.Th e da ta obtain ed in the in vestigation of t he phase equilibria in the systems ber~' llia a lumina, ber yllia-titania, and a lumina-titan ia suggest that the published equilibrium diagrams of these systems n eed to be revised : the system BeO-Ti02 shows no compounds, an eutectic at about 85 weight per cent of Ti02 and 1,670° ± 3° C, and an area of Ti02 solid-solu tion . The system BeO-A120 3 has three eu tectics: (1) at 1,890° ± 10° C a nd abo u t mole r atio 1BeO: 4Ah03 (94. 2% AI,03); (2) at 1,850° ± 10° C a nd abou t mol e ratio 2BcO : 3AI,03 (85.9% Ah03); and (3) at 1,835° ± 10° C and about 75 weight percen t of A1,03, an d t wo co ngru ently melt ing co mpounds, Be O.3 A1,03 (92.4% A1,03) at 1,9 10° ± 10° C and chr,vsobery l (B eO.-AI,03-80. 3% A1,03) at 1,870° ± 10° C. The system Al, 0 3-TiOz has two eutect ics: ( 1) at 1,705° ± 5° C and about 20 weight percen t of A1,03; a nd (2) at 1,840° ± 10 0 C and about mo le rat io 5AJ,03:4TiO, (6 1.5% AI,03), and a hig h-and low-temperat ure form (a lpha a nd beta) of aluminum t itanate (AIz03.TiOz-56. 1% AI,03); t he a lpha form is stable from t he alpha-beta inversion te mperat ure of 1,820° ± 10° C and melts co ngruently at 1,860° ± 10° C, and t he beta form seems to be stable for p eriods up to 100 hours from room temperature to abo ut 750° C and from abo u t 1,300° C to its inversion te mperature. The eq uilibria for t he system BeO-AL,03-Ti02 was found to contain four invarient points : (1) at 1,572° ± 5° C and abou t mole ratio ZBeO: 1A120 3: 2Ti02 (16.1% BeO, 32.7% A1,03, 51.2 % TiO,); (2) at 1,577° ± 5° C and abou t mole ratio 2BeO: l A1,03: 4Ti02 (10.6% Be O, 21.6 % A.120 3, 67.8% TiO,); (3) a t 1,580° ± 5° C and about mole ratio IBeO:lAI20 3 :1Ti02 (12.1% B eO, 49.3% A1,03 38.6 % TiO,); and (4) probabl y at abo ut 1,755° ± 10° C and abo ut mole mlio 2Beo': 5AI,03: 2Ti02 (7.0 % B eO, 79. 8% AI, 0 3, 22.2 % TiO,). No ternary co mpounds were foun d in t his system.The genera l physical propert ies of practically imper vious porcelai ns of t hi s syste m were found to be : maturing range, usua lly 1,525° to 1,575° C, bu t with some of t he higha lumina-con tain ing bodies maturing between 1,600° and 1,700° C ; apparent d ensity. 3.3 to 3.7 g/ cm3 ; shrinkage, 11 to 19 percent ; Toom-temperature co mpressive strength , 187,000 to 280000 Ib/in.2; room-te mpera t ure transverse strengt h, 13,700 t o 25,000 Ib/ in . 2 ; Young's modulus at room temperature, 42,000,000 to 47,000,000 Ib/in .2; tran sverse strength a t 1,800° F (982° C), 10,500 to 17,000 Ib/ in.2; approximate Young's modulus at 1,800° F , 22,000,000 to 41 ,000,000 Ib/ in.2; relative the rmal-shock Tesistance, pOol' ; and the lin ear t her mal expansion of a few selected bodies, in t he range 25° to 950° C, usua lly was regular and ranged from 0 .81 to 0. 89 per cent.
The following physica,l properties were d etermined fo r so m e BeO-TiO,-ZrO, an d l3 eOCeO,-ZrO, porcelain specimens of less t ha n 0.10 perce nt equi valen t water a bsorptio n: Maturing range, 1,450° to 1,750° C; shrinkage, 13.9 to 18 .7 percent; bulk d ensity, 3.0 to 5.8 g/ cm 3; room -temp erature so ni c elastic properties-Yo ung's modulus, 18.7 to 43.6 X ] 06 Ib/ in . 2 , shear rn odulus, 8.0 to 18. 1 X 10 6 Ib/in.2, Poisson 's ratio, 0.1 7 to 0.28, and bulk m odulus, 5.3 to 12. 1 X ] 0 6 Ib/ in. 2 -for each specimen tested for transve rse strength; room-temperatu re static strength properties-transverse, 12.0 to 23.4 X 103 Ibjin.2, and comp ressive, 11 2 to 271 X I0 3 Ibjin. 2 -a nd Young's m odul us, 18.7 to 46.8 X 106 Ib/in .2; a nd , at 1,800° F (982° C), static t ransverse strength, 9.1 to 18.1 X 103 Ibjin. 2, Young's m odulus, 21.5 to 38.3 X 10 6 Ib jin.', a nd strain rates und er various str e ses. Because of t he loss of chromi a from the samples dur in g prelimi nary heatin g t ri al , no specim ens of BeO-Cr,03-ZrO, m ixtu res we re p re pared for t hese tests. The co njecture is m ade t llat po rous ox id e por celains with requ isite strength propert ies m ay prove of consid erable i ntere t in t he search for matcrials of greater thermal-s hock resistance than t hat associated with dense, practically imper vious oxide porcelain s with hi gh-strength p ropert ies.It is p roposed t hat t he phase di agram of t he BeO-T i0 2-ZrO, system in cludes a n invariant po in t at about 20-BeO, 35-TiO" a nd 45-ZrO, (wt %) a nd 1,630° C; a n invaria nt point at abo ut 20-B eO, 55-Ti 0 2, an d 25-ZrO, (wt %) and I ,610° C; and primary crystalli ;r.ation fi elds of BeO, tet ragonal ZrO, solid sol ut ion, ZrO, ·Ti02 solid sol utio n, and Ti02 solid sol ution .The limited X -ray d at a indicate t hat the BeO-CeOz-Zr02 system is a simple one lVi th an in vari a nt poin t at ap prox im ately 40-BeO , 30-CeO" and 30-ZrO, (wt %) a nd 1,845° C, a nd p r imary crystalli zation fi elds of BeO, tetragonal Zr0 2 solid solu tion, and CeO, solid solution. Based upon extremely limited data and consid erable amo un t of s pec ulation, a suggested co nfi g uratio n of t he liquidu s surfaces of the BeO-Cr, 0 3-ZrO, system would be one that contain s three invariant po in ts an d p rimary crystallization [-ields of BeO, tetragonal Zr02, BeO· C r,03, BeO · 3Cr,03, a nd Cr,0 3' B eryllium chromate (BeO· Cr, 0 3), the chl'om ia a nalog of chrysobe ryl, was id ent ified; crystallog rap hi c parameters of thi s or thorhomb ic compound were ten tatively d etermin ed as bein g a= 10.0 A, b=( 3 . lA, and c= 4.5 A.
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