Papers by nehal elkhoshkhany
Chalcogenide Letters
The primary application of radiation shielding is to safeguard against the harmful effects of rad... more The primary application of radiation shielding is to safeguard against the harmful effects of radiation. This study investigated the addition of thulium oxide (Tm2O3) to a glass system with a composition of 75 TeO2–5 Li2O–10 ZnO– (10-x)Nb2O5. Multiple radiationshielding parameters, including linear and mass attenuation coefficients, half-value layers, mean free paths, atomic and electronic cross-sections, effective atomic numbers, and effective electron density, were evaluated. The study compared the half-value layer values of the new composite to those of well-known radiation-shielding materials, which include ordinary concrete and commercial glass. The addition of Tm2O3 to glass systems efficiently increases the atomic and electronic cross-sections. While all samples had the greatest linear and attenuation coefficients of 201.5–232.84 cm2 /g at 15 keV, the denser glass had the highest mass attenuation coefficient of 42.80 cm2 /g. The shielding effectiveness depends on the phases s...
Journal of Alloys and Compounds, 2017
Ceramics International, 2018
The thermal characteristics of the quaternary TeO 2-ZnO-Na 2 O-Er 2 O 3 glass system as a functio... more The thermal characteristics of the quaternary TeO 2-ZnO-Na 2 O-Er 2 O 3 glass system as a function of rising Er 2 O 3 mol% have been studied from the kinetic point of view. Differential scanning calorimetry technique under non-isochronal conditions at various heating rates has been used to define the characteristic temperatures of the glasses (i.e glass transition, crystallization) in addition to the glass stability parameters. The activation energies required for both the glass transition and amorphous to crystalline transformation have been computed by different methods. The mode of the glass crystallization has been determined in terms of the Avrami kinetic constant to identify the crystallization succession. Quantitative analysis of the thermal characteristics and kinetic parameters of the glass were achieved in terms of cross-linking density, number of bonds, and the bond stretching force.
Results in Physics, 2019
This article aims to study the detailed thermal behavior, characterization of kinetics and the lu... more This article aims to study the detailed thermal behavior, characterization of kinetics and the luminescence properties of TeO 2-Li 2 O-ZnO-Nb 2 O 5-Er 2 O 3 glass system as a function of increasing Er 2 O 3 (mol%). Kinetic parameters of the glass series have been studied by the data obtained from the differential scanning calorimetry (DSC) under non-isochronal circumstances at heating rates (β) 10, 15, 20 and 25 K min −1 using the continuousheating technique. The glass thermal stability (ΔT), the thermal relaxation resistance (ΔS) and the glass stability parameter (K SP) have been calculated to state the applicability of using the glass in specific fields and applications. Activation energies of both the glass transition (E g) and crystallization (E c) processes were determined from the shift of the transition (Tg) and crystallization (Tc) temperatures with the different heating rates using Kissinger's and Ozawa's techniques. The kinetic Avrami number (order of the crystallization reaction) (n) was also calculated to define the mechanism of the crystallization process. Quantitative interpretation of the kinetic parameters (the relation between thermal and structural properties with changing the chemical composition) also has been provided. The luminescence properties showed that the glass with the least concentration of Er 2 O 3 (0.5 mol %) exhibited the higher emission intensity which might be a suitable candidate for the green laser applications.
Ceramics International, 2017
In continuation of our earlier work on (the mechanical and thermal properties of TeO 2-Bi 2 O 3-V... more In continuation of our earlier work on (the mechanical and thermal properties of TeO 2-Bi 2 O 3-V 2 O 5-Na 2 O-TiO 2 glass system), in this study, we have investigated the kinetic parameters of this system as a function of increasing TiO 2 mol% by using differential scanning calorimetry (DSC) data under non-isothermal (isochronal) conditions. The thermodynamic fragility (F) and the glass forming tendency (), () factors of the present glass have been evaluated to determine the relationship between the change in the structure and the thermal stability of the glass. The activation energies of both glass transition (E g) and crystallization (E c) processes have been evaluated by the methods of Kissinger and Ozawa by the data obtained from (DSC) at heating rates 2 (β) 10, 15, 20 and 25 K/min. The quantitative interpretation of these kinetic parameters has been carried out by coupling with the previous estimated elastic moduli. The kinetic Avrami coefficient (n) was also calculated by several estimation methods to determine and confirm the mechanism of the crystallization process.
Journal of Materials Science, 2009
... The compressibility model has been used to find the difference volume Vd due to the exchange ... more ... The compressibility model has been used to find the difference volume Vd due to the exchange of one formula unit between Te and both of La and V in the binary glass system and the mean volume VA per formula unit in the present binary glass in order to check whether or not ...
Ceramics International, 2017
Journal of Materials Science: Materials in Electronics, 2021
Novel series of fluorotellurite lithium niobate glasses with compositions TeO2–LiNbO3–BaO–BaF2–La... more Novel series of fluorotellurite lithium niobate glasses with compositions TeO2–LiNbO3–BaO–BaF2–La2O3 coded as Pr3, Pr4, Pr5, Pr6, and Pr7 were fabricated using the traditional process of quenching the melt. The density of the fabricated glasses was varied from 5.1689 to 5.4088 g/cm3, while optical packing density (o.p.d) was taken values from 50.85 to 64.4 g atom l−1. The thermal features glasses were determined by using (DSC), while their optical properties were determined in ultraviolet–visible–near-IR (UV–Vis–NIR) spectral region. Results revealed that the glass transition temperature (Tg) has the lowest value for Pr6 glass sample otherwise the highest value in Pr3 sample. The thermal stability (ΔT) was equal to 133, 149,154,127, and 153 °C for Pr3, Pr4, Pr5. Pr6, and Pr7 glass samples, respectively. The optical energy gap (Eopt) varied from 2.81 to 3.12 eV, while the Sellmeier gap energy (ES) changed from 6.6 to 8.55 eV. Also, gamma-ray shielding competences of the fabricated glasses were evaluated in terms of their mass and linear attenuation coefficients (MAC, LAC), half-value layer (HVL), and mean free path (MFP). The obtained values showed that LAC was in the order of Pr7 > Pr6 > Pr3 > P4 > Pr5, while HVL arranged in the order of Pr7 < Pr6 < Pr3 < Pr4 < Pr5. Therefore, Pr7 glass has the highest LAC and the lowest HVL which assured its best shielding capacity among all the proposed glasses.
Results in Physics, 2021
The present manuscript reports the synthesis of tungsten-incorporated molybdenum disulphide terna... more The present manuscript reports the synthesis of tungsten-incorporated molybdenum disulphide ternary compounds in particle form at the nanoscale using existing solid state reactions, followed by ultrasonication and a density functional theory (DFT) investigation of the compound system. The effect of W in the W-inserted MoS 2 ternary compound system is the subject of current research. A comparative study shows enhanced photoluminescence (PL) at room temperature in the as-synthesized transition metal dichalcogenide (TMD) ternary compound. The compositional and structural characterization studies of the materials are performed using XRD, SEM, EDX, TEM and Raman spectroscopy. We have observed that a combination of W and S leads to better crystallinity than the combination of Mo and S in the compound system. The high band gap (BG) energy also confirms the nanoscale dimension of the material system which may be attributed to the formation of excitonic states from spin splitting and band nesting effects. A theoretical investigation of the effect of W in the MoS 2 system using DFT also reveals that insertion of W leads the system toward a direct BG semiconductor (SC). Multiple BGs of the material in the visible light range as found by UV-Visible (UV-Vis) spectroscopy, suggest applicability of these materials in luminescence devices and photocatalytic activity.
Journal of Non-Crystalline Solids, 2020
In mineral exploration, pressure is growing to develop innovative technologies and methods with a... more In mineral exploration, pressure is growing to develop innovative technologies and methods with a lower impact on the social and physical environment. To assess the performance and impact of these technologies and methods, test sites are required. Embedded in the literature on sustainable development, this paper explores how social and environmental measures can be implemented in the design of test sites and what industry stake can learn from sustainable test sites. Through qualitative research, two value networks were developed, one for a sustainable test site approach and another for the existing business practice in mineral exploration. Respondents include public sector officials as well as experts in the social, environmental, business, geoscience, and industry fields. The analysis identifies key drivers for the development of socially and environmentally accepted test sites, thus drawing up actionable points for the mineral exploration industry to increase sustainability. The findings of this paper suggest that the integration of experts and partners from social, as well as environmental, sciences drives sustainability at test sites. For industry application, this results in the need to adapt the activities performed, align resource use with sustainability indicators, and also reconfigure the network of partners towards more socially and environmentally oriented business practices.
Journal of Materials Research and Technology, 2020
Oxy-Fluoro Boro Tellurite glasses with formula (85-x) TeO 2-xB 2 O 3-5Bi 2 O 3-5BaO-5LiF, where x... more Oxy-Fluoro Boro Tellurite glasses with formula (85-x) TeO 2-xB 2 O 3-5Bi 2 O 3-5BaO-5LiF, where x = 0, 10, 20, 30, 40, 50 and 60 mol% were prepared by melt-quenching method. All the prepared glasses were extensively studied by several apparatus such as, X-ray diffraction (XRD), Fourier transform infrared spectroscopy, UV-Vis-NIR spectroscopy and differential scanning calorimetric (DSC). The optical energy gap and refractive index of the prepared glasses were estimated by UV-Vis spectra. Moreover, the thermal stability, transition activation energy, crystallization activation energy and Avrami parameter of prepared glasses were determined. The optical and thermal properties of the prepared glasses were found to be attributed to the concentrations of phase TeO 4 and BO 4 units in the glass network. From these results, Oxy-Fluoro Boro Tellurite glass could be used in the optical application such as fiber laser with doping rare earth.
Clean Technologies and Environmental Policy, 2020
Concrete is the basic building material in the world, and cement is the main material used in the... more Concrete is the basic building material in the world, and cement is the main material used in the production of concrete. However, there is an urgent need to reduce the consumption of cement, where cement production leads to 5-8% of global emissions of carbon dioxide. Geopolymer concrete is an innovative building material produced by alkaline activation of pozzolanic materials such as fly ash, granulated blast furnace slag, and kaolin clay. Geopolymers are widely used in the production of geopolymer concrete due to their ability to reduce carbon dioxide emissions and reduce high energy consumption. During the present study, the environmental impact of two strength grades (30 MPa and 40 MPa) of metakaolin geopolymer concrete (GPC) was evaluated to study its applicability in the construction sector. The kaolin clay extracted from the Aswan quarries was activated by a mixture of sodium hydroxide and sodium silicate solution. To introduce geopolymer concrete in the Egyptian industry sector, its environmental performance, together with its technical performance, should be competitive to the cement concrete used mainly for the time being. The cost of this new concrete system should also be evaluated. The environmental impact of GPC was evaluated and compared with cement concrete using life cycle assessment analysis and IMPACT 2002+ methodology. The cost of production was calculated for 1 m 3 of geopolymer concrete and conventional cement concrete. Metakaolin geopolymer concrete achieved a high compressive strength of ~ 56 MPa, splitting tensile strength of 24 MPa, and modulus of elasticity of 8.5 MPa. The corrosion inhibition of metakaolin geopolymer concrete was ~ 80% better than that of conventional cement concrete. Geopolymer concrete achieved a reduction in global warming potential by 61% and improved the human health category by 9.4%. However, due to the heavy burdens of sodium silicate, the geopolymer concrete negatively affected the quality of the ecosystem by 68% and showed a slightly higher impact than cement concrete on the resource damage category for low strength grade of 30 MPa. The high cost of the basic ingredients of the geopolymer resulted in a high production cost of geopolymer concrete (~ 92 US$) that was three times that of cement concrete (~ 31 US$). Based on the environmental results, geopolymer concrete based on locally available metakaolin clay can be applied in the construction sector as a green alternative material for cement concrete.
Materials Chemistry and Physics, 2019
Synthesis and characterization of quaternary erbium tellurite glass within the molar percentages ... more Synthesis and characterization of quaternary erbium tellurite glass within the molar percentages of (75-x) TeO 2-20ZnO-5Na 2 O-xEr 2 O 3 where (0 ≤ x ≤ 2.5) were carried out. The optical properties were determined by recording the UV-Vis spectra in the range 200-800 nm which exhibited increasing the band gap with increasing Er 2 O 3. The thermal characteristics of the glass were determined and showed higher thermal stability of the system suggesting its applicability for fiber drawing. The heat treatment was performed for the samples (0.5 and 2.5 mol %) of Er 2 O 3 at different temperatures and times
Results in Physics, 2019
The prepared glass samples within the composition (85-x) TeO 2-xB 2 O 3-5Bi 2 O 3-5SrCl 2-5LiF (T... more The prepared glass samples within the composition (85-x) TeO 2-xB 2 O 3-5Bi 2 O 3-5SrCl 2-5LiF (TBBSL) with x = 0, 10, 20, 30, 40, 50 and 60 mol% were synthesized. The X-ray diffraction patterns (XRD) showed the amorphous nature of the system. The density (ρ), molar volume (v m) and oxygen packing density (OPD) have been measured and calculated. The Fourier Transform Infrared (FTIR) of TBBSL glasses showed the presence of TeO 3 , TeO 4 , BO 3 , BO 4 , LiF, SrO and BiO 6. Also, FTIR spectra identified that the substitution of B 2 O 3 with TeO 2 in glass system led to convert the TeO 4 to TeO 3 and the formation of bridging structure Te-O-B with increasing the B 2 O 3 mol%, consequently the BO 4 units convert to BO 3 and so the number of non-bridging oxygen (NBO) increases. The optical band gaps (E opt), the Urbach energy (ΔE) and refractive index (n) have been calculated from optical absorption spectra. Thermal characterization was determined by using Differential Scanning Calorimetry (DSC) at different heating rates 10, 15, 20, 25°C/min. The prepared glasses showed high thermal stability. High reflective index and higher thermal stability made the synthesized glass system is a suitable candidate for the large bulk glass and optical fiber production.
Journal of Materials Science: Materials in Electronics, 2019
By melt quenching technique, a series of transparent bulk glasses with compositions (75TeO 2-5Li ... more By melt quenching technique, a series of transparent bulk glasses with compositions (75TeO 2-5Li 2 O-10ZnO-(10-S) Nb 2 O 5-(S) Yb 2 O 3) have been obtained, where S = 0.0, 0.5, 1, 1.5, 2, 2.5 mol%. For the prepared glass samples, physical properties such as density, molar volume, and oxygen packing density were studied. Spectroscopic parameters such as gain, absorption cross-section, and emission cross-section were measured. Differential scanning calorimetry curves indicated that the prepared glass compositions have a good stability factor. At different wavelengths, Urbach energy, optical band gap, and refractive index were obtained. Effective functional groups were detected by applying Raman and FT-IR spectroscopies. This work showed that the prepared glasses are promising candidates for different optical applications and amplifiers including solid state lasers, sensors, data storage, and optical switches.
Journal of Non-Crystalline Solids, 2018
Quinary tellurite glass system in the percentages of 75TeO 2-5Li 2 O-10ZnO-(10-x) Nb 2 O 5-xEr 2 ... more Quinary tellurite glass system in the percentages of 75TeO 2-5Li 2 O-10ZnO-(10-x) Nb 2 O 5-xEr 2 O 3 where (x = 0.0, 0.5, 1.0, 1.5, 2.0, and 2.8 mol%) have been prepared and characterized. Both Fourier-transform-infrared (FTIR) and Raman spectroscopies were performed to study the structural changes correlated with the glass network. The thermal characteristics of the system were specified which showed a higher thermal stability (> 100°C) due to the formation of more bridging oxygen's (BO's) revealed by (FTIR) and Raman spectroscopies. The optical absorption spectra within near UV-visible regions were performed, and exhibited nine absorption bands centered around 1536, 977, 798, 653, 545, 524, 490, 450, and 443 nm corresponding to the 4 I 15/2 ground state to the various excited states 4 I 13/2 , 4 I 11/2 , 4 I 9/2 , 4 F 9/2 , 4 S 3/2 , 2 H 11/2 , 4 F 7/2 , 4 F 5/2, and 4 F 3/2 respectively. The same measurement also showed increasing values of the optical band gap (E g) form 2.70 to 2.90 (eV) and decreasing the refractive index (n) from 2.48 to 2.42. Both the extinction coefficient data and the complex dielectric functions of the glasses were estimated. The different optical parameters were distinctly affected by increasing the Er 2 O 3 (mol %) and the structural changes. The radiative properties of the glass were calculated using J-O parameters. The Branching ratio (β) of 4 I 13/2 → 4 I 15/2 transition peaked at 1520.48 nm for Er 3+ ions has the highest value (1.000) also, the radiative lifetime (τ) of the same transition changed from 1.4510 to 1.8483. The gain cross-section of the laser transition level from 4 G 11/2 → 4 I 15/2 changed from 1.44 × 10 −20 to 1.92 × 10 −20 cm −1 in the existing glass system. The acquired results exhibited that the existent glass can be a good candidate in the fiber drawing and laser, non-linear optical applications.
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Papers by nehal elkhoshkhany