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This study presents a new approach towards the production of sol-gel silica-coated Bi2O3/Gd2O3 cement additives towards the improvement of early mechanical performance and radiation attenuation. Two types of silica coatings, which varied in synthesis method and morphology, were used to coat Bi2O3/Gd2O3 structures and evaluated as a cement filler in Portland cement pastes. Isothermal calorimetry studies and early strength evaluations confirmed that both proposed coating types can overcome retarded cement hydration process, attributed to Bi2O3 presence, resulting in improved one day compressive strength by 300% and 251% (depending on coating method) when compared to paste containing pristine Bi2O3 and Gd2O3 particles. Moreover, depending on the type of chosen coating type, various rheological performances of cement pastes can be achieved. Thanks to the proposed combination of materials, both gamma-rays and slow neutron attenuation in cement pastes can be simultaneously improved. The introduction of silica coating resulted in an increment of the gamma-ray and neutron shielding thanks to the increased probability of radiation interaction. Along with the positive early age effects of the synthesized structures, the 28 day mechanical performance of cement pastes was not suppressed, and was found to be comparable to that of the control specimen. As an outcome, silica-coated structures can be successfully used in radiation-shielding cement-based composites, e.g. with demanding early age performances. [ABSTRACT FROM AUTHOR]

In this study, graphene nanopowder was used as an impurity material in lead borovanadate glass that contained fixed amounts of Ca2+ and Na+ cations. The rapid quenching method was adopted to prepare five samples that differ in their graphene content. X-ray diffraction patterns proved the amorphous nature of all prepared samples, where the patterns showed two broad humps for the graphene-free sample and three broad humps for each graphene-doped sample. Fourier transform infrared (FTIR) spectra showed that the glass networks of the prepared samples are composed of multi-structural units (BO3, BO4, VO4, and PbO4). FTIR spectral analysis showed an increase in the concentration of VO2 isolated group as the graphene content was increased, which was corroborated by the evident increase in the electron spin resonance absorption spectra. UV–Vis spectra revealed an increase in the value of the optical absorbance (A) as graphene content increased, with five different absorption overlapped detectable peaks. The deconvolution of the A-λ curve showed five overlapped peaks located at 210, 270, 310, and 485 nm in the case of the graphene-free sample. But in the case of graphene-doped samples, the peak center at 485 nm moved to 460 nm. The hydrogenic exciton model was used to simulate the absorption coefficient spectra of the studied samples. The extracted values of the absorption strength parameter Co reveals the capacity of the studied samples to absorb electromagnetic energy, and it also shows that absorption at λ = 310 nm is dominant for all samples. On the other hand, the average value of Co increased with the increase in graphene nanopowder content, which was assigned to an increase in the glass surface area. The consistency in the values of both the exciton binding energy R and continuum line width гc is an indication that the graphene nanoparticles settled into interstitial vacancies. All of these findings suggest that the investigated samples can be used as active components in electronic devices. [ABSTRACT FROM AUTHOR]

This work examines the influence of iron oxide nanoparticles (Fe3O4 NPs) on neutron and gamma-ray radiation shielding characteristics of Portland cement paste. Experimental evaluations were supplemented with theoretical studies using NXCom program. Portland cement pastes with 5, 10, 15, 20, and 30 wt% of nanomagnetite cement replacement were produced. Moreover, rheological, early strength development, compressive strength, and mercury intrusion porosimetry (MIP) tests were performed. The results showed that increasing the amount of Fe3O4 NPs in a mix leads to a gradual increment in measured viscosity and yield stress. High nano-Fe3O4 content substantially impeded the early strength development process and led to a decrement in the 7- and 28-day compressive strength of cement paste. The MIP studies exhibited a gradual increment in total porosity, and average pore volume, as nano-Fe3O4 content was increased. All the macroscopic cross-sections of slow, fast and thermal neutrons constantly increased as a result of the addition of magnetite nanoparticles, with their variations being markedly linear. Similarly, gamma attenuation test results indicated that the addition of Fe3O4 powder enhances the shielding capability of paste in the energy range of interest (0.08–2.614 MeV). In conclusion, Fe3O4 nanoparticles can be successfully used in producing lead-free cementitious composites with improved gamma-ray and neutron shielding properties. However, certain drawbacks related to an increment in matrix porosity and thus a decrement in mechanical performance should be taken into account. [ABSTRACT FROM AUTHOR]

In this study, four solid samples of borosilicate glass containing BaTiO3 were prepared using the standard melt quenching technique. The amorphous nature of the produced samples was confirmed using x-ray diffraction (XRD), where the XRD patterns showed that all the prepared samples possessed a high degree of disordered internal structure. The UV–Vis spectra demonstrated that when BaTiO3 content increased, the sample transmittance increased and their absorbance decreased in the visible light region, and vice versa in the UV region. For all samples, the refractive index value was constant at 2.9 in the UV range, while falling from 2.2 to 1.7 in the visible range. As the BaTiO3 content rose, the optical bandgap value underwent a redshift. The n(R) relation was updated, and was then compared with the previously published relations. [ABSTRACT FROM AUTHOR]

In this work, a new approach has been developed to correlate the relation between both the optical and electrical conductivities of some cerium sodium borate glasses that have been prepared using the traditional fast quenching technique. The amorphous nature has been proven for all studied samples based on their X-ray diffraction patterns. Lorentz–Drude and Cole–Cole models have been used to fit both the optical conductivity and the optical dielectric parameters, respectively. The extraction of the terahertz parameters was performed using UV–Vis spectra while the calculated electrical conductivity has been fitted using different theoretical models. The correlated barrier hopping CBH model is considered as the applicable conduction mechanism for the studied cerium sodium borate glasses. The increase in CeO2 content caused an increase in the values of the optical transmittance, the plasmon frequency, the dielectric activation energy, barrier height, the exponent factor, and the characteristic relaxation time. On the other hand, the increase in CeO2 content caused a decrease in the values of the optical reflectance, the linear refractive index, the optical dielectric constant, and electrical and optical conductivities. [ABSTRACT FROM AUTHOR]

In this study, glass samples of composition 20PbO-20CaO-20Sand-(40 − x)B2O3-xCeO2, where x = 0, 2.5, 5, 7.5, and 10 in wt.% and sand = SiO2 (90.4%) + CaO (2.8%) + ZrO2 (2.3%) + Fe2O3 (2.1%), were fabricated via the ordinary melt quenching technique. The thermal and optical properties of the glasses were experimentally investigated using differential scanning calorimetry (DSC) analysis, which is measured as a function of temperature based on the difference in the amount of heat needed to raise the temperature of a sample and reference. All glasses were found to be thermally stable up to 550°C. The glass transition temperature (Tg) varied from 211°C to 219°C, crystallization temperature (Tc) varied from 303°C to 310°C, and melting point (Tm) was 577°C. The values of the indirect optical energy band gaps (EOptical, Indirect) reduced from 2.63 eV to 2.28 eV, while the direct gaps (EOptical, Direct) reduced from 5.07 eV to 4.17 eV. Urbach's energy (EU) was changed from 0.42 eV to 0.46 eV. The dielectric constant behaved similarly to the refractive index and absorption coefficient of the proposed glasses. The refractive index data were analyzed to obtain important optical information and the corresponding derivative electrical parameters, namely, the oscillator energy, dispersion energy, dielectric constant at high frequency, the dielectric loss, and the energy-loss functions. There was a remarkable increase in the optical conductivity (σopt) with increasing CeO2 content, with peaks appearing in all samples doped by CeO2 and reaching a peak maxima of about 2.72–3.10 eV. Volume energy loss (VELF) and surface energy loss (SELF) functions were increased with increasing CeO2 content, with a characteristic peak at around 3.47 eV for all proposed samples. [ABSTRACT FROM AUTHOR]

Sodium borate glass doped with cerium oxide, 0–10 wt%, has been prepared based on the quenching method from the melting point. The XRD, DSC, FTIR, and UV–Vis are used to study the structure, thermal, optical properties and shielding attenuation of the studied materials. XRD analysis showed that the as-prepared samples are amorphous in nature. Increased CeO2 content in the glassy matrix led to an increase in the glass stability, the dielectric constant value, as well as the optical transparency. The measured shielding parameters of the present study revealed that the glass system containing 10 wt% of CeO2 exhibits the better photon shielding performance than the glass of 0 wt% CeO2. Cerium-rich glass showed the highest resistance for both gamma-ray and the fast neutrons among all the present samples. The removal cross-sections varied from between 89 × 10–3 cm−1, for the cerium-free sample, and 97 × 10–3 cm−1 for cerium-rich sample. Such observation may nominated Ce-rich glass to be used in some shielding and attenuation applications, especially for gamma-ray and fast neutrons applications. [ABSTRACT FROM AUTHOR]

Cadmium lead-borate reinforced with Nd3+ ions glass systems in the composition (60 − x) B2O3+20CdO+20PbO+xNd2O3, where x = (0, 1, 2, 3, 4, and 5 wt%) were prepared using the melt and quench method. The fabricated glasses were coded as BCPNdx. The direct effect of Nd3+ ions on fabrication, physical, structure, and optical characteristics of the fabricated glasses has been investigated. XRD patterns confirmed that all fabricated glasses were in amorphous state. Density was increased from 5.034 g/cm3 for BCPNd0 (with free Nd3+ ions) to 5.282 g/cm3 for BCPNd5 (with 5 wt% of Nd2O3). Both indirect and direct optical band gaps (Eg) were found to increase from (1.52 to 2.57 eV) and (1.95 to 3.19 eV), respectively, with the increase in the content of Nd2O3. Urbach energy ( E U ) values of the synthesized glass samples decreased by the increase in Nd2O3 content and changed inversely with (Eg) of the samples. Values of the oscillator energy (Eo) of the fabricated glasses varied from 2.58 to 6.34 eV, while the dispersion energy (Ed) varied from 3.34 to 8.41 eV. Real part of dielectric values decreases with the increase in the wavelength up to 350 nm, and then stays almost constant, with minor differences between different samples. Both bulk energy loss and surface energy loss increase with the increase in Nd3+ content corresponding to an increase of the bulk and surface energy loss. The amorphous nature of the glasses can be identified from the broad peaks of FTIR absorbance spectra. [ABSTRACT FROM AUTHOR]