polyvinyl alcohol nanocomposites

polyvinyl alcohol nanocomposites

Accepted Manuscript Title: Influence of CdS Nano-additives on Optical, Thermal and Mechanical Performance of CdS/Polyvinyl alcohol Nanocomposites Auth...

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Accepted Manuscript Title: Influence of CdS Nano-additives on Optical, Thermal and Mechanical Performance of CdS/Polyvinyl alcohol Nanocomposites Author: A. Abdel-Galil H.E. Ali M.R. Balboul PII: DOI: Reference:

S0030-4026(16)31228-1 http://dx.doi.org/doi:10.1016/j.ijleo.2016.10.061 IJLEO 58329

To appear in: Received date: Accepted date:

15-8-2016 19-10-2016

Please cite this article as: A.Abdel-Galil, H.E.Ali, M.R.Balboul, Influence of CdS Nano-additives on Optical, Thermal and Mechanical Performance of CdS/Polyvinyl alcohol Nanocomposites, Optik - International Journal for Light and Electron Optics http://dx.doi.org/10.1016/j.ijleo.2016.10.061 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Influence of CdS Nano-additives on Optical, Thermal and Mechanical Performance of CdS/Polyvinyl alcohol Nanocomposites A. Abdel-Galila*, H.E. Alib, M.R. Balboula

a

Solid State Physics and Accelerators Department, NCRRT, Atomic Energy Authority, Cairo, Egypt Radiation Chemistry Department, NCRRT, Atomic Energy Authority, Cairo, Egypt

b

*Corresponding author, E-mail: [email protected]

Abstract CdS /PVA nanocomposites have been prepared by solution casting method where 0.5, 1, 2 and 3 wt% of CdS nanoparticles (NPs) were taken as filler. The structure and the particle size of CdS/PVA nanocomposites films were identified by the transmission electron microscopy (TEM) and X-ray diffraction (XRD). The measurement of the thermal stability and mechanical properties of CdS /PVA nanocomposites has been done using thermogravimetric analysis (TGA) and mechanical testing, respectively. The effect of concentration of the filler particles (CdS NPs) and γ-irradiation on the thermal stability and mechanical properties of CdS/PVA nanocomposites has been studied. The variation of thermal stability and mechanical properties with the concentration of the filler particles and γ-irradiation also has been discussed in terms of dispersion of filler particles into polymer matrix. The optical band gap of PVA films was investigated with different ratios of CdS NPs. All of the CdS/PVA nanocomposites films have direct optical band gap which was decreased by increasing the CdS NPs ratio. The effect of γirradiation, with different doses on the optical band gap of CdS/PVA nanocomposites also has been studied.

Keywords: CdS/PVA nanocomposites; TGA; Optical absorption; Mechanical properties; Gamma radiation

1. Introduction Polymeric materials have many advantages, such as being light weight, resistant to corrosion, flexible, and low cost. Polymers are widely used materials in a large variety of commercial and technical applications [1]. Polyvinyl alcohol, PVA as a polymeric material is soluble in water, optically transparent polymer and characterizes by good chemical resistance and film forming ability [2]. Also, it has a high dielectric strength and good charge storage capacity. PVA polymer is a good candidate for incorporation into multilayer coatings of organic solar cells due to its optical properties and ability to form a barrier to oxygen [3]. It has carbon chain backbone with hydroxyl groups attached that can be a source of hydrogen bonding which assist the formation of polymer composite [4, 5]. It is a good host material; it can be blended with other materials such as metal, metal oxide and semiconductor nanoparticles (NPs) to improve its properties. Nano-

structured semiconductors represent significant category of materials for specific applications, like optoelectronic devices, solar cells, IR detectors and lasers. Recently, combinations between PVA and semiconductor (NPs) to form semiconductor (NPs)/ PVA nanocomposites have attracted considerable interest due to their size-dependent properties (quantum confinement effect) and the effect of this on the optical and electrical properties of PVA polymer [6-10].

CdS is an important II–VI semiconductor compound with a wide band gap (~ 2.42 eV). It has attracted much research interest due to its excellent properties (photoconductivity, and high electron affinity) for opto-electronics, being used in both of photosensitive and photovoltaic devices. It has also been extensively studied due to its potential applications in field effect transistors, light emitting diodes, bio-logical sensors, heterogeneous photo catalysis and thin film solar cells [11-14]. The incorporation of semiconducting CdS NPs in polymer matrix has been done by various processing techniques. Photon induced formation of CdS NPs in selected areas of polymer matrix has been proposed [15]. Nanosecond laser irradiation synthesis of CdS NPs in a PVA system [16]. CdS/PVA nanocomposite thin films have been deposited on glass substrates by in situ thermolysis of precursors dispersed in PVA [17]. Gamma-irradiation induced method used to synthesize CdS/PVA nanocomposites [10]. The nanocomposites of CdS can provide the possibility to give combinations of functionalities, such as thermally and electrically conducting composites with good mechanical and optical properties. Such properties can result because CdS NPs, with diameters distinctly below the Rayleigh scattering limit, still display their solid-state physical properties when embedded in transparent matrices. Basically CdS nanocomposites are optical composites and most of the studies of these are concerning optical characterization [1821]. In this work, CdS nanostructured powder sample was prepared separately by hydrothermal method. CdS /PVA nanocomposites films have been prepared by solution casting method. Mechanical properties of the PVA polymer were evaluated as a function of CdS NPs ratio (0.5%, 1%, 2% and 3%), before and after being exposed to different gamma irradiation doses. Thermogravimetric analysis (TGA) of pure PVA film and CdS/PVA nanocomposites (fresh and irradiated films) has been carried out from room temperature to 600oC. The optical band gap of PVA and CdS/PVA nanocomposite films was investigated with the different ratios of CdS NPs.

The effect of γ-irradiation, with different doses on the optical band gap of CdS/PVA nanocomposites also has been studied.

2. Experimental 2.1. Synthesis of CdS NPs and CdS/PVA nanocomposite films CdS nanostructured powder sample was prepared by hydrothermal method as reported in [22]. CdS/PVA nanocomposites have been prepared by solution casting method where PVA with a weight of 5 g was added to 100 ml of distilled water with stirring for 4 hours until complete miscibility. During the stirring, the required amount of CdS (0.5%, 1%, 2% and 3%) was added to the solution. The mixture was removed, the foam was skimmed off, and the solution was poured on leveled hydrophobic polystyrene petri dishes and dried for 48 hours at room temperature to form the desired films. The films were finally removed from the trays.

The particle size of CdS NPs as a filler in PVA polymer matrix and the surface morphology of the CdS/PVA nanocomposites films were investigated by transmission electron microscope (TEM), Jeol Electron Microscope type JEM100CS working at acceleration voltage of 80kV. The structure of PVA polymer and CdS/PVA nanocomposites films were carried out by a fully computerized X-ray diffractometer (XRD), Shimadzu type XD-6000. Thermogravimetric analysis (TGA) of PVA and CdS/PVA nanocomposites was performed using Shimadzu-50 TGA in Nitrogen atmosphere. The optical absorbance measurements of the prepared films were carried out at room temperature using a double beam Shimadzu UV-VIS spectrophotometer in the wavelength range 200–1100 nm. A Cobalt-60 Indian Gamma cell GC 4000A was used for samples γ-irradiation.

3. Results and Discussion 3.1. TEM images X-Ray Diffraction Figure 1. shows the TEM images of CdS/PVA nanocomposites film with 0.025% of CdS NPs dispersed into PVA as a represented sample with two magnifications (20000x and 50000x). It is observed from Fig. 1(a), at low magnification (20000x) the CdS NPs are uniformly dispersed into the PVA polymer matrix. Also, Fig. 1(b) at high magnification (50000x) shows

the distribution of CdS NPs within PVA polymeric chains with an average size in the range of 11-16 nm and there are no voids or craks on the surface of the CdS/PVA nanocomposites film. The X-ray diffraction pattern of PVA film, as in Fig. 2 shows only a broad amorphous scattering peak at 2θ=19.5o which indicates that the polymeric chains of PVA are strongly disordered [23]. Also, there are no clear peaks for 0.5%CdS/PVA nanocomposites film while the diffraction peaks of 1%CdS, 2%CdS and 3%CdS/PVA nanocomposite films are well assigned to the hexagonal phase (wurtzite type) of CdS reported in JCPDS card (No. 06-0314). The average particle size (D) of CdS NPs in the CdS/PVA films under study was calculated by Scherrer’s equation [24] at (002) plane: D  K  2 cos 

(1)

where λ is the wavelength of the X-ray beam (in our case λ = 0.15418 nm of CuKα1), β2θ is the full width at half maximum, θ is the corresponding Bragg angle and K is Scherrer constant. Table 1 gives the structure parameters and the particle size results of CdS/PVA films. The results indicated that the particle sizes are slightly less than TEM values in addition the average particle sizes gradually increased with the increasing of CdS ratio.

3.2. Thermal properties The thermal stability and various kinetic parameters related to the thermal degradation for pure PVA film and CdS/PVA nanocomposites films with different ratios of CdS NPs were investigated using TGA under nitrogen flow, in temperature range from room temperature to 600oC and at heating rate of 10 ◦C min−1. TGA thermograms for these samples and the corresponding rate of thermal decomposition reaction (DTG) have been recorded and are presented in Figs. 3 and 5. Table 2 shows the maximum (peak) temperatures for pure PVA and CdS/PVA nanocomposites films. As shown in Figs. 3 and 5 the thermal decomposition of pure PVA film and CdS/PVA nanocomposites films fits a two stage phenomenon, the first stage from 250 oC to 450 oC and the second stage from 450 oC to 550 oC. The major weight loss took place between 250 and 450 ◦C where the pure PVA began to degrade, followed by a further weight loss between 450 and 550 ◦C due to the structural decomposition of PVA polymer. The residues left after the thermal decomposition are greater in the CdS/PVA films than in the pure PVA polymer film, and the

difference could be attributed to the CdS NPs content. The results were consistent with the elimination of side-groups at lower temperatures, followed by breakdown of the PVA polymer backbone at higher temperatures [25]. Also, Figs. 3 and 5 show that the thermal stability of pure PVA was found to be higher than that of CdS/PVA nanocomposites. However, the presence of CdS NPs caused a decrease in the decomposition temperature of the PVA. This confirms that there is a strong interaction between PVA chains and CdS NPs. It is known that the high thermal stability of PVA polymer results from the strong intermolecular interaction between PVA chains through the intermolecular hydrogen bonding [26]. Thus, it is possible that in our study the interactions between PVA chains and CdS NPs led to the decrease in intermolecular interaction between the PVA chains and hence the thermal stability [27]. Different types of nano-fillers have been found to have different influences on the thermal stability of PVA matrix. For example, the Ag NPs improved the thermal stability of the PVA matrix by about 40 ◦C, while the thermal decomposition of the PVA is unchanged in the presence of montmorillonite. On the other hand, in the presence of the magnetite NPs, decomposition of the PVA is shifted toward lower temperatures by approximately 20 ◦C [28]. Lowering the thermal stability of polymer in the presence of CdS NPs had also been reported by Kuljanin-Jakovljevi´c et al. [29]. In their report, polystyrene (PS) was used as the polymer with PS-CdS ratio of 80/20. The low thermal stability was attributed to the concentration of the CdS NPs. This result was in agreement with the observation of Hongmei Wang et al [26]. Who demonstrated that the obtained TGA results suggested incorporation of CdS NPs significantly altered the thermal properties of PVA matrix and the thermal decomposition temperature of CdS/PVA nanocomposite film lowered for about 100 oC. The activation energy corresponding to the major degradation process (250-450oC) for pure PVA film and CdS/PVA nanocomposites fresh and γ-irradiated films was calculated using the approximation method of Horowitz and Metzger according to the following relation [30]:

  W0  W f ln ln    Wr  W f

 Ea      R  T 2 p 

(2)

Where W0, Wf are the initial and final weights, Wr is the remaining weight at temperature T, Ea is the degradation activation energy, R is a gas constant (R=8.314 JK-1mol-1) and θ=T-Tp where Tp is the DTG peak temperature.

In the light of Eq.(2), the degradation activation energy Ea can be calculated from the slope of the linear fitted line between Ln(ln((W0–Wf)/(Wr-Wf))) and θ as shown in Fig. 7 and Fig. 8 (a, b, c, d) for pure PVA film and CdS/PVA nanocomposites fresh and γ-irradiated films, respectively. The values of the degradation activation energy Ea for pure PVA film, as observed in Table 2 decreases with adding and increasing of the CdS NPs ratio. This behavior confirms the decrease in the thermal stability of PVA polymer by adding CdS NPs due to the decrease in the intermolecular interaction between the PVA chains with the introducing of CdS NPs as discussed previously.

Figures 4 (a, b, c, d) and 6 (a, b, c, d) show TGA and DTG thermogrames for CdS/PVA nanocomposites before and after γ-irradiation with two different doses (10kGy and 30kGy). As shown in these figures the major degradation process of CdS/PVA nanocomposites films with different ratios of CdS NPs shifted to higher temperatures with the γ-irradiation doses. Table 2 and Table 3 show the values of the peak temperature Tp and the degradation activation energy Ea for CdS/PVA nanocomposites fresh and γ-irradiated films. As shown in these tables, the thermal stability of CdS/PVA nanocomposites films gradually improved with γ-irradiation doses. The improvement of the thermal stability of the CdS/PVA nanocomposites with the γ-irradiation doses can be explained as a result of the cross-linking process of the PVA polymer chains under the effect of the γ-irradiation.

3.3. Mechanical properties The tensile strength of a polymer is usually defined as the maximum stress reached during the stress-strain test, and the yield strength (𝜎𝑦) is the point where deviation from linearity occurs in the stress-strain curve. The total area under the stress-strain curve represents the fracture energy or toughness of the sample, and the elongation at break is the maximum strain reached during the stress-strain curve or the value of strain when the sample breaks.

In the early (low strain) portion of the stress strain curve, many materials obey Hooke’s law to a reasonable approximation, so that stress σe is proportional to strain εe with the constant of proportionality being the modulus of elasticity or Young’s modulus, denoted E:

 e  E e

(3) Figures 9 and 10 show the tensile behavior of CdS/PVA nanocomposite films as a function of CdS NPs ratio. It is observed that the value of the tensile strength has been increased while the elongation at break has been decreased with increasing the filler content (CdS NPs) into polymer matrix. The increase in tensile strength and decrease in elongation at break of CdS/PVA nanocomposite is due to the formation of compact structure which can be considered as a result of the strong interfacial adhesion between PVA matrix and the CdS NPs surface as a filler. Hence the dispersion of CdS NPs provides strength to PVA matrix. The molecular mobility decreases owing to the formation of physical bonds among CdS NPs and PVA chains. The interfacial adhesion (physical bonding) increases with increasing CdS NPs content into PVA polymer matrix. These results were in agreement with observations of Vishal Mathur et al and J. Kraus et al [31, 32], who demonstrated that physical bonding between NPs and polymer matrix leads good adhesion between matrix and the CdS NPs.

On the other hand the improvement in mechanical properties with the irradiation doses (Fig. 9 and Fig. 10) can be explained mainly by considering the formation of cross-linked structure of the PVA polymer as a consequence of the γ-irradiation. The increase in cross-linking can be considered as the responsible for the increase of tensile strength and the decrease of elongation [33, 34]. This behavior agrees with the improvement of the thermal stability of the CdS/PVA nanocomposites films with the γ-irradiation doses.

3.4. Optical studies Figure 11 shows the absorbance of pure PVA and CdS/PVA nanocomposite films as a function of the wavelength in the UV-Vis range (200-1100 nm). It is observed from that figure, the absorbance of pure PVA film increases with adding the CdS NPs and also increases systematically with the increasing of CdS NPs content over all the wavelength range. The

changes of the absorbance spectra may be correlated to the interface adhesion and network structure of CdS/PVA nanocomposites. The absorption coefficient α of the pure PVA and CdS/PVA nanocomposite films was calculated from absorbance (ABS) and the film thickness (t) using the Beer–Lambert’s relation [35]: 𝛼 = (2.302 × 𝐴𝐵𝑆)⁄𝑡

(4)

The optical band gap Eopt of the pure PVA and CdS/PVA nanocomposite films can be obtained in the high absorption region from the following relation [36]:

h  B(h  Eopt ) m ,

(5) Where B is constant, hν is the incident photon energy and m is an index its value determines the type of electronic transitions causing the optical absorption. It takes values 1/2 and 2 for direct and indirect transition, respectively. Fig. 12(a, b, c) shows the relation between (αhν)2 versus hυ for pure PVA and CdS/PVA nanocomposite films. The direct optical band gap can be obtained from the intercept of the resulting straight lines with the energy axis at (αhν)2=0 for all samples under investigation [37]. The values of Eopt for the PVA polymer film and CdS/PVA nanocomposites films are listed in Table 4. We note from that Table, the optical band gap Eopt decreases gradually with increasing of the particle size of CdS NPs which increased with the CdS NPs ratio (the concentration of the filler NPs). This effect can be explained on the basis of two reasons. Firstly, it is known that as the size of semiconductor particles decreases to the nanoscale, the band gap of the semiconductor increases, causing a blue shift in the UV–Vis absorption spectra. It could indicate the presence of quantum confinement effect [38]. Secondly, it was reported that the NPs themselves could act as conductive junctions between the polymer chains that resulted in an increase of the electrical conductance of the nanocomposites and hence lead to a decrease in their optical band gap [39, 40]. Fig. 13(a, b, c, d) shows the effect of γ-irradiation on the optical band gap of CdS/PVA nanocomposites films. As shown in that figure, the optical band gap of 0.5%CdS/PVA increases with increasing the irradiation dose, while it was slightly changed in case of 1%CdS/PVA, 2%CdS/PVA and 3%CdS/PVA nanocomposite films. In case of 0.5%CdS/PVA nanocomposite film the optical band gap was gradually shifted to higher energy with the increase of the

irradiation dose; this effect may be due the generation of high structural disorder of 0.5%CdS/PVA nanocomposite film i.e. decrease in the crystallinity with the increase of the irradiation doses [41]. The band gap increases with the decrease of the particle size and the absorption edge is shifted to a higher energy with decrease of the particle size [42, 43]. Table 4 shows the optical band gaps for fresh and irradiated CdS/PVA nanocomposite films. The main observation from that Table is that the radiation hardness of CdS/PVA nanocomposites increases with increase of the CdS content, the optical band gap slightly changes with the increase of irradiation doses.

4. Conclusion TEM images of CdS/PVA composites showed the uniform dispersion of CdS into the PVA polymer matrix and the nanostructure nature of CdS. XRD patterns confirmed the nanostructure nature of CdS/PVA composites and also the particle size of CdS NPs. The thermal stability of PVA polymer decreased with adding CdS NPs. This effect may be attributed to the interactions between PVA chains and CdS NPs. Such interaction could lead to decrease in the intermolecular interaction between the PVA chains and hence the thermal stability. The value of tensile strength has been increased, and elongation at break has been decreased as the CdS ratio increased, this effect was expected due to the incorporation of rigid CdS nanoparticles in the polymeric matrix. The increase in the tensile strength and decrease in the elongation with the irradiation doses can be explained mainly by considering the formation of cross-linked structure of the polymer as a consequence of the irradiation. Pure PVA and CdS/PVA nanocomposite films have direct optical band gap. The optical band gap Eopt of CdS/PVA nanocomposites decreased with increasing CdS NPs ratio. The optical band gap of 0.5%CdS/PVA increases with increasing the irradiation dose, while it was slightly changed in case of 1%CdS/PVA, 2%CdS/PVA and 3%CdS/PVA nanocomposite films.

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Figures captions: Fig. 1: TEM images of PVA film containing CdS nanoparticles a-Mag. 20000x and b-Mag. 50000x. Fig. 2: X-ray diffraction patterns for pure PVA and CdS/PVA nanocomposites films. Fig. 3: TGA thermograms of the investigated PVA and CdS/PVA nanocomposites. Fig. 4 (a, b, c, d): TGA thermograms of a- 0.5%CdS/PVA, b- 1%CdS/PVA, c- 2%CdS/PVA and d- 3%CdS/PVA nanocomposites fresh and γ- irradiated films. Fig. 5: DTG thermograms of the investigated pure PVA and CdS/PVA nanocomposites. Fig. 6 (a, b, c, d): DTG thermograms of a- 0.5%CdS/PVA, b- 1%CdS/PVA, c- 2%CdS/PVA and d- 3%CdS/PVA nanocomposites fresh and γ- irradiated films. Fig. 7: Plot of Ln(ln((W0–Wf)/(Wr-Wf))) versus θ using Horowitz-Metzger method for pure PVA and CdS/PVA nanocomposites. Fig. 8 (a, b, c, d): Plot of Ln(ln((W0–Wf)/(Wr-Wf))) versus θ for a- 0.5%CdS/PVA, b1%CdS/PVA, c- 2%CdS/PVA and d- 3%CdS/PVA nanocomposites fresh and γ- irradiated films. Fig. 9: Plot of tensile strength versus irradiation dose for CdS/PVA nanocomposites films. Fig. 10: Plot of elongation (%) versus irradiation dose for CdS/PVA nanocomposites films. Fig. 11: The absorbance of pure PVA and CdS/PVA nanocomposite films as a function of the wavelength. Fig. 12(a, b, c): Energy dependence of (αhυ)2 for a- pure PVA, b- 0.5%CdS/PVA and 1%CdS /PVA and c- 2%CdS/PVA and 3%CdS /PVA nanocomposites films. Fig. 13: Energy dependence of (αhυ)2 for a- 0.5%CdS/PVA, b- 1%CdS/PVA, c- 2%CdS/PVA and d- 3%CdS/PVA fresh and γ-irradiated nanocomposites films.

Fig. 1 (b)

(a)

Fig. 2 PVA 0.5CdS/PVA 1CdS/PVA 2CdS/PVA 3CdS/PVA

(112)

(110)

1000

(103)

1500

(100) (002) (101)

Int. (Arab. Units)

2000

500

0 10

20

30

40

50

2 (Deg.)

60

70

80

Fig.3

PVA 0.5CdS/PVA 1CdS/PVA 2CdS/PVA 3CdS/PVA

Weight remaining (%)

100

80

60

40

20

0 0

100

200

300

400

500

600

o

Temperature ( C)

Fig. 4

(d)

90 60 3CdS/PVA fresh 10kGy 30kGy

30

Weight remaining (%)

0 90

(c)

60 2CdS/PVA fresh 10kGy 30kGy

30 0 90

(b)

60

1CdS/PVA fresh 10kGy 30kGy

30 0

(a)

90 60 0.5CdS/PVA fresh 10kGy 30kGy

30 0 0

100

200

300

400 o

Temperature ( C)

500

600

Fig.5

Rate of reaction (mg/sec)

0.0000 -0.0004 -0.0008 -0.0012 PVA 0.5CdS/PVA 1CdS/PVA 2CdS/PVA 3CdS/PVA

-0.0016 -0.0020

0

100

200

300

400

500

600

o

Temperature ( C)

Fig. 6

0.0000 -0.0008

(d)

3CdS/PVA fresh 10kGy 30kGy

(c)

2CdS/PVA fresh 10kGy) 30kGy

(b)

1CdS/PVA fresh 10kGy 30kGy

(a)

0.5CdS/PVA fresh 10kGy 30kGy

-0.0016 -0.0024

Rate of reaction (mg/sec)

0.0000 -0.0005 -0.0010 0.0000 -0.0007 -0.0014 -0.0021

0.0000 -0.0008 -0.0016

0

100

200

300

400 o

Temperature ( C)

500

600

Fig. 7 3

ln(ln((W0-Wf)/(Wr-Wf)))

2

1

0

-1 PVA 0.5CdS/PVA 1CdS/PVA 2CdS/PVA 3CdS/PVA

-2

-3 -60

-30

0

30

60

90

120

150

 (K) Fig.8 2 0 (d)

3CdS/PVA fresh 10kGy 30kGy

(c)

2CdS/PVA fresh 10kGy 30kGy

-2 (b)

1CdS/PVA fresh 10kGy 30kGy

-2

ln(ln((W0-Wf)/(Wr-Wf)))

2 0 -2 -4 2 0

2 0 0.5CdS/PVA fresh 10kGy 30kGy

-2 (a)

-4 -120

-90

-60

-30

0

 (K)

30

60

90

120

150

Fig. 9 32 0.5%CdS/PVA 1%CdS/PVA 2%CdS/PVA 3%CdS/PVA

Tensile strength (MPa)

30

28

26

24

22 0

5

10

15

20

25

30

35

Dose (kGy)

Fig. 10

0.5CdS/PVA 1CdS/PVA 2CdS/PVA 3CdS/PVA

11.2

Elongation (%)

10.8 10.4 10.0 9.6 9.2 8.8

0

5

10

15

Dose (kGy)

20

25

30

Fig. 11 1.0

PVA 0.5CdS/PVA 1CdS/PVA 2CdS/PVA 3CdS/PVA

0.8

ABS

0.6

0.4

0.2

0.0 200

400

600

800

1000

1200

 (nm)

Fig. 12 (c)

4

9.0x10

4

6.0x10

4

3.0x10

2CdS/PVA 3CdS/PVA (b)

2

(h) (cm eV )

0.0 3

2

-2

6.0x10

3

3.0x10

0.5CdS/PVA 1CdS/PVA 0.0

2.1x10

3

1.4x10

3

7.0x10

2

(a)

PVA 0.0 0

1

2

3

4

h (eV)

5

6

7

Fig. 13

4

9.0x10

(d)

4

6.0x10

3CdS/PVA fresh 10kGy 20kGy 30kGy

4

3.0x10

0.0 4

(c) 2CdS/PVA fresh 10kGy 20kGy 30kGy

2

(h) (cm eV )

4.40x10

4

-2

2.20x10

0.00

(b)

3

2

6.0x10

1CdS/PVA fresh 10kGy 20kGy 30kGy

3

3.0x10

0.0

(a)

3

5.00x10

0.5CdS/PVA fresh 10kGy 20kGy 30kGy

3

2.50x10

0.00 0

1

2

3

h (eV)

4

5

6

7

Table 1 Structure parameters for 1%CdS/PVA, 2%CdS/PVA and 3%CdS/PVA samples. Comp.

2θ (Deg.)

β2θ (Radian)

d (Å)

D (nm)

1%CdS/PVA

28.16

1.54

3.17

5.33

2%CdS/PVA

27.02

1.18

3.30

6.91

3%CdS/PVA

28.22

0.86

3.16

9.53

Table 2 DTG peak temperature and degradation activation energy for PVA and CdS/PVA nanocomposites. Comp.

Tp( C)

Ea(kJ mol-1)

PVA

340

82.88

0.5%CdS/PVA

283

57.70

1%CdS/PVA

286

55.36

2%CdS/PVA

262

48.76

3%CdS/PVA

281

45.3

Table 3 DTG peak temperature and degradation activation energy for γ-irradiated CdS/PVA nanocomposites. Comp.

Dose (kGy)

Tp(C)

Ea(kJ mol-1)

10

305

76.74

30

360

85.62

10

281

63.97

30

286

67.16

10

350

58.83

30

365

61.76

10

325

75.81

30

320

80.98

0.5%CdS/PVA

1%CdS/PVA

2%CdS/PVA

3%CdS/PVA

Table 4 Optical band gap for PVA and CdS/PVA (fresh and irradiated) nanocomposites films. Comp.

Eg (eV) fresh

10 (kGy)

20 (kGy)

30 (kGy)

PVA

3.02

0.5%CdS/PVA

2.68

2.85

2.87

3.04

1%CdS/PVA

2.45

2.40

2.45

2.42

2%CdS/PVA

2.29

2.29

2.30

2.23

3%CdS/PVA

1.68

1.64

1.62

1.62