Joseph Yanez - Academia.edu (original) (raw)
Papers by Joseph Yanez
European Polymer Journal, Jun 1, 2006
... It shows that the primary effect of polymer deformation is a shear-induced nucleation of the ... more ... It shows that the primary effect of polymer deformation is a shear-induced nucleation of the amorphous fragments of the polymer. This nucleation process generates sheared micro-domains or SMD's which are associated with the inelastic component of deformation [9] and [10]. ...
Journal of The European Ceramic Society, 1998
29Si NMR, d@use reflectance infrared fourier transform (DRIFT) spectroscopy, X-ray photoelectron ... more 29Si NMR, d@use reflectance infrared fourier transform (DRIFT) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet spectroscopy (U V), ellipsometry, and atomic force microscopy (AFM) measurements were used to characterize the interaction of N-(triethoxysilylpropyl)-O-polyethylene oxide urethane with a SisN4 surface in water. The experimental results show that this tri alkoxy silane molecule covalently bonds to the surface of SijN4. Maximum adsorption of this compound was 2,13 pmolm-2, but less than 0-I ~molm-2 of this amount is chemically grafted to the surface. However, AFM results show that such a low amount of material is su@cient to increase the repulsive potential between SijN4 surfaces.
Journal of the American Ceramic Society, Nov 1, 1996
The shear modulus and yield stress of attractive alumina particle networks in aqueous slurries wa... more The shear modulus and yield stress of attractive alumina particle networks in aqueous slurries was determined as a function of volume fraction (0.1 to 0.5), pH (2, 4, 5, 6, and 9), and salt (NH4l) concentration (0.25M to 2.34) using both vane and couette rheological tools. Consistent with previous observations concerning the relative strength of attractive particle networks, the shear modulus increased to a plateau value with salt concentration. In this work we have shown that the salt concentration at which this plateau value is achieved is a function of the pH, and thus, the surface charge density. The values of the shear modulus [G′], yield stress [τy], and yield strain [γy] of the attractive networks can be described with power law functions for particle volume fraction [φ] (G′∝φ4.75, τy∝φ3.6, and γy∝φ−1.1) and salt concentration [c] (G′∝ [c]2.0, τ, ∝ [c]1.15, and γy∝ [c]−0.85).
L'invention concerne un procede de fabrication de ponts dentaires artificiels consistant en u... more L'invention concerne un procede de fabrication de ponts dentaires artificiels consistant en un noyau en ceramique separe a haute resistance, fritte de maniere dense plaque avec de la porcelaine au moyen de procedes de la metallurgie des poudres. Selon ce procede, les pieces de pont frittees de maniere dense sont reliees a un noyau de pont par un verre renforce de particules. Etant donne que seul le materiau de verre humidifie la surface des pieces frittees de maniere dense, le verre joue le role de materiau de liaison qui maintient le noyau ensemble et qui permet a la fonction des particules d'uniquement augmenter la force (par exemple valeur Kc) de la masse de materiau de verre.
Unlike freeform fabrication of ceramics via stereolithography, this work deals with the feasibili... more Unlike freeform fabrication of ceramics via stereolithography, this work deals with the feasibility of a novel rapid prototyping process route for indirectly producing ceramic parts. By using a newly developed in situ temperature induced forming (TIF) technology, concentrated ceramic slurries are vacuum cast into a polymeric mold, which was produced by stereolithography. Through stereolithography the complex-shaped mold with precise surface quality can be produced quickly and the TIF technology enables the change of particle potential in the slurry from a repulsive into a weekly attractive particle network during consolidation. Therefore, a green body with high and homogeneous density without any crack can be realized. The design of the 3D mold is critical in order to achieve components which are complex near-net shape and easy to demold. Ceramic parts having a complex geometry with improved fine surface quality can be made and no burnout is required since only a minor amount of organic additives is used.
Journal of the European Ceramic Society, 1998
29Si NMR, d@use reflectance infrared fourier transform (DRIFT) spectroscopy, X-ray photoelectron ... more 29Si NMR, d@use reflectance infrared fourier transform (DRIFT) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet spectroscopy (U V), ellipsometry, and atomic force microscopy (AFM) measurements were used to characterize the interaction of N-(triethoxysilylpropyl)-O-polyethylene oxide urethane with a SisN4 surface in water. The experimental results show that this tri alkoxy silane molecule covalently bonds to the surface of SijN4. Maximum adsorption of this compound was 2,13 pmolm-2, but less than 0-I ~molm-2 of this amount is chemically grafted to the surface. However, AFM results show that such a low amount of material is su@cient to increase the repulsive potential between SijN4 surfaces.
Journal of the American Ceramic Society, 1996
The shear modulus and yield stress of attractive alumina particle networks in aqueous slurries wa... more The shear modulus and yield stress of attractive alumina particle networks in aqueous slurries was determined as a function of volume fraction (0.1 to 0.5), pH (2, 4, 5, 6, and 9), and salt (NH4l) concentration (0.25M to 2.34) using both vane and couette rheological tools. Consistent with previous observations concerning the relative strength of attractive particle networks, the shear modulus increased to a plateau value with salt concentration. In this work we have shown that the salt concentration at which this plateau value is achieved is a function of the pH, and thus, the surface charge density. The values of the shear modulus [G′], yield stress [τy], and yield strain [γy] of the attractive networks can be described with power law functions for particle volume fraction [φ] (G′∝φ4.75, τy∝φ3.6, and γy∝φ−1.1) and salt concentration [c] (G′∝ [c]2.0, τ, ∝ [c]1.15, and γy∝ [c]−0.85).
Journal of the American Ceramic Society, 2004
Direct measurements of forces between silicon nitride surfaces in the presence of poly(acrylic ac... more Direct measurements of forces between silicon nitride surfaces in the presence of poly(acrylic acid) (PAA) are presented. The force-distance curves were obtained at pH > pHiep with an atomic force microscopy (AFM) colloidal-probe technique using a novel spherical silicon nitride probe attached to the AFM cantilever. We found that PAA adsorbs onto the negatively charged silicon nitride surface, which results in an increased repulsive surface potential. The steric contribution to the interparticle repulsion is small and the layer conformation remains flat even at high surface potentials or high ionic strength. The general features of the stabilization of ceramic powders with PAA are discussed; we suggest that PAA adsorbs onto silicon nitride by sequential adsorption of neighboring segments (“zipping”), which results in a flat conformation. In contrast, the long-range steric force found in the ZrO2/PAA system at pH > pHiep arises because the stretched equilibrium bulk conformation of the highly charged polymer is preserved via the formation of strong, irreversible surface-segment bonds on adsorption.
Journal of Colloid and Interface Science, 1999
The effect of strength of attraction and volume fraction on the mechanical properties of alumina ... more The effect of strength of attraction and volume fraction on the mechanical properties of alumina particle networks were investigated. Alumina particle gels were formed reversibly and in situ in the rheometer by cooling alumina particle suspensions with adsorbed poly(12-hydroxy stearic acid) suspended in a marginal solvent, hexanol. The collapse of the polymer layer with decreasing solvency (temperature) induces flocculation when the longrange van der Waals force overcomes the remaining steric repulsion. The gelation temperature depends on volume fraction. At the gel temperature, T gel , the gel becomes predominantly elastic; at temperatures below T gel , the elasticity increases with decreasing temperature. We find that the elastic modulus data, measured over a wide range of volume fraction (0.2 < < 0.425) and temperature (10-14°C), follows: G ؍ G 0 (؊ g) s. This scaling suggests the prefactor and exponent to be independent of temperature. We present some arguments for why subjecting a particle gel to a preshear procedure might result in an temperature-dependent prefactor. By invoking such an effect, we are able to rescale and collapse previously published moduli data on presheared suspensions according to the (؊ g) expression.
Powder Technology, 2001
This study introduces the atomic force microscope (AFM) for direct measurement of internal and ex... more This study introduces the atomic force microscope (AFM) for direct measurement of internal and external friction in ceramic powder pressing. The friction measurements were performed between two single granules, and a granule and a hard metal substrate as a function of granule binder concentration, relative humidity and sliding velocity. We found that the friction coefficient decreased with increasing humidity for a specific binder concentration, the effect being more pronounced for low concentrations. The friction coefficient also decreased with increasing binder concentration. Evaluation of the adhesion force showed a steady increase with both humidity and binder concentration. A substantial difference, more than an order of magnitude, was seen for the highest binder concentration at low and high humidities. We attribute these findings to the hygroscopic nature of the binder, poly(ethylene glycol) (PEG). Softening of the PEG at increasing humidities lowers the friction coefficient but increases the adhesion force. The results are consistent with flowability and angle of friction measurements.
European Polymer Journal, Jun 1, 2006
... It shows that the primary effect of polymer deformation is a shear-induced nucleation of the ... more ... It shows that the primary effect of polymer deformation is a shear-induced nucleation of the amorphous fragments of the polymer. This nucleation process generates sheared micro-domains or SMD's which are associated with the inelastic component of deformation [9] and [10]. ...
Journal of The European Ceramic Society, 1998
29Si NMR, d@use reflectance infrared fourier transform (DRIFT) spectroscopy, X-ray photoelectron ... more 29Si NMR, d@use reflectance infrared fourier transform (DRIFT) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet spectroscopy (U V), ellipsometry, and atomic force microscopy (AFM) measurements were used to characterize the interaction of N-(triethoxysilylpropyl)-O-polyethylene oxide urethane with a SisN4 surface in water. The experimental results show that this tri alkoxy silane molecule covalently bonds to the surface of SijN4. Maximum adsorption of this compound was 2,13 pmolm-2, but less than 0-I ~molm-2 of this amount is chemically grafted to the surface. However, AFM results show that such a low amount of material is su@cient to increase the repulsive potential between SijN4 surfaces.
Journal of the American Ceramic Society, Nov 1, 1996
The shear modulus and yield stress of attractive alumina particle networks in aqueous slurries wa... more The shear modulus and yield stress of attractive alumina particle networks in aqueous slurries was determined as a function of volume fraction (0.1 to 0.5), pH (2, 4, 5, 6, and 9), and salt (NH4l) concentration (0.25M to 2.34) using both vane and couette rheological tools. Consistent with previous observations concerning the relative strength of attractive particle networks, the shear modulus increased to a plateau value with salt concentration. In this work we have shown that the salt concentration at which this plateau value is achieved is a function of the pH, and thus, the surface charge density. The values of the shear modulus [G′], yield stress [τy], and yield strain [γy] of the attractive networks can be described with power law functions for particle volume fraction [φ] (G′∝φ4.75, τy∝φ3.6, and γy∝φ−1.1) and salt concentration [c] (G′∝ [c]2.0, τ, ∝ [c]1.15, and γy∝ [c]−0.85).
L'invention concerne un procede de fabrication de ponts dentaires artificiels consistant en u... more L'invention concerne un procede de fabrication de ponts dentaires artificiels consistant en un noyau en ceramique separe a haute resistance, fritte de maniere dense plaque avec de la porcelaine au moyen de procedes de la metallurgie des poudres. Selon ce procede, les pieces de pont frittees de maniere dense sont reliees a un noyau de pont par un verre renforce de particules. Etant donne que seul le materiau de verre humidifie la surface des pieces frittees de maniere dense, le verre joue le role de materiau de liaison qui maintient le noyau ensemble et qui permet a la fonction des particules d'uniquement augmenter la force (par exemple valeur Kc) de la masse de materiau de verre.
Unlike freeform fabrication of ceramics via stereolithography, this work deals with the feasibili... more Unlike freeform fabrication of ceramics via stereolithography, this work deals with the feasibility of a novel rapid prototyping process route for indirectly producing ceramic parts. By using a newly developed in situ temperature induced forming (TIF) technology, concentrated ceramic slurries are vacuum cast into a polymeric mold, which was produced by stereolithography. Through stereolithography the complex-shaped mold with precise surface quality can be produced quickly and the TIF technology enables the change of particle potential in the slurry from a repulsive into a weekly attractive particle network during consolidation. Therefore, a green body with high and homogeneous density without any crack can be realized. The design of the 3D mold is critical in order to achieve components which are complex near-net shape and easy to demold. Ceramic parts having a complex geometry with improved fine surface quality can be made and no burnout is required since only a minor amount of organic additives is used.
Journal of the European Ceramic Society, 1998
29Si NMR, d@use reflectance infrared fourier transform (DRIFT) spectroscopy, X-ray photoelectron ... more 29Si NMR, d@use reflectance infrared fourier transform (DRIFT) spectroscopy, X-ray photoelectron spectroscopy (XPS), ultraviolet spectroscopy (U V), ellipsometry, and atomic force microscopy (AFM) measurements were used to characterize the interaction of N-(triethoxysilylpropyl)-O-polyethylene oxide urethane with a SisN4 surface in water. The experimental results show that this tri alkoxy silane molecule covalently bonds to the surface of SijN4. Maximum adsorption of this compound was 2,13 pmolm-2, but less than 0-I ~molm-2 of this amount is chemically grafted to the surface. However, AFM results show that such a low amount of material is su@cient to increase the repulsive potential between SijN4 surfaces.
Journal of the American Ceramic Society, 1996
The shear modulus and yield stress of attractive alumina particle networks in aqueous slurries wa... more The shear modulus and yield stress of attractive alumina particle networks in aqueous slurries was determined as a function of volume fraction (0.1 to 0.5), pH (2, 4, 5, 6, and 9), and salt (NH4l) concentration (0.25M to 2.34) using both vane and couette rheological tools. Consistent with previous observations concerning the relative strength of attractive particle networks, the shear modulus increased to a plateau value with salt concentration. In this work we have shown that the salt concentration at which this plateau value is achieved is a function of the pH, and thus, the surface charge density. The values of the shear modulus [G′], yield stress [τy], and yield strain [γy] of the attractive networks can be described with power law functions for particle volume fraction [φ] (G′∝φ4.75, τy∝φ3.6, and γy∝φ−1.1) and salt concentration [c] (G′∝ [c]2.0, τ, ∝ [c]1.15, and γy∝ [c]−0.85).
Journal of the American Ceramic Society, 2004
Direct measurements of forces between silicon nitride surfaces in the presence of poly(acrylic ac... more Direct measurements of forces between silicon nitride surfaces in the presence of poly(acrylic acid) (PAA) are presented. The force-distance curves were obtained at pH > pHiep with an atomic force microscopy (AFM) colloidal-probe technique using a novel spherical silicon nitride probe attached to the AFM cantilever. We found that PAA adsorbs onto the negatively charged silicon nitride surface, which results in an increased repulsive surface potential. The steric contribution to the interparticle repulsion is small and the layer conformation remains flat even at high surface potentials or high ionic strength. The general features of the stabilization of ceramic powders with PAA are discussed; we suggest that PAA adsorbs onto silicon nitride by sequential adsorption of neighboring segments (“zipping”), which results in a flat conformation. In contrast, the long-range steric force found in the ZrO2/PAA system at pH > pHiep arises because the stretched equilibrium bulk conformation of the highly charged polymer is preserved via the formation of strong, irreversible surface-segment bonds on adsorption.
Journal of Colloid and Interface Science, 1999
The effect of strength of attraction and volume fraction on the mechanical properties of alumina ... more The effect of strength of attraction and volume fraction on the mechanical properties of alumina particle networks were investigated. Alumina particle gels were formed reversibly and in situ in the rheometer by cooling alumina particle suspensions with adsorbed poly(12-hydroxy stearic acid) suspended in a marginal solvent, hexanol. The collapse of the polymer layer with decreasing solvency (temperature) induces flocculation when the longrange van der Waals force overcomes the remaining steric repulsion. The gelation temperature depends on volume fraction. At the gel temperature, T gel , the gel becomes predominantly elastic; at temperatures below T gel , the elasticity increases with decreasing temperature. We find that the elastic modulus data, measured over a wide range of volume fraction (0.2 < < 0.425) and temperature (10-14°C), follows: G ؍ G 0 (؊ g) s. This scaling suggests the prefactor and exponent to be independent of temperature. We present some arguments for why subjecting a particle gel to a preshear procedure might result in an temperature-dependent prefactor. By invoking such an effect, we are able to rescale and collapse previously published moduli data on presheared suspensions according to the (؊ g) expression.
Powder Technology, 2001
This study introduces the atomic force microscope (AFM) for direct measurement of internal and ex... more This study introduces the atomic force microscope (AFM) for direct measurement of internal and external friction in ceramic powder pressing. The friction measurements were performed between two single granules, and a granule and a hard metal substrate as a function of granule binder concentration, relative humidity and sliding velocity. We found that the friction coefficient decreased with increasing humidity for a specific binder concentration, the effect being more pronounced for low concentrations. The friction coefficient also decreased with increasing binder concentration. Evaluation of the adhesion force showed a steady increase with both humidity and binder concentration. A substantial difference, more than an order of magnitude, was seen for the highest binder concentration at low and high humidities. We attribute these findings to the hygroscopic nature of the binder, poly(ethylene glycol) (PEG). Softening of the PEG at increasing humidities lowers the friction coefficient but increases the adhesion force. The results are consistent with flowability and angle of friction measurements.