Colloidal processing of low-concentrated zirconia nanosuspension using osmotic consolidation

Colloidal processing was applied to a water-based suspension with 5 vol% zirconia nanoparticles of 10–15 nm in size. The nanosuspension was concentrated by evaporation or by a newly developed method of osmotic dehydration. The viscosity and stability of concentrated nanosuspensions were investigated. Osmotic consolidation of both nanosuspensions, concentrated by evaporation and osmotically dehydrated, was performed in a solution of polyethylene oxide separated from the nanosuspensions using a permeable membrane. Osmotic pressure generated a water flow from the nanosuspension to the polymer solution, concentrating the nanosuspension and eventually consolidating the nanoparticle network. The pore size distribution in dried nanoparticle compacts and pore size evolution during sintering were evaluated and discussed. The nanozirconia compacts were densified by pressure-less sintering to a relative density of up to 99.7% while maintaining the nanocrystalline structure.     

High‐Throughput Miniaturized Screening of Nanoparticle Formation via Inkjet Printing

The self‐assembly of specific polymers into well‐defined nanoparticles (NPs) is of great interest to the pharmaceutical industry as the resultant materials can act as drug delivery vehicles. In this work, a high‐throughput method to screen the ability of polymers to self‐assemble into NPs using a picoliter inkjet printer is presented. By dispensing polymer solutions in dimethyl sulfoxide (DMSO) from the printer into the wells of a 96‐well plate, containing water as an antisolvent, 50 suspensions are screened for nanoparticle formation rapidly using only nanoliters to microliters. A variety of polymer classes are used and in situ characterization of the submicroliter nanosuspensions shows that the particle size distributions match those of nanoparticles made from bulk suspensions. Dispensing organic polymer solutions into well plates via the printer is thus shown to be a reproducible and fast method for screening nanoparticle formation which uses two to three orders of magnitude less material than conventional techniques. Finally, a pilot study for a high‐throughput pipeline of nanoparticle production, physical property characterization, and cytocompatibility demonstrates the feasibility of the printing approach for screening of nanodrug delivery formulations. Nanoparticles are produced in the well plates, characterized for size and evaluated for effects on metabolic activity of lung cancer cells.     

Problems in Characterizing Transparent Particles by Laser Light Diffraction Spectrometry

Laser diffraction spectrometry is an optical technique that uses information from the scattered light distribution to determine particle size distribution. When laser light diffraction spectrometry is used with small transparent particles, secondary scattering effects are present. As a result, the particle size distribution determined via the Fraunhofer approximation predicts the existence of a fine particle fraction that in reality does not exist. Application of the Mie theory eliminates the false prediction of a fine particle fraction, but only if the material's refractive index and absorption index are exactly known. This phenomenon was confirmed theoretically for transparent particles by simulating the scattered light distribution and experimentally by comparing results with those obtained using non‐optical methods.     

HAN基液体推进剂喷雾场液滴尺寸分布的简化模型

为了建立HAN基液体推进剂喷雾场液滴尺寸分布的简化模型,基于最大熵原理,在质量守恒与概率和为定值的约束条件下,用拉格朗日因子法则推导了液滴尺寸分布函数,将该函数应用于HAN基液体推进剂模拟工质喷雾场液滴尺寸的预估;采用相位多普勒粒子动态分析仪(PDA)测量了HAN基液体推进剂模拟工质在1.8~2.6MPa喷射压力下对撞式喷嘴雾化液滴尺寸分布;通过最小二乘法优化Nukiyama-Tanasawa分布函数式中的q值对数目微分分布进行了修正,拟合得到q值与喷射压力p之间的函数关系为q(p)=-0.344p2+1.525p+1.268。结果表明,计算得出的液滴尺寸数目微分分布与HAN基液体推进剂喷雾场实测数据变化趋势相符,表明建立的液滴尺寸分布模型是合理的。     

Analysis of the Stability of Metal Working Fluid Emulsions by Turbidity Spectra

The physical stability of emulsions can be related to changes in the droplet size distribution over time. Stability control of emulsions used as metal working fluids is an important factor for the machining industry due to the decreased performance of aged and broken emulsions. Results of turbidimetric spectra measurements of metal working fluids for process control purposes and emulsion stability monitoring are discussed. Metal working emulsions were artificially destabilized by admixing salts which resulted in droplet coagulation. The destabilization process was investigated by measuring the droplet size distribution and the turbidity spectra over time. The results were evaluated based on quantitative criteria proposed in the literature. The applicability of these criteria to evaluate metal working fluids during machining operations is discussed.     

Determination of crystal size distributions in alumina ceramics by a novel X‐ray diffraction procedure

A novel X‐ray diffraction based method is presented, capable of determining volume‐based crystal size distribution (CSD) of polycrystalline materials and crystalline powders with unprecedented sampling statistics; the method is named fast X‐ray diffraction crystal size distribution analysis (FXD‐CSD). FXD‐CSD can be performed with standard laboratory X‐ray diffractometers equipped with a position sensitive detector and uses a software package written in Python for the data analysis. FXD‐CSD is a destruction‐free and generally applicable method to establish CSDs of polycrystalline materials as well as powders for sizes well below 1 μm up to about 100 μm; it even allows for studies of samples enclosed in complex environments, e.g., for in situ measurements in a furnace or in a pressure cell. To show the capability of the method the microstructural evolution of four alumina substrates with different time‐spans of sintering (4, 8, 16, and 24 hour at 1600°C) is investigated via FXD‐CSD and SEM imaging. The corresponding CSDs and average grain sizes are determined, results obtained by FXD‐CSD and the line‐intersection methods are compared and clear evidence for the presence of abnormal grain growth (AGG) during sintering is shown. From three tested probability density functions (PDF) describing the CSDs a log‐normal PDF fits best to the volume based CSDs; the method provides size distributions with unprecedented precision opening the way to a systematic and meaningful comparison between theoretically predicted and observed CSDs.     

Kinetic Modeling of the Gas Antisolvent Process for Synthesis of 5‐Fluorouracil Nanoparticles

Mathematical modeling for 5‐fluorouracil (5‐FU) nanoparticle synthesis via gas antisolvent (GAS) process was investigated. 5‐FU was precipitated from a dimethyl sulfoxide (DMSO) solution using CO₂ as antisolvent. The particle size was controlled by nucleation and growth rates, therefore, the kinetic modeling study is essential. Thermodynamic modeling was applied to determine optimal operating conditions for experimental 5‐FU synthesis. Kinetic parameters were evaluated by fitting the particle size distribution predicted by the model to experimental data. The experimental and modeling results indicated that the particle size decreased with increasing the antisolvent addition rate.     

Distinguishing between Two Aerosol Size Distributions

A technique is presented to quantitatively determine the similarity or dissimilarity between aerosol size distributions measured with cascade impactors. The method is useful regardless of the mass loading as long as an accurate size distribution can be obtained from the data. The technique uses lognormal best fits of the data and an augmented Student's t-test to quantitatively determine the difference between the two particle size distributions.     

Determination of the relative importance of process factors on particle size distribution in suspension polymerization using a Bayesian experimental design technique

The use of a Bayesian experimental design technique to determine the relative importance of factors that control particle size distribution (PSD) in suspension copolymerization of styrene and divinylbenzene is reported. Six factors and two responses are considered in this study. The experimental trials are of the two‐level factorial type designed with a Bayesian method. The experiments were carried out in a 5‐L pilot plant reactor. The matrix of variances of the parameter means (the prior knowledge) was estimated with the use of a preliminary compartment‐mixing (CM) model for PSD in suspension polymerization and our subjective judgement (process understanding). The responses, mean particle size and coefficient of variation, were calculated from distributions obtained with a Coulter particle counter. The results of this study provided the criteria needed to guide the future improvement of our CM‐PSD model in a balanced and effective way. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:5577–5586, 2006     

Monte Carlo modeling of fluidized bed coating and layering processes

A stochastic modeling approach based on a Monte Carlo method for fluidized bed layering and coating is presented. In this method, the process is described by droplet deposition on the particle surface, droplet drying and the formation of a solid layer due to drying. The model is able to provide information about the coating coverage (fraction of the particle surface covered with coating), the particle‐size distribution, and the layer thickness distribution of single particles. Analytical solutions for simplified test cases are used to validate the model theoretically. The simulation results are compared with experimental data on particle‐size distributions and layer thickness distributions of single particles coated in a lab‐scale fluidized bed. Good agreement between the simulation results and the measured data is observed. © 2016 American Institute of Chemical Engineers AIChE J, 62: 2670–2680, 2016     

Droplet‐Shooting and Size‐Filtration (DSSF) Method for Synthesis of Cell‐Sized Liposomes with Controlled Lipid Compositions

We report a centrifugal microfluidic method, droplet‐shooting and size‐filtration (DSSF), for the production of cell‐sized liposomes with controlled lipid compositions. This involves the generation of large and small droplets from the tip of a glass capillary and the selective transfer of small droplets through an oil‐water interface, thus resulting in the generation of cell‐sized liposomes. We demonstrate control of the microdomain formation as well as the formation of asymmetric lipid bilayer liposomes of uniform size by the control of lipid composition. The DSSF method involves simple microfluidics and is easy to use. In addition, only a small volume (0.5–2 μL) of sample solution is required for the formation of hundreds of cell‐sized liposomes. We believe that this method can be applied to generate cell‐sized liposomes for a wide variety of uses, such as the construction of artificial cell‐like systems.     

Generation and Deposition of Organic Nanoparticles in a Liquid Ring Pump

A new method for the production of organic nanoparticles or nanosuspensions in a liquid ring vacuum pump is presented. A hot carrier gas charged under vacuum conditions with poorly water‐soluble organic substances is compressed and simultaneously cooled by the partially evaporating sealant water of the liquid ring vacuum pump. During compression and quenching, the gas‐vapor mixture becomes highly supersaturated and aerosol formation initiated by homogeneous nucleation occurs in the compression chambers between the impeller blades of the pump. The thus generated gas‐borne droplets or solid particles are mainly trapped and enriched in the sealant ring liquid, which is discharged, separated from the carrier gas in an external separator and returned to the pump. Experiments yielded aqueous nanosuspensions of insoluble organic substances with typical particle sizes between 50 and 300 nm, as well as foam in the external gas‐liquid separator. The foam showed stable structures due to incorporated solid nanoparticles.     

Large‐Scale Preparation of Polymer Nanocarriers by High‐Pressure Microfluidization

Polymer nanocarriers are used as transport modules in the design of the next generation of drug delivery technology. However, the applicability of nanocarrier‐based technology depends strongly on our ability to precisely control and reproduce their synthesis on a large scale because their properties and performances are strongly dependent on their size and shape. Fundamental studies and practical applications of polymer nanocarriers are hampered by the difficulty of using the current methods to produce monodispersed nanocarriers in large quantities and with high reproducibility. Here, a versatile and scalable approach is reported for the large‐scale synthesis of polymer nanocarriers from water‐in‐oil miniemulsions. This method uses microfluidization to perform a controlled emulsification and is proven to be effective to prepare nanocarriers of different biopolymers (polysaccharides, lignin, proteins) up to 43 g min^?1 with reproducible size and distribution.     

Simulation of a Bubble Column by Computational Fluid Dynamics and Population Balance Equation Using the Cell Average Method

An axisymmetric computational fluid dynamics (CFD) simulation coupled with a population balance equation (PBE) has been applied in simulating the gas‐liquid flow in a bubble column with an in‐house code. The novel feature of this simulation is the application of the cell average method in a CFD‐PBE coupled model for the first time. The predicted results by this method are compared with those by the traditional fixed pivot method and experimental data. For both methods, the simulated results are in reasonable agreement with the reported experimentally measured values. However, the bubble size distributions determined by the cell average method are slightly better than those found by means of the fixed pivot method, i.e., the latter provides a smaller peak value and a wider bubble size distribution, and the probability density function of large bubbles is higher.     

Particle-Size-Distribution Analysis by a Modification of the Turbidimetric Procedure of Musgrave and Harner

The turbidimetric method of determining particle-size distribution, developed by Musgrave and Harner, has been modified and adapted for use with tales, clays, and similar nonmetallic minerals and ceramic raw materials. Results obtained by this method have been found to be reproducible to within ±2%, and check with those obtained by the Andreasen pipette method within the same limits of accuracy. The turbidimetric method is useful for the direct determination of sizes from 60 to 0.25μ, equivalent spherical diameter. The entire procedure for a complete particle-size-distribution analysis usually requires less than 1 hour as compared with several days for the analysis of similar materials by the pipette method.     

低场核磁法测定凝胶过滤介质的孔径分布

凝胶过滤介质在蛋白质、多糖等生物大分子的分离纯化过程中具有非常重要的作用,其中介质的孔径分布是决定分离纯化效果的关键因素。由于绝大部分凝胶过滤介质是软凝胶,因此很难用常规的方法如压汞法、低温氮吸附法等测定其孔径分布。本文探索了利用低场核磁共振测定凝胶过滤介质的孔径分布的方法。首先通过抽滤、自制琼脂糖凝胶块等实验确定了峰的归属,明确了介质孔内水、介质间隙水和自由水在核磁共振横向弛豫时间(T₂)图谱上的分布范围;随后与逆体积排阻层析法(ISEC)测定的结果相对比,得出层析介质孔径和介质孔内水弛豫时间的关系;最后通过高斯正态拟合得到了介质的孔径分布。实验结果证实了低场核磁共振法测定凝胶过滤介质孔径分布的可行性。该法操作简单、测定迅速,并可以为其他层析介质孔径分布的测定提供参考。     

Dispersion of TiO2 nanopowders to obtain homogeneous nanostructured granules by spray-drying

This work deals with the dispersion and stabilisation of nanosized TiO₂ particles in an aqueous medium as a first step in the preparation of spray-dried nanostructured powders.A colloidal route leading to the production of titania nanostructured feedstocks to obtain nanostructured powders was developed. The process was based on the production of homogeneous and concentrated TiO₂ nanosuspensions dispersed in deionised water with a suitable control of pH and the use of an appropriate anionic dispersant. Concentrated suspensions could be obtained by mixing with an ultrasounds probe at different times depending on the dispersing conditions.Homogeneous suspensions prepared were then reconstituted by spray drying into free-flowing powders with an adequate granule size distribution for diverse purposes, such as atmospheric plasma spraying coatings.     

Floc Formation,Size Distribution,and its Transformation Detected by Online Laser Particle Counter

Abstract

Coagulation and flocculation are widely applied in water and wastewater treatment. Removal of suspended particles is essential in water treatment and greatly depends upon the performance of the coagulant and the production of flocs with suitable properties. For monitoring floc size, formation, and size transformation, no particle size method now can be considered ideal. In this work an on‐line laser particle counter was used to follow coagulation with aluminum sulfate. The experiments showed that the floc formation and floc size distribution could be well monitored. The results showed that it is feasible to use particle counting for dosage control and for monitoring changes in floc formation, transformation and size distribution.     

Testing the Fit of a Vector Autoregressive Moving Average Model

Abstract. A new procedure for testing the fit of multivariate time series model is proposed. The method evaluates in a certain way the closeness of the sample spectral density matrix of the observed process to the spectral density matrix of the parametric model postulated under the null and uses for this purpose nonparametric estimation techniques. The asymptotic distribution of the test statistic is established and an alternative, bootstrap‐based method is developed in order to estimate more accurately this distribution under the null hypothesis. Goodness‐of‐fit diagnostics useful in understanding the test results and identifying sources of model inadequacy are introduced. The applicability of the testing procedure and its capability to detect lacks of fit is demonstrated by means of some real data examples.     

Application of the turbidimetric titration method to study the molecular-weight distribution of sulfite cellulose in acetylation

Conclusions -- It is recommended to the central plant laboratories of man-made fibres to use the method of turbidimetric titration to determine the molecular-weight distribution of sulfite cellulose in the process of working it up.-- A rapid method has been developed for determining a molecular-weight distribution of sulfite cellulose for acetylation using a selective solvent—precipitant system.Translated from Khimicheskie Volokna, No. 6, pp. 36–38, November–December, 1990.