Characteristics investigation on heat transfer growth of sonochemically synthesized ZnO-DW based nanofluids inside square heat exchanger

Journal of Thermal Analysis and Calorimetry - In recent decades, the growth of heat transfer using nanomaterials in the conventional base fluid has caught the attention of researchers...     

Controlled hydrothermal growth of ZnO nanostructures by sequestering the Zn metal ions with the chelating agent EDTA

In the present work, a controlled growth of ZnO nanostructures by manipulating Zn metal ion concentration by the chelating action of ethylene diaminetetra acetic acid in hydrothermal method is studied. EDTA produces metal–chelate complex by the formation of bidentate ligand with Zn²⁺ in the solution and diminishes the reactivity of Zn metal cations. Concentration of EDTA in the mother solution was varied in different ranges like 3, 5 and 10 mM while retaining the zinc metal salt and the NaOH concentration the same. Three different morphologies of wurtzite structured ZnO nanostructures such as nanorods-bunch, separate/discrete uniformly sized hexagonal nanorods and tapered flower petals like shapes are achieved by 3, 5 and 10 mM strengths of EDTA, respectively. The medium concentration 5 mM of EDTA is found to have moderate control over producing ZnO nanostructures of uniform diameter and a high aspect (length to diameter) ratio. An array of vertically aligned free standing ZnO nanorods with uniform spacing is successfully achieved by the addition of 5 mM of EDTA in the mother solution and the same is studied for its fluorescence property at an excitation of 325 nm and it has exhibited a characteristic UV emission of ZnO around 383 nm.     

Hydrogen bonding interaction and topological insights of the electron localization/delocalization of l- arginine acetate

The vibrational spectral studies of the semi-organic material l- arginine acetate (LAA) are carried out with the help of density functional calculations to derive the equilibrium geometry as well as the vibrational wavenumbers and intensities of the spectral bands. The vibrational spectrum assignments are performed using normal coordinate analysis (NCA) in accordance with the scaled quantum mechanical force field approach (SQMFF). Vibrational spectra confirm the COO- modes split due to intra- and intermolecular association based on C–O….H, N–H….O, and O–H?O hydrogen bonding in the molecule, which lowers carboxylate wavenumbers. The natural bond orbital (NBO) analysis and DFT computations also confirm the occurrence of strong intra and intermolecular N–H?O and O–H?O ionic hydrogen bonding between charged species, providing the non-centrosymmetric structure in the LAA crystal.     

The effect of rapid rotation on a vertical bridgman furnace at large Rayleigh number

In quasi-steady operation, convection currents in a Bridgmandevice, used for producing a semi-conductor crystal, createinhomogeneities that may make the crystal unusable. It has oftenbeen suggested that additional forces due to rotation or magnetismmight be efficacious in reducing the segregation of the elementsof the alloy. It has been found that, over a wide range of rotationrates, there is no improvement in performance due to rotationabout the vertical axis. However, numerical results that havebeen obtained previously (Lee & Pearlstein, J. Crys. Growth240, 2002) indicate that, when effects of centrifugal buoyancyare introduced, a substantial reduction in segregation is achieved.In the work reported here, by contrast, in which we extend previouslarge-Rayleigh-number asymptotic analysis to include centrifugalbuoyancy, we find no improvement in radial segregation, butrather increasing segregation with increasing rotation rate.     

TDI CAMERA APPLICATION IN DYNAMIC PHOTOMECHANICS

Optical methods for dynamic stress analysis require fast recording of the fringe patterns representing the stress distribution. Various recording techniques exist using fast framing cameras and short light pulse systems.¹ In all of these techniques the wet film processing is tedious and time consuming. Manual data analysis from the fringe patterns is cumbersome. Also, optical processing of the photographs for extracting further information requires complicated optical hardware. Hence, there were efforts from researchers to record the patterns in computer memories. The software image processing methods ease the data analysis and contrast enhancement.^2,3 Here we report the use of a special type CCD camera for dynamic applications. Details of the CCD camera operation are discussed. Application of the camera for dynamic problems is illustrated by performing a simple experiment.     

Natural bond orbital analysis, electronic structure, non-linear properties and vibrational spectral analysis of L-histidinium bromide monohydrate: a density functional theory

The spectroscopic properties of the crystallized nonlinear optical molecule L-histidinium bromide monohydrate (abbreviated as L-HBr-mh) have been recorded and analyzed by FT-IR, FT-Raman and UV techniques. The equilibrium geometry, vibrational wavenumbers and the first order hyperpolarizability of the crystal were calculated with the help of density functional theory computations. The optimized geometric bond lengths and bond angles obtained by using DFT (B3LYP/6-311++G(d,p)) show good agreement with the experimental data. The complete assignments of fundamental vibrations were performed on the basis of the total energy distribution (TED) of the vibrational modes, calculated with scaled quantum mechanics (SQM) method. The natural bond orbital (NBO) analysis confirms the occurrence of strong intra and intermolecular N-H?O hydrogen bonding.     

Intramolecular charge delocalization and nonlinear optical properties of push-pull chromophore 1-(4-N,N-dimethylaminopyridinium) acetic acid bromide monohydrate from vibrational spectra

FT-Raman and FT-IR spectra of the nonlinear optical crystal 1-(4-N,N-dimethylaminopyridinium) acetic acid bromide monohydrate have been recorded and analyzed. The equilibrium geometry, vibrational wavenumbers and the first order hyperpolarizability of the crystal have been calculated with the help of density functional theory computations. The assignments of the vibrational spectra have been carried out with the help of Scaled Quantum Mechanic force field theory. Optimized geometry gives the charge transfer interaction of the pyridine ring and the amino group in the electron-donor side of the nonlinear optic chromophore. Electron–phonon coupling and O–H?O interactions in making the molecule nonlinear optical active have been analyzed based on the vibrational spectral features. The Natural Bond Orbital analysis confirms the occurrence of strong intermolecular O–H?O hydrogen bonding.     

Molecular structure, spectroscopic studies and first-order molecular hyperpolarizabilities of p-amino acetanilide

The infrared absorption, Raman spectra and SERS spectra of p-amino acetanilide have been analyzed with the aid of density functional theory calculations at B3LYP/6-311G(d,p) level. The electric dipole moment (mu) and the first hyperpolarizability (beta) values of the investigated molecule have been computed using ab initio quantum mechanical calculations. The calculation results also show that the synthesized molecule might have microscopic nonlinear optical (NLO) behavior with non-zero values. Computed geometries reveal that the PAA molecule is planar, while secondary amide group is twisted with respect to the phenyl ring is found, upon hydrogen bonding. The hyperconjugation of the C=O group with adjacent C-C bond and donor-acceptor interaction associated with the secondary amide have been investigated using computed geometry. The carbonyl stretching band position is found to be influenced by the tendency of phenyl ring to withdraw nitrogen lone pair, intermolecular hydrogen bonding, conjugation and hyperconjugation. The existence of intramolecular C=O...H hydrogen bonded have been investigated by means of the natural bonding orbital (NBO) analysis. The influence of the decrease of N-H and C=O bond orders and increase of C-N bond orders due to donor-acceptor interaction has been identified in the vibrational spectra. The SERS spectral analysis reveals that the large enhancement of in-plane bending, out of plane bending and ring breathing modes in the surface-enhanced Raman scattering spectrum indicates that the molecule is adsorbed on the silver surface in a 'atleast vertical' configuration, with the ring perpendicular to the silver surface.     

Vibrational spectra and ab initio computations of sarcosinium oxalate monohydrate

Single crystals of sarcosinium oxalate monohydrate (SOM) are grown by the slow-evaporation technique at ambient temperature, and vibrational spectroscopic analysis is carried out using NIR-FT Raman, FT-IR, and SERS spectra. The normal mode frequencies and corresponding vibrational analysis of SOM are examined theoretically using the Gaussian’98 set of quantum chemical codes. The two bands present in the SOM ν C=O region, clearly observed in the Raman spectrum, are assigned to “free” and “bonded” carbonyl groups with the hydrogen atom. Vibrational analysis indicates the presence of C-H—O hydrogen bonding interaction producing a blueshift of the C-H stretching frequency.