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Color performance and near infrared reflectance property of novel yellow pigment based on Fe2TiO5 nanorods decorated mica composites
Accepted Manuscript Color performance and near infrared reflectance property of novel yellow pigment based on Fe2TiO5 nanorods decorated mica composites Qiang Gao, Xiaomei Wu, Yueming Fan, Qinglin Meng PII:
S0143-7208(17)31190-7
DOI:
10.1016/j.dyepig.2017.07.035
Reference:
DYPI 6124
To appear in:
Dyes and Pigments
Received Date: 24 May 2017 Revised Date:
12 July 2017
Accepted Date: 16 July 2017
Please cite this article as: Gao Q, Wu X, Fan Y, Meng Q, Color performance and near infrared reflectance property of novel yellow pigment based on Fe2TiO5 nanorods decorated mica composites, Dyes and Pigments (2017), doi: 10.1016/j.dyepig.2017.07.035. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
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Color Performance and Near Infrared Reflectance Property of Novel Yellow Pigment Based on Fe2TiO5 Nanorods
Qiang Gaoa,b,*, Xiaomei Wu a, Yueming Fan a, Qinglin Meng b a
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Decorated Mica Composites
School of Materials Science and engineering, South China University of Technology, Guangzhou, 510641,
People’s Republic of China b
State Key Laboratory of Subtropical Building Science, School of Architecture, South China University of
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Technology, Guangzhou, 510641, People’s Republic of China
Abstract: To obtain cool yellow pigments with high near-infrared reflectance, mica/
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Fe2TiO5 composite pigments were synthesized by a chemical liquid deposition method. The developed composite pigment powders were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS) , UV–vis–NIR diffuse reflectance spectra, and CIEL*a*b* color
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scales. Different sized Fe2TiO5 nanorods were coated on the surface of mica particles. The particle size of the nanorods increased with increasing molar ratio of Fe3+ to Ti4+.
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The obtained composite pigments showed strong ultraviolet shielding ability and high near-infrared reflectance property. What’s more, the Fe2TiO5 coating with smaller
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particle size possessed higher reflectance in the region of 700～1500nm in accordance with the Kubelka-Munk theory. The near-infrared solar reflectance of mica/ Fe2TiO5 composites was as high as 80.3%. An approximately 3 °C decrease in interior temperature was obtained for the heat box coated with the composite pigments. Furthermore, the composite pigments exhibit brilliant yellow colors. Therefore, mica/ Fe2TiO5 composites are excellent near infrared reflective yellow pigments for efficient solar reflective coatings. 1
ACCEPTED MANUSCRIPT Key words: Fe2TiO5; Nanorod; Composite pigment; NIR reflectance; Thermal insulation; Yellow pigment * Corresponding author. Tel.: +86-020-87114243; fax: +86-020-87114243.
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Email address: [email protected] (Qiang Gao).
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1 Introduction Due to the high weather resistance and thermal stability, inorganic colored pigments with high near infrared (NIR, 700~2500nm) reflectance are widely applied
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to cool coatings and cool ceramics for building energy-saving [1-4]. It is well-known that near infrared irradiation accounts for 52% of the energy in the solar irradiance spectrum [5]. Thus, colored NIR reflective inorganic pigments can help to reduce
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solar heat gain and cooling loads of urban buildings while improving indoor thermal
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conditions [6, 7].
In particular, yellow pigments have been popularly used in the past due to their excellent thermal stability, high hiding power and good coloring strength [8, 9]. The common used yellow pigments include cadmium yellow ((Cd,Zn)S) and chrome
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yellow (PbCrO4) [10-13]. However, these yellow pigments are composed of toxic metals like Pb, Cd, and Cr, which have negative effects on human health and environment [14]. Thus there is a strong incentive to develop novel environment
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friendly yellow NIR reflective inorganic pigment with less toxicity.
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Fe2TiO5, which has recently received much attention owing to its narrow bandgap (Eg=2.2 eV), outstanding photochemical stability, and low cost [15]. Although pseudo-brookite iron titanate nanoparticles have been widely studied for their interesting gas sensing applications, catalytic properties, magnetic properties, fuel cells, and many other applications [16-19], its color property and NIR reflective property have not been reported. Moreover, the color properties of the pigments are mainly determined by the shell part instead of the core part [20]. Therefore, the 3
ACCEPTED MANUSCRIPT coating of Fe2TiO5 over an inexpensive core leads to a composite core-shell material that would help in reducing the cost of the pigments. Hence, it is quite valuable to develop pseudo-brookite iron titanate nanoparticles coated mica composite pigments
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and investigate their optical properties. In this paper, mica/ Fe2TiO5 core-shell structured yellow pigments were synthesized by a simple and facile solution method. The morphology, color properties, near
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infrared reflectance property and thermal insulation property of mica/ Fe2TiO5
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composite pigments were investigated.
2 Experimental 2.1 Materials
Synthetic mica was used as the substrate in this study. Analytical grade titanium
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tetrachloride (TiCl4), ferric chloride (FeCl3), sodium hydroxide (NaOH), and hydrochloric acid (HCl) were used in the experiments. Distilled water was also used
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throughout the experiments.
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2.2 Preparation method
The synthesis of mica/ Fe2TiO5 composite pigment was carried out in the following
way [21]. Mica particles (10～100µm ) were dispersed in distilled water. The batch was then heated to 80℃ and the pH value was adjusted to 2.2 with dilute hydrochloric acid. Then certain amount of TiCl4 solution (1 mol/L) and FeCl3 solution (1 mol/L) was introduced into the agitated slurry. The pH value of the slurry was kept constant by simultaneous addition of NaOH solution. After the addition was completed, the slurry was aged for 0.5 h and then allowed to settle and cool to room 4
ACCEPTED MANUSCRIPT temperature. The resulting products were separated , washed with distilled water and dried at 70℃ for 24h. Finally, the samples were calcined at 800 °C for 2 h. The molar ratio of Fe3+ to Ti4+ was 1:3, 1:2, and 1:1, respectively. These samples were marked as
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FT-1, FT -2, and FT -3, respectively.
2.3 Characterization
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Field Emission Scanning Electron Microscope (FEI, Nova NanoSEM 430) equipped with an Oxford Inca X-Act were used to characterize the surface
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morphology of the composite pigments. The operation voltage was 10 KV. Crystal phase composition of the pigments was performed by a PANalytical X'Pert Pro diffractometer with Cu Kα radiation at 40 kV and 2θ range from 20° to 70°. The chemical composition of the pigments was characterized by X-ray photoelectron
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spectroscopy (XPS, ESCALAB 250, Thermo-VG Scientific). The optical properties of the pigments were analyzed by diffuse reflectance spectroscopy (UV–vis–NIR)
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performed with a Lambda950 (PerkinElmer) spectrophotometer. The reference standard reflectance material used for the measurement was BaSO4. The solar
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reflectance in the wavelength range from λ1 to λ2 can be figured out by the formula R=
( )( ) ( ) ( ) ( )
(1)
Where r (λ) is the spectral reflectance (Wm-2) obtained from the experiment and i(λ) is the solar spectral irradiance (Wm-2nm-1) obtained from ASTM standard G173. The CIE L*a*b* of the pigment samples were measured by the X-Rite Inc model spectrophotometer (D65 illuminant). In the CIE color coordinate system, L* 5
ACCEPTED MANUSCRIPT represents the lightness axis ranges from 0 (black) to 100 (white), a* is the green (<0) to red (>0) axis, and b* is the blue (<0) to yellow (>0) axis [22]. A mixture solution of obtained yellow pigment particles and acrylic resin
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emulsion (mass ratio of 1:5) was coated on aluminium plates for thermal insulation test. The thermal insulation test was carried out by a self-designed equipment (Fig.1). An infrared lamp (OSRAM, 250 W) was used to simulate the solar irradiation. The
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heat box was insulated with polystyrene foam (with the exception of the test surface
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opening). The testing plates were placed at the top of the heat box. A thermometer was inserted into the middle of the box. The change of the interior temperature of the heat box was recorded by the thermometer.
3 Results and discussion
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3.1 Phase and morphology of mica/ Fe2TiO5 composite pigments The XRD patterns of mica/ Fe2TiO5 pigments prepared with different molar ratio of
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Fe3+ to Ti4+ are shown in Fig.2. The XRD peaks with 2θ values of 27.1° and 54.0° correspond to (110) and (211) planes of rutile TiO2 (JCPDS 21-1276). All peaks
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belonging to orthorhombic phase of Fe2TiO5 are identified with database in Joint Committee of Powder Diffraction System (JCPDS 41-1432). It is found that when the molar ratio of Fe3+ to Ti4+ is as low as 1/3, both XRD peaks of orthorhombic Fe2TiO5 and rutile TiO2 appear (Fig.2 (b)). Then the intensity of Fe2TiO5 increases and the peaks of Fe2TiO5 sharpen with increasing molar ratio of Fe3+ to Ti4+. It is noteworthy that the rutile diffraction peaks decrease as increasing Fe3+/Ti4+molar ratio. When the
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D=
(2)
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broadening using Scherer’s formula:
where D is the crystalline size, λ is the wavelength of X-ray used, β is the full line
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width at the half-maximum height of the main intensity peak, K is the shape factor,
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and θ is the Bragg angle. The (101) diffraction peak (2θ=25.4) of Fe2TiO5 was used to calculated the crystalline size of the samples. From this equation, the average crystallite sizes of Fe2TiO5 were 51nm, 51nm and 102nm for FT-1, FT -2, and FT -3. The SEM image of the naked mica shows that the mica powder has a flaky shape
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with a fairly smooth surface (Fig.3a). Fig.3b shows SEM images of Fe2TiO5 thin layers (shell) deposited on the surface of mica (core). Thus, the core/shell structure of mica/Fe2TiO5 composite pigments is achieved. It is obvious that the Fe2TiO5 coating
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is composed of nanorods. When the molar ratio of Fe3+ to Ti4+ is low (Fig.4ab), the
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mica surface is coated by densely Fe2TiO5 rod-like structures, which have widths of 70～200 nm and lengths of 150～700 nm. As for FT-2, more densely nanorods with an average widths of 114 nm and lengths of 351 nm (Fig.4cd) appears. Then, long square cylinders could be observed for FT-3 (Fig.4ef), which have widths of 0.2～ 1.1µm and lengths of 1.9～6.3µm. The particle size of the products are summarized in Table 1. It is interesting that the average particle size of the nanorods increases with increasing molar ratio of Fe3+ to Ti4+. Moreover, the energy dispersive X-ray 7
ACCEPTED MANUSCRIPT spectroscopy (EDX) analysis (Fig.4g) confirms that the Fe2TiO5 nanostructures are composed of Ti, Fe and O. The Fe/Ti atomic ratio is 2.2.
3.2 Surface chemical analysis of mica/Fe2TiO5 composite pigments
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In order to investigate the valence states and the surfacechemical compositions of
the mica/Fe2TiO5 composites, X-ray photoelectron spectroscopy (XPS) analysis was
employed. Fig. 5a presents the overview of XPS spectrum of mica and mica/Fe2TiO5.
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The raw mica reveals Mg (48.9 eV) and Si (100.4 eV) in the low binding energy
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regions, C at 282.9 eV, O at 529.4.1 eV, F at 683.0 eV, and some Auger peaks. The C signal may originate from adventitious carbon contamination. For the mica/Fe2TiO5, Ti peaks and Fe peaks are clearly detected in the high binding energy regions. The binding energies of Ti 2p core-level have two peaks located at about 456.5 eV and
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462.1 eV, which are attributed to Ti 2p3/2 and Ti 2p1/2 respectively as shown in Fig. 5b. These results indicate that the oxidation state of Ti at the surface of mica/Fe2TiO5
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is +4. As shown in Fig. 5c, the peaks of Fe 2p locate at 708.9 and 722.8 eV are attributed to the spectra of Fe 2p3/2 and Fe 2p1/2, revealing that Fe elements exist
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mainly in the form of Fe3+ oxidation state in the sample. In addition, the spectrum of O 1 s of mica/Fe2TiO5 is different from that of mica (Fig. 5d), revealing that the chemical states of O is changed. The spectrum of O 1 s (Fig. 5e) is an asymmetric curve which can be divided into three peaks at 527.2, 528.2 and 530 eV, respectively. The peak at 528.2 eV is assigned to the lattice oxygen binding with Si and Mg elements. The peak at 527.2 eV is assigned to the lattice oxygen binding with Ti
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3.3 Optical property of mica/Fe2TiO5 composite pigments
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Figure 6 illustrates the UV-Vis-NIR diffuse reflectance spectra of mica particles
and mica/Fe2TiO5. The mica/Fe2TiO5 composite pigments absorb strongly in the near
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UV region. The reflectance of the composite pigments is lower than 0.1 in the UV region. So the mica/Fe2TiO5 composite pigments could be used as UV blocker in
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coatings to screen the active UV radiation. The reflectance of mica particles is higher than 0.8 in the visible region. The increase of molar ratio of Fe3+ to Ti4+, an obvious red shift of UV-Vis diffuse reflectance spectra of the samples is observed, reflecting that the band gaps of the samples are decreased. Moreover, the reflectance of the
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samples in the visible region decreases with increasing molar ratio of Fe3+ to Ti4+. Fig.6b shows that the NIR reflectance of mica particles is higher than 0.9. As for
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mica/Fe2TiO5, the reflectance in the 700-1500nm decreases with increasing Fe3+/Ti4+ molar ratio. Kubelka-Munk (KM) theory is widely accepted for explaining the optical
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properties of complex systems such as powders and the theory is discussed briefly below[23].According to the KM theory: (1 −
) ⁄2
≡ ( )=
⁄
(3)
Where S is the scattering coefficient, K is the absorption coefficient, R∞ is the reflectance of the sample at infinite thickness, and F(R) is called the KM function. According to previous reports [5], the scattering coefficient is inversely proportional to the average particle size. As can be seen from Table1, the particle size of the 9
ACCEPTED MANUSCRIPT Fe2TiO5 increases with increasing molar ratio of Fe3+ to Ti4+. Thus, the scattering coefficient decreases with the increase of particle size, resulting in a decrease of reflectance in the region of 700~1500nm.
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The NIR solar reflectance of the samples has been summarized in Table 2. The solar reflectance of mica/Fe2TiO5 composite pigments in UV region is as low as 10%, indicating a strong UV shielding property. Due to the yellow color of the pigments,
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the solar reflectance of mica/Fe2TiO5 composite pigments in the visible region is
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lower than 50%.What’s more, the NIR solar reflectance of the composite pigments is as high as 80.3%. The NIR solar reflectance of the composite pigments decreases with increasing molar ratio of Fe3+ to Ti4+.
3.4 Color coordinates and thermal insulation property of mica/Fe2TiO5 pigments
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In order to further investigate the color characteristics of the pigments, CIE L * a* b* values of the pigment samples are summarized in Table 2. The lightness of the
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pigments decreases with increasing Fe3+/Ti4+ molar ratio, reflecting that the color of the pigments become dark. Moreover, the increased molar ratio of Fe3+ to Ti4+ results
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in a reduction of yellow and an increase in red. Color aspects of mica/Fe2TiO5 composite pigments is shown in Fig.7. The while color of mica particles can be observed. Moreover, mica/Fe2TiO5 composite pigments exhibit brilliant yellow color. The thermal insulation property of mica/Fe2TiO5 composite pigments was investigated. The interior temperature changes of the heat box covered with painted aluminium plates versus time are shown in Fig.8. It can be seen that the interior temperature of the heat boxes increases with increasing molar ratio of Fe3+ to Ti4+. 10
ACCEPTED MANUSCRIPT Moreover, the interior temperature of the heat box with mica/Fe2TiO5 composite pigments is 3℃ lower than that of the box without pigments, further confirming the high NIR reflectance of mica/Fe2TiO5 composite pigments. Thus, mica/Fe2TiO5
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composite pigments could be well used for colorful NIR reflective coatings.
4 Conclusions
Nanometer Fe2TiO5 coatings with different morphology were deposited on mica
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flakes as environmentally friendly inorganic NIR reflective yellow pigments. As the
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increase of Fe3+/Ti4+ molar ratio, the particle size of Fe2TiO5 nanorods increases. XPS analysis confirms the formation of Ti-O and Fe-O bond. We also investigate the effect of molar ratio of Fe3+ to Ti4+ and morphology on the optical properties of as prepared composite pigments. Firstly, the increase of Fe3+/Ti4+ molar ratio leads to the decrease
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of reflectance in the region of 700~1500 nm. This decreased reflectance property can be ascribe to an increase in the mean particle size of Fe2TiO5 nanorods in accordance with the KM theory. Secondly, the increased molar ratio of Fe3+ to Ti4+ results in a
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reduction of yellow and an increase in red of the composite pigments. Thirdly, The
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NIR solar reflectance of the mica/Fe2TiO5 is as high as 80.3%. In the thermal insulation test, the coating coated with composite pigments reduced the interior temperature of the heat box by 3 °C. A combination of their unique features of low-cost, brilliant yellow color, and high NIR reflectance suggests that these Fe2TiO5 coated mica composite pigments will provide possibility to future industrial applications in thermal insulation.
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ACCEPTED MANUSCRIPT Acknowledgements The work was funded by Science and Technology Program of Guangzhou (NO.201707010336), the Foundation for Science and Technology Project
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of Guangdong Province (NO.2016A040403042), and Fundamental Research Funds for the Central Universities (NO.2015ZM095), and their financial support is gratefully
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acknowledged.
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References
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[1] Smith AE, Comstock MC, Subramanian MA. Spectral properties of the UV absorbing and near-IR reflecting blue pigment, YIn1-xMnxO3. Dyes Pigments. 2016;133:214-21. [2] Schildhammer D, Fuhrmann G, Petschnig L, Weinberger N, Schottenberger H, Huppertz H. Synthesis and characterization of a new high NIR reflective ytterbium molybdenum oxide and related doped pigments. Dyes Pigments. 2017;138:90-9. [3] Yang R, Han A, Ye M, Chen X, Yuan L. Synthesis, characterization and thermal performance of Fe/N co-doped MgTiO3 as a novel high near-infrared reflective pigment. Sol Energ Mat Sol C. 2017;160:307-18. [4] Levinson R, Berdahl P, Akbari H. Solar spectral optical properties of pigments-Part I: model for deriving scattering and absorption coefficients from transmittance and reflectance measurements. Sol Energ Mat Sol C. 2005;89(4):319-49. [5] Gao Q, Wu X, Fan Y. Solar spectral optical properties of rutile TiO2 coated mica–titania pigments. Dyes Pigments. 2014;109(0):90-5. [6] Jovaní M, Sanz A, Beltrán-Mir H, Cordoncillo E. New red-shade environmental-friendly multifunctional pigment based on Tb and Fe doped Y2Zr2O7 for ceramic applications and cool roof coatings. Dyes Pigments. 2016;133:33-40. [7] Gao Q, Wu X, Xia Z, Fan Y. Coating mechanism and near-infrared reflectance property of hollow fly ash bead/TiO2 composite pigment. Powder Technol. 2017;305:433-9. [8] Wang J-L, Li Y-Q, Byon Y-J, Mei S-G, Zhang G-L. Synthesis and characterization of NiTiO3 yellow nano pigment with high solar radiation reflection efficiency. Powder Technol. 2013;235:303-6. [9] Llusar M, García E, García MT, Esteve V, Gargori C, Monrós G. Synthesis and coloring performance of Ni-geikielite (Ni,Mg)TiO3 yellow pigments: Effect of 12
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temperature, Ni-doping and synthesis method. J Eur Ceram Soc. 2015;35(13):3721-34. [10] Rosi F, Grazia C, Gabrieli F, Romani A, Paolantoni M, Vivani R, et al. UV–Vis-NIR and micro Raman spectroscopies for the non destructive identification of Cd1 − xZnxS solid solutions in cadmium yellow pigments. Microchem J. 2016;124:856-67. [11] Buxbaum G, Pfaff G. Industrial Inorganic Pigments: Wiley-VCH Verlag GmbH & Co. KGaA; 2005. [12] Xiang J-H, Yu S-H, Xu Z. Polymorph and Phase Discrimination of Lead Chromate Pigments by a Facile Room Temperature Precipitation Reaction. Crystal Growth & Design. 2004;4(6):1311-5. [13] Amat A, Miliani C, Fantacci S. Structural and electronic properties of the PbCrO4 chrome yellow pigment and of its light sensitive sulfate-substituted compounds. RSC Advances. 2016;6(43):36336-44. [14] Masui T, Honda T, Wendusu, Imanaka N. Novel and environmentally friendly (Bi,Ca,Zn)VO4 yellow pigments. Dyes Pigments. 2013;99(3):636-41. [15] Seitz G, Penin N, Decoux L, Wattiaux A, Duttine M, Gaudon M. Near the Ferric Pseudobrookite Composition (Fe2TiO5). Inorg Chem. 2016;55(5):2499-507. [16] Min K-M, Park K-S, Lim A-H, Kim J-C, Kim D-W. Synthesis of pseudobrookite-type Fe2TiO5 nanoparticles and their Li-ion electroactivity. Ceram Int. 2012;38(7):6009-13. [17] Agafonov AV, Afanasyev DA, Gerasimova TV, Krayev AS, Kashirin MA, Vinogradov VV, et al. Nanoparticle Self-Assembly Mechanisms in the Colloidal Synthesis of Iron Titanate Nanocomposite Photocatalysts for Environmental Applications. ACS SUSTAIN CHEM ENG . 2016;4(5):2814-21. [18] Enhessari M, Razi MK, Etemad L, Parviz A, Sakhaei M. Structural, optical and magnetic properties of the Fe2TiO5 nanopowders. J EXP NANOSCI. 2014;9(2):167-76. [19] Salarizadeh P, Javanbakht M, Pourmahdian S, Bagheri A, Beydaghi H, Enhessari M. Surface modification of Fe2TiO5 nanoparticles by silane coupling agent: Synthesis and application in proton exchange composite membranes. J Colloid Interf Sci. 2016;472:135-44. [20] Guan L, Fan J, Zhang Y, Guo Y, Duan H, Chen Y, et al. Facile preparation of highly cost-effective BaSO4@BiVO4 core-shell structured brilliant yellow pigment. Dyes Pigments. 2016;128:49-53. [21] Gao Q, Wu X, Fan Y, Zhou X. Low temperature synthesis and characterization of rutile TiO2-coated mica–titania pigments. Dyes Pigments. 2012;95(3):534-9. [22] Wang Y, Liu M, Liu Y, Luo J, Lu X, Sun J. A novel mica-titania@graphene core-shell structured antistatic composite pearlescent pigment. Dyes Pigments. 2017;136:197-204. [23] Lagorio MG. Why Do Marbles Become Paler on Grinding? Reflectance, Spectroscopy, Color, and Particle Size. J Chem Educ. 2004;81(11):1607.
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Table 1 The average particle size of the Fe2TiO5 nanorods.
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Table 2 Solar reflectance and color coordinates of the products.
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Fig.1 Schematic of the set up used for the thermal insulation test.
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(d) FT-3.
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Fig.2 XRD patterns of mica/ Fe2TiO5 composite pigments: (a) mica, (b) FT-1, (c) FT-2,
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Fig.3 SEM images of the samples: (a) low magnification of mica particles, (c) low
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magnification of mica/ Fe2TiO5 composite pigments (FT-2).
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ACCEPTED MANUSCRIPT Fig.4 SEM images of mica/ Fe2TiO5 composite pigments: (a) low magnification of FT-1, (b) high magnification of FT-1, (c) low magnification of FT-2, (d) high magnification of FT-2, (e) low magnification of FT-3, (f) high magnification of FT-3,
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(g) EDS image of FT-3.
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Fig.5 XPS spectra of the samples: (a) XPS survey of mica and mica/Fe2TiO5, (b) Ti 2p
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of mica/Fe2TiO5, (c) Fe 2p of mica/Fe2TiO5, (d) O 1s of mica and mica/Fe2TiO5, (e) O 1s of mica/Fe2TiO5.
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Fig.6 (a) UV-Vis diffuse reflectance spectra of the samples, (b) NIR reflectance
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spectra of the samples: (1) mica, (2) FT-1, (3) FT-2, (4) FT-3.
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Fig.7 Color aspects of mica/Fe2TiO5 composite pigments: (a) mica, (b) FT-1, (c) FT-2, (a) FT-3.
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Fig.8 The interior temperatures of the heat box coated with different types of pigments: (a) blank
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sample, (b) FT-1, (c) FT-2, (d) FT-3.
ACCEPTED MANUSCRIPT Highlights
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The mica/ Fe2TiO5 composite pigments exhibit brilliant yellow colors. Different sized Fe2TiO5 nanorods were coated on the surface of mica particles. The NIR solar reflectance of the composites was as high as 80.3%. The composite pigments exibit strong UV shielding property.
S0143-7208(17)31190-7
DOI:
10.1016/j.dyepig.2017.07.035
Reference:
DYPI 6124
To appear in:
Dyes and Pigments
Received Date: 24 May 2017 Revised Date:
12 July 2017
Accepted Date: 16 July 2017
Please cite this article as: Gao Q, Wu X, Fan Y, Meng Q, Color performance and near infrared reflectance property of novel yellow pigment based on Fe2TiO5 nanorods decorated mica composites, Dyes and Pigments (2017), doi: 10.1016/j.dyepig.2017.07.035. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Color Performance and Near Infrared Reflectance Property of Novel Yellow Pigment Based on Fe2TiO5 Nanorods
Qiang Gaoa,b,*, Xiaomei Wu a, Yueming Fan a, Qinglin Meng b a
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Decorated Mica Composites
School of Materials Science and engineering, South China University of Technology, Guangzhou, 510641,
People’s Republic of China b
State Key Laboratory of Subtropical Building Science, School of Architecture, South China University of
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Technology, Guangzhou, 510641, People’s Republic of China
Abstract: To obtain cool yellow pigments with high near-infrared reflectance, mica/
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Fe2TiO5 composite pigments were synthesized by a chemical liquid deposition method. The developed composite pigment powders were characterized by X-ray diffraction (XRD), scanning electronic microscopy (SEM), X-ray photoelectron spectroscopy (XPS) , UV–vis–NIR diffuse reflectance spectra, and CIEL*a*b* color
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scales. Different sized Fe2TiO5 nanorods were coated on the surface of mica particles. The particle size of the nanorods increased with increasing molar ratio of Fe3+ to Ti4+.
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The obtained composite pigments showed strong ultraviolet shielding ability and high near-infrared reflectance property. What’s more, the Fe2TiO5 coating with smaller
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particle size possessed higher reflectance in the region of 700～1500nm in accordance with the Kubelka-Munk theory. The near-infrared solar reflectance of mica/ Fe2TiO5 composites was as high as 80.3%. An approximately 3 °C decrease in interior temperature was obtained for the heat box coated with the composite pigments. Furthermore, the composite pigments exhibit brilliant yellow colors. Therefore, mica/ Fe2TiO5 composites are excellent near infrared reflective yellow pigments for efficient solar reflective coatings. 1
ACCEPTED MANUSCRIPT Key words: Fe2TiO5; Nanorod; Composite pigment; NIR reflectance; Thermal insulation; Yellow pigment * Corresponding author. Tel.: +86-020-87114243; fax: +86-020-87114243.
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Email address: [email protected] (Qiang Gao).
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1 Introduction Due to the high weather resistance and thermal stability, inorganic colored pigments with high near infrared (NIR, 700~2500nm) reflectance are widely applied
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to cool coatings and cool ceramics for building energy-saving [1-4]. It is well-known that near infrared irradiation accounts for 52% of the energy in the solar irradiance spectrum [5]. Thus, colored NIR reflective inorganic pigments can help to reduce
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solar heat gain and cooling loads of urban buildings while improving indoor thermal
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conditions [6, 7].
In particular, yellow pigments have been popularly used in the past due to their excellent thermal stability, high hiding power and good coloring strength [8, 9]. The common used yellow pigments include cadmium yellow ((Cd,Zn)S) and chrome
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yellow (PbCrO4) [10-13]. However, these yellow pigments are composed of toxic metals like Pb, Cd, and Cr, which have negative effects on human health and environment [14]. Thus there is a strong incentive to develop novel environment
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friendly yellow NIR reflective inorganic pigment with less toxicity.
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Fe2TiO5, which has recently received much attention owing to its narrow bandgap (Eg=2.2 eV), outstanding photochemical stability, and low cost [15]. Although pseudo-brookite iron titanate nanoparticles have been widely studied for their interesting gas sensing applications, catalytic properties, magnetic properties, fuel cells, and many other applications [16-19], its color property and NIR reflective property have not been reported. Moreover, the color properties of the pigments are mainly determined by the shell part instead of the core part [20]. Therefore, the 3
ACCEPTED MANUSCRIPT coating of Fe2TiO5 over an inexpensive core leads to a composite core-shell material that would help in reducing the cost of the pigments. Hence, it is quite valuable to develop pseudo-brookite iron titanate nanoparticles coated mica composite pigments
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and investigate their optical properties. In this paper, mica/ Fe2TiO5 core-shell structured yellow pigments were synthesized by a simple and facile solution method. The morphology, color properties, near
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infrared reflectance property and thermal insulation property of mica/ Fe2TiO5
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composite pigments were investigated.
2 Experimental 2.1 Materials
Synthetic mica was used as the substrate in this study. Analytical grade titanium
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tetrachloride (TiCl4), ferric chloride (FeCl3), sodium hydroxide (NaOH), and hydrochloric acid (HCl) were used in the experiments. Distilled water was also used
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throughout the experiments.
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2.2 Preparation method
The synthesis of mica/ Fe2TiO5 composite pigment was carried out in the following
way [21]. Mica particles (10～100µm ) were dispersed in distilled water. The batch was then heated to 80℃ and the pH value was adjusted to 2.2 with dilute hydrochloric acid. Then certain amount of TiCl4 solution (1 mol/L) and FeCl3 solution (1 mol/L) was introduced into the agitated slurry. The pH value of the slurry was kept constant by simultaneous addition of NaOH solution. After the addition was completed, the slurry was aged for 0.5 h and then allowed to settle and cool to room 4
ACCEPTED MANUSCRIPT temperature. The resulting products were separated , washed with distilled water and dried at 70℃ for 24h. Finally, the samples were calcined at 800 °C for 2 h. The molar ratio of Fe3+ to Ti4+ was 1:3, 1:2, and 1:1, respectively. These samples were marked as
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FT-1, FT -2, and FT -3, respectively.
2.3 Characterization
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Field Emission Scanning Electron Microscope (FEI, Nova NanoSEM 430) equipped with an Oxford Inca X-Act were used to characterize the surface
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morphology of the composite pigments. The operation voltage was 10 KV. Crystal phase composition of the pigments was performed by a PANalytical X'Pert Pro diffractometer with Cu Kα radiation at 40 kV and 2θ range from 20° to 70°. The chemical composition of the pigments was characterized by X-ray photoelectron
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spectroscopy (XPS, ESCALAB 250, Thermo-VG Scientific). The optical properties of the pigments were analyzed by diffuse reflectance spectroscopy (UV–vis–NIR)
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performed with a Lambda950 (PerkinElmer) spectrophotometer. The reference standard reflectance material used for the measurement was BaSO4. The solar
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reflectance in the wavelength range from λ1 to λ2 can be figured out by the formula R=
( )( ) ( ) ( ) ( )
(1)
Where r (λ) is the spectral reflectance (Wm-2) obtained from the experiment and i(λ) is the solar spectral irradiance (Wm-2nm-1) obtained from ASTM standard G173. The CIE L*a*b* of the pigment samples were measured by the X-Rite Inc model spectrophotometer (D65 illuminant). In the CIE color coordinate system, L* 5
ACCEPTED MANUSCRIPT represents the lightness axis ranges from 0 (black) to 100 (white), a* is the green (<0) to red (>0) axis, and b* is the blue (<0) to yellow (>0) axis [22]. A mixture solution of obtained yellow pigment particles and acrylic resin
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emulsion (mass ratio of 1:5) was coated on aluminium plates for thermal insulation test. The thermal insulation test was carried out by a self-designed equipment (Fig.1). An infrared lamp (OSRAM, 250 W) was used to simulate the solar irradiation. The
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heat box was insulated with polystyrene foam (with the exception of the test surface
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opening). The testing plates were placed at the top of the heat box. A thermometer was inserted into the middle of the box. The change of the interior temperature of the heat box was recorded by the thermometer.
3 Results and discussion
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3.1 Phase and morphology of mica/ Fe2TiO5 composite pigments The XRD patterns of mica/ Fe2TiO5 pigments prepared with different molar ratio of
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Fe3+ to Ti4+ are shown in Fig.2. The XRD peaks with 2θ values of 27.1° and 54.0° correspond to (110) and (211) planes of rutile TiO2 (JCPDS 21-1276). All peaks
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belonging to orthorhombic phase of Fe2TiO5 are identified with database in Joint Committee of Powder Diffraction System (JCPDS 41-1432). It is found that when the molar ratio of Fe3+ to Ti4+ is as low as 1/3, both XRD peaks of orthorhombic Fe2TiO5 and rutile TiO2 appear (Fig.2 (b)). Then the intensity of Fe2TiO5 increases and the peaks of Fe2TiO5 sharpen with increasing molar ratio of Fe3+ to Ti4+. It is noteworthy that the rutile diffraction peaks decrease as increasing Fe3+/Ti4+molar ratio. When the
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D=
(2)
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broadening using Scherer’s formula:
where D is the crystalline size, λ is the wavelength of X-ray used, β is the full line
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width at the half-maximum height of the main intensity peak, K is the shape factor,
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and θ is the Bragg angle. The (101) diffraction peak (2θ=25.4) of Fe2TiO5 was used to calculated the crystalline size of the samples. From this equation, the average crystallite sizes of Fe2TiO5 were 51nm, 51nm and 102nm for FT-1, FT -2, and FT -3. The SEM image of the naked mica shows that the mica powder has a flaky shape
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with a fairly smooth surface (Fig.3a). Fig.3b shows SEM images of Fe2TiO5 thin layers (shell) deposited on the surface of mica (core). Thus, the core/shell structure of mica/Fe2TiO5 composite pigments is achieved. It is obvious that the Fe2TiO5 coating
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is composed of nanorods. When the molar ratio of Fe3+ to Ti4+ is low (Fig.4ab), the
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mica surface is coated by densely Fe2TiO5 rod-like structures, which have widths of 70～200 nm and lengths of 150～700 nm. As for FT-2, more densely nanorods with an average widths of 114 nm and lengths of 351 nm (Fig.4cd) appears. Then, long square cylinders could be observed for FT-3 (Fig.4ef), which have widths of 0.2～ 1.1µm and lengths of 1.9～6.3µm. The particle size of the products are summarized in Table 1. It is interesting that the average particle size of the nanorods increases with increasing molar ratio of Fe3+ to Ti4+. Moreover, the energy dispersive X-ray 7
ACCEPTED MANUSCRIPT spectroscopy (EDX) analysis (Fig.4g) confirms that the Fe2TiO5 nanostructures are composed of Ti, Fe and O. The Fe/Ti atomic ratio is 2.2.
3.2 Surface chemical analysis of mica/Fe2TiO5 composite pigments
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In order to investigate the valence states and the surfacechemical compositions of
the mica/Fe2TiO5 composites, X-ray photoelectron spectroscopy (XPS) analysis was
employed. Fig. 5a presents the overview of XPS spectrum of mica and mica/Fe2TiO5.
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The raw mica reveals Mg (48.9 eV) and Si (100.4 eV) in the low binding energy
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regions, C at 282.9 eV, O at 529.4.1 eV, F at 683.0 eV, and some Auger peaks. The C signal may originate from adventitious carbon contamination. For the mica/Fe2TiO5, Ti peaks and Fe peaks are clearly detected in the high binding energy regions. The binding energies of Ti 2p core-level have two peaks located at about 456.5 eV and
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462.1 eV, which are attributed to Ti 2p3/2 and Ti 2p1/2 respectively as shown in Fig. 5b. These results indicate that the oxidation state of Ti at the surface of mica/Fe2TiO5
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is +4. As shown in Fig. 5c, the peaks of Fe 2p locate at 708.9 and 722.8 eV are attributed to the spectra of Fe 2p3/2 and Fe 2p1/2, revealing that Fe elements exist
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mainly in the form of Fe3+ oxidation state in the sample. In addition, the spectrum of O 1 s of mica/Fe2TiO5 is different from that of mica (Fig. 5d), revealing that the chemical states of O is changed. The spectrum of O 1 s (Fig. 5e) is an asymmetric curve which can be divided into three peaks at 527.2, 528.2 and 530 eV, respectively. The peak at 528.2 eV is assigned to the lattice oxygen binding with Si and Mg elements. The peak at 527.2 eV is assigned to the lattice oxygen binding with Ti
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3.3 Optical property of mica/Fe2TiO5 composite pigments
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Figure 6 illustrates the UV-Vis-NIR diffuse reflectance spectra of mica particles
and mica/Fe2TiO5. The mica/Fe2TiO5 composite pigments absorb strongly in the near
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UV region. The reflectance of the composite pigments is lower than 0.1 in the UV region. So the mica/Fe2TiO5 composite pigments could be used as UV blocker in
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coatings to screen the active UV radiation. The reflectance of mica particles is higher than 0.8 in the visible region. The increase of molar ratio of Fe3+ to Ti4+, an obvious red shift of UV-Vis diffuse reflectance spectra of the samples is observed, reflecting that the band gaps of the samples are decreased. Moreover, the reflectance of the
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samples in the visible region decreases with increasing molar ratio of Fe3+ to Ti4+. Fig.6b shows that the NIR reflectance of mica particles is higher than 0.9. As for
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mica/Fe2TiO5, the reflectance in the 700-1500nm decreases with increasing Fe3+/Ti4+ molar ratio. Kubelka-Munk (KM) theory is widely accepted for explaining the optical
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properties of complex systems such as powders and the theory is discussed briefly below[23].According to the KM theory: (1 −
) ⁄2
≡ ( )=
⁄
(3)
Where S is the scattering coefficient, K is the absorption coefficient, R∞ is the reflectance of the sample at infinite thickness, and F(R) is called the KM function. According to previous reports [5], the scattering coefficient is inversely proportional to the average particle size. As can be seen from Table1, the particle size of the 9
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The NIR solar reflectance of the samples has been summarized in Table 2. The solar reflectance of mica/Fe2TiO5 composite pigments in UV region is as low as 10%, indicating a strong UV shielding property. Due to the yellow color of the pigments,
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the solar reflectance of mica/Fe2TiO5 composite pigments in the visible region is
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lower than 50%.What’s more, the NIR solar reflectance of the composite pigments is as high as 80.3%. The NIR solar reflectance of the composite pigments decreases with increasing molar ratio of Fe3+ to Ti4+.
3.4 Color coordinates and thermal insulation property of mica/Fe2TiO5 pigments
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In order to further investigate the color characteristics of the pigments, CIE L * a* b* values of the pigment samples are summarized in Table 2. The lightness of the
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pigments decreases with increasing Fe3+/Ti4+ molar ratio, reflecting that the color of the pigments become dark. Moreover, the increased molar ratio of Fe3+ to Ti4+ results
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in a reduction of yellow and an increase in red. Color aspects of mica/Fe2TiO5 composite pigments is shown in Fig.7. The while color of mica particles can be observed. Moreover, mica/Fe2TiO5 composite pigments exhibit brilliant yellow color. The thermal insulation property of mica/Fe2TiO5 composite pigments was investigated. The interior temperature changes of the heat box covered with painted aluminium plates versus time are shown in Fig.8. It can be seen that the interior temperature of the heat boxes increases with increasing molar ratio of Fe3+ to Ti4+. 10
ACCEPTED MANUSCRIPT Moreover, the interior temperature of the heat box with mica/Fe2TiO5 composite pigments is 3℃ lower than that of the box without pigments, further confirming the high NIR reflectance of mica/Fe2TiO5 composite pigments. Thus, mica/Fe2TiO5
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composite pigments could be well used for colorful NIR reflective coatings.
4 Conclusions
Nanometer Fe2TiO5 coatings with different morphology were deposited on mica
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flakes as environmentally friendly inorganic NIR reflective yellow pigments. As the
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increase of Fe3+/Ti4+ molar ratio, the particle size of Fe2TiO5 nanorods increases. XPS analysis confirms the formation of Ti-O and Fe-O bond. We also investigate the effect of molar ratio of Fe3+ to Ti4+ and morphology on the optical properties of as prepared composite pigments. Firstly, the increase of Fe3+/Ti4+ molar ratio leads to the decrease
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of reflectance in the region of 700~1500 nm. This decreased reflectance property can be ascribe to an increase in the mean particle size of Fe2TiO5 nanorods in accordance with the KM theory. Secondly, the increased molar ratio of Fe3+ to Ti4+ results in a
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reduction of yellow and an increase in red of the composite pigments. Thirdly, The
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NIR solar reflectance of the mica/Fe2TiO5 is as high as 80.3%. In the thermal insulation test, the coating coated with composite pigments reduced the interior temperature of the heat box by 3 °C. A combination of their unique features of low-cost, brilliant yellow color, and high NIR reflectance suggests that these Fe2TiO5 coated mica composite pigments will provide possibility to future industrial applications in thermal insulation.
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ACCEPTED MANUSCRIPT Acknowledgements The work was funded by Science and Technology Program of Guangzhou (NO.201707010336), the Foundation for Science and Technology Project
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of Guangdong Province (NO.2016A040403042), and Fundamental Research Funds for the Central Universities (NO.2015ZM095), and their financial support is gratefully
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acknowledged.
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References
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[1] Smith AE, Comstock MC, Subramanian MA. Spectral properties of the UV absorbing and near-IR reflecting blue pigment, YIn1-xMnxO3. Dyes Pigments. 2016;133:214-21. [2] Schildhammer D, Fuhrmann G, Petschnig L, Weinberger N, Schottenberger H, Huppertz H. Synthesis and characterization of a new high NIR reflective ytterbium molybdenum oxide and related doped pigments. Dyes Pigments. 2017;138:90-9. [3] Yang R, Han A, Ye M, Chen X, Yuan L. Synthesis, characterization and thermal performance of Fe/N co-doped MgTiO3 as a novel high near-infrared reflective pigment. Sol Energ Mat Sol C. 2017;160:307-18. [4] Levinson R, Berdahl P, Akbari H. Solar spectral optical properties of pigments-Part I: model for deriving scattering and absorption coefficients from transmittance and reflectance measurements. Sol Energ Mat Sol C. 2005;89(4):319-49. [5] Gao Q, Wu X, Fan Y. Solar spectral optical properties of rutile TiO2 coated mica–titania pigments. Dyes Pigments. 2014;109(0):90-5. [6] Jovaní M, Sanz A, Beltrán-Mir H, Cordoncillo E. New red-shade environmental-friendly multifunctional pigment based on Tb and Fe doped Y2Zr2O7 for ceramic applications and cool roof coatings. Dyes Pigments. 2016;133:33-40. [7] Gao Q, Wu X, Xia Z, Fan Y. Coating mechanism and near-infrared reflectance property of hollow fly ash bead/TiO2 composite pigment. Powder Technol. 2017;305:433-9. [8] Wang J-L, Li Y-Q, Byon Y-J, Mei S-G, Zhang G-L. Synthesis and characterization of NiTiO3 yellow nano pigment with high solar radiation reflection efficiency. Powder Technol. 2013;235:303-6. [9] Llusar M, García E, García MT, Esteve V, Gargori C, Monrós G. Synthesis and coloring performance of Ni-geikielite (Ni,Mg)TiO3 yellow pigments: Effect of 12
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temperature, Ni-doping and synthesis method. J Eur Ceram Soc. 2015;35(13):3721-34. [10] Rosi F, Grazia C, Gabrieli F, Romani A, Paolantoni M, Vivani R, et al. UV–Vis-NIR and micro Raman spectroscopies for the non destructive identification of Cd1 − xZnxS solid solutions in cadmium yellow pigments. Microchem J. 2016;124:856-67. [11] Buxbaum G, Pfaff G. Industrial Inorganic Pigments: Wiley-VCH Verlag GmbH & Co. KGaA; 2005. [12] Xiang J-H, Yu S-H, Xu Z. Polymorph and Phase Discrimination of Lead Chromate Pigments by a Facile Room Temperature Precipitation Reaction. Crystal Growth & Design. 2004;4(6):1311-5. [13] Amat A, Miliani C, Fantacci S. Structural and electronic properties of the PbCrO4 chrome yellow pigment and of its light sensitive sulfate-substituted compounds. RSC Advances. 2016;6(43):36336-44. [14] Masui T, Honda T, Wendusu, Imanaka N. Novel and environmentally friendly (Bi,Ca,Zn)VO4 yellow pigments. Dyes Pigments. 2013;99(3):636-41. [15] Seitz G, Penin N, Decoux L, Wattiaux A, Duttine M, Gaudon M. Near the Ferric Pseudobrookite Composition (Fe2TiO5). Inorg Chem. 2016;55(5):2499-507. [16] Min K-M, Park K-S, Lim A-H, Kim J-C, Kim D-W. Synthesis of pseudobrookite-type Fe2TiO5 nanoparticles and their Li-ion electroactivity. Ceram Int. 2012;38(7):6009-13. [17] Agafonov AV, Afanasyev DA, Gerasimova TV, Krayev AS, Kashirin MA, Vinogradov VV, et al. Nanoparticle Self-Assembly Mechanisms in the Colloidal Synthesis of Iron Titanate Nanocomposite Photocatalysts for Environmental Applications. ACS SUSTAIN CHEM ENG . 2016;4(5):2814-21. [18] Enhessari M, Razi MK, Etemad L, Parviz A, Sakhaei M. Structural, optical and magnetic properties of the Fe2TiO5 nanopowders. J EXP NANOSCI. 2014;9(2):167-76. [19] Salarizadeh P, Javanbakht M, Pourmahdian S, Bagheri A, Beydaghi H, Enhessari M. Surface modification of Fe2TiO5 nanoparticles by silane coupling agent: Synthesis and application in proton exchange composite membranes. J Colloid Interf Sci. 2016;472:135-44. [20] Guan L, Fan J, Zhang Y, Guo Y, Duan H, Chen Y, et al. Facile preparation of highly cost-effective BaSO4@BiVO4 core-shell structured brilliant yellow pigment. Dyes Pigments. 2016;128:49-53. [21] Gao Q, Wu X, Fan Y, Zhou X. Low temperature synthesis and characterization of rutile TiO2-coated mica–titania pigments. Dyes Pigments. 2012;95(3):534-9. [22] Wang Y, Liu M, Liu Y, Luo J, Lu X, Sun J. A novel mica-titania@graphene core-shell structured antistatic composite pearlescent pigment. Dyes Pigments. 2017;136:197-204. [23] Lagorio MG. Why Do Marbles Become Paler on Grinding? Reflectance, Spectroscopy, Color, and Particle Size. J Chem Educ. 2004;81(11):1607.
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Table 1 The average particle size of the Fe2TiO5 nanorods.
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Table 2 Solar reflectance and color coordinates of the products.
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Fig.1 Schematic of the set up used for the thermal insulation test.
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(d) FT-3.
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Fig.2 XRD patterns of mica/ Fe2TiO5 composite pigments: (a) mica, (b) FT-1, (c) FT-2,
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Fig.3 SEM images of the samples: (a) low magnification of mica particles, (c) low
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magnification of mica/ Fe2TiO5 composite pigments (FT-2).
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ACCEPTED MANUSCRIPT Fig.4 SEM images of mica/ Fe2TiO5 composite pigments: (a) low magnification of FT-1, (b) high magnification of FT-1, (c) low magnification of FT-2, (d) high magnification of FT-2, (e) low magnification of FT-3, (f) high magnification of FT-3,
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(g) EDS image of FT-3.
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Fig.5 XPS spectra of the samples: (a) XPS survey of mica and mica/Fe2TiO5, (b) Ti 2p
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of mica/Fe2TiO5, (c) Fe 2p of mica/Fe2TiO5, (d) O 1s of mica and mica/Fe2TiO5, (e) O 1s of mica/Fe2TiO5.
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Fig.6 (a) UV-Vis diffuse reflectance spectra of the samples, (b) NIR reflectance
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spectra of the samples: (1) mica, (2) FT-1, (3) FT-2, (4) FT-3.
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Fig.7 Color aspects of mica/Fe2TiO5 composite pigments: (a) mica, (b) FT-1, (c) FT-2, (a) FT-3.
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Fig.8 The interior temperatures of the heat box coated with different types of pigments: (a) blank
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sample, (b) FT-1, (c) FT-2, (d) FT-3.
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The mica/ Fe2TiO5 composite pigments exhibit brilliant yellow colors. Different sized Fe2TiO5 nanorods were coated on the surface of mica particles. The NIR solar reflectance of the composites was as high as 80.3%. The composite pigments exibit strong UV shielding property.