Pentagon Stability in Cycloarsanes

The orbital phase theory leads to the prediction that the saturated arsenic cyclic molecules prefer pentagons, which is substantiated by the negative strain energy of cyclic As 5 H 5 . The puckered five-membered arsenic ring is an important structural unit for the pentagon stability. Possible structures and conformers of polycycloarsanes As 8 H 4 , As 11 H 3 , "roof-like" and "cage-like" As 12 H 4 , As 13 H 3 , As 14 H 2 , and As 15 H 3 with relatively low strain energies were predicted due to many puckered pentagon units in them. The low stability of the dodecahedron As 20 with 12 planar pentagon units was suggested by the high strain energy.     

金属纳米颗粒在Lu_2O_3薄膜中的应变场分析

利用有限元分析法对镶嵌在Lu2O3薄膜中的Au、Cu、Pt、Co金属纳米颗粒的应变场分布进行分析.分析表明:金属纳米颗粒在生长过程中受Lu2O3薄膜的压缩应力作用,从而在纳米颗粒内部和表面产生相应应变,应变分布与金属纳米颗粒的杨氏模量和泊松比有关.杨氏模量大的金属纳米颗粒表面应变和内部应变差异较大;而杨氏模量小的金属纳米颗粒内外应变差相对较小.随着金属纳米颗粒在基体材料内部不断生长,其受到的偏应变也逐渐增大.金属纳米颗粒生长过程中的这种偏应变的存在和变化将极大地影响其内部晶格结构和表面形貌,进而影响金属纳米颗粒的性能.     

应变纤锌矿GaN/A10.15Ga0.85N柱形量子点的光学性质:流体静压力效应

在有效质量近似下,考虑强的内建电场和应变对材料参量的影响,变分研究了流体静压力对有限高势垒应变纤锌矿GaN/Al_0.15Ga_0.85N柱形量子点中重空穴激子的结合能、发光波长和电子空穴复合率的影响.数值结果表明,激子结合能和电子空穴复合率随流体静压力的增大而近线性增大,发光波长随流体静压力的增大而单调减小.在量子点尺寸较小的情况下,流体静压力对激子结合能和电子空穴复合率的影响更明显.由于应变效应,为了获得有效的电子-空穴复合过程,GaN量子点的高度必须小于5.5 nm.     

Strain evolution and morphological transition of magnetron-sputtered CeO2 thin films induced by deposition parameters

Cerium dioxide (CeO₂) films were fabricated on yttria-stabilized zirconia (YSZ) single crystals using unbalanced radio frequency (RF) magnetron sputtering. X-ray diffraction measurements revealed film strain discrepancies under different deposition parameters. Strain evolution was induced by varying sputtering pressure, RF power, and sputtering gas. A distinct morphological transition from a granular surface to an interwoven surface was also realized by varying the above parameters. On the basis of the “atomic peening” mechanism, the influence of different parameters on film strain was discussed. The film surface characteristics were revealed to be highly correlated with film strain. YBa₂Cu₃O_7−δ (YBCO) films were post-deposited on the as-grown CeO₂/YSZ(001) stack by using the trifluoroacetate metal-organic deposition (TFA-MOD) method. The superconducting property of the YBCO layer varied significantly with the morphology of the CeO₂ buffer films.     

Catalytic Formal [2π+2σ] Cycloaddition of Aldehydes with Bicyclobutanes: Expedient Access to Polysubstituted 2-Oxabicyclo[2.1.1]hexanes

Synthesis of bicyclic scaffolds has attracted tremendous attention because they are playing an important role as saturated bioisosteres of benzenoids in modern drug discovery. Here, we report a BF₃-catalyzed [2π+2σ] cycloaddition of aldehydes with bicyclo[1.1.0]butanes (BCBs) to access polysubstituted 2-oxabicyclo[2.1.1]hexanes. A new kind of BCB containing an acyl pyrazole group was invented, which not only significantly facilitates the reactions, but can also serve as a handle for diverse downstream transformations. Furthermore, aryl and vinyl epoxides can also be utilized as substrates which undergo cycloaddition with BCBs after in situ rearrangement to aldehydes. We anticipate that our results will promote access to challenging sp³-rich bicyclic frameworks and the exploration of BCB-based cycloaddition chemistry.     

Regulating Cation Interactions for Zero-Strain and High-Voltage P2-type Na2/3Li1/6Co1/6Mn2/3O2 Layered Oxide Cathodes of Sodium-Ion Batteries

Deep sodium extraction/insertion of sodium cathodes usually causes undesired Jahn–Teller distortion and phase transition, both of which will reduce structural stability and lead to poor long-cycle reliability. Here we report a zero-strain P2- Na_2/3Li_1/6Co_1/6Mn_2/3O₂ cathode, in which the lithium/cobalt substitution contributes to reinforcing the host structure by reducing the Mn³⁺/Mn⁴⁺ redox, mitigating the Jahn–Teller distortion, and minimizing the lattice change. 94.5 % of Na⁺ in the unit structure can be reversibly cycled with a charge cut-off voltage of 4.5 V (vs. Na⁺/Na). Impressively, a solid-solution reaction without phase transitions is realized upon deep sodium (de)intercalation, which poses a minimal volume deviation of 0.53 %. It attains a high discharge capacity of 178 mAh g⁻¹, a high energy density of 534 Wh kg⁻¹, and excellent capacity retention of 95.8 % at 1 C after 250 cycles.     

Fast and Non-equilibrium Uptake of Hydrogen by Pd Icosahedral Nanocrystals

We report for the first time that Pd nanocrystals can absorb H via a “single-phase pathway” when particles with a proper combination of shape and size are used. Specifically, when Pd icosahedral nanocrystals of 7- and 12-nm in size are exposed to H atoms, the H-saturated twin boundaries can divide each particle into 20 smaller single-crystal units in which the formation of phase boundaries is no longer favored. As such, absorption of H atoms is dominated by the single-phase pathway and one can readily obtain PdH_x with anyx in the range of 0–0.7. When switched to Pd octahedral nanocrystals, the single-phase pathway is only observed for particles of 7 nm in size. We also establish that the H-absorption kinetics will be accelerated if there is a tensile strain in the nanocrystals due to the increase in lattice spacing. Besides the unique H-absorption behaviors, the PdH_x (x=0–0.7) icosahedral nanocrystals show remarkable thermal and catalytic stability toward the formic acid oxidation due tothe decrease in chemical potential for H atoms in a Pd lattice under tensile strain.     

Strong and Ultra-tough Ionic Hydrogel Based on Hyperbranched Macro-Cross-linker: Influence of Topological Structure on Properties

The application of hydrogels often suffers from their inherent limitation of poor mechanical properties. Here, a carboxyl-functionalized and acryloyl-terminated hyperbranched polycaprolactone (PCL) was synthesized and used as a macro-cross-linker to fabricate a super strong and ultra-tough ionic hydrogel. The terminal acryloyl groups of hyperbranched PCL are chemically incorporated into the network to form covalent cross-links, which contribute to robust networks. Meanwhile, the hydrophobic domains formed by the spontaneous aggregation of PCL chains and coordination bonds between Fe³⁺ and COO⁻ groups serve as dynamic non-covalent cross-links, which enhance the energy dissipation ability. Especially, the influence of the hyperbranched topological structure of PCL on hydrogel properties has been well investigated, exhibiting superior strengthening and toughening effects compared to the linear one. Moreover, the hyperbranched PCL cross-linker also endowed the ionic hydrogel with higher sensitivity than the linear one when used as a strain sensor. As a result, this well-designed ionic hydrogel possesses high mechanical strength, superior toughness, and well ionic conductivity, exhibiting potential applications in the field of flexible strain sensors.     

Isolation and characterization of poly(butylene succinate)-degrading fungi

We isolated 12 poly(butylene succinate) (PBSu)-degrading fungi from various soil environments. Among the isolates, the NKCM1706 strain exhibited the fastest degradation rate for the PBSu film (10.5 μg cm⁻² h⁻¹). Phylogenetic analysis revealed that this strain is closely related to Aspergillus fumigatus (internal transcribed spacer (ITS) identity, 100%). Further, this strain exhibited PBSu-hydrolytic activity in the presence of poly(?-caprolactone) (PCL), PBSu, and poly(butylene succinate-co-adipate) (PBSA). On adding this strain into the soil sample, the PBSu degradation rate accelerated approximately sixfold, suggesting that this strain plays a crucial role in PBSu degradation in actual soil environments. In addition to PBSu, the NKCM1706 strain could degrade PBSA, poly(ethylene succinate) (PESu), poly(3-hydroxybutyrate) (P(3HB)), and PCL.     

On the measurement of true fracture strain of thermoplastics materials

In tensile testing, engineering thermoplastic materials can sustain large deformation after necking. This property can be advantageous to the manufacturing process and mechanical performance. However, it causes difficulties in strain measurement and in the determination of true stress and true strain, particularly at higher strain rates. This paper discussed the measurement of true fracture strain. The true fracture strain was estimated using three different methods: the area reduction, elongation over the necked zone, and elongation over the gage length. With strain localization, strain measured by an extensometer becomes gage length dependent. To address the issue, an algorithm was formulated that estimates the average fracture strain over an arbitrary gage length from the fracture strain measured over the necked zone. The proposed algorithm provides a way to estimate the mesh dependence of the fracture strain for finite element (FE) analysis. This paper also presents an analysis-based two-step correction scheme for the crosshead extension to be used to supplement the strain measurement from the extensometer.