A SrO-Al2O3 - 2SrO2 (SAS) glass ceramic matrix is reinforced with CVD SiC continuous fibers. This material is prepared by casting a slurry of SAS glass powder into tapes. Mats of continuous CVD-SiC fibers are alternately stacked with the matrix tapes. This tape-mat stack is warm-pressed to produce a 'green' composite. Organic constituents are burned out of the 'green' composite, and the remaining interim material is hot pressed

Bansal, Narottam

English

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NASA Case No. LEW-15,263-1
PRINT FIG. 1
NOTICE
The invention disclosed in this document resulted from research in aero-
nautical and space activities performed under programs of the National
Aeronautics and Space Administration. The invention is owned by NASA and is,
therefore, available for licensing in accordance with the NASA Patent
Licensing Regulation (14 Code of Federal Regulations 1245.2).
To encourage commercial utilization of NASA-owned inventions, it is NASA
policy to grant licenses to commercial concerns. Although NASA encourages
nonexclusive licensing to promote competition and achieve the widest possible
utilization, NASA will consider the granting of a limited exclusive license,
pursuant to the NASA Patent Licensing Regulations, when such a license will
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application of the invention.
Address inquiries and all applications for license for this invention to
NASA Patent Counsel, Lewis Research Center, Mail Stop LE-LAW, 21000 Brookpark
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nonexclusive or exclusive license are available from the above address.
Serial No.:
Filed Date:
INVENTOR :
EMPLOYER :
892,054
6/4/92
Narot tam Bansal
NASA Lewis Research Ctr.
(NASA-C_se-LEW-152o3-1) SILICON
CARBIDE FIBER RFINF_RCED STRONTIUM
ALU_INOSILICATE GLASS-CERAMIC
MATRIX COmPOSITe Patent Application
(_A3A) 7 p
LeRC
N93-I1543
Unclas
GB/24 012"_&51
https://ntrs.nasa.gov/search.jsp?R=19930002355 2020-03-17T09:54:10+00:00Z
NASA CASE NO. LEW-15,263-1 PATENT
Silicon Carbide Fiber Reinforced Strontium
Aluminosilicate Glass-Ceramic Matrix Composite
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0riqin of the Invention
The invention described herein was made by an employee of
the U.S. Government and may be manufactured or used by or for
the Government without the payment of any royalties thereon or
therefor.
Technical Field
This invention is concerned with a ceramic fiber-
reinforced glass-ceramic matrix composite. The invention is
particularly concerned with a high strength ceramic fiber-
reinforced composite which is refractory, strong, and tough
for applications as high temperature structural materials.
It has been suggested that lithium aluminosilicate,
magnesium aluminosilicate (cordierite), and calcium alumino-
silicate glass ceramics reinforced with SiC fibers derived
from polymers be used for such applications. Commercially
available SiC fibers, known as Nicalon, have been
satisfactory. However, the potential use of such prior art
materials is limited to somewhat low temperatures of about
1000°C to ii00 ° C.
The fabrication of a composite by infiltration of melt of
SrO-AI203 - SiO z (SAS) composition into a preform made out of
SiC powder, siC whiskers and CVD SiC fibers has been
attempted. However, the fiber-reinforced composites made by
this method showed no improvement in flexural strengths over
the ones with no reinforcements.
It is, therefore, an object of the present invention to
provide a new composite material having superior mechanical
properties at high temperatures.
Another object of the invention is to provide a method of
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NASA CASE NO. LEW-15,263-1
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making a ceramic fiber-reinforced glass-ceramic matrix
composite material for use in gas turbine and diesel engines.
Backqround Art
Hillig patent No. 4,725,567 is directed to a composite
material processed by infiltration. The object of the
invention is the production of a high temperature composite
material. Hillig patent No. 4,788,162 discloses a method for
the production of high temperature composite materials. This
patent notes that the SrSiO 3 has unique characteristics, such
as expansion while freezing. The combination of CaSiO 3 and
SrSiO 3 provides a material which is stable at a variety of
temperature ranges.
Hillig and McGuigan patent No. 4,917,941 is directed to a
ceramic matrix produced with continuous SiC fibers and a slip
casting technique. A porous mold in the shape of the material
desired is used in the process. It is capable of removing the
liquid from the suspension leaving only the matrix material.
Prior to drying, continuous sic fibers are wrapped around the
mold. The process may be repeated to add thickness to the
material. Drying occurs in an ambient environment.
Gadkaree patent No. 4,919,991 is concerned with another
composite. The only pertinency of this patent is the use of
SrSiO 3 as an alternative material in the composite structure.
Singh et al patent No. 4,944,904 discloses a ceramic matrix
having a boron nitride coating. A carbon cloth is dipped into
a slurry layer into a preform. At this point infiltration is
used to form the composite.
Disclosure of the Invention
The objects of the invention are achieved with a fiber-
reinforced composite which is composed of a SrO-Al203-2sio 2
(SAS) glass ceramic matrix that has been reinforced with CVD
sic continuous fibers. The method of assembly includes
NASA CASE NO. LEW-15,263-1
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preparing a slurry of SAS glass powders and casting this
slurry into tapes. After the tapes are dried they are cut to
the proper size.
Continuous CVD-SiC fibers are formed into mats of the
desired size. The matrix tapes and the fiber mats are
alternately stacked in the proper orientation. This tape-mat
stack is warm pressed to produce a "green" composite.
The "green" composite is then heated to an elevated
temperature to burn out organic constituents. The remaining
interim material is then hot pressed to form a SAS glass-
ceramic fiber-reinforced composite which may be machined to
size.
Description of the Drawing
The objects, advantages and novel features of the
invention will be more fully apparent from the following
detailed description when read in conjunction with the
accompanying drawing which is a graph showing three point
flexural stress-strain behavior of a 24 volume percent silicon
carbide fiber-reinforced SAS glass-ceramic composite material
at room temperature.
Best Mode for Carrying Out the Invention
The composite of the present invention is produced by a
tape method in which an aqueous slurry of SAS glass powder
along with a fugitive organic binder, plasticizer, glycerine,
and surfactant is prepared. Glass powders having an average
particle size of about 2.5 _m have been satisfactory. A
binder identified as Methocel 20-214 which is a commercially
available material from the Dow Chemical Company has been
suitable. A plasticizer known commercially as Polyglycol E-
400 from the Dow Chemical Company has been adequate. A
surfactant material sold commercially as Tritonex i00 has
provided satisfactory results.
NASA CASE NO. LEW-15,263-1
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This slurry is first ball milled and then cast into
tapes. This may be facilitated by using a doctor blade.
After the tape has dried, it is cut to size. The composition
of the matrix is preferably about 31.8 w/o SrO, about 31.3 w/o
A1203, and about 36.9 w/o SiO2. This composition is also
expressed as 25 mole % SrO, 25 Mole % AI20_, and 50 mole% SiO 2.
Continuous CVD SiC fibers that were supplied by Textron
Specialty Materials are wound onto a drum. Commercially
available adhesive tape is used to hold the fibers in their
proper position on the drum. The fibers are then cut into
unidirectional mats of desired predetermined size whose fiber
orientation and integrity are maintained by the adhesive tape.
The required number of matrix tapes and fiber mats are
alternately stacked in a desired orientation in a warm press
die. After stacking, this material is warm pressed to produce
a "green" composite.
The "green" composite is then removed from the warm press
die and wrapped in either graphite foil or molybdenum foil.
The wrapped "green" composite is loaded into a hot pressing
die where it is heated to an elevated temperature between
about 400 ° C to 500 ° C to burn out organic constituents to
produce an interim material.
The interim material is then hot pressed under vacuum
using temperatures of 1200 ° C - 1500 ° C, a pressure of 2 to 4
KSI, and a time of 15 to 120 minutes. After cooling to room
temperature and pressures, the resulting composites are then
removed from the die.
A number of the composites were cut into test bars for
flexural strength measurements and other characterizations.
Referring to the drawing there is shown a graph of the 3-point
flexural stress-strain behavior for a 24 volume percent SiC
fiber/SAS glass-ceramic composite material. Unidirectional
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composites having room temperature 3-point flexural stress of
greater than i000 MPa have been fabricated with 27 volume
percent fiber loading.
While the preferred embodiment of the invention has been
shown and described, it will be appreciated that various
modifications may be made to the invention without departing
from the spirit thereof or the scope of the subjoined claims.
This silicon carbide fiber-reinforced SAS glass-ceramic matrix
composite is a new and improved structural material. The
composite fabricated by the aforementioned method has
mechanical properties superior to existing materials and a
potential for use at temperatures as high as 1450°C to 1500°C.
NASA CASE NO. LEW-15,263-1
Abstract of the Disclosure
SILICON CARBIDE FIBER REINFORCED STRONTIUM
ALUMINOSILICATE GLASS-CERAMIC MATRIX COMPOSITE
A SrO-Al203 - 2SrO 2 (SAS) glass ceramic matrix is reinforced
with CVD SiC continuous fibers. This material is prepared by
casting a slurry of SAS glass powder into tapes. Mats of
continuous CVD-SiC fibers are alternately stacked with the
matrix tapes.
This tape-mat stack is warm-pressed to produce a "green"
composite. Organic constituents are burned out of the "green"
composite, and the remaining interim material is hot pressed.
INVENTOR: Narottam Bansal
EMPLOYER: NASA Lewis Research Ctr.
S#RIAL NO.: 892,054
FILED : 6/4/92
NASA CASE NO. LEWo/_263-1
NAROTTAM BANSAL
SHEET 1 OF 1
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Silicon carbide fiber reinforced strontium aluminosilicate glass-ceramic matrix composite

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