Effect of Adiabatic Flame Temperature on Nano Alumina Powders during Solution Combustion Process

Nano ceramic alumina powders are synthesized by solution combustion synthesis using aluminium nitrate as oxidizer and urea as fuel with different fuel to oxidizer ratio. The variation of adiabatic flame temperatures are calculated theoretically for different fuel/oxidizer ratio according to thermodynamic concept and correlated with the observed flame (reaction) temperatures. A ``multi channel thermocouple setup connected to computer interfaced Keithley multi meter 2700'' is used to monitor the thermal events occurring during the process. The combustion products, characterized by XRD, show that the powders are composed of polycrystalline oxides with crystallite size of 32 to 52 nm. An interpretation based on maximum combustion temperature and the amount of gases produced during reaction for various fuel to oxide ratio has been proposed for the nature of combustion and its correlation with the characteristics of as-synthesized powder.

Synthesis, Structure, and Magnetic Properties of a New Eight-Connected Metal-Organic Framework (MOF) based on Co-4 Clusters

A hydrothermal reaction of cobalt nitrate, 4,4'-oxybis(benzoic acid) (OBA), 1,2,4-triazole, and NaOH gave rise to a deep purple colored compound Co-4(triazolate)(2)(OBA)(3)], I, possessing Co-4 clusters. The Co-4 clusters are connected together through the tirazolate moieties forming a two-dimensional layer that closely resembles the TiS2 layer. The layers are pillared by the OBA units forming the three-dimensional structure. To the best of our knowledge, this is the first observation of a pillared TiS2 layer in a metal-organic framework compound. Magnetic studies in the temperature range 1.8-300 K indicate strong antiferromagetic interactions for Co-4 clusters. The structure as well as the magnetic behavior of the present compound has been compared with the previously reported related compound Co-2(mu 3-OH)(mu(2)-H2O)(pyrazine)(OBA)(OBAH)] prepared using pyrazine as the linker between the Co-4 clusters.

Synthesis of BiFeO by carbonate precipitation

Magnetoelectric multiferroic BiFeO3 (BFO) was synthesized by a simple carbonate precipitation technique of metal nitrate solutions. X-ray powder diffraction and thermo-gravimetric analysis (TGA) revealed that the precipitate consists of an intimate mixture of crystalline bismuth carbonate and an amorphous hydroxide of iron. The precipitate yielded BiFeO3 at an optimal calcination temperature of similar to 560A degrees C. Energy dispersive X-ray (EDX) analysis showed 1:1 ratio between Bi and Fe in the oxide. X-ray photoelectron spectroscopy (XPS) studies confirmed that Fe to be in +3 oxidation states both in the precipitated powder and BiFeO3. The synthesized BFO exhibits a very weak ferromagnetic correlation at room temperature and the degree of which increases slightly on cooling down to 10 K suggesting alteration in the long range spatial modulation of the spins arrangement as compared to the bulk BiFeO3.

Nitrates-melt synthesized LiNi0.8Co0.2O2 and its performance as cathode in Li-ion cells

Layered LiNi0.8Co0.2O2 crystallizing in R (3) over barm space group is synthesized by decomposing the constituent metal-nitrate precursors. Oxidizing nature of metal nitrates stabilizes nickel in +3 oxidation state, enabling a high degree of cation ordering in the layered LiNi0.8Co0.2O2. The powder sample characterized by XRD Rietveld refinement reveals <2% Li-Ni site exchange in the layers. Scanning electron microscopic studies on the as-synthesized LiNi0.8Co0.2O2 sample reflect well defined particles of cubic morphology with particle size ranging between 200 and 250 nm. Cyclic voltammograms suggest that LiNi0.8Co0.2O2 undergoes phase transformation on first charge with resultant phase being completely reversible in subsequent cycles. The first-charge-cycle phase transition is further supported by impedance spectroscopy that shows substantial reduction in resistance during initial de-intercalation. Galvanostatic charge-discharge cycles reflect a first-discharge capacity of 184 mAh g(-1) which is stabilized at 170 mAh g(-1) over 50 cycles.

Preparation and characterization chemistry of nano-crystalline Ni-Cu-Zn ferrite

In submitted research; nanocrystalline powders having elements Ni0.5Cu0.25Zn0.25Fe2 xInxO4 with varied amounts of indium ( x = 0.0, 0.1, 0.2, 0.3 and 0.4) were grown-up by modified citrate to nitrate alchemy. The realism of single phase cubic spinel creation of the synthesized ferrite samples was studied by the DTA-TGA, XRD, SEM, EDX, FT-IR, VSM and dielectric measurements. SEM was applied to inspect the morphological variations and EDX was used to determine the compositional mass ratios. The studies on the dielectric constant (epsilon'), dielectric loss (epsilon `'), loss tangent (tan delta), ac conductivity (sigma(ac)), resistive and reactive parts of the impedance analysis (Z' and Z `') at room temperature were also carried out. The saturation magnetizations (Ms) were determined using the vibrating sample magnetometer (VSM). Ms. decreased with the increase In3+ doping content, as Fe3+ of 5(mu B) ions are replaced by In3+ of 5 mu(B) ions. (C) 2012 Elsevier B. V. All rights reserved.

Rapid synthesis and characterization of an oxygen-deficient defect perovskite La4BaCu5O13+d phase

Oxygen-deficient defect perovskite La4BaCu5O13+d phase has been synthesized by the nitrate-citrate gel combustion method at 950 C for 2 h. Structural parameters were refined by the Rietveld refinement method using room-temperature powder XRD data. The La4BaCu5O13+d crystallizes in the tetragonal structure with space group P4/m (no. 83) and having the lattice parameters a=8.6508 c=3.8606 (1) Å and (2) Å, respectively. Oxygen content was determined by the iodometric titration. Low-temperature resistivity result reveals that La4BaCu5O13+d compound exhibit metallic behavior up to 15 K.

YGa1-xMnxO3: A novel purple inorganic pigment

A purple inorganic pigment, YGa1-xMnxO3 (0 < x <= 0.10), based on hexagonal YGaO3 is reported here. The metastable series of oxides were prepared by a sol-gel technique where the dried gels, obtained from aqueous solutions of metal nitrate-citric acid mixtures, were calcined for a short duration in a preheated furnace around 850 degrees C. The purple colour of the oxides arises from the specific trigonal bipyramidal ligand field around Mn-III in a YGaO3 host. Other hexagonal RGaO3 hosts for R = Lu, Tm and Ho substituted with Mn-III also produce similar purple coloured materials.

Influence of anthropogenic contamination on groundwater chemistry in Mulbagal town, Kolar District, India

Geochemical studies are performed to examine the impact of leachate infiltration from on-site sewage disposal systems on the groundwater chemistry in Mulbagal town, Kolar District, Karnataka State, India. The leachate infiltration imposed nitrate concentrations ranging from 4 mg/L to 388 mg/L in the groundwater samples; it was observed that 79% of the samples exhibited nitrate concentrations in excess of drinking water permissible limit (45 mg/L). The average (of 43 measurements) E. coli levels in the groundwater samples corresponded to 189 MPN/100 mL and 55% of the samples tested exhibit pathogen contamination. Results also showed that the groundwater in the study area is characterized by acidic pH, large calcium + magnesium ion and Na/Cl ratios of < unity causing majority of the ground water samples to classify as Ca-Mg-Cl type and Na-Cl type. Saturation index (SI) computation using Visual MINTEQ program showed that the groundwater samples are under-saturated with respect to calcite. The theoretical SI values (of calcite) however suggested that the groundwater samples ought to be over-saturated with calcite. Under-saturation of the groundwater samples with calcite is attributed to increased dissolution of the mineral in the acidic environment of the groundwater.

Bismuth carboxylates with Brucite- and Fluorite-related structures: synthesis structure and properties

Three new compounds of bismuth, C4N2H10]center dotBi(C7H4NO4)(C7H3NO4)]center dot H2O, I, Bi(C5H3N2O4) (C5H2N2O4)], II, and Bi(mu(2)-OH)(C7H3NO4)], III, have been prepared by the reaction between bismuth nitrate and heterocyclic aromatic dicarboxylic acids, 2,6-pyridinedicarboxylic acid, 4,5-imidazoledicarboxylic acid, and 3,4-pyridinedicarboxylic acid, respectively, under hydrothermal conditions. The structures of all the compounds have linkages between Bi2O2 and the corresponding dicarboxylate forming a simple molecular unit in I, a bilayer arrangement in II, and a three-dimensional extended structure in III. The topological arrangement of the nodal building units in the structures indicates that a brucite-related layer (II) and fluorite-related arrangement (III) can be realized in these structures. By utilizing the secondary interactions, one can correlate the structure of III to a Kagome-related one. The observation of such classical inorganic related structures in the bismuth carboxylates is noteworthy. Lewis acid catalytic studies on the formation of ketal suggest the possible participatory role of the lone pair of electrons. All the compounds are characterized employing elemental analysis, IR, UV-vis, and thermal studies.

Heat mediated synthesis of silver nanoparticles using citrus limon (lemon) extract

In the present study, silver nanoparticles were rapidly synthesized by treating silver ions with Citrus limon (lemon) extract at higher temperature. The effect of process parameters like reductant concentration, mixing ratio of the reactants, concentration of silver nitrate and heating time period were studied. The formation of silver nanoparticles was confirmed by surface plasmon resonance as determined by UV-visible spectra in the range of 400-500 nm. X-ray diffraction analysis revealed the distinctive facets (111, 200, 220, 222 and 311 planes) of silver nanoparticles. Nanoparticles below 50 nm with spherical and spheroidal shape were observed from microscopic studies. The study offers a rapid method to synthesize silver nanoparticles within ten minutes of interaction with the bio-reductant.

Study of the effect of alkali mixture on V-O bond length in Oxyfluoro Vanadate glasses using Raman spectroscopy

Raman spectroscopic study on Oxyfluoro Vanadate glasses containing various proportions of lithium fluoride and rubidium fluoride was carried out to see an effect of mixture of alkali on vanadium-oxygen (V-O) bond length. Glasses with a general formula 40V(2)O(5) - 30BaF(2) - (30 - x) LiF - xRbF (x = 0-30) were prepared. Room temperature Raman spectra of these glass samples were recorded in back scattering geometry. The data presented is in ``reduced Raman intensity'' form with maximum peak scaled to 100. We have used v = Aexp(BR), where A and B are fitting parameters, to correlate the bond length R with Raman scattering frequency v. We observed that variation in bond length and its distribution about a most probable value can be correlated to the alkali environment present in these glasses. We also observed that all rubidium environment around the network forming unit is more homogenous than all lithium environment.

Metal doped nanosized titania used for the photocatalytic degradation of rhodamine B dye under visible-light

Metal-doped anatase nanosized titania photocatalysts were successfully synthesized using a sal gel process. Different amounts of the dopants (0.2, 0.4, 0.6, 0.8 and 1.0%) of the metals (Ag, Ni, Co and Pd) were utilized. The UV-Vis spectra (solid state diffuse reflectance spectra) of the doped nanoparticles exhibited a red shift in the absorption edge as a result of metal doping. The metal-doped nanoparticles were investigated for their photocatalytic activity under visible-light irradiation using Rhodamine B (Rh B) as a control pollutant. The results obtained indicate that the metal-doped titania had the highest activity at 0.4% metal loading. The kinetic models revealed that the photodegradation of Rh B followed a pseudo first order reaction. From ion chromatography (IC) analysis the degradation by-products Rhodamine B fragments were found to be acetate, chloride, nitrite, carbonate and nitrate ions.

Treatment efficacy of algae-based sewage treatment plants

Lagoons have been traditionally used in India for decentralized treatment of domestic sewage. These are cost effective as they depend mainly on natural processes without any external energy inputs. This study focuses on the treatment efficiency of algae-based sewage treatment plant (STP) of 67.65 million liters per day (MLD) capacity considering the characteristics of domestic wastewater (sewage) and functioning of the treatment plant, while attempting to understand the role of algae in the treatment. STP performance was assessed by diurnal as well as periodic investigations of key water quality parameters and algal biota. STP with a residence time of 14.3 days perform moderately, which is evident from the removal of total chemical oxygen demand (COD) (60 %), filterable COD (50 %), total biochemical oxygen demand (BOD) (82 %), and filterable BOD (70 %) as sewage travels from the inlet to the outlet. Furthermore, nitrogen content showed sharp variations with total Kjeldahl nitrogen (TKN) removal of 36 %; ammonium N (NH4-N) removal efficiency of 18 %, nitrate (NO3-N) removal efficiency of 22 %, and nitrite (NO2-N) removal efficiency of 57.8 %. The predominant algae are euglenoides (in facultative lagoons) and chlorophycean members (maturation ponds). The drastic decrease of particulates and suspended matter highlights heterotrophy of euglenoides in removing particulates.

Pt-6(II) nanoscopic cages with an organometallic backbone as sensors for picric acid

An organometallic building block 1,3,5-tris(4-trans-Pt(PEt3)(2)I(ethynyl)phenyl)benzene (1) incorporating Pt-ethynyl functionality has been synthesized and characterized. 2 + 3] self-assembly of its nitrate analogue 1,3,5-tris(4-trans-Pt(PEt3)(2)(ONO2)(ethynyl)phenyl)benzene (2) with ``clip'' type bidentate donors (L-1-L-3) separately afforded three trigonal prismatic architectures (3a-3c), respectively. All these prisms were characterized and their shapes/sizes are predicted through geometry optimization employing molecular mechanics universal force field (MMUFF) simulation. The extended p-conjugation including the presence of Pt-ethynyl functionality makes them electron rich as well as luminescent in nature. Macrocycles 3b and 3c exhibit fluorescence quenching in solution upon addition of picric acid PA], which is a common constituent of many explosives. Interestingly, the non-responsive nature of fluorescent intensity towards other electron-deficient nitro-aromatic explosives (NAEs) makes them promising selective sensors for PA with a detection limit predicted to be ppb level. Furthermore, solid-state quenching of fluorescent intensity of the thin film of 3b upon exposure to saturated vapor of picric acid has drawn special attention for infield applications.

Role of Crystal Field in Mixed Alkali Metal Effect: Electron Paramagnetic Resonance Study of Mixed Alkali Metal Oxyfluoro Vanadate Glasses

The mixed alkali metal effect is a long-standing problem in glasses. Electron paramagnetic resonance (EPR) is used by several researchers to study the mixed alkali metal effect, but a detailed analysis of the nearest neighbor environment of the glass former using spin-Hamiltonian parameters was elusive. In this study we have prepared a series of vanadate glasses having general formula (mol %) 40 V2O5-30BaF(2)-(30 - x)LiF-xRbF with x = 5, 10, 15, 20, 25, and 30. Spin-Hamiltonian parameters of V4+ ions were extracted by simulating and fitting to the experimental spectra using EasySpin. From the analysis of these parameters it is observed that the replacement of lithium ions by rubidium ions follows a ``preferential substitution model''. Using this proposed model, we were able to account for the observed variation in the ratio of the g parameter, which goes through a maximum. This reflects an asymmetric to symmetric changeover of. the alkali metal ion environment around the vanadium site. Further, this model also accounts for the variation in oxidation state of vanadium ion, which was confirmed from the variation in signal intensity of EPR spectra.