聚甲基丙烯酸/SBA-15复合物的制备

采用超声波分散技术,通过原位合成法将pH敏感的功能单体甲基丙烯酸(MAA)引入到介孔二氧化硅SBA-15的孔道内聚合,制备了pH敏感SBA-15/聚甲基丙烯酸(PMAA)纳米复合材料,对材料的结构和性能进行了测试。结果表明,介孔分子筛SBA-15/PMAA复合材料有较好的光学性能、热性能。聚合反应的发生并没有破坏SBA-15的有序介孔结构,显示出pH敏感性,有望在药物缓释领域得到应用。     

单分散介孔纳米载体合成及表征

通过St(o)ber法制备粒径约100 nm的SiO2纳米粒子,并以非离子表面活性剂嵌段共聚物为模板剂在纳米粒子表面再合成介孔SiO2层.在磷酸盐诱导剂的作用下可使核/壳结构的纳米粒子快速沉淀出来.再通过煅烧除去表面活性剂获得粒径均匀的球形介孔纳米载体.通过动态光散射(DLS)、扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)、比表面积测定(BET)和氮气吸附脱附测定等技术对材料进行表征.纳米载体的平均有效粒径约为183 nm,介孔孔道为5.5 nm,具有良好的分散性(PDI:0.076),比表面积高达158.6 m2/g,孔容积0.22 cm3/g.结果表明,该法可以简单快速地制备纳米载体.     

核-壳结构二氧化硅介孔材料的制备与表征

采用溶胶凝胶法在一定条件下合成了具有核-壳结构的二氧化硅介孔材料,使用透射电子显微镜对微球样品的超微结构进行了观察,使用傅里叶红外光谱分析了样品的光谱性质。分析结果表明:制备的核-壳结构介孔二氧化硅微球样品,是由外表面为孔径约8纳米,厚度约30纳米的有序介孔二氧化硅壳层,包裹着内核为直径约200纳米的二氧化硅微球所组成,介孔壳层具有较大的比表面积,具有良好的光谱性质。     

智能化二氧化硅纳米控释肥设计与控释机理研究

为了提高肥料的利用率,本文研究了共沉淀法制备介孔二氧化硅纳米粒子(MSN)作为载体材料,以异硫氰酸荧光素(FITC)为目标物质代替化学肥料,以壳聚糖(CS)为介孔封堵物,探究纳米粒子的控释机理。结果表明,接枝前MSN的缓释率为52.62%,接枝CS后,缓释率降低到了34.2%,明显提高了缓释效果,为智能化纳米控释肥的研究提供理论依据。     

介孔二氧化硅花球的制备及药物缓释性能研究

采用溶胶-凝胶法,以正硅酸乙酯为硅源、十六烷基三甲基溴化铵(CTAB)为模板,在碱性条件下合成了尺寸均匀、形状规则的花状形貌的介孔状二氧化硅微球。基于二氧化硅花球特殊的表面褶皱和内部的介孔孔道,将其作为载体负载模型药物布洛芬,探究其药物缓释性能。结果表明,所制备的介孔二氧化硅花球对布洛芬模型药物的负载量为701.63 mg·g~(-1),明显高于传统药物载体材料。此外,对介孔二氧化硅/布洛芬复合粒子进行缓释实验研究,发现10 h后布洛芬的释放量为74.60%,表明其具有较好的药物缓释性能。     

乙烷桥联型介孔二氧化硅纳米球的制备与表征

本文采用表面活性剂导向溶胶-凝胶法,在碱性条件下,通过两种硅源成功制备了乙烷桥联型介孔纳米粒子(MSN)。在合成MSN的基础上,以γ-(甲基丙烯酰氧基)丙基三甲氧基硅烷(MPS)为改性剂对MSN表面进行了修饰。结果表明:合成的MSN呈规整的纳米级球体,界面高度交联,具有直径分布均匀(260nm)的无机-有机杂化骨架,其比表面积、介孔尺寸和孔容分别为540m~2/g、3.7nm和0.52cm~3/g。     

fnSiO2@mSiO2核壳粒子的制备及表征

本文将掺杂有三元荧光共振能量转移染料对的SiO2纳米核引入介孔SiO2球形粒子中,形成在单一波长激发下能产生多色荧光发射的核壳结构。产物通过TEM、XRD、BET等方法进行了表征。结果表明:成功制备得到以荧光纳米粒子为核,介孔SiO2为壳层的核壳粒子(fnSiO2@mSiO2),介孔孔径为2.5nm。     

纳米介孔二氧化硅的制备和修饰研究

以十六烷基三甲基溴化铵(CATB)为模板剂、正硅酸乙酯(TEOS)为硅源,采用化学沉淀法制备纳米介孔二氧化硅;通过氨基硅烷偶联剂和巯基硅烷偶联剂(1∶1)的共同作用,在无水体系中制备氨基和巯基共同修饰的纳米介孔二氧化硅,并通过扫描电镜、X-射线衍射仪和傅立叶变换红外光谱仪对修饰前后的纳米介孔二氧化硅进行表征。结果表明,纳米介孔二氧化硅粒子形态均一,平均粒径在100nm左右,分散性良好;修饰后的纳米介孔二氧化硅粒子形貌及分散性依然良好,平均粒径在150nm左右。该研究为纳米介孔二氧化硅载药体系的研究提供了新思路和实验基础。     

纳米铁粒子表面接枝聚合甲基丙烯酸甲酯

采用直流电弧等离子体法制备纳米铁粉,利用甲基丙烯酸(MAA)和盐酸处理纳米铁粉,通过乳液聚合方法,在纳米铁粉存在下MMA原位聚合,形成纳米铁/聚甲基丙烯酸甲酯复合粒子。分析结果表明,MMA在纳米铁粒子表面接枝聚合,纳米铁粉表面的双键参与了聚合反应,所形成的复合粒子具有核壳结构,这种复合粒子具有较高的稳定性。     

Pd/CMK-3的合成及其在Suzuki-Miyaura碳-碳偶联反应中的应用

利用介孔二氧化硅（SBA-15）为模板、蔗糖为碳源,制备了有序介孔碳材料CMK-3,然后以CMK-3为载体,利用浸渍还原法得到介孔碳负载Pd纳米粒子的复合催化剂（Pd/CMK-3）,通过XRD、TEM以及氮气吸附-脱附等手段对催化剂的微结构和组分进行分析,结果表明CMK-3为有序介孔结构,孔径约为5nm,Pd/CMK-3保留了介孔结构,且孔道中负载有不同尺寸的Pd粒子。应用于无配体催化的Suzuki-Miyaura相似文献   

Wet Milling of Fe/Al/Al2O3 and Fe2O3/Al/Al2O3 Powder Mixtures

Wet milling of Al₂O₃-aluminide alloy (3A) precursor powders in acetone has been investigated by milling Fe/Al/Al₂O₃ and Fe₂O₃/Al/Al₂O₃ powder mixtures. The influence of the milling process on the physical and chemical properties of the milled powders has been studied. Particle refinement and homogenization were found not to play a dominant role, whereas plastic deformation of the metal particles leads to the formation of dislocations and a highly disarranged polycrystalline structure. Although no chemical reactions among the powder components in Fe₂O₃/Al/Al₂O₃ powder mixtures were observed, the formation of a nanocrystalline, ordered intermetallic FeAl phase in Fe/Al/Al₂O₃ powder mixtures caused by mechanical alloying was detected. Chemical reactions of Fe and Al particle surfaces with the atmosphere and the milling media lead to the formation of highly porous hydroxides on the particle surfaces. Hence the specific surface area of the powders increases, while the powder density decreases during milling. The fraction of Fe oxidized during milling was determined to be 0.13. The fraction of Al oxidized during milling strongly depends on the metal content of the powder mixture. It ranges between 0.4 and 0.8.     

Preparation and properties of poly(Nε,Nε-dicarboxymethyl-l-lysine)

A new ampholytic homopolypeptide, $\text{poly}\text{(N}{}^{\mathrm{\epsilon }}\text{,N}{}^{\mathrm{\epsilon }}\text{-}\text{dicarboxy-methyl-}\text{l}\text{-lysine}\text{)}$, which has one tertiary amino and two carboxyl groups in the side chain has been derived from a hydrochloride salt of poly(L-lysine). The polymer in aqueous solution seems to be in the coil form with locally extended structure (LES) at neutral pH. In both the acidic and alkaline regions, the molar ellipticity of the polymer changes as a result of change in net charge on the side chain. The conformational changes may be from the coil with LES to other coiled forms. 5–7 M NaClO₄ and 80% aqueous methanol induce the α-helix in the polymer at neutral pH. Divalent cations, Cu²⁺ and Ca²⁺, do not induce any remarkably ordered structures such as α-helix or β-structure in the polymer in aqueous solution at any pH. Ultraviolet absorption studies show an absorption peak of the polymer-Cu²⁺ complex near 240 nm. Dependence of the peak intensity on pH at various q values ($\text{q =}\text{[}\text{Cu}{}^{\mathrm{2+}}\text{]}\text{[}\text{residue}\text{]}$) indicates the two steps of the complex formation. At q less than 0.64, the formation is described only with the first step. An average coordination number for Cu²⁺ at the first step was calculated to be about 2 by the method of Mandel and Leyte. The association constant of Cu²⁺ with the residue at the step was determined from the absorption data to be far smaller than that for the Cu²⁺-EDTA complex. The second step of the formation occurs in the case of large q but the absorption data for the second step cannot be obtained exactly due to precipitation.     

Participation of lewis base on vinyl chloride polymerization with Al(C2H5)3CCl4 catalyst system

The polymerization of vinyl chloride has been investigated using an $\text{Al}\text{(}\text{C}{}_2\text{H}{}_5\text{)}{}_3\text{CCl}{}_4$ catalyst system in the presence of various Lewis bases. Effective Lewis bases are γ-butyrolactone, diglyme and diethylenetriamine which are multidentate. The rate of polymerization is dependent not only on the basicity of the Lewis base used but also on a coordination number of one. The latter is the predominant factor. For the effect of polymeric amines, a tentative hypothesis is discussed.     

Ag2O-Doped Bi2Sr2Ca1Cu2Ox Superconductors Prepared via Melt-Quenching

Ag₂O-doped superconducting Bi₂Sr₂Ca₁Cu₂O _x ceramics were prepared by a melt-quenching–reheating method. It is found that the Ag₂O-doped, as-cast specimens exhibit superconductivity ( T _c= around 80 K) by heat treatment at temperatures around 800°C even in an evacuated and sealed silica glass tube, while the undoped specimens do not and vaporize by the corresponding heat treatment. Conversion of the Ag₂O-doped, as-cast specimens into superconducting ceramics when heated in an evacuated vessel is explained in terms of the oxygen donor of Ag₂O in the specimen. This finding enables us to fabricate a desired shape of superconducting Bi₂Sr₂Ca₁Cu₂O _x ceramics sealed in metals or glasses. The addition of Ag₂O to Bi₂Sr₂Ca₁Cu₂O _x melt, however, had deleterious influences on the superconducting properties ( T _c and J _c) of the resultant ceramics when obtained by heat treatment in air.     

Synthesis and Characterization of Ti0.33Ta0.33Nb0.33C and Ti0.33Ta0.33Nb0.33CxN1-x Whiskers

Ta_0.33Ti_0.33Nb_0.33C and Ta_0.33Ti_0.33Nb_0.33C _x N_{1− x} whiskers were synthesized via a carbothermal vapor-liquid-solid growth mechanism in the temperature range 900°-1450°C in Ar or N₂. The optimum temperature was 1250°C. Whiskers were obtained in a yield of 70-90 vol%. The whiskers were 0.5–1 µm in diameter and 10–30 µm in length. The starting materials that produced the highest whisker yield were: TiO₂, Ta₂O₅, Nb₂O₅, C, Ni, and NaCl. C was added to reduce the oxides, and Ni to catalyze whisker growth. NaCl was used as a source of Cl for vapor-phase transportation of Ta and Nb oxochlorides and Ti chlorides to the catalyst. The catalyst metal was recycled several times during the synthesis and was transported as NiCl₂( g ) according to thermodynamic calculations. The rate of formation and the chemical composition of the whiskers depended on the synthesis temperature, the choice of catalyst, and the atmosphere. At low temperatures, the whiskers were enriched in Nb and Ta, whereas the Ti content increased with increased synthesis temperature.