固-固可逆热致变色膜的制备及性能

制备以溴甲酚绿为电子给体，MgCl2·6H2O为电子受体，聚乙二醇／二醋酸纤维素共混物为熔融性化合物制备了一种固．固可逆热致变色膜，用DSC、UV及XRD对该膜的热致变色性能及热致变色机理进行了探讨。结果表明：选择具有固．固相转变的聚乙二醇／二醋酸纤维素共混物为熔融性化合物能使溴甲酚绿．氯化镁发生热致变色。     

溴甲酚绿-碱土金属离子-十六醇热变色复配物制备及热变色性

制备了溴甲酚绿－碱土金属离子一十六醇热变色复配物。改变原料的配比可以得到一系列不同变色温度的复配物,该热变色复配物具有可逆性好、变色迅速敏锐、变色温度低、稳定性好等特点。用ＵＶ－Ｖｉｓ、ＤＳＣ对复配物的热变色性进行了研究。     

热致变色过渡金属配合物的变色机理及应用

社会的智能化是未来发展的必然趋势。智能材料作为智能化变革的基础，成为了近几年研究的热点。热致变色材料是一种智能变色材料，可以随着外界温度的改变发生颜色变化，被广泛应用于智能窗、温度传感、防伪、智能纺织、变色涂料等领域。热致变色材料的种类繁多，其中过渡金属配合物热致变色材料通常变色温度较低、变色现象明显并且拥有较独特的电子传递特性，具有良好的应用前景，受到了研究者的广泛关注。在热致变色过渡金属配合物发展初期，科学家们主要研究的是配合物的结构和变色机理，关于配合物应用方面的研究很少，这主要是由于热致变色过渡金属配合物自身具有缺陷(如摩尔吸光系数低、变色需要溶剂等)。在最近十几年，科学家们通过各种方法手段增加热致变色过渡金属配合物的实用性，例如使用离子液、新型配体以及与其他功能材料复合等手段，使热致变色过渡金属配合物在各个领域的应用都取得了很大进展，但相关综述还较少。只有掌握热致变色材料的变色机理，才能更好地设计符合不同应用场景的热致变色材料，本文首先对热致变色过渡金属配合物的变色机理进行介绍，常见变色机理包括构型变化、配体改变、自旋交叉，然后归纳总结了最近几年热致变色过渡金属配合物在温度传...     

超低温热致变色复合物的制备与微胶囊包封研究

为了拓宽低温可逆热致变色材料变色温度和变色时间的范围,以聚乙二醇400(PEG400)为辅剂,十二醇等为隐色剂,变色母料为显色剂,无水乙醇为溶剂制备了超低温热致变色复合物;采用原位聚合法制备了以阿拉伯树胶为壁材,热致变色复配物为芯材的微胶囊,并对其进行显微结构、粒径、变色温度和变色时间等方面的测试与分析。结果表明:使用十二醇时,变色温度为5~15℃,变色时间为210s,颜色按照深蓝-蓝色-浅蓝的顺序变化。聚氨酯的引入使变色膜变色温度下降,但降幅较小,可以起到保温隔热的作用。微胶囊化后材料具有优良的耐疲劳性能,还扩展了变色材料的应用领域。     

溴甲酚酯类复配物制备及其热变色性能的研究

制备了溴甲酚紫-硼酸、羧酸及其衍生物系列热变色复配物,考察其配比、填料的种类与用量、光照、高温等因素对其热色性能的影响.研究结果表明,以硼酸作显色剂,适合选用A12O3或硅胶为填料,当溴甲酚紫、硼酸、填料质量比为1:100:100～250时,变色效果好,由黄色变到粉红色,变色温度为110℃左右,复色时间小于60s;以羧酸类为显色剂,适合选用十六醇为填料,溴甲酚紫、显色剂、十六醇的质量比为1:1:10～1:4:40,变色效果好,由红色变成黄色,变色温度在40℃左右,复色时间小于100s.     

金属表面配合物保护膜述评(Ⅱ)——银的防变色配合物膜

银镀层存放和装机2～3个月后就会发生变色,降低银层的性能.分析了银层变色的原因,提出了相应的无铬防银变色工艺,介绍了其防变色效果,并对防变色配合物膜的性能、组成和结构进行了研究.     

单分散Eu3+-co-PMMA共聚荧光微球的制备及性能研究

通过乳液聚合的方法,将具有双键的稀土铕配合物与甲基丙烯酸甲酯单体共聚,得到具有稀土特征荧光的单分散微球。采用红外光谱仪(IR)、扫描电子显微镜(SEM)、X射线粉末衍射仪(XRD)对产物的形貌进行分析,结果表明共聚微球粒径均一性较好;借助同步热分析(STA)研究了产物的热性能,紫外光谱仪(UV)和荧光光谱仪测试了产物的光学性能,结果表明共聚微球具有稀土(Eu~(3+))的特征光学性质,并且通过改变稀土配合物含量,可以改变共聚微球的荧光强度。     

Schiff碱稀土配合物以共价键连接方式组装到介孔块体材料的研究

将3-氨丙基三乙氧基硅烷(APTES)与水杨醛在室温下合成有机配体,用于与稀土离子(Tb3+、Sm3+、Dy2+)配位,制得了3种稀土有机配合物.用"后合成法"将稀土配合物以共价键结合的方式连接到以硅基介孔块体为主体的材料上得到组装材料.通过红外光谱、元素分析、BET分析及荧光光谱分析对稀土配合物及其组装材料的组成、结构及性能进行了表征.结果表明,与纯配合物相比,在组装体材料中(Tb3+、Sm3+组装)有机配体的发射峰强度变弱,而稀土离子的特征发射峰强度变强.这表明在组装体材料中从有机配体到稀土离子的能量传递变得更加有效.     

2,2,2-胺三乙酰二苄胺及其稀土配合物的合成、表征与荧光性质

为研究三脚架型配体稀土配合物的组成、可能的配位状态及荧光性质,合成了三脚架型配体--2,2,2-胺三乙酰二苄胺(L)及其6个稀土配合物.通过红外光谱、核磁共振波谱、元素分析、差热-热重分析、摩尔电导率及荧光光谱等方法对L及其稀土配合物的组成及性质进行了表征.结果表明, L能够与稀土离子配位,生成n(RE)∶n(L)=1∶1的配合物;Tb(Ⅲ)配合物在紫外光激发下,在490nm、545nm、590nm、620nm附近出现强度不同的Tb3+特征荧光发射峰,分别归属于Tb3+的5D4→7F6、5D4 →7F5、5D4→7F4、5D4→7F3能级跃迁;而其Eu(Ⅲ)配合物的荧光发射微弱,其它配合物没有荧光发射.说明L的三重态能量与Tb3+最低激发态能级匹配较好,能起到较好的敏化作用,提高Tb3+的发光强度.     

SiO_2凝胶玻璃中Eu~(3+)、Tb~(3+)与1,10-邻菲罗啉配合物的原位化学合成及其荧光和热学性能

应用原位化学复合方法，将Eu3＋、Tb3十与1；10-邻菲罗啉配合物光学均匀复合到SiO2凝胶玻璃中，解决了因稀土含氮配合物易水解而难以用溶胶-凝胶工艺将其均匀掺入无机基质的问题研究了原位配合物的荧光和热学性能结果表明，由于配合物的形成使稀土离子特征荧光强度显著增加，而无机基质的保护作用则使原位配合物的热稳性提高200℃以上化学合成纯配合物Eu（Phen）2Cl3·2H2O的高分辨荧光谱表明，Eu3+在其中的格位对称性为C1或C2或C3．     

Crystal field effects in the anomalous Hall coefficient

The anomalous Hall coefficient is calculated for rare earth ions in cubic matrices, including crystal field effects and virtual boundd states associated with the rare earth ions. The results suggest that the temperature dependence of the Hall coefficient should follow the ionic susceptibility and thus be sensitive to modifications in temperature dependence of the susceptibility due to crystal field effects. The validity of this result is tested using available results for rare earths in noble metal hosts.Supported by the Ministère de l'Education de Québec and the National Research Council.     

Refinement of Cast Microstructure of Hypereutectic Al-Si Alloys Through the Addition of Rare Earth Metals

Microstructural observation and thermal analysis of Al-21 wt % Si alloys with different rare earth metals were performed to examine the effect of rare earth metal on the refinement of primary silicon phase. Simultaneous refinement of both primary and eutectic silicon morphology is achieved with the addition of rare earth and its effect increases with the amount of rare earth addition and cooling rate. Depression of 12–17 °C in primary reaction temperature and 2–7 °C in eutectic temperature is measured with the addition of rare earth. Rare earth bearing compounds were not believed to act as a nucleation agent of primary silicon phase. Some rare earth bearing compounds determined to AlCe were around primary silicon in the matrix. The twin density of eutectic silicon remains same regardless of the addition of rare earth. The refinement of silicon in rare earth treated hypereutectic Al-Si alloys is supposed to be due to the suppression of the nucleation temperature of silicon phase.     

Preparation and magnetic property of new rare earth compounds R2GeBe2O7 (R = La,Pr, Sm,Gd, Dy,Er) and Y2GeBe2O7

New rare earth compounds which are isostructural with silicate minerals of the melilite family have been prepared. The cell dimensions vary linearly with the radii of rare earth ions, showing a typical Lanthanoid contraction. Magnetic susceptibilities of the rare earth compounds were measured in the temperature range from 77 K to 1000 K. A trend toward weak ferromagnetism with decreasing temperature was observed in the heavy rare earth compounds.     

Magnetodielectric properties of rare earth metal-doped BiFeO3 nanoparticles

Pure and rare earth metal ions (Gd³⁺, Tb³⁺, Dy³⁺)-doped BiFeO₃ nanoparticles have been synthesized by the sol–gel method. The effect of doping of rare earth metal ions on structural, magnetic, dielectric and magnetodielectric properties of synthesized nanoparticles have been investigated. Synthesized nanoparticles have been found to be possessing spherical morphology, with average particle size, 25–46 nm. Structural study confirms that 15 % mole fraction doping of the rare earth metal ions results in structural transformation from rhombohedral to orthorhombic phase. Magnetic study reveals that the synthesized nanoparticles exhibit well saturated ferromagnetic magnetic loops. Dielectric measurements show that doping of rare earth metal ions results in high dielectric constant as compared to that of pure BiFeO₃. Magnetoelectric coupling in the synthesized nanoparticles, established by performing magnetodielectric measurements, reveals that the doped nanoparticles exhibit high magnetodielectric coefficient as compared to its pure form. The high value of saturation magnetization, 5.22 emu/g, dielectric constant, 900 and magnetodielectric coefficient, 5.82 %, have been observed in Dy-doped BiFeO₃ nanoparticles. The observed trend in the properties of the synthesized nanoparticles has been explained on the basis of doping as well as size of the synthesized nanoparticles.     

具可变价态稀土氧化物对Mg2Ni合金储氢性能的催化作用

采用球磨法制备Mg2Ni-Ni-5%RExOy(CeO2,Nd2O3,Tb4O7)复合材料。通过XRD,SEM,面扫描能谱分析,电化学及动力学测试系统研究材料的组织及储氢性能。结果表明:添加稀土氧化物后复合材料的结晶程度降低,稀土氧化物催化剂在合金表面分布均匀。复合材料的最大放电容量明显提高,含Tb4O7样品室温下最大放电容量达871mAh·g-1,且具有较高循环稳定性。CeO2及Tb4O7催化剂可有效提高合金电极表面电荷转移能力,增大氢原子在合金内部的传输速率。稀土氧化物催化剂还可提高复合材料的气态吸氢容量,其中含Tb4O7样品的吸氢量最高,在250℃时吸氢量达到2.02%(质量分数),但在较低温度时吸氢速率稍慢。稀土氧化物的催化作用主要与稀土离子的变价特性有关,离子的易变价性越强,则催化活性越高。催化活性由大到小的顺序为Tb4O7>CeO2>Nd2O3。     

无机为主无铬复合钝化的综合对比研究与展望

基于镀锌层表面无铬钝化技术,从钝化膜性质、钝化液稳定性和成膜耐蚀机理3大方面,总结了以硅酸盐、钼酸盐、钛盐以及稀土金属盐为主要成膜物质的4种复合钝化体系的优缺点,认为耐蚀性最优的体系为硅酸盐体系;对比了各体系钝化液稳定性的差异及不同影响因素,总结了不同体系的相应改善方法,认为硅酸盐体系稳定性最好.阐明了硅酸盐、钼酸盐和...     

新型螯合纤维在金属离子富集分离中的应用

近年来,螯合纤维在金属离子的提取、分离、分析等方面的研究成为分离科学领域的研究热点。螯合纤维对金属离子具有很强的吸附性和高的选择性,可以用于放射性金属、贵金属、过渡金属和稀土金属离子的回收、富集和分离等方面。为了进一步提高螯合纤维的吸附性和选择性,众多学者对如何制备出性能优良的螯合纤维进行了大量的研究工作。综述了近年来新型螯合纤维的制备和吸附性能。     

Nanocrystalline tetragonal zirconium oxide stabilization at low temperatures by using rare earth ions: Sm and Tb

Zirconium oxide was synthesized by the sol–gel method and the tetragonal structure was stabilized up to 1000 °C by doping with different rare earth ions. The evolution of the crystalline structure as a function of the annealing temperature and rare earth concentration of doped and undoped samples were investigated by X-ray diffraction. Our experimental results show that it is possible to obtain up to 73 wt.% of tetragonal content by doping the ZrO₂ with 2 mol% of Sm₂O₃ or Tb₂O₃ and annealing at 1000 °C. Variations in the lattice parameters and nanocrystallite size were also obtained. Our results suggest that the stabilization of tetragonal structure can be obtained with other rare earth ions.     

稀土元素对低合金高强度钢焊缝机械性能的影响

通过改变焊条药皮中的重稀土含量,向焊缝过渡不同含量的重稀土以提高焊缝的机械性能。研究结果表明,通过向焊缝金属过渡微量的稀土元素,可以对焊缝金属起着净化和变质的作用,同时由于稀土元素对焊缝金属中的夹杂物的细化,球化作用,增加了焊缝中针状铁素体的数量,提高了焊缝的低温冲击韧性,     

Stark level analysis for Er-doped ZBLAN glass

From the absorption and emission spectra recorded in a conventional way at 13 K, the Stark levels in manifolds from ⁴I_15/2 to ²H_9/2 for Er³⁺-doped ZBLAN (ZrF₄–BaF₂–LaF₃–AlF₃–NaF) glass have been investigated by means of the effective crystal field model previously proposed to describe the average of local symmetries occupied by rare earth ions in oxide glasses [1]. This model, based on the principle of descending symmetry, used the symmetry group chain scheme. Crystal field strength, homogeneous and inhomogeneous widths of levels have been determined, and the former models and results about optical properties for rare earth ions in heavy metal fluoride glasses are discussed. In fluoride glasses, the rare earth ions appear more evenly distributed than in oxide glasses, and the crystal field strength is weaker than in oxide glasses.