Orientation Dependence of Photochemical Reduction Reactions on SrTiO3 Surfaces

2002 ◽  
Vol 751 ◽  
Author(s):  
Jennifer L. Giocondi ◽  
Gregory S. Rohrer
Keyword(s):  
Photochemical Activity ◽  
Orientation Dependence ◽  
Reaction Site ◽  
Electron Backscattered Diffraction ◽  
Photochemical Reduction ◽  
Force Microscopy ◽  
Atomic Force ◽  
Individual Grains ◽  
Silver Metal ◽  
Silver Cations

ABSTRACTPolished and annealed surfaces of randomly oriented crystallites were used to study the orientation dependence of the photochemical activity of SrTiO3 surfaces. Silver cations reduced from an aqueous solution produce solid silver metal at the reaction site. The amounts of silver produced by a fixed exposure were used as a relative measure of each grain's activity. The surface structure of the grains was observed using atomic force microscopy and the surface orientation of each grain was determined by electron backscattered diffraction. Surfaces annealed in air for 6h at 1200° C were bound by some combination of the following three planes: {110}, {111}, and a complex facet inclined approximately 24° from {100}. By correlating the orientations of individual grains to the amount of deposited silver, we conclude that surfaces with the complex {100} facet are the most active.

Photochemical Reactivity of Sr2Nb2O7 and Sr2Ta2O7 as a Function of Surface Orientation

2002 ◽  
Vol 755 ◽  
Author(s):  
Jennifer L. Giocondi ◽  
Ariana M. Zimbouski ◽  
Gregory S. Rohrer
Keyword(s):  
Perovskite Structure ◽  
Orientation Dependence ◽  
Layered Perovskite ◽  
Reaction Products ◽  
Force Microscopy ◽  
Atomic Force ◽  
Wide Range ◽  
Layered Perovskite Structure ◽  
Relationship Of ◽  
The Relationship

ABSTRACTSr2Nb2O7 and Sr2Ta2O7 have a (110) layered perovskite structure and are efficient photolysis catalysts. Aqueous silver and lead cations were photochemically reduced and oxidized, respectively, on the surfaces of Sr2Nb2O7 and Sr2Ta2O7 crystals with a wide range of orientations. Atomic force microscopy has been used to observe the distribution of photochemically reduced and oxidized products and determine the orientation dependence of the reactivity. On surfaces with the same orientation, reaction products frequently had a non-uniform distribution. The reactivity of both compounds proved to be only weakly anisotropic, with the highest relative reactivity for both oxidation and reduction occurring for surfaces oriented between (010), (110), and (011). These low index orientations have structures similar to the ideal {110} and {100} planes in the perovskite structure, respectively. The relationship of the perovskite structure to the reactivity is discussed.

Crystallographic dissolution of high purity aluminium

2007 ◽  
Vol 463 (2083) ◽  
pp. 1729-1748 ◽  
Author(s):  
E.V Koroleva ◽  
G.E Thompson ◽  
P Skeldon ◽  
B Noble
Keyword(s):  
High Purity ◽  
Zone Melting ◽  
Force Microscopy ◽  
Alkaline Etching ◽  
Atomic Force ◽  
Purity Aluminium ◽  
Grain Orientations ◽  
High Purity Aluminium ◽  
Complementary Techniques ◽  
Individual Grains

Alkaline etching of high purity aluminium has been examined using the complementary techniques of scanning electron microscopy and atomic force microscopy. Provision of specific grain orientations, generated by zone melting, has revealed dissolution rates of individual grains which decrease in the order {334}>{225}>{119}. Further, the faceting of the {334} grain, which has an orientation close to (111), reveals the crystallographic nature of alkaline etching of high purity aluminium, with the limited presence of discrete cathodic sites. For the {119} grain orientation, distinct faceting is replaced by a cellular texture that is elongated in the 〈120〉 direction. The {225} grain reveals cells elongated in the 〈111〉 direction, with step-like features present across the surface. These step features are explained by dissolution along preferred crystallographic directions to reveal facets of low-energy planes of appropriate separation and associated steps.

scholarly journals Atomic force microscopy observation of threading dislocation density reduction in lateral epitaxial overgrowth of gallium nitride by MOCVD

1998 ◽  
Vol 3 ◽  
Author(s):  
H. Marchand ◽  
J.P. Ibbetson ◽  
Paul T. Fini ◽  
Peter Kozodoy ◽  
S. Keller ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Rectangular Cross Section ◽  
Orientation Dependence ◽  
Threading Dislocation ◽  
Large Area ◽  
Extended Defect ◽  
Lateral Epitaxial Overgrowth ◽  
Force Microscopy ◽  
Bond Density ◽  
Atomic Force

Extended defect reduction at the surface of GaN grown by lateral epitaxial overgrowth (LEO) on large-area GaN/Al2O3 wafers by low pressure MOCVD is demonstrated by atomic force microscopy. The overgrown GaN has a rectangular cross section with smooth (0001) and {110} facets. The density of mixed character threading dislocations at the surface of the LEO GaN is reduced by at least 3-4 orders of magnitude from that of bulk GaN. Dislocation-free GaN surfaces exhibit an anisotropic step structure that is attributed to the orientation dependence of the dangling bond density at the step edges.

Technique for Monitoring the Etching Rate of Alumina

2004 ◽  
Vol 819 ◽  
Author(s):  
B. Deb ◽  
A. Altay ◽  
S. R. Gilliss ◽  
N.E. Munoz ◽  
C. B. Carter
Keyword(s):  
Grain Boundaries ◽  
Etching Rate ◽  
Thermal Treatments ◽  
Electron Backscattered Diffraction ◽  
Dissolution Rates ◽  
Force Microscopy ◽  
Chemical Treatments ◽  
Atomic Force ◽  
Microscopy Techniques ◽  
Grain Boundary Grooves

AbstractThe effect of chemical and thermal treatments on the grains and grain boundaries of polycrystalline μ-Al2O3 has been examined using a combination of microscopy techniques. Commercially available alumina samples (Lucalox™) were chemically etched in phosphoric acid at 200°C in increments of 15 min. Thermal treatments were carried out at 1650°C before chemical treatments. Using maps obtained by visible-light microscopy (VLM) as a guide, the same regions were re-examined using atomic force microscopy (AFM) after subsequent treatments. Variations in the dissolution rates of different grains and grain boundaries could then be studied using AFM. The geometry of the grain-boundary grooves was compared after thermal and chemical treatments. Electron backscattered diffraction (EBSD) patterns recorded in the scanning electron microscope (SEM) were used to obtain crystallographic orientations of the grains which enabled variations in dissolution rates between grains to be correlated to orientation.

Correlation between the Grain Orientation Dependence of Color Etching and Chemical Etching

2012 ◽  
Vol 18 (6) ◽  
pp. 1389-1392 ◽  
Author(s):  
Attila Bonyár ◽  
Peter J. Szabó
Keyword(s):  
Atomic Force Microscopy ◽  
Grain Orientation ◽  
Chemical Etching ◽  
Gray Cast Iron ◽  
Layer Structure ◽  
Orientation Dependence ◽  
Force Microscopy ◽  
Atomic Force ◽  
Uniformly Smooth ◽  
Iron Specimen

AbstractA gray cast iron specimen was investigated by color and chemical etching with optical and atomic force microscopy, and the effect of grain orientation on the effectiveness of etching was examined. It was proven that the grain orientation dependence of chemical and color etching is just the opposite, and that the specimen surface after color etching is not uniformly smooth. Explanation for the layer structure of the color etched iron specimen is given.

scholarly journals Atomic Force Microscopy and Raman Microspectroscopy Investigations of the Leaching of Chalcopyrite (112) Surface

Minerals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 485
Author(s):  
Gujie Qian ◽  
Christopher T. Gibson ◽  
Sarah Harmer-Bassell ◽  
Allan Pring
Keyword(s):  
Surface Roughness ◽  
Atomic Force Microscopy ◽  
Elemental Sulfur ◽  
Raman Microspectroscopy ◽  
Reaction Site ◽  
Raman Analysis ◽  
Force Microscopy ◽  
No Formation ◽  
Atomic Force ◽  
Initial Stage

The aim of this study was to determine the reactivity of the chalcopyrite (112) surface under industrially relevant leaching conditions. Leaching of the chalcopyrite (112) surface was carried out at approximately pH 1 and in the presence of 0.01 M ferric or ferrous. The atomic force microscopy (AFM) and Raman microspectroscopy analyses suggested that the chalcopyrite (112) surface was relatively inert, with no formation of elemental sulfur observed over 42 days of leaching. In addition, it was found that the distribution of Fe-S and Cu-S bonds was always negatively correlated, as revealed by Raman analysis. This suggested that the breakage of the Fe-S and Cu-S bonds did not occur concurrently at a specific reaction site. The rate of variation of surface roughness, as reflected by AFM data, also suggested that leaching of the chalcopyrite (112) surface in the ferric or ferrous solution medium likely occurred more rapidly in the initial stage (fewer than seven days) than in the later stage (after seven days).

scholarly journals Nanoscale Morphology of Apatite Precipitated onto Synthetic Hydroxyapatite from Simulated Body Fluid

2005 ◽  
Vol 284-286 ◽  
pp. 497-500 ◽  
Author(s):  
Jennifer Vandiver ◽  
Nelesh Patel ◽  
William Bonfield ◽  
Christine Ortiz
Keyword(s):  
Contact Angle ◽  
Simulated Body Fluid ◽  
Photoelectron Spectroscopy ◽  
Body Fluid ◽  
Lateral Dimension ◽  
Force Microscopy ◽  
Angle Measurements ◽  
Atomic Force ◽  
Synthetic Hydroxyapatite ◽  
Individual Grains

Dense, polycrystalline, synthetic hydroxyapatite (HA) was incubated for 36 days in modified simulated body fluid (SBF) with increased HCO3 - and reduced Cl- ion concentrations (27 and 120 mM, respectively) closer to actual blood plasma than typical SBF. The resulting precipitated apatite layer was characterized by X-ray photoelectron spectroscopy (XPS) and contact angle measurements and found to be nonstoichiometric, calcium deficient (Ca/P~1.06), non-carbonate containing, and of intermediate hydrophilicity (advancing contact angle, qa=76.5±1.3°). The nanoscale surface topography of the SBF-incubated HA sample was imaged by tapping mode atomic force microscopy (TMAFM), observed to be ≤100 nm in thickness, and composed of three distinct morphologies. These topographically distinct regions were localized within individual grains and facets of the initial HA surface and included: hemispherical, globular structures (maximum lateral dimension, d=44.7±12.7 nm, peak-tovalley height, h=3.6±2.7 nm); elongated, needle-like structures (minimum lateral dimension, w=31.0±8.5 nm, d=104.4±31.1 nm, h=5.0±3.2 nm), and regions of larger, irregularly shaped structures that were relatively smooth (d=504.9±219.1 nm, h=104.0±51.7 nm).

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