高分子保护溶液还原法制备球形超细镍粉

高分子保护溶液还原法制备球形超细镍粉沈勇，张宗涛，赵斌，朱裕贞，胡黎明（华东理工大学国家超细粉末工程研究中心，上海２００２３７）戴慕仉（华东理工大学分析测试中心，上海２００２３７）超细镍粉由于表面活性高、导电性和导热性好而被广泛用于电池电极、硬质合金...     

超细镍粉复合材料的微波电磁特性研究

以蒸馏水为溶剂,利用快捷、温和的液相还原法制备超细镍粉,将得到的超细镍粉作为填料制备了复合材料,考察了复合材料的电磁屏蔽和吸波性能．结果表明,超细镍粉质量分数为80％的树脂基复合材料在130MHz～1．5GHz测试频段范围内的电磁屏蔽性能高于45dB;而厚度为2mm的超细镍粉／石蜡复合材料在7GHz附近的反射率可达-27dB．     

SDS-PVP水溶液中超细镍粉的制备

在十二烷基硫酸钠(SDS)-聚乙烯吡咯烷酮(PVP)混合水溶液中, 采用水合肼还原氯化镍制备超细镍粉. SEM结果表明, 该超细镍粉为球形, 表面呈现针状叠合的特殊形貌. XRD结果表明,该超细镍粉由平均粒径约为10 nm的面心立方结构(fcc)的原生纳米镍晶粒组成, 且主要沿(111)晶面生长. TEM清晰观察到原生纳米镍晶粒在PVP的空间桥联作用下自组装成超细镍粉的中间过程. SDS-PVP的组成对超细镍粉的粒径和表面形貌有显著影响, 在一定浓度范围内, 随着SDS或PVP浓度增大, 原生纳米镍晶粒和超细镍粉的平均粒径均呈减小趋势, 表明通过改变SDS-PVP组成可以调控超细镍粉的粒径和形貌.     

喷雾热解法制备YBO3：Eu球形发光粉

用喷雾热解两段法制备了YBO3：Eu荧光粉．其粒径分布窄(1～2μm)，为规则的球形，且在高温下不会团聚．考察了PEG浓度(聚乙二醇，分子量为10 000)对发光粉形貌和发光强度的影响、温度对结晶性和发光强度的影响、前躯体溶液的浓度对粒径大小的影响以及掺杂浓度对发光强度的影响．当PEG的浓度为0．004mol/L时．得到实心球形的发光粉，PEG的浓度过高或过低都会使小球产生破裂和空心．从而降低发光粉的发光强度；样品在700℃时开始结晶，1100℃时结晶性最好，相应的发光强度也最强；通过改变前驱体溶液的浓度．可以很容易地调控发光粉小球的粒径，控制前驱体溶液的浓度在0．07mol／L，可以得到粒径为1～2μm的球形发光粉；Eu^3 在YBO3基质中的最佳掺杂摩尔分数为10％。     

交联聚苯乙烯单分散微球的制备

微米级粒度均匀的聚合物微球作为功能高分子材料在分析化学、生物化学、标准计量以及某些高新技术领域中应用广泛。制备聚合物微球的传统方法有乳液和悬浮聚合法。乳液聚合只能制备粒径为0．1-0．7μm的颗粒，采用无皂或低皂乳液聚合法制成的单分散聚合物微球粒径接近1μm，但难于达到1μm以上，且后处理比较麻烦；悬浮聚合制备的聚合物微球粒径则一般在100-1000μm之间，且是多分散性的。而分散聚合获得的微球呈单分散性，是制备粒径为1-10μm的单分散聚合物微球的有效方法。     

水性体系中超细镍粉的液相还原制备

采用快捷、温和的液相还原法,在水溶液中,以氢氧化钠为pH值调节剂,利用水合肼的还原作用将氯化镍还原得到超细镍粉．利用扫描电镜（SEM）及X射线衍射（XRD）的表征手段研究了反应条件对超细镍粉微观结构的影响．结果表明,所得到的产物是纯的面心立方结构的镍材料,颗粒的尺寸介于200～500nm之间,且分布较为均匀．     

Silica lite-1纳米晶的尺寸控制合成

全硅 Silicalite- 1沸石作为 MFI结构的 ZSM- 5分子筛家族中不含 Al的成员 ,不仅具有良好的热稳定性和特殊的十元环孔道结构 ,而且具有憎水和亲油等特性 [1,2 ] ,通常以四丙基铵根离子为模板剂在水热条件下进行合成 ,所得到的晶粒尺寸处于几微米至几十微米之间 [2～ 11] .如李军等 [3 ] 制得了晶粒在1 0μm左右的 Silicalite- 1膜 . Kath等 [4 ] 以硅酸铵为硅源、四丙基溴化铵为模板剂制备了粒径为 5 0μm的 Silicalite- 1 ;但以正硅酸乙酯为硅源、四丙基氢氧化铵为模板剂时 ,在乙醇的参与下合成了晶粒为0 .5 μm的超细 Silicalite- 1…     

磁场对超细镍粉的磁性能及电磁屏蔽性能的影响

分别在水和乙二醇溶液中,于搅拌条件下采用液相还原法制备超细镍粉,研究反应过程中外加磁场对产物形貌及性能的影响。结果表明,水中得到的产品为刺球状颗粒,外加磁场对产物的形貌影响不大;乙二醇中得到类球形颗粒,加磁场后得到短链状结构。外加磁场使超细镍粉的饱和磁化强度值降低而矫顽力值升高。将水体系中得到的超细镍粉作为导电填料制备电磁屏蔽涂料,结果发现外加磁场条件下得到的超细镍粉/树脂复合涂料在130 MHz～1.5 GHz频段内具有更好的电磁屏蔽性能。     

液相还原法制备超细球形镍粉

本文论述了液相还原法直接制备高振实密度球形镍粉的新工艺。采用NiSO_4·5H_2O为原料,利用NaOH调节溶液的pH值并形成Ni(OH)_2,还原剂采用N_2H_4·H_2O,还原过程中加入晶核引发剂及表面活性剂。采用正交实验表安排实验,对影响镍粉振实密度及粒径的因素进行了极差分析。实验数据表明,溶液中镍的初始浓度对产品质量的影响最大,较优工艺组合条件为:初始Ni~(2+)的浓度1.5mol·L~(-1),NaOH用量为理论量的1.1倍,反应温度80℃,表面活性剂用量为每克镍5mg,晶种添加量为还原剂理论用量的0.1％。新工艺可制备振实密度高达3.0以上、质量中位径为1μm的球形镍粉。     

电化学方法制备超细氧化铋粉末

超细氧化铋用途广泛。目前超细氧化铋的制备一般通过四个途径；一、机械粉碎法，可以获得粒径1μm的细粉，但在粉碎的过程中易混入杂质；二、熔融喷雾法，该法可以在短时间(45—48s)内获得超细Bi2O3，但均匀性差，氧化不易完全，生产过程有粉尘污染；三、通过水解氧化铋的     

Study of support effects on the reduction of Ni2+ ions in aqueous hydrazine

We have studied the effect of silica of quartz-type on the reducibility of nickel acetate in aqueous hydrazine (80 degrees C, pH = 10-12) and metal particle formation. The obtained materials were characterized by X-ray diffraction, transmission electron microscopy, and thermodesorption experiments. With nickel acetate alone, the reduction was partial (45%) and a metal film at the liquid-gas interface or a powdered metal precipitate with an average particle size of 120 nm was obtained. In the presence of silica as the surfactant, the reduction of nickel acetate was total and the nickel phase deposited as a film on the support with an average particle size of 25 nm. Supported nickel acetate was also totally reduced. Crystallites of a mean particle size of about 3 nm were obtained. Decreasing the nickel content or increasing the hydrazine/nickel ratio decreased the metal particle size. Whiskers were formed for low nickel loadings. Hydrogen thermal treatment of the reduced phase showed that the organic acetate fragment, belonging to the precursor salt, still remained strongly attached to the nickel phase. The amount of the retained organic matrix depended on the metal particle size. Surface defects are suggested as active sites, which enhanced nickel ion reduction in the presence of silica as the surfactant or support. Metal-support interactions and the nucleation/ growth rate were the main factors determining the size and morphology of the supported metal particles formed. The organic matrix covered the reduced nickel phase.     

Preparation of Disperse Silver Particles by Chemical Reduction

Mastery over the microscopic shape and size of a nanoparticle enables accurate control of its properties for some strict application. The mechanism of shape-controlled synthesis was discussed by investigating the formation of silver nanospheres prepared by chemical reduction method using Ag(NH₃)₂⁺ as metal source, ascorbic acid as reducing agent and polyvinylpyrrolidone (K-30) as dispersant. The effects of temperature, PVP/AgNO₃ mass ratio, pH value and the interaction between PVP and silver on the shape and particle size were studied by XRD and SEM. The results show that the morphology of silver particles could transform from branched to spherical and the particle size gradually decrease with the increase of PVP/AgNO₃ mass ratio. The particles size can also be significantly influenced by pH value and temperature. The key point for preparing high dispersity spherical silver powder is that the growth rate of each plane of the particle must be uniform and synchronous. Silver powders with spherical particles with mean size of 0.2 μm were synthesized under the optimum conditions (PVP/AgNO₃ mass ratio 0.6, pH 7, reaction temperature of 40°C).     

毛细管区带电泳法测定超细β分子筛的平均粒径及粒径分布

建立了毛细管区带电泳(CZE)测定超细β分子筛平均粒径及粒径分布的测定方法。通过研究β分子筛的等电点,确定了CZE法测定过程中β分子筛悬浮液分散稳定的方法。以激光粒度仪粒径分布测量数据为基准,结合β分子筛电泳谱图,建立了β分子筛粒径-迁移时间校正方程及含量校正方程。样品用量小、分析成本低、测试速度快是该方法的主要特点。     

纳米铬粉的制备研

以ＣrＣ１３为原料,三乙基硼氢化钠为还原剂,聚乙烯吡咯烷酮为分散剂,ＰdＣ１２为成核剂,于甲苯溶剂中制备出平均粒径约５０ｎｍ的铬粉,反应温度、反应物浓度、分散剂与成核剂的添加是影响粒径的主要因素。同时探讨了反应的机理与铬粉的热稳定性。     

Synthesis of nickel metal nanoparticles via a chemical reduction of nickel ammine and alkylamine complexes by hydrazine

Nickel nanoparticles were prepared from their coordination compounds, such as [Ni(NH₃)₆]Cl₂, [Ni(N₂H₄)₂Cl₂], [Ni(HNEt₂)₆]Cl₂, and [Ni(H₂NBu)₆]Cl₂ in aqueous solution by chemical reduction. The reaction of nickel ammine and alkylamine complexes with hydrazine monohydrate as a reducing agent was carried out at 90 °C and pH = 10–12. Depending on the influencing parameters such as oxidizing agent, pH, and temperature, the hydrazine reaction can be carried out in different pathways. The chemical reduction method is a simple procedure and also is the best one in the controlling of composition, size, and shape of Ni powder. The reduction of nickel complexes into the metallic Ni powder occurs via the dissociation of complexes and reduction by hydrazine in alkaline solution. Therefore, complexing agents have the most effect on the reduction reaction. The results show that, when the ligands in complexes were changed from ammine to diethylamine and butylamine, respectively, the crystalline size and morphology of nickel metal nanoparticles are changed. The chemical reduction of nickel complexes into metallic nickel can be accompanied with a change in the crystalline system. The pure nickel crystalline has a face-centered cubic structure. The nickel nanoparticles were characterized using IR spectroscopy, X-ray powder diffraction, scanning electron microscopy and vibrating sample magnetometer analyses.     

多相体系中Ni-PMMA纳米复合材料的γ辐射制备

在多相体系中,运用γ射线辐射法, 在常温常压下成功地一步合成了镍-聚甲基丙烯酸甲酯(Ni-PMMA)纳米复合材料.XRD、 TEM分析和IR光谱表明,在此实验条件下,镍离子和甲基丙烯酸甲酯已成功地被还原或聚合,镍粒子为面心立方,尺寸为7.33 nm.研究显示,用醋酸钠代替氢氧化钠或氨水作为碱性试剂,可以有效地控制体系的pH,同时不影响单体的聚合.     

Comparison of droplet flocculation in hexadecane oil-in-water emulsions stabilized by beta-lactoglobulin at pH 3 and 7

The influence of surface and thermal denaturation of adsorbed beta-lactoglobulin (beta-Lg) on the flocculation of hydrocarbon oil droplets was measured at pH 3 and compared with that at pH 7. Oil-in-water emulsions (5 wt % n-hexadecane, 0.5 wt % beta-Lg, pH 3.0) were prepared that contained different levels of salt (0-150 mM NaCl) added immediately after homogenization. The mean particle diameter (d43) and particle size distribution of diluted emulsions were measured by laser diffraction when they were either (i) stored at 30 degrees C for 48 h or (ii) subjected to different thermal treatments (30-95 degrees C for 20 min). In the absence of salt, little droplet flocculation was observed at pH 3 or 7 because of the strong electrostatic repulsion between the droplets. In the presence of 150 mM NaCl, a progressive increase in mean particle size with time was observed in pH 7 emulsions during storage at 30 degrees C, but no significant change in mean particle diameter with time (d43 approximately 1.4 +/- 0.2 microm) was observed in the pH 3 emulsions. Droplet aggregation became more extensive in pH 7 emulsions containing salt (added before thermal processing) when they were heated above 70 degrees C, which was attributed to thermal denaturation of adsorbed beta-Lg leading to interdroplet disulfide bond formation. In contrast, the mean particle size decreased and the creaming stability improved when pH 3 emulsions were heated above 70 degrees C. These results suggest that the droplets in the pH 3 emulsions were weakly flocculated at temperatures below the thermal denaturation temperature of beta-Lg (T < 70 degrees C) but that flocs did not form so readily above this temperature, which was attributed to a reduction in droplet surface hydrophobicity due to protein conformational changes. The most likely explanation for the difference in behavior of the emulsions is that disulfide bond formation occurs much more readily at pH 7 than at pH 3.     

用于甲烷水蒸气重整的镍基催化剂的失活和再生

The deactivation of nickel catalysts used in Arak and Razi petrochemical complexes followed by catalyst regeneration was evalu-ated. The characterization of the different structures was made by powder X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS),transmission electron microscopy(TEM),and carbon & sulfur analyzer. The Ni particle size was estimated from XRD patterns and TEM graphs. The agglomeration of nickel particle and the poison by sulfur components were recognized as the main reasons in deactivation of Arak and Razi catalysts,respectively. The activity of the used catalysts before and after regeneration was measured on methane steam reforming at a CH4:H2O ratio of 1:3 at 850 oC. The regeneration processes for Arak and Razi samples were performed with CO2 as an oxidative atmosphere and steam as a regenerating agent,respectively. The results show that,(1) no residual sulfur components were on the regenerated Razi catalyst surface without changing the structure of the catalyst and the regenerated catalyst has gained 80% of its catalytic activity,and that(2) the nickel particle size of regenerated Arak specimen decreased remarkably as measured by Debye-Scherrer equation from XRD patterns. TEM images were in agreement with the XRD results and indicated a decrease in nickel particle size of regenerated catalyst. Additionally,in both regenerated catalysts all the coke on the surface of the support was eliminated after regeneration.     

以无机硫为原料制备硫化铅量子点及其表征

根据高温下快速成核低温下慢速生长的量子点制备原理, 采用胶体化学的方法成功制备了不同粒径的硫化铅半导体量子点. 这种方法的特点是以无味和低毒的硫化钠作为制备硫化铅量子点硫的前驱物, 因此这是一种量子点的绿色化学合成方法. 油酸作为稳定剂控制硫化铅的粒径. 采用X射线衍射和高分辨透射电镜表征了量子点的晶体结构、形貌和粒径, 采用可见-近红外吸收光谱研究了硫化铅量子点的量子尺寸效应. 通过降低油酸的添加量可以促进量子点的生长, 得到较大粒径量子点. 并探讨了量子点的生长机理.