Doğal kayaçlardan radyasyon kalkanlama özelliğine sahip camların geliştirilmesi
Development of Radiation Shielding Glasses from Natural Rocks
- Tez No: 917614
- Danışmanlar: PROF. DR. ŞENOL YILMAZ
- Tez Türü: Doktora
- Konular: Fizik ve Fizik Mühendisliği, Metalurji Mühendisliği, Nükleer Mühendislik, Physics and Physics Engineering, Metallurgical Engineering, Nuclear Engineering
- Anahtar Kelimeler: Belirtilmemiş.
- Yıl: 2025
- Dil: Türkçe
- Üniversite: Sakarya Üniversitesi
- Enstitü: Fen Bilimleri Enstitüsü
- Ana Bilim Dalı: Metalurji ve Malzeme Mühendisliği Ana Bilim Dalı
- Bilim Dalı: Belirtilmemiş.
- Sayfa Sayısı: 207
Özet
Bu çalışmada, doğal volkanik kayaç bazaltlardan elde edilen bazalt camının radyasyon kalkanlama özelliği incelenmiştir. Bazalt camları katkısız ve ağırlıkça %10, 20, 30 oranında La2O3, BaCO3, TeO2 ve WO3 katkısı yapılarak cam harmanları hazırlanmıştır. Homojen karışım elde edildikten sonra ergitme ve döküm süreçleri kullanılarak cam üretimi gerçekleştirilmiştir. Cam numunelerin karakterizasyonu ve radyasyon zırh kabiliyetinin ölçümü amacıyla birtakım testler ve analizler yapılmıştır. Bu testler sonucunda cam numunelere ait fiziksel, yapısal, ısıl, mekanik ve radyasyon soğurma parametreleri ölçülmüştür. Fiziksel testlerde yoğunluk değerinin 2.729 g/cm3 ile 3.305 g/cm3 aralığında değiştiği belirlenmiştir. Bazalt bileşimine yapılan katkı oranının artmasıyla yoğunluk değerleri de artış göstermiştir. %20 ve %30 WO3 katkılı cam numunelerde görülen kısmi kristalizasyon dışında bütün camların tamamen amorf yapıda oldukları tespit edilmiştir. Mekanik testler sonucunda La2O3 katkılı camlarda mikrosertlik değeri artış sergilerken diğer camlarda mikro sertlik değeri katkı oranındaki artışla düşüş eğilimi göstermiştir. Isıl özelliklerin tespiti için yapılan analizler sonucunda farklı katkı maddelerinde farklı sonuçlar elde edilmiştir. BaCO3 ve TeO2 katkılı camlarda Tg sıcaklıklarında düşüş gözlemlenirken La2O3 katkılı camlarda artış görülmüştür. Cam numunelerin radyasyon parametrelerinin tayini amacıyla deneysel olarak uygulanan gama-ışını spektroskopi analizleri sonucunda lineer zayıflatma katsayıları, deneysel kütle zayıflatma katsayıları, yarı değer kalınlık parametreleri, ortalama serbest yol değerleri elde edilirken, EpiXS programı vasıtasıyla teorik kütle zayıflatma katsayıları, enerji emilim birikim ve maruziyet birikim faktörleri de elde edilmiştir. Bazalt bileşimine tez çalışması kapsamında yapılan La2O3, BaCO3, TeO2 ve WO3 katkılarının bazalt camının lineer ve kütle zayıflatma katsayılarını arttırırken, yarı değer kalınlıklarını ve ortalama serbest yol değerlerini düşürdüğü görülmüştür. Birikim faktörü parametlerinde ise cam numunelerin düşük enerji bölgesinde daha az saçılma yaptığı belirlenmiştir. Bütün sonuçlar ele alınarak değerlendirme yapıldığında tez çalışması kapsamında yapılan katkılandırmaların bazalt camının radyasyon zırh kabiliyetini arttırdığı tespit edilmiştir. Ayrıca yapılan bu katkılar içinde en çok etkiyi sırasıyla WO3> La2O3>BaCO3> TeO2 katkılı camlar sağlamıştır. Elde edilen sonuçlara dayanarak bazalt camının farklı katkılandırmalar yapılarak radyasyon zırh malzemesi uygulamalarında kurşun içermeyen alternatif bir malzeme olarak kullanılabilirliği gösterilmiştir.
Özet (Çeviri)
Radiation is defined as the emission of electromagnetic waves or the flow of radioactive particles. With the rapid advancements in technology, radiation is encountered or utilized across numerous fields, leading to dual impacts on human health, encompassing both positive and negative effects. It is essential to highlight that radiation exposure is not exclusively from technological sources; natural radiation also poses a potential threat to humans. While an intuitive approach to radiation protection might suggest eliminating the radiation source, this is often not a feasible solution due to the widespread and essential applications of radiation in areas such as medical treatments, material analysis, nuclear power, and others. Consequently, instead of focusing on the complete elimination of radiation, efforts are directed toward methods of protection. There are three basic strategies for radiation protection: time, distance, and shielding. Minimizing the time duration of radiation exposure reduces the extent of exposure and its harmful effects. Maintaining a greater distance from the radiation source lowers the radiation dose received. The third method, shielding, involves the placement of a barrier to absorb radiation energy, preventing its transmission to humans. The materials used for shielding depend on the type of radiation. For example, a sheet of paper is effective against alpha radiation, aluminum shields beta radiation, lead is used for gamma rays and x-rays, and concrete is employed for neutron shielding. Typically, materials possessing high atomic numbers and high densities, such as lead, concrete, and steel, have great application for radiation protection. However, these materials have limitations, thus many researchers have been conducting reseach on alternative shielding materials. Among these alternative materials, glass systems, such as borate, germanate, silicate, phosphate, and tellurite glasses, as well as their waste glass derivatives, have gained attention due to their promising shielding properties and their role in nuclear waste management. Research efforts continue to enhance the radiation shielding effectiveness of these glass systems through the incorporation of various additives. The radiation shielding parameters of basalt glass obtained from natural volcanic basalt rocks were investigated. Glass batches were prepared using pure basalt glass and with 10%, 20% and 30% (by weight) La2O3, BaCO3, TeO2, and WO3 additions. The powders were weighed precisely, combined in a pot, and ground and mixed for 1 hour using a ball mill. After achieving a homogeneous mixture, glass production was carried out through melting and casting processes. The glasses were heated with 5°C per minute rate until reaching 1500°C and they were held at that temperature for 2 hours to melt. Then they were poured into alumina crucibles. To prevent the glass from cracking due to thermal stress after casting, glasses were annealed 1 hour at 600°C. The samples were then cooedl in the furnace environment. In addition to measurements conducted to determine the radiation shielding capabilities of doped and undoped basalt glasses, mechanical and characterization tests of the glasses were also performed. Through these tests, physical, structural, thermal, mechanical, and radiation absorption parameters of the glass samples were measured. In the physical tests, density measurements were carried out using Archimedes' principle. The unmodified basalt glass exhibited the lowest density value at 2.729 g/cm³, whereas the basalt glass with 30% La2O3 additive had the highest density value, measured at 3.305 g/cm³. An increase in the additive ratio in the basalt composition led to an increase in density values. It was observed that all additives increased the density of basalt glass. Theoretical molar volumes of the unmodified basalt glass and basalt glasses with La2O3, BaCO3, TeO2, and WO3 additives were calculated and found to increase with the rising additive ratios. X-ray diffraction (XRD) analysis was performed in the 0–90° range to obtain information about the crystalline structure of the glasses. Except for partial crystallization observed in the glass samples containing 20% and 30% WO3 additives, all the glasses were determined to be completely amorphous. Vickers hardness tester was applied to determine the mechanical properties of undoped and doped basalt glasses. The resin embedding process was applied to the samples and their surfaces were subjected to sanding and polishing to prepare them for measurement. For verification, each sample underwent 10 repeated measurements. The microhardness measurements revealed an increase in microhardness values for La2O3-doped glasses, whereas the microhardness values of other glasses tended to decrease with increasing doping ratios. The elastic constants of the glasses were theoretically calculated using the Makishima–Mackenzie model. In the Makishima–Mackenzie model, the elastic constants are calculated by using packing density (Vt), dissociation energy per unit volume (Gt) and chemical composition values. These elastic constants include Young's modulus (Y), bulk modulus (K), shear modulus (S), longitudinal modulus (L), and Poisson's ratio (σ). The addition of La2O3generally did not cause significant changes in the elastic properties of basalt glass, leading only to slight increases in Y, K, S, and L constants. However, in basalt glasses doped with BaCO3, TeO2, and WO3, the elastic constants and Poisson's ratio decreased as the doping ratio increased. Differential Thermal Analysis (DTA) was performed starting from room temperature, with the temperature increased up to 1100°C at a rate of 10°C per minute. The glass transition temperature (Tg) of the undoped basalt glass was determined to be 696°C, and the Tc (crystallization temperature) was found to be 890°C. The results from the DTA analyses varied with different additives. While a decrease in Tg temperatures was observed in BaCO3- and TeO2-doped glasses, an increase was noted in La2O3-doped glasses. For WO3-doped basalt glasses, the Tg temperature for the sample with 10% doping was measured at 687°C, but Tg temperatures could not be identified in the other compositions from the graphs. Gamma-ray spectroscopy analyses were experimentally conducted to evaluate the radiation parameters of the glass samples. In gamma-ray spectroscopy, a beam is directed at the material, and the decrease in beam intensity after interacting with the material is measured. The variations in the beam's energy are utilized, through different equations, to assess the material's radiation shielding effectiveness. Parameters including the linear and mass attenuation coefficient, mean free path (MFP) and half-value layer (HVL) were determined, following the gamma-ray experiments. Moreover, theoretical energy absorption buildup and exposure buildup factors were obtained by the EpiXS program. The linear attenuation coefficient quantifies the probability of a photon interacting per unit path length, encompassing the combined probabilities of the photoelectric effect, Compton scattering, and pair production. The mass attenuation coefficient is obtained by dividing the linear attenuation coefficient by the material's density. The half-value layer refers to the material thickness necessary to reduce the photon energy by half, whereas the mean free path represents the average distance a photon traverses within the material without undergoing interaction with its atoms. These parameters cannot be used independently to evaluate a radiation shielding material and must be assessed collectively. Moreover, designing a radiation shielding material requires consideration of not only these parameters but also factors such as the number of people in the environment, the number of equipment, exposure durations, and other influencing factors. As part of the thesis study, the addition of La2O3 to the basalt composition increased the linear and mass attenuation coefficients of the basalt glass. Furthermore, with the increasing lanthanum oxide content, the half-value layer (HVL) and mean free path (MFP) values of the basalt glass decreased. The inclusion of high-density and high-atomic-number lanthanum atoms into the basalt composition made the glass denser. Gamma rays directed at the basalt glass interacted more frequently and lost their energy over shorter distances. This indicates that lanthanum oxide addition positively affected the radiation parameters of the basalt glass. In La2O3-doped basalt glasses, a decrease in linear and mass attenuation coefficients was observed with increasing energy. This phenomenon, as noted in the literature, is primarily due to the increased penetration power of photons at higher energies. The radiation shielding capability of La2O3-doped glasses diminished as the energy reached higher levels. The energy absorption buildup factor and exposure buildup factor parameters were found to be quite low in low-energy regions but increased as the energy moved toward the medium-energy region. However, as the energy continued to rise into the high-energy region, this increase diminished and showed a decreasing trend. In the low-energy region, the photoelectric absorption mechanism was dominant, while in the high-energy region, the pair production mechanism became effective, resulting in photon energy absorption by the glass material and keeping these parameters low. In the medium-energy region, the Compton scattering mechanism became dominant, leading to secondary scattering and an increase in these parameters. Additionally, these parameters showed a decreasing trend with increasing lanthanum oxide content. When the radiation parameters were evaluated collectively, it was concluded that lanthanum oxide-doped glasses would be more effective in low-energy regions. The linear coefficients and mass attenuation coefficients of BaCO3-doped basalt glasses increased with higher doping levels, while their half-value layer (HVL) and mean free path (MFP) values decreased inversely with the doping ratio. Increasing the amount of BaCO3 in the basalt composition enhanced the radiation shielding capability of basalt glass. The inclusion of barium atoms, which have high density and atomic number, allowed photons directed at the glass to interact more frequently over shorter distances, thereby absorbing their energy. Additionally, it enabled photons of the same energy to be shielded with thinner glass materials. As with lanthanum oxide-doped basalt glasses, the buildup factors of BaCO3-doped basalt glasses were low in both low- and high-energy regions but higher in the medium-energy region. This indicates that secondary scattering in the medium-energy region caused an increase in the buildup factors of BaCO3-doped basalt glasses. Similarly, TeO2 and WO3 additives increased the linear and mass attenuation coefficients of basalt glass while reducing the HVL and MFP values. For buildup factors, it was determined that glass samples exhibited less scattering in the low-energy region. After individually evaluating the effects of each additive on the radiation shielding capabilities of basalt glass, the glass with the highest performance for each additive was selected. In all additives, the highest values were achieved in basalt glasses with 30% doping. The mass attenuation coefficient, linear attenuation coefficient, HVL, MFP, and exposure buildup factors of these glasses were compared. Among the undoped and 30%-doped basalt glasses, WO3-doped glass had the highest linear and mass attenuation coefficients and the lowest HVL and MFP values. Across all energy regions, WO3-doped glass exhibited the lowest buildup factor values. When a comprehensive evaluation of all results is conducted, it was concluded that the additives studied in this thesis significantly enhanced the radiation shielding capabilities of basalt glass. Among the additives, WO3 had the most pronounced effect, followed by La2O3, BaCO3, and TeO2. These findings demonstrate the potential of basalt glass, with various additives, to serve as a lead-free alternative material for radiation shielding applications.
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