Hyphae-mediated bioassembly of carbon fibers derivatives for advanced battery energy storage

Ingenious design and fabrication of advanced carbon-based sulfur cathodes are extremely important to the development of high-energy lithium-sulfur batteries,which hold promise as the next-generation power source.Herein,for the first time,we report a novel versatile hyphae-mediated biological assembly technology to achieve scale production of hyphae carbon fibers(HCFs)derivatives,in which different components including carbon,metal compounds,and semiconductors can be homogeneously assembled with HCFs to form composite networks.The mechanism of biological adsorption assembly is also proposed.As a representative,reduced graphene oxides(rGOs)decorated with hollow carbon spheres(HCSs)successfully co-assemble with HCFs to form HCSs@rGOs/HCFs hosts for sulfur cathodes.In this unique architecture,not only large accommodation space for sulfur but also restrained volume expansion and fast charge transport paths are realized.Meanwhile,multiscale physical barriers plus chemisorption sites are simultaneously established to anchor soluble lithium polysulfides.Accordingly,the designed HCSs@rGOs/HCFs-S cathodes deliver a high capacity(1189 mA h g^(-1)at 0.1 C)and good high-rate capability(686 mA h g^(-1)at 5 C).Our work provides a new approach for the preparation of high-performance carbon-based electrodes for energy storage devices.

MOF-derived porous graphitic carbon with optimized plateau capacity and rate capability for high performance lithium-ion capacitors

The development of anode materials with high rate capability and long charge-discharge plateau is the key to improve per-formance of lithium-ion capacitors(LICs).Herein,the porous graphitic carbon(PGC-1300)derived from a new triply interpenetrated co-balt metal-organic framework(Co-MOF)was prepared through the facile and robust carbonization at 1300°C and washing by HCl solu-tion.The as-prepared PGC-1300 featured an optimized graphitization degree and porous framework,which not only contributes to high plateau capacity(105.0 mAh·g^(−1)below 0.2 V at 0.05 A·g^(−1)),but also supplies more convenient pathways for ions and increases the rate capability(128.5 mAh·g^(−1)at 3.2 A·g^(−1)).According to the kinetics analyses,it can be found that diffusion regulated surface induced capa-citive process and Li-ions intercalation process are coexisted for lithium-ion storage.Additionally,LIC PGC-1300//AC constructed with pre-lithiated PGC-1300 anode and activated carbon(AC)cathode exhibited an increased energy density of 102.8 Wh·kg^(−1),a power dens-ity of 6017.1 W·kg^(−1),together with the excellent cyclic stability(91.6%retention after 10000 cycles at 1.0 A·g^(−1)).

Effect of heat treatment on LPSO morphology and mechanical properties of Mg-Zn-Y-Gd alloys

The mechanical properties and microstructure were investigated under different Zn content and heat treatment conditions in a Mg-Zn-YGd cast alloy.A part of the long period stacking order(LPSO)phases transformed to W-M^ZnaRE?phases with an increase in Zn content from 0.9 at.%to 1.8 at.%,and the ultimate tensile strength(UTS)increased from 229 MPa to 248 MPa.With solution treatment at 480°C,the content of the LPSO phase and strength sharply decreased in the Mg-1.8Zn-0.8Y-0.8Gd alloy,whereas this change was not significantly observed in the Mg-0.9Zn-O.8Y-O.8Gd alloy.After solution treatment,the elongation significantly improved and the UTS sharply decreased in both alloys.The lamellar and filminess LPSO phases were observed with aging treatment at 200℃.Moreover,the strengthening efficiency of lamellar and filminess LPSO phases was lower than that of the block LPSO phases.Therefore,the UTS of the T6 state was lower than that of the as-cast alloy.

Corrosion properties in a simulated body fluid of Mg/β-TCP composites prepared by powder metallurgy

Magnesium matrix composites （MMC） reinforced with 5wt% tricalcium phosphate （TCP） particles were prepared by powder metallurgy. Pure magnesium （CP-Mg） was fabricated by the same procedure for comparison. Scanning electron microscopy and en- ergy-dispersive X-ray spectroscopy analyses revealed that TCP particles were distributed homogeneously in the MMC. In order to investi- gate the corrosion properties, MMC samples were immersed in a simulated body fluid （SBF） at 310~0.5 K for 72 h. The mass loss of the samples in SBF and the pH values of the SBF were evaluated. Moreover, electrochemical measurements were conducted in the SBF. It was shown that the corrosion rate of the MMC decreased with the addition of TCP compared with CP-Mg. Hydroxyapatite was formed on the surface of MMC samples after immersion in the SBF for 72 h but not on the surface of CP-Mg.

Studies on Kinetics of Crystallization of PA6/UFAPR Composites

The influence of Ultrafine Full-Vulcanized Acrylate Powdered Rubber(UFAPR) on the isothermal crystallization kinetics and nonisothermal crystallization behavior of PA6 has been studied by means of DSC. The results show that with the introduction of a small amount of UFAPR, the crystallization rate of PA6 can be increased obviously, and the crystallization temperature range can be augmented and the crystallite size distribution of the crystal can be narrowed down. The change of free energy perpendicular to the crystal nucleus, which has been calculated according to the Hoffman theory, is consistent with the result of Avrami′s equation. The unit surface free energy of the radial-developing crystal spherulite decreases while the crystallization rate of PA6 increases with the introduction of UFAPR. Meanwhile, it is shown by means of the polarizing microscope(PLM) that the crystal size drops down and the number of the crystal grains augments with the addition of UFAPR, which shows that UFAPR can function as a nucleating agent.

Fully Bio-Based Composites of Poly(Lactic Acid)Reinforced with Cellulose-Graft-Poly-(ε-Caprolactone)Copolymers

Due to the increasing demand for modified polylactide(PLA)meeting“double green”criteria,the research on sustainable plasticizers for PLA has attracted broad attentions.This study reported an open-ring polymerization method to fabricate cellulose(MCC)-g-PCL(poly(ε-caprolactone))copolymers with a fully sustainable and biodegradable component.MCC-g-PCL copolymers were synthesized,characterized,and used as green plasticizers for the PLA toughening.The results indicated that the MCC-g-PCL derivatives play an important role in the compatibility,crystallization,and toughening of the PLA/MCC-g-PCL composites.The mechanical properties of the fully bio-based PLA/MCC-g-PCL composites were optimized by adding 15 wt%MCC-g-PCL,that is,the elongation at break was 22.6%(~376%higher than that of neat PLA),the tensile strength was 47.3 MPa(comparable to that of neat PLA),and the impact strength was 26 J/m(~130%higher than that of neat PLA).DSC results indicated that MCC-g-PCL reduced the Tg of the PLA blend.When the addition amount was 15 wt%,the Tg of the blend was 58.4°C.Compared with MCC,MCC-g-PCL polyester plasticizer has better thermal stability,T5%(°C)can still be maintained above 300°C.The rheological results showed that MCC-g-PCL acted as a plasticizer,the introduction of PCL flexible chain increased the mobility of PLA molecular chain,and decreased the complex viscosity,storage modulus and loss modulus of PLA blends.The MCC-g-PCL derivatives,as a new green plastic additive,have shown an interesting prospect to prepare fully bio-based composites.

Effect of high pressure on microstructure of cast Mg-8Zn-0.5Zr-0.5Gd alloy

Mg-8Zn-0.5Zr-0.5Gd alloy was prepared by high pressure solidification. Effect of high pressure on microstructure, micro-hardness and corrosion behavior in Hank＇s solution of the Mg-8Zn-0.5Zr-0.5Gd alloy were investigated by means of optical microscopy （OM）, scanning electron microscopy （SEM）, energy dispersive spectroscopy （EDS）, and X-ray diffractometer （XRD）. The results showed that, compared with the conventional solidification, high pressure solidification obviously refined the grain size of Mg-8Zn-0.5Zr-0.5Gd alloy. The grain size was refined from 200-300 pm to 100-200 pm and the secondary dendrite arm spacing reduced from 30- 50 pm to 10-30 pro. Moreover, the solubility of Zn in the alloy increased and the amount and size of Mg-Zn-Gd phases significantly decreased. The micro-hardness of the alloy solidified under high pressure was improved significantly from 56.17 HV to 63.14 HV. The polarization resistance （Rp） of the alloy had a substantial increase in simulated body fluid, thus the corrosion rate was significantly reduced from 4.0 to 2.7 mm.year-1.

Towards Solar-Driven Formation of Robust and Self-Healable Waterborne Polyurethane Containing Disulfide Bonds via in-situ Incorporation of 2D Titanium Carbide MXene

Waterborne polymers are vital for coating industry to reduce carbon emissions.However,formation of robust and self-healable films at ambient temperature remains a challenge owing to high energy cost of film formation process.This work reports a solar-driven film formation of waterborne polyurethanes(WPUs)containing disulfide bonds via in-situ incorporation of 2D titanium carbide(MXene)with ability to convert light to heat.Instead of directly mixed with WPUs,MXene is added to join the reaction with isocyanate-terminated pre-polymer before emulsification process.This approach not only prevents aggregation of MXene in water but stabilizes MXene against thermal degradation which is the key hurdle for mass production of MXene/WPU composites.More importantly,our results show that mechanical performance of WPU films under visible light(100 mW/cm^(2))is overwhelmingly competitive with that processed in oven.Furthermore,the existence of disulfide bonds in PU chains enables fast self-healing of micro-cracks under natural visible light which could vanish completely within 40 min.The fractured specimens were repaired under natural visible light for 2 h,and the self-healing efficiency of tensile strength and elongation at break reached over 94.00%.

Selective core-shell doping enabling high performance 4.6 V-LiCoO_(2)

Constructing robust surface and bulk structure is the prerequisite for realizing high performance high voltage LiCoO_(2)(LCO).Herein,we manage to synthesize a surface Mg-doping and bulk Al-doping coreshell structured LCO,which demonstrates excellent cycling performance.Half-cell shows 94.2%capacity retention after 100 cycles at 3.0-4.6 V(vs.Li/Li^(+))cycling,and no capacity decay after 300 cycles for fullcell test(3.0-4.55 V).Based on comprehensive microanalysis and theoretical calculations,the degradation mechanisms and doping effects are systematically revealed.For the undoped LCO,high voltage cycling induces severe interfacial and bulk degradations,where cracks,stripe defects,fatigue H2 phase,and spinel phase are identified in grain bulk.For the doped LCO,Mg-doped surface shell can suppress the interfacial degradations,which not only stabilizes the surface structure by forming a thin rock-salt layer but also significantly improves the electronic conductivity,thus enabling superior rate performance.Bulk Al-doping can suppress the lattice"breathing"effect and the detrimental H3 to H1-3 phase transition,which minimizes the internal strain and defects growth,maintaining the layered structure after prolonged cycling.Combining theoretical calculations,this work deepens our understanding of the doping effects of Mg and Al,which is valuable in guiding the future material design of high voltage LCO.

High-throughput screening of CO_(2) cycloaddition MOF catalyst with an explainable machine learning model

The high porosity and tunable chemical functionality of metal-organic frameworks(MOFs)make it a promising catalyst design platform.High-throughput screening of catalytic performance is feasible since the large MOF structure database is available.In this study,we report a machine learning model for high-throughput screening of MOF catalysts for the CO_(2) cycloaddition reaction.The descriptors for model training were judiciously chosen according to the reaction mechanism,which leads to high accuracy up to 97%for the 75%quantile of the training set as the classification criterion.The feature contribution was further evaluated with SHAP and PDP analysis to provide a certain physical understanding.12,415 hypothetical MOF structures and 100 reported MOFs were evaluated under 100℃ and 1 bar within one day using the model,and 239 potentially efficient catalysts were discovered.Among them,MOF-76(Y)achieved the top performance experimentally among reported MOFs,in good agreement with the prediction.

A chlorinated lactone polymer donor featuring high performance and low cost

The development of low-bandgap nonfullerene acceptors and wide-bandgap polymer donors speeds up the advance of organic solar cells(OSCs)[1-17]. Wide-bandgap copolymers based on fused-ring acceptor units are ideal donor materials due to their low-lying HOMO levels, high hole mobilities and complementary light absorption to nonfullerene acceptors[18-25]. Currently, high-performance donors with 18%power conversion efficiencies(PCEs) belong to this type.

Unveiling the planar deformation mechanisms for improved formability in pre-twinned AZ31 Mg alloy sheet at warm temperature

To investigate the role of pre-twins in Mg alloy sheets during warm planar deformation,the stretch forming is conducted at 200℃.Results suggest the formability of the pre-twinned AZ31 Mg alloy sheet is enhanced to 11.30 mm.The mechanisms for the improved formability and the deformation behaviors during the planar stretch forming are systematically investigated based on the planar stress states.The Schmid factor for deformation mechanisms are calculated,the results reveal that planar stress states extremely affect the Schmid factor for{10-12}twinning.The detwinning is activated and the prismatic slip is enhanced in the pre-twinned sheet,especially under the planar extension stress state in the outer region.Consequently,the thickness-direction strain is accommodated better.The dynamic recrystallization(DRX)type is continuous DRX(CDRX)regardless of the planar stress state.However,the CDRX degree is greater under the planar extension stress state.Some twin lattices deviate from the perfect{10-12}twinning relation due to the planar compression stress state and the CDRX.The basal texture is weakened when the planar stress state tends to change the texture components.

An ultra-porous g-C_(3)N_(4) micro-tube coupled with MXene(Ti_(3)C_(2)TX)nanosheets for efficient degradation of organics under natural sunlight

It remains as a challenge for realizing efficient photo-responsive catalysts towards largescale degradation of organic pollutants under natural sunlight.This work reports a new pore engineering strategy for creating ultra-porous g-C_(3)N_(4) micro-tubes with an unprecedentedly high specific surface area of 152.96 m^(2)/g.This is mainly associated with releasing internal vapor pressure in the autoclave where the hydrothermal treatment of the urea/melamine mixture is processed.Supported by microscopic observation,porosity measurement and spectroscopic characterization,it is found that releasing the pressure at halfway of hydrothermal process is vital for forming exfoliated rod-like precursors and the de-aggregation of these rods presents substantial benefits on the production of mesopores on g-C_(3)N_(4) microtubes during the calcination of precursors.This offers a large number of reactive sites required by photocatalytic reaction.Coupling these micro-tubes with Ti_(3)C_(2)T_(X) nanosheets via electrostatic interaction yields a 1D/2D heterojunction with a close interfacial contact.The addition of metallically conductive Ti_(3)C_(2)T_(X) nanosheets accelerates the separation between electrons and holes,and also enhances the light absorption.All these merits of structural design lead to forming a group of highly efficient catalysts demonstrating an excellent photocatalytic degradation rate of k=0.0560 min^(-1)for RhB dyes under 100 mW/cm~2 visible light radiation that micks sunlight outdoors.This laboratory valuation is further supported by an outdoor test that shows a fast degradation rate of 0.0744 min^(-1)under natural sunlight.

Efficient capture of difluorocarbene by pyridinium 1,4-zwitterionic thiolates:A concise synthesis of difluoromethylene-containing 1,4-thiazine derivatives

A practical method for the construction of difluoromethylene-containing 1,4-thiazine moieties using readily available diethyl bromodifluoromethanephosphonate(BrCF_(2)PO(OEt)_(2))as difluorocarbene precusor has been developed.This transformation features the efficient capture of difluorocarbene by pyridinium 1,4-zwitterionic thiolates.A series of structurally novel and functionalized difluoromethylene-containing 1,4-thiazine derivatives were thus synthesized in good yields.

Gas-phase synthesis of Ti_(2)CCl_(2) enables an efficient catalyst for lithiumsulfur batteries

MXenes have aroused intensive enthusiasm because of their exotic properties and promising applications.However,to date,they are usually synthesized by etching technologies.Developing synthetic technologies provides more opportunities for innovation and may extend unexplored applications.Here,we report a bottom-up gas-phase synthesis of Cl-terminated MXene(Ti_(2)CCl_(2)).The gas-phase synthesis endows Ti_(2)CCl_(2) with unique surface chemistry,high phase purity,and excellent metallic conductivity,which can be used to accelerate polysulfide conversion kinetics and dramatically prolong the cyclability of Li-S batteries.In-depth mechanistic analysis deciphers the origin of the formation of Ti_(2)CCl_(2) and offers a paradigm for tuning MXene chemical vapor deposition.In brief,the gas-phase synthesis transforms the synthesis of MXenes and unlocks the hardly achieved potentials of MXenes.

Structures and formation mechanisms of dislocation-induced precipitates in relation to the age-hardening responses of Al-Mg-Si alloys

In the slightly deformed Al-Mg-Si alloys,dislocation-induced precipitates are frequently observed,and they usually line up,forming sophisticated precipitation microstructures.Using atomic-resolution electron microscopy in association with hardness measurements,we systematically investigated these precipitates in relation to the age-hardening responses of the alloys.Our study reveals that the majority of dislocation-induced complex precipitates are actually short-range ordered while long-range disordered polycrystalline precipitates and multiphase composite precipitates,including polycrystalline U2 precipitates,B’/U2,B’-2/U2,B’/B’-2/U2 and’/U2 composite precipitates.It is suggested that the formation of these complex precipitates is mainly owing to a high nucleation rate and rapid growth of different precipitate phases parallel to the associated dislocation lines.Since dislocation-induced precipitates consume more Mg than Si from the matrix and have a high formation kinetics,they will have different impacts on the matrix precipitation in different types of Al-Mg-Si alloys.Our results further demonstrate that for the"normally-β"-hardened"alloy,their formation leads to a coarser precipitate microstructure in the matrix,whereas for the"normally-β’-hardened"alloy,their formation reverses the precipitation pathway in the matrix,resulting in a reduced age-hardening potential of the former alloy and an improved age-hardening potential of the latter alloy.

An improved neural network model for prediction of mechanical properties of magnesium alloys

An improved neural network model was developed for prediction of mechanical properties in the de-sign and development of new types of magnesium alloys by refining the types of input variables and using a more reasonable algorithm. The results showed that the improved model apparently decreased the prediction errors, and raised the accuracy of the prediction results. Better preprocessing parame-ters were found to be [0.15, 0.90] for the tensile strength, [0.1, 0.9] for the yield strength, and [0.15, 0.90] for the elongation. When the above parameters were used, the relativity for predicition of strength was bigger than 0.95. By using improved ANN analysis, more reasonable process parameters and compo- sition could be obtained in some magnesium alloys without addition of strontoum.

Abrasive wear behavior of PTFE for seal applications under abrasive-atmosphere sliding condition

Abrasive wear is a common failure phenomenon that often limits the service life of sealing elements. Evaluation and comparison of the abrasion resistance of polytetrafluoroethylene (PTFE) were conducted using Al2O3particleswithsizesintherange5to200 μmonapin-on-flattribo-testerunderdryreciprocatingsliding conditions at room temperature. Based on the examined worn surface characteristics of both PTFE and 316L stainless steel (as a counterpart) and the analyzed coefficient of friction (COF) evolutions, the wear mechanism and particle size effect have been explored in detail. The results demonstrate that the abrasive size is the main contributing factor, which can drastically impact the wear mechanism and tribological properties of tribo-pairs. The COF exhibits different evolution characteristics (trends) for different abrasive sizes. For moderate particle sizes, the COF trends become more complicated and the most evident wear of the metallic counterpart is evident. The activity behaviors of abrasives are dominated by the particle size. Particles can becomes embedded in one of the tribo-pair materials to plough-cut the counterpart, thus causing two-body abrasive wear. The abrasives can also behave as free rolling bodies, which play the role of third body to realize three-body "PTFE-abrasive-316L"abrasion. When abrasives are involved in the wear process, both the wear rate and COF of the metallic counterpart increase, but the material removal rate of the PTFE is reduced. The results obtained can offer guidelines regarding the design and protection of seals.

Fluorescence detection of hydroxyl radical generated from oxygen reduction on Fe/N/C catalyst

Pyrolyzed Fe/N/C catalyst has been considered as the most promising candidate to replace Pt for oxygen reduction reaction(ORR) in fuel cells.However,poor stability of Fe/N/C catalyst,mainly attributed to the oxidation corrosion by aggressive ·OH radical,severely hampers its applications.However,the exact mechanism for generation of ·OH is unclear yet.Herein,we developed a fluorescent method to effectively detect ·OH generated from ORR on Fe/N/C catalyst by using coumarin as a fluorescent probe.A great difference in potential dependence between ·OH and H2O2 generated from the ORR was observed,which suggests that ·OH is not generated from the decomposition of H2O2 as traditional viewpoint.

Atomic-scale roles of Zn element in age-hardened AlMgSiZn alloys

Adding alloying elements to improve the performances or the manufacturing processes of Al-Mg-Si alloys has long been a serious issue in developing advanced automotive aluminum materials.The Zn element,among those promising ones,has demonstrated positive alloying effects on Al-Mg-Si alloys.However,the atomic-scale roles of Zn in an age-hardened Al-Mg-Si-Zn alloy have not been adequately understood.Using atomic-resolution electron microscopy,here we report the precise locations of Zn elements in all hardening precipitates involved and their alloying mechanism at the atomic scale when alloying the alloy.Our results show that Zn atoms enter all the major hardening phases to occupy specific featured atomic sites of the original elements,e.g.the Si1 and Mg2 sites in theβ’-2 phase,and modify their crystal structures,interfacial structures and morphologies in characteristic manners.It is revealed that for theβ’-phase,Zn atoms occupy unique atomic sites,whereas for other phases,they demonstrate similar behaviors as other additive alloying elements such as Ag and Cu do.