Powders of Ba0.65Sr0.35TiO3 have been prepared by solution-based and conventional mixed-oxide routes. Powders made by freeze-drying a precursor solution of mixed catecholate complexes of BaTiO3 and SrTiO3 had the smallest particle size, but secondary grain growth during sintering negated the anticipated benefits of the nano-sized powder in relation to ceramic densification and microstructural control. Addition of manganese oxide suppressed secondary grain growth for catecholate powders, allowing 97% dense ceramics to be produced at a sintering temperature of 1300 °C, with grain sizes of ≤5 μm. Doped mixed-oxide samples continued to show secondary grain growth, leading to coarse microstructures with grain sizes ≤100 μm after sintering at 1400 °C. Curie peaks for catecholate samples were sharper than those for mixed-oxide samples, suggesting a more uniform distribution of Ba and Sr ions in the powders. Difficulties were encountered in controlling the (Ba + Sr)/Ti ratio of powders made by an oxalate solution-precipitation route.

Experimental studies of fibrous eutectic growth in succinonitrile–camphor reveal that models of the stable range of interfibrous spacings must incorporate the dynamic effects and the instability of the growth front of the fibrous phase, which determines the fineness and regularity of the microstructures. An analytical mathematical model for fibrous eutectic growth has been developed and compared with the experimental results. The selected wavelength scales obey , where d0, ls, lt are the capillary, diffusion, and thermal lengths, respectively. While only at a relatively high growth rate or steep temperature gradient, the scaling law λ2V = constant is fulfilled. It is found that the selected band of interfibrous spacings is very narrow. This means that the interfibrous spacing is almost unique at a given growth rate and a fixed temperature gradient. The effects of convection on the interfibrous spacing selection and fibrous phase instability of short wavelength perturbations have also been investigated. These studies reveal that the controlled solidification of a fibrous eutectic produces a very fine and regular microstructure.

A novel microwave-assisted combustion method was used to prepare Ni powder. The method involves the combustion reaction of nickel nitrate and urea as a fuel in the microwave field. The initiation of the exothermic peak of the combustion reaction was found to vary as a function of urea content. The microwave-prepared Ni powder was characterized using x-ray diffraction (XRD), scanning electron microscopy, atomic force microscopy, Fourier transform infrared spectroscopy, thermogravimetric (TG) analysis, differential thermal analysis (DTA), and magnetic measurement. The XRD pattern revealed that the Ni powder crystallizes with the cubic phase when the molar ratio of fuel to nitrate is varied between 5:1 and 6:1. Above or below that molar ratio, NiO phase coexists as an impurity along with the Ni phase. The magnetization value of Ni measured at room temperature is 53.5 Am2/kg, which is close to the value observed for commercial Ni powder (55.0 Am2/kg). The mechanism for the formation of the Ni and NiO phase is discussed based on the infrared, TG, and DTA data. The method shows that highly pure Ni powder can be prepared using urea as a fuel and microwaves as a source of energy via the solution combustion method.

We introduce the concept of meta-nanotubes, among which are hybrid carbon nanotubes (X@CNTs), which are CNTs whose hollow core is filled—fully or partially—with foreign atoms, molecules, or compounds. The article focuses on the latter, describing their potential interest and the various ways currently available to synthesize them, while providing examples of the resulting materials mainly taken from the author’s works but also from literature, as characterized by means of high-resolution microscopy and related techniques. We discuss advantages and drawbacks of the various synthesis routes to help willing scientists and engineers to define a strategy for X@CNT synthesis with respect to their specific goals and expectations. Some examples of peculiar properties and behaviors of X@CNTs will be provided as well, although such related investigations are still scarcely reported because we are dealing with quite new nanomaterials.

The surface tension of the Fe-P binary liquid solution was computed using a Butler's model in wide composition and temperature ranges by adopting the activity coefficient data that were evaluated from the phase diagram calculation. In the surface tension modeling, the Fe-P binary system was assumed as the Fe-Fe3P pseudo-binary system. The results of the computation were critically compared with the experimental data of the literature considering the effects of the size of the adsorbed elements and the interactions among them. The results of the computation at 1823 K showed good agreement with the selected experimental data of the literature in a wide composition range from 0 to 15 mass%P. Furthermore, the results of the computation at 0.5 mass%P showed good correlation with the selected experimental data of the literature in a wide temperature range from 1823 K to 1923 K.

We studied the deformation mechanisms and mechanics during indentation of polycrystalline gold thin films at depths below 100 nm. The measured material hardness decreased from 2.1 ± 0.1 to 1.7 ± 0.1 GPa after annealing for 4 h at 177 °C. Upon closer inspection, the hardness trends in the gold thin films were discovered to vary according to the indentation depth. At nanometer depths, the material hardness was quantified using multiple parameters, some of which were independent of the area calibration for the tip. The annealed specimen was very “hard” at low indentation depths, relatively soft at moderate indentation depths, and finally harder until the grain-size limit was reached. The as-deposited specimen demonstrated a relatively continuous harness trend as function of indentation depth, exhibiting monotonic convergence to Hall–Petch limited behavior. Discrete displacement jump events (excursions or “pop-ins”) were frequently observed for the annealed specimen but not for the as-deposited specimen. Variation in hardness, excursion activity, and displacement during the hold at maximum load was observed according to the applied loading, which was parametrically varied at constant strain rates. Hardness results are explained in terms of the population and evolution of defects present within the specimens. The population of point defects is also influential, and critical thermal fluctuations, as well as the thermally activated process of diffusion, are believed to influence hardness at the specimen’s free surface and further into its volume. After converging to a monotonic trend (proper tip engagement), the modulus of the gold was measured to be 106.0 ± 12.9 and 101.3 ± 6.0 GPa for the respective Au/Cr/Si specimens. These values exceeded predictions from the aggregate polycrystalline material theory, a representation used to estimate results for anisotropic single crystals. Exaggerated modulus measurements are explained as the result of the contribution of modulus mismatch with the substrate, pileup at the indentor tip, residual stress in the films, and crystallographic anisotropy of the gold.

Boron nitride nanotube (BNNT)/polystyrene (PS) composite films were fabricated for the first time using high-quality BNNTs synthesized via a chemical-vapor-deposition method. The composite films exhibited good transparency. Tensile tests indicated that the elastic modulus of the films was increased by ∼21% when a ∼1 wt% soluble BNNT fraction was in use. Dispersion of BNNTs in PS and interfacial interactions between them were investigated using transmission electron microscopy. The film thermal properties, such as stability to oxidation and glass transition temperatures were measured. The experimental results and simple theoretical estimates indicate that BNNTs is a promising additive material for polymeric composites.

Cu47Ti33Zr11Ni8Si1 metallic glass powder was prepared by gas atomization. Decomposition in the amorphous alloy and primary crystallization has been studied by differential scanning calorimetry (DSC), x-ray diffraction (XRD), and transmission electron microscopy (TEM). The glassy powder exhibits a broad DSC exotherm prior to bulk crystallization. Controlled annealing experiments reveal that this exotherm corresponds to a combination of structural relaxation and nanocrystallization. A uniform featureless amorphous contrast is observed in the TEM prior to the detection of nanocrystals of 4–6 nm in size. High-resolution TEM studies indicate that this nanocrystalline phase has a close crystallographic relationship with the γ–CuTi phase having a tetragonal structure. The product of the main crystallization event is also nanocrystalline, hexagonal Cu51Zr14, having dimensions of 20 nm. However, there is no evidence for possible amorphous phase separation prior to the nanocrystallization events.

Ultrafine, PbZr0.53Ti0.47O3 powder was synthesized by homogeneous precipitation of metal ions in aqueous solution using urea. The results obtained from different characterization methods were compared with those obtained from the conventional precipitation method using ammonia in terms of crystallization, homogeneity, and microstructure. The as-dried precipitate converted to the single-phase crystalline lead zirconate titanate powder when calcined at 550 °C and above. The calcined powder showed smaller particle size, minimum agglomeration, and uniform shape. The growth of the particles was very little at higher temperatures. Powdered samples that precipitated using urea crystallized directly to rhombohedral lead zirconate titanate, without any intermediate pyrochlore phase formation. The NH3-precipitated powder converted to rhombohedral lead zirconate titanate via metastable pyrochlore and it showed phase segregation upon annealing at higher temperatures. The reaction kinetics has been studied by x-ray diffraction, differential thermal analysis, and differential scanning calorimetry.

Nickel mono-silicide has been considered a promising silicide candidate for sub-90 nm nodes of integrated circuits manufacturing. To form high-quality nickel mono-silicide as source/drain contact electrodes, a two-step low temperature rapid thermal process has been proposed, in which the as-deposited Ni will react with silicon during a low temperature (<310 °C) first anneal. Due to the lower annealing temperature Ni2Si will form after the first anneal. To better control the silicidation process the growth kinetics of Ni2Si thin film fabricated by solid-state reaction of sputtered Ni thin film on n+/p junction at low temperature is investigated in this paper. It is demonstrated that between 260 and 280 °C the thickness of Ni2Si thin film has a linear rather than parabolic dependence on annealing time. The corresponding activation energy for this linear growth is found to be ∼1.35 eV.

Spider silk fibers were obtained by the monitored forced silking method. This procedure allows measurement of the silking force during the process and retrieving the fibers so their tensile behavior can be characterized. Silking conditions, including the reeling speed and the use of an anaesthetising gas, were varied to ascertain their influence on the tensile properties of the silk. In all cases, it was found that the tensile properties are determined by the silking stress, obtained by dividing the silking force by the diameter of the fiber. This suggests that the sophisticated spinning system of the spider can be characterized essentially by a single parameter, which controls the properties of spider silk almost independently of the reeling conditions.

We report a novel phenomenon in which minor element additions (∼1 at.%) can dramatically enhance the glass-forming ability (GFA) of CuZr(Al) metallic alloy, which can be cast into glasses with large cross-section sizes using a conventional casting method. The minor additions cause the liquidus temperature Tl to decrease from 1219 (for Cu50Zr50) to 1139 K [for (Cu50Zr50)92Al7Gd1], and the reduced glass transition temperature Trg (=Tg/Tl) of the alloys increases from 0.550 (for Cu50Zr50) to 0.613 [for (Cu50Zr50)92Al7Gd1]. The mechanism involved in the achievement of the superior GFA is explained by the stronger tendency of short-range ordering in the stronger microalloyed alloys as well as the thermodynamic and kinetic aspects.

The mechanical properties of NiAl/Ni micro-laminated composites with highly gradient microstructure have been investigated. Two types of composites with different gradient microstructures were prepared by reaction synthesis. Intermetallics of type I and type II composites mainly consisted of Al-rich Ni0.45Al0.55 with variable thickness and Ni-rich Ni0.58Al0.42 with similar thickness, respectively. As intermetallic volume fraction increased, yield strength of type II followed the rule-of-mixture well, while that of type I deviated due to the composition variation of intermetallic phases. Fracture toughness of type II was higher than that of type I, and all showed KR curves with upward curvature by large-scale bridging. Even though the relative strength of constituent phases in intermetallic/metal laminates was not constant due to the gradient microstructure, the fracture mode transition showed similar behavior to that of metal/ceramic laminates.

An investigation of Ni–Cu alloys electrodeposited from aqueous bath, using bothdirect current (dc) and pulsed current (pc) deposition techniques, has revealed many interesting features: A modulated structure with typical layer thickness of 90 and75 nm of copper-rich and nickel-rich layers, respectively, is formed in dc plating. A surprising observation was that the modulation direction was parallel to the substrate, unlike in the case of artificial multilayers wherein it is along the growth direction. No such compositional modulations were observed in pc-plating in the present work. Spinodal phase separation, accompanied by L10 ordering, was found to have occurred in the as deposited samples in both the cases. The size of the deposited crystals in both the cases has been found to be in the range of 2.5–30 nm. Detailed high-resolution transmission electron microscopy has shown that the atomic arrangements are nearly perfect right upto the boundaries of the nanosized grains.

This article is a study of monodispersed, submeter-sized solid carbon spheres having smooth surfaces and almost perfectly round shapes. These spheres were synthesized by pyrolysis of tetrahydrofuran in the absence of a catalyst. Microstructures of carbon spheres before and after graphitization were systematically investigated using electron microscopy, thermogravimetric analysis, and x-ray diffraction. The sphere is believed to consist of an underdeveloped spiral-shell core and a surface with discrete fragments of concentrically arranged graphene layers. Under lower temperature heat treatment, the underdeveloped spiral-shell structure changes to a well-developed spiral-shell structure. After graphitization, the spiral-shell core is shown to transform into continuous and closed polyhedral secondary shells, whereas the exterior discrete fragments of graphene sheets transform into discontinuous polyhedral surface shells. The mechanisms of these microstructural changes are discussed.

Growth morphologies and mechanisms of the carbide of group IVB and VB elements (MC carbide), a typical faceted crystal, were studied with an estimated cooling rate from 102 to 105 K/s. Results showed that although the growth morphologies of the MC carbide vary remarkably with solidification cooling rate, the solid/liquid interface is always atomically smooth, and the growth mechanisms are always lateral growth. The growth mechanism transition from lateral to continuous growth mode, which was predicted by the classic crystal growth theory, was not observed for the TiC type MC carbide within the estimated cooling rate range of 102–105 K/s.

Based on the best bulk metallic glass (BMG) forming alloy in the Mg−Cu−Y ternary system, we introduced Ag (or Ni) to partially substitute for Cu to improve the glass-forming ability (GFA). The objective of this paper is twofold. First, we illustrate in detail a recently developed search strategy, which was proposed but only briefly outlined in our previous publication [H. Ma, L.L. Shi, J. Xu, Y. Li, and E. Ma: Discovering inch-diameter metallic glasses in three-dimensional composition space. Appl. Phys. Lett. 87, 181915 (2005)]. The protocol to navigate in three-dimensional composition space to land large BMGs is spelled out step-by-step using the pseudo-ternary Mg−(Cu,Ag)−Y as the model system. Second, our ability to locate the best BMG former in the composition tetrahedron allows us to systematically examine, and conclude on, the effects of a given alloying element. The large improvement in glass-forming ability in the Mg−(Cu,Ag)−Y system relative to the based ternary will be contrasted with the reduced glass-forming ability in the Mg−(Cu,Ni)−Y pseudo ternary system. It is demonstrated that the improvement of glass-forming ability requires judicious choice of substitutional alloying elements and concentrations, rather than simple additions of multiple elements assuming the “confusion principle.”

Finite element analyses were carried out to simulate the loading, unloading, and reloading processes of indentation tests. It was found that the validity of applying the elastic contact theory to the indentation unloading process is strongly related to the strain hardening and residual stress in impression. It is the combination of strain hardening and residual stress that causes the unloading or reloading curves to show elastic loading in the range from zero to the maximum load whereas the reloading curve on the impression without strain hardening and residual stress shows elastic–plastic loading in the same range. These computations indicate that applying the elastic contact theory to the unloading or reloading processes, the fundamental prerequisite of the instrumented indentation technique, is valid because of the existence of strain hardening and residual stress. The mechanism of this hardening effect is discussed through energy analysis.

A novel, high-resolution remote Raman microscope was used for the direct in situ assessment of deformation on bridging fibers in a double-edge-notched SiC-Nicalon reinforced ceramic-glass matrix composite at various stages of monotonic tensile loading. The effect of notch length on the bridging strain profiles obtained by individually probing a large number of fibers across the bridged ligament of the composite was investigated. Bridging strain measurements in the microscale are used to identify the role and sequence of the failure micromechanisms developing within the bridging zone and are compared with their macromechanically derived counterparts. The difference of 25% in failure strain between the as-received fiber and the maximum value obtained on composite-fibers through laser Raman microscopy (LRM), is attributed to the different patterns of fiber failure in composites as compared to the techniques used for fibers characterization such as monofilament and bundle testing in air. This article demonstrates how the LRM-strain data can be utilized to obtain a direct, microscale measure of the interfacial-shear strength of the composite. The obtained interfacial shear strength (ISS) value of 7 MPa compares well with the macromechanically predicted value and offers a much higher precision compared to other experimental techniques.

The spectroscopic properties of Ba2Mg(BO3)2:Ce3+ and Ba2Mg(BO3)2:Eu2+ in vacuum-ultraviolet-vis range were investigated. The 5d crystal-field splitting components and the barycenter of Ce3+, the lowest 5d levels, the emission and the Stokes shifts of Eu2+ and Ce3+ in the host lattices, as well as the host-related absorption are identified and discussed in terms of the crystal structure of the host lattice.