Thermal stability of fullerene amines host-guest crystals

Fullerences C₆₀ with adamantane (C₁₀H₁₆), hexamethylotetramine (HMT, C₆H₁₂N₄) or 1,4-diazabicyclooctane (DABCO, C₆H₁₂N₂) crystallize, at the relative concentration C₆₀/guest=2/1, in the pseudotetragonal lattice in which C₆₀ retains almost the same positions as in pure fullerides. The ‘guest’ molecules occupy the octahedral interstitial sites. The mixed crystals which exhibit interesting physical properties are thermally unstable. The decomposition starts at 40–50°C.     

Development of thermally stable tellurite glasses designed for fabrication of microstructured optical fibers

We optimize the composition of tellurite glass for the manufacture of photonic crystal fibers with a large spectrum of transparency. The glasses, synthesized in four and five component (TeO₂-WO₃-Na₂O-Nb₂O₅ and TeO₂-WO₃-PbO-Na₂O-Nb₂O₅) oxide systems with variable contents of WO₃ (5-38 mol%) and PbO (0-18 mol%), are designed and manufactured, and the transmission properties of the obtained glasses for the spectral range of 200 nm-7 μm have been determined. Thermal expansion coefficients and glass characteristic temperatures are determined by the dilatometer and Leitz heat microscope methods. Differential Scanning Calorimetry (DSC) measurements as well as crystallization tests by isothermal heat treatment are used to measure the thermal stability of the glasses and their ability to crystallize. Diffractive X-ray (XRD) measurements are used to determine the crystalline phases of the glass samples and the glasses with the highest resistance to recrystallization during thermal treatment were selected and used for the manufacture of photonic crystal fibers.     

Thermogravimetric investigation ofwastes from electrical and electronic equipment (WEEE)

Two components of electronic wastes (sample A – a mixture of three types of printed circuit boards, sample B – a mixture of electronic junctions with metal wires) were investigated using thermogravimetric analysis (TG). Thermogravimetric and derivative thermogravimetric data (TG and DTG) give information on the thermal stability of A and B samples and allows finding the correct conditions for their degradation using pyrolysis in an experimental system, built on the laboratory scale for utilization of hazardous wastes. X-ray fluorescence measurements prove that brominated flame retardant is present in sample A, whilst chlorinated flame retardant is a probable component of sample B. Preliminary liquid chromatography of oil products obtained as a result of thermal waste degradation shows that the hydrocarbons released during pyrolysis could be used as a fuel.     

Tb3Sc2Al3O12-TbScO3 eutectic self-organized microstructure for metamaterials and photonic crystals application

Eutectics are the materials with foreseen application in the field of photonic crystals and metamaterials. In this paper, the dependence on chemical composition of the microstructures of terbium-scandium-aluminium gamet and terbium-scandium perovskite (Tb₃Sc₂Al₃O₁₂-TbScO₃) eutectics has been studied. The growth of the eutectic rods by the micro-pulling down method is presented, using compositions with several different volume fractions of the garnet and the perovskite phases, V_TSAG:V_TSP = 4, 3, 2, 1, 1/2. The phases have been characterized by powder X-ray diffraction and energy dispersive spectrometry. The relationship between the lattice constant of individual phases and the chemical composition is presented. The unidirectional growth of microrods has been also investigated by electron backscattering diffraction.     

Investigation of Phase Transition inLa1–xPrxGaO3 and La1–xNdxGaO3 Crystals

The solid solution crystals, La_1–xNd_xGaO₃ and La_1–xPr_xGaO₃ have been studied by differential scanning calorimetry method; the crystals exhibit the first order phase transition, the temperature of the transition linearly increases with the concentration of Pr or Nd. The structure of the crystals has been determined by X-ray diffraction. The correlation between the phase transition temperature and crystalline structure at the temperature of the phase transition in both solid solution families is discussed. This revised version was published online in July 2006 with corrections to the Cover Date.     

A new material in the nuclear technology: gadolinium zirconate pyrochlore prepared by reactive sintering

The ability of gadolinium zirconate pyrochlore for actinides incorporation in its lattice makes this material a possible matrix for the immobilization of nuclear wastes. The aim of the presented work was to develop a novel method of gadolinium zirconate synthesis by using a reactive sintering procedure under high pressure based on commercial ZrO₂ and Gd₂O₃ nanopowders. Samples were analyzed using X-ray diffraction and SEM to check their phase composition and microstructure. The obtained sintered pellets demonstrated peaks characteristic for pyrochlore structure for a wide range of preparation temperatures and high density (99.5 % of the theoretical value). It was found that the resulting materials exhibited a homogeneous microstructure and the average grain size dependent on sintering temperature.     

Preparation and characterization of Nd doped gadolinium gallium garnet nanopowders and crystals

The structural and optical features of gallium gadolinium garnet (GGG) nanopowders doped with neodymium were investigated. Nanopowders of GGG:Nd were prepared by modified sol‐gel method using acetic acid as complexing agent. This way permitted to incorporate large amounts of dopant (up to 10 %) without destroying garnet structure. Small single crystals of Nd:GGG were grown by a μ‐pulling down method and spectroscopic features of nanopowders and their single crystal counterparts were compared. It has concluded that the Nd³⁺ ions are located preferentially in the same type of sites in crystal lattices of GGG:Nd nanopowders and their single crystal counterparts. In addition, it follows from the perfect agreement of emission wavelengths and line width recorded for nanopowders and single crystal samples that the crystal lattice of GGG in nanopowders is not distorted. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Thermal properties of Fe-fullerene systems is reaction C60+Fe→Fe@C60 in solid fullerite possible?

Iron in the fullerite lattice binds fullerences in a sandwich type C₆₀FeC₆₀ complexes. At the concentration C₆₀Fe₂ it crystallizes in the monoclinic lattice. The structure is thermally unstable, with the energy release of 606 kJ·mol^?1 it returns to fee lattice. Two possible sites in the reconstructed fee lattice are discussed, Fe bond to C₆₀ and Fe inside the C₆₀ cage.     

Nd(III) and Yb(III) ions incorporated in Y4Al2O9 obtained by sol‐gel method: synthesis,structure, crystals and luminescence

The nanocrystalline powders of Y₄Al₂O₉ (YAM) pure and doped by Nd, Yb and codoped by Nd and Yb were obtained via modified sol‐gel method. These powders were characterized by X‐ray diffraction method, scanning electron microscopy and high resolution scanning electron microscopy, luminescence spectroscopy and differential thermal analysis (DTA). We obtained single phase powders of crystalline structure with average size 70 nm exhibiting interesting luminescent properties. Efficient non‐radiative energy transfer between Nd and Yb was found. DTA confirmed the phase transition at about 1400 °C. From these nanocrystalline powders, the crystals YAM:Yb, YAM:Yb,Nd were grown by micro‐pulling down technique. They were cracking during cooling owing to the phase transition. Luminescent properties of YAM:Nd,Yb crystals were identical with properties of corresponding nanopowders within experimental incertitude. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Characterization of tetragonal SAT0.3: LA0.075: CAT0.625 perovskite crystal: spectroscopic and microscopic investigations

We report room temperature measurements of X‐ray diffraction (XRD), optical transmission microscopy (OTM), atomic force microscopy (AFM), infrared‐absorption (IR), and micro‐Raman spectroscopy (µ‐RS) of the oriented SAT_0.3: LA_0.075: CAT_0.625 single crystal. The final structure refinement of SAT_0.3: LA_0.075: CAT_0.625 crystal was performed for I4/m space group at room temperature. Vibrational spectra of the crystal were discussed in terms of group‐theoretical predictions for untilted (Fm3 m) and tilted tetragonal (I4/m) perovskite structure. The confocal µ‐Raman measurements of depth profiling of SAT_0.3: LA_0.075: CAT_0.625 crystal suggest a relationship between sensitivities of the ordering‐related Raman‐active modes and the variation of order parameter η. Copyright © 2009 John Wiley & Sons, Ltd.