Aluminous Keatite—An Improved Rotary Ceramic Regenerator Core Material

1978 ◽  
Vol 100 (1) ◽  
pp. 36-39 ◽  
Author(s):  
D. G. Grossman ◽  
J. G. Lanning
Keyword(s):  
Thermal Expansion ◽  
Gas Turbines ◽  
Combustion Process ◽  
Diesel Oil ◽  
Hydrogen Ion ◽  
Core Material ◽  
Aluminum Silicate ◽  
Lithium Aluminum ◽  
Low Thermal Expansion ◽  
New Material

Rotary lithium aluminum silicate (LAS) ceramic regenerator cores for gas turbines have had limited durability in applications using sulphur bearing hydrocarbon fuels such as diesel oil. The presence of sulphuric acid from the combustion process caused a lithium/hydrogen ion exchange and resulted in core failure. This paper describes a unique low thermal expansion aluminous keatite material (Corning Code 9460) which was developed to overcome the foregoing problem. Cores made from this new material have now operated over 6000 hr in Ford 707 gas turbines.

Influence of Nitride on Sinterability of the Composite of Lithium Aluminum Silicate and Silicon Carbide

2006 ◽  
Vol 317-318 ◽  
pp. 177-180 ◽  
Author(s):  
Mabito Iguchi ◽  
Motohiro Umezu ◽  
Masako Kataoka ◽  
Hiroaki Nakamura ◽  
Mamoru Ishii
Keyword(s):  
Silicon Carbide ◽  
Thermal Expansion ◽  
Melting Point ◽  
Liquid Phase ◽  
Room Temperature ◽  
Aluminum Silicate ◽  
Lithium Aluminum ◽  
Sintering Process ◽  
Thermal Expansion Coefficients ◽  
Expansion Coefficients

Ceramics with zero thermal expansion coefficients at room temperature (293K) were investigated. We found the thermal expansion coefficient was controlled by a compounding ratio of lithium aluminum silicate (LAS) and silicon carbide (SiC), which have negative and positive thermal expansion coefficients respectively. Although it was difficult to densify the composite of the LAS and SiC (LAS/SiC) in the sintering process, an addition of nitride improved the sinterability of the LAS/SiC. In order to examine the effect of the nitride additive, at first, the melting point of the LAS with silicon nitride (Si3N4) or aluminum nitride was measured by TG-DTA. The melting point of the LAS decreased with existence of nitride. It is believed that the densification of the LAS/SiC was promoted by the nitride, because the nitride causes the LAS/SiC to form a liquid phase, thereby decreasing the melting point. Next, the lattice constant of the LAS with Si3N4 was measured by XRD and it was verified that the a-axis was longer and the c-axis was shorter than those of the LAS without additive. It is supposed that this phenomenon is due to the substitution of nitrogen for oxygen in the LAS lattice, and the decrease of the melting point of the LAS with nitride seems to be influenced by this substitution of nitrogen.

A New Low-Thermal-Expansion, High-Strength Alloy for Gas Turbines

1989 ◽  
Author(s):  
S. K. Srivastava ◽  
George Y. Lai
Keyword(s):  
Thermal Expansion ◽  
Gas Turbine ◽  
Gas Turbines ◽  
High Strength ◽  
Environmental Resistance ◽  
Minor Elements ◽  
Low Thermal Expansion ◽  
Strength Alloy ◽  
Long Range Ordering ◽  
Cr System

HAYNES® alloy No. 242, based on Ni-Mo-Cr system, was developed primarily for turbine seal applications. The key characteristics of the alloy are derived from critical control of Ni, Mo, Cr, and several minor elements. The high strength — about twice that of alloy B — is achieved from a long-range ordering reaction. The paper reviews comparative evaluation of 242™ alloy versus several currently used gas-turbine alloys such as alloys B, S, N and INCOLOY® alloy 909. Environmental resistance is particularly emphasized. It is shown that 242 alloy possesses an excellent combination of low-thermal-expansion, high strength, and environmental resistance for gas turbine service up to 1400°F (760°C).

Low Thermal Expansion of Alkali Zirconium Phosphates Using a Microcomputer Automated Diffractometer

1984 ◽  
Vol 28 ◽  
pp. 345-352
Author(s):  
G. E. Lenain ◽  
H. A. McKinstry ◽  
S. Y. Limaye
Keyword(s):  
Thermal Expansion ◽  
Thermal Shock Resistance ◽  
Fused Silica ◽  
Lithium Aluminum ◽  
The Past ◽  
Low Thermal Expansion ◽  
Zirconium Phosphates ◽  
Stable Space ◽  
Shock Resistance ◽  
Ceramics Industry

The thermal expansion of ceraptic materials has become a property of interest to more people recently since the desirability of a thermally stable space platform was recognized. The interest in low thermal expansion materials in the past has been driven mildly by the recognition that low thermal expansion will foster good thermal shock resistance. The tradition of the ceramics industry for nearly one hundred years has been that zircon and cordierite were the low expanding materials. Fused silica has long been recognized for its low expansion. But when in 1947 Hummel (1957, I960) found ultra-low-expanding bodies in the lithium aluminum silicates with spodumene and later β-eucryptite structures, a new kind of phenomena had been introduced. Roy (1949), Roy, Roy and Osborn (1950) and Roy and Osborn (1959) provided much of the crystal chemical and phase diagram background on this family.

scholarly journals Development of a Low Thermal Expansion Magnesium-Aluminum-Silicate Ceramic for Gas Turbine Heat Exchanger Applications

1975 ◽  
Author(s):  
Sergej-Tomislav Buljan ◽  
R. N. Kleiner
Keyword(s):  
Thermal Expansion ◽  
Heat Exchanger ◽  
Gas Turbine ◽  
Ceramic Materials ◽  
Aluminum Silicate ◽  
Factors Influencing ◽  
Low Thermal Expansion ◽  
Magnesium Aluminum Silicate ◽  
Silicate Ceramic

A review of the factors influencing the thermal expansion of ceramic materials is presented. Studies have shown that thermal expansions lower than the theoretical value predicted for cordierite can be obtained. The properties of a low thermal expansion magnesium-aluminum-silicate ceramic developed for gas turbine heat exchanger applications are described.

Effect of LaCl3 on the Properties of LAS Ceramics

2009 ◽  
Vol 66 ◽  
pp. 112-114
Author(s):  
Yong Li ◽  
Xiao Li Zhang ◽  
Ling Li ◽  
Hong Sheng Wang ◽  
Hong Yi Jiang
Keyword(s):  
Thermal Expansion ◽  
Bending Strength ◽  
Sol Gel ◽  
Aluminum Silicate ◽  
Lithium Aluminum ◽  
Gel Method ◽  
Sol Gel Method

In this research, different amounts of LaCl3 were added to the lithium aluminum silicate (LAS) ceramics and the sample powder was prepared by sol-gel method. The effect of LaCl3 on the density, bending strength and the thermal expansion of the obtained ceramics was mainly investigated because LaCl3 is heavier than the lithium aluminum silicate (LAS) ceramics and the superfluous of La2O3 can be introduced into the sol solution.

Some Significant Highlights in Allison Regenerator Development

1996 ◽  
Author(s):  
Leonard C. Davis ◽  
Anthony J. Jackman
Keyword(s):  
Gas Turbines ◽  
Waste Heat ◽  
Low Cost ◽  
Strength Loss ◽  
Cyclic Strength ◽  
Aluminum Silicate ◽  
Lithium Aluminum ◽  
Rotating Disc ◽  
Ceramic Disc ◽  
Endurance Testing

Allison Engine Company has 26 years of experience in vehicular gas turbines with rotating disc regenerators for waste heat recovery including 7 different engine models ranging up to 350 hp. We have completed the first 140 hr of endurance testing on a one-piece extruded ceramic disc regenerator of 231 mm (9.1 in.) diameter. Our disc supplier is finalizing extrusion additives and firing schedule for a lithium aluminum silicate material with up to 85% mined mineral content for low cost. Unique Allison regenerator experience is cited as follows: first gas turbine with rotating regenerator in production, thermal cyclic strength loss of ceramic disc materials and cyclic oxidation of metal disc materials, regenerator leakage as low as 3.4%, metal regenerator time versus temperature ignition limits of various metals, and damping of friction-induced torsional vibration of regenerator discs.

The influence of heat treatment on the fiber/matrix interface in a SiC-reinforced glassceramic

1988 ◽  
Vol 46 ◽  
pp. 742-743
Author(s):  
E. Bischoff ◽  
O. Sbaizero
Keyword(s):  
Heat Treatment ◽  
Aluminum Silicate ◽  
Lithium Aluminum ◽  
Interfacial Region ◽  
Specimen Preparation ◽  
Crack Wake ◽  
Pull Out ◽  
Annealed Material ◽  
Ultrasonic Drilling ◽  
Fiber Matrix Interface

Fiber or whisker reinforced ceramics show improved toughness and strength. Bridging by intact fibers in the crack wake and fiber pull-out after failure contribute to the additional toughness. These processes are strongly influenced by the sliding and debonding resistance of the interfacial region. The present study examines the interface in a laminated 0/90 composite consisting of SiC (Nicalon) fibers in a lithium-aluminum-silicate (LAS) glass-ceramic matrix. The material shows systematic changes in sliding resistance upon heat treatment.As-processed samples were annealed in air at 800 °C for 2, 4, 8, 16 and 100 h, and for comparison, in helium at 800 °C for 4 h. TEM specimen preparation of as processed and annealed material was performed with special care by cutting along directions having the fibers normal and parallel to the section plane, ultrasonic drilling, dimpling to 100 pm and final ionthinning. The specimen were lightly coated with Carbon and examined in an analytical TEM operated at 200 kV.

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