Recent experiments, at room temperature, have shown that near-field radiative heat transfer (NFRHT) via surface phonon polaritons (SPhPs) exceeds the blackbody limit by several orders of magnitude. Yet, SPhP-mediated ...
详细信息
Recent experiments, at room temperature, have shown that near-field radiative heat transfer (NFRHT) via surface phonon polaritons (SPhPs) exceeds the blackbody limit by several orders of magnitude. Yet, SPhP-mediated NFRHT at cryogenic temperatures remains experimentally unexplored. Here, we probe thermal transport in nanoscale gaps between a silica sphere and a planar silica surface from 77–300 K. These experiments reveal that cryogenic NFRHT has strong contributions from SPhPs and does not follow the T3 temperature (T) dependence of far-field thermal radiation. Our modeling based on fluctuational electrodynamics shows that the temperature dependence of NFRHT can be related to the confinement of heat transfer to two narrow frequency ranges and is well accounted for by a simple analytical model. These advances enable detailed NFRHT studies at cryogenic temperatures that are relevant to thermal management and solid-state cooling applications.
In this study, the predominant mechanical properties and deformation mechanisms of CoCrFeNiMnx high entropy alloys (HEAs) were explored by using the molecular dynamics (MD) simulation. A uniaxial tensile process with ...
详细信息
The complementary properties of corrosion resistance and ballistic resistance of AA5083 and AA7075, respectively, explain the significance of welding these two alloys in the marine armor industry. This study investiga...
详细信息
The extruded plate of powder metallurgy AA2024 aluminum alloy was successfully solid-state joined by friction stir welding(FSW) to demonstrate potential applications in the aerospace and automotive industries. For det...
详细信息
The extruded plate of powder metallurgy AA2024 aluminum alloy was successfully solid-state joined by friction stir welding(FSW) to demonstrate potential applications in the aerospace and automotive industries. For determining the optimal processing parameters of FSW, the microstructure, mechanical properties, and fracture behavior of FSW joints were evaluated. When the processing parameters were optimized with 2000 r/min rotation speed and100 mm/min traverse speed, high quality welds were achieved. The ultimate tensile strength yield strength and elongation of the joint can reach 415 MPa(85% of the base metal strength), 282 MPa, and 9.5%, respectively. The hardness of the joint gradually decreased from the alloy matrix to the heat-affected zone. The lowest strength and hardness appeared near the heat-affected zone because of the over-aging caused by heat flow from repeated stirring during FSW. The average grain size of the stir zone(2.15 μm) was smaller than that of the base metal(4.43 μm) and the heat-affected zone(5.03 μm), whose grains had <110> preferred orientation.
Semiconductor heterojunctions have gained significant attention for efficient optoelectronic devices owing to their unique interfaces and synergistic effects. Interaction between charge carriers with the heterojunctio...
详细信息
3D Printing has become a popular additive manufacturing method for fabricating various components, both in industry as well as at the hobbyist level. While it is often used for prototypes or decorative trinkets, it is...
详细信息
This work demonstrates a first-principles-based approach to obtaining finite temperature thermal and electronic transport properties which can be employed to model and understand mesoscale structural evolution during ...
详细信息
This work demonstrates a first-principles-based approach to obtaining finite temperature thermal and electronic transport properties which can be employed to model and understand mesoscale structural evolution during electronic, magnetic, and structural phase transitions. A computationally tractable model was introduced to estimate electron relaxation time and its temperature dependence. The model is applied to Ca3Ru2O7 with a focus on understanding its electrical resistivity across the electronic phase transition at 48 K. A quasiharmonic phonon approach to the lattice vibrations was employed to account for thermal expansion while the Boltzmann transport theory including spin-orbit coupling was used to calculate the electron-transport properties, including the temperature dependence of electrical conductivity.
The primary advantage of the high energy ball milling (HEBM) process is its ability to synthesize a homogeneous mixture with submicron (up to nanoscale) particle size. This approach is a viable process for particle si...
详细信息
The ferroelectric material usually exhibits temperature-dependent spontaneous polarization, known as pyroelectricity, which can be used to directly convert thermal energy to electricity from ambient low-grade waste he...
详细信息
The ferroelectric material usually exhibits temperature-dependent spontaneous polarization, known as pyroelectricity, which can be used to directly convert thermal energy to electricity from ambient low-grade waste heat. When utilizing the structural phase transformations of the material, the conversion capability can be magnified, consequently the device performance can be strongly boosted by orders of magnitude. However, common ferroelectric oxides suffer mechanical fatigue and functional degradation over cyclic phase transformations, hindering widespread applications of the energy conversion device. In this paper, we investigate the mechanical and functional reversibility of the material by lattice tuning and grain coarsening. We discover the lead-free compound Ba(Ce0.005Zr0.005)Ti0.99O3−0.10(Ba0.7Ca0.3)TiO3 (BaCeZrTiO3−0.10BaCaTiO3) satisfying the compatibility condition among all present phases by its lattice parameters, making the phase transformations highly reversible. We demonstrated that the energy conversion device with equiaxial coarse grains exhibits exceptional fatigue resistance, with stable pyroelectric current output at 4µA/cm2 over 3000 energy conversion cycles. Our work opens another way to fabricate high-performance materials that advances the pyroelectric energy conversion for practical applications in engineering.
Owing to the rich physical-chemistry properties, phosphates have found diverse applications. Their behaved interesting characteristics mainly benefit from the flexibility of PO4 tetrahedra. The development of new phos...
详细信息
暂无评论