Superconducting NbTi by combustion synthesis

Electrothermal explosion (ETE) initiated by the heavy current (500 A) allowed to pass through mechanically activated Nb-Ti mixtures for 180 s yielded the products containing a mixture of ??-NbTi and ??-NbTi preliminary characterized by XRD, FESEM, EDX, and AES.     

SHS quenching as a route to bulk glassy Fe<Subscript>34</Subscript>Co<Subscript>34</Subscript>B<Subscript>10</Subscript>Si<Subscript>14</Subscript>Nb<Subscript>8</Subscript> alloys

The method of SHS quenching combined with dynamic annealing was used to prepare bulk amorphous metallic glass alloys Fe₃₄Co₃₄B₁₀Si₁₄Nb₈ in a two-stage process. The structural properties and microstructure of thus prepared materials were found to be close to those produced by other methods, such as melting-injection-molding and melt spinning.      

A predictive hybrid force modeling in turning: application to stainless steel dry machining with a coated groove tool

The International Journal of Advanced Manufacturing Technology - This paper presents an hybrid numerical/analytical modeling for estimation of cutting forces in machining process. The approach...     

Structural characterization and superconducting properties of MgB<Subscript>2</Subscript> prepared by SHS-method

Self-propagating high-temperature synthesis (SHS) of bulk MgB₂ superconductor from Mg-2B powder blend is reported. This reaction proceeds violently at 100 A under a protective atmosphere. Since the heat of reaction of Mg and B was not enough for chain reaction, then (Ti + C) mixed powders were used as the ignition agent to assist the reaction (Mg + 2B). In this case, the combustion front moved without any difficulty. The diffraction lines of the product can be indexed to a hexagonal MgB₂ phase, with lattice constants a = 3.0845 Å, and c = 3.5259 Å. For comparison, the direct synthesis of (Mg + 2B) mixture was carried out at (800°C–1000°C). It can be found, that high-temperature sintering (1000°C) will induce the formation of impurities. The MgB₂ grains are fine, well compacted and more homogenous. The structure of materials was studied using XRD, FESEM and EDX. M-H curvatures were measured under the magnetic fields between ?80 kOe and 80 kOe. J _c was calculated from width of magnetization hysteresis loops based on the extended Bean Model.     

Sintering behavior of magnesium aluminate spinel MgAl2O4 synthesized by different methods

This paper is focusing basically on the ceramic technology, of which several methods for the synthesis of MgAl₂O₄ have been investigated. The synthesis conditions regarding the powders cleanliness, microstructure, and sintering parameters of MgAl₂O₄ were studied. MgAl₂O₄ powder was synthesized via conventional solid-state route using different milling process: vertical attrition milling, WAB as a high-energy horizontal attrition milling, and Pulverisette as a planetary ball miller, and via solution combustion route using Urea, Glycine, and a mixture of Urea/Glycine. Urea and Glycine was used as fuel. The white powders were obtained for all solid-state routes and for Urea-combustion technique. The black and gray powders were obtained in the case of combustion technique, respectively, using a fuel of Glycine and Glycine/Urea mixture. The obtained powders and pellets were characterized by XRD, SEM, and Dilatometry. The results show that, among all the solid-state route processes, wet attrition milling gives the better and clean spinel phase. The WAB milling and Pulverisette miller introduce a contamination by some yttria-stabilized zirconia balls in the corresponding powder. Furthermore, the flash combustion technique permit to have nanoparticles with a dense spinel phase of MgAl₂O₄ and with lower sintering temperature in less time and with no calcination step.     

Combustion synthesis and characterization of Cu—Nb<Subscript>3</Subscript>Sn superconducting monofilamentary composite wires

Cu-Nb₃Sn superconducting monofilamentary composite wires were fabricated by using SHS, electrothermal explosion (ETE), and ETE followed by annealing and characterized by FESEM, XRD, and AES. The composite wires under study represented Nb₃Sn filaments (with an admixture of Nb₆Sn₆ and NbO) embedded in a high purity Cu tube.     

Icosahedral quasicrystalline Fe<Subscript>10</Subscript>Cu<Subscript>20</Subscript>Al<Subscript>70</Subscript> by electrothermal explosion: Structural and magnetic properties

A systematic study on the formation and stability of the icosahedral quasicrystalline (IQC) Al₇₀Cu₂₀Fe₁₀ alloy has been carried out using electrothermal explosion (ETE) reaction as a preparation method. The influence of added elements on the formation of icosahedral phase has been investigated by Mössbauer spectroscopy, XRD, and field emission scanning electron microscopy (FESEM). Combined ball milling and ETE reaction (BM-ETE) of Al₆₃Cu₂₅Fe₁₂ composition resulted in the formation of the ICQ Fe₁₀Cu₂₀Al₇₀ phase with a face-centered structure. In all cases, an Al(Cu, Fe) solid solution and β-Fe₃Al have been detected along with the ICQ phase. The icosahedral phase appears to form in a peritectoid-type reaction between Fe₃Al and Al₂Cu. A mechanism for formation of the IQC phase in the Al-Cu-Fe system was suggested. VSM measurements showed the ferromagnetic behavior of the alloy. The Mössbauer measurements in transmission and XRD data showed that the reaction product contained 65% Fe₁₀Cu₂₀Al₇₀ with an admixture of β-Fe₃Al and Al₂Cu.     

Quasi-crystalline Al<Subscript>70</Subscript>Cu<Subscript>20</Subscript>Fe<Subscript>10</Subscript> by thermal explosion: Effect of AlCu doping on magnetic properties

Polycrystalline quasi-crystals of icosahedral Al₇₀Cu₂₀Fe₁₀(i-Al₇₀Cu₂₀Fe₁₀) were prepared by thermal explosion (TE) of mechanically activated mixture of Al, Cu, Fe powders doped with AlCu. The effect of AlCu dopant was studied by XRD, field emission scanning electron (FESEM), optical microscopy (OM), atomic emission spectroscopy (AES), and energy-dispersive X-ray microanalysis (EDX). The synthesized i-Al₇₀Cu₂₀Fe₁₀ and intermetallics (Al₃Fe, Al₂Cu) show soft ferromagnetic and paramagnetic properties, respectively.      

FeAlPCBGa metallic glasses by heavy current annealing/electrothermal explosion: Structural and soft magnetic properties

Rapidly quenched FeAlPCBGa ribbons were cut into small pieces and milled in a Retsch PM 4000 planetary ball mill under argon atmosphere at a rotation velocity of 250 rpm for 150 h. The powders were compacted in the shape of small discs (2−6 × 10 mm) at the compacting pressure P = 8000 psi and then subjected to heavy current annealing (HCA) at 50–150 A, concomitant electrothermal explosion (ETE) in argon or in vacuum, and uniaxial compaction to obtain resultant metallic glasses. The products were characterized by XRD, thermomagnetic, and hysteresis measurements. After HCA, the coercivity reaches its lowest value of 2.14 A/m at 75 W/cm².