Materials Literature
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We show that the delivery of fracture work to the tip of an advancing planar crack is strongly reduced by surface phonon emission, leading to forbidden ranges of crack speed. The emission can be interpreted through dispersion of the group velocity, and Rayleigh and Love branches contribute as well as other high freque…
The interaction of vacancy with dislocations in Al is studied using the semidiscrete variational Peierls-Nabarro model with ab initio determined gamma surface. For the first time, we confirm theoretically the so-called vacancy lubrication effect on dislocation motion in Al, a discovery that can settle a long-standing…
Redispersible near-infrared emitting lanthanide-doped nanoparticles are reported. The emission and excitation spectra have been examined and the luminescence lifetimes of these materials have been determined. High quantum yields and lifetimes in the millisecond region were found. It is furthermore demonstrated that th…
The limited thermal stability of alkylammonium cations intercalated into smectite minerals (e.g., montmorillonite, MMT) and the processing instability of some polymers [polyamide-6 (PA-6) and polystyrene (PS)] in the presence of nanodispersed MMT have motivated the development of improved organophillic treatments for…
We report on the electrochemical study of three carbon nanotube ensemble electrodes: single-walled nanotube paper, as-produced multiwalled nanotube towers, and heat-treated multiwalled nanotube towers. Cyclic voltammetry was used in 0.10 M KCl containing 5.0 mM K 4 Fe(CN) 6 to obtain information on both the capacitive…
Thermoresponsive polymer brushes have been grown via surface-initiated atom-transfer radical polymerization from micropatterned substrates (see Figure). Atomic force microscopy both in topography and adhesion force mode shows that the brush domains undergo reversible phase changes in water around the polymer’s lower c…
Micelle-templated mesoporous silica materials are rapidly becoming important in many fields of chemistry for hosting reactants or catalysts in confined space. Fine control of the pore size, wall structure, surface functionalization, defects, and morphology is needed for fine-tuning the pores as nanoreactors. We review…
Large-area silicon nanowire arrays have been prepared on a silicon wafer without the use of a template. The simple method, which can be carried out near room temperature, involves the nanoelectrochemistry of silver nanowires in an aqueous HF solution containing silver nitrate. This technique may be generally applicabl…
Experimental evidence is provided that colossal dielectric constants ${\ensuremath{\varepsilon}}^{\ensuremath{'}}>~1000,$ sometimes reported to exist in a broad temperature range, can often be explained by Maxwell-Wagner-type contributions of depletion layers at the interface between sample and contacts or at grain…
Ambient optical detection of labeled molecules is limited for fluorescent dyes by photobleaching and for semiconducting nanoparticles by "blinking" effects. Because nanometer-sized metal particles do not optically bleach, they may be useful optical labels if suitable detection signals can be found. We demonstrate far-…
Crystalline silicon microcavities resonant at 1.1 μm were fabricated by using submicron thick Si membranes from a silicon on insulator substrate. These membranes were composed of a single crystalline Si film layered above and below two thin silicon dioxide layers. The low temperature photoluminescence (PL) of the memb…
Geometry optimization and harmonic vibrational frequency calculations have been carried out on various structures and low-lying, high- and low-spin electronic states of Al 2 N 4 and AlN n clusters, where n = 4 to 7, at the B3LYP, MP2, and QCISD levels. The aim of these calculations was to search for states/structures…
DC resistivity of Mn x Ni 0.5- x Zn 0.5 Fe 2 O 4 with compositions x =0.05 to 0.4 prepared by the citrate precursor method has been investigated. It has been observed that resistivity decreases with increase in Mn concentration. The observed temperature variation curves show two linear regions. Activation energy corre…
Investigation of Intrinsic Defect Structure in 0.91Pb(Zn1/3Nb2/3)O3–0.09PbTiO3 Single Crystal through AC Conductivity, James, Ajit R., Priya, Shashank, Uchino, Kenji, Srinivas, Kuchipudi, Kiran, Vemuri V.
In this paper we present a new approach to simulation methods for classical statistical mechanics relying on a field-theoretical formalism. It is based on applying the complex Hubbard–Stratonovich transformation to the canonical and grand-canonical partition function, which allows one to reexpress their particle repre…
Results of investigation of phenomena preceding the phase transition from paraelectric to dipole-ordered phases in Pb1−x(Li1/2La1/2)x(Zr1−yTiy)O3 solid solutions with compositions close to the ferroelectric–antiferroelectric–paraelectric triple point in the Ti-concentration-temperature phase diagram are presented. X-r…
In a recent paper Liang et al. [Nature (London) 411, 665 (2001)] showed experimentally, that metallic nanotubes, strongly coupled to external electrodes, may act as coherent molecular wave guides for electronic transport. The experimental results were supported by theoretical analysis based on the scattering matrix ap…
We discuss the formation of pretilt by oblique irradiation of photosensitive polymers that homogeneously align liquid crystals in the direction corresponding to the maximum density of unreacted polymer. We show that a tilted polymer distribution is formed by oblique illumination with one beam of unpolarized or partial…
We present an in situ study of the formation of the interfaces between TiO2 and SiO2 evaporated thin films using spectroscopic ellipsometry and x-ray photoemission spectroscopy (XPS). The growth of TiO2 on SiO2 was studied previously, but the reverse case has not received much attention up to now. In this article, we…
Voids exist in proteins as packing defects and are often associated with protein functions. We study the statistical geometry of voids in two-dimensional lattice chain polymers. We define voids as topological features and develop a simple algorithm for their detection. For short chains, void geometry is examined by en…