稀土对高强Al-Zn-Mg-Cu合金耐蚀性能的影响

采用化学失重法，考察了稀土对Al－Zn－Mg－Cu高强铝合金耐腐蚀性能的影响。研究结果表明，在不同介质中，加稀土的Al-Zn-Mg-Cu比Al-Zn-Mg-Cu高强铝合金有较高的耐腐蚀性能，在还原性介质中的耐腐蚀性更好。稀土含量控制在0．05％为宜。

Activation of a ring methyl substituent in pentamethylcyclopentadienyl rhenium(V) compounds: Synthesis and characterization of the 1,2,3,4-tetramethyl-5,6-dihydrofulvene-5,6-dithiolato complex [ReO{(S)(SCH2)C(5)Me(4)}(C(5)Me(5))]

Reaction of the half-sandwich rhenium(v) complexes [Re-Cl-4(C(5)Me(5))] or [Re(O)Cl-2(C(5)Me(5))] with H2S in chloroform in the presence of pyridine leads to the chiral dithiolato complex [ReO((S)(SCH2)C(5)Me(4))(C(5)Me(5))] 1.

3,4－聚异成二烯的合成及所得聚合物结构与性能表征

近二十多年来，在异成二烯的络合催化聚合中，由Ni、Co、Ti及稀土等过渡金属元素络合物组成的催化体系，研究报道得很多，有些已投入工业生产。但由最常见的过渡金属元素铁络合物组成的催化体系，对异成二烯聚的聚合却不多见。本工作研究了三乙酰基丙酮铁为主催化剂，烷基铝为助催化剂，添加含氮类给电子试剂组成三元体系，对异成二烯聚合的催化作用。Fe(a cac)_3 - Al(i-Bu)_3二元体系不能引起异成二烯聚合，而加入少量的含氮类给电子试剂如邻菲啰啉、α,α'－联吡啶等，催化活性显著提高。聚合活性与含氮类给电子试剂的性质有关，并随着下列顺序依次递减：邻菲啰啉、α,α'－联吡啶、对苯二胺、邻苯二胺，对硝基苯胺、邻硝基苯胺；吡啶和已二胺对催化活性的提高几乎没有贡献。烷基铝的不同对催化活性也有明显的影响。其活性顺序为：Al(i-Bu)_3 approx Al Eτ_3 > Al(i-Bu)_2H。首次合成了结晶的3,4－聚异成二烯，3,4－链节含量为70％左右时，Tm为121 ℃左右， Tc为65 ℃左右，透射电镜下观察到结晶的3,4－聚异成二烯具有球晶状结构。初步研究了铁系三元催化体系的反应机理，设想铁化合物和烷基铝生成的烷基铁必须与含氮类给电子试剂作用才能形成活性中心；可见光谱和催化活性实验数据证实了含氮类给电子试剂参与活性中心的形成，并起着稳定活性中心的作用。本文详细地研究了Fe(a cac)_3 - phen - Al(i-Bu)_3催化体系对异成二烯的聚合，考察了起始单体浓度、聚合温度，催化剂总用量以及催化剂各组分配比对聚合速率、聚合物的特性粘数和链节结构的影响，从实验结果讨论了Fe(a cac)_3 - phen - Al(i-Bu)_3体系催化异成二烯的聚合机理，并进行了一些动力学的基本计算，得到了与实验结果基本相符的结果，解释了一些实验现象。铁系聚异成二烯橡胶的表征工作未见诸文献，本工作对铁系聚异成二烯生胶的结晶、力学、流变及阻尼性能作了较系统的研究，并对硫化胶的物理机械性能，弹性及阻尼性能作了初步的表征。铁系聚异成二烯橡胶在室温具有较好的阻尼性能，并且生热值和冲击弹性均较低，可作为室温阻尼材料使用。

铈对单向凝固Al－3Li合金腐蚀性能的影响

研究了单向凝固Ａｌ－３Ｌｉ－（０～０．７４）Ｃｅ合金在３．５％ＮａＣｌ溶液中的腐蚀行为。结果表明：Ｃｅ可明显提高合金的耐腐蚀性能，细化合金的微观组织，使合金腐蚀源分散、细小，是影响腐蚀性能的主要元素。

［（μ－CF＿3CO＿2）＿2Ln（μ－CF＿3HCO＿2）Al（i－Bu）＿2·2THFl＿2（Ln＝Nd，Y）配合物的NMR和X－射线衍射研究

对［μ－ＣＦ＿３ＣＯ＿２）＿２Ｌｎ（μ－ＣＦ＿３ＨＣＯ＿２）Ａｌ（ｉ－Ｂｕ）＿２·ＴＨＦｌ＿２（Ｌｎ＝Ｎｄ，Ｙ）配合物单晶结构的Ｘ－射线分析指出，配合物具有中心对称性，配位中心由两个稀土和两个Ａｌ离子组成，稀土由两个ＴＨＦ和６个ＴＦＡ分子配位形成畸变的三盖三棱柱结构，Ａｌ由两个ＴＦＡＧ和两个ｉ－Ｂｕ配位形成四面体结构。桥连Ａｌ与两个稀土的ＴＦＡ分子的羧基发生歧化加氢，其碳原子由ＳＰ￣２型转变为ＳＰ￣３型．ＮＭＲ研究表明，在ＴＨＦ溶液中，该配合物保持了它在单晶中的配位结构，所不同的是两个ｉ－Ｂｕ在溶液中有两种异构形成，二者间为慢交换过程。

ISOPRENE POLYMERIZATION WITH (ETA(3)-C3H5)(2)CECL5MG2(TMED)(2)/ALKYLALUMINUM

(eta(3)-C3H5)(2)CeCl5Mg2(tmed)(2) combined with HAl(i-Bu)(2) or Al(i-Bu)(3) can initiate the polymerization of isoprene with about 50% of the cis-1, 4 microstructure contained in the polymer. The insertion reaction of isoprene occurring between Ce3+ and e

AlⅠ及UⅠ原子光电离截面相对论及非相对论理论计算

本文给出了在自洽场近似下,入射光子能量在x射线范围内(132.3～1500eV),使用相对论及非相对论计算AlI及UI原子壳层光电离截面及总截面。讨论了相对论效应及辐射场的多极展开对光电离截面数值的影响。

Al含量对MLNi_(4-x)MnAl_x贮氢电极性能的影响

在稀土镍合金贮氢电极(MH)的研究中,曾报道电解液浓度对MLNia_(3.5)MnCo_(0.4)Al_(0.1)(ML代表富镧混合稀土)电极放电性能的影响。本文报道Al含量对MLNi_(4-x)MnAl_x电极性能的影响,并用循环伏安法对电极反应机理进行了探讨。实验方法同前报。 结果与讨论 MLNi_(4-x)MnAl_x电极性能测试 用100mA/S恒电流将MLNi_(4-x)MnAl_x电极充电至300mAh/g,停充10分钟,再用100mA/g恒电流放电至—0.60V(vs Hg/HgO),得如图1的放电曲线。可见随

多核Nd-Al双金属配合物对丁二烯的聚合——Ⅱ.聚合的一般规律

在从均相稀土Ziegler-Natta催化剂中分离出有双烯聚合活性的Nd-Al双金属配合物的基础上,利用该配合物可在无助催化剂烷基铝存在下单独引发丁二烯聚合的特性,详细研究了活性体、外加烷基铝、单体浓度,温度及时间等变量对聚合的影响;对比了活性体引发聚合与一般Ziegler-Natta催化聚合在一般规律上的异同。以更客观的实验事实论证了烷基铝在聚合过程中的作用,通过聚合产物的GPC测定讨论了活性体聚合中存在的键转移反应,确认外加烷基铝的键转移能力最强。所得结果有助于对稀土催化定向聚合过程的深入了解。

Formation of nano-crystalline corrosion products on Zn-Al alloy coating exposed to seawater

Hot dip Zn-Al alloy coating performs better than hot dip galvanized coating and 55% Al-Zn-Si coating as well with regard to general seawater corrosion protection. A characterization of the corrosion products on Zn-Al alloy coating immersed in dynamic aerated seawater has been performed mainly based on transmission electron microscopy (TEM) for morphological analysis and X-ray diffraction (XRD) technique for crystalline phase identification. The XRD and TEM analyses showed that the corrosion products mainly were typical nanometer Zn4CO3(OH)(6).H2O, Zn-5(OH)(8)Cl-2 and Zn6Al2CO3(OH)(16). 4H(2)O microcrystals. This probably is connected to the co-precipitation of Zn2+ and Al3+ ions caused by adsorption. Zn-Al alloy coating being suffered seawater attacks, AI(OH)(3) gel was first produced on the coating surface. Zn and Al hydroxides would co-precipitate and form double-hydroxide when the concentration of adsorbed Zn2+ ions by the newly produced gel exceeded the critical degree of supersaturation of the interphase nucleation. However, because the growth of the crystals was too low to keep in step with the nucleation, a layer of nano-crystalline corrosion products were produced on the surface of the coating finally. (C) 2001 Elsevier Science Ltd. All rights reserved.

Study on growth factors of intermetallic layer within hot-dipped 25% Al-Zn alloy coating on steel

25%Al-Zn alloy coating performs better than hot dip galvanized coating and 55%Al-Zn-Si coating with regard to general seawater corrosion protection. This study deals with the interfacial intermetallic layer's growth, which affects considerably the corrosion resistance and mechanical properties of 25%Al-Zn alloy coatings, by means of three-factor quadratic regressive orthogonal experiments, The regression equation shows that the intermetallic layer thickness decreases rapidly with increasing content of Si added to the Zn-Al alloy bath, increases with rise in bath temperature and prolonging dip time. The most effective factor that determined the thickness of intermetallic layer was the amount of Si added to Zn-Al alloy bath, while the effect of bath temperature and dip time on the thickness of intermetallic layer were not very obvious.