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Honeycomb cordierite coated with Cu-SSZ-13 zeolite is widely used for the selective catalytic reduction of NOx with NH3 (NH3-SCR) to reduce pollutants from vehicle emissions. However, conventional ...

Zeolites are of great industrial relevance as catalysts, adsorbents, and ion-exchangers and typically synthesized under hydrothermal conditions. Rational regulation of their crystallization process...

The longevity and reusability of N95‐grade filtering facepiece respirators (N95 FFRs) are limited by consecutive donning and disinfection treatments. Herein, we developed stable N97 nanofibrous respirators based on chemically modified surface to enable remarkable filtration characteristics via polarity driven interaction. This was achieved by a thin‐film coated polyacrylonitrile nanofibrous membrane (TFPNM), giving an overall long‐lasting filtration performance with high quality factor at 0.42 Pa−1 (filtration efficiency: over 97 %; pressure drop: around 10 Pa), which is higher than that of the commercial N95 FFRs (0.10–0.41 Pa−1) tested with a flow rate of 5 L min−1 and the 0.26 μm NaCl aerosol. A coxsackie B4 virus filtration test demonstrated that TFPNM also had strong virus capture capacity of 97.67 %. As compared with N95 FFRs, the TFPNM was more resistant to a wider variety of disinfection protocols, and the overall filtration characteristics remained N97 standard., A polarity‐driven air filtration approach is achieved based on the thin‐film coated PAN nanofibrous membranes (TFPNMs), possessing a superior filtration efficiency reaching to N97 grade with outstanding longevity and reusability compared with the N95 FFRs. The TFPNMs can be reused upon various disinfection treatments, giving great potential for personal health care.

Porous materials have become a burgeoning research interest in materials science because of their intrinsic porous characteristics, versatile chemical compositions, and abundant functionalities. Re...

There has been great interest in the fabrication of solid surfaces with desirable under-liquid wettability, and especially under-liquid dual-lyophobicity, because of their potential for widespread use. However, there remains the lack of a general principle to modulate the under-liquid wettability in terms of surface energy (SE). Herein, we found that the relative proportion between the polar and dispersive components in SE that reflects the competition between hydrophilicity and lipophilicity governs the under-liquid wettability of the solid surface. For the first time, we introduced hydrophilic–lipophilic balance (HLB) calculated solely based on the amount and type of hydrophilic and lipophilic fragments in surface molecules to rapidly predict the under-liquid wettability of a solid surface, thereby guiding the fabrication of solid surfaces with desirable under-liquid wettability. Accordingly, the under-liquid dual superlyophobic surfaces in a nonpolar oil–water-solid system were fabricated by grafting molecules with appropriate HLB values (e.g., 6.341–7.673 in a cyclohexane–water–solid system) onto porous nanofibrous membranes, which were able to achieve continuous separation of oil–water mixtures. This work provides reasonable guidance for the fabrication of solid surfaces with targeted under-liquid wettability, which may lead to advanced applications in oil–water–solid systems., Hydrophilic–lipophilic balance calculated based on the component of surface molecules is introduced to predict the under-liquid wettability of solid surfaces, thereby guiding the fabrication of solid surface with desirable under-liquid wettabilities.

An imaging system is designed with a liquid crystal (LC) lens as the focusing element. The aperture of the LC lens plays the role of the aperture stop of the system. An entrance pupil larger than t...

The effective removal of oil contaminants from wastewater, especially dispersed tiny oil droplets, is an emerging technology, yet remains challenging. Core–shell structured nanoparticles with magnetic cores and hydrophobic shells have been explored for oil removal, but the adsorption capacity is unsatisfactory due to the low surface area and smooth surface. Herein, superhydrophobic magnetic core–shell mesoporous organosilica nanoparticles with dendritic architecture (Fe3O4@DMONs) were fabricated in a step-by-step condensation process, which could realize the rapid and efficient separation of dispersed tiny oil droplets from oil-in-water emulsions, giving a separation efficiency of higher than 98.1%. Meanwhile, thanks to the magnetically responsive property, the dispersed Fe3O4@DMONs could be collected simply by applying a magnetic field. In addition, the mesoporous structure as well as the dendritic architecture afforded Fe3O4@DMONs large adsorption capacities for various oils, ranging from 1.37 to 2.04 g g−1. Fe3O4@DMONs showed good reusability with the remaining separation efficiency of 97.9% during five separation cycles for a cyclohexane-in-water emulsion. Furthermore, Fe3O4@DMONs could also adsorb a water-soluble dye in an oil-in-water emulsion with an adsorption efficiency up to 89.4%. Therefore, Fe3O4@DMONs hold promising potential as candidates for the practical purification of industrial wastewater.

Printable mesoscopic perovskite solar cells are usually fabricated by drop-casting perovskite precursor solution on a screen-printed mesoporous TiO2/ZrO2/carbon triple-layer followed by thermal annealing. They have attracted much attention due to their simple fabrication process and remarkable stability. However, challenges lie in how to achieve complete pore fillings of perovskites in the meso-pores and to obtain high-quality perovskite crystals. Here, we report an in situ crystal transfer (ICT) process based on gas-solid interaction to deposit perovskite CH3NH3PbI3 absorber in the scaffold. CH3NH3PbI3 single crystals are first transformed into a liquid phase via exposure to methylamine gas flow. After complete infiltration into the nano-structured scaffolds, the liquid phase is converted back to the solid phase with reduction of methylamine gas partial pressure, maintaining the high-quality of CH3NH3PbI3 single crystals. Compared with the conventional drop-casting method, the ICT method effectively leads to interconnected morphology and prolongs the charge-carrier lifetime (from ∼37.52 ns to ∼110.85 ns) of the perovskite absorber in the scaffold. As a result, the devices can deliver a power conversion efficiency of 15.89%, which is attributed to the suppressed charge recombination and correspondingly enhanced open-circuit voltage of 0.98 V.

Controlling the crystal orientation of organic–inorganic hybrid perovskites is crucial in tuning the optoelectronic properties and improving the device performance. Herein, the favored crystal orientation of MAPbI3 perovskite is finely tuned by additive engineering for carbon based printable mesoscopic perovskite solar cells (PSCs). By introducing biguanide hydrochloride (BH), the out-of-plane crystal orientation of perovskite film is notably enhanced along the (001) and (002) crystal plane, which affects charge transportation and collection properties of perovskite films. More importantly, the BH added perovskite has the most appropriate energy level. Under the optimized condition, the hole-conductor free printable mesoscopic PSCs deliver a champion power conversion efficiency of 16.35% by introducing a 30% molar ratio of BH. The unsealed device retains 98% of its original PCE after 2500 h storage in air with humidity of 50 ± 5%. The results provide a novel and effective approach toward fabricating highly efficient and stable PSCs for future commercialization.

Summary Although water-in-salt (WiS) electrolyte has triggered a relatively clean Li2O2 redox reaction, the practical stored energy density and energy efficiency of current Li-O2 battery systems remains incomparable with that of the state-of-the-art Li-ion batteries. Besides, the awkward position of the cathodic stability limit of WiS further squeezes the practical output voltage. Herein, we make a breakthrough in this “output-voltage limitation” by adopting hybrid-electrolyte design into a dual-compartment cell architecture, in which the WiS catholyte and ionic liquid anolyte are segregated by a flexible under-liquid dual superlyophobic polymer membrane. Moreover, the boosted capacity and restrained overpotential are systematically ascribed to a solution-based Li2O2 accumulation-hydrolysis mechanism. Controlling with 3.6 V charging cut-off voltage, Li-O2 cell performs high areametric capacity (2.5 mAh/cm2), remarkable energy efficiency (∼0.47 V overpotential), and impressive long-term reversibility (Coulombic efficiency, 99.5%) over 250 cycles, which makes the Li-O2 battery technology really competitive.

Ag-incorporated zincosilicate zeolite scaffolds (Ag-3DPZS) for bone tissue engineering are successfully constructed via the extrusion 3D printer. In the printing process, the nano-fibrous attapulgites with suitable rheological properties and good bioactivities are utilized as inorganic binders, which can enhance the compressive strength and Young's modulus of Ag-3DPZS up to 8.38 MPa and 111 MPa, respectively, similar to the mechanical properties of human cancellous bone. Moreover, the obtained Ag-3DPZS possess excellent antibacterial properties and bioactivity, demonstrating that Ag-3DPZS can be applied as antimicrobial materials for bone substitutes.

Printable mesoscopic perovskite solar cells (PSCs) have shown promising prospects for practical applications due to their simple fabrication process, low material cost and high stability. The device is based on a mesoporous triple-layer scaffold, and the perovskite is deposited in the scaffold as a light absorber. Various solvents have been employed to prepare the perovskite precursors. However, the coordination between lead halides and the solvent molecules may lead to the formation of precipitates after a period of storage. The precipitates significantly influence the stoichiometric compositions of the precursors, and result in undesired variations in the device performance. Herein, we introduce ethanol (EtOH) into a typical γ-butyrolactone (GBL) based perovskite precursor. The addition of EtOH not only weaken the coordination between Pb and solvent molecules, but also facilitate the crystallization of the perovskite absorber. Besides, the EtOH modified precursor shows improved wettability on the mesoporous scaffold, spreading and penetrating more efficiently than typical precursor. Correspondingly, highly reproducible device performance with an average power conversion efficiency (PCE) of 14.95% and best PCE of 15.11% are achieved. This work makes it possible to stabilize the perovskite precursors for a long-term period, and will significantly benefit the potential mass-production of this emerging photovoltaic technology.

To explore the dynamic mechanical properties and crack propagation law of rock under high strain rate impact loading, an experimental investigation with 12 sets of Brazilian disk (BD) rock specimens under Split Hopkinson Pressure Bar (SHPB) loading was undertaken. Unlike the previous researches that study the dynamic mechanical properties and crack propagation law individually, the relationship of them has also been investigated and discussed. More specifically, a dynamic resistance strain gauge and a high-frame camera were employed to simultaneously record stress wave data and rock destruction process videos under different impact velocities. Based on image processing technique, a new calculation method of crack propagation velocity was proposed and then the stress-strain characteristics and crack propagation features were analyzed. The experimental results indicate that: (1) Crack propagation rate of the crack along X-Y direction both rises with the impact velocity increase; (2) the strain of rock along the loading axis is much larger than the vertical direction; (3) there is a certain quantitative relationship between the stress-strain state and the crack area of the rock specimen after it has been damaged. Finally, a numerical model based on Peridynamic theory was developed to simulate crack propagation and dynamic constitutive relationship of rock materials with BD configuration in indirect tension test under SHPB loading, and further reveal the fracture behavior and mechanism of rock materials under high strain rate loading.

The crystallization mechanism of the perovskite crystals inside the mesopores of printable mesoscopic perovskite solar cells is demonstrated by in situ grazing-incidence X-ray diffraction. Ionic liquids can universally tune the crystallization process of different perovksites in the mesopores regradless of the precursor solvents, resulting in enhanced efficiency.

Surfaces with under-liquid dual superlyophobicity have garnered tremendous interest because of their promising applications, but their unexplored underlying nature restricts the designed construction of such surfaces. Herein, we coated the thin-film composites with different terminal groups over the electrospun polyacrylonitrile nanofibrous membranes, which afforded the membranes excellent stability in organic solvents, as well as modulated under-liquid wetting behaviors. Among them, the representative under-liquid dual superlyophobic 4-cyan-Ph-terminated membrane could realize highly efficient separation of all types of oil/water mixtures and even emulsions. Moreover, we found that the under-liquid wetting behaviors could be classified in terms of the intrinsic water contact angle (θw). By comparing the total interfacial energy, we proved that the under-liquid dual lyophobic surfaces were thermodynamically metastable. On this basis, we could predict the θw of rough surfaces with the under-liquid dual lyophobicity in a given oil–water–solid system (e.g., 47.3–89.1° in cyclohexane–water–solid system, R = 2). This work provides a design principle for the fabrication of under-liquid dual superlyophobic surfaces, which will open potential applications in diverse fields in terms of such smart surfaces.

Uniform and hydrophilic carbon quantum dots (C-QDs) were synthesized by calcination and NaOH treatment from an organo-templated zeolite precursor. The color of luminescence was determined by the concentration of C-QDs. These variable-color C-QDs were applied for the first time in the imaging of Caenorhabditis elegans (C. elegans) as a model organism. The effects of C-QDs and possible behavioral changes in C. elegans were evaluated under treatment conditions. We could clearly observe distribution of C-QDs in C. elegans from the fluorescence images. Furthermore, we observed significant and detectable fluorescence quenching of the C-QDs by free radicals in C. elegans. Our work affirms that C-QDs can be developed as imaging probes and as potential fluorescent quantitative probes for detecting free radicals.

Particulate matter (PM) discharged along with the rapid industrialization and urbanization hazardously threatens ecosystems and human health. Membrane-based filtration technology has been proved to be an effective approach to capture PM from the polluted air. However, the fabrication of filtration membranes with excellent reusability and antibacterial activity has rarely been reported. Herein, the flexible multifunctional porous nanofibrous membranes were fabricated by embedding Ag nanoparticles into the electrospun porous SiO2-TiO2 nanofibers via an impregnation method, which integrated the abilities of PM filtration and antibacterial performance. Compared with the reported air filters, the resultant membrane (Ag@STPNM) with high surface polarity and porous structure possessed the low density, high removal efficiency, and small pressure drop. For instance, the removal efficiency and the pressure drop of Ag@STPNM with a basis weight of only 3.9 g m-2 for PM2.5 reached 98.84% and 59 Pa, respectively. In terms of the excellent thermal stability of Ag@STPNM, the adsorbed PM could be removed simply by a calcination process. The filtration performance of Ag@STPNM kept stable during five purification-regeneration cycles and the long-time filtration for 12 h, exhibiting excellent recyclability and durability. Furthermore, the embedded Ag nanoparticles could achieve the effective resistance to the breeding of bacteria on Ag@STPNM, giving the bacteriostatic rate of 95.8%. Therefore, Ag@STPNM holds promising potentials as a highly efficient, reusable, and antibacterial air filter in the practical purification of the indoor environment or personal air.

Solution-processable organic-inorganic perovskite solar cells have attracted much attention in the past few years. Energy level alignment is of great importance for improving the performance of perovskite solar cells because it strongly influences charge separation and recombination. In this report, we introduce three amide additives, namely, formamide, acetamide, and urea, into the MAPbI3 perovskite by mixing them directly in perovskite precursor solutions. The Fermi level of MAPbI3 shifts from -4.36 eV to -4.63, -4.65, and -4.61 eV, respectively, upon addition of these additives. The charge transfer between perovskite and mp-TiO2 is found to be promoted as determined via TRPL spectra, and recombination in the perovskite is suppressed. As a result, the built-in electric field (Vbi) of the printable, hole-conductor-free mesoscopic perovskite solar cells based on these perovskites with amide additives is enhanced and a peak power conversion efficiency of 15.57% is obtained.

Perovskite solar cells (PSCs) usually suffer from a hysteresis effect in current–voltage measurements, which leads to an inaccurate estimation of the device e fficiency. Although ion migration, charge trapping/ detrapping, and accumulation have been proposed as a b asis for the hysteresis, the origin of the hysteresis has not been apparently unraveled. Herein we reporte d a tunable hysteresis effect based uniquely on open- circuit voltage variations in printable mesos copic PSCs with a simplified triple-layer TiO 2 /ZrO 2 /carbon architecture. The electrons are collected by the compact TiO 2 /mesoporous TiO 2 (c-TiO 2 /mp-TiO 2 )bilayer, and the holes are collected by the carbon layer. By adj usting the spray deposition cycles for the c-TiO 2 layer andUV-ozonetreatment,weachievedhysteresis-norm al, hysteresis-free, and hysteresis-inverted PSCs. Such unique trends of tunable hysteresis are anal yzed by considering the polarization of the TiO 2 /perovskite interface, which can accumulate positive charges reversibly. Successfully tuning of the hysteresis effect clarifies the critical importance of the c-TiO 2 /perovskite interface in controlling the hysteretic trends observed, providing important insights towards the understanding of this rapidly developing photovoltaic technology.

Nanomaterials mimicking the nano-features of bones and offering unique smart functions are promising for better bone fracture repair. This review provides an overview of the current state-of-the-art research in developing and using nanomaterials for better bone fracture repair. This review begins with a brief introduction of bone fracture repair processes, then discusses the importance of vascularization, the role of growth factors in bone fracture repair, and the failure of bone fracture repair. Next, the review discusses the applications of nanomaterials for bone fracture repair, with a focus on the recent breakthroughs such as nanomaterials leading to precise immobilization of growth factors at the molecular level, promoting vascularization without the use of growth factors, and re-loading therapeutic agents after implantation. The review concludes with perspectives on challenges and future directions for developing nanomaterials for improved bone fracture repair.

To investigate the crack propagation and dynamic mechanical properties of coal under high strain rate loading, 24 sets of Brazilian disk (BD) coal specimens with vertical and horizontal beddings were made, and tests were conducted by a split Hopkinson pressure bar (SHPB) system. Under different impact velocities, a high-frame and high-resolution camera was employed to capture the fracture process, and two high-dynamic strain gauges were used to record the stress pulse signals simultaneously. Using one-dimensional stress wave theory, the dynamic mechanical properties of coal with different bedding directions under different impact velocities were analyzed and discussed. Experimental results indicate that bedding directions not only have a major influence on dynamic mechanical properties such as dynamic tensile strength, strain rate and strain energy but also have a great influence on the crack propagation path. Then, based on the image processing technique and fractal method, cracks conforming to the fractal have been proven, and the results further illustrate that the fractal dimension of cracks on the coal surface increased in the fracture process under SHPB loading. Finally, a numerical model based on bond-based Peridynamic theory was proposed to simulate crack propagation and dynamic mechanical properties of coal under the SHPB test, and the displacement-strain-stress fields were also calculated, which further reveal the fracture mechanism and dynamic behavior of coal under different impact loading conditions.

Both oil spill and heavy-metal ions in the industrial wastewater cause severe problems for aquatic ecosystem and human health. In the present work, the electrospun superamphiphilic SiO2-TiO2 porous nanofibrous membranes (STPNMs) comprised of intrafiber mesopores and interfiber macropores are modified by an amino-silanization reaction, which affords the membrane (ASTPNMs) the ability to simultaneously remove the oil contaminants and the water-soluble heavy-metal ions from wastewater. The underwater superoleophobicity of ASTPNMs facilitates the highly efficient separation of water and various oils, even emulsifier-stabilized emulsion. Meanwhile, an optimal modification time (15 min, ASTPNM-15) is important for maintaining the under-oil superhydrophilicity of the membrane, based on which the oil contaminant in membrane can be easily cleaned by water alone, showing excellent self-cleaning performance. The adsorption of Pb2+ over ASTPNM-15 reaches equilibrium at around 20 min, and the monolayer adsorption capacity is 142.86 mg g-1 at pH = 5 at 20 °C. In the breakthrough processes, the permeation volume of ASTPNM-15 for the purification of Pb2+ (5 ppm, pH = 5) reaches 160 mL when the concentration of Pb2+ in the filtrate increases to 0.05 ppm. The separation efficiencies of ASTPNM-15 for simulated wastewater containing both oil spill and various heavy-metal ions (Pb2+, Cr3+, Ni2+) are larger than 99.5%. In addition, the separation capacity keeps stable over five purification-regeneration cycles without obvious decrease, proving excellent recyclability and reusability of ASTPNM-15 for practical applications.

We report on the synthesis, crystal structures, optoelectronic properties and solar cell device studies of three novel organic-inorganic iodobismuthates -- [C3H4NS]3[Bi2I9] ([TH]3[Bi2I9]), [C3H4N2]3[Bi2I9] ([IM]3[Bi2I9]) and [C3H5N2S][BiI4] ([AT][BiI4]) as lead-free light harvesters. [TH]3[Bi2I9] and [IM]3[Bi2I9] show zero-dimensional structures, whereas a one-dimensional edge-sharing chain structure of BiI6-octahedra was observed in [AT][BiI4], with interchain short I…I contacts also giving rise to the possibility of three-dimensional charge transport ability. Accordingly, greater energy dispersion in the band structure of [AT][BiI4] can be observed, and less contribution from the organic moities at the conduction band minimum in [AT][BiI4] than [TH]3[Bi2I9] have been confirmed by density functional theory calculations. Moreover, bandgap values are redshiffted from 2.08 eV for [TH]3[Bi2I9] and 2.00 eV for [IM]3[Bi2I9] to 1.78 eV for [AT][BiI4], determined by UV-Vis reflectance spectroscopy. Power conversion efficiency of 0.47% has been achieved by using ([AT][BiI4]) as the light absorber in a hole-conductor-free, fully printable solar cell, with relatively good reproducibility. We also note the observation of a capacitance effect for the first time in a photovoltaic device with bismuth-based solar absorber, which may be related to the mesoporous carbon counter-electrode.

A bifunctional conjugated organic molecule 4-(aminomethyl) benzoic acid hydroiodide (AB) is designed and employed as an organic cation in organic-inorganic halide perovskite materials. Compared with the monofunctional cation benzylamine hydroiodide (BA) and the nonconjugated bifunctional organic molecule 5-ammonium valeric acid, devices based on AB-MAPbI3 show a good stability and a superior power conversion efficiency of 15.6% with a short-circuit current of 23.4 mA cm-2 , an open-circuit voltage of 0.94 V, and a fill factor of 0.71. The bifunctional conjugated cation not only benefits the growth of perovskite crystals in the mesoporous network, but also facilitates the charge transport. This investigation helps explore new approaches to rational design of novel organic cations for perovskite materials.

The nanoscale structure and water and charge diffusion in cross-linked and sulfonated poly(1,3-cyclohexadiene) (xsPCHD) hydrated membranes based on xsPCHD homopolymer, xsPCHD/polyethylene glycol (x...

Atomistic and coarse-grained (CG) molecular dynamics (MD) simulations were conducted for a cross-linked and sulfonated poly(1,3-cyclohexadiene) (xsPCHD) hydrated membrane with λ(H2O/HSO3) = 10 and ...

Atomistic and coarse-grained (CG) models of cross-linked sulfonated Poly (1, 3-cyclohexadiene) (xsPCHD) were developed and implemented in Molecular Dynamics (MD) simulations of PCHD chains with different architectures. In the atomistic model, PCHD chains are cross linked by a sulfur–sulfur bond. Sulfonic acid groups are evenly distributed along the chain. The architecture is specifically aimed for application as a proton exchange membrane used in fuel cells. An atomistic force field for this architecture was tested and applied in the atomistic MD simulation of xsPCHD for the first time. The atomistic simulations generate the density and cross-linker separation distribution. To further study the structural properties of longer chain systems, a CG model was proposed. The bonded structural probability distribution functions (PDFs) and non-bonded pair correlation function (PCF) of the CG beads were obtained from the atomistic simulation results. The bonded CG potentials are obtained by simple inversion of the corresponding PDFs. The CG non-bonded potential is parameterized to the PCF using the Iterative Boltzmann Inversion (IBI) method. The CGMD simulations of xsPCHD chains using potentials from above method satisfactorily reproduce the structural properties from atomistic MD simulation of the same system. The transferability of the CG potentials has been further tested through CGMD simulation of xsPCHD homopolymer with different architectures.

High-density polyethylene (HDPE)/(ethylene-vinyl alcohol) (EVOH) copolymer alloys were prepared through reactive extrusion method with high-density polyethylene-graft-maleic anhydride (HDPE-g-MAH) as a compatibilizer to improve the compatibility of the blending system. The results of the morphologies and properties of HDPE/EVOH blends show that the size of dispersed EVOH phase in HDPE/EVOH/HDPE-g-MAH blends is greatly diminished, the crystallization of EVOH is retarded and the impact strength of the blends is improved, which mean that specific interactions could be existed between the functional groups of the EVOH and HDPE-g-MAH. Rheological experiments and FTIR spectra reveal that network structures are formed in the blends when the content of compatibilizer is >20%. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

An experiment simulating coal seam under forced vibration conditions was conducted. Acceleration response and microseism signal during the experiment were collected and analyzed. It is found that, with an increasing amount of vibration, the natural frequency of the specimen decreases, and this phenomenon reflects fractures appearing in the specimen. Acceleration response signals show that peaks in shock excitation frequency and shock excitation acceleration affect the acceleration response, which reflects damage to the specimen. When shock excitation frequency nears natural frequency, the acceleration response first decreases and then increases. When resonance occurs, it reaches its maximum value. As shock excitation acceleration peaks increase, the acceleration response peak of the specimen also increases. We conclude that destruction is mainly concentrated in the coal seam evidenced by specimen destruction situation. Then shock excitation frequency and shock excitation acceleration influence on microseism signals were analyzed by Hilbert-Huang transform. By receiving these signals and analyzing their characteristics, it is beneficial to develop new methods to predict disasters underground dynamically in the future.

New carbon composite materials are being developed that contain carbon nanocrystallites in the range of 5–17 A in radius dispersed within an amorphous carbon matrix. Evaluating the applicability of these materials for use in battery electrodes requires a molecular-level understanding of the thermodynamic, structural, and dynamic properties of the nanocrystallites. Herein, molecular dynamics simulations reveal the molecular-level mechanisms for such experimental observations as the increased spacing between carbon planes in nanocrystallites as a function of decreasing crystallite size. As the width of this spacing impacts Li-ion capacity, an explanation of the origin of this distance is relevant to understanding anode performance. It is thus shown that the structural configuration of these crystallites is a function of entropy. The magnitude of out-of-plane ripples, binding energy between layers, and frequency of characteristic planar modes are reported over a range of nanocrystallite sizes and temperatures. This fundamental information for layered carbon nanocrystallites may be used to explain enhanced lithium ion diffusion within the carbon composites.

Molecular dynamics simulations of poly(ethylene terephthalate) (PET) oligomers are performed in the isobaric-isothermal (NpT) ensemble at a state point typical of a finishing reactor. The oligomer size ranges from 1 to 10 repeat units. We report thermodynamic properties (density, potential energy, enthalpy, heat capacity, isothermal compressibility, and thermal expansivity), transport properties (self-diffusivity, zero-shear-rate viscosity, thermal conductivity), and structural properties (pair correlation functions, hydrogen bonding network, chain radius of gyration, chain end-to-end distance) as a function of oligomer size. We compare the results with existing molecular-level theories and experimental data. Scaling exponents as a function of degree of polymerization are extracted. The distribution of the end-to-end distance is bimodal for the dimer and gradually shifts to a single peak as the degree of polymerization increases. The scaling exponents for the average chain radius of gyration and end-to-end distance are 0.594 and 0.571, respectively. The values of the heat capacity, isothermal compressibility, and thermal expansivity agree well with the available experimental data, which are of much longer PET chains. The scaling exponents for the self-diffusivity and zero-shear-rate viscosity are, respectively, -2.01 and 0.96, with the latter one being close to the theoretical prediction 1.0 for short-chain polymers.