SOME THERMAL AND MECHANICAL PROPERTIES OF PURE-OXIDE CERAMICS
Refractoriness under a 2 kg/cm/sup 2/ load, coefficient of linear expansion ( alpha ), bending strength ( sigma /sub b/), compressive strength, ( sigma /sub comp/), and thermal-shock resistance were determined in pure-oxide sintered refractories. Samples based on alumina (Al/sub 2/O/sub 3/), zirconia (ZrO/sub 2/), magnesia (MgO), and beryllia (BeO) were compacted and fired at 15501950 deg C to form 4 x 4 x 20 mm specimens. Refractorinessunder-load and alpha were determined in a vacuum furnace, which fs described in detail. The softening point under load was found to be: in the 1860-- 1930 deg C range for Al/ sub 2/O/sub 3/base samples annd 1900 deg C for pure Al/sub 2/O/sub 3/ samples; in the technical-grade ZrO/sub 2/-based samples; and 2300 and 2450 deg C for MgO and BeO samples, respectively. It is noted, however, that the figures for MgO and BeO may not be correct because of considerable vaporization in vacuum at their softening points. Linear expansion at 1800-2000 deg C amounted to 2--3%. Both sigma /sub comp/ and sigma /sub b/ declined rapidly at 1600-- 1800 deg C. The highest sigma /sun ob/-at 1630 deg C and 483--505 kg/cm/sup 2/ was found for the pure-ZrO/sub 2/-base samples stabilized with MgO. Among Al/sub 2/O/sub 3/- base samples, those with 5% ZrO/sub 2/ had the highest sigma /sub ob/ (290 kg/cm/ sup 2/ at 1630 deg C) and sigma /sub comp/(300 kg/cm sup 2/ at 1800 deg C). MgO/ and BeO exhibited sigma /sub comp/ at 1800 deg C of 340 and 360 kg/cm/sup 2/, respectively, which are the highest of all the oxide ceramics, but their sigma / sub b/were low. BeO displayed the highest thermal-shock resistance of all the oxide ceramics studied, as evidenced by sigma /sub b/, which remained practically unchanged after one 1300 deg C-air cycle and decreased by only 30% after one 850 deg C-water cycle. Samples based on Al/sub 2/O/sub 3/ with 5% ZrO/ sub 2/ and on pure ZrO/sub 2/ with optimum CaO or MgO content showed the highest thermal-shock resistance of all Al/sub 2/O/sub 3/- or ZrO/sub 2/base samples. Additions of 1% TiO/sub 2/ and 5% ZrO/sub 2/ to Al/sub 2/O/sub 3/ contributed to a decrease in sintering temperature combined with an increase in thermal-shock resistance. (TCO)
- Research Organization:
- Originating Research Org. not identified
- NSA Number:
- NSA-17-041469
- OSTI ID:
- 4699099
- Journal Information:
- Ogneupory (U.S.S.R.) For English translation see Refractories (USSR) (Engl. Transl.), Journal Name: Ogneupory (U.S.S.R.) For English translation see Refractories (USSR) (Engl. Transl.) Vol. Vol: No. 7; ISSN OGNPA
- Country of Publication:
- Country unknown/Code not available
- Language:
- English
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Related Subjects
ALUMINUM OXIDES
BERYLLIUM OXIDES
CALCIUM OXIDES
CERAMICS
COMPACTING
EVAPORATION
EXPANSION
FURNACES
HIGH TEMPERATURE
MAGNESIUM OXIDES
MECHANICAL PROPERTIES
METALS, CERAMICS, AND OTHER MATERIALS
PRESSURE
PYROLYSIS
REFRACTORIES
SINTERED MATERIALS
SINTERING
STABILITY
TENSILE PROPERTIES
THERMAL STRESSES
THERMODYNAMICS
TITANIUM OXIDES
VACUUM
ZIRCONIUM OXIDES