Raman spectroscopy, at laser excitation wavelengths of 514.5, 785, and 1064 nm, is used to study a set of chemical-vapor-deposited (CVD) diamond wafers of known thermal conductivity κ. The in-plane thermal conductivity (at 25 °C) of the diamond wafers ranges from 4 to 22 W cm−1 K−1 and represents a wide range of diamond quality. The spectra were obtained from both macro/micro- sampling measurements, examining the top and bottom wafer surface, as well as wafer cross-sections. Discussed are the peak positions and linewidths of the Raman bands and their relation to sp3-bonded diamond and sp2-bonded carbon in the context of diamond quality and perfection, and the effects of wafer heterogeneities. The detailed analysis of the Raman spectra provides a robust correlation with the room-temperature bulk (or macroscopic) thermal conductivity of these samples. The correlation is made through the determination of the band area ratios of the diamond Raman line at 1333 cm−1 to that of the 1550 cm−1 band characteristic of nondiamond carbon impurities. This dependence is most pronounced for the Fourier-transform Raman data obtained with infrared excitation at 1064 nm, due to resonance enhancement, and therefore allows the detection of carbon impurities, especially for high-quality CVD diamond.

Nanostructured WC–18% Co powder was synthesized by using cryogenic mechanical milling, and the thermal stability of the nanostructured powder was investigated in detail. The results indicated that the as-synthesized WC–18% Co powder had an average WC particle size of 25 nm. Growth of WC particles occurred above 873 K; however, the average WC particle size remained smaller than 100 nm in the powder isothermally heated for 4 h at 1273 K. Thermal exposure in air at T < 623 K did not result in significant oxidation of the cryomilled powder. The thermal exposure did promote the formation of WO2 and WO3 oxides. The Co6W6C phase was detected by x-ray diffraction in the powder heated in nitrogen at 1273 K, and the phases associated with decarburization of WC, such as W2C, W3C phases, were not observed. With increasing temperature, the dissolution of W and C elements in the Co matrix led to a gradual increase in {111} crystallographic plane spacing, eventually leading to the formation of an amorphous phase.

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.

When a homogeneous amorphous Pd40.5Ni40.5P19 alloy was subjected to thermal annealing for 30 min at various temperatures, novel microstructures were observed. At an annealing temperature of 603 K, phase separation of the amorphous phase dominated. At 628 K, a precipitation reaction proceeded first. After its completion, a eutectic growth set in. At 638 K, metastable spinodal decomposition occurred first, followed by a eutectic growth. Finally at 673 K, crystal growth of crystalline spinodal network was fast enough to compete with a eutectic growth.

An optimization study on crystallization annealing of (Ba,Sr)TiO3 (BST) thin films, grown by metalorganic chemical vapor deposition at a wafer temperature of 420 °C, was performed. The as-grown film had an amorphous structure with a dielectric constant of about 20. The annealing parameters, including temperature, atmosphere, time, and sequence, were varied considering the limitations imposed by integration processes for ultralarge-scale integrated dynamic random access memory devices. The dielectric constants of the crystallized films were largely determined by the maximum temperature that the films experienced with minor effects from the annealing atmosphere. However, the leakage current densities were quite dependent on the annealing sequence and atmosphere. It was concluded that the major factors which determine leakage characteristics were concentrations of impurities, especially carbon, oxygen vacancies, and interfacial defects caused by top electrode sputtering.

The magnetic Nd–Fe–B powders were prepared by a mechanochemical method, including the processes of spray drying, debinding, milling, H2 reduction, Ca reduction, and washing. The liquid solution dissolved with various metal salts was first spray-dried to prepare the precursor powders having uniformly dispersed Nd, Fe, and B components. The precursor powders in turn were subjected to the subsequent processes. The particle size of the resultant Nd–Fe–B powders was about 1 μm. Effects of the process parameters on phases, morphologies, microstructures, compositions, and thermal properties of the powders were investigated.

A new reliable embedded atom method potential for hydrogen in body-centered-cubic (bcc) iron is developed by fitting not only to the properties of hydrogen in a perfect bcc iron lattice but also to the properties of hydrogen binding to vacancies. The validity of the potential is examined by calculating the properties of hydrogen trap binding to surfaces and dislocations that are in good accordance with the experiments. A brief application of the potential by molecular dynamic simulation reveals that hydrogen accumulated ahead of the crack tip induces serious hydrogen embrittlement.

This paper reports on the role of boron in situ doping on enhancing crystallization of silicon germanium deposited at 400 °C and 2 torr. The dependence of growth rate on germanium content and boron concentration is investigated. The minimum boron concentration and the minimum germanium content required for crystallizing the as-grown layers is experimentally determined. The texture and grain microstructure of doped and undoped poly SiGe layers has been investigated by means of x-ray diffraction spectroscopy and transmission electron microscopy. The low deposition temperature coupled with the low tensile stress of the polycrystalline material enable postprocessing of surface micromachined microelectromechanical systems on top of standard complementry metal oxide semiconductor wafers with Al interconnects. Furthermore, the resistivity of the as-grown layers is as low as 1 mΩ cm, and hence, it can be used as a seeding layer for polycrystalline Si solar cells compatible with glass substrates.

Hydrodynamic cavitation was shown to be a powerful tool for the synthesis of nanostructured catalysts, ceramics, and piezoelectrics in high phase purities. The macro-, micro-, and nano- properties of solid-state materials could be controlled through adjusting the cavitational regime during synthesis by simple mechanical adjustment. The synthesis of nanostructured titania, piezoelectrics, perovskites, supported and unsupported cobalt molybdates, and Pd and Ag supported on alumina illustrate changes in morphology and size of crystals, growth in a preferred orientation of crystallites, and control of crystallographic strain and size compared to classically prepared materials. The high shear and cavitational forces during synthesis induce micro-strain into the materials and are a function of the Reynolds and cavitation numbers.

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.

The variation of mechanical properties (hardness, indentation modulus) within a carbon-implanted region of a Ti–6Al–4V alloy—about 350-nm thick—was, for the first time, related with the microstructure and the chemical composition with a depth accuracy as small as ±20 nm. Microstructure, chemical composition, and mechanical properties of the implanted alloy were determined using transmission electron microscopy, Auger electron spectroscopy, and nanoindentation, respectively. The microstructure within the implanted region contains TiC precipitates, the density of which changes with depth in accordance with the carbon content. The hardness depends on the precipitate density: the maximum hardness occurs at the depth where an almost continuous TiC layer had formed. The depth profiles of hardness and indentation modulus were measured using three different methods: the cross-section method (CSM); the constant-load method (CLM); and the load-variation method (LVM). Only the hardness– depth profile obtained using the CSM, in which the indentations are performed perpendicular to the hardness gradient on a cross section of the specimen, reflects the microstructural variations present in the implanted region.

A series of metal-matrix composites were formed by extrusion freeform fabrication of a sinterable aluminum alloy in combination with silicon carbide particles and whiskers, carbon fibers, alumina particles, and hollow flyash cenospheres. Silicon carbide particles were most successful in that the composites retained high density with up to 20 vol% of reinforcement and the strength approximately doubles over the strength of the metal matrix alone. Comparison with simple models suggests that this unexpectedly high degree of reinforcement can be attributed to the concentration of small silicon carbide particles around the larger metal powder. This fabrication method also allows composites to be formed with hollow spheres that cannot be formed by other powder or melt methods.

Portions of the same epitaxial (103)-oriented SrBi2Nb2O9 film grown on (111) SrTiO3 for which we recently reported the highest remanent polarization (Pr) ever achieved in SrBi2Nb2O9 (or SrBi2Ta2O9) films, i.e., Pr = 15.7 μC/cm2, have been characterized microstructurally by plan-view and cross-sectional transmission electron microscopy (TEM) along three orthogonal viewing directions. SrBi2Nb2O9 grows with its c axis tilted 57° from the substrate surface normal in a three-fold twin structure about the substrate [111], with the growth twins' c axes nominally aligned with the three 〈100〉 SrTiO3 directions. (103) SrBi2Nb2O9 films with and without an underlying epitaxial SrRuO3 bottom electrode have been studied. Dark-field TEM imaging over a 12 μm2 area shows no evidence of second phases (crystalline or amorphous). A high density of out-of-phase boundaries exists in the films.

We provide a phenomenological grain growth stagnation force incorporating a near-linear temperature dependence of stagnated grain sizes and irreversible growth. The resulting law captures the observation of the restart of grain growth in the size versus time plateau on temperature increases. This description also reduces to standard laws commonly used for data fitting. The law may be useful for workers who wish to characterize a nanocrystalline film or powder annealing process predictively from a limited number of measurements or may be useful in a designed experiment. Other laws are discussed and compared. Fits to size versus time data from the literature are successfully made.

Phase formation characteristics of Sr0.7Bi2.4Ta2O9 (SBT) powder, synthesized via the sol-gel and pyrolysis processes, was investigated using the thermal analysis technique. The two exotherms, appearing in the differential thermal analysis (DTA) curve, were identified as crystallization of fluorite phase and transformation of fluorite to Aurivillius phase, respectively, using x-ray diffraction. Nonisothermal kinetic analysis of the DTA results shows activation energy values for the formation of fluorite and Aurivillius phases as 192 and 375 kJ/mol, respectively, and Avrami exponent values for each reaction as 0.91 and 0.96, respectively. The results of this investigation are presented and discussed in detail to understand the phase formation mechanism in the SBT system.

The effect of graphite particles on the damping behavior of 6061 Al–graphite composites was investigated with an aim to develop a high damping, stiffness, and hardness material. The composites were processed by mixing 6061 alloy powder with graphite particles, hot pressed as a billet and consolidated by reciprocating extrusion 10 times. The results showed that the graphite particles were greatly refined and niformly distributed in the matrix. The graphite in situ reacted with the Al matrix to orm fine dispersed Al4C3 particles during both reciprocating extrusion and subsequent olution treatment. The Al4C3 phase could result in a pronounced dispersion trengthening effect. The damping capacity of the composite increased with increasing raphite content. The composite showed a peak in damping capacity during aging reatment. The 6061 Al–20% (graphite, Al4C3) composite solution-treated for 24 h and eak-aged displayed an excellent combination of damping capacity, stiffness, and ardness. The composite retained high damping while maintaining a high modulus ecause of the coexistence of graphite and Al4C3. The operative damping mechanisms, ncluding intrinsic damping of graphite particle, interface damping, dislocation amping, and grain boundary damping, are discussed with consideration of material icrostructure.

TiO2 thin films prepared by metalorganic decomposition (MOD-TiO2) and sol-gel processes (SG-TiO2) were investigated in terms of the anatase-to-rutile phase transformation and microstructural evolution. It was found that the chemical reactivity of the ligand groups initially coordinated on the titanium precursor plays a decisive role in the structure development of as-deposited SG- and MOD-TiO2 films. MOD-TiO2 films consist of small aggregated particles and therefore, tend to coalesce together to form an inhomogeneous microstructure during the anatase-to-rutile phase transformation. On the other hand, SG-TiO2 films consist of uniform large particles that tend to grow homogeneously. MOD-TiO2 films showed a higher crystallization temperature than the SG-TiO2 films but the temperature of the anatase-to-rutile phase transformation is much lower in MOD- (approximately 775 °C) as compared to SG-TiO2 films (approximately 930 °C). The activation energy (Q) was estimated as 524 and 882 kJ/mol for the MOD- and SG-TiO2 films, respectively. The lower transformation temperature and activation energy in MOD-TiO2 films were due to smaller grain size and more potential nucleation sites existing in the un-transformed MOD-TiO2 film structure, which can accelerate the rate of anatase-to-rutile transformation.

Y2-xLnxO3 (Ln 4 Ce, Pr, Nd, Eu, Gd, Ho, and Er) powders obtained by propellant synthesis have been characterized using small-angle x-ray scattering, wide-angle x-ray scattering, and transmission and scanning electron microscopy. All the samples showed a very porous, open microstructure with fractal scaling properties. The building blocks of the fractal aggregates are nanocrystallites of lanthanide-doped Y2O3, with variations in the cubic lattice constant proportional to the composition of the solid solution and to the lanthanide ionic radius. The particles had a narrow distribution of sizes with an average value in the 20–50 nm range. They are made of a core of 10–20 nm, consisting of almost perfectly ordered crystals and a “fuzzy” layer, characterized by either a growing lattice disorder or by a compositional gradient. From this dimension, up to at least 200 nm, the particle aggregate is a mass fractal with a fractal dimension, DMf, in the 1.6–2.0 range.

Antimony oxide nanoparticles were synthesized in the presence of the polyvinyl alcohol in water solution through the reaction between SbCl3 and NaOH. The size of the particle ranges from 10 to 80 nm, and the largest one can even reach 200 nm, which may begin to grow in the initial stage of the reflux. Transmission electron microscopy and high-resolution electron microscopy (HREM) were used to characterize the microstructure of these nanoparticles. Using silicon single crystals as internal standards, the polycrystalline diffraction pattern analysis shows only presence of cubic Sb2O3 phase. The bright-field micrograph displays that the particles may have various polyhedral configurations. HREM results show that the particles are crystallographically perfect. Moreover, the formation mechanism of nanoparticles is discussed.

Al alloys were infiltrated into alumina preforms without the aid of pressure in N2 as well as in air at and above 750 °C. It was possible to eliminate termination of infiltration that was seen in open conditions (where N2 was in continuous contact with the melt) by modifying the infiltration geometry. This configuration enables the infiltration to continue for longer periods of time, consequently producing greater thickness of composite. In air, Mg placed at the interface getters the in-coming oxygen until the alloy billet melts and seals off the front from the ingress of the furnace atmosphere thereby eliminating the need for prealloying Al with Mg and N2 atmosphere. In addition, experiments in argon revealed that the infiltration requires some critical amount of N2 in the atmosphere.