Fluoro-modified elastomeric polyurethanes: effects of synthesis procedure on properties and morphology

Fluorinated polyurethanes characterized by a segmented structure, containing hard segments based on 4,4′-methylenebis (phenylisocyanate) (MDI), chain-extender 1,4 n-butandiol (BDO), and soft blocks like perfluoropolyether (PFPE), and poly-ε-caprolactone (PCL) were synthesized keeping constant the equivalent ratio among reagents, but varying the experimental conditions. Copolymers show a complex micro- and macrostrucrture with different morphology and calorimetry, similar tensile properties and undistinguishable, but strongly upgraded surface properties. The morphology should be governed by the different fluorine content of the polymeric chains along with the hard segment structure; tensile properties are little influenced by the morphology. All these characteristics are interpreted in terms of polymerization procedure which results to be a key parameter for ruling the composition of the different polymeric chains, due to a very limited mutual solubility of the reagents. Surprisingly, a beneficial effect of the catalyst dibutyltindilaurate for the increase of the reaction kinetics among segregated phases in the reaction mass was observed.     

自组装囊泡的结构与单分子膜的性质

研究了具有不同主链分子量和侧链长度的N,N-双烷基化壳聚糖单分子膜的性质.结果表明,主链分子量越大,所形成的N,N-双烷基壳聚糖单分子膜的结构越紧密.在主链分子量相同的条件下,N,N-双烷基壳聚糖单分子膜的致密度随着侧链长度的增大而增大,表明N,N-双烷基化壳聚糖分子间的缠结嵌套和疏水相互作用力的增大.比较N,N-双烷基化壳聚糖单分子膜与相应自组装囊泡的性质发现,囊泡的药物平衡释放率随着其相应材料单分子膜压缩模量的增大而减小,呈现出一定的线性关系.单分子膜压缩模量的大小反映囊泡膜结构的紧密程度.     

PFCY沙土固结材料的结构与性能

以水溶性聚合物、农作物秸秆、工业固体废弃物和水泥为主要原料制备PFCY沙土固结材料,研究了PFCY的微观结构特征和力学性能,以及各组分之间的作用机理,并分析了PFCY强度体系的形成过程。研究结果表明,在水灰比为0.4,聚丙烯酰胺掺量为1%,麦秸纤维掺量为2%时,PFCY的抗折强度提高了24.7%,聚丙烯酰胺、麦秸纤维和无机胶凝材料能够均匀分布在PFCY体系中,聚丙烯酰胺以丝状和网络状形态存在,材料内部颗粒之间的粘结得到增强,麦秸纤维与硬化水泥浆体界面结构有所改善。     

The morphology and structure of chemically vapour-deposited Ti(C,N) coatings

Thin films of Ti(C,N) were prepared by chemical vapour deposition onto cemented tungsten carbide substrates. It was found that the growth rate of the Ti(C,N) coatings increased with the total flow rate of the reactant gas and with the deposition temperature. The microstructure and morphology of the Ti(C,N) coatings vary with their deposition temperature and composition. The composition of the Ti(C,N) determines the extent of the secondary growth features, and the characteristic morphology of the Ti(C,N) coatings is determined by the deposition temperature. It is also shown that the lattice constant of the Ti(C,N) coatings increases with the carbon content of the coatings.     

聚氨酯微胶囊的合成、结构及形态研究

首先合成了聚氨酯(PU)水溶液,再采用凝聚相分离法合成了PU微胶囊.研究了二异氰酸酯单体种类、聚乙二醇分子量、单体摩尔比、总单体含量、CaCl2浓度对PU微胶囊的影响,通过FTIR和SEM表征了微胶囊的化学结构和形态结构.实验结果表明,选用异佛尔酮二异氰酸酯与分子量为200的聚已二醇以摩尔比6∶2反应,总单体含量为45%,CaCl2浓度4%可以制得球形度好的PU微胶囊.FTIR表明合成的微胶囊为PU;SEM照片显示微胶囊为较光滑的圆球形,表面有孔隙,直径为3mm左右,内有空腔,空腔直径为2mm左右.     

Synthesis and photo-catalytic degradation property of nanostructured-ZnO with different morphology

ZnO nanostructures with different morphology have been successfully fabricated by a simple relative low temperature approach at 90 °C for 5 h without surfactant assistance. These structures can be easily tailed using varied concentrations of sodium hydroxide (NaOH) and different amounts of the hydrazine hydrate (N₂H₄·H₂O). X-ray diffraction (XRD) result proves the formation of ZnO with wurtzite structure. Microstructure as revealed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) indicates that the rod-like and chrysanthemum-like ZnO nanostructures contain many radial nanorods, which grow along the [0001] direction. Furthermore, the as-prepared ZnO nanomaterials exhibit high activity on the photo-catalytic degradation of typical persistent organic pollutants (POPs), indicating that they are promising as semiconductor photo-catalysts.     

利用自组装单分子膜对表面结构和性质的研究进展

以硅烷和硫醇两种体系为代表介绍了自组装单分子膜的结构和形成机理，指出自组装单分子膜具有单分子层性质和灵活的分子设计特性，综述了其作为表面结构和性质研究工具的最新进展。     

干燥控制化学添加剂对SiO_2气凝胶薄膜形貌和性能的影响

为了快速制备平整高透过率SiO_2气凝胶薄膜,以正硅酸乙酯(TEOS)为硅源,乙二醇甲醚(EGME)为溶剂,氟化铵为催化剂,甲酰胺(FORM)等为干燥控制化学添加剂(DCCA),通过浸渍提拉法制备SiO_2气凝胶薄膜。采用傅里叶变换红外分析仪(FTIR)、X射线衍射仪(XRD)、场发射扫描电子显微镜(FESEM)、原子力显微镜(AFM)、表面孔径吸附仪对材料的结构和性能进行表征,紫外-可见分光光度计(UV-Vis)考察了材料的减反性能。结果表明,所制SiO_2气凝胶薄膜的比表面积为890.9m2/g,孔径集中分布在22.6nm处,孔容集中分布在0.69cm3/g,400~800nm范围平均透过率可达95.71%。这种均匀、平整、致密的膜层,是理想的光学减反膜。     

Self-assembled light lanthanide oxalate architecture with controlled morphology, characterization, growing mechanism and optical property

Flower-like Sm₂(C₂O₄)₃·10H₂O had been synthesized by a facile complex agent assisted precipitation method. The flower-like Sm₂(C₂O₄)₃·10H₂O was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, thermogravimetry-differential thermal analysis and photoluminescence. The possible growth mechanism of the flower-like Sm₂(C₂O₄)₃·10H₂O was proposed. To extend this method, other Ln₂(C₂O₄)₃·nH₂O (Ln = Gd, Dy, Lu, Y) with different morphologies also had been prepared by adjusting different rare earth precursors. Further studies revealed that besides the reaction conditions and the additive amount of complex agents, the morphologies of the as-synthesised lanthanide oxalates were also determined by the rare earth ions. The Sm₂(C₂O₄)₃·10H₂O and Sm₂O₃ samples exhibited different photoluminescence spectra, which was relevant to Sm³⁺ energy level structure of 4f electrons. The method may be applied in the synthesis of other lanthanide compounds, and the work could explore the potential optical materials.     

多形貌纳米TiO2的合成、结构和光活性研究

以廉价的、易得的无机含钛盐、氨水以及氢氧化纳等简单原料，以低温水热法合成出一系列的纳米锐钛矿相、板钛矿相以及混晶产品。该工艺具有操作简单易行、干扰因素少、易于工业化生产等优点。TEM结合SEM形貌观察，产品为纳米结构，粒度大小均匀，无团聚，颗粒尺寸20-70nm，且通过实验条件的控制，得到了球状、棒状、羽毛状等多种形貌和不同晶态结构的产品，应用实验表明，产品具有较高的光催化活性，在太阳光下有机染料在60min内脱色率超过96％。     

Growth,morphology and structure of CsRP4O12 crystals

We have grown CsRP₄O₁₂ (R³⁺ is a rare-earth ion) crystals from 85% phosphoric acid solutions. Morphological, optical and X-ray studies have been carried out on all the crystals. CsRP₄O₁₂ crystallizes in four different structural modifications. The variation in growth temperature causes variation in their morphology and crystal structure.     

纳滤膜孔结构、荷电性质、分离机理及动电性质研究进展

纳滤膜拥有介于反渗透膜和超滤膜之间的截留分子量,同时对无机盐的截留率随着盐的种类和浓度而改变,广泛应用于各种水净化处理和产品精制分离过程.文章从纳滤膜孔结构和荷电性质、纳滤膜分离机理及其模型、纳滤膜动电性质等三个方面对纳滤膜分离技术20多年来的基础及应用研究进展进行回顾和总结,简要分析了今后纳滤膜分离技术的发展方向及趋势.     

负载Ni炭气凝胶的制备及结构性能研究

以间苯二酚、甲醛为原料,添加适量的十二烷基苯磺酸钠,再加入不同浓度的乙酸镍溶液,在85℃水浴中聚合;经溶胶-凝胶、溶剂置换、常压干燥和1000℃氮气气氛下热解,得到负载不同含量金属Ni的炭气凝胶.利用透射电镜(TEM)、扫描电境(SEM)、X射线衍射(XRD)、比表面积及孔径分析(BET)和直流充放电测试等手段,对比讨论了负载不同含量金属Ni对炭气凝胶的结构和性能的影响.结果表明,这种方法可以均匀地将Ni纳米粒子分散于炭气凝胶中;适量的金属Ni可使发气凝胶的比表面积及充放电性能得到显著提高;如负载Ni含量过高则炭气凝胶石墨化程度增加.     

Solution-deposited GdCeOx thin films: Microstructure,band structure,and dielectric property

The microstructural and electrical properties of solution-deposited GdCeO_x dielectric thin films with different mixing ratios were studied. The Ce incorporation enhanced the degree of crystallization and the refractive index of the Gd₂O₃ film, reduced the hysteresis and increased the dielectric constant. According to reflective electron energy loss spectroscopy and X-ray photoelectron spectroscopy analyses, the bandgap of the GdCeO_x film gradually decreased with increasing Ce/(Gd + Ce) atomic ratio, which was primarily affected by the reduction of the valence band offset.     

Effects of chemical structure of diisocyanate in polyurethanes on the diffraction efficiency

In this study, we report the syntheses and diffraction efficiency of four different disperse red-polyurethanes (DR-PUn’s) containing azobenzene group in the side chain. The effects of chemical structures of diisocyanates in four different DR-PUn’s were studied on the diffraction efficiency induced by the laser beam. The DR-PUn’s with toluene-2,4-diisocyanate or toluene-2,6-diisocyanate exhibited diffraction efficiencies, but the DR-PUn’s with diphenyl structure of diisocyanate in the main chain did not show diffraction efficiencies. It was found that for the DR-PU2 having the molecular weight larger than 16,000 shows good optical storage behavior and that the maximum diffraction efficiency reached to 0.35%.     

Surfactant-controlled morphology and magnetic property of manganese ferrite nanocrystal contrast agent

MnFe(2)O(4) nanocrystals (NCs) coated with three different surfactants (oleic acid, oleylamine or 1,2-hexadecanediol) and their mixtures, with sizes in range 6-12 nm, were synthesized by high-temperature decomposition of organometallic precursors. The effects of morphology and surface chemistry of MnFe(2)O(4) NCs on the magnetic properties were systematically investigated by comparing their saturation magnetization values and their capability to improve the negative contrast for magnetic resonance imaging (MRI) after converting the hydrophobic NCs to hydrophilic ones by a ligand exchange protocol. An important finding is that the magnetization values and proton relaxivity rates of MnFe(2)O(4) NCs are strongly dependent on the size and surface state of the particles that covalently bonded with different hydrophobic ligands before ligand exchange. In particular, monodisperse cubic MnFe(2)O(4) NCs could be obtained when oleylamine and 1,2-hexadecanediol were used as mixed stabilizers, and showed excellent morphology and magnetic properties. Furthermore, the low cytotoxicity and good cell uptake MR imaging of the dopamine capped MnFe(2)O(4) NCs make them promising candidates for use as bio-imaging probes.     

Electronic structure and optical property of semiconductor nanocrystallites

Semiconductor nanostructures show many special physical properties associated with quantum confinement effects, and have many applications in the opto-electronic and microelectronic fields. However, it is difficult to calculate their electronic states by the ordinary plane wave or linear combination of atomic orbital methods. In this paper, we review some of our works in this field, including semiconductor clusters, self-assembled quantum dots, and diluted magnetic semiconductor quantum dots. In semiconductor clusters we introduce energy bands and effective-mass Hamiltonian of wurtzite structure semiconductors, electronic structures and optical properties of spherical clusters, ellipsoidal clusters, and nanowires. In self-assembled quantum dots we introduce electronic structures and transport properties of quantum rings and quantum dots, and resonant tunneling of 3-dimensional quantum dots. In diluted magnetic semiconductor quantum dots we introduce magnetic-optical properties, and magnetic field tuning of the effective g factor in a diluted magnetic semiconductor quantum dot.     

稀土La掺杂Mg2Si的几何结构、弹性性能和电子结构的第一性原理研究EI北大核心CSCD

采用密度泛函理论(DFT)的第一性原理平面波赝势方法对稀土元素镧(La)掺杂Mg2Si的几何结构、弹性性能和电子结构进行计算与分析。首先,结合形成焓、Born力学稳定性以及差分电荷密度的结果可知,掺杂稀土元素La之后,形成的Mg8Si4La和Mg8Si3La均不能稳定存在,La掺杂的Mg2Si优先占据体系Mg原子的位置;其次,晶体的体模量(B),剪切模量(G),杨氏模量(E),泊松比(ν),以及各向异性系数(A)的计算结果表明本征Mg2Si为脆性相,而Mg7Si4La为韧性相,掺杂La可以提高Mg2Si的延展性;最后,态密度、Mulliken布居数和电荷差分密度的计算结果表明掺杂稀土镧后费米面向高能级区域偏离,进入导带,提高了Mg2Si的导电性。