D. D. Zaitsev

Synthesis and Magnetic Properties of SrO–Fe2O3–B2O3 Glass-Ceramics

Glasses with nominal compositions of SrFe12O19 + 8SrB2O4 (I) and SrFe12O19 + 12Sr2B2O5 (II) are prepared by rapid quenching from the liquid state and are converted to glass-ceramics containing fine magnetic particles of SrFe12O19 by heat treatment between 600 and 950°C. The materials are characterized by x-ray diffraction, differential thermal analysis, electron microscopy, and magnetic measurements. The phase transformations accompanying glass crystallization are identified. The glass composition and heat-treatment conditions are shown to influence the aspect ratio of the forming submicron-sized strontium hexaferrite particles. The strongest coercive fields reached in glass-ceramics I and II are 504 and 456 kA/m, respectively.

Preparation of magnetic glass-ceramics through glass crystallization in the Na2O-SrO-Fe2O3-B2O3 system

Glasses with the nominal compositions SrFe12O19 + nNa2Sr2B4O9 (n = 4, 6, 8, 10) and SrFe12O19 + 6Na2Sr3B4O10 were prepared via rapid quenching of oxide melts and were then heat-treated between 500 and 800°C in order to produce glass-ceramics containing fine SrFe12O19 particles. The materials were characterized by x-ray diffraction, differential thermal analysis, electron microscopy, and magnetic measurements. The crystallization behavior of the glasses was investigated. The coercivity of the glass-ceramics was shown to increase with heat-treatment temperature, up to 486 kA/m. By dissolving the nonmagnetic matrix of the glass-ceramics with the nominal compositions SrFe12O19 + 6Na2Sr3B4O10 and SrFe12O19 + 4Na2Sr2B4O9, submicron-sized strontium hexaferrite particles were obtained.

A Few More Useful 8-valued Logics for Reasoning with Tetralattice EIGHT 4

In their useful logic for a computer network Shramko and Wansing generalize initial values of Belnap’s 4-valued logic to the set 16 to be the power-set of Belnap’s 4. This generalization results in a very specific algebraic structure — the trilattice SIXTEEN3 with three orderings: information, truth and falsity. In this paper, a slightly different way of generalization is presented. As a base for further generalization a set 3 is chosen, where initial values are a — incoming data is asserted, d — incoming data is denied, and u — incoming data is neither asserted nor denied, that corresponds to the answer “don’t know”. In so doing, the power-set of 3, that is the set 8 is considered. It turns out that there are not three but four orderings naturally defined on the set 8 that form the tetralattice EIGHT4. Besides three ordering relations mentioned above it is an extra uncertainty ordering. Quite predictably, the logics generated by a–order (truth order) and d–order (falsity order) coincide with first-degree entailment. Finally logic with two kinds of operations (a–connectives and d–connectives) and consequence relation defined via a–ordering is considered. An adequate axiomatization for this logic is proposed.

Glass crystallization synthesis of ultrafine hexagonal M-type ferrites: Particle morphology and magnetic characteristics

This review concerns the synthesis and functional properties of ultrafine particles of M-type hexagonal ferrites prepared by the most advanced process of oxide glass crystallization. Hexaferrite phase formation during the heat treatment of multicomponent oxide glasses of various chemical compositions containing boron and/or silicon oxides as glass formers is considered. This route is useful to prepare assemblies of single-crystal strontium barium hexaferrite particles in the range of average particle sizes from tens of nanometers to several micrometers. The resulting glass ceramics and magnetic particle assemblies recovered from them are characterized by high coercive forces, approaching the theoretical limit for such compounds, and high magnetizations, close to the magnetization value for coarse-grained materials.

Fine particles of lanthanum- and cobalt-doped strontium hexaferrite prepared through glass crystallization

Glass of nominal composition Sr0.6La0.4Fe11.6Co0.4O19 + 12SrB2O4 was prepared by rapidly quenching an oxide melt and was then heat-treated at temperatures from 550 to 900°C to give glass-ceramics containing fine lanthanum-and cobalt-doped strontium hexaferrite particles and microcrystalline SrB2O4. The materials were characterized by x-ray diffraction, scanning electron microscopy, electron probe x-ray microanalysis, and magnetic measurements. The coercivity of the glass-ceramic samples was shown to increase up to 427 kA/m with increasing heat-treatment temperature. The saturation magnetization of the samples increases up to 25.0 A m2/kg as the heat-treatment temperature is raised to 750°C, and decreases slightly at higher temperatures. Dissolving the nonmagnetic matrix of the glass-ceramic prepared at 900°C, we obtained submicron powder of composition Sr0.88La0.12Fe10.74Co0.47Oy, as determined by x-ray microanalysis.

Preparation of submicron strontium sodium zirconate powder in alkaline solutions

Fine-particle (Sr,Na)ZrO3 was prepared by boiling a suspension of zirconium and strontium hydroxides in concentrated NaOH and was characterized by powder x-ray diffraction, thermogravimetry, IR spectroscopy, scanning electron microscopy, and x-ray microanalysis. Its structure was refined by the Rietveld method. (Sr,Na)ZrO3 has an orthorhombically distorted perovskite (ABO3) structure, with the Sr2+ and Na+ ions in the A site and Zr4+ in the B site. The relative A- and B-site occupancies are 100 and 79%, respectively. The cation deficiency is compensated by OH groups, which contain about one-third of the oxygens. In the range 100–900°C, (Sr,Na)ZrO3 loses water but retains the perovskite structure (with reduced lattice parameters). The synthesized powder consists of ≃40-nm particles, which form micron-sized spherical aggregates. The aggregates retain their shape during annealing at temperatures of up to 1000°C.

Bi-facial Truth: a Case for Generalized Truth Values

We explore a possibility of generalization of classical truth values by distinguishing between their ontological and epistemic aspects and combining these aspects within a joint semantical framework. The outcome is four generalized classical truth values implemented by Cartesian product of two sets of classical truth values, where each generalized value comprises both ontological and epistemic components. This allows one to define two unary twin connectives that can be called “semi-classical negations”. Each of these negations deals only with one of the above mentioned components, and they may be of use for a logical reconstruction of argumentative reasoning.

Phase Relations in the Bi–Sr–Ca–Cu–M–O (M = Y, Dy, Ho, Er, Tm, Yb, Lu) Systems

The phase relations in the Bi–Sr–Ca–Cu–M–O (M = Y, Dy, Ho, Er, Tm, Yb, Lu) systems near Bi2Sr2CaCu2O8+ x(Bi-2212) were studied between 850 and 990°C. The results demonstrate that larger sized rare earths (Y, Dy, Ho, Er) substitute on the Ca site in Bi-2212, leading to the formation of CaO. Smaller sized rare earths (Tm, Yb, Lu) replace lesser amounts of Ca and form Sr2MBiO6phases. In the material of nominal composition Bi2Sr2Ca0.85M0.15Cu2O8 + x+ 0.25Sr2YBiO6prepared via melt processing, a major fraction of the Y atoms substitute for Ca in Bi-2212, resulting in a low-Tcmultiphase superconductor. In the analogous Yb system, a Bi-2212–Sr2YbBiO6composite with Tc= 87 K is obtained.

Preparation of magnetic composites through SrO-Fe2O3-Al2O3-B2O3 glass crystallization

Glasses with nominal compositions 11SrO · 5.5Fe2O3 · 4.5Al2O3 · 4B2O3 (1) and 15SrO · 5.5Fe2O3 · 4.5Al2O3 · 4B2O3 (2) were prepared by rapidly quenching oxide melts between counterrotating steel rollers. The glasses were then heat-treated in the range 650–950°C to produce glass-ceramic samples. The samples were characterized by X-ray diffraction, electron microscopy, and magnetic measurements. The phase composition of the glass-ceramics was determined, and their microstructure and magnetic properties were studied. The annealing temperature was shown to have a strong effect on the coercivity of the materials, which reaches 650 and 570 kA/m for compositions 1 and 2, respectively.

Preparation of magnetic coatings from strontium hexaferrite on tin and cardboard by cold rolling

A finely dispersed powder of strontium hexaferrite doped with aluminum of the composition SrFe12−x AlxO19 with an aluminum content x = 0.6 ± 0.1 is prepared through crystallization of oxide glasses. The powder is characterized by a saturation magnetization of 60.2 A m2/kg and a coercive force of 550 kA/m. The hexaferrite particles predominantly have the shape of thick hexagonal platelets with a diameter ranging from 300 to 500 nm and a thickness-to-diameter ratio varying from 0.3 to 0.5. Magnetic coatings on tin and cardboard substrates are produced by cold rolling of strontium hexaferrite powders. It is shown that hexaferrite particles in the magnetic coatings have the preferred orientation of the well-developed facets along the rolling plane, which manifests itself in anisotropy of the magnetic properties of the coatings. The degree of texturing in the strontium hexaferrite coatings on cardboard and tin substrates is equal to 44 and 66%, respectively.