Materials Literature
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Water soluble poly( p -phenylene) derivatives, poly[2,5-bis(3-sulfonatopropoxy)-1,4-phenylene- alt -1,4-phenylene] sodium salt (PPP−OPSO 3 ) and poly[2,5-bis(3-sulfonatopropoxy)-1,4-phenylene- alt -4,4‘-biphenylene] sodium salt (PPBP−OPSO 3 ), have been synthesized through a Suzuki coupling reaction of 1,4-dibromo-2,5…
Viscoelastic properties of reversible networks formed in solutions of associating polymers are considered theoretically in the Rouse−Zimm (unentangled) regime. It is shown that the dynamics is governed primarily by the network strand size and by the effective lifetime of reversible junctions. Both frequency and concen…
The optical activity of Er-doped silicon is related to the presence of defects which enhance the typical radiative transition at 0.8 eV but whose nature and properties are still largely unknown. We have investigated the deep levels present in Er-doped liquid phase epitaxy silicon to identify the traps possibly related…
We have characterized the gap states from photoinduced absorption and photoinduced ESR studies on one-dimensional (1D) halogen-bridged metal complexes with degenerate and nondegenerate charge-density wave (CDW) ground state. A comparison of excitation profiles of self-trapped exciton (STE) luminescence with those of t…
We have grown epitaxial strontium titanate films on lanthanum aluminate substrates at a range of oxygen pressures and substrate temperatures. The complex dielectric function was measured as a function of temperature and electric field bias using a microwave ring resonator and a flip-chip technique. The films having th…
Magnetostriction at room temperature under various conditions of compressive prestress and applied fields of TbyDy1−y(Fe1−xTx)2 (T=Al, Mn) twin-free single crystals was investigated. The substitution of Al or Mn for Fe lowers the magnetostriction under ordinary temperature and pressure, and decreases the saturation fi…
A simple two-step process is reported here to deposit diamond coatings on titanium alloys at temperatures equal to or lower than 600 °C. The first step allows us to increase the carbon nucleation rate and to deposit a sacrificial layer which contains more than about 25% sp2 carbon. Its thickness is selected both to li…
A Raman-scattering study performed on ( -BBO) at room temperature allows us to assign all the vibrational modes detected in the Raman spectra. The internal and external vibration modes are properly obtained by taking account of the light polarization, mode contamination and isotope effects. A correspondence between th…
In this Letter we describe measurements of the light emission evolution for single-bubble sonoluminescence. In particular, we show that the evolution of intensity for an air bubble depends on whether or not the bubble has previously been in a steady sonoluminescence state. Our results provide strong experimental evide…
The dielectric relaxation of Ba0.7Sr0.3TiO3 thin films was investigated up to K band (20 GHz) using time domain and frequency domain measurements. Our results show that from 1 mHz to 20 GHz, the dielectric relaxation of the complex capacitance of Ba0.7Sr0.3TiO3 thin films can be understood in terms of a power law depe…
We report x-ray diffraction measurements of the structure factor S ( Q ) and the radial distribution function g ( r ) of levitated liquid silicon in the stable and supercooled states. Supercooling results in a sharpening of the first peak in S ( Q ) and shift to an 8% higher Q value, the appearance of a double shoulde…
The $\mathrm{SiC}\left(111\right)\ensuremath{-}\left(3\ifmmode\times\else\texttimes\fi{}3\right)$ phase was analyzed by scanning tunneling microscopy (STM), low-energy electron diffraction (LEED) holography, density functional theory (DFT), and conventional LEED. A single adatom per unit cell found in STM acts as a be…
Dynamic fracture experiments measure crack velocity versus energy flux to the tip. We report here the first calculation of this quantity in a realistic setting, using molecular dynamics to study silicon. The results require relating the short length and time scales of simulations to the long length and time scales of…
Measured distortions of the $\mathrm{Mn}\ensuremath{-}\mathrm{O}$ bond length distribution from x-ray-absorption fine-structure measurements are found to relate linearly to the doped hole concentration $x$ at room temperature in ${\mathrm{La}}_{1\ensuremath{-}x}{\mathrm{Ca}}_{x}{\mathrm{MnO}}_{3}$. Comparison of the d…
Experiments on ferromagnetic thin films have measured the dependence of the hysteresis loop area on the amplitude and frequency of the external field, $A$=$A(H_{0},ω)$, and approximate agreement with numerical simulations of Ising models has been reported. Here we present numerical and theoretical calculations of $A$…
The theory of epitaxial strain energy is extended beyond the harmonic approximation to account for large film/substrate lattice mismatch. We find that for fcc noble metals (i) directions 〈001〉 and 〈111〉 soften under tensile biaxial strain (unlike zincblende semiconductors) while (ii) 〈110〉 and 〈201〉 soften under compr…
We study how an axisymmetric drop of inviscid fluid breaks under the action of surface tension. The evolution of various initial shapes is calculated numerically using a boundary-element method, and finite-time breakage is observed in detail. The pinchoff region is shown to have lengths scaling as ${\ensuremath{\tau}}…
Microscopic models of the interaction between grain boundaries (GBs) and both dislocations and cracks are of importance in understanding the role of microstructure in altering the mechanical properties of a material. A recently developed mixed atomistic and continuum method is reformulated to allow for the examination…
The dynamic structure factor of fractal colloidal gels is shown to exhibit a stretched exponential decay to a finite plateau with an exponent of about 0.7. The value of the plateau depends on both initial particle volume fraction ${\ensuremath{\varphi}}_{0}$ and scattering wave vector. We show that this behavior resul…
The Kondo lattice Hamiltonian with ferromagnetic Hund's coupling as a model for manganites is investigated. The classical limit for the spin of the (localized) ${t}_{2g}$ electrons is analyzed on lattices of dimension 1, 2, 3, and $\ensuremath{\infty}$ using several numerical methods. The phase diagram at low temperat…