Fracturing of porous alumina into thin platelets
| Autor: | S.R. Morrison, B.K. Miremadi |
|---|---|
| Rok vydání: | 1990 |
| Předmět: |
Aqueous solution
Materials science Mechanical Engineering Aluminate chemistry.chemical_element Mineralogy engineering.material Condensed Matter Physics chemistry.chemical_compound Lattice constant Chemical engineering chemistry Coating Mechanics of Materials engineering General Materials Science Lithium Crystallite Porosity Powder diffraction |
| Zdroj: | Materials Research Bulletin. 25:1139-1153 |
| ISSN: | 0025-5408 |
| Popis: | A new technique is developed, involving introduction of lithium into porous alumina and subsequent immersion of the powder in water, to fracture a porous material into angstrom-size particles. The process leads to wafer-like platelets that tend to be hexagonal in shape. The hexagonal-shaped crystallites may be a distorted alpha alumina. The X-ray powder diffraction pattern is different from known types of transition alumina. The lattice spacing of the crystallites is 7.572 A in the c- direction and 5.537 A in the a-direction. The platelets are stable in shape up to 1150°C and above this temperature tend to crumble to yet smaller size particles. The platelets are estimated to be less than 50 A in thickness and from 1 to 3 μm across. In the lithiated alumina, before immersion in water, Li 5 AlO 4 , LiOH and LiAlO 2 are present. We suggest at this stage a Li 5 AlO 4 coating on the incipient platelets protects them from reaction with the lithium metal. During immersion in water, the aluminates apparently dissolve in the water (at low pH), convert to Al(OH) 3 at medium pH, or form in part a Li-containing insoluble aluminate that coats the platelets at pH > 10. Thus the final composition of the platelets depends on the pH of the aqueous solution during immersion of the lithiated alumina. If the pH is 4 to 7, the platelets are lithium-free. |
| Databáze: | OpenAIRE |
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