Materials Literature
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X-ray photoelectron emission microscopy (X-PEEM) was used to study the surface orientation of stylized and rubbed polyimide thin films. Using soft X-rays produced by a synchrotron light source, this technique combines high spatial resolution imaging with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy…
Dendrimers and arborols with a carbosilane core have been prepared by a divergent hydrosilylation/vinylation reaction sequence followed by methoxylation of the silicon chloride end groups. Dendrimers with respectively 12 [first generation (1G)] and 36 [second generation (2G)] methoxysilane groups and arborols with oct…
A Raman study of a highly oriented PbTiO3 thin film deposited on a MgO single crystal has been performed as a function of the temperature. The results have been compared with those obtained from a single crystal prepared from the same batch and those reported in the literature for polycrystalline thin films and single…
In this work we present a structural study of the smectic C(SC) and columnar (Colh) liquid-crystalline phases exhibited by a biforked molecule. This study was performed by means of dilatometry and X-ray diffraction measurements performed at different temperatures. Following these measurements, molecular packing within…
We study the first order solid-fluid phase transition of a system of semi-flexible Lennard-Jones chains using molecular dynamics simulations. Thermodynamic integration methods are used to calculate the free energy of the solid and fluid phases. The solid phase free energy per chain can be calculated to an accuracy of…
A 20 MHz single-element ultrasonic probe using 0.91Pb(Zn(1/3 )Nb(2/3))O(3)-0.09PbTiO(3) (PZN-PT 91/9) single crystal has been fabricated. The single crystal of PZN-PT 91/9 orientated to the (001) plane has longitudinal coupling factor of k(33)>90%, which is much larger than the k(33)=70 to 80% of conventional Pb(Zr(1-…
The `frozen-lattice' model is a semi-classical approach for calculating electron diffuse scattering in crystals that has arisen from thermal vibration of crystal atoms. This quasi-elastic scattering approach is, however, unproven since its equivalence with the incoherent phonon-excitation model is not yet established.…
More than 130 years ago it was first recognized that the observed response from many diverse substances may exhibit two distinct types of nonexponential relaxation. Although the Kohlrausch-Williams-Watts (KWW) stretched exponential and Curie-von Schweidler (CvS) power law have since been used to characterize the obser…
Reactive ion etching of PbZrxTi1−xO3 (PZT) thin films was studied by using Cl2/C2F6/Ar gas chemistry in an inductively coupled plasma (ICP). PZT films were deposited on Pt/Ti/SiO2/Si substrates by the sol–gel process. PZT films were etched by varying the etching parameters including coil rf power, dc-bias voltage to t…
High-resolution surface tension measurements have been carried out on the free-standing films of more than 30 selected liquid-crystal compounds in their smectic phases. Surface tension (γ) values falling into major categories of 27, 24, 21, 13, and 11.5 dyn/cm have been obtained. The dependence of γ on specific termin…
Biologically compatible implant materials are commonly used in medical applications. The physico-chemical nature of the implant surface influences macromolecular binding. In the case of titanium implants, these interactions are influenced by a thin titanium oxide layer (5–70 Å), the main oxide species is titanium diox…
A new layered nanocomposite, which is one-to-one interstratified with a montmorillonite layer and a mixed SiO 2 /TiO 2 sol particle one, has been prepared by ion exchange reaction of the Na + ion in montmorillonite with the positively charged SiO 2 /TiO 2 sol particles. The ion exchange reaction was performed at three…
The performance and safety of rechargeable batteries depend strongly on the materials used. Lithium insertion materials suitable for negative and positive insertion electrodes are reviewed. Future trends, such as alternative materials for achieving higher specific charges—the Figure shows a scheme for reversible lithi…
Optically isotropic films of an amorphous copolymer containing azobenzene moieties (pDR1M- co -MMA) were irradiated by interfering two circularly contrarotating polarized laser beams and permanent holographic diffraction gratings were prepared. These involve the formation of both birefringence and surface relief grati…
Abstract Soils, subsoils, and aquifer materials can be modified with hydrophobic cationic surfactants to increase their sorptive capabilities for organic contaminants. In this study, we evaluated the adsorption/desorption of hexadecyltrimethylammonium (HDTMA) by smectitic soils, and the sorptive characteristics of the…
We report here a detailed experimental study, establishing the surface-initiated mechanism for the photoinduced relief grating formation on azobenzene functionalized polymer films. The grating formation process is found to be strongly dependent on the nature of the surface (20−200 Å), while the birefringent grating ap…
The packing in self-assembled nanocrystal superlattices is determined to a large extent by the geometry of the nanocrystals, as is demonstrated here by the preparation and analysis of wellordered arrays of predominantly tetrahedral silver nanocrystals. The Figure shows the model proposed to explain the monolayer self-…
The zero shear melt viscosity, eta0, for a variety of dendritic poly(benzyl ether) macromolecules has been measured. The viscosity of low generation dendrimers exhibits a strong molecular mass, M, dependence, yet, direct proportionality between eta0 and M is observed at higher generations. The viscosity scales with M…
The magnetization of a ${\mathrm{Mn}}_{12}$-acetate single crystal was measured with a cantilever magnetometer to temperatures below 60 mK. Contrary to expectations we did not observe steps in the hysteretic magnetization with indices higher than 11. The data suggest a significant degree of higher-order anisotropy. Th…
Abstract The most common cause of composition modification to a specimen during electron probe microanalysis is the field induced migration of light elements. This is an indirect effect which occurs in response to the long range electric fields that form when dielectric specimens suffer charge imbalance. The result is…