Three-dimensional(3 D)printing has revolutionized the design and production of customized scaffolds,but the minimally invasive implantation of 3 D-printed structures into the human body remains challenging.This has pr...Three-dimensional(3 D)printing has revolutionized the design and production of customized scaffolds,but the minimally invasive implantation of 3 D-printed structures into the human body remains challenging.This has prompted the exploration of innovative materials and technical solutions.Shape-memory polymers,as advanced intelligent materials,exhibit considerable potential in minimally invasive surgical applications.Herein,we developed a novel thermosetting shape-memory polymer,poly(L-lactic acid)-trimethylene carbonate-glycolic acid(PLLA-TMC-GA),for the fabrication of bioengineered scaffolds with body temperature-activated shape-memory functionality.We comprehensively evaluated the mechanical properties,thermal stability,shape-memory capabilities,biocompatibility,biodegradability,and 3 D printing performance of PLLA-TMC-GA terpolymers with various compositions.The results indicate that PLLA-TMC-GA exhibits exceptional shape-memory performance,adjustable material properties,favorable biocompatibility,and the potential for controlled biodegradation and reabsorption.The use of PLLA-TMC-GA as a biodegradable shape-memory polymer allows the reduction of implant volume,simplifies implantation,and enables on-demand activation at body temperature.These characteristics present new opportunities for the advancement of minimally invasive surgical techniques.展开更多
Shape-memory polymers(SMPs)and their composite materials are stimuliresponsive materials that have the unique characteristics of lightweight,large deformation,variable stiffness,and biocompatibility.This paper reviews...Shape-memory polymers(SMPs)and their composite materials are stimuliresponsive materials that have the unique characteristics of lightweight,large deformation,variable stiffness,and biocompatibility.This paper reviews the research status of the mechanical models for SMPs,shape-memory nanocomposites and shape-memory polymer composites(SMPCs);it also introduces some spatially deployable structures,such as hinges,beams,and antennae based on SMPCs.In addition,the deformation types of 4D printing structures and the potential applications of this technology in robots and medical devices are also summarized.展开更多
Elemental titanium(Ti)and nickel(Ni)powders were consolidated by spark plasma sintering(SPS)to fabricate Ti-51%Ni(mole fraction)shape-memory alloys(SMAs).The objective of this study is to enhance the superelasticity o...Elemental titanium(Ti)and nickel(Ni)powders were consolidated by spark plasma sintering(SPS)to fabricate Ti-51%Ni(mole fraction)shape-memory alloys(SMAs).The objective of this study is to enhance the superelasticity of SPS produced Ti-Ni alloy using free forging as a secondary process.Products from two processes(with and without free forging)were compared in terms of microstructure,transformation temperature and superelasticity.The results showed that,free forging effectively improved the tensile and shape-memory properties.Ductility increased from 6.8%to 9.2%after forging.The maximum strain during superelasticity increased from 5%to 7.5%and the strain recovery rate increased from 72%to 92%.The microstructure of produced Ti-51%Ni SMA consists of the cubic austenite(B2)matrix,monoclinic martensite(B19′),secondary phases(Ti3Ni4,Ti2Ni and TiNi3)and oxides(Ti4Ni2O and Ti3O5).There was a shift towards higher temperatures in the martensitic transformation of free forged specimen(aged at 500°C)due to the decrease in Ni content of B2 matrix.This is related to the presence of Ti3Ni4 precipitates,which were observed using transmission electron microscope(TEM).In conclusion,free forging could improve superelasticity and mechanical properties of Ti-51%Ni SMA.展开更多
Nature has been inspiring material researchers to fabricate biomimetic functional devices for various applications, and shape-memory polymer materials(SMPMs) have received tremendous attention since the promising inte...Nature has been inspiring material researchers to fabricate biomimetic functional devices for various applications, and shape-memory polymer materials(SMPMs) have received tremendous attention since the promising intelligent materials possess more advantages over others for the fabrication of biomimetic functional devices. As is well-known, SMPMs can be stimulated by heat, electricity, magnetism, pH, solvent and light. From the viewpoint of practical applications, ultraviolet(UV)-visible(Vis)-near infrared(NIR) light-responsive SMPMs are undoubtedly more advantageous. However, up to now, UV-Vis-NIR light-deformable SMPMs by combining photothermal and photochemical effects are still rarely reported. Here we designed a UV-Vis-NIR light-deformable SMP composite film via incorporating a liquid crystal(LC) mixture and graphene oxide(GO) into a shape-memory polyurethane matrix. The elongated composite films exhibited interesting photomechanical bending deformations with different light-triggered mechanisms,(1) photochemically induced LC phase transition upon UV exposure,(2) photochemically and photothermally induced LC phase transition upon visible-light irradiation,(3) photothermally triggered LC phase transition and partial stress relaxation upon low-intensity NIR exposure. All the deformed objects could recover to their original shapes by high-intensity NIR irradiation.Moreover, the biomimetic circadian rhythms of acacia leaves and the biomimetic bending/spreading of fingers were successfully achieved, which could blaze a way in the field of biomimetic functional devices due to the excellent light-deformable and shape-memory properties of the SMP composite films.展开更多
3D porous scaffold could provide suitable bone-like structure for cell adhesion and proliferation;however,surgical suffering from large volume implantation is a great challenge for patients.In this study,a shape progr...3D porous scaffold could provide suitable bone-like structure for cell adhesion and proliferation;however,surgical suffering from large volume implantation is a great challenge for patients.In this study,a shape programmable porous poly(ε-caprolactone)(PCL)-based polyurethane scaffold with memory effect was synthesized via gas foaming method,using Citrate modified Amorphous calcium Phosphate(CAP)as bioactive factor.The bending experiments indicated that the scaffolds achieved excellent shape-memory effect,which could be influenced by particle weight content.In vitro mineralization results suggested that the deposition of hydroxyapatite was promoted by scaffolds.Additionally,cell assay showed that composite scaffolds presented good cell toxicity and osteogenicity by the differentiation of rat Mesenchymal Stem Cells(rMSCs)into the osteogenic lineage.In the model of rat cranial implantation,the reparative tissue covered the defect site and bone-like structure deposited on the scaffold due to the formation of new bones.In summary,the porous smart shape-memory composite scaffolds could be a potential candidate in future distinctive bone repair applications.展开更多
Shape-memory poly（p-dioxanone）–poly（e-caprolactone）/sepiolite（PPDO–PCL/OSEP） nanocomposites with different OSEP nanofiber loading were fabricated by chain-extending the PPDO-diol and PCL/OSEP precursors. The p...Shape-memory poly（p-dioxanone）–poly（e-caprolactone）/sepiolite（PPDO–PCL/OSEP） nanocomposites with different OSEP nanofiber loading were fabricated by chain-extending the PPDO-diol and PCL/OSEP precursors. The precursors and the composites were characterized by1 H NMR, FT-IR, GPC, SEM and TEM.The results demonstrate that a part of PCL segments grafted on the surface of OSEP and composites display a fine dispersion of OSEP fiber in nanoscale with low OSEP content. The shape memory effect（SME） was evaluated by DMA, the results reveal that the PPDO–PCL/OSEP nanocomposites exhibit desirable shape-memory performance. The reinforcement of composites by incorporation of trace OSEP nanofiber evokes an effective improvement in shape-memory recovery stress.展开更多
BACKGROUND Comminuted manubrium sterni fractures are rare,and internal fixation methods are limited.This report explored a practical and feasible method of internal fixation for comminuted manubrium sterni fractures.C...BACKGROUND Comminuted manubrium sterni fractures are rare,and internal fixation methods are limited.This report explored a practical and feasible method of internal fixation for comminuted manubrium sterni fractures.CASE SUMMARY A 17-year-old female was injured in a car accident for which she underwent debridement and suturing of her head and anterior chest wounds in another hospital.Eight days later,the patient was transferred to our hospital for surgical treatment.The manubrium sterni was found intraoperatively to be split into three irregular fragments with obvious overlap and separation displacement.Meanwhile,a manubriosternal joint dislocation and left first rib cartilage fracture were observed.The retraction force of the shape-memory alloy staples was used to pull the fracture fragments together.Two more titanium locking plates were then used to fix the manubrium sterni and corpus sterni longitudinally,and the left first rib cartilage fracture was repositioned and fixed with a titanium locking plate.A postoperative computed tomography scan showed reduced and rigid fixation of the comminuted manubrium sterni fractures.The patient recovered well with no significant complaints of discomfort.The patient was discharged 10 days postoperatively after the stitches had been removed.CONCLUSION Shape-memory alloy staples had the advantage of being safe and effective during the repositioning and internal fixation of comminuted manubrium sterni fractures.Therefore,they provided a new surgical option for comminuted manubrium sterni fractures.展开更多
The valence changes of doped samarium and the creation as well as the annihilation of F-centers in the processes of thermostimulated luminescence (TSL) and photostimulated luminescence (PSL) of BaFCl∶Sm crystal have ...The valence changes of doped samarium and the creation as well as the annihilation of F-centers in the processes of thermostimulated luminescence (TSL) and photostimulated luminescence (PSL) of BaFCl∶Sm crystal have been studied. As being irradiated by X-ray,a large number of electron-hole pairs are created in the crystal.Most of the electrons may be trapped at the anion vacancies,producing F-centers.The doped samarium ions,which existed mostly in trivalent state (Sm^(3+)),may capture the holes and convert themselves to tetravalent state.So that part of the incident X-ray energy are stored in this nonequilibrium system.On optical and thermal stimulation the stored energy can be liberated as a characteristic emission of trivalent samarium ion.This emission originates from the recombination of the F-center electrons with tetravalent samarium ions,i.e.the F-center electrons may be excited to the conduction band by optical or thermal stirnulation and then recombine with tetravalent samarium ions.This recombination makes the samarium ions to be in situ reduced to the excited state of Sm^(3+),and gives rise to the characteristic emission of Sm^(3+). On the other hand,during X-irradiation a few electrons can be trapped at the sites of trivalent samarium ions and reduce them to divalent state.But the formation of divalent samarium On X-irradiation is very small as compared with that of F-centers and so their influence on the PSL and TSL can be neglected.展开更多
As an important kind of intelligent materials,shape-memory materials have been received increasing attention on account of their interesting properties and potential applications in recent years.Particularly,the rise ...As an important kind of intelligent materials,shape-memory materials have been received increasing attention on account of their interesting properties and potential applications in recent years.Particularly,the rise of shape-memory polymers by far surpasses well-known metallic shape-memory alloys in their shape-memory properties.The advantages of polymers compared to other materials are their easier availability and their wide range of mechanical and physical properties.The polymers designed to exhibit a shape-memory effect require two components on the molecular level:crosslinks to determine the permanent shape and switching segments with Ttrans to fix the temporary shape.Up to now almost all papers on shape-memory polymers introduce switching segments with the covalent linking method.On the other hand,only several cases concern non-covalent interaction.However,the research works mentioned above is based on a single Trans(i.e.,Tm or Tg).展开更多
The integration of smart materials and alloys with additive manufacturing(AM)technologies represents a paradigm shift in modern manufacturing,enabling the creation of highly functional,adaptive,and customizable compon...The integration of smart materials and alloys with additive manufacturing(AM)technologies represents a paradigm shift in modern manufacturing,enabling the creation of highly functional,adaptive,and customizable components.Smart materials have special qualities that allow them to react dynamically to environmental stimuli like temperature,electric fields,and mechanical stress.Examples of these materials include shape-memory alloys(SMAs),piezoelectric materials,magnetostrictive alloys,and self-healing polymers.The integration of smart materials and alloys with additive manufacturing holds transformative potential across industries,offering new avenues for innovation and product design.These materials,combined with AM processes such as selective laser sintering(SLS),fused deposition modeling,and direct ink writing,enable the creation of complex geometries and multifunctional components that were previously unattainable through traditional manufacturing methods.Furthermore,the paper examines the applications of smart materials and alloys in creating adaptive systems and multifunctional devices,such as self-healing structures,shape-changing actuators,and flexible sensors.The study provides a comprehensive overview of recent advances in the integration of smart materials and alloys into various AM techniques,such as powder bed fusion,direct ink writing,and stereolithography.Key challenges,including material-process compatibility,thermal and mechanical limitations,and scalability,are critically analyzed in the study.This study attempts to assist academics and companies in realizing the full potential of AM-enabled smart material applications by analyzing current advancements,challenges,and opportunities for the future research works.As a result,the review concludes with potential future research directions and the transformative impact of this integration on modern manufacturing and product design.展开更多
Developing advanced polymeric materials with enhanced mechanical properties and functionalities has been a long-standing goal in materials science.Recently,supramolecular polymeric materials (SPMs) have drawn increase...Developing advanced polymeric materials with enhanced mechanical properties and functionalities has been a long-standing goal in materials science.Recently,supramolecular polymeric materials (SPMs) have drawn increased attention due to their unique properties and potential applications in self-healing,shape memory,sensors,and flexible electronics.Here,we develop an ionic cluster-optimized microphase separation strategy to enhance the toughening and energy dissipation capabilities of polydisulfide-based supramolecular polymers.The mechanical properties,including Young’s modulus and toughness,are significantly improved by integrating the quadruple H-bonding 2-ureido-4-pyrimidone (UPy) induced microphase separation with iron(Ⅲ)-to-carboxylate ionic clusters.By combining established chemical approaches with adjustable polymer phase ratios,it is revealed that the synergistic effect of these factors expands the interchain spacing,facilitates the formation of microphase domains,and enhances the tolerance of polythioctic acid-based polymers to external mechanical and thermal stimuli,meeting the practical requirements for industrial plastic applications.Moreover,the UPy-functionalized polymers incorporating iron carboxylate clusters exhibit good one-way shape memory behavior with practical applicability at a relatively low recovery temperature.Our work demonstrates a novel strategy for constructing industrially viable shape memory dynamic SPMs and paves the way for future innovations in developing SPMs.展开更多
A shape-memory double network hydrogel consists of two polymer networks:a chemically crosslinked primary network that is responsible for the permanent shape and a physically crosslinked secondary network that is used ...A shape-memory double network hydrogel consists of two polymer networks:a chemically crosslinked primary network that is responsible for the permanent shape and a physically crosslinked secondary network that is used to fix the temporary shapes.The formation/melting transition of the secondary network serves as an effective mechanism for the double network hydrogel’s shape-memory effect.When the crosslinks in the secondary network are dissociated by applying an external stimulus,only the primary network is left to support the load.When the secondary network is re-formed by removing the stimulus,both the primary and secondary networks support the load.In the past,models have been developed for the constitutive behaviors of double network hydrogels,but the model of shape-memory double network hydrogels is still lacking.This work aims to build a constitutive model for the polyacrylamide-gelatin double network shape-memory hydrogel developed in our previous work.The model is first calibrated by experimental data of the double network shape-memory hydrogel under uniaxial loading and then employed to predict the shape-fixing performance of the hydrogel.The model is also implemented into a three-dimension finite element code and utilized to simulate the shape-memory behavior of the double network hydrogel with inhomogeneous deformations related to applications.展开更多
The structures, the martensitic transformations, and the magnetic properties are studied systematically in Mn50Ni40-xCuxIn10, Mn50-xCuxNi40In10, and Mn50Ni40In10-xCux alloys. The partial substitution of Ni by Cu reduc...The structures, the martensitic transformations, and the magnetic properties are studied systematically in Mn50Ni40-xCuxIn10, Mn50-xCuxNi40In10, and Mn50Ni40In10-xCux alloys. The partial substitution of Ni by Cu reduces the martensitic transformation temperature, but has little influence on the Curie temperature of austenite. Comparatively, the martensitic transformation temperature increases and the Curie temperature of austenite decreases with the partial replacement of Mn or In by Cu. The magnetization difference between the austenite phase and the martensite phase reaches 70 emu/g in Mn50Ni39Cu1In10; a field-induced martensite-to-austenite transition is observed in this alloy.展开更多
基金supported by the National Natural Science Foundation of China(Nos.82402822,82360427,82372425,82072443,and 32200559)the Priority Union Foundation of Yunnan Provincial Science and Technology Department and Kunming Medical University(No.202301AY070001-164)+1 种基金the Natural Science Foundation of Sichuan Province(No.23NSFSC5880)the Central Government of Sichuan Province Guiding the Special Project of Local Science and Technology Development(No.2024ZYD0155).
文摘Three-dimensional(3 D)printing has revolutionized the design and production of customized scaffolds,but the minimally invasive implantation of 3 D-printed structures into the human body remains challenging.This has prompted the exploration of innovative materials and technical solutions.Shape-memory polymers,as advanced intelligent materials,exhibit considerable potential in minimally invasive surgical applications.Herein,we developed a novel thermosetting shape-memory polymer,poly(L-lactic acid)-trimethylene carbonate-glycolic acid(PLLA-TMC-GA),for the fabrication of bioengineered scaffolds with body temperature-activated shape-memory functionality.We comprehensively evaluated the mechanical properties,thermal stability,shape-memory capabilities,biocompatibility,biodegradability,and 3 D printing performance of PLLA-TMC-GA terpolymers with various compositions.The results indicate that PLLA-TMC-GA exhibits exceptional shape-memory performance,adjustable material properties,favorable biocompatibility,and the potential for controlled biodegradation and reabsorption.The use of PLLA-TMC-GA as a biodegradable shape-memory polymer allows the reduction of implant volume,simplifies implantation,and enables on-demand activation at body temperature.These characteristics present new opportunities for the advancement of minimally invasive surgical techniques.
基金This work is supported by the National Natural Science Foundation of China(Grant Nos.11772109,11632005 and 11672086)the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(Grant No.11421091).
文摘Shape-memory polymers(SMPs)and their composite materials are stimuliresponsive materials that have the unique characteristics of lightweight,large deformation,variable stiffness,and biocompatibility.This paper reviews the research status of the mechanical models for SMPs,shape-memory nanocomposites and shape-memory polymer composites(SMPCs);it also introduces some spatially deployable structures,such as hinges,beams,and antennae based on SMPCs.In addition,the deformation types of 4D printing structures and the potential applications of this technology in robots and medical devices are also summarized.
基金the Ministry of Higher Education of Malaysia for the Malaysian International Scholarship and research funding under FRGS vote No. R.J13000.7824.4F810
文摘Elemental titanium(Ti)and nickel(Ni)powders were consolidated by spark plasma sintering(SPS)to fabricate Ti-51%Ni(mole fraction)shape-memory alloys(SMAs).The objective of this study is to enhance the superelasticity of SPS produced Ti-Ni alloy using free forging as a secondary process.Products from two processes(with and without free forging)were compared in terms of microstructure,transformation temperature and superelasticity.The results showed that,free forging effectively improved the tensile and shape-memory properties.Ductility increased from 6.8%to 9.2%after forging.The maximum strain during superelasticity increased from 5%to 7.5%and the strain recovery rate increased from 72%to 92%.The microstructure of produced Ti-51%Ni SMA consists of the cubic austenite(B2)matrix,monoclinic martensite(B19′),secondary phases(Ti3Ni4,Ti2Ni and TiNi3)and oxides(Ti4Ni2O and Ti3O5).There was a shift towards higher temperatures in the martensitic transformation of free forged specimen(aged at 500°C)due to the decrease in Ni content of B2 matrix.This is related to the presence of Ti3Ni4 precipitates,which were observed using transmission electron microscope(TEM).In conclusion,free forging could improve superelasticity and mechanical properties of Ti-51%Ni SMA.
基金financially supported by the National Natural Science Foundation of China(Nos.51373025,51773002 and 51921002)。
文摘Nature has been inspiring material researchers to fabricate biomimetic functional devices for various applications, and shape-memory polymer materials(SMPMs) have received tremendous attention since the promising intelligent materials possess more advantages over others for the fabrication of biomimetic functional devices. As is well-known, SMPMs can be stimulated by heat, electricity, magnetism, pH, solvent and light. From the viewpoint of practical applications, ultraviolet(UV)-visible(Vis)-near infrared(NIR) light-responsive SMPMs are undoubtedly more advantageous. However, up to now, UV-Vis-NIR light-deformable SMPMs by combining photothermal and photochemical effects are still rarely reported. Here we designed a UV-Vis-NIR light-deformable SMP composite film via incorporating a liquid crystal(LC) mixture and graphene oxide(GO) into a shape-memory polyurethane matrix. The elongated composite films exhibited interesting photomechanical bending deformations with different light-triggered mechanisms,(1) photochemically induced LC phase transition upon UV exposure,(2) photochemically and photothermally induced LC phase transition upon visible-light irradiation,(3) photothermally triggered LC phase transition and partial stress relaxation upon low-intensity NIR exposure. All the deformed objects could recover to their original shapes by high-intensity NIR irradiation.Moreover, the biomimetic circadian rhythms of acacia leaves and the biomimetic bending/spreading of fingers were successfully achieved, which could blaze a way in the field of biomimetic functional devices due to the excellent light-deformable and shape-memory properties of the SMP composite films.
基金supported by the National Natural Science Foundation of China(NO.41673109)Sichuan Science and Technology Program(2021YFH0098)+2 种基金Sichuan University Panzhihua school city strategic cooperation special fund project(2019CDPZH-6)the Science and Technology Department Project of Sichuan Province(2018SZDZX0022)Key Project of Sichuan Vanadium and Titanium Industry Development Research Center(2018VTCY-Z-01).
文摘3D porous scaffold could provide suitable bone-like structure for cell adhesion and proliferation;however,surgical suffering from large volume implantation is a great challenge for patients.In this study,a shape programmable porous poly(ε-caprolactone)(PCL)-based polyurethane scaffold with memory effect was synthesized via gas foaming method,using Citrate modified Amorphous calcium Phosphate(CAP)as bioactive factor.The bending experiments indicated that the scaffolds achieved excellent shape-memory effect,which could be influenced by particle weight content.In vitro mineralization results suggested that the deposition of hydroxyapatite was promoted by scaffolds.Additionally,cell assay showed that composite scaffolds presented good cell toxicity and osteogenicity by the differentiation of rat Mesenchymal Stem Cells(rMSCs)into the osteogenic lineage.In the model of rat cranial implantation,the reparative tissue covered the defect site and bone-like structure deposited on the scaffold due to the formation of new bones.In summary,the porous smart shape-memory composite scaffolds could be a potential candidate in future distinctive bone repair applications.
基金supported financially by the National Science Foundation of China (Nos. 51473096, 51421061, J1103315)Program for Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China (No. IRT 1026)
文摘Shape-memory poly（p-dioxanone）–poly（e-caprolactone）/sepiolite（PPDO–PCL/OSEP） nanocomposites with different OSEP nanofiber loading were fabricated by chain-extending the PPDO-diol and PCL/OSEP precursors. The precursors and the composites were characterized by1 H NMR, FT-IR, GPC, SEM and TEM.The results demonstrate that a part of PCL segments grafted on the surface of OSEP and composites display a fine dispersion of OSEP fiber in nanoscale with low OSEP content. The shape memory effect（SME） was evaluated by DMA, the results reveal that the PPDO–PCL/OSEP nanocomposites exhibit desirable shape-memory performance. The reinforcement of composites by incorporation of trace OSEP nanofiber evokes an effective improvement in shape-memory recovery stress.
基金Supported by Shenyang Medical College Youth Scientific Research Fund,No.20202027.
文摘BACKGROUND Comminuted manubrium sterni fractures are rare,and internal fixation methods are limited.This report explored a practical and feasible method of internal fixation for comminuted manubrium sterni fractures.CASE SUMMARY A 17-year-old female was injured in a car accident for which she underwent debridement and suturing of her head and anterior chest wounds in another hospital.Eight days later,the patient was transferred to our hospital for surgical treatment.The manubrium sterni was found intraoperatively to be split into three irregular fragments with obvious overlap and separation displacement.Meanwhile,a manubriosternal joint dislocation and left first rib cartilage fracture were observed.The retraction force of the shape-memory alloy staples was used to pull the fracture fragments together.Two more titanium locking plates were then used to fix the manubrium sterni and corpus sterni longitudinally,and the left first rib cartilage fracture was repositioned and fixed with a titanium locking plate.A postoperative computed tomography scan showed reduced and rigid fixation of the comminuted manubrium sterni fractures.The patient recovered well with no significant complaints of discomfort.The patient was discharged 10 days postoperatively after the stitches had been removed.CONCLUSION Shape-memory alloy staples had the advantage of being safe and effective during the repositioning and internal fixation of comminuted manubrium sterni fractures.Therefore,they provided a new surgical option for comminuted manubrium sterni fractures.
文摘The valence changes of doped samarium and the creation as well as the annihilation of F-centers in the processes of thermostimulated luminescence (TSL) and photostimulated luminescence (PSL) of BaFCl∶Sm crystal have been studied. As being irradiated by X-ray,a large number of electron-hole pairs are created in the crystal.Most of the electrons may be trapped at the anion vacancies,producing F-centers.The doped samarium ions,which existed mostly in trivalent state (Sm^(3+)),may capture the holes and convert themselves to tetravalent state.So that part of the incident X-ray energy are stored in this nonequilibrium system.On optical and thermal stimulation the stored energy can be liberated as a characteristic emission of trivalent samarium ion.This emission originates from the recombination of the F-center electrons with tetravalent samarium ions,i.e.the F-center electrons may be excited to the conduction band by optical or thermal stirnulation and then recombine with tetravalent samarium ions.This recombination makes the samarium ions to be in situ reduced to the excited state of Sm^(3+),and gives rise to the characteristic emission of Sm^(3+). On the other hand,during X-irradiation a few electrons can be trapped at the sites of trivalent samarium ions and reduce them to divalent state.But the formation of divalent samarium On X-irradiation is very small as compared with that of F-centers and so their influence on the PSL and TSL can be neglected.
基金Supported by the National Natural Science Foundation of China(Grant No.50373045)
文摘As an important kind of intelligent materials,shape-memory materials have been received increasing attention on account of their interesting properties and potential applications in recent years.Particularly,the rise of shape-memory polymers by far surpasses well-known metallic shape-memory alloys in their shape-memory properties.The advantages of polymers compared to other materials are their easier availability and their wide range of mechanical and physical properties.The polymers designed to exhibit a shape-memory effect require two components on the molecular level:crosslinks to determine the permanent shape and switching segments with Ttrans to fix the temporary shape.Up to now almost all papers on shape-memory polymers introduce switching segments with the covalent linking method.On the other hand,only several cases concern non-covalent interaction.However,the research works mentioned above is based on a single Trans(i.e.,Tm or Tg).
文摘The integration of smart materials and alloys with additive manufacturing(AM)technologies represents a paradigm shift in modern manufacturing,enabling the creation of highly functional,adaptive,and customizable components.Smart materials have special qualities that allow them to react dynamically to environmental stimuli like temperature,electric fields,and mechanical stress.Examples of these materials include shape-memory alloys(SMAs),piezoelectric materials,magnetostrictive alloys,and self-healing polymers.The integration of smart materials and alloys with additive manufacturing holds transformative potential across industries,offering new avenues for innovation and product design.These materials,combined with AM processes such as selective laser sintering(SLS),fused deposition modeling,and direct ink writing,enable the creation of complex geometries and multifunctional components that were previously unattainable through traditional manufacturing methods.Furthermore,the paper examines the applications of smart materials and alloys in creating adaptive systems and multifunctional devices,such as self-healing structures,shape-changing actuators,and flexible sensors.The study provides a comprehensive overview of recent advances in the integration of smart materials and alloys into various AM techniques,such as powder bed fusion,direct ink writing,and stereolithography.Key challenges,including material-process compatibility,thermal and mechanical limitations,and scalability,are critically analyzed in the study.This study attempts to assist academics and companies in realizing the full potential of AM-enabled smart material applications by analyzing current advancements,challenges,and opportunities for the future research works.As a result,the review concludes with potential future research directions and the transformative impact of this integration on modern manufacturing and product design.
基金supported by the National Natural Science Foundation of China(No.22375063)Science and Technology Commission of Shanghai Municipality(No.23JC1401700)the Fundamental Research Funds for the Central Universities.
文摘Developing advanced polymeric materials with enhanced mechanical properties and functionalities has been a long-standing goal in materials science.Recently,supramolecular polymeric materials (SPMs) have drawn increased attention due to their unique properties and potential applications in self-healing,shape memory,sensors,and flexible electronics.Here,we develop an ionic cluster-optimized microphase separation strategy to enhance the toughening and energy dissipation capabilities of polydisulfide-based supramolecular polymers.The mechanical properties,including Young’s modulus and toughness,are significantly improved by integrating the quadruple H-bonding 2-ureido-4-pyrimidone (UPy) induced microphase separation with iron(Ⅲ)-to-carboxylate ionic clusters.By combining established chemical approaches with adjustable polymer phase ratios,it is revealed that the synergistic effect of these factors expands the interchain spacing,facilitates the formation of microphase domains,and enhances the tolerance of polythioctic acid-based polymers to external mechanical and thermal stimuli,meeting the practical requirements for industrial plastic applications.Moreover,the UPy-functionalized polymers incorporating iron carboxylate clusters exhibit good one-way shape memory behavior with practical applicability at a relatively low recovery temperature.Our work demonstrates a novel strategy for constructing industrially viable shape memory dynamic SPMs and paves the way for future innovations in developing SPMs.
基金supported by the Air Force Office of Scientific Research under Award(Grant FA9550-19-1-0395)the National Science Foundation(Grant 1935154)。
文摘A shape-memory double network hydrogel consists of two polymer networks:a chemically crosslinked primary network that is responsible for the permanent shape and a physically crosslinked secondary network that is used to fix the temporary shapes.The formation/melting transition of the secondary network serves as an effective mechanism for the double network hydrogel’s shape-memory effect.When the crosslinks in the secondary network are dissociated by applying an external stimulus,only the primary network is left to support the load.When the secondary network is re-formed by removing the stimulus,both the primary and secondary networks support the load.In the past,models have been developed for the constitutive behaviors of double network hydrogels,but the model of shape-memory double network hydrogels is still lacking.This work aims to build a constitutive model for the polyacrylamide-gelatin double network shape-memory hydrogel developed in our previous work.The model is first calibrated by experimental data of the double network shape-memory hydrogel under uniaxial loading and then employed to predict the shape-fixing performance of the hydrogel.The model is also implemented into a three-dimension finite element code and utilized to simulate the shape-memory behavior of the double network hydrogel with inhomogeneous deformations related to applications.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.51001010 and 11174030)the Research Fund for the Doctoral Program of Higher Education of China(Grant No.20100006120001)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,State Education Ministry of China
文摘The structures, the martensitic transformations, and the magnetic properties are studied systematically in Mn50Ni40-xCuxIn10, Mn50-xCuxNi40In10, and Mn50Ni40In10-xCux alloys. The partial substitution of Ni by Cu reduces the martensitic transformation temperature, but has little influence on the Curie temperature of austenite. Comparatively, the martensitic transformation temperature increases and the Curie temperature of austenite decreases with the partial replacement of Mn or In by Cu. The magnetization difference between the austenite phase and the martensite phase reaches 70 emu/g in Mn50Ni39Cu1In10; a field-induced martensite-to-austenite transition is observed in this alloy.
