Thermal crystallization experiments carried out using calorimetry on several a-Si:H materials with different microstructures are reported. The samples were crystallized during heating ramps at constant heating rates up to 100 K/min. Under these conditions, crystallization takes place above 700 °C and progressively deviates from the standard kinetics. In particular, two crystallization processes were detected in conventional a-Si:H, which reveal an enhancement of the crystallization rate. At 100 K/min, such enhancement is consistent with a diminution of the crystallization time by a factor of 7. In contrast, no systematic variation of the resulting grain size was observed. Similar behavior was also detected in polymorphous silicon and silicon nanoparticles, thus showing that it is characteristic of a variety of hydrogenated amorphous silicon materials.

Microscale zirconia structures with intricate three-dimensional (3D) shapes and nanoscale features were synthesized using diatom (single-celled algae) microshells as transient scaffolds. After exposure to a zirconium alkoxide-bearing solution and firing at 550–850 °C, silica-based diatom microshells were coated with a thin, continuous nanocrystalline zirconia layer. Predominantly tetragonal or monoclinic zirconia could be produced with appropriate heat treatments. Selective silica dissolution then yielded freestanding zirconia micro-assemblies that retained the microshell shape and fine features. Such hybrid (biological/synthetic chemical) processing may be used to mass-produce nanostructured micro-assemblies with a variety of 3D, biologically replicable shapes and tailored compositions for use in numerous applications.

Highest strength for 7075 Al alloy was obtained by combining the equal-channel-angular pressing (ECAP) and natural aging processes. The tensile yield strength and ultimate strength of the ECAP processed and naturally aged sample were 103% and 35% higher, respectively, than those of the coarse-grained 7075 Al alloy counterpart. The enhanced strength resulted from high densities of Guinier–Preston (G-P) zones and dislocations. This study shows that severe plastic deformation has the potential to significantly enhance the mechanical properties of precipitate hardening 7000 series Al alloys.

Epitaxial anatase TiO2 thin films were successfully grown on lattice-matched SrTiO3 (001) substrates by a novel hydrothermal method at very low temperatures (120–200 °C). This method is extremely simple and inexpensive in that the SrTiO3 substrate itself provides the source material for the TiO2 film. X-ray diffraction confirmed the high crystallinity and phase purity of the anatase films. The epitaxial relationship between the film and the substrate was determined as (001)[100]anatase // (001)[100]SrTiO3. Atomic force microscopy revealed the average size of the anatase crystallites as approximately 50 to 200 nm.

It was found that after treatment under 10T magnetic field and temperature 900 °C the bending strength of NiAl–Cr(Mo)–Hf alloy is increased by about 75%. The fracture section observation shows that the specimens' ductility is enhanced by the magnetic field treatment. Electron probe microanalysis shows that after treatment of the magnetic field the Heusler phases at NiAl/Cr(Mo) grain boundaries are partially dissolved and the small Heusler phases particles at Cr(Mo) and matrix phases interfaces almost dissolved into NiAl matrix.

Measuring the toughness of brittle coatings has always been a difficult task. Coatings are often too thin to easily prepare a freestanding sample of a defined geometry to use standard toughness measuring techniques. Using standard indentation techniques gives results influenced by the effect of the substrate. A new technique for measuring the toughness of coatings is described here. A precracked micro-beam was produced using focused ion beam (FIB) machining, then imaged and loaded to fracture using a nanoindenter.

The primary transformation reaction of the Zr65Al7.5Cu27.5 ternary glassy alloy with a low oxygen impurity of approximately 100 mass ppm was investigated. We have discovered the precipitation of the metastable icosahedral phase with a fine grain size of 50–100 nm in diameter accompanying with the formation of stable Zr2Cu phase at the annealing temperatures ranging from 715 to 730 K. The lattice spacing of Zr2Cu phase decreases at higher temperatures, which is attributed to the rearrangement of Zr and Cu in the decomposition of the icosahedral phase. It is suggested that the formation of the icosahedral phase in the primary stage originates from the existence of the quenched-in icosahedral local atomic configuration in the glassy state.

The solid-state reactions between Al and TiO2 that occur during heating an Al/TiO2 nanocomposite powder produced using high-energy mechanical milling have been studied using thermal analysis, x-ray diffractometry (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) in combination with compositional microanalysis. It has been found that Al and TiO2 react in the temperature range from 650 to 800 °C, forming Al3Ti, but XRD analysis, SEM examination, and detailed TEM characterization of the powder particles heated to 800 °C show that the expected Al2O3 does not form. However, α–Al2O3 particles form during heating from 800 to 1000 °C. The possible reasons for the time gap between formation of Al3Ti and Al2O3 are discussed.

We report the formation of microstructure- and property-controllable Nd60Al10Ni10Cu20−xFex (0 ≤ x ≤ 20) alloys by varying the content of Fe element. The microstructure of the Nd-based alloy can be changed progressively from a full glassy state into a composite state with nanocrystalline particles in the glassy matrix and, finally, into a nanostructured state, accompanied by variation in magnetic property gradually from paramagnetic to hard magnetic. The role of Fe addition in the control of microstructure and magnetic property is clarified. We expect that the results would have implication in the development of the microstructure- and property-controllable functional materials for various applications.

Polyvinylpyrrolidone (PVP) reduction effect on free and complex Ag+ and Au3+ ions was studied from optical measurements by adding a metal precursor (K-30), commonly used as a stabilizer, to PVP. It was found that PVP has a strong reduction effect on free ionic metal, such as Ag+ ion in AgNO3, but much weaker on complex ionic metals, AuCl4− in HAuCl4 and Ag(NH3)2+ in Ag(NH3)2OH. This is explained based on the coordinative field of polar group in PVP molecules.

A facile solvothermal approach was successfully developed for the large-scale synthesis of amorphous phosphorus nitride imide (H3xP3N5+x) nanotubes with high luminescent properties by the reaction of 1,3,5-hexachlorotriphosphazene (P3N3Cl6) with sodium amide (NaNH2) at low temperatures. Transmission electron microscope images showed that the inner diameter of nanotubes is 120 ± 20 nm, wall thickness is 40 ± 10 nm, and length ranges from several to ten micrometers. Scanning electron microscope images revealed that the proportion of the nanotubes exceeds 90%. X-ray photoelectron spectroscopy spectra indicated that the binding energies of P2p and N1s are 133.30 and 398.40 eV, respectively, and the atomic ratio of P:N is 3:5.13. The infrared spectra of the sample are comparable to those of the reported HPN2 and HP4N7. Thermogravimetric analysis revealed that the product is very robust in a nonoxidizing atmosphere. The structure and the optical properties of the product and the annealed samples were investigated by x-ray diffraction and photoluminescence measurements, respectively.

Characteristics of the dynamic strain aging (DSA) in the Portevin-Le Chatelier effect are experimentally investigated by dynamic indentation tests and numerically analyzed by using literature models. Experimental results obtained on Al–Mg alloys show that the occurrence and development of the plastic instabilities—serrated indentation—depend strongly on the solute content. During dynamic microindentation tests the amplitude of microhardness drops—similarly to the global hardness—and is changing as a power law function of Mg solute content with an exponent of 2/3. It has been shown that the term describing the effect of DSA in serrated flow is not proportional but rather a power expression of the local solute concentration, Cs, on the dislocation line with the exponent of 1/2. Together with this, the kinetics of solute segregation during DSA is controlled by the pipe diffusion.

A two-step replication strategy to two-dimensional ordered polymer hollow sphere and convex structure arrays is presented based on polystyrene colloidal monolayer and inverse opal made of FeO(OH). We can control formation of a small hole on top of the hollow spheres by the concentration of polymer precursors, which could be of importance in selective permeability, nutrient and drug deliver, biotechnology, and even study of black-body irradiation in micro or nano space. In addition, the fabrication strategy is suitable for the most soluble polymer materials, which can solidify when they are concentrated.

Brillouin scattering has been used to study the elastic properties of alkaline-calcium silica hydrogels synthesized from the precipitation of sodium silicate solution with calcium hydroxide. To the best of our knowledge, this is the first determination of the bulk elastic moduli for this type of alkaline-calcium silica hydrogel, also referred to as the alkali-silica reaction (ASR) gel. The measured bulk moduli for the alkaline-calcium silica hydrogels were found to be between 4 and 8 GPa for the gel containing 0.08 M Ca(OH)2 and between 10 and 25 GPa for the gel containing 0.8 M Ca(OH)2, increasing with increasing pressure. Fourier transform infrared measurements were made to correlate the moduli to the silica speciation and network formation within the gels as a function of Ca(OH)2 content. Significantly, for the concentrations considered, both the interconnection of the silica species and the bulk modulus increased with increasing Ca(OH)2 content. On this basis, Brillouin scattering was confirmed to be a useful method for distinguishing between the bulk moduli of alkaline-calcium silica hydrogels in terms of chemical composition. The potential for further characterization of ASR gels as a function of composition and water content by this technique is highly promising.

High-temperature dilatometric studies on (Pb1−xCax)TiO3 (x = 0.35, 0.35, 0.40, 0.45) ferroelectric ceramics reveal negative thermal expansion for x ≤ 0.40. The negative thermal expansion coefficient for x = 0.30, as obtained by dilatometry and powder x-ray diffraction, were found to be −8.541 × 10−6 K−1 and −11 × 10−6 K−1, respectively, which are comparable to those of other well-known negative thermal expansion materials like ZrW2O8, NaZr2(PO4)3. Results of temperature-dependent x-ray diffraction studies are also presented to show that the large negative thermal expansion behavior for x = 0.30 persists in a very wide range of temperatures, 70–570 K. Ca2+ substitution reduces the value of the negative thermal expansion coefficient of pure PbTiO3 crystal, but it enables the preparation of strong sintered ceramic bodies. The negative thermal expansion behavior is shown to disappear above the ferroelectric Curie point and is restricted to only the tetragonal compositions of (Pb1−xCax)TiO3.

The surfactant cetyltrimethylammonium ion (CTA+) was confined within the galleries of montmorillonite (MMT) to obtain a series of organo-montmorillonites (C16-MMTs) through an ion-exchange intercalation reaction. The C16-MMT formed a single precipitate layer when CTA+ loading was 18.3 wt% but stratified at high loadings. The conformational disorder increased with increasing CTA+ loading. The upper precipitate was characterized by a larger gallery height and a higher surfactant loading in comparison with lower precipitate. The confined methylene chains adopted a lateral monolayer with a small percentage of conformation freedoms at CTA+ loading of 18.3 wt%. The intercalated methylene chains were arranged either in a lateral monolayer or in a tilted interdigitated bilayer at CTA+ loading of 24.7 wt% while in either a tilted interdigitated bilayer or a lateral bilayer at high CTA+ loadings. The different arrangements of methylene chains intercalated in the MMT galleries are believed to be the reason for the stratification.

Electrical conductivity of electronic interconnects made with Sn-based solders undergo a significant amount of deterioration during service. Several factors, such as anisotropy of Sn, coefficient of thermal expansion mismatches between the entities that make up the joint, and growth of intermetallic compounds present within the solder and solder/substrate interface, may contribute to the damage accumulation during thermal excursions and cause deterioration of properties. This study dealing with effects of aging and thermal shock on electrical conductivity, carried out with bulk Sn, and eutectic Sn–Ag in bulk and joint configurations, is aimed at evaluating the roles of the above factors on the deterioration of electrical conductivity from these thermal excursions.

Ti–Al–Si–C powder mixtures of two different compositions, namely, 58Ti–30Al–6Si–6C (at.%) and 50Ti–15Al–20Si–15C (at.%), were mechanically alloyed to investigate the solid-state reactions during such a process. The mechanically alloyed powders were characterized as a function of milling time by x-ray diffraction (XRD), scanning electron microscopy, energy-dispersive spectrometry, and transmission electron microscopy (TEM). XRD results showed that solid solutions of Ti were formed for a powder mixture of 58Ti–30Al–6Si–6C in about 20 h of milling, whereas Ti5(Al,Si)3 and Ti(Al,Si)C compounds started to form in the powder mixture of 50Ti–15Al–20Si–15C within just 5 h of milling. TEM observations demonstrated that the particle sizes were of nano and submicron scale in both cases. This investigation indicated that in mechanically alloyed Ti–Al–Si–C powder mixtures, the main solid-state reactions are due to interdiffusion and mechanically induced self-propagating reaction.

The carburization process of nanocrystalline iron in a flow of CH4/H2 mixture under atmospheric pressure at 580 °C in a differential reactor–thermobalance was studied. The course of reaction was followed by thermogravimetry, and the phase composition of the samples carburized to different degrees was determined by x-ray diffraction (XRD) and Mössbauer spectroscopy techniques. The XRD method was also used for calculating the mean crystallite size of unconverted iron after reaction at different time intervals. An unexpected relation between the average size of iron crystallites and the degree of conversion was found. The nucleation mechanism of the nanocrystalline iron carbide in the kinetic area of the reaction, limited by the dissociative adsorption of methane, has been suggested. According to this mechanism, iron crystallites are carburized successively, from the smallest to the largest.

Bulk metallic glasses with a maximum diameter of 2.5–5 mm were formed in Mg75Cu5Ni10Gd10, Mg70Cu15Ni5Gd10, and Mg65Cu20Ni5Gd10 systems by copper mold casting. There is a clear tendency for glass-forming ability (GFA) to increase with increasing solute content. These bulk glassy alloys exhibit a large supercooled liquid region (ΔTx) of 44–64 K, indicating high thermal stability of the supercooled liquid. The Young’s modulus, fracture strength, elastic elongation limit, and plastic strain are in the range of 54–59 GPa, 854–904 MPa, 1.50–1.55%, and 0.10–0.20%, respectively. The Mg65Cu20Ni5Gd10 alloy exhibited the highest values of Young’s modulus and strength, while the largest plastic strain was obtained for the Mg75Cu5Ni10Gd10 alloy. The bulk Mg–Cu–Ni–Gd-based metallic glasses exhibited distinct enhanced corrosion resistance compared to Mg65Cu25Gd10 glassy alloy in NaCl aqueous solutions. The fabrication of the Mg-based bulk glassy alloys exhibiting a high strength level of about 900 MPa and plastic strains of ∼0.2%, in conjunction with good corrosion resistance, indicates that the Mg-based bulk glassy alloys may be used as a new generation of structural material.