Non-woven fibers were produced by sol-gel and electrospinning methods, from a solution containing cerium nitrate, zinc acetate, titanium isopropoxide, polyvinylpyrrolidone, acetic acid, ethanol, and water. The fibers were calcined at various temperatures ranging from 300 to 900 degrees C and were characterized using Scanning Electron Microscopy (SEM), X-Ray diffraction (XRD), Brunauer-Emmett-Teller (BET) surface area analysis, En-ergy Dispersive X-ray (EDX), Raman spectroscopy, Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Structural characterization revealed the fluorite nanocrystalline phase of ceria (CeO2) at all temperatures, the wurtzite zinc oxide (ZnO) phase in the 300-500 degrees C range, and a variety of zinc titanate phases (such as ZnTiO3, Zn2Ti3O8 and Zn2TiO4) at higher temperatures. Titania (TiO2) phases were not observed following calcination up to 900 degrees C. The average ceria nanocrystallite size increases with calcination temperature, as revealed by XRD and confirmed by the Phonon Confinement Model (PCM) of Raman spectra. The opposite trend is observed for the BET specific surface area of the nanofibers, where this value decreases with calcination temperatures above 400 degrees C. These nanofibers containing ceria and zinc titanates are potential candidates for photocatalytic applications.

We discuss how a powder X-ray diffraction (XRD) system can be used to probe large pyrite (FeS2) crystals to reveal a peak generally not documented in the literature. The ability to detect this peak is attributed to the use of a large crystal, which gives large signal intensities. This type of experiment provides a research-like experience and gives students the opportunity to deepen their understanding of diffraction orders. In this experiment students are first challenged to be creative and determine how to mount a mineral crystal in a powder XRD system and then practice critical thinking in order to determine the origin of the unknown XRD peak. This experiment may also be generalized to crystals other than pyrite.

We present results from light scattering experiments on tetragonal FeS with the focus placed on lattice dynamics. We identify the Raman active A1g and B1g phonon modes, a second order scattering process involving two acoustic phonons, and contributions from potentially defect-induced scattering. The temperature dependence between 300 and 20K of all observed phonon energies is governed by the lattice contraction. Below 20K the phonon energies increase by 0.5-1 cm^-1 thus indicating putative short range magnetic order. Along with the experiments we performed lattice-dynamical simulations and a symmetry analysis for the phonons and potential overtones and find good agreement with the experiments. In particular, we argue that the two-phonon excitation observed in a gap between the optical branches becomes observable due to significant electron-phonon interaction.

A. Baum,1,2 A. Milosavljević,3 N. Lazarević,3 M. M. Radonjić,4 B. Nikolić,5 M. Mitschek,1,2,* Z. Inanloo Maranloo,1,† M. Šćepanović,3 M. Grujić-Brojčin,3 N. Stojilović,3,6 M. Opel,1 Aifeng Wang ( ),7 C. Petrovic,7 Z. V. Popović,3,8 and R. Hackl1 1Walther Meissner Institut, Bayerische Akademie der Wissenschaften, 85748 Garching, Germany 2Fakultät für Physik E23, Technische Universität München, 85748 Garching, Germany 3Center for Solid State Physics and New Materials, Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia 4Scientific Computing Laboratory, Center for the Study of Complex Systems, Institute of Physics Belgrade, University of Belgrade, Pregrevica 118, 11080 Belgrade, Serbia 5Faculty of Physics, University of Belgrade, Studentski trg 12, Belgrade, Serbia 6Department of Physics and Astronomy, University of Wisconsin Oshkosh, Oshkosh, Wisconsin 54901, USA 7Condensed Matter Physics and Materials Science Department, Brookhaven National Laboratory, Upton, New York 11973-5000, USA 8Serbian Academy of Sciences and Arts, Knez Mihailova 35, 11000 Belgrade, Serbia

When single crystals are probed by powder X-ray diffraction (PXRD) systems, the peak widths are smaller and signal intensities are greater than those from powdered samples. Instead of the expected single peak, a doublet can be observed, and undergraduate students face a big challenge explaining its origin. This activity is suitable as an inquiry-based, upper-level undergraduate laboratory activity. Students typically engage in an extensive literature search and reading in order to understand observed diffraction data. With a little bit of guidance from the instructor, students can learn how X-rays are generated, and which X-rays are used in PXRD experiments. They can also learn about the electronic transitions in the target electrode leading to characteristic X-rays and learn about the role of spin-orbit coupling.

Irradiation of biocompatible polymers is generally performed using 60Co gamma sources delivering high doses of radiation, ranging from kGy to MGy levels. This irradiation is typically employed for sterilization and/or crosslinking purposes. However, exposure to gamma rays may generate free radicals responsible for polymer degradation and, therefore, studies of the irradiation effects on these polymers are of great practical interest. In this study, ultra-high molecular weight polyethylene (UHMWPE) films were exposed to high-energy photons to doses comparable to those used in radiotherapy for patients with cancer. Specifically, three dose levels of 30, 60, and 120Gy were delivered utilizing linear accelerator X-rays (6MV) and irradiation effects were studied using X-ray Diffraction (XRD), Fourier Transform Infrared (FTIR), and Ultraviolet–visible (UV–vis) spectroscopy. It was found that radiation doses up to 120Gy do not change the polymer crystallinity but affect its optical properties. In particular, the decrease in the optical band gap is observed in irradiated polymers.

We studied magneto-optical response of a canonical topological insulator Bi 2 Se 3 with the goal of addressing a controversial issue of electron-phonon coupling.Magnetic-field induced modifications of reflectance are very pronounced in the infrared part of the spectrum, indicating strong electron-phonon coupling.This coupling causes an asymmetric line-shape of the 60 cm -1 phonon mode, and is analyzed within the Fano formalism.The analysis reveals that the Fano asymmetry parameter (q) changes sign when the cyclotron resonance is degenerate with the phonon mode.To the best of our knowledge this is the first example of magnetic field driven q-reversal.

Sub-micron sized alumina fibres were fabricated by electrospinning and calcination of a polymer template fibre. In the calcination step, different controlled temperature heating cycles were conducted to obtain fibres of different crystalline structures. Their biodurabilities were tested at pH 7.4 with lung airway epithelial lining fluid or serum ultrafiltrate (SUF) and at pH 4.5 with macrophage phagolysosomal simulant fluid (PSF). Potential to generate free radicals was tested in vitro. Through the variation in the soak temperature from 650 °C to 950 °C (experiments S650-S950), the heating protocol affected the morphological characteristics, crystal structure, surface area, and density of the alumina fibres while their dissolution half-times were not significantly affected in SUF or PSF. Fibre samples formed at different heating ramp rates (experiments R93-R600) showed significant variation in the dissolution rates with the highest ramp rate corresponding to the highest dissolution rate. Thus, by increasing the calcination temperature ramp rate the alumina fibres may be produced that have reduced biodurability and lower inflammogenic potential. The fibres with the highest dissolution rated had the least aluminium content. The solubility half-times of the alumina fibres were shortest for fibres calcined at the fastest temperature ramp rate (though soak temperature did not have an effect). The ramp rates also affected the aluminium content of the fibres suggesting that the content may affect the structural strength of the fibres and control the dissolution.

In this work, we explore possible topological insulating state in bismuth doped with arsenic Bi1-xAsx. Infrared and magneto-optical spectroscopy are employed to probe the electrodynamic response of Bi1-xAsx with x = 0.01, as well as topological insulator Bi1-xSbx with x = 0.20. The spectra are reported in magnetic fields up to 18 T, and at temperatures between 10 and 300 K. The results indicate strong sensitivity of optical properties to these external stimuli in both Bi1-xAsx and Bi1-xSbx, but also some differences introduced by arsenic doping. Most notably, the field dependence of cyclotron resonance in Bi1-xAsx implies that it is due to bulk carriers, as opposed to surface carriers in Bi1-xSbx. (C) 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Mn5Ge3 is a ferromagnetic compound with high Curie temperature (Tc = 293 K), high spin polarization, and a good lattice match to germanium. Doping Mn5Ge3 with carbon increases Tc above room temperature and makes these compounds promising candidates for spin injectors for potential spintronics applications. The resistivity and magnetic susceptibility measurements show anisotropic behavior of these compounds. Optical spectroscopy is employed to measure near-normal reflectance of Mn5Ge3C0.89 in the frequency range from far-infrared to ultraviolet at three different temperatures (10, 200, and 300 K), and results are compared with those on pure Mn5Ge3. Both Mn5Ge3 and Mn5Ge3C0.89 have weak temperature dependence of the optical properties in the 10–300 K range, and both have similar electrodynamics responses with similar temperature trends. However, important differences in the region of interband transitions, indicating the electronic nature of the increased ferromagnetic stability of carbon doped compound, are observed.

Titania nanofibers were fabricated via electrospinning for use as a catalyst support structure for the reduction of NO and CO gases. Palladium nanoparticles were incorporated into the titania electrospun fibers by adding PdCl2 salt particles to the electrospinning solution. The composition and properties of the fibers were characterized by SEM, XEDS, TEM, XRD, and BET. These fibers were fabricated into a disk-shaped nonwoven porous medium. Experiments were conducted to measure the outlet gas composition after the NO and CO gases passed through the porous medium as a function of reaction temperature. The test results showed significant conversion of NO and CO to N2 and CO2 due to the presence of Pd nanoparticles in the fibers. Higher catalyst loading resulted in higher conversion efficiency at lower temperatures.

We present the results of an infrared spectroscopy study of topological insulators Bi2Se3, Bi2Te3 and Sb2Te3. Reflectance spectra of all three materials look similar, with a well defined plasma edge. However, there are some important differences. Most notably, as temperature decreases the plasma edge shifts to lower frequencies in Bi2Se3, whereas in Bi2Te3 and Sb2Te3 it shifts to higher frequencies. In the loss function spectra we identify asymmetric broadening of the plasmon, and assign it to the presence of charge inhomogeneities. It remains to be seen if charge inhomogeneities are characteristic of all topological insulators, and whether they are of intrinsic or extrinsic nature.

Literature describing X-ray photoelectron spectroscopy (XPS) generally assumes that the reader will understand why the method cannot detect hydrogen atoms. On the other hand, students struggle finding the answer even after extensive literature search and reading.