Unveiling the influence of dendrite characteristics on the slip/twinning activity and the strain hardening capacity of Mg-Sn-Li-Zn cast alloys

This work explores the correlation between the characteristics of the cast structure(dendrite growth pattern,dendrite morphology and macro-texture)and strain hardening capacity during high temperature deformation of Mg-5Sn-0.3Li-0 and 3Zn multi-component alloys.The three dimensional(3D)morphology of the dendrite structure demonstrates the transition of the growth directions from<1123>,<1120>and<1122>to<1123>and<1120>due to the addition of Zn.The simultaneous effects of growing tendency and the decrement of dendrite coarsening rate at the solidification interval lead to dendrite morphology transition from the globular-like to the hyper-branch structure.This morphology transition results in the variation of the solidification macro-texture,which has effectively influenced the dominant deformation mechanisms(slip/twin activity).The higher activity of the slip systems increases the tendency of the dendrite arms for bending along the deformation direction and fragmentation.Apart from this,the dendrite holding hyper-branch structure with an average thickness below 20μm are more favorable for fragmentation.The dendrite fragmentation leads to considerable softening fractions,and as an effective strain compensation mechanism increases the workability of dendritic structure.

Occurrence of anionic redox with absence of full oxidation to Ru^(5+) in high-energy P2-type layered oxide cathode

The anionic redox has been widely studied in layered-oxide-cathodes in attempts to achieve highenergy-density for Na-ion batteries(NIBs).It is known that an oxidation state of Mn^(4+) or Ru^(5+) is essential for the anionic reaction of O^(2-)/O~-to occur during Na^(+) de/intercalation.However,here,we report that the anionic redox can occur in Ru-based layered-oxide-cathodes before full oxidation of Ru^(4+)/Ru^(5+).Combining studies using first-principles calculation and experimental techniques reveals that further Na^(+) deintercalation from P2-Na_(0.33)[Mg_(0.33)Ru_(0.67)]O_(2) is based on anionic oxidation after 0.33 mol Na^(+) deintercalation from P2-Na_(0.67)[Mg_(0.33)Ru_(0.67)]O_(2) with cationic oxidation of Ru^(4+)/Ru^(4.5+).Especially,it is revealed that the only oxygen neighboring 2Mg/1 Ru can participate in the anionic redox during Na^(+) de/intercalation,which implies that the Na-O-Mg arrangement in the P2-Na_(0.33)[M9_(0.33)Ru_(0.67)]O_(2) structure can dramatically lower the thermodynamic stability of the anionic redox than that of cationic redox.Through the O anionic and Ru cationic reaction,P2-Na_(0.67)[Mg_(0.33)Ru_(0.67)]O_(2) exhibits not only a large specific capacity of~172 mA h g^(-1) but also excellent power-capability via facile Na^(+) diffusion and reversible structural change during charge/discharge.These findings suggest a novel strategy that can increase the activity of anionic redox by modulating the local environment around oxygen to develop high-energy-density cathode materials for NIBs.

Structural and electrochemical stabilization enabling high-energy P3-type Cr-based layered oxide cathode for K-ion batteries

Layered-type transition metal(TM)oxides are considered as one of the most promising cathodes for K-ion batteries because of the large theoretical gravimetric capacity by low molar mass.However,they suffer from severe structural change by de/intercalation and diffusion of K^(+)ions with large ionic size,which results in not only much lower reversible capacity than the theoretical capacity but also poor power capability.Thus,it is important to enhance the structural stability of the layered-type TM oxides for outstanding electrochemical behaviors under the K-ion battery system.Herein,it is investigated that the substitution of the appropriate Ti^(4+)contents enables a highly enlarged reversible capacity of P3-type KxCrO_(2) using combined studies of first-principles calculation and various experiments.Whereas the pristine P3-type KxCrO_(2) just exhibits the reversible capacity of∼120 mAh g^(−1) in the voltage range of 1.5-4.0 V(vs.K^(+)/K),the∼0.61 mol K^(+)corresponding to∼150 mAh g^(−1) can be reversible de/intercalated at the structure of P3-type K0.71[Cr_(0.75)Ti_(0.25)]O_(2) under the same conditions.Furthermore,even at the high current density of 788 mA g^(−1),the specific capacity of P3-type K0.71[Cr_(0.75)Ti_(0.25)]O_(2) is∼120 mAh g^(−1),which is∼81 times larger than that of the pristine P3-type KxCrO_(2).It is believed that this research can provide an effective strategy to improve the electrochemical performances of the cathode materials suffered by severe structural change that occurred during charge/discharge under not only K-ion battery system but also other rechargeable battery systems.

Unexpected Li displacement and suppressed phase transition enabling highly stabilized oxygen redox in P3-type Na layered oxide cathode

Oxygen redox is considered a new paradigm for increasing the practical capacity and energy density of the layered oxide cathodes for Na-ion batteries. However, severe local structural changes and phase transitions during anionic redox reactions lead to poor electrochemical performance with sluggish kinetics.Here, we propose a synergy of Li-Cu cations in harnessing the full potential of oxygen redox, through Li displacement and suppressed phase transition in P3-type layered oxide cathode. P3-type Na_(0.7)[Li_(0.1)Cu_(0.2)Mn_(0.7)]O_(2) cathode delivers a large specific capacity of ~212 mA h g^(-1)at 15 mA g^(-1). The discharge capacity is maintained up to ~90% of the initial capacity after 100 cycles, with stable occurrence of the oxygen redox in the high-voltage region. Through advanced experimental analyses and first-principles calculations, it is confirmed that a stepwise redox reaction based on Cu and O ions occurs for the charge-compensation mechanism upon charging. Based on a concrete understanding of the reaction mechanism, the Li displacement by the synergy of Li-Cu cations plays a crucial role in suppressing the structural change of the P3-type layered material under the oxygen redox reaction, and it is expected to be an effective strategy for stabilizing the oxygen redox in the layered oxides of Na-ion batteries.

High efficiency and stable solid-state fiber dye-sensitized solar cells obtained using TiO_(2) photoanodes enhanced with metal organic frameworks

Solid-state fiber dye-sensitized solar cells(SS-FDSSCs) have been the subject of intensive attention and development in recent years. Although this field is only in its infancy, metal–organic frameworks(MOFs) are one such material that has been utilized to further improve the power conversion efficiency of solar cells. In this study, MOF-integrated DSSCs were shown to have potential in the development of solar cell devices with efficiency comparable to or better than that of conventional solar cells. The power conversion efficiency(PCE) of SS-FDSSCs was improved by embedding MOF-801 into a mesoporous-TiO_(2)(mp-TiO_(2)) layer, which was used as a photoanode in SS-FDSSCs, which are inherently flexible. The PCE of the MOF-integrated SS-FDSSCs was 6.50%, which is comparable to that of the reference devices(4.19%).The MOF-801 enhanced SS-FDSSCs decreased the series resistance(R_(s)) value, resulting in effective electron extraction with improved short-circuit current density(J_(SC)), while also increasing the shunt resistance(R_(sh)) value to prevent the recombination of photo-induced electrons. The result is an improved fill factor and, consequently, a higher value for the PCE.

Ternary layered double hydroxide oxygen evolution reaction electrocatalyst for anion exchange membrane alkaline seawater electrolysis

Anion exchange membrane(AEM)water electrolyzers are promising energy devices for the production of clean hydrogen from seawater.However,the lack of active and robust electrocatalysts for the oxygen evolution reaction(OER)severely impedes the development of this technology.In this study,a ternary layered double hydroxide(LDH)OER electrocatalyst(NiFeCo-LDH)is developed for high-performance AEM alkaline seawater electrolyzers.The AEM alkaline seawater electrolyzer catalyzed by the NiFeCo LDH shows high seawater electrolysis performance(0.84 A/cm^(2)at 1.7 Vcell)and high hydrogen production efficiency(77.6%at 0.5 A/cm^(2)),thus outperforming an electrolyzer catalyzed by a benchmark IrO_(2)electrocatalyst.The NiFeCo-LDH electrocatalyst greatly improves the kinetics of the AEM alkaline seawater electrolyzer,consequently reducing its activation loss and leading to high performance.Based on the results,this NiFeCo-LDH-catalyzed AEM alkaline seawater electrolyzer can likely surpass the energy conversion targets of the US Department of Energy.

ATH浓度对PP/ATH复合材料力学性能的影响(英文)

ATH被广泛添加到聚丙烯(PP)中用于制成阻燃复合材料。PP/ATH复合材料比纯PP材料更具防火性。材料中成分的比例最终取决于应用要求。已有文献对这种复合材料的阻燃性能的提高进行了研究,但对机械强度的影响还没有涉及。本文研究了ATH浓度对PP/ATH复合材料的影响,利用实验测试、ASTM分析公式和有限元方法研究了材料的拉伸、弯曲和断裂特性。研究结果表明:增加ATH对材料的机械强度有不利的影响。

烧结方法对CP-Ti粉末烧结块显微组织和力学性能的影响(英文)

研究不同烧结方法,包括放电等离子体烧结(SPS)、热压(HP)和电阻烧结(ERS),对商用纯钛(CP-Ti)粉末固结后显微组织和力学性能的影响。选用的粉末粒度分别为【147μm,【74μm和【43μm,粉末粒度越小,其致密化过程越快。在850°C、30 MPa条件下进行SPS和HP,获得烧结体的相对密度高达99%。而通过ERS,则在950°C、30 MPa条件下才发生CP-Ti粉末的致密化。在850~950°C获得烧结钛的显微组织由等轴晶构成。对于粒度【43μm粉末,在850°C、30 MPa条件下通过SPS制备烧结体,其屈服强度为868 MPa。随着小尺寸颗粒含量的升高,通过SPS和HP制备烧结体的屈服强度得到提高。然而在950°C、30MPa条件下,通过ERS制备样品的最高屈服强度仅为441 MPa,比SPS和HP样品的低。与SPS和HP相比,ERS需要较短的烧结时间,但较高的烧结温度导致材料的脆性断裂,使其强度和伸长率降低。

Influence of rare earth on the microstructure and age hardening response of indirect-extruded Mg-5Sn-4Zn alloy

The effects of Ce addition on the microstructure, age hardening response and mechanical properties of an indirect-extruded Mg-5wt.%Sn-4Zn (TZ54) alloy were investigated. Addition of Ce accelerated the aging response with the peak aging time moving from 300 h in TZ54 to 30 h in Mg-5wt.%Sn-4Zn-1Ce (TZE541), while the peak harness was similar to each other. The addition of Ce also caused an increase in the precipitation stability during overageing. Though the tensile strength of extruded TZ54 was improved by t...

Flexible highly-effective energy harvester via crystallographic and computational control of nanointerfacial morphotropic piezoelectric thin film

Controlling the properties of piezoelectric thin films is a key aspect for designing highly efficient flexible electromechanical devices. In this stud）~ the crystallographic phenomena of PbZr1-xTixO3 （PZT） thin films caused by distinguished interfacial effects are deeply investigated by overlooking views, including not only an experimental demonstration but also ab initio modeling. The polymorphic phase balance and crystallinity, as well as the crystal orientation of PZT thin films at the morphotropic phase boundary （MPB）, can be stably modulated using interfacial crystal structures. Here, interactions with MgO stabilize the PZT crystallographic system well and induce the texturing influences, while the PZT film remains quasi-stable on a conventional A1203 wafer. On the basis of this fundamental understanding, a high-output flexible energy harvester is developed using the controlled-PZT system, which shows significantly higher performance than the unmodified PZT generator. The voltage, current, and power densities are improved by 556%, 503%, and 822%, respectively, in comparison with the previous flexional single-crystalline piezoelectric device. Finally, the improved flexible generator is applied to harvest tiny vibrational energy from a real traffic system, and it is used to operate a commercial electronic unit. These results clearly indicate that atomic-scale designs can produce significant impacts on macroscopic applications.

Tribological properties of multilayer tetrahedral amorphous carbon coatings deposited by filtered cathodic vacuum arc deposition

Tetrahedral amorphous carbon(ta‐C)has emerged as an excellent coating material for improving the reliability of application components under high normal loads.Herein,we present the results of our investigations regarding the mechanical and tribological properties of a 2‐μm‐thick multilayer ta‐C coating on high‐speed steel substrates.Multilayers composed of alternating soft and hard layers are fabricated using filtered a cathodic vacuum arc with alternating substrate bias voltages(0 and 100 V or 0 and 150 V).The thickness ratio is discovered to be 1:3 for the sp2‐rich and sp3‐rich layers.The results show that the hardness and elastic modulus of the multilayer ta‐C coatings increase with the sp3 content of the hard layer.The hardness reached approximately 37 GPa,whereas an improved toughness and a higher adhesion strength(>29 N)are obtained.The friction performance(μ=0.07)of the multilayer coating is similar to that of the single layer ta‐C thick coating,but the wear rate(0.13×10^(–6) mm^(3)/(N∙m))improved under a high load of 30 N.We further demonstrate the importance of the multilayer structure in suppressing crack propagation and increasing the resistance to plastic deformation(H3/E2)ratio.

Effect of molybdenum on interfacial properties of titanium carbide reinforced Fe composite

This study shows that the mechanical strength of the composite of Fe matrix and titanium carbide(Ti C)ceramic particles is significantly enhanced with addition of molybdenum(Mo) atoms. Ti C reinforced Fe(Fe-0.2C-7Mn) composites with and without Mo were fabricated by a liquid pressing infiltration(LPI)process and the effect of Mo on interfacial properties of TiC–Fe composite was investigated using atomic probe tomography(APT) analysis, molecular dynamics(MD) simulations, first-principle density functional theory(DFT), and thermodynamic calculations. First, DFT calculations showed that total energies of the Mo-doped Ti C–Fe superlattices strongly depend on the position of Mo defects, and are minimized when the Mo atom is located at the TiC/Fe interface, supporting the probable formation of MoC-like interphase at the TiC/Fe interface region. Then, APT analysis confirmed the DFT predictions by finding that about6.5 wt.% Mo is incorporated in the Ti C–Fe(Mo) composite and that sub-micrometer thick(Ti,Mo)C interphase is indeed formed near the interface. The MD simulations show that Mo atoms migrate to the Mo-free TiC–Fe interface at elevated temperatures and the mechanical strength of the interface is considerably enhanced, which is in good agreement with experimental observations.

Application of 3D bioprinting in the prevention and the therapy for human diseases

Rapid development of vaccines and therapeutics is necessary to tackle the emergence of new pathogens and infectious diseases.To speed up the drug discovery process,the conventional development pipeline can be retooled by introducing advanced in vitro models as alternatives to conventional infectious disease models and by employing advanced technology for the production of medicine and cell/drug delivery systems.In this regard,layer-by-layer construction with a 3D bioprinting system or other technologies provides a beneficial method for developing highly biomimetic and reliable in vitro models for infectious disease research.In addition,the high flexibility and versatility of 3D bioprinting offer advantages in the effective production of vaccines,therapeutics,and relevant delivery systems.Herein,we discuss the potential of 3D bioprinting technologies for the control of infectious diseases.We also suggest that 3D bioprinting in infectious disease research and drug development could be a significant platform technology for the rapid and automated production of tissue/organ models and medicines in the near future.

Superelastic metastable Ti-Mo-Sn alloys with high elastic admissible strain for potential bio-implant applications

The demand for titanium alloys simultaneously having high elastic admissible strain and large recovery strain for bio-implant applications is increasing.Ni-free Ti-based shape memory alloys are promising candidates for obtaining the required multifunctional properties.In this study,a wide content range of(0-15)wt%of low-cost,toxicity-free,and high-biocompatible Sn element was added to the Ti-8Mo(wt%)alloy to study its effect on the superelastic recovery and mechanical properties of biomedical Ti-Mo-Sn alloys.By tailoring Sn content,desired multifunctional properties of high elastic admissible strain and room temperature superelasticity were achieved in the studied Ti-Mo-Sn alloys.It was found that the increase in Sn content stabilized theβphase and a singleβphase was obtained at room temperature in Ti-8Mo-(13,15)Sn alloys.The addition of Sn modified the lattice parameters of theα″martensite andβphase and affected the lattice deformation stain ofβ→α″.The lattice deformation strain along the[011]βdirection was found to be decreased by-0.26%/wt%Sn.The room temperature superelasticity with a recovery strain of 3.1%and an elastic admissible strain of 1%was obtained in the Ti-8Mo-13Sn alloy.As Sn content increased to 15 wt%,a high elastic admissible strain of 1.56%and a recovery strain of 2.0%were obtained.These Ti-Mo-Sn alloys with excellent multifunctional properties are promising candidates for bio-implant applications.

Heterostructures in two-dimensional colloidal metal chalcogenides:Synthetic fundamentals and applications

As a new class of two-dimensional materials, two-dimensional (2D) heterostructures constructed from metal chalcogenides (MCs) have been gaining tremendous attention due to their unprecedented physical and chemical phenomena, mainly originated from their distinct structural features such as composition, architecture type, spatial arrangement of each component, crystal structure, exposed facet and interface, dimensionality in their heterostructures. Towards the realization of practical applications, synthetic approaches need a rational design with a variety of architecture types including laterally-combined, vertically-aligned, and conformally-coated 2D MC heterostructures. Among various synthetic routes, solution-based synthesis is thought of as an alternative to fabrication through high-cost setups since it can control those structural features in a cheap fashion. This review presents recent progress on solution-based synthesis to produce various 2D MC heterostructures with a focus on the synthetic fundamentals in terms of thermodynamic and kinetic aspects related to the growth mechanism. Four different synthetic approaches are reviewed: seeded growth, cation exchange reaction, colloidal atomic layer deposition, direct synthesis including one-step process and modified electrochemical method. We also provide some representative applications of 2D MC heterostructures and their hybrid composites in various fields including optoelectronics, thermoelectrics, catalysis, and battery. Finally, we offer an insight into challenges and future directions in a synthetic improvement of 2D MC heterostructures.

Super-resolving material microstructure image via deep learning for microstructure characterization and mechanical behavior analysis

The digitized format of microstructures,or digital microstructures,plays a crucial role in modern-day materials research.Unfortunately,the acquisition of digital microstructures through experimental means can be unsuccessful in delivering sufficient resolution that is necessary to capture all relevant geometric features of the microstructures.The resolution-sensitive microstructural features overlooked due to insufficient resolution may limit one’s ability to conduct a thorough microstructure characterization and material behavior analysis such as mechanical analysis based on numerical modeling.Here,a highly efficient super-resolution imaging based on deep learning is developed using a deep super-resolution residual network to super-resolved low-resolution(LR)microstructure data for microstructure characterization and finite element(FE)mechanical analysis.Microstructure characterization and FE model based mechanical analysis using the super-resolved microstructure data not only proved to be as accurate as those based on high-resolution(HR)data but also provided insights on local microstructural features such as grain boundary normal and local stress distribution,which can be only partially considered or entirely disregarded in LR data-based analysis.

Stabilized sub-grain and nano carbides-driven 1.2 GPa grade ultra-strong CrMnFeCoNi high-entropy alloy additively manufactured by laser powder bed fusion

High-entropy alloys(HEAs)with interstitial atoms that are produced by additive manufacturing have gained intensive interest in the materials science community because of their suitability for constructing high-strength net-shape components.Here,a strategy to additionally enhance the strength of selective laser melted carbon-containing HEAs was investigated.The as-built carbon-containing HEAs(C_(x)(Cr_(20)Mn_(20)Fe_(20)Co_(20)Ni_(20))_(100-x)(x=0.5 at.%,1.0 at.%,and 1.5 at.%))contain supersaturated carbon,and the extent of supersaturation increases as the carbon content increases.When subjected to aging treatment at 650°C for 1 h,the microstructure of the three alloys did not change at the grain scale.However,the microstructure at the sub-grain scale changed markedly,and these changes influenced the tensile properties and deformation mechanism.In particular,the tensile strength of aged 1.5C-HEA at 650°C was∼1.2 GPa at room temperature,which is higher than those reported for CrMnFeCoNi HEAs.Furthermore,the main deformation mechanism changed from deformation twinning to dislocation-mediated slip,resulting in much higher strain hardening capacity after the aging treatment.This work led to the development of an alternative promising method that involves tailoring the microstructure,to enhance the mechanical properties of additively manufactured metallic materials that contain interstitial atoms.

Improving high-temperature oxidation behavior by modifying Al and Co content in Al-Co-Cr-Fe-Ni high-entropy alloy

Composition modification was introduced to improve the oxidation resistance by varying Al and excluding Co from the Al-Co-Cr-Fe-Ni system. Since adjusting the composition shifted the valence electron concentration(VEC) of the alloys, the dual-phase structure of the alloys is expected to be more stable. At low temperatures(T < 1273 K), the alloys formed mixed oxide products. As oxidation temperature increased,only Cr_(2)O_(3)or Al_(2)O_(3)dominated the alloy’s surface. Compared to equiatomic AlCoCrFeNi(5-Equi), nonequiatomic AlCoCrFeNi(5-B 40) and four-component AlCrFeNi(4-B 2013) had better oxidation resistance due to monocrystalline-Al_(2)O_(3)formation. Besides the role of oxide formation, maintaining BCC and B2phases within the alloys is also beneficial to supporting the stable Cr_(2)O_(3)or Al_(2)O_(3).

Highly efficient and stable solid-state fiber dye-sensitized solar cells with Ag-decorated SiO_(2) nanoparticles

Fiber-shaped dye-sensitized solar cells(FDSSCs)represent promising futuristic flexible or wearable power sources,owing to their simple fabrication process,light weight,weavability,and wearability.Along with strategies on changing the properties of semiconductor materials,the effects of incorporating silver-embedded SiO_(2) nanoparticles(Ag@SiO_(2)NPs)on the photoanodes of solid-state FDSSCs(SS-FDSSCs)are investigated.The power conversion efficiency(PCE)of SS-FDSSCs with Ag@SiO_(2) NPs reaches 5.38%,which is comparable to the reference(3.98%).The PCEs remain at 95%between-16.9 and 91.7℃,indicating the operational stability of SS-FDSSCs within this temperature range.The fabricated SS-FDSSCs,whose radii were 2 mm,maintains more than 90%of their efficiency over 500 bending cycles and 10 washing cycles.

SU-8 cantilever with integrated pyrolyzed glass-like carbon piezoresistor

Glass-like carbon(GC)is a nongraphitizing material composed entirely of carbon atoms produced from selected organic polymer resins by controlled pyrolysis in an inert atmosphere.The GC properties are a combination of the properties of glass,ceramic,and graphite,including hardness,low density,low thermal conductivity,high chemical inertness,biocompatibility,high electrical conductivity,and microfabrication process compatibility.Despite these unique properties,the application of GC in mechanical sensors has not been explored thus far.Here,we investigate the electrical,structural,and chemical properties of GC thin films derived from epoxy-based negative photoresist SU-8 pyrolyzed from 700 to 900°C.In addition,we fabricated microGC piezoresistors pyrolyzed at 700 and 900°C and integrated them into nonpyrolyzed SU-8 cantilevers to create microelectromechanical systems(MEMS)mechanical sensors.The sensitivities of the GC sensor to strain,force,surface stress,and acceleration are characterized to demonstrate their potential and limits for electromechanical microdevices.