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1.
Direct dual layer spinning of aminosilica/Torlon® hollow fiber sorbents with a lumen layer for CO2 separation by rapid temperature swing adsorption
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Ying Labreche Yanfang Fan Ryan. P. Lively Christopher W. Jones William J. Koros 《应用聚合物科学杂志》2015,132(17)
The direct dual layer spinning of Torlon®/silica hollow fibers with a neat Torlon® lumen layer is reported here for the first time. The dual layer fibers containing a porous Torlon®/silica main structure and a dense, pure Torlon® polymer bore‐side coating provide a simplified, scalable platform from which to construct hollow fiber amine sorbents for postcombustion CO2 capture. After fiber spinning, an amine infusion process is applied to incorporate PEI into the silica pores. After combining dilute Neoprene treatment followed by poly(aramid)/PDMS treatment, a helium permeance of the fiber sorbents of 2 GPU with a He/N2 selectivity of 7.4 is achieved. Ten of the optimized amine‐containing hollow fibers are incorporated into a 22‐inch long, 1/2 inch OD shell‐and‐tube module and the module is then exposed on the shell side to simulated flue gas with an inert tracer (14 mol % CO2, 72 mol % N2, 14 mol % He [at 100% R.H.]) at 1 atm and 35°C in a RTSA system for preliminary CO2 sorption experiments. The fibers are found to have a breakthrough and equilibrium CO2 capacity of 0.8 and 1.2 mmol/g‐ dry fiber sorbent, respectively. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41845. 相似文献
2.
《Ceramics International》2022,48(16):23051-23060
To obtain both plasticity and toughness of the material at the same time, various manufacturing techniques of ceramic-metal composites and structures have been studied. In this work, a bio-inspired Al2O3 ceramic scaffold with Gyroid structure was designed and prepared by stereolithographic (SL) additive manufacturing, then the Al2O3/Al ceramic-metal hybrid structure was prepared by infiltrating molten Al into the Al2O3 ceramic structure. The performances of the Al2O3 ceramic scaffold and the Al2O3/Al ceramic-metal hybrid structure were compared and analyzed by a quasi-static compression experiment. The quasi-static compressive strength of the pristine Al2O3 scaffold was 14.36 MPa, while that of the Al2O3/Al ceramic-metal hybrid structure was up to 89.06 MPa. Moreover, the plasticity of the Al2O3/Al ceramic-metal hybrid structure was much higher than that of the Al2O3 scaffold. During compression, the Al2O3/Al ceramic-metal hybrid structure had excellent energy absorption, reaching up to 2569.16 KJ/m³, 15 times that of the Al2O3 scaffold. Therefore, this method can obtain materials with excellent ductility and toughness. 相似文献
3.
Enhancing CO2 absorption efficiency using a novel PTFE hollow fiber membrane contactor at elevated pressure
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Fushan Wang Guodong Kang Dandan Liu Meng Li Yiming Cao 《American Institute of Chemical Engineers》2018,64(6):2135-2145
The internal structure design of membrane module is very important for gas removal performance using membrane contactor via physical absorption. In this study, a novel membrane contactor developed by weaving polytetrafluoroethylene (PTFE) hollow fibers was applied to remove CO2 from 60% N2 + 40% CO2 mixture (with CO2 concentration similar to that of biogas) at elevated pressure (0.8 MPa) using water as absorbent. Compared with the conventional module with randomly packed straight fibers, the module with woven PTFE fibers exhibited much better CO2 absorption performance. The weaving configuration facilitated the meandering flow or Dean vortices and renewing speed of water around hollow fibers. Meanwhile, the undesired influences such as channeling and bypassing were also eliminated. Consequently, the mass transfer of liquid phase was greatly improved and the CO2 removal efficiency was significantly enhanced. The effects of operation pressure, module arrangement, feed gas, and water flow rate on CO2 removal were systematically investigated as well. The overall mass‐transfer coefficient (KOV) varied from 1.96 × 10?5 to 4.39 × 10?5 m/s (the volumetric mass‐transfer coefficient KLa = 0.034–0.075 s?1) under the experimental conditions. The CO2 removal performance of novel woven fiber membrane contactor matched well with the simulation results. © 2017 American Institute of Chemical Engineers AIChE J, 64: 2135–2145, 2018 相似文献
4.
《Ceramics International》2019,45(15):18988-18993
Aiming to prepare high-performance electromagnetic interference (EMI) shielding materials, chopped carbon fibers were incorporated into mullite ceramic matrix via rapid prototyping process of spark plasma sintering (SPS). Results indicate that Cf/mullite composites with only 1 wt% of carbon fibers exhibit highest shielding effectiveness (SET) over 40 dB at a small thickness of 2.0 mm, showing great advantages both in terms of performance and thickness compared with many mature carbon/ceramic composites. The high EMI shielding properties mainly depend on two mechanisms of absorption and reflection in this present work. The enhanced absorption and reflection of electromagnetic wave are ascribed to the promotional electrical conductivity arising from the formation of conductive network by introduction of carbon fibers. Regarding enhanced electrical conductivity, notable intensified interfacial polarization on a large number of interfaces between mullite matrix and carbon fibers is also the key factor to the improved absorption, which makes absorption play a dominant role in the significant improvement of EMI SET. The Cf/mullite composites with excellent EMI shielding properties and thin thickness show great potential application as EMI materials. 相似文献
5.
《Ceramics International》2022,48(6):7448-7455
The matrix material in a Molten Carbonate Fuel Cell, usually LiAlO2, has an important role in the ionic conduction, gas sealing and electrolyte retention. To avoid cracking, this material has been reinforced with various additives, mostly Al-based, which are subject to in situ lithiation. In this work, matrices were systematically synthesized through a fast and more environmentally friendly route and characterized, with two types of reinforcing agent, either Al powder or Al2O3 fibers, both with and without carbonates. Then, a comparative analysis was done, in terms of mechanical strength and porosity, on the effect of adding Al powder and Al2O3 fibers and their subsequent lithiation. This reaction was found to be quantitative after 50 h at 650 °C, and matrices with reinforcing agent and carbonates featured increased mechanical strength by a factor up to 2 compared to matrices with only reinforcing agent, reaching 0.61 kgf.mm?2. Al powder was also found to be better suited than Al2O3 fibers for addition in a matrix, also contributing to enhance the porosity, particularly after lithiation. 相似文献
6.
Matthias Schulz Ute Pippardt Lutz Kiesel Katrin Ritter Ralf Kriegel 《American Institute of Chemical Engineers》2012,58(10):3195-3202
Ba0.5Sr0.5Co0.8Fe0.2O3‐δ tubes, capillaries, capillary modules, and asymmetric membranes were prepared and tested for oxygen permeation in a dead‐end vacuum operation mode at temperatures up to 850°C. The capillary module was built up by reactive air brazing using seven capillaries and a supply tube. Two machined discs were used as an end cap and as a connector plate. The oxygen permeation behaves according to Wagner at small driving forces, but significant negative deviations were observed for asymmetric membranes and single capillaries at higher ones. This is caused by pressure drops at the vacuum side for single capillaries. The highest oxygen flux was revealed for the capillary module with 175.5 mL(STP)/min at a low‐vacuum pressure of 0.042 bar at 850°C, but the asymmetric membrane showing a little bit higher flux at moderate vacuum pressures above 0.07 bar. © 2012 American Institute of Chemical Engineers AIChE J, 58: 3195–3202, 2012 相似文献
7.
ABSTRACT The viscous flow fields around multifiber filters have been investigated in a previous paper. The results of the previous work show that the flow becomes periodic immediately after the first fiber array downstream from the entrance if the fibers are arranged uniformly along the flow direction. The characteristics of such flow fields enable the pressure drop and the particle interception efficiency of a multifiber filter to be represented by single-fiber models. The total filtration efficiency, however, cannot be so represented since fibers interact during filtration processes. In this study, the pressure drop and the interception efficiency were investigated by making use of the viscous flow fields modeled in the previous research. The fiber separation ratio was found to have significant effects on pressure drop and efficiency. At a given volume fraction, changes in the fiber separation ratio will result in changes to the patterns of fluid flow and aerosol particle motion. Therefore, the fiber separation ratio significantly affects pressure drop and interception efficiency. 相似文献
8.
Ye Yuan Yayuan Xiong Jianjun Li Weilong Yin Qingyu Peng Haibao Lu Yibin Li Xiaodong He 《Journal of the American Ceramic Society》2020,103(10):5629-5637
Hollow carbon fibers (HCF) with ultra-large diameter have been synthesized and the versatility to convert them into the corresponding carbon-based composites has been demonstrated. The hollow carbon fibers were fabricated by thermal controlled carbonization of electrospun polyacrylonitrile fibers. For the existence of inorganic silica shell during pyrolysis, heat release will be blocked at the boundary, driving the polyacrylonitrile precursor fiber to form hollow structure. The diameter of the as-prepared hollow carbon fibers can exceed 150 nm. Sol-gel-derived Fe3O4 nanoparticles can grow on the outer-surface and the inner-surface of hollow carbon fibers. The microwave absorption performance of ternary HCF@Fe3O4@PPy composite is testified and the values of reflection loss exceeding −10 dB can be obtained in the frequency of 3.3-11.3 GHz. The large diameter of hollow carbon fibers can have inner and outer interfaces in the corresponding composites, which make them great potential for a variety of applications in future. 相似文献
9.
A new air-gap membrane distillation (AGMD) module for desalination with internal latent-heat-recovery which consisted of parallel hollow fiber membranes and heat exchange hollow fibers was successfully developed. The influences of feed flow rate, feed temperature and feed initial concentration on AGMD process were investigated. The vapor pressure polarization coefficient (η) was introduced to measure the reduction in the effective driving force for mass transfer with regard to the driving force imposed. Among all AGMD experiments, the maximum water vapor permeate flux (JD) of 5.30 kg/m2 h and the gained output ratio (GOR) of 5.70 were obtained. A theoretical model based on the mass and energy balances of the hot feed side was established to calculate the temperature and the local water vapor permeate flux distributions along the hollow fiber membrane, which showed that the temperature drop and local water vapor permeate flux drop were much larger at the upper part than those at the lower part of the membrane module in the hot feed side. 相似文献
10.
《分离科学与技术》2012,47(1-3):343-359
Abstract In recent years there has been significant interest in utilizing microporous hollow fiber membranes for liquid-liquid extraction. The membrane extractor resembles the shell and tube heat exchanger with the tube section composed of 1000–2500 fibers/in2. The diameter of each fiber is approximately 300 microns. In this process, the feed may be passed through the shell side, while the solvent is passed through the fiber side, or vice versa. Mass transfer occurs across the liquid-liquid interface formed in the pores of the fiber wall. The advantages of this technology are high throughput capacities, independence of density difference between the feed and solvent, and potentially high mass transfer areas. The mass transfer performance of an available commercial scale nonbaffled membrane extraction module was determined to be lower than expected from results obtained in smaller scale modules. Mass transfer studies of a commercial-scale membrane extraction module at the Separations Research Program have shown that a significant portion of the fibers are bypassed by the shell side fluid and consequently only a fraction of the total fiber surface area is utilized. A hydraulic study using a dye tracer technique verified this finding with an aqueous flow on the shell side. A model which incorporates mass transfer correlations reported by others has been developed and shown to have excellent agreement with the experimental data obtained. In this paper, the efficiency of the membrane extractor is compared with conventional spray, sieve tray, and packed columns; the effect of shell side bypassing is also presented. 相似文献
11.
《Ceramics International》2017,43(18):16204-16209
Cf/Ti3SiC2-SiC composites with different content of short carbon fibers were fabricated by the combination of compression molding and pressureless sintering. Microstructure and mechanical behavior of the composites were studied to evaluate the comprehensive performance of the material. In comparison, composites without carbon fibers were also fabricated in the same way. The results indicate that Ti3SiC2 phases were synthesized in each cases and exhibit typical laminated structure with smooth surface. With the increase of carbon fiber content, composites turn from brittle to toughness, and show obvious elastic and no-linear regions on the force-displacement curve. Moreover, composite with 30% (volume fraction) carbon fiber shows the highest flexural strength (284.03 MPa), open porosity (15.78%), and lowest density (2.37 g cm−3). There were chemical reactions occurred between carbon fibers and matrix which formed strong covalent bonds and interfaces. The micrographs also reveal that fiber bridging and pulling-out are the most important reinforcement mechanisms which contribute to the mechanical properties of the composites. 相似文献
12.
Yuan Li Mingzhi Zhang Yuanyuan Chu Xiaoyao Tan Jun Gao Shaobin Wang Shaomin Liu 《American Institute of Chemical Engineers》2018,64(10):3662-3670
Cost‐effective and robust nickel (Ni) membrane for H2 separation is a promising technology to upgrade the conventional H2 industries with improved economics and environmental benignity. In this work, Ni hollow fibers (HFs) with one closed end were fabricated and assembled into a membrane module for pure H2 separation by applying vacuum to the permeate side. The separation behavior of the HF module was investigated both experimentally and theoretically. Results indicate that H2 recovery can be improved significantly by changing the operation conditions (temperature or feed pressure). Ni HF is a promising membrane geometry, but the negative effect of pressure drop when H2 passes through the lumen cannot be ignored. Under the vacuum operation mode, there is little difference in term of H2 recovery efficiency whether the feed gas flow is controlled in countercurrent or recurrent operation. This work provides important insight to the development of superior membrane H2 separation system. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3662–3670, 2018 相似文献
13.
Altaf H. Carim 《Journal of the American Ceramic Society》1990,73(9):2764-2766
Reaction products at the boundary between Si3 N4 and Ag-Cu-Ti braze alloy have been characterized by transmission electron microscopy. Beyond the TiN adjoining the Si3 N4 substrate is a continuous layer of a previously unreported, orthorhombic Ti-Si-Cu-N compound. Evidence of additional cubic and hexagonal Ti-Si-Cu-N phases is also found; these exist as isolated grains farther from the substrate. The cubic compound is probably an η-type M6 X phase of the sort observed at other ceramic-metal interfaces. These "dilute ceramics," in which metallic constituents dominate, are common transitional phases in ceramic-metal systems. 相似文献
14.
Dewei Lin Shengwei Tan Fen Lin Zhengwei Dong Jiajia Yan Dian Tang Hsiwen Yang Kongfa Chen Teng Zhang 《Journal of the European Ceramic Society》2018,38(13):4488-4494
The rigid nature of sealing glass-ceramics restricts the thermal cycling stability of Solid Oxide Fuel Cells (SOFCs), which thus evokes an interest in designing a sealing glass without crystallization under the operational condition of SOFCs. In this paper, we report that the sealing performance of 30Na2O-70SiO2 (in mole%) glass-ceramic can be significantly improved by Fe2O3 dopant through a composite approach. In particular, the crystallization in glass can be suppressed by appropriate Fe2O3 dopant amount (8?mol%), which results in the improved sealing property of glass. In addition, the glass modified with Fe2O3 shows good chemical compatibility with 8?mol% yttria-stabilized zirconia (8YSZ) electrolyte and metallic interconnect (430 stainless steel) in dual atmospheres. The possible mechanism for the improved sealing performance of 30Na2O-70SiO2 glass-ceramic by this unique composite approach is also discussed. 相似文献
15.
Simulation of gas separation using partial element stage cut modeling of hollow fiber membrane modules
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Sina Gilassi Seyed Mohammad Taghavi Denis Rodrigue Serge Kaliaguine 《American Institute of Chemical Engineers》2018,64(5):1766-1777
A mathematical model is developed to simulate a gas separation process using a hollow fiber membrane module. In particular, a new numerical technique is introduced based on flash calculation. Such analysis allows identifying the required membrane properties needed to reach module performance of interest. This model is validated for six different gas separation cases taken from literature. Then, the validated model is used to investigate the effect of O2 and N2 permeances on O2 recovery and O2 mole fraction in the permeate stream. A realistic two‐stage air enrichment process is also proposed for O2 production using an industrial module with different fibers numbers. Moreover, this model is used to simulate a natural gas purification process using a single unit to determine the required membrane separation area and CH4 loss. Finally, a two‐stage process is proposed to equally enhance CH4 retentate mole fraction and decrease CH4 loss. © 2017 American Institute of Chemical Engineers AIChE J, 64: 1766–1777, 2018 相似文献
16.
Pietro Galizia Simone Failla Luca Zoli Diletta Sciti 《Journal of the European Ceramic Society》2018,38(2):403-409
One of the biggest challenges of the materials science is the mutual exclusion of strength and toughness. This issue was minimized by mimicking the natural structural materials. To date, few efforts were done regarding materials that should be used in harsh environments. In this work we present novel continuous carbon fiber reinforced ultra-high-temperature ceramic matrix composites (UHTCMCs) for aerospace featuring optimized fiber/matrix interfaces and fibers distribution. The microstructures – produced by electrophoretic deposition of ZrB2 on unidirectional carbon fibers followed by ZrB2 infiltration and hot pressing – show a maximum flexural strength and fracture toughness of 330 MPa and 14 MPa m1/2, respectively. Fracture surfaces are investigated to understand the mechanisms that affect strength and toughness. The EPD technique allows the achievement of a peculiar salami-inspired architecture alternating strong and weak interfaces. 相似文献
17.
Controlled reactions on the inner side, outer side, and both sides of the surfaces of polysulfone ultrafiltration hollow fibers with propane sultone and Friedel-Crafts catalysts were developed. EPMA measurements and MTR spectra for the chemically modified fibers suggested existence of CH2CH2CH2SO3− segments on the modified surfaces. The modified fibers were found to have smaller molecular weight cut-off than nonmodified fibers, and the fibers modified on the internal surfaces gave better rejection of polyethylene glycol 6000 than those modified on the external surfaces, although the fibers that reacted with solution of the propane sultone and SnCl4 at 70°C and 80°C showed negative rejection of the polyethylene gylcol. Absorption of polyethylene glycol on the modified fibers is estimated to be less than the nonmodified fibers from the flux ratios of aqueous polyethylene glycol solution to pure water. This effect is attributed to the heparinlike active group of modified segments. 相似文献
18.
《Journal of the European Ceramic Society》2019,39(6):2003-2009
Ceramic Ti2AlC building blocks of 4 × 1.24 × 1.24 mm³ size were prepared by injection molding and assembled to brick-and-mortar structures with tetragonal, monoclinic and triclinic unit cells. The single building blocks were bonded with an Al-loaded polysiloxane adhesive, which was afterwards pyrolized. Afterwards the 3D-assemblies were infiltrated with an Al-melt to fabricate dense 0–3 ceramic-metal composites. The influence of the unit cell of the resulting Ti2AlC-Al composites was investigated regarding the mechanical properties and damage mechanisms in bending tests. The developed near-net shape fabrication process shows great potential to manufacture structured ceramic-metal composites with high toughness and complex shape. Due to their ductile behavior scaffold applications are possible. The calculated initial fracture toughness of monolithic Ti2AlC could be improved from 5.0 MPa m0.5 to 14.5 MPa m0.5 for the monoclinic assembly and 14.7 MPa m0.5 for the triclinic assembly, corresponding to an increase of 191%. 相似文献
19.
Degradation of Nextel™ 610‐based oxide‐oxide ceramic composites by aluminum oxychloride decomposition products
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Randall S. Hay Kristin A. Keller Larry P. Zawada Nathan S. Jacobson Geoff E. Fair 《Journal of the American Ceramic Society》2018,101(9):4203-4223
Nextel? 610 alumina fibers and alumina‐YAG (yttrium‐aluminum garnet) matrices were used to make oxide‐oxide ceramic matrix composites (CMCs) with and without monazite (LaPO4) fiber‐matrix interfaces. Twelve sequential aluminum oxychloride (AlOCl) infiltrations with 1 hour heat treatments at 1100°C and a final 1 hour heat treatment at 1200°C were used for matrix densification. This matrix processing sequence severely degraded CMC mechanical properties. CMC tensile strengths and interlaminar tensile (ILT) strengths were less than 10 MPa and 1 MPa, respectively. Axial fracture of Nextel? 610 fibers was observed after ILT testing, highlighting the extreme degradation of fiber strength. Extensive characterization was done to attempt to determine the responsible degradation mechanisms. Changes in Nextel? 610 fiber microstructure after CMC processing were characterized by optical microscopy, SEM, and extensively by TEM. In AlOCl degraded fibers, grain boundaries near the fiber surface were wetted with a glass that contained Y2O3/SiO2 or Y2O3/La2O3/P2O5/SiO2, and near‐surface pores were partially filled with Al2O3. This glass must also contain some Al2O3 and initially some chlorine. AlOCl decomposition products were predicted using the FactSage® Thermochemical code, and were characterized by mass spectrometry. Effects of AlOCl precursors on monazite coated and uncoated Nextel? 610 fibers tow and filament strength were evaluated. A mechanism for the severe degradation of the oxide‐oxide CMCs and Nextel? 610 fibers that involves subcritical crack growth promoted by release of chlorine containing species during breakdown of intergranular glasses in an anhydrous environment is proposed. 相似文献
20.
《Journal of the European Ceramic Society》2003,23(3):445-454
Within the framework of a cooperation project, ceramic components of alumina, Al2O3, were sealed in a gastight manner for chemical applications using a sealing compound based on ceramic raw materials. The sealing is adapted to the Al2O3 ceramic with respect to expansion coefficient and wettability and it is inert, mechanically stable, chemically resistant and above all gastight at application temperatures of approx. 1000 °C. This was achieved with high reproducibility by a composition in the SiO2–Al2O3–CaO–K2O quaternary system. The ceramic sealing compound is selectively crystallized by adequate temperature control and shows then the required high temperature resistance. The strengths achieved are sufficient for the planned application as a sealing material for a ceramic microreactor. The temperature cycling resistance and the thermal shock resistance are also adapted to Al2O3. Additional tests of commercial glass sealants were carried out to evaluate the results obtained. 相似文献