1,127 research outputs found
Interaction between superconductor and ferromagnetic domains in iron sheath: peak effect in MgB2/Fe wires
Interaction between the superconductor and ferromagnet in MgB2/Fe wires
results in either a plateau or a peak effect in the field dependence of
transport critical current, Ic(H). This is in addition to magnetic shielding of
external field. Current theoretical models cannot account for the observed peak
effect in Ic(H). This paper shows that the theoretical explanation of the peak
effect should be sought in terms of interaction between superconductor and
magnetic domain structure, obtained after re-magnetization of the iron sheath
by the self-field of the current. There is a minimum value of critical current,
below which the re-magnetization of the iron sheath and peak effect in Ic(H)
are not observed
Effect of carbon nanotube doping on critical current density of MgB2 superconductor
The effect of doping MgB2 with carbon nanotubes on transition temperature,
lattice parameters, critical current density and flux pinning was studied for
MgB2-xCx with x = 0, 0.05, 0.1, 0.2 and 0.3. The carbon substitution for B was
found to enhance Jc in magnetic fields but depress Tc. The depression of Tc,
which is caused by the carbon substitution for B, increases with increasing
doping level, sintering temperature and duration. By controlling the extent of
the substitution and addition of carbon nanotubes we can achieve the optimal
improvement on critical current density and flux pinning in magnetic fields
while maintaining the minimum reduction in Tc. Under these conditions, Jc was
enhanced by two orders of magnitude at 8T and 5K and 7T and 10K. Jc was more
than 10,000A/cm2 at 20K and 4T and 5K and 8.5T, respectively
Economic and environmental life cycle perspectives on two engineered wood products: Comparison of LVL and GLT construction materials
The embodied carbon of building materials and the energy consumed during construction have a significant impact on the
environmental credentials of buildings. The structural systems of a building present opportunities to reduce environmental emissions and energy. In this regard, mass timber materials have considerable potential as sustainable materials over other alternatives such as steel and concrete. The aim of this investigation was to compare the environment impact, energy consumption, and life cycle cost (LCC) of different wood-based materials in identical single-story residential buildings. The materials compared are laminated veneer lumber (LVL) and glued laminated timber (GLT). GLT has less global warming potential (GWP), ozone layer depletion (OLD), and land use (LU), respectively, by 29%, 37%, and 35% than LVL. Conversely, LVL generally has lower terrestrial acidification potential (TAP), human toxicity potential (HTP), and fossil depletion potential (FDP), respectively, by 30%, 17%, and 27%. The comparative outcomes revealed that using LVL reduces embodied energy by 41%. To identify which of these materials is the best alternative, various environmental categories, embodied energy, and cost criteria require further analysis. Therefore, the multi-criteria decision-making (MCDM) method has been applied to enable robust decision-making. The outcome showed that LVL manufacturing using softwood presents the most sustainable choice. These research findings contribute to the body of knowledge about the use of mass timber in construction
Growth rate of YBCO single grains containing Y-2411(M)
Y-Ba-Cu-O (YBCO) single grains have the potential to generate large trapped magnetic fields for a variety of engineering applications, and research on the processing and properties of this material has attracted world-wide interest. In particular, the introduction of flux pinning centres to the large grain microstructure to improve its current density, Jc, and hence trapped field, has been investigated extensively over the past decade. Y 2Ba4CuMOx [Y-2411(M)], where M = Nb, Ta, Mo, W, Ru, Zr, Bi and Ag, has been reported to form particularly effective flux pinning centres in YBCO due primarily to its ability to exist as nano-size inclusions in the superconducting phase matrix. However, the addition of the Y-2411(M) phase to the precursor composition complicates the melt-processing of single grains. We report an investigation of the growth rate of single YBCO grains containing Y-2411(Bi) phase inclusions and Y2O3. The superconducting properties of these large single grains have been measured specifically to investigate the effect of Y2O3 on broadening the growth window of these materials
Superconductivity in Layerd Cuprate
A series of layered cuprate (Rut_xNb)Sr2GdCups (Ru1212) for 0 :5 x :5 1 has been synthesized by the solid state reaction method. Powder X-ray diffraction
analysis indicates that oxygen flow is important in the formation of the Ru1212 phase and superconductivity in the system. Samples with nominal composition
(Rul_ x b)Sr2GdCu20 S can be indexed as a tetragonal structure with space group P4/mmm. The undoped compound exhibits the highest superconducting
transition with Tc onsel of 65 K and Tc zero of 55 K. Our results also show that doping with b decreases the normal state conductivity and suppresses
superconductivity in the system
Effect of nano-particle doping on the upper critical field and flux pinning in MgB2
The effect of nano particle doping on the critical current density of MgB2 is reviewed. Most nano-particle doping leads to improvement of Jc(H) performance while some shows a negative effect as with Cu and Ag. Nano-carbon containing dopants have two distinguishable contributions to the enhancement of Jc field performance: increase of upper critical field and improvement of flux pinning. Among all the dopants studied so far, nano SiC doping showed the most significant and reproducible enhancement in Jc(H). The nano SiC doping introduced many precipitates at a scale below 10 nm, which serve as strong pinning centers. Jc for the nano SiC doped samples increased by more than an order of magnitude at high fields and all temperatures compared to the undoped samples. The significant enhancement in Jc(H) of nano-SiC doping has been widely verified and confirmed, having a great potential for applications. An attempt is made to clarify the controversy on the effects of nano Fe and Ti doping on Jc
Effect of carbon nanotube doping on critical current density of MgB2 superconductor
The effect of doping MgB2 with carbon nanotubes on transition temperature, lattice parameters, critical current density and flux pinning was studied for MgB2–xCx with x = 0, 0.05, 0.1, 0.2, and 0.3. The carbon substitution for B was found to enhance Jc in magnetic fields but depress Tc. The depression of Tc, which is caused by the carbon substitution for B, increases with an increasing doping level, sintering temperature, and duration. By controlling the extent of the substitution and addition of carbon nanotubes we can achieve the optimal improvement on critical current density and flux pinning in magnetic fields while maintaining the minimum reduction in Tc. Under these conditions, Jc was enhanced by two orders of magnitude at 8 T and 5 K and 7 T and 10 K. Jc was more than 10 000 A/cm2 at 20 K and 4 T and 5 K and 8.5 T, respectively
Magnetic field processing to enhance critical current densities of MgB2 superconductors
Magnetic field of up to 12 T was applied during the sintering process of pure
MgB2 and carbon nanotube (CNT) doped MgB2 wires. We have demonstrated that
magnetic field processing results in grain refinement, homogeneity and
significant enhancement in Jc(H) and Hirr. The Jc of pure MgB2 wire increased
by up to a factor of 3 to 4 and CNT doped MgB2 by up to an order of magnitude
in high field region respectively, compared to that of the non-field processed
samples. Hirr for CNT doped sample reached 7.7 T at 20 K. Magnetic field
processing reduces the resistivity in CNT doped MgB2, straightens the entangled
CNT and improves the adherence between CNTs and MgB2 matrix. No crystalline
alignment of MgB2 was observed. This method can be easily scalable for a
continuous production and represents a new milestone in the development of MgB2
superconductors and related systems
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
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