The Experts below are selected from a list of 297 Experts worldwide ranked by ideXlab platform
William L Johnson - One of the best experts on this subject based on the ideXlab platform.
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correlation between Fracture Surface Morphology and toughness in zr based bulk metallic glasses
Journal of Materials Research, 2010Co-Authors: Dale R Conner, Marios D Demetriou, William L JohnsonAbstract:Fracture Surfaces of Zr-based bulk metallic glasses of various compositions tested in the as-cast and annealed conditions were analyzed using scanning electron microscopy. The tougher samples have shown highly jagged patterns at the beginning stage of crack propagation, and the length and roughness of this jagged pattern correlate well with the measured Fracture toughness values. These jagged patterns, the main source of energy dissipation in the sample, are attributed to the formation of shear bands inside the sample. This observation provides strong evidence of significant “plastic zone” screening at the crack tip.
Dale R Conner - One of the best experts on this subject based on the ideXlab platform.
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correlation between Fracture Surface Morphology and toughness in zr based bulk metallic glasses
Journal of Materials Research, 2010Co-Authors: Dale R Conner, Marios D Demetriou, William L JohnsonAbstract:Fracture Surfaces of Zr-based bulk metallic glasses of various compositions tested in the as-cast and annealed conditions were analyzed using scanning electron microscopy. The tougher samples have shown highly jagged patterns at the beginning stage of crack propagation, and the length and roughness of this jagged pattern correlate well with the measured Fracture toughness values. These jagged patterns, the main source of energy dissipation in the sample, are attributed to the formation of shear bands inside the sample. This observation provides strong evidence of significant “plastic zone” screening at the crack tip.
Maria Dolores Baró - One of the best experts on this subject based on the ideXlab platform.
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Fracture Surface Morphology of compressed bulk metallic glass-matrix-composites and bulk metallic glass
Intermetallics, 2006Co-Authors: M. Kusy, J Eckert, L Schultz, Uta Kühn, A. Concustell, Annett Gebert, Jayanta Das, Maria Dolores BaróAbstract:Abstract The Fracture Morphology of Zr-based bulk metallic glass-matrix-composites (BMGCs) and Cu-based bulk metallic glass (BMG) after compression testing has been studied. The quasi-static compression Fracture Surface displays a mixture of three different distinct patterns: vein-like, smooth featureless and river-like features. The last one corresponds to the Morphology known from tensile tests of BMGs. Moreover, randomly distributed transversal steps on the Fracture plane are also present. This is in contrast to previous studies where a characteristic vein-like pattern is considered a unique feature of the Fracture of BMGs under quasi-static uniaxial compression. The presence of different Fracture features indicates that the development of the Fracture plane occurs in a stepwise mode.
Marios D Demetriou - One of the best experts on this subject based on the ideXlab platform.
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correlation between Fracture Surface Morphology and toughness in zr based bulk metallic glasses
Journal of Materials Research, 2010Co-Authors: Dale R Conner, Marios D Demetriou, William L JohnsonAbstract:Fracture Surfaces of Zr-based bulk metallic glasses of various compositions tested in the as-cast and annealed conditions were analyzed using scanning electron microscopy. The tougher samples have shown highly jagged patterns at the beginning stage of crack propagation, and the length and roughness of this jagged pattern correlate well with the measured Fracture toughness values. These jagged patterns, the main source of energy dissipation in the sample, are attributed to the formation of shear bands inside the sample. This observation provides strong evidence of significant “plastic zone” screening at the crack tip.
Ali Ashraf Derakhshan - One of the best experts on this subject based on the ideXlab platform.
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Epoxy/alumoxane and epoxy/boehmite nanocomposites: cure behavior, thermal stability, hardness and Fracture Surface Morphology
Iranian Polymer Journal, 2014Co-Authors: Laleh Rajabi, Mehdi Marzban, Ali Ashraf DerakhshanAbstract:Functionalized nanostructures such as, boehmite, salicylate alumoxane (Sal-A) and p -hydroxybenzoate alumoxane (PHB-A), were studied in varying amounts with respect to curing behavior, thermal stability, hardness and Fracture Surface Morphology of their corresponding epoxy-based nanocomposites, emphasizing on the dispersabilities of the nanostructures in the epoxy matrix and the potential mechanisms of the interactions between various species. TG–DTA, Vickers hardness test and SEM were used to characterize the composite specimens. Addition of nanostructures into the epoxy matrix accelerated the curing process. The experimental tests proved that Sal-A acted most effectively as a co-curing agent through the autocatalytic curing process of the epoxy resin and also produced the highest values of Vickers hardness in its corresponding nanocomposites. The presence of the nanostructures also lowered the heat of reaction in curing process with an exception of PHB-A containing nanocomposites. Thermal stability of the nanocomposites was improved due to existence of the functionalized nanostructures. Mechanisms are proposed for the possible interactions between various species, constructing the three types of nanocomposites, divided into positive and negative types. The functional groups on the Surfaces of the nanostructures not only facilitated chemical interactions with the polymer matrix but also improved their dispersion in the epoxy matrix. Dispersability tendency of the nanostructures in the epoxy matrix was of the order: boehmite
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epoxy alumoxane and epoxy boehmite nanocomposites cure behavior thermal stability hardness and Fracture Surface Morphology
Iranian Polymer Journal, 2014Co-Authors: Laleh Rajabi, Mehdi Marzban, Ali Ashraf DerakhshanAbstract:Functionalized nanostructures such as, boehmite, salicylate alumoxane (Sal-A) and p-hydroxybenzoate alumoxane (PHB-A), were studied in varying amounts with respect to curing behavior, thermal stability, hardness and Fracture Surface Morphology of their corresponding epoxy-based nanocomposites, emphasizing on the dispersabilities of the nanostructures in the epoxy matrix and the potential mechanisms of the interactions between various species. TG–DTA, Vickers hardness test and SEM were used to characterize the composite specimens. Addition of nanostructures into the epoxy matrix accelerated the curing process. The experimental tests proved that Sal-A acted most effectively as a co-curing agent through the autocatalytic curing process of the epoxy resin and also produced the highest values of Vickers hardness in its corresponding nanocomposites. The presence of the nanostructures also lowered the heat of reaction in curing process with an exception of PHB-A containing nanocomposites. Thermal stability of the nanocomposites was improved due to existence of the functionalized nanostructures. Mechanisms are proposed for the possible interactions between various species, constructing the three types of nanocomposites, divided into positive and negative types. The functional groups on the Surfaces of the nanostructures not only facilitated chemical interactions with the polymer matrix but also improved their dispersion in the epoxy matrix. Dispersability tendency of the nanostructures in the epoxy matrix was of the order: boehmite < PHB-A < Sal-A. Extent of agglomeration of the nanostructures in the epoxy matrix depended on the types of the functional groups on their Surfaces and consequently, their interactions with the epoxy matrix and hardener.
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Epoxy/alumoxane and epoxy/boehmite nanocomposites: cure behavior, thermal stability, hardness and Fracture Surface Morphology
Iranian Polymer Journal, 2014Co-Authors: Laleh Rajabi, Mehdi Marzban, Ali Ashraf DerakhshanAbstract:Functionalized nanostructures such as, boehmite, salicylate alumoxane (Sal-A) and p-hydroxybenzoate alumoxane (PHB-A), were studied in varying amounts with respect to curing behavior, thermal stability, hardness and Fracture Surface Morphology of their corresponding epoxy-based nanocomposites, emphasizing on the dispersabilities of the nanostructures in the epoxy matrix and the potential mechanisms of the interactions between various species. TG–DTA, Vickers hardness test and SEM were used to characterize the composite specimens. Addition of nanostructures into the epoxy matrix accelerated the curing process. The experimental tests proved that Sal-A acted most effectively as a co-curing agent through the autocatalytic curing process of the epoxy resin and also produced the highest values of Vickers hardness in its corresponding nanocomposites. The presence of the nanostructures also lowered the heat of reaction in curing process with an exception of PHB-A containing nanocomposites. Thermal stability of the nanocomposites was improved due to existence of the functionalized nanostructures. Mechanisms are proposed for the possible interactions between various species, constructing the three types of nanocomposites, divided into positive and negative types. The functional groups on the Surfaces of the nanostructures not only facilitated chemical interactions with the polymer matrix but also improved their dispersion in the epoxy matrix. Dispersability tendency of the nanostructures in the epoxy matrix was of the order: boehmite < PHB-A < Sal-A. Extent of agglomeration of the nanostructures in the epoxy matrix depended on the types of the functional groups on their Surfaces and consequently, their interactions with the epoxy matrix and hardener.
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Effects of three surfactant types of anionic, cationic and non-ionic on tensile properties and Fracture Surface Morphology of epoxy/MWCNT nanocomposites
Iranian Polymer Journal, 2012Co-Authors: Shima Ghorabi, Laleh Rajabi, Sayed Siavash Madaeni, Sirus Zinadini, Ali Ashraf DerakhshanAbstract:Three types of surfactants were used to enhance the dispersion of multi-wall carbon nanotubes (MWCNTs) in the epoxy matrix. MWCNTs were separately treated with non-ionic (polyoxyethylene octyl phenyl ether, Triton X-100), cationic (hexadecyl-trimethyl-ammonium bromide, CTAB) and anionic (sodium dodecyl sulfate, SDS) surfactants and their effects were evaluated on the dispersion state and Surface chemistry, as well as on the tensile properties and tensile Fracture Surface Morphology of MWCNTs/epoxy nanocomposites. The active Surfaces of the carbon nanotubes were characterized by FTIR. The non-ionic surfactant, Triton X-100, had the best effect on dispersion of the MWCNT in the epoxy matrix, thus, positively affecting the tensile parameters of the corresponding nanocomposites which were attributed to the “bridging” effects between the MWCNT and epoxy, introduced by the hydrophobic and hydrophilic heads of the corresponding surfactant. Presence of MWCNTs as reinforcing agent increased the elastic modulus of nanocomposites, indicating the improved interfacial adhesion between CNTs and polymer matrix. The regions of nucleation and propagation of cracks were clearly seen in the SEM micrographs of the tensile Fracture Surface of the nanocomposites. The cracks deviated on reaching the carbon nanotubes. The dispersing aiding capabilities of the three surfactants used in the present study were as follows: cationic
