碳纳米管表面羧基对纳米RuO2颗粒的分散作用

采用硝酸氧化方法对多壁碳纳米管(CNT)的侧壁进行修饰,得到表面羧基含量可控的CNT,并进一步考察了碳管表面基团分布与纳米RuO2催化剂在CNT上的分散度及催化氧化活性之间的关系.以多齿羧酸配体作为稳定剂,合成了RuO2和IrO2纳米颗粒水溶胶,并通过改变配体的种类及数最对纳米颗粒团聚体粒径进行调控.研究结果表明,羧酸配体和碳管表面的羧基均有助于纳米氧化物颗粒的分散.     

CeO2基磨粒在化学机械抛光中的研究进展

CeO₂由于其适当的机械性能及高的化学活性,更重要的是其对Si₃N₄/SiO₂的高选择性去除,使其被广泛应用于浅槽隔离化学机械抛光工艺中。本文论述了CeO₂基抛光液的抛光机制的研究进展,从CeO₂磨料的形貌尺寸、晶体结构、力学性能方面分析了磨料性质对抛光性能的影响,并进一步讨论了CeO₂基研磨颗粒及相关辅助抛光技术在CMP应用上的研究进展。以此为CeO₂基磨料的可控制备及新型抛光技术的发展提供借鉴,并希望能够促进CeO₂基研磨颗粒在抛光工艺中作用机制的揭示,使CeO₂抛光液更广泛地应用于材料的平坦化处理中。     

尺寸可控的球型DNA纳米颗粒构筑策略及其应用

为探究球型DNA纳米颗粒的尺寸对细胞摄取的影响，提出了一种新型构筑策略，制备了一系列尺寸精准可控的球型DNA纳米颗粒，并进一步揭示了球型DNA纳米颗粒的尺寸与MCF-7细胞内化效率的关系；此外，该策略还可以与框架诱导策略相结合，构筑尺寸可控的磷脂囊泡.该结果为构建新型高效的DNA纳米颗粒载药系统提供了理论参考，为特定尺寸的药物载体设计和开发拓展了思路.     

锐钛矿型纳米TiO2介孔粉体表面织构的研究

以硫酸钛和尿素为原料,聚乙二醇-1000为空间构造剂,104℃下经尿素水解均匀沉淀法研制颗粒分散均匀、粒径可控的高热稳定性锐钛矿型纳米TiO2介孔粉体,并对其晶相、颗粒大小、比表面积、形貌和孔道结构进行了表征.结果表明,未经任何热处理的TiO2粉体即为锐钛型晶相,颗粒为均匀分散的类球型颗粒,且颗粒间形成直通型的介孔孔道,其孔径在10～30nm之间.控制焙烧温度可以达到控制颗粒大小及形貌的目的,经850℃焙烧5h的样品仍保持锐钛矿型晶相,未出现向金红石型晶相转变的迹象.     

《颗粒分散科学与技术》

该书从胶体化学、表面(界面)化学理论、材料学及颗粒技术出发,系统地介绍了颗粒的性质、颗粒间的相互作用、颗粒表面改性、颗粒在不同介质中的分散理论、分散特征、分散方法与技术。该书对分散剂、分散的评价方法、典型设备以及分散技术的应用等也作了介绍。     

高速乳化对悬浮聚合墨粉形貌和性能的影响

以铁黑为颜料粒子,采用悬浮聚合技术,通过高速乳化机对反应体系进行预分散,制备出平均粒径为12μm的球形墨粉颗粒.通过在反应体系中加入span-80,克服铁黑粒子在墨粉表面的趋附现象.研究了乳化速度对墨粉颗粒性能的影响.     

TiO2在水及丙二醇介质中表面电性质的研究

0引言 固体颗粒在液相介质中的分散是基础研究领域和工业技术部门普遍遇到的问题 ?在化学工业领域,如涂料 ? 染料 ? 油墨 ? 化妆品等,固体颗粒的分散及分散稳定性直接影响着产品的质量和性能 ?TiO 2 颗粒的水基分散体系广泛应用于涂料 ? 油墨以及化妆品中,也是陶瓷制备过程中重     

纳米香料技术的现状与发展

纳米加香技术可以提高香料在基材内的负载并实现可控释放,从而提高芳香产品质量,增加产品对消费者的吸引力.本文对国内外的纳米加香技术的当前状况和研究进展进行了评述,指出了当前香精加香技术存在的问题,提出了基于基材纳米结构的直接纳米加香技术具有的发展潜力和优势,并讨论了实现该技术在芳香高端产品的大规模应用上仍需解决的关键科学问题.     

化学键分散剂在PZN-PZT浆料中的分散性研究

利用异丙醇钛与长链羧酸合成了一种化学键分散剂,采用沉降实验及FT-IR技术研究了该分散剂在PZN-PZT浆料中的分散性能.结果表明,该分散剂在PZN-PZT浆料中具有良好的分散性,浆料体系达到稳定状态时所需的分散剂量对应分散剂在颗粒表面上呈单分子层成键状态,分散剂分子与颗粒表面上的羟基发生化学反应,导致二者之间呈较强的化学键结合状态,从而有力地改善了PZN-PZT浆料中的分散性、均匀性.     

层状复合金属氢氧化物-聚丙烯酸钠水分散体系的双絮凝现象及机理探讨

研究了聚丙烯酸钠(PAAS)对镁铝型层状复合金属氢氧化物(MgAl-LDH)的胶体水分散体系稳定性的影响. 利用总有机碳(TOC)分析技术测定了PAAS在LDH颗粒上的吸附量, 并利用ζ电位表征了LDH颗粒的电性质. 实验结果表明, 在质量分数为1%的LDH水分散体系中加入0.006~2.400 mmol/L PAAS, 随着PAAS浓度的增加, LDH-PAAS混合体系出现了絮凝-分散-再絮凝变化. 同时, 随着PAAS浓度的增加, PAAS在LDH颗粒上的吸附导致颗粒ζ电位由正减至0, 并进一步负向增加, 颗粒间静电斥力先减小后增加, 因此体系先絮凝再分散. 随着LDH颗粒负电性的进一步增强, 未吸附的PAAS引发颗粒间产生的空缺引力成为体系再次絮凝的主要原因. 对吸附PAAS的LDH颗粒的红外光谱分析表明, PAAS主要通过-COO-与LDH的相互作用而吸附在颗粒上.     

Potential of low-temperature post processing of silica gel for high-temperature stable LED encapsulant

In this study, a low-temperature post processing of silica gel for high-temperature stable LED encapsulant was developed. The results indicated that the silica gels prepared by 1st post heat treatment at 300?°C for 5?h and then 2nd post processing at 80?°C for 50?h can have similar low weight loss and high transmittance as the silica gels were processed at 800?°C for 5?h. The result of such low processing temperature implies it may be possible to encapsulate inorganic gel on LED as the convenient potting method is being used in silicone encapsulation technology. However, the processing time can be greatly reduced if vacuum oven is used. Further surface impermeability improvement is also possible by additional local surface heat treatment. The advantages of adopting silica encapsulant in LED modules include higher thermal stability and better optical performance consistency in lumen, color temperature, etc. in new applications.     

正交试验优化土壤萃取法及常见无机阴离子的离子色谱分析

实验采用超声提取离子色谱法测定土壤中常见无机阴离子的含量,以正交试验优化土壤中阴离子的提取条件。研究土壤粒径、料液比、提取功率、提取时间对土壤中阴离子提取量的影响。结果表明:土壤中阴离子提取的最佳条件为A1B2C3D3。即超纯水为提取液,土壤粒径为180μm,料液比为1:30,超声波作用时间为40 min,提取功率为320W,提取次数为一次。该方法可用于土壤中常见可溶性无机阴离子含量的提取测定。     

Layer-by-layer processing and optical properties of core/alloy nanostructures

A novel hydrothermal layer-by-layer processing method for the fabrication of core/alloy nanoparticles with highly tunable surface plasmon resonance is described. For a model system of Au/Au(x)Ag(1-x), the processing temperature, alloy composition, and alloy thickness resulted in unique and tailorable plasmonic signatures. The discrete dipole approximation and selective alloy etching were used to correlate this optical response with the particle morphology and alloy phase ultrastructure.     

Low-temperature synthesis and microstructural control of titania nano-particles

Nanocrystalline titania powders were synthesized at low temperature (⩽100°C) by a sol–gel method that achieved fine control of particle size and polymorph fraction. X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV–Vis spectroscopy were used to characterize the phase assemblages, crystal size and band gap of the powders. It was demonstrated that larger, well-ordered titania crystals can be obtained by increasing aging temperature and time. These processing parameters can be adjusted to select specific polymorphs from the gel precursors with particular size and shape. The quantum size effect was observed in the size-controlled nanocrystalline titania particles, leading to a blue shift in UV absorption with decreasing in particle size. The anatase to rutile transformation, which may proceed with brookite as a transition phase, is dependent on both particle size and surface structure of the nascent crystals.     

Structure and Dielectric Properties of NiTiO3 Powders Synthesized by the Modified Sol–Gel Method

This study reports the synthesis of nickel titanate (NiTiO₃) powders by using the modified sol‐gel method, with nickel acetate tetrahydrate as the nickel source, titanium isopropoxide as the titanium source, and 2‐methoxyethanol as the solvent, followed by post‐heat treatment in air at temperatures ranging from 500 °C to 900 °C. The characteristics of powders were determined by X‐ray diffraction (XRD), FT‐infrared spectroscopy (FT‐IR), ultraviolet/visible spectroscopy (UV/Vis), and Raman spectroscopy. The particle size and surface area of the powders were also measured. The results indicated that single‐phase NiTiO₃ can be prepared using the modified sol‐gel method, followed by post‐heat treatment at the relatively low temperature of 550 °C. The crystallite sizes and particle sizes of NiTiO₃ powders increase in conjunction with the post‐heat treatment temperatures. However, the surface area of the powders shrinks as the post‐heat treatment temperatures increase. The dielectric constants of NiTiO₃ powders, based on the capacitance‐voltage analysis, are within a range of 13.2 to 17.8.     

Dielectrophoretic manipulation of particle mixtures employing asymmetric insulating posts

A novel scheme for particle separation with insulator‐based dielectrophoresis (iDEP) was developed. This technique offers the capability for an inverted order in particle elution, where larger particles leave the system before smaller particles. Asymmetrically shaped insulating posts, coupled with direct current (DC) biased low‐frequency alternating current (AC) electric potentials, were used to successfully separate a mixture of 500 nm and 1 μm polystyrene particles (size difference of 0.5 μm in diameter). In this separation, the 1 μm particles were eluted first, demonstrating the discriminatory potential of this methodology. To extend this technique to biological samples, a mixture containing Saccharomyces cerevisiae cells (6.3 μm) and 2 μm polystyrene particles was also separated, with the cells being eluted first. The asymmetric posts featured a shorter sharp half and a longer blunt half; this produced an asymmetry in the forces exerted on the particles. The negative DC offset produced a net displacement of the smaller particles toward the upstream direction, while the post asymmetry produced a net displacement of the larger particles toward the downstream direction. This new iDEP approach provides a setup where larger particles are quickly concentrated at the outlet of the post array and can be released first when in a mixture with smaller particles. This new scheme offers an extra set of parameters (alternating current amplitude, DC offset, post asymmetry, and shape) that can be manipulated to obtain a desired separation. This asymmetric post iDEP technique has potential for separations where it is important to quickly elute and enrich larger and more fragile cells in biological samples.     

Measurement of the fluidized velocity in gas-solid fluidized beds based on AE signal analysis by wavelet packet transform

An energy distribution theory was presented based on regular evolvement of energy fraction of acous-tic signals with fluidization velocity. Wavelet packet analysis was used in processing the acoustic sig-nals originated from particle impact on the wall of a fluidized bed. A new criterion of judging incipient fluidization(Umf) velocity and minimum turbulent velocity(Umt) was proposed according to the energy distribution theory. Experiments were performed with five groups of high density polyethylene(PE) particles and one bimodal PE to acquire incipient fluidization velocity and minimum turbulent velocity by using the criterion. The feasibility of this method in obtaining characteristic fluidization parameters was further verified by comparing it to results from the pressure drop method and the empirical value from industry.     

苯乙烯/二乙烯基苯在乙醇/乙二醇单甲醚中分散共聚合速率及粒子大小的研究

以乙醇 乙二醇单甲醚 (EOH EGME)为介质 ,羟丙基纤维素 (HPC)为稳定剂 ,偶氮二异丁腈 (AIBN)为引发剂进行了苯乙烯和二乙烯基苯的分散共聚合研究 .制得粒径在 6～ 10 μm范围内的单分散交联聚苯乙烯微球 (CPS) .探讨了不同介质配比 ,以及苯乙烯、二乙烯基苯、引发剂的浓度对微球大小、粒径分布、聚合速率及稳定性的影响 .当苯乙烯和AIBN浓度增加时 ,聚合速率和平均粒子尺寸增加 ,而粒子分布变宽 ,粒子数先增加 ,而后降低 .随着EOH EGME比例的增加 ,平均粒子尺寸增加 ,而分布指数降低 ,稳定剂增加 ,粒子尺寸降低和粒子数增加 ,但对聚合速率及粒子分布影响不太明显 .另外还探讨了单体和交联剂的后滴加法对微球大小、粒径分布的影响     

Electrodeless dielectrophoresis: Impact of geometry and material on obstacle polarization

Insulator‐based (electrodeless) dielectrophoresis (iDEP) is a promising particle manipulation technique, based on movement of matter in inhomogeneous fields. The inhomogeneity of the field arises because the excitatory field distorts at obstacles (posts). This effect is caused by accumulation of polarization charges at material interfaces. In this study, we utilize a multipole expansion method to investigate the influence of geometry and material on field distortion of posts with arbitrary cross‐sections in homogeneous electric fields applied perpendicular to the longitudinal axis of the post. The post then develops a multipole parallel or anti parallel to the excitatory field. The multipoles intensity is defined by the post's structure and material properties and directly influences the DEP particle trapping potential. We analyzed posts with circular and rhombus‐shaped cross‐sections with different cross‐sectional width‐to‐height ratios and permittivities for their polarization intensity, multipole position, and their particle trapping behavior. A trade‐off between high maximum field gradient and high coverage range of the gradient is presented, which is determined by the sharpness of the post's edges. We contribute to the overall understanding of the post polarization mechanism and expect that the results presented will help optimizing the structure of microchannels with arrays of posts for electrodeless DEP application.     

直接沉淀法制备ZnO超细粉末及其性质测定

用直接沉淀法制备ZnO超细粉末,利用激光散射测定其粒径,与其比表面积的大小作对比。利用红外光谱(IR)、X-射线衍射(XRD)、差热分析(DTA)对ZnO超细粉末进行分析。确定了最佳的制备工艺条件。