originally predicted but the development costs continue to be high. Thus, only the big companies will remain. This same sequence has occurred in the past, for example, in the area of carbon fibers, where 20 companies are now 5 to 7. Similar declines have been seen in the areas of mesophase pitch, intercalation of carbonaceous materials, and the diamond surfaces. It is recommended that communications be continued with this organization because of the diversity of the R&D programs being conducted here that have resulted in a broad spectrum of applications using carbonaceous materials. Nippon Steel's strongly expressed desire to consider cooperative programs with the United States may be useful in the support of research programs at universities in this country. TOYOHASHI UNIVERSITY OF TECHNOLOGY Dept. of Materials Science Background The host of this site visit was Prof. Mototsugu Sakai, who is the head of the ceramics and carbon materials effort at this university. In addition, he is internationally known for his research in the field of fracture phenomenology and theoretical analysis. His staff consists of 2 assistant professors and 15 graduate students. The major research emphasis of this group is in the areas of the rheology of mesophase pitch and understanding the science of microfracturing of ceramics and carbonaceous materials. About 80% of Sakai's group is working in fracture behavior and mechanics. These efforts are about equally divided between carbons and ceramics, in which the latter has been growing more rapidly than the former in the last few years. The other 20% of the effort is concerned with the rheological characteristics of mesophase pitch. Thus, the carbon effort consumes about 60% of the total effort in this group at this time. In general, Sakai is interested in the "scientific" aspect of this field and will only take financial support from industry if they are also interested in these aspects. Sakai's general impression is that industry does not readily use the talent at the Japanese universities in order to maintain their confidentiality status with respect to their competitors knowing what they are developing. But industry is very eager to obtain his best students. His experience has shown that 95% of the undergraduates and graduates are employed by industry and the remainder go to the universities or government laboratories. Program Status The general philosophy of the research here is to study the fracture physics from which the fracture mechanics is subsequently derived. Specifically, the breadth of possible causes is very impressive and ranges from the influence of atomic and molecular bonding to the overall strength and work to fracture of these materials and how these forces are being modified by stress shielding and crack wake effects. Fracturing phenomena are being evaluated on the basis of energy considerations. Şakai believes that 80% to 90% of the energy that is consumed in fracturing is caused by fiber pullout, 15% to 10% is due to fiber bridging, and the remaining energy is consumed by cracking of the matrix. But it should be remembered that this assessment is based primarily on current data that have been obtained with C/Cs that are composed of carbon rather than graphitic matrices. Fiber pullout tests are being conducted to determine their bonding characteristics. Single yarn bundles, 0.1 mm in diameter and 1 mm long, are being carved out of unidirectional samples. This operation is done with a razor blade with lots of patience and a steady hand. Then, the bundle is gripped and pulled out of the unidirectional C/C sample. The other major area of research at Toyohashi is the viscoelastic studies of different pitch systems. The transition of molten pitch from an amorphous to a liquid crystalline or mesophase state is of primary interest in order to understand the kinetics of how pitch enters and diffuses throughout porous materials that are being densified or how pitches possess the ability to be drawn into fibers. Therefore, the phenomenology of this transition is being investigated by heat treating different types of pitches at 400 °C to advance them into the mesophase state. The viscosities of these various pitches are determined as a means of studying their flow characteristics. It has been found that if the mesophase concentration is less than 60%, the flow characteristics are Newtonian, whereas if it is greater than 60%, the flow has viscoelastic characteristics. The flow measurements are taken between 250 and 300 °C in order not to advance the pitch while it is being measured. There is interest concerning the influence of matrix microstructure, but as yet the group's experience is with carbon matrices as they are just beginning to work with samples that have been heat treated to graphitization temperatures. In general, their microstructural examinations are performed using optical methods. The SEM is used only to evaluate fractured surfaces. Crack growth is measured by optical means. As a result, there are problems in identifying the initiation point and specific growth rates of cracks in C/Cs. The C/C samples from Nippon Steel are unidirectional with a phenolic prepreg and three to four pitch impregnations, where each cycle is heat The laboratory capabilities are There was an excellent response to the idea of having cooperative programs with organizations in the United States and especially with the University of California at Santa Barbara (UCSB). Collaboration could take many forms, from discussions about data to having an exchange of students and even several week visits between faculty members from Japan or the United States. The quality of the research is excellent under the leadership of Prof. Sakai and it is expected that this will continue for a number of years in the future. This is one of two organizations in Japan doing fundamental research in the area of fracture phenomenology of C/Cs. Based on the above observations, it is recommended that further communications be continued and that consideration be given toward determining the possible areas of common interest for establishing one or more collaborative programs that would be of mutual interest to both Prof. Sakai and organizations in the United States. Osaka Research Laboratory Dr. Mitsunao Kakuta, the general manager of this laboratory, was my host. The main purpose at this laboratory is to develop products from heavy oils and pitches that are derived from the company's refineries. These products include cokes, special carbonaceous materials, and pitch-based fibers. C/C composites were being developed for about 7 years when this effort was terminated 3 years ago. This decision was made because it was estimated that there would be a limited market in Japan for C/Cs and there were too many other organizations competing. At this time a major effort is being directed at the development of pitch-based carbon/ graphite fibers. High quality fibers, having >100 Mpsi modulus of elasticity values, are being produced on a prototype production basis. The major technological problem is to determine procedures for manufacturing these fibers at a lower cost. It is necessary to reduce this cost by a factor of 2 to 2.5 in order to be competitive with PAN-based fibers. This development effort is expensive as the production plant requires five persons per shift, three shifts per day, and 7 days per week of continuous operation. It is expected that a decision will be made in about 3 years on whether to continue this aspect of Koa Oil's developmental program. The are 38 people in the carbon R&D group, of which 10 are staff members and the rest are support, including those who are on the shifts for the fiber prototype production line. In addition, there are three managers who are responsible for the new materials efforts, which are fibers from mesophase pitch, elastic graphite, and sensors from carbonaceous materials. Program Status Research has been ongoing for about 7 years in the area of pitch-based fibers. The spinning process occurs between 400 and 480 °C with a light molecular weight oil that is on the alkaline side with toluene insolubles in the range of 70 to 80 ppm and quinoline insolubles from 30 to 35 ppm. It has been determined that better spinnability, which means more spinning time without fracturing a fiber, and a higher degree of anisotropic orientation of the molecules within the fiber are attained with precursors that have molecular weights in the range of 500 to 1,400. Apparently, the larger values of the modulus of elasticity and the strengths of fibers vary inversely with the molecular weight. The heat treatment temperatures can be as high as 2,800 °C in order to obtain a modulus as high as 113 Mpsi, which is comparable to the values attained by Amoco. At this time a new and small 2-micron-diameter fiber is being developed. Although it is possible to process 2-micron fibers, their diameter has a variable cross section that must be controlled. chemical absorptive surfaces, dry chemical cells, and other uses where a low density, compressible, and high surface area material can be used. Other R&D efforts have resulted in unique types of carbonaceous materials that are being evaluated or marketed, e.g., 200-micron-thick carbon paper and electrodes or moisture sensors for the water content of different types of atmospheres that are used in chemical processing steps. In both applications, the electrical resistivity of the material is altered, adjusting the degree of the feed stock's acidity in order to adjust its process procedures to provide the desired characteristics. For example, the resistivity of this material can be made high, which means small currents will pass through it. But if moisture is absorbed into the material from the atmosphere, the electrical rial from the atmosphere, the electrical resistivity will decrease, the current will increase, and a change of humidity will be indicated. Another research effort has been directed toward the development of an "elastic graphite." This is a material with a very low density between 0.2 and 0.5 g/cc and a surface area of 10 to 30 m2/g that is composed of spherical particles that are 10 to 300 micrometers in diameter. Each one of the spheres is hollow with a wall thickness that is approximately one-tenth of the particle's diameter. The microstructure of the walls is very unique and gives this material its unusual properties. TEM observations show that they are composed of a graphitic structure where the a-b planes are oriented in a circumferential manner, like onion skins. In general, this material is formed by dispersing the mesophase in an alkaline aqueous solution that is heat treated at about 300 °C to form the material with a final heat treatment at 2,400 °C to obtain the graphitic microstructure. It is this special type of structure that allows the material to be compressed to <50% of its original thickness with a pressure of 5,000 kg/cm2 and to return to its original dimension when the pressure is released. This recovery can occur because microcracking takes piace in the walls of the spheres as pressure is applied, which allows the walls to be flattened and still retain their integrity. When the pressure is released, these microcracks close and allow the spheres to return to their original shapes. Thus, this material can be recompressed innumerable times without losing it original shape. There are many possibil- Assessment ities for applying this material, such as for gaskets, absorbers of vibrational mechanical energy, catalytic and derived from fundamental studies to develop new and different types of carbonaceous materials. Furthermore, it is one of the few remaining organizations that is developing advanced types of mesophase pitch-based carbon fibers with both improved properties and lower production cost. Whether these costs can be reduced sufficiently to be competitive with PAN-based fibers is still a question. It is expected these R&D directions will continue for the next 3 to 5 years. It is interesting to note that 5 to 8 years ago there were more than 15 companies in Japan involved in the development of methods for the manufacture of pitch-based carbon fiber. Now this number has been reduced to three or four. The question of possible collaboration between Koa Oil and other U.S. organizations was discussed. In general, there is very little collaboration with any organization or individuals in Japan. However, there might be the possibility of a limited amount in the United States on the basis of programs that are of mutual interest to both parties. In addition, there would have to be strict controls on how the derived information is communicated outside of Koa Oil. It is recommended that further communications be continued because this organization has shown the capability of developing new concepts in the development of materials, including pitch-based fibers. A laboratory tour was conducted of the R&D prototype production facility for pitch-based carbon fibers. This facility has a capacity of 20 kg/day and it was installed about 5 years ago. In addition to the spinning facility, whose temperature is controlled within 1°, there is a stabilization furnace through which the fibers are oxidized in air at between 200 and 300 °C and a graphitization furnace that can operate up to 2,800 °C. Other laboratory facilities were visited, and it was evident that equipment is available to test for the physical and chemical properties of the precursors SHIKIBO LTD. that are used in the various processes and to characterize the finished products. These facilities included an SEM, an NMR for the characterization of organic substances, and a laser diffractometer to measure the diameter of fibers. This organization shows that it is capable of using information that is 1500-5 Shibahara Minami, Yakaichi, Shiga 527, Japan Background My host for this visit was Tokuzo Kadotani, the director/general manager of the research department of the Industrial Textile Division. My contact was Takeshi Tanamura, who is in charge of the processing R&D. The third person in this discussion was T. Hirokawa, who is in charge of R&D of composite material, including C/Cs. The primary C/C effort at Shikibo is to weave carbon fiber substrates of all shapes and then to densify them. The initial patent for the weaving methods was bought from the Research Institute of Polymers, which is located in Tsukuba, Japan. Using the principles of the basic method, other weaving variations and improvements have been made. In addition, processing procedures have been developed to densify these preforms. Shikibo does not take any money from the Government, so its techniques do not have to be divulged. The C/C development group consists of about 10 persons, with half of these having university degrees. This operation has been going on for about 7 years. Program Status The general concept of the Shikibo weave is that the x and y yarns are woven into a cloth, which is laid up and stacked to form the third dimension. These layers are held together by a continuous yarn that is threaded in the z direction between the x and y yarns. Consequently, the z yarns form a loop on the outside of the preform as it exits and reenters the preform. No z yarns are broken as they are in France or the United States. Furthermore, no x or y yarns are broken as they are by the Societe Europeenne de Propulsion (SEP) method of piercing the fabrics in order to tie them together. Apparently the Shikibo method can produce preforms with a maximum fiber volume of 60% and with yarn spacings of less than 1 mm if 1K yarns are used. Also, the weaving procedure is capable of placing the yarns at different orientations of 0°, 45°, and 90°. Both PAN and pitch fibers are used to weave different shapes including L and T cross sections or Although I didn't tour the laboratory, I was informed that equipment is available for making all the thermalmechanical property determinations that are necessary as well as the chemical evaluations of the precursors. There is also a close cooperative program with the GIRI Osaka laboratory where high temperature equipment can be used if it is not available at Shikibo. turbine rotors, where the blades are an Currently densification of the pre- Shikibo has demonstrated a unique capability in Japan for weaving 3D preforms and densifying them. Shikibo seems to be innovative in its approaches for developing advanced materials. It appears that the research being conducted here is closely tied to the development phase of its operation. The company is certainly interested in collaborating, especially if it could supply material that would be analyzed for its fracturing behavior in the United States. It is recommended that communications be continued with this organization, especially as it may relate to advanced weaving techniques. 1,400 psi at a temperature of 650 °C is 3-18, Wakinohamacho 1-chome My host was Dr. Mitsuo Suzuki, who is the general manager of this research center and an advisor to the technical development group of the corporation. The contact was Katsunori Shimasaki, who is a senior researcher in the Chemical Technology Research Laboratory. This center is primarily directed toward the development of processes that will enhance the reliability of existing products and the invention of new products. The approach is to use data is performing R&D in the area of C/Cs A small fraction of the total C/C effort is for fundamental research to define and select alternative paths for future developments. The efforts at this center are divided into different categories, namely: • New carbon products that include woven carbon fiber composites. A primary target for this activity is the development of C/Cs for the Japanese space plane. The efforts in C/Cs started about 1985, although it was not known outside the company until 2 or 3 years later. • Nonwoven or randomly oriented products such as brake disks for high speed trains. Some of this material has a relatively high density of 1.6 g/cc. Included in this division of effort is the production of paper thin sheets of carbon that are composed of 5- to 10-microndiameter carbon particles. This material is also used in brakes and for self-lubricating applications. The development, production, and sales of high pressure impregnation autoclaves to be used for HIP operations for the densification of C/Cs. Most of their units are sold in Japan, although a few units have been sold abroad, such as in the United States. The maximum operating conditions for such units are in excess of 2,000 atm pressure and 1,000 °C. Each of these units costs about $100,000 including the controls. The carbon development group has about 30 persons, with two-thirds of these having university degrees, of which 10 have Ph.D. degrees. The others are support persons. Of this, the team that One of the topics of discussion was the procedures used to densify C/Cs by the high pressure method of infiltrating preforms with liquid pitch. The purpose of doing so is primarily to reduce production costs by minimizing the number of impregnations that must be performed so that the preform can attain a desired density. Data show that for five impregnations, a 30% higher density can be obtained in carbon fiber preforms than if the same type of preform was impregnated at 1 atm of pressure. Kobe's research indicates getting the pitch into the preform is no problem. The challenge is to keep the pitch in the preform while it is undergoing pyrolysis. This is because the pitch is generating gases that want to escape from the preform. This action, in turn, tends to push the remaining pitch out of the perform, thereby reducing the efficiency of each impregnation operation. Therefore, much R&D time has been devoted to determining what parameters must be considered to improve the HIP cycle. One of these parameters is defining what temperature the pitch should be when the autoclave pressure is first applied to force the pitch into the preform. Apparently, there are two boundary conditions to consider. One is to keep the pitch outside the preform as long as possible while it is being heated to prevent the gascous products that are being generated from accumulating in the preform. But as pyrolysis is occurring, the viscosity of the pitch is increasing and it becomes more difficult to force the pitch into the small pores of the preform, especially as the preform's density is increased with multiple numbers of impregnations. The Kobe studies have shown that applying the pressure at about 150 °C above the pitch's softening point will usually result in the maximum carbon yield in the preform for each densification step. The HIP process is also useful for impregnating preforms with compounds or elements that are not in a carbonaceous state. Additional studies show that preforms impregnated by the HIP process have mechanical properties that are more isotropic. The range of tensile and flexural strengths of some of Kobe's multidirectional C/Cs is between 300 (43,500 psi) and 200 MPa (~29,000 psi). The usual heat treatment conditions for the processing of C/Cs are 1,000 °C for carbonization and between 2,400 and 3,000 °C for graphitization. Measurements of the modulus of some C/Cs show an increase of the effective modulus of the fibers after being heat treated at these maximum temperatures. It is not clear whether this is due to changes of the fiber's modulus because the C/C heat treatment temperature exceeds that at which the fiber was processed. Another possibility is that the matrix has been graphitized and is sufficiently bonded to the fibers to raise the effective modulus of the fibers. More research is being performed to try and understand what is happening. It is expected that the developmental efforts concerning C/Cs will continue until at least 1997, which is the time the support by MITI for the development of the Japanese space plane is scheduled to end. In an unofficial manner, some of the targets of the C/C properties that are to be achieved for this project were presented. For example, at a temperature of 2,000 °C, the tensile modulus should be 200 GPa (29 Mpsi) and the strength equal to 700 MPa (>100 kpsi) with a strain of 0.4%. Furthermore, this C/C material is to operate without any loss of properties for 200 hours. Several interesting C/Cs are being made for this project. One is a <2-mm-thick cylinder whose diameter is to be 300 mm (~12 inches) with a length of 600 mm (24 inches). The other material is thin (2 |