17 stability of the coating under the experimental flow rate regime Neti
Joshi, 2010. iv.
Scratch test
, a simple test by using sophisticated equipment. A stylus with diamond tipped glass marker will be used to scratch the coating surface, thus
examining the hardness and durability of the coating material.
2.5.2 X-ray Diffraction XRD
Glancing angle x-ray diffraction can be used to analyse the composition of thin films such as the antimicrobial coating because crystalline material diffracts x-rays in a
material specific manned. However, the XRD that needed to be investigated onto the substrate is using the method of glancing angle due to the nature of the thin films. An angle
of incidence of 1.5° over an angular range of 10-90° was used to investigate the thin film by using glancing angle. The XRD has the X-ray wavelength A is typically 0.7-2
Å,
which corresponds to X-ray energies E = 12.4 keVA of 6 - 17 keV Brundle, et al., 1992. An
example of the anatase peaks of TiO
2
thin film on stainless steel XRD in Figure 2.3:
18
Figure 2.3: XRD patterns of the TiO
2
thin films on 316L Stainless steel, calcined at different temperatures of 350-550 °C Barati, et al., 2009
The peaks as stated in the Figure 2.3 showed that once the diffracted X-ray intensity recorded at diffraction angles meet the Bragg condition. The anatase peaks exists
at the degree 25.3°, 37°, 48°, 54°, 55.6°. The XRD results will be analysed to achieve the calculations for the percentage of anataserutile in the crystalline phases and the crystallite
nanoparticle size. The anataserutile phase was determined through the intensity XRD peaks and the Spurr and Myers equation Spurr Myers, 1957 in Equation 2.1.
= 1
1 + 1.26[ 101
101 ] 2.1
Equation 2.1: Anataserutile ratio where F
R
is the percentage content of rutile at each temperature, I
A
101 and I
R
110 are the integral intensities of 101 anatase and 110 rutile, respectively.
19 While the average crystallite size was estimated by Scherrer equation Cullit, 1987 is as
shown in the Equation 2.2.
= × cos
2.2 Equation 2.2: Scherrer equation, where L is the crystallite size, K is Scherrer constant
given value at 0.89, is the wavelength of the X-ray radiation CuK = 0.15418, is the width at half maximum height and cos is the Bragg angle.
Another study conducted by Atabaki, et al., 2010, they had investigated the degree of crystallinity influences dissolution of hydroxyapatite HA coating. The results
showed that the presence of higher extent of crystalline structure induced lesser dissolution of the coating. The strongest peaks for HA coating sintered at 900 °C appears in the range
29.234–31.038 of 2 angles. They concluded that as the sintering temperature increases, intensity also increases due to high crystallization rates at high temperature.
2.5.3 Scanning Electron Microscopy SEM
