scholarly journals In-situlaser synthesis of Nd–Al–O coatings: the role of sublattice cations in eutectic formation

2015 ◽  
Vol 71 (1) ◽  
pp. 95-111 ◽  
Author(s):  
Isabel de Francisco ◽  
Jose Antonio Bea ◽  
Angel Vegas ◽  
Juan Bautista Carda ◽  
German Francisco de la Fuente
Keyword(s):  
Phase Composition ◽  
Metal Oxide ◽  
Composite Coating ◽  
Driving Force ◽  
Zone Melting ◽  
Oxide Formation ◽  
Eutectic Formation

Neodymium aluminate coatings have been preparedin-situby the laser zone melting (LZM) method, using a CO2SLAB-type laser emitting at 10.6 µm. Polycrystalline Al2O3commercial plates have been used as substrates, and coatings were prepared from the corresponding mixtures of powdered neodymium and aluminium oxides as starting materials. Microstructure, studied by SEM and phase composition, studied by XRD, proved thein-situformation of a NdAlO3/NdAl11O18eutectic. As a result, a well integrated composite coating was formed. Nanoindentation tests are consistent with excellent integration between coating and substrate. Structural similarities between the eutectic components within the coating, as well as between these and the substrate, are consistent with the crystallographic concepts proposed by Vegas (Ramos-Gallardo & Vegas, 1997), where cation sub-arrays play an important role governing metal oxide structures. These structure sublattices are suggested as the driving force behind eutectic oxide formation.

scholarly journals Role of Phase Composition of PEO Coatings on AA2024 for In-Situ LDH Growth

Coatings ◽  
2017 ◽  
Vol 7 (11) ◽  
pp. 190 ◽  
Author(s):  
Maria Serdechnova ◽  
Marta Mohedano ◽  
Anissa Bouali ◽  
Daniel Höche ◽  
Boris Kuznetsov ◽  
...  
Keyword(s):  
Phase Composition ◽  
Peo Coatings

scholarly journals In situ formation of ZnOx species for efficient propane dehydrogenation

Nature ◽  
2021 ◽  
Vol 599 (7884) ◽  
pp. 234-238
Author(s):  
Dan Zhao ◽  
Xinxin Tian ◽  
Dmitry E. Doronkin ◽  
Shanlei Han ◽  
Vita A. Kondratenko ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Supported Catalysts ◽  
Decisive Role ◽  
Propane Dehydrogenation ◽  
Propane Conversion ◽  
Characterization Methods ◽  
Oh Groups ◽  
Reductive Treatment

AbstractPropane dehydrogenation (PDH) to propene is an important alternative to oil-based cracking processes, to produce this industrially important platform chemical1,2. The commercial PDH technologies utilizing Cr-containing (refs. 3,4) or Pt-containing (refs. 5–8) catalysts suffer from the toxicity of Cr(vi) compounds or the need to use ecologically harmful chlorine for catalyst regeneration9. Here, we introduce a method for preparation of environmentally compatible supported catalysts based on commercial ZnO. This metal oxide and a support (zeolite or common metal oxide) are used as a physical mixture or in the form of two layers with ZnO as the upstream layer. Supported ZnOx species are in situ formed through a reaction of support OH groups with Zn atoms generated from ZnO upon reductive treatment above 550 °C. Using different complementary characterization methods, we identify the decisive role of defective OH groups for the formation of active ZnOx species. For benchmarking purposes, the developed ZnO–silicalite-1 and an analogue of commercial K–CrOx/Al2O3 were tested in the same setup under industrially relevant conditions at close propane conversion over about 400 h on propane stream. The developed catalyst reveals about three times higher propene productivity at similar propene selectivity.

The Role of Diatomic SiO in Dry Oxidation of Si

1987 ◽  
Vol 105 ◽  
Author(s):  
Stanley I. Raider ◽  
Robert E. Walkup
Keyword(s):  
Gas Phase ◽  
Film Growth ◽  
Oxide Formation ◽  
Sensitivity Limit ◽  
Tracer Studies ◽  
Isotope Tracer ◽  
Good Spatial Resolution ◽  
Standard Models

AbstractThe interaction of O2(g) with clean Si(s) surfaces at high temperature and low pressure leads to an etching reaction, 1/2 O2(g) + Si(s) → SiO(g), which results in the evolution of SiO molecules from the surface. Above a critical O2 pressure, an oxide film SiO2(s) begins to grow. The evolution of diatomic SiO during the early stages of film growth may provide a mechanism to account for deviations from standard models of oxidation kinetics for thin oxides, and for the results of oxygen isotope tracer studies of oxide formation. In order to monitor the rate of SiO evolution, we have made in-situ measurements of the SiO concentration in the gas phase, using a laser-induced fluorescence technique. With this method, SiO(g) can be monitored in the furnace with good spatial resolution and a sensitivity limit of ˜ 106 molecules cm−3. Measurements of SiO evolution and the implications for oxide growth will be discussed.

In situ TEM Studies of agglomeration of sub-nanometer Ru layers in Ru/C multilayers

1992 ◽  
Vol 50 (1) ◽  
pp. 256-257
Author(s):  
Tai D. Nguyen ◽  
Ronald Gronsky ◽  
Jeffrey B. Kortright
Keyword(s):  
Layered Structure ◽  
Driving Force ◽  
High Energy ◽  
Superior Performance ◽  
In Situ Tem ◽  
Rayleigh Instability ◽  
Practical Applications ◽  
Transmission Electron ◽  
Diffraction Patterns

Nanometer period Ru/C multilayers are one of the prime candidates for normal incident reflecting mirrors at wavelengths < 10 nm. Superior performance, which requires uniform layers and smooth interfaces, and high stability of the layered structure under thermal loadings are some of the demands in practical applications. Previous studies however show that the Ru layers in the 2 nm period Ru/C multilayer agglomerate upon moderate annealing, and the layered structure is no longer retained. This agglomeration and crystallization of the Ru layers upon annealing to form almost spherical crystallites is a result of the reduction of surface or interfacial energy from die amorphous high energy non-equilibrium state of the as-prepared sample dirough diffusive arrangements of the atoms. Proposed models for mechanism of thin film agglomeration include one analogous to Rayleigh instability, and grain boundary grooving in polycrystalline films. These models however are not necessarily appropriate to explain for the agglomeration in the sub-nanometer amorphous Ru layers in Ru/C multilayers. The Ru-C phase diagram shows a wide miscible gap, which indicates the preference of phase separation between these two materials and provides an additional driving force for agglomeration. In this paper, we study the evolution of the microstructures and layered structure via in-situ Transmission Electron Microscopy (TEM), and attempt to determine the order of occurence of agglomeration and crystallization in the Ru layers by observing the diffraction patterns.

Routes of metal oxide formation from metal β-diketonates used as CVD precursors

1999 ◽  
Vol 09 (PR8) ◽  
pp. Pr8-65-Pr8-72 ◽  
Author(s):  
A. E. Turgambaeva ◽  
V. V. Krisyuk ◽  
A. F. Bykov ◽  
I. K. Igumenov
Keyword(s):  
Metal Oxide ◽  
Oxide Formation

Economic Growth: New Problems and New Risks

2006 ◽  
pp. 20-37 ◽  
Author(s):  
M. Ershov
Keyword(s):  
Economic Growth ◽  
Foreign Exchange ◽  
Driving Force ◽  
Structural Changes ◽  
Rate Of Growth

The economic growth, which is underway in Russia, raises new questions to be addressed. How to improve the quality of growth, increasing the role of new competitive sectors and transforming them into the driving force of growth? How can progressive structural changes be implemented without hampering the rate of growth in general? What are the main external and internal risks, which may undermine positive trends of development? The author looks upon financial, monetary and foreign exchange aspects of the problem and comes up with some suggestions on how to make growth more competitive and sustainable.

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