The preparation of TiO2/poly（L-lactide-co-ε-caprolactone）（PLCL） nanocomposites and their properties were reported.TiO2nanoparticles were surface modified by ring-opening polymerization of ε-caprolactone（ε-CL）...The preparation of TiO2/poly（L-lactide-co-ε-caprolactone）（PLCL） nanocomposites and their properties were reported.TiO2nanoparticles were surface modified by ring-opening polymerization of ε-caprolactone（ε-CL）.The resulting poly（ε-caprolactone）-grafted TiO2（g-TiO2） was characterized by Fourier transform infrared spectroscopy（FTIR）,thermogravimetric analysis（TGA） and transmission electron microscopy（TEM）.The g-TiO2can be uniformly dispersed in chloroform and the g-TiO2/PLCL nanocomposites were successfully fabricated through solvent-casting method.The effects of the content of g-TiO2nanoparticles on tensile properties and shape memory properties were investigated.A significant improvement in the tensile properties of the 5% g-TiO2/PLCL mass fraction nanocomposite is obtained：an increase of 113% in the tensile strength and an increase of 11% in the elongation at break over pure PLCL polymer.The g-TiO2/PLCL nanocomposites with a certain amount of g-TiO2content have better shape memory properties than pure PLCL polymer.The g-TiO2nanoparticles play an additional physical crosslinks which are contributed to improvement of the shape memory properties.展开更多
The excellent shape memory and mechanical properties of Ti Ni shape memory alloys(SMAs) fabricated using selective laser melting(SLM) are highly desirable for a wide range of critical applications. In this study, we e...The excellent shape memory and mechanical properties of Ti Ni shape memory alloys(SMAs) fabricated using selective laser melting(SLM) are highly desirable for a wide range of critical applications. In this study, we examined the simultaneous enhancement of mechanical and shape memory properties using heat-treatment homogenization of Ti_(2)Ni precipitates in a Ti_(50.6)Ni_(49.4)SMA fabricated using SLM. Specifically, because of the complete solution treatment, nanoscale spherical Ti_(2)Ni precipitates were homogeneously dispersed throughout the grain interior. Interestingly, the resultant SMA exhibited an ultrahigh tensile strength of 880 ± 13 MPa, a large elongation of 22.4 ± 0.4%, and an excellent shape memory effect, with a recovery rate of > 98% and ultrahigh recoverable strain of 5.32% after ten loading–unloading cycles. These simultaneously enhanced properties are considerably superior than those of most previously reported Ti Ni SMAs fabricated using additive manufacturing. Fundamentally, the enhancement in tensile strength is ascribed to precipitation strengthening and work hardening, and the large plasticity is mainly attributed to the homogeneous nanoscale globular Ti_(2)Ni precipitates, which effectively impeded the rapid propagation of microcracks. Furthermore, the enhanced shape memory properties are derived from the suppression of dislocation movement and formation of retained stabilized martensite by the presence of high-density dislocations, nanoscale Ti_(2)Ni precipitates, and abundant interfaces. The obtained results provide insight into the enhancement of the two types of properties in Ti Ni SMAs and will accelerate the wider application of SMAs.展开更多
In this contribution, we reported a novel synthesis of block copolymer networks composed of poly(ε-caprolactone)(PCL) and polyethylene(PE) via the co-hydrolysis and condensation of α,ω-ditriethoxylsilane-terminated...In this contribution, we reported a novel synthesis of block copolymer networks composed of poly(ε-caprolactone)(PCL) and polyethylene(PE) via the co-hydrolysis and condensation of α,ω-ditriethoxylsilane-terminated PCL and PE telechelics. First, α,ω-dihydroxylterminated PCL and PE telechelics were synthesized via the ring-opening polymerization of ε-caprolactone and the ring-opening metathesis polymerization of cyclooctene followed by hydrogenation of polycyclooctene. Both α,ω-ditriethoxylsilane-terminated PCL and PE telechelics were obtained via in situ reaction of α,ω-dihydroxyl-terminated PCL and PE telechelics with 3-isocyanatopropyltriethoxysilane. The formation of networks was evidenced by the solubility and rheological tests. It was found that the block copolymer networks were microphase-separated. The PCL and PE blocks still preserved the crystallinity. Owing to the formation of crosslinked networks, the materials displayed shape memory properties. More importantly, the combination of PCL with PE resulted that the block copolymer networks had the triple shape memory properties, which can be triggered with the melting and crystallization of PCL and PE blocks. The results reported in this work demonstrated that triple shape memory polymers could be prepared via the formation of block copolymer networks.展开更多
Metallurgical and mechanical properties along with shape memory and corrosion behavior of Cu-11.8% AI-3.7% Ni-1 %Mn and Cu-11% A1 5.6% Mn shape memory alloys （SMAs） were comparatively studied. The influence of grain...Metallurgical and mechanical properties along with shape memory and corrosion behavior of Cu-11.8% AI-3.7% Ni-1 %Mn and Cu-11% A1 5.6% Mn shape memory alloys （SMAs） were comparatively studied. The influence of grain refinement on the properties was studied by optical microscopy （OM）, scanning electron microscopy （SEM）, differential scanning calorimetry （DSC）, potentiodynamic polarizations and bend and tensile tests. Static recrystallization and kinetic grain growth show a rapid recrystallization in the first 15 s of annealing at 800℃ followed by grain growths. The minimum grain sizes obtained after 15 s are 90 and 260 μm for Cu-A1-Ni-Mn and Cu-A1-Mn, respectively. Tensile tests show typical three-stage curves for both alloys, and it is seen that alloys exhibit high fracture stress and strain after grain refinement. Microstructural observations show zig-zag morphology of β 1martensite in the Cu-A1-Ni-Mn and coexistence of β1 and y1 in the Cu-A1-Mn, which were confirmed by differential scanning calorimetry results. The shape memory ratios （17） of the alloys before thermomechanieal treatment, and after thermomechanical annealing at 800 ℃ for different time up to 15 min followed by water quenching, were evaluated. In addition, corrosion behavior of alloys after grain refinement was analyzed by means of potentiodynamic polarization measurements. The results showed that the anodic reactions were dominated by dissolution of copper, and Cu-AI-Ni-Mn alloy exhibits a better corrosion resistance than Cu-A1-Mn alloy.展开更多
The goal of this study is to design and synthesize a linear segmented shape memory poly（urethane-urea） （SMPUU） that possesses near-body-temperature shape memory temperature （Ttran） and enhanced mechanical proper...The goal of this study is to design and synthesize a linear segmented shape memory poly（urethane-urea） （SMPUU） that possesses near-body-temperature shape memory temperature （Ttran） and enhanced mechanical properties by incorporating flexible poly（ethylene glycol） 400 （PEG400） to form poly（D,L-lactic acid）-based macro- diols （PDLLA-PEG400-PDLLA） and then rigid piperazine （PPZ） as a chain extender to form the desired SMPUUs （PEG400-PUU-PPZ）. PEG400 increased Mn while maintaining a lower Tg of PDLLA-PEG400-PDLLA, which together with PPZ improved the mechanical properties of PEG400-PUU-PPZ. The obtained optimum SMPUU with enhanced mechanical properties （O＇y = 24.28 MPa; zf = 698%; Uf = 181.5 MJIm3） and a Tg of 40.62~C exhibited sound shape memory properties as well, suggesting a promising SMPUU for in vivo biomedical applications.展开更多
基金Project(50903023) supported by the National Natural Science Foundation of ChinaProject(HEUCF201210005) supported by the Fundamental Research Funds for the Central Universities,ChinaProject(2010RFQXG037) supported by Harbin Special Fund for Innovation Talents of Science and Technology,China
文摘The preparation of TiO2/poly（L-lactide-co-ε-caprolactone）（PLCL） nanocomposites and their properties were reported.TiO2nanoparticles were surface modified by ring-opening polymerization of ε-caprolactone（ε-CL）.The resulting poly（ε-caprolactone）-grafted TiO2（g-TiO2） was characterized by Fourier transform infrared spectroscopy（FTIR）,thermogravimetric analysis（TGA） and transmission electron microscopy（TEM）.The g-TiO2can be uniformly dispersed in chloroform and the g-TiO2/PLCL nanocomposites were successfully fabricated through solvent-casting method.The effects of the content of g-TiO2nanoparticles on tensile properties and shape memory properties were investigated.A significant improvement in the tensile properties of the 5% g-TiO2/PLCL mass fraction nanocomposite is obtained：an increase of 113% in the tensile strength and an increase of 11% in the elongation at break over pure PLCL polymer.The g-TiO2/PLCL nanocomposites with a certain amount of g-TiO2content have better shape memory properties than pure PLCL polymer.The g-TiO2nanoparticles play an additional physical crosslinks which are contributed to improvement of the shape memory properties.
基金supported financially by the Key-Area Research and Development Program of Guangdong Province (No. 2020B090923001)the National Natural Science Foundation of China (No. U19A2085)+3 种基金the Key Basic and Applied Research Program of Guangdong Province (No. 2019B030302010)the financial support from the China Postdoctoral Science Foundation (No. 2019M662908)Guangdong Basic and Applied Basic Research Foundation (No.2019A1515110215)the Fundamental Research Funds for the Central Universities (No.2020ZYGXZR030)。
文摘The excellent shape memory and mechanical properties of Ti Ni shape memory alloys(SMAs) fabricated using selective laser melting(SLM) are highly desirable for a wide range of critical applications. In this study, we examined the simultaneous enhancement of mechanical and shape memory properties using heat-treatment homogenization of Ti_(2)Ni precipitates in a Ti_(50.6)Ni_(49.4)SMA fabricated using SLM. Specifically, because of the complete solution treatment, nanoscale spherical Ti_(2)Ni precipitates were homogeneously dispersed throughout the grain interior. Interestingly, the resultant SMA exhibited an ultrahigh tensile strength of 880 ± 13 MPa, a large elongation of 22.4 ± 0.4%, and an excellent shape memory effect, with a recovery rate of > 98% and ultrahigh recoverable strain of 5.32% after ten loading–unloading cycles. These simultaneously enhanced properties are considerably superior than those of most previously reported Ti Ni SMAs fabricated using additive manufacturing. Fundamentally, the enhancement in tensile strength is ascribed to precipitation strengthening and work hardening, and the large plasticity is mainly attributed to the homogeneous nanoscale globular Ti_(2)Ni precipitates, which effectively impeded the rapid propagation of microcracks. Furthermore, the enhanced shape memory properties are derived from the suppression of dislocation movement and formation of retained stabilized martensite by the presence of high-density dislocations, nanoscale Ti_(2)Ni precipitates, and abundant interfaces. The obtained results provide insight into the enhancement of the two types of properties in Ti Ni SMAs and will accelerate the wider application of SMAs.
基金the National Natural Science Foundation of China for the financial supports of this work(Nos.51973113,51133003 and 21774078)。
文摘In this contribution, we reported a novel synthesis of block copolymer networks composed of poly(ε-caprolactone)(PCL) and polyethylene(PE) via the co-hydrolysis and condensation of α,ω-ditriethoxylsilane-terminated PCL and PE telechelics. First, α,ω-dihydroxylterminated PCL and PE telechelics were synthesized via the ring-opening polymerization of ε-caprolactone and the ring-opening metathesis polymerization of cyclooctene followed by hydrogenation of polycyclooctene. Both α,ω-ditriethoxylsilane-terminated PCL and PE telechelics were obtained via in situ reaction of α,ω-dihydroxyl-terminated PCL and PE telechelics with 3-isocyanatopropyltriethoxysilane. The formation of networks was evidenced by the solubility and rheological tests. It was found that the block copolymer networks were microphase-separated. The PCL and PE blocks still preserved the crystallinity. Owing to the formation of crosslinked networks, the materials displayed shape memory properties. More importantly, the combination of PCL with PE resulted that the block copolymer networks had the triple shape memory properties, which can be triggered with the melting and crystallization of PCL and PE blocks. The results reported in this work demonstrated that triple shape memory polymers could be prepared via the formation of block copolymer networks.
文摘Metallurgical and mechanical properties along with shape memory and corrosion behavior of Cu-11.8% AI-3.7% Ni-1 %Mn and Cu-11% A1 5.6% Mn shape memory alloys （SMAs） were comparatively studied. The influence of grain refinement on the properties was studied by optical microscopy （OM）, scanning electron microscopy （SEM）, differential scanning calorimetry （DSC）, potentiodynamic polarizations and bend and tensile tests. Static recrystallization and kinetic grain growth show a rapid recrystallization in the first 15 s of annealing at 800℃ followed by grain growths. The minimum grain sizes obtained after 15 s are 90 and 260 μm for Cu-A1-Ni-Mn and Cu-A1-Mn, respectively. Tensile tests show typical three-stage curves for both alloys, and it is seen that alloys exhibit high fracture stress and strain after grain refinement. Microstructural observations show zig-zag morphology of β 1martensite in the Cu-A1-Ni-Mn and coexistence of β1 and y1 in the Cu-A1-Mn, which were confirmed by differential scanning calorimetry results. The shape memory ratios （17） of the alloys before thermomechanieal treatment, and after thermomechanical annealing at 800 ℃ for different time up to 15 min followed by water quenching, were evaluated. In addition, corrosion behavior of alloys after grain refinement was analyzed by means of potentiodynamic polarization measurements. The results showed that the anodic reactions were dominated by dissolution of copper, and Cu-AI-Ni-Mn alloy exhibits a better corrosion resistance than Cu-A1-Mn alloy.
文摘The goal of this study is to design and synthesize a linear segmented shape memory poly（urethane-urea） （SMPUU） that possesses near-body-temperature shape memory temperature （Ttran） and enhanced mechanical properties by incorporating flexible poly（ethylene glycol） 400 （PEG400） to form poly（D,L-lactic acid）-based macro- diols （PDLLA-PEG400-PDLLA） and then rigid piperazine （PPZ） as a chain extender to form the desired SMPUUs （PEG400-PUU-PPZ）. PEG400 increased Mn while maintaining a lower Tg of PDLLA-PEG400-PDLLA, which together with PPZ improved the mechanical properties of PEG400-PUU-PPZ. The obtained optimum SMPUU with enhanced mechanical properties （O＇y = 24.28 MPa; zf = 698%; Uf = 181.5 MJIm3） and a Tg of 40.62~C exhibited sound shape memory properties as well, suggesting a promising SMPUU for in vivo biomedical applications.
