Materials Literature
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Light diffraction from shear ordered colloidal dispersions is discussed in terms of the scattering power distribution I(l) along Bragg rods of hexagonal layers. For a charge stabilized dispersion the angle dependence of the light scattering intensity is used to determine I(l), from which conclusions on the mutual regi…
Novel photoelectron yield experiments performed with a dynamical range of 8 orders of magnitude reveal a new excitation channel for electron emission on diamond (100) and (111) surfaces with negative electron affinity which is due to defect states 2.0 and 4.1 eV below the conduction band minimum. Analyzing the competi…
Abstract Materials research is an interdisciplinary field in which engineers and physical scientists work together. Since the major binary oxides, nitrides, and carbides, which are currently used as high‐performance ceramics, were discovered in the last century, the role of chemistry in the development of materials ha…
We present a novel surface-controlled bistable nematic liquid crystal display. This black and white device uses simple monostable planar anchorings and a dielectrically positive nematic. The two bistable textures are, respectively, quasiuniform U and almost half-turn twisted T. Short electric pulses break the surface…
Until very recently the Ni and Cu corroles, already described in the sixties, were regarded as the MII complexes 1 (M = Ni, Cu). Some doubt arose about this interpretation after the existence of FeIV corroles demonstrated that corroles can stabilize metals in unusual oxidation states. Thorough physical studies have no…
In extension of our previous study of KNbO_3 by the semiempirical Hartree-Fock method we present parameterization and total-energy results for non-ferroelectric KTaO_3 as a pure crystal (concentrating on the frozen phonon calculations) and that with Li impurities. The magnitudes of off-center Li displacements and the…
We point out that contrary to a recent suggestion by Boero et al. (PRL 78, 887 (1997)) the +1 charge state of the oxygen vacancy in alpha-quartz cannot be invoked as a candidate E' center in alpha-quartz and silica.
A minimum in resistivity as a function of temperature for an as-quenched Au80Co20 ribbon prepared by melt-spinning using a wheel surface speed of 20 m s^{-1} is found at 25 K. No resistivity minimum is found for an as-quenched ribbon using a wheel surface speed of 60 m s^{-1}, however, upon heat treatment of this ribb…
By exploiting the extremely large effective cross sections ( ${10}^{\ensuremath{-}17}--{10}^{\ensuremath{-}16}{\mathrm{cm}}^{2}/\mathrm{molecule}$) available from surface-enhanced Raman scattering (SERS), we achieved the first observation of single molecule Raman scattering. Measured spectra of a single crystal violet…
Abstract. In fenite data books the reversible permeability for small excitation levels is usually given vs. external dc magnetic field for different values of the effective permeability. To determine these curves the incremental permeability has to be measured on cores with different air gaps. Due to the grinding of d…
A simple model for the continuous recycle of mother liquors from a crystallization or precipitation is discussed. It is shown that the impurity profile of the mother liquors, at moderate recycle levels, quickly reaches a steady state according to (1 − x n +1 )/(1 − x ), where n is the number of times the process is op…
The etching of nondiamond carbon present in diamond thin films which were grown using the CVD method has been studied with UV irradiation in air. The etching of nondiamond carbon was accelerated by UV irradiation, and hence the temperature required was lowered from 600 °C to 250 °C. On the other hand, the temperature…
The effect of Ta2O5 additive on the electric and magnetic properties of MnZn ferrites with fine grain size was studied. A adding small amounts of Ta2O5 to the MnZn ferrite increased electric resistivity, while an excessive addition of Ta2O5 caused decrease in resistivity without significant grain growth. In a small am…
Ultrafine particles of SrFe12O19 have been synthesized by citrate precursor technique. Solid state reactivity studies of citrate precursor lead to the formation of fine particles of SrFe12O19 below 823K. The size and morphology of these particles were studied by SEM. The surface area measured by BET method for5.2nm cr…
The optical properties of Co and Mg ferrigallate spinels have been studied near the magnetic transition. The cluster (CoFeO10)15 is characterized by a strong intensification of iron pair excitations and by the existence in ferrimagnetic compounds of a large electronic transition assigned to Co2+ → Fe3+ metal-metal cha…
Size-quantization effects (short-wavelength shift of the structure and broadening) in low-temperature absorption spectra of PbI 2 and HgI 2 nanocrystals embedded in porous sodium borosilicate glass matrix with pores ranging in size from 2 to 50 nm have been observed and studied. The nanocrystal size was evaluated in t…
Porous silicon was formed using highly phosphorous-diffused n-type silicon. Dislocation generation mechanisms due to the force caused by marked volume expansion at the early stage of porous silicon oxidation and strain generation caused by oxidation are investigated. The height of the step produced by oxidation and th…
Abstract The stability of some heterocyclic poly(amide imide)s in acidic and alkaline medium was compared to the structurally related polyimide and poly(amide imide)s without other heterocyclic groups. All the polymers have high stability in acidic medium. The introduction of additional heterocycles such as 1,3,4‐0xad…
Abstract A high‐performance trifunctional epoxy resin based on the triglycidyl ether of tris (4‐hydroxyphenyl)‐methane (TETM) was synthesized by the condensation of 4‐hydroxybenzaldehyde with phenol followed by epoxidation with epichlorohydrin. The structure of TETM was confirmed by mass spectra, infrared and nuclear…
A new, nickel-based alloy resistant to a very wide range of corrosive media is described. The main alloying additions are chromium and molybdenum; however, the alloy also contains {approximately} 1.6% copper, which significantly enhances its resistance to dilute sulfuric and hydrochloric acids. The safe operating regi…