镁固溶对钙钛锆石陶瓷固化体的影响北大核心CSCD

以CaTiO_(3)、ZrO_(2)、TiO_(2)和MgO为原料,经固相烧结法在1350℃下制备镁固溶钙钛锆石陶瓷固化体(Ca_(1-x)Zr_(1+x)Ti_(2-x)Mg_(x)O_(7),0≤x(固溶度)≤0.20),并研究Mg^(2+)固溶度对固化体物相组成、微观形貌和晶体结构的影响。X射线衍射结果表明:Ca_(1-x)Zr_(1+x)Ti_(2-x)Mg_(x)O_(7)结构中的Ti位可容纳固溶度x=0.05~0.15的Mg^(2+);并通过选区电子衍射实验进一步验证,固化体的主要晶体结构为单斜相钙钛锆石(2M,空间群C2/c)。当固溶度x=0.05~0.15时,钙钛锆石产物的相对质量分数高于97%,仅有微量的钙钛矿杂质相生成;随着Mg^(2+)固溶度的进一步增加(x=0.20时),Mg^(2+)浓度超过固溶度极限,使杂质相含量大幅增加。同时,扫描电子显微镜观察结果表明,固化体抛光面结构致密;在Mg^(2+)固溶度x≤0.15时,阳离子浓度符合所设计的化学计量比。     

稀土、铀、钍苦味酸盐与喹哪啶酸氮氧化物配合物的合成与表征

研究了稀土、铀、钍苦味酸盐与喹哪啶酸氮氧化物的配合作用,合成了组成为Ln_2(Pie)_3·(ANO)_3·3H_2O(Ln=La、Pr、Nd、Sm、Eu、Gd、Er、Y;Pic为苦味酸根离子;ANO-为喹哪啶酸氮氧化物阴离子)、UO_2(ANO)_2和Th(Pic)·(ANO)_3·5H_2O的固态配合物,并对配合物的组成,红外、紫外光谱,热稳定性,X射线衍射物相分析及摩尔电导等性质进行了测试和表征。     

高效液相色谱法分离镧系元素

本工作采用柱后衍生高效液相色谱法分离镧系元素，所用仪器为日本岛津公司LC-10AT高效液相色谱仪，色谱柱为安捷伦300一SCX阳离子柱。La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb和Lu的氧化物的纯度均大于99．9％。     

低温离子束混合形成非晶态Pd_(0.67)B_(0.33)合金

Stritzker和Becker用离于注入法制备了PdB_(1.5)合金,证实它具有超导性。Orsay组曾系统地研究过离子注入Pd_(1-x)B_x系(0≤x≤0.54)的电学性质,表明当B的浓度达到共晶浓度(x=0.27)时,Pd_(1-x)B_x为非晶态;当B的浓度x≥0.40时,样品具有超导性。 离子束混合利用载能离子穿越不同元素薄层和固体原子碰撞,引起原子离位的输运作用,     

模拟动力堆高放废液玻璃固化体的析晶行为及其对浸出率的影响北大核心CSCD

玻璃固化技术是国内外目前主要的高放废液固化处理手段。针对模拟高燃耗动力堆高放废液,研究了废物氧化物包容量为24%(质量分数,下同)和30%时玻璃固化体在不同热处理温度下的析晶行为以及析晶对玻璃固化体抗浸出性能的影响。根据X射线衍射、拉曼光谱和扫描电子显微镜分析结果,当热处理温度为800℃时,玻璃固化体析出晶体相为树枝状的钼酸钙CaMoO_(4)和丝状的锆铈氧化物Zr_(x)Ce_(1-x)O_(2);当热处理温度为950℃时,除钼酸钙和锆铈氧化物之外,玻璃固化体中还有大量的空心六方柱形的硅氧磷灰石相Ca_(2)Ln_(8)(SiO_(4))_(6)O_(2)析出。根据抗浸出性能检测结果,玻璃固化体经热处理析晶后其归一化质量损失降低了约1/3,B、Na、Mo、Ca等的归一化质量损失也有明显下降。且950℃热处理比800℃热处理后的玻璃固化体归一化质量损失更小。结果表明热处理析晶可提升玻璃固化体抗浸出性能。     

纳米复合永磁合金Nd9Fe85-xMnxB6的结构和磁性

利用X射线衍射(XRD)和X射线吸收精细结构(XAFS)技术对淬火速度为20m／s的退火和未退火Nd9Fe85-xMnxB6(x=0，0．5和1．0)样品分别进行了晶体结构和Fe原子局域环境的分析，并用振动样品磁强计分析了样品的磁性。结果表明：退火前，掺杂微量Mn原子对纳米复合Nd-Fe-B磁性材料的晶体结构和近邻配位无序度都有显著影响，随着Mn含量的增加，Nd2Fe14B硬磁相和α-Fe软磁相的结晶度明显增加；在温度为973K、5min退火后，Nd9Fe85-xMnxB6(x=0，0．5和1．0)磁体的主相结构基本相同，但矫顽力由339kA／m增加到398kA／m,我们认为这是由于掺杂的Mn原子影响Nd2Fe14B和α-Fe颗粒晶界的交换耦合作用所致。     

Zr（Fe,Cr）2金属间化合物的氧化

用非自耗电弧炉熔炼了比值(重量比值)不同的Zr(Fe,Cr)_2,并在773K和973K的空气中氧化。经X射线衍射和电子衍射分析表明:当Fe/Cr≤4.5时,Zr(Fe,Cr)_2,是MgZn_2型(六方)的Laves相,它的晶格常数随Fe/Cr比增加而收缩。Zr(Fe,Cr)_2氧化后生成的稳定氧化物是单斜ZrO_2和六方(Fe,Cr)_2O_3。在形成稳定氧化物之前,还会出现亚稳定的立方ZrO_2。根据本实验结果讨论了Zr-4合金中Zr(Fe,Cr)_2第二相对腐蚀性能的影响。     

铈掺杂诱导U3O8晶型变化

铈是核反应的重要裂变元素,其氧化物CeO_2容易与UO_2燃料形成U_(1-x)Ce_xO_2固溶体。铀铈固溶体会因为U4+发生氧化而生成(U_(1-x)Ce_x)3O_(8-δ)混合氧化物。Ce在U_3O_8中的存在会改变U_3O_8母体的局域结构,影响着(U_(1-x)Ce_x)3O_(8-δ)产物的物理化学性质。研究铀铈混合氧化物的局域结构,可以帮助理解处于苛刻环境中乏燃料的性状。使用共沉淀方法制备了铈掺杂的U_3O_8混合氧化物样品,即(U_(1-y)Ce_y)3O_(8-δ)(y=0,0.05,0.20),利用粉末X射线衍射(X-ray Diffraction,XRD)获取其物相信息,借助同步辐射X射线吸收精细结构(X-ray Absorption Fine Structure,XAFS)技术来获取(U_(1-y)Ce_y)3O_(8-δ)中铀和铈的局域结构。结果表明:与掺杂前的U_3O_8具有C2mm空间群不同,掺入Ce后的(U_(1-y)Ce_y)3O_(8-δ)转变成了与U_3O_8的P62m空间群一样的晶型,Ce的存在还导致铀的平均价态升高,层内最近邻Ce-U(Ce)的原子距离减小。     

喷雾热解合成An_2Zr_2O_7(An=La、Nd)烧绿石及结构分析

锆基烧绿石An2Zr2O7以优异抗辐照性能和化学稳定性成为高放废物中锕系核素的理想固化基材。镧系核素常作为替代核素进行锕系核素的固化研究,实验以硝酸盐为原料,以三价的镧系元素(La、Nd)模拟锕系元素,采用sol-喷雾热解方法在1 200℃、6h内合成了(La、Nd)2Zr2O7烧绿石。采用粉末X射线衍射(XRD)、扫描电镜(SEM)、拉曼光谱分析方法对合成的样品进行了结构表征,结果表明:利用该方法合成了单一物相的烧绿石立方结构An2Zr2O7;相对于La2Zr2O7的烧绿石结构,Nd2Zr2O7烧绿石具有向萤石结构转变的趋势。该合成方法为目前的高放废液人造岩石固化提供了一定的技术基础。     

Nd0.5Sr0.4Pb0.1MnO3的晶体结构研究

钙钛矿型锰氧化物以其大的磁电阻（CMR）效应和丰富的物理内涵而成为当前凝聚态物理研究的热点、本工作通过中于衍射和X射线技术研究Nd0.5Sr0.4Pb0.1MnO3的晶体结构,以确定氧原子的原子坐标和占位,并获得与磁学特性密切相关的晶胞常数以及键长、键角等信息。 样品用传统的高温固相反应法制得。所选的氧化物原料均为分析纯以上。将一定摩尔比的原料在无水乙醇的保护下研磨后,把粉体放在坩埚中预烧24h,然后,将所得的粉体研磨均匀、干燥、压块,在箱式炉中长时烧结。为保持样品的均匀性,中间经历一次打断、研磨、压块和烧结过程。用X射线衍射确定样品的单相性。     

XPS analysis of UxCe1−xO2±δ and determination of oxygen to metal ratio

The chemical states of U and Ce in the solid solutions of UO₂ and CeO₂ are studied using the X-ray photoelectron spectroscopy. A detailed analyses on U 4f and Ce 3d photoelectron peaks revealed the presence of Ce³⁺ and U⁵⁺/U⁶⁺ states in the mixed oxides. The oxygen to metal ratios in different compositions of mixed oxides were estimated from the quantity of different chemical states of U and Ce present in mixed oxides.     

Magnetovolume and chemical bonding effects of Sn atom in the γ'-(Fe1-xSnx)4N compounds

Combining x-ray diffraction and high pressure Mossbauer spectroscopy,the structure and the hyperfine parameters of Sn substituted for Fe in γ'-Fe4N were in-vestigated. The results of x-ray diffraction indicate that single phase γ'-(Fel-xSnx)4Ncompounds can be synthesized in the composition range 0≤ x ≤ 0.3, and the latticeparameter can be well fitted with two linear formulas α0(x) = 3.795 + 0.019 × x (0.0≤x ≤0.10) and α0(x) = 3.795+ 0.228 × (x- 0.1)(0.10 ≤ x ≤0.30) for different contentof Sn. Using high pressure Mossbauer spectra, the influences of the magnetovolunceffect and the chemical bonding effect of Sn atom on the hyperfine magnetic field andthe isomer shift were first distinguished. It is found that the magnetovolume and thechemical bonding have different influences on the properties of γ'-(Fe1-xSnx)4N, andthe latter plays a more important role.     

Lattice Parameters of Mixed Oxides in Sm-U-O System

The oxidation-reduction properties of mixed oxides in the system Sm-U-O and the variation of their lattice parameters due to oxidation and reduction were examined by means of thermogravimetry and X-ray diffraction. For mixed oxides Sm_yU_1-yO_2±x prepared in air, the O/M ratio decreased linearly from 2.667 at y= 0 to nearly stoichiometric 2.02 at y=0.5. The 0/M ratios at y>0.5 were on the line connecting 2.667 at y= 0 with 1.50 at y =1. The single phase region of the fluorite structure was between y = 0.5 and 0.6. The lattice parameters of the fluorite phase at ≤0.6 were constant, 5.418×10^?10m. For mixed oxides prepared in hydrogen, the 0/M ratio decreased linearly from 2.00 at y = 0 to 1.84 at y = 0.5, and from 1.84 at y = 0.5 to 1.50 at y = 1. The quenched oxides were single phase compounds except those for y = 0.1, 0.6 and 0.9. The lattice parameter of the fluorite structure decreased from 5.4700 at y = 0 to 5.427 × 10^?10 m of Smo.₄U0.6O_1.854. and was kept constant between y = 0.4 and 0.5, then increased to 5.466 × m at y = 0.7. The Sm-U-O phase diagram at 1,000°C was constructed on the basis of the X-ray diffraction work.     

Gd1.6Nd0.4Zr2O7烧绿石的快速合成及其组织结构研究

为探索Gd₂Zr₂O₇烧绿石快速固化高放废物中锕系核素的新途径,实验用高温高压固相反应法在3～4GPa压力、1573～1673K温度范围内合成了Gd_1.6Nd_0.4Zr₂O₇烧绿石固化体,并利用X射线衍射仪、扫描电镜对样品进行了分析。结果表明：高温高压固相反应法可在极短时间（15min）内合成完全固溶的Gd_1.6Nd_0.4Zr₂O₇立方烧绿石固化体,较常用制备方法（一般合成时间不低于48h）快近200倍;用该技术合成的样品在常温常压下的相转变温度及压力得以显著提高,烧绿石相更趋稳定;样品晶格常数随Nd含量的增加及合成温度的升高而逐渐增大,随合成压力的增加而逐渐减小。这种快速高效的合成方法为未来开展高放核素的工业固化提供了一种新的技术途径和基本数据参考。     

Oxidation-Reduction Properties of Mixed Oxides in Lanthanum-Uranium-Oxygen System

The oxidation-reduction properties and the phase relations of mixed oxides in the system La-U-O were examined by means of thermogravimetry and X-ray diffraction method. The O/M ratios of the mixed oxides La_yU_1-y O_2±x, prepared at 1,650°C in vacuo by the reaction of La₂O₃ and UO₂, were expressed as 2–0.5 y except 0.2≤y≤0.4. The oxides were the single fluorite phase at y0.7. These oxides of 0.2≤y≤0.6 were oxidation-susceptible in air even at room temperature. For the oxides heated or prepared in air at 1,000°C, the O/M ratio vs. y relationship was composed of three line with the turning points, 2.26 at y = 0.27 and 1.92 at y = 0.70. The fluorite phase was observed in the regions of 0.3≤y≤0.45 and 0.7≤y≤0.9, and the rhombohedral phase was in ?0.55≤y-0.7. The O/M ratios of the oxides reduced with hydrogen were nearly 2 at y ≤0.2 and decreased with increasing y at y >0.2. The oxide of y =0.5 showed the curious property: The O/M ratio had a minimum when the oxide reduced with hydrogen was oxidized in air.     

动力堆模拟高放废液的甲醛脱硝及脱硝过程中的沉淀行为北大核心CSCD

两步法玻璃固化工艺中,高放废液可通过化学脱硝达到降低酸度的目的,常用的化学脱硝剂有甲酸、甲醛、蔗糖等。以甲醛为化学脱硝剂,对动力堆模拟高放废液进行脱硝及脱硝过程中沉淀行为进行研究。模拟高放废液在90℃、脱硝比例为1.0~2.0范围内进行脱硝,对脱硝后各物质运用电感耦合等离子发射光谱(ICP-OES)、X射线荧光光谱(XRF)、扫描电镜-能谱分析(SEM-EDS)、Raman光谱、X射线衍射(XRD)、热重分析仪(TG)进行分析。结果表明:脱硝后废液中NO_(3)^(-)含量明显降低,随脱硝比例增大,NO_(3)^(-)的含量逐渐降低,甲醛含量增加。脱硝过程中出现由Zr、Mo、La、Ce、Nd、Fe、Te、Pr、Cs、Sm、Cr、Sr、Y、Co、Ni组成的沉淀,沉淀的形成有两个过程:一个过程为形成颗粒状的结晶物Ln_(2)Zr_(3)(MoO_(4))_(9)(Ln=La、Ce、Nd、Pr、Eu、Sm)和MoO_(2);另外一个过程为形成由O、Fe、Zr、Mo、Te构成的无定形粉末物质;脱硝产物的热分解主要发生在约360℃以下。     

元素在长石、云母、角闪石表面吸附的XPS研究 Ⅱ.钛、铬、钴、镍、铜、钕、钐、钆

用X射线光电子能谱(XPS)初步研究了Ti、Cr、Co、Ni、Cu、Nd、Sm、Gd 8种元素在长石、云母、角闪石表面的吸附行为。结合各矿物在吸附不同元素后O(1s)结合能的化学位移,对吸附机理进行了初步探讨。     

Plasma Syntheses of Carbon Nanotube-Supported Pt-Pd Nanoparticles

It is reported that the highly dispersed Pt nanoparticles on carbon nanotubes can be synthesized under mild conditions by in situ plasma treatment.The carbon nanotube was pretreated by O₂ plasma to transform into oxide carbon nanotubes（O-CNTs）,and then it was mixed with the precursors（the mixture of H₂ PtCl₆and PdCl₆）.After that,the O-CNTs and the precursors were simultaneously treated by H₂ plasma.The precursors were transformed into Pt-Pd nanoparticles（NPs）and the O-CNTs transformed into CNT.The synthesized CNT-based Pt-Pd nanoparticles were characterized by scanning electron microscopy,transmission electron microscopy,X-ray diffraction and X-ray photoelectron spectroscopy.All the analysis showed that the Pt-Pd nanoparticles were deposited on CNT as a form of face-centered cubical structure.