Situated in the Salawusu River Valley, southeast of China's Mu Us Desert, the MGS2 (Milanggouwan section) portion of the Milanggouwan stratigraphic section records 5.5 sedimentary cycles consisting of alternations ...Situated in the Salawusu River Valley, southeast of China's Mu Us Desert, the MGS2 (Milanggouwan section) portion of the Milanggouwan stratigraphic section records 5.5 sedimentary cycles consisting of alternations between dune sand deposits and fluvial or lacustrine facies. We analyzed the grain-size and CaCO3 distributions in MGS2, and found that Mz (mean particle diameter) and o (standard deviation) displayed clear variations in peaks and valleys within different sedimentary facies. The CaCO3 content averaged 0.4% in the dune sand deposits, 1.43% in the fluvial facies, and 8.82% in the lacustrine facies. Both the grain-size distribution and CaCO3 contents, which equal the indicators for the alternation among the sedimentary facies, suggest the occurrence of 5.5 cycles. These results suggest that the observed cycles mainly resulted from fluctuations between a cold and dry winter monsoon climate and a warm and humid summer monsoon climate, and that the MGS2 portion experienced at least 5.5 fluctuations between these two extremes. This high-frequency climatic fluctuation indicates a strong influence of millennium-scale variations in the strength of the East Asian winter and summer monsoons in our study area during the Pleniglacial.展开更多
Transparent conducting oxides(TCOs)have attracted intensive attention because of their broad application in photoelectric devices such as solar cells,light-emitting diodes,and flat-panel displays.Current TCOs used in ...Transparent conducting oxides(TCOs)have attracted intensive attention because of their broad application in photoelectric devices such as solar cells,light-emitting diodes,and flat-panel displays.Current TCOs used in industry,including tin(IV)oxide(SnO_2),indium oxide(In_2O_3),indium tin oxide(ITO),and zinc oxide(ZnO),are primarily n-type semiconductors[1-3].Suitable p-type TCOs are still展开更多
Higher manganese silicide(HMS)is a P-type medium temperature thermoelectric(TE)material,which has attracted widespread attention over the past few decades due to its remarkable mechanical properties,excellent chemical...Higher manganese silicide(HMS)is a P-type medium temperature thermoelectric(TE)material,which has attracted widespread attention over the past few decades due to its remarkable mechanical properties,excellent chemical and thermal stability,as well as the non-toxicity,abundance and competitive price.The peak power factor(PF)of HMS is as high as~1.50×10^(-3)W m^(-1)K^(-2)because of its intrinsic high electrical conductivity and Seebeck coefficient.However,the thermal conductivity of HMS is also high,resulting in relatively low z T values.Introducing nano-dispersion in the matrix is one of the most effective methods to enhance the TE properties via reducing the lattice thermal conductivity significantly without drastic changes on the other parameters.In this study,Cs Pb BrQDs with uniform size were synthesized and introduced into HMS bulks.The PF(at 823 K)was enhanced to 1.71×10^(-3)W m^(-1)K^(-2),which is improved 14.0%approximately compared with that of pure HMS owing to the combined effect of element doping and energy filtering.The lattice thermal conductivity(at 823 K)decreased from 2.56W mKto 1.99 W mKsynchronously(~22.0%)due to the intensive phonon scattering caused by Cs doping,and the embedding of Pb riched CsPbBr_(3)QDs and Pb QDs.A maximum z T value of 0.57(823 K)is achieved in Cs Pb BrQDs/HMS composites,which is 36.0%higher than that of pure HMS.Predictably,for other TE materials,it is also feasible to improve the TE properties via introducing metastable quantum dots.展开更多
The effect of sintering temperature on thermoelectric properties of CdO ceramics was investigated by solid-state reaction method within the temperature range of 700-1000℃.With the increase of sintering temperature,bo...The effect of sintering temperature on thermoelectric properties of CdO ceramics was investigated by solid-state reaction method within the temperature range of 700-1000℃.With the increase of sintering temperature,both the grain size and the carrier concentration of these samples increased,while the Seebeck coefficient decreased.The highest dimensionless figure of merit ZT,0.34,was obtained at 1023 K for the sample sintered at 800℃,suggesting the potential application of CdO ceramics in thermoelectric(TE)devices.展开更多
Element doping and nano-inclusion embedding are effective approaches to enhance the electrical conductivities and decrease the lattice thermal conductivities of thermoelectric(TE)materials,respectively.However,the int...Element doping and nano-inclusion embedding are effective approaches to enhance the electrical conductivities and decrease the lattice thermal conductivities of thermoelectric(TE)materials,respectively.However,the intrinsic low electrical thermal conductivities and high electrical properties are severely sacrificed,and the final figure of merit(ZT)is usually restricted.In this study,Ag doping and Pt quantum dot(QD)embedding were synchronously achieved via embedding Ag/Pt alloy QDs into the higher manganese silicides to avoid the conventional single-element doping strategy.The power factor(at 823 K)was enhanced from 1.57×10^(-3) W m^(-1) K^(-2) to 1.82×10^(-3) W m^(-1) K^(-2)(-16%)due to the-18%increase in carrier concentration that was derived from the Ag doping effect.Simultaneously,the lattice thermal conductivity(at 823 K)decreased from 2.65 W m^(-1) K^(-1) e1.92 W m^(-1) K^(-1)(-28%)because of the broadband phonon scattering effect that resulted from the residual Pt QDs inclusions.Synthetically,the optimal ZT value increased by-52%from 0.42 to 0.64 at 823 K.This study demonstrated that incorporating metastable alloy QDs to obtain element doping and nano-inclusion embedding effects is a novel and feasible means to enhance the ZT value of HMS.This method is also possibly applicable to other alloy QD/TE composites.展开更多
基金funded by the National Basic Research Program of China (2010CB833405, 2004CB720206)the National Natural Science Foundation of China (40772118, 49971009)+2 种基金Foundation of the State Key Laboratory of Loess and Quaternary Geology, Institute of Earth Environment, Chinese Academy of Sciences (SKLLQG0309)the Research Grants Council Grant of the Hong Kong Special Administrative Region(HKU7243/04H)the Knowledge Innovation Project of Chinese Academy of Sciences (KZCX2-SW-118)
文摘Situated in the Salawusu River Valley, southeast of China's Mu Us Desert, the MGS2 (Milanggouwan section) portion of the Milanggouwan stratigraphic section records 5.5 sedimentary cycles consisting of alternations between dune sand deposits and fluvial or lacustrine facies. We analyzed the grain-size and CaCO3 distributions in MGS2, and found that Mz (mean particle diameter) and o (standard deviation) displayed clear variations in peaks and valleys within different sedimentary facies. The CaCO3 content averaged 0.4% in the dune sand deposits, 1.43% in the fluvial facies, and 8.82% in the lacustrine facies. Both the grain-size distribution and CaCO3 contents, which equal the indicators for the alternation among the sedimentary facies, suggest the occurrence of 5.5 cycles. These results suggest that the observed cycles mainly resulted from fluctuations between a cold and dry winter monsoon climate and a warm and humid summer monsoon climate, and that the MGS2 portion experienced at least 5.5 fluctuations between these two extremes. This high-frequency climatic fluctuation indicates a strong influence of millennium-scale variations in the strength of the East Asian winter and summer monsoons in our study area during the Pleniglacial.
基金supported by the National Natural Science Foundation of China(51972094 and 52002107)Hebei Provincial Department of Science and Technology(236Z4403G)+1 种基金Research Innovation Team Project of Hebei University(IT2023A04,150000321008)supported in part by the Micro-analysis Center and the High-Performance Computing Center of Hebei University。
基金supported by the National Natural Science Foundation of China(Grant Nos.51372064,and 11703004)the Nature Science Foundation of Hebei Province,China(Grant Nos.E2017201227,E2017201209,and QN2017017)
文摘Transparent conducting oxides(TCOs)have attracted intensive attention because of their broad application in photoelectric devices such as solar cells,light-emitting diodes,and flat-panel displays.Current TCOs used in industry,including tin(IV)oxide(SnO_2),indium oxide(In_2O_3),indium tin oxide(ITO),and zinc oxide(ZnO),are primarily n-type semiconductors[1-3].Suitable p-type TCOs are still
基金financially supported by the National Science Foundation for Young Scientists of China(No.51802071)the Advanced Talent Incubation Program of Hebei University(No.521000981162)+4 种基金the Outstanding Youth Science Foundation project of Hebei Province(No.A2020201032)the Local Science and Technology Development Fund Projects Guided by the Central Government(Nos.206Z4403G and 042000520091)the National Natural Science Foundation of China(No.51372064)the Hebei Province High-level Talents Funding project(No.A201801003)supported in part by the Microanalysis Center and the High-Performance Computing Center of Hebei University。
文摘Higher manganese silicide(HMS)is a P-type medium temperature thermoelectric(TE)material,which has attracted widespread attention over the past few decades due to its remarkable mechanical properties,excellent chemical and thermal stability,as well as the non-toxicity,abundance and competitive price.The peak power factor(PF)of HMS is as high as~1.50×10^(-3)W m^(-1)K^(-2)because of its intrinsic high electrical conductivity and Seebeck coefficient.However,the thermal conductivity of HMS is also high,resulting in relatively low z T values.Introducing nano-dispersion in the matrix is one of the most effective methods to enhance the TE properties via reducing the lattice thermal conductivity significantly without drastic changes on the other parameters.In this study,Cs Pb BrQDs with uniform size were synthesized and introduced into HMS bulks.The PF(at 823 K)was enhanced to 1.71×10^(-3)W m^(-1)K^(-2),which is improved 14.0%approximately compared with that of pure HMS owing to the combined effect of element doping and energy filtering.The lattice thermal conductivity(at 823 K)decreased from 2.56W mKto 1.99 W mKsynchronously(~22.0%)due to the intensive phonon scattering caused by Cs doping,and the embedding of Pb riched CsPbBr_(3)QDs and Pb QDs.A maximum z T value of 0.57(823 K)is achieved in Cs Pb BrQDs/HMS composites,which is 36.0%higher than that of pure HMS.Predictably,for other TE materials,it is also feasible to improve the TE properties via introducing metastable quantum dots.
基金supported by the Natural Science Foundation of Hebei Province,China(Grant No.A2014201176)the Science and Technology Research Projects of Colleges and Universities in Hebei Province,China(Grant No.ZD2014018).
文摘The effect of sintering temperature on thermoelectric properties of CdO ceramics was investigated by solid-state reaction method within the temperature range of 700-1000℃.With the increase of sintering temperature,both the grain size and the carrier concentration of these samples increased,while the Seebeck coefficient decreased.The highest dimensionless figure of merit ZT,0.34,was obtained at 1023 K for the sample sintered at 800℃,suggesting the potential application of CdO ceramics in thermoelectric(TE)devices.
基金supported by the National Science Foundation for Young Scientists of China(51802071)Advanced Talents Incubation Program of the Hebei University(521000981162)+3 种基金Outstanding Youth Science Foundation project of Hebei Province(A2020201032)Local Science and Technology Development Fund Projects Guided by the Central Government(206Z4403G)National Natural Science Foundation of China(No.51372064)Hebei Province High-level Talents Funding project(No.A201801003).
文摘Element doping and nano-inclusion embedding are effective approaches to enhance the electrical conductivities and decrease the lattice thermal conductivities of thermoelectric(TE)materials,respectively.However,the intrinsic low electrical thermal conductivities and high electrical properties are severely sacrificed,and the final figure of merit(ZT)is usually restricted.In this study,Ag doping and Pt quantum dot(QD)embedding were synchronously achieved via embedding Ag/Pt alloy QDs into the higher manganese silicides to avoid the conventional single-element doping strategy.The power factor(at 823 K)was enhanced from 1.57×10^(-3) W m^(-1) K^(-2) to 1.82×10^(-3) W m^(-1) K^(-2)(-16%)due to the-18%increase in carrier concentration that was derived from the Ag doping effect.Simultaneously,the lattice thermal conductivity(at 823 K)decreased from 2.65 W m^(-1) K^(-1) e1.92 W m^(-1) K^(-1)(-28%)because of the broadband phonon scattering effect that resulted from the residual Pt QDs inclusions.Synthetically,the optimal ZT value increased by-52%from 0.42 to 0.64 at 823 K.This study demonstrated that incorporating metastable alloy QDs to obtain element doping and nano-inclusion embedding effects is a novel and feasible means to enhance the ZT value of HMS.This method is also possibly applicable to other alloy QD/TE composites.