A two-stage model for the formation of clay minerals from tephra-derived volcanic glass

Clay Minerals ◽  
1990 ◽  
Vol 25 (3) ◽  
pp. 313-327 ◽  
Author(s):  
A. P. W. Hodder ◽  
B. E. Green ◽  
D. J. Lowe
Keyword(s):  
Clay Minerals ◽  
Late Quaternary ◽  
Volcanic Glass ◽  
Chemical Processes ◽  
Diffusion Controlled ◽  
Tephra Layers ◽  
Clay Formation ◽  
Kinetics Of ◽  
Calculated Activation ◽  
Rhyolitic Tephra

AbstractThe kinetics of clay formation in buried paleosols developed from late Quaternary rhyolitic tephra layers near Rotorua, New Zealand, can be described in terms of a combination of parabolic and linear kinetics, reflecting the hydration of glass, and the formation of clay minerals, respectively. Such a model is consistent with the formation of clay minerals showing an Arrhenian temperature dependence and suggests, on the basis of calculated activation energies, that the process of formation of Al-rich allophane (imogolite) is diffusion controlled, whereas the rate of formation of Si-rich allophane is controlled by the chemical processes at the site of reaction.

Correlation of Distal Tephra Layers in Loess in the Channeled Scabland and Palouse of Washington state

1992 ◽  
Vol 37 (3) ◽  
pp. 281-303 ◽  
Author(s):  
Alan J. Busacca ◽  
Kevin T. Nelstead ◽  
Eric V. McDonald ◽  
Michael D. Purser
Keyword(s):  
Late Quaternary ◽  
Volcanic Glass ◽  
Similarity Coefficients ◽  
Regional Study ◽  
Radiocarbon Age ◽  
Stratigraphic Position ◽  
Normal Polarity ◽  
Tephra Layers ◽  
Future Work ◽  
Mount St Helens

AbstractThirty-two distal tephra layers that are interbedded in Quaternary loess at 13 sites in the Channeled Scabland and Palouse were sampled as part of a regional study of the stratigraphy and chronology of dominantly windblown sediments on the Columbia Plateau. An electron microprobe was used to determine the elemental composition of volcanic glass in all of the samples and also to determine the composition of ilmenite in 14 of them. Two of the distal tephra layers correlate with Glacier Peak eruptions (11,200 yr B.P.), five with Mount St. Helens tephra set S (13,000 yr B.P.), and nine with Mount St. Helens tephra set C (ca. 36,000 yr B.P.) based on analysis of glass and ilmenite in reference pumices from Glacier Peak, Mount St. Helens, Mount Mazama, Mount Rainier, and Mount Jefferson, on the calculation of similarity coefficients for comparisons of both glass and ilmenite reference compositions with those of distal tephras, and on considerations of stratigraphic position. The composition of glass and ilmenite and the stratigraphic position of one distal tephra layer in the loess suggests that it is from an eruption of Mount St. Helens at least several thousand years older than the set C eruptions. Glass composition and stratigraphic position of a distal tephra at another site in loess suggested a possible correlation with some layers of the Pumice Castle eruptive sequence at Mount Mazama (ca. 70,000 yr B.P.), but similarity coefficients on ilmenite of only 45 and 48 fail to support the correlation and show why multiple correlation methods should be used. Similarity coefficients higher than 96 for both glass and ilmenite establish a correlation with Mount St. Helens layer Cw for distal layers in two widely separated sites. These layers are in sedimentary successions that are closely associated with giant floods in the Channeled Scabland. The 36,000 yr B.P. radiocarbon age of the Mount St. Helens set C establishes a minimum limiting date for an episode of flooding that predates the widespread late Wisconsin floods. A correlation of distal tephra layers at two other sites in the Scabland and Palouse establishes a chronostratigraphic link to a still-older episode of flooding within the Brunhes Normal Polarity Chron. Six distal tephra layers in pre-late Quaternary loess that are not correlated with known or dated eruptions have compositions and distinctive stratigraphic positions relative to magnetic reversal boundaries that make them key markers for future work.

Experimental Investigation of Interfacial Compounds Evolution in Ultra-Thin Roll Bonded Cu/Al/Cu Strip

2014 ◽  
Vol 622-623 ◽  
pp. 492-500 ◽  
Author(s):  
Hong Wu Song ◽  
Yang Yu ◽  
Yong Xu ◽  
Yan Chen ◽  
Shi Hong Zhang
Keyword(s):  
Intermetallic Layer ◽  
Optical Microscope ◽  
Interfacial Structure ◽  
Tensile Fracture ◽  
X Ray Diffraction ◽  
Roll Bonding ◽  
X Ray ◽  
Diffusion Controlled ◽  
Kinetics Of ◽  
Calculated Activation

Ultra-thin Cu/Al clad strip with 0.12 mm thickness was successfully fabricated by accumulative roll bonding and the interfacial structure of Cu/Al clad strip has been characterized by means of optical microscope (OM), energy dispersive spectroscopy (EDS), scanning electron microscopy (SEM) and also X-ray diffraction (XRD). The intermetallic phases and their formation sequence at the interface was experimentally verified. And the growth kinetics of each phase was also modeled considering the diffusion controlled reaction mechanism. The effect of interfacial compounds on tensile fracture of ultra-thin Cu/Al clad strip was also studied. The obtained results indicate that, intermetallic compounds formed in the interface region of ultra-thin Cu/Al clad strip within the experimental condition are confirmed to be Al2Cu, Al4Cu9 and AlCu in sequence. The calculated activation energies for the growth of Al4Cu9, AlCu and Al2Cu are 101.45、114.30 and 95.15 kJ/mol, respectively. The major cracks propagate through the AlCu intermetallic layer and the Al2Cu / AlCu interface.

scholarly journals Synthesis and Polymerization Kinetics of Rigid Tricyanate Ester

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1686
Author(s):  
Andrey Galukhin ◽  
Roman Nosov ◽  
Ilya Nikolaev ◽  
Elena Melnikova ◽  
Daut Islamov ◽  
...  
Keyword(s):  
Kinetic Analysis ◽  
Single Step ◽  
Polymerization Kinetics ◽  
Scanning Calorimetry ◽  
Modulated Differential Scanning Calorimetry ◽  
Diffusion Controlled ◽  
Polymerization Product ◽  
The One ◽  
Kinetics Of

A new rigid tricyanate ester consisting of seven conjugated aromatic units is synthesized, and its structure is confirmed by X-ray analysis. This ester undergoes thermally stimulated polymerization in a liquid state. Conventional and temperature-modulated differential scanning calorimetry techniques are employed to study the polymerization kinetics. A transition of polymerization from a kinetic- to a diffusion-controlled regime is detected. Kinetic analysis is performed by combining isoconversional and model-based computations. It demonstrates that polymerization in the kinetically controlled regime of the present monomer can be described as a quasi-single-step, auto-catalytic, process. The diffusion contribution is parameterized by the Fournier model. Kinetic analysis is complemented by characterization of thermal properties of the corresponding polymerization product by means of thermogravimetric and thermomechanical analyses. Overall, the obtained experimental results are consistent with our hypothesis about the relation between the rigidity and functionality of the cyanate ester monomer, on the one hand, and its reactivity and glass transition temperature of the corresponding polymer, on the other hand.

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