MWCNT ve manyetik nanopartikül takviyeli PMMA'nınradyasyon zayıflatma katsayısının karşılaştırmalı olarak incelenmesi
Comparative investigation of radiation attenuation coefficient of MWCNT and magnetic nanoparticle reinforced PMMA
- Tez No: 942963
- Danışmanlar: PROF. DR. NİLGÜN BAYDOĞAN
- Tez Türü: Yüksek Lisans
- Konular: Nükleer Mühendislik, Nuclear Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2025
- Dil: Türkçe
- Üniversite: İstanbul Teknik Üniversitesi
- Enstitü: Lisansüstü Eğitim Enstitüsü
- Ana Bilim Dalı: Nükleer Araştırmalar Ana Bilim Dalı
- Bilim Dalı: Radyasyon Bilim ve Teknoloji Bilim Dalı
- Sayfa Sayısı: 98
Özet
Bu çalışmada, PMMA/MWCNT nanokompozitin ( çok duvarlı karbon nanotüp kompozit) örneklerin yapısal, beta, gama ışını ve nötron zırhlama özellikleri incelenmiştir.PMMA/MWCNT nanokompozit esaslı polimer-x 8 örnek hesaplanmıştır, Burada x = 3,4,15 ve 30 wt.% dir. (wt% (ağırlık yüzdesi) ). PMMA/MWCNT nanokompozit malzemesi NaI gama spektrometresi cihazı ile radyasyon zayıflatma katsayısı,PM 1405 Survey meter ile Beta radyasyonu zayıflatma katsayısı ve Thermo Sciencitific Radeye Nl Nötron dedektörü ile radyasyon zayıflatma katsayısı analizleri gerçekleştirildi. Sayım sonuçlarında , Spektrum eğrisine sahip PMMA/MWCNT nanokompozit malzemeleri artan MWCNT yüzdesiyle arttığını gösterdi.PMMA/MWCNT kompozit malzemelerinin kütle zayıflama katsayıları, yarı değer kalınlıkları (HVL) ve gama spektrumundaki ortalama pik konumları, Co-60 (1,17 MeV ve 1,33 MeV), Cs-137 (0,662 MeV) ve Ba-133 (0,546 MeV) radyoizotopları kullanılarak deneysel olarak belirlenmiştir.PMMA/MWCNT nanokompozit malzemeleri beta,gama ve nötron zırhlama parametreleri belirlendi . Kompozit (PMMA) yapıya daha yüksek miktarda MWCNT eklenmesinin örneklerin radyasyona ve nötronlara karşı zırhlama yeteneğini önemli ölçüde iyileştirdiği gözlemlendi.Gama ışınları ile yapılan deneylerde,PMMA/MWCNT nanokompozit malzemelerde radyasyon iletimi eksponansiyel olarak azalmış, yüksek kütlesel soğurma katsayısına (μ) sahip yapılar daha düşük HVL değerleri ile daha ince tabakalarda etkili koruma sağlamıştır. Ölçümlerde R² değerleri yüksek olup, sonuçlar güvenilir ve tutarlıdır. NaI sintilasyon cihazıyla elde edilen spektrumlar, malzeme kalınlığı arttıkça radyasyonun yoğunluğunun belirgin şekilde düştüğünü göstermiştir.Beta ışınları için yapılan ölçümlerde, MWCNT katkısının iyonizasyon ve saçılma etkilerini artırarak beta partiküllerinin soğurulmasını iyileştirdiği görülmüştür. Metal oksit nanoparçacıkların (Co₃O₄, Fe₃O₄) kullanımı beta zayıflama performansını anlamlı şekilde artırmıştır. HVL değerleri, katkı oranına bağlı olarak değişmekle birlikte, yoğunluğu yüksek malzemelerin daha düşük HVL ile daha iyi koruma sağladığı tespit edilmiştir.Nötron ölçümlerinde ise, CoFe₂O₄ ve Fe₃O₄ nanoparçacıklı kompozitlerin nötron akısını belirgin şekilde azalttığı belirlenmiştir. Bu etki, nötronların elastik ve inelastik saçılma ile nötron yakalama mekanizmalarına bağlanmıştır. PMMA/MWCNT nanokompozitin' yüksek elektriksel iletkenliği ve nanoparçacıkların homojen dağılımı, nötron soğurma başarısında kritik faktör olarak öne çıkmıştır. En iyi performans %3-4 oranında nanoparçacık katkılı kompozitlerde gözlenmiştir.Bu çalışmada MWCNT katkılı PMMA malzemesine homojenize etmek için Atom Transfer Radikal Polimerizasyon (ATRP) yöntemi kullanılmıştır. MWCNT, PMMA'nın radyasyon zırhlama özelliklerini arttırmak için kullanılmıştır.
Özet (Çeviri)
In this study, structural, beta, gamma and neutron radiation shielding properties PMMA/MWCNT nanocomposites and (multiwalled carbon nanotube ) composite samples were investigated in detail. These composite samples were synthesized with different MWCNT content ratios to evaluate their effectiveness in radiation attenuation applications. MWCNT concentration in the polymer matrix was adjusted as x = 2, 3, 4, 15 and 30 mole percent, and a total of eight different PMMA/MWCNT nano composite samples were obtained. The composite samples were produced using the atom transfer radical polymerization (ATRP) method, which provides controlled dispersion of fillers in the polymer matrix. This method was preferred due to its ability to provide better control over the molecular architecture of the polymer composites and to increase homogeneity. In addition to MWCNT, colemanite filler was also used in some formulations to evaluate the synergistic effects on shielding performance. The obtained samples exhibited varying degrees , mechanical stability and optical clarity depending on the MWCNT concentration. Various spectrometric and dosimetric techniques were used to analyze the radiation attenuation capabilities. Gamma radiation measurements were performed using a NaI(Tl) scintillation gamma spectrometer, where the mass attenuation coefficient was determined for photon energies of 0.662 MeV, 1.17 MeV, 1.33 MeV. These energy values correspond to common gamma emitters such as Cs-137 and Co-60. Gamma spectroscopy and NaI scintillation device consists of collimator, source and material and computer. Its general principle consists of measuring one or more of these single energy photons with a detector capable of generating a pulse signal proportional to the amount of energy deposited in the sensitive volume. It provides a smooth display of the recorded pulse height histogram with the help of a multi-channel analyzer (MCA). Scintillation detectors are systems that detect ionizing radiation by converting it into visible light. When NaI(Tl) crystal interacts with gamma rays, it produces light (scintillation). Gamma ray interaction: Gamma rays lose energy by interacting with the NaI(Tl) crystal via photoelectric effect, Compton scattering or pair production mechanisms. Light production: This energy loss results in the production of visible light photons within the NaI(Tl) crystal. The photomultiplier tube (PMT) is activated: The light emitted by the crystal is detected by a photomultiplier tube (PMT). The PMT produces a signal by converting the light photons into electrons. Electronic signal processing: The signal from the PMT is amplified, converted to digital data and analyzed. Gamma spectrometry results showed that the attenuation capability of the composite samples improved significantly as the MWCNT concentration increased. This is evident from the shift in the spectrum curve and the increased intensity of the MWCNT-related peaks superimposed with the characteristic signals of the polymer, indicating that the MWCNT was successfully and homogeneously integrated into the polymer matrix. Beta radiation shielding efficiency was evaluated using a Polimaster model PM-1405 measuring device and a beta counting spectrometer using a Strontium 90 source at 0.546 MeV and 2.28 MeV photon energies. At the bottom of the beta measuring device, the metal plate is elevated with glass material and the source is placed on it. The photons passing through the material coming out of the source reach the detector and show us the count. If the beta filter in front of the detector is in the closed position, only gamma rays are measured because beta particles cannot pass through the filter. The measurement obtained shows the background gamma radiation (gamma dose rate). If the detector's beta filter is in the open position, beta particles can also reach the detector and are included in the measurement. In this case, the measurement obtained gives the total of (Beta + Gamma). To find the beta number, gammas are subtracted from the total number to find pure beta. Then, a graph showing the count amount depending on the thickness is created.The recorded spectra showed a significant increase in beta absorption with increasing MWCNT content. This indicates the potential use of these composites in applications requiring beta shielding, especially in environments where low energy electrons pose a radiological hazard. Neutron radiation interactions were investigated by measuring equivalent dose rates for 5.486 MeV and 0.059 MeV neutrons using an Americium 241 source and by calculating the neutron cross-section and flux using calibrated neutron detectors and analytical models. Neutron measurement; It consists of a Howitzer and a neutron hand detector source. Since the source being worked on is active, a protective cap and rope are used inside the howitzer to minimize radiation exposure, and when the source and the material are at the same height, the scattering that passes through the material and reaches the detector is measured. Neutron measurements showed that samples with higher MWCNT content exhibited a greater capacity for neutron attenuation. Although PMMA alone has moderate neutron shielding capacity, the inclusion of carbon nanotubes significantly increased the moderation and absorption of neutron particles due to their high surface area and scattering properties. The radiation attenuation capacity of the materials was analyzed by measuring the linear attenuation coefficient (µ) and half-value thickness (HVL). Radiation measurements were made using NaI(Tl) sodium iodide scintillation detector, PM105 beta measurement detector and neutron hand detector howitzer. These detectors detect photons with high sensitivity and allow accurate determination of radiation attenuation coefficients. We see the relationship between the linear attenuation coefficient and thickness of materials containing nanoparticle doped PMMA/MWCNT with beta neutron and gamma measurement values. The graphical results increase exponentially in all measured materials. In addition, since the R2 values of the materials are between 0-1, the measurements are at a reliable level. PMMA, a transparent thermoplastic polymer from the acrylate family, is widely known for its high strength, optical clarity, and resistance to abrasion and heat. Its excellent thermal and mechanical properties make it suitable for various engineering applications. However, its inherent radiation shielding capacity can be significantly enhanced by the incorporation of nanostructured fillers such as MWCNTs. The resulting PMMA/MWCNT nanocomposites exhibit enhanced mechanical strength, thermal stability, and radiation resistance, expanding their usability in high-demand sectors. These novel polymer-based nanocomposite samples hold promise for application in the aerospace industries, where materials must be lightweight, durable, and resistant to various forms of radiation. Moreover, the use of environmentally stable polymer matrices such as PMMA, combined with the superior shielding properties of MWCNTs, opens avenues for developing a new generation of smart shielding materials with shape memory behavior. PMMA/MWCNT nanocomposites can be evaluated as lightweight and effective radiation shielding materials. These materials offer significant advantages in many sectors such as nuclear power plants, medical imaging devices, aviation applications, space technologies, defense industry and industrial radiation shielding. Thanks to their unique properties, they have great potential especially in the aviation and space industry due to their electromagnetic shielding capacity, high temperature resistance and mechanical strength. In addition, their integration with smart technologies such as machine learning, artificial intelligence, internet of things (IoT) and data analytics offers new opportunities in industrial automation and robotic systems.For the first time in the literature, it fills a scientific gap by presenting an experimental direct comparative analysis of PMMA/MWCNT nanocomposites reinforced with different magnetic nanoparticles against gamma, beta, and neutron radiation types.
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