NaLn(WO_4)_2晶体的研究(Ln=La,Pr,Nd)

用助熔剂缓冷法从Na_2WO_4—LiCl熔体中生长出NaLn(WO_4)_2(Ln=La,Pr,Nd)晶体。化学组成分析证明了所得晶体是NaLa(WO_4)_2、NaPr(WO_4)_2和NaNd(WO_4)_2。测定表明该类晶体属白钨矿型结构,四方晶系,空间群I4_1/a。计算了它们的晶胞参数,发现随着稀土元素(La、Pr、Nd)原子序数的增加,Ln~(3+)离子半径减小,Ln—O键长呈规律地递减,NaLn(WO_4)_2晶体的晶胞体积减小。测定了晶体的红外光谱和NaPr(WO_4)_2的激发光谱和荧光光谱。

Nd(C_8H_(11))Cl_2·3THF-R_3Al对丁二烯聚合的催化活性

Nd(C_8H_(11))Cl_2·3THF与不同烷基铝〔Et_3Al,i-Bu_3Al,HAl(i-Bu_2)〕组成的催化体系可催化丁二烯聚合。实验结果表明,催化剂活性取决于所用的烷基铝、铝钕比和催化剂用量,而溶剂对催化活性影响不大。聚合物的微观结构则不受烷基铝种类、溶剂、铬钕比和催化剂用量的影响,均可得到高顺式(97—98％)聚丁二烯。

中性芳烃稀土有机配合物的合成、结构及性能研究——Ⅲ.RE(C_6H_6)(AlCl_4)_3C_6H_6(RE=La,Nd)的合成及Nd(C_6H_6)(AlCl_4)_3C_6H_6的晶体结构

将加热活化的AlCl_3与三氯化稀土在苯溶液中反应,合成了2个新的轻稀土中性芳烃配合物RE(C_6H_6)(AlCl_4)_3C_6H_6(RE=La或Nd)。并用元素分析和红外光谱对其进行了表征。测定了含Nd配合物的晶体结构。对2个配合物结构的比较表明,中心金属离子对配合物的结构无明显影响,其键参数的差别主要来自“镧系收缩”。

La和Nd在其氯化物熔体中的电化学腐蚀

稀土金属在其氯化物熔盐中的自腐蚀是导致电解制备稀土金属时电流效率降低的一个重要原因。但由于实验技术上的困难,有关这方面的研究报道不多。本文将在水溶液体系中常用的电化学弱极化测量腐蚀速度及电化学参数的方法用之于La、Nd在其氯化物熔盐体系中的腐蚀,表明同样适用。

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。

由氯化稀土体系获得的Nd-Al双金属活性体的组成及其定向聚合活性

研究了从三氯化钕甲基磷酸二仲辛酯配合物(NdCl_3·3p_(350))与烷基铝(AlR_3)反应体系中分离出的Nd-A]双金属活性体的组成及其定向聚合活性。由Ndcl_3·3P_(350)-Al[(CH_2)_7-CH_3]_3及Al(C_2H_5)_3体系所得活性体的激光拉曼光谱发现,该活性体中存在稀土—碳键,可能的组成为Nd-(CH_2)_7CH_3及Nd-CH_2CH_3。这是稀土催化体系中存在稀土烷基化反应的直接证据。据此提出了一个可能的活性中心形成过程。实验结果表明,无需AlR_3存在,单独使用上述活性体即可引发双烯烃聚合,并具有较高的活性和高的定向性。

激光晶体YAG中Er~(3+)的辐射跃迁

本文讨论和分析了激光晶体YAG中Er~(3+)离子的激光上能级的~4S_(3/2)、~4I_(11/2)和~4I_(13/2)辐射跃迁的有关因素。

多核Nd-Al双金属配合物对丁二烯的聚合——Ⅰ.聚合物的分子量与微观结构间的关系及其聚合机理的讨论

在从均相稀土催化剂中分离出有聚合活性的Nd-Al双金属配合物的基础上,利用该配合物可单独引发丁二烯聚合的特点,较详细地研究了活性体浓度,外加烷基铝浓度,单体浓度以及聚合温度等因素对聚合产物分子量及微观结构的影响,确认二者之间存在着一定的内在联系,即分子量越高,顺式含量也越高;反之,分子量越低,顺式含量也越低。对此,本文提出了增长链对聚合过程起反作用的观点,从聚合机理的角度给予了解释。

Ln_xYb_(1-x)Ba_2Cu_3O_(7-δ)(Ln=La 或 Nd)的结构和超导电性的研究

本文系统地研究了轻稀土元素 La、Nd 等部分取代 YbBa_2Cu_3O(7-δ)化合物中的 Yb 对结构和超导电性所产生的影响。少量(约0.1摩尔比)轻稀土元素可有效抑制 YbBa_2Cu_3O(7-δ)化合物中杂相的生成,提高体系中 Cu~(3+)/Cu~(2+)之值。

Nd-Fe-B-Si合金的研究

为了探索提高Nd-Fe-B磁性材料的居里温度T_C,我们采用了与文献不同的组成和制 条件,研究了Si对合金的物相、T_C等的影响,得出Nd-Fe-B-Si是一种有希望的非钴高居里温度合金体系. 试样系以钕铁、硅铁、硼铁和还原铁粉为原料,按 Nd_(15)Fe_(77-x)Si_xB_8(x=4、8、16、18 at％)配比,在石墨电阻炉内于Ar气保护下熔炼而成.T-σ曲线在日本MB-2型磁天平上测得;微区分析和x-射线衍射分别用JXA-840扫描电镜和日本理学2028x-射线衍射仪进行.

利用歧化反应的逆反应合成C_5H_5LnCl_2·2LiCl·5THF配合物(Ln=La,Nd)

由于镧系收缩和配位不饱和性,导致长期不能合成轻稀土环戊二烯基氯化物。陈文启等借严格控制氯化稀土与环戊二烯基钠的摩尔比为1:0.5,制备了环戊二烯基轻稀土二氯化物(Pr、Ce、Nd),但即使将这一摩尔比调整为1:0.25也不能得到类似的镧的化合物。李毅等以LnCl_3—LiCl(Ln=La、Nd)的四氢呋喃溶液和等摩尔的C_5H_5Na反应,以比较高的收率制备了[Li(THF)_2]_2(μ-Cl)_4C_5Ln·THF,并测定了其晶体结构。我们

REE and epsilon(Nd) of clay fractions in sediments from the eastern Pacific Ocean: Evidence for clay sources

Clay fractions in the non-calcareous surface sediments from the eastern Pacific were analyzed for clay minerals, REE and Nd-143/Nd-144. Montmorillonite/illite ratio (M/I ratio), total REE contents (Sigma REE), LREE/HREE ratio and cerium anomaly (delta Ce) may effectively indicate the genesis of clay minerals. Clay fractions with M/I ratio > 1, delta Ce < 0.85, Sigma REE > 400 mu g/g, LREE/HREE ratio approximate to 4, and REE patterns similar to those of pelagic sediments are terrigenous and autogenetic mixed clay fractions and contain more autogenetic montmorillonite. Clay fractions with M/I ratio < 1, delta Ce=0.86 to 1.5, Sigma REE=200 to 350 mu g/g, LREE/HREE ratio approximate to 6 and REE distribution patterns similar to that of China loess are identified as terrigenous clay fraction. The Nd-143/Nd-144 ratios or epsilon(Nd) values of clay fractions inherit the features of terrigenous sources of clay minerals. Clay fractions are divided into 4 types according to epsilon(Nd) values. Terrigenous clay minerals of type I with the eNd values of -8 to -6 originate mainly from North American fluvial deposits. Those of type 11 with the epsilon(Nd) Values of -9 to -7 are mainly from the East Asia and North American fluvial deposits. Those of type III with epsilon(Nd) values of -6 to -3 could come from the central and eastern Pacific volcanic islands. Those of type IV with epsilon(Nd) values of -13 to -12 may be from East Asia eolian. The terrigenous and autogenetic mixed clay fractions show patchy distributions, indicating that there are volcanic or hot-spot activities in the eastern Pacific plate, while the terrigenous clay fractions cover a large part of the study area, proving that the terrigenous clay minerals are dominant in the eastern Pacific.

Nd isotope as the tracer of seawater evolution of early Miocene in the eastern Pacific Ocean

Fifty-six samples of nannofossil ooze were collected from Core PC5794 in the northern equatorial Pacific at 5 em intervals. With the methods of mass spectrometer (VG354) and ICP, the Nd isotopic compositions (epsilon(Nd)(t)), Mn contents and Mg/Sr ratios of carbonate phase have been analyzed. CaCO3 contents of bulk sediments were obtained by dissolution of 0.5 mol/L HCl. Based on these data, the high-resolution epsilon(Nd)(t) profile of seawater in early Miocene with core depth(or time) have been established. The values of epsilon(Nd)(t) range from -6.2 to -2.97 and 4 fluctuation cycles existed during 24.06-22.02 Ma. 4 low epsilon(Nd)(t) values (about -6.4) correspond to high CaCO3 contents, which implicates that there were 4 cold epochs or 4 times of Antarctic Bottom Water activity. They occurred at the time of 24.06 Ma, 23.85 Ma, 22.88 Ma and 22.26 Ma, respectively. High epsilon(Nd)(t) values correspond to the high Mn contents and high values of Mg/Sr ratio, which indicates the existence of 4 intense hydrothermal activity periods during 24.06-22 Ma, the durations of them are 4.05-23.98 Ma, 23.69-23.15 Ma, 22.74-22.37 Ma and 22.06-22.02 Ma, respectively.

Major element, trace element, and Sr, Nd and Pb isotope studies of Cenozoic basalts from the South China Sea

The whole rock K-Ar ages of basalts from the South China Sea basin vary from 3.8 to 7.9 Ma, which suggest that intra-plate volcanism after the cessation of spreading of the South China Sea (SCS) is comparable to that in adjacent regions around the SCS, i.e., Leiqiong Peninsula, northern margin of the SCS, Indochina block, and so on. Based on detailed petrographic studies, we selected many fresh basaltic rocks and measured their major element, trace element, and Sr-Nd-Pb isotope compositions. Geochemical characteristics of major element and trace element show that these basaltic rocks belong to alkali basalt magma series, and are similar to OIB-type basalt. The extent of partial melting of mantle rock in source region is very low, and magma may experience crystallization differentiation and cumulation during the ascent to or storing in the high-level magma chamber. Sr-Nd-Pb isotopic data of these basaltic rocks imply an inhomogeneous mantle below the South China Sea. The nature of magma origin has a two end-member mixing model, one is EM2 (Enriched Mantle 2) which may be originated from mantle plume, the other is DMM (Depleted MORB Mantle). Pb isotopic characteristics show the Dupal anomaly in the South China Sea, and combined with newly found Dupal anomaly at Gakkel ridge in Arctic Ocean, this implies that Dupal anomaly is not only limited to South Hemisphere. In variation diagrams among Sr, Nd and Pb, the origin nature of mantle below the SCS is similar to those below Leiqiong peninsula, northern margin of the SCS and Indochina peninsula, and is different from those below north and northeast China. This study provides geochemical constraints on Hainan mantle plume.