Characteristics of gas evolution profiles during coal pyrolysis and its relation with the variation of functional groups

Strict relation between the substituents or functional groups attached to the coal macromolecules and the generation of the volatile products, e.g., CH4 H2O, CO, CO2, etc., during the coal pyrolysis is an important but confusing subject. In this paper, quadrupole mass spectronletry, gas chromatography, and ^l3C nuclear magnetic resonance are applied to real-time monitoring the formations of volatile products, off-line quantitative determination of the total products from the pyrolysis of a sub-bituminous coal (SC), and the changes of diverse substitents in the SC along with coke foamation, respectively. These measurements are also performed for the pyrolysis of a caking coal to contrast SC. The qualitative and quantitative data reveal that, during coal pyrolysis, the functional groups related with the formation of CO, i.e., ether, carbonyl, and anhydride, can directly gen erate CO via bond breaking, or take a detour of the formation of other intermediates via condensation and recombination firstly. Moreover, the formations of CO2 and CH4 are related to the direct removal of -COO- and -CH3,respectively.

Light-responsive adsorbentswithtunableadsorbent-adsorbate interactions forselective CO_(2) capture

Amines in porous materials have been employed as active species for the selective CO_(2) adsorption from natural gas because of their target-specific interactions.Nevertheless,it is difficult to modulate such strong interactions to reach a high efficiency in the adsorption processes.Herein,we fabricated lightresponsive adsorbents with tunable adsorbent–adsorbate interactions for CO_(2) capture.The adsorbents were synthesized by introducing primary and secondary amines into a mesoporous silica that had been grafted with azobenzene groups on the surfaces.The target-specific amine sites render the adsorbents significantly selective in the uptake of CO_(2) over CH_(4),and the azobenzene groups were used as lightresponsive switches to influence the adsorbent–adsorbate interactions.The adsorbents can freely adsorb CO_(2) when the azobenzene groups are in the trans state.Ultraviolet-light irradiation makes the azobenzene groups transform to the cis configuration,which greatly hinders amines in the uptake of CO_(2).The caused difference of adsorption capacity can reach 34.9%.The alternative irradiation by ultravioletand visible-light can lead to a recyclable regulation on adsorption performance.The changes of the electrostatic potentials of amines are responsible for the light-induced regulation on adsorption.

Quantum Griffiths singularity in two-dimensional superconducting 4Ha-TaSe_(2) nanodevices

The layered transition metal dichalcogenides(TMDs)have raised considerable interest in the past decades for both fundamental physics and low-dimensional nanodevice applications.Recently,intriguing phenomena of Ising superconductivity and quantum metallic state have been reported in two-dimensional(2D)4Ha-TaSe2 nanodevices.Here,we report the magnetic field induced superconductor–metal transition(SMT)in mechanical exfoliated 4Ha-TaSe2 nanodevices with thickness down to 2.5 nm.We observe the quantum Griffiths singularity(QGS)of SMT in thin 4Ha-TaSe2 nanodevices by performing ultralow temperature transport measurements and activated scaling analysis.With increasing the thickness of TaSe2 nanodevice to 10.6 nm,the signature of magnetoresistance crossing region can hardly be detected,revealing the thickness dependence of SMT.In this procedure,the disorder strength plays a dominant role.This work enriches the platform for studying QGS and may stimulate further investigations on the correlation between different novel quantum phenomena in the same 2D superconducting system.

Planckian dissipation and non-Ginzburg-Landau type upper critical field in Bi2201

Resistivity and Hall effect measurements have been carried out on a micro-fabricated bridge of Bi2201 single crystal at low temperatures down to 0.4 K under high magnetic fields.When superconductivity is crashed by a high magnetic field,the recovered "normal state" resistivity still shows a linear temperature dependence in the low temperature region.Combining with the effective mass and the charge carrier density,we get a linear scattering rate 1/τ=αkBT/h with 0.77 <α <1.16,which gives a strong evidence of the Planckian dissipation.Furthermore,our results reveal a new type of temperature dependence of the upper critical field,H_(c2)(T)=H*■,which is totally different from the expectation of the Ginzburg-Landau theory,and suggests the existence of uncondensed Cooper pairs above H_(c2)(T) line.