scholarly journals Dissolution Kinetics of International Simple Glass and Formation of Secondary Phases at Very High Surface Area to Solution Ratio in Young Cement Water

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1254
Author(s):  
Karine Ferrand ◽  
Martina Klinkenberg ◽  
Sébastien Caes ◽  
Jenna Poonoosamy ◽  
Wouter Van Renterghem ◽  
...  
Keyword(s):  
High Surface ◽  
High Surface Area ◽  
Dissolution Kinetics ◽  
Dissolution Behavior ◽  
Secondary Phases ◽  
Residual Rate ◽  
Glass Dissolution ◽  
Ph Decrease ◽  
Kinetics Of ◽  
Very High

Static dissolution experiments were carried out with the reference International Simple Glass under hyperalkaline pH at 70 °C and very high SA/V ratio. Three aspects of glass dissolution behavior were investigated, (1) the rate drop regime and the residual rate (stage II), (2) the formation of secondary phases including thermodynamic aspects, and (3) the microstructure of the interface of altered glass and secondary phases. A very low residual rate of 6 × 10−6 g/m2d was determined based on boron release, which was several orders of magnitude lower than the initial rate established between the start of the experiments and the first sampling on day 59. The presence of a porous layer with a thickness varying between 80 nm and 250 nm and a pore size between 10 nm and 50 nm was observed. CSH phases with a low Ca/Si ratio of 0.3–0.4 and zeolites were also visible at the surface of the altered glass grains, but no glass alteration resumption occurred, probably due to an important pH decrease already at day 59. Thermodynamic calculations assuming congruent glass dissolution and precipitation of the dissolved aqueous species confirmed the precipitation of CSH phases and zeolites.

scholarly journals Transparent Monolithic Metal Ion Containing Nanophase Aerogels

1999 ◽  
Vol 581 ◽  
Author(s):  
William M. Risen ◽  
Xiangjun Hu ◽  
Shuang Ji ◽  
Kenneth Littrell
Keyword(s):  
Metal Ion ◽  
Structural Integrity ◽  
High Surface ◽  
High Surface Area ◽  
Visible Range ◽  
High Surface Area Materials ◽  
Kinetics Of ◽  
Subsequent Modification ◽  
Very High ◽  
Kinetics Of Gelation

ABSTRACTThe formation of monolithic and transparent transition metal containing aerogels has been achieved through cooperative interactions of high molecular weight functionalized carbohydrates and silica precursors, which strongly influence the kinetics of gelation. After initial gelation, subsequent modification of the ligating character of the system, coordination of the group VIII metal ions, and supercritical extraction afford the aerogels. The structures at the nanophase level have been probed by photon and electron transmission and neutron scattering techniques to help elucidate the basis for structural integrity together with the small entity sizes that permit transparency in the visible range. They also help with understanding the chemical reactivities of the metal-containing sites in these very high surface area materials. These results are discussed in connection with new reaction studies.

Son68 Glass Dissolution Kinetics at High Reaction Progress: Mechanisms Accounting for The Residual Alteration Rate

2006 ◽  
Vol 932 ◽  
Author(s):  
P. Frugier ◽  
S. Gin ◽  
J.E. Lartigue ◽  
E. Deloule
Keyword(s):  
Diffusion Mechanism ◽  
Dissolution Kinetics ◽  
Solution Chemistry ◽  
Behavior Modeling ◽  
Secondary Phases ◽  
Residual Rate ◽  
Glass Dissolution ◽  
Geological Repository ◽  
Element Speciation ◽  
Constituent Elements

ABSTRACTIn a highly confined medium corresponding to geological repository conditions, the alteration rate of the French SON68 inactive nuclear reference glass drops by about four orders of magnitude below the initial rate. However, extended experiments lasting months or years provide evidence of a virtually constant or slowly decreasing residual alteration rate. Although very low, this rate could account for most of the altered glass thickness after 10 000 years. Experiments at high temperatures and especially high glass-surface-area-to-solution-volume ratios were performed to reveal and quantify the predominant mechanisms underlying the residual rate. The authors describe the characterization of the solution chemistry, the crystallized secondary phases, and the amorphous gel observed after alteration of the French SON68 inactive reference glass, and discuss their implications in terms of long-term behavior modeling. A slow diffusion mechanism is identified in the solid, involving alkalis in particular but also boron. This mechanism results in higher concentrations in solution that affect the system chemistry, not only by slightly modifying the pH and element speciation in solution (e.g. silicon), but also by inducing the precipitation of new crystallized secondary phases that can consume glass constituent elements in the same way as simple solution renewal. Diffusion and the precipitation of secondary phases are two mechanisms to be considered to account for the residual rate.

scholarly journals The initial dissolution rates of simulated UK Magnox–ThORP blend nuclear waste glass as a function of pH, temperature and waste loading

2015 ◽  
Vol 79 (6) ◽  
pp. 1529-1542 ◽  
Author(s):  
N. Cassingham ◽  
C.L. Corkhill ◽  
D.J. Backhouse ◽  
R.J. Hand ◽  
J.V. Ryan ◽  
...  
Keyword(s):  
Dissolution Kinetics ◽  
Intrinsic Rate ◽  
Waste Glass ◽  
High Level Waste ◽  
Dissolution Mechanism ◽  
Dissolution Rates ◽  
Forward Rates ◽  
Glass Dissolution ◽  
High Level ◽  
Kinetics Of

AbstractThe first comprehensive assessment of the dissolution kinetics of simulant Magnox–ThORP blended UK high-level waste glass, obtained by performing a range of single-pass flow-through experiments, is reported here. Inherent forward rates of glass dissolution were determined over a temperature range of 23 to 70°C and an alkaline pH range of 8.0 to 12.0. Linear regression techniques were applied to the TST kinetic rate law to obtain fundamental parameters necessary to model the dissolution kinetics of UK high-level waste glass (the activation energy (Ea), pH power law coefficient (η) and the intrinsic rate constant (k0)), which is of importance to the post-closure safety case for the geological disposal of vitreous products. The activation energies based on B release ranged from 55 ± 3 to 83 ± 9 kJ mol–1, indicating that Magnox–THORP blend glass dissolution has a surface-controlled mechanism, similar to that of other high-level waste simulant glass compositions such as the French SON68 and LAW in the US. Forward dissolution rates, based on Si, B and Na release, suggested that the dissolution mechanism under dilute conditions, and pH and temperature ranges of this study, was not sensitive to composition as defined by HLW-incorporation rate.

HSA-Cercanam®: A New Material with a Continuous Nanopore Network

2003 ◽  
Vol 788 ◽  
Author(s):  
A. Akash ◽  
B. Nair ◽  
K. Minnick ◽  
M. Wilson ◽  
J. Hartvigsen
Keyword(s):  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Unique Nature ◽  
Catalyst Type ◽  
Reaction Chambers ◽  
New Material ◽  
One Step ◽  
Very High ◽  
Functional Ceramic

ABSTRACTA novel nano-ceramic material, called HSA-CERCANAM®, which has a very high surface area with a nanopore network has been developed. HSA-CERCANAM® can be casted in various shapes and forms resulting in a monolithic piece that has surface area as high as 80–100 m2/g. The surface area and the nanopore network of HSA-CERCANAM® remains stable at temperatures as high as 1000°C. Furthermore, the unique nature of HSA-CERCANAM® allows it to be casted on and around features, either sacrificial or permanent. Using sacrificial features, microchannels can be incorporated internally into the monolithic HSA-CERCANAM® piece in a simple, one-step process. Further, this monolithic ceramic component, which has an intrinsically high surface area and a nanopore network, can be infiltrated with a desired catalyst. This could offer clear technological advantages over currently available microreactors. The surface area, porosity, catalyst type and infiltration levels are some of the ways in which tailored microstructures can be realized in components such as mixers, heat exchangers, extractors, filters or reaction chambers thereby leading to highly efficient, multi-functional ceramic micro-devices.

Adsorption of different dyes from aqueous solution using Si-MCM-41 having very high surface area

2016 ◽  
Vol 23 (5) ◽  
pp. 1227-1237 ◽  
Author(s):  
Haribandhu Chaudhuri ◽  
Subhajit Dash ◽  
Ashis Sarkar
Keyword(s):  
Aqueous Solution ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Very High ◽  
Mcm 41

Three-Dimensional Cage Type Mesoporous CN-Based Hybrid Material with Very High Surface Area and Pore Volume

2007 ◽  
Vol 19 (17) ◽  
pp. 4367-4372 ◽  
Author(s):  
Ajayan Vinu ◽  
Pavuluri Srinivasu ◽  
Dhanashri P. Sawant ◽  
Toshiyuki Mori ◽  
Katsuhiko Ariga ◽  
...  
Keyword(s):  
Surface Area ◽  
Hybrid Material ◽  
Pore Volume ◽  
High Surface ◽  
High Surface Area ◽  
Three Dimensional ◽  
Very High

Molecular Architecture and its role in Silica Sol-Gel Polymerization

1990 ◽  
Vol 180 ◽  
Author(s):  
P. C. Cagle ◽  
W. G. Klemperer ◽  
C. A. Simmons
Keyword(s):  
Molecular Level ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Silica Sol ◽  
Molecular Architecture ◽  
Model Studies ◽  
Large Size ◽  
Neutral Conditions ◽  
Very High

ABSTRACTSol-gel polymerization of [Si8O12](OCH3)8 in CH3CN under neutral conditions yields very high surface area (SBET > 900 m2/g) xerogels. This property is seen to result from the structure of the gel on the molecular level. According to N2 adsorption studies, model studies, and TEM studies, the large size and rigidity of the cubic [Si8O12] core structure leads to polymers whose rigidity inhibits extensive crosslinking of the type observed in orthosilicate derived xerogels.

Removal of single component chlorinated hydrocarbon vapor by activated carbon of very high surface area

1999 ◽  
Vol 15 (1) ◽  
pp. 79-90 ◽  
Author(s):  
Yasushi Takeuchi ◽  
Mitsuharu Hino ◽  
Yukihiro Yoshimura ◽  
Toshiro Otowa ◽  
Hisatsugu Izuhara ◽  
...  
Keyword(s):  
Activated Carbon ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Single Component ◽  
Chlorinated Hydrocarbon ◽  
Very High ◽  
Hydrocarbon Vapor
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