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
Organisms have evolved a strain limiting mechanism,reflected as a non-linear elastic constitutive,to prevent large deformations from threatening soft tissue integrity.Compared with linear elastic substrates,the wrinkl...Organisms have evolved a strain limiting mechanism,reflected as a non-linear elastic constitutive,to prevent large deformations from threatening soft tissue integrity.Compared with linear elastic substrates,the wrinkle of films on non-linear elastic substrates has received less attention.In this article,a unique wrinkle evolution of the film-substrate system with a J-shaped non-linear stress-strain relation is reported.The result shows that a concave hexagonal array pattern is formed with the shrinkage strain of the film-substrate systems developing.As the interconnection of hexagonal arrays,a unit cell ridge network appears with properties such as chirality and helix.The subparagraph maze pattern formed with high compression is mainly composed of special single-cell ridge networks such as spiral single cores,chiral double cores,and combined multi-cores.This evolutionary model is highly consistent with the results of experiments,and it also predicts wrinkle morphology that has not yet been reported.These findings can serve as a novel explanation for the surface wrinkle of biological soft tissue,as well as provide references for the preparation of artificial biomaterials and programmable soft matter.展开更多
(γ’+β)two-phase Ni-Al is a promising high-temperature protective coating material used on Ni-base superalloys since it has good interfacial compatibility with superalloys due to the low Al content compared to singl...(γ’+β)two-phase Ni-Al is a promising high-temperature protective coating material used on Ni-base superalloys since it has good interfacial compatibility with superalloys due to the low Al content compared to single-phaseβ-NiA l.In this paper,we aim to improve the oxidation resistance,whereby Ni-34Al-0.1Dy,a(γ’+β)two-phase Ni-Al alloy,was treated by laser shock processing(LSP)and the oxidation behavior at 1150℃ was investigated.The results showed that after oxidation,Al_(2)O_(3)scale formed on the originalβphase of the untreated alloy with a small grain size(200-800 nm),while for the LSP-treated samples,the scale grown on the originalβphase was dominantly composed of larger Al_(2)O_(3)grains with a size of 2-3μm.The distinction was attributed to the promotion ofθ-Al_(2)O_(3)toα-Al_(2)O_(3)transformation induced by the LSP,because the dislocation density,as well as surface roughness,were increased during LSP treatment which can provide heterogeneous nucleation sites forα-Al_(2)O_(3).In addition,the larger-size Al_(2)O_(3)particles,derived from the direct conversion of needle-likeθ-Al_(2)O_(3)in the initial oxidation stage,could rapidly overspread the wholeβphase surface thus reducing the scale growth rate.展开更多
In this study, the maleic anhydride （MAH） and styrene （St） dual monomers grafted polypropylene （PP） and poly[styrene-b- （ethylene-co-butylene）-b-styrene] （SEBS）, i.e. PP-g-（MAH-co-St） and SEBS-g-（MAH-co-S...In this study, the maleic anhydride （MAH） and styrene （St） dual monomers grafted polypropylene （PP） and poly[styrene-b- （ethylene-co-butylene）-b-styrene] （SEBS）, i.e. PP-g-（MAH-co-St） and SEBS-g-（MAH-co-St） are prepared as multi-phase compatibilizers and used to compatibilize the PA6/PS/PP/SEBS （70/10/10/10） model quaternary blends. Both PS and SEBS are encapsulated by the hard shell of PP-g-（MAH-co-St） in the dispersed domains （about 2 μm） of the PA6/PS/PP-g-（MAH-co-St）/SEBS （70/10/10/10） quaternary blend. In contrast, inside the dispersed domains （about 1 μm） of the PA6/PS/PP/SEBS-g-（MAH-co-St） （70/10/10/10） quaternary blend, the soft SEBS-g-（MAH-co-St） encapsulates both the hard PS and PP phases and separates them. With increasing the content of the compatibilizers equally, the morphology of the PA6/PS/（PP＋PP-g-（MAH-co-St））/（SEBS＋SEBS-g-（MAH-co-St）） （70/10/10/10） quaternary blends evolves from the soft （SEBS＋SEBS-g-（MAH-co-St）） encapsulating PS and partially encapsulating PP （about 1 μm）, then to PS exclusively encapsulated by the soft SEBS-g-（MAH-co-St） and then separated by PP-g-（MAH-co-St） inside the smaller domains （about 0.6 μm）. This morphology evolution has been well predicted by spreading coefficients and explained by the reaction between the matrix PA6 and the compatibilizers. The quaternary blends compatibilized by more compatibilizers exhibit stronger hierarchical interfacial adhesions and smaller dispersed domain, which results in the further improved mechanical properties. Compared to the uncompatibilized blend, the blend with both 10 wt% PP-g-（MAH-co-St） and 10 wt% SEBS-g-（MAH-co-St） has the best mechanical properties with the stress at break, strain at break and impact failure energy improved significantly by 97%, 71% and 261%, respectively. There is a strong correlation between the structure and property in the blends.展开更多
The microstructure, chemical composition and morphology evolution of icosahedral quasicrystalline phase of Mg67.4Zn28.9Y3.7 ternary alloy were investigated in detail at different pouring temperatures by X-ray diffract...The microstructure, chemical composition and morphology evolution of icosahedral quasicrystalline phase of Mg67.4Zn28.9Y3.7 ternary alloy were investigated in detail at different pouring temperatures by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and energy-dispersive spectrum （EDS）. Low interracial energy favors the formation of l-phase. The experimental results show that the primary l-phase reveals petal-shaped with five and six branches, where each branch has facetted growth morphology with the size ranging from 50 to 100μm. As the temperature decreases, the polygon-shaped l-phase forms, attributed to the decomposition of branch of petal-shaped l-phase, and then it grows bigger and some of the fine polygons join together to form large polygons. Besides these, （α-Mg＋l-phase） eutectic structures disappear and the relative amount of Mg7Zn3 phase increases as the pouring temperature decreases. The chemical composition and morphology evolution of l-phase were also discussed.展开更多
The morphology evolution of AI9（Mn,Ni）2 eutectic phase in AI-4Ni-2Mn alloy at 350 .C was examined. Two kinds of morphology evolution trends of AIg（Mn, Ni）2 eutectic phase were observed by using scanning electron m...The morphology evolution of AI9（Mn,Ni）2 eutectic phase in AI-4Ni-2Mn alloy at 350 .C was examined. Two kinds of morphology evolution trends of AIg（Mn, Ni）2 eutectic phase were observed by using scanning electron microscopy and transmission electron microscopy. The ribbon-like AIg（Mn, Ni）2 eutectic phase taking up a small portion of the eutectic structures gradually changes from ribbon-like morphology to rod-like during the heat treatment. The rod-like AIg（Mn, Ni）2 eutectics, primary eutectic structure in the alloy, become unstable at the transverse sub- boundaries of the eutectic rod when the samples are heat treated at 350 .C, and then split up into short rods with the extension of heat treatment time. Also, the Vickers microhardness test was used to characterize the change of local mechanical properties. The hardness test results indicate that local morphology evolution of eutectic phase has no obvious effect on the local mechanical properties of the alloy. The microhardness of the eutectic area increases slightly when the heat treatment time is extended to 192 h or 360 h.展开更多
Quenching experiments were performed at different cooling rates under non-directional solidification by differential thermal analysis, and the morphologic variation of primary phase, phase transition temperature and h...Quenching experiments were performed at different cooling rates under non-directional solidification by differential thermal analysis, and the morphologic variation of primary phase, phase transition temperature and hardness change at the same quenching temperature were investigated. The experimental results show that, with the gradual decrease of the cooling rate from 25 K/min, the morphology of ferrite starts to transform experiencing the dendrite, radial pattern, Widmanstatten-like and wire-net. Sample starts to present the Widmanstatten-like microstructure at 10 K/min which does not exist at higher or lower cooling rates, and this microstructure is detrimental to the mechanical property. Except 10 K/min, the hardness decreases with decreasing cooling rate.展开更多
The hydrodynamic effects of molten surface of titanium alloy on the morphology evolution by intense pulsed ion beam （IPIB） irradiation are studied. It is experimentally revealed that under irradiation of IPIB pulses...The hydrodynamic effects of molten surface of titanium alloy on the morphology evolution by intense pulsed ion beam （IPIB） irradiation are studied. It is experimentally revealed that under irradiation of IPIB pulses, the surface morphology of titanium alloy in a spatial scale of μm exhibits an obvious smoothening trend. The mechanism of this phenomenon is explained by the mass transfer caused by the surface tension of molten metal. Hydrodynamic simulation with a combination of the finite element method and the level set method reveals that the change in curvature on the molten surface leads to uneven distribution of surface tension. Mass transfer is caused by the relief of surface tension, and meanwhile a flattening trend in the surface morphology evolution is achieved.展开更多
A petal-like icosahedral quasicrystal with five branches,which is considered to be the representative morphology of the icosahedral quasicrystal,has been observed in the Y-rich Mg-Zn-Y ternary alloys. Moreover,the pol...A petal-like icosahedral quasicrystal with five branches,which is considered to be the representative morphology of the icosahedral quasicrystal,has been observed in the Y-rich Mg-Zn-Y ternary alloys. Moreover,the polygon-like morphology,another pattern of the icosahedral quasicrystal,has also been found in the Y-rich Mg-Zn-Y ternary alloys. The latter morphology results from the evolution of the former one. The growth mechanism of the petal-like morphology of the icosahedral quasicrystal was also discussed. Alloying composition,i.e.,Y element content,is a major factor inducing the morphology evolution of the icosahedral quasicrystal.展开更多
A series of AIN nanostructures were synthesized by an ultrahigh-temperature, catalyst-free, physical vapor transport（PVT） process. Energy dispersive X-ray spectroscopy（EDX）, X-ray diffraction（XRD）, X-Ray photoel...A series of AIN nanostructures were synthesized by an ultrahigh-temperature, catalyst-free, physical vapor transport（PVT） process. Energy dispersive X-ray spectroscopy（EDX）, X-ray diffraction（XRD）, X-Ray photoelectron spectroscopy（XPS）,high resolution transmission electron microscopy（HRTEM） detection show that high quality AIN nanowires were prepared. Nanostructures including nanorings, nanosprings, nanohelices, chainlike nanowires, six-fold symmetric nanostructure and rod-like structure were successfully obtained by controlling the growth duration and temperature. The morphology evolution was attributed to electrostatic polar charge model and the crystalline lattice structure of AIN.展开更多
Sm-Co nanoparticles (NPs) are promising candidates for preparing superstable magnets and exchange-coupled nanocomposite magnets with unprecedented magnetic properties.However,the morphology evolution of the NPs remain...Sm-Co nanoparticles (NPs) are promising candidates for preparing superstable magnets and exchange-coupled nanocomposite magnets with unprecedented magnetic properties.However,the morphology evolution of the NPs remains unclear.Here,single crystalline SmCox(x=4.07,4.79,6.94,and 8.61) NPs with dimensions below the critical size of a single magnetic domain were synthesized.These NPs consist of Sm_(2)Co_(7),SmCo_(5),and Sm2Co17phases with divergent typical morphologies.An evolution model for the different morphological characteristics was proposed based on phase-structure changes and surface-energy calculations using the density functional theory.The results show that these SmCo_(4.79) NPs can be well aligned along the easy magnetization axis and exhibit an ultrahigh coercivity of 5.7 T,thus enabling to advance the control of NP morphology and to facilitate their use in superstable or nanocomposite magnets.展开更多
High-performance perovskite solar cells(PVSCs)with low energy consumption and green processing are highly desired,but constrained by the difficulty in morphology control and the poor understanding on morphology evolut...High-performance perovskite solar cells(PVSCs)with low energy consumption and green processing are highly desired,but constrained by the difficulty in morphology control and the poor understanding on morphology evolution mechanisms.To address this issue,here we studied the effect of antisolvents on the perovskite film formation.We found that both the antisolvents and the perovskite composition affect the perovskite film morphology greatly via influencing the intermediate phase,and different perovskite compositions require different antisolvents to reach the optimal morphology.This provides the opportunity to achieve high-performance PVSCs with green antisolvent,that is,isopropanol(iPA)by changing the perovskite compositions,and leads to a powerconversionefficiency(PCE)of 21.50% for PVSCs based on MA_(0.6)FA_(0.4)PbI_(3).Further,we fabricated“fully green”PVSCs with all layers prepared by green sol-vents,and the optimal PCE can reach 19%,which represents the highest among PVSCs with full-green processing.This work provides insight into the perovskite morphology evolution and paves the way toward“green”processing PVSCs.展开更多
The paper explores applications of genetic programming to co-evolution of morphology and low-level control. In most reasonably difficult tasks, facilitation provided by modularity has proved to be vital for successful...The paper explores applications of genetic programming to co-evolution of morphology and low-level control. In most reasonably difficult tasks, facilitation provided by modularity has proved to be vital for successful application of genetic programming. However, the need for sharing data among nodes in the syntactic tree becomes especially acute when evolving modular programs. It has been shown before that it may be beneficial that modules themselves be node-attached. The paper presents extensions to standard genetic programming （the so-called contexts and context blocks） that allow for straight-forward storage, retrieval, transfer, and modification of data stored in the context of a syntactic tree, and shared by multiple nodes. Framework is thus provided for both： data sharing and node-attached modules. Finally, using context blocks, a genetic algorithm has been embedded within genetic programming to evolve values of constants. In genetic programming evolution of constants has been a long-standing problem. The paper shows how context blocks can be utilized to provide a more granular and flexible approach to their evolution. As shown in previous works, node-attached modules perform favorably when compared with existing approaches. Concerning evolution of context block constants, it is shown here that they too perform favorably when compared with ephemeral constants.展开更多
Polyacrylonitrile （PAN） based carbon fibers with different surface morphology were electrochemically treated in 3 wt% NH4HCO3 aqueous solution with current density up to 3.47 A/m 2 at room temperature, and surface s...Polyacrylonitrile （PAN） based carbon fibers with different surface morphology were electrochemically treated in 3 wt% NH4HCO3 aqueous solution with current density up to 3.47 A/m 2 at room temperature, and surface structures, surface morphology and residual mechanical properties were characterized. The crystallite size （La） of carbon fibers would be interrupted due to excessive electrochemical etching, while the crystallite spacing （d（002）） increased as increasing current density. The disordered structures on the surface of carbon fiber with rough surface increased at the initial oxidation stage and then removed by further electrochemical etching, which resulting in continuous increase of the extent of graphitization on the fiber surface. However, the electrochemical etching was beneficial to getting ordered morphology on the surface for carbon fiber with smooth surface, especially when the current density was lower than 1.77 A/m 2 . The tensile strength and tensile modulus could be improved by 17.27% and 5.75%, respectively, and was dependent of surface morphology. The decreasing density of carbon fibers probably resulted from the volume expansion of carbon fibers caused by the abundant oxygen functional groups intercalated between the adjacent graphite layers.展开更多
Didelphid marsupials are considered a morphologically unspecialized group with a generalist diet that includes vertebrates,invertebrates,and plant matter.While cranium and scapula variation has alreadybeen examined wi...Didelphid marsupials are considered a morphologically unspecialized group with a generalist diet that includes vertebrates,invertebrates,and plant matter.While cranium and scapula variation has alreadybeen examined within Didelphidae,variation inmandible shape,usually associated with diet or phylogeny in other mammalian groups,has not yet been properly assessed in the family.We evaluated the variation in mandible shape and size of didelphids(2470 specimens belonging to 94 species)using 2D geometric morphometrics.We classified the diet of the didel-phids into four broad categories to assess whether morphospace ordination relates to dietary habits.We also provided the most comprehensive phylogeny for the family(i23 out of the 126 living species)using 10 nuclear and mitochondrial genes.We then mapped mandible size and shape onto that phylogeny for 93 selected taxa and ancestral size and shapes were reconstructed by parsimony.We found phylogenetically structured variation in mandible morphology between didelphid groups,and our results indicate that they have a significant phylogenetic signal.The main axis of shape variation is poorly related to size,but the second is strongly allometric,indicating that allometry is not the main factor in shaping morphological diversity on their mandibles.Our results indicate that the shape and size of the ancestral mandible of didelphids would be similar to that of the current species of the genus Marmosa.展开更多
Bio-based cyclodextrins(CDs)are a common research object in supramolecular chemistry.The special cavity structure of CDs can form supramolecular self-assemblies such as vesicles and microcrystals through weak interact...Bio-based cyclodextrins(CDs)are a common research object in supramolecular chemistry.The special cavity structure of CDs can form supramolecular self-assemblies such as vesicles and microcrystals through weak interaction with vip molecules.The different forms of supramolecular self-assemblies can be transformed into each other under certain conditions.The regulation of supramolecular self-assembly is not only helpful to understand the self-assembly principle,but also beneficial to its application.In the present study,the self-assembly behavior of epoxy-β-cyclodextrin(EP-β-CD)and mixed anionic and cationic surfactant system(sodium dodecyl sulfate/dodecyltrimethylammonium bromide,SDS/DTAB)in aqueous solution was studied.Morphological and particle size characterization found that the SDS/DTAB@EP-β-CD complex,as the basic building unit,self-assembled into worm-like micelles at lower temperatures and vesicles at higher temperatures.Nuclear magnetic resonance(NMR)and Fourier transform infrared spectroscopy(FT-IR)analysis revealed that the driving force for the formation of vesicles and worm-like micelles was the hydrogen bonds between EP-β-CD molecules,while water molecules played an important role in promoting vesicle formation between SDS/DTAB@EP-β-CD units.Herein,the mechanism of the morphologic transformation of SDS/DTAB@EP-β-CD supramolecular aggregates induced by temperature was elucidated by exploring the self-assembly process,which may provide an excellent basis for the development of delivery carriers.展开更多
Porous anodic oxide films were fabricated galvanostatically on titanium alloy Ti-10V-2Fe-3Al in ammonium tartrate solution with different anodizing time.Scanning electron microscopy(SEM) and field emission scanning el...Porous anodic oxide films were fabricated galvanostatically on titanium alloy Ti-10V-2Fe-3Al in ammonium tartrate solution with different anodizing time.Scanning electron microscopy(SEM) and field emission scanning electron microscopy(FE-SEM) were used to investigate the morphology evolution of the anodic oxide film.It is shown that above the breakdown voltage,oxygen is generated with the occurrence of drums morphology.These drums grow and extrude,which yields the compression stress.Subsequently,microcracks are generated.With continuous anodizing,porous oxides form at the microcracks.Those oxides grow and connect to each other,finally replace the microcrack morphology.The depth profile of the anodic oxide film formed at 1 800 s was examined by Auger electron spectroscopy(AES).It is found that the film is divided into three layers according to the molar fractions of elements.The outer layer is incorporated by carbon,which may come from electrolyte solution.The thickness of the outer layer is approximately 0.2-0.3 μm.The molar fractions of elements in the intermediate layer are extraordinarily stable,while those in the inner layer vary significantly with sputtering depth.The thicknesses of the intermediate layer and the inner layer are 2 μm and 1.0-1.5 μm,respectively.Moreover,the growth mechanism of porous anodic oxide films in neutral tartrate solution was proposed.展开更多
The evolution of self organized Ge quantum dots structure is investigated by scanning tunneling microscopy and atomic force microscopy during annealing treatment up to 700℃ in an ultra high vacuum(UHV) system.When t...The evolution of self organized Ge quantum dots structure is investigated by scanning tunneling microscopy and atomic force microscopy during annealing treatment up to 700℃ in an ultra high vacuum(UHV) system.When the sample temperature rises to 630℃,a great amount of new dots emerge on the wetting layer,which are believed to be incoherent islands compared with the dislocation free coherent islands formed during molecular beam epitaxy growth.展开更多
The tidal flats of the Wanggang area, on the Jiangsu coast, represent the largest continuously distributed coastal wetland in terms of area coverage in China, and the dynamics of tidal flat accretion and erosion is hi...The tidal flats of the Wanggang area, on the Jiangsu coast, represent the largest continuously distributed coastal wetland in terms of area coverage in China, and the dynamics of tidal flat accretion and erosion is highly complicated. The cord-grass Spartina alterniflora, which was introduced artificially into the Jiangsu coast, has significant influences on the regional tidal flat evolution in terms of deposition rate, spacial sediment distribution patterns and tidal creek morphology. On the basis of the data set of bed elevation and accumulation rate for different periods of time, the applicability of the Pethick - Allen model to the Jiangsu tidal salt marshes is discussed. In addition, caesium-137 dating was carried out for sediment samples collected from the salt marsh of the Wangang area. In combination with the caesium-137 analysis and the data collected from literature, the Pethick - Allen model was used to derive the accumulation rate in the Wanggang tidal flat for the various periods. The results show that the pattern of tidal flat accretion has been modified, due to more rapid accretion following the iatroduction of S. alterniflora to the region. Surficial sediment samples were collected from representative profiles and analyzed for grain size with a laser particle analyzer. The result shows that fine-grained sediment has been trapped by the plant, with most of the sediment deposited on the Suaeda salsa and Spartina angelica flats being derived from drainage creeks rather than the from gently sloping tidal flats. Remote sensing analysis and in situ observations indicate that the creeks formed in the S. alterniflora flat have a relatively small ratio of width to depth, a relatively high density, and are more stable than the other tidal flat creek systems in the study area.展开更多
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This work was supported by the Youth Project of Hunan Provincial Department of Education(Grant No.22B0334)the Bridge and Tunnel Engineering Innovation Project of Changsha University of Science&Technology(Grant No.11ZDXK11)and the Practical Innovation and Entrepreneurship Capacity Improvement Plan of Changsha University of Science and Technology(Grant No.CLSJCX23029).
文摘Organisms have evolved a strain limiting mechanism,reflected as a non-linear elastic constitutive,to prevent large deformations from threatening soft tissue integrity.Compared with linear elastic substrates,the wrinkle of films on non-linear elastic substrates has received less attention.In this article,a unique wrinkle evolution of the film-substrate system with a J-shaped non-linear stress-strain relation is reported.The result shows that a concave hexagonal array pattern is formed with the shrinkage strain of the film-substrate systems developing.As the interconnection of hexagonal arrays,a unit cell ridge network appears with properties such as chirality and helix.The subparagraph maze pattern formed with high compression is mainly composed of special single-cell ridge networks such as spiral single cores,chiral double cores,and combined multi-cores.This evolutionary model is highly consistent with the results of experiments,and it also predicts wrinkle morphology that has not yet been reported.These findings can serve as a novel explanation for the surface wrinkle of biological soft tissue,as well as provide references for the preparation of artificial biomaterials and programmable soft matter.
基金financially supported by the National Natural Science Foundation of China(Grant No.51901011)the National Science and Technology Major Project(Grant Nos.2017-Ⅵ-0002-0072 and 2017-VII-0007-0100)+1 种基金the Fundamental Research Funds for Central Universities(Grant No.YWF-21-BJ-J-1034)the support from Youth Talent Support Program of Beihang University。
文摘(γ’+β)two-phase Ni-Al is a promising high-temperature protective coating material used on Ni-base superalloys since it has good interfacial compatibility with superalloys due to the low Al content compared to single-phaseβ-NiA l.In this paper,we aim to improve the oxidation resistance,whereby Ni-34Al-0.1Dy,a(γ’+β)two-phase Ni-Al alloy,was treated by laser shock processing(LSP)and the oxidation behavior at 1150℃ was investigated.The results showed that after oxidation,Al_(2)O_(3)scale formed on the originalβphase of the untreated alloy with a small grain size(200-800 nm),while for the LSP-treated samples,the scale grown on the originalβphase was dominantly composed of larger Al_(2)O_(3)grains with a size of 2-3μm.The distinction was attributed to the promotion ofθ-Al_(2)O_(3)toα-Al_(2)O_(3)transformation induced by the LSP,because the dislocation density,as well as surface roughness,were increased during LSP treatment which can provide heterogeneous nucleation sites forα-Al_(2)O_(3).In addition,the larger-size Al_(2)O_(3)particles,derived from the direct conversion of needle-likeθ-Al_(2)O_(3)in the initial oxidation stage,could rapidly overspread the wholeβphase surface thus reducing the scale growth rate.
基金financially supported by the National Natural Science Foundation of China (No. 51633003)State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology (No. OIC-201601006)
文摘In this study, the maleic anhydride （MAH） and styrene （St） dual monomers grafted polypropylene （PP） and poly[styrene-b- （ethylene-co-butylene）-b-styrene] （SEBS）, i.e. PP-g-（MAH-co-St） and SEBS-g-（MAH-co-St） are prepared as multi-phase compatibilizers and used to compatibilize the PA6/PS/PP/SEBS （70/10/10/10） model quaternary blends. Both PS and SEBS are encapsulated by the hard shell of PP-g-（MAH-co-St） in the dispersed domains （about 2 μm） of the PA6/PS/PP-g-（MAH-co-St）/SEBS （70/10/10/10） quaternary blend. In contrast, inside the dispersed domains （about 1 μm） of the PA6/PS/PP/SEBS-g-（MAH-co-St） （70/10/10/10） quaternary blend, the soft SEBS-g-（MAH-co-St） encapsulates both the hard PS and PP phases and separates them. With increasing the content of the compatibilizers equally, the morphology of the PA6/PS/（PP＋PP-g-（MAH-co-St））/（SEBS＋SEBS-g-（MAH-co-St）） （70/10/10/10） quaternary blends evolves from the soft （SEBS＋SEBS-g-（MAH-co-St）） encapsulating PS and partially encapsulating PP （about 1 μm）, then to PS exclusively encapsulated by the soft SEBS-g-（MAH-co-St） and then separated by PP-g-（MAH-co-St） inside the smaller domains （about 0.6 μm）. This morphology evolution has been well predicted by spreading coefficients and explained by the reaction between the matrix PA6 and the compatibilizers. The quaternary blends compatibilized by more compatibilizers exhibit stronger hierarchical interfacial adhesions and smaller dispersed domain, which results in the further improved mechanical properties. Compared to the uncompatibilized blend, the blend with both 10 wt% PP-g-（MAH-co-St） and 10 wt% SEBS-g-（MAH-co-St） has the best mechanical properties with the stress at break, strain at break and impact failure energy improved significantly by 97%, 71% and 261%, respectively. There is a strong correlation between the structure and property in the blends.
基金supported by the National Natural Science Foundation of China (Grant No.50571081)the Aeronautical Science Foundation of China (Grant No.04G53042)
文摘The microstructure, chemical composition and morphology evolution of icosahedral quasicrystalline phase of Mg67.4Zn28.9Y3.7 ternary alloy were investigated in detail at different pouring temperatures by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and energy-dispersive spectrum （EDS）. Low interracial energy favors the formation of l-phase. The experimental results show that the primary l-phase reveals petal-shaped with five and six branches, where each branch has facetted growth morphology with the size ranging from 50 to 100μm. As the temperature decreases, the polygon-shaped l-phase forms, attributed to the decomposition of branch of petal-shaped l-phase, and then it grows bigger and some of the fine polygons join together to form large polygons. Besides these, （α-Mg＋l-phase） eutectic structures disappear and the relative amount of Mg7Zn3 phase increases as the pouring temperature decreases. The chemical composition and morphology evolution of l-phase were also discussed.
文摘The morphology evolution of AI9（Mn,Ni）2 eutectic phase in AI-4Ni-2Mn alloy at 350 .C was examined. Two kinds of morphology evolution trends of AIg（Mn, Ni）2 eutectic phase were observed by using scanning electron microscopy and transmission electron microscopy. The ribbon-like AIg（Mn, Ni）2 eutectic phase taking up a small portion of the eutectic structures gradually changes from ribbon-like morphology to rod-like during the heat treatment. The rod-like AIg（Mn, Ni）2 eutectics, primary eutectic structure in the alloy, become unstable at the transverse sub- boundaries of the eutectic rod when the samples are heat treated at 350 .C, and then split up into short rods with the extension of heat treatment time. Also, the Vickers microhardness test was used to characterize the change of local mechanical properties. The hardness test results indicate that local morphology evolution of eutectic phase has no obvious effect on the local mechanical properties of the alloy. The microhardness of the eutectic area increases slightly when the heat treatment time is extended to 192 h or 360 h.
基金Funded by the National Natural Science Foundation of China(No.2010DFB70630)
文摘Quenching experiments were performed at different cooling rates under non-directional solidification by differential thermal analysis, and the morphologic variation of primary phase, phase transition temperature and hardness change at the same quenching temperature were investigated. The experimental results show that, with the gradual decrease of the cooling rate from 25 K/min, the morphology of ferrite starts to transform experiencing the dendrite, radial pattern, Widmanstatten-like and wire-net. Sample starts to present the Widmanstatten-like microstructure at 10 K/min which does not exist at higher or lower cooling rates, and this microstructure is detrimental to the mechanical property. Except 10 K/min, the hardness decreases with decreasing cooling rate.
基金Supported by the National Natural Science Foundation of China under Grant No 1175012the China Postdoctoral Science Foundation under Grant No 2016M600897the National Science and Technology Major Project of the Ministry of Science and Technology of China under Grant No 2013ZX04001-071
文摘The hydrodynamic effects of molten surface of titanium alloy on the morphology evolution by intense pulsed ion beam （IPIB） irradiation are studied. It is experimentally revealed that under irradiation of IPIB pulses, the surface morphology of titanium alloy in a spatial scale of μm exhibits an obvious smoothening trend. The mechanism of this phenomenon is explained by the mass transfer caused by the surface tension of molten metal. Hydrodynamic simulation with a combination of the finite element method and the level set method reveals that the change in curvature on the molten surface leads to uneven distribution of surface tension. Mass transfer is caused by the relief of surface tension, and meanwhile a flattening trend in the surface morphology evolution is achieved.
基金the National Natural Science Foundation of China (No. 50571081)the Aviation Foundation of China (No. 04G53024).
文摘A petal-like icosahedral quasicrystal with five branches,which is considered to be the representative morphology of the icosahedral quasicrystal,has been observed in the Y-rich Mg-Zn-Y ternary alloys. Moreover,the polygon-like morphology,another pattern of the icosahedral quasicrystal,has also been found in the Y-rich Mg-Zn-Y ternary alloys. The latter morphology results from the evolution of the former one. The growth mechanism of the petal-like morphology of the icosahedral quasicrystal was also discussed. Alloying composition,i.e.,Y element content,is a major factor inducing the morphology evolution of the icosahedral quasicrystal.
基金Project supported by the Natural Science Foundation of Tianjin,China(No.15JCQNJC03700)the National Natural Science Foundation of China(Nos.51702297)
文摘A series of AIN nanostructures were synthesized by an ultrahigh-temperature, catalyst-free, physical vapor transport（PVT） process. Energy dispersive X-ray spectroscopy（EDX）, X-ray diffraction（XRD）, X-Ray photoelectron spectroscopy（XPS）,high resolution transmission electron microscopy（HRTEM） detection show that high quality AIN nanowires were prepared. Nanostructures including nanorings, nanosprings, nanohelices, chainlike nanowires, six-fold symmetric nanostructure and rod-like structure were successfully obtained by controlling the growth duration and temperature. The morphology evolution was attributed to electrostatic polar charge model and the crystalline lattice structure of AIN.
基金supported by the National Natural Science Foundation of China (Grant Nos.52031001,and 91960101)。
文摘Sm-Co nanoparticles (NPs) are promising candidates for preparing superstable magnets and exchange-coupled nanocomposite magnets with unprecedented magnetic properties.However,the morphology evolution of the NPs remains unclear.Here,single crystalline SmCox(x=4.07,4.79,6.94,and 8.61) NPs with dimensions below the critical size of a single magnetic domain were synthesized.These NPs consist of Sm_(2)Co_(7),SmCo_(5),and Sm2Co17phases with divergent typical morphologies.An evolution model for the different morphological characteristics was proposed based on phase-structure changes and surface-energy calculations using the density functional theory.The results show that these SmCo_(4.79) NPs can be well aligned along the easy magnetization axis and exhibit an ultrahigh coercivity of 5.7 T,thus enabling to advance the control of NP morphology and to facilitate their use in superstable or nanocomposite magnets.
基金This work was supported by the National Natural Sci-ence Foundation of China(Grant Nos.51961145301,51620105006,and 61721005)the National Key Research and Development Program of China(No.2019YFA0705900).
文摘High-performance perovskite solar cells(PVSCs)with low energy consumption and green processing are highly desired,but constrained by the difficulty in morphology control and the poor understanding on morphology evolution mechanisms.To address this issue,here we studied the effect of antisolvents on the perovskite film formation.We found that both the antisolvents and the perovskite composition affect the perovskite film morphology greatly via influencing the intermediate phase,and different perovskite compositions require different antisolvents to reach the optimal morphology.This provides the opportunity to achieve high-performance PVSCs with green antisolvent,that is,isopropanol(iPA)by changing the perovskite compositions,and leads to a powerconversionefficiency(PCE)of 21.50% for PVSCs based on MA_(0.6)FA_(0.4)PbI_(3).Further,we fabricated“fully green”PVSCs with all layers prepared by green sol-vents,and the optimal PCE can reach 19%,which represents the highest among PVSCs with full-green processing.This work provides insight into the perovskite morphology evolution and paves the way toward“green”processing PVSCs.
文摘The paper explores applications of genetic programming to co-evolution of morphology and low-level control. In most reasonably difficult tasks, facilitation provided by modularity has proved to be vital for successful application of genetic programming. However, the need for sharing data among nodes in the syntactic tree becomes especially acute when evolving modular programs. It has been shown before that it may be beneficial that modules themselves be node-attached. The paper presents extensions to standard genetic programming （the so-called contexts and context blocks） that allow for straight-forward storage, retrieval, transfer, and modification of data stored in the context of a syntactic tree, and shared by multiple nodes. Framework is thus provided for both： data sharing and node-attached modules. Finally, using context blocks, a genetic algorithm has been embedded within genetic programming to evolve values of constants. In genetic programming evolution of constants has been a long-standing problem. The paper shows how context blocks can be utilized to provide a more granular and flexible approach to their evolution. As shown in previous works, node-attached modules perform favorably when compared with existing approaches. Concerning evolution of context block constants, it is shown here that they too perform favorably when compared with ephemeral constants.
基金supported by the National Basic Research Program of China (No. 2011CB605602)
文摘Polyacrylonitrile （PAN） based carbon fibers with different surface morphology were electrochemically treated in 3 wt% NH4HCO3 aqueous solution with current density up to 3.47 A/m 2 at room temperature, and surface structures, surface morphology and residual mechanical properties were characterized. The crystallite size （La） of carbon fibers would be interrupted due to excessive electrochemical etching, while the crystallite spacing （d（002）） increased as increasing current density. The disordered structures on the surface of carbon fiber with rough surface increased at the initial oxidation stage and then removed by further electrochemical etching, which resulting in continuous increase of the extent of graphitization on the fiber surface. However, the electrochemical etching was beneficial to getting ordered morphology on the surface for carbon fiber with smooth surface, especially when the current density was lower than 1.77 A/m 2 . The tensile strength and tensile modulus could be improved by 17.27% and 5.75%, respectively, and was dependent of surface morphology. The decreasing density of carbon fibers probably resulted from the volume expansion of carbon fibers caused by the abundant oxygen functional groups intercalated between the adjacent graphite layers.
文摘Didelphid marsupials are considered a morphologically unspecialized group with a generalist diet that includes vertebrates,invertebrates,and plant matter.While cranium and scapula variation has alreadybeen examined within Didelphidae,variation inmandible shape,usually associated with diet or phylogeny in other mammalian groups,has not yet been properly assessed in the family.We evaluated the variation in mandible shape and size of didelphids(2470 specimens belonging to 94 species)using 2D geometric morphometrics.We classified the diet of the didel-phids into four broad categories to assess whether morphospace ordination relates to dietary habits.We also provided the most comprehensive phylogeny for the family(i23 out of the 126 living species)using 10 nuclear and mitochondrial genes.We then mapped mandible size and shape onto that phylogeny for 93 selected taxa and ancestral size and shapes were reconstructed by parsimony.We found phylogenetically structured variation in mandible morphology between didelphid groups,and our results indicate that they have a significant phylogenetic signal.The main axis of shape variation is poorly related to size,but the second is strongly allometric,indicating that allometry is not the main factor in shaping morphological diversity on their mandibles.Our results indicate that the shape and size of the ancestral mandible of didelphids would be similar to that of the current species of the genus Marmosa.
基金China Postdoctoral Science Foundation(2020M681125)National Natural Science Foundation of China(32272254,31901618)Collaborative Innovation Center of Fragrance Flavour and Cosmetics.
文摘Bio-based cyclodextrins(CDs)are a common research object in supramolecular chemistry.The special cavity structure of CDs can form supramolecular self-assemblies such as vesicles and microcrystals through weak interaction with vip molecules.The different forms of supramolecular self-assemblies can be transformed into each other under certain conditions.The regulation of supramolecular self-assembly is not only helpful to understand the self-assembly principle,but also beneficial to its application.In the present study,the self-assembly behavior of epoxy-β-cyclodextrin(EP-β-CD)and mixed anionic and cationic surfactant system(sodium dodecyl sulfate/dodecyltrimethylammonium bromide,SDS/DTAB)in aqueous solution was studied.Morphological and particle size characterization found that the SDS/DTAB@EP-β-CD complex,as the basic building unit,self-assembled into worm-like micelles at lower temperatures and vesicles at higher temperatures.Nuclear magnetic resonance(NMR)and Fourier transform infrared spectroscopy(FT-IR)analysis revealed that the driving force for the formation of vesicles and worm-like micelles was the hydrogen bonds between EP-β-CD molecules,while water molecules played an important role in promoting vesicle formation between SDS/DTAB@EP-β-CD units.Herein,the mechanism of the morphologic transformation of SDS/DTAB@EP-β-CD supramolecular aggregates induced by temperature was elucidated by exploring the self-assembly process,which may provide an excellent basis for the development of delivery carriers.
基金Project(50571003) supported by the National Natural Science Foundation of China
文摘Porous anodic oxide films were fabricated galvanostatically on titanium alloy Ti-10V-2Fe-3Al in ammonium tartrate solution with different anodizing time.Scanning electron microscopy(SEM) and field emission scanning electron microscopy(FE-SEM) were used to investigate the morphology evolution of the anodic oxide film.It is shown that above the breakdown voltage,oxygen is generated with the occurrence of drums morphology.These drums grow and extrude,which yields the compression stress.Subsequently,microcracks are generated.With continuous anodizing,porous oxides form at the microcracks.Those oxides grow and connect to each other,finally replace the microcrack morphology.The depth profile of the anodic oxide film formed at 1 800 s was examined by Auger electron spectroscopy(AES).It is found that the film is divided into three layers according to the molar fractions of elements.The outer layer is incorporated by carbon,which may come from electrolyte solution.The thickness of the outer layer is approximately 0.2-0.3 μm.The molar fractions of elements in the intermediate layer are extraordinarily stable,while those in the inner layer vary significantly with sputtering depth.The thicknesses of the intermediate layer and the inner layer are 2 μm and 1.0-1.5 μm,respectively.Moreover,the growth mechanism of porous anodic oxide films in neutral tartrate solution was proposed.
文摘The evolution of self organized Ge quantum dots structure is investigated by scanning tunneling microscopy and atomic force microscopy during annealing treatment up to 700℃ in an ultra high vacuum(UHV) system.When the sample temperature rises to 630℃,a great amount of new dots emerge on the wetting layer,which are believed to be incoherent islands compared with the dislocation free coherent islands formed during molecular beam epitaxy growth.
基金supported financially by the National Natural Science Foundation of China under contract Nos 40231010 and 40476041the Marine Science Youth Fund of State 0ceanic Administration of China under contract No.2006312.
文摘The tidal flats of the Wanggang area, on the Jiangsu coast, represent the largest continuously distributed coastal wetland in terms of area coverage in China, and the dynamics of tidal flat accretion and erosion is highly complicated. The cord-grass Spartina alterniflora, which was introduced artificially into the Jiangsu coast, has significant influences on the regional tidal flat evolution in terms of deposition rate, spacial sediment distribution patterns and tidal creek morphology. On the basis of the data set of bed elevation and accumulation rate for different periods of time, the applicability of the Pethick - Allen model to the Jiangsu tidal salt marshes is discussed. In addition, caesium-137 dating was carried out for sediment samples collected from the salt marsh of the Wangang area. In combination with the caesium-137 analysis and the data collected from literature, the Pethick - Allen model was used to derive the accumulation rate in the Wanggang tidal flat for the various periods. The results show that the pattern of tidal flat accretion has been modified, due to more rapid accretion following the iatroduction of S. alterniflora to the region. Surficial sediment samples were collected from representative profiles and analyzed for grain size with a laser particle analyzer. The result shows that fine-grained sediment has been trapped by the plant, with most of the sediment deposited on the Suaeda salsa and Spartina angelica flats being derived from drainage creeks rather than the from gently sloping tidal flats. Remote sensing analysis and in situ observations indicate that the creeks formed in the S. alterniflora flat have a relatively small ratio of width to depth, a relatively high density, and are more stable than the other tidal flat creek systems in the study area.
