Nickel and iron nano-particles in natural rubber composites

In this work, the mechanical, electrical, and magnetic properties of natural rubber (NR) composites containing iron or nickel nanoparticles at different percentage varying from 0 to 120 phr (part of magnetic particle per hundred rubber) have been investigated at room temperature. It was found that the optimum concentration of magnetic fillers in NR is 30 phr, which improve the rheometric characteristics and physico-mechanical properties. Magnetic properties of the rubber composites have been investigated using vibrating sample magnetometer (VSM) at room temperature. The magnetic measurements show superparamagnetic behavior for all Ni and Fe nanoparticles percentage. The electrical measurements show a strong dependency of the conductivity on the percentage of magnetic nanoparticles.     

不同添加剂对聚偏氟乙烯膜结构和性能的影响

利用非溶剂相转化法(NIPS),以N,N-二甲基乙酰胺(DMAc)为溶剂,聚乙烯吡咯烷酮(PVPK30)和一水合氯化锂(LiCl·H2O)为混合添加剂,改变PVPK30-LiCl·H2O配比得到不同性能和结构的聚偏氟乙烯(PVDF)膜。考察了不同种类添加剂(PVP、LiCl·H2O、H2O和PEG200)及不同配比的PVPK30-LiCl·H2O添加剂对PVDF成膜分相延时时间、分相速率的影响。实验结果表明,采用PVPK30为添加剂,铸膜液呈瞬时分相行为,膜通量很大;增大混合添加剂中PVPK30/LiCl·H2O的比例,会增加液液分相速率,使膜结构中的大孔贯通整个膜结构。     

Influence of electrolyte and poloxamer 188 on the aggregation kinetics of solid lipid nanoparticles (SLNs)

Solid lipid nanoparticles (SLNs) have attracted increasing attention as colloidal drug carriers due to theirs advantages including low toxicity, drug targeting and modified release. However, undesired particle aggregation in aqueous dispersions would limit the applicability of SLNs for drug delivery. The purpose of the present article is to investigate the aggregation behavior of the SLNs and quantitatively evaluate how the concentration of NaCl and F68 affect the stability of the SLNs. The early stage aggregation kinetics of the SLNs was investigated over a wide range of NaCl concentrations by employing dynamic light scattering (DLS). In the presence of the NaCl, aggregation kinetics of the SLNs exhibited reaction-limited (slow) and diffusion-limited (fast) regimes. These results indicated that the aggregation behavior of these new nanoparticles can be well explained by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The critical coagulation concentration (CCC) of SLNs containing 0.0%, 0.1%, 0.5%, 2.0%, and 4.0% of Poloxamer 188 (F68) was 416, 328, 519, 607, and 602 mM, respectively, suggesting that the F68 influences the aggregation behavior of the SLNs. F68 made the SLNs more sensitive to the electrolyte when its concentration is low (0.1%), the bush of the polymer F68 has a bridging effect that accelerated the aggregation process of the SLNs. However, at the high concentration, F68 can provide the steric repulsion to the nanoparticles, which effectively stabilized the SLNs dispersions.     

Size- and shape-controlled synthesis of colloidal gold through autoreduction of the auric cation by poly(ethylene oxide)-poly(propylene oxide) block copolymers in aqueous solutions at ambient conditions

Gold nanoparticles with an average diameter in the range 5-20?nm have been synthesized from hydrogen tetrachloroaureate (III) hydrate (HAuCl(4)·3H(2)O) in air-saturated aqueous PEO-PPO-PEO block copolymer solutions at ambient temperature in the absence of any other reducing agent (PEO: poly(ethylene oxide), PPO: poly(propylene oxide)). The particle size was controlled by the block copolymer concentration and PEO and PPO block lengths. Our findings indicate that longer PEO blocks lead to an increase in particle size because of an increase in reaction activity. Adsorption of PO segments on gold nanoparticles seems to prevent particle growth from aggregation, and results in small particle size and high colloidal stability. An increase of the HAuCl(4) concentration causes a change in the particle shape from spherical to triangular or hexagonal nanoplates.     

高分子添加剂PVPK30对酚酞基聚芳醚砜超滤膜成膜性能的影响

采用凝胶相转化法,以新型耐高温工程塑料——含酚酞侧基的聚芳醚砜(PES-C)为膜材料,N,N-二甲基乙酰胺(DMAC)为溶剂,通过改变铸膜液中添加剂聚乙烯吡咯烷酮(PVPK30)的含量,在平板刮膜机上制备了一系列超滤膜。考察了添加剂PVPK30含量对铸膜液黏度、凝胶速度、膜性能和结构的影响,对PES-C/DMAC铸膜液体系中添加剂PVPK30的作用规律进行了研究。     

Preparation of gold nanoparticles in an aqueous medium using 2-mercaptosuccinic acid as both reduction and capping agent

Monolayer protected gold nanoparticles with diameters above 10 nm were prepared by a simple, one step reaction in water. 2-mercaptosuccinic acid (MSA) was used both as reduction agent for hydrogen tetrachloroaurate (HAuCl4) and as stabilizing agent for the gold nanoparticles. Size distribution and surface chemistry were investigated by UV-Vis spectroscopy, scanning electron microscopy and Fourier Transform Infrared Spectroscopy. Particle size can be controlled by adjusting the molar portions of the reactants. The resulting particles are efficiently stabilized against aggregation when MSA is used in a concentration of 40% and above. Below a minimum MSA concentration a long-term particle growth is observed.     

纳米四氧化三铁/埃洛石复合材料及水基磁性流体的制备

以天然埃洛石纳米管(HNTs)为载体,采用部分还原共沉淀法,在HNTs的管内、外沉积Fe3O4纳米晶粒.利用HNTs独特的空间结构,所制备的Fe3O4粒子尺寸为10-30nm,并有效控制其粒子团聚.XRD表明Fe3O4/HNTs复合材料为Fe3O4和埃洛石两相组成,不同温度(373,423,523K)热处理条件下该复合...     

Quantitative characterization of nanoparticles in blood by transmission electron microscopy with a window-type microchip nanopipet

Transmission electron microscopy (TEM) is a unique and powerful tool for observation of nanoparticles. However, due to the uneven spatial distribution of particles conventionally dried on copper grids, TEM is rarely employed to evaluate the spatial distribution of nanoparticles in aqueous solutions. Here, we present a microchip nanopipet with a narrow chamber width for sorting nanoparticles from blood and preventing the aggregation of the particles during the drying process, enabling quantitative analysis of their aggregation/agglomeration states and the particle concentration in aqueous solutions. This microchip is adaptable to all commercial TEM holders. Such a nanopipet proves to be a simple and convenient sampling device for TEM image-based quantitative characterization.     

Influence of electrolyte and poloxamer 188 on the aggregation kinetics of solid lipid nanoparticles (SLNs)

Solid lipid nanoparticles (SLNs) have attracted increasing attention as colloidal drug carriers due to theirs advantages including low toxicity, drug targeting and modified release. However, undesired particle aggregation in aqueous dispersions would limit the applicability of SLNs for drug delivery. The purpose of the present article is to investigate the aggregation behavior of the SLNs and quantitatively evaluate how the concentration of NaCl and F68 affect the stability of the SLNs. The early stage aggregation kinetics of the SLNs was investigated over a wide range of NaCl concentrations by employing dynamic light scattering (DLS). In the presence of the NaCl, aggregation kinetics of the SLNs exhibited reaction-limited (slow) and diffusion-limited (fast) regimes. These results indicated that the aggregation behavior of these new nanoparticles can be well explained by the classical Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. The critical coagulation concentration (CCC) of SLNs containing 0.0%, 0.1%, 0.5%, 2.0%, and 4.0% of Poloxamer 188 (F68) was 416, 328, 519, 607, and 602?mM, respectively, suggesting that the F68 influences the aggregation behavior of the SLNs. F68 made the SLNs more sensitive to the electrolyte when its concentration is low (0.1%), the bush of the polymer F68 has a bridging effect that accelerated the aggregation process of the SLNs. However, at the high concentration, F68 can provide the steric repulsion to the nanoparticles, which effectively stabilized the SLNs dispersions.     

Study of viscosity and specific heat capacity characteristics of water-based Al2O3 nanofluids at low particle concentrations

In this paper, the specific heat capacity and viscosity properties of water-based nanofluids containing alumina nanoparticles of 47 nm average particle diameter at low concentrations are studied. Nanofluids were prepared with deionised water as base fluid at room temperature by adding nanoparticles at low volume concentration in the range of 0.01%–1% to measure viscosity. The effect of temperature on viscosity of the nanofluid was determined based on the experiments conducted in the temperature range of 25°C to 45°C. The results indicate a nonlinear increase of viscosity with particle concentration due to aggregation of particles. The estimated specific heat capacity of the nanofluid decreased with increase of particle concentration due to increase in thermal diffusivity. Generalised regression equations for estimating the viscosity and specific heat capacity of nanofluids for a particular range of particle concentration, particle diameter and temperature are established.     

The role of surfactant in the miniemulsion polymerization of biodegradable polyurethane nanoparticles

The influence of surfactant type and concentration on particle size, formulation yield and stability of the polyurethane (PUR) nanoparticles synthesized by miniemulsion polymerization was investigated. SDS, Tween 80 and Pluronic F68 were employed as surfactants in concentration ranging from 5 to 20% (vs monomer concentration). The surfactant SDS was found not efficient in our system, resulting in a low formulation yield (about 53%), two particle size distributions and zeta potential equal to − 52.3mV. On the other hand, the nonionic surfactants gave monomodal particle size distribution, good yields (> 85%) and zeta potential around to− 24mV. The particles synthesized with Tween 80 or Pluronic F68 were very similar to each other in terms of efficiency, particle size distribution and zeta potential. For instance, the particle diameter slightly decreases from 292nm to 261nm as the amount of Tween 80 surfactant increases from 5 to 20wt.% vs monomer. Moreover, we have observed that a concentration of at least 5wt. % of Tween 80 was necessary to favor particle stability and therefore to avoid aggregation.     

Preparation and characterization of NiO nanoparticles through calcination of malate gel

NiO nanoparticles have been successfully prepared by calcining malate gel, using basic nickel carbonate (BNC) and malic acid as the raw materials and H₂O as the solvent. The reaction was studied by TG–DTA, XRD and FT-IR. The particle size and morphology of NiO nanoparticles was characterized by TEM. The results show that nickel malate could be formed by the reaction of BNC and malic acid; the gel was composed of nickel malate and residual malic acid; the precursor can translate into NiO nanoparticles completely at 400 °C under the air, and the as-prepared sample has a cubic crystal structure with about 14 nm of average diameter by the Scherrer formula. The NiO calcined at 400 °C for 1 h was of narrow particle size distribution, weak agglomeration and small particle size. The particle size of NiO increased with the increase in temperature. Compared with other methods, the developed method is simple and the raw materials were inexpensive, so that it has the potential for further scale-up application in the industry. Furthermore, the reason for the metallic nickel formation in the course of the preparation was explained.     

Nanoparticles from polylactide and polyether block copolymers: formation, properties, encapsulation, and release of pyrene--fluorescent model of hydrophobic drug

Polylactide-b-polyglycidol-b-poly(ethylene oxide) terpolymers and their derivatives with carboxyl and 4-(phenylazo)phenyl labels in polyglycidol blocks were used for formation of nanoparticles. Nanoparticles were produced by self assembly of terpolymer macromolecules in water above the critical aggregation concentration and by dialysis of terpolymer solutions in 1,4-dioxane against water. For terpolymers with 4-(phenylazo)phenyl labels critical aggregation concentrations increased after irradiation with UV light (300 < lambda < 400 nm) inducing conformational change of the label from trans- to cis-conformation. Diameters of nanoparticles obtained by self-assembly of macromolecules ranged from 20 to 44 nm. Dialysis yielded nanoparticles with bimodal diameter distribution. One fraction had diameters below 35 nm and diameters of the second fraction were in a range from 350 to 2300 nm, depending on terpolymer structure. Mixtures of terpolymers with poly(L,L-lactide) and poly(D,D-lactide) blocks yielded nanoparticles with diameters from 350 to 440 nm. Pyrene was incorporated into nanoparticles by partition between solution and nanoparticles or directly during particle formation by dialysis. Monitoring of pyrene release from nanoparticles suggests that a fraction of this compound was entrapped into the polylactide core whereas the remaining one was located in the polyether rich shell. The release from shells is faster for nanoparticles made from copolymers with carboxyl labels in polyglycidol blocks.     

聚合物保护纳米镍粉的制备与表征

采用改进的多元醇液相还原工艺,用 1,2 丙二醇作还原剂,在聚乙烯吡咯烷酮(PVP)稳定剂保护下,通过调整反应条件,在均相成核条件下,合成了粒径 25nm,具有面心立方晶体结构的纳米镍粉,运用XRD、TEM、SAED、FTIR 等微观分析手段,研究了NaOH浓度、PVP加入量等因素对制备纳米镍粉的影响。研究发现NaOH可以提高成核速率,调节颗粒生长溶质浓度,是形成粒径均匀纳米颗粒的重要条件。适量的聚合物保护剂,可以阻止成核颗粒生长,减小粒径,防止颗粒团聚,FTIR分析显示PVP分子与纳米颗粒之间存在化学作用。     

Synthesis of high concentration colloid solution of silica-coated AgI nanoparticles

Methods for high concentration silica-coated silver iodide (AgI/SiO2) particles, which could be practically used as X-ray contrast agent, were examined. The first was a single-step method, which was to prepare AgI nanoparticles at an AgI concentration of 5 x 10(-3) M and coat the AgI nanoparticles with silica shell by a St?ber method. The second was a multiple-step method, which was to repeat a step for preparing a AgI/SiO2 particle colloid solution with 10(-3) M AgI 5 times for adjusting a final AgI concentration to 5 x 10(-3) M. In the two methods, dominant particle aggregation took place, though core-shell particles were also produced. The third was a salting-out method, which was to salt out AgI/SiO2 particles in their colloid solution prepared at an AgI concentration of 10(-3) M, remove supernatant by decantation, and redisperse the particles in a fresh solvent. Consequently, AgI/SiO2 particles with an AgI concentration as high as 0.05 M were successfully prepared with the salting-out method, and their core-shell structure was not damaged during the salting-out.     

Physicochemical interaction mechanism between nanoparticles and tetrasaccharides (stachyose) during freeze-drying

Nanoparticle suspensions are thermodynamically unstable and subject to aggregation. Freeze-drying on addition of saccharides is a useful method for preventing aggregation. In the present study, tetrasaccharides (stachyose) was employed as an additive. In addition, we hypothesize the interactive mechanism between stachyose and the nanoparticles during freeze-drying for the first time. The mean particle size of the rehydrated freeze-dried stachyose-containing nanoparticles (104.7?nm) was similar to the initial particle size before freeze-drying (76.8?nm), indicating that the particle size had been maintained. The mean particle size of the rehydrated normal-dried stachyose-containing nanoparticles was 222.2?nm. The powder X-ray diffraction of the freeze-dried stachyose-containing nanoparticles revealed a halo pattern. The powder X-ray diffraction of the normally dried stachyose-containing nanoparticles produced mainly a halo pattern and a partial peak. These results suggest an interaction between the nanoparticles and stachyose, and that this relationship depends on whether the mixture is freeze-dried or dried normally. In the case of normal drying, although most molecules cannot move rapidly thereby settling irregularly, some stachyose molecules can arrange regularly leading to some degree of crystallization and potentially some aggregation. In contrast, during freeze-drying, the moisture sublimed, while the stachyose molecules and nanoparticles were immobilized in the ice. After sublimation, stachyose remained in the space occupied by water and played the role of a buffer material, thus preventing aggregation.     

The size-controlled synthesis of uniform Mn2O3 octahedra assembled from nanoparticles and their catalytic properties

Uniform Mn(2)O(3) octahedral nanoparticles were synthesized by a mediated N, N-dimethylformamide (DMF) solvothermal route. On the basis of a time-dependent experiment, we propose that the Mn(2)O(3) octahedra were formed through oriented aggregation of primary nanocrystals. Meanwhile, poly(vinyl-pyrrolidone) (PVP) was applied as a surfactant to facilitate the oriented aggregation of small Mn(2)O(3) nanoparticles into octahedral crystallites. By tuning the amount of Mn(NO(3))(2), particles with average sizes 1 μm to 300 nm, with a narrow size distribution, could be fabricated. The catalytic test results show that the as-obtained Mn(2)O(3) octahedra exhibited desirable CO catalytic oxidation properties and the surface texture and particle size significantly affected the catalytic activity. By contrast, the larger Mn(2)O(3) octahedral nanoparticles prepared at a lower concentration of Mn(NO(3))(2) exhibited relatively high activities.     

Fabrication of gold nanoparticle/multi walled carbon nanotube hybrids by in situ reaction in water using poly(acryloyl beta-alanine)

Fabrication of a hybrid consists of gold nanoparticles and multi walled carbon nanotubes (MWCNTs) with the help of poly (amino acid) was investigated. Poly(acryloyl beta-alanine) was synthesized by precipitation polymerization in tetrahydrofuran. The polymers were used to form hybrids with MWCNTs in aqueous media. Subsequently, the polymer functionalized MWCNTs were fabricated by in situ formed gold nanoparticles. The fabrication by gold nanoparticles was confirmed by transmission electron microscopic analyses. The fabrication was attempted with different concentrations of lithium auric chloride solutions in the range of 0.1-1.2 mM in water. The lower concentration of the gold precursor solution resulted in the formation and attachment of gold nanoparticles without aggregation while the higher concentration above 1.0 mM led to the aggregation of gold nanoparticles. The gold nanoparticles were observed only on the surface of MWCNTs and none was in the bulk aqueous phase.     

Mechanical properties and interfaces of zirconia/nickel in micro - and nanocomposites

The effect of processing parameters on the hardness and toughness of yttria-doped zirconia/nickel nanocomposites is reported. The experimental procedure consists in the deposition of nickel nanoparticles––previously obtained from nickel nitrate salts––on the surface of the zirconia powders. Slight changes in the proposed processing route (i.e. drying temperature of powders) gave rise to a noticeable decrease in the hardness (15–20%). However, no effect was observed on the toughness values in the studied composition range (0–30 vol% Ni). These results have been explained in terms of the nickel particle size distribution and agglomeration due to differences in the melting temperature of nickel nanoparticles, and because of epitaxial growth of nickel on the zirconia surface. For comparison purposes, samples obtained following a conventional wet-processing route starting from micrometric nickel and yttria-doped zirconia powders were prepared. In this case, the toughness is strongly dependent on the nickel fraction. This fact has been related to the weak bonding between metal and ceramic particles.     

Kinetics of gas phase reduction of nickel chloride in preparation for nickel nanoparticles

We investigated the chemical kinetics of NiCl₂ reduction to apply to the synthesis of nickel nanoparticles in a tubular furnace reactor. The conversion of NiCl₂ increased monotonically with reaction temperature up to 99% at 950 °C, and in turn, the rate constant of the reaction increased from 78 to 286 with an increase in the temperature from 800 to 950 °C. The reaction rate was estimated to be the first order with respect to chloride concentration, and the rate constant obeyed the Arrhenius law, of which the activation energy and pre-exponential factor were 103.79 kJ/mol and 7.34 × 10⁶ min⁻¹, respectively. Taking advantage of the kinetics, we synthesized crystalline nickel nanoparticles with average primary particle size ranging from 31 to 106 nm by systematically controlling the reactor temperature and chloride concentration.