Gold surfaces for condensation heat transfer

Westwater, J. W.

doi:10.1007/bf03216737

Cited by 10 publications

(14 citation statements)

References 20 publications

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“…Alumina polishing does not produce water spreading. The values reported in Table Vindicate that the results discussed above are valid for these various surfaces also, and is in agreement with other work published for different gold surfaces (21).…”

Section: Energy Of Dispersive Interactions Of Gold Surfacessupporting

confidence: 92%

“…The wettable gold surface is clearly a metastable state under atmospheric conditions. From available experimental results, contamination by (21), and commented in the following terms: 'dropwise condensation will have commercial application as soon as the troublesome problem of how to maintain it for a long time period is solved. Gold may offer the solution or indicate how to obtain the solution'.…”

Section: Discussionmentioning

confidence: 99%

“…Some authors state that a gold surface is hydrophilic and organic contaminants change it into a hydrophobic state while others insist that wetting is observed only over oxidized surfaces. It is now well established (21,26) that wetting of gold by water may be observed. We have presented the experimental conditions that are found in the literature in Table VI; it is striking that wetting is observed shortly after quenching or etching the outer gold layer for a short period of time.…”

Section: Hydrophobicity Of Gold From Electrochemical Studiesmentioning

confidence: 98%

“…None of the usual methods used to obtain clean surfaces, free of organic contaminants, such as -heating in air at 500°C (21) -exposure to ultraviolet + ozone oxidation (5) -degassing in vacuum at 500°C (21) -heating in hydrogen (or inert gas) at 1000°C (22) -plasma etching in oxygen (21) could change the contact angle value of water on gold although these methods are effective on other metals such as stainless steel.…”

Section: Dependence Of Surface Energy On Surface Treatmentmentioning

confidence: 99%

“…Westwater (21), this hydrophobic character has been the subject of much controversy in the literature. Some authors state that a gold surface is hydrophilic and organic contaminants change it into a hydrophobic state while others insist that wetting is observed only over oxidized surfaces.…”

Section: Hydrophobicity Of Gold From Electrochemical Studiesmentioning

confidence: 99%

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Adhesion to gold: A review

Cognard¹

1984

Gold Bull

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Asulab S.A., Passage Max-meuron 6, CH-2001 Neuchatel, Switzerland The adhesion ofsubstances to gold,, and our understanding ofit, is ofpotentialindustrial importance in a number of diverse fields such as heat transfer surfaces and jewelleiy manufacture.Adhesion is a complex subject and is not fully understood as yet. This explains the many different approaches followed in the field. For instance, in physics we calculate the ideal strength (1) and from a mechanics approach the force of adherence (2), while physical chemists try to understand the molecular interactions which are responsible for the adhesion (3).In the first part of this review the more important results obtained from these approaches will be discussed. These results will relate the force of adherence to the energy of adhesion or the substrate surface tension. The middle section is devoted to surface tension on gold and the controversial matter of whether or not gold is wettable. Recent findings on gold wettability will be discussed and it will be shown that contamination by hydrocarbons is not directly related to the apparent hydrophobicity of the metal. The final part of the article discusses experimental results on the strength of adhesive joints between gold surfaces under various stresses.The review concludes with a presentation of the view that slow superficial reconstruction of gold surfaces may be an important reason for the apparent discrepancies in their behaviourwhich have been recorded.Discussion of the various approaches is of necessity somewhat mathematical. The detail has, however, been kept to a minimum and interested readers should consult the references quoted for a fuller treatment. A glossary of terms used has been compiled to assist those readers less conversant with the subject to follow the arguments presented in this article. The Physics of AdhesionIn considering adhesion from a physical point ofviewwe attempt to discover how the force (or energy) necessary to separate a solid body into two parts can be calculated, from a knowledge of the bulk and surface properties. The solutions derived give the ideal adhesion, as discussed below:The Thermodynamic Solution (Ideal Adhesion)Adamson (1) defines the ideal adhesion as `the adhesion expected under one or another model situation', and some models and theircorresponding solutionswill be considered below. The first could be called the thermodynamic approach as it considers the reversible work of adhesion. In this case the energy required to separate the two parts is equal to the energy necessary to assemble them. Breaking a SolidIn the process of breaking a solid, two new surfaces of energy ys* are created. The energy required is W.• W=2y, 1 2y, is the cohesive energy, w/ , of the solid, and is equal to the work done against the cohesive forces, F^, over the effective range of atomic distance, a, during the breaking process: W, =FF .a.A 2 Thus in this model the energy required to break the solid is equated with the cohesive energy I-Y/, and the corresponding force is 1. This cou...

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Section: Energy Of Dispersive Interactions Of Gold Surfacessupporting

confidence: 92%

Section: Discussionmentioning

confidence: 99%

Section: Hydrophobicity Of Gold From Electrochemical Studiesmentioning

confidence: 98%

Section: Dependence Of Surface Energy On Surface Treatmentmentioning

confidence: 99%

Section: Hydrophobicity Of Gold From Electrochemical Studiesmentioning

confidence: 99%

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Adhesion to gold: A review

Cognard¹

1984

Gold Bull

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Droplets on Soft Surfaces Exhibit a Reluctance to Coalesce due to an Intervening Wetting Ridge

Roy

Seiler

Weibel

et al. 2020

Adv Materials Inter

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Microscale interactions with deformable substrates are of fundamental interest for studying self‐assembly processes and the mobility of cells on soft surfaces, with applications in traction force microscopy. The behavior of microscale water droplets on a soft polymer substrate is investigated. Droplets formed by condensation on the soft substrate are reluctant to coalesce, which leads to coverage of the surface with clusters of droplets assembled in a honeycomb‐like pattern. Cryogenically fixed in this state, scanning electron microscopy of these droplets reveals the presence of an intervening wetting ridge of the polymer that acts as a barrier between neighboring droplets and prevents coalescence. A linear elastic deformation model is developed to predict this surface profile and corroborate the observed behavior.

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Electropolishing of gold

C.L.¹

1984

Gold Bull

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hydrocarbon may not be the best explanation of the two surface energy states of a gold surface. Recent studies of the surface of solids show that a gold surface may exist either with its bulk atomic properties (unreconstructed surface) or with shorter (reconstructed) atom bond lengths at the surface. This could be the reason for the apparent experimental duality which exists, with the unreconstructed surfaces behaving in a hydrophylic manner while the reconstructed surfaces show hydrophobic behaviour.

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Gold surfaces for condensation heat transfer

Cited by 10 publications

References 20 publications

Adhesion to gold: A review

Adhesion to gold: A review

Droplets on Soft Surfaces Exhibit a Reluctance to Coalesce due to an Intervening Wetting Ridge

Electropolishing of gold

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