Dissertation summary: Study on effect of Fe3O4 nanoparticles on polymer nanocomposite coating for corrosion protection

The main contents of the thesis: Synthesis and characterization of Fe3O4 nanoparticles, -Fe2O3 nanoparticles and γ-Fe2O3 nanoparticles by hydrothermal method. Compare the corrosion protection ability of epoxy film containing synthetic iron oxide particles. Fabrication and evaluation of steel corrosion protection effect of epoxy membrane containing magnetic iron oxide nanoparticles and nano iron oxide from organic denaturation with some silane compounds and with corrosion inhibiting compound.

MINISTRY OF EDUCATION

AND TRAINING

VIETNAM ACADEMY OF SCIENCE AND TECHNOLOGY

GRADUATE UNIVERSITY OF SCIENCE AND

TECHNOLOGY -

NGUYEN THU TRANG

STUDY ON EFFECT OF Fe3O4 NANOPARTICLES IN POLYMER NANOCOMPOSITE COATING FOR CORROSION

PROTECTION

Scientific Field: Polymer and Composite Classification Code: 62.44.01.25 DISSERTATION SUMMARY

HANOI – 2019

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The dissertation was completed at: Institute for Tropical Technology - Vietnam Academy of Science and Technology and Faculty of Chemistry, Hanoi University of Science - Vietnam National University

Scientific Supervisors:

1 Assoc Prof Dr Trinh Anh Truc

Institute for Tropical Technology - Vietnam Academy of Science and Technology

2 Assoc Prof Dr Nguyen Xuan Hoan

Dept Physical Chemistry, Faculty of Chemistry, Hanoi University of Science - Vietnam National University

1st Reviewer:

2nd Reviewer:

3rd Reviewer:

The dissertation will be defended at Graduate University of Science And Technology, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Cau Giay District, Hanoi City

At… hour… date… month… 2019

The dissertation can be found in National Library of Vietnam and library of Graduate University of Science And Technology, Vietnam Academy of Science and Technology

Protecting metal with organic coating has been widely used because of its effectiveness, ease of processing and reasonable cost Currently, the new trend in the field of organic coatings is to find new inhibitors to replace toxic chromates, creating an environmentally friendly coating, etc Nanotechnology has come to life and created tremendous breakthroughs Highly reactive pigments with nano dimensions when applied to organic coatings to protect metal corrosion from concentrations of 2 - 3% show breakthrough properties In particular, iron oxides are considered as pigments used in paint with all colors depending on the type of iron oxide used, especially Fe3O4 magnetic iron oxide, corrosion protection ability so far The mechanism is still unclear

For the above reasons, we propose the dissertation: “Study on effect

of Fe3O4 nanoparticles on polymer nanocomposite coating for corrosion protection”

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2 The main contents of the thesis

- Synthesis and characterization of Fe3O4 nanoparticles, -Fe2O3

nanoparticles and γ-Fe2O3 nanoparticles by hydrothermal method Compare the corrosion protection ability of epoxy film containing synthetic iron oxide particles

- Fabrication and evaluation of steel corrosion protection effect of epoxy membrane containing magnetic iron oxide nanoparticles and nano iron oxide from organic denaturation with some silane compounds and with corrosion inhibiting compound

- Research on using microstructure analysis methods to clarify the role

of nanoparticles in improving the anti-corrosion protection of products

DISSERTATION CONTENTS CHAPTER 1 LITERATURE REVIEW

The literature review provided an overview:

 Introduction about iron oxides and their applications containing: FeO,

α-Fe2O3, γ-Fe2O3, Fe3O4 This chapter focus on characteristic of structure, properties and thermal synthesis method of Fe3O4

 Introduction about surface modification of Fe3O4 nanoparticles: surface properties, modification method of particles, stabilization of particle surface

 Introduction about corrosion protection of coating prepared by polymer nanocomposite

CHAPTER 2 EXPERIMENTS 2.1 Material and equipments

 FeSO4.7H2O , FeCl3.6H2O, KOH, C2H5OH, Xylene, HCl, HNO3,

Diethoxy(methyl)phenylsilane (DMPS), Tetraethoxysilane ( TEOS), Indol 3-Butyric axit (IBA), Irgacor 252, 2-(1,3-Benzothiazol-2-ylthio) succinic axit (BTSA), epoxy resin (Diglycidyl ete of Bisphenol A,

Epotec YD 011-X75) and hardener polyamide 307D-60

2.2 Synthesis iron oxides by hydrothermal method

 Synthesis α-Fe2O3 nanoparticles : FeCl3.6H2O was dissolved with distilled water Under stirring, a KOH solution was added to the solution until the formation of a precipitate occurred Hydrothermal

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reaction was conducted at 180oC for 15 h After reaction, the precipitate

was washed with distilled water and dried in a vacuum oven

 Synthesis Fe3O4 nanoparticles: a mixture of FeCl3.6H2O/FeSO4.7H2O (molar ratio Fe2+/Fe3+ = 1/1) was dissolved with distilled water Under stirring, a KOH solution was added to the solution until the formation

of a precipitate occurred Hydrothermal reaction was conducted at

150oC for 7 h After reaction, the precipitate was washed with distilled water to remove impurity ions (Cl- , SO42- , K+ ) and dried in a vacuum

oven

 Synthesis γ-Fe2O3 nanoparticles: Thermal treatment process for synthesized Fe3O4 nanoparticles at190oC for 2 hours

2.3 Modification Fe3O4 nanoparticles with organic compounds

 Modification Fe3O4 nanoparticles with silane: Silane was dissolved with mixture solvent of etanol/distilled water (19/1 ratio) Fe3O4 was added to the solution then stirring and using ultrasonic vibration The reaction mixture was kept at 60oC for 60 minutes with mechanical stirring Afterwards, particles were washed and dried in oven at 50oC for 10 hours

 Modification Fe3O4 nanoparticles with corrosion inhibitors: IBA (or BTSA) was dissolved in a water/ethanol mixture (1/19 ratio) Then, the

Fe3O4 nanoparticles were dispersed by disperser and then mechanically stirred and ultrasonic vibrated for 15 minutes and 30 minutes, respectively The mixture was left in 3 hours Afterwards, the precipitate was filtered and washed with ethanol several times to remove the excess IBA The modified Fe3O4 nanoparticles were finally dried in a vacuum oven at 60oC for 10 hours

2.4 Preparation of epoxy coating containing iron oxides and modified iron oxides

Carbon steel plates (150 mm x 100 mm x 2 mm) were used as substrates which were cleaned and dried before coating The pre-polymer mixtures (with or without particles) were applied by spin-coating at a speed of 600 rpm for 1 min After polymerization and drying at room temperature for 24 hours, the coatings were about 30 µm

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2.5 Analytical characterizations for nanoparticles

FT-IR analysis, X-rays diffraction, UV-Vis, TGA analysis, SEM, Zeta potential, saturation magnetization

2.6 Method for evaluation properties of coatings:

Evaluation method for physical and mechanical properties of coatings: impact strength, pull-off strength, wet adherence

Corrosion testing for coatings:

+ Electrochemical impedance spectroscopy

+ Salt spray test was used in order to evaluate the corrosion protection of the samples

CHAPTER 3 RESULTS AND DISSCUSIONS 3.1 CHARACTERISTICS AND PROPERTIES OF IRON OXIDES 3.1.1 Characterization of Fe3O4 nanoparticles

Figure 3.1 The XRD pattern of pure magnetite obtained by hydrothermal method

Figure 3.1 showed the diffraction pattern that allowed for unequivocal identification of magnetite; using the ICSD (Inorganic Crystal Structure Database) reference code 01-076-1849 for magnetite the diffraction peaks were identified

Figure 3.2 showed SEM images of Fe3O4 particles obtained by the hydrothermal treatment. The uniform particle morphology and size of synthesized Fe3O4 were observed The results confirm that nanoparticles with average particle size around 50 - 70 nm were observed

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FTIR spectrum of Fe3O4 nanoparticles is shown in Figure 3.3

Figure 3.3 FT-IR spectrum of

The result showed that absorptions in

3431 cm–1 and 1629 cm–1 are responsible to O-H that adsorbed on the surface of the nanoparticles and absorption at 586 cm–1 and

447 cm–1 are related to Fe-O bonds in nanoparticles

3.1.2 Characterization of α-Fe2O3 nanoparticles

Figure 3.4 The XRD pattern of pure

magnetite obtained by hydrothermal

method

Figure 3.4 showed the diffraction pattern that allowed for unequivocal

identification of hematite; using the ICSD (Inorganic Crystal Structure

Database) reference code 01-079-0007 for hematite the diffraction peaks

were identified

hydrothermal method

Figure 3.5 showed SEM images of α-Fe 2 O 3 particles obtained by the

hydrothermal method The uniform particles in morphology and size of

synthesized Fe3O4 were observed The results confirm that nanoparticles had

average particle size around 70 - 80 nm which was not good in comparison

with Fe3O4

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FTIR spectrum of α-Fe2O3

nanoparticles is shown in Figure 3.6 The

result showed that absorption at 565 cm–1 and

476 cm–1 are related to Fe-O bonds in

nanoparticles and absorptions in 3420 cm–1

and 1625 cm–1 are responsible to O-H that

absorbed on the surface of the nanoparticles

Figure 3.6 FT-IR spectrum of

3.1.3 Characterization of γ-Fe2O3 nanoparticles

Figure 3.7 The XRD pattern of a)

In comparison with XRD pattern of Fe3O4, the peaks were shifted slightly that allowed for unequivocal identification of maghemite; using the ICSD card no 01-083-0112 No additional diffraction peaks of any impurity were detected, demonstrating the high purity of the synthesized samples

maghemite nanoparticles were manipulated by

magnet (small image)

These results showed clearly that the Fe3O4and γ- Fe2O3 nanoparticles exhibited superparamagnetic behavior which obtained the highest magnetization saturation value (Ms) of 81 emu/g and 60 emu/g, respectively

The results SEM confirm that γ-Fe2O3 nanoparticles are similar in size with

3.1.4 Effect of nanoparticles on corrosion protection of epoxy coating

Corrosion protection of epoxy coating containing 3% wt particles was

demonstrated by electrochemical impedance spectroscopy (EIS)

After 1 hour immersion in 3 % NaCl solution, electrolyte had not penetrated in the coating yet After 14 days immersion, the EIS diagram of pure epoxy coating presented two circles well defined In the other hand, EIS diagram of epoxy/ γ-Fe2O3 showed that a third time constant appeared in the medium frequency range because of the reaction between particles and epoxy coating The particles filled the holes in the surface of coating and prevented the electrochemical process taking place

Figure 3.11 Nyquist plots for the epoxy coating

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After 42 days of immersion, for the epoxy coating containing α-Fe2O3, the second cycle at low frequencies was determined The result showed that α-Fe2O3 play the role of a pigment which increase the barrier property of coating The EIS diagram of epoxy coating containing γ-Fe2O3 are did not change the shape

After 84 days immersion, impedance value of epoxy coating containing

Fe3O4 was higher than this value of another coatings because of interacting

of particles and oxides appearing at the steel/coating interface

Figure 3.13 Nyquist plots for the epoxy coating containing 3 % wt

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3.1.5 Mechanical properties of epoxy coating containing iron oxides

Table 3.1 Pull-off strengths and impact strengths for epoxy coating

and epoxy coating containing 3% wt iron oxides

Samples Pull-off strength (MPa) Impact strength

(kg/cm)

Epoxy/Fe3O4 6,0

>200 Epoxy/α-Fe2O3 7,0

Epoxy/γ-Fe2O3 6,2

Figure 3.16 Delaminated area showing the adhesive loss vs immersion time in water: pure epoxy coating (a),

The increasing of wet adhesion of epoxy coating containing iron oxides can be explained by the cooperative bonds between the iron oxides (Fe3O4, α- Fe2O3 or γ-Fe2O3) and the oxide layer at the steel/coating interface which prevent water penetrated through the coating

3.1.6 Morphology of epoxy coating containing 3% wt Fe3O4 nanoparticles

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3.2 CHARACTERIZATION OF CORROSION PROTECTION OF

EPOXY CONTAINING Fe3O4 AND MODIFIED Fe3O4

3.2.1 Characterization of corrosion protection of epoxy coating

containing silane modified Fe3O4 nanoparticles

FT-IR analysis

DMPS, and TEOS

The spectrum of silane modified Fe3O4 nanoparticles presents the bands at 1120 cm-1 and 1050 cm-1 characteristic of Si-O-Fe and Si-O-Si groups, respectively This result indicates that silanes have been successfully grafted onto the surface of Fe3O4 nanoparticles

modified by silanes: APTS, DMPS và TEOS

The surface potential of Fe3O4 and modified Fe3O4 nanoparticles were measured in a zeta potential analyzer (Figure 3.19) In the surface potentials distribution plot of Fe3O4, there were 2 peaks focus on the value at -40 mV and indicates the average value -21.8 mV As a result of -OH groups in the surface of Fe3O4 nanoparticles due to the following model: (surface)(-

OH–)n The average surface potential of modified Fe3O4 with APTS, DMPS and TEOS are -19.31 mV; -19.05 mV and -18.15 mV, respectively

Magnetic property of silane modified Fe3O4 nanoparticles

Figure 3.20 Hysteresis loops of

The hysteresis loops of the modified magnetic particles obtained using a magnetometer are show in Figure 3.20 The values of saturation magnetization the Fe3O4

nanoparticles modified by APTS, DMPS and TEOS are 79.8 emu/g, 81.8 emu/g and 81.9 emu/g, respectively

3.2.1.2 Characterization of corrosion protection of epoxy coating containing silane modified magnetite nanoparticles

EIS measurements were carried out to evaluate the corrosion resistance

of the carbon steel covered by epoxy coating containing 3% wt silane modified magnetite nanoparticles

Figure 3.21 Nyquist plots for the epoxy coating containing

After 1 hour immersion in 3 % NaCl solution, the EIS diagram of three kinds of coatings presented one circle with very high value After 24 days immersion, for epoxy coating containing Fe3O4/TEOS the second cycle at low frequencies were not determined When immersion time reach to 42 days, the EIS diagram of all coatings presented two circles well defined This indicates that electrolyte penetrated in the coating and the corrosion process occurred at metal surface However, the impedance values of epoxy coating

70 75

Fe 3 O 4 /APTS

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containing silane modified Fe3O4 nanoparticles were high after along immersion time This result showed that surface modification by silanes enhanced protection efficiency of Fe3O4 on epoxy coating

Figure 3.22 Nyquist plots for the epoxy coating containing 3 % wt

Figure 3.23 Nyquist plots for the epoxy coating containing 3 % wt

with immersion time in NaCl 3% solution of

The SEM micrographs (figure 3.25 to 3.27) showed that surface modification Fe3O4 by silanes decreased the cluster in the epoxy matrix significantly The images indicated that Fe3O4/APTS had highest dispersion

in the polymer matrix