Zirconium oxide conductivity

The equilibrium is more favorable to acetone at higher temperatures. At 325°C 97% conversion is theoretically possible. The kinetics of the reaction has been studied (23). A large number of catalysts have been investigated, including copper, silver, platinum, and palladium metals, as well as sulfides of transition metals of groups 4, 5, and 6 of the periodic table. These catalysts are made with inert supports and are used at 400—600°C (24). Lower temperature reactions (315—482°C) have been successhiUy conducted using 2inc oxide-zirconium oxide combinations (25), and combinations of copper-chromium oxide and of copper and silicon dioxide (26). 

The heavy mineral sand concentrates are scmbbed to remove any surface coatings, dried, and separated into magnetic and nonmagnetic fractions (see Separation, magnetic). Each of these fractions is further spHt into conducting and nonconducting fractions in an electrostatic separator to yield individual concentrates of ilmenite, leucoxene, monazite, mtile, xenotime, and zircon. Commercially pure zircon sand typically contains 64% zirconium oxide, 34% siUcon oxide, 1.2% hafnium oxide, and 0.8% other oxides including aluminum, iron, titanium, yttrium, lanthanides, uranium, thorium, phosphoms, scandium, and calcium. 

The dehydration of 1-hexanol to hexene was conducted over heterogeneous sulfated zirconium oxide catalyst [19, 138]. The zirconia was treated with sulfuric acid and is known as super acid catalyst, having well documented performance for many reactions [19]. The reaction conditions are notably milder as for other acid catalysts, such as silica-alumina. 

OS 80] [R 7] [P 60] The acid-catalyzed dehydration of of 1-hexanol to hexene was conducted in a micro reactor made of PDMS, which also contained a heahng fimc-hon [19, 138], Sulfated zirconium oxide was coated as catalyst on the top plate of the micro reactor. A yield of 85-95% was obtained by-products could not be detected. This performance exceeds those of conventional reactors (30%). 

One pair of electrodes conduct an electrical current through the zirconium oxide wall, thereby transporting oxygen from the external atmosphere through the cell wall, into the nitrogen carrier gas. The other pair is used to measure the potential difference over the zirconium oxide. 

Modern ceramic materials now include zirconium oxide (Zr02), titanium carbide (TiC), and silicon nitride (SiN). There are now many more uses of these new ceramic materials. For example, vehicle components such as ceramic bearings do not need lubrication - even at high speeds. In space technology, ceramic tiles protected the Space Shuttle from intense heat during its re-entry into the Earth s atmosphere. In the power supply industry, they are used as insulators due to the fact that they do not conduct electricity (Figure 3.39). 

Solid Oxide Fuel Cell In SOFCs the electrolyte is a ceramic oxide ion conductor, such as yttrium-doped zirconium oxide. The conductivity of this material is 0.1 S/cm at 1273 K (1832°F) it decreases to 0.01 S/cm at 1073 K (1472°F), and by another order of magnitude at 773 K (932°F). Because the resistive losses need to be kept below about 50 mV, the operating temperature of the... 

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. 

Zr02+ 15 mole%CaO calcia-stabilized zirconium oxide 17.3.7 defect structure and mechanism of ionic conduction 17.3.7.3 oxygen ion resistivity of polycrystalline material 17.3.7... 

Fig. 7.16.2 shows a cross section of the sensing element. The sensing element mainly consists of six layers of yttrium-doped zirconium oxide, which has a high capability against thermal stress and promotes O2- conductivity. The basis for such Oz conductivity is the temperature of more than 600 °C. The pumping electrodes mainly consist of platinum. 

The most frequently used source of infrared light for infrared spectrometers is so called the Nemst stick. This stick is about two to four centimeters long and one to three millimeters thick, and is made from zirconium oxide with additions of yttrium oxide and oxides of other metals. This mixture of oxides has a negative temperature coefficient of electrical resistance. This means that its electrical conductivity increases with an increase in temperature. At room temperature, the Nemst stick is a non-conductor. Thus, an auxiliary heating is necessary for ignition of the Nernst stick. Even if the Nernst stick is red-hot, it can be heated further by electricity. The normal operating temperature of this infrared light source is approximately 1900 K. 

Production of ZrCl4. Zirconium oxide from the hafnium-separation step was mixed with carbon black, dextrin, and water in proportions 142 Zr02, 142 C, 8 dextrin, and 8 water. The mixture was pressed into small briquettes (3.8 X 2.5 X 1.9 cm) and dried at 120°C in a tray drier. The oxide briquettes were charged to the reaction zone of a vertical-shaft chlorinator lined with silica brick. The charge was first heated by carbon resistance strips until it became conductive. During production, the bed temperature was maintained at 600 to 800 C by an electric current passed directly through the bed. After steady conditions were reached, a reactor 66 cm in diameter produced about 25 kg ZrCLt/h. The ZrCU was condensed from the reaction products in two cyclone-shaped aftercondensers in series, and the chlorine off-gas was removed in a water scrubbing tower. 

Calcia-stabilized zirconium oxide 18, 17.3.7 Defect structure and mechanism of ionic conduction 18,17.3.7.3 Oxygen ion resistivity of polycrystalline material 18, 17.3.7 OiZr... 

Complex FCC oxides of the fluorite type represent oxygen-conduction solid electrolytes (SOE s). They comprise a typical class of materials for the manufacture of sensors of oxygen activity in complex gas mixtures, oxygen pumps, electrolyzers and high-temperature fuel elements. These materials are based on doped oxides of cerium and thorium, zirconium and hafnium, and bismuth oxide. Materials based on zirconium oxide, for example, yttrium stabilized zirconia (YSZ) are the most known and studied among them. This fact is explained both by their processibility and a wide spectrum of practical applications and by the possibility to conduct studies on single crystals, which have the commercial name "fianites" and are used in jewelry. 

The technology is developed and production with output of high-density electrical conductivity ceramics from stabilized zirconium oxide is organized in O.J.S.C. Ukrainian research institute of refractories named after A.S. Berezhnoy . The application of this ceramics is developed when using it in high-temperature electrochemical devices. 

The unique property of solid solutions on the basis of zirconium oxide is oxygen-ionic conductivity and it is due to their crystal structure type. The solid solution of stabilized zirconium oxide has a cubic structure of fluorite type with anionic vacancies that leads to electrical conductivity abrupt increase at temperature increase of > 600° C. 

Among the most important demands that are made for electrolytes on the basis of zirconium oxide is combination of high electrical conductivity with ageing stability in the range of operating temperatures (900-1000° C). 

In the present feature there are research results of influence of stabilized additions of scandium, yttrium or lutecium oxides and their amount on its phase composition, temperature and time dependence of electrical conductivity of zirconium oxide samples that are fired at 1900° C. 

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