Influence of a mixed ionic/nonionic surfactant system and the emulsification process on the properties of paraffin emulsions

Paraffin emulsions are important in technological applications such as coating in the food packaging industry or to provide waterproof properties to particleboard panels. Small particle size (about 1.0 μm) and low polydispersity are required to form stable paraffin emulsions for these applications. In this context, the main objective of the present work is to study the influence of the surfactant system and the emulsification process on the properties of paraffin emulsions. A high pressure homogenizer was used to prepare the emulsions and its characterization was made by means of optical microscopy, laser diffraction and electrophoretic mobility measurements. Emulsions were prepared as a function of the ionic/nonionic surfactant ratio, the total surfactant concentration and the homogenization pressure. A simple theoretical model to predict the minimum particle size was used, assuming that surfactant is either at the oil-water interface or as monomer in the external phase. Experimental and theoretical data are on good agreement and the formation of stable emulsions is explained according to such model. This result could be of prime importance in order to formulate new paraffin emulsions.     

Study on the synthesis,morphology and structural analysis of fly ash–cyclodextrin composite

This study investigates the surface morphology, structure analysis and the effect on the porosity and particle size of a new composite prepared using fly ash with α and β cyclodextrins. The dry mix and solution methods were used to synthesize these composite samples. The X-ray diffraction analysis shows the new peaks that indicate the interaction between the materials. These results are in agreement with the Fourier transform infrared spectroscopic analysis that suggested the possibility of interaction of fly ash particles with cyclodextrin. Morphology changes between the composite material and the constituent materials were observed using the scanning electron microscopic. The porosity and particle size analyses show the significant changes with respect to preparation methods.     

TiO2纳米粒子制备方法对其光催化活性的影响

分别用胶溶法、金属醇盐水解法和低温水解法制备了TiO2纳米粒子;采用XRD和BET技术,测试了TiO2粒子的粒径、晶型及表面积。以庚烷的气相光催化氧化为探针反应,考察了不同方法、不同温度处理的TiO2粒子的光催化活性。结果表明,以胶溶法和金属醇盐水解法制备的TiO2粒子,随焙烧温度的增加TiO2粒子长大,晶型由锐钛矿向金红石型转变,光催化活性降低。用低温水解法,可在低温下制得金红石型TiO2粒子,但其催化活性很低。说明由原料和制备方法所决定的TiO2粒子的物理化学性质,影响其光催化行为。锐钛矿型TiO2粒子催化活性较金红石型TiO2好。这是由于前者的表面羟基含量较高且带隙能较大的缘故。     

Comparison of different chemometric and analytical methods for the prediction of particle size distribution in pharmaceutical powders

This work compares the estimation of the particle size distribution of a pharmaceutical powder using near-infrared spectroscopy (NIRS), powder flowability properties, and components concentration. The estimations were made by considering the former data blocks separately and together using a multi-block approach. The powders were based on a formulation of paracetamol as the pharmaceutical active ingredient. The reference method used to determine particle size distribution was sieving. Partial least squares methods were used to estimate the multivariate regression models, and the results were compared in terms of figures of merit. It was shown that the partial least squares methods gave similar prediction errors. Regarding the data blocks used, the NIRS block was proven the most advantageous to estimate the particle size distribution. The prediction error of the NIRS block was similar to the other data blocks with additional advantages such as less generalization problems and the possibility of its use to predict additional physical and chemical properties with an improvement to analysis time. The multi-block approach produced the worst results but nevertheless allowed a deeper understanding of the individual contributions of the data blocks in the prediction of the particle size distribution.     

Effect of solvent type on the nanoparticle formation of atorvastatin calcium by the supercritical antisolvent process

The aims of this study were to identify how the solvent selection affects particle formation and to examine the effect of the initial drug solution concentration on mean particle size and particle size distribution in the supercritical antisolvent (SAS) process. Amorphous atorvastatin calcium was precipitated from seven different solvents using the SAS process. Particles with mean particle size ranging between 62.6 and 1493.7 nm were obtained by varying organic solvent type and solution concentration. By changing the solvent, we observed large variations in particle size and particle size distribution, accompanied by different particle morphologies. Particles obtained from acetone and tetrahydrofuran (THF) were compact and spherical fine particles, whereas those from N-methylpyrrolidone (NMP) and dimethylsulfoxide (DMSO) were agglomerated, with rough surfaces and relatively larger particle sizes. Interestingly, the mean particle size of atorvastatin calcium increased with an increase in the boiling point of the organic solvent used. Thus, for atorvastatin particle formation via the SAS process, particle size was determined mainly by evaporation of the organic solvent into the antisolvent phase. In addition, the mean particle size was increased with increasing drug solution concentration. In this study, from the aspects of particle size and solvent toxicity, acetone was the better organic solvent for controlling nanoparticle formation of atorvastatin calcium.     

Investigation of particle size and heterogeneity effects on analysis of thorium in powdered ore

The particle size and heterogeneity effects on the analyte line were investigated for the analysis of powdered samples by X-ray fluorescence technique. In the analysis of samples utilizing the powder method, these effects caused serious errors with variations in particle size for the emitted intensity. These effects were minimized by applying certain treatment methods to the sample. Standard addition method was based on the measurement of the L line for thorium.     

Influence of polymer particle size on the percolation threshold of electrically conductive latex‐based composites

Monodispersed copolymer emulsions, each with a different polymer particle size, were used to investigate the effect of particle size on the electrical and thermomechanical properties of carbon black (CB)‐filled segregated network composites. These emulsions were synthesized with equal moles of methyl methacrylate and butyl acrylate, with latex particle size ranging from 83 to 771 nm. The electrical percolation threshold was found to decrease from 2.7 to 1.1 vol % CB as the latex particle size was increased. Microstructural images reveal diminished latex coalescence, and improved CB segregation, with increasing latex particle size. In general, coalescence is shown to increase for all systems with increasing CB concentration. Furthermore, all systems exhibited a similar maximum electrical conductivity plateau of 0.7 S cm^?1, albeit at lower concentration for larger latex particle size. This ability to tailor percolation threshold with latex particle size provides an important tool for manipulating electrical and mechanical properties of polymer nanocomposites. © 2011 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 49: 1547–1554, 2011     

Multivariate statistical analysis of aerosol immission data — An exemplary investigation on the North Frisian island of Pellworm

Element concentrations of 23 elements in different particle size fractions of aerosol samples from the island of Pellworm in the German Bight were analyzed by the help of total reflection X-ray fluorescence analysis. These immission data were investigated with multivariate statistical methods. Multivariate correlation analysis, as a newer chemometric method, demonstrates the autocorrelation of the immission state for different particle size fractions of dustlike aerosols. The immission of smaller particles is more strongly autocorrelated than that of larger particles. The factor analysis of each particle size fraction allows the extraction of two pollution factors for each fraction. The weights of these factors, anthropogenic and sea spray, change with size. The anthropogenic factor is more highly weighed for smaller particles, the sea spray factor is stronger in larger particles. The dependence of factor scores for smaller particles on wind direction indicates the sources of the extracted factors.     

纳米ZrO2的合成对负载Ni催化剂的CH4/CO2重整反应的影响

采用共沉淀法、醇热合成法和干法分别合成了纳米ZrO2（ZrO2 CP、ZrO2 ET和ZrO2 S）,用XRD、 BET、SEM等对其结构和表面性质进行表征,以CH4/CO2重整为探针反应研究了不同方法合成的纳米ZrO2负载Ni催化剂的催化性能,并与载体的物化性质进行了关联。实验结果表明,以干法合成的纳米介孔ZrO2 S具有较大的比表面积（133m2/g）和较好的孔径分布(4.9nm),Ni/ZrO2 S催化剂在CH4/CO2重整反应中表现出较好的催化性能。     

Study of the composition and morphology of new modifications of titanium‐magnesium catalysts with improved properties in ethylene polymerization

Data on new modifications of supported titanium‐magnesium catalysts (TMCs) with improved performance in ethylene polymerization are reported. These catalysts possess a high and stable activity, an enhanced ability to regulate molecular weight of the polymer by hydrogen, a controllable particle size at a narrow particle size distribution, and the ability to produce the polymer with an increased bulk density. Various physicochemical methods were used to obtain data on the chemical composition of novel supports and catalysts, their phase composition and crystal structure as well as the pore structure. The results obtained were used to discuss possible correlations between composition and structure of TMCs and their catalytic properties. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 2545–2558     

Study the effect of HLB of surfactant on particle size distribution of hematite nanoparticles prepared via the reverse microemulsion

Hematite nanoparticles have been synthesized via reverse microemulsion route at room temperature. The microemulsion system, contained water, chloroform, 1-butanol, and surfactant, was combined with iron nitrate solution to result iron oxide nanoparticles precipitation. Three technical surfactants, with different structures and HLB (hydrophile–lipophile balance) values were employed and the effects of the HLB values on the hematite particle size were investigated. The prepared particles were evaluated by BET, XRD and TEM techniques. These results showed that the iron oxide particle size and particle size distribution increased with increasing surfactant HLB values.     

The role of surfactant in controlling particle size and stability in the miniemulsion polymerization of polymeric nanocapsules

The influence of surfactant concentration on particle size and stability of nanocapsules with liquid cores, synthesized by an in situ miniemulsion polymerization process, was investigated. Although the role of surfactant in the synthesis of particles in the nanometer range has frequently been documented, the transition to structured particles, which almost consist of a 1:1 weight ratio of encapsulated liquid hydrophobe to polymeric shell, has not received much attention. Capillary hydrodynamic fractionation (CHDF) analyses were used to evaluate particle size. Results were subsequently used to stoichiometrically calculate the area which is occupied per surfactant molecule on the particle surface. These results were compared with “classical” miniemulsion data, i.e. data generated from the synthesis of polymeric latexes in the presence of a hydrophobe, but at a much lower hydrophobe:monomer ratio as was used here. The surface coverage per surfactant molecule could be related to the surface tension of the latex, thus providing a relationship between particle size and stability. CHDF was furthermore used to investigate particle size after grafting of a secondary PMMA shell. Data obtained from CHDF experiments were in all cases confirmed by TEM analysis of the synthesized particles. To conclude, the synthesis of nanocapsules with liquid cores could be successfully scaled-up, with retention of all the characteristics of the final latex.     

Effects of the physicochemical properties of the emulsion formulation on the bioavailability of ethyl 2-chloro-3-[4-(2-methyl-2-phenylpropyloxy)phenyl]propionate in rats

The effect of the physicochemical properties of the emulsion formulation on the absorption of ethyl 2-chloro-3-[4-(2-methyl-2-phenylpropyloxy)phenyl]propionate (AL-294) in rats and dogs was studied. When emulsions of different particle sizes were administered to rats, the higher the ratio of Tween-80 to the drug was, the smaller was the particle size and the higher was the absorption. When the emulsions of similar particle size (2 microns) with different Tween-80 ratios were administered to rats, no significant difference was observed in the extent of absorption. The absorption of AL-294 was correlated with the dissolution rate from the oil phase to the aqueous phase but not correlated with the amount of AL-294 solubilized by Tween-80. These results indicate that the absorption of AL-294 from emulsions depends mainly on the particle size in the gastro-intestinal fluid and that Tween-80 serves only to reduce the particle size in the emulsion.     

石墨烯负载的金属氧化物纳米颗粒的可控制备及催化性能

采用直接浸渍法、过氧化氢均相氧化沉积法和氨水催化水解法制备了石墨烯负载的铁、钴、镍金属氧化物纳米颗粒.研究了三种沉积方法对颗粒尺寸分布的影响;采用透射电子显微镜、傅里叶变换红外光谱、X射线衍射和X射线光电子能谱表征了催化剂的形貌与结构.用过氧化氢均相氧化沉淀法可制得粒径分布最均匀的纳米颗粒.过氧化氢的氧化作用可使石墨烯表面的氧化基团含量最大化,为纳米颗粒提供了足够的吸附与成核点.氨水加速了金属离子的水解与成核,导致纳米颗粒的粒径增大与不均.以苯甲醇氧化为探针反应考察了催化剂的性能.催化剂的活性按以下顺序逐渐下降:过氧化氢辅助沉积法>直接浸渍法>氨水催化水解法,与纳米颗粒尺寸增长趋势一致.纳米催化剂颗粒尺寸与其活性的良好关联性显示,发展石墨烯负载尺寸可控的纳米催化剂的方法具有重要意义.     

纳米Au/TS-1催化剂的制备及用于甲醇羰基化体系

采用负压沉积沉淀法、等体积浸渍法、负压等体积浸渍法等方法制备了纳米Au/TS-1催化剂,研究了深床焙烧和等离子体焙烧,以及焙烧温度和焙烧气氛对催化剂中纳米金粒子大小和催化性能的影响,并采用ICP、TEM、XRD、UV-vis、XPS对催化剂金粒子进行了物化性能表征,采用甲醇羰基化制乙酸甲酯反应表征催化性能.结果表明,不同制备方法、不同焙烧方法、不同焙烧温度和焙烧气氛对负载型纳米Au/TS-1沸石分子筛催化剂中金粒子的大小、形貌、物化性质和催化性能有明显影响.其中,3种制备方法中,氢气气氛下焙烧均比空气和氮气气氛下焙烧得到的催化剂的金粒子尺寸更小,分散更均匀,约为5~10 nm.与其它方法相比,负压沉积沉淀法可制得分散更均匀的金粒子,Au/TS-1沸石催化剂中的金粒子尺寸更小,平均粒径为1~5 nm.催化性能评价结果显示,3种方法制备出的负载型金催化剂用于催化甲醇羰基化制乙酸甲酯反应体系中,甲醇的转化率分别为85%、75%、60%,乙酸甲酯选择性可高达68%,反应温度200℃为最好.     

Particle size effects on the thermal behavior of hematite

Hematite with different particle sizes was obtained through isothermal annealing and mechanochemical ball-milling methods. The hematite phase is very stable under air atmosphere. The thermal stabilities of hematite under argon atmosphere were characterized by thermal analysis studies up to 800 °C using a simultaneous DSC–TG technique. The lattice parameters a and c of hematite with different particle sizes were extracted from the Rietveld structural refinement of powder X-ray diffraction patterns. Decomposition of hematite into a lower oxidation state in inert argon atmosphere was studied by the TG experiments for the first time and the enthalpy associated with the decomposition reaction was determined from the DSC studies. Particle size has a strong effect on the thermal behavior of hematite samples. Ball-milled hematite samples with smaller particle size showed that the phase transformation was extended to higher temperature range with larger enthalpy. Hematite with larger average particle size showed higher stability under argon atmosphere.     

Filler size effects on the conductivity of polymer nanocomposites: Semiconductive phthalocyanine nanoparticles in epoxy matrices

Three Cobalt(III) phthalocyanine (Phthalcon) powders with different particle sizes and chemical compositions, but almost equal XRD spectra and powder conductivity were synthesized and used as conductive fillers in crosslinked epoxy matrices. Two of these Phthalcons are new compounds. The relation between the conductivity of the composites and the type and amount of filler used was determined. The influence of particle size and chemical composition on this relation appeared to be minimal. These composites had a percolation threshold of 0.9 vol % and a maximum volume conductivity of 10^?7 S/cm. Detailed analysis showed that the particle networks have very similar fractal structures and that they are likely to be formed by diffusion limited cluster‐cluster aggregation during processing. Evidence is presented that these particle networks are formed at an early stage of crosslinking and that the charge transfer between particles in the networks is neither limited by the Phthalcon particle size, nor by the presence of polymer matrix between the particles. The maximum volume conductivity of these composites is likely to be limited by the amount of filler used, the crystal structure defects on the particle surface, and the fractality and the imperfection of the particle networks. The impact of these findings on the conductivity of other polymer nanocomposites is discussed. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1079–1093, 2008     

焙烧方法和焙烧条件对纳米Au/HZSM-5催化剂金粒径和催化性能的影响

采用负压沉积沉淀法制备了纳米Au/HZSM-5催化剂前体,研究了深床焙烧和等离子体焙烧两种方法,以及焙烧温度和焙烧气氛对催化剂中纳米金粒径和催化性能的影响,并采用ICP、TEM、XRD、UV-vis、XPS等表征方法对催化剂金粒子进行了物化性能表征,采用合成气羰基化制乙酸甲酯反应表征催化性能。结果表明,不同焙烧方法和不同焙烧温度及气氛对负载型纳米Au/HZSM-5催化剂中金粒径、形貌、物化性质和催化性能有明显影响。其中,以等离子体焙烧方法在500℃氮气气氛下制备的纳米1.86%Au/HZSM-5催化剂中的金粒径最小,为2-5 nm。用于催化合成气羰基化制乙酸甲酯反应,原料中CO的转化率为67%,乙酸甲酯选择性可达78%。     

Effect of synthesis method variables on particle size in the preparation of homogeneous doped nano ZnO material

Homogeneous doped ZnO nanoparticles were synthesised by the Pechini method. A statistical experimental design was used to study the effects of the synthesis method variables on the particle size. The variables were the molar ratios of the reagents and the calcination temperature. The results indicated that the calcination temperature was the only factor that had a significant effect on the particle size. The particle size of ZnO varied between 16 and 76 nm with calcination temperatures of 400–800 °C. The homogeneity was studied by the ICP-MS technique, and the powders were found to be highly homogeneous.     

Effect of PVA surrounding medium on ZnSe nanoparticles: size, optical, and electrical properties

Polyvinyl alcohol (PVA) matrix was used to confine the particle size of ZnSe nanocrystallites as well as the variation of zinc (Zn) to selenium (Se) ion ratio which showed a remarkable decrease on the particle size as this ratio increased. The particle size decrease was monitored from the UV-vis absorption measurement as well as photoluminescence which suffered a blue shift with particle size decrease. The particle size was characterized with the aid of X-ray diffraction (XRD). The Raman spectra showed that, as the particle size increases, the peak position of the line centers (LO) mode were found to be red shifted from 239 to 234 cm(-1), accompanied by an increase in the full-width at half-maximum (FWHM). The electrical measurements and FT-IR spectra (overtone and normal) band vibration were used to study the effect of ZnSe NPs size on the PVA matrix.