Zirconium oxide, deposition

Ultraflltraiion membranes are commonly asymmetric (skinned) polymeric membranes prepared by the phase inversion process. Materials commercially made into membranes include cellulose nitrate, cellulose acetate, polysulfone. aramids, polyvinylidene fluoride, and nctylonitrile polymers and copolymers. Inorganic meni-braues of hydrous zirconium oxide deposited on a tubular carbon backing are also commercially available. 

Eudialyte, (Na,Ca)gZr0H(Si20 )2, from a large deposit near Narssaq in southwest Greenland, is the source of pure zirconium oxide. The hafnium ratio in the ore is 2.2% Hf/Zr + Hf. 

Carbide. Zirconium carbide [12020-14-3] nominally ZrC, is a dark gray brittle soHd. It is made typically by a carbothermic reduction of zirconium oxide in a induction-heated vacuum furnace. Alternative production methods, especially for deposition on a substrate, consist of vapor-phase reaction of a volatile zirconium haHde, usually ZrCl, with a hydrocarbon in a hydrogen atmosphere at 900—1400°C. 

Ceramic Membranes Alumina-based microfiltration membranes and porous carbon substrates are tightened for use as UF membranes usually by depositing a layer of zirconium oxide on the surface. 

Liu, J.-F. Nistorica, C. Gory, I. Skidmore, G. Mantiziba, F. M. Gnade, B. E. 2005. Layer-by-layer deposition of zirconium oxide films from aqueous solutions for friction reduction in silicon-based microelectromechanical system devices. 

Zirconium oxide occurs in nature as mineral baddeleyite. Ore is mined from natural deposits and subjected to concentration and purifcation by various processes. The oxide, however, is more commonly obtained as an intermediate in recovering zirconium from zircon, ZrSi04 (See Zirconium, Recovery). 

Chang, J. P., et al. (2001), Rapid thermal chemical vapor deposition of zirconium oxide for metal-oxide-semiconductor field effect transistor application, J. Vac. Sci. Technol. B Microelectron. Nanometer Struct., 19(5), 1782-1787. 

Zirconium oxide has also been used as a substrate by itself. Researchers at Cornell University evaporated some of the yttrium superconductor with beams of high-energy electrons, deposited the vapors onto bits of the zirconia, and then etched a circuit pattern a fraction of an inch long. Not only did the superconductor film carry current of around 1,000,000 amps per square centimeter, but it conducted electrical impulses as brief as ten to fifteen-trilli-onths of a second without distortion—impossible with conventional materials—and at very high levels of current. Those incredibly short pulses raise the distinct possibility that an enormous amount of electronic data, not only in a computer but in a telephone line as well, can be transmitted via the new superconductors at ultrafast speeds. 

In tubular assemblies the membrane is deposited either on the inside or outside of porous tube, most commonly inside for reverse osmosis and outside for ultrafiltration. Figure 19.3(a) shows a single-tube construction, but units with 7 or 19 tubes in a single shell are made as standard items. Table 19.5 lists some available sizes. Dynamic membranes may be deposited on porous stainless steel tubes from a feed solution that consists of polyacrylic acid and hydrous zirconium oxide. Such a membrane can be deposited in 1 hr and replaced as quickly. Fluxes are very high 100 gal/(sqft)(day) is shown in Table 19.6(a). Some apphca-tions are described by Turbak (Vol. II, 1981, pp. 434-A53). 

The MF membranes are usually made from natural or synthetic polymers such as cellulose acetate (CA), polyvinylidene difiuoride, polyamides, polysulfone, polycarbonate, polypropylene, and polytetrafiuoroethylene (FIFE) (13). Some of the newer MF membranes are ceramic membranes based on alumina, membranes formed during the anodizing of aluminium, and carbon membrane. Glass is being used as a membrane material. Zirconium oxide can also be deposited onto a porous carbon tube. Sintered metal membranes are fabricated from stainless steel, silver, gold, platinum, and nickel, in disks and tubes. The properties of membrane materials are directly reflected in their end applications. Some criteria for their selection are mechanical strength, temperature resistance, chemical compatibility, hydrophobility, hydrophilicity, permeability, permselectivity and the cost of membrane material as well as manufacturing process. 

Following a brief review of the development of dynamic membranes and an overview of the current state of the art, Spencer (10) discusses dynamic polyblend membranes. In particular, he looks at the Influence that polymer selection and membrane preparation procedures have on membrane performance. Dynamic membranes composed of a poly(acrylic acid)/basic polyamine blend deposited on a ZOSS (hydrous zirconium oxide on stainless steel) ultrafiltration membrane are discussed. Their hyperfiltration or reverse osmosis properties are compared to the more traditional ZOPA (zirconium oxide plus poly(acrylic acid)) membrane. 

Two useful membranes developed by the group at the Oak Ridge National Laboratory have dominated the application of dynamic membranes the hydrous zirconium oxide ultrafilter and the hydrous zirconium oxide-poly(acrylic acid) hyperfilter. The technology of formation and utilization of zirconium oxide-poly(acrylic acid) dynamic membranes has been described in detail by Thomas ( ). The effects of molecular weight of the poly(acrylic acid), pore diameter of the porous support, formation cross-flow velocity, formation pressure, and pH of poly(acrylic acid) solution during initial deposition of the polyacid on the hyperfiltration performance are described and discussed. 

Tanny (9 ) has prepared ultrafilters by depositing hydrous zirconium oxide on pliable porous materials in a fluted configuration, providing a large membrane area in a small volume suitable for low pressure ultrafiltration. 

It has been established from these studies that the different catalytic properties of transition metal oxides (chromium, cobalt) on zirconium dioxide are attributed to their different acidic properties determined by TPDA and IR-spectroscopy. The most active catalyst is characterized by strong acidic Bronsted centers. The cobalt oxide deposited by precipitation on the zirconium-containing pentasils has a considerable oxidative activity in the reaction N0+02 N02, and for SCR-activity the definite surface acidity is necessary for methane activation. Among the binary systems, 10% CoO/(65% H-Zeolite - 35% Z1O2)... 

Aluminium oxide (AI2O3) or zirconium oxide (Zr02) are also used as supports of reticulated deposits based upon polymers of butadiene or styrene-divinylbenzene or hydroxymethylstyrene. Porous graphite, in the form of spheres whose surface is 100 per cent carbon and therefore completely hydrophobic, has been used in applications with compounds possessing atoms carrying lone pairs of electrons thus having high retention factors. 

Thin film preparation by chemical vapor deposition (CVD) and electrochemical vapor deposition (EVD) 18, 17.3.7.3.3 Yttria-stabilized zirconium oxide ... 

Ti or Zr salts deposited on silicon dioxide the titanium or zirconium oxide supported on Si02 is sulfate-activated and physically blended with an acidic montmorillonite clay... 

Vapor deposition polymerization Tungsten oxide Zirconium oxide... 

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