Low temperature synthesis and characterisation of pecoraite, a nickel containing phyllosilicate

A new procedure has been used for the fast preparation of pecoraite under n on-hydrothermal conditions of 90 degrees C and 1 atmosphere. Pecoraite was synthesised from a mixture of amorphous SiO2, a nickel salt, urea and water . The resulting products were either directly characterised by X-ray diffra ction, infrared spectroscopy and transmission electron microscopy or hydrot hermally treated at 190 degrees C and autogenous water vapour pressure for 7 days before characterisation. X-ray diffraction and transmission electron microscopy confirmed the formation of small, flaky and low crystalline pec oraite. Aging under hydrothermal conditions resulted in an increased curvat ure of the flakes and minor crystal growth. The infrared spectra are charac terised by broad bands associated with either Si-O, Ni-O or Ni-OH vibration al modes. Characteristic Ni-O(H) bands are observed around 707, 467, 456 an d 425 cm(-1), with Si-O bands around 1,043, 1,005 (single band 1,027 in the hydrothermally treated pecoraite), 899, 668 and 426 cm(-1). The bands arou nd 1,200 and 795 cm(-1) are characteristic for some amorphous silica. The O H-stretching region shows two sharp bands around 3,650 and 3,630 cm(-1) ass ociated with the external and internal Ni-OH-stretching modes of the pecora ite. Two broad H2O OH-stretching modes around 3,440 and 3,230 cm(-1), toget her with bending modes around 1,675 and 1,632 cm(-1) are related to water a dsorbed to the amorphous silica.