Action of water on calcium aluminoferrites
1964; The National Institute of Standards and Technology; Volume: 68A; Issue: 5 Linguagem: Inglês
10.6028/jres.068a.044
ISSN2376-5704
Autores Tópico(s)Aluminum Alloys Composites Properties
ResumoThe action of \I'ater o n scven p reparatio ns of t he calcium a luminorer ri te sol id solution seri es, ranging in composit ion from 6CaO• 2A120 3• F e 20 a to 2CaO• Fc20 a, was studi cd (a) by leaching the p owdered prcparations \\'ith water, (b) by sti rrin g in a largC' volu nll' of lI'atN at different temperatures from 10 to 100 °C, and (c) by paste hydration at 1, 25, and 45 °C.The in it ial reaction occ urri ng immediatcl.v on eontact bet\l'ce n the alumin ofcrritc and water is one of incongru e nt solution.T he A120 3, most of the CaO, and a t race of FezOa pass into solution, and a residue of Fe20 " possibly hyd rated a nd amo rphous, remains.If the suspension is suffi cie ntly co ncentrated to give a s upersaturated solution, a hyd rated p recip itate w ill fo rm .At room tempe rature the major p recipitated phase is 2CaO • A120 3• 8H , 0, or a limi ted soli d solu t ion of the same.At 70 °C a soli d solu t ion of 3CaO • AI20 , ' 6H 20, in \\' hi ch about one-te nth of the Al, 0 3 is rep laced by Fe 20 3, is precipitated.The rate of reaction increases with temperature and with the proportion of alumina in the alu minofer rite.Hydration in pas te form progrcsses in a d iffe rent mann er.The hydroga rnet phase prod lI ced va ri es in com posit ion wit h the pa re nt a lu m i nofe rrite, but is a l ways some \I' hat poorer in Fe 20 3. The hexagonal plate phase, 4CaO• (A I20 3,Fe 2 0 a) •nH zO is p roduced from the alumin ofe rri tes hi g h in Fe 20 a, esp ecia ll y at the 10IVer tempe ratures.Anothe r platy phase, 2CaO•A I20 a•81-I 20 (o r its limited soli d solu tion ) is formed from preparations hi ghest in AI20 a, also at 10IVer temperatures.Inte rmed iate m e mbers give ch iefly the hydroga rn et p hase cven at 25 °C.
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