Examining Learning of Atomic Level Ideas About Precipitation Reactions with a Resources Framework

2021 ◽  
Author(s):  
Resa M. Kelly ◽  
Sevil Akaygun ◽  
Sarah J. R. Hansen ◽  
Adrian Villalta-Cerdas ◽  
Jonathan Adam
Keyword(s):  
Atomic Level ◽  
Chemical Processes ◽  
Atomic Models ◽  
Chemistry Learning ◽  
Precipitation Reactions

One particular challenge in chemistry learning is developing students’ atomic level understanding of chemical processes. It is necessary to help students learn how to critique atomic models rather than accept...

Designing Advanced Ceramic Structures with Novel Environmental Microscopy and Related Methods

2001 ◽  
Vol 7 (S2) ◽  
pp. 386-387
Author(s):  
Pratibha L. Gai
Keyword(s):  
Phase Transformations ◽  
Room Temperature ◽  
Single Phase ◽  
Atomic Level ◽  
Chemical Processes ◽  
Atomic Resolution ◽  
Vast Array ◽  
Β Phase ◽  
Silica And Titania

Silica and titania based ceramics and their analogs are some of the most fundamental in crystal chemistry and ceramic science Our interests include applications of nanostructures and chemical composites of the ceramics in nanoelectronics, chemical processes and as scaffolds in biotechnologies. Finely divided titania is used in a vast array of products including paper, paint, food and clothing. Novel microscopy methods including dynamic environmental-high resolution transmission EM (EHREM) at the atomic level, FESEM and cathodoluminescence are leading to striking progress in the development of the ceramic nanotechnologies.Phase transformations in the cristobalite form of silica, from the tetragonal a phase (low or room temperature form) to the cubic β phase (high temperature, (270°C) form) result in discontinuous thermal expansion and are not conducive to nanotechnology. Here we report fundamental in situatomic resolution studies of the phase transformations using EHREM and have used the results to design a number of stable, single-phase structures at room temperature (RT).

In Situ hot-stage high-resolution Transmission Electron Microscope studies of the mechanisms and kinetics of precipitation reactions

1995 ◽  
Vol 53 ◽  
pp. 228-229
Author(s):  
James M. Howe
Keyword(s):  
High Resolution ◽  
Low Cost ◽  
Atomic Level ◽  
Material Interfaces ◽  
Specimen Holder ◽  
Transmission Electron ◽  
Precipitation Reactions ◽  
Kinetics Of Precipitation ◽  
Kinetics Of

In situ hot-stage high-resolution transmission electron microscopy (HRTEM) provides unique capabilities for quantifying the mechanisms and kinetics of precipitation reactions at the atomic level. Such information is required to understand phase transformations and the behavior of material interfaces. This paper provides a brief summary of the in situ hot-stage HRTEM technique and illustrates the use of this technique to obtain information about heterogeneous nucleation processes in precipitation and crystallization reactions. Examples of other types of in situ HRTEM studies can be found in previous papers by Sinclair et al. and Howe et al.The specimen and microscope requirements for in situ hot-stage HRTEM are the same as those for static HRTEM except that one must have a hot-stage specimen holder and equipment for recording and analyzing dynamic images. A high-resolution television-rate camera connected to a standard videocassette recorder (VCR) can be used to store hours of data for low cost. The dynamic images can then be analyzed directly during playback or sent to a computer for image processing and analysis.

scholarly journals Hydrogen spillover and its relation to catalysis: observations on structurally defined single-atom sites

2021 ◽  
Author(s):  
Max Hülsey ◽  
Victor Fung ◽  
Ning Yan
Keyword(s):  
Catalyst Support ◽  
Structural Evolution ◽  
Hydrogen Spillover ◽  
Atomic Level ◽  
Chemical Processes ◽  
Single Atom ◽  
Hydrogenation Kinetics ◽  
Level Information ◽  
Kinetics Of ◽  
Characterisation Techniques

Abstract Hydrogen spillover, involving the transfer of H atoms from metal sites onto the catalyst support, is ubiquitous in chemical processes such as catalytic hydrogenation and hydrogen storage and is therefore of tremendous fundamental and technological interest. However, atomic level information concerning the kinetics of this process, the structural evolution of the catalysts during hydrogen spillover, as well as the nature of participation of the spilled over H in catalysis, remain vastly lacking. Here, we provide insights to those questions with the development of a solubilised polyoxometalate-supported single-atom catalyst which allows for the use of characterisation techniques generally inaccessible to study heterogeneous catalysis. Hydrogenation kinetics together with poisoning studies further reveal that hydrogen spillover can be either detrimental or beneficial for catalysis – the direction and magnitude of which depends predominantly on the nature of the reducible bond in the substrate. Similar trends were observed on one of the most prototypical hydrogen spillover catalysts, Pt/WO3, supporting the generalisability of the observations.

Atomic-level imaging of the surface structure of Ag2O

1984 ◽  
Vol 42 ◽  
pp. 656-657
Author(s):  
William Krakow
Keyword(s):  
High Vacuum ◽  
Atomic Level ◽  
Ultra High Vacuum ◽  
Research Groups ◽  
Resolution Electron ◽  
Surface Reconstructions ◽  
Order Of Magnitude ◽  
High Resolution Electron Microscope ◽  
Saturated Structure ◽  
Transmission And Reflection

In recent years electron microscopy has been used to image surfaces in both the transmission and reflection modes by many research groups. Some of this work has been performed under ultra high vacuum conditions (UHV) and apparent surface reconstructions observed. The level of resolution generally has been at least an order of magnitude worse than is necessary to visualize atoms directly and therefore the detailed atomic rearrangements of the surface are not known. The present author has achieved atomic level resolution under normal vacuum conditions of various Au surfaces. Unfortunately these samples were exposed to atmosphere and could not be cleaned in a standard high resolution electron microscope. The result obtained surfaces which were impurity stabilized and reveal the bulk lattice (1x1) type surface structures also encountered by other surface physics techniques under impure or overlayer contaminant conditions. It was therefore decided to study a system where exposure to air was unimportant by using a oxygen saturated structure, Ag2O, and seeking to find surface reconstructions, which will now be described.

Surface roughness measurements of vanadium-contaminated fluidized cracking catalysts by atomic force microscopy

1996 ◽  
Vol 54 ◽  
pp. 866-867
Author(s):  
H. Kinney ◽  
M.L. Occelli ◽  
S.A.C. Gould
Keyword(s):  
Surface Roughness ◽  
Zeolite Y ◽  
Atomic Level ◽  
Microporous Structure ◽  
Contact Mode ◽  
Force Microscopy ◽  
Atomic Force ◽  
Before And After ◽  
Roughness Measurements ◽  
Cracking Catalysts

For this study we have used a contact mode atomic force microscope (AFM) to study to topography of fluidized cracking catalysts (FCC), before and after contamination with 5% vanadium. We selected the AFM because of its ability to well characterize the surface roughness of materials down to the atomic level. It is believed that the cracking in the FCCs occurs mainly on the catalysts top 10-15 μm suggesting that the surface corrugation could play a key role in the FCCs microactivity properties. To test this hypothesis, we chose vanadium as a contaminate because this metal is capable of irreversibly destroying the FCC crystallinity as well as it microporous structure. In addition, we wanted to examine the extent to which steaming affects the vanadium contaminated FCC. Using the AFM, we measured the surface roughness of FCCs, before and after contamination and after steaming.We obtained our FCC (GRZ-1) from Davison. The FCC is generated so that it contains and estimated 35% rare earth exchaged zeolite Y, 50% kaolin and 15% binder.

Guinier-Preston Platelets Interaction with Dislocations: Study at the Atomic Level

1996 ◽  
Vol 6 (7) ◽  
pp. 825-829 ◽  
Author(s):  
M. Karlík ◽  
B. Jouffrey
Keyword(s):  
Atomic Level
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