共查询到19条相似文献,搜索用时 234 毫秒
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核能的安全利用是我国目前高度关注的重点,但核废料中含有的强放射性元素Cs及其同位素由于产率较高、半衰期较长且溶解性高而难以处理,如何对其进行安全处置亟待解决.铯榴石因其类似方沸石的结构而具有浸出率低、热稳定性好等优点,被认为是一种理想的固化放射性Cs的陶瓷材料.但是,传统的固相烧结工艺由于合成温度高而容易造成部分Cs的挥发造成二次污染,限制了铯榴石的应用.近年来,基于地聚物前驱体技术可以实现较低温度下铯榴石陶瓷的合成,但是所得陶瓷材料的力学性能及化学稳定性不佳.针对铯榴石在陶瓷制备中的问题,引入玻璃粉降低铯榴石陶瓷体的合成温度(<1000℃),同时实现对铯榴石中铯的二次保护.采用X射线衍射、拉曼光谱、扫描电子显微镜、硬度和密度测量以及电感耦合等离子体质谱等现代分析测试技术对系列样品的结构、微结构及化学稳定性进行了表征.结果 表明:采用地聚物前驱体为原料,并加入适量的玻璃粉作为粘结剂,可以有效地降低铯榴石的合成温度,并改善微结构,增加致密度.经过浸出测试,玻璃粉的引入提高了铯榴石陶瓷的稳定性,实现了对铯榴石中铯的双重保护. 相似文献
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以SiO2和Al2(SO4)3.18H2O为原料,在K2SO4熔盐介质中,分别于800℃、900℃、1000℃、1100℃和1200℃下保温3h,经溶解、分离、烘干后得到莫来石粉体,利用XRD和SEM对合成粉体的相组成和形貌进行了表征。研究结果表明:合成的莫来石粉体由纳米尺度的束状莫来石晶须组成;在900℃时开始形成莫来石,但仍有石英相存在;在1000℃时石英相完全消失,合成了高纯的莫来石粉体;当温度超过1100℃时,合成的莫来石开始分解。由此得出合理的合成反应温度为1000℃左右。同时,还根据液-固体系中晶体生长的基本理论,对束状莫来石晶须的形成机理进行了探讨。 相似文献
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制备了一种聚(丙烯酸-共聚-苯并-18-冠醚-6-丙烯酰胺)(PAB)线形共聚物,并系统研究了不同丙烯酸含量的PAB线形共聚物对铯离子的响应特性及其用于铯离子浓度检测的性能。结果表明,在不同浓度的铯离子溶液中,PAB线形共聚物的低临界溶解温度(LCST)会随着铯离子浓度增加向低温迁移;在实验范围内,当PAB线形共聚物中的丙烯酸质量分数为30%时,其铯离子响应特性最有利于水溶液中铯离子浓度的检测。通过系统实验研究,确立了PAB共聚物的LCST与水溶液中铯离子浓度的关系函数;利用该关系函数,可简单地通过测定未知铯离子浓度的PAB溶液LCST,即可推断出该溶液中的铯离子浓度。该研究为铯离子的便捷检测提供了新手段。 相似文献
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纳米氧化镍制备及表征 总被引:1,自引:0,他引:1
以六水硝酸镍和氨水为原料,采用配位均匀沉淀法制备了纳米氧化镍。探讨了制备条件对氧化镍前驱体产率和纳米氧化镍平均粒径的影响,得出最佳工艺条件:镍离子浓度为0.8 mol/L,反应物配比[n(氨水)/n(硝酸镍)]为3∶1,沉淀反应温度为80 ℃,反应时间为90 min,焙烧温度为400 ℃,焙烧时间为1 h。同时,利用X射线衍射(XRD)和透射电镜(TEM)等分析方法对产品组成和形貌进行了表征,结果显示,实验制得的氧化镍纳米晶属标准面心立方晶系结构,晶粒呈球形,平均粒径约为12 nm。 相似文献
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对低浓度含铜废水(10~50 mg/L)进行了电渗析浓缩实验研究。实验在自制电渗析装置中进行,电渗析反应槽内置交替排列的阴、阳离子交换膜,从而将反应槽分隔成阴、阳极极室、清室和浓室。废水中的铜离子由于电场力的作用透过离子交换膜被富集浓缩。实验分别考察了直流电压、极板间距、通电时间等因素对铜离子去除效率和浓缩倍数的影响,并分析其原因。结果显示,温度20 ℃、电压8 V、pH=7,极板间距360 mm、通电时间1 h时,铜离子去除效率可达90.4%,浓缩倍数为3.5,清室铜离子浓度为1.44 mg/L。 相似文献
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Sharon E. Ashbrook Karl R. Whittle Laurent Le Pollès Ian Farnan 《Journal of the American Ceramic Society》2005,88(6):1575-1583
Pollucite, CsAlSi2 O6 , a Cs polymorph of leucite (KAlSi2 O6 ), has been proposed for ceramic immobilization of 135 Cs and 137 Cs fission products. 133 Cs NMR of both low- (tetragonal) and high-temperature (cubic) forms of pollucite exhibit a considerable distribution of local Cs environments. 29 Si and 27 Al NMR data from directly prepared pollucite show greater Al/Si disorder than either leucite, or pollucite produced by ion exchange. Little evidence for Cs motion is observed in tetragonal or cubic pollucite, and only at high temperatures (∼850°C) is any substantial dynamic behavior detected. Dynamic NMR lineshape calculations allow a determination of the frequency of Cs motion and diffusivity. 相似文献
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Jei-Kwon Moon Eil-Hee Lee Yoon-Ju Han Byung-Chul Lee Hyung-Tae Kim 《Korean Journal of Chemical Engineering》2005,22(1):127-132
An ion exchange kinetic study was performed using PAN-KCoFC for removal of cesium ion from mixed solution of Cs, Sr, Ni and
Ba ions. Uptake curves were obtained for a multi-component ion exchange system as well as binary system. A PAN-KCoFC composite
ion exchanger showed higher selectivity for Cs ion over the Sr, Ba, Ni ions. A homogeneous model could predict accurately
the uptake curve for both the binary and multi-component systems. Solid phase effective pore diffusivities obtained by modeling
ranged between 10−5 cm2/min and 10−6 cm2/min. 相似文献
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The cesium trapping characteristics with changing reaction temperature, carrier gas and gas velocity by the fly ash filter
were analyzed. The SEM (Scanning electron microscope) on the pore structure of the fly ash filter showed that pores up to
0.1 mm in diameter were widely interconnected with each other throughout the whole structure of the filter. According to the
XRD (X-ray diffraction) analysis for the cesium compound trapped on the fly ash filter, the thermally stable pollucite phase
was formed. The cesium trapping quantity of the fly ash filter was increased with increasing reaction temperature, whereas
it was decreased with increasing gas velocity. SEM showed that the fly ash filter after trapping gaseous cesium had mullite
phase of needle-like crystals and pollucite phase of bulky crystals with rough surface.
Presented at the Int’l Symp. on Chem. Eng. (Cheju, Feb. 8-10, 2001), dedicated to Prof. H. S. Chun on the occasion of his
retirement from Korea University. 相似文献
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Ian MacLaren † Jesus Cirre Clive B. Ponton 《Journal of the American Ceramic Society》1999,82(11):3242-3244
Pollucite (CsAlSi2 O6 ) powders were produced by hydrothermal synthesis from relatively inexpensive precursors. The pollucite powders were comprised of polycrystalline particles with dimensions of hundreds of nanometers consisting of 25-75 nm crystallites. The polycrystalline particles were near stoichiometric composition. The pollucite powders were mixed with a poly(ethylene glycol) binder, pressed into disks, and sintered at temperatures from 1450° to 1550°C for 10 h. The resulting sintered ceramics had densities >80% of theoretical density and, in the best case, >97% of theoretical density. 相似文献
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以3种不同孔径的介孔材料MCM-41,SBA-15,大孔SBA-15(SBA-15-L)为载体,采用离子交换法制备了Ag/Al-MCM-41,Ag/Al-SBA-15和Ag/Al-SBA-15-L介孔材料吸附剂。利用XRD,N2吸附,SEM-EDS,ICP-MS等手段对所制备的吸附剂进行了表征,并在固定床上对航空煤油进行了吸附脱硫研究。结果表明,交换Ag+所制备的吸附剂依然保持介孔材料的特性,并可将含S量为150×10-6的航空煤油中的硫化物,选择性的吸附脱除到S含量低于1.0×10-6。其中,在Ag/Al-MCM-41,Ag/Al-SBA-15和Ag/Al-SBA-15-L吸附剂上,可分别得到8.0,9.0和17.0mL的清洁航空煤油(含硫量小于1.0×10-6)。实验结果也表明,所制备的吸附剂吸附脱硫性能主要取决于介孔材料载体的孔径大小,载体的孔径越大,Ag+的利用率越高,吸附剂的吸附脱硫性能越强。将吸附饱和的Ag/Al-SBA-15-L吸附剂,于空气中在350℃进行再生5h,吸附剂的吸附性能可以100%的恢复。 相似文献
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以草酸铌和醋酸钾为原料,加水研磨干燥后得到前驱体,前驱体分别在500℃和800℃焙烧3 h合成高纯相和高结晶度的铌酸钾粉末。红外光谱分析表明,草酸铌和醋酸钾发生离子交换反应生成前驱体K[NbO(C_2O_4)_2]·xH_2O。500℃合成的铌酸钾颗粒粒径约50 nm,800℃合成的颗粒粒径在100 nm以上。以制备的铌酸钾粉末为光催化剂,在高压汞灯照射下,对亚甲基蓝溶液进行光催化降解。实验表明,500℃焙烧合成的铌酸钾粉末具有光催化性能,而800℃焙烧合成的不具有催化性能。催化动力学分析表明,亚甲基蓝溶液的光催化降解反应符合一级动力学方程。 相似文献
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Jingkun Yuan Peigang He Xiaomin Liang Dechang Jia Lingyu Jia Delong Cai Zhihua Yang Xiaoming Duan Shengjin Wang Yu Zhou 《Ceramics International》2018,44(9):10047-10054
In this paper, a high temperature treatment procedure was designed to evaluate the effect of holding temperature on thermal evolution process of Li+ substituted Cs-based geopolymer (Cs0.7Li0.3GP), including the thermal analysis, phase composition and microstructure evolution. With rising of holding temperature, amorphous unheated Cs0.7Li0.3GP gradually transformed into a multiphase system during the high temperature treatment process, which consisted of pollucite (CsAlSi2O6), spodumene (LiAlSi2O6) and amorphous glass phase. In the multiphase system, Cs+ ions were in the form of pollucite grains, while Li+ ions were in the form of spodumene nanocrystallines distributed in amorphous matrix. The pollucite grains gradually coarsened with rise in holding temperature, and the densification of the resulting products were also improved synchronously, which were related to the presence of amorphous glass phases. The amorphous glass phase would be in a molten state when holding temperature over 800?°C. And the presence of molten amorphous phase would make the mass transfer process easier, which could contribute to the growth of the crystal grains and the elimination of the pores. 相似文献