Studies of binary and ternary combinations of magnesia, calcia, baria, beryllia, alumina, thoria and zirconia in relation to their use as porcelains

Abstract

Barium oxide (BaO).-Introduced as reagent quality BaCOa. Beryllia (BeO).-(1) Commercial "SP grade," usually used in making the porcelain specimens, and nominally of 99.7-percent purity. Spectrograms showed only traces of copper, iron and magnesium, and very weak lines for silicon.(2) Commercial "CP grade," usually used in specimens for fusionpoint and softening-range determinations, nominally of over 99.9-percent purity.Calcium oxide (CaO).-Introduced as reagent quality CaCOa. Magnesium oxide (MgO).-(l) Fused MgO (periclase) of approximately 97-percent purity, usually used in making porcelain specimens.(2) Calcined MgCOa (calcining temperature given by producer as 2,000° F). Very fine grained, purity about 99 percent, and used in a relatively small number of specimens.(3) Especially selected, water clear, crystals of periclase,2 which were hand ground in agate or mullite mortars and usually used in bodies for fusion-point and softening-range tests. The purity is nominally over 99 percent.Silica (Si02).-Pulverized natural quartz of 99.6-percent purity. Strontia (SrO).-Introduced as reagent quality SrC03• Titania (Ti02).-Trade designation "pigment grade," purity about 99 percent, with Fe20a given by the producer as less than 0.2 percent.Thoria (Th02).-Calcined thoria, nominally of over 99-percent purity. Spectrograms showed only very weak lines for calcium, copper, and silicon, and no other impurities were indicated.Zirconia (Zr02).-A CP grade of calcined zirconia, and recalcined at 1,440° C. The spectrogram showed medium lines for columbium and titanium and only very weak lines or traces for calcium, copper, iron, magnesium, lead, and silicon.In order to obtain the desired fineness of particle size, it was necessary to grind the SP BeO, the commercial grade AI20 a, and the Th02• The BeO described above had been ground wet for 2 hours in porcelain-lined mills with flint pebbles. The A120 a and the Th02 had been ground for 48 hr. in a steel mill ",ith steel rods, and then purified by treatment with diluted HOI until the wash water gave a negative test for iron. 3 III. METHODSSpecimens were prepared during the first stages of the work by hand-mixing the ingredients in slip form, drying, pulverizing in an agate or in a mullite mortar, remL'{ing with a 5-percent solution of soluble starch, and pressing in hardened steel moulds. About 14 g of the starch solution was used for 100 g of dry batch, and the forming pressure was 9,300 Ib/in 2 • Later, the method was improved by machine-blunging the slip with a chemical-Iaboratory-type stirrer, and by vibrating the dampened mixture in the steel moulds before pressing. The pressed specimens were matured in an electric furnace, heated with eight Th02-Y20a resistors, described in Bureau Research Paper RP1662 [12]. The heating and cooling rates were maintained very close to 3°0 per min, and the holding time at the maximum temperature usually was 1 hr. A typical setup with three specimens , Furnisbed by tbo Vitrefrax Corporation and by the Norton Co .• Comparative tests were made ...

Atomic thermal parameters and thermodynamic functions for chrysoberyl (BeAl2O4) from vibrational spectra and transfer of empirical force fields

“…For a, the estimate (=13.8+0.011TIxK -~) reported by Hofmeister, Hoering & Virgo (1987) can be adopted, in line with the data reported by Fizeau (1888) and by Geller, Yavorsky, Steierman & Creamer (1946). This estimate is surely inadequate for the lowest temperatures, since it is not zero at 0 K as it should be according to theory.…”

The Passivity and Breakdown of Beryllium in Aqueous Solutions

“…The dielectric constant used for beryllium oxide was 6.3. 23 The thickness for the oxide layer formed at the OCP was determined to be 20.1 1.3 A.…”

Twinning and epitaxial growth of taaffeite-type modulated structures in BeO-doped MgAl2O4

“…4 In addition to indirect evidences for Be provided by transmission electron microscopy (TEM) methods and Pauling's principle of electroneutrality the authors further supported their hypothesis by the existence of close structural relationship between spinel (MgAl 2 O 4 ) 6 and chrysoberyl (BeAl 2 O 4 ), 7 and the existence of intermediate polytypic, taaffeite-type (Be x Mg y Al 2(x+y) O 4(x+y) ) series. [8][9][10][11][12][13][14][15][16][17][18] The common feature that can be observed on twin boundaries, taaffeite compounds as well as in the chrysoberyl structure is the presence of Be 2+ on the tetrahedral sites next to the hcp stacking of the oxygen sublattice. In the spinel structure, oxygen-sublattice is repeated in cubic, ccp stacking, along all four ,111.-axes, whereas in the chrysoberyl structure, the oxygen sublattice is repeated in hcp stacking along the ,0001.-axis.…”