EFFECT OF GAMMA IRRADIATION ON THE THERMAL
AND OPTICAL PROPERTIES OF CELLULOSE NITRATE NUCLEAR TRACK DETECTOR
*
HAFEZ, F.M. and EL-HAGG, A.A.
Physics
Department, Faculty of Science, Al-Azhar University,
Girls Branch, Egypt.
Key words: Gamma irradiation, Thermal properties, Colour changes, SSNTDs.
تأثير أشعة جاما على الخواص الحرارية والضوئية للكاشف النووى نترات السليلوز
فاتن مصطفى حافظ و عزة عبد الرءوف الحاج
خلاصـــة
تم فى هذا البحث دراسة تأثير أشعة جاما على الخواص الحرارية والضوئية للكاشف النووى نترات السليلوز (CN-85). تم تشعيع عينات الكاشف النووى بجرعات مختلفة من أشعة جاما فى المدى 5-49 كيلوجراى ولدراسة الخواص الحرارية، تم استخدام جهاز التحليل الوزنى الحرارى (TGA) لحساب قيم الطاقة الحرارية اللازمة لتكسير الروابط فى العينة.
أوضحت النتائج أن نترات السليلوز تنحل خلال مرحلة أساسية وحيدة عند درجات حرارة قليلة جداً بالمقارنة بالعديد من الكواشف النووية الأخرى وذلك نظراً لضعف الرابطة بين الأكسجين والنيتروجين.
وبالإضافة إلى ذلك، تم قياس معاملات النفاذية للعينات فى مدى الأطوال الموجية 200-2500 نانومتر ومنها تم حساب قيم فرق اللون الثلاثية وكذلك فرق اللون بين العينات المشععة بجرعات مختلفة من أشعة جاما والغير مشععة ووجد أن الكاشف النووى نترات السليلوز له استجابة عالية لتغير اللون تحت تأثير أشعة جاما.
ABSTRACT
The effect of gamma dose on the thermal and optical properties of cellulose nitrate (CN-85) solid state nuclear track detector (SSNTD) was investigated. Non-isothermal studies were carried out using thermogravimetric analysis (TGA) to obtain the thermal activation energy of decomposition for CN-85 detector. The experimental results of TGA indicated that the CN-85 samples were decomposed in one main break down stage. Samples from CN-85 sheets were irradiated with gamma radiation in the dose range 5-40 KGy. The onset temperature of decomposition (To) and the thermal activation energy of decomposition (Ea) were calculated, using the TGA curves for the non-irradiated and irradiated CN-85 samples. The results indicated that the cellulose nitrate detector was decomposed at temperatures much lower than that of several other SSNTDs due to the weak nitrogen oxygen bonds. Also, the variation of transition temperatures with the gamma dose has been determined using differential thermal analysis (DTA). The CN-85 thermograms were characterized by the appearance of one endothermic peak due to melting. These melting temperatures were found to be dependent on the gamma dose. The results indicated that the CN-85 detector is a material that did not have a high resistance to degradation and its tendency to cross linking was much lower than that of several other SSNTDs.
In addition, the transmission of these samples in the wavelength range 200-2500 nm, as well as any colour changes, was studied. A characteristic absorption bands with different intensities were observed. Using the transmission data, both the tristimulus and the Commission Internationale de l’Eclairage (CIE) LAB coordinate values were calculated. Also, the colour differences between the non-irradiated samples and those irradiated with different gamma doses were calculated. The CN-85 detector has a response to colour change by gamma irradiation.
