Microstructural effects on properties and new processing techniques of silicon nitride. Part I: Microstructural effects on mechanical, thermal and thermomechanical Properties of Silicon Nitride

This paper explores a new processing method to fabricate porous zirconium tungstate (ZrW2O8 or ZT) with the porosity content up to 40% in volume. The method uses spherical graphite powders that are mechanically stable, allowing us to compact with ceramic powders in dry condition. Thus, the ceramic powders mixed with spherical graphite powders can be compacted and sintered to a near full density. During sintering, the graphite powders burn out without damaging the powder compact due to their inherent near-zero thermal expansion. The processing route discussed in this paper is applicable to all oxide ceramics where the sintering can take place in air and above 700°C to dissociate the graphite. In this paper, we have applied this processing technique to fabricate porous ZrW2O8. Many porous ZrW2O8 with a range of porosity levels were fabricated and tested for their theromomechanical properties including elastic modulus (E) and coefficient of thermal expansion (CTE). The experimentally determined properties were compared with the predictions based on the micromechanical Mori-Tanaka scheme.

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Status of Silicon Nitride Component Fabrication Processes, Material Properties, and Applications

Volume 4: Manufacturing Materials and Metallurgy; Ceramics; Structures and Dynamics; Controls, Diagnostics and Instrumentation; Education; IGTI Scholar Award ◽

10.1115/97-gt-321 ◽

1997 ◽

Cited By ~ 4

Author(s):

John P. Pollinger

Keyword(s):

Power Generation ◽

Silicon Nitride ◽

Gas Turbines ◽

Process Development ◽

Low Cost ◽

Turbine Blades ◽

Hybrid Vehicle ◽

Thermomechanical Properties ◽

Commercial Aircraft ◽

Ceramic Components

Silicon nitride monolithic structural ceramic components have recently been introduced as production parts in commercial aircraft turbomachinery pump and seal applications to take advantage of their unique thermomechanical properties. Additionally, extensive efforts are in progress to develop, evaluate, and productionize silicon nitride components for commercial aircraft turbomachinery hot sections, industrial power generation turbines, and automotive hybrid vehicle turbogenerators. AlliedSignal Ceramic Components has developed a family of in-situ reinforced silicon nitride materials for these applications and is developing and implementing a suite of component fabrication processes to achieve production-viable manufacturing of complex shaped components, including turbine seals, blades, nozzles, wheels, and combustors. A key focus of the manufacturing process development is the need to achieve low cost fabrication of components in order to meet cost targets required for commercial introduction. Finally, the status and plans for a number of aerospace, industrial, and automotive turbomachinery applications are discussed, including commercial aircraft turbomachinery production components (pump and seal parts) and development components (auxiliary power unit turbine blades and nozzles, and propulsion engine wheels and starter wheels), nozzle, blade, wheel and combustor components for automotive hybrid vehicle turbogenerators, and turbine blades and nozzles for industrial power generation gas turbines.

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Selection of Sintering Aid for Silicon Nitride for Improvement of Thermomechanical Properties

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.25-26.411 ◽

1992 ◽

Vol 25-26 ◽

pp. 411-420

Author(s):

J. Mukerji

Keyword(s):

Silicon Nitride ◽

Thermomechanical Properties ◽

Sintering Aid ◽

Selection Of

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THE POTENTIAL OF DIGITAL SEISMIC RECORDINGS FOR MULTICHANNEL PROCESSING

Geophysics ◽

10.1190/1.1440107 ◽

1970 ◽

Vol 35 (3) ◽

pp. 461-470 ◽

Cited By ~ 1

Author(s):

J. P. Lindsey

Keyword(s):

Dynamic Range ◽

Single Channel ◽

Recording Equipment ◽

Field Equipment ◽

Reflection Data ◽

Field Recording ◽

Amplifier Gain ◽

Multichannel Processing ◽

New Processing ◽

Processing Techniques

The availability of seismic digital field recording equipment has made possible new processing techniques which achieve significant reflection data enhancement. Typical of the processes that are now used routinely are deconvolution, autocorrelation and crosscorrelation, Fourier transformation, and spectral alteration. A recording fidelity that reduces errors to 1 part in 10,000 has provided the motive for developing and using these techniques. An additional capability of digital field equipment is the recording of amplifier gain information to a precision of 0.1 percent. This appears to provide a motive for developing multichannel processes which expand further our processing capabilities beyond the essentially single channel ones now in use. The present study evaluates the multichannel processing potential afforded by present day seismic digital field recording systems. The evaluation is based on measurement and computation of the effects of channel performance deviations. Each component of the field recording system (geophone, cable, amplifier, filters, sampling skew) separately, and the system as a whole, are evaluated in this context. Results of the study indicate that whereas any given channel possesses a dynamic range of 80 db, channel‐to‐channel variations establish a dynamic range of only 15 db. The 15 db range sets a serious limit on the performance of multichannel processes and points up the need for additional improvements in field hardware capabilities.

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New Processing Techniques for the Creation of Micro-Opto-Mechanical Machines and Photonic Devices Embedded in Glass

MRS Proceedings ◽

10.1557/proc-739-h1.6 ◽

2002 ◽

Vol 739 ◽

Author(s):

Meg Abraham ◽

Peter Fuqua ◽

David P. Taylor ◽

William W. Hansen ◽

Henry Helvajian ◽

...

Keyword(s):

Silver Halide ◽

Three Dimensional ◽

Direct Write ◽

Buried Structures ◽

Nucleation Sites ◽

New Processing ◽

Meta Silicate ◽

Processing Techniques ◽

Aerospace Corporation ◽

Nano Wires

ABSTRACTThe use of lasers to create intricate three-dimensional and buried structures [1] in photostructural glass has been well demonstrated at The Aerospace Corporation over the past four years. In these instances the glass used (Foturan™, made by the Schott Group) forms a silver nucleation sites on exposure to intense UV laser light via a two-photon process. Subsequent annealing causes a localized crystal growth to form a meta-silicate phase which can be etched in dilute hydrofluoric acid at rates of 20 to 50 times that of the unprocessed glass. We are now in the process of experimenting with another formulation of photosensitive glass, also pioneered by Corning Glass Works, that behaves differently during the bake process. In the second case, a photoexposure and bake process creates a silver-halide crystal and forms an adjacent void in the glass. A second photoexposure and bake allows for the migration of more silver into the void creating patterned formations of silver nano-wires [2]. Recent experiments with this type of glass have shown that the manipulation of the size and density of the embedded nano-wires as well as the overall pattern of the clusters can be controlled using direct-write exposure to laser processing.

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Approaches to the Design and Processing of Novel Titanium Alloys

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.29-30.127 ◽

2007 ◽

Vol 29-30 ◽

pp. 127-130

Author(s):

Colleen J. Bettles ◽

Rimma Lapovok ◽

H.P. Ng ◽

Dacian Tomus ◽

Barry C. Muddle

Keyword(s):

Titanium Alloys ◽

High Performance ◽

Powder Processing ◽

Low Cost ◽

Cost Effective ◽

Processing Technologies ◽

Shape Processing ◽

New Processing ◽

The Cost ◽

Processing Techniques

The range of commercial titanium alloys available is currently extremely restricted, with one alloy (Ti-6Al-4V), and derivatives of it, accounting for a very large proportion of all applications. High performance alloys are costly to fabricate and limited to low-volume applications that can sustain the cost. With the emergence of new processing technologies that promise to reduce significantly the cost of production of titanium metal, especially in powder form, there is an emerging imperative for cost-effective near net shape powder processing techniques to permit the benefit of reduced metal cost to be passed on to higher-volume applications. Equally, there is a need for the design and development of new alloys that are intrinsically low-cost and lend themselves to fabrication by novel cost-effective net shape processing. The approaches that might be used to select, design and process both conventional alloys and novel alloy systems will be reviewed, with a focus on innovation in design of low-cost alloys amenable to new processing paths and increasingly tolerant of variability in composition.

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The Fabrication and Magnetic Shielding Properties of Melt Cast Bi‐Sr‐Ca‐Cu‐O

MRS Proceedings ◽

10.1557/proc-169-1279 ◽

1989 ◽

Vol 169 ◽

Author(s):

R.J. Rayne ◽

L.E. Toth ◽

B.A. Bender ◽

S.H. Lawrence ◽

R.J. Soulen ◽

...

Keyword(s):

Superconducting Devices ◽

Heat Treating ◽

Superconducting Properties ◽

Dimensional Control ◽

Magnetic Shields ◽

Bulk Superconductors ◽

Complex Shapes ◽

Shielding Properties ◽

New Processing ◽

Processing Techniques

AbstractMagnetic shields for SQUID applications were successfully fabricated using high Tc superconducting BSCCO. To produce shields with appropriate superconducting properties and close dimensional control, it was necessary to develop new processing techniques. Shields were produced by casting liquid BSCCO into molds, heat treating and machining. This technique is applicable to fabricating other types of superconducting devices requiring bulk superconductors with complex shapes and close dimensional control.

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