994 resultados para MG-GD ALLOYS
Resumo:
利用CO_2-TPD法考察了La-Me-O(Me=Mg,Ca,Sr,Ba)系催化剂的表面碱性,并用O_2-TPD、CH_4-TPD法对该体系的表面活性氧种进行了表征,并与催化性能相关联。结果表明,La-Ba-O催化剂由于表面强碱性中心数目多,产生活性氧种的数目也多,有利于甲烷的活化,因而具有最高的甲烷转化率和C_2烃选择性。脉冲反应表明,在无气相氧存在下,表面晶格氧参与了氧化偶联,而且是选择氧化的活性氧种。
Resumo:
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.
Resumo:
The reaction of lanthanide trichlorides with sodium tetrahydrofurfurylcyclopentadienyl in THF afforded bis(tetrahydrofurfurylcyclopentadienyl)lanthanide chloride complexes (C4H7OCH2C5H4),LnCl (Ln = Nd, Gd, Dy, Yb). All of the complexes were characterized
Resumo:
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