Preparation and Properties of FeNi-Mg/MgO Nanocomposite

The FeNi-Mg/MgO nanocomposite synthesized by spark erosion of pure Mg and Fe₇₀Ni₃₀ electrodes was investigated by X-ray diffraction, Mössbauer spectroscopy and magnetic measurements. From the X-ray diffraction measurements Mg, MgO, and -FeNi were recognized. According to the Mössbauer spectra analysis, iron atoms were identified in -FeNi, Fe_1-x O, and FeNi in Mg/MgO phases. The FeNi in Mg/MgO phase consists of fcc -FeNi phase which is antiferromagnetic below T _N 40 K and weakly ferromagnetic bcc -FeNi clusters. The magnetic measurements confirmed the presence of the -FeNi phase and the composite model in the form of isolated magnetic particles in Mg/MgO matrix.     

Bi-2223喷雾热分解粉末热处理工艺优化

Bi-2223带材目前在电流引线、超导电机、超导电缆、超导限流器等领域实现了许多示范性应用,载流性能是表征其性能的重要指标,而高质量的前驱体粉末是最终带材性能的关键保障.本文选用具有工艺简单、粉末效率高、批次稳定性好等优点的喷雾热分解法制备的Bi-2223前驱体粉末,利用TG-DSC、XRD、SEM等测试手段对低氧条件下不同保温时间烧结的粉末进行分析,并结合最终带材的载流性能测试结果,获得了最优粉末烧结参数,为后续喷雾热分解粉末的进一步生成Bi-2223相以及高性能粉末的制备提供了依据.     

收集方式对喷雾热分解Bi-2223 前驱粉末的影响

采用国产喷雾热分解设备制备了Bi-2223 前驱粉末, 分别选用一步收集和分级收集热分解后的粉末, 对不同方式收集的粉末进行了XRD 分析、SEM 观察以及ICP-AES 分析, 对比了粉末在相成份以及含量、 外观形貌、 粒径大小和元素原子配比等方面的差别, 最终发现采用一步收集方式采集的粉末在相组成、 成分均匀度以及原子配比方面均优于分级收集粉末, 一步收集方式更适合于收集Bi-2223 喷雾热分解粉末.     

Size Tunable Synthesis of Highly Crystalline BaTiO3 Nanoparticles using Salt-Assisted Spray Pyrolysis

Highly crystalline, dense BaTiO₃ nanoparticles in a size range from 30 to 360nm with a narrow size distribution (_g = 1.2–1.4) were prepared at various synthesis temperatures using a salt-assisted spray pyrolysis (SASP) method without the need for post-annealing. The effect of synthesis temperature on particle size, crystallinity and surface morphology of the nanoparticles were characterized by X-ray diffraction and scanning/transmission electron microscopy. The nature of the crystalline structure was analyzed by Rietveld refinement and Raman spectroscopy. The particle size decreased with decreasing operation temperature. The crystal phase was transformed from tetragonal to cubic at a particles size of about 50nm at room temperature. SASP can be used to produce high weight fraction of tetragonal BaTiO₃ nanoparticles down to 64nm in a single step.     

Synthesis of Single Crystalline ZnO Nanoparticles by Salt-Assisted Spray Pyrolysis

LiNO₃ was used as a shield in the preparation of single crystalline ZnO particles by a spray pyrolysis process in order to prevent agglomeration and enhance the crystallinity of the ZnO. LiNO₃ was added to a precursor solution of zinc acetate dihydrate prior to its atomization by means of an ultrasonic transducer. Agglomerate-free particles having a mean particle size of 26 nm were successfully obtained after washing the product. X-ray diffractometry, field-emission scanning electron micrograph and transmission electron micrograph data indicate that the size and morphology of ZnO were strongly influenced by the operating temperature used and the residence time of the particle in the reactor.     

透明莫来石陶瓷薄膜的光电子能谱研究

采用溶胶－凝胶工艺合成了莫来石透明陶瓷薄膜。用Ｘ射线光电子能谱分析技术，通过Ｏ１ｓＡｌ２ｐ太Ｓｉ２ｐ的Ｘ射线光电子能谱分析，探讨了透明膜的结构，组成及阳离子的配位形态。研究表明，干凝胶中铝以ＡｌＯ６八面体为主，硅为ＳｉＯ４四面体，随温度的升高ＡｌＯ６向ＡｌＯ４转化，引进透明膜结构的相应变化。     

Preparation and Characterization of Polypyrrole/Ferrospinel Nanocomposite by W/O Microemulsion Pathway

A polypyrrole/ferrospinel(NiFe₂O₄) nanocomposite was prepared by the in situ chemical oxidizing of pyrrole in the presence of NiFe₂O₄ nanoparticles in water-in-oil (w/o) microemulsion. The structural, morphological, and magnetic properties of the as-prepared polypyrrole/NiFe₂O₄ nanocomposite were characterized by X-ray diffraction (XRD), Fourier transform infrared spectra, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and magnetic measurements. XRD and FTIR revealed the presence of NiFe₂O₄ in the nanocomposite. SEM and TEM images illustrated that polypyrrole was coated on the NiFe₂O₄ surface. The electromagnetic parameters, such as conductivity, saturation magnetization, and coercivity of NiFe₂O₄ nanoparticles varied after coating with polypyrrole.     

Homogeneous ZnO Nanoparticles by Flame Spray Pyrolysis

Zinc oxide (ZnO) nanoparticles were made by flame spray pyrolysis (FSP) of zinc acrylate–methanol–acetic acid solution. The effect of solution feed rate on particle specific surface area (SSA) and crystalline size was examined. The average primary particle diameter can be controlled from 10 to 20nm by the solution feed rate. All powders were crystalline zincite. The primary particle diameter observed by transmission electron microscopy (TEM) was in agreement with the equivalent average primary particle diameter calculated from the SSA as well as with the crystalline size calculated from the X-ray diffraction (XRD) patterns for all powders, indicating that the primary particles were rather uniform in diameter and single crystals. Increasing the solution feed rate increases the flame height, and therefore coalescence and/or surface growth was enhanced, resulting in larger primary particles. Compared with ZnO nanoparticles made by other processes, the FSP-made powder exhibits some of the smallest and most homogeneous primary particles. Furthermore, the FSP-made powder has comparable BET equivalent primary particle diameter with but higher crystallinity than sol–gel derived ZnO powders.     

CeOx与ZnO纳米复合粉体的制备及其发光性能

通过溶胶-凝胶法制备CeOx／ZnO纳米复合粉体,并对其结构和光致发光特性进行了研究。发现500℃烧结出的复合粉体在502nm处的绿光发射同纯ZnO的相比有显著的增强;600℃烧结的样品在603nm出现新的发光峰。通过XRD和XPS分析认为荧光增强的主要原因同粉体中铈主要以Ce^3 形式存在有关,新的发光峰可能来源于ZnO／CeO2界面处形成的新的能级跃迁。     

Electrospun Cellulose Nanocrystals/Polycaprolactone Nanocomposite Fiber Mats

Cellulose nanocrystals (CNCs), a kind of biocompatible and biodegradable nanofiller, were prepared by sulfuric-acid hydrolysis of commercial α-cellulose. CNC/ polycaprolactone (PCL) nanocomposite fiber mats were produced via electrospinning and characterized by scanning electron microscopy, differential scanning calorimetry (DSC) analysis, thermogravimetric analysis (TGA), uniaxial tensile tests, and static water-contact-angle analysis. The results showed the mechanical properties and thermal stability of the nanocomposite fiber mats were improved and the surface hydrophilicity was increased in comparison with neat PCL fiber mats.     

Emulsion Polymerized Polystyrene/Montmorillonite Nanocomposite and its Viscoelastic Characteristics

A novel polystyrene (PS)/clay nanocomposite was synthesized using a simple emulsion polymerization method in the presence of sodium ion exchanged montmorillonite (Na‐MMT). Prior to the radical polymerization procedure with potassium persulfate (KPS) as an initiator, the hydrophobic styrene monomer was intercalated into hydrophilic clay layers using sodium dodecyl sulfate (SDS) as a surfactant. The FTIR spectra of the products showed the characteristic absorbance peaks of both the synthesized PS and Na‐MMT. The x‐ray diffraction patterns of the products exhibited an increase in the d ₀₀₁‐spacing, pointing to the intercalation of the PS chains into the intergalleries of the Na‐MMT. The enhancement of the thermal properties of the nanocomposite materials, such as the increase in the glass transition temperature of the PS, was investigated by differential scanning calorimetry (DSC). Furthermore, based on the viscoelastic properties of the products examined using a rotational rheometer with a parallel plate geometry, the nanocomposites were found to exhibit more rapid shear thinning and increased storage (G′) and loss (G″) moduli with increasing clay content.     

喷雾热解法制备发光材料研究进展

喷雾热解法是近年来新兴的合成无机功能材料的方法，使用这种方法制备的发光材料一般具有均匀的球形形貌，粒子的粒度分布窄，这不仅有利于提高材料的发光强度，还可以改善发光粉的涂敷性能并提高发光显示的分辨率。本文综述了喷雾热解法的基本过程及其制备的发光材料的特点，并对其未来发展趋势进行了展望。     

Paraelectric--ferroelectric interface dynamics induced by latent heat transfer and irreversibility of ferroelectric phase transitions

The temperature gradients that arise in the paraelectric--ferroelectric interface dynamics induced by the latent heat transfer are studied from the point of view that a ferroelectric phase transition is a stationary, thermal-electric coupled transport process. The local entropy production is derived for a ferroelectric phase transition system from the Gibbs equation. Three types of regions in the system are described well by using the Onsager relations and the principle of minimum entropy production. The theoretical results coincides with the experimental ones.     

Nonisothermal Crystallization of the Polypropylene/Organosilica Nanocomposite

Abstract

Nonisothermal crystallization of the neat isotactic polypropylene homopolymer (PP‐0) and of the nanocomposite containing 4.68 wt.% of organosilica (PP‐4.68) was studied in the standard differential scanning calorimetry (DSC) mode during constant‐rate cooling from the melt state. Analysis of the nucleation parameters derived from cooling rate dependencies of the temperatures for the onset of crystallization exotherms suggested a slight increase of the nucleation barrier for lamellar crystallization of PP within a confined space between neighboring nanoparticles of an infinite cluster of the nanocomposite, concomitant to stronger restrictions to transport of PP segments across the melt/lamellar crystal interface. The overall crystallization rate data for PP‐4.68 were consistent with the assumption of two separate contributions from the initial (unconstrained) and the subsequent (constrained) nucleation mechanisms, respectively. The obtained results were considered as evidence for a coexistence in an undercooled PP melt of the nanocomposite of initial nucleation sites characteristic for the neat PP‐0, and the basically different nucleation sites (presumably, PP chains anchored by both ends to the surfaces of two adjacent nanoparticles).     

喷雾热解法制备的SrWO4膜的阴极射线发光

利用超声喷雾热解法制备了钨酸锶SrWO₄多晶发光膜,并研究了制备条件及掺杂对其阴极射线发光特性的影响.生成的发光膜在300℃以上退火后具有白钨矿结构,其阴极射线发光为一宽带的蓝光,包括一个位于448nm的蓝色发光带和一个位于488.6nm的蓝绿色发光带,是由阴离子络合物WO₄^2-的电荷转移跃迁引起的.发光强度随着退火温度的升高而增强,而退火气氛对其影响不大.在SrWO₄膜中掺入银离子Ag⁺和镧离子La³⁺后,不影响其发光特性,但铕离子Eu³⁺的掺入对发光特性有影响.     

Thermo-mechanical performance of PVC/ZnO nanocomposites

The present paper deals with the study of thermo-mechanical performance of PVC/ZnO nanocomposites. The samples have been prepared by solution casting technique with different (0, 2, 4, 6 and 8) wt. % of ZnO nanoparticles in poly (vinyl chloride) (PVC) matrix and structurally characterized through scanning electron microscopy. In thermo-mechanical analysis, dynamic mechanical analyzer gives the information about storage modulus and phase transition temperature (T_g). From these viscosities, profile at elevated temperature and activation energy of phase transition can be evaluated. This study reveals that dispersion of nano-ZnO significantly altered the thermo-mechanical properties of neat PVC but the effect is composition-dependent.     

Photoluminescence from TiO2/PMMA Nanocomposite Prepared by γ Radiation

The surface of anatase TiO₂ nanocrystals with an average size of ~20 nm was modified by PMMA through γ radiation. The modified nanocrystals were investigated with photoluminescence (PL) and Fourier transform infrared (FTIR) spectra. A stable blue luminescence peak (~420 nm) can be observed for the modified anatase TiO₂ nanocrystal.     

LuTaO$lt;sub$gt;4$lt;/sub$gt;相变及结构

LuTaO₄是最高密度的闪烁体基质, 研究它的结构及其相变对单晶制备具有指导意义. 用固相法制备了Lu₂O₃和Ta₂O₅摩尔比为1:1时在不同温度下形成的多晶粉末, 用X射线衍射及Rietveld全谱拟合研究了多晶粉末的物相和结构. 结果表明, Lu₂O₃: Ta₂O₅摩尔比为1:1的样品在1740 ℃时合成的物相为M'-LuTaO₄, 在1800 ℃时为M'-LuTaO₄和M-LuTaO₄的混合物, 在1840 ℃时全部转变为M-LuTaO₄. 当温度升高到2058 ℃时, 样品呈熔融状态, 对淬火得到的样品进行结构精修, 给出了M-LuTaO₄, Lu₃TaO₇和Ta₂O₅的晶胞和原子坐标参数, 它们的重量比分别占78.1%, 18.9%和3.0%. 这些结果为制备以LuTaO₄为基质的高密度闪烁体单晶具有参考价值. 关键词： 4')" href="#">LuTaO₄ 相变 粉末衍射 Rietveld精修     

A Solvable Model of Interface Depinning in Random Media

We study the mean-field version of a model proposed by Leschhorn to describe the depinning transition of interfaces in random media. We show that evolution equations for the distribution of forces felt by the interface sites can be written directly for an infinite system. For a flat distribution of random local forces the value of the depinning threshold can be obtained exactly. In the case of parallel dynamics (all unstable sites move simultaneously), due to the discrete character of the interface heights allowed in the model, the motion of the center of mass is non-uniform in time in the moving phase close to the threshold, and the mean interface velocity vanishes with a square-root singularity.     

Nanocomposite TiC/a-C：H film prepared on titanium aluminium alloy substrates by PSII assistant MW-ECRCVD

Thin films of titanium carbide and amorphous hydrogenated carbon have been synthesized on titanium aluminium alloy substrates by PSII assisted MW-ECRCVD with a mirror field. The microstructure, chemical composition and mechanical property were investigated. Using XPS and TEM, the films were identified to be a-C：H film containing TiC nanometre grains （namely, the so-called nanocomposite structure）. The size of TiC grains of nanocomposite TiC/DLC film is about 5 nm. The nanocomposite structure has obvious improvement in the mechanical properties of DLC film. The hardness of a-C：H film with Ti is enhanced to 34 G Pa~ while that of a-C：H film without Ti is about 12 G Pa, and the coherent strength is also obviously enhanced at the critical load of about 35N.