The effect of scale and interfacial tension on liquid–liquid dispersion in in-line Silverson rotor–stator mixers

The effect of scale, processing conditions, interfacial tension and viscosity of the dispersed phase on power draw and drop size distributions in three in-line Silverson rotor–stator mixers was investigated with the aim to determine the most appropriate scaling up parameter. The largest mixer was a factory scale device, whilst the smallest was a laboratory scale mixer. All the mixers were geometrically similar and were fitted with double rotors and standard double emulsor stators. 1 wt.% silicone oils with viscosities of 9.4 mPa s and 339 mPa s in aqueous solutions of surfactant or ethanol were emulsified in single and multiple pass modes. The effect of rotor speed, flow rate, dispersed phase viscosity, interfacial tension and scale on drop size distributions was investigated.     

Transport properties of sulfonated poly (styrene‐isobutylene‐styrene) membranes with counter‐ion substitution

In this study, the transport properties of poly(styrene‐isobutylene‐styrene) (SIBS) were determined as a function of sulfonation level (0–94.9%) and counter‐ion substitution (Ba⁺², Ca⁺², Mg⁺², Mn⁺², Cu⁺², K⁺¹) for fuel cell applications. Increasing the sulfonation level improved the ion exchange capacity (IEC) of the membranes up a maximum (1.71 mequiv/g), suggesting a complex three‐dimensional network at high sulfonation levels. Results show that proton conductivity increases with IEC and is very sensitive to hydration levels. Methanol permeability, although also sensitive to IEC, shows a different behavior than proton conductivity, suggesting fundamental differences in their transport mechanism. The incorporation of counter‐ion substitution decreases both methanol and proton transport. Methanol permeability seems to be related to the size of the counter‐ion studied, while proton conductivity is more sensitive to water content, which is also reduced upon the incorporation of counter‐ions. To complement the studies, selectivity (i.e., proton conductivity/methanol permeability) of the studied membranes was determined and compared to Nafion® 117. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

The Synthesis of Ba‐ and Fe‐ Substituted CsAlSi2O6 Pollucites

Barium‐substituted CsAlSi₂O₆ pollucites, Cs_xBa_(1?x)/2AlSi₂O₆, and barium‐ and iron‐substituted pollucites, Cs_xBa_(1?x)/2Al_xFe_1?xSi₂O₆ and Cs_xBa_1?xAl_xFe_1?xSi₂O₆ were synthesized with 1 ≥ x≥ 0.7 using a hydrothermal synthesis procedure. Rietveld analysis of X‐ray diffraction data confirmed the substitution of Ba for Cs and Fe for Al, respectively. The crystallographic analysis also describes the effects of three different types of pollucite substitutions on the pollucite unit cell: Ba²⁺ for Cs¹⁺ cation results in little effect on cell dimensions, intermediate concentrations of Ba²⁺ and Fe³⁺ substitution result in net minor expansion due to Fe³⁺ addition, and large Ba and Fe substitutions result in overall framework contraction. Elemental analysis combined with microscopy further supports the phase purity of these new phases. These materials can be used to study the stability of CsAlSi₂O₆ as a durable ceramic waste form, which could accommodate with time Cs and its decay product, Ba. Furthermore, success in iron substitution for aluminum into the pollucite lattice predicts that redox charge compensation for Cs cation decay is possible.     

Chemical Analysis with High Spatial Resolution by Rutherford Backscattering and Raman Confocal Spectroscopies: Surface Hierarchically Structured Glasses

Copper and iron in glasses constitute classical aims of study because of the optical effects that they produce. Structured materials are also interesting due to the incorporated functionalities derived from their spatial organization. Here, CuO and Fe₂O₃ were incorporated into a standard glass, from which glass coatings with different thicknesses were studied. Whereas iron cations dissolved in the glassy matrix, copper cations saturated it and crystallized at the surface, forming a hierarchical microstructure. The surface microstructure consisted of crystallizations of Tenorite (CuO) forming interconnected walls. The walls surrounding areas of glassy matrix gave rise to a cells microstructure. Rutherford Backscattering Spectrometry provided the composition of the samples with high depth resolution, and Raman Confocal Microscopy determined the phases location and their distribution forming the microstructure. The joint information from both techniques allowed high chemical and spatial resolution of the main cations location for the hierarchical surface microstructure.     

Characterizing Weave Geometry in Textile Ceramic Composites Using Digital Image Correlation

Techniques for characterizing tow architectures and defects in woven ceramic composites are required for generating high‐fidelity geometric models and subsequently probing effects of defects on composite performance. Although X‐ray computed tomography (CT) has been shown to provide the requisite information with potentially sub‐μm resolution, the technique is inherently limited to probing only small volumes: on the order of a few unit cells of typical weaves. Here, we present an assessment of the efficacy of a complementary 2D technique, based on surface topography mapping via 3‐D (three‐dimensional) digital image correlation (DIC), with potential for ascertaining long‐range features in weaves and defects that cannot be gleaned from CT imaging alone. Upon comparing surfaces reconstructed from CT and DIC data, we find that DIC is capable of resolving surface heights with a root mean square(RMS) error of ~10 μm (about twice the CT voxel size, 4.4 μm) and a spatial resolution of ~20 μm over areas of several cm². Achieving this level of resolution requires use of sufficiently small speckles (~50 μm) and small subset size (~300 μm) relative to the characteristic tow dimensions (~1 mm). The error is somewhat higher (about 20 μm) in areas where surface discontinuities or rapid changes in topography exist (e.g., at tow boundaries).     

Controlled Mesoporosity in SiOC via Chemically Bonded Polymeric “Spacers”

Silicon oxycarbides with controlled porosity in the mesopore range have been obtained through high‐temperature pyrolysis of newly developed reactive siloxane formulations. The starting gels have been synthesized via Pt catalyzed hydrosilylation reaction between polyhydromethylsiloxane (PHMS) and vinyl‐terminated polydimethylsiloxane (PDMS) of different molecular weights in the presence of tetravinyltetramethylcyclotetrasiloxane as a crosslinking enhancer. In our approach, the PDMS serves the double purpose of size‐controlling templating agent as well as solvent at the early stages of the synthesis. During the curing step, the vinyl‐terminated PDMS is chemically bonded to the preceramic network through the extremely efficient hydrosilylation reaction and “solidify.” Accordingly, its removal during pyrolysis occurs through decomposition of a solid phase with retention of the formed porosity. The structural and morphological evolution of the preceramic gels containing the molecular spacers have been investigated as a function of the thermal treatment temperature by N₂ physisorption measurements, thermogravimetry, and SEM analyses. The results show that the pore size distribution of the resulting SiOCs depends on the molecular weight of the PDMS and is directly related to the molecular volume assumimg that the PDMS chains are entangled into spheroidal shapes. The total pore volume is related to the initial amount of templating PDMS assuming its complete decomposition during pyrolysis.     

Stress Analysis of Adhesively Bonded Electroprimed Steel Lap Shear Joints

Structural applications for adhesive bonding have been increasing in recent years due to improvements in the types of adhesives available and in improved knowledge of bonding procedures. Consequently, there exists a demand for precise numerical modeling of adhesive joint behavior, particularly along bondline interfaces where low surface energy adhesives contact high surface energy metallic oxides. The purpose of the present study is to determine the effect of electrodeposited organic paint primer (ELPO) on the stress and strain distributions within an adhesively bonded single-lap-shear joint. Initial experimental studies have shown that bonding to ELPO-primed steel adherends has enhanced strength and durability characteristics compared to conventional bonds to unprimed steel surfaces. Recent studies based on finite element analysis of varied single-lap-shear joint moduli and thicknesses, and subsequent testing of joints with two different adhesive moduli, have indicated the mechanisms involved in this phenomenon. The presence of the ELPO-primer reduced peak peel and shear stresses and allowed for more uniform stress distribution throughout the joint.     

A graphical approach to process synthesis and its application to steam reforming

It is common practice in chemical engineering to design processes sequentially. The type of product desired determines the choice of the feed materials that are introduced into the reactor networks. These in turn lead into the separation networks. The flows of heat and work are the final part of the sequence to be considered, with the application of heat exchanger networks, and any deficiency or excess in these flows is usually compensated for with the use of utilities. Although the ongoing research into reactor, separation, and heat exchanger optimization is of indubitable value, an aspect that is often overlooked in conventional research is the question: How do changes to one of the elements in the sequence affect the others? Most process designers do not address such matters until the next optimization of the sequence begins. The result of this sequential approach to design is that processes may contain a few very efficient units, but may also have others that are highly inefficient. A graphical technique that incorporates the flows of heat and work into the design of the process at a very early stage is proposed. The technique can be used to prepare flow sheets that represent a synthesized version of the elements that make up the complete process, rendering each component highly efficient. This new design tool uses the thermodynamic properties of enthalpy (representative of process heat requirements) and Gibbs free energy (representative of process work requirements) to develop process flow sheets that operate as close to reversibly as possible, and can be used as a foundation for more detailed refinements to achieve the best possible result. A case was described in a previous paper in which the graphical technique was applied to gasification. The application of the technique to the production of syngas by the steam reforming of natural gas is detailed. We show that the steam reforming process can be operated with increased reversibility and can actually consume carbon dioxide, thus representing a process with a carbon efficiency of greater than 100%, if the way in which all the process units interact with one another is used to utmost advantage. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3714–3729, 2013