The structure and dielectric properties of （Pb,Sr）Nb2O6-NaNbO3-SiO2 glass-ceramics with different Pb and Sr contents were investigated. The XRD pattern of glass-ceramics without Sr substitution is different from tha...The structure and dielectric properties of （Pb,Sr）Nb2O6-NaNbO3-SiO2 glass-ceramics with different Pb and Sr contents were investigated. The XRD pattern of glass-ceramics without Sr substitution is different from that with Sr substitution, which indicates the existence of orthorhombic phase in the latter ones. TEM bright field observation shows nanosized microstructures, while for samples with Sr, typical eutectic microstrncture with separated crystallized bands is found in the glass matrix. Dielectric properties measurement of the samples indicates an obvious improvement of dielectric constant, dielectric loss, DC field and temperature dependence of dielectric constant when the molar ratio of Sr to Pb is 4：6.展开更多
The effect of blending routes on the morphology and properties of Polyamide-6 (PA-6)/nano-CaCO3/Maleated ethylene-octane copolymer (MA-POE) ternary composite was analyzed using static mechanical test (DMA), TEM (trans...The effect of blending routes on the morphology and properties of Polyamide-6 (PA-6)/nano-CaCO3/Maleated ethylene-octane copolymer (MA-POE) ternary composite was analyzed using static mechanical test (DMA), TEM (transmission electronic microscope) and SEM (scanning electron microscope). It was found that MA-POE, as an impact modifier, had a profound effect upon the toughness of the PA-6/nano-CaCO3 composite. In particular, by adopting two-stage blending route, the microstructure of the ternary composites turned to core-shell structure, and the impact toughness was improved greatly. At the same time, tensile strength and dynamic storage modulus (E1) were higher than those with one-stage blending route processed ternary composite. The results suggest that blending routes may improve the properties of PA-6/nano-CaCO3/MA-POE ternary composites.展开更多
This paper discusses the utilization of nano-sized fillers in Polyamide 6 to increase the fracture resistance of the composites, which are crucial for various engineering applications. The toughening of the composites...This paper discusses the utilization of nano-sized fillers in Polyamide 6 to increase the fracture resistance of the composites, which are crucial for various engineering applications. The toughening of the composites is achieved by using dispersed nano-scaled rubber particles (Polyether block copolymer) as the inclusion in Polyamide 6 matrix. For a better understanding of the mechanical behavior of the composites, it is indispensable to use analytical and numerical models for evaluating the overall mechanical behavior and damage mechanism of the composite. In this work the toughening mechanism is studied through literature review and by analytical modeling. The mechanical behavior of the composites such as elastic plastic and damage properties are calculated numerically with 3D representative volume element (RVE) models. The numerical results are compared with previously obtained experiments. The influence of volume fraction and aspect ratio of inclusions on the macroscopic stress strain curve as well as the size effect of inclusions and also the failure properties of the composite are studied in detail.展开更多
In this paper the physical influences on the mechanical behavior of a Polyamide 6 (PA 6)/Mont- morillonit (MMT)-nanocomposite are examined by a selected structure modification in a numerical parameter study. Experimen...In this paper the physical influences on the mechanical behavior of a Polyamide 6 (PA 6)/Mont- morillonit (MMT)-nanocomposite are examined by a selected structure modification in a numerical parameter study. Experimental data of tensile tests of three different volume fractions at ambient temperature are used as reference. These were compared to homogenized stress-strain curves calculated with 3D representative volume elements (RVE) under periodic boundary conditions, in which the curve areas are considered until the tensile yield strength is reached. Besides the influence of filler orientation, exfoliation and its volume fraction, both adhesive interface behavior between the filler and matrix, and local partially crystalline interphases around the MMT-plates were also taken into account. A good approximation of the numerical representation of the experimental curves was achieved only after the introduction of the 30 - 40 nm thick partially crystalline interphases with higher stiffness and strength around the MMT-plates. The use of an exclusively isotropic matrix led to an underestimation of the mechanical values. The local modifications of the morphology were assumed to be transversely isotropic both in the elastic and in the plastic region. The transverse plane is defined by the lateral particle surface. Compared with the experimentally determined values of the corresponding Young’s Modulus, an excellent correlation was achieved. The yield strength for the largest volume fraction shows the best agreement with experimental values.展开更多
文摘The structure and dielectric properties of （Pb,Sr）Nb2O6-NaNbO3-SiO2 glass-ceramics with different Pb and Sr contents were investigated. The XRD pattern of glass-ceramics without Sr substitution is different from that with Sr substitution, which indicates the existence of orthorhombic phase in the latter ones. TEM bright field observation shows nanosized microstructures, while for samples with Sr, typical eutectic microstrncture with separated crystallized bands is found in the glass matrix. Dielectric properties measurement of the samples indicates an obvious improvement of dielectric constant, dielectric loss, DC field and temperature dependence of dielectric constant when the molar ratio of Sr to Pb is 4：6.
基金This work was financially supported by the National Natural Science Foundation of China under grant No.29934070.
文摘The effect of blending routes on the morphology and properties of Polyamide-6 (PA-6)/nano-CaCO3/Maleated ethylene-octane copolymer (MA-POE) ternary composite was analyzed using static mechanical test (DMA), TEM (transmission electronic microscope) and SEM (scanning electron microscope). It was found that MA-POE, as an impact modifier, had a profound effect upon the toughness of the PA-6/nano-CaCO3 composite. In particular, by adopting two-stage blending route, the microstructure of the ternary composites turned to core-shell structure, and the impact toughness was improved greatly. At the same time, tensile strength and dynamic storage modulus (E1) were higher than those with one-stage blending route processed ternary composite. The results suggest that blending routes may improve the properties of PA-6/nano-CaCO3/MA-POE ternary composites.
文摘This paper discusses the utilization of nano-sized fillers in Polyamide 6 to increase the fracture resistance of the composites, which are crucial for various engineering applications. The toughening of the composites is achieved by using dispersed nano-scaled rubber particles (Polyether block copolymer) as the inclusion in Polyamide 6 matrix. For a better understanding of the mechanical behavior of the composites, it is indispensable to use analytical and numerical models for evaluating the overall mechanical behavior and damage mechanism of the composite. In this work the toughening mechanism is studied through literature review and by analytical modeling. The mechanical behavior of the composites such as elastic plastic and damage properties are calculated numerically with 3D representative volume element (RVE) models. The numerical results are compared with previously obtained experiments. The influence of volume fraction and aspect ratio of inclusions on the macroscopic stress strain curve as well as the size effect of inclusions and also the failure properties of the composite are studied in detail.
文摘In this paper the physical influences on the mechanical behavior of a Polyamide 6 (PA 6)/Mont- morillonit (MMT)-nanocomposite are examined by a selected structure modification in a numerical parameter study. Experimental data of tensile tests of three different volume fractions at ambient temperature are used as reference. These were compared to homogenized stress-strain curves calculated with 3D representative volume elements (RVE) under periodic boundary conditions, in which the curve areas are considered until the tensile yield strength is reached. Besides the influence of filler orientation, exfoliation and its volume fraction, both adhesive interface behavior between the filler and matrix, and local partially crystalline interphases around the MMT-plates were also taken into account. A good approximation of the numerical representation of the experimental curves was achieved only after the introduction of the 30 - 40 nm thick partially crystalline interphases with higher stiffness and strength around the MMT-plates. The use of an exclusively isotropic matrix led to an underestimation of the mechanical values. The local modifications of the morphology were assumed to be transversely isotropic both in the elastic and in the plastic region. The transverse plane is defined by the lateral particle surface. Compared with the experimentally determined values of the corresponding Young’s Modulus, an excellent correlation was achieved. The yield strength for the largest volume fraction shows the best agreement with experimental values.
