We describe a novel mechanism for the synthesis of a stable high-entropy alloy powder from an otherwise immiscible Mg-Ti rich metallic mixture by employing high-energy mechanical milling.The presented methodology expe...We describe a novel mechanism for the synthesis of a stable high-entropy alloy powder from an otherwise immiscible Mg-Ti rich metallic mixture by employing high-energy mechanical milling.The presented methodology expedites the synthesis of amorphous alloy powder by strategically injecting entropic disorder through the inclusion of multi-principal elements in the alloy composition.Predictions from first principles and materials theory corroborate the results from microscopic characterizations that reveal a transition of the amorphous phase from a precursor intermetallic structure.This transformation,characterized by the emergence of antisite disorder,lattice expansion,and the presence of nanograin boundaries,signifies a departure from the precursor intermetallic structure.Additionally,this phase transformation is accelerated by the presence of multiple principal elements that induce severe lattice distortion and a higher configurational entropy.The atomic size mismatch of the dissimilar elements present in the alloy produces a stable amorphous phase that resists reverting to an ordered lattice even on annealing.展开更多
We present here the results of broadband spectral analysis of a low-mass X-ray binary and a black hole candidate 4 U 1957+11.The source was observed nine times with the Nuclear Spectroscopic Telescope A rray(NuSTAR)be...We present here the results of broadband spectral analysis of a low-mass X-ray binary and a black hole candidate 4 U 1957+11.The source was observed nine times with the Nuclear Spectroscopic Telescope A rray(NuSTAR)between September 2018 and November 2019.During these observations,the spectral state of 4 U 1957+11 evolved marginally.The disc dominant spectra are described well with a hot,multicolor disc blackbody with disc temperature varying in the range kT_(in)~1.35-1.86 keV and a non-thermal component having a steep slope(Γ=2-3).A broad Fe emission line feature(5-8 keV)was observed in the spectra of all the observations.The relativistic disc model was used to study the effect of distance,inclination and the black hole mass on its spin.Simulations indicate a higher spin for smaller distances and lower black hole masses.At smaller distances and higher masses,spin is maximum and almost independent of the distance.An inverse correlation exists between the spin and the spectral hardening factor for all the cases.The system prefers a moderate spin of about 0.85 for black hole masses between 4-6 M⊙for a 7 kpc distance.展开更多
基金supported in part by the National Science Foundation(NSF)award#CMMI-1944040。
文摘We describe a novel mechanism for the synthesis of a stable high-entropy alloy powder from an otherwise immiscible Mg-Ti rich metallic mixture by employing high-energy mechanical milling.The presented methodology expedites the synthesis of amorphous alloy powder by strategically injecting entropic disorder through the inclusion of multi-principal elements in the alloy composition.Predictions from first principles and materials theory corroborate the results from microscopic characterizations that reveal a transition of the amorphous phase from a precursor intermetallic structure.This transformation,characterized by the emergence of antisite disorder,lattice expansion,and the presence of nanograin boundaries,signifies a departure from the precursor intermetallic structure.Additionally,this phase transformation is accelerated by the presence of multiple principal elements that induce severe lattice distortion and a higher configurational entropy.The atomic size mismatch of the dissimilar elements present in the alloy produces a stable amorphous phase that resists reverting to an ordered lattice even on annealing.
基金supported by the grant awarded to Dr.A.Beri through the INSPIRE faculty award(DST/Inspire/04/2018/001265)by the Department of Science and Technology,Government of Indiafinancial support from the Council of Scientific&Industrial Research(CSIR)under the Junior Research Fellowship(JRF)scheme。
文摘We present here the results of broadband spectral analysis of a low-mass X-ray binary and a black hole candidate 4 U 1957+11.The source was observed nine times with the Nuclear Spectroscopic Telescope A rray(NuSTAR)between September 2018 and November 2019.During these observations,the spectral state of 4 U 1957+11 evolved marginally.The disc dominant spectra are described well with a hot,multicolor disc blackbody with disc temperature varying in the range kT_(in)~1.35-1.86 keV and a non-thermal component having a steep slope(Γ=2-3).A broad Fe emission line feature(5-8 keV)was observed in the spectra of all the observations.The relativistic disc model was used to study the effect of distance,inclination and the black hole mass on its spin.Simulations indicate a higher spin for smaller distances and lower black hole masses.At smaller distances and higher masses,spin is maximum and almost independent of the distance.An inverse correlation exists between the spin and the spectral hardening factor for all the cases.The system prefers a moderate spin of about 0.85 for black hole masses between 4-6 M⊙for a 7 kpc distance.
