Recently,organic materials have emerged as nextgeneration thermoelectric(TE)materials because of their unique advantages including low cost,high mechanical flexibility,low or no toxicity,and low intrinsic thermal cond...Recently,organic materials have emerged as nextgeneration thermoelectric(TE)materials because of their unique advantages including low cost,high mechanical flexibility,low or no toxicity,and low intrinsic thermal conductivity over inorganic TE materials.However,the Seebeck coefficient of organic materials with high TE properties is remarkably lower than that of its inorganic counterparts.Therefore,it is important to improve their Seebeck coefficient and thus,overall TE properties.展开更多
The previous works commonly adjust the carrier concentration through acceptor doping,but at the same time,the decrease of the Seebeck coefficient limits the further improvement of electrical properties in Cu_(3)SbSe_(...The previous works commonly adjust the carrier concentration through acceptor doping,but at the same time,the decrease of the Seebeck coefficient limits the further improvement of electrical properties in Cu_(3)SbSe_(4)-based materials.In this work,a microwave-assisted hydrothermal synthesis method was used to synthesize Cu_(3)SbSe_(4)/TiO_(2) hollow microspheres.Part of TiO_(2) participates in the reaction,replaces the Sb site of Cu_(3)SbSe_(4) to form holes,and the rest is dispersed in the matrix in the form of the second phase.The first-principles calculations reveal that the doping of Ti significantly changes the band structure and phonon spectrum,thereby regulating carrier concentration while increasing phonon scattering.In addition,experimental results show that the energy filtering effect generated by the extra-mixed TiO_(2) nano particles,which suppresses the decrease of Seebeck coefficient by acceptor doping.Consequently,the highest average power factor 897.5 mW m^(-1) K^(-2) and the zT peak value of 0.70 can be obtained in Cu_(3)SbSe_(4)/6%TiO_(2) sample at 298e623 K.This work provides a new sight to improve the thermoelectric properties in Cu_(3)SbSe_(4) through carrier concentration regulation and nano-phase composition.展开更多
Interface engineering has been regarded as an effective strategy to manipulate the thermoelectric performance of materials.Here,we use a facile chemical electroless plating and a spark plasma sintering process to fabr...Interface engineering has been regarded as an effective strategy to manipulate the thermoelectric performance of materials.Here,we use a facile chemical electroless plating and a spark plasma sintering process to fabricate Ag-plated SnTe bulk.After sintering,a small amount of plated Ag can be doped into SnTe to suppress the Sn vacancies and the others form Ag precipitates with a size distribution from nanoscale to microscale,which introduces Ag/SnTe interfaces to enhance the Seebeck coefficient via energy filtering effect.Simultaneously,these structures result in strong scattering to reach a low lattice thermal conductivity of-0.62 W·m^(–1)·K^(–1).Consequently,a maximum figure of merit(zT)of-0.67 at 823 K is achieved in 2 wt%Ag-plated SnTe,which is-60%higher than that of pristine SnTe.Moreover,the microhardness indentation test results show that the mean microhardness of 2 wt%Ag-plated SnTe is HV 64.26,which is much higher than that of pristine SnTe,indicating that Ag electroless plating can improve the mechanical properties of SnTe.This work has provided a facile and eco-friendly method to realize the interface engineering for manipulating the thermoelectric and mechanical properties of SnTe.展开更多
Thermally expanded graphite was functionalized with 4-bromophenyl addends using the in situ diazonium formation procedure,and after mild sonication treatment in N,N’-dimethylformamide,thin graphene layers were exfoli...Thermally expanded graphite was functionalized with 4-bromophenyl addends using the in situ diazonium formation procedure,and after mild sonication treatment in N,N’-dimethylformamide,thin graphene layers were exfoliated from the bulk graphite.These chemically-assisted exfoliated graphene(CEG)sheets had higher solubility than pristine graphene without any stabilizer additive.More than 70%of these soluble flakes had less than 5 layers.Energy filtered transmission electron microscopy(EFTEM)elemental mapping provided evidence of the edge-selective diazonium functionalization with graphene.A majority of the Br signals came from the edges of the CEG indicating that the basal planes were not highly functionalized.The CEG was also characterized by X-ray photoelectron spectroscopy,atomic force microscopy,Raman spectroscopy,and transmission electron microscopy.展开更多
The spatial diversity of distributed network demands the individual filter to accommodate the topology of interference environment. In this paper, a type of distributed adaptive beamformer is proposed to mitigate inte...The spatial diversity of distributed network demands the individual filter to accommodate the topology of interference environment. In this paper, a type of distributed adaptive beamformer is proposed to mitigate interference over coordinated antenna arrays network. The proposed approach is formulated as generalized sidelobe canceller （GSC） structure to facilitate the convex combination of neighboring nodes＇ weights, and then it is solved by unconstrained least mean square （LMS） algorithm due to simplicity. Numerical results show that the robustness and convergence rate of antenna arrays network can be significantly improved in strong interference scenario. And they also clearly illustrate that mixing vector is optimized adaptively and adjusted according to the spatial diversity of the distributed nodes which are placed in different power of received signals to interference ratio （SIR） environments.展开更多
基金support from the Ministry of Education,Singapore(no.R-284-000-228-112).
文摘Recently,organic materials have emerged as nextgeneration thermoelectric(TE)materials because of their unique advantages including low cost,high mechanical flexibility,low or no toxicity,and low intrinsic thermal conductivity over inorganic TE materials.However,the Seebeck coefficient of organic materials with high TE properties is remarkably lower than that of its inorganic counterparts.Therefore,it is important to improve their Seebeck coefficient and thus,overall TE properties.
基金This work was financially supported by the National Natural Science Foundation of China(No.51871240).The calculations were carried out at the National Supercomputing Center in Shenzhen(Shenzhen Cloud Computing Center).
文摘The previous works commonly adjust the carrier concentration through acceptor doping,but at the same time,the decrease of the Seebeck coefficient limits the further improvement of electrical properties in Cu_(3)SbSe_(4)-based materials.In this work,a microwave-assisted hydrothermal synthesis method was used to synthesize Cu_(3)SbSe_(4)/TiO_(2) hollow microspheres.Part of TiO_(2) participates in the reaction,replaces the Sb site of Cu_(3)SbSe_(4) to form holes,and the rest is dispersed in the matrix in the form of the second phase.The first-principles calculations reveal that the doping of Ti significantly changes the band structure and phonon spectrum,thereby regulating carrier concentration while increasing phonon scattering.In addition,experimental results show that the energy filtering effect generated by the extra-mixed TiO_(2) nano particles,which suppresses the decrease of Seebeck coefficient by acceptor doping.Consequently,the highest average power factor 897.5 mW m^(-1) K^(-2) and the zT peak value of 0.70 can be obtained in Cu_(3)SbSe_(4)/6%TiO_(2) sample at 298e623 K.This work provides a new sight to improve the thermoelectric properties in Cu_(3)SbSe_(4) through carrier concentration regulation and nano-phase composition.
基金supported by the National Natural Science Foundation of China(52162029)Yunnan Provincial Natural Science Key Fund(202101AS070015)+1 种基金the National Key R&D Program of China(2022YFF0503804)the Outstanding Youth Fund of Yunnan Province(202201AV070005)。
基金This work was financially supported by the National Natural Science Foundation of China(No.51802205)Australian Research Council.
文摘Interface engineering has been regarded as an effective strategy to manipulate the thermoelectric performance of materials.Here,we use a facile chemical electroless plating and a spark plasma sintering process to fabricate Ag-plated SnTe bulk.After sintering,a small amount of plated Ag can be doped into SnTe to suppress the Sn vacancies and the others form Ag precipitates with a size distribution from nanoscale to microscale,which introduces Ag/SnTe interfaces to enhance the Seebeck coefficient via energy filtering effect.Simultaneously,these structures result in strong scattering to reach a low lattice thermal conductivity of-0.62 W·m^(–1)·K^(–1).Consequently,a maximum figure of merit(zT)of-0.67 at 823 K is achieved in 2 wt%Ag-plated SnTe,which is-60%higher than that of pristine SnTe.Moreover,the microhardness indentation test results show that the mean microhardness of 2 wt%Ag-plated SnTe is HV 64.26,which is much higher than that of pristine SnTe,indicating that Ag electroless plating can improve the mechanical properties of SnTe.This work has provided a facile and eco-friendly method to realize the interface engineering for manipulating the thermoelectric and mechanical properties of SnTe.
基金We thank the U.S.Department of Energy's Office of Energy Efficiency and Renewable Energy within the Hydrogen Sorption Center of Excellence,No.DE-FC-36-05GO15073,the Air Force Office of Scientific Research(CONTACT),the Office of Naval Research through a Multidisciplinary University Research Initiative(MURI)with the University of California,Berkeley(00006766)and the Advanced Energy Consortium(member companies include BP America Inc.,Baker Hughes Inc.,Conoco-Phillips,Halliburton Energy Services Inc.,Marathon Oil Corp.,Occidental Oil and Gas,Petrobras,Schlumberger,Shell,and Total)for financial support.Thanks to Dr.Wenhua Guo for assistance with the TEM.
文摘Thermally expanded graphite was functionalized with 4-bromophenyl addends using the in situ diazonium formation procedure,and after mild sonication treatment in N,N’-dimethylformamide,thin graphene layers were exfoliated from the bulk graphite.These chemically-assisted exfoliated graphene(CEG)sheets had higher solubility than pristine graphene without any stabilizer additive.More than 70%of these soluble flakes had less than 5 layers.Energy filtered transmission electron microscopy(EFTEM)elemental mapping provided evidence of the edge-selective diazonium functionalization with graphene.A majority of the Br signals came from the edges of the CEG indicating that the basal planes were not highly functionalized.The CEG was also characterized by X-ray photoelectron spectroscopy,atomic force microscopy,Raman spectroscopy,and transmission electron microscopy.
基金supported by National Basic Research Program of China (No. 2010CB731903)
文摘The spatial diversity of distributed network demands the individual filter to accommodate the topology of interference environment. In this paper, a type of distributed adaptive beamformer is proposed to mitigate interference over coordinated antenna arrays network. The proposed approach is formulated as generalized sidelobe canceller （GSC） structure to facilitate the convex combination of neighboring nodes＇ weights, and then it is solved by unconstrained least mean square （LMS） algorithm due to simplicity. Numerical results show that the robustness and convergence rate of antenna arrays network can be significantly improved in strong interference scenario. And they also clearly illustrate that mixing vector is optimized adaptively and adjusted according to the spatial diversity of the distributed nodes which are placed in different power of received signals to interference ratio （SIR） environments.
