scholarly journals Rheological Characterization of a Concentrated Phosphate Slurry

Fluids ◽  
2021 ◽  
Vol 6 (5) ◽  
pp. 178
Author(s):  
Souhail Maazioui ◽  
Abderrahim Maazouz ◽  
Fayssal Benkhaldoun ◽  
Driss Ouazar ◽  
Khalid Lamnawar
Keyword(s):  
Flow Behavior ◽  
Continuous Phase ◽  
Raw Material ◽  
Rheological Characterization ◽  
Phosphate Ore ◽  
Insoluble Particles ◽  
Experimental Protocols ◽  
Solid Liquid

Phosphate ore slurry is a suspension of insoluble particles of phosphate rock, the primary raw material for fertilizer and phosphoric acid, in a continuous phase of water. This suspension has a non-Newtonian flow behavior and exhibits yield stress as the shear rate tends toward zero. The suspended particles in the present study were assumed to be noncolloidal. Various grades and phosphate ore concentrations were chosen for this rheological investigation. We created some experimental protocols to determine the main characteristics of these complex fluids and established relevant rheological models with a view to simulate the numerical flow in a cylindrical pipeline. Rheograms of these slurries were obtained using a rotational rheometer and were accurately modeled with commonly used yield-pseudoplastic models. The results show that the concentration of solids in a solid–liquid mixture could be increased while maintaining a desired apparent viscosity. Finally, the design equations for the laminar pipe flow of yield pseudoplastics were investigated to highlight the role of rheological studies in this context.

scholarly journals On the role of higher alcohols in the characterization of cachaça

2020 ◽  
Vol 9 (10) ◽  
pp. e8299109135
Author(s):  
Amazile Biagioni Maia ◽  
Lorena Simão Marinho ◽  
David Lee Nelson
Keyword(s):  
Isoamyl Alcohol ◽  
Raw Material ◽  
Alcoholic Beverages ◽  
Higher Alcohols ◽  
Isobutyl Alcohol ◽  
Higher Alcohol ◽  
Three Samples ◽  
Typical Range

There is a growing interest in chemical markers for the identification and certification of cachaça as a cane spirit produced in Brazil. It is known that the higher alcohols that are usually analyzed (propyl alcohol, Isobutyl alcohol and isoamyl alcohol) occur in all alcoholic beverages (fermented and distilled), but the relative proportions can vary markedly according to the peculiarities of the raw material and the production process. In this work, the contents of higher alcohols in 300 samples of alembic cachaça were compared, 220 from the state of Minas Gerais and 80 from other states, as well as three samples of industrial cachaça and 14 samples of whiskeys of various brands. The typical range of total higher alcohols in cachaça was 180-360 mg/100 mL ethanol. Cachaça containing higher alcohol concentrations greater than 360 mg/100 mL ethanol do not comply with Brazilian legislation. However, cachaças with higher alcohols concentrations below 180 mg/100 mL ethanol, as was found in one of the industrial cachaças, signify adulteration, for example, by mixing with fuel alcohol. The C4/C5 ratio varied less than the C3/C5 ratio, being consistently within the range of 0.20-0.50. In the whiskeys analyzed, the concentrations of higher alcohols were in the range of 160 and 270 mg/100 mL. Therefore, this parameter would not assist in differentiating between cachaça and whiskey. But the C4/C5 ratio was consistently different, being always greater than 0.50 for the whiskeys. Thus, the routine analysis of higher alcohols provides useful information both for tracking possible fraud and for assessments related to the identity or origin of cachaça.

Rheological Characterization of a New Alloy for Thixoforming

2008 ◽  
Vol 141-143 ◽  
pp. 301-306 ◽  
Author(s):  
Annalisa Pola ◽  
Roberto Roberti ◽  
Michael Modigell ◽  
Lars Pape
Keyword(s):  
Flow Behavior ◽  
Thermodynamic Simulation ◽  
Semisolid State ◽  
Rheological Characterization ◽  
Scanning Calorimetry ◽  
Globule Size ◽  
Semisolid Alloy ◽  
Dependent Flow ◽  
Mechanical Performances

A new aluminum alloy (AlSi5Mg0.5Cu0.3Ag) for semisolid die-casting applications was designed, starting from computational thermodynamics calculations by Computherm Database. The goal was to obtain a combination of good castability and proper concentration of hardening elements for strengthening precipitation treatment. The predicted thixotropic properties were verified by measuring the microstructural conventional parameters, such as globule size and shape factor, and the solidification range, by means of differential scanning calorimetry. To complete the characterization of this new alloy and to evaluate its applicability in industrial production, the shear rate and time-dependent flow behavior of the alloy in the semisolid state was studied in a Searle-type rheometer. A future aim of the present research is to try to use rheology testing as the tool to optimize the chemical composition, in order to design an alloy characterized by good mechanical performances and easy processability. Considering the strong influence of the solid fraction content on semisolid alloy viscosity, the rheology tests were interrupted after a certain time and the alloy was deeply freezed using vaporized liquid nitrogen, in order to fix the microstructure and verify the correctness of the thermodynamic simulation.

Evaluation and role of rheological properties in sludge management

1997 ◽  
Vol 36 (11) ◽  
pp. 1-8 ◽  
Author(s):  
Steven K. Dentel
Keyword(s):  
Rheological Properties ◽  
Initial Value ◽  
Rheological Characterization ◽  
Practical Applications ◽  
Treatment Processes ◽  
Technological Advances ◽  
Sludge Characterization ◽  
Empirical Perspective

Rheological characterization of sludges represents one of the few examples of fundamentally derivable properties that has also been successfully related to actual sludge treatment processes. In understanding the relevance and utility of sludge rheology for practical applications, an historical perspective is of some initial value, and this paper summarizes previous developments in the rheological characterization of sludges and other non-Newtonian slurries, both from a theoretical and empirical perspective. In both cases, attention is brought to subtleties that must be considered if uniform and consistent rheological descriptions are to be obtained. Causes of the complex and variable rheological properties observed in sludges are then considered, with attention brought to particular aspects of upstream processes where some influence on sludge viscosity might be exerted. Finally, some practical aspects of rheometry are described. Recent research suggests that a variety of methods for sludge characterization and process optimization can be based on rheological measurements. Examples are presented that utilize both complex and relatively simplified technologies for this purpose, and some predictions are attempted of the probable directions for future developments. Internationally, approaches have differed and, while this diverse and competitive environment favors technological advances, the paper concludes by pointing out the need for consistency in rheological methods where fundamentally based parameters or regulatory concerns may be involved.

scholarly journals Development of a Rheology Die and Flow Characterization of Gas-Containing Polymer Melts

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3305
Author(s):  
Clemens Kastner ◽  
Dominik Altmann ◽  
Eva Kobler ◽  
Georg Steinbichler
Keyword(s):  
Polymer Melts ◽  
Flow Behavior ◽  
Volumetric Flow Rate ◽  
Thermal Characterization ◽  
Polymer Processing ◽  
Rheological Characterization ◽  
Process Measurement ◽  
Flow Characterization ◽  
Chemical Blowing Agents

We present a novel measurement die for characterizing the flow behavior of gas-containing polymer melts. The die is mounted directly on the injection-molding cylinder in place of the mold cavity and thus enables near-process measurement of viscosity (i.e., under the conditions that would be present were a mold attached). This integration also resolves the issue of keeping gas-containing polymer melts under pressure during measurement to prevent desorption. After thermal characterization of the die, various correction approaches were compared against each other to identify the most suitable one for our case. We conducted measurements using polypropylene in combination with two different chemical blowing agents. Increasing the blowing-agent content to up to 6% revealed an interestingly low influence of gases on melt viscosity, which was confirmed by elongational viscosity measurements. For verification, we compared our results to corresponding measurements taken on a high-pressure capillary rheometer and found that they were in excellent agreement. Our die cannot only be used for rheological characterization. Combined with ultrasound sensors, it provides an innovative way of measuring the volumetric flow rate. This development represents an important step in improving the sustainability of gas-containing polymer processing.

scholarly journals Printing of Zirconia Parts via Fused Filament Fabrication

Materials ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 5467
Author(s):  
Dorit Nötzel ◽  
Ralf Eickhoff ◽  
Christoph Pfeifer ◽  
Thomas Hanemann
Keyword(s):  
Flow Behavior ◽  
Special Focus ◽  
Fused Filament Fabrication ◽  
Rheological Characterization ◽  
Structural Details ◽  
Low Shear Stress ◽  
Flow Situation ◽  
The Individual ◽  
Low Shear

In this work, a process chain for the fabrication of dense zirconia parts will be presented covering the individual steps feedstock compounding, 3D printing via Fused Filament Fabrication (FFF) and thermal postprocessing including debinding and sintering. A special focus was set on the comprehensive rheological characterization of the feedstock systems applying high-pressure capillary and oscillation rheometry. The latter allowed the representation of the flow situation especially in the nozzle of the print head with the occurring low-shear stress. Oscillation rheometry enabled the clarification of the surfactant’s concentration, here stearic acid, or more general, the feedstocks composition influence on the resulting feedstock flow behavior. Finally, dense ceramic parts (best values around 99 % of theory) were realized with structural details smaller than 100 µm.

scholarly journals Development and Multiscale Characterization of 3D Warp Interlock Flax Fabrics with Different Woven Architectures for Composite Applications

Fibers ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 15 ◽  
Author(s):  
Henri Lansiaux ◽  
Damien Soulat ◽  
François Boussu ◽  
Ahmad Rashed Labanieh
Keyword(s):  
Mechanical Properties ◽  
Natural Fibers ◽  
Three Dimensional ◽  
Tensile Tests ◽  
Woven Fabrics ◽  
Flax Fiber ◽  
Raw Material ◽  
Mechanical Tensile

Multiscale characterization of the textile preform made of natural fibers is an indispensable way to understand and assess the mechanical properties and behavior of composite. In this study, a multiscale experimental characterization is performed on three-dimensional (3D) warp interlock woven fabrics made of flax fiber on the fiber (micro), roving (meso), and fabric (macro) scales. The mechanical tensile properties of the flax fiber were determined by using the impregnated fiber bundle test. The effect of the twist was considered in the back-calculation of the fiber stiffness to reveal the calculation limits of the rule of mixture. Tensile tests on dry rovings were carried out while considering different twist levels to determine the optimal amount of twist required to weave the flax roving into a 3D warp interlock. Finally, at fabric-scale, six different 3D warp interlock architectures were woven to understand the role of the architecture of binding rovings on the mechanical properties of the dry 3D fabric. The results reveal the importance of considering the properties of the fiber and roving at these scales to determine the more adequate raw material for weaving. Further, the characterization of the 3D woven structures shows the preponderant role of the binding roving on their structural and mechanical properties.

scholarly journals Physicochemical, Microstructural, and Rheological Characterization of Tigernut (Cyperus esculentus) Starch

2019 ◽  
Vol 2019 ◽  
pp. 1-7
Author(s):  
P. T. Akonor ◽  
C. Tortoe ◽  
C. Oduro-Yeboah ◽  
E. A. Saka ◽  
J. Ewool
Keyword(s):  
Physicochemical Properties ◽  
Amylose Content ◽  
Flow Behavior ◽  
Pasting Properties ◽  
Cyperus Esculentus ◽  
Rheological Characterization ◽  
Freeze Thaw ◽  
Starch Gels

The aim of this study was to characterize the physicochemical properties of starch isolated from two varieties of tigernuts. The results showed wide variations between the two types of tigernuts. Mean granule sizes were 11.1 and 6.1 μm, respectively, for starch from the yellow and black while amylose content ranged from 19 to 21%. Starch gels from the yellow variety were more stable to freeze-thaw and recorded 37.1% syneresis, compared to 56.5% after the first storage cycle. Pasting properties were significantly different (p < 0.05) among starch from the two tigernut varieties, with black recording higher peak viscosity, lower breakdown, and higher setback viscosity. Gels made from the yellow variety were clearer, softer, more adhesive, and more cohesive. Both gels showed a pseudoplastic flow behavior without thixotropy.

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

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