Bu tez çalışmasında, alternatif bir gamma ışını zırhlama malzemesi olarak seryum oksit (CeO₂) içeren borosilikat camların potansiyelini incelemektedir. Gamma radyasyonunun tıp, sanayi, tarım ve araştırma tesisleri gibi birçok alanda giderek daha fazla kullanılması, güvenlik endişelerini artırmaktadır. Gamma ışınları, yüksek geçirgenlik özellikleri nedeniyle uzun süreli maruziyet durumunda ciddi doku hasarına ve kansere yol açabilmektedir. Kurşun gibi geleneksel zırhlama malzemeleri etkili olmakla birlikte, yüksek yoğunlukları, maliyetleri, toksik yapıları ve çevresel etkileri, hafif, uygun maliyetli ve çevre dostu yeni malzemelere olan ihtiyacı artırmaktadır. Bu tezde, farklı CeO₂ katkı seviyelerinin borosilikat cam kompozitlerinin gamma zırhlama performansı üzerindeki etkileri incelenmiştir. %0, 2.5, 5, 7.5 ve 10 ağırlık oranlarında CeO₂ içeren bileşimler test edilmiştir. CeO₂ oranı arttıkça, camların yoğunluğu 2.43 g/cm³'ten 2.87 g/cm³'e yükselmiştir. Gamma zayıflatma özellikleri, 0,02 MeV ile 15 MeV aralığında enerji kaynakları kullanılarak bir gamma spektrometresi ile test edilmiştir. Deneysel doğrusal zayıflama katsayıları (LAC) ve kütle zayıflama katsayıları (MAC), NIST XCOM verileri ve Geant4 simülasyonlarından elde edilen teorik değerlerle karşılaştırılmıştır. Özellikle düşük enerji seviyelerinde fotoelektrik absorpsiyonun etkisiyle daha yüksek CeO₂ içeriklerinde zırhlama performansı iyileşmiştir. Yarı değer katmanı (HVL), onuncu değer katmanı (TVL) ve ortalama serbest yol (MFP) gibi zırhlama parametreleri analiz edilmiştir. CeO₂ konsantrasyonunun artması, HVL ve TVL değerlerini önemli ölçüde azaltarak daha ince ve etkili zırhlama sağlayabilecek malzemelere işaret etmiştir. Atomik kesit (ACS), elektronik kesit (ECS), efektif atom numarası (Zeff) ve efektif elektron yoğunluğu (Neff) gibi hesaplanan değerler de CeO₂'nin zırhlama performansını özellikle düşük enerji seviyelerinde artırdığını doğrulamıştır. Deneysel sonuçlar, teorik ve simülasyon bulguları ile uyumlu bulunmuştur. BNCP-5, Gd-4, GN2, BCZLM1, SiBBSZ1 ve S2 gibi diğer malzemelerle karşılaştırıldığında, CeO₂ katkılı borosilikat camların rekabetçi ya da üstün performans sergilediği görülmüştür. 1 MeV enerji seviyesinde, ABS-Ce10, çoğu malzemeden daha yüksek MAC değerleri göstermiştir. SiBBSZ1 daha yüksek bir MAC gösterse de, düşük yoğunluğu nedeniyle genel etkinliği azalmıştır. ABS-Ce10, yoğunluk ve zırhlama verimliliği arasında dengeli bir kombinasyon sunarak, gamma ışını zırhlama uygulamaları için güçlü bir aday olarak öne çıkmıştır. Özellikle tıbbi, endüstriyel ve sterilizasyon uygulamalarında yaygın olarak kullanılan enerji seviyelerinde bu malzeme oldukça uygun bulunmuştur. Gelecekteki araştırmalar için, CeO₂ oranının %10'un üzerine çıkarılması, zırhlama verimliliği ve mekanik özellikler arasındaki dengenin daha iyi anlaşılmasına olanak tanıyabilir. Ayrıca, yüksek enerjili gamma foton seviyelerinde daha ayrıntılı performans analizleri yapılması, malzemenin nükleer ve tıbbi ortamlardaki uygunluğunu daha iyi anlamaya katkı sağlayabilir. CeO₂ katkılı kompozitlerin uzun vadeli dayanıklılığının incelenmesi de ekonomik ve teknik ömürleri açısından değerlendirilmelidir. Bunun yanı sıra, CeO₂'nin diğer nadir toprak elementleri veya metal oksitlerle birleştirilmesi, belirli uygulamalara uygun optimize edilmiş malzemeler elde edilmesini sağlayabilir. Sonuç olarak, CeO₂ katkılı borosilikat camlar, etkili, hafif ve çevre dostu gamma ışını zırhlama malzemeleri olarak güçlü bir potansiyel sergilemektedir. Üstün zayıflatma özellikleri, yapısal kararlılığı ve maliyet etkinliği ile geleneksel ağır metal bazlı zırhlama malzemelerine sürdürülebilir bir alternatif sunabilir.
The increasing reliance on gamma radiation across a wide spectrum of fields including medicine, industry, agriculture, nuclear energy, and advanced research facilities such as particle accelerators has led to heightened concerns about the safety and health implications of prolonged exposure. Gamma rays, known for their highly penetrating nature, can easily pass through conventional materials, making them particularly challenging to block or absorb. While they serve critical functions, such as sterilizing medical equipment, imaging internal structures in the body, or testing the integrity of industrial components, their use also amplifies the risk of harmful effects on human health. Prolonged exposure to gamma radiation can cause severe tissue damage, compromise the immune system, and significantly increase the risk of developing cancers. As these applications become more prevalent, the demand for more effective and efficient radiation shielding materials has grown. Traditional shielding solutions, such as lead-based materials, often present additional challenges, including high density, toxicity, and environmental concerns. As a result, researchers have intensified their efforts to develop innovative shielding materials that not only offer superior radiation attenuation but also address other key criteria. Low density, cost-effectiveness, sustainability, and environmental friendliness are increasingly regarded as essential characteristics. Developing novel materials that meet these requirements is critical for enhancing safety standards and ensuring sustainable, long-term use of gamma radiation in a wide range of applications. In this thesis, the gamma radiation shielding properties of borosilicate glasses containing cerium oxide (CeO₂) were investigated. The principal objective was to determine how different CeO₂ doping ratios influence the gamma shielding capabilities of borosilicate glass composites, thereby providing a potential alternative to conventional lead-based shielding materials, which are often limited due to toxicity, high density, high cost, and environmental concerns. CeO₂ was chosen for its favorable properties, including high atomic number (Z = 58), considerable density, excellent chemical stability, thermal resistance, and environmental safety. The glass compositions studied were systematically prepared with a borosilicate base and varying concentrations of CeO₂. The compositions were labeled ABS-Ce0, ABSCe2.5, ABS-Ce5, ABS-Ce7.5, and ABS-Ce10, corresponding to CeO₂ concentrations of 0%, 2.5%, 5%, 7.5%, and 10% by weight. Other components of the glasses remained constant: Na2O, Li2O, Al2O3, SiO2, CaO, MgO, and B2O3. As CeO₂ content increased, the concentration of SiO2 decreased accordingly to maintain the overall composition. The densities of the glass samples ranged from 2.43 g/cm³ for ABSCe0 to 2.87 g/cm³ for ABSCe10, reflecting the progressive addition of CeO₂. Gamma attenuation performance was evaluated using a gamma spectrometer equipped with a sodium iodide activated with thallium NaI(Tl) scintillation detector. Gamma-ray energies of 511 keV and 1274 keV from a 22Na source, 663 keV from a 137Cs source, and 1173 keV and 1332 keV from a 60Co source were selected, providing a comprehensive energy spectrum typical in medical imaging, industrial gamma radiography, sterilization, and nuclear applications. Each sample was irradiated multiple times, and the average counts were calculated to ensure statistical reliability. The linear attenuation coefficients (LAC) and mass attenuation coefficients (MAC) were then determined experimentally and compared to theoretical values obtained from the widely accepted NIST XCOM database and simulations performed using the Geant4 Monte Carlo toolkit. The results showed significant improvements in gamma shielding properties with increasing CeO₂ concentrations, especially notable at lower photon energies. At energies below 0.2 MeV, the presence of CeO₂ significantly increased the MAC values due to the dominance of the photoelectric absorption process, which is heavily dependent on atomic number (Z³–Z⁴). At intermediate energies (0.2–1 MeV), Compton scattering became dominant, and the MAC values gradually decreased with increasing photon energy. At higher energies (above 1 MeV), although MAC values decreased further, CeO₂ still maintained better shielding performance compared to pure borosilicate glass due to its higher electron density and atomic number. Detailed analyses of shielding parameters such as half-value layer (HVL), tenth-value layer (TVL), and mean free path (MFP) were conducted. The HVL and TVL represent the thickness of material required to reduce radiation intensity by half and by a factor of ten, respectively. Results indicated that higher CeO₂ concentrations considerably reduced both HVL and TVL values, suggesting thinner and thus lighter material can be effectively utilized for radiation protection. Specifically, the ABS-Ce10 glass exhibited the lowest HVL and TVL values, highlighting its superior performance in practical radiation shielding applications. Moreover, calculated values of the atomic cross-section (ACS), electronic cross-section (ECS), effective atomic number (Zeff), and effective electron density (Neff) were obtained and analyzed. Increasing CeO₂ content systematically enhanced these parameters, particularly evident in the low-energy region dominated by photoelectric interactions. The effective atomic number, an essential parameter reflecting a material's ability to attenuate radiation, demonstrated a strong positive correlation with CeO₂ content, further confirming the composite's enhanced shielding capability. The study also included comprehensive comparisons of experimental and theoretical data, validating the reliability and accuracy of both Geant4 simulations and NIST XCOM theoretical predictions. While minor discrepancies were observed at low photon energies, attributed mainly to variations in simulation physics models and inherent assumptions within the theoretical calculations, overall agreement was high. Experimental measurements consistently supported theoretical and simulation results, emphasizing the effectiveness of CeO₂-doped borosilicate glasses as a reliable radiation shielding material. A comparison of borosilicate glasses containing cerium oxide with various shielding materials reported in the literature, such as other rare-earth-doped glasses and high-Z metal oxides, revealed that ABS-Ce10 demonstrates competitive or superior shielding performance in certain energy regions, particularly at photon energies around 1 MeV and above. At 1 MeV gamma photon energy, ABSCe10 exhibited MAC values that outperformed several previously studied materials, including Gd-based glasses and other polymer-based shielding composites, underscoring its potential as a lightweight, cost-effective alternative to conventional shielding materials. Additionally, the structural integrity, mechanical strength, thermal stability, and environmental advantages of these borosilicate glasses contribute significantly to their practical applicability. Their relatively low density, recyclability, and ease of fabrication present a significant advantage, making these glasses suitable for a wide range of applications, including medical radiology rooms, nuclear facilities, portable shielding equipment, aerospace radiation protection, and safety applications in industrial environments. The research carried out in this thesis clearly demonstrates the potential of borosilicate glasses containing cerium oxide as novel and efficient gamma-ray shielding materials. In particular, the findings highlight that increasing the CeO₂ content within the borosilicate matrix significantly improves the shielding efficiency, especially in the lower energy photon range, where photoelectric absorption plays a dominant role. At concentrations up to 10% CeO₂, the glasses exhibit superior attenuation capabilities, enhanced structural stability, thermal resistance, and cost-effectiveness compared to conventional heavy-metal-based shielding materials, such as lead or tungsten alloys. Moreover, their relatively low density, recyclability, and environmental friendliness underline their suitability for diverse applications, spanning medical radiology, industrial safety, portable shielding devices, nuclear facilities, aerospace, and various radiation-intensive environments. By addressing these advantages, this study provides a clear pathway toward developing lightweight, sustainable, and highly effective gamma-ray shielding materials for both current and emerging applications. The comparative analysis of the performance of CeO₂-doped borosilicate glass (ABS-Ce10) against other materials, highlighting its significant potential as a gamma shielding material. ABS-Ce10 demonstrated superior mass attenuation coefficients (MAC) at key energies such as 1 MeV and 1.5 MeV, surpassing materials like BNCP-5, Gd-4, GN2, and BCZLM1, which have lower MAC values around 0.060 cm²/g. Although SiBBSZ1 showed a notably higher MAC, its lower density (2.27 g/cm³) limited its overall shielding effectiveness. ABS-Ce10 achieved a competitive balance of density (2.879 g/cm³) and attenuation performance, providing enhanced shielding efficiency within a smaller volume. Even though its density is slightly lower than S2 and GN2, ABS-Ce10 offers a well-balanced combination of properties, making it a strong candidate for gamma shielding applications. Recommendations for future research include increasing CeO₂ content above 10% to further explore the relationship between radiation shielding efficiency and mechanical strength, while considering economic and density implications. Detailed studies on the performance of ABS-CeO₂ composites at high-energy gamma photon levels (≥1 MeV) were suggested to improve their suitability for nuclear facilities and medical radiology. Additionally, long-term durability under environmental conditions should be assessed to better understand the material's economic and technical lifespan. Finally, combining ABS with other rare-earth elements or metal oxides could provide optimized materials tailored to specific applications.
Except where otherwise noted, this item's license is described as http://creativecommons.org/licenses/by/4.0/
