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Dino Aquilano - One of the best experts on this subject based on the ideXlab platform.
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Theoretical Equilibrium Morphology and Twin Energy of Monoclinic Hydroxyapatite
Acta Crystallographica Section A Foundations and Advances, 2014Co-Authors: Linda Pastero, Marco Rubbo, Marco Bruno, Fernando Cámara, Dino AquilanoAbstract:Microsized hydroxyapatite (HAp), we synthesized under mild hydrothermal conditions, shows both monoclinic and hexagonal polymorphs made by rod-shaped single crystals along with simple and multiple twins. The theoretical Morphology, obtained through the Hartman-Perdok analysis on the P21/c polymorph, allowed to predict the stable surfaces of the main {hkl} forms. Their surface energies have been evaluated, at 0 K, by ab initio quantum-mechanical calculations. The resulting HAp Equilibrium shape (ES) [1] is dominated by a pseudo-hexagonal prism formed by the the {001}, {100} and {-102} forms (having close energy values), all developing around the OH channels of the structure. The basal {010} form truncates the pseudo-hexagonal prism perpendicularly to the OH channels, while three other less important prisms {012}, {110} and {11-2}, lying in between the pseudo-hexagonal prism and the basal pinacoid, enter the ES. A simple kinetic model based on 2D nucleation is proposed to explain the Morphology of the single crystals [1]. Assuming [2, 3] that the simplest twin law for the monoclinic phase is generated by a threefold rotation about the 21axis, we found that the three original composition planes (OCP) of the twin coincide with the faces of the {001}, {100} and {-102} forms. For each OCP there are two different surface terminations, according to whether the frontier between parent (P) and twinned (T) crystals intercepts (or not) the centers of mass of PO4and Ca ions and of the O atoms of the OH groups. We examined, as an example, the two kinds of interfaces for the twin (100)P/(001)T. The calculated twin energies result to be very close and low (3.3 and 4.2 erg cm-2), when compared to the value of the HAp surface energy in the [010] zone (≍ 1500 erg cm-2). This means that the probability of formation of a 2D-nucleus oriented in twin position on all the [010] zone is practically equivalent to that needed to generate a normally oriented 2D nucleus in the same zone
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Low Symmetry Polymorph of Hydroxyapatite. Theoretical Equilibrium Morphology of the Monoclinic Ca5(OH)(PO4)3
Crystal Growth & Design, 2014Co-Authors: Dino Aquilano, Francesco Roberto Massaro, Marco Rubbo, Marco Bruno, Linda PasteroAbstract:The Hartman–Perdok analysis has been carried out on the monoclinic P21/c polymorph of Hydroxyapatite (HAp) in order to find the character of the main {hkl} forms and foresee the possible profiles of the related surfaces. Then, the corresponding specific surface energies have been calculated, at 0 K, by ab initio quantum-mechanical calculations, and the HAp Equilibrium shape has been obtained: a striking pseudohexagonal prism comes out from the close similarity of the surface energy of the three pinacoids {001}, {100}, and {102}, all developing around the [010] zone axis which runs parallel to the OH channels of the structure bulk. The most stable form, the pinacoid {010}, truncates the pseudohexagonal prism perpendicularly to the OH channels, while the less morphologically important monoclinic prisms {012}, {110}, and {112} complete the HAp Equilibrium shape. Preliminary considerations are exposed about the morphological path: monoclinic polymorph → twinning → hexagonal polymorph. Finally, a simple kine...
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Experimental and theoretical aspects of the growth and Equilibrium Morphology of NaNO3
Crystal Research and Technology, 2011Co-Authors: R. Benages Vilau, Emanuele Costa, Marco Bruno, M. A. Cuevas-diarte, T. Calvet I Pallas, Dino AquilanoAbstract:Sodium nitrate (mineral nitratine, NaNO3, space group Rc at room temperature) is a material used in a great variety of fields, such as the molten salt technology. It is also of very interest from a crystallographic point of view, being iso-structural with calcite (CaCO3). We performed several growth experiments in aqueous solution, near-Equilibrium, with the aim of finding the ideal conditions for investigating both face-by-face growth kinetics and surface characterization, as well as the influence of K+ and Li+ ions on the growth Morphology. Single {10.4} rhombohedral crystals have been systematically grown from pure aqueous solution, while {00.1} truncated rhombohedra were obtained in the presence of K+ and Li+ ions in the mother solution. When determining the theoretical Equilibrium Morphology of NaNO3 crystals, the {00.1} and {10.4} surfaces were studied by using the 2D-slab model and relaxed and athermal surface energies (surfaces energies at T = 0 K) were evaluated at DFT level (B3LYP Hamiltonian) by using the CRYSTAL06 package. The {00.1} dipolar surfaces were reconstructed by the octopolar Hartman-Lacmann's model, already proposed for NaCl-like lattices. This type of reconstruction is the only one which respects the bulk symmetry of the crystal. The octopolar Na+ terminated {00.1} form resulted to be more stable than the NO3– terminated one. However, the {00.1} form does not enter the theoretical athermal Equilibrium shape of nitratine crystals, being γ(10.4)Na=160, γ(00.1)Na= 695 and γ(00.1)NO3=1535 erg/cm2. Finally, a simple 2D-epitaxy model is proposed to explain the appearance of NaNO3{00.1} truncated rhombohedra in the presence of K+ and Li+ ions. (© 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
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Theoretical Equilibrium Morphology of Gypsum (CaSO4·2H2O). 2. The Stepped Faces of the Main [001] Zone
Crystal Growth & Design, 2011Co-Authors: Francesco Roberto Massaro, Marco Rubbo, Dino AquilanoAbstract:The athermal Equilibrium shape (ES) of gypsum crystal is calculated, in a vacuum, in the zone interval of the stepped {1k0} forms (3 ≤ k ≤ 8). The surface profiles are obtained by applying either the Hartman―Perdok method of the periodic bond chains (PBC) or the method of systematic cuts (SC) generated under the only conditions of stoichiometry, electroneutrality, and annihilation of the dipole moment perpendicular to each d 1k0 slice. The specific surface energy values γ 1k0 have been calculated, both for ideal and relaxed surface profiles, using a semiempirical potential function proposed by Adam. From calculations, it follows that the ES in the [001] zone is characterized not only by the well-known {120} and {010} flat forms and by the stepped {100} pinacoid but also by the {140} and {180} stepped forms. Further, following the PBC method, the stepped {130} and {170} forms also should enter the ES. Finally, an unambiguous analogy arises between our results and the systematic presence of the {1k0} faces on the giant crystals found in the Naica mine, whose growth occurs very near the Equilibrium.
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theoretical Equilibrium Morphology of gypsum caso4 2h2o 2 the stepped faces of the main 001 zone
Crystal Growth & Design, 2011Co-Authors: Francesco Roberto Massaro, Marco Rubbo, Dino AquilanoAbstract:The athermal Equilibrium shape (ES) of gypsum crystal is calculated, in a vacuum, in the zone interval of the stepped {1k0} forms (3 ≤ k ≤ 8). The surface profiles are obtained by applying either the Hartman―Perdok method of the periodic bond chains (PBC) or the method of systematic cuts (SC) generated under the only conditions of stoichiometry, electroneutrality, and annihilation of the dipole moment perpendicular to each d 1k0 slice. The specific surface energy values γ 1k0 have been calculated, both for ideal and relaxed surface profiles, using a semiempirical potential function proposed by Adam. From calculations, it follows that the ES in the [001] zone is characterized not only by the well-known {120} and {010} flat forms and by the stepped {100} pinacoid but also by the {140} and {180} stepped forms. Further, following the PBC method, the stepped {130} and {170} forms also should enter the ES. Finally, an unambiguous analogy arises between our results and the systematic presence of the {1k0} faces on the giant crystals found in the Naica mine, whose growth occurs very near the Equilibrium.
Francesco Roberto Massaro - One of the best experts on this subject based on the ideXlab platform.
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Low Symmetry Polymorph of Hydroxyapatite. Theoretical Equilibrium Morphology of the Monoclinic Ca5(OH)(PO4)3
Crystal Growth & Design, 2014Co-Authors: Dino Aquilano, Francesco Roberto Massaro, Marco Rubbo, Marco Bruno, Linda PasteroAbstract:The Hartman–Perdok analysis has been carried out on the monoclinic P21/c polymorph of Hydroxyapatite (HAp) in order to find the character of the main {hkl} forms and foresee the possible profiles of the related surfaces. Then, the corresponding specific surface energies have been calculated, at 0 K, by ab initio quantum-mechanical calculations, and the HAp Equilibrium shape has been obtained: a striking pseudohexagonal prism comes out from the close similarity of the surface energy of the three pinacoids {001}, {100}, and {102}, all developing around the [010] zone axis which runs parallel to the OH channels of the structure bulk. The most stable form, the pinacoid {010}, truncates the pseudohexagonal prism perpendicularly to the OH channels, while the less morphologically important monoclinic prisms {012}, {110}, and {112} complete the HAp Equilibrium shape. Preliminary considerations are exposed about the morphological path: monoclinic polymorph → twinning → hexagonal polymorph. Finally, a simple kine...
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Theoretical Equilibrium Morphology of Gypsum (CaSO4·2H2O). 2. The Stepped Faces of the Main [001] Zone
Crystal Growth & Design, 2011Co-Authors: Francesco Roberto Massaro, Marco Rubbo, Dino AquilanoAbstract:The athermal Equilibrium shape (ES) of gypsum crystal is calculated, in a vacuum, in the zone interval of the stepped {1k0} forms (3 ≤ k ≤ 8). The surface profiles are obtained by applying either the Hartman―Perdok method of the periodic bond chains (PBC) or the method of systematic cuts (SC) generated under the only conditions of stoichiometry, electroneutrality, and annihilation of the dipole moment perpendicular to each d 1k0 slice. The specific surface energy values γ 1k0 have been calculated, both for ideal and relaxed surface profiles, using a semiempirical potential function proposed by Adam. From calculations, it follows that the ES in the [001] zone is characterized not only by the well-known {120} and {010} flat forms and by the stepped {100} pinacoid but also by the {140} and {180} stepped forms. Further, following the PBC method, the stepped {130} and {170} forms also should enter the ES. Finally, an unambiguous analogy arises between our results and the systematic presence of the {1k0} faces on the giant crystals found in the Naica mine, whose growth occurs very near the Equilibrium.
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theoretical Equilibrium Morphology of gypsum caso4 2h2o 2 the stepped faces of the main 001 zone
Crystal Growth & Design, 2011Co-Authors: Francesco Roberto Massaro, Marco Rubbo, Dino AquilanoAbstract:The athermal Equilibrium shape (ES) of gypsum crystal is calculated, in a vacuum, in the zone interval of the stepped {1k0} forms (3 ≤ k ≤ 8). The surface profiles are obtained by applying either the Hartman―Perdok method of the periodic bond chains (PBC) or the method of systematic cuts (SC) generated under the only conditions of stoichiometry, electroneutrality, and annihilation of the dipole moment perpendicular to each d 1k0 slice. The specific surface energy values γ 1k0 have been calculated, both for ideal and relaxed surface profiles, using a semiempirical potential function proposed by Adam. From calculations, it follows that the ES in the [001] zone is characterized not only by the well-known {120} and {010} flat forms and by the stepped {100} pinacoid but also by the {140} and {180} stepped forms. Further, following the PBC method, the stepped {130} and {170} forms also should enter the ES. Finally, an unambiguous analogy arises between our results and the systematic presence of the {1k0} faces on the giant crystals found in the Naica mine, whose growth occurs very near the Equilibrium.
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Theoretical Equilibrium Morphology of Gypsum (CaSO4·2H2O)- 1. A Syncretic Strategy to Calculate the Morphology of Crystals
Crystal Growth & Design, 2010Co-Authors: Francesco Roberto Massaro, Marco Rubbo, Dino AquilanoAbstract:The theoretical and Equilibrium Morphology of gypsum (CaSO4·2H2O) is reassessed, starting from the historical papers by Simon and Bienfait (1965) and by Heijnen and Hartman (1991). The surface profiles of the most frequently observed crystal forms have been determined following two ways: in the first one we used the Hartman−Perdok method based on the periodic bond chain (PBC) analysis, while in the second one the profile of each face was obtained using the GDIS program. In both cases, the calculation of the specific surface energy values has been made using the general utility lattice program (GULP) code. From the synthesis of the two methods, a new and much more isotropic Equilibrium shape is calculated, in the case of both unrelaxed and relaxed surfaces. Further, and for the first time, beyond the well-known and singular {010}, {120}, {011}, and {111} F-forms, two stepped, {100} and {122}, and one kinked form, {102}, are found to build the Equilibrium shape of gypsum.
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theoretical Equilibrium Morphology of gypsum caso4 2h2o 1 a syncretic strategy to calculate the Morphology of crystals
Crystal Growth & Design, 2010Co-Authors: Francesco Roberto Massaro, Marco Rubbo, Dino AquilanoAbstract:The theoretical and Equilibrium Morphology of gypsum (CaSO4·2H2O) is reassessed, starting from the historical papers by Simon and Bienfait (1965) and by Heijnen and Hartman (1991). The surface profiles of the most frequently observed crystal forms have been determined following two ways: in the first one we used the Hartman−Perdok method based on the periodic bond chain (PBC) analysis, while in the second one the profile of each face was obtained using the GDIS program. In both cases, the calculation of the specific surface energy values has been made using the general utility lattice program (GULP) code. From the synthesis of the two methods, a new and much more isotropic Equilibrium shape is calculated, in the case of both unrelaxed and relaxed surfaces. Further, and for the first time, beyond the well-known and singular {010}, {120}, {011}, and {111} F-forms, two stepped, {100} and {122}, and one kinked form, {102}, are found to build the Equilibrium shape of gypsum.
Marco Rubbo - One of the best experts on this subject based on the ideXlab platform.
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Theoretical Equilibrium Morphology and Twin Energy of Monoclinic Hydroxyapatite
Acta Crystallographica Section A Foundations and Advances, 2014Co-Authors: Linda Pastero, Marco Rubbo, Marco Bruno, Fernando Cámara, Dino AquilanoAbstract:Microsized hydroxyapatite (HAp), we synthesized under mild hydrothermal conditions, shows both monoclinic and hexagonal polymorphs made by rod-shaped single crystals along with simple and multiple twins. The theoretical Morphology, obtained through the Hartman-Perdok analysis on the P21/c polymorph, allowed to predict the stable surfaces of the main {hkl} forms. Their surface energies have been evaluated, at 0 K, by ab initio quantum-mechanical calculations. The resulting HAp Equilibrium shape (ES) [1] is dominated by a pseudo-hexagonal prism formed by the the {001}, {100} and {-102} forms (having close energy values), all developing around the OH channels of the structure. The basal {010} form truncates the pseudo-hexagonal prism perpendicularly to the OH channels, while three other less important prisms {012}, {110} and {11-2}, lying in between the pseudo-hexagonal prism and the basal pinacoid, enter the ES. A simple kinetic model based on 2D nucleation is proposed to explain the Morphology of the single crystals [1]. Assuming [2, 3] that the simplest twin law for the monoclinic phase is generated by a threefold rotation about the 21axis, we found that the three original composition planes (OCP) of the twin coincide with the faces of the {001}, {100} and {-102} forms. For each OCP there are two different surface terminations, according to whether the frontier between parent (P) and twinned (T) crystals intercepts (or not) the centers of mass of PO4and Ca ions and of the O atoms of the OH groups. We examined, as an example, the two kinds of interfaces for the twin (100)P/(001)T. The calculated twin energies result to be very close and low (3.3 and 4.2 erg cm-2), when compared to the value of the HAp surface energy in the [010] zone (≍ 1500 erg cm-2). This means that the probability of formation of a 2D-nucleus oriented in twin position on all the [010] zone is practically equivalent to that needed to generate a normally oriented 2D nucleus in the same zone
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Low Symmetry Polymorph of Hydroxyapatite. Theoretical Equilibrium Morphology of the Monoclinic Ca5(OH)(PO4)3
Crystal Growth & Design, 2014Co-Authors: Dino Aquilano, Francesco Roberto Massaro, Marco Rubbo, Marco Bruno, Linda PasteroAbstract:The Hartman–Perdok analysis has been carried out on the monoclinic P21/c polymorph of Hydroxyapatite (HAp) in order to find the character of the main {hkl} forms and foresee the possible profiles of the related surfaces. Then, the corresponding specific surface energies have been calculated, at 0 K, by ab initio quantum-mechanical calculations, and the HAp Equilibrium shape has been obtained: a striking pseudohexagonal prism comes out from the close similarity of the surface energy of the three pinacoids {001}, {100}, and {102}, all developing around the [010] zone axis which runs parallel to the OH channels of the structure bulk. The most stable form, the pinacoid {010}, truncates the pseudohexagonal prism perpendicularly to the OH channels, while the less morphologically important monoclinic prisms {012}, {110}, and {112} complete the HAp Equilibrium shape. Preliminary considerations are exposed about the morphological path: monoclinic polymorph → twinning → hexagonal polymorph. Finally, a simple kine...
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Theoretical Equilibrium Morphology of Gypsum (CaSO4·2H2O). 2. The Stepped Faces of the Main [001] Zone
Crystal Growth & Design, 2011Co-Authors: Francesco Roberto Massaro, Marco Rubbo, Dino AquilanoAbstract:The athermal Equilibrium shape (ES) of gypsum crystal is calculated, in a vacuum, in the zone interval of the stepped {1k0} forms (3 ≤ k ≤ 8). The surface profiles are obtained by applying either the Hartman―Perdok method of the periodic bond chains (PBC) or the method of systematic cuts (SC) generated under the only conditions of stoichiometry, electroneutrality, and annihilation of the dipole moment perpendicular to each d 1k0 slice. The specific surface energy values γ 1k0 have been calculated, both for ideal and relaxed surface profiles, using a semiempirical potential function proposed by Adam. From calculations, it follows that the ES in the [001] zone is characterized not only by the well-known {120} and {010} flat forms and by the stepped {100} pinacoid but also by the {140} and {180} stepped forms. Further, following the PBC method, the stepped {130} and {170} forms also should enter the ES. Finally, an unambiguous analogy arises between our results and the systematic presence of the {1k0} faces on the giant crystals found in the Naica mine, whose growth occurs very near the Equilibrium.
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theoretical Equilibrium Morphology of gypsum caso4 2h2o 2 the stepped faces of the main 001 zone
Crystal Growth & Design, 2011Co-Authors: Francesco Roberto Massaro, Marco Rubbo, Dino AquilanoAbstract:The athermal Equilibrium shape (ES) of gypsum crystal is calculated, in a vacuum, in the zone interval of the stepped {1k0} forms (3 ≤ k ≤ 8). The surface profiles are obtained by applying either the Hartman―Perdok method of the periodic bond chains (PBC) or the method of systematic cuts (SC) generated under the only conditions of stoichiometry, electroneutrality, and annihilation of the dipole moment perpendicular to each d 1k0 slice. The specific surface energy values γ 1k0 have been calculated, both for ideal and relaxed surface profiles, using a semiempirical potential function proposed by Adam. From calculations, it follows that the ES in the [001] zone is characterized not only by the well-known {120} and {010} flat forms and by the stepped {100} pinacoid but also by the {140} and {180} stepped forms. Further, following the PBC method, the stepped {130} and {170} forms also should enter the ES. Finally, an unambiguous analogy arises between our results and the systematic presence of the {1k0} faces on the giant crystals found in the Naica mine, whose growth occurs very near the Equilibrium.
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Theoretical Equilibrium Morphology of Gypsum (CaSO4·2H2O)- 1. A Syncretic Strategy to Calculate the Morphology of Crystals
Crystal Growth & Design, 2010Co-Authors: Francesco Roberto Massaro, Marco Rubbo, Dino AquilanoAbstract:The theoretical and Equilibrium Morphology of gypsum (CaSO4·2H2O) is reassessed, starting from the historical papers by Simon and Bienfait (1965) and by Heijnen and Hartman (1991). The surface profiles of the most frequently observed crystal forms have been determined following two ways: in the first one we used the Hartman−Perdok method based on the periodic bond chain (PBC) analysis, while in the second one the profile of each face was obtained using the GDIS program. In both cases, the calculation of the specific surface energy values has been made using the general utility lattice program (GULP) code. From the synthesis of the two methods, a new and much more isotropic Equilibrium shape is calculated, in the case of both unrelaxed and relaxed surfaces. Further, and for the first time, beyond the well-known and singular {010}, {120}, {011}, and {111} F-forms, two stepped, {100} and {122}, and one kinked form, {102}, are found to build the Equilibrium shape of gypsum.
Dazhuang Liu - One of the best experts on this subject based on the ideXlab platform.
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Effect of initiator on Morphology in poly(vinyl acetate)/polystyrene and poly(butyl acrylate)/polystyrene composite latexes
Polymer Bulletin, 2005Co-Authors: Peiqin Sun, Dazhuang Liu, Shaohui Sun, Ke ZhaoAbstract:A simple method of related sensitivity range to predict thermodynamic Equilibrium Morphology of a core-shell latex particle (J Appl Polym Sci. 2004, 92, 3144), is recently explored. The article proposed that it is necessary to classify core-shell latex systems as sensitivity and no-sensitivity by their Equilibrium Morphology sensitivity to initiator and emulsifier. As for the sensitivity system, the final Morphology may change by adjusting initiator and emulsifier, whereas, for the no-sensitivity system, it is hard to change its final Morphology in this way. Equilibrium morphologies in system poly(vinyl acetate) (PVAc)/polystyrene (PSt) and poly(butyl acrylate) (PBA)/ PSt composite latexes particles were observed by changing initiator. Composite latexes of the two systems were synthesized by two-stage semi-continuous emulsion polymerization. The types or/and concentration of initiator changed in two stages in which the oil-soluble initiator 2,2-azobis(isobutyronitrile) (AIBN) and the water-soluble initiator potassium persulfate (KPS) were used respectively, the concentration of which was 0.5% or 2% based on the weight of monomer. The results showed that the two systems had different characteristics. At different experiment conditions designed, the same Equilibrium morphologies with PSt as core and PVAc as shell were obtained in system PVAc/PSt, whereas, three different Equilibrium morphologies, core-shell, inverted core-shell and hemisphere, were obtained in system PBA/PSt. The Equilibrium Morphology in system PVAc/PSt is no-sensitive to initiator, and the Equilibrium Morphology in system PBA/PSt is sensitive to initiator.
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Simple method of related sensitivity range to predict the thermodynamic Equilibrium Morphology of a core–shell latex particle
Journal of Applied Polymer Science, 2004Co-Authors: Ke Zhao, Dazhuang Liu, Peiqin Sun, Lijun WangAbstract:The Equilibrium morphologies of different core–shell latices are predicted, and a related sensitivity analysis is given for the predictions. This article proposes a related sensitivity range for estimating the accuracy of predictions, made with the simple method, of the thermodynamically preferred Morphology of a core–shell latex particle in two-stage seeded emulsion polymerization. The related sensitivity range of the predictions is defined and calculated, and the results show that different core–shell latices have different sensitivity ranges. The wider the sensitivity range is, the more reliable the prediction is of the Morphology of the core–shell latex. The simple method of related sensitivity range has been verified in the literature and with experiments. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3144–3152, 2004
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simple method of related sensitivity range to predict the thermodynamic Equilibrium Morphology of a core shell latex particle
Journal of Applied Polymer Science, 2004Co-Authors: Ke Zhao, Dazhuang Liu, Peiqin Sun, Lijun WangAbstract:The Equilibrium morphologies of different core–shell latices are predicted, and a related sensitivity analysis is given for the predictions. This article proposes a related sensitivity range for estimating the accuracy of predictions, made with the simple method, of the thermodynamically preferred Morphology of a core–shell latex particle in two-stage seeded emulsion polymerization. The related sensitivity range of the predictions is defined and calculated, and the results show that different core–shell latices have different sensitivity ranges. The wider the sensitivity range is, the more reliable the prediction is of the Morphology of the core–shell latex. The simple method of related sensitivity range has been verified in the literature and with experiments. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3144–3152, 2004
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morphologies of polybutylacrylate poly styrene co methyl methacrylate latex prepared by starved emulsion polymerization part i thermodynamics Equilibrium Morphology
Polymer International, 2002Co-Authors: Dongxia Huo, Dazhuang LiuAbstract:Heterogeneous latexes were prepared by a semicontinuous seeded emulsion polymerization process under monomer starved conditions at 80 °C using potassium persulfate as the initiator and sodium dodecyl sulfate as the emulsifier. Poly(butyl acrylate) latexes were used as seeds. The second-stage polymer was poly(styrene-co-methyl methacrylate). By varying the amounts of methyl methacrylate (MMA) in the second-stage copolymer, the polarity of the copolymer phase could be controlled. Phase separation towards the thermodynamic Equilibrium Morphology was accelerated either by ageing the composite latex at 80 °C or by adding a chain-transfer agent during polymerization. The morphologies of the latex particles were examined by transmission electron microscopy (TEM). The Morphology distributions of latex particles were described by a statistical method. It was found that the latex particles displayed different Equilibrium morphologies depending on the composition of the second-stage copolymers. This series of Equilibrium morphologies of [poly(butyl acrylate)/poly(styrene-co-methyl methacrylate)] (PBA/P(St-co-MMA)) system provides experimental verification for quantitative simulation. Under limiting conditions, the Equilibrium morphologies of PBA/P(St-co-MMA) were predicted according to the minimum surface free energy change principle. The particle Morphology observed by TEM was in good agreement with the predictions of the thermodynamic model. Therefore, the Morphology theory for homopolymer/homopolymer composite systems was extended to homopolymer/copolymer systems. © 2002 Society of Chemical Industry
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Morphologies of polybutylacrylate/poly(styrene‐co‐methyl methacrylate) latex prepared by starved emulsion polymerization Part I. Thermodynamics Equilibrium Morphology
Polymer International, 2002Co-Authors: Dongxia Huo, Dazhuang LiuAbstract:Heterogeneous latexes were prepared by a semicontinuous seeded emulsion polymerization process under monomer starved conditions at 80 °C using potassium persulfate as the initiator and sodium dodecyl sulfate as the emulsifier. Poly(butyl acrylate) latexes were used as seeds. The second-stage polymer was poly(styrene-co-methyl methacrylate). By varying the amounts of methyl methacrylate (MMA) in the second-stage copolymer, the polarity of the copolymer phase could be controlled. Phase separation towards the thermodynamic Equilibrium Morphology was accelerated either by ageing the composite latex at 80 °C or by adding a chain-transfer agent during polymerization. The morphologies of the latex particles were examined by transmission electron microscopy (TEM). The Morphology distributions of latex particles were described by a statistical method. It was found that the latex particles displayed different Equilibrium morphologies depending on the composition of the second-stage copolymers. This series of Equilibrium morphologies of [poly(butyl acrylate)/poly(styrene-co-methyl methacrylate)] (PBA/P(St-co-MMA)) system provides experimental verification for quantitative simulation. Under limiting conditions, the Equilibrium morphologies of PBA/P(St-co-MMA) were predicted according to the minimum surface free energy change principle. The particle Morphology observed by TEM was in good agreement with the predictions of the thermodynamic model. Therefore, the Morphology theory for homopolymer/homopolymer composite systems was extended to homopolymer/copolymer systems. © 2002 Society of Chemical Industry
Rampi Ramprasad - One of the best experts on this subject based on the ideXlab platform.
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the Equilibrium Morphology of wc particles a combined ab initio and experimental study
Acta Materialia, 2011Co-Authors: Yang Zhong, Hong Zhu, Leon L. Shaw, Rampi RamprasadAbstract:Abstract We report an ab initio density functional theory study, complemented by parallel experimental work, of the Equilibrium shape of WC particles. The Equilibrium shape is simulated under the condition of little or no liquid-phase sintering. The effects of the carbon-rich and carbon-deficient conditions and the adsorption of Co and Ni atoms on the surface of WC particles are investigated. The Equilibrium shape of WC particles is found to be a truncated triangular prism under both carbon-rich and carbon-deficient conditions. The adsorption of Co and Ni on the WC surface can promote the formation of either truncated triangular prisms or near-hexagonal prisms, depending on their specific combination with the carbon chemical potential. Under all the conditions investigated, the Equilibrium shapes of WC crystals can be described as “bulky” rather than “plate-like”. The findings in this study are consistent with the experimental observations.
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The Equilibrium Morphology of WC particles – A combined ab initio and experimental study
Acta Materialia, 2011Co-Authors: Yang Zhong, Hong Zhu, Leon L. Shaw, Rampi RamprasadAbstract:Abstract We report an ab initio density functional theory study, complemented by parallel experimental work, of the Equilibrium shape of WC particles. The Equilibrium shape is simulated under the condition of little or no liquid-phase sintering. The effects of the carbon-rich and carbon-deficient conditions and the adsorption of Co and Ni atoms on the surface of WC particles are investigated. The Equilibrium shape of WC particles is found to be a truncated triangular prism under both carbon-rich and carbon-deficient conditions. The adsorption of Co and Ni on the WC surface can promote the formation of either truncated triangular prisms or near-hexagonal prisms, depending on their specific combination with the carbon chemical potential. Under all the conditions investigated, the Equilibrium shapes of WC crystals can be described as “bulky” rather than “plate-like”. The findings in this study are consistent with the experimental observations.