Статті в журналах: "Polymer sublayer"

1

Makarenkova, Anastasiia, and Inna Starovoit. "INVESTIGATION OF VORTEX FEEDING OF POLYMER INTO THE TURBULENT BOUNDARY LAYER." Bulletin of the National Technical University "KhPI". Series: Mathematical modeling in engineering and technologies, no. 1 (August 1, 2023): 149–53. http://dx.doi.org/10.20998/2222-0631.2023.01.22.

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The results of the experimental studies of the efficiency of the method of vortex feeding of polymers developed by the authors are presented. The novelty of the device lies in the fact that when the polymer is fed into the boundary layer, the longitudinal velocity and the additional circumferential velocity are reported simultaneously. It has been established that with the introduction of polyethylene oxide solutions into the boundary layer of the model, using the proposed device, a reduction in hydrodynamic resistance by 60% and hydrodynamic noise up to 14 dB were obtained, which indicates the high efficiency of the proposed vortex feed device to reduce resistance and noise. The paper presents a physical model that shows that polymers affect directly the inner region of the boundary layer. This leads to a thickening of the viscous sublayer and a decrease in the intensity of vortex structures in it. As a result, the process of migration of vortices from the viscous sublayer to the outer region of the boundary layer slows down. All this reduces the turbulence of the boundary layer, thereby leading to a decrease in hydrodynamic resistance and noise.

2

Jovanovic, Jovan, Bettina Frohnapfel, Mira Pashtrapanska, and Franz Durst. "The effect of polymers on the dynamics of turbulence in a drag reduced flow." Thermal Science 9, no. 1 (2005): 13–41. http://dx.doi.org/10.2298/tsci0501013j.

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An experimental investigation of a polymer drag reduced flow using state-of-the-art laser-Doppler anemometry in a refractive index-matched pipe flow facility is reported. The measured turbulent stresses deep in the viscous sublayer are analyzed using the tools of invariant theory. It is shown that with higher polymer concentration the anisotropy of the Reynolds stresses increases. This trend is consistent with the trends extracted from DNS data of non-Newtonian fluids yielding different amounts of drag reduction. The interaction between polymer and turbulence is studied by considering local stretching of the molecular structure of a polymer by small-scale turbulent motions in the region very close to the wall. The stretching process is assumed to re-structure turbulence at small scales by forcing these to satisfy local axisymmetry with invariance under rotation about the axis aligned with the main flow. It is shown analytically that kinematic constraints imposed by local axisymmetry farce turbulence near the wall to tend towards the one-component state and when turbulence reaches this limiting state it must be entirely suppressed across the viscous sublayer. Based on this consideration it is suggested that turbulent drag reduction by high polymers resembles the reverse transition process from turbulent to laminar. Theoretical considerations based on the elastic behavior of a polymer and spatial intermittency of turbulence at small scales enabled quantitative estimates to be made for the relaxation time of a polymer and its concentration that ensure maximum drag reduction in turbulent pipe flows, and it is shown that predictions based on these are in very good agreement with available experimental data.

3

Shugurov, A. R., A. I. Kozel’skaya, and A. V. Panin. "Viscoelastic wrinkling in compression-stressed metal film-polymer sublayer system." Technical Physics Letters 37, no. 10 (October 2011): 896–99. http://dx.doi.org/10.1134/s1063785011100130.

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4

Pavlovsky, V., and О. Orlov. "Specific features of coordinated variations in friction resistance and flow velocity profile in tubes at Toms effect." Transactions of the Krylov State Research Centre 3, no. 397 (August 6, 2021): 25–32. http://dx.doi.org/10.24937/2542-2324-2021-3-397-25-32.

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Object and purpose of research. Relationships between friction resistance coefficient and velocity distributions in the turbulent boundary layer of low-concentrated polymer solutions are investigated. These relationships are different from water because in polymer solutions the friction resistance at constant Reynolds numbers is additionally changed with solution concentrations. Materials and methods. The known experimental data on variations of the friction resistance coefficient and the velocity profiles in turbulent flows in circular tubes at changes in polymer solution concentrations. Main results. The general law of coordinated variations in friction resistance coefficient λ and flow velocity profile in the turbulent boundary layer depending on Reynolds number and polymer solution concentration. The flow models are validated, which describe the laws of velocity variations in all characteristic sections of boundary layer: laminar sublayer, buffer and logarithmic flow areas. A new non-dimensional number is introduced, which characterizes the ability of low concentrated water solutions of polymers to reduce the friction resistance. It is called the Toms effect parameter in the work. Conclusion. Results of the investigation will be useful in developing the theoretical methods for estimation of boundary layer characteristics in polymer solutions.

5

Morimoto, Masahiro, Atsuhiro Kusakabe, Kazuya Sakamoto, Junji Gonda, and Atsushi Kubono. "Formation of Interfacial Layer between Liquid Crystal and Polymer Alignment Sublayer." Japanese Journal of Applied Physics 48, no. 7 (July 6, 2009): 070220. http://dx.doi.org/10.1143/jjap.48.070220.

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6

YANG, SHU-QING, and G. DOU. "Turbulent drag reduction with polymer additive in rough pipes." Journal of Fluid Mechanics 642 (December 11, 2009): 279–94. http://dx.doi.org/10.1017/s002211200999187x.

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Friction factor of drag-reducing flow with presence of polymers in a rough pipe has been investigated based on the eddy diffusivity model, which shows that the ratio of effective viscosity caused by polymers to kinematic viscosity of fluid should be proportional to the Reynolds number, i.e. u∗R/ν and the proportionality factor depends on polymer's type and concentration. A formula of flow resistance covering all regions from laminar, transitional and fully turbulent flows has been derived, and it is valid in hydraulically smooth, transitional and fully rough regimes. This new formula has been tested against Nikuradse and Virk's experimental data in both Newtonian and non-Newtonian fluid flows. The agreement between the measured and predicted friction factors is satisfactory, indicating that the addition of polymer into Newtonian fluid flow leads to the non-zero effective viscosity and it also thickens the viscous sublayer, subsequently the drag is reduced. The investigation shows that the effect of polymer also changes the velocity at the top of roughness elements. Both experimental data and theoretical predictions indicate that, if same polymer solution is used, the drag reduction (DR) in roughened pipes becomes smaller relative to smooth pipe flows at the same Reynolds number.

7

Singh, Rashi, and Ashwini Bharati. "Review: Controlled Release of Analgesics." International Journal for Research in Applied Science and Engineering Technology 11, no. 2 (February 28, 2023): 654–59. http://dx.doi.org/10.22214/ijraset.2023.49109.

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Abstract: The regulated release of medication into the patient provided by the patch makes transdermal drug delivery superior to other methods of pharmaceutical administration. The medication instantly enters the bloodstream through the skin. Low concentration in the blood and high concentration on the patch. The usage of polymers is successful in achieving analgesics' sustained release. To evaluate effectiveness, in vitro and in vivo investigations were conducted. Due to the advantages that biodegradable polymers have over other materials in use, there is currently a huge demand for them. A biodegradable preparation of polymer and active ingredient is made for wound healing with a synthetic porous drug-loaded top layer and a spongy collagen sublayer. This method of analgesic delivery is slowly progressing among people and would further require few advancements as it is completely contrast to the conventional forms.

8

Jovanović, J., M. Pashtrapanska, B. Frohnapfel, F. Durst, J. Koskinen, and K. Koskinen. "On the Mechanism Responsible for Turbulent Drag Reduction by Dilute Addition of High Polymers: Theory, Experiments, Simulations, and Predictions." Journal of Fluids Engineering 128, no. 1 (August 2, 2005): 118–30. http://dx.doi.org/10.1115/1.2073227.

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Turbulent drag reduction by dilute addition of high polymers is studied by considering local stretching of the molecular structure of a polymer by small-scale turbulent motions in the region very close to the wall. The stretching process is assumed to restructure turbulence at small scales by forcing these to satisfy local axisymmetry with invariance under rotation about the axis aligned with the main flow. It can be shown analytically that kinematic constraints imposed by local axisymmetry force turbulence near the wall to tend towards the one-component state and when turbulence reaches this limiting state it must be entirely suppressed across the viscous sublayer. For the limiting state of wall turbulence, the statistical dynamics of the turbulent stresses, constructed by combining the two-point correlation technique and invariant theory, suggest that turbulent drag reduction by homogeneously distributed high polymers, cast into the functional space which emphasizes the anisotropy of turbulence, resembles the process of reverse transition from the turbulent state towards the laminar flow state. These findings are supported by results of direct numerical simulations of wall-bounded turbulent flows of Newtonian and non-Newtonian fluids and by experiments carried out, under well-controlled laboratory conditions, in a refractive index-matched pipe flow facility using state-of-the art laser-Doppler anemometry. Theoretical considerations based on the elastic behavior of a polymer and spatial intermittency of turbulence at small scales enabled quantitative estimates to be made for the relaxation time of a polymer and its concentration that ensure maximum drag reduction in turbulent pipe flows, and it is shown that predictions based on these are in very good agreement with available experimental data.

9

Morimoto, Masahiro, Yoshio Makino, Junji Gonda, Masahiro Misaki, Kenji Ishida, Yasukiyo Ueda, and Atsushi Kubono. "Electrorheological response of the interfacial layer between a liquid crystal and a polymer alignment sublayer." Thin Solid Films 558 (May 2014): 227–30. http://dx.doi.org/10.1016/j.tsf.2014.02.065.

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10

Kalutskii, V. N., V. G. Shigorin, L. V. Lomova, and N. I. Lebedinskaya. "Effect of metallising conditions on structural characteristics of the aluminium sublayer of metallised-polymer coatings." Welding International 5, no. 11 (January 1991): 883–84. http://dx.doi.org/10.1080/09507119109446808.

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11

Sergeevichev, David S., Svetlana I. Dorovskikh, Evgeniia S. Vikulova, Elena V. Chepeleva, Maria B. Vasiliyeva, Tatiana P. Koretskaya, Anastasiya D. Fedorenko, et al. "Vapor-Phase-Deposited Ag/Ir and Ag/Au Film Heterostructures for Implant Materials: Cytotoxic, Antibacterial and Histological Studies." International Journal of Molecular Sciences 25, no. 2 (January 16, 2024): 1100. http://dx.doi.org/10.3390/ijms25021100.

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Using gas-phase deposition (Physical Vapor Deposition (PVD) and Metal Organic Chemical Vapor Deposition (MOCVD)) methods, modern implant samples (Ti alloy and CFR-PEEK polymer, 30% carbon fiber) were functionalized with film heterostructures consisting of an iridium or gold sublayer, on the surface of which an antibacterial component (silver) was deposited: Ag/Ir(Au)/Ti(CFR-PEEK). The biocidal effect of the heterostructures was investigated, the effect of the surface relief of the carrier and the metal sublayer on antibacterial activity was established, and the dynamics of silver dissolution was evaluated. It has been shown that the activity of Ag/Ir heterostructures was due to high Ag+ release rates, which led to rapid (2–4 h) inhibition of P. aeruginosa growth. In the case of Ag/Au type heterostructures, the inhibition of the growth of P. aeruginosa and S. aureus occurred more slowly (from 6 h), and the antibacterial activity appeared to be due to the contribution of two agents (Ag+ and Au+ ions). It was found, according to the in vitro cytotoxicity study, that heterostructures did not exhibit toxic effects (cell viability > 95–98%). An in vivo biocompatibility assessment based on the results of a morphohistological study showed that after implantation for a period of 30 days, the samples were characterized by the presence of a thin fibrous capsule without volume thickening and signs of inflammation.

12

Millot, M. C., L. Loehman, B. Sébille, and H. Hommel. "Chromatographic properties of chiral stationary phases based on human serum albumin. Influence of the polymer sublayer." Chromatographia 50, no. 11-12 (December 1999): 641–48. http://dx.doi.org/10.1007/bf02497297.

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13

Hirpa, Mehmet Meric, Sumanth Kumar Arnipally, and Ergun Kuru. "Effect of the Particle Size on the Near-Wall Turbulence Characteristics of the Polymer Fluid Flow and the Critical Velocity Required for Particle Removal from the Sand Bed Deposited in Horizontal Wells." Energies 13, no. 12 (June 18, 2020): 3172. http://dx.doi.org/10.3390/en13123172.

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Water-based polymer drilling fluids are commonly used for drilling long horizontal wells where eliminating the drilling fluid-related formation damage and minimizing the environmental impact of the drilling fluids are the main concerns. An experimental study was conducted to investigate the turbulent flow of a polymer fluid over a stationary sand bed deposited in a horizontal pipeline. The main objectives of the study were to determine the effects of sand particle size on the critical velocity required for the onset of the bed erosion and the near-wall turbulence characteristics of the polymer fluid flow over the sand bed. Industrial sand particles having three different size ranges (20/40, 30/50, 40/70) were used for the experiments. The particle image velocimetry (PIV) technique was used to determine instantaneous local velocity distributions and near-wall turbulence characteristics (such as Reynolds stress, axial and turbulence intensity profiles) of the polymer fluid flow over the stationary sand bed under turbulent flow conditions. The critical velocity for the onset of the particle removal from a stationary sand bed using a polymer fluid flow was affected by the sand particle size. The critical velocity required for the particle removal from the bed deposits did not change monotonously with the changing particle size. When polymer fluids were used for hole cleaning, the particle size effect on the critical velocity varied (i.e., critical velocity increased or decreased) depending on the relative comparison of the sand particle size with respect to the thickness of the viscous sublayer under turbulent flow condition.

14

Mizunuma, H., K. Ueda, and Y. Yokouchi. "Synergistic Effects in Turbulent Drag Reduction by Riblets and Polymer Additives." Journal of Fluids Engineering 121, no. 3 (September 1, 1999): 533–40. http://dx.doi.org/10.1115/1.2823501.

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Drag reduction was investigated for the combined system of polymer additives and a riblet pipe. The riblet grooves were V-shaped, the spacing of which was 1.3 mm and the height of which was 1.01 mm. For higher h+, a triangular riblet system including other geometries increases the drag to levels similar to those of normal transient roughness. This drag increase was generally given as a function of h+. The polymer additives were Aronfloc N-110 and Separan AP-30. The critical shear stress τ*, at which N-110 started the drag reduction, was approximately eight times higher than τ* for AP-30. In the combined system, the synergistic drag reduction for higher h+ was discussed under the assumption that the additives suppressed the drag increase resulting from riblets. Since the additives thicken a wall layer covering the region from a viscous sublayer to a buffer layer, the relative height of h to this wall layer thickness is lowered. In addition, the flow enhancement due to additives relatively suppresses the riblet-induced drag increase. The analysis based on velocity profiles indicated that these effects can produce synergistic drag reduction for higher h+.

15

White, C. M., Y. Dubief, and J. Klewicki. "Properties of the mean momentum balance in polymer drag-reduced channel flow." Journal of Fluid Mechanics 834 (November 17, 2017): 409–33. http://dx.doi.org/10.1017/jfm.2017.721.

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Mean momentum equation based analysis of polymer drag-reduced channel flow is performed to evaluate the redistribution of mean momentum and the mechanisms underlying the redistribution processes. Similar to channel flow of Newtonian fluids, polymer drag-reduced channel flow is shown to exhibit a four layer structure in the mean balance of forces that also connects, via the mean momentum equation, to an underlying scaling layer hierarchy. The self-similar properties of the flow related to the layer hierarchy appear to persist, but in an altered form (different from the Newtonian fluid flow), and dependent on the level of drag reduction. With increasing drag reduction, polymer stress usurps the role of the inertial mechanism, and because of this the wall-normal position where inertially dominated mean dynamics occurs moves outward, and viscous effects become increasingly important farther from the wall. For the high drag reduction flows of the present study, viscous effects become non-negligible across the entire hierarchy and an inertially dominated logarithmic scaling region ceases to exist. It follows that the state of maximum drag reduction is attained only after the inertial sublayer is eradicated. According to the present mean equation theory, this coincides with the loss of a region of logarithmic dependence in the mean profile.

16

ROBERT, ASHISH, T. VAITHIANATHAN, LANCE R. COLLINS, and JAMES G. BRASSEUR. "Polymer-laden homogeneous shear-driven turbulent flow: a model for polymer drag reduction." Journal of Fluid Mechanics 657 (June 28, 2010): 189–226. http://dx.doi.org/10.1017/s0022112010001394.

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Drag reduction (DR) under a turbulent boundary layer implies the suppression of turbulent momentum flux to the wall, a large-eddy phenomenon. Our hypothesis is that the essential mechanisms by which dilute concentrations of long-chain polymer molecules reduce momentum flux involve only the interactions among turbulent velocity fluctuations, polymer molecules and mean shear. Experiments indicate that these interactions dominate in a polymer-active ‘elastic layer’ outside the viscous sublayer and below a Newtonian inertial layer in a polymer-laden turbulent boundary layer. We investigate our hypothesis by modelling the suppression of momentum flux with direct numerical simulation (DNS) of homogeneous turbulent shear flow (HTSF) and the finite extensible nonlinear elastic with Peterlin approximation (FENE-P) model for polymer stress. The polymer conformation tensor equation was solved using a new hyperbolic algorithm with no artificial diffusion. We report here on the equilibrium state with fixed mean shear rate S, where progressive increases in non-dimensional polymer relaxation time WeS (shear Weissenberg number) or concentration parameter 1 − β produced progressive reductions in Reynolds shear stress, turbulence kinetic energy and turbulence dissipation rate, concurrent with increasing polymer stress and elastic potential energy. The changes in statistical variables underlying polymer DR with 1 − β, WeS, %DR and polymer-induced changes to spectra are similar to experiments in channel and pipe flows and show that the experimentally measured increase in normalized streamwise velocity variance is an indirect consequence of DR that is true only at lower DR. Comparison of polymer stretch and elastic potential energy budgets with channel flow DNS showed qualitative correspondence when distance from the wall was correlated to WeS. As WeS increased, the homogeneous shear flow displayed low-DR, high-DR and maximum-DR (MDR) regimes, similar to experiments, with each regime displaying distinctly different polymer–turbulence physics. The suppression of turbulent momentum flux arises from the suppression of vertical velocity fluctuations primarily by polymer-induced suppression of slow pressure–strain rate correlations. In the high-Weissenberg-number MDR-like limit, the polymer nearly completely blocks Newtonian inter-component energy transfer to vertical velocity fluctuations and turbulence is maintained by the polymer contribution to pressure–strain rate. Our analysis from HTSF with the FENE-P representation of polymer stress and its comparisons with experimental and DNS studies of wall-bounded polymer–turbulence supports our central hypothesis that the essential mechanisms underlying polymer DR lie directly in the suppression of momentum flux by polymer–turbulence interactions in the presence of mean shear and indirectly in the presence of the wall as the shear-generating mechanism.

17

Ye, Peng, Dong Zhang, Lian Bin Zhong, Guang Wang, Bin Fu, and Hong Guang Jin. "The Influence of Geology Factor on Alkaline Surfactant Polymer Flood Effect and the Corresponding Strategy." Key Engineering Materials 703 (August 2016): 251–55. http://dx.doi.org/10.4028/www.scientific.net/kem.703.251.

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This study gives the influence laws of abandoned channel, in-layer interlayer, sand body contact relationship on the development effect of the Alkaline Surfactant Polymer (ASP) flooding based on the data of the industry promotion block ( Pu I32、Pu I33 sedimentation), and give out corresponding adjustment strategy at the same time. The result shows that: The ‘abruptly abandoned’ channels have a bad connection with the main channel and possesses a far lower reservoir producing degree (16.1%) than the ‘gradually-abandoned’ channels (79.9%). The injection wells located upon the channel sand need high concentration inject fluid with lower injection rate to handle the polymer breakthrough; The injection wells located between the channels need lower concentration injection; The injection wells located upon the abandoned channels firstly need high concentration injection to achieve the profile control and then inject low concentration fluid to adjust low permeable sublayer; The production wells located upon abandoned channels need timely fracturing measures. By July 2014, water content of this area is 90.7%, oil recovery improved 18.08% and is expected to reach 22.0%. Similar the success experience we get from this area can guide the study of block geologic factors that affect development result and has important guiding significance to the implementation of pointed development adjustment.

18

Fathanah, Umi, Izarul Machdar, Medyan Riza, Nasrul Arahman, Mirna Rahmah Lubis, and Mukramah Yusuf. "The Improvement of Hydrophilic Property of Polyethersulfone Membrane with Chitosan as Additive." Jurnal Rekayasa Kimia & Lingkungan 15, no. 1 (March 16, 2020): 53–61. http://dx.doi.org/10.23955/rkl.v15i1.15916.

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Membrane technology has been implemented broadly for clean water treatment. To produce a better membrane, modification is carried out by adding chitosan into a polymer solution. Materials used in this research are polyethersulfone (PES) 18%, the n-methyl pyrrolidone solvent modified with a chitosan solution (at 0.2 – 1 wt%) as an additive, and deionized water as a non-solvent. The membrane synthesis is carried out with the non-solvent induced phase separation method of blending the polymer. Membrane characterization includes functional group analysis, morphological structure, and water contact angle. Membrane performance is monitored at the filtration process, resulting in the permeability coefficient, and for the rejection of a contaminant (humic acid) with dead-end filtration. Research results show that the modified membrane characterization has an asymmetric morphological structure with a thinner top layer, and the membrane sublayer has a finger-like macrovoid structure with a larger size as compared to the original PES membrane (without the chitosan solution addition). The chitosan additive into the PES membrane improves the membrane’s hydrophilic property. The highest value of the permeability coefficient is achieved with a 1% chitosan addition, which provides a permeability coefficient value of 10.524 L/m2.h.bar and a rejection coefficient of 70.3%.

19

Bandyopadhyay, Promode R. "Stokes Mechanism of Drag Reduction." Journal of Applied Mechanics 73, no. 3 (September 20, 2005): 483–89. http://dx.doi.org/10.1115/1.2125974.

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The mechanism of drag reduction due to spanwise wall oscillation in a turbulent boundary layer is considered. Published measurements and simulation data are analyzed in light of Stokes’ second problem. A kinematic vorticity reorientation hypothesis of drag reduction is first developed. It is shown that spanwise oscillation seeds the near-wall region with oblique and skewed Stokes vorticity waves. They are attached to the wall and gradually align to the freestream direction away from it. The resulting Stokes layer has an attenuated nature compared to its laminar counterpart. The attenuation factor increases in the buffer and viscous sublayer as the wall is approached. The mean velocity profile at the condition of maximum drag reduction is similar to that due to polymer. The final mean state of maximum drag reduction due to turbulence suppression appears to be universal in nature. Finally, it is shown that the proposed kinematic drag reduction hypothesis describes the measurements significantly better than what current direct numerical simulation does.

20

Calvez, Ingrid, Caroline R. Szczepanski, and Véronic Landry. "Effect of Copolymer on the Wrinkle Structure Formation and Gloss of a Phase-Separated Ternary Free-Radical/Cationic Hybrid System for the Application of Self-Matting Coatings." Polymers 14, no. 12 (June 11, 2022): 2371. http://dx.doi.org/10.3390/polym14122371.

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Hybrid free-radical/cationic systems can generate phase-separated polymers or interpenetrating networks driven by photopolymerization. In this study, phase separation of a ternary mixture composed of a polybutadiene urethane diacrylate (PBUDA), a cycloaliphatic diepoxyde (CE), and hexanediol dimethacrylate (HDDMA) was investigated. Using systematic variations of the initial composition of the mixture, a miscibility phase diagram of the ternary mixture was established. Based on this diagram, a reactive copolymer (poly(butyl acrylate-co-glycidyl methacrylate) (PBGMA)) was introduced in a reference hybrid system to manipulate the crosslinking network, polymer morphology, and properties (e.g., roughness, gloss, strain at break, and glass transition temperature Tg). When cured as a coating, the ternary hybrid system showed a depthwise gradient of epoxy conversion, and thereby developed a mostly cured skin above a viscous sublayer of uncured monomer. This skin can develop compressive stress due to the swelling from the diffusion of unreacted monomers beneath, and if the compressive stress is significantly high, wrinkles appear on the coating’s surface. This work highlights how both skin thickness and elastic modulus impact wrinkle frequency and amplitude. It was demonstrated that these wrinkle parameters can be manipulated in the ternary system by the addition of PBGMA. We also demonstrated that by employing UV irradiation and varying the PBGMA content, it is possible to engineer coatings that range from smooth surfaces with high gloss to wrinkled topographies with a very low associated gloss.

21

Ma, Deng-hao, En-ze Jin, Jun-ping Li, Zhen-hua Hou, Jian Yin, Xin Sun, Jin-ming Fang, Xiao-dong Gong, and Li-na Huang. "Mechanical Properties and Failure Behavior of 3D-SiCf/SiC Composites with Different Interphases." Scanning 2020 (December 9, 2020): 1–7. http://dx.doi.org/10.1155/2020/6678223.

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Continuous silicon carbide fiber-reinforced silicon carbide ceramic matrix composites (SiCf/SiC) are promising as thermal structural materials. In this work, the microstructure and static mechanical properties of 3D-SiCf/SiC with PyC, SiC, and PyC/SiC and without an interface prepared via polymer infiltration and pyrolysis (PIP) were investigated systematically in this paper. The results show that the microstructure and static mechanical properties of SiCf/SiC with an interphase layer were superior to the composites without an interlayer, and the interface debondings are existing in the composite without an interphase, resulting in a weak interface bonding. When the interphase is introduced, the interfacial shear strength is improved, the crack can be deflected, and the fracture energy can be absorbed. Meanwhile, the shear strength of the composites with PyC and PyC/SiC interfaces was 118 MPa and 124 MPa, respectively, and showing little difference in bending properties. This indicates that the sublayer SiC of the PyC/SiC multilayer interface limits the binding state and the plastic deformation of PyC interphase, and it is helpful to improve the mechanical properties of SiCf/SiC.

22

Medeiros, Keila Machado, Dayanne Diniz Souza, Taciana Regina de Gouveia Silva, Edcleide Maria Araújo, and Hélio Lucena Lira. "Polyamide66/National Bentonite Clay Nanocomposites Membranes for Water-Oil Separation." Materials Science Forum 727-728 (August 2012): 1807–11. http://dx.doi.org/10.4028/www.scientific.net/msf.727-728.1807.

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Membranes can be defined as polymer film that acts as a semipermeable barrier to filtration in a molecular scale, separating two phases. In this work, microporous membranes were obtained from hybrid organic/inorganic polyamide66 (PA66) and clay mineral from Paraíba State, treated with a quaternary ammonium salt in order to make it organophilic. The membranes in the form of thin films were prepared by immersion-precipitation technique from the nanocomposites obtained by solution, with a pre-determined reaction time of 2 h, with characteristics suitable to be used in microfiltration process for separation of the oil present in water. Samples of natural and organophilic clay were characterized by X-ray fluorescence (XRF) and Fourier transform infrared spectroscopy (FTIR). Meanwhile, the membranes were characterized by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). The results of FRX and FTIR confirmed the presence of quaternary ammonium salt in the clay structure after treatment with organic salt. Through DSC analysis it was observed almost no change in the melting temperature of the pure polyamide66 membranes. By SEM, it was revealed an asymmetric morphology consisting of a skin layer and a porous sublayer, showing the pore size distribution appropriated to water-oil separation.

23

Ortiz-Villafuerte, Javier, and Yassin A. Hassan. "Investigation of Microbubble Boundary Layer Using Particle Tracking Velocimetry." Journal of Fluids Engineering 128, no. 3 (October 11, 2005): 507–19. http://dx.doi.org/10.1115/1.2174062.

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Particle tracking velocimetry has been used to measure the velocity fields of both continuous phase and dispersed microbubble phase, in a turbulent boundary layer, of a channel flow. Hydrogen and oxygen microbubbles were generated by electrolysis. The average size of the microbubbles was 15μm in radius. Drag reductions up to 40% were obtained, when the accumulation of microbubbles took place in a critical zone within the buffer layer. It is confirmed that a combination of concentration and distribution of microbubbles in the boundary layer can achieve high drag reduction values. Microbubble distribution across the boundary layer and their influence on the profile of the components of the liquid mean velocity vector are presented. The spanwise component of the mean vorticity field was inferred from the measured velocity fields. A decrease in the magnitude of the vorticity is found, leading to an increase of the viscous sublayer thickness. This behavior is similar to the observation of drag reduction by polymer and surfactant injection into liquid flows. The results obtained indicate that drag reduction by microbubble injection is not a simple consequence of density effects, but is an active and dynamic interaction between the turbulence structure in the buffer zone and the distribution of the microbubbles.

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Watanabe, Keizo, and Satoshi Ogata. "Drag Reduction by Dried Malted Rice Solutions in Pipe Flow." Liquids 4, no. 2 (June 12, 2024): 432–42. http://dx.doi.org/10.3390/liquids4020023.

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In this study, the friction factor of a turbulent pipe flow for dried rice malt extract solutions was experimentally reduced to that of a Newtonian fluid. The friction factor was measured for four types of solutions at different culture times and concentrations. The results indicate that the experimental data points of the test solutions diverged from the maximum drag reduction asymptote at and above Re√f ≅ 200~250 and aligned parallel to those of Newtonian fluids. This drag reduction phenomenon differed from that observed in artificial high-molecular-weight polymer solutions, called Type A drag reduction, in which the drag reduction level is dependent on the Reynolds number in the intermediate region. This is classified as a Type B drag reduction phenomenon in biopolymer solutions and fine solid particle suspensions. The order of drag reduction corresponded to approximately 5–50 ppm xanthan gum solutions, as reported previously. Furthermore, the velocity profile in a turbulent pipe flow was predicted using a semi-theoretical equation in which the friction factors were determined using the difference between the experimental results of the tested solutions and Newtonian fluids. The results indicate considerable thickening of the viscous sublayer in the turbulent pipe flow of the test solutions compared with that of Newtonian fluids.

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Chai, Liguo, Xiao Liu, Xiaoli Sun, Lin Li, and Shouke Yan. "In situ observation of the melting behaviour of PEO single crystals on a PVPh substrate by AFM." Polymer Chemistry 7, no. 10 (2016): 1892–98. http://dx.doi.org/10.1039/c5py02037a.

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26

FROHNAPFEL, B., P. LAMMERS, J. JOVANOVIĆ, and F. DURST. "Interpretation of the mechanism associated with turbulent drag reduction in terms of anisotropy invariants." Journal of Fluid Mechanics 577 (April 19, 2007): 457–66. http://dx.doi.org/10.1017/s0022112007005083.

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A central goal of flow control is to minimize the energy consumption in turbulent flows and nowadays the best results in terms of drag reduction are obtained with the addition of long-chain polymers. This has been found to be associated with increased anisotropy of turbulence in the near-wall region. Other drag reduction mechanisms are analysed in this respect and it is shown that close to the wall highly anisotropic states of turbulence are commonly found. These findings are supported by results of direct numerical simulations which display high drag reduction effects of over 30% when only a few points inside the viscous sublayer are forced towards high anisotropy.

27

Grzeszczuk, Maria, Jerzy Kalenik, and Anna Kępas-Suwara. "Phase boundaries in layer-by-layer electrodeposited polypyrrole resulted from 2D–3D growths of polymer sublayers." Journal of Electroanalytical Chemistry 626, no. 1-2 (February 2009): 47–58. http://dx.doi.org/10.1016/j.jelechem.2008.11.002.

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28

Domenges, Bernadette, and Karine Charlet. "Direct Insights on Flax Fiber Structure by Focused Ion Beam Microscopy." Microscopy and Microanalysis 16, no. 2 (January 26, 2010): 175–82. http://dx.doi.org/10.1017/s1431927609991292.

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AbstractIn this article, it is shown that focused ion beam (FIB) systems can be used to study the inner structure of flax fibers, the use of which as a reinforcing material in polymer composites still draws much interest from multiple disciplines. This technique requires none of the specific preparations necessary for scanning electron microscopy or transmission electron microscopy studies. Irradiation experiments performed on FIB prepared cross sections with very low Ga+ion beam currents revealed the softer material components of fibers. Thus, it confirmed the presence of pectin-rich layers at the interfaces between the fibers of a bundle, but also allowed the precise localization of such layers within the secondary cell wall. Furthermore, it suggested new insights on the transition modes between the sublayers of the secondary cell wall.

29

Kesari, Kavindra Kumar, Padraic O’Reilly, Jani Seitsonen, Janne Ruokolainen, and Tapani Vuorinen. "Infrared photo-induced force microscopy unveils nanoscale features of Norway spruce fibre wall." Cellulose 28, no. 11 (June 16, 2021): 7295–309. http://dx.doi.org/10.1007/s10570-021-04006-2.

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AbstractInfrared photo-induced force microscopy (IR PiFM) was applied for imaging ultrathin sections of Norway spruce (Picea abies) at 800–1885 cm−1 with varying scanning steps from 0.6 to 30 nm. Cell wall sublayers were visualized in the low-resolution mode based on differences in their chemical composition. The spectra from the individual sublayers demonstrated differences in the orientation of cellulose elementary fibrils (EFs) and in the content and structure of lignin. The high-resolution images revealed 5–20 nm wide lignin-free areas in the S1 layer. Full spectra collected from a non-lignified spot and at a short distance apart from it verified an abrupt change in the lignin content and the presence of tangentially oriented EFs. Line scans across the lignin-free areas corresponded to a spatial resolution of ≤ 5 nm. The ability of IR PiFM to resolve structures based on their chemical composition differentiates it from transmission electron microscopy that can reach a similar spatial resolution in imaging ultrathin wood sections. In comparison with Raman imaging, IR PiFM can acquire chemical images with ≥ 50 times higher spatial resolution. IR PiFM is also a surface-sensitive technique that is important for reaching the high spatial resolution in anisotropic samples like the cell wall. All these features make IR PiFM a highly promising technique for analyzing the recalcitrant nature of lignocellulosic biomass for its conversion into various materials and chemicals. Graphic abstract

30

ZUO, Danying. "DIFFERENT INFLUENCES OF SOLVENTS ON PVDF CASTING SOLUTION PHASE INVERSION AND MEMBRANE SKIN-SUBLAYER STRUCTURE." Acta Polymerica Sinica 008, no. 6 (September 15, 2008): 522–28. http://dx.doi.org/10.3724/sp.j.1105.2008.00522.

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31

Irfan, Muhammad, Yousuf Khan, Atiq Ur Rehman, Naqeeb Ullah, Svetlana N. Khonina, Nikolay L. Kazanskiy, and Muhammad A. Butt. "Plasmonic Perfect Absorber Utilizing Polyhexamethylene Biguanide Polymer for Carbon Dioxide Gas Sensing Application." Materials 16, no. 7 (March 26, 2023): 2629. http://dx.doi.org/10.3390/ma16072629.

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In this paper a perfect absorber with a photonic crystal cavity (PhC-cavity) is numerically investigated for carbon dioxide (CO2) gas sensing application. Metallic structures in the form of silver are introduced for harnessing plasmonic effects to achieve perfect absorption. The sensor comprises a PhC-cavity, silver (Ag) stripes, and a host functional material—Polyhexamethylene biguanide polymer—deposited on the surface of the sensor. The PhC-cavity is implemented within the middle of the cell, helping to penetrate the EM waves into the sublayers of the structure. Therefore, corresponding to the concentration of the CO2 gas, as it increases, the refractive index of the host material decreases, causing a blue shift in the resonant wavelength and vice versa of the device. The sensor is used for the detection of 0–524 parts per million (ppm) concentration of the CO2 gas, with a maximum sensitivity of 17.32 pm (pico meter)/ppm achieved for a concentration of 366 ppm with a figure of merit (FOM) of 2.9 RIU−1. The four-layer device presents a straightforward and compact design that can be adopted in various sensing applications by using suitable host functional materials.

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Sun, Xiaoli, Zhen Chen, Feng Wang, Shouke Yan, and Isao Takahashi. "Influence of Poly(vinylphenol) Sublayer on the Crystallization Behavior of Poly(3-hydroxybutyrate) Thin Films." Macromolecules 46, no. 4 (February 8, 2013): 1573–81. http://dx.doi.org/10.1021/ma302349a.

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33

Li, Quan, Jiandong Zhou, Liguo Chai, Jamil Memon, Zhongjie Ren, Huihui Li, Xiaoli Sun, and Shouke Yan. "The effect of the poly(vinyl phenol) sublayer on the melting behavior of poly(butylene adipate) crystals." Polymer Chemistry 5, no. 14 (2014): 4293. http://dx.doi.org/10.1039/c4py00119b.

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34

Semenov, Alexander, and Irina Nyrkova. "Adsorption of Wormlike Chains onto Partially Permeable Membranes." Polymers 15, no. 1 (December 22, 2022): 35. http://dx.doi.org/10.3390/polym15010035.

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Reversible adsorption of a single stiff wormlike macromolecule to flat membranes with various permeabilities is considered theoretically. It is shown that the adsorbed layer microstructure is significantly different from either a flexible chain or a stiff chain adsorption at a solid surface. Close to the critical point, the adsorbing wormlike chain forms a strongly anisotropic proximal layer near the membrane in addition to a nearly isotropic distal layer. The proximal layer is characterized by the algebraic monomer concentration profile, c(x)∝x−β, due to the self-similar distribution of aligned polymer loops. For a perfectly penetrable membrane, β=1 which is different from β=4/3 obtained for semiflexible chain adsorption at a solid surface. Moreover, we establish that the critical exponent for a partially permeable membrane depends on its properties (porosity w) and propose an asymptotically exact theory (based on the generalized Edwards equation) predicting this dependence, β=β(w). We also develop a scaling theory elucidating, in particular, an intricate competition of loops and tails in both proximal and distal sublayers.

35

Jiang, Yue, Shanzhu Guo, Jingjing Jiao, and Long Li. "A Biphasic Hydrogel with Self-Healing Properties and a Continuous Layer Structure for Potential Application in Osteochondral Defect Repair." Polymers 15, no. 12 (June 20, 2023): 2744. http://dx.doi.org/10.3390/polym15122744.

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The treatment of osteochondral defects remains challenging due to the limited healing capacity of cartilage and the poor results of traditional methods. Inspired by the structure of natural articular cartilage, we have fabricated a biphasic osteochondral hydrogel scaffold using a Schiff base reaction and a free radical polymerization reaction. Carboxymethyl chitosan (CMCS), oxidized sodium alginate (OSA), and polyacrylamide (PAM) formed a hydrogel (COP) as the cartilage layer, while hydroxyapatite (HAp) was incorporated into the COP hydrogel to obtain a hydrogel (COPH) as an subchondral bone layer. At the same time, hydroxyapatite (HAp) was incorporated into the COP hydrogel to obtain a hydrogel (COPH) as an osteochondral sublayer, combining the two to obtain an integrated scaffold for osteochondral tissue engineering. Interlayer interpenetration through the continuity of the hydrogel substrate and good self-healing properties due to the dynamic imine bonding of the hydrogel resulted in enhanced interlayer bond strength. In addition, in vitro experiments have shown that the hydrogel exhibits good biocompatibility. It shows great potential for osteochondral tissue engineering applications.

36

Silva Almeida, Marcilio, Livia Da Silva Oliveira, David Barbosa de Alencar, and Francisco Carlos Tavares Amorim. "Mechanical Analysis of Asphalt Pavements with Alternative Materials in Manaus - Amazonas." International Journal for Innovation Education and Research 7, no. 10 (October 31, 2019): 646–62. http://dx.doi.org/10.31686/ijier.vol7.iss10.1811.

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Pathologies in urban roads are common and recurring problems in the municipality of Manaus - AM, where defects have appeared early and successfully, especially the climatic condition of the differentiated region and the non-participation of the coarse aggregate in the asphaltic coating and sublayers. predominantly made of clay. Nevertheless, the Government often performs simple "hole-covering" operations to recover and restore such a structure, corroborating all the problems that trigger poor paving in the State Capital of Amazonas. Another challenge of the municipal administration is the disposal of construction waste, making it necessary to recycle it, highlighting the serious environmental problem caused by the extraction of the pebble. Aiming to contribute with alternatives the scarcity of stone material and the natural aggregate (pebble), substitute of gravel in the regional civil construction, it is proposed the use of construction and demolition waste (RCD). Asphalt concrete (AS) mixtures were made with recycled material, residual sand, portland cement, petroleum asphalt cement (CAP 50/70) and this binder modified with the addition of SBS (styrene and butadiene copolymer). Characterization tests were performed with aggregates, filler and petroleum asphalt cement (original and polymer), dosed by the Marshall method, and the asphalt mixtures were subjected to the Beam Fatigue Test at three different stress levels. The studies indicated satisfactory results of asphalt mixtures with the participation of RCD and SBS binder, compared to regional composites.

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Ovari, Tamara-Rita, Árpád Ferenc Szőke, Gabriel Katona, Gabriella Stefánia Szabó, and Liana Maria Muresan. "Temporary Anti-Corrosive Double Layer on Zinc Substrate Based on Chitosan Hydrogel and Epoxy Resin." Gels 9, no. 5 (April 25, 2023): 361. http://dx.doi.org/10.3390/gels9050361.

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In practice, metal structures are frequently transported or stored before being used. Even in such circumstances, the corrosion process caused by environmental factors (moisture, salty air, etc.) can occur quite easily. To avoid this, metal surfaces can be protected with temporary coatings. The objective of this research was to develop coatings that exhibit effective protective characteristics while also allowing for easy removal, if required. Novel, chitosan/epoxy double layers were prepared on zinc by dip-coating to obtain temporary tailor-made and peelable-on-demand, anti-corrosive coatings. Chitosan hydrogel fulfills the role of a primer that acts as an intermediary between the zinc substrate and the epoxy film to obtain better adhesion and specialization. The resulting coatings were characterized using electrochemical impedance spectroscopy, contact angle measurements, Raman spectroscopy, and scanning electron microscopy. The impedance of the bare zinc was increased by three orders of magnitude when the protective coatings were applied, proving efficient anti-corrosive protection. The chitosan sublayer improved the adhesion of the protective epoxy coating. The structural integrity and absolute impedance of the protective layers were conserved in both basic and neutral environments. However, after fulfilling its lifespan, the chitosan/epoxy double-layered coating could be removed after treatment with a mild acid without damaging the substrate. This was because of the hydrophilic properties of the epoxy layer, as well as the tendency of chitosan to swell in acidic conditions.

38

Huang, Zheng-Qing, Long Chen, Kun Chen, Zhi Zhang, and Hong-Tao Xu. "A novel method for controlling the sublayer microstructure of an ultrafiltration membrane: The preparation of the PSF-Fe3O4ultrafiltration membrane in a parallel magnetic field." Journal of Applied Polymer Science 117, no. 4 (April 1, 2010): 1960–68. http://dx.doi.org/10.1002/app.32191.

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39

Kawamoto, Teppei, Taro Kimura, Makoto Aoki, Norifumi L. Yamada, Takako Mizusawa, Junpei Miyake, Kenji Miyatake, and Junji Inukai. "Sublayered Thin Films of Polymer Electrolyte for Fuel Cells Formed on SiO2 and Pt Substrates Analyzed By Neutron Reflectometry Under Controlled Temperature and Humidity." ECS Meeting Abstracts MA2020-02, no. 35 (November 23, 2020): 2265. http://dx.doi.org/10.1149/ma2020-02352265mtgabs.

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40

Kim, Sung-Chul, and Byung-Yun Lim. "Preparation of composite Membranes of Dense PAA-Poly(BMA-co-MMA) IPN Supported on Porous and Crosslinked Poly(BMA-co-MMA) Sublayer and Their Pervaporation Characteristics." Macromolecular Research 11, no. 3 (June 2003): 163–71. http://dx.doi.org/10.1007/bf03218347.

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41

Feng, Guanghui, Xiyuan Yao, Yulan Yu, and Hejun Li. "Response mechanism study of alternate ZrC-10vol.% SiC/ZrC-70vol.% SiC coatings with various sublayer thicknesses for cyclic and long-term thermal exposure." Journal of Materials Science & Technology 140 (March 2023): 153–62. http://dx.doi.org/10.1016/j.jmst.2022.09.013.

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42

Semenov, V. V., A. A. Kurygin, S. D. Tarbaev, and A. A. Mamoshin. "Rives – Stoppa surgery – the foundation of the modern concept of treatment of patients with ventral hernias (55 years in surgery)." Grekov's Bulletin of Surgery 179, no. 6 (April 2, 2021): 107–10. http://dx.doi.org/10.24884/0042-4625-2020-179-6-107-110.

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The treatment of ventral hernias in the history of surgery has always been an urgent problem. In the 90s of the XIX century, hernioplasty using metal threads and plates began, but the long-term results of treatment of patients remained unsatisfactory. A particularly urgent problem in herniology during the last century was the treatment of postoperative ventral hernias, and patients with large and even more giant hernias were often recognized as incurable. The great revolution in herniology was the introduction into practice of biologically inert mesh polymer materials. A fundamentally different method of endoprosthesis of the abdominal wall is retromuscular («sublay») hernioplasty, proposed by the French surgeon of Algerian origin Rene Stoppa in 1965. In 1966, a compatriot, colleague and friend R. Stoppa Jean Rives used the principles of this technique when eliminating postoperative median hernia by prosthetics of the anterior abdominal wall retromuscularly through the xiphopubic incision. Decades later, during the rapid development of endovideosurgery, the principle of operation Rives-Stoppa was the foundation for the development of modern minimally invasive and highly effective methods for eliminating inguinal and other ventral hernias. Thus, the method of prosthetics of the anterior abdominal wall proposed 55 years ago by Rives-Stoppa was an ideological breakthrough in herniology and significantly improved the results of operations for external abdominal hernias.

43

Ujiie, Seiji, Yumi Yano, and Akira Mori. "Thermal and Liquid Crystalline Properties of a Polymer with Amphiphilic-Mesogenic Side-Chains." MRS Proceedings 709 (2001). http://dx.doi.org/10.1557/proc-709-cc5.19.1.

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ABSTRACTA low-molecular-weight liquid crystalline amphiphilic compound (Az6Bu) and a liquid crystalline polymethacrylate [P(Az6Bu)] with amphiphilic-mesogenic side-chains are reported in this present paper. A polyethyleneimine chain with 2-hydroxyethyl side-groups was used as the water-soluble spacer. Az6Bu exhibited a lyotropic columnar phase and no thermotropic mesophase. P(Az6Bu) showed thermotropic and lyotropic liquid crystalline properties. P(Az6Bu) formed thermotropic smectic A and C mesophases on the heating and cooling processes. The lyotropic systems consisting of P(Az6Bu) and water exhibited a smectic C lyomesophase with oilystreak and schlieren textures. The layered structures formed in the thermotropic and lyotropic mesophases are composed of a sublayer produced by the anisotropic alignment of aromatic-mesogenic groups and a sublayer of hydrophilic groups.

44

Vinceković, Marko, Marija Bujan, and Maja Dutour Sikirić. "Nano- and microcomplexes of biopolymer carrageenans and dodecylammonium chloride." Journal of Polymer Engineering 31, no. 2-3 (July 1, 2011). http://dx.doi.org/10.1515/polyeng.2011.028.

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Abstract Polymer and surfactant complexation was investigated in systems containing anionic biopolymers and cationic surfactants by various classical and modern methods. Differently charged carrageenans (one, two or three sulfate groups per monomeric unit) and dodecylammonium chloride (DDACl) were used as model systems. Formation of various soluble and insoluble complexes (from nano- to microdimensions) and gelation strongly depends on carrageenan and DDACl concentrations, their molar ratio and linear charge density on carrageenan chains. The main factors governing complexation include electrostatic and hydrophobic interactions as well as conformation of carrageenan chains. With increasing carrageenan concentration, the intramacromolecular complexes change to intermacromolecular, which subsequently reorganize into better ordered structures, giant vesicles, and precipitated stoichiometric compounds, dodecylammonium carrageenates. Structural analysis of the new compounds revealed the formation of a lamellar structure with the polar sublayer containing carrageenan chains and the non-polar sublayer consisting of disordered dodecylammonium chains electrostatically attached to the carrageenan backbone. At gelling carrageenan concentration, progressive addition of DDACl caused gradual transitions from the structure of carrageenan gel alone to lamellar ordering of collapsed gel balanced by intermolecular forces within the gel network, i.e., by hydrogen bonding, electrostatic, hydrophobic and van der Waals forces.

45

Yuan, Hailin, Jinsong Yan, Ping Gao, Sanat K. Kumar, and Ophelia K. C. Tsui. "Microscale mobile surface double layer in a glassy polymer." Science Advances 8, no. 45 (November 11, 2022). http://dx.doi.org/10.1126/sciadv.abq5295.

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This study examines the origin of the widely different length scales, h t —nanometers to micrometers—that have been observed for the propagation of the near-surface enhanced mobility in glassy polymers. Mechanical relaxations of polystyrene films with thicknesses, h , from 5 nm to 186 μm have been studied. For h < ~1 μm, the films relaxed faster than the bulk and the relaxation time decreased with decreasing h below ~100 nm, consistent with the enhanced dynamics originating from a near-surface nanolayer. For h > ~1 μm, a bulk-like relaxation mode emerged, while the fast mode changed to one that extended over ~1 μm from the free surface. These findings evidence that the mobile surface region is inhomogeneous, comprising a nanoscale outer layer and a slower microscale sublayer that relax by different mechanisms. Consequently, measurements probing the enhanced mobility of different mechanisms may find vastly different h t ’s as shown by the literature.

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Oveshnikov, L. N., S. A. Zav’yalov, I. N. Trunkin, D. R. Streltsov, N. K. Chumakov, P. V. Dmitryakov, G. V. Prutskov, O. A. Kondratev, A. A. Nesmelov, and S. N. Chvalun. "Structural characterization and magnetic response of poly(p-xylylene)–MnSb and MnSb films deposited at cryogenic temperature." Scientific Reports 11, no. 1 (August 6, 2021). http://dx.doi.org/10.1038/s41598-021-95475-9.

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AbstractIn this study, we employed several experimental techniques to investigate structure and magnetic properties of poly(p-xylylene)–MnSb composites synthesized by low-temperature vapor deposition polymerization technique and MnSb films deposited at various temperatures. The presence of MnSb nanocrystallites in the studied films was verified by the results of X-ray diffraction, electron microscopy and Raman spectroscopy studies. The obtained data revealed the formation of Sb-rich sublayer with well-oriented Sb grains near the susbtrate, which seems to act as a buffer for the consequent poly(p-xylylene)–MnSb or MnSb layer growth. Increasing the polymer content results in qualitative change of surface morphology of studied films. At high polymer content the hybrid nanocomposite with MnSb nanoparticles embedded into poly(p-xylylene) matrix is formed. All investigated samples demonstrated detectable ferromagnetic response at room temperature, while the parameters of this response revealed a complex correlation with nominal composition, presented crystal phases and surface morphology of studied films. Estimated values of the Curie temperature of the samples are close to that of bulk MnSb.

47

Zikalala, Sithembela A., Nozipho N. Gumbi, Jianxin Li, Bhekie B. Mamba, and Edward N. Nxumalo. "Polymer blending and nanophotocatalyst loading synergy in visible light‐driven photocatalytic PES/SPSf mixed matrix membranes." Journal of Polymer Science, May 22, 2024. http://dx.doi.org/10.1002/pol.20230752.

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AbstractThe synergy of polymer blending and loading photocatalytic titania–amorphous carbon nanotubes (TiO2–aCNT) in tailoring the morphological, surface, and optoelectrical properties of membranes is investigated. High energy band gap (Eg) polyethersulfone (PES), and low Eg sulfonated polyethersulfone (SPSf) polymer blends were loaded with TiO2–aCNT nanocomposite fillers. SEM reveals membranes consisting of a selective layer, a dense sublayer and a spongy layer with the latter two consisting of a network of nanofibers whose diameters decrease with increasing TiO2–aCNT loading. The downshifting in the wavenumbers of sulfonyl and sulfone peaks in Fourier transform infrared and Raman spectra confirms bonding of TiO2–aCNT with PES/SPSf via these groups. Blending PES with SPSf decreases the Eg of the membranes while loading TiO2–aCNT produces a second band edge corresponding to = 2.8 eV. Suppression of charge recombination in membranes is realized at 1.2 filler wt.%. Charge separation occurrs via shuttling of the positive holes to the aCNTs and valence band of TiO2 while electrons are shuttled to the conduction bands of PES and SPSf. Electron impedance spectroscopy shows TiO2–aCNT loading reduces polymer membrane resistance to charge transport. Dye degradation up to 85% is realized under direct sunlight irradiation accompanied by mineralization.

48

Brown, Steven, and Richard Partch. "Boron Nitride Coatings on Silicon Carbide Whiskers." MRS Proceedings 458 (1996). http://dx.doi.org/10.1557/proc-458-421.

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ABSTRACTBoron nitride thin films have been produced on silicon carbide whiskers (SiCw) by a novel processing method. A polydivinylbenzene (PDVB) coating was formed in situ on the whisker surface which was subsequently thermally degraded creating a highly porous carbon layer. The total available pore volume of the carbon layer/ SiCw system (SiCwC) was varied by controlling the quantity of PDVB adsorbed. Next, anhydrous sodium borate was mixed with the SiCwC, and upon heating, the precursor melted and absorbed into the porous carbon layer followed by nitridation with anhydrous ammonia. Under certain reaction conditions, silicon oxynitride was also produced as a sublayer. The amount of the latter can be controlled by varying the reaction temperature and time. Control over the thickness of the BN film was achieved by varying the amount of the carbonized polymer layer in proportion to the quantity of sodium borate.

49

Kong, Jing'an, Yulei Zhang, Hanhui Wang, Guohui Chen, Wenhan Gai, Pengfei Zhang, and Hejun Li. "Sublayer design and ablation resistance of CVD-TaC alternate coatings with different crystallite morphologies for C/C composites." Journal of Materials Science & Technology, November 2022. http://dx.doi.org/10.1016/j.jmst.2022.08.045.

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50

Li, Jinjing, Yiban Wu, Baining Li, Ming Hu, and Jie Zhang. "Enhanced hydrophilicity and antifouling performance of PES-C/emodin ultrafiltration membrane." High Performance Polymers, August 4, 2021, 095400832110359. http://dx.doi.org/10.1177/09540083211035963.

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In this article, an ultrafiltration membrane was fabricated from phenolphthalein polyethersulfone (PES-C) modified with emodin using a phase-inversion method. ATR-FTIR and UV-vis analysis showed that emodin had good compatibility with the PES-C ultrafiltration membrane. SEM showed that the prepared ultrafiltration membranes consisted of a porous skin layer and a macroporous support sublayer. The contact angle value of the pure PES-C ultrafiltration membrane was 77.71° and that of the PES-C ultrafiltration membrane blended with 0.105 wt.% emodin decreased to 65.71°, which explained the fact why its pure water flux significantly increased from 190 L/m2·h to 387 L/m2·h. The antifouling properties of the obtained ultrafiltration membranes were assessed by static protein adsorption, bacterial adhesion, antibacterial tests, and filtration experiments with BSA. The PES-C (13.895 wt.%)/emodin (0.105 wt.%) ultrafiltration membrane presented the lowest protein adsorption rate (1.44%), the highest flux recovery ratio (57%), and the largest inhibition zone diameter (3.0 ± 0.06 mm). Compared with that of the pure PES-C ultrafiltration membrane, the bacterial adhesion effect of the PES-C/emodin (0.105 wt.%) ultrafiltration membrane was significantly reduced. In addition, PES-C incorporated into the emodin ultrafiltration membrane had excellent stability in a deionized water system.

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