PVP为偶联剂制备核壳型PS/CdS纳米复合粒子及表征

以聚乙烯吡咯烷酮(PVP)为偶联剂,利用超声化学法制备了PS/CdS核壳型复合纳米粒子。为了深入理解核壳型纳米粒子的界面行为和形成机制,详细考察了PVP加入与否及用量、前体加入顺序、Cd2+与S2-摩尔比和反应时间等实验参数对核壳复合材料结构的影响。结果表明,适量PVP可改善CdS纳米粒子与PS聚合物基体间的亲和性,增强壳与核之间的相互作用,成功地将PS与CdS复合成单分散的、壳层完整且厚度可控的三维核壳型PS/CdS纳米复合粒子;且复合物比纯CdS粒子具有更高的可见光响应活性。     

BaTiO_3@Cu核-壳复合粒子电/磁双响应性能

以平均粒径约为500nm的BaTiO_3微球为基核,通过"一步法"成功地制备了BaTiO_3@Cu核-壳复合粒子。利用SEM、TEM、XPS、介电测量分析仪和阻抗分析仪等对复合粒子的组成、结构、介电性能和磁性能进行测定。另外将纯BaTiO_3和BaTiO_3@Cu核-壳复合粒子分别分散到水凝胶中,通过测量和分析在有/无电场、磁场和电磁复合场作用下得到的水凝胶的储能模量,考察粒子在水凝胶中的电、磁和电磁响应性能。结果表明,BaTiO_3@Cu复合粒子具有完整清晰的核-壳结构,在整个表面壳层铜元素中,Cu(0)的原子分数达到了90at%,具有优良的介电性能和磁性能。BaTiO_3@Cu核-壳复合粒子是一种对外加电场和磁场作用都具有响应性能的多功能新型智能材料,且其电磁复合响应性能显著强于纯BaTiO_3粒子。     

单分散Fe3O4@SiO2/Au复合纳米颗粒的制备

制备了尺寸为30nm,具有磁响应的单分散Fe3O4@SiO2/Au核壳纳米颗粒,并研究其光学性质。首先利用热分解法制备油酸修饰的Fe3O4纳米粒子,再用反相微乳法制备Fe3O4@SiO2纳米粒子,最后利用表面修饰的氨基还原性,获得Fe3O4@SiO2/Au核壳复合纳米颗粒。分别用TEM、XRD、Zeta电位与粒度分析仪对产物形貌、结构、表面电位和粒径分布进行表征,用紫外-可见分光光度计对光学性质进行了测试。     

核/壳结构复合纳米材料研究进展

核/壳结构复合纳米材料是具有特殊性能的功能材料,是由一种纳米材料通过化学键或其他相互作用将另一种纳米材料包覆起来形成的纳米尺度的有序组装结构.这种结构可以产生单一纳米粒子无法得到的许多新性能,因而具有许多不同于核、壳材料的独特的光、电、磁、催化等物理和化学性质.主要介绍了核/壳型复合纳米材料的特点、形成机理以及制备方法,并结合最近的科研工作对其研究进展进行了综述.     

Fe_3O_4@TiO_2复合纳米颗粒稳定Pickering乳液的光磁双响应性研究

利用三甲基氯硅烷修饰的核壳结构Fe_3O_4@TiO_2复合纳米颗粒来稳定Pickering乳液,并对乳液的磁响应性和光响应性进行了评价,结果表明:Fe_3O_4@TiO_2复合纳米颗粒稳定的Pickering乳液具有良好的磁响应性和光响应特性。     

Ni／MnO纳米复合粒子的生长机制

以Ni和MnO2微米粉为原料,采用直流电弧等离子法在氢-氩混合气氛中合成了MnO包覆Ni纳米复合粒子.用XRD、TEM、TG-SDTA等方法分析了纳米粒子的相组成、形貌和热稳定性.结果表明:Ni/MnO复合纳米粒子具有一致的"核/壳"微结构,尺寸分布在100-120nm范围.核和壳分别为Ni和MnO相.根据定量氧辅助V-L-S机制,Ni纳米核在复合粒子生长过程中的催化作用,是"核/壳"结构形成的重要因素.     

The Analysis and Growth Mechanism of Core/Shell-type Ni/MnO Nanoparticls

以Ni和MnO2微米粉为原料,采用直流电弧等离子法在氢--氩混合气氛中合成了MnO包覆Ni纳米复合粒子.用XRD、TEM、TG--SDTA等方法分析了纳米粒子的相组成、形貌和热稳定性.结果表明: Ni/MnO 复合纳米粒子具有一致的“核/壳”微结构,尺寸分布在100--120 nm范围. 核和壳分别为Ni和MnO相.根据定量氧辅助V--L--S机制, Ni纳米核在复合粒子生长过程中的催化作用,是“核/壳”结构形成的重要因素.     

核壳式纳米Al2O3/PS复合粒子的表征及增韧选区激光烧结聚苯乙烯的研究

运用TEM,FTIR对乳液聚合方法制备纳米Al2O3/PS复合粒子结构进行了表征,结果表明,制备出的复合粒子具备以纳米氧化铝为核、以聚苯乙烯为壳的核壳式结构;并将核壳式复合粒子用来增韧选区激光烧结聚苯乙烯,结果发现,其缺口冲击强度达到12.1kJ/m2,较纯聚苯乙烯提高了50%左右,比添加未经任何改性处理纳米氧化铝粒子的复合材料提高了30%;利用FE-SEM对试件的冲击断面进行了微观结构分析,结果表明:核壳式纳米Al2O3/PS复合粒子改善了纳米粒子与基体表面极性的差异,增强了其与聚合物基体之间的界面相容性,从而改性了选区激光烧结制备聚苯乙烯基复合材料,并很好地起到增韧的效果.     

双重磁响应温敏复合微球的制备及表征

在Fe3O4纳米粒子表面聚合包覆温敏性聚N-异丙基丙烯酰胺(PNIPAM)及其与聚苯乙烯(PS)、聚α-甲基丙烯酸(PMAA)的共聚物,制备表面不同亲水/疏水性质的双重磁响应温敏复合微球。利用透射电镜(TEM)、红外光谱(FT-IR)及Zeta粒度仪(DLS)等对复合微球进行了表征。结果表明,复合微球呈现核壳结构,粒径约为150nm~300nm;在复合微球温敏聚合物中引入亲水/疏水链段可以有效调节其最低临界溶解温度(LSCT),随着温敏聚合物亲水性的提高,微球LSCT向高温移动,且该微球具有良好的双重磁响应特性(磁靶向响应性和磁热响应性)。     

纳米CaCO_3/ACR复合物的制备及在PVC改性中的应用

采用种子乳液聚合法合成了具有核壳结构的纳米C aCO3/ACR复合胶乳。将其与PVC进行共混,考察了不同界面结构对复合材料力学性能的影响,并用TEM、SEM对复合粒子分散情况及共混物断面形态进行了考察。结果表明,纳米复合粒子在PVC基质中达到了纳米级分散;用钛酸酯处理的纳米C aCO3优于用硬脂酸处理的纳米C aCO3的改性效果;核层与壳层单体比、壳层单体比都存在最佳值。     

Insertion of triangulated surfaces into a meccano tetrahedral discretization by means of mesh refinement and optimization procedures

In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method.     

Certification Institutions Expected to Update and Transfer Information on Present Standards

Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.……     

Flow calorimeter for enthalpy increment measurements on condensed gases

A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa.     

Refrigerators Enter a New Era of Health Preservation Frestech initiates the establishment of China's first standard for household sterilization refrigerators

On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.……     

Optimum-Simulation von Ernteprozessen

Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß.     

A study of centrifugal cast high boron high speed steel

In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M₂(B,C), (W,Mo)₂(B,C), M₃(B,C), M₂₃(B,C)₆ type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm². The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K₁ mill housing of bar mill.     

Thixotropy of Systems with Shear Thinning and Plastic Flow Behavior

The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ...     

Effect of Oxide Assisted Metal Nanoparticles on Microstructure and Morphology of Gallium oxide Nanowires

Several researches have been reported about the characteristic of β-Ga2O3 nanowires which was synthesized on nickel oxide particle. But indeed, recent researches about synthesis of β-Ga2O3 nanowires on oxide-assisted transition metal are limited to nickel or cobalt oxide catalyst. In this work, Gallium oxide (β-Ga2O3 ) nanowires were synthesized by a simple thermal evaporation method from gallium powder in the range of 700 - 1000℃ using the iron, nickel, copper, cobalt and zinc oxide as a catalyst, respectively. The β-Ga2O3 nanowires with single crystalline without defects were successfully synthesized at the reaction temperature of 850, 900 and 950℃ in all the catalysts. But optimum experimental condition in synthesis of nanowires varied with the kind of catalyst. As increasing synthesis temperature,the morphology of gallium oxide nanowires changed from nanowires to nanorods, and its diameter increased. From these results, we could be proposed that the growth mechanism of β-Ga2O3 nanowires was changed with synthesis temperature of nanowires. Microstructure and morphology of Synthesized nanowire was characterized by HR-TEM, FE-SEM, EDX and XRD.     

The Influence of Nitrogen and Boron Implant into Silicon Substrate on the Phase and Internal Stress of c-BN Films

Cubic boron nitride(c-BN) film was deposited on a Si (100) substrate by the RF-magnetron sputtering.The mainly problems for fabrication of c-BN films are the low purity and high intrinsic compressive stress. In order to solve the two problems, the c-BN film with the buffer interlayer was deposited on the substrate which had been implanted with nitrogen and/or boron ions. The results show: the implantation of nitrogen ions can obviously increase c-BN content and reduce the internal stress slightly; while the implantation of boron shows no obvious improvement to the content of c-BN, which can reduce the internal stress in the film obviously. In addition, it is suggested that the implantation of nitrogen and boron shows the best result, which not only can increase the content of c-BN, but also reduce the internal stress in the c-BN film obviously.