Preparation of Ultra Fine Particles by Using Gel Membrane And Its Applications

随着颗粒尺寸的减小，超细颗粒(UFP)本质上应该表现出不寻常的性质。在传统方法中，粒子很容易发生聚集。为了消除这一缺点，似乎更可取的是一步完成UFP的形成和处理。在此，尝试了用凝胶膜制备UFP。UFP的大小由凝胶网络控制。利用反应溶液通过膜的相互扩散，通过沉淀法将颗粒浸渍到醋酸纤维凝胶膜中。以无机盐或醇铝为原料，采用Sol-Gel法制备了氧化铝凝胶。直接从水合氧化铁复合凝胶膜的热分解中得到铁磁性颗粒(20-80 nm)。这些颗粒很可能被覆盖了一层碳。BaFe氧化物…复合膜的热分解可得到20~80 nm的巴尔铁氧体颗粒更多的ES。400ﾟC的氢气还原了金属氧化物复合膜，形成了高度分散的金属/碳催化剂。与Raney Ni相比，Ni/C催化剂对环辛二烯合成环辛烯的反应具有更高的选择性。以超细氧化铝溶胶为原料，采用脱水法制备了透明氧化铝薄膜。该薄膜在900ﾟC下热处理前是透明的，对从紫外光到近红外光有很高的透过率。在低温条件下，多种有机染料包埋在薄膜中，均匀度较好。通常在水溶液中观察到的不希望看到的染料聚集在薄膜中大大减少，即使在浓度高达10^~(-2)M时也是如此。这样的掺杂薄膜作为一种染料激光发射薄膜或适用于高密度光存储的光化学烧孔器件。以上述水合氧化铝溶胶为原料，采用Sol-Gel法制备了高分散镍铝催化剂。该催化剂在1，3-环辛二烯和1，5-环辛二烯的液相加氢反应中具有较高的选择性。然而，它的活性低于雷尼镍。这可能是由于镍颗粒被包裹在氧化铝颗粒中的趋势所致。以异丙醇铝为原料，采用溶胶-凝胶法制备透明氧化铝膜。孔径分布在2~10 nm之间。永久气体的渗透系数随分子量的增加而减小。从胶体均质复合材料的角度研究了聚乙烯醇(PVA)/氧化铝凝胶复合材料的形成。考察了分散氧化铝对复合材料力学性能的影响。PVA含量为40~50%的复合材料具有一定的柔韧性。较少

As the particle size decreases, the ultrafine particles(UFP) should be essentially exhibit unusual properties. In conventional methods,the aggregations of particles occur easily. To remove this drawback, it seems preferable to perform the formation and processing of UFP in one step. Here, the preparation of UFP was tried by using gel film. The size of UFP is controlled by gel network. The particles were impregnated into the cellulose acetate gel membrane by precipitation process using the mutual diffusions of reacting solutions through the membrane. Alumina gel was prepared by sol-gel process using fine hydrous alumina oxide sol derived from inorganic salt or aluminum alkoxide. Ferromagnetic particles (20-80nm) were obtained from directly from thermal decomposition of hydrous Fe oxide composite gel membrane. It is likely that the particles are coated with carbon. Barrium ferrite particles (20-80nm) were obtained from thermal decomposition of composite membrane of hydrous Ba and Fe oxid … More es. Hydrogen at 400ﾟC reduces the hydrous metal oxide composite membrane and leads to the formation of highly dispersed metal/C catalysts. The Ni/C catalyst shows higher selectivity for the reaction of cyclooctadiene to cyclooctene, compared to Raney Ni. Transparent alumina film was prepared by dehydration from ultrafine alumina sol. The film is transparent up to annealing at 900ﾟC. It shows high transmittance for light ranging from UV to near IR. A variety of organic dyes are embedded in the films at low temperature with good homogeneity. The undesirable dye aggregation usually observed in aqueous solution is, largely reduced in the film, even at concentration as high as 10^<-2>M. The film thus doped acts as a dye laser emission thin film or device of photochemical hole burning which is applicable to high density optical data storage. A highly disperted nickel-alumina catalyst has been prepared by the sol-gel process using hydrous alumina sol described above. This new catalyst shows higher selectivity in the liquid phase hydrogenation of 1,3 and 1,5-cyclooctadiene. However, it shows lower activity than Raney nickel. This may be due to the tendency of the nickel particles to be encapsulated within the alumina particles. Transparent alumina membrane was prepared from the hydrolysis of aluminum isopropoxide by the sol-gel method. The pore size was distributed from 2 to 10nm. The permeability coefficient of permanent gas decreased as the molecular weight increased. A formation of polyvinyl alcohol (PVA)/alumina gel composite was investigated with a view of homogeneous composite at colloidal level. The effects of dispersed alumina on the mechanical properties of composite were examined. The composites containing PVA 40-50% are flexible. Less