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Angel L Ortiz - One of the best experts on this subject based on the ideXlab platform.
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Manufacturing B4C parts with Ti-Al intermetallics by aqueous Colloidal Processing
Journal of the European Ceramic Society, 2020Co-Authors: Cristina Ojalvo, Fernando Guiberteau, Rodrigo Moreno, Angel L OrtizAbstract:Abstract The aqueous Colloidal Processing of submicrometre B4C powder (∼0.6 μm) with coarse Ti-Al powder (∼40 μm) as sintering additive was investigated. Firstly, by measuring the zeta potential, pHs were identified that promote the individual Colloidal stability of the B4C and Ti-Al particles as well as their co-dispersion in water with two different deflocculants (one anionic and the other cationic). It was found that the anionic and cationic deflocculants shift the isoelectric points of B4C and Ti-Al to more acidic and more basic pHs, respectively, making their co-dispersion possible at neutral pH. And secondly, by means of rheological studies, conditions were identified (sonication time, deflocculant type, and deflocculant content) that at quasi-neutral pH yield B4C + Ti-Al shear-thinning concentrated suspensions (30 vol.% total solids) with low viscosity and small hysteresis loop. Interestingly, those deflocculated with the cationic polyelectrolyte had better rheological behaviour, being also less viscous and almost non-thixotropic. These suspensions were freeze-dried, obtaining powder mixtures that were compacted by conventional spark plasma sintering (SPS), and also slip-cast, obtaining robust green pieces that were densified by pressureless SPS. The two B4C composites thus obtained are superhard, with Vickers hardnesses greater than 30 GPa.
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liquid phase assisted flash sintering of sic from powder mixtures prepared by aqueous Colloidal Processing
Journal of The European Ceramic Society, 2017Co-Authors: Victor M Candelario, Rodrigo Moreno, Richard I Todd, Angel L OrtizAbstract:The effects were investigated of the starting particle size (i.e., nanometer or submicrometer powders), content of Y3Al5O12 additives (YAG; in the range 5–20 wt.%), and difference of size scales between the two particle types on the liquid-phase assisted flash sintering of SiC from powder mixtures prepared by aqueous Colloidal Processing. It was found that flash sintering benefits from the refinement of the particles size, the increase in additive content, and the smaller size scale of the particulate additive. It was also found that under the present flash sintering conditions (i.e., 900 °C furnace temperature, 13 A current, and 50 s in flash state) the resulting ceramics are, despite the formation of liquid phase, porous to a greater or lesser extent, and exhibit decreasing porosity gradients from their surface to the centre. These observations are rationalized to extract guidelines for powder batch design contributing to the pressureless ultrafast sintering of non-oxide advanced ceramics.
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aqueous Colloidal Processing of near net shape b4c ni cermet compacts
Journal of The European Ceramic Society, 2016Co-Authors: F Rodriguezrojas, Fernando Guiberteau, Rodrigo Moreno, Angel L OrtizAbstract:Abstract Aqueous Colloidal Processing was optimized for the environmentally friendly preparation of concentrated suspensions (29–40 vol.% solids loadings) suitable for the near-net shaping of B4C + 16.6 vol.%Ni cermet compacts by slip casting. Specifically, on the basis of studies with dilute suspensions, it was confirmed that using very basic pHs (i.e., 10) is the key to ensuring the inertness and dispersibility of the Ni particles in water, and that deflocculant contents of at least ∼0.5 wt.% PKV and PAA are required to promote the Colloidal stability of the B4C and Ni particles, respectively. Concentrated B4C + 16.6 vol.%Ni suspensions were consequently prepared at pH 11 with 1 wt.% PKV and PAA, and it was found that sonication for 1 min optimizes the rheological properties. Lastly, these concentrated suspensions were proven to be suitable for the slip casting of robust, highly-dense B4C–Ni cermet compacts with near-net shape, whose green microstructures are very uniform, exhibit well-dispersed and packed particles, with no evidence of cracks or macrodefects, and with relative densities greater than 58% of the theoretical.
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Aqueous Colloidal Processing of near-net shape B4C–Ni cermet compacts
Journal of The European Ceramic Society, 2016Co-Authors: Fernando Rodríguez-rojas, Fernando Guiberteau, Rodrigo Moreno, Angel L OrtizAbstract:Abstract Aqueous Colloidal Processing was optimized for the environmentally friendly preparation of concentrated suspensions (29–40 vol.% solids loadings) suitable for the near-net shaping of B4C + 16.6 vol.%Ni cermet compacts by slip casting. Specifically, on the basis of studies with dilute suspensions, it was confirmed that using very basic pHs (i.e., 10) is the key to ensuring the inertness and dispersibility of the Ni particles in water, and that deflocculant contents of at least ∼0.5 wt.% PKV and PAA are required to promote the Colloidal stability of the B4C and Ni particles, respectively. Concentrated B4C + 16.6 vol.%Ni suspensions were consequently prepared at pH 11 with 1 wt.% PKV and PAA, and it was found that sonication for 1 min optimizes the rheological properties. Lastly, these concentrated suspensions were proven to be suitable for the slip casting of robust, highly-dense B4C–Ni cermet compacts with near-net shape, whose green microstructures are very uniform, exhibit well-dispersed and packed particles, with no evidence of cracks or macrodefects, and with relative densities greater than 58% of the theoretical.
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aqueous Colloidal Processing of nano sic and its nano y3al5o12 liquid phase sintering additives with carbon nanotubes
Journal of The European Ceramic Society, 2015Co-Authors: Victor M Candelario, Rodrigo Moreno, Zhijian Shen, Angel L OrtizAbstract:Abstract Carbon nanotubes (CNTs) have occasionally been observed to benefit the aqueous Colloidal Processing of nano-SiC with its nano-Y3Al5O12 liquid-phase-sintering additives. Experimental evidence is here presented for a broad set of CNTs with different morphology and/or surface functionalization confirming that CNTs (7 vol.% addition), regardless of their features, prevent the coagulation of these nanoceramic suspensions, whence it is inferred that aqueous Colloidal Processing is well-suited for the environmentally friendly preparation of the homogeneous mixtures of nanoceramic particles and CNTs required for the fabrication of CNT-reinforced ceramic matrix nanocomposites. Furthermore, it is shown that surface-functionalized CNTs seem to work better than deflocculated CNTs for the preparation of stable concentrated Colloidal suspensions, whose rheological properties are in general very close, but with thinner CNTs being nonetheless preferable. Finally, the feasibility is demonstrated of fabricating SiC/CNT nanocomposites by aqueous Colloidal Processing followed by liquid-phase assisted spark-plasma sintering.
Yoshio Sakka - One of the best experts on this subject based on the ideXlab platform.
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Densification of SiC by Colloidal Processing and SPS without sintering additives
Advances in Applied Ceramics, 2014Co-Authors: Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio SakkaAbstract:Silicon carbide is one of the most important ceramics used as structural and functional materials in a wide variety of applications. Many studies have reported the densification of SiC using oxide and nonoxide additives such as the Al2O3, B4C and Al–B–C system. However, it is difficult to densify SiC at temperatures below 2000°C without sintering additives even if spark plasma sintering (SPS) is used. The authors attempted to densify SiC using Colloidal Processing and SPS without sintering additives. A commercially available SiC powder with the average particle size of 0·55 μm was used as the starting material. The densities of the green body prepared by slip casting and the sintered body by SPS were 65·5 and 98·7% respectively.
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Effect of starting powders on the sintering of nanostructured ZrO2 ceramics by Colloidal Processing
Science and technology of advanced materials, 2009Co-Authors: Gustavo Suarez, Yoshio Sakka, Tohru S. Suzuki, Tetsuo Uchikoshi, Xinwen Zhu, E F AgliettiAbstract:The effect of starting powders on the sintering of nanostructured tetragonal zirconia was evaluated. Suspensions were prepared with a concentration of 10 vol.% by mixing a bicomponent mixture of commercial powders (97 mol.% monoclinic zirconia with 3 mol.% yttria) and by dispersing commercially available tetragonal zirconia (3YTZ, Tosoh). The preparation of the slurry by bead-milling was optimized. Colloidal Processing using 50 μm zirconia beads at 4000 rpm generated a fully deagglomerated suspension leading to the formation of high-density consolidated compacts (62% of the theoretical density (TD) for the bicomponent suspension). Optimum Colloidal Processing of the bicomponent suspension followed by the sintering of yttria and zirconia allowed us to obtain nanostructured tetragonal zirconia. Three different sintering techniques were investigated: normal sintering, two-step sintering and spark plasma sintering. The inhibition of grain growth in the bicomponent mixed powders in comparison with 3YTZ was demonstrated. The inhibition of the grain growth may have been caused by inter-diffusion of cations during the sintering.
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effect of starting powders on the sintering of nanostructured zro2 ceramics by Colloidal Processing
Science and Technology of Advanced Materials, 2009Co-Authors: Gustavo Suarez, Yoshio Sakka, Tohru S. Suzuki, Tetsuo Uchikoshi, E F AgliettiAbstract:AbstractThe effect of starting powders on the sintering of nanostructured tetragonal zirconia was evaluated. Suspensions were prepared with a concentration of 10 vol.% by mixing a bicomponent mixture of commercial powders (97 mol.% monoclinic zirconia with 3 mol.% yttria) and by dispersing commercially available tetragonal zirconia (3YTZ, Tosoh). The preparation of the slurry by bead-milling was optimized. Colloidal Processing using 50 μm zirconia beads at 4000 rpm generated a fully deagglomerated suspension leading to the formation of high-density consolidated compacts (62% of the theoretical density (TD) for the bicomponent suspension). Optimum Colloidal Processing of the bicomponent suspension followed by the sintering of yttria and zirconia allowed us to obtain nanostructured tetragonal zirconia. Three different sintering techniques were investigated: normal sintering, two-step sintering and spark plasma sintering. The inhibition of grain growth in the bicomponent mixed powders in comparison with 3YTZ...
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Fabrication and some properties of textured alumina-related compounds by Colloidal Processing in high-magnetic field and sintering
Journal of the European Ceramic Society, 2008Co-Authors: Yoshio Sakka, Tohru S. Suzuki, Tetsuo UchikoshiAbstract:Recently to improve properties, highly microstructure controlled ceramics such as fine-grained, textured and laminated structures are required. We have demonstrated a new Processing of textured ceramics with a feeble magnetic susceptibility by Colloidal Processing in a high-magnetic field and subsequent heating. As Colloidal Processing, slip casting and electrophoretic deposition (EPD) have been conducted successfully. Colloidal Processing is known to be a powerful method for consolidating fine particles with a high density and homogeneous microstructure. Crystalline-textured controlled laminated alumina can be fabricated using EPD by varying the angle between the vectors of electric field and magnetic field. Also textured ceramics with complicated structure such as β-alumina and alumina-based nanocomposite can be fabricated by reaction sintering. The textured alumina-related compounds showed anisotropic properties depending on the crystal plane. The Colloidal Processing in a high-magnetic field confers several advantages and can be applied to many non-cubic ceramics.
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Fabrication and Some Properties of Textured Ceramics by Colloidal Processing in High Magnetic Field
Key Engineering Materials, 2007Co-Authors: Yoshio Sakka, Tohru S. Suzuki, Tetsuo UchikoshiAbstract:Recently to improve properties, highly microstructure controlled ceramics such as fine-grained, textured and laminated structures are required. We have demonstrated a new Processing of textured ceramics with a feeble magnetic susceptibility by Colloidal Processing in a high magnetic field and subsequent heating. As Colloidal Processing, slip casting and electrophoretic deposition (EPD) have been conducted successfully. Colloidal Processing is known to be a powerful method for consolidating fine particles with a high density and homogeneous microstructure. The degree of orientation strongly depends on the particle dispersion and some Processing factors, such as particle size, applied magnetic field, concentration of the suspension, sintering temperature, etc. Crystalline-textured controlled laminated composites can be fabricated using EPD by varying the angle between the vectors of electric field and magnetic field. Also textured ceramics with complicated structure can be fabricated by reaction sintering. The Colloidal Processing in a high magnetic field confers several advantages and it is possible for this type of Processing to be applied to non-cubic ceramics, such as alumina, titania, zinc oxide, tin oxide, hydroxy apatite, aluminium nitride, silicon carbide, silicon nitride, etc. The textured ceramics showed anisotropic properties depending on the crystal plane.
Rodrigo Moreno - One of the best experts on this subject based on the ideXlab platform.
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Microstructure and mechanical properties of 4YTZP-SiC composites obtained through Colloidal Processing and Spark Plasma Sintering
Boletín de la Sociedad Española de Cerámica y Vidrio, 2020Co-Authors: Amparo Borrell, Lucia Navarro, C. F. Gutiérrez-gonzález, Carmen Alcazar, María Dolores Salvador, Rodrigo MorenoAbstract:Abstract Bulk composites of silicon carbide reinforced zirconia were obtained through Colloidal Processing and spark plasma sintering, and their microstructural and mechanical properties were investigated. Mixtures of powders of 4 mol% yttria-doped zirconia and silicon carbide, with percentages of 15 and 20 wt% of silicon carbide, were prepared by Colloidal Processing and freeze-drying to guarantee the homogeneity of powders, and sintered by SPS at temperatures ranging from 1300 to 1400 °C to obtain dense composites. The spark plasma sintering technique makes it possible to control sintering energy and speed, and impedes the oxidation of silicon carbide to ensure larger reproducibility. The microstructure of the composites reveals that some defects arise during sintering due to the differences of coefficient of thermal expansion between zirconia and silicon carbide. Mechanical properties were studied, such as Vickers hardness, Young's modulus, and bending strength. Compared with 4YTZP monolithic material, composites have better fracture strength values (∼588 MPa and 492 MPa, for 15 wt% and 20 wt% of silicon carbide, respectively) when sintered at 1400 °C. It is also demonstrated that silicon carbide particles act as an absorption centre for propagating cracks.
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Manufacturing B4C parts with Ti-Al intermetallics by aqueous Colloidal Processing
Journal of the European Ceramic Society, 2020Co-Authors: Cristina Ojalvo, Fernando Guiberteau, Rodrigo Moreno, Angel L OrtizAbstract:Abstract The aqueous Colloidal Processing of submicrometre B4C powder (∼0.6 μm) with coarse Ti-Al powder (∼40 μm) as sintering additive was investigated. Firstly, by measuring the zeta potential, pHs were identified that promote the individual Colloidal stability of the B4C and Ti-Al particles as well as their co-dispersion in water with two different deflocculants (one anionic and the other cationic). It was found that the anionic and cationic deflocculants shift the isoelectric points of B4C and Ti-Al to more acidic and more basic pHs, respectively, making their co-dispersion possible at neutral pH. And secondly, by means of rheological studies, conditions were identified (sonication time, deflocculant type, and deflocculant content) that at quasi-neutral pH yield B4C + Ti-Al shear-thinning concentrated suspensions (30 vol.% total solids) with low viscosity and small hysteresis loop. Interestingly, those deflocculated with the cationic polyelectrolyte had better rheological behaviour, being also less viscous and almost non-thixotropic. These suspensions were freeze-dried, obtaining powder mixtures that were compacted by conventional spark plasma sintering (SPS), and also slip-cast, obtaining robust green pieces that were densified by pressureless SPS. The two B4C composites thus obtained are superhard, with Vickers hardnesses greater than 30 GPa.
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Controlling Colloidal Processing of (K,Na)NbO3-based materials in aqueous medium
Journal of the European Ceramic Society, 2019Co-Authors: M. Venet, Washington Santa-rosa, Jean-claude M’peko, Harvey Amorín, Miguel Algueró, Rodrigo MorenoAbstract:Abstract K0.5Na0.5NbO3-based materials are serious candidates to replace lead-based piezoceramics since they show excellent electrical and piezoelectric properties. The tape casting technique can be used to obtain highly textured KNN-based ceramics; however, despite industrial and environmental advantages of water-based Processing, there are not reports about the control of Colloidal Processing conditions to obtain optimized K0.5Na0.5NbO3-based slurries in aqueous medium. This paper reports a procedure for controlling Colloidal stability and rheological behavior of aqueous (K0.5Na0.5)0.97Li0.03Nb0.8Ta0.2O3 suspensions. Zeta potential and cationic solubility measurements as a function of pH showed that pH 8.5 is adequate for concentrated suspensions, while flow curves analysis allowed optimizing Processing parameters, such as, powder content, amount of deflocculant and binder, and sonication time. Optimized Colloidal suspensions were prepared and used to obtain high quality tapes. Processed ceramics from these stacked tapes show equivalent properties to those processed directly from powders, which demonstrates the effectiveness of the Colloidal route reported here.
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liquid phase assisted flash sintering of sic from powder mixtures prepared by aqueous Colloidal Processing
Journal of The European Ceramic Society, 2017Co-Authors: Victor M Candelario, Rodrigo Moreno, Richard I Todd, Angel L OrtizAbstract:The effects were investigated of the starting particle size (i.e., nanometer or submicrometer powders), content of Y3Al5O12 additives (YAG; in the range 5–20 wt.%), and difference of size scales between the two particle types on the liquid-phase assisted flash sintering of SiC from powder mixtures prepared by aqueous Colloidal Processing. It was found that flash sintering benefits from the refinement of the particles size, the increase in additive content, and the smaller size scale of the particulate additive. It was also found that under the present flash sintering conditions (i.e., 900 °C furnace temperature, 13 A current, and 50 s in flash state) the resulting ceramics are, despite the formation of liquid phase, porous to a greater or lesser extent, and exhibit decreasing porosity gradients from their surface to the centre. These observations are rationalized to extract guidelines for powder batch design contributing to the pressureless ultrafast sintering of non-oxide advanced ceramics.
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aqueous Colloidal Processing of near net shape b4c ni cermet compacts
Journal of The European Ceramic Society, 2016Co-Authors: F Rodriguezrojas, Fernando Guiberteau, Rodrigo Moreno, Angel L OrtizAbstract:Abstract Aqueous Colloidal Processing was optimized for the environmentally friendly preparation of concentrated suspensions (29–40 vol.% solids loadings) suitable for the near-net shaping of B4C + 16.6 vol.%Ni cermet compacts by slip casting. Specifically, on the basis of studies with dilute suspensions, it was confirmed that using very basic pHs (i.e., 10) is the key to ensuring the inertness and dispersibility of the Ni particles in water, and that deflocculant contents of at least ∼0.5 wt.% PKV and PAA are required to promote the Colloidal stability of the B4C and Ni particles, respectively. Concentrated B4C + 16.6 vol.%Ni suspensions were consequently prepared at pH 11 with 1 wt.% PKV and PAA, and it was found that sonication for 1 min optimizes the rheological properties. Lastly, these concentrated suspensions were proven to be suitable for the slip casting of robust, highly-dense B4C–Ni cermet compacts with near-net shape, whose green microstructures are very uniform, exhibit well-dispersed and packed particles, with no evidence of cracks or macrodefects, and with relative densities greater than 58% of the theoretical.
Tohru S. Suzuki - One of the best experts on this subject based on the ideXlab platform.
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Densification of SiC by Colloidal Processing and SPS without sintering additives
Advances in Applied Ceramics, 2014Co-Authors: Tohru S. Suzuki, Tetsuo Uchikoshi, Yoshio SakkaAbstract:Silicon carbide is one of the most important ceramics used as structural and functional materials in a wide variety of applications. Many studies have reported the densification of SiC using oxide and nonoxide additives such as the Al2O3, B4C and Al–B–C system. However, it is difficult to densify SiC at temperatures below 2000°C without sintering additives even if spark plasma sintering (SPS) is used. The authors attempted to densify SiC using Colloidal Processing and SPS without sintering additives. A commercially available SiC powder with the average particle size of 0·55 μm was used as the starting material. The densities of the green body prepared by slip casting and the sintered body by SPS were 65·5 and 98·7% respectively.
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effect of starting powders on the sintering of nanostructured zro2 ceramics by Colloidal Processing
Science and Technology of Advanced Materials, 2009Co-Authors: Gustavo Suarez, Yoshio Sakka, Tohru S. Suzuki, Tetsuo Uchikoshi, E F AgliettiAbstract:AbstractThe effect of starting powders on the sintering of nanostructured tetragonal zirconia was evaluated. Suspensions were prepared with a concentration of 10 vol.% by mixing a bicomponent mixture of commercial powders (97 mol.% monoclinic zirconia with 3 mol.% yttria) and by dispersing commercially available tetragonal zirconia (3YTZ, Tosoh). The preparation of the slurry by bead-milling was optimized. Colloidal Processing using 50 μm zirconia beads at 4000 rpm generated a fully deagglomerated suspension leading to the formation of high-density consolidated compacts (62% of the theoretical density (TD) for the bicomponent suspension). Optimum Colloidal Processing of the bicomponent suspension followed by the sintering of yttria and zirconia allowed us to obtain nanostructured tetragonal zirconia. Three different sintering techniques were investigated: normal sintering, two-step sintering and spark plasma sintering. The inhibition of grain growth in the bicomponent mixed powders in comparison with 3YTZ...
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Effect of starting powders on the sintering of nanostructured ZrO2 ceramics by Colloidal Processing
Science and technology of advanced materials, 2009Co-Authors: Gustavo Suarez, Yoshio Sakka, Tohru S. Suzuki, Tetsuo Uchikoshi, Xinwen Zhu, E F AgliettiAbstract:The effect of starting powders on the sintering of nanostructured tetragonal zirconia was evaluated. Suspensions were prepared with a concentration of 10 vol.% by mixing a bicomponent mixture of commercial powders (97 mol.% monoclinic zirconia with 3 mol.% yttria) and by dispersing commercially available tetragonal zirconia (3YTZ, Tosoh). The preparation of the slurry by bead-milling was optimized. Colloidal Processing using 50 μm zirconia beads at 4000 rpm generated a fully deagglomerated suspension leading to the formation of high-density consolidated compacts (62% of the theoretical density (TD) for the bicomponent suspension). Optimum Colloidal Processing of the bicomponent suspension followed by the sintering of yttria and zirconia allowed us to obtain nanostructured tetragonal zirconia. Three different sintering techniques were investigated: normal sintering, two-step sintering and spark plasma sintering. The inhibition of grain growth in the bicomponent mixed powders in comparison with 3YTZ was demonstrated. The inhibition of the grain growth may have been caused by inter-diffusion of cations during the sintering.
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Fabrication and some properties of textured alumina-related compounds by Colloidal Processing in high-magnetic field and sintering
Journal of the European Ceramic Society, 2008Co-Authors: Yoshio Sakka, Tohru S. Suzuki, Tetsuo UchikoshiAbstract:Recently to improve properties, highly microstructure controlled ceramics such as fine-grained, textured and laminated structures are required. We have demonstrated a new Processing of textured ceramics with a feeble magnetic susceptibility by Colloidal Processing in a high-magnetic field and subsequent heating. As Colloidal Processing, slip casting and electrophoretic deposition (EPD) have been conducted successfully. Colloidal Processing is known to be a powerful method for consolidating fine particles with a high density and homogeneous microstructure. Crystalline-textured controlled laminated alumina can be fabricated using EPD by varying the angle between the vectors of electric field and magnetic field. Also textured ceramics with complicated structure such as β-alumina and alumina-based nanocomposite can be fabricated by reaction sintering. The textured alumina-related compounds showed anisotropic properties depending on the crystal plane. The Colloidal Processing in a high-magnetic field confers several advantages and can be applied to many non-cubic ceramics.
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Fabrication and Some Properties of Textured Ceramics by Colloidal Processing in High Magnetic Field
Key Engineering Materials, 2007Co-Authors: Yoshio Sakka, Tohru S. Suzuki, Tetsuo UchikoshiAbstract:Recently to improve properties, highly microstructure controlled ceramics such as fine-grained, textured and laminated structures are required. We have demonstrated a new Processing of textured ceramics with a feeble magnetic susceptibility by Colloidal Processing in a high magnetic field and subsequent heating. As Colloidal Processing, slip casting and electrophoretic deposition (EPD) have been conducted successfully. Colloidal Processing is known to be a powerful method for consolidating fine particles with a high density and homogeneous microstructure. The degree of orientation strongly depends on the particle dispersion and some Processing factors, such as particle size, applied magnetic field, concentration of the suspension, sintering temperature, etc. Crystalline-textured controlled laminated composites can be fabricated using EPD by varying the angle between the vectors of electric field and magnetic field. Also textured ceramics with complicated structure can be fabricated by reaction sintering. The Colloidal Processing in a high magnetic field confers several advantages and it is possible for this type of Processing to be applied to non-cubic ceramics, such as alumina, titania, zinc oxide, tin oxide, hydroxy apatite, aluminium nitride, silicon carbide, silicon nitride, etc. The textured ceramics showed anisotropic properties depending on the crystal plane.
Satoshi Tanaka - One of the best experts on this subject based on the ideXlab platform.
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Particle Rotation in Colloidal Processing under a Strong Rotating Magnetic Field
Langmuir : the ACS journal of surfaces and colloids, 2018Co-Authors: Shoko Baba, Satoshi TanakaAbstract:Functional ceramics with oriented crystals prepared by Colloidal Processing in a strong magnetic field are expected to show improved functionality. In this study, the orientation rate of particles with low magnetic susceptibility in a concentrated slurry under a strong rotating magnetic field was experimentally demonstrated using a fast photopolymerization reaction. A slurry of (Sr,Ca)2NaNb5O15 particles dispersed in an ultraviolet curable resin with a catalyst was consolidated using UV irradiation under a strong rotating magnetic field. The degree of particle orientation increased with increasing Processing time and became saturated after 20 s. The orientation time was observed experimentally; the period required to achieve particle orientation was proportional to the measured viscosity of the slurry and the inverse of the square of the magnetic flux density.
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fabrication of transparent grain oriented polycrystalline alumina by Colloidal Processing
Journal of the American Ceramic Society, 2016Co-Authors: Antoine Pringuet, Shoko Baba, Takuma Takahashi, Yuta Kamo, Zenji Kato, Keizo Uematsu, Satoshi TanakaAbstract:Grain-oriented polycrystalline alumina (PCA) ceramics with very high, nearly single-crystal transparency were successfully fabricated through Colloidal Processing in a high magnetic field followed by hot isostatic pressing. The c-axis of the produced material was oriented along the direction parallel to the magnetic field. The transmittance of the specimen with a thickness of 0.8 mm was 78% at a wavelength of 650 nm, close to the reported value of 84.5% for sapphire and more than 10% higher than the largest transmittance magnitude ever reported for PCA ceramics. In addition, the Na salt of 4,5-dihydroxy-1,3-benzenedisulfonic acid (named “Tiron”) was found to be a highly effective dispersant for Processing high-purity materials.
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Fabrication of Transparent Grain‐Oriented Polycrystalline Alumina by Colloidal Processing
Journal of the American Ceramic Society, 2016Co-Authors: Antoine Pringuet, Shoko Baba, Takuma Takahashi, Yuta Kamo, Zenji Kato, Keizo Uematsu, Satoshi TanakaAbstract:Grain-oriented polycrystalline alumina (PCA) ceramics with very high, nearly single-crystal transparency were successfully fabricated through Colloidal Processing in a high magnetic field followed by hot isostatic pressing. The c-axis of the produced material was oriented along the direction parallel to the magnetic field. The transmittance of the specimen with a thickness of 0.8 mm was 78% at a wavelength of 650 nm, close to the reported value of 84.5% for sapphire and more than 10% higher than the largest transmittance magnitude ever reported for PCA ceramics. In addition, the Na salt of 4,5-dihydroxy-1,3-benzenedisulfonic acid (named “Tiron”) was found to be a highly effective dispersant for Processing high-purity materials.
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Colloidal Processing using UV curable resin under high magnetic field for textured ceramics
Journal of the European Ceramic Society, 2016Co-Authors: Shoko Baba, Tomohiro Harada, Hiroyuki Shimizu, Yutaka Doshida, Satoshi TanakaAbstract:Abstract A novel Colloidal Processing method using UV curable resin was examined in Colloidal Processing under a high magnetic field. This technique can help shorten the shaping time under the magnetic field as a result of fast UV curing. We prepared the dispersed (Sr,Ca) 2 NaNb 5 O 15 (SCNN) slurry with a UV curable resin and fabricated c-axis-oriented SCNN ceramics within a short time under a rotating high magnetic field. The Lotgering factor was 0.81 for (00 l ) in the green compact and increased to 0.94 after sintering. The Colloidal Processing under the high magnetic field was thus effective not only in shortening the drying time under the magnetic field but also in obtaining highly particle-oriented structures.