Mechanism of Inorganic-organic Surface Modification of Anhydrous Calcium Sulfate Whisker

doi:10.15541/jim20160249

Abstract

Abstract:

Anhydrous calcium sulfate whisker (ACSw) was modified by dual-surface modification with sodium silicate solution as inorganic modifer and stearic acid as organic modifier. The samples were characterized by water contact angle (WCA), X-ray diffraction (XRD), field emission scanning electron microscope(FESEM), fourier infrared spectrum (FT-IR), and X-ray photoelectron spectroscope (XPS). The results showed that ACSw surface property changed to Hydrophobic after inorganic-organic modification, while its crystal structure remained unchanged. FT-IR and XPS resutls indicated that -Ca-SiO₃ structure was generated firstly on the surface of whiskers after reaction with sodium silicate solution. And then a mixing coating layer containing both -Ca-HSiO₃ and -Ca-COOR structures were formed through bonding interaction with stearic acid rather than physical absorption after particle hydrolyzation of -Ca-SiO₃ structure.

Key words: anhydrous calcium sulfate whisker, dual-surface modification, chemical adsorption

CLC Number:

O611

LV Zhi-Hui, HONG Tian-Zeng, NAI Xue-Ying, DONG Ya-Ping, LI Wu. Mechanism of Inorganic-organic Surface Modification of Anhydrous Calcium Sulfate Whisker[J]. Journal of Inorganic Materials, 2017, 32(1): 81-85.

Figures/Tables 9

Fig. 1 Contact angles of (a) organic modified sample, (b) unmodified sample, (c) inorganic modified sample, and (d) inorganic-organic modified sample

Fig. 2 XRD patterns of (a) unmodified sample, (b) inorganic modified sample and (c) inorganic-organic modified sample

Fig. 3 SEM images of (a) unmodified sample, (b) inorganic modified sample and (c) inorganic-organic modified sample

Fig. 4 FT-IR spectra of (a) unmodified sample, (b) inorganic modified sample, (c) inorganic-organic modified sample, (d) stearic acid, and (e) calcium stearate

Fig. 5 XPS spectra of (a) unmodified sample, (b) inorganic modified sample and (c) inorganic-organic modified sample

Table 1 Atomic percentage of different element in samples

	Unmodified sample	Inorganic modified sample	Inorganic-organic modified sample
Ca/at%	11.41	10.38	3.91
S/at%	12.72	1.38	0.41
O/at%	49.57	56.96	26.52
Si/at%	-	16.38	7.43
C/at%	26.3	14.89	61.73
O/atSi	-	3.48	3.57
C/atCa	2.30	1.43	15.79

Fig. 6 C1s spectra of (a) unmodified sample, (b) inorganic modified sample and (c) inorganic-organic modified sample

Fig. 7 Ca2p3/2 spectra of (a) unmodified sample, (b) inorganic modified sample and (c) inorganic-organic modified sample

Fig. 8 Modification mechanism of anhydrous calcium sulfate whisker

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