Adsorption characteristics of parent and copper-sputtered RD silica gels

Surface modification of type RD silica gel was achieved by depositing layers of thin-film copper on the parent silica gel surfaces so as to improve their performances, circumventing the poor thermal conductivity of the adsorbent. Porous properties (surface area, pore size and volume) were determined using nitrogen adsorption/desorption isotherm measurements, which were performed on adsorbents for both parent and Cu-sputtered silica gels in liquid nitrogen at a temperature of 77.4?K. The copper sputtering experiments were conducted in a chamber of inert argon gas where the chamber was bombarded with a radio frequency (RF) of 13.56?MHz. The comparative performance of the parent and Cu-sputtered silica gels was determined via various key measurements such the Brunauer–Emmett–Teller (BET), the Horvath and Kawazoe (HK) and the hot-disc sensor methods.     

X-ray diffraction and Mössbauer spectroscopy studies of cementite dissolution in cold-drawn pearlitic steel

Cementite dissolution in cold-drawn pearlitic steel (0.8 wt.% carbon) wires has been studied by quantitative X-ray diffraction (XRD) and Mössbauer spectroscopy up to drawing strain 1.4. Quantification of cementite-phase fraction by Rietveld analysis has confirmed more than 50% dissolution of cementite phase at drawing strain 1.4. It is found that the lattice parameter of the ferrite phase determined by Rietveld refinement procedure remains nearly unchanged even after cementite dissolution. This confirms that the carbon atoms released after cementite dissolution do not dissolve in the ferrite lattice as Fe-C interstitial solid solution. Detailed analysis of broadening of XRD line profiles for the ferrite phase shows high density of dislocations (～10¹⁵/m²) in the ferrite matrix at drawing strain 1.4. The results suggest a dominant role of ?1?1?1? screw dislocations in the cementite dissolution process. Post-deformation heat treatment leads to partial annihilation of dislocations and restoration of cementite phase. Based on these experimental observations, further supplemented by TEM studies, we have suggested an alternative thermodynamic mechanism of the dissolution process.     

The effect of non-mesogenic biphenyl impurity on the orientational order parameter of 4-cyano-4′-n-octyl-biphenyl (8CB)

The role of non-mesogenic impurities on a mesogen and the consequent alteration of mesogenic properties have always been of great interest in the tailoring of mesogenic behaviour. In the present work the effect of rigid, non-polar, nonmesogenic solute ‘biphenyl’ on the optical properties of the mesogen 4-cyano-4′-n-octyl-biphenyl (8CB) has been reported. The phase transitions and thermal variations of the refractive index, polarisability and order parameter ?P₂? of the 8CB–biphenyl systems of various concentrations have been investigated using a He–Ne laser beam. The results have been compared with ?P₂? of pure 8CB. It has been observed that biphenyl lowers both smecticA–nematic and nematic–isotropic transition temperatures by an amount that depends on impurity concentration.     

Optical and dielectric properties of the mesogen 4-cyano-4′-n–octyl biphenyl as a function of temperature

The effect of temperature on certain optical and dielectric properties of one member, namely 4-cyano-4′-n–octyl biphenyl (8CB) of the mesogenic series 4-cyano-4′-n–alkyl biphenyl (nCB), is reported. The dependence of the ordinary and extraordinary components of polarisability, α_o and α_e, on temperature is studied using a He–Ne laser beam, and the variation of orientational order parameter with temperature in the entire mesogenic phase determined from the optical studies. The dependence of the effective molecular dipole moment, μ_eff, in the liquid-crystal phase, and the angle of inclination, β, of the dipole moment with the preferred direction have been investigated. An experimental estimate of the correlation factor ‘g’, which is indicative of the nature of the molecular association in the mesophase, has been obtained.     

Microwave irradiation solvothermal technique: an optimized protocol for size‐control synthesis of Ru nanoparticles

Ruthenium (III) chloride salt and Poly (N‐vinyl‐2‐pyrrolidone) (PVP as a capping agent) was dissolved in ethylene glycol, which played a dual role for synthesis, as solvent and also as reducing agent. Microwave (MW) irradiation was applied to the solvent which provided controllable thermal activation for synthesis of ruthenium nanoparticles and also restricted the agglomeration of particles in presence of excess amount of solvent, which was recovered by distillation after completion of reaction. Synthesized particle was found to be in the range of 2–20 nm with narrow size distribution and average particle size was around 14 nm. Particle size and size distribution were studied by varying different parameters e.g. reaction temperature, time, PVP/RuCl₃ molar ratio and irradiation power and was characterized by Transmission electron microscopy (TEM). Mathematical model has been developed using matlab software to obtain the particle size as a function of microwave power.     

An alternative f(R, T) gravity theory and the dark energy problem

Recently, a generalized gravity theory was proposed by Harko et al. where the Lagrangian density is an arbitrary function of the Ricci scalar R and the trace of the stress-energy tensor T, known as F(R,T) gravity. In their derivation of the field equations, they have not considered conservation of the stress-energy tensor. In the present work, we have shown that a part of the arbitrary function f(R,T) can be determined if we take into account of the conservation of stress-energy tensor, although the form of the field equations remain similar. For homogeneous and isotropic model of the universe the field equations are solved and corresponding cosmological aspects has been discussed. Finally, we have studied the energy conditions in this modified gravity theory both generally and a particular case of perfect fluid with constant equation of state.     

Dynamical System Analysis for Anisotropic Universe in Brans-Dicke Theory

In this work, we have studied the Brans-Dicke (BD) cosmology in anisotropic models. We present three dimensional dynamical system describing the evolution of anisotropic models containing perfect fluid and BD scalar field with self-interacting potential. The relevant equations have been transformed into the dynamical system. The critical points and the corresponding eigen values have been found in radiation, dust, dark energy, ΛCDM and phantom phases of the universe. The natures and the stability around the critical points have also been investigated.