Zirconium oxide films

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. 

Ammonium zirconyl carbonate, (NH4)3[ZrOH(COj)3] 2H2O is a constituent of flame-retarding systems used for cotton fabrics designed for outdoor use, such as tenting. It is also employed as a water repellent in floor polishes and paper coatings, for the production of zirconium oxide films and as an adhesive in lithography. The anion has a polymeric, hydroxide-bridged structure (5). 

An investigation of the stoichiometry of the ceramic films deposited for this project was conducted. Using an rf sputter unit, 1000 A-thick chromium oxide and zirconium oxide films were deposited on freestanding diamond film substrates. Rutherford Backscattering (RBS) measurements were performed on an unco.ated diamond film and on the coated films. The oxide films were found to be rich in oxygen. The chromium oxide is actually Cr2042, and the zirconium oxide is Zr02a. 

After the stoichiometry of the films was determined, several chromium oxide and zirconium oxide films were grown on sapphire. One specimen of each oxide was implanted with 340 keV chromium ions to doses of either 1 x 10 or 1x10 ions/cm These samples will now be examined using Rutherford backscattermg spectrometry. 

Brenier R., Urlacher C., Mugnier J., Brunei M. Stress development in amorphous zirconium oxide films prepared by sol-gel processing. Thin Solid Films 19 338 136-141 Brinker C.J., Scherer G.W. Sol-Gel Science. Boston Academic Press, 1990a Brinker C.J., Hurd A.J., Schunk P.R, Frye G.C., Ashley C.S. Review on sol-gel thin film formation. 

Zirconium oxide films have been prepared by an ultrasonic nebulization and pyrolysis technique. A solution (0.02M) of zirconium acetylacetonate in ethanol was nebulized by a commercial ultrasonic humidifier (Holmes Air transducer operates at 1.63 MHz) and was carried into a horizontal reactor by argon (Fig. 1). The reactor was heated by a two-zone mirror furnace (Transtemp Co., Chelsea, MA). 

X-ray diffraction patterns of the zirconium oxide films were obtained using a Philips diffractometer and monochromated high-intensity Cu radiation... 

Zirconium is a highly active metal which, like aluminum, seems quite passive because of its stable, cohesive, protective oxide film which is always present in air or water. Massive zirconium does not bum in air, but oxidizes rapidly above 600°C in air. Clean zirconium plate ignites spontaneously in oxygen of ca 2 MPa (300 psi) the autoignition pressure drops as the metal thickness decreases. Zirconium powder ignites quite easily. Powder (<44 fim or—325 mesh) prepared in an inert atmosphere by the hydride—dehydride process ignites spontaneously upon contact with air unless its surface has been conditioned, ie, preoxidized by slow addition of air to the inert atmosphere. Heated zirconium is readily oxidized by carbon dioxide, sulfur dioxide, or water vapor. 

Corrosion Resistance. Zirconium is resistant to corrosion by water and steam, mineral acids, strong alkaUes, organic acids, salt solutions, and molten salts (28) (see also Corrosion and corrosion control). This property is attributed to the presence of a dense adherent oxide film which forms at ambient temperatures. Any break in the film reforms instantly and spontaneously in most environments. 

Borides are inert toward nonoxidizing acids however, a few, such as Be2B and MgB2, react with aqueous acids to form boron hydrides. Most borides dissolve in oxidizing acids such as nitric or hot sulfuric acid and they ate also readily attacked by hot alkaline salt melts or fused alkaU peroxides, forming the mote stable borates. In dry air, where a protective oxide film can be preserved, borides ate relatively resistant to oxidation. For example, the borides of vanadium, niobium, tantalum, molybdenum, and tungsten do not oxidize appreciably in air up to temperatures of 1000—1200°C. Zirconium and titanium borides ate fairly resistant up to 1400°C. Engineering and other properties of refractory metal borides have been summarized (1). 

The zirconium sponge thus obtained is highly pyrophoric. The industrial practice is to condition this sponge by the controlled admittance of air-argon mixtures at around 50 °C. Such a treatment results in the formation of a thin, protective oxide film on the sponge this eliminates any major fire hazard in subsequent handling and crushing operations. 

Continuous (barrier, passivation) films have a high resistivity (106Q cm or more), with a maximum thickness of 10 4cm. During their formation, the metal cation does not enter the solution, but rather oxidation occurs at the metal-film interface. Oxide films at tantalum, zirconium, aluminium and niobium are examples of these films. 

Finely divided metals (without oxide film) Aluminum, calcium, cobalt, iron, magnesium, manganese, palladium, platinum, titanium, tin, zinc, zirconium... 

C) gave reasonable service at normal temperature, but for severe jobs it may be appropriate to use the more exotic metals such as tantalum. Zirconium or titanium may also be used, though in high strength acids with an appreciable content of dissolved nitrogen oxides these metals can develop unstable, potentially hazardous oxide films. The newer varieties of high silicon austenitic stainless steels may be of service. 

Principles and Development of a Thick-Film Zirconium Oxide Oxygen Sensor... 

Kinetic Mechanism of Zirconium and Hafnium Oxide Film Deposition. . . 494... 

In molecular models, a surface site is modeled using an analogous molecular reaction. This is the simplest approach, which requires the least amount of computational resources. The selection of a molecule that can more or less adequately reproduce the properties of the surface site under study determines the success or failure of the approach. This approach was used in Ref. [20] in the multiscale simulation of zirconium and hafnium oxide film growth. 

The activation of aluminum with ultrasound or dispersion of liquid aluminum. The suspension of powder aluminum in petrol or n-geptane without oxygen is subjected to ultrasound the tough oxide film on the surface of aluminum is removed and aluminum becomes reactive. The second activation technique is the dispersion of liquid aluminum with argon or purified nitrogen flow into a finely dispersed state. It should be noted, however, that the most reactive aluminum powder for direct synthesis is the powder alloyed with transition metals (titanium, zirconium, niobium, tantalum) with the size of particles from 10 to 125 pm. 

---