The purpose of this  paper, study the  effect of  addition Krum chloride on optical properties of polyvinyl-alcohol . The composites prepare by casting technique with different weight percentages of CrCl2 are (0,1,2,3). Results showed that the absorbance increases with increase the concentration of  CrCl2, absorption coefficient, extinction coefficient, refractive index and real and imaginary parts of dielectric constants are increasing with increase CrCl2 concentration. keywords: Polyvinyl alcohol, Optical Properties, Composites.   

Abd-alkadhim, Nahida

Habeeb, Majeed Ali

Hashim, Ahmed

Marza, Amjed

Rabee, Bahaa H.

Saad, Athraa

English

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Chemistry and Materials Research                                                                                                                                                    www.iiste.org ISSN 2224- 3224 (Print) ISSN 2225- 0956 (Online) Vol.3 No.7, 2013  59    Optical Properties of (PVA-CrCl2) Composites ( 1)Ahmed Hashim ,( 2)Amjed Marza,(3)Bahaa H. Rabee ,(4) Majeed Ali Habeeb, (5)Nahida Abd-alkadhim,                    (6)Athraa Saad (1,3,4)Babylon University, College of Education , Department of physics,  Iraq. (2,6)Babylon University, College of Science , Department of chemistry,  Iraq. (5)Babylon University, Enjineering Affairs,  Iraq. E-Mail: ahmed_taay@yahoo.com  Abstract The purpose of this  paper, study the  effect of  addition Krum chloride on optical properties of polyvinyl-alcohol . The composites prepare by casting technique with different weight percentages of CrCl2 are (0,1,2,3). Results showed that the absorbance increases with increase the concentration of  CrCl2, absorption coefficient, extinction coefficient, refractive index and real and imaginary parts of dielectric constants are increasing with increase CrCl2 concentration. keywords: Polyvinyl alcohol, Optical Properties, Composites.   Introduction          Optical properties of polymers constitute an important aspects in study of electronic transition and the possibility of their application as optical filters, a cover in solar collection, selection surfaces and green house. The information about the electronic structure of crystalline and amorphous semiconductors has been mostly accumulated from the studies of optical properties in wide frequency range. The significance of amorphous semiconductors is in its energy gap[1]. The typical advantages of organic polymers are flexibility, toughness, formability, and low density, whereas ceramics have excellent mechanical, thermal, and optical properties, such as surface hardness, modulus, strength, heat resistance, and high refractive index. The combination of organic polymers and ceramics promises new hybrid materials with high performance. Numerous technological applications have been identified for these composite materials, such as electromagnetic and radio frequency interference shielding for electronic devices (for example, computer and cellular housings), over-current protection devices, photothermal optical recording, and direction-finding antennas[2].  Experimental work          The materials used in this work are polyvinyl alcohol and CrCl2. The weight percentages of CrCl2 are ( 0,1,2 and 3) wt.%. The casting technique is used to prepare the samples with thickness ranged between (350-475)µm.           The transmission and  absorption spectra of PVA-CrCl2 composites have been recording in the length range (200-800) nm using double-beam spectrophotometer (UV-210oA shimedza ).  Results and Discussion        Figure(1) shows the variation of the optical absorbance with the wavelength of the incident light for (PVA- CrCl2) composites.  00.511.522.533.54200 300 400 500 600 700 800Wavelength(nm)Absorbancepure1 wt .%2 wt .%3 wt .%FIG.1Variation of Optical absorbance for (PVA-CrCl2) composite with  wavelengthChemistry and Materials Research                                                                                                                                                    www.iiste.org ISSN 2224- 3224 (Print) ISSN 2225- 0956 (Online) Vol.3 No.7, 2013  60     The figure indicate that the absorbance increases with increase of CrCl2 concentration, this attributed to the high absorbance of CrCl2.    The variation of the absorption coefficient, α, as a function photon energy are presented in figure(2) . It  was calculated from equation[3]:                                              …………………………………(1)    Where : A is absorbance   and d is the thickness of sample                 The values of the absorption coefficient are less than 104cm–1 in the investigation spectral range. The fundamental absorption, which corresponds to electron excitation from the valence band to conduction band, can be used to determine the nature and value of the optical band gap, Eg. The relation between the absorption coefficient, α, and the incident photon energy, hν, can be written as[4] :                (αhν)n =B(hν −Eg)     …………………………………(2) where B is an constant depending on the transition probability and n is an index that characterizes the optical absorption process and is theoretically equal to 1/2,2, 1/3 or 2/3 for indirect allowed, direct allowed, indirect forbidden and direct forbidden transition, respectively. The usual method to calculate the band gap energy is to plot  a graph between (αhν)n and photon energy, hν, and find the value of the n which gives the best linear graph. This value of n decides the nature of the energy gap or transition involved. If an appropriate value of n is used to obtain linear plot, the value of Eg will be given by intercept on the hν-axis as shown in figures(3,4).      00.511.522.533.544.550 1 2 3 4 5 6 7Photon energy(eV)pure1 wt.%2 wt.%3 wt.%FIG.2 absorption coefficient  for (PVA-CrCl2) composite with  various photon energyα(cm)-1.303.2dA=αChemistry and Materials Research                                                                                                                                                    www.iiste.org ISSN 2224- 3224 (Print) ISSN 2225- 0956 (Online) Vol.3 No.7, 2013  61     The attenuation coefficient (k) is directly proportional to the absorption coefficient(α):[4]              k=αλ/4π                …………………………(3) Where λ is the free space wavelength of light.   024681012140 1 2 3 4 5 6 7Photon energy(eV)pure1 wt .%2 wt.%3 wt.%FIG.3 the relationship between (αhυ)1/2(cm-1.eV)1/2 and photon energy of (PVA-CrCl2) composites. (αhυ)1/2(cm-1.eV)1/201234560 1 2 3 4 5 6 7Photon energy(eV)pure1 wt.%2 wt.%3 wt.%(αhυ)1/3(cm-1.eV)1/3FIG.4 the relationship between (αhυ)1/3(cm-1.eV)1/3 and photon energy of (PVA-CrCl2) composites.Chemistry and Materials Research                                                                                                                                                    www.iiste.org ISSN 2224- 3224 (Print) ISSN 2225- 0956 (Online) Vol.3 No.7, 2013  62          Figure(6) shows the variation of the refractive index (   RRn−+=11 ) of composites a function of photon energy. It has been found that the value of refractive index increases with increasing the concentration of CrCl2 which is a result of increasing the number of atomic refractions due to the increase of the linear polarizability in agreement with Lorentz - Lorentz formula[4]. 0.0E+001.0E-062.0E-063.0E-064.0E-065.0E-066.0E-067.0E-068.0E-06200 300 400 500 600 700 800kpure1 wt.%2 wt.%3 wt.%λ(nm)FIG.5 extinction coefficient  for (PVA-CrCl2) composite with  various photon energy11.21.41.61.822.22.42.62.830 1 2 3 4 5 6 7photon energy(eV)npure1 wt.%2 wt.%3 wt.%FIG.6the relationship between refractive index for (PVA-CrCl2) composite with photon energyChemistry and Materials Research                                                                                                                                                    www.iiste.org ISSN 2224- 3224 (Print) ISSN 2225- 0956 (Online) Vol.3 No.7, 2013  63              Figures(7,8) show the variation of real and imaginary parts of dielectric constants (ε1 =n2-k2and ε2=2nk) of (PVA- CrCl2) composites .It is concluded that the variation of ε1 mainly depends on (n2) because of small values of (k2), while ε2 mainly depends on the (k) values which are related to the variation of absorption coefficients[5].  Conclusions   1. The absorbance increases with increase the weight  percentages of  CrCl2. 2. The absorption coefficient, extinction coefficient, refractive index and real and imaginary parts of dielectric constants are increasing with increase of  CrCl2 concentration. 3. The forbidden energy gap decreases with increase of CrCl2 concentration.  References [1] Gabriel Pinto and Abdel-Karim Maaroufi, 2011, "Critical filler concentration for electroconductive polymer composites", Society of Plastics Engineers (SPE), 10.1002/spepro.003521. [2] JAE-WAN KIM, WON-JEI CHO, CHANG-SIK HA, 2002, " Morphology, Crystalline Structure, and Properties of Poly(vinylidene fluoride)/Silica Hybrid Composites, J. of Polymer Science: Part B: Polymer Physics,Vol.40, PP.(19–30).  01234567890 1 2 3 4 5 6 7photon energy(eV)pure1 wt.%2 wt.%3 wt.%ε 1FIG.7variation of real part of dielectric constant (PVA-CrCl2) composite with photon energy0.E+005.E-061.E-052.E-052.E-053.E-053.E-054.E-054.E-055.E-050 1 2 3 4 5 6 7photon energy(eV)pure1 wt.%2 wt.%3 wt.%ε 2FIG.8 variation of  imaginary part of dielectric constant(PVA-CrCl2) composite with  photon energyChemistry and Materials Research                                                                                                                                                    www.iiste.org ISSN 2224- 3224 (Print) ISSN 2225- 0956 (Online) Vol.3 No.7, 2013  64 [3] Hutagalwng. S. D. and Lee. B. Y. ,2007, Proceeding of the 2nd international conference Nano/Micro Engineered and Molecular systems, January, Bangkok,Thailand. [4] NICOLAE ÞIGÃU, 2008, " STRUCTURAL CHARACTERIZATION AND OPTICAL PROPERTIESOF ANNEALED Sb2S3 THIN FILMS", Rom. Journ. Phys., Vol. 53, Nos. 1–2, P. 209–215, Bucharest. [5] Ahmed R.m. , 2008, "Optical study on poly(methyl methacrylate)/poly(vinyl acetate)", Zagazig Uni., Zagazig, Egypt, E-mail-rania 8_7@hotmail. com.      This academic article was published by The International Institute for Science, Technology and Education (IISTE).  The IISTE is a pioneer in the Open Access Publishing service based in the U.S. and Europe.  The aim of the institute is Accelerating Global Knowledge Sharing.  More information about the publisher can be found in the IISTE’s homepage:  http://www.iiste.org  CALL FOR PAPERS The IISTE is currently hosting more than 30 peer-reviewed academic journals and collaborating with academic institutions around the world.  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Optical Properties of (PVA-CrCl2) Composites

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Optical Properties of (PVA-CrCl2) Composites

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