Preparation of Nd-doped BiFeO3 films and their electrical properties

The Nd-doped BiFeO₃ thin films were prepared on SnO₂(FTO) substrates spin-coated by the sol–gel method using Nd(NO₃)₃·6H₂O, Fe(NO₃)₃·9H₂O and Bi(NO₃)₃·5H₂O as raw materials. The microstructure and electric properties of the BiFeO₃ thin films were characterized and tested. The results indicate that the diffraction peak of the Nd-doped BiFeO₃ films is shifted towards right as the doping amounts are increased. The structure is transformed from the rhombohedral to pseudotetragonal phase. The crystal grain is changed from an elliptical to irregular polyhedron. Structure transition occurring in the Bi_0.85Nd_0.15FeO₃ films gives rise to the largest Pr of 64 μC/cm². The leakage conductance of the Nd doped thin films is reduced. The dielectric constant and dielectric loss of Bi_0.85Nd_0.15FeO₃ thin film at 10 kHz are 190 and 0.017 respectively.     

Electroluminescence properties of In-doped Zn2SiO4 thin films prepared by sol–gel process

The effect of In doping on the electroluminescence (EL) properties of Zn₂SiO₄:In thin films was investigated. In-doped Zn₂SiO₄ thin films were deposited on BaTiO₃ substrates and their EL properties were characterized in this study. X-ray powder diffraction patterns of In-doped Zn₂SiO₄ powders revealed a single phase of Zn₂SiO₄ for In concentrations up to approximately 1.5 mol%, whereas a secondary phase of In₂O₃ was observed for In concentrations in the range of 2–10 mol%. The maximum luminance of thin film electroluminescent (TFEL) devices varied significantly with the amount of In doping. The highest luminance with blue emission was obtained when 2 mol% In was doped. The blue emission of In-doped Zn₂SiO₄ thin film may be related to the In substitution for Zn. The 2 mol% In-doped Zn₂SiO₄ thin film exhibited blue emission with CIE color coordinates of x=0.208 and y=0.086.     

The Effect of an Absorbed Polyelectrolyte Layer on the Dynamic Mobility of a Colloidal Particle

Electroacoustic measurements can be used for determining the characteristics of polymer layers on colloidal particles. In this paper a theoretical formula is derived for calculating the effect of a polyelectrolyte layer on the colloid electroacoustic signal. Representative calculations are presented, and the application of these results for polyelectrolyte characterisation are discussed.     

Dc-bias-field-induced dielectric relaxation and ac conduction in CaCu3Ti4O12 ceramics

The dielectric relaxation and ac conduction of CaCu₃Ti₄O₁₂ (CCTO) ceramics were investigated at different temperatures under a dc bias. The dc bias gives rise to space charge accumulation, i.e. an electrode response, resulting in the significant increase of dielectric permittivity and dielectric loss tangent. Two Debye-like relaxations, arising from electrode and grain boundary responses, are present at low frequency with an increase of the dc bias. The electrode and grain boundary relaxations are distinguished according to the impedance spectroscopy and the frequency-dependent ac conductivity. The relaxation times of electrode and grain boundary relaxation are 0.955 ms and 0.026 ms, respectively, with a dc bias of 10 V at 328 K.     

Synthesis and characterization of immobilized activated carbon doped TiO2 thin films

Immobilized activated carbon doped TiO₂ thin films were prepared by sol–gel dip coating method by using Titanium IV isopropoxide as a precursor. Aim of our work is to synthesize and investigate the structural, surface morphology and optical properties of the synthesized thin film. X-ray diffraction pattern reveals that the crystallinity of the film increases with increase in temperature. Also, the structural parameters such as particle size, microstrain and dislocation density have been calculated. The formation of nanosphere of diameter ranging from 300 nm to 500 nm has been confirmed by Scanning electron microscope. Photocatalytic active large optical band gap at 3.75 eV was found by using UV–visible sspectrum.     

Effect of Alkyl Side Chain on the Conformational Properties of Polysulfones with Quaternary Groups

Modification of intrinsic viscosity, temperature coefficient, and preferential adsorption coefficient of polysulfones with different alkyl side groups in N,N-dimethylformamide/methanol and N,N-dimethylformamide/water was investigated at different compositions and temperatures. The specific interactions, such as hydrogen bonding and polyelectrolyte effect induced by an enhanced dissociation of the ionizable groups, determine both the modification of the solvation power of the polymer coil and the difference in the composition of the mixed solvent inside and outside the coil.     

Preparation of functional composite grafted particles PDMAEMA/SiO2 and preliminarily study on functionality

Micron-sized silica gel particles were first surface-modified with coupling agent, γ-methacryloylpropyl trimethoxysilane (MPS), and the polymerizable double bonds were introduced onto the surfaces of silica gel particles, forming the modified particles MPS-SiO₂. Subsequently, N,N-dimethylaminoethyl methacrylate (DMAEMA) was graft-polymerized on the surfaces of particles MPS-SiO₂ in the manner of “grafting through”, resulting in the grafted particles PDMAEMA/SiO₂. The grafted particles PDMAEMA/SiO₂ were fully characterized with several means. The graft polymerization process of DMAEMA on particles MPS-SiO₂ was studied in detail, and the optimal reaction conditions were determined. Thereafter, the adsorption properties of the grafted particles PDMAEMA/SiO₂ for chromate anion and Cu²⁺ ion were preliminarily examined respectively. The experimental results indicate that the PDMAEMA grafting degree on PDMAEMA/SiO₂ particles is limited because an enwinding polymer layer as a kinetic barrier on the surfaces of silica gel particles will be formed during the graft polymerization, and blocks the graft polymerization. In order to enhance PDMAEMA grafting degree, reaction time and temperature, and the used amount of initiator as well as the monomer concentration should be effectively controlled. The preliminary adsorption tests show that the grafted particles PDMAEMA/SiO₂ are multi-functional. They possess very strong adsorption ability for CrO₄²⁻ anion by right of strong electrostatic interaction, and have also adsorption action towards heavy metal ion by dint of complexing action.     

负载型镍催化剂的磁性

用磁化学方法研究了浸渍在硅胶上的镍的分散度。对镍含量为0.05wt%至20wt%的一系列样品的磁性进行了测量。按磁化曲线的起始部分估算了含镍等于及小于1wt%镍的粒子大小。根据经验公式,计算了样品的饱和磁化强度。用Michel—Selwood方法得到了每个样品的粒子大小分布曲线。对部     

Wetting at a polymer gel–vapor interface; a system not influenced by a long-range van der Waals contribution

The exterior of a cross-linked polymer gel resembles a polymer brush. Such gel including its brush can be swollen by a good solvent. The detachment of the solvent–vapor (L–V) interface from the brush is controlled by the adsorption of polymer segments onto this interface and is to a very good approximation not influenced by long-range van der Waals contributions. A wetting transition in this system coincided with the adsorption–desorption transition for chains onto such L–V interface and has various unusual features. There are several indications that in practice this system should feature a second-order wetting transition.     

HPLC法测定人体尿液样品中的4'-羟基黄烷酮和6-甲氧基黄烷酮

报道一种快速测定人体尿液中4'-羟基黄烷酮和6-甲氧基黄烷酮的HPLC方法.采用自制的大蒜新素键合硅胶填充柱(DTSP,4.6 mm i.d.×15 mm,10 μm),以乙腈/1.5%三乙胺-甲酸(65:35,v/v,pH=3.0) 为流动相,流速设定为1.0 mL·minn~(-1),检测波长为 257 nm时,实现了人体尿样品中上述黄烷酮化合物的良好分离.4'-羟基黄烷酮的线性范围为5～100 mg·L~(-1),r=0.992 0;6-甲氧基黄烷酮线性范围为5～100 mg·L~(-1),r=0.999 1,它们的最低检出限分别为1.03 ng和1.56 ng,平均回收率分别为99.02%～99.26%和98.21%~98.62%,相应的RSD分别小于0.354%和0.605%(n=5).该方法快速、简便、可靠,适用于人体尿液样品中上述黄烷酮分离分析.