Comparison of Cell Wall Microstructure of Aluminum Foams Produced by Melt Foaming and Gas Injection Foaming Processes

2013 ◽  
Vol 457-458 ◽  
pp. 540-543
Author(s):  
Yu Tong Zhou ◽  
Yan Xiang Li ◽  
Xing Nan Liu ◽  
Wen Wen Yuan
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Base Alloy ◽  
Gas Injection ◽  
Secondary Phases ◽  
Practical Application ◽  
Aluminum Foams ◽  
Foaming Process ◽  
Metallurgical Structure ◽  
The Difference

Aluminum foams from A356 base alloy were produced by both the melt foaming process and gas injection foaming process. A comparison of microstructures between the two kinds of aluminum foams was carried out. The related causes were analyzed to form the difference in microstructure. Results indicate that aluminum foams produced by different processes are distinct in metallurgical structure. The average thickness of cell wall, the species and area fraction of secondary phases or particles and other metallurgical features have been all comparatively studied. The difference in microstructure features of the cell walls will also make the aluminum foams different in mechanical properties. Therefore, we need to select proper foaming process for aluminum foams according to the property requirements in practical application.

scholarly journals Differences in cell wall of thin and thick filaments of cyanobacterium Aphanizomenon gracile SAG 31.79 and their implications for different resistance to Daphnia grazing

2016 ◽  
Author(s):  
Lukasz Wejnerowski ◽  
Slawek Cerbin ◽  
Maria K. Wojciechowicz ◽  
Marcin K. Dziuba
Keyword(s):  
Cell Wall ◽  
Wall Thickness ◽  
Cell Walls ◽  
Cell Wall Thickness ◽  
Filamentous Cyanobacterium ◽  
Thin Sections ◽  
Thick Filaments ◽  
Transmission Electron ◽  
The Difference ◽  
Aphanizomenon Gracile

<p>Recent studies have shown that the filamentous cyanobacterium <em>Aphanizomenon gracile</em> Lemmermann, strain SAG 31.79, consists of two types of filaments that differ in thickness. These two types are known to vary in resistance to <em>Daphnia</em> <em>magna</em> grazing: thin filaments (&lt;2.5 µm) are more vulnerable to grazing than the thick ones (&gt;2.5 µm). In this study, we investigated whether the difference in the vulnerability to grazing of thin and thick filaments is a result of different thickness of their cell walls, a filament stiffness determinant. We expected thick filaments to have thicker cell walls than the thin ones. Additionally, we analysed whether cell wall thickness correlates with filament thickness regardless of the filament type. A morphometric analysis of cell walls was performed using transmission electron micrographs of ultra-thin sections of the batch-cultured cyanobacterial material.  Our study revealed that the thin type of filaments had thinner cell walls than the thick filaments. Moreover, cell wall thickness was positively correlated with filament thickness. TEM (transmission electron microscopy) observations also revealed that the thin type of filaments was often at different stages of autocatalytic cell destruction, which was mainly manifested in the increase in cell vacuolization and degradation of the cytoplasm content. Based on our findings, we assume that previously reported higher resistance of thick filaments to <em>Daphnia</em> grazing results from greater stiffness and excellent physiological conditions of thick filaments. </p>

Solidification Structure and Sound Absorbability of A356 Alloy Foams

2010 ◽  
Vol 654-656 ◽  
pp. 994-997
Author(s):  
Yan Xiang Li ◽  
W.W. Yuan ◽  
X. Chen
Keyword(s):  
Cell Walls ◽  
Foam Cell ◽  
Base Alloy ◽  
Eutectic Silicon ◽  
A356 Alloy ◽  
Solidification Structure ◽  
Metallic Foams ◽  
Foaming Agent ◽  
Foaming Process ◽  
Α Phase

Metallic foams of A356 alloy with a uniform porosity of 75-85% were produced with the melt foaming process. The microstructure inside the foam cell walls was experimentally studied. It is found that the microstructure is greatly different from the as-cast structure of the base alloy. It is believed that the thickening process with calcium, the adding of foaming agent and the mixing process during the production process all play important roles on the solidification microstructure of the cell walls. The morphology and grain size of primary α-phase, the amount and morphology of eutectic silicon, the distribution and size of CaSi2Al2 and residual titanium hydride particles were studied. The sound absorption coefficient of the alloy foams was measured. Two methods, drilling small holes and compressing the foam, have been developed to improve the sound absorbability of the alloy foam in low and middle frequency ranges.

scholarly journals STAYMAN FRUIT CRACKING AS RELATED TO CW COMPOSITION

HortScience ◽  
1990 ◽  
Vol 25 (9) ◽  
pp. 1093G-1094
Author(s):  
Russell L. Weiser
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Cell Structure ◽  
Cell Wall Composition ◽  
Distilled Water ◽  
Fruit Cracking ◽  
Consequent Effect ◽  
The Difference ◽  
Treated Apple ◽  
Wall Extensibility

Stayman apples are predisposed to cracking. Trees whose trunks were scored and foliage sprayed with GA4+7, NAA 800, and Vapor Guard had significantly fewer apples crack than controls. The skin strength and stretch distance were the same for control and treated apples. However, slices of treated apple expanded significantly more than control apples when immersed in distilled water for 45 minutes. During this treatment the amount of water taken up was not significantly different, which may indicate the difference lies in the cell structure. Hypodermal cells of control apples appear to be more elongated and have thicker cell walls than treated apples. Cell wall sugar and amino acid components will be measured to see if this discrepancy can be attributed to cell wall structural properties. These results suggest that stayman cracking occurs when the expansion of the hypodermic cannot keep pace with expansion of the fruit. It is further hypothesized that this difference is due to a difference in cell wall composition and consequent effect on wall extensibility.

scholarly journals A Report on Fungal (1→3)-α-d-glucans: Properties, Functions and Application

Molecules ◽  
2019 ◽  
Vol 24 (21) ◽  
pp. 3972 ◽  
Author(s):  
Katarzyna Złotko ◽  
Adrian Wiater ◽  
Adam Waśko ◽  
Małgorzata Pleszczyńska ◽  
Roman Paduch ◽  
...  
Keyword(s):  
Cell Wall ◽  
Immune System ◽  
Physicochemical Properties ◽  
Aspergillus Fumigatus ◽  
Cell Walls ◽  
Practical Application ◽  
Fungal Cell ◽  
Plant Infection ◽  
Potential Use

The cell walls of fungi are composed of glycoproteins, chitin, and α- and β-glucans. Although there are many reports on β-glucans, α-glucan polysaccharides are not yet fully understood. This review characterizes the physicochemical properties and functions of (1→3)-α-d-glucans. Particular attention has been paid to practical application and the effect of glucans in various respects, taking into account unfavourable effects and potential use. The role of α-glucans in plant infection has been proven, and collected facts have confirmed the characteristics of Aspergillus fumigatus infection associated with the presence of glucan in fungal cell wall. Like β-glucans, there are now evidence that α-glucans can also stimulate the immune system. Moreover, α-d-glucans have the ability to induce mutanases and can thus decompose plaque.

Reduction In Young's Modulus Of Aluminum Foams Due To Cell Wall Curvature And Corrugation

1998 ◽  
Vol 521 ◽  
Author(s):  
W. Sanders ◽  
L. J. Gibson
Keyword(s):  
Compressive Strength ◽  
Cell Wall ◽  
Young’S Modulus ◽  
Cell Walls ◽  
Young's Modulus ◽  
Cell Structure ◽  
Microstructural Characterization ◽  
Aluminum Foams ◽  
Element Analysis ◽  
Simple Bounds

ABSTRACTMeasurements of the Young's modulus and compressive strength of several closedcell aluminum foams indicate that they are lower than expected from models for foam behaviour. Microstructural characterization has revealed that there are a number of defects in the cell structure which may contribute to the reduction in mechanical properties. These include: cell wall curvature, cell wall corrugations, density variations and non-equiaxed cell shape. Finite element analysis of a closed-cell tetrakaidecahedral unit cell with idealized curved or corrugated cell walls indicates that these two types of defects can reduce the Young's modulus and compressive strength by up to 70%. In this paper we report the results of measurements of the curvature of the cell walls and of the amplitude and frequency of corrugations in the cell walls and use simple bounds to estimate the reduction in modulus that they are responsible for.

scholarly journals The mechanics of solid-state nanofoaming

2019 ◽  
Vol 475 (2230) ◽  
pp. 20190339
Author(s):  
Frederik Van Loock ◽  
Victoria Bernardo ◽  
Miguel Angel Rodríguez Pérez ◽  
Norman A. Fleck
Keyword(s):  
Cell Wall ◽  
Solid State ◽  
Cell Walls ◽  
Uniaxial Stress ◽  
Nucleation Density ◽  
One Dimensional ◽  
Foaming Process ◽  
Cell Nucleation ◽  
Foaming Temperature ◽  
Versus Strain

Solid-state nanofoaming experiments are conducted on two polymethyl methacrylate (PMMA) grades of markedly different molecular weight using CO 2 as the blowing agent. The sensitivity of porosity to foaming time and foaming temperature is measured. Also, the microstructure of the PMMA nanofoams is characterized in terms of cell size and cell nucleation density. A one-dimensional numerical model is developed to predict the growth of spherical, gas-filled voids during the solid-state foaming process. Diffusion of CO 2 within the PMMA matrix is sufficiently rapid for the concentration of CO 2 to remain almost uniform spatially. The foaming model makes use of experimentally calibrated constitutive laws for the uniaxial stress versus strain response of the PMMA grades as a function of strain rate and temperature, and the effect of dissolved CO 2 is accounted for by a shift in the glass transition temperature of the PMMA. The maximum achievable porosity is interpreted in terms of cell wall tearing and comparisons are made between the predictions of the model and nanofoaming measurements; it is deduced that the failure strain of the cell walls is sensitive to cell wall thickness.

Compressive Behavior of Aluminium Foams Prepared by Powder Metallurgy Method

2012 ◽  
Vol 157-158 ◽  
pp. 600-603 ◽  
Author(s):  
Li Wei ◽  
Csaba Sinka ◽  
Simon Lawes ◽  
Tao Han
Keyword(s):  
Cell Wall ◽  
Cell Walls ◽  
Small Deformation ◽  
Structural Deformation ◽  
Powder Metallurgy Method ◽  
Aluminum Foams ◽  
Stress Strain ◽  
Compression Behavior ◽  
Closed Cell ◽  
Fracture Area

The compression behavior of closed cell aluminum foams with different density has been examined. Stress-strain curves were obtained. The microstructure evaluation of cell walls was investigated using X-ray computer tomography. A series of images of internal microstructures were given, the structural deformation evolution was analyzed. The images of cell wall evolution shown that crack appeared in cell wall after a small deformation of elastic deformation. As the compression proceeded, further cracks occur and some of the cell walls fracture. The fracture area become expanded, a part of dislocation on the sample side is formed. As the fracture area spreads, some regions become dense. The stress-strain curves showed brittle characteristics. As the relative density increases, yield strength and elastic modulus of aluminum foams increased. The best fit lines are obtained, where, is 0.97 and 0.2 respectively.

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