceramic has a pore size of 6 to 36 μm, depending on starting particle size and sintering temperature, while the pore size distribution is independent of sintering time. The flexural strength is 33 to 150 MPa depending mostly on crystallization-annealing treatment. The crystalline phases are β−Ca2P2O7 and CaP2O6. After being implanted into rabbits, these porous implants show remarkable biocompatibility and induce the ingrowth of new bone within 30 days. They are partly resorbed after 90 days and replaced by new bone. In spite of the original small porosity, the ingrowth of blood vessels and bone cells is abundantly seen after 90 days, due to enlarged pores produced by progressive resorption. This glassceramic is a good candidate for resorbable tooth and bone implants. The loose-powder-sintering technique resulting in intricate bulk shapes with controllable pore size distribution and good machinability as well as adjustable mechanical strength hence is a powerful technique for the preparation of porous glassceramics.

Thin, oriented films of poly-1,4-phenylene (PPP) were prepared with a specially designed reaction vessel. Various kinds of metals were deposited by vacuum evaporation on the PPP substrate, the temperature of which was able to be changed up to 400 °C. Of the studied metals, tellurium and bismuth exhibited the oriented crystallization on it. The oriented overgrowth of tellurium crystallites occurred in the temperature range of 150 °C–200 °C. There were two modes of oriented overgrowths of crystallites in the case of bismuth; one was performed by deposition around room temperature and the other at about 100 °C. The oriented overgrowths of bismuth and tellurium on PPP were examined in terms of the mismatch parameter of the crystal lattice, and it was found that the overgrowths were caused by the lattice matching at the interface between the crystallites of the metals and the PPP substrate.

Results on hydrogenated carbon nitride (CNxHy) thin films grown by reactive magnetron sputtering in a mixed Ar/NH3 discharge are reported. Depending on the growth temperature (Ts) and negative substrate bias voltage (Vs), both the composition and the microstructure were altered. Using nuclear reaction analysis and resonant backscattering spectroscopy, the maximum N and H content were both 15 at. %. Both the hydrogen and nitrogen content of the films was found to decrease with increasing growth temperature. The results also show pronounced chemical resputtering effects, resulting in no net film growth for Vs > 75–100 V. X-ray photoelectron spectroscopy showed no signs of N bound to sp3 hybridized C. Also, the microstructure of the films was found to change with Ts. For Ts < 150 °C, a structure with crystalline clusters embedded in an “fullerene-like” matrix was observed by high-resolution transmission electron microscopy. Power-spectra obtained from the clusters could be identified with the cubic diamond structure. For Ts ≥ 300 °C, no crystalline clusters were found and the films had a homogeneous “fullerene-like” microstructure with strongly bent planes and closed shell-like features resembling bucky-onions. Evaluation of nanoindentation results from the homogeneous “fullerene-like” films gave hardness values between 7 and 11 GPa and elastic recoveries of 55–60%. This should be compared with hardness and elastic recoveries of 40–60 GPa and 85–90%, respectively, previously reported for on nonhydrogenated carbon nitride CNx films grown under the same conditions, but in pure N2 discharges.

Near stoichiometric titanium nitride (TiN) was deposited from tetrakis(dimethylamido)titanium (TDMAT) and ammonia using atmospheric pressure chemical vapor deposition. Experiments were conducted in a belt furnace; static experiments provided kinetic data and continuous operation uniformly coated 150-mm substrates. Growth rate, stoichiometry, and resistivity are examined as functions of deposition temperature (190−420 °C), ammonia flow relative to TDMAT (0−30), and total gas-flow rate (residence time 0.3−0.6 s). Films were characterized by sheet resistance measurements, Rutherford Backscattering Spectrometry, and X-Ray Photoelectron Spectrometry. Films deposited without ammonia were substoichiometric (N/Ti, 0.6−0.75), contained high levels of carbon (C/Ti = 0.25−0.40) and oxygen (O/Ti = 0.6−0.9), and grew slowly. Small amounts of ammonia (NH3/TDMAT ≥ 1) brought impurity levels down to C/Ti, 0.1 and O/Ti = 0.3−0.5. Ammonia increased the growth rates by a factor of 4−12 at temperatures below 400 °C. Films 500 Å thick had resistivities as low as 1600 μΩ-cm when deposited at 280 °C and 1500 μΩ-cm when deposited at 370 °C. Scanning electron micrographs indicate a smooth surface and poor step coverage for films deposited with high ammonia concentrations.

Heteroepitaxial diamond has been successfully deposited on a Si(110) substrate by the microwave plasma chemical vapor deposition method. The pretreatment consisted of carburization and bias-enhanced nucleation steps. Cross-sectional transmission electron microscopy reveals that diamond can be in the cube-on-cube epitaxial relationship with the Si substrate. Various orientation relationships between diamond and Si substrates have also been observed, depending on the location where the plasma applied. Near the center of the plasma, twins were rarely observed in cube-on-cube epitaxial regions. Away from the center of the plasma ball, Σ3 twins are seen first, and then additional Σ9 and Σ27 twins occur near the edge of the plasma. In general, defect density in the epitaxial films is less than that observed in polycrystalline ones. No interlayer could be observed between diamond and silicon. In addition, 2H-type hexagonal diamond has also been found, and is in epitaxy with the Si substrate.

Monocrystalline GaN(0001) thin films have been grown at 950 °C on high-temperature, ≈ 100 nm thick, monocrystalline AlN(0001) buffer layers predeposited at 1100 °C on α(6H)−SiC(0001)Si substrates via OMVPE in a cold-wall, vertical, pancake-style reactor. These films were free of low-angle grain boundaries and the associated oriented domain microstructure. The PL spectra of the GaN films deposited on both vicinal and on-axis substrates revealed strong bound excitonic emission with a FWHM value of 4 meV. The near band-edge emission from films on the vicinal substrates was shifted slightly to a lower energy, indicative of films containing residual tensile stresses. A peak attributed to free excitonic emission was also clearly observed in the on-axis spectrum. Undoped films were too resistive for accurate Hall-effect measurements. Controlled n-type, Si-doping in GaN was achieved for net carrier concentrations ranging from approximately 1 × 1017 cm−3 to 1 × 1020 cm−3. Mg-doped, p-type GaN was achieved with nA−nD ≈ 3 × 1017 cm−3, ρ ≈ 7 Ω · cm, and μ ≈ 3 cm2/V · s. Double-crystal x-ray rocking curve measurements for simultaneously deposited 1.4 μm GaN films revealed FWHM values of 58 and 151 arcsec for deposition on on-axis and off-axis 6H−SiC(0001)Si substrates, respectively. The corresponding FWHM values for the AlN buffer layers were approximately 200 and 400 arcsec, respectively.

A very high vacuum compatible microwave plasma chemical vapor deposition system has been fabricated for the growth of diamond thin films. Microcrystalline diamond thin films have been grown on silicon substrates from the CH4−H2 gas mixture. Scanning electron microscopy and x-ray diffraction have been used to study the surface morphology and the crystallographic structure of the films. Optical emission spectroscopy has been used for the detection of chemical species present in the plasma. The strong dependence of the film microstructure on the intensity of CH emission line has been observed.

We have grown Nb-doped TiO2 epitaxial films on (100) and (110)-oriented TiO2 rutile substrates by molecular beam epitaxy. Nb substitutionally incorporates at cation sites in the rutile lattice, forming NbxTi1−xO2 solid solutions. However, the crystal quality and surface roughness of the films depend strongly on the substrate orientation. Surface roughening and defect formation occur at lower values of x on (100) than on (110). This result is due to anisotropic changes in the metal-oxygen bond lengths within the rutile structure in going from TiO2 to NbO2; there are 1% and 12% changes in the metal atom to octahedron-base oxygen and metal atom to octahedron-vertex oxygen bond lengths, respectively. Every metal atom in the (100) growth surface has in-plane components of the 12% mismatch. However, only half of the metal atoms in the (110) growth plane have such components. Thus, there is substantially larger in-plane lattice mismatch when the growth surface is (100) compared to (110), resulting in surface roughening and formation of defects at a lower doping level for (100)-oriented NbxTi1−xO2 epitaxial films.

Two materials of α-type manganese dioxide were synthesized and examined. They were prepared by the pyrolysis of mixtures of MnCO3 and (CH3)3COK. An ill-ordered material was obtained when prepared at large (CH3)3COK content. Both samples behave as acids, but their apparent capacities are obviously different: about 0.9 meq/g for a well-ordered sample and about 2.6 meq/g for an ill-ordered sample. Ion-exchange properties were examined on Kielland's plot. Zero intersections of the two samples are almost the same but slopes are different (about −50 for a well-ordered sample and about −10 for an ill-ordered sample). The difference in slope is likely caused by the flexibility. An evidence of the flexibility can be seen by x-ray diffractometry.

Rapid, spontaneous infiltration can be achieved by dipping a SiC preform that contains pyrolyzed carbon into an Al–Si alloy bath in an open air environment. The mechanism for infiltration is investigated in the present work by studying the effects of several relevant parameters on the infiltration process. Experimental results have shown that the requirements for rapid spontaneous infiltration are an infiltration temperature higher than 1400 °C, the presence of a pyrolyzed carbon, and the presence of SiC particle in the preforms. The concentration of Si in the alloy does not have significant influence on the infiltration rate, but it strongly affects the resulting microstructures in the infiltrated composites.