Spectroscopic and thermal analysis of lead-free multipurpose radiation shielding glasses

The genetic algorithm was used to identify glasses, of the composition 50Bi₂O₃-(50-x) B₂O₃-xBaO with $25\ge x\ge 5$ wt%, that have a similar half-value layer (HVL) and neutron removal cross-section. The structure of these glasses was further explored using a combination of spectroscopic and thermal analysis in order to ascertain whether they possess advantageous physical properties comparable to traditional materials used in nuclear reactor design. Differential scanning calorimetry (DSC) analysis was used to examine the thermal profile of the glass system and to identify glass transition temperature T_g and softening temperature T_s. Glass of the composition 50Bi₂O₃–30B₂O₃–20BaO had exhibited the highest thermal stability. Analysis of the Raman spectra of the samples confirmed the presence of BiO₆ octahedrons and B-O-B bonds in poly borate chains. A deconvolution of the IR spectra was carried out to determine the relative proportions of BO₃ triangles to BO₄ tetrahedral units in the glass network that would affect the density and bulk modulus. Optical absorption spectrum of the samples exhibited absorption peaks in the blue region along with a broad band of absorption at longer red wavelengths associated with excitation of bismuth ions. When compared to traditional heavy concretes used in radiation shielding, the bismuth-barium borate glasses exhibited superior performance over conventional barite concrete as a gamma-radiation shield and was comparable to limonite concrete as a neutron radiation shield. The bulk modulus of the glass series was also found to be comparable to that of regular concrete at approximately to 30?GPa.     

Rheological Characterization of MR Polishing Fluid Used for Silicon Polishing in BEMRF Process

The finishing mechanism of the ball-end magnetorheological finishing (BEMRF) process mainly depends on the stiffened hemispheroid, which is formed at the tool tip. Magnetorheological (MR) polishing fluid imparts strength to the polishing spot because of the effect of magnetic field strength. Behavior of this polishing fluid mainly depends on the size and shape of its constituents, volume concentration, particle size distribution, and applied magnetic field strength. A detailed study was undertaken on the role of carbonyl iron particle (CIP) size on the rheological behavior of the MR polishing fluid under various magnetic flux densities. Evaluation of the behavior of MR polishing fluid for silicon polishing was attempted through designing and fabrication of a parallel-plate magnetorheometer. Rheological characterization study was carried out using the Casson fluid model and the MR polishing fluid rheological properties, namely field-induced yield stress and shear viscosity were evaluated.     

Porous water repellent silica coatings on glass by sol–gel method

Development of the solid surfaces with water-repellent and self-cleaning ability has attracted much research interest in recent years. In the present research work, we have prepared water repellent silica coatings on glass at room temperature (~27 °C) by sol gel process and surface silylation technique. Coating sol was prepared by keeping the molar ratio of tetramethoxysilane (TMOS), methanol (MeOH) and water (H₂O) constant at 1:12.36:4.25, respectively, with 0.01 M NH₄F. The dip coated silica films were surface silylated using two different silylating agents namely hexamethyldisiloxane (HMDSO) and hexamethyldisilazane (HMDZ). The HMDSO and HMDZ in hexane solvent were varied from 0 to 1 vol.% and silylation period was varied from 1 to 3 h. The HMDSO and HMDZ modified films showed dense and porous surface morphology, respectively. The HMDSO modified silica films showed static water contact angle of 122° whereas HMDZ modified films showed 165°. The HMDZ modified films displayed the extreme water repellency comparing with that of lotus leaves. The silica films were characterized by surface profilometer, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared microscopy, thermal and chemical aging tests, optical transmission and static water contact angle measurements.     

Theoretical Prediction of Pressure and Temperature of an Aluminized High Explosive in Underwater Explosion

The blast wave propagation in underwater explosion was studied. The shock propagation in water medium was different from that in air. The blast effect in water lasted longer and offered resistance to the expansion of hot gases and release of energy. A theoretical analysis of the expansion of blast wave in water was carried out and numerical results for pressures and temperatures were obtained as functions of distance and time by analytically solving the governing equations. The initial peak pressures of blast waves, which were required for theoretical analysis were calculated using the blast wave theory. Underwater blasts with different weights (0.045, 0.5, and 1.0 kg) of the aluminized high explosive HBX‐3 were conducted to record pressure as a function of distance and time from the blast point. Theoretical results were compared with experimental data and empirical data for HBX‐3 from literature. Since the measurement of pressure and temperature at close proximity of point of detonation is difficult, theoretical modeling of underwater blast is of significant importance.     

Influence of surfactants on rheological characteristics of dough and quality of parotta

The effect of the surfactants glycerol monostearate (GMS), lecithin, diacetyl tartaric acid esters of monoglycerides (DATEM), polyoxyethylene sorbitan monostearate (PS‐60) and sodium stearoyl‐2‐lactylate (SSL) on the rheological characteristics of dough and quality of parotta was studied. Use of the surfactants increased stability as measured by the farinograph, valorimeter value, extensograph ratio figure and extensograph area, indicating an increase in the strength of the dough. Surfactants reduced the mixograph peak height, mixograph area, apparent biaxial extensional viscosity, compressive stress, force decay parameter, hardness and adhesiveness, and increased the cohesiveness of dough. The values for peak viscosity increased with DATEM, PS‐60 and SSL and decreased with GMS and lecithin. Among the surfactants tested, SSL and PS‐60 brought about the greatest improvement in the quality of parotta, followed in decreasing order by DATEM, lecithin and GMS.     

Magnetic properties of (Co,Al) co-doped SnO<Subscript>2</Subscript> nanoparticles

The desired size of pure SnO₂ and Co (1, 3, 5 mol%) with constant 5 mol% of Al co-doped into SnO₂ nanoparticles are synthesized by chemical co-precipitation method. The raw materials used in synthesis are SnCl₂.2H₂O, AlCl₃, Co (C₂H₃O₂).4H₂O, aqueous NH₄OH and Polyethyleneglycol (PEG) from AR grade. The XRD pattern of pure and co-doped samples confirm the formation of tetragonal rutile phase of SnO₂ nanoparticles with average particle size 25 and 20 nm respectively. Micrographs of scanning electron microscope (SEM) for pure and (Co, Al) co-doped into SnO₂ show that the prepared nanoparticles are agglomerate and spherical in shape. The EDAX spectra of prepared nanoparticles indicate the presence of Co²⁺, Al³⁺, Sn⁴⁺ and O²⁺ and also confirm stoichiometric proportions of raw material in the formation of SnO₂. Transmission electron microscope (TEM) reveals that the surface morphology of pure and co-doped samples are spherical, and average size of particles is ~20 nm. Magnetization measurements from M-H curves of VSM show that the ferromagnetism at low concentration of Co and at higher concentration of Co shows weak ferromagnetism due to super exchange coupling among neighboring ions. The bound magnetic polarons model supports the observed ferromagnetic behavior.     

Growth of larger and more perfect single crystals of KClO4 in silica gel

As part of a continuing effort on crystal growth in gels, this paper describes the growth of large transparent single crystals of KClO₄ by the improved design. The effect of various anionic and cationic components on nucleation, growth and quality of these crystals has been studied. It has been found that a combination of KNO₃ and HClO₄ as the reactants resulted in the best crystals in terms of crystal size, quality and inter-crystalline separation. The effect of various impurities on nucleation, growth and quality of these crystals has been studied. It has been found that the impurities which enhance the solubility of KClO₄ have a positive effect on the size and quality of the crystals. A new etchant, consisting of concentrated HCl and H₂SO₄ in the volume ratio 2:3 has been found to reveal as-grown as well as freshly introduced dislocations.     

A Simple Aqueous Solution Based Chemical Methodology for Preparation of Mesoporous Alumina: Efficient Adsorbent for Defluoridation of Water

In this paper, we report a simple aqueous solution based chemical method for preparation of mesoporous γ-Al₂O₃ which can be used for removal of fluoride ions from water. The synthesized Al₂O₃ and commercial Al₂O₃(Grade AD101-F, ACE Manufacturing and Marketing, Baroda, India) were characterized by using powder x-ray diffractometer, N₂ adsorption–desorption surface area and pore size analyzer, and high resolution transmission electron microscope. Synthesized Al₂O₃ contains a wormhole-like mesoporous structure with 358.7 m² g^?1 Brunauer–Emmett–Teller (BET) surface area and 0.8 cm³ g^?1 pore volume. Batch adsorption studies were performed to determine the fluoride adsorption capacity of Al₂O₃. The effect of different parameters such as contact time, initial fluoride concentration, pH, and adsorbent dose was studied to understand the fluoride adsorption behavior of the synthesized Al₂O₃ under various conditions. The kinetics results showed that the fluoride adsorption on synthesized Al₂O₃ followed pseudo-second-order kinetics. Adsorption equilibrium data fitted well to the Freundlich equation and indicated multilayer adsorption of fluoride on the surface of Al₂O₃. Synthesized Al₂O₃ demonstrated significantly improved fluoride adsorption capacity and faster kinetics than commercial Al₂O_3.