Nanophase Ni particles (<10 nm in diameter) were produced by a blown arc method. A helium gas stream directed at the arc reduces the Ni vapor concentration and increases the quench rate. The helium gas velocity is the predominant factor influencing the size of the Ni particles. Gas velocities of 20 m/s and 56 m/s (at 26.6 kPa total helium pressure) resulted in Ni particle sizes of 13 nm and 7 nm, respectively.

Aluminum oxide powders doped with MgO (300 to 500 nm) were sintered to almost theoretical density within just 10–15 min at 1150 °C using a plasma-activated sintering process based on charging the loosely filled powders with an electric discharge prior to densification by resistance heating. The microstructure of the consolidated disks was examined by high resolution transmission electron microscopy (HREM) and electron energy loss spectroscopy (EELS) and revealed excellent grain to grain contact with virtually no grain growth and structurally clean grain boundaries.

Phase relationships in the system Si3N4−SiO2−Yb2O3 have been investigated at 1750 °C and compared with those in the system Si3N4−SiO2−Y2O3. Two types of ytterbium silicon oxynitride, Yb2Si3O3N4 (tetragonal) and Yb4Si2O7N2 (monoclinic), were confirmed to exist. The x-ray powder diffraction data of two compounds were indexed based on the space group and unit cells. Melting temperature of Yb4Si2O7N2 was determined as 1870 °C. Yb4Si2O7N2 is a better intergranular phase of silicon nitride ceramics for its high melting temperature.

Zircon, ZrSiO4, is a well-characterized, naturally occurring phase that is extremely durable. Zircon has been synthesized with Pu-concentrations up to 10 wt. % and radiation-damage effects studied to saturation doses of nearly 0.8 displacements per atom. We propose that zircon be used as a waste form for the disposal of the more than 100 metric tons of plutonium that will result from the dismantling of nuclear weapons. There are already several demonstrated processing technologies, of which hot pressing offers the most potential. This highly durable material, even under hydrothermal conditions, with its high waste loading and smaller volume allows deep, permanent disposal of the weapons plutonium in geologic environments in which the borosilicate waste-form glass would not be stable.

The first use of continuous vapor grown carbon fiber (VGCF) as reinforcement in aluminum metal matrix composite (Al MMC) is reported. Al MMC represents a new material for thermal management in high-power, high-density electronic devices. Due to the ultrahigh thermal conductivity of VGCF, 1950 W/m-K at room temperature, VGCF-reinforced Al MMC exhibits excellent thermal conductivity that cannot be achieved by using any other carbon fiber as reinforcement. An unprecedented high thermal conductivity of 642 W/m-K for Al MMC was obtained by using 36.5% of VGCF.

A new method of preparing carbon nanotubes and their derivatives using silica aerogels as a matrix for the deposition of carbon is repeated. We present results of observations of graphite tubes and rings including nested structures in nanometer dimensions using high resolution transmission electron microscopy. Furthermore, we propose a model for the growth of carbon nanotubes in three steps including nucleation, growth, and closure of tubes.

Elastic properties of small volumes of materials can be measured from the unloading of small indentations using the so-called nanoindenters The analytic elastic solutions for axisymmetric indenters are currently used to calculate modulus from the unloading curve, sometimes using corrections derived for flat, rigid punches. It is shown that these corrections represent an upper limit for the correction. More realistic corrections are derived for the Vickers, Berkovich, and Knoop indenter shapes, using the assumption of a uniformly loaded area. Results show that the axisymmetric solution overestimates the elastic compliance of the Vickers indenter by a factor of 1.0055, of the Berkovich indenter by a factor of 1.0226, and of the Knoop indenter by a factor of 2.682.

The electroplastic effect in materials is an interesting and potentially useful phenomenon in which an applied electric field affects the plastic flow properties of materials under strain. We have undertaken a study to use optical methods to monitor changes in alkali halide crystals undergoing the electroplastic effect. Some preliminary results from this work are presented along with more conventional quasi-static measurements of the electroplastic effect.

We prepared YBa2Cu3Ox films on (100) MgO and (100) SrTiO3 substrates by rf thermal plasma evaporation, and investigated microstructure and growth mechanisms of these films by observation of the surfaces using an AFM technique. As a result, 2D nucleation and further coalescence between vicinal grains were observed in the initial stage of growth. In the films prepared for a deposition time of 3 min, the different complex growth modes, including spiral growth, “birth and spread” growth, and 2D growth, were observed, which might be due to high growth rate over 55 nm/min of this process.

We present optical observations of magnetically melt-textured DyBa2Cu3O7−x with and without 20 wt. % excess of Dy2BaCuO5. From these observations, we propose some kinetic mechanism of the growth of 123 compounds. Kinetic processes can be simulated on computers. Two (very) simple models derived from the well-known Eden model are presented. They simulate the growth of the grain front. The simulated patterns agree with the observations. The microstructure of such materials cannot be explained by thermodynamic and chemical considerations alone, but explanations must include the kinetics of the growth front as well. From our observations, we conclude that the growth probability ratios g110/g100 and g100/g001 are of the order of 10 and 50, respectively.

We deposited (Mn,Zn,Fe)1−xO thin films of a wüstite structure on SiO2/Si(100) by ion beam sputtering using a single-crystal Mn-Zn ferrite target. The wüstite structure of the as-deposited film, confirmed by XRD, TEM, and XPS analysis, appeared to originate from an oxygen-deficit ambient and also from the preferential resputtering of the oxygen ions in films during deposition. The as-deposited films showed ferrimagnetic characteristics having quite a large Ms in spite of their crystallographic structure, wüstite. Such an unusual phenomenon is presumably due to the different magnetic moments of the constituent cations with disordered distribution. This wüstite phase could be transformed into the spinel ferrite phase with the same preferred orientation during postannealing under an appropriate oxygen partial pressure. The interplanar distance of the as-deposited films decreased with increasing Ts due to a release of compressive stress. The Ms of the film had a maximum value at about 275 °C, while the resistivity, mainly governed by the grain boundaries, was almost the same irrespective of Ts.

The possibility that crystal-to-amorphous phase transformations can be induced by one or more underlying instabilities of the crystalline phase has been investigated in highly supersaturated solid solutions of Nb-Pd. Several unusual properties were discovered that may be identified as precursor effects of the collapse of the bcc α-Nb terminal solution to the amorphous phase. Elastic neutron diffraction measurements of α-Nb solutions found, with increasing Pd concentration, an anomalously large increase of the average atomic root-mean-square displacement to about half of the value at which the Lindemann criterion predicts the lattice should melt. Low-temperature heat capacity measurements yielded a concomitant decrease in the Debye temperature, suggesting that supersaturation causes an elastic modulus to soften. Single crystals of α-Nb solutions at high supersaturations have a highly anisotropic structure that is visible in transmission electron microscopy images; it is consistent with the development of a soft phonon mode leading to a bcc-to-ω phase transformation. Considered together with the results of other recent experiments, these findings suggest that shear instability of the crystalline phase plays an important role in the crystal-to-amorphous transformation and that the average static mean-square displacement of atoms in the lattice acts as a useful parameter for the stability of the crystal with respect to amorphization.

Systematic studies have been carried out about the effects of the thermal treatment parameters on melt-spun materials quenched at different cooling rates and based on the 2:14:1 hard magnetic phase. Samples of nominal compositions Dy3Nd10.2Fe79.6B6Si1.2 and Pr3Nd10.2Fe79.6B6Si1.2 were annealed at temperatures above that of crystallization of the amorphous phases present upon quenching, for times ranging from 1 to 30 min and by using different heating rates up to the annealing temperature. It is concluded that best hysteretic properties can be achieved in samples quenched at intermediate cooling rates by means of short-time thermal treatments performed by using high heating rates up to the treatment temperature. Low heating rates and long time anneals led to the deterioration of the hard magnetic behavior, due to the segregation of soft crystalline phases.

Alumina films were fabricated by the sol-gel route under various preparation conditions. The peptization rate and the structure of colloidal particles depend on these conditions. In particular, the peptization of a dried boehmite precipitate prepared from aluminum alkoxide was achieved within a few seconds without heating. The resulting sol is made of highly dispersed crystallites; this allows the formation of well-textured xerogel films as evidenced by the Weissenberg x-ray method.

Bremsstrahlung-excited Auger electron spectroscopy (AES) was used to study the oxidation kinetics of an aluminum nitride powder oxidized in air at 750, 800, 850, and 900 °C. An equation was derived to calculate the average surface oxide film thickness from the aluminum AES spectra. The oxidation of this powder was found to follow a parabolic rate law within this temperature range. The measured activation energy was 230 ± 17 kJ/mol (55 ± 4 kcal/mol). Analysis with x-ray photoelectron spectroscopy (XPS) showed that in addition to the nitride N 1s peak, there was a second N 1s peak. This peak has been observed in previous studies and can be attributed to N-O bonding either within the growing oxide film or at the Al2O3/AlN interface.

Using titanium nitrate solution stabilized by chelation, amorphous fine particles of the Ba-Ti-O system were prepared by the mist decomposition method in air. After calcination of these particles, barium titanate ceramics were prepared using the hot uniaxial pressing method, and various properties were investigated. As a result, the grain sizes could be controlled over the range from 58 nm to 187 nm by the sintering temperatures and/or the calcination temperatures, keeping the density almost constant. Moreover, the dielectric properties of the samples showed that the relative permittivity decreased with decreasing grain size, and Curie temperature also shifted to lower temperatures in the same way. In this study, we first found that Curie temperature existed in the barium titanate ceramics with grain sizes from 58 to 147 nm.

Microwave dielectric properties and microstructures of BaPr2Ti4O12 and BaPr2Ti5O14 ceramics which have extremely similar crystal structures, were investigated, including those of the solid solution represented by the formula of Ba6−xPr8+2x/3Ti18O54 ceramics. It is suggested that BaPr2Ti5O14 ceramics are composed of mixed phases, approximately 85.0 vol. % Ba4.05Pr9.3Ti18O54 (x = 1.95), 8.1 vol. % TiO2, and 6.9 vol. % BaTi4O9. The microwave dielectric properties of the Ba6−xPr8+2x/3Ti18O54 system are strongly dependent on the x value, which is interesting for studying the relationship between microstructures and dielectric properties. Far infrared reflection spectra were also measured to study the mixed phases formed in these ceramics in more detail.

In this study, films consisting of B-N-C-H have been synthesized by low pressure chemical vapor deposition using the liquid precursor triethylamine borane complex (TEAB) both with and without ammonia. When no NH3 is present, the growth rate was observed to follow an Arrhenius behavior in the temperature range of 600 to 800 °C with an apparent activation energy of 11 kcal/mol. A linear dependence of growth rate is observed as a function of square root of flow rate for the TEAB range of 20 to 60 sccm, indicating that the reaction rate is controlled by the adsorption of borane. The addition of NH3 to TEAB had the effect of lowering the deposition temperature down to 300 °C and increasing the apparent activation energy to 22 kcal/mol. Above 650 °C, the carbon concentration of the deposits increased significantly, reflecting the breakup of the amine molecule. X-ray diffraction measurements indicated the films to be in all cases amorphous. Infrared spectra of the films showed absorption peaks representing the vibrational modes of B-N, B-N-B, B-H, and N-H. The index of refraction varied between 1.76 and 2.47, depending on composition of the films. Films deposited with no NH3 above 700 °C were seen to be compressive while films below that temperature were tensile. In the range of 350 to 475 °C, the addition of NH3 to TEAB resulted in films that were mildly tensile, while below 325 °C and above 550 °C, the films were found to be compressive. Both the hardness and Young's modulus of the films decreased with higher temperatures, reflecting the influence of the carbon presence.

An Ir metal target was reactively rf sputtered in a planar magnetron source to develop iridium oxide deposition conditions. Gas blends of hydrogen, oxygen, and argon were used to provide competitive control over the reduction/oxidation characteristics of the sputter plasma. Optical emission spectroscopy allowed direct observation of hydrogen, oxygen, and iridium atomic peaks and OH molecular bands. Each of the twelve gas flow conditions could be clearly defined as either reducing or oxidizing by plasma emission spectroscopy. A given plasma reduction/oxidation state can be maintained over a wide range of gas flow conditions by coordinated adjustment of hydrogen and oxygen flows. The electrochemical properties of the iridium oxide films change dramatically in the vicinity of the reduction/oxidation plasma transition.

Two reaction routes have been tried for the synthesis of magncsium sulfide by applying microwave irradiation. In the first trial, finely ground Mg and S were mixed thoroughly and heated in a microwave oven for various lengths of time (5 + 5 + 8 + 10 and 12 + 12 + 35 + 45 min) in a sealed quartz tube. In the second trial, the pro-heating medium (PHM) of graphite was introduced into the mixture of Mg and S and microwaved for only 1 min. Results of x-ray diffraction analyses of the reaction products indicated that MgS polycrystallites (cubic, a0 = 5.201 ± 0.001) had formed in the second trial, and that the MgS yield was greater than 98%. Data of EDAX and EPMA gave a formula of MgS with atomic ratio of Mg:S = 1.0:1.0. In contrast, MgS could not be identified in the reaction mixtures in the first trial. Obviously, graphite, as a PHM, played a key role in the dramatic enhancement of the rate of the reaction between Mg and S powders. Furthermore, the effect of different molar ratios of graphite to Mg on the rate of microwave synthesis was investigated.