Synthesis and Characterization of Yellow Pigments of Bi1. 7RE0. 3W0

Subscriber access provided by TUFTS UNIV

Article

Synthesis and characterization of yellow pigments of Bi1.7RE0.3W0.7Mo0.3O6 (RE: Y, Yb, Gd, Lu) with highly NIR reflectance Bin Huang, Yu Xiao, Haiyue Zhou, Jinqing Chen, and Xiaoqi Sun ACS Sustainable Chem. Eng., Just Accepted Manuscript • DOI: 10.1021/acssuschemeng.8b02049 • Publication Date (Web): 06 Jul 2018 Downloaded from http://pubs.acs.org on July 6, 2018

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

ACS Sustainable Chemistry & Engineering

Synthesis

and

characterization

of

yellow

pigments

of

Bi1.7RE0.3W0.7Mo0.3O6 (RE: Y, Yb, Gd, Lu) with highly NIR reflectance

Bin Huanga, Yu Xiaoa,c, Haiyue Zhoua, Jinqing Chenc, and Xiaoqi Suna,b*

a.

CAS Key Laboratory of Design and Assembly of Functional Nanostructures, and Fujian Key Laboratory of Nanomaterials, Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou, Fujian 350002, P. R. China.

b. Ganzhou Rare Earth Group Co., Ltd., Ganzhou, 341000, China c.

School of Metallurgy and Chemical Engineering, Jiangxi University of Science & Technology, Ganzhou, 341000, China.

*Corresponding author: X.Q. Sun. Tel./fax: +865926376370. E-mail address: [email protected]

ACS Paragon Plus Environment

ACS Sustainable Chemistry & Engineering 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Abstract:

Brilliant

yellow-orange

pigments

based

on

Page 2 of 24

the

formula

of

Bi1.7RE0.3W0.7Mo0.3O6 (RE = Y, Yb, Gd, Lu) is developed by the traditional solid-state reaction method. Relevant techniques are used for the characterizations of crystal structure, morphology feature, reflectance property and color performance of prepared pigment. The doping of RE/Mo in Bi2WO6 results in the colors of pigments varying from faint yellow to brilliant yellow-orange. Compared with Bi2WO6 pigment, the typical pigment of Bi1.7Lu0.3W0.7Mo0.3O6 greatly improves the yellow hue component (b*) value to be 72.03. Moreover, the NIR reflectances of all the samples are higher than 95% as well as their NIR solar reflectances are above 94%. The typical pigment of Bi1.7Lu0.3W0.7Mo0.3O6 coated on galvanized sheet exhibits excellent coloring performance with a high NIR solar reflectance (83.32%). The acid/alkali resistance studies reveal that the pigments are chemically stable under the atrocious weather conditions. Thus, the superior performances of synthesized pigments have exhibited potentials for energy saving.

Keyword: Bi2WO6; Solid-state reaction; Cool pigment; Near-infrared reflectance

Introduction With the continuous development of urban construction, the urban environment aggravates the crowding of space, which makes the airflow difficult to be circulated. As a result, the so-called ‘urban heat island’ is formed after the heat accumulation [1, 2]. Afterwards, the buildings absorb the excess of solar radiation power, increasing the


Page 3 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


demand of additional energy for cooling. Literature has reported that the Urban Heat Island Effect made the temperature of city center 3-5oC higher than the surrounding area [3, 4]. In order to achieve sustainable development strategy, the energy conservation and environment-friendly are two major global problems [5]. Therefore, it is a challenge to use less source of energy to cool the surrounding environment. According to our knowledge, the heat of object is from absorbing the near infrared band of sunlight. The cool pigment with the capacity of absorbing less solar energy in infrared radiation can effectively reduce the interior temperature [6]. Accordingly, the extra energy for cooling can be saved. The near infrared reflectance pigment coating is different to the ordinary pigment coated in the roof. For instance, the indoor temperature of simulated house coated with Y2Ce1.9Fe0.1O7+δ pigment is lower than that with standard pigment coating for 3.5oC [7]. Hence, it is necessary to develop high near infrared reflectance pigment. Inorganic pigments are widely used in building material, paint, plastics, vehicle and ink, due to their high chemical and physical stability as well as rich colors [8-10]. Unfortunately, some of the inorganic pigments based on complex metal oxides contain heavy metals like chromium, lead, cobalt, cadmium, and antimony [11-13], which increase the importance of developing environmentally friendly pigment to replace traditional heavy metal based pigment. Based on this goal, the environment-friendly inorganic pigment with high NIR reflectance has been widely studied. The molybdenum doped Y2Ce2O7 and silicon doped Y6MoO12 explored rare earth based pigments and obtained cool pigments [14,15]. Typically, the most studied



is the yellow pigment possessed high near infrared reflectance. Recently, the yellow pigments based on iron and tungsten co-doped La2Ce2O7 [16] and BiVO4 coated mica-titanium oxide pigment [17] have been reported. Notably, Rao et al. has also reported that a suite of BiVO4-base brilliant yellow pigment [18-21] and Y-doped Bi2MoO6 yellow pigments [22,23], which are friendly alternatives to the toxic pigments (PbCrO4-based pigment and PbSbO3 pigment) [24,25]. These pigments with high near-infrared reflectance can be served for cold pigments. Bi2WO6 possesses excellent physical and chemical properties [26], which have been widely applied in photocatalysis [27-29]. It is known that Bi2WO6 has three different phases as the temperature is changed. At room-temperature, the structure of Bi2WO6 is orthorhombic Aurivillius, comprising of alternating fluorite-like [Bi2O2]2+ layers and [WO4]2- layers [30], also the layers structure is beneficial to charge transfer. The moderate-temperature forms an orthorhombic structure with high symmetry and the monoclinic phase can be formed at high-temperature [31]. To our knowledge, the near-infrared reflection of Bi2WO6-based pigment has been less reported. In this article, a series of yellow pigments based on the formula of Bi1.7RE0.3W0.7Mo0.3O6 (RE=Y, Yb, Gd, Lu) with a monoclinic structure are obtained by the conventional solid-state reaction route. The morphology, color hue as well as near infrared reflection of RE/Mo co-doped Bi2WO6 have been evaluated.

EXPERIMENTAL SECTION Material and methodology The pigments based on the general formula of Bi1.7RE0.3W0.7Mo0.3O6 (RE=Y, Yb,


Page 4 of 24

Page 5 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Gd, Lu) were synthesized by the conventional solid-state reaction route. Y2O3, Yb2O3, Gd2O3, Lu2O3 (99.99%, purity, Fujian Changting Golden Dragon Rare Earth Co., Ltd. of China), WO3 (AR, sinopharm chemical reagent Co., Ltd), (NH4)6Mo7O24·4H2O (AR, Aladding Reagent (Shanghai) Co., Ltd) and Bi2O3 (99.9%, purity, Aladding Reagent (Shanghai) Co., Ltd) were weighed in the stoichiometric proportions, the raw materials were transferred into an agate mortar and wet milled thoroughly by using acetone as the medium. The slurry was dried in an air oven at 80°C for 1h for getting dried mixture and then calcined in a corundum crucible by electrical furnace, the furnace was heated to 500°C at 10 °C/min and subsequently to 900°C at 5°C/min, the samples were soaked at the final temperature of 900°C for 6h. The calcined compounds were ground once again in an agate mortar into fine powders.

Characterization techniques and instrumentations Phase analysis of synthesized pigment samples were identified by Rigaku Miniflex 600 XRD system using a Cu-Kα radiation. Data were captured at the step scanning mode of ranging from 10° to 80° 2θ at a rate of 10°/min (a step size of 0.02°), the operating conditions was of 40 kV and 15 mA. The morphology of sample was also observed by scanning electron microscopy (S4800, Hitachi, Japan). The chemical composition and element distribution of sample were measured by energy dispersive X-ray spectroscopy (EDS) analysis and elemental mapping using the EMAX x-act- liquid nitrogen less X-ray detector of scanning electron microscopy.



Page 6 of 24

The optical reflectance of pigment sample and corresponding coating sheet were characterized using a UV-vis-NIR spectrophotometer (Agilent carry 5000, America) with polytetrafluoroethylene (PTFE) as a white standard. The powder samples were placed in the cuvette and the reflection spectra were performed in the range of 200-2500 nm with a step size of 1 nm. The NIR solar reflectance (R*) of pigment and coating in the wavelength range of 700 nm to 2500 nm were figured out by the following formula: 2500

R*=

‫׬‬700 rሺλሻiሺλሻdλ 2500

‫׬‬700 iሺλሻdλ

(1)

where r(λ) is the spectral reflectance obtained from experiment and the i(λ) is the solar spectral irradiance obtained from the standard of ASTM G173-03 Reference Spectra (W*m-2*nm-1) [32-34]. The absorption edge was determined by reflectance spectra in the wavelength range from 200 nm to 700 nm and the band gap was calculated according to the equation E(ev)=h·c/λ=1239 (eV·nm)/λ (nm), where λ is the absorption edge. The color performance of synthesized sample was recorded using the spectrophotometer CS-580A (Hangzhou CHN Spec) with CLEDs light source. The CIE L*a*b* (1976) color space was recommended by the Commission Internationale de l’Eclairage (CIE). In the color coordinate system, L* indicates the brightness axis (from black=0 to white=100), a* is from green (-) to red (+), and b* for blue (-) and yellow (+) axis. Moreover, the L*C*H° color model can be also used to describe color performance. The parameter of C*= [(a*)2+(b*)2]1/2 represents the saturation of the color, H°=tan-1(b*/a*) indicates the hue angle, H°=70-105° represents for yellow.


Page 7 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


RESULTS AND DISCUSSION Powder x-ray diffraction analysis The X-ray diffractograms (XRDs) of Bi1.7RE0.3W0.7Mo0.3O6 (RE=Y, Yb, Gd, Lu) samples are shown in Fig.1. As can be seen from XRD patterns, the diffraction peaks of undoped Bi2WO6 compound well match the JCPDS Card of No.39-0256, forming an orthorhombic phase. When the RE/Mo are doped in Bi2WO6 according to the formula of Bi1.7RE0.3W0.7Mo0.3O6, the orthorhombic phase occurs transform. All the doped samples show a pure and monoclinic phase with the space of A2/m, which is similar

to

the

previous

reports

[30,35,36].

The

diffraction

peaks

of

Bi1.7RE0.3W0.7Mo0.3O6 are similar to BiNdWO6 (JCPDS Card No. 34-0057). In additon, there is no found impurity peak and all the peaks of samples are kindred, verifying

Bi1.7RE0.3W0.7Mo0.3O6

solid

solution

is

complete

formation.

Fig.1 (a) X-ray powder diffraction patterns of Bi1.7RE0.3W0.7Mo0.3O6 (RE=Y, Yb, Gd, Lu) pigments; (b) zoom-in part of the range of 2theta from 31.8-32.8°



Morphological studies The scanning electron microscopy (SEM) was used to analyze the size and morphology of Bi1.7RE0.3W0.7Mo0.3O6 pigment. To observe the size and morphology of particles associated to dopants, the Bi2WO6 sample has also been characterized. As shown in Fig. 2, the morphology of particles is irregular shaped. In some degree, the particles are agglomerations. Besides, there is a widespread distribution of particle sizes of Bi1.7RE0.3W0.7Mo0.3O6 sample, the average size of sample varies from 2 to 11um. Compared to Bi2WO6, there is a little difference in morphology and particle size.

Fig. 2 SEM micrographs of Bi1.7RE0.3W0.7Mo0.3O6 (RE = Y, Yb, Gd, Lu) pigments

The chemical composition of obtained pigment was further determined using


Page 8 of 24

Page 9 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


EDS analysis. Fig. 3 presents the EDS spectra and X-ray dot mapping of the typical sample Bi1.7Lu0.3W0.7Mo0.3O6. The EDS spectra of Bi1.7Lu0.3W0.7Mo0.3O6 sample indicates the presence of Bi, Lu, W, Mo and O element (all the expected elements), which are close approximation to the stoichiometric proportion of theoretical composition. X-ray dot mapping of typical Bi1.7Lu0.3W0.7Mo0.3O6 pigment reveals that the elements are uniformly distributed in the sample, which further confirm the homogeneity of formed phases.

Fig. 3 EDS spectra and X-ray dot mapping of Bi1.7Lu0.3W0.7Mo0.3O6 pigment

Optical properties studies The reflectance spectra and absorption spectra of Bi1.7RE0.3W0.7Mo0.3O6 (RE=Y, Yb, Gd, Lu) pigments in the UV-vis region are shown in Fig. 4. As can be seen in Fig.



4, the different rare earths contribute to the shift in absorption edge. A strong absorption around 443 nm in the UV-vis reflectance spectrum of Bi2WO6 sample can be attributed to the charge-transfer transition of hybrid orbitals consisting of Bi 6s and O 2p to W 5d orbitals, the absorption of Bi2WO6 pigment fallen in the blue region of visible light, and a complementary faint yellow can be observed (Fig.5 shows the photographs of designed pigments). In the doped brilliant yellow-orange pigments, the coloring mechanism is based on the shift of the charge transfer band of O(2p)-W(5d) to higher wavelengths (red shifting) by introducing an additional electronic energy level of RE. Being a lower electronegativity element, the molybdenum may induce higher covalency and shift the charge transfer band to higher wavelength. The diffuse reflectance spectra reveal that the RE3+, Mo6+ doping of Bi2WO6 based pigments have an effect on the optical properties, which further confirms the effective doping of Bi2WO6. The band gap energies of designed pigments were calculated from reflectance spectra in the UV-vis region. As seen from Table 1, the band gap of Bi1.7RE0.3W0.7Mo0.3O6 is decreased compared to Bi2WO6 pigment, which means that the empty 5d orbital of W6+in solid solution is combined with extra energy levels. With the doping of rare earth, a shift of spectra toward higher wavelength can be observed. Prokofiev et al. [37] has explored the rule of the optical band gap variation of rare earth sesquioxides. According to their research, the occupied 4f band in rare earth sesquioxides are located above the O 2p level, therefore, the 4f-d transition contributing to determining the band gap value. For the doping rare earth element of Y,


Page 10 of 24

Page 11 of 24

there is no f electron and the orbitals of Y 4d and Mo 4d are inserted below the W 5d orbitals. As a result, the interaction between O 2p and W 5d orbital is strengthened, this in turn decreases the bandgap energy significantly. Differently, the occupied 4f band in Yb oxide locates above the O 2p band, hence the band gap energy can be determined by 4f-d transition. Rao et al [18] stated that the increase of atomic number of rare earth became gradually lowered 4f electronic level, finally approached to the valence band, which resulted in an increase of band gap energy. Whereas, the band gap energy of Gd-doped pigment is 2.40eV, it is higher than 2.37eV of Yb (with higher atomic number than Gd) -doped pigment in this study. The freak variation of band gap value can be explained by the stability of shell, the high stability of half-4f shell makes the position of the 4f orbital of Gd oxide approaching in the valence band, causing the high band gap value. As a result, the band gap value is also high. When the f-band gradually enters into the 2p band, the Eg values increase accordingly. On the other hand, the different RE 4f levels and band gaps result in the different colors

1.0 Reflectance(%)

100

0.8

Absorbance(a.u)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0.6

80

60

Bi2WO6 Y Yb Gd Lu

40

20

0 200

300

0.2

400

500

600

700

800

Wavelength(nm)

0.4 Y Yb Gd Lu

0.0 200

300

400

500

600

700

Wavelength(nm)


800


Page 12 of 24

Fig. 4 UV-vis absorption and reflectance spectra (insert) of Bi1.7RE0.3W0.7Mo0.3O6 (RE=Y, Yb, Gd, Lu) pigments

Fig. 5 Photographs of Bi1.7RE0.3W0.7Mo0.3O6 (RE=Y, Yb, Gd, Lu) pigments Table 1 Color coordinates, band gap values of Bi1.7RE0.3W0.7Mo0.3O6 (RE = Y, Yb, Gd, Lu) pigments RE

L*

a*

b*

C*

Ho

Eg (eV)

Gd

84.98

4.04

67.34

67.46

86.57

2.40

Y

83.44

10.42

71.80

71.53

83.49

2.37

Yb

84.21

10.46

71.20

70.53

84.16

2.37

Lu

84.48

10.33

72.03

71.20

84.60

2.38

Bi2WO6

91.32

-3.72

20.43

20.77

100.32

2.79

Objects accumulated heat is mainly related to their abilities of absorbing near infrared reflectance, possessing high near infrared reflectance can reserve less heat. In order to study the near infrared reflectance properties of pigments, The NIR reflectance spectra of Bi1.7RE0.3W0.7Mo0.3O6 (RE = Y, Yb, Gd, Lu) pigments are measured and illustrated in Fig.6. To compare the NIR reflectance associated to different dopants, the Bi2WO6 samples have also been analyzed. As can be seen from the reflectance spectra, the parent pigment of Bi2WO6 exhibits average NIR reflectance (R) of about 97.08%. With the doping of RE3+, Mo6+ to substitute Bi3+and W6+, the NIR reflectances of pigments slightly change. All of the pigments possess high NIR reflectances (＞95%), which are higher than those of yellow pigments of


Page 13 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Li0.1La0.1Bi0.8Mo0.2V0.8O4 (R = 90%), (LiLaZn)1/3MoO4-BiVO4 (R=89%-95%) and iron doped La2Mo2O7 pigments (R = 71%-93%) [18,19,38]. Not only the doping of additives into pigments possess high NIR reflectance, but also the colors of pigments are switched from faint yellow to yellow-orange, which contributes to satisfy the public demands for colors. In accordance with the ASTM standard G173-03, the NIR solar reflectance spectra of Bi1.7RE0.3W0.7Mo0.3O6 (RE=Y, Yb, Gd, Lu) pigments are computed and displayed in Fig.7. The detailed information of NIR reflectance value and NIR solar reflectance value are listed in Table 2. As can be seen from Table 2, the pigment of Bi2WO6 possesses an NIR solar reflectance (R*) of 95.71%. With the different doping of RE element, the near-infrared solar reflectance of all the pigments (yellow-orange, ＞94%) changes relatively little. It means that the pigments barely absorb NIR solar energy. The designed pigments with high NIR solar reflectance possess the potentials as good insulation materials [39].

Table 2 NIR reflectance and NIR solar reflectance of Bi1.7RE0.3W0.7Mo0.3O6 (RE = Y, Yb, Gd, Lu) pigments RE

Bi2WO6

Gd

Y

R%

97.08

97.49

96.64

97.26

95.71

R*%

95.71

94.96

95.74

94.75

95.25


Yb

Lu


100

Reflectance(%)

80

60 Bi2WO6 Y Yb Gd Lu

40

20

0 750

1000

1250

1500

1750

2000

2250

2500

Wavelength(nm)

Fig.6 NIR reflectance spectra of Bi1.7RE0.3W0.7Mo0.3O6 (RE=Y, Yb, Gd, Lu) pigments

120

NIR Solar Reflectance(R%)

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 24

Bi2WO6

100

Y Yb Gd Lu

80 60 40 20 0

750

1000

1250

1500

1750

2000

2250

2500

Wavelength(nm)

Fig.7 NIR Solar reflectance spectra of Bi1.7RE0.3W0.7Mo0.3O6 (RE=Y, Yb, Gd, Lu) pigments

Color performance The chromatic properties of Bi1.7RE0.3W0.7Mo0.3O6 (RE = Y, Yb, Gd, Lu) pigments were evaluated by CIE 1976 L*a*b* color coordinate values. Table 1 summarizes clearly the color coordinate values of designed pigments. Doping RE3+


Page 15 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


for Bi3+and Mo6+ for W6+ results in the decrease of L* values for 7, which means that the colors of the samples become darken. The a* value of Bi2WO6 pigment is -3.72, indicating that the color of pigment trends to be green. Subsequently, the greenness transforms to be redness (RE/Mo doped pigment). Namely, the greenness hues of pigments are weakened whereas the redness are enhanced. It is worth mentioning that the b* values of pigments have been greatly enhanced. The Lu doped pigment gives the highest b* value of 72.03, indicating that the pigment possesses high yellowness. Furthermore, the colors of pigments become saturation, which can be observed from C* (from 20.77 to 71.53). Because the Ho value of samples are closed to 90 (H° = 70-105° for yellow), the hue angles (Ho) make an allusion to the intense yellow color of synthetic pigments [19,40], which further indicates the excellent yellow pigments. As mentioned above, the colors of samples are tuned from faint yellow to brilliant yellow-orange.

Coating studies To study the properties of coating pigments, the typical pigment of Bi1.7Lu0.3W0.7Mo0.3O6 is studied in this article. Bi1.7Lu0.3W0.7Mo0.3O6 exhibits better chromatic properties to be coated on the galvanized sheet (roofing material). In this study, the weight ratio of pigment to alkyd resin (binder) was 1:1. The pigment powder was uniformly mixed with alkyd resin after grinding, then the above mixture slurry of coating was coated on the galvanized sheet. Finally, the metal sheet sample was dried in an oven at 90oC. The coating films of Bi1.7Lu0.3W0.7Mo0.3O6 pigment



were estimated using QNix8500 profiler in the range of 80-85µm. Fig. 8 exhibits the NIR reflectance spectra and corresponding NIR solar reflectance spectra of bare galvanized sheet and pigment coating. It is obvious that the coatings greatly enhance the thermal insulation property of galvanized sheet. The bare metal sheet possesses a low NIR solar reflectance (calculated in accordance with ASTM standard G173-03) of 16.48% and NIR reflectance of 18.04%. Whereas, the value of Bi1.7Lu0.3W0.7Mo0.3O6 pigment coating is 83.32%, the pigment coating indicates a high average NIR reflectance of 79.73%. Fig. 8 has also shown the photographs of coatings, the coating of Bi1.7Lu0.3W0.7Mo0.3O6 exhibits bright color (L*=81.28, a*=6.35, b*=63.71) with excellent coating performance.

Fig.8 NIR solar reflectance spectra of Bi1.7Lu0.3W0.7Mo0.3O6 pigment and bare galvanized sheet. (NIR reflectance spectra and photographs of coatings in the insets)

Acid/alkali resistance studies of the pigments


Page 16 of 24

Page 17 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


In order to make the designed pigments useful in substrate, it is necessary to evaluate their chemical stabilities in acidic and alkaline media. Here, we chose the typical pigments of Bi1.7Yb0.3W0.7Mo0.3O6 soaked in 5% HNO3, HCl, H2SO4 and NaOH solution for 30 minutes, respectively. Then the suspension liquid of pigment was filtered and washed with deionized water repeatedly. Finally, the wet pigments were dried in the oven. The color coordinates of the soaked powder were measured and compared with the original pigment. Table 3 lists the color coordinates and calculated the total color difference (∆E*) of all the samples. BecauseΔE* ≤ 5 units is considered good [19], the ∆E* values of all the samples indicate that the synthesized pigments are chemically stable after the acid/alkali tests. Table 3 Color coordinates and total color difference (∆E*) after acid/alkali resistance test 5% Acid/alkali

∆L *

∆a *

∆b *

∆E*

HNO3

1.05

1.01

1.99

2.46

HCl

1.65

0.56

2.31

2.89

H2SO4

0.5

0.84

0.14

0.98

NaOH

0.65

0.69

0.12

0.95

∆E* = [(∆L*)2+(∆a*)2+(∆b*)2]1/2

CONCLUSIONS In

this

article,

some

inorganic

pigments

with

the

formula

of

Bi1.7RE0.3W0.7Mo0.3O6 (RE=Y, Yb, Gd, Lu) have been successfully developed via solid state reaction method. The doping of RE/Mo in Bi2WO6 changes the colors of pigments from faint yellow to brilliant yellow-orange. The pigment of Bi1.7Lu0.3W0.7Mo0.3O6 exhibits excellent color properties (L*=84.48, a*=10.33,



b*=72.03) with high NIR reflectance of 95.71%. Furthermore, the typical pigment of Bi1.7Lu0.3W0.7Mo0.3O6 used as coating reveals favorable color properties. The NIR reflectance and NIR solar reflectance of Bi1.7Lu0.3W0.7Mo0.3O6 pigment coating achieves 79.73% and 83.32%, respectively. The designed samples reveal chemical stabilities in the acid/alkali tastings. In summary, the developed pigments with high NIR solar reflectance possess the potentials necessary to be used as cool materials for reducing the heat build-up.

ACKNOWLEDGMENTS This work is supported by ‘Hundreds Talents Program’ and Science and Technology Service Network Initiative from Chinese Academy of Sciences, Science and Technology Major Project of Ganzhou (2017-8) and Xiamen Technology Plan (3502Z20172032).

REFERENCES [1] Santamouris, M.; Synnefa, A.; Karlessi, T. Using advanced cool materials in the urban built environment to mitigate heat islands and improve thermal comfort conditions. Sol. Energy. 2011, 85, DOI 10.1016/j.solener.2010.12.023. [2] Liu, L.; Han, A.; Ye, M.; Zhao, M. Synthesis and characterization of Al3+ doped LaFeO3 compounds: A novel inorganic pigments with high near-infrared reflectance. Sol. Energy Mater. Sol. Cells. 2015, 132, DOI 10.1016/j.solmat.2014.08.048. [3] Zinzi, M.; Agnoli, S. Cool and green roofs. An energy and comfort comparison between passive cooling and mitigation urban heat island techniques for residential buildings in the Mediterranean


Page 18 of 24

Page 19 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


region. Energ. Buildings. 2012, 55, DOI 10.1016/j.enbuild.2011.09.024. [4] Kaur, B.; Quazi, N.; Ivanov, I.; Bhattacharya, SN. Near-infrared reflective properties of perylene derivatives. Dyes Pigm. 2012, 92, DOI 10.1016/j.dyepig.2011.06.011. [5] Baltrusaitis, J.; Sviklas, A .M. Phase Composition of Aqueous Urea–Ammonium Nitrate (UAN)– Zinc Nitrate Solutions for Sustainable Reuse of Zinc Containing Industrial Pigment Waste. ACS Sustainable Chem.Eng. 2015, 3, DOI 10.1021/acssuschemeng.5b00067. [6] Raj, A. K. V.; Rao, P.; Divya, S., Ajuthara, T. R. Terbium doped Sr2MO4 [M=Sn and Zr] yellow pigments with high infrared reflectance for energy saving applications. Powder Technol. 2017, 311, DOI 10.1016/j.powtec.2017.01.089. [7] Zhao, M.; Han, A.; Ye, M.; Wu, T. Preparation and characterization of Fe3+ doped Y2Ce2O7 pigments

with

high

near-infrared

reflectance.

Sol.

Energy.

2013,

97,

DOI

10.1016/j.solener.2013.08.007. [8] Mariani, F. Q.; Borth, K. W.; Müller, M.; Dalpasquale, M.; Anaissi, F. J. Sustainable innovative method to synthesize different shades of iron oxide pigments. Dyes Pigm. 2017, 137, DOI 10.1016/j.dyepig.2016.10.024. [9] Chen, S.; Cai, M.; Ma, X. Environmental-friendly yellow pigments based on Zr doped Y4MoO9. J. Alloys Compd. 2016, 689, DOI 10.1016/j.jallcom.2016.07.174. [10] Karlessi, T.; Santamouris, M.; Apostolakis, K.; Synnefa, A.; Livada, I. Development and testing of thermochromic coatings for buildings and urban structures. Sol. Energy. 2009, 83, DOI 10.1016/j.solener.2008.10.005. [11] Chung, J. W.; Yang, H. K.; Moon, B. K.; Choi, B. C.; Jeong, J. H.; Kim, J. H. Luminescence characteristics of Pr3+ ion doped CaTiO3 nanopowder phosphors synthesized by solvothermal method. J.



Nanosci. Nanotechno. 2011, 11, DOI 10.1166/jnn.2011.4407. [12] Bae, B.; Tamura, S.; Imanaka, N. Novel environment-friendly yellow pigments based on praseodymium(III) tungstate. Ceram. Inter. 2017, 43, DOI 10.1016/j.ceramint.2017.02.103. [13] Levinson, R.; Berdahl, P.; Akbari, H. Solar spectral optical properties of pigments—Part II: survey of common colorants. Sol. Energy Mater. Sol. Cells. 2005, 89, DOI 10.1016/j.solmat.2004.11.013. [14] Vishnu, V. S.; Reddy, M. L. Near-infrared reflecting inorganicpigments based on molybdenum and praseodymium doped yttrium cerate: Synthesis, characterization and optical properties. Sol. Energy Mater. Sol. Cells. 2011, 95, DOI 10.1016/j.solmat.2011.05.042. [15] George, G.; Vishnu, V. S.; Reddy, M. L. The synthesis, characterization and optical properties of silicon and praseodymium doped Y6MoO12 compounds: Environmentally benign inorganic pigments with high NIR reflectance. Dyes Pigm. 2011, 88, DOI 10.1016/j.dyepig.2010.05.010. [16] Chen, J.; Xiao, Y.; Huang, B.; Sun, X. Sustainable cool pigments based on iron and tungsten co-doped lanthanum cerium oxide with high NIR reflectance for energy saving. Dyes Pigm. 2018, 154, DOI 10.1016/j.dyepig.2018.02.032. [17] Yuan, L.; Han, A.; Ye. M.; Chen, X.; Ding, C.; Yao, L. Preparation, characterization and thermal performance evaluation of coating colored with NIR reflective pigments: BiVO4 coated mica-titanium oxide. Sol. Energy. 2018, 163, DOI 10.1016/j.solener.2018.01.009. [18] Sameera, S.; Rao, P.; Divya, S.; Raj, A. K. V. Brilliant IR Reflecting Yellow Colorants in Rare Earth Double Molybdate Substituted BiVO4 Solid Solutions for Energy Saving Applications. ACS Sustainable Chem.Eng. 2015, 3, DOI 10.1021/acssuschemeng.5b00198. [19] Aju, T. T. R.; Rao, P.; Divya, S.; Raj, A. K. V. Sreedharan, S. T. Enhanced NIR reflectance with brilliant yellow hues in scheelite type solid solutions, (LiLaZn)1/3MoO4-BiVO4 for energy saving


Page 20 of 24

Page 21 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


products. ACS Sustainable Chem.Eng. 2017, 5, DOI 10.1021/acssuschemeng.7b00485. [20] Kumari, L. S.; Rao, P.; Radhakrishnan, A. N. P.; James, V.; Sameera, S.; Koshy, P. Brilliant yellow color and enhanced NIR reflectance of monoclinic BiVO4 through distortion in VO43− tetrahedra. Sol. Energy Mater. Sol. Cells. 2013, 112, DOI 10.1016/j.solmat.2013.01.022. [21] Fathimah, S. S.; Rao, P.; Sandhya, K. L. Potential NIR reflecting yellow pigments in (BiV)1-x(YNb)xO4 solid solutions. Chem. Lett. 2013, 42, DOI 10.1246/cl.130111. [22] Kumari, L. S.; Gayathri, T. H.; Sameera, S. F.; Rao, P. Y-Doped Bi2MoO6 Yellow Pigments for the Coloration of Plastics. J. Am. Ceram. Soc. 2011, 94, DOI 10.1111/j.1551-2916.2010.04268.x. [23] Kumari, L. S.; Rao, P.; Sameera, S.; James, V.; Koshy, P. Effects of rare earth substitution on the optical properties of Bi2MoO6 for coloring applications. Mater. Res. Bull. 2015, 70, DOI 10.1016/j.materresbull.2015.04.025. [24] Cao, L.; Fei, X.; Zhao, H. Environmental substitution for PbCrO4 pigment with inorganic-organic hybrid pigment. Dyes Pigm. 2017, 142, DOI 10.1016/j.dyepig.2017.03.024. [25] Badenes, J. A.; Vicent, J. B.; Llusar, M.; Tena, M. A.; Monros, G. The nature of Pr-ZrSiO4 yellow ceramic pigment. J. Mater. Sci. 2002, 37, DOI 10.1023/A:101453700. [26] Li, G. Electrospinning fabrication and photocatalytic activity of Bi2WO6 nanofibers. J. Mater. SciMater. El. 2017, 28, DOI 10.1007/s10854-017-7050-z. [27] Gu, H.; Yu, L.; Wang, J.; Ni, M.; Liu, T.; Chen, F. Tunable luminescence and enhanced photocatalytic activity for Eu(III) doped Bi2WO6 nanoparticles. Spectrochim. Acta A. 2017, 177, DOI 10.1016/j.saa.2017.01.034. [28] Wang, Q.; Lu, Q.; Ji, X.; Liu, Z.; Wei, M.; Guo, E. One-dimensional Bi2MoxW1-xO6 sosoloids: controllable synthesis by electrospinning process and enhanced photocatalytic performance. J.



Nanopart. Res. 2017, 19, DOI 10.1007/s11051-017-3919-2. [29] Zhang, F.; Song, N; Zhang, S.; Zou, S.; Zhong, S. Synthesis of sponge-loaded Bi2WO6/ZnFe2O4 magnetic photocatalyst and application in continuous flow photocatalytic reactor. J. Mater. Sci- Mater. El. 2017, 28, DOI 10.1007/s10854-017-6530-5. [30] Berdonosov, P. S.; Charkin, D. O.; Knight, K. S.; Johnston, K. E.; Goff, R. J.; Dolgikh, V. A.; Lightfoot, P. Phase relations and crystal structures in the systems (Bi,Ln)2WO6 and (Bi,Ln)2MoO6 (Ln=lanthanide). J. Solid State Chem. 2006, 179, DOI 10.1016/j.jssc.2006.07.008. [31] Mcdowell, N. A.; Knight, K. S.; Lightfoot, P. Unusual high‐temperature structural behaviour in ferroelectric Bi2WO6. Chem-Eur. J. 2010, 12, DOI 10.1002/chem.200500904. [32] Thongkanluang, T.; Kittiauchawal, T.; Limsuwan, P. Preparation and characterization of Cr2O3– TiO2–Al2O3–V2O5 green pigment. Ceram. Int. 2011, 37, DOI 10.1016/j.ceramint.2010.09.044. [33] Levinson, R.; Akbari, H.; Berdahl, P. Measuring solar reflectance—Part I: Defining a metric that accurately predicts solar heat gain. Sol. Energy. 2010, 84, DOI 10.1016/j.solener.2010.04.018. [34] Standard tables for reference solar spectral irradiances: Direct normal and hemispherical on 37° tilted surface; ASTM International:West Conshohocken, PA, 2012, DOI 10.1520/G0173-03R12. [35] Pasternak, S.; Levy, D.; Paz, Y.; Pokroy, B. Structural analysis and optical properties of the Bi2−xYxWO6 system. CrystEngComm. 2016, 18, DOI 10.1039/C6CE01094F. [36] Santha, N.; Koshy, P.; Sebastian, M. T.; Ratheesh, R. Preparation and characterization of bismuth rare earth tungstate (BiREWO6) dielectric ceramics. J. Mater. Sci-Mater. El. 2002, 13, DOI 10.1023/A:1014884118353. [37] Prokofiev, A. V.; Shelykh, A. I.; Golubkov, A. V.; Smirnov, I. A. Crystal growth and optical properties of rare earth sesquiselenides and sesquisulphides-new magneto-optic materials. J. Alloys


Page 22 of 24

Page 23 of 24 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Compd. 1995, 219, DOI 10.1016/0925-8388(94)05058-9. [38] Han, A.; Ye, M.; Liu, L.; Feng W.; Zhao M. C. Estimating thermal performance of cool coatings colored with high near-infrared reflective inorganic pigments: iron doped La2Mo2O7 compounds. Energ. Buildings, 2014, 84, DOI 10.1016/j.enbuild.2014.08.024. [39] Huang, B.; Xiao, Y.; Huang, C.; Chen, J.; Sun, X. Environment-friendly pigments based on praseodymium and terbium doped La2Ce2O7 with high near-infrared reflectance: Synthesis and characterization. Dyes Pigm. 2017, 147, DOI 10.1016/j.dyepig.2017.08.004. [40] 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 Pigm. 2017, 138, DOI 10.1016/j.dyepig.2016.11.024.

Graphical Abstract



To achieve sustainable development strategy, the synthesized near infrared reflectance pigment (Bi1.7RE0.3W0.7Mo0.3O6) have exhibited potentials for energy saving.


Page 24 of 24

Synthesis and Characterization of Yellow Pigments of Bi1. 7RE0. 3W0

Recommend Documents