Resolution in Focused Electron- and Ion-Beam Induced Chemical Vapor Deposition

The key physical processes governing resolution of focused electron-beam and ion-beam-assisted chemical vapor deposition are analyzed via an adsorption rate model. We quantify for the first time how the balance of molecule depletion and replenishment determines the resolution inside the locally irradiated area. Scaling laws are derived relating the resolution of the deposits to molecule dissociation, surface diffusion, adsorption, and desorption. Supporting results from deposition experiments with a copper metalorganic precursor gas on a silicon substrate are presented and discussed.Comment: 4 pages, 4 figures, 1 tabl

RHENIUM CARBIDES PREPARED BY THERMOBARIC TREATMENT OF NANOSIZED PRECURSORS

PACS 61.05.cp; 61.50.Ks The products of thermobaric treatment (P = 6 GPa; T = 1800 • C) of mechanical mixtures of nanosized rhenium powder and sibunit have been studied. The formation of high-temperature phases with composition Re 2 C has been revealed

Changes in the structure of MgxAly(OH)z layered double hydroxides during the adsorption of organic compounds

International audienceLayered double hydroxides (LDHs) are used as sorbents, catalysts, and carriers for catalytic species. In general, they are natural or synthetic minerals with part of their cations being replaced isomorphically with cations of higher oxidation states, which results in the formation of positively charged two-dimensional layers containing solvate molecules and counterions capable of anion exchange [1]. LDHs are solid bases [2]. Since there are both Brønsted and Lewis sites, anion exchange processes occur in the interlayer internal space of LDHs [3]. The interlayer distance depends on the nature of anions and solvate molecules as well as the degree of isomorphic substitution. When the interlayer distance changes, LDH properties also change (for example, sorption capacity changes because of the changing number of available active sites). A study of the LDH structure and its changes during the sorption of various compounds provides conclusions about the mechanism of these processes and prospects of creating new materials with desired properties. This work reveals regular changes in the structure of synthetic MgxAly(OH)z hydrotalcites of various composition, which occur during the adsorption of amyl alcohol, naphthalene, and β-naphthol. The hydrotalcite structure is shown in Fig. 1

Thin films of unsubstituted and fluorinated palladium phthalocyanines: structure and sensor response toward ammonia and hydrogen

In the present work, we study and compare the structure and sensing properties of thin films of unsubstituted palladium phthalocyanine (PdPc) and hexadecafluorosubstituted palladium phthalocyanine (PdPcF16). Thin films of PdPc and PdPcF16 were obtained by the method of organic molecular beam deposition and their structure was studied using UV-visible spectroscopy, X-ray diffraction and atomic force microscopy techniques. The electrical sensor response of PdPc films toward ammonia and hydrogen was investigated and compared with that of PdPcF16 films. The nature of interaction between the phthalocyanines films and some gaseous analyte molecules has been clarified using Quantum chemical (DFT) calculations

First hexagonal close packed high-entropy alloy with outstanding stability under extreme conditions and electrocatalytic activity for methanol oxidation

High-entropy alloys containing 5 and 6 platinum group metals have been prepared by thermal decomposition of single-source precursors non requiring high temperature or mechanical alloying. The prepared Ir0.19Os0.22Re0.21Rh0.20Ru0.19 alloy is the first example of a single-phase hexagonal high-entropy alloy. Heat treatment up to 1500 K and compression up to 45 GPa do not result in phase changes, a record temperature and pressure stability for a single-phase high-entropy alloy. The alloys show pronounced electrocatalytic activity in methanol oxidation, which opens a route for the use of high-entropy alloys as materials for sustainable energy conversion

Self-Lubricating Nano-Ball-Bearings

No abstract.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/55898/1/82_ftp.pd

Effect of fluorosubstitution on the structure of single crystals, thin films and spectral properties of palladium phthalocyanines

In this work, the crystalline structure of single crystals grown by vacuum sublimation of unsubstituted palladium phthalocyanines (PdPc), its tetrafluorinated (PdPcF4) and hexadecafluorinated (PdPcF16) derivatives have been investigated using X-ray diffraction measurements. Two crystalline phases have been identified for PdPc; the molecules in both phases crystallize in stacks with herringbone arrangement in the monoclinic space groups (C2/c for -PdPc; P21/n for -PdPc). Both PdPcF4 and PdPcF16 crystallize in the triclinic P-1 space group, forming stacks of molecules in columnar arrangement with molecules in adjacent columns are aligned parallel to one another. X-ray diffraction measurements have also been used to elucidate the structural features and molecular orientation of thin films of PdPc, PdPcF4 and PdPcF16, grown by organic molecular beam deposition at different substrate temperatures. The effect of fluorosubstitution on UV-visible optical absorption and vibrational spectra of palladium phthalocyanine derivatives is also discussed

Ir–Re binary alloys under extreme conditions and their electrocatalytic activity in methanol oxidation

The formation of the hcp-Ir0.70Re0.30 alloy from the single-source precursor (NH4)2[Ir0.70Re0.30Cl6] upon heating in hydrogen atmosphere can be associated with the formation of two intermediates: a crystalline iridium-based intermediate and a fcc-structured alloy. Ir–Re alloys show lower thermal expansion coefficients and smaller compressibility in comparison with individual metals. The high-temperature high-pressure treatment of hcp-Ir0.70Re0.30 alloy enable us to probe the Ir–Re pressure dependent phase diagram. The miscibility gap between hcp and fcc alloys slightly shifts towards the rhenium side below 4 GPa. Above 4 GPa, the miscibility gap does not drift with pressure and narrows with compression. The electrocatalytic activity of Ir–Re alloys has been tested for methanol oxidation in acidic water solution. Ir–Re alloys show higher electrocatalytic activity in comparison with pure Ir and Re, which makes them perspective candidates for fuel cells application. The highest electrocatalytic activity has been obtained for the two-phase Ir0.85Re0.15 composition

Completely discontinuous organic/ inorganic hybrid nanocomposites by self-curing of nanobuilding blocks constructed from reactions of [HMe 2 SiOSiO 1.5 ] 8 with vinylcyclohexene

The reaction of 4-vinyl-1-cylcohexene with [HMe 2 SiOSiO 1.5 ] 8 provides tetra- and octa-2-cyclohexenylethyloctasilsesquioxanes. The tetrabifunctional [cyclohexenylethylMe 2 SiOSiO 1.5 ] 4 -[HMe 2 SiOSiO 1.5 ] 4 (average degree of functionalization) melts near 80 °C and can be cast and then cured (by thermal hydrosilylation) into transparent nanocomposite shapes. These materials, while not nanoporous, offer dielectric constants of 2.8–2.9 at 100 kHz to 3 MHz, and are air stable to temperatures ≥ 400 °C. The resulting materials appear (by X-ray diffraction) to be partially ordered after curing. The octafunctional material also melts at low temperatures ( ca 120 °C) and can be copolymerized with hydridosiloxanes to give similar materials with lower thermal stability. The synthesis and characterization of the starting materials is described, as well as thermal curing studies and properties characterization of the resultant nanocomposites. Copyright © 2007 Society of Chemical IndustryPeer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/57384/1/2281_ftp.pd

Effect of fluorosubstitution on the structure of single crystals, Effect of fluorosubstitution on the structure of single crystals,thin films and spectral properties of palladium phthalocyanines

In this work, the crystalline structure of single crystals grown by vacuum sublimation of unsubstituted palladium phthalocyanines (PdPc), its tetrafluorinated (PdPcF4) and hexadecafluorinated (PdPcF16) derivatives have been investigated using X-ray diffraction measurements. Two crystalline phases have been identified for PdPc; the molecules in both phases crystallize in stacks with herringbone arrangement in the monoclinic space groups (C2/c for -PdPc; P21/n for -PdPc). Both PdPcF4 and PdPcF16 crystallize in the triclinic P-1 space group, forming stacks of molecules in columnar arrangement with molecules in adjacent columns are aligned parallel to one another. X-ray diffraction measurements have also been used to elucidate the structural features and molecular orientation of thin films of PdPc, PdPcF4 and PdPcF16, grown by organic molecular beam deposition at different substrate temperatures. The effect of fluorosubstitution on UV-visible optical absorption and vibrational spectra of palladium phthalocyanine derivatives is also discussed