Giant magnetoresistance of Fe3O4-polymethylmethacrylate nanocomposite aligned fibers via electrospinning
13 Jun 2007-Journal of Applied Physics (American Institute of Physics)-Vol. 101, Iss: 11, pp 114317
TL;DR: In this paper, the results of investigations on giant negative magnetoresistance (GMR) in nanocomposite aligned fibers prepared using electrospinning were described, and the fibers were characterized using scanning electron microscope and high resolution transmission electron microscope.
Abstract: This paper describes the results of investigations on giant negative magnetoresistance (GMR) in nanocomposite aligned fibers prepared using electrospinning. The nanocomposite contains polymethylmethacrylate (PMMA) matrix and the nanoparticles of polymer (PMMA) grafted magnetite, Fe3O4 (PGM). Even for the low magnetic field (1T) a GMR of about 50% was observed for low loading (5wt%) of PGM at room temperature. The fibers were characterized using scanning electron microscope and high resolution transmission electron microscope. X-ray diffraction (XRD) patterns were recorded for clean PMMA fibers, PMMA granules, and PGM nanoparticles. The dc conductivity was calculated from the I-V characteristics for the fibers at room temperature.
TL;DR: The factors that influence the efficiency of H2 production are addressed and effective ways of engineering catalyst combinations to overcome the current performance barriers are suggested.
Abstract: Hydrogen is an attractive alternative to fossil fuels in terms of environmental and other advantages. Of the various production methods for H2, photocatalysis requires further development so that it can be applied economically on an industrial scale. One- and two-dimensional nanostructures in both pristine and modified forms have shown great potential as catalysts in the generation of H2. We review here recent developments in these nanostructure catalysts and their efficiency in the generation of H2 under UV/visible/simulated solar light. Despite much research effort, many photocatalysts do not yet meet the practical requirements for the generation of H2, such as visible light activity. H2 production is dependent on a variety of parameters and factors. To meet future energy demands, several challenges in H2 production still need to be solved. We address here the factors that influence the efficiency of H2 production and suggest alternatives. The nanostructures are classified based on their morphology and their efficiency is considered with respect to the influencing parameters. We suggest effective ways of engineering catalyst combinations to overcome the current performance barriers.
TL;DR: In this article, a novel approach combining in-situ composite method with electrospinning was used to prepare high magnetic Fe 3 O 4 /poly(vinyl alcohol) (PVA) composite nanofibers.
Abstract: A novel approach, combining in-situ composite method with electrospinning, was used to prepare high magnetic Fe 3 O 4 /poly(vinyl alcohol) (PVA) composite nanofibers. Fe 3 O 4 magnetic fluids were synthesized by chemical co-precipitation method in the presence of 6 wt.% PVA aqueous solution. PVA was used as stabilizer and polymeric matrix. The resulting Fe 3 O 4 /PVA composite nanofibers were characterized with field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM) and X-ray diffractometer (XRD), respectively. These composite fibers showed a uniform and continuous morphology, with the Fe 3 O 4 nanoparticles embedded in the fibers. Magnetization test confirmed that the composite fiber showed a high saturated magnetization ( M s = 2.42 emµ·g –1 ) although only 4 wt.% content.
TL;DR: The potential of hybrid solar cells over the other types are reviewed in this paper, where the ability of aligned nanofibers to provide higher solar conversion efficiency is discussed and the fabrication of various nanostructures such as thin films, quantum dots, nanoparticles and composite nanofiber is highlighted.
Abstract: The increased global demand for low-cost renewable energy sources has motivated scientists and engineers to derive and explore novel methods for converting solar energy into electricity Among those methods, solar cell is one of the clean technologies that has been adopted to produce electricity However, low efficiency, high cost associated with the preparation of materials and subsequent device fabrication prevented their extensive use to satisfy the growing demand Hence the technologies based on silicon, organic solar cells, dye-sensitised solar cells or a combination of these two (hybrid solar cells) were developed, where the latter has gathered advantages from both inorganic and organic materials In this article, the potential of hybrid solar cells over the other types are reviewed Nanostructured morphologies with high surface area offer significant energy conversion efficiency In this direction, industrially applicable electrospun nanofibers are more appropriate when compared to the other nano-fabrication technologies Furthermore the ability of aligned nanofibers to provide higher solar conversion efficiency is discussed We have also highlighted the fabrication of various nanostructures such as thin films, quantum dots, nanoparticles and composite nanofibers and juxtaposed their morphology with efficiency
TL;DR: A first magnetic characterization of the nanostructured composites reveals a modest magnetic anisotropy, which opens new opportunities in a wide range of applications.
Abstract: Ultra-high aspect ratio nanofibers composed of poly(vinyl alcohol) and CoFe2O4 nanoparticles (PVA/CoFe2O4) and moderate aspect ratio nanofibers composed of poly(vinyl chloride) and Fe3O4 nanoparticles (PVC/Fe3O4) have been prepared. Magnetopolymeric one-dimensional (1D) nanostructures with any diameter and length can be prepared by template synthesis using anodic aluminum oxide (AAO) followed by the replication methods presented in this work. These replication methods are very effective, and allow the nanomoulding of any polymer–nanoparticle 1D composite. A first magnetic characterization of the nanostructured composites reveals a modest magnetic anisotropy. The development of magnetopolymeric nanofibers with adjusted length and diameter opens new opportunities in a wide range of applications.
01 Jan 1970
•29 Oct 1993
TL;DR: This book presents a meta-modelling framework for analysing two or more samples of unimodal data from von Mises distributions, and some modern Statistical Techniques for Testing and Estimation used in this study.
Abstract: Preface 1. The purpose of the book 2. Survey of contents 3. How to use the book 4. Notation, terminology and conventions 5. Acknowledgements Part I. Introduction: Part II. Descriptive Methods: 2.1. Introduction 2.2. Data display 2.3. Simple summary quantities 2.4. Modifications for axial data Part III. Models: 3.1. Introduction 3.2. Notation trigonometric moments 3.3. Probability distributions on the circle Part IV. Analysis of a Single Sample of Data: 4.1. Introduction 4.2. Exploratory analysis 4.3. Testing a sample of unit vectors for uniformity 4.4. Nonparametric methods for unimodal data 4.5. Statistical analysis of a random sample of unit vectors from a von Mises distribution 4.6. Statistical analysis of a random sample of unit vectors from a multimodal distribution 4.7. Other topics Part V. Analysis of Two or More Samples, and of Other Experimental Layouts: 5.1. Introduction 5.2. Exploratory analysis 5.3. Nonparametric methods for analysing two or more samples of unimodal data 5.4. Analysis of two or more samples from von Mises distributions 5.5. Analysis of data from more complicated experimental designs Part VI. Correlation and Regression: 6.1. Introduction 6.2. Linear-circular association and circular-linear association 6.3. Circular-circular association 6.4. Regression models for a circular response variable Part VII. Analysis of Data with Temporal or Spatial Structure: 7.1. Introduction 7.2. Analysis of temporal data 7.3. Spatial analysis Part VIII. Some Modern Statistical Techniques for Testing and Estimation: 8.1. Introduction 8.2. Bootstrap methods for confidence intervals and hypothesis tests: general description 8.3. Bootstrap methods for circular data: confidence regions for the mean direction 8.4. Bootstrap methods for circular data: hypothesis tests for mean directions 8.5. Randomisation, or permutation, tests Appendix A. Tables Appendix B. Data sets References Index.
01 Mar 1991
TL;DR: In this paper, the main aim of the second edition is to present reliable, well-tested, up-to-date methods of synthesizing pure iron oxides, including monodispersed particles, presently of great interest to industry.
Abstract: Iron Oxides play an important role in numerous disciplines. Since the publication of the first edition, there has been a surge of interest in synthetic fine to ultrafine iron oxides in a wide range of scientific and technological disciplines, especially in mineralogy, geosciences and environmental science and in various branches of technology. As before, the main aim of the second edition is to present reliable, well-tested, up-to-date methods of synthesizing pure iron oxides. The section on monodispersed particles, presently of great interest to industry, has been expanded. Furthermore the methods of characterization have been focused on their relevance to iron oxides. The well tried syntheses have been retained and some new ones have been incorporated.
TL;DR: The electrospun nanofibers developed highly oriented structure in CL-unit sequences during the electrospinning process and the biocompatibility of the nanofiber scaffold has been investigated by culturing cells on the nan ofibers.
Abstract: Poly( l -lactide- co - e -caprolactone) [P(LLA-CL)] with l -lactide to e -caprolactone ratio of 75 to 25 has been electrospun into nanofibers. The relationship between electrospinning parameters and fiber diameter has been investigated. The fiber diameter decreased with decreasing polymer concentration and with increasing electrospinning voltage. The X-ray diffractometer and differential scanning colorimeter results suggested that the electrospun nanofibers developed highly oriented structure in CL-unit sequences during the electrospinning process. The biocompatibility of the nanofiber scaffold has been investigated by culturing cells on the nanofiber scaffold. Both smooth muscle cell and endothelial cell adhered and proliferated well on the P(LLA-CL) nanofiber scaffolds.