Polystyrene/Fe3O4 magnetic emulsion and nanocomposite prepared by ultrasonically initiated miniemulsion polymerization

Ultrasonically initiated miniemulsion polymerization of styrene in the presence of Fe3O4 nanoparticles was successfully employed to prepare polystyrene (PS)/Fe3O4 magnetic emulsion and nanocomposite. The effects of Fe3O4 nanoparticles on miniemulsion polymerization process, the structure, morphology and properties of PS/Fe3O4 nanocomposite were investigated. The increase in the amount of Fe3O4 nanoparticles drastically increases the polymerization rate due to that Fe3O4 nanoparticles increase the number of radicals and the cavitation bubbles. Polymerization kinetics of ultrasonically initiated miniemulsion polymerization is similar to that of conventional miniemulsion polymerization. PS/Fe3O4 magnetic emulsion consists of two types of particles: latex particles with Fe3O4 nanoparticles and latex particles with no encapsulated Fe3O4 nanoparticles. Fe3O4 nanoparticles lower the molecular weight of PS and broaden the molecular weight and particle size distribution. Thermal stability of PS/Fe3O4 nanocomposite increases with the increase in Fe3O4 content. PS/Fe3O4 emulsion and nanocomposite exhibit magnetic properties. PS/Fe3O4 magnetic particles can be separated from the magnetic emulsion by an external magnetic field and redispersed into the emulsion with agitation.     

O(1/m) and nuclear effects in radiative muon capture in Ca

Motivated by a theorem which shows that the photon asymmetry in radiative muon capture (RMC) is determined by terms of O(1/m²) in an expansion in powers of the nucleon mass m, we have obtained a hamiltonian which is consistent within the standard theory to O(1/m²) and have applied it to a new calculation of RMC in ⁴⁰Ca, obtaining for the first time the O(1)×O(1/m²) contributions to the rate. The results show that the O(1/m²) terms are definitely necessary but that the most important ones come from O(1/m)×O(1/m) contributions obtainable from the usual hamiltonian. A number of nuclear effects were considered using this O(1/m²) hamiltonian including an improved giant dipole resonance model and a model using Hartree-Fock wave functions, as well as the usual closure harmonic oscillator model. Results were obtained for both photon spectrum and asymmetry in the various models.     

EXAFS analysis of Er sites in Er–O and Er–F co-doped crystalline Si

We present extended X-ray absorption fine structure (EXAFS) and photoluminescence (PL) analyses of Er–O and Er–F co-doped Si. Samples were prepared by multiple implants at 77 K of Er and co-dopant (O or F) ions resulting in the formation of a2 μm thick amorphous layer uniformly doped with 1×10¹⁹ Er/cm³ and 3×10¹⁹ O/cm³, 1×10²⁰ O/cm³ or 1×10²⁰ F/cm³. EXAFS measurements show that the local environment of the Er sites in the amorphous layers consists of 6 Si first neighbors. After epitaxial regrowth at 620°C for 3 h, Er is fully coordinated with 8 F ions in the Er–F samples, while Si and O ions are concomitantly present in the first shell of O co-doped samples. Post regrowth thermal treatments at 900°C leave the coordination unchanged in the Er+F, while the Er+O (ratio 1 : 10) doped samples present Er sites with a fully O coordinated shell with an average of 5 O atoms and 4 O atoms after 30 s and 12 h, respectively. We have also found that the fine structure and intensity of the high-resolution PL spectra are strongly dependent on the Er-impurity ratio and on thermal process parameters in the Er–O co-doped samples, while this is not observed for the F-doped samples. The most intense PL response at 15 K was obtained for the 1 : 3 E : O ratio, suggesting that an incomplete O shell around Er is particularly suitable for optical excitation.     

磁性纳米TiO_2/Fe_3O_4的制备及其光催化性能

采用特殊液相沉淀法分两步制备了壳核结构的磁性纳米TiO2/Fe3O4,并讨论了TiO2/Fe3O4比例对其磁性的影响。利用XRD、TEM和VSM对其进行了表征,用它做催化剂,甲基橙溶液为降解目标,在日光作用下对其光催化活性进行了研究,并测出了其回收率。结果表明,在本实验条件下制备的磁性纳米TiO2/Fe3O4表现为超顺磁性,具有较强的光催化活性和较高的回收率。当TiO2∶Fe3O4为4∶1,在450℃焙烧30min条件下得到的催化剂,对20mg/L的甲基橙溶液在60min内降解率高达91.5%,明显高于纯TiO2的催化活性,在外加强磁场的作用下,此催化剂很快从溶液中分离出来,测得其回收率为88.2%。     

磁性聚苯胺纳米微球的合成与表征

报道了具有核壳结构的Fe3 O4 聚苯胺磁性纳米微球的合成方法和表征结果 .微球同时具有导电性和磁性能 .在优化的实验条件下 ,可得到饱和磁化强度Ms 为 5 5 .4emu/g ,矫顽力Hc 为 6 2Oe的磁性微球 .微球的导电性随着微球中Fe含量的增加而下降 .微球的磁性能则随着Fe含量的增加而增大 .Fe3 O4 磁流体的粒径和磁性聚苯胺微球的粒径均在纳米量级 .纳米Fe3 O4 粒子能够提高复合物的热性能 .实验表明 ,磁流体和聚苯胺之间可能存在着一定的相互作用 ,但这种相互作用较为复杂 ,难于研究 .     

Epitaxial growth and magnetic exchange anisotropy in Fe3O4<Emphasis Type="Bold">/NiO bilayers grown on MgO(001) and Al</Emphasis>2O3(0001)

Epitaxial Fe3O4/NiO bilayers were epitaxially grown on MgO(001) and Al2O3(0001) substrates to investigate the influence of the fully spin compensated (001) and the non-compensated (111) NiO interface planes between the ferromagnetic (F) and antiferromagnetic (AF) layers on the AF/F exchange coupling. Bilayers of different magnetite thicknesses and constant NiO thickness were investigated. The structural characterizations indicate a perfect epitaxy of the two layers for the both growth directions in the two Fe3O4/NiO/MgO(001) and NiO/Fe3O4/Al2O3(0001) systems. An epitaxial ferrimagnetic (Ni,Fe)Fe2O4 phase is observed at the AF/F interface when the NiO oxide is grown on the top of the Fe3O4 layer while a perfectly flat AF/F interface is observed in the Fe3O4/NiO/MgO(001) system exhibiting only a very slight interdiffusion. Magnetic measurements indicate a relative strong bias at 300 K for the bilayers grown on Al2O3(0001), which decreases with the inverse of the ferrimagnetic layer thickness as theoretically expected. On the contrary, a zero exchange biasing is observed at 300 K for the bilayers grown on MgO(001).     

CuO/Al2O3、CuO/CeO2-Al2O3和CuO/La2O3-Al2O3催化剂中CuO物种被CO氧化的比较

用浸渍法制备了CuO/Al2O3 (Cu/Al)、CuO/CeO2- Al2O3 (Cu/CeAl)和CuO/La2O3-Al2O3(Cu/LaAl)催化剂. 通过原位XRD、Raman和H2-TPR方法， 对催化剂中的CuO物种以及CuO-Al2O3的固-固相反应进行了表征. 结果表明，对于Cu/Al催化剂，CuAl2O4存在于CuO与Al2O3层之间，CuO以高分散和晶相两种相态存在于催化剂的表层；对于Cu/CeAl催化剂，除了少量高分散和晶相的CuO存在于表层外，大部分CuO迁移到了CeO2的内层，     

水热法制备In2O3/ZnO异质结及其高的光催化性能

采用简单的两步水热法合成了不同In₂O₃质量比的In₂O₃/ZnO异质结复合材料．通过X射线衍射仪(XRD)、紫外-可见分光光度计(UV-vis)和扫描电子显微镜(SEM)对复合材料的结构、形貌和性能进行了表征．同时还使用UV-vis分光光度计测试了异质结降解罗丹明B(RhB)的光催化活性．实验结果表明,与纯ZnO和In₂O₃相比,In₂O₃的引入将ZnO的吸收光谱扩展到可见光区域,从而提高了其光生电子和空穴的分离．此外,In₂O₃/ZnO异质结在可见光照射对RhB具有较高的光催化活性．5 wt%-In₂O₃/ZnO异质结对RhB的降解率为84.3%,且具有良好的光催化稳定性．In₂O₃/ZnO异质结复合材料在有机染料废水的降解中有更广阔的应用前景．     

Structural and Magnetic Properties of the Al2O3/Ge-p/Al2O3/Co System

Technical Physics - The Al2O3/Ge-p/Al2O3/Co system with an Al2O3 buffer layer deposited by ion-plasma sputtering has been experimentally investigated. The dependences of the magnetic properties of...     

Crystallization,Flame Retardancy and Mechanical Properties of Poly(Butylene Terephthalate)/Brominated Epoxy/Nano-Sb2O3 Composites Dispersed By High Energy Ball Milling

Nano-Sb2O3 particles and brominated epoxy resin (BEO) powders were dispersed in poly (butylene terephthalate) (PBT) by high energy ball milling (HEBM). Then the nanocomposites were prepared by a twin screw extruder. The influence of the nano-Sb2O3 particles on the crystallization, thermal stability, flame retardancy and mechanical properties of the PBT/BEO/nano-Sb2O3 composites were investigated by X-ray diffraction (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), limiting oxygen index (LOI), UL-94 tests and scanning electron microscopy (SEM). The results showed that the nano-Sb2O3 particles improved the crystallizability, thermal stability and flame retardancy properties of the PBT/BEO/nano-Sb2O3 composites. When the content of nano-Sb2O3 particles was 2.0?wt%, the LOI of nano-Sb2O3/BEO/PBT composites increased from 22.0 to 27.8 and the tensile strength reached its maximum value (62.44?MPa), which indicated that the optimum value of flame retardancy and mechanical properties of PBT/BEO/nano-Sb2O3 composites were obtained.     

Calculation and Comparison of Electronic,Vibrational, Polarization,and Magnetic Properties of Double Perovskites CaMnTi 2 O 6 and CaFeTi 2 O 6

Vibrational, polarization, magnetic, and electronic properties of double perovskites CaMnTi2O6 and CaFeTi2O6 with a rare type of “column” ordering of divalent metal cations have been calculated based on the density functional theory. Analysis of the crystal lattice dynamics for paraelectric phase P42/nmc of both compounds has revealed that ferroelectric instability exists only in CaMnTi2O6. It is found that the structure distortion of the paraphrase of CaMnTi2O6 in the eigenvector of the unstable polar mode leads to a structure with the P42/nmc space group. The calculated spontaneous polarization for the ferroelectric phase of CaMnTi2O6 is Ps = 25 μC/cm2. The spin-polarization calculations have shown that the ground state is ferromagnetic in the CaFeTi2O6 crystal and antiferromagnetic in the CaMnTi2O6 crystal. The exchange interaction constants have been calculated using the Heisenberg model and the mean field approximation; the phase transition temperature for each compound has been estimated.     

LBO晶体上1 064，532 nm倍频增透膜的镀制及性能分析

 用电子束蒸发沉积方法在X切LBO（X-LBO）晶体上镀制了两种不同膜系结构的1 064和532 nm倍频增透膜，其中一种膜系结构为基底/ZrO₂/Y₂O₃/Al₂O₃/SiO₂/空气，另一种为基底/0.5Al₂O₃/ZrO₂/Y₂O₃/Al₂O₃/SiO₂/空气，两种膜系结构的主要差别在于有无氧化铝过渡层。测量了薄膜的反射率光谱曲线，发现两种增透膜在1 064和532 nm处的反射率均小于0.5％，实际镀制结果与理论设计曲线的差异主要是由材料折射率的变化引起的。且对样品在空气环境中进行了温度为473 K的退火处理，结果发现两种膜系结构均表现了较优异的光学性能，氧化铝过渡层的加入使薄膜具有强的热应力性能。     

激光驱动含能复合飞片速度特性

采用真空磁控溅射方法制备了CuO/Al2O3/Al,(CuO/Al)Ⅱ/CuO/Al2O3/Al,(CuO/Al)Ⅷ/Al2O3/Al三种复合飞片,利用激光共聚焦显微镜和扫描电镜对复合飞片进行表征,结果表明,不同材料膜层的分界面清晰可见,复合薄膜的表面结构致密,颗粒基本尺寸可以达到nm级,均匀性好。利用光子多普勒测速技术对三种复合飞片速度进行测量,结果表明:将飞片靶放置在空气电离点偏前的位置(入射激光方向),增大聚焦光斑,能改善激光电离空气引起的能量屏蔽作用;含能烧蚀层CuO/Al的存在,有助于提高飞片速度。在含能薄膜烧蚀层厚度一定的情况下,增大周期、减小每层薄膜厚度,有助于提高含能薄膜反应程度,减小飞片上升沿时间。在同等激光能量密度下,(CuO/Al)Ⅷ/Al2O3/Al的上升沿时间低于(CuO/Al)Ⅱ/CuO/Al2O3/Al。     

Carbon and oxygen isotope working standards from C3 and C4 photosynthates

A preparation of organic working standards for the online measurement of 13C/12C and 18O/16O ratios in biological material is presented. The organic working standards are simple and inexpensive C3 and C4 carbohydrates (sugars or cellulose) from distinct geographic origin, including white sugar, toilet and XEROX papers from Switzerland, maize from Ivory Coast, cane sugar from Brazil, papyrus from Egypt, and the core of the stem of a Cyperus papyrus plant from Kenya. These photosynthetic products were compared with International Atomic Energy standards CH-3 and CH-6 and other calibration materials. The presented working standards cover a 15% range of 13C/12C ratios and 9% for 18O/16O, with a precision<+/-0.2% for n>10.     

Ordered Si/Si–O nanowire array and its optical properties

Glancing angle deposition (GLAD) has been employed to fabricate the Si/Si–O nanowires (NWs). The perpendicular NW on silicon substrate shows the amorphous nature. The visible light emission from the NWs was observed from the Si/Si–O nanoparticles. High light absorption inside the Si/Si–O NW structure was recorded.     

Influence of substituents and cooperativity in doubly hydrogen-bonded complexes of 2-pyridone and oxalic acid

We performed a systemic investigation of the substitution and cooperative effects on the O–H···O and N–H···O H-bonds in the complexes of 2-pyridone and its derivatives with oxalic acid. Generally, the electron-withdrawing substituent in 2-pyridone weakens the O–H···O H-bond but strengthens the N–H···O H-bond, while the opposite effect is for the electron-donating group. In addition, the substitution effect is associated with its substitution position in 2-pyridone. The total interaction energy of a chainlike trimer with oxalic acid as a middle molecule exhibits some additivity. When oxalic acid combines with two 2-pyridone/2-pyridinethione molecules, the O–H···O/S H-bond is weakened but the N–H···O H-bond is enhanced. When three oxalic acid molecules are linked by the double O–H···O H-bonds, one H-bond with the middle oxalic acid as the proton donor is weakened and the other H-bond with the middle oxalic acid as the proton acceptor is strengthened.     

CH4、CO2、O2制合成气用Ni-Ce/Al2O3催化剂的XPS研究

用XPS表征浸渍法制备的Ni-Ce／Al2O3催化剂,并与活性评价结果相关联,研究了添加Ce对催化剂性能的影响,探讨了催化剂失活的原因。结果表明,稀土Ce在反应过程中存在着部分还原变价过程(Ce^4 e→Ce^2 ),Ce^3 能够迁移至A12O3晶格,增强载体Al2O3的抗烧结能力,提高催化剂的稳定性;Ni-Ce/Al2O3催化剂表面的Ni和Ce在反应过程中向体相迁移,以及Ni晶粒的烧结是造成催化剂活性逐步下降的主要原因。     

RuIII@CMC/Fe3O4 hybrid: an efficient,magnetic, retrievable,self-organized nanocatalyst for green synthesis of pyranopyrazole and polyhydroquinoline derivatives

Molecular Diversity - RuIII incorporated with magnetic nanosized CMC/Fe3O4 hybrid (RuIII@CMC/Fe3O4) has readily developed by a very simple self-organized procedure of RuCl3 and Na–CMC/Fe3O4...     

ZnO/Cu_2O异质结纳米阵列制备及光催化性能

利用湿化学法在FTO玻璃基底上制备了高度规整的ZnO纳米棒阵列(ZnO NRAs),以此为衬底,采用磁控溅射法在ZnO NRAs表面沉积Cu_2O薄膜。分别用X射线衍射仪、X射线光电子能谱、扫描电镜、光致光谱、紫外可见分光光度计和电化学工作站对样品的物相、形貌、吸收光谱、光电性能进行了表征,用甲基橙(MO)模拟有机物废水研究复合材料的光催化性能。结果表明:ZnO纳米棒为六方纤锌矿结构,其直径约为80~100 nm,长约2~3μm,棒间距约100~120 nm。立方晶系的Cu_2O颗粒直径约为100~300 nm,形成致密膜层并紧密覆盖在ZnO NRAs表面上,构成ZnO/Cu_2O异质结纳米阵列(ZnO/Cu_2O HNRAs)结构。与纯ZnO NRAs和Cu_2O相比,ZnO/Cu_2O HNRAs在可见光范围内的吸收显著增强,吸收波长向可见光方向偏移。ZnO/Cu_2O HNRAs的载流子传递界面的电荷转移速度快,有效促进了光生电子和空穴的分离。在紫外-可见光照射65 min后,ZnO/Cu_2O HNRAs的降解效率为94%,分别是纯ZnO NRAs和Cu_2O的18倍和1.7倍。     

Growth and ordering of CuO chains on Ag(110) surface

Growth of CuO chains and their ordering on Ag(110) surface were monitored by scanning tunneling microscopy (STM). When Cu atoms were deposited on a (2 × 1)AgO/Ag(110) surface at room temperature, the AgO chains in the [001] direction diminished and new strings of CuO grew along the [110] direction and yield a (2 × 2) p2mg ordering. When a Ag(110) surface with coexisting AgO and CuO chains was exposed to CO at room temperature, the AgO chains were selectively reduced.