667 research outputs found
Observation of Precipitation Evolution in Fe-Ni-Mn-Ti-Al Maraging Steel by Atom Probe Tomography
We describe the full decomposition sequence in an Fe-Ni-Mn-Ti-Al maraging steel during isothermal annealing at 550 °C. Following significant pre-precipitation clustering reactions within the supersaturated martensitic solid solution, (Ni,Fe)3Ti and (Ni,Fe)3(Al,Mn) precipitates eventually form after isothermal aging for ~60 seconds. The morphology of the (Ni,Fe)3Ti particles changes gradually during aging from predominantly plate-like to rod-like, and, importantly, Mn and Al were observed to segregate to these precipitate/matrix interfaces. The (Ni,Fe)3(Al,Mn) precipitates occurred at two main locations: uniformly within the matrix and at the periphery of the (Ni,Fe)3Ti particles. We relate this latter mode of precipitation to the Mn-Al segregation
Enhancement of Transition Temperature in FexSe0.5Te0.5 Film via Iron Vacancies
The effects of iron deficiency in FexSe0.5Te0.5 thin films (0.8<x<1) on
superconductivity and electronic properties have been studied. A significant
enhancement of the superconducting transition temperature (TC) up to 21K was
observed in the most Fe deficient film (x=0.8). Based on the observed and
simulated structural variation results, there is a high possibility that Fe
vacancies can be formed in the FexSe0.5Te0.5 films. The enhancement of TC shows
a strong relationship with the lattice strain effect induced by Fe vacancies.
Importantly, the presence of Fe vacancies alters the charge carrier population
by introducing electron charge carriers, with the Fe deficient film showing
more metallic behavior than the defect-free film. Our study provides a means to
enhance the superconductivity and tune the charge carriers via Fe vacancy, with
no reliance on chemical doping.Comment: 15 pages, 4 figure
Quantification of graphene based core/shell quantum dots from first principles
Density functional calculations are performed to study the electronic structure of recently proposed graphene/graphane based core/shell quantum dots, which have a type I band alignment and exhibit quantized carrier energy levels. Strong confinement is robust with shell thickness. The bandgap, band offset, and the number of confined carrier orbitals with different size and geometry are determined. Our findings indicate that these core/shell dots are potentially well suited for the design of advanced diode lasers and room-temperature single electron devices. The proposed method to determine the number of confined orbitals is applicable for other quantum dot systems.We acknowledge the computing resources provided by
the National Computational Infrastructure (Australia) and
support from the Australian Research Council. Support from
AMMRF node at the University of Sydney (ACMM) is
gratefully acknowledged
In Vitro Studies of Cells Grown on the Superconductor PrOxFeAs
The recent discovery of arsenic-based high temperature superconductors has
reignited interest in the study of superconductor : biological interfaces.
However, the new superconductor materials involve the chemistry of arsenic,
their toxicity remain unclear [ Nature, 2008, 452(24):922]. In this study the
possible adverse effects of this new family of superconductors on cells have
been examined. Cell culture studies in conjunction with microscopy and
viability assays were employed to examine the influence of arsenic-based
superconductor PrOxFeAs (x=0.75) material in vitro. Imaging data revealed that
cells were well adhered and spread on the surface of the superconductor.
Furthermore, cytotoxicity studies showed that cells were unaffected during the
time-course of the experiments, providing support for the biocompatibility
aspects of PrOxFeAs-based superconductor material.Comment: Are the FeAs based superconductors toxic
Graphene doping to enhance flux pinning and supercurrent carrying ability in magnesium diboride superconductor
It has been shown that graphene doping is sufficient to lead to an
improvement in the critical current density - field performance (Jc(B)), with
little change in the transition temperature in MgB2. At 3.7 at% graphene doping
of MgB2 an optimal enhancement in Jc(B) was reached by a factor of 30 at 5 K
and 10 T, compared to the un-doped sample. The results suggested that effective
carbon substitutions by grapheme, 2D nature of grapheme and the strain effect
induced by difference thermal coefficient between single grapheme sheet and
MgB2 superconductor may play an important role in flux pinning enhancement
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