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Materials

Ceramics

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Displaying 951 - 975 of 1323

Crack Growth in Soda-Lime Silicate Glass Near the Static Fatigue Limit

September 1, 2002
Author(s)
Sheldon M. Wiederhorn, A Dretzke, J Rodel
The atomic force microscope (AFM) was used to explore the nature of features formed on the surfaces of cracks in soda-lime-silicate glass that were held at stress intensity factors below the crack growth threshold. All studies were conducted in water

Crystal Structures and Reference Diffraction Patterns of BaSrR 4 O 8

September 1, 2002
Author(s)
Winnie K. Wong-Ng, James A. Kaduk, J Dillingham
The structure of BaSrR4O8 (where R = La, Nd, Sm, Gd, Eu, Dy, Ho, Y, Er, Tm, Yb, and Lu) has been investigated, and the X-ray reference patterns of these compounds have been prepared using the Rietveld refinement technique. BaSrR2O4 are isostructural to

Finite Element Simulation of Straight Plunge Grinding for Advanced Ceramics

September 1, 2002
Author(s)
Tze J. Chuang, S Jahanmir, Hai C. Tang
The objective of this work is to model the grinding forces and the associated stress and deformation fields generated in a ceramic workpiece during surface plunge grinding. A two-dimensional finite element model is constructed with the grinding parameters

Polarized Ultraviolet Raman Spectroscopy of B-Si 3 N 4

September 1, 2002
Author(s)
R Vogelgesang, M Grimsditch, Jay S. Wallace
We have studied single crystals of Β-Si 3N 4 with polarization-resolved Raman spectroscopy in order to unambiguously obtain the symmetry character of zone center optical phonon modes. By applying ultraviolet excitation radiation, approaching resonance

First Principles Studies of KnbO 3 , KtaO 3 and LiTaO 3 Solid Solutions

August 1, 2002
Author(s)
S A. Prosandeev, Eric J. Cockayne, Benjamin P. Burton
KTaO3-based solid solutions exhibit a variety of interesting physical phenomena. To better understand these phenomena, we performed first-principles calculations on [K1-x,Lix]TaO3 (KLT) and K[Ta1-xNbx]O3 (KTN) supercells. Our results show Li displacements

Grain Growth in Relaxor Ferroelectrics

August 1, 2002
Author(s)
J Blendell, Jay S. Wallace
The mechanisms controlling normal and exaggerated grain growth in lead magnesium niobate - lead titanate (PMN - PT) ceramics have been investigated by varying the PbO-based liquid phase volume fraction, the PT content and the MgO stoichiometry. There is a

Site-Specific Valence-Band Photoemission Study of A-Fe 2 O 3

August 1, 2002
Author(s)
C Y. Kim, Michael Bedzyk, E J. Nelson, Joseph Woicik, L E. Berman
We have measured the site-specific valence-electronic structure of α-Fe 2O 3 by using a spatially modulated X-ray standing wave as the excitation source for photoemission. Contributions to the valence band density of states from oxygen and iron ions are

The Nature and Origin of Tribochemistry

August 1, 2002
Author(s)
Stephen M. Hsu, J Zhang, Z Yin
The origin of tribochemistry is from the rubbing of surfaces together. The precise nature of the chemical reactions and the driving force behind the reactions are not known except for a few simple chemical systems. In boundary lubrication, it is difficult

Crystal Structure of Ba 27 Fe 16 Ti 33 O 117

July 1, 2002
Author(s)
T Siegrist, Terrell A. Vanderah, C Svensson, Robert S. Roth
Single-crystal X-ray diffraction studies indicate that the compound Ba 27Fe 16Ti 33O 117- crystallizes in the rhombohedral space group R-3m, with a hexagonal unit cell a=5.7400(8) , c=127.11(3) ; Z=1.5. The arrangement may be described as a 54-layer (54L)

Fabricating Planar Nanoparticle Assemblies With Number Density Gradients

July 1, 2002
Author(s)
R R. Bhat, Daniel A. Fischer, Jan Genzer
We report on preparing assemblies of gold nanoparticles with continuous gradients in number density on flat silica-covered substrates. The methodology consists of: i) first forming a one dimensional molecular gradient of amino groups (-NH2) on the

Some Issues in Particle Size and Size Distribution Characterization of Powders

July 1, 2002
Author(s)
Ajitkumar Jillavenkatesa, James F. Kelly, S J. Dapkunas
Size and size distribution measurement of powders are conducted using different techniques of size analysis.Underlying all these techniques are certain fundamental issues that influence the accuracy and reproducibility ofthe results. A thorough

Ceramic Based Layer Structures for Biomechanical Applications

June 1, 2002
Author(s)
Brian R. Lawn
A survey of recent advances in the analysis of ceramic-based layer structures for biomechanical applications is presented. Data on model layer systems, facilitating development of explicit fracture mechanics relations for predicting critical loads to

Compact Force Sensors for Low-Force Mechanical Probe Calibration

June 1, 2002
Author(s)
Douglas T. Smith, S Woody, Jon R. Pratt
The loading mechanisms of instrumented indentation machines are often calibrated using deadweights. In many cases, due to the geometry of the loading frame, the applied deadweight is tensile, while the indentation leads to be measured are compressive. In

Cracking in Brittle Laminates from Concentrated Loads

June 1, 2002
Author(s)
H Chai, Brian R. Lawn
A study is made of the crack resistance of multilaminates consisting of brittle layers interleaved with compliant interlayers and bonded to compliant substrates. Specific attention is paid to flexure generated radial cracks in the undersurfaces of
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