Preparation of high solid loading and low viscosity ceramic slurries for photopolymerization-based 3D printing

In this study, high solid loading and low viscosity cordierite slurries are successfully developed for the first time for photopolymerization-based additive manufacturing. The processability of the slurries is mainly determined by their rheological properties and photocuring parameters. The slurry preparation involves the orthogonal optimization of compositions in order to achieve suitable viscosity, stability and homogeneity. The photocuring parameters of the as-prepared slurries, including penetration depth D_p and critical exposure E_c, are also determined experimentally. Results show that viscosity increases with reduction in particle size. A higher solid-volume fraction also results in an exponential growth in viscosity. As for the dispersant amount, a concentration of 5?wt% leads to the lowest viscosity. Particle size also play an important role in the solid loading capacity of the slurries, as results suggest that smaller particles improve performance. In terms of the photocuring behaviors, the addition of 2?wt% photoinitiator generates an optimal curing process. 40?vol% solid loading leads to the thickest curing depth for all slurries with different types of particle sizes. Finally, a cordierite part with a complex hollow structure and a fine resolution is successfully fabricated. The present study offers a material basis for the polymerization-based 3D printing of porous cordierite structures.     

Chromium redox couples for application to redox flow batteries

Both anodic and cathodic chromium-EDTA (ethylenediaminetetra-acetate) complex redox processes have been studied using cyclic voltammetry. Their potential use in a redox battery has been evaluated by comparing the charge and discharge performance of a simple redox battery employing several redox couples including the conventional Fe-Cr redox couples. The cyclic voltammetry experiments suggested that oxidation of Cr(III)-EDTA formed Cr(V)-EDTA rather than a hexavalent chromium species. It was found that the kinetics of the Cr(III)-EDTA/Cr(II)-EDTA redox reaction are fast at a graphite rod electrode, whereas the Cr(V)-EDTA/Cr(III)-EDTA redox reaction is relatively slow. In spite of the slow kinetics, the battery employing solely these chromium-EDTA based redox couples provided higher energy output and longer life than the conventional Fe-Cr redox system.     

高固体分低粘度羟基丙烯酸树脂的合成

报道了高固体分低粘度羟基丙烯酸树脂的合成方法，讨论了羟基单体、溶剂、引发剂、分子量调节剂、工艺条件等因素对产品的影响，介绍了该树脂的特性和应用效果。     

复合可聚合乳化剂制备高固含量低黏度聚丙烯酸酯乳液

以DNS-86和F-6为复合可聚合乳化剂APS为引发剂,MMA、BA为单体采用半连续法制备20%固含量种子乳液,以种子乳液为介质,选用4种不同类型乳化剂:非离子可聚合乳化剂F-6,阴离子可聚合乳化剂DNS-86、常规非离子乳化剂OP-10、常规阴离子乳化剂SDS进行不同组合,同时滴加预乳化液、引发剂、缓冲剂直接二次成核制备62%固含量二元粒径分布乳液。重点研究了乳化剂复合方式、用量及配比、反应温度等对聚合稳定性、乳液流变性等的影响。,     

A computationally-cost effective model for fluid flow in redox flow batteries

Redox flow batteries (RFBs) hold great potential for large-scale, extended-duration stationary energy storage. Here, a novel computationally cost-effective hydraulic-electrical analogous model (HEAM) for fluid flow in RFBs is developed. The HEAM demonstrated that lowering the electrode compression and enhancing the channel area lowers the pump power loss independent of the flow fields and electrodes. Additionally, the HEAM helped elucidate the deficiencies of flow distribution in interdigitated flow fields (IFFs) and suggested designing wider manifolds and/or shorter channels improve the flow distribution. Moreover, the HEAM suggested shallower and/or wider channels, and more permeable electrodes enhance the flow penetration rate above the channels. Finally, the HEAM showed that the average penetration depth in the electrode above the ribs (h_pen) was the critical parameter in the fluid-flow modeling of IFFs and was inversely proportional to the permeability. Hence, there is a trade-off between the pump power loss and h_pen when configuring electrode permeability.     

Modeling flow distribution and pressure drop in redox flow batteries

The combination of interdigitated flow fields (IDFF) with porous electrodes offers lower pressure drop and better performance than conventional flow‐through porous electrodes in redox flow batteries. Comprehensive three‐dimensional and simplified one‐dimensional + two‐dimensional models describing flow uniformity and pressure losses within flow through, parallel, and interdigitated flow fields were developed and used to demonstrate the benefits of IDFF. Analytical solutions for IDFF that compare favorably with computational fluid dynamics quantify the trade between pressure loss and velocity maldistribution both along the channels and within the electrode. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3746–3755, 2018     

高固含量低黏度耐蒸煮复膜胶的合成研究

研究了一种可用于高温蒸煮双组分溶剂型复膜胶的合成方法.对催化剂的选择、真空度、反应温度的控制等进行了探讨.对合成复膜胶所用的高分子质量聚酯二醇的制备工艺进行了详细说明;同时探讨了添加剂对复膜胶粘接性能的影响.实验结果表明,该胶粘剂完全适用于135℃、30min蒸煮的要求,且固含量高、黏度低,是一种性能优良的复膜胶.     

Comparing velocities and pressures in redox flow batteries with interdigitated and serpentine channels

Serpentine channels adjacent to a thin, porous medium are a potentially attractive alternative to a conventional thick flow-through electrode for redox flow batteries. The hydrodynamics of serpentine flow fields were investigated with computational fluid dynamics, a two-dimensional model of the porous electrode based on Darcy's law, and a resistance network model at the scale of the active area. Predictions from the three models were used to map the available design space. The optimal electrode thickness, in terms of minimizing nonuniformity, was identified and compared to the result for an interdigitated flow field. Serpentine favors thicker electrodes and higher flows than interdigitated, in qualitative agreement with experimental findings. Furthermore, interdigitated designs deliver more uniform intraelectrode velocities and lower overall pressure drops than serpentine flow fields.     

A generalized reduced fluid dynamic model for flow fields and electrodes in redox flow batteries

High-dimensional models typically require a large computational overhead for multiphysics applications, which hamper their use for broad-sweeping domain interrogation. Herein, we develop a modeling framework to capture the through-plane fluid dynamic response of electrodes and flow fields in a redox flow cell, generating a computationally inexpensive two-dimensional (2D) model. We leverage a depth-averaging approach that also accounts for variations in out-of-plane fluid motion and departures from Darcy's law that arise from averaging across three-dimensions (3D). Our resulting depth-averaged 2D model successfully predicts the fluid dynamic response of arbitrary in-plane flow field geometries, with discrepancies of <5% for both maximum velocity and pressure drop. This corresponds to reduced computational expense, as compared to 3D representations (<1% of duration and 10% of RAM usage), providing a platform to screen and optimize a diverse set of cell geometries.     

高固含、低粘度丙烯酸乳液压敏胶工业化生产中粘度控制讨论

对高固含、低粘度丙烯酸乳液压敏胶工业化生产过程中粘度控制及成品贮存稳定性进行了讨论与观察。     

适用于低温固化的低黏度高强度环氧树脂结构胶

以碳酸丙烯酯(PC)为活性稀释剂、自制增韧型421固化剂/快固型DETA(二乙烯三胺)固化剂作为复合固化剂,制备环氧树脂(EP)结构胶。研究结果表明:当m(EP)∶m(PC)∶m(421)∶m(DETA)=100∶20∶24∶6.0时,EP结构胶的初始黏度(60 mPa.s)相对较低,其强度和韧性俱佳(拉伸强度为45 MPa、压缩强度为70 MPa和钢/钢剪切强度为12.0 MPa);该EP结构胶可低温固化(5℃或常温固化7 d后的拉伸强度基本一致),也是一款适用于冬季施工的低黏度高强度EP结构胶。     

Capacity balancing for vanadium redox flow batteries through continuous and dynamic electrolyte overflow

Journal of Applied Electrochemistry - The vanadium crossover through the membrane can have a significant impact on the capacity of the vanadium redox flow battery (VFB) over long-term...     

低粘度高固含量醋酸乙烯-丙烯酸酯共聚乳液胶粘剂的研制

介绍了一种低粘度、高固体含量的醋酸乙烯-丙烯酸丁酯-丙烯酸异辛酯共聚乳液胶粘剂的合成工艺及性能。该乳液粘度低于2500mPa.s,固体含量≥52%,较低的玻璃化温度和良好的耐水性能,应用于卷烟和防水涂料的生产。     

Nafion membranes with a sulfonated organic additive for the use in vanadium redox flow batteries

Sulfonated copper phthalocyanine (CuPCSA) was embedded into Nafion membranes in ratios of 0, 1.25, 2.5, 5, and 7.5 wt %. The absence of CuPCSA related peaks in WAXS patterns indicated that CuPCSA did not form crystalline phases during membrane formation. Tensile strength and Young's modulus were highest in the range of 2.5–5 wt % CuPCSA. As demonstrated for Nafion 212, the weight gain and swelling in water-based solutions decreases when the sulfuric acid concentration increases from 0 to 2 M. In 2 M sulfuric acid, addition of CuPCSA increases the weight gain. In contact with VO₂⁺, blue CuPCSA is oxidatively hydrolyzed to form colorless sulfonated phthalimide. XPS analysis showed that (1) this reaction is quantitative and (2) that the sulfonated phthalimide does not leach out from the membrane during operation in the flow battery. The coulomb efficiency increases with the amount of phthalimide. This affects the energy efficiency so strongly, that it follows the same trend as the coulomb efficiency. During cycling, the cell with Nafion/7.5 wt % filler showed the highest discharge capacity and the lowest difference between charge and discharge capacity. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47547.     

环保型高固含量低粘度聚氨酯复膜胶的研究

选用低毒溶剂做稀释剂,合成了一种在较宽固含量范围,低粘度、贮存稳定的纸塑复合用双组分聚氨酯胶粘剂。探讨了初粘剂用量、NCO/OH摩尔比、固含量等因素对胶粘剂性能的影响,并用红外光谱仪对双组分聚氨酯胶粘剂的固化过程进行了表征。结果表明,控制NCO/OH摩尔比值在0.97-0.99之间,主剂与固化剂的质量比为10:1—1.5时,复膜效果最佳,剥离强度最高,且在常温下,经24h即可完全固化;羟基原料/初粘剂质量比为1/0.45时,初粘性最好,剥离强度最大;固含量为30%-50%时,涂胶效果、剥离强度均较好,使用时可根据情况选择。最终产品溶剂低毒,固含量高,粘度低,涂膜光亮、无白霜,粘接性能好,适合于纸塑复合。     

高锂盐含量聚氨酯基固态电解质的制备与性能

以异佛尔酮二异氰酸酯、聚碳酸酯二元醇和一缩二乙二醇为原料,合成硬段质量分数为30%的聚碳酸酯型聚氨酯(PCPU),将合成的聚氨酯和双三氟甲烷磺酰亚胺锂(LiTFSI)复合制得不同锂盐质量分数的固态聚合物电解质(SPE)。通过红外光谱分析了聚氨酯结构,采用TG、DSC测试了聚氨酯及电解质的热学性能,并采用交流阻抗、线性扫描伏安测试探究了不同LiTFSI质量分数对电解质电化学性能的影响。结果表明,随着LiTFSI质量分数的增加,聚氨酯基固态聚合物电解质的室温离子电导率呈现先增大后减小再增大的趋势,当锂盐质量分数为70%时,制备的电解质离子电导率达到最大值(1.28×10~(–8)S/cm),以此固态电解质与LiFePO4正极组装的固态电池在60℃、0.2 C电流密度时放电比容量为153 mA·h/g,循环100次容量保持率为84%。     

Surfactant-free ionic liquid-based nanofluids with remarkable thermal conductivity enhancement at very low loading of graphene

We report for the first time the preparation of highly stable graphene (GE)-based nanofluids with ionic liquid as base fluids (ionic liquid-based nanofluids (Ionanofluids)) without any surfactant and the subsequent investigations on their thermal conductivity, specific heat, and viscosity. The microstructure of the GE and MWCNTs are observed by transmission electron microscope. Thermal conductivity (TC), specific heat, and viscosity of these Ionanofluids were measured for different weight fractions and at varying temperatures, demonstrating that the Ionanofluids exhibit considerably higher TC and lower viscosity than that of their base fluids without significant specific heat decrease. An enhancement in TC by about 15.5% and 18.6% has been achieved at 25 °C and 65 °C respectively for the GE-based nanofluid at mass fraction of as low as 0.06%, which is larger than that of the MWCNT-dispersed nanofluid at the same loading. When the temperature rises, the TC and specific heat of the Ionanofluid increase clearly, while the viscosity decreases sharply. Moreover, the viscosity of the prepared Ionanofluids is lower than that of the base fluid. All these advantages of this new kind of Ionanofluid make it an ideal fluid for heat transfer and thermal storage.     

Effects of additives on the stability of electrolytes for all-vanadium redox flow batteries

The stability of the electrolytes for all-vanadium redox flow battery was investigated with ex-situ heating/cooling treatment and in situ flow-battery testing methods. The effects of inorganic and organic additives have been studied. The additives containing the ions of potassium, phosphate, and polyphosphate are not suitable stabilizing agents because of their reactions with V(V) ions, forming precipitates of KVSO₆ or VOPO₄. Of the chemicals studied, polyacrylic acid and its mixture with CH₃SO₃H are the most promising stabilizing candidates which can stabilize all the four vanadium ions (V²⁺, V³⁺, VO²⁺, and VO₂ ⁺) in electrolyte solutions up to 1.8 M. However, further effort is needed to obtain a stable electrolyte solution with >1.8 M V⁵⁺ at temperatures higher than 40 °C.