Zinc borates

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Zinc borates are chemical compounds of zinc from the group of borates (salts of boric acid ). They are usually in the form of hydrates .

Extraction and presentation

Zinc borates can be obtained by reacting zinc oxide and boric acid.

links

The crystalline phases in the system ZnO · B 2 O 3 · H 2 O at 20 ° C are confirmed to be 2ZnO · 3B 2 O 3 · 7H 2 O and 2ZnO · 3B 2 O 3 · 7.5H 2 O. Both hydrates can be specifically represented , but do not differ either in terms of X-ray or IR spectroscopy. In addition, the following were obtained from zinc oxide and boric acid with and without the addition of water: 2ZnO · 3B 2 O 3 · 3H 2 O, ZnO · 5B 2 O 3 · 4.5H 2 O and 6ZnO · 5B 2 O 3 · 3H 2 O. The latter compound is Can not be distinguished from 4ZnO · 3B 2 O 3 by X-ray, but by IR spectroscopy .

The compounds Zn 2 B 6 O 11 · 7H 2 O and Zn 3 B 10 O 18 · 14H 2 O are also known.

In addition, several anhydrous compounds (for example ZnB 4 O 7 and Zn 4 O (B 6 O 12 )) are known.

Zinc borates
Structural formula 2ZnO • 3B 2 O 3 • 3.5H 2 O 2ZnO · 3B 2 O 3 4ZnO • B 2 O3 • H 2 O 4ZnO • 6B 2 O 3 • 7H 2 O 2ZnO • 2B 2 O 3 • 3H 2 O Zn 3 B 2 O 6
CAS number 138265-88-0 12767-90-7 149749-62-2 1332-07-6 1332-07-6 10361-94-1
PubChem 56846126 167155

properties

Various hydrates of zinc borate are accessible from zinc oxide and boric acid. They form water-insoluble, white powders, for example:

  • ZnO · B 2 O 3 · 2H 2 O (density 3.64 g / cm 3 , stable against water loss up to 190 ° C)
  • 2ZnO 3 · B 2 O 3 · 3.5H 2 O (density 2.69 g / cm 3 , loses crystal water from 290-300 ° C).
  • 2ZnO · 3B 2 O 3 · 3.5H 2 O (Zn [B 3 O 4 (OH) 3 ]), monoclinic crystal structure with the space group P 2 1 / n (space group no. 14, position 2) and the lattice parameters a = 6.845 (2) Å, b = 9.798 (2) Å, c = 7.697 (2) Å, β = 106.966 (4) °, V = 493.8 (2) Å3 and Z = 4.Template: room group / 14.2

use

Zinc borates are used as flame retardants for plastics such as PVC , halogenated polyester and nylon , as a flux for ceramic products, and fungicides .

Individual evidence

  1. ↑ Deniz Gürhan, Gaye Ö. Çakal, İnci Eroğlu, Saim Özkar: Improved synthesis of fine zinc borate particles using seed crystals , Journal of Crystal Growth, Volume 311, Issue 6, 2009, pp. 1545–1552, doi : 10.1016 / j.jcrysgro.2009.01.111 .
  2. ↑ a b Yi-Hong Gao, Zhi-Hong Liu: Synthesis and thermochemistry of two zinc borates, Zn 2 B 6 O 11 -7H 2 O and Zn 3 B 10 O 18 -14H 2 O. In: Thermochimica Acta. 484, 2009, p. 27, doi : 10.1016 / j.tca.2008.11.013 .
  3. ↑ Lehmann, H.-A & Sperschneider, K. & Kessler, Gideon. (1967). On the chemistry and constitution of boric acid salts. XVIII. About water-containing zinc borates. Journal of inorganic and general chemistry. 354. 37-43. doi : 10.1002 / zaac.19673540109 .
  4. ↑ Azmi Seyhun Kipcak, Nil Acarali et al. a .: Synthesis of dehydrated zinc borates using the solid-state method: Characterization and investigation of the physical properties. In: Main Group Chemistry. 15, 2016, p. 301, doi : 10.3233 / MGC-160210 .
  5. ↑ a b c Entry on zinc borates. In: Römpp Online . Georg Thieme Verlag, accessed April 30, 2020.
  6. ↑ David M. Schubert, Fazlul Alam et al. a .: Structural Characterization and Chemistry of the Industrially Important Zinc Borate, Zn [B 3 O 4 (OH) 3 ]. In: Chemistry of Materials. 15, 2003, p. 866, doi : 10.1021 / cm020791z .
  7. ↑ Yao Cui, Xiaoli Liu, Yumei Tian, ​​Na Ding, Zichen Wang: Controllable synthesis of three kinds of zinc borates and flame retardant properties in polyurethane foam . In: Colloids and Surfaces A: Physicochemical and Engineering Aspects . tape 414 , 2012, p. 274-280 , doi : 10.1016 / j.colsurfa.2012.08.028 .