When undercooled molten Cu30Ni70 crystallizes at an undercooling ΔT≅ 145 K (ΔT is defined as Tl – Tk where Tl is the liquidus of Cu30Ni70 and Tk is the kinetic crystallization temperature), its grain size undergoes a rapid decrease by as much as two orders of magnitude in a narrow temperature range. This phenomenon is termed grain refinement. It was found that grain refinement is brought about by multiplication of dendrites. Composition analysis of the dendrite indicates that it has the least Ni concentration at its axis. The Ni content then increases radially from the central axis. Therefore, the dendrite is unstable against melting since the melting temperature of Cu–Ni increases with Ni content. The origin of grain refinement is attributed to the remelting of these dendrites.

Effects of electroless nickel plating on resistivity-temperature (R-T) characteristics of (Ba1-xPbx)TiO3 thermistor were studied. Comparison experiments showed that not only the permeation of plating solution, but also the reaction of electroless nickel plating influences the positive temperature coefficient (PTC) effect, and that the two effects are different in nature. It is first proposed in this paper that hydrogen atoms generated in electroless nickel plating may reduce components of PTC ceramics.

Melt textured single crystals of YBa2Cu3O6.5 (123) superconductors were produced by isothermal solidification from a semisolid melt using single crystal NdBa2Cu3O6.5 or SmBa2Cu3O6.5 seeds. The microstructure within the single crystals shows an inhomogeneous segregation of Y2BaCO5 (211) particles trapped in the 123 crystals during solidification. The concentration of 211 particles varies with the crystal axes in 123 crystals produced from precursors with compositions of 80 wt.% 123 powder and 20 wt.% excess 211. The 211 particle concentration along the c-axis in the crystal is much lower than that along the a- or b-axes during initial crystallization. This concentration increases in both directions as the crystal grows larger. The 211 concentration along the c-axis increases more quickly than the concentration along the other axes during solidification, which allows the 211 concentration to approach that on the other axes as the solidification continues. 211 particle segregation in stoichiometric 123 samples formed “X”-shaped tracks instead of the variations in 211 concentration described above. A single crystal growth model of 123 is proposed and employed to interpret these experimental observations. Quenched samples were prepared to investigate the volume fraction of 211 particles in the liquid phase. A constant distribution of 211 particles was observed in the liquid, except very near the crystal interface, where the 211 concentration decreased rapidly. Copper oxide content in the liquid was also measured. It is found that the copper content is lower at the (001) interface compared with (100) or (010) interfaces.

Hard x-rays from a synchrotron source were utilized in diffraction experiments performed at elevated temperatures (up to ˜ 870 °C) on (Bi, Pb)2Sr2Ca2Cu3O10 (Bi-2223) tapes completely encased in silver. The general behavior of the phase and texture development under typical processing conditions was determined, and the effects that several variations in processing conditions had on the phase and texture development were examined. These results and their implications for improving processing conditions are discussed.

The decomposition of Yba2Cu4O8 (Y-124) into Yba2Cu3O7-δ (Y-123) and CuO at high temperatures has been expected to create Y-123 with finely dispersed CuO precipitates suitable for flux pinning. In fact, samples of thermally decomposed Y-124 exhibit a critical current density, Jc, which is enhanced with respect to the starting material as well as to pure Y-123. Transmission electron microscopy (TEM) studies of furnace annealed Y-124 were not suitable to clarify the reason for this Jc enhancement. Nevertheless, the formation and growth of CuO precipitates have been observed by in situ decomposition of the Y-124 starting material due to electron beam heating within the TEM.

Polysilicon microfracture specimens were fabricated using surface micromachining techniques identical to those used to fabricate microelectromechanical systems (MEMS) devices. The nominal critical J-integral (the critical energy release rate) for crack initiation, Jc, was determined in specimens whose characteristic dimensions were of the same order of magnitude as the grain size of the polysilicon. Jc values ranged from 16 to 62 N/m, approximately a factor of four larger than Jc values reported for single crystal silicon.

Porosity-free nanocrystalline element selenium (nc-Se) samples with the mean grain sizes ranging from 8 to 70 nm were synthesized by complete crystallization of the melt-quenched amorphous Se solid. Mechanical properties including microhardness (Hv) and elastic modulus (E) of the nc-Se samples were measured by means of nanoindentation tests and microhardness tests, respectively. With a reduction of grain size, the nc-Se samples were found to be substantially hardened. But the grain size dependence of Hv does not follow a simple Hall–Petch relation over the whole grain size range, exhibiting three distinct stages corresponding to three different Hall–Petch slopes. The maximum Hall–Petch slope was found to be in the grain size range of 15–20 nm, corresponding to large values of the elastic modulus. This behavior can be explained in terms of the lattice distortion in the nc-Se samples that was experimentally determined by using quantitative x-ray diffraction measurements. A conclusion is drawn that the lattice structure of the nm-sized crystallites may play an important role in mechanical properties of nanocrystalline materials.

Using the pulsed laser ablation (PLA) technique, conductive LaNiO3 thin films have been successfully grown on (001) Si substrates. The XRD θ-2θ scan patterns indicate a preferential (110) orientation, and the electron probe microanalyzer (EPMA) investigations show that the three elements La, Ni, and O distribute uniformly in the films. The resistivity of the as-deposited LaNiO3 films display a metallic character. Polycrystalline PbTiO3films are deposited by metalorganic chemical vapor deposition (MOCVD) on these LaNiO3 electrodes. Ferroelectricity measurements of the PbTiO3/LaNiO3 heterostructure prove LaNiO3 to be a promising electrode material in the integration of ferroelectrics and Si wafer.

Mechanical alloying (MA) has been performed in the CoxCu(100-x) (x = 10, 25, 50, 60, 75, and 90) system. High resolution electron microscopy (HREM) and field emission gun transmission electron microscopy (FEG TEM) were used to characterize the microstructure and homogeneity of the nanocrystalline Co25Cu75 solid solution. After 20 h of MA, all the mixtures show an entirely face-centered cubic (fcc) phase. HREM shows that the ultrafine-grained (UFG) materials prepared by MA contain a high density of defects. Two kinds of typical defects in UFG Co25Cu75 are deformation twins and dislocations. The dislocations are mostly 60° type, and in many cases they dissociate into 30° and 90° partials. The grain boundaries are ordered in structure, curved, and slightly strained, which is similar to that observed in NC–Pd. Nanoscale energy dispersive x-ray spectroscopy (EDXS) shows that the Co concentration in both the interior of grains and the GB's is close to the global composition, which proves that supersaturated solid solutions are indeed formed. In the meantime EDXS revealed that the mixing of Co and Cu in the solid solutions is homogeneous at nanometer scale. MA in the Co–Cu system is suggested to be a diffusion-controlled process, and stress-stimulated diffusion is proposed to be the reason for the formation of supersaturated solid solutions in this immiscible system.

Although numerous studies of high-energy, ball-milled metal powders have been conducted, to date few studies have characterized the mechanical processing of identical elemental compositions of prealloyed powders and of powder blends. This study reports on the mechanical processing (attritor ball milling) in argon and nitrogen gas environments of (a) iron powder and prealloyed iron–2 wt.% aluminum powder, and (b) iron-aluminum, iron-aluminum nitride, and iron-iron nitride powder blends. When nitrogen was milled into iron particles either from nitride powder or by gas infusion, the nitrogen dissolved interstitially in bcc-Fe (principally at the grain boundaries) or was present as bct-Fe nanoparticles at the bcc-Fe nanograin boundaries. The resulting nitrogen distribution was independent of how the nitrogen was added. Milled blends of iron and aluminum powder and prealloyed iron-aluminum powder resulted in similar microstructures: micrometer size particles with similar nanograin size. The aluminum in the blended powder mixture developed an ultrafine distribution on the grain boundaries, but it did not become uniformly distributed within the bcc-Fe grains. In contrast, the aluminum in prealloyed Fe–Al powder remained in solid solution during the mechanical milling

Furnace brazing is commonly used in the electronic industry to attach I/O pins, lid-seal rings, and heat spreaders to cofired multilayer ceramic packages. Despite the widespread industry usage of electrolytic and electroless Ni coatings to render base metal surfaces wettable by braze fillers, there is no fundamental treatment of “brazeability” in the published literature that can be used by the materials technologist to design coatings for a given application. In this study, dynamic hot stage microscopy is used to establish the parameters that control the spreading of eutectic Ag–Cu braze on surfaces plated with electrolytic Ni. The effects of plating thickness, substrate type, plating annealing, and the braze thermal cycle are considered. A braze spreading mechanism developed for polycrystalline Ni foil in Part I of this study is linked to Ni-plated surfaces through consideration of differences in microstructure. Eventual extension of this improved understanding to surfaces plated with electroless Ni–B and Ni–P deposits will result in shortened product design time and improved manufacturing process control.

Analysis of ball-indentation process was made by the finite element (FE) method. A series of indentation FE analyses were made on materials with different elastic modulus (E), and a simple relationship between E and the load-depth (F-h) unloading data is presented. In order to check for the influence of other material properties, thorough research has been performed, introducing a combination of response surface (RS) and FE analysis. As a result, a relationship between the indentation unloading slope, E, and the strain hardening exponent was derived. Also, the indenter compliance effect has been investigated. The indenter compliance correction was calculated and applied to the experimentally measured F-h results. Experimental testing was made on three materials with essentially different elastic moduli. Comparison of the results obtained by newly developed equations with the results from other well-known equations is also presented.

The morphology of Cu thin films is strongly dependent on the temperature of the substrate during and after deposition. Films grown at temperatures between 300 °C and 400 °C form clusters distributed in close packed domains and isolated clusters across the surface. Increased substrate temperatures result in cluster shape evolution indicative of mass flow and sintering. Deposition of Cu at substrate temperatures higher than 500 °C results in a completely different morphology of the film and the suppression of cluster formation. Annealing these Cu films to temperatures of 700 °C allows the system to relax into an equilibrium state characterized by large facets in the film and large areas of exposed surface. These observations are discussed in terms of basic thermodynamic data for bulk Cu oxidation and surface tensions for this system.

A quantitative study was made of the composition and microstructure of RuO2 films deposited on three different substrates using reactive sputtering. Most of the films had a composition within 2.5 wt.% of the correct stoichiometry; the only exceptions were films grown on Al2O3 (0001) at 150 °C, which had an oxygen-to-ruthenium ratio of 1: 2.24. The excess oxygen was attributed to a thin oxygen-rich layer that encapsulated the grains. Hydrogen concentrations for the films deposited on Al2O3 (0001) were 14, 6, 6, and < 0.5 at.% for room, 150, 300, and 450 °C growth temperatures respectively. The films deposited at room temperature were amorphous on Al2O3 (0001) and SrTiO3 (100), but weakly crystalline on Al2O3 (1102). Highly oriented RuO2 (100) films were produced on Al2O3 (0001) at deposition temperatures ≥150 °C. The in-plane alignment was and a threefold mosaic microstructure was observed. The grain boundaries in these films were discontinuous until the substrate temperature was raised to 450 °C, where coherent grain boundaries were formed. The films grown on Al2O3 (1102) at 450 °C exhibited the epitaxial relationship: RuO2(101)//Al2O3 (1102). The in-plane alignment was RuO2〈101〉//Al2O3〈1101〉, and the lattice parameters were the same as found in bulk RuO2. Transmission electron microscopy indicated a large degree of imperfection in the region between coalescing grains. The RuO2 films grown on SrTiO3 (100) at room temperature were amorphous. The film grown at 450 °C showed a preferential orientation with RuO2 (100)//SrTiO3 (100), but without in-plane orientation.

Thin films of lead titanate were prepared in situ using radio-frequency magnetron sputter deposition. The in situ perovskite phase formation has been studied as a function of the substrate temperature, the sputtered lead flux, and the substrate nature. The incident lead flux is controlled by the lead content in the target. An equilibrium zone, i.e., a saturation effect of the lead incorporation, exists where the films are stoichiometric. The temperature at which this zone appears depends on the sputtered lead flux and the substrate type. The growth mechanism is governed by a competition between the arrival rate of Pb and their re-evaporation from the film during the growth. The in situ formation temperature of the perovskite phase increased when the incident Pb flux increased. As a result, PbTiO3 films have been prepared at low temperature with appropriate combination of the substrate temperature and the lead content in the target, i.e., the sputtered lead flux. Since the lead sticking coefficient is very sensitive to the substrate material, the perovskite phase appears at different temperatures, depending on the substrate nature. PbTiO3 films are obtained at 550 °C on Al2O3 and SrTiO3 substrates; on Si/SiO2/Ti/Pt substrates, stoichiometric films are obtained at 440 °C. The structure and the microstructure of the films were examined at various deposition conditions. The substrate temperature strongly influenced the film orientation, and the crystallinity depended on the incident lead flux. High quality thin films (FWHM = 0.2°) are obtained at 550 °C on SrTiO3 substrates. The films deposited at 440 °C on Si/SiO2Ti/Pt show ferroelectric properties. This self-controlling mechanism of the stoichiometric composition allows the growth of ferroelectric films at low temperature, compatible with semi-conductor technologies for the realization of integrated circuits

Silica thin films containing organic groups were directly deposited from aqueous solutions of silicon alkoxides. Effects of functional groups of the alkoxides and the deposition conditions on the preparation of the films were investigated in order to clarify the deposition process. Silica films containing methyl and phenyl groups were deposited from aqueous solutions of methyl- and phenyltrialkoxysilanes, respectively, in the pH region lower than 3 or higher than 6. The composition and the property of the deposited films were influenced by pH and the temperature of the solutions and the starting materials. The adhesion of the deposited films on hydrophobic substrates was lower than that on hydrophilic ones, although the films were formed on both surfaces. The refractive index of the methyl-containing films, ca. 1.44, decreased with removal of methyl groups by heating up to 500 °C.

A LaAlO3 precursor solution was prepared via an all alkoxide sol-gel route. The solution of lanthanum methoxyethoxide and aluminum methoxyethoxide in 2-methoxyethanol was prepared via ligand exchange starting from lanthanum isopropoxide and aluminum sec-butoxide and was used to make both LaAlO3 powders and films. Complete hydrolysis of the solution formed a gel that yielded well-crystallized LaAlO3 powders when fired in air at 800 °C. A partially hydrolyzed solution was spun-cast on SrTiO3 (100) single crystal substrates. Epitaxial films of LaAlO3 were subsequently formed during pyrolysis in O2 at 800 °C in a rapid thermal annealing furnace for a total of 8 min. The films were strongly c-axis oriented, verified by x-ray rocking curve results from the (003) plane with full-width at half-maximum (FWHM) = 0.87°, and had good in-plane texture shown by a φ scan of the (202) plane with FWHM = 1.07°.

The “aging” characteristics of an acetic acid/methanol solvent-based lead zirconate titanate (PZT) precursor solution, prepared by the Inverted Mixing Order (IMO) process, have been studied for an extended period of time. The changes in film properties were characterized using optical microscopy, optical scattering, and ferroelectric testing. Films generated from the IMO process exhibit an increase in thickness as a function of solution age due to chemical “aging” (esterification) of the precursor solution. This increased thickness results in a decrease in the microstructural uniformity, which affects the electrical and optical properties. In order to understand and eventually control this phenomenon, we have quantified the “aging” of this solution using a variety of analytical methods, including 1H NMR spectroscopy, pH measurements, and Fourier transform infrared (FTIR) spectroscopy. It is of note that we have discovered a method that circumvents this “aging” problem by removal of the volatile material, forming an IMO powder which can be redissolved to produce high quality PZT thin films whenever desired.

Nanophase particles with precisely controlled characteristics are made by oxidation of their halide vapors in electrically assisted hydrocarbon flames using needle-shaped or plate electrodes. The particle size and crystallinity decrease with increasing field strength across the flame. The field generated by the electrodes across the flame decreases the particle residence time in the high temperature region of the flame. Furthermore, it charges the newly formed particles, resulting in electrostatic repulsion and dispersion that decreases particle growth by coagulation. Electric fields reduced the primary particle size of TiO2, the agglomerate size of SnO2, and both the agglomerate and primary size of SiO2.

The lead zirconate titanate (PZT) thin films were fabricated using sol-gel spin coating onto Pt/Ti/glass substrates. Effects of the holding time for pyrolysis and the coating cycle on the preferred orientation of the PZT thin films were studied. The films were fabricated with different coating cycles (3, 5, 7, 9, 11), dried at 330 °C for different holding times (5, 30, 60 min), and then annealed at the same temperature of 650 °C using rapid thermal annealing (RTA). The preferred orientations of the films were investigated using x-ray diffraction and glancing angle x-ray diffraction. The microstructure and the selected area diffraction pattern of the PZT thin films were also investigated using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively.