Browsing by Author "R.S.B. Reddi"

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Crystal growth and nonlinear optical studies of m-dinitrobenzene doped urea
(2011) R.N. Rai; S.R. Mudunuri; R.S.B. Reddi; V.S.A. Kumar Satuluri; S. Ganeshmoorthy; P.K. Gupta
Urea is an attractive material for frequency conversion of high power lasers to UV but the frequent use of urea (U) crystal at normal atmosphere is troublesome due to its hygroscopic nature. The hygroscopic character of urea has been modified by making the solid solution with m-dinitrobenzene (DNB). The phase diagram of DNB and U shows the formation of a monotectic and a eutectic. There is also a large region of immiscibility, where two immiscible liquid phases are in equilibrium with a liquid of single phase. The solubility of U, DNB and UDNB and the stability of solutions have been studied in methanol at different particular temperatures. vant Hoff equation was used to determine the enthalpy and entropy for the different saturation temperatures for each material. Transparent single crystals of UDNB have been grown from a saturated solution in methanol and the optimum conditions to grow the good quality crystals have been determined. Optical properties, e.g., second harmonic generation (SHG), refractive index and band gap of the UDNB crystal were measured and their values compared with parent compounds. Besides modification in hygroscopic nature, UDNB also shows the higher SHG signal than the parent components. © 2011 Elsevier B.V. All rights reserved.
Crystallization, thermal, phase diagram and microstructural studies of organic analog of metal-nonmetal monotectic alloy: 4-Bromochlorobenzene-succinonitrile
(2009) R.S.B. Reddi; Shiva Kant; U.S. Rai; R.N. Rai
The phase equilibrium data on an organic analog of a metal-nonmetal system involving 4-bromochlorobenzene-succinonitrile show the formation of a eutectic and a monotectic with a large miscibility gap containing 0.96 and 0.03 mole fractions of succinonitrile, respectively, with the consolute temperature of 180.0 °C. The heat of mixing, entropy of fusion, roughness parameter, interfacial energy and excess thermodynamic functions were calculated from the enthalpy of fusion values, determined by the DSC method using TA Instruments DSC-2010. The effects of solid-liquid interfacial energy on morphological change of monotectic have also been discussed. The microstructures of monotectic and eutectic show the lamellar growth characteristic. © 2009 Elsevier B.V. All rights reserved.
Developments and future directions of phase diagram, physicochemical and optical studies of binary organic complexes
(Elsevier Ltd, 2013) R.N. Rai; R.S.B. Reddi; U.S. Rai
The aim of this review is to emphasize solvent free or green synthesis, a most efficient utilization of starting materials to give maximum yield, and an alternative route to producing novel promising materials. In this regard the phase diagram study has shown applications in the determination of the precise composition of binary compounds of a specific nature and in the identification of the parameters that affect the crystal growth. To provide an overview worthy of phase diagram, physicochemical, thermal and structure investigations; studies of eleven systems, namely, urea–m-nitrobenzoic acid, urea–p-nitrophenol, urea–resorcinol, benzoin–o-phenylenediamine, pyrene–m-dinitrobenzene, vanillin–p-anisidine, resorcinol–p-dimethylaminobenzaldehyde, benzophenone–diphenylamine, anthracene–picric acid, 8-hydroxyquinoline–salicylic acid and 8-hydroxyqunoline–1,2,3-trihydroxybenzene forming organic complexes, have been reported. In addition, the original data of a newly synthesized complex of m-hydroxybenzaldehyde (HB) and p-chloroaniline (CA) is being reported for the first time. The phase diagram of HB–CA system also shows the formation of a complex in 1:1 M ratio, and two eutectics on either side of the complex. The complex's formation was studied using FTIR, NMR, DSC and powder X-ray diffraction techniques. The thermodynamic parameters such as heat of mixing, entropy of fusion, roughness parameter, interfacial energy and excess thermodynamic functions were calculated using the heat of fusion values. The single crystal growth and the atomic packing studies of some of the complexes have confirmed the formation of complexes. The optical transmittance efficiency and transparency of novel HB–CA complex crystal were found to be 70% and 399 nm, respectively. © 2013 Elsevier Ltd
Phase equilibria, crystallization, thermal and microstructural studies on organic monotectic analog of nonmetal-nonmetal system; urea-4-bromo-2-nitroaniline
(2012) R.S.B. Reddi; S. Ganesamoorthy; P.K. Gupta; R.N. Rai
The phase diagram of urea-4-bromo-2-nitroaniline system was studied which shows a large miscibility gap and the formation of a eutectic and a monotectic where the mole fractions of 4-bromo-2-nitroaniline are 0.899 and 0.020, respectively. The critical temperature is being 61.5 °C above the monotectic horizontal. The formation of solid solution of 4-bromo-2-nitroaniline in urea was studied by powder X-ray diffraction technique. Using differential scanning calorimetry (DSC), the enthalpies of fusion of the pure components, the eutectic and the monotectic were determined. The different thermodynamic parameters such as heat of mixing, entropy of fusion, roughness parameter, interfacial energy and excess thermodynamic functions were calculated utilizing the heat of fusion values. The solid-liquid interfacial energy has also been calculated and their effects on morphological change of microstructure of monotectic and eutectic have been discussed. © 2011 Elsevier B.V.
Solid state synthesis, crystal growth and optical properties of urea and p-chloronitrobenzene solid solution
(Academic Press Inc., 2016) R.N. Rai; Shiva Kant; R.S.B. Reddi; S. Ganesamoorthy; P.K. Gupta
Urea is an attractive material for frequency conversion of high power lasers to UV (for wavelength down to 190 nm), but its usage is hindered due to its hygroscopic nature, though there is no alternative organic NLO crystal which could be transparent up to 190 nm. The hygroscopic character of urea has been modified by making the solid solution (UCNB) of urea (U) and p-chloronitrobenzene (CNB). The formation of the solid solution of CNB in U is explained on the basis of phase diagram, powder XRD, FTIR, elemental analysis and single crystal XRD studies. The solubility of U, CNB and UCNB in ethanol solution is evaluated at different temperatures. Transparent single crystals of UCNB are grown from its saturated solution in ethanol. Optical properties e.g., second harmonic generation (SHG), refractive index and the band gap for UCNB crystal were measured and their values were compared with the parent compounds. Besides modification in hygroscopic nature, UCNB has also shown the higher SHG signal and mechanical hardness in comparison to urea crystal. © 2015 Published by Elsevier Inc.
Solid-liquid equilibria, thermochemical and microstructural studies of binary organic monotectic and eutectic alloy
(2012) K.P. Sharma; R.S.B. Reddi; R.N. Rai
The phase diagram of 1,4-dibromobenzene (DBB) with pyrogallol (PG) shows the formation of a monotectic and a eutectic alloys at 0.12 and 0.99 mol fractions of DBB, respectively. The phase equilibrium shows the large miscibility gap region with the upper consolute temperature 159.0 °C at 0.55 mol fraction of DBB. Growth kinetics of pure compounds and their monotectic and eutectic at different undercooling (δT) obey Hillig-Turnbull's equation: v = u (δT)n. Thermodynamic parameters such as enthalpy of mixing, entropy of fusion, interfacial energy, roughness parameters and excess thermodynamic functions were computed based on enthalpy of fusion values obtained from DSC studies. The Cahn wetting condition is applicable for monotectic alloy. The optical microphotographs of binary alloys show lamellar and dendritic features. © Akademiai Kiado, Budapest, Hungary 2012.
Solid-liquid equilibrium, thermal and physicochemical studies of organic eutectics
(2012) R.S.B. Reddi; V.S.A. Kumar Satuluri; R.N. Rai
The solid-liquid phase equilibrium data of two binary organic systems, namely, urea (U)-3-aminophenol (AP) and 3-hydroxybenzaldehyde (HB)-β-napthaol (BN) show formation of a eutectic in each case. The enthalpies of fusion of the pure components and binary eutectics have been determined using differential scanning calorimeter (Mettler DSC-4000) system. The thermal properties of the materials such as heat of mixing, entropy of fusion, roughness parameter, interfacial energy and excess thermodynamic functions were computed using the enthalpy of fusion values. The microstructures of eutectics were developed using unidirectional thermal gradient and interested region were photographed. © 2011 Akadémiai Kiadó, Budapest, Hungary.
Solid-liquid equilibrium, thermal, crystallization and microstructural studies of organic monotectic alloy
(2010) Shiva Kant; R.S.B. Reddi; R.N. Rai
A monotectic and a eutectic organic alloy have been synthesized with the help of phase diagram study. The phase diagram of an organic analogue of a metal-nonmetal system involving succinonitrile-1,4-diiodobenzene shows two immiscible liquid phases are in equilibrium with a single liquid phase. Growth behaviour of the eutectic, the monotectic and the pure components, studied at different undercooling temperatures, suggests that the data obey the square relationship between growth velocity and undercoolings. The thermal study such as heat of mixing, entropy of fusion, roughness parameter, interfacial energy and excess thermodynamic functions were calculated via the enthalpy of fusion values, determined using differential scanning calorimeter (DSC) method. The effects of solid-liquid interfacial energy on morphology of monotectic have also been discussed. The microstructures of monotectic, eutectic and pure components show their peculiar characteristic features. © 2010 Elsevier B.V. All rights reserved.
Synthesis, crystal growth, structural and physicochemical studies of novel binary organic complex: 4-chloroaniline-3-hydroxy-4-methoxybenzaldehyde
(2012) K.P. Sharma; R.S.B. Reddi; S. Bhattacharya; R.N. Rai
The solid-state reaction, which is solvent free and green synthesis, has been adopted to explore the novel compound. The phase diagram of 4-chloroaniline (CA) and 3-hydroxy-4-methoxybenzaldehyde (HMB) system shows the formation of a novel 1:1 molecular complex, and two eutectics on either sides of complex. Thermochemical studies of complex and eutectics have been carried out for various properties such as heat of fusion, entropy of fusion, Jacksons parameters, interfacial energy and excess thermodynamic functions. The formation of molecular complex was also studied by IR, NMR, elemental analysis and UV-Vis absorption spectra. The single crystal of molecular complex was grown and its XRD study confirms the formation of complex and identifies the crystal structure and atomic packing of crystal of complex. Transmission spectra of grown crystal of the complex show 70% transmittance efficiency with cut off wavelength 412 nm. The band gap and refractive index of the crystal of complex have also been studied. © 2012 Elsevier Inc.
Thermal, physicochemical and microstructural studies of binary organic eutectic systems
(2012) R.S.B. Reddi; V. S. A. Kumar Satuluri; U.S. Rai; R.N. Rai
Solid-liquid phase equilibrium data of three binary organic systems, namely, 3-hydroxybenzaldehyde (HB)-4-bromo-2-nitroanilne (BNA), benzoin (BN)-resorcinol (RC) and urea (U)-1,3-dinitrobenzene (DNB), were studied by the thaw-melt method. While the former two systems show the formation of simple eutectic, the third system shows the formation of a monotectic and a eutectic with a large immiscibility region where two immiscible liquid phases are in equilibrium with a liquid of single phase. Growth kinetics of the pure components, the monotectic and the eutectics, studied by measuring the rate of movement (v) of solid-liquid interface in a thin U-tube at different undercoolings (ΔT) suggests the applicability of the Hillig-Turnbull's equation: v = u (ΔT) n, where v and n are the constants depending on the nature of the materials involved. The thermal properties of materials such as heat of mixing, entropy of fusion, roughness parameter, interfacial energy, and excess thermodynamic functions were computed from the enthalpy of fusion values, determined by differential scanning calorimeter (Mettler DSC-4000) system. The role of solid-liquid interfacial energy on morphologic change of monotectic growth has also been discussed. The microstructures of monotectic and eutectics were taken which showed lamellar and federal features. © 2011 Akadémiai Kiadó, Budapest, Hungary.
Thermal, physicochemical and microstructural studies of organic analog of nonmetal-nonmetal monotectic alloy
(2010) K.P. Sharma; R.S.B. Reddi; Shiva Kant; R.N. Rai
The phase equilibrium of an organic analogue of a nonmetal-nonmetal system, involving resorcinol (R)-1,4-diiodobenzene (DIB), was established which shows solid is in equilibrium with liquid as well as two immiscible liquid phases are also in equilibrium with a liquid of single phase. The phase diagram study infers the formation of a monotectic and a eutectic at 0.05 and 0.97 mole fractions of resorcinol, respectively. Using X-ray diffraction technique, the range of solid solubility of R in DIB and DIB in R was studied. The thermal properties of materials such as heat of mixing, entropy of fusion, roughness parameter, interfacial energy and excess thermodynamic functions were computed from the enthalpy of fusion values, determined using differential scanning calorimeter (DSC) method. The solid-liquid interfacial energy shows the applicability of non-wetting condition. The effect of solid-liquid interfacial energy on morphological change of monotectic growth has also been discussed. The microstructures of monotectic, eutectic and pure components were taken and have shown their peculiar characteristic features. © 2009 Elsevier B.V. All rights reserved.
Thermal, solid-liquid equilibrium, crystallization, and microstructural studies of organic monotectic alloy: 4,4′-Dibromobiphenyl-succinonitrile
(2009) R.N. Rai; R.S.B. Reddi
The phase equilibrium data on an organic analogue of a metal-nonmetal system involving succinonitrile-4,4′-dibromobiphenyl shows two immiscible liquid phases are in equilibrium with a single liquid phase. The phase diagram study infers the formation of a eutectic and a monotectic with a large miscibility gap containing 0.9997 and 0.15 mole fractions of succinonitrile, respectively. The consolute temperature being 67.0 °C above the monotectic horizontal. The thermal study such as heat of mixing, entropy of fusion, roughness parameter, interfacial energy and excess thermodynamic functions were calculated from the enthalpy of fusion values, determined using differential scanning calorimeter (DSC) method. The effects of solid-liquid interfacial energy on morphological change of monotectic have also been discussed. The microstructures of monotectic, eutectic and pure components show their peculiar characteristic features. © 2009.