共沸蒸馏法合成CeO2纳米颗粒研究

分别以乙醇、正丙醇、异丙醇、正丁醇、异丁醇、仲丁醇及叔丁醇等七种有机醇作为共沸剂,采用液相沉淀法结合共沸蒸馏处理前驱体成功合成了分散性良好、粒子尺寸分布为10-20nm的纳米CeO2颗粒,运用TG／DTA、FI—IR、XRD、TEM等方法对不同有机醇的共沸蒸馏作用以及产品性能进行了分析和表征,探讨了共沸蒸馏法制备纳米CeO2的机理。结果表明：共沸蒸馏能起到有效脱除前驱体凝胶中的水分,防止其干燥和焙烧过程中的硬团聚形成的作用,其中七种醇中以正丁醇的共沸蒸馏效果最佳,所得纳米CeO2颗粒的粒度、均匀及分散性能最好。     

无团聚纳米氧化锆的制备及应用

采用高分子表面修饰－共沸蒸馏工艺成功地制备了纳米氧化锆微粒;合成过程中高 分子的空间位阻作用阻碍了前驱体颗粒的长大,通过与正丁醇的共沸蒸馏有效地脱除了前驱体 内的水分,在颗粒表面形成了正丁醇分子的包裹结构,在随后的干燥过程中避免了颗粒间形成 强化学键,获得了平均粒径在２０ｎｍ的无团聚的纳米微粒．纳米氧化锆微粒加入到润滑脂中能 明显改善后者的耐磨性能．     

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。     

ITO废靶回收制备超细ITO粉末的研究

以ITO废靶为原料,硫酸浸出,均相共沉淀-共沸蒸馏法制备出了均匀分散、粒径小于100nm的类球状高纯纳米级ITO粉体.用本工艺制备回收超细ITO粉末,制备工艺简单,设备投资小,可适用于工业化生产.     

超声模板法制备纳米二氧化铈的研究

采用超声模板法结合共沸蒸馏和水热法处理前驱体成功制备出了纳米CeO2颗粒,通过TEM、XRD、FT-IR、UV-Vis等分析方法对产物形貌、结构和性能进行了表征;研究了模板剂的性质、模板剂的用量、共沸蒸馏和水热处理对纳米CeO2颗粒形态、尺寸的影响。实验结果表明,与OP-10和SDBS比较,CTAB最适合应用于制备纳米CeO2颗粒。当模板剂用量为n(CTAB)∶n(Ce(NO3)3.6H2O)=1∶2,制备出粒径约为6.1nm的球形纳米CeO2;共沸蒸馏能有效去除前驱体中的模板剂和吸附水,丁氧基的取代吸附及其空间位阻作用有利于制得分散性好、粒度分布均匀、粒径约为1.5～2.2nm的纳米CeO2颗粒;水热处理改善了纳米CeO2颗粒的晶化度,避免了高温焙烧过程时硬团聚体的生成,颗粒尺寸为2.5～3.8nm;纳米CeO2颗粒具有良好的可见光透过和优异的紫外光吸收性能。     

纳米粉体干燥方法的研究

采用三种干燥方法：冷冻干燥、共沸蒸馏和烘箱干燥对溶胶-沉淀法制备的沉淀进行干燥处理,得到了立方相BaTiO₃纳米粉．研究发现：冷冻干燥和共沸蒸馏都能防止粉体中形成硬团聚,提高了烧结活性,其中冷冻干燥法效果更明显．文章同时对两种干燥方法防止硬团聚形成的机理进行了讨论．     

沉淀法制备低成本纳米氧化铝粉体

用沉淀法中的氯化铝-硫酸铝铵反应体系制备纳米氧化铝原料便宜,工艺简单,制得的粉体纯度高,粒径小.用正交实验优化了其主要反应条件,以表面活性剂为分散剂,制备出了成本低、质量较好的纳米氧化铝.经粗略计算,成本约为30元/kg.     

表面活性剂对二氧化钛纳米流体分散性的影响

通过二步法将纳米二氧化钛分散到去离子水中,制备TiO2-水纳米流体。通过加入3种不同的表面活性剂作为分散剂,即阴离子表面活性剂十二烷基苯磺酸钠(SDBS)、非离子表面活性剂聚乙烯吡咯烷酮(PVP)和阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)制备出3种不同的纳米流体。用纳米粒度分析仪测定纳米流体中的纳米粒子的粒径和粒径分布,用Zeta电位分析仪测量纳米流体的电位,分析了不同浓度、不同种类的表面活性剂对水基TiO2纳米流体分散性的影响。     

纳米SiO_2粉体在水泥液相中的分散性

针对纳米SiO_2存在颗粒团聚现象,借助LS13320激光粒度仪、SEM和TEM测试手段,研究水泥液相中纳米SiO_2粉体的粒度分布及其分散性。通过超声脉冲技术分散纳米SiO_2粉体,并确定最优超声功率;研究表面活性剂添加顺序对水泥液相中纳米SiO_2粒度分布的影响。结果表明:超声脉冲与表面活性剂协同作用为纳米SiO_2最佳分散方式;获得纳米SiO_2最佳粒度分布的实验条件为超声时间5 min、超声功率360 W;在纳米SiO_2加入到水泥液相之后再加入表面活性剂,这种添加顺序更有利于提高纳米SiO_2分散性。     

超声电沉积制备纳米铜粉末的机理研究

利用超声电沉积法制备金属纳米铜粉,平均粒径30nm,分散性较好;利用XRD、TEM等进行了成分、粒度、形貌及结构分析,对影响纳米粉末制备的主要工艺因素进行分析和优化。试验表明,电流密度对纳米粉末形成起控制作用,表面活性剂和超声场对粉末分散更为重要。     

Influence of different parameters and their coupled effects on the stability of alumina nanofluids by a fractional factorial design approach

Nanofluids have been introduced as new-generation fluids able to improve energy efficiency in heat exchangers. However, stability problems related to both agglomeration and sedimentation of nanoparticles have limited industrial-level scaling. A fractional factorial experimental 2^k?1 design was applied in order to evaluate the effects of nanoparticle concentration, surfactant type and concentration, ultrasonic amplitude as well as ultrasonic time on the stability of alumina (Al₂O₃) nanofluids. Commercial alumina nanoparticles (particle diameter <50 nm) were dispersed in deionized water using ultrasonic probe dispersion equipment. Sodium dodecylbenzenesulfonate (SDBS) and cetyltrimethylammonium bromide (CTAB) were used as surfactants. The stability of the nanofluids in static mode was monitored by visual inspection and UV visible spectroscopy. The results of the experimental design showed that the coupled effects between surfactant type and surfactant concentration and between ultrasonication tip amplitude and ultrasonication time had the most pronounced effects on nanofluid stability. The experimental conditions providing the best stability were 0.5 wt% of Al₂O₃, CTAB, critical micelle surfactant concentration, 30% ultrasonic amplitude and 30 min of ultrasonication.     

镍 -纳米氧化铝复合电镀液的制备及影响因素研究

性质均匀稳定的镍/纳米颗粒复合镀液是制备镍/纳米复合镀层的物质和工艺基础.在瓦特镀镍溶液中加入纳米Al2O3粉末,混合液静置10 h后,因颗粒沉淀而产生不同程度的分层,通过比色法研究了分散剂、分散形式、镀液pH值对纳米Al2O3粉末在镀液中均匀稳定分散的影响.结果表明,在镀液中加入适量的聚羧酸铵、柠檬酸三铵或十六烷基三甲基溴化铵分散剂,并通过超声分散,可得到稳定分散10 h以上的复合电镀液.原子力显微镜分析表明,复合镀液中纳米颗粒的平均尺寸为63 nm,略大于其原料颗粒的尺寸(40 nm),大部分的纳米颗粒在复合镀液中能实现高度分散.     

Unsaturated polyester nanocomposites filled with nano alumina

Alumina nanoparticles (60–70 nm) were prepared by the sol–gel technique using citric acid and aluminum nitrate. Casting technique was used to make nanocomposites of unsaturated polyester (UPR) and nano alumina. Transmission Electron Microscopy (TEM) study demonstrated that nano alumina particles were dispersed uniformly in the UPR matrix and agglomeration of particles was found at higher filler loading (>5 wt%). The nanocomposites show higher tensile, flexural and impact strength than pristine UPR. Scanning Electron Microscopy (SEM) of the fractured surface of tensile test samples show that the ductile fracture of UPR was converted to brittle fracture with the addition of nano alumina. Dynamic Mechanical Analysis (DMA) studies showed the storage modulus increased up to 5 wt% loading of nano alumina. The impact strength and storage modulus results agree well. The thermogravimetric studies revealed that the nanocomposites were having higher thermal stability than the pure UPR. As the concentration of the nano alumina in the UP resin increased, the char yield was also increased.     

Nanocrystalline particle coatings on alpha-alumina powders by a carbonate precipitation and thermal-assisted combustion route

We have suggested ultrafine particle coating processes for preparing nanocrystalline particle coated alpha-alumina powders by a carbonate precipitation and thermal-assisted combustion route, which is environmentally friendly. The nanometric ammonium aluminum carbonate hydroxide (AACH) as a precursor for coating of alumina was produced from precipitation reaction of ammonium aluminum sulfate and ammonium hydrogen carbonate. The synthetic crystalline size and morphology were greatly dependent on pH and temperature. By adding ammonium aluminum sulfate solution dispersed the alpha-alumina core particle in the ammonium hydrogen carbonate aqueous solution, nanometric AACH with a size of 5 nm was tightly bonded and uniformly coated on the core powder due to formation of surface complexes by the adsorption of carbonates, hydroxyl and ammonia groups on the surface of aluminum oxide. The synthetic precursor rapidly converted to amorphous- and y-alumina phase without significant change in the morphological features through decomposition of surface complexes and thermal-assisted phase transformation. As a result, the nanocrystalline polymorphic particle coated alpha-alumina core powders with highly uniform distribution were prepared from the route of carbonate precipitation and thermal-assisted combustion.     

水中高度分散的纳米羟基磷灰石分散剂的选择

采用粒度分析和测定zeta电位的方法研究了三种分散剂,包括十二烷基硫酸钠(DSS)、聚乙烯醇(PEG)和六偏磷酸钠(NaP)对纳米羟基磷灰石(HA)在水中分散行为的影响.结果显示,使用六偏磷酸钠作为分散剂可以使纳米羟基磷灰石在水中高度分散,形成溶胶.当NaP/HA=12.5(重量比)时,溶胶含有88%粒径在65-86nm之间的纳米粒子,可以用作给药系统中的药物载体.     

透射模式电子背散射衍射技术在纳米材料研究中的应用

为了提高电子背散射衍射技术的空间分辨率, 使之能够对纳米尺度的晶粒或超细粉末进行相鉴定和取向分析, 本研究通过自主设计的透射模式电子背散射衍射技术的样品台, 及调整EBSD探头位置及角度, 收集到清晰、完整的透射电子菊池衍射花样。研究了减薄块体样品厚度对透射电子菊池衍射花样的影响, 对减薄氧化锆涂层样品进行了t-EBSD面分布分析, 其结果的平均角度偏差(MAD)值仅为0.38, 成功鉴定出小于30 nm尺度的纳米氧化锆涂层立方相; 将超声分散后的纳米TiO₂粉体滴在铜网上, 采用t-EBSD对纳米颗粒进行点分析, 成功鉴定了锐钛矿相和金红石相TiO₂, 其中纳米锐钛矿TiO₂粉体的最小尺寸为20 nm左右, 使得扫描电镜中相鉴定的最小分辨率从目前的约100 nm提高到小于30 nm, 大大拓展了电子背散射衍射技术在纳米材料研究中的应用范围。     

纳米二氧化钛增强硬质聚氨酯泡沫塑料的制备

采用功率超声,将纳米二氧化钛颗粒分散到多次甲基多苯基多异氰酸酯(PAPI)体系内,然后与聚醚多元醇聚合制得了纳米二氧化钛增强的硬质聚氨酯泡沫塑料.SEM分析表明纳米二氧化钛均匀分散在聚氨酯泡沫塑料中.在较低添加量时纳米二氧化钛对压缩强度和冲击强度有一定提高,但会引起PAPI粘度迅速增加,从而导致发泡反应困难,当添加量为10%(质量分数)时压缩强度和冲击强度开始下降.