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Preparation Films from Nano Tungsten Oxide Powders and Studying Their Sensing Properties for Ethanol Vapor

تحضير أغشية من مساحيق أكسيد التنغستين النانوية, ودراسة خصائصها التحسسية تجاه بخار الإيثانول

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 Publication date 2014
  fields Physics
and research's language is العربية
 Created by Shamra Editor




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Thick Films have been prepared by the chemical painting method from Tungsten Oxide nanopowdersas the source compound, which are prepared by milling in a high energy ball mill for variousspans of time (1-18h) on cleanedglasssubstratesunder limited thermal conditions. The temperature of the films have been changed from 25°C to 350°C. The films have been investigated for their sensing properties relating to 100 ppm ethanol vapor adsorption, using the (I–V) characteristics.The activation energy Ea for deposition films is deduced from the Arrhenius equation. The effect of the grain size and the thermal conditions on the sensing properties of the WO3thick films to ethanol vapor adsorption, as well as the correlations between The electrical conductivity of the WO3 thick films and the grain size of the material films are reported.The response time for films which have particle size about 70.54nm is defined at 300°C.



References used
GIL-SU K, YOUNG JUNG L, DAE-GUN K, YOUNG DO K; Consolidation Behavior Of Mo Powder Fabricated From Milled MO Oxide By Hydrogen-Reduction. Journal of Alloys and Compounds, Vol.454, 2008, 327–330
SAFAEI A, ATTARIAN SHANDIZ M, SANJABI S, BARBER Z H; Modelling The Size Effect On The Melting Temperature Of Nanoparticles, Nanowires And Nanofilms. J. Phys.: Condens. Matter, Vol. 19, 2007, 1-9
Dae-Gun Kim, Kyung Ho Min, Si-Young Chang, Sung-Tag Oh, Chang-Hee Lee, Young Do KimaEffect of pre-reduced Cu particles on hydrogen-reduction of W-oxide in WO3–CuO powder mixtures. Materials Science and Engineering A, Vol. 399, 2005, 326–331
C. V. Ramana, S. Utsunomiya, R. C. Ewing, C. M. Julien, and U. Becker; Structural Stability and Phase Transitions in WO3 Thin Films. J. Phys. Chem. B, Vol. 110, 2006, 10430-10435
S. Saloum and B. Alkhaled; Growth Rate and Sensing Properties of Plasma Deposited Silicon Organic Thin Films from HexamethyldisilazaneCompound.ActaPhysicaPolonica A. Vol. 117, No. 3, 2010, 484- 489
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There are wide uses of tin oxide thin films, especially in the field of transparent conductors, solar cells, gas sensors and piezoelectric materials. Laser deposition is considered one of the most important techniques followed to obtain these film s. In this research, we develop a technique to obtain homogeneous thin films of tin oxide depending on vaporization of pile targets of this oxide by continuous CO2 laser in the atmosphere, with a fan which guarantees obtaining homogenous films. Some of these films were annealed in different conditions. The optical microscope images revealed the presence of high degree of homogeneity, while the X-Ray study showed different crystallization grain orientations which depend on the preparation conditions. The preferred direction is (110). The optical absorption gives information about the value of the effective band gal for the samples before and after thermal annealing. We have found that some films have Eg = 3.2 ev. before annealing, and after long annealing they have Eg=1.3ev. In addition, the hard annealed thin films reveal anisotropy in the optical and electrical. Characteristics, they have different absorption coefficients in two perpendicular directions, also there is an electrical resistance anisotropy along these two directions especially after hard annealing. The Eb was 0.73 ev before annealing, it became 0.37 ev for one direction and 0.32 ev for the other direction.
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يعد الميتانول و الإيتانول من أكثر المحلات شيوعاً، و بما أن درجة غليانها أقل من مئة درجة مئوية فإنها تتطاير بشكل سريع. و على سبيل المثال، يستعمل الميتانول في تصنيع الأصبغة و العقاقير و العطور.. و هو شديد السمية، لذلك من الضروري تطوير محسات لكشفه. أ ما غاز الأمونيا فهو من ملوثات الهواء و له مصادر كثيرة مثل صناعة الأسمدة و أنظمة التبريد.. و من هنا أهمية كشفه.
In this work, multi-layer thin films (insulator - metal - insulator) were prepared on glass substrates. Where we deposited the following order of (zinc oxide - silver - zinc oxide) by magnetron sputtering of zinc oxide and vacuum thermal evaporation technique for silver.

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