operated at 40 kV and 30 mA, equipped with Cu Kα radiation
at a wavelength of 0.1546 nm and a curved graphite crystal
monochromator.
Samples were scanned over the range of diffraction
angle of 2θ = 1 to 10◦ with a scanning rate of 0.4◦/min at
room temperature.
The basal spacing of the silicate layer (d001) was
calculated using the Bragg’s equation, λ = 2d sin θ, where λ is
the wavelength of the X-ray radiation used (0.1546 nm), d is the
spacing between diffractional lattice planes, and θ is the measured
diffraction angle.