CeF3纳米微粒的合成、结构及摩擦学行为研究

在溶液中化学合成了有机化合物表面修饰的油溶性CeF3纳米微粒,初步探讨了表面修饰CeF3纳米微粒的制备条件,并表征了表面修饰CeF3纳米微粒的结构和性能.结果表明,表面修饰CeF3纳米微粒添加剂具有良好的减摩抗磨性,并且可以有效地提高基础油的承载性能,其性能优于商品添加剂T202(ZDDP).     

高能球磨时间对W-Cu纳米晶复合粉体组织和性能的影响

采用机械合金化法制备W-20％Cu(质量分数)纳米晶复合粉体.通过XRD,SEM等方法对球磨后的复合粉体进行表征,研究球磨时间对复合粉体的物相成分、晶粒尺寸、微观应变以及表面形貌的影响,并探讨机械合金化过程中过饱和固溶体的形成机制.结果表明:随着球磨时间的延长,W的晶粒尺寸及晶格常数不断减小,微观应变逐渐增大；球磨40...     

CeF_3纳米微粒的合成、结构及摩擦学行为研究

在溶液中化学合成了有机化合物表面修饰的油溶性 Ce F3纳米微粒 ,初步探讨了表面修饰 Ce F3纳米微粒的制备条件 ,并表征了表面修饰 Ce F3纳米微粒的结构和性能。结果表明 ,表面修饰 Ce F3纳米微粒添加剂具有良好的减摩抗磨性 ,并且可以有效地提高基础油的承载性能 ,其性能优于商品添加剂 T2 0 2 (ZDDP)。     

铝合金表面纳米化——微弧氧化复合涂层摩擦行为

通过表面机械研磨处理在LY12CZ铝合金表面制备表面纳米化(SNC)过渡层,再采用微弧氧化(MAO)技术对纳米晶过渡层进行微结构重构,设计制备出纳米化-微弧氧化(SNC-MAO)复合涂层,并对比研究了铝合金表面微弧氧化涂层及纳米化-微弧氧化复合涂层的摩擦学行为.与微弧氧化涂层相比,纳米化-微弧氧化复合涂层因硬度较高而具有较好的耐磨性.微弧氧化涂层及纳米化-微弧氧化复合涂层与GCr15钢球对磨时具有相同的磨损机理,为对磨钢球向涂层的材料转移和氧化磨损.      

高能球磨合成W-Ni-Fe纳米复合粉末特性

采用X射线衍射分析,BET氮吸附法和DTA差热分析对球磨后的90W-7Ni-3Fe(质量分数)纳米复合粉的组织结构变化,表面特性和热稳定性系统地进行了研究,XRD和DTA的分析结果表明球磨可以生成纳米复合粉,晶粒内部产生很大的晶格畸变,同时球磨产生的密度和缺陷使原子扩散加快,形成超饱和固溶体、非晶和扩大W在粘结相中的溶解度,BET氮吸附结果证明了球磨使粉末产生微孔,比表面中孔和孔径降低。     

新型无硒电解金属锰添加剂的性能研究

采用电化学测试手段,研究新型添加剂对电极过程的影响,同时通过SEM、XRD等测试手段,考察了添加剂对阴极锰表面、对锰晶体结构的影响。发现添加剂具有显著增强阴极极化,促进电解锰由γ-Mn(体心四方晶系)向α-Mn(体心立方晶系)的相变转换作用。综合各类试验结果,判定新型添加剂作用机理符合"选择吸附理论",即添加剂在电解过程中分解成极性小分子,在锰表面选择性吸附,阻滞了螺旋位错生长的发生,使得阴极沉积物平整致密。     

静电纺丝技术制备Y2O3∶Eu3+ 纳米纤维

采用静电纺丝技术制备了PVP/[Y(NO3)3+Eu(NO3)3]复合纳米纤维,研究了反应体系的最佳组成,系统地讨论了静电纺丝工艺的影响,获得了最佳制备条件.将PVP/[Y(NO3)3+Eu(NO3)3]复合纳米纤维在900℃焙烧10h,获得了晶态的Y2O3∶Eu3+ 纳米纤维.XRD分析表明,PVP/[Y(NO3)3+Eu(NO3)3]复合纤维为无定型,Y2O3∶Eu3+ 发光纳米纤维属于体心立方晶系,空间群为Ia3.SEM分析表明,PVP/[Y(NO3)3+Eu(NO3)3]复合纳米纤维表面光滑,平均直径约为150nm;Y2O3∶Eu3+ 发光纳米纤维的直径约为50nm.     

表面机械研磨工业纯钛表面纳米化研究

表面机械研磨处理可以使工业纯钛形成纳米表面层, 通过扫描电镜、透射电镜和高分辨电镜观察SMAT处理后的工业纯钛表层组织, 并研究了工业纯钛表面纳米化机制. 工业纯钛表面纳米化机制为: 孪晶的形成和孪晶的交割使得原始晶粒尺寸减小, 同时使晶格取向发生改变, 有利于位错滑移; 孪晶通过自身交割, 以及位错密度增加及其相互作用, 形成了细小的孪晶与胞状组织; 胞状组织转变为多边形亚晶; 亚晶不断吸收位错形成大角度晶界, 亚晶以及取向不同的细小孪晶逐渐转变为随机取向的纳米晶.     

FePt纳米珊瑚的湿化学制备及生长过程

利用乙酰丙酮铁(Fe(acac)3)和乙酰丙酮铂(Pt(acac)2)为前驱物质,油胺(Oleylamine)做表面活性剂,通过湿化学法制备了珊瑚状FePt粒子(纳米珊瑚).透射电镜(TEM)分析表明:FePt纳米粒子形貌类似珊瑚,由短棒、球粒子交叉连接在一起;粒子具有良好的分散性,尺寸均匀,是化学无序的FCC结构.借助高分辨透射电镜(HRTEM)研究,推测其生长机制为:在反应初始阶段,前驱物质被还原,形成球形的Fe Pt晶核,晶核长大成均匀的单分散球形纳米粒子;随后在表面活性剂的作用下,当粒子界面晶格取向一致时,球形粒子自组装排列到一起,并"焊接"生长成各向异性的短棒状;随着反应继续进行,球形粒子或短棒持续交叉连接、生长,最终形成FePt纳米珊瑚.     

微波法合成硫化铋纳米棒

以柠檬酸铋、硫脲为反应原料,在表面活性剂存在下,采用微波法合成了直径为30～50nm的硫化铋纳米棒.利用X射线衍射(XRD)、扫描电子显微镜(SEM)和透射电子显微镜(TEM)等对其进行了表征.考察了表面活性剂种类、用量对硫化铋纳米棒形貌和晶型的影响.结果表明:β-环糊精(β-CD)和十六烷基三甲基溴化铵(CTAB)有利于形成硫化铋纳米棒,并且较低浓度的β-CD(约0.005mo.lL-1)有利于形成分散性较好的硫化铋纳米棒.初步探讨了制备方法对硫化铋纳米棒晶型和合成时间的影响.结果发现,微波法制备纳米硫化铋与回流法相比,其晶格的生长方向不同,并且可以节省约80%的反应时间.     

氧化铁复合颜料表面包覆层结构的X射线光电子能谱研究

表面包覆无机膜是改善粒子性能的重要方式,实验在铁红超细微粒子中掺杂稀土元素Nd和SiO₂,形成氧化铁复合颜料,采用X射线光电子能谱(XPS)研究表面无机膜的成分、化学状态及其含量,推测Fe₂O₃复合颜料表面包覆无机膜及稀土掺杂涂层的情况。结果表明,根据O 1s和Fe 2p谱图分析Fe-O键反应弱,推知Fe₂O₃粒子表面包覆情况良好,根据Si 2p和Nd 3d、Nd 4d化学位移,推测Nd、Si原子可能进入Fe₂O₃晶格,取代了O、Fe原子,降低了Fe-O的比例,重新结合形成新键,使复合粒子表面形成Nd-O-Si键,稀土原子成功掺杂在Fe₂O₃粒子表面包覆的SiO₂无机膜中。因稀土元素且有丰富的谱线特征,使制备的颜料色彩效果更佳,提高了粒子的性能。     

Pseudo-symmetry in multiple twinned crystals having M3M point group symmetry

The pseudo-symmetry elements of the composite lattice of a twinned crystal havingm3m point group symmetry are determined on the basis of group theory. Twinning across the {111} planes is considered. The results for different composite lattices are given.     

Review on Rare Earth／Polymer Composite

The epecial properties of rare earth/polymer composite were described.More emphasis was put on the radiation shielding and magnetic properties,In the application to X-ray shielding,rare earth/polymer composite can make up the feeble absorbing area.If the rare earth content is high enough,it can demonstrate strong ability for thermal neutron absorption,The composite has strong paramagnetism.The feasibility of preparing magnetic rare earth/polymer compostite was discussed,In addition,three preparation methods were introducde:simlle polymerization,mixing and reaction processing,The effect of the rare earth/polymer composties pre-sturcture and the coordinate number of rare eatrh ions on the light property was analyzed,Rare earth/polmer compostie may have the structure and property simlar to those of the ionomer,The feasibility of the in-situ preparation of the rare earth/polymer nano structure is indicated ,Besides,the relationship between struchture and properties of the rare earth/polymer composite was discussed,The problems associated with such composite materials were also presented.     

Lattice Parameter Change of Nd∶Gd3Ga5O12 Crystal with Growth Direction

The lattice parameter change of Nd∶GGG crystal was studied by X-ray powder diffraction and the least square fitting method. The results indicate that the lattice parameters of Nd∶GGG increase along the crystal growth direction. By analyzing the Nd∶GGG crystal structure and ions occupying site, the reason of lattice parameter change is mainly attributed to the volatilization of gallium ingredient and lead to the Ga vacancy sites(Oxygen octahedral center) were occupied by Gd3 with large ionic radii, and that the substitute increases with the crystal growth direction. In addition, the Gd sites(oxygen dodecahedron center) were occupied by dopant Nd3 with large ionic radii and the Nd3 distribution coefficient in GGG crystal is smaller than 1, therefore, the substitute also increased with the crystal growth direction, which is another reason led to the lattice parameter increase along the crystal growth direction. In order to decrease the lattice parameter change and improve the crystal quality, some methods were adopted to restrain effectively the Ga2O3 volatilization and decrease the Nd3 concentration change along the crystal growth direction.     

201无镍不锈钢溅射沉积金属钛膜研究

采用常温直流磁控溅射法在廉价201无镍不锈钢表面沉积了纯钛薄膜.通过XRD和SEM分析了201上钛薄膜的结构和形态受沉积条件的影响.结果表明,在溅射功率为78.4 W时钛薄膜由紧密排列的柱状晶构成,但功率过大薄膜反而疏松.多种工艺参数下,钛薄膜具有高度的择优取向,但其择优取向的晶面并不固定.XRD结果还表明:由于钛原子的渗入,基底会发生较严重的晶格畸变.并探讨了以沉积量表征膜厚的可能性及工艺参数对薄膜沉积量的影响.      

Researches on preparation and properties of polypropylene nonwovens containing rare earth luminous materials

Polypropylene composite nonwovens containing rare-earth strontium aluminates Sr Al2O4：Eu2＋,Dy3＋ and functional additives were fabricated by the spun-bonded technique.The optical properties, morphology and mechanical properties of the samples were characterized.Results from scanning electron microscopy photographs（SEM） indicated that the surface of the fiber was destroyed by the addition of rare earth luminescent materials lightly but the thickness of the fiber was uniform.Differential scanning calorimetry results showed that pure polypropylene has the double crystallization peak at 162.3 and 165.1 °C.Studies from X-ray diffraction showed that the nonwoven prepared with the luminescent materials contained the α-monoclinic crystal and β crystalline phase.Furthermore, the afterglow properties were tested, which showed that the afterglow curve of the luminous nonwoven was similar to that of strontium aluminate, and the intensity was more intensive than luminous nonwoven at the beginning.The nonwoven fabricated with the luminescent material did not affect the crystal lattice of the polymer making the materials have potential applications in fluorescent lamps and field emission displays（FEDs）.     

Enhanced visible light photoactivity of TiO2/SnO2 films by tridoping with Y/F/Ag ions

The Y, F, and Ag tridoped TiO₂/SnO₂ composite nanocrystalline film (YFAg–TS) with prominent photocatalytic performance was prepared by the modified sol–gel method and was characterized by utilizing X-ray diffraction (XRD), differential thermal and thermogravimetric (DTA–TG) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) method, ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), and photoluminescence (PL). The XRD and DTA–TG results expose that the YFAg–TS catalyst is a mixed phase consisting of anatase, rutile, and chlorargyrite, which is beneficial to improving the photocatalytic performance of TiO₂. The SEM, TEM, and BET results disclose that the YFAg–TS film has smaller nanoparticles, higher specific surface area, and narrower pore size compared with pure TiO₂ film. The XRD and TEM results exhibit that a part of yttrium can enter the TiO₂ lattice to induce lattice distortion. The XPS results confirm the presence of Y³⁺ state in the YFAg–TS sample, and Y³⁺ ions can act as the trapping site of electrons to expedite the separation of electrons and holes. The UV–vis DRS results reveal that the YFAg–TS film has an obvious absorption edge shift and a narrower bandgap (2.70 eV) compared with pure TiO₂ film. The PL results show that the YFAg–TS film has the highest photogenerated electrons and holes separation efficiency and charges transfer efficiency among all samples. The photocatalytic activity of the YFAg–TS was assessed by monitoring the degradation of methyl green and formaldehyde solution. The results manifest that the YFAg–TS film has high stability and excellent photocatalytic performance. The possible synergistic photocatalytic mechanism of YFAg–TS films has been discussed in this paper.     

High temperature deformation of an alumina composite reinforced with silicon carbide whiskers

Four-point bending creep tests were carried out in air on an alumina matrix composite reinforced with 9.3 vol.% of silicon carbide whiskers. Typical three-stage creep was observed. In the temperature range of 1673–1823 K, the composite exhibited an average stress exponent of 3.8. The activation energy for creep was estimated as ∼820–830 kJ mol⁻¹. Microstructure of the composite was characterized before and after deformation. Dislocation networks and other configurations were observed in samples deformed to large strains. It is concluded that the deformation mechanism consists of intragranular dislocation movement controlled by the lattice diffusion of oxygen ions.     

Optical fluorescence from chromium ions in sapphire: A probe of the image stress

The concentration dependent frequency shift of the fluorescence from chromium ions in sapphire is shown to be a direct probe of the image stress produced by the chromium substituting for the smaller aluminium ions in sapphire. Our analysis is based on a comparison of the frequency shift produced when the volume of a sapphire crystal is changed by an external pressure to that produced by a concentration of substitutional solute. The volumetric strain sensed by the fluorescing chromium ion when the lattice is expanded by substitutional solute is approximately one-third of that determined from X-ray lattice parameter measurements, in accord with the Eshelby analysis of the strain field due to a concentration of elastic defects in a finite body.     

Physical aspects of the solid-phase reduction of metals

The electric-charge and mass transfer processes in the crystal lattices of oxides are analyzed under conditions of high-temperature reduction of metals. As follows from the ionic character of the bond and defects in real oxide crystals, the electric-charge and mass transfer in them is shown to be caused by ion displacements. During high-temperature reduction, oxides are in a pseudoliquid state, where the cation sublattice is stable and provides the stability of the crystal lattice of an oxide as a whole and the anion sublattice is saturated by vacancies ensuring fast (superionic) oxygen transfer. The removal of oxygen ions from the lattice leads to the localization of “excess” electrons by the cations nearest to a vacancy and the transformation of these cations into metal atoms or cations with a lower charge. As a result, the oxide composition changes gradually from the highest oxide to a metal, and clusters whose structures correspond to all intermediate oxides form in the initial structure.