Sol techniques

Colloidal suspensions of silver or gold particles in water can be prepared typically by the reduction of a silver salt (e.g., silver nitrate) using a reducing agent such as D-glucose or a citrate. A novel technique [32] involves the laser ablation of silver foil in water using a 355-nm laser with a pulse energy of about 50 mJ and a 10-Hz repetition rate. 

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Therefore, by using the sol technique different 1 % Au/ C catalysts have been prepared using the same supporting material (activated carbon) but var5nng the preparation method with the aim of changing the particle size. PVA/ NaBH4, THPC/NaOH and citrate methods were used (Table 3) obtaining sol of different mean size in the order citrate > PVA > TMPC. 

In this work a combination of polymeric and colloidal sol techniques has been investigated as an alternative method to fabricate electrolyte layers on warm-pressed anode substrates. Sol-gel thin film deposition is applied on dense or very fine porous substrates. Therefore, multilayer structure electrolyte layers are manufactured. Gas-tightness and the electrochemical performance were tested. 

J. W. Fleming, "Sol-Gel Techniques for Lightwave AppUcations," paper no. MH-1 in Technica/ Digest of Optica/ Fiber Communications Conference, Reno, Nev., Optical Society of America, Washington, D.C., 1987. 

The sol—gel technique has been used mosdy to prepare alumina membranes. Figure 18 shows a cross section of a composite alumina membrane made by sHp coating successive sols with different particle sizes onto a porous ceramic support. SiUca or titanium membranes could also be made by the same principles. Unsupported titanium dioxide membranes with pore sizes of 5 nm or less have been made by the sol—gel process (57). 

The gels precipitated as described above are not useful in ion-exchange systems because their fine size impedes fluid flow and allows particulate entrainment. Controlled larger-sized particles of zirconium phosphate are obtained by first producing the desired particle size zirconium hydrous oxide by sol—gel techniques or by controlled precipitation of zirconium basic sulfate. These active, very slightly soluble compounds are then slurried in phosphoric acid to produce zirconium bis (monohydrogen phosphate) and subsequently sodium zirconium hydrogen phosphate pentahydrate with the desired hydrauhc characteristics (213,214). 

Sol-Gel Techniques. Sol-gel powders (2,13,15,17) are produced as a suspension or sol of coUoidal particles or polymer molecules mixed with a Hquid that polymerizes to form a gel (see Colloids SoL-GELtechnology). Typically, formation of a sol is foUowed by hydrolysis, polymerization, nucleation, and growth. Drying, low temperature calciaation, and light milling are subsequently required to produce a powder. Sol-gel synthesis yields fine, reactive, pseudo-crystalline powders that can be siatered at temperatures hundreds of degrees below conventionally prepared, crystalline powders. 

There is also growing iaterest ia thin-film dielectric capacitors. For example, through the use of processiag techniques such as sol—gel solution deposition, thin (--- 0.25 fim) ceramic layers having dielectric constants ranging from 500 to 2000 ia the PZT, Pb(Zr,Ti)03, and PMN—PT, Pb(Mn2 3Nb2 3)03-PbTi03, compositional families respectively, have been prepared (3). 

A new generation of mesoporous silica (SG) materials obtained by sol-gel technique where polymers and ionic or non-ionic surfactant act as stmcture - directed templates is widely developed during last year s. Final materials can be synthesized as thin films and used as sensitive elements of optical and electrochemical sensors. 

In the present work it was studied the dependence of analytical characteristics of the composite SG - polyelectrolyte films obtained by sol-gel technique on the content of non-ionic surfactant in initial sol. Triton X-100 and Tween 20 were examined as surfactants polystyrene sulfonate (PSS), polyvinyl-sulfonic acid (PVSA) or polydimethyl-ammonium chloride (PDMDA) were used as polyelectrolytes. The final films were applied as modificators of glass slides and pyrolytic graphite (PG) electrode surfaces. 

The need to identify replacements for chromate-based technologies has also resulted in the development of alternatives to resin-based corrosion-inhibiting primers. These are primarily inorganic barrier coating techniques, such as sol-gel processes, which may or may not include corrosion inhibitors. These are discussed in a later section. 

Sol-gel is one of the most useful techniques for preparation of inorganic membranes with fine pores in the nanometer range (1-5 nm). The sol is a stable suspension of colloidal solid particles within soft uniform solution. The gel was obtained by hydrolysis with open reflux in 24 hours at 85-90 °C. The advantage of sol-gel technology is the ability to produce... 

In this case study, a zirconia-alumina membrane has been developed using the sol-gel technique with and without support.6-7 The porous ceramic was prepared to fabricate the membrane support. A thin film of aluminum and zirconium were formed on the porous ceramic support. Unsupported membrane was also prepared. The unsupported membrane was not strong enough to hold a high-pressure gradient it was very fragile and not useful... 

Once the membrane was successfully produced, it was analysed for characterisation and scanning. The sol-gel technique was successfully used to obtain a crack-free unsupported membrane, which was expected to have pore size of 1-2 nm. The development of the crack-free membrane may not have the same strength without strong, solid support. The next stage of this work was to characterise the fabricated membrane. Hie objectives of this study were to develop a zirconia-coated 7-alumina membrane with inorganic porous support by the sol-gel method and to characterise the surface morphology of the membrane and ceramic support. 

The vast increase in the application of membranes has expanded our knowledge of fabrication of various types of membrane, such as organic and inorganic membranes. The inorganic membrane is frequently called a ceramic membrane. To fulfil the need of the market, ceramic membranes represent a distinct class of inorganic membrane. There are a few important parameters involved in ceramic membrane materials, in terms of porous structure, chemical composition and shape of the filter in use. In this research, zirconia-coated y-alumina membranes have been developed using the sol-gel technique. 

We have successfully developed a new inorganic ceramic membrane coated with zirconium and alumina. A thin film of alumina and zirconia unsupported membrane was also fabricated. The successful method developed was the sol-gel technique. 

Kaye (Ref 1 lb) has detd the purity of Ba02 using a non-aqueous titrimetry technique. Nor-witz (Ref 16a) has reported techniques for the detn of impurities in Ba02. In a subsequent report (Ref 32), he evolved a method for the detn of Ba02 (or Sn02) in small arms igniter compns. The technique consists of HC1 so In of the peroxide, filtn of in sol mats, reaction of the... 

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