Boehmite properties

The possible content of hydrated alumina and iron. Hydrated alumina minerals like gibbsite [14762-49-3] Al(OH)2, boehmite [1318-23-6] AlOOH, and diaspore [14457-84-2] AlOOH, occur ia bauxitic clays. Bauxites grade chemically iato hydrated fermgiaous and manganiferous laterites. Hence, finely divided M2O2, usually hydrated, may be a significant constituent of a clay where M may be A1 or Fe. Hydrated colloidal s ica may play a role ia the sHppery and sticky properties of certain clays. 

A comparison of boehmite with other raw materials is included in Table 6. In this table the soda and lithia contents of compositions based on a range of raw materials and the resultant properties are detailed. The level of / "-alumina was always higher with the hydrate-type raw material the hydrothermally prepared raw materials gave the highest content of / " -alumina. 

Mineralogical properties of boehmite, 2 423t of diaspore, 2 423t of gibbsite, 2 423t Mineralogy, 16 601-603 Mineral oil... 

Norbornene-ethene copolymer, 16 113 Norbornene-ethylene copolymers, 20 433 physical properties of, 20 420-422 Norbornenodiazetine derivatives, 13 306 Nordel IP (metallocene), 7 637 Nordihydroguaiaretic acid, antioxidant useful in cosmetics, 7 830t Nordstrandite, 2 421, 425 activation, 2 394 classification, 2 422 decomposition sequence, 2 392 from gelatinous boehmite, 2 427 structural properties of, 2 423t NO-reduction reactions, TWC catalyst, 10 49... 

Colloidal boehmite nanorods have been included in a PA-6 matrix to yield a homogeneous dispersion by in situ polymerization.91 At weight fractions up to 9%, improvements in the Young s modulus of the composite and changes in the crystalline morphology of the PA-6 matrix were observed, although fire properties were not reported. 

Besides trihydrated alumina, less hydrated structures, such as boehmite (monohydrate AlOOH), can be combined with FRs. Boehmite has a layered structure, like montmorillonite. Camino et al.91 have studied the incorporation of boehmite in EVA. It was concluded that boehmite improved the char forming properties but its fire retardant activity was less than that of ATH. 

Pawlowski and Schartel92 have added 1 or 5 wt % of boehmite to blends of PC/ABS with PTFE and RDP or bisphenol A bis(diphenylphosphate). The release of water from AlOOH influences the decomposition of the material by enhancing the hydrolysis of PC and RDP. Consequently, the condensed action of RDP or BDP is perturbed. The reaction of the arylphosphate with boehmite replaces both the formation of anhydrous alumina and alumina phosphate on the one hand, and the cross-linking of arylphosphate with PC on the other hand, since less phosphate is available to perform condensed-phase action. The reaction with arylphosphate therefore decreases the char formation, but the formation of aluminum phosphate could enhance barrier properties. On the whole, even high levels of fire retardancy can be achieved (V-0 ratings) the combination of boehmite with arylphosphates acting in the condensed phase seems very complex, particularly when the host polymer can undergo hydrolysis reactions due to water release. 

Standard-State chemical potentials for aqueous and solid A1(III) species are discussed carefiilly in the context of dissolution-precipitation reactions by B. S. Hemingway, R. A. Robie, and J. A. Apps, Revised values for the thermodynamic properties of boehmite, A10(OH), and related species and phases in the system Al-H-O, Am. Mineralog. 76 445 (1991). 

The procedure for the preparation of alumina spheres is as follows. Pseudo-boehmite powder (AIOOH.2H2O) is dispersed in an aqueous solution of urea and a monovalent inorganic acid, e.g. HNO3. The type of powder or powder mixture may exert considerable influence on the properties of the sol and the end product [12]. The type of acid which is used for the peptization of the pseudoboehmite powder is not very important [12], so nitric acid is used, being the most suitable one. 

Yang C. Y., Shih W. Y. and Shih W. H., Gelation, consolidation, and rheological properties of boehmite-coated silicon carbide suspensions. J. Am. Ceram. Soc. 83 (2000)pp. 1879-1884. 

In concliasion a novel class of boehmite-like Si02 Al203 has been discovered v ich shew a unique combination of properties ... 

The hydroxy oxides, especially y boehmite, have excellent coalescing properties so they are particularly good for forming large support pellets and granules. They are also used as wash coats to provide porous surfaces for catalyst adhesion to non-porous materials such as metals and ceramics. 

The sequence of phase transformations shown in Figure 2 is an approximationp largely because process variables such as time, atmosphere and properties of precursor hydroxides are not included. Thus, for example, bayerite and glbbslte may be converted to boehmite and thence to y-alumina during calcination if the particle size Is large and the precipitate Is moist [18]. 

Apps JA, Neil JM, Jun CH (1989) Thermochemical properties of gibbsite, bayerite, boehmite, diaspora, and the aluminate ion between 0 and 350°C. Washington, DC US Nuclear Regulatory Commission (prepared by Lawrence Berkeley Laboratory), p 98... 

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