钇离子在铜电极上的电极过程及表面合金化

钇离子在铜电极上的电极过程及表面合金化周春根,段淑贞（北京科技大学理化系,北京１０００８３）通过熔盐电化学表面合金化方法获得的镀层非常均匀、无裂纹,具有很强的抗腐蚀性能,其原因是获得的合金镀层系由一种金属原子向另一种基体金属表面扩散的结果￣［１,２］...     

Yttrium complexation with benzoic acid and tris(hydroxymethyl)aminomethane

Yttrium complexation in extraction systems with benzoic acid (BA) and tris(hydroxymethyl)aminomethane (THMAM) was studied. The growth of yttrium distribution ratios in this system is caused by the formation of different-ligand coordination compounds of yttrium with BA and THMAM. Quantum chemical calculations for the formation energy of different-ligand complex showed that the most stable complex forms when yttrium atom coordinates to two THMAM molecules via oxygen and nitrogen atoms and to one THMAM molecule via nitrogen atom. The complex is stable in both bidentate and monodentate coordination of the carboxyl groups of benzoic acid to yttrium atom. Obtained yttrium extracts were used for the synthesis of complex-oxide nanosized cathodophosphors by extraction-pyrolytic technique.     

Influence of hydrolysis method on the sol-gel formation of the yttria-alumina system with use of alcoholates

The influence exerted by hydrolysis methods and introduction of a hydrolyzing agent into the systems formed by the alkoxide technology, which uses yttrium salts and alumium secondary butylate as the initial components, was determined. It was found that the hydrolysis stage affects the conditions of the subsequent thermal treatment, the phase formation in the system, and the granulometric composition of the prepared powders. The most favorable conditions for formation of yttrium aluminum garnet are achieved upon excess water hydrolysis in the presence of an aqueous solution of yttrium salt.     

碳酸钇铵复盐结晶的形成及影响因素

对碳酸氢铵沉淀钇时碳酸钇铵复盐结晶的形成条件与ｐＨ变化特征进行了研究,发现其结晶过程与平衡溶液ｐＨ有对应关系。溶液ｐＨ由碳酸钇铵结晶化反应和碳酸氢铵的水解反应所控制。根据溶液ｐＨ的变化可以判断结晶反应是否发生或完成,以及结晶速度的快慢和结晶的程度。Ｘ－射线衍射及差热－热重分析结果表明,产物为复盐结晶２,加料方式对结晶的形成有很大影响。     

Thermodynamics of formation of lanthanide hydroxo complexes in aqueous solutions

Gibbs energies of formation have been determined by conductometric titration for hydroxo complexes of cerium, samarium, europium, erbium, ytterbium, and yttrium. All these elements form monohydroxo complexes; yttrium, erbium, and terbium also form dihydroxo complexes. The Gibbs energies of formation of lanthanide hydroxo complexes from ions have virtually equal values of −47.3 ± 0.6 kJ/mol monohydroxo complexes and −44.5 ± 0.5 kJ/mol for dihydroxo complexes, respectively. These values were used to estimate the Gibbs energies of formation of hydroxo complexes for the entire lanthanide series.     

Influence of the synthesis conditions on the particle size and morphology of yttrium orthoferrite obtained from aqueous solutions

The size and morphology of yttrium orthoferrite nanoparticles were examined in relation to the synthesis conditions. The chemical composition of the crystalline phases resulted from heat treatment of the samples at 650°C varies with the procedure of coprecipitation of yttrium and iron(III) hydroxides. At the same time, heat treatment at 750°C leads to formation of yttrium orthoferrite solely. The size of the YFeO₃ crystals is weakly dependent on the initial composition preparation procedure, and the size and shape of their agglomerates are sensitive to the conditions of coprecipitation of the hydroxides.     

Spectrophotometric studies and application on the beta-type complex of Y-CPApK

The beta-type complex formed between yttrium and p-carboxychlorophosphonazo (CPApK) has been studied. It was found that Y-CPApK complex can give a maximum absorptivity in a buffer media of HAc-NaAc ranging from pH 3.5-4.3 and at a wavelength of 732 nm. Under the conditions employed, the molar absorptivity was found to be 7.72x10(4) l mol(-1) cm(-1) and the molar ratio of Y-CPApK was 1:2. The linear range was within 2-16 mug of yttrium in 25 ml solution. One of the characteristics of the complex was its high tolerance for calcium and hence a method of separation and enrichment of microamounts of yttrium by using calcium oxalate precipitate was developed and applied to measure yttrium in nickel-base alloys. The parameters which were related to the formation of the beta-type complex of Y-CPApK were discussed and a comparison of existing beta-type complexes between yttrium and the chlorophosphonazo reagents of chromotropic acid was made.     

Comparison of yttrium,lanthanides and actinides in respect to unit cell volumes of isostructural compounds and thermodynamic functions of complex formation

The investigations carried out till now and presented in this paper show that apart from the well known itinerant properties of yttrium in respect to free energy of complex formation, also actinides(III) change their position in the lanthanide series in respect to G. It has also been shown that yttrium and actinides exhibit itinerant behaviour in respect to unit cell volumes. Evidence has been presented that delocalization of 4f and 5f orbitals is the reason for the two types of migratory properties. Since the itinerant behaviour of yttrium and actinides(III) in respect to stability constants (free energies of complex formation) is the basis for yttrium-lanthanides and lanthanides-actinides group separations, a better qualitative understanding of the mechanism involved may contribute to the development of more efficient separation procedures.     

Langmuir–Blodgett Films of Fatty Acid Salts of Bi- and Trivalent Metals: Y, Ba, and Cu Stearates

Dependences of the composition and properties of the monolayers and Langmuir–Blodgett films of yttrium, barium, and copper stearates on the conditions of their formation were studied by FTIR spectroscopy, X-ray photoelectron spectroscopy, and quartz crystal microbalance technique. The identity of film compositions on the surfaces of liquid and solid substrates was established. It was shown that, in the case of copper and yttrium, the Langmuir–Blodgett films are formed from corresponding basic salts of stearic acid at high subphase pH values. The conditions of the preparation of high-quality Langmuir–Blodgett films from yttrium, barium, and copper stearates are determined.     

Formation mechanism of nanocrystalline yttrium orthoferrite under heat treatment of the coprecipitated hydroxides

Formation of nanocrystalline yttrium orthoferrite of ～30 nm average crystallite size from coprecipitated iron(III) and yttrium hydroxides was studied by thermo-X-ray diffractometry and simultaneous thermal analysis over 25–900°C temperature range. A mechanism of physicochemical transformations leading to the formation of YFeO₃ nanoparticles was suggested.     

Formation of molecular glasses and the aggregation in solutions for lanthanum(III), calcium(II), and yttrium(III) complexes of octanoyl-DL-alaninate

Octanoylalaninato-metal (metal = calcium(II), yttrium(III), lanthanum(III), and zinc(II)) complexes were prepared and the first three metal complexes were found to readily form transparent and stable molecular glasses from methanol and chloroform solutions. The process of glass formation from solution was studied in detail. The effect of the central metal ions on the formation of glassy states was remarkable: the lanthanum and calcium complexes assumed glassy or crystalline states depending on the isolation method and the yttrium complex had a large tendency to assume an amorphous state, whereas the zinc complex did not assume a pure and stable glassy-state. The glass transition temperatures were 50 degrees C for the yttrium complex and 70-75 degrees C for the lanthanum and calcium complexes when these complexes are monohydrates prepared by a solvent-cast method, whereas they increase by 10-30 degrees for the hemihydrates which were obtained by an annealing treatment at 110 degrees C. The coordinated water was eliminated from the solid above the glass transition temperature. The glassy state was regarded as a result of the self-aggregation of the metal complex in solution by an entanglement of the methylene chains with one another. SAXS showed the presence of two disordered bilayer structures with 2.2 nm and 4.5 nm periods in the glassy states. The structures of the molecular assemblies in the solid states and solutions were compared by SAXS and NMR studies. EXAFS studies confirmed the coordination numbers of oxygen atoms around the yttrium and lanthanum atoms in the glassy states for the yttrium and lanthanum complexes to be about 7.     

Synthesis of yttrium orthoborate powders

Yttrium orthoborate YBO₃ is synthesized by calcining precursors precipitated with aqueous ammonium hydroxide from yttrium nitrate or yttrium chloride solutions (with concentrations ranging from 4.8 × 10^?3 to 0.0165 mol/L) and with a more than tenfold excess of boric acid. Single-phase YBO₃ is obtained at pH 5–6. Higher pHs result in the formation of mixtures of yttrium orthoborate and yttrium hydroxide phases. Dehydration occurs up to 288°C as shown by differential thermal analysis. Further heating induces crystallization. Addition of surfactants (polyvinylpyrrolidone (PVP) or ammonium polyacrylate (APA)) to the starting solution in an amount of 1 wt % of the yttrium salt affects the sizes and shapes of the precipitated particles. YBO₃ platelets with nanometer thicknesses are obtained. The temperature of the low-temperature ? high-temperature vaterite phase transition in YBO₃ is 977°C upon heating and 640°C upon cooling.     

Effect of yttrium oxide on the formation of the phase composition and porous structure of titanium dioxide

The formation of the structure of TiO₂ (anatase) doped with 1–5 mol % Y₂O₃ is reported. The dopant changes the anatase structure from regular to nanocrystalline. The nanocruystalline structure consists of incoherently intergrown 5- to 7-nm anatase crystallites (500°C) separated by interblock boundaries accommodating yttrium ions. The formation of the nanocrystalline anatase structure stabilizes small anatase crystallites and raises the anatase-to-rutile phase transition temperature above 900°C. Owing to this structure, the developed specific surface area and fine porous texture of yttrium oxide-doped titanium dioxide survive up to higher temperatures than those of undoped titanium dioxide.     

Evolution of yttrium trifluoroacetate during thermal decomposition

A detailed analysis of the thermal decomposition of yttrium trifluoroacetate under different atmospheres is presented. Thermogravimetry, differential thermal analysis, and evolved gas analysis have been used for this in situ analysis. Solid residues at different stages have been characterized by means of X-ray diffraction, elemental analysis, Fourier transform infrared spectroscopy, and scanning electron microscopy. The first decomposition stage (310 °C) is exothermic and involves the complete removal of carbon (organic part) and the formation of yttrium fluoride. This process is characterized by a fast mass loss rate. Afterwards, yttria (Y₂O₃) is formed at 1200 °C through a slow process controlled by the out diffusion of fluorine that involves the formation of yttrium oxyfluoride as an intermediate. The evolution of the mass during the decomposition and the structure of the yttria particles is not affected by the presence of oxygen or water. However, when the oxygen (water) partial pressure is as low as 0.02% (<0.002%), the kinetics and final particle structure are strongly affected.     

Beziehungen zwischen den thermodynamischen Potentialen der Bildung der Yttrium- und Seltenerd-Eisen-Perowskite und -Granate und den Ionenradien des Yttriums und der Seltenen Erden

Relations between the Thermodynamic Potentials for the Formation of Yttrium and Rare Earth Iron Perovskites and Garnets and the Ionic Radii of Yttrium and the Rare Earth Elements General formulas are derived for the Gibbs energies, enthalpies, entropies, and derived thermodynamic quantities related to the formation of yttrium and rare earth iron perovskites and garnets. Only the ionic radii of yttrium or the rare earth elements are required besides the temperature.     

Catalytic Induced Thermal Conversion of Amorphous Carbon into Single Walled Carbon Nanotubes

Single walled carbon nanotubes (SWNTs) have caught extensive attention in the field of material science and electronics. Their formation typically uses plasma arc or CVD techniques [1–3]. So far, formation of SWCNTs just by thermal conversion of amorphous, non graphitic carbon which is a nearly ubiquitous carbon source is challenging but has not been reported so far. We herein demonstrate the catalytic growth of SWNTs from an amorphous carbon source (activated charcoal powder, ‘Aktivkohle’) mediated by three different catalytically active metals; metallic nickel, nickel derived from bis(η⁵‐cyclopentadienyl)nickel (nickelocene) and yttrium formed in situ from yttrium oxide.     

掺钇锆醇盐水解Sol-Gel的物化过程及其机理

醇盐水解法广泛用于金属氧化物溶胶-凝胶的制备．一般，醇盐水解有二种方式，一是通过金属醇盐的完全水解、生成沉淀、继而胶溶形成溶胶；另一种是通过控制水解直接制得溶胶或凝胶．其中，由于醇盐控制水解法成胶容易，胶凝时间可以通过控制参数进行调节，所得胶粒细小均匀，因     

The thermodynamic properties of hydroxo compounds and the mechanism of ion flotation for cerium,europium, and yttrium

The pH values of formation of hydroxo complexes and hydrates in solutions of cerium(III), europium(III), and yttrium salts were determined by conductometric titration. The instability constants of hydroxo complexes, solubility products of hydroxides, and Gibbs energies of formation of the compounds specified were calculated. Conclusions about the mechanism of extraction and ion flotation of these metal cations from aqueous solutions were drawn.     

Extraction of Lanthanide(III) and Yttrium(III) Nitrates with a Toluene Solution of Trialkylbenzylammonium Naphthenate

Extraction of lanthanides(III) [La(III)-Lu(III)] and yttrium(III) with toluene solution of trialkylbenzylammonium naphthenate mixture was studied. The equations of extraction isotherms taking into account formation of the extractable complexes (R₄N)₂[Ln(NO₃)₃A₂] (A is naphthenate anion) were obtained. The extraction constants of lanthanides [La(III)-Lu(III] and yttrium(III) were calculated.     

Synthesis,crystal structure modeling and thermal decomposition of yttrium propionate [Y2(CH3CH2COO)6·H2O]·3.5H2O

An yttrium propionate complex was synthesized and characterized for its application as precursor for Y₂O₃ based oxide thin films deposition and YBa₂Cu₃O_7 − x superconducting thin films. The TG–DTA and FT-IR analyses have revealed the formation of an yttrium propionate complex with the formula [Y₂(CH₃CH₂COO)₆·H₂O]·3.5H₂O. The molecular structure of the yttrium propionate complex was determined by modeling the FT-IR spectra. The coordination numbers for the yttrium ions are eight and nine, respectively being coordinated by bridging bimetallic triconnective and chelating bidentate propionate groups.The thermal decomposition of yttrium propionate has been investigated by thermogravimetric (TG) and differential thermal analysis (DTA) coupled with quadrupole mass spectrometry (QMS), X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) techniques.