Zirconate formation Zirconium

With allowances for the actual metal content of zirconium (a small correction is also necessary for the hafnium content of about 2 /2%) and postulation of barium zirconate formation (see Table 27), reasonable accord between calculated and measured caloric output is established. However, the situation is more complex with boron mixtures where one encounters increase of heat output with increase of the percentage of boron in the mixtures much beyond the amounts of Equation (la). Thus, even with the reasonable assumption of secondary barium borate formation, the stoichiometry and heat output of the mixtures with more than about 10% of technical boron theoretical 8%) is obscure. Chromium boride formation may be a fector. 

Another important class of titanates that can be produced by hydrothermal synthesis processes are those in the lead zirconate—lead titanate (PZT) family. These piezoelectric materials are widely used in manufacture of ultrasonic transducers, sensors, and minia ture actuators. The electrical properties of these materials are derived from the formation of a homogeneous soHd solution of the oxide end members. The process consists of preparing a coprecipitated titanium—zirconium hydroxide gel. The gel reacts with lead oxide in water to form crystalline PZT particles having an average size of about 1 ]lni (Eig. 3b). A process has been developed at BatteUe (Columbus, Ohio) to the pilot-scale level (5-kg/h). 

Thermolysis of tin and lead alkoxozirconates leads to the formation of metals. The mass-spectral data indicate the presence ofbarium and aluminium derivatives in the gas phase, but no preparative data are accessible for them. The major application of zirconium and hafnium alkoxides lies now in the sol-gel technology of zirconate-titanate and solid solutions Zr02-Y203 (see Section 10.3), Except in the synthesis of oxide materials, the alkoxides of zirconium and hafnium are traditionally used in the polymer chemistry, where they are applied as the components in catalysts [1278, 1269] and as additives to polymers, improving their characteristics [825, 1403] and so on. Already in 1930s Meerwein has proposed the use of zirconium alkoxides for the reduction of aldehydes intoprimary alcohols (Meerwein-Schmidt reaction) [1420],... 

De Wet A process proposed for extracting zirconium from zircon in the form of zirconium sulfate tetrahydrate. The sodium silicate byproduct should be free from radioactive elements. The key to this process is the formation of an insoluble basic zirconium sulfate as an intermediate. Invented by W. De Wet in South Africa. 

X-ray diffraction data obtained for some of those ate complexes are consistent with a zwitterionic form incorporating a four coordinate cyclic phospho-nium center and a pentavalent 18-electron zirconium metal center. It is reasonable to postulate that the first step of the reaction is the nucleophilic attack of the phosphino group in 16a on an acetylenic carbon atom with formation of the corresponding transient zwitterion. In the second step, an intramolecular cyclization of the carbanionic center on the zirconium metal fragment occurs to form stable zirconate products 20 a -f. It was shown that the nature of the het-... 

White, heavy, amorphous, odorless, tasteless powder nr monoclinic crystals. Also forms tetragonal crystals above — 1100° cubic above —1900". d 5.85. mp 2680°. bp 4300°. Practically insol in water slightly sol in HC1, HNO, slowly sol in HP dissolves on heating with a mixl of 2 parts HjS04 and 1 part H20. Fusion with sodium carbonate results in the formation of sodium zirconate which dec hydrolytically with water to form sodium hydroxide and practically insol zirconium hydroxide. 

In the formation of lead zirconate titanate (PZT) nanorods, lead acetate, titanium isopropoxide, zirconium w-propoxide, glacial acetic acid, lactic acid, ethylene glycol, and glycerol were used for the PZT sols. The template membranes used for the growth of nanorods were track-etched hydrophilic polycarbonate (PC) with pore diameters of 100 and 200 mn and a thickness of 10 /xm. The PC membrane attached to Al cathode is placed... 

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