16 resultados para NAF

em Chinese Academy of Sciences Institutional Repositories Grid Portal


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制备了一种新型的氧卤碲酸盐玻璃:(80-x)TeO2—15ZnCl2-xBaO-5NaF(x=30、20、10、0mol%),对玻璃的机械强度、热稳定性、拉曼光谱、紫外吸收光谱、红外透过光谱等特性进行了研究.通过拉曼光谱分析研究了玻璃组分含量的变化对玻璃结构和红外透过性能的影响.结果表明,随着BaO含量的增加,玻璃在红外波段透过率显著增加,并且红外透过截止波长向长波方向移动,本文对这一实验结果进行了机理性的研究探讨.同时,通过在熔制过程中通入高纯O2,以及引入适量的卤化物有效地除去玻璃中的[OH]基团,使

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Surface tension and density of NaCl-NaF-RE2O, melts have been measured by means of maximum buble pressure and Archimedes methods. The results are expressed by two mathematic models. Mass fraction of RE2O5 in the melts from 0.0 to 0.6% and that of NaF/NaCl, 50-90%. This investigation shows that there might be com plexes in the melts. The information obtained can be used as a reference in the preparation of Al-RE alloys.

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以NaCl-NaF体系为还原介质,以RE_2O_3,REOCl,或RE_2(CO_3)_3为原料,以铝为还原剂,在铝熔融过程中直接制备Al-RE应用合金已获得了应用.结果表明,这一方法使用简单,操作方便,不需额外设备,容易为工厂采用.本工作是为这一工艺开展的基础研究工作. 资料对LaCl_3-碱金属氯化物,碱土金属氯化物的表面张力和密度进行了专门总结,对NaCl-NaF-RE_2O_3体系未见报导。

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Liquid segregation phenomena have been found and explained in the F(Li)-rich granites in south China by Wang Linakui et al. (1979; 1983). A number of experimental investigations into the liquid immiscibilities in the granites systems have been carried out (Anfilogov et al., 1983; Glyuk et al., 1971; Glyuk et al., 1973a; 1973b; kovalenko, 1978; Wang Liangkui et al., 1987). Nevertheless, the detailed scenarios of the liquid immiscibilities in the granitic magmas are much less understood. This experimental study is amide to get access to this problem. Starting materials are biotite granite +LiF(3-10%)+NaF(3-10%)+H_2O(30%). The experimental results have shown that the liquid immiscibilities of melts of different compositions occur at 1 kbar and 840 ℃ when 5wt% (LiF + NaF) are added to the granite samples. three kinds of glasses indicating of three types of coexisting immiscible melts have been observed: light blue matrix glass, melanocratic glass balls and leucocratic glass balls. It is interesting that we have observed various kinds of textures as follows: spherulitic texture, droplets, flow bands, swirls. All these textures can be comparable to those in the natural granitic bodies. Electron microprobe data suggest that these different kinds of glasses are of different chemical compositions respectively; matrix glasses are F-poor silicate melts; melanocratic balls correspond to F-rich silicate melts; and leucocratic balls are the melts consisting mainly of fluorides. Raman spectrometric data have indicated that different glasses have different melt structures. TFM Diagrams at 1000 * 10~5 Pa have been plotted, in which two miscible gaps are found. One of the two gaps corresponds to the immiscibility between F - poor silicate melt and F-rich silicate melt, another to that between the silicate melt and fluoride melt. The experiments at different pressures have suggested that the decreases in pressures are favorable to the liquid immiscibility. Several reversal experiments have indicated that the equilibria in different runs have been achieved. We have applied the experimental results to explain the field evidence of immiscibilities in some of granites associated with W-Sn-Nb-Ta mineralization. These field phenomena include flow structure, globular structures,mineralized globular patche and glass inclusions in topaz. We believe that the liquid immiscibility (liquid segregation) is a possible way of generation of F(Li)-rich granites. During the evolution of the granitic magmas, the contents of Li, F, H_2O and ore-forming elements in the magmas become higher and higher. The granites formed in the extensional tectonic settings commonly bear higher abundences of the above-mentioned elements. the pressures of the granitic magmas are relatively lower during the processes of their emplacements and cooling. The late-staged magmas will produce liquid immiscibilities, leading to the production of several coexisting immiscible melts with different chemical compositions. The flow of immiscible consisting magmas will produce F(Li)-rich granites. It is also considered that liquid immiscibilities are of great significance in the production of rare metal granites. The ore-forming processes and magmatic crystallization and metasomatic processes can be occur at the same time. The mineralisations of rare metals are related to both magmatic and hydrothermal processes.

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A physical model is presented to describe the kinds of static forces responsible for adhesion of nano-scale copper metal particles to silicon surface with a fluid layer. To demonstrate the extent of particle cleaning, Received in revised form equilibrium separation distance (ESD) and net adhesion force (NAF) of a regulated metal particle with different radii (10-300 nm) on the silicon surface in CO2-based cleaning systems under different pressures were simulated. Generally, increasing the pressure of the cleaning system decreased the net adhesion force between spherical copper particle and silicon surface entrapped with medium. For CO2 + isopropanol cleaning system, the equilibrium separation distance exhibited a maximum at temperature 313.15 K in the Equilibrium separation distance regions of pressure space (1.84-8.02 MPa). When the dimension of copper particle was given, for example, High pressure 50 nm radius particles, the net adhesion force decreased and equilibrium separation distance increased with increased pressure in the CO2 + H2O cleaning system at temperature 348.15 K under 2.50-12.67 MPa pressure range. However, the net adhesion force and equilibrium separation distance both decreased with an increase in surfactant concentration at given pressure (27.6 or 27.5 MPa) and temperature (318 or 298 K) for CO2 + H2O with surfactant PFPE COO-NH4+ or DiF(8)-PO4-Na+. (C) 2008 Elsevier B.V. All rights reserved.

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Er3+/Yb3+ cocloped fluorophosphate glasses were prepared and their thermal stabilities, Raman spectra, absorption spectra, and fluorescence spectra were measured. It is found that proper content of NaF or PbF2 is helpful for the increase of stability against crystallization. The variation of AI(PO3)3 or NaF content in the composition affects not the maximum phonon energy but the phonon density. The introduction of PbF2 decreases the phonon energy slightly. Intense green and red upconversion luminescence was observed for the fluorophosphate glass with low phosphate content. A glass matrix for upconversion luminescence requiring neither expensive raw material nor special atmospheric conditioned preparation is provided. Infrared luminescence around 1530 nm was researched. Fluorophosphate glasses with bandwidth properties and stimulated-emission cross sections better than tellurite, germanate and silicate glasses are obtained. Through the introduction of NaF, the bandwidth properties are decreased. Through the introduction of PbF2 the gain properties are increased. On the whole, it is difficult to obtain a material with the best gain properties and bandwidth properties simultaneously. There should be a compromise between them according to the demand. (C) 2006 Elsevier B.V. All rights reserved.

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在椭圆曲线密码体制里面。标量乘法是一个非常重要的运算。它的性能对整个密码体制的效率有着举足轻重的作用。论文首先提出一个快速窗口算法用以实现标量乘法,此算法利用了NAF表示的窗口算法和边信道原子块(side channel atomicity)方法。所以算法有效。快速而且可以边信道攻击。在此基础上提出了一个并行算法,它对于边信道攻击是安全的,高效的。

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在现代化学和材料科学中,纳米/微米材料的尺寸和形貌控制引起了学术界的广泛关注,如何合理控制材料的定向生长,调节其组成、形貌、尺寸以及维度,进而更好的理解晶体生长的复杂现象、揭示其潜在的基本理论和原理并最终实现按照人们的设计合成功能材料具有十分重要的意义。本论文在稀土氟化物和钨酸盐纳米/微米材料的设计合成、形貌控制、形成机制以及发光性质等方面进行了一些探索性的研究。 发展了一种简单、整体、没有模板、环境友好的水热方法合成系列稀土氟化物。用有机添加剂柠檬酸钠(Na3C6H5O7•2H2O)作为配位剂和形貌控制剂,通过改变氟源(NaF, NH4F或NaBF4)和最初溶液的pH值,得到了具有不同成分、晶体结构、尺寸和形貌的稀土氟化物,包括二元氟化物LnF3 (Ln = La-Lu)和三元氟化物NaREF4 (RE = Y, Yb, Lu);首次研究了具有各种晶体结构和形貌的含镱(Yb)和镥(Lu)的二元和三元氟化物的可控合成;对各种产物可能的形成机理进行了合理、系统的讨论;并对各种基质中Eu3+, Tb3+掺杂的下转换和Yb3+/Er3+, Yb3+/Ym3+共掺杂的上转换发光性质进行了详细的研究。由于具有优良的荧光性质和可控的形貌和尺寸,这些发光材料可能在光显示、光发射二级管(LEDs)、固体激光器等领域有着潜在的应用价值。这些研究结论不仅丰富了稀土氟化物化学的内容,而且探索了纳米/微米材料的晶体生长规律和形成机理。 采用超声化学途径合成了CaWO4, CaWO4:Eu3+和CaWO4:Tb3+亚微米尺寸的球形荧光粒子,详细讨论了合成材料的结构、形成机理、光致发光、阴极射线发光性质以及能量传递现象,为其它钨酸盐的合成提供了新的思路。

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稀土纳米材料因其独特的光、电、磁和催化等性能,在纳米器件和功能材料等诸多领域具有重要的应用价值。大量研究表明,纳米材料的物理和化学性质与其尺寸、成分、形貌和晶型密切相关。稀土纳米材料的合成方法有许多,然而,要真正实现这类材料的简单可控合成仍然是个艰难的课题。超声化学法由于具有操作简单、合成周期短、反应温度低、成本低廉并且产物均匀、粒径分布窄和纯度高等突出优点,已经在无机纳米材料制备领域中显示出独特的魅力。因此,本论文的工作是运用超声化学法合成有广泛应用前景的稀土纳米材料,对产物的形貌和粒径进行有效的调控,研究和分析其形成机理,并进一步考察其形貌、结构与性能之间的相互关系。 在本论文中,我们研究的体系集中在稀土磷酸盐、稀土氟化物和稀土钒酸盐三类纳米材料。 采用超声化学法得到的CePO4:Tb和CePO4:Tb/LaPO4(核/壳)纳米棒结晶完好,具有CePO4体材料的六方相结构。CePO4:Tb纳米棒直径为10-30 nm,长度为200 nm,CePO4:Tb/LaPO4(核/壳)纳米棒的LaPO4壳的厚度为2-10 nm。CePO4:Tb和CePO4:Tb/LaPO4(核/壳)纳米棒均具有Ce3+ (5d - 4f)和Tb3+ 5D4-7FJ(J = 6-3)的特征发射。与CePO4:Tb纳米棒核相比,CePO4:Tb/LaPO4(核/壳)纳米棒的光谱强度及荧光寿命均有较大的提高,这是由于形成核/壳结构后发光中心镧系金属离子与表面淬灭中心的距离增大,减少了能量传递过程中非辐射复合的路径,使能量淬灭受到抑制。 采用简单、快速、无模板辅助的超声化学法合成了稀土氟化物,并对产物的形貌和粒径进行了有效的调控。通过应用不同氟源(KBF4、NaF和NH4F)选择性合成了具有不同形貌的CeF3纳米材料,如片状、棒状和颗粒状。对具有不同形貌的CeF3样品进行了UV-Vis吸收光谱和荧光光谱测试和比较。研究结果表明不同形貌的样品,它们的光学性质存在很大差异,这说明纳米材料的光学性质与其形貌、粒径、晶体结构等因素有密切的关系。得到的EuF3单晶纳米材料具有三维花状形貌。这些纳米花的外形为球状,平均直径为0.9 μm-1.0 μm,每个花瓣的厚度约为0.14 μm。在其他实验条件不变的情况下,采用搅拌法而不经过超声辐射的对比实验只能得到二维纳米片,这表明超声辐射对花状EuF3的形成起到了至关重要的作用。基于不同反应时间的实验结果,我们提出了这种三维花状EuF3纳米材料可能的形成机理。 采用超声化学法选择性地合成了介孔及棒状CeVO4和纺锤状的YVO4:Eu3+ 纳米材料。CeVO4纳米棒的平均直径为5 nm,长度为150 nm。介孔CeVO4材料的比表面积较高(122 m2•g-1),孔径分布窄,其催化性能有望得到提高。纺锤状的YVO4:Eu3+ 纳米粒子具有四方相锆石结构,其直径为90-150 nm,长度为250-300 nm。超声辐射对样品的形貌起着关键作用,在其他反应条件不变,未采用超声辐射的情况下只能得到团聚严重的纳米颗粒。荧光测试表明,纺锤状YVO4:Eu样品表现为Eu3+ 5D0-7FJ(J = 1- 4)的特征跃迁,以5D0-7F2电偶极跃迁(614nm)为最强峰,属于红光发射。

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本文是以液态铝为阴极,在稍高于铝-钕合金低共晶点的温度下,熔盐电解制备铝-钕母合金。工作内容分两部分:I、在较低温度(660-700℃)下电解NdCl_3-KCl·NaCl熔体及氟化物添加剂对电解的影响,II、NdCl_3-KCl·NaCl-NaF及NdCl_3-KCl·NaCl-CaF_2熔体部分熔度图。本文第一部分,在30重量%NaCl_3-70重量%KCl·NaCl熔体中,首次于700℃下较系统地研究电解制备铝-钕母合金,电流效率达到78%,加机械搅拌时可达90%,大大超过熔盐电解制备金属钕的电流效率(50%)。但是,实验中看出纯氯化物熔体存在着下列缺点:1、造渣较多,2、当阴极电流密度高于0.75安培/厘米~2时,阴极上生成枝状物沉积;虽然机械搅拌能避免枝状物生成,但操作不便,搅拌棒材料不易解决。本工作的重点是通过添加氟化物改善熔体性能,提高电流效率。实验得出:何氯化物熔体添加氟化物,不仅能改善金属在熔体中的凝聚性能;还能增加熔体流动性、减少造渣、提高熔体稳定性,便于电解质的连续使用;特别是能促进Nd~(3+)离子被铝热还原,使Nd~(3+)离子被电化学还原的同时,伴随的化学还原作用加剧了,提高了钕的沉积效率。本工作还确定,多种氟化物均可作为添加剂,添加量为1%左右,便可得到满意的结果,而无需机械搅拌。实验证实,在熔盐电解制备铝-钕合金时,温度是一个重要因素。除电解质的温度外,阴极合金的温度也有影响,二者的温度愈低,愈有利于提高电流效率。当阴极合金温度不高于675 ℃时,电流效率最高。为配合熔盐电解制取铝-钕母合金,还研究了熔盐的部分物理化学性质。Nd~(3+)离子的析出电势测量结果表明,无论在纯氯化物熔体,还是加有少量氟化物的熔体中,钕在液态铝阴极上的析出电势都比在固态钼阴极上的低1伏左右;不论在液态或固态阴极上,也不论于纯氯化物或加有少量氟化物的电解质中,Nd~(3+)离子的析出电势均随其浓度的增加而下降;但氟化钠的加入使钕的析出电势升高了90毫伏。表面张力测量结果表明,氟化钠使熔体表面张力增大。第二部分,绘制了NdCl_3-KCl·NaCl-NaF及NdCl_3-KCl·NaCl-CaF_2两个熔体的部分熔度图。在实际电解所采用的浓度范围,即NdCl_3含量为10~30重量%时,向熔体添加NaF和CaF_2,对体系初晶点有不同的影响:加1%左右的NaF,体系初晶温度即达到最低点,而加CaF_2,需8%左右才能达到最低点。所得熔度图表明,往溶有10~30重量% NdCl_3的KCl·NaCl熔体添加1%左右的NaF或CaF_2,其初晶点均低于645 ℃,均适于作为在较低温度下电解制备铝-钕母合金的电解质。此外,在附录中还综述了熔盐电解铝-钕母合金的有关研究概况和主要研究方向。

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本论文较系统地研究了Naf:on聚合物薄膜冠醚修饰电极阳极溶出伏安法在分析中的应用。首次将Naf:on薄膜冠醚类化合物修饰电极应用于铊、银和铅三种离子的测定,得到了高灵敏度的分析方法亦用于实际样品测定。用涂层法制备了Naf:on聚合物薄膜冠醚(二环已基18-冠-6)化学修饰电极,用这种修饰电极测定金属离子的高灵敏度来源于将Naf:on对大阳离子的强离子交换能力、冠醚类化合物络合金属阳离子形成大阳离子的能力与溶出伏安法的高灵敏度三者的结合,冠醚化合物中性分子可与金属阳离子络合形成大络阳离子:M~(n+)+qC=(MC_q)~(n+) Naf:on膜由于其具有的对大阳离子的强交换能力而将冠醚与和金属离子形成的大阳离子络合并吸附于电极表面,在溶出伏安法的富集过程中,电位置于是以令(MCq)~(n+)还原的位置以使(MCq)~(n+)还原:(MCq)~(n+)+ne=M+qC 析出的零价态的金属可在Naf:on膜内固定,同时又放出冠醚分子成为新的未被占据的络合吸附中心,继续捕获溶液中的阳离子从而起到富集作用。由于使用溶出伏安法排除电极表面络合吸附饱和的问题,从而使本方法灵敏度大大高于一般的使用化学修饰电极进行预富集的分析测定方法。提出了Naf:on薄膜冠醚修饰电极阳极溶出伏安法测定水溶液中Te(I)的方法,在电位为-1.30 Vvs.Ag/Ag ce处0.1高氯酸锂溶液中,用该修饰电极富集30分钟,检测下限可低至2×10~(-12)M(0.4 ppt)。溶液中Te(I)浓度在5×10(-12)M~1×10(-8)M范围内与溶出峰电流成良好的线性关系且通过原点,可以用标准加入法测定。常见共存元素Zn(II),Su(II),Cu(II),Fe(II),Co(II),Ni(II),In(III)等无干扰。Pb(II)与Cd(II)共存时对Te(I)有干扰,同1×10~(-3)M EDTA掩蔽可有消除干扰。测定了合成样品中的Te(I)含量,平行测定七组样品相对标准偏差4.2%。本文法是目前Te(I)的分析中最灵敏的电化学方法之一。提出了Naf:on薄膜冠醚修饰电极阳极溶出伏安法测定水溶液中Ag(I)的方法。在0.01MHNO_3 4~7×10~(-3)M Cl混合溶液中,检测电位在-0.30Vvs.SCE富集30分钟,检出下限可低至2×10~(-12)M,是迄今所见Ag(I)的分析中灵敏度最高的电分析方法。Ag(I)浓度在2×10~(-11)M~1×10~(-8)M范围内与溶出峰电流成良好的线性关系且通过原点。五到十倍量的Hg(II)和Au(II)有干扰。用本法测定了分析纯硝酸铵中的银含量为0.000048%,平行测定七组样品相对标准偏差为3.7%。提出用Naf:on薄膜冠醚修饰电极阳极溶出伏安法测定水样中铅的方法。在0.lMLiNO_3底液中,电位在-1.10Vvs.SCE富庥3分钟检测限达5×10~(-10)M,方法快速灵敏。Pb(II)浓度在1×10~(-9)~1×10~(-7)M范围内与溶出峰电流呈线性关系。1×10~(-6)以上Cu(II)存在使Pb(II)的峰电流时显增加。用本方法测定了自来水样中的铅含量,平行测定七组样品相对标准偏差8.0%。该修饰电极在K~+浓度为1×10~(-5)~1×10~(-7)M范围内对K~+有能斯特响应。本工作为铊、铅、银的痕量分析提供了高灵敏度的方法,为溶出伏安法摆脱汞污染的问题做出了贡献,为化学修饰电极用于分析化学领域提供了新的途径。

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我国江西龙南稀土矿是目前世界上储量最大的富钇稀土矿、研制具有多种用途的钇(Y)-铝(Al)或富钇混合稀土(Ymm)-铝中间合金,对于开拓我国龙南稀土矿的应用领域扩大稀土合金出口具有重要意义。基于这一背景并针对目前氟化物体系制取Ymm-Al合金时存在着电解温度高,腐蚀现象严重,电效偏低等缺点,本文系统开展了在氯化物熔盐体系中电解制取Ymm-Al合金的研究工作。本工作由三部分组成:在第一部分工作中,开展了熔盐电解所需要基本原料-无水稀土氯化物制取的工艺研究。利用化学分析和结构分析手段,弄清了干法氯化过程中YmmCl_3水解的机理,提出了减弱水解的措施,即YmmCl_3先在850-900 ℃灼烧1.5 + 0.2hr,脱掉吸附水并将碱式碳酸盐转化为氧化物,增加稀土氧化物的比表面。通过条件试验得到最佳工艺条件为:采用NH_4 Cl:Ymm_2 O_3 = 14:1(摩尔比)的配料比,每次投入氯化装置的原料量为0.26 - 0.36 kg, 在400-450 ℃氯化反应激烈开始后迅速降温至400 ℃以下,待物料粘结现象消失后,再行升温氯化。出料及后期控制温在475 ± 25 ℃。经过3.8 ± 0.2hr氯化,可制得水不溶物小于1%并符合熔盐电解要求的YmmCl_3原料。此新工艺与原有干法工艺相比,流程短,装置简单,不需密闭抽真空,成本低,适于制取任何量的优质熔盐电解所需氯化稀土原料。在第二部分工作中,利用上述YmmCl_3原料,以液态铝为阴极,在氯化物体系中进行熔盐电解,通过试验得出在小型试验规模制取Ymm-Al合金的最隹工艺条件为:电解质组成(重量比)40%YmmCl_3-1%NaF-59%等摩尔的NaCl-KCl;电解温度为790 ± 5 ℃;阴极电流密为0.7 - 0.02A/cm~2;电解电量为333 ± 5库仑/克铝,制得钇铝合金中Ymm含量为10 ± 2%。添加1%的NaF可消除阴极表面生成枝状物,减少合金中夹渣和熔盐中沉渣。在电解工作中,将方差分析应用于试验数据处理,方差分析结果表明,各种试验因素对电效有明显影响,试验数据可靠,试验误差在允许范围以内。在第三部分工作中,利用线性扫描伏安法测定了在最隹电解工艺条件下Y~(3+)和Ymm在液态铝及钼电极上的析出电位。测定结果表明:Y~(3+)和Ymm~(3+)在液态铝阴极上的析出电位比在钼阴极上偏正0.2 ~ 0.8伏,氟离子的加入要比不加氟时析出电位不有同程度的负移,但考虑到氟离了具有消渣作用,加入少量氟比物添加剂对提高电效有利。

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beta-NaYF4 hexagonal microprisms and microrods with different aspect ratios have been prepared via a simple hydrothermal route. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence (PL) spectra as well as kinetic decays were used to characterize the samples. The influences of reaction temperature and the molar ratio of NaF to y(3+) on the crystal phases and shapes of final products have been studied in detail. The aspect ratios of products increase gradually with the increase of reaction temperature and NaF/Y3+ molar ratio. The growth mechanisms of crystals prepared under the different conditions are presented systematically. More importantly, the systematical investigation on the luminescence properties of beta-NaYF4:xEu(3+) (x = 0.5, 1, 2, 3, 5, and 10 mol %) with hexagonally microprismatic morphology shows the characteristic emissions of Eu3+ (D-5(J)-F-7(J'), J, J' = 0, 1, 2, 3). Under the excitation of single wavelength light of 397 nm, the luminescence colors of the corresponding products can be tuned feasibly from bluish white to yellow to red by changing the doping concentration of Eu3+.

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The nanocrystals of CeF3 with the hexagonal structure and different morphologies such as the disk, the rod, and the dot have been successfully synthesized via a mild ultrasound assisted route from an aqueous solution of cerium nitrate and different fluorine sources (KBF4, NaF, NH4F). The use of different fluorine sources has a remarkable effect on the morphology of the final product. The luminescence and UV-vis absorption properties of CeF3 nanocrystals with different morphologies have been investigated. Compared with other shape nanocrystals, the luminescence intensity of the disklike nanocrystals is obviously enhanced. It is suggested that the function-improved materials could be obtained by tailoring the shape of the CeF3 nanocrystals.

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用X射线座滴照像法测量了铝液-氟化物熔盐间的界面张力。采用曲线拟合液滴轮廓坐标的计算机程序处理座滴图像。用逐步回归分析方法获得了计算熔盐密度值的回归方程。讨论了熔盐中NaF/AlF_3分子比,Li_2CO_3和稀土氧化物含量对熔盐-铝液间界面张力的影响。测量了铝液在熔盐中对石墨、工业碳块以及TiB_2涂层的润湿角。