Synthesis of nano-crystalline multifibrous zirconia needle

• Zirconia needles have been successfully prepared by simple inorganic sol–gel route.
• The shape of the needles was retained after firing with aspect ratio > 400.
• Needles are composed of multiple fibres.
• Fibres are composed of nano crystals.

Zirconia needles have been successfully synthesized using a simple inorganic sol–gel process without using any template. The method employs mixture of zirconium oxychloride octahydrate and sulphuric acid in aqueous medium. This process requires heat treatment at 40 °C for 2 h in an oven for nucleus formation. Complete formation of needle occurs after 17 days. The green needle retained its original shape after calcination at 1200 °C. Fired needles were of 1–2 cm in length and 5–50 μm in diameter and possess monoclinic phase. Needles are composed of multiple fibres. Depending on the heat treatment temperature, crystallite size varies in the range of 8 to around 300 nm.

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