Amorphous alloys were synthesized by interface-assisted ion beam mixing in the W-rich portion of the Ag–W system. These alloys are characterized by the largest positive heat of formation among the transition-metal alloys and were formed through a two-step structural transition in the alternately deposited Ag–W films. First, during alternate deposition of the nano-sized Ag and W layers, the interfacial free energy drove the Ag–W interaction, which resulted in an intermediate body-centered-cubic (bcc) supersaturated solid solution. Second, the bcc solid solution transformed into an amorphous state upon irradiation at room temperature by 200-keV xenon ions. We report the experimental observations of the Ag–W amorphous alloy formation and a brief discussion concerning the effects of the interfacial free energy and ion irradiation dose on the structural transition observed in the Ag–W films.

A new Mg65Cu25Gd10 alloy having significantly improved glass-forming ability (GFA) has been developed. In this article, we show that the ternary Mg65Cu25Gd10 bulk metallic glass with diameter of at least 8 mm can successfully be fabricated by a conventional Cu-mold casting method in air atmosphere. The critical cooling rate for glass formation was estimated on the order of magnitude of approximately 1 K/s. When compared with the GFA of Mg65Cu25Y10 alloy, the significantly improved GFA of Mg65Cu25Gd10 alloy cannot be explained by ΔTx and Trg values.

A nanoscale continuous coating of In2O3 on phosphors for low-voltage display applications is proposed in which the electrical conductivity of phosphor screen plays a major role. The effect of In2O3 coating by the sol-gel method on the cathodoluminescence (CL) of ZnGa2O4:Mn phosphors improves the intensity of low-voltage CL noticeably compared with that of In2O3 mixing. It is understood that electrically conductive channels are formed by a much smaller amount of In2O3 addition than that of In2O3 mixing. Especially, based on transmission electron microscopy analysis, the formation of uniform nanoscale continuous In2O3 layers on the phosphor surface was confirmed. Also, the structural and CL characterizations presented in this paper clearly demonstrate that the nanoscale encapsulation of In2O3 layers on phosphors served as protective layers retarding the CL degradation introduced by the low-energy electron irradiation, which is critically important for the development of low-voltage display applications.

A series of novel liquid-crystalline polymer (LCP) systems, including a heterocyclic 2,5-thiophene unit, were synthesized and studied using a modified thin-film polymerization method as part of a continuing investigation of molecular structural effects on liquid crystallinity. The monomers used in the reaction included p-acetoxybenzoic acid (ABA)/2,6-acetoxynaphtholic acid (ANA), 4,4′-biphenol (BP)/4,4′-diacetoxybiphenyl (DABP)/p-acetoxyacetanilide (AAA), and 2,5-thiophenedicarboxylic acid (TDA). Polarizing light microscopy and Fourier transform infrared spectra were used to study, in situ record the evolution of morphological change in the thin-film polymerization process, and confirm the occurrence of polymerization. Experimental results indicated that monomer structure and composition as well as temperature influence the formation of the liquid crystalline (LC) phase greatly and revealed that 2,5-thiophene structure is a viable mesogenic core unit. It is more effective than isophthalic acid (IA) in assisting in the LC formation as polymers containing TDA have a better developed LC phase and lower critical ABA content than those with IA. Stripe texture was observed in the ANA/DABP/TDA system, possibly due to the structural characteristics and matching of the monomers. The decrease of isotropic round areas in the LC phase and the annihilation between two pairs of defects with reaction time were also studied.

Two age-hardenable AlCuMg alloys (Cu 4.5 wt.% and Cu/Mg ratios of 2.5 and 8) were studied by electrical resistivity, differential scanning calorimetry, and microhardness measurements during natural and artificial aging at 110 °C. The results were interpreted in terms of Guinier–Preston/Guinier–Preston–Bagariatskij zone formation followed by a modification in θ″ and S″ intermediate phases.

The microstructure, melting point, and mechanical properties of Sn–8.55Zn–0.45Al–XAg lead-free solders were investigated. The Ag content of the solders investigated was 0–3 wt.%. The results indicate that the AgZn3 and Ag5Zn8 compounds are formed at the addition of Ag to Sn–8.55Zn–0.45Al solders. The adding of Ag also results in the formation of hypoeutectic structure, increasing the melting point of the solders and decreasing the ductility. Results of thermal analysis reveal that the Sn–8.55Zn–0.45Al–XAg solder has eutectic temperature at 198 °C when the addition of Ag is 0.5 wt.%. The eutectic solder exhibits greater tensile strength and higher ductility than the 63–Sn–37Pb solder.

While processing techniques for deposition of CuOx/Al multilayer foils were being developed, a method for synthesizing paramelaconite (Cu4O3) was serendipitously discovered. These paramelaconite films were successfully synthesized by sputter-deposition from a CuO target. Milligram quantities of uncontaminated material were produced enabling new studies of the morphology, stoichiometry, and thermodynamics of this unique copper oxide. At moderate temperatures, equiaxed paramelaconite grains deposited with a strong out-of-plane texture; at lower temperatures the paramelaconite grains showed no texture but were columnar in geometry. X-ray photoelectron spectroscopy showed that the as-deposited Cu4O3 had a nonstoichiometric Cu:O ratio of 1.7:1; the ratio of Cu+ to Cu2+ was 1.8:1. On heating, this phase decomposed into CuO and Cu2O at temperatures ranging from 400 to 530 °C. Using differential scanning calorimetry, the heat of formation and Gibbs free energy for Cu4O3 were estimated to be −453 and −279 kJ/mol, respectively. On the basis of these calculations and our observations, we confirmed that Cu4O3 is a metastable phase.

Microstructures of a TiC/Ni80Cr20 cermet, subjected to single high-current-density electropulsing, were characterized by x-ray diffraction, transmission electron microscopy, and high-resolution transmission electron microscopy. Under the electropulsing, the shift of NiCr peaks versus the reverse change of TiC counterparts illustrates that the treatment gives rise to strong thermal stress impacting on the cermet. The stress, accompanied by the transient rise of temperature, led to microstructural evolutions of the cermet. Some nanostructured TiC grains, consisting of many nanocrystallites with small-angle grain boundaries, developed during electropulsing. Also, many regions teemed with coexisting nanosized TiC and NiCr crystallites, which possessed good bonding. Within the NiCr regions, large amounts of deformation twins were produced by the electropulsing.

NiO-yttria-stabilized zirconia powder mixtures were prepared from reactive citrate-nitrate gels using the combustion technique. The influence of the fuel/oxidant molar ratio in the precursor on the combustion rate and its thermal characteristics was studied by thermal analysis and evolved gas analysis. It was found that the precursor thermal decomposition properties depended strongly on the citrate/nitrate ratio prior to the combustion. Intermediate precursors and final powder ashes were also analyzed by x-ray diffraction.

Diamondlike carbon (DLC) films were electrodeposited on nickel substrates from a solution of acetylene in liquid ammonia at low temperature and low potential using a three-electrode cell. Raman spectra showed a shoulder D peak at 1365 cm−1 and a broad G peak at 1558 cm−1 for the films, indicating an sp3 and sp2 carbon mixture. The presence of a 1230 cm−1 peak also indicated some four-fold-coordinated bonds of microcrystalline diamond. Fitting of the peaks in the Raman spectra specified the electrodeposited films were hydrogenated amorphous alloys, a-C:H. X-ray photoelectron spectra also pointed to the films containing a mixture of sp3 and sp2 carbon. Fourier transform infrared spectra of the electrodeposited films had C-H stretching vibrations, which is consistent with hydrogenated DLC films.

Ultrafine SiC and Al2O3 particles with 30–50 nm sizes were used to codeposit with Ni in a sulfamate bath to form composite coatings. The microstructure and mechanical properties of the layers were investigated by x-ray diffractometry, scanning and transmission electron microscopy, high-resolution transmission electron microscopy, microindentation, and wear testing. The microstructural results revealed that 7 vol% of SiC or Al2O3 particles dispersed randomly in the Ni matrix. The addition of the ultrafine SiC or Al2O3powder into the Ni matrix apparently reduced the size of Ni grains during the electroplating and inhibited the grain growth during heat treatment. The microhardness and wear resistance were improved by the addition of SiC and Al2O3 particles, especially for SiC/Ni samples after heat treatment at 400 °C for 24 h. The mechanisms of hardening and wearing of Ni-based electroplated layers are discussed.

We present results on the thermomechanical behavior of bare and nanocoated gold/polysilicon (Au/Si) bilayer cantilever beams for microelectromechanical system applications. The cantilever beams have comparable thicknesses of the Au and Si layers and thus experience significant out-of-plane curvature due to a temperature change. The experiments focus on the inelastic behavior of the bilayer beams due to thermal holding and thermal cycling. In uncoated Au/Si beams, thermal holding directly after release or thermal cycling both lead to a curvature decrease as a function of time or cycle number, respectively. The drop in curvature during thermal cycling or thermal holding in uncoated beams was not accompanied by a change in the slope of the thermoelastic curvature–temperature relationship. The absolute change in curvature depends on the temperature and the holding time. When holding or cycling to a temperature of 175 °C, the curvature change in uncoated beams is minimal for hold times up to 4500 min or 15,000 cycles. When holding or cycling to temperatures of 200 or 225 °C, the curvature in uncoated beams drops by a factor of three for hold times up to 4500 min or 15,000 cycles. The surface structure induced by long-term holding of uncoated beams shows grooving at the grain boundaries while the surface structure induced by cycling of uncoated beams shows consolidation of the grain boundaries. The Au/Si beams with a conformal 40-nm atomic layer deposition Al2O3 coating show a considerably different response compared to identical Au/Si bare beams subjected to the same thermal histories. The coating completely suppresses decreases in curvature when the beams are held at 225 °C for 4500 min. On the contrary, the coating does not always suppress thermal ratcheting when the beam is cycled from a low temperature to 225 °C. In the coated beams, the drop in curvature due to thermal cycling was accompanied by a change in the thermoelastic slope of the curvature–temperature relationship. Negligible microstructural changes were detected on the Al2O3-coated Au surface after holding or cycling. The results are discussed in light of potential deformation mechanisms and a simple analysis linking the mismatch strain between the layers to the curvature in the beams.

A pseudoternary alloy system was constructed by combining icosahedral quasicrystal (IQC), decagonal quasicrystal (DQC), and Zr into one alloy system. Different proportions of Zr were added into pseudobinary alloy IQC80DQC20 (in wt.%). The structural evolution in these alloys is discussed. An amorphous alloy composition was found in this system. Melt-spinning amorphous alloy was produced in this composition. Through differential scanning calorimetry experiments, the amorphous alloy exhibited a high glass-forming ability comparable to that of the Inoue alloy Zr65Al7.5Cu17.5Ni10.

Undoped and nitrogen-doped amorphous diamond were deposited on n-type Si(100) substrate by a cathodic arc process. By varying nitrogen partial pressure of the gas mixture in the range of 0 to 55.6%, up to 23 at.% of nitrogen was incorporated in amorphous diamond. The electron spectroscopy for chemical analysis, Raman, and atomic force microscopy measurements indicated that most nitrogen atoms replaced carbon atoms in the amorphous structure. The electron concentration, mobility, and its resistivity were determined by the measurement of Hall effect. With the increasing of nitrogen content, the resistivity curve is U-shaped with a local minimum. The electron emission current in vacuum was characterized based on the diode design. It was found that the electron emission was highly reproducible. This is in contrast to the high variability observed for carbon nanotubes. The lowest resistivity coating had the lowest “turn-on” electrical field of 0.7 V/μxm at the current density of 10 μA/cm2.

Nanostructured Cu/304 stainless steel (SS) multilayers were prepared by magnetron sputtering. 304SS has a face-centered-cubic (fcc) structure in bulk. However, in the Cu/304SS multilayers, the 304SS layers exhibit the fcc structure for layer thickness of ≤5 nm in epitaxy with the neighboring fcc Cu. For 304SS layer thickness larger than 5 nm, body-centered-cubic (bcc) 304SS grains grow on top of the initial 5 nm fcc SS with the Kurdjumov-Sachs orientation relationship between bcc and fcc SS grains. The maximum hardness of Cu/304SS multilayers is about 5.5 GPa (factor of two enhancement compared to rule-of-mixtures hardness) at a layer thickness of 5 nm. Below 5 nm, hardness decreases with decreasing layer thickness. The peak hardness of fcc/fcc Cu/304SS multilayer is greater than that of Cu/Ni, even though the lattice-parameter mismatch between Cu and Ni is five times greater than that between Cu and 304SS. This result may primarily be attributed to the higher interface barrier stress for single-dislocation transmission across the {111} twinned interfaces in Cu/304SS as compared to the {100} interfaces in Cu/Ni.

Enthalpies of drop solution in molten 52 wt.% LiBO2-48 wt.% NaBO2 at 1078 K were measured for RE1.1Si1.7Al0.6O6-1.5xNx (x = 0, 0.2, 0.4, 0.6, 0.8) glasses for RE = Nd, Gd, Dy, Er, and Y. Linear relations between enthalpies of formation from elements and nitrogen content indicate that, within the experimental composition range, sites occupied by nitrogen ions are approximately equivalent in energy for a given substitutional series. The energetics of different rare-earth SiAlON glasses appears to be dominated by differences in the acid/base character of the cations. The onset glass-transition temperature increases linearly with increasing nitrogen content for the same rare earth and with decreasing rare-earth ionic radius for the same nitrogen content.

A cosolvent-assisted spray pyrolysis process was developed for the formation of phase-pure metal particles from metal salt precursors without the direct addition of hydrogen or other reducing gas. Generation of phase-pure copper and nickel particles from aqueous solutions of copper acetate, copper nitrate, and nickel nitrate over the temperature range of 450 to 1000 °C was demonstrated. Addition of ethanol as a cosolvent plays a crucial role in producing phase-pure metal powders. Results of a modeling study of ethanol decomposition kinetics suggest that cosolvent decomposition creates a strong reducing atmosphere during spray pyrolysis via in situ production of hydrogen and carbon monoxide.

This work addresses the issues of coating of oxide fibers or laminates with debondable oxide interphases. It fabricates a model system for an alumina matrix reinforced with alumina fibers, wherein an enstatite interphase is transformation weakened, resulting in interphase debonding. A suitable multilayer coating sequence was chosen to act as a chemical bridge between the alumina fiber and matrix. The pulsed excimer laser ablation method (KrF excimer laser of λ = 248 nm) was used to deposit several oxide materials individually onto silicon wafers. Titania (TiO2 or T), aluminum titanate (Al2O3 · TiO2,Al2TiO5 or AT), and enstatite (MgO · SiO2, MgSiO3 or EN) layers were deposited from sintered target materials. X-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy investigations indicated that as-deposited coatings were amorphous or partially crystallized into nanosize grains, and their thicknesses were uniformly distributed over the Si-substrate, growing in columnar texture (although not as pronounced for enstatite). Transmission electron microscopy/energy dispersive spectroscopy analysis confirmed that the chemical composition of the coating materials was the same as that of the target materials and that the coatings were completely crystallized into nano- or submicrometer grain size after annealing at 1200 °C for 1 h. With these data, sapphire monofilaments were sequentially coated with five layers of Al2TiO5, TiO2, MgSiO3, TiO2, and Al2TiO5. This construction provided a chemical bridge between the alumina monofilament and the enstatite debondable interphase.

It is confirmed on the basis of extensive test results for various ceramic and metallic materials that the indentation load P versus penetration depth h curves (P–h curves) both in loading and unloading processes are well approximated with the quadratic formulas of P = k1h2 and P = k2(h – hr)2, respectively, and unloading parameter k2 is quantitatively related to the elastic modulus E′ of the material indented, where hr is the residual penetration depth after a complete unload. The unloading/reloading indentation processes for a locally deformed conical/pyramidal impression are well represented by the equivalent mechanical process of a conical/pyramidal indenter with the effective face angle of βeff = (β – βr) on a flat elastic half-space, in terms of the inclined face angles β and βr of the indenter used and of the residual impression formed, respectively. With utilization of the unloading parameter k2 and the relative residual depth of penetration ξr, a novel method is proposed for estimating E′. Theoretical considerations for a nonquadratic P–h unloading behavior are also made.

A moderate chemical method [i.e., the reaction of diborane (B2H6) and a mixture gas of ammonia and nitrogen (NH3/N2) over nanoscale iron boride at 1100 °C] was developed to explore the boron nitride (BN) nanostructures. The products were well characterized by high-resolution electron microscopy and energy-dispersive x-ray spectroscopy. Two types of novel core–shell nanocapsules of amorphous boron core encapsulated in crystalline boron nitride shell were obtained. The first one looked like a peanut with an amorphous B core containing a trace of BN crystallites, a transition layer of BN nanofibers and amorphous B, and a thornlike shell of BN nanofibers. The second one looked like a perfect sphere consisting of a pure amorphous B core and a rather smooth crystalline BN shell. These results not only provided us a new chemical method for preparing BN nanostructures but also enriched the important BN nanostructures family. A growth mechanism is also briefly discussed.