This work reveals the significant effects of cobalt(Co)on the microstructure and impact toughness of as-quenched highstrength steels by experimental characterizations and thermo-kinetic analyses.The results show that ...This work reveals the significant effects of cobalt(Co)on the microstructure and impact toughness of as-quenched highstrength steels by experimental characterizations and thermo-kinetic analyses.The results show that the Co-bearing steel exhibits finer blocks and a lower ductile-brittle transition temperature than the steel without Co.Moreover,the Co-bearing steel reveals higher transformation rates at the intermediate stage with bainite volume fraction ranging from around 0.1 to 0.6.The improved impact toughness of the Co-bearing steel results from the higher dense block boundaries dominated by the V1/V2 variant pair.Furthermore,the addition of Co induces a larger transformation driving force and a lower bainite start temperature(BS),thereby contributing to the refinement of blocks and the increase of the V1/V2 variant pair.These findings would be instructive for the composition,microstructure design,and property optimization of high-strength steels.展开更多
This article examines the influence of annealing temperature on fracture toughness and forming limit curves of dissimilar aluminum/silver sheets.In the cold roll bonding process,after brushing and acid washing,the pre...This article examines the influence of annealing temperature on fracture toughness and forming limit curves of dissimilar aluminum/silver sheets.In the cold roll bonding process,after brushing and acid washing,the prepared surfaces are placed on top of each other and by rolling with reduction more than 50%,the bonding between layers is established.In this research,the roll bonding process was done at room temperature,without the use of lubricants and with a 70%thickness reduction.Then,the final thickness of the Ag/Al bilayer sheet reached 350μm by several stages of cold rolling.Before cold rolling,it should be noted that to decrease the hardness created due to plastic deformation,the roll-bonded samples were subjected to annealing heat treatment at 400℃for 90 min.Thus,the final samples were annealed at 200,300 and 400℃for 90 min and cooled in a furnace to examine the annealing temperature effects.The uniaxial tensile and microhardness tests measured mechanical properties.Also,to investigate the fracture mechanism,the fractography of the cross-section was examined by scanning electron microscope(SEM).To evaluate the formability of Ag/Al bilayer sheets,forming limit curves were obtained experimentally through the Nakazima test.The resistance of composites to failure due to cracking was also investigated by fracture toughness.The results showed that annealing increases the elongation and formability of the Ag/Al bilayer sheet while reduces the ultimate tensile strength and fracture toughness.However,the changing trend is not the same at different temperatures,and according to the results,the most significant effect is obtained at 300℃and aluminum layers.It was also determined that by increasing annealing temperature,the fracture mechanism from shear ductile with small and shallow dimples becomes ductile with deep cavities.展开更多
Hydrogel scaffolds have numerous potential applications in the tissue engineering field.However,tough hydrogel scaffolds implanted in vivo are seldom reported because it is difficult to balance biocompatibility and hi...Hydrogel scaffolds have numerous potential applications in the tissue engineering field.However,tough hydrogel scaffolds implanted in vivo are seldom reported because it is difficult to balance biocompatibility and high mechanical properties.Inspired by Chinese ramen,we propose a universal fabricating method(printing-P,training-T,cross-linking-C,PTC&PCT)for tough hydrogel scaffolds to fill this gap.First,3D printing fabricates a hydrogel scaffold with desired structures(P).Then,the scaffold could have extraordinarily high mechanical properties and functional surface structure by cycle mechanical training with salting-out assistance(T).Finally,the training results are fixed by photo-cross-linking processing(C).The tough gelatin hydrogel scaffolds exhibit excellent tensile strength of 6.66 MPa(622-fold untreated)and have excellent biocompatibility.Furthermore,this scaffold possesses functional surface structures from nanometer to micron to millimeter,which can efficiently induce directional cell growth.Interestingly,this strategy can produce bionic human tissue with mechanical properties of 10 kPa-10 MPa by changing the type of salt,and many hydrogels,such as gelatin and silk,could be improved with PTC or PCT strategies.Animal experiments show that this scaffold can effectively promote the new generation of muscle fibers,blood vessels,and nerves within 4 weeks,prompting the rapid regeneration of large-volume muscle loss injuries.展开更多
[Objectives]To explore the mediating effect of social support between depression and resilience in elderly patients with first-episode stroke.[Methods]The general information questionnaire,PHQ-9 depression screening s...[Objectives]To explore the mediating effect of social support between depression and resilience in elderly patients with first-episode stroke.[Methods]The general information questionnaire,PHQ-9 depression screening scale,Social Support Rating scale and Connor-Davidson Resilience Scale were used to construct and test the mediation model.[Results]The total score of depressive symptoms was(8.64±3.28)points,the detection rate of depressive symptoms was 51.65%,the score of social support was(37.28±5.98)points,and the score of psychological resilience was(22.05±5.25)points.The resilience of patients was positively correlated with social support(r=0.470,P<0.01),and negatively correlated with depressive symptoms(r=-0.470,P<0.01).Social support was negatively correlated with depressive symptoms(r=-0.523,P<0.01).Social support played a partial mediating role between depression and resilience in elderly patients with first-episode stroke,and the mediating effect accounted for 16.1%of the total effect.[Conclusions]Social support can mediate the effect of depression on resilience in elderly patients with first-episode stroke.Medical staff can improve patients'psychological resilience by psychological counseling of depression and improving their social support,so as to promote their subjective well-being and maintain a healthy and positive mental state.展开更多
Inspired by brick-and-mortar architectures and suture interfaces,we propose a design of bioinspired nacre-like materials with interlocking sutures to improve the toughness of brittle materials.Laser-engraved glass int...Inspired by brick-and-mortar architectures and suture interfaces,we propose a design of bioinspired nacre-like materials with interlocking sutures to improve the toughness of brittle materials.Laser-engraved glass interlockers are laminated with soft interlayers in a staggered arrangement,and the fundamental mechanical properties of the structure are investigated through experiments and numerical modeling.It is found that the tensile performance,such as the strength and toughness,is strongly affected by the interlocking angle and suture line spacing.The geometric interlocking originated from suture interfaces as well as tablet sliding arising from the staggered arrangement of interlockers cooperatively contribute to enhancing the strength and toughness of this bioinspired design.Additionally,the finite element modeling shows the interfacial failure and plastic deformation,revealing the interplay of the geometric interlocking mechanism and the sliding mechanism.This novel bioinspired design paves a new path for fabrication of structural materials combining high stiffness,high strength,and enhanced toughness.展开更多
Integrated conductive elastomers with excellent mechanical performance,stable high conductivity,self-healing capabilities,and high transparency are critical for advancing wearable devices.Nevertheless,achieving an opt...Integrated conductive elastomers with excellent mechanical performance,stable high conductivity,self-healing capabilities,and high transparency are critical for advancing wearable devices.Nevertheless,achieving an optimal balance among these properties remains a significant challenge.Herein,through in situ free-radical copolymerization of 2-[2-(2-methoxyethoxy)ethoxy]ethyl acrylate(TEEA)and vinylimidazole(VI)in the presence of polyethylene glycol(PEG;Mn=400),tough P(TEEA-co-VI)/PEG elastomers with multiple functionalities were prepared,in which P(TEEA-co-VI)was dynamically cross-linked by imidazole-Zn^(2+)metal coordination crosslinks,and physically blended with PEG as polymer electrolyte to form a homogeneous mixture.Notably,Zn^(2+)has a negligible impact on the polymerization process,allowing for the in situ formation of numerous imidazole-Zn^(2+)metal coordination crosslinks,which can effectively dissipate energy upon stretching to largely reinforce the elastomers.The obtained P(TEEA-co-VI)/PEG elastomers exhibited a high toughness of 10.0 MJ·m^(-3) with a high tensile strength of 3.3 MPa and a large elongation at break of 645%,along with outstanding self-healing capabilities due to the dynamic coordination crosslinks.Moreover,because of the miscibility of PEG with PTEEA copolymer matrix,and Li+can form weak coordination interactions with the ethoxy(EO)units in PEG and PTEEA,acting as a bridge to integrate PEG into the elastomer network.The resulted P(TEEA-co-VI)/PEG elastomers showed high transparency(92%)and stable high conductivity of 1.09×10_(-4) S·cm^(-1).In summary,the obtained elastomers exhibited a well-balanced combination of high toughness,high ionic conductivity,excellent self-healing capabilities,and high transparency,making them promising for applications in flexible strain sensors.展开更多
Supramolecular materials that combine toughness,transparency,self-healing,and environmental stability are crucial for advanced applications,such as flexible electronics,wearable devices,and protective coatings.However...Supramolecular materials that combine toughness,transparency,self-healing,and environmental stability are crucial for advanced applications,such as flexible electronics,wearable devices,and protective coatings.However,integrating these properties into a single system remains challenging because of the inherent trade-offs between the mechanical strength,elasticity,and structural reconfigurability.Herein,we report a supramolecular ionogel designed via a simple one-step polymerization strategy that combines hydrogen bonding and ion-dipole interactions in a physically crosslinked network.This dual-interaction architecture enables the ionogel to achieve high tensile strength(9 MPa),remarkable fracture toughness(23.6 MJ·m^(−3)),and rapid self-healing under mild thermal stimulation.The material remains highly transparent and demonstrates excellent resistance to moisture,acid,and salt environments,with minimal swelling and performance degradation.Furthermore,it effectively dissipates over 80 MJ·m^(−3) of energy during high-speed impacts,providing reliable protection to fragile substrates.This study offers a broadly applicable molecular design framework for resilient and adaptive soft materials.展开更多
Mechanically robust transparent materials that can be repaired have many advantages for practical applications.In this study,a supramolecular strategy is used to introduce healing capacity and mechanical toughness int...Mechanically robust transparent materials that can be repaired have many advantages for practical applications.In this study,a supramolecular strategy is used to introduce healing capacity and mechanical toughness into artificial glass.Non-covalent/dynamic covalent polymerization of thioctic acid(TA)and(±)-trans-1,2-diaminocyclohexane(DC)generates supramolecular glass with versatile attractive properties,including high optical transmittance(>90%),strong impact resistance(2.47 k J/m^(2)),good mechanical strength(21.6 MPa),and high rigidity(65 HD on Shore hardness).The adhesive bonding of poly[TA],along with its photopolymerization behavior,enables damaged areas in poly[DC/TA]to be rebuilt in-situ.Subsequent solidification and hardening of the repaired areas are notably accelerated by hydrogen bonding between poly[TA]and DC.The newly healed poly[DC/TA]exhibits considerable optical and mechanical properties compared to those of untreated poly[DC/TA].This study presents a new design concept for constructing the high-performance glass from low-molecular-weight organic compounds.展开更多
Coal and rock dynamic disasters are always major hidden dangers threatening mine safety production.Many researchers use cement concrete material as filling and energy-absorption materials.However,the current material ...Coal and rock dynamic disasters are always major hidden dangers threatening mine safety production.Many researchers use cement concrete material as filling and energy-absorption materials.However,the current material toughness is not sufficient to meet the requirements of mine disaster prevention.Based on this,in order to find the optimal-ratio material that combines strength and toughness,the synergistic mechanism of lithium slag(LS),ethylene-vinyl acetate(EVA)copolymer,and polyvinyl alcohol(PVA)fiber mixtures in improving the mechanical properties of cement concrete,as well as the mechanism of microscopic phase evolution,was analyzed through macroscopic experiments,mesoscopic characterization,microscopic analysis,theoretical calculations,and comprehensive evaluation.The stress-strain curves obtained from the uniaxial compressive strength tests of specimens with different admixtures and fibers were investigated,and the characteristics of different stages were analyzed.The mechanical properties of different admixtures and fiber-reinforced materials,including their advantages and disadvantages,were compared through weighted comprehensive evaluation.The entire process of material failure,ranging from pore compaction,crack initiation,crack propagation,specimen instability to crack penetration,was explained via macroscopic fracture morphology,and the mechanical mechanism of how different admixtures affect the mechanical properties of concrete materials was revealed.The microscopic mechanism and the phase-evolution process of how the admixture affects concrete properties were elucidated using X-ray diffraction(XRD),hydration reaction theory,and Fourier transform infrared spectroscopy(FTIR).Furthermore,scanning electron microscopy-energy dispersive spectroscopy(SEM-EDS)was used to reveal the interfacial pore state and element distribution of the internal microstructure of concrete.The results show that PVA fiber bars can play the role of a“skeleton bridge”to improve the toughness of materials.LS can effectively promote the hydration process and cooperate with PVA fiber bars to enhance the mechanical properties of the material.EVA will inhibit the hydration reaction and degrade the material’s mechanical properties through the“organic isolation”effect.In addition,the on-site application has proven that the R3-group materials in this study can effectively inhibit the deformation of the roadway and possess strong reliability.Finally,the advantages and feasibility of LS-and-fiber-reinforced concrete were discussed from four perspectives:environmental protection,economy,disaster prevention,and development.This paper is expected to provide technical reference for the large-scale disposal of solid waste LS,the performance-optimization direction of concrete materials,and the prevention and control of coal and rock dynamic disasters.展开更多
Polyaniline(PANi)hydrogels have a wide range of applications in artificial skin,flexible robotics,and movement monitoring.Nevertheless,limited by the modulus mismatch between rigid PANi and the soft hydrogel matrix,th...Polyaniline(PANi)hydrogels have a wide range of applications in artificial skin,flexible robotics,and movement monitoring.Nevertheless,limited by the modulus mismatch between rigid PANi and the soft hydrogel matrix,the high strength and toughness of the PANi hydrogel are mutually exclusive.Although the introduction of sacrificial bonds into the hydrogel network can alleviate this contradiction to a certain extent,it always causes pronounced energy hysteresis during hydrogel deformation.Inspired by the energy storage and release of macroscopic springs,in this work,we propose a molecular entanglement approach for the fabrication of PANi hydrogels featuring high toughness and low hysteresis,where flexible poly(ethylene glycol)(PEG)is entangled with chemically cross-linked poly(acrylic acid)(PAA)as a hydrogel matrix,and rigid PANi as a conductive filler.The resultant PAA/PEG/PANi hydrogel exhibited high mechanical properties(fracture strength of 0.75 MPa and toughness of 4.81 MJ·m^(-3))and a low energy dissipation ratio(28.2%when stretching to 300%).Moreover,the PAA/PEG/PANi hydrogel possesses a good electrical response to external forces and can be employed as a strain sensor to monitor human joint movements by producing specific electrical signals.This work provides a straightforward strategy for preparing tough conductive PANi hydrogels with low hysteresis,showing potential for the development of healthcare devices.展开更多
The effect ofωiso andαprecipitation on microstructure,microhardness,tensile properties and impact toughness of Ti-25Nb-10Ta-1Zr-0.2Fe(TNTZF)alloy was investigated.The results showed that the solution treated TNTZF a...The effect ofωiso andαprecipitation on microstructure,microhardness,tensile properties and impact toughness of Ti-25Nb-10Ta-1Zr-0.2Fe(TNTZF)alloy was investigated.The results showed that the solution treated TNTZF alloy with a small amount of nano-sizedωath particles inβmatrix possesses tensile strength of 697 MPa,elongation of~34%,Young’s modulus(YM)of 75 GPa,and impact toughness of 58.7 J/cm^(2).After aging at relatively lower temperatures of 400℃,the hardness and modulus of the alloy increased significantly,while the plasticity and toughness dropped sharply due to the precipitation ofωiso phase.ωiso phase displayed an ellipsoidal morphology with high volume fraction and a size of about 50 nm after aging at 400℃,leading to the highest hardness of 364 HV and YM of 108 GPa,along with completely embrittlement since elongation and toughness were almost zero.A brittle impact fracture morphology was observed in the alloy,which is dominated by intergranular fracture,with a mixed fracture characteristics of cleavage surfaces,terraces and tiny dimples.When aged at 550℃,plate-likeαdistributed inβmatrix uniformly and inβgrain boundaries in parallel,resulting in the high strength of 804 MPa,as well as lowest YM of 72 GPa,elongation of 9%and toughness of 35.8 J/cm^(2).The fracture morphology of the alloy aged at 550℃showed a ductile fracture mechanism with a large number of dimples.展开更多
Proteoglycans,key components of non-collagenous proteins in the bone matrix,attract water through their negatively charged glycosaminoglycan chains.Among these proteoglycans,biglycan(Bgn)and decorin(Dcn)are major subt...Proteoglycans,key components of non-collagenous proteins in the bone matrix,attract water through their negatively charged glycosaminoglycan chains.Among these proteoglycans,biglycan(Bgn)and decorin(Dcn)are major subtypes,yet their distinct roles in bone remain largely elusive.In this study,we utilized single knockout(KO)mouse models and successfully generated double KO(dKO)models despite challenges with low yield.Bgn deficiency,but not Dcn deficiency,decreased trabecular bone mass,with more pronounced bone loss in dKO mice.Low-field nuclear magnetic resonance measurements showed a marked decrease in bound water among all KO groups,especially in Bgn KO and dKO mice.Moreover,both Bgn KO and dKO mice exhibited reduced fracture toughness compared to Dcn KO mice.Dcn was significantly upregulated in Bgn KO mice,while a modest upregulation of Bgn was observed in Dcn KO mice,indicating Bgn’s predominant role in bone.High resolution atomic force microscopy showed decreased in situ permanent energy dissipation and increased elastic modulus in the extrafibrillar matrix of Bgn/Dcn deficient mice,which were diminished upon dehydration.Furthermore,we found that both Bgn and Dcn are indispensable for the activation of ERK and p38 MAPK signaling pathways.Collectively,our results highlight the distinct and indispensable roles of Bgn and Dcn in maintaining bone structure,water retention,and bulk/in situ tissue properties in the bone matrix,with Bgn exerting a predominant influence.展开更多
The effects of isocyanate(IA)incorporation on the toughness and volume stability of AAFS were systematically investigated.Various IA dosages were introduced into AAFS,and their influence on mechanical properties,micro...The effects of isocyanate(IA)incorporation on the toughness and volume stability of AAFS were systematically investigated.Various IA dosages were introduced into AAFS,and their influence on mechanical properties,microstructure,and shrinkage behavior was evaluated.The experimental results indicate that,with the incorporation of 5%IA,the 28-day compressive strength reaches 48.6 MPa,the 56-day drying shrinkage decreases by 35.91%,and minimal cracking is observed in the ring test.Microstructural analyses using SEM,XRD,and FTIR reveal that IA reacts with water to form urethane and biuret,which crosslinks into a durable network structure.This network fills pores,reducing internal stresses and improving both toughness and volume stability.These findings offer new insights into optimizing alkali-activated materials for construction applications and provide a potential pathway for the development of more durable and stable geopolymers.展开更多
The demand for oil casing steel with ultra-high strength and excellent impact toughness for safe application in ultra-deep wells is pressing.In improving the combination of strength,ductility,and impact toughness,the ...The demand for oil casing steel with ultra-high strength and excellent impact toughness for safe application in ultra-deep wells is pressing.In improving the combination of strength,ductility,and impact toughness,the designed Cr-Mo-V micro-alloyed oil casing steel was quenched at 800,900,and 1000℃,followed by tempering at 600,680,and 760℃,respectively,to obtain distinct microstruc-tures.The results showed that the microstructure of the samples quenched at 800℃ followed by tempering comprised untransformed ferrite and large undissolved carbides,which considerably deteriorated tensile strength and impact toughness.For other conditions,the nuc-leated carbides and the boundaries are key factors that balance the tensile strength from 1226 to 971 MPa and the impact toughness from 65 to 236 J.From the perspective of carbide,optimal precipitation strengthening is achieved with a smaller carbide size obtained by a low tempering temperature of 600℃,while larger-sized carbides would remarkably soften the matrix to improve the toughness but deteriorate the tensile strength.Additionally,an increase in prior austenite grain size with the corresponding enlarged sub-boundaries obtained by high quenching temperatures substantially diminishes grain refinement strengthening,dislocation strengthening,and the energy absorbed in the crack propagation process,which is unfavorable to strength and toughness.展开更多
Electrically conductive carbide ceramics with high hardness and fracture toughness are promising for advanced applications.However,enhancing both electrical conductivity and fracture toughness simultaneous is challeng...Electrically conductive carbide ceramics with high hardness and fracture toughness are promising for advanced applications.However,enhancing both electrical conductivity and fracture toughness simultaneous is challenging.This study reports the synthesis of(Ti_(0.2)W_(0.2)Ta_(0.2)Hf_(0.2)Mo_(0.2))C-diamond composites with varying densities using high-pressure and high-temperature(HPHT)method.The carbides are uniformly dispersed in a titanium carbide matrix,forming conductive channels that reduce resistivity to 4.6×10^(-7)W·m.These composite materials exhibit metallic conductivity with a superconducting transition at 8.5 K.Superconducting behavior may result from d-p orbital hybridization and electron-phonon coupling in transition metal carbides,such as TaC,Mo_(2)C,and MoC.Optimizing intergranular bonding improves the fracture toughness without compromising hardness.The highest indentation toughness value is 10.1±0.4 MPa·m^(1/2),a 130%increase compare to pure TiC.Enhanced toughness arises from transgranular and intergranular fracture modes,multiple crack bridging,and large-angle crack deflection,which dissipate fracture energy and inhibit crack propagation.This study introduces a novel microstructure engineering strategy for carbide ceramics to achieve superior mechanical and electrical properties.展开更多
Poly(vinyl alcohol)(PVA)is a biodegradable and environmentally friendly material known for its gas barrier characteristics and solvent resistance.However,its flammability and water sensitivity limit its application in...Poly(vinyl alcohol)(PVA)is a biodegradable and environmentally friendly material known for its gas barrier characteristics and solvent resistance.However,its flammability and water sensitivity limit its application in specialized fields.In this study,phytic acid(PA)was introduced as a halogen-free flame retardant and biochar(BC)was introduced as a reinforcement to achieve both flame resistance and mechanical robustness.We thoroughly investigated the effects of BC particle sizes(100-3000 mesh)and addition amounts(0 wt%-10 wt%),as well as PA addition amounts(0 wt%-15 wt%),on the properties of PVA composite films.Notably,the PA10/1000BC5 composite containing 10 wt%PA and 5 wt%1000 mesh BC exhibited optimal properties.The limiting oxygen index increased to 39.2%,and the UL-94 test achieved a V-0 rating.Additionally,the PA10/1000BC5 composite film demonstrated significantly enhanced water resistance,with a swelling ratio reaching 800%without dissolving,unlike that of the control PVA.The water contact angle was 70°,indicating that hydrophilic properties remained essentially unaffected.Most importantly,the tensile modulus and elongation at break were 213 MPa and 281.7%,respectively,nearly double those of the PVA/PA composite film.This study presents an efficient and straightforward method for preparing PVA composite films that are flame-retardant,tough,and waterresistant,expanding their potential applications in various fields.展开更多
This work used 5CrMnMo steel and titanium carbide(TiC)powders to fabricate particulate metal matrix composites(PMMCS).The composites’microstructure,hardness,and impact toughness were compared with four different tita...This work used 5CrMnMo steel and titanium carbide(TiC)powders to fabricate particulate metal matrix composites(PMMCS).The composites’microstructure,hardness,and impact toughness were compared with four different titanium carbide ceramic particle sizes.The phase composition and microstructure of composites were studied.Vickers hardness and Charpy impact tests were employed to analyze composites’hardness and impact ductility,respectively.The results showed that the four groups of composites are mainly composed of martensite,trace residual austenite,and titanium carbide(undissolved TiC and primary TiC particles).With the growth of the ceramic particle dimension in the composite layer,the number of primary titanium carbide ceramics gradually decreased.When the initial ceramic particle size was small,it tended to generate dendritic primary TiC,and when the particle size was large,it tended to generate polygons and ellipsoids.Furthermore,with the growth of titanium carbide ceramic particle dimension in the composites,the hardness of the composites decreased but the impact toughness of the composites rose first and then descended.When the ceramic particle size was 50-75μm,the composite had the highest hardness,and the impact energy of the composites was the highest,which is 8 J.This was because there were more undissolved titanium carbide ceramics in the composite,and there was a thicker matrix metal between the ceramic particles.展开更多
Because of the large coefficient of thermal expansion (CTE) (23 ppm K^(–1)), aluminum faces challenges in meeting the demands of high dimensional stability in precision instruments, microelectronics, and aerospace. F...Because of the large coefficient of thermal expansion (CTE) (23 ppm K^(–1)), aluminum faces challenges in meeting the demands of high dimensional stability in precision instruments, microelectronics, and aerospace. Filling negative thermal expansion (NTE) particles into aluminum can create composites with either zero or low CTEs. However, the resulting composites usually have poor thermal conductivity due to their monolithic configuration, i.e., the NTE particles are filled randomly. Thus, heat sinks should be equipped to assist their usage (e.g., in thermal management). This in turn causes strong thermal stress in the packaging system owing to the high contrast in the CTEs between those monolithic composites and heat sinks typically made of copper or aluminum. Here, we propose a gradient configuration for low-CTE aluminum composite, inspired by the bamboo structure. The gradient distribution of NTE particles (Zn_(0.5)Sn_(0.3)Mn_(0.2)NMn_(3), ZSM) was obtained by laying up several layers of ZSM/Al with the ZSM fraction ranging from 0 to 28 vol.%. In the gradient composite, the CTE near room temperature varies from 3.4 pm K^(–1) on one side to 21 ppm K^(–1) on the other side. Such a gradient CTE distribution would facilitate the low-thermal-stress designs and thus help stabilize the dimension of a precision system. Furthermore, this composite has a high thermal conductivity of 130 W m^(–1) K^(–1) and strong toughness when the flexural loading is applied on the 28 vol.% ZSM/Al side. Our research provides a novel approach to designing metallic matrix composites with unprecedented performance.展开更多
The toughness of thermoplastic polymers such as polypropylene(PP)can be improved by adding elastomers-based toughening agents,and the phase morphology of these toughening agents is very important for the strength and ...The toughness of thermoplastic polymers such as polypropylene(PP)can be improved by adding elastomers-based toughening agents,and the phase morphology of these toughening agents is very important for the strength and toughness of PP.The low-temperature toughness of PP was improved by inserting high-density polyethylene(HDPE)between PP and polystyrene-b-ethylene-co-propyleneb-polystyrene(SEPS)to form an unusual SEPS@HDPE core–shell structure,with SEPS as the core and HDPE as the shell.Based on the microtopography and rheological behavior characterization,HDPE in PP/SEPS/HDPE composites was found to serve as an emulsifier,decrease the size of SEPS particles,and promote the homogeneous dispersion of dispersed phase particles in the matrix.An increase in the HDPE content shifted the toughening mechanism of PP composites from cavitation to matrix shear yielding.The reduction in the distance between the dispersed core–shell structure particles promoted shear yielding in the PP composites,leading to increased toughness.The creation of an intermediate HDPE layer with a moderate modulus was crucial for dispersing stress concentrations and significantly improving toughness without compromising the tensile strength.These findings will facilitate the fabrication of high-toughness PP products at low temperatures.展开更多
The effects of Ti/N ratio on the number densities of nano particles,the size of the prior austenite grain(PAG)and the toughness of the heat-affected zone(HAZ)of Mg-deoxidized steels were studied after high heat input ...The effects of Ti/N ratio on the number densities of nano particles,the size of the prior austenite grain(PAG)and the toughness of the heat-affected zone(HAZ)of Mg-deoxidized steels were studied after high heat input welding of 400 kJ/cm.With increasing the Ti/N ratio from 2.7 to 5.7,the cuboid nano-sized particles are formed,and their number density increases.The area fractions of ductile intragranular acicular ferrites(IAFs)have the highest value and the area fractions of brittle microstructures of ferrite side plates and upper bainites have the lowest value in TN30 steel.With the Ti/N ratio of about 3.0,the HAZ of steel plate has the best low-temperature toughness.With increasing the Ti/N ratio from 2.7 to 5.7,the PAG sizes after the high-temperature laser scanning confocal microscopy observation decrease linearly with increasing the number densities of nano-sized particles.The PAG size of TN30 steel is between 100 and 150μm,which is conducive to the nucleation of IAFs.展开更多
基金supported by the National Natural Science Foundation of China(No.52271089)the financial support from the C hina Postdoctoral Science Foundation(No.2023M732192)。
文摘This work reveals the significant effects of cobalt(Co)on the microstructure and impact toughness of as-quenched highstrength steels by experimental characterizations and thermo-kinetic analyses.The results show that the Co-bearing steel exhibits finer blocks and a lower ductile-brittle transition temperature than the steel without Co.Moreover,the Co-bearing steel reveals higher transformation rates at the intermediate stage with bainite volume fraction ranging from around 0.1 to 0.6.The improved impact toughness of the Co-bearing steel results from the higher dense block boundaries dominated by the V1/V2 variant pair.Furthermore,the addition of Co induces a larger transformation driving force and a lower bainite start temperature(BS),thereby contributing to the refinement of blocks and the increase of the V1/V2 variant pair.These findings would be instructive for the composition,microstructure design,and property optimization of high-strength steels.
基金Project(4013311)supported by the National Science Foundation of Iran(INSF)。
文摘This article examines the influence of annealing temperature on fracture toughness and forming limit curves of dissimilar aluminum/silver sheets.In the cold roll bonding process,after brushing and acid washing,the prepared surfaces are placed on top of each other and by rolling with reduction more than 50%,the bonding between layers is established.In this research,the roll bonding process was done at room temperature,without the use of lubricants and with a 70%thickness reduction.Then,the final thickness of the Ag/Al bilayer sheet reached 350μm by several stages of cold rolling.Before cold rolling,it should be noted that to decrease the hardness created due to plastic deformation,the roll-bonded samples were subjected to annealing heat treatment at 400℃for 90 min.Thus,the final samples were annealed at 200,300 and 400℃for 90 min and cooled in a furnace to examine the annealing temperature effects.The uniaxial tensile and microhardness tests measured mechanical properties.Also,to investigate the fracture mechanism,the fractography of the cross-section was examined by scanning electron microscope(SEM).To evaluate the formability of Ag/Al bilayer sheets,forming limit curves were obtained experimentally through the Nakazima test.The resistance of composites to failure due to cracking was also investigated by fracture toughness.The results showed that annealing increases the elongation and formability of the Ag/Al bilayer sheet while reduces the ultimate tensile strength and fracture toughness.However,the changing trend is not the same at different temperatures,and according to the results,the most significant effect is obtained at 300℃and aluminum layers.It was also determined that by increasing annealing temperature,the fracture mechanism from shear ductile with small and shallow dimples becomes ductile with deep cavities.
基金supported by the Innovative Research Group Project of the National Natural Science Foundation of China(T2121004)Key Programme(52235007)National Outstanding Youth Foundation of China(52325504).
文摘Hydrogel scaffolds have numerous potential applications in the tissue engineering field.However,tough hydrogel scaffolds implanted in vivo are seldom reported because it is difficult to balance biocompatibility and high mechanical properties.Inspired by Chinese ramen,we propose a universal fabricating method(printing-P,training-T,cross-linking-C,PTC&PCT)for tough hydrogel scaffolds to fill this gap.First,3D printing fabricates a hydrogel scaffold with desired structures(P).Then,the scaffold could have extraordinarily high mechanical properties and functional surface structure by cycle mechanical training with salting-out assistance(T).Finally,the training results are fixed by photo-cross-linking processing(C).The tough gelatin hydrogel scaffolds exhibit excellent tensile strength of 6.66 MPa(622-fold untreated)and have excellent biocompatibility.Furthermore,this scaffold possesses functional surface structures from nanometer to micron to millimeter,which can efficiently induce directional cell growth.Interestingly,this strategy can produce bionic human tissue with mechanical properties of 10 kPa-10 MPa by changing the type of salt,and many hydrogels,such as gelatin and silk,could be improved with PTC or PCT strategies.Animal experiments show that this scaffold can effectively promote the new generation of muscle fibers,blood vessels,and nerves within 4 weeks,prompting the rapid regeneration of large-volume muscle loss injuries.
基金Supported by the National Natural Science Foundation of China(71774049).
文摘[Objectives]To explore the mediating effect of social support between depression and resilience in elderly patients with first-episode stroke.[Methods]The general information questionnaire,PHQ-9 depression screening scale,Social Support Rating scale and Connor-Davidson Resilience Scale were used to construct and test the mediation model.[Results]The total score of depressive symptoms was(8.64±3.28)points,the detection rate of depressive symptoms was 51.65%,the score of social support was(37.28±5.98)points,and the score of psychological resilience was(22.05±5.25)points.The resilience of patients was positively correlated with social support(r=0.470,P<0.01),and negatively correlated with depressive symptoms(r=-0.470,P<0.01).Social support was negatively correlated with depressive symptoms(r=-0.523,P<0.01).Social support played a partial mediating role between depression and resilience in elderly patients with first-episode stroke,and the mediating effect accounted for 16.1%of the total effect.[Conclusions]Social support can mediate the effect of depression on resilience in elderly patients with first-episode stroke.Medical staff can improve patients'psychological resilience by psychological counseling of depression and improving their social support,so as to promote their subjective well-being and maintain a healthy and positive mental state.
基金Project supported by the National Natural Science Foundation of China(Nos.12202257,12072184,12002197)。
文摘Inspired by brick-and-mortar architectures and suture interfaces,we propose a design of bioinspired nacre-like materials with interlocking sutures to improve the toughness of brittle materials.Laser-engraved glass interlockers are laminated with soft interlayers in a staggered arrangement,and the fundamental mechanical properties of the structure are investigated through experiments and numerical modeling.It is found that the tensile performance,such as the strength and toughness,is strongly affected by the interlocking angle and suture line spacing.The geometric interlocking originated from suture interfaces as well as tablet sliding arising from the staggered arrangement of interlockers cooperatively contribute to enhancing the strength and toughness of this bioinspired design.Additionally,the finite element modeling shows the interfacial failure and plastic deformation,revealing the interplay of the geometric interlocking mechanism and the sliding mechanism.This novel bioinspired design paves a new path for fabrication of structural materials combining high stiffness,high strength,and enhanced toughness.
基金supported by the National Natural Science Foundation of China(Nos.52273023,51973103,and 21774069).
文摘Integrated conductive elastomers with excellent mechanical performance,stable high conductivity,self-healing capabilities,and high transparency are critical for advancing wearable devices.Nevertheless,achieving an optimal balance among these properties remains a significant challenge.Herein,through in situ free-radical copolymerization of 2-[2-(2-methoxyethoxy)ethoxy]ethyl acrylate(TEEA)and vinylimidazole(VI)in the presence of polyethylene glycol(PEG;Mn=400),tough P(TEEA-co-VI)/PEG elastomers with multiple functionalities were prepared,in which P(TEEA-co-VI)was dynamically cross-linked by imidazole-Zn^(2+)metal coordination crosslinks,and physically blended with PEG as polymer electrolyte to form a homogeneous mixture.Notably,Zn^(2+)has a negligible impact on the polymerization process,allowing for the in situ formation of numerous imidazole-Zn^(2+)metal coordination crosslinks,which can effectively dissipate energy upon stretching to largely reinforce the elastomers.The obtained P(TEEA-co-VI)/PEG elastomers exhibited a high toughness of 10.0 MJ·m^(-3) with a high tensile strength of 3.3 MPa and a large elongation at break of 645%,along with outstanding self-healing capabilities due to the dynamic coordination crosslinks.Moreover,because of the miscibility of PEG with PTEEA copolymer matrix,and Li+can form weak coordination interactions with the ethoxy(EO)units in PEG and PTEEA,acting as a bridge to integrate PEG into the elastomer network.The resulted P(TEEA-co-VI)/PEG elastomers showed high transparency(92%)and stable high conductivity of 1.09×10_(-4) S·cm^(-1).In summary,the obtained elastomers exhibited a well-balanced combination of high toughness,high ionic conductivity,excellent self-healing capabilities,and high transparency,making them promising for applications in flexible strain sensors.
基金supported by the National Natural Science Foundation of China(Nos.T2222019 and T2225016)the National Key R&D Program of China(No.2024YFA0919300)the Fundamental Research Funds for the Central Universities(Nos.020414380232 and 021414380534).
文摘Supramolecular materials that combine toughness,transparency,self-healing,and environmental stability are crucial for advanced applications,such as flexible electronics,wearable devices,and protective coatings.However,integrating these properties into a single system remains challenging because of the inherent trade-offs between the mechanical strength,elasticity,and structural reconfigurability.Herein,we report a supramolecular ionogel designed via a simple one-step polymerization strategy that combines hydrogen bonding and ion-dipole interactions in a physically crosslinked network.This dual-interaction architecture enables the ionogel to achieve high tensile strength(9 MPa),remarkable fracture toughness(23.6 MJ·m^(−3)),and rapid self-healing under mild thermal stimulation.The material remains highly transparent and demonstrates excellent resistance to moisture,acid,and salt environments,with minimal swelling and performance degradation.Furthermore,it effectively dissipates over 80 MJ·m^(−3) of energy during high-speed impacts,providing reliable protection to fragile substrates.This study offers a broadly applicable molecular design framework for resilient and adaptive soft materials.
基金the Natural Science Foundation of Hunan Province(No.2024JJ6202)the National Natural Science Foundation of China(No.22271087)+1 种基金the Outstanding Youth Scientist Foundation of Hunan Province(No.2021JJ10010)the Huxiang Young Talent Program from Hunan Province(No.2018RS3036)。
文摘Mechanically robust transparent materials that can be repaired have many advantages for practical applications.In this study,a supramolecular strategy is used to introduce healing capacity and mechanical toughness into artificial glass.Non-covalent/dynamic covalent polymerization of thioctic acid(TA)and(±)-trans-1,2-diaminocyclohexane(DC)generates supramolecular glass with versatile attractive properties,including high optical transmittance(>90%),strong impact resistance(2.47 k J/m^(2)),good mechanical strength(21.6 MPa),and high rigidity(65 HD on Shore hardness).The adhesive bonding of poly[TA],along with its photopolymerization behavior,enables damaged areas in poly[DC/TA]to be rebuilt in-situ.Subsequent solidification and hardening of the repaired areas are notably accelerated by hydrogen bonding between poly[TA]and DC.The newly healed poly[DC/TA]exhibits considerable optical and mechanical properties compared to those of untreated poly[DC/TA].This study presents a new design concept for constructing the high-performance glass from low-molecular-weight organic compounds.
基金supported by the National Natural Science Foundation of China(Nos.U23B2093 and 52034009)the National Key R&D Program of China(No.2024YFC3013801)the Fundamental Research Funds for the Central Universities(Ph.D.Top Innovative Talents Fund of CUMTB)(No.BBJ2025001).
文摘Coal and rock dynamic disasters are always major hidden dangers threatening mine safety production.Many researchers use cement concrete material as filling and energy-absorption materials.However,the current material toughness is not sufficient to meet the requirements of mine disaster prevention.Based on this,in order to find the optimal-ratio material that combines strength and toughness,the synergistic mechanism of lithium slag(LS),ethylene-vinyl acetate(EVA)copolymer,and polyvinyl alcohol(PVA)fiber mixtures in improving the mechanical properties of cement concrete,as well as the mechanism of microscopic phase evolution,was analyzed through macroscopic experiments,mesoscopic characterization,microscopic analysis,theoretical calculations,and comprehensive evaluation.The stress-strain curves obtained from the uniaxial compressive strength tests of specimens with different admixtures and fibers were investigated,and the characteristics of different stages were analyzed.The mechanical properties of different admixtures and fiber-reinforced materials,including their advantages and disadvantages,were compared through weighted comprehensive evaluation.The entire process of material failure,ranging from pore compaction,crack initiation,crack propagation,specimen instability to crack penetration,was explained via macroscopic fracture morphology,and the mechanical mechanism of how different admixtures affect the mechanical properties of concrete materials was revealed.The microscopic mechanism and the phase-evolution process of how the admixture affects concrete properties were elucidated using X-ray diffraction(XRD),hydration reaction theory,and Fourier transform infrared spectroscopy(FTIR).Furthermore,scanning electron microscopy-energy dispersive spectroscopy(SEM-EDS)was used to reveal the interfacial pore state and element distribution of the internal microstructure of concrete.The results show that PVA fiber bars can play the role of a“skeleton bridge”to improve the toughness of materials.LS can effectively promote the hydration process and cooperate with PVA fiber bars to enhance the mechanical properties of the material.EVA will inhibit the hydration reaction and degrade the material’s mechanical properties through the“organic isolation”effect.In addition,the on-site application has proven that the R3-group materials in this study can effectively inhibit the deformation of the roadway and possess strong reliability.Finally,the advantages and feasibility of LS-and-fiber-reinforced concrete were discussed from four perspectives:environmental protection,economy,disaster prevention,and development.This paper is expected to provide technical reference for the large-scale disposal of solid waste LS,the performance-optimization direction of concrete materials,and the prevention and control of coal and rock dynamic disasters.
基金financially supported by the Beijing Natural Science Foundation(No.L233016)。
文摘Polyaniline(PANi)hydrogels have a wide range of applications in artificial skin,flexible robotics,and movement monitoring.Nevertheless,limited by the modulus mismatch between rigid PANi and the soft hydrogel matrix,the high strength and toughness of the PANi hydrogel are mutually exclusive.Although the introduction of sacrificial bonds into the hydrogel network can alleviate this contradiction to a certain extent,it always causes pronounced energy hysteresis during hydrogel deformation.Inspired by the energy storage and release of macroscopic springs,in this work,we propose a molecular entanglement approach for the fabrication of PANi hydrogels featuring high toughness and low hysteresis,where flexible poly(ethylene glycol)(PEG)is entangled with chemically cross-linked poly(acrylic acid)(PAA)as a hydrogel matrix,and rigid PANi as a conductive filler.The resultant PAA/PEG/PANi hydrogel exhibited high mechanical properties(fracture strength of 0.75 MPa and toughness of 4.81 MJ·m^(-3))and a low energy dissipation ratio(28.2%when stretching to 300%).Moreover,the PAA/PEG/PANi hydrogel possesses a good electrical response to external forces and can be employed as a strain sensor to monitor human joint movements by producing specific electrical signals.This work provides a straightforward strategy for preparing tough conductive PANi hydrogels with low hysteresis,showing potential for the development of healthcare devices.
基金supported by the Natural Science Foundation of Hunan Province(2023JJ50055,2023JJ30081)the Science Research Foundation of Hunan Provincial Education Department(21A0546)+1 种基金the Youth Project of the National Natural Science Foundation of China(62003056)the Open Fund of Hunan Engineering Research Center of Research and Development of Degradable Materials and Molding Technology(2023KFKT05).
文摘The effect ofωiso andαprecipitation on microstructure,microhardness,tensile properties and impact toughness of Ti-25Nb-10Ta-1Zr-0.2Fe(TNTZF)alloy was investigated.The results showed that the solution treated TNTZF alloy with a small amount of nano-sizedωath particles inβmatrix possesses tensile strength of 697 MPa,elongation of~34%,Young’s modulus(YM)of 75 GPa,and impact toughness of 58.7 J/cm^(2).After aging at relatively lower temperatures of 400℃,the hardness and modulus of the alloy increased significantly,while the plasticity and toughness dropped sharply due to the precipitation ofωiso phase.ωiso phase displayed an ellipsoidal morphology with high volume fraction and a size of about 50 nm after aging at 400℃,leading to the highest hardness of 364 HV and YM of 108 GPa,along with completely embrittlement since elongation and toughness were almost zero.A brittle impact fracture morphology was observed in the alloy,which is dominated by intergranular fracture,with a mixed fracture characteristics of cleavage surfaces,terraces and tiny dimples.When aged at 550℃,plate-likeαdistributed inβmatrix uniformly and inβgrain boundaries in parallel,resulting in the high strength of 804 MPa,as well as lowest YM of 72 GPa,elongation of 9%and toughness of 35.8 J/cm^(2).The fracture morphology of the alloy aged at 550℃showed a ductile fracture mechanism with a large number of dimples.
基金National Institutes of Health(NIH)Grants:RO1 AR076190(to X.W and J.X.J)Welch Foundation grant:AQ-1507(to J.X.J.)。
文摘Proteoglycans,key components of non-collagenous proteins in the bone matrix,attract water through their negatively charged glycosaminoglycan chains.Among these proteoglycans,biglycan(Bgn)and decorin(Dcn)are major subtypes,yet their distinct roles in bone remain largely elusive.In this study,we utilized single knockout(KO)mouse models and successfully generated double KO(dKO)models despite challenges with low yield.Bgn deficiency,but not Dcn deficiency,decreased trabecular bone mass,with more pronounced bone loss in dKO mice.Low-field nuclear magnetic resonance measurements showed a marked decrease in bound water among all KO groups,especially in Bgn KO and dKO mice.Moreover,both Bgn KO and dKO mice exhibited reduced fracture toughness compared to Dcn KO mice.Dcn was significantly upregulated in Bgn KO mice,while a modest upregulation of Bgn was observed in Dcn KO mice,indicating Bgn’s predominant role in bone.High resolution atomic force microscopy showed decreased in situ permanent energy dissipation and increased elastic modulus in the extrafibrillar matrix of Bgn/Dcn deficient mice,which were diminished upon dehydration.Furthermore,we found that both Bgn and Dcn are indispensable for the activation of ERK and p38 MAPK signaling pathways.Collectively,our results highlight the distinct and indispensable roles of Bgn and Dcn in maintaining bone structure,water retention,and bulk/in situ tissue properties in the bone matrix,with Bgn exerting a predominant influence.
基金Funded by the National Key R&D Program of China(No.2022YFC3803400)。
文摘The effects of isocyanate(IA)incorporation on the toughness and volume stability of AAFS were systematically investigated.Various IA dosages were introduced into AAFS,and their influence on mechanical properties,microstructure,and shrinkage behavior was evaluated.The experimental results indicate that,with the incorporation of 5%IA,the 28-day compressive strength reaches 48.6 MPa,the 56-day drying shrinkage decreases by 35.91%,and minimal cracking is observed in the ring test.Microstructural analyses using SEM,XRD,and FTIR reveal that IA reacts with water to form urethane and biuret,which crosslinks into a durable network structure.This network fills pores,reducing internal stresses and improving both toughness and volume stability.These findings offer new insights into optimizing alkali-activated materials for construction applications and provide a potential pathway for the development of more durable and stable geopolymers.
基金supported from the National Nat-ural Science Foundation of China(Nos.52274342 and 52130408)the Fundamental Research Funds for the Central Universities of Central South University,China(No.1053320213826).
文摘The demand for oil casing steel with ultra-high strength and excellent impact toughness for safe application in ultra-deep wells is pressing.In improving the combination of strength,ductility,and impact toughness,the designed Cr-Mo-V micro-alloyed oil casing steel was quenched at 800,900,and 1000℃,followed by tempering at 600,680,and 760℃,respectively,to obtain distinct microstruc-tures.The results showed that the microstructure of the samples quenched at 800℃ followed by tempering comprised untransformed ferrite and large undissolved carbides,which considerably deteriorated tensile strength and impact toughness.For other conditions,the nuc-leated carbides and the boundaries are key factors that balance the tensile strength from 1226 to 971 MPa and the impact toughness from 65 to 236 J.From the perspective of carbide,optimal precipitation strengthening is achieved with a smaller carbide size obtained by a low tempering temperature of 600℃,while larger-sized carbides would remarkably soften the matrix to improve the toughness but deteriorate the tensile strength.Additionally,an increase in prior austenite grain size with the corresponding enlarged sub-boundaries obtained by high quenching temperatures substantially diminishes grain refinement strengthening,dislocation strengthening,and the energy absorbed in the crack propagation process,which is unfavorable to strength and toughness.
基金support from the Science and Technology Development Project of Jilin Province(Grant No.SKL202402004)the Program for the Development of Science and Technology of Jilin Province(Grant No.YDZJ202201ZYTS308)the Open Research Fund of State Key Laboratory of Inorganic Synthesis and Preparative Chemistry(Jilin University,Grant Nos.2022-16 and 2022-23).
文摘Electrically conductive carbide ceramics with high hardness and fracture toughness are promising for advanced applications.However,enhancing both electrical conductivity and fracture toughness simultaneous is challenging.This study reports the synthesis of(Ti_(0.2)W_(0.2)Ta_(0.2)Hf_(0.2)Mo_(0.2))C-diamond composites with varying densities using high-pressure and high-temperature(HPHT)method.The carbides are uniformly dispersed in a titanium carbide matrix,forming conductive channels that reduce resistivity to 4.6×10^(-7)W·m.These composite materials exhibit metallic conductivity with a superconducting transition at 8.5 K.Superconducting behavior may result from d-p orbital hybridization and electron-phonon coupling in transition metal carbides,such as TaC,Mo_(2)C,and MoC.Optimizing intergranular bonding improves the fracture toughness without compromising hardness.The highest indentation toughness value is 10.1±0.4 MPa·m^(1/2),a 130%increase compare to pure TiC.Enhanced toughness arises from transgranular and intergranular fracture modes,multiple crack bridging,and large-angle crack deflection,which dissipate fracture energy and inhibit crack propagation.This study introduces a novel microstructure engineering strategy for carbide ceramics to achieve superior mechanical and electrical properties.
基金supported by the Zhejiang Provincial"Vanguard"and"Leading Goose"R&D Program(No.2025C02203)the Zhejiang Provincial Natural Science Foundation of China(No.LTGS24C130001)the Fund for Key Scientific Research in the Public Interest of Ningbo(No.2024S009)。
文摘Poly(vinyl alcohol)(PVA)is a biodegradable and environmentally friendly material known for its gas barrier characteristics and solvent resistance.However,its flammability and water sensitivity limit its application in specialized fields.In this study,phytic acid(PA)was introduced as a halogen-free flame retardant and biochar(BC)was introduced as a reinforcement to achieve both flame resistance and mechanical robustness.We thoroughly investigated the effects of BC particle sizes(100-3000 mesh)and addition amounts(0 wt%-10 wt%),as well as PA addition amounts(0 wt%-15 wt%),on the properties of PVA composite films.Notably,the PA10/1000BC5 composite containing 10 wt%PA and 5 wt%1000 mesh BC exhibited optimal properties.The limiting oxygen index increased to 39.2%,and the UL-94 test achieved a V-0 rating.Additionally,the PA10/1000BC5 composite film demonstrated significantly enhanced water resistance,with a swelling ratio reaching 800%without dissolving,unlike that of the control PVA.The water contact angle was 70°,indicating that hydrophilic properties remained essentially unaffected.Most importantly,the tensile modulus and elongation at break were 213 MPa and 281.7%,respectively,nearly double those of the PVA/PA composite film.This study presents an efficient and straightforward method for preparing PVA composite films that are flame-retardant,tough,and waterresistant,expanding their potential applications in various fields.
基金supported by the Equipment Pre-research and Sharing Technology(41423030503)provided funding for this workThe Equipment Pre-research and Sharing Technology(41423030503)funded this work.
文摘This work used 5CrMnMo steel and titanium carbide(TiC)powders to fabricate particulate metal matrix composites(PMMCS).The composites’microstructure,hardness,and impact toughness were compared with four different titanium carbide ceramic particle sizes.The phase composition and microstructure of composites were studied.Vickers hardness and Charpy impact tests were employed to analyze composites’hardness and impact ductility,respectively.The results showed that the four groups of composites are mainly composed of martensite,trace residual austenite,and titanium carbide(undissolved TiC and primary TiC particles).With the growth of the ceramic particle dimension in the composite layer,the number of primary titanium carbide ceramics gradually decreased.When the initial ceramic particle size was small,it tended to generate dendritic primary TiC,and when the particle size was large,it tended to generate polygons and ellipsoids.Furthermore,with the growth of titanium carbide ceramic particle dimension in the composites,the hardness of the composites decreased but the impact toughness of the composites rose first and then descended.When the ceramic particle size was 50-75μm,the composite had the highest hardness,and the impact energy of the composites was the highest,which is 8 J.This was because there were more undissolved titanium carbide ceramics in the composite,and there was a thicker matrix metal between the ceramic particles.
基金supported by the National Natural Foundation of China(No.52171146)the HFIPS Director's Fund(No.BJPY2023A08)the Natural Science Foundation of Anhui Province(No.2108085ME145).
文摘Because of the large coefficient of thermal expansion (CTE) (23 ppm K^(–1)), aluminum faces challenges in meeting the demands of high dimensional stability in precision instruments, microelectronics, and aerospace. Filling negative thermal expansion (NTE) particles into aluminum can create composites with either zero or low CTEs. However, the resulting composites usually have poor thermal conductivity due to their monolithic configuration, i.e., the NTE particles are filled randomly. Thus, heat sinks should be equipped to assist their usage (e.g., in thermal management). This in turn causes strong thermal stress in the packaging system owing to the high contrast in the CTEs between those monolithic composites and heat sinks typically made of copper or aluminum. Here, we propose a gradient configuration for low-CTE aluminum composite, inspired by the bamboo structure. The gradient distribution of NTE particles (Zn_(0.5)Sn_(0.3)Mn_(0.2)NMn_(3), ZSM) was obtained by laying up several layers of ZSM/Al with the ZSM fraction ranging from 0 to 28 vol.%. In the gradient composite, the CTE near room temperature varies from 3.4 pm K^(–1) on one side to 21 ppm K^(–1) on the other side. Such a gradient CTE distribution would facilitate the low-thermal-stress designs and thus help stabilize the dimension of a precision system. Furthermore, this composite has a high thermal conductivity of 130 W m^(–1) K^(–1) and strong toughness when the flexural loading is applied on the 28 vol.% ZSM/Al side. Our research provides a novel approach to designing metallic matrix composites with unprecedented performance.
基金supported by the Taiyuan Major Science and Technology Project Fund in 2021,Fund for Shanxi“1331 Project,”Key Research and Development Program of Shanxi Province(202102040201011)the Zhanjiang Marine Equipment and Marine Biological Industry Unveiled the Talent Team Project(2021E05034).
文摘The toughness of thermoplastic polymers such as polypropylene(PP)can be improved by adding elastomers-based toughening agents,and the phase morphology of these toughening agents is very important for the strength and toughness of PP.The low-temperature toughness of PP was improved by inserting high-density polyethylene(HDPE)between PP and polystyrene-b-ethylene-co-propyleneb-polystyrene(SEPS)to form an unusual SEPS@HDPE core–shell structure,with SEPS as the core and HDPE as the shell.Based on the microtopography and rheological behavior characterization,HDPE in PP/SEPS/HDPE composites was found to serve as an emulsifier,decrease the size of SEPS particles,and promote the homogeneous dispersion of dispersed phase particles in the matrix.An increase in the HDPE content shifted the toughening mechanism of PP composites from cavitation to matrix shear yielding.The reduction in the distance between the dispersed core–shell structure particles promoted shear yielding in the PP composites,leading to increased toughness.The creation of an intermediate HDPE layer with a moderate modulus was crucial for dispersing stress concentrations and significantly improving toughness without compromising the tensile strength.These findings will facilitate the fabrication of high-toughness PP products at low temperatures.
基金financially supported by the National Natural Science Foundation of China(52474361).
文摘The effects of Ti/N ratio on the number densities of nano particles,the size of the prior austenite grain(PAG)and the toughness of the heat-affected zone(HAZ)of Mg-deoxidized steels were studied after high heat input welding of 400 kJ/cm.With increasing the Ti/N ratio from 2.7 to 5.7,the cuboid nano-sized particles are formed,and their number density increases.The area fractions of ductile intragranular acicular ferrites(IAFs)have the highest value and the area fractions of brittle microstructures of ferrite side plates and upper bainites have the lowest value in TN30 steel.With the Ti/N ratio of about 3.0,the HAZ of steel plate has the best low-temperature toughness.With increasing the Ti/N ratio from 2.7 to 5.7,the PAG sizes after the high-temperature laser scanning confocal microscopy observation decrease linearly with increasing the number densities of nano-sized particles.The PAG size of TN30 steel is between 100 and 150μm,which is conducive to the nucleation of IAFs.
