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Binding agents are a critical component of Si-based anodes for lithium-ion batteries. Herein, we introduce a composite hydrogel binder consisting of carbon black (CB) and guar, which is chemically cross-linked with glutaraldehyde as a means to reinforce the electrode structure during lithiation and improve electronic conductivity. Dynamic rheological measurements are used to monitor the cross-linking reaction and show that rheology plays a significant role in binder performance. The cross-linking reaction occurs at a faster rate and produces stronger networks in the presence of CB, as evidenced from higher gel elastic modulus in guar + CB gels than guar gels alone. Silicon nanoparticle (SiNP) electrodes that use binders with low cross-link densities (trxn 99.8% after 300 cycles at 1-C rate. Low cross-link densities likely increase the capacity of SiNP anodes because of binder-Si hydrogen-bonding interactions that accommodate volume expansions. In addition, the cross-linked binder demonstrates the potential for self-healing, as evidenced by an increased elastic modulus after the gel was mechanically fragmented, which may preserve the electrode microstructure during lithiation and increase capacity retention. The composite hydrogel with integrated conductive additives gives promise to a new type of binder for next-generation lithium-ion batteries.

The primary focus of the presented research is to come up with a model that could be utilized to evaluate the permeate content (concentration) of oil drops using a straight (nonconverging) slotted microstructured membrane. The content (concentration) of crude drops in the permeate with a nonconverging slit structure membrane has not been studied before, and the study presented would be a good contribution to the literature. A comparison between the use of a converging (narrowing toward the inside) and a nonconverging slotted pore microstructured membrane is made for the purpose of removing oil content from the produced water. Due to the drag force, the droplets pass through the membrane slots; however, the static force acts in the opposite direction and tries to reject droplets by the membrane. At a certain point, these two forces balance the effect of each other, which is known as "100% cutoff through the membrane". A linear line is obtained by joining the 100% cutoff or rejection point to the 0% rejection point, which is referred to as the "linear fit" in this paper. The linear fit approach could be utilized for estimating rejection below the 100% cutoff point. Various types of crude oil drops obtained from different locations were analyzed experimentally, and the results were compared with the presented model. The proposed model was found to be in agreement with the different types of oil drops. Experimental and predicted results showed that the nonconverging slotted microstructured membrane provided low friction to oil drops through the membrane as compared to the converging slots. Furthermore, the developed model can be utilized to predict the overall oil content in the permeate. This research has great importance and will allow researchers around the globe to estimate crude oil concentration within the allowable limits.

Funding Information: The authors gratefully acknowledge The Nonwovens Institute (NWI) at North Carolina State University, Raleigh, for supporting this study. This work was performed in part at the North Carolina State University Analytical Instrumentation Facility (AIF), which is supported by the State of North Carolina and the National Science Foundation (ECCS-2025064). The AIF is a member of the North Carolina Research Triangle Nanotechnology Network (RTNN), a site in the National Nanotechnology Coordinated Infrastructure (NNCI). Publisher Copyright: © We study the interfacial energy parameters that explain the reinforcement of polymers with nanodiamond (ND) and the development of mechanical strength of electrospun ND-reinforced composites. Thermodynamic parameters such as the wettability ratio, work of spreading and dispersion/aggregation transition are used to derive a criterion to predict the dispersibility of carboxylated ND (cND) in polymeric matrices. Such a criterion for dispersion (Dc) is applied to electrospun cND-containing poly(vinyl alcohol) (PVA), polyacrylonitrile (PAN), and polystyrene (PS) fiber composites. The shifts in glass transition temperature (ΔTg), used as a measure of polymer/cND interfacial interactions and hence the reinforcement capability of cNDs, reveal a direct correlation with the thermodynamic parameter Dc in the order of PAN < PS < PVA. Contrary to expectation, however, the tensile strength of the electrospun fibers correlates with the Dc and ΔTg only for semicrystalline polymers (PAN < PVA) while the amorphous PS displays a maximum reinforcement with cND. Such conflicting results reveal a synergy that is not captured by thermodynamic considerations alone but also factor in the contributions of polymer/cND interface stress transfer efficiency. Our findings open the possibility for tailoring the interfacial interactions in polymer-ND fiber composites to achieve maximum mechanical reinforcement.

The friction forces between the wheel and rail depend on a number of variables including the third body layer at the wheel–rail interface, the wheel and rail profiles, and the train dynamics. The third body layer significantly influences the damage mechanisms at the wheel-rail interface, especially wear, rolling contact fatigue (RCF), corrugations and other surface defects that then require maintenance. The introduction of additional constituents at the wheel–rail interface in the form of an additive with anti-wear and anti-crack properties can reduce the wear and RCF. In general, such an additive also reduces the friction. However, it is important to avoid the friction coefficient between the wheel tread and the top of the rail falling below 0.3 because the result would be wheel slip and long braking distances. Measuring friction coefficients accurately is still a challenge, as most existing tribometers are unable to replicate the wheel-rail contact conditions, specifically the contact pressure and sliding speed. The present study used a newly designed handheld tribometer that is able to match the typical contact pressure. Results obtained with the handheld tribometer have been compared with values extracted from the traction-force measurement system of a locomotive. The tribometer field measurements have shown that by using a top-of-rail friction modifier (TOR-FM), both the wear and the friction coefficients can be reduced, but also that heavy TOR-FM films may cause unacceptably low friction. Comparing the results of field and laboratory tests confirms that weather and realistic third bodies present on the track have a significant effect on friction and wear.

This study presents dual-responsive colloidal microgels to repair nonwoven fiber mats (NWFs) and recover their native morphological and functional properties. The formulation comprises poly(N-isopr...

Hypothesis We envisage the use of hydroxylated detonation nanodiamonds (ND-OH), a relatively novel carbonaceous filler with high adsorption activity, small size, and large surface area to create Pickering emulsions. The emulsion behavior under shear and the extent to which the microstructure can rebuild after breakdown is dependent on its yield stress. Experiments Using a model system consisting of isopropyl palmitate and water stabilized by ND-OH particles, we investigate the stability of these emulsions, their microstructure and rheological behavior as a function of ND-OH concentration. Findings Confocal microscopy reveals that increasing ND-OH concentration results in smaller droplet sizes in the emulsions. This behavior is consistent with our rheological results of higher elastic modulus G′ and yield stress of the emulsion with increased ND-OH, as the presence of smaller droplets facilitates the formation of a densely packed network. We find the rheological behavior of these emulsions to be a hybrid of colloidal gels and surfactant-stabilized emulsions, with interparticle interactions and droplets deformability dictating their elasticity and yield stress behavior. Structure recovery following large shear reveals the degree of microstructure recovery to depend on the applied stress, with the recovered modulus collapsing into a single master-curve when the applied stress is scaled by the yield stress.

openaire: EC/H2020/788489/EU//BioELCell Aqueous suspensions of cellulose nanocrystals (CNCs) can spontaneously form a chiral nematic mesophase at a critical concentration (c*). Unfortunately, no current analytical technique permits rapid detection of c*. Herein, we introduce a facile and accurate approach to assess c* rapidly (

Cellulosic nanomaterials constitute a topic of growing commercial interest for numerous applications, many of which demand a working knowledge of the rheology of the materials. We demonstrate here that aqueous suspensions of micro/nanofibrillated cellulose (MNFC) exhibit complex shear behavior governed primarily by fibrillar floc dynamics. Regimes corresponding to structure formation, persistence, and breakdown are quantitatively differentiated. We assess the recovery of the network structure as a function of the applied breakdown conditions and identify critical conditions that characterize the floc dynamics as isotropic or anisotropic. A two-step yield behavior generates persistent anisotropic flocs that effectively prohibit recovery of the initial gel structure under certain conditions. Processing within this stress window entails a risk of generating heterogeneous, potentially irreproducible structures and properties. An in-depth understanding of the rheology of aqueous MNFC suspensions and their floc-dominated, rather than fibril-dominated, nature is critical to rationally tailoring properties through judicious selection of processing conditions.

Ionic liquids (ILs) containing reactive groups provide a tunable medium for bulk polymerization and network formation with potential applications as 3D-printable materials. In this study, dynamic r...

In this study, we present the fabrication of fibers with tunable morphology and porosity from an intrinsically microporous polymer, PIM-1, using a simple one-step electrospinning technique. The met...

Thermoset polymers are examples of chemically cured, network-forming materials whose bulk properties depend sensitively on formulation chemistry and reaction conditions. In this work, we employ mol...

Oil-in-water (O/W) emulsions are widely used in food, pharmaceutical, and personal care applications. These types of systems often contain hydrophobically modified polymers and phospholipids, where...

The application of top-of-rail friction modifiers (TOR-FMs) is claimed by their manufacturers as a well-established technique for minimising the damages in the wheel–rail interface. There are various methods for applying friction modifiers at the wheel–rail interface, among which stationary wayside systems are recommended by TOR-FM manufacturers when a distance of a few kilometres is to be covered. An on-board system is recommended when an area of many kilometres has to be covered and focus is more on particular trains. Trafikverket in Sweden is considering the implementation of the TOR-FM technology on the iron ore line. Directly implementing such technology can be inappropriate and expensive, because the life cycle cost of a TOR-FM system has never been assessed for the conditions of the iron ore line. In the present study, the life cycle cost is calculated for wayside and on-board application systems, by taking inputs from the research performed on iron ore line. The present research has taken the iron ore line as a case study, but the results will be applicable to other infrastructure with similar conditions. The results have shown that the wayside equipment is economically unfeasible for the iron ore line. In this case, the life cycle cost increases by 4% when the friction modifier is applied on all curves with a radius smaller than 550 m and by 19% when the friction modifier is applied on all curves with a radius smaller than 850 m. The on-board system used in this study is shown to be economically feasible, as it has a significantly lower operation and maintenance cost than the wayside equipment. The reduction in the maintenance (grinding and rail replacement) cost when the cost of the friction modifier application is added is 27% when the friction modifier is applied on curves with a radius smaller than 550 m and 23% when the friction modifier is applied on curves with a radius smaller than 850 m.

Funding Information: This work was supported by the Eastman Chemical Company at North Carolina State University and was performed, in part, at the North Carolina State University Molecular Education, Technology and Research Innovation Center (METRIC) and Analytical Instrumentation Facility (AIF), the latter of which is supported by the State of North Carolina and the National Science Foundation (award number ECCS-1542015 ). The AIF is a member of the North Carolina Research Triangle Nanotechnology Network (RTNN), a site in the National Nanotechnology Coordinated Infrastructure (NNCI). We also thank one of the reviewers for insightful comments and recommendations. Publisher Copyright: © 2021 Elsevier Inc. Copyright: Copyright 2021 Elsevier B.V., All rights reserved. Cellulose nanocrystals (CNCs) exhibit a cholesteric mesophase above a critical concentration in aqueous suspensions. Above this concentration, CNCs self-organize into left-handed helicoidal structures that can be preserved in dried, stratified films. In this systematic study, we have prepared optically-active CNC films cast from different electrolyte suspensions and investigated, via circular dichroism and other techniques, the effects of counterion type (six mono/divalent salts, including those responsible for promoting “salting-out” and “salting-in” in the Hofmeister series) and ionic strength on mesomorphic behavior and cholesteric arrangement. The presence of electrolytes influences CNC colloidal stability by compressing the electric double layer and altering interactions among neighboring CNCs and water, thereby affecting the extent to which the CNCs form a mesophase. Interestingly, mesomorphic behavior and CNC alignment appear to be sensitive to cationic radius and charge valence, in which case the optical properties of CNC films can be adjusted for targeted sustainable applications. Such heuristic rules can be valuable for predicting the stability and characteristics of CNC microstructure in designer coatings and thin films prepared by introducing suitable cations prior to film formation.

A new method is proposed to increase the rejection in microfiltration by applying membrane oscillation, using a new type of microfiltration membrane with slotted pores. The oscillations applied to the membrane surface result in reduced membrane fouling and increased separation efficiency. An exact mathematical solution of the flow in the surrounding solution outside the oscillating membrane is developed. The oscillation results in the appearance of a lift velocity, which moves oil particles away from the membrane. The latter results in both reduced membrane fouling and increased oil droplet rejection. This developed model was supported by the experimental results for oil water separation in the produced water treatment. It was proven that the oil droplet concentration was reduced notably in the permeate, due to the membrane oscillation, and that the applied shear rate caused by the membrane oscillation also reduced pore blockage. A four-times lower oil concentration was recorded in the permeate when the membrane vibration frequency was 25 Hz, compared to without membrane vibration. Newly generated microfiltration membranes with slotted pores were used in the experiments.

Silicone composites featuring inclusions of liquid metal particles are soft and stretchable materials with useful electric, dielectric, mechanical, and thermal properties. Until recently, these materials have primarily been cast as films. This work examines the possibility of using uncured liquid metal-elastomer (LME) composites as inks for direct writing. The liquid metal inclusions act as rheological modifiers for the silicone, forming a gel-structure that can be extruded from a nozzle and hold its shape after printing. Additionally, by tuning the particle size, larger particles in the printed structures can settle to form metal-rich regions at the bottom of the structures, encased by metal-depleted (insulating) regions. Using mechanical force, the liquid metal-rich interior can be rendered conductive by sintering without affecting the insulating exterior. Thus, it is possible to print this soft and stretchable material while creating conductors with self-insulating shells.

Because of their utility in diverse coatings applications, a model series of polyester–polyol films possessing different diol formulations and cross-linked with an aliphatic isocyanate cross-linker...

Hypothesis Wetting characteristics of epoxy and phenolic resins on metals depend on the molecular interactions between resins’ functional groups and metal surface. Those interactions affect the practical adhesion strength of epoxy-phenolic coatings on metals. Estimation of the theoretical adhesion energies can reveal this system’s microscopic adhesion mechanisms. Experiments Adhesion is estimated theoretically based on resins’ wettability on metals, and experimentally through pull-off adhesion testing of cured coatings. The effect of various functional groups on adhesion is decoupled using epoxy and phenolic resins with different functionalities. To assess the impact of the metal passivation on adhesion, tinplated and tin-free steel substrates are used. Differences in their surface chemical composition and polarity are investigated using XPS. Findings Theoretical adhesion results reveal a superior adhesion of epoxy compared to phenolic resins. Moreover, epoxy resins having a higher content of epoxide-to-hydroxyl groups show improved theoretical and practical adhesion. The importance of epoxides in driving resins’ initial adhesion on metals is attributed to the formation of direct chemical bonds with active hydrogen on metal surfaces. The adhesion of coatings on tin-free steel is found to be higher than on tinplated steel. This is associated to the increased hydroxyl fraction on tin-free steel surface leading to more hydrogen bonds formation.

Made available in DSpace on 2021-06-25T11:11:52Z (GMT). No. of bitstreams: 0 Previous issue date: 2021-06-01 Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) Ghulam Ishaq Khan Institute of Engineering Sciences and Technology Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) A simple novel electrochemical reduction approach was developed for the self-doping of Nb4+ in niobium oxide nanochannels (Nb2O5NC), changing the conductivity, optical properties, and photocatalytic properties of the material. Nb2O5NC was synthesized using different electrolytes: 0.4 wt% HF in 1 M H2SO4 (EI), 0.4 M NH4F in glycerol (EII), and 0.25 g NH4F with 4 vol% water in glycol at 50 °C (EIII). Field emission scanning electron microscopy (FEG-SEM) analysis showed well-organized arrays of Nb2O5 nanochannels produced on Nb foil, with varying tube diameters in the order EII < EI < EIII and film thickness in the order EI < EII < EIII, which drastically affected the photocurrent vs. potential curves. In order to self-dope the Nb2O5, the samples were electrochemically reduced in 0.1 M KH2PO4 buffer solution (pH 10) for 5 min, at −2.5 V vs. Ag/AgCl, resulting in the doped samples denoted P-EI, P-EII, and P-EIII. The results showed that reduction of Nb5+ to Nb4+ occurred for all the Nb2O5NC samples, leading to decreased surface charge transfer resistance between the Nb2O5NC and the electrolyte, as well as increases of the charge carrier density and photocurrent for all the self-doped samples, compared to undoped samples. Sample P-EI was also tested for the degradation of reactive red 120 (RR120) dye, achieving efficient photoelectrocatalytic degradation of a 10 mg L−1 dye solution. These results reveal that the self-doping approach can enhance the photoelectrocatalytic properties of Nb2O5 photoanode, offering an alternative way for the removal of reactive dyes. Faculty of Materials and Chemical Engineering GIK Institute of Engineering Sciences and Technology São Paulo State University (UNESP) Institute of Chemistry, Rua Prof. Francisco Degni 55 National Institute for Alternative Technologies of Detection Toxicological Evaluation and Removal of Micropollutants and Radioactives (INCT-DATREM) São Paulo State University (UNESP) Institute of Chemistry São Paulo State University (UNESP) Institute of Chemistry, Rua Prof. Francisco Degni 55 National Institute for Alternative Technologies of Detection Toxicological Evaluation and Removal of Micropollutants and Radioactives (INCT-DATREM) São Paulo State University (UNESP) Institute of Chemistry FAPESP: 2014/50945–4 FAPESP: 2016/18057–7

The present work was conducted to examine the beneficial effects of activating natural pozzolan (NP) using hydrated lime (HL) for its efficient utilization in concrete. Optimum dosages of NP and HL determined based on the performance of several trial mixtures to be used in concrete as a partial replacement of ordinary Portland cement (OPC). Three mixtures were finally considered for detailed evaluation of the performance of NP-HL concrete. Activation of NP by HL increased the early- and later-age strength and decreased the depth of water penetration, coefficient of chloride diffusion, depth of carbonation, strength loss due to salt weathering, and reinforcement corrosion. Although the loss of strength due to sulfate attack and shrinkage strain increased due to the inclusion of HL, these values were less than those measured in the concrete prepared using OPC alone. In summary, the results of this study indicate that natural pozzolan can be used as a supplementary cementitious material by activating it using hydrated lime.

A novel analytical approach for estimating the shear rate over the membrane surface and away from the membrane surface as a result of the membrane oscillation has been presented. The model was developed and modified according to our system using the Stokes boundary layer equation. Generation of the shear over the membrane surface is an important phenomenon that not only mitigates the fouling but also enhances the separation efficiency. It is investigated that membrane oscillating frequency, amplitude and viscosity of the souring fluid are important parameters that influence the intensity of the shear on the membrane surface and away from the surface. The model presented was tested with various set of frequencies, amplitudes and viscosities. While, keeping the amplitude constant and changing the frequencies, ahigherintensity of shear over the membrane surface was noticed. On the other hand, keeping the frequency constant and changing the amplitude, a lower shear on the membrane surface was observed. Similarly, as expected, a lower shear over the membrane surface was noticed when the viscosity of the surrounding fluid was increased. The model was supported with the experimental results where separation of oil drops from produced water was the focus of the experiments conducted. It was clear from the experimental results that membrane oscillation enhanced the separation efficiency of the membrane used and therefore, concentration of oil drops in the permeate decreased. Further, the application of the shear was greatly influenced by the pore blocking; higher the shear rate; lower was the pore blocking and vice versa.

Made available in DSpace on 2020-12-12T02:42:10Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-10-01 Ghulam Ishaq Khan Institute of Engineering Sciences and Technology Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) The present work describes the synthesis of niobium oxide nanochannels (Nb2O5NCs) with high surface area, porosity, photocurrent density, and photoelectrochemical stability as photocatalyst. The Nb2O5NCs were prepared by electrochemical anodization of niobium foil in different electrolytes: 1 M H2SO4 containing 0.4 wt% HF (S1); glycerol containing 0.4 M NH4F (S2); 0.25 g NH4F with 4 vol% water in glycol at 50 °C (S3); and glycerol containing 10 wt% K2HPO4, at 130 °C (S4, annealed in air; S5, annealed in N2). All the Nb2O5NCs showed well-organized arrays of nanochannels grown on the Nb foil, with tube diameters in the order S4

Nanomaterials are regularly added to crosslinkable polymers to enhance mechanical properties; however, important effects related to gelation behavior and crosslinking kinetics are often overlooked. In this study, we combine cellulose nanocrystals (CNCs) with a photoactive poly(vinyl alcohol) derivative, PVA-SbQ, to form photocrosslinked nanocomposite hydrogels. We investigate the rheology of PVA-SbQ with and without CNCs to decipher the role of each component in final property development and identify a critical CNC concentration (1.5 wt%) above which several changes in rheological behavior are observed. Neat PVA-SbQ solutions exhibit Newtonian flow behavior across all concentrations, while CNC dispersions are shear-thinning6 wt% and gel at high concentrations. Combining semi-dilute entangled PVA-SbQ (6 wt%) with1.5 wt% CNCs forms a percolated microstructure. In situ photocrosslinking experiments reveal how CNCs affect both the gelation kinetics and storage modulus (G') of the resulting hydrogels. The modulus crossover time increases after addition of up to 1.5 wt% CNCs, while no modulus crossover is observed1.5 wt% CNCs. A sharp increase in G' is observed1.5 wt% CNCs for fully-crosslinked networks due to favorable PVA-SbQ/CNC interactions. A percolation model is fitted to the G' data to confirm that mechanical percolation is maintained after photocrosslinking. A ∼120% increase in G' for 2.5 wt% CNCs (relative to neat PVA-SbQ) confirms that CNCs provide a reinforcing effect through the percolated microstructure formed from PVA-SbQ/CNC interactions. The results are testament to the ability of CNCs to significantly alter the storage moduli of crosslinked polymer gels at low loading fractions through percolation-induced reinforcement.

The use of bulk polymer melt additives provides a facile, industrially relevant approach to tailor properties of polymer surfaces for many different applications. These melt additives, when blended with polymers prior to melt spinning, migrate to the fiber surface and influence surface functionality. While the use of bulk polymer melt additives to impart hydrophilicity or oleophobicity is well studied, the impact of the fiber formation process on additive migration and resultant repellency of nonwoven media products remains largely unexplored. In this study, we produce fluorochemical melt additive containing meltblown nonwovens, and establish methods for characterization of fiber mat surface composition and repellency. Repellency of low surface tension fluids is a significant challenge and is of particular importance in the creation of medical garments such as surgical gowns and masks which must perform as liquid barriers even when exposed to alcohol based solutions. Similarly, melt additives are also used in the production of electret air filtration devices. Electret filters are imbued with charges to enhance particle capture performance, but this charge can be negated through wetting by low surface tension fluids. To address this challenge, the changing composition of fiber surfaces due to the migration of additives is monitored via X-ray Photoelectron Spectroscopy, then related to repellency of alcohol solutions by contact angle analysis. We demonstrate that for the samples tested a fluorine to carbon (F/C) ratio of 0.35 is sufficient to prevent wicking of isopropanol droplets, and higher surface tension fluids could be repelled by fiber mats with lower fluorine content. Through the use of cross-sectional ToF-SIMS analysis, we find that migration of additives is key to the performance of samples with low additive loadings, and that these phenomena are heavily influenced by many nonwoven manufacturing parameters including fiber size, die-to-collector distance, and polymer resin melt flow rates.

Aluminum trihydroxide/polydimethylsiloxane (ATH/PDMS) systems are often used as potting compounds in electronic assemblies to guard the electronics from shock, vibration, corrosive agents, and moisture. In this study, we use dynamic rheology and confocal/optical microscopy to understand the dramatic effects miniscule levels of water have on the microstructure and corresponding rheological behavior of PDMS filled with ATH. In the absence of water, PDMS containing 20 wt % ATH readily flows, exhibiting viscoelastic behavior with some weak particle flocculation. However, the addition of only 0.045 wt % water to the system results in the formation of a sample-spanning, self-supporting physical gel that exhibits an elastic modulus ( G') five orders of magnitude higher than the water-free system. A structure formation mechanism consisting of hydration layer formation followed by interparticle water bridging has been proposed to explain the observed behavior. Recovery of the original viscoelastic fluid is demonstrated by adding molecular sieves (e.g., zeolites) to the fully flocculated system. The recovery can likely be attributed to the adsorption of water by the sieves and the corresponding breakup of water bridges between the ATH particles. On the basis of the proposed mechanism, a variety of other polar and nonpolar solvents have been found to induce physical gelation in ATH/PDMS dispersions with gel modulus being related to the Hildebrand solubility parameter mismatch between the solvent and PDMS fluid.

We apply a recently developed coarse-graining method to build models for polyester polyols, versatile polymers with applications in coatings, by combining models for the component monomers. This strategy employs the corresponding states correlation to the group-contribution SAFT-γ Mie equation of state [Mejia, A.; et al. Ind. Eng. Chem. Res. 2014, 53, 4131–4141] to obtain force-field parameters for the constituent monomer species. Results from simulations agree favorably with experimental values of mass density, glass transition temperature (Tg), and specific heat capacity change at Tg. Further simulations over a range of Mie parameters and polymer chemical compositions yield a correlation that relates the parameters directly to Tg. This correlation is validated by experimental data and can be used as a predictive tool within the tested parameter space to expedite the design of these coating materials.

Rail issues such as corrugation, rolling contact fatigue, noise and wear have been increasing with the increase in railway traffic. The application of top-of-rail friction modifiers (TOR-FMs) is claimed by their manufacturers in the railway industry to be a well-established technique for resolving the above-mentioned issues. There are various methods for applying friction modifiers at the wheel–rail interface, among which stationary wayside systems are recommended by TOR-FM manufacturers when a distance of a few kilometres is to be covered. TOR-FM manufacturers also claim that by using wayside equipment, the TOR-FM can be spread over a minimum distance of 3 km, over which it maintains a coefficient of friction of µ = 0.35 ± 0.05. To determine the carry distance of TOR-FMs, some researchers use tribometers to measure the coefficients of friction. However, moisture and deposits from the environment and trains can alter the top-of-rail friction and give a misleading indication of the presence of a friction modifier. Therefore, the coefficient of friction itself is not a clear indicator of the presence of TOR-FMs. In the present study, cotton swabs dipped in a mixture of alcohol and ester were used to collect surface deposits (a third body) from both the wheel and rail at various distances from the point of application. Subsequently, the third body collected on the cotton swab was analysed using an energy dispersive X-ray analysis. The results have shown that the maximum carry distance of TOR-FMs on the top of the rail is limited to 70 m when using a TOR-FM from one manufacturer and to 450 m when using a TOR-FM from another manufacturer. The carry distance on the contact band of the wheel is limited to 100 m and 340 m. The friction modifier on the edges of the contact band was detected over a distance of up to 3 km; however, this will not minimise the damage or friction at the wheel–rail interface.

The brittle nature of early aerogels developed from inorganic precursors fueled the discovery of their organic counterparts. Prominent among these organics are cellulose aerogels because of their natural abundance, biocompatibility, sustainable precursors, and tunable properties. The hierarchical structure of cellulose, from polymers to nano/microfibers, further facilitates fabrication of materials across multiple length scales with added applicability. However, the inherent flammability, structural fragility, and low thermal stability have limited their use. Recently developed cellulose-based hybrid aerogels offer strong potential owing to their tunability and enhanced functionality brought about by combining the inherent properties of cellulose with organic and inorganic components. A survey of the historical background and scientific achievements in the design and development of cellulose-based hybrid aerogel materials is encompassed here. The impacts of incorporating organic and inorganic ingredients with cellulose and the corresponding synergistic effects are discussed in terms of their design and functionality. The underlying principles governing the structural integration and functionality enhancement are also analyzed. The latest developments of cellulose-based hybrid aerogels fabricated from nontraditional incipient aerogels, such as fibrous webs, are also explored. Finally, future opportunities that could make these materials achieve even greater impacts through improved scalability, rationally designed synthesis, and multifunctional properties are discussed.

Purpose The purpose of this study is to investigate the influence of hemispherical structures fabricated by hot micro-coining on the resulting wear performance. Hemispherical structures with different area densities (20 and 30 per cent), depths (50 and 100 µm) and diameters (100 and 200 µm) were fabricated by hot micro-coining on stainless steel samples. Design/methodology/approach The wear performance of these samples was studied using a ball-on-disk tribometer in rotational sliding mode using a normal load of 30 N and a fixed sliding velocity of 2 cm/s. Two different poly-(alpha)-olefin (PAO) oils without any additive having a kinematic viscosity of 4 and 40 cSt, were used to study the influence of the oil viscosity on the wear behavior. Findings Concerning the polished reference, an enlarged wear volume with an increase in the cycle number and the oil viscosity was observed. In the case of the micro-coined surfaces, all samples demonstrate a pronounced reduction in the wear volume (up to a factor of 100 for PAO 40) compared to the polished reference irrespective of the oil viscosity used. Originality/value This study details new research work studying the wear behavior of hot micro-coined surfaces.

Rolling contact fatigue (RCF) and wear, two major deterioration processes, limit the lifetime of rails. These deterioration processes are even more severe on the curves of tracks used by heavy haul trains. Because wear is a material removing process, it can suppress the formation of RCF (also known as surface initiated cracks). In railways, cracks have a higher risk of instigating a catastrophic failure than wear; hence, it is comparatively better to have wear than to have cracks. By controlling the top-of-rail friction, both of these deteriorating processes can be reduced to enhance the lifetime of rails. In order to achieve these possible advantages, the infrastructure manager of the Swedish railway is planning to implement a top-of-rail friction control technology on the iron ore line in northern Sweden wherein RCF is a major problem on the curves. The present study uses a damage index model in a multi-body simulation software and predicts the probability of RCF formation with suppressing effect of wear for different friction control values. The effect of friction control is simulated on curve radii ranging from 200 to 3000 m and axle loads ranging from 30 to 40 t at a constant train speed of 60 km/h. Findings show that on a very sharp circular curve, radius

openaire: EC/H2020/788489/EU//BioELCell The prediction of the morphology of wet-spun fibers has so far been only possible by complex and experimentally intensive approaches that include the construction of ternary phase diagrams. Ultimately, however, the available models give approximate information. Here we propose an alternative predictive approach that uses design principles based on the combination of (1) relative energy difference (RED) of Hansen solubility and (2) a kinetic parameter "T" that considers mass transfer effects. Such a model is applied and experimentally validated for a priori determination of the diameter and internal morphology of wet-spun fibers. Remarkably, only three. variables relevant to wet-spinning are needed, namely, the choice of polymer, solvent, and nonsolvent types. A combination of systems is tested, and the morphology of the obtained fibers is determined via electron microscopy. Aspects related to demixing, internal specific surface area (BET), and layer formation on the fibers are described qualitatively. The facile implementation of the design parameters is further confirmed through comparison with data published on the subject. Our proposed model is expected to accelerate future developments in nanomaterials, especially in the context of ongoing efforts related to fiber spinning with biopolymers.

We present a facile approach to electrospin nanofibers of guar galactomannan by blending high- and low-molecular weights (MWs) of guar. We discover that while neither native high MW guar nor hydrolyzed low MW guar is electrospinnable on its own, their combination leads to synergism in producing defect-free nanofibers. Such an approach of fabricating nanofibers from blending multiple MWs of the same polymer may provide an easy route to produce nanofibers of biopolymers which are typically hard to electrospin. Rheological studies reveal that a limiting amount of native guar is needed for electrospinnability, and for those systems that have the proportionate amount of native guar, there is a critical total concentration above which fibers form. Interestingly, a plot of blend viscosity versus guar concentration reveals two power-law regimes with an inflection point, above which fiber formation can be achieved akin to the behavior observed for pure (i.e., nonblend) polymers.

Water swellable crosslinked polymers are widely used in oil-in-water emulsions for the healthcare and cosmetic industries due to their thickening properties. In this study, we investigate the rheological and lubrication behavior of a microgel-forming polymer, a lightly-crosslinked hydrophobically modified polyacrylic acid (HMPAA), in an aqueous medium and in an emulsion. Hydrogenated phosphatidylcholine, a class of phospholipids, is used as a surfactant in the emulsions composed of different oil content. Rheological behavior is probed both in the linear and non-linear regimes using small strain amplitude and large amplitude oscillatory shear (LAOS) experiments, respectively. We observe all systems to exhibit gel-like behavior with the elastic modulus (G’) dominating and being frequency independent. Lissajous-Bowditch plots and nonlinear parameters obtained under large deformation show that the emulsions can resist greater deformations with smaller increase in the viscous dissipation when compared to a HMPAA gel. For tribology experiments, friction curves in a range of entrainment speeds are examined using substrates to mimic the skin surface (PDMS and Bioskin®). The role of polymer hydrophobicity on the different substrates are also explored by comparing the behavior of HMPAA to that of its hydrophilic analog, a polyacrylic acid highly crosslinked. We find the friction coefficient to be dependent on the hydrophobicity of the substrate and the polymer as well as the substrate roughness. These results taken together provide insights in the formulation of skincare products with efficient lubrication properties for different skin characteristics.

Tin is a promising replacement for graphite anodes in Li-ion batteries (994 mA h g−1 for Sn vs. 372 mA h g−1 for graphite), but suffers from particle pulverization upon lithiation that causes capacity fade. Herein, thermally reduced graphene oxide-containing carbon nanofibers (TRGO/CNFs) are used as scaffolds to house Sn/SnO2 particles, enhance anode capacity beyond that of graphite, and prolong cycle life of Sn-based electrodes. This study attempts to elucidate structure–composition relationships of tin-TRGO/CNF electrodes that lead to increased capacity retention. The composition and morphology of tin-TRGO/CNFs are assessed as a function of heat-treatment temperature and Sn loading as a means to understand and correlate electrochemical performance with physical features. We find: (1) the oxidation state of tin in TRGO/CNFs is in part determined by temperature-dependent, thermal-decomposition products of polyacrylonitrile-derived CNFs, and (2) precursor Sn(IV) loadings ≤10 wt% in the tin-TRGO/CNFs lead to Sn(0) or SnO2 particles embedded within the fiber + TRGO matrix. Electrodes with precursor Sn(IV) loading ≤10 wt% have smaller tin particles than electrodes with Sn(IV) loadings >10 wt%, and have longer cycle-lives; reversible capacities of ∼600 mA h g−1 are observed at 0.2C rates, while capacities of ∼400 mA h g−1 are observed after hundreds of cycles at 2C rates. The durable graphene-containing nanofiber matrix, coupled with the high-capacity of tin, provides a promising anode material for Li-ion cells.

Rolling contact fatigue is a major problem connected with railway tracks, especially in curves, since it leads to highermaintenance costs. By optimising the top-of-rail friction, the wear and cracks on the top of the rail can eventually bereduced without causing very long braking distances. There are several research articles available on crack prediction,but most of the research is focused either on rail without a friction modifier or on wheels with and without frictioncontrol. In the present study, in order to predict the formation of surface-initiated rolling contact fatigue, a range offriction coefficients with different Kalker’s reduction factors has been assumed. Kalker’s reduction factor takes care ofthe basic tendency of creepage as a function of the traction forces at lower creepage. The assumed range covers possiblefriction values from those for non-lubricated rail to those for rail with a minimum measured friction control on the top ofthe rail using a friction modifier. A fatigue index model based on the shakedown theory was used to predict thegeneration of surface-initiated rolling contact fatigue. Simulations were performed using multi-body simulation, forwhich inputs were taken from the Iron Ore line in the north of Sweden. The effect of friction control was studiedfor different curve radii, ranging from 200 m to 3000 m, and for different axle loads from 30 to 40 tonnes at a constanttrain speed of 60 km/h. One example of a result is that a maximum friction coefficient (m) of 0.2 with a Kalker’s reductionfactor of 15% is needed in the case of trains with a heavy axle load to avoid crack formation. Validerad;2018;Nivå 2;2018-02-12 (svasva) top of rail project

Endodontic treatments of teeth with post-core systems is generally accompanied by increased brittle fracture of the restored teeth. This research aimed to evaluate the combined effect of dental posts and luting cements on fracture resistance and failure mode of the endodontically-treated teeth. Sixty endodontically-treated upper central incisors were randomly restored using titanium, fiber, or stainless steel posts and luted by zinc phosphate or composite resin cements. The teeth were then thermocycled and loaded at 135° until failures were observed. Moreover, a three-dimensional model of teeth was analyzed using the finite element method to compare the stress distributions generated by different post-core systems. The results showed that zinc phosphate cement provided relatively higher fracture resistances, whereas luting with composite resin resulted in more restorable failures. Moreover, the teeth restored by fiber posts exhibited desirable fracture resistances with more restorable failure modes, compared to those treated by stainless steel or titanium posts.

This paper describes an extremely facile method to fabricate metallic wires at room temperature. The wires form by stretching viscoelastic polymer substrates supporting a drop of gallium-based liquid metal. Stretching the polymer causes the metal to also elongate due to the adhesion between the two materials. The diameters of the resulting wires, which can be as small as 10 μm, decrease with increasing strain. This method is inspired by the process used for drawing optical fibers, which involves pulling a pre-form cylinder of molten glass until it thins to the size of a fiber. In contrast, the process here is done at room temperature and realized without the need for large forces. Moreover, geometries beyond simple wires are possible including parallel, core–shell, branched, and helix structures. The resulting wires can be elastic (stretchable), viscoelastic (soft), or plastic (stiff) depending on the chemistry and post-processing of the polymer. Wires can make electrical contacts by allowing the metal to sink through the viscoelastic polymer onto a substrate containing electrodes. In addition, removing the polymer substrate after elongation produces freestanding liquid metal wires stabilized by the surface oxide on the metal. Rheological studies show that polymers with a variety of properties can be utilized to form these wires including viscoelastic materials and gels. The ability to form metallic wires in a simple manner may find uses in soft and stretchable electronics, or enable new applications, such as ‘wires on demand’ for repairing electrical connections.

We report the fabrication of a composite containing nanostructured GaOOH and Matrigel with tunable radiosensitizing and stiffness properties. Composite characterization was done with microscopy and rheology. The utility of the interface was tested in vitro using fibroblasts. Cell viability and reactive oxygen species assays quantified the effects of radiation dosages and GaOOH concentrations. Fibroblasts' viability decreased with increasing concentration of GaOOH and composite stiffness. During ionizing radiation experiments the presence of the scintillating GaOOH triggered a different cellular response. Reactive oxygen species data demonstrated that one can reduce the amount of radiation needed to modulate the behavior of cells on interfaces with different stiffness containing a radiosensitizing material.

The meltblowing process employs high-speed hot air jets to attenuate polymer streams injected from a die head. In this study, we examine design strategies to control the air flow field below the polymer injection point to achieve higher fiber attenuation and meltblown webs with smaller fiber diameters. Computational fluid dynamics (CFD) simulations for new die configurations show that vertical or inclined air constrictors around the primary air jets keep the centerline air velocity and temperature at their maximum values for 10–15 mm longer below the die face than the reference die. Polymer streams are kept near their melting temperatures at higher air velocities for a longer period, resulting in higher fiber attenuation. The underlying mechanisms leading to such behavior are discussed. Experimental results show reduction in fiber diameter and pore size, validating the simulation. Improved filtration properties are also obtained from the nonwovens webs.

This study presents the development and characterization of nonwoven fiber mats (NWFs) with stimuli-controlled permeability. An ensemble of membranes was initially constructed by coating the fibers of polypropylene NWFs with a layer of poly ((N-isopropyl acrylamide)-co-(acrylic acid)) (PNIPAm-co-AA) hydrogel. Different coatings were produced by varying the PNIPAm/AA monomer ratio between 3.9 and 18.6. The thermo-responsive layer is expanded at room temperature and contracts when heated above its lower critical solution temperature (LCST). The resulting membranes were first characterized via laser scanning microscopy and fluorescence confocal microscopy to evaluate the thickness and morphology of the hydrogel layer. Microscopy shows uniform coating of the fibers, with a thickness comparable to the fiber diameter, and homogeneous filling of the pore space. The permeability of the NWFs was then evaluated using different solutes, namely an inorganic salt (sodium chloride), an organic acid (citric acid), and an amphiphilic drug (Doxorubicin). These tests consistently show that the flux of the solute is (1) higher at temperatures > LCST, where the hydrogel layer collapses and opens the pore space, and (2) decreases at room temperature (

Made available in DSpace on 2020-12-12T02:38:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-08-01 Ghulam Ishaq Khan Institute of Engineering Sciences and Technology In this study, computational and statistical models were applied to optimize the inherent parameters of an electrochemical decontamination of synozol red. The effect of various experimental variables such as current density, initial pH and concentration of electrolyte on degradation were assessed at Ti/RuO0·3TiO0·7O2 anode. Response surface methodology (RSM) based central composite design was applied to investigate interdependency of studied variables and train an artificial neural network (ANN) to envisage the experimental training data. The presence of fifteen neurons proved to have optimum performance based on maximum R2, mean absolute error, absolute average deviation and minimum mean square error. In comparison to RSM and empirical kinetics models, better prediction and interpretation of the experimental results were observed by ANN model. The sensitive analysis revealed the comparative significance of experimental variables are pH = 61.03%>current density = 17.29%>molar concentration of NaCl = 12.7%>time = 8.98%. The optimized process parameters obtained from genetic algorithm showed 98.6% discolorization of dye at pH 2.95, current density = 5.95 mA cm−2, NaCl of 0.075 M in 29.83 min of electrolysis. The obtained results revealed that the use of statistical and computational modeling is an adequate approach to optimize the process variables of electrochemical treatment. Faculty of Materials and Chemical Engineering GIK Institute of Engineering Sciences and Technology Faculdade de Engenharias Arquitetura e Urbanismo e Geografia Universidade Federal de Mato Grosso do Sul Cidade Universitária Faculty of Computer Sciences and Engineering GIK Institute of Engineering Sciences and Technology Institute of Chemistry Araraquara São Paulo State University (UNESP), Av. Prof. Francisco Degni 55 National Institute for Alternative Technologies of Detection Toxicological Evaluation and Removal of Micropollutants and Radioactivies (INCT-DATREM) São Paulo State University (UNESP) Institute of Chemistry Institute of Chemistry Araraquara São Paulo State University (UNESP), Av. Prof. Francisco Degni 55 National Institute for Alternative Technologies of Detection Toxicological Evaluation and Removal of Micropollutants and Radioactivies (INCT-DATREM) São Paulo State University (UNESP) Institute of Chemistry

This study investigates the formation of monolayers of microgel particles comprising poly[(N-isopropylacrylamide)-co-(acrylic acid)] on solid substrates, their surface morphology, and stimuli-responsiveness. Crosslinked microgels with different chemical composition were produced to show a broad range of responses in hydrodynamic radius and degree of self-assembly with temperature and pH. Microgels were deposited on silicon wafers primed with a bilayer of poly(octadecene-alt-maleic anhydride) and polyethyleneimine by either incubation or spin coating of aqueous suspension of microgels at different temperature and pH. The characterization of the microgel-coated wafers led to the identification of three metrics describing microgel arrangement: density (ρ); heterogeneity (H), which correlates strongly with ρ and depends on deposition temperature and pH with statistical significance, but not on microgel composition; and packing efficiency (PE), which portrays the regularity of microgel arrangement and exhibits no correlation with ρ nor H. The values of ρ, H, and PE calculated for in silico models of microgel coatings confirmed that these three metrics portray distinct characteristics of surface topology. Finally, profilometry analysis showed that microgel coatings respond to thermal stimuli with sensible variations in surface roughness; notably, the thermal variation of roughness correlates strongly with ρ and H, and to a lesser extent with PE.

openaire: EC/H2020/788489/EU//BioELCell Heterogeneous acetylation of wood fibers is proposed for weakening their interfibrillar hydrogen bonding, which facilitates their processing into micro- and nanocelluloses that can be further used to synthesize filaments via wet-spinning. The structural (SEM, WAXD), molecular (SEC), and chemical (FTIR, titration) properties of the system are used to propose the associated reaction mechanism. Unlike the homogeneous acetylation, this method does not alter the main morphological features of cellulose fibrils. Thus, we show for the first time, the exploitation of synergies of compositions simultaneously comprising dissolved cellulose esters and suspended cellulose micro- and nanofibrils. Such colloidal suspension forms a co-continuous assembly with a matrix that interacts strongly with the micro- and nanofibrils in the dispersed phase. This facilitates uninterrupted and defect-free wet-spinning. Upon contact with an antisolvent (water), filaments are easily formed and display a set of properties that set them apart from those reported so far for nanocelluloses: a remarkable stretchability (30% strain) and ultrahigh toughness (33 MJ/m3), both surpassing the values of all reported nanocellulose-based filaments. All the while, they also exhibit competitive stiffness and strength (6 GPa and 143 MPa, respectively). Most remarkably, they retain 90% of these properties after long-term immersion in water, solving the main challenge of the lack of wet strength that is otherwise observed for filaments synthesized from nanocelluloses.

We introduce a generalized approach to synthesize aerogels that allows remarkable control over its mechanical properties. The Hansen solubility parameters are used to predict and regulate the swelling properties of the precursor gels and, consequently, to achieve aerogels with tailored density and mechanical properties. As a demonstration, crosslinked organogels were synthesized from cellulose esters to generate aerogels. By determination of Hansen’s Relative Energy Difference, it was possible to overcome the limitations of current approaches that solely rely on the choice of precursor polymer concentration to achieve a set of aerogel properties. Hence, from a given concentration, aerogels were produced in a range of mass densities, from 25 to 113 mg/cm3. Consequently, it was possible to tailor the stiffness, toughness and compressive strength of the aerogels, in the ranges between 14–340, 4–103 and 22–373 kPa, respectively. Additionally, unidirectional freeze-drying introduced pore alignment in aerogels with honeycomb morphologies and anisotropy. Interestingly, when the swelling of the polymeric gel was arrested in a non-equilibrium state, it was possible to gain additional control of the property space. The proposed method is a novel and generic solution to achieving full control of aerogel development, which up to now has been an intractable challenge.

With the recent advances in the development of novel protein based therapeutics, controlled delivery of these biologics is an important area of research. Herein, we report the synthesis of microparticles from bovine serum albumin (BSA) as a model protein using Particle Replication in Non-wetting Templates (PRINT) with specific size and shape. These particles were functionalized at room temperature using multifunctional chlorosilane that cross-link the particles to render them to slowly-dissolving in aqueous media. Mass spectrometric study of the reaction products of diisopropyldichlorosilane with individual components of the particles revealed that they are capable of reacting and forming cross-links. Energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were also used to confirm the functionalization of the particles. Cross sectional analysis using focused ion beam (FIB) and EDS proved that the functionalization occurs throughout the bulk of the particles and is not just limited to the surface. Circular dichroism data confirmed that the fraction of BSA molecules released from the particles retains its secondary structure thereby indicating that the system can be used for delivering protein based formulations while controlling the dissolution kinetics.

The challenge to incorporate Si into Li-ion battery anodes has attracted much attention. Binding agents are a critical component in a battery that may also be used to enhance electrode performance. Herein, we report the use of galactomannans—a low-cost, environmentally friendly, biorenewable polymer—as a novel binding agent for Si-containing electrodes. Silicon-containing electrodes with as low as 5 wt% binder show large reversible capacities with >90% charge retention after 100 cycles without the use of electrolyte additives. Large capacities and low binder content when compared to carboxymethyl cellulose allows for greater energy densities and fast Li-extraction for high-power applications. The performance enhancement may be attributed to polymer–particle interactions between the hydroxyl groups of galactomannans and the native-oxide layer of Si. These interactions, coupled with the inherent mechanical integrity of galactomannan thin films, allow for minimal cracking and delamination of the electrode upon lithiation. An undamaged electrode microstructure during large volume expansions allows for coulombic efficiencies >99%. Galactomannans also experience ample polymer swelling in common electrolyte solvents, which leads to rapid Li transport and higher ionic conductivities than other biopolymer-bound electrodes. Galactomannan binders may thus provide a critical step forward in next-generation lithium-ion batteries.