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51.
52.
A systematic study on the water-intake capacity of the microemulsion formed using a catanionic surfactant (synthesized by taking equimolar mixture of acid and amine) with varying hydrocarbon chain length of the acid has been carried out. A decrease in the water-intake capacity with increase in the chain length was observed. Shorter chain length of co-surfactant (1-butanol compared to 1-octanol) led to higher water-intake capacity of microemulsions which may also be attributed to the high hydrophilic-lipophilic balance (HLB) of 1-butanol. Three new microemulsions based on catanionic surfactants have been used to synthesize quantum dots of CdS. The size of CdS quantum dots decreased with increase in chain length of the acid component of the catanionic surfactant. 相似文献
53.
Stable, high-power, second-harmonic-generation (SHG) of a compact CW Ytterbium (Yb) fiber laser at 1064 nm into the green
and its use as a pump source for CW singly-resonant optical parametric oscillator (SRO) is demonstrated. Using a simple single-pass
SHG configuration in MgO:sPPLT, as much as 9.6 W of single-frequency green radiation at 532 nm is generated from 30 W of fundamental
power at a conversion efficiency of 32.7% in a Gaussian spatial profile with a beam quality factor of M
2 < 1.3. Thermal effects have been investigated at different fundamental power levels and various thermal management schemes
are employed to maximize the second-harmonic power. The green source is successfully deployed to pump a CW SRO tunable over
855–1408 nm, generating up to 2.1 W of idler at 1168 nm. The peak-to-peak idler power stability is better than 10.7% over
40 min, with beam quality factor M
2 < 1.26 for the idler and M
2 < 1.52 for the signal. 相似文献
54.
U. P. Verma N. Devi S. Sharma P. Jensen 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,81(4):381-386
First-principles calculations based on the density functional theory are
performed to study the structural properties, spin-polarized electronic band
structures, density of states and magnetic properties of the zinc blende
In1−
x
Mn
x
Sb (x = 0.125, 0.25, 0.50, 0.75, 1.0).
The calculated lattice constants of In1−
x
Mn
x
Sb
obey the Vegard’s law with a marginal upward bowing. With the increase of Mn
concentration in In1−
x
Mn
x
Sb, a transition from
the semi-metallic to the half-metallic behavior happens such that the
majority-spin valence states crosses the Fermi level and the minority-spin
states have a gap at the Fermi level. A large exchange splitting
(∼ 4 eV) is observed between Mn 3d states of the majority-spins
and the minority-spins. The total magnetic moment of
In1−
x
Mn
x
Sb half-metallic ferromagnets per Mn
atom basis is 4μ
B. The total magnetic moment per Mn atom
indicate that Mn atoms act as acceptors in InSb and contribute to holes in
the lattice of InSb. Due to p-d hybridization, the free space charge of Mn
reduces that results a loss in its magnetic moment. The loss in the magnetic
moment of the Mn atoms is converted into a small local magnetic moments on
the In and Sb sites. 相似文献
55.
We report ab-initio calculations of the structural, electronic, magnetic and optical properties of the alloy Cd1-xMnxTe as a function of the Mn concentration ‘x’. Ab-initio calculations are based on the density functional theory (DFT) within the generalized gradient approximation (GGA). The calculated lattice constants of the Cd1-xMnxTe alloys exhibit Vegard's law downward bowing parameter. For the minority spin channel the Fermi level shifts toward higher energy with the value of ‘x’ in Cd1-xMnxTe. The spin-exchange splitting energy Δx(d) increases with increasing ‘x’ in Cd1-xMnxTe and the values of p-d exchange splitting energy Δx(pd) of Cd1-xMnxTe show that the effective potential for the minority spin is more attractive than that for the majority spin. The values of exchange constants N0α and N0β obtained for Cd1-xMnxTe are in agreement with the reported data. The magnetic moment per Mn atom reduces from its free space charge value of 5μB to around 4μB due to p-d hybridization and this results into an appearance of small local magnetic moments on the non-magnetic Cd and Te sites. The absorption threshold shifts toward higher energy and the static refractive index decreases with the increasing value of ‘x’ in Cd1-xMnxTe. 相似文献
56.
U.P. Verma Sonu SharmaNisha Devi P.S. BishtP. Rajaram 《Journal of magnetism and magnetic materials》2011,323(5):394-399
We have investigated the structural, electronic and magnetic properties of the diluted magnetic semiconductor (DMS) Cd1−xMnxTe (for x=0.75 and 1.0) in the zinc blende (B3) phase by employing the ab-initio method. Calculations were performed by using the full potential linearized augmented plane wave plus local orbitals (FP-L/APW+lo) method within the frame work of spin-polarized density functional theory (SP-DFT). The electronic exchange-correlation energy is described by generalized gradient approximation (GGA). We have calculated the lattice parameters, bulk modulii and the first pressure derivatives of the bulk modulii, spin-polarized band structures, and total and local densities of states. We estimated the spin-exchange splitting energies Δx(d) and Δx(pd) produced by the Mn3d states, and we found that the effective potential for the minority spin is more attractive than that of the majority spin. We determine the s-d exchange constant N0α (conduction band) and p-d exchange constant N0β (valence band) and these somewhat agree with a typical magneto-optical experiment. The value of calculated magnetic moment per Mn impurity atom is found to be 4.08 μB for Cd0.25Mn0.75Te and 4.09 μB for Cd0.0Mn1.0Te. Moreover, we found that p-d hybridization reduces the local magnetic moment of Mn from its free space charge value of 5.0 μB and produces small local magnetic moments on the nonmagnetic Cd and Te sites. 相似文献
57.
58.
Dehydration of 1,4-dioxane through blend membranes of poly(vinyl alcohol) and chitosan by pervaporation 总被引:1,自引:0,他引:1
D. Anjali Devi B. Smitha S. Sridhar T.M. Aminabhavi 《Journal of membrane science》2006,280(1-2):138-147
Blend membranes prepared from poly(vinyl alcohol) (PVA) and chitosan (CS) were crosslinked with glutaraldehyde and used in the pervaporation dehydration of 1,4-dioxane. Membranes were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and X-ray diffraction (X-RD) to assess, respectively, the intermolecular interactions, thermal stability and crystallinity. Equilibrium sorption studies were carried out in pure liquids and binary mixtures of different compositions of water + 1,4-dioxane mixtures to assess the polymer–liquid interactions. The crosslinked membrane showed a good potential in breaking the azeotrope of 82 wt.% aqueous 1,4-dioxane giving a selectivity of 117 with a reasonable water flux of 0.37 kg/m2 h. The effect of operating parameters such as feed composition, membrane thickness and permeate pressure was evaluated. 相似文献
59.
P Sujatha Devi 《Journal of Non》2004,336(2):128-134
Vanadium doped silica gels were prepared from tetraethyl orthosilicate and three different inorganic vanadium precursors with formal oxidation states of V3+, V4+ and V5+ respectively. Optical and EPR studies were carried out on the dried gels to understand the changes in the oxidation state and coordination of vanadium in the doped silica gel matrix. The observed optical and EPR results provide very strong evidence to establish that irrespective of the starting material, vanadium is stabilized as vanadyl ion in the gel monoliths. EPR studies on the powdered samples corroborate the optical data on the gel samples and confirmed that the stabilized vanadyl ion is situated in a distorted octahedral geometry in these silica gels. 相似文献
60.
Shiva Raj Sarala Devi Ch. Seshikala G. Ram Reddy M. G. 《Journal of Chemical Sciences》1992,104(1):15-20
The proton ligand constants of 4-chloro and 4-amino picolinic acid N-oxide and the formation constants of corresponding binary
chelates of Cu(II) and Ni(II) have been measured at 30°C and 0.1M ionic strength in varying percentages of dioxane-water,
acetone-water, ethanol-water and isopropanol-water. The results are discussed with reference to the change in dielectric constants
of water in the presence of organic solvent, change in the structuredness of water, change in hydrogen bonding ability of
the organic solvent in water, solvent basicity and proton solvation by organic solvent. The values have been compared with
aqueous and mixed aqueous systems of picolinic acid N-oxide and 4-methoxy picolinic acid N-oxide. 相似文献