A comprehensive approach is presented for defining hydrogen activation and absorbing kinetics in heterogeneous Mg2Ni/Ni powder composites that were subjected to mechanical refinement. Hydriding tests were performed under conventional hydrogen dissolving and under reactive milling. Irrespective of the absorbing mode, the absorption kinetics is deceleratory throughout. Under conventional thermodynamic conditions, the hydriding rate depends strongly on the microstructural features of both the absorbing Mg2Ni intermetallic and the Ni phase. The latter plays an important role in the dissociative chemisorption of hydrogen. Under milling the hydrogen uptake and the hydriding kinetics also depend on the intensity of the milling processing, IM (watt g−1), with the absorption rate increasing exponentially with IM. The mechanical treatment was found effective even when thermodynamic absorption reached saturation level. Hydriding rates, mechanochemical gains, and instantaneous mechanochemical yields (mol J−1) were used to compare the processes on an absolute scale and to spotlight possible mechanisms controlling kinetics trends and absorbing features under milling.

Nanocrystalline BaTiO3 particle–polymer hybrid was synthesized by polymerization and hydrolysis of [2-(methacryloxy)ethoxy]triisopropoxytitanium (MEPT) and barium alkoxide. The precursor for hybrid was synthesized from prepolymerized MEPT and barium alkokide, which was then hydrolyzed to form BaTiO3 particle–polymer hybrids below 100 °C. BaTiO3 particles increased in crystallinity when the amount of water for hydrolysis increased. The nanocrystalline particles were identified to be BaTiO3 by electron diffraction. Nanometer-sized BaTiO3 particle–polymer hybrid was shaped to a film with a dielectric constant of 8.2 at 10 kHz. A suspension consisting of the hybrid and silicone oil responded to a direct-current field, exhibiting a typical electrorheological behavior.

The determination of the mechanical properties of polymers is more complex than that of many other structural materials, because they display time-dependence in their response to load. Generally, dynamic analysis techniques, such as dynamic mechanical thermal analysis (DMTA), are used to characterize the viscoelastic properties of bulk polymers. However, polymers are increasingly being used as thin films, the properties of which are not readily determined using conventional techniques. Nanoindentation offers the possibility of determining the properties of thin films but has generally only been used to measure static properties. Dynamic nanoindentation equipment has recently become available, but its accuracy with soft polymers is unproven. This paper presents results of a comparison between dynamic nanoindentation, DMTA, and differential scanning calorimetry (DSC) for the determination of the thermal response of four different polymers. A favorable comparison is shown, indicating that dynamic nanoindentation is capable of measuring the time-dependent properties of small samples of polymers.

Hardness and elastic modulus of micromaterials can be evaluated by analyzing instrumented sharp-tip-indentation load–depth curves. The present study quantified the effects of tip-blunting and pile-up or sink-in on the contact area by analyzing indentation curves. Finite-element simulation and theoretical modeling were used to describe the detailed contact morphologies. The ratio f of contact depth, i.e., the depth including elastic deflection and pile-up and sink-in, to maximum indentation depth, i.e., the depth measured only by depth sensing, ignoring elastic deflection and pile-up and sink-in, was proposed as a key indentation parameter in evaluating real contact depth during indentation. This ratio can be determined strictly in terms of indentation-curve parameters, such as loading and unloading slopes at maximum depth and the ratio of elastic indentation energy to total indentation energy. In addition, the value of f was found to be independent of indentation depth, and furthermore the real contact area can be determined and hardness and elastic modulus can be evaluated from f. This curve-analysis method was verified in finite-element simulations and nanoindentation experiments.

The definitions of hardness from nanoscratch and nanoindentation analyses with a spherical indenter were compared and shown to be mathematically equivalent for the case of zero interface shear stress (surface traction). The definition of nanoindentation hardness was taken as the ratio of the resultant force to the area of contact projected on a plane normal to the line of action of the resultant force, whereas in the case of the nanoscratch technique, the hardness and interfacial shear stress were related to the measured normal and lateral forces in a nanoscratch experiment, as well as to the cross-sectional area of the groove. The two definitions of hardness were then applied to nanoscratch experimental data from material systems covering a wide range of hardness values. The calculated values of hardness from the two definitions were based on the contact area, determined from the scratch residual profile and the elastic recovery of the plastically deformed surface, and yielded the same values of hardness within experimental error. The contact angle, and thus the contact area, was shown experimentally to be sensitive to interface shear stress: a positive increase in interface shear stress led to a reduction in contact area as compared to the case of a frictionless contact. For a material with given hardness, normal indenter force, and contact area, a positive or negative interface shear stress is balanced by a positive or negative change, respectively, in the lateral force about the value needed to maintain a static balance for a frictionless nanoscratch contact. A comparison of these effects with experimental data indicates that very hard materials tend to have negative to zero interface shear stress, which correlates to a sink-in effect, whereas the soft materials tend to have positive interface shear stress, which correlates to a pileup effect.

The stable mechanical property polystyrene (PS) nanotubes with array structure were first prepared by filtrating a solution or melt of normal molecular weight PS (Mn ≈ 180,000) into anodic aluminum oxide (AAO) template with only 200-nm pores. The results of transmission electron microscopy and scanning electron microscopy illuminated that PS tubules were successfully obtained and the wall thickness of PS tubules prepared by the 2.5 wt%, 5.0 wt%, and 10.0 wt% PS solution were respectively 50 nm, 70 nm, and 80 nm. The structure of polymer nanotubes depends strongly on the concentration of PS solution. It was found that the wall of the nanotubes derived from melt is thicker than that of the nanotubes from solution. When the polymer solution wets AAO template, a thin polymer film will be formed on the inner porous wall. The thin film/AAO composite membrane acts as a “second-order” template and is soaked repeatedly. So PS solution wets the template and forms nanotubes according to the multi-time wetting mechanism.

Friction stir processing (FSP) has been developed as a potential grain refinement technique. In the current study, a commercial 5083 Al alloy was friction stir processed with three combinations of FSP parameters. Fine-grained microstructures with average grain sizes of 3.5–8.5 μm were obtained. Tensile tests revealed that the maximum ductility of 590 was achieved at a strain rate of 3 × 10−3 s−1 and 530 °C in the 6.5-μm grain size FSP material, whereas for the material with 8.5-μm grain size, maximum ductility of 575 was achieved at a strain rate of 3 × 10−4 s−1 and490 °C. The deformation mechanisms for both the materials were grain boundary sliding (m ∼0.5) However, the 3.5-μm grain size material showed maximum ductility of 315 at 10−2 s−1 and 430 °C. The flow mechanism was solute-drag dislocation glide (m ∼0.33) This study indicated that establishing a processing window is crucial for obtaining optimized microstructure for optimum superplasticity.

Electroconductive ceramic composites, constituted of an insulating matrix (a composite AlN-SiC) containing 30 vol% of an electroconductive phase (MoSi2, ZrB2, or ZrC), were densified through hot-pressing. Microstructure and mechanical properties were compared to those of the AlN-SiC matrix material. All the ternary composites are good electrical conductors, with resistivities in the range 0.3 × 10-3 to 4 × 10-3 Ω·cm. Room temperature properties are improved by the addition of the electroconductive particles. Strength and toughness measurements at high temperature show that MoSi2-containing composite is stable up to 1300 °C (strength 611 MPa, toughness 3.7 MPa·m1/2), whereas ZrB2-containing composite is stable up to 1000 °C. ZrC-containing composite is not suitable for high-temperature applications due to poor oxidation resistance.

The low limit of the deposition temperature for atomic layer deposition (ALD) of noble metals has been studied. Two approaches were taken; using pure oxygen instead of air and using a noble metal starting surface instead of Al2O3. Platinum thin films were obtained by ALD from MeCpPtMe3 and pure oxygen at deposition temperature as low as 200 °C, which is significantly lower than the low-temperature limit of300 °C previously reported for the platinum ALD process in which air was used as the oxygen source. The platinum films grown in this study had smooth surfaces, adhered well to the substrate, and had low impurity contents. ALD of ruthenium, on the other hand, took place at lower deposition temperatures on an iridium seed layer than on an Al2O3 layer. On iridium surface, ruthenium films were obtained from RuCp2 and oxygen at 225 °C and from Ru(thd)3 and oxygen at 250 °C, whereas no films were obtained on Al2O3 at temperatures lower than 275 and 325 °C, respectively. The crystal orientation of the ruthenium films was found to depend on the precursor. ALD of palladium from a palladium β-ketoiminate precursor and oxygen at 250 and 275 °C was also studied. However, the film-growth rate did not saturate to a constant level when the precursor pulse times were increased.

The kinetics of methanol transport in 2-hydroxyethyl methacrylate (HEMA) homopolymer and 75/25 and 50/50 mol fraction HEMA/DHPMA (2,3-dihydroxypropyl methacrylate) copolymers at five different temperatures has been investigated using the sorption experiment technique. A combined case I and case II diffusion model was used to describe the transport processes. Four replicates for each temperature of each material having a nominal thickness of 0.1 mm were immersed in methanol maintained at 35, 40, 45, 50, and 55 °C, and the mass uptake as a function of time was measured gravimetrically. Experimental results are found to be in good agreement with model prediction at all temperatures and for all three materials. Both the diffusion coefficients of case I transport and velocity of case II transport increase with increasing temperature. D values at low temperatures (35 and 40 °C), which are in the 10−9 cm2/s range, of the HEMA homopolymer are less than those of the copolymers. On the other hand, the activation energies of case I transport of the copolymers are substantially higher than those of the HEMA homopolymer; however, the level of DHPMA loading in the copolymer does not seem to affect the activation energy. In addition, thermodynamic heat and free energy of mixing values indicate heat is released when HEMA/DHPMA copolymers are exposed to methanol and that the solvent/copolymer systems exist as a continuous phase. In contrast, the methanol/HEMA homopolymer system exists as separate phases.

The microstructure and composition of aluminum oxide films, formed by a two-step anodization process in various electrolytes at 100 V then subject to an intermediate heat treatment (500 °C, 2 min), were investigated. The anodization electrolytes used included ammonium adipate electrolyte, phosphoric acid electrolyte, ammonium dihydrogen phosphate electrolyte, and their mixtures. The cross-section morphologies, crystal structure, and chemical composition of aluminum anodic oxides were examined by transmission electron microscopy. X-ray photoelectron spectroscopy was carried out to study the surface chemical state of the anodic films. The corresponding capacitances and retention voltages of these oxide films were also explored. The results indicated that amorphous-to-crystalline transformation of the oxide, primarily in films formed in ammonium adipate electrolyte, was induced by the heat treatment. Electron diffraction analyses further revealed the oxide films consisted of two distinct zones, which included an inner amorphous layer and an outer layer containing crystalline γ′-Al2O3. This study found that the phosphorous species in either the primary or the re-anodization electrolytes had a potential to cause changes of Al and O distributions within the oxides. The oxide film primarily anodized in ammonium adipate and re-anodized in phosphoric acid had the highest capacitance due to its high degree of crystallinity and thinness compared to oxides formed in other electrolytes. The presence of phosphorus, from the primary anodization electrolytes, in the oxides could inhibit the formation of crystalline γ′-Al2O3 and, consequently, decrease the capacitances of the anodic films. At the same time, the retention voltage and hydration resistance of these oxide films were improved.

Heat treatment of γ-Ni(Al)/γ′-Ni3Al multilayer thin films demonstrates that multilayer hardness correlates with the magnitude of biaxial stress in alternating layers. Films with a columnar grain morphology and (001) texture were fabricated over a range of volume fraction and bilayer thickness via direct current magnetron sputtering onto NaCl (001) substrates at 623 K. The films were removed from substrates, heat-treated at either 673 K or 1073 K in argon, and then mounted for nanoindentation and x-ray diffraction. The biaxial stress state in each phase was furnished from x-ray diffraction measurement of (002) interplanar spacings. The 673 K treatment increases the magnitude of alternating biaxial stress state by 70 to 100% and increases hardness by 25 to 100%, depending on bilayer thickness. In contrast, the 1073 K heat treatment decreases the stress magnitude by 70% and decreases hardness by 50%. The results suggest that the yield strength of these thin films is controlled, in part, by the magnitude of internal stress. Further, thermal treatments are demonstrated to be an effective means to manipulate internal stress.

The plasticity-controlled growth rate of cavities during superplastic deformationwas statistically investigated for 5083 Al alloy and AZ31 Mg alloy. When the cavity growth rate was evaluated on the basis of macroscopic strain calculated using the displacement of the specimen, the growth rate for the Al alloy was larger than thatfor the Mg alloy. However, the growth rate of the Al alloy was in agreement withthat of the Mg alloy when the cavity growth rate was evaluated on the basis of the microscopic strain due to grain boundary sliding. The results obtained lead to two conclusions: (i) the rate of cavity growth is not affected by the kind of materials,that is, the nature of the grain boundary, and (ii) the microscopic strain due to grain boundary sliding should be used to evaluate exactly the rate of cavity growth for superplastic deformation.

A new Auger electron spectroscopical sputter depth profiling method was developed to determine the interdiffusion coefficient for the initial stage of diffusion annealing of thin films. The method is based on (i) adoption of an interdiffusion model appropriate for the specimen investigated and (ii) convolution of an accordingly calculated diffusion-induced concentration profile with the smearing effects due to atomic mixing, surface/interface roughness, escape depth of the Auger electrons, and preferential sputtering. The diffusion-induced concentration profile and the interdiffusion coefficient are determined by fitting in an iterative least-squares procedure of the calculated Auger electron spectroscopical depth profile to the measured one. The method was applied to bilayered and multilayered structures, exhibiting dominant grain-boundary diffusion and dominant volume diffusion, respectively. A very small extent of interdiffusion, characterized by diffusion distances as small as 1 nm, could be quantified.

The luminescence properties of nanocrystalline Y2O3:Er3+ prepared via wet chemical synthesis were investigated. A broadening of both the reflectance spectrum and 77 K luminescence spectrum (λexc = 488 nm) was observed in the nanocrystalline material compared to bulk Y2O3:Er3+. The spectral broadening was attributed to the presence of Er3+ ions on the surface of the particle, which experienced different crystal fields than the ions buried in the core of the particle. Upconversion was observed in both the bulk and nanocrystal material following excitation with 650-nm or 800-nm radiation. Following excitation with 800-nm radiation, an enhancement of the red (4F9/2 → 4I15/2) upconverted emission was observed and occurred as a result of the (4I9/2, 4I11/2) → (4I13/2, 4F9/2) ion-pair process that directly populated the 4F9/2 state. The magnitude of the red enhancement in the nanocrystalline material prepared via wet chemical synthesis was less than that of the identically doped bulk sample and less still than Y2O3:Er3+ nanocrystals prepared via a combustion synthesis technique. An explanation is proposed to account for the drastic difference in the red upconverted luminescence intensity.

In this paper, single-phase Yb α-SiAlON powder with rod-like crystals was fabricated by combustion synthesis. The microstructural development of the rod-like α-SiAlON crystals was studied, and anisotropic grain growth was observed. Furthermore, the growth mechanism of the rod-like α-SiAlON crystals was investigated, and the experimental results indicated that during the anisotropic grain growth, the fast growth plane was the basal plane in the hexagonal crystal lattice.

Preferred orientation in textured ceramics is often assessed by comparing the relative intensities of x-ray diffraction reflections to those of a randomly oriented ceramic using the Lotgering degree of orientation (f). However, this paper provides evidence that indiscriminate assessments of f can be misleading. Using measured intensities of a modestly textured tape cast bismuth titanate (Na0.5Bi4.5Ti4O15) ceramic, calculated f values vary from 7.4 to 73.2% depending on the reflections included in the calculation. The texture is also quantified by calculating the orientation distribution function (ODF) using measured pole figures. A model is then presented that demonstrates f is nonlinear with the multiple of preferred (00l)-orientations, the standard unit of the 00l pole figure.

Nix and Gao established an important relation between microindentation hardnessand indentation depth. Such a relation has been verified by many microindentation experiments (indentation depths in the micrometer range), but it does not always hold in nanoindentation experiments (indentation depths approaching the nanometer range). We have developed a unified computational model for both micro- and nanoindentation in an effort to understand the breakdown of the Nix–Gao relation at indentation depths approaching the nanometer scale. The unified computational model for indentation accounts for various indenter shapes, including a sharp, conical indenter, a spherical indenter, and a conical indenter with a spherical tip. It is based on the conventional theory of mechanism-based strain gradient plasticity established from the Taylor dislocation model to account for the effect of geometrically necessary dislocations. The unified computational model for indentation indeed shows that the Nix–Gao relation holds in microindentation with a sharp indenter, but it does not hold in nanoindentation due to the indenter tip radius effect.