J. Hemalatha

Magnetic and ultrasonic investigations on magnetite nanofluids.

Magnetite nanofluids of various concentrations have been prepared through co-precipitation method. The structural and magnetic properties of the magnetic nanofluids have been analyzed which respectively revealed their face centered cubic crystal structure and super paramagnetic behavior. Ultrasonic investigations have been made for the nanofluids at different temperatures and magnetic fields. Open- and close-packed water structure is considered to explain the temperature effects. The inter particle interactions of surface modified nanomagnetite particle and the cluster formation are realized through the variations in ultrasonic parameters.

Magnetic and ultrasonic studies on stable cobalt ferrite magnetic nanofluid.

Stable cobalt ferrite nanofluids of various concentrations have been prepared through co-precipitation method. Structural and morphological studies of nanoparticles are made with the help of X-ray diffraction technique and Transmission Electron Microscope respectively and it is found that the particles exhibit face centered cubic structure with an average size of 14 nm. The magnetic properties of the nanofluids have been analyzed at room temperature which revealed ferromagnetic behavior and also the very low value of coupling constant which ensures the negligible interparticle interaction in the absence of magnetic field. Ultrasonic investigations have been made for the nanofluids at different temperatures and magnetic fields. The temperature effects are explained with the help of open and close-packed water structure. The inter particle interactions of surface modified CoFe2O4 particles and the cluster formation at higher concentrations are realized through the variations in ultrasonic parameters.

Ultrasonic Studies and Microchannel Flow Behavior of Copper Oxide Nanofluid

Stable suspensions of nanosized copper oxide nanoparticles in Ethylene glycol are prepared at various concentrations through ultrasonically assisted sol gel method. The structural studies are made through X‐ray diffraction technique and the nanoparticle‐fluid interaction studies are made through acoustical technique. The molecular interaction is studied as a function of concentration and temperature. The flow behaviors of nanofluids of various concentrations are investigated using the circular and rectangular microchannels of various diameters.

Acoustical Studies of the Intermolecular Interaction in Copper Oxide-Ethylene Glycol Nanofluid

Stable Copper oxide-Ethylene glycol nanofluids of different concentrations have been synthesized. The structural, morphological and particle–fluid interaction studies have been made through X-ray diffraction, HRSEM and ultrasonic technique respectively. The intermolecular interactions between nanosized copper oxide and ethylene glycol have been discussed elaborately for different concentrations and temperatures.

Negative giant magnetoresistance effect in single layered superparamagnetic polymer nanocomposite structures of poly(vinyl alcohol)–polyaniline/bismuth ferrite

Superparamagnetic polyaniline/bismuth ferrite (PANI/BFO) nanocomposite powder is synthesized through an in situ sol–gel polymerization method and it is embedded in non-magnetic poly(vinyl alcohol) (PVA) matrix to fabricate high performance flexible films. The interaction between PANI/BFO filler and PVA matrix and hence the formation of composite is identified through XRD and it is further confirmed through FTIR spectra. Vibration sample magnetometry (VSM) studies ensure the superparamagnetic nature of the composite films. The magnetoresistance measurements are made at room temperature for various current values from which it is observed that the samples exhibit a negative giant magnetoresistance (GMR) effect. The variation of GMR from 21% to 66% with filler concentration and also the non-ohmic V–I characteristics of the composite films are reported.

Ferroelectric Studies On Poly (Vinylidene Fluoride)/NiFe2O4 Polymer Nanocomposite Structures

Polyvinylidene Fluoride (PVDF) based nano composite structures are prepared by using nanosized NiFe2O4 as filler at different concentrations. The structural and morphological studies made with the help of X‐ray Diffractometer and Transmission Electron microscope are presented in this paper. The Ferroelectric property exhibited by the unpoled polymer and composite samples at different temperatures are reported. The dependence of polarization on the filler concentration and temperature are also discussed.

A Review of: “Nanofluids: Science and Technology, S. K. Das, S. U. S. Choi, W. Yu, and T. Pradeep”

“Nanofluids: Science and Technology” is an excellent book that elicits the current research developments in the field of nanofluidics which is interdisciplinary in nature. It is written in such a way that it helps the researchers in all areas of science and technology. Chapter 1 offers a comprehensive introduction of nanofluids. It begins with the pressing need for liquid cooling process in power electronics and optoelectronic devices and transportation industries. The brief account of conventional techniques such as solid-liquid suspensions and microchannel cooling which are used to enhance heat transfer is presented next. The authors have highlighted distinctly the properties of conventional fluids such as the inherently poor thermal conductivity, rapid settling, and clogging in comparison to the superior properties of the emerging nanofluids. Despite considerable previous research and development efforts on heat transfer enhancement, major improvements in cooling capabilities have been constrained because the traditional heat transfer fluids used currently in thermal management systems, such as water, oils, and ethylene glycol, have very poor thermal conductivities in the ordersof-magnitude smaller than those of most solids. This chapter also provides a review on the experimental discoveries on nanofluids which clearly show that the nanofluids exhibit superior thermal properties compared to those of conventional fluids. It reviews the mechanisms and models for the enhanced thermal transport and classifies them into structure-based, dynamics-based, and near-field radiation models. Moreover, in this chapter, the authors suggest the topics to be evaluated in future research as mentioned below: i) the basic research on nanofluids can aim at the expansion properties, cooling performance, new theories, models, and mechanisms for enhanced thermal properties; ii) the applied research can be on high volume, low cost production of stable nanofluids for commercial use; and iii) to develop green nanofluids by choosing nontoxic nanoparticles that would pose no environmental, health danger. Chapter 2 focuses on the chemical and physical aspects of synthesis techniques of varieties of nanofluids including metal and semiconductor spherical nanoparticles, anisotropic nanostructures, fullerenes, and nanotubes. The scope of the chapter is restricted to stable nanofluids and the free standing nanosystems in fluid forms. The parameters such as thermal stability, dispensability in diverse media, and chemical compatibility which are of interest in synthesis are discussed in detail. The chemical, physical, mechanical, and biological routes of synthesis are outlined. In the case of nanoparticles, emphasis has been given primarily to the solution chemistry approaches which form stable and redispersible nanoparticles. A concise summary of various methods used for the synthesis of diverse nanosystems is also included. Microemulsion-based methods and solvothermal synthesis for nanofluids, are discussed. Characterization methods such as transmission electron microscopy, optical spectroscopy, X-ray diffraction, infrared, Raman, and other spectroscopies, and Zeta potential are outlined with specific examples in the entire range of particle sizes, from nanoparticles to clusters. Chapter 3 addresses the techniques used for the measurement of thermal conductivity of liquids. The principle and experimental techniques of the transient hot wire method and temperature oscillation method are elaborated. The principle of measurement, design of apparatus, and the design of experimental procedures of both methods are discussed. The heat transfer mechanism for various types of media is also provided. The heat conduction equations for isotropic medium, steady state, and several other simpler cases are clearly explained. Four different boundary conditions viz Dirichlet, Neumann, convective, and adiabatic, which are required to solve the above equations, are also discussed fairly well. The enhancement of thermal conductivity of oxide nanofluids, metallic nanofluids, and carbon nanotube (CNT) nanofluids are discussed elaborately with strong experimental evidences. The next chapter covers the theoretical/modeling of thermal conductivity in nanofluids. The properties of nanofluids depend on the details of their microstructures such as the component particles, component volume concentrations, particle dimension, particle geometry, particle distribution, particle motion, and matrix-particle interfacial effects. It is well known that to estimate the effective properties of nanofluids is impossible without dealing with studies on the microstructure. The authors are reasonably justified in bringing out this point lucidly with several suggestions. One way to avoid this problem is to attempt to determine upper and lower bounds on the effective properties from partial statistical information on

Ultrasonics—An Effective Non-invasive Tool to Characterize Nanofluids

Nanofluids are smart colloidal suspensions of fine nanomaterials in the size range of 1–100 nm in base fluids. For the last few years, nanofluids have been an important focus of research, due to their superior thermo physical properties and promising heat transfer applications. Regardless of various experimental studies, it is still unclear whether the thermal conductivity enhancement in nanofluids is anomalous, or lies within the predictions of theoretical models. Moreover, most of the reported values on their thermo physical properties are inconsistent, due to the complexity associated with the surface chemistry of nanofluids. In this chapter, the versatility of ultrasonics, as an effective non-invasive tool in characterizing nanofluids, is discussed. The chapter encompasses the significance and measurement methods of various ultrasonic parameters. The ultrasonic investigations, being non-invasive in nature, highly efficient and relatively cheap, can provide a powerful means to explore complex colloidal systems, like nanofluids and ferrofluids.

Highly flexible poly (vinyldine fluoride)/bismuth iron oxide multiferroic polymer nanocomposites

Magnetoelectric multiferroic PVDF/BFO free standing polymer nanocomposite films are fabricated by using solvent casting method. The structural, chemical, electrical and magnetic properties of the composites were characterized. The structural and chemical analysis proves the formation of the composites. The magnetoresistance measurements are under in process.

A Review of: “The Physics of Solar Cells, Jenny Nelson”

1. Suitable for undergraduate and post-graduate students aspiring to know the Basics of Solar Cells; 2. Simple, elaborative, and excellent explanation; 3. Illustrations are simple and self explanatory; 4. Figure captions are informative; 5. Good continuity in reading; 6. Boxes provide useful tail piece information; 7. Good theoretical evidence; 8. Consulted vast number of published article, books, and reviews in each chapter; 9. Worked out exercises/examples lucidly explained; 10. Third chapter on semiconductors—quite elaborate and elementary for physics major students.