S.K. Mandal

Bio: S.K. Mandal is an academic researcher from Central Mechanical Engineering Research Institute. The author has contributed to research in topics: Nanocrystalline material & Sputter deposition. The author has an hindex of 10, co-authored 17 publications receiving 203 citations. Previous affiliations of S.K. Mandal include Indian Association for the Cultivation of Science & Indian Institutes of Technology.

Optical properties of nanocrystalline ZnS films prepared by high pressure magnetron sputtering

Abstract: Nanocrystalline ZnS films with different thickness (10–40 nm) were deposited onto quartz and NaCl substrates by magnetron sputtering of a ZnS target in argon plasma. All the films showed a zinc blende structure and the photoluminescence peak positions depended on the surface to volume ratio of the films. The optical absorption in these films could be explained by the combined effects of phonon and inhomogeneity broadening along with optical loss due to light scattering at the nanocrystallites.

Nanocrystalline CdTe films deposited by high-pressure sputtering: carrier transport at low temperature

Abstract: Electrical conductivities of nanocrystalline CdTe films deposited onto quartz substrates by high-pressure (~20 Pa) DC magnetron sputtering were studied as a function of temperature (188–298 K). The grain size varied within 4 to 4.7 nm with the variation of deposition temperature (Ts) within 253 to 273 K. The conductivity (σ) showed (T0/T)p dependence with p~0.5 indicating the presence of a Coulomb gap near the Fermi level. Efros–Shklovskii (ES) hopping was found to be the predominant carrier conduction mechanism in the nanocrystalline CdTe films. The width of the Coulomb gap varied within 27–41 meV depending on the deposition conditions. Cross-over from ES to Mott's hopping was observed. The existing theoretical models were used for estimating hopping energy (29 to 42 meV) and hopping distance (2.8 to 5.1 nm) in the films.

Analgesic activity of methanol extract of Eupatorium adenophorum Spreng. leaves.

Abstract: The methanol extract of the leaves of E. adenophorum (100, 200 and 300 mg/kg, po) showed significant analgesic activity, as compared to standard drugs diclofenac sodium and pentazocine, employing acetic acid-induced writhing test, tail immersion test and tail flick test models.

Precision farming for small agricultural farm: Indian scenario.

Abstract: Aims: Precision farming becomes more and more an accepted way of crop production and helps to achieve a sustainable environmental friendly agriculture. Furthermore, growing interest in automated data acquisition and information processing is going to form another milestone towards improved farm management and an overall trace ability in agricultural food production. The benefit and effectiveness of using precision farming techniques is highly dependent on the capabilities of the utilized technology. Study Design: The study was design based on the available report and hence it was decided to design the research work so as to collect maximum information including case studies. Place and Duration of Study: The study was undertaken at our Institute i.e. CSIR-Central Mechanical Engineering Research Institute, Durgapur, India during the period Aug. 2011 to Feb. 2012. Methodology: This research is basically focused on the work done so far on the subject precision farming for small agricultural farm. Accordingly work was reviewed and consolidated points are discussed in this paper in the subsequent sections. Results: Precision farming provides a new solution using a systems approach for today's agricultural issues, namely the need to balance productivity with environmental concerns. Review Article American Journal of Experimental Agriculture, 3(1): 200-217, 2013 201 Precision farming aims at increased economic returns, as well as reducing the energy input and the environmental impact of agriculture. Conclusion: The potential of this technology has already been demonstrated, but in practice, meaningful delivery is difficult as it needs large scale commercial application to realize the benefits. PA is facilitating the prospects and scope for switching over to modern agriculture leaving the traditional one by utilizing right resources in right time and management, which results an environment friendly sustainable agriculture.

Au/CdS Schottky Diode Fabricated with Nanocrystalline CdS Layer

Abstract: Schottky diodes of structure Au/nano-CdS/CBD-CdS/SnO 2 were fabricated with the nanocrystalline CdS layer deposited by the high pressure magnetron sputtering technique. The devices were characterized by current-voltage (I-V) anti capacitance-voltage (C-V) measurements. It was observed that the presence of a large amount of surface states might explain the high values of n in the nano-devices. The quantization effects of the active nano-CdS layer in the devices was confirmed from the observed peaks in the plot of conductance versus reverse bias voltage.

Hexagonal ferrites: A review of the synthesis, properties and applications of hexaferrite ceramics

Abstract: Since their discovery in the 1950s there has been an increasing degree of interest in the hexagonal ferrites, also know as hexaferrites, which is still growing exponentially today. These have become massively important materials commercially and technologically, accounting for the bulk of the total magnetic materials manufactured globally, and they have a multitude of uses and applications. As well as their use as permanent magnets, common applications are as magnetic recording and data storage materials, and as components in electrical devices, particularly those operating at microwave/GHz frequencies. The important members of the hexaferrite family are shown below, where Me = a small 2+ ion such as cobalt, nickel or zinc, and Ba can be substituted by Sr: • M-type ferrites, such as BaFe12O19 (BaM or barium ferrite), SrFe12O19 (SrM or strontium ferrite), and cobalt–titanium substituted M ferrite, Sr- or BaFe12−2xCoxTixO19 (CoTiM). • Z-type ferrites (Ba3Me2Fe24O41) such as Ba3Co2Fe24O41, or Co2Z. • Y-type ferrites (Ba2Me2Fe12O22), such as Ba2Co2Fe12O22, or Co2Y. • W-type ferrites (BaMe2Fe16O27), such as BaCo2Fe16O27, or Co2W. • X-type ferrites (Ba2Me2Fe28O46), such as Ba2Co2Fe28O46, or Co2X. • U-type ferrites (Ba4Me2Fe36O60), such as Ba4Co2Fe36O60, or Co2U . The best known hexagonal ferrites are those containing barium and cobalt as divalent cations, but many variations of these and hexaferrites containing other cations (substituted or doped) will also be discussed, especially M, W, Z and Y ferrites containing strontium, zinc, nickel and magnesium. The hexagonal ferrites are all ferrimagnetic materials, and their magnetic properties are intrinsically linked to their crystalline structures. They all have a magnetocrystalline anisotropy (MCA), that is the induced magnetisation has a preferred orientation within the crystal structure. They can be divided into two main groups: those with an easy axis of magnetisation, the uniaxial hexaferrites, and those with an easy plane (or cone) of magnetisation, known as the ferroxplana or hexaplana ferrites. The structure, synthesis, solid state chemistry and magnetic properties of the ferrites shall be discussed here. This review will focus on the synthesis and properties of bulk ceramic ferrites. This is because the depth of research into thin film hexaferrites is enough for a review of its own. There has been an explosion of interest in hexaferrites in the last decade for more exotic applications. This is particularly true as electronic components for mobile and wireless communications at microwave/GHz frequencies, electromagnetic wave absorbers for EMC, RAM and stealth technologies (especially the X and U ferrites), and as composite materials. There is also a clear recent interest in nanotechnology, the development of nanofibres and fibre orientation and alignment effects in hexaferrite fibres, and composites with carbon nanotubes (CNT). One of the most exciting developments has been the discovery of single phase magnetoelectric/multiferroic hexaferrites, firstly Ba2Mg2Fe12O22 Y ferrite at cryogenic temperatures, and now Sr3Co2Fe24O41 Z ferrite at room temperature. Several M, Y, Z and U ferrites have now been characterised as room temperature multiferroics, and are discussed here. Current developments in all these key areas will be discussed in detail in Sections 7 The microwave properties of hexagonal ferrites , 8 Magnetoelectric (ME), multiferroic (MF) and dielectric properties of hexaferrites , 9 Hexaferrite composites , 10 Hexagonal ferrite fibres , 11 Nanoscale hexagonal ferrite particles, ceramics and powders of this review, and for this reason now is the appropriate time for a fresh and critical appraisal of the synthesis, properties and applications of hexagonal ferrites.

Introduction to the Finite Element Method

Abstract: This chapter introduces the finite element method (FEM) as a tool for solution of classical electromagnetic problems. Although we discuss the main points in the application of the finite element method to electromagnetic design, including formulation and implementation, those who seek deeper understanding of the finite element method should consult some of the works listed in the bibliography section.

Theory of the linear and nonlinear optical properties of semiconductor microcrystallites

Abstract: We analyze theoretically the optical properties of ideal semiconductor crystallites so small that they show quantum confinement in all three dimensions [quantum dots (QD's)]. In the limit of a QD much smaller than the bulk exciton size, the linear spectrum will be a series of lines, and we consider the phonon broadening of these lines. The lowest interband transition will saturate like a two-level system, without exchange and Coulomb screening. Depending on the broadening, the absorption and the changes in absorption and refractive index resulting from saturation can become very large, and the local-field effects can become so strong as to give optical bistability without external feedback. The small QD limit is more readily achieved with narrow-band-gap semiconductors.

Effect of the size-induced structural transformation on the band gap in CdS nanoparticles

Abstract: The interrelation between particle size, crystal structure and optical properties in semiconductor quantum dots has elicited widespread interest. We report the first attempt at relating the size-induced transformation from a hexagonal to a cubic structure in CdS nanoparticles to a change in the band gap. CdS nanoparticles with particle size in the 0.7-10 nm range were prepared by chemical precipitation using thiophenol as a capping agent. Whereas the band gap for bulk hexagonal CdS is about 2.5 eV, that for 1 nm cubic CdS nanoparticles was found to be almost 3.9 eV. We also suggest a simple mechanism (based on the periodic insertion of stacking faults) for the transformation from the cubic zinc blende structure to the hexagonal wurtzite structure.