燃煤飞灰中铁质微珠的显微结构及其组成研究

选用我国三个典型燃煤煤种的电厂飞灰中铁质微珠,进行显微结构与物相组成等方面的研究。揭示出铁质微珠中存在空心微珠、子母珠和实心微珠三种显微颗粒类型,在这些显微颗粒表面可识别出以微粒状和八面体自形晶两种方式存在的赤铁矿和磁铁矿析晶;元素分析表明,燃烧褐煤电厂铁质微珠主要由Fe、Ca、Al、和Si元素组成,燃烧烟煤和无烟煤的电厂铁质微珠主要由Fe、Al和Si元素组成;物相分析发现,Fe在铁质微珠中以四种存在形式：Fe3O4、α-Fe2O3、γ-Fe2O3和Fe3+-玻璃相。这些物相在三个电厂飞灰中呈现出不同的分布特征,反映出不同的燃煤煤种在锅炉中燃烧温度的差异。随着温度的升高,Fe3O4先氧化为γ-Fe2O3,或γ-Fe2O3与Fe3O4的固熔体,然后再转变为α-Fe2O3,当温度超过 1 400 ℃时,Fe2O3又转化为Fe3O4。     

季戊四醇三丙烯酸酯-丙烯酸丁酯共聚微球的合成及孔结构特性研究

以季戊四醇三丙烯酸酯、丙烯酸丁酯为共聚单体,乙酸丁酯为致孔剂,用悬浮聚合法合成了-系列不同表面结构的共聚微球.使用扫描电镜、BET氮气吸附,傅立叶红外光谱等分析手段,对微球进行了结构测定,并研究了单体与致孔剂比例、两种单体比例及不同致孔剂对于聚合物孔结构的影响.经过合成条件的筛选,得到了平均孔径为100nm左右的球形聚合物.     

Static and dynamic light-scattering of colloidal gases,liquids and crystals

Static and dynamic light-scattering measurements are made for colloidal-crystals,-liquids and-gases of silica spheres, 103 nm in diameter, in the exhaustively deionized suspension and in the presence of sodium chloride. Sharp peaks in the scattering curve are observed, for the first time, for the colloidal crystals in very diluted aqueous suspension. The product of the effective diffusion coefficient and the scattered light intensity is found constant over the whole range of the scattering angle measured for the colloidal crystals and liquids. Three and two dynamic processes have been extracted separately from time profiles of autocorrelation function of colloidal crystals and liquids, respectively from Marquadt histogram analysis. Decay curves of colloidal gases are characterized by a single translational diffusion coefficient,D ₀.D ₀ of the gases is always lower than the calculation from the Stokes-Einstein equation with the true diameter of spheres, and increases as ionic concentration increases. These experimental results emphasize the important role of the expanded electrical double layers on the diffusive properties in the colloidal crystals, liquids and gases.     

Synthesis of SiO2/Y2O3:Eu core-shell materials and hollow spheres

The SiO₂/Y₂O₃:Eu core-shell materials and hollow spheres were first synthesized by a template-mediated method. X-ray diffraction patterns indicated that the broadened diffraction peaks result from nanocrystals of Y₂O₃:Eu shells and hollow spheres. X-ray photoelectron spectra showed that the Y₂O₃:Eu shells are linked with silica cores by Si-O-Y chemical bond. SEM and TEM observations showed that the size of SiO₂/Y₂O₃:Eu core-shell structure is in the range of 140-180 nm, and the thickness of Y₂O₃:Eu hollow spherical shell is about 20-40 nm. The photoluminescence spectra of SiO₂/Y₂O₃:Eu core-shell materials and Y₂O₃:Eu hollow spheres have better red luminescent properties, and the broadened emission bands came from the size effects of nanocrystals composed of Y₂O₃:Eu shell.     

Alternate sign reversal in the ζ potential and synchronous expansion and contraction in the absorbed multi-layers of poly(4-vinyl-N-n-butylpyridinium bromide) cations and poly(styrene sulfonate) anions on colloidal silica spheres

Alternative multiple absorbed layers of up to ten macrocations [poly(4-vinyl-N-n-butylpyridinium bromide)] and macroanions [sodium poly(styrene sulfonate)] are formed on colloidal silica spheres above the critical concentration of macroions, m*. The m* value is the minimum number of macroions required to reverse the sign of the ζ potential of the spheres in the first absorption step. Alternative sign reversal in the ζ potential and expansive–contractive thickness changes are observed by the repeated and alternate addition of macrocations first and macroanions next. During multiple absorption, the pH and conductivity values decrease and increase continuously as the number of absorbed layers increases. When the macroanions are added first, sign reversal in the ζ potential and reversible expansion and contraction do not occur. Breaking of the alternate multiple-type absorption occurs when equivalency in the number of dissociative groups of macrocations and macroanions is broken. Synchronous conformational changes of macrocations and macroanions in the multiple- absorbed layers, where balancing of the conformational rigidities with the multiple electrostatic attraction and repulsion between macrocations and anions occurs, are supported strongly. Received: 12 January 1999 Accepted in revised form: 25 March 1999     

部分水解聚丙烯酰胺/柠檬酸铝胶态分散凝胶体系的剪切稠化现象

一般认为 ,能够产生剪切稠化现象的体系为分散稳定的固 -液浓悬浮体 ,分散相 (固相 )体积分数 30 %～ 6 0 % [1～ 4] .最近 ,我们在研究固含量仅为 0 .0 3%的部分水解聚丙烯酰胺 (简称PHPA) /柠檬酸铝胶态分散凝胶体系流变性时 ,也发现了剪切稠化现象 .胶态分散凝胶( CDG)主要由交联剂在单个聚合物分子中通过内交联形成[5,6] ,形成条件是低聚合物质量分数 (一般为 0 .0 1 %～ 0 .1 2 % )和低交联剂 /聚合物质量比 (一般为 1∶ 2 0～ 1 0 0 ) .由于不能象常规凝胶一样形成三维网络结构 ,因而 CDG的分子结构状态介于常规聚合物凝胶和自由…     

Use of marker ion and cationic surfactant plastic membrane electrode for potentiometric titration of cationic polyelectrolytes

A plasticized poly (vinyl chloride) (PVC) membrane electrode sensitive to stearyltrimethylammonium (STA) ion is applied to the determination of cationic polyelectrolytes such as poly (diallyldimethylammonium chloride) (Cat-floc) by potentiometric titration, using a potassium poly (vinyl sulfate) (PVSK) solution as a titrant. The end-point of the titration is detected as the potential change of the plasticized PVC membrane electrode caused by decrease in the concentration of STA ion added to the sample solution as a marker ion due to the ion association reaction between the STA ion and PVSK. The effects of the concentration of STA ion, coexisting electrolytes in the sample solution and pH of the sample on the degree of the potential change at the end-point were examined. A linear relationship between the concentration of cationic polyelectrolyte and the end-point volume of the titrant exists in the concentration range from 2×10⁻⁵ to 4×10⁻⁴ N for Cat-floc, glycol chitosan, and methylglycol chitosan.     

Stability and thermosensitive properties of various poly (N-vinylcaprolactam) microgels

Thermally responsive microgels have been synthesised by polymerising N-vinylcaprolactam under various conditions. Stabilisation of the latices was of special interest and, thus, electrostatically, sterically, and electrosterically stabilised particles were prepared. Electrostatic stabilisation was achieved by the use of an ionic initiator and/or an ionic detergent. Steric stabilisation was realised through a macromonomer technique, where polymerisable poly(ethylene oxide)-containing macromonomers were utilised as a detergent. Capillary electrophoresis was used to compare the electrokinetic properties of the polymer particles. All the product particles show thermal behaviour typical of poly(vinylcaprolactam), but sterically stabilised ones are superior in the stability against added electrolytes. Received: 24 April 2001 Accepted: 13 August 2001     

Metal-Organic Framework Derived Hierarchical Co/C@V2O3 Hollow Spheres as a Thin,Lightweight, and High-Efficiency Electromagnetic Wave Absorber

Developing high-efficiency electromagnetic (EM) wave absorbing materials with light weight, thin thickness, and wide absorption bandwidth is highly desirable for ever-developing electronic and telecommunication devices. Herein, hierarchical metal–organic framework (MOF)-derived Co/C@V₂O₃ hollow spheres were designed and synthesized through a facile hydrothermal, precipitation, and pyrolysis method. The composite exhibits both excellent impedance matching and light weight due to the rational combination of hollow V₂O₃ spheres and porous Co/C. Additionally, multiple components enable a large dielectric and magnetic loss of the composite, giving rise to enhanced EM wave absorption performance with a maximum reflection loss (RL) of −40.1 dB and a broad effective absorption bandwidth (RL < −10 dB) of 4.64 GHz at a small thickness of 1.5 mm. This work provides insights into the design of hierarchical hollow and porous composites as thin and lightweight EM wave absorbers with efficient absorption, which can also be extended to energy storage, catalysis, and sensing.     

Fabrication and characterization of a α,β,γ,δ-Tetrakis(1-methylpyridinium-4-yl)porphine/silica nanocomposite thin-layer membrane for detection of ppb-level heavy metal ions

A new detection membrane for filtration enrichment combined with colorimetric determination of Cd(II), Zn(II), Pb(II) and Cu(II) ions is presented. We have demonstrated the use of a dye nanoparticle coated test strip (DNTS) structured with a reagent layer for on-site analysis of trace metal ions. In this study, a [TMPyP/SA] DNTS coated with a nanocomposite layer (average thickness: 5.39 μm) of α,β,γ,δ-Tetrakis(1-methylpyridinium-4-yl)porphine (TMPyP) and silica-SA on the top surface of a cellulose ester membrane filter was fabricated by a simple filtration of an aqueous TMPyP/silica-SA nanocomposite dispersion through a membrane filter. The nanocomposite formation of cationic TMPyP and negatively charged colloidal SA (9–80 nm) was based on electrostatic interaction and was confirmed in the 120–800 nm diameter range by a dynamic light scattering photometer (DLS). To optimize the DNTS nanocomposite layer, surface uniformity, mechanical strength, the percent retention of TMPyP, and sensitivity to Cd(II) detection for six DNTSs with five different types of silica were examined. A half[TMPyP/SA] DNTS with an average layer thickness of 2.60 μm, which was prepared by controlling the amount of TMPyP and SA, demonstrated the highest sensitivity to Cd(II) ion because it had the lowest background absorbance. In addition, factors that affected the percent retention of TMPyP, such as pH and TMPyP/SA ratio, were determined. More than 99% of the TMPyP was retained on a membrane filter at pH 7.8 with a TMPyP and SA concentration of 2 × 10⁻⁵ M and 4 × 10⁻⁵ wt%, respectively. Filtration enrichment of 100 mL of an aqueous solution containing Cd(II), Zn(II), and Pb(II) at ppb levels was achieved by concentrating the metal ions in a nanocomposite layer (the effective TMPyP area was 1.77 cm², pH 10.2). The signaling surface changed from a brown color to green when the ions were captured. The percent extraction for metal ions on a half[TMPyP/SA] DNTS were estimated by TLC scanning and ICP-MS. It was observed that, when using the half[TMPyP/SA] DNTS, Cd(II) concentrations as low as 1 ppb were detectable at a filtration rate of 4.0–5.0 mL min⁻¹.