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Recent progress in thermoelectric nanocomposites based on solution-synthesized nanoheterostructures

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Nano Research 2017年第5期10卷 1498-1509页

作者： Wei Zheng Biao Xu Lin Zhou Yilong Zhou Haimei Zheng Chenghan Sun Enzheng Shi Tanner Dale Fink Yue Wu Department of Chemical and Biological Engineering Iowa State University Ames IA 50011 USA ames laboratory Department of Energy Iowa State University Ames IA 50011 USA Material Science Division Lawrence Berkeley National Laboratory Berkeley CA 94720 USA

Thermoelectric materials, which can convert waste heat into electricity, have received increasing research interest in recent years. This paper describes the recent progress in thermoelectric nanocomposites based on solution-synthesized nanoheterostructures. We start our discussion with the strategies of improving the power factor of a given material by using nanoheterostructures. Then we discuss the methods of decreasing thermal conductivity. Finally, we highlight a way of decoupling power factor and thermal conductivity, namely, incorporating phase-transition materials into a nanowire heterostructure. We have explored the lead telluride-copper telluride thermoelectric nanowire heterostructure in this work. Future possible ways to improve the figure of merit are discussed at the end of this paper.

关键词： thermoelectrics nanoheterostructures phase change

Conversion of confined metal@ZIF-8 structures to intermetallic nanoparticles supported on nitrogen-doped carbon for electrocatalysis

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Nano Research 2018年第6期11卷 3469-3479页

作者： Zhiyuan Qi Yuchen Pei Tian Wei Goh Zhaoyi Wang Xinle Li Mary Lowe Raghu V. Maligal-Ganesh Wenyu Huang Department of Chemistry Iowa State University Ames Iowa 50011 USA ames laboratory U.S. Department of Energy Ames Iowa 50011 USA Department of Chemistry Beijing Normal University Beijing 100875 China

We report a facile strategy to synthesize intermetallic nanoparticle （iNP） electrocatalysts via one-pot pyrolysis of a zeolitic imidazolate framework, ZIF-8, encapsulating precious metal nanoparticles （NPs）. ZIF-8 serves not only as precursor for N-doped carbon （NC）, but also as Zn source for the formation of intermetallic or alloy NPs with the encapsulated metals. The resulting sub-4 nm PtZn iNPs embedded in NC exhibit high sintering resistance up to 1,000℃. Importantly, the present methodology allows fine-tuning of both composition （e.g., PdZn and RhZn iNPs, as well as AuZn and RuZn alloy NPs） and size （2.4, 3.7, and 5.4 nm PtZn） of the as-formed bimetallic NPs. To the best of our knowledge, this is the first report of a metal-organic framework （MOF） with multiple functionalities, such as secondary metal source, carbon precursor, and size-regulating reagent, which promote the formation of iNPs. This work opens a new avenue for the synthesis of highly uniform and stable iNPs.

关键词： intermetallic compounds cage confinement pyrolysis electrocatalysis sintering resistance

Tensorial stress−strain fields and large elastoplasticity as well as friction in diamond anvil cell up to 400 GPa

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npj Computational Materials 2019年第1期5卷 313-323页

作者： Valery I.Levitas Mehdi Kamrani Biao Feng Departments of Aerospace Engineering and Mechanical Engineering Iowa State UniversityAmesIA 50011USA Division of Materials Science and Engineering Ames LaboratoryAmesIA 50011USA Department of Aerospace Engineering Iowa State UniversityAmesIA 50011USA Los Alamos National laboratory Los AlamosNM 87545USA

Various phenomena(fracture,phase transformations,and chemical reactions)studied under extreme pressures in diamond anvil cell are strongly affected by fields of all components of stress and plastic strain ***,they could not be ***,we suggest a coupled experimental−theoretical−computational approach that allowed us(using published experimental data)to refine,calibrate,and verify models for elastoplastic behavior and contact friction for tungsten(W)and diamond up to 400 GPa and reconstruct fields of all components of stress and large plastic strain tensors in W and *** the generally accepted strain-induced anisotropy,strain hardening,and path-dependent plasticity,here we showed that W after large plastic strains behaves as isotropic and perfectly plastic with path-independent surface of perfect ***,scale-independence of elastoplastic properties is found even for such large field *** results open opportunities for quantitative extreme stress science and reaching record high pressures.

关键词： friction stress strain

Synthesis of nickel selenide thin films for high performance all-solid-state asymmetric supercapacitors

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Chinese Chemical Letters 2020年第9期31卷 2275-2279页

作者： Hao Li Jiangfeng Gong Jing-Chang Li Xincheng Zhang Chunmei Tang Hongbing Yao Qingping Ding College of Science Hohai UniversityNanjing 210098China ames laboratory US DOEAmesIA 50011United States

As a significant semiconductor,nickel selenide shows enormous potential and extensive application pro spects in the field of sensor,photocatalysis and supercapacito *** this paper,nickel selenide(Ni3Se2,NiSe) thin films were successfully fabricated on stainless-steel sheet using a facile,effective electrodeposition *** morphologies,microstructures and chemical compositions of the thin films are characterized *** tests exhibit that the Ni3Se2 and NiSe possess high specific capacitance of 581.1 F/g and 1644.7 F/g,respectively.A flexible,all-solid-state asymmetric supercapacitor is assembled by utilizing NiSe film as positive electrode and activated carbon as negative *** solid device delivers a high areal capacitance of 27.0 mF/cm2 at the current density of 0.7 mA/*** maximum volumetric energy density and powerdensity of the NiSe//AC asymmetric SCs can achieve 0.26 mWh/cm3 and 33.35 mW/cm3,*** device shows robust cycling stability with 84.6% capacitance retention after 10,000 cycles,outstanding flexibility and satis factory mechanical ***,two devices in series can light up a red light-emitting diode,which displayed great potential applications for energy storage.

关键词： Nickel selenide Electrochemical properties Asymmetric All-solid-state Supercapacitors

Prediction of Van Hove singularity systems in ternary borides

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npj Computational Materials 2023年第1期9卷 247-257页

作者： Yang Sun Zhen Zhang Andrew P.Porter Kirill Kovnir Kai-Ming Ho Vladimir Antropov Department of Physics Xiamen University361005 XiamenChina Department of Physics and Astronomy Iowa State UniversityAmesIA 50011USA Department of Chemistry Iowa State UniversityAmesIA 50011USA ames National laboratory U.S.Department of EnergyAmesIA 50011USA

A computational search for stable structures among bothαandβphases of ternary ATB4 borides(A=Mg,Ca,Sr,Ba,Al,Ga,and Zn,T is 3d or 4d transition elements)has been *** found thatα-ATB4 compounds with A=Mg,Ca,Al,and T=V,Cr,Mn,Fe,Ni,and Co form a family of structurally stable or almost stable *** systems are metallic in non-magnetic states and characterized by the formation of the localized molecular-like state of 3d transition metal atom dimers,which leads to the appearance of numerous Van Hove singularities in the electronic *** closeness of such singularities to the Fermi level can be easily tuned by electron *** the atoms in the middle of the 3d row(Cr,Mn,and Fe),these singularities led to magnetic instabilities and magnetic ground states with a weakly metallic or semiconducting *** states appear as non-trivial coexistence of the different spin ladders formed by magnetic dimers of 3d *** magnetic states can be characterized as an analog of the spin glass *** attempts to produce MgFeB4 and associated challenges are discussed,and promising directions for further synthetic studies are formulated.

关键词： metallic ternary magnetic

Electron correlation effects on exchange interactions and spin excitations in 2D van der Waals materials

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npj Computational Materials 2021年第1期7卷 33-40页

作者： Liqin Ke Mikhail I.Katsnelson ames laboratory U.S.Department of EnergyAmesIowa 50011USA Institute for Molecules and Materials Radboud UniversityHeijendaalseweg 1356525AJ NijmegenThe Netherlands

Despite serious effort,the nature of the magnetic interactions and the role of electron-correlation effects in magnetic twodimensional(2D)van der Waals materials remains *** CrI3 as a model system,we show that the calculated electronic structure including nonlocal electron correlations yields spin excitations consistent with inelastic neutron-scattering ***,this approach identifies an unreported correlation-enhanced interlayer super-superexchange,which rotates the magnon Dirac lines off,and introduces a gap along the high-symmetryΓ-K-M *** discovery provides a different perspective on the gap-opening mechanism observed in CrI3,which was previously associated with spin–orbit coupling through the Dzyaloshinskii–Moriya interaction or Kitaev *** observation elucidates the critical role of electron correlations on the spin ordering and spin dynamics in magnetic van der Waals materials and demonstrates the necessity of explicit treatment of electron correlations in the broad family of 2D magnetic materials.

关键词： interaction materials excitation

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Magnetic Cooling

Journal of Rare Earths 2005年第4期23卷 I0001-I0002页

作者： Karl A. Gschneidner Jr. Materials and Engineering Physics Ames Laboratory Department of Materials Science and Engineering Iowa State University Ames IA 50011-3020 USAMaterials and Engineering Physics Ames Laboratory Department of Materials Science and Engineering Iowa State University Ames IA 50011-3020 USA

The world has become highly dependent on reliable refrigeration technology. Without it, our food supply would be still seasonal and limited to locally produced nonperishable items; comfortable living conditions via climate control would be impossible; and certain medical advancements, e.g. MRI diagnostics, organ transplantation, organ and tissue cryo-storage, and cryo-surgery would be impossible. This technology remains essentially unchanged since it was invented 100 years ago.

关键词： Magnetic Cooling

Distilling physical origins of hardness in multi-principal element alloys directly from ensemble neural network models

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npj Computational Materials 2022年第1期8卷 1450-1460页

作者： D.Beniwal P.Singh S.Gupta M.J.Kramer D.D.Johnson P.K.Ray Metallurgical&Materials Engineering Indian Institute of Technology RoparRupnagar140001PunjabIndia ames laboratory US Department of EnergyAmesIA50011USA Materials Science&Engineering Iowa State UniversityAmesIA50011USA

Despite a plethora of data being generated on the mechanical behavior of multi-principal element alloys,a systematic assessment remains inaccessible via Edisonian *** approach this challenge by considering the specific case of alloy hardness,and present a machine-learning framework that captures the essential physical features contributing to hardness and allows high-throughput exploration of multi-dimensional compositional *** model,tested on diverse datasets,was used to explore and successfully predict hardness in Al_(x)Ti_(y)(CrFeNi)_(1-x-y),Hf_(x)Co_(y)(CrFeNi)_(1-x-y)and Al_(x)(TiZrHf)_(1-x)systems supported by data from density-functional theory predicted phase stability and ordering *** experimental validation of hardness was done on *** selected systems pose diverse challenges due to the presence of ordering and clustering pairs,as well as vacancy-stabilized novel *** also present a detailed model analysis that integrates local partial-dependencies with a compositional-stimulus and model-response study to derive material-specific insights from the decision-making process.

关键词： alloys alloy element

Metal intercalation-induced selective adatom mass transport on graphene

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Nano Research 2016年第5期9卷 1434-1441页

作者： Xiaojie Liu Cai-Zhuang Wang Myron Hupalo Hai-Qing Lin Kai-Ming Ho Patricia A. Thiel Michael C. Tringides Center for Quantum Science and School of Physics Northeast Normal University Changchun 730777 China ames laboratory-U.S. Department of Energy and Department of Physics and Astronomy Iowa State University Ames IA 50011 USA Beijing Computational Science Research Center Beijing 100084 China ames laboratory-U.S. Department of Energy Department of Chemistry and Department of Materials Science and Engineering Iowa State University Ames IA 50011 USA

Recent experiments indicate that metal intercalation is a very effective method to manipulate the graphene-adatom interaction and control metal nanostructure formation on graphene. A key question is mass transport, i.e., how atoms deposited uniformly on graphene populate different areas depending on the local intercalation. Using first-principles calculations, we show that partially intercalated graphene, with a mixture of intercalated and pristine areas, can induce an alternating electric field because of the spatial variations in electron doping, and thus, an oscillatory electrostatic potential. This alternating field can change normal stochastic adatom diffusion to biased diffusion, leading to selective mass transport and consequent nucleation, on either the intercalated or pristine areas, depending on the charge state of the adatoms.

关键词： graphene intercalation electrostatic potential selective adsorption first-principle calculation