Zirconium dioxide ceramics

Exposure limits for siHcon carbide and powders of zirconium compounds (including zirconium dioxide) have been estabHshed by ACGIH. TLV—TWA s are 10 mg/m and 5 mg/m, respectively. OSHA guidelines for zirconium compounds call for a PEL of 5 mg/m. There are no exposure limits for siHcon nitride powder, but pmdent practice suggests a TLV—TWA of 0.1 mg/m. The soHd ceramics present no apparent health hazard. In machining such ceramics, however, care should be taken to prevent inhalation of respirable particles in amounts in excess of estabHshed limits. Disposal should be in approved landfills the materials are inert and should pose no danger to the environment. 

The following laboratory method was used for the introduction of zirconium phosphate into ceramic porous strucmres. The method is based on impregnation of the porous materials with crystalline sol of zirconium dioxide. 

For the preparation of sol, 25% solution of NH3 was added in small portions (2 mL) to 1 L of 1 M solution of ZrOCU while heating under mechanical stirring. The temperature of solution did not exceed 90°C. Each following portion of NH3 solution was added only after complete dissolution of the zirconium hydroxide precipitate. The addition of the NH3 solution was terminated once the zirconium hydroxide precipitate did not dissolve within 20 min. The raw sol obtained was boiled using a reflux condenser for 25 h to allow the formation of the crystalline strucmre. Thereafter the sol was cooled to ambient temperature and filtered. Ceramic materials were immersed in 1 M sol of zirconium dioxide that was prepared as described... 

Zirconia, see also zirconium dioxide ceramics, 339—340 stabilized, 23, 339—340 Zirconium boride, 345, 346 Zirconium dioxide, 22—23, 374, 387—389 see also zirconia Zirconium silicate, see zircon... 

A third class of bioceramics are based on Zr02, stabilized by Y2O3 or Ce02. These materials are close to aluminum oxide materials in terms of biocompatibility but exhibit a higher bend strength and crack resistance, though with lower compressive strength. Zirconium dioxide ceramics can be used for many of... 

Zirconium dioxide, Zr02, displays a variety of desirable properties including hardness, chemical durability and corrosion resistance. It is employed in numerous applications such as coatings for cutting tools, optical filters, thermal barrier coating, interfacial coatings in fiber reinforced ceramic matrix composites, dielectric films in microelectronics [24] and other applications such as mirrors [25] and sensors [26]. 

ADA/DEN] Adair, J. H., Denkewicz, R. P., Arriagada, F. J., Osseo-Asare, K., Precipitation and in situ transformation in the hydrothermal synthesis of crystalline zirconium dioxide, Ceram. Trans., 1, (1987), 135-145. Cited on page 409. 

The working time of HT-probes decreases quickly over glass meltings with increasing temperature [55]. Vapors of the oxides, above all of sodium, potassium, silicium, lead, an-timon and arsen condense on the probe material in the temperature gradient from the inside to the outside of the tank wall. The condensed substances penetrate into the ceramic material over grain boundaries and lead to tube bursts. Thereby the stabilized zirconium dioxid is more sensitive than alumina. Componenu which contain Si02 must not be used in HT-probes [56]. 

The method of Zintl and Brauer uses pieces of pure Li milled clean under an Ar blanket. These pieces are then transferred in the absence of air to a vessel described by Zintl and Woltersdorf (Fig. 272) and nitrided. The crucible t is made of zirconium dioxide coated with fused lithium fluoride (m.p. 840°C). In contrast to most ceramic and metal vessels, these crucibles are completely resistant to liquid Li up to 800°C, thus allowing the preparation of pure Li compoimds from the metal. Crucible t is set inside an iron protective crucible e, which is placed in a ceramic tube r. 

Makarenko A.N., Belous A.G., Pashkova Y.V. Structure Formation and Degradation Partially Stabilized Zirconium Dioxide, J. Europ. Ceram. Soc., 1999, V.19, p. 945-947. 

In 1997-98, in connection with the contract with LLNL, experiments on the synthesis of ceramics for immobilization of surplus weapons plutonium are being carried out. For these purposes, the ceramic used is mainly zirconium on the basis of zircon (ZrSi04) and zirconium dioxide (Zr02). Samples with a 10% Pu content are synthesized. 

The given material is characterized not only by chemical, but also by phase heterogeneity. The various phases have unequal reaction ability, i. e., during the synthesis of ceramics the preservation of the unreacted free phases of plutonium is rather probable. To increase the reaction ability of the precursor, it was offered to use an additive of surplus quantity of metal zirconium powder with a subsequent synthesis of polyphase ceramics on the basis of zircon/zirconium dioxide (Zr,Pu)Si04/(Zr,Pu)02, as well as other phases of non-radioactive elements -impurities. 

We are studying the possibility of applying ceramics on the basis of the cubic modification of zirconium dioxide (Zr,Pu)02, taking into account that PUO2 not only forms wide varieties of solid solutions with Zr02, but also is capable of stabilizing the cubic modification of zirconium dioxide. 

Dudnik EV, Zaitseva ZA, Shevchenko AV, Lopato LM (1995) Sintering of ultradisperse powders based on zirconium dioxide (Rev). Powder Metall Met Ceram 34 263-271... 

Single oxide ceramics, e.g. aluminium oxide (AI2O3, alumina) and zirconium dioxide (Zr02, zirconia), are bioceramics of an inert nature. An inert ceramic does not form a bonding to bone similar to those bioceramics of bioactive nature. Alumina bioceramics are in the pure aluminium oxide form, whereas zirconia bioceramics are partially stabilized by additional oxides, e.g. yttrium oxide, calcium oxide or magnesium oxide. 

An important class of zirconium dioxide ceramics is known as partially stabilized zirconia (PSZ),... 

Defects also can be found from the film (point 3 in Fig. 21(b)). The colour of defects is similar to the film but obviously different from the original material. Moreover, defect is smaller and shallower than the original material. The results indicated that the material composition of the defect and film is roughly the same. Zirconium dioxide is ionic crystal, the adsorption affinity to the chip is higher. The ceramic chips mixed with workpiece chips and form the continuous film, the defect is the damage of the mixed film... 

A schematic view of a lambda probe is given in Fig. 7.12. A hollow part in the form of a finger made of zirconium dioxide ceramics protrudes into the studied gas compartment. The ceramic body is covered on either side by a gas-permeable platinum layer. Its inner volume is in contact with ambient air. The emf E is measured between the inner and outer platinum layers. The oxygen partial pressure in the compartment studied is calculated by means of Eq. (7.11). 

Zirconia ceramics are used for a variety of applications as catalysts, structural materials, and electrolytes for solid-oxide fuel cells. Zirconia (zirconium dioxide ZrOg) exhibits a phase transition sequence, " ... 

TEXTURE AND SINTERTNG OF ZIRCONIUM DIOXIDE-YTTRIUM OXIDE CERAMICS... 

Powders of partially stabilized zirconium dioxide-yttrium oxide ceramics (PSZs) were prepared at room temperature and under nitrogen at atmospheric pressure by hydroiysis of zirconium and yttrium alcoholates solutions containing a carboxyiic acid. 

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