Effect of rounded corners on the magnetic properties of pyramidal-shaped shell structures

In recent years, the advance of novel chemical growth techniques has led to the fabrication of complex, three-dimensional magnetic nanostructures. The corners and edges of such realistic geometries are generally not sharp but rounded. In a previous article we have argued that high demagnetization fields in the vicinity of sharp edges lead to the formation of an asymmetric vortex state in pyramidal-shaped magnetic shell structures. The asymmetric vortex state is potentially interesting with respect to future magnetic memory devices. In this work a micromagnetic model is used to investigate the effect of rounded corners and edges on the magnetic reversal process within these pyramidal-shaped magnetic shell structures. In particular, we explore the degree of rounding, which has to be introduced in order to suppress the asymmetric vortex state. Another emphasis is placed on the magnetic reversal of (quasi-)homogeneous states within these structures. We demonstrate that the rounding of corners significantly reduces the coercivity. This complies with former studies on cuboidal structures, which suggest the important effect of corners on the magnetic reversal of homogeneous magnetic states. The present study uses a finite-element discretization for the numerical solution of the micromagnetic equations, which provides flexibility with respect to the modeling of complex shapes. In particular, this method is very accurate with respect to structures with a smooth surface

Towards environmental friendly multi-step processing of efficient mixed-cation mixed halide perovskite solar cells from chemically bath deposited lead sulphide

Organic-inorganic hybrid perovskite is the most promising active layer for new generation of solar cells. Despite of highly efficient perovskite active layer conventionally fabricated by spin coating methods, the need for using toxic solvents like dimethylformamide (DMF) required for dissolving low soluble metal precursors as well as the difficulties for upscaling the process have restricted their practical development. To deal with these shortcomings, in this work, lead sulphide as the lead metal precursor was produced by aqueous chemical bath deposition. Subsequently, PbS films were chemically converted to PbI2 and finally to mixed-cation mixed halide perovskite films. The microstructural, optical and solar cell performance of mixed cation mixed halide perovskite films were examined. Results show that controlling the morphology of PbI2 platelets achieved from PbS precursor films enabled efficient conversion to final perovskite films. Using this processing technique, smooth and pin hole-free perovskite films having columnar grains of about 800 nm and a bandgap of 1.55 eV were produced. The solar cell performance consisting of such perovskite layers gave rise to a notable power conversion efficiency of 11.35% under standard solar conditions. The proposed processing technique is very promising towards an environmentally friendly method for the production of large-scale high efficient perovskite solar cells

Nanomagnetism and spintronics: fabrication, materials, characterization and applications

Nanomagnetism and spintronics are two close subfields of nanoscience, explaining the effect of substantial magnetic properties of matter when the materials fabrication is realized at a comparable length size. Nanomagnetism deals with the magnetic phenomena specific to the structures having dimensions in the submicron range. The fact that the electronic transport properties of materials are dependent on the magnetic properties' artificial nanostructures, i.e., giant magnetoresistance (GMR) or tunneling magnetoresistance (TMR), has revolutionized spintronics science and technology. This book ex

Three-dimensional ferromagnetic architectures with multiple metastable states

We demonstrate controllable dual-bath electrodeposition of nickel on architecture-tunable three-dimensiona

Effect of Disinfectants on the Hardness of Dental Stones

Background and Aim : Considering the risk of cross contamination, disinfection of dental stones is essential provided that their mechanical and structural properties remain unchanged. The aim of this study was to evaluate the effect of disinfection on the hardness of dental stones .   Materials and Methods : In this experimental study, 40 discs were fabricated of type III and IV dental stones and divided into three groups. The three understudy chemical disinfectants namely 1% Virkon, 0.525% hypochlorite and slurry water were sprayed on samples in each group. The hardness of sprayed samples was evaluated by measuring the width of scratch according to the Mohs scale of mineral hardness. Surfaces of sprayed samples were also inspected by optical microscopy. Data were analyzed using Kruskal-Wallis and Mann-Whitney tests (P<0.05 ).   Results : Mohs scale of mineral hardness revealed that the width of scratches was narrower in samples sprayed with Virkon than in those sprayed with hypochlorite and slurry water. In type III dental stone specimens, the maximum width was observed in samples sprayed with slurry water (1.35±0.02) and the minimum width was observed in Virkon group samples (0.97±0.01). For type IV, the maximum and minimum widths were observed in samples sprayed with slurry water (1.20±0.01) and Virkon (0.61±0.01), respectively . In both types of stones, no significant differences were noted between the sprayed groups, while the differences between each sprayed group and the control stones (no spraying) were significant .   Conclusion : Surface hardness of dental stones decreased after spraying them with the three understudy disinfectants. Dental stones sprayed with Virkon exhibited the lowest reduction in hardness

Dimethylformamide-free synthesis and fabrication of lead halide perovskite solar cells from electrodeposited PbS precursor films

A multi-step dimethylformamide (DMF)-free green synthesizing method based on (i) initial electrodeposition of lead precursor, i.e. lead sulfide (PbS) on mesoporous TiO2/fluorine-doped tin oxide (FTO) conductive glasses substrates, (ii) subsequent conversion of PbS to PbI2 and (iii) synthesis of methylammonium lead triiodide (CH3NH3PbI3) perovskite film and their microstructural, optical and solar cell performance are described. Different electrodeposition techniques including direct current and cyclic voltammetry deposition were investigated to produce PbS films. We find that the perovskite films produced based on PbS deposited by cyclic voltammetry exhibit compact layer consisting of cuboid grains with an average size of approximately 800 nm and a bandgap of 1.58 eV whose properties are comparable to those of perovskite films generally prepared by conventional methods like spin coating. It was observed that uniform perovskite layers deposited under different conditions as the absorber layer generate a power conversion efficiency (PCE) of up to 7.72% under the standard AM 1.5 condition in the first attempt by this fabrication approach. PCEs obtained under different electrodeposition conditions were improved by eliminating of pores between the cuboid perovskite crystallites. This approach neglects employing hazardous solvents from the routine perovskite solar cell fabrication method and has potential to enhance its PCE similar to the common strategies by spin-coating methods improved over last decade by further modification of the electrodeposition process of the metal precursors and other steps towards highly efficient green perovskite solar cells

Corrosion Behavior of a Nickel-Base Dental Casting Alloy in Artificial Saliva Studied by Weight Loss and Polarization Techniques

Objectives:Corrosion of Ni-Cr base dental alloys in saliva influences their application in prostheses. Material and methods: Corrosion behaviour of the NiCr alloy was studied using two techniques including weight lossdescribed by corrosion rate (CR) per mil per year (mpy)and potentiodynamic polarizationdescribed by corrosion potential (CP) in mV and current density (CD) in mA/cm2in artificial saliva with different pH.Surface morphology was studied using scanning electron microscopy (SEM). Statistical difference was assessed using one-way ANOVA and post-HOC Tukey-HSD tests with a difference significance of 95%. Results:In weight loss method,CRwas 71.95±3.40, 17.26±1.03, 8.92±0.35 and 6.93±0.54mpy in pH values of 2.5, 5, 7 and 9, respectively. CR obtained in pH of 2.5 was significantly different with that in other groups, but those obtained in pH of 5, 7 and 9 were not significantly different. In polarization method, CPwere significantly different. CD measured in pH of 2.5 and 5 was significantly different with the rest of pH values. Corrosion rates in pH of 7 and 9 were not significantly different. Conclusion:The results obtained by both techniques are consistent. Corrosion resistance decreases as pH increases. In more acidic saliva, corrosion rate is greater likely due to the higher dissolution rate of Ni through weak passivation. However, the less acidic saliva leads to formation of more stable passive film on Ni and therefore the dissolution of Ni decreases leading to lower corrosion rates