We present comprehensive first-principles Density Functional Theory (DFT) analyses of the interfacial strength and bonding mechanisms between crystalline and amorphous selenium (Se) with graphene (Gr), a promising duo...
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Shape Memory Alloys (SMAs) are smart materials that regain their original shape after significant deformation, typically over 1 % under uniaxial tension. Ni-Ti alloys stand out for their low elastic modulus, high reco...
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Shape Memory Alloys (SMAs) are smart materials that regain their original shape after significant deformation, typically over 1 % under uniaxial tension. Ni-Ti alloys stand out for their low elastic modulus, high recoverable strain, and excellent corrosion resistance. However, nickel raises biocompatibility concerns due to potential adverse effects. As an alternative, Ni-free Ti-Nb-based SMA, composed entirely of biocompatible elements, have emerged as a promising option for biomedical applications. This study investigated and characterized Ti-xNb-based, alloys with x = 23 %, 25 % and 27 % (at%), manufactured by arc melting, cold rolling, and vacuum annealing followed by quenching. The focus was on their mechanical and microstructural properties, particularly cyclic mechanical loading, thermomechanical behavior, and ultramicroindentation, areas still underexplored in the literature. XRD confirmed the predominance of the β phase and EDS verified good compositional homogeneity. mechanical testing showed that increasing niobium content reduced the elastic modulus, hardness, and reduction modulus due to β-phase stabilization. Tensile tests indicated changes in shape recovery through superelasticity. Overall, Ti-Nb-based alloys presented excellent mechanical properties with potential for biomedical applications.
Molten salts play a crucial role in Generation IV nuclear energy technology, with chloride salts like NaCl-UCl 3 garnering significant attention due to their distinctive properties and potential applications in fast-s...
Molten salts play a crucial role in Generation IV nuclear energy technology, with chloride salts like NaCl-UCl 3 garnering significant attention due to their distinctive properties and potential applications in fast-spectrum molten salt reactors (MSRs). The corrosive nature of molten salts can cause the dissolution of structural materials, leading to the formation of new species in molten chlorides. In addition, the radioactive decay of nuclear fuels results in the accumulation of fission products in the salts. Understanding the behavior of these corrosion and fission products and their impacts on the properties of molten salts is critical for the design of MSRs. This paper presents a systematic study on the properties of eutectic NaCl-UCl 3 molten salt in the presence of corrosion products (CrCl 2 and CrCl 3 ) and fission products (CsCl and SrCl 2 ) utilizing ab initio molecular dynamics (AIMD) simulations. We focus on essential structural and thermophysical properties such as density, mixing energy, coordination numbers (CN), and Radial Distribution Functions (RDF) with varying compositions of these corrosion and fission products from 0 % to 15.8 %. It is found that the mixing behavior of these corrosion and fission products is strongly driven by their coordination chemistry in eutectic NaCl-UCl 3 . Both CrCl 2 and SrCl 2 have identical coordination to eutectic NaCl-UCl 3 , thus exhibit negative mixing energies at a lower concentration. In contrast, CsCl exhibits significant different coordination compared to NaCl-UCl 3 , resulting to positive mixing energies. Our results offer valuable insights into the coordination chemistry and mixing behavior of corrosion and fission products in chloride molten salts and provide essential data that can be used as input to property databases to supplement experimental data.
In this study, AA2519 alloy was initially processed by multi axial forging (MAF) at room and cryogenic temperatures. Subsequently, the microstructure and the mechanical behavior of the processed samples under quasi-st...
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In this study, AA2519 alloy was initially processed by multi axial forging (MAF) at room and cryogenic temperatures. Subsequently, the microstructure and the mechanical behavior of the processed samples under quasi-static loading were investigated to determine the influence of cryogenic forging on alloys’ subgrains dimensions, grain boundaries interactions, strength, ductility and toughness. In addition, the failure mechanisms at the tensile rupture surfaces were characterized using scanning electron micro-scope (SEM). The results show significant improvements in the strength, ductility and toughness of the alloy as a result of the cryogenic MAF process. The formation of nanoscale crystallite microstructure, heavily deformed grains with high density of grain boundaries and second phase breakage to finer particles were characterized as the main reasons for the increase in the mechanical properties of the cryogenic forged samples. The cryogenic processing of the alloy resulted in the formation of an ultrafine grained material with tensile strength and toughness that are ~41% and ~80% higher respectively after 2 cycles MAF when compared with the materials processed at ambient temperature. The fractography analysis on the tested materials shows a substantial ductility improvement in the cryoforged (CF) samples when compared to the room temperature forged (RTF) samples which is in alignment with their stress-strain profiles. However, extended forging at higher cycles than 2 cycles led only to increase in strength at the expense of ductility for both the CF and RTF samples.
Spectroscopic ellipsometry and Fourier transform infrared spectroscopy were applied to extract the ultraviolet to far-infrared (150–33333cm−1) complex dielectric functions of high-quality, sputtered indium-doped cadm...
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Spectroscopic ellipsometry and Fourier transform infrared spectroscopy were applied to extract the ultraviolet to far-infrared (150–33333cm−1) complex dielectric functions of high-quality, sputtered indium-doped cadmium oxide (In:CdO) thin crystalline films on MgO substrates possessing carrier densities (Nd) ranging from 1.1×1019cm−3 to 4.1×1020cm−3. A multiple oscillator fit model was used to identify and analyze the three major contributors to the dielectric function and their dependence on doping density: interband transitions in the visible, free-carrier excitations (Drude response) in the near- to far-infrared, and IR-active optic phonons in the far-infrared. More specifically, values pertinent to the complex dielectric function such as the optical band gap (Eg), are shown here to be dependent upon carrier density, increasing from approximately 2.5–3 eV, while the high-frequency permittivity (ɛ∞) decreases from 5.6 to 5.1 with increasing carrier density. The plasma frequency (ωp) scales as Nd, resulting in ωp values occurring within the mid- to near-IR, and the effective mass (m*) was also observed to exhibit doping density-dependent changes, reaching a minimum of 0.11mo in unintentionally doped films (1.1×1019cm−3). Good quantitative agreement with prior work on polycrystalline, higher-doped CdO films is also demonstrated, illustrating the generality of the results. The analysis presented here will aid in predictive calculations for CdO-based next-generation nanophotonic and optoelectronic devices, while also providing an underlying physical description of the key properties dictating the dielectric response in this atypical semiconductor system.
The modulation of the atom spacings in the sheets of two-dimensional (2D) materials offers a modality for the tuning of related physical and chemical attributes of materials. In this context, we present a methodology,...
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