单分散纳米二氧化硅的制备与表征

利用Stober溶胶-凝胶法,合成了大小约为80～150nm的单分散纳米二氧化硅微球,并且探讨了温度、氨水浓度以及TEOS浓度等因素对合成二氧化硅的影响.利用XRD、 IR 、SEM、 TEM 等手段对样品进行了表征.结果表明:水解温度的升高加速二氧化硅颗粒在溶液中的熟化引起团聚;氨水浓度的增加使得成核速度增加,水解速度加剧,二氧化硅的粒径增大,团聚程度也增大.TEOS的量的增加也导致二氧化硅粒径稍有增加,团聚程度加深.     

纳米二氧化硅制备工艺的研究

以正硅酸乙酯(TEOS)为前驱液、氨水为催化剂和去离子水、无水乙醇为溶剂,采用溶胶-凝胶法制备出了纳米二氧化硅。利用傅里叶变换红外光谱仪(FT-IR)、动态激光散射粒度分析仪(DLS)、透射电子显微镜(TEM)对纳米二氧化硅的元素组成结构、粒径范围及分布、颗粒形状结构等一系列的性能进行了表征。实验结果表明:产品微观形貌为规整的圆球状;当催化剂氨水浓度为0.4 mol/L,TEOS浓度为0.17 mol/L时,纳米二氧化硅颗粒的峰平均值为215.4 nm,平均粒径为299.6 nm。     

羧基改性单分散二氧化硅纳米球的制备与表征

以浓氨水为催化剂、四乙氧基硅烷(TEOS)为原料,利用Stober溶胶-凝胶法制得二氧化硅(SiO2)微球。粒度仪测试结果表明,SiO2微球粒径为30～100nm,其平均粒径随着催化剂用量的增加而增大。进一步用γ-氨丙基三乙氧基硅烷对SiO2纳米球进行表面改性,后与苯偏三酸酐反应,得到羧基改性的SiO2纳米球。利用TEM、FT-IR对羧基改性纳米球进行表征。结果表明,改性过程对SiO2纳米球的粒径无影响,羧基通过化学键结合在SiO2纳米球表面。     

纳米二氧化硅溶胶粒子的制备研究

以TEOS为前驱体,氨水作为催化剂,制备了单分散纳米二氧化硅溶胶,并且探讨了反应条件对二氧化硅溶胶粒径的影响。结果表明:在保持其它条件不变的情况下,随着NH4OH/TEOS摩尔比的增大,二氧化硅溶胶的粒径也增大;随着H2O/TEOS摩尔比的逐渐增大,二氧化硅溶胶的粒径先增大后基本不变;随着EtOH/TEOS摩尔比的增大,二氧化硅溶胶的粒径减小;随着反应温度的升高,二氧化硅溶胶的粒径显著减小。     

温度调控法合成单分散二氧化硅球

单分散性的纳米二氧化硅微球粒子在标准化、情报信息、分析化学、医学及生物化学、电子封装材料等许多科学领域中有着广阔的应用前景。采用在氨水(NH3·H2O)存在的条件下催化正硅酸四乙酯(TEOS)水解缩聚反应来制备单分散二氧化硅微球。与此同时通过改变氨水在体系中的浓度和实验温度使二氧化硅球的粒径得到了改变。然后通过扫描电镜、红外光谱、X射线衍射、反射光谱等仪器对微球进行了表征,结果表明通过温度调控法成功制备了粒径均匀的单分散二氧化硅微球。     

表面改性球形二氧化硅的制备与表征

在醇水混合溶剂中,以氨作催化剂,通过正硅酸乙酯(TEOS)水解制备SiO2球形颗粒,并以十八醇作为改性剂对SiO2进行表面修饰。研究了TEOS浓度对SiO2球形颗粒粒径的影响,并用TEM、XPS、IR、TG-DTG对所得产品进行了表征。结果表明:在TEOS∶NH3∶H2O(物质的量比)为1∶4.4∶12.7时,可得到粒径约为450nm的球形SiO2颗粒;在其它条件不变的情况下,SiO2颗粒粒径随TEOS浓度的增大而增大;用十八醇作为改性剂得到的二氧化硅能在环己烷中很好地分散。     

氟烷基改性的二氧化硅纳米球的制备与应用研究

以浓氨水为催化剂、正硅酸乙酯(TEOS)为原料,通过种子生长法制得二氧化硅纳米球;进一步以十三氟辛基三乙氧基硅烷(F-8261)对二氧化硅纳米球的表面进行改性,得到氟烷基改性二氧化硅纳米球.利用IR、UV、TEM等手段对氟烷基改性纳米球进行了表征.结果表明,改性单体F-8261通过化学键结合在二氧化硅纳米球表面;通过改变催化剂的用量,可制得平均粒径分别为35 nm和86 nm的纳米球.用含氟烷基改性二氧化硅纳米球的乙醇溶液处理玻璃、基准混凝土,其表面与水的的静态接触角分别从32°和0°提高到104°和141°,表明处理过的基材表面具有良好的防水和防污性能.     

纳米二氧化硅制备工艺的研究

以TEOS(正硅酸乙酯)为前驱体、氨水为催化剂和无水乙醇为溶剂,采用溶胶-凝胶法制备了纳米二氧化硅。利用傅里叶变换红外光谱(FT-IR)仪和纳米激光粒度分布仪对纳米二氧化硅的结构、粒径及其分布进行了表征,并着重探讨了反应温度、催化剂浓度和反应时间等对纳米二氧化硅粒径的影响。研究结果表明:当反应温度为60℃、催化剂浓度为0.82 mol/L和反应时间为3~4 h时,制得的纳米二氧化硅平均粒径为300 nm左右。     

微乳液法制备无定形纳米二氧化硅

采用Triton X-100／正己醇／环己烷／氨水体系配制反相微乳液，在碱性条件下正硅酸乙酯在反相微乳液中发生受控水解，合成了具有无定形结构的球形二氧化硅纳米粒子。通过红外光谱（FT-IR）、X衍射（XRD）、透射电镜（TEM）分别对样品的结构及形貌尺寸进行了表征和分析。结果表明：改变表面活性剂加入量可以得到不同粒径（50～110nm）、不同粒度分布及不同分散程度的球形二氧化硅纳米粒子。随着表面活性剂在微乳液中体积分数的增大，二氧化硅纳米粒子的粒径先减小后增大，团聚程度也呈现先减小后增大的趋势。当表面活性剂在微乳液体系中的体积分数为20％时，所合成的二氧化硅纳米粒子粒径最小（50nm），粒度均匀且呈现出良好的分散性。     

KH-570原位改性纳米二氧化硅的制备与表征

以正硅酸乙酯(TEOS)为原料,采用溶胶-凝胶法制备纳米二氧化硅溶胶,再用γ-(甲基丙烯酰氧基)丙基三甲氧基硅烷(KH-570)对其进行改性,得到KH-570改性的纳米二氧化硅。采用红外光谱(FT-IR)、粒径分析、透射电镜(TEM)以及热重分析(TG)等对原料及产物进行表征。结果表明:KH-570能够成功改性纳米二氧化硅,改性后的纳米二氧化硅尺寸主要分布在30～115nm。     

硅酸乙酯为原料反相微乳液法制备纳米二氧化硅

采用NP-5/环己烷/去离子水体系制备反相微乳液,绘制了该体系的三元相图,并以正硅酸乙酯(TEOS)为原料,在碱性条件下受控水解反应制备了纳米SiO2粒子,探讨了[n(水)∶n(表面活性剂)](用R表示)和[n(水)∶n(TEOS)](用H表示)对SiO2纳米粒子粒径的影响。通过扫描电镜(SEM)和激光粒度仪对样品形貌和粒子大小和粒径分布进行了表征。结果显示:扫描电镜下观察到的SiO2粒子为无定型球形颗粒,粒径在200～500 nm的范围,激光粒度仪分析得到的平均粒径随着R和H的增大而增大。     

Generation of Silica Nanoparticles from Tetraethylorthosilicate (TEOS) Vapor in a Diffusion Flame

Silica (SiO2) nanoparticles were synthesized by the gas phase thermal oxidation of tetraethylorthosilicate (TEOS) in a laminar diffusion flame reactor. Characteristics of the formation of silica nanoparticles along the axial distance above the burner outlet were investigated. Effects of maximum flame temperature, TEOS concentration, residence time, and water vapor on the particle size were also investigated. Silica nanoparticles less than 20 nm in average particle diameter were synthesized in all of the experiments. Morphological changes of particles were found along axial distance above the burner outlet; many small aggregates of particles (dp = ～ 7 nm) were found up to 2 cm, isolated smaller particles ( dp = ～ 5 nm) at 4 cm, and aggregates of bigger particles (dp = ～ 10 nm) at 10 cm. Larger particles at higher TEOS concentrations are generated in the flame synthesis. As the maximum flame temperature increased, the average particle size of silica also increased. Smaller particles were produced with decrease of the residence time of TEOS vapor in the flame. The average particle size decreased with the injection of water vapor to the flame.     

Effect of molar ratio of TiO2/SiO2 on the properties of particles synthesized by flame spray pyrolysis

Titania (TiO₂)–silica (SiO₂) nanoparticles were synthesized from sprayed droplets of a mixture of TEOS and TTIP by flame spray pyrolysis (FSP). The effect of molar ratio between TEOS and TTIP in the mixture on the particle properties such as particle morphology, average particle diameter, specific surface area, crystal structure, etc., were determined using TEM, XRD, BET, and FT-IR. A UV-spectrometer was also used to measure the absorption spectrum and the band gap energy of the product particles. As the molar ratio of TEOS/TTIP increased by increasing TEOS concentration at the fixed TTIP concentration, the average particle diameter of the mixed oxide nanoparticles increased with maintaining uniform dispersion between TiO₂ and SiO₂, and crystal structure was transformed from anatase to amorphous. The band gap energy of the TiO₂–SiO₂ nanoparticles increased with respect to the increase of the molar ratio due to the decrease of width of UV-absorption spectrum. Photocatalytic activity of TiO₂–SiO₂ composite particles decreased with the concentration of TEOS.     

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。     

Synthesis of Silica Nanoparticles by Ultrasound‐Assisted Sol‐Gel Method: Optimized by Taguchi Robust Design

Silica nanoparticles were prepared by ultrasound‐assisted and conventional sol‐gel method. The synthesis procedures were designed and optimized by the Taguchi experimental design method. Molar concentrations of TEOS, H₂O, NH₄OH, and reaction temperature were chosen as main factors. The results showed that the molar concentration of ammonia is the main factor which affects the particle size of the silica nanoparticles. The chemical structure, size, and morphology of the product were investigated by X‐ray diffraction, Fourier transform infrared spectroscopy, laser light scattering, and scanning electron microscopy. By the optimum conditions of the ultrasound‐assisted sol‐gel method, silica nanoparticles with an average particle size of 13 nm were prepared.     

Abrasion resistance of waterborne polyurethane films incorporated with PU/silica hybrids

We describe polyurethane (PU)/silica hybrids (PSHs) prepared through hydrolysis and condensation reactions of tetraethoxysilane (TEOS) with or without methyltriethoxysilane (MTES) in the presence of polyurethane dispersion, which were subsequently incorporated into waterborne polyurethane (WPU) to prepare composites. The effects of the solid mass ratio of PSHs/WPU on the particle size of composite emulsions, the dispersion of silica nanoparticles in composite films, and the hardness and abrasion resistance of the corresponding films were examined. Composite emulsions possess a nanoscale particle size when incorporated with PSHs prepared using TEOS and MTES as precursors, and are superior to those with PSHs prepared using TEOS alone. Transmission electron microscopy revealed that silica nanoparticles had a uniform distribution in the polymer matrix and agglomerates could be almost completely avoided through in situ modification of silica with Si-CH₃ groups in the polyurethane dispersion. Composite films prepared with this method exhibited a superior hardness and abrasion resistance even at a lower silica content compared with that containing unmodified silica. In particular, optical microscopy and scanning probe microscopy observations demonstrated wear behavior differences among these composite films from the macro- and nanoscale viewpoints, respectively. It is proved that abrasive wear occurs, and surface morphology studies are in accordance with the results of abrasion resistance tests.     

乙醇对溶胶-凝胶法制备SiO_2溶胶性能的影响

以HNO3为催化剂,用正硅酸乙酯(TEOS)溶胶-凝胶工艺制备纳米多孔二氧化硅薄膜。较详细地研究了工艺参数乙醇/TEOS摩尔比对溶胶性能的影响.结果表明,随着乙醇/TEOS摩尔比的增大,溶胶粘度减小,凝胶时间变长,胶体粒径有变小趋势。     

单分散二氧化硅微球的制备与表征

通过Stober法合成了单分散的二氧化硅微球,系统地研究了反应条件对成球粒径及单分散性的影响,通过透射电子显微镜对其进行了表征。随着氨水和正硅酸乙酯浓度的提高,生成的二氧化硅微球的粒径逐渐减小。而温度升高的条件下则会形成粒径较小的微球,溶剂粘度的升高也会增大形成的微球的粒径。另一方面,向反应体系中加入电解质可以有效地增大球的粒径,从而为制备微米级的二氧化硅微球提供了一种简单有效的方法。研究了相关的反应机理,根据这些反应条件的变化可以确定制备不同粒径单分散二氧化硅微球的条件。