查看更多>>摘要：Methanol-to-olefins(MTO)process is one of the most critical pathways to produce low carbon olefins.Typically,the reaction is driven by thermal catalysis,which inevitably needs to consume large amounts of fossil fuel.Developing a new technique to substitute for the fuel burning is urgent for MTO process to improve the industry prospects and sustainability.Herein,we report a novel W18O49/Au/SAPO-34(W/Au/S),a multifunctional pho-tothermal catalyst for the MTO reaction.A high methanol conversion was achieved under xenonum(Xe)lamp irra-diation,yielding methyl ether(ME)and ethylene as the main products.The optimized W/Au/S catalysts showed ethylene yield as high as 250 μmol in 60 min,which was 2.5 times higher than that of Au/SAPO-34.The physio-chemical characterization revealed that the SAPO-34 molecular sieves were surrounded by Au and W18O49 nanoparticles,which exhibited a strong localized surface plasmon resonance excitation around 540 nm and light absorption beyond 500 nm.The multifunctional catalysts showed a strong photothermal effect,arising from the broadened light absorption of Au and W18O49 nanoparticles,leading to a temperature as high as 250 ℃ on the surface of the catalysts.Mechanism study showed that the superior ethylene selectivity of W/Au/S catalysts was attributed to the moderating acidic sites of W18O49 for methanol dehydration to ethylene.This research may pro-vide new insight for designing heterostructures to improve photo-to-chemical conversion performance and is expected to accelerate progress toward the excellent multifunctional photothermal catalysts with broad light absorption for methanol activation and C-C bond formation.
查看更多>>摘要：The Li-Mg-B-H composite(2LiBH4+MgH2)has a high capacity of 11.4 wt％as a hydrogen storage material.However,the slow kinetics and poor cycling stability severely restrict its practical applications.In this work,a layered Nb2C MXene was first synthesized and then introduced to tailor the kinetics and cycling stability of the Li-Mg-B-H composite.The milled 2LiH+MgB2 composites were initially hydrogenated to obtain the 2LiBH4+MgH2 composites.The 2LiBH4+MgH2+5 wt％Nb2C can release 9.0 wt％H2 in 30 min at 400 ℃,while it is only 2.7 wt％for the undoped 2LiBH4+MgH2.The dehydrogenation activation energies of MgH2 and LiBH4 are 123 and 154 kJ·mol-1 respectively for the 5 wt％Nb2C-doped composite,lower than the undoped composite(164 and 165 kJ·mol-1).The 2LiBH4+MgH2+5 wt％Nb2C possesses excellent cycling stabil-ity,with the reversible capacity only slightly reduced from 9.4 wt％for the 1st cycle to 9.3 wt％for the 20th cycle.Nb2C keeps stable in the composite and acts as an efficient catalyst for the Li-Mg-B-H composite.It is believed that both the layered structure and the active Nb element con-tribute to the enhanced hydrogen storage performances of the Li-Mg-B-H composite.This work confirms that the Nb2C MXene with layered structure has a significant enhancing impact on the Li-Mg-B-H hydrogen storage materials,which is different from the bulk NbC.
查看更多>>摘要：SiGe-based thermoelectric(TE)materials have gained increasing interests due to their low maintenance costs,environmental friendliness and long lifespan.How-ever,the intrinsically high thermal conductivity of Si-based materials also results in poor TE properties.In this inves-tigation,a zirconia(ZrO2)composite strategy was applied to an n-type SiGe alloy,tremendously elevating its TE performance.After mechanical alloying and spark plasma sintering(SPS)processes,the ZrO2 induced the formation of nanopores in the SiGe matrix via phosphorus adsorption.Moreover,such increase in porosity enhanced the phonon scattering and dramatically suppressed lattice thermal conductivity,from 2.83 to 1.59 W·m-1·K-1 at 873 K.Additionally,reduced phosphorus doping led to an increase in Seebeck coefficients and a relatively minor decrease in electrical conductivity.The power factor didn't deteriorate significantly,either,as its maximum of～3.43 mW·m-1-K-2 was achieved at 873 K with(Si0.8Ge0.2)0.097 P0.03(ZrO2)0.003 In short,a peak figure of merit(ZT)of～1.27 at 873 K and an average ZT～0.7 from 323 to 873 K were obtained.This study demonstrates that the electrical and thermal transportation of SiGe material can be synergistically tuned by compositing ZrO2,illustrating a novel strategy to optimize the TE properties of bulk materials.
查看更多>>摘要：As a typical candidate of optoelectronic mate-rials,vanadium dioxide(VO2)has wide applications in photodetectors(PDs),but is still challenging in largely enhancing the photodetecting performance for low-power human radiation.Herein,high-performance Si/VO2 nanorods(NRs)heterojunction PDs based on the pho-tothermoelectric(PTE)effect are presented.The uniform VO2-NRs array films were deposited on Si by using mag-netron sputtering technique,and a Si/VO2 heterojunctions were fabricated.The device exhibits a four-stage photore-sponse and broadband photoresponse from ultraviolet to long-wavelength infrared.Benefited from the unique nanorods structure and the strong PTE effect,the fabricated device exhibits a large enhancement of the photodetecting performance,showing an ultrahigh photodetectivity of 1.6 × 1013 Jones and ultrafast response rates with a rising-edge time of～65.0 μs,three orders of magnitude higher than other VO2-based devices.Furthermore,the device exhibits unique abilities to detect human radiation even when the human fingers are far away from the device surface up to 10.0 cm.Additionally,the fabricated SiNO2 devices can also be applied as breath sensors to distinguish different breathing patterns.These results supply an effective route to design high-performance photodetectors toward detecting human thermal radiation and respiration.
查看更多>>摘要：Hydrogel-based triboelectric nanogenerator(TENG)has a promising applied prospect in wearable electronic devices.However,its low performance,poor stability,insufficient recyclability and inferior self-healing seriously hinder its development.Herein,we report a robust route to a liquid metal(LM)/polyvinyl alcohol(PVA)hydrogel-based TENG(LP-TENG).Owing to the intrinsically liquid feature of conductive LM within the flexible PVA hydrogel,the as-prepared LP-TENG exhib-ited comprehensive advantages of adaptability,biocom-patibility,outstanding electrical performance,superior stability,recyclability and diverse applications,which were unattainable by traditional systems.Concretely,the LP-TENG delivered appealing open circuit voltage of 250 V,short circuit current of 4 μA and transferred charge of 120 nC with high stability,outperforming most advanced TENG systems.The LP-TENG was successfully employed for versatile applications with multifunctionality,including human motion detection,handwriting recognition,energy collection,message transmission and human-machine interaction.This work presents significant prospects for crafting advanced materials and devices in the fields of wearable electronics,flexible skin and smart robots.
查看更多>>摘要：Chiral metamaterials have been a topic of sig-nificant research interest in recent years due to their potential for various applications in nanophotonic devices and chiral biosensors.However,the intrinsic Ohmic loss in surface plasmonic resonance has limited their practical use,resulting in large light dissipation and weak chiroptical resonance.Here,we report on the development of high-performance dielectric chiral shells(DCS)through a two-step Si deposition process on a self-assembled micro-sphere monolayer.The form DCS sample completely overcomes the cancelation effect originated from the dis-order property of the micro-sphere monolayer in macro-scale,and at a wavelength of approximately 710 nm,the measured optimal chiral signal(g-factor)and transmittance can reach up to 0.7 and 0.3,respectively.The strong chi-roptical effect comes from the asymmetric circular dis-placement currents(i.e.,magnetic modes)enabled by the specific shell geometry.The chiral shell geometry,elec-tromagnetic properties,sensor sensitivity of chiral mole-cules and figure of merit are systematically investigated.The DCSs demonstrate highly sensitive detection of chiral biomolecules owing to their easily accessible geometry and enhanced uniform chiral field.
查看更多>>摘要：Malignant obstruction makes gallbladder cancer have a high mortality rate.Nickel-titanium alloy(nitinol)stents are commonly used as a local intervention to maxi-mize patient survival time,but the stents lack antitumor and antibacterial capacity and are vulnerable to secondary obstruction.Arsenic-based drugs show good therapeutic promise against gallbladder cancer.To meet clinical needs,the layered double hydroxides(LDHs)film is constructed on the nitinol,whose arsenite loading amounts rose by 60％after simple heat treatment compared with the conventional anion-exchange strategy.In addition,calcination promotes the dissolution of nickel ions from the LDHs lattice,resulting in a powerful synergistic killing effect on tumor cells together with the released arsenic.More importantly,the calcined arsenic-loaded LDHs are sensitive to the acidic microenvironment of tumor tissues,which presents a much lower arsenic and nickel release amount in the nor-mal tissues,guaranteeing its biosafety.Meanwhile,the vertically sharp LDHs nanosheets can synergize with arsenic to achieve effective physical cleavage and chemical killing of adherent and planktonic bacteria.In short,we attempt to use arsenic drugs for local interventions and reasonably avoid their toxic side effects,which provides a new design idea for nitinol stents applied in the treatment of gallbladder cancer.
查看更多>>摘要：Thermal energy storage(TES)systems based on molten salt are widely used in concentrating solar power(CSP)plants.The investigation of the corrosion behavior of alloy materials in molten salt is crucial for the correct selection of alloy materials and the design of TES systems.In this study,the corrosion behavior of 304,310S,316,and In625 alloys in molten chloride salts(27 mol％NaCl-22 mol％KCl-51 mol％MgCl2)was investigated.The evolution of mass loss of the alloy samples with corrosion time and temperature and the analysis of the experimental results by scanning electron microscopy(SEM),energy dispersive spectrometer(EDS),and X-ray diffraction(XRD)revealed the corrosion mechanism of the alloy samples in molten chloride salts.The main factors affect-ing the corrosion of the alloy samples were further ana-lyzed.It was found that the loose multi-layer corrosion was formed on the surface of the corroded alloy samples with the increase in corrosion degree.Moreover,the experi-mental results showed that Mo played a positive role in improving the corrosion resistance of the alloy samples because the presence of Mo could inhibit the outward diffusion of alloying element Cr.This work enriches the molten salt corrosion database and provides a reference for the selection of alloy materials for TES systems with potential application in CSP plants.
查看更多>>摘要：This paper presents a systematic investigation of the microstructure and magnetocaloric properties of melt-extracted Sm20Gd20Dy20Co20Al20 high-entropy microwires.The fabricated wires exhibited an amorphous structure,and the temperature interval of the undercooled liquid ΔT was 45 K.The microwires underwent a second-order magnetic transition from a ferromagnetic to a para-magnetic state near the Curie temperature(Tc=52 K).The maximum magnetic entropy change(-ΔSmaxM),the relative cooling power and the refrigeration capacity reached 6.34 J·kg-1·K-1,422.09 J·kg-1 and 332.94 J·kg-1,respectively,under a magnetic field change of 5 T.In addition,the temperature-averaged entropy changes with two temperature lifts(3 and 10 K)were 6.32 and 6.27 J·kg-1·K-1,respectively.The good magnetocaloric performance highlights the significant potential for the Sm20Gd20Dy20Co20Al20 microwires to be used as magnetic refrigerant materials in low-temperature region applica-tions.This work will serve as a valuable reference for future investigations on low-temperature high-entropy magnetocaloric materials.
查看更多>>摘要：Pt-Ir alloy is potential superalloys used above 1300 ℃ because of their high strength and creep resistance.However,the ductility of Pt-Ir alloy has rapidly deteriorated with the increase of Ir,resulting in poor machinability.This work quantitatively evaluated the solid solution strength-ening(SSS)and grain refinement strengthening(GRS)of Pt-Ir alloy using first-principles calculations combined with experimental characterization.Here,the stretching force constants in the second nearest neighbor region(SFC2nd)of pure Ir(193.7 eV·nm-2)are 3.40 times that of pure Pt(57.0 eV·nm-2),i.e.,the interatomic interaction is greatly enhanced with the increase of Ir content,which leads to the decrease of ductility,and modulus misfit plays a dominant role in SSS.Then,the physical mechanisms responsible for the hardness(Hv)of Pt-Ir alloy,using the power-law-scaled function of electron work function coupled SSS and GRS,are attributed to the electron redistribution caused by different Ir content.Furthermore,a thorough assessment of the thermodynamic characteristics of Pt-Ir binary alloy was conducted,culminating in development of a mapping model that effectively relates composition,temperature and strength.The results revealed that the compressive strength increases with the Ir content,and the highest strength was observed in Pt0.25Ir0.75.This study provides valuable insights into the Pt-Ir alloy system.
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