The Experts below are selected from a list of 246 Experts worldwide ranked by ideXlab platform
Cecile Monteux - One of the best experts on this subject based on the ideXlab platform.
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mixtures of latex particles and the surfactant of opposite charge used as interface stabilizers influence of particle contact angle zeta potential flocculation and shear energy
Soft Matter, 2014Co-Authors: Remi Deleurence, Caroline Parneix, Cecile MonteuxAbstract:We investigate the stabilization of air–water interfaces by mixtures of negatively charged latex particles (sulfate polystyrene) and cationic surfactants (alkyl trimethylammonium bromides). First we report results concerning the binding of surfactant molecules to the latex particles. As the surfactant concentration increases, the charge of the particles reverses, from negative to positive, because CnTAB first binds electrostatically to the latex particles and then through hydrophobic interaction with the monolayer already adsorbed on the particles as well as directly with the hydrophobic surface of the latex. Over a large range of surfactant concentrations around the charge inversion, a strong flocculation is observed and 100 μm large aggregates form in the suspension. Unlike previous studies published on mixtures of inorganic particles with oppositely charged surfactants, we show that we can vary the sign of the zeta potential of the particles without changing the contact angle of the particles over a large range of surfactant concentrations. Indeed, the latex particles that we study are more hydrophobic than inorganic particles, hence adding moderate concentrations of the surfactant results in a Weak Variation of the contact angle while the charge of the particles can be reversed. This enables decoupling of the effect of zeta potential and contact angle on the interfacial properties of the mixtures. Our study shows that the contact angle and the charge of the particles are not sufficient parameters to control the foam properties, and the key-parameters are the flocculation state and the shear energy applied to produce the foam. Indeed, flocculated samples, whatever the sign of the zeta potential, enable production of a stable armour at the interface. The large aggregates do not adsorb spontaneously at the interface because of their large size, however when a large shear energy is used to produce the foam very stable foam is obtained, where particles are trapped at interfaces. We suggest that the large aggregates may be broken during shear and may reform at the interface to form a solid armour. A simple calculation taking into account the adsorption dynamics of the aggregates as a function of their size is consistent with this hypothesis.
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Mixtures of latex particles and the surfactant of opposite charge used as interface stabilizers – influence of particle contact angle, zeta potential, flocculation and shear energy
Soft Matter, 2014Co-Authors: Remi Deleurence, Caroline Parneix, Cecile MonteuxAbstract:We investigate the stabilization of air-water interfaces by mixtures of negatively charged latex particles (sulfate polystyrene) and cationic surfactants (alkyl trimethylammonium bromides). First we report results concerning the binding of surfactant molecules to the latex particles. As the surfactant concentration increases, the charge of the particles reverses, from negative to positive, because C(n)TAB first binds electrostatically to the latex particles and then through hydrophobic interaction with the monolayer already adsorbed on the particles as well as directly with the hydrophobic surface of the latex. Over a large range of surfactant concentrations around the charge inversion, a strong flocculation is observed and 100 mu m large aggregates form in the suspension. Unlike previous studies published on mixtures of inorganic particles with oppositely charged surfactants, we show that we can vary the sign of the zeta potential of the particles without changing the contact angle of the particles over a large range of surfactant concentrations. Indeed, the latex particles that we study are more hydrophobic than inorganic particles, hence adding moderate concentrations of the surfactant results in a Weak Variation of the contact angle while the charge of the particles can be reversed. This enables decoupling of the effect of zeta potential and contact angle on the interfacial properties of the mixtures. Our study shows that the contact angle and the charge of the particles are not sufficient parameters to control the foam properties, and the key-parameters are the flocculation state and the shear energy applied to produce the foam. Indeed, flocculated samples, whatever the sign of the zeta potential, enable production of a stable armour at the interface. The large aggregates do not adsorb spontaneously at the interface because of their large size, however when a large shear energy is used to produce the foam very stable foam is obtained, where particles are trapped at interfaces. We suggest that the large aggregates may be broken during shear and may reform at the interface to form a solid armour. A simple calculation taking into account the adsorption dynamics of the aggregates as a function of their size is consistent with this hypothesis.
Bernard Bonin - One of the best experts on this subject based on the ideXlab platform.
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the itiuba alkaline syenite massif bahia state brazil mineralogical geochemical and petrological constraints relation to the genesis of rapakivi magmatism
Precambrian Research, 1991Co-Authors: Herbet Conceição, Pierre Sabaté, Bernard BoninAbstract:Abstract Numerous alkaline massifs occur throughout the state of Bahia (Brazil). Isotopic dates fall into two age groups: Brasiliano (0.45–0.70 Ga) and Trans-Amazon (1.8–2.1 Ga) ones. Brasiliano alkaline provinces comprise a silica-undersaturated association, with related volcanic rocks; their emplacement is always controlled by fault zones. Trans-Amazon alkaline massifs are characterized by large plutons (more than 100 km2) of K-rich syenite and granite associated with mafic cumulates and abundant dyke swarms. No associated volcanic rocks have been so far recorded. The shape of the plutons varies as a function of their location within the Sao Francisco Craton. In its northeastern and southern parts, syenite massifs are elongated, trending N-S, while in its western part, they are emplaced as circular bodies displaying contact metamorphic aureoles. The presence of older (Archaean?) alkaline rocks cannot be ruled out, as some granulitic facies display syenite compositions. The Itiuba massif provides a good example of Proterozoic alkaline syenite. Located in the northern part of the Sao Francisco Craton, this 150-km-long pluton covers 1800 km2 in area. Whole-rock Rb-Sr isotopic data yield a lower Proterozoic age. A N-S-trending foliation at the margins is gradually replaced by isotropic textures toward the core. Two sets of faults, both of Trans-Amazonian age, have been defined: N-S-trending reverse faults, accompanied by intense mylonitization, and younger NW-trending arcuate transcurrent faults related to a NE-SW compressive regime. Alkaline syenites constitute 98% of the exposures and are medium- to coarse-grained clinopyroxene-amphibole, hypersolvus leucratic rocks. Cumulates are represented by mafic layers and clinopyroxene-apatite enclaves. Dykes are composed of alkaline syenite, hypersolvus and transsolvus quartz-syenites and alkaline granites. Syenites are metaluminous and rich in K, Mg, P, Ti and Ba, and their geochemical trends are controlled by alkali feldspar, clinopyroxene, apatite and FeTi oxide fractionation. Oxidizing conditions are reflected by the Weak Variation in the mg-ratio, the reverse Fe → Mg mineral zonation, the synchronous precipitation of oxides and clinopyroxene in mafic layers and the late development of uralitic amphibole and low-Ti phlogopite. Temperatures for oxide equilibration of 930-880°C are compatible with the hypersolvus feldspar mineralogy. The evolution of feldspar mineralogy is a good indicator of varying thermodynamical conditions during late-stage crystallization of the pluton. Minimum values for initial crystallization temperature have been evaluated at 950°C. Structural and petrological results indicate that the presently exposed syenite massif represents the roof of a Proterozoic magma chamber, emplaced in granulite-gneiss formations. Rapakivi magmatism may represent disrupted and floating portions of the roof of earlier magma chambers refilled by new syenite-granite melts.
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The Itiúba alkaline syenite massif, Bahia State (Brazil): mineralogical, geochemical and petrological constraints—relation to the genesis of rapakivi magmatism
Precambrian Research, 1991Co-Authors: Herbet Conceição, Pierre Sabaté, Bernard BoninAbstract:Abstract Numerous alkaline massifs occur throughout the state of Bahia (Brazil). Isotopic dates fall into two age groups: Brasiliano (0.45–0.70 Ga) and Trans-Amazon (1.8–2.1 Ga) ones. Brasiliano alkaline provinces comprise a silica-undersaturated association, with related volcanic rocks; their emplacement is always controlled by fault zones. Trans-Amazon alkaline massifs are characterized by large plutons (more than 100 km2) of K-rich syenite and granite associated with mafic cumulates and abundant dyke swarms. No associated volcanic rocks have been so far recorded. The shape of the plutons varies as a function of their location within the Sao Francisco Craton. In its northeastern and southern parts, syenite massifs are elongated, trending N-S, while in its western part, they are emplaced as circular bodies displaying contact metamorphic aureoles. The presence of older (Archaean?) alkaline rocks cannot be ruled out, as some granulitic facies display syenite compositions. The Itiuba massif provides a good example of Proterozoic alkaline syenite. Located in the northern part of the Sao Francisco Craton, this 150-km-long pluton covers 1800 km2 in area. Whole-rock Rb-Sr isotopic data yield a lower Proterozoic age. A N-S-trending foliation at the margins is gradually replaced by isotropic textures toward the core. Two sets of faults, both of Trans-Amazonian age, have been defined: N-S-trending reverse faults, accompanied by intense mylonitization, and younger NW-trending arcuate transcurrent faults related to a NE-SW compressive regime. Alkaline syenites constitute 98% of the exposures and are medium- to coarse-grained clinopyroxene-amphibole, hypersolvus leucratic rocks. Cumulates are represented by mafic layers and clinopyroxene-apatite enclaves. Dykes are composed of alkaline syenite, hypersolvus and transsolvus quartz-syenites and alkaline granites. Syenites are metaluminous and rich in K, Mg, P, Ti and Ba, and their geochemical trends are controlled by alkali feldspar, clinopyroxene, apatite and FeTi oxide fractionation. Oxidizing conditions are reflected by the Weak Variation in the mg-ratio, the reverse Fe → Mg mineral zonation, the synchronous precipitation of oxides and clinopyroxene in mafic layers and the late development of uralitic amphibole and low-Ti phlogopite. Temperatures for oxide equilibration of 930-880°C are compatible with the hypersolvus feldspar mineralogy. The evolution of feldspar mineralogy is a good indicator of varying thermodynamical conditions during late-stage crystallization of the pluton. Minimum values for initial crystallization temperature have been evaluated at 950°C. Structural and petrological results indicate that the presently exposed syenite massif represents the roof of a Proterozoic magma chamber, emplaced in granulite-gneiss formations. Rapakivi magmatism may represent disrupted and floating portions of the roof of earlier magma chambers refilled by new syenite-granite melts.
Remi Deleurence - One of the best experts on this subject based on the ideXlab platform.
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mixtures of latex particles and the surfactant of opposite charge used as interface stabilizers influence of particle contact angle zeta potential flocculation and shear energy
Soft Matter, 2014Co-Authors: Remi Deleurence, Caroline Parneix, Cecile MonteuxAbstract:We investigate the stabilization of air–water interfaces by mixtures of negatively charged latex particles (sulfate polystyrene) and cationic surfactants (alkyl trimethylammonium bromides). First we report results concerning the binding of surfactant molecules to the latex particles. As the surfactant concentration increases, the charge of the particles reverses, from negative to positive, because CnTAB first binds electrostatically to the latex particles and then through hydrophobic interaction with the monolayer already adsorbed on the particles as well as directly with the hydrophobic surface of the latex. Over a large range of surfactant concentrations around the charge inversion, a strong flocculation is observed and 100 μm large aggregates form in the suspension. Unlike previous studies published on mixtures of inorganic particles with oppositely charged surfactants, we show that we can vary the sign of the zeta potential of the particles without changing the contact angle of the particles over a large range of surfactant concentrations. Indeed, the latex particles that we study are more hydrophobic than inorganic particles, hence adding moderate concentrations of the surfactant results in a Weak Variation of the contact angle while the charge of the particles can be reversed. This enables decoupling of the effect of zeta potential and contact angle on the interfacial properties of the mixtures. Our study shows that the contact angle and the charge of the particles are not sufficient parameters to control the foam properties, and the key-parameters are the flocculation state and the shear energy applied to produce the foam. Indeed, flocculated samples, whatever the sign of the zeta potential, enable production of a stable armour at the interface. The large aggregates do not adsorb spontaneously at the interface because of their large size, however when a large shear energy is used to produce the foam very stable foam is obtained, where particles are trapped at interfaces. We suggest that the large aggregates may be broken during shear and may reform at the interface to form a solid armour. A simple calculation taking into account the adsorption dynamics of the aggregates as a function of their size is consistent with this hypothesis.
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Mixtures of latex particles and the surfactant of opposite charge used as interface stabilizers – influence of particle contact angle, zeta potential, flocculation and shear energy
Soft Matter, 2014Co-Authors: Remi Deleurence, Caroline Parneix, Cecile MonteuxAbstract:We investigate the stabilization of air-water interfaces by mixtures of negatively charged latex particles (sulfate polystyrene) and cationic surfactants (alkyl trimethylammonium bromides). First we report results concerning the binding of surfactant molecules to the latex particles. As the surfactant concentration increases, the charge of the particles reverses, from negative to positive, because C(n)TAB first binds electrostatically to the latex particles and then through hydrophobic interaction with the monolayer already adsorbed on the particles as well as directly with the hydrophobic surface of the latex. Over a large range of surfactant concentrations around the charge inversion, a strong flocculation is observed and 100 mu m large aggregates form in the suspension. Unlike previous studies published on mixtures of inorganic particles with oppositely charged surfactants, we show that we can vary the sign of the zeta potential of the particles without changing the contact angle of the particles over a large range of surfactant concentrations. Indeed, the latex particles that we study are more hydrophobic than inorganic particles, hence adding moderate concentrations of the surfactant results in a Weak Variation of the contact angle while the charge of the particles can be reversed. This enables decoupling of the effect of zeta potential and contact angle on the interfacial properties of the mixtures. Our study shows that the contact angle and the charge of the particles are not sufficient parameters to control the foam properties, and the key-parameters are the flocculation state and the shear energy applied to produce the foam. Indeed, flocculated samples, whatever the sign of the zeta potential, enable production of a stable armour at the interface. The large aggregates do not adsorb spontaneously at the interface because of their large size, however when a large shear energy is used to produce the foam very stable foam is obtained, where particles are trapped at interfaces. We suggest that the large aggregates may be broken during shear and may reform at the interface to form a solid armour. A simple calculation taking into account the adsorption dynamics of the aggregates as a function of their size is consistent with this hypothesis.
Herbet Conceição - One of the best experts on this subject based on the ideXlab platform.
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the itiuba alkaline syenite massif bahia state brazil mineralogical geochemical and petrological constraints relation to the genesis of rapakivi magmatism
Precambrian Research, 1991Co-Authors: Herbet Conceição, Pierre Sabaté, Bernard BoninAbstract:Abstract Numerous alkaline massifs occur throughout the state of Bahia (Brazil). Isotopic dates fall into two age groups: Brasiliano (0.45–0.70 Ga) and Trans-Amazon (1.8–2.1 Ga) ones. Brasiliano alkaline provinces comprise a silica-undersaturated association, with related volcanic rocks; their emplacement is always controlled by fault zones. Trans-Amazon alkaline massifs are characterized by large plutons (more than 100 km2) of K-rich syenite and granite associated with mafic cumulates and abundant dyke swarms. No associated volcanic rocks have been so far recorded. The shape of the plutons varies as a function of their location within the Sao Francisco Craton. In its northeastern and southern parts, syenite massifs are elongated, trending N-S, while in its western part, they are emplaced as circular bodies displaying contact metamorphic aureoles. The presence of older (Archaean?) alkaline rocks cannot be ruled out, as some granulitic facies display syenite compositions. The Itiuba massif provides a good example of Proterozoic alkaline syenite. Located in the northern part of the Sao Francisco Craton, this 150-km-long pluton covers 1800 km2 in area. Whole-rock Rb-Sr isotopic data yield a lower Proterozoic age. A N-S-trending foliation at the margins is gradually replaced by isotropic textures toward the core. Two sets of faults, both of Trans-Amazonian age, have been defined: N-S-trending reverse faults, accompanied by intense mylonitization, and younger NW-trending arcuate transcurrent faults related to a NE-SW compressive regime. Alkaline syenites constitute 98% of the exposures and are medium- to coarse-grained clinopyroxene-amphibole, hypersolvus leucratic rocks. Cumulates are represented by mafic layers and clinopyroxene-apatite enclaves. Dykes are composed of alkaline syenite, hypersolvus and transsolvus quartz-syenites and alkaline granites. Syenites are metaluminous and rich in K, Mg, P, Ti and Ba, and their geochemical trends are controlled by alkali feldspar, clinopyroxene, apatite and FeTi oxide fractionation. Oxidizing conditions are reflected by the Weak Variation in the mg-ratio, the reverse Fe → Mg mineral zonation, the synchronous precipitation of oxides and clinopyroxene in mafic layers and the late development of uralitic amphibole and low-Ti phlogopite. Temperatures for oxide equilibration of 930-880°C are compatible with the hypersolvus feldspar mineralogy. The evolution of feldspar mineralogy is a good indicator of varying thermodynamical conditions during late-stage crystallization of the pluton. Minimum values for initial crystallization temperature have been evaluated at 950°C. Structural and petrological results indicate that the presently exposed syenite massif represents the roof of a Proterozoic magma chamber, emplaced in granulite-gneiss formations. Rapakivi magmatism may represent disrupted and floating portions of the roof of earlier magma chambers refilled by new syenite-granite melts.
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The Itiúba alkaline syenite massif, Bahia State (Brazil): mineralogical, geochemical and petrological constraints—relation to the genesis of rapakivi magmatism
Precambrian Research, 1991Co-Authors: Herbet Conceição, Pierre Sabaté, Bernard BoninAbstract:Abstract Numerous alkaline massifs occur throughout the state of Bahia (Brazil). Isotopic dates fall into two age groups: Brasiliano (0.45–0.70 Ga) and Trans-Amazon (1.8–2.1 Ga) ones. Brasiliano alkaline provinces comprise a silica-undersaturated association, with related volcanic rocks; their emplacement is always controlled by fault zones. Trans-Amazon alkaline massifs are characterized by large plutons (more than 100 km2) of K-rich syenite and granite associated with mafic cumulates and abundant dyke swarms. No associated volcanic rocks have been so far recorded. The shape of the plutons varies as a function of their location within the Sao Francisco Craton. In its northeastern and southern parts, syenite massifs are elongated, trending N-S, while in its western part, they are emplaced as circular bodies displaying contact metamorphic aureoles. The presence of older (Archaean?) alkaline rocks cannot be ruled out, as some granulitic facies display syenite compositions. The Itiuba massif provides a good example of Proterozoic alkaline syenite. Located in the northern part of the Sao Francisco Craton, this 150-km-long pluton covers 1800 km2 in area. Whole-rock Rb-Sr isotopic data yield a lower Proterozoic age. A N-S-trending foliation at the margins is gradually replaced by isotropic textures toward the core. Two sets of faults, both of Trans-Amazonian age, have been defined: N-S-trending reverse faults, accompanied by intense mylonitization, and younger NW-trending arcuate transcurrent faults related to a NE-SW compressive regime. Alkaline syenites constitute 98% of the exposures and are medium- to coarse-grained clinopyroxene-amphibole, hypersolvus leucratic rocks. Cumulates are represented by mafic layers and clinopyroxene-apatite enclaves. Dykes are composed of alkaline syenite, hypersolvus and transsolvus quartz-syenites and alkaline granites. Syenites are metaluminous and rich in K, Mg, P, Ti and Ba, and their geochemical trends are controlled by alkali feldspar, clinopyroxene, apatite and FeTi oxide fractionation. Oxidizing conditions are reflected by the Weak Variation in the mg-ratio, the reverse Fe → Mg mineral zonation, the synchronous precipitation of oxides and clinopyroxene in mafic layers and the late development of uralitic amphibole and low-Ti phlogopite. Temperatures for oxide equilibration of 930-880°C are compatible with the hypersolvus feldspar mineralogy. The evolution of feldspar mineralogy is a good indicator of varying thermodynamical conditions during late-stage crystallization of the pluton. Minimum values for initial crystallization temperature have been evaluated at 950°C. Structural and petrological results indicate that the presently exposed syenite massif represents the roof of a Proterozoic magma chamber, emplaced in granulite-gneiss formations. Rapakivi magmatism may represent disrupted and floating portions of the roof of earlier magma chambers refilled by new syenite-granite melts.
Caroline Parneix - One of the best experts on this subject based on the ideXlab platform.
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mixtures of latex particles and the surfactant of opposite charge used as interface stabilizers influence of particle contact angle zeta potential flocculation and shear energy
Soft Matter, 2014Co-Authors: Remi Deleurence, Caroline Parneix, Cecile MonteuxAbstract:We investigate the stabilization of air–water interfaces by mixtures of negatively charged latex particles (sulfate polystyrene) and cationic surfactants (alkyl trimethylammonium bromides). First we report results concerning the binding of surfactant molecules to the latex particles. As the surfactant concentration increases, the charge of the particles reverses, from negative to positive, because CnTAB first binds electrostatically to the latex particles and then through hydrophobic interaction with the monolayer already adsorbed on the particles as well as directly with the hydrophobic surface of the latex. Over a large range of surfactant concentrations around the charge inversion, a strong flocculation is observed and 100 μm large aggregates form in the suspension. Unlike previous studies published on mixtures of inorganic particles with oppositely charged surfactants, we show that we can vary the sign of the zeta potential of the particles without changing the contact angle of the particles over a large range of surfactant concentrations. Indeed, the latex particles that we study are more hydrophobic than inorganic particles, hence adding moderate concentrations of the surfactant results in a Weak Variation of the contact angle while the charge of the particles can be reversed. This enables decoupling of the effect of zeta potential and contact angle on the interfacial properties of the mixtures. Our study shows that the contact angle and the charge of the particles are not sufficient parameters to control the foam properties, and the key-parameters are the flocculation state and the shear energy applied to produce the foam. Indeed, flocculated samples, whatever the sign of the zeta potential, enable production of a stable armour at the interface. The large aggregates do not adsorb spontaneously at the interface because of their large size, however when a large shear energy is used to produce the foam very stable foam is obtained, where particles are trapped at interfaces. We suggest that the large aggregates may be broken during shear and may reform at the interface to form a solid armour. A simple calculation taking into account the adsorption dynamics of the aggregates as a function of their size is consistent with this hypothesis.
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Mixtures of latex particles and the surfactant of opposite charge used as interface stabilizers – influence of particle contact angle, zeta potential, flocculation and shear energy
Soft Matter, 2014Co-Authors: Remi Deleurence, Caroline Parneix, Cecile MonteuxAbstract:We investigate the stabilization of air-water interfaces by mixtures of negatively charged latex particles (sulfate polystyrene) and cationic surfactants (alkyl trimethylammonium bromides). First we report results concerning the binding of surfactant molecules to the latex particles. As the surfactant concentration increases, the charge of the particles reverses, from negative to positive, because C(n)TAB first binds electrostatically to the latex particles and then through hydrophobic interaction with the monolayer already adsorbed on the particles as well as directly with the hydrophobic surface of the latex. Over a large range of surfactant concentrations around the charge inversion, a strong flocculation is observed and 100 mu m large aggregates form in the suspension. Unlike previous studies published on mixtures of inorganic particles with oppositely charged surfactants, we show that we can vary the sign of the zeta potential of the particles without changing the contact angle of the particles over a large range of surfactant concentrations. Indeed, the latex particles that we study are more hydrophobic than inorganic particles, hence adding moderate concentrations of the surfactant results in a Weak Variation of the contact angle while the charge of the particles can be reversed. This enables decoupling of the effect of zeta potential and contact angle on the interfacial properties of the mixtures. Our study shows that the contact angle and the charge of the particles are not sufficient parameters to control the foam properties, and the key-parameters are the flocculation state and the shear energy applied to produce the foam. Indeed, flocculated samples, whatever the sign of the zeta potential, enable production of a stable armour at the interface. The large aggregates do not adsorb spontaneously at the interface because of their large size, however when a large shear energy is used to produce the foam very stable foam is obtained, where particles are trapped at interfaces. We suggest that the large aggregates may be broken during shear and may reform at the interface to form a solid armour. A simple calculation taking into account the adsorption dynamics of the aggregates as a function of their size is consistent with this hypothesis.
