| 摘要 |
PURPOSE:To obtain an acicular alumina particle with good reproducibility, the length of which is easily controlled, by previously adding acid or base into an aq. soln. of NH4HCO3 used in a ripening stage for crystallizing a reaction product of Al salt with NH4HCO3. CONSTITUTION:The reaction product, which is obtained by allowing a water-soluble Al salt such as ammonium alum or aluminium sulfate and NH4HCO3 to cause an aq. soln. reaction, is heated and applied with the ripening treatment in the aq. soln. of NH4HCO3. The ripening treatment is usually applied at 60-150 deg.C and is held at the temp. for 1-140hr. In this case, it is necessary that the acid or the base is previously added to the aq. soln. of NH4HCO3 used for the ripening treatment and then the ripening treatment is applied. In this case, the length of the generated alumina particle is controlled with the amt. of the added acid or base. Then, sulfuric acid or hydrochloric acid, etc., for example, is used as the acid, and KOH, NaOH, etc., for example, is used as the base, respectively.
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