17,373 research outputs found
The Optimization of Jaw Crusher with Complex Motion Aimed at Reducing Stroke Feature Value of Its Outlet
Volume 8 Issue 1 (January 201
A Novel Solid-acid Catalyst Using Sulfonated Crosslinked Chitosan Resin
Sulfonated crosslinked chitosan resins (SCCRs) were prepared by firstly crosslinking chitosan to crosslinked chitosan resins (CCRs) using a reverse emulsion crosslinking method, followed by sulfonating CCRs with concentrated H2SO4 as the sulfonation agent.
The properties and application of SCCRs as solid acid catalysts were studied. The acidic sites in SCCRs, including C6–O and C2–N sulfate groups, are all weak acidic sites. SCCRs of higher crosslinking degrees have a higher sulfonation rate of the C6 primary hydroxyl
groups, thus more C6–O sulfate groups. High-temperature treatment and TG analysis verified that the crosslinking can improve the thermostability of both SCCR backbone and its acidic groups, and a higher crosslinking degree leads to better thermostability.
Catalytic esterification of citric acid with butanol and propionic acid with n-butyl alcohol demonstrated that SCCRs have good catalytic activity and can be repetitively used as efficient solid acid catalysts
Evolutions of helical edge states in disordered HgTe/CdTe quantum wells
We study the evolutions of the nonmagnetic disorder-induced edge states with
the disorder strength in the HgTe/CdTe quantum wells. From the supercell band
structures and wave-functions, it is clearly shown that the conducting helical
edge states, which are responsible for the reported quantized conductance
plateau, appear above a critical disorder strength after a gap-closing phase
transition. These edge states are then found to decline with the increase of
disorder strength in a stepwise pattern due to the finite-width effect, where
the opposite edges couple with each other through the localized states in the
bulk. This is in sharp contrast with the localization of the edge states
themselves if magnetic disorders are doped which breaks the time-reversal
symmetry. The size-independent boundary of the topological phase is obtained by
scaling analysis, and an Anderson transition to an Anderson insulator at even
stronger disorder is identified, in-between of which, a metallic phase is found
to separate the two topologically distinct phases.Comment: 7 pages, 5 figure
Doping dependent evolution of magnetism and superconductivity in Eu1-xKxFe2As2 (x = 0-1) and temperature dependence of lower critical field Hc1
We have synthesized the polycrystalline samples of Eu1-xKxFe2As2 (x = 0-1)
and carried out systematic characterization using x-ray diffraction, ac & dc
magnetic susceptibility, and electrical resistivity measurements. We have seen
a clear signature of the coexistence of superconducting transition (Tc = 5.5 K)
with SDW ordering in our under doped sample viz. x = 0.15. The spin density
wave transition observed in EuFe2As2 get completely suppressed at x = 0.3 and
superconductivity arises below 20 K. Superconducting transition temperature Tc
increases with increase in K content and a maximum Tc = 33 K is reached for x =
0.5, beyond which it decreases again. The doping dependent T(x) phase diagram
is extracted from the magnetic and electrical transport data. It is found that
magnetic ordering of Eu-moments coexists with superconductivity up to x = 0.6.
The isothermal magnetization data taken at 2 K for the doped samples suggest 2+
valence states of Eu ions. We also present the temperature dependence of the
lower critical field Hc1 of superconducting polycrystalline samples. The value
of Hc1(0) obtained for x = 0.3, 0.5, and 0.7 after taking the demagnetization
factor into account is 248, 385, and 250 Oe, respectively. The London
penetration depth {\lambda}(T) calculated from the lower critical field does
not show exponential behaviour at low temperature, as would be expected for a
fully gapped clean s-wave superconductor. In contrast, it shows a T2 power-law
feature down to T = 0.4 Tc, as observed in Ba1-xKxFe2As2 and BaFe2-xCoxAs2.Comment: 17 pages, 10 figure
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