Effect of stirring and KOH/NaOH ratio on phase formation in hydrothermal synthesis of KNbO3-NaNbO3 particles

IF 3.4 3区 工程技术 Q2 CHEMISTRY, PHYSICAL
Ellawala K. Chandima Pradeep, Alexandre Chauvel, Cenk Abdurrahmanoglu, Ragnar Kiebach, Astri Bjørnetun Haugen
{"title":"Effect of stirring and KOH/NaOH ratio on phase formation in hydrothermal synthesis of KNbO3-NaNbO3 particles","authors":"Ellawala K. Chandima Pradeep,&nbsp;Alexandre Chauvel,&nbsp;Cenk Abdurrahmanoglu,&nbsp;Ragnar Kiebach,&nbsp;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":null,"pages":null},"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}
引用次数: 0

Abstract

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.

Abstract Image

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
本研究探讨了 KNbO3-NaNbO3 粒子的水热合成,其中包含可用作无铅压电材料的成分。含有 Nb2O5、NaOH/KOH 的前驱体溶液在 190 0C 温度下,使用传统反应器或带搅拌的反应器进行 15 小时的水热反应。当使用 50% 或更低的 KOH 时,生成物为立方体或细长的立方体/带状 NaNbO3,而仅使用 KOH 则生成六方板状 KNbO3。当使用 75% 的 KOH 时,生成物是大的 K5Na3Nb6O19-9 H2O 六方板和较小的 NaNbO3 立方体的混合物。我们假设这种相分离是由高浓度微环境引起的,而搅拌可以防止这种情况。因此,对 75% KOH 溶液进行搅拌水热处理后,只产生了 K5Na3Nb6O19-H2O 六方板,煅烧后可转化为 K0.7Na0.3NbO3。通过将水热处理时间缩短至 1 - 6 小时,我们分离出了反应中间产物,并在此基础上提出了 Nb2O5 和 KOH/NaOH 水热反应的动力学控制机制。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
求助全文
约1分钟内获得全文 求助全文
来源期刊
Journal of Supercritical Fluids
Journal of Supercritical Fluids 工程技术-工程:化工
CiteScore
7.60
自引率
10.30%
发文量
236
审稿时长
56 days
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.
×
引用
GB/T 7714-2015
复制
MLA
复制
APA
复制
导出至
BibTeX EndNote RefMan NoteFirst NoteExpress
×
提示
您的信息不完整,为了账户安全,请先补充。
现在去补充
×
提示
您因"违规操作"
具体请查看互助需知
我知道了
×
提示
确定
请完成安全验证×
copy
已复制链接
快去分享给好友吧!
我知道了
右上角分享
点击右上角分享
0
联系我们:info@booksci.cn Book学术提供免费学术资源搜索服务,方便国内外学者检索中英文文献。致力于提供最便捷和优质的服务体验。 Copyright © 2023 布克学术 All rights reserved.
京ICP备2023020795号-1
ghs 京公网安备 11010802042870号
Book学术文献互助
Book学术文献互助群
群 号:481959085
Book学术官方微信