Fractional Free-Volume dependence of Oxygen in Beta-Irradiated Polystyrene Probed by Positron life time
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چکیده
Positron annihilation lifetime (PAL) technique has been employed to investigate the effect of low doses of -irradiation (in air and vacuum) on the type of polymers namely: polystyrene (PS). A conventional fast-slow coincidence system was used for measuring the positron lifetime spectra. The time resolution of the system was ٤٢٢±٢٠ ps (the full width at half maximum (FWHM)) at Na energy window. The lifetime spectra were resolved into three components by using PFPOSFIT program. The irradiation performed in air (in the presence of oxygen) and under vacuum with -rays by using (Sr/Y) source at room temperature for ten different total dose, ranging from (٠٫٣-١٢٫٣) Gy . The oPs lifetime parameters were used to determine the microstructure properties, namely: free volume hole size (Vh) and free volume hole fraction (Fh). The parameters were measured as a function of irradiation dose. The results of -irradiation show that, the influence of -irradiation on o-Ps lifetime, hence the Vh and Fh values for samples irradiated in air are less than their values for samples irradiated under vacuum, due to the effect of peroxy and hydroperoxide radicals formed in the presence of oxygen. The results show that cross-linking process is the predominant process as a result of irradiation PS. ھصلاخلا نورتزوبلا ءانف رمع نمز ةیفایطم ةینقت تمدختسا ) PALS ( قئاقد نم ةئطاو عرج تاریثأت ةساردل ةبلاسلا اتیب ) غارفلا و ءاوھلا يف ( نیریاتس يلوبلا ) PS .( ةئیطب قباطت ةموظنم تمدختسا ثیح زیمب ةعیرس هرادقم لثمأ ينمز ) ٤٢٢ ٢٢ ( مویدوصلا ةذفان دنع ھیناث وكیب ٢٢ . و جذامنلا نم ناتعومجم تععش دق ةیرمیلوبلا ) ةینزولا ریداقملا سفنبو ( ةساردلل ةمدختسملا , مویتنورتسلا ردصمب ٩٠ ) Sr/Y ( ثعابلا اتیب تامیسجل . ةیناثلا ةعومجملا تععش امنیب ةفرغلا ةرارح ةجرد دنع ءاوھلا يف ىلولأا ةعومجملا تععش هرادقم عرجلا نم ىدملو غارفلاب ٠٫٣ رك ىلإ يا ١٢،٣ لدعمبو يارك ٣٫٦ يارك / ةعاس , ىلإ جئاتنلا تللح جمانرب ةطاسوب ةینمز تابكرم PFPOSFIT . رحلا مجحلاب ةلثمتملا تارمیلوبلل ةقیقدلا ةیوینبلا صئاصخلا تددح ) Vh ( يئزجلا رحلا مجحلاو Fh) ( نم موینورتزوبوثرولاا ءانف رمع نمز سایق للاخ (٣) ةقلاعلا تدجوو ةمدختسملا ةیعاعشلإا عرجلا نیبو امھنیب . اھیلع لصح يتلا جئاتنلا تنیب , نیتلاحلا نیب ھنراقم ءارجإ دعبو ) غارفلا يفو ءاوھلا يف ( , نمز میق نإ ةثلاثلا ةبكرملا ٣) ( نم لقا يھ ءاوھلا يف ةععشملا جذامنلل يئزجلا رحلا مجحلاو رحلا مجحلل ةبسنلاب كلذكو ةععشملا كلت غارفلا يف , لعافتل ةجیتن ةنوكتملا يسكوریبوردیاھلاو يسكوریبلا روذج ریثأت ىلإ كلذ دوعیو نیجسكولأا عم اتیب قئاقد ریثأت ببسب ةدلوتملا ةرحلا روذجلا . رحلا مجحلاو رحلا مجحلا لازتخا ىلإ يدؤت يتلا ةیرولبلا قطانملا ةدایزل ةجیتن يئزجلا , صقانت يلاتلاب ) ٣ .( اتنلا تحضوأ كباشتلا تایلمع نأ جئ رصاولأا يف ةیرمیلوبلا نیریاتس يلوبلا ةنیعل ةدئاسلا تایلمعلا يھ . نورتزوبلا ءانف رمع نمز ةینقت نأ ةساردلا هذھ تدكأ تاددعتمل قیقدلا يرھجملا بیكرتلا صئاصخ ةساردلو رحلا مجحلا صئاصخ ةساردل ةیلاع ةءافك تاذ ةینقت دعت رتمونانلا سایقب تائیزجلا سایق ةقدبو رتمونانلا نودو يلاوح ٧ بعكمرتموكیب (pm) .
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