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• The crystal structure evolutions of the Pb m Bi 2 S 3+ m (m = 1–10) compounds with increasing m values are revealed. • The origin of the intrinsically low lattice thermal conductivities of PbBi 2 S 4 , Pb 3 Bi 2 S 6 , and Pb 6 Bi 2 S 9 is systematically explored from both theoretical and experimental perspectives. • Strong lattice anharmonicity leads to the extremely low lattice thermal conductivities 0.57, 0.56, and 0.80 W m−1 K−1 in PbBi 2 S 4 , Pb 3 Bi 2 S 6 , and Pb 6 Bi 2 S 9 compounds at room temperature. Ternary Pb-Bi-S compounds emerge as potential thermoelectric materials owing to low thermal conductivity, but the origin of their intrinsic low lattice thermal conductivities lacks further investigation. Herein, a series of ternary Pb m Bi 2 S 3+ m (m = 1–10) compounds are synthesized and their crystal structure evolutions with increasing m values are clearly unclosed. The room-temperature lattice thermal conductivities in PbBi 2 S 4 , Pb 3 Bi 2 S 6 and Pb 6 Bi 2 S 9 can reach at 0.57, 0.56 and 0.80 W m−1 K−1, respectively, outperforming other ternary sulfur-based compounds. Theoretical calculations show that the low lattice thermal conductivities in Pb m Bi 2 S 3+ m (m = 1–10) mainly originate from soft phonon dispersion caused by strong lattice anharmonicity, and both asymmetric chemical bond and lone pair electrons (Pb 6 s 2 and Bi 6 s 2) can favorably block phonon propagation. Furthermore, the elastic measurements also confirm relatively low sound velocities and shear modulus, and the Grüneisen parameter (γ) calculated by sound velocities can reach at 1.67, 1.85 and 1.94 in PbBi 2 S 4 , Pb 3 Bi 2 S 6 and Pb 6 Bi 2 S 9 , respectively. Finally, the intrinsic low lattice thermal conductivities in Pb m Bi 2 S 3+ m (m = 1–10) contribute to promising thermoelectric performance, and the maximum ZT values of 0.47, 0.38 and 0.45 can be achieved in undoped PbBi 2 S 4 , Pb 3 Bi 2 S 6 and Pb 6 Bi 2 S 9 , respectively. [Display omitted] [ABSTRACT FROM AUTHOR]

Efficient and precise calculations of thermal transport properties and figures of merit, alongside a deep comprehension of thermal transport mechanisms, are essential for the practical utilization of advanced thermoelectric materials. In this study, we explore the microscopic processes governing thermal transport in the distinguished crystalline material Tl9SbTe6by integrating a unified thermal transport theory with machine learning-assisted self-consistent phonon calculations. Leveraging machine learning potentials, we expedite the analysis of phonon energy shifts, higher-order scattering mechanisms, and thermal conductivity arising from various contributing factors, such as population and coherence channels. Our finding unveils an exceptionally low thermal conductivity of 0.31 W m–1K–1at room temperature, a result that closely correlates with experimental observations. Notably, we observe that the off-diagonal terms of heat flux operators play a significant role in shaping the overall lattice thermal conductivity of Tl9SbTe6, where the ultralow thermal conductivity resembles that of glass due to limited group velocities. Furthermore, we achieve a maximum ZTvalue of 3.17 in the c-axis orientation for p-type Tl9SbTe6at 600 K and an optimal ZTvalue of 2.26 in the a-axis and b-axis direction for n-type Tl9SbTe6at 500 K. The crystalline Tl9SbTe6not only showcases remarkable thermal insulation but also demonstrates impressive electrical properties owing to the dual-degeneracy phenomenon within its valence band. These results not only elucidate the underlying reasons for the exceptional thermoelectric performance of Tl9SbTe6but also suggest potential avenues for further experimental exploration.

Peripheral nerve injury (PNI) is one of the most serious causes of disability and loss of work capacity of younger individuals. Although PNS has a certain degree of regeneration, there are still challenges like disordered growth, neuroma formation, and incomplete regeneration. Regarding the management of PNI, conventional methods such as surgery, pharmacotherapy, and rehabilitative therapy. Treatment strategies vary depending on the severity of the injury. While for the long nerve defect, autologous nerve grafting is commonly recognized as the preferred surgical approach. Nevertheless, due to lack of donor sources, neurological deficits and the low regeneration efficiency of grafted nerves, nerve guide conduits (NGCs) are recognized as a future promising technology in recent years. This review provides a comprehensive overview of current treatments for PNI, and discusses NGCs from different perspectives, such as material, design, fabrication process, and composite function.

• A facile method of gradient rolling is provided to attain inverse gradient nanostructure (iGNS). • The iGNS is firstly demonstrated in a Ti-Ni shape memory alloy (SMA) wire. • The iGNS leads to a reversible gradient martensitic transformation upon stressing. • The iGNS SMA exhibits quasi-linear superelasticity in a wide temperature range with improved SE strain and efficiency. Gradient nanostructured (GNS) metallic materials are commonly achieved by gradient severe plastic deformation with a gradient of nano- to micro-sized structural units from the surface/boundaries to the center. Certainly, such GNS can be inversely positioned, which however has not yet been reported. The present work reports a facile method in deformation gradient control to attain inverse gradient nanostructured (iGNS), i.e., tailoring the cross-section shape, successfully demonstrated in Ti-50.3Ni shape memory alloy (SMA) wire through cold rolling. The microstructure of the rolled wire is characterized by a macroscopic inverse gradient from boundaries to the center—the average sizes of grain and martensite domain evolve from micrometer to nanometer scale. The iGNS leads to a gradient martensitic transformation upon stress, which has been proved to be effectively reversible via in-situ bending scanning electron microscopy (SEM) observations. The iGNS Ti-50.3Ni SMA exhibits quasi-linear superelasticity (SE) in a wide temperature range from 173 to 423 K. Compared to uniform cold rolling, the gradient cold rolling with less overall plasticity further improves SE strain (up to 4.8 %) and SE efficiency. In-situ tensiling synchrotron X-ray diffraction (SXRD) analysis reveals the underlying mechanisms of the unique SE in the iGNS SMAs. It provides a new design strategy to realize excellent SE in SMAs and sheds light on the advanced GNS metallic materials. [Display omitted] [ABSTRACT FROM AUTHOR]

• To choose the best seed alloy and suitable dopants, the assumed screening criteria include small anisotropy, high specific modulus, high dynamical stability, and high ductility. • As compared to a traditional trial-and-error concept, our proposed multi-principal element alloy design strategy and screening criteria can substantially reduce the exploration of alloy space and thus accelerate alloy design. • We find a shortcut to design U-based high-entropy alloy from typical binary (UTi and UNb) to ternary (UTiNb), quaternary (UTiNbTa), and quinary (UTiNbTaFe). The dynamical stability and mechanical properties of candidates are greatly enhanced with increasing the number of multi-principal element, indicating the feasibility and effectiveness of adopted alloying strategy. • As compared to the empirical strength-hardness relationship, improved strength prediction can be achieved using a parameter-free theory considering volume mismatch and temperature effect on yield strength. It is found that larger volume mismatch corresponds to higher yield strength. Reducing the exploration of multi-principal element alloy space is a key challenge to design high-performance U-based high-entropy alloy (UHEA). Here, the best combination of multi-principal element can be efficiently acquired because proposed alloying strategy and screening criteria can substantially reduce the space of alloy and thus accelerate alloy design, rather than enormous random combinations through a trial-and-error approach. To choose the best seed alloy and suitable dopants, the screening criteria include small anisotropy, high specific modulus, high dynamical stability, and high ductility. We therefore find a shortcut to design UHEA from typical binary (UTi and UNb) to ternary (UTiNb), quaternary (UTiNbTa), and quinary (UTiNbTaFe). Finally, we find a best bcc senary UHEA (UTiNbTaFeMo), which has highest hardness and yield strength, while maintains good ductility among all the candidates. Compared to overestimation from empirical strength-hardness relationship, improved strength prediction can be achieved using a parameter-free theory considering volume mismatch and temperature effect on yield strength. This finding indicates that larger volume mismatch corresponds to higher yield strength, agreeing with the available measurements. Moreover, the dynamical stability and mechanical properties of candidates are greatly enhanced with increasing the number of multi-principal element, indicating the feasibility and effectiveness of adopted alloying strategy. The increasing of multi-principal element corresponds to the increasing valence electron concentration (VEC). Alternatively, the mechanical properties significantly improve as increasing VEC, agreeing with measurements for other various bcc HEAs. This work can speed up research and development of advanced UHEA by greatly reducing the space of alloy composition. [ABSTRACT FROM AUTHOR]

Valence electron concentration (VEC) is widely accepted as an effective guideline for designing the mechanical properties of Ti-containing refractory high-entropy alloys (RHEAs). In the present work, a series of Ti–Zr–Nb–Ta and Ti–Zr–Nb–Mo RHEAs with body-centered-cubic (bcc) structure are carefully designed by tailoring their VEC through changing the alloying composition. The elastic properties and mechanical properties are systematically calculated by using a first-principles method. Comparison with available experimental data demonstrates that the employed approach accurately describes the VEC dependence of the elastic and mechanical properties of RHEAs. In general, the elastic stability, elastic properties, ideal shear strength, Vickers hardness, and yield strength increase, whereas Zener anisotropy decreases with increasing VEC. Among all the considered RHEAs, the most isotropic RHEA Ti30Zr30Nb20Mo20has the best strength-ductility trade-off. Mo has a stronger solid solution strengthening effect than Ta. The higher strength associates with larger lattice distortion induced by increasing VEC. Both elastic stability and mechanical properties are related to the electronic density of states of the alloys. The present work sheds deep insight into the design of high-performance RHEAs through tailoring the VEC.

• Fine equiaxed grains strengthened by coherent Laves nanoprecipitates were successfully prepared in FeCrAl alloy using a novel processing method. • The novel FeCrAl alloys exhibit a ultrahigh yield strength over ∼992 MPa, excellent uniform elongation of ∼7.6% at room temperature, and superior thermal stability at temperature ∼1200 °C. • The enrichment of Si element in Laves precipitates not only decreases their stacking fault energy but also improves their thermal stability. • The advantage of nanoprecipitation engineering in this paper is also applicable to other precipitate-strengthened alloys. Designing microstructurally stable FeCrAl alloys with excellent strength-ductility synergy is highly desirable for their engineering applications. However, due to the preference nucleation of precipitates at grain boundaries (GBs), the improved precipitation strengthening of these alloys is usually accompanied by intergranular embrittlement. Here, we propose a novel thermomechanical processing route coupled with the Si alloying strategy via precipitation of coherent deformable Laves precipitates inside equiaxed fine-grains to achieve FeCrAl alloys with ultrahigh yield strength over ∼992 MPa, excellent uniform elongation of ∼7.6% at room temperature, and superior thermal stability at temperature ∼1200 °C. The Si alloying not only decreases the stacking fault energy of Laves precipitates favorable for their stacking-fault-mediated deformation but also hinders grain coarsening at 1200 °C due to the Si-enrichment favorable for GB pinning effects. Our results prove the possibility of achieving the collaborative enhancement of mutually exclusive properties in alloys, such as strength-ductility-thermal stability via nanoprecipitation engineering, and offer a promising route to prepare dispersion-strengthened materials. [Display omitted] [ABSTRACT FROM AUTHOR]

The Farm Animal Genotype-Tissue Expression (FarmGTEx) project has been established to develop a public resource of genetic regulatory variants in livestock, which is essential for linking genetic polymorphisms to variation in phenotypes, helping fundamental biological discovery and exploitation in animal breeding and human biomedicine. Here we show results from the pilot phase of PigGTEx by processing 5,457 RNA-sequencing and 1,602 whole-genome sequencing samples passing quality control from pigs. We build a pig genotype imputation panel and associate millions of genetic variants with five types of transcriptomic phenotypes in 34 tissues. We evaluate tissue specificity of regulatory effects and elucidate molecular mechanisms of their action using multi-omics data. Leveraging this resource, we decipher regulatory mechanisms underlying 207 pig complex phenotypes and demonstrate the similarity of pigs to humans in gene expression and the genetic regulation behind complex phenotypes, supporting the importance of pigs as a human biomedical model.

Critical challenges remain in applying shape memory alloys to solid-state refrigeration. In particular, addressing the degradation of elastocaloric response during repetitive loading is an outstanding issue. Refined grains or dispersed precipitates provide high resistance to dislocation activity during transformation and therefore would be expected to improve elastocaloric stability in shape memory alloys. To this end, we age a cold-rolled (Ni,Cu)-rich Ti–Ni–Cu alloy at different temperatures to tailor the microstructure with refined grains and dispersed Ti(Ni,Cu)2precipitates. We find that with increasing aging temperature, precipitates coarsen with a reduction in density. Simultaneously, the microstructure evolves from being in a nanocrystalline state to an equiaxed coarse-grained state. The synergy between nanocrystalline structure and dispersed coherent Ti(Ni,Cu)2nanoprecipitates in the alloy aged at 400 ∘C gives rise to stable elastocaloric response with a respectable adiabatic temperature change (ΔTad) of 13.9 K and a recoverable strain of 3%. Further increase in the aging temperature increases the transformation strain and ΔTad, however, this is at the expense of cyclic stability due to prominent plastic activity in parallel with phase transformation. These findings offer microstructural design insights into the development of high-performance elastocaloric materials and superelastic alloys.

Covalent organic frameworks (COFs) with crown ether units have drawn great attention due to their potential applications in adsorption, catalysis, and sensing. However, employing crown ethers to construct COFs is still challenging in light of the flexible nature of macrocycles. Here, a highly crystalline one-dimensional covalent organic framework (1D-18C6-COF) with crown ether units on the ribbon edge was synthesized. The water-mediated hydrogen bond network and π–π stacking hold the 1D COF ribbons together. The combination of experimental and DFT studies demonstrated that the hydrogen bond network plays a crucial role in the structure crystallinity. The 1D-18C6-COF was applied as an adsorbent for strontium, and it exhibited rapid kinetics with good selectivity. In the competitive adsorption experiment, a separation factor of 1900 was achieved, representing one of the largest values for cesium/strontium separation. This work provides new insights into the design and functional exploration of crystalline COFs with flexible units.

• Stress-induced martensitic transformation in the target alloy proceeds in a homogeneous deformation mannar, instead of a conventional Lüders-like deformation. • Microstructural features of the target alloy including nanocrystallinity and dispersed nanoprecipitates yield the homogeneous deformation and are achieved by directly aging a cold-rolled Ti-51.5Ni alloy. • Stable room-temperature superelasticity and elastocaloric effect are obtained and ascribed to the low dislocation activity during stress cycling. Functional stability of superelasticity is crucial for practical applications of shape memory alloys. It is degraded by a Lüders-like deformation with elevated local stress concentration under tensile load. By increasing the degree of solute supersaturation and applying appropriate thermomechanical treatments, a Ti-Ni alloy with nanocrystallinity and dispersed nanoprecipitates is obtained. In contrast to conventional Ti-Ni alloys, the superelasticity in the target alloy is accompanied by homogeneous deformation due to the sluggish stress-induced martensitic transformation. The alloy thus shows a fully recoverable strain of 6% under tensile stress over 1 GPa and a large adiabatic temperature decrease of 13.1 K under tensile strain of 4.5% at room temperature. Moreover, both superelasticity and elastocaloric effect exhibit negligible degradation in response to applied strain of 4% during cycling. We attribute the improved functional stability to low dislocation activity resulting from the suppression of localized deformation and the combined strengthening effect of nanocrystalline structure and nanoprecipitates. Thus, the design of such a microstructure enabling homogeneous deformation provides a recipe for stable superelasticity and elastocaloric effect. [Display omitted] [ABSTRACT FROM AUTHOR]

A yield phenomenon was firstly reported in an extruded Mg-6.8Y-2.5Cu alloy and the corresponding microstructure was also investigated in this work. The cast alloy is mainly composed of α-Mg, 18R long period stacking order (LPSO) phase, eutectic phase (Mg20Cu4Y1), and Mg2Cu phase. The 18R LPSO phase at the dendritic grain boundary transforms into the 14H LPSO phase in the grain interior during homogenization. After extrusion, the grain size of the homogenized alloy is remarkably refined to –3.69 μm and the second phase is significantly broken and distributed in the extrusion direction. Tensile testing curves of the extrude alloy at room temperature indicate that the yield strength and ultimate tensile strength increase while the elongation of the alloy decreases with increasing strain rate. Interestingly, a yield plateau forms and gradually decreases with increasing strain rate. The yield phenomenon is related to the dislocation multiplication and the interaction between the movable dislocations and solute atoms.

• The heterogeneous fiberous structured ZK60 Mg alloy was obtained by conventional extrusion method with high yield strength of ∼ 345 MPa, ultimate tensile strength of ∼ 370 MPa and high tensile strain of ∼ 20.5%, superior than most ZK60 Mg alloys reported so far. • The excellent mechanical properties were mainly attributed to the heterogeneous fiberous structure that was characterized by alternating coarse- and fine-grain layers, nanoscale precipitates and profuse < c + a > dislocations. The novel heterogeneous fiberous structured ZK60 Mg alloy have achieved superior strength-ductility synergy. • A novel design of alternating coarse- and fine-grain layered structure was considered to be a general strategy for promoting the strength-ductility synergy of hexagonal close-packed (hcp) metals. Here we reported a heterogeneous fiberous structured Mg-5.6Zn-0.6Zr (wt%) alloy obtained by conventional extrusion method, which exhibited high yield strength of ∼ 345 MPa, ultimate tensile strength of ∼ 370 MPa, and high tensile strain of ∼ 20.5%, superior to most of the Mg-Zn based alloys reported so far. The extraordinarily high mechanical properties were mainly attributed to the heterogeneous fiberous structure consisting of alternating coarse- and fine-grain layers. Grains in the different layers grew into the neighboring layers, ensuring a good layer bonding. A high Schmid factor and geometric compatibility factor for pyramidal slip led to full slip transfer between the neighboring coarse grains and fine grains, which could help to release the stress concentration and avoid early fracture. The profuse activated glide dislocations could render the unprecedented high tensile strain. The constraint by the hard fine-grain domains made the soft coarse-grain domains strong like the hard fine-grain domains, as well as the nanoscale precipitates pinning dislocations, contributed to the high strength. The heterogeneous microstructure design was shown to have synergistic improvement in strength-ductility balance, which could be an inspiring strategy to improve mechanical properties of hexagonal close-packed (hcp) metals. [Display omitted] [ABSTRACT FROM AUTHOR]

Superelasticity in bulk is known to originate from thermal-elastic martensitic transformation in shape memory alloys. The driving force arises from the volume free energy difference between the martensite and the parent phase. Here we review the observations of this novel superelastic behavior in various non-transformed systems driven by the nonuniform strain. We present several cases of shape recovery upon bending or torsion in metallic and non-metallic materials at small scale, such as α-Fe whisker, twinned CuAlNi martensite and BaTiO3membrane. The mechanism(s) of shape recovery were revealed by molecular dynamics simulations. The strain gradient could induce the formation of the nontypical interfaces, which could store a high interfacial energy to drive the deformed sample to recover to its original shape. The present paper provides insight on the origin of novel superelasticity induced by strain gradient.

• The incipient plasticity and dislocation behavior in nanocrystalline (NC) CrCoNi alloy were systematically investigated and compared with its coarse-grained (CG) counterpart and NC Ni. • Multiple pop-ins appear in the P-h curves of NC and CG CrCoNi alloys but disappear in the curves of NC Ni. • The incipient plasticity is mediated by dislocation nucleation in NC CrCoNi alloy but by GBs in NC Ni. • Chemically complex GBs in NC CrCoNi alloy facilitate dislocation nucleation but impede dislocation propagation. • Spatial restrictions from GBs in NC CrCoNi alloy induce size-dependent pop-in behaviors. The incipient plasticity and dislocation behavior in a nanocrystalline (NC) CrCoNi medium-entropy alloy were systematically investigated in terms of pop-in events during instrumental nano-indentation tests. Quantitative statistical analysis and molecular dynamic simulations were performed to reveal the effects of grain boundaries (GBs) on initial stages of plastic deformation. Multiple pop-in events appeared during loading on the NC CrCoNi. The first pop-in that represents the initial yielding was identified to be controlled by dislocation nucleation, which is in sharp contrast to the continuous elastic-plastic transition mediated by GB mechanisms in NC pure metals. This can be attributed to the sluggish kinetics of the chemically complex GBs (CCGBs) in the NC CrCoNi that hinders diffusive GB activities but facilitates dislocation nucleation. Subsequent pop-ins were also found to be closely related to the extra dragging effects imposed by the CCGBs on dislocation propagation in the NC alloy. Moreover, the extremely small grain sizes and the consequent high-volume fraction of GBs in the NC alloy severely restrict the lengths of dislocation source and the radii of dislocation loop, giving rise to a higher critical stress, smaller activation volume and lower pop-in width as compared with its coarse-grained counterpart. These results provide new insights into the onset of nano-plasticity in concentrated multi-principal element alloys. [ABSTRACT FROM AUTHOR]

Effects of Zn addition on microstructure and mechanical properties of the extruded Mg97.8Y1.4Co0.8(at.%, WC) alloy were investigated at room temperature. It was found that the as-cast WC alloy was mainly composed of α-Mg, MgYCo4, Mg3(Co,Y) and 15R-LPSO phases distributed at the grain boundary. All particles of as-homogenized WC alloy were remarkably refined after extrusion, but there was no phase transition during the subsequent homogenized and extruded states. With the replacement of Co from Zn, the as-cast Mg97.8Y1.4Co0.2Zn0.6(at.%, WZC) alloy consisted of α-Mg, 18R-LPSO with lamellar and blocky shape, and a small amount of rich-Y phases. Parts of 18R-LPSO phases transformed into fine 14H-LPSO phases and stacking faults (SFs) in the grain interior during homogenization and extrusion. The extruded WZC alloy exhibited a smaller average grain size (∼3.2 μm) than the extruded WC alloy (∼3.9 μm) owing to fully dynamic recrystallization (DRX). Both the extruded WC and WZC alloys had a basal plane texture parallel to the normal direction (ND). Tensile testing results indicated that the Zn replacement improved tensile strengths of the extruded WC alloy and maintained the high elongation of the alloy (∼32.2%). The tensile yield strength, ultimate tensile strength and fracture elongation of the extruded WZC alloy were 212 MPa, 281.5 MPa and 32.2%, respectively. The alloy exhibited a good strength and ductility balance. The high tensile strengths of the extruded WZC alloy at room temperature were mainly attributed to grain refinement and the precipitation strengthening of different particles, and the good ductility was mainly due to grain refinement and texture weakening.

Fat deposition in pigs is not only closely related to pig production efficiency and pork quality but also an ideal model for human obesity. Transcriptome sequencing is widely used to study fat deposition. However, due to small sample sizes, high false positive rates, and poor consistency of results from different studies, new strategies are urgently needed. Machine learning, a new analysis method, can effectively fit complex data and accurately identify samples and genes. In this study, 36 samples of adipose tissue, muscle tissue, and liver tissue were collected from Songliao black pigs and Landrace pigs, and the mRNA of all the samples was sequenced. In addition, we collected transcriptome data for 64 samples in the GEO database from four different sources. After standardization and imputation of missing values in the data set comprising 100 samples, traditional differential expression analysis was carried out, and different numbers of expressed genes were selected as features for the training model of eight machine learning methods. In the 1000 replications of fourfold cross validation with 100 samples, AdaBoost performed best, with an average prediction accuracy greater than 93% and the highest mean area under the curve in predicting the high- and low-fat content groups among the eight ML methods. According to their performance-based ranks inferred by AdaBoost, 12 genes related to fat deposition were identified; among them, FASNand APODwere specifically expressed in adipose tissue, and APOA1was specifically expressed in the liver, which could be important candidate biomarkers affecting fat deposition.

Lead-free ceramic-based dielectric capacitors show huge potential in electrical energy storage in pulsed power systems due to their fast charge/discharge rate, ultrahigh power density and environmental friendliness. However, unsatisfied charge/discharge performance characterized by inferior recoverable energy storage density (Wrecgenerally <5 J/cm3) has become a key bottleneck to restrict their applications in cutting-edge energy storage devices. In this paper, we focus on simultaneously realizing ultrahigh Wrecand efficiency (ƞ) in eco-friendly Bi0.5Na0.5TiO3(BNT)-based dielectric ceramics via chemical doping. Interestingly, highly dynamic polar nanoregions (PNRs) and nanodomains are constructed by incorporating Sr0.7Nd0.2TiO3(SNT) into 0.94BNT-0.06BaTiO3. Of great importance, the resulting relaxor ferroelectrics (RFEs) exhibit high bulk resistivity, submicron grain size and wide band gap due to high level of SNT doping accompanying with 1 at% Nb donor doping. Therefore, excellent energy storage properties with ultrahigh Wrec∼8.08 J/cm3and ƞ∼92.1% are achieved due to coexistence of large polarization difference (ΔP=Pmax−Pr) and giant dielectric breakdown electric field (Eb∼540 kV/cm). Furthermore, excellent temperature/frequency/cycling stability characterized by ΔWrec< ±4% and Δη< ±2% ensure the energy storage applications of the studied dielectric ceramics over an enormous range of scales.

Metals with nanocrystalline grains have ultrahigh strengths approaching two gigapascals. However, such extreme grain-boundary strengthening results in the loss of almost all tensile ductility, even when the metal has a face-centred-cubic structure—the most ductile of all crystal structures1–3. Here we demonstrate that nanocrystalline nickel–cobalt solid solutions, although still a face-centred-cubic single phase, show tensile strengths of about 2.3 gigapascals with a respectable ductility of about 16 per cent elongation to failure. This unusual combination of tensile strength and ductility is achieved by compositional undulation in a highly concentrated solid solution. The undulation renders the stacking fault energy and the lattice strains spatially varying over length scales in the range of one to ten nanometres, such that the motion of dislocations is thus significantly affected. The motion of dislocations becomes sluggish, promoting their interaction, interlocking and accumulation, despite the severely limited space inside the nanocrystalline grains. As a result, the flow stress is increased, and the dislocation storage is promoted at the same time, which increases the strain hardening and hence the ductility. Meanwhile, the segment detrapping along the dislocation line entails a small activation volume and hence an increased strain-rate sensitivity, which also stabilizes the tensile flow. As such, an undulating landscape resisting dislocation propagation provides a strengthening mechanism that preserves tensile ductility at high flow stresses.

• The elastocaloric effect appears in a wide temperature range for a strain glass alloy. • An inverse elastocaloric effect is observed in the strain glass alloy with history of zero-field cooling. • The temperature-history dependence of elastocaloric effect can be attributed to the slow dynamics of strain nanodomains in response to the external stress. The singular change of the order parameter at the first order martensitic transformation (MT) temperature restricts the caloric response to a narrow temperature range. Here the MT is tuned into a sluggish strain glass transition by defect doping and a large elastocaloric effect appears in a wide temperature range. Moreover, an inverse elastocaloric effect is observed in the strain glass alloy with history of zero-field cooling and is attributed to the slow dynamics of the nanodomains in response to the external stress. This study offers a design recipe to expand the temperature range for good elastocaloric effect. [Display omitted] [ABSTRACT FROM AUTHOR]

• As-cast Mg-2.5Cu-xAl (x = 4.5, 6.0 wt.%) alloys were developed for application in fracturing balls. • The degradable Mg-2.5Cu-6.0Al alloy exhibits a combined high compressive strength (378 MPa), good compressive strain (27%) and rapid degradation rate (383 mm/y). • The addition of Al could improve the strength and ductility simultaneously in Mg-2.5Cu alloy. • A discontinuous network of β-Mg 17 Al 12 +Al 2 Cu and MgAlCu phases is formed in the immersion tests, acting as cathodes to accelerate micro-galvanic corrosion. Specially designed Mg-Cu-Al alloys were prepared for the application in fracturing balls. In comparison to Mg-2.5Cu alloy, Mg-2.5Cu-6.0Al alloy exhibits an improved compressive strength of 378 MPa and compressive strain of 27%, combined with a high degradation rate of 383 mm/y. Two kinds of second-phases are found in Mg-Cu-Al alloys, i.e. MgAlCu and β-Mg 17 Al 12 +Al 2 Cu phases. They form a discontinuous network and act as cathodes for micro-galvanic corrosion, leading to a high degradation rate. Moreover, the addition of Al could improve the strength and ductility simultaneously in Mg-Cu alloys. The enhancement of strength primarily arises from the solid-solution strengthening and second-phase hardening. A high density of basal, non-basal dislocations and stacking faults were activated upon mechanical deformation. This accounts for the good ductility in Mg-Cu-Al alloys. [Display omitted] [ABSTRACT FROM AUTHOR]

• A multivalued E ~ A2 correlation is found in low Ni content-316L stainless steel. • AE signals from moving dislocations show slow energy decay, long avalanche durations and high energies. • AE signals during martensitic transformations/detwinning-twinning show fast energy decay, short avalanche durations and low energies. • Martensitic transformation can be further distinguished from detwinning-twinning AE signals by different energy exponents of their avalanches. • Combination of statistical analysis with machine learning algorithms allows online assessment of strain-induced martensitic transformations under high strain. Acoustic emission (AE) of 316L stainless steel with of low Ni content shows, under tension, simultaneously three avalanche processes. One avalanche process relates to the movement of dislocations, the others to martensitic transformations and detwinning/twinning. Detwinning/twinning occurs predominantly at the early stage of the plastic deformation while martensitic transformations only become observable after large plastic deformation. All processes coincide during deformation with variable effect on AE. An excellent fingerprint for the detection of the coincidence between the several mechanisms is the observation of multivalued E ~ A2 correlations. AE signals from moving dislocations decay more slowly (~ 7×10−3s) and show long avalanche durations. In contrast, AE signals during martensitic transformations and detwinning/twinning decay rapidly (<4×10−4s) and show short avalanche durations. They can be distinguished by different energy exponents of their avalanches. The energy distributions of the mechanisms differ because energies are defined as the integral over the squared AE amplitudes, where the integration extends over the avalanche durations. A combination of statistical analysis with Convolutional Neural Network calculations provides an accurate and straightforward method for online, non-destructive avalanche monitoring of strain-induced martensitic transformations in 316L steel under high strain. [Display omitted] [ABSTRACT FROM AUTHOR]

At high pressures, simple metals such as potassium have a rich phase diagram including an insulating electride phase in which electrons have a localized, anionic character. Measurements in the liquid phase have shown a transition between two states, but experimental challenges have prevented detailed thermodynamic measurements. Using potassium as an example, we present numerical evidence that the liquid–liquid transition is a continuous transformation from free electron to electride behaviour. We show that the transformation manifests in anomalous diffusivity, thermal expansion, speed of sound, coordination number, reflectivity and heat capacity across a wide range of pressures. The abnormalities stem from a significant change in the local electronic and ionic structure. Although primarily a pressure-induced phenomenon, there is also a thermal expansion anomaly. By establishing the electride nature of the high-pressure liquid phase, we resolve the long-standing mystery of how a liquid can be denser than a close-packed solid. Our work is relevant for high-pressure thermodynamic properties of all alkali metal liquids.

Piezoelectric vibration energy harvesting has attracted considerable attention because of its prospects in self-powered electronic applications. There are a many low-velocity waters in nature, such as rivers, seas and oceans, which contain abundant hydrokinetic energy. In this paper, an optimal geometric piezoelectric beam combining magnetic excitation is identified and applied to a vortex-induced vibration energy harvester (ViVEH) for low velocity water flow, which is composed of a continuous variable-width piezoelectric beam carrying a cylindrical bluff body. The finite element simulation and experiment are first carried out to study the harvesting characteristics of the designed variable-width beam ViVEH without considering the magnetic excitation. The influence of the width-ratio and flow velocity on the harvesting voltage is studied in detail. The optimal structure, a ViVEH equipped with triangular piezoelectric beam, is then obtained by the superior energy harvesting performance for low velocity water flow. From the experimental results, at a flow velocity of 0.6 m/s, the highest root mean square (RMS) voltage and RMS voltage per unit area are 19.9 V and 0.07 V/mm2, respectively. Furthermore, magnetic excitation is introduced to improve the scavenging performance of the optimal triangular beam ViVEH, different polarity arrangements are compared, and the optimal case, the arrangement of horizontal repulsion and vertical attraction (HR-VA), is obtained. This case can scavenge the highest power of 173 μW at a flow velocity of 0.5 m/s, which is increased by 127% compared to a conventional constant-width beam ViVEH with no magnetic excitation.

As one of the most effective mechanisms, precipitation-hardening is widely used to strengthen high-entropy alloys. Yet, heavy precipitation-hardened high-entropy alloys usually exhibit serious embrittlement. How to effectively achieve ultra-high strength and maintain reliable ductility remains a challenge. Here, we report a study of doping extremely little boron to meet this target. We found that adding of 30 ppm boron into the heavy Ti and Al alloyed FCC FeCoNiCr high-entropy, (FeCoNiCr) 88 Ti 6 Al 6 HEA (at.%) which is strengthened mainly by both coarse BCC-based (Ni, Co) 2 TiAl Heusler and fine L1 2 -type FCC-based (Ni, Co) 3 TiAl precipitates and shows ultrahigh strength but poor ductility, could significantly change the original microstructure and consequently improve mechanical performance, owing to the well-known effect of boron on reducing the energy of grain boundaries. The boron addition can (1) eliminate microcavities formed at Heusler precipitate-matrix interfaces; (2) suppress the formation and segregation of coarse BCC Heusler precipitates; (3) promote the formation of L1 2 nanoparticles. This changes of microstructure substantially improve the tensile ductility more than by ∼86 % and retain comparable or even better ultimate tensile strength. These findings may provide a simple and costless solution to produce heavy precipitation-strengthened HEAs with ultrahigh strength and prevent accidental brittleness. [ABSTRACT FROM AUTHOR]

Defects are pervasive in electrochemical systems across multiple length scales. The defect chemistry largely differs from the bulk behavior and often dictates the rate performance for battery materials. However, the impact of material defects on Li kinetics remains elusive because of their complex nature and the sensitivity of the reaction kinetics on the local atomic environment. Here we focus on the grain boundaries (GBs) in layered-oxide cathodes and address their role in Li transport using the first-principles theoretical approach. We construct the coincidence site lattices of ∑2(11̅04̅), ∑3(1̅102̅), ∑5(11̅01̅), and ∑9(1̅104̅) GBs. The energy profiles for Li migration across and along the grain planes are plotted. We discuss in detail how the atomistic features associated with various grain structures such as the local structural distortion and charge redistribution determine the Li transport kinetics. Specifically, the coherent ∑2 GBs facilitate Li migration with 1–2 orders of magnitude increased diffusivity than the bulk diffusion, the asymmetric ∑3 GBs significantly impede Li diffusion, and the locally disordered ∑5 and ∑9 GBs cause slightly increased Li diffusivity at the intermediate diffusion distance (∼15 Å). We further evaluate the overall Li diffusivity and conductivity in the layered-oxide lattice by a distinction of Li transport in the bulk, across the GBs, and along the grain planes. The fundamental understanding sheds insight on a prevalent defect in the state-of-the-art cathode and its potential optimization of Li kinetics.

A 24 kW narrow-spectral-width near-diffraction-limited monolithic fiber laser system at ${\sim}{1045.2}\;{\rm{nm}}$ in a fiber Bragg grating (FBG)-based master oscillator power amplifier (MOPA) configuration is demonstrated in this paper. The near-diffraction-limited beam quality (${{\rm{M}}^2}\sim{1.2}$) and a spectral width of 0.35 nm (${\sim}{{96}}\;{\rm{GHz}}$) are achieved. The stimulated Raman scattering (SRS) is theoretically and experimentally investigated. The SRS has been suppressed by carefully optimizing the length of the Yb-doped fiber and the pumping scheme, and a signal-to-noise ratio of ${\sim}{{33}}\;{\rm{dB}}$ between the laser signal and the Raman Stokes component is achieved. The stimulate Brillouin scattering and the transverse mode instability are not observed. To our best knowledge, this is the highest-output power for ${{104}} \times {\rm{nm}}$ single-mode fiber laser with ${\sim}{{96}}\;{\rm{GHz}}$ spectral width by using an FBG-based MOPA configuration.

Grain boundary precipitation and segregation play an important role in determining mechanical properties of Mg alloys. In the present work, we studied work focuses on the strengthening and deformation mechanism of coarse-grained (CG) and fine-grained (FG) Mg-Gd-Y-Ag-Zr-Ce alloy. The CG alloy is strengthened by means of age-strengthening with the formation of both basal plate γ′′ and prismatic plate β′ precipitates in the grain interior. While the strengthening of FC alloy is completed by intergranular alloying segregation and intragranular precipitates γ′′ and β′. The segregation of alloying elements at the grain boundary and formation of sub-micron particles can stabilize the grain boundary and suppress the intergranular deformation. Consequently, dislocations could be trapped near γ′′ and β′ precipitates in the grain interior. Unlike CG alloys, the FG alloys exhibit a heterogeneous transition from elastic to plastic deformation via the Lüders plateau. The rapid gliding dislocation multiplications and fine-grained size are necessary and sufficient conditions for the Lüders strains. Our work provides the insights on the evolution of fine-grained microstructure and helps for the design of Mg alloys with good mechanical properties. [ABSTRACT FROM AUTHOR]

Descriptors play a central role in constructing composition–structure–property relationships to guide materials design. We propose a material descriptor, δτ, for the composition dependence of the Curie temperature (Tc) on single doping elements in BaTiO3ferroelectrics, which is then generalized to a linear combination of multiple dopants in the solid solutions. The descriptor δτ depends linearly on the Curie temperature and also serves to separate the ferroelectric phase from the relaxor phase. We compare δτ to other commonly used descriptors such as the tolerance factor, electronegativity, and ionic displacement. By using regression analysis on our assembled experimental data, we show how it outperforms other descriptors. We use the trained machine-learned models to predict compositions in our search space with the largest ferroelectric, dielectric, and piezoelectric properties, namely, d33, electrostrain, and recoverable energy storage density. We experimentally verify our predictions for Tcand classification into ferroelectrics and relaxors by synthesizing and characterizing six solid solutions in BaTiO3ferroelectrics. Our definition of δτ can shed light on the design of knowledge-based descriptors in other systems such as Pb-based and Bi-based solid solutions.

The separation of lithium isotopes (6Li and 7Li) is of great importance for the nuclear industry. The lithium amalgam method is the only lithium isotopes separation process in industry, and the extensive use of mercury has raised concerns about its potential environmental hazards, which have prompted the search for more efficient and environmentally friendly alternatives. Crown ethers can bind lithium ions highly selectively and separate lithium isotopes effectively. A chemical exchange-based lithium isotopes separation method using crown ether decorated materials could be a viable and cost-effective alternative to the lithium amalgam method. In this review, we provide a systematic summary of the recent advances in lithium isotopes separation using crown ether decorated materials.

Cervical cancer remains an important public health problem in Chinese women owing to the lack of a national screening program. The aim of the present study was to evaluate human papillomavirus (HPV) and Papanicolaou (Pap) test results preceding the histologic diagnosis of cervical intraepithelial neoplasia 2/3 (CIN2/3) in China’s largest College of American Pathologists-certified clinical laboratory.

The multiple collapse mechanisms of complex materials produced by additive manufacturing (AM) were identified by measurements of the acoustic emission (AE) of the samples under tension. A perfect correlation between AE avalanches and deformation mechanisms is shown to hold in the extremely complex AM metallic materials such as ‘as-built’ and ‘stress-relieved’ AM 316L stainless steel (SS). The main criterion is that multibranches of the energy-amplitude scaling in AE proves the coexistence of several deformation mechanisms. The as-built AM 316L SS shows three branches in the energy-amplitude scaling of AE signals, which originate from dislocation movements, twinning-detwinning processes and stress-induced martensitic transformations. After stress-relieving annealing at 600 °C for 1 h, two branches remain visible with the dominant deformation mechanisms of dislocation movement and twinning-detwinning. The energy exponent of dislocation avalanches is ε = 1.6, which is not affected by the heat treatment. The twinning-detwinning exponent increases from 1.8 to 2.0 after annealing. The avalanche behavior of the martensitic transformation shows power laws with energy exponents near ε = 1.65 in stress-induced martensite in as-built AM 316L SS and ε = 1.8 for strain-induced martensite in stress-relieved AM 316L SS. This multibranching phenomenon can, thus, be used to identify the mechanisms underlying the deformation of AM-alloys and facilitates online monitoring of deformation processes.

Nanoribbons (NRs) of two-dimensional (2D) materials have attracted intensive research interests because of exotic physical properties at edges as well as tunable properties via width control. In this paper, using density functional theory (DFT) calculations, we discover sensitive dependence of magnetic properties of 1T′-MoS2NRs, that is, periodic variation of magnetic moments between 0.1 and 1.2 μB, on NR width (even or odd number of MoS2units). Our results reveal that a special edge reconstruction, which is not recognized before, stabilizes the ferromagnetic (FM) ground state. Our results also suggest that the FM state could be stable under ambient condition. This study indicates a promising means to integrate multiple magnetic units for small-scale functional devices, such as information storage and spintronics, on a single piece of MoS2NR by designing segments with different width.

Ferroelectric (FE) semiconductors that simultaneously exhibit spectrally suitable band gaps and room temperature stable FE polarizations necessary for separation of photo-excited carriers have been extensively investigated for FE-photovoltaic (PV) applications. Di tin hexathiohypodiphosphate, Sn2P2S6, is one of the rare semiconducting FE materials. However, owing to the indirect nature of its energy band gap and relatively large direct band gap, FE Sn2P2S6absorbs only a small portion of the visible light spectrum. In the current work, we propose substitution of S by Se anion as an experimental feasible route to enhance the visible light absorption for FE Sn2P2S6. Using first-principles calculations, we demonstrate that the effective “band gap engineering” with respect to Se substitution concentration can be achieved in Sn2P2S6(1–x)Se6xsolid solutions. Especially, Sn2P2S4.5Se1.5compound is predicted to be an indirect band gap semiconductor, with a direct band gap at Γ point even lower than that of BiFeO3, and meanwhile exhibits a stable ferroelectricity comparable with single-phase Sn2P2S6. As a result, the improved visible light absorption can be achieved in Sn2P2S4.5Se1.5compound, making Se-doped FE Sn2P2S6more suitable for PV applications.

Flexible organic-based composites embedding nanosheet-like inorganics with high energy storage density (U) are imperatively demanded for applications in portable electronics and sensors. However, the breakdown phases can easily bypass the discontinuous nanosheets, leading to the failure of conduction barriers. Here, continuous flexible Sm-doped BiFeO3-BaTiO3(Sm-BFBT) membranes with superparaelectric characteristics were synthetized via etching a water-soluble Sr3Al2O6buffer layer. With the single-crystal Sm-BFBT membranes embedded into poly(vinylidene fluoride), a giant Uof 46.4 J/cm3at 770 MV/m is achieved in the sandwich-structured composites, attributed to a formation of depolarized field induced by interfacial ions. Meanwhile, the composites exhibit a stable Uof ∼20 J/cm3at 550 MV/m during bending process, owing to the excellent flexibility of Sm-BFBT membranes originating from nanodomain switching. The proposed composites containing flexible 2D inorganic membranes offer unprecedented structural insights into the integration of high energy storage and stability of bending, and suggest potential uses in flexible energy storage devices.

Using first-principles calculations, we systematically evaluated a series of single-layer porous graphene membranes with different sized pores passivated by hydrogen atoms for separating short alkane isomers (C = 5–7). We found that graphene membranes with appropriate pore size (e.g., the pore19model whose pore size is 8.0 × 5.8 Å) could efficiently separate dibranched isomers from their monobranched and linear counterparts. When alkane molecules diffused through a membrane, the porous graphene might exhibit significant distortion. At the same time, the passing molecule would be forced to change its own geometry as well. More importantly, we found that the geometric deformations of both the penetrating molecule and the membrane concertedly lowered the diffusion barrier by similar magnitudes. Therefore, when designing two-dimensional (2D) separation materials, it is necessary to consider the geometric flexibility of both the separation material and the molecules to be separated. Our results theoretically verified the feasibility of utilizing porous graphene and possibly other 2D materials for screening alkane isomers, which could lead to a wide range of energy and environment related applications.

There is still a challenge to rapidly and accurately acquire the composition dependence of mechanical properties of multi-principal element alloys due to their huge composition space and complex electronic structures. Aiming to straightforwardly tune the mechanical properties through alloying, we systematically calculate the elastic and mechanical properties for four selected body-centered-cubic (bcc) Ti–Nb–M (M = Zr, Mo, Sn, Ta) refractory medium-entropy alloys (RMEAs) using a first-principles method. It is shown that the elastic stability of the bcc RMEAs can be significantly (weakly) improved with the increase in Nb, Mo, and Ta (Sn) content, but it is insensitive to Zr. The elastic stability, elastic modulus, hardness, and strength generally enhance, whereas Pugh’s ratio and Zener anisotropy (AZ) decrease with the increase in valence electron concentration. Additionally, there is a correlation between the magnitude of the AZand the shape of the single-crystal Young’s modulus (E[hkl]). The largest (smallest) E[hkl]appears in the <111> (<100>) direction. Particularly, the most isotropic Ti60Nb20Mo20has the highest hardness and strength among all the Ti–Nb–M alloys. Moreover, the change of elastic properties induced by alloying is related to the change of density of states. This work sheds deep light on the design of high-performance Ti-based multi-principal element alloys.

Highly efficient and eco-friendly thermoelectric generators rely on low-cost and nontoxic semiconductors with high symmetry and ultralow lattice thermal conductivity κL. We report the rational synthesis of the novel cubic (Ag, Se)-doped Cu2GeTe3semiconductors. A localized symmetry breakdown (LSB) was found in the composition of Cu1.9Ag0.1GeTe1.5Se1.5(i.e., CAGTS15) with an ultralow κLof 0.37 W/mK at 723 K, the lowest value outperforming all Cu2GeCh3(Ch = S, Se, and Te). A joint investigation of synchrotron X-ray techniques identifies the LSB embedded into the cubic CAGTS15 host matrix. This LSB is an Ångström-scale orthorhombic symmetry unit, characteristic of multiple bond lengths, large anisotropic atomic displacements, and distinct local chemical coordination of anions. Computational results highlight that such an unusual orthorhombic symmetry demonstrates low-frequency phonon modes, which become softer and more predominant with increasing temperatures. This unconventional LSB promotes bond complexity and phonon scattering, highly beneficial for extraordinarily low lattice thermal conductivity.

Lithium isotope separation has attracted extensive interest due to its important role in fusion and fission reactions. Up to now, it is still a great challenge to separate lithium isotopes (6Li and 7Li) in an efficient manner due to the low capture ability for lithium ions of related materials and highly similar physicochemical properties between lithium isotopes. In this work, three calix[4]arene-decorated crystalline covalent organic frameworks (COFs) with wave-like extension and AA-stacking configuration were designed and utilized for lithium adsorption and its isotope separation. Experimental studies show that these COFs exhibit an outstanding lithium adsorption capacity up to 94.66 mg·g–1, which is about 2 times beyond that of adsorbents reported in the literature. The high adsorption capacity of COFs could be attributed to the abundant adsorption sites from calix[4]arene unit. More importantly, this study demonstrates for the first time that calixarene groups can separate lithium isotopes with an excellent separation factor up to 1.053 ± 0.002, comparable to the most successful solid-phase lithium separation adsorbent. The calculation based on density functional theory showed that calixarene played an important role in the lithium adsorption. Interestingly, the lithium isotope separation performance is mainly affected by the amine bridging units. This work demonstrated that calixarene COFs are promising adsorbents for lithium isotope separation.

We systematically investigated the role of surface on the B2–B19 transformation of free-standing nanoparticles by classical molecular dynamics simulations. It was found that the surface of particles has a shell structure with a thickness of 2 unit cells, suppressing the B2–B19 transformation locally. Below a critical size, this surface shell leads to the reduction of the transformation latent heat and the vanishing of B2–B19 transformation. We propose a Landau-type model based on the core–shell structure of particles, which reproduces well the relation between transformation temperature and particle size. Our results provide a microscopic insight into the origin of surface-induced size effect on the structural phase transformations in nanosized shape memory alloys.

The interactions between NOx, N and O atoms, and aluminum (Al) surfaces including crystal planes and nanoparticles (ANPs) are systematically investigated by using density functional theory (DFT) calculations, canonical Monte Carlo (CMC) simulations, and reactive molecular dynamics (RMD) simulations. NOxhas two adsorption states (molecular and dissociated) on the Al surfaces, which are separated by a low energy barrier. The adsorption of NOxin either state does not favor Al nanoparticles (ANPs), opposite to its behavior on transition metals. In addition, NOxdoes not show preference toward smaller ANPs or their vertices or edges; instead, it prefers threefold sites that resemble the fcc or hcp sites on a (111) surface. The big deformation energy of ANPs is found to be the reason. The N* adatoms are most stable at the tetrahedron interstitial sites between the surface and the first sublayer, where an aluminum nitride (AlN)-like structure is formed. Similar to O* adatoms on Al, the isotropic attraction between N* adatoms has a significant influence on their diffusion, both in-plane and in cross-layer. Besides, the attraction within a N–O pair as the first nearest neighbors (1NN) is roughly twice that of their respective attraction (about 0.1 eV/O–O or N–N). However, RMD simulations ignore the attraction among the N* adatoms as well as between the N* and O* adatoms, though O–O attractions are somehow incorporated. CMC simulations prove that the attraction still governs the configuration of the adatoms at 600 K with all adatoms congregating into a single polygonal island, and it is still influential even when reaching 1500 K. In addition, the fragmented products (AlxNy) of Al combustion in NOxaccording to DFT feature the tetra-coordinated Al centered inside the tetrahedron of four N atoms, different from the pyramidal unit structure with Al as the vertex by RMD simulations. Our results demonstrate that the unusual behaviors of NOxincluding the dissociated atoms on Al are caused by both the softness (low Young’s modulus) of Al and the attractions among adsorbates, which have important implications for understanding the behaviors of gas molecules on main group metals in general.

Manageable thermal expansion (MTE) of metal trifluorides can be achieved by introducing local structure distortion (LSD) in the negative thermal expansion ScF3. However, an open issue is why isostructural TiF3, free of LSD, exhibits positive thermal expansion. Herein, a combined analysis of synchrotron X-ray diffraction, X-ray pair distribution function, and rigorous first-principles calculations was performed to reveal the important role of itinerant electrons in mediating soft phonons and lattice dynamics. Metallic TiF3demonstrates itinerant electrons and a suppressed Grüneisen parameter γ ≈ −20, while insulating ScF3absence of itinerant electrons has a considerable γ ≈ −120. With increasing electron doping concentrations in ScF3, soft phonons become hardened and the γ is repressed significantly, identical to TiF3. The presented results update the thermal expansion transition mechanism in framework structure analogues and provide a practical approach to obtaining MTE without inducing sizable structure distortion.