A Holographic Non-Destructive Technique for the Detection of Cracks of 100 μm Length or Less in Ceramic Materials

1980 ◽  
pp. 491-495
Author(s):  
Cesar A. Sciammarella ◽  
R. Narayanan
Keyword(s):  
Ceramic Materials ◽  
Non Destructive

Some Comments on the Production of Medium Sized Spherical Particles by Anion and Water Extraction Variant of Sol-Gel Process

1994 ◽  
Vol 372 ◽  
Author(s):  
A. Deptula ◽  
W. Łstoke;ada ◽  
T. Olczak ◽  
A. Chmielewski
Keyword(s):  
Particle Size ◽  
Sol Gel ◽  
Ceramic Materials ◽  
Extraction Process ◽  
Spherical Particles ◽  
Drastic Reduction ◽  
Sol Gel Process ◽  
Emulsion Drops ◽  
Clustering Effect ◽  
Non Destructive

AbstractMedium sized spherical particles (with diameters below 100 μm) of ceramic materials (Al203 and Al203 +8%TiO2) were produced in the following steps: (1) preparation of concentrated hydroxide sols of cations by extraction of anions using Primene JMT, (2) formation of sol emulsion in 2-ethylhexanol-1 containing various amounts of surfactants (EH), (3) gelation of emulsion drops by extraction of water with partially dehydrated EH, (4) non-destructive thermal treatment. Principal properties of the sol depend on the temperature of the extraction process. For preparation of lowanionic sols a two step extraction process, separated by digestion of the aqueous phase at boiling point, was necessary. It was found that the parameters of emulsion formation as well as the properties of the sols significantly influence the particle size distribution. It was concluded that lowering of the sol- EH interracial tension by the surfactant does not influence the process. On the contrary the “anti-clustering” effect of surfactants is essential for preparation of perfect spherical powders. The thermal decomposition of gels to oxides is determinant for densities, specific surface area and carbon content. Medium sized spherical powders are free flowing. The compactibility and sinterability of those powders are poor. However drastic reduction of particle size by milling (connected with their transformation to irregular shape) significantly improves the sinterability.

IMPEDANCE SPECTROSCOPY (IS), XRD AND SEM OF OXIDE-ADDED Si3N4

2002 ◽  
Vol 16 (14) ◽  
pp. 525-537
Author(s):  
SAADAT. A. SIDDIQI ◽  
NASIR A. KHAN ◽  
M. SABIEH ANWAR
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Impedance Spectroscopy ◽  
Ceramic Materials ◽  
Dielectric Constants ◽  
X Ray Diffraction ◽  
X Ray ◽  
Nyquist Plots ◽  
Non Destructive ◽  
Scanning Electron

Impedance spectroscopy (IS) is a non-destructive technique used for obtaining valuable information about bulk conductivities, dielectric constants, phase composition and grain boundaries of important ceramic materials, amongst many others. We obtained Nyquist plots for four different hot-pressed Si 3 N 4 samples in two different frequency regimes: 1 Hz to 30 MHz and 1 kHz to 100 kHz. The information obtained was compared against results from scanning electron microscopy (SEM) and X-ray diffraction (XRD). The limitations of the frequency response techniques are also discussed.

scholarly journals Acoustic Emission Technique, an Overview as a Characterization Tool in Materials Science

2011 ◽  
Vol 9 (03) ◽  
Author(s):  
C. R. Ríos-Soberanis
Keyword(s):  
Acoustic Emission ◽  
Composite Materials ◽  
Mechanical Behavior ◽  
Structural Integrity ◽  
Materials Science ◽  
Ceramic Materials ◽  
Fracture Mechanisms ◽  
External Stresses ◽  
Characterization Of Materials ◽  
Non Destructive

In order to predict the mechanical behavior of a composite during its service life, it is important to evaluate itsmechanical response under different types of external stresses by studying the initiation and development of cracksand the effects induced by damage and degradation. The onset of damage is related to the structural integrity of thecomponent and its fatigue life. For this, among other reasons, non-destructive techniques such as acoustic emission(AE) have been widely used nowadays for composite materials characterization. This method has demonstratedexcellent results on detecting and identifying initiations sites, cracking propagation and fracture mechanisms ofpolymer matrix composite and ceramic materials. This paper focuses on commenting the importance of the acousticemission technique as a unique tool for characterizing mechanical parameters in response to external stresses anddegradation processes by reviewing previous investigations carried out by the author as participant. Acoustic emissionwas employed to monitor the micro-failure mechanisms in composites in relation to the stress level in real-time duringthe tests carried out. Some results obtained from different analysis are discussed to support the significance of usingAE, technique that will be increasingly employed in the composite materials field due to its several alternatives forunderstanding the mechanical behavior; therefore, the objective of this manuscript is to involve the benefits andadvantages of AE in the characterization of materials.

Application of Sans to Ceramic Characterization

1986 ◽  
Vol 73 ◽  
Author(s):  
K. G. Frase ◽  
K. A. Hardman-Rhyne ◽  
N. F. Berk
Keyword(s):  
Neutron Scattering ◽  
Small Angle ◽  
Small Angle Neutron Scattering ◽  
Ceramic Materials ◽  
Pore Size Distributions ◽  
Mdf Cements ◽  
Characterization Of Materials ◽  
Non Destructive

ABSTRACTTraditionally, small angle neutron scattering (SANS) has been used to study dilute concentrations of defects 1 -100 nm in size. Recent extensions of the scattering theory have allowed the expansion of the technique to include larger sizes through the use of multiple scattering. With multiple small angle neutron scattering, defects (pores, microcracks, precipitates) up to 10 μm in size can be studied. SANS is inherently a non-destructive, bulk probe of microstructure, with wide applications in the characterization of materials.A number of studies of ceramic materials using multiple and traditional (single particle diffraction) small angle neutron scattering will be discussed. The emphasis will be on the strength of the technique in the characterization of materials. Particular examples will include: the assessment of pore size distributions in spinel compacts as a function of sintering and agglomeration, the characterization of primary and secondary particle sizes in precipitated aggregates, and the determination of microporosity in MDF cements.

Replicas as a Technique for Examining Fracture Surfaces of Ceramics

2009 ◽  
Vol 409 ◽  
pp. 107-112 ◽  
Author(s):  
James R. Varner
Keyword(s):  
Cellulose Acetate ◽  
Direct Observation ◽  
Silicone Rubber ◽  
Ceramic Materials ◽  
Surface Scattering ◽  
Scattering Of Light ◽  
Fracture Surfaces ◽  
Polycrystalline Ceramics ◽  
Non Destructive ◽  
Actual Fracture

This paper discusses reasons for using replicas of fracture surfaces of ceramics, describes several replicating methods and materials, and presents examples that compare replicas with actual fracture surfaces. Advantages of using replicas include being able (1) to examine large pieces without having to cut them down to size, (2) to provide convenient archiving of fracture surfaces, and (3) to eliminate sub-surface scattering of light. Many times, replicas provide clearer views of untreated (uncoated) fracture surfaces than can be obtained by direct observation. Replication using cellulose acetate tape and two types of silicone rubber (filled and unfilled) are described. Both methods are fast, relatively inexpensive, and non-destructive. Images of replicas of fracture surfaces of a glass and several ceramic materials (including electrical porcelain and several polycrystalline ceramics) are compared with images of actual fracture surfaces.

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