The effect of time and environment on the dimension precision and mass of LOM prototypes was experimentally investigated.It is to identify the stability of the dimension of LOM prototypes after forming.The results sho...The effect of time and environment on the dimension precision and mass of LOM prototypes was experimentally investigated.It is to identify the stability of the dimension of LOM prototypes after forming.The results show that the dimension and the mass tendency to grow,which is mainly caused by elastic recovery and moisture absorption and is characterized principally by the growth of Z dimension.Self restraint can be a significant factor to influence Z growth of LOM prototypes.展开更多
It is difficult for polyethylene terephthalate （PET） to degrade,which caused severe pollution.In this work,polylactic acid （PLA） was introduced to improve the degradation of PET.PET/PLA was synthesized by extrusio...It is difficult for polyethylene terephthalate （PET） to degrade,which caused severe pollution.In this work,polylactic acid （PLA） was introduced to improve the degradation of PET.PET/PLA was synthesized by extrusion blending.The thermal,crystalline and mechanical properties of blends were investigated with TGA,DSC,WAXD and universal testing machine.The degradation of the blends in soil,acid and alkaline buffer solutions was assessed,respectively.It was found that the introduction of a little PLA promoted crystallization of PET during injection molding process.The starting decomposition temperature lowered from 412.1 ℃ of pure PET to 330.4 ℃ at 50% PLA content,tensile and bending strength of blends gradually decreased with the PLA content increasing,while the degradation rate improved.Alkaline environment was most beneficial for blends to degrade.The degradation mechanism was discussed.展开更多
Due to the strong shearing field during processing,untra-thin injection molded CNT-filled polypropylene(PP) always forms a strong CNT orientation along the flow direction,which results in its anisotropic conductivity....Due to the strong shearing field during processing,untra-thin injection molded CNT-filled polypropylene(PP) always forms a strong CNT orientation along the flow direction,which results in its anisotropic conductivity.In order to evaluate the mechanism on recovery of the orientation,we processed the molding under the condition of different thermal compressive strains with modified hot-rolling machine.The stability of the molding's conductivity after rolling was studied under the action of alternated loading.The disoriented behavior of the microstructures during rolling was observed by SEM and 2 D-WAXD,and the degree of orientation of CNT was calculated.The conductivity of the sample was measured using a standard two-terminal DC resistor.The results showed that the deformation resistance in the rolling direction was greater than that in the transverse deformation under the action of large thermal compressive strain.The samples would mainly deform in the transverse direction and not elongate in the direction of the rolling,which could speed up the recovery of the orientation structure and reduce the anisotropy of the conductivity.The recovery speed of the orientation was related to the level of the thermal compressive strain.After the hotrolling processing,the stability of the sample's conductivity under the alternating load was improved because of the effect induced by polymer strengthening.展开更多
Three-dimensional(3 D)printing has had a large impact on various fields,with fused deposition modeling(FDM)being the most versatile and cost-effective 3 D printing technology.However,FDM often requires sacrificial sup...Three-dimensional(3 D)printing has had a large impact on various fields,with fused deposition modeling(FDM)being the most versatile and cost-effective 3 D printing technology.However,FDM often requires sacrificial support structures,which significantly complicates the processing and increases the cost.Furthermore,poor layer-to-layer adhesion greatly affects the mechanical stability of 3D-printed objects.Here,we present a new Print-Healing strategy to address the aforementioned challenges.A polymer ink(Cu-DOU-CPU)with synergetic triple dynamic bonds was developed to have excellent printability and room-temperature self-healing ability.Objects with various shapes were printed using a simple compact 3D printer,and readily assembled into large sophisticated architectures via self-healing.Triple dynamic bonds induce strong binding between layers.Additionally,damaged printed objects can spontaneously heal,which significantly elongates their service life.This work paves a simple and powerful way to solve the key bottlenecks in FDM 3D printing,and will have diverse applications.展开更多
In this paper,we introduce different forms of mobility into a quantitative phase-field model to produce arbitrary Ehrlich-Schwoebel(ES)effects.Convergence studies were carried out in the one-side step-flow model,which...In this paper,we introduce different forms of mobility into a quantitative phase-field model to produce arbitrary Ehrlich-Schwoebel(ES)effects.Convergence studies were carried out in the one-side step-flow model,which showed that the original mobility not only induces the ES effect,but also leads to larger numerical instability with increase of the step width.Thus,another modified form of the ES barrier is proposed,and is found to be more suitable for large-scale simulations.Model applications were performed on the wedding-cake structure,coarsening and coalescence of islands and spiral growth.The results show that the ES barrier exhibits more significant kinetic effects at the larger deposition rates by limiting motions of atoms on upper steps,leading to aggregation on the top layers,as well as the roughening of growing surfaces.展开更多
Ultrasound(US) imaging in combination with US contrast agents(UCAs) is a powerful tool in the modern biomedical field because of its high spatial resolution, easy access to patients and minimum invasiveness.The microb...Ultrasound(US) imaging in combination with US contrast agents(UCAs) is a powerful tool in the modern biomedical field because of its high spatial resolution, easy access to patients and minimum invasiveness.The microbubble-based UCAs have been widely used in clinical diagnosis; however, they are only limited to the blood pool imaging and not applicable to the tissue-penetrated imaging due to their large particle size and structural instability. Inorganic nanoparticles(NPs), such as silica,gold and Fe x O y, featured with both satisfactory echogenic properties and structural stability have the potential to be used as a new generation of UCAs. In this review, we present the most recent progresses in the tailored construction of inorganic UCAs and their biomedical applications in the US imaging-involved fields. Firstly, the typical inorganic NPs with different structures including solid, hollow and multiple-layer forms will be comprehensively introduced in terms of their structure design,physicochemical property, US imaging mechanism and diverse applications; secondly, the recent progress in exploring the gas-generating inorganic NP system for US imaging purpose will be reviewed, and these intelligent UCAs are multifunctional for simultaneous US imaging and disease therapy; thirdly, several nanocomposite platforms newly constructed by combining inorganic UCAs with other functional components will be presented anddiscussed. These multifunctional NPs are capable of further enhancing the imaging resolution by providing more comprehensive anatomical information simultaneously.Last but not the least, the design criteria for developing promising UCAs to satisfy both clinical demands and optimized US imaging capability will be discussed and summarized in this review.展开更多
文摘The effect of time and environment on the dimension precision and mass of LOM prototypes was experimentally investigated.It is to identify the stability of the dimension of LOM prototypes after forming.The results show that the dimension and the mass tendency to grow,which is mainly caused by elastic recovery and moisture absorption and is characterized principally by the growth of Z dimension.Self restraint can be a significant factor to influence Z growth of LOM prototypes.
文摘It is difficult for polyethylene terephthalate （PET） to degrade,which caused severe pollution.In this work,polylactic acid （PLA） was introduced to improve the degradation of PET.PET/PLA was synthesized by extrusion blending.The thermal,crystalline and mechanical properties of blends were investigated with TGA,DSC,WAXD and universal testing machine.The degradation of the blends in soil,acid and alkaline buffer solutions was assessed,respectively.It was found that the introduction of a little PLA promoted crystallization of PET during injection molding process.The starting decomposition temperature lowered from 412.1 ℃ of pure PET to 330.4 ℃ at 50% PLA content,tensile and bending strength of blends gradually decreased with the PLA content increasing,while the degradation rate improved.Alkaline environment was most beneficial for blends to degrade.The degradation mechanism was discussed.
基金Sponsored by the National Natural Science Foundation of China(Grant Nos.51373048 and U1604253)
文摘Due to the strong shearing field during processing,untra-thin injection molded CNT-filled polypropylene(PP) always forms a strong CNT orientation along the flow direction,which results in its anisotropic conductivity.In order to evaluate the mechanism on recovery of the orientation,we processed the molding under the condition of different thermal compressive strains with modified hot-rolling machine.The stability of the molding's conductivity after rolling was studied under the action of alternated loading.The disoriented behavior of the microstructures during rolling was observed by SEM and 2 D-WAXD,and the degree of orientation of CNT was calculated.The conductivity of the sample was measured using a standard two-terminal DC resistor.The results showed that the deformation resistance in the rolling direction was greater than that in the transverse deformation under the action of large thermal compressive strain.The samples would mainly deform in the transverse direction and not elongate in the direction of the rolling,which could speed up the recovery of the orientation structure and reduce the anisotropy of the conductivity.The recovery speed of the orientation was related to the level of the thermal compressive strain.After the hotrolling processing,the stability of the sample's conductivity under the alternating load was improved because of the effect induced by polymer strengthening.
基金supported by the National Natural Science Foundation of China(21991123,52073049 and 51703148)the Natural Science Foundation of Shanghai(20ZR1402500 and18ZR1401900)+4 种基金the Belt&Road Young Scientist Exchanges Project of Science and Technology Commission Foundation of Shanghai(20520741000)Shanghai Belt and Road Joint Laboratory of Advanced Fiber and Low-dimension Materials(Donghua University(DHU),18520750400)the Fundamental Research Funds for the Central UniversitiesDHU Distinguished Young Professor Program(LZA2019001)the Open Research Fund of Shanghai Center for High-performance Fibers and Composites and the Center for Civil Aviation Composites of Donghua University。
文摘Three-dimensional(3 D)printing has had a large impact on various fields,with fused deposition modeling(FDM)being the most versatile and cost-effective 3 D printing technology.However,FDM often requires sacrificial support structures,which significantly complicates the processing and increases the cost.Furthermore,poor layer-to-layer adhesion greatly affects the mechanical stability of 3D-printed objects.Here,we present a new Print-Healing strategy to address the aforementioned challenges.A polymer ink(Cu-DOU-CPU)with synergetic triple dynamic bonds was developed to have excellent printability and room-temperature self-healing ability.Objects with various shapes were printed using a simple compact 3D printer,and readily assembled into large sophisticated architectures via self-healing.Triple dynamic bonds induce strong binding between layers.Additionally,damaged printed objects can spontaneously heal,which significantly elongates their service life.This work paves a simple and powerful way to solve the key bottlenecks in FDM 3D printing,and will have diverse applications.
基金The National Natural Science Foundation of China(Grant Nos.61078057,61471301,51172183,51402240 and 51471134)The NPU Foundation for Fundamental Research(Grant No.JC20120246)+2 种基金The National Science Foundation of Shaanxi Province,China(Grant No.2012JQ8013)The Doctorate Foundation of Northwestern Polytechnical University(Grant No.CX201325)The Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.20126102110045)
文摘In this paper,we introduce different forms of mobility into a quantitative phase-field model to produce arbitrary Ehrlich-Schwoebel(ES)effects.Convergence studies were carried out in the one-side step-flow model,which showed that the original mobility not only induces the ES effect,but also leads to larger numerical instability with increase of the step width.Thus,another modified form of the ES barrier is proposed,and is found to be more suitable for large-scale simulations.Model applications were performed on the wedding-cake structure,coarsening and coalescence of islands and spiral growth.The results show that the ES barrier exhibits more significant kinetic effects at the larger deposition rates by limiting motions of atoms on upper steps,leading to aggregation on the top layers,as well as the roughening of growing surfaces.
基金supported by China National Funds for Distinguished Young Scientists(51225202)the National Natural Science Foundation of China(51402329)+1 种基金Science Foundation for Youth Scholar of State Key Laboratory of High Performance Ceramics and Superfine Microstructures(SKL201404)Shanghai Excellent Academic Leaders Program(14XD1403800)
文摘Ultrasound(US) imaging in combination with US contrast agents(UCAs) is a powerful tool in the modern biomedical field because of its high spatial resolution, easy access to patients and minimum invasiveness.The microbubble-based UCAs have been widely used in clinical diagnosis; however, they are only limited to the blood pool imaging and not applicable to the tissue-penetrated imaging due to their large particle size and structural instability. Inorganic nanoparticles(NPs), such as silica,gold and Fe x O y, featured with both satisfactory echogenic properties and structural stability have the potential to be used as a new generation of UCAs. In this review, we present the most recent progresses in the tailored construction of inorganic UCAs and their biomedical applications in the US imaging-involved fields. Firstly, the typical inorganic NPs with different structures including solid, hollow and multiple-layer forms will be comprehensively introduced in terms of their structure design,physicochemical property, US imaging mechanism and diverse applications; secondly, the recent progress in exploring the gas-generating inorganic NP system for US imaging purpose will be reviewed, and these intelligent UCAs are multifunctional for simultaneous US imaging and disease therapy; thirdly, several nanocomposite platforms newly constructed by combining inorganic UCAs with other functional components will be presented anddiscussed. These multifunctional NPs are capable of further enhancing the imaging resolution by providing more comprehensive anatomical information simultaneously.Last but not the least, the design criteria for developing promising UCAs to satisfy both clinical demands and optimized US imaging capability will be discussed and summarized in this review.
