Correlation of Laboratory and Stripa Field Leaching Studies

1988 ◽  
Vol 127 ◽  
Author(s):  
B. K. Zoitos ◽  
D. E. Clark ◽  
A. R. Lodding ◽  
G. G. Wicks
Keyword(s):  
Laboratory Study ◽  
Secondary Ion Mass Spectrometry ◽  
Field Tests ◽  
Surface Layers ◽  
Infrared Reflection ◽  
Significant Difference ◽  
Field Samples ◽  
Surface Alteration ◽  
Infrared Reflection Spectroscopy ◽  
Secondary Ion

ABSTRACTA variety of surface sensitive techniques has been used to assess surface layers formed on SRL 165 waste glass specimens from the Stripa burial study and from a laboratory study designed to simulate conditions of the Stripa environment. The laboratory study included static and slow flow tests carried out for periods up to 6 and 24 months, respectively. Comparisons of leached layers formed in the two studies are based upon secondary ion mass spectrometry (SIMS), Fourier transform infrared reflection spectroscopy (FTIRRS), and scanning electron microscopy-electron microprobe (SEM-EMP) analysis.Results demonstrate that surface layers having similar trends in elemental profiles were developed in both lab and field tests. It was also found that both sets of samples showed similar changes in FTIRR spectra. One significant difference between the lab and field samples was that surface alteration, as indicated by changes in FTIRR spectra and leached layer thickness (from SIMS), occurred more rapidly in the lab tests.

The Effect of Temperature and Si Concentration on the Mixing of AlAs/GaAs Superlattices

1986 ◽  
Vol 77 ◽  
Author(s):  
Ping Mei ◽  
H. W. Yoon ◽  
T. Venkatesan ◽  
S. A. Schwarz ◽  
J. P. Harbison
Keyword(s):  
Activation Energy ◽  
Molecular Beam ◽  
Secondary Ion Mass Spectrometry ◽  
Diffusion Length ◽  
Dopant Concentration ◽  
Effect Of Temperature ◽  
Surface Layers ◽  
Near Surface ◽  
Depth Profiles ◽  
Secondary Ion

ABSTRACTThe intermixing of AlAs/GaAs superlattices has been investigated as a function of Si concentration following anneals in the range of 500 to 900 C. The superlattice samples were grown by molecular beam epitaxy(MBE) and the near surface layers were doped with silicon at concentrations of 2×10 to 5×1018 cm-3. Si and Al depth profiles were measured with secondary ion mass spectrometry (SIMS).The diffusion length and activation energy of Al as a function of silicon dopant concentration are derived from the SIMS data. In the temperature range studied an activation energy for the Al interdiffusion of -4eV is observed with the diffusion coefficients increasing rapidly with Si concentration.

Waste Glass Alteration Processes, Surface Layer Evolution and Rate Limiting Steps

1993 ◽  
Vol 333 ◽  
Author(s):  
D. E. Clark ◽  
R. L. Schulz ◽  
G. G. Wicks ◽  
A. R. Loading
Keyword(s):  
Field Experiments ◽  
Secondary Ion Mass Spectrometry ◽  
Volume Ratio ◽  
Waste Glass ◽  
Aqueous Environment ◽  
Surface Layers ◽  
Factors Affecting ◽  
Alteration Processes ◽  
Rate Limiting ◽  
Secondary Ion

ABSTRACTThis paper provides an overview of waste glass alteration. Emphasis is on the evolution of surface layers and factors affecting the alteration rate when glass is subjected to an aqueous environment. The extent, type and rate of alteration is determined by a variety of parameters including time, temperature, glass composition, pH, Eh, composition of leachate/geology, the presence of other engineered barriers, flow conditions and surface area/volume ratio. Models (based on kinetic and thermodynamic considerations) developed by other researchers that are consistent with the experimental observations from the laboratory and field experiments are discussed. The morphology of the surface layers as described by interpretation of secondary ion mass spectrometry (SIMS) analyses on waste glasses and the role the various layers play in the alteration process is presented as well.

Early Stages of Film Formation During the Leaching of Radioactive Waste Glasses

1984 ◽  
Vol 44 ◽  
Author(s):  
C. A. Houser ◽  
C. G. Pantano
Keyword(s):  
Radioactive Waste ◽  
Film Formation ◽  
Layer Formation ◽  
Surface Layers ◽  
Depth Profiles ◽  
Glass Dissolution ◽  
Early Stages ◽  
Surface Alteration ◽  
Secondary Ion ◽  
Subsequent Incorporation

AbstractThe early stages of surface alteration-layer formation were examined during the leaching of some candidate radioactive waste glasses. The composition-depth profiles of the leached surfaces were obtained with sputter-induced photon spectroscopy (SIPS) and secondary-ion mass spectroscopy (SIMS). It was observed that the formation of multiple surface layers is a general feature of the glass dissolution process. The sequence of the layer compositions depends upon the order in which solubility limits are attained in solution, the adsorption or precipitation of insoluble hydrates at the glass/water interface, and subsequent incorporation of these insoluble hydrates behind the advancing reaction front. The boundary between the surface layer and bulk glass is sharp.

Hydrogen Passivation of Be-Acceptors in AiGaAs/GaAs Quantum Well Structures

1998 ◽  
Vol 513 ◽  
Author(s):  
Q. X. Zhaoa ◽  
U. Södervall ◽  
M. Willandera ◽  
B. O. Fimland ◽  
D. Crawford ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Molecular Beam ◽  
Secondary Ion Mass Spectrometry ◽  
Hydrogen Passivation ◽  
Quantum Well Structures ◽  
Significant Difference ◽  
20 Nm ◽  
First Time ◽  
Secondary Ion ◽  
Gas Pressures

ABSTRACTHigh quality Al0.3Ga0.7As/GaAs quantum wells with centrally doped Be-acceptors were grown by molecular beam epitaxy (MBE). The well width is either 10 nm or 20 nm, and the concentration of Be-acceptors is varied between 5× 1016/cm3 and 2×1018/cm3. The structures were treated systematically by dc H-plasma at different sample temperatures, gas pressures and cooling down procedures. The passivation of Be-acceptors were characterized by photoluminescence spectroscopy and secondary ion mass spectrometry (SIMS). Without causing degradation of the A1GaAs/GaAs interfaces, we have obtained, for the first time, a deactivation of above 80% of the Be-acceptors. The influence of the Be-doping on the bandgap excitons in the QW structures is also investigated in detail. A significant difference is found in comparison with the earlier reports for 150 Å wide quantum wells, in which different samples were used for different doping concentrations.

Sims Depth Profiling Studies of Sphene-Based Ceramics and Glass Ceramics Leached in Synthetic Groundwater

1981 ◽  
Vol 11 ◽  
Author(s):  
P.J. Hayward ◽  
W.H. Hocking ◽  
F.E. Doern ◽  
E.V. Cecchetto
Keyword(s):  
Secondary Ion Mass Spectrometry ◽  
Depth Profiling ◽  
Glass Ceramics ◽  
High Ionic Strength ◽  
Ceramic Surface ◽  
Surface Alteration ◽  
Synthetic Groundwater ◽  
Secondary Ion ◽  
Fuel Reprocessing ◽  
Sims Depth Profiling

ABSTRACTGlass ceramics and ceramics based on the mineral sphene (CaTiSiO5) are being developed to host the wastes arising from possible future CANDU* fuel reprocessing. Results from leaching tests in deionized water and in synthetic groundwater indicate that these materials are highly durable. Secondary Ion Mass Spectrometry (SIMS) depth profiling of leached specimens suggests that leaching in the glass ceramics is predominantly confined to the glass phase. The high ionic strength and composition of the groundwater have a significant passivating effect on leaching and surface alteration phenomena, and encourage the precipitation of new phases on the ceramic surface. Leaching results, scanning electron microscope (SEM) observations and SIMS depth profile measurements are compared and discussed.

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