Oxide liquid phase deposition

Very acidic (high valent) cations will readily hydrolyse in aqueous solution, often even at low pH. These cations tend to form the polymeric metal oxide chains mentioned previously. This hydrolysis can be controlled by addition of boric acid (see Sec. 3.2.4.4) and forms the basis of a technique referred to as liquid phase deposition. This method can be reasonably included in the more general term of chemical solution deposition, and is treated, although not comprehensively, in this book. Ref 5 deals more thoroughly with this technique and describes many cases of SiOi as well as some examples of several other oxides not covered in this chapter. 

Abstract. Liquid phase deposition methods are a useful way to create mineral oxide films from aqueous solution under near-ambient conditions. These approaches have been applied to the creation of ceramic coatings on polymers and on polymer-matrix composites. Control has been achieved over the adherence and crystallinity of the solution-deposited thin films based on controlling the composition of both the deposition solution and the substrate surface. The challenge of depositing such films from water, while minimizing film cracking has also been addressed. Crack-free ceramic films of up to 200 nm thickness have been achieved on a variety of polymer substrates. 

Most film and particle formation techniques can be divided into gas-phase and liquid-phase deposition processes, which are briefly discussed in this section. Deposition of metal and metal oxides from metal enolate sources results from application of CVD, ALD, spin-coating, electrochemical and sol-gel methods, which are discussed in detail... 

On the other hand, liquid phase deposition (LPD) has been demonstrated as a flexible wet chemical method for preparing metal oxide nanostructured films on electrode surfaces. By the LPD process, electroactive titanium dioxide (Ti02) films were prepared on graphite, glassy carbon and ITO. The electrochemical properties of such LPD Ti02 films were dependent upon the film thickness controlled by the deposition time. The LPD technique was easily combined with other techniques, e.g., seed-mediated growth, which could provide metal/metal oxide composite nanomaterials. Moreover, hybrid nanostructured films were facilely obtained by doping dyes, surfactants and other... 

Liquid phase deposition (LPD) process is the formation of oxide thin films from an aqueous solution of a metal-fluoro complex which is slowly hydrolyzed by adding fluoride scavengers such as boric acid or aluminum metal [47], namely... 

In recent years, the IR absorption of fluorinated silicon oxide (FjcSiOj,) has been actively studied [68-74]. These films are very easily deposited by several PECVD or liquid-phase deposition (LPD) methods and are characterized by a low dielectric constant, which decreases with increased concentration of fluorine in the film. Decreasing the dielectric constant of the intermetal dielectric film is the most efficient way to reduce the adjacent wiring capacitance, which will improve the performance of submicrometer integrated circuits. However, the F SiOy films become reactive to water as the fluorine concentration increases. The film desorbs H2O and HF under thermal annealing after humidification, which causes reliability problems in the VLSI fabrication [68]. 

Thin films prepared using the sol-gel method are usually amorphous before heat treatment. High-temperature heat treatment is generally required for the films crystallization and densification of the films. For application of thin films to substrates with low thermal stability such as polymer substrates, lowering of the crystallization temperature is necessary. Consequently, many researchers have recently reported formation of oxide crystals, such as T1O2, Sn02 and ZnO, at low temperatures [1, 2]. For example, the preparation of various oxide thin films from aqueous metal-fluoro complex solutions using the liquid phase deposition method... 

Liquid-phase deposition is a method for the non-electrochemical production of polycrystalline ceramic films at low temperatures, along with other aqueous solution methods [chemical bath deposition (CBD), successive ion layer adsorption and reaction (SILAR), and electroless deposition (ED) with catalyst] has been developed as a potential substitute for vapor-phase and chemical-precursor systems. The method involves immersion of a substrate in an aqueous solution containing a precursor species (commonly a fluoro-anion) which hydrolyzes slowly to produce a supersaturated solution of the desired oxide, which then precipitates preferentially on the substrate surface, producing a conformal coating... 

Drew, C., X. Y. Wang, F. F. Bruno, L. A. Samuelson, and J. Kumar (2005). Electrospun pol5mer nanofibers coated with metal oxides by liquid phase deposition. Composite Interfaces 11(8—9) 711—724. 

Besides the sol-gel processing, there are many aqueous routes to synthesize ceramic powders, fibers, films and bulks. Niesen and DeGuire reviewed these low temperature and non-electrochemical processes (Niesen and DeGuire, 2001). According to them, the processes include a chemical-bath deposition (CBD), successive ionic-layer adsorption and reaction (SILAR), liquid-phase deposition (LPD), electroless deposition (ED), and film deposition on organic self-assembled monolayers (SAMs). Of course, an electrochemical route is an important process. Another non-sol-gel route is a spray pyrolysis of solution or sol, and is applied to the direct preparation of oxide powders and films. Since these processes do not form the gel phase, they are not described here. 

This chapter reviewed recent advances in the preparation of hollow oxide nanoparticles by liquid-phase deposition methods. Hollow particles with various compositions, controlled shell structures, and controlled shapes and sizes have successfully been obtained by employing either template or template-free method, and many interesting properties arising from their unique structural features have been reported. Large-scale and low-cost production by environment-friendly processes promises practical applications in many fields. 

Aoi Y, Kobayashi S, Kamijo E, Deki S (2005) Fabrication of thiee-dimensiraial ordered macroporous titanium oxide by the liquid-phase deposition method using colloidal template. J Mater Sci 40 5561-5563... 

Carbon fibers, when used without surface treatments, produce composites with low mechanical properties. This has been attributed to weak adhesion and poor bonding between the fiber and matrix. Therefore, the carbon fibers are given surface treatments, the exact nature of which is a trade secret. This surface treatment increases the surface active sites which results in the improvements of the bonding between the fibers and the resin matrix. This tends to increase the wettability of the carbon fibers and enhances the mechanical properties [4-7]. Surface treatments may be classified into oxidative and nonoxidative treatments. An oxidative treatment involves gaseous oxidation, liquid-phase oxidation carried out chemically or electrochemically and catalytic oxidation. The nonoxidative surface treatments involves deposition of more active forms of carbon or metals such as whiskerization, pyrolytic coating, the grafting of the polymers, and metal deposition on the carbon fiber surfaces [8-11]. 

The approach comprises deposition-precipitation (DP) of Au(OH)3 onto the hydroxide surfaces of metal oxide supports from an alkaline solution of HAUCI4 [26] and grafting of organo gold complexes such as dimethyl gold (Ill)acetylacetonate (hereafter denoted as Au acac complex) [27] and Au(PPh3)(N03) [28] either in gas and liquid phase are advantageous in that a variety of metal oxides commercially available in the forms of powder, sphere, honeycomb can be used as supports. 

Liquid-Phase Reductive Deposition of Metal Nanoclusters Selective onto Oxide Surfaces... 

Among various methods to synthesize nanometer-sized particles [1-3], the liquid-phase reduction method as the novel synthesis method of metallic nanoparticles is one of the easiest procedures, since nanoparticles can be directly obtained from various precursor compounds soluble in a solvent [4], It has been reported that the synthesis of Ni nanoparticles with a diameter from 5 to lOnm and an amorphous-like structure by using this method and the promotion effect of Zn addition to Ni nanoparticles on the catalytic activity for 1-octene hydrogenation [4]. However, unsupported particles were found rather unstable because of its high surface activity to cause tremendous aggregation [5]. In order to solve this problem, their selective deposition onto support particles, such as metal oxides, has been investigated, and also their catalytic activities have been studied. 

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