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has been developed for obtaining a 90° reorientation of the matrix, it would be a real breakthrough for the whole C/C world. The photo micrographs that were shown looked very encouraging as more than 80% of the matrices were oriented transversely to the fiber surfaces. This research is ongoing and, as might be expected, no details of the mechanism or processing conditions were divulged other than the fibers are heated between 600 and 800 °C before the pitch is introduced into the yarns. If the fibers are heated >800°C, the matrix ab planes will lay down parallel to the fiber surface. This implies that some sort of a radical type of bonding may be involved between the fibers and the surrounding matrix. This is an area of research that should be pursued, for an understanding of this phenomenon will certainly add a great deal to the ability to alter the properties of C/Cs according to the design and applications requirements.

Another unique development that was devised in this carbon group is the two phase carbonaceous spring. This is achieved by codrawing, at a relatively low spinning temperature, a mixture of isotropic and anisotropic pitch through an orifice and then processing the fibers

in the usual manner. This results in a fiber, which is 10 to 15 microns in diameter, that is coiled into a springlike shape that acts like a spring. The tensile strength of this type of fiber is approximately 60 kpsi. Apparently, the two types of pitches are not miscible and there is a differential contraction between them during the pyrolysis phase of the process that results in the springlike configuration, which has a diameter of 1 to 2 mm and a length of 0.5 to 1 cm. There are numerous possible applications for this type of spring because of its inertness to the body and high temperature properties. Apparently the geometry of the coils is controlled by the mixture of the two types of pitches and the extrusion procedures.

1,200 °C) and excellent friction-wear properties at high temperatures (0.1 at 500 °C). In all of this they are trying to understand all fundamental processes that are causing the carbon to change its characteristics.

This organization is certainly a leader in Japan in the development of new types of carbon systems. This effort should continue in the future, since within the past 2 years MITI has initiated a new thrust to develop C/Cs that is expected to continue at least until 1997. Dr. Nakamizo expressed the desire for collaboration between this institute and organizations in the United States. There have been such collaborations with DLR in Germany, in Sweden, and in Australia.

A number of other of carbonaceous artifacts have been developed here based on Dr. Yamada's knowledge of the chemistry of the precursors and the influence of the pyrolysis conditions on the development of the different types of carbons with various microstructures and properties. One of the Assessment systems is elastic graphite, which was discussed in the Koa Oil site visit of 7-8 January 1991. At this site, the heat treatment for this material is 2,800 °C, which results in a pore size of <1 micron. Another example has been the development of fibers from various types of pitch over the past 10 years. Their tensile strengths have been in the range of 360 kpsi with moduli of 90 Mpsi or less. Another approach has been the solubilizing of the mesophase in water by sulfination, nitridization, and other chemical modifications. Such modifications have permitted the formation of unique types of carbon and coatings. In the former case, the unique carbons can be used as a sensor of atmospheric water content. In the latter case, thin carbon coatings can be applied to steel rods that are being used for medical purposes. Other unique applications are also being investigated.

It is recommended that we keep in touch with this organization and possibly initiate some cooperative projects, as this carbon group has shown the most innovations of carbonaceous materials of any single group that was

KYUSHU UNIVERSITY

Institute of Advanced Material Study
Dept. of Molecular Engineering,
Graduate School of Engineering Science
86 Kasuga, Fukuoka 816, Japan
Tel: 092-573-9611 x620
Fax: 092-575-3634
Dates: 28-29 Jan 1991

Research in the enhancement of resistance to oxidation of C/Cs is being undertaken at this site. One of the approaches is to determine if oxidation stable, submicron size particles can be stable, submicron size particles can be dispersed on the surface of carbon fibers to act as oxygen "getters." At this time, the processing procedure has successfully dispersed carbon black powder. Another approach has been the use of Background two newly developed processes in which the carbon is mixed with zirconium carbide and boron carbide. One method of forming this material is to hot press using the boron compounds as a sintering aid and the other is the pressureless method using a sinterable carbon powder. The carbon/ceramic composites are found to have high oxidation resistance (<0.25% in 10 hours at

Prof. Isao Mochida is the head of this institute. His major research interest is the chemistry of pitch systems and how this knowledge can be utilized to make them more useful. Mochida is one of the three or four foremost carbon researchers in Japan and the principal contributor in the mesophase field of research. He has been doing so for

the past 15 years and is internationally known for his research contributions. Mochida spent a year at the University of Illinois as a postdoctoral student and at the University of Newcastle upon Tyne in England, which was the world center at that time for mesophase, coal, and coke research.

Mochida's institute consists of 3 assistant professors, 2 postdoctoral students (1 from Japanese industry, 1 from China), 4 Ph.D. candidates (2 Japanese, 2 Chinese), 10 master's candidates, 2 undergraduates (1 is the wife of one of the Chinese graduate students), and 3 part-time support staff. Funding for these efforts comes from Kyushu University, the Ministry of Education, MITI, and industry. There is frequently a delay in getting money from the Ministry of Education and good graduate students have been lost or research programs are not accomplished on schedule. So other sources of funding must be found to overcome these delays such as having a researcher from an industrial firm spend time at the institute doing a project of mutual interest and receiving company support. Program Status

The research program at the institute is composed of three major areas:

• Carbon science, which is concerned with understanding the phenomena of the mesophase transformations of pitches and the application of this information to the formation of optimum structures of cokes and fibers.

• Coal and heavy crude oil refinement processes, including liquefaction and catalytic reaction phenomena that occur with these processes.

Solid state catalysis, including pollution control through activated carbons and fibers.

About 6 years ago research began to formulate the proper processing procedures to derive mesophase pitch for the production of fibers in the most economical manner. The purpose of the research was to determine how to chemically and thermally treat the pitch so that it would have the proper chemical structure for spinning and stabilizing the fibers and obtaining the desired microstructure and the desired physical properties after a high temperature treatment. One example of such a research program involves the preparation of mesophase pitches from methylnaphthalene with the aid of HF/ BF3. This study was undertaken because it has been shown that pure aromatic it has been shown that pure aromatic hydrocarbons are excellent precursors for mesophase pitch with the aid of HF/BF,, but clarification is needed as to the influences of the methyl group on the condensation reactivity of the aromatic hydrocarbons and properties of the resulting mesophase pitch. A number of methyl groups on the mesogen molecules are expected to reduce the softening point further and should enhance the stabilization reactivity of the mesophase pitch which, of course, will assist in the formation of fibers. Actually, the experiments did. show that the mesophase pitch had a lower softening point and higher spinnability, and the desired degree of stabilization reactivity was successfully achieved. Furthermore, it was found that the methyl group changed its position between 1- and 2-work state, indicating that it is not necessary to separate the methylnaphthalenes before the synthesis of mesophase pitch. Thus, it is concluded from this investigation that the roles of the methyl group in the stabilization are as follows:

C-H as well as the adjacent aromatic C-H. Further studies are currently underway to explore better preparation conditions.

Another example of the type of research that is being conducted in these laboratories involves the improvement of the microstructure and properties of fibers that are derived from mesophase pitch. Usually, the fibers are drawn through orifii, which results in the high degree of orientation of the molecules parallel to the axis of the fiber, thereby resulting, after completing the entire processing procedure, in the high specific strengths and moduli that are characteristic of this type of fiber. Such mechanical properties are governed by the microscopic alignment of carbon planes, which inherit the basic arrangement or orientation of the aromatic or mesogen molecules. The purpose of this investigation was to determine if the mechanical properties of pitch fibers could be improved by applying external forces during the carbonization step (<600 °C) and then unloading while the temperature is raised to 1,300 °C. These carbonized bundles were then graphitized at 2,500 °C. It appears from the current data that the strain during carbonization certainly influenced the structure and properties of the carbonized and graphitized fibers, which were stabilized with an amorphous skin and an oriented core. In this core the carbon planes appeared to be aligned into an onionlike texture that resulted in a significant increase in the tensile strength of the fibers. Some change of the fiber's modulus was noted, sometimes positive but sometimes negative, without apparent reasons. So far, the tensile strength and modulus are not always improved by the carbonization The methyl group itself has a high of pitch fibers that have a skin-core reactivity against oxygen.

Methyl group substitutes for the
aromatic ring activate the naphthenic

microstructure. Therefore, more extensive studies are underway to determine if processing differences are the possible causes of these variations.

More recently there have been investigations initiated into preparing pitch systems that are specifically designed for use as impregnants for the densification of preforms. The goal is to obtain a high degree of fluidity and also maintain a large percentage of carbon yield for the pitch. The approach is to continue the molecular studies and to determine how the different pyrolysis conditions alter the structure of the molecules within each type of pitch. In some cases the carbon yield has been as high as 98%! The eventual goal is to reduce the costs of processing and fabricating C/Cs by requiring fewer impregnation cycles. Another approach for reducing costs that is now being tried is to mix chopped fibers with pitch, partially pyrolyze the mixture to drive off the low molecular weight volatile gases, but still maintain enough organic residuals so that the pitch-covered fibers are bonded together when they are hot pressed to the desired preform shape. There are two distinct advantages for reducing cost. First, it is very cheap to chop fibers instead of weaving preforms with continuous fibers. Second, allowing most of the volatile gases to leave the low density preform while they can readily escape saves fabrication time. Then, the preform is densified by hot pressing so that there is no need to reimpregnate to fill the voids that are otherwise left by the escaping gases. The disadvantage of this system is that it is difficult to properly distribute the fibers in the preform and to maintain their orientation throughout the pyrolysis stage of the process. Another unknown factor is the degree of utilization of the fiber's mechanical properties that can be achieved in the composite form. Clearly the answer will depend on numerous factors such as bond strength, matrix microstructure, and processing conditions. At this time.

none of these answers are available, as no mechanical property data exist. Nevertheless, it is expected that this method of fabricating cheap C/Cs will find an application where the demand for high mechanical properties is not too great.

Areas of research that are just beginning are the nature of chemical bonding between the fiber and the matrix and the influence of the type of pitch and its processing conditions on the matrix microstructure. Both areas require in-depth characterization of the chemical nature of the pitches and how they vary as processing proceeds.

Other areas of research activity at this institute that are relevant to C/Cs include:

• Development of carbon fiber reinforced carbon of which the matrix is derived from mesophase pitches

The laboratory capabilities for the characterization of the chemical nature and crystalline structure of all materials in any state are outstanding as might be expected at such an institution as this. There are no SEMs or TEMS at this site, although they are available in other parts of the university. Several pieces of equipment are available for determining the mechanical properties of fibers and composites. In addition, there are centrifuges for separating chemical compounds, pressure autoclaves, solid and liquid state NMR, mass spectrometer, and ESR equipment.

• Characterization of ethylene tar and coal liquids by nuclear magnetic Assessment resonance (NMR) in the liquid or solid state

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This institute, under the direction of Prof. Mochida, is unique in its capabilities to provide significant information about the processes and compositions of the precursors and their transformations during processing of fibers and impregnants that are used to densify preforms. It is expected that this high quality of research will continue for years to come and that the information will be of use to the United States as well as to the world of carbon as it has for many years. Prof. Mochida is interested in collaborating with organizations in the United States. Therefore, it is recommended that communications be maintained with this group as it is active and prolific in the pursuit of research papers. Consequently, it is expected that there is a good chance that some collaboration can occur in the near future if there is enough interaction between the parties that they can determine what areas of collaboration would be most valuable.

TOKYO INSTITUTE OF
TECHNOLOGY

Research Laboratory of Engineering
Materials

Division of Materials Processing
4249 Nagatsuta

Midori-ku, Yokohama 227, Japan
Tel: 045-922-1111 x2317
Fax: 045-921-1015 or 6953
Dates: 5,9,10 Feb 1991 and
18 Mar 1992

Background

the section come from the Ministry of
Education. There are five sections in
the Division of Materials Processing,
which is part of the Research Labora-
tory of Engineering Materials that was
established in 1958. The Tokyo Insti-
tute of Technology was promoted to
national university status in 1929.

About one-quarter of the section's
efforts are devoted to research on car-
bonaceous materials. The research is
focused on the influence of microstruc-
ture on the fracture behavior of car-
bonaceous materials between room
temperature and >2,200 °C. The mate-
rials being investigated have varied from
measuring single carbon/graphite fibers
at 1,600 °C to studying the influence of
microstructure and additives on the
thermal and mechanical properties of
multidirectional C/Cs after they were
heat treated to 3,000 °C or subjected to
neutron irradiation.

My host was Prof. Eiichi Yasuda, who is the head of the Very High Pressure and Temperature Section and is internationally known for his research in ceramics and carbonaceous materials. He was a postdoctoral research fellow more than 20 years ago at the University of Karlsruhe with Prof. Eric Fitzer, also internationally known for his research in the field of carbon. Program Status Now Yasuda is one of the leaders in carbon research in Japan. He was a cochair of the last Japanese international conference on carbon that was held in November 1990.

Yasuda's section specializes in research on high temperature properties of ceramic and carbonaceous materials and the influence of microstructure. At the time of my first visit, Yasuhiro Tanabe was Yasuda's research associate and received his Ph.D. in the area of multidirectional C/Cs. It is with these two researchers that most of the time was spent in discussing the influence of temperature, microstructure, and neutron irradiation on the physical properties of C/Cs. Since 1991, Tanabe has been an associate professor and is doing research in another section on thin carbon coatings, including diamond layers on metals to enhance their wear resistance. Yasuda's section consists of two doctoral, three master's, and two undergraduate candidates. A majority of the finances that support

One of the current research programs of interest is determining and identifying what functional groups may exist on PAN and pitch-based fibers after they have been oxidized in air between 500 and 560 °C for different times from 1 to 48 hours. These oxidized fibers are analyzed for changes in weight, surface area by the BrunauerEmmett-Teller (BET) method, wettability, and identification of surface groups by ESCA. Each of the differently treated fibers are then used to make unidirectional resin matrix samples. These are double notched and tested in compression with the load axis parallel to the fiber axis to determine if oxidizing the fibers changes the bond strength between the fiber and the matrix. The results of the analysis are compared to the variations of strength to identify, if possible, the factors causing the bonds to change. Some of the preliminary observations are as follows:

The weight loss is 2% for PAN fibers and only 1% for pitch fibers after being exposed in air at "500°C for 48 hours.

• There are no significant observable effects of oxidation on the surfaces of the PAN or pitch fibers after 48 hours in air at 500 °C as viewed with an SEM at a magnification of 7,500X. No deep pits or deep grooves were visible. A small difference was noted in that the longitudinal marks left by the die during the drawing operation were less distinct for the pitch fiber as compared to the PAN fiber after being oxidized.

There is a significant difference of specific surface areas with heat treatment as the PAN fibers exceeded the pitch fiber values by almost a factor of two after 48 hours oxidation at 500 °C and by a factor of almost three as a function of weight loss.

• The wetting angles of the fibers in water decreased with oxidation time from approximately 60° at 0 hour for both PAN and pitch fibers to about 25° for pitch fibers and 35° for PAN fibers after approximately 15 hours of oxidation at "500 °C.

• The ESCA results indicated that heat treatment at 2,600 °C of all the "as-received" fibers did eliminate an oxygen functional group that was very evident on the PAN fibers. However, for the as-received pitch fiber there was only a slight indication of this group but none after the heat treatment. After oxidation in air, there was no evidence of any groups on either type of fiber even after 4 hours at 500 °C or after 14 hours for pitch and 4 hours for PAN at 560 °C.

The shear strengths between the resin and the fibers seemed to be nearly constant irrespective of the oxidation time.

This investigation is still continuing as it is not clear what phenomena are occurring. At the moment, it appears that no functional groups are introduced by air oxidation treatment at 500 °C possibly because they are removed very rapidly at this temperature. The next approach is to expose these fibers at a lower temperature (~250 °C) in a pure oxygen atmosphere to determine if any functional groups can be generated. Another interesting question is why are there no bond strength variations measured between the two types of fibers after oxidation since there are differences between their weight losses, specific surface areas, and contact angles? What does this indicate about the type of fiber surface that must be generated before a significant type of frictional bond is generated?

Another interesting result and subject of discussion is the apparent increase of the work to fracture of C/Cs that have been irradiated with 6 x 1024 neutrons per square meter. It appears this effect is more pronounced if the irradiation temperature in 640 °C as compared to 22 or 240 °C. This effect is contrary to that which has been observed for graphites under the same type of irradiation conditions where the irradiation effects are reduced as the temperature is increased so the work to fracture is reduced. No clear cause or explanation of this effect on C/Cs was put forth at this time. The answer is important because C/Cs are now considered to be the baseline material for deflectors in fusion reactors.

It is evident from the our discussions that a lot of consideration is being given by this group to the interactions between the fiber-to-matrix bond and the matrix microstructure, as they influence the fracturing behavior and change the physical properties of C/Cs. This is

the only group in Japan that is doing research on the combined effects of microstructure and high temperatures on the fracturing behavior of C/Cs. Another factor that no other group in Japan seems to be considering is the influence of temperatures >1,400 °C on the mechanical properties of C/Cs. It appears from Yasuda's research that the fracturing mode is influenced by the same bonding and matrix factors between 20 and 1,650 °C. But above 1,650 °C there seem to be other possible influences such as defects and dislocations. Clearly a better understanding of this phenomenon is needed if C/Cs are to be used for high temperature and impulse turbines and other applications.

research that would be of interest to both himself and to us. It is strongly recommended that communications be continued and serious consideration be given to forming some sort of a collaborative effort between us.

R&D INSTITUTE OF METALS
AND COMPOSITES FOR
FUTURE INDUSTRIES
(RIMCOFI)

Toranomon Hirai Bldg.
17-7 Toranomon 3-chome
Minato-ku, Tokyo 105, Japan
Tel: (03) 3459-6900
Fax: (03) 3459-6911
Date: 8 Feb 1991

The laboratory tour indicated that
the proper types of equipment are Background
available to carry out the experiments
being conducted and to characterize
the material before and after the tests
have been performed. In particular, there
are two special types of equipment
available in this section but not in any
other university. One of these is a test-
ing machine with the ability to conduct
mechanical tests at >2,000 °C. The other
equipment is a hot press that can form
ceramic samples at 2,200 °C. Also, there
are furnaces that can heat treat samples
to 3,000 °C, pyrolyze up to 1,800 °C,
and densify samples by CVD.

Assessment

The research efforts at this institute are clearly unique both in Japan and in any other country. Important information and concepts about the parameters that influence the mechanical properties of C/Cs have been coming from Yasuda's group for many years. It is expected that this situation will continue for at least another 5 to 8 years. There is a good communication link between Yasuda and a number of universities in the United States, so a form of collaboration has already started. He is most willing to extend this as time and money permit to do the type of

Discussions were held with Hajime Nishimura, who is the executive director of this organization, and Yoshio Minoda, a director. This meeting was arranged by Prof. E. Yasuda of the Tokyo Institute of Technology. The objective was to obtain further insight into MITI's mode of operation and plans for the development of C/Cs through research. After numerous discussions with Profs. Yasuda and Inagaki, their recommendation was to visit RIMCOFI to obtain the desired information from the organization that is actually managing the R&D activities for the composite programs, including C/Cs.

There are several organizational layers between MITI and RIMCOFI that need to be identified in order to understand why RIMCOFI can reflect the MITI operational attitude. MITI has the overall responsibility and does so through its Agency of Industrial Science and Technology (AIST). This organization's general and overall technical program objectives are generated by recommendations that are made by a Program Steering Committee that is composed of representatives from industry, government laboratories, and universities. This general program is

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