Plastic zone evolution in Al–2 wt% Si metal films on silicon and sapphire substrates was studied using nanoindentation and atomic force microscopy (AFM). AFM was used to measure the extent of plastic pileup, which is a measure of the plastic zone radius in the film. It was found that the plastic zone size develops in a self-similar fashion with increasing indenter penetration when normalized by the contact radius, regardless of film hardness or underlying substrate properties. This behavior was used to develop a hardness model that uses the extent of the plastic zone radius to calculate a core region within the indenter contact that is subject to an elevated contact pressure. AFM measurements also indicated that as film thickness decreases, constraint imposed by the indenter and substrate traps the film thereby reducing the pileup volume.

Process parameter dependency on the phase transition from anatase to rutile phase of laser-ablated TiO2 films was investigated. Lower ambient argon pressure, longer deposition time, higher laser fluence, and smaller target–substrate separation give rutile phase from anatase phase at comparatively lower temperature. The relationship between thickness and onset temperature of anatase–rutile transformation can be comprehensively explained in terms of film thickness. Thinner films have higher phase transition temperature. The presence of helium gas during deposition favors the anatase–rutile transition at a temperature lower than that expected from the above relationship.

Aligned fibers of barium and strontium M hexaferrite (BaFe12O19 and SrFe12O19) were manufactured from an aqueous inorganic sol-gel-based spinning process, but halides have been found to be retained up to 1000 °C, inhibiting the formation of the hexagonal ferrite phases. Therefore an investigation was carried out into the removal of the halides at lower temperatures through steaming between 500 and 900 °C/3 h, and the subsequent effects upon microstructure and magnetic properties. The fibers were prefired to 400 °C to remove all organic components, and in all cases the steaming process resulted in loss of alignment of the fibers. It was found that the M phase began to form at only 600 °C, becoming single-phase SrM or virtually pure phase BaM at 700 °C, confirming that halides had indeed delayed M phase formation. Both materials had a grain size below 100 nm, but other unusual surface features not seen before on ferrite fibers were observed. The fibers steamed at 700 °C had Ms and Hc values comparable to random M ferrite fibers fired to 1000 °C in air, while steaming over a temperature range from 400 to 800 °C/3 h gave products with improved magnetic properties, with SrM fibers having an Ms of 81.4 emu g–1 and Hc of 457 kA m−1.

The ball indentation technique has the potential to be an excellent substitute for a standard tensile test, especially in the case of small specimens or property-gradient materials such as welds. In our study, the true stress–true strain relationships of steels with different work-hardening exponents (0.1–0.3) were derived from ball indentations. Four kinds of strain definitions in indentation were attempted: 0.2sinγ, 0.4hc/a, ln[2/(1 + cosγ)], and 0.1tanγ. Here, γ is the contact angle between the indenter and the specimen, hc is the contact depth, and a is the contact radius. Through comparison with the standard data measured by uniaxial tensile testing, the best strain definition was determined to be 0.1tanγ. This new definition of strain, in which tanγ means the shear strain at contact edge, reflected effectively the work-hardening characteristics. In addition, the effects of pileup or sink-in were considered in determining the real contact between the indenter and the specimen from the indentation load–depth curve. The work-hardening exponent was found to be a main factor affecting the pileup/sink-in phenomena of various steels. These phenomena influenced markedly the absolute values of strain and stress in indentation by making the simple traditional relationship Pm/σR ≈ ≈ 3 valid for the fully plastic regime.

A novel sol-gel processing method has been developed to fabricate epitaxial (SrBa)Nb2O6 (SBN) thin films on MgO substrates. It involves the introduction of a SBN self-template layer on MgO by pulsed laser deposition (PLD). Effects of the SBN self-template layer on the structural and morphological properties of the sol-gel-derived SBN films were investigated. Compared to the sol-gel-derived SBN films without a self-template layer, our new technique produces SBN films of excellent epitaxy and more dense grains with uniform distribution. This can be explained by the self-template-layer-induced homoepitaxial growth. The innovative processing method with combination of PLD and sol-gel is a promising technique in preparing high-quality, thick epitaxial SBN films for electro-optics device applications.

Exposure of benzyldimethylketal (BDK)-doped sol-gel hybrid glass films to ultraviolet light produces a refractive index increase up to 43 × 10−3 and an increase in thickness due to photolocking of the BDK into the sol-gel hybrid glass matrix. Thus, single mode ridge waveguides at λ = 1550 nm can be fabricated by direct laser exposure without using photomask and development processes. The slower laser writing speed gives greater refractive index change producing more circular guided mode profiles.

The thermal stability of carbon nitride films, deposited by reactive direct current magnetron sputtering in N2 discharge, was studied for postdeposition annealing temperatures TA up to 1000 °C. Films were grown at temperatures of 100 °C (amorphous structure) and 350 and 550 °C (fullerenelike structure) and were analyzed with respect to thickness, composition, microstructure, bonding structure, and mechanical properties as a function of TA and annealing time. All properties investigated were found to be stable for annealing up to 300 °C for long times (>48 h). For higher TA, nitrogen is lost from the films and graphitization takes place. At TA = 500 °C the graphitization process takes up to 48 h while at TA = 900 °C it takes less than 2 min. A comparison on the evolution of x-ray photoelectron spectroscopy, electron energy loss spectroscopy and Raman spectra during annealing shows that for TA > 800 °C, preferentially pyridinelike N and –C≡N is lost from the films, mainly in the form of molecular N2 and C2N2, while N substituted in graphite is preserved the longest in the structure. Films deposited at the higher temperature exhibit better thermal stability, but annealing at temperatures a few hundred degrees Celsius above the deposition temperature for long times is always detrimental for the mechanical properties of the films.

A new analysis technique for calculating the hardness, modulus, and contact area from indentation data obtained using pyramidal or conical indenters was formulated and compared with another commonly used technique. Experimental data using a Berkovich indenter to indent fused silica and tungsten were examined. In addition, finite element modeling results were used to examine the effectiveness of the analytical techniques when a wide range of materials properties was considered. The new technique relies on the slope of the loading curve rather than the indenter displacement as an input. It is shown that the new technique is far less affected by the deviation of the geometry of the indenter from its intended shape. This effect removes the necessity to have detailed descriptions of the precise tip geometry in some cases. The new technique does not reduce errors associated with pile up of material near the indenter.

Ce1−xNdxO2−δ (x = 0.05 to 0.55) nanocrystalline solid solutions were prepared by a sol-gel route. X-ray diffraction analysis showed that Ce1−xNdxO2−δ crystallized in a cubic fluorite structure. The lattice parameter for the solid solutions increased linearly with the dopant content. The solid solubility of Nd3+ in ceria lattice was determined to be about x = 0.40 in terms of the nearly constant lattice parameters at a dopant level larger than x = 0.40. First-order Raman spectra for Ce1−xNdxO2−δ at a lower dopant content exhibited one band associated with the F2g mode. At higher dopant contents, F2g mode became broadened and asymmetric, and a new broad band appeared at the higher frequency side of the F2g mode. This new band was assigned to the oxygen vacancies. The electron paramagnetic resonance spectrum for x = 0.05 showed the presence of O2− adsorbed on sample surface at g = 2.02 and 2.00 and of Ce3+ with a lower symmetry at g = 1.97 and 1.94. Further increasing dopant content led to the disappearance of the signals for O2−. Impedance spectra showed the bulk and grain boundary conduction in the solid solutions. The bulk conduction exhibited a conductivity maximum and an activation energy minimum with increasing dopant content. Ce0.80Nd0.20O2−δ was determined to give promising conduction properties such as a relatively high conductivity of σ700 °C = 2.44 × 10−2 S cm−1 and moderate activation energy of Ea = 0.802 eV. The variations of conductivity and activation energy were explained in terms of relative content of oxygen vacancies Vö and defect associations {CeCe ′Vö}/{NdCe ′Vö}.

Polymer thick film (PTF) resistors were fabricated using a new laser-based transfer technique called matrix-assisted pulsed laser evaporation direct write (MAPLE-DW). MAPLE-DW is a versatile direct writing technique capable of writing a wide variety of materials on virtually any substrate in air and at room temperature. Epoxy-based PTF resistors spanning four decades of sheet resistances (10 Ω/sq. to 100 kΩ/sq.) were deposited on alumina substrates under ambient conditions. Electrical characteristics of these MAPLE-DW deposited resistors were studied at a wide frequency range (1 MHz to 1.8 GHz), and the results were explained through an equivalent circuit model and impedance spectroscopy. Temperature coefficient of resistance measurements for the PTF resistors were performed between 25 and 125 °C. The results based on the percolation theory were used to explain the temperature dependence of the resistance behavior of the PTF resistors.

The wetting of mullite (3Al2O3 · 2SiO2) by a Y2O3–Al2O3–SiO2 (YAS) glass and by a B2O3–SiO2 (borosilicate) glass was investigated in air as a function of temperature through a sessile drop technique. The wetting behavior was found to be strongly dependent on the glass composition and on the temperature. For the YAS glass, the contact angle showed a rapid decrease from 100° to 20° in the temperature range of 1400 to 1450 °C followed by a more gradual decrease to a value of 10–15° at approximately 1600 °C. In the case of the borosilicate glass, the change in the contact angle with temperature was more uniform, with the value decreasing from 100° to 45° between 1300 and 1600 °C. Microstructural observations of the interfacial region between the solidified sessile drop and the mullite substrate revealed significant corrosion of the interface and penetration into the mullite grain boundaries by the YAS glass. In the case of the borosilicate glass, corrosion was limited and the interface was clearly defined. The consequences of the data for the design of in situ toughened mullite are discussed.

Solid-phase epitaxy was examined in deep amorphous volumes formed in silicon wafers by multi-energy self-implantation through a mask. Crystallization was effected at elevated temperatures with the amorphous volume being transformed at both lateral and vertical interfaces. Sample topology was mapped using an atomic force microscope. Details of the process were clarified with both plan-view and cross-sectional transmission electron microscopy analyses. Crystallization of the amorphous volumes resulted in the incorporation of a surprisingly large number of dislocations. These arose from a variety of sources. Some of the secondary structures were identified to occur uniquely from the crystallization of volumes in this particular geometry.

Hydroxyapatite (HA) coatings with different thicknesses were produced on Ti and Si substrates using the radio frequency magnetron sputtering method. The mechanical properties, for example, modulus and hardness, of the coatings were measured using nanoindentation. The measured values of modulus and hardness were close to the upper limit of that reported for bulk HA, indicating a fully dense structure. Interfacial strengths between the HA coatings and substrates were also evaluated using a nanoscratch technique. The HA–Ti interface appeared to be stronger than the HA–Si interface. The microstructures of the HA coating and the HA–Ti interface were examined using high-resolution electron microscopy. Chemical compositions of the HA coating and the HA–Ti interface were also analyzed using x-ray energy dispersive spectrometer and electron energy loss spectroscopy. The results indicated that the strong HA–Ti bonding is associated with an outward diffusion of Ti into HA layer and concomitant formation of TiO2 at or near the interface.

Microstructures of well-aligned multiwall carbon nanotubes grown on patterned nickel nanodots and uniform thin films by plasma-enhanced chemical vapor deposition have been studied by electron microscopy. It was found that growth of carbon nanotubes on patterned nickel nanodots and uniform thin films is different. During growth of carbon nanotubes, a nickel particle sits at the tip of each nanotube, and its [220] is preferentially oriented along the plasma direction, which can be explained by a channeling effect of ions coming into nickel particles in plasma. The alignment of nanotubes is induced by the electrical field direction relative to substrate surface.

High-temperature fracture behavior of a Yb2O3–SiO2–doped hot-pressed silicon nitride (Si3N4) ceramic was investigated in four-point flexure between 1000 and 1500 °C at five crosshead speeds, using the specimens precracked with three indentation loads. Above 1000 °C, a temperature and stressing rate dependence of fracture stress was seen. At 1200 °C the fracture stress of the precracked specimens increased with decreasing stressing rates due to a toughening effect, the absence of slow crack growth (SCG). However, at 1400 and 1500 °C the fracture stress decreased with decreasing stressing rate. In particular, this dependence was stronger at 1500 °C than at 1400 °C. The SCG was observed only in the specimens precracked with indentation loads of 98 and 196 N. This crack extended with increasing test temperature and/or decreasing stressing rate. The dependence of fracture stress on stressing rate was attributed to a SCG behavior at higher temperatures.

Oxides with significant mesopore volume can be produced from gels through ambient pressure drying (APD) if the oxide network within the gel is sufficiently strong. To obtain a strong alumina gel, a commercial alumina powder (100 nm diameter) was combined with different amounts of ethanol, water, and acid. Significant mesoporosity was observed in dried and calcined gels prepared from this precursor and ethanol alone, particularly when “poor wettability” was established in the gel through azeotropic distillation in toluene. When water (or water and nitric acid) was also utilized the pore volume decreased dramatically; this observation may be attributed to the creation of amorphous alumina from the crystalline precursor that is displaced into the interparticle pores, and in which mesopores are poorly preserved during APD.

Single-crystal thulium phosphide (TmP) was grown heteroepitaxially on (001) GaAs substrates by molecular beam epitaxy with the orientation relationship [100]TmP//[100]GaAs and {001}TmP//{001}GaAs. The crystal properties and the defects in TmP/GaAs, GaAs/TmP/GaAs heterostructure were characterized through x-ray diffraction, atomic force microscopy, and transmission electron microscopy. TmP was found to have a huge difference in thermal expansion coefficient compared GaAs, which produced high tensile residual stress and may result in the formation of defects. The major defects in the top GaAs layer are stacking faults or microtwins, and they directly correlated with the islandlike surface morphology of the GaAs overlayer. The composition profiles of the TmP/GaAs heterostructure were measured by secondary ion mass spectrometry. The reason for surface segregation of Tm and Ga atoms is discussed and is primarily due to their higher diffusion coefficient near the surface as compared to that in the TmP epilayer bulk. The thermally stable characters of the TmP/GaAs heterostructures allow them to be promising candidates in various device applications.

Controlled pyrolysis of polymer ceramic precursors provides a new way of obtaining silicon nitride ceramics with high creep resistance. In this study, crack-free bulk amorphous Si–N–C materials were produced by warm-pressing followed by pyrolysis or alternatively by prepyrolysis and binding followed by pyrolysis. Amorphous compacts were then heat-treated at different temperatures to promote crystallization. High-resolution electron microscopy revealed that, at about 1650 °C, silicon nitride/silicon carbide nanocomposites with a high degree crystallinity can be achieved with grain sizes of about 30 nm. Aside from heterogeneous crystallization, which is closely related to gaseous phase reactions that happen along outer or inner surfaces, homogenous crystallization is responsible for crystallization of the bulk material. Although a certain amount of amorphous Si–N–C usually remains in intergranular regions, clean boundaries free of amorphous interlayers can be observed between grains when they come into contact.

The diffusion characteristics of Mg–rare-earth diffusion couples were studied. Cylinders of pure Mg and rare earth (Dy, Nd, and Pr) were abutted and annealed at 500 °C for 100 h or 300 h. Point-by-point composition profiles were collected starting in pure Mg, across the diffusion zone, and ending in the pure rare earth, using energy dispersive x-ray spectroscopy with a scanning electron microscope. The intermetallic phases that resulted due to diffusion were identified and compared to existing phase diagrams, for which the data is limited. For each diffusion couple, a plot of concentration versus distance perpendicular to the original plane of contact was obtained and analyzed using the Boltzman–Matano method. The interdiffusion coefficients for each set of phases were then calculated. The results show that diffusion through the intermetallic phases is much slower than is expected in a solid solution.

The life of TiN-coated tools can be improved by a post-coating ion implantation treatment, but the mechanism by which this occurs is still not clear. Nitrogen implantation of both physical-vapor-deposited TiN and CVD TiN leads to surface softening as the dose increases, which has been attributed to amorphization. In this study a combination of transmission electron microscopy and atomic force microscopy was used to characterize the microstructure of implanted TiN coatings on cemented carbide for comparison with mechanical property measurements (nanoindentation, residual stress, etc.), made on the same samples. Ion implantation leads to a slight reduction in the grain size of the TiN in the implanted zone, but there is no evidence for amorphization. Surface softening is observed for physical-vapor-deposited TiN, but this is probably due to a combination of changes in surface composition and the presence of a layer of bubbles generated by the very high implantation doses used.