{"title":"水热合成 KNbO3-NaNbO3 粒子过程中搅拌和 KOH/NaOH 比率对相形成的影响","authors":"Ellawala K. Chandima Pradeep, Alexandre Chauvel, Cenk Abdurrahmanoglu, Ragnar Kiebach, Astri Bjørnetun Haugen","doi":"10.1016/j.supflu.2024.106340","DOIUrl":null,"url":null,"abstract":"<div><p>This study investigates the hydrothermal synthesis of KNbO<sub>3</sub>-NaNbO<sub>3</sub> particles, which contains compositions of interest as lead-free piezoelectric materials. Precursor solutions containing Nb<sub>2</sub>O<sub>5</sub>, NaOH/KOH were hydrothermally reacted at 190 <sup>0</sup>C for 15 hours using either a conventional reactor or a reactor with stirring. For 50 % KOH or lower, the product was cubic or elongated cuboid/belt-shaped NaNbO<sub>3</sub>, whereas solely KOH resulted in hexagonal plate-like KNbO<sub>3</sub>. When 75 % KOH was used, the product was a mixture of large K<sub>5</sub>Na<sub>3</sub>Nb<sub>6</sub>O<sub>19</sub>·9 H<sub>2</sub>O hexagonal plates and smaller NaNbO<sub>3</sub> cubes. We hypothesized this phase segregation was induced by highly concentrated microenvironments, and stirring would prevent that. Accordingly, stirring hydrothermal treatment of 75 % KOH solution produced only K<sub>5</sub>Na<sub>3</sub>Nb<sub>6</sub>O<sub>19</sub>·H<sub>2</sub>O hexagonal plates, which could be transformed to K<sub>0.7</sub>Na<sub>0.3</sub>NbO<sub>3</sub> by calcination. By reducing the hydrothermal treatment time to 1 – 6 hours we isolated reaction intermediates, and based on them propose a kinetics-controlled mechanism for hydrothermal reactions of Nb<sub>2</sub>O<sub>5</sub> and KOH/NaOH.</p></div>","PeriodicalId":17078,"journal":{"name":"Journal of Supercritical Fluids","volume":"212 ","pages":"Article 106340"},"PeriodicalIF":3.4000,"publicationDate":"2024-06-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.sciencedirect.com/science/article/pii/S089684462400175X/pdfft?md5=9896c0d608550f2b36abe1d0085df976&pid=1-s2.0-S089684462400175X-main.pdf","citationCount":"0","resultStr":"{\"title\":\"Effect of stirring and KOH/NaOH ratio on phase formation in hydrothermal synthesis of KNbO3-NaNbO3 particles\",\"authors\":\"Ellawala K. Chandima Pradeep, Alexandre Chauvel, Cenk Abdurrahmanoglu, Ragnar Kiebach, Astri Bjørnetun Haugen\",\"doi\":\"10.1016/j.supflu.2024.106340\",\"DOIUrl\":null,\"url\":null,\"abstract\":\"<div><p>This study investigates the hydrothermal synthesis of KNbO<sub>3</sub>-NaNbO<sub>3</sub> particles, which contains compositions of interest as lead-free piezoelectric materials. Precursor solutions containing Nb<sub>2</sub>O<sub>5</sub>, NaOH/KOH were hydrothermally reacted at 190 <sup>0</sup>C for 15 hours using either a conventional reactor or a reactor with stirring. For 50 % KOH or lower, the product was cubic or elongated cuboid/belt-shaped NaNbO<sub>3</sub>, whereas solely KOH resulted in hexagonal plate-like KNbO<sub>3</sub>. When 75 % KOH was used, the product was a mixture of large K<sub>5</sub>Na<sub>3</sub>Nb<sub>6</sub>O<sub>19</sub>·9 H<sub>2</sub>O hexagonal plates and smaller NaNbO<sub>3</sub> cubes. We hypothesized this phase segregation was induced by highly concentrated microenvironments, and stirring would prevent that. Accordingly, stirring hydrothermal treatment of 75 % KOH solution produced only K<sub>5</sub>Na<sub>3</sub>Nb<sub>6</sub>O<sub>19</sub>·H<sub>2</sub>O hexagonal plates, which could be transformed to K<sub>0.7</sub>Na<sub>0.3</sub>NbO<sub>3</sub> by calcination. By reducing the hydrothermal treatment time to 1 – 6 hours we isolated reaction intermediates, and based on them propose a kinetics-controlled mechanism for hydrothermal reactions of Nb<sub>2</sub>O<sub>5</sub> and KOH/NaOH.</p></div>\",\"PeriodicalId\":17078,\"journal\":{\"name\":\"Journal of Supercritical Fluids\",\"volume\":\"212 \",\"pages\":\"Article 106340\"},\"PeriodicalIF\":3.4000,\"publicationDate\":\"2024-06-30\",\"publicationTypes\":\"Journal Article\",\"fieldsOfStudy\":null,\"isOpenAccess\":false,\"openAccessPdf\":\"https://www.sciencedirect.com/science/article/pii/S089684462400175X/pdfft?md5=9896c0d608550f2b36abe1d0085df976&pid=1-s2.0-S089684462400175X-main.pdf\",\"citationCount\":\"0\",\"resultStr\":null,\"platform\":\"Semanticscholar\",\"paperid\":null,\"PeriodicalName\":\"Journal of Supercritical Fluids\",\"FirstCategoryId\":\"5\",\"ListUrlMain\":\"https://www.sciencedirect.com/science/article/pii/S089684462400175X\",\"RegionNum\":3,\"RegionCategory\":\"工程技术\",\"ArticlePicture\":[],\"TitleCN\":null,\"AbstractTextCN\":null,\"PMCID\":null,\"EPubDate\":\"\",\"PubModel\":\"\",\"JCR\":\"Q2\",\"JCRName\":\"CHEMISTRY, PHYSICAL\",\"Score\":null,\"Total\":0}","platform":"Semanticscholar","paperid":null,"PeriodicalName":"Journal of Supercritical Fluids","FirstCategoryId":"5","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S089684462400175X","RegionNum":3,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q2","JCRName":"CHEMISTRY, PHYSICAL","Score":null,"Total":0}
Effect of stirring and KOH/NaOH ratio on phase formation in hydrothermal synthesis of KNbO3-NaNbO3 particles
This study investigates the hydrothermal synthesis of KNbO3-NaNbO3 particles, which contains compositions of interest as lead-free piezoelectric materials. Precursor solutions containing Nb2O5, NaOH/KOH were hydrothermally reacted at 190 0C for 15 hours using either a conventional reactor or a reactor with stirring. For 50 % KOH or lower, the product was cubic or elongated cuboid/belt-shaped NaNbO3, whereas solely KOH resulted in hexagonal plate-like KNbO3. When 75 % KOH was used, the product was a mixture of large K5Na3Nb6O19·9 H2O hexagonal plates and smaller NaNbO3 cubes. We hypothesized this phase segregation was induced by highly concentrated microenvironments, and stirring would prevent that. Accordingly, stirring hydrothermal treatment of 75 % KOH solution produced only K5Na3Nb6O19·H2O hexagonal plates, which could be transformed to K0.7Na0.3NbO3 by calcination. By reducing the hydrothermal treatment time to 1 – 6 hours we isolated reaction intermediates, and based on them propose a kinetics-controlled mechanism for hydrothermal reactions of Nb2O5 and KOH/NaOH.
期刊介绍：
The Journal of Supercritical Fluids is an international journal devoted to the fundamental and applied aspects of supercritical fluids and processes. Its aim is to provide a focused platform for academic and industrial researchers to report their findings and to have ready access to the advances in this rapidly growing field. Its coverage is multidisciplinary and includes both basic and applied topics.
Thermodynamics and phase equilibria, reaction kinetics and rate processes, thermal and transport properties, and all topics related to processing such as separations (extraction, fractionation, purification, chromatography) nucleation and impregnation are within the scope. Accounts of specific engineering applications such as those encountered in food, fuel, natural products, minerals, pharmaceuticals and polymer industries are included. Topics related to high pressure equipment design, analytical techniques, sensors, and process control methodologies are also within the scope of the journal.
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