The electrical and mechanical properties of conducting polymer poly(3,4-ethylenedioxythiophene) coatings on microfabricated neural probes have been evaluated by electrochemical impedance spectroscopy and nanoindentation techniques. Our results reveal that for poly(3,4-ethylenedioxythiophene) coatings, the minimum impedance correlates well with the mechanical properties. The lowest impedance films are also those that are the softest. This is consistent with microstructural observations by atomic force microscopy and scanning electron microscopy showing an increase in the effective surface area (“fuzziness”) of the coatings. The presence of these conducting polymer coatings provides an intermediate step along the interface between the devices and brain tissue. This information provides clues for the design of strategies for improving the long-term performance of these electrodes in vivo.

The secondary osteon is the fundamental building block of compact cortical bone at the tissue level. Light and scanning electron microscopy have shown that the osteon consists of a laminated cylindrical composite of mineralized collagen fibril lamellae ∼5–7 μm thick. Using scanning nanoindentation and quantitative backscattered electron imaging on secondary osteons from the human femoral midshaft, we found that the indentation modulus shows a periodic variation between ∼24 GPa and ∼27 GPa within a single lamella. The average lamellar value remains nearly constant across the osteon and increases abruptly to more than 30 GPa at the interstitial bone interface. The local mineral content, determined from quantitative backscattered electron imaging at the indented locations, shows also a lamellar level modulation and is positively correlated with the indentation modulus at the same tissue position. We propose that such a mechanically and compositionally modulated structure may be an effective crack-stopping mechanism in bone.

Carbon nitrogen nanotubes and nanofibers with controlled nitrogen concentration have been prepared by reaction of cyanuric chloride and hexachlorobenzene (HCB) with sodium metal at 250 °C in cyclohexane. Electron microscopy and spectroscopic analysis were used to characterize the products. The total yields of the tubes and fibers decrease as the ratio of cyanuric chloride to HCB increases, and nitrogen content in the products could be controlled by the ratio. The nanostructures depended strongly on the nitrogen content. Lower nitrogen content was favorable for producing linear products.

Polymerized nitrogen-containing carbon nanobell structures were fabricated by microwave plasma-assisted chemical vapor deposition using the mixture of source gases: methane, nitrogen, and hydrogen. The nanobells with one end sealed and another open contained a nitrogen concentration of about 1–10 at.%. A first-principles calculation was performed to understand the nitrogen effect on the formation of a bell structure. Based on the growth mechanism, a continual nanojunction formed between nanobell and nanotube. The unique structures with a weak connection between two adjacent nanobells were useful for producing short nanotubes several tens of nanometers in length and diameter. In addition, the short length and open edges at the outside surfaces of nanobells also benefited the electron field emission, energy storage, and chemical reactivity.

Gold nanorods 100 nm in diameter were grown within polycarbonate membranes as templates by the electrodeposition technique. A low-temperature sulfidation process was used to make gold sulfide nanoshells around the nanorods with a thickness of ∼7 nm. Optical absorption measurements were carried out on sulfide-coated gold nanorods obtained by dissolving the polycarbonate membrane. Several peaks were observed. These were analyzed on the basis of longitudinal and transverse modes of gold nanorods, the core–shell structure of gold–gold sulfide, and the presence of nanoparticles of gold. Theoretical analysis was carried out using a modified Mie scattering formalism. Satisfactory agreement between experimental results and theoretical fits were obtained.

ZnO films are grown by the ultrasonic spray pyrolysis method on ZnO seeding layer deposited on Si (100) by pulsed laser deposition. The resultant film possesses a columnar microstructure perpendicular to the substrate and exhibits smooth, dense, and uniform morphology. The preferred orientation along the c-axis of the film is significantly enhanced compared to that without the seeding layer. ZnO film grown on ZnO-seeded silicon exhibits higher hall mobility, lower resisitivity, and higher photoluminescence intensity.

Fully dense aluminium nitride (AlN) ceramics consolidated by aqueous slip casting were obtained after sintering at 1750 °C for 2 h. The obtained samples were characterized by Vickers hardness (1000 Hv), flexural strength (200 MPa) and thermal conductivity (115 W/mK). YF3 and CaF2 were used as sintering additives in total amounts ranging from 5 to 7 wt% in YF3/CaF2 weight ratios of 1.25, 1.5, and 2. The compatibility between the thermochemically treated AlN powder and the sintering additives in the aqueous suspensions was investigated by rheological and zeta potential measurements. Highly concentrated (50 vol%) and well-dispersed suspensions could be prepared and used to consolidate homogeneous green bodies by slip casting. The phosphate species used to protect the surface AlN particles against hydrolysis could no longer be detected at temperatures higher than 1400 °C. X-ray diffraction results revealed that all the new crystalline phases formed upon sintering belong to the system Al–Y–O–Ca, but their specific compositions as well as the thermal properties of the sintered materials were shown to depend on the total amount and ratio of sintering aids.

Nanocomposite particles of anatase-type titania (TiO2) and cubic/tetragonal zirconia were synthesized from hydrothermal processing of TiCl4 and ZrOCl2·8H2O or ZrCl4 alcohol solutions at 160–200 °C. It was found that the morphologies and composition of the composite particles were mainly controlled by the precursors and the sequence by which the precursors were added. The TiO2–ZrO2 composite particles with nanoscale uniformity can be obtained by solvothermal processing of TiCl4 or a ZrO2 precursor together with preformed ZrO2 or yttria stabilized zirconia (YSZ) nanoparticles in ethanol. A novel one-step and non-template method for preparing ZrO2–TiO2 core–shell structured composite particles with hollow interior was identified, and possible reaction mechanism was suggested.

The paper is a brief retrospective review of our contribution to the Si:Er problem in the last decade. It contains a description of the experimental facilities, results of the light-emitting media (Si:Er and Si1−xGex:Er) research, and device applications.

Titanium dioxide (TiO2) was synthesized in the water-in-oil (w/o) microemulsion system of n-heptane/water/sodium bis (2-ethylhexyl) sulfosuccinate (AOT) surfactant. This study reports the effect of microstructure of the synthesized TiO2 nanoparticles on the photocatalysis degradation of phenol in an aqueous solution, as compared to commercial TiO2 (P25) and TiO2 synthesized by bulk precipitation. The results indicated that the rate of phenol decomposition catalyzed by the synthesized TiO2 from microemulsion techniques is faster than those of TiO2 synthesized by bulk precipitation and commercial P25. This is due to the small crystal size of TiO2 prepared by the microemulsion technique. The exposed titanium sites on the surface controlled by the morphology of synthesized TiO2 are critical for photocatalytic activity.

The use of rutile-type titanium dioxide (TiO2) thin films as advanced gate dielectrics has been hampered by thermodynamic instability during the high deposition or annealing temperature of 800 °C. In this work, we demonstrate that rutile-type TiO2 thin films can be produced on p-type Si (100) at lower substrate temperature by means of bias-assisted cathodic arc deposition. The influence of the substrate bias on the microstructural and dielectric characteristics of the TiO2 thin films is investigated in detail. Our results show that by applying a suitable bias to the Si substrate, as-deposited rutile-type TiO2 thin films can be obtained at 450 °C. The permittivity of the materials increases significantly from 21 up to 76. The interfacial and electrical properties of TiO2/Si (100) are also improved. The effects and mechanism of the bias on the microstructural and dielectric characteristics are described.

Here, we report investigations on the instability in luminescence of bare (trioctylphosphine oxide [TOPO]-stabilized) and CdS-capped CdSe particles under infrared radiation. During thermal annealing under radiation, the formation of oxide layers on the surfaces of the particles create defect states. Consequently, there is a reduction in particle size. These two effects control the light output from the samples. We make a quantitative comparison of the stability of bare CdSe and core-shell-type CdSe-CdS particles during annealing under infrared radiation. Using diffusion theory, we show that the volume of the oxide layer, adhered to the crystallites, plays a dominant role in controlling the luminosity of the particles.

A recently developed fast oxide ion conductor, namely lanthanum molybdenum oxide (La2Mo2O9, LAMO), was synthesized instantaneously by a citrate-nitrate auto-ignition process at a fixed citrate to nitrate ratio of 0.3 and characterized by thermal analysis, x-ray diffraction, impedance spectroscopy, and thermal expansion measurements. Crystalline LAMO has formed instantaneously during the combustion process. The signature of the order–disorder transition of stoichiometric LAMO around 570 °C was evident from differential thermal analysis, differential scanning calorimetry electrical conductivity, and thermal expansion measurements. Though the in situ x-ray measurements did not indicate any clear evidence of a phase transition, a stepwise change in the lattice parameter near the vicinity of the transition temperature was apparent thereby confirming the phase transition to be of first order in nature. The thermal expansion coefficient of LAMO was calculated to be 13.92 × 10−6/°K at 950 °C. The present method formed phase pure LAMO instantaneously and produced sintered samples with high conductivity, namely, 0.052 S/cm at 800 °C and 0.08 S/cm at 950 °C compared to LAMO prepared through various other solution routes.

A framework is presented for modeling the nucleation in the constitutionally supercooled liquid ahead of the advancing solid/liquid interface. The effects of temperature gradient, imposed velocity, slope of liquidus, and initial concentration have been taken into account in this model by considering the effect of interface retardation, which is caused by solute buildup at the interface. Furthermore, the effect of solute concentration on the chemical driving force for nucleation has been considered in this model. The model is used for describing the nucleation of Al–Si and Al–Cu alloys. It was found that the solute of Si has a significant impact on the chemical driving force for nucleation in Al–Si alloys whereas Cu has almost no effect in Al–Cu alloys.

Copper segregation in a subsurface layer during annealing of Cu60Zr30Ti10 bulk metallic glass at 773 K under oxygen atmosphere has been investigated by x-ray diffraction, Auger electron spectroscopy, x-ray photoelectron spectroscopy, and scanning electron microscopy. The formation of metallic copper is strongly dependent on the annealing environment. Various oxides with metallic copper are formed after annealing in oxygen atmosphere, but only crystalline intermetallic phases are found under vacuum annealing. Besides, surface characterization results show that the sample annealed in oxygen and vacuum result in enrichment and depletion of Cu on the surface region, respectively.

The synthesis of BaPbO3 from a wide range of mixtures containing metalorganic precursors, nitrate precursors, lead oxides, barium oxide and peroxide was investigated, and the kinetics was analyzed using the Johnson–Mehl–Avrami (JMA) equation. It was found that Ba and Pb stearate soaps and Pb oxalate that were used as metalorganic precursors formed BaCO3 and PbO or Pb3O4 after firing at 440 °C. The formation rate of BaPbO3 from a metalorganic precursor system is not higher than that from the conventional BaCO3–PbO system and does not depend on mixing methods or the kinds of metalorganic precursors but instead on the synthesis atmosphere. In the case of the BaCO3–PbO system, the Avrami exponent (n) is ∼1, indicating that the reaction is controlled by the phase-boundary-contraction interface reaction. For the BaO2–PbO2 system, n has two values ∼1 and ∼0.3, depending on the reaction temperature and time, indicating that the reaction is either controlled by the phase-boundary-contraction interface reaction or diffusion-controlled reaction. In the Ba nitrate–Pb nitrate system, phase-pure BaPbO3 is obtained at 550 °C, which is 250 °C lower than in the case of the BaCO3–PbO system. The value of n for the nitrate system is ∼1.5, indicating that the reaction is controlled by a three-dimensional (3D) diffusion-controlled nucleation mechanism. In the BaO–PbO system, the formation of BaPbO3 started at 350 °C by an exothermic reaction and the content of BaPbO3 in the product was ∼40 wt%, which is independent of reaction temperature as well as time in the temperature range of 350–500 °C.

High-temperature oxide melt drop solution calorimetry was used to study the energetics of formation of cubic silicon nitride prepared at high pressure. The standard enthalpy of formation of c-Si3N4 is −776.3 ± 9.5 kJ/mol. The calorimetric measurement of Si3N4 in 3Na2O·4MoO3 solvent was validated by comparing the enthalpy of formation for β–Si3N4 with previous work using alkali borate solvent. The enthalpy of transformation from β– to c-Si3N4 is 80.2 ± 9.6 kJ/mol. This value appears consistent with the observed synthesis conditions, which do not represent reversed equilibrium reactions.

This paper presents a shear assay method for the determination of the viscoelastic properties of biological cells. The method was applied to the measurement of the viscoelastic properties of human osteosarcoma (HOS) cells. It involves a combination of shear assay experiments and digital image correlation techniques. Following in situ observations of cell deformation during shear assay experiments, a digital image correlation (DIC) technique was used to determine the local displacement and strain fields. The creep curves were also extracted from multiple digital images that were used to extract the time dependence of local strain under constant stress conditions. The measured creep curves were well described by a generalized viscoelastic Maxwell model. The extracted elastic and viscous parameters were in good agreement with results obtained from prior studies with other techniques. The results also suggested that the nucleus is stiffer than the surrounding cytoplasm of HOS cells.

The data on the compositional dependence of glass-forming ability, glass transition, and properties of bulk metallic glasses (BMGs) are important for understanding the nature and glass-forming ability of metallic glasses and for their application. In this paper, we report the formation of rare-earth-based Pr–(Cu,Ni)–Al pseudo-ternary BMGs with a large bulk glass-forming composition range and distinct glass transition. The compositional dependence of glass-forming ability, glass transition, and properties were systematically studied. The contrasting effects of Al and Pr on glass formation and glass transition, unique elastic properties, and phonon softening of the BMGs are discussed from the structural point of view.

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.