共沸蒸馏法制备单分散氧化镍微粉

先采用均匀沉淀法制得单分散的氧化镍前驱体粉末 ,然后用正丁醇进行共沸蒸馏脱水处理。经干燥、煅烧后成功地制成了单分散性相当好的氧化镍微粉。实验证明 ,共沸蒸馏能有效地脱除湿粉末中的水分 ,丁氧基取代了颗粒表面的羟基 ,从而防止了颗粒间Ni—O—Ni的形成 ,消除了硬团聚形成的可能性。     

Facile Synthesis of Monodispersed Polysulfide Spheres for Building Structural Colors with High Color Visibility and Broad Viewing Angle

The synthesis and assembly of monodispersed colloidal spheres are currently the subject of extensive investigation to fabricate artificial structural color materials. However, artificial structural colors from general colloidal crystals still suffer from the low color visibility and strong viewing angle dependence which seriously hinder their practical application in paints, colorimetric sensors, and color displays. Herein, monodispersed polysulfide (PSF) spheres with intrinsic high refractive index (as high as 1.858) and light‐absorbing characteristics are designed, synthesized through a facile polycondensation and crosslinking process between sodium disulfide and 1,2,3‐trichloropropane. Owing to their high monodispersity, sufficient surface charge, and good dispersion stability, the PSF spheres can be assembled into large‐scale and high‐quality 3D photonic crystals. More importantly, high structural color visibility and broad viewing angle are easily achieved because the unique features of PSF can remarkably enhance the relative reflectivity and eliminate the disturbance of scattering and background light. The results of this study provide a simple and efficient strategy to create structural colors with high color visibility, which is very important for their practical application.     

微波辅助polyol法制备的纳米镍颗粒

采用微波辅助polyol还原法制备了单分散的纳米Ni颗粒。分别用X射线衍射(XRD)和透射电镜(TEM)观测样品的相结构和微观形貌,用振动样品磁强计(VSM)测试Ni颗粒的磁性。XRD显示样品为面心立方结构,TEM观察显示金属镍颗粒的形貌是理想的球型。当把反应温度提高到400℃,并且在实验过程中加入适量的PVP时,发现镍颗粒呈现出一种毛茸茸的多毛形态,这种分散均匀的单一态形貌类似于纳米头发的结构。同时,VSM测试结果表明球型纳米Ni颗粒具有典型的铁磁性。     

SiO2单分散溶胶微球制备的工艺条件研究

在乙醇介质中,以氨作为催化剂,正硅酸乙酯作为硅源,制备了单分散的二氧化硅溶胶微球。通过激光粒度分析仪及透射电镜测定溶胶粒子的大小。研究了不同工艺参数如催化剂和水的量、硅源的量以及溶剂的类型对二氧化硅粒子大小及形貌的影响,并考察了粒子的形成机理。结果显示:随着氨浓度的升高,溶液初始解离的[OH-]增大,二氧化硅粒子的粒径增大;随着硅源浓度的增加,溶液中水解的中间产物增加,二氧化硅微球的粒径显著增加;在r(水/正硅酸乙酯)值远大于4的情况下,随着初始加入水量的增加,二氧化硅微球的粒径有所增加,但当水量太多时,粒径反而下降;使用不同溶剂作为制备二氧化硅的介质,在丙醇和丁醇中二氧化硅严重团聚,没有得到单分散微球。     

二次膜射流乳化法制备单分散乳状液研究

为解决传统膜乳化法制备单分散O/W型乳状液中存在的粒径和通量的矛盾,介绍了采用二级陶瓷膜乳化在射流条件下制备单分散O/W乳状液的方法。2套一体式陶瓷膜乳化装置被串联使用,一级膜乳化采用孔径为0.16μm的ZrO2陶瓷膜,二级膜乳化采用孔径为1.5μm的-αA l2O3陶瓷膜。以甲苯/水体系为研究对象,阴离子表面活性剂(SDS)和非离子表面活性剂(乳化剂OP)分别被用作乳化剂。2种情况下均可获得单分散的乳液,能耗分别是1.53×105J/m3和1.21×105J/m3。因此,该方法可在较低的能耗下制备单分散乳液。     

制备均分散铁红微粉的新方法

以ＦｅＳＯ４为原料,采用两步法液相氧化工艺制备了均匀α Ｆｅ２Ｏ３微粉,研究了反应悬浮液中Ｆｅ（Ⅱ）浓度及初始ｐＨ值对 ＦｅＯＯＨ相转化的影响。结果表明,Ｆｅ（Ⅱ）浓度及ｐＨ值对 ＦｅＯＯＨ→α Ｆｅ２Ｏ３相转化时间有很大影响,在ｐＨ值近中性时,少量的Ｆｅ（Ⅱ）离子对相转化具有显著的催化作用,因而缩短了反应周期。通过改变生长与成核两阶段消耗ＦｅＳＯ４的比值,可方便地人为控制α Ｆｅ２Ｏ３的粒度。     

Preparation and characterization of P(St‐co‐4VP) particles produced by using emulsifier‐free emulsion polymerization

Emulsifier‐free emulsion polymerization of styrene (St) and copolymerization of St and 4‐vinyl pyridine (4VP) in the presence of ammonium persulfate were studied. A comparison between the two polymerization systems was made. It was found that there were big differences comparing polymerization rate, the number and size of the particles and distribution, and molecular weight. For the St–4VP system, it was found that the additional amount of 4VP influenced the copolymerization of St and 4VP, molecular weight, and particle size. The formation mechanism of the particles was discussed. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 1502–1507, 1999     

Surfactant effect on production of monodispersed microspheres by microchannel emulsification method

Super-monodispersed oil-in-water (O/W) microspheres (MS) were produced using a microchannel (MC) emulsification technique. To investigate the effect of the surfactant on the behavior of the O/W-MS formation, the MS size and its distribution, various surfactants were used for the MC emulsification process. An MC plate with 8.9 μm equivalent diameter was employed. It was found that the super-monodispersed O/W-MS production depends on the type of surfactant used. When nonionic and anionic surfactants were used, supermonodispersed O/W-MS were produced, and the average droplet diameter was about 30 μm with a standard deviation less than 1 μm. For cationic surfactants, the super-monodispersed O/W-MS production was not successful, especially for the case where hydrophobic surfactant was dissolved in the oil phase. The results indicated that it is very important to maintain the hydrophilicity of the MC surface during the MC emulsification process. It is considered that the hydrophilic group of the anionic and nonionic surfactant was repulsed from the negatively charged MC surface so that the hydrophilicity of the MC surface was maintained. Otherwise, adsorption of the positively charged group of the cationic surfactant occurred on the MC surface which improved wetting of the MC surface and deteriorated the MC emulsification process. The analysis was supported by contact angle measurement.