Size-controlled synthesis of nano α-alumina particles through the sol–gel method

Nano α-alumina particles were synthesized by a sol–gel method using aqueous solutions of aluminum isopropoxide and 0.5 M aluminum nitrate. 1/3-benzened disoulfonic acid disodium salt (SDBS) and sodium bis-2-ethylhexyl sulfosuccinate (Na(AOT)) were used as surfactant stabilizing agents. Solution was stirred for different periods (24, 36, 48 and 60 h) at 60 °C. The samples were then analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Introduction of surfactant stabilizing agents and different stirring times will affect the size and shape of particle formed and also the degree of aggregation. SDBS, however, produced better dispersion, finer particles and spherical shape nanoparticles, compared to Na(AOT). The finest particle size (20–30 nm) was obtained at 48 h stirring time with SDBS surfactant.     

Preparation and application of silver nanoparticles on silk for imparting antimicrobial properties

Silver nanoparticles were produced by a chemical reduction method that reduced silver nitrate with reducing agents such as hydrazine and glucose. The silver nanoparticles were characterized with transmission electron microscope, scanning electron microscope, and optical microscope. The effects of process parameters such as the stirring speed, temperature, type of reducing agent, and dispersing agent on the particle size were studied. The particle size decreased with an increase in the stirring speed and a decrease in the process temperature. Smaller particles were formed when the silver nitrate was reduced by glucose versus those that were formed by reduction with hydrazine. Silver nanoparticles with average sizes of 10 and 35 nm, produced by reduction with hydrazine at 5 and 40°C, were applied to silk by an exhaust method. Silk fabrics treated with 40 ppm silver hydrosol produced at 5°C and 60 ppm silver hydrosol produced at 40°C showed 100% antimicrobial activity against the gram‐positive bacterium Staphylococcus aureus. The durability of the antimicrobial property of the treated silk fabric to washing was also examined and is presented. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Influence of zinc oxide on thermoplastic elastomer‐based composites: Synthesis,processing, structural,and thermal characterization

It was aimed to investigate how thermal conductivity and stability properties of synthesized thermoplastic elastomers were influenced by zinc oxide (ZnO) additives which differed in size and surface treatment. ZnO particles were prepared by the homogeneous precipitation method by mixing aqueous solutions of hexamethylenetetramine (HMT) and zinc nitrate. The obtained particles were characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Poly(vinyl pyrrolidone) (PVP) was used as a modifier to reduce aggregation among the ZnO particles. The composites, prepared by melt compounding method, were characterized in terms of their morphology and thermal properties. Uniformly distributed surface treated particles caused an enhancement in thermal conductivity properties. At 10 wt% ZnO concentration the thermal conductivity of composite reached 1.7 W/mK compared with 0.3 W/mK for the neat polymer. At the same filler loading, ZnO nanoparticles exhibited a greater effect on thermal conductivity compared with submicron sized particles. It was found that the coefficient of thermal expansion of composites decreased at low temperature (55°C) with increasing ZnO content. Thermal gravimetric analysis (TGA) showed that the neat polymer and the composites were resistant up to 340°C without significant mass loss. POLYM. COMPOS., 37:2369–2376, 2016. © 2015 Society of Plastics Engineers     

Contributions of TMAH Surfactant on Hierarchical Structures of PVA/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>–TMAH Ferrogels by Using SAXS Instrument

The magnetic hydrogels combining polyvinyl-alcohol (PVA) and Fe₃O₄ (magnetite)–TMAH (tetra-methyl ammonium hydroxide) have been successfully fabricated via a Freezing-thawing route. The magnetite nanoparticles were prepared from iron sands by using coprecipitation method. The transmission electron microscopy image revealed that the magnetite nanoparticles with a reaction temperature of 30 °C had the average particle size of 12 nm in clusters of aggregation. The result was similar to the particle size obtained from X-ray diffraction data analyzed by Scherer equation. Furthermore, synchrotron small angle X-ray scattering data were analyzed by using two lognormal distributions to calculate the distribution of the individual magnetite particles. Meanwhile, Teubner-Strey and Beaucage models were employed to observe the distribution of magnetite particles coated by TMAH as a surfactant. The data analysis showed that the magnetite particles within the magnetic hydrogels formed aggregations with diameters of cluster particles in the range from 13.1 to 31.8 nm. Interestingly, the diameter of clusters particle increased from 13.1 to 31.8 nm along with the increasing concentration of ferrofluids from 1 to 15 wt%. This phenomenon was predicted to result from the effect of TMAH as a surface reactant agent that prevented the aggregation by coating the surface of the magnetite nanoparticles.     

乳化法明胶亚微米粒子的制备

以A型明胶为原料,石蜡油为油相,采用乳化化学交联方法制备了明胶亚微米粒子. 用扫描电子显微镜(SEM)观察了明胶亚微米粒子的形貌和粒径. 研究了影响微球粒径的多种因素,包括明胶溶液浓度、乳化搅拌速度、乳化温度、乳化剂和固化剂. 结果表明,采用戊二醛为固化剂、增加明胶的浓度、提高乳化搅拌速度、使用混合性的乳化剂都有利于降低明胶粒子的粒径. 此外,对制备工艺进行了优化,并在7000 r/min左右高速搅拌的条件下,得到了成球性较好的粒径约为450 nm的明胶亚微米粒子.     

Synthesis of CaCO3 nanoparticles by controlled precipitation of saturated carbonate and calcium nitrate aqueous solutions

Calcium carbonate nanoparticles (CCNP) were synthesised by precipitation from saturated sodium carbonate and calcium nitrate aqueous solutions. The effect of agitation rate, mixing time, calcium/carbonate ions concentration and temperature on particle size and morphology were investigated. Particles were characterised using X‐ray diffraction (XRD), transmission electron microscopy (TEM) and thermogravimetric analysis (TGA). Increasing the mixing time from 30 to 180 min resulted in a decrease in particles size. Mixing rate variation between 300 and 14 000 rpm decreased the particle size. Temperature increase favoured a significant growth in particle size and in the formation of aragonite beginning from 80°C. Calcium and carbonate ion concentrations are key parameters controlling the CCNP particle size. Calcite is the main polymorph obtained as revealed by XRD analysis. © 2011 Canadian Society for Chemical Engineering     

Preparation of polymer microspheres in supercritical carbon dioxide and their evaluation as cold‐flow improvers in diesel

Polymeric microspheres were synthesized by the precipitation copolymerization of methacrylic acid and styrene in supercritical carbon dioxide. Scanning electron microscopy showed that the products were spherical microparticles. The mean diameter of the particles was 0.2–2 μm. The synthesis conditions affecting the particle size and morphology were examined in detail. The well‐distributed copolymer microspheres were applied as low‐temperature improvers for diesel. The results showed excellent performance for high‐paraffin diesel at low temperatures. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

The Influence of Microencapsulation with a Modified Chitosan (Water Soluble) on β-Galactosidase Activity

The aim of this work was to investigate the possibility of producing microparticles containing β-galactosidase, using a modified chitosan (water soluble) as encapsulating agent. β-galactosidase microparticles were prepared by a spray-drying method and were characterized in terms of particle size, surface morphology, zeta potential, and stability over a storage period of six months. Microparticles were also analyzed by FTIR spectroscopy and thermogravimetry techniques. Structural analysis of the surface of the particles was performed by scanning electron microscopy (SEM). SEM results show that the obtained microparticles have an average diameter smaller than 3.5 µm and a regular shape. The β-galactosidase activity decreases when microencapsulated. The parameters Km and Vmax of the Michaelis-Menten equation were calculated for the different experimental conditions. The optimal pH ranges from 6.4 to 7.2, approximately, depending on the enzyme concentration in the microcapsule. After six months of storage, the enzyme activity presents a small decrease, although no significant differences in the appearance, color, and particle size distribution were identified.     

SiO_2复合纳米粒子的制备及其性能

用反相微乳液法制备SiO2复合纳米粒子,考察了温度、pH等条件对其光催化降解甲基橙的影响,并用高倍透射电镜对其结构形态进行表征。结果表明:在100mL质量浓度为20mg/L的甲基橙溶液中加入0.50g复合纳米粒子,353K强酸性条件下降解率可高达95%以上。提出了复合纳米粒子光催化降解机理,其中复合纳米粒子对甲基橙的吸附作用是光催化降解作用的前置步骤。电镜结果表明,复合纳米粒子各组分间分布均匀,粒径跨度较小,具有较好的催化性能。     

Size‐controlled preparation of nanosoy for potential biomedical applications

Soy protein isolate nanoparticles (nanosoy) have significant applications in drug delivery, wound care systems and tissue engineering. We report an optimum technique named nanoprecipitation which enabled one‐step formation of near‐monodisperse nanosoy based on solvent displacement. Excellent control over protein aggregation was achieved, producing nanoparticles in the size range of 5–15 nm. The effect of various process parameters such as temperature, solvent/non‐solvent ratio, crosslinker content and type of surfactant on the particle size was investigated. The structural and morphological features were analysed using dynamic light scattering, X‐ray diffraction and high‐resolution transmission electron microscopy. The morphological examination indicated that the particles formed were spherical in shape and further reduction in the average particle diameter was achieved by reducing the temperature and solvent/non‐solvent ratio of the reaction medium. Surface charge and stability of nanosoy dispersions were analysed using zeta potential measurements. Further, ciprofloxacin release was monitored using nanosoy as a drug carrier. This technique provides an effective and straightforward approach offering considerable advantages in terms of economic, technical and environmental performance. © 2016 Society of Chemical Industry     

Coating of Silica and Titania Aerosol Nanoparticles by Silver Vapor Condensation

Silica and titania aerosol nanoparticles are coated with silver through a physical coating process. The silver is evaporated in a tubular furnace flow system and condensed on the ceramic carrier particles with diameters of approximately 100?nm. The temperature gradient in the furnace system is optimized in order to avoid homogeneous nucleation of the silver. The generated ceramic–silver composite nanoparticles are characterized with aerosol measurements and analytical transmission electron microscopy. Two completely different particle morphologies are clearly observed, silver-decoration and composite doublet, with amorphous silica and crystalline rutile titania as the carrier particles, respectively. The former morphology consists of multiple silver nanodots with diameters of 1–10?nm, while in the latter morphology the silver had formed a larger structure with a size comparable to that of the carrier particle. Different shapes are observed in these larger silver structures, such as triangular, rodlike, and hexagonal. Differences in the silver particle migration on the surface of the silica and titania particles is proposed to be the key factor resulting into the two distinct particle morphologies.

Copyright 2015 American Association for Aerosol Research     

Controlling nanostructure in thermal plasma processing: Moving from highly aggregated porous structure to spherical silica nanoparticles

The synthesis of SiO₂ nanoparticles in a radio frequency (RF) plasma reactor is studied. Scanning electron microscopy (SEM), nitrogen absorption (BET), and laser diffractometry techniques are used to determine the morphology, product size and aggregation level of the resulting nanopowder. Computational fluid dynamics (CFD) modelling employing Fluent 6.2.16 is used to better understand the flow and temperature fields inside the reactor and their effect on the nanoparticles. The theoretical and experimental results are later combined to describe the effects of the above mentioned parameters on the formation (nucleation and growth) of the nanoparticles by different mechanisms. It is demonstrated that the quench gas configuration and reactor geometry can now be designed to control the morphology and size of nanoparticles in these reactors. Various nanostructured products have been synthesised: i.e., highly aggregated nanostructure, partially sintered nanospheres and spherical nanoparticles with very low levels of aggregation. These nanostructures have their primary particles sized between 10 and 200 nm, while the aggregate sizes can lie in the range of between hundreds of nanometers to several micrometers. The critical parameters that should be considered for the large-scale production process are finally identified.     

High molecular weight polypropylene nanospheres: Synthesis and characterization

The high molecular weight (MW) polypropylene with average particle size of 60 nm was synthesized by controlled growth mechanism using Ziegler–Natta catalyst. The atomic force microscopy (AFM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) studies showed that PP nanoparticles were spherical in shape. Structure and crystallinity were concomitantly studied through Fourier transform infrared spectroscopy and X‐ray diffraction, respectively. It shows nanospherical PP particles with more crystallinity (～ 75%) compared with macrosized PP (～ 59%). In addition, differential scanning calorimetry studies revealed the finite particle size effect on T_g and the scale dependence T_g followed a first order exponential trend. As particle size goes down to nano‐ scale from macrosize, continuous elevation of T_g's were observed from ?25 to ?11°C. This phenomenon was directed to configuration entropy of single spherical nanoparticles of PP. The mechanical properties and surface roughness were also evaluated through AFM. At last, the properties of nanosized PP were compared with micron and macrosized particles. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Preparation of nano‐encapsulated polyethylene wax particles for color toner by in situ emulsion polymerization

Polystyrene‐acrylate resin coated polyethylene (PE) wax composite particles used for color toner were prepared by in situ emulsion polymerization. The laser particle analyzer and transmission electron microscope (TEM) were applied to show the size and morphology of composite particles, and thermogravimetric analysis (TGA) was used to characterize the thermal properties of the nanoparticles. With the increase of emulsifier triton x‐100 (TX‐100), the size of composite particles decreased at first and then increased and the shell thickness increased gradually. When the mass ratio of TX‐100 to monomers was 1:10, the core–shell structure of the latex particles was the clearest. The homopolymer of styrene (St) and copolymer of styrene‐butyl acrylate (St‐BA) showed few differences on the size of the composite particles, but a significant difference on the thermal performance. The FTIR spectra and dissolution experiments of PE wax/P(St‐BA) composite particles provided supporting evidence for encapsulation. With the increasing percentage of polyethylene wax, the particles size got larger and emulsion shelf stability became worse. The size and the shelf stability got optimized when the reaction temperature was 80 °C. The average size of the particles initiated by 2,2‐azobisisobutyronitrile (AIBN) was smaller and the size distribution was narrower than those of initiated by potassium persulfate (KPS). © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44399.     

Erodent size effect on the erosion of polyphenylene sulfide composite

The effect of erodent particle size on solid particle erosion of randomly oriented short glass fiber and mineral particle reinforced polyphenylene sulfide (PPS) was investigated. To examine the effect of erodent size on the erosion resistance of the PPS composite, aluminum oxide particles at three different sizes, namely, 300–425 μm, 150–212 μm, and 45–75 μm, were used. The erosion tests were performed at six different contact angles of 15°, 30°, 45°, 60°, 75°, and 90°, respectively. The results showed a strong relationship between the erodent particle size and erosion rates of PPS composite. Maximum erosion rate for the erodent particles with sizes of 45–75 μm and 150–212 μm occurred at contact angle of 30°, on the other hand maximum erosion rate for particles having 300–425 μm size occurred between 45° and 60°. The morphologies of eroded surfaces were characterized by the scanning electron microscopy (SEM). Possible erosion mechanisms were discussed. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers     

纳米氢氧化镁阻燃剂的制备研究

以氯化镁和氨水为原料,加入适量聚乙二醇(PEG2000)作为表面活性剂,利用直接沉淀法合成了粉末状、粒度均匀且分散性好的纳米氢氧化镁。考察了体系温度、沉淀时间、搅拌速率、反应物配比、PEG2000用量对氢氧化镁颗粒平均粒径的影响,并采用透射电镜(TEM)、X射线衍射(XRD)对颗粒结构进行表征。结果表明,制备纳米氢氧化镁的适宜的工艺条件为:体系温度25℃,沉淀时间20 min,搅拌速率500 r/min,反应物氯化镁和氨水的配比(摩尔比)为1∶3.0,PEG2000用量为1.50 g/mol MgCl2。     

Effects of heat-treatment temperature and starting composition on morphology of boron carbide particles synthesized by carbothermal reduction

Carbothermal reduction using B₂O₃ and carbon black was applied for synthesis of B₄C powder and the effects of heat-treatment temperature and starting composition of raw mixture on morphology of B₄C particles were investigated. Morphology of B₄C particles synthesized at 1450 °C was mainly spherical shapes. The B₄C powder synthesized at 1550 °C was large and changed in morphology from polyhedral to skeletal shape, and particle size of B₄C increased with an increase in the amount of B₂O₃ in the starting mixtures. The B₄C powder synthesized beyond 1650 °C consisted from dendrite-like particles aggregated by small primary particles. Morphology of the primary B₄C particles synthesized at 1750 °C changed from polyhedral to rounded shape with increasing the amount of B₂O₃ in the starting mixtures. It is clarified that heat-treatment temperature and the starting compositions of raw mixtures mainly affected B₄C nuclei number along with primary particle size and morphology of primary B₄C particles, respectively.     

Synthesis of polystyrene/poly(butyl acrylate) core–shell latex and its surface morphology

A polystyrene (PS)/poly(butyl acrylate) (PBA) composite emulsion was produced by seeded emulsion polymerization of butyl acrylate (BA) with PS seed particles which were prepared by emulsifier‐free polymerization of styrene with potassium persulfate (KPS) under a nitrogen atmosphere at 70°C for 24 h with stirring at 60 rpm and swelled with the BA monomer in an ethanol/water medium. The structure of the PS/PBA composite particles was confirmed by the presence of the characteristic absorption band attributed to PS and PBA from FTIR spectra. The particles for pure PS and PS/PBA with a low content of the BA monomer were almost spherical and regular. As the BA monomer content was increased, the particle size of the PS/PBA composite particles became larger, and more golf ball‐like particles were produced. The surface morphology of the PS/PBA composite particles was investigated by AFM and SEM. The T_g's attributed to PS and PBA in the PS/PBA composite particles were found at 110 and ?49°C, respectively. The thermal degradation of the pure PS and PS/PBA composite particles occurred in one and two steps, respectively. With an increasing amount of PBA, the initial thermal decomposition temperature increased. On the contrary the residual weight at 450°C decreased with an increasing amount of PBA. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 595–601, 2003     

Monitoring the particle size and shape in the crystallization of paracetamol from water

In this work, a technique capable of restoring bidimensional particle size distributions from images of the particles in suspension is applied to the seeded cooling crystallization of paracetamol from water. The effects of cooling rate and stirring rate on the final particle size and shape are studied and the average growth rates along different directions of particles are found to be strongly dependend on supersaturation. This observation is in line with previous studies, though in this work it has been established for the first time using populations of particles. The technique was capable of quantifying changes in particle size and shape, indicating particle sizes and shapes that correlated well with observations from electron microscopy images.     

Dispersion polymerization of aniline using hydroxypropylcellulose as stabilizer: role of rate of polymerization

Hydroxypropylcellulose (HPC) has been used as a steric stabilizer for preparing polyaniline dispersions using the route of oxidative dispersion polymerization of aniline. Using strongly acidic conditions (1 mol l^?1 HCl), low temperature of about 2 °C and a concentration of aniline as low as 0.5%, ammonium peroxodisulfate at 1.25% and hydroxypropylcellulose concentrations at 0.5–1 g d l^?1, unstable dispersions were obtained not only in water but also in aqueous alcohols (ethanol and methanol) up to at least 70 vol% alcohol. In contrast, dispersions that remained stable for at least 72 h were obtained when the alcohol concentration of the medium was as high as about 80 vol%. Kinetic studies of the polymerization systems suggested that success in the latter case was due to a lowering of the rate of polymerization. Transmission electron microscopy studies showed that dispersion particles prepared in 80 vol% alcohol media are spherical in shape and their diameter decreases with increasing stabilizer concentration. However, a change of morphology from spherical to aggregated needle‐shaped was observed when the rate was increased by increasing the aniline concentration from 0.5% to 0.75% g d l^?1 in the above recipe. The aggregated particles were found to be broken down to spherical nanoparticles when the as‐prepared dispersions were sonicated for about 30 min. The sonicated dispersion on drying showed the presence of fractal clusters of polyaniline particles in the dried film. The fractal dimension was determined to be 1.77 which agreed well with the theoretical value determined by computer simulation based on a diffusion limited cluster–cluster aggregation model in three dimensions. © 2001 Society of Chemical Industry