稀土对喷焊层耐蚀性的影响机制

通过在镍基自熔合金粉末中添加微量稀土、研究了稀土对喷焊层耐蚀性的影响规律及其作用机制。实验结果表明：稀土元素的微合金化作用使喷焊试样在腐蚀过程中的表面活性点减少，腐蚀速度下降，从而提高了耐蚀性。     

稀土对喷焊层耐磨性的影响机制

通过在镍基自熔合金粉未中添加微量稀土,研究稀土对喷焊层耐磨性的影响规律及其作用机制。实验结果表明:稀土元素的微合金化作用使喷焊层的组织细化,并使硬质相数量、尺寸、形状及分布发生变化,从而提高喷焊层的耐磨性能。     

纳米Y2O3对Ni-WC合金喷焊层组织和耐磨性的影响

通过在含35%WC的Ni基自熔合金粉末中添加微量的纳米Y2O3,研究纳米Y2O3对合金喷焊层组织、硬度和耐磨性影响规律及其作用机制.实验结果表明,添加适量的纳米Y2O3可细化合金喷焊层组织,提高合金喷焊层硬度和耐磨性,改善合金喷焊层和基体的结合状态,并且经一定温度的后续热处理,可进一步提高合金喷焊层硬度和耐磨性.     

La2O3对钛合金表面镍基喷焊涂层组织和性能的影响

采用火焰喷焊技术在钛合金基体上制备了不加La2O3和加4％(质量分数)La2O3两种镍基涂层，分析了它们的显微组织、合金元素的扩散、显微硬度以及耐磨性能。结果表明：La2O3的加人，改善了涂层合金的流动性和显微组织的均匀性，并使涂层与基体的熔合更加明显，结合性能得到进一步提高；虽然一定程度上减弱了基体Ti元素对喷焊层的强化作用，使表层显微硬度略有下降，但磨损失重却较未加La2O3的喷焊涂层下降了20％。     

氧化铈对M80S20喷涂层和喷焊层显微组织及耐磨性的影响

通过光学金相和扫描电镜观察、X射线能谱和X射线衍射分析及干滑动磨擦磨损试验,探讨了稀土氧化物(CeO_2)对M_(80)S_(20)合金喷涂层和喷焊层的显微组织及耐磨性的影响。试验结果表明,加入8％CeO_2可以明显改善喷涂层和喷焊层的显微组织,提高显微硬度和耐磨性。     

喷焊合金粉末中稀土总量的测定

以RE-CPⅢ-CTMAB三元络合物直接比色法测定喷焊合金粉末中稀土总量时,发现用CTMAB的水溶液,在气温较低时,特别是北方的冬季,往往有大量白色结晶析出,不利于分析测定。本法将CTMAB的水溶液改为20%(V/V)乙醇溶液就不再有结晶析出。对于测定含20%铬、10%镍、3%钼、4%硅和2%硼的合金粉末中的稀土总量,勿需冒高氯酸白烟和用铜试剂分离。方法快速、准确。     

钇基稀土合金在超高硬度堆敷金属中的应用研究

运用OM，SEM，XRD探究了重钇基稀土合金在超高硬度堆敷金属中的作用。钇基稀土合金对堆敷金属中析出的碳化物有变质球化作用。增加碳化物在基体中弥散分布的程度。稀土钇与氧、硫结合在净化堆敷金属的同时，改善了堆敷金属中夹渣物的形态。最终结果表明适量钇基稀土合金加入可以在对堆敷金属硬度提高的同时，改善其冲击功。     

W离子注入Ni-Mo合金电极的析氢性能

本文在镍基上电沉积Ni-Mo合金层,用W^+束注入,得到活性和稳定性极佳的新型析氢电极。     

ICP-AES法测定镍基高温合金中的铂

采用电感耦合等离子体原子发射光谱法测定镍基高温合金中铂元素。通过实验探讨了镍基高温合金中基体元素镍,主量元素如铬、钴、铝、钼、镍、钽等对铂元素测量的干扰情况,确定了适合的分析谱线。测定结果的相对标准偏差不大于6.55%(n=6),加标回收率为94%～105%。该法可用于镍基高温合金中铂元素的测定。     

贮氢合金LaNi_（3．8）Co_（0．5）Mn_（0．4）Al_（0．3）表面

贮氢合金ＬａＮｉ_（３．８）Ｃｏ_（０．５）Ｍｎ_（０．４）Ａｌ_（０．３）表面化学镀镍的研究张允什，陈军（南开大学新能源材料化学研究所，天津，３０００７１）关键词贮氢合金，化学镀镍，镍／氢电池目前，稀土系贮氢合金应用于镍／金属氢化物（镍／氢）电池存在的...     

A note on successive complexometric determination of thorium and rare earths

An improved method for successive determination of thorium and rare earths is described. It is based on the EDTA titration of thorium at pH 2 (Xylenol Orange as indicator) followed by addition of acetylacetone-acetone mixture, adjustment of the pH to 5-5.5 with hexamine, and by further EDTA titration of rare earths with the same indicator.     

Dosage par activation neutronique des terres rapes dans des roches uraniferes

The determination of rare earths by activation analysis in uranium containing rocks is disturbed either by fission-produced rare earths, or by neptunium-239 originating from uranium-238. In order to eliminate of these interferences the chemical separation of rare earths from uranium prior to activation should be performed. The purpose of this work was the elaboration of a chemical process to separate rare earths prior to irradiation in a nuclear reactor. The rock sample is fused with sodium borate, then, after addition of hydrochloric acid, the resulting solution is passed through a Dowex 1×8 column. Uranium is retained on the resin and rare earths and scandium are eluted. Aluminium is added as a carrier to the solution and rare earths and scandium are coprecipitated with aluminium hydroxide. This precipitate is irradiated in the nuclear reactor. Gamma spectrometry is used for the determination of each radionuclide. Activities measurements are performed in successive steps during one month. The following elements are determinated: Pr, La, Sm, Nd, Yb, Lu, Ce, Tb, Eu, and Sc. The chemical yield is measured by using scandium as an internal standard.     

“常乐”稀土微肥对糯玉米冠层光合特性及产量的影响

在50,100,200,400,600,800 mg.kg-1浓度的"常乐"稀土微肥条件下,研究了其对糯玉米冠层叶的叶绿素含量、荧光参数及产量构成因素的影响。结果表明,糯玉米授粉后棒三叶的叶绿素含量及荧光参数的增大幅度明显随常乐处理剂量的增大而呈规律性变化:即T1至T4处理不仅叶绿素含量呈现明显增大趋势,而当处理浓度为600 mg.L-1时叶绿素含量则表现下降,而且PSII的潜在活性(FV/F0)、光化学最大效率(FV/Fm)和量子效率(ΦPSII)亦表现出相似的规律;但PSII的光化学猝灭系数(qP)则随常乐处理浓度的增大,表现出先增后减的规律,优势明显并具有较高的光合速率,尤其是400 mg.kg-1光合功能强,籽粒产量最高达16320.0 kg.hm-2。另外,授粉后的生育期也对鲜食糯玉米冠层叶绿素荧光参数具有明显正效应,在授粉后16 d时,不同浓度"常乐"稀土微肥处理的鲜食糯玉米不同叶位叶光合速率最大。     

稀土在烤烟植株中的分布及其对烟叶化学成份影响的研究

作为一种生理活性物质,稀土施用在烟草上平均增产11％,上中等烟比例提高7．53％左右,稀土应用于烤烟大部分限于田间试验,缺深入的机理研究^[2-4]。本试验用低浓度混合硝酸稀土喷施烤烟叶面,研究了稀土在烤烟植株中的含量,分布及土壤中可溶态稀土的变化情况及稀土对烟叶化学成份的影响,旨在为烤烟施用稀土提供科学依据。     

Activation analysis of rare earths : The determination of rare earths in minerals by the single comparator technique

The determination of rare earths in minerals by activation analysis is described. The rare earths are separated as a group from the bulk of the material before irradiation. After irradiation the rare earths are separated from each other by gradient elution with ammonium α-hydroxyisobutyrate on a cation-exchange column. The elements are determined by the single comparator technique. This method permits a practical application of activation analysis to the routine determination of rare earths in complex matrices,     

Ion-exchange chromatography of glycolatocomplexes of rare earths

Summary The ion-exchange behavior of glycolatocomplexes of the rare earths (Sc, Y and lanthanides) with 1-octanesulfonate as the hydrophobic ion has been investigated in aqueous glycolate media. The system is capable of separating adjacent light intra rare earths, La-Ce-Pr-Nd-Y-Sm, and heavy rare earths, Ho-Er-Tm-Yb-Lu-Sc, from each other with good resolution by gradient elution at room temperature. Intermediate rare earths, Dy-Tb-Gd-Eu-Sm, are difficult to separate from each other. The position of Y in the eluate is different from that found with most other eluent systems used for rare earth separations, being between Nd and Sm.     

稀土复合钴基HMS催化剂的制备及其氯苯催化燃烧性能

以钴基HMS催化剂为主体,从稀土复合方式、不同稀土元素、稀土元素含量等方面系统考察了稀土元素对钴基HMS催化剂氯苯催化燃烧性能的影响。并将孔结构、XRD以及紫外可见漫反射等表征结果与催化活性进行了有效关联。结果发现:Ce较La和Nd能更好地改善钴基HMS的催化性能。同时发现,通过负载法进入HMS孔道的Ce较通过原位法掺杂在骨架的Ce具有更佳的促进作用,且当Ce盐(硝酸铈)的负载量为20%(质量分数)时,效果最好。     

偶氮氯膦Ⅲ吸光光度法测定轻、重稀土元素和钇

本文研究了稀土元素与偶氮氯膦Ⅲ的α型及β型显色反应。在一定条件下,重稀土元素(Gd-Lu)同偶氮氯膦Ⅲ螯合物可由α型转变成β型,其中钇的螯合物转成β型倾向最大,而轻稀土元素在相同条件下仅形成α型,利用Zn-EDTA和Zn-CyDTA的掩蔽效应,可扩大显色反应的差异性。提出了在HCl-NaAc介质中分别测定轻、重稀土元素及钇的方法:在pH2.9-3.4范围内,用Zn-CyDTA作掩蔽剂,可在重稀土存在下测定轻稀土元素。在pH1.8-2.4和pH2.8-3.6,用Zn-EDTA、NaF或NaF作掩蔽剂可分别测定钇及重稀土元素。     

Determination of traces of rare earths in high-purity thorium dioxide by neutron activation analysis

The use of thorium dioxide as a nuclear fuel requires the determination of individual rare earth impurities at 0.08–1 mg kg^?1 levels. Neutron activation is sufficiently sensitive but separation from the matrix is essential. In the proposed method, thorium dioxide (5–20 g) is dissolved in concentrated nitric acid with a little hydrofluoric acid; after evaporation, thorium is complexed with ammonium carbonate and the solution is passed through a small column of Chelex-100 resin which retains the rare earths quantitatively without retaining thorium. The rare earth elements are eluted with dilute nitric acid, concentrated, and irradiated with standards; after irradiation the rare earth are collected on a lanthanum carrier and measured by γ-ray spectrometry. The recoveries of rare earths were checked with tracers and by standard addition to thorium dioxide matrices. The reproducibility for La, Eu and Dy was satisfactory at 0.01, 0.003 and 0.002 mg kg^?1, respectively; as was the reproducibility for all rare earths added to thorium dioxide (1–4 μg/5 g). Limits of detection are adequate for certification of nuclear-grade material.