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Most of the state-of-the-art thermoelectric materials are inorganic semiconductors. Owing to the directional covalent bonding, they usually show limited plasticity at room temperature1,2, for example, with a tensile strain of less than five per cent. Here we discover that single-crystalline Mg3Bi2 shows a room-temperature tensile strain of up to 100 per cent when the tension is applied along the (0001) plane (that is, the ab plane). Such a value is at least one order of magnitude higher than that of traditional thermoelectric materials and outperforms many metals that crystallize in a similar structure. Experimentally, slip bands and dislocations are identified in the deformed Mg3Bi2, indicating the gliding of dislocations as the microscopic mechanism of plastic deformation. Analysis of chemical bonding reveals multiple planes with low slipping barrier energy, suggesting the existence of several slip systems in Mg3Bi2. In addition, continuous dynamic bonding during the slipping process prevents the cleavage of the atomic plane, thus sustaining a large plastic deformation. Importantly, the tellurium-doped single-crystalline Mg3Bi2 shows a power factor of about 55 microwatts per centimetre per kelvin squared and a figure of merit of about 0.65 at room temperature along the ab plane, which outperforms the existing ductile thermoelectric materials3,4.The thermoelectric material Mg3Bi2 is shown to be ductile in single-crystal form along certain directions, with a room-temperature tensile strain of 100%, which is attributed to the gliding of dislocations. [ABSTRACT FROM AUTHOR]

With the widespread use of nuclear energy, the storage of surplus spent fuel has emerged as a critical issue that needs to be solved, especially for the efficient absorption of neutron radiation and secondary γ-rays generated by spent fuel produced when 10B absorbs neutrons. In this work, B4C/Al and W/B4C/Al coating were prepared on 316 L stainless steel by cold spraying. The microstructure and tensile properties of the coatings were investigated. The performance of the thermal neutron and secondary γ-rays absorption of the two coatings were simulated using the Monte Carlo approach. The results indicated that, compared to the B4C/Al coating, the W/B4C/Al coating exhibited better mechanical properties due to the tamping effect of the W particles. In addition, the secondary γ-rays absorption property was improved due to the addition of W. [ABSTRACT FROM AUTHOR]

Al-based metal matrix composites (MMCs) coatings, prepared by cold spray, have been extensively investigated in recent years. However, only a fraction of the ceramic reinforcement particles could be retained in the final deposit due to the rebound of the hard ceramic particles. Thus, improving the ceramic content in MMCs has been a longstanding issue. To address this issue, for the first time, the effect of particle size of the metal matrix as well as the reinforcement phases on the retention of ceramic particles (in the composite) was simultaneously studied. For this purpose, 12 different kinds of mechanically blended Al/B4C feedstock powders (with different particle sizes) were deposited by cold spray to prepare composite coatings. The results showed that the content of B4C in the prepared Al/B4C coating increases from ~ 20 to ~ 30 vol.% with the decrease in Al particle size from 42 to 11 µm. Finally, a mechanism, elaborating the influence of metal matrix particle size on the retention of ceramic particles in the coating, was proposed. The hardness test for selected Al/B4C composite coatings was performed, which is consistent to the change trend of B4C content. [ABSTRACT FROM AUTHOR]

The effects of molecular weight (Mw) and content of poly(vinyl acetate) (PVAc) on the crystallization behaviors, competing crystallization of homocrystallites and stereocomplex crystallites (SCs), crystalline structure, and mechanical properties of poly(L-lactic acid) (PLLA)/poly(D-lactic acid) (PDLA) blends were investigated. The crystallization of PLLA/PDLA component is accelerated after the addition of low-Mw PVAc and is suppressed with high-Mw PVAc. The ability of SC formation is enhanced via blending with PVAc, irrespective of its Mw, and becomes prominent with low-Mw PVAc. The exclusive SCs are obtained in the blends with 30 mass % low-Mw PVAc. The improvement in thermomechanical property above 170 °C is ascribed to the enhancement of SC content. This work presents guidance for achieving the melt processability of SC-PLA, thus proving their potential as a high-performance substitute for conventional plastics. [ABSTRACT FROM AUTHOR]

Under the joint action of electromagnetic swirling flow in the nozzle (EMSFN) and mold electromagnetic stirring, Liquid level fluctuation in the mold is investigated to find the optimal combination parameters for the occurrence time of the minimum macrosegregation degree in continuous casting of round billet. When the current intensity of EMSFN device is 450 A, the optimal carbon range 0.045 pct appears, after the fluctuation reaches the minimum with the current intensity at 400 A. [ABSTRACT FROM AUTHOR]

Stereocomplexable polylactide (sc-PLA) with improved thermomechanical performance had been prepared by melt compounding of poly(L-lactide) (PLLA), poly(D-lactide) (PDLA), and nanosilica. The silica nanoparticles dispersed evenly in the sc-PLA matrix and there were no air bubbles because of good compatibility between nanosilica and sc-PLA. The aggregates size of nanosilica increased with increasing nanosilica content. The introduction of nanosilica facilitated the formation of stereocomplex, which was manifested as the degree of crystallinity of sc-PLA increased from 17.0 to 24.3% as the nanosilica content increased from 0 to 10 wt%. Thermal stability of sc-PLA was greatly improved by adding nanosilica, and the onset of decomposition temperature of sc-PLA/silica nanocomposites was ~33 °C higher than that of neat sc-PLA. Superior storage modulus was found for sc-PLA/silica nanocomposites compared to neat sc-PLA. The tensile strength and modulus of sc-PLA nanocomposites were greatly improved by the addition of nanosilica, but the elongation at break decreased. [ABSTRACT FROM AUTHOR]

To alleviate macrosegregation, it is the first time that an electromagnetic nozzle swirling flow is applied with a mold electromagnetic stirrer (M-EMS) during continuous casting of square and round billets. Compared with those by only M-EMS, the carbon ranges in square and round billets can be reduced to 0.022 and 0.046 pct, respectively, and the equiaxed crystal ratios are 18 and 33 pct, respectively, by using opposite nozzle swirling flow. [ABSTRACT FROM AUTHOR]

The aim of this study was to prepare a new blend system by blending equimolar poly(L-lactic acid) (PLLA) and poly(D-lactide acid) (PDLA) with poly(butylene adipate-co-terephthalate) (PBAT) and to form stereocomplex polylactide (sc-PLA) during blending process. Then, sc-PLA would improve the performance of PBAT without compromising its biodegradability. Torque-time curve, differential scanning calorimetry (DSC), and wide angle X-ray diffraction (WAXD) measurements indicated that only sc-PLA formed in PBAT matrix. The phase morphology showed that sc-PLA particles were uniformly dispersed in PBAT matrix, and the sizes were independent of their contents. The rheological properties of PBAT were significantly enhanced by addition of sc-PLA, especially after the formation of a percolation network structure. With the increase of sc-PLA content, the blends displayed increased yield strength and modulus and decreased elongation at break and tensile strength. The sc-PLA particles could reinforce PBAT matrix. Compared with pure PBAT, the heat resistance of PBAT/sc-PLA blends was improved. [ABSTRACT FROM AUTHOR]

Phase transformation from austenite to ferrite is an important process to control the microstructures of steels. To obtain finer ferrite grains for enhancing its mechanical property, various thermomechanical processes followed by static ferrite transformation have been carried out for austenite phase. This article reviews the dynamic transformation (DT), in which ferrite transforms during deformation of austenite, in a 6Ni-0.1C steel recently studied by the authors. Softening of flow stress was caused by DT, and it was interpreted through a true stress-true strain curve analysis. This analysis predicted the formation of ferrite grains even above the Ae temperature (ortho-equilibrium transformation temperature between austenite and ferrite), where austenite is stable thermodynamically, under some deformation conditions, and the occurrence of DT above Ae was experimentally confirmed. Moreover, the change in ferrite grain size in DT was determined by deformation condition, i.e., deformation temperature and strain rate at a certain strain, and ultrafine ferrite grains with a mean grain size of 1 μm were obtained through DT with subsequent dynamic recrystallization of ferrite. [ABSTRACT FROM AUTHOR]

A mechanical analysis is done to find the evolution of the interface profile between binary immiscible fluids induced by a three-dimensional orthogonal magnetic field gradient. In the experiments, the changes of the interface profile between four groups of binary immiscible fluids are investigated under the same horizontal magnetic field gradients. The binary immiscible fluids are made of benzene and other liquids, like CuSO, Fecl, FeSO or Cucl aqueous solutions. In addition, the interface profile between the benzene and CuSO aqueous solution is examined under different horizontal magnetic field gradients. The experimental results are consistent with the theoretical analysis. This study explains the enhanced Moses effect from a mechanics standpoint. Furthermore, a new method for susceptibility measurement is proposed based on this enhanced Moses effect. [ABSTRACT FROM AUTHOR]

Dynamic recrystallization (DRX) is an important grain refinement mechanism to fabricate steels with high strength and high ductility (toughness). The conventional DRX mechanism has reached the limitation of refining grains to several microns even though employing high-strain deformation. Here we show a DRX phenomenon occurring in the dynamically transformed (DT) ferrite, by which the required strain for the operation of DRX and the formation of ultrafine grains is significantly reduced. The DRX of DT ferrite shows an unconventional temperature dependence, which suggests an optimal condition for grain refinement. We further show that new strategies for ultra grain refinement can be evoked by combining DT and DRX mechanisms, based on which fully ultrafine microstructures having a mean grain size down to 0.35 microns can be obtained without high-strain deformation and exhibit superior mechanical properties. This study will open the door to achieving optimal grain refinement to nanoscale in a variety of steels requiring no high-strain deformation in practical industrial application. [ABSTRACT FROM AUTHOR]