The effect of TiO2 addition on the crystallization and phase transformation process in Li2O · Al2O3 · 4SiO2 gels with various TiO2 contents was investigated using differential thermal analysis, x-ray diffraction, and transmission electron microscopy. The activation energy increased from 98.2 to 184.6 kcal/mol as the TiO2 content rose from 2.0 to 8.0 wt. %. The crystallization sequence and phase transformation were similar in LAS gels with various wt.% of TiO2 additions, except in the case of a 2.0 wt.% TiO2 content. During calcination from 800 to 1200 °C, crystallization of the β-spodumene phase progressed with increasing temperature, and a minor crystalline phase, rutile, also appeared.

Binary SiO2/TiO2 and SiO2/Fe2O3 nanoparticle (diameter < 100 nm) aerosols of varying mole ratios of Ti or Fe to Si were generated in a premixed Bunsen-type aerosol flame reactor. The distribution of species within the particles was investigated using transmission electron microscopy, electron energy loss spectrometry, x-ray diffraction, and Fourier transform infrared spectroscopy. Phase segregation was observed to varying degrees in qualitative agreement with segregation expected from binary phase diagrams for the bulk systems. Differences between the SiO2/TiO2 and SiO2/Fe2O3 systems can be explained by considering the variation in the thermodynamically stable liquid-phase solubility and differences in the ability of iron and titanium ions to substitute for silicon ions in the network structure.

Supported and unsupported γ-alumina membranes and alumina–titania composite membranes were prepared using the sol-gel method. In the course of preparation, effects of acid concentration, type of acid, alkoxide, and binder on the particle size of the sols and pore size of the membranes were investigated by thermogravimetry and differential thermal analysis, N2 physisorption, and light scattering. It was observed that the particle sizes of all the sols had only a small affect on the pore sizes of the membranes. Qualities of the membranes were improved by addition of polyvinyl alcohol as binder to the boehmite precursor. This resulted in less critical but more controllable drying and calcining procedures. Composite membranes with different pore sizes from 3.2 to 4.8 nm and surface areas retained above 100 m2/g could be regulated by different alumina-to-titania ratios.

The effect of thermal aging at 473 K on martensitic transformation characteristics have been studied in the Cu–Al–Ni shape memory alloys. An increase of martensitic transformation temperatures as a result of aging has been observed. Furthermore, the martensitic transformation shows an evolution with aging time from a single β3 ⇒ β′3 structural transformation to a β3 ⇒ γ′3 + β′3 transformation. Using internal friction and thermoelectric power measurements, as well as specific thermal treatments, it has been determined that the mechanism responsible for this evolution is an increase in the degree of order, thus rejecting the participation of a γ1 precipitation process. Finally, the increase of order at the next nearest neighbors has been established as the main factor responsible of the evolution of the martensitic transformation characteristics.

Substrate curvature measurements were used to study stress changes during thermal cycling and isothermal tensile stress relaxation in 800 nm Al–0.5 wt% Cu and Al–1 wt% Si–0.5 wt% Cu films. For both compositions dislocation glide can describe the relaxation data well for temperatures up to 120 °C for Al–Si–Cu and up to 100 °C for Al–Cu. The average activation energy for Al–Si–Cu and Al–Cu is 1.7 ± 0.2 eV and 3.0 ± 0.3 eV, respectively. The athermal flow stress is the same for both and equal to 600 ± 200 MPa. This result is consistent with the obstacles for glide being Al2Cu precipitates, which, in the case of Al–Si–Cu, are fine and can be cut by the dislocations, and, in the case of Al–Cu, are strong and provide Orowan strengthening. Also, the stress changes during thermal cycling in the Al–Cu films are different from those in the Al–Si–Cu films. For Al–Cu films, the room temperature stress decreases after each thermal cycle, while for Al–Si–Cu stress changes during thermal cycling are stable from the second cycle on. These observations are supported by thorough transmission electron microscopy (TEM) studies.

We investigate the effects of layer thickness (t) on hardness (H) and rate sensitivity of the hardness (∂H/∂ ln ) in 1 μm-thick Cu/Nb nanolayer composites. For t < 10 nm, we find that H correlates with t according to H = H0 = H1t-1/2, suggestive of a Hall–Petch mechanism with layer interfaces replacing grain boundaries as barriers against dislocation motion. The measured levels of ∂H/∂ ln clearly indicate the operation of bulk-like dislocation mechanisms consistent with a Hall–Petch mechanism. However, based on a Haasen-plot activation analysis, it appears that the Hall–Petch coefficient, H1, is strongly rate-dependent, inconsistent with a conventional Hall–Petch mechanism. For specimens with t < 10 nm there is a saturation in hardness, but the rate sensitivity data indicate no clear evidence of a corresponding change in mechanism. Simple models are proposed.

Composite materials containing amorphous iron embedded in poly(methylacrylate) or poly(methylmethacrylate) and amorphous cobalt embedded in poly(methylacrylate) were formed using a sonochemical method. The physical and thermal properties of the composite materials were probed. A significant difference in the solubility of the iron–poly(methylacrylate) and cobalt–poly(methylacrylate) in various solvents was observed. This difference is accounted for by the stronger interaction existing between the cobalt and the surrounding polymer. For iron–poly(methylacrylate) this interaction is weakened due to the formation of an iron complex.

Details of microindentation of silicon, such as the semiconductor-to-metal transformation, which takes place on loading, have been examined using spherical indenters. Various forms of silicon are studied, including heavily boron-doped wafers and silicon damaged and amorphized by ion implantation as well as material containing dislocations. Results indicate that only silicon, which contains high concentrations of point defects or is amorphous, exhibits mechanical properties that differ significantly from undoped, defect-free crystal. Amorphous silicon exhibits plastic flow under low indentation pressures and does not appear to undergo phase transformation on loading and unloading. Indentation of compound semiconductors is also studied and the load/unload behavior at room temperature is quite different from that of silicon. Both gallium arsenide and indium phosphide, for example, undergo slip-induced plasticity above a critical load.

Ultrafine Fe–Ni(C) particles of various compositions were prepared by arc discharge synthesis in a methane atmosphere. The particles were characterized by x-ray diffraction, transmission electron microscopy, energy disperse spectroscopy, chemical analysis, x-ray photoelectron spectroscopy, Mössbauer spectroscopy, and magnetization measurement. The carbon atoms solubilizing at interstitial sites in γ–(Fe, Ni, C) solution particles have the effects of forming austenite structure and changing microstructures as well as magnetic properties. A carbon layer covers the surface of Fe–Ni(C) particles to form the nanocapsules and protect them from oxidization. The mechanism of forming Fe–Ni(C) nanocapsules in the methane atmosphere was analyzed.

Two intermetallic phases, R2Fe17 carbide and R2Fe14C, which are promising candidates for permanent magnets, are formed in the iron-rich R–Fe–C ternary alloy system (R = rare earths). Using x-ray diffraction and thermomagnetometry the phase formation, transformation, and thermodynamic relations between the two structures, prepared by high energy ball milling, are studied quantitatively for R = Sm. The results lead to a free energy diagram for the pseudobinary system of Sm2Fe17 and C. A maximum equilibrium carbon content, xc, has been established for the carbide Sm2Fe17Cx and its temperature dependence determined. Beyond the equilibrium concentration, Sm2Fe17Cx transforms into a mixture of Sm2Fe17Cxc, Sm2Fe14C, and α–Fe. Although not thermodynamically stable, Sm2Fe17Cx can still be formed through nonequilibrium processes by being kinetically favored over the stable phase(s). This feature is important for the production of Sm–Fe–C-based permanent magnets.

The microstructure of sputtered 10-nm thin films of equiatomic binary alloys of CoPt and FePt was characterized using transmission electron microscopy (TEM). Grain growth kinetics was examined using manual and digital analysis of bright-field TEM images and was seen to take two stages during annealing in these films. A rapid growth stage concurrent with the formation of a [111] fiber texture was observed to occur within the first 5–10 min of annealing, followed by a much slower growth stage after the fiber texturing was well advanced. Differences in grain growth rate and ultimate grain size were also observed to depend on heating rate.

A series of titanium composites, with varying volume fractions of titanium monoboride (TiB) whiskers, were made by mixing various proportions of titanium (Ti) and titanium diboride (TiB2) powders followed by hot pressing. The phases present were identified by x-ray diffraction. Microstructural examination revealed three different types of TiB whisker morphologies: (i) long and needle-shaped TiB whiskers that are isolated and randomly oriented in the Ti matrix at relatively low volume fractions (0.3), (ii) colonies of refined and densely packed TiB whiskers from intermediatevolume (0.55) to high volume (0.73 and 0.86) fractions, and (iii) coarse and elongated TiB particles with a few needle-shaped whiskers at the highest volume fraction (0.92). In all the composites, TiB was found to be the predominant reinforcement. However, in Ti–TiB composites with 0.86 and 0.92 volume fractions of TiB, a significant amount of TiB2 was also present. The relative volume fractions of Ti, TiB, and TiB2 phases were estimated from the integrated intensities of diffraction peaks by the direct comparison method employing the calculated structure factors and Lorentz polarization factors. The composite microstructure, as well as the evolution of different morphologies, of TiB whiskers is discussed.

The stabilization stage in the processing of carbon–silicon alloy (CSA) precursor fibers is investigated in this study. The critical stabilization parameters are identified and shown to control the mechanical properties of fibers both at the stabilization stage and, after further pyrolysis and controlled oxidation, to produce oxidation-resistant fibers. The attainment of infusibility in the stabilized fibers, necessary for the production of CSA fibers, determines the lowest stabilization degree, whereas the highest stabilization degree can be identified from the relationship between stabilization temperature and tensile properties of CSA fibers, thus enabling the optimum stabilization conditions to be determined. The CSA fibers produced by proper control of stabilization conditions significantly enhance mechanical properties, which are more than double those of CSA fibers obtained previously. Fourier transform infrared spectroscopy and nuclear magnetic resonance studies show that at stabilization temperatures above the optimum there is significant formation of silica in the stabilized fibers. This leads to a higher modulus but lower tensile strength and elongation.

The structure and composition of passive films electrochemically formed on AISI 304 and 316L stainless steels in a chloride-containing solution have been studied by soft x-ray absorption spectroscopy. Soft x-ray absorption spectra were taken at the oxygen 1s edge and at the transition metals (Cr, Fe, Ni) 2p edges, making it possible to determine the main contributions to the passive film's composition. The soft x-ray absorption spectra at the Cr 2p edges indicate that in all cases the passive film is mainly formed by Cr2O3. Spectra at the Fe and Ni 2p edges exhibit no significant contribution of Ni and Fe oxides to the passive layer composition. However, differences in spectral shape with respect to metallic Ni and Fe suggest the presence of a small amount of hydroxides, which is maximum for the AISI 304 stainless steel polarized at the lowest scan rate. The spectra at the O 1s edges confirm the results obtained at the transition metal edges.

By measuring the electrical resistance of a continuous unidirectional carbon fiber epoxy-matrix composite along the fiber direction during loading in this direction, fiber breakage was progressively monitored in real time. Fiber breakage occurred in spurts involving 1000 or more fibers. It started at about half of the failure strain during static tensile loading and at about half of the fatigue life during tension–tension fatigue testing. Immediately before static failure, at least 35% of the fibers were broken. Immediately before fatigue failure, at least 18% of the fibers were broken. The fiber breakage was accompanied by decrease in modulus.

A totally new technique of surface modification—thermal surface-alloying treatment for pure copper—was developed. A 0.2–1.8 mm copper alloy layer, which has a hardness 4 to 5 times higher than the pure copper substrate, was formed after the treatment. The significance of this technique is that the surface of pure copper can be efficiently hardened without significant reduction of the overall thermal and electrical conductivity. Variations of composition and microstructure in the alloy layer were studied after pure copper was surface alloy treated with aluminum.

A knowledge of the formation and rupture mechanisms for agglomerates is essential when seeking to model equipment designed to produce and process such materials. In the work described here, nanoindentation of “two-dimensional” agglomerate films, basically particulate coatings, was carried out to establish a means of identifying the generic breakage mechanisms for agglomerates. Selected applied load and penetration depth data in the range (0.02 mN and 700 nm, respectively) are provided as a function of the loading time during continuous loading for a model system composed rather of monodispersed colloidal silica particles (20–24 nm diameter) bound with a poly(methyl methacrylate) at 5 vol%. It is argued that these data enable the sequence of binder bridge failures to be observed, thus giving an indication of the breakage mechanism of the agglomerate and also the strength of the individual junctions. These data are also incorporated into a mechanical model that describes the rupture and deformation behavior of these planar agglomerate systems.

Novel biomaterials for application to artificial bone with modulus of elasticity close to that of natural bone were prepared using bioresorbable poly-L-lactic acid (PLLA) and high-strength β–Ca(PO3)2 fibers treated with dilute NaOH solution. PLLA dissolved by using methylene chloride was mixed with the fibers. After drying the mixture, it was hot-pressed uniaxially under a pressure of 40 MPa at 180 °C, resulting in fabrication of a PLLA composite containing β–Ca(PO3)2 fibers. Almost no degradation in the bending strength was observed even when a large amount of the fibers (≈50 wt. %) was introduced, and the modulus of elasticity was increased effectively with increasing the fiber content. The PLLA composite with modulus of elasticity of <5 GPa similar to that of natural bone was found to be prepared when the fiber content was over 35 wt. %. The bending test of the composites showed that very high energy is consumed for their fracture and that the fracture proceeds step by step, even beyond the maximum stress.

Chemical element properties are generally classified in six groups: size, atomic number, electrochemical factor, valence-electron, cohesive energy, and angular valence-orbital. It is well known that some bulk properties of materials, like electrical conductivity and heat capacity of metals, may be interpreted in principle based on their constituent chemical element properties. In this study, effects of additives in galvanizing have been correlated to the chemical element properties of the additives. By screening all chemical elements (in the periodic table of elements) with this model, new additives, like Ca, Sc, Ge, Sr, and Y, have been predicted to reduce the steel weight loss in galvanizing. This model may also help to design new alloys as additives.

Phase separation during the synthesis and decomposition of lead magnesium niobate (PMN)–ethylenediaminetetraacetic acid (EDTA) and PMN–citrate gels strongly affects perovskite Pb(Mg1/3Nb2/3)O3 phase formation. The PMN–EDTA gel was synthesized from a solution containing Pb–EDTA, Mg–EDTA, and peroxo–citrato–niobium complexes at pH 8. Pb–EDTA precipitation was avoided by using Pb:EDTA in the mole ratio >1:2.5 and flash pyrolyzing the PMN–EDTA solution at 225 °C. Consequently, the PMN yield increased from 80 to 98 wt%. The sequential decomposition of Pb–EDTA, Mg–EDTA, and peroxo–citrato–Nb in the PMN–EDTA precursor in 1 vol% O2 leads to phase separation of Pb and PbO and thus lowers the PMN yield to 92 wt%. At PO2 > 2.5 vol% the Pb, Mg, and Nb complexes cothermolyze to form ≥97 % perovskite PMN. The presence of a heterometallic citrato–Pb–Mg–Nb complex in PMN–citrate leads to oxygen partial pressure independent codecomposition of the Pb, Mg, and Nb complexes. Accordingly, PMN yields of ≥96 wt% were obtained from the PMN–citrate precursor for oxygen partial pressures between 1 and 5 vol%.