ZINC OXIDE (ZnO)

ZINC OXIDE (ZnO)

Introduction

Zinc Oxide (ZnO), also known as Zinc White, is a fine, white, odorless powder. ZnO is an amphoteric oxide with a very high melting point (≈ 1975 °C). In industry, ZnO is well known for its UV absorption, semiconductor properties, and its role as an important fluxing agent in ceramic glazes.

1. Classification and Composition

• Chemical formula: ZnO
• Main chemical components: Zinc and Oxygen
  • Purity: Typically ≥ 99.5% (industrial grade) or ≥ 99.8% (pharmaceutical grade)
• Characteristic behavior: ZnO turns yellow when heated above 300 °C and returns to white upon cooling.

2. Technical Properties

3. Key Applications in Industry and Ceramics

● Ceramics & Glazes

• Fluxing agent:
  ZnO acts as a flux, lowering the melting temperature of ceramic glazes (fluxing action typically begins around 1000 °C).
• Thermal expansion control:
  With its relatively low thermal expansion, ZnO is used to partially replace higher-expansion fluxes to reduce glaze crazing.
• Matting and opacity effects:
  At higher contents, ZnO can function as a matting or opacifying agent, producing matte or crystalline glaze surfaces.
• Color interactions:
  ZnO interacts complexly with coloring oxides (such as Cr and Co), creating a wide range of color effects.

● Rubber Industry (Largest Application)

• Used together with stearic acid as an activator in rubber vulcanization, improving mechanical strength, durability, and resistance to mold growth and UV radiation.

● Pharmaceuticals & Cosmetics

• Sunscreens: UV absorber providing skin protection.
• Medicinal uses: Skin protectant for diaper rash and minor irritations; component in dental cements (zinc phosphate).

● Other Industries

• Production of anti-corrosion paints (especially effective on galvanized steel)
• Additive in concrete formulations