Effect of Mo microstructure on the critical volume fraction for conduction in Mo-alumina cermets

1997 ◽  
Vol 12 (3) ◽  
pp. 738-744 ◽  
Author(s):  
J. F. Kelso ◽  
R. R. Higgins ◽  
F. J. Krivda
Keyword(s):  
Volume Fraction ◽  
Critical Volume ◽  
Glass Content ◽  
Alumina Powder ◽  
Particle Sizes ◽  
Initial Particle ◽  
Electrical Percolation ◽  
Metal Contents ◽  
Critical Volume Fraction ◽  
The Matrix

The microstructure of Mo in an alumina/frit matrix was found to be dependent on the initial particle sizes of the alumina and Mo powders, the glass content in the matrix ceramic, and the amount of moisture in the firing atmosphere. The Mo microstructure had a significant influence on the critical volume fraction for conductivity in these cermets. Coarser alumina powder, finer Mo powder, and higher glass content promoted coalescence of Mo into conductive networks at lower metal contents. Drier firing atmospheres produced a more coarsened Mo microstructure with a slight decrease in the amount of network contiguity, causing an increase in the amount required for electrical percolation.

Numerical Analysis of the GF/UHMWPEF Interply Hybrid NOL Ring Critical Volume Fraction

2012 ◽  
Vol 457-458 ◽  
pp. 449-452
Author(s):  
Ming Lin Xu ◽  
Xiao Qing Wu ◽  
Ming Kang An
Keyword(s):  
Finite Element ◽  
Volume Fraction ◽  
Critical Volume ◽  
Tooth Contact Analysis ◽  
Breaking Strain ◽  
Finite Element Software ◽  
Critical Volume Fraction ◽  
The Matrix ◽  
The Relationship ◽  
Strain Model

The tensile test of NOL ring composites with different interply hybrid ratio is simulated by finite element software. The relationship between the stress of Naval Ordnance Laboratory(NOL) ring and the volume fraction of UHMWPEF is linear when the matrix suffering from the equal loading, but tower suddenly appears at the point of 56.25% which is about the critical volume fraction. The critical volume fraction of hybrid NOL ring is figured out on the basis of the constant strain model. By contrast, the results of the Finite Element Method (FEM) and constant strain model have subtle differences. Tooth contact analysis can exactly predict the stress of the interply hybrid NOL ring and the critical volume fraction of GF in interply hybrid NOL ring which has lower breaking strain than UHMWPEF does.

scholarly journals The AC and DC Conductivity of Nanocomposites

2007 ◽  
Vol 2007 ◽  
pp. 1-9 ◽  
Author(s):  
David S. McLachlan ◽  
Godfrey Sauti
Keyword(s):  
Electrical Properties ◽  
Volume Fraction ◽  
Matrix Material ◽  
Dc Conductivity ◽  
Critical Volume ◽  
Matrix Structure ◽  
Electrical Measurements ◽  
Conducting Component ◽  
Critical Volume Fraction ◽  
The Matrix

The microstructures of binary (conductor-insulator) composites, containing nanoparticles, will usually have one of two basic structures. The first is the matrix structure where the nanoparticles (granules) are embedded in and always coated by the matrix material and there are no particle-particle contacts. The AC and DC conductivity of this microstructure is usually described by the Maxwell-Wagner/Hashin-Shtrikman or Bricklayer model. The second is a percolation structure, which can be thought to be made up by randomly packing the two types of granules (not necessarily the same size) together. In percolation systems, there exits a critical volume fraction below which the electrical properties are dominated by the insulating component and above which the conducting component dominates. Such percolation systems are best analyzed using the two-exponent phenomenological percolation equation (TEPPE). This paper discusses all of the above and addresses the problem of how to distinguish among the microstructures using electrical measurements.

Constitutive Equations of Power-Law Composites and Failure of Materials Having Multiple Cracks

1994 ◽  
Vol 116 (3) ◽  
pp. 359-366 ◽  
Author(s):  
S. C. Lin ◽  
Y. Hirose ◽  
T. Mura
Keyword(s):  
Power Law ◽  
Constitutive Equations ◽  
Fracture Criterion ◽  
Volume Fraction ◽  
Piecewise Linear ◽  
Pure Shear ◽  
Failure Criteria ◽  
Multiple Cracks ◽  
Critical Volume Fraction ◽  
The Matrix

Based upon the Mori-Tanaka method, the constitutive equations of power-law materials and the failure criteria of multiple cracks materials are investigated. The piecewise linear incremental approach is also employed to analyze the effective stress and strain of the power-law materials. Results are presented for the case of pure shear where the matrix is a power-law material with rigid or void inhomogeneities. For the multiple cracked materials, the Griffith fracture criterion is applied to determine the critical volume fraction which causes the catastrophic failure of a material. The failure criteria of penny shaped, flat ellipsoidal, and slit-like cracked materials are examined and it is found that the volume fraction of cracks and critical applied stress are in linear relation.

scholarly journals Effects of Bentonite Nanoclay and Cetyltrimethyl Ammonium Bromide Modified Bentonite Nanoclay on Phase Inversion of Water-in-Oil Emulsions

2020 ◽  
Vol 4 (1) ◽  
pp. 2
Author(s):  
Sileola B. Ogunlaja ◽  
Rajinder Pal
Keyword(s):  
Contact Angle ◽  
Aqueous Phase ◽  
Phase Inversion ◽  
Volume Fraction ◽  
Critical Volume ◽  
Ammonium Bromide ◽  
Cetyltrimethyl Ammonium Bromide ◽  
Modified Bentonite ◽  
Critical Volume Fraction ◽  
Cetyltrimethyl Ammonium

The effects of unmodified and modified bentonite nanoclays (with various degrees of surfactant modification) on the catastrophic phase inversion from water-in-oil (W/O) emulsion to oil-in-water (O/W) emulsion were determined experimentally. The bentonite nanoclay (NC-Bt) was suspended in the aqueous phase, and the critical volume fraction of water where phase inversion from W/O to O/W emulsion took place was determined through conductivity measurements. Cetyltrimethyl ammonium bromide (CTAB) was used as a surfactant to modify the nanoclay. The adsorption of CTAB onto nanoclay had a strong influence on the contact angle and the critical volume fraction of water where phase inversion took place. The modification of the nanoclay brought about by the adsorption of CTAB increased the three-phase contact angle (measured through the aqueous phase), thereby making it more hydrophobic, and prolonged the phase inversion point. CTAB alone and CTAB-modified nanoclay delayed the phase inversion process in a similar manner, showing a strong dependence on the CTAB concentration.

Effect of the Matrix and Reinforcement Sizes on the Microstructure, the Physical and Mechanical Properties of Al-SiC Composites

2016 ◽  
Vol 139 (1) ◽  
Author(s):  
M. A. Salem ◽  
I. G. El-Batanony ◽  
M. Ghanem ◽  
Mohamed Ibrahim Abd ElAal
Keyword(s):  
Mechanical Properties ◽  
Powder Metallurgy ◽  
Volume Fraction ◽  
Physical And Mechanical Properties ◽  
Particle Sizes ◽  
Matrix Composites ◽  
Volume Fractions ◽  
The Matrix ◽  
Sic Composites ◽  
Sic Particle

Different Al-SiC metal matrix composites (MMCs) with a different matrix, reinforcement sizes, and volume fractions were fabricated using ball milling (BM) and powder metallurgy (PM) techniques. Al and Al-SiC composites with different volume fractions were milled for 120 h. Then, the Al and Al-SiC composites were pressed under 125 MPa and finally sintered at 450 °C. Moreover, microsize and combination between micro and nano sizes Al-SiC samples were prepared by the same way. The effect of the Al matrix, SiC reinforcement sizes and the SiC volume fraction on the microstructure evolution, physical and mechanical properties of the produced composites was investigated. The BM and powder metallurgy techniques followed by sintering produce fully dense Al-SiC composite samples with different matrix and reinforcement sizes. The SiC particle size was observed to have a higher effect on the thermal conductivity, electrical resistivity, and microhardness of the produced composites than that of the SiC volume fraction. The decreasing of the Al and SiC particle sizes and increasing of the SiC volume fraction deteriorate the physical properties. On the other hand, the microhardness was enhanced with the decreasing of the Al, SiC particle sizes and the increasing of the SiC volume fraction.

Compressive deformation and damage of Mg-based metallic glass interpenetrating phase composite containing 30–70 vol% titanium

2010 ◽  
Vol 25 (11) ◽  
pp. 2192-2196 ◽  
Author(s):  
Yu Sun ◽  
Haifeng Zhang ◽  
Aimin Wang ◽  
Huameng Fu ◽  
Zhuangqi Hu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Metallic Glass ◽  
Fracture Strength ◽  
Deformation Behavior ◽  
Volume Fraction ◽  
Critical Volume ◽  
Strengthening Mechanisms ◽  
Phase Volume ◽  
Phase Volume Fraction ◽  
Critical Volume Fraction

Mg-based metallic glass interpenetrating phase composites (IPCs) containing 30–70 vol% titanium was fabricated in this study. The effects of reinforced phase volume fraction and interspace on the mechanical properties were investigated systematically. With increasing the volume fraction of titanium, the fracture strength and strain increased up to 1860 MPa and 44%, respectively. The results showed that the critical volume fraction (around 40%) of Ti metal should be required for significantly improving plasticity of IPC. Decreasing the interspace of the titanium phase could lead to enhancement of yield and fracture strength. The deformation behavior and strengthening mechanisms were discussed in detail.

Hollow metal cylinders produced from diacetylenic lipid

2000 ◽  
Vol 15 (11) ◽  
pp. 2368-2374 ◽  
Author(s):  
Dan Zabetakis
Keyword(s):  
Electrical Properties ◽  
Packing Density ◽  
Parallel Plate ◽  
Volume Fraction ◽  
Bulk Material ◽  
Critical Volume ◽  
Critical Volume Fraction ◽  
Specific Packing ◽  
Improved Technique ◽  
Hollow Metal

A method was presented for the formation and metallization of cylindrical tubules from a diacetylenic lipid. This improved technique allowed for the production of metal microcylinders without the need for preliminary lipid purification and in large quantities. The physical and electrical properties of the material were investigated, and composites were used to form parallel plate capacitors. A comparison of the conductivity of the bulk material with the derived conductivity of a composite showing electromagnetic percolation showed the proportionality of the specific packing density and the critical volume fraction characteristic of percolating systems.

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