锌镀层表面稀土转化膜成膜机理分析(Ⅰ)

将镀锌层浸泡于以Ce(NO3)3.6H2O为主盐、以30%H2O2为氧化剂的稀土转化膜处理液中,通过计算界面上pH可达到的最大值、Ce-H2O系电位-pH图及Zn-H2O系电位-pH图,推断稀土转化膜可能是由ZnO、CeO2、Ce2O3、Ce(OH)3及Ce(OH)4构成;同时利用X射线光电子能谱仪对该铈盐转化膜表面进行成分分析,结果表明,铈盐转化膜主要是由ZnO、CeO2、Ce2O3、Ce(OH)3、Ce(OH)4构成的复合膜层,这与热力学分析计算相吻合。     

草酸共沉淀制备超细Ce0.8Sm0.2O1.9工艺优化

掺杂铈基电解质由于具有高电导率用于中温固体氧化物电解质材料.实验采用草酸盐共沉淀法制备20%(摩尔分数)Sm2O3掺杂CeO2(Ce0.8Sm0.2O1.9)氧化物粉末,采用XRD、SEM分析粉末的相结构和颗粒形貌,500℃～1000℃煅烧草酸沉淀物,得到氧化物粉末.XRD分析结果表明,Ce0.8Sm0.2O1.9为立方萤石结构,表明在低温合成了纯相的Sm2O3掺杂CeO2固溶体.激光粒度分析仪分析沉淀反应过程中草酸盐沉淀物和氧化物粉末的粒度分布.通过优化沉淀反应pH值、溶液浓度、添加表面活化剂及沉淀物水洗和干燥处理等制备工艺条件,实现对沉淀反应过程中草酸沉淀物的团聚控制,得到分散良好的亚微米草酸共沉淀物,进一步选择合适煅烧温度,得到亚微米级超细Ce0.8Sm0.2O1.9粉末.     

Sm、Ce单掺以及Sm、Ce共掺CaO-B_2O_3-SiO_2玻璃中稀土离子的荧光性质研究

分别研究了单掺Sm2O3和CeO2以及共掺Sm2O3、CeO2的CaO-SiO2-B2O3玻璃的发光性质。单掺Sm2O3的CaO-SiO2-B2O3玻璃的光谱中出现典型的Sm3+的光谱性质;单掺CeO2的CaO-SiO2-B2O3玻璃的光谱中出现Ce3+的光谱性质,在332nm激发下,Ce3+发射蓝紫光,其发射光谱为一宽谱带,从350nm延展到500nm附近,主发射峰位于393nm,Stokes位移为61nm,只形成一个发光中心。当CaO-SiO2-B2O3玻璃共掺Sm2O3和CeO2时,出现Ce4+的发射峰,同时Sm3+的发光强度下降,说明作为一种新的激活剂Ce引入基质后,提高了Sm3+的局部对称性,Sm3+的f→f跃迁减弱,从而导致Sm3+的发光强度下降。在共掺Sm2O3、CeO2的CaO-SiO2-B2O3玻璃中Ce4+和Sm3+通过桥氧键相连。     

Fe2O3粉末表面非均匀成核法包覆

为解决氧化铁红在高温下呈现不稳定性的问题, 采用非均匀成核法使Si（OH）4和Al（OH）3均匀包覆在氧化铁红粉末颗粒表面, 用X射线衍射仪、透射电镜、 Zeta电位测定仪对包覆前后的Fe2O3粉末颗粒进行分析. 结果表明, 通过非均匀成核法可以制备出被SiO2和Al2O3包覆的Fe2O3复合粒子, 其技术的关键是如何控制反应溶液pH值和涂层物质沉淀的反应浓度, 以保持被覆颗粒稳定的悬浮特性.     

GdCl_3·3H_2O-18C6-C_2H_5OH体系(25℃)的相化学及固态配合物的合成与表征

采用半微量相平衡方法研究了 Gd Cl3· 3H2 O - 18C6 - C2 H5 OH三元体系 (2 5℃ )的溶解度 ,测定了各饱和溶液的折光率 ,考察了相平衡过程中水的行为。绘制了体系的溶解度图与饱和溶液折光率曲线。发现了两种未见文献报道的配合物 :3Gd Cl3· 18C6· 9H2 O· C2 H5 OH与 Gd Cl3· 18C6· 3H2 O。前者为固液异成分溶解的配合物 ,后者为固液同成分溶解的配合物。制备了固态配合物 ,通过化学分析、IR、DTG、TG以及 DSC研究了配合物的组成与性质 ,由 DSC得到了配合物若干分解步骤的焓变。用热化学方法求得了固态配合物 Gd Cl3· 18C6· 3H2 O(s)的标准生成焓     

Synthesis and characterization of Ce0.8Sm0.2–xPrxO2–δ（x=0.02–0.08）solid electrolyte materials

Solid electrolytes Ce0.8Sm0.2–xPrxO2–δ(x=0.02, 0.04, 0.06, 0.08) were prepared by citric-nitrate method. The microstructure and electrical properties of such materials were examined by X-ray diffraction(XRD), atomic force microscopy(AFM), Raman spectroscopy(Raman), X-ray photoelectron spectroscopy(XPS) and impedance spectroscopy analyses. Specifically, results from XRD analysis showed that samples calcined at 800 oC for 4 h possessed single-phase cubic fluorite structure, and the average grain size was found to be 36–45 nm. Further Raman spectral analysis indicated that oxygen vacancies should be present in the cubic fluorite structure of Ce0.8Sm0.12Pr0.08O2–δ, and Pr-doping seemed to increase their concentration significantly. AFM images showed that the grain size grew with the increase of Pr substitution. XPS analysis confirmed the existence of oxygen vacancies in the lattice of Ce0.8Sm0.12Pr0.08O2–δ in which Pr3+ and Pr4+ co-existed. AC impedance spectra indicated that the conductivity of Ce0.8Sm0.2–xPrxO2–δincreased with the increase of Pr-doping but the conduction activation energy decreased. Notably, it appeared that sample Ce0.8Sm0.12Pr0.08O2–δ(σ600 oC=1.21×10–2 S/cm, Ea=0.77 e V) exhibited conductivity superior to Ce0.8Sm0.2O1.9(σ600 oC=2.22×10–3 S/cm, Ea=1.02 e V) because it possessed higher conductivity and lower activation energy. At 600 oC, the conductivity of Ce0.8Sm0.12Pr0.08O2–δwas 4.45 times higher than that of the un-doped material.     

共沉淀法制备Sm2Fe17合金前驱体的热力学分析

对制备钐铁合金前驱体的Sm(Ⅲ)-Fe(Ⅱ)-NH3·H2O-NH4HCO3-H2O体系进行了热力学分析,给出了溶液中Sm(Ⅲ)、Fe(Ⅱ)浓度与pH值的关系,确定了两种金属离子完全共沉淀的最佳pH为7.0.     

Synthesis and Properties of Heteropoly Complexes LnHSiW_(12)O_(40)·xH_2O

The present paper covers seven rare earth-containing tungstosilicate heteropoly complexesLnHSiW_(12)O_(40)·xH_2O with Keggin structure(Ln=La,Ce,Pr,Nd,Sm,Eu and Gd)snythesized by doubledecomposition reaction.The synthesized heteropoly complexes were characterized by ICP,~(29)Si-NMR,XPS,XRD,IR,UV,polarogram,CV and TG-DTA.The relationship between the structure of the synthesizedheteropoly complexes and their properties is discussed.     

水相介质中纳米CeO2的分散行为

通过测定悬浮液体系润湿性、表面电性及分散性研究了纳米CeO2在不同条件下水相介质中的分散行为.结果表明 纳米CeO2 在水相介质中的润湿与分散受体系pH值的影响很大, 与Zeta电位有相当好的一致关系, 其分散机理主要是双电层静电排斥作用; 纳米CeO2的等电点(pHPZC)为6.8左右; 纳米CeO2颗粒在酸性水介质中表面带正电, 在碱性水介质中表面带负电, Zeta电位分别在pH值为4和11左右时较高, 相应润湿性和分散性较好; 随机械搅拌速率和时间的增加, 纳米CeO2的分散性增强; 超声波对纳米CeO2的分散作用明显优于机械搅拌, 20 kHz频率下超声波分散1 min便能显著改善纳米CeO2的分散状态; 加入六偏磷酸钠(SHP)作为分散剂将改变纳米CeO2颗粒表面电性, 使其带负电, Zeta电位随SHP浓度增加而增大, 起增强双电层的静电排斥作用; 当SHP浓度达225 mg·L-1时, Zeta电位趋于稳定, 并使纳米CeO2在广泛的pH值范围内获得较高的Zeta电位和很好的分散效果, 从而降低了体系pH值的影响.     

NH4HCO3沉淀法制备纳米CeO2棒状晶的研究

以Ce(NO3)3·6H2O和NH4HCO3为原料,采用化学沉淀法制得了平均长度84nm,直径15nm的CeO2棒状晶.利用XRD、TEM对CeO2粉体及其前驱体进行分析表征,发现CeO2晶粒继承了前驱体的棒状形貌.借助FTIR确定了前驱体的化学组成为Ce2O(CO3)2·H2O,从化学反应过程出发研究了CeO2棒状晶的具体形成过程.     

CaO-La2O3-B2O3-Eu2O3转光玻璃的合成及荧光性质

X射线衍射研究表明CaO-La2O3-B2O3-Eu2O3体系的玻璃化温度在1025℃附近。荧光光谱和ESR谱研究表明,在CaO-La2O3-B2O3-Eu2O3玻璃体系中存在着Eu2 和Eu3 两种价态离子。316,360,379,394,413,462和532nm锐线激发峰和592,616和650红区发射峰分别对应Eu3 的f-f激发跃迁和5D0-7FJ(J=1,2,3)跃迁发射;351nm和427nm宽带激发峰和蓝区发射分别对应Eu2 的5d-4f激发跃迁和发射。     

Vitrification and Crystallization Behavior of CaO-SiO2-MgO-Al2O3-Fe2O3-Cr2O3 System

Metallurgical and Materials Transactions B - The effect of basicity and Cr2O3 content on vitrification of the CaO-MgO-SiO2-Al2O3-Fe2O3-Cr2O3 system during a melt-quenched process and the...     

Wettability of silicon carbide ceramic by Al2O3/Dy2O3 and Al2O3/Yb2O3 systems

Wettability is an important phenomenon in the liquid phase sintering of silicon carbide (SiC) ceramics. This work involved a study of the wetting of SiC ceramics by two oxide systems, Al₂O₃ /Dy₂O₃ and Al₂O₃ /Yb₂O₃, which have so far not been studied for application in the sintering of SiC ceramics. Five mixtures of each system were prepared, with different compositions close to their respective eutectic ones. Samples of the mixtures were pressed into cylindrical specimens, which were placed on a SiC plate and subjected to temperatures above their melting points using a graphite resistance furnace. The behavior of the melted mixtures on the SiC plate was observed by means of an imaging system using a CCD camera and the sessile drop method was employed to determine the contact angle, the parameter that measures the degree of wettability. The results of variation in the contact angle as a function of temperature were plotted in graphic form which showed that the curves displayed a fast decline and good spreading. All the samples of the two systems presented final contact angles of 40° to 10° indicating their good wetting on SiC in the argon atmosphere. The melted/solidified area and interface between SiC and melted/solidified phase were evaluated by scanning electron microscopy (SEM) and their crystalline phases were identified by X-ray diffraction (DRX). The DRX analysis showed that Al₂O₃ and RE₂O₃ reacted and formed the Dy₃Al₅O₁₂ (DyAg) and Yb₃Al₅O₁₂ (YbAg) phases. The results indicated that the two systems had a promising potential as additives for the sintering of SiC ceramics.     

Solid-phase reactions of Ta2O5 with Ga2O3 and In2O3

Conclusions Using the techniques of DTA and x-ray phase analysis, a study was made of the reactions between Ta₂O₅ and M₂O₃ (M = Ga or In), and the phase compositions of the relevant binary systems were determined. The existence was confirmed of stable compounds of composition MTaO₄ and eutectoidally decomposing phases containing 7.5–12.5 mole % M₂O₃. MTaO₄ are dielectrics, whose room-temperature _v is of the order of 10¹⁰ -cm. The temperature dependence of _v of MTaO₄ was investigated in the range 293–873°K and their energies of activation for conductivity were calculated. The melting points, pyknometric densities, dielectric losses, and relative dielectric permeabilities of MTaO₄ were determined.Translated from Poroshkovaya Metallurgiya, No. 2 (110), pp. 69–73, February, 1972.     

镁砂中Fe2O3、Al2O3、P2O5、TiO2的联合测定

镁砂产品检验中,采用碱熔融法共同预处理样品,在同一母液中,联合测定铁、铝、磷、钛的含量,缩短了检测时间。通过分别控制各元素的显色酸度,各元素线性良好,测得的Fe2O3、Al2O3、P2O5、TiO2的相对标准偏差分别小于1.11%、2.78%、4.84%、5.88%。实验结果表明,方法的准确度和精密度都较高。     

X射线荧光光谱法测定Dy_2O_3及其杂质Eu_2O_3,Gd_2O_3,Tb_4O_7,Ho_2O_3,Er_2O_3和Y_2O_3

当前稀土应用范围越来越广,尤其Dy2O3和金属Dy其出口量不断增大．Dy2O3中所含杂质总量通常在0．1％～5％之间,该范围内的测定方法以XRFR为合适,快速、准确、无破坏．1实验部分1．l原理本法采用粉末直接压片法制样,在各元素分析线峰位上测量X射线强度,根据待测元素的X射线荧光光谱强度与含量的定量关系,选择相应的数学模型,由计算机自动计算出待测成份含量．1．2仪器和试剂荷兰飞利浦PW—1400顺序式X射线荧光光谱仪;康柏486计算机;电动小型油压机;万分之一精度分析天平．DyZO399．999％;EnD3,GdD3,ThAn,HoAn,ErD3…     

Al_2O_3La_2O_3Y_2O_3/Cu复合材料的电弧侵蚀特性研究

采用喷射沉积和内氧化法制备出Al2O3La2O3Y2O3/Cu复合材料,研究该材料在直流20 V/20 A的工作条件下触点的电弧侵蚀特性,并与Al2O3/Cu材料进行了对比分析.利用电子天平、扫描电镜等方法分析电弧侵蚀后触点的质量变化和表面微观结构.结果表明,通过添加Y2O3、La2O3稀土氧化物颗粒,可有效降低触头材料的材料转移量.Al2O3La2O3Y2O3/Cu材料的抗熔焊性和抗烧损性优于Al2O3/Cu材料的性能.在直流阻性负载条件下Al2O3La2O3Y2O3/Cu阳极触头表面形成凹坑,阴极触头表面形成凸起,触点表面显示出浆糊状凝固物和喷发坑等电弧侵蚀形貌特征.     

Dispersibility and Gelcasting Process of BN-Al2O3 -Y2O3 System

The influence of dispersants and decentralization condition on rheological properties and gelcasting of BNA12O3-Y2 O3 slurry was discussed, and the thermodynamics of cross-linking process was studied. The results show that PAA is more effective and proper density of cross-linking can form unitary, stable gelinite system.     

Viscosity of CaO-SiO2-Al2O3-MgO-B2O3 slags

The viscosity of CaO-SiO₂-Al₂O₃ slags with 8% MgO and 4% B₂O₃ is investigated over a broad range of composition, by means of a simplex-lattice experiment design. For slag of basicity 6–8 in the upper left region of the local simplex, with 15–25% Al₂O₃, 8% MgO, and 4% B₂O₃, the viscosity is high: 9.4–26.4 P over the range 1500–1530°C. Displacement of the slags of basicity 5–8 to the lower region of the local simplex ensures high fluidity in the given range of Al₂O₃ concentration: the viscosity is 1.5–6.1 P over the range 1500–1530°C.     

Effect of Gd2O3 and La2O3 on BaTiO3 -Based Ceramics

The addition of rare-earth oxides Gd2O3 and La2O3 to BaTiO3-based ceramics can restrain the growth of grain size, which obtained small grain size below 1 μm and high density. The dielectric constant at room temperature increased and the curve of ε-T was flattened which illustrated that the ferroelectricity of BaTiO3-based ceramics was weakened. In addition, it is illustrated that Gd2O3 leads to chemical nonhomogeneous property, i.e. core-shell structure and La2 O3 leads to chemical homogenous property, which take different effects on capacitance- temperature characteristic.