Materials Literature
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Nonlinear behaviour of power piezoceramic materials has to be studied under strong electric fields. A bridge designed for measuring it at low frequency is described. It consists basically of a capacitance comparison bridge that can be used in two different modes: balanced and unbalanced. The nonlinear electric displac…
Colloidal suspensions of clay particles in aqueous salt solutions make ideal model systems for the study of interactions between plate-shaped particles, due to the ease in tuning their electrostatic repulsion with the concentration of the salt. Numerous gel and sol structures are possible, including nematic liquid cry…
We achieved enhancement of colossal magnetoresistance at room temperature in a tensile strained ${\mathrm{La}}_{0.8}{\mathrm{Ba}}_{0.2}{\mathrm{MnO}}_{3}$ thin film (52% at 297 K under an applied field of 0.8 T). Surprisingly, the tensile strain increased the Curie temperature ${T}_{C}$ from 270 K in the bulk to 320 K…
The weak signal obtained from the anomalous scattering (at lambda = 1.54 A) of naturally occurring elements such as sulfur, phosphorus and ordered solvent chloride ions is used to determine the atomic positions of these atoms. Two examples are discussed: the sulfur and chlorine substructure of tetragonal hen egg-white…
Abstract The present work focuses on the compatibization of styrene‐ co ‐butadiene rubber (SBR)/acrylonitrile‐ co ‐butadiene rubber (NBR) blends with dichlorocarbene modified styrene‐ co ‐butadiene rubber (DCSBR) as a function of concentration of compatibilizer and composition of the blend. FTIR studies, differential…
By a direct combination of the fast initiation technique and a selective quantitative termination reaction, terminally functionalized poly( N -propionylethylenimine)s (PPEIs) were prepared by cationic living ring-opening polymerization of 2-ethyl-2-oxazoline in a one-pot multistep reaction. The chain ends of the linea…
We investigated the influence of catalyst preparation on the growth of coil-shaped nanotubes by varying the pH of the solution during catalyst impregnation, to elucidate their formation process. The spirals were observed by transmission electron microscopy, and we determined the dimensions of these coils for a large n…
Trends in the stability of alpha- and beta-Keggin heteropolytungstates of the second-row main-group heteroatoms Al(III), Si(IV), and P(V) are elaborated by data that establish the roles of kinetic and thermodynamic control in the formation and isomerization of Keggin tungstoaluminates. Slow, room-temperature co-conden…
ADVERTISEMENT RETURN TO ISSUEPREVCommunication to the...Communication to the EditorNEXTSynthesis and Characterization of Star-Shaped PLLA−PEO Block Copolymers with Temperature-Sensitive Sol−Gel Transition BehaviorSang Yeob Park, Dong Keun Han, and Sung Chul KimView Author Information Center for Advanced Functional Pol…
A new synthesis method is presented to prepare multi-structured porous materials through a fully chemical route that allows control of the smaller and larger mesopore sizes independently.
We present the results of first-principles molecular-dynamics simulations of molten silicates, based on the density functional formalism. In particular, the structural properties of a calcium aluminosilicate $[\mathrm{CaO}\ensuremath{-}{\mathrm{Al}}_{2}{\mathrm{O}}_{3}\ensuremath{-}{\mathrm{SiO}}_{2}]$ melt are compar…
The domain morphology of the disordered relaxor ferroelectric strontium barium niobate doped with cerium, ${\mathrm{Sr}}_{0.61\ensuremath{-}x}{\mathrm{Ba}}_{0.39}{\mathrm{Nb}}_{2}{\mathrm{O}}_{6}{:\mathrm{C}\mathrm{e}}_{x}^{3+},$ has been investigated by piezoelectric force microscopy. The evolution of natural and wri…
The likelihood-based approach to density modification [Terwilliger (2000), Acta Cryst. D56, 965-972] is extended to include the recognition of patterns of electron density. Once a region of electron density in a map is recognized as corresponding to a known structural element, the likelihood of the map is reformulated…
The important role of alkali additives in heterogeneous catalysis is, to a large extent, related to the high promotion effect they have on many fundamental reactions. The wide application of alkali additives in industry does not, however, reflect a thorough understanding of the mechanism of their promotional abilities…
We describe and analyze selected surface impedance data recently obtained by different groups on cuprate, ruthenate and diboride superconducting films on metallic and dielectric substrates for fundamental studies and microwave applications. The discussion includes a first review of microwave data on MgB2, the weak-lin…
The structure of the antiphase domain boundaries of strontium titanate ${\mathrm{SrTiO}}_{3}$ that exist at temperatures below the antiferrodistortive transition, is analyzed. It is found that some boundaries are similar to N\'eel domain walls, as an additional component of the order parameter develops within them. We…
We report the observation of a field-induced transformation from the easy-plane antiferromagnetic structure to the easy-axis ferrimagnetic structure in a single crystal of TbFe_4.4Al_7.6 (tetragonal ThMn_12 structure) at 5 K. Such a field-induced, irreversible transition has been identified for the first time. This tr…
Results of X-ray diffraction experiments on solid oxygen at low temperature and at pressures up to 10 GPa are presented.A careful sample preparation and annealing around 240 K allowed to obtain very good diffraction patterns in the orthorhombic delta-phase. This phase is stable at low temperature, in contrast to some…
In quasicrystals, there are not only conventional, but also phason displacement fields and associated Burgers vectors. We have calculated approximate solutions for the elastic fields induced by two-, three- and fivefold straight screw- and edge-dislocations in infinite icosahedral quasicrystals by means of a generaliz…
A simple and convenient procedure for chemoselectively protecting the amino groups of chitosan has been developed to provide N-phthaloyl-chitosan that is indispensable as a soluble N-protected precursor for further controlled modification reactions of chitosan. Although the conventional N-phthaloylation of chitosan in…