Search

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]

Long-lived thermally activated delayed fluorescence (TADF) emission has gained extensive attention due to its potential application in information encryption, illumination, and bioimaging. However, developing visible light-excited TADF materials is still a significant challenge. Herein, visible light triggered TADF emission was achieved by embedding chlorine doped carbon dots (Cl-CDs) into a g-C3N4 nanosheet matrix through a simple microwave treatment. The strong electron-withdrawing effect of the chlorine dropping redshifts the excitation wavelength, and the covalent bonds between Cl-CDs and the matrix significantly stabilize the triplet state. Green TADF with a peak at 520 nm could be obtained in the Cl-CD composite when excited by the UV to visible light, and the afterglow signal can be observed by the naked eye for up to 5 s after a mobile phone flashlight irradiation. The composite also exhibited temperature-responsive color stability under UV light irradiation. Consequently, the Cl-CD composite was successfully employed in concepts of information encryption and single-component time delay WLED development. This research provides materials and strategies that may motivate the visible light-excited TADF applied in advanced information encryption and illumination areas. [ABSTRACT FROM AUTHOR]

Cold spray is a rapidly developing solid-state deposition technology in recent years. It has the characteristics of low spraying temperature and high velocity of spraying particles, hence showing a good prospect for preparing metal matrix composite (MMC) coatings and bulk materials. In particular, aluminum matrix composites have received great attention in electronics, aerospace and automobile industries due to their excellent physical and mechanical properties. In this paper, the research progress of cold-sprayed aluminum matrix composite coatings and materials was systematically introduced. Firstly, state of the art on cold sprayed coatings and materials with different reinforcing phases was presented. Then, research progress on different post-spray treatments, to improve the properties of as-sprayed deposit, was briefly discussed. Finally, the application fields and problems of cold-sprayed aluminum matrix composite coatings and materials were summarized. [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]

In this work, a bifunctional ligand 2,2′-disulfonic acid benzidine (H2L) was selected, and we adopted a mixed ligand strategy, in which the ligand reacted with 2,2′-bipyridine and 1,10-o-phenanthroline, where two new silver-based coordination polymer materials [Ag2(2,2′-bipy)2L]·H2O (BAg-1) and [Ag2(phen)2L] (BAg-2) were obtained. BAg-1 was zero-dimensional, which could interconnect with one-dimensional hydrogen bonds to form a three-dimensional stacking structure, while BAg-2 was a one-dimensional chain structure, and the one-dimensional chains formed a two-dimensional planar structure through hydrogen bonding between the sulfonic acid group and the amino group. Their proton conductivity reached a high level among the coordination polymers at 98% relative humidity (RH) and 90 °C, where their proton conductivity values were 0.455 × 10−4 S cm−1 (BAg-1) and 1.09 × 10−4 S cm−1 (BAg-2), respectively. Combining their respective single crystal data with the results of Hirshfeld surface analysis, water adsorption experiments, and activation energy calculations, we determined their proton conduction pathways and mechanisms. The results showed that the abundant hydrogen bond chains and hydrogen bond networks co-constructed using sulfonic acid groups, amino groups and crystal water molecules in the framework and numerous uncoordinated sulfonic acid groups as proton carriers in the material were the reasons for efficient proton transfer. [ABSTRACT FROM AUTHOR]

In this work, the two example rare earth‐based metal‐organic frameworks (LaIII‐based MOFs), Eu‐ETTB and Gd‐ETTB, were obtained by self‐assembly. Both materials showed extremely high proton conductivity, with the proton conductivity of Eu‐ETTB being 1.53×10−2 S cm−1 at 98 % relative humidity (RH) and 85 °C and that of Gd‐ETTB being 2.63×10−2 S cm−1 at 98 % RH and 75 °C. This was almost the best performance observed for three‐dimensional porous MOFs without post‐synthetic modification and was based on milder conditions than for most materials. Furthermore, cycle test experiments and continuous work tests showed that both materials had excellent performance both in terms of stability and durability. Water vapor adsorption experiments showed that a large number of water molecules are adsorbed the hydrogen‐bond network's being rebuilt by the adsorbed water molecules in the pore channel and thus optimizing the channels for proton transfer explained the MOF's high performance. [ABSTRACT FROM AUTHOR]