A5079026231- Thermal properties of materials
- Advanced Thermoelectric Materials and Devices
- Thermal Radiation and Cooling Technologies
- Graphene research and applications
- Advanced Thermodynamics and Statistical Mechanics
- Boron and Carbon Nanomaterials Research
- Chalcogenide Semiconductor Thin Films
- Heat Transfer and Optimization
- Thermography and Photoacoustic Techniques
- Perovskite Materials and Applications
- Advanced Sensor and Energy Harvesting Materials
- Composite Material Mechanics
- Phase-change materials and chalcogenides
- Diamond and Carbon-based Materials Research
- Optical properties and cooling technologies in crystalline materials
- 2D Materials and Applications
- Carbon Nanotubes in Composites
- Force Microscopy Techniques and Applications
- Advancements in Semiconductor Devices and Circuit Design
- Surface and Thin Film Phenomena
- Metal and Thin Film Mechanics
- Semiconductor materials and interfaces
- Semiconductor materials and devices
- Machine Learning in Materials Science
- Dielectric materials and actuators
Cornell University
2018-2025
Max Planck Institute for the Structure and Dynamics of Matter
2023
Center for Free-Electron Laser Science
2023
University of Virginia
2023
DEVCOM Army Research Laboratory
2023
United States Army Combat Capabilities Development Command
2023
Flatiron Health (United States)
2023
Rice University
2023
Oak Ridge National Laboratory
2023
United States Naval Research Laboratory
2023
We apply first-principles calculations to lead selenide (PbSe) and telluride (PbTe) their alloys (PbTe${}_{1\ensuremath{-}x}$Se${}_{x}$), which are potentially good thermoelectric materials, investigate phonon transport properties. By accurately reproducing the lattice thermal conductivity, we validate approaches adopted in this work. We, then, compare contrast PbSe PbTe, evaluate importance of optical phonons estimate impacts nanostructuring alloying on further reducing conductivity. The...
By adding aluminium (Al) into lead selenide (PbSe), we successfully prepared n-type PbSe thermoelectric materials with a figure-of-merit (ZT) of 1.3 at 850 K. Such high ZT is achieved by combination Seebeck coefficient caused very possibly the resonant states in conduction band created Al dopant and low thermal conductivity from nanosized phonon scattering centers.
Knowledge on phonon transmittance as a function of frequency and incidence angle at interfaces is vital for multiscale modeling heat transport in nanostructured materials. Although thermal conductivity reduction materials can usually be described by scattering due to interface roughness, we show how Green's method conjunction with the Landauer formalism suggests that roughness induced atomic mixing increase transmission interfacial conductance. This an attempt incorporate first-principles...
The mean-free-paths (MFPs) of energy carriers are critical importance to the nanoengineering better thermoelectric materials.Despite significant progress in first-principlesbased understanding spectral distribution phonon MFPs recent years, electron remains unclear.In this work, we compute dependent scatterings and silicon from first-principles.The electrical conductivity accumulation with respect is compared that thermal illustrate quantitative impact nanostructuring on transport.By...
The contribution of optical phonons to thermal conductivity has typically been ignored. However, when the system size decreases nanoscale regime, are no longer negligible. In this study, contributions different phonon polarizations silicon discussed based on lifetimes extracted from a first principles approach. results indicate that around room temperature, can contribute over 20% nanostructures as compared 5% in bulk materials. addition, temperature and dependence acoustic fully explored.
Solid-state thermoelectric devices are currently used in applications ranging from thermocouple sensors to power generators space missions, portable air-conditioners and refrigerators. With the ever-rising demand throughout world for energy consumption CO2 reduction, conversion has been receiving intensified attention as a potential candidate waste-heat harvesting well generation renewable sources. Efficient critically depends on performance of materials devices. In this review, we discuss...
Abstract Single‐crystal tin selenide (SnSe), a record holder of high‐performance thermoelectric materials, enables high‐efficient interconversion between heat and electricity for power generation or refrigeration. However, the rigid bulky SnSe cannot satisfy applications flexible wearable devices. Here, method is demonstrated to achieve ultralong single‐crystal wire with rock‐salt structure high performance diameters from micro‐ nanoscale. This starts thermally drawing into fiber‐like...
The traditional atomistic Green's function (AGF) was formulated in the harmonic regime, preventing it from capturing role of anharmonicity interfacial thermal transport. Incorporating into AGF has long been desired but remains challenging. We developed a rigorous anharmonic model to incorporate at interfaces 3-D structures with first-principles force constants. Thermal conductance silicon- and aluminum-based is significantly enhanced resulting new channels opened by inelastic scattering....
Solid-state thermoelectric devices are currently used in applications ranging from thermocouple sensors to power generators satellites, portable air-conditioners and refrigerators. With the ever-rising demand throughout world for energy consumption CO2 reduction, conversion has been receiving intensified attention as a potential candidate waste-heat harvesting well generation renewable sources. Efficient critically depends on performance of materials devices. In this chapter, we discuss heat...
The thermal interface conductance between Al and Si was simulated by a non-equilibrium molecular dynamics method. In the simulations, coupling electrons phonons in are considered using stochastic force. results show size dependence of effect electron-phonon on conductance. To understand mechanism resistance, vibration power spectra calculated. We find that atomic level disorder near is an important aspect interfacial phonon transport, which leads to modification states interface. There,...
The thermal conductance across solid-liquid interfaces is of interest for many applications. Using time-domain thermoreflectance, we measure the self-assembled monolayers, grown on Au, to ethanol. We systematically study effect different functional groups and alkyl chain length conductance. results show that adding this extra molecular layer can enhance transport interface. While enhancement up 5 times from hexanedithiol, hexanethiol, undecanethiol, hexadecanethiol approximately a factor 2.
A unified understanding of interfacial thermal transport is missing due to the complicated nature interfaces which involves complex factors such as bonding, mixing, surface chemistry, crystal orientation, roughness, contamination, and disorder. This especially true for metal nonmetal incorporate multiple fundamental heat mechanisms elastic inelastic phonon scattering well electron coupling in across interface. All these jointly affect boundary conductance (TBC). As a result, experimentally...
Abstract This review introduces relevant nanoscale thermal transport processes that impact abatement in power electronics applications. Specifically, we highlight the importance of mechanisms at each layer material hierarchies make up modern electronic devices. includes those through: (1) substrates, (2) interfaces and two-dimensional materials, (3) heat spreading materials. For layer, provide examples recent works demonstrate improvements performance and/or improve our understanding...
Thermoelectrics represent a unique opportunity in energy to directly convert thermal or secondary waste heat into primary resource. The development of thermoelectric materials has improved over the decades leaps, rather than by increments—each leap forward recapitulated science its time: from crystal growth semiconductors, controlled doping, nanostructuring, and 2D confinement. Each those leaps was, arguably, more result physics. is now ripe for another forward, many probable advances rely...
Two-dimensional (2D) hybrid organic–inorganic perovskites consisting of alternating organic and inorganic layers are a new class layered structures. They have attracted increasing interest for photovoltaic, optoelectronic, thermoelectric applications, where knowing their thermal transport properties is critical. We carry out both experimental computational studies on 2D butylammonium lead iodide crystals find conductivity ultralow (below 0.3 W m–1 K–1) with very weak anisotropy (around 1.5)...
High-temperature polymers are attractive for applications in extreme temperatures, where they maintain their mechanical flexibility and electrical insulating properties. However, heat dissipation capability is limited due to intrinsically low thermal conductivities. Hexagonal boron nitride (hBN) a chemically inert, thermally stable, electrically insulative compound with high conductivity, making it an ideal candidate as filler within high-temperature polymer matrix increase the conductivity....
Understanding thermal transport mechanisms in phase change materials is critical to elucidating the microscopic picture of transitions and advancing energy conversion storage. Experiments consistently show that cubic germanium telluride (GeTe) has an unexpected increase lattice conductivity with rising temperature. Despite its ubiquity, resolving origin remained elusive. In this work, we carry out temperature-dependent calculations for GeTe through efficient, high-order machine-learned...
We used temperature-dependent spark plasma sintering to induce phase transformations of metastable 3D c-BN mixed-phase 3D/2D c-BN/h-BN and ultimately the stable 2D h-BN at high temperature, useful for extreme-temperature technology.
The relaxation of an one-dimensional transient thermal grating (TTG) in a medium with phonon-mediated transport is analyzed within the framework Boltzmann equation (BTE), goal extracting phonon mean free path (MFP) information from TTG measurements non-diffusive transport. Both gray-medium (constant MFP) and spectrally dependent MFP models are considered. In approximation, analytical solution derived. For large periods compared to MFP, model yields exponential decay amplitude time agreement...
Understanding and manipulating coherent phonon transport in solids is of interest both for enhancing the fundamental understanding thermal as well many practical applications, including thermoelectrics. In this study, we investigate transmission across Si/Ge superlattices using Green's function method with first-principles force constants derived from ab initio density functional theory. By keeping period thickness fixed while changing number periods, show that interface roughness partially...