Anisotropic character of talc surfaces as revealed by streaming potential measurements, atomic force microscopy, and molecular dynamics simulations

Book ChapterA study of the interfacial properties of the basal plane and the edge surfaces of talc is described in this paper. The isoelectric-point measured at the two different crystallographic planes by the streaming potential method was found to be similar and exists at about pH 3.0. In the case of the edge surface the zeta potential increases at higher pH values which can be attributed to the hydration of magnesium ions at the edge surface. The atomic force microscopy (AFM) colloidal probe technique was used to measure interaction forces

Anisotropic character of talc surfaces as revealed by streaming potential measurements, atomic force microscopy, molecular dynamics simulations and contact angle measurements

Journal ArticleA study of the interfacial properties of the basal plane and the edge surfaces of talc is described in this paper. The isoelectric points measured at two different crystallographic surfaces by the streaming potential method were found to be similar and exist at about pH 3.0. In the case of the edge surface, the zeta potential increases at higher pH values which can be attributed to the hydration of surface magnesium ions. The forces between the edge of a 20 urn talc particle and the two different crystallographic surfaces of talc were measured at various pH values using atomic force microscopy (AFM). These measurements show differences between the properties of the basal plane and edge of the talc. Finally, the differences in the hydration of the basal plane and the edge of talc are revealed from molecular dynamics (MD) simulations. The basal plane of talc is much less hydrated than the edge as can be seen from the water density distribution functions which correlate quite well with the contact angle measurements at the basal plane surface and the edge surface. Improved quality of the edge surface was achieved by sandblasting (erosion with alumina) and research regarding the characteristics of this edge surface is in progress

Engineering of Niobium Surfaces Through Accelerated Neutral Atom Beam Technology For Quantum Applications

A major roadblock to scalable quantum computing is phase decoherence and energy relaxation caused by qubits interacting with defect-related two-level systems (TLS). Native oxides present on the surfaces of superconducting metals used in quantum devices are acknowledged to be a source of TLS that decrease qubit coherence times. Reducing microwave loss by surface engineering (i.e., replacing uncontrolled native oxide of superconducting metals with a thin, stable surface with predictable characteristics) can be a key enabler for pushing performance forward with devices of higher quality factor. In this work, we present a novel approach to replace the native oxide of niobium (typically formed in an uncontrolled fashion when its pristine surface is exposed to air) with an engineered oxide, using a room-temperature process that leverages Accelerated Neutral Atom Beam (ANAB) technology at 300 mm wafer scale. This ANAB beam is composed of a mixture of argon and oxygen, with tunable energy per atom, which is rastered across the wafer surface. The ANAB-engineered Nb-oxide thickness was found to vary from 2 nm to 6 nm depending on ANAB process parameters. Modeling of variable-energy XPS data confirm thickness and compositional control of the Nb surface oxide by the ANAB process. These results correlate well with those from transmission electron microscopy and X-ray reflectometry. Since ANAB is broadly applicable to material surfaces, the present study indicates its promise for modification of the surfaces of superconducting quantum circuits to achieve longer coherence times.Comment: 22 pages, 7 figures, will be submitted to Superconductor Science and Technology Special Focus Issue Journa

A study of bubble-particle interaction using atomic force microscopy

Interaction between solid particles and air bubbles is central to froth flotation. Measurement of such interaction forces has only recently been possible with the invention of the atomic force microscopy (AFM). In this paper, the AFM colloidal probe technique was used to measure hydrodynamic interaction forces between a solid sphere attached to an AFM cantilever and an air bubble placed on an AFM piezoelectric stage at different approach speeds. Strong repulsive forces due to the hydrodynamic interaction were established and quantified for both hydrophobic and hydrophilic particles, and bubbles in deionised water and I mM KCl aqueous solutions. No surfactants were used. In the case of hydrophobic spheres, strong attraction between the surfaces, in addition to the repulsive hydrodynamic force, was observed, leading to the rupture of the intervening water film due to submicroscopic bubbles and the attachment of the particle to the air bubble at relatively large separation distances, which were of the order of 500-2000 nm. In the case of hydrophilic spheres, the rupture of the intervening water film and the attachment of the particle to the air bubble did not take place. An analysis of the AFM data was carried out to obtain the interaction force and relative separation distance. Theoretical hydrodynamic force calculation shows agreement with experimental data for larger separation distances. Deviations at shorter distances are related to the deformation of air-water interface due to the particle approach and surface forces. (C) 2003 Elsevier Ltd. All rights reserved

Rozdzielność sieci - szanse i nowe trendy w kanalizacji

Wywiad z Jackiem Nalaskowskim i Józefem Dziopakiem o kanalizacji, elementach systemu kanalizacyjnego oraz racjonalnej gospodarce wodnej

Preparation of spherical toner particles for atomic force microscopic studies of colloidal forces

The experimental procedure for the preparation of spherical toner particles with diameters of a few micrometers is described. This procedure involves the formulation of a toner-in-glycerol emulsion at an elevated temperature (90-100°C), solidification of dispersed toner droplets at a reduced temperature (35-45°C), and filtration of toner particles with a cellulose acetate membrane. Such prepared toner particles can be used for the determination of particle interaction forces in wastepaper deinking systems by atomic force microscopy

Attraction between hydrophobic surfaces studied by atomic force microscopy

Attraction between hydrophobic surfaces, known as the hydrophobic force, is critically important for attachment of particles to air bubbles in flotation. However, the origins and models for this attractive force between hydrophobic surfaces have been a source of debate since the first direct measurements of this force in the early 1980s. Using an atomic force microscope (AFM) we studied the attraction between an AFM hydrophobic probe and a flat hydrophobic surface in water, in water-ethanol mixtures, and in water saturated by gases with different solubility. The strong attractive force with long-range jump-in attachment positions decreases with an increase in the ethanol content and disappears in pure ethanol. The size of steps on the force curves depends on the gas solubility. However, the measured forces do not depend on the gas solubility significantly. The influence of surface roughness and heterogeneity appear to be significant. Experimental results indicate the role of surface stabilized submicron-sized bubbles in the hydrophobic attraction. This is in line with recent direct and indirect evidences for the presence of gaseous bubbles at hydrophobic surfaces as well as with the early insights of flotation scientists. (C) 2003 Elsevier B.V. All rights reserved

Hydrodynamic interaction between an air bubble and a particle: atomic force microscopy measurements

Study of interaction forces between solid particles and air bubbles is a key to understanding a range of technologically important phenomena, including the flotation separation of particles. Measurement of such interaction forces has only recently been made possible with the introduction of the atomic force microscopy (AFM). In this paper, the AFM probe technique was used to measure hydrodynamic interaction forces between a solid sphere attached to an AFM cantilever and an air bubble placed on an AFM piezoelectric stage at different approach speeds. Interaction forces before the interfacial water film rupture, as well as hydrophobicity of the particle can be established. In the case of hydrophobic spheres, strong attraction between the surfaces, leading to the rupture of the intervening water film and the attachment of the particle to the air bubble was observed. In the case of hydrophilic spheres, the rupture of the intervening water film and the attachment of the particle to the air bubble did not take place. Strong repulsive forces due to the hydrodynamic interaction are quantified. Theoretical hydrodynamic force shows agreement with experimental data for larger separation distances. Deviations at shorter distances are related to the deformation of air-water interface due to the particle approach, as well as intermolecular and surface forces. (C) 2003 Elsevier Inc. All rights reserved