Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 145 (2015) 376–383
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Spectroscopic investigation of amber color silicate glasses and factors affecting the amber related absorption bands Morsi M. Morsi a,⇑, Samya I. El-sherbiny b, Karam M. Mohamed c a
Glass Research Dept., National Research Centre, 33 E l Bohoth st., Dokki, Giza, P.O. 12622, Egypt Chemistry Department, Faculty of Science, Helwan University, Helwan, Egypt c Cairo for Glass Manufacturing Co., 10th of Ramadan City, Egypt b
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
The amber color is due two
Decolorization effect of ZnO added per 100 g glass on the amber bands with peaks at 420 nm and 478 nm. The decomposition rate of these bands indicates that they are of different origin. 8 7 6
Absorbance
absorption bands with peaks at 420 and 478 (nm). The two amber related bands are of different origin. NaNO3, ZnO, Cu2O cause decolorization of the amber glass color. Se intensifies the amber color. Amber chromophores are converted into Fe3+ in tetrahedral sites when deteriorate.
5 0.0g
4 0.1g
0.0g 0.1g 0.2g 0.5g 1.0g
3 2
0.2g
1 0
0.5g 1.0g 300
400
500
600
700
800
900 1000 1100
Wavelength (nm)
a r t i c l e
i n f o
Article history: Received 7 September 2014 Received in revised form 8 February 2015 Accepted 1 March 2015 Available online 9 March 2015 Keywords: Optical properties UV–Vis spectroscopy Amber glass Amber chromophore Absorption bands
a b s t r a c t The effects of carbon, Fe2O3 and Na2SO4 contents on the amber color of glass with composition (wt%) 64.3 SiO2, 25.7 CaO, 10 Na2O were studied. The effect of some additives that could be found in glass batch or cullets on the amber related absorption band(s) was also studied. An amber related absorption band due to the chromophore Fe3+O3S2 was recorded at 420 nm with shoulder at 440 nm. A second amber related band recorded at 474 nm with shoulder at 483 nm was assigned to FeS. Increasing melting time at 1400 °C up to 6 h caused fainting of the amber color, decreases the intensities of the amber related bands and shifted the first band to 406 nm. Addition of ZnO, Cu2O and NaNO3 to the glass produced decolorizing effect and vanishing of the amber related bands. The effects of melting time and these additives were explained on the bases of destruction the amber chromophore and its conversion into Fe3+ in tetrahedral sites or ZnS. Addition of Se intensifies the amber related bands and may cause dark coloration due to the formation of Se° and polyselenide. Amber color can be monitored through measuring the absorption in the range 406–420 nm. Ó 2015 Elsevier B.V. All rights reserved.
Introduction Glass containers have a number of indisputable qualitative advantages over other forms of packaging: transparency, chemical ⇑ Corresponding author. Tel.: +20 1223733794. E-mail address: [email protected] (M.M. Morsi). http://dx.doi.org/10.1016/j.saa.2015.03.001 1386-1425/Ó 2015 Elsevier B.V. All rights reserved.
inertness, safety, the possibility of recycling and salvaging of wastes. Brown, red and green glass containers have another important characteristic: strong absorption of ultraviolet and shortwavelength of visible light. These characteristics provide long-term biological protection of the contents against 2900–4500 angstrom of light [1]. Many chemicals and drugs should be protected from deterioration. This draws attention, to the protective function of
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the colored packaging. Colored filters are also used to protect the lens, retina and other ocular tissues against the hazard of light damage [2]. Coloration of glass can be produced by the different means of which by ions of the transition elements or by the mutual interaction of valance electrons of ions that have more than one valence [3,4]. Iron ions of Fe3+ oxidation state show absorption bands in sodium silicate glass at 380, 420, 435 (nm) giving rise to a yellow green coloration to the glass, while Fe2+ ions show absorption band at 1050 nm associated with blue green coloration to the glass [5,6]. In some cases, iron ions are added to the glass batch in order to produce a special type of colored glass called amber glass. Sulfur, together with carbon and iron compounds, is used to form iron polysulfides and produce amber glass ranging from yellowish to almost black. In binary alkali borate glasses containing sulphur and dissolved water attained blue coloration. This color is suggested to be due to S2 (hypersulfide) ion [7]. Imparting amber and brown colors to glass containers are achieved in the presence of iron oxides, sulfide sulfur and a reducing atmosphere. Several researchers [8–12] have investigated the nature of the amber glass and the conditions for its production. They reported that amber chromophore is a colorant complex consists of the central Fe3+ ion in a tetrahedral coordination surrounded by three ions of oxygen O2 and one sulfide sulfur ion S2 , [Fe3+O3S2 ]5 . Amber glass is classed traditionally as an unstable glass. It has been found experimentally that amber chromophore is thermally decomposed with increasing temperature [13]. The UV–Vis spectroscopic measurement indicated that, with increasing temperature, the intensity of the absorption bands of the amber chromophore decreases. These glasses are made by melting batch containing iron and sulfate ions as well as carbon (reducing agent). Carbon reduces part of the sodium sulfate to sulfide. Sulfur in the course of amber glass melting may exist in different degrees of oxidation: S6+ (Na2SO4, SO3), S4+ (SO2), S2 (Na2S, FeS) [14–16]. In a reducing atmosphere the content of sulfide sulfur varies insignificantly, whereas the reduction of iron oxides proceeds more intensely. Thus, the preservation of sulfide sulfur in glass facilitates the reduction of iron oxides and increases the content of Fe2+ which, as reported [11], does not participate in the formation of the amber chromophore. A rapid method for monitoring the amber color of glasses has been developed by measuring light transmission at 525 nm [17]. The amber color intensity at a wavelength of 410 nm has been measured for soda-lime-silica glasses [10]. The dominant wavelength of green and brown glass bottles has been reported to fall within the ranges 552–558 nm and 578–586 nm, respectively, to guarantees that the bottles will have high protective qualities [12]. In recent years the glass industry has begun to use the CIE (international commission on illumination) system of color notation, where the data can be obtained directly from a recording spectrophotometer [18–21]. Determination of the amber color with measurements of its absorption at certain position represents a rapid method that could be used in quality control during the production process. So the position of this band is of prime importance, yet the literature reported different positions for measuring light transmission at 525 nm. [17] or in the range 578–586 nm [12] or at 410 nm [10]. The aim of the present work is to study the nature and position of the amber absorption band(s) that could be used for monitoring amber color in quality control purposes. The effect of graphite, Na2SO4 and Fe2O3 content added to glass batch will be studied. The study will also include the effect of melting time and effect of some additives such as ZnO, Cu2O, NaNO3 and Se on the amber color and the amber related absorption band(s). These additives may affect the color during production of amber glass.
Experimental details Soda lime silica glass of the composition 64.3 SiO2, 25.7 CaO, 10 Na2O (wt%) was used for preparation of samples containing different additives. Glass batches were prepared using sands, and limestone of the chemical composition listed in Table 1. Sodium carbonate of 99.5% purity, graphite (99.3 wt% C) and chemical grade additives of Na2SO4, Fe2O3, ZnO, NaNO3, Cu2O and Se were used. Table 2 lists the nominal composition of the glasses studied. Batches of 100 g were prepared by weighing the appropriate proportions of the powdered ingredients. The batches were mixed, and then melted in a platinum (2% rhodium) crucible, in an electrically heated Globar furnace. The furnace temperature was raised slowly and gradually up to temperature of (1400 °C), to avoid spattering or splashing of the batch materials during melting. The molten batches were held for 2 h with occasional swirling to ensure homogenization of the melts. The melts were then cast onto hot steel rectangular moulds and the glass samples were then rapidly transferred to a muffle furnace adjusted at 550 °C for annealing to obtain strain – free glass samples. The furnace was then turned off to cool to room temperature. Samples were polished to a thickness around 3 mm for spectrophotometer measurements. A Perkin Elmer Lambda 25 UV/Vis Spectrophotometer was used for absorption spectra measurements in the range of wavelengths of 300–1100 nm. Results and discussion The optical absorption characteristics of the parent base glass The absorption spectrum of the base soda-lime-silica glass (No. A1) free of additives (Fig. 1) shows a sharp absorption peak at 335 nm and no noticeable absorption at the visible or at the NIR. The absorption band appeared at 335 nm for sample No. A1 seems to be due to impurities of iron oxide in the glass batch. Effect of Fe2O3 content Fig. 2 shows the absorption spectra of the base soda-lime-silica glass containing 0.5 g carbon and 0.72 g Na2SO4 after doping with different amounts of Fe2O3. The spectra show several absorption bands in the UV–Visible-NIR. These bands appear at 346 nm, 370 nm, 420 nm (with a shoulder at 440 nm), 474 nm (with a shoulder at 483 nm) and a broad band around 1020 nm. The intensities of these bands increase with iron oxide content. The glasses appeared visually with different intensities of amber color. Sample A2 appeared with orange hue and sample No. A5 with 0.5 g/100 g glass has the darker amber color. The optical spectra of the glass samples containing 0.5 g carbon and 0.72 Na2SO3 doped with different Fe2O3contents (g/100 g glass) are shown in Fig. 2. Iron in glass exists as equilibrium between ferric ion (Fe3+) and ferrous ion (Fe2+). Several typical spectral features due to the transitions originating from both Fe2+ and Fe3+ oxidation states of iron are clearly seen in this figure. The main band of Fe2+ is observed as broad band at wavelength
Table 1 Chemical composition of raw materials. Contents
Sand
Lime stone
SiO2 Al2O3 CaO Mgo Fe2O3 LOI
99.60 0.20 0.05 0.03 0.02 0.05
0.15 0.10 55.20 0.10 0.02 44.42
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Table 2 Nominal composition (wt%) and melting times of glasses studied. No.
SiO2
CaO
Na2O
A1 A2 A3 A4 A5 A6 A7 A8 A9 10 A11 A12 A13 A14 A15 A16 A17 A18 A19 A20 A21 A22 A23 A24 A25 A26 A27 A28 A29 A30 A31 A32
64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3
25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7
10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0
Additives g/100 g glass Na2SO4
C
Fe2O3
ZnO
NaNO3
Cu2O
Se
– 0.72 0.72 0.72 0.72 0.72 0.72 0.72 0.72 0.56 0.64 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8
– 0.5 0.5 0.5 0.5 0.1 0.2 0.3 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4
– 0.063 0.125 0.25 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5
–
–
–
–
0.1 0.2 0.5 1.0 0.01 0.05 0.2 0.5 1.0 0.01 0.02 0.04 0.1 0.1 0.2 0.5 1.0 Melted at 1400 °C for 3 h Melted at 1400 °C for 4 h Melted at 1400 °C for 6 h
0.50
420
8
474 483
Fe2O3 added (g/100g glass)
0.45
Base Glass
0.40
7 6
Absorbance
Absorbance
0.35 0.30 0.25 0.20
5 4
370
2
0.10
1
346
0.25 0.125 0.06
0
0.00 300
400
500
600
700
800
900 1000 1100
Wavelength (nm )
A5 A4 A3 A2 0.5
3
0.15
0.05
0.50 g 0.25 g 0.125 g 0.06 g
440
300
400
500
600
700
800
900 1000 1100
Wavelength (nm)
Fig. 1. UV–Vis-NIR spectra of the parent base glass sample A1 without any additives.
Fig. 2. UV–Vis-NIR spectra of glass samples containing 0.5 g carbon and 0.72 g Na2SO3 doped with different Fe2O3 contents (g/100 g glass): 0.063 (A2), 0.125 (A3), 0.25 (A4) and 0.5 (A5).
around 1020 nm. Similar absorption band has been observed in some silicate glasses at 1000–1050 nm and attributed to Fe2+ in tetrahedral coordination [4,22,23], which has been attributed to the spin-allowed transitions corresponding to 5E (D) ? 5T2 (D) for tetrahedral coordinated Fe2+ sites [24,25]. The absorption bands of Fe3+ have been reported to be usually observed at 385, 417, 440 and 500 (nm) and are attributed to Fe3+ in tetrahedral coordination [22,26,27,6]. The absorption bands due to Fe3+ observed in the present study (Fig. 2) are recorded at 346, 370 (nm). The bands at 420 with
shoulder at 440 and 474 with shoulder at 483 (nm) are expected to be related to the amber color. From Fig. 2 it can be noticed that increasing the iron oxide content increases the absorption bands of Fe3+ and Fe2+. The highest intense peak at 474 and 483 (nm) for glass No. A5 may explain its deeper amber color relative to the other samples Nos. A2, A3 and A4. The increase of the band of ferrous ions can be assigned to increasing the proportion of Fe2+ as the total iron oxide amount increases. The absorption band appeared at 335 nm due to impurities of iron oxide in sample No. A1 (Fig. 1) is shifted to 346 nm in the
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spectra of other glasses due to the effect of the tails of the neighboring band at 370 nm.
2.0
Effect of reducing agent (carbon)
1.6
Absorbance
Fig. 3 shows ultraviolet–visible spectra of glass samples A6–A9 in comparison of with that of glass A5. It shows the effect of adding different amounts of carbon (graphite) to glass batch containing 0.5 g Fe2O3 and 0.72 g Na2SO4 on their absorption spectra in comparison with that of glass A5 with 0.5 g carbon (g per 100 g glass). Glasses Nos. A5 and A9 containing 0.5 g Fe2O3 and 0.72 g Na2SO4, and doped with 0.5 and 0.4 g carbon, respectively, appeared visually amber in color. Glasses Nos. A6, A7, and A8, with 0.1, 0.2 and 0.3 g carbon / 100 g glass, respectively, appeared greenish blue in color. From Fig. 3 it can be seen that absorption peaks related to amber color at 420 (with shoulder at 440 nm) and 474 nm (with shoulder at 483 nm) are developed in the spectra of glasses Nos. A9 and A5 with 0.4 and 0.5 g/100 g glass, respectively. These bands which are related to amber color are not observed in glasses Nos. A6–A8 that contains low carbon content (less than 0.3 g/100 g glass). The absorption bands in the spectra of samples A6–A8 in the regions of 346 nm and 370 nm are clearly decreased with increasing carbon content (more clear in Fig. 4). At the same time the NIR band around 1020 nm of the glasses appears in all the intended samples, increases with carbon contents. Carbon acts as reducing agent and sodium sulfate acts as oxidizing agent, then with increasing carbon, the sulfate is reduced to sulfide which response with iron forming amber chromophore. On increasing carbon content the Fe3+ is expected to decrease and that Fe2+ to increase. These facts explain the observed (Fig. 4) decrease of the Fe3+ bands around 346 nm and 370 nm in the spectra of samples A6–A8 with increasing carbon content. The appearance of these bands with high intensity in glass sample A.9 (with 0.4 g carbon) can be attributed to development of the amber related bands at 420 nm (with shoulder at 440 nm) and 474 nm (with shoulder at 483 nm). These bands in glass A5 (with 0.5 g carbon) appeared with lower intensity than those of glass A9, yet the NIR absorption band around 1020 nm due to Fe2+ is of higher intensity than the corresponding band of glass A9 (with 0.4 g carbon). It has been reported [10] that, the Fe+3 ions produce absorption peaks at about 325 nm, 350 nm, 380 nm, 450 nm and 490 nm while Fe+2 indicates a broad band peak at around
Carbon added (g/100g glass)
1.8
0.3 0.2
1.4 1.2
0.1
1.0 0.8
0.1g 0.2g 0.3g
0.6 0.4
A6 A7 A8
0.2 300
400
500
600
700
800
900 1000 1100
Wavelength (nm ) Fig. 4. Details of UV–Vis-NIR spectra of glasses A7–A9 containing 0.5 g Fe2O3 and 0.72 g Na2SO4 and doped with different carbon contents (g/100 g glass).
1020 nm. Furthermore the amber glass has a strong absorption at a wavelength of about 410 nm which is stable for oxygen activities of the melt in the range of 10 5–10 9 bar, measured at 1400 °C. The amber color intensity vanishes above these activity levels and decreases below oxygen activities level of 10 9 bar (at 1400 °C). The report [10] claimed that, the Fe3+O3S2 complex (stabilized by alkali ions in the glass and acting as basis for the amber color chromophore) is formed during cooling of the glass melt. In very strong reduced condition, the ferric iron content and the sulphite level in the glass will be rather low and during cooling of the melt any ferric iron hardly can be formed. The concentration of ferric iron (Fe3+) sulfide complex in the glass structure will decrease for melting conditions with oxygen activities levels below 10 9 bar and this weakens the amber color. Accordingly, in the present work the increased reducing conditions in sample A5 (with 0.5 g carbon and 0.5 g Fe2O3) relative to the reducing conditions of sample A9 (with 0.4 g carbon and 0.5 g Fe2O3) causes more Fe3+ ions to convert to Fe2+ and consequently the chromophore complex Fe3+O3S2 is expected to decrease. This assumption is confirmed by the decrease of the bands assigned to the amber color related bands at 420 nm with shoulder at 440 nm and 474 nm with shoulder at 483 nm in glass A5.
Effect of salt cake
Carbon added (g/100g glass)
12
Absorbance
10
0.5g 0.1g 0.2g 0.3g 0.4g
8 6 4
A5 A6 A7 A8 A9
0.4
0.5 0.3 0.2
2 0.1
0 300
400
500
600
700
800
900 1000 1100
Wavelength (nm ) Fig. 3. UV–Vis-NIR spectra of glasses A6–A9 containing 0.5 g Fe2O3 and 0.72 g Na2SO4 and doped with 0.1 g, 0.2 g, 0.3 and 0.4 g carbon contents, respectively, (g/100 g glass) in comparison with glass A5 containing 0.5 g carbon.
Fig. 5 shows the effect of increasing different amounts of Na2SO4 on the absorption spectra of glasses A10, A11 and A12 containing 0.5 g Fe2O3 and 0.4 g carbon (g/100 g glass). It can be seen that the amber color related bands have higher intensities as the salt cake increases; mean while Fe2+ band around 1020 nm decreases in intensity. These glass samples appeared visually amber in color with different orange hues. The observed increase (Fig. 5) of the amber color related bands at 420, 440, 474, 483 (nm) in the spectra of glasses A10, A11 and A12 as the amount of the salt cake increases can be attributed to formation of more proportions of Fe3+ ions, consequently more amber chromophore complex.
Effect of ZnO content Fig. 6 shows the effect of ZnO on the optical absorption spectrum of the amber glass sample No. A12. The recorded absorption spectra show a decrease in the amber related bands at 420 nm (with shoulder at 440 nm) and 478 nm (with shoulder at
M.M. Morsi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 145 (2015) 376–383
Na2SO4 Added (g/100g glass)
8 7
Absorbance
6
0.56g 0.64g 0.80g
5 4
A10 A11 A12
3 0.56 2 0.8
1 0 300
400
500
600
700
800
900 1000 1100
Wavelength (nm) Fig. 5. UV–Vis-NIR spectra of glasses A10, A11 and A12 containing 0.5 g Fe2O3 and 0.4 g carbon and doped with 0.56 g, 0.64 g and 0.8 g Na2SO4, respectively, (g/100 g glass).
ZnO Added (g/100g glass)
8 7
Absorbance
6 5 0.0
4
A12 A13 A14 A15 A16
0.1
3 2
0.2
1
0.5
0
0.0g 0.1g 0.2g 0.5g 1.0g
1.0 300
400
500
600
700
800
900 1000 1100
Wavelength (nm) Fig. 6. UV–Vis-NIR spectra of glasses, A13,14,15 and 16 containing 0.5 g Fe2O3 and 0.4 g carbon and 0.8 g Na2SO4 doped with 0.1 g, 0.2 g, 0.5 g and 1.0 g ZnO, respectively, (g/100 g glass) in comparison with A12 containing no ZnO addition.
483 nm) as the amount of ZnO increases. The broad band with a peak around 1020 nm decreases with increasing zinc oxide. Visually it was noticed that ZnO additions causes gradual decrease in the intensity of amber color. The color of glasses A12–A16 changes from a dark amber (in sample A12) to a yellow-green (in samples A13 and A14), to a faint bluish-green (in sample 15 and A16) on addition and increasing the amounts of ZnO. This behavior indicates a decolorization effect of ZnO. It has been reported [28] that, the amber color in glass is caused by a charge transfer in the chromophore groups between sulfide and ferric ions. Consequently, the effect of decolorization occurs through reduction effect of the melt to remove ferric ions, or oxidation of the melt to remove sulfide ions, or by changing the chemistry of the chromophore. The conclusions reached that reduction is the cause for decolorization and that oxidation of sulphur is not the cause of decreasing the absorption due to the amber color are unlikely. The most likely explanation given for the decolorization [28] is the removal of the sulfur ion from the Fe3+O3S2 chromophore due to preferential bond between the Zn ion and the S ion. The present results (Fig. 6) confirm the occurrence of preferential bonding between Zn ion and the S ion as the cause for
decolorization, because the amount of ZnO required for reducing the absorption of the amber related bands is small. The glass progressively turned from amber to greenish yellow to greenish blue, with small increasing amounts of ZnO. This effect is believed to be due to the destruction of the Fe–S complex, converting it to ZnS, which does not produce the amber color. Effect of Cu2O Fig. 7 shows the effect of addition of 0. 01 g, 0.05 g, 0.2 g, 0.5 g and 1.0 g Cu2O on the absorption spectra of glasses A17- A21 containing 0.5 g Fe2O3 and 0.4 g carbon and 0.8 g Na2SO4 (per 100 g glass), respectively. The absorption spectrum of glass A12 containing no Cu2O is included in the figure for comparison. It can be noticed that, addition or increasing Cu2O content leads to decreasing the amber related bands at 420 nm with shoulder at 440 nm and 478 nm with shoulder at 483 (nm) such that the latter band completely vanishes and the former attains a peak at 384 nm in samples A17, A18 and A19, respectively. This decrease of the amber related bands proceed till 0.2 g content is reached then the absorption bands are increased again with 0.5 g and 1.0 g Cu2O in glasses A20 and A21, respectively. It can also be noticed that, with 0.5 and 1.0 g additions a broad band appeared at 776 nm while the broad band around 1020 nm cannot be observed. Visually, the amber color of glass A12, retained the amber color on addition 0.01 Cu2O (sample A17), yet it is lighter in color. On addition of 0.02 g Cu2O the color is changed to dirty brown in color with greenish striations. On addition of 0.2., 0.5 or 1.0 g Cu2O the color of the samples turned greenish blue or grass green or dark grass green, for samples A19, A20 and A21, respectively. This color change is associated with the development of the broad band at 776 nm (Fig. 7), which is attributed to Cu2+ ions [3,4]. From Fig. 7 it can be noticed that the addition of 0. 01 g, Cu2O decreases the intensity of the amber related bands at 420 nm with shoulder at 440 nm and 474 nm with shoulder at 483 nm in glass A17. The latter band seems to decrease sharply and disappears on increasing the amount of Cu2O up to 0.2 g in glass A19. Taking into consideration that glass A17 still has light amber color, it can be concluded that the band at 474–483 nm is not an essential part of the amber chromophore units. It is known that sulfur in the course of amber glass melting may exist in different degrees of oxidation: S6+ (Na2SO4, SO3), S4+ (SO2), S2 (Na2S, FeS), and the production of amber color is related to
9
CuO Added (g/100g glass)
8 7
Absorbance
380
6 5
0.01 0.05
0.00g 0.01g 0.05g 0.20g 0.50g 1.00g
A12 A17 A18 A19 A20 A21
1.0
4 3 2 1
0.5 0.2
0 300
400
500
600
700
800
900 1000 1100
Wavelength (nm) Fig. 7. UV–Vis-NIR spectra of glasses, A17, 18, 19, 20 and 21 containing 0.5 g Fe2O3 and 0.4 g carbon and 0.8 g Na2SO4 doped with 0. 01 g, 0.05 g, 0.2 g,0.5 g and 1.0 g Cu2O, respectively, (g/100 g glass) in comparison with A12 containing no Cu2O additions.
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NaNO3 Added (g/100g glass)
8 7
0.00g 0.01g 0.02g 0.04g 0.10g
6
Absorbance
these transformations [11]. It is reported that iron–sulfur (FeS) cluster assembly proteins from Escherichia coli was initiated by cysteine addition and monitored every 5 min using UV–Vis spectrophotometer at 456 nm [29]. Accordingly, the observed band at 474 nm with shoulder at 483 nm can be attributed to FeS groups. The decrease of these groups in glasses A18 and A19 with 0.05 and 0.2 g Cu2O, respectively, may proceed by the reaction of Fe– sulfide with the added Cu2O according to the reaction [30,31]: Cu2O + FeS ? Cu2S + FeO. The remaining of the broad band due to Fe2+ ions around 1020 nm in the spectra of glasses A18 and A19 (Fig. 7) confirms this attribution. The decrease of the band at 420 nm (sample A12) and its shifting to 406 nm with remaining the amber color in sample A17 indicates that the amber color can be monitored at the range 406–420 nm. The further decrease of the amber related band and its shift to 397 nm and to 384 nm in samples A18 and A19, respectively, indicates decomposition of the Fe3+O3–S2 chromophore group into Fe3+ ion in tetrahedral coordination with its characteristic absorption at 385 nm [22,28]. The decomposition can be made by the interaction of the sulfide ions with Cu2O ions to form Cu2S. Accordingly it can be said that, the removal of the sulfur ion from the chromophore group is due to preferential bond between the Cu ion and the S ion, similar to ZnO. The appearance of glasses A17 and A20 as green color indicates the presence of copper ions in Cu+ and Cu2+ states. The latter ions may be formed during cooling by converting Cu+ ions into Cu2 by disproportionation process of excess Cu2O. The formation of the absorption band at 776 nm confirms the formation of Cu2+. Glass A17 with 0.01 g Cu2O shows (Fig. 7) a shift of the amber related band 420 nm to 405 nm then to 397 nm (in glass A18) and to 384 nm (in glass A19). This shift indicates complete destruction of the amber chromophore complex with the formation of the Fe3+ ions in tetrahedral units which absorb at 384 nm [27,28]. The destruction seems to occur through the removal of the sulfur ion from the Fe3+O3–S2 complex by preferential bonding between the Cu ion and the S ion. The absorption band at 776 nm may overlap with the 1020 nm band so the latter band is difficult to be seen. The different bleaching rate of the bands at 420 nm with shoulder at 440 nm and 474 with shoulder at 483 nm, in either case of addition of ZnO (Fig. 6) or Cu2O (Fig. 7), confirms the different precursors and different bonding of S ions in the precursors of the two bands. Sulphur ions bonded to Fe2+ in FeS are expected to be less tightly bonded compared with those bonded to Fe3+. Therefore sulphur is easily removed in FeS than in the amber chromophore group.
5
0.00
4 3 2
0.01 0.02 0.04
1 0.1 0 300
400
500
600
700
800
900
1000
1100
Wavelength (nm) Fig. 8. UV–Vis-NIR spectra of glasses, A22–25 containing 0.5 g Fe2O3 and 0.4 g carbon and 0.8 g Na2SO4 with 0. 01 g, 0.05 g, 0.2 g, 0.5 g and 1.0 g NaNO3, respectively, (g/100 g glass) in comparison with A12 containing no NaNO3 additions.
disappearance of the amber color in these samples as a result of destruction of the chromophore groups. This destruction can be attributed to the oxidation of the sulfide ion in either the Fe3+O3– S2 or the Fe–sulfide (FeS) groups. The oxidation of S2 in the latter seems faster than that in the chromophore groups. As previously explained, the different oxidation rates at these two bands is attributed to different bonding of S to Fe2+ or to Fe3+ ions. It can be noticed that the destruction of the amber chromophore are much stronger in the case of ZnO than in the case of Cu2O or NaNO3. Effect of Se Fig. 9 shows the effect of selenium addition of 0.1 g, 0.2 g, 0.5 g and 1.0 g Se (g/100 g glass) on the absorption spectra of glasses A26–29 containing 0.5 g Fe2O3 and 0.4 g carbon and 0.8 g Na2SO4, in comparison with A12 containing no Se additions. It can be seen that Se increases the intensities of the amber related bands at 420 nm with shoulder at 440 nm, and 474 with shoulder at 484 nm. It can also be seen that in the spectrum of sample A28 the shoulder at 484 nm becomes broader with a peak at 505 nm. In glass A29 with 1.0 g Se /100 g glass the intensity of the amber
Se added (g/100g glass)
10
0.5
Effect of NaNO3
Absorbance
8
Fig. 8 shows the effect of addition of 0. 01 g, 0.02 g, 0.04 g and 0.1 g NaNO3 on the absorption spectra of glasses A22–A25 containing 0.5 g Fe2O3 and 0.4 g carbon and 0.8 g Na2SO4 (g /100 g glass), respectively. The absorption spectrum of glass A12 containing no NaNO3 is included in the figure for comparison. It can be noticed that, addition or increasing NaNO3 content leads to decreasing the amber related bands at 420 nm (with shoulder at 440 nm) and 478 nm (with shoulder at 483 nm). The decrease of the latter band is faster than the former. The band at 420 nm of the complex chromophore Fe3+O3–S2 decreases in intensity with a shift towards 384 nm in glass A25. Visually the amber color of glass A12 becomes green with dirty yellow strikes in glasses A22 and A23, and becomes inhomogeneous yellowish green in color for glasses A24 and A25. The observed decrease of the amber related bands at 420 nm with shoulder at 440 nm and 474 nm with shoulder at 483 nm (Fig. 8) upon addition and increasing NaNO3, explains the
A12 A22 A23 A24 A25
6
0.2 0.1 0.0
1.0 1.0
0.0g 0.1g 0.2g 0.5g 1.0g
A12 A26 A27 A28 A29
0.5
4
2
0.0 0 300
400
500
600
700
800
900 1000 1100
Wavelength (nm) Fig. 9. UV–Vis-NIR spectra of glasses, A26–29 containing 0.5 g Fe2O3 and 0.4 g carbon and 0.8 g Na2SO4 doped with 0. 1 g, 0.2 g, 0.5 g and 1.0 g Se, respectively, (g/ 100 g glass) in comparison with A12 containing no Se additions.
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7 6
Absorbance
Conclusions
Effect of melting time (h) at 1400 oC
8
2h 3h 4h 6h
5 4
A12 A30 A31 A32
3 2 1 0 300
400
500
600
700
800
900 1000 1100
Wavelength (nm) Fig. 10. UV–Vis-NIR spectra of glasses, A12 and A30–32 containing 0.5 g Fe2O3 and 0.4 g carbon and 0.8 g Na2SO4 (g/100 g glass) melted for different times 2, 3, 4 and 6 (h) at 1400 °C.
related band at 420 nm with shoulder at 440 nm is decreased and attained lower values than that of glass A12. Visually glasses A26– A28 are amber in color with orange hues which becomes very dark brown in glass A29 with increasing Se content. Selenium in the course of glass melting may exist in different degrees of oxidation: Se6+, Se4+, Se0, Se2 , which strongly depend on the redox state in the melt. Only the Se0 is said to generate the pink color. Selenium Se0 in glass has two absorption peaks in the visible range, a steep peak at 500 nm, and a flat peak at 750 nm, whereas ferrous selenide has a very strong peak at 490 nm [32]. It is found that the combination of iron and selenium melted in a soda-lime-silica glass gives a reddish-brown color [4]. Accordingly, the increase of absorption (Fig. 9) in the range 480– 750 nm of the absorption spectrum of sample A29, which appeared dark brown, confirms the formation of Se° and ferrous selenides. Effect of melting time Fig. 10 shows the effect of melting time on the absorption spectra of glasses containing 0.5 g Fe2O3 and 0.4 g carbon and 0.8 g Na2SO4 (g/100 g glass). It can be seen that as the temperature time is increased the intensities of the amber related bands at 420 nm with shoulder at 440 and 474 with shoulder at 483 nm decrease. The band at 474 nm with shoulder at 483 nm decreases faster than that at 420 nm with shoulder at 440 nm. The latter band shifts towards shorter wavelength to reach 386 nm as its intensity decreases. Increasing the melting time slightly affects the Fe2+ ions that absorb at 1020 nm. The glasses retained their amber color for melting times 2, 3 and 4 h, then the color becomes dirty amber for melting time 6 h. From Fig. 10 it can be seen that the intensities of the amber related bands at 420 nm (with shoulder at 440 nm) and 474 nm (with shoulder at 483 nm) decrease as the melting time at 1400 °C was increased. The first band decreases with slower rate than that of 474 nm with shoulder at 483 nm. This behavior confirms the different precursors of both bands. The amber related band at 420 nm with shoulder at 440 nm persists bleaching up to 4 h at 1400 °C before the color being affected. During destruction of Fe3+O3–S2 chromophore group the band at 420 nm shifts towards 363 nm which has been assigned to Fe3+ [10,6]. This shift in the amber related band indicates that the chromophore groups being converted into Fe3+ in tetrahedral sites. The precursors of the band at 474 nm with shoulder at 483 nm seems less stable than that at 420 nm with shoulder at 440 nm.
The effects of oxidation/reduction conditions prevailing during melting of the amber glass were studied. The effect of different amounts of graphite, Na2SO4 and Fe2O3 on the nature and position of amber related absorption band(s) were studied. Carbon content of 0.4 g (as well 0.5 g) in presence of 0.5 g Fe2O3 and 0.65–0.8 g Na2SO4 (g per 100 g glass) produces glasses with beautiful amber color. Several typical spectral features due to the transitions originating from both Fe2+ and Fe3+ oxidation states of iron are recorded. The broad band observed at wavelength around 1020 nm is assigned to Fe2+ ions+ in tetrahedral coordination. The absorption bands due to Fe3+ observed in the present study are recorded at 346, 370 (nm). The bands at 420 nm(with shoulder at 440 nm) and 474 nm (with shoulder at 483 nm) are expected to be related to the amber color, yet they are of different precursors. Amber color related band at 420 nm (with shoulder at 440 nm) is assigned to the chromophore group Fe3+O3–S2 . This band appears at 406 nm in glass melted for relatively long periods. The second amber related band at 474 nm (with shoulder at 483 nm) is found to participate in intensifying the amber color and is attributed to FeS formation. The precursor (FeS) of the amber related band at 474 nm (with shoulder at 483 nm) is less stable than that of (Fe3+O3–S2 ) at 420 nm (with shoulder at 440 nm). ZnO has a decolorization effect and its addition turns the amber color into faint bluish-green color. So its presence in the cullets to be added during amber glass manufacturing deteriorates the amber color. The decolorization is due to the removal of the sulfur ion from the Fe3+O3–S2 chromophore as a result of preferential bonding between the Zn ion and the S ion. Cu2O causes destruction of the chromophore group through the removal of the sulfur ion from the Fe3+O3–S2 complex by preferential bonding between the Cu ion and the S ion, similar to ZnO. Addition NaNO3 causes destruction of the chromophore group of the amber color which can be attributed to the oxidation of the sulfide ion in either the Fe3+O3–S2 or the FeS groups. Its presence by accident in glass batch can deteriorate the amber color. Increasing melting time at 1400 °C up to 6 h is not recommended as it weakens the intensities of the amber color and the amber related bands as a result of destruction of the amber chromophore groups. The amber chromophore groups are converted into Fe3+ in tetrahedral sites. This conversion is much stronger in the case of ZnO than in the case of Cu2O or NaNO3. Presence of Se produces dark amber color due to the formation of Se° and polyselenide.
Acknowledgments The authors would like to express their appreciations to Cairo for Glass Manufacturing Co., 10th of Ramadan City, Egypt, for the facilities given that enabled the performance of the experimental work of this investigation.
References [1] M.T. Utkarsh, P. Dhaval, P. Ankit, K.M. Moin, J. Pharm. Cosmetol. 1 (2011) 56– 60. [2] Y.Z. Rosenblum, P.P. Zak, M.A. Ostrovsky, I.L. Smolyaninova, E.V. Bora, U.V. Dyadina, N.N. Trofimova, A.G.D. Aliyev, Ophthalmic Physiol. Opt. 20 (2000) 335–341. [3] A.M. Nassar, M.M. Morsi, Egypt. J. Phys. 1 (1976) 17–20.
M.M. Morsi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 145 (2015) 376–383 [4] C.R. Bamford, Colour Generation and Control in Glass. Glass Science and Technology, Vol. 2, Elsevier, NY, 1977. [5] C.S. Glafo, Glasteknisk Tidskrift 55 (2000) 65–71. [6] B. Mehdikhani, G.H. Borhani, Process. Appl. Ceram. 7 (2013) 117–121. [7] A. Paul, A. Ward, S. Gomolka, J. Mater. Sci. 9 (1974) 1133–1138. [8] F.R. Bacon, C.J. Billlan, J. Am. Ceram. Soc. 37 (1953) 60–66. [9] W.L. Spix, F.R. Bacon, J. Am. Ceram. Soc. 36 (1952) 377–383. [10] R.G.C. Beerkens, K. Kahl, Phys. Chem. Glasses 43 (2002) 189–198. [11] Yu.A. Guloyan, Glass Ceram. 62 (2005) 301–303. [12] N.F. Zhernovaya, V.I. Onishchuk, B. Davydoglu, Glass Ceram. 64 (2007) 111–114. [13] M. Muller, C. Russel, O. Claussen, Glasstech. Ber. 72 (1999) 362–366. [14] P. Lagarde, A.M. Flank, J. Jupille, H. Montigaud, J. Phys, Conf. Ser. 190 (2009) 1–4. [15] J. Klouzˇek, M. Arkosiová, L. Nìmec, Ceram. Silikáty 50 (2006) 134–139. [16] K.D. Kim, J.H. Hwang, J. Korean Ceram. Soc. 48 (2011) 205–210. [17] W.H. Manring, J. Am. Ceram. Soc. 30 (1946) 27–31. [18] E. Reinhard, G. Ward, S. Pattanaik, P. Debevec, High Dynamic Range Imaging: Acquisition, Display, and Image-Based Lighting (The Morgan Kaufmann Series in Computer Graphics), Morgan Kaufmann Publishers Inc., 2005. [19] D.H. Brainard, Color Res. Appl. 14 (1989) 23–34.
383
[20] W.B. Cowan, Comput. Graphics 17 (1983) 315–321. [21] HunterLab, Insight on Color 8 (2008) 1–2. [22] R.W. Douglas. Symposium on Coloured Glasses, Int. Commission on Glasszechoslovak Scientific and Technical Society of the Silicate Industry, Praha, 1967, pp. 161–191. [23] W.A. Weyl, Colored Glasses, Soc. Glass Tech, Sheffield, 1951. [24] P.A. Bingham, J.M. Parker, T.M. Searle, I. Smith, J. Non-Cryst. Solids 353 (2007) 2479–2494. [25] R. Klement, J. Kraxner, M. Liška, Ceram. Silikáty 53 (2009) 180–183. [26] J.P. Traverse, T. Toganidis, C. Ades, Glasstech. Ber. 65 (1992) 201–206. [27] L.B. Glebov, E.N. Boulos, J. Non-Cryst. Solids 242 (1998) 49–62. [28] M.A. Patton, The decolorization of amber container glass, Final report to the Center for Environmental and Energy Research, Alfred University, Summer undergraduate research fellowships, 2003, pp.1–14. [29] G. Wu, L. Li, Biochemistry (Moscow) 77 (2012) 135–142. [30] J.D. Lee, Concise Inorganic Chemistry, Fifth Ed., Wiley India Pvt. Limited, 2008. [31] J.C. Kuriacose, J. Rajaram, Chemistry in Engineering and Technology, Vol. 2, Tata McGraw-Hill Publishing Company Limited, New Delhi, 1998. [32] T. Jitwatcharakomol (PhD. Thesis), Fakultät für Georessourcen und Materialtechnik der Rheinisch-Westfälischen, Technischen Hochschule Aachen, Germany,2 005.
Contents lists available at ScienceDirect
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
Spectroscopic investigation of amber color silicate glasses and factors affecting the amber related absorption bands Morsi M. Morsi a,⇑, Samya I. El-sherbiny b, Karam M. Mohamed c a
Glass Research Dept., National Research Centre, 33 E l Bohoth st., Dokki, Giza, P.O. 12622, Egypt Chemistry Department, Faculty of Science, Helwan University, Helwan, Egypt c Cairo for Glass Manufacturing Co., 10th of Ramadan City, Egypt b
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
The amber color is due two
Decolorization effect of ZnO added per 100 g glass on the amber bands with peaks at 420 nm and 478 nm. The decomposition rate of these bands indicates that they are of different origin. 8 7 6
Absorbance
absorption bands with peaks at 420 and 478 (nm). The two amber related bands are of different origin. NaNO3, ZnO, Cu2O cause decolorization of the amber glass color. Se intensifies the amber color. Amber chromophores are converted into Fe3+ in tetrahedral sites when deteriorate.
5 0.0g
4 0.1g
0.0g 0.1g 0.2g 0.5g 1.0g
3 2
0.2g
1 0
0.5g 1.0g 300
400
500
600
700
800
900 1000 1100
Wavelength (nm)
a r t i c l e
i n f o
Article history: Received 7 September 2014 Received in revised form 8 February 2015 Accepted 1 March 2015 Available online 9 March 2015 Keywords: Optical properties UV–Vis spectroscopy Amber glass Amber chromophore Absorption bands
a b s t r a c t The effects of carbon, Fe2O3 and Na2SO4 contents on the amber color of glass with composition (wt%) 64.3 SiO2, 25.7 CaO, 10 Na2O were studied. The effect of some additives that could be found in glass batch or cullets on the amber related absorption band(s) was also studied. An amber related absorption band due to the chromophore Fe3+O3S2 was recorded at 420 nm with shoulder at 440 nm. A second amber related band recorded at 474 nm with shoulder at 483 nm was assigned to FeS. Increasing melting time at 1400 °C up to 6 h caused fainting of the amber color, decreases the intensities of the amber related bands and shifted the first band to 406 nm. Addition of ZnO, Cu2O and NaNO3 to the glass produced decolorizing effect and vanishing of the amber related bands. The effects of melting time and these additives were explained on the bases of destruction the amber chromophore and its conversion into Fe3+ in tetrahedral sites or ZnS. Addition of Se intensifies the amber related bands and may cause dark coloration due to the formation of Se° and polyselenide. Amber color can be monitored through measuring the absorption in the range 406–420 nm. Ó 2015 Elsevier B.V. All rights reserved.
Introduction Glass containers have a number of indisputable qualitative advantages over other forms of packaging: transparency, chemical ⇑ Corresponding author. Tel.: +20 1223733794. E-mail address: [email protected] (M.M. Morsi). http://dx.doi.org/10.1016/j.saa.2015.03.001 1386-1425/Ó 2015 Elsevier B.V. All rights reserved.
inertness, safety, the possibility of recycling and salvaging of wastes. Brown, red and green glass containers have another important characteristic: strong absorption of ultraviolet and shortwavelength of visible light. These characteristics provide long-term biological protection of the contents against 2900–4500 angstrom of light [1]. Many chemicals and drugs should be protected from deterioration. This draws attention, to the protective function of
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the colored packaging. Colored filters are also used to protect the lens, retina and other ocular tissues against the hazard of light damage [2]. Coloration of glass can be produced by the different means of which by ions of the transition elements or by the mutual interaction of valance electrons of ions that have more than one valence [3,4]. Iron ions of Fe3+ oxidation state show absorption bands in sodium silicate glass at 380, 420, 435 (nm) giving rise to a yellow green coloration to the glass, while Fe2+ ions show absorption band at 1050 nm associated with blue green coloration to the glass [5,6]. In some cases, iron ions are added to the glass batch in order to produce a special type of colored glass called amber glass. Sulfur, together with carbon and iron compounds, is used to form iron polysulfides and produce amber glass ranging from yellowish to almost black. In binary alkali borate glasses containing sulphur and dissolved water attained blue coloration. This color is suggested to be due to S2 (hypersulfide) ion [7]. Imparting amber and brown colors to glass containers are achieved in the presence of iron oxides, sulfide sulfur and a reducing atmosphere. Several researchers [8–12] have investigated the nature of the amber glass and the conditions for its production. They reported that amber chromophore is a colorant complex consists of the central Fe3+ ion in a tetrahedral coordination surrounded by three ions of oxygen O2 and one sulfide sulfur ion S2 , [Fe3+O3S2 ]5 . Amber glass is classed traditionally as an unstable glass. It has been found experimentally that amber chromophore is thermally decomposed with increasing temperature [13]. The UV–Vis spectroscopic measurement indicated that, with increasing temperature, the intensity of the absorption bands of the amber chromophore decreases. These glasses are made by melting batch containing iron and sulfate ions as well as carbon (reducing agent). Carbon reduces part of the sodium sulfate to sulfide. Sulfur in the course of amber glass melting may exist in different degrees of oxidation: S6+ (Na2SO4, SO3), S4+ (SO2), S2 (Na2S, FeS) [14–16]. In a reducing atmosphere the content of sulfide sulfur varies insignificantly, whereas the reduction of iron oxides proceeds more intensely. Thus, the preservation of sulfide sulfur in glass facilitates the reduction of iron oxides and increases the content of Fe2+ which, as reported [11], does not participate in the formation of the amber chromophore. A rapid method for monitoring the amber color of glasses has been developed by measuring light transmission at 525 nm [17]. The amber color intensity at a wavelength of 410 nm has been measured for soda-lime-silica glasses [10]. The dominant wavelength of green and brown glass bottles has been reported to fall within the ranges 552–558 nm and 578–586 nm, respectively, to guarantees that the bottles will have high protective qualities [12]. In recent years the glass industry has begun to use the CIE (international commission on illumination) system of color notation, where the data can be obtained directly from a recording spectrophotometer [18–21]. Determination of the amber color with measurements of its absorption at certain position represents a rapid method that could be used in quality control during the production process. So the position of this band is of prime importance, yet the literature reported different positions for measuring light transmission at 525 nm. [17] or in the range 578–586 nm [12] or at 410 nm [10]. The aim of the present work is to study the nature and position of the amber absorption band(s) that could be used for monitoring amber color in quality control purposes. The effect of graphite, Na2SO4 and Fe2O3 content added to glass batch will be studied. The study will also include the effect of melting time and effect of some additives such as ZnO, Cu2O, NaNO3 and Se on the amber color and the amber related absorption band(s). These additives may affect the color during production of amber glass.
Experimental details Soda lime silica glass of the composition 64.3 SiO2, 25.7 CaO, 10 Na2O (wt%) was used for preparation of samples containing different additives. Glass batches were prepared using sands, and limestone of the chemical composition listed in Table 1. Sodium carbonate of 99.5% purity, graphite (99.3 wt% C) and chemical grade additives of Na2SO4, Fe2O3, ZnO, NaNO3, Cu2O and Se were used. Table 2 lists the nominal composition of the glasses studied. Batches of 100 g were prepared by weighing the appropriate proportions of the powdered ingredients. The batches were mixed, and then melted in a platinum (2% rhodium) crucible, in an electrically heated Globar furnace. The furnace temperature was raised slowly and gradually up to temperature of (1400 °C), to avoid spattering or splashing of the batch materials during melting. The molten batches were held for 2 h with occasional swirling to ensure homogenization of the melts. The melts were then cast onto hot steel rectangular moulds and the glass samples were then rapidly transferred to a muffle furnace adjusted at 550 °C for annealing to obtain strain – free glass samples. The furnace was then turned off to cool to room temperature. Samples were polished to a thickness around 3 mm for spectrophotometer measurements. A Perkin Elmer Lambda 25 UV/Vis Spectrophotometer was used for absorption spectra measurements in the range of wavelengths of 300–1100 nm. Results and discussion The optical absorption characteristics of the parent base glass The absorption spectrum of the base soda-lime-silica glass (No. A1) free of additives (Fig. 1) shows a sharp absorption peak at 335 nm and no noticeable absorption at the visible or at the NIR. The absorption band appeared at 335 nm for sample No. A1 seems to be due to impurities of iron oxide in the glass batch. Effect of Fe2O3 content Fig. 2 shows the absorption spectra of the base soda-lime-silica glass containing 0.5 g carbon and 0.72 g Na2SO4 after doping with different amounts of Fe2O3. The spectra show several absorption bands in the UV–Visible-NIR. These bands appear at 346 nm, 370 nm, 420 nm (with a shoulder at 440 nm), 474 nm (with a shoulder at 483 nm) and a broad band around 1020 nm. The intensities of these bands increase with iron oxide content. The glasses appeared visually with different intensities of amber color. Sample A2 appeared with orange hue and sample No. A5 with 0.5 g/100 g glass has the darker amber color. The optical spectra of the glass samples containing 0.5 g carbon and 0.72 Na2SO3 doped with different Fe2O3contents (g/100 g glass) are shown in Fig. 2. Iron in glass exists as equilibrium between ferric ion (Fe3+) and ferrous ion (Fe2+). Several typical spectral features due to the transitions originating from both Fe2+ and Fe3+ oxidation states of iron are clearly seen in this figure. The main band of Fe2+ is observed as broad band at wavelength
Table 1 Chemical composition of raw materials. Contents
Sand
Lime stone
SiO2 Al2O3 CaO Mgo Fe2O3 LOI
99.60 0.20 0.05 0.03 0.02 0.05
0.15 0.10 55.20 0.10 0.02 44.42
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Table 2 Nominal composition (wt%) and melting times of glasses studied. No.
SiO2
CaO
Na2O
A1 A2 A3 A4 A5 A6 A7 A8 A9 10 A11 A12 A13 A14 A15 A16 A17 A18 A19 A20 A21 A22 A23 A24 A25 A26 A27 A28 A29 A30 A31 A32
64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3 64.3
25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7 25.7
10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0 10.0
Additives g/100 g glass Na2SO4
C
Fe2O3
ZnO
NaNO3
Cu2O
Se
– 0.72 0.72 0.72 0.72 0.72 0.72 0.72 0.72 0.56 0.64 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8
– 0.5 0.5 0.5 0.5 0.1 0.2 0.3 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4
– 0.063 0.125 0.25 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5
–
–
–
–
0.1 0.2 0.5 1.0 0.01 0.05 0.2 0.5 1.0 0.01 0.02 0.04 0.1 0.1 0.2 0.5 1.0 Melted at 1400 °C for 3 h Melted at 1400 °C for 4 h Melted at 1400 °C for 6 h
0.50
420
8
474 483
Fe2O3 added (g/100g glass)
0.45
Base Glass
0.40
7 6
Absorbance
Absorbance
0.35 0.30 0.25 0.20
5 4
370
2
0.10
1
346
0.25 0.125 0.06
0
0.00 300
400
500
600
700
800
900 1000 1100
Wavelength (nm )
A5 A4 A3 A2 0.5
3
0.15
0.05
0.50 g 0.25 g 0.125 g 0.06 g
440
300
400
500
600
700
800
900 1000 1100
Wavelength (nm)
Fig. 1. UV–Vis-NIR spectra of the parent base glass sample A1 without any additives.
Fig. 2. UV–Vis-NIR spectra of glass samples containing 0.5 g carbon and 0.72 g Na2SO3 doped with different Fe2O3 contents (g/100 g glass): 0.063 (A2), 0.125 (A3), 0.25 (A4) and 0.5 (A5).
around 1020 nm. Similar absorption band has been observed in some silicate glasses at 1000–1050 nm and attributed to Fe2+ in tetrahedral coordination [4,22,23], which has been attributed to the spin-allowed transitions corresponding to 5E (D) ? 5T2 (D) for tetrahedral coordinated Fe2+ sites [24,25]. The absorption bands of Fe3+ have been reported to be usually observed at 385, 417, 440 and 500 (nm) and are attributed to Fe3+ in tetrahedral coordination [22,26,27,6]. The absorption bands due to Fe3+ observed in the present study (Fig. 2) are recorded at 346, 370 (nm). The bands at 420 with
shoulder at 440 and 474 with shoulder at 483 (nm) are expected to be related to the amber color. From Fig. 2 it can be noticed that increasing the iron oxide content increases the absorption bands of Fe3+ and Fe2+. The highest intense peak at 474 and 483 (nm) for glass No. A5 may explain its deeper amber color relative to the other samples Nos. A2, A3 and A4. The increase of the band of ferrous ions can be assigned to increasing the proportion of Fe2+ as the total iron oxide amount increases. The absorption band appeared at 335 nm due to impurities of iron oxide in sample No. A1 (Fig. 1) is shifted to 346 nm in the
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spectra of other glasses due to the effect of the tails of the neighboring band at 370 nm.
2.0
Effect of reducing agent (carbon)
1.6
Absorbance
Fig. 3 shows ultraviolet–visible spectra of glass samples A6–A9 in comparison of with that of glass A5. It shows the effect of adding different amounts of carbon (graphite) to glass batch containing 0.5 g Fe2O3 and 0.72 g Na2SO4 on their absorption spectra in comparison with that of glass A5 with 0.5 g carbon (g per 100 g glass). Glasses Nos. A5 and A9 containing 0.5 g Fe2O3 and 0.72 g Na2SO4, and doped with 0.5 and 0.4 g carbon, respectively, appeared visually amber in color. Glasses Nos. A6, A7, and A8, with 0.1, 0.2 and 0.3 g carbon / 100 g glass, respectively, appeared greenish blue in color. From Fig. 3 it can be seen that absorption peaks related to amber color at 420 (with shoulder at 440 nm) and 474 nm (with shoulder at 483 nm) are developed in the spectra of glasses Nos. A9 and A5 with 0.4 and 0.5 g/100 g glass, respectively. These bands which are related to amber color are not observed in glasses Nos. A6–A8 that contains low carbon content (less than 0.3 g/100 g glass). The absorption bands in the spectra of samples A6–A8 in the regions of 346 nm and 370 nm are clearly decreased with increasing carbon content (more clear in Fig. 4). At the same time the NIR band around 1020 nm of the glasses appears in all the intended samples, increases with carbon contents. Carbon acts as reducing agent and sodium sulfate acts as oxidizing agent, then with increasing carbon, the sulfate is reduced to sulfide which response with iron forming amber chromophore. On increasing carbon content the Fe3+ is expected to decrease and that Fe2+ to increase. These facts explain the observed (Fig. 4) decrease of the Fe3+ bands around 346 nm and 370 nm in the spectra of samples A6–A8 with increasing carbon content. The appearance of these bands with high intensity in glass sample A.9 (with 0.4 g carbon) can be attributed to development of the amber related bands at 420 nm (with shoulder at 440 nm) and 474 nm (with shoulder at 483 nm). These bands in glass A5 (with 0.5 g carbon) appeared with lower intensity than those of glass A9, yet the NIR absorption band around 1020 nm due to Fe2+ is of higher intensity than the corresponding band of glass A9 (with 0.4 g carbon). It has been reported [10] that, the Fe+3 ions produce absorption peaks at about 325 nm, 350 nm, 380 nm, 450 nm and 490 nm while Fe+2 indicates a broad band peak at around
Carbon added (g/100g glass)
1.8
0.3 0.2
1.4 1.2
0.1
1.0 0.8
0.1g 0.2g 0.3g
0.6 0.4
A6 A7 A8
0.2 300
400
500
600
700
800
900 1000 1100
Wavelength (nm ) Fig. 4. Details of UV–Vis-NIR spectra of glasses A7–A9 containing 0.5 g Fe2O3 and 0.72 g Na2SO4 and doped with different carbon contents (g/100 g glass).
1020 nm. Furthermore the amber glass has a strong absorption at a wavelength of about 410 nm which is stable for oxygen activities of the melt in the range of 10 5–10 9 bar, measured at 1400 °C. The amber color intensity vanishes above these activity levels and decreases below oxygen activities level of 10 9 bar (at 1400 °C). The report [10] claimed that, the Fe3+O3S2 complex (stabilized by alkali ions in the glass and acting as basis for the amber color chromophore) is formed during cooling of the glass melt. In very strong reduced condition, the ferric iron content and the sulphite level in the glass will be rather low and during cooling of the melt any ferric iron hardly can be formed. The concentration of ferric iron (Fe3+) sulfide complex in the glass structure will decrease for melting conditions with oxygen activities levels below 10 9 bar and this weakens the amber color. Accordingly, in the present work the increased reducing conditions in sample A5 (with 0.5 g carbon and 0.5 g Fe2O3) relative to the reducing conditions of sample A9 (with 0.4 g carbon and 0.5 g Fe2O3) causes more Fe3+ ions to convert to Fe2+ and consequently the chromophore complex Fe3+O3S2 is expected to decrease. This assumption is confirmed by the decrease of the bands assigned to the amber color related bands at 420 nm with shoulder at 440 nm and 474 nm with shoulder at 483 nm in glass A5.
Effect of salt cake
Carbon added (g/100g glass)
12
Absorbance
10
0.5g 0.1g 0.2g 0.3g 0.4g
8 6 4
A5 A6 A7 A8 A9
0.4
0.5 0.3 0.2
2 0.1
0 300
400
500
600
700
800
900 1000 1100
Wavelength (nm ) Fig. 3. UV–Vis-NIR spectra of glasses A6–A9 containing 0.5 g Fe2O3 and 0.72 g Na2SO4 and doped with 0.1 g, 0.2 g, 0.3 and 0.4 g carbon contents, respectively, (g/100 g glass) in comparison with glass A5 containing 0.5 g carbon.
Fig. 5 shows the effect of increasing different amounts of Na2SO4 on the absorption spectra of glasses A10, A11 and A12 containing 0.5 g Fe2O3 and 0.4 g carbon (g/100 g glass). It can be seen that the amber color related bands have higher intensities as the salt cake increases; mean while Fe2+ band around 1020 nm decreases in intensity. These glass samples appeared visually amber in color with different orange hues. The observed increase (Fig. 5) of the amber color related bands at 420, 440, 474, 483 (nm) in the spectra of glasses A10, A11 and A12 as the amount of the salt cake increases can be attributed to formation of more proportions of Fe3+ ions, consequently more amber chromophore complex.
Effect of ZnO content Fig. 6 shows the effect of ZnO on the optical absorption spectrum of the amber glass sample No. A12. The recorded absorption spectra show a decrease in the amber related bands at 420 nm (with shoulder at 440 nm) and 478 nm (with shoulder at
M.M. Morsi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 145 (2015) 376–383
Na2SO4 Added (g/100g glass)
8 7
Absorbance
6
0.56g 0.64g 0.80g
5 4
A10 A11 A12
3 0.56 2 0.8
1 0 300
400
500
600
700
800
900 1000 1100
Wavelength (nm) Fig. 5. UV–Vis-NIR spectra of glasses A10, A11 and A12 containing 0.5 g Fe2O3 and 0.4 g carbon and doped with 0.56 g, 0.64 g and 0.8 g Na2SO4, respectively, (g/100 g glass).
ZnO Added (g/100g glass)
8 7
Absorbance
6 5 0.0
4
A12 A13 A14 A15 A16
0.1
3 2
0.2
1
0.5
0
0.0g 0.1g 0.2g 0.5g 1.0g
1.0 300
400
500
600
700
800
900 1000 1100
Wavelength (nm) Fig. 6. UV–Vis-NIR spectra of glasses, A13,14,15 and 16 containing 0.5 g Fe2O3 and 0.4 g carbon and 0.8 g Na2SO4 doped with 0.1 g, 0.2 g, 0.5 g and 1.0 g ZnO, respectively, (g/100 g glass) in comparison with A12 containing no ZnO addition.
483 nm) as the amount of ZnO increases. The broad band with a peak around 1020 nm decreases with increasing zinc oxide. Visually it was noticed that ZnO additions causes gradual decrease in the intensity of amber color. The color of glasses A12–A16 changes from a dark amber (in sample A12) to a yellow-green (in samples A13 and A14), to a faint bluish-green (in sample 15 and A16) on addition and increasing the amounts of ZnO. This behavior indicates a decolorization effect of ZnO. It has been reported [28] that, the amber color in glass is caused by a charge transfer in the chromophore groups between sulfide and ferric ions. Consequently, the effect of decolorization occurs through reduction effect of the melt to remove ferric ions, or oxidation of the melt to remove sulfide ions, or by changing the chemistry of the chromophore. The conclusions reached that reduction is the cause for decolorization and that oxidation of sulphur is not the cause of decreasing the absorption due to the amber color are unlikely. The most likely explanation given for the decolorization [28] is the removal of the sulfur ion from the Fe3+O3S2 chromophore due to preferential bond between the Zn ion and the S ion. The present results (Fig. 6) confirm the occurrence of preferential bonding between Zn ion and the S ion as the cause for
decolorization, because the amount of ZnO required for reducing the absorption of the amber related bands is small. The glass progressively turned from amber to greenish yellow to greenish blue, with small increasing amounts of ZnO. This effect is believed to be due to the destruction of the Fe–S complex, converting it to ZnS, which does not produce the amber color. Effect of Cu2O Fig. 7 shows the effect of addition of 0. 01 g, 0.05 g, 0.2 g, 0.5 g and 1.0 g Cu2O on the absorption spectra of glasses A17- A21 containing 0.5 g Fe2O3 and 0.4 g carbon and 0.8 g Na2SO4 (per 100 g glass), respectively. The absorption spectrum of glass A12 containing no Cu2O is included in the figure for comparison. It can be noticed that, addition or increasing Cu2O content leads to decreasing the amber related bands at 420 nm with shoulder at 440 nm and 478 nm with shoulder at 483 (nm) such that the latter band completely vanishes and the former attains a peak at 384 nm in samples A17, A18 and A19, respectively. This decrease of the amber related bands proceed till 0.2 g content is reached then the absorption bands are increased again with 0.5 g and 1.0 g Cu2O in glasses A20 and A21, respectively. It can also be noticed that, with 0.5 and 1.0 g additions a broad band appeared at 776 nm while the broad band around 1020 nm cannot be observed. Visually, the amber color of glass A12, retained the amber color on addition 0.01 Cu2O (sample A17), yet it is lighter in color. On addition of 0.02 g Cu2O the color is changed to dirty brown in color with greenish striations. On addition of 0.2., 0.5 or 1.0 g Cu2O the color of the samples turned greenish blue or grass green or dark grass green, for samples A19, A20 and A21, respectively. This color change is associated with the development of the broad band at 776 nm (Fig. 7), which is attributed to Cu2+ ions [3,4]. From Fig. 7 it can be noticed that the addition of 0. 01 g, Cu2O decreases the intensity of the amber related bands at 420 nm with shoulder at 440 nm and 474 nm with shoulder at 483 nm in glass A17. The latter band seems to decrease sharply and disappears on increasing the amount of Cu2O up to 0.2 g in glass A19. Taking into consideration that glass A17 still has light amber color, it can be concluded that the band at 474–483 nm is not an essential part of the amber chromophore units. It is known that sulfur in the course of amber glass melting may exist in different degrees of oxidation: S6+ (Na2SO4, SO3), S4+ (SO2), S2 (Na2S, FeS), and the production of amber color is related to
9
CuO Added (g/100g glass)
8 7
Absorbance
380
6 5
0.01 0.05
0.00g 0.01g 0.05g 0.20g 0.50g 1.00g
A12 A17 A18 A19 A20 A21
1.0
4 3 2 1
0.5 0.2
0 300
400
500
600
700
800
900 1000 1100
Wavelength (nm) Fig. 7. UV–Vis-NIR spectra of glasses, A17, 18, 19, 20 and 21 containing 0.5 g Fe2O3 and 0.4 g carbon and 0.8 g Na2SO4 doped with 0. 01 g, 0.05 g, 0.2 g,0.5 g and 1.0 g Cu2O, respectively, (g/100 g glass) in comparison with A12 containing no Cu2O additions.
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NaNO3 Added (g/100g glass)
8 7
0.00g 0.01g 0.02g 0.04g 0.10g
6
Absorbance
these transformations [11]. It is reported that iron–sulfur (FeS) cluster assembly proteins from Escherichia coli was initiated by cysteine addition and monitored every 5 min using UV–Vis spectrophotometer at 456 nm [29]. Accordingly, the observed band at 474 nm with shoulder at 483 nm can be attributed to FeS groups. The decrease of these groups in glasses A18 and A19 with 0.05 and 0.2 g Cu2O, respectively, may proceed by the reaction of Fe– sulfide with the added Cu2O according to the reaction [30,31]: Cu2O + FeS ? Cu2S + FeO. The remaining of the broad band due to Fe2+ ions around 1020 nm in the spectra of glasses A18 and A19 (Fig. 7) confirms this attribution. The decrease of the band at 420 nm (sample A12) and its shifting to 406 nm with remaining the amber color in sample A17 indicates that the amber color can be monitored at the range 406–420 nm. The further decrease of the amber related band and its shift to 397 nm and to 384 nm in samples A18 and A19, respectively, indicates decomposition of the Fe3+O3–S2 chromophore group into Fe3+ ion in tetrahedral coordination with its characteristic absorption at 385 nm [22,28]. The decomposition can be made by the interaction of the sulfide ions with Cu2O ions to form Cu2S. Accordingly it can be said that, the removal of the sulfur ion from the chromophore group is due to preferential bond between the Cu ion and the S ion, similar to ZnO. The appearance of glasses A17 and A20 as green color indicates the presence of copper ions in Cu+ and Cu2+ states. The latter ions may be formed during cooling by converting Cu+ ions into Cu2 by disproportionation process of excess Cu2O. The formation of the absorption band at 776 nm confirms the formation of Cu2+. Glass A17 with 0.01 g Cu2O shows (Fig. 7) a shift of the amber related band 420 nm to 405 nm then to 397 nm (in glass A18) and to 384 nm (in glass A19). This shift indicates complete destruction of the amber chromophore complex with the formation of the Fe3+ ions in tetrahedral units which absorb at 384 nm [27,28]. The destruction seems to occur through the removal of the sulfur ion from the Fe3+O3–S2 complex by preferential bonding between the Cu ion and the S ion. The absorption band at 776 nm may overlap with the 1020 nm band so the latter band is difficult to be seen. The different bleaching rate of the bands at 420 nm with shoulder at 440 nm and 474 with shoulder at 483 nm, in either case of addition of ZnO (Fig. 6) or Cu2O (Fig. 7), confirms the different precursors and different bonding of S ions in the precursors of the two bands. Sulphur ions bonded to Fe2+ in FeS are expected to be less tightly bonded compared with those bonded to Fe3+. Therefore sulphur is easily removed in FeS than in the amber chromophore group.
5
0.00
4 3 2
0.01 0.02 0.04
1 0.1 0 300
400
500
600
700
800
900
1000
1100
Wavelength (nm) Fig. 8. UV–Vis-NIR spectra of glasses, A22–25 containing 0.5 g Fe2O3 and 0.4 g carbon and 0.8 g Na2SO4 with 0. 01 g, 0.05 g, 0.2 g, 0.5 g and 1.0 g NaNO3, respectively, (g/100 g glass) in comparison with A12 containing no NaNO3 additions.
disappearance of the amber color in these samples as a result of destruction of the chromophore groups. This destruction can be attributed to the oxidation of the sulfide ion in either the Fe3+O3– S2 or the Fe–sulfide (FeS) groups. The oxidation of S2 in the latter seems faster than that in the chromophore groups. As previously explained, the different oxidation rates at these two bands is attributed to different bonding of S to Fe2+ or to Fe3+ ions. It can be noticed that the destruction of the amber chromophore are much stronger in the case of ZnO than in the case of Cu2O or NaNO3. Effect of Se Fig. 9 shows the effect of selenium addition of 0.1 g, 0.2 g, 0.5 g and 1.0 g Se (g/100 g glass) on the absorption spectra of glasses A26–29 containing 0.5 g Fe2O3 and 0.4 g carbon and 0.8 g Na2SO4, in comparison with A12 containing no Se additions. It can be seen that Se increases the intensities of the amber related bands at 420 nm with shoulder at 440 nm, and 474 with shoulder at 484 nm. It can also be seen that in the spectrum of sample A28 the shoulder at 484 nm becomes broader with a peak at 505 nm. In glass A29 with 1.0 g Se /100 g glass the intensity of the amber
Se added (g/100g glass)
10
0.5
Effect of NaNO3
Absorbance
8
Fig. 8 shows the effect of addition of 0. 01 g, 0.02 g, 0.04 g and 0.1 g NaNO3 on the absorption spectra of glasses A22–A25 containing 0.5 g Fe2O3 and 0.4 g carbon and 0.8 g Na2SO4 (g /100 g glass), respectively. The absorption spectrum of glass A12 containing no NaNO3 is included in the figure for comparison. It can be noticed that, addition or increasing NaNO3 content leads to decreasing the amber related bands at 420 nm (with shoulder at 440 nm) and 478 nm (with shoulder at 483 nm). The decrease of the latter band is faster than the former. The band at 420 nm of the complex chromophore Fe3+O3–S2 decreases in intensity with a shift towards 384 nm in glass A25. Visually the amber color of glass A12 becomes green with dirty yellow strikes in glasses A22 and A23, and becomes inhomogeneous yellowish green in color for glasses A24 and A25. The observed decrease of the amber related bands at 420 nm with shoulder at 440 nm and 474 nm with shoulder at 483 nm (Fig. 8) upon addition and increasing NaNO3, explains the
A12 A22 A23 A24 A25
6
0.2 0.1 0.0
1.0 1.0
0.0g 0.1g 0.2g 0.5g 1.0g
A12 A26 A27 A28 A29
0.5
4
2
0.0 0 300
400
500
600
700
800
900 1000 1100
Wavelength (nm) Fig. 9. UV–Vis-NIR spectra of glasses, A26–29 containing 0.5 g Fe2O3 and 0.4 g carbon and 0.8 g Na2SO4 doped with 0. 1 g, 0.2 g, 0.5 g and 1.0 g Se, respectively, (g/ 100 g glass) in comparison with A12 containing no Se additions.
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7 6
Absorbance
Conclusions
Effect of melting time (h) at 1400 oC
8
2h 3h 4h 6h
5 4
A12 A30 A31 A32
3 2 1 0 300
400
500
600
700
800
900 1000 1100
Wavelength (nm) Fig. 10. UV–Vis-NIR spectra of glasses, A12 and A30–32 containing 0.5 g Fe2O3 and 0.4 g carbon and 0.8 g Na2SO4 (g/100 g glass) melted for different times 2, 3, 4 and 6 (h) at 1400 °C.
related band at 420 nm with shoulder at 440 nm is decreased and attained lower values than that of glass A12. Visually glasses A26– A28 are amber in color with orange hues which becomes very dark brown in glass A29 with increasing Se content. Selenium in the course of glass melting may exist in different degrees of oxidation: Se6+, Se4+, Se0, Se2 , which strongly depend on the redox state in the melt. Only the Se0 is said to generate the pink color. Selenium Se0 in glass has two absorption peaks in the visible range, a steep peak at 500 nm, and a flat peak at 750 nm, whereas ferrous selenide has a very strong peak at 490 nm [32]. It is found that the combination of iron and selenium melted in a soda-lime-silica glass gives a reddish-brown color [4]. Accordingly, the increase of absorption (Fig. 9) in the range 480– 750 nm of the absorption spectrum of sample A29, which appeared dark brown, confirms the formation of Se° and ferrous selenides. Effect of melting time Fig. 10 shows the effect of melting time on the absorption spectra of glasses containing 0.5 g Fe2O3 and 0.4 g carbon and 0.8 g Na2SO4 (g/100 g glass). It can be seen that as the temperature time is increased the intensities of the amber related bands at 420 nm with shoulder at 440 and 474 with shoulder at 483 nm decrease. The band at 474 nm with shoulder at 483 nm decreases faster than that at 420 nm with shoulder at 440 nm. The latter band shifts towards shorter wavelength to reach 386 nm as its intensity decreases. Increasing the melting time slightly affects the Fe2+ ions that absorb at 1020 nm. The glasses retained their amber color for melting times 2, 3 and 4 h, then the color becomes dirty amber for melting time 6 h. From Fig. 10 it can be seen that the intensities of the amber related bands at 420 nm (with shoulder at 440 nm) and 474 nm (with shoulder at 483 nm) decrease as the melting time at 1400 °C was increased. The first band decreases with slower rate than that of 474 nm with shoulder at 483 nm. This behavior confirms the different precursors of both bands. The amber related band at 420 nm with shoulder at 440 nm persists bleaching up to 4 h at 1400 °C before the color being affected. During destruction of Fe3+O3–S2 chromophore group the band at 420 nm shifts towards 363 nm which has been assigned to Fe3+ [10,6]. This shift in the amber related band indicates that the chromophore groups being converted into Fe3+ in tetrahedral sites. The precursors of the band at 474 nm with shoulder at 483 nm seems less stable than that at 420 nm with shoulder at 440 nm.
The effects of oxidation/reduction conditions prevailing during melting of the amber glass were studied. The effect of different amounts of graphite, Na2SO4 and Fe2O3 on the nature and position of amber related absorption band(s) were studied. Carbon content of 0.4 g (as well 0.5 g) in presence of 0.5 g Fe2O3 and 0.65–0.8 g Na2SO4 (g per 100 g glass) produces glasses with beautiful amber color. Several typical spectral features due to the transitions originating from both Fe2+ and Fe3+ oxidation states of iron are recorded. The broad band observed at wavelength around 1020 nm is assigned to Fe2+ ions+ in tetrahedral coordination. The absorption bands due to Fe3+ observed in the present study are recorded at 346, 370 (nm). The bands at 420 nm(with shoulder at 440 nm) and 474 nm (with shoulder at 483 nm) are expected to be related to the amber color, yet they are of different precursors. Amber color related band at 420 nm (with shoulder at 440 nm) is assigned to the chromophore group Fe3+O3–S2 . This band appears at 406 nm in glass melted for relatively long periods. The second amber related band at 474 nm (with shoulder at 483 nm) is found to participate in intensifying the amber color and is attributed to FeS formation. The precursor (FeS) of the amber related band at 474 nm (with shoulder at 483 nm) is less stable than that of (Fe3+O3–S2 ) at 420 nm (with shoulder at 440 nm). ZnO has a decolorization effect and its addition turns the amber color into faint bluish-green color. So its presence in the cullets to be added during amber glass manufacturing deteriorates the amber color. The decolorization is due to the removal of the sulfur ion from the Fe3+O3–S2 chromophore as a result of preferential bonding between the Zn ion and the S ion. Cu2O causes destruction of the chromophore group through the removal of the sulfur ion from the Fe3+O3–S2 complex by preferential bonding between the Cu ion and the S ion, similar to ZnO. Addition NaNO3 causes destruction of the chromophore group of the amber color which can be attributed to the oxidation of the sulfide ion in either the Fe3+O3–S2 or the FeS groups. Its presence by accident in glass batch can deteriorate the amber color. Increasing melting time at 1400 °C up to 6 h is not recommended as it weakens the intensities of the amber color and the amber related bands as a result of destruction of the amber chromophore groups. The amber chromophore groups are converted into Fe3+ in tetrahedral sites. This conversion is much stronger in the case of ZnO than in the case of Cu2O or NaNO3. Presence of Se produces dark amber color due to the formation of Se° and polyselenide.
Acknowledgments The authors would like to express their appreciations to Cairo for Glass Manufacturing Co., 10th of Ramadan City, Egypt, for the facilities given that enabled the performance of the experimental work of this investigation.
References [1] M.T. Utkarsh, P. Dhaval, P. Ankit, K.M. Moin, J. Pharm. Cosmetol. 1 (2011) 56– 60. [2] Y.Z. Rosenblum, P.P. Zak, M.A. Ostrovsky, I.L. Smolyaninova, E.V. Bora, U.V. Dyadina, N.N. Trofimova, A.G.D. Aliyev, Ophthalmic Physiol. Opt. 20 (2000) 335–341. [3] A.M. Nassar, M.M. Morsi, Egypt. J. Phys. 1 (1976) 17–20.
M.M. Morsi et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 145 (2015) 376–383 [4] C.R. Bamford, Colour Generation and Control in Glass. Glass Science and Technology, Vol. 2, Elsevier, NY, 1977. [5] C.S. Glafo, Glasteknisk Tidskrift 55 (2000) 65–71. [6] B. Mehdikhani, G.H. Borhani, Process. Appl. Ceram. 7 (2013) 117–121. [7] A. Paul, A. Ward, S. Gomolka, J. Mater. Sci. 9 (1974) 1133–1138. [8] F.R. Bacon, C.J. Billlan, J. Am. Ceram. Soc. 37 (1953) 60–66. [9] W.L. Spix, F.R. Bacon, J. Am. Ceram. Soc. 36 (1952) 377–383. [10] R.G.C. Beerkens, K. Kahl, Phys. Chem. Glasses 43 (2002) 189–198. [11] Yu.A. Guloyan, Glass Ceram. 62 (2005) 301–303. [12] N.F. Zhernovaya, V.I. Onishchuk, B. Davydoglu, Glass Ceram. 64 (2007) 111–114. [13] M. Muller, C. Russel, O. Claussen, Glasstech. Ber. 72 (1999) 362–366. [14] P. Lagarde, A.M. Flank, J. Jupille, H. Montigaud, J. Phys, Conf. Ser. 190 (2009) 1–4. [15] J. Klouzˇek, M. Arkosiová, L. Nìmec, Ceram. Silikáty 50 (2006) 134–139. [16] K.D. Kim, J.H. Hwang, J. Korean Ceram. Soc. 48 (2011) 205–210. [17] W.H. Manring, J. Am. Ceram. Soc. 30 (1946) 27–31. [18] E. Reinhard, G. Ward, S. Pattanaik, P. Debevec, High Dynamic Range Imaging: Acquisition, Display, and Image-Based Lighting (The Morgan Kaufmann Series in Computer Graphics), Morgan Kaufmann Publishers Inc., 2005. [19] D.H. Brainard, Color Res. Appl. 14 (1989) 23–34.
383
[20] W.B. Cowan, Comput. Graphics 17 (1983) 315–321. [21] HunterLab, Insight on Color 8 (2008) 1–2. [22] R.W. Douglas. Symposium on Coloured Glasses, Int. Commission on Glasszechoslovak Scientific and Technical Society of the Silicate Industry, Praha, 1967, pp. 161–191. [23] W.A. Weyl, Colored Glasses, Soc. Glass Tech, Sheffield, 1951. [24] P.A. Bingham, J.M. Parker, T.M. Searle, I. Smith, J. Non-Cryst. Solids 353 (2007) 2479–2494. [25] R. Klement, J. Kraxner, M. Liška, Ceram. Silikáty 53 (2009) 180–183. [26] J.P. Traverse, T. Toganidis, C. Ades, Glasstech. Ber. 65 (1992) 201–206. [27] L.B. Glebov, E.N. Boulos, J. Non-Cryst. Solids 242 (1998) 49–62. [28] M.A. Patton, The decolorization of amber container glass, Final report to the Center for Environmental and Energy Research, Alfred University, Summer undergraduate research fellowships, 2003, pp.1–14. [29] G. Wu, L. Li, Biochemistry (Moscow) 77 (2012) 135–142. [30] J.D. Lee, Concise Inorganic Chemistry, Fifth Ed., Wiley India Pvt. Limited, 2008. [31] J.C. Kuriacose, J. Rajaram, Chemistry in Engineering and Technology, Vol. 2, Tata McGraw-Hill Publishing Company Limited, New Delhi, 1998. [32] T. Jitwatcharakomol (PhD. Thesis), Fakultät für Georessourcen und Materialtechnik der Rheinisch-Westfälischen, Technischen Hochschule Aachen, Germany,2 005.
