Directed energy deposition (DED) is an efficient method to fabricate functionally graded materials (FGMs) with gradient composition and complex structures, allowing for local tailoring of properties instead of the costly need for extraneous welds and joints. In this study, a FGM from stainless steel to Inconel alloy was successfully fabricated using the powder-based laser DED. A very refined grain structure has been observed in at the composition with 75 wt.% Inconel alloy content, which also exhibits the highest (entropy). For the first time, the post heat treatments, microstructure and aging precipitation behaviors of FGMs were systematically studied via experimental characterization and computation, to elucidate their effects on the gradient smoothing and mechanical properties. The diffusion and segregation of Ni, Nb and Ti elements underly the transformation mechanism between Laves, δ, γ’ and γ’’ phases during precipitation. Homogenization on FGMs not only eliminates the heterogeneity inherited from the AM process, but also provides a practical way to smoothen the gradient on composition and microstructure for the eventual good gradient properties. It has a direct influence on the following precipitation behaviors in the FGM, which highly relies on the diffusion degree of the elements in the matrix and grain boundaries. The high-throughput thermodynamic modeling and kinetic modeling were exploited to evaluate the experimental microstructure and address computational uncertainty using different thermodynamic conditions and databases, which enables an accelerated design through local tailoring of process-structure-property relationships to develop new functional materials.
We have performed a series of ∼100 fs time‐resolved measurements on YBCO thin films. The dependence of the transient optical properties on probing laser frequency, pumping laser intensity, sample thickness, and ambient film temperature is discussed. Our results are compared to existing models and provide new insights on nonequilibrium properties of YBCO.
Kerr soliton frequency-comb generation in microresonators has attracted extensive interest since soliton microcombs offer the potential for integration and can be widely used in many fields, such as spectroscopy, communications, precision metrology, sensing, etc. Here, the mechanism of turnkey soliton generation in a microresonator with an organic material coating is illustrated and investigated in both analytical and numerical ways. In particular, based on the thermal curve under a stable state and soliton power from analytical analysis, the turnkey soliton generation regime is calculated and proved by coupled equations with the split-step Fourier method. In addition, the physical parameters of the hybrid modes in the coated resonators are studied, and a suitable design is given in this paper. This research will be helpful for increasing the accessibility of Kerr solitons and make them easier to integrate.
The orbital riveting process has been successively adopted in the assembly of wheel hub bearing, due to its special merits of high efficiency, low cost, and so on. The forming process and deformation behavior of the inner ring have significant influence on the axial clamping force and bearing clearance, however, which haven't been addressed yet. In this study, a numerical simulation platform for the assembly of the hub bearing is established by the joint use of the static implicit and dynamic explicit algorithms. Based on the platform, the deformation process and deformation behavior of the inner ring are investigated, along with the interference assembly and riveting assembly on the loading process of the inner ring. Finally, relevant experimental verifications are carried out to consolidate the simulation results. The research findings could be used to guide the design and optimization of the axial clamping force and bearing clearance.
Abstract Semiconductors are the cornerstones of the current information age. Next‐generation integrated optoelectronics calls for ultrahigh‐resolution manufacturing of sophisticated three‐dimensional (3D) semiconductor products, which introduces tremendous challenges for conventional planar lithography techniques. State‐of‐the‐art 3D printing techniques are promising but hampered by the absence of functional precursors for semiconductor formation. Here, a facile method to synthesize versatile and customizable metal‐bound composite photoresins for 3D printing various nano‐architected metal oxide semiconductors is reported. These photoresins can be readily synthesized using metal‐organic framework (MOF) precursors and commercially available monomers, which are free of the nanoparticle‐induced scattering effect. Arbitrary 3D architectures of metal oxide semiconductors (e.g., ZnO and Co 3 O 4 ) are additively manufactured with a high resolution of 170 nm, high shape fidelity, and high surface quality. A ZnO‐based micro‐ultraviolet photodetector is fabricated to demonstrate its potential applications in optoelectronic devices. The versatile photoresins are expected to have broad applicability for various functional materials and pave the way for the fabrication of 3D integrated functional devices.
In this paper, periodic peaks in a terahertz absorption spectrum are confirmed to be induced from interference effects. Theoretically, we explained the periodic peaks and calculated the locations of them. Accordingly, a technique was suggested, with which the interference peaks in a terahertz spectrum can be eliminated and therefore a real terahertz absorption spectrum can be obtained. Experimentally, a sample, Methamphetamine, was investigated and its terahertz fingerprint was successfully extracted from its interference destruction spectrum. This technique is useful in getting samples' terahertz fingerprint spectra, and furthermore provides a fast nondestructive testing method using a large size terahertz beam to identify materials.
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