scholarly journals Reducing the Irreducible: Dispersed Metal Atoms Facilitate Reduction of Irreducible Oxides

2022 ◽  
Author(s):  
Ville Korpelin ◽  
Marko M. Melander ◽  
Karoliina Honkala
Keyword(s):  
Metal Atoms

Incommensurate modulated phases of the NbxTa1-xTe4 charge density wave system

1992 ◽  
Vol 50 (1) ◽  
pp. 58-59
Author(s):  
S. Ritchie ◽  
J. C. Bennett ◽  
A. Prodan ◽  
F.W. Boswell ◽  
J.M. Corbett
Keyword(s):  
Charge Density ◽  
Charge Density Wave ◽  
Direct Evidence ◽  
Density Wave ◽  
Wave System ◽  
Modulated Phases ◽  
Metal Atoms ◽  
Incommensurate Modulation ◽  
End Members ◽  
Modulation Wave Vector

A continuous sequence of compounds having composition NbxTa1-xTe4; 0 ≤ x ≤ 1 have been studied by electron diffraction and microscopy. Previous studies have shown that the end members of the series, TaTε4 and NbTε4 possess a quasi-one-dimensional character and exhibit charge density wave (CDW) distortions. In these compounds, the subcell structure is tetragonal with axes (a × a × c) and consists of the metal atoms (Nb or Ta) centered within an extended antiprismatic cage of Te atoms. At room temperature, TaTε4 has a commensurate modulation structure with a 2a × 2a × 3c unit cell. In NbTε4, an incommensurate modulation with × ∼ 16c axes is observed. Preliminary studies of the mixed compounds NbxTα1-xTε4 showed a discontinuous jump of the modulation wave vector commensurate to incommensurate when the Nb dopant concentration x, exceeded x ≃ 0.3, In this paper, the nature of the compositional dependence of is studied in greater detail and evidence is presented for a stepwise variation of . This constitutes the first direct evidence for a Devil's staircase in CDW materials.

Ultra high resolution SEM at high voltage images individual fab fragments applied as molecular label to cell surface receptors

1989 ◽  
Vol 47 ◽  
pp. 70-71
Author(s):  
Klaus-Ruediger Peters
Keyword(s):  
High Resolution ◽  
High Energy ◽  
Metal Coating ◽  
Beam Diameter ◽  
Surface Receptors ◽  
Surface Mobility ◽  
Metal Atoms ◽  
Shadowing Effect ◽  
Imaging Mode ◽  
Deposition Techniques

Topographic ultra high resolution can now routinely be established on bulk samples in cold field emission scanning electron microscopy with a second generation of microscopes (FSEM) designed to provide 0.5 nm probe diameters. If such small probes are used for high magnification imaging, topographic contrast is so high that remarkably fine details can be imaged on 2DMSO/osmium-impregnated specimens at ribosome surfaces even without a metal coating. On TCH/osmium-impregnated specimens topographic resolution can be increased further if the SE-I imaging mode is applied. This requires that beam diameter and metal coating thickness be made smaller than the SE range of ~1 nm and background signal contributions be reduced. Subnanometer small probes can be obtained (only) at high accelerating voltages. Subnanometer thin continuous metal films can be produced under the following conditions: self-shadowing effect between metal atoms must be reduced through appropriate deposition techniques and surface mobility of metal atoms must be diminished through high energy sputtering and/or specimen cooling.

Structure and Thermoelectric Properties of New Quaternary Tin and Lead Bismuth Selenides, K1+xM4-2xBi7+xSe15 (M = Sn, Pb) and K1+xSn5-xBi11+xSe22

2000 ◽  
Vol 626 ◽  
Author(s):  
Antje Mrotzek ◽  
Kyoung-Shin Choi ◽  
Duck-Young Chung ◽  
Melissa A. Lane ◽  
John R. Ireland ◽  
...  
Keyword(s):  
Thermal Conductivity ◽  
Single Crystal ◽  
Thermoelectric Properties ◽  
Three Dimensional ◽  
Structure Type ◽  
Narrow Gap ◽  
Low Thermal Conductivity ◽  
Seebeck Coefficients ◽  
Metal Atoms ◽  
Anionic Framework

ABSTRACTWe present the structure and thermoelectric properties of the new quaternary selenides K1+xM4–2xBi7+xSe15 (M = Sn, Pb) and K1-xSn5-xBi11+xSe22. The compounds K1+xM4-2xBi7+xSe15 (M= Sn, Pb) crystallize isostructural to A1+xPb4-2xSb7+xSe15 with A = K, Rb, while K1-xSn5-xBi11+xSe22 reveals a new structure type. In both structure types fragments of the Bi2Te3-type and the NaCl-type are connected to a three-dimensional anionic framework with K+ ions filled tunnels. The two structures vary by the size of the NaCl-type rods and are closely related to β-K2Bi8Se13 and K2.5Bi8.5Se14. The thermoelectric properties of K1+xM4-2xBi7+xSe15 (M = Sn, Pb) and K1-xSn5-xBi11+xSe22 were explored on single crystal and ingot samples. These compounds are narrow gap semiconductors and show n-type behavior with moderate Seebeck coefficients. They have very low thermal conductivity due to an extensive disorder of the metal atoms and possible “rattling” K+ ions.

Covalent Atomic Bridges Enable Unidirectional Enhancement of Electronic Transport in Aligned Carbon Nanotubes

2019 ◽  
Author(s):  
Mingguang Chen ◽  
Wangxiang Li ◽  
Anshuman Kumar ◽  
Guanghui Li ◽  
Mikhail Itkis ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Electrical Transport ◽  
Large Scale ◽  
The Novel ◽  
Electrical Measurements ◽  
Metal Atoms ◽  
Aligned Carbon Nanotubes ◽  
Transport Channels ◽  
Walled Carbon Nanotubes ◽  
Bulk Structures

<p>Interconnecting the surfaces of nanomaterials without compromising their outstanding mechanical, thermal, and electronic properties is critical in the design of advanced bulk structures that still preserve the novel properties of their nanoscale constituents. As such, bridging the p-conjugated carbon surfaces of single-walled carbon nanotubes (SWNTs) has special implications in next-generation electronics. This study presents a rational path towards improvement of the electrical transport in aligned semiconducting SWNT films by deposition of metal atoms. The formation of conducting Cr-mediated pathways between the parallel SWNTs increases the transverse (intertube) conductance, while having negligible effect on the parallel (intratube) transport. In contrast, doping with Li has a predominant effect on the intratube electrical transport of aligned SWNT films. Large-scale first-principles calculations of electrical transport on aligned SWNTs show good agreement with the experimental electrical measurements and provide insight into the changes that different metal atoms exert on the density of states near the Fermi level of the SWNTs and the formation of transport channels. </p>

Synthesis and Characterization of New Zinc Phthalocyanine - Dodecenyl Succinic Anhydride Benzoic Groups

2020 ◽  
Vol 17 (6) ◽  
pp. 488-495
Author(s):  
Hussein Ali Al-Bahrani ◽  
Mohanad Mousa Kareem ◽  
Abdul Amir Kadhum ◽  
Nour A. Alrazzak
Keyword(s):  
Salicylic Acid ◽  
Succinic Anhydride ◽  
Zinc Phthalocyanine ◽  
Central Metal ◽  
Target Compound ◽  
Compound I ◽  
Metal Phthalocyanines ◽  
Metal Atoms ◽  
Amino Salicylic Acid

Background: The phthalocyanines a series of compounds involves four iso-indole units linked by aza nitrogen atoms bonded with metal atoms that are normally located in the center a phthalocyanines ring. Some of the central metal-phthalocyanines can be excited by ultraviolet light and emit a fluorescence in far-red region. Objective: To synthesize a derivative of phthalocyanines namely 4,4',4' '-tri-(dodecenyl succinic anhydride)- 4' ' '-(5-amino salicylic acid) zinc phthalocyanine with a zinc central metal. Materials and Methods: The reaction of 4- nitro Phthalonitrile and 4- amino Phthalonitrile with ZnCl2 in the presence of dimethyl amino ethanol afforded 4,4',4' '-triamino-4' ' '-nitro zinc phthalocyanine. This product reacted with 5-amino salicylic acid to yield tetra-(5-amino salicylic acid) zinc phthalocyanine. A dodecenyl succinic anhydride was added on the amine group of benzoic rings to afford 4,4',4' '-tri-(dodecenyl succinic anhydride)-4' ' '-(5-amino salicylic acid) zinc phthalocyanine(I), the target compound. Results and Discussion: Compound I is successfully synthesized with a yield of 72% from tetra-(5-amino salicylic acid) zinc phthalocyanine with dodecenyl succinic anhydride. Conclusion: The newly synthesized molecule of 4,4',4' '-tri-(dodecenyl succinic anhydride)-4' ' '-(5-amino salicylic acid) zinc phthalocyanine (I), tetra-(5-amino salicylic acid) zinc phthalocyanine(E) and 4,4',4' '- triamino-4' ' '-nitro zinc phthalocyanine (S). The reaction of 4- nitro Phthalonitrile and 4- amino and the structure of compound I is confirmed and its formation was proven.

Theoretical modelling of porous silicon decorated with metal atoms for hydrogen storage

2020 ◽  
Vol 45 (49) ◽  
pp. 26321-26333
Author(s):  
Israel González ◽  
Francisco De Santiago ◽  
Lucía G. Arellano ◽  
Álvaro Miranda ◽  
Alejandro Trejo ◽  
...  
Keyword(s):  
Porous Silicon ◽  
Hydrogen Storage ◽  
Theoretical Modelling ◽  
Metal Atoms

A synchrotron X-ray study of the electron density in C-type rare earth oxides

1996 ◽  
Vol 52 (3) ◽  
pp. 414-422 ◽  
Author(s):  
E. N. Maslen ◽  
V. A. Streltsov ◽  
N. Ishizawa
Keyword(s):  
Heavy Metal ◽  
Rare Earth ◽  
Electron Density ◽  
Approximate Symmetry ◽  
Data Set ◽  
X Ray ◽  
Metal Atoms ◽  
Structure Factors ◽  
Deformation Electron Density ◽  
Synthetic Crystals

Structure factors for small synthetic crystals of the C-type rare earth (RE) sesquioxides Y2O3, Dy2O3 and Ho2O3 were measured with focused λ = 0.7000 (2) Å, synchrotron X-radiation, and for Ho2O3 were re-measured with an MoKα (λ = 0.71073 Å) source. Approximate symmetry in the deformation electron density (Δρ) around a RE atom with pseudo-octahedral O coordination matches the cation geometry. Interactions between heavy metal atoms have a pronounced effect on the Δρ map. The electron-density symmetry around a second RE atom is also perturbed significantly by cation–anion interactions. The compounds magnetic properties reflect this complexity. Space group Ia{\bar 3}, cubic, Z = 16, T = 293 K: Y2O3, Mr = 225.82, a = 10.5981 (7) Å, V = 1190.4 (2) Å3, Dx = 5.040 Mg m−3, μ 0.7 = 37.01 mm−1, F(000) = 1632, R = 0.067, wR = 0.067, S = 9.0 (2) for 1098 unique reflections; Dy2O3, Mr = 373.00, a = 10.6706 (7) Å, V = 1215.0 (2) Å3, Dx = 8.156 Mg m−3, μ 0.7 = 44.84 mm−1, F(000) = 2496, R = 0.056, wR = 0.051, S = 7.5 (2) for 1113 unique reflections; Ho2O3, Mr = 377.86, a = 10.606 (2) Å, V = 1193.0 (7) Å3, Dx = 8.415 Mg m−3, μ 0.7 = 48.51 mm−1 F(000) = 2528, R = 0.072, wR = 0.045, S = 9.2 (2) for 1098 unique reflections of the synchrotron data set.

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