Retardation of Cs+ and Cl− Diffusion Using Blended Cement Admixtures

Diffusion of cesium chloride through thin plates of hardened cement pastes was studied. Blast-furnace slag and condensed silica fume were used as blending admixtures in an attempt to retard the diffusion of cesium and chloride ions. The curing and diffusion temperatures were varied from 27° to 60°C, and the water/solid ratio was varied from 0.30 to 0.40. Results indicate that the cesium ion diffuses more slowly than the chloride ion in hardened cement paste systems. Blending admixtures caused a further reduction in diffusivity for both ions, which is important for preventing corrosion or restricting radionuclide transport.     

Mechanical and morphological investigation of virgin polyethylene and silver nanoparticle-loaded nanocomposites film: comprehensive analysis of kinetic models for non-isothermal crystallization

This research was accomplished to examine the mechanical, morphological and crystallization kinetics study of polyethylene/silver nanoparticles (Ag-NPs) nanocomposite films. In this research, low-density polyethylene (LDPE) nanocomposite films were prepared containing Ag-NPs using maleic-anhydride-grafted low-density polyethylene (LDPE-g-MAH) as a compatibilizer by the melt mixing process. From mechanical property evaluation, it is revealed that the LDPE/LDPE-g-MAH/Ag-NPs nanocomposite films showed decreased tensile strength as compared with virgin LDPE matrix. Thermal characteristics of the prepared virgin LDPE and its nanocomposite films were studied by differential scanning calorimetry (DSC). Comprehensive analysis of different kinetic models such as the Avrami and Mo model on non-isothermal crystallization kinetics was performed in order to correlate the rate of crystallization and its various kinetic parameters. Further, the macrokinetic equation as proposed by Malkin has been applied to describe the kinetics of crystallization in the light of the Avrami equation. Concerning virgin LDPE and Ag-NP-reinforced LDPE, the former shows primary crystallization, whereas the later exhibits both primary and secondary crystallization with varying Avrami exponents. Kinetic parameters are recognized, and confirm the influence of Ag-NPs on crystallization kinetics. X-ray diffraction spectroscopy and transmission electron microscopic analysis of the nanocomposite films were conducted to verify the dispersion of inorganic filler particles in the resulting hybrids.     

Luminescence properties of ZnO/TiO<Subscript><Emphasis Type="Bold">2</Emphasis></Subscript> nanocomposite activated by Eu<Superscript><Emphasis Type="Bold">3</Emphasis><Emphasis Type="Bold">+</Emphasis></Superscript> and their spectroscopic analysis

A new type of novel orange-red emitting Eu-doped ZnO/TiO ₂ nanocomposite phosphors have been synthesized by simple low temperature co-precipitation route. Structure and morphology of the prepared sample have been investigated using X-ray diffraction and field emission scanning electron microscopy (FESEM) techniques. XRD pattern confirmed the presence of both phases of ZnO and TiO ₂ simultaneously. The luminescence properties, such as photoluminescence (PL) excitation and emission spectra, Judd–Ofelt parameters, CIE colour coordinates and the dependence of luminescence intensity on the doping level were investigated. The luminescence spectrum characteristics of Eu ³⁺ ions have a strong dependence on Eu ³⁺ doping levels as well as ZnO/TiO ₂ ratio variations. The photoluminescence results indicate that these phosphors could be efficiently excited by near-ultraviolet radiation, which causes emissions in orange–red regions.     

Assessment of mechanical and three-body abrasive wear peculiarity of TiO<Subscript>2</Subscript>- and ZnO-filled bi-directional E-glass fibre-based polyester composites

This paper is about the development of bi-directional E-glass fibre-based polyester composites filled with zinc oxide (ZnO) and titanium dioxide (TiO₂) fillers, respectively. The mechanical characterization of these composites is performed. The three-body abrasive wear characteristic of fabricated composites has been assessed under different operating conditions. For this, the three-body abrasion test is done on dry abrasion test rig (TR-50) and analysed using Taguchi’s experimental design scheme and analysis of variance. The results obtained from these experiments are also validated against existing microscopic models of Ratner–Lancaster and Wang. A good linear relationship is obtained between specific wear rate and the reciprocal of ultimate strength and strain at tensile fracture of these composites. It indicates that the experimentally obtained results are in good agreement with these existing models. It is found that the tensile strength decreases with filler loading, while hardness, flexural strength, inter-laminar shear strength and impact strength are increased. TiO₂-filled composites were observed to perform better than ZnO-filled composites under abrasive wear situations. The wear mechanism is studied in correlation with the SEM micrograph of the worn-out surface of composites. Performance optimization of composites is done by using VIKOR method.     

Luminescence performance of Eu<Superscript>3+</Superscript>-doped lead-free zinc phosphate glasses for red emission

In this study, the luminescence performance of zinc phosphate glasses containing Eu³⁺ ion with the chemical compositions (60–x)NH₄H₂PO₄-20ZnO-10BaF₂-10NaF–x Eu₂O₃ (where x = 0.2, 0.5, 1.0 and 1.5 mol%) has been studied. These glasses were characterized by several spectroscopic techniques at room temperature. All the glasses showed relatively broad fluorescence excitation and luminescence spectra. Luminescence spectra of these glasses exhibit characteristic emission of Eu³⁺ ion with an intense and most prominent red emission (614 nm), which is attributed to ⁵D₀ → ⁷F₂ transition. Judd-Ofelt (Ω₂, Ω₄) parameters have been evaluated from the luminescence intensity ratios of ⁵D₀ → ⁷F_J (where J = 2 and 4) to ⁵D₀ → ⁷F₁ transition. Using J-O parameters and excitation spectra, the radiative parameters are calculated for different Eu³⁺-doped glasses. Effect of γ-irradiation at fixed dose has been studied for all the Eu³⁺-doped glass matrices. The lifetimes of the excited level, ⁵D₀, have been measured experimentally through decay profiles. The colour chromaticity coordinates are calculated and represented in the chromaticity diagram for Eu³⁺-doped zinc phosphate glasses for all concentrations.     

Formation of Silicon-Aluminum Spinel

Characterization of the intermediate cubic phase formed during the transformation of coprecipitated SiO₂-Al₂O₃ gel on heating was studied and X-ray diffraction methods are reviewed and criticized. Coprecipitated gels of different SiO₂/Al₂O₃ ratios were prepared; all showed a 980°C exotherm followed by crystallization of the cubic phase and liberation of SiO₂. Alkali extraction of SiO₂ showed two types present in the 980°-heated product. One variety is free amorphous SiO₂ and the other, chemically bonded to alumina in the crystalline cubic phase, was isolated and characterized as Si-Al spinel with the same composition as mullite. Thus, its formation from the gel of mullite composition shows the highest exotherm and the measured density agrees approximately with the theoretically calculated value.     

Reflectivity dependence of the lasing photon energy in GaAs junction lasers at 77°K

The reflectivity dependence, of the lasing photon energy in GaAs junction lasers at 77° K is studied. It is found that the lasing photon energy decreases with increasing values of the laser reflectivity.     

Identification of β-SiC surrounded by relatable surrounding diamond medium using weak Raman surface phonons

It is difficult to detect β-SiC using micro-Raman scattering, if it is surrounded by carbon medium. Here, β-SiC is identified in the presence of a relatable surrounding diamond medium using subtle, but discernible Raman surface phonons. In this study, diamond/β-SiC nanocomposite thin film system is considered in which nanosized β-SiC crystallites are surrounded by a relatable nanodiamond medium that leads to the appearance of a weak Raman surface phonon band at about 855 cm^???1. Change in the nature of the surrounding material structure and its volume content when relatable, will affect the resultant Raman response of β-SiC phase as seen in the present case of diamond/β-SiC nanocomposite thin films.     

Competing risk theory approach to the nature of the outcome of conception

An attempt has been made to obtain the probabilities of pregnancy termination by live birth, still birth and abortion, in any particular order, assuming that the termination of pregnancy is associated with three competing ‘risks’, i.e. live birth, still birth and abortion, which need not necessarily operate at the same point of time. A probability model has been constructed to obtain the conditional probability of live birth/still birth/abortion given that the previous pregnancy has been terminated by a particular one of the three. The correlation coefficient between the outcomes of two particular consecutive pregnancy terminations, viz. live birth and reproductive wastage (which includes both abortion and still birth), has also been obtained. Given data pertaining to sample correlation coefficients between the nature of consecutive orders of the outcomes of conception from first to sixth, an exercise has been undertaken to estimate parameters relating to the ‘hazard’ rates of live births, still birth and abortion. The exercise further enables one to test the well-known demographic hypothesis that reproductive wastages follow each other in succession over consecutive orders of the outcomes of conception.