Materials Literature
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We examine the effect of dipolar interactions on the liquid-crystalline phase behaviour of L/D = 5 hard spherocylinders with a terminal point dipole. The hard spherocylinder consists of a cylinder of length L and diameter D with hemispherical caps on each end; the point dipole is located at the centre of the hemispher…
A complex sequence of ferro- and antiferromagnetic interactions occurs in the compound [Ni(N,N′-dmen)(μ-N3)2] (N,N′-dmen N,N′-dimethylethylenediamine), which exists as a one-dimensional chain in the solid state (shown below; C atoms of the amine ligands are omitted). The magnetic behavior of this unusual spin system…
The effects of an applied magnetic field during anodization on the structural and optical isotropy of luminescent porous silicon (PS) are investigated. The PS layers are prepared by anodizing p-type Si wafers in HF solutions with an external magnetic field of 0–1.7 T applied perpendicular to the Si surface. It is show…
A qualitative description of a spinodal decomposition kinetics is proposed. It is made of a linear stage followed by two nonlinear stages, leading, respectively, to higher and lower frequency generation in the spatial order parameter distribution, then followed by the classical Ostwald ripening. This general scheme is…
A structure reminiscent of the YBa2Cu3O7 superconductor is shown by the novel reduced manganese perovskite YBaMn2O5 (on the right), in which double layers of MnO5 square pyramids enclose the Ba2+ ions (large spheres), while Y3+ ions (medium-sized black spheres) lie between the layers. Unlike many oxidized Mn perovskit…
The highest negative charge of a 16-electron system known to date is shown by the CO2-analogous anion (CBC)5− in Al3BC3. This has been confirmed by the vibrational spectroscopic and structural characterization of this compound, which revealed the linearity and bond lengths given below. Al3BC3 can be regarded as the…
Analytic solutions for a sonoluminescing gas bubble have been obtained, which provide density, pressure, and temperature distributions for the gas inside a bubble oscillating under an ultrasonic field. The solutions show that sonoluminescence occurs due to the increase and subsequent decrease in bubble wall accelerati…
Under strong nanosecond excitation, we demonstrate that II–VI semiconductor quantum dots exhibit optical gain up to room temperature. The CdS nanocrystallites, fabricated by sol-gel process, are embedded in a sodium borosilicate glass matrix. The gain is spectrally broad and the crossing between absorption and gain is…
Mit elongierten, hexagonal‐prismatischen Keimen beginnt das hierarchische Wachstum anisotroper Kugelaggregate aus Fluorapatit in Gelatine‐Matrices. Durch selbstähnlich verzweigte, nadelförmige Aufwachsungen an den Enden der Keime entstehen diskrete Hantelaggregate (rasterelektronenmikroskopische Aufnahme rechts), die…
The isotropic - nematic (I - N) phase transition in dispersions of sterically stabilized rod-like boehmite (AlOOH) colloids is studied. We have examined the influence of the steric stabilizer, the dispersion medium and the presence of non-adsorbing polymer on the phase transition process. Dispersions in cyclohexane sh…
The rheological properties of colloidal suspensions of spheres and rods have been studied using dissipative particle dynamics (DPD). We have measured the viscosity as a function of shear rate and volume fraction of the suspended particles. The viscosity of a 30 vol% suspension of spheres displays characteristic shear-…
Amorphous Si/SiO2 superlattices with 100–525 periods and a 2–3 nm periodicity were deposited by radio frequency magnetron sputtering onto silicon and quartz substrates. All samples exhibited visible photoluminescence (PL) at room temperature and the PL peak wavelength shifted towards shorter wavelengths with decreasin…
We report Monte Carlo simulations that show both vapor-liquid and closed-loop liquid-liquid equilibrium in a pure substance, for a model fluid that forms orientation-dependent intermolecular bonds. This is the first time that direct evidence of liquid-liquid immiscibility in a pure fluid has been found using exact met…
One of the most serious forms of damage that occurs during the integration of Pt/PZT/Pt ferroelectric capacitors [where PZT is Pb(ZrxTi1−x)O3] is the disappearance of polarization hysteresis characteristics during the passivation process. The hydrogen content of the atmosphere during this process affects the ferroelec…
Scanning force microscopy has been used to perform a comparative nanoscale study of domain structures and switching behavior of Pb(ZrxTi1−x)O3 (PZT) thin films integrated into heterostructures with different electrodes. The study revealed a significant difference between polarization state of as-deposited PZT films on…
We provide a systematic test of empirical theories of covalent bonding in solids using an exact procedure to invert ab initio cohesive energy curves. By considering multiple structures of the same material, it is possible for the first time to test competing angular functions, expose inconsistencies in the basic assum…
Some recent progress in the study of liquid foams is reviewed in outline. Calculations of foam conductivity are presented, which further improve upon the approximation recently proposed by us, in accounting for the nonlinearity in the dependence of conductivity on liquid fraction.
Slow sublimation of the dithiadiazolyl radical 1 yields crystals of a new polymorph 1β (orthorhombic, space group Fdd2). Below 36 K this new phase exhibits a spontaneous magnetic moment, which is described in terms of canted antiferromagnetism.
We design three-phase composites having maximum thermal expansion, zero thermal expansion, or negative thermal expansion using a numerical topology optimization method. It is shown that composites with effective negative thermal expansion can be obtained by mixing two phases of positive thermal expansions with a void…
We report on the fabrication of a new class of trilayer epitaxial thin film devices based on the doped perovskite manganates La–Ca–Mn–O and La–Sr–Mn–O. We show that large resistance changes, up to a factor of 2, can be induced by a moderate applied magnetic field below 200 Oe in these trilayers supporting current-perp…