Real-time measurement of submicron aerosol particles having a log-normal size distribution by simultaneously using unipolar diffusion charger and unipolar field charger

Recently, Park et al. [(2007). Development and performance test of a unipolar diffusion charger for real-time measurements of submicron aerosol particles having a log-normal size distribution. Journal of Aerosol Science, 38, 420–430] have introduced a methodology for performing simple and fast measurements of submicron aerosol particles having a log-normal size distribution, using a unipolar diffusion charger, an electrometer, and a condensation particle counter (CPC). The methodology can be applied to particles of 30–700 nm and requires an assumption of their geometric standard deviation in size. In this paper we propose a much cheaper but faster method which involves substituting a unipolar field charger and another electrometer for the CPC. With the data obtained using this dual-charger system, we developed a data inversion algorithm and estimated the particle size distribution by minimizing the differences between the measured aerosol currents and the calculated values. To compare the size distribution with the data measured using a scanning mobility particle sizer (SMPS), sodium chloride (NaCl) particles smaller than in diameter, and dioctyl sebacate (DOS) particles with a diameter of 0.1–, were used. The estimated results for the NaCl and DOS particles were within 10% of the data measured with the SMPS, while a 33% deviation from the SMPS results was obtained in Park et al. [(2007). Development and performance test of a unipolar diffusion charger for real-time measurements of submicron aerosol particles having a log-normal size distribution. Journal of Aerosol Science, 38, 420–430]. Furthermore, the detection time obtained with the use of our dual-charger system was faster () than the 5 s obtained by Park et al. [(2007). Development and performance test of a unipolar diffusion charger for real-time measurements of submicron aerosol particles having a log-normal size distribution. Journal of Aerosol Science, 38, 420–430].     

The effect of a crystal size distribution on ZLC experiments

This paper reports the results of a theoretical investigation of the effect of a sorbent size distribution on the zero length column (ZLC) method for measuring intracrystalline diffusion. A new model incorporating a continuous log-normal distribution of crystal size is introduced. It is shown that such a distribution introduces tailing into the normally linear long time region of the desorption curve, although this curvature is not obvious when the initial concentration drop is fast. Analysing such a curve with the standard ZLC model causes the diffusional time constant to be underpredicted, whereas the adsorption related parameter L is overpredicted. The error increases with increasing distribution width. It is shown that the curve may be well approximated by summing the desorption curves of the individual, discrete size fractions, weighted by their volume fraction. The systematic error introduced into the measured diffusion coefficient when analysing data for sorbent samples with a size distribution with the standard model may be reduced if the mean particle size is defined as the ratio of the sample's volume to its surface area.     

The effect of liquid push out of the material capillaries under sulfate ion diffusion in cement composites

The paper treats complex phenomena that accompany the diffusion of sulfate ions into cement paste or systems. The ion distribution within the material was studied by designing a specific diffusion model. The model accounts for two phenomena: capillary filling with products of the chemical reactions and the subsequent liquid push out of the capillary. The approach allows to quantify the concentration of free ions having penetrated the cement stone and that of chemically reacted ions, and to assess the liquid push out. Experimental data are also presented.     

Effect of diffusion and convection on the flux of depositing particles near a preadsorbed particle

A steady state convective-diffusion equation is solved using a collocation method to find the concentration profile and flux of adsorbing particles near a particle adsorbed on a line. At small values of the gravity number, N_G=πd⁴ Δρg/6kT, the concentration profile and flux vary slowly near the preadsorbed particle, while they are highly non-uniform at large values of N_G. The numerical results are compared with Brownian dynamics simulation for a range of N_G values. The effect of the position of the system boundary on the collocation calculation is discussed and it is shown how the concept of flux balance may be used to improve the accuracy of the results. Finally, we develop a truncated power series that accurately fits the numerical data.     

制备条件对碳酸钡沉淀粒度分布的影响

一种功能陶瓷用碳酸钡的制备方法。采用正交试验法考察加料次序、反应温度、加料速度与表面活性剂这4种因素对制备的碳酸钡沉淀颗粒大小及粒度分布的影响。找出了功能陶瓷用碳酸钡制备的较佳条件：慢速反加料、反应温度25℃、添加表面活性剂。     

The particle size distribution effect on the drying efficiency of polymeric fibers containing castables

Refractory castables present several placing methods, defined mainly by the application requirements and material characteristics. Considering the same chemical composition, the particle size distribution (PSD) is the key property related to the large differences in their rheology, creep and corrosion resistance. It also plays an important role on their fluids permeation and drying behaviors. Therefore, it is reasonable to consider that the benefits promoted by polymeric fibers, added as drying agents, would be affected by PSD changes. In this work, the permeability and drying behaviors of fiber containing refractory castables were correlated to their PSD. Typical pumpable, self-flowing and vibrated formulations were tested in combination with polypropylene fibers. Permeability measurements and explosion tests were associated to the maximum paste thickness (MPT) and interparticle separation (IPS) parameters and to the fine/coarse particles ratio. The different classes of castables presented distinct needs of drying additives and the fibers’ efficiency was strongly dependent on castables PSD.     

Model for parallel surface and pore diffusion of an adsorbate in a spherical adsorbent particle

A model is presented to describe the rate of uptake of a species by a spherical adsorbent particle when intraparticle transport can occur by parallel diffusion through the pore space and along the surfaces of pore walls. Although the conventional shrinking core model (SCM) has been applied to such systems previously, its use is valid only when adsorption onto the pore walls is described by a rectangular isotherm. As with the SCM, the new model differs from homogeneous models by envisaging the advance of the adsorbate to be marked by a distinct inward-moving interface, but it generalizes the SCM to allow for an incompletely saturated adsorbed shell behind the front governed by any Langmuir isotherm. The model has been applied to previously published experimental data for the uptake of bovine serum albumin by chitosan beads and compared to the results obtained when the same data are analysed using the corresponding homogeneous model. The fit of the two models to the convension-time data yields comparable results, but significant differences in the predicted absorbate concentration profiles within adsorbent particles are observed, particularly at high conversions.     

Effects of solution pH on ion distribution and drug release behaviors of a weak polyelectrolyte hydrogel

A triphasic model is developed and the finite element method is adopted to investigate a weak polyelectrolyte hydrogel. The influence of HCl concentrations in external solution on ion concentrations inside the hydrogel and the evolution of water volume fraction are discussed. The conservation of charge can be satisfied everywhere in the hydrogel. Also, a drug release equation which considers both convection and diffusion effects is employed to analyze the drug release rate. The results show that the drug release rate has a very close relationship with the pH value. The simulated results are compared with experimental results of Beebe to validate the reliability and accuracy of this simulation. This work is significant for the study of oral drug controlled release in the gastrointestinal tract. © 2017 Society of Chemical Industry     

The additive effect of zwitterion and nano-particles on ion dissociation in polyelectrolytes

To realise the battery potential of gel polyelectrolytes greater ion dissociation, ultimately leading to higher conductivities, must be achieved. Higher conductivities will result through increasing the ion-dissociating properties of the gel polyelectrolyte. The poor degree of ion dissociation arises as the active ion tends to remain in close proximity to the backbone charge. Nano-particle inorganic oxides, and zwitterionic compounds have been shown to act as dissociation enhancers in certain polyelectrolyte systems. In an attempt to further increase ion dissociation the addition of both TiO₂ nano-particles and a zwitterionic compound based on 1-butylimidazolium-3-N-(butanesulphonate) were added to the gel polyelectrolyte system poly (Li-2-acrylamido-2-methyl-1-propane sulphonate-co-N,N′-dimethylacrylamide), poly(Li-AMPS-co-DMAA) to determine if a synergistic effect occurs. Two different solvents were used to determine the breadth of applicability of the additive effect. The use of both dissociators resulted in the maximum ionic conductivity being achieved at lower nano-particle concentrations when compared to an identical system without zwitterion.     

Coupling of diffusion and chemical stress: The case of ion exchange in glass

The chemical strengthening of glass results from an ion exchange process in which smaller alkali ions in a glass are replaced with larger alkali ions from a molten salt bath. This interdiffusion process leads to a buildup of chemical stress in the glass. However, traditional modeling of the ion exchange process has not fully accounted for interaction effects between mass diffusion and the chemical stress developed during the process. In this study, we develop the general theory of coupling between diffusion and stress, resulting in a single flux equation with a concentration- and stress-dependent interdiffusion coefficient. We apply the theory to the specific cases of chemically strengthened soda lime silicate and aluminosilicate glasses, demonstrating the impact of interaction terms on concentration profiles and interdiffusion coefficient. Following a phenomenological approach, this study demonstrates the effect of the interdiffusion on stress generation and vice versa to account for deviations from the simple expressions published hitherto in the literature.     

Large improvement in trap level and space charge distribution of polypropylene by enhancing the crystalline − amorphous interface effect in blends

The accumulation of space charge in high voltage direct current cable will bring the insulation to failure; the addition of nanoparticles can markedly improve the space charge distribution characteristics inside the cable insulation, but particle agglomeration and cavitation lead to difficulty in controlling the properties of nanocomposites. In this paper, polypropylene (PP)/propylene‐ethylene copolymer (PEC) and PP/ethylene‐octene copolymer (EOC) blends were prepared by mechanical blending in order to improve both mechanical properties and space charge distribution. Dynamic mechanical thermal analysis shows that both blends have excellent mechanical properties for recyclable power cable. Pulsed electro‐acoustic and thermally stimulated depolarization current tests illustrate that PP/EOC blends significantly decrease space charge accumulation and remarkably increase the trap density in the bulk compared with PP and PP/PEC blends. The increase of the trap density in PP/EOC blends can be explained as the result of the shallow traps introduced by the crystalline ? amorphous interface existing in the boundaries of spherulites. The shallow traps can act as hopping sites to improve the transportation of space charges. © 2016 Society of Chemical Industry     

十二胺体系中铁离子对霓石浮选的影响及其作用机理

以十二胺(DDA)为捕收剂,通过单矿物浮选实验考察了不同矿浆pH值和铁离子浓度下霓石的浮选行为,利用人工混合矿浮选实验研究了铁离子对霓石?镜铁矿分离效果的影响。结合Zeta电位检测、Fe3+水解组分浓度计算、玻尔兹曼理论分析和分子动力学模拟研究了在DDA体系中铁离子对霓石的抑制机理。结果表明,铁离子对霓石的可浮性抑制作用较大,在pH=6.8及DDA浓度3.6×10?4 mol/L、无铁离子条件下,霓石回收率高达75.72%,溶液中铁离子浓度为3.0×10?4 mol/L时,霓石回收率仅为25.32%,同时人工混合矿浮选泡沫产品中铁品位由34.20%降低至28.71%,回收率由33.29%降低至18.35%。pH=3~11时,铁离子以荷正电的羟基络合物沉淀形式吸附在霓石表面,增大了霓石的亲水性,降低了霓石的可浮性,铁离子在霓石表面吸附使霓石零电点由2.14增至6.70,表面正电性增大减弱了阳离子捕收剂DDA与霓石表面的静电吸附,使霓石界面层内的RNH3+浓度小于界面层外,DDA吸附层松散程度增大,霓石(110)面法线方向DDA浓度分布向正方向偏移,造成霓石可浮性下降。     

The effect of particle size distribution on the microstructure and properties of Al2O3 ceramics formed by stereolithography

Stereolithography (SL) shows advantages for preparing alumina-based ceramics with complex structures. The effects of the particle size distribution, which strongly influence the sintering properties in ceramic SL, have not been systematically explored until now. Herein, the influence of the particle size distribution on SL-manufactured alumina ceramics was investigated, including bending strength at room temperature, post-sintering shrinkage, porosity, and microstructural morphology. Seven particle size distributions of alumina ceramics were studied (in μm/μm: 30/5, 20/3, 10/2, 5/2, 5/0.8, 3/0.5, and 2/0.3); a coarse:fine particle ratio of 6:4 was maintained. At the same sintering temperature, the degree of sintering was greater for finer particle sizes. The particle size distribution had a larger influence on flexural strength, porosity and shrinkage than sintering temperature when the particle size distribution difference reached 10-fold but was weaker for 10 μm/2 μm, 5 μm/2 μm and 5 μm/0.8 μm. The sintering shrinkage characteristics of cuboid samples with different particle sizes were studied. The use of coarse particles influenced the accuracy of small-scale samples. When the particle size was comparable to the sample width, such as 30 μm/5 μm and 5 mm, the width shrinkage was consistent with the height shrinkage. When the particle size was much smaller than the sample width, such as 2 μm/0.3 μm and 5 mm, the width shrinkage was consistent with the length shrinkage. The results of this study provide meaningful guidance for future research on applications of SL and precise control of alumina ceramics through particle gradation.     

Preparation of poly(vinyl chloride) latexes using a dual surfactant system: The effect in the particle size distribution

The control of the average particle size and size distribution in the emulsion polymerization of vinyl chloride monomer is an important parameter to determine, not only the latex characteristics, but also the properties of the final dispersion powder in several industrial applications. It is possible to manipulate the particle size distribution (PSD) by applying a mixture of an anionic surfactant‐fatty alcohol before the start of the free radical polymerization. Contrary to the procedures of the miniemulsion and the derivative diffusional swelling techniques, no kind of high shear is applied to the monomer and/or surfactant mixtures. In fact, the concentration and selection of the anionic surfactant, together with the fatty‐alcohol, can play an interesting role on the final PSD of the polymer's particles. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The influence of the riser exit on the particle residence time distribution in a circulating fluidised bed riser

This paper reports measurements of the influence of riser exit geometry upon the particle residence time distribution in the riser of a square cross section, cold model, circulating fluidised bed. The bed is operated within the fast fluidisation regime. The fast response particle RTD technique developed by Harris et al. (Chem. Eng. J. 89 (2002) 127-142) was used to measure the residence time distribution.The geometry of the riser exit is shown to have a modest but consistent influence upon the particle RTD; the influence of operating conditions, i.e. superficial gas velocity and solids flux is more significant.Increasing the refluxing effect of the riser exit increases the mean, variance and breakthrough time and decreases the coefficient of variation of the residence time distribution. Changes in reflux do not have a systematic effect upon the skewness of the RTD.     

The effect of multiple martensitic transformations on diffusion of Fe and Ni atoms in Fe-31.7%Ni-0.06%C alloy

Diffusion characteristics of iron and nickel atoms were investigated using radioactive isotopes method in phase-hardened metastable iron-nickel Fe-31.7%Ni-0.06%C alloy with nanofragmented structure. It has been found that diffusion mobility of nickel and iron atoms in reverted austenite of Fe-31.7%Ni-0.06%C alloy significantly increases as the result of multiple γ-α-γ martensitic transformations. The diffusion coefficients of nickel and iron in the austenite at 400°C corresponded to the stationary diffusion coefficients at the temperatures above 900°C. The revealed diffusion acceleration at low temperatures is caused by high-density dislocations and additional low-angle subboundaries of disoriented nanofragments of reverted austenite and deformation twin subboundaries formed during multiple γ-α-γ cycles.     

The effect of surface tension on phase distribution of two-phase flow in a micro-T-junction

An experimental investigation has been conducted to study the effect of surface tension on phase distribution of gas–liquid two-phase ?ow through a T-junction with diameter 0.5 mm. It is found that the decrease in liquid surface tension makes the liquid taken off reduce when inlet flow pattern is slug flow, slug-annular and annular flow. These results highlight that phase distribution is remarkably influenced by surface tension in micro-T-junctions. To be specific, the surface tension contributes positively to liquid taking off. High surface tension seems to make the liquid capture more kinetic energy transported from the gas and dissipate it in form of vortexes. It is suggested that phase distribution in micro-T-junctions can be partly controlled by adjusting liquid surface tension.     

Synergic effect of benzotriazole and chloride ion on Cu passivation in a phosphate electrochemical mechanical planarization electrolyte

In this study, the effect of chloride ion (Cl⁻) in phosphate electrolytes of pH 2 containing benzotriazole (BTAH) developed for use in electrochemical mechanical planarization (ECMP) was investigated at various anodic potentials. According to D.C. and A.C. electrochemical analyses, the inhibition effect of the BTAH passive film formed in phosphate electrolyte containing both BTAH and Cl⁻ was superior to that formed in phosphate electrolytes containing BTAH alone, even at high anodic potential. The effective window for BTAH passivation reached ∼1.3 V vs. Ag/AgCl nearly three times that of the ∼0.5 V vs. Ag/AgCl recorded for electrolyte containing BTAH alone. According to analyses conducted by atomic force microscopy (AFM) and secondary ion mass spectrometer (SIMS), the thickness of the passive film grown from the BTAH-only electrolyte at 0.3 V vs. Ag/AgCl was ∼52 ± 7 nm and ∼55 nm, respectively. As for the passive film grown from the BTAH and Cl⁻ electrolyte, the thickness increased to ∼104 ± 18 nm and ∼106 nm, respectively. The mechanism for the enhanced inhibition capability was that the passive film grown from the BTAH and Cl⁻ electrolyte was thicker compared to that formed from the BTAH-only electrolyte due to the incorporation of Cl⁻ into the BTAH passive film. The ECMP polishing results also demonstrated an obvious step height reduction of ∼1000 nm in a patterned structure for only 60 s polishing at a high potential of 1.0 V vs. Ag/AgCl under a low downward pressure (∼0.5 psi). Subsequently, this study proposes that the control of Cl⁻ in a phosphate ECMP electrolyte of pH 2 may be useful in enhancing the passivation capability of BTAH passive film, thus expanding the operating potential window.     

Corrosion of carbon steel in compacted bentonite and its effect on neptunium diffusion under reducing condition

The corrosion of carbon steel and its effect on neptunium diffusion were studied by corrosion tests of carbon steel and neptunium diffusion tests under conditions designed with consideration of constituents of a repository for High-level Radioactive Waste disposal. The major constituents of the conditions were carbon steel, corrosion products pre-formed under aerobic conditions, compacted bentonite, reductant and a low-oxygen glove box. The corrosion tests were performed in the presence of water-saturated compacted bentonite. The neptunium diffusion tests were performed with and without carbon steel. The carbon steel and the bentonite were observed by taking photographs and analyzed by X-ray diffraction. The color of the corroded surface of the carbon steel changed from red/orange/black under aerobic conditions to a dark-green under reducing conditions. Portions of the bentonite changed their original color, pale-gray, to a brownish color after the test. Gas-induced cracks were also observed in some bentonite specimens. These changes were discussed combining thermodynamic predictions under the present experimental conditions. The results revealed that anaerobic corrosion of carbon steel occurred in the bentonite. The corrosion processes were also discussed. The corrosion rate of carbon steel was estimated to be 0.1 μm/year from iron profiles in the bentonite. This value was much lower than the conservative setting value 20 μm/year in the current performance assessment. The significant restriction in corrosion could be attributed to the presence of bentonite and corrosion products. Oxidation states of neptunium in the bentonite were investigated by thenoyltrifluoroacetone in xylene extraction technique. It was found that tetravalent neptunium accounted for 99% of the total neptunium in the presence of carbon steel and only 63% without. The results revealed that anaerobic corrosion of carbon steel could maintain strong reducing conditions to keep most tetravalent neptunium from being oxidized to pentavalent neptunium, thus effectively restraining migration of neptunium in the bentonite. The apparent diffusions were estimated to be in the order of 10⁻¹⁵–10⁻¹⁴ m²/s for tetravalent neptunium and 10⁻¹³–10⁻¹² m²/s for the pentavalent. No significant effect of the corrosion products on neptunium sorption was found through comparing the apparent diffusion coefficients obtained in the diffusion with and without carbon steel. Corrosion of carbon steel under conditions relevant to the repository is essential for further studies, providing a confident and defensible value of corrosion rate for repository design. The effects of corrosion on radionuclide migration, especially redox-sensitive radionuclides in the buffer, should be considered for a reliable safety assessment of geological disposal.