Infrared nonlinear optical (IR NLO) materials are significant in laser technology for civil and military uses. Here, we report the synthesis, structural chemistry and NLO properties of a halogen‐rich ...chalcohalide Sn7Br10S2. Its noncentrosymmetric (NCS, P63) structure can be considered as partially aliovalent anion substitution of SnBr2 (P63/m) induced centrosymmetric (CS) to NCS structural transformation. The 3D ∞Sn(1)6Sn(2)6Br6X66− (X=Br/S) channel framework consists of Sn(1)BrX2 and Sn(2)X3 trigonal pyramids. It exhibits excellent NLO performance, including a strong phase‐matchable NLO response of 1.5 × AgGaS2and high laser‐induced damage threshold of 6.3 × AgGaS2.Investigation of the structure–NLO performance relationship confirms that the effective arrangement of Sn(1)BrX2 and Sn(2)X3 units predominantly contributes to the large SHG response. These results indicate Sn7Br10S2 is a potential IR NLO candidate and provides a new feasible system for promising NLO materials.
The first ternary halogen‐rich nonlinear optical chalcohalide Sn7Br10S2 exhibits a strong phase‐matchable second‐harmonic generation response (1.5 × AGS@2.1 μm) and high laser‐induced damage threshold (6.3 × AGS). This work provides a competitive candidate with good performance, facile synthesis and simple chemical composition for infrared nonlinear optical (IR NLO) applications, and also introduces a facile strategy to obtain high‐performance NLO materials via a symmetry break.
Metal chalcogenophosphates are receiving increasing interest, specifically as promising infrared nonlinear optical (NLO) candidates. Here, a rare‐earth chalcogenophosphate Eu2P2S6 crystallizing in ...the monoclinic noncentrosymmetric space group Pn was synthesized using a high‐temperature solid‐state method. Its structure features isolated P2S64− dimer, and two types of EuS8 bicapped triangular prisms. Eu2P2S6 exhibits a phase‐matchable second‐harmonic generation (SHG) response ≈0.9×AgGaS2@2.1 μm, and high laser‐induced damage threshold of 3.4×AgGaS2, representing the first rare‐earth NLO chalcogenophosphate. The theoretical calculation result suggests that the SHG response is ascribed to the synergetic contribution of P2S64− dimers and EuS8 bicapped triangular prisms. This work provides not only a promising high‐performance infrared NLO material, but also opens the avenue for exploring rare‐earth chalcogenophosphates as potential IR NLO materials.
Eu2P2S6 exhibits excellent NLO properties, including a phase‐matchable second‐harmonic generation (SHG) response ≈0.9×AgGaS2@2.1 μm, and a high laser‐induced damage threshold of 3.4×AgGaS2. Eu2P2S6 is the first NLO‐active rare‐earth‐based chalcogenophosphate.
Tin diselenide (SnSe2) nanosheets as novel 2D layered materials have excellent optical properties with many promising application prospects, such as photoelectric detectors, nonlinear optics, ...infrared photoelectric devices, and ultrafast photonics. Among them, ultrafast photonics has attracted much attention due to its enormous advantages; for instance, extremely fast pulse, strong peak power, and narrow bandwidth. In this work, SnSe2 nanosheets are fabricated by using solvothermal treatment, and the characteristics of SnSe2 are systemically investigated. In addition, the solution of SnSe2 nanosheets is successfully prepared as a fiber‐based saturable absorber by utilizing the evanescent field effect, which can bear a high pump power. 31st‐order subpicosecond harmonic mode locking is generated in an Er‐doped fiber laser, corresponding to the maximum repetition rate of 257.3 MHz and pulse duration of 887 fs. The results show that SnSe2 can be used as an excellent nonlinear photonic device in many fields, such as frequency comb, lasers, photodetectors, etc.
Tin diselenide (SnSe2) nanosheets as novel 2D layered materials have excellent optical properties. SnSe2 nanosheets fabricated by using solvothermal treatment are successfully prepared as fiber‐based saturable absorbers by utilizing the evanescent field effect, which can bear a high pump power. 31st‐order subpicosecond harmonic mode‐locking is generated, corresponding to 257.3 MHz repetition rate.
Rare‐earth (RE) chalcogenides have been extensively studied as infrared nonlinear optical (NLO) materials because of their nice integrated performances; however, very few RE chalcophosphates are ...involved for this topic. Here, three quaternary RE selenophosphates, KSmP2Se6 (1), KGdP2Se6 (2), and KTbP2Se6 (3), are profoundly studied for their NLO potentials. Their noncentrosymmetric P21 structures feature RESe8‐bicapped trigonal prisms and ethane‐like P2Se64− dimers built {REP2Se6−}∞ layers. As the first studied NLO‐active RE selenophosphates, 1–3 exhibit second harmonic generation (SHG)responses ≈0.34–1.08 × AgGaS2 at 2.10 µm and laser‐induced damage thresholds (LIDTs) ≈1.43–4.33 × AgGaS2, and they all show phase‐matchable behaviors, indicating their wonderful balanced NLO properties. Theoretical calculations demonstrate that the synergistic effect between RESe8 and P2Se6 units makes the major contribution to the SHG responses.
As the first studied nonlinear optical (NLO) active rare‐earth (RE) selenophosphates, a series of chiral selenophosphates, KSmP2Se6 (1), KGdP2Se6 (2), and KTbP2Se6 (3), are profoundly studied for their NLO potentials. Their structures can be derived from breaking the centrosymmetric structure of KLaP2Se6 via RE3+ ion substitution. They exhibit pronounced NLO properties and all show phase‐matchable behaviors.
Inorganic metal halides play important roles in wide range of areas including fluorescence, X‐ray detection, and nonlinear‐optics. Herein, two new mixed alkali metal tantalum fluorides, CsKTaF7 and ...CsNaTaF7, have been obtained based on the strategy of cations regulation in A2MF7 (A represents monovalent cations and M is d0 transition‐metal cation) system by a conventional hydrothermal route. CsKTaF7 crystallizes in the centric Pnma space group, while CsNaTaF7 crystallizes in the polar Cmc21 space group and exhibits moderate and phase‐matchable NLO activity. Both halides possess large optical band gaps above 5.0 eV. The crystal structure evolution, optical properties, and detailed theory calculations of these two halides were elucidated in this work.
Two new mixed‐alkali metal tantalum fluorides CsATaF7 (A=K, Na) were synthesized by hydrothermal reactions based on the parent compounds A2MF7 (A=monovalent cations and M‐d0 transition‐metal cation). Interesting structure transformation for β‐K2TaF7, CsKTaF7, and CsNaTaF7 are induced via alkali metal cation regulations. Among them, CsNaTaF7 crystallizes in polar structure and own moderate SHG effect.
During laser powder bed fusion (LPBF) the powder bed undergoes several thermal cycles incorporating complex thermo-mechanical processing. Different restoration mechanisms such as dynamic recovery, ...dynamic recrystallization and grain growth can be activated at different thermal cycles, leading to a very fine average grain size. This is modelled via classical and thermostatistical approaches for an austenitic stainless steel. Four subsequent thermal cycles in each layer induce various microstructural transitions for each individual grain. The high cooling rate solidification in the first two thermal cycles leads to the formation of a highly deformed cellular microstructure. Discontinuous and continuous dynamic recrystallization are activated in the third thermal cycle to induce grain refinement. The fourth thermal cycle undergoes dynamic recovery and grain growth. The as-built alloys exhibit an excellent combination of high yield and ultimate tensile strength. The high strength is attributed to the activation of the various dynamic recrystallization mechanisms, as well as to the development of the cellular structures resulting from a high cooling rate upon solidification. A methodology to design alloys with tailored microstructures is presented.
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•Detailed characterisation of recrystallized laser powder bed fusion 316L structure•Dynamic recrystallization is essential to promote grain refinement in 316L.•A methodology for tailoring grain refinement via recrystallization is suggested.•Zener-Hollomon and thermostatistical approaches described grain refinement features.
The balance between large nonlinear optical (NLO) effect and wide bandgap is the key scientific issue for the exploration of infrared NLO materials. Targeting this issue, two new pentanary ...chalcogenides KGaGe1.37Sn0.63S6 (1) and KGaGe1.37Sn0.63Se6 (2) are obtained by the three‐in‐one strategy, viz. three types of fourfold‐coordinated metal elements co‐occupying the same site. They crystallize in the tetragonal P43 (1) and monoclinic Cc (2) space group. Their structures can be evolved from benchmark AgGaS2 (AGS) by suitable substitution. Remarkably, 1 is the first NLO sulfide crystallizing with the P43 space group, representing a new structure‐type NLO material. The structural relationship between 1 and 2 and the evolution from 1, 2 to AGS are also analyzed. Both 1 and 2 show balanced NLO properties. Specifically, 1 exhibits phase‐matchable SHG response of 0.6 × AGS, a wide bandgap of 3.50 eV, and a high laser damage threshold of 6.24 × AGS. Theoretical calculation results suggest that the Ga/Ge/Sn element ratios of the co‐occupied sites of 1 and 2 are the most appropriate for stabilizing the structures. The strategy adopted here will provide some inspiration for exploring new high‐performance NLO materials.
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•Process/microstructure/strength in laser powder bed fusion are related.•Yield strength scales with subgrain size through a Hall–Petch-type relationship.•Dynamic recovery is essential ...to promote low-angle grain boundaries.•In situ dynamic recovery and recrystallization modelled via two approaches.
A new approach to modelling the microstructure evolution and yield strength in laser powder bed fusion components is introduced. Restoration mechanisms such as discontinuous dynamic recrystallization, continuous dynamic recrystallization, and dynamic recovery were found to be activated during laser powder bed fusion of austenitic stainless steels; these are modelled both via classical Zener-Hollomon and thermostatistical approaches. A mechanism is suggested for the formation of dislocation cells from solidification cells and dendrites, and their further transformation to low-angle grain boundaries to form subgrains. This occurs due to dynamic recovery during laser powder bed fusion. The yield strength is successfully modelled via a Hall–Petch-type relationship in terms of the subgrain size, instead of the actual grain size or the dislocation cell size. The validated Hall–Petch-type equation for austenitic stainless steels provides a guideline for the strengthening of laser powder bed fusion alloys with subgrain refinement, via increasing the low-angle grain boundary fraction (grain boundary engineering). To obtain higher strength, dynamic recovery should be promoted as the main mechanism to induce low-angle grain boundaries. The dependency of yield stress on process parameters and alloy composition is quantitatively described.
Crop productivity is challenged by abiotic stresses, among which drought stress is the most common. NF-Y genes, especially NF-YA genes, regulate tolerance to abiotic stress.
Soybean NF-Y gene GmNFYA5 ...was identified to have the highest transcript level among all 21 NF-YA genes in soybean (Glycine max L.) under drought stress. Drought-induced transcript of GmNFYA5 was suppressed by the ABA synthesis inhibitor naproxen (NAP). GmNFYA5 transcript was detected in various tissues at vegetative and reproductive growth stages with higher levels in roots and leaves than in other tissues, which was consist with the GmNFYA5 promoter: GUS fusion assay. Overexpression of GmNFYA5 in transgenic Arabidopsis plants caused enhanced drought tolerance in seedlings by decreasing stomatal aperture and water loss from leaves. Overexpression and suppression of GmNFYA5 in soybean resulted in increased and decreased drought tolerance, respectively, relative to plants with an empty vector (EV). Transcript levels of ABA-dependent genes (ABI2, ABI3, NCED3, LEA3, RD29A, P5CS1, GmWRKY46, GmNCED2 and GmbZIP1) and ABA-independent genes (DREB1A, DREB2A, DREB2B, GmDREB1, GmDREB2 and GmDREB3) in transgenic plants overexpressing GmNFYA5 were higher than those of wild-type plants under drought stress; suppression of GmNFYA5 transcript produced opposite results. GmNFYA5 probably regulated the transcript abundance of GmDREB2 and GmbZIP1 by binding to the promoters in vivo.
Our results suggested that overexpression of GmNFYA5 improved drought tolerance in soybean via both ABA-dependent and ABA-independent pathways.
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