The type and magnitude of stress in electroless Ni–Cu–P deposits on Al were manipulated by controlling the concentration of saccharin in the plating solution. Tensile, zero, and compressive stress of the electroless Ni–Cu–P deposits was obtained with 0, 8, and 10 g/l saccharin for studying the effect of stress on the diffusion and crystallization behavior of the deposit. The effect of stress on the diffusion behavior of Cu, Ni, and Al elements during annealing was investigated. Interdiffusion between Al and Ni in an amorphous Ni–Cu–P/crystal Al diffusion couple is abated by the effects of amorphous structure, atomic affinity, and backstress. Therefore, the effect of stress on diffusion is manifested by Cu elemental diffusion. The tensile stress promotes the formation of Ni3P and the diffusion of Cu into the substrate.

The role of a compliant adhesive interlayer in determining critical conditions for radial fracture at the undersurfaces of brittle coatings bonded to substrates of dissimilar materials is investigated. Semi-empirical relations for the critical loads are derived by treating the adhesive as part of an effective substrate, thereby reducing the problem to that of a bilayer. A finite-element analysis of a model silicon/epoxy/glass system is used to evaluate adjustable parameters in the analytical relations. In situ experimental observations of crack initiation on the same material system are used to verify these relations. The critical loads depend sensitively on the adhesive thickness and modulus. Delamination at the interface in poorly bonded specimens greatly reduces the critical loads. This analysis affords a basis for predicting the prospective fracture resistance of brittle coatings joined by adhesives.

The evolution of agglomerate structure during drying of particles from suspension has been studied for a nanocrystalline Y2O3 (8% mol fraction)-stabilized ZrO2 powder. Agglomerates in drying and dried suspensions were examined at the smallest size scales (1 nm to 1 μm) using ultra-small angle x-ray scattering (USAXS) and at the largest size scales (100 nm to 10 μm) using scanning electron microscopy. The results were correlated with the degree of particle dissolution in each suspension (measured by flame absorption spectroscopy of the suspension filtrate) and the zeta potential of the particles in suspension prior to drying. Results show that large agglomerates readily form across a pH range from 2 to 9. The fact that Y+3 ion dissolution varies by over four orders of magnitude in this range leads to the conclusion that there is little direct correlation between the degree of Y dissolution and agglomeration in this system (Zr ion dissolution was below the detection limit at all pH values studied). The observation of large agglomerates well before the introduction of air-water interfaces into the drying mass likewise leads to the conclusion that capillary forces are not essential to agglomerate formation. Instead, agglomerates appear to form as a direct consequence of increasing suspension concentration. Zeta potential also plays a role. Specifically, there was a notable change in agglomerate morphology as the isoelectric point was approached, at approximately pH 8. Here USAXS shows the particles in suspension to have a layered interior structure, with small primary particles aggregated in sheets to form each blocky particle. This is in contrast to the more rounded agglomerates formed away from the isoelectric point, which appear to be composed of the same primary particles arranged in chainlike structures. USAXS of powders from the dried suspensions confirms that the structures seen after drying are the same as those present in suspension. The two structural morphologies are attributed to diffusion-limited (sheets) versus reaction-limited (chains) aggregation, respectively.

The optical absorption spectra of cobalt-doped MgIn2S4, CdIn2S4, and HgIn2S4 single crystals grown by a chemical transport reaction were investigated at 7 K. The values of Dq and B calculated from the observed spectra show that the d electrons are more delocalized in the order of MgIn2S4, CdIn2S4, and HgIn2S4. Because this order corresponds to the decreasing order of the electronegativity differences between the metal and sulfur atoms of the host crystals, we conclude that as the metal-sulfur bonds in the host crystals are more covalent, the d electrons of the cobalt impurities are more spread out and the cobalt-sulfur bonds are also more covalent.

AlOx thin films were grown on ZnO-deposited glass substrates under different conditions using magnetron sputtering. The influence of processing parameters (mainly direct-current power and oxidizing atmosphere) on the structure and optical properties were investigated. The AlOx films for all samples in this study showed the coexistence of amorphous and polycrystalline structures. The kinetics of crystal growth could influence the dominant crystal orientation. Fast-growing planes were not the most thermodynamically stable, but were kinetically controlled under the film growth condition. Oxidizing the sample in O2 atmosphere made the AlOx film grow in random directions. The excess oxygen was chemisorbed at the interface between AlOx and ZnO. Therefore, the neighboring oxygen–oxygen distance of AlOx and that of ZnO on their closest-packed planes seriously mismatched. At high power, the particles arrived at the substrate with high kinetic energy and high rate, which led to low density due to porous structure. The transmission decreased with an increase of the pores and surface roughness of AlOxfilm on ZnO-deposited glass. However, the diffusion of oxygen into the grains improved transmission when the sample was oxidized in O2 atmosphere.

We investigated the impact of the presence of dislocations on room-temperature photoluminescence intensity in GaN films grown by molecular beam epitaxy. To determine both screw and edge dislocation densities, we employed x-ray diffraction in conjunction with a geometrical model, which relate the width of the respective reflections to the polar and azimuthal orientational spread. There is no direct dependence of the emission efficiency on the density of either type of dislocation in the samples under investigation. We conclude that dislocations are not the dominant nonradiative recombination centers for GaN grown by molecular beam epitaxy.

We report the growth of titanium nitride microcolumns under multipulse Nd:yttrium aluminum garnet (λ = 1.064 μm, τ ∼ 300 ns, ν = 30 kHz) laser irradiation of titanium targets in nitrogen atmosphere. The laser intensity value was chosen below the single-pulse melting threshold of titanium. The evolution with the number of laser pulses of the target morphology, crystalline state, and chemical composition at the surface as well as in depth were investigated by scanning electron microscopy, x-ray diffractometry, Raman spectroscopy, and wavelength dispersive x-ray spectroscopy. Under the action of the laser pulses, during progressive surface nitridation, an initial rippled morphology developed, which evolved with further irradiation to TiN microcolumns. In-depth investigations showed a granular zone beneath the surface consisting of rutile and anatase phase TiO2, followed by a compact needlelike layer of titanium until the interface with the unaffected target material.

To ascertain how the substrate influences the quality of AlOx films, AlOx films were grown on a bare glass and a ZnO-deposited glass in this study. By applying a ZnO interlayer before the AlOx deposition, AlOx films exhibited polycrystalline structure rather than amorphous as obtained by sputtering on a bare glass. For AlOx film on the ZnO-deposited glass, the transmission electron microscopy observation showed the coexistence of amorphous and polycrystalline structure, which reveals that the (122) plane in AlOx film is parallel to the surface of the substrate. The grains of the AlOx film grown on a ZnO-deposited glass comprising many small crystallites aggregated with sizes varying between 38 and 54 nm with irregular grain shapes. Besides, the ZnO interlayer with different deposition parameters had a significant effect in the diffusion interface between AlOx and ZnO. The ZnO interlayer could improve the optical transmission of AlOx films, especially when ZnO films are prepared with a high power of 200 W. Therefore, the glass/ZnO may be a good alternative substrate for producing high-quality AlOx films by controlling the epitaxial grain growth. The AlOx films grown on ZnO-deposited glasses have very good qualities in terms of crystallinity and optical properties.

Poly(ethylene glycol) (PEG) additives with different molecular weights were used to modify sol-gel precursor solutions for preparing lead zirconate titanate (PZT) thin films. The morphology, crystalline structure, and mechanical and electrical properties of the films were characterized. The relationship between the characteristics of the films and the molecular weight of PEG was investigated. It was observed that the PEG eliminated cracking of the films during multiple pyrolysis treatments. However, with the increase of the PEG molecular weight, the films became less dense, which led to decreased Young's modulus and dielectric constant and increased coercive field. Our experiments showed that films prepared from sols modified by PEG with a molecular weight of 200 exhibited a dense morphology and excellent mechanical and electric properties without cracking.

The microstructural changes associated with the reduced dependence of critical current density (Jc) versus thickness of thick, epitaxial YBa2Cu3O7–δ (YBCO) films on rolling-assisted biaxially textured substrates (RABiTS) were investigated. Pulsed laser deposited YBCO films varying in thickness from 1.0 to 6.4 ?m on RABiTS with an architecture of Ni–3 at.% W/Y2O3/yttrium-stabilized-zirconia/CeO2/YBCO were prepared for cross-sectional transmission electron microscopy studies. Dramatic improvements in physical properties and microstructural quality were observed resulting from the use of Ni–3 at.% W substrates, which provided a sharper texture over earlier Ni substrates, and replacement of CeO2 with Y2O3 as the seed layer within the buffers. The YBCO films showed exceptional orientation up to 6.4 μm thickness, with no misoriented grains or dead layers observed and only limited reaction between the YBCO and CeO2 cap layer. The high quality of the films was also attributed in part to the formation of a tungsten oxide layer forming at the top of the Ni–3% W substrate, limiting the growth of deleterious NiO into the conductor.

Enthalpies of formation from constituent oxides and elements at 298 K were determined by high-temperature oxide melt solution calorimetry for a group of technologically important perovskites LaBO3 (B = La, Ga, Sc, and In). Enthalpies of formation from oxides of LaAlO3 and LaGaO3 are −69.61 ± 3.23 kJ/mol and −52.39 ± 1.99 kJ/mol, respectively. The data were consistent with literature values obtained using other methods. The enthalpies of formation of LaScO3 and LaInO3 from oxides were reported for the first time as −38.64 ± 2.30 kJ/mol and −23.99 ± 2.31 kJ/mol, respectively. As seen for other perovskites, as the tolerance factor deviates more from unity (in the order Al, Ga, Sc, In), the enthalpy of formation from oxides becomes less exothermic, indicating a less stable structure with respect to the constituent oxides.

Subsurface cracking after nano- and Vickers indentation on transparent silica–(meth)acrylate hybrid coatings deposited on a polycarbonate substrate was observed for the first time. It appeared that after initiation at the interface, these cracks propagated toward the surface and in radial directions as the indentation load increased. It was found that, for chemically identical coatings, the thicker the coating, the higher load necessary to initiate these cracks. Subsurface cracks formed during nanoindentation occur at lower loads than the normally observed surface cracks and are accompanied by a very small change in the slope of the loading curve.

Electroceramics are used in a variety of applications such as sensors, actuators, capacitors, and varistors. In these applications, the ceramic microstructure often consists of equiaxed, randomly oriented grains. Ferroelectric transducers require poling to obtain useful piezoelectric properties. Poling is difficult for some ferroelectric ceramics because the symmetry-related orientations available for the spontaneous polarization are limited.

Quantified wavelength dispersive spectroscopy (WDS) x-ray element maps were used to characterize active (Pb,La)(Ti,Zr)O3 (PLZT) layers on Pt/PLZT/Al2O3 substrates, one fired at 1050 °C and the other at 1150 °C. In the layer fired at 1050 °C, randomly distributed micrometer-sized compositional irregularities were observed as La-rich regions that were in most cases enriched also with Ti and deficient in Pb and Zr compared to the matrix. Such compositional imperfections were not observed in the PLZT layer fired for the same duration at 1150 °C. The level of microheterogeneity for all elements in the specimen fired at 1150 °C and for Pb, Ti, and Zr in the specimen fired at 1050 °C was below 1% relative at confidence level of 99% while for La it was as much as 2.5% relative. In point-beam line profiles across the active layer starting from the Pt electrode toward the outer surface of the cross-section of the PLZT film, the Pb concentration decreased continuously in both samples, confirming the importance of providing a properly equilibrated partial pressure of Pb around the sample during the entire firing process. Better dielectric and ferroelectric characteristics of the specimen fired at 1150 °C compared to the sample fired at 1050 °C were attributed to the differences in compositional heterogeneity between these samples. The study of the micro-compositional characteristics of these ceramic materials with quantitative WDS mapping has contributed to the optimization of processing parameters and hence to the understanding of the properties of ferroelectric PLZT materials.

Metal contamination in Si and SiO2 films deposited by plasma-enhanced chemical vapor deposition (PECVD) in the fabrication of low-temperature poly Si thin-film transitor was investigated. Aluminum was the major metal impurity to have the highest concentration. Segregation of Al was always observed in the films deposited at temperatures above 400 °C. The impurity level in the segregated region was 1018 ∼ 1020 atoms/cm3 for Al, while the concentration in matrix was about 1016 atoms/cm3. From the transmission electron microscopy image, the Al segregated region contains small-size Al precipitates. Although the Al impurity level of 1016 atoms/cm3 did not cause any serious degradation of device performance, the level of 1018 atom/cm3 and higher can induce a fatal degradation of the threshold voltage. This study revealed that the Al originated from the PECVD chamber, carbon precipitates provided the preferred sites for Al precipitates, and the solubility and diffusivity of Al in Si accelerated the segregation of Al.

Effects of TiO2 addition on the conduction mechanism of buried resistors in low temperature cofired ceramics were investigated. Remarkable increases in electrical resistivity and attractive decreases in the temperature coefficient of resistance were observed by the addition of TiO2 for all ratios of RuO2/glass investigated. Such significant effects can be attributed to a larger separation observed between RuO2 particles. The results were compared with the calculated data from theoretical model of tunneling barrier, showing that good agreement could be obtained. In addition, while the distance separation was taken into account as a fixed constant, it was found that the resistivity of buried resistor decreased with increasing TiO2 contents in the glass at higher weight ratios of TiO2/glass. This result implies that a substitution takes place due to the Si+4 displacement by Ti+4 in the glass, resulting in a looser network structure and a lower resistivity value.

MgO–C–Al refractories were used in this study to evaluate high-temperature refractory–metal reactions with molten Fe–Mn–Al alloys. Dynamic reaction tests at 1570 °C and static reaction tests at 1500 °C and 1600 °C, respectively, were used. MgAl2O4 and Al4C3 phases were observed in the refractory bulk, and a large amount of protective MgAl2O4 phase formed due to the decomposition of Al4C3 phases on the refractory–metal reaction interface of the MgO–C–Al brick to retard the high-temperature attack of Fe–Mn–Al alloy melts. The oxygen partial pressure was substantially reduced by the oxidation of graphite in the MgO–C–Al brick during high-temperature test. This resulted in the nitridation of aluminum in molten Fe–Mn–Al alloy. White aluminum nitride (AlN) with the shape of whisker-like powder was formed and adhered to the surface of the MgO–C–Al brick. Aluminum was depleted from the Fe–Mn–Al alloy by nitridation or the oxidation reaction by CO gas. The alloy would also be carburized due to the absorption of CO gas or the reaction between aluminum and CO gas, which was produced by the oxidation of graphite in the MgO–C–Al refractory after static reaction test. It is argued that the MgO–C–Al refractory is not suitable to be used in the melting of Fe–Mn–Al alloys with high aluminum contents.

Double-walled carbon nanotubes (DWNTs), synthesized by the catalytic decomposition of methane, were explored by resonance Raman spectroscopy using different energies for laser excitation. Based on the radial breathing mode frequencies, the indices of the two layers of a DWNT were approximately assigned, depending on the interlayer separation of the two coaxial layers of the DWNT, which ranged from 0.34 to 0.40 nm. From the tentatively assigned results, it was found that the two walls of the DWNT are not strongly selected by chirality and diameter. The results, however, suggest that, for the tubes that are resonant with the available laser excitation energies, most of the outer layers of the observed DWNTs in our samples are semiconducting, while the inner layers of the observed DWNTs are either semiconducting or metallic based on the assembled DWNTs. The characteristics of the G, D, and G′ band of the DWNTs are discussed, and a double peak feature in the D and G′ band, originating from the inner and outer layers of the DWNTs, is reported.

Molybdenum-containing films electrochemically deposited from an aqueous solution of 12-molybdphosphate (PMo12O40)3− (denoted as PMo12) have been characterized by x-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR), and electron spin resonance (ESR) techniques. XPS and FTIR data indicate that electrolysis of PMo12 leads to the formation of Mo–O–Mo linkage by condensation of the polyanions accompanied by decomposition of the phosphate moiety. The ESR spectrum of the deposited film exhibits an asymmetric signal with g ∼1.92, indicative of pentavalent molybdenum (d1). The feature of this signal is close to that for a MoV ion in the amorphous MoO3 phase, but not in the PMo12 framework. It is therefore suggested that the deposited film no longer has the Keggin structure PMo12, but consists of a continuous structure containing molybdenum oxide.

Controlled introduction of defects into aligned multiwalled carbon nanotubes (MWCNTs) was achieved by time-dependent plasma etching. The subsequent morphological changes in MWCNTs have been fingerprinted using Raman and x-ray photoelectron spectroscopy, by which induction of defects by functionalization was confirmed. We found that the introduction of defects along the nanotube body affects all Raman vibrational modes. A systematic analysis of the relationship between D, D′, D*, and G modes leads us to believe that no one peak can be used as an accurate standard for estimation of defects in nanotubes.