Influence of surface-area estimation on rates of plagioclase weathering determined from naturally weathered 3400 y old Hawaiian basalt

2008 ◽  
Vol 72 (1) ◽  
pp. 91-94 ◽  
Author(s):  
M. A. Velbel ◽  
A. I. Losiak
Keyword(s):  
Surface Area ◽  
Three Dimensional ◽  
Field Studies ◽  
Weathering Rate ◽  
Weathering Rates ◽  
Electron Imaging Mode ◽  
Electron Imaging ◽  
Geometric Surface ◽  
Geometric Surface Area ◽  
Hawaiian Basalt

AbstractDimensions of plagioclase (An65) crystals in a polished thin section of naturally weathered 3400 y old Hawaiian basalt were measured by scanning electron microscopy (in backscattered electron imaging mode). The three-dimensional shape, size, volume and surface area of the plagioclase crystals were then estimated using the method of Morgan and Jerram (2006). The weathering rate of plagioclase (mass loss divided by initial geometric surface area during 3400 y) is –12.116 log10 mol m–2 s–1. This weathering rate represents a time span (3.4 ka) intermediate between laboratory experimental timescales and the ages of regoliths in field studies of natural weathering rates. Weathering rates of the same plagioclase are recalculated using different assumptions concerning the method of estimating surface area, including simple geometric surface area and geometric surface area adjusted for surface roughness. Varying assumptions about surface area result in variations of up to two orders of magnitude in rates estimated from the same basic crystal geometry. The slowest rate estimated here approaches but does not fall within the range of previously determined field rates of plagioclase weathering.

Hydrophobic hydrogen anode with a nickel catalyst

1982 ◽  
Vol 47 (12) ◽  
pp. 3230-3235 ◽  
Author(s):  
Olga Marholová ◽  
Karel Smrček
Keyword(s):  
Surface Area ◽  
Nickel Catalyst ◽  
Raney Nickel ◽  
Platinum Catalyst ◽  
Raney Nickel Catalyst ◽  
Electrochemical Parameters ◽  
Geometric Surface ◽  
Geometric Surface Area ◽  
Hydrogen Anode ◽  
In Cells

A hydrophobic porous hydrogen anode was prepared whose electrochemical parameters are comparable with anodes containing a platinum catalyst. For its successful preparation, oxidation of the Raney nickel catalyst with air oxygen or with fluorine from Teflon must be prevented. The electrodes of a geometric surface area up to 450 cm2 were tested in cells and modules filled with 7M-KOH.

A Molecular Dynamics Study on the Effects of Nanostructural Clearances on Thermal Resistance at a Liquid-Solid Interface

2009 ◽  
Author(s):  
Masahiko Shibahara ◽  
Kiyoshi Takeuchi
Keyword(s):  
Molecular Dynamics ◽  
Thermal Resistance ◽  
Surface Area ◽  
Solid Wall ◽  
Potential Parameter ◽  
Liquid Region ◽  
Solid Interface ◽  
Dynamics Simulations ◽  
Geometric Surface ◽  
Geometric Surface Area

The effects of the surface structures and the surface structural clearances at the nanometer scale on the thermal resistance at a liquid water-solid interface, as well as the dynamic behaviors of liquid molecules, were investigated directly by the classical molecular dynamics simulations. The thermal resistance between the solid wall and the liquid region was calculated by the temperature discontinuity at a liquid-solid interface and the energy flux that was added or subtracted by the Langevin method per unit area so as to maintain a constant solid wall temperature. When the potential parameter between liquid molecules and nanostructure atoms is equal to that between liquid molecules and solid wall atoms, the geometric surface area change depending on the nanostructures as well as their clearances and the dynamic behaviour change of the fluid molecules at the interface depending on the nanostructural clearances cause the thermal resistance reduction depending on the nanostructures at the liquid-solid interface. When the potential parameter between liquid molecules and nanostructure atoms is different from that between liquid molecules and solid wall atoms, the thermal resistance at the interface is dependent on the potential parameter between liquid molecules and nanostructure atoms rather than the geometric surface area in a molecular scale depending on the nanostructures as well as their clearances.

Effect of Reduced Universal Adhesive Application Time on Enamel Bond Fatigue and Surface Morphology

2019 ◽  
Vol 44 (1) ◽  
pp. 42-53 ◽  
Author(s):  
Y Nagura ◽  
A Tsujimoto ◽  
NG Fischer ◽  
AG Baruth ◽  
WW Barkmeier ◽  
...  
Keyword(s):  
Fatigue Strength ◽  
Surface Area ◽  
Shear Bond Strength ◽  
Test Group ◽  
Application Time ◽  
Universal Adhesive ◽  
Shear Fatigue ◽  
Universal Adhesives ◽  
Geometric Surface ◽  
Geometric Surface Area

SUMMARY Objective: The purpose of this study was to evaluate the effect of reduced application times of universal adhesives on enamel bond fatigue and surface morphology of the treated enamel with constant force atomic force microscopy (AFM). Methods: Four universal adhesives—Adhese Universal (AU), Clearfil Universal Bond Quick (CU), G-Premio Bond (GP), and Scotchbond Universal Adhesive (SU)—were evaluated in a laboratory for their ability to adhesively bond resin composite to enamel. Shear bond strengths were initially determined using 15 specimens per test group for each adhesive. Shear fatigue strengths were then determined using 20 specimens per test group for each the adhesives. The fatigue specimens were loaded using a sine wave at a frequency of 20 Hz for 50,000 cycles or until failure occurred. AFM observations, surface Ra roughness measurements, and geometric surface area evaluations of enamel surface treated with the adhesive agents were also conducted. Results: A strong relationship was found between the initial shear bond strength and shear fatigue strength for enamel surface Ra roughness but not for geometric surface area. The initial shear bond strength and shear fatigue strength of CU and GP were not influenced by different application times, unlike those of AU and SU. While the surface area of enamel treated with the adhesive agents was not significantly influenced by different application times and type of adhesive, surface Ra roughness of the enamel in the AU and SU groups significantly increased with increasing application time, unlike CU and GP. Conclusions: The results of this study suggest that universal adhesives, used with reduced application times, have adequate Ra surface roughness to provide sufficient resistance to enamel bond fatigue at application times from <1 second to 20 seconds, while the geometric surface area of adhesive-treated enamel did not show any significant changes at these different application times.

A new instrument prototype to measure the geometric surface area of nanoparticles with a time resolution of 1s

2019 ◽  
Vol 132 ◽  
pp. 32-43 ◽  
Author(s):  
Lipeng Su ◽  
Qisheng Ou ◽  
Leo N.Y. Cao ◽  
Qian Du ◽  
David Y.H. Pui
Keyword(s):  
Surface Area ◽  
Time Resolution ◽  
New Instrument ◽  
Geometric Surface ◽  
Geometric Surface Area
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