均分散球形氧化铕超细微粒的制备和表征

采用尿素分解法制备了均分散球形Eu(OH)CO~3·H~2O超细沉淀粒子,进一步在空气中750℃下焙烧4h,得到了均分散球形氧化铕超细微粒。考察了各种反应条件的影响,获得了最佳的制备条件。用XRD,IR,TEM,TG以及比表面测定等手段对样品进行了表征。     

Preparation of monodispersed polymer-modified colloidal silica particles of less than 50 nm diameter

The preparation of monodisperse, ultrafine polymermodified colloidal silica, 11 or 42 nm in diameter, were studied. The reaction of the colloidal silica with polymeric silane coupler in 1,2-dimethoxyethane and removal of the unreacted polymer with granular silica gel (10–20 mesh) in acetone gave a suspension of monodisperse composite particles.     

Preparation of monodispersed colloidal particles

The procedures and the backgrounds for the formation of monodispersed colloidal particles are reviewed, along with the personal view of the author's own, by classifying a wide variety of the systems. This article consists of the size distribution control for uniform colloidal systems with typical examples, including homogeneous and heterogeneous systems, and the crystal habit control of monodispersed particles.     

超细均分散稀土化合物胶粒的生长动力学

研究了尿素体系中超细均分散碳酸钕/碱式碳酸钇胶粒形成时, 粒子的尺寸随,以并运用Nielsen的时间因子分析法(Chronomal Analysis)表征了两种胶粒的生长机理, 获得了相应的速率常数。实验表明, 两种胶粒的生长(<40min)主要遵循表面反应控制的一级多核层增长机理。时间的变化规律     

Synthesis,characterization and thermal (tg-dsc) study of yttrium methanesulfonate coordination compounds with pyridine N-oxide and 2-,3- and 4-picoline N-oxides

The synthesis, characterization and thermal (TG and DSC) study of the coordination compounds Y(MS)₃A(py-NO)₂AH₂O, Y(MS)₃A(2-picNO)₃, Y(MS)₃A(3-picNO)₂ and La(MS)₃A(4-picNO)₂ are reported (MS?=?methanesulfonate, py-NO?=?pyridine N-oxide, and 2-picNO, 3-picNO and 4-picNO are 2-, 3- and 4-picoline N-oxides, respectively). The observed thermal stability trend is: 2-picNO?≈?4-picNO< 3-picNO< py-NO. Release of ligand molecules (endothermic) is followed by thermal degradation of the ligands (exothermic) with an increase in the exothermic values from 2-picNO to 4-picNO.     

Mechanism of the growth of monodispersed spherical silica particles to the submicron size

Summary Monodispersed spherical submicron silica particles were obtained by the precipitation of soluble silica on the surface of preliminary obtained smaller particles. Silica was added into the system at low concentrations to prevent both its polymerization in the solution and the formation of new particles. The kinetics of the particle growth is controlled by the diffusion of soluble silica through the double diffusion layer.     

Preparation of monodispersed plate-like particles of tungstic acid

 To understand the properties of colloidal dispersions it is often vital to prepare model materials with particles that have a small polydispersity in order to make experimental tests of theories or models. However few preparations have been developed that yield anisotropic particles with a narrow size distribution and precise shape. In this paper the preparation of a dispersion of charge stabilized, tungstic acid particles is described. The particles are rectangular and have a length of 7.0 μm, a width of 2.8 μm and a thickness of 0.2 μm. The polydispersity is 8% in length and 10% in width, making it one of the most monodisperse dispersions of anisotropic particles. Each particle is monocrystalline and the crystal orientation is fixed with respect to the particle morphology. Some interesting behavior is observed: these particles aggregate perpendicular and parallel to each other to give flat, ordered flocs when the stability is reduced. Received: 22 January 1998 Accepted: 4 February 1998     

Adsorption of large macromolecules on fine colloidal particles

A simple model of adsorption of large macromolecules on ultra-fine colloidal particles is presented. The basic assumption of the model is that the number of particles attached to a single molecule is a random quantity. Both the reversible and irreversible polymerparticle binding is considered. Also, effects of the non-ideal mixing of polymer solution with suspension and of the polymer/particle size ratio on the shape of the adsorption isotherm are examined. The predictions of the model are confronted with experimental results of the study on the adsorption of very high molecular weight polyacrylamide on fine AgI colloidal particles.     

Ion imprinted polymer particles for separation of yttrium from selected lanthanides

Lanthanide(III) (Dy, Gd, Tb and Y) ion imprinted polymer (IIP) materials were synthesized via single pot reaction by mixing lanthanide imprint ion with 5,7-dichloroquinoline-8-ol, 4-vinylpyridine, styrene, divinylbenzene and 2,2'-azobisisobutyronitrile in 2-methoxyethanol porogen. The imprint ion was removed by stirring the above materials (after powdering) with 6 mol/L HCl to obtain the respective lanthanide IIP particles. Y-Dy, Y-Gd and Dy-Gd polymer particles were obtained by physically mixing equal amounts of the respective leached individual lanthanide(III) particles. Control polymer (CP) particles were similarly prepared without imprint ion. Application of the above synthesized polymer particles was tested for separation of Y from Dy, Gd and Tb employing batch and column SPE methods using inductively coupled plasma atomic emission spectrometry for the determination. Optimization studies show that Y present in 500 mL can be preconcentrated using Dy-Gd IIP particles and eluted with 20 mL of 1.0 mol/L of HCl, providing an enrichment factor of approximately 25. Dy-Gd IIP particles offer higher selectivity coefficients for Y over other lanthanides compared to other IIP particles and commercial liquid-liquid extractants. Selectivity studies for Y over other coexisting inorganic species (other than lanthanides) were also conducted and the results obtained show a quantitative separation of Y from other inorganics other than Cu(II) and Fe(III). Furthermore, both batch and column studies indicate the purification of yttrium concentrate from 55.0 +/- 0.2 to 65.2 +/- 0.2% in a single stage of operation.     

Stability of dispersions of colloidal hematite/yttrium oxide core-shell particles

The colloidal stability of suspensions of hematite/yttria core/shell particles is investigated in this work and compared with that of the pure hematite cores. The different electrical surface characteristics of yttrium and iron oxides, as well as the diameters of both types of spherical particles, dominate the overall process of particle aggregation. The aggregation kinetics of the suspensions was followed by measuring their optical absorbance as a function of time. By previously calculating the extinction cross section of particle doublets, it was demonstrated that for both core and core/shell particles the turbidity of the suspensions should increase on aggregation. Such an increase was in fact found in the systems in spite of the ever-present tendency of the particles to settle under gravity. The authors used the initial slope of the turbidity increment time plots as a measure of the ease of aggregation between particles. Thus, they found that the essential role played by pH on the charge generation on the two oxides and the shift of one pH unit between the isoelectric points of hematite and yttria manifest in two features: (i) the stability decreases on approaching the isoelectric point from either the acid or basic side and (ii) the maximum instability is found for hematite at pH 7 and for hematite/yttria at pH 8, that is, close to the isoelectric points of alpha-Fe(2)O(3) and Y(2)O(3), respectively. The role of added electrolyte is simply to yield the suspensions of either type more unstable. Using the surface free energy of the particles, the authors could estimate their Hamaker constants in water. From these and their zeta potentials, the DLVO theory of stability was used to quantitatively explain their results.     

Surface modification of colloidal silica particles

Colloidal silica particles in organic solvents were grafted, using several reagents, in order to make them hydrophobic. The hydrophobicity of the beads could be easily varied. Quasielastic light scattering and transmission electron microscopy experiments showed that no aggregation occurs during the reaction when monofunctional agents are used. Elemental analysis and solid-state NMR measurements gave us the rate of surface modification of the silanol groups. We also studied the rheological behaviour of the grafted particles as a function of the volume fraction in solvents of various hydrophobicity. Hexamethyldisilazane-grafted particles display hard-sphere behaviour in polar solvents such as 2-propanol, but not in alkanes, whereas dimethyldodecylchlorosilane-grafted particles flocculated in polar solvents but could easily be dispersed in apolar solvents. Received: 15 March 2000 Accepted: 11 July 2000     

Highly efficient formation of metal and metal alloy particles from methyl metal compounds by a single pulse laser irradiation

Highly efficient processes for fine particle formation of metal alloys and metal oxides were developed using a high-power laser. In these processes, laser light was used only for the ignition of a thermal chain reaction. This reaction was suppressed by adding inert gases, and the suppression effect was in the order C₃H₈ > C₂H₆ > CH₄ > He > Ar > Xe. Oxygen accelerated the reaction because of the large exothermicity of the reaction of oxygen with methyl metal compounds.     

Controlling stages of supramolecular crystallization in suspensions of monodispersed spherical silica particles

Supramolecular crystallization in alcohol suspensions of monodispersed spherical silica particles at pH ~ 7-7.8 is controlled by sedimentation of structural units. At pH ~ 7.8-10.5 or in the presence of indifferent (inert) electrolytes, the crystallization is controlled by the linear growth of supramolecular crystals. The peculiarities of crystallization and nucleation in both cases are discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Controlling the morphology of yttrium oxide through different precursors synthesized by hydrothermal method

Y₂O₃ sheets, rods, needles and tubes were synthesized from three precursors through hydrothermal reactions followed by calcination. The phase distribution and decomposition behaviors of the three precursors, Y₂(OH)_5.14(NO₃)_0.86·H₂O, Y₄O(OH)₉(NO₃) and hexagonal Y(OH)₃, were investigated. The reaction temperature and initial pH value during the hydrothermal reaction showed great influence on the shape and particle size of the products. The precursors were converted to Y₂O₃ particles with the retained original morphology of the precursors.     

Electrorheological properties of suspensions of monodispersed micron‐sized polyaniline composite particles

Monodispersed micron‐sized polyaniline (PANi) composite particles were synthesized by chemically oxidative polymerization of aniline in the presence of functional porous polymer particles. The formation of the PANi‐coated composite particles was confirmed by scanning electron microscopy. Electrorheological (ER) properties of the monosized composite particle suspensions were then investigated under different DC electric fields by altering the particle characteristics. The ER effect of the PANi composite suspensions was largely dependent on the composition ratio (PANi loading), the particle conductivity, and the particle concentration. Dynamic oscillation measurements revealed that the applied electric field induced the viscoelastic property of the ER suspensions by generating the chain structures of the suspended particles. © 2002 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 40: 1163–1170, 2002     

Controllable synthesis of monodisperse nonspherical colloidal particles with cavity structures

This article reports a facile controllable approach to prepare monodisperse nonspherical colloidal particles with cavity structures by one‐pot soap‐free emulsion polymerization of styrene (St), 3‐(trimethoxysilyl)propyl methacrylate (MPS), and acrylic acid (AA). In our strategy, only by varying the feeding time of AA to the as‐polymerized St and MPS, the nonspherical latex particles with single cavity of different surface roughness and multicavity structures could be successfully synthesized. The depth and width of the cavity can be also easily controlled by adjusting the amount of MPS and AA. A possible formation mechanism is proposed on the basis of experimental results. These nonspherical colloidal particles, which have controllable cavity structures, are good building blocks or templates for the construction of functional coating and complex colloidal architectures. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 1645–1652     

Methyltriethoxysilane-derived sol-gel coatings doped with silver metal particles

Silica sol-gel films were prepared by dipping, starting from an acid catalyzed solution of methyltriethoxysilane (MTES) and tetraethoxysilane (TEOS). Silver metal nanoparticles were produced in the silica layer by introducing in the sol-gel precursor solution AgNO₃ or AgClO₄·H₂O. The silver ions were thermally reduced in air at 800°C, giving an intense yellow coating film. The silver metal particles were observed by transmission electron microscopy and X-ray diffraction. The diameter of the silver particles was found to be about 10 nm. Absorption measurements in the UV-Vis were used to evaluate the volume fraction of silver colloids embedded in the silica layer.     

The preparation of sol-gel materials doped with ionic liquids and trialkyl phosphine oxides for yttrium(III) uptake

A new material (IL923SGs) composed of ionic liquids and trialkyl phosphine oxides (Cyanex 923) for Y(III) uptake was prepared via a sol-gel method. The hydrophobic ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate (C₈mim⁺PF₆⁻) was used as solvent medium and pore templating material. The extraction of Y(III) by IL923SGs was mainly due to the complexation of metal ions with Cyanex 923 doped in the solid silica. Ionic liquid was stably doped into the silica gel matrix providing a diffusion medium for Cyanex 923, and this will result in higher removal efficiencies and excellent stability for metal ions separation. IL923SGs were also easily regenerated and reused in the subsequent removal of Y(III) in four cycles.     

Sedimentation equilibrium of suspensions of colloidal particles at finite concentrations

Equilibrium concentration profiles of non-dilute colloidal suspensions are calculated by means of the Carnahan-Starling expression for the osmotic compressibility of hard sphere liquids. The profiles depend on the average volume fraction of the suspension, , and on the field interaction parameter, ₀ (reciprocal of the Péclet number at infinite dilution). Profiles are computed for values of and ₀ typical of those encountered in sedimentation field-flow fractionation experiments. It is found that, in most cases, the volume fraction at the depletion wall is negligibly small and that the volume fraction at the accumulation wall ₀, depends on the ratio <>₀/₀ only. An inflexion point is found in the concentration profile if ₀ is larger than 0.13 whatever the value of ₀.