•The presence of discontinuous precipitation (DP) of the β-(Mg17Al2) phase at grain boundaries below 150 °C and continuous precipitation (CP) within the α-Mg grains above 350 °C.•The crystallization ...kinetics of the dissolution reaction of the β-(Mg17Al2) phase in magnesium alloy AZ91 was studied using non-isothermal and isothermal methods.•The activation energy reaction rate constant growth and nucleation coefficients for the β-phase dissolution reaction (Mg17Al2) were calculated.•The results show that the activation energy for the dissolution reaction of β-(Mg17Al2) phase is 116.781 kJ/mol and 129.7383 kJ/mol under non-isothermal and isothermal conditions.•The avrami coefficient n relevant for the dissolution kinetics of the β-(Mg17Al2) phase is 1.152 and 1.211 in non-isothermal and isothermal conditions. n and m are 1.152 and 0.993, where these values converge to 1, indicating that the dissolution mechanism of the β-(Mg17Al2) phase occurs by diffusion accompanied by interactions with the surface.
In this study, the phase transformations, crystallization kinetics and dissolution mechanism of β phase (Mg17Al12) in magnesium alloy AZ91 were investigated by optical microscopy, X-ray diffraction, differential scanning calorimetry and differential dilatometry. The results indicate that this AZ91 alloy undergoes a phase transformation during aging, a discontinuous precipitation of the β phase (Mg17Al12) at 150 °C at the grain boundaries and another continuous at 350 °C within the grains. The activation energy of the dissolution reaction of the β phase (Mg17Al12) under non-isothermal conditions is 116.781 kJ/mol, while it is 129.7383 kJ/mol under isothermal conditions. The Avrami coefficient, n, relevant for the dissolution kinetics of the β phase (Mg17Al12) is 1.152 and 1.211 in the non-isothermal and isothermal conditions respectively. The numerical coefficients m and Avrami n are 0.993 and 1.152.
As radiation is an essential tool in various technological applications, searching for a suitable shield is an urgent demand to minimize its damaging effects on human beings. In this research ...article, we report on the radiation shielding properties of some commercially available polymers namely poly(N‐isopropylacrylamide), polyethylene terephthalate, polystyrene, and polycarbonate (denoted by P1, P2, P3, and P4, respectively). The gamma ray attenuation parameters are calculated using the Geant4 simulation, PHITS code, and XCOM program. Half value layer (HVL), linear attenuation coefficient (LAC), gamma dose rate at different energy levels, mean free path (MFP), specific gamma ray constant, effective atomic number (Zeff) and effective electron density (Neff), removal cross section for fast neutron, and total cross section for thermal neutron are investigated at energies of 0.01, 0.03, 0.05, 0.07, and 0.1 MeV. The results indicate that the highest LAC values were observed for P2 polymer at 0.1 MeV, while the lowest LAC values were noted for P3 polymer at 0.01 MeV among the studied commercial polymers. The total cross sections of thermal neutrons for the investigated polymers change from 24.0717 to 31.8611 cm−1. Moreover, the MFPs and HVLs of the investigated polymers were very close to those of ordinary concrete and RS‐253‐G18 commercial glass, especially at the low energies. This suggests the utility of using the present polymer samples for shielding applications against gamma and/or neutron radiations.
The techniques of melt-quenching have been used to generate 53B
2
O
3
—2NaF—27PbO –
(
20
-
x
)
BaO—
x
La
2
O
3
(
0
≤
x
≥
15
)
g
l
a
s
s
s
y
s
t
e
m
. XRD patterns have been established the amorphous ...character of glass samples. There is a clear evidence of the role of the La
2
O
3
modifier in the glass network. The thermal characteristics have been identified to increase with an increase in La
2
O
3
content. Increasing La
2
O
3
increases the linear and non-linear optical bandgap energy and the Urbach energy. By adding La
2
O
3
to the glass samples, the refractive index, molar polarizability, polarizability, and optical basicity increased. The bulk modulus and the glass transition temperature increased because of the increase in bond strength. The number of bonds per unit increased with the increase in La
2
O
3
content because of the modifier character of La
2
O
3
in the glass samples. Many optical parameters (
ε
∞
), (
ε
o
),
χ
(
1
)
,
χ
(
3
)
and
(
n
2
)
as a function of linear and non-linear
E
opt
have been obtained. The extent of shielding in this article has been examined with the increment in La
2
O
3
at the expense of BaO. The results correspond with similar studies conducted before.
In present work, Variable Angle Spectroscopic Ellipsometer (VASE) is used to determine the optical properties of thermally evaporated thin films Se15Te62.5Ge22.5 and Se10Te67.5Ge22.5 from 0.8 to 5.1 ...eV. The experimental data of VASE parameters were fit using two group of models to extract the dielectric function. First group consist from mixtures of several Gaussian, and one Tauc–Lorentz (TL group ). The other group is a mixed from several Gaussian and one Cody-Lorentz dispersion functions (CL group). The models’ factors such as resonance, optical band gap, Urbach energies, oscillator's amplitude and width for both Se15Te62.5Ge22.5 and Se10Te67.5Ge22.5 films were estimated. Extinction coefficients and refractive indices as function of photon energy of the films were calculated. Both models perform very equally and precisely adequate to the experimental data. However the CL model shows a good accuracy in recounting dielectric function at the beginning absorption area.
For safe immobilization of nuclear waste, lead-iron phosphate glasses are promising as high-level commercial and defense materials. In this research article, the compositional, elastic, and gamma ...shielding properties of the glasses containing (80 − x)P
2
O
5
– xFe
2
O
3
–20PbO with x = 20, 25, 30, 35 mol% were reported. The compositional and elastic parameters including the micro-hardness of the investigated glass samples were obtained based on Makishima-Mackenzie’s theory (MM-theory) and R model. We found that the deviation between these two methods decreased as Fe
2
O
3
concentrations increased from 20 to 35 mol %. Additionally, γ-ray attenuation properties of the P
2
O
5
– Fe
2
O
3
–PbO glass system were evaluated using Geant4 simulation toolkit. The simulation results were compared with the theoretical ones extracted from Py-MLBUF software. The obtained results reveal that the MACs of the glasses vary from 0.030 to 40.014 cm
2
/g for PFP-A, from 0.031 to 41.502 cm
2
/g for PFP-B, 0.031 to 43 cm
2
/g for PFP-C and from 0.031 to 44.400 cm
2
/g for PFP-D. Maximum Z
eff
values of present glasses are obtained at 0.10 MeV whereas minimum Z
eff
values are obtained at 1.5 MeV. Finally, the fundamental γ-ray attenuation properties of the P
2
O
5
– Fe
2
O
3
–PbO glass system are found to be comparable with those of traditional and commercial radiation shields such as RS-253-G18 and RS-360 commercial glasses, ordinary concrete, barite concrete and TBZP10 from scientific literature. The results indicated that MFPs of the investigated glasses are lower than those of RS-360 glass, but they are higher than those of barite concrete and TBZP10.
In the current work, the effect of zinc doping on the structural and optical properties of iron oxide has been explored for optoelectronic applications. Undoped and different (2–10 wt%) Zn-doped iron ...oxide (Fe
2
O
3
/Zn) nanostructured films (nFs) were successfully prepared via spray pyrolysis technique. The structural, morphological, bonds vibrations and optical properties of the prepared films were examined using X-ray diffraction (XRD), scanning electron microscope (SEM), FT-IR and UV-Vis-NIR spectroscopy techniques, respectively. The XRD measurements reveal the formation of the rhombohedral hematite phase structure of iron oxide (α-Fe
2
O
3
) for all prepared films. The FT-IR spectra analysis exhibits the existence of absorption bands corresponded to the stretching and bending vibrations of Fe–O and O–Fe–O bonds, respectively. The UV–Vis–NIR measurements of the prepared samples indicate the significant effect of Zn doping on various optical properties of Fe
2
O
3
films. The achieved optical bandgap of Fe
2
O
3
/Zn nFs is tuned from 2.38 eV (undoped Fe
2
O
3
) to 2.83 eV (10 wt% of Fe
2
O
3
/Zn). These findings are explained on the basis of the created localized energy levels and Burstein–Moss effect. As a novel result of this study, Fe
2
O
3
/Zn nFs are well-qualified for the use in modern optoelectronic applications.
The conventional technique has been used to prepare a quaternary glass based on the chemical composition 5Al
2
O
3
-
(
10
+
x
)
Li
2
O-
(
70
-
x
)
B
2
O
3
-15TiO
2
:
(
0
≤
x
≤
25
)
mol.%. The Fourier ...transform infrared spectrometer spectra were investigated for the structural change of these glasses. Ultraviolet spectroscopic at ambient temperature of the investigated glass system. The optical bandgap and refractive index of these glasses were decreased, while Urbach energy was increased. The polarizability and basicity of these glasses have been established. To demonstrate the influence of titanium oxide on dispersion parameters, these glasses were applied. Under controlled heating, the glass–ceramic was prepared and investigated using X-ray diffraction and mechanical characteristic. Glass–ceramic surface morphology has been examined by scanning electron microscope.
Using generalized gradient approximation (GGA) and local density approximation (LDA), the phase stability, electronic, and optical characteristics of BiGaO3 in the Pcca, R3c, and Pm‐3m phases are ...examined. The structural phase transition can be caused by the few soft modes between F and Z points in the R3c phase. Because it is coupled to isotropic deformation, the bulk modulus of BiGaO3 is an indicator of its high hardness. When electrons travel from the top of the valence band (O‐2p) to the bottom of the conduction band (Ga‐4p or Bi‐6p), optical transitions are detected. The pyroxene Pcca phase of BiGaO3 is the most stable, according to GGA–Perdew–Burke–Ernzerhof (PBE) total energy calculations. At 5 GPa, the phase change from the Pcca to the R3c structure occurs. Because of the smaller reticular lengths and higher Coulomb forces, the elastic constants of BiGaO3 are quite significant.
Using GGA and LDA approximations, phase stability, electronic, and optical characteristics of BiGaO3 in the Pcca, R3c, and Pm‐3m phases were examined. The structural phase transition could be caused by the few soft modes between F and Z points in the R3c phase. Because of the smaller reticular lengths and higher Coulomb forces, the elastic constants of BiGaO3 are quite significant.
In this study we present the optical features including several parameters, gamma-ray photon and fast neutron absorption parameters of quaternary glasses with the chemical structure: xBi2O3 ...+ (80-x)TeO2 + 10B2O3 + 10GeO2 for x = 40, 50, and 60 mol% and coded as Bi/Te-BGe1, Bi/Te-BGe2, and Bi/Te-BGe3 respectively. The FLUKA Monte Carlo and XCOM code were used to evaluate the photon shielding parameters of the glasses for energies between 0.284 and 2.506 MeV. The optical quantities such as the molar refractivity Rm, molar polarizability αmol, reflectance loss (Rloss), optical transmission (Topt), metallization criterion (M) and the static dielectric constant εstaof the glasses were estimated to understand their optical characteristic. Mass attenuation coefficient of 0.345, 0.368, and 0.386 cm2/g was obtained for Bi/Te-BGe1–3 respectively at 0.284 MeV. Evaluated Zeff ranged from 30.94 to 53.22, 32.73 – 56.29, 34.52 – 58.75 for the Bi/Te-BGe1–3 glasses respectively. The HVL within the investigated energy similar to other estimated photon shielding parameters showed great enhancement as the density and Bi2O3 content of the glasses improved. Similar improvement on the fast neutron removal cross section also increased from 0.1141 to 0.1178 cm−1 as bismuth oxide increases in the glass system. The estimated optical parameters also showed great dependence on the chemical structure of the glasses. The present Bi/Te-BGe1–3 glasses showed excellent fast neutron and photon absorption capacity compared to some common shields; this makes them potentially useful for radiation protection applications.
Structural, thermal, radiation shielding efficiency, and buildup factors of the successfully synthesized (100-
x
) (0.5V
2
O
5
–0.5P
2
O
5
) (
x
B
2
O
3
):
x
= 0 (VPB0), 2 (VPB2), 4 (VPB4), 6 ...(VPB6), 8 (VPB8) mol % glasses have been investigated. Scanning electron microscope (SEM), EDX, Raman spectroscopy, and differential scanning calorimetry (DSC) thermograms measurements of the proposed glasses have been used to perform the mentioned aims. Indeed, radiation protection quantities like linear reduction (μ), and transmission factors (TF), radiation protection efficiency (RPE), and buildup factors (EBF and EABF) have been evaluated via Phy-X/PSD software. The SEM and EDX spectra measurements proved that the structure of the proposed glasses is amorphous. Raman spectroscopy revealed that in VPB8 glass structure, the different phosphate units were formed and thus (PO
3
)
−
groups decreased. Thermal stabilities varied between 168 °C (VPB0) and 199 °C (VPB4). The maximum values for the (μ) at 0.015 MeV, where they changed between 45.689 and 42.992 cm
−1
for the investigated glasses VPB0–VPB8, respectively, and followed the trend: (μ)
VPB0
> (μ)
VPB2
> (μ)
VPB4
> (μ)
VPB6
> (μ)
VPB8
. The (TF) was linearly increased with the progressing of the photon energy, while the (RPE) has a totally opposite trend with the (TF). The values of the EBF and EABF increased with the increase in the B
2
O
3
substitution ratio, where the lowest and highest buildup factors were obtained at 0 and 8 mol% B
2
O
3
for VPB0 and VPB8, respectively. VPB8 is also found as an effective material to shield the fast neutrons, and its effective removal cross section (ERCSFN) ∑
R
is found equal 0.0324 (cm
2
g
−1
).
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