The polymer-ceramic composites of epoxy resin (EP) and barium titanate (BT) were prepared. BT powders of different BT particle sizes from 100 nm to 1 μm were used in the preparation. The dielectric properties, such a...The polymer-ceramic composites of epoxy resin (EP) and barium titanate (BT) were prepared. BT powders of different BT particle sizes from 100 nm to 1 μm were used in the preparation. The dielectric properties, such as dielectric constant, dielectric loss and electrical breakdown strength, of the EP/BT composites were studied. The morphology of the composites was characterized by the means of scanning electron microscopy (SEM). The results show that the dielectric constant of the composites is much higher than the epoxy matrix at frequency range from 1 kHz to 10 MHz, and it is also obviously dependent on the size of BT particles. The electrical breakdown strength of the composites decreases with the increase of the BT content. The dependence of electrical breakdown strength on BT particle sizes was also discussed.展开更多
Mechanical properties and abrasive wear behaviour of bi-directional jute fabric reinforced epoxy (J/Ep) with micron sized TiO<sub>2</sub> particles at different wt% (2.5, 5, 7.5 and 10) were investigated. ...Mechanical properties and abrasive wear behaviour of bi-directional jute fabric reinforced epoxy (J/Ep) with micron sized TiO<sub>2</sub> particles at different wt% (2.5, 5, 7.5 and 10) were investigated. The tribo-potential of combined effect of TiO<sub>2</sub> and jute fiber in epoxy (J/Ep) for enhancing the abrasion resistance has not been studied so far. Hence, the present work aims to explore the possibility of using TiO<sub>2</sub> filler and jute fiber to reinforce the epoxy and thus open a new way to implement inexpensive reinforcements and produce new candidate tribo-material for industrial applications. Silane treated TiO<sub>2</sub> filled J/Ep composites were prepared by hand lay-up method. Selected mechanical properties and three-body abrasive wear tests were evaluated as per ASTM standards. Results indicate an enhancement in the J/Ep composite mechanical properties due to addition of TiO<sub>2</sub> particles up to 7.5 wt% of loading. Highest tensile and flexural properties were found at 7.5 wt% TiO<sub>2</sub> loading. Results of abrasion tests show resistance to abrasion at 5 wt% TiO<sub>2</sub> filled J/Ep composite. Scanning electron micrographs evidenced that the fiber and filler have fairly good bonding with matrix. Finally, this investigation confirms the applicability of TiO<sub>2</sub> as secondary reinforcement in J/Ep composite.展开更多
Colony formation of cyanobacteria is crucial for the formation of surface blooms in lakes.However,the underlying mechanisms of colony formation involving in physiological and cell surface characteristics remain to not...Colony formation of cyanobacteria is crucial for the formation of surface blooms in lakes.However,the underlying mechanisms of colony formation involving in physiological and cell surface characteristics remain to not well be established.Six cyanobacterial Microcystis strains(including both unicellular and colonial ones)were employed to estimate the influences of their physiological traits and the composition of extracellular polymeric substances(EPS)on colony or aggregate formation.Results show that raising the number of the photosynthetic reaction center and light-harvesting antenna in the PSII and reducing the growth rate were the major physiological strategies of Microcystis to produce excess EPS enhancing colony formation.Tightly bound EPS(T-EPS)was responsible for colony formation,which approximately accounted for 50%of the total amount of EPS.Five fluorescent components(protein-,tryptophan-,and tyrosine-like components and two humic-like components)were found in the T-EPS,although the amounts of these components varied with strains.Importantly,colonial strains contained much higher tyrosine-like substances than unicellular ones.We suggest that tyrosine-like substances might serve as a crosslinking agent to connect other polymers in EPS(e.g.,proteins or polysaccharides)for colony formation.Our findings identified key physiological traits and chemical components of EPS for colony formation in Microcystis,which can contribute to a better understanding on the formation of Microcystis blooms.展开更多
To prevent expanded polystyrene(EPS) beads from rising up to the surface in the molding process of EPS lightweight concrete,vibration with pressure was applied and the polyvinyl acetate(PVA) emulsion was adopted to im...To prevent expanded polystyrene(EPS) beads from rising up to the surface in the molding process of EPS lightweight concrete,vibration with pressure was applied and the polyvinyl acetate(PVA) emulsion was adopted to improve its mechanical properties.The mechanical properties,thermal properties and durability of EPS lightweight concrete were tested.The microstructures of EPS lightweight concrete were observed by scanning electron microscope(SEM).Vibration with pressure reduces the number of small cracks.The 180 d compressive strength and flexural strength increase obviously as a large amount of PVA was added.The mixed amount of PVA has no obvious influence on the thermal performance when it is not more than 10% of the cement.Vibration with pressure and surface modification of EPS beads by PVA improve the combination of EPS beads with cement stone and the mechanical properties of EPS lightweight concrete.展开更多
A graphene oxide/nano-silica(GOS)hybrid was rapidly and easily synthesized using graphene oxide(GO)and nano-silica(nano-SiO_(2))as raw materials,and the synthesized GOS was used to improve the mechanical properties of...A graphene oxide/nano-silica(GOS)hybrid was rapidly and easily synthesized using graphene oxide(GO)and nano-silica(nano-SiO_(2))as raw materials,and the synthesized GOS was used to improve the mechanical properties of epoxy resin(EP).The modified EP with different mass fractions of GOS(0,0.1%,0.2%,0.3%and 0.4%)were prepared and studied.The structure,thermal stability,mechanical properties,fracture toughness and failure morphology of the modified EP were analyzed.The results showed that the tensile strength of GOS modified EP increased from 40.6 MPa to 80.2 MPa compared with EP,the critical stress intensity factor of GOS modified EP increased by 65.9%from 0.82 MPa·m^(1/2)to 1.36 MPa·m^(1/2),indicating a significant enhancement in fracture toughness.In addition,failure morphology was observed by scanning electron microscopy(SEM)observation.The toughness mechanism of the modified EP was also discussed.Finally,the thermal stability of the modified EP was improved by the addition of GOS.Compared with neat EP,the initial thermal degradation temperature and glass transition temperature of GOS modified EP increased by 4.5℃and 10.3℃,respectively.展开更多
文摘The polymer-ceramic composites of epoxy resin (EP) and barium titanate (BT) were prepared. BT powders of different BT particle sizes from 100 nm to 1 μm were used in the preparation. The dielectric properties, such as dielectric constant, dielectric loss and electrical breakdown strength, of the EP/BT composites were studied. The morphology of the composites was characterized by the means of scanning electron microscopy (SEM). The results show that the dielectric constant of the composites is much higher than the epoxy matrix at frequency range from 1 kHz to 10 MHz, and it is also obviously dependent on the size of BT particles. The electrical breakdown strength of the composites decreases with the increase of the BT content. The dependence of electrical breakdown strength on BT particle sizes was also discussed.
文摘Mechanical properties and abrasive wear behaviour of bi-directional jute fabric reinforced epoxy (J/Ep) with micron sized TiO<sub>2</sub> particles at different wt% (2.5, 5, 7.5 and 10) were investigated. The tribo-potential of combined effect of TiO<sub>2</sub> and jute fiber in epoxy (J/Ep) for enhancing the abrasion resistance has not been studied so far. Hence, the present work aims to explore the possibility of using TiO<sub>2</sub> filler and jute fiber to reinforce the epoxy and thus open a new way to implement inexpensive reinforcements and produce new candidate tribo-material for industrial applications. Silane treated TiO<sub>2</sub> filled J/Ep composites were prepared by hand lay-up method. Selected mechanical properties and three-body abrasive wear tests were evaluated as per ASTM standards. Results indicate an enhancement in the J/Ep composite mechanical properties due to addition of TiO<sub>2</sub> particles up to 7.5 wt% of loading. Highest tensile and flexural properties were found at 7.5 wt% TiO<sub>2</sub> loading. Results of abrasion tests show resistance to abrasion at 5 wt% TiO<sub>2</sub> filled J/Ep composite. Scanning electron micrographs evidenced that the fiber and filler have fairly good bonding with matrix. Finally, this investigation confirms the applicability of TiO<sub>2</sub> as secondary reinforcement in J/Ep composite.
基金Supported by the National Natural Science Foundation of China(No.32071569)the Scientific Instruments and Equipment Development Project+2 种基金Chinese Academy of Sciences,2020(No.YJKYYQ20200048)the Fundamental Research Funds for the Central Universities(No.B210202010)the China Postdoctoral Foundation(No.2020M681472)。
文摘Colony formation of cyanobacteria is crucial for the formation of surface blooms in lakes.However,the underlying mechanisms of colony formation involving in physiological and cell surface characteristics remain to not well be established.Six cyanobacterial Microcystis strains(including both unicellular and colonial ones)were employed to estimate the influences of their physiological traits and the composition of extracellular polymeric substances(EPS)on colony or aggregate formation.Results show that raising the number of the photosynthetic reaction center and light-harvesting antenna in the PSII and reducing the growth rate were the major physiological strategies of Microcystis to produce excess EPS enhancing colony formation.Tightly bound EPS(T-EPS)was responsible for colony formation,which approximately accounted for 50%of the total amount of EPS.Five fluorescent components(protein-,tryptophan-,and tyrosine-like components and two humic-like components)were found in the T-EPS,although the amounts of these components varied with strains.Importantly,colonial strains contained much higher tyrosine-like substances than unicellular ones.We suggest that tyrosine-like substances might serve as a crosslinking agent to connect other polymers in EPS(e.g.,proteins or polysaccharides)for colony formation.Our findings identified key physiological traits and chemical components of EPS for colony formation in Microcystis,which can contribute to a better understanding on the formation of Microcystis blooms.
基金Supported by Tianjin Natural Science Foundation (No.06YFJMJC05900)Science and Technology Key Project of Hebei Province (No.05213810)
文摘To prevent expanded polystyrene(EPS) beads from rising up to the surface in the molding process of EPS lightweight concrete,vibration with pressure was applied and the polyvinyl acetate(PVA) emulsion was adopted to improve its mechanical properties.The mechanical properties,thermal properties and durability of EPS lightweight concrete were tested.The microstructures of EPS lightweight concrete were observed by scanning electron microscope(SEM).Vibration with pressure reduces the number of small cracks.The 180 d compressive strength and flexural strength increase obviously as a large amount of PVA was added.The mixed amount of PVA has no obvious influence on the thermal performance when it is not more than 10% of the cement.Vibration with pressure and surface modification of EPS beads by PVA improve the combination of EPS beads with cement stone and the mechanical properties of EPS lightweight concrete.
基金Natural Science Foundation of Jiangsu Province,China(No.BK 20180244)Foundation of Qing Lan Project,ChinaOpening Project of Key Laboratory of Jiangsu Province for Silk Engineering,Soochow University,China(No.KJS2278)。
文摘A graphene oxide/nano-silica(GOS)hybrid was rapidly and easily synthesized using graphene oxide(GO)and nano-silica(nano-SiO_(2))as raw materials,and the synthesized GOS was used to improve the mechanical properties of epoxy resin(EP).The modified EP with different mass fractions of GOS(0,0.1%,0.2%,0.3%and 0.4%)were prepared and studied.The structure,thermal stability,mechanical properties,fracture toughness and failure morphology of the modified EP were analyzed.The results showed that the tensile strength of GOS modified EP increased from 40.6 MPa to 80.2 MPa compared with EP,the critical stress intensity factor of GOS modified EP increased by 65.9%from 0.82 MPa·m^(1/2)to 1.36 MPa·m^(1/2),indicating a significant enhancement in fracture toughness.In addition,failure morphology was observed by scanning electron microscopy(SEM)observation.The toughness mechanism of the modified EP was also discussed.Finally,the thermal stability of the modified EP was improved by the addition of GOS.Compared with neat EP,the initial thermal degradation temperature and glass transition temperature of GOS modified EP increased by 4.5℃and 10.3℃,respectively.
