Study of Kinetics Involved in Oxidation of Nonferrous Metal Sulphides

In the present investigation, an attempt has been done to study the simultaneous effects of the major processing variables on the extent of oxidation of commercially pure sphalerite ore pellets. These process variables taken into consideration were time and temperature. The oxidation was carried inside a muffle furnace where there was mild oxidation in the presence of atmospheric air. The pellets were charged for roasting inside the furnace in a graphite crucible. This process of roasting was carried out at four temperatures 7500 C, 8000 C , 8500 C and 9000 C .The project goal is to compare the oxidation or roasting at different temperature and time. At all instance of comparison one of the parameter was kept constant. The percentage (degree) of oxidation of sphalerite pellets was calculated at 15, 30, 45 and60 minutes, after the furnace reached the predetermined oxidation temperature. The experiments were statistically designed such that the effect of each variable can be quantitatively assessed and compared. The results showed that, temperatures above 8500C, time remaining constant, with the increase in temperature there is increase in the rate of oxidation (roasting) of sphalerite ore pellets. Further more for a constant temperature with the increase in time of exposure, rate of oxidation of Sphalerite (ZnS) pellets increases. This is valid for temperature range above 8500C. Another observation was made that temperature remaining constant, the rate of oxidation of Sphalerite (ZnS) ore pellets increases with time of exposure to attain a maximum limit than suddenly decreases followed by increment in the rate again. This observation was made in the temperature range of less than 8000C

Organically templated rare earth sulfates with three-dimensional and layered structures

Amine-templated rare earth sulfates of the compositions: [Ln2(H2O)2(SO4)5][C2N2H10]2, I, with Ln=La, Pr or Nd, [Nd2(SO4)4(H2O)2][C4N2H12], II, [Ln2(SO4)4][C2N2H10], III, with Ln=La or Nd, [La2(SO4)4][C3N2H12], IV and [Ln2(SO4)4(H2O)4][C6N2H14]2[C2N2H8][SO4][H2O]3, with V, Ln=La, Pr or Nd, have been synthesized under hydrothermal conditions. Both I and II have three-dimensional architectures with I possessing eight-membered apertures surrounding 16-membered apertures, and II having 12 membered apertures. Both III and V have interesting layered structures with LnO3 layers possessing (6, 3) net topology and the amine located in between the layers. V has a layered structure wherein the SO4 tetrahedra and the LnO9 polyhedra join together to form (4, 4) net sheets, with two different amines as well as the sulfate ions residing in the interlamellar space

The first organically templated open-framework metal selenate with a three-dimensional architecture

A three-dimensional metal selenate of the formula [C2N2H10][La2(SeO4)4(H2O)3]·H2O, comprising La2Se4 building units and possessing 12-membered channels, has been prepared in an acidic medium under hydrothermal conditions

Anisotropic ferromagnetism in carbon doped zinc oxide from first-principles studies

A density functional theory study of substitutional carbon impurities in ZnO has been performed, using both the generalized gradient approximation (GGA) and a hybrid functional (HSE06) as exchange-correlation functional. It is found that the non-spinpolarized C$_\mathrm{Zn}$ impurity is under almost all conditions thermodynamically more stable than the C$_\mathrm{O}$ impurity which has a magnetic moment of $2\mu_{\mathrm{B}}$, with the exception of very O-poor and C-rich conditions. This explains the experimental difficulties in sample preparation in order to realize $d^{0}$-ferromagnetism in C-doped ZnO. From GGA calculations with large 96-atom supercells, we conclude that two C$_\mathrm{O}$-C$_\mathrm{O}$ impurities in ZnO interact ferromagnetically, but the interaction is found to be short-ranged and anisotropic, much stronger within the hexagonal $ab$-plane of wurtzite ZnO than along the c-axis. This layered ferromagnetism is attributed to the anisotropy of the dispersion of carbon impurity bands near the Fermi level for C$_{\mathrm{O}}$ impurities in ZnO. From the calculated results, we derive that a C$_{\mathrm{O}}$ concentration between 2% and 6% should be optimal to achieve $d^{0}$-ferromagnetism in C-doped ZnO.Comment: 9 pages, 7 figure

Economics and yield performance of some short duration fruit and medicinal crops under agrisilvicultural system in rainfed uplands of Odisha

A field experiment was conducted during 2011-12 in an agrisilvicultural system consisting of two silvicultural species viz. Acacia mangium (mangium) and Gmelina arborea (gamhar) planted in 2000 at a spacing of 8m x 2m and four agricultural crops viz. Ananas comosus (pineapple), Aloe vera (aloevera), Andrographis paniculata(kalmegh) and Curcuma amada (mangoginger) were raised in the 1st week of July, 2011.The maximum volume increment were achieved by mangium with pineapple (16.53 m3/ha). Pineapple also registered the maximum fruit yield of 9981Kgha-1 under mangium and minimum under gamhar (9106 Kgha-1). The fresh leave yield of aloevera (8635Kg ha-1) was maximum under mangium which is statistically at par with gamhar. However, kalmegh recorded maximum dry plant yield of 1239 Kgha-1 under open condition followed by 1072 Kgha-1 under gamhar and 823 Kgha-1 under mangium. Similarly, mangoginger exhibited maximum rhizome yield of 3300 Kgha-1 under open condition followed by 1979 Kgha-1 under gamhar and 1597 Kgha-1 under mangium. The trend of crop yield under both the trees and open condition was: Pineapple >Aloevera>Mangoginger>Kalmegh. A. mangium with pineapple based agrisilvicultural system recorded the highest gross return, net return and BCR as compared to other agrisilvicultural systems and sole crops

Pressure Drop Prediction in Fluidized Dense Phase Pneumatic Conveying using Machine Learning Algorithms

Modeling of pressure drop in fluidized dense phase conveying (FDP) of powders is a tough work as the flow comprises of various interactions among solid, gas and pipe wall. It is difficult to incorporate these interactions into a model. The pressure drop depends on flow, material and geometrical parameters. The existing models show high error when applied to other pipeline configurations of varying pipeline lengths or diameters. The current study investigates the capability of machine learning (ML) techniques to estimate the drop in pressure in FDP conveying of powders. Pneumatic conveying experimental data were used for training the network and then for predicting the pressure drop. For estimating the pressure drop, four distinct ML algorithms light gradient boosting machine (LighGBM)), multilayer perception (MLP), K-nearerst neighbors (KNN), extreme gradient boosting (XGBoost), and were selected. XGBoost model performed better than other models chosen for the study with ±5% error margin while training and testing the data, and ±10% error margin in validating the data.  MLP, XGBoost, KNN, and LightGBM models predicted the data of pressure drop with MAE of 5.05, 1.19, 5.72, and 2.85, respectively, for training as well as testing data. Among the four models considered, the model using XGBoost algorithm performed the best, whereas the model using KNN algorithm performed poorly in predicting the FDP conveying pressure drop

Co3(SO4)3(OH)2[enH2]: a newS= 3/2 Kagome-type layered sulfate with a unique connectivity

The Kagome lattice, comprising a two-dimensional array of corner-sharing equilateral triangles, is central to the exploration of magnetic frustration. In such a lattice, antiferromagnetic coupling between ions in triangular plaquettes prevents all of the exchange interactions being simultaneously satisfied and a variety of novel magnetic ground states may result at low temperature. Experimental realization of a Kagome lattice remains difficult. The jarosite family of materials of nominal composition AM3(SO4)2(OH)6 (A = monovalent cation; M= Fe3+, Cr3+), offers perhaps one of the most promising manifestations of the phenomenon of magnetic frustration in two dimensions. The magnetic properties of jarosites are however extremely sensitive to the degree of coverage of magnetic sites. Consequently, there is considerable interest in the use of soft chemical techniques for the design and synthesis of novel materials in which to explore the effects of spin, degree of site coverage and connectivity on magnetic frustration

Exact Thermodynamics of the Double sinh-Gordon Theory in 1+1-Dimensions

We study the classical thermodynamics of a 1+1-dimensional double-well sinh-Gordon theory. Remarkably, the Schrodinger-like equation resulting from the transfer integral method is quasi-exactly solvable at several temperatures. This allows exact calculation of the partition function and some correlation functions above and below the short-range order (``kink'') transition, in striking agreement with high resolution Langevin simulations. Interesting connections with the Landau-Ginzburg and double sine-Gordon models are also established.Comment: 4 pages, 3 figures (embedded using epsf), uses RevTeX plus macro (included). Minor revision to match journal version, Phys. Rev. Lett. (in press

Fragmentation of a Circular Disc by Impact on a Frictionless Plate

The break-up of a two-dimensional circular disc by normal and oblique impact on a hard frictionless plate is investigated by molecular dynamics simulations. The disc is composed of numerous unbreakable randomly shaped convex polygons connected together by simple elastic beams that break when bent or stretched beyond a certain limit. It is found that for both normal and oblique impacts the crack patterns are the same and depend solely on the normal component of the impact velocity. Analysing the pattern of breakage, amount of damage, fragment masses and velocities, we show the existence of a critical velocity which separates two regimes of the impact process: below the critical point only a damage cone is formed at the impact site (damage), cleaving of the particle occurs at the critical point, while above the critical velocity the disc breaks into several pieces (fragmentation). In the limit of very high impact velocities the disc suffers complete disintegration (shattering) into many small fragments. In agreement with experimental results, fragment masses are found to follow the Gates-Gaudin-Schuhmann distribution (power law) with an exponent independent of the velocity and angle of impact. The velocity distribution of fragments exhibit an interesting anomalous scaling behavior when changing the impact velocity and the size of the disc.Comment: submitted to J. Phys: Condensed Matter special issue on Granular Medi