单分散纳米介孔二氧化硅的制备

在温和碱性条件下,以十六烷基三甲基溴化铵为模板剂,正硅酸乙酯为硅源,三嵌段共聚物F127为助剂,制备出粒径为60～80 nm的单分散纳米介孔二氧化硅MCM-41.研究了F127的用量对介孔结构和纳米粒子分散性的影响.结果表明,适量的非离子表面活性剂F127具有助模板剂的作用,可以有效地提高纳米介孔粉体的有序性;过量的F127阻碍六方介孔相的形成,降低样品的有序性.F127与十六烷基三甲基溴化铵的摩尔比在0.04～0.08范围内,可以得到有序性好、孔径均一和孔隙率大的单分散纳米介孔二氧化硅MCM-41.     

表面活性剂对纳米MCM-41分子筛分散性的影响

采用聚乙二醇为分散剂,十六烷基三甲基溴化铵为模板剂,正硅酸乙酯为硅源,在室温碱性条件下合成了粒径为40～60 nm的单分散纳米球形MCM-41分子筛.利用XRD、TEM和N2吸附脱附等手段研究了聚乙二醇用量对纳米球形MCM-41的分散性和介孔结构的影响.结果表明,表面活性剂PEG的加入,可以明显改善纳米颗粒的分散性并且对颗粒形貌影响不大;表面活性剂PEG的加入,样品的六方结构有序性和孔尺寸发生变化.PEG量在1%～20%范围内,样品仍具有较高的六方孔道有序性;PEG量过大(60%)有序性明显下降.随着PEG加入量的增加,纳米MCM-41的晶面间距增大,孔尺寸增大.适量的聚乙二醇可以得到有序性好、比表面积大、孔径均一和孔隙率大的单分散纳米球形MCM-41分子筛.     

介孔分子筛孔尺寸表征方法比较

MCM-41是由表面活性剂十六烷基三甲基溴化铵为模板剂经水热合成，550℃煅烧5h制备的规则硅质六方介摘要孔材料；Ti-MCM-41是在MCM-41的基础上，将Ti离子涂敷引入到MCM-41的介孔中合成的。该类材料孔尺寸的表征方法有N2吸附、透射电镜TEM、SAXS等，其中N2吸附、透射电镜是传统的介孔尺寸的表征方法，SAXS是近年新的介孔尺寸的表征方法。比较了Ti-MCM-41材料的孔尺寸的表征方法，得出：SAXS得到的Ti-MCM-41孔径与TEM照片的结果符合较好，但与N2吸附的结果偏差较大。SAXS、TEM、N2吸附-脱附等温线给出的Ti-MCM-41的平均孔径分别为2.00nm、2.15nm、3.60nm。     

MCM-41介孔分子筛和纳米TiO2/MCM-41的合成与结构表征

以工业水玻璃为硅源,表面活性剂十六烷基三甲基溴化铵为结构模板剂,利用室温晶化法合成出MCM-41介孔分子筛,并以钛酸丁酯为前驱体,通过溶胶凝胶法及液相沉积法对介孔分子筛MCM-41进行纳米TiO2的组装。运用XRD、FT-IR、N2吸附-脱附等表征手段对其结构特征和氧化钛分散状态进行了研究,结果表明：TiO2与MCM-41端基硅氧键反应形成Ti-O-Si键;纳米TiO2不仅进入孔道,较均匀地修饰了介孔分子筛MCM-41的孔壁,而且使介孔分子筛MCM-41仍保持有序的孔道结构。     

短通道介孔二氧化硅的制备与水蒸气吸附性能EI北大核心CSCD

在高速搅拌条件下调整分子组装过程的外界应力,制备出短通道(500~700 nm)、条棒状的有序介孔二氧化硅,研究不同模板剂脱除方式对介孔二氧化硅的水蒸气吸附性能影响,获得强化介孔二氧化硅吸附性能的方法。结果表明:在短通道、条棒状介孔二氧化硅的制备过程中模板剂脱除的温度对材料表面羟基浓度影响较大,选择萃取与低温煅烧相结合方法脱除模板剂,萃取4次,250℃煅烧脱除模板剂的材料水蒸气吸附性能最好,在实验条件下平衡吸附时间约为7.5 min,是商品SBA-15的78.95%;平衡吸附量0.73 g·g^(-1),是商品SBA-15的1.49倍。     

用稻壳灰为硅源合成有序介孔二氧化硅材料的研究

用稻壳灰为硅源,用十六烷基三甲基溴化铵作为模板剂,在酸性或碱性条件下均成功地合成了有序介孔SiO2材料MCM-41.利用XRD、N2吸附曲线、SEM、TEM等测试方法分别对稻壳灰及介孔SiO2样品进行了表征.结果表明,稻壳灰为非晶体,呈粒状的多孔结构,其比表面积为250m2/g;在酸性条件下合成的MCM-41具有周期性规则排列的介孔结构,最可几孔径为2.4nm,比表面积为1100m2/g.     

不同结构的颗粒填充对环氧树脂纳米复合材料性能的影响

通过溶液共混法制备了环氧树脂/纳米介孔MCM-41和环氧树脂/纳米SiO2复合材料,研究了结构不同的填充颗粒、不同的填充颗粒含量及其复合材料的分散性与力学性能.结果表明,由于这种具有双重纳米结构(纳米级颗粒尺寸和纳米级的介孔结构)的介孔分子筛MCM-41能与基体形成新型网络复合结构,因此在纳米介孔MCM-41的含量适当(小于10%,质量分数,下同)时,纳米介孔MCM-41能均匀地分散在环氧树脂基体中,有效地提高复合材料的拉伸强度.而含量较高(不低于5%)的实心纳米SiO2将在环氧树脂基体中产生大量团聚体,使复合材料的拉伸强度降低.     

模板剂对MCM-41介孔分子筛结构的影响

以微硅粉为硅源,利用水热合成法成功制备出MCM-41介孔分子筛,利用XRD、N2吸附曲线和TEM等测试方法对样品进行了表征,结果表明,模板剂的用量对样品的结构具有显著的影响,当CTAB／SiO2的摩尔比为0．15时,样品的结构有序性最高;混合模板剂可明显提高样品的比表面积和孔容,合成的MCM-41介孔分子筛比表面积从299m2／g提高到837．3m2／g,孔容从0．051cm。／g提高到0．79cm3／g。     

纳米介孔MCM-41填充物对聚丙烯基复合材料性能的影响

用熔融共混法制备出聚丙烯基纳米复合材料,研究了形状和大小不同的纳米介孔MCM-41填充物对聚丙烯基纳米复合材料的拉伸性能与热性能的影响.结果表明,对于MCM-41(with template),无论是尺寸为20～40nm的颗粒形填料还是长条形填料,由于延伸到介孔孔口处的混合模板剂与聚丙烯有一定的相互作用,在填充量适当时,都对聚丙烯有明显的增强和增韧的作用.20～40nm的填料和长条形填料填充聚丙烯后复合材料的强度和模量明显优于80～100nm的填料与圆形填料的填充效果.各种介孔填料的加入,虽然并没有改变聚丙烯的晶型,但各种填料与聚丙烯存在着强的相互作用,使链段运动受到束缚,均提高了复合体系的耐热性.     

碱性条件下二氧化硅介孔颗粒的形态控制

在碱性条件下，以十六烷基三甲基溴化铵为模板剂，制备出二氧化硅介孔颗粒材料．本文应用TEM和XRD等测试手段研究了pH值、反应温度、前驱体及共溶剂浓度等因素对SiO2介孔颗粒形态的影响．结果证明，在适当的温度下，通过适当降低前驱体的浓度可以制备出粒径为30-50nm，孔道分布均匀，结构稳定的介孔材料．     

Blending effect of sucrose and surfactant templating agents on silica mesostructure

We report the blending effect of surfactant and sucrose as a nonsurfactant templating agent on the silica mesostructure. The CTAB/sucrose-templated mesoporous silica (SCS) was compared with CTAB-templated MCM-41. The MCM-41 showed spherical morphology with a particle diameter of 1.1–1.5 μm, and gave a bimodal size distribution, centered at 2.1 nm and 8.9 nm, which is assigned to hexagonally-arrayed cylindrical pores and interparticle-pores between small MCM-41 clusters, respectively. SCS gave unique and extraordinary morphology in which two different mesostructures have grown with both of them facing each other. The ordered MCM-41 pore structure clung to silica nanosphere-framed wormlike mesostructure, resulting in a bimodal pore size distribution centered at 2.1 nm and 7.0 nm. It was revealed that both of CTAB and sucrose act independently as a surfactant and a nonsurfactant template.     

H<Subscript>3</Subscript>PW<Subscript>12</Subscript>O<Subscript>40</Subscript> supported on mesoporous MCM-41 and Al–MCM-41 materials: preparation and characterisation

MCM-41 and Al–MCM-41 has been synthesized using cetyl-trimethylammonium bromide (CTAB) surfactant as template and adding the silica precursor to aqueous solutions containing CTAB. The obtained solids were calcined at 600 °C for 4 h. HPW heteropolyacid supported on the mesoporous were prepared using the incipient wetness method. The characterization of materials was performed by X-ray diffraction, Transmission Electron Microscopy, N₂ adsorption, ²⁹Si Cross Polarization–Magic Angle Spinning and ²⁷Al MAS NMR. Results showed that the hexagonal structure is obtained in both cases. The Aluminium species are located inside an extra-framework. The impregnation reduces the surface area of the mesoporous materials especially of the Al–MCM-41 suggesting a participation of aluminium during the impregnation. HPW is well dispersed in the mesoporous materials and is located inside the pores interacting with the silanol group of the pores wall. ²⁷Al MAS NMR measurements have showed that the impregnation causes the removal of the non-framework aluminium.     

Fabrication of mesoporous silica/carbon black nanospheres and load-sensitive conducting rubber nanocomposites

Mesoporous silica nanospheres (MSNs) with regular pores have been fabricated using cetyltrimethylammonium bromide (CTAB) as surfactant in high pH solution. The average size of the MCM-41 silica nanospheres was reduced from 95 to 48 nm, while the concentration of CTAB increases from 7.7 to 11.5 mmol/L. Carbon black was deposited on MSNs using hexane as the carbon source. By mixing such materials with silicone rubber, the composites become conducting when equivalent carbon volume fraction is higher than a certain region, which is less sensitive to the morphology of the deposited carbon. The improved piezoresistance repeatability has been found on the composite sample of MSNs/carbon plus extra high conducting carbon black. The load and strain sensitive range up to 0.35 MPa and 0.10, respectively, with less resistance fluctuation during multiple press loading cycles.     

资源化利用铁尾矿制备全硅介孔分子筛MCM-41

以鞍山铁尾矿为硅源,CTAB为模板剂,采用水热合成法合成出全硅介孔分子筛MCM-41。采用X射线衍射分析研究了pH值、CTAB与SiO2配比、晶化温度和晶化时间对MCM-41结构的影响,结果表明MCM-41的合成条件为n（CTAB）/n（SiO2）=0.05～0.60,pH值=8～11,晶化时间〉24h,晶化温度60～100℃。TEM可观察到样品具有典型的按六方对称性排列的孔道结构,孔径在2～4nm变化。FT-IR证明了分子筛具有硅氧四面体骨架。     

The investigation of MCM-48-type and MCM-41-type mesoporous silica as oral solid dispersion carriers for water insoluble cilostazol

Objective: To explore the suitable application of MCM-41 (Mobil Composition of Matter number forty-one)-type and MCM-48-type mesoporous silica in the oral water insoluble drug delivery system.

Methods: Cilostazol (CLT) as a model drug was loaded into synthesized MCM-48 (Mobil Composition of Matter number forty-eight) and commercial MCM-41 by three common methods. The obtained MCM-41, MCM-48 and CLT-loaded samples were characterized by means of nitrogen adsorption, thermogravimetric analysis, ultraviolet-visible spectrophotometry, scanning electron microscopy, transmission electron microscopy, differential scanning calorimetry and powder X-ray diffractometer.

Results: It was found that solvent evaporation method was preferred according to the drug loading efficiency and the maximum percent cumulative drug dissolution. MCM-48 with 3D cubic pore structure and MCM-41 with 2D long tubular structure are nearly spherical particles in 300–500?nm. Nevertheless, the silica carriers with similar large specific surface areas and concentrating pore size distributions (978.66?m²/g, 3.8?nm for MCM-41 and 1108.04?m²/g, 3.6?nm for MCM-48) exhibited different adsorption behaviors for CLT. The maximum percent cumulative drug release of the two CLT/silica solid dispersion (CLT-MCM-48 and CLT-MCM-41) was 63.41% and 85.78% within 60?min, respectively; while in the subsequent 12?h release experiment, almost 100% cumulative drug release were both obtained. In the pharmacokinetics aspect, the maximum plasma concentrations of CLT-MCM-48 reached 3.63?mg/L by 0.92?h. The AUC_0–∞ values of the CLT-MCM-41 and CLT-MCM-48 were 1.14-fold and 1.73-fold, respectively, compared with the commercial preparation.

Conclusion: Our findings suggest that MCM-41-type and MCM-48-type mesoporous silica have great promise as solid dispersion carriers for sustained and immediate release separately.     

Prediction of Thermal Conductivity of Aluminum Nanocluster-Filled Mesoporous Silica (Al/MCM-41)

MCM-41 consists of a hexagonal array of long, unconnected cylindrical pores with diameters that can be tailored within the range 1.6 nm to 10 nm. As a porous silica nanomaterial, MCM-41 is a promising porous substrate for mesoporous composites with extremely high or low thermal conductivity. In this article, the structural unit of MCM-41 was established first and an equilibrium molecular dynamics simulation was performed to determine the shell thermal conductivity of MCM-41. Then, based on one-dimensional (1D) heat transfer analysis, a mathematical expression for the effective thermal conductivity (ETC) of Al nanocluster-filled mesoporous MCM-41 (Al/MCM-41) was obtained. The effects of porosity and the filling ratio of nanoclusters in the mesochannels were further investigated. As the porosity is greater than 75 %, the ETC of only-air-filling mesoporous MCM-41 in all directions tends to approach the thermal conductivity of air. It seems that Al nanoclusters have negligible effects on the ETC of the composite, except that mesochannels are almost completely filled with Al nanowires.     

有序介孔氧化硅孔道氧化锰团簇组装研究

以有序介孔氧化硅MCM-41为主体材料,通过浸渍法及后续热处理工艺,在孔道中组装氧化锰的团簇粒子,并对其进行结构表征。通过XRD、HR—TEM、XPS及N2吸附表明氧化锰的团簇粒子已经成功组装到MCM-41有序孔道中。通过对不同孔径有序介孔材料的氧化锰团簇粒子的组装,表明随着孔道中组装量的增加,350nm附近光致发光强度增强,吸收边发生红移,同时1000nm附近吸收带宽化。