N,N-bis(sulfopropyl)aminyl-4-phenyl polysulfone and O,O′-bis(sulfopropyl)resorcinol-5-yl-4-phenyl polysulfone composite membrane for proton exchange membrane fuel cells

Novel functionalized polysulfone with high local density of sulfonic acid groups, N,N-bis(sulfopropyl)aminyl-4-phenyl polysulfone or O,O′-bis(sulfopropyl)resorcinol-5-yl-4-phenyl polysulfone (PSF-X-C₃H₆SO₃H, X = N or O) are synthesized. These polymers are synthesized by bromination of polysulfone followed by Suzuki cross-coupling reaction to graft the aminophenyl groups and the dimethoxyphenyl groups onto the polymeric backbone, followed by introduction of the sulfopropyl groups via sultone ring-opening reaction. In addition, the composite membrane of PSF-O-C₃H₆SO₃H and PSF-N-C₃H₆SO₃H is also synthesized for comparison. The maximum proton conductivity of composite PSF-O-C₃H₆SO₃H and PSF-N-C₃H₆SO₃H reaches 46.66 mS cm⁻¹ at 95 °C and 90% RH, higher than PSF-O-C₃H₆SO₃H (42.06 mS cm⁻¹) and PSF-N-C₃H₆SO₃H (38.76 mS cm⁻¹). Meanwhile, the composite exhibits compromised water uptake and swelling ratio, and low methanol permeability. The excellent overall performance of the composite is attributed to phase-separation between the hydrophilic and the hydrophobic subphases, and the hydrogen-bonding network developed in the hydrophilic subphases.     

An SOFC anode model using TPB-based kinetics

Fundamental studies focusing on the electrode kinetics are essential in understanding the fuel cell operation and optimizing the electrode designs. In this study, we determined the triple-phase boundary (TPB)-based kinetics of hydrogen electrochemical oxidation using nickel patterned electrode experimental data and the Butler-Volmer formalism of the oxidation process. The same kinetics are then incorporated in a cermet electrode electrochemical model to estimate the effective TPB density of the nickel/yittrium-stabilized zirconia cermet anode. The kinetics are found to be of the same order of magnitude as previously determined by the microstructure reconstruction of cermet anode. Simulation results further revealed that the effective TPB density is several orders of magnitude lower than the typically reported physical densities of the cermet anode that possibly suggests that only a minor fraction of the physical TPB is actually required or available to produce the cell current at given cell voltage. The effect of various operating conditions on the anode activation overpotential is also investigated and discussed in this study.     

Thermal history and its implications: A case study for ion exchange

Glasses containing monovalent species can be chemically strengthened by the replacement of smaller ions in the glass with larger external ions in the near glass surface. This type of ion exchange puts glass surface under high compressive stress (CS). Glass mainly fails from tension with the presence of surface flaws. Chemical strengthening can change the stress at the flaw tip from tension to compression and further stop the flaw from propagating. Glass damage resistance is therefore significantly improved. For the same glass composition, glass thermal histories can affect the magnitude and depth of the CS generated during ion exchange. In this study, the impact of thermal history on glass physical properties and ion exchange attributes in one alkali-containing glass formed by fusion draw process was investigated. Multiple thermal treatments were done to rewrite the glass thermal histories. Glass density, refractive index, and ion-exchange properties as a function of the thermal treatment were studied. It is concluded that ion exchange-related properties change dramatically with the glass thermal history.     

Density functional theory and machine learning guided search for RE2Si2O7 with targeted coefficient of thermal expansion

Density functional theory (DFT) calculations and machine learning (ML) methods are used to establish a relationship between the crystal structures of rare-earth (RE) disilicates (RE₂Si₂O₇) and their coefficient of thermal expansion (CTE). The DFT total energy data predict the presence of several energetically competing crystal structures, which is rationalized as one of the reasons for observing polymorphism. An ensemble of support vector regression models is trained to rapidly predict the CTE as a function of RE₂Si₂O₇ crystal chemistry. Experiments subsequently validated the structure and CTE predictions for Sm₂Si₂O₇.     

使用不同催化剂转产过程中淤浆法HDPE脱气仓结块原因分析

在英力士淤浆环管工艺高密度聚乙烯(HDPE)装置上,由采用钛系催化剂生产PE100级管材专用HDPE转换成用铬系催化剂生产的过程中,使用钛系催化剂的停车期间以及使用铬系催化剂的开车期间,粉料输送至低压闪蒸脱气仓都会产生块状的聚乙烯,严重影响装置的正常运行;通过对块状聚乙烯进行密度与凝胶渗透色谱分析,发现结块的聚乙烯主要为低相对分子质量、低密度的聚乙烯粉料黏结物。停车期间,将第一反应器氢气进料量降低50%,提前终止1-己烯进料,从而完全消除结块的形成。     

Nitrogen-doped carbon stabilized LiFe0.5Mn0.5PO4/rGO cathode materials for high-power Li-ion batteries

Exploring high ion/electron conductive olivine-type transition metal phosphates is of vital significance to broaden their applicability in rapid-charging devices. Herein, we report an interface engineered LiFe_0.5Mn_0.5PO₄/rGO@C cathode material by the synergistic effects of rGO and polydopamine-derivedN-doped carbon. The well-distributed LiFe_0.5Mn_0.5PO₄ nanoparticles are tightly anchored on rGO nanosheet benefited by the coating of N-doped carbon layer. The design of such an architecture can effectively suppress the agglomeration of nanoparticles with a shortened Li⁺ transfer path. Meantime, the high-speed conducting network has been constructed by rGO and N-doped carbon, which exhibits the face-to-face contact with LiFe_0.5Mn_0.5PO₄ nanoparticles, guaranteeing the rapid electron transfer. These profits endow the LiFe_0.5Mn_0.5PO₄/rGO@C hybrids with a fast charge-discharge ability, e.g. a high reversible capacity of 105 mAh·g^-1 at 10 C, much higher than that of the LiFe_0.5Mn_0.5PO₄@C nanoparticles (46 mA·h·g^-1). Furthermore, a 90.8% capacity retention can be obtained even after cycling 500 times at 2 C. This work gives a new avenue to fabricate transition metal phosphate with superior electrochemical performance for high-powerLi-ion batteries.     

Survey of acceptor dopants in SrTiO3: Factors limiting room temperature hole concentration

Unintentional impurities often found in strontium titanate (doped or undoped) have hindered efforts to study individual impurities experimentally. To fill this gap, a computational survey of acceptor-type point defects of common intentional or unintentional impurities (Al, Cu, Fe, K, Mg, Mn, N, Na, Ni, and Zn) is presented. Utilizing defect formation energies from density functional theory using hybrid exchange correlation functionals in a grand canonical model of the defect chemistry, the equilibrium Fermi level (μ_e) was calculated as a function of processing conditions for pure SrTiO₃, SrTiO₃ individually doped with each impurity, and SrTiO₃ co-doped with Al and N. Above a certain concentration, each impurity reduced the maximum predicted hole concentration relative to the intrinsic case. Al, Mg, Zn, K, and Na exhibited similar trends and behaved more like ideal acceptors while N, Ni, Fe, Mn, and Cu were all unique and pinned μ_e near or above the mid-gap in most conditions. Al/N:SrTiO₃ also exhibited similar trends at 800°C for all Al/N ratios, but more variation at 25°C. Additionally, the behavior of Al:SrTiO₃ was not recovered until Al/N = 10⁴. This suggests that to achieve SrTiO₃ with free holes at room temperature, the concentration of most impurities must be controlled.     

Oscillatory power number,power density model,and effect of restriction size for a moving-baffle oscillatory baffled column using CFD modelling

Although single-hole oscillatory columns have been studied since the 1990s, to this day there is an absence of appropriate dimensionless groups to express the hydrodynamic conditions and power requirement for the moving-baffle oscillatory baffled column (OBC). This paper uses computational fluid dynamic (CFD) software coupled with moving overset meshing to aid in the derivation of the first dimensionless oscillatory power number for OBCs. In terms of the moving-baffle OBC, this work marks the first time a power density equation has been derived specifically to account for this column's unique hydrodynamic profile. Equations for period-averaged Reynolds number and period-averaged Strouhal numbers were developed to better estimate the fluid intensity within these moving-baffle columns. This work serves as an example of how complex and challenging flow regimes, such as periodically oscillating flow, can be simplified and analyzed to produce appropriate design equations.     

The effects of thermoresponsive microgel density on cell adhesion,proliferation, and detachment

In recent years, poly(N-isopropylacrylamide)-based microgels have been emerged as a new thermoresponsive coating for cell/cell sheet harvesting, yet few work reports their effect on cell attachment, morphology, activity, and proliferation in details. In this work, poly(N-isopropylacrylamide-co-styrene) (pNIPAAmSt) microgel was selected as the model to study its density on NIH3T3 cell adhesion, morphology, activity, and detachment. Results showed that 0.5 wt % pNIPAAmSt microgel density leads to more cells adhesion, higher cell activity yet lower cell proliferation. Moreover, cell adhesion location can be well controlled either by manipulating the sub-cellular scale distances between microgels or by fabricating large scale surface patterns of the microgels on higher microgel density. By temperature stimuli, similar ratio cells detached from the microgel density surface from 0.5 to 1.5 wt %. The results in this article are worthy for the application of thermoresponsive microgels in cell regulation. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48773.     

Remarkably enhanced energy storage properties of lead-free Ba0.53Sr0.47TiO3 thin films capacitors by optimizing bottom electrode thickness

The lead-free Ba_0.53Sr_0.47TiO₃ (BST) thin films buffered with La_0.67Sr_0.33MnO₃ (LSMO) bottom electrode of different thicknesses were fabricated by pulsed laser deposition method on a (001) SrTiO₃ substrate. It was found that the roughness of electrode decreases and substrate stress relaxes gradually with the increase of LSMO thickness, which is beneficial for weakening local high electric field and achieving higher E_b. Therefore, the recoverable energy density (W_rec) of BST films can be greatly improved up to 67.3 %, that is, from 30.6 J/cm³ for the LSMO thickness of 30 nm up to 51.2 J/cm³ for the LSMO thickness of 140 nm after optimizing the LSMO thickness. Furthermore, the thin film capacitor with a 140 nm LSMO bottom electrode shows an outstanding thermal stability from 20 °C to 160 °C and superior fatigue resistance after 10⁸ electrical cycles with only a slightly decrease of W_rec below 1.6 % and 3.7 %, respectively. Our work demonstrates that optimizing bottom electrodes thickness is a promising way for enhancing energy storage properties of thin-film capacitors.