980 resultados para Sr (x) Ba (1-x) SnO3 e BaSnO3
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合成了具有磁铅石结构的Sr1-xLaxNiAl11O19系列催化剂,并用XRD、UV-DRS、H2-O2滴定及Py-IR等方法对其体相及表面性质进行了表征.结果表明,La3+离子能够同晶取代Sr2+离子进入催化剂晶格内部;随着La3+含量增加,催化剂的结晶度提高,从而降低了镍的还原性,并使金属镍在表面上的分散度略有提高;在SrNiAl11O19中掺入La3+离子,能够抑制晶体沿c轴方向的生长,提高其比表面积;同时La3+离子对Sr2+离子的调变,减少了表面的酸中心数目
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对具有磁铅石结构的Sr1-xLaxNiAl11O19对甲烷与二氧化碳重整反应的催化活性、积炭量和稳定性进行了研究.不同还原温度下催化剂的XRD和催化活性的实验结果表明,金属镍是CH4+CO2重整反应的活性组分,金属镍含量越大,反应活性越高.反应后催化剂积炭量的分析结果说明,在相同镍含量和分散度的情况下,La3+离子对Sr2+离子调变,可以降低催化剂的表面酸性,提高催化剂的抗积炭能力.LaNiAl11O19是一种具有较好催化活性、稳定性和抗积炭性能的催化剂.
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用溶胶-凝胶法合成了系列钙钛矿结构的BaCe1-xRExO3-0.5x(RE=La,Nd,Sm,Eu,Gd,Dy,Ho,Er和Y)复合氧化物,通过XRD和热分析对样品结构及生成过程进行了研究.测定了不同温度下样品的交流阻抗谱,讨论了稀土离子掺杂对BaCeO3电性质的影响.溶胶-凝胶法比固相反应法合成温度降低了600~800℃,稀土掺杂使BaCeO3离子导电率提高了10~40倍.
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Pr~(3+)离子的能级结构丰富,在紫外可见区有很好的荧光发射。因此,以Pr~(3+)为激活离子的发光材料研究工作引起了人们的关注。轻稀土五磷酸盐晶体结构为单斜晶系,空间群为P_(1/2)/C,稀土离子处在隔离的多面体中,离子间的作用减弱,即使在化学计量比的PrP_5O_(14)仍得到激光输出。本文采用水热法生长出La_(1-x)Pr_xP_5O_(14)
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KMF3(M = Mg, Ca, Sr, Ba) compounds were synthesized by solid state reaction under argon atmosphere. Their structures were determined by X-ray diffraction. It belongs to cubic system with perovskite structure. The excitation and emission spectra of KMF3:Ce3+ were measured. According to the characteristics of spectral structures, the occupation site of Ce3+ is discussed.
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二酚(邻苯二酚,对苯二酚)是重要的化工原料,二酚生产一直是人们所关注的课题,70年代以前主要采用的一些污染严重的生产过程正被逐渐淘汰。目前,利用过氧化氢和苯酚为原料联产邻苯二酚和对苯二酚,在化工生产中占有重要的地位。常见的催化剂有等。但这些催化剂也具有明显的不足之处,前两者具有均相催化反应本身难以克服的缺点,后者虽具有多相催化过程的优点,但由于此类催化剂难以制取,而且此类催化剂主要反应孔道的孔径较小(<0.9 nm),反应物和生成物难以在孔道中扩散,使得反应速度较慢。当前国际上还正在积极寻找新的催化体系以达到高效无污染生产二酚的目的。
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Two systems of La2-xSrxCuO4+/-lambda and La2-xThxCuO4+/-lambda, mixed oxides with K2NiF4 structure were synthesized. The compositions and structures of the catalysts were characterized by means of XRD, XPS, chemical analysis and so on. The catalytic behavior for the direct decomposition of NO has been investigated. The results show that the catalytic activity is closely related to the oxygen vacancy and lower valence metallic ion in the direct decomposition of NO. The presence of oxygen vacancy is necessary for mixed oxide to have steady activity in NO decomposition.
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A series of samples having the composition of La2-xSrxNiO4(0 less than or equal to x less than or equal to 1) were prepared and used as catalysts for NH3 oxidation. It was found that the La and oxygen vacancies exist in the La2-xSrxNiO4-lambda(0 less than or equal to x less than or equal to 1). The unit cell volume decreases with the increase of x. For bath c and a parameters there appeared a turning point at x = 0.5. Doping with a lower valence cation Sr2+ in the case of La2NiO4 resulted in an increase of Ni3+, consequently the formation of oxygen vacancies, the increase of reducing ability and the increase of catalytic activity. In the oxygen TPD of La2-xSrxNiO4(0 less than or equal to x less than or equal to 1) appeared three peaks, the alpha' peak at about 400K was attributed to the surplus oxygen desorption, the a peak at 700K which approaches to a maxium at x = 0.6 was attributed to the oxygen adsorbed at oxygen vacancies. The beta peak at about 1000K which depends closely on the x and favors the catalytic activity was attributed to the reduction of Ni3+. The catalytic activity of La-2-x SrxNiO4 mixed oxides in the NH3 oxidation in general could be attributed to the extent of the redox reaction: 2Ni(2+) + O-2 + V-0(..) reversible arrow 2Ni(3+) + 20(-) where V-0(..) representes the oxygen vacancies and O- the oxygen species adsorbed at the vacancies.
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The compounds O(CH2CH2C5H4)(2)Ln(THF)(2) [Ln = Sm(1), Yb(2)] were synthesized by the reduction of O(CH2CH2C5H4)(2)LnCl with sodium metal in tetrahydrofuran (THF) at room temperature. Recrystallization of 2 from dimethoxyethane (DME) produced the single-crystal O(CH2CH2C5H4)(2)Yb(DME) (3) whose structure has been determined by an X-ray diffraction study. The crystals are orthorhombic, space group Pcab, with a = 14.168(4), b = 13.541(6), c = 19.314(8) Angstrom, Z = 8, D-calc. = 1.66 g cm(-3).
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铬离子取代对LaGa_(1-x)Cr_xO_3性质的影响杨健美,苏锵(中国科学院长春应用化学研究所稀土化学与物理开放实验室长春130022)关键词铬离子,取代,LaGa_(1-x)Cr_xO_3,镓酸镧,稀土化合物含过渡元素的ABO3型复合氧化物的许多性质...
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The redox potential, surface composition and oxygen species of a series of complex oxides LaMn1-xFexO3 (x=0-1) having perovskite structure (ABO(3)) have been investigated by means of XI'S. The variation of binding energies referring to Mn2p and Fe 2p under different treatment offerred an obvious evidence of redox between Mn and Fe, which could be expressed as Mn4+ + Fe(3-delta)+ Mn(4-delta)+ Fe3+ Feat Through computer fit three kinds of adsorbed oxygen species (O-I, O-II, O-III) have been evaluated based on the XPS spectra of O1s. From the variation of contents of different oxygen species, it could be concluded that. the redox occuring in the surface might be related with the adsorbed oxygen species O-I and O-II, furthermore the possibility of transfer of electron between adsorption site and oxygen was also discussed.
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用固相反应法合成了三个新的交生相氧化物:Sm_2SrCo_2O_7,Gd_2SrCO_2O_7和Sm_2BaCo_2O_7.它们均具有Sr_3Ti_2O_7型的结构,其中Sm_2BaCo_2O_7属于正交晶系,其它属于四方晶系.与LnSrCoO_4相比,Ln_2SrCo_2O_7(Ln=Sm,Gd)中CoO_2平面上的Co-O键缩短,电子离域化趋势增强,导电能力提高.在300~1100K之间,电阻率与温度关系表明,五个氧化物均表现弱定域系统的特性. 300~1100K之间的磁化率与温度关系表明,在较低温度下,GdSrCoO_4和Gd_2SrCo_2O_7符合Curie-Weiss定律,但前者的CoO_2平面上的磁交换作用是反铁磁性的,而后者是铁磁性的;含Sm~(3+)的三个氧化物表现出较为复杂的磁性质,这可能与Sm~(3+)离子磁性质的复杂性有关.
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用XPS方法研究了具有ABO3结构的LaMn1-xFexO3(x=0-1)氧化物的氧化还原性能、表面组成和吸附氧种.样品经还原和再氧化处理后,Mn2p和Fe2p结合能的变化对Fe和Mn之间发生的氧化还原提供了明显的证据.可表示如下:Me4++Fe(3-δ)→Mn(4-δ)++Fe3+通过计算机用三种氧物种(OⅠ,OⅡ和OⅢ)对O1s峰进行拟合,确定了每种氧物种的状态.同时,以氧物种含量随还原、再氧化的变化,确定了发生在表面上的氧化还原反应同OⅠ和OⅡ吸附氧物种有关.在此基础上,对吸附位与氧之间的电子转移过程进行了讨论.
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本文报道9种新的含磷杂环化合物的电子轰击质谱(EIMS),并应用B/E、B2/E联动扫描及精确质量测量技术,探讨了该类化合物的质谱断裂机理,发现骨架重排及开环反应是该类化合物主要的质谱特征,而R2基因对重排过程有很大影响。
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Three new oxides Sm2SrCo2O7, Sm2BaCo2O7 and Gd2SrCo2O7 have been successfully synthesized by a solid state reaction method.The X - Ray diffraction spectra show that they are all isostructural with Sr8Ti 2O7, Ln2SrCo2O7(Ln=Sm, Gd) crystallized in the tetra