We have investigated how ion irradiation can selectively promote the formation of dense sp3-bonded cubic boron nitride (cBN) over the graphite-like sp2-bonded phases. We have conducted a series of experiments using ion-assisted pulsed laser deposition in which either the ion mass (mion) or ion energy (E) was varied in conjunction with the ratio of ion flux to depositing atom flux (J/a). For a fixed ion energy and mass, there is a critical J/a above which cBN formation is initiated, a window of J/a values in which large cBN percentages are obtained, and a point at which J/a is so large that the resputter and deposition rates balance and there is no net film deposition, in agreement with Kester and Messier. As do Kester and Messier, we find that cBN formation is controlled by a combination of experimental parameters that scale with the momentum of the ions. However, unlike Kester and Messier, we do not find that cBN formation scales with the maximum momentum that can be transferred in a single binary collision, as either incorrectly formulated by Targove and Macleod and used by Kester and Messier, or as correctly formulated. Instead we observe that cBN formation best scales with the total momentum of the incident ions, (mionE)1/2. We also consider the mechanistic origins of this (mionE)1/2 dependence. Computer simulations of the interaction of ions with BN show that cBN formation cannot be simply scaled to parameters such as the number of atomic displacements or the number of vacancies produced by the ion irradiation. A critical examination of the literature shows that none of the proposed models satisfactorily accounts for the observed (mionE)1/2 dependence. We present a quantitative model that describes the generation of stress during ion-assisted film growth. The model invokes a kinetic approach to defect production and loss. We apply a simplified version of the model to cBN synthesis, and find that it predicts an approximate (mionE)1/2 dependence for cBN formation.

Free-standing CVD diamond disk-shaped films of varying thicknesses between ∼40 and 1000 μm were fractured in ball-on-ring flexure using a high-precision hydraulic testing machine. Some of the films were smooth on the side formerly in contact with the substrate and rough (large crystallites) on the reverse side and some of the films were polished. Raman spectroscopic examination showed some of the films to be of high quality and others to be of lower quality (higher levels of non-diamond carbon mixed with diamond phase). All fracture surfaces were examined to identify the origin of failure. Strength varied between 650 and 971 MPa, and the fracture toughness was determined from fracture surface analysis to average 8 ± 1 MPam1/2.

Epitaxial lead lanthanum zirconate titanate [PLZT(9/50/50)] thin films were fabricated on various single crystal substrates using the spin coating of metallo-organic solutions. The films were heat-treated at 700 °C for 1 h using the direct insertion method. The films were epitaxially grown with (100), (100), and (110) being parallel to the SrTiO3(100), the MgO(100), and the sapphire (0112) substrates, respectively. The epitaxy of the films was investigated using x-ray diffraction, pole figures, rocking curves, and scanning electron microscopy.

A method that determines the work done in shearing atom pairs straddling the slip plane, Φ, during emission of dislocations from a crack tip in an atomic model is presented. The model is based on an EAM-type potential for nickel. The dislocations are emitted as partials, and the disregistry, Δ, across the slip plane is found to be fit accurately by a simple arctan function of position for each partial. The width of the partials is also found to remain essentially constant as they are emitted and move away from the crack tip. Rice's unstable stacking energy is extracted from the Φ - Δ curves for the atom pairs along the slip plane and is observed to vary somewhat, particularly near the crack tip. In addition to the Φ (Δ) at points on the slip plane, the total work done on the entire slip plane is determined as a function of the dislocation position in the spirit of the Peierls approach. The derivative of this total work with respect to dislocation position leads to the lattice resistance, ŝr. The first partial dislocation to be emitted experiences a maximum in ŝr at about 0.2 nm from the crack tip, and several contributions to the overall resistance can be identified including the creation of a new surface at the tip as emission occurs, the creation of stacking fault as the dislocation glides away from the tip, and a small but discernible periodic component with a period related to the lattice. A string of hydrogen interstitials is introduced at various locations in the lattice and its effect on Δ, Φ - Δ curves along the slip plane, and the lattice resistance is examined. A substantial effect on the unstable stacking energy results as the dislocation passes an interstitial on the slip plane, but the effect of an interstitial on the resistance to dislocation emission expressed in terms of the maximum ŝr is small and then only if it is confined to a region very near the crack tip. The significance of these results is discussed together with some additional observations including dislocation pinning on the interstitials.

Using x-ray and neutron diffraction data, the degree of order of the octahedral site cations has been determined for the perovskites Sr2AlNbO6 and Sr2AlTaO6, which have been prepared by several different methods and annealed at temperatures up to 1690 °C. The degree of order generally increases with increasing synthesis temperature. The amount of cation ordering is, therefore, primarily controlled by kinetic processes and not by thermodynamic equilibrium considerations. Increased order obtained with increased heating time confirms this general kinetic limitation on the degree of order. However, annealing Sr2AlNbO6 in the highest temperature region resulted in some decrease in order, presumably due to thermodynamic considerations. The cubic edge of both compounds decreases significantly with increasing order. Ordered domains are separated by antiphase boundaries which occur in high concentrations. The cubic cell edge within the ordered domains is significantly smaller than the overall cell edge when the concentration of antiphase boundaries is high. The antiphase boundaries cause significant lattice strain which generally decreases as the concentration of antiphase boundaries decreases. Results on other A2M3+M5+O6 systems are briefly presented.

A microstructural characterization of the La2−xSrxNiO4+δ (0 ⋚ x ⋚ 1) system, prepared with accurate control of the oxygen content, has been performed. The electron diffraction study shows the evolution of the accommodation of compositional variations as a function of δ. For δ > 0.06, interstitial oxygens are ordered, leading to new K2NiF4 superstructural types. Samples with δ < 0.06 accommodate the nonstoichiometry by means of random distribution of anionic vacancies.

Metallization of ceramic substrates by laser activation and subsequent electroless deposition has been demonstrated recently in aluminum nitride and alumina. However, the bond strength between the electroless copper and the ceiamic substrate is weak (less than 14 MPa). Low temperature annealing of electroless copper films deposited on substrates activated at low laser energies strongly increases the adhesion strength. The effectiveness of the annealing for improving the metal-ceramic bonding is dependent upon the laser treatment performed on the substrate prior to deposition. Faster deposition kinetics are obtained for both substrates by increasing the laser energy density. On the other hand, an increase in the laser energy density leads to poor adhesion strengths. The dislocation microstructure produced during laser irradiation in aluminum nitride is analyzed as a possible cause of laser activation. Free aluminum produced by laser irradiation of aluminum nitride and of alumina is discussed as another factor of laser activation. The chemical and microstructural changes taking place in the near-surface region as a consequence of laser-induced processes are correlated with adhesion enhancement promoted by the annealing treatment.

Fatigue damage in a mica-containing glass-ceramic is examined using Hertzian contact tests. For the material in its base glass state, such tests indicate that fatigue occurs solely by chemically enhanced cone crack extension. In the glass-ceramic, fatigue is evident as an expansion of a macroscopic subsurface microfracture zone. Comparative observations of the subsurface damage in static and cyclic loading, and tests in different environments, indicate that the fatigue in the glass-ceramic is mechanical in origin, although it is enhanced by moisture. This result is reinforced by load-point-displacement data, which reveal significant hysteresis in the glass-ceramic but not in the base glass. Flexure tests on Hertz-indented glass-ceramic specimens show only a slight loss of strength, <5%, over 105 cycles. This contrasts with the base glass which, although of higher laboratory strength, is subject to abrupt and severe strength degradation from cone crack pop-in. High magnification examination of the subsurface damage in the glass-ceramic suggests the underlying cause of the mechanical fatigue mechanism to be attrition of frictional tractions at closed microcrack interfaces.

EPR and magnetization measurements of La2NiO4 samples prepared by two different methods are discussed. From the comparison with magnetization and EPR properties of metallic nickel it can be concluded that the sample prepared by the ceramic method is contaminated with ∼ 1% of metallic nickel whereas no evidence of contamination is found in a sample prepared by the so-called liquid-mix technique.

The growth behavior of Pb2+-containing ferroelectric thin films has been systematically examined. The kinetics of the formation of perovskite phase were successfully enhanced by using a material containing no Zr4+-ions, viz., Pb0.95La0.05Ti0.9875O3 (PLT) films, and by utilizing platinum coating on silicon substrate. Meanwhile, the formation of TiO2 phase (rutile) on PLT/Pt(Si) films has been observed and was ascribed to both the outward diffusion of Ti4+-ions from the Ti-layer underneath the Pt-coating and the loss of Pb2+-ions on the surface of the films. The perovskite materials, which were free of either pyrochlore, Zr-rich phase, or TiO2 phase, can be obtained by in situ depositing the PLT films at 450 °C substrate temperature and 1 mbar oxygen pressure. Thus obtained thin films possessed high dielectric constant, ∊r = 1346 and tan δ = 0.071 at 10 kHz, and large charge storage density, Qc = 5.4 μC/cm2 at 50 kV/cm.

SiO2 films, formed by spin coating acid-catalyzed TEOS-based sol-gel on Si substrates, were annealed at 300–1000 °C and analyzed using ellipsometry, FTIR, and in situ stress measurements. Film porosity ranged from an average of 28% before annealing to 7% after annealing 3 h at 1000 °C. Below ≍800 °C, water and silanol removal caused a decrease in refractive index and increase in the in-plane tensile stress. Infrared spectra indicated compressive strain normal to the plane, however. Above ≍800 °C, further densification and structural relaxation occurred. Exposure to H2O also caused relaxation after annealing, as the most compressed Si–O–Si units reacted preferentially with moisture.

A multilayer composite of an oxide superconductor and a compositional gradient layer composite of a ferrite chip component was prepared by the aerosol filtration method. Homogeneous, minute, and arbitrary control of the composition profile was possible for the multilayer composite of the Bi system superconductor. High controllability for designing the composition profile of the compositional gradient layer of nickel zinc ferrite was confirmed by EPMA analysis.

This work has been motivated by the current interest in using fullerenes as a possible reinforcement in structural materials. The fullerenes (of which C60 is the most common) are nanometer in size and have been observed to be stable in contact with various metal systems. Therefore, they offer a nanosize reinforcement that is lightweight and hollow. In this research the emphasis was on processing metals with fullerene additions where the fullerenes were dispersed throughout the metal. Various processing approaches were employed to produce nanocrystalline materials, thin films, and powder-processed composites. Indications are that fullerenes remained unaltered with each processing approach in matrices of tin, copper, and aluminum. A key aspect of the processing of metals containing dispersed fullerenes was the use of fullerene sublimation. Along with the various processing methods identified, the methods of characterizing the fullerenes in the metals were also identified.

The flocculation of an unstabilized suspension of fine ceramic particles is advanced as the explanation for the formation of cracks in a “liquid” suspension. The development of cracks was observed several minutes after reheating wax-based ceramic moldings above the melting point of the wax and was accompanied by phase separation of the wax from the molding. Calculations of the acceleration of particles under London dispersion forces in a viscous fluid show the “time to impact” as a function of initial separation distance, fluid viscosity, and particle size. This is compared with the intercollision time calculated from classical flocculation theory, and it is shown that for crowded suspensions initial interparticle distances are such that the London force field cannot be neglected. Methods of preventing the flocculation are described.

Thin films of BaTiO3 deposited on (100)LaAlO3 substrate by metal-organic chemical vapor deposition (MOCVD) are investigated using several electron-optical techniques. Combined high resolution transmission electron microscopy (HRTEM), electron energy loss spectrometry (EELS), and convergent beam electron diffraction (CBED) indicate a substantial influence of lattice strain on the structural and optical characteristics of BaTiO3 films. Spatially resolved EELS and CBED studies indicate that the substrate influence persists up to about 40 nm away from the interface. The changes in the dielectric function of the films, as inferred from spatially resolved EELS, appear to correlate well with internal lattice strain in the films as deduced from convergent beam electron diffraction (CBED).

We describe a growth mechanism of CVD diamond films consisting of a series of surface reactions. It is derived from experimental observations of a sequential deposition process in which incident carbon flux and atomic hydrogen flux were independently varied. In this sequential process, film growth rate increased with atomic hydrogen exposure, and a saturation in the utilization of carbon was observed. These features are consistent with a surface growth process consisting of the following steps: (i) the carburization of the diamond surface, (ii) the deposition of highly disordered carbon on top of this surface, (iii) the etching of disordered carbon by atomic hydrogen, (iv) the conversion of the carburized diamond surface to diamond at growth sites by atomic hydrogen, and (v) the carburization of newly grown diamond surface. The nature of the growth sites on the diamond surface has not been determined experimentally, and the existence of the carburized surface layer has not been demonstrated experimentally. The surface growth mechanism is the only one consistent with the growth observed in conventional diamond reactors and the sequential reactor, while precluding the necessity of gas phase precursors.

Chromium-carbon coatings have been deposited on various substrates by direct sputtering of a chromium carbide, Cr3C2, target in pure argon atmosphere. The composition of coatings determined by Rutherford backscattering spectroscopy and the deposition rate were investigated as functions of the sputtering gas pressure and self-bias voltage applied to substrates. The atom number ratio C/Cr in the coatings was equal to 0.7 regardless of the deposition conditions investigated. Oxygen and argon atoms were the major impurities incorporated in the amorphous coatings. Oxygen-free Cr-C coatings were prepared at low argon pressures or on substrates biased to a voltage in the range −100 to −320 V. The Cr-C coatings deposited on biased substrates contained less than 2 at. % of argon. The morphological features of Cr-C coatings examined by scanning electron microscopy were also dependent on the sputtering gas pressure and bias voltage of substrates. Fully dense structures were observed for coatings deposited at low argon pressures or on biased substrates. The electrical resistivity of Cr-C coatings was extremely dependent on the concentration of oxygen atoms incorporated in the coatings. Oxygen-free Cr-C coatings exhibited electrical resistivity values as low as 120 μΩ cm, i.e., less than twice the bulk resistivity of Cr3C2. The residual stresses in the coatings and microhardness of the deposited material were also investigated as functions of the deposition parameters. Tensile residual stresses were lower than 0.8 GPa, and the maximum microhardness of coatings was about 13000 MPa, i.e., similar to that of the bulk material.

Thin films of potassium tantalate niobate (KTN) were prepared by means of pulsed excimer-laser deposition and investigated with a number of analytical techniques, including electrical and electro-optical measurements. For applications in longitudinal electro-optic modulators, a transparent electrode is required between substrate and electro-optic layers. Suitable electrode materials, which at the same time permit epitaxial growth of KTN, were identified and prepared. The resulting layered samples were not only of good epitaxial and optical quality, but also exhibited the expected maximum of the longitudinal electro-optic effect at temperatures between the phase transitions from cubic to tetragonal and from tetragonal to orthorhombic. However, the maximum achievable electro-optic phase shift was found to be limited to roughly τ/100 for KTN films in the thickness range around 1 μm. Therefore, much thicker films are probably necessary for most practical applications, which requires significant improvements in the long-term stability and homogeneity of the deposition process.

Hydroxyapatite ceramics have been fabricated by microwave sintering in a 500 W microwave oven. Circular-plate specimens of various green densities were sintered in the oven at 1200 and 1300 °C, for 5, 10, and 20 min, respectively. Ceramics with density up to 97% of the theoretical were obtained. Density, grain size, microstructure, and strength of the ceramics sintered by microwave and by conventional methods were compared. The results show that microwave sintering of hydroxyapatite is not only highly efficient in saving time and energy, but can also improve the microstructure and thus enhance mechanical strength of the ceramics.

The lanthanum-rich calcium lanthanum sulfide (CLS) was formed by a carbonate coprecipitating method followed by sulfurizing in a CS2 atmosphere at 950 °C for 3 h sulfurization. This powder then was densified by hot-press sintering at the temperature range from 1050 to 1150 °C for 0.5-2 h. The sintered pellets were resulfurized in a CS2 atmosphere at 950 °C for 1 h to restore the sulfur loss. The pellet sintered at 1050 °C for 0.5 h with 1.3 mm thickness had about 46% transmission at 13 μm.