In this work, Sr4La2Ti4Nb6O30 ceramics with tetragonal filled tungsten bronze structure were prepared, and the dielectric characteristics and ferroelectric transition were investigated. The room-temperature dielectric constant of the present ceramics showed very weak frequency dependency; it decreased from 570.4 to 561.7 when the frequency varied from 200 Hz to 1 MHz, and a comparatively low-dielectric loss was observed (in the order of 10−3). Unlike the situation for Ba4Ln2Ti4Nb6O30 (Ln = La, Nd and Sm), Sr4La2Ti4Nb6O30 ceramics showed a diffuse ferroelectric phase transition, and the diffuseness exponent γ was 1.61. Moreover, the obvious frequency dispersion was observed over a broad frequency range from 200 Hz to 1 MHz, and the maximum dielectric constant temperature Tmax shifted to higher temperatures with increasing frequency. The dielectric data agreed closely with the Vogel–Fulcher relationship. We concluded that tungsten bronze Sr4La2Ti4Nb6O30 has the relaxor ferroelectric nature.

Carbon nanotubes (CNTs) were grown on micron-sized Al2O3 particles in an atmosphere of methane and hydrogen at 700 °C under the catalysis of Fe–Ni nanoparticles that had been deposited on the surface of Al2O3 particles by an electroless plating technique. The individual and competitive adsorption capacities of Pb2+, Cu2+, and Cd2+ from aqueous solution by CNTs on Al2O3 particles were studied. The results showed that the adsorption behavior of these metal ions by as-grown CNTs on Al2O3 particles is in good agreement with the Langmuir adsorption model. The maximum individual adsorption capacities of Pb2+, Cu2+, and Cd2+ from water by as-grown CNTs on Al2O3 particles are 62.50, 27.03, and 9.30 mg/g, respectively. The CNTs on Al2O3 particles have promising potential applications in removing soluble heavy metals from aqueous solutions.

Highly (100)- and (111)-oriented lead magnesium niobate–lead zirconate titanate (PMN-PZT) films were deposited on Pt(111)/Ti/SiO2/Si substrates using a sol containing polyvinylpyrrolidone (PVP). The molar ratio of Zr/Ti in the PZT was fixed at 60/40, and the PMN content was changed in the range of 0–30 mol%. The films had a dense and columnar microstructure with a thickness of about 1 μm as a result of being spun four times. The crystallographic orientation of the films was controlled by adjusting the pyrolysis temperature; a (100) orientation was obtained by pyrolyzing at 300 °C and a (111) orientation by pyrolyzing at 350 °C. The electrical properties of the films were strongly dependent on the crystallographic orientation and PMN content. With increasing PMN content, the dielectric constant of all of the films increased. On the other hand, the remnant polarization of the (111)-oriented films decreased steadily with increasing PMN content, while that of the (100)-oriented films remained unchanged up to a PMN content of 20%. The piezoelectric coefficients of the (100)-oriented film were consistently higher than those of the (111)-oriented film with the same composition. The highest piezoelectric coefficient was observed for the (100)-oriented film with a composition of 0.2PMN–0.8PZT, indicating the morphotropic phase boundary between the rhombohedral PZT phase and the pseudocubic PMN phase is in the vicinity of this composition.

Technical issues surrounding the use of nanoindentation at elevated temperatures are discussed, including heat management, thermal equilibration, instrumental drift, and temperature-induced changes to the shape and properties of the indenter tip. After characterizing and managing these complexities, quantitative mechanical property measurements are performed on a specimen of standard fused silica at temperatures up to 405 °C. The extracted values of hardness and Young's modulus are validated against independent experimental data from conventional mechanical tests, and accuracy comparable to that obtained in standard room-temperature nanoindentation is demonstrated. In situ contact-mode images of the surface at temperature are also presented.

Electrochemically grown cadmium sulfide (CdS) nanorod arrays were studied with Raman spectroscopy. The resonant Raman spectroscopy unravels the enhanced electron-phonon interaction up to the fifth-order multiphonon process in the vertically aligned CdS nanorods after annealing. Resonant Raman scattering at room temperature reveals a surface phonon mode at 253 cm−1 in the annealed nanorod. This unprecedented observation is accounted for by the lateral confinement in the nanorod whose average aspect ratio is approximately 5. An intersubband transition near 3000 cm−1 is also observed. These results point to important optoelectronic applications of this material.

The silica skeleton of the deep-sea sponge Euplectella aspergillum was recently shown to be structured over at least six levels of hierarchy with a clear mechanical functionality. In particular, the skeleton is built of laminated spicules that consist of alternating layers of silica and organic material. In the present work, we investigated the micromechanical properties of the composite material in spicules of Euplectella aspergillum and the giant anchor spicule of Monorhaphis chuni. Organic layers were visualized by backscattered electron imaging in the environmental scanning electron microscope. Raman spectroscopic imaging showed that the organic layers are protein-rich and that there is an OH-enrichment in silica near the central organic filament of the spicule. Small-angle x-ray scattering revealed the presence of nanospheres with a diameter of only 2.8 nm as the basic units of silica. Nanoindentation showed a considerably reduced stiffness of the spicule silica compared to technical quartz glass with different degrees of hydration. Moreover, stiffness and hardness were shown to oscillate as a result of the laminate structure of the spicules. In summary, biogenic silica from deep-sea sponges has reduced stiffness but an architecture providing substantial toughening over that of technical glass, both by structuring at the nanometer and at the micrometer level.

We report on significant asymmetry phenomena, including failure mode, fracture strength, and plasticity under compression and tension, for Zr- and Ti-based composites containing ductile dendrites. The failure of the Zr-based composite always occurs in a shear mode with a small strength asymmetry and different plasticity under tension and compression. In contrast, the Ti-based composite exhibits a significant high strength asymmetry and zero tensile plasticity although its compressive plasticity is high. We propose that the ratio, α=τ0/σ0 (τ0 and σ0 are the intrinsic shear and cleavage strengths), is a substantial parameter controlling the strength asymmetry and the failure mode of various materials.

Lotus-type porous stainless steel (SUS304L), possessing cylindrical pores aligned in one direction, was fabricated by means of a continuous zone melting technique undera pressurized hydrogen/helium atmosphere. Compression tests were carried out on the resultant lotus stainless steel not only in the directions parallel and perpendicular tothe elongated-pore direction but also in other directions to reveal its anisotropic compressive behavior. The macroscopic deformation modes depend on porosity and the angle between the elongated-pore direction and compression direction, which is a unique characteristic resulting from its anisotropic porous structure. The yield stress in the pore direction decreases almost linearly with increasing porosity, while that in the perpendicular direction decreases more rapidly. The yield stress in the direction of θ from the elongated-pore direction decreases monotonically with increase in θ. The yield behavior of lotus stainless steel was described using micromechanical mean-field theory.

The photoluminescence spectra of the rod-shaped pure and Ti-doped MgAl2O4 single crystals, grown by the micro-pulling-down (μ-PD) method, have been systematically investigated under high-intensity pulsed Nd3+: YAG laser excitation in the ultraviolet (UV) region (266 nm). The chemical properties of the grown crystals under reducing argon atmosphere will be reported and the annealing effect under oxidizing atmosphere will be discussed. The room temperature luminescence properties of Ti-doped MgAl2O4 single crystals were performed before and after annealing as a function of the titanium concentration. Three broad bands absorption in the UV/VIS (visible) spectral regions and a broadband visible blue emission were observed from Ti-doped MgAl2O4. An estimation of the decay time value of theses emissions was determined from the time-resolved spectra and the energies of the vibrational modes of the MgAl2O4 crystal are obtained from the infrared spectra.

Binder-free macroscopic single-walled carbon nanotube (SWCNT) solids were prepared by spark plasma sintering (SPS) of purified SWCNTs. The effects of processing temperatures and pressures on the mechanical properties of the SWCNT solids and structural change of SWCNTs in the SWCNT solids were investigated. Transmission electron microscope observation of the SWCNT solids revealed thatthe high-temperature treatment has transformed some part of the SWCNTs into amorphous-like structure and the rest of the SWCNTs remained buried into the above structure. The mechanical properties of the SWCNT solids increased with the increasing processing temperature, probably reflecting the improvement of interfacial strength between SWCNTs and disordered structure of carbon due to the spark plasma generated in the SPS process.

Tendons may be classified as intrasynovial or extrasynovial based upon their anatomic location. We studied the physical properties of extrasynovial and intrasynovial tendons. Extrasynovial tendon has a rougher surface and higher friction than intrasynovial tendon. A number of carbodiimide derivatized biomaterials were developed to modify the irregular surface of an extrasynovial tendon to mimic the smooth surface of an intrasynovial tendon. We found that carbodiimide derivatized hyaluronic acid-gelatin (cd-HA-gelatin) chemically bonded to the extrasynovial tendon surface and optimally reduced gliding resistance in vitro. This biosynthetic, biomimetic modification of the extrasynovial tendon surface may prove to be a useful clinical product.

Nanoporous silica zeolite thin films are promising candidates for future generation low-dielectric constant (low-k) materials. During the integration with metal interconnects, residual stresses resulting from the packaging processes may cause the low-k thin films to fracture or delaminate from the substrates. To achieve high-quality low-k zeolite thin films, it is important to carefully evaluate their adhesion performance. In this paper, a previously reported laser spallation technique is modified to investigate the interfacial adhesion of zeolite thin film-Si substrate interfaces fabricated using three different methods: spin-on, seeded growth, and in situ growth. The experimental results reported here show that seeded growth generates films with the highest measured adhesion strength (801 ± 68 MPa), followed by the in situ growth (324 ± 17 MPa), then by the spin-on (111 ± 29 MPa). The influence of the deposition method on film–substrate adhesion is discussed. This is the first time that the interfacial strength of zeolite thin films-Si substrates has been quantitatively evaluated. This paper is of great significance for the future applications of low-k zeolite thin film materials.

Existing indentation models (both analytical models and numerical analysis) show a linear relationship between δr/δm and H/Er, where δr and δm are the residual and maximum indentation depth, and Er and H are the reduced Young's modulus and hardness of the test material. Based on the analysis of Oliver and Pharr, a new relationship between δr/δm and H/Er has been derived in a different way without any additional assumptions, which is nonlinear, and this has been verified by finite element analysis for a range of bulk materials. Furthermore, this new relationship for residual depth is used to derive an analytical relationship for the radius of the plastic deformation zone Rp in terms of the residual depth, Young’s modulus, and hardness, which has also been verified by finite element simulations for elastic perfectly plastic materials with different work hardening behavior. The analytical model and finite element simulation confirms that the conventional relationship used to determine Rp developed by Lawn et al. overestimates the plastic deformation, especially for those materials with high E/H ratio. The model and finite element analysis demonstrate that Rp scales with δr, which is sensible given the self-similarity of the indentations at different scales, and that the ratio of Rp/δr is nearly constant for materials with different E/H, which contradicts the conventional view.

Generally, ratcheting is studied on round specimens under tension–compression tests with a nonzero mean load. This work explored the possibility of studying ratcheting by indentation fatigue with a flat cylindrical indenter. In the experiment, emphasis was concentrated on the influence of maximum indentation load (Pmax.), indentation load variance (ΔP = Pmax − Pmin) and frequency of cycling (f) on the indentation depth–cycle curves. The experimental results showed that the indentation depth–cycle curves are analogous to the conventional strain–cycle curve of uniaxial fatigue testing, which has a primary stage of decaying indentation depth per cycle followed by a secondary stage of nearly constant rate of indentation depth per cycle. It was found that the steady-state indentation depth per cycle is an approximate linear function of maximum indentation load (Pmax) and indentation load variance (ΔP = Pmax − Pmin) in the log–log grid. This relationship can be given with a power-law expression as an analogous equation of steady-state ratcheting rate. Further study showed that the influence of frequency of cycling on the steady state indentation depth per cycle can be ignored when the frequency of cycling exceeds a certain value. Finally, comparison was made between the conventional uniaxial fatigue test and indentation fatigue test for the steady-state stage. It was shown that the conventional uniaxial fatigue parameters can be obtained by the indentation fatigue method.

Minor additions of Sn in the bulk glass-forming Fe61−xSnxY2Zr8Co5Cr2Mo7B15 (x = 0% to 2%) system were studied in detail. It was found that combinations of Y and Sn can scavenge oxygen out of the undercooled liquids to form innocuous oxides, thus stabilizing the liquids. Besides this beneficial scavenging effect, Sn additions in the present Fe-based alloys also showed complex alloying effects on glass formation, which can be divided into three stages. At stage I (x ≤ 0.5%), the microalloyed compositions associate with the same eutectic as that of the base alloy. The glass-forming ability (GFA) of the resulting alloys is determined primarily by their liquidus temperature and similar to that of the base alloy. At stage II (0.85% ≤ x ≤ 1.15%), glass-matrix composite structures start to form because the alloy compositions are adjusted into a new “deeper” eutectic system. At stage III (x > 1.15%), however, alloy compositions shift to another new eutectic system, and the GFA is dramatically decreased due to the strong formation of primary phase α–Fe. Homogeneous glass-matrix composites with a diameter of 7 mm in the alloy containing 1.0–1.15% Sn were successfully produced.

Biaxially textured magnesium oxide (MgO) templates of 10-nm thickness were successfully fabricated on glass and silicon substrates without any buffer layers using Ar+ ion beam assisted e-beam evaporation. With an additional layer of 100 nm homoepi MgO on top, the in-plane misorientation of ∼6.5° and out-of-plane misorientation of ∼2.0° have been obtained. Prior to growth, the substrates were bombarded with the same Ar+ ion beam for a certain period ranging from 5 to 35 min to provide initial substrate conditions for textured MgO formation. The ion beam induced modification of the substrate surface morphology was characterized using atomic force microscopy. Reduced surface roughness Ra from 2 to 3 nm on the original glass substrates to below 1.0 nm after 5 min ion beam bombardment was found to be an important condition for the textured MgO formation. The nearly unchanged Ra ≤ 1 nm of the silicon substrate after the ion beam bombardment, however, suggests that additional surface modification is required for the textured MgO to form.

NiCoCrAlYSiB coatings were deposited on the Co-based superalloy K40 by arc ion plating (AIP). The oxidation behavior of the bare alloy and of the coated specimens was tested in static air for 200 h at 1000 °C and 100 h at 1050 °C. The results showed that the oxidation rate of the system was greatly reduced by the addition of the NiCoCrAlYSiB coatings. Thin and adherent α–Al2O3 scales that formed on the coated specimens protected the substrates from further oxidation attack while non-protective oxide scales, mainly of Cr2O3 and CoCr2O4, appeared on bare K40 alloy. Element profiles on metallographic cross sections indicated that apparent interdiffusion occurred between the coatings and the substrates. The interdiffusion behavior and the resulting microstructure were investigated. As compared to aluminide coatings, NiCoCrAlYSiB coatings have less influence on the substrate microstructure.

A novel cyclotriphosphazene-based low-molecular weight organogelator was prepared by immobilization of six dialkylated L-glutamide derivatives on a cyclotriphosphazene core, and its ability as a self-assembling organogelator was investigated. The organogelator exhibited enhanced gelation ability and chirality, and thixotropic property for self-restoring to a gel state; this was compared to the corresponding L-glutamide-derived organogelator without the core. The gelation test, transmission electron microscopy observation, and circular dichroism (CD) spectral study showed that the gelation and aggregation ability were enhanced by immobilization onto the cyclotriphosphazene core. Gels in chloroform and cyclohexane-ethanol (95:5) mixture showed an unusual thixotropic property.

Carbon nanotubes are interesting for studying the remarkable electronic properties of one-dimensional (1D) quantum systems. Electron flow in such systems is not described by Fermi liquid theory—restricted dimensionality leads to the appearance of collective excitations—or Luttinger liquid behavior. Previous studies have probed Luttinger liquid behavior by tunneling into or between one-dimensional systems. We propose to extend these studies by using narrow top gates to introduce tunable tunnel barriers within nanotubes. We report on the scalable fabrication of carbon nanotube-based transistors with nanowire top gates. We have used electron-beam lithography (EBL) to create single-walled carbon nanotube (SWNT) transistors with source-drain spacings down to 200 nm and with sub-30 nm metal top gates for creating tunable tunnel barriers. The top metal gate is isolated from the nanotube by a thin aluminum oxide layer deposited by atomic layer deposition. We fabricated chips with 100 devices using multiple electron-beam lithography alignment steps and achieved overall placement better than 30 nm. The details of top-gated SWNT transistor fabrication are presented, and initial transport measurements on fabricated devices are discussed.

This paper quantitatively describes the loading-unloading response in nanoindentation with sharp indenters using scaling analyses and finite element simulations. Explicit forward and inverse scaling functions for an indentation unloading have been obtained and related to those functions for the loading response [L. Wang et al., J. Material Res.20(4), 987–1001 (2005)]. The scaling functions have been obtained by fitting the large deformation finite element simulations and are valid from the elastic to the full plastic indentation regimes. Using the explicit forward functions for loading and unloading, full indentation responses for a wide range of materials can be obtained without use of finite element calculations. The corresponding inverse scaling functions allow one to obtain material properties from the indentation measurements. The relation between the work of indentation and the ratio between hardness and modulus has also been studied. Using these scaling functions, the issue of nonuniqueness of the determination of material modulus, yield stress, and strain-hardening exponent from nanoindentation measurements with a single sharp indenter has been further investigated. It is shown that a limited material parameter range in the elastoplastic regime can be defined where the material modulus, yield stress, and strain-hardening exponent may be determined from only one full indentation response. The error of such property determination from scattering in experimental measurements is determined.