Porous Film Deposition by Electrohydrodynamic Atomization of Nanoparticle Sols (original) (raw)
Related papers
Electrohydrodynamic atomization (EHDA), also called electrospray technique, has been studied for more than one century. However, since 1990s it has begun to be used to produce and process micro-/nanostructured materials. Owing to the simplicity and flexibility in EHDA experimental setup, it has been successfully employed to generate particulate materials with controllable compositions, structures, sizes, morphologies, and shapes. EHDA has also been used to deposit micro- and nanoparticulate materials on surfaces in a well-controlled manner. All these attributes make EHDA a fascinating tool for preparing and assembling a wide range of micro- and nanostructured materials which have been exploited for use in pharmaceutics, food, and healthcare to name a few. Our goal is to review this field, which allows scientists and engineers to learn about the EHDA technique and how it might be used to create, process, and assemble micro-/ nanoparticulate materials with unique and intriguing properties. We begin with a brief introduction to the mechanism and setup of EHDA technique. We then discuss issues critical to successful application of EHDA technique, including control of composition, size, shape, morphology, structure of particulate materials and their assembly. We also illustrate a few of the many potential applications of particulate materials, especially in the area of drug delivery and regenerative medicine. Next, we review the simulation and modeling of Taylor cone-jet formation for a single and co-axial nozzle. The mathematical modeling of particle transport and deposition is presented to provide a deeper understanding of the effective parameters in the preparation, collection and pattering processes. We conclude this article with a discussion on perspectives and future possibilities in this field.
Fabrication of high quality zinc-oxide layers through electrohydrodynamic atomization
Thin Solid Films, 2012
Zinc oxide (ZnO) is a useful material in the fabrication of many electronic devices because of its wide bandgap, excellent transparency and high electron mobility. Thin films of ZnO have been fabricated where an alcosol solution containing 7 wt.% ZnO nano-particles was synthesized and subjected to controlled flow through a metal capillary exposed to an electric field at the ambient temperature to generate an electrohydrodynamic jet, which subsequently disintegrated into droplets thereby depositing a uniform thin film of zinc oxide on the glass substrates with an average thickness of 115 nm at a constant substrate speed of 0.25 mm/s. Pure and perfectly uniform transparent films with an average transmittance of 88% have been deposited with wurtzite crystal structure and an electrical resistivity of approximately 64 Ω.cm.
Electrohydrodynamic Spray Deposition of ZnO Nanoparticles
Japanese Journal of Applied Physics, 2010
This paper presents the electrospray deposition of solution-based ZnO nanoparticles. Transparent thin film transistors in active matrix displays have become the most interested research area. Electrospray assures direct deposition by eliminating etching steps required after deposition by other techniques. Uniform layers of minimum thickness 87 nm on glass and 356 nm on polyimide using electrospray experiment is achieved. Contact angle analyzer has been used for finding properties like wetting energy, spreading coefficient and work of adhesion of the ink on glass and polyimide substrates. All experiments were performed in ambient conditions.
Quantitative evaluation about property of thin-film formation
Applied Surface Science, 2006
Chemical vapor deposition (CVD) is gradually emphasized as one promising method for nanomaterial formation. Such growth mechanism has been mainly investigated on basis of experiment. Due to large cost of the equipment of experiment and low level of current measurement, the comprehension about authentic effect of formation condition on properties of nanomaterial is limited in qualitative manner. Three quantitative items: flatness of primary deposition, adhesion between cluster and substrate, and degree of epitaxial growth were proposed to evaluate the property of thin film. In this simulation, three different cluster sizes of 203, 653, 1563 atoms with different velocities (0, 10, 100, 1000, 3000 m/s) were deposited on a Cu(0 0 1) substrate whose temperatures were set between 300 and 1000 K. Within one velocity range, not only the speed of epitaxial growth and adhesion between thin film and substrate were enhanced, but also the degree of epitaxy increased and the shape of thin film became more flat with velocity increasing. Moreover, the epitaxial growth became well as the temperature of substrate was raised within a certain range, and the degree of epitaxy of small cluster was larger than larger cluster. The results indicated that the property of thin film could be controlled if the effect of situations of process was made clear. #
Electrostatic Sol–Spray Deposition of Nanostructured Ceramic Thin Films
Journal of Aerosol Science, 1999
Electrospraying has been developed into an electrostatic spray deposition technique for the deposition of ceramic thin "lms. The cone-jet spraying mode appears to be the most preferable for this purpose, and the domain where the cone-jet mode exists was found to depend strongly on the nozzle design. A nozzle with a large diameter and a tilted outlet widens the windows for both the applied high DC voltage and the #ow rates of a precursor liquid keeping the cone-jet mode intact. The results of three nozzle designs are compared, one of which has been selected for feeding two di!erent precursor liquids simultaneously. With three relevant sols as precursor liquids, nanostructured thin "lms of ZnO, ZrO , and Al O have been deposited. Their morphologies are dependent on the preparation of the precursor sols and the deposition temperature. Highly porous "lms were obtained by using a high deposition temperature and a sol prepared from a metal alkoxide or a metal acetate.
Property modification and synthesis by low energy particle bombardment concurrent with film growth
Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms, 1987
Ion bombardment during the deposition of a thin film has been observed to strongly modify some of the properties of the thin film. This paper examines the effects of low energy ion beam bombardment during the deposition of a thin film by either sputtering or evaporation. The ion bombardment can cause physical changes in the film, such as a change in the grain size, the degree or direction of orientation, the film density and number of voids, the film stress, and other related properties such as the electrical resistivity the dielectric constant, and the stability of the film. Chemical changes can also be induced, such as the formation of compounds or the incorporation of gas into the film. Generally, the change observed in the film is a combination of these and other • effects. The understanding of this phenomena is at an early stage. Models have been presented which examine such features as the change in density and void structure, or the changes in stress and resistivity that have been observed in other cases.
Effect of particle morphology on film morphology and properties
2019
One of the greatest challenges facing modern society is the reduction of climate change and the development of sustainable materials. With this in mind, the production of protective and decorative coatings, which has traditionally been dominated by solvent based products, is gradually being shifted towards the use of waterborne dispersions. Such coatings imply the formation of a film which often needs to satisfy several seemingly contradictory requirements with regards to mechanical properties. One common example is the necessity for outdoor coatings to be both capable of forming a film at relatively low temperatures whilst being hard at the same temperature. Solvent based coatings easily fulfill these requirements. Matching their performance with waterborne coatings is not trivial and often potentially toxic additives, such as coalescing agents, have to be added to the formulation. Efforts are now devoted to synthesize latexes presenting good properties whilst adding a minimum of additives. One way to do this is through the use of a blend of two latexes with different glass transition temperatures (Tgs). One latex with a low Tg to form a film at low temperature and the other one with a higher Tg, to provide film hardness. However, blending leads to non homogenous films and the properties of the film are affected. 1 A more uniform distribution of the two phases in the film can be obtained by using heterogeneous polymer particles (also called hybrid particles). In this case, two different polymers are present in the same particle which offers the opportunity to combine the Chapter 1 2 positive properties of their constituents. Although such polymers are typically incompatible, their phase separation during film formation can be controlled by grafting reactions. 2-6 Recent works showed that controlling the morphology of hybrid particles is not trivial. 1,7-13 Interestingly, much less attention has been paid to the fact that application properties are really determined by the film morphology and that the relationship between the particle morphology and the film morphology is not evident. The goal of this PhD Thesis is to shed some light on this relationship. Therefore, as it is expected that the film morphology is affected by the particle morphology and the film formation process, the knowledge available about these aspects will be summarized in the next sections. 1.2 Synthesis of hybrid particles A variety of chemical and physical methods exists for the synthesis of structured polymer particles with different morphologies. Of these, emulsion polymerization is the most common for the synthesis of waterborne polymer-polymer hybrids due to its versatility to control the properties of the final product. Miniemulsion polymerization is more adequate when hydrophobic monomers, preformed polymers and inorganic particles should be included in the polymer particles. 14-19 12 Miniemulsion is also used in the synthesis of polymer-inorganic material hybrid because no transport through the water phase is needed. Aguirre et. al. incorporated cerium oxide (CeO2) in acrylate latex particles hybrid by semi-batch emulsion polymerization. 55,56 The seed was produced by miniemulsion polymerization containing the whole load of the metal oxide. It was found that the nanoparticles were preferentially located at the surface of the seed particles. They obtained a single aggregate of CeO2 particles per polymer particle due to the incompatibility between the CeO2 and the polymer (see Figure 1-4 a)). The hybrid dispersion led to UV protective coatings. Another example is the work of de San Luis et al. 57. They used miniemulsion to encapsulate quantum dots into acrylic particles. This hybrid system can be used to improve the electronic transmission in electronic devices such as light emission diodes or solar cells. 58-60 They showed that inefficient encapsulation led to a loss of fluorescent intensity of the quantum dots. This issue was solved by formation of cross-linked core/shell particles composed by a core of cross-linked polystyrene and quantum dots and a shell of cross-linked polymethyl methacrylate produced by seeded semi-batch miniemulsion polymerization (Figure 1-4 b)). Sun et al. 15 encapsulated Laponite clay into polystyrene particles. Hydrophobicity of the clay is the key point for the success of the encapsulation and the stability of the latex. A quaternary ammonium salt was mixed with the clay in the monomer phase in order to disintegrate the agglomerates in the clay under sonication. Then, the miniemulsion was prepared by ultrasonication. The salt helped to stabilize the system with a nonionic surfactant. Gong et al. 61 encapsulated magnetite into cross linked PS latex particles. After optimization of the formulation (surfactant and crosslinker amount), a homogeneous distribution of the magnetite in the particles was obtained (see Figure 1-4 c)). The magnetic
Engineered nanoporous and nanostructured films
Materials Today, 2009
Engineered nanoporous and nanostructured films Nanoporous and nanostructured films and surfaces have been exploited by nature to spectacular effect. Plant leaves use nanostructured surfaces to shed water 1, 2 as shown in Fig. 1 and the Namib desert beetle uses a similar surface to collect water from dew 3, 4. Butterflies have fashioned nanostructured surfaces to attract mates, deter predators, and provide camouflage 5, 6 (Fig. 2). Geckos 7, 8 , flies, and other insects 9 use nanostructured surfaces to adhere to walls (Fig. 3), and all cell membranes can be thought of as sophisticated nanoporous films 10. The development of nanoporous or nanostructured thin films is relatively recent and has been driven by the need for low dielectric constant materials in the semiconductor industry 11-15 , the need for low refractive index materials in the photonics industry 16-20 , the need for nearly blackbody absorptivity in the solar cell industry 21 , the need for nanoporous membranes in the gas separations industry 22 , the need for superhydrophobic or superoleophobic materials to control wetting and spreading 23, 24 , and the general need for thin film catalytic and separations processes in the fuel cell 25, 26 , and biotechnology 27, 28 fields. Since the range Nanoporous and nanostructured films have become increasingly important to the microelectronics and photonics industries. They provide a route to low dielectric constant materials that will enable future generations of powerful microprocessors. They are the only route to achieving materials with refractive indices less than 1.2, a key feature for the future development of photonic crystal devices, enhanced omnidirectional reflectors, enhanced anti-reflection coatings and black-body absorbers. In addition, these films exhibit tremendous potential for separations, catalytic, biomedical and heat transfer applications. This article will review two primary techniques for manufacturing these films, evaporation induced self-assembly and oblique or glancing angle deposition, and will discuss some of the film properties critical to their use in the microelectronics and photonics industries.