表面活性剂调节高矫顽力FePt纳米颗粒的合成

在表面活性剂聚乙烯吡咯烷酮(PVP)存在的体系中,通过NaBH4还原前驱体Fe(acac)3和H2PtCl6·6H2O,制备出了单分散的尺寸在3.0 nm左右的FePt纳米颗粒。XRD和TEM表征结果显示,表面活性剂PVP的用量影响FePt纳米颗粒相变,但对颗粒的尺寸无明显作用。由此推测,PVP对FePt纳米颗粒的相变起"催化"作用,适量的PVP诱导纳米颗粒的相变,可以通过改变表面活性剂的用量来调节FePt纳米颗粒的磁性能,当表面活性剂PVP单体与FePt前驱体的摩尔比(PVP/FePt)为7时,制得的FePt纳米颗粒经过500℃保温30 min热处理后,矫顽力高达5.2 kOe。     

多元醇还原法制备FePt纳米颗粒

以乙酰丙酮铁和氯铂酸作为Fe源和Pt源,1,2-十二烷二醇为还原剂,通过多元醇还原法制备出单分散的FePt纳米颗粒,研究了表面活性剂油酸和油胺对FePt纳米颗粒形貌和分散性的影响。结果显示,未使用表面活性剂制得的FePt纳米颗粒粒度范围是1.0～6.0 nm,平均粒径为3.4 nm;使用油酸和油胺制得的FePt纳米颗粒粒度范围是2.5～5.5 nm,平均粒径4.1 nm。通过XRD、TEM和VSM分析表明,油酸和油胺修饰的FePt纳米颗粒为面心立方结构,形状近似球形,分散性良好,粒径分布较未使用表面活性剂时变窄;VSM显示其矫顽力趋近于0,呈现超顺磁性。     

纳米SiO_2/表面活性剂对油水界面张力的影响

以液体石蜡为油相,考察了疏水性纳米SiO_2对阴离子表面活性剂SDS、阳离子表面活性剂CTMAB与非离子表面活性剂OP-10的协同效应,以及Na Cl浓度对复配体系油水界面张力的影响。试验结果表明:纳米SiO_2与SDS和CTMAB之间具有良好的协同作用,且油水界面张力在400 s内变化明显,超过600 s后几乎不再变化;质量分数0.004%的纳米SiO_2与SDS和CTMAB复配后随着表面活性剂浓度升高(0.001 mol/L升至0.1 mol/L),协同效应越来越不明显,但表面活性剂浓度稀释至0.1 mmol/L后纳米颗粒分散稳定性差;随着NaCl浓度升高,与单一表面活性剂相比,SDS/SiO_2协同作用先增强后减弱,CTMAB/SiO_2协同作用持续减弱且200 s内界面张力变化幅度较大;纳米SiO_2与OP-10之间未观察到明显的协同作用,但OP-10分散稳定性强,即使在高矿化度也具有良好的分散能力。     

纳米颗粒表面特性对可逆乳状液的影响

可逆乳状液可集中不同液体形式的优势,但其由表面活性剂稳定时不耐高温,考虑用纳米颗粒与表面活性剂复配制备可逆乳状液。本文研究纳米颗粒表面特性对可逆乳状液的影响,结果表明,纳米二氧化硅颗粒的表面性质对"纳米二氧化硅与表面活性剂复合制备的乳状液"的性质有决定性作用,亲水性纳米二氧化硅与表面活性剂复配稳定的乳状液不能实现pH响应可逆转化,亲油性纳米二氧化硅与表面活性剂复配稳定的乳状液能实现pH响应的可逆转化。     

表面活性剂对Sm2Zr2O7纳米热障涂层材料烧结性能的影响

采用水热合成法制备Sm2Zr2O,纳米晶体,研究了聚乙二醇(PEG)、十六烷基三甲基溴化铵(CTAB)、十二烷基苯磺酸钠(SDBS)三种不同类型的表面活性剂对材料相结构、分散性能以及烧结性能的影响.实验结果表明:材料的物化性能与表面活性剂的类型密切相关,阳离子表面活性剂的添加抑制了材料由萤石结构向烧绿石结构的转变,样品比表面积为174.67 m2·g-1,经过高温烧结后块材的体积收缩和相对密度分别为24.5％和81.2％.相比之下,阳离子表面活性剂CTAB对于提高材料的抗烧结性能方面要明显好于非离子表面活性剂PEG和阴离子表面活性剂SDBS.     

颗粒稳定乳液和泡沫体系的原理和应用(Ⅳ)——颗粒与表面活性剂的协同作用对泡沫稳定性的影响

综述了颗粒和表面活性剂复配体系对气/水界面稳定性的影响。重点阐述了纳米颗粒与不同类型表面活性剂之间的协同效应及其对分散液发泡性和泡沫稳定性的影响,并且简要介绍了气/水界面上蛋白质和表面活性剂的竞争吸附效应,最后对颗粒和表面活性剂复配体系的优点进行了概括总结。     

三种表面活性剂对Fe3O4纳米颗粒的形貌影响

选用十六烷基三甲基溴化铵(CTAB)、聚乙烯吡咯烷酮(PVP)、十二烷基磺酸钠(SDS)3种表面活性剂,研究了这3类不同表面活性剂和不同添加量对Fe3O4纳米颗粒的形貌调控作用,利用透射电镜(TEM)对样品进行表征分析,并给出了机理解释。结果表明:1)3种不同的表面活性剂的加入都获得球形或近球形的纳米颗粒。根据TEM及沉积时间的综合分析,3种活性剂的平均粒径比较:SDS相似文献   

棒状二氧化钛纳米晶的制备及表征

以钛酸丁酯为前驱物,阴阳离子表面活性剂十二烷基苯磺酸钠（SDBS）/十六烷基三甲基溴化铵（CTAB）复配形成囊泡溶液,制备棒状二氧化钛纳米晶.并用TEM,XRD,IR,UV-Vis等分析方法对制备的二氧化钛纳米晶进行表征.结果表明,制备的二氧化钛纳米晶尺寸在90-110 nm之间,二氧化钛纳米晶为锐钛矿相和金红石相,合成样品在紫外光下对活性艳红降解率为82.5％.     

复配改性黏土/丁腈橡胶纳米复合材料的结构及性能

用不同阴离子表面活性剂十二烷基磺酸钠(SDS)和十二烷基苯磺酸钠(SDBS)与阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)复配改性无机黏土,制备了有机改性黏土/丁腈橡胶(NBR)纳米复合材料,并表征了有机黏土与纳米复合材料,考察了不同表面活性剂及配比对纳米复合材料物理机械性能的影响。结果表明,CTAB/SDS复配改性黏土/NBR纳米复合材料的层间距比CTAB改性黏土/NBR纳米复合材料增加了1.15 nm,具有更多的插层结构,橡胶基体中黏土颗粒分布细致、均匀,且黏土片层间无聚集体存在;CTAB/SDS复配改性黏土/NBR纳米复合材料的物理机械性能优于CTAB/SDBS复配改性黏土/NBR纳米复合材料及CTAB改性黏土/NBR纳米复合材料,且当CTAB/SDS(质量比)为4∶2时,纳米复合材料的拉伸强度、撕裂强度及扯断伸长率出现最大值,其中,拉伸强度和撕裂强度较CTAB改性黏土/NBR纳米复合材料分别提高了62.7%和12.3%。     

表面活性剂对甲烷水合物生成影响研究进展

由于甲烷水合物在自然条件下的生成存在着诱导期时间过长,晶体生长速率过慢等问题,导致其工业化制备受阻,在分析了众多促进水合物生成的研究后,综述了表面活性剂作为高效促生成化学试剂,其复配使用和与多孔介质的协同作用对甲烷水合物生成的影响,并分析了胶束的产生对甲烷水合物生成的促进因素,完整地归纳了表面活性剂溶液中水合物生成的动力学模型。最后提出,表面活性剂分子的结构性质与其在溶液中发生的复杂电化学行为对甲烷水合物生成的影响还需进一步的证明与探讨;表面活性剂分子间的相互作用是否存在着提高表面活性剂活性强度仍需作进一步研究。     

Synthesis of vertically aligned single-walled carbon nanotubes with metallic chirality through facet control of catalysts

For nanotube synthesis, iron platinum (FePt) alloy particles have been prepared on a single crystalline magnesium oxide (MgO) substrate by alternate sputter deposition of FePt and MgO. Partially facetted {1 1 1}-nano particles of FePt have been epitaxially formed on the substrate and periodically exposed on the surface. The particles of FePt were half-buried between deposited MgO showed superior thermal stability and microparticulations were also achieved by optimization of film layer thickness. By using the substrates for growth of carbon nanotubes, vertically aligned single-walled carbon nanotubes (forest) have been successfully grown on the substrate containing the faceted FePt nanoparticles. Raman spectra of the forest have revealed prominent features of metallic nanotubes in the radial breathing-mode region.     

One-pot fabrication of FePt/reduced graphene oxide composites as highly active and stable electrocatalysts for the oxygen reduction reaction

FePt nanoparticles (NPs)/reduced graphene oxide (rG-O) composites have been synthesized using a one-pot strategy without surfactants. Monodisperse FePt NPs were homogenously loaded onto rG-O sheets. By controlling the concentration of dispersed graphene oxide (GO), uniform FePt flower-like nanoclusters can be obtained. FePt/rG-O composites exhibited exceptionally high electrocatalytic performance in the activity and durability for the oxygen reduction reaction (ORR), much superior to that of the commercial Pt/C (60%). The straightforward synthesis of FePt/rG-O composites provides a low-cost and high performance catalyst for the ORR, which is also a promising strategy for the synthesis of various Pt-based bimetallic alloy/rG-O composites for potential uses in catalysis and energy fields.     

Formation of FePt intermetallic compound nanoparticles by plasma-induced cathodic discharge electrolysis

Magnetic nanoparticles of FePt intermetallic compound were formed in molten LiCl-KCl-CsCl electrolyte under 1 atm of Ar atmosphere by plasma-induced cathodic discharge electrolysis. By utilizing the displacement reaction between the Fe(0) and Pt(II), FePt intermetallic compound nanoparticles were obtained from the melt. The displacement reaction produced small primary particles that considerably aggregated to form larger secondary particles. The coercivity of the obtained FePt intermetallic compound nanoparticle increased with a longer residence time in the melt. The coercivity of the FePt intermetallic compound nanoparticle obtained after a residence time of 3 h was measured to be 199 mA m⁻¹. FePt intermetallic compound nanoparticles could also be obtained by the co-depositing Fe and Pt from Fe(II) and Pt(II) in the melt. In this case, the primary particle size distribution became broader, but the aggregation of primary particles was suppressed. The coercivity of the obtained FePt intermetallic compound nanoparticles showed a quite high value of 245 mA m⁻¹ that did not depend on the residence time.     

Synthesis and Characterization of FePt/NiO Core–Shell Nanoparticles

Monodisperse FePt nanoparticles were successfully synthesized using the chemical polyol process. Annealing at the high temperatures is required to achieve the hard ferromagnetic behavior with L1₀ phase. Annealing causes the surfactant surrounding particles to be decomposed. Under such circumstances, FePt particles are agglomerated, and their size increases. In this research, NiO oxide particle with a high melting point was used for the first time as the shell around FePt core particles to prevent agglomeration. As a result, coercivity, H_c, of FePt and FePt/NiO nanoparticles after annealing at 750?°C are equal to 10 and 7?kOe, respectively.     

Dispersion polymerization of <Emphasis Type="Italic">N</Emphasis>-vinyl caprolactam in supercritical carbon dioxide

Dispersion polymerization of N-vinyl caprolactam (NVCL) was carried out in supercritical carbon dioxide (scCO₂) using three surfactants. The polymerization was performed in the presence of fluorine-based poly(heptadecafluorodecyl acrylate) (PHDFDA), poly(heptadecafluorodecyl methacrylate) (PHDFDMA) or siloxane-based PDMS-g-pyrrolidonecarboxylic acid (Monasil PCA) as a surfactant. FE-SEM and image analyzer were used to characterize particle morphology, size, and size distribution. When fluorine-based surfactants were used, spherical PVCL particles were obtained. Using Monasil PCA resulted in agglomerated and irregular polymer particles. The effect of concentration of surfactants, initiators, and monomer, and reaction pressure on the particle morphology, average particle size and particle size distribution (PSD) was also investigated with fluorine-based surfactant, PHDFDA or PHDFDMA.     

表面活性剂对丁二酸冷却结晶中聚结的抑制

借助聚焦光束反射测量仪(FBRM)和颗粒录影显微镜(PVM)对丁二酸冷却结晶过程中的聚结现象进行研究,通过加晶种实验和不加晶种实验初步推断大小颗粒的共存及颗粒间的相互结合力是形成聚结需要考虑的两个因素。在此基础上,将3种类型的表面活性剂十六烷基三甲基溴化铵(CTAB)、十二烷基苯磺酸钠(SDBS)和吐温80(Tween80)加入到丁二酸冷却结晶系统,考察了表面活性剂对结晶过程中颗粒聚结的抑制作用。晶体形貌变化表明,所选的表面活性剂均能吸附于晶体表面,且可大大降低聚结,可推测表面吸附产生的机械隔离能够降低晶体间的相互结合力,并促使结晶产品的粒度更为均匀。这一研究证明添加表面活性剂可降低结晶过程的聚结程度。     

Study on Composition Distribution and Ferromagnetism of Monodisperse FePt Nanoparticles

Monodisperse FePt nanoparticles with size of 4.5 and 6.0 nm were prepared by simultaneous reduction of platinum acetylacetonate and thermal decomposition of iron pentacarbonyl in benzylether. The crystallography structure, size, and composition of the FePt nanoparticles were examined by X-ray diffraction and transmission electron microscopy. Energy dispersive X-ray spectrometry measurements of individual particles indicate a broad compositional distribution in both the 4.5 and 6 nm FePt nanoparticles. The effects of compositional distribution on the phase-transition and magnetic properties of the FePt nanoparticles were investigated.     

Cleaning Efficiency of Amino‐Acid Surfactants with Polyoxyethylene Ether and Isopropanol in Liquid Carbon Dioxide

Although anionic surfactants have a distinct positive influence on the removal of particulate soil, the removal of particulate soils is insufficient in CO₂ compared to perchloroethylene. A series of amino‐acid surfactants was selected as main surfactants to study the influence of polyoxyethylene ether and cosolvent on the cleaning effect. Glu‐C12 and C16(3) gave the best cleaning results, which increased from a detergency value of 4.6 when no surfactants were used to 8.32 when surfactants were used. In all experiments, charged anionic surfactant particles were formed, which are responsible for the removal of particulate soil from fabric by electrostatic repulsion. The use of a cosolvent (Isopropanol [IPA]) had a positive effect on the removal of particulate soil when using Glu‐C12 and TX‐45. However, for other compounding combinations, the addition of IPA had a negative effect on particulate soil removal. Of the cosolvents investigated, IPA was the most suitable. With the polarity of the system increasing after adding IPA, the ethylene oxide groups of TX‐45 were partially extended to CO₂. Through the steric effects of branched methyl groups, the cleaning effect was improved.