Showing papers by "Wright-Patterson Air Force Base published in 2004"
TL;DR: Measurements of plastic yielding for single crystals of micrometer-sized dimensions for three different types of metals find that within the tests, the overall sample dimensions artificially limit the length scales available for plastic processes.
Abstract: When a crystal deforms plastically, phenomena such as dislocation storage, multiplication, motion, pinning, and nucleation occur over the submicron-to-nanometer scale. Here we report measurements of plastic yielding for single crystals of micrometer-sized dimensions for three different types of metals. We find that within the tests, the overall sample dimensions artificially limit the length scales available for plastic processes. The results show dramatic size effects at surprisingly large sample dimensions. These results emphasize that at the micrometer scale, one must define both the external geometry and internal structure to characterize the strength of a material.
2,113 citations
TL;DR: In this article, the first compelling atomic structural model for metallic glasses is presented, which is based on a new sphere-packing scheme and combines random positioning of solvent atoms and medium-range atomic order of solute atoms.
Abstract: Despite the intense interest in metallic glasses for a variety of engineering applications, many details of their structure remain a mystery. Here, we present the first compelling atomic structural model for metallic glasses. This structural model is based on a new sphere-packing scheme—the dense packing of atomic clusters. Random positioning of solvent atoms and medium-range atomic order of solute atoms are combined to reproduce diffraction data successfully over radial distances up to ∼1 nm. Although metallic glasses can have any number of chemically distinct solute species, this model shows that they contain no more than three topologically distinct solutes and that these solutes have specific and predictable sizes relative to the solvent atoms. Finally, this model includes defects that provide richness to the structural description of metallic glasses. The model accurately predicts the number of solute atoms in the first coordination shell of a typical solvent atom, and provides a remarkable ability to predict metallic-glass compositions accurately for a wide range of simple and complex alloys.
1,084 citations
TL;DR: This work demonstrates that the uniform dispersion of 1–5 vol.% of carbon nanotubes in a thermoplastic elastomer yields nanocomposites that can store and subsequently release, through remote means, up to 50% more recovery stress than the pristine resin.
Abstract: Stimuli-responsive (active) materials undergo large-scale shape or property changes in response to an external stimulus such as stress, temperature, light or pH1,2. Technological uses range from durable, shape-recovery eye-glass frames, to temperature-sensitive switches, to the generation of stress to induce mechanical motion3,4,5,6,7,8,9. Here, we demonstrate that the uniform dispersion of 1–5 vol.% of carbon nanotubes in a thermoplastic elastomer yields nanocomposites that can store and subsequently release, through remote means, up to 50% more recovery stress than the pristine resin. The anisotropic nanotubes increase the rubbery modulus by a factor of 2 to 5 (for 1–5 vol.%) and improve shape fixity by enhancing strain-induced crystallization. Non-radiative decay of infrared photons absorbed by the nanotubes raises the internal temperature, melting strain-induced polymer crystallites (which act as physical crosslinks that secure the deformed shape) and remotely trigger the release of the stored strain energy. Comparable effects occur for electrically induced actuation associated with Joule heating of the matrix when a current is passed through the conductive percolative network of the nanotubes within the resin. This unique combination of properties, directly arising from the nanocomposite morphology, demonstrates new opportunities for the design and fabrication of stimuli-responsive polymers, which are otherwise not available in one material system.
947 citations
TL;DR: It is shown that butyrylcholinesterase entrapped during the precipitation of silica nanospheres retained all of its activity and was substantially more stable than the free enzyme.
Abstract: Robust immobilization techniques that preserve the activity of biomolecules have many potential applications. Silicates, primarily in the form of sol-gel composites or functionalized mesoporous silica, have been used to encapsulate a wide variety of biomolecules but the harsh conditions required for chemical synthesis limit their applicability. Silaffin polypeptides from diatoms catalyze the formation of silica in vitro at neutral pH and ambient temperature and pressure. Here we show that butyrylcholinesterase entrapped during the precipitation of silica nanospheres retained all of its activity. Ninety percent of the soluble enzyme was immobilized, and the immobilized enzyme was substantially more stable than the free enzyme. The mechanical properties of silica nanospheres facilitated application in a flow-through reactor. The use of biosilica for enzyme immobilization combines the excellent support properties of a silica matrix with a benign immobilization method that retains enzyme activity.
582 citations
TL;DR: In the 21st century, it is becoming more apparent that the next technological frontiers will be opened not through a better understanding and application of a particular material, but rather by understanding and optimizing material combinations and their synergistic function, hence blurring the distinction between a material and a functional device comprised of distinct materials.
360 citations
TL;DR: A method for removing ocular artifacts based on adaptive filtering that is easy to implement and stable, converges fast and is suitable for on-line removal of EOG artifacts.
Abstract: The electro-encephalogram (EEG) is useful for clinical diagnosts and in biomedical research. EEG signals, however, especially those recorded from frontal channels, often contain strong electro-oculogram (EOG) artifacts produced by eye movements. Existing regression-based methods for removing EOG artifacts require various procedures for preprocessing and calibration that are inconvenient and timeconsuming. The paper describes a method for removing ocular artifacts based on adaptive filtering. The method uses separately recorded vertical EOG and horizontal EOG signals as two reference inputs. Each reference input is first processed by a finite impulse response filter of length M (M=3 in this application) and then subtracted from the original EEG. The method is implemented by a recursive leastsquares algorithm that includes a forgetting factor (λ=0.9999 in this application) to track the non-stationary portion of the EOG signals. Results from experimental data demonstrate that the method is easy to implement and stable, converges fast and is suitable for on-line removal of EOG artifacts. The first three coefficients (up to M=3) were significantly larger than any remaining coefficients.
334 citations
TL;DR: In this article, an experimental investigation of the mixing and combustion processes that occur in and around a cavity-based flameholder in a supersonic flow is reported, which is part of an ongoing research program aimed at providing information to help fill these voids and improve the overall understanding of cavities for use as scramjet flameholders.
Abstract: An experimental investigation of the mixing and combustion processes that occur in and around a cavity-based flameholder in a supersonic flow is reported. Cavity-based flameholders are commonly found in hydrocarbon-fueledscramjet combustors; however, detailed information concerning the behavior of these devices, their optimal shape and fueling strategies, combustion stability, and interactions with disturbances in the main airflow (i.e., shock trains or shock-boundary layer interactions) is largely unavailable in the existing literature. This work is part of an ongoing research program aimed at providing information to help fill these voids and improve the overall understanding of cavities for use as scramjet flameholders.
332 citations
TL;DR: These studies indicate that it is possible to design chimeric cages, using specific peptide templates, for the growth of other inorganic nanoparticles.
Abstract: Self-assembled particles of genetically engineered human L subunit ferritin expressing a silver-binding peptide were used as nanocontainers for the synthesis of silver nanoparticles. The inner cavity of the self-assembled protein cage displays a dodecapeptide that is capable of reducing silver ions to metallic silver. This chimeric protein cage when incubated in the presence of silver nitrate exhibits the growth of a silver nanocrystal within its cavity. Our studies indicate that it is possible to design chimeric cages, using specific peptide templates, for the growth of other inorganic nanoparticles.
265 citations
TL;DR: In this paper, a review of crack deflecting coatings for fiber-reinforced ceramic composites is presented, and the implications on the design of coatings and of composite systems using alternative coatings are discussed.
Abstract: Fiber-reinforced ceramic composites achieve high toughness through distributed damage mechanisms. These mechanisms are dependent on matrix cracks deflecting into fiber/matrix interfacial debonding cracks. Oxidation resistance of the fiber coatings often used to enable crack deflection is an important limitation for long-term use in many applications. Research on alternative, mostly oxide, coatings for oxide and non-oxide composites is reviewed. Processing issues, such as fiber coatings and fiber strength degradation, are discussed. Mechanics work related to design of crack deflecting coatings is also reviewed, and implications on the design of coatings and of composite systems using alternative coatings are discussed. Potential topics for further research are identified.
261 citations
TL;DR: Carbon nanotubes (CNTs), whether single or multi-walled (SWNT or MWNT, respectively), have, in an unparalleled fashion, grabbed the attention of both researchers and business leaders within the polymer community as discussed by the authors.
248 citations
TL;DR: In this paper, the impact of uncertainty on aeroelastic response prediction has begun to receive substantial attention in the research literature, and several challenges and needs are explored to suggest future steps that will enable practical application of uncertainty quantification in aero-elasticity design and certification.
Abstract: Static and dynamic aeroelasticity considerations are a particularly important component of airframe design because they often control safety and performance. Consequently, the impact of uncertainty on aeroelastic response prediction has begun to receive substantial attention in the research literature. In this paper, general sources of uncertainty that complicate airframe design and testing are briefly described. Recent applications of uncertainty quantification to various aeroelastic problems, for example, flutter flight testing, prediction of limit-cycle oscillations, and design optimization with aeroelastic constraints, are reviewed with an emphasis on new physical insights and promising paths toward improved design methods that have resulted from these studies. Several challenges and needs are explored to suggest future steps that will enable practical application of uncertainty quantification in aeroelasticity design and certification.
TL;DR: The ABC deformation method for large-scale billets with submicro-crystalline structure was developed in this paper, where a large billet of Ti-6Al-4V alloy with a homogeneous submicrocrystallized structure was produced, with a grain/subgrain size of about 0.4μm.
TL;DR: Direct atomic resolution images have been obtained that illustrate how a range of rare-earth atoms bond to the interface between the intergranular phase and the matrix grains in an advanced silicon nitride ceramic to critically improve the materials' performance in wide-ranging applications.
Abstract: Direct atomic resolution images have been obtained that illustrate how a range of rare-earth atoms bond to the interface between the intergranular phase and the matrix grains in an advanced silicon nitride ceramic. It has been found that each rare-earth atom bonds to the interface at a different location, depending on atom size, electronic configuration, and the presence of oxygen at the interface. This is the key factor to understanding the origin of the mechanical properties in these ceramics and will enable precise tailoring in the future to critically improve the materials' performance in wide-ranging applications.
TL;DR: The identification of a unique set of sequences that bind to silver and cobalt nanoparticles from a phage peptide display library using a polymerase chain reaction (PCR)‐driven method is described.
Abstract: Phage peptide display libraries are commonly used to select peptides that bind to inorganic surfaces (metals, metal oxides, and semiconductors). These binding peptides can serve as templates to control the nucleation and growth of inorganic nanoparticles in vitro. In this report, we describe the identification of a unique set of sequences that bind to silver and cobalt nanoparticles from a phage peptide display library using a polymerase chain reaction (PCR)-driven method. The amino acid sequences obtained by the PCR method are a distinct set of sequences that would otherwise be missed using the regular panning method. Peptides identified by the method described here are also shown to function as templates for the synthesis of silver and cobalt platinum nanoparticles.
TL;DR: A computationally efficient procedure for quantifying uncertainty and finding significant parameters of uncertainty models is presented, using the polynomial chaos expansion with Latin hypercube sampling to represent the response of an uncertain system.
Abstract: A computationally efficient procedure for quantifying uncertainty and finding significant parameters of uncertainty models is presented. To deal with the random nature of input parameters of structural models, several efficient probabilistic methods are investigated. Specifically, the polynomial chaos expansion with Latin hypercube sampling is used to represent the response of an uncertain system. Latin hypercube sampling is employed for evaluating the generalized Fourier coefficients of the polynomial chaos expansion. Because the key challenge in uncertainty analysis is to find the most significant components that drive response variability, analysis of variance is employed to find the significant parameters of the approximation model. Several analytical examples and a large finite element model of a joined-wing are used to verify the effectiveness of this procedure.
15 May 2004-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, rigorous stereological procedures have been developed for quantifying four important microstructural features in α/β Ti alloys: thickness of Widmanstatten α laths, colony scale factor, prior β grain size, and volume fraction.
Abstract: Mechanical properties of α/β Ti alloys are closely related to their microstructure. The complexity of the microstructural features involved makes it rather difficult to develop models for predicting properties of these alloys. Developing predictive rules-based models for α/β Ti alloys requires a huge database consisting of quantified microstructural data. This in turn requires the development of rigorous stereological procedures capable of quantifying the various microstructural features of interest imaged using optical and scanning electron microscopy (SEM) micrographs. In the present paper, rigorous stereological procedures have been developed for quantifying four important microstructural features in these alloys: thickness of Widmanstatten α laths, colony scale factor, prior β grain size, and volume fraction of Widmanstatten α laths.
TL;DR: In this article, an unbiased, efficient, and robust practical technique is presented for estimation of direction dependent as well as orientation averaged two-point correlation functions in 3D microstructures from the measurement performed on vertical metallographic planes.
TL;DR: The ability to create complex 2-D and 3-D silica networks in vitro via polycationic peptide-mediated biosilicification under experimentally altered chemical and physical influences is reported on.
TL;DR: In this paper, the static coarsening behavior of the alpha-beta titanium alloy, Ti-6Al-4V, was established via a series of heat treatments at typical forging-preheat and final-heat treatment temperatures followed by quantitative metallography.
Abstract: The static-coarsening behavior of the alpha-beta titanium alloy, Ti-6Al-4V, was established via a series of heat treatments at typical forging-preheat and final-heat-treatment temperatures followed by quantitative metallography. For this purpose, samples of an ultra-fine-grain (UFG) size billet with a microstructure of equiaxed alpha in a beta matrix were heated at temperatures of 843 °C, 900 °C, 955 °C, and 982 °C for times between 0.25 and 144 hours followed by water quenching. The coarsening of the primary alpha particles was found to follow r
3-vs-time kinetics, typical of volume-diffusion-controlled behavior, at the three lower temperatures. At the highest temperature, the kinetics appeared to be fit equally well by an r
3 or r
4 dependence on time. The observations were interpreted in terms of the modified LSW theory considering the effect of volume fraction on kinetics and the fact that the phases are not terminal solid solutions. Prior models, which take into account the overall source/sink effects of all particles on each other, provided the best description of the observed dependence of coarsening on the volume fraction of primary alpha. In addition, the volume-diffusion kinetics derived for the UFG material were found to be capable of describing the coarsening behavior observed for industrial-scale billet of Ti-6Al-4V with a coarser starting equiaxed-alpha microstructure.
TL;DR: In this paper, a method was developed for modeling the aerodynamic coupling between aircraft lying in close proximity, where velocities induced on a trailing aircraft by vortices from an aircraft upstream were written as a function of the relative separation and relative orientation between the two aircraft.
Abstract: A method is developed for modeling the aerodynamic coupling between aircraft Hying in close proximity. Velocities induced on a trailing aircraft by vortices from an aircraft upstream are written as a function of the relative separation and relative orientation between the two aircraft. The nonuniform vortex-induced wind and wind gradients acting on the trail aircraft are approximated as effective uniform wind and wind gradients. In a dynamic simulation, the effective wind can be used directly in the equations of motion, whereas the wind gradient can be used in the standard buildup equations for the aerodynamic moments. This removes necessity to explicitly compute the induced forces and moments. Various vortex models for estimating induced velocities and averaging schemes for computing effective wind components and gradients are assessed
TL;DR: In this paper, random laser action is demonstrated in organic-inorganic, disordered hybrid materials consisting of ZnO semiconductor nanoparticles dispersed in an optically inert polymer matrix.
Abstract: Random laser action is demonstrated in organic–inorganic, disordered hybrid materials consisting of ZnO semiconductor nanoparticles dispersed in an optically inert polymer matrix. The ZnO particles provide both the gain and the strong scattering power that leads to light trapping due to multiple elastic scattering, whereas the polymer matrix offers ease of material fabrication and processability in view of potential applications. Excitation of the nanohybrids by a laser pulse with duration shorter than the ZnO photoluminescence lifetime leads to a dramatic increase in the emitted light intensity accompanied by a significant spectral and temporal narrowing above a certain threshold of the excitation energy density. Critical laser and material parameters that influence the observed laser-like emission behavior are investigated in a series of nanocomposites.
15 Sep 2004-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this paper, the effect of matrix to reinforcement size ratio (PSR) on the reinforcement spatial distribution, fabricability, and resulting mechanical properties of a P/M processed AlCuMn/SiC/15p composite was investigated.
Abstract: Matrix to reinforcement particle size ratio (PSR) is the main factor governing the homogeneity of the reinforcement particle distribution in composites manufactured by the powder metallurgy route. To improve the homogeneity of the distribution, reinforcements with larger average particle size should be used. At the same time, increasing the reinforcement particle size leads to worsening of the mechanical properties due to lower work hardening and higher damage accumulation rates. It is therefore important to optimize the microstructure somewhere in between a smaller reinforcement particle size and a more homogeneous spatial distribution. The effect of PSR on the reinforcement spatial distribution, fabricability, and resulting mechanical properties of a P/M processed AlCuMn/SiC/15p composite was investigated. It was shown that increasing the PSR results in a less-uniform reinforcement distribution, which in turn leads to a decrease in the material fabricability and a general worsening of the mechanical properties. A close to linear dependence of the mechanical properties (yield stress, UTS, elongation before fracture, Young’s modulus) on PSR was found. Tensile elongation shows the highest sensitivity to the worsening of the homogeneity of the reinforcement spatial distribution caused by increasing the PSR. The effect of microstructural homogeneity on the relative change of mechanical properties does not seem to depend on matrix alloy plasticity.
TL;DR: In this article, a wind-tunnel test of two delta-wing aircraft in close proximity is presented and compared with predictions from a vortex lattice method, and large changes in lift, pitching moment, and rolling moment are found on the trail aircraft as it moves laterally relative to the lead aircraft.
Abstract: Results from a wind-tunnel test of two delta-wing aircraft in close proximity are presented and compared with predictions from a vortex lattice method. Large changes in lift, pitching moment, and rolling moment are found on the trail aircraft as it moves laterally relative to the lead aircraft. The magnitude of these changes is reduced as the trail aircraft moves vertically with respect to the lead aircraft. Lift-to-drag ratio of the trail aircraft is increased when the wing tips are slightly overlapped. Wake-induced lift is overpredicted slightly when the aircraft overlap in the spanwise direction. Wake-induced pitching and rolling moments are well predicted. A maximum induced drag reduction of 25% is measured on the trail aircraft, compared with a 40% predicted reduction. Three positional stability derivatives, change in lift and pitching moment with vertical position and change in rolling moment with lateral position, are studied. Predicted boundaries between stable and unstable regions were generally in good agreement with experimentally derived boundaries.
TL;DR: In this paper, the authors simulated the store-induced limit-cycle oscillation of a rectangular wing with tip store in transonic flow using a variety of mathematical models for the flow field.
Abstract: Store-induced limit-cycle oscillation of a rectangular wing with tip store in transonic flow is simulated using a variety of mathematical models for the flowfield: transonic small-disturbance theory (with and without inclusion of store aerodynamics) and transonic small-disturbance theory with interactive boundary layer (without inclusion of store aerodynamics). For the conditions investigated, assuming inviscid flow, limit-cycle oscillations are observed to occur as a result of a weakly subcritical Hopf bifurcation and are obtained at speeds lower than those predicted 1) nonlinearly for clean-wing flutter and 2) linearly for wing/store flutter. The ability of transonic small-disturbance theory to predict the occurrence and strength of this type of limit-cycle oscillation is compared for the different models. Differences in unmatched and matched aeroelastic analysis are described. Solutions computed for the clean rectangular wing are compared to those computed with the Euler equations for a case of static aeroelastic behavior and for a case of forced, rigid-wing oscillation at Mach 0.92.
TL;DR: In this paper, the progress of the reaction was conveniently monitored with FT-IR spectroscopy following the growth of the keto-carbonyl band at 1664 cm−1 associated with the product.
Abstract: Electrophilic functionalization of vapour-grown carbon nanofibers (VGCNF) was accomplished via Friedel–Crafts acylation with 2,4,6-trimethylphenoxybenzoic acid in polyphosphoric acid using the improved conditions that we previously described. The progress of the reaction was conveniently monitored with FT-IR spectroscopy following the growth of the keto-carbonyl band at 1664 cm−1 associated with the product. In addition to scanning electron microscopic and UV-vis spectroscopic data, the combined results from the elemental analysis and thermogravimetric analysis further suggested that there were 3 arylcarbonyl groups covalently attached to the nanotube structure for every 100 carbon sites. Because of the presence of significant hydrogen content in the starting VGCNF, the covalent attachment of the arylcarbonyl groups most probably occurred at the sp2C–H sites.
TL;DR: In this paper, the deformation and dynamic recrystallization behavior of Waspaloy-ingot material with coarse, columnar grains were established using isothermal uniaxial and double-cone compression tests.
Abstract: The deformation and dynamic recrystallization behavior of Waspaloy-ingot material with coarse, columnar grains was established using isothermal uniaxial and double-cone compression tests. Testing was conducted along different test directions relative to the columnar-grain microstructure at supersolvus temperatures (1066 °C and 1177 °C) and strain rates (0.005 and 0.1 s−1), which bracket typical ingot-breakdown conditions for the material. The flow behavior of axial samples (i.e., those compressed parallel to the columnar-grain direction) showed an initial strain-hardening transient followed by steady-state flow. In contrast, the stress-strain curves of samples upset transverse to the columnar grains exhibited a peak stress at low strains, whose magnitude was greater than the steady-state flow stress of the axial samples, followed by flow softening. The two distinct flow behaviors were explained on the basis of the solidification texture associated with the starting ingot structure, differences in the kinetics of dynamic recrystallization revealed in the double-cone tests, and the evolution of deformation and recrystallization textures during hot working. Dynamic recrystallization kinetics were measurably faster for the transverse samples as well as specimens oriented at ∼45 deg to the forging direction, an effect partially rationalized based on the initial texture and its effect on the input rate of deformation work driving recrystallization. Despite these differences, the overall strains required for dynamic recrystallization were comparable to those measured previously for fine-grain (wrought) Waspaloy. However, the Avrami exponents (∼2 to 3) were somewhat higher than those for wrought material (∼1 to 2), an effect attributable to the particle-stimulated nucleation in the ingot material.
TL;DR: In this paper, two-photon absorption spectra of a series of model chromophores were measured via a newly developed nonlinear absorption spectral technique based on a single and powerful femtosecond white-light continuum beam.
Abstract: Two-photon absorption (2PA) spectra (650–1000 nm) of a series of model chromophores were measured via a newly developed nonlinear absorption spectral technique based on a single and powerful femtosecond white-light continuum beam. The experimental results suggested that when either an electron-donor or an electron-acceptor was attached to a trans-stilbene at a para-position, an enhancement in molecular two-photon absorptivity was observed in both cases, particularly in the 650–800 nm region. However, the push–pull chromophores with both the donor and acceptor groups showed larger overall two-photon absorption cross-sections within the studied spectral region as compared to their mono-substituted analogues. The combined results of the solvent effect and the 1H-NMR studies indicated that stronger acceptors produce a more efficient intramolecular charge transfer character upon excitation, leading to increased molecular two-photon responses in this model-compound set. A fairly good 2PA based optical power limiting behavior from one of the model chromophores is also demonstrated.
TL;DR: In this article, the subsonic flow through highly loaded low-pressure turbines is simulated numerically using a high-order method and pulsed injection vortex generator jets are used to help mitigate separation, thereby reducing wake losses.
Abstract: The subsonic flow through highly loaded low-pressure turbines is simulated numerically using a high-order method. The configuration approximates cascade experiments that were conducted to investigate a reduction in turbine stage blade count, which can decrease both weight and mechanical complexity. At a nominal Reynolds number of 25 × 10 3 based upon axial chord and inlet conditions, massive separation occurs on the suction surface of each blade as a result of uncovered turning. Pulsed injection vortex generator jets were then used to help mitigate separation, thereby reducing wake losses. Computations were performed for both uncontrolled and controlled cases and reproduced the transitional flow occurring in the aft-blade and near-wake regions. The numerical method utilizes a centered compact finite difference scheme to represent spatial derivatives, which is used in conjunction with a low-pass Pade-type nondispersive filter operator to maintain stability. An implicit approximately factored time-marching algorithm is employed, and Newton-like subiterations are applied to achieve second-order temporal accuracy. Calculations were carried out on a massively parallel computing platform, using domain decomposition to distribute subzones on individual processors. A high-order overset grid approach preserved spatial accuracy in locally refined embedded regions. Features of the flowfields are elucidated, and simulations are compared with each other and with available experimental data. Relative to the uncontrolled case, it was found that pulsed injection maintained attached flow over an additional 15% of the blade chord, resulting in a 22% decrease of the wake total pressure loss coefficient.
TL;DR: In this paper, the authors present a collective vision for advancements in structures technology within the allotted timeframe of the next 20 years, covering experimental, general, military, and commercial aviation.
Abstract: The journey in advancing flight is far from complete. Challenges to improve performance while reducing costs to acquire and operate air vehicles to fully exploit the potential benefits of flight for humankind remain formidable. Toward this goal, what progress can we anticipate in the next 20 years? The authors attempt to answer this question, sharing their collective vision for advancements in structures technology within the allotted timeframe. Their coverage spans experimental, general, military, and commercial aviation.
TL;DR: In this article, an alternative approach based on the addition to the PEO-LiX blend of an anion-trapping supermolecular component was reported, and the polymer electrolytes with unity values of t Li+ but still maintaining a true solid configuration combined with appreciable conductivity have been obtained.
Abstract: State-of-the-art poly(ethylene oxide) (PEO)-based polymer electrolytes have a t Li+ much lower than I; it is typically around 0.2-0.3. Thus, the development of single-cation-conductive, solvent-free polymer electrolytes is considered of prime importance for the progress of the technology of lithium batteries. Attempts mainly directed at immobilization of the anion in the polymer architecture have been reported in the past, but with only modest success because this approach generally depresses the conductivity to unacceptably low values. In this work, we report an alternative, new approach based on the addition to the PEO-LiX blend of an anion-trapping supermolecular component. In this way, polymer electrolytes with unity values of t Li+ but still maintaining a true solid configuration combined with appreciable conductivity have been obtained. To our knowledge, this strategy has never been used, and we believe that this breakthrough result is associated with the immobilization of the anion (X - ) by the additive and, possibly, by an ordering of the PEO-LiX system.