Studies on the synthesis of nanocrystalline yttria powder by oxalate deagglomeration and its sintering behaviour |
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| Affiliation: | 1. Chemistry Group, Indira Gandhi Centre for Atomic Research, Kalpakkam, India;2. Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai, India;1. Department of Chemistry, R.V.R. & J.C. College of Engineering, Guntur 522019, India;2. Department of Chemistry, Indian Institute of Technology Madras, Chennai 600036, India;3. Department of Chemistry, J. K. C. C. Acharya Nagarjuna University, Guntur 522006, India;4. Department of Chemistry, K. L. University, Guntur 522502, India;1. Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, GSP-2, Moscow 119992, Russia;2. CNRS, Institut Néel, 25 rue des Martyrs BP166 x, F-38042 Grenoble, France;3. Université Grenoble Alpes, Institut Néel, F-38042 Grenoble, France;4. Indian Institute of Technology Madras, Chennai 600036, India;5. Departamento de Física Teórica e Experimental, Universidade Federal do Rio Grande do Norte, Natal 59082-970, Brazil;1. College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang, Jiangxi 330022, PR China;2. Institute of Physics and Communication Engineering, Jiangxi Normal University, Nanchang, Jiangxi 330022, PR China;1. School of Material Sciences & Engineering, Shanghai University, Shanghai 200436, China;2. Key Laboratory of Transparent Opto-functional Inorganic Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China;3. Shanghai Key Laboratory of Crime Scene Evidence, Shanghai Research Institute of Criminal Science and Technology, Shanghai 200083, China;4. Department of Physics, Shanghai Normal University, Shanghai 200234, China |
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| Abstract: | Nanocrystalline yttria powders were synthesized from deagglomerated yttrium oxalate. The precipitation of this oxalate was carried in two different modes viz., addition of aqueous oxalic acid into yttrium nitrate solution (forward strike) and vice versa (reverse strike) followed by ultrasonication in acetone and water. Nanocrystalline yttria was obtained by calcining the oxalate in air at 1073 K. The bulk densities, specific surface area, X-ray crystallite size, size distribution of particles as well as the quantity of carbon residue in these powders were determined. The influence of the deagglomeration medium on the powder properties was analyzed. Scanning electron microscopy (SEM) showed that these powders comprised irregular agglomerates while the high resolution transmission electron microscopy (HRTEM) revealed that the constituent units of these agglomerates were randomly oriented cuboidal nanocrystallites (20–40 nm). These powders were compacted at 120 MPa without any lubricant or binder and their sinterability was studied. Pellets with sintered density as high as 97.5% T.D. (theoretical density) could be obtained at a relatively low sintering temperature of 1873 K. Synthesis of nanocrystalline yttria powders by oxalate deagglomeration route as well as the systematic studies of their properties and sinterabilities are being reported for the first time. It was further demonstrated in this study that higher sintered densities could be obtained with less number of process steps and at a much lower compaction pressure. Samples prepared by reverse strike yielded a powder with characteristics most suitable for fabricating high density yttria bodies. 1673 K would be the optimum temperature for sintering the compacts made out of this powder. |
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| Keywords: | Yttria Oxalate Sintering Precipitation Deagglomeration |
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