Yüksek sıcaklık ve yapısal uygulamalar için alüminit tabanlı çok bileşenli intermetaliklerin geliştirilmesi, modellenmesi ve karakterizasyonu

TÜBİTAK MAG-COST535 Proje01.06.200

Güç kaynakları ve otomotiv elektroniği uygulamaları için bor tabanlı kalın kesitli metalik cam / nanokristal manyetik malzemelerin geliştirilmesi

TÜBİTAK MAG Proje01.06.2008This study is pertinent to setting a connection between glass forming ability (GFA) and topology of Fe-B based metallic glasses, identifying atomic effect order of elements increasing GFA and developing soft magnetic bulk metallic glasses (BMG) / bulk nanocrystalline alloys (BNCA) for industrial applications by combining intimate investigations on spatial atomic arrangements conducted via solid computer simulations with experimentations on high GFA bulk metallic glasses. In order to construct a theoretical framework, the nano-scale phase separation encountered in metallic glasses is investigated for amorphous Fe80B20 and Fe83B17 alloys via Monte Carlo and Reverse Monte Carlo simulations. All topological aspects revealed by developed analysis tools are compiled into a new model called Two-Dimensional Projection Model for predicting contributions to short and medium range order (MRO) and corresponding spacing relations. The outcome geometrically involves proportions approximating golden ratio. Soft magnetic Fe-Co-Nb-B-Si BMG and FeCo-Nb-B-Si-Cu BMG/BNCAs are produced with a totally conventional route, thermally characterized and their magnetic properties are measured. Influences of alloying elements that increase GFA and promote nanocristalization, on structural units and crystallization modes are identified by the developed model and radial distributions. While Co atoms substitute for Fe atoms, Nb and Si atoms deform trigonal prismatic units to provide local compactions at the outset of MRO. The GFA can be described by a new parameter quantifying the MRO compaction, cited as Φ. Moreover, after annealing Fe-Co-Nb-B-Si-Cu BMG alloy at 873 K for 300 s., the the precipitation is altered from Fe23B6 meta-sTablo phase to α-Fe nanocrystals, BNCAs are produced and this phenomenon is investigated structurally. It has been shown that developed Fe-B based BMGs and BNCAs show very good soft magnetic properties and optimum alloy composition is determined as (Fe36Co36B19.2Si4.8Nb4)99.25Cu0.75 with 3 mm thickness, 1.58 T saturation induction and 0.148 Oe coercivity

Atomic ordering characteristics of Ni3Al intermetallics with substitutional ternary additions

The effects of substitutional ternary additions of Me = Zn, Ti, Si, Cr, Mn, Mo, W, Nb, Ta, V, Hf, or Zr on the energetical and structural characteristics of atomic short-range ordering (SRO) of Ni-3(Al(1-x)Me(x)) intermetallics with L1(2) type ordered structure have been analysed by combining the statistical theory of ordering with the electronic theory of alloys in pseudopotential approximation. The partial ordering energies and pairwise SRO parameters were calculated by taking into account the influence of the first three coordination spheres. The results of calculation show that the atoms of Zn, Ti, Si, Mo or V elements substitute mainly for Al sublattice sites, whereas W, Nb, Ta, Hf, or Zr clement atoms substitute preferentially for the Ni sublattice sites and Cr or Mn element atoms tend to substitute for both Ni and Al sublattice sites. These theoretical results are in a good qualitative agreement with experimental observations for most of the third component Me elements. Copyright (C) 1997 Acta Metallurgica Inc

Effect of Thickness on Magnetic Properties of Fe 36

Fe36Co36B19.2Si4.8Mo2W2 amorphous thin films have been produced by thermionic vacuum arc with thickness varying from 200 nm to 260 mn. X-ray diffraction has been employed to reveal a predominant amorphous phase in the as-prepared samples, although a small crystalline fraction cannot be excluded. The bulk magnetic properties of thin films were examined at room temperature using an ADE Magnetics EV9 vibrating sample magnetometer with maximum magnetic field strength of 1750 kA/m, real-time field control and dynamic gauss range capable of reaching a resolution of 0.08 A/m at low fields. The minimum value of the coercivity for the as-prepared samples was about 7 kA/m

Effect of Thickness on Magnetic Properties of Fe36Co36B19.2Si4.8Mo2W2 Thin Film Prepared by Thermionic Vacuum Arc

Fe36Co36B19.2Si4.8Mo2W2 amorphous thin films have been produced by thermionic vacuum arc with thickness varying from 200 nm to 260 mn. X-ray diffraction has been employed to reveal a predominant amorphous phase in the as-prepared samples, although a small crystalline fraction cannot be excluded. The bulk magnetic properties of thin films were examined at room temperature using an ADE Magnetics EV9 vibrating sample magnetometer with maximum magnetic field strength of 1750 kA/m, real-time field control and dynamic gauss range capable of reaching a resolution of 0.08 A/m at low fields. The minimum value of the coercivity for the as-prepared samples was about 7 kA/m

Synthesis of AlNiCo core/shell nanopowders

Magnetic core/shell nanostructures have been recently received much interest owing to their utmost potential in permanent magnetic applications. In the present work, AlNiCo permanent magnet powders were synthesized by ball milling and a core/shell nanostructure was obtained using RF induced plasma. The effects of particle size and nanoshell structure on the magnetic properties were investigated in details. The coercivity of AlNiCo powders was found to increase with decreasing particle size, exclusively nanopowders encapsulated with Fe3O4 shell showed the highest coercivity values. The shell structure produced during plasma reaction was found to form a resistant layer against oxidation of metallic nanoparticles

Obstructive Sleep Apnea and Cardiovascular Disease: Where Do We Stand?

Obstructive sleep apnea is common in adults with cardiovascular disease. Accumulating evidence suggests an association between obstructive sleep apnea and cardiovascular disease independent of the traditionally recognized cardiovascular disease risk factors. Observational studies indicate that obstructive sleep apnea is a risk factor for development of cardiovascular disease and that alleviation of obstructive events with positive airway pressure may improve cardiovascular disease outcomes. However, recent randomized controlled trials have not supported the beneficial effect of positive airway pressure in cardiac populations with concomitant obstructive sleep apnea. Some evidence suggests that the relationship between obstructive sleep apnea and traditionally recognized cardiovascular disease risk factors is bidirectional, suggesting that patients with cardiovascular disease may also develop obstructive sleep apnea and that efficient treatment of cardiovascular disease may improve obstructive sleep apnea. Recent data also indicate that the apnea–hypopnea index, which is commonly used as a diagnostic measure of obstructive sleep apnea severity, has limited value as a prognostic measure for cardiovascular disease outcomes. Novel markers of obstructive sleep apnea-associated hypoxic burden and cardiac autonomic response seem to be strong predictors of adverse cardiovascular disease outcomes and response to treatment of obstructive sleep apnea. This narrative review and position paper from the Turkish Collaboration of Sleep Apnea Cardiovascular Trialists aims to update the current evidence about the relationship between obstructive sleep apnea and cardiovascular disease and, consequently, raise awareness for health professionals who deal with cardiovascular and respiratory diseases to improve the ability to direct resources at patients most likely to benefit from treatment of obstructive sleep apnea and optimize treatment of the coexisting cardiovascular diseases. Moreover, the Turkish Collaboration of Sleep Apnea Cardiovascular Trialists aims to contribute to strengthening the efforts of the International Collaboration of Sleep Apnea Cardiovascular Trialists in this context