Fracture Mechanisms in SiC-Whisker Reinforced Alumina

1988 ◽  
Vol 120 ◽  
Author(s):  
Christophe H. Boulanger ◽  
Yih-Cherng Chiang ◽  
Azar P. Majidi ◽  
Tsu-Wei Chou
Keyword(s):  
Experimental Data ◽  
Fracture Toughness ◽  
Room Temperature ◽  
Crack Deflection ◽  
Fracture Mechanisms ◽  
Alumina Composite ◽  
Good Agreement

AbstractThe fracture mechanisms involved in the toughening of alumina by whisker reinforcement are studied at room temperature. The fracture toughness of a hot pressed SiC-whisker/alumina composite is measured and good agreement is found between the experimental data and a model that takes into account the effects of crack deflection and whisker pullout mechanisms. From the model, it is seen that the role of whisker pullout is negligible compared to that of crack deflection.

scholarly journals Effect of Crack Bridging on the Toughening of Ceramic/Graphene Composites

2018 ◽  
Vol 57 (1) ◽  
pp. 54-62 ◽  
Author(s):  
S.V. Bobylev ◽  
A.G. Sheinerman
Keyword(s):  
Experimental Data ◽  
Fracture Toughness ◽  
Crack Growth ◽  
Crack Deflection ◽  
Yttria Stabilized Zirconia ◽  
Stabilized Zirconia ◽  
Crack Bridging ◽  
The Matrix ◽  
Graphene Content ◽  
Graphene Platelets

Abstract A model is proposed describing the effect of crack bridging on the fracture toughness of ceramic/graphene composites. The dependences of the fracture toughness on the graphene content and the sizes of the graphene platelets are calculated in the exemplary case of yttria stabilized zirconia (YSZ)/graphene composites. The calculations predict that if crack bridging prevails over crack deflection during crack growth, the maximum toughening can be achieved in the case of long graphene platelets provided that the latter do not rupture and adhere well to the matrix. The model shows good correlation with the experimental data at low graphene concentrations.

Inelastic electric and magnetic electron scattering form factors of 24Mg nucleus: Role of g factors

2017 ◽  
Vol 26 (05) ◽  
pp. 1750032 ◽  
Author(s):  
Anwer A. Al-Sammarraie ◽  
M. L. Inche Ibrahim ◽  
Muna Ahmed Saeed ◽  
Fadhil I. Sharrad ◽  
Hasan Abu Kassim
Keyword(s):  
Experimental Data ◽  
Electron Scattering ◽  
Form Factors ◽  
Wave Functions ◽  
Matrix Elements ◽  
Model Hamiltonian ◽  
Transverse Electron ◽  
Magnetic Electron ◽  
Good Agreement

The electric and magnetic transitions in the [Formula: see text]Mg nucleus are studied based on the calculations of the longitudinal and the transverse electron scattering form factors. The universal sd-shell model Hamiltonian (USDA) is used for calculations. The wave functions of radial single-particle matrix elements are calculated using the Skyrme potential. For the longitudinal form factors, a good agreement is obtained between the calculations and the experimental data. For the transverse form factors, the effective [Formula: see text] factors are made as adjustable parameters in order to describe the experimental data.

LARGE ROOM TEMPERATURE MAGNETORESISTANCE IN (La0.7Sm0.3)0.7Sr0.3MnO3/Agx COMPOSITES

2005 ◽  
Vol 19 (30) ◽  
pp. 4467-4473 ◽  
Author(s):  
XIAO-BO YUAN ◽  
YI-HUA LIU ◽  
CHENG-JIAN WANG ◽  
LIANG-MO MEI
Keyword(s):  
Experimental Data ◽  
Grain Boundaries ◽  
Room Temperature ◽  
Composite System ◽  
Molar Ratio ◽  
Ag Addition ◽  
Brillouin Function ◽  
Spin Clusters ◽  
Good Agreement

The effects of Ag addition in the composite ( La 0.7 Sm 0.3)0.7 Sr 0.3 MnO 3/ Ag x (abbreviated as LSSMO/Ag x) has been studied. The results showed that Ag addition induces the decrease in resistivity (ρ) due to the improvement of grain boundaries resulted from the segregation of Ag on the grain surfaces. In addition, 27% molar ratio of Ag addition induces a large room temperature magnetoresistance (MR) ratio of 35%. The good agreement of experimental data with Brillouin function indicates that the MR behavior in this composite system accounts for the spin-dependent hopping of the electrons between the spin clusters.

Ligand Redistribution Equilibria in Aqueous Fluoroberyllate Solutions

1998 ◽  
Vol 53 (11) ◽  
pp. 1294-1300 ◽  
Author(s):  
Michael Schmidt ◽  
Hubert Schmidbaur
Keyword(s):  
Experimental Data ◽  
Ligand Exchange ◽  
Room Temperature ◽  
Chemical Shifts ◽  
Equilibrium Constants ◽  
Individual Species ◽  
Ph Values ◽  
Exchange Processes ◽  
The Individual ◽  
Good Agreement

The composition of aqueous fluoroberyllate solutions has been studied by 9Be and 19F NMR spectroscopy for various ratios of the beryllium and fluorine concentrations, and at different pH values. The equilibrium constants have been determined for the ligand exchange processes, which involve the species [Be(OH2)4]2+, [BeF(OH2)3]+, [BeF2(OH2)2], [BeF3(OH2)]- , and [BeF4]2-. These equilibria are shifted towards [BeF4]2- at high pH. No polynuclear fluoroberyllates have been detected. The fluoride exchange between the individual species is slow on the NMR time scale at room temperature, and separate sharp signals with the expected multiplicity are therefore recorded. Calculated 9Be chemical shifts are in good agreement with experimental data.

scholarly journals CHAIN CONFIGURATIONS IN LIGHT NUCLEI

2007 ◽  
Vol 16 (06) ◽  
pp. 1757-1764 ◽  
Author(s):  
S. YU. TORILOV ◽  
K. A. GRIDNEV ◽  
W. GREINER
Keyword(s):  
Experimental Data ◽  
Light Nuclei ◽  
Deformed Nuclei ◽  
Semiclassical Model ◽  
Good Agreement ◽  
Α Particles

We consider a semiclassical model of light nuclei, where the nucleus has a crystal-like shape and is built solely from α-particles. We analyze the role of linear configurations in this model, which correspond to super-deformed nuclei. The strong deformed shape for the doubly even nuclei from 12 C to 24 Mg has been determined according to this model. The obtained results show a good agreement with the experimental data.

Dual Role of Nanoparticles in the Thermal Conductivity Enhancement of Nanoparticle Suspensions

2005 ◽  
Author(s):  
Calvin H. Li ◽  
G. P. Peterson
Keyword(s):  
Experimental Data ◽  
Thermal Conductivity ◽  
Brownian Motion ◽  
Theoretical Models ◽  
Conductivity Enhancement ◽  
Nanoparticle Suspensions ◽  
The Difference ◽  
Physical Phenomena ◽  
Good Agreement

Experimental evidence exists that the addition of a small quantity of nanoparticles to a base fluid, can have a significant impact on the effective thermal conductivity of the resulting suspension. The causes for this are currently thought to be due to a combination of two distinct mechanisms. The first is due to the change in the thermophysical properties of the suspension, resulting from the difference in the thermal conductivity of the fluid and the particles, and the second is thought to be due to the transport of thermal energy by the particles, due to the Brownian motion of the particles. In order to better understand these phenomena, a theoretical model has been developed that examines the effect of the Brownian motion. In this model, the well-known approach first presented by Maxwell, is combined with a new expression that incorporates the effect of the Brownian motion and describes the physical phenomena that occurs because of it. The results indicate that the enhanced thermal conductivity may not in fact be due to the transport of energy by the particles, but rather, due to the stirring motion caused by the movement of the nanoparticles which enhances the heat transfer within the fluid. The resulting model shows good agreement when compared with the existing experimental data and perhaps more importantly helps to explain the trends observed from a fundamental physical perspective. In addition, it provides a possible explanation for the differences that have been observed between the previously obtained experimental data, the predictions obtained from Maxwell’s equation and the theoretical models developed by other investigators.

Picosecond molecular relaxations: the role of the fluid in electron solvation

1977 ◽  
Vol 55 (11) ◽  
pp. 2009-2016 ◽  
Author(s):  
G. A. Kenney-Wallace
Keyword(s):  
Experimental Data ◽  
Room Temperature ◽  
Fluid Layer ◽  
Liquid Structure ◽  
Polar Fluid ◽  
Electron Solvation ◽  
Orientational Polarization ◽  
Excess Electrons ◽  
Electron Migration

The role of the fluid is considered for a model of electron solvation in liquid alcohols. The events that lead to trapping and solvation of excess electrons are reconstructed from experimental data on the time and frequency-dependent electron absorptions (kmol) and the appropriate molecular rotational relaxations (τ2, τc), local liquid structure, viscosity (η), and orientational polarization (β) of the supporting fluid. The quasifree electron is captured at subpicosecond times in a preexisting trap in the liquid, which in alcohols is identified as an alcohol cluster whose local configurational fluctuations will be frozen in on this timescale. Rapid configurational relaxation of the cluster molecules, including multi-phonon processes, then occurs in the field of the excess electron at times ≤10−12 s. Finally, the molecules in the fluid layer adjacent to the initial trapping site align in the now screened field of the localized electron in a manner comparable to solvation of an ion embedded in a polar fluid. The relaxation may occur in competition with electron migration and reaction. The observed rate constant of the final step kmol is shown to be proportional to βη−1 for a range of alcohols at room temperature. The implications of this model for photobleaching experiments in liquids are briefly discussed.

Nernst–Ettingshausen Effects in GaxIn1–xAs alloys

1973 ◽  
Vol 51 (22) ◽  
pp. 2369-2375 ◽  
Author(s):  
Denis J. E. Demars ◽  
John C. Woolley
Keyword(s):  
Experimental Data ◽  
Magnetic Fields ◽  
Effective Mass ◽  
Room Temperature ◽  
Optical Scattering ◽  
Temperature Measurements ◽  
Scattering Coefficient ◽  
Alloy Sample ◽  
Alloy Scattering ◽  
Good Agreement

Room temperature measurements of longitudinal and transverse Nernst–Ettingshausen coefficients [Formula: see text] have been made on samples of GaxIn1–xAs alloys for a range of magnetic fields (B) up to 3.2 Wb/m2. Previous theoretical expressions for the values of these coefficients have been extended to the case of electrons in a single Kane band, and hence expressions for [Formula: see text] and [Formula: see text] obtained in terms of B, the bottom of the band effective mass m0*, and the scattering coefficient s. Fitting of these expressions to the experimental data thus has given values of m0* and s for each alloy sample. The values of m0* are found to be in good agreement with those obtained previously from plasma reflectance work, while the values of s indicate that over most of the alloy range polar optical scattering is predominant, but that in the range 0.4 < x < 0.7, alloy scattering may also have some contribution.

scholarly journals The Role of Surfaces in Gas Transport Through Polymer Membranes

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 910 ◽  
Author(s):  
Giuseppe Firpo ◽  
Elena Angeli ◽  
Patrizia Guida ◽  
Denise Pezzuoli ◽  
Diego Repetto ◽  
...  
Keyword(s):  
Transport Process ◽  
Room Temperature ◽  
Gas Transport ◽  
Polymer Membranes ◽  
Polymer Membrane ◽  
Pdms Membrane ◽  
Transmembrane Pressure ◽  
Physical Quantities ◽  
Good Agreement

This paper describes a procedure to measure the permeability P, diffusivity D, and rate of adsorption k1, thus determining the solubility S and rate of desorption k2 of He, N2, O2, CH4, and CO2 on a polydimethylsiloxane (PDMS) membrane. The described procedure is able to determine experimentally all the physical quantities that characterize the gas transport process through a thin rubber polymer membrane. The experiments were carried out at room temperature and at a transmembrane pressure of 1 atm. The results are in good agreement with the available data in the literature and offer an evaluation of k1 and k2.

Springback Behavior of an Invar Sheet and Its Perforated Form

2006 ◽  
Vol 505-507 ◽  
pp. 781-786
Author(s):  
Yi Che Lee ◽  
Fuh Kuo Chen
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Test Results ◽  
Bending Tests ◽  
Predicted Values ◽  
Springback Behavior ◽  
Good Agreement

The springback behavior of an invar sheet and its perforated form were examined in the present study. The mechanical properties for invar sheet and perforated invar-sheet at elevated temperatures were first obtained from tensile tests. The test results suggest that both invar sheet and perforated invar-sheet have favorable formability at temperature higher than 200oC. An analytical model was also established to predict the springback of the invar sheet and its perforated form under bending conditions at various elevated temperatures. In order to verify the predicted results, the V-bending tests were conducted for the invar sheet at various temperatures ranging from room temperature to 300. The experimental data indicate that the springback decreases with the rise in temperature for both invar sheet and perforated invar-sheet. The good agreement between the experimental data and the predicted values confirms the validity of the proposed theoretical model as well.

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