New high piezoelectric coupling PLuNT binary system ceramics

The new (1 − x)Pb(Lu_1/2Nb_1/2) O₃ − x PbTiO₃ binary system ceramics in the interval 0 <> 0.49). The morphotropic region extends over the interval X = 0.38–0.49, the concentration ratio M:T 1 corresponds to X = 0.41. The maximum values of the electromechanical coupling coefficients k_p = 0.663, k_t = 0.481, k₃₁ = 0.355 of (1 − x)PLuN-xPT ceramics were attained in compositions PLuNT 59/41 (T_m = 353 °C) near the morphotropic phase boundary (MPB). The PLuNT system, having large values of electromechanical coupling and the highest T_m (> 350 °C) among binary Pb(B′,B″)O₃-PT perovskites may be favorable for piezoelectric sensors and actuators, and may have an interest as promising basis for thin film and single crystal performance.

Characterization of ferrites synthesized by mechanical alloying and soft chemistry

For the purpose of comparing nanostructured materials prepared by different synthesis methods, nanocrystalline Fe-based spinels were synthesized using two different routes: soft chemistry and high-energy ball milling. The as-prepared powders -were characterized notably by thermogravimetric analyses and ⁵⁷Fe Mössbauer spectrometry.

Characteristics of nanostructured TiO2 powders synthesized by combustion flame-chemical vapor condensation process

Combustion Flame-Chemical Vapor Condensation(CF-CVC) process-which can continuously produce nanostructured powders has been used to produce non-agglomerated TiO₂ powder. The synthesized powders are characterized for crystal structure, chemical composition, and particle size by using HRTEM, X-ray, TG-DTA, and SIMS. Nanostructured TiO₂ powders have mixed state of mostly anatase phase and small amount of rutile phase with particle size of about 20nm and 60˜70nm, respectively.

Ordering of Nanocrystalline FeAl produced by cluster condensation

The ordering kinetics of nanocrystalline Fe₅₀Al₅₀ alloys the specimens were prepared by sputtering, crystallite condensation in an Ar atmosphere, and subsequent compaction (2–4 GPa) at room temperature. The lattice structure is B2 as in coarse grained FeAl but with a significantly lower degree (≤ 0.5) of order. The crystallite size is about 20 nm and strains exceed 1.5 % in the {110} direction and are higher than in nanocrystalline Fe. The ordering process takes place mainly in the temperature range from 400 to 500 K, which is measured by the x-ray intensities of the superlattice reflections. This may indicate a higher vacancy diffusivity in the disordered than in the ordered state. The crystallite site remains smaller than 50 nm even after annealing at 0.8 T_m (melting temperature T_m = 1488K) as evidenced by transmission electron microscopy. Furthermore the strains decrease during annealing.

Characterisation of the Microstructure of Nanophase Ni: A Molecular Dynamics Simulation Study

The microstructure of computer generated Ni nanophase samples with mean grain sizes ranging from 3 to 12 nm is studied by means of atom energetics, coordination number, and local crystalline order. Two types of samples are considered: those with random crystallographic orientation, representing a sample with mainly High Angle (HA) grain boundaries, and those with a limited misorientation, representing samples with mainly Low Angle (LA) grain boundaries. Overall density, grain boundary density and grain boundary excess enthalpy are discussed in terms of grain size and grain boundary type.

Nanocrystalline BCC solid solutions of Al---Fe---V system prepared by mechanical alloying

Solid state reactions in Al₅₀Fe₅₀, Al₅₀Fe₄₅V₅ and Al₅₀Fe₂₅V₂₅ powder mixtures by Mechanical Alloying (MA) and following annealing were studied. MA was performedin the high energy planetary ball mill in an argon atmosphere. X-ray diffraction (XRD) and Mossbauer spectroscopy (MS) methods were used. It was established that the partially ordered solid solution of B2 type has been formed in the Al₅₀Fe₅₀ alloy and the BCC (A2) phase has been formed in the V containing alloys. According to MS one can conclude that the short range order of B2 type in the mechanically alloyed Al₅₀Fe₄₅V₅ and Al₅₀Fe₂₅V₂₅ alloys was presented too. MA phases were characterized by a crystallite size of 10 nm. Annealing at 750 °C for 2h of mechanically alloyed Al₅₀Fe₅₀ and Al₅₀Fe₄₅V₅ resulted in the formation of completely ordered B2 phases. After annealing of the Al₅₀Fe₂₅V₂₅ alloy the A2 structure transformed in two phases — with B2 and D8_a structure.

New Gd-Al nanophase obtained by crystallization of Gd4Al3 metallic glass

Crystallization behavior of Gd₄Al₃ metallic glass has been studied by X-ray diffraction and differential scanning calorimetric. It has been found that the crystallization of Gd₄Al₃ glass is a two-stage process with the first stage occurring at 710 K — 715 K and the second — at approximately 770 K. The product of the first stage in the crystallization of Gd₄Al₃ glass has been identified as a Gd₄Al₃ nanophase having a primitive tetragonal (t) lattice with parameters A = b = 15.4893(8) Å, C = 5.3020(5) Å Nanophase t-Gd₄Al₃, has been found to decompose into well-known tetragonal Gd₃Al₂ and cubic GdAl, which are the products of the second stage in the crystallization of Gd₄Al₃ glass. The kinetics of the crystallization of Gd₄Al₃ glass and the morphology of t-Gd₄Al₃ nanophase has also been easily described.