مجلة إبن الھیثم للعلوم الصرفة و التطبیقیة 2012 السنة 25 المجلد 1 العدد Ibn Al-Haitham Journal for Pure and Applied Science No. 1 Vol. 25 Year 2012 Using Gamma Ray Transmission for Determination of Porosity in Doped Alumina Samples A. J. Al- Saadiand A. K. Saadon College of Dentistry, University of Karbala Department of Physics, College of Education Ibn Al-Haitham, University of Baghdad Received in: 27April 2011,Accepted in: 18October2011 Abstract In this study, gamma ray t ransmission method have been used to determine the total porosity in four samples: pure Alumina ( Al2O3 ), Al2O3 + (0.2wt%)MgO , Al2O3 + (0.6wt% )Y2O3 and Al2O3+ (8wt% ) ZrO2 . T he experimental setup for the gamma ray t ransmission consist of 13 7Cs gamma source ( 662 KeV ), a NaI (T l) scint illation detector measured the at tenuation of strongly collimated gamma beam through alumina samples. The porosity obtained by the gamma ray t ransmission method were compared with the measurements by convent ional (Archimedes) method. It was observed that the porosity measurement by gamma ray transmission method has the advant age of being accurate, nondestructive and fast analysis. Keywords: Gamma ray, Attenuation coefficients, Porosity, Doped alumina Introduction Porosity is an important parameter commonly used to describe the behavior of prose material, that is of great int erest in many areas such as medicine, petroleum, engineering, metallurgy , nuclear reactor technology and other applicat ions [1, 2]. The porosity of a medium can be expressed as a rat io of volume of the void space to the bulk volume, that is a dimensionless quantity usually expressed in percentage. Measurement of material's porosity are usually performed by convent ional methods like Archimedes porosimetry and mercury inject ion porosimetry [3, 4]. However the gamma ray transmission technique is allows determination of the porosity without int erfering in the physical int egrity of the sample [5]. T he method of gamma ray t ransmission was applied in the measurement of reservoir rocks porosity by Phogat and Aylmore [6]. Oliveira et al. uses x ray in porosity measurements of t itanium sintered foams [7]. Demir et al. uses gamma ray t ransmission in porosity measurements of soil[8]. Alumina exhibit low volume dilatat ion and high t hermal conductivity coefficient, another application of this material is to cover recipients exposed to thermal shocks and high temperatures (up to 1700 °C) It is very important to determine the porosity of sintered materials because this parameter has a large influence the efficiency of there applications. In the present work, gamma ray attenuation coefficient and porosity of pure Alumina ( Al2O3 ), Al2O3 + (0.2wt%)MgO, Al2O3 + (0.6wt%) Y2O3 and Al2O3+ (8wt% )ZrO2 are determined by using gamma ray transmission method. The gamma ray attenuation measurements have carried out , using 137 Cs radioactive source. مجلة إبن الھیثم للعلوم الصرفة و التطبیقیة 2012 السنة 25 المجلد 1 العدد Ibn Al-Haitham Journal for Pure and Applied Science No. 1 Vol. 25 Year 2012 Experimentation 1. Samples preparation High purity α-Alumina was used as the starting powder. The powder characteristic was 0.3µm average particle size. Samples of alumina containing weight percentages of MgO ( 0.2wt% ), Y2O3 ( 0.6wt% ) and ZrO2 (8wt%.) were prepared by mixing for (20 hrs). After that, the mixture was pressed to pellets with 20mm diameter and approximately 2mm thickness. These pellets were heated at 1550°C in air for 14hrs. Sintered densities were measured by using the Archimedes method with mercury as the immersion medium. 2. Experimental setup The gamma ray transmission system consisted of radioactive source 137Cs ( 662 KeV ) with an activity 100 µci . The radioactive source was shielded by the pin-hole lead collimator to obtain a narrow beam ( 3mm diameter ). The intensities of gamma photons were measured by using NaI(Tl) scintillation detector (Saint- Gobain Crystals Bicron model 1.5in.× 2 in. made in U.S.A.). The detector was coupled to pre-amplifier, amplifier, power supply and computer analyzer with LD Didactic GmbH sensor-cassy for data acquisition and analysis the obtain areas. The detector was also housed in a thick lead jacket with a 10 mm diameter holed collimator. Fig.1 shows schematic arrangement of the experimental setup used in the present study. Samples were used in the form of a tablets plates with approximately 20mm diameter and 2mm thickness. Each spectrum was recorded for a period of 1000 sec, to reduce the statistical error. Background spectra were recorded for the same time period and subtracted from each spectrum. 3. Porosity determination For determination of the total porosity by gamma ray transmission method, it is necessary to determine the linear attenuation coefficient for the materials. The attenuation of a narrow collimated beam of gamma rays for a given energy can be obtained by the relationship [ 8,9 ]: )1(...................0 xeII  Where I0 is the initial intensity of gamma rays , I is the intensity of gamma rays after attenuation through a media of thickness x and µ is the linear attenuation coefficient of the material. Equation (1) may also be written as: )2(...................ln 1 0 I I x  Total porosity ( Pt ) of a medium can be described as[10,11 ]: مجلة إبن الھیثم للعلوم الصرفة و التطبیقیة 2012 السنة 25 المجلد 1 العدد Ibn Al-Haitham Journal for Pure and Applied Science No. 1 Vol. 25 Year 2012 )3(................. p apPt     Where µp ( cm-1) is the linear attenuation coefficient of the sample at the particle density and µa ( cm-1) is the linear attenuation coefficient of the sample crossed gamma ray beam. The linear attenuation coefficient of the sample (µa ) was experimentally determined by measuring the gamma attenuation through a known thickness of sample for 662 KeV photons. The linear attenuation coefficient of the sample at the particle density (µp ) was accomplished by the application of the software XCOM [12], taking into account the chemical composition and bulk density of the sample. For determination of the total porosity by conventional method ( Archimedes ), using the following relation [10, 11 ]: )4(............... sss ds ww ww Pt    Where Ws is the weight in the air of the sample saturated with water, Wd is the dry sample weight in the air and Wss is the weight saturated of water suspended in water. Results and Discussion Measurement of material bulk density involves the determination of the mass and the volume of a given amount of alumina samples. Table 1 shows the measured bulk density , average values obtained for linear attenuation coefficients of the samples(µa ) and linear attenuation coefficients of the samples at particle density (µp ). Table 2 shows the average total porosity for the alumina samples by gamma-ray transmission method (calculated by eq.3 ) and by Archimedes method (calculated by eq.4 ). The values obtained by gamma ray method are larger than that obtained by Archimedes method, because the gamma ray transmission method characterizes total porosity while the Archimedes method characterizes only connected pores that represents apportion of the total porosity. Conclusions The total porosity( % ) of alumina samples were determined by gamma ray transmission method and Archimedes method. The results obtained for the total porosity( % ) by gamma ray method shown deceasing behavior with increasing the linear attenuation coefficient of the sample (µa ) crossed gamma ray beam. The gamma ray transmission method gives characterizes total porosity while the Archimedes method characterizes only effective porosity or connected pores that represents apportion of the total porosity. The comparison between experimental results gives the gamma ray transmission method appears to offer advantages such as inexpensive, non destructive and fast analysis according to conventional Archimedes method. مجلة إبن الھیثم للعلوم الصرفة و التطبیقیة 2012 السنة 25 المجلد 1 العدد Ibn Al-Haitham Journal for Pure and Applied Science No. 1 Vol. 25 Year 2012 References 1. Ouellet, S.; Bussière, B.; Aubertin, M. and Benzaazoua, M.(2007), Research ,Micro structural evolution of cemented paste backfill: mercury intrusion porosimetry test results, Cement and Concrete Research , 37,1654-1665. 2. Medvedovski, E. (2006) Ceramics International ,Alumina–mullite ceramics for structural applications, 32 ,369–375. 3 . Innocentini, M. D.; Pardo, A. R. and Salvini, V. R. (2002), Cerâmica ,Prediction of permeability constants through physical properties of refractory castables, Issn 0366-6913, 48(305): 05-10 . 4. Moreira, A.C. and Appoloni, C. R.( 2009), International Nuclear Atlantic Conference - INAC. Porosity determination of alumina and boron carbide ceramic samples by gamma ray transmission, ISBN: 978-85-99141-03-8. 5. Bodwakar, S.V.and Reis, J.C.( 1994 ). Porosity measurements of core samples using gamma-ray attenuation Nucl. Geophys 8 (1):61–78. 6 . Phogat, V.K. and Aylmore, L.A. (1989), . Evaluation of soil structure by using computer assisted tomography Soil Phys. Hydrol 27,313–323. 7. Oliveira, M. V.; Moreira, A. C., Appoloni C. R, Lopes R. T., Pereira L. C. and Cairo C. A., (2006) , Porosity study of sintered titanium foams ,M aterials Science Forum 530-531,.22-28 8. Demir D.; Ozgul, A. and Sahin, Y.(2008). Determination of photon attenuation coefficient, porosity and field capacity of soil by gamma ray transmission for 60,356 and 662KeVgamma ray ,Appl. Radiat. and Isot 66,1834-1837. 9.Raje, D.V. and Chaudhari, L.M.( 2010), Mass attenuation of soil samples in Maharashtra (India ) by using gamma energy at 0.662 MeV Bulg. J. Phys. 37,158-164. 10 . Pottker, W.E. and Appoloni, C.R.( 2001),Measurement of amorphous materials porosity by gamma-ray transmission methodology, Radiation Physics and Chemistry 61,535–536. 11. Appoloni, C. R. and Pottker ,W. E.( 2004),Non-Destructive porosity profile measurement of amorphous materials by gamma-ray transmission, Applied Radiation and Isotopes 61, 1133-1138. 12. Hubbel, J.H.and Berger, M.J.(1987), NBSIR ,photon cross sections on a personal computer ,3597-3598. Table (1): Experimental values of bulk density , linear attenuation coefficients of the samples at particle density (µp ) and linear attenuation coefficients of the samples crossed gamma ray beam. (µa ) Material Bulk Density (g.cm-3) µp (cm -1 ) µa (cm -1 ) Al2O3 2.40±0.013 0.18211 0.1349±0.0004 Al2O3 + 0.2wt%MgO 2.65±0.015 0.20108 0.1537±0.0009 Al2O3 + 0.6wt% Y2O3 2.75±0.016 0.20864 0.1714±0.0010 Al2O3+ 8wt%ZrO2 2.89±0.015 0.21891 0.1855±0.0005 مجلة إبن الھیثم للعلوم الصرفة و التطبیقیة 2012 السنة 25 المجلد 1 العدد Ibn Al-Haitham Journal for Pure and Applied Science No. 1 Vol. 25 Year 2012 Table (2): Average values of total porosity for the alumina samples obtained by gamma-ray transmission method and by conventional method ( Archimedes) Total porosity (%) Material gamma transmission Archimedes Al2O3 25.9198±0.2196 22.10±1.00 Al2O3 + 0.2wt%MgO 23.5323±0.4477 20.67±1.30 Al2O3 + 0.6wt% Y2O3 17.8733±0.5195 16.64±1.50 Al2O3+ 8wt% ZrO2 15.2619±0.2283 13.78±1.12 Fig.(1): Experimental setup for the measuring of linear attenuation coefficients مجلة إبن الھیثم للعلوم الصرفة و التطبیقیة 2012 السنة 25 المجلد 1 العدد Ibn Al-Haitham Journal for Pure and Applied Science No. 1 Vol. 25 Year 2012 استخدام نفاذیة أشعة كاما لتعیین المسامیة في عینات األلومینا المشوبة عباس كریم سعدون ، دي عباس جواد السع كربالءكلیة طب األسنان ، جامعة بغدادقسم الفیزیاء ، كلیة التربیة ابن الهیثم، جامعة 2011 تشرین االول 18: في ث بل البح ق،2011 نیسان27: استلم البحث في الخالصة ِتم في هذه الدراسة استخدام تقنیة نفاذیة أشعة كاما لتعیین المسامیة الكلیة ألربع عینات ِ األلومینا النقیة: ِّ (Al2O3) ، Al2O3 +(0.6wt%) Y2O3 ، Al2O3 +( 0.2wt%)MgO و Al2O3+ (8wt% )ZrO2. 662ذو الطاقـة ) فوتـون ( الباعـث ألشـعة كامـا 137 –الـسیزیوم تـضمنت منظومـة القیـاس كـل مـن مـصدر أشـعة كامـا ا فــي NaI(Tl( الومیـضي یـود یـد الـصودیوم المنـشط بالثـالیوم كاشـف فولـت والإلكتـرون كیلـو لقیـاس تـوهین حزمـة أشـعة كامـ .عینات األلومینا ا مـع الطریقـة التقلیدیـةُ قورنت المسامیة التي تم الحص َلـوحظ ). طریقـة أرخمیـدس (ِول علیها بطریقة نفاذیة أشعة كامـ . ِإعطاء نتائج دقیقة وغیر اتالفیة للنماذج وسریعة: منها عدیدة طریقة نفاذیة أشعة كاما تمتلك فوائدان لكلمات المفتاحیة األلومینا المشوبة،المسامیة، معامالت التوهین،أشعة كاما : ا