The crystallization behavior, rheological behavior, mechanical properties and microstructures of injection molded isotactic polypropylene （iPP）, polypropylene random copolymer （co-PP） and iPP/co-PP blends were inv...The crystallization behavior, rheological behavior, mechanical properties and microstructures of injection molded isotactic polypropylene （iPP）, polypropylene random copolymer （co-PP） and iPP/co-PP blends were investigated. Differential scanning calorimetry （DSC） and dynamic rheological analysis illustrated that iPP and co-PP were compatible in the blends and co-PP uniformly dispersed in the/PP phase. Polarizing optical microscope （POM） was adopted to observe the crystal size and morphology evolution. The results of mechanical properties and scanning electron microscopy （SEM） indicated that the crystal size of iPP in iPP/co-PP blends （10 wt% co-PP ＋ 90 wt% iPP and 30 wt% co-PP ＋ 70 wt% iPP） radically decreased after the incorporation of co-PP. During crystallization, the molecular chain segments of co-PP could penetrate iPP spherulites and form a network-like crystalline structure. The network-like crystal structure could effectively transmit stress and consume more energy to overcome intermolecular forces to resist stretching. In this way, the strength would improve to a certain degree. The impact fracture mechanism of iPP/co-PP blends is quasi ductile fracture by multiple crazes. Our work discovered that the blends containing 10 wt% and 30 wt% ofco-PP exhibited prominent toughness and reinforcement.展开更多
Reasonable design of effective and durable electrocatalysts for methanol oxidation reaction(MOR)is crucial for promoting the commercialization of direct methanol fuel cells(DMFCs).In this work,a network-like PtCu stru...Reasonable design of effective and durable electrocatalysts for methanol oxidation reaction(MOR)is crucial for promoting the commercialization of direct methanol fuel cells(DMFCs).In this work,a network-like PtCu structure supported on three-dimensional N-doped graphene-carbon nanotube(n-PtCu/3DNG-CNT)was successfully prepared via a rational design strategy.The three-dimensional N-doped graphene with an open porous structure facilitates methanol molecule transfer,exposes activity sites,and anchors metal catalysts effectively.The designed network-like PtCu structure,with lattice defects,steps,and twin grain boundaries,is befeficial for inducing new properties(lattice structure,electronic structure,and chemical structure),forming more effective active centers while enhancing its anti-CO poisoning ability through a bifunctional mechanism.Further characterizations reveal the existence of a complex interface effect between N-doped graphene and carbon nanotube,which is demonstrated in detail.The n-PtCu/3DNG-CNT catalyst exhibits excellent MOR activity and durability in an acidic medium.展开更多
In this paper, we have studied a general kind of n-species Lotka-Volterra network- like food-chain system with delays and impulses on time scales. Applying Mawhin＇s continuation theorem of coincidence degree theory a...In this paper, we have studied a general kind of n-species Lotka-Volterra network- like food-chain system with delays and impulses on time scales. Applying Mawhin＇s continuation theorem of coincidence degree theory and some skills of inequalities, some sufficient criteria have been established to guarantee the existence of at least 2n periodic solutions to this model. One example is given to illustrate the effectiveness of our results.展开更多
文摘The crystallization behavior, rheological behavior, mechanical properties and microstructures of injection molded isotactic polypropylene （iPP）, polypropylene random copolymer （co-PP） and iPP/co-PP blends were investigated. Differential scanning calorimetry （DSC） and dynamic rheological analysis illustrated that iPP and co-PP were compatible in the blends and co-PP uniformly dispersed in the/PP phase. Polarizing optical microscope （POM） was adopted to observe the crystal size and morphology evolution. The results of mechanical properties and scanning electron microscopy （SEM） indicated that the crystal size of iPP in iPP/co-PP blends （10 wt% co-PP ＋ 90 wt% iPP and 30 wt% co-PP ＋ 70 wt% iPP） radically decreased after the incorporation of co-PP. During crystallization, the molecular chain segments of co-PP could penetrate iPP spherulites and form a network-like crystalline structure. The network-like crystal structure could effectively transmit stress and consume more energy to overcome intermolecular forces to resist stretching. In this way, the strength would improve to a certain degree. The impact fracture mechanism of iPP/co-PP blends is quasi ductile fracture by multiple crazes. Our work discovered that the blends containing 10 wt% and 30 wt% ofco-PP exhibited prominent toughness and reinforcement.
基金supported by Local Science and Technology Development Fund Projects Guided by the Central Government(No.2022ZY0204)Key Scientific Research Projects of Inner Mongolian Higher Educational System(No.NJZZ23070)+4 种基金Research Project of Inner Mongolia University of Technology(No.ZY202103)Scientific Research Startup Fund of Inner Mongolia University of Technology(No.DC2200000898)the National Natural Science Foundation of China(No.22472023)the Fundamental Research Funds for the Central Universities(No.2412024QD014)the Science and Technology Development Plan Project of Jilin Province,China(No.20250102077JC).
文摘Reasonable design of effective and durable electrocatalysts for methanol oxidation reaction(MOR)is crucial for promoting the commercialization of direct methanol fuel cells(DMFCs).In this work,a network-like PtCu structure supported on three-dimensional N-doped graphene-carbon nanotube(n-PtCu/3DNG-CNT)was successfully prepared via a rational design strategy.The three-dimensional N-doped graphene with an open porous structure facilitates methanol molecule transfer,exposes activity sites,and anchors metal catalysts effectively.The designed network-like PtCu structure,with lattice defects,steps,and twin grain boundaries,is befeficial for inducing new properties(lattice structure,electronic structure,and chemical structure),forming more effective active centers while enhancing its anti-CO poisoning ability through a bifunctional mechanism.Further characterizations reveal the existence of a complex interface effect between N-doped graphene and carbon nanotube,which is demonstrated in detail.The n-PtCu/3DNG-CNT catalyst exhibits excellent MOR activity and durability in an acidic medium.
文摘In this paper, we have studied a general kind of n-species Lotka-Volterra network- like food-chain system with delays and impulses on time scales. Applying Mawhin＇s continuation theorem of coincidence degree theory and some skills of inequalities, some sufficient criteria have been established to guarantee the existence of at least 2n periodic solutions to this model. One example is given to illustrate the effectiveness of our results.
