scholarly journals On the Role of Stirring on Microstructure and Ductility of Rheocast Al Alloys

JOM ◽  
2021 ◽  
Author(s):  
Qing Zhang ◽  
Stefan Jonsson ◽  
Anders E. W. Jarfors
Keyword(s):  
Particle Size ◽  
Fracture Surface ◽  
Oxide Films ◽  
Al Alloys ◽  
Combined Effect ◽  
Liquid Feeding ◽  
Oxide Particles ◽  
Large Clusters ◽  
Mg Content

AbstractTwo alloys containing different Mg contents have been used to study the combined effect of stirring and oxidation on microstructure and ductility. The results show that intensive stirring can sufficiently disperse the α-Al particles and enable better liquid feeding during solidification and consequently reduce the porosity. The morphology of the oxides is determined by the amount of both Mg and stirring. With lower Mg content, the oxides present as oxide films, which can be broken up during stirring. In alloy with higher Mg content, the oxides exist as particles with numerous cracks, and the particle size increases slightly after stirring. In the Magsimal 59 alloy, due to the presence of large clusters of pores in the fracture surface, the influence of the small oxide particles on the ductility is negligible. In contrast, in the 42000 alloy, large oxide films on the fracture surface are correlated with the ductility.

Role of anodic oxide films in the corrosion of aluminum and its alloys

2018 ◽  
Vol 36 (1) ◽  
pp. 35-54 ◽  
Author(s):  
Hideaki Takahashi ◽  
Makoto Chiba
Keyword(s):  
Synergistic Effects ◽  
Pure Water ◽  
Pure Aluminum ◽  
Oxide Films ◽  
Anodic Oxide ◽  
Al Alloys ◽  
Anodic Oxide Films ◽  
Pore Sealing ◽  
Barrier Type

AbstractAnodic oxide films on aluminum are classified into two groups: porous-type anodic oxide films (PAOF) and barrier-type anodic oxide films (BAOF). The present paper is a review of the corrosion of pure aluminum (Al) and Al alloys covered with PAOF and BAOF, focusing on the role of anodic oxide films in the process of corrosion. Several topics are discussed in detail, including (a) changes in the dissolution mode of PAOF in acidic media by pore sealing, (b) hydration and dissolution of BAOF in pure water and neutral solutions containing organic and inorganic electrolytes, (c) pitting corrosion during the cathodic polarization of Al covered with PAOF and BAOF, (d) corrosion of PAOF-covered Al/Bi/Sn alloys in alcohols at 142°C, and (e) synergistic effects of Cl− and Cu2+ ions in the corrosion of PAOF-covered Al alloys in aqueous solutions.

scholarly journals Surface Modification of PES Hollow Fiber Membranes using Iron Oxide Particles for Water Treatment Does Particle Size Really Matter?

2021 ◽  
Vol 17 (5) ◽  
pp. 621-635
Author(s):  
Nadiene Salleha Mohd Nawi ◽  
Lau Woei Jye ◽  
Norhaniza Yusof ◽  
Noresah Said ◽  
Ahmad Fauzi Ismail
Keyword(s):  
Particle Size ◽  
Surface Modification ◽  
Iron Oxide ◽  
Water Treatment ◽  
Polymeric Membranes ◽  
Particle Sizes ◽  
Particle Type ◽  
Iron Oxide Particles ◽  
Oxide Particles

Factors such as particle type and its loading have been previously studied in tailoring the efficiency of particles-modified polymeric membranes for water treatment. However, the role of particle sizes in membrane modification is often overlooked. 

Fibrin Formation: The Role of the Fibrinogen-Fibrin Monomer Complex

1976 ◽  
Vol 36 (01) ◽  
pp. 037-048 ◽  
Author(s):  
Eric P. Brass ◽  
Walter B. Forman ◽  
Robert V. Edwards ◽  
Olgierd Lindan
Keyword(s):  
Particle Size ◽  
Induction Period ◽  
Fibrin Clot ◽  
Clot Formation ◽  
Appreciable Amount ◽  
Buffer System ◽  
Homeostatic Mechanism ◽  
Fibrin Formation ◽  
Fibrin Monomer

SummaryThe process of fibrin formation using highly purified fibrinogen and thrombin was studied using laser fluctuation spectroscopy, a method that rapidly determines particle size in a solution. Two periods in fibrin clot formation were noted: an induction period during which no fibrin polymerization occurred and a period of rapid increase in particle size. Direct measurement of fibrin monomer polymerization and fibrinopeptide release showed no evidence of an induction period. These observations were best explained by a kinetic model for fibrin clot formation incorporating a reversible fibrinogen-fibrin monomer complex. In this model, the complex serves as a buffer system during the earliest phase of fibrin formation. This prevents the accumulation of free polymerizable fibrin monomer until an appreciable amount of fibrinogen has reacted with thrombin, at which point the fibrin monomer level rises rapidly and polymerization proceeds. Clinically, the complex may be a homeostatic mechanism preventing pathological clotting during periods of elevated fibrinogen.

Study of the microstructure and particles of vanadium (III) oxide, vanadium (V) oxide and lithium aluminate powders

2020 ◽  
Vol 86 (1) ◽  
pp. 32-37
Author(s):  
Valeria A. Brodskaya ◽  
Oksana A. Molkova ◽  
Kira B. Zhogova ◽  
Inga V. Astakhova
Keyword(s):  
Particle Size ◽  
Particle Size Distribution ◽  
Vanadium Oxide ◽  
Size Distribution ◽  
Microstructural Analysis ◽  
Coherent Scattering ◽  
Powder Materials ◽  
Lithium Aluminate ◽  
Range Limit ◽  
Oxide Particles

Powder materials are widely used in the manufacture of electrochemical elements of thermal chemical sources of current. Electrochemical behavior of the powders depends on the shape and size of their particles. The results of the study of the microstructure and particles of the powders of vanadium (III), (V) oxides and lithium aluminate obtained by transmission electron and atomic force microscopy, X-ray diffraction and gas adsorption analyses are presented. It is found that the sizes of vanadium (III) and vanadium (V) oxide particles range within 70 – 600 and 40 – 350 nm, respectively. The size of the coherent-scattering regions of the vanadium oxide particles lies in the lower range limit which can be attributed to small size of the structural elements (crystallites). An average volumetric-surface diameter calculated on the basis of the surface specific area is close to the upper range limit which can be explained by the partial agglomeration of the powder particles. Unlike the vanadium oxide particles, the range of the particle size distribution of the lithium aluminate powder is narrower — 50 – 110 nm. The values of crystallite sizes are close to the maximum of the particle size distribution. Microstructural analysis showed that the particles in the samples of vanadium oxides have a rounded (V2O3) or elongated (V2O5) shape; whereas the particles of lithium aluminate powder exhibit lamellar structure. At the same time, for different batches of the same material, the particle size distribution is similar, which indicates the reproducibility of the technologies for their manufacture. The data obtained can be used to control the constancy of the particle size distribution of powder materials.

Positive Role of Synthesis Method and Hard Template on the Catalytic Performance of SAPO-34 in Methanol to Olefin Reaction.

2020 ◽  
Vol 23 ◽  
Author(s):  
Sajjad Rimaz ◽  
Reza Katal
Keyword(s):  
Particle Size ◽  
Synthesis Method ◽  
Catalytic Performance ◽  
Hard Template ◽  
Structure Directing Agent ◽  
Positive Role ◽  
Methanol To Olefin ◽  
Dg Method ◽  
Synthesis Procedure

: In the present study, SAPO-34 particles were synthesized using hydrothermal (HT) and dry gel (DG) conversion methods in the presence of diethyl amine (DEA) as an organic structure directing agent (SDA). Carbon nanotubes (CNT) were used as hard template in the synthesis procedure to introduce transport pores into the structures of the synthesized samples. The synthesized samples were characterized with different methods to reveal effects of synthesis method and using hard template on their structure and catalytic performance in methanol to olefin reaction (MTO). DG conversion method results in smaller particle size in comparison with hydrothermal method, resulting in enhancing catalytic performance. On the other side, using CNT in the synthesis procedure with DG method results in more reduction in particle size and formation of hierarchical structure which drastically improves catalytic performance.

Effect of grain size on the vapour phase hydration of monoclinic and triclinic modifications of tricalcium silicate; role of high temperature activation

1991 ◽  
Vol 56 (10) ◽  
pp. 1993-2008
Author(s):  
S. Hanafi ◽  
G. M. S. El-Shafei ◽  
B. Abd El-Hamid
Keyword(s):  
Particle Size ◽  
Vapour Phase ◽  
Tricalcium Silicate ◽  
Active Centers ◽  
Thermally Activated ◽  
Grain Sizes ◽  
Intermediate Size ◽  
Surface Active ◽  
Temperature Activation

The hydration of tricalcium silicate (C3S) with three grain sizes of monoclinic (M) and triclinic (T) modifications and on their thermally activated samples were investigated by exposure to water vapour at 80°C for 60 days. The products were investigated by XRD, TG and N2 adsorption. The smaller the particle size the greater was the hydration for both dried and activated samples from (M). In the activated samples a hydrate with 2θ values of 38.4°, 44.6° and 48.6° could be identified. Hydration increased with particle size for the unactivated (T) samples but after activation the intermediate size exhibited enhanced hydration. Thermal treatment at 950°C of (T) samples increased the surface active centers on the expense of those in the bulk. Changes produced in surface texture upon activation and/or hydration are discussed.

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