Sample records for FUERZAS DE VAN DER WAALS (van der waals forces)
from WorldWideScience.org

Sample records 1 - 16 shown.



1

FUERZAS DE SUPERFICIE Y ADHESIÓN EN SISTEMAS CELULÓSICOS: NUEVA FORMA DE EVALUAR FIJACIÓN/DISPERSIÓN DE RESINA EN LA FABRICACIÓN DE PAPEL/CELULOSA/ SURFACE FORCES AND ADHESION IN CELLULOSE SYSTEMS: NEW WAY TO EVALUATE RESIN FIXATION/DISPERSION IN THE MANUFACTURE OF PAPER/CELLULOSE

Acuña, Sergio M; Toledo, Pedro G
2010-01-01

Resumen en español Las fuerzas superficiales entre partículas coloidales de resina y fibra dominan el comportamiento y las propiedades finales de papel y celulosa. Aquí se describe el uso de Microscopía de Fuerza Atómica (AFM) para medir directamente las fuerzas de interacción entre la superficie de un substrato plano "funcionalizado" con resina de madera y la superficie de una microesfera de vidrio en soluciones de electrolito a pH controlado y a temperatura ambiente. El substrato con (mas) vertido en hidrofílico es una hoja de poliestireno recubierta con una película ultra fina de resina natural. La carga superficial del substrato "funcionalizado" imita la de las micelas de resina, la microestructura preferida de la resina en agua, y la carga sobre la microesfera imita la de las fibras de madera. Las curvas de fuerza AFM son interpretadas a la luz del balance entre fuerzas atractivas -van der Waals- y repulsivas -electrostáticas- de la teoría continua clásica DLVO de fuerzas para sistemas coloidales. Las medidas muestran una fuerte y persistente repulsión de muy corto rango, a distancias de separación menores a 100 Å que no puede ser explicada por la teoría DLVO. Estas fuerzas repulsivas que actúan como barreras al contacto o a la coagulación tienen su origen en capas de agua altamente ordenadas en la vecindad de las superficies eléctricamente cargadas. El tamaño e intensidad de la barrera dependen de la magnitud y densidad de la carga eléctrica en las superficies que interactúan, que a su vez dependen de sus composiciones químicas y del medio acuoso. La repulsión aumenta con el pH y disminuye con la concentración y tamaño del electrolito. Fuerzas AFM de alejamiento entre substrato y microesfera, después de ocurrido el contacto, revelan una correlación aparentemente no reportada antes entre concentración de electrolito y adhesión. La adhesión aumenta con la concentración y tamaño del electrolito. Fenómenos complejos como dusting, desprendimiento de resina durante el uso del papel, pueden ser controlados mediante regulación del ambiente fluido durante el proceso de fabricación Resumen en inglés Surface and adhesive forces between colloidal wood particles of resin and fiber dominate the behavior and final properties of paper and cellulose. This paper describes the use of Atomic Force Microscopy (AFM) to measure the interaction force between a resin "functionalized" substrate and a glass microsphere in aqueous pH-controlled electrolyte solutions at ambient temperature. The water-wet made substrate is a hydrophobic polystyrene film coated with an extremely thin fil (mas) m of wood fatty and resin acids. The surface charge on the "functionalized" substrate mimics that on resin micelles, the preferred microstructure of resin in water, and the charge on the microsphere mimics that on wood fibers. AFM force curves are analyzed to the light of the balance between attractive forces -van derWaals- and repulsive forces -electrostatic- from the classical continuum DLVO theory of colloidal forces. Force measurements show strong and persistent short-range repulsive forces at distances less than 100 Å which are not explained by the DLVO theory. These repulsive forces that act as barriers to contact or coagulation originate on highly ordered water in the neighborhood of the charged surfaces. The barrier size and intensity depend on the magnitude and density of the electrical charges on the interacting surfaces, which in turn depends on their chemical composition, and on the aqueous media. Repulsion increases with pH and decreases with electrolyte concentration. AFM flat-microsphere pull-off forces reveal an apparently unreported correlation between electrolyte concentration and adhesion. Adhesion increases with electrolyte concentration and size. Complex phenomena such as dusting, the release of resin upon paper use due to poor resin-fiber bondage, can thus be controlled by regulating the aqueous media during papermaking

Scientific Electronic Library Online (Spanish)

2

Strong covalent bonding between two graphene layers

Andrés Rodríguez, Pedro Luis de; Ramírez, Rafael; Vergés, José A.
2008-01-14

Digital.CSIC (Spain)

3

Magnetic dipolar ordering and relaxation in the high-spin molecular cluster compound Mn6

Morello, A.; Mettes, F. L.; Bakharev, O. N.; Brom, H. B.; Jongh, L. J. de; Luis, F.; Fernández, Julio F.; Aromí, G.
2006-04-01

Digital.CSIC (Spain)

4

Interaction forces between particles stabilized by a hydrophobically modified inulin surfactant

Nestor, Jérémie; Esquena, Jordi; Solans, Conxita; Luckham, Paul F.; Musoke, Michael; Levecke, Bart; Booten, Karl; Tadros, Tharwat F.
2007-03-15

Digital.CSIC (Spain)

5

Interaction forces between particles stabilized by a hydrophobically modified inulin surfactant

Nestor, Jérémie; Esquena, Jordi; Solans, Conxita; Luckham, Paul F.; Musoke, Michael; Levecke, Bart; Booten, Karl; Tadros, Tharwat F.
2007-07-15

Digital.CSIC (Spain)

7

Estructura cristalina del N-isopropil-2-ciano-3(5'-nitrofuril)acrilamida/ Crystal structure of N-isopropyl-2-cyano-3(5'-nitrofuryl)acrylamide

Pomés Hernandéz, Ramón; Duque Rodrigues, Julio; Novoa de Armas, Héctor; Toscano, Ruben Alfredo
1997-12-01

Resumen en inglés C11H11N3O4 , Mr = 249.23, triclinic, , a = 5.453(1), b = 22.873(5), c = 4.893(1) Å, a = 94.47(3), b = 96.36(3), g = 86.27(3)º, V = 603.7(8)ų,Z = 2, Dx = 1.371 Mg/m-3,l(Cu Ka1) = 1.54178Å, m = 0.86mm-1, room temperature. The crystal structure of N-isopropyl-2-cyano-3(5'-nitrofuryl) - acrylamide has been determined by Direct Methods and refined to R = 0.086 for 797 observed reflections. The molecules in the crystal are packed at normal van der Waals forces and by an hydrogen bond between N1-H1...02i (N1...02i: 2.910(1)Å), with i=x,y,z+1).

Scientific Electronic Library Online (Spanish)

8

Cluster-surface and cluster-cluster interactions: ab initio calculations and modelling of Van der Waals forces

Botti, Silvana; Castro, Alberto; Andrade, Xavier; Rubio Secades, Ángel; Marques, Miguel A. L.

10 pages, 7 figures.-- PACS nrs.: 34.35.+a, 34.20.Gj, 31.15.ee.-- ArXiv pre-print available at: http://arxiv.org/abs/0806.2946 | We present fully ab initio calculations of van der Waals coefficients for two different situations: (i) the interaction between hydrogenated silicon clusters and (ii) the ...

DRIVER (Spanish)

9

Cluster-surface and cluster-cluster interactions: ab initio calculations and modelling of Van der Waals forces

Botti, Silvana; Castro, Alberto; Andrade, Xavier; Rubio Secades, Ángel; Marques, Miguel A. L.
2008-07-29

Digital.CSIC (Spain)

10

An inversion technique for the calculation of embedding potentials

Roncero, Octavio; Lara Castells, M. Pilar de; Villarreal, Pablo; Flores, F.; Ortega, J.; Paniagua, Miguel

12 pages, 9 figures.-- PACS nrs.: 31.15.eg; 33.15.Bh; 31.15.xr; 31.15.vn; 31.50.Df; 34.20.Cf. | A new embedding method to include local correlation in large systems is proposed. In this method the density of the whole system, calculated via density functional theory approaches, is partitioned in two...

DRIVER (Spanish)

11

An inversion technique for the calculation of embedding potentials

Roncero, Octavio; Lara Castells, M. Pilar de; Villarreal, Pablo; Flores, F.; Ortega, J.; Paniagua, Miguel; Aguado, Alfredo
2008-11-10

Digital.CSIC (Spain)

12

Accurate ab initio intermolecular potential energy surface for the quintet state of the O2(3Σ(-)(g))-O2((3)Σ(-)(g)) dimer

Bartolomei, Massimiliano; Carmona-Novillo, Estela; Hernández, Marta I.; Campos-Martínez, José; Hernández-Lamoneda, Ramón

10 pages, 5 figures, 3 tables.-- PACS nrs.: 31.15.bw; 34.20.Gj; 33.15.Bh; 33.20.Tp; 31.50.-x; 31.15.A-. | A new potential energy surface (PES) for the quintet state of rigid O2(3Σ(-)(g))+O2((3)Σ(-)(g)) has been obtained using restricted coupled-cluster theory with singles, doubles, and perturbative ...

DRIVER (Spanish)

13

Accurate ab initio intermolecular potential energy surface for the quintet state of the O2(3Σ(-)(g))-O2((3)Σ(-)(g)) dimer

Bartolomei, Massimiliano; Carmona-Novillo, Estela; Hernández, Marta I.; Campos-Martínez, José; Hernández-Lamoneda, Ramón
2008-06-03

Digital.CSIC (Spain)

14

Ab initio potential-energy surface for the reaction Ca+HCl --> CaCl+H

Verbockhaven, Gilles; Sanz, Cristina; Groenenboom, Gerrit C.; Roncero, Octavio; Avoird, Ad van der

12 pages, 9 figures, 7 tables.-- PACS nrs.: 31.15.Ar; 82.20.Kh; 33.15.Bh; 34.20.Gj; 31.15.Dv; 33.20.Ea; 33.20.Vq. | The potential-energy surface of the ground electronic state of CaHCl has been obtained from 6400 ab initio points calculated at the multireference configuration-interaction level and r...

DRIVER (Spanish)

15

Ab initio potential-energy surface for the reaction Ca+HCl --> CaCl+H

Verbockhaven, Gilles; Sanz, Cristina; Groenenboom, Gerrit C.; Roncero, Octavio; Avoird, Ad van der
2005-05-23

Digital.CSIC (Spain)

16

Ab initio calculations, potential representation and vibrational dynamics of He2Br2 van der Waals complex

Valdés, Álvaro; Prosmiti, Rita; Villarreal, Pablo; Delgado Barrio, Gerardo
2005-01-05

Digital.CSIC (Spain)