Influence of MgO contents on silica supported nano-size gold catalyst for carbon monoxide total oxidation

A series of nano-size gold catalysts were prepared by deposition-precipitation method using silica material promoted with different amounts of MgO as the carrier. The influences of MgO addition on the structure and property of the nano-size gold catalysts were characterized by X-ray diffraction （XRD）, transmission electron microscopy （TEM）, O2 temperature-programmed desorption （O2-TPD）, and inductively coupled with plasma atomic emission spectroscopy （ICP-AES） techniques. The total oxidation of CO was chosen as the probe reaction. The results suggest that for the gold catalysts supported on the silica material after MgO modification, the size of the gold particles is pronouncedly reduced, the oxygen mobility is enhanced, and the catalytic activity for low-temperature CO oxidation is greatly improved. The gold catalyst modified by 6 wt% MgO （Mg/SiO2 weight ratio） shows higher CO oxidation activity, over which the temperature of CO total oxidation is lower about 150 K than that over the silica directly supported gold catalyst.

Modeling and simulation of neodymium oxide dissolution in molten fluorides

By combining the mass transfer mechanism of neodymium oxide with dissolution kinetics,a solution strategy for neodymium oxide dissolution was proposed to predict the dissolved neodymium oxide concentration during the process under complex flow field conditions.The factors affecting neodymium oxide dissolution were analyzed in detail.Aiming at the pulse feeding and continuous feeding modes in industrial practice,the characteristics of the dissolution process under the two feeding modes were compared.Simulation results showed that pulse feeding took shorter time to distribute evenly than continuous feeding.Finally,the dissolution time of single-particle neodymium oxide under static flow field conditions was compared with the literature results.Except for only one set of data with a maximum error of about 10%,the errors of other data are all within 5%.

Preparation of High Purity Neodymium Oxide from Brazilian Monazite by Ion Exchange

A simple and economical chemical process for obtaining high purity neodymium oxide is discussed. The raw material in the form of RE （rare earth） carbonates is produced industrially in Brazil from monazite. Using this concentrate as the feed material, ion exchange with a strong cationic resin, commonly used for water treatment, and without the use of retention ions was used for the fractionating of the REE （rare earth elements）. The eluent was ammonium salt of EDTA （ethylenediaminetetraacetic acid） at pH 4.0. The complex of EDTA-neodymium was transformed into neodymium oxides via oxalate precipitation. We produced 99.9% pure Nd203 in yields greater than or equal to 80%. Molecular absorption spectrophotometry was used to monitor the neodymium content during the process and sector field inductively coupled plasma mass spectrometry was used to certify the purity of the neodymium oxides. The typical neodymium oxides obtained contained the followings contaminants in micrograms per gram： Sc （4.09）; Y （0.39）; La （0.78）; Ce （5.62）; Pr （4.56）; Sm （11.10）; Eu （1.10）; Gd （14.30）; Tb （29.3）; Dy （4.15）; Ho （8.39）; Er （13.80）; Tm （0.23）; Yb （2.29）; Lu （0.39）. High purity neodymium oxides obtained from this procedure replaced the imported product used in research and development work on rare earth at IPEN/CNEN-SP （Instituto de Pesquisas Energeticas e Nucleares/Comissfio Nacional de Eneergia Nuclear-Sao Paulo）.

Modification of separators with neodymium oxide/graphene composite to enhance lithium-sulfur battery performance

Lithium-sulfur(Li-S) batteries have generated significant attention due to their high theoretical specific capacity and energy density among a host of energy storage power devices.Nevertheless,the lithium polysulfide dissolution shuttle that occurs within Li-S batteries will lead to capacity deterioration and inadequate cycling stability.In the paper,we proposed a measure to deal with the above problems by modifying the separator with Nd_(2)O_(3)/graphene composite in Li-S batteries.Graphene's special chemical properties and structural qualities make it an excellent choice for Li-S batteries.Meanwhile,Nd_(2)O_(3) has a strong binding affinity with lithium polysulfide due to its low electronegativity,which exhibits Lewis' s acidity and forms strong interactions with lithium polysulfide,which is strongly Lewis basic.By utilizing these advantageous properties,Li-S batteries assembling Nd_(2)O_(3)-decorated reduced graphite oxide modified polypropylene separators(Nd_(2)O_(3)/RGO/PP) demonstrate outstanding electrochemical performance,including a mere 0.0525% capacity attenuation rate under 2C during 1000 cycles and with exceptional rate performance of 614 mAh/g even at 3C.This study presents valuable knowledge for effectively modifying separators using rare earth oxides to incorporate graphene,ultimately promoting the practical application of Li-S batteries.

Gasoline Sensor Based on Rare Earth-Doped Indium Oxide with Low Power Consumption

Nanocrystalline indium oxide powders were prepared by microemulsion and then Y2O3 and Nd2O3 doped In2O3 were synthesized separately by impregnation and chemical co-deposition. The structure and morphology were characterized by XRD and TEM, respectively. Gas sensing properties were tested at static state. The results show that homogeneous indium oxide nanopowder with main grain size of 20 nm can be obtained from microemulsion after sintered at 600 ℃ for 1 h. Pure indium oxide gas sensor has higher sensitivity to gasoline than that to ethanol, HCHO, C6H6, NH3, C4H10, but the selectivity is not as well as sensitivity.

Effect of nano-size nickel particles on wear resistance and high temperature oxidation resistance of ultrafine ceramic coating

In order to improve the wear resistance and high temperature oxidation resistance of titanium and titanium alloy, the high temperature ultra fine ceramic coating containing nano-size nickel particles was prepared by flow coat method on the surface of industrially pure titanium TB1-0. The effects of nano-size nickel particles on the wear resistance and high temperature oxidation resistance of coating substrate system were investigated through oxidation kinetics experiment and wear resistance test. The morphologies of the specimens were examined by means of optical microscopy, scanning electron microscopy and X-ray diffraction. The results show that the high temperature ultra fine ceramic coating has notable protection effect on industrially pure titanium TB1-0 from oxidation. The oxidation and wear resistance properties of the coating can be effectively improved by adding nano-size nickel particles. The oxidative mass gain of the specimen decreases from 11.33 mg·cm-2 to 5.25 mg·cm-2 and the friction coefficient decreases from 1.1 to 0.6 by adding nano-size nickel particles, and the coating containing 10% （mass fraction） nano-size nickel shows the optimum properties.

Research on the Impact of CeO2 -based Solid Solution Metal Oxide on Combustion Performance of Diesel Engine and Emissions

This paper mainly studies on the performance of high-speed diesel engines and emission reduction when the engine uses heavy oil mixed with nanometer-sized additives Ce0.9 Cu0.1 O2 and Ce0.9 Zr0.1 O2.During the test,Indiset 620 combustion analyzer made by AVL,was used to make a real-time survey on the cylinder pressure,the fuel ignition moment,and establish a relation between the change trend of temperature in cylinder and the crank angle.For the engine burning heavy oil and heavy oil mixed with additives,combustion analysis software Indicom and Concerto were used to analyze its combustion process and emission conditions.Experimental investigation shows that nano-sized complex oxide can improve the performance of diesel engine fueled with heavy oil,and reduce the emission of pollutants like NOx and CO,comparing it with the pure heavy oil.According to the consequences of this experiment,the additives improve the overall performance in the use of heavy oil.

EFFECTS OF NEODYMIUM ON OXIDATION BEHAVIOUR OF Ti-11Al ALLOY

The oxidation behaviours of pure 77,Ti-11 at% Al and Ti-11 at% Al-Nd alloys in air at the tempera- ture range 800～1000℃ have been investigated in the present paper.Their oxidation kinetics follows substantially the parabolic rate law.The activation energies of oxidation processes are 103 and 91 kcal/mole for Ti-11 Al and Ti-11 Al-Nd alloys,respectively.The platinum wire tagging tests have shown that oxygen atoms diffuse into the substrate during oxidation of pure Ti and that Ti,Al and Nd atoms diffuse across a scale of oxides outwards during oxidations of these alloys.Nd addition promotes the selective oxidation of aluminium.The addition of Al and Nd decreases the extent of penetration of oxygen atoms into the Ti substrate.The X-ray diffraction analysis confirms that the oxide scales of the alloys consist of TiO_2 and α-Al_2O_3,or TiO_2,α-Al_2O_3 and a small amount of Nd_2O_3 for Ti-11 Al and Ti-11 Al-Nd alloys, respectively.

Synthesis and Crystal Structure of Tri-(2-mercaptopyridine N-oxide)bis(dimethyl sulfoxide) Dysprosium(III)

A range of rare earth metal complexes of 2-mercaptopyridine N-oxide (Hmpo) have been synthesized, and studied by elemental analysis and IR spectroscopic technique. Crystal structure of Dy(mpo)3(DMSO)2 (DMSO = dimethyl sulfoxide) has been determined. The complex crystallizes in the triclinic system, space group P with lattice parameters: a = 9.602(3), b = 9.803(3), c = 15.498(5) ? a = 89.51(1), b = 85.73(1), g = 62.99(1)? Dc = 1.787 g/cm3, C19H24N3O5S5Dy, Mr = 697.21, Z = 2, F(000) = 690, = 3.321mm-1, the final R = 0.0237 and wR = 0.0587 for 4116 reflections with I > 2s(I). The coordination number of dysprosium (Ⅲ) is eight, and its coordination geometry is a somewhat distorted square antiprism with O(3), O(4), O(5), S(3) and O(1), O(2), S(1), S(2) at the tetragonal bases (dihedral angle between their mean planes is 2.9(1)). Around the Dy atom, three five-membered ring planes (Dy, O, N, C, S) make the dihedral angles of 74.42, 11.31 and 83.72, respectively.

Influence of nano-SiC on microstructure and property of MAO coating formed on AZ91D magnesium alloy

Ceramic coating incorporated with nano-SiC was obtained on AZ91D magnesium alloy during MAO by adding nano-SiC into the silicate-aluminate-based composite electrolyte. The microstructure, thickness, phase analysis, element composition and hardness of the coatings were respectively investigated by scanning electron microscopy（SEM）, film thickness meter, X-ray diffraction （XRD）, energy disperse spectroscopy（EDS） and Vickers hardness tester. The wear resistance of Mg alloy and coatings were evaluated by friction and wear apparatus, while the corrosion resistance of Mg alloy and coatings were evaluated by potentiodynamic polarization test and electrochemical impedance spectroscopy （EIS）. The results show that after adding nano-SiC into the electrolyte, both the striking voltage and final voltage decrease, the size and number of the micropore on the surface of the coating decrease, the thickness and hardness of the coating increase, both the wear resistance and corrosion resistance of the coating raise.

基于模糊天牛须PID的稀土电解温度浓度解耦控制

稀土电解过程中电解槽内温度是影响出料金属品质、电解能耗的关键条件,同时槽内氧化物浓度决定了出料金属的效率和电解过程的稳定性。但实际电解槽内化学反应多、过程复杂,电解槽温度、熔盐氧化物浓度两者存在非线性的耦合关系。电解槽模型具有高滞后、强耦合、时变系统的特点,单独以电解温度或氧化物浓度作为被控变量难以保证出料金属的品质。以6 kA氧化钕电解温度、氧化物浓度作为输入,阴极电流密度、氧化物下料率作为输出,对输出变量进行解耦补偿,实现多变量解耦控制,从而提高氧化钕电解的品质;通过模糊PID控制器引入专家知识库对温度、浓度实现有效控制,改善了以往稀土电解过程中控制变量单一效果不理想的难题;借助天牛须的寻优迭代能力优化模糊PID的初始参数。利用Simulink平台对模糊PID解耦控制器和常规PID控制器进行仿真对比实验,实验结果表明:模糊PID解耦控制系统较单一温度PID控制效果更好,超调量提高了6%,系统响应速度提高25%。

Improving the wear resistance of plasma electrolytic oxidation(PEO)coatings applied on Mg and its alloys under the addition of nano-and micro-sized additives into the electrolytes:A review

As an efficient surface modification approach,the plasma electrolytic oxidation(PEO)technique can boost the capability of wear protection in Mg and its alloys by applying a hard and thick ceramic coating.In this procedure,more efficient protection can be acquired via adding additives(in the form of particle,powder,sheet,etc.)into solutions and producing composite coatings.These additives result in more efficient protection against wear via getting stuck in the cracks and pores of coatings and rising the thickness,hardness,and diminishing the porosity size and content.The efficiency of each additive can be changed owing to its intrinsic properties like melting point,size,participation type(reactive,partly reactive,or inert)and potential of zeta.In this review,the effects of distinct additives in nano-and micro-scale size on wear behavior of PEO coatings on Mg and its alloys is going to be reviewed.

15 kA稀土熔盐电解槽炉底结瘤形成机制与对策

稀土金属镨钕合金生产过程中,易在熔盐电解槽炉底形成结瘤,不但影响生产的连续化,还对产品质量产生影响,目前相关文献多集中在结瘤产物成分及电解参数对结瘤的影响方面,鲜有文献对结瘤形成机理进行研究。本文分析了炉底结瘤物形貌和结晶物组成,发现结瘤物的成分为氧化钕、氧化镨、氟氧化钕以及少量氟化钕和金属钕。采用数值模拟的方法对电解流场进行了分析,得出炉底结瘤物形成原因:加料速度过快是形成结瘤物的主要原因,氟氧化钕的熔点比熔盐高,易在石墨坩埚台阶上沉积形成结瘤物;稀土金属出炉时会带走大量的热,导致炉底温度出现较大变化,氧化钕在温度较低的区域容易析出,沉积在石墨坩埚台阶上;电解槽底部区域熔盐的流动性较差,使得在石墨坩埚台阶上析出的产物不能随熔盐流动而沉积。通过控制下料速度和保持合理电解温度,可以避免过剩的物料或者析出物料在坩埚台阶上沉积,及时清理炉底和台阶上积料可以控制结瘤物的增长速度。

碳酸氢钠沉淀法制备大粒度高纯度氧化镨钕研究

以碳酸氢钠为沉淀剂,采用正序分段加料的方式制备氧化镨钕,研究了沉淀终点pH值、沉淀温度对氧化镨钕前驱体及产品氧化镨钕粒度、杂质含量的影响。结果表明,当沉淀终点pH值为5.10、沉淀温度50℃时,制备的氧化镨钕粉体中位粒度D_(50)为21.45μm,粒度分布窄,形貌为片状结晶团聚形成的类球形粉体,其中Cl^(-)含量为0.017%,Na_(2)O含量为0.012%,关键指标优于国家标准的要求。

Nd_(2)O_(3)取代CaO对硼硅酸盐玻璃物相、结构和化学稳定性的影响

以典型Na_(2)O-CaO-ZrO_(2)-B_(2)O_(3)-SiO_(2)为基础玻璃组分,通过Nd_(2)O_(3)替换CaO,采用传统的高温熔融冷却法制备了固化体。通过X射线衍射(XRD)、傅里叶变换红外光谱(FTIR)和扫描电子显微镜(SEM)对固化体进行了物相和结构的表征,并通过产品一致性检测法(PCT)和溶解速率法(MCC-1)对化学稳定性进行了分析和评估。结果表明:随着Nd_(2)O_(3)取代量的增加,ZrO_(2)的析晶逐渐减弱,当Nd_(2)O_(3)的含量为5%时,6%的ZrO_(2)能完全溶于玻璃相中。通过Nd_(2)O_(3)替换CaO促进ZrO_(2)在该硼硅酸盐玻璃结构中的溶解,可提高固化体的化学稳定性。浸泡28天后,固化体的LRSi、LRCa、LRZr和LRNd在10^(-4)g/(m^(2)·d)数量级及以下,失重速率在10^(-9)g/(cm^(2)·min)数量级,其主要浸出的元素是Na和Ca。因此,本研究为富含Zr和Nd的高放废液固化提供了理论支撑和实验指导。

混合稀土Nd_(2)O_(3)和CeO_(2)对氧化镁陶瓷硬度及抗热震性能的影响

采用轻质微米级(0.5μm)MgO粉末为原料,Nd_(2)O_(3)、CeO_(2)为添加剂,聚乙烯醇为黏结剂,以242 MPa压强干压成型,常压1 550℃下烧结并保温2 h制得MgO陶瓷,对所得试样进行硬度、抗热震性能、显微结构及物相的测定。先探究不同添加量的单一稀土对MgO陶瓷的硬度及抗热震性能的影响,得到Nd_(2)O_(3)和CeO_(2)的最佳添加量ω分别为3%、8%。然后探究混合稀土Nd_(2)O_(3)和CeO_(2)对MgO陶瓷的性能影响,结果表明混合稀土添加总量ω为3%,Nd_(2)O_(3)与CeO_(2)的质量比为3∶7时,氧化镁陶瓷具有最好性能,硬度值为68 HRA,抗热震次数高达19次。

NdF_3-LiF-Nd_2O_3系熔盐密度的研究

用阿基米德法研究了NdF3 LiF体系熔盐的密度。采用二因子二次回归正交设计 ,得出密度 ( ρ)与NdF3含量 (c)、温度 (t)的回归方程 ,讨论了NdF3 含量及温度对熔体密度的影响 ,并考察了加入Nd2

用碳酸氢铵作沉淀剂制取碳酸钕和氧化钕

用农用碳酸氢铵作稀土沉淀剂 ,制得了易沉降、过滤的晶型碳酸钕 ,这种碳酸钕灼烧成氧化钕 ,各项质量指标均优于氧化钕产品国家标准。并对碳酸钕及其烧成的氧化钕分别进行了化学分析以及红外光谱、差热、热重分析、扫描电镜、X射线衍射分析 ,确定合成的碳酸钕组成为 Nd2 (CO3) 3· 2 .3H2 O,碳酸钕烧成的氧化钕

结晶条件对碳酸钕中氧化钕含量的影响

以碳酸氢铵作沉淀剂，从氯化钕料液中沉淀钕，经陈化结晶制备碳酸钕。研究了温度、加料比等结晶条件对结晶速度和结晶碳酸钕中氧化钕含量的影响。结果表明：随着结晶陈化温度的提高，结晶碳酸钕中氧化钕含量升高，而增大碳酸氢铵加入量则使氧化钕含量降低。当碳酸氢铵与氯化钕的物质的量之比控制在2．0：1～3．0：1，陈化温度控制在60℃以上，均可制得氧化钕含量在60％以上的碳酸钕结晶。

NdF_3-LiF-Nd_2O_3体系粘度的研究

采用坩埚扭摆法研究了 Nd F3- L i F熔盐体系的粘度 ,讨论了 Nd F3含量及温度对体系粘度的影响 ,并考察了加入 Nd2 O3对体系粘度的影响。