Strength developement with burial in fine-grained sediments from the Saguenay Fjord, Quebec: Discussion

1996 ◽  
Vol 33 (1) ◽  
pp. 206-206
Author(s):  
John H Schmertmann
Keyword(s):  
Fine Grained ◽  
Saguenay Fjord

Strength development with burial in fine-grained sediments from the Saguenay Fjord, Quebec

1995 ◽  
Vol 32 (2) ◽  
pp. 247-262 ◽  
Author(s):  
D. Perret ◽  
J. Locat ◽  
S. Leroueil
Keyword(s):  
Organic Matter ◽  
Strength Development ◽  
Creep Tests ◽  
Fine Grained ◽  
Episodic Events ◽  
Depositional Processes ◽  
Liquidity Index ◽  
Saguenay Fjord ◽  
Continuous Sedimentation ◽  
Marine Clays

Following a sedimentological and geotechnical investigation, two main types of materials were identified in the Saguenay Fjord: (1) organic-rich sediments deposited by continuous sedimentation, and (2) unbioturbated sediments deposited rapidly by episodic events. The consolidation state of sediments with depth were analysed. In all subsurface deposits, sediments are overconsolidated irrespective of the depositional processes. However, in continuously deposited sediments, strength develops more rapidly than in turbidites or mass flows. In the surficial bioturbated layer, strength and liquidity index gradients are at a maximum and the rate of strength variation can reach values as high as 9 kPa/kPa. Results from one-dimensional creep tests suggest that in the organic-poor turbidites, the strength development is controlled, at least partly, by thixotropic strengthening. For bioturbated clays, it appears that the viscosity and the aggregating potential of organic matter controls the evolution of the strength with burial. Key words : Saguenay Fjord, marine clays, consolidation, turbidite, organic matter, bioturbation.

Mercury in the Sediments of the Gulf of St. Lawrence

1975 ◽  
Vol 12 (7) ◽  
pp. 1219-1237 ◽  
Author(s):  
D. H. Loring
Keyword(s):  
Organic Matter ◽  
Total Mercury ◽  
Terrestrial Organic Matter ◽  
Sedimentation Pattern ◽  
Lawrence Estuary ◽  
Fine Grained ◽  
Depositional Processes ◽  
Saguenay Fjord ◽  
Shelf Sediments ◽  
St Lawrence Estuary

In sediments collected from the Saguenay fjord, the St. Lawrence estuary, and open Gulf of St. Lawrence, total mercury varies with sediment texture and location from 10 to 12 300 ppb (average 386 ppb). The highest concentrations occur in the Saguenay fjord (average 2980 ppb) and the lowest in the open Gulf of St. Lawrence (average 150 ppb). The concentration of mercury increases with decreasing grain size, the highest concentrations occur in the fine-grained sediments of the submarine troughs and shelf valleys and the lowest in the sandy shelf sediments. Analyses of the sediments from the Saguenay fjord, where mercury values range from 12 300 ppb at its head to > 500 ppb in the lower reaches, indicate that most of the mercury (70 to 90% of the total) is held by the organic matter in the sediments. The distribution of mercury in the fjord is apparently controlled by the downstream dispersal from local industrial sources of mercury-rich organic matter, most likely of terrestrial origin because of its high C/N ratio. In the St. Lawrence estuary where mercury values range from 30 to 950 ppb, and in the open Gulf where correlations between variables are lower and scattered anomalies exist, analyses indicate that mercury accumulates along with the fine-grained inorganic and organic matter in response to the present depositional processes. The distribution of mercury appears to be controlled by the sedimentation pattern. Terrestrial organic matter and industrial waste originating in the Saguenay drainage area have the strongest influence on its distribution.

Distribution and partition of cobalt, nickel, chromium, and vanadium in the sediments of the Saguenay fjord

1976 ◽  
Vol 13 (12) ◽  
pp. 1706-1718 ◽  
Author(s):  
D. H. Loring
Keyword(s):  
Sedimentation Pattern ◽  
Lawrence Estuary ◽  
Inorganic Particles ◽  
Fine Grained ◽  
Nickel Chromium ◽  
Cobalt Nickel ◽  
Saguenay Fjord ◽  
St Lawrence Estuary ◽  
Sandy Sediments ◽  
Fjord Sediments

In the Saguenay fjord sediments, cobalt (Co) concentrations vary between 5 and 20 ppm, nickel (Ni) concentrations between 7 and 36 ppm, chromium (Cr) concentrations from 33 to 70 ppm, and vanadium (V) concentrations from 67 to 149 ppm in relation to texture and location. The highest concentrations are found in the fine-grained sediments from the upper part of the fjord and the lowest concentrations occur in the sandy sediments near the mouth of the fjord. On the average, the fjord's muds are neither greatly enriched nor depleted in Co, Ni, Cr, and V when compared to muds from the St. Lawrence estuary and the open Gulf of St. Lawrence.Acetic acid extractions indicate that 8 to 25% of the total Co, 11 to 29% of the total Ni, 2 to 9% of the total Cr, and 5 to 23% of the total V are contributed by the non-detrital fraction and may be available to the biota in the fjord. Non-detrital Co, Ni, Cr, and V appear to have been removed from solution by adsorption onto fine-grained inorganic particles and their distribution controlled by the sedimentation pattern. Non-delrital Cr, V, and Ni are also associated with Mn and Fe oxides, which are present as grain coatings. Most of the Co, Ni, Cr, and V in the detrital fraction, which accounts for 71 to 98% of the total elemental concentrations are found in sulphide, oxide, and ferromagnesian minerals. These minerals accumulate at the same rate as other detrital sedimentary material in response to the present depositional conditions.The discharge of industrial waste has not resulted in an increase in the concentrations of Co, Ni, Cr, and V in the sediments above their natural levels.

The distribution and partition of zinc, copper, and lead in the sediments of the Saguenay fjord

1976 ◽  
Vol 13 (7) ◽  
pp. 960-971 ◽  
Author(s):  
D. H. Loring
Keyword(s):  
Soluble Fraction ◽  
Insoluble Fraction ◽  
Sediment Texture ◽  
Terrestrial Organic Matter ◽  
Lawrence Estuary ◽  
Sulphide Minerals ◽  
Fine Grained ◽  
Saguenay Fjord ◽  
Zn And Cu In ◽  
St Lawrence Estuary

Zinc (Zn) concentrations vary between 43 and 145 ppm, copper (Cu) concentrations between 6 and 33 ppm, and lead (Pb) concentrations between 14 and 66 ppm in relation to sediment texture and location in the Saguenay fjord. The concentrations of the elements increase with decreasing grain size; the highest concentrations occur in the fine grained sediments (muds) in the upper part of the fjord and they decrease downstream. On the average, the fjord muds are enriched in Zn and Pb when compared to sediments from the St. Lawrence estuary and the open Gulf of St. Lawrence.Acetic acid extractions of the sediments indicate that 14 to 29% of the total Zn, 14 to 21% of the total Cu, and 12 to 25% of the total Pb is contributed by the non-detrital (acid soluble) fraction, and the remainder (70–88%) is contributed by the detrital (acid insoluble) fraction. Most of the Zn, Cu, and Pb in the detrital fraction is held in discrete sulphide minerals. These minerals accumulate at the same rate as other detrital sedimentary material in response to the present depositional conditions. Non-detrital Zn, Cu, and Pb contributions represent the portion of the total element content adsorbed by fine grained inorganic and organic material during transport and deposition. The distributions of non-detrital Pb and to a lesser extent of Zn and Cu in the fjord are apparently controlled by the downstream dispersal from local industrial sources of mercury (Hg)-rich terrestrial organic matter.

Strength development with burial in fine-grained sediments from Saguenay Fjord, Quebec: Reply

1996 ◽  
Vol 33 (1) ◽  
pp. 207-207
Author(s):  
D Perret ◽  
J Locat ◽  
S Leroueil
Keyword(s):  
Strength Development ◽  
Fine Grained ◽  
Saguenay Fjord

Application of an image management system in microscopy

1992 ◽  
Vol 50 (2) ◽  
pp. 1052-1053
Author(s):  
Richard S. Chemock
Keyword(s):  
Data Storage ◽  
Cost Savings ◽  
Image Data ◽  
Analytical Techniques ◽  
Operational Mode ◽  
Fine Grained ◽  
Image Recording ◽  
Primary Output ◽  
Capacity Data ◽  
Image Management System

One of the most common tasks in a typical analysis lab is the recording of images. Many analytical techniques (TEM, SEM, and metallography for example) produce images as their primary output. Until recently, the most common method of recording images was by using film. Current PS/2R systems offer very large capacity data storage devices and high resolution displays, making it practical to work with analytical images on PS/2s, thereby sidestepping the traditional film and darkroom steps. This change in operational mode offers many benefits: cost savings, throughput, archiving and searching capabilities as well as direct incorporation of the image data into reports.The conventional way to record images involves film, either sheet film (with its associated wet chemistry) for TEM or PolaroidR film for SEM and light microscopy. Although film is inconvenient, it does have the highest quality of all available image recording techniques. The fine grained film used for TEM has a resolution that would exceed a 4096x4096x16 bit digital image.

Use of fractals to describe microstructures of porous thick-film platinum electrodes

1992 ◽  
Vol 50 (1) ◽  
pp. 314-315
Author(s):  
Steven D. Toteda
Keyword(s):  
Fractal Dimension ◽  
Power Plants ◽  
Electrical Response ◽  
Cubic Phase ◽  
Platinum Electrodes ◽  
Fine Grained ◽  
Impedance Response ◽  
Platinum Particles ◽  
Energy Surfaces ◽  
Highly Porous

Zirconia oxygen sensors, in such applications as power plants and automobiles, generally utilize platinum electrodes for the catalytic reaction of dissociating O2 at the surface. The microstructure of the platinum electrode defines the resulting electrical response. The electrode must be porous enough to allow the oxygen to reach the zirconia surface while still remaining electrically continuous. At low sintering temperatures, the platinum is highly porous and fine grained. The platinum particles sinter together as the firing temperatures are increased. As the sintering temperatures are raised even further, the surface of the platinum begins to facet with lower energy surfaces. These microstructural changes can be seen in Figures 1 and 2, but the goal of the work is to characterize the microstructure by its fractal dimension and then relate the fractal dimension to the electrical response. The sensors were fabricated from zirconia powder stabilized in the cubic phase with 8 mol% percent yttria. Each substrate was sintered for 14 hours at 1200°C. The resulting zirconia pellets, 13mm in diameter and 2mm in thickness, were roughly 97 to 98 percent of theoretical density. The Engelhard #6082 platinum paste was applied to the zirconia disks after they were mechanically polished ( diamond). The electrodes were then sintered at temperatures ranging from 600°C to 1000°C. Each sensor was tested to determine the impedance response from 1Hz to 5,000Hz. These frequencies correspond to the electrode at the test temperature of 600°C.

Amorphous silica coating on α-alumina particles

1995 ◽  
Vol 53 ◽  
pp. 210-211
Author(s):  
J. W. Mellowes ◽  
C. M. Chun ◽  
I. A. Aksay
Keyword(s):  
Amorphous Silica ◽  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Silica Coating ◽  
Full Density ◽  
Optimal Conditions ◽  
Fine Grained ◽  
Alumina Particles ◽  
Complete Mullitization ◽  
Powder Compacts

Mullite (3Al2O32SiO2) can be fabricated by transient viscous sintering using composite particles which consist of inner cores of a-alumina and outer coatings of amorphous silica. Powder compacts prepared with these particles are sintered to almost full density at relatively low temperatures (~1300°C) and converted to dense, fine-grained mullite at higher temperatures (>1500°C) by reaction between the alumina core and the silica coating. In order to achieve complete mullitization, optimal conditions for coating alumina particles with amorphous silica must be achieved. Formation of amorphous silica can occur in solution (homogeneous nucleation) or on the surface of alumina (heterogeneous nucleation) depending on the degree of supersaturation of the solvent in which the particles are immersed. Successful coating of silica on alumina occurs when heterogeneous nucleation is promoted and homogeneous nucleation is suppressed. Therefore, one key to successful coating is an understanding of the factors such as pH and concentration that control silica nucleation in aqueous solutions. In the current work, we use TEM to determine the optimal conditions of this processing.

Interfacial structures of dissimilar materials joined by capacitor-discharge welding

1994 ◽  
Vol 52 ◽  
pp. 534-535
Author(s):  
C. P. Doğan ◽  
R. D. Wilson ◽  
J. A. Hawk
Keyword(s):  
Rapid Solidification ◽  
Fusion Zone ◽  
Dissimilar Materials ◽  
Solidification Process ◽  
Weld Interface ◽  
Capacitor Discharge ◽  
Fine Grained ◽  
Iron Aluminum ◽  
Conductive Ceramics ◽  
Capacitor Discharge Welding

Capacitor Discharge Welding is a rapid solidification technique for joining conductive materials that results in a narrow fusion zone and almost no heat affected zone. As a result, the microstructures and properties of the bulk materials are essentially continuous across the weld interface. During the joining process, one of the materials to be joined acts as the anode and the other acts as the cathode. The anode and cathode are brought together with a concomitant discharge of a capacitor bank, creating an arc which melts the materials at the joining surfaces and welds them together (Fig. 1). As the electrodes impact, the arc is extinguished, and the molten interface cools at rates that can exceed 106 K/s. This process results in reduced porosity in the fusion zone, a fine-grained weldment, and a reduced tendency for hot cracking.At the U.S. Bureau of Mines, we are currently examining the possibilities of using capacitor discharge welding to join dissimilar metals, metals to intermetallics, and metals to conductive ceramics. In this particular study, we will examine the microstructural characteristics of iron-aluminum welds in detail, focussing our attention primarily on interfaces produced during the rapid solidification process.

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