Fe304纳米颗粒的表面改性

通过实验对FE304纳米颗粒表面改性的最佳条件进行了摸索．并根据表面改性的包覆机理对不同酸度、温度和表面活性剂的用量对Fe304纳米颗粒的尺寸，磁性和稳定性的影响进行了理论上的分析．     

纳米氮化硅粉粒的表面改性研究

纳米氮化硅具有很高的化学稳定性、耐高温性能、良好的机械性能及优异的介电性能(高介电常数、高介电强度)犤9犦,在许多领域有着广泛的应用。作为一种重要的陶瓷材料,目前对它的表面改性大多是采用烧结助剂包覆氮化硅粉粒,提高烧结助剂在氮化硅浆料中的分散程度及浆料的流动性,     

Fe3O4纳米颗粒的表面改性

通过实验对Fe3O4纳米颗粒表面改性的最佳条件进行了摸索.并根据表面改性的包覆机理对不同酸度,温度和表面活性剂的用量对Fe3O4纳米颗粒的尺寸,磁性和稳定性的影响进行了理论上的分析.     

辛醇改性纳米二氧化硅表面的研究

纳米粒子由于粒径小,所以具有很高的比表面积,表面原子处于高度活化状态,使得表面能很高,粒子易于团聚,填充未经表面处理的纳米粒子,不但起不到特殊作用,反而会成为复合材料的力学弱点。所以要对纳米粒子进行表面改性,提高分散性,增加纳米粒子与聚合物间的界面结合力。用醇类对许多粉体进行酯化反应是常用的表面改性方法。金属氧化物与醇的反应是酯化反应[1]。酯化反应修饰法对于表面为弱酸性和中性的纳米粒子最为有效,例如SiO2等。醇的羟基与SiO2的表面羟基发生反应脱掉一分子水,达到表面接枝的目的。方程式为:这样R基团接枝到SiO2的表面,由于R基团是亲油性的,从而增加了极性的SiO2纳米粒子与有机物的润湿性。为了推动反应正向进行,关键在于及时将产生的水份引出反应体系。目前国内外用醇对纳米粒子进行表面改性主要采用常规回流法和高压反应釜法[2]。由于微波照射具有对物质高效、均匀的加热作用,同时还具有电磁场对反应分子间行为的直接作用而引起的所谓“非热效应”,所以本实验采用微波照射法用正辛醇对SiO2纳米微粒进行表面酯化反应并与常规回流法进行比较。关于该方面的研究报道国内外较少。1实验部分1.1实验原料纳米SiO2:(10~20nm...     

纳米二氧化硅改性CPE的研究

采用纳米级SiO2改性氯化聚乙烯（CPE），探讨了SiO2用量、表面处理方法、加工工艺等因素对改性CPE力学性能的影响。通过机械共混制备了CPE／SiO2共混材料，性能测试表明：改性后CPE的硬度、300％定伸应力、断裂伸长率、拉伸强度等力学性能均有较大的提高。     

纳米碳酸钙的表面改性研究

纳米产品(材料)是当今世界高科技产品之一.纳米碳酸钙作为粉体产品中的一种,以高纯、超细、改性和功能性为标志,广泛应用于橡胶、塑料、造纸、油墨、涂料、医药、化妆品等各行各业[1-2].主要用作填充材料,因粒度超细、分散性好,可以增加填充量,降低制品成本,改善制品性能,提高制品档次,拓宽制品使用范围.近年来,随着CaCO3的超细化、结构复杂化及表面改性技术的发展,极大地提高了它的应用价值.对不同形态的超细CaCO3制备技术的研究,已成为许多先进国家竞相开发的热点[3-5].     

不同链长表面活性剂修饰的金纳米颗粒的制备、稳定性及二维排列

采用反胶束的方法, 制备了C₁₀NH₂, C₁₂NH₂, C₁₆NH₂, C₁₈NH₂不同链长脂肪胺修饰的金纳米颗粒; 利用UV-Vis吸收光谱, LB膜等研究了其稳定性和二维排列; 同时对链长和颗粒分布等因素对有序排列的影响进行了探讨. 实验表明, 表面活性剂的碳链越长, 制备的纳米金颗粒越稳定, 其二维排列越有序.     

气相二氧化硅/季铵Gemini表面活性剂稳定的泡沫体系

以zeta电位法研究了季铵Gemini表面活性剂亚甲基-α, ω-双(十二烷基二甲基溴化铵) (12-s-12, s=2, 6)在水溶液中修饰气相二氧化硅(F-SiO₂)粒子。这些粒子随表面活性剂浓度C增加经历了表面从原先的亲水到疏水再重新亲水的改变,其中疏水粒子可以自发吸附在气泡液膜中,从而很好地稳定泡沫。重新亲水的粒子脱附出液膜,仅留下表面活性剂稳定气泡。强的液膜弹性对应于稳定的泡沫。联接链长度影响了Gemini在F-SiO₂粒子表面的吸附,因而也影响了液膜的弹性和对泡沫的稳定。超短s=2联接链的12-2-12由于反离子解离不完全而带有较少的正电荷,在粒子表面的初始吸附弱于12-6-12,但因此减少了吸附分子头基间的静电排斥,可以形成更致密的吸附层。由于12-2-12本身比12-6-12具有更强的界面吸附能力,F-SiO₂粒子和12-2-12的协同作用可以更好地稳定泡沫体系。     

双子表面活性剂修饰金纳米流体的制备及稳定性

以双子表面活性剂丁烷-1,4(N-十四烷基-N,N-二甲基)溴化铵为表面修饰剂,石油醚/正丁醇为溶剂,抗坏血酸为还原剂,在不同温度条件下一步法分别得到油基-金纳米流体和水基-金纳米流体.对纳米流体中悬浮纳米金属颗粒的形貌、粒径、光谱性质等进行了表征.结果表明,p H=7~8的冰水浴条件下制得的纳米金颗粒具有亲油性,粒径均一且分散稳定性较好.采用紫外光谱法分别考察了极性有机溶剂和热作用对油基-金纳米流体稳定性的影响.结果表明,极性有机溶剂添加量超过30%(体积分数)时,对纳米流体稳定性的影响显著;随着热处理温度的升高,纳米流体中分散的纳米金颗粒的稳定时间逐渐缩短.     

微波辐射下纳米二氧化硅接枝正辛醇的表面改性

在微波辐射下用正辛醇对SiO2纳米粒子进行表面接枝改性。改性SiO2纳米粒子的表征结果显示其亲油疏水性得到了很大提高。     

表面活性剂疏水链长对高温下泡沫稳定性的影响

选用不同疏水链长的α-烯烃磺酸盐(AOS)形成泡沫, 分别用泡沫衰减法和泡沫岩芯封堵法测定不同温度下的泡沫稳定性, 并采用动态表面张力、界面流变、分子模拟等方法研究了表面活性剂在气/液界面的吸附行为和界面吸附层的性质, 分析了高温下泡沫的稳定机制. 实验结果表明, 在高温下, 极性头的“锚定作用”减弱, 表面活性剂疏水链难以在气液界面保持以直立状态吸附, 疏水链碳数大于20的表面活性剂分子难以分立吸附, 其疏水链相互交叉缠绕, 增强了泡沫膜的强度, 减缓了气体通过液膜的扩散, 形成的泡沫在高温下具有较好的稳定性.     

Stability and Degradation Mechanisms of Copper‐Based Catalysts for Electrochemical CO2 Reduction

To date, copper is the only monometallic catalyst that can electrochemically reduce CO₂ into high value and energy‐dense products, such as hydrocarbons and alcohols. In recent years, great efforts have been directed towards understanding how its nanoscale structure affects activity and selectivity for the electrochemical CO₂ reduction reaction (CO₂RR). Furthermore, many attempts have been made to improve these two properties. Nevertheless, to advance towards applied systems, the stability of the catalysts during electrolysis is of great significance. This aspect, however, remains less investigated and discussed across the CO₂RR literature. In this Minireview, the recent progress on understanding the stability of copper‐based catalysts is summarized, along with the very few proposed degradation mechanisms. Finally, our perspective on the topic is given.     

Synergistic improvement of foam stability with SiO2 nanoparticles (SiO2-NPs) and different surfactants

Foam fluids are widely used in petroleum engineering, but long-standing foam stability problems have limited the effectiveness of their use. The study explores the synergistic effects and influencing factors of SiO₂ nanoparticles (SiO₂-NPs) with different wettability properties and three different surfactants. The paper investigates the foaming performance of different types of surfactants and analyzes and compares the stability of foam after adding hydrophilic and hydrophobic SiO₂-NPs from macroscopic as well as microscopic perspectives, and the effects of temperature and inorganic salts on the stability of mixed solutions. The experimental results show that: 1) hydrophilic nanoparticles can significantly enhance the foam stability of amphoteric surfactants, with a small increase in the foam stability of anionic and cationic surfactants; 2) The concentration of nanoparticles did not have a significant effect on the stability of the cationic surfactants and this conclusion was verified in the experimental results of the surface tension measured below;3) The cationic surfactants showed better temperature resistance at temperatures of 50–90 °C. Both amphoteric surfactant solutions with the addition of hydrophilic SiO₂-NPs or hydrophobic SiO₂-NPs significantly improved the temperature resistance of the foam at high temperatures. The anionic surfactant solution with hydrophobic SiO₂-NPs did not enhance the solution temperature resistance; 4) The surface tension of the surfactant solution gradually increases with increasing concentration of hydrophilic or hydrophobic SiO₂-NPs and then levels off; 5) the hydrophilic SiO₂-NPs had a significant effect on the salt tolerance of the anionic and amphoteric surfactant solutions. The salt tolerance of cationic surfactant solutions with hydrophobic SiO₂-NPs was better than that of surfactants with hydrophilic SiO₂-NPs.     

Stability and Degradation Mechanisms of Copper-Based Catalysts for Electrochemical CO2 Reduction

To date, copper is the only monometallic catalyst that can electrochemically reduce CO₂ into high value and energy-dense products, such as hydrocarbons and alcohols. In recent years, great efforts have been directed towards understanding how its nanoscale structure affects activity and selectivity for the electrochemical CO₂ reduction reaction (CO₂RR). Furthermore, many attempts have been made to improve these two properties. Nevertheless, to advance towards applied systems, the stability of the catalysts during electrolysis is of great significance. This aspect, however, remains less investigated and discussed across the CO₂RR literature. In this Minireview, the recent progress on understanding the stability of copper-based catalysts is summarized, along with the very few proposed degradation mechanisms. Finally, our perspective on the topic is given.     

Strategies for Designing Nanoparticles for Electro‐ and Photocatalytic CO2 Reduction

Conversion of carbon dioxide (CO₂) into value‐added chemicals has attracted much attention because it can not only resolve global warming issues by reducing CO₂ accumulation in the atmosphere, but also produce renewable hydrocarbon fuels that are important feedstocks for the chemical industry. Among the diverse approaches reported, CO₂ reduction via electro‐ and photocatalytic methods is at the center of topics due to potential engineering of reaction performance through rational design of catalyst features. In this Minireview, we highlight recent strategies for designing nanoparticles to maximize the reaction efficiency and selectivity; from a materials viewpoint, these strategies can provide critical information to guide future research directions.     

On the Origin of Foam Stability: Understanding from Viscoelasticity of Foaming Solutions and Liquid Films

The foam stability (drainage half-life) of α-olefin sulfonate (AOS) with partially hydrolyzed polyacrylamide (HPAM) or xanthan gum (XG) solution was evaluated by the Warring Blender method. With the increase of polymer (HPAM or XG) concentration, foam stability of the surfactant–polymer complexes increased, and the drainage half-life of AOS-XG foam was higher than that of AOS-HPAM foam at the same polymer and surfactant concentration. With the addition of polymer (HPAM or XG), the viscoelasticity of bulk solution and the liquid film were enhanced. The viscoelasticity of AOS-XG bulk solution and liquid film were both higher than that of AOS-HPAM counterparts.      

Catalytic Activity and Stability of Mo_2N in CO Oxidation

Inrecentyears,Mo2Nhasreceivedgreatattenti0ninheter0geneouscatalysisduetoitshighspecificsurfaceareal-4.IthasgoodcaIalyticactivityinawidevarietyofreactions,suchasthehydr0genati0nofCO,synthesis0fNH3,methanation,hydrodenitrogentionandhydrodesulfurization"'andInightbeaprondsingcatalyticmaterial.ThepreparationofMo2Nasacatalyticmaterialhasgainedgreatprogress.Theproduction0fMo2Nwithhighspecificsurfacearea(l7Om'g-')intemperatureprogranunedreactions(TPR)0fMoo3innowingN-H3wasreported'.InthisLab,…     

还原氧化石墨烯@泡沫镍载CoO纳米花电极制备及催化CO2性能

本文以氧化石墨烯包覆泡沫镍电极(GO@NF)作为基底,采用水热法在GO@NF基底上原位生长CoO纳米花,同时GO在水热过程中被同步热还原为还原氧化石墨烯(RGO),从而一步制得还原氧化石墨烯包覆泡沫镍负载CoO纳米花电极(CoO/RGO@NF)。使用XRD和SEM对CoO/RGO@NF电极进行表征,发现CoO纳米花均匀生长在泡沫镍三维网络结构上,CoO纳米花为大量针状纳米棒围绕一个中心而成的花状结构,纳米棒的长度约为10 ~ 15 μm,直径约为100 ~ 200 nm。使用循环伏安和线性扫描法测试了CoO/RGO@NF电极电催化CO₂的还原性能,在-0.76 V（vs. SHE）电位下,CoO/RGO@NF电极电催化CO₂还原的电流效率达到70.9%,产甲酸法拉第效率达到65.2%,甲酸产率为59.8 μmol·h^-1·cm^-2,且电极可持续稳定电催化还原CO₂ 4 h,表明CoO/RGO@NF电极对CO₂电还原有着优良的催化活性、选择性和稳定性。     

Evaluation of Stability of Mesoporous Silica Nanoparticles and Their Further Formulation in Tablet Form

Mesoporous silica nanoparticles have been widely investigated as drug delivery systems. The present study evaluated physical stability of indomethacin loaded mesoporous MCM-41 nanoparticles. The size, polydispersity index, zeta-potential, and drug loading degree of nanoparticles were determined immediately after their preparation and after 6 months storage at 25°C in dry state. The results showed insignificant changes in these parameters, suggesting high stability of nanoparticles and loaded indomethacin. The nanoparticles were formulated in tablets by direct compression. The low friability indicated good resistance during handling and storage. The formulation of the nanoparticles into tablets decreased the initial release of indomethacin.