Fundamental aspects of NOx adsorption on BaO

The nature of NO₂ and nitrite/nitrate pairs adsorbed on BaO has been studied within the density functional theory. Size effects are investigated by comparing results for the BaO molecule, BaO clusters [(BaO)_x, x = 4, 6, 9, 12] and BaO(1 0 0). The adsorption energies show weak dependence on size, which is a manifestation of the fast size convergence of the BaO electronic structure and the local character of the NO₂ adsorption bond. Nitrite/nitrate pair formation is associated with a significant energy gain. For BaO(1 0 0), the stability of the pair is insensitive to the nitrite-nitrate separation, a finding that demonstrates a surface mediated non-local mechanism of molecular pair formation on oxide surfaces. The results have implications for the understanding of NO_x storage and reduction catalysts.     

Synthesis and Raman study on needlelike silicates in ancient Chinese Pb‐Ba glass in Qin and Han dynasties

Two ancient green Chinese Pb‐Ba glass (Qin and Han dynasties) were studied with Raman microspectroscopy, scanning electron microscopy, and energy dispersive X‐ray spectrometry. Some needlelike silicates were found in the samples and inferred as BaSiO₃, BaSi₂O₅, and PbSiO₃ according to the results of energy dispersive X‐ray spectrometry analysis. Then BaSiO₃, BaSi₂O₅, and PbSiO₃ were synthetized in laboratory in order to obtain their Raman spectra. Through comparative study, the needlelike silicates in the ancient Pb‐Ba glass samples were proved to be PbSiO₃, BaSiO₃, and Al₂O₃. According to the ternary phase diagram analysis, a mechanism of local element enrichment was put forward for the barium silicate needlelike silicates (by‐products) formation in the ancient Pb‐Ba glass. Copyright © 2014 John Wiley & Sons, Ltd.     

Pt-Rh型三效催化剂中BaO的作用

研究了以浸溃法制备的以BaO为助剂的Pt-Rh型三效催化剂对C3H8，CO，NOx的三效催化活性。主要考察了BaO不同的添加方式对催化剂三效转化活性的影响，并对催化剂样品进行了XRD，H2-TPR和O2-TPD表征。结果表明：BaO的添加方式的不同，直接影响催化剂的活性。特别是Ba与Ce，Zr以共沉淀的方式形成CeO2-ZrO2-BaO固溶体，可促进催化剂在低温时的水汽转换反应，显著降低了催化剂的起燃温度。     

BaO对Pd/Al2O3催化性能的影响

以 Pd(C2 H3O2 ) 2 为前身 ,制备了系列 Ba O- Al2 O3复合氧化物负载钯的催化剂 .用质量滴定法 ,测定了复合载体的零电荷点 (pzc) .结果表明 ,体系的 pzc随 Ba O含量的增加而增大 ,在 5 %～ 10 %之间存在一拐点 ,并与XRD所测 Ba O在 Al2 O3上的单层分散阈值相对应 .复合载体在制备中发生固相反应 ,所生成的 Ba Al2 O4可以阻止 Al2 O3的相变 ,并极大地提高载体的热稳定性 ,其中 5 % Ba O的作用最为明显 .Ba O的引入 ,增强了 Pd/Al2 O3对 CO的氧化能力 ,同时 ,提高了其热稳定性     

溶胶-凝胶法制备BTN陶瓷材料及其性能研究

采用溶胶0凝胶法制备BTN前躯体,用XRD,IR和TEM等方法对粉体的结构和形貌进行了表征,采用等静压工艺将粉体成型,进行常压烧结,结果表明,粉体含有的团聚较少,粒径在30nm左右,至800℃时,晶体结构已经完全形成,主晶相为Nd2Ti2O7,与固相法相比,其成瓷范围宽（1270－1410℃）,介电常数（ε）稳定,介质损耗(tgδ)小。     

Physical foundations of the oxide cathodes

A novel explanation of the low values of work function in case of activated (partly deoxidized) polycrystalline oxides of alkali and alkaline earth metals is offered. Use of the metallic plasma model to the conducting oxides leads to the following values (in eV): 1.00, 1.67, 1.50, 1.44, 1.46 and 1.59 for activated Cs₂O, CaO, SrO, BaO, Y₂O₃ and La₂O₃, respectively. The main reason of low work function of the oxide cathodes is very low density of free electrons in the emitting surface layer.     

钡改性对Cr_2O_3/Al_2O_3催化剂异丁烷脱氢性能的影响

采用浸渍法制备了不同BaO负载量的Cr_2O_3/Al_2O_3催化剂,利用XRD、BET、NH3-TPD和O2-TPO等表征方法对钡改性前后的催化剂进行了分析;在反应温度560℃、反应压力0.1MPa、催化剂用量10mL、GHSV=400h-1的条件下,在固定床反应器上考察了其异丁烷脱氢反应的性能。结果表明,钡的引入影响了活性组分Cr2O3的分散,导致了催化剂比表面积的降低,但影响并不显著;钡的引入降低了催化剂表面的酸性、减少了反应过程中催化剂的积炭,改善了催化剂的选择性,提高了催化剂的稳定性。当BaO负载量为3%时,催化剂的性能最佳。     

Reaction Mechanism of the Exchange Reaction between CuCl and BaO Studied by Time-Resolved X-ray Absorption Spectroscopy

The solid state reaction 2CuCl+BaO→Cu₂O+BaCl₂ has been examined in situ using energy-dispersive X-ray absorption fine-structure spectroscopy (DXAFS). A high time resolution on the order of seconds between two Cu K-XANES spectra has been achieved by this experimental setup. The spectra suggest that the transformation of CuCl to Cu₂O is preceded by an unidentified, intermediate state. Fingerprint methods as well as principal component analysis have been applied, which confirm the formation of exactly one new intermediate phase. The nature of this phase remains unidentified and could not be elucidated by the experimental investigations.     

The surface structure of BaO on Pt(1 1 1): (2 × 2)-reconstructed BaO(1 1 1)

The surface structure of BaO(1 1 1) has been determined using STM and computer modelling. The BaO(1 1 1) surface was prepared in thin film form on Pt(1 1 1) and presents a surface with twice the lattice parameter expected for that of the bulk termination, i.e. a (2 × 2) reconstruction. Computer modelling indicates that the bulk termination is unstable, but that the (2 × 2) reconstructed BaO(1 1 1) surface has a low surface energy and is hence a stable surface reconstruction. The (2 × 2) reconstruction consists of small, three-sided pyramids with (1 0 0) oriented sides and either oxygen or barium ions at the apices. Less regular surface reconstructions containing the same pyramids are almost equally stable, indicating that we may also expect less regular regions to appear with a fairly random distribution of these surface species. The simulations further suggest that a regular (4 × 4) reconstruction built up of bigger pyramids is even more energetically favourable, and some evidence is found for such a structure in the STM.