MONODISPERSED AND NANOSIZED DENDRIMER／POLYSTYRENE LATEX PARTICLES

Emulsion polymerization of styrene was carried out using dendrimer DAB-dendr-(NH2)64 as seed. The size and size distribution of the emulsion particles were characterized by transmission electron microscopy (TEM) and dynamic light scattering (DLS), and the effects o.f emulsion polymerization conditions on the preparation of emulsion particle were investigated. It has been found that the nanosized dendrimer/polystyrene polymer emulsion particles obtained were in the range of 26～64nm in diameter, and were monodisperse; the size and size distribution of emulsion particles were influenced by the contents of dendrimer DAB-dendr-(NH2)64, emulsifier and initiator, as well as the pH value.     

Effect of nanoparticle concentration on zeta-potential measurement results and reproducibility

The effect of nanoparticle concentration on zeta-potential measurement results at dilute concentrations was evaluated.The values of the zeta-potential for four different types of nanoparticles,Ludox(silica),multi-walled carbon nanotubes(bamboo-shaped and hollow nanotubes)and gold,at various concentrations,were obtained using a laser Doppler electrophoresis instrument.The size of the nanoparticles on dilution was measured using dynamic light scattering(DLS).The results show that there is a concentration range within which the zeta-potential,and particle size,are not affected by nanoparticle concentration.The lower concentration limit for the system to produce consistent results was dependent on the nature of the sample under study and ranged between 10-2 and 10 4wt%.Below this concentration,there was an apparent shift in zeta-potential values to less negative values,which was accompanied by an increase in the particle size.The shift in zeta-potential was attributed to an increase in contribution of the signal from extraneous particulate matter.The increase in particle size was attributed to the nature of the homodyne optical configuration of the instrument.The aim of this study was to elucidate the range in nanopatticle concentration that allows for accurate and reliable measurement of the zeta-potential and DLS data.     

Novel one-step synthesis of silica nanoparticles from sugarbeet bagasse by laser ablation and their effects on the growth of freshwater algae culture

Scientific research involving nanotechnology has grown exponentially and has led to the development of engineered nanoparticles（NPs）.Silica NPs have been used in numerous scientific and technological applications over the past decade,necessitating the development of efficient methods for their synthesis.Recent studies have explored the potential of laser ablation as a convenient way to prepare metal and oxide NPs.Due to its high silica content,low cost,and widespread availability,sugarbeet bagasse is highly suitable as a raw material for producing silica NPs via laser ablation.In this study,two different NP production methods were investigated：laser ablation and NaOH treatment.We developed a novel,one-step method to produce silica NPs from sugarbeet bagasse using laser ablation,and we characterized the silica NPs using environmental scanning electron microscopy（ESEM）,energy dispersive spectrometry（EDS）,dynamic light scattering（DLS）,transmission electron microscopy（TEM）,attenuated total reflectanceFourier transform infrared spectroscopy（ATR-FT1R）,X-ray photoelectron spectroscopy（XPS） and Raman spectroscopy.EDS analysis and XPS confirmed the presence of silica NPs.The NPs produced by laser ablation were smaller（38-190 nm） than those produced by NaOH treatment（531-825 nm）.Finally,we demonstrated positive effects of silica NPs produced from laser ablation on the growth of microalgae,and thus,our novel method may be beneficial as an environmentally friendly procedure to produce NPs.     

爆轰法合成碳包覆纳米铜颗粒

以硝酸铜和柠檬酸制成的干凝胶为主要反应物,加入油酸有机碳源和黑索今炸药,在氮气保护气 氛下在爆炸容器中引爆,成功地合成了碳包覆纳米铜颗粒。分别采用X射线衍射、透射电镜对产物形貌特征 进行表征。结果表明,在爆轰产物中富含碳包覆纳米铜颗粒,产物呈圆球体,具有完好的核壳结构形貌,颗粒 粒径在10~40nm 之间,外层碳壳结构主要由无定型碳和石墨构成。并对爆轰法合成碳包覆纳米铜颗粒的 形成机理进行了分析。     

SYNTHESIS OF HIGH PURITY TiO2 NANOPARTICLES FROM Ti（SO4）2 IN PRESENCE OF EDTA AS COMPLEXING AGENT

TiO2 nanoparticles were synthesized by a homogeneous controlled precipitation method using industrial titanium sulfate （Ti（SO4）2）. The obtained powders were characterized by X-ray diffraction （XRD）, transmission electron microscope （TEM）, Fourier transform infrared spectroscopy （FTIR） and ICP plasma spectrometer. EDTA was used as complexing agent to improve the purity and the formation of TiO2 nanoparticles. Experimental results indicated that the high-purity TiO2 nanoparticles were 20 nm in mean size and nearly monodispersed.     

Experimental study to obtain the viscosity of CuO-loaded nanofluid: effects of nanoparticles’ mass fraction,temperature and basefluid’s types to develop a correlation

In this study, the impacts of temperature, nanoparticles mass fraction, and basefluid types were investigated on the dynamic viscosity of CuO-loaded nanofluids. The nanoparticles were dispersed in deionized water, ethanol, and ethylene glycol as basefluids separately and the measurements were performed on samples with nanoparticles loads ranging from 0.005 to 5 wt%, and the temperature range of 25 to 70 °C. TEM analysis were performed on dried nanoparticles and the results showed the average mean diameter of CuO nanoparticles ranged from 10 to 50 nm. The results of DLS analysis confirmed the results of nanoparticles size obtained by TEM analysis in mentioned basefluids and Zeta-Potential tests exhibited the high stability of the nanoparticles in the basefluids environment. The results indicate that by adding tiny amount of CuO nanoparticles to basefluids, relative viscosity of nanofluid increases. By the increase in nanoparticles load higher than 0.1 wt% the effect of both nanoparticles mass fraction and temperature would be more tangible, while for nanoparticles mass fraction lower than 0.1 wt% no significant change in viscosity was observed. In addition, the results declare that viscosity of nanofluid remains constant at various applied shear rates indicating Newtonian behavior of nanofluid at various nanoparticles load and temperature. According to experimental data, it is also evident that with the increase in temperature, the value of relative dynamic viscosity decreases significantly. Also it is concluded that for CuO/ethanol nanofluid, more interfacial interaction is resulted that causes higher relative dynamic viscosity while for CuO/water lower interfacial interaction between nanoparticles surface and water molecules are resulted which leads to the lower values for this parameter. The results of this study implied that with increase the temperature from 25 to 70 °C at the condition where nanoparticles mass fraction was chosen to be 5 wt%, the value of dynamic viscosity of CuO/ethanol, CuO/deionized water, CuO/ethylene glycol declined 69%, 66%, and 65% respectively. Finally, a correlation was proposed for the relative dynamic viscosity of nanofluid based on the CuO nanoparticles mass fraction and temperature of the basefluid and nanoparticles.     

Novel one-step synthesis of silica nanoparticles from sugarbeet bagasse by laser ablation and their effects on the growth of freshwater algae culture

Scientific research involving nanotechnology has grown exponentially and has led to the development of engineered nanoparticles (NPs). Silica NPs have been used in numerous scientific and technological applications over the past decade, necessitating the development of efficient methods for their synthesis. Recent studies have explored the potential of laser ablation as a convenient way to prepare metal and oxide NPs. Due to its high silica content, low cost, and widespread availability, sugarbeet bagasse is highly suitable as a raw material for producing silica NPs via laser ablation. In this study, two different NP production methods were investigated: laser ablation and NaOH treatment. We developed a novel, one-step method to produce silica NPs from sugarbeet bagasse using laser ablation, and we characterized the silica NPs using environmental scanning electron microscopy (ESEM), energy dispersive spectrometry (EDS), dynamic light scattering (DLS), transmission electron microscopy (TEM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR–FTIR), X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. EDS analysis and XPS confirmed the presence of silica NPs. The NPs produced by laser ablation were smaller (38–190 nm) than those produced by NaOH treatment (531–825 nm). Finally, we demonstrated positive effects of silica NPs produced from laser ablation on the growth of microalgae, and thus, our novel method may be beneficial as an environmentally friendly procedure to produce NPs.     

Novel methanol-tolerant Ir-S/C chalcogenide electrocatalysts for oxygen reduction in DMFC fuel cell

Novel methanol-tolerant oxygen-reduction catalysts,iridium-sulphur (Ir-S) chalcogenides with different Ir/S atomic ratios,were synthesized via a precipitation method using H 2 IrCl 6 and Na 2 SO 3 as the Ir and S precursors.Powder X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to characterize the Ir x S 1 x/C chalcogenide catalysts.Particle size ranging from 2.5 to 2.8 nm though obvious agglomeration was found on carbon support.However,these chalcogenide catalysts showed strong...     

石墨包覆纳米镍颗粒的结构及磁性能的表征

在密闭容器中,用爆轰分解掺杂含有镍离子的混合炸药前驱体合成了核壳结构石墨包覆镍纳米颗 粒。调整混合炸药前驱体中碳源材料和金属源材料的有效摩尔比合成了球形、不同尺寸、核壳结构的磁性石 墨包覆纳米镍颗粒。采用X 射线衍射仪(XRD)、透射电镜(TEM)、能谱分析仪(EDX)和振动样品磁强计 (VSM)表征化学构成、结构形貌及磁性能。结果表明:颗粒大小主要分布在10~55nm 之间,复合纳米颗粒 主要由面心立方镍纳米晶体和石墨碳构成,常温下这些复合纳米颗粒主要表现出超顺磁性和铁磁性能。     

Single quantum dot (QD) imaging of fluid flow near surfaces

We introduce the use of quantum dot (QD) nanoparticles for near-surface velocimetry and provide preliminary data to demonstrate its feasibility. Evanescent wave illumination is used to image the motion of water-soluble (CdSe)ZnS QDs with a core size of 6 nm within a region of order 100 nm of a surface . Results are presented for the two in-plane components of the velocity field.     

Temperature and particle-size dependent viscosity data for water-based nanofluids – Hysteresis phenomenon

In the present paper, we have investigated experimentally the influence of both the temperature and the particle size on the dynamic viscosities of two particular water-based nanofluids, namely water–Al₂O₃ and water–CuO mixtures. The measurement of nanofluid dynamic viscosities was accomplished using a ‘piston-type’ calibrated viscometer based on the Couette flow inside a cylindrical measurement chamber. Data were collected for temperatures ranging from ambient to 75 °C, for water–Al₂O₃ mixtures with two different particle diameters, 36 nm and 47 nm, as well as for water–CuO nanofluid with 29 nm particle size. The results show that for particle volume fractions lower than 4%, viscosities corresponding to 36 nm and 47 nm particle-size alumina–water nanofluids are approximately identical. For higher particle fractions, viscosities of 47 nm particle-size are clearly higher than those of 36 nm size. Viscosities corresponding to water-oxide copper are the highest among the nanofluids tested. The temperature effect has been investigated thoroughly. A more complete viscosity data base is presented for the three nanofluids considered, with several experimental correlations proposed for low particle volume fractions. It has been found that the application of Einstein’s formula and those derived from the linear fluid theory seems not to be appropriate for nanofluids. The hysteresis phenomenon on viscosity measurement, which is believed to be the first observed for nanofluids, has raised serious concerns regarding the use of nanofluids for heat transfer enhancement purposes.     

Detection of viscoelasticity in aggregating dilute protein solutions through dynamic light scattering-based optical microrheology

This study illustrates the applicability of dynamic light scattering (DLS)-based optical microrheology in generating new insights into the rheological response of dilute protein solutions as they start to form insoluble aggregates under the influence of a thermal stress. The technique is also shown to provide a quick method for measuring the viscosity in protein solutions. The optical microrheological technique, which is based on DLS with improved single scattering detection, is shown here to capture the rich dynamics in these systems, where traditional mechanical rheometry cannot be effectively employed due to low torque generation and high sample volume requirements and the more widely known diffusing wave spectroscopy microrheology technique is not desirable due to the required high probe particle concentrations The study illustrates the careful consideration which must be given to the tracer particle surface chemistry, tracer particle concentration and tracer particle size in order to extract out rheological responses that are truly representative of the underlying protein dynamics and microstructure. We outline a procedure for ensuring that the pitfalls inherent to this type of measurement are avoided.     

Visible light-driven photocatalysis of W,N co-doped TiO2

W, N co-doped TiO2 nanoparticles were synthesized by a sol-gel method. The prepared samples were characterized by X-ray diffraction （XRD）, field emission scanning electron microscopy （FE-SEM）, trans- mission electron microscopy （TEM）, Fourier transform infrared spectroscopy （FT-1R）, X-ray photoelectron spectroscopy （XPS） and diffuse reflectance spectrophotometry （DRS）. The results showed that the co- doped photocatalysts were essentially uniform spherical particles with the smallest particle size of 22.5 nm. Compared to un-doped TiO2, N-TiO2 and P-25, the absorption edge of the W, N co-doped TiO2 shifted to longer wavelength and its photocatalytic activity for degradation of methyl orange （MO） under Xe-lamp （350W） was higher.     

Role of interfacial layer and clustering on the effective thermal conductivity of CuO-gear oil nanofluids

Copper oxide nanoparticles (∼40 nm) are dispersed in gear oil (IBP Haulic-68) at different volume fractions (0.005-0.025) with oleic acid added as a surfactant to stabilize the system. Prepared nanofluids are characterized by Fourier Transform Infrared spectroscopy (FTIR) and Dynamic light scattering (DLS) measurements. DLS data confirmed the presence of agglomerated nanoparticles in the prepared nanofluids. Thermal conductivity measurements are performed both as a function of CuO volume fraction and temperature between 5 and 80 °C. An enhancement in thermal conductivity at 30 °C of 10.4% with 0.025 volume fraction of CuO nanoparticle loading is observed. Measured volume fraction dependence of the thermal conductivity enhancement at room temperature is predicted fairly well considering contributions from both nanolayer at the solid-liquid interface and particle agglomeration in the suspension, as visualized by Feng et al.     

ZrO_2纳米微粒的制备、表征及作为MACs添加剂的摩擦学性能

制备了氧化三辛基膦表面修饰的油溶性ZrO2纳米微粒,用透射电镜(TEM)、X-射线衍射仪、红外光谱仪对其进行表征,研究了其作为多烷基环戊烷(MACs)添加剂的摩擦学性能及润滑机理.结果表明:ZrO2纳米微粒粒径大约为7～8 nm,分布比较均匀,无明显团聚,在非极性溶剂中能很好地溶解和稳定分散;作为MACs添加剂,在摩擦过程中,无机ZrO2纳米微粒以沉积膜形式沉积在摩擦副表面,有机修饰剂中的活性P元素在摩擦副表面发生了化学反应,形成了FePO4极压润滑膜,ZrO2沉积膜和FePO4极压润滑膜的协同作用起到了良好的抗磨和抗极压作用.     

Bi-Pb-Sn-Cd四元合金纳米微粒的制备及其摩擦磨损性能研究

通过直接对Bi-Pb-Sn-Cd四元块状合金进行超声分散制备了相应的四元合金纳米微粒;采用X射线衍射仪和热分析仪分析所制备的纳米微粒结构;采用透射电子显微镜考察了纳米颗粒的形貌及尺寸分布;采用四球摩擦磨损试验机考察了纳米颗粒的摩擦学性能.结果表明,所制备的纳米颗粒为低熔点共晶合金纳米微粒,颗粒平均尺寸在10～20 nm之间,其作为润滑油添加剂表现出良好的摩擦学性能.     

快凝粉末冶金铝合金的微观结构

利用Ｘ射线衍射,透射电镜及高分辨电镜对快凝粉末冶金Ａ１－８．５Ｆｅ－１．３Ｖ－１．７Ｓｉ铝合金的微观结构进行了初步观察。结果表明,合金中仅含有一种硅化物强化相,即Ａｌ＿１３（Ｆｅ,Ｖ）＿３Ｓｉ,点阵常数为１．２５６ｎｍ。发现有些分布于晶内的硅化物相与合金基体具有确定的取向关系,即｛１１０｝Ａ１基体／｛１１０｝硅化物＜１１１＞Ａｌ基体／（１１０）硅化物但是位于晶界上的硅化物与基体没有确定的取向关系,而常常存在厚度约为５０Ａ的非晶层。      

爆轰法合成纳米CeO粉末*2

爆轰合成过程中采用Ce(NO₃)₃·6H₂O制备的可爆药剂,并利用X射线衍射仪(XRD)和透射电子显微镜(TEM)对合成的纳米CeO₂粉末进行了检测,研究了起爆方式对于合成产物结晶化度、粒径和形貌的影响。结果表明,采用Ce(NO₃)₃·6H₂O制备的可爆药剂,可以合成立方晶系的球形纳米CeO₂; 提高可爆药剂的爆速,可有效降低纳米CeO₂的粒径,得到球形化更好的纳米粒子。     

Catalytic oxidation of benzene over Ce–Mn oxides synthesized by flame spray pyrolysis

Flame spray pyrolysis (FSP) was utilized to synthesize Ce–Mn oxides in one step for catalytic oxidation of benzene. Cerium acetate and manganese acetate were used as precursors. The materials synthesized were characterized using X-ray diffraction (XRD), N₂ adsorption, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), Raman spectroscopy, and H₂-temperature programmed reduction (H₂-TPR) and their benzene catalytic oxidation behavior was evaluated. Mn ions were evidenced in multiple chemical states. Crystalline Ce–Mn oxides consist of particles with size <40 nm and specific surface areas (SSA) of 20–50 m²/g. Raman spectrums and H₂-TPR results indicated the interaction between cerium and manganese oxides. Flame-made 12.5%-Ce–Mn oxide exhibited excellent catalytic activity at relatively low temperatures (T₉₅ about 260 °C) compared to other Ce–Mn oxides with different cerium-to-manganese ratios. Redox mechanism and strong interaction conform to structure analysis that Ce–Mn strong interaction formed during the high temperature flame process and the results were used to explain catalytic oxidation of benzene.     

Modification of silica with PMMA via ultrasonic irradiation and its application for reinforcement of polyacrylates

Polymethyl methacrylate （PMMA） encapsulated silica nanocomposite particles were prepared by ultra- sonically induced in situ polymerization of methyl methacrylate （MMA） on the surface of silica sol. The nanoparticles were characterized by Fourier transform infrared spectroscopy （FFIR）, transmission electron microscopy （TEM）, thermogravimetry （TG）, scanning electron microscopy （SEM）. The results showed that core-shell structure nanocomposite particles with an average size of 36 nm were obtained, and the thickness of polymer encapsulating layer was about 8 nm. The pretreatment of silica sol with tert-butyl hydroperoxide （TBHP） and the addition of ~-methacryloxypropyl trimethoxysilane （MAPTS） significantly enhanced the encapsulation effect. Modified by the polymer layer, the silica particles could be well dispersed in matrices and utilized to improve the mechanical performance of polyacrylates.