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YASUMASA TAKAO 1 , MAKIO NAITO 2 and HIDEHIRO KAMIYA 3
1 National Industrial Research Institute of Nagoya, Agency of Industrial and Science Technology, Ministry of International Trade and Industry, 1-1 Hirate-cho, Kita-ku, Nagoya 462-8510, Japan
2 Japan Fine Ceramics Center, 2-4-1 Mutsuno, Atsuta-ku, Nagoya 456-8587, Japan
3 Graduate School of Bio-Applications and Systems Engineering, Tokyo University of Agriculture and Technology, 2-24-16 Naka-machi, Koganei-shi, Tokyo 184-8588, Japan Received 18 April 2000; accepted 13 June 2000
Particulate structural contributions to viscosity of silica filled epoxy resin system could be revealed as one of intrinsic silica-properties by using transparent optical microscopy with normal/cross-polarized lights; which was reliable tool for identifying particle-aggregated structures and their peculiar characteristics in viscosity. Silica filled epoxy resin system inherently contained the elliptical shaped features at transparent microscopy in normal light, which were observed as brightened domains at crossed polarization. The elliptical feature exhibited the repeated changes between bright and dark under rotating specimens at every 45?‹ increments. Origin of the elliptical brightness was induced from the particle-aggregated structures. The elliptical brightness, i.e., optical anisotropic property, was often observed in silica particle system with smaller amounts of fine-particle on the surface of SiO2 filler core-particle. The optical anisotropy explained well deconstruction/reconstruction process of particle agglomeration and viscosity in changing the particulate composite structures, although their rheological properties remained unclear solely from the well-mentioned filler primary properties on the characterization of silica filled epoxy resin system; median diameters, size distributions, specific surface areas and surface hydroxyl group structures.
Epoxy resin composite filled with SiO2 particles is one of widely attracted material systems for recent electrical devices such as insulators, electrorheological fluids, chemical mechanical polishing (planarization, CMP) and VLSI package materials [1-7]. There is a keen interest to clarify the relevance of primary properties of silica particles onto rheological characteristics of the composite system. As a rule of thumb, a largish SiO2 primary particle size or a smallish specific surface area decreases the viscosity of the composite system, because the resin supplied on the particle surface per unit weight apparently increases [8, 9]. These works could empirically show some intrinsic SiO2 filler primary-properties for lowering viscosity; such as the broader size distribution, the lower viscosity [8-19]. However, that was highly stereotyped, and there might be remained other intrinsic silica-properties which affected the viscosity. There was still limited on the decisive understanding of rheological characteristics solely from these SiO2 primary properties. Several theoretical approaches were also attempted [20, 21]. These theoretical works could explain the relevance of aggregation of simplified particles likely as mono-modal spherical one, but that of practically used raw powder was still unknown; which commercial had complicated morphology and particle size distribution, much rather ellipse and bimodal. Linkage study is supposedly necessary for connecting the former empirical works of SiO2 primary properties and the later theoretical ones. Observing directly the SiO2 internal particle-aggregated structures must be promising to consolidate the scientific foundation. Thus far, that was very few, although some polymeric materials without silica filler, having much rather solidified matrix, were investigated with transmission microscopy [22]. A cause of the lack of understanding was presumably a deficiency of appropriate observation method of this material system having the liquid typed-matrix of epoxy resin. Recently, a new optical microscopic technique was developed to elucidate defects, structural anisotropy and specific orientation included in ceramics [23-27]. Specimens were thinned to make them transparent, and were examined with polarized microscopy. The volume of specimen under the examination was a few cubic millimeters, which was enough to contain some large, but very few, processing defects; such as the optical anisotropy of corundum particles of elongated shapes on the granule surface made by compaction process. The boundary of the granules of elongated corundum particles was observed as brightened feature as comparing to their surrounding region. This brightness was inductively discussed, as which was base on mismatching of refractive index of the interface between ceramic matrix and pores. This method could possess the possibility to identify the particle-aggregated structure directly, which was contained in the epoxy composite system filled with silica particles [28]. Particulate surface structural contribution, such as fine-particle amounts adhered onto a core-particle, was referred as representing the strategy for improvement of polymeric materials, which was a mandatory-clause in resin composite systems filled with SiO2 particles; not to mention ordinary ceramic materials [4, 29-37]. One of important differences in ordinary ceramic materials and resin composite systems was as to the sintering of constituent particles being carried out or not. Primary properties of raw powder could conceivably affect rather in resin system characteristics directly, but they were backward region. To pack densely the commercialized raw powder in resin system, various particle treatments to make more spherical shape are commonly applied for commercialized powder. The flame conditions, e.g., fuel/oxidizer ratio, flame temperature, gas flow rate and precursor constituents, should affect the morphology [38-40]. The treatment could also affect the particulate surface structure. Thus far, there were very little concerns on it, and few linkage studies to connect microscopically the particulate surface structural contribution and rheological properties in resin systems; although many reports were presented on particle size distribution at seeing in broad perspective, likely as Hosfield model of the distribution [11, 16]. Previous papers were described the principle of transparent microscopy using the photo-elasticity of resin polymer covered around SiO2 agglomerates, which locally provided a stress toward the resin distributed in the surrounding areas, and structured the rearrangement of polymer molecules [28, 41]. Also concerned its validity to clarify the particle-size distribution or coupling treatment influence on rheological property. This paper notes that the particulate geometrical surface structure affected strongly the rheological properties of epoxy composite system filled with silica particles, and concerns an understanding of the particulate surface structural contribution on rheological properties in resin systems with using the optical anisotropy observation method.
2.1 Sample preparation procedure
As a filler particle, the commercialized spherical SiO2 particles were provided, which were used practically in the semiconductor package material field [28]. Figure 1 shows the scanning electron microphotographs (SEM); Fig. 1-a) is the intact powder of 13 ƒÊm in median diameters. Figure 1-b) is its spherical-treated commercialized one, which was prepared with a flame condition control, etc. [39, 40] They were a high-purity amorphous SiO2; their impurity contents, such as Fe, Na and Cl, were below 10 ppm. Hereafter, the raw powder of Fig. 1-a) is called as "intact," and the morphology controlled one for "spherical-treated." Although the characteristics of spherical-treated particles were described in detail at previous papers, the median diameter was 17 ƒÊm and the specific surface area was 3.82 m2/g [28, 41]. Both particulate surface structures of intact and spherical-treated were confirmed visibly, which many smaller particles under 1 ƒÊm in diameters were agglomerated onto a larger one. To bring into prominent the particulate surface structural contributions, smaller particles contained in powders, but not adhered coherently onto the larger-sized particle, were removed via conventional classification route in water. The classification result is shown as particle size analyzer and SEM. Hereafter, the classified intact raw powder is called as "stratified," and the powder of spherical-treated as "interspersed." Each powder was dispersed in an ion-exchanged water with 20 vol% solid loading for 1 hour, and then, the filtrated slurry was dried at 110 C?‹for 1 day. Bisphenol-A type epoxy resin (RE-310S, Nihon Kayaku Co. Ltd.) was utilized as solvent for the composite system. The particles were filled into the epoxy resin with a solid loading of 70 mass%. This amount typifies the constituent of recent electrical devices such as insulator material and semiconductor package [8, 9]. The more amount loading, likely 80 or 90 mass%, should result in larger viscosity rather than the representative value; and vice versa. Other cases are conceivable by analogical reasoning, and the first aim of our work is to give an outline of the particulate structural contribution to viscosity; so then, this paper concerns 70 mass%. The composite system was mixed with AR-360M, Shinky Co. Ltd. for 5 minutes at 1800 and 600 rpm for revolution and rotation speeds, respectively.
2.2 Evaluation
The SiO2 particle size distribution in the composite system was measured with an X-ray particle size analyzer (SediGraph 5100, Micrometrics Co.) for the slurry of SiO2 solid content of 7 mass% in water. Specific surface area of the SiO2 filler particle was measured by the BET method. Surface hydroxyl structure of SiO2 and so forth were determined with reflectance Fourier transform infrared (FT-IR) spectrum in flowing dry nitrogen gas for the mixed powder with KBr of SiO2 content of 50mass%. The internal structure of the epoxy composite system filled with SiO2 was examined with an optical microscope (Model E600, POL-TP21, Nikon Co. Ltd.) in transmission mode by using both normal and cross-polarized lights. The specimens were thinned to the thickness about 50 ƒÊm. Features having specific orientation, such as alignment of elongated particle and/or polymer molecule, could polarize the incident linearly-polarized light, and pass the ray though the analyzer-filter of microscope. Optic positional configuration is shown in Fig. 2. Optical anisotropy of the features was confirmed under a crossed polarized light transmission microscope; i.e., repeated changes between bright and dark with the specimen rotation of every 45?‹increments and positive/negative optical characters of elongation. The apparent viscosity of the composite systems was measured with a viscometer (VT550, HAAKE Co. Ltd.) at 80 C?‹with the shear rate varied from 0 to 500 s-1.
Figure 3 shows the scanning electron microphotographs of classification-treated of raw powders. Figure 3-a) is the classified intact raw powder of Fig. 1-a) (i.e., the stratified particles), and Fig. 3-c) is for spherical-treated one of Fig. 1-b) (the interspersed particles). Figures 3-b) and 3-d) are typical examples of structural features on the surface of a larger-sized particle over 10 ƒÊm in diameters, respectively. At seeing in broad perspective, smaller particles less than 1 ƒÊm in diameters, which were contained much rather in starting powders of Fig. 1, were drastically reduced in the processed powders. However, the conventional morphology control procedure of commercialized powder clearly affects the particulate structural surfaces. Many amounts of fine-particles, which sizes were less than 500 nm, were survived through the operation and adhered onto the surface of the SiO2 filler core-particle in the classified intact raw powder (Figs. 3-a) and 3-b)). Moreover, the fine-particles formed their plural stratification or multilayered structure on the core-particle (Fig. 3-b)). Meanwhile, the fine-particles less than 500 nm decreased comparatively in the classified spherical-treated powder. The fine-particles figured their mere layer, and the surface of core-particle was peeped out through their interspersed layer as shown in Figs. 3-c) and 3-d). These fine-particles were supposed to chip off during the reforming procedure to make more spherical shape the core-particles. Figure 4 shows the apparent viscosity of epoxy composite systems filled with SiO2 of various particulate structural surfaces, intact powder (Fig. 1-a)), stratified (Figs. 3-a) and 3-b)) and interspersed (Figs. 3-c) and 3-d)). The figure was illustrated with magnifying the ordinate to emphasize the differences of data, although the viscosity had a limited value at 0 s-1 in shear velocity, i.e., not infinite. The viscosity values of resin system of spherical-treated powder (Fig. 1-b)) were almost the same as those of intact-powder system in the present experiments [28]. The viscosity values of interspersed-SiO2 particle system were larger than those of stratified and intact-particle systems, and could not be measured over 300 s-1 because of the limits in torque of viscometer ability. The viscosity of stratified-SiO2 particle system did not increase so much compared as those of intact-particle system, although the values were larger below 100 s-1 in shear velocity. Notably, there was a decreasing tendency in the stratified-system over 100 s-1 rather than the intact-particle system. The hysteresis values of intact-particle system were not absent, but smaller than those of the stratified and interspersed-particle systems. Figure 5 shows the particle size distributions and specific surface areas of various particulate structural surfaces; intact, stratified and interspersed powders. The both stratified and interspersed powders constituted few amount of smaller-sized particle inclusions, and then, narrow size distributions and increased median diameters. Almost the same particle size distributions were figured at both powders, which was reasoned seeing what similar configurational features appeared in SEM at broad perspective. Similar values of specific surface area were noted in the intact and the stratified powders, although that of the interspersed powder was small a little. The reason was supposed to be based on particulate structural surfaces (Figs. 3-b) and 3-d)). Figure 6 shows the FT-IR spectra for surface hydroxyl groups in 4000 to 3000cm-1 of SiO2 fillers at various particulate structural surfaces. Absorption bands of hydrogen-bonded silanol groups and/or water were noted. There were not conspicuous differences, however, of FT-IR spectra for stratified and interspersed powders. The band at 3660 cm-1 was almost the same as each powder; intact, stratified and interspersed powders. The bands around 3500 cm-1 of stratified and interspersed powders increased to some extent rater than those of intact powder. Figure 7 shows the optical photographs of SiO2 filled epoxy resin composite systems taken in transmission mode by using normal light; a) intact, b) stratified and c) interspersed powders. Similar features to intact-powder system were confirmed in spherical-treated one. There are many gray spherical/elliptical features and their surrounding darker spaces. Each elliptical-like feature was previously identified to each SiO2 particle or their agglomerate, and the darkened spaces were their boundaries [28]. Dark shadowed features of 30-50 ƒÊm in diameters shown in Figs. 7-b) and 7-c) were also assigned in the previous work to the larger SiO2 particle or its rigidly joined aggregate, which was so huge for the focus in transmission. The features of elliptical shapes appeared to fill up at similar density under the normal light transmission, which was supposedly conceivable seeing what the powders prepared in same series were used. Figure 8 shows the optical photographs of SiO2 filled epoxy resin composite systems taken in transmission mode by using cross-polarized light; a) intact, b) stratified and c) interspersed powders. Similar brightness features to intact-powder system were confirmed in spherical-treated one. Some features of elliptical shapes noted in normal light transmission were observed as brightened features at transmission crossed polarization, which were consisted of the larger and brighter features and the rather smaller ones in the background. The features changed their brightness repeatedly with rotating specimen of every 45?‹increments. Note that the features located close together, simultaneously, changed their brightness with rotating specimen. These features had optically the same diagonal and extinction positions, i.e., anisotropic properties. The ellipse major axis of the feature in addition retardation was parallel with the oscillating direction of low velocity ray of tint plate, which ray was made by birefringence. The features of elliptical shape had the positive optical character of elongation, which optical configuration is shown in Fig. 2. These optical phenomena should be presented in the reference [41]. Figure 8-c) notes that the resin system of interspersed-powder contains the brightened features rather than other two systems to some extents; especially the smaller-brightened features in the background.
Epoxy resin composite system filled with silica particle characteristically contained the elliptical shaped features observed as brightened domains at crossed polarization, which were affected strongly with particulate structural surfaces. The elliptical feature exhibited optical anisotropic properties, and was often observed in silica particle system with smaller amounts of fine-particle on the surface of SiO2 filler core-particle (interspersed-powder). Origin of the elliptical brightness was induced from the particle-aggregated structures. The optical anisotropy explained deconstruction/reconstruction process of particle agglomeration and apparent viscosity as a rule of thumb. Particulate structural contributions to viscosity of silica filled epoxy resin system could be revealed as one of new intrinsic silica-properties by using transparent cross-polarized microscopy. Present experiments showed that the silica particle filled epoxy composite systems had the larger viscosity values in interspersed-powder system. This is out of order to well-known recognition of previous work about SiO2 primary properties; median diameters, size distributions and specific surface areas. Narrower size distribution is reported to increase the viscosity values, because much rather resin solvent is necessary for packing the silica filler with same weight as compared with broader particle system [3, 9, 15]. Whereas, the prominent increase in viscosity was noted in the interspersed-system; although the increasing in the stratified-system, which was still lower than the interspersed, was also confirmed at lower shear velocities. Further, the interspersed-system constituted smaller specific surface area. This was referred as decreasing viscosity, because the resin supplied on the particle surface per unit weight apparently reduced [8, 9]; but the result was encountered an objection. These indecisive conclusions should be assigned to complicated primary properties of practically used raw powder provided in the present experiments; i.e., many variations in size distribution and specific surface area, insufficient spherical morphology, etc. It is conceivable conclusion that particular mechanism of viscosity is still unknown solely from median diameters, size distributions and specific surface areas. Surface hydroxyl group structure on silica surface is important for understanding their interfacial property with resin [10, 17-19]. Classification in water of the present experiments might affect the property. Stratified and interspersed-powders noted an increase of the bands around 3500 cm-1 to some extents, but the bands were frequently reported to decrease at increasing the pretreatment temperature of specimens. A little increase of the bands around 3500 cm-1 of stratified and interspersed-powders was supposedly assigned that the dry condition during classification was insufficient. The increase should not be inherent to the difference in particulate geometrical structures of stratified and interspersed-powders. Further, stratified and interspersed-powders showed the same spectra, apparently. So then, the surface hydroxyl groups were presumably irrelevant to larger viscosity values noted in interspersed-powder system. Present work, transparent optical microscopy, visualized directly the particle-flocculated group in resin by using the photo-elasticity phenomena of resin polymer. The epoxy resin composite is predicted to have a primary or a secondary flocculated group of each SiO2 particles before shearing, and the groups break up as the shear velocity increases at a thixotropic softening and hardening range [20, 21]. Elliptical features observed in epoxy system were assigned to the primary and/or secondary flocculated groups which were predicted at previous theoretical studies, by using notions in ceramics as described [23-28, 41]. Particle flocculated groups in the composite system is supposed previously to contain a solvent among them before applying shear force [20]. The shearing breaks the flocculation, disperses the solvent into the system, and lowers apparently the SiO2 filler concentrations in the structure. This means the reduction of viscosity. The amount of the flocculation expects to increase with the enlargement of the extent of non-spherical particle shape, narrow size distribution and reinforced interaction of particle and solvent. The larger amount of flocculation means the higher apparent concentration of SiO2 filler particle in the structure. At broad perspective, tendency of apparent viscosity of present experiments might be understood by seeing the explanations (Fig. 4). The optical anisotropy in transmission microscopy showed in increase at the interspersed-system, although the values of anisotropy were almost the same as intact and stratified-systems. Clearly, it could be concluded a linkage role of transmission optical microscopy for correlating with experimental results of viscosity and the theoretical model of flocculation. The so-called 'Hosfield model' in filler particle size distribution is supposedly understood as the significant contribution of fine-particles contained between, and/or adhered onto the larger ones. The viscosity values of resin system of spherical-treated powder (Fig. 1-b)) were almost the same as those of intact-powder (Fig. 1-a)) system in the present experiments [28]. Before classification in both cases, the fine-particles, such as less than 1 ƒÊm in diameters, were contained between larger-sized particles over 10 ƒÊm as shown in Fig. 1. After classification, overall particle size distributions were almost same in both particle systems, which meant the contribution of fine-particles contained between larger-sized ones come minor. As shown in Fig. 4, however, the viscosity of stratified-SiO2 particle system did not increase so much compared as those of other systems. It might be possible to suggest a preventing role in making the flocculation of the fine-particles adhered on core-particle, which was reckoned with correlating the optical anisotropic amounts shown in Fig.8. Figure 8-b) shows that the amount of optical anisotropic region in stratified system is clearly less than the interspersed, although is not so little than the intact. It follows that the amount of powder flocculation built in resin shows same tendency. Viscosity value decreases with shear velocity increase, because the flocculation breaks with, disperses the solvent into the system and lowers apparently the SiO2 filler concentrations in the structure. At seeing in broad perspective, it could be concluded that the viscosity values in stratified system reached to the intact at lower shear velocity rather than the interspersed. At larger velocity, likely as more than 100 s-1, the viscosity values in stratified system were smaller than the intact, if anything. It presumably followed that the particle could be packed rather uniformly at larger shearing in former case. Surely, it is still uncertain as to the minute viscosity characteristics at lower shear velocities, likely as less than 100 s-1, the thixotropic rheological phenomena and the difference of fine-particles in contained between or adhered onto the larger ones, etc. Further analysis is important to clarify the precise mechanism, but the information of this work could be one of useful practical data for SiO2 filled epoxy resin composite system and contribute to understand the particle-resin (ceramics-polymer) interrelationship, which should be the decisive condition of the composite material.
1) The structural features in SiO2 filled epoxy resin composite system were visualized directly through the characterization with transparent optical microscopy with normal/cross-polarized lights. The composite system essentially possessed the elliptical shaped features observed as brightened domains at transparent crossed polarization. The elliptical feature exhibited the repeated changes between bright and dark under rotating specimens at every 45?‹ increments, and the positive optical character of elongation. Origin of the elliptical brightness was inductively assigned to the particle-aggregated structures. The elliptical brightness, i.e., optical anisotropic properties, was often observed in silica particle system with smaller amounts of fine-particle on the surface of SiO2 filler core-particle.
2) Optical anisotropy at transparent crossed polarization was supposedly affected by deconstruction and reconstruction process of primary/secondary-flocculated groups of each primary SiO2 particle, which process was recognized as one of explanation of peculiar rheological characteristics of SiO2 filled epoxy resin composite system. Elliptical brightness extents at crossed polarization were increased in silica particle system with smaller amounts of fine-particle on the surface of SiO2 filler core-particle. Values of apparent viscosity observed in the silica systems were directly proportional to the optical anisotropy extents. Optical anisotropy in transparent microscopy could be one of reliable guide for identifying particle-aggregated structure, and understand the rheological properties in SiO2 particle filled epoxy resin composite system; nevertheless, the rheological property remained unclear solely from SiO2 primary properties such as median diameters, size distributions, specific surface areas and surface hydroxyl structures. Particulate structural contributions to viscosity of silica filled epoxy resin system could be revealed as one of new intrinsic silica primary properties by using transparent cross-polarized microscopy.
1. Y. Otsubo, M. Sekine and S. Katayama, Effect of adsorbed water on the electrorheology of silica suspensions, J. Colloid and Interface Sci. 150, 324-330 (1992).
2. S. W. Shang, J. W. Williams and K-J. M. Soderholm, Work of adhesion influence on the rheological properties of silica filled polymer composites, J. Mater. Sci. 30, 4323-4334 (1995).
3. S. Nakajima, Electrical insulating filler, Filler 3, 160-167 (1998).
4. T. K. Gupta and J. H. Jean, Principles of the development of a silica dielectric for microelectronics packaging, J. Mater. Res. 11, 243-263 (1999).
5. M.K. McMurray and S. Amagi, The effect of time and temperature on flexural creep and fatigue strength of a silica particle filled epoxy resin, J. Mater. Sci. 34, 5927-5936 (1999).
6. P. E. Wayne-Lougher, Ceramic application in chemical mechanical planarization, Am. Ceram. Soc. Bull. 78, 97-100 (1999).
7. H. Homma, Application of polymeric insulation materials for electric power facilities, Bull. Inst. Electrical Eng., Japan 120, 152-155 (2000).
8. K. Otsuka, Rheology on fine ceramics, Bull. Ceram. Soc.,Japan 28, 1124-1129 (1993).
9. T. Kitano, Rheological properties of filler-polymer slurry, Filler 3, 96-107 (1998).
10. K. K. Unger; Surface structure of amorphous and crystalline porous silicas, The Colloid Chemistry of Silica, H. E. Bergne, ed., pp.165-181. American Chemical Society, Washington, USA (1994).
11. K. Takahashi, Spherical silica filler, Kogyozairyo, 42, No.15, 112-116 (1994).
12. H. Liao and T.W. Coyle, Effects of organotitanate additions on the dispersion of aluminum nitride in nonpolar solvents, J. Am. Ceram. Soc. 78, 1291 (1995).
13. Y. Nagai and G. Lai; Thermal conductivity of epoxy resin filled with particulate aluminum nitride powder, J. Ceram. Soc. Japan. 105, 197-200 (1997).
14. Y. Yoshida, T. Higashihara, Y. Nomura, E. Usui and S. Hibi; The effect of silane agent on tensile and bending properties of silica filled epoxy after water absorption by boiling, Trans.IEE Japan 117-A, 1004-1012 (1997).
15. S. Hagiwara; Trend of package material of semiconductor device, Plastics 49, 58-62 (1998).
16. T. Yoshida; Application of silicon technology for package material of semiconductor device, Plastics 49, 63-67 (1998).
17. T. Takei, M. Ataku, T. Konishi, M. Fuji, T. Watanabe and M. Chikazawa; Investigation of the structure of surface hydroxyl groups on silica - chemical reaction and molecular adsorption method, J. Soc. Powder Technol., Japan 36, 179-184 (1999).
18. M. Fuji and M. Chikazawa, Reactivity to water and alcohol of siloxane formed by heat-treatment on silica powder surface, J. Soc. Powder Technol., Japan 37, 19-25 (2000).
19. H. Kamiya, M. Mitsui, S. Miyazawa and H. Takano; Influence of particle diameter on surface silanol structure, hydration forces and aggregation behavior of alkoxide derived silica particles, J. Am. Ceram. Soc., 83, 287-293 (2000).
20. K. Umeya; Rheological studies on slurry materials - on the hardening and softening properties of suspending systems, Bull. Ceram. Soc., Japan 28, 1115-1123 (1993).
21. H. Usui, Rheological model for agglomerative slurry of mono-modal silica particles, Kagaku Kogaku Ronbunshu 25, 459-465 (1999).
22. H. Sano and T. Komoto; "Transmission Electron Microscopy for Polymeric Materials," Electron Microscopy, 32, 71-76 (1997).
23. K. Uematsu, Immersion microscopy for detailed characterization of defects in ceramic powders and green bodies, Powder Technol. 88, 291-298 (1996).
24. K. Uematsu, S. Ohsaka, N. Shinohara and M. Okumiya; Grain-oriented microstructure of alumina ceramics made through the injection molding process, J. Am. Ceram. Soc. 80, 1313-1315 (1997).
25. M. Naito, T. Hotta, O. Hayakawa, N. Shinohara, M. Okumiya and K. Uematsu; New characterization techniques to control the manufacturing process of fine ceramics; a case study of the origin of property variation with spray dryer size, Advance in Process Measurements for the Ceramic Industry, A. Jillavenkatesa and G.Y. Onoda eds., pp.87-105, American Ceramic Society, Ohio, USA (1999).
26. N. Shinohara, M. Okumiya, T. Hotta, K. Nakahira, M. Naito and K. Uematsu; Formation mechanism of processing defects and their relevance to the strength in alumina ceramics made by powder compaction process, J. Mater. Sci., 34, 4271-4277 (1999).
27. Y. Takao, T. Hotta, K. Nakahira, M. Naito, N. Shinohara, M. Okumiya and K. Uematsu, Processing defects and their relevance to strength in alumina ceramics made by slip casting, J. Euro. Ceram. Soc., 20, 389-395 (2000).
28. Y. Takao and M. Naito, Particle aggregated structure in silica particle filled epoxy resin composite system, J. Chem. Eng. Japan, 33, 317-322 (2000).
29. S. Okuda, Functional polymeric materials filled with fine particles, J. Soc. Mat. Sci., Japan, 39, 1054-1060 (1990).
30. A. Kato, Improvement of chemical processing in synthesis of ceramic materials, Bull. Ceram. Soc. Japan, 26, 187-190 (1991).
31. M. Naito, A. Kondo and T. Yokoyama, Application of comminution techniques for the surface modification of powder materials, ISIJ international, 33, 915-924 (1993).
32. M. Sando, Composite particle by nano-scale coating, Bull. Ceram. Soc., Japan, 31, 185-187 (1996).
33. Y. Takao, M. Awano and Y. Kuwahara, Preparation of composite particles of bulk Ba2YCu3O7-x by electrostatic adhesion process, AIChE J., 43, 2616-2623 (1997).
34. M. Naito, T. Hotta, S. Asahi, T. Tanimoto and S. Endoh, Effect of processing condition on particle composite process by a high-speed elliptical-rotor-type mixer, Kagaku Kogaku Ronbunshu 24, 99-103 (1998).
35. Y. Takao, M. Awano and M. Sando, SnO2 multilayered gas sensor with high selectivity prepared by an aerosol electrostatic process, Advanced Powder Technol., 9, 293-316 (1998).
36. M. Naito, T. Hotta, T. Tanimoto, S. Endoh and K. Nogi, Effect of fine particle size on particle composite process by a high-speed elliptical-rotor-type mixer, Kagaku Kogaku Ronbunshu 26, 62-67 (2000).
37. G. Wegner, Functional polymers, Acta mater., 48, 253-262 (2000).
38. C. H. Hung and J. L. Katz, Formation of mixed oxide powders in flames, J. Mater. Res. 7, 1861-1869 (1992).
39. M. Iwasa, Y. Sakaguchi and H. Torizoe, Japanese Patent No. H10-95607.
40. S. Naito, Y. Iizuka and M. Iwasa, Japanese Patent No. H11-60234.
41. Y. Takao, M. Naito and H. Kamiya, Particle aggregated structure and their correlation to viscosity in silica particle filled epoxy resin composite system, AIChE J. submitted for publication.
Fig. 1 Scanning electron microphotographs of commercialized amorphous spherical SiO2 starting powders; a) intact powder and b) spherical-treated one. Fig. 2 Scheme of detecting optical anisotropy with transparent polarization microscopy.
Fig. 3 Scanning electron microphotographs of amorphous spherical SiO2 particles; a), b) stratified and c), d) interspersed powder.
Fig. 4 Apparent viscosity of epoxy composite systems filled with SiO2 at various particulate structural surfaces.
Fig. 5 Particle size distributions, median diameters and specific surface areas at various particulate structural surfaces.
Fig. 6 FT-IR spectra for surface hydroxyl groups of SiO2 fillers at various particulate structural surfaces.
Fig. 7 Optical photographs of epoxy resin composite systems filled with SiO2 at various particulate structural surfaces; a) intact, b) stratified and c) interspersed powders. Photos were taken in transmission mode by using normal light.
Fig. 8 Optical photographs of epoxy resin composite systems filled with SiO2 at various particulate structural surfaces; a) intact, b) stratified and c) interspersed powders. Photos were taken in transmission mode by using cross-polarized light.