Bulks of Al-B-C obtained by reactively spark plasma sintering and impact properties by Split Hopkinson Pressure Bar

Mixtures of B4C, α-AlB12 and B powders were reactively spark plasma sintered at 1800 °C. Crystalline and amorphous boron powders were used. Samples were tested for their impact behavior by the Split Hopkinson Pressure Bar method. When the ratio R = B4C/α-AlB12 ≥ 1.3 for a constant B-amount, the major phase in the samples was the orthorhombic AlB24C4, and when R < 1 the amount of AlB24C4 significantly decreased. Predictions that AlB24C4 has the best mechanical impact properties since it is the most compact and close to the ideal cubic packing among the Al-B-C phases containing B12-type icosahedra were partially confirmed. Namely, the highest values of the Vickers hardness (32.4 GPa), dynamic strength (1323 MPa), strain and toughness were determined for the samples with R = 1.3, i.e., for the samples with a high amount of AlB24C4. However, the existence of a maximum, detectable especially in the dynamic strength vs. R, indicated the additional influence of the phases and the composite’s microstructure in the samples. The type of boron does not influence the dependencies of the indicated mechanical parameters with R, but the curves are shifted to slightly higher values for the samples in which amorphous boron was used

Heterostructures based on small molecules organic compounds

Heterostructures with layers from small molecules organic compounds were deposited on ITO/glass substrate by thermal vacuum evaporation (TVE) technique. Structural, optical and morphological investigations were carried out on the realisedlayers (zinc phthalocyanine - ZnPc, fullerene - C60 and 1,4,5,8-naphthalene - tetracarboxylic dianhydride - NTCDA). The films are polycrystalline keeping the morphological features characteristic to these materials. The prepared hetero structures reveal a large absorption domain in the visible domain. The current-voltage (I-V) characteristics of the investigated structures, recorded in dark, present an improvement in the current value (~one order of magnitude) for the standard structure (ITO/PEDOT:PSS/ZnPc/C60/NTCDA/Al) with a supplimentary layer of poly(3,4 ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS). For the inverted structure (Al/NTCD/C60/ZnPc/ITO) was also noticed an increased curent value in comparasion with that observed for the standard structure

Electrode interface controlled electrical properties in epitaxial Pb(Zr0.52Ti0.48)O-3 films grown on Si substrates with SrTiO3 buffer layer

International audienceElectrical properties of ferroelectric capacitors based on PbZr0.52Ti0.48O3 thin films grown by pulsed laser deposition on silicon substrate with SrTiO3 buffer layer grown by molecular beam epitaxy were studied. A SrRuO3 layer was deposited as bottom electrode also by pulse laser deposition and Pt, Ir, Ru, SrRuO3 were used as top contacts. Electrical characterization comprised hysteresis and capacitance-voltage measurements in the temperature range from 150 K to 400 K. It was found that the macroscopic electrical properties are affected by the electrode interface, by the choice of the top electrode. However, even for metals with very different work functions (e.g. Pt and SrRuO3) the properties of the top and bottom electrode interfaces remain fairly symmetric suggesting a strong influence from the bound polarization charges located near the interface. (C) 2015 Elsevier B.V. All rights reserved

Comparison between the ferroelectric/electric properties of the PbZr0.52Ti0.48O3 films grown on Si (100) and on STO (100) substrates

International audienceFerroelectric/electric properties of PbZr0.52Ti0.48O3 (PZT) thin films grown by pulsed laser deposition (PLD) on two different substrates, Si (001) and SrTiO3 (STO) (001), were comparatively analyzed. The structural characterization has revealed the epitaxial relationship between the grown layers and the two types of substrates, with larger density of structural defects for the films deposited on Si (001) with buffer STO layer. The ferroelectric/electric properties are also different, with lower remnant polarization (about half of the value obtained on STO substrate), higher dielectric constant (about two times larger), and lower leakage current (about two orders of magnitude lower) for the PZT films deposited on Si (001) compared to those deposited on (001) STO substrates. Nevertheless, the results show that the use of a STO buffer layer on Si can be a solution to obtain good quality PZT capacitor structures without using expensive single-crystal oxide substrates. In this way, applications based on PZT capacitors (e.g. non-volatile memories, pyroelectric detectors, light switches, etc.) would be more easily integrated directly on Si wafers

The development of the Institute in the field of technology and equipment for production of slugs from sand-resin mixtures, hardened by the gaseous catalyzers blowout

There is given the retrospective and modern analysis of scientific-research and searching works of the Institute BelNIIlit in the field of technology and equipment for production of slugs with blowout by gaseous catalyzers

Reproducibility of small Ge2C6H10O7-added MgB2 bulks fabricated by ex situ Spark Plasma Sintering used in compound bulk magnets with a trapped magnetic field above 5 T

Abstract Bulk discs (20 mm diameter and 4.3 mm thickness) of MgB2 added with Ge2C6H10O7 were obtained by Spark Plasma Sintering. Six samples with composition MgB2(Ge2C6H10O7)0.0014 and one undoped sample were fabricated under similar conditions and were magnetically characterized in order to determine the scattering of properties and reproducibility. The main source of the scattering of the properties is the decomposition of the additive due to elimination of the organic part in gas form, which occurs stepwise with intensive vacuum drops at around ~ 560 and ~ 740 °C. A third drop, which is sometimes not well resolved being part of the second peak at 740 °C, occurs at ~ 820 °C. The critical temperature at the midpoint of the transition, T c, shows only a relatively small variation between 37.4 and 38 K, and the irreversibility field at a low temperature of 5 K takes values between 8 and 10 T. The pinning force and pinning force related parameters do not correlate with the carbon substituting for boron in MgB2 and suggest a synergetic influence of the microstructural details and carbon. Overall, despite the superconducting properties scattering, the samples are of high quality. Stacked into a column of six samples, they can trap at the center and on the surface of the column a magnetic field of 6.78 and 5.19 T at 12 K, 5.20 and 3.98 T at 20 K and 2.39, and 1.96 T at 30 K. These promising values, combined with facile fabrication of the samples with relatively high quality and reproducibility, show the feasibility of their use in building complex and large compound arrangements for bulk magnets and other applications