New Compounds Consisting of Turbostratic Intergrowths: Ultra-low Thermal Conductivities and Tunable Electric Properties

2011 ◽  
Vol 1329 ◽  
Author(s):  
Matt Beekman ◽  
Daniel B. Moore ◽  
Ryan Atkins ◽  
Colby Heideman ◽  
Qiyin Lin ◽  
...  
Keyword(s):  
Electrical Transport ◽  
Scanning Transmission Electron Microscopy ◽  
X Ray Diffraction ◽  
Electrical Transport Properties ◽  
Transmission Electron ◽  
Plane Component ◽  
Structural Space ◽  
Scanning Transmission ◽  
New Compounds ◽  
Film Form

ABSTRACTA recently discovered synthetic route to new kinetically stable [(MSe)y]m[TSe2]n layered intergrowths has been applied to prepare several different compositions (M = Pb or Sn, T = Ta, Nb, Mo, or W) with m = n = 1, in thin film form. Scanning transmission electron microscopy and synchrotron X-ray diffraction show the nanostructure of these materials is characterized by a combination of in-plane component crystallinity with misregistration and rotational mis-orientation between adjacent layers. Extremely low cross-plane thermal conductivity as low as 0.1 W m-1 K-1 are attributed to the turbostratic nanostructure. By appropriate choice of M and T, we demonstrate that a range of electrical transport properties are possible, from metallic to semiconducting. Annealing (PbSe)0.99WSe2 and (PbSe)1.00MoSe2 specimens in a controlled atmosphere of PbSe or WSe2 is observed to systematically influence carrier properties, and is interpreted in terms of reduction of the concentration of electrically active defects. Considering these observations and the large composition and structural space that can be explored in such [(MSe)y]m[TSe2]n intergrowths, these materials are of interest for further investigation as potential thermoelectric materials.

Core–shell structures with metallic silver as nucleation agent of low expansion phases in BaO/SrO/ZnO/SiO2 glasses

CrystEngComm ◽  
2019 ◽  
Vol 21 (29) ◽  
pp. 4373-4386 ◽  
Author(s):  
Christian Thieme ◽  
Michael Kracker ◽  
Katrin Thieme ◽  
Christian Patzig ◽  
Thomas Höche ◽  
...  
Keyword(s):  
Scanning Transmission Electron Microscopy ◽  
Nucleating Agent ◽  
Shell Structures ◽  
Metallic Silver ◽  
X Ray Diffraction ◽  
Nucleation Agent ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission

The role of silver as a nucleating agent in BaO/SrO/ZnO/SiO2 glasses is studied with a range of microstructure-characterization techniques, such as scanning transmission electron microscopy, ultraviolet-visible spectroscopy, and X-ray diffraction.

scholarly journals The Effect of Nanosizing on the Oxidation of Partially Oxidized Copper Nanoparticles

Materials ◽  
2020 ◽  
Vol 13 (12) ◽  
pp. 2878
Author(s):  
Jindřich Leitner ◽  
David Sedmidubský ◽  
Michal Lojka ◽  
Ondřej Jankovský
Keyword(s):  
Copper Nanoparticles ◽  
Scanning Transmission Electron Microscopy ◽  
Oxidation Mechanism ◽  
Oxidation Reactions ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Final State ◽  
Micro Particles ◽  
Transmission Electron ◽  
Scanning Transmission

Copper nanoparticles are of great interest in various applications, such as catalysis, cooling fluids, conductive inks or for their antibacterial activity. In this paper, the thermal behavior of copper nanoparticles was studied using thermogravimetry, differential thermal analysis and differential scanning calorimetry. Original Cu samples as well as the products of oxidation were analysed by X-ray diffraction, scanning/transmission electron microscopy and energy dispersive spectroscopy. A step-by-step oxidation mechanism during the oxidation of Cu nano-powders was observed. The Cu-nano oxidation starts slightly above 150 °C when bulk copper does not yet react. The dominant oxidation product in the first step is Cu2O while CuO was identified as the final state of oxidation. Our results confirm an easier oxidation process of Cu-nano than Cu-micro particles, which must be attributed to kinetic not thermodynamic aspects of oxidation reactions.

scholarly journals MINERALOGICAL AND SPECTROSCOPIC STUDY OF NESQUEHONITE SYNTHESIZED BY REACTION OF GASEOUS CO2 WITH MG CHLORIDE SOLUTION

2017 ◽  
Vol 50 (4) ◽  
pp. 2009
Author(s):  
V. Skliros ◽  
A. Anagnostopoulou ◽  
P. Tsakiridis ◽  
M. Perraki
Keyword(s):  
Scanning Transmission Electron Microscopy ◽  
Chloride Solution ◽  
Raw Material ◽  
X Ray Diffraction ◽  
X Ray ◽  
Raman Spectroscopic ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Permanent Storage ◽  
Ir And Raman

Nesquehonite, a hydrous carbonate with promising uses such as building raw material and treatment of wastewaters, was synthesized under low pressure conditions by reaction of gaseous CO2 with Mg chloride solution and it was studied by means of X-Ray Diffraction, optical and scanning/transmission electron microscopy, and FTIR and Raman spectroscopic methods. Synthesized nesquehonite forms elongated fibers, exhibiting transparent to translucent diaphaneity and vitreous luster. It is characterized by high crystallinity. IR and Raman spectroscopy indicated the presence of OHand HCO3 - in the crystal structure of nesquehonite. The nesquehonite synthesis described herein constitutes a potential permanent storage of CO2 emissions.

Hydrothermal Synthesis and Photocatalytic Activity of TiO2@CNTs Nanocomposite

2013 ◽  
Vol 743-744 ◽  
pp. 817-822
Author(s):  
Xuan Hui Zhang ◽  
Xiang Zheng ◽  
Yuan Cheng ◽  
Guo Hua Li ◽  
Xian Chao Hu
Keyword(s):  
Photocatalytic Activity ◽  
Scanning Transmission Electron Microscopy ◽  
Element Distribution ◽  
X Ray Diffraction ◽  
First Order ◽  
Uv Illumination ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
20 Nm ◽  
Better Than

TiO2@CNTs nanocomposite was synthetized by a hydrothermal method at 453 K, using titanium tetrachloride as a precursor and nitrified CNTs as a support. The crystal phase, morphology, microstructure and element distribution of the sample were characterized by X-ray diffraction (XRD), high-resolution transmission electron microscope (TEM), and scanning transmission electron microscopy (STEM-Mapping). The photocatalytic activity of the sample was measured by degrading methyl orange under UV illumination. The results showed that the titania particles in the shape of regular polygon decorate on the outer surface of CNTs evenly, and their sizes were about 7-20 nm. Moreover, photocatalytic activity of the nanocomposite was better than that of P25 Degussa and nitrated CNTs followed the apparent pseudo-first-order rate law. These results point out that synergistic effect exists between the titania and the carbon nanotubes in the nanocomposite.

Enhancing the photocatalytic degradation of selected chlorophenols using Ag/zno nanocomposites

MRS Advances ◽  
2018 ◽  
Vol 3 (36) ◽  
pp. 2129-2136
Author(s):  
Kate Kotlhao ◽  
Fanyana M. Mtunzi ◽  
Vusumzi Pakade ◽  
Neelan Laloo ◽  
Ikechukwu P. Ejidike ◽  
...  
Keyword(s):  
Scanning Transmission Electron Microscopy ◽  
Silver Content ◽  
Zinc Nitrate ◽  
Nitrate Hexahydrate ◽  
X Ray Diffraction ◽  
Water Contaminants ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission ◽  
Xrd Patterns

Chlorophenols are among the priority listed water contaminants due to their estrogenic, mutagenic or carcinogenic health effects. The Ag/ZnO nanocomposites (NCs) were synthesized, characterized and tested for photacatalytic degradation of chlorophenols in water. The synthesis was done using zinc nitrate hexahydrate (ZnNO3. 6H2O) precursor and sodium hydroxide (NaOH). Silver nitrate (AgNO3) was added to ZnO and reduced with sodium brohydride to produce the silver nanoparticles (NPs) within the ZnO structure. The silver content was varied from 1, 3 and 5wt% for optimisation. The nanocomposites were characterised using ultraviolet - visible spectroscopy (UV-Vis), photolumniscence (PL), x-ray diffraction (XRD), and scanning transmission electron microscopy (STEM). The nanocomposites were tested for their photocatalytic properties on 2- chlorophenol (CP), 2- chlorophenol (CP) and 2,4- dichlorophenol (DCP) in water. The UV-Vis results showed that, as the amount of silver was increased a gradual slight red shift was observed. The XRD patterns for Ag/ZnO exhibited peaks that were characteristic of the hexagonal wurzite structure and peaks characteristic for Ag appeared at 38.24o, 44.37o, 64.67oand 77.58ocorresponding to (111), (200), (220) and (311) reflection planes. STEM results showed the presence of Ag in ZnO with ZnO appearing as rods shapes. The EDX elemental analysis confirmed the presence of Ag in the Ag/ZnO nanocomposites with no contaminants peaks. On testing the nanocomposites for phohotocatalytic degradation of chlorophenols, addition of Ag to ZnO improved degradation of the chlorophenols compared to the pristine ZnO.

Microstructure of Epitaxial SrTiO3/Pt/Ti/ Sapphire Heterostructures

2005 ◽  
Vol 20 (9) ◽  
pp. 2261-2265 ◽  
Author(s):  
Steffen Schmidt ◽  
Young-Woo Ok ◽  
Dmitri O. Klenov ◽  
Jiwei Lu ◽  
Sean P. Keane ◽  
...  
Keyword(s):  
Scanning Transmission Electron Microscopy ◽  
Film Plane ◽  
Growth Mechanisms ◽  
Radio Frequency Magnetron Sputtering ◽  
X Ray Diffraction ◽  
Orientation Relationships ◽  
Pt Electrode ◽  
X Ray ◽  
Transmission Electron ◽  
Scanning Transmission

The microstructure and orientation relationships of epitaxial (111)-oriented SrTiO3 thin films grown by radio frequency magnetron sputtering on epitaxial (111)-oriented Pt/Ti electrodes on sapphire were investigated using x-ray diffraction, conventional and scanning transmission electron microscopy. We show that the epitaxial growth of (111)-oriented SrTiO3 films was promoted by thin Ti adhesion layers underneath the Pt electrode. The SrTiO3 films nucleated with two twin-related orientation variants, rotated by 180° about the 〈111〉 surface normal. The twin boundaries were oriented approximately normal to the film plane, but no strong preference for a specific boundary plane was observed. Growth mechanisms and the relationships to the dielectric properties are discussed.

scholarly journals Structure refinement of the δ1pphase in the Fe–Zn system by single-crystal X-ray diffraction combined with scanning transmission electron microscopy

2014 ◽  
Vol 70 (2) ◽  
pp. 275-282 ◽  
Author(s):  
Norihiko L. Okamoto ◽  
Katsushi Tanaka ◽  
Akira Yasuhara ◽  
Haruyuki Inui
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Single Crystal ◽  
Scanning Transmission Electron Microscopy ◽  
Unit Cell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Scanning Transmission Electron ◽  
Transmission Electron ◽  
Scanning Transmission

The structure of the δ1pphase in the iron−zinc system has been refined by single-crystal synchrotron X-ray diffraction combined with scanning transmission electron microscopy. The large hexagonal unit cell of the δ1pphase with the space group ofP63/mmccomprises more or less regular (normal) Zn12icosahedra, disordered Zn12icosahedra, Zn16icosioctahedra and dangling Zn atoms that do not constitute any polyhedra. The unit cell contains 52 Fe and 504 Zn atoms so that the compound is expressed with the chemical formula of Fe13Zn126. All Fe atoms exclusively occupy the centre of normal and disordered icosahedra. Iron-centred normal icosahedra are linked to one another by face- and vertex-sharing forming two types of basal slabs, which are bridged with each other by face-sharing with icosioctahedra, whereas disordered icosahedra with positional disorder at their vertex sites are isolated from other polyhedra. The bonding features in the δ1pphase are discussed in comparison with those in the Γ and ζ phases in the iron−zinc system.

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