Theoretical and experimental study of initial cracking mechanism of an expansive soil due to moisture-change

Swelling and shrinkage due to moisture-change is one of the characteristics of the expansive soil, which is similar to the behavior of most materials under thermal effect. If the deformation is restricted, stress in expansive soil is caused by the swell-shrinking. The stress is defined as “moisture-change stress” and is adopted to analyze swell-shrinkage deformation based on the elasticity mechanics theory. The state when the total stress becomes equal to the soil tensile strength is considered as the cracking criterion as moisture-change increases. Then, the initial cracking mechanism due to evaporation is revealed as follows: Different rates of moisture loss at different depths result in greater shrinkage deformation on the surface while there is smaller shrinkage deformation at the underlayer in expansive soil; cracks will grow when the nonuniform shrinkage deformation increases to a certain degree. A theoretical model is established, which may be used to calculate the stress caused by moisture-change. The depth of initial cracks growing is predicted by the proposed model in expansive soil. A series of laboratory tests are carried out by exposing expansive soil samples with different moisture-changes. The process of crack propagation is investigated by resistivity method. The test results show good consistency with the predicted results by the proposed theoretical model.     

Synthesis of resource conservation network with sink–source interaction

This article presents a mathematical model for the synthesis of resource conservation networks with interception placement. A comprehensive superstructure that incorporates all possible network configurations is used to facilitate the formulation. The synthesis task involves the allocation and interception of process sources to satisfy process sinks and environmental constraints. In particular, the interaction between the sinks and sources is addressed as the subject of the present study. Two literature case studies are solved to illustrate the proposed approach.     

UV‐cured natural polymer‐based membrane for biosensor application

Chitosan, a natural product, is inherently biodegradable, biocompatible, and nontoxic. These properties make chitosan ideal for inclusion in matrices designed for use in enzyme immobilization for clinical analysis. This study demonstrates the feasibility of using chitosan in electrochemical biosensor fabrication. The enzyme sulfite oxidase (SOX) was covalently immobilized onto the matrix of chitosan–poly(hydroxyethyl methacrylate) (chitosan–pHEMA), a natural/synthetic polymer hybrid obtainable via UV curing. p‐Benzoquinone, which served as an electron transfer mediator, was coupled onto the polymer network for activation of the chitosan–pHEMA copolymer, after completion of the photo‐induced polymerization reaction. The biological activity of the immobilized SOX and the electroactivity of the coupled p‐benzoquinone were investigated. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 466–472, 2001     

Effect of polymer compositions on the fabrication of poly(ortho‐ester) microspheres for controlled release of protein

Eight kinds of self‐catalyzed poly(ortho‐esters) (POEs) are used to fabricate bovine serum albumin (BSA)‐containing microspheres using a W/O/W double‐emulsion solvent extraction/evaporation method. All eight kinds of POE polymers used in this study are shown able to form microspheres under proposed fabrication conditions. The surface morphology and inner structure of the microspheres are analyzed using scanning electron microscopy (SEM). The microspheres have a size range from 64.7 to 120.2 μm. POE with a higher viscosity leads to bigger microspheres. It was found that the POE composition has a significant effect on BSA release profiles. POEs, which are more hydrophilic and contain a greater amount of glycolide or lactate (latent acid), yield higher BSA release rates. Specifically, POE containing 1,6‐hexanediol diglycolide (HD‐diGL) microspheres have the highest BSA release rate after a 20‐day test through a combination of surface erosion and diffusion mechanisms. POE containing a high percentage of the trans‐cyclohexanedimethanol (CDM) segment tends to yield microspheres with a lower release rate because of its hydrophobic nature. It was also found that the BSA release rate is more rapid at 37°C than at 22°C because of faster polymer degradation and water penetration at 37°C. Experimental results suggest that various protein release rates can be achieved by using different compositions of POEs. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 1630–1642, 2001     

Cure efficiency of dodecyl succinic anhydride as a cross‐linking agent for elastomer blends based on epoxidized natural rubber

Blends of a highly epoxidized natural rubber (ENR50) with unmodified natural rubber (NR) and ethylene propylene elastomers (EPDM) were produced to evaluate the mixing and curing characteristics. Dodecyl succinic anhydride was used to cross‐link the ENR50 component and the reactivity was assessed by monitoring the evolution of the torque in an oscillatory co‐axial cylinder rheometer, as well as by DSC thermal analysis. A physical model was used to obtain a single parameter for the reactivity of the system, which corresponds to the rate constant for first order curing reactions. Although the blends were thermodynamically immiscible, displaying no significant change in T_g, the components were well dispersed at microscopic level. Better mechanical properties were obtained for blends with EPDM. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41448.     

Metastable boundary conditions of water‐in‐oil emulsions in the hydrate formation region

A stepwise pressurization method was proposed for determining the metastable boundary conditions of water‐in‐oil emulsions in the hydrate formation region. The metastable boundary pressures of four water‐in‐n‐octane emulsions in the presence of methane gas were determined at four specified temperatures. The experimental results show that the metastable boundary pressures increase with decreasing water droplet sizes. A thermodynamic model was developed for calculating the metastable boundary conditions of a water‐in‐oil emulsion in which assuming that the collapse of a metastable emulsion requires the formation of a stable hydrate film with a critical thickness on the surfaces of water droplets. The model was used to correlate the experimental data and determine the critical thickness of the hydrate film. It was demonstrated that the calculated results were in good agreement with the experimental data. The determined critical thickness is at nanoscale, ranging from 14 to 40 nm, which decreases with decreasing water droplet sizes. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

Solid terpolymer electrolyte based on poly(vinyl butyral‐co‐vinyl alcohol‐co‐vinyl acetate) incorporated with lithium salt and tetraglyme for EDLCs

Solid terpolymer electrolytes (STEs) consist of different ratios of poly(vinyl butyral-co-vinyl alcohol-co-vinyl acetate) (PVBVA) and bis(trifluoromethane) sulfonamide lithium salt (LiTFSi) were prepared and the ionic conductivity of the prepared STEs was evaluated. The optimized STE (denoted as STE 20) was further doped with various amount of tetraglyme (10, 20, and 30 wt % and denoted as G10, G20, and G30, respectively). G20 enhanced the ionic conductivity from 6.22 (for STE 20) to 21.9 µS cm⁻¹. This enhancement is due to the presence of abundant oxygen-containing functional group in tetraglyme that provides more charge carrier mobility in the polymer matrix. The structure and complexation of the materials are authenticated via X-ray diffraction and Fourier transform infrared spectroscopy analysis. The performance of electric double layer capacitors based on activated carbon (AC) fabricated with STE 20 (AC/STE 20/AC) and G20 (AC/G 20/AC) were studied via cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy. AC/G 20/AC achieved the maximum specific capacitance of 10.20 F/g [which is higher than AC/STE 20/AC (9.30 F/g)] with 75% of specific capacitance retention after 1500 cycles. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45902.     

Adsorbed species and reaction rates for NO-CO-O2 over Rh(111)

We have studied the NO-CO-O₂ reaction over a Rh(111) catalyst by monitoring the reaction products (CO₂, N₂O, and N₂) and the infrared (IR) intensity of surface CO and NO at various partial pressures of NO, CO and O₂, and sample temperatures. The selectivity for N₂O formation, apparent activation energy for product formation, and NO consumption rate during NO-CO-O₂ are identical to those measured during the NO-CO reaction. The IR measurements show that during NO-CO-O₂ the same two adsorbed species, NO at 1640 cm^-1 and linear CO at ~2040 cm^-1, are present in the same surface concentrations as during NO-CO. For this reason the NO-CO-O₂ kinetics are dominated by the NO-CO kinetics, the NO consumption is rate limited by dissociation of adsorbed NO, and the N₂O selectivity is dominated by surface NO coverage. In contrast, O₂ consumption is adsorption rate limited with the NO-CO adsorption-desorption equilibrium controlling the vacant sites required to dissociatively adsorb O₂. These kinetic and IR data of the CO-NO-O₂ reaction and our interpretation of them agree with previous studies over supported Rh catalysts and thus confirm the previously proposed explanation. From RAIRS and kinetic data we estimate the rate constant for the CO+O→CO₂ elementary step. The pre-exponential factor for this rate is 2×10¹⁰ s^-1, a factor of 50 smaller than previous estimates. This rate constant is important to the NO-CO-O₂ kinetics because it affects O coverage, which, under certain conditions, inhibits NO consumption. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synergistic interaction of metal–acid sites for phenol hydrodeoxygenation over bifunctional Ag/TiO_2 nanocatalyst

The use of silver metal for hydrodeoxygenation(HDO) applications is scarce and different studies have indicated of its varying HDO activity. Several computational studies have reported of silver having almost zero turnover frequency for HDO owing to its high C\\O bond breaking energy barrier and low carbon and oxygen binding energies.Herein this work, titania supported silver catalysts were synthesized and firstly used to examine its phenol HDO activity via experimental reaction runs. BET, XRD, FESEM, TEM, EDX, ICP–OES, Pyridine-FTIR, NH_3-TPD and H_2-TPD analyses were done to investigate its physicochemical properties. Phenomena of hydrogen spillover and metal–acid site synergy were examined in this study. With the aid of TiO_2 reducible support, hydrogen spillover and metal–acid site interactions were observed to a certain extent but were not as superior as other Pt, Pd, Ni-based catalysts used in other HDO studies. The experimental findings showed that Ag/TiO_2 catalyst has mediocre phenol conversion but high benzene selectivity which confirms the explanation from other computational studies.     

P3HT : PCBM solar cells—The choice of source material

Bulk heterojunction solar cells based on P3HT : PCBM blend films are among the most intensively studied polymer solar cells. In spite of that, there is a huge variation of reported efficiencies in the literature, even for same device architectures and film preparation procedures. Here we investigated the influence of starting properties of P3HT and PCBM (different suppliers) on blend film morphology and device performance. We found that there was a strong dependence of the film morphology and device performance on the source of chemicals used. Both P3HT and PCBM affected the results, and higher nominal purity did not necessarily result in better device performance. The dependence of the film morphology and device performance on the properties of P3HT and PCBM is discussed in detail. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39776.