The surface layer of A319 alloy was refined by selective remelting using laser energy. Instrumented indentation technique was used to measure hardness (H) and elastic modulus (E) of the laser-melted layer. Berkovich tip was used to indent the material for 100-nm, 200-nm, 500-nm, and 1000-nm depths. The H and the E were found to be 1.22 GPa and 78.2 GPa, respectively, for 1000-nm indentation depths. The variances associated with H and E were minimal, whereas, the same for substrate possessed significant scattering. Also, H and E increased with decreasing depth of indentation. Closer examination suggested that when the heterogeneity in the material was in the scale of indentation depth, significant scattering took place and the hard phase Si influenced the average hardness. However, the influence of indentation depth on elastic modulus was not statistically significant.

The effects of mesoporous structure on grain growth were investigated in this study. The synthesis was accomplished using block copolymer as the organic template and tungsten chloride as the inorganic precursor. Thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy, x-ray diffractometry (XRD), transmission electron microscopy, and N2 adsorption/desorption isotherms were used to characterize the microstructures obtained for different temperatures. TGA and XRD analyses demonstrate that copolymers were expelled at 150–250 °C, and mesoporous structure was stable up to 350 °C. The pore diameter and the surface area evaluated from the Barrett-Joyner-Halenda model and Brunauer–Emmett–Teller method indicated that the average pore diameter is 4.11 nm and specific surface area is 191.5 m2/g for 250 °C calcination. Arrhenius equation used to calculate the activation energy for grain growth demonstrates that the activation energy for grain growth was about 38.1 kJ/mol before mesostructure collapse and 11.3 kJ/mol after collapse. These results show evidence of two different mechanisms governing the process of grain growth. The presence of the pore can be related to the obstacle for grain growth.

We report the growth of epitaxial nanowire arrays using the technique of glancing- angle deposition with substrate rotation. Epitaxial copper nanowire arrays were deposited on H-terminated Si(110) using electron beam evaporation. The nanowire arrays were characterized by x-ray diffraction, atomic force microscopy, and scanning electron microscopy. Individual nanowires were confirmed to be single crystalline by examination with transmission electron microscopy. The epitaxial growth involves twin formation with the epitaxial orientation relationships: Cu(111)//Si(110) with Cu[110]//Si[001] and Cu[110//Si[001] for each of the twins. As the angle of incidence is increased, Cu grows as isolated columns with a spacing that increases as the angle of incidence is increased. However, the thickness limit for epitaxial growth is reduced as the angle of incidence is increased, and it is reduced to approximately 300 nm for a deposition angle of 75°. The x-ray rocking curves for samples deposited at increasing polar angles show steadily improving crystal orientation up to a deposition angle of about 35°. Beyond 65° deposition angle, the rocking curves show significantly sharper split diffraction peaks indicating that there are distinct orientations. In addition, the split peaks have a much lower full width at half maximum. The observed behavior is explained based on arguments involving unidirectional diffusion arising from adatom parallel momentum.

Effects of loading rate and temperature on tensile behavior have been studied in air using two kinds of orthogonal three-dimensional woven Si–Ti–C–O fiber-reinforced Si–Ti–C–O matrix composites, processed by polymer infiltration and pyrolysis (PIP) and chemical vapor infiltration (CVI). Since the interphase and porosity of the two composites are controlled in as similar a manner as possible, the effect of matrix processing method is understood. The strength of the PIP composite is greater than that of the CVI composite at room temperature, but they are almost the same at high temperatures. It was found that the PIP composite is more sensitive to loading rate than the CVI composite due to more glassy phases in the PIP composite.

A novel approach in determining the transition temperatures of NiTi shape memory alloys was investigated and compared with conventional techniques. The technique is based on microthemal analysis using a scanning thermal microscope (SThM). In particular, this method has the potential to allow the transformation temperatures of thin films to be investigated in situ. Thin film shape memory alloys have potential applications, such as microactuators, where conventional analysis techniques are either not directly applicable to such samples or are difficult to perform.

This paper analyses the influence of the inner structure of a SiO2 coating deposited on SiC particles by a sol-gel route on reactivity and wettability between SiC particles and molten aluminium during composite manufacturing. Different heat treatments were applied to the sol-gel coatings to change the porous structure of the amorphous silica. The coatings subjected to the mildest heat treatment were more reactive with molten aluminium, enriching the Si content of the matrix composite, and hence inhibiting direct reaction of the SiC particles and the formation of aluminium carbide. Thermal analysis showed that Si enrichment altered the solidification behavior of the aluminium matrix and its resultant microstructure, influencing the manufacturing conditions and final properties of the fabricated composites.

Al2O3-dispersed Yb2O3-stabilized cubic-ZrO2 (YbSZ) composites are fabricated by pressureless sintering of composite powders to obtain fine and homogeneous microstructures by the solution chemistry route. Al2O3 particles are deposited on ZrO2 powders by the precipitation of aluminum nitrate followed by calcination in air. The sinterability of the composites was affected by the calcination temperature. Microstructures of the sintered bodies are dependent on the Al2O3 content. For the5 vol% Al2O3-dispersed composite, fine Al2O3 particles were mainly located insidethe grains of zirconia, whereas relatively large Al2O3 particles almost dispersed at the grain boundaries when the Al2O3 content was increased. The grain growth of YbSZ was suppressed by the Al2O3 addition, and the refinement of the matrix grain improved the fracture strength of YbSZ. The YbSZ and YbSZ/Al2O3 composites exhibited almost similar ionic conductivity at high temperatures of around 1000 °C.

Influences of the continuity of the matrix on Young's modulus and tensile strength of unidirectional SiC/SiC mini-composite prepared by the polymer impregnation and pyrolysis method were studied experimentally by observation of appearance of matrix and tensile test and analytically by a shear lag–Monte Carlo simulation. The continuity of the matrix was improved by the addition of particles such as ZrSiO4, barium magnesium aluminosilicate, and Pyrex (borosilicate glass) into the matrix. The improved continuity of the matrix led to the increase in stress carrying capacity of the matrix and therefore to the increase in Young's modulus and tensile strength of the composite. Such a correlation between the continuity of the matrix and the property of the composite was verified numerically by the shear lag–Monte Carlo simulation.

Under prolonged electron-beam exposure, perovskite-structured SrTiO3:Pr,Al,Ga (STO) phosphor can be easily reduced due to oxygen loss. In particular, it is well known that dissociative H2O molecules are well adsorbed on reduced STO surfaces. The hydroxyl species produced by such dissociative adsorption of H2O strongly decompose organic compounds chemisorbed on the surface from vacuum ambient used in display devices into carbon species due to the photocatalytic properties of STO. Consequently, it is very likely that this mechanism attributes to the larger amounts of carbon adsorption by electron-stimulated chemical reactions on the STO phosphor surface than other phosphors.

The definitions of hardness from nanoscratch and nanoindentation analyses with a spherical indenter were compared and shown to be mathematically equivalent for the case of zero interface shear stress (surface traction). The definition of nanoindentation hardness was taken as the ratio of the resultant force to the area of contact projected on a plane normal to the line of action of the resultant force, whereas in the case of the nanoscratch technique, the hardness and interfacial shear stress were related to the measured normal and lateral forces in a nanoscratch experiment, as well as to the cross-sectional area of the groove. The two definitions of hardness were then applied to nanoscratch experimental data from material systems covering a wide range of hardness values. The calculated values of hardness from the two definitions were based on the contact area, determined from the scratch residual profile and the elastic recovery of the plastically deformed surface, and yielded the same values of hardness within experimental error. The contact angle, and thus the contact area, was shown experimentally to be sensitive to interface shear stress: a positive increase in interface shear stress led to a reduction in contact area as compared to the case of a frictionless contact. For a material with given hardness, normal indenter force, and contact area, a positive or negative interface shear stress is balanced by a positive or negative change, respectively, in the lateral force about the value needed to maintain a static balance for a frictionless nanoscratch contact. A comparison of these effects with experimental data indicates that very hard materials tend to have negative to zero interface shear stress, which correlates to a sink-in effect, whereas the soft materials tend to have positive interface shear stress, which correlates to a pileup effect.

Dislocation–interface interactions in Fe–0.4 wt% C tempered martensitic steel were studied through in situ nanoindentation in a transmission electron microscope (TEM). Two types of boundaries were imaged in the dislocated martensitic structure: a low-angle (probable) lath boundary and a coherent, high-angle (probable) block boundary. In the case of a low-angle grain boundary, the dislocations induced by the indenter piled up against the boundary. As the indenter penetrated further, a critical stress appeared to have been reached, and a high density of dislocations was suddenly emitted on the far side of the grain boundary into the adjacent grain. In the case of the high-angle grain boundary, the numerous dislocations that were produced by the indentation were simply absorbed into the boundary, with no indication of pileup or the transmission of strain. This surprising observation is interpreted on the basis of the crystallography of the block boundary.

Microstructures and morphological features of a series of sintered quasicrystalline Al62.5−xCu25.3Fe12.2Bx alloys, with x ranging from 0 to 5 at.% were studied using x-ray diffraction, scanning electron microscopy, x-ray mapping, and electron probe microanalysis. Electron backscattering diffraction (EBSD) was also used to get information about the structures of some phases and identify the crystalline relationship in-between phases. Increasing x results in the change of the nature of extra phases. These secondary phases are all less than 1% in volume of the total matter except for the β phase at 5% of boron. Whatever the percentage of boron considered, boron seems to concentrate essentially in the parasite phases confirming doubts found in literature about the solubility of boron inside the face-centered-icosahedral Al–Cu–Fe phase. No special crystallographic relationship in between the tested phases could be spotted. EBSD is thus also confirmed as an excellent technique to get quasicrystalline grains orientations.

The dielectric, ferroelectric, and piezoelectric properties of (001) BiScO3–PbTiO3 epitaxial films near the morphotropic phase boundary were investigated. Epitaxial films, 1-μm thick, were grown on (100) SrRuO3/(100) LaAlO3 substrates by pulsed laser deposition from a BiScO3–PbTiO3 (40/60) ceramic target. The films had room temperature dielectric constant of 850, tanδ = 0.08, and maximum dielectric constant of 5530 at 455 °C. Well-saturated hysteresis loops with a remanent polarization of 42 μC/cm2 and a coercive field of 75 kV/cm were observed. The effective transverse piezoelectric coefficient e31,f was −12 C/m2. This result is quite encouraging for sensor and actuator device development because the observed piezoelectric properties are as good as (001) oriented Pb(Zr,Ti)O3 films (e31,f ∼ –12 C/m2) while the transition temperature is 100 °C higher.

Nanoindentation test at scale of hundreds of nanometers has shown that measured hardness increases strongly with decreasing indent depth, which is frequently referred to as the size effect. Usually, the size effect is displayed in the hardness-depth curves. In this study, the size effect is characterized in both the load–displacement curves and the hardness–depth curves. The experimental measurements were performed for single-crystal copper specimen and for surface-nanocrystallized Al-alloy specimen. Moreover, the size effect was characterized using the dislocation density theory. To investigate effects of some environmental factors, such as the effect of surface roughness and the effect of indenter tip curvature, the specimen surface profile and the indentation imprint profile for single-crystal copper specimen were scanned and measured using the atomic force microscopy technique. Furthermore, the size effect was characterized and analyzed when the effect of the specimen surface roughness was considered.

Sol-gel derived catalyst systems of cobalt, nickel, and iron were used in the growth of gallium nitride (GaN) nanowires by thermal chemical vapor deposition. A diffusion barrier matrix of titania (TiO2) has been used in which the catalysts were dispersed to have control of the catalyst particle sizes and hence on the size and morphology of the GaN nanowires. This single-step and cost-effective processing of the catalyst bed produced good-quality GaN naowires with comparable structural and optical properties with those previously reported. In a particular case, a stress-induced cubic admixture to the otherwise hexagonal structural symmetry was observed. The samples were characterized by high-resolution scanning electron microscopy, x-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, and cathodo-luminescence studies.

Oxides and silicates of zirconium and hafnium are actively being considered and tested to replace SiO2 as the gate material. Though these materials have the high-dielectric constant (k ∼ 20–25) needed to provide a larger equivalent oxide thickness, they are very refractory and difficult to etch by wet and dry methods. In this paper, work done on wet etching of ZrO2, HfO2, and HfSixOy in dilute hydrofluoric acid (HF) solutions is presented and discussed. Experiments were done on various high-k films deposited by metalorganic chemical vapor deposition. It was found that the as-deposited high-k films can be dissolved with a good selectivity over SiO2 in dilute HF solutions, but heat-treated high-k films are difficult to etch with good selectivity over SiO2 under the same conditions.

The electrical breakdown strength of TiO2 nanoparticle-filled low-density polyethylene (LDPE) nanocomposites was investigated. It was found that the surface water on the nanoparticles played a very important role in determining the breakdown strength. The breakdown strength at 63.2% cumulative failure probability (E0) for the composites filled with dried nanoscale TiO2 was similar to that of neat LDPE and 50% higher than that for the samples filled with as-received nanoscale TiO2. This increase was due to a better dispersion, a better interface, and a morphology change of the matrix. It was also found that surface modification of nanoscale TiO2 had a significant influence on the breakdown strength. N-(2-aminoethyl) 3-aminopropyl-trimethoxysilane (AEAPS)-coated TiO2-filled samples showed about 40% higher E0 than that of uncoated, as-received TiO2-filled samples. This was mainly due to enhanced electron scattering because of the presence of polar groups in AEAPS.

Room-temperature photoluminescence (PL) was observed at 1540 nm in erbium-implanted amorphous silicon carbide (a-SiC:Er) films grown by thermal chemical vapor deposition at 800 °C. The PL spectra of the a-SiC:Er samples did not exhibit any defect-generated luminescence, with the PL intensity at 1540 nm dropping only by a factor of 3.6 as the sample temperature was increased from 14 K to room temperature. Time-resolved PL measurements showed that the Er3+ luminescence lifetime of approximately 0.6 ms was nearly independent of sample temperature. In addition, luminescence quenching was observed as implanted Er dose exceeded 7 × 1015 ions/cm2. It is suggested that the lower density of Si and C vacancies in the stoichiometric a-SiC:Er, as compared to its non-stoichiometric a-Si1-xCx counterpart, along with the incorporation of a higher Er dopant concentration, can effectively quench defect-produced luminescence and lead to a significant improvement in PL performance. These properties indicate that stoichiometric a-SiC is potentially a viable candidate for optoelectronic devices operating in the 1540 nm region.

The mechanical properties of monolayer and multilayer structures of several symmetrically substituted alkoxy copper phthalocyanine, CuPc(OR)8, Langmuir–Blodgett (LB) films were evaluated. One-dimensional compliance of the monolayers was determined from the slopes of the surface pressure–area isotherms. Multilayers were examined using a SPM and a commercial nanoindentation system. The nanomechanical studies show a distinct relationship between the position and length of alkoxy substituents on the Pc macrocycle and the LB film elasticity and hardness. The phthalocyanine complexes with peripheral octabutoxy and octaoctyloxy substituents form stiff LB monolayers and multilayers. The nonperipheral alkoxy derivetized CuPc films were less stiff. For monolayer films, it appears that the extent of π-π interaction determines the strength of the film. In multilayers, significant additional stability can be imparted through interdigitation of long paraffinic chains which play a significant role in determining the interlayer structure of the LB layers.

Epitaxial lanthanum zirconate (LZO) buffer layers have been grown by sol-gel processing on Ni–W substrates. We report on the application of these oxide films as seed and barrier layers in coated conductor fabrication as potentially simpler, lower cost coated-conductor architecture. The LZO films, about 80–100-nm thick, were found to have dense, crack-free surfaces with high surface crystallinity. Using 0.2-μm YBCO deposited by pulsed laser deposition, a critical current density of 2 MA/cm2 has been demonstrated on the LZO films (YBCO/LZO/Ni–W). Using 0.8-μm YBCO deposited using metal organic decomposition, a critical current density of 1.7 MA/cm2 and a critical current of 135 A/cm have been demonstrated on the LZO barrier layer with a sputtered CeO2 cap layer (YBCO/CeO2/LZO/Ni–W). These results offer promise to replace several of the vacuum-deposited layers in the typical coated conductor architecture (YBCO/CeO2/YSZ/Y2O3/Ni/Ni-W).