Entrapment of organosilicon molecules in nonhydrolytic alumina gels and thermal behavior of the resulting composite

2001 ◽  
Vol 16 (5) ◽  
pp. 1413-1419 ◽  
Author(s):  
G. S. Grader ◽  
S. A. Melchior ◽  
Y. De-Hazan ◽  
S. Melamed ◽  
G. E. Shter
Keyword(s):  
Thermal Behavior ◽  
Amorphous Silica ◽  
Atomic Scale ◽  
Decomposition Products ◽  
Alumina Gels

This work describes the entrapment of tetrakis(trimethylsilyl)silane (TK) and tetrakis(chlorodimethylsilyl)silane (TKCl) in nonhydrolytic alumina gels, and the materials' thermal behavior. During gelation and drying TK and TKCl are physically entrapped in the gel up to a limit of Si/Al = 0.33. Above this limit, sublimation and decomposition of TK and TKCl occur during heating. A larger fraction of TKCl decomposition products is retained due to their higher reactivity. Below and above Si/Al = 0.33, the gel converts to mullite + α−Al2O3or mullite + amorphous silica, respectively. Conversion to hexagonal mullite indicates atomic scale homogeneity of Si and Al during firing.

scholarly journals Thermal behavior of Sr-form of gordaite

2021 ◽  
Vol 82 (3) ◽  
pp. 19-21
Author(s):  
Zlatka Delcheva ◽  
Tsveta Staminirova ◽  
Nadia Petrova
Keyword(s):  
Thermal Decomposition ◽  
Ion Exchange ◽  
Thermal Behavior ◽  
Mass Loss ◽  
Exchangeable Cations ◽  
Decomposition Products ◽  
Ion Exchange Reaction ◽  
Reaction Data ◽  
Thermal Decomposition Products ◽  
First Time

Cation-exchanged Sr-form of gordaite was successfully obtained from Ca-form of gordaite by an ion-exchange reaction. Data of XRD, SEM-EDS and DTA-TG-MS were used to characterize the Sr-form. Thermal decomposition of Sr-gordaite was studied for the first time in regards of thermal events and mass loss during volatile releasing. It was found similarity with Sr-gordaite and Ca-gordaite in terms of processes, type, and amount of volatiles released, but also some differences were found concerning the temperature correspondence of the volatiles evolving and the type of thermal decomposition products. The influence of the exchangeable cations (Na, Ca, or Sr) on the dehydration of the interlayer in the gordaite type structure were also established.

scholarly journals Shedding light on the atomic-scale structure of amorphous silica–alumina and its Brønsted acid sites

2019 ◽  
Vol 21 (35) ◽  
pp. 19529-19537 ◽  
Author(s):  
Frédéric A. Perras ◽  
Zichun Wang ◽  
Takeshi Kobayashi ◽  
Alfons Baiker ◽  
Jun Huang ◽  
...  
Keyword(s):  
Amorphous Silica ◽  
Acid Sites ◽  
Atomic Scale ◽  
Bronsted Acid ◽  
Brønsted Acid ◽  
Brønsted Acid Sites ◽  
Brönsted Acid ◽  
Silica Alumina ◽  
Brönsted Acid Sites ◽  
Bronsted Acid Sites

Advanced solid-state NMR methods, using dynamic nuclear polarization (DNP), are applied to probe the atomic-scale bulk structure of amorphous silica–alumina catalysts prepared by flame-spray pyrolysis, and the structure of their Brønsted acid sites.

scholarly journals Disordered hyperuniformity in two-dimensional amorphous silica

2020 ◽  
Vol 6 (16) ◽  
pp. eaba0826 ◽  
Author(s):  
Yu Zheng ◽  
Lei Liu ◽  
Hanqing Nan ◽  
Zhen-Xiong Shen ◽  
Ge Zhang ◽  
...  
Keyword(s):  
Amorphous Silica ◽  
Density Functional ◽  
Large Scale ◽  
Single Layer ◽  
Topological Defects ◽  
Density Functional Theory Calculations ◽  
Density Fluctuations ◽  
Atomic Scale ◽  
Two Dimensional ◽  
Wave Localization

Disordered hyperuniformity (DHU) is a recently proposed new state of matter, which has been observed in a variety of classical and quantum many-body systems. DHU systems are characterized by vanishing infinite-wavelength normalized density fluctuations and are endowed with unique novel physical properties. Here, we report the discovery of disordered hyperuniformity in atomic-scale two-dimensional materials, i.e., amorphous silica composed of a single layer of atoms, based on spectral-density analysis of high-resolution transmission electron microscopy images. Moreover, we show via large-scale density functional theory calculations that DHU leads to almost complete closure of the electronic bandgap compared to the crystalline counterpart, making the material effectively a metal. This is in contrast to the conventional wisdom that disorder generally diminishes electronic transport and is due to the unique electron wave localization induced by the topological defects in the DHU state.

Monitoring of thermal behavior and decomposition products of soybean oil

2013 ◽  
Vol 115 (1) ◽  
pp. 19-29 ◽  
Author(s):  
Qing Zhang ◽  
Ahmed S. M. Saleh ◽  
Jing Chen ◽  
Peiran Sun ◽  
Qun Shen
Keyword(s):  
Soybean Oil ◽  
Thermal Behavior ◽  
Decomposition Products

scholarly journals Atomic-scale thermal behavior of nanoimprinted 0.3-nm-high step patterns on PMMA polymer sheets

2015 ◽  
Vol 48 (2) ◽  
pp. 225-227 ◽  
Author(s):  
Goon Tan ◽  
Yasuhisa Nozawa ◽  
Tomoyuki Funabasama ◽  
Koji Koyama ◽  
Masahiro Mita ◽  
...  
Keyword(s):  
Thermal Behavior ◽  
Atomic Scale ◽  
Polymer Sheets ◽  
Pmma Polymer

Structure and migration of planar defects in crystals observed in atomic scale

1978 ◽  
Vol 36 (1) ◽  
pp. 284-285 ◽  
Author(s):  
H. Hashimoto ◽  
Y. Sugimoto ◽  
Y. Takai ◽  
H. Endoh
Keyword(s):  
Electron Microscope ◽  
Rotation Angle ◽  
Crystal Surface ◽  
Electron Gun ◽  
Atomic Scale ◽  
Present Observation ◽  
Twist Boundary ◽  
Optical Magnification ◽  
Zinc Crystal ◽  
And Migration

As was demonstrated by the present authors that atomic structure of simple crystal can be photographed by the conventional 100 kV electron microscope adjusted at “aberration free focus (AFF)” condition. In order to operate the microscope at AFF condition effectively, highly stabilized electron beams with small energy spread and small beam divergence are necessary. In the present observation, a 120 kV electron microscope with LaB6 electron gun was used. The most of the images were taken with the direct electron optical magnification of 1.3 million times and then magnified photographically.1. Twist boundary of ZnSFig. 1 is the image of wurtzite single crystal with twist boundary grown on the surface of zinc crystal by the reaction of sulphur vapour of 1540 Torr at 500°C. Crystal surface is parallel to (00.1) plane and electron beam is incident along the axis normal to the crystal surface. In the twist boundary there is a dislocation net work between two perfect crystals with a certain rotation angle.

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