Improved synthesis of fine zinc borate particles using seed crystals

Guerhan D., Cakal G. O., Eroglu I., ÖZKAR S.

JOURNAL OF CRYSTAL GROWTH, vol.311, no.6, pp.1545-1552, 2009 (SCI-Expanded) identifier identifier

  • Publication Type: Article / Article
  • Volume: 311 Issue: 6
  • Publication Date: 2009
  • Doi Number: 10.1016/j.jcrysgro.2009.01.111
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus
  • Page Numbers: pp.1545-1552
  • Keywords: Crystallites, Growth models, Growth from solutions, Seed crystals, Borates, Zinc compounds, BORIC-ACID, KINETICS, OXIDE
  • Middle East Technical University Affiliated: Yes


Zinc borate is a flame retardant additive used in polymers, wood applications and textile products. There are different types of zinc borate having different chemical compositions and structures. in this study, the production of zinc borate having the molecular formula of 2ZnO center dot 3B(2)O(3) center dot 3.5H(2)O Was reexamined by studying the effects of reaction parameters on the properties of product as well as the reaction kinetics. Production of zinc borate from the reaction of boric acid and zinc oxide in the presence of seed crystals was performed in a continuously stirred, temperature-controlled batch reactor having a volume of 1.5 L. Samples taken in regular time intervals during the experiments were analyzed for the concentration of zinc oxide and boron oxide in the solid as well as for the conversion of zinc oxide to zinc borate versus time. The zinc borate production reaction was fit to the logistic model. The reaction rate, reaction completion time, composition and particle size distribution of zinc borate product were determined by varying the following parameters: the boric acid to zinc oxide ratio (H3BO3:ZnC=3:1, 3.5:1, 5:1 and 7:1), the particle size of zinc oxide (10 and 25 mu m), stirring rate (275, 400, 800 and 1600 rpm), temperature (75, 85 and 95 degrees C) and the size of seed crystals (10 and 2 mu m). The products were also analyzed for particle size distribution. The experimental results showed that the reaction rate increases with the increase in H3BO3:ZnO ratio, particle size of zinc oxide, stirring rate and temperature. Concomitantly, the reaction completion time is decreased by increasing the H3BO3:ZnO ratio, stirring rate and temperature. The average particle sizes of the zinc borate products are in the range 4.3-16.6 mu m (wet dispersion analysis). (C) 2009 Elsevier B.V. All rights reserved.