Secondary minimum interactions and heterocoagulation encountered in the aqueous processing of alumina—zirconia ceramic composites

Rheology and Microstructure of Concentrated Zirconia-Alumina Suspensions for Gelcasting Composites

“…Suitable drying and sintering can then yield composites of complex shape with tailored microstructures and controlled properties. aTosoh, TZ-3Y; bReynolds, RCHP-DBM" Cln water [4]; dFor m-ZrO 2. 4and 5; bTransient mode" =After shear at rate i, 15 and 300 s"i, respectively; dOrea=iv exceeds 240 s" eShear rate is 200 s"l Maximum loadings for ZrOz, A1203, and a mixture with 20 vol% ZrO2, based on the solids, as functions of pM.…”

“…However, as this shear rate was exceeded, within the limits of the rheometer, an "infinite" shear stress was observed for shear rates greater than 200 s "I. in Stages (I), (2), and (4). When _ was reduced to 0 s -I in Stages 3and 5, a high degree of hysteresis was observed (r remained "infinite") until7 approached 30 s -I, at which point the shear stress plummeted; hysteresis was not observed between 30 and 0 s-I.…”

“…Comparison of the data for Systems C and D reveals, after consideration of their locations in Figure 2, i.e., relative to the transitions between Regions I and II for each unary system and for the binary systems, that the high yield stresses of Systems C and D are induced by the colloidal properties of ZrO 2. For instance, the f-potential of the ZrO z particles in System C is -32 mV, an insufficient value for this [3] and similar ZrO 2 powders [4,7,8] to be colloidally stable against the strong London-van der Waals forces that promote agglomeration; note the comparatively large Hamaker constant for this material in Table I. In comparison, the AI203 powder possesses a higher fpotential in System C ( Figure I), while having a lower Hamaker constant; thus, it is the more colloidally stable component and the less pH-sensitive one in the present system.…”

“…60 s at 300 s-I, (3) 60 s to reduce # to 0 s "l,(4) 60 s to increase 7 again from 0 to 300 s"I, and (5) 60 s to reduce it again to 0 s°l This strategy allowed the study of (i) apparent viscosity (_app _ r/7), Bingham plastic flow with yield stress (rB) and constant differential viscosity (_di_ _ d_/dT) when _ e _B, (ii) pseudoplastic flow (_app and Nd_z differ regularly with increasing 7), (iii) hysteresis (r4 _ rs, subscripts specify stages), and (iv) thixotropy (timedependent r). [5] The four stages in the transient mode were (I) 60 s at 15 s-l, ....... , ........ _ _-i !_.,_ 040 S a_ 0,01 s -I.…”

Rheology and Microstructure of Concentrated Zirconia-Alumina Suspensions for Gelcasting Composites

“…Suitable drying and sintering can then yield composites of complex shape with tailored microstructures and controlled properties. aTosoh, TZ-3Y; bReynolds, RCHP-DBM" Cln water [4]; dFor m-ZrO 2. 4and 5; bTransient mode" =After shear at rate i, 15 and 300 s"i, respectively; dOrea=iv exceeds 240 s" eShear rate is 200 s"l Maximum loadings for ZrOz, A1203, and a mixture with 20 vol% ZrO2, based on the solids, as functions of pM.…”

“…However, as this shear rate was exceeded, within the limits of the rheometer, an "infinite" shear stress was observed for shear rates greater than 200 s "I. in Stages (I), (2), and (4). When _ was reduced to 0 s -I in Stages 3and 5, a high degree of hysteresis was observed (r remained "infinite") until7 approached 30 s -I, at which point the shear stress plummeted; hysteresis was not observed between 30 and 0 s-I.…”

“…Comparison of the data for Systems C and D reveals, after consideration of their locations in Figure 2, i.e., relative to the transitions between Regions I and II for each unary system and for the binary systems, that the high yield stresses of Systems C and D are induced by the colloidal properties of ZrO 2. For instance, the f-potential of the ZrO z particles in System C is -32 mV, an insufficient value for this [3] and similar ZrO 2 powders [4,7,8] to be colloidally stable against the strong London-van der Waals forces that promote agglomeration; note the comparatively large Hamaker constant for this material in Table I. In comparison, the AI203 powder possesses a higher fpotential in System C ( Figure I), while having a lower Hamaker constant; thus, it is the more colloidally stable component and the less pH-sensitive one in the present system.…”

“…60 s at 300 s-I, (3) 60 s to reduce # to 0 s "l,(4) 60 s to increase 7 again from 0 to 300 s"I, and (5) 60 s to reduce it again to 0 s°l This strategy allowed the study of (i) apparent viscosity (_app _ r/7), Bingham plastic flow with yield stress (rB) and constant differential viscosity (_di_ _ d_/dT) when _ e _B, (ii) pseudoplastic flow (_app and Nd_z differ regularly with increasing 7), (iii) hysteresis (r4 _ rs, subscripts specify stages), and (iv) thixotropy (timedependent r). [5] The four stages in the transient mode were (I) 60 s at 15 s-l, ....... , ........ _ _-i !_.,_ 040 S a_ 0,01 s -I.…”

Nonelectrostatic Ionic Forces between Dissimilar Surfaces: A Mechanism for Colloid Separation

“…Heterocoagulation, involving interactions between dissimilar surfaces, is a problem of wide application. − With symmetric systems of identical surfaces, a large volume of recent literature − has shown that the inclusion of ionic dispersion forces is necessary to deal with Hofmeister effects or ion specificity of interactions. With dissimilar or asymmetrically charged particle interactions, ,− no work has been done to address such contributions.…”

Rheology and Microstructure of Concentrated Zirconia-Alumina Suspensions for Gelcasting Composites

“…Suitable drying and sintering can then yield composites of complex shape with tailored microstructures and controlled properties. aTosoh, TZ-3Y; bReynolds, RCHP-DBM" Cln water [4]; dFor m-ZrO 2. 4and 5; bTransient mode" =After shear at rate i, 15 and 300 s"i, respectively; dOrea=iv exceeds 240 s" eShear rate is 200 s"l Maximum loadings for ZrOz, A1203, and a mixture with 20 vol% ZrO2, based on the solids, as functions of pM.…”

“…However, as this shear rate was exceeded, within the limits of the rheometer, an "infinite" shear stress was observed for shear rates greater than 200 s "I. in Stages (I), (2), and (4). When _ was reduced to 0 s -I in Stages 3and 5, a high degree of hysteresis was observed (r remained "infinite") until7 approached 30 s -I, at which point the shear stress plummeted; hysteresis was not observed between 30 and 0 s-I.…”

“…Comparison of the data for Systems C and D reveals, after consideration of their locations in Figure 2, i.e., relative to the transitions between Regions I and II for each unary system and for the binary systems, that the high yield stresses of Systems C and D are induced by the colloidal properties of ZrO 2. For instance, the f-potential of the ZrO z particles in System C is -32 mV, an insufficient value for this [3] and similar ZrO 2 powders [4,7,8] to be colloidally stable against the strong London-van der Waals forces that promote agglomeration; note the comparatively large Hamaker constant for this material in Table I. In comparison, the AI203 powder possesses a higher fpotential in System C ( Figure I), while having a lower Hamaker constant; thus, it is the more colloidally stable component and the less pH-sensitive one in the present system.…”

“…60 s at 300 s-I, (3) 60 s to reduce # to 0 s "l,(4) 60 s to increase 7 again from 0 to 300 s"I, and (5) 60 s to reduce it again to 0 s°l This strategy allowed the study of (i) apparent viscosity (_app _ r/7), Bingham plastic flow with yield stress (rB) and constant differential viscosity (_di_ _ d_/dT) when _ e _B, (ii) pseudoplastic flow (_app and Nd_z differ regularly with increasing 7), (iii) hysteresis (r4 _ rs, subscripts specify stages), and (iv) thixotropy (timedependent r). [5] The four stages in the transient mode were (I) 60 s at 15 s-l, ....... , ........ _ _-i !_.,_ 040 S a_ 0,01 s -I.…”

Nonelectrostatic Ionic Forces between Dissimilar Surfaces: A Mechanism for Colloid Separation

“…Heterocoagulation, involving interactions between dissimilar surfaces, is a problem of wide application. − With symmetric systems of identical surfaces, a large volume of recent literature − has shown that the inclusion of ionic dispersion forces is necessary to deal with Hofmeister effects or ion specificity of interactions. With dissimilar or asymmetrically charged particle interactions, ,− no work has been done to address such contributions.…”

Rheology and Microstructure of Concentrated Zirconia-Alumina Suspensions for Gelcasting Composites

“…Suitable drying and sintering can then yield composites of complex shape with tailored microstructures and controlled properties. aTosoh, TZ-3Y; bReynolds, RCHP-DBM" Cln water [4]; dFor m-ZrO 2. 4and 5; bTransient mode" =After shear at rate i, 15 and 300 s"i, respectively; dOrea=iv exceeds 240 s" eShear rate is 200 s"l Maximum loadings for ZrOz, A1203, and a mixture with 20 vol% ZrO2, based on the solids, as functions of pM.…”

“…However, as this shear rate was exceeded, within the limits of the rheometer, an "infinite" shear stress was observed for shear rates greater than 200 s "I. in Stages (I), (2), and (4). When _ was reduced to 0 s -I in Stages 3and 5, a high degree of hysteresis was observed (r remained "infinite") until7 approached 30 s -I, at which point the shear stress plummeted; hysteresis was not observed between 30 and 0 s-I.…”

“…Comparison of the data for Systems C and D reveals, after consideration of their locations in Figure 2, i.e., relative to the transitions between Regions I and II for each unary system and for the binary systems, that the high yield stresses of Systems C and D are induced by the colloidal properties of ZrO 2. For instance, the f-potential of the ZrO z particles in System C is -32 mV, an insufficient value for this [3] and similar ZrO 2 powders [4,7,8] to be colloidally stable against the strong London-van der Waals forces that promote agglomeration; note the comparatively large Hamaker constant for this material in Table I. In comparison, the AI203 powder possesses a higher fpotential in System C ( Figure I), while having a lower Hamaker constant; thus, it is the more colloidally stable component and the less pH-sensitive one in the present system.…”

“…60 s at 300 s-I, (3) 60 s to reduce # to 0 s "l,(4) 60 s to increase 7 again from 0 to 300 s"I, and (5) 60 s to reduce it again to 0 s°l This strategy allowed the study of (i) apparent viscosity (_app _ r/7), Bingham plastic flow with yield stress (rB) and constant differential viscosity (_di_ _ d_/dT) when _ e _B, (ii) pseudoplastic flow (_app and Nd_z differ regularly with increasing 7), (iii) hysteresis (r4 _ rs, subscripts specify stages), and (iv) thixotropy (timedependent r). [5] The four stages in the transient mode were (I) 60 s at 15 s-l, ....... , ........ _ _-i !_.,_ 040 S a_ 0,01 s -I.…”

Nonelectrostatic Ionic Forces between Dissimilar Surfaces: A Mechanism for Colloid Separation

“…Heterocoagulation, involving interactions between dissimilar surfaces, is a problem of wide application. − With symmetric systems of identical surfaces, a large volume of recent literature − has shown that the inclusion of ionic dispersion forces is necessary to deal with Hofmeister effects or ion specificity of interactions. With dissimilar or asymmetrically charged particle interactions, ,− no work has been done to address such contributions.…”