Zircon nitrate

Zirconates and hafnates can be prepared by firing appropriate mixtures of oxides, carbonates or nitrates. None of them are known to contain discrete [M04]" or [MOs] ions. Compounds M ZrOs usually have the perovskite structure whereas M2Zr04 frequently adopt the spinel structure. 

Arsenate. — The arsenates of the rare earths crystallize [263] in two structural types, the huttonite and the zircon. The structural change from huttonite (La—Nd) to zircon (Sm—Lu) occurs at samarium. The lattice parameters of EuAsCU are a = 7.167 and c — 6.374 A. The rare earth arsenates can be prepared by reacting the nitrates with (NEU HAsCU, and heating the product to 700° C. 

Heavy minerals and accessory minerals Zircon, rutile, tourmaline, orthoclase, biotite — Chlorides, sulfates, nitrates —... 

The first step is preparation of the solution. Aqueous solutions are prepared by dissolving either soluble salts in solvents (usually water) or metals in acids. For multicomponent systems, the mutual solubility of the various components must be considered. For example, a solution for lead zirconate cannot be prepared from lead nitrate and zirconium sulfate, both of which are soluble in water, because lead sulfate, which is insoluble, will precipitate. A solution of nitrates of both cations is satisfactory. 

Separation of hafnium from zirconium. In a zirconium-hafnium separation process developed by Eldorado Nuclear, a mixture of sodium zir-conate and hafnate can be obtained by fusing zircon sand with NaOH and dissolving the product in water. Acidification with nitric acid then gives aqueous zirconyl (ZrO +, or hydrolyzed Zr + ) and hafnyl (HfO " ") nitrates. Extraction with TBP then gives an extract containing mainly [Hf0(N03)2(TBP) ], but most of the ZrO " " remains in the aqueous phase and can be recovered on evaporation as essentially Hf-free Zr0(N03)2(s). The effectiveness of this process can be ascribed to compounding of factors... 

The minerals found in United States coals continue to be studied with the availability of improved instrumental procedures such as x-ray diffraction, infrared absorption, and scanning electron microscopy beyond the traditional optical and chemical mineralogical techniques as applied to thin sections, polished pellets, and isolated particles. The minerals may be grouped into the silicates (kaolinite, illite montmorillonite, and chlorite), the oxides (quartz, chalcedony, hematite) the sulfides (pyrite, marcasite, and sphalerite) the sulfates (jarosite, gypsum, barite, and numerous iron sulfate minerals) the carbonates (ankerite, calcite, dolomite, and siderite) and numerous accessory minerals (apatite, phosphorite, zircon, rutile, chlorides, nitrates, and trace minerals). 

The Barin tables are far more complete in coverage than any of the sources described above. All of the natural elements and their compounds are included. In addition to the substance types listed in USBM Bull 677, the Barin tables include a large number of ternary oxides - aluminates, arsenates, borates, chromates, molybdates, nitrates, oxy-halides, phosphates, titanates, tungstates, selenates, vanadates, zirconates, etc. - as well as cyanides, hydroxides, complex silicates and inter-metallic compounds. The only substances not included by Barin, for which tables can be found elsewhere, are the ionized-gas species and a limited number of gas species important only at very high temperatures, which are listed in the JANAF tables. For each table Dr. Barin gives references for each of the major thermochemical values employed (enthalpy of formation and entropy at 298 K, and heat capacity). Like the USBM Bulletins, no attempt is made to discuss the choice between conflicting data sources. 

Thin films of BaTi03 [11] and lead zirconate titanate [12] have been prepared by cathodic reduction. Konno and co-workers [13] have obtained thin films of La, M Cr03 (M = Ca, Sr) by heat treatment (700 °C, 10 min) of the hydroxy-chromate precursor obtained by cathodic reduction of a mixed metal nitrate solution containing (NH )2Cr20.j. Films of LaFeOj are prepared by heat treatment of an electrosynthesized hydroxide precursor at 7(X) °C (which is much lower than the temperature (>1000 C) used in the conventional ceramic preparation)... 

Powders from All-Salt Compositions. An all-salt procedure has been described by Schafer et al. (1997) for the synthesis of lead zirconate titanate powders. The first step in the process was the mixing of aqueous solutions ofzirconyl and titanyl nitrates in stoichiometric proportions. Lead nitrate and citric acid were dissolved in this mixed solution. Nitric acid was also added to keep the solution clear after a water-evaporation step at 90°C. When the concentration of citric acid was higher than 22.1 mmol, there was no precipitation and the dehydrated solutions formed gels. Suitable thermal treatments (180°C, followed by 550°C/2 h) led to the formation of lead zirconate titanate solid solutions according to compositional variations. The primary particles had a size of about 50 nm. 

Takenaka S., Kozuka H. Sol-gel preparation of single-layer, 0.75 /xm thick lead zirconate titanate films from lead nitrate-titanium and zirconium alkoxide solutions containing poly vinylp3rrolidone. Appl. Phys. Lett. 2001 79 3485-3487... 

The sintering behavior of an amorphous zircon powder synthesized by sol-gel processing has been studied by Veytizou et al. (2002). Gel samples were prepared from a reactive precursor solution of zirconyl nitrate and tetraethoxy silane. N2-adsorption-desorption measurements on the porous precursor powder of surface area 412 m /g indicated the presence of spheroidal mesoporous cavities with narrow necks created by a packing of spherical particles. The precursor powder with irregularly shaped and different sized agglomerates or aggregates had a microporous volmne of 27 mm /g and a... 

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