Formation Process of Calcium‐α SiAlON Hollow Balls Composed of Nanosized Particles by Carbothermal Reduction–Nitridation

Hotta, Mikinori; Tatami, Junichi; Komeya, Katsutoshi; Zhang, Cheng; Meguro, Takeshi; Terner, Mark R.; Cheng, Yi

doi:10.1111/j.1551-2916.2007.02224.x

Cited by 13 publications

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References 23 publications

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“…42) A large number of solid spherical particles consisting of a SiAlCaO amorphous phase were formed at the initial stage of CRN. Very fine particles were subsequently generated on the surface of these solid spheres, and the solid spheres gradually changed into hollow spheres with the progress of nitridation.…”

Section: Jcs-japanmentioning

confidence: 99%

Microstructural control for ultrafine-grained non-oxide structural ceramics

Hotta

2012

J. Ceram. Soc. Japan

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Ultrafine-grained non-oxide ceramics were prepared by combining the synthesis technology for fine-grained starting powders and the rapid sintering technology for spark plasma sintering (SPS); the two technologies were combined for obtaining ceramics with improved heat and corrosion resistance and improved mechanical properties. Hollow spherical Ca-¡ SiAlON powders composed of nanosized particles were synthesized by carbothermal reductionnitridation of a SiO 2 Al 2 O 3 CaCO 3 powder mixture. Using the Ca-¡ SiAlON powder, dense Ca-¡ SiAlON nanoceramics and porous Ca-¡ SiAlON ceramics with excellent mechanical properties and high heat and corrosion resistance were fabricated by the SPS technique. Ultrafine-grained Si 3 N 4 and SiC ceramics were prepared from fine-grained Si 3 N 4 and SiC powders by SPS. The densification of cubic-BN-dispersed ceramics composites was achieved without the phase transformation of cubic BN to low-hardness hexagonal BN, at a moderate pressure by the SPS technique.

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Section: Jcs-japanmentioning

confidence: 99%

Microstructural control for ultrafine-grained non-oxide structural ceramics

Hotta

2012

J. Ceram. Soc. Japan

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“…Thus, the characteristics of starting powders may have an influence on the formation of the Ca-a SiAlON hollow spheres. The Ca-a SiAlON hollow spheres were obtained by using nanosized and amorphous SiO 2 starting powder as major components for the synthesis of SiAlON powder in our previous study [15,16]. In the present work, the formation process of the Ca-a SiAlON hollow spheres was investigated using SiO 2 starting powders with different particle sizes, shapes and crystalline states.…”

Section: Introductionmentioning

confidence: 98%

“…In our previous study, Ca-a SiAlON powders were synthesized by CRN of mixtures of SiO 2 , Al 2 O 3 and CaCO 3 fine powders [15,16] Al-Ca-O liquid phase were formed at the initial stage of CRN, and nanosized particles were subsequently generated on the surface of their solid spherical particles. The solid spherical particles gradually changed into hollow particles with progression of the reaction to Ca-a SiAlON.…”

Section: Introductionmentioning

confidence: 99%

Ca-α SiAlON hollow spheres prepared by carbothermal reduction–nitridation from different SiO2 powders

Hotta

Tatami

Zhang

et al. 2010

Ceramics International

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“…In our previous work, Si 2 14),15) The ¢-SiAlON to Ca-¡ SiAlON XRD peak intensity ratio was higher in the specimens prepared at 1450°C without any holding time than in that prepared with a 120-min holding time, indicating the higher proportion of ¢-SiAlON in the former specimen. In the specimens prepared by CRN at 1450°C without any holding time, an amorphous shoulder was observed at low 2ª values in the XRD patterns, 14), 15) while no amorphous shoulder was detected in specimens prepared by GRN. The XRD peaks of the crystalline phases in the specimens prepared by GRN at 1450°C without any holding time were higher and sharper than those obtained in the case of CRN.…”

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“…The solid spheres subsequently changed into hollow spheres as the reduction-nitridation reaction proceeded. 14) In the case of GRN with C 3 H 8 gas, on the other hand, the SiAlCaO liquid phase did not lead to the formation of spheres, because the hydrocarbon gas was not conducive to the formation of spherical particles. Hence, agglomerated and bonded particles would be generated in the initial stage of the GRN process, and Ca-¡ SiAlON would be produced while maintaining the particle morphology (Figs.…”

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Preparation of Ca-α SiAlON powder by reduction-nitridation in a gas mixture of C3H8 and NH3

Hotta

Kita

Yamakawa

et al. 2012

J. Ceram. Soc. Japan

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Ca-¡ SiAlON powders were synthesized from a SiO 2 Al 2 O 3 CaCO 3 powder mixture by reduction-nitridation with C 3 H 8 NH 3 gas. Ca-¡ SiAlON with small amounts of AlN and ¢-SiAlON phases was produced at 1450°C for 120 min. Angular particles and agglomerated and bonded particles with irregular shapes were formed. In the product prepared at 1450°C without any holding time, Si 2 N 2 O was detected as an intermediate phase, in addition to the Ca-¡ SiAlON, ¢-SiAlON and AlN phases. A large number of agglomerated and bonded particles were observed.©2012 The Ceramic Society of Japan. All rights reserved.Key-words : SiAlON, Powder, Reduction-nitridation, Gas, Morphology, Formation process [Received December 13, 2011; Accepted February 2, 2012] SiAlON ceramics possess high hardness and excellent oxidation and corrosion resistance. In our previous study, Ca-¡ SiAlON powders were prepared from mixtures of SiO 2 , Al 2 O 3 , CaCO 3 and carbon powders by CRN.13)16) The powders prepared had hollow spheres composed of nanosized particles.13) Solid spherical particles that consisted of a liquid phase containing Si, Al, Ca, O were generated at the initial stage of the CRN process. As the reaction proceeded from the liquid phase to the crystalline Ca-¡ SiAlON, the solid spheres changed into hollow spheres. 14),15)High-purity and fine-grained AlN powders were obtained by gas reduction-nitridation (GRN) of fine-grained Al 2 O 3 using a gas mixture of C 3 H 8 and NH 3 as a reduction-nitridation agent.17),18) This indicated that the resultant particles retained the morphology of the starting powders because of a gas-solid reaction between Al 2 O 3 and NH 3 , and that the use of a hydrocarbon gas as reducing agent promoted more reduction-nitridation compared to the case of CRN with carbon powder.In the present work, Ca-¡ SiAlON powders were prepared through GRN of a mixture of SiO 2 , Al 2 O 3 , and CaCO 3 powders using a C 3 H 8 NH 3 gas mixture, and the crystalline phases and particle morphology of the products were investigated. The effect of hydrocarbon gas as a reducing agent on the particle morphology of the products was also discussed.As starting materials, SiO 2 (QS-102, Tokuyama Co., particle size: 0.0050.05¯m), Al 2 O 3 (AKP-50, Sumitomo Chemical Co., Ltd., 0.21¯m) and CaCO 3 (Junsei Chemical Co., Ltd., 1.0¯m) powders were used. The proportions of these powders were adjusted so as to obtain a nominal composition of Ca 13) The starting powders were mixed with a small amount of ethanol. The mixture was dried, sieved, placed in an Al 2 O 3 boat, and heated in a horizontal electric furnace under a flowing gas mixture of C 3 H 8 (20 mL/min) and NH 3 (4 L/min) at a rate of 10°C/min up to 1450°C, for holding times of 0 to 120 min. The crystalline phases that appeared in the specimens were identified by X-ray diffractometry (XRD). The content of the Ca-¡ SiAlON phase was calculated from the XRD peak intensities.15) Scanning electron microscopy (SEM) was used to characterize the particle morphology of the specimens. Figure 1 shows ...

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Formation Process of Calcium‐α SiAlON Hollow Balls Composed of Nanosized Particles by Carbothermal Reduction–Nitridation

Cited by 13 publications

References 23 publications

Microstructural control for ultrafine-grained non-oxide structural ceramics

Microstructural control for ultrafine-grained non-oxide structural ceramics

Ca-α SiAlON hollow spheres prepared by carbothermal reduction–nitridation from different SiO2 powders

Preparation of Ca-α SiAlON powder by reduction-nitridation in a gas mixture of C<sub>3</sub>H<sub>8</sub> and NH<sub>3</sub>

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