Phase evolution and microstructural characterization of sintered ceramic bodies from contaminated marine sediments

The microstructure of a microwave-densified silicon nitride based ceramic has been assessed in the as-sintered, post-sinter hot-isostatically pressed (HIPed) and annealed conditions. The grain size of the as-sintered material, which is a low substitution β′-Sialon, was significantly finer than observed in conventionally processed materials of similar composition. The as-sintered ceramic exhibits a reverse porosity gradient (with the highest porosity level at the surface) due to heat dissipation to the cooler surroundings during microwave processing. This also results in a higher β′ aspect ratio close to the surface arising from an increased glass viscosity (due to heat loss) and compositional change in this region during sintering. HIPing results in removal of all porosity from the sample core; however, a reduced porosity surface layer is retained. Significant β′-Sialon grain growth is also apparent after HIPing. A fine β′ grain structure was retained after annealing, with partial devitrification of the glassy grain boundary phase to β-Y2Si2O7.

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Microstructural characterization of CoPtCr/Cr thin film disks by cross-section TEM and elongated probe micro-diffraction

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100088129 ◽

1991 ◽

Vol 49 ◽

pp. 762-763

Author(s):

M.A. Parker ◽

K.E. Johnson ◽

C. Hwang ◽

A. Bermea

Keyword(s):

Magnetic Recording ◽

Electron Probe ◽

Microstructural Characterization ◽

Crystallographic Structure ◽

Recording Media ◽

Layer By Layer ◽

Cross Sectional ◽

New Techniques ◽

Polished Side

We have reported the dependence of the magnetic and recording properties of CoPtCr recording media on the thickness of the Cr underlayer. It was inferred from XRD data that grain-to-grain epitaxy of the Cr with the CoPtCr was responsible for the interaction observed between these layers. However, no cross-sectional TEM (XTEM) work was performed to confirm this inference. In this paper, we report the application of new techniques for preparing XTEM specimens from actual magnetic recording disks, and for layer-by-layer micro-diffraction with an electron probe elongated parallel to the surface of the deposited structure which elucidate the effect of the crystallographic structure of the Cr on that of the CoPtCr.XTEM specimens were prepared from magnetic recording disks by modifying a technique used to prepare semiconductor specimens. After 3mm disks were prepared per the standard XTEM procedure, these disks were then lapped using a tripod polishing device. A grid with a single 1mmx2mm hole was then glued with M-bond 610 to the polished side of the disk.

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Microstructural Characterization of Au-Ge-Ni based ohmic contacts to GaAs/AlGaAs modfet device

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100126433 ◽

1987 ◽

Vol 45 ◽

pp. 326-327

Author(s):

A.K. Rai ◽

A.K. Petford-Long ◽

A. Ezis ◽

D.W. Langer

Keyword(s):

Contact Resistance ◽

Ohmic Contact ◽

Ohmic Contacts ◽

Microstructural Characterization ◽

Almost Everywhere ◽

Spacer Layer ◽

Good Contact ◽

The Relationship ◽

Lower Contact

Considerable amount of work has been done in studying the relationship between the contact resistance and the microstructure of the Au-Ge-Ni based ohmic contacts to n-GaAs. It has been found that the lower contact resistivity is due to the presence of Ge rich and Au free regions (good contact area) in contact with GaAs. Thus in order to obtain an ohmic contact with lower contact resistance one should obtain a uniformly alloyed region of good contact areas almost everywhere. This can possibly be accomplished by utilizing various alloying schemes. In this work microstructural characterization, employing TEM techniques, of the sequentially deposited Au-Ge-Ni based ohmic contact to the MODFET device is presented.The substrate used in the present work consists of 1 μm thick buffer layer of GaAs grown on a semi-insulating GaAs substrate followed by a 25 Å spacer layer of undoped AlGaAs.

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Characterization of microwave-sintered ceramic composites

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100151519 ◽

1993 ◽

Vol 51 ◽

pp. 1136-1137

Author(s):

X. Zhang ◽

Y. Pan ◽

T.T. Meek

Keyword(s):

Matrix Material ◽

Maximum Output Power ◽

Ceramic Matrix Composite ◽

Ceramic Composites ◽

Processing Technique ◽

Structure Characterization ◽

Alumina Powder ◽

Maximum Output ◽

Sintered Ceramic

Industrial microwave heating technology has emerged as a new ceramic processing technique. The unique advantages of fast sintering, high density, and improved materials properties makes it superior in certain respects to other processing methods. This work presents the structure characterization of a microwave sintered ceramic matrix composite.Commercial α-alumina powder A-16 (Alcoa) is chosen as the matrix material, β-silicon carbide whiskers (Third Millennium Technologies, Inc.) are used as the reinforcing element. The green samples consisted of 90 vol% Al2O3 powder and 10 vol% ultrasonically-dispersed SiC whiskers. The powder mixture is blended together, and then uniaxially pressed into a cylindrical pellet under a pressure of 230 MPa, which yields a 52% green density. The sintering experiments are carried out using an industry microwave system (Gober, Model S6F) which generates microwave radiation at 2.45 GHz with a maximum output power of 6 kW. The composites are sintered at two different temperatures (1550°C and 1650°C) with various isothermal processing time intervals ranging from 10 to 20 min.

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Microstructural characterization of a cast RENi5-based alloy

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100151714 ◽

1993 ◽

Vol 51 ◽

pp. 1176-1177

Author(s):

G. M. Micha ◽

L. Zhang

Keyword(s):

Electron Microscopy ◽

Rare Earth ◽

Microstructural Characterization ◽

Binary Compound ◽

Nickel Metal ◽

Cast Material ◽

Nickel Metal Hydride ◽

Transmission Electron ◽

Cast Condition

RENi5 (RE: rare earth) based alloys have been extensively evaluated for use as an electrode material for nickel-metal hydride batteries. A variety of alloys have been developed from the prototype intermetallic compound LaNi5. The use of mischmetal as a source of rare earth combined with transition metal and Al substitutions for Ni has caused the evolution of the alloy from a binary compound to one containing eight or more elements. This study evaluated the microstructural features of a complex commercial RENi5 based alloy using scanning and transmission electron microscopy.The alloy was evaluated in the as-cast condition. Its chemistry in at. pct. determined by bulk techniques was 12.1 La, 3.2 Ce, 1.5 Pr, 4.9 Nd, 50.2 Ni, 10.4 Co, 5.3 Mn and 2.0 Al. The as-cast material was of low strength, very brittle and contained a multitude of internal cracks. TEM foils could only be prepared by first embedding pieces of the alloy in epoxy.

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