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。在常规方法中，颗粒的聚集容易发生。为了消除这个缺点，似乎优选在一个步骤中进行UFP的形成和加工。在此，我们尝试用凝胶膜制备超微粒子。超微粒子的尺寸由凝胶网络控制。通过沉淀过程，利用反应溶液通过膜的相互扩散，将颗粒浸渍到乙酸纤维素凝胶膜中。以无机盐或铝醇盐为原料，采用溶胶-凝胶法制备了氧化铝凝胶。水合氧化铁复合凝胶膜经热分解后直接得到20- 80 nm的铁磁性颗粒。这些颗粒很可能被碳覆盖。水合Ba和Fe氧化物复合膜经热分解得到了20- 80 nm的钡铁氧体颗粒 ...更多信息 es. 400 ℃的氢气还原水合金属氧化物复合膜，并导致形成高度分散的金属/C催化剂。与Raney Ni相比，Ni/C催化剂显示出更高的环辛烯生成环辛烯的反应选择性。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 ℃退火时仍是透明的。该薄膜对紫外到近红外的光都有很高的透过率，在低温下可将多种有机染料包埋在薄膜中，且均匀性好。通常在水溶液中观察到的不希望的染料聚集在膜中大大减少，甚至在浓度高达10 μ <-2>M时。这样掺杂的膜用作染料激光发射薄膜或光化学烧孔器件，其适用于高密度光数据存储。使用上述水合氧化铝溶胶通过溶胶-凝胶法制备了高度分散的镍-氧化铝催化剂。该催化剂在1，3和1，5-环辛二烯液相加氢反应中表现出较高的选择性。然而，它显示出比雷尼镍低的活性。这可能是由于镍颗粒倾向于包封在氧化铝颗粒内。以异丙醇铝为原料，采用溶胶-凝胶法制备了透明氧化铝膜。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。从胶体水平上的均匀复合出发，研究了聚乙烯醇（PVA）/氧化铝凝胶复合材料的形成。研究了分散氧化铝对复合材料力学性能的影响。含PVA 40-50%的复合材料具有一定的柔韧性。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