Download or read book Fabrication and Robustness Testing of Superhydrophobic Nanostructured Surfaces for Enhanced Jumping Condensation written by Jean Hope Sack and published by . This book was released on 2015 with total page 58 pages. Available in PDF, EPUB and Kindle. Book excerpt: Increasing worldwide and domestic demands for power and clean water will require advanced heat transfer materials. Superhydrophobic micro- and nano-structured surfaces which promote a jumping droplet mode of condensation have been shown to enhance heat transfer over conventional film wise condensation surfaces, but limited robustness testing has been reported validating feasibility of industrial implementation. This thesis seeks to quantify the robustness of a variety of nanostructures, substrates and coatings by analyzing contact angle measurements and SEM imaging over the course of accelerated robustness testing. This testing was enabled through the design and construction of three custom-built setups intended to accelerate the onset of failure mechanisms. These setups consist of a flow setup to observe resistance to shear flows from internal condensation steam flow, a droplet impingement setup to test mechanical durability, and an elevated temperature condensation chamber to characterize thermal stability. Methods for fabricating nanostructures were also developed, and scalable zinc oxide nanowires (ZnO) and copper oxide nanoblades (CuO) were used. CuO nanoblades were etched into copper, and ZnO nanowires were grown on silicon, low carbon steel, titanium, stainless steel, and electroplated nickel. Hydrophobic coatings tested on these surfaces included stearic acid and two polymer coatings: P2i (40nm) and Semblant. Observed failure mechanisms were coating degradation and poor nanostructure adhesion. Nanostrucure adhesion issues were observed as delamination of ZnO nanowires primarily on stainless steel substrates. Adhesion was improved through the addition of an electroplated nickel layer before nanowire growth, but delamination was still observed. This is likely the result a large mismatch in coefficient of thermal expansion between the ZnO nanowires and the substrate. The etched CuO nanostructures with a fluorinated polymer coating (P2i) showed very little change in performance throughout robustness testing. Characterization methods included contact angle measurements to monitor surface uniformity and durability, and scanning electron microscope (SEM) imaging to observe nanostructure degradation and delamination. Preliminary work was also done to functionalize the inside of tubes and design a dedicated test setup to characterize heat transfer measurements for internal jumping condensation. This setup will allow for extended robustness testing over a range of temperatures, pressures, and geometries, and give baseline heat flux values for comparison with dropwise or filmwise internal condensation. While ZnO nanowires still require additional testing and development, CuO nanoblades are good candidates for internal heat transfer measurements and scaled up robustness testing. Assuming this characterization confirms the expected benefits of jumping condensation from increased droplet removal and nucleation density, this technology has the potential to significantly improve power plant efficiency and output worldwide.

Download or read book Design and Fabrication of an Internal Condensation Loop for Effectiveness and Robustness Testing of Nanostructured Superhydrophobic Steam Condenser written by Dhananjai V. Saranadhi and published by . This book was released on 2014 with total page 47 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Rankine cycle is at the heart of steam-electric power stations, which are responsible for generating about 90% of the world's electricity. Improving the efficiency of the cycle thus of great importance, and the greatest possible gain lies in improving the condensation process. Industrial condensers feature once-through water cooling, and the substantial amount of water they consume coupled with the increasing scarcity of freshwater supplies provides further motivation to focus on the condensation process. Condensation in these systems occurs predominantly via the filmwise mechanism, in which a thin film of water forms upon the condensing surface, adversely affecting its heat transfer abilities. However, forming a nanostructure and adding certain hydrophobic coatings on the heat exchanging surface of the condenser can render them superhydrophobic. This causes condensation to instead occur via the jumping droplet mechanism, which promises drastically improved heat exchanging performance. This thesis discusses the design and fabrication of an internal condensation loop which will allow us to test the heat transfer, fluid dynamic performance of the novel jumping droplet internal mode, and the durability and robustness of various hydrophobic coatings at the lab scale.

Download or read book Development and Characterization of Micro nano Structured Surfaces for Enhanced Condensation written by Nenad Miljkovic and published by . This book was released on 2013 with total page 185 pages. Available in PDF, EPUB and Kindle. Book excerpt: Micro/nanostructures have long been recognized to have potential for heat transfer enhancement in phase-change processes by achieving extreme wetting properties, which is of great importance in a wide range of applications including thermal management, building environment control, water harvesting, desalination, and industrial power generation. This thesis focuses on the fundamental understanding of water vapor condensation on superhydrophobic surfaces, as well as the demonstration of such surfaces for enhanced condensation heat transfer performance. We first studied droplet-surface interactions during condensation on superhydrophobic surfaces to understand the emergent droplet wetting morphology. We demonstrated the importance of considering local energy barriers to understand the condensed droplet morphologies and showed nucleation-mediated droplet-droplet interactions can overcome these barriers to develop wetting states not predicted by global thermodynamic analysis. To minimize these droplet-droplet interactions and ensure the formation of favorable morphologies for enhanced condensation heat transfer, we show that the structure length scale needs to be minimized while ensuring the local energy barriers satisfy the morphology dependent criteria. This mechanistic understanding offers insight into the role of surface-structure length scale and provides a quantitative basis for designing surfaces optimized for condensation in engineered systems. Using our understanding of emergent droplet wetting morphology, we experimentally and numerically investigated the morphology dependent individual droplet growth rates. By taking advantage of well-controlled functionalized silicon nanopillars, the growth and shedding behavior of both suspended and partially wetting droplets on the same surface during condensation was observed. Environmental scanning electron microscopy was used to demonstrate that initial droplet growth rates of partially wetting droplets were 6 times larger than that of suspended droplets. A droplet growth model was developed to explain the experimental results and showed that partially wetting droplets had 4-6 times higher heat transfer rates than that of suspended droplets. Based on these findings, the overall performance enhancement created by surface nanostructuring was examined in comparison to a flat hydrophobic surface. These nanostructured surfaces had 56% heat flux enhancement for partially wetting droplet morphologies, and 71% heat flux degradation for suspended morphologies in comparison to flat hydrophobic surfaces. This study provides fundamental insights into the previously unidentified role of droplet wetting morphology on growth rate, as well as the need to design nanostructured surfaces with tailored droplet morphologies to achieve enhanced heat and mass transfer during dropwise condensation. To create a unified model for condensation capable of predicting the surface heat transfer for a variety of surface length scales, geometries, and condensation conditions, we incorporated the emergent droplet wetting morphology, individual droplet heat transfer, and size distribution. The model results showed a specific range of characteristic length scales (0.5 - 2 ptm) allowing for the formation of coalescence-induced jumping droplets with a 190% overall surface heat flux enhancement over conventional flat dropwise condensing surfaces. This work provided a unified model for dropwise condensation on micro/nanostructured superhydrophobic surfaces and offered guidelines for the selection of ideal structured surfaces to maximize heat transfer. Using the insights gained from the developed model and optimization, a scalable synthesis technique was developed to produce functionalized oxide nanostructures on copper surfaces capable of sustaining superhydrophobic condensation. Nanostructured copper oxide (CuO) films were formed via chemical oxidation in an alkaline solution resulting in dense arrays of sharp CuO nanostructures with characteristic heights and widths of -1 pm and -300 nm, respectively. Condensation on these surfaces was characterized using optical microscopy and environmental scanning electron microscopy to quantify the distribution of nucleation sites and elucidate the growth behavior of individual droplets with characteristic radii of -1 to 10 pm at supersaturations

Download or read book Characterization of the Robustness of Superhydrophobic Surfaces During Condensation written by Emmanuel E. Simpri and published by . This book was released on 2016 with total page 30 pages. Available in PDF, EPUB and Kindle. Book excerpt: Condensation is a process utilized by about 85% of power plants in their power generation cycles. Superhydrophobic surfaces can potentially improve the heat transfer due to condensation when compared to the untreated surfaces typically used in condensers. This can improve the efficiency of power plants by up to 3%. These surfaces are made by combining nanoscale roughness with chemical hydrophobicity, and can promote the mode of condensation that has the least resistance to heat transfer. However, it is unclear how long these surfaces will last under industrial conditions. This thesis is focused on testing the robustness of the surfaces in multiple experiments and analyzing the data gathered from these experiments, along with theorizing the mechanism behind any surface functionality deterioration that may be seen. Hydrophobic and superhydrophobic surface samples that have been prepared previously were subjected to water immersion and continuous condensation tests. For the water immersion tests, samples were submerged in water under neutral (pH = 7) and basic (pH = 10) conditions at room (~25°C) and elevated (~50°C) temperatures. The continuous condensations tests were run at a steam temperature of 27°C as well as 100°C. To understand the change in surface properties over the duration of the tests, the surface contact angle was chosen as the metric to be measured. The contact angles of water droplets on the samples were taken beforehand and throughout the tests using a micro-goniometer in order to quantify the change in surface functionality. The data gathered from these experiments were processed in Matlab to produce plots of the change in contact angle over the duration of each test. These plots showed significant contact angle decreases for the hydrophobic surfaces but little change in the contact angle for the superhydrophobic surfaces. This suggests that the addition of nanostructures on the surface, and thus the promotion of super- hydrophobicity, inhibits the surface functionality deterioration mechanism that is seen with the hydrophobic surfaces.

Download or read book Condensation and Wetting Dynamics on Micro Nano Structured Surfaces written by Emre Olceroglu and published by . This book was released on 2017 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: Because of their adjustable wetting characteristics, micro/nanostructured surfaces are attractive for the enhancement of phase-change heat transfer where liquid-solid-vapor interactions are important. Condensation, evaporation, and boiling processes are traditionally used in a variety of applications including water harvesting, desalination, industrial power generation, HVAC, and thermal management systems. Although they have been studied by numerous researchers, there is currently a lack of understanding of the underlying mechanisms by which structured surfaces improve heat transfer during phase-change. This PhD dissertation focuses on condensation onto engineered surfaces including fabrication aspect, the physics of phase-change, and the operational limitations of engineered surfaces. While superhydrophobic condensation has been shown to produce high heat transfer rates, several critical issues remain in the field. These include surface manufacturability, heat transfer coefficient measurement limitations at low heat fluxes, failure due to surface flooding at high supersaturations, insufficient modeling of droplet growth rates, and the inherent issues associated with maintenance of non-wetted surface structures. Each of these issues is investigated in this thesis, leading to several contributions to the field of condensation on engineered surfaces. A variety of engineered surfaces have been fabricated and characterized, including nanostructured and hierarchically-structured superhydrophobic surfaces. The Tobacco mosaic virus (TMV) is used here as a biological template for the fabrication of nickel nanostructures, which are subsequently functionalized to achieve superhydrophobicity. This technique is simple and sustainable, and requires no applied heat or external power, thus making it easily extendable to a variety of common heat transfer materials and complex geometries. To measure heat transfer rates during superhydrophobic condensation in the presence of non-condensable gases (NCGs), a novel characterization technique has been developed based on image tracking of droplet growth rates. The full-field dynamic characterization of superhydrophobic surfaces during condensation has been achieved using high-speed microscopy coupled with image-processing algorithms. This method is able to resolve heat fluxes as low as 20 W/m2 and heat transfer coefficients of up to 1000 kW/m2, across an array of 1000's of microscale droplets simultaneously. Nanostructured surfaces with mixed wettability have been used to demonstrate delayed flooding during superhydrophobic condensation. These surfaces have been optimized and characterized using optical and electron microscopy, leading to the observation of self-organizing microscale droplets. The self-organization of small droplets effectively delays the onset of surface flooding, allowing the superhydrophobic surfaces to operate at higher supersaturations. Additionally, hierarchical surfaces have been fabricated and characterized showing enhanced droplet growth rates as compared to existing models. This enhancement has been shown to be derived from the presence of small feeder droplets nucleating within the microscale unit cells of the hierarchical surfaces. Based on the experimental observations, a mechanistic model for growth rates has been developed for superhydrophobic hierarchical surfaces. While superhydrophobic surfaces exhibit high heat transfer rates they are inherently unstable due to the necessity to maintain a non-wetted state in a condensing environment. As an alternative condensation surface, a novel design is introduced here using ambiphilic structures to promote the formation of a thin continuous liquid film across the surface which can still provide the benefits of superhydrophobic condensation. Preliminary results show that the ambiphilic structures restrain the film thickness, thus maintaining a low thermal resistance while simultaneously maximizing the liquid-vapor interface available for condensation.

Download or read book Bioinspired Structures and Design written by Wole Soboyejo and published by Cambridge University Press. This book was released on 2020-09-17 with total page 374 pages. Available in PDF, EPUB and Kindle. Book excerpt: Master simple to advanced biomaterials and structures with this essential text. Featuring topics ranging from bionanoengineered materials to bio-inspired structures for spacecraft and bio-inspired robots, and covering issues such as motility, sensing, control and morphology, this highly illustrated text walks the reader through key scientific and practical engineering principles, discussing properties, applications and design. Presenting case studies for the design of materials and structures at the nano, micro, meso and macro-scales, and written by some of the leading experts on the subject, this is the ideal introduction to this emerging field for students in engineering and science as well as researchers.

Download or read book Ice Adhesion written by K. L. Mittal and published by John Wiley & Sons. This book was released on 2020-12-15 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt: This unique book presents ways to mitigate the disastrous effects of snow/ice accumulation and discusses the mechanisms of new coatings deicing technologies. The strategies currently used to combat ice accumulation problems involve chemical, mechanical or electrical approaches. These are expensive and labor intensive, and the use of chemicals raises serious environmental concerns. The availability of truly icephobic surfaces or coatings will be a big boon in preventing the devastating effects of ice accumulation. Currently, there is tremendous interest in harnessing nanotechnology in rendering surfaces icephobic or in devising icephobic surface materials and coatings, and all signals indicate that such interest will continue unabated in the future. As the key issue regarding icephobic materials or coatings is their durability, much effort is being spent in developing surface materials or coatings which can be effective over a long period. With the tremendous activity in this arena, there is strong hope that in the not too distant future, durable surface materials or coatings will come to fruition. This book contains 20 chapters by subject matter experts and is divided into three parts— Part 1: Fundamentals of Ice Formation and Characterization; Part 2: Ice Adhesion and Its Measurement; and Part 3: Methods to Mitigate Ice Adhesion. The topics covered include: factors influencing the formation, adhesion and friction of ice; ice nucleation on solid surfaces; physics of ice nucleation and growth on a surface; condensation frosting; defrosting properties of structured surfaces; relationship between surface free energy and ice adhesion to surfaces; metrology of ice adhesion; test methods for quantifying ice adhesion strength to surfaces; interlaboratory studies of ice adhesion strength; mechanisms of surface icing and deicing technologies; icephobicities of superhydrophobic surfaces; anti-icing using microstructured surfaces; icephobic surfaces: features and challenges; bio-inspired anti-icing surface materials; durability of anti-icing coatings; durability of icephobic coatings; bio-inspired icephobic coatings; protection from ice accretion on aircraft; and numerical modeling and its application to inflight icing.

Download or read book Fabrication of Surface Micro and Nanostructures for Superhydrophobic Surfaces in Electric and Electronic Applications written by Yonghao Xiu and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In our study, the superhydrophobic surface based on biomimetic lotus leave is explored to maintain the desired properties for self-cleaning. In controlling bead-up and roll-off characteristics of water droplets the contact angle and contact angle hysteresis were very important and we investigated the determining conditions on different model surfaces with micro- and nanostructures. Two governing equations were proposed, one for contact angle based on Laplace pressure and one for contact angle hysteresis based on Young-Dupré equation. Based on these understanding on superhydrophobicity, possible applications of the superhydrophobicity for self-cleaning and water repellency were explored and application related technical issues were addressed. Based on our understanding of the roughness effect on superhydrophobicity (both contact angle and hysteresis), structured surfaces from polybutadiene, polyurethane, silica, and Si etc were successfully prepared. For engineering applications of superhydrophobic surfaces, stability issues regarding UV, mechanical robustness and humid environment need to be investigated. Among these factors, UV stability is the first one to be studied. Silica surfaces with excellent UV stability were prepared. UV stability on the surface currently is 5,500 h according the standard test method of ASTM D 4329. No degradation on surface superhydrophobicity was observed. New methods for preparing superhydrophobic and transparent silica surfaces were investigated using urea-choline chloride eutectic liquid to generate fine roughness and reduce the cost for preparation of surface structures.

Download or read book Wetting and Phase change Phenomena on Micro nanostructures for Enhanced Heat Transfer written by Rong Xiao (Ph. D.) and published by . This book was released on 2013 with total page 76 pages. Available in PDF, EPUB and Kindle. Book excerpt: Micro/nanostructures have been extensively studied to amplify the intrinsic wettability of materials to create superhydrophilic or superhydrophobic surfaces. Such extreme wetting properties can influence the heat transfer performance during phase-change which is of great importance in a wide range of applications including thermal management, building environment, water harvesting and power production. In particular, superhydrophilic surfaces have been of interest to achieve thin film evaporation with high heat fluxes. Meanwhile, superhydrophobic surfaces with dropwise condensation promises higher heat transfer coefficients than typical filmwise condensation. My thesis work aims at improving fundamental understanding as well as demonstrating practical enhancements in these two areas. A key challenge to realizing thin film evaporation is the ability to achieve efficient fluid transport using superhydrophilic surfaces. Accordingly, we developed a semi-analytical model based on the balance between capillary pressure and viscous resistance to predict the propagation rates in micropillar arrays with high aspect ratios. Our experimental results showed good agreement with the model, and design guidelines for optimal propagation rates were proposed. For micropillar arrays with low aspect ratio and large spacing between pillars, however, we identified that the microscopic sweeping of the liquid front becomes important. We studied this phenomenon, explained the effect of such microscale dynamics on the overall propagation behavior, and proposed a strategy to account for these dynamics. While these propagation studies provide a means to deliver liquid to high heat flux regions, we investigated a different configuration using nanoporous membrane that decouples capillarity from the viscous resistance to demonstrate the potential heat dissipation capability. With nanoporous membranes with average pore diameters of 150 nm and thicknesses of 50 [mu]m, we achieved interfacial heat fluxes as high as 96 W/cm2 via evaporation with isopropyl alcohol. The effect of membrane thickness was studied to offer designs that promise dissipation of 1000 W/cm 2 . Meanwhile, we developed new metrology to measure transient heat transfer coefficients with a temporal resolution of 0.2 seconds during the evaporation process. Such a technique offers insight into the relationship between liquid morphology and heat transfer behavior. Finally, for enhanced condensation, we demonstrated immersion condensation using a composite surface fabricated by infusing hydrophobic oil into micro/nanostructures with a heterogeneous coating. With this approach, three key attributes to maximize heat transfer coefficient, low departure radii, low contact angle, and high nucleation density, were achieved simultaneously. We specifically elucidated the mechanism for the increase in nucleation density and attribute it to the combined effect of reduced water-oil interfacial energy and local high surface energy sites. As a result, we demonstrated approximately 100% enhancement in heat transfer coefficient over state-of-the-art superhydrophobic surfaces with the presence of non-condensable gases. This thesis presents improved fundamental understanding of wetting, evaporation, and condensation processes on micro/nanostructures as well as practical implementation of these structures for enhanced heat transfer. The insights gained demonstrate the potential of new nanostructure engineering approaches to improve the performance of various thermal management and energy production applications.

Download or read book Superhydrophobic Silicone based Nanocomposites for Application to High Voltage Insulator written by Elham Vazirinasab and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Wettability is one of the fundamental characterizations of each solid surface which might affect the final surface properties in different manners. In the light of various Mother Nature's masterpieces, specifically Lotus leaves, as a symbol of purity, the nature-inspired superhydrophobic surfaces have received immense attention. In the present thesis, two different approaches are opted to effectively create artificial self-cleaning/superhydrophobic surfaces to enhance the water-repellency of the engineered silicone rubber and Teflon materials. Firstly, the atmospheric-pressure plasma treatment was used to produce self-cleaning/superhydrophobic high-temperature vulcanized silicone rubber (HTV-SR) surfaces via etching technique. This approach is significant since the use of an atmospheric-pressure plasma system as a simple, fast and environmentally friendly technique is combined with compressed air as an eco-friendly plasma gas which offers great potential for the mass production of superhydrophobic surfaces in an industrial scale. Using plasma treatment, a substantial enhancement in the water-repellency of HTV-SR surfaces, i.e., static water contact angle (WCA) >160° and a contact angle hysteresis (CAH) 3°, was attained due to the formation of coral-like micro-nanostructures on the surface. Possessing the appropriate surface structures depends highly on the composition of plasma jet affected by plasma operating parameters. Thus, the role of significant plasma operating parameters on the surface water-repellency was assessed with the help of a design of experiment (DoE) method to determine the near-optimal operating parameters. The icephobic properties are divided into two categories of anti-icing and de-icing properties. Anti-icing properties correspond to the delay in the ice formation, while de-icing properties illustrate the reduction of the adhesion strength of the ice formed on the surface. The well-known ice adhesion measurement techniques, i.e., the centrifuge adhesion and push-off tests, were used to provide quantitative comparisons of the ice adhesion strength of the produced surfaces. The delayed ice formation and considerable low ice adhesion strength of the plasma-treated superhydrophobic HTV-SR surface confirmed their desirable icephobicity. However, the robustness of the superhydrophobic surfaces can be considered as the Achilles heel toward industrialization and real-life applications. To ensure long-lasting superhydrophobic properties, the mechanical durability and chemical stability of the produced superhydrophobic surface were rigorously evaluated. Although the produced surface preserved its water-repellent properties in multiple tests, under some harsh mechanical damages, the superhydrophobic properties were reduced. Secondly, regarding the poor mechanochemical robustness of superhydrophobic surfaces susceptible to damage, a non-fluorinated volumetric superhydrophobic nanocomposite was produced through embedding diatomaceous earth and fumed silica particles into the HTV-SR matrix. The volumetric superhydrophobic nanocomposite is a new concept in fabrication of damage-tolerant superhydrophobic surfaces where each face and every layer of the nanocomposites is superhydrophobic. Given the importance of the diatomaceous earth/fumed silica mass ratio in final surface structure and crosslinking density of the nanocomposite, an in-depth assessment of the water-repellency, crosslinking density, and hardness of the produced nanocomposites was accomplished as a function of various diatomaceous earth to fumed silica mass ratios. Regarding the surface robustness, multiple severe mechanical and chemical tests were conducted including sandpaper and knife scratching, tape peeling, water jet impact, and sandblasting after which the surface retained its initial water-repellency. Moreover, even if during mechanical and/or chemical damages, the superhydrophobicity of the nanocomposite was deteriorated, the water-repellency could be restored by removing the outermost layer. It was due to the presence of embedded low surface energy micro-nanostructures within the entire body of the nanocomposite. Thirdly, to scrutinize the potential application of plasma treatment approach to various polymers, a thermoplastic insulating material, i.e., polytetrafluoroethylene (PTFE) commercially known as Teflon, was selected to fabricate superhydrophobic surfaces. The produced superhydrophobic Teflon surfaces possessed ultra-water-repellency, icephobicity, and self-cleaning. Although the plasma treatment did not alter the chemical composition of the Teflon surface, the lotus leaf-like hierarchical micro-nanostructures created on the plasma-treated surface were responsible for its surface water-repellency. Both water droplet rolling off and impact test ascertained the significant role of the hierarchical micro-nanostructures on the surface water-repellency as well as the consistency of Cassie-Baxter regime. In addition to the self-cleaning properties, the micro-nanostructured Teflon surface substantially reduced the ice adhesion strength to a content that the produced surface could be categorized as a passive anti-icing surface. Moreover, the onset of freezing of a water droplet was reduced on the superhydrophobic surface due to the presence of air pockets trapped within its surface asperities. The approaches introduced in this thesis can be implemented in different industries as they are cost-effective, quickly adaptable, and environmentally friendly methods. La mouillabilité est l'une des caractéristiques fondamentales de chaque surface solide qui peut affecter de différentes manières les propriétés finales de surface. À la lumière de divers chefs-d'oeuvre de Mère Nature, particulièrement les feuilles de lotus, en tant que symbole de pureté, les surfaces superhydrophobes inspirées de la nature ont reçu une immense attention. Dans la présente thèse, deux approches distinctes sont choisies pour créer efficacement des surfaces autonettoyantes / superhydrophobes. Ces surfaces possèdent une excellente hydrofugation pour améliorer la durée de vie de différents matériaux d'ingénierie tels que le caoutchouc de silicone et le Teflon. Dans un premier temps, le traitement au plasma à pression atmosphérique a été utilisé pour produire des surfaces autonettoyantes / superhydrophobes de caoutchouc de silicone vulcanisé à haute température (HTV-SR) via une technique de gravure. Cette approche est importante car l'utilisation d'un système plasma à pression atmosphérique est une technique simple, rapide et respectueuse de l'environnement. Ainsi utilisé l'air comprimé en tant que gaz écologique à plasma, cette technique offre un grand potentiel pour la production des surfaces superhydrophobes à grande échelle. Grâce au traitement au plasma, une amélioration substantielle de l'hydrofugation des surfaces HTV-SR (c'est-à-dire un angle de contact statique avec l'eau (WCA) 160° et une hystérésis d'angle de contact (CAH)

Download or read book Surfaces and Interfaces of Biomimetic Superhydrophobic Materials written by Zhiguang Guo and published by John Wiley & Sons. This book was released on 2017-10-10 with total page 401 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive and systematic treatment that focuses on surfaces and interfaces phenomena inhabited in biomimetic superhydrophobic materials, offering new fundamentals and novel insights. As such, this new book covers the natural surfaces, fundamentals, fabrication methods and exciting applications of superhydrophobic materials, with particular attention paid to the smart surfaces that can show switchable and reversible water wettability under external stimuli, such as pH, temperature, light, solvents, and electric fields. It also includes recent theoretical advances of superhydrophobic surfaces with regard to the wetting process, and some promising breakthroughs to promote this theory. As a result, materials scientists, physicists, physical chemists, chemical engineers, and biochemists will benefit greatly from a deeper understanding of this topic.

Download or read book Superhydrophobic Surfaces written by Mehdi Khodaei and published by . This book was released on 2020-07 with total page 132 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Handbook of Phase Change written by S.G. Kandlikar and published by Routledge. This book was released on 2019-01-22 with total page 786 pages. Available in PDF, EPUB and Kindle. Book excerpt: Provides a comprehensive coverage of the basic phenomena. It contains twenty-five chapters which cover different aspects of boiling and condensation. First the specific topic or phenomenon is described, followed by a brief survey of previous work, a phenomenological model based on current understanding, and finally a set of recommended design equa

Download or read book Microscale Surface Tension and Its Applications written by Pierre Lambert and published by MDPI. This book was released on 2019-10-21 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: Building on advances in miniaturization and soft matter, surface tension effects are a major key to the development of soft/fluidic microrobotics. Benefiting from scaling laws, surface tension and capillary effects can enable sensing, actuation, adhesion, confinement, compliance, and other structural and functional properties necessary in micro- and nanosystems. Various applications are under development: microfluidic and lab-on-chip devices, soft gripping and manipulation of particles, colloidal and interfacial assemblies, fluidic/droplet mechatronics. The capillary action is ubiquitous in drops, bubbles and menisci, opening a broad spectrum of technological solutions and scientific investigations. Identified grand challenges to the establishment of fluidic microrobotics include mastering the dynamics of capillary effects, controlling the hysteresis arising from wetting and evaporation, improving the dispensing and handling of tiny droplets, and developing a mechatronic approach for the control and programming of surface tension effects. In this Special Issue of Micromachines, we invite contributions covering all aspects of microscale engineering relying on surface tension. Particularly, we welcome contributions on fundamentals or applications related to: Drop-botics: fluidic or surface tension-based micro/nanorobotics: capillary manipulation, gripping, and actuation, sensing, folding, propulsion and bio-inspired solutions; Control of surface tension effects: surface tension gradients, active surfactants, thermocapillarity, electrowetting, elastocapillarity; Handling of droplets, bubbles and liquid bridges: dispensing, confinement, displacement, stretching, rupture, evaporation; Capillary forces: modelling, measurement, simulation; Interfacial engineering: smart liquids, surface treatments; Interfacial fluidic and capillary assembly of colloids and devices; Biological applications of surface tension, including lab-on-chip and organ-on-chip systems.

Download or read book Fundamentals of Heat and Mass Transfer written by T. L. Bergman and published by John Wiley & Sons. This book was released on 2011-04-12 with total page 2249 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fundamentals of Heat and Mass Transfer, 7th Edition is the gold standard of heat transfer pedagogy for more than 30 years, with a commitment to continuous improvement by four authors having more than 150 years of combined experience in heat transfer education, research and practice. Using a rigorous and systematic problem-solving methodology pioneered by this text, it is abundantly filled with examples and problems that reveal the richness and beauty of the discipline. This edition maintains its foundation in the four central learning objectives for students and also makes heat and mass transfer more approachable with an additional emphasis on the fundamental concepts, as well as highlighting the relevance of those ideas with exciting applications to the most critical issues of today and the coming decades: energy and the environment. An updated version of Interactive Heat Transfer (IHT) software makes it even easier to efficiently and accurately solve problems.

Download or read book Heat Transfer written by Konstantin Volkov and published by BoD – Books on Demand. This book was released on 2018-06-27 with total page 372 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book focuses on new analytical, experimental, and computational developments in the field of research of heat and mass transfer phenomena. The generation, conversion, use, and exchange of thermal energy between physical systems are considered. Various mechanisms of heat transfer such as thermal conduction, thermal convection, thermal radiation, and transfer of energy by phase changes are presented. Theory and fundamental research in heat and mass transfer, numerical simulations and algorithms, experimental techniques, and measurements as they applied to all kinds of applied and emerging problems are covered.

Download or read book Nucleation of Water written by Ari Laaksonen and published by Elsevier. This book was released on 2021-11-25 with total page 296 pages. Available in PDF, EPUB and Kindle. Book excerpt: Nucleation of Water: From Fundamental Science to Atmospheric and Additional Applications provides a comprehensive accounting of the current state-of-the-art regarding the nucleation of water. It covers vapor-liquid, liquid-vapor, liquid-ice and vapor-ice transitions and describes basic kinetic and thermodynamic concepts in a manner understandable to researchers working on specific applications. The main focus of the book lies in atmospheric phenomena, but it also describes engineering and biological applications. Bubble nucleation, although not of major atmospheric relevance, is included for completeness. This book presents a single, go-to resource that will help readers understand the breadth and depth of nucleation, both in theory and in real-world examples. - Offers a single, comprehensive work on water nucleation, including cutting- edge research on ice, cloud and bubble nucleation - Written primarily for atmospheric scientists, but it also presents the theories in such a way that researchers in other disciplines will find it useful - Written by one of the world's foremost experts on ice nucleation