Nasir Amin

Enhancement in growth and yield of mushroom using magnetic field treatment

Abstract The magnetic treatment effects on mushroom spawn growth and yield were studied. The spawn of mushroom were exposed to full-wave rectified sinusoidal magnetic field. The spawn were grown after magnetic field treatment under controlled laboratory conditions. The magnetic field treatment resulted in significant increase (P<0.05) in the growth and yield of mushroom. The number of pin heads formed, number of pin heads developed into mature mushrooms, fresh (wet) and dry masses increased up to 38.18, 34.83, 76.43, and 38.26%, respectively, while reduction in number of days for spawn complete running and number of days for appearance of pin heads was found to be -3.14 and -26.86%, respectively.

Thermodynamic, electronic, and magnetic properties of intrinsic vacancy defects in antiperovskite Ca3SnO

The density functional theory based total energy calculations are performed to examine the effect of charge neutral and fully charged intrinsic vacancy defects on the thermodynamic, electronic, and magnetic properties of Ca3SnO antiperovskite. The chemical stability of Ca3SnO is evaluated with respect to binary compounds CaO, CaSn, and Ca2Sn, and the limits of atomic chemical potentials of Ca, Sn, and O atoms for stable synthesis of Ca3SnO are determined within the generalized gradient approximation parametrization scheme. The electronic properties of the pristine and the non-stoichiometric forms of this compound have been explored and the influence of isolated intrinsic vacancy defects (Ca, Sn, and O) on the structural, bonding, and electronic properties of non-stoichiometric Ca3SnO are analyzed. We also predict the possibility of achieving stable ferromagnetism in non-stoichiometric Ca3SnO by means of charge neutral tin vacancies. From the calculated total energies and the valid ranges of atomic chemical potentials, the formation energetics of intrinsic vacancy defects in Ca3SnO are evaluated for various growth conditions. Our results indicate that the fully charged calcium vacancies are thermodynamically stable under the permissible Sn-rich condition of stable synthesis of Ca3SnO, while tin and oxygen vacancies are found to be stable under the extreme Ca-rich condition.The density functional theory based total energy calculations are performed to examine the effect of charge neutral and fully charged intrinsic vacancy defects on the thermodynamic, electronic, and magnetic properties of Ca3SnO antiperovskite. The chemical stability of Ca3SnO is evaluated with respect to binary compounds CaO, CaSn, and Ca2Sn, and the limits of atomic chemical potentials of Ca, Sn, and O atoms for stable synthesis of Ca3SnO are determined within the generalized gradient approximation parametrization scheme. The electronic properties of the pristine and the non-stoichiometric forms of this compound have been explored and the influence of isolated intrinsic vacancy defects (Ca, Sn, and O) on the structural, bonding, and electronic properties of non-stoichiometric Ca3SnO are analyzed. We also predict the possibility of achieving stable ferromagnetism in non-stoichiometric Ca3SnO by means of charge neutral tin vacancies. From the calculated total energies and the valid ranges of atomic chemica...

The role of intrinsic vacancy defects in the electronic and magnetic properties of Sr3SnO: a first-principles study

In this study, we use first-principles electronic structure calculations to investigate the structural, electronic and magnetic properties of pristine and intrinsic vacancy containing Sr3SnO inverse perovskite. The thermodynamic stability diagram of Sr3SnO is computed which provides useful information regarding stable synthesis of this material. The limits of atomic chemical potentials of Sr, Sn and O are obtained to determine the relative stability of the formation of metal-atom and oxygen vacancies in Sr3SnO. The DFT calculations reveal Sr vacancy to be the most stable form of vacancy defect under O-rich conditions, while O and Sn vacancies are found to have low formation energies under O-poor and Sn-poor conditions, respectively. It is concluded that Sr and O vacancy containing Sr3SnO is non-magnetic, while Sn vacancy containing Sr3SnO gives rise to stable ferromagnetism. The electronic properties of pristine and Sn, O, and Sr deficient Sr3SnO are discussed. The Sn vacancy containing Sr3SnO, displays stable ferromagnetism which originates from spin-polarization of partially filled Sr dangling bonds with a predominant Sr-4d character. Our results explain the origins of experimentally observed room temperature ferromagnetism in non-stoichiometric Sr3SnO.

Phase transformation from cubic ZnS to hexagonal ZnO by thermal annealing

We have investigated the mechanism of phase transformation from ZnS to hexagonal ZnO by high-temperature thermal annealing. The ZnS thin films were grown on Si (001) substrate by thermal evaporation system using ZnS powder as source material. The grown films were annealed at different temperatures and characterized by X-ray diffraction (XRD), photoluminescence (PL), four-point probe, scanning electron microscope (SEM) and energy dispersive X-ray diffraction (EDX). The results demonstrated that as-deposited ZnS film has mixed phases but high-temperature annealing leads to transition from ZnS to ZnO. The observed result can be explained as a two-step process: (1) high-energy O atoms replaced S atoms in lattice during annealing process, and (2) S atoms diffused into substrate and/or diffused out of the sample. The dissociation energy of ZnS calculated from the Arrhenius plot of 1000/T versus log (resistivity) was found to be 3.1 eV. PL spectra of as-grown sample exhibits a characteristic green emission at 2.4 eV of ZnS but annealed samples consist of band-to-band and defect emission of ZnO at 3.29 eV and 2.5 eV respectively. SEM and EDX measurements were additionally performed to strengthen the argument.

Synthesis of Mn1-xZnxFe2O4 ferrite powder by co-precipitation method

Ferrimagnetic substances referred to as ferrites are ionic crystals whose chemical composition is of the form XFe2 O4 where X signifies a divalent metal. Magnetic Nano sized ferrites have found a significant potential in many applications, such as magnetic recording media, Ferro fluids and radar absorbing coating. Ferrites are widely used in many industrial applications due to their spontaneous magnetization. Soft ferrites of Mn-Zn, Ni-Zn and Mg-Mn are well known for their high magnetic permeability. In the present research work we have prepared fine Mn1-xZnxFe2O4 ferrite powder with varying x concentrations (0.25-0.75) by metal chloride precursors through a co-precipitation technique by pipette drop method using aqueous NaOH solution for comparing their spontaneous magnetization and particle size. The co-precipitation technique is a high way to produce chemically homogeneous powder with fine particle size in nanometers (22.5nm-74.5nm).The effect of x-concentration on the particle size of the Mn(1-x) Zn(x) ferrite has been discussed on the basis of XRD. The crystalline phases have been identified by X-ray diffraction with Cu-K? radiations. The XRD patterns have verified that the specimen has spinal type structure. The observable peaks are broad since the size of the particles is small. We have concluded that at constants temperature particle size increases with increasing x-concentrations. Effect of different concentrations of x (Zn+2) on the spontaneous magnetization of different Mn(1-x) Zn(x) Fe2O4 sample is determined. We have reached the conclusion that all the samples of Mn(1-x) Zn(x) Fe2 O4 ferrites were magnetic either of low or high magnetization. The maximum spontaneous magnetization and minimum particle size is obtained at x=0.25 (at digestion temperature=65?C).

First-principles evaluation of electronic and optical properties of (Mo, C) codoped BaHfO3 for applications in photocatalysis

In this paper, we report first-principles spin-polarized density functional theory calculations for exploring the effect of aliovalent Mo and C dopants on the electronic properties and photocatalysis potential of doped modifications of wide-bandgap cubic perovskite oxide BaHfO3 for water splitting. The structural and thermodynamic properties are computed by using the generalized gradient approximation, whereas the modified Becke-Johnson local density approximation is used to calculate the electronic structures of pristine, cation (Mo), and anion (C) monodoped and cation-anion (Mo, C) codoped BaHfO3. The spin-polarized calculations reveal that substitutional dopants CO and MoHf in the BaHfO3 lattice are thermodynamically stable. The incorporation of C in the O site reduces the bandgap of BaHfO3 and acts as a double-acceptor system, whereas a metallic character is obtained when Mo is doped into the Hf site giving rise to a double-donor system. We show that the acceptor and donor states of the C- and Mo-monodoped BaHfO3 can be passivated by (Mo, C) codoping at nearest-neighbor Hf and O sites of the BaHfO3 lattice, respectively. Analysis of the calculated electronic structure and optical absorption of (Mo, C) codoped BaHfO3 with reference to the H2O oxidation and reduction potentials reveals that this system is a suitable candidate for efficient splitting of water through photocatalysis in the visible region of the electromagnetic spectrum.In this paper, we report first-principles spin-polarized density functional theory calculations for exploring the effect of aliovalent Mo and C dopants on the electronic properties and photocatalysis potential of doped modifications of wide-bandgap cubic perovskite oxide BaHfO3 for water splitting. The structural and thermodynamic properties are computed by using the generalized gradient approximation, whereas the modified Becke-Johnson local density approximation is used to calculate the electronic structures of pristine, cation (Mo), and anion (C) monodoped and cation-anion (Mo, C) codoped BaHfO3. The spin-polarized calculations reveal that substitutional dopants CO and MoHf in the BaHfO3 lattice are thermodynamically stable. The incorporation of C in the O site reduces the bandgap of BaHfO3 and acts as a double-acceptor system, whereas a metallic character is obtained when Mo is doped into the Hf site giving rise to a double-donor system. We show that the acceptor and donor states of the C- and Mo-mono...

Enhancement of phosphors-solubility in ZnO by thermal annealing

We have demonstrated the effect of annealing temperature on the diffusion density of phosphors in zinc oxide. The P-dopant P430 was sprayed on ZnO pellets and annealed at different temperatures from 500 to 1000 °C with a step of 100 °C for one hour using a programmable furnace. The concentration of P was controlled by varying the annealing temperature and the maximum solubility of P (3% At) was achieved at annealing 800 °C determined by energy dispersive X-ray diffraction (EDX) measurements. X-ray diffraction (XRD) confirmed the hexagonal structure of ZnO and showed that the growth direction was along the c-axis. We observed a maximum up shift in the (002) plane at an annealing temperature of 800 °C, suggesting that P atoms replaced Zn atoms in the structure which results in the reduction of the lattice constant. Room temperature photoluminescence (PL) spectrum consists of a peak at 3.28 eV and related to band edge emission, but samples annealed at 800 and 900 °C have an additional donor acceptor pair peak at 3.2 eV. Hall effect measurements confirmed the p-type conductivity of the sample annealed at 800 °C.